1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988--2020 Free Software Foundation, Inc.
5 @c makeinfo ignores cmds prev to setfilename, so its arg cannot make use
6 @c of @set vars. However, you can override filename with makeinfo -o.
13 @settitle Debugging with @value{GDBN}
14 @setchapternewpage odd
23 @c To avoid file-name clashes between index.html and Index.html, when
24 @c the manual is produced on a Posix host and then moved to a
25 @c case-insensitive filesystem (e.g., MS-Windows), we separate the
26 @c indices into two: Concept Index and all the rest.
30 @c readline appendices use @vindex, @findex and @ftable,
31 @c annotate.texi and gdbmi use @findex.
34 @c !!set GDB manual's edition---not the same as GDB version!
35 @c This is updated by GNU Press.
38 @c !!set GDB edit command default editor
41 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
43 @c This is a dir.info fragment to support semi-automated addition of
44 @c manuals to an info tree.
45 @dircategory Software development
47 * Gdb: (gdb). The GNU debugger.
48 * gdbserver: (gdb) Server. The GNU debugging server.
52 @c man begin COPYRIGHT
53 Copyright @copyright{} 1988-2020 Free Software Foundation, Inc.
55 Permission is granted to copy, distribute and/or modify this document
56 under the terms of the GNU Free Documentation License, Version 1.3 or
57 any later version published by the Free Software Foundation; with the
58 Invariant Sections being ``Free Software'' and ``Free Software Needs
59 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
60 and with the Back-Cover Texts as in (a) below.
62 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
63 this GNU Manual. Buying copies from GNU Press supports the FSF in
64 developing GNU and promoting software freedom.''
69 This file documents the @sc{gnu} debugger @value{GDBN}.
71 This is the @value{EDITION} Edition, of @cite{Debugging with
72 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
73 @ifset VERSION_PACKAGE
74 @value{VERSION_PACKAGE}
76 Version @value{GDBVN}.
82 @title Debugging with @value{GDBN}
83 @subtitle The @sc{gnu} Source-Level Debugger
85 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
86 @ifset VERSION_PACKAGE
88 @subtitle @value{VERSION_PACKAGE}
90 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
94 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
95 \hfill {\it Debugging with @value{GDBN}}\par
96 \hfill \TeX{}info \texinfoversion\par
100 @vskip 0pt plus 1filll
101 Published by the Free Software Foundation @*
102 51 Franklin Street, Fifth Floor,
103 Boston, MA 02110-1301, USA@*
104 ISBN 978-0-9831592-3-0 @*
113 @top Debugging with @value{GDBN}
115 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
117 This is the @value{EDITION} Edition, for @value{GDBN}
118 @ifset VERSION_PACKAGE
119 @value{VERSION_PACKAGE}
121 Version @value{GDBVN}.
123 Copyright (C) 1988-2020 Free Software Foundation, Inc.
125 This edition of the GDB manual is dedicated to the memory of Fred
126 Fish. Fred was a long-standing contributor to GDB and to Free
127 software in general. We will miss him.
130 * Summary:: Summary of @value{GDBN}
131 * Sample Session:: A sample @value{GDBN} session
133 * Invocation:: Getting in and out of @value{GDBN}
134 * Commands:: @value{GDBN} commands
135 * Running:: Running programs under @value{GDBN}
136 * Stopping:: Stopping and continuing
137 * Reverse Execution:: Running programs backward
138 * Process Record and Replay:: Recording inferior's execution and replaying it
139 * Stack:: Examining the stack
140 * Source:: Examining source files
141 * Data:: Examining data
142 * Optimized Code:: Debugging optimized code
143 * Macros:: Preprocessor Macros
144 * Tracepoints:: Debugging remote targets non-intrusively
145 * Overlays:: Debugging programs that use overlays
147 * Languages:: Using @value{GDBN} with different languages
149 * Symbols:: Examining the symbol table
150 * Altering:: Altering execution
151 * GDB Files:: @value{GDBN} files
152 * Targets:: Specifying a debugging target
153 * Remote Debugging:: Debugging remote programs
154 * Configurations:: Configuration-specific information
155 * Controlling GDB:: Controlling @value{GDBN}
156 * Extending GDB:: Extending @value{GDBN}
157 * Interpreters:: Command Interpreters
158 * TUI:: @value{GDBN} Text User Interface
159 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
160 * GDB/MI:: @value{GDBN}'s Machine Interface.
161 * Annotations:: @value{GDBN}'s annotation interface.
162 * JIT Interface:: Using the JIT debugging interface.
163 * In-Process Agent:: In-Process Agent
165 * GDB Bugs:: Reporting bugs in @value{GDBN}
167 @ifset SYSTEM_READLINE
168 * Command Line Editing: (rluserman). Command Line Editing
169 * Using History Interactively: (history). Using History Interactively
171 @ifclear SYSTEM_READLINE
172 * Command Line Editing:: Command Line Editing
173 * Using History Interactively:: Using History Interactively
175 * In Memoriam:: In Memoriam
176 * Formatting Documentation:: How to format and print @value{GDBN} documentation
177 * Installing GDB:: Installing GDB
178 * Maintenance Commands:: Maintenance Commands
179 * Remote Protocol:: GDB Remote Serial Protocol
180 * Agent Expressions:: The GDB Agent Expression Mechanism
181 * Target Descriptions:: How targets can describe themselves to
183 * Operating System Information:: Getting additional information from
185 * Trace File Format:: GDB trace file format
186 * Index Section Format:: .gdb_index section format
187 * Man Pages:: Manual pages
188 * Copying:: GNU General Public License says
189 how you can copy and share GDB
190 * GNU Free Documentation License:: The license for this documentation
191 * Concept Index:: Index of @value{GDBN} concepts
192 * Command and Variable Index:: Index of @value{GDBN} commands, variables,
193 functions, and Python data types
201 @unnumbered Summary of @value{GDBN}
203 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
204 going on ``inside'' another program while it executes---or what another
205 program was doing at the moment it crashed.
207 @value{GDBN} can do four main kinds of things (plus other things in support of
208 these) to help you catch bugs in the act:
212 Start your program, specifying anything that might affect its behavior.
215 Make your program stop on specified conditions.
218 Examine what has happened, when your program has stopped.
221 Change things in your program, so you can experiment with correcting the
222 effects of one bug and go on to learn about another.
225 You can use @value{GDBN} to debug programs written in C and C@t{++}.
226 For more information, see @ref{Supported Languages,,Supported Languages}.
227 For more information, see @ref{C,,C and C++}.
229 Support for D is partial. For information on D, see
233 Support for Modula-2 is partial. For information on Modula-2, see
234 @ref{Modula-2,,Modula-2}.
236 Support for OpenCL C is partial. For information on OpenCL C, see
237 @ref{OpenCL C,,OpenCL C}.
240 Debugging Pascal programs which use sets, subranges, file variables, or
241 nested functions does not currently work. @value{GDBN} does not support
242 entering expressions, printing values, or similar features using Pascal
246 @value{GDBN} can be used to debug programs written in Fortran, although
247 it may be necessary to refer to some variables with a trailing
250 @value{GDBN} can be used to debug programs written in Objective-C,
251 using either the Apple/NeXT or the GNU Objective-C runtime.
254 * Free Software:: Freely redistributable software
255 * Free Documentation:: Free Software Needs Free Documentation
256 * Contributors:: Contributors to GDB
260 @unnumberedsec Free Software
262 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
263 General Public License
264 (GPL). The GPL gives you the freedom to copy or adapt a licensed
265 program---but every person getting a copy also gets with it the
266 freedom to modify that copy (which means that they must get access to
267 the source code), and the freedom to distribute further copies.
268 Typical software companies use copyrights to limit your freedoms; the
269 Free Software Foundation uses the GPL to preserve these freedoms.
271 Fundamentally, the General Public License is a license which says that
272 you have these freedoms and that you cannot take these freedoms away
275 @node Free Documentation
276 @unnumberedsec Free Software Needs Free Documentation
278 The biggest deficiency in the free software community today is not in
279 the software---it is the lack of good free documentation that we can
280 include with the free software. Many of our most important
281 programs do not come with free reference manuals and free introductory
282 texts. Documentation is an essential part of any software package;
283 when an important free software package does not come with a free
284 manual and a free tutorial, that is a major gap. We have many such
287 Consider Perl, for instance. The tutorial manuals that people
288 normally use are non-free. How did this come about? Because the
289 authors of those manuals published them with restrictive terms---no
290 copying, no modification, source files not available---which exclude
291 them from the free software world.
293 That wasn't the first time this sort of thing happened, and it was far
294 from the last. Many times we have heard a GNU user eagerly describe a
295 manual that he is writing, his intended contribution to the community,
296 only to learn that he had ruined everything by signing a publication
297 contract to make it non-free.
299 Free documentation, like free software, is a matter of freedom, not
300 price. The problem with the non-free manual is not that publishers
301 charge a price for printed copies---that in itself is fine. (The Free
302 Software Foundation sells printed copies of manuals, too.) The
303 problem is the restrictions on the use of the manual. Free manuals
304 are available in source code form, and give you permission to copy and
305 modify. Non-free manuals do not allow this.
307 The criteria of freedom for a free manual are roughly the same as for
308 free software. Redistribution (including the normal kinds of
309 commercial redistribution) must be permitted, so that the manual can
310 accompany every copy of the program, both on-line and on paper.
312 Permission for modification of the technical content is crucial too.
313 When people modify the software, adding or changing features, if they
314 are conscientious they will change the manual too---so they can
315 provide accurate and clear documentation for the modified program. A
316 manual that leaves you no choice but to write a new manual to document
317 a changed version of the program is not really available to our
320 Some kinds of limits on the way modification is handled are
321 acceptable. For example, requirements to preserve the original
322 author's copyright notice, the distribution terms, or the list of
323 authors, are ok. It is also no problem to require modified versions
324 to include notice that they were modified. Even entire sections that
325 may not be deleted or changed are acceptable, as long as they deal
326 with nontechnical topics (like this one). These kinds of restrictions
327 are acceptable because they don't obstruct the community's normal use
330 However, it must be possible to modify all the @emph{technical}
331 content of the manual, and then distribute the result in all the usual
332 media, through all the usual channels. Otherwise, the restrictions
333 obstruct the use of the manual, it is not free, and we need another
334 manual to replace it.
336 Please spread the word about this issue. Our community continues to
337 lose manuals to proprietary publishing. If we spread the word that
338 free software needs free reference manuals and free tutorials, perhaps
339 the next person who wants to contribute by writing documentation will
340 realize, before it is too late, that only free manuals contribute to
341 the free software community.
343 If you are writing documentation, please insist on publishing it under
344 the GNU Free Documentation License or another free documentation
345 license. Remember that this decision requires your approval---you
346 don't have to let the publisher decide. Some commercial publishers
347 will use a free license if you insist, but they will not propose the
348 option; it is up to you to raise the issue and say firmly that this is
349 what you want. If the publisher you are dealing with refuses, please
350 try other publishers. If you're not sure whether a proposed license
351 is free, write to @email{licensing@@gnu.org}.
353 You can encourage commercial publishers to sell more free, copylefted
354 manuals and tutorials by buying them, and particularly by buying
355 copies from the publishers that paid for their writing or for major
356 improvements. Meanwhile, try to avoid buying non-free documentation
357 at all. Check the distribution terms of a manual before you buy it,
358 and insist that whoever seeks your business must respect your freedom.
359 Check the history of the book, and try to reward the publishers that
360 have paid or pay the authors to work on it.
362 The Free Software Foundation maintains a list of free documentation
363 published by other publishers, at
364 @url{http://www.fsf.org/doc/other-free-books.html}.
367 @unnumberedsec Contributors to @value{GDBN}
369 Richard Stallman was the original author of @value{GDBN}, and of many
370 other @sc{gnu} programs. Many others have contributed to its
371 development. This section attempts to credit major contributors. One
372 of the virtues of free software is that everyone is free to contribute
373 to it; with regret, we cannot actually acknowledge everyone here. The
374 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
375 blow-by-blow account.
377 Changes much prior to version 2.0 are lost in the mists of time.
380 @emph{Plea:} Additions to this section are particularly welcome. If you
381 or your friends (or enemies, to be evenhanded) have been unfairly
382 omitted from this list, we would like to add your names!
385 So that they may not regard their many labors as thankless, we
386 particularly thank those who shepherded @value{GDBN} through major
388 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
389 Jim Blandy (release 4.18);
390 Jason Molenda (release 4.17);
391 Stan Shebs (release 4.14);
392 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
393 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
394 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
395 Jim Kingdon (releases 3.5, 3.4, and 3.3);
396 and Randy Smith (releases 3.2, 3.1, and 3.0).
398 Richard Stallman, assisted at various times by Peter TerMaat, Chris
399 Hanson, and Richard Mlynarik, handled releases through 2.8.
401 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
402 in @value{GDBN}, with significant additional contributions from Per
403 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
404 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
405 much general update work leading to release 3.0).
407 @value{GDBN} uses the BFD subroutine library to examine multiple
408 object-file formats; BFD was a joint project of David V.
409 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
411 David Johnson wrote the original COFF support; Pace Willison did
412 the original support for encapsulated COFF.
414 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
416 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
417 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
419 Jean-Daniel Fekete contributed Sun 386i support.
420 Chris Hanson improved the HP9000 support.
421 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
422 David Johnson contributed Encore Umax support.
423 Jyrki Kuoppala contributed Altos 3068 support.
424 Jeff Law contributed HP PA and SOM support.
425 Keith Packard contributed NS32K support.
426 Doug Rabson contributed Acorn Risc Machine support.
427 Bob Rusk contributed Harris Nighthawk CX-UX support.
428 Chris Smith contributed Convex support (and Fortran debugging).
429 Jonathan Stone contributed Pyramid support.
430 Michael Tiemann contributed SPARC support.
431 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
432 Pace Willison contributed Intel 386 support.
433 Jay Vosburgh contributed Symmetry support.
434 Marko Mlinar contributed OpenRISC 1000 support.
436 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
438 Rich Schaefer and Peter Schauer helped with support of SunOS shared
441 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
442 about several machine instruction sets.
444 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
445 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
446 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
447 and RDI targets, respectively.
449 Brian Fox is the author of the readline libraries providing
450 command-line editing and command history.
452 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
453 Modula-2 support, and contributed the Languages chapter of this manual.
455 Fred Fish wrote most of the support for Unix System Vr4.
456 He also enhanced the command-completion support to cover C@t{++} overloaded
459 Hitachi America (now Renesas America), Ltd. sponsored the support for
460 H8/300, H8/500, and Super-H processors.
462 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
464 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
467 Toshiba sponsored the support for the TX39 Mips processor.
469 Matsushita sponsored the support for the MN10200 and MN10300 processors.
471 Fujitsu sponsored the support for SPARClite and FR30 processors.
473 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
476 Michael Snyder added support for tracepoints.
478 Stu Grossman wrote gdbserver.
480 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
481 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
483 The following people at the Hewlett-Packard Company contributed
484 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
485 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
486 compiler, and the Text User Interface (nee Terminal User Interface):
487 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
488 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
489 provided HP-specific information in this manual.
491 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
492 Robert Hoehne made significant contributions to the DJGPP port.
494 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
495 development since 1991. Cygnus engineers who have worked on @value{GDBN}
496 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
497 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
498 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
499 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
500 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
501 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
502 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
503 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
504 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
505 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
506 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
507 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
508 Zuhn have made contributions both large and small.
510 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
511 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
513 Jim Blandy added support for preprocessor macros, while working for Red
516 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
517 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
518 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
519 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
520 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
521 with the migration of old architectures to this new framework.
523 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
524 unwinder framework, this consisting of a fresh new design featuring
525 frame IDs, independent frame sniffers, and the sentinel frame. Mark
526 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
527 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
528 trad unwinders. The architecture-specific changes, each involving a
529 complete rewrite of the architecture's frame code, were carried out by
530 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
531 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
532 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
533 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
536 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
537 Tensilica, Inc.@: contributed support for Xtensa processors. Others
538 who have worked on the Xtensa port of @value{GDBN} in the past include
539 Steve Tjiang, John Newlin, and Scott Foehner.
541 Michael Eager and staff of Xilinx, Inc., contributed support for the
542 Xilinx MicroBlaze architecture.
544 Initial support for the FreeBSD/mips target and native configuration
545 was developed by SRI International and the University of Cambridge
546 Computer Laboratory under DARPA/AFRL contract FA8750-10-C-0237
547 ("CTSRD"), as part of the DARPA CRASH research programme.
549 Initial support for the FreeBSD/riscv target and native configuration
550 was developed by SRI International and the University of Cambridge
551 Computer Laboratory (Department of Computer Science and Technology)
552 under DARPA contract HR0011-18-C-0016 ("ECATS"), as part of the DARPA
553 SSITH research programme.
555 The original port to the OpenRISC 1000 is believed to be due to
556 Alessandro Forin and Per Bothner. More recent ports have been the work
557 of Jeremy Bennett, Franck Jullien, Stefan Wallentowitz and
561 @chapter A Sample @value{GDBN} Session
563 You can use this manual at your leisure to read all about @value{GDBN}.
564 However, a handful of commands are enough to get started using the
565 debugger. This chapter illustrates those commands.
568 In this sample session, we emphasize user input like this: @b{input},
569 to make it easier to pick out from the surrounding output.
572 @c FIXME: this example may not be appropriate for some configs, where
573 @c FIXME...primary interest is in remote use.
575 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
576 processor) exhibits the following bug: sometimes, when we change its
577 quote strings from the default, the commands used to capture one macro
578 definition within another stop working. In the following short @code{m4}
579 session, we define a macro @code{foo} which expands to @code{0000}; we
580 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
581 same thing. However, when we change the open quote string to
582 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
583 procedure fails to define a new synonym @code{baz}:
592 @b{define(bar,defn(`foo'))}
596 @b{changequote(<QUOTE>,<UNQUOTE>)}
598 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
601 m4: End of input: 0: fatal error: EOF in string
605 Let us use @value{GDBN} to try to see what is going on.
608 $ @b{@value{GDBP} m4}
609 @c FIXME: this falsifies the exact text played out, to permit smallbook
610 @c FIXME... format to come out better.
611 @value{GDBN} is free software and you are welcome to distribute copies
612 of it under certain conditions; type "show copying" to see
614 There is absolutely no warranty for @value{GDBN}; type "show warranty"
617 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
622 @value{GDBN} reads only enough symbol data to know where to find the
623 rest when needed; as a result, the first prompt comes up very quickly.
624 We now tell @value{GDBN} to use a narrower display width than usual, so
625 that examples fit in this manual.
628 (@value{GDBP}) @b{set width 70}
632 We need to see how the @code{m4} built-in @code{changequote} works.
633 Having looked at the source, we know the relevant subroutine is
634 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
635 @code{break} command.
638 (@value{GDBP}) @b{break m4_changequote}
639 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
643 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
644 control; as long as control does not reach the @code{m4_changequote}
645 subroutine, the program runs as usual:
648 (@value{GDBP}) @b{run}
649 Starting program: /work/Editorial/gdb/gnu/m4/m4
657 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
658 suspends execution of @code{m4}, displaying information about the
659 context where it stops.
662 @b{changequote(<QUOTE>,<UNQUOTE>)}
664 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
666 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
670 Now we use the command @code{n} (@code{next}) to advance execution to
671 the next line of the current function.
675 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
680 @code{set_quotes} looks like a promising subroutine. We can go into it
681 by using the command @code{s} (@code{step}) instead of @code{next}.
682 @code{step} goes to the next line to be executed in @emph{any}
683 subroutine, so it steps into @code{set_quotes}.
687 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
689 530 if (lquote != def_lquote)
693 The display that shows the subroutine where @code{m4} is now
694 suspended (and its arguments) is called a stack frame display. It
695 shows a summary of the stack. We can use the @code{backtrace}
696 command (which can also be spelled @code{bt}), to see where we are
697 in the stack as a whole: the @code{backtrace} command displays a
698 stack frame for each active subroutine.
701 (@value{GDBP}) @b{bt}
702 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
704 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
706 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
707 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
709 #4 0x79dc in expand_input () at macro.c:40
710 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
714 We step through a few more lines to see what happens. The first two
715 times, we can use @samp{s}; the next two times we use @code{n} to avoid
716 falling into the @code{xstrdup} subroutine.
720 0x3b5c 532 if (rquote != def_rquote)
722 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
723 def_lquote : xstrdup(lq);
725 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
728 538 len_lquote = strlen(rquote);
732 The last line displayed looks a little odd; we can examine the variables
733 @code{lquote} and @code{rquote} to see if they are in fact the new left
734 and right quotes we specified. We use the command @code{p}
735 (@code{print}) to see their values.
738 (@value{GDBP}) @b{p lquote}
739 $1 = 0x35d40 "<QUOTE>"
740 (@value{GDBP}) @b{p rquote}
741 $2 = 0x35d50 "<UNQUOTE>"
745 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
746 To look at some context, we can display ten lines of source
747 surrounding the current line with the @code{l} (@code{list}) command.
753 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
755 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
758 538 len_lquote = strlen(rquote);
759 539 len_rquote = strlen(lquote);
766 Let us step past the two lines that set @code{len_lquote} and
767 @code{len_rquote}, and then examine the values of those variables.
771 539 len_rquote = strlen(lquote);
774 (@value{GDBP}) @b{p len_lquote}
776 (@value{GDBP}) @b{p len_rquote}
781 That certainly looks wrong, assuming @code{len_lquote} and
782 @code{len_rquote} are meant to be the lengths of @code{lquote} and
783 @code{rquote} respectively. We can set them to better values using
784 the @code{p} command, since it can print the value of
785 any expression---and that expression can include subroutine calls and
789 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
791 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
796 Is that enough to fix the problem of using the new quotes with the
797 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
798 executing with the @code{c} (@code{continue}) command, and then try the
799 example that caused trouble initially:
805 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
812 Success! The new quotes now work just as well as the default ones. The
813 problem seems to have been just the two typos defining the wrong
814 lengths. We allow @code{m4} exit by giving it an EOF as input:
818 Program exited normally.
822 The message @samp{Program exited normally.} is from @value{GDBN}; it
823 indicates @code{m4} has finished executing. We can end our @value{GDBN}
824 session with the @value{GDBN} @code{quit} command.
827 (@value{GDBP}) @b{quit}
831 @chapter Getting In and Out of @value{GDBN}
833 This chapter discusses how to start @value{GDBN}, and how to get out of it.
837 type @samp{@value{GDBP}} to start @value{GDBN}.
839 type @kbd{quit} or @kbd{Ctrl-d} to exit.
843 * Invoking GDB:: How to start @value{GDBN}
844 * Quitting GDB:: How to quit @value{GDBN}
845 * Shell Commands:: How to use shell commands inside @value{GDBN}
846 * Logging Output:: How to log @value{GDBN}'s output to a file
850 @section Invoking @value{GDBN}
852 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
853 @value{GDBN} reads commands from the terminal until you tell it to exit.
855 You can also run @code{@value{GDBP}} with a variety of arguments and options,
856 to specify more of your debugging environment at the outset.
858 The command-line options described here are designed
859 to cover a variety of situations; in some environments, some of these
860 options may effectively be unavailable.
862 The most usual way to start @value{GDBN} is with one argument,
863 specifying an executable program:
866 @value{GDBP} @var{program}
870 You can also start with both an executable program and a core file
874 @value{GDBP} @var{program} @var{core}
877 You can, instead, specify a process ID as a second argument or use option
878 @code{-p}, if you want to debug a running process:
881 @value{GDBP} @var{program} 1234
886 would attach @value{GDBN} to process @code{1234}. With option @option{-p} you
887 can omit the @var{program} filename.
889 Taking advantage of the second command-line argument requires a fairly
890 complete operating system; when you use @value{GDBN} as a remote
891 debugger attached to a bare board, there may not be any notion of
892 ``process'', and there is often no way to get a core dump. @value{GDBN}
893 will warn you if it is unable to attach or to read core dumps.
895 You can optionally have @code{@value{GDBP}} pass any arguments after the
896 executable file to the inferior using @code{--args}. This option stops
899 @value{GDBP} --args gcc -O2 -c foo.c
901 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
902 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
904 You can run @code{@value{GDBP}} without printing the front material, which describes
905 @value{GDBN}'s non-warranty, by specifying @code{--silent}
906 (or @code{-q}/@code{--quiet}):
909 @value{GDBP} --silent
913 You can further control how @value{GDBN} starts up by using command-line
914 options. @value{GDBN} itself can remind you of the options available.
924 to display all available options and briefly describe their use
925 (@samp{@value{GDBP} -h} is a shorter equivalent).
927 All options and command line arguments you give are processed
928 in sequential order. The order makes a difference when the
929 @samp{-x} option is used.
933 * File Options:: Choosing files
934 * Mode Options:: Choosing modes
935 * Startup:: What @value{GDBN} does during startup
939 @subsection Choosing Files
941 When @value{GDBN} starts, it reads any arguments other than options as
942 specifying an executable file and core file (or process ID). This is
943 the same as if the arguments were specified by the @samp{-se} and
944 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
945 first argument that does not have an associated option flag as
946 equivalent to the @samp{-se} option followed by that argument; and the
947 second argument that does not have an associated option flag, if any, as
948 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
949 If the second argument begins with a decimal digit, @value{GDBN} will
950 first attempt to attach to it as a process, and if that fails, attempt
951 to open it as a corefile. If you have a corefile whose name begins with
952 a digit, you can prevent @value{GDBN} from treating it as a pid by
953 prefixing it with @file{./}, e.g.@: @file{./12345}.
955 If @value{GDBN} has not been configured to included core file support,
956 such as for most embedded targets, then it will complain about a second
957 argument and ignore it.
959 Many options have both long and short forms; both are shown in the
960 following list. @value{GDBN} also recognizes the long forms if you truncate
961 them, so long as enough of the option is present to be unambiguous.
962 (If you prefer, you can flag option arguments with @samp{--} rather
963 than @samp{-}, though we illustrate the more usual convention.)
965 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
966 @c way, both those who look for -foo and --foo in the index, will find
970 @item -symbols @var{file}
972 @cindex @code{--symbols}
974 Read symbol table from file @var{file}.
976 @item -exec @var{file}
978 @cindex @code{--exec}
980 Use file @var{file} as the executable file to execute when appropriate,
981 and for examining pure data in conjunction with a core dump.
985 Read symbol table from file @var{file} and use it as the executable
988 @item -core @var{file}
990 @cindex @code{--core}
992 Use file @var{file} as a core dump to examine.
994 @item -pid @var{number}
995 @itemx -p @var{number}
998 Connect to process ID @var{number}, as with the @code{attach} command.
1000 @item -command @var{file}
1001 @itemx -x @var{file}
1002 @cindex @code{--command}
1004 Execute commands from file @var{file}. The contents of this file is
1005 evaluated exactly as the @code{source} command would.
1006 @xref{Command Files,, Command files}.
1008 @item -eval-command @var{command}
1009 @itemx -ex @var{command}
1010 @cindex @code{--eval-command}
1012 Execute a single @value{GDBN} command.
1014 This option may be used multiple times to call multiple commands. It may
1015 also be interleaved with @samp{-command} as required.
1018 @value{GDBP} -ex 'target sim' -ex 'load' \
1019 -x setbreakpoints -ex 'run' a.out
1022 @item -init-command @var{file}
1023 @itemx -ix @var{file}
1024 @cindex @code{--init-command}
1026 Execute commands from file @var{file} before loading the inferior (but
1027 after loading gdbinit files).
1030 @item -init-eval-command @var{command}
1031 @itemx -iex @var{command}
1032 @cindex @code{--init-eval-command}
1034 Execute a single @value{GDBN} command before loading the inferior (but
1035 after loading gdbinit files).
1038 @item -directory @var{directory}
1039 @itemx -d @var{directory}
1040 @cindex @code{--directory}
1042 Add @var{directory} to the path to search for source and script files.
1046 @cindex @code{--readnow}
1048 Read each symbol file's entire symbol table immediately, rather than
1049 the default, which is to read it incrementally as it is needed.
1050 This makes startup slower, but makes future operations faster.
1053 @anchor{--readnever}
1054 @cindex @code{--readnever}, command-line option
1055 Do not read each symbol file's symbolic debug information. This makes
1056 startup faster but at the expense of not being able to perform
1057 symbolic debugging. DWARF unwind information is also not read,
1058 meaning backtraces may become incomplete or inaccurate. One use of
1059 this is when a user simply wants to do the following sequence: attach,
1060 dump core, detach. Loading the debugging information in this case is
1061 an unnecessary cause of delay.
1065 @subsection Choosing Modes
1067 You can run @value{GDBN} in various alternative modes---for example, in
1068 batch mode or quiet mode.
1076 Do not execute commands found in any initialization file.
1077 There are three init files, loaded in the following order:
1080 @item @file{system.gdbinit}
1081 This is the system-wide init file.
1082 Its location is specified with the @code{--with-system-gdbinit}
1083 configure option (@pxref{System-wide configuration}).
1084 It is loaded first when @value{GDBN} starts, before command line options
1085 have been processed.
1086 @item @file{system.gdbinit.d}
1087 This is the system-wide init directory.
1088 Its location is specified with the @code{--with-system-gdbinit-dir}
1089 configure option (@pxref{System-wide configuration}).
1090 Files in this directory are loaded in alphabetical order immediately after
1091 system.gdbinit (if enabled) when @value{GDBN} starts, before command line
1092 options have been processed. Files need to have a recognized scripting
1093 language extension (@file{.py}/@file{.scm}) or be named with a @file{.gdb}
1094 extension to be interpreted as regular @value{GDBN} commands. @value{GDBN}
1095 will not recurse into any subdirectories of this directory.
1096 @item @file{~/.gdbinit}
1097 This is the init file in your home directory.
1098 It is loaded next, after @file{system.gdbinit}, and before
1099 command options have been processed.
1100 @item @file{./.gdbinit}
1101 This is the init file in the current directory.
1102 It is loaded last, after command line options other than @code{-x} and
1103 @code{-ex} have been processed. Command line options @code{-x} and
1104 @code{-ex} are processed last, after @file{./.gdbinit} has been loaded.
1107 For further documentation on startup processing, @xref{Startup}.
1108 For documentation on how to write command files,
1109 @xref{Command Files,,Command Files}.
1114 Do not execute commands found in @file{~/.gdbinit}, the init file
1115 in your home directory.
1121 @cindex @code{--quiet}
1122 @cindex @code{--silent}
1124 ``Quiet''. Do not print the introductory and copyright messages. These
1125 messages are also suppressed in batch mode.
1128 @cindex @code{--batch}
1129 Run in batch mode. Exit with status @code{0} after processing all the
1130 command files specified with @samp{-x} (and all commands from
1131 initialization files, if not inhibited with @samp{-n}). Exit with
1132 nonzero status if an error occurs in executing the @value{GDBN} commands
1133 in the command files. Batch mode also disables pagination, sets unlimited
1134 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1135 off} were in effect (@pxref{Messages/Warnings}).
1137 Batch mode may be useful for running @value{GDBN} as a filter, for
1138 example to download and run a program on another computer; in order to
1139 make this more useful, the message
1142 Program exited normally.
1146 (which is ordinarily issued whenever a program running under
1147 @value{GDBN} control terminates) is not issued when running in batch
1151 @cindex @code{--batch-silent}
1152 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1153 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1154 unaffected). This is much quieter than @samp{-silent} and would be useless
1155 for an interactive session.
1157 This is particularly useful when using targets that give @samp{Loading section}
1158 messages, for example.
1160 Note that targets that give their output via @value{GDBN}, as opposed to
1161 writing directly to @code{stdout}, will also be made silent.
1163 @item -return-child-result
1164 @cindex @code{--return-child-result}
1165 The return code from @value{GDBN} will be the return code from the child
1166 process (the process being debugged), with the following exceptions:
1170 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1171 internal error. In this case the exit code is the same as it would have been
1172 without @samp{-return-child-result}.
1174 The user quits with an explicit value. E.g., @samp{quit 1}.
1176 The child process never runs, or is not allowed to terminate, in which case
1177 the exit code will be -1.
1180 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1181 when @value{GDBN} is being used as a remote program loader or simulator
1186 @cindex @code{--nowindows}
1188 ``No windows''. If @value{GDBN} comes with a graphical user interface
1189 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1190 interface. If no GUI is available, this option has no effect.
1194 @cindex @code{--windows}
1196 If @value{GDBN} includes a GUI, then this option requires it to be
1199 @item -cd @var{directory}
1201 Run @value{GDBN} using @var{directory} as its working directory,
1202 instead of the current directory.
1204 @item -data-directory @var{directory}
1205 @itemx -D @var{directory}
1206 @cindex @code{--data-directory}
1208 Run @value{GDBN} using @var{directory} as its data directory.
1209 The data directory is where @value{GDBN} searches for its
1210 auxiliary files. @xref{Data Files}.
1214 @cindex @code{--fullname}
1216 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1217 subprocess. It tells @value{GDBN} to output the full file name and line
1218 number in a standard, recognizable fashion each time a stack frame is
1219 displayed (which includes each time your program stops). This
1220 recognizable format looks like two @samp{\032} characters, followed by
1221 the file name, line number and character position separated by colons,
1222 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1223 @samp{\032} characters as a signal to display the source code for the
1226 @item -annotate @var{level}
1227 @cindex @code{--annotate}
1228 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1229 effect is identical to using @samp{set annotate @var{level}}
1230 (@pxref{Annotations}). The annotation @var{level} controls how much
1231 information @value{GDBN} prints together with its prompt, values of
1232 expressions, source lines, and other types of output. Level 0 is the
1233 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1234 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1235 that control @value{GDBN}, and level 2 has been deprecated.
1237 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1241 @cindex @code{--args}
1242 Change interpretation of command line so that arguments following the
1243 executable file are passed as command line arguments to the inferior.
1244 This option stops option processing.
1246 @item -baud @var{bps}
1248 @cindex @code{--baud}
1250 Set the line speed (baud rate or bits per second) of any serial
1251 interface used by @value{GDBN} for remote debugging.
1253 @item -l @var{timeout}
1255 Set the timeout (in seconds) of any communication used by @value{GDBN}
1256 for remote debugging.
1258 @item -tty @var{device}
1259 @itemx -t @var{device}
1260 @cindex @code{--tty}
1262 Run using @var{device} for your program's standard input and output.
1263 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1265 @c resolve the situation of these eventually
1267 @cindex @code{--tui}
1268 Activate the @dfn{Text User Interface} when starting. The Text User
1269 Interface manages several text windows on the terminal, showing
1270 source, assembly, registers and @value{GDBN} command outputs
1271 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1272 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1273 Using @value{GDBN} under @sc{gnu} Emacs}).
1275 @item -interpreter @var{interp}
1276 @cindex @code{--interpreter}
1277 Use the interpreter @var{interp} for interface with the controlling
1278 program or device. This option is meant to be set by programs which
1279 communicate with @value{GDBN} using it as a back end.
1280 @xref{Interpreters, , Command Interpreters}.
1282 @samp{--interpreter=mi} (or @samp{--interpreter=mi3}) causes
1283 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} version 3 (@pxref{GDB/MI, ,
1284 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 9.1. @sc{gdb/mi}
1285 version 2 (@code{mi2}), included in @value{GDBN} 6.0 and version 1 (@code{mi1}),
1286 included in @value{GDBN} 5.3, are also available. Earlier @sc{gdb/mi}
1287 interfaces are no longer supported.
1290 @cindex @code{--write}
1291 Open the executable and core files for both reading and writing. This
1292 is equivalent to the @samp{set write on} command inside @value{GDBN}
1296 @cindex @code{--statistics}
1297 This option causes @value{GDBN} to print statistics about time and
1298 memory usage after it completes each command and returns to the prompt.
1301 @cindex @code{--version}
1302 This option causes @value{GDBN} to print its version number and
1303 no-warranty blurb, and exit.
1305 @item -configuration
1306 @cindex @code{--configuration}
1307 This option causes @value{GDBN} to print details about its build-time
1308 configuration parameters, and then exit. These details can be
1309 important when reporting @value{GDBN} bugs (@pxref{GDB Bugs}).
1314 @subsection What @value{GDBN} Does During Startup
1315 @cindex @value{GDBN} startup
1317 Here's the description of what @value{GDBN} does during session startup:
1321 Sets up the command interpreter as specified by the command line
1322 (@pxref{Mode Options, interpreter}).
1326 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1327 used when building @value{GDBN}; @pxref{System-wide configuration,
1328 ,System-wide configuration and settings}) and the files in the system-wide
1329 gdbinit directory (if @option{--with-system-gdbinit-dir} was used) and executes
1330 all the commands in those files. The files need to be named with a @file{.gdb}
1331 extension to be interpreted as @value{GDBN} commands, or they can be written
1332 in a supported scripting language with an appropriate file extension.
1334 @anchor{Home Directory Init File}
1336 Reads the init file (if any) in your home directory@footnote{On
1337 DOS/Windows systems, the home directory is the one pointed to by the
1338 @code{HOME} environment variable.} and executes all the commands in
1341 @anchor{Option -init-eval-command}
1343 Executes commands and command files specified by the @samp{-iex} and
1344 @samp{-ix} options in their specified order. Usually you should use the
1345 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1346 settings before @value{GDBN} init files get executed and before inferior
1350 Processes command line options and operands.
1352 @anchor{Init File in the Current Directory during Startup}
1354 Reads and executes the commands from init file (if any) in the current
1355 working directory as long as @samp{set auto-load local-gdbinit} is set to
1356 @samp{on} (@pxref{Init File in the Current Directory}).
1357 This is only done if the current directory is
1358 different from your home directory. Thus, you can have more than one
1359 init file, one generic in your home directory, and another, specific
1360 to the program you are debugging, in the directory where you invoke
1364 If the command line specified a program to debug, or a process to
1365 attach to, or a core file, @value{GDBN} loads any auto-loaded
1366 scripts provided for the program or for its loaded shared libraries.
1367 @xref{Auto-loading}.
1369 If you wish to disable the auto-loading during startup,
1370 you must do something like the following:
1373 $ gdb -iex "set auto-load python-scripts off" myprogram
1376 Option @samp{-ex} does not work because the auto-loading is then turned
1380 Executes commands and command files specified by the @samp{-ex} and
1381 @samp{-x} options in their specified order. @xref{Command Files}, for
1382 more details about @value{GDBN} command files.
1385 Reads the command history recorded in the @dfn{history file}.
1386 @xref{Command History}, for more details about the command history and the
1387 files where @value{GDBN} records it.
1390 Init files use the same syntax as @dfn{command files} (@pxref{Command
1391 Files}) and are processed by @value{GDBN} in the same way. The init
1392 file in your home directory can set options (such as @samp{set
1393 complaints}) that affect subsequent processing of command line options
1394 and operands. Init files are not executed if you use the @samp{-nx}
1395 option (@pxref{Mode Options, ,Choosing Modes}).
1397 To display the list of init files loaded by gdb at startup, you
1398 can use @kbd{gdb --help}.
1400 @cindex init file name
1401 @cindex @file{.gdbinit}
1402 @cindex @file{gdb.ini}
1403 The @value{GDBN} init files are normally called @file{.gdbinit}.
1404 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1405 the limitations of file names imposed by DOS filesystems. The Windows
1406 port of @value{GDBN} uses the standard name, but if it finds a
1407 @file{gdb.ini} file in your home directory, it warns you about that
1408 and suggests to rename the file to the standard name.
1412 @section Quitting @value{GDBN}
1413 @cindex exiting @value{GDBN}
1414 @cindex leaving @value{GDBN}
1417 @kindex quit @r{[}@var{expression}@r{]}
1418 @kindex q @r{(@code{quit})}
1419 @item quit @r{[}@var{expression}@r{]}
1421 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1422 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1423 do not supply @var{expression}, @value{GDBN} will terminate normally;
1424 otherwise it will terminate using the result of @var{expression} as the
1429 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1430 terminates the action of any @value{GDBN} command that is in progress and
1431 returns to @value{GDBN} command level. It is safe to type the interrupt
1432 character at any time because @value{GDBN} does not allow it to take effect
1433 until a time when it is safe.
1435 If you have been using @value{GDBN} to control an attached process or
1436 device, you can release it with the @code{detach} command
1437 (@pxref{Attach, ,Debugging an Already-running Process}).
1439 @node Shell Commands
1440 @section Shell Commands
1442 If you need to execute occasional shell commands during your
1443 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1444 just use the @code{shell} command.
1449 @cindex shell escape
1450 @item shell @var{command-string}
1451 @itemx !@var{command-string}
1452 Invoke a standard shell to execute @var{command-string}.
1453 Note that no space is needed between @code{!} and @var{command-string}.
1454 On GNU and Unix systems, the environment variable @code{SHELL}, if it
1455 exists, determines which shell to run. Otherwise @value{GDBN} uses
1456 the default shell (@file{/bin/sh} on GNU and Unix systems,
1457 @file{cmd.exe} on MS-Windows, @file{COMMAND.COM} on MS-DOS, etc.).
1460 The utility @code{make} is often needed in development environments.
1461 You do not have to use the @code{shell} command for this purpose in
1466 @cindex calling make
1467 @item make @var{make-args}
1468 Execute the @code{make} program with the specified
1469 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1475 @cindex send the output of a gdb command to a shell command
1477 @item pipe [@var{command}] | @var{shell_command}
1478 @itemx | [@var{command}] | @var{shell_command}
1479 @itemx pipe -d @var{delim} @var{command} @var{delim} @var{shell_command}
1480 @itemx | -d @var{delim} @var{command} @var{delim} @var{shell_command}
1481 Executes @var{command} and sends its output to @var{shell_command}.
1482 Note that no space is needed around @code{|}.
1483 If no @var{command} is provided, the last command executed is repeated.
1485 In case the @var{command} contains a @code{|}, the option @code{-d @var{delim}}
1486 can be used to specify an alternate delimiter string @var{delim} that separates
1487 the @var{command} from the @var{shell_command}.
1520 (gdb) | -d ! echo this contains a | char\n ! sed -e 's/|/PIPE/'
1521 this contains a PIPE char
1522 (gdb) | -d xxx echo this contains a | char!\n xxx sed -e 's/|/PIPE/'
1523 this contains a PIPE char!
1529 The convenience variables @code{$_shell_exitcode} and @code{$_shell_exitsignal}
1530 can be used to examine the exit status of the last shell command launched
1531 by @code{shell}, @code{make}, @code{pipe} and @code{|}.
1532 @xref{Convenience Vars,, Convenience Variables}.
1534 @node Logging Output
1535 @section Logging Output
1536 @cindex logging @value{GDBN} output
1537 @cindex save @value{GDBN} output to a file
1539 You may want to save the output of @value{GDBN} commands to a file.
1540 There are several commands to control @value{GDBN}'s logging.
1544 @item set logging on
1546 @item set logging off
1548 @cindex logging file name
1549 @item set logging file @var{file}
1550 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1551 @item set logging overwrite [on|off]
1552 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1553 you want @code{set logging on} to overwrite the logfile instead.
1554 @item set logging redirect [on|off]
1555 By default, @value{GDBN} output will go to both the terminal and the logfile.
1556 Set @code{redirect} if you want output to go only to the log file.
1557 @item set logging debugredirect [on|off]
1558 By default, @value{GDBN} debug output will go to both the terminal and the logfile.
1559 Set @code{debugredirect} if you want debug output to go only to the log file.
1560 @kindex show logging
1562 Show the current values of the logging settings.
1565 You can also redirect the output of a @value{GDBN} command to a
1566 shell command. @xref{pipe}.
1568 @chapter @value{GDBN} Commands
1570 You can abbreviate a @value{GDBN} command to the first few letters of the command
1571 name, if that abbreviation is unambiguous; and you can repeat certain
1572 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1573 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1574 show you the alternatives available, if there is more than one possibility).
1577 * Command Syntax:: How to give commands to @value{GDBN}
1578 * Command Settings:: How to change default behavior of commands
1579 * Completion:: Command completion
1580 * Command Options:: Command options
1581 * Command aliases default args:: Automatically prepend default arguments to user-defined aliases
1582 * Help:: How to ask @value{GDBN} for help
1585 @node Command Syntax
1586 @section Command Syntax
1588 A @value{GDBN} command is a single line of input. There is no limit on
1589 how long it can be. It starts with a command name, which is followed by
1590 arguments whose meaning depends on the command name. For example, the
1591 command @code{step} accepts an argument which is the number of times to
1592 step, as in @samp{step 5}. You can also use the @code{step} command
1593 with no arguments. Some commands do not allow any arguments.
1595 @cindex abbreviation
1596 @value{GDBN} command names may always be truncated if that abbreviation is
1597 unambiguous. Other possible command abbreviations are listed in the
1598 documentation for individual commands. In some cases, even ambiguous
1599 abbreviations are allowed; for example, @code{s} is specially defined as
1600 equivalent to @code{step} even though there are other commands whose
1601 names start with @code{s}. You can test abbreviations by using them as
1602 arguments to the @code{help} command.
1604 @cindex repeating commands
1605 @kindex RET @r{(repeat last command)}
1606 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1607 repeat the previous command. Certain commands (for example, @code{run})
1608 will not repeat this way; these are commands whose unintentional
1609 repetition might cause trouble and which you are unlikely to want to
1610 repeat. User-defined commands can disable this feature; see
1611 @ref{Define, dont-repeat}.
1613 The @code{list} and @code{x} commands, when you repeat them with
1614 @key{RET}, construct new arguments rather than repeating
1615 exactly as typed. This permits easy scanning of source or memory.
1617 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1618 output, in a way similar to the common utility @code{more}
1619 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1620 @key{RET} too many in this situation, @value{GDBN} disables command
1621 repetition after any command that generates this sort of display.
1623 @kindex # @r{(a comment)}
1625 Any text from a @kbd{#} to the end of the line is a comment; it does
1626 nothing. This is useful mainly in command files (@pxref{Command
1627 Files,,Command Files}).
1629 @cindex repeating command sequences
1630 @kindex Ctrl-o @r{(operate-and-get-next)}
1631 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1632 commands. This command accepts the current line, like @key{RET}, and
1633 then fetches the next line relative to the current line from the history
1637 @node Command Settings
1638 @section Command Settings
1639 @cindex default behavior of commands, changing
1640 @cindex default settings, changing
1642 Many commands change their behavior according to command-specific
1643 variables or settings. These settings can be changed with the
1644 @code{set} subcommands. For example, the @code{print} command
1645 (@pxref{Data, ,Examining Data}) prints arrays differently depending on
1646 settings changeable with the commands @code{set print elements
1647 NUMBER-OF-ELEMENTS} and @code{set print array-indexes}, among others.
1649 You can change these settings to your preference in the gdbinit files
1650 loaded at @value{GDBN} startup. @xref{Startup}.
1652 The settings can also be changed interactively during the debugging
1653 session. For example, to change the limit of array elements to print,
1654 you can do the following:
1656 (@value{GDBN}) set print elements 10
1657 (@value{GDBN}) print some_array
1658 $1 = @{0, 10, 20, 30, 40, 50, 60, 70, 80, 90...@}
1661 The above @code{set print elements 10} command changes the number of
1662 elements to print from the default of 200 to 10. If you only intend
1663 this limit of 10 to be used for printing @code{some_array}, then you
1664 must restore the limit back to 200, with @code{set print elements
1667 Some commands allow overriding settings with command options. For
1668 example, the @code{print} command supports a number of options that
1669 allow overriding relevant global print settings as set by @code{set
1670 print} subcommands. @xref{print options}. The example above could be
1673 (@value{GDBN}) print -elements 10 -- some_array
1674 $1 = @{0, 10, 20, 30, 40, 50, 60, 70, 80, 90...@}
1677 Alternatively, you can use the @code{with} command to change a setting
1678 temporarily, for the duration of a command invocation.
1681 @kindex with command
1682 @kindex w @r{(@code{with})}
1684 @cindex temporarily change settings
1685 @item with @var{setting} [@var{value}] [-- @var{command}]
1686 @itemx w @var{setting} [@var{value}] [-- @var{command}]
1687 Temporarily set @var{setting} to @var{value} for the duration of
1690 @var{setting} is any setting you can change with the @code{set}
1691 subcommands. @var{value} is the value to assign to @code{setting}
1692 while running @code{command}.
1694 If no @var{command} is provided, the last command executed is
1697 If a @var{command} is provided, it must be preceded by a double dash
1698 (@code{--}) separator. This is required because some settings accept
1699 free-form arguments, such as expressions or filenames.
1701 For example, the command
1703 (@value{GDBN}) with print array on -- print some_array
1706 is equivalent to the following 3 commands:
1708 (@value{GDBN}) set print array on
1709 (@value{GDBN}) print some_array
1710 (@value{GDBN}) set print array off
1713 The @code{with} command is particularly useful when you want to
1714 override a setting while running user-defined commands, or commands
1715 defined in Python or Guile. @xref{Extending GDB,, Extending GDB}.
1718 (@value{GDBN}) with print pretty on -- my_complex_command
1721 To change several settings for the same command, you can nest
1722 @code{with} commands. For example, @code{with language ada -- with
1723 print elements 10} temporarily changes the language to Ada and sets a
1724 limit of 10 elements to print for arrays and strings.
1729 @section Command Completion
1732 @cindex word completion
1733 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1734 only one possibility; it can also show you what the valid possibilities
1735 are for the next word in a command, at any time. This works for @value{GDBN}
1736 commands, @value{GDBN} subcommands, command options, and the names of symbols
1739 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1740 of a word. If there is only one possibility, @value{GDBN} fills in the
1741 word, and waits for you to finish the command (or press @key{RET} to
1742 enter it). For example, if you type
1744 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1745 @c complete accuracy in these examples; space introduced for clarity.
1746 @c If texinfo enhancements make it unnecessary, it would be nice to
1747 @c replace " @key" by "@key" in the following...
1749 (@value{GDBP}) info bre @key{TAB}
1753 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1754 the only @code{info} subcommand beginning with @samp{bre}:
1757 (@value{GDBP}) info breakpoints
1761 You can either press @key{RET} at this point, to run the @code{info
1762 breakpoints} command, or backspace and enter something else, if
1763 @samp{breakpoints} does not look like the command you expected. (If you
1764 were sure you wanted @code{info breakpoints} in the first place, you
1765 might as well just type @key{RET} immediately after @samp{info bre},
1766 to exploit command abbreviations rather than command completion).
1768 If there is more than one possibility for the next word when you press
1769 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1770 characters and try again, or just press @key{TAB} a second time;
1771 @value{GDBN} displays all the possible completions for that word. For
1772 example, you might want to set a breakpoint on a subroutine whose name
1773 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1774 just sounds the bell. Typing @key{TAB} again displays all the
1775 function names in your program that begin with those characters, for
1779 (@value{GDBP}) b make_ @key{TAB}
1780 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1781 make_a_section_from_file make_environ
1782 make_abs_section make_function_type
1783 make_blockvector make_pointer_type
1784 make_cleanup make_reference_type
1785 make_command make_symbol_completion_list
1786 (@value{GDBP}) b make_
1790 After displaying the available possibilities, @value{GDBN} copies your
1791 partial input (@samp{b make_} in the example) so you can finish the
1794 If you just want to see the list of alternatives in the first place, you
1795 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1796 means @kbd{@key{META} ?}. You can type this either by holding down a
1797 key designated as the @key{META} shift on your keyboard (if there is
1798 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1800 If the number of possible completions is large, @value{GDBN} will
1801 print as much of the list as it has collected, as well as a message
1802 indicating that the list may be truncated.
1805 (@value{GDBP}) b m@key{TAB}@key{TAB}
1807 <... the rest of the possible completions ...>
1808 *** List may be truncated, max-completions reached. ***
1813 This behavior can be controlled with the following commands:
1816 @kindex set max-completions
1817 @item set max-completions @var{limit}
1818 @itemx set max-completions unlimited
1819 Set the maximum number of completion candidates. @value{GDBN} will
1820 stop looking for more completions once it collects this many candidates.
1821 This is useful when completing on things like function names as collecting
1822 all the possible candidates can be time consuming.
1823 The default value is 200. A value of zero disables tab-completion.
1824 Note that setting either no limit or a very large limit can make
1826 @kindex show max-completions
1827 @item show max-completions
1828 Show the maximum number of candidates that @value{GDBN} will collect and show
1832 @cindex quotes in commands
1833 @cindex completion of quoted strings
1834 Sometimes the string you need, while logically a ``word'', may contain
1835 parentheses or other characters that @value{GDBN} normally excludes from
1836 its notion of a word. To permit word completion to work in this
1837 situation, you may enclose words in @code{'} (single quote marks) in
1838 @value{GDBN} commands.
1840 A likely situation where you might need this is in typing an
1841 expression that involves a C@t{++} symbol name with template
1842 parameters. This is because when completing expressions, GDB treats
1843 the @samp{<} character as word delimiter, assuming that it's the
1844 less-than comparison operator (@pxref{C Operators, , C and C@t{++}
1847 For example, when you want to call a C@t{++} template function
1848 interactively using the @code{print} or @code{call} commands, you may
1849 need to distinguish whether you mean the version of @code{name} that
1850 was specialized for @code{int}, @code{name<int>()}, or the version
1851 that was specialized for @code{float}, @code{name<float>()}. To use
1852 the word-completion facilities in this situation, type a single quote
1853 @code{'} at the beginning of the function name. This alerts
1854 @value{GDBN} that it may need to consider more information than usual
1855 when you press @key{TAB} or @kbd{M-?} to request word completion:
1858 (@value{GDBP}) p 'func< @kbd{M-?}
1859 func<int>() func<float>()
1860 (@value{GDBP}) p 'func<
1863 When setting breakpoints however (@pxref{Specify Location}), you don't
1864 usually need to type a quote before the function name, because
1865 @value{GDBN} understands that you want to set a breakpoint on a
1869 (@value{GDBP}) b func< @kbd{M-?}
1870 func<int>() func<float>()
1871 (@value{GDBP}) b func<
1874 This is true even in the case of typing the name of C@t{++} overloaded
1875 functions (multiple definitions of the same function, distinguished by
1876 argument type). For example, when you want to set a breakpoint you
1877 don't need to distinguish whether you mean the version of @code{name}
1878 that takes an @code{int} parameter, @code{name(int)}, or the version
1879 that takes a @code{float} parameter, @code{name(float)}.
1882 (@value{GDBP}) b bubble( @kbd{M-?}
1883 bubble(int) bubble(double)
1884 (@value{GDBP}) b bubble(dou @kbd{M-?}
1888 See @ref{quoting names} for a description of other scenarios that
1891 For more information about overloaded functions, see @ref{C Plus Plus
1892 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1893 overload-resolution off} to disable overload resolution;
1894 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1896 @cindex completion of structure field names
1897 @cindex structure field name completion
1898 @cindex completion of union field names
1899 @cindex union field name completion
1900 When completing in an expression which looks up a field in a
1901 structure, @value{GDBN} also tries@footnote{The completer can be
1902 confused by certain kinds of invalid expressions. Also, it only
1903 examines the static type of the expression, not the dynamic type.} to
1904 limit completions to the field names available in the type of the
1908 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1909 magic to_fputs to_rewind
1910 to_data to_isatty to_write
1911 to_delete to_put to_write_async_safe
1916 This is because the @code{gdb_stdout} is a variable of the type
1917 @code{struct ui_file} that is defined in @value{GDBN} sources as
1924 ui_file_flush_ftype *to_flush;
1925 ui_file_write_ftype *to_write;
1926 ui_file_write_async_safe_ftype *to_write_async_safe;
1927 ui_file_fputs_ftype *to_fputs;
1928 ui_file_read_ftype *to_read;
1929 ui_file_delete_ftype *to_delete;
1930 ui_file_isatty_ftype *to_isatty;
1931 ui_file_rewind_ftype *to_rewind;
1932 ui_file_put_ftype *to_put;
1937 @node Command Options
1938 @section Command options
1940 @cindex command options
1941 Some commands accept options starting with a leading dash. For
1942 example, @code{print -pretty}. Similarly to command names, you can
1943 abbreviate a @value{GDBN} option to the first few letters of the
1944 option name, if that abbreviation is unambiguous, and you can also use
1945 the @key{TAB} key to get @value{GDBN} to fill out the rest of a word
1946 in an option (or to show you the alternatives available, if there is
1947 more than one possibility).
1949 @cindex command options, raw input
1950 Some commands take raw input as argument. For example, the print
1951 command processes arbitrary expressions in any of the languages
1952 supported by @value{GDBN}. With such commands, because raw input may
1953 start with a leading dash that would be confused with an option or any
1954 of its abbreviations, e.g.@: @code{print -p} (short for @code{print
1955 -pretty} or printing negative @code{p}?), if you specify any command
1956 option, then you must use a double-dash (@code{--}) delimiter to
1957 indicate the end of options.
1959 @cindex command options, boolean
1961 Some options are described as accepting an argument which can be
1962 either @code{on} or @code{off}. These are known as @dfn{boolean
1963 options}. Similarly to boolean settings commands---@code{on} and
1964 @code{off} are the typical values, but any of @code{1}, @code{yes} and
1965 @code{enable} can also be used as ``true'' value, and any of @code{0},
1966 @code{no} and @code{disable} can also be used as ``false'' value. You
1967 can also omit a ``true'' value, as it is implied by default.
1969 For example, these are equivalent:
1972 (@value{GDBP}) print -object on -pretty off -element unlimited -- *myptr
1973 (@value{GDBP}) p -o -p 0 -e u -- *myptr
1976 You can discover the set of options some command accepts by completing
1977 on @code{-} after the command name. For example:
1980 (@value{GDBP}) print -@key{TAB}@key{TAB}
1981 -address -max-depth -raw-values -union
1982 -array -null-stop -repeats -vtbl
1983 -array-indexes -object -static-members
1984 -elements -pretty -symbol
1987 Completion will in some cases guide you with a suggestion of what kind
1988 of argument an option expects. For example:
1991 (@value{GDBP}) print -elements @key{TAB}@key{TAB}
1995 Here, the option expects a number (e.g., @code{100}), not literal
1996 @code{NUMBER}. Such metasyntactical arguments are always presented in
1999 (For more on using the @code{print} command, see @ref{Data, ,Examining
2002 @node Command aliases default args
2003 @section Automatically prepend default arguments to user-defined aliases
2005 You can tell @value{GDBN} to always prepend some default arguments to
2006 the list of arguments provided explicitly by the user when using a
2009 If you repeatedly use the same arguments or options for a command, you
2010 can define an alias for this command and tell @value{GDBN} to
2011 automatically prepend these arguments or options to the list of
2012 arguments you type explicitly when using the alias@footnote{@value{GDBN}
2013 could easily accept default arguments for pre-defined commands and aliases,
2014 but it was deemed this would be confusing, and so is not allowed.}.
2016 For example, if you often use the command @code{thread apply all}
2017 specifying to work on the threads in ascending order and to continue in case it
2018 encounters an error, you can tell @value{GDBN} to automatically preprend
2019 the @code{-ascending} and @code{-c} options by using:
2022 (@value{GDBP}) alias thread apply asc-all = thread apply all -ascending -c
2025 Once you have defined this alias with its default args, any time you type
2026 the @code{thread apply asc-all} followed by @code{some arguments},
2027 @value{GDBN} will execute @code{thread apply all -ascending -c some arguments}.
2029 To have even less to type, you can also define a one word alias:
2031 (@value{GDBP}) alias t_a_c = thread apply all -ascending -c
2034 As usual, unambiguous abbreviations can be used for @var{alias}
2035 and @var{default-args}.
2037 The different aliases of a command do not share their default args.
2038 For example, you define a new alias @code{bt_ALL} showing all possible
2039 information and another alias @code{bt_SMALL} showing very limited information
2042 (@value{GDBP}) alias bt_ALL = backtrace -entry-values both -frame-arg all \
2043 -past-main -past-entry -full
2044 (@value{GDBP}) alias bt_SMALL = backtrace -entry-values no -frame-arg none \
2045 -past-main off -past-entry off
2048 (For more on using the @code{alias} command, see @ref{Aliases}.)
2050 Default args are not limited to the arguments and options of @var{command},
2051 but can specify nested commands if @var{command} accepts such a nested command
2053 For example, the below defines @code{faalocalsoftype} that lists the
2054 frames having locals of a certain type, together with the matching
2057 (@value{GDBP}) alias faalocalsoftype = frame apply all info locals -q -t
2058 (@value{GDBP}) faalocalsoftype int
2059 #1 0x55554f5e in sleeper_or_burner (v=0xdf50) at sleepers.c:86
2064 This is also very useful to define an alias for a set of nested @code{with}
2065 commands to have a particular combination of temporary settings. For example,
2066 the below defines the alias @code{pp10} that pretty prints an expression
2067 argument, with a maximum of 10 elements if the expression is a string or
2070 (@value{GDBP}) alias pp10 = with print pretty -- with print elements 10 -- print
2072 This defines the alias @code{pp10} as being a sequence of 3 commands.
2073 The first part @code{with print pretty --} temporarily activates the setting
2074 @code{set print pretty}, then launches the command that follows the separator
2076 The command following the first part is also a @code{with} command that
2077 temporarily changes the setting @code{set print elements} to 10, then
2078 launches the command that follows the second separator @code{--}.
2079 The third part @code{print} is the command the @code{pp10} alias will launch,
2080 using the temporary values of the settings and the arguments explicitly given
2082 For more information about the @code{with} command usage,
2083 see @ref{Command Settings}.
2086 @section Getting Help
2087 @cindex online documentation
2090 You can always ask @value{GDBN} itself for information on its commands,
2091 using the command @code{help}.
2094 @kindex h @r{(@code{help})}
2097 You can use @code{help} (abbreviated @code{h}) with no arguments to
2098 display a short list of named classes of commands:
2102 List of classes of commands:
2104 aliases -- User-defined aliases of other commands
2105 breakpoints -- Making program stop at certain points
2106 data -- Examining data
2107 files -- Specifying and examining files
2108 internals -- Maintenance commands
2109 obscure -- Obscure features
2110 running -- Running the program
2111 stack -- Examining the stack
2112 status -- Status inquiries
2113 support -- Support facilities
2114 tracepoints -- Tracing of program execution without
2115 stopping the program
2116 user-defined -- User-defined commands
2118 Type "help" followed by a class name for a list of
2119 commands in that class.
2120 Type "help" followed by command name for full
2122 Command name abbreviations are allowed if unambiguous.
2125 @c the above line break eliminates huge line overfull...
2127 @item help @var{class}
2128 Using one of the general help classes as an argument, you can get a
2129 list of the individual commands in that class. If a command has
2130 aliases, the aliases are given after the command name, separated by
2131 commas. If an alias has default arguments, the full definition of
2132 the alias is given after the first line.
2133 For example, here is the help display for the class @code{status}:
2136 (@value{GDBP}) help status
2141 @c Line break in "show" line falsifies real output, but needed
2142 @c to fit in smallbook page size.
2143 info, inf, i -- Generic command for showing things
2144 about the program being debugged
2145 info address, iamain -- Describe where symbol SYM is stored.
2146 alias iamain = info address main
2147 info all-registers -- List of all registers and their contents,
2148 for selected stack frame.
2150 show, info set -- Generic command for showing things
2153 Type "help" followed by command name for full
2155 Command name abbreviations are allowed if unambiguous.
2159 @item help @var{command}
2160 With a command name as @code{help} argument, @value{GDBN} displays a
2161 short paragraph on how to use that command. If that command has
2162 one or more aliases, @value{GDBN} will display a first line with
2163 the command name and all its aliases separated by commas.
2164 This first line will be followed by the full definition of all aliases
2165 having default arguments.
2168 @item apropos [-v] @var{regexp}
2169 The @code{apropos} command searches through all of the @value{GDBN}
2170 commands, and their documentation, for the regular expression specified in
2171 @var{args}. It prints out all matches found. The optional flag @samp{-v},
2172 which stands for @samp{verbose}, indicates to output the full documentation
2173 of the matching commands and highlight the parts of the documentation
2174 matching @var{regexp}. For example:
2185 alias -- Define a new command that is an alias of an existing command
2186 aliases -- User-defined aliases of other commands
2194 apropos -v cut.*thread apply
2198 results in the below output, where @samp{cut for 'thread apply}
2199 is highlighted if styling is enabled.
2203 taas -- Apply a command to all threads (ignoring errors
2206 shortcut for 'thread apply all -s COMMAND'
2208 tfaas -- Apply a command to all frames of all threads
2209 (ignoring errors and empty output).
2210 Usage: tfaas COMMAND
2211 shortcut for 'thread apply all -s frame apply all -s COMMAND'
2216 @item complete @var{args}
2217 The @code{complete @var{args}} command lists all the possible completions
2218 for the beginning of a command. Use @var{args} to specify the beginning of the
2219 command you want completed. For example:
2225 @noindent results in:
2236 @noindent This is intended for use by @sc{gnu} Emacs.
2239 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
2240 and @code{show} to inquire about the state of your program, or the state
2241 of @value{GDBN} itself. Each command supports many topics of inquiry; this
2242 manual introduces each of them in the appropriate context. The listings
2243 under @code{info} and under @code{show} in the Command, Variable, and
2244 Function Index point to all the sub-commands. @xref{Command and Variable
2250 @kindex i @r{(@code{info})}
2252 This command (abbreviated @code{i}) is for describing the state of your
2253 program. For example, you can show the arguments passed to a function
2254 with @code{info args}, list the registers currently in use with @code{info
2255 registers}, or list the breakpoints you have set with @code{info breakpoints}.
2256 You can get a complete list of the @code{info} sub-commands with
2257 @w{@code{help info}}.
2261 You can assign the result of an expression to an environment variable with
2262 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
2263 @code{set prompt $}.
2267 In contrast to @code{info}, @code{show} is for describing the state of
2268 @value{GDBN} itself.
2269 You can change most of the things you can @code{show}, by using the
2270 related command @code{set}; for example, you can control what number
2271 system is used for displays with @code{set radix}, or simply inquire
2272 which is currently in use with @code{show radix}.
2275 To display all the settable parameters and their current
2276 values, you can use @code{show} with no arguments; you may also use
2277 @code{info set}. Both commands produce the same display.
2278 @c FIXME: "info set" violates the rule that "info" is for state of
2279 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
2280 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
2284 Here are several miscellaneous @code{show} subcommands, all of which are
2285 exceptional in lacking corresponding @code{set} commands:
2288 @kindex show version
2289 @cindex @value{GDBN} version number
2291 Show what version of @value{GDBN} is running. You should include this
2292 information in @value{GDBN} bug-reports. If multiple versions of
2293 @value{GDBN} are in use at your site, you may need to determine which
2294 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
2295 commands are introduced, and old ones may wither away. Also, many
2296 system vendors ship variant versions of @value{GDBN}, and there are
2297 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
2298 The version number is the same as the one announced when you start
2301 @kindex show copying
2302 @kindex info copying
2303 @cindex display @value{GDBN} copyright
2306 Display information about permission for copying @value{GDBN}.
2308 @kindex show warranty
2309 @kindex info warranty
2311 @itemx info warranty
2312 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
2313 if your version of @value{GDBN} comes with one.
2315 @kindex show configuration
2316 @item show configuration
2317 Display detailed information about the way @value{GDBN} was configured
2318 when it was built. This displays the optional arguments passed to the
2319 @file{configure} script and also configuration parameters detected
2320 automatically by @command{configure}. When reporting a @value{GDBN}
2321 bug (@pxref{GDB Bugs}), it is important to include this information in
2327 @chapter Running Programs Under @value{GDBN}
2329 When you run a program under @value{GDBN}, you must first generate
2330 debugging information when you compile it.
2332 You may start @value{GDBN} with its arguments, if any, in an environment
2333 of your choice. If you are doing native debugging, you may redirect
2334 your program's input and output, debug an already running process, or
2335 kill a child process.
2338 * Compilation:: Compiling for debugging
2339 * Starting:: Starting your program
2340 * Arguments:: Your program's arguments
2341 * Environment:: Your program's environment
2343 * Working Directory:: Your program's working directory
2344 * Input/Output:: Your program's input and output
2345 * Attach:: Debugging an already-running process
2346 * Kill Process:: Killing the child process
2347 * Inferiors Connections and Programs:: Debugging multiple inferiors
2348 connections and programs
2349 * Threads:: Debugging programs with multiple threads
2350 * Forks:: Debugging forks
2351 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
2355 @section Compiling for Debugging
2357 In order to debug a program effectively, you need to generate
2358 debugging information when you compile it. This debugging information
2359 is stored in the object file; it describes the data type of each
2360 variable or function and the correspondence between source line numbers
2361 and addresses in the executable code.
2363 To request debugging information, specify the @samp{-g} option when you run
2366 Programs that are to be shipped to your customers are compiled with
2367 optimizations, using the @samp{-O} compiler option. However, some
2368 compilers are unable to handle the @samp{-g} and @samp{-O} options
2369 together. Using those compilers, you cannot generate optimized
2370 executables containing debugging information.
2372 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
2373 without @samp{-O}, making it possible to debug optimized code. We
2374 recommend that you @emph{always} use @samp{-g} whenever you compile a
2375 program. You may think your program is correct, but there is no sense
2376 in pushing your luck. For more information, see @ref{Optimized Code}.
2378 Older versions of the @sc{gnu} C compiler permitted a variant option
2379 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
2380 format; if your @sc{gnu} C compiler has this option, do not use it.
2382 @value{GDBN} knows about preprocessor macros and can show you their
2383 expansion (@pxref{Macros}). Most compilers do not include information
2384 about preprocessor macros in the debugging information if you specify
2385 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
2386 the @sc{gnu} C compiler, provides macro information if you are using
2387 the DWARF debugging format, and specify the option @option{-g3}.
2389 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
2390 gcc, Using the @sc{gnu} Compiler Collection (GCC)}, for more
2391 information on @value{NGCC} options affecting debug information.
2393 You will have the best debugging experience if you use the latest
2394 version of the DWARF debugging format that your compiler supports.
2395 DWARF is currently the most expressive and best supported debugging
2396 format in @value{GDBN}.
2400 @section Starting your Program
2406 @kindex r @r{(@code{run})}
2409 Use the @code{run} command to start your program under @value{GDBN}.
2410 You must first specify the program name with an argument to
2411 @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
2412 @value{GDBN}}), or by using the @code{file} or @code{exec-file}
2413 command (@pxref{Files, ,Commands to Specify Files}).
2417 If you are running your program in an execution environment that
2418 supports processes, @code{run} creates an inferior process and makes
2419 that process run your program. In some environments without processes,
2420 @code{run} jumps to the start of your program. Other targets,
2421 like @samp{remote}, are always running. If you get an error
2422 message like this one:
2425 The "remote" target does not support "run".
2426 Try "help target" or "continue".
2430 then use @code{continue} to run your program. You may need @code{load}
2431 first (@pxref{load}).
2433 The execution of a program is affected by certain information it
2434 receives from its superior. @value{GDBN} provides ways to specify this
2435 information, which you must do @emph{before} starting your program. (You
2436 can change it after starting your program, but such changes only affect
2437 your program the next time you start it.) This information may be
2438 divided into four categories:
2441 @item The @emph{arguments.}
2442 Specify the arguments to give your program as the arguments of the
2443 @code{run} command. If a shell is available on your target, the shell
2444 is used to pass the arguments, so that you may use normal conventions
2445 (such as wildcard expansion or variable substitution) in describing
2447 In Unix systems, you can control which shell is used with the
2448 @code{SHELL} environment variable. If you do not define @code{SHELL},
2449 @value{GDBN} uses the default shell (@file{/bin/sh}). You can disable
2450 use of any shell with the @code{set startup-with-shell} command (see
2453 @item The @emph{environment.}
2454 Your program normally inherits its environment from @value{GDBN}, but you can
2455 use the @value{GDBN} commands @code{set environment} and @code{unset
2456 environment} to change parts of the environment that affect
2457 your program. @xref{Environment, ,Your Program's Environment}.
2459 @item The @emph{working directory.}
2460 You can set your program's working directory with the command
2461 @kbd{set cwd}. If you do not set any working directory with this
2462 command, your program will inherit @value{GDBN}'s working directory if
2463 native debugging, or the remote server's working directory if remote
2464 debugging. @xref{Working Directory, ,Your Program's Working
2467 @item The @emph{standard input and output.}
2468 Your program normally uses the same device for standard input and
2469 standard output as @value{GDBN} is using. You can redirect input and output
2470 in the @code{run} command line, or you can use the @code{tty} command to
2471 set a different device for your program.
2472 @xref{Input/Output, ,Your Program's Input and Output}.
2475 @emph{Warning:} While input and output redirection work, you cannot use
2476 pipes to pass the output of the program you are debugging to another
2477 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2481 When you issue the @code{run} command, your program begins to execute
2482 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2483 of how to arrange for your program to stop. Once your program has
2484 stopped, you may call functions in your program, using the @code{print}
2485 or @code{call} commands. @xref{Data, ,Examining Data}.
2487 If the modification time of your symbol file has changed since the last
2488 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2489 table, and reads it again. When it does this, @value{GDBN} tries to retain
2490 your current breakpoints.
2495 @cindex run to main procedure
2496 The name of the main procedure can vary from language to language.
2497 With C or C@t{++}, the main procedure name is always @code{main}, but
2498 other languages such as Ada do not require a specific name for their
2499 main procedure. The debugger provides a convenient way to start the
2500 execution of the program and to stop at the beginning of the main
2501 procedure, depending on the language used.
2503 The @samp{start} command does the equivalent of setting a temporary
2504 breakpoint at the beginning of the main procedure and then invoking
2505 the @samp{run} command.
2507 @cindex elaboration phase
2508 Some programs contain an @dfn{elaboration} phase where some startup code is
2509 executed before the main procedure is called. This depends on the
2510 languages used to write your program. In C@t{++}, for instance,
2511 constructors for static and global objects are executed before
2512 @code{main} is called. It is therefore possible that the debugger stops
2513 before reaching the main procedure. However, the temporary breakpoint
2514 will remain to halt execution.
2516 Specify the arguments to give to your program as arguments to the
2517 @samp{start} command. These arguments will be given verbatim to the
2518 underlying @samp{run} command. Note that the same arguments will be
2519 reused if no argument is provided during subsequent calls to
2520 @samp{start} or @samp{run}.
2522 It is sometimes necessary to debug the program during elaboration. In
2523 these cases, using the @code{start} command would stop the execution
2524 of your program too late, as the program would have already completed
2525 the elaboration phase. Under these circumstances, either insert
2526 breakpoints in your elaboration code before running your program or
2527 use the @code{starti} command.
2531 @cindex run to first instruction
2532 The @samp{starti} command does the equivalent of setting a temporary
2533 breakpoint at the first instruction of a program's execution and then
2534 invoking the @samp{run} command. For programs containing an
2535 elaboration phase, the @code{starti} command will stop execution at
2536 the start of the elaboration phase.
2538 @anchor{set exec-wrapper}
2539 @kindex set exec-wrapper
2540 @item set exec-wrapper @var{wrapper}
2541 @itemx show exec-wrapper
2542 @itemx unset exec-wrapper
2543 When @samp{exec-wrapper} is set, the specified wrapper is used to
2544 launch programs for debugging. @value{GDBN} starts your program
2545 with a shell command of the form @kbd{exec @var{wrapper}
2546 @var{program}}. Quoting is added to @var{program} and its
2547 arguments, but not to @var{wrapper}, so you should add quotes if
2548 appropriate for your shell. The wrapper runs until it executes
2549 your program, and then @value{GDBN} takes control.
2551 You can use any program that eventually calls @code{execve} with
2552 its arguments as a wrapper. Several standard Unix utilities do
2553 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2554 with @code{exec "$@@"} will also work.
2556 For example, you can use @code{env} to pass an environment variable to
2557 the debugged program, without setting the variable in your shell's
2561 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2565 This command is available when debugging locally on most targets, excluding
2566 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2568 @kindex set startup-with-shell
2569 @anchor{set startup-with-shell}
2570 @item set startup-with-shell
2571 @itemx set startup-with-shell on
2572 @itemx set startup-with-shell off
2573 @itemx show startup-with-shell
2574 On Unix systems, by default, if a shell is available on your target,
2575 @value{GDBN}) uses it to start your program. Arguments of the
2576 @code{run} command are passed to the shell, which does variable
2577 substitution, expands wildcard characters and performs redirection of
2578 I/O. In some circumstances, it may be useful to disable such use of a
2579 shell, for example, when debugging the shell itself or diagnosing
2580 startup failures such as:
2584 Starting program: ./a.out
2585 During startup program terminated with signal SIGSEGV, Segmentation fault.
2589 which indicates the shell or the wrapper specified with
2590 @samp{exec-wrapper} crashed, not your program. Most often, this is
2591 caused by something odd in your shell's non-interactive mode
2592 initialization file---such as @file{.cshrc} for C-shell,
2593 $@file{.zshenv} for the Z shell, or the file specified in the
2594 @samp{BASH_ENV} environment variable for BASH.
2596 @anchor{set auto-connect-native-target}
2597 @kindex set auto-connect-native-target
2598 @item set auto-connect-native-target
2599 @itemx set auto-connect-native-target on
2600 @itemx set auto-connect-native-target off
2601 @itemx show auto-connect-native-target
2603 By default, if the current inferior is not connected to any target yet
2604 (e.g., with @code{target remote}), the @code{run} command starts your
2605 program as a native process under @value{GDBN}, on your local machine.
2606 If you're sure you don't want to debug programs on your local machine,
2607 you can tell @value{GDBN} to not connect to the native target
2608 automatically with the @code{set auto-connect-native-target off}
2611 If @code{on}, which is the default, and if the current inferior is not
2612 connected to a target already, the @code{run} command automaticaly
2613 connects to the native target, if one is available.
2615 If @code{off}, and if the current inferior is not connected to a
2616 target already, the @code{run} command fails with an error:
2620 Don't know how to run. Try "help target".
2623 If the current inferior is already connected to a target, @value{GDBN}
2624 always uses it with the @code{run} command.
2626 In any case, you can explicitly connect to the native target with the
2627 @code{target native} command. For example,
2630 (@value{GDBP}) set auto-connect-native-target off
2632 Don't know how to run. Try "help target".
2633 (@value{GDBP}) target native
2635 Starting program: ./a.out
2636 [Inferior 1 (process 10421) exited normally]
2639 In case you connected explicitly to the @code{native} target,
2640 @value{GDBN} remains connected even if all inferiors exit, ready for
2641 the next @code{run} command. Use the @code{disconnect} command to
2644 Examples of other commands that likewise respect the
2645 @code{auto-connect-native-target} setting: @code{attach}, @code{info
2646 proc}, @code{info os}.
2648 @kindex set disable-randomization
2649 @item set disable-randomization
2650 @itemx set disable-randomization on
2651 This option (enabled by default in @value{GDBN}) will turn off the native
2652 randomization of the virtual address space of the started program. This option
2653 is useful for multiple debugging sessions to make the execution better
2654 reproducible and memory addresses reusable across debugging sessions.
2656 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2657 On @sc{gnu}/Linux you can get the same behavior using
2660 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2663 @item set disable-randomization off
2664 Leave the behavior of the started executable unchanged. Some bugs rear their
2665 ugly heads only when the program is loaded at certain addresses. If your bug
2666 disappears when you run the program under @value{GDBN}, that might be because
2667 @value{GDBN} by default disables the address randomization on platforms, such
2668 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2669 disable-randomization off} to try to reproduce such elusive bugs.
2671 On targets where it is available, virtual address space randomization
2672 protects the programs against certain kinds of security attacks. In these
2673 cases the attacker needs to know the exact location of a concrete executable
2674 code. Randomizing its location makes it impossible to inject jumps misusing
2675 a code at its expected addresses.
2677 Prelinking shared libraries provides a startup performance advantage but it
2678 makes addresses in these libraries predictable for privileged processes by
2679 having just unprivileged access at the target system. Reading the shared
2680 library binary gives enough information for assembling the malicious code
2681 misusing it. Still even a prelinked shared library can get loaded at a new
2682 random address just requiring the regular relocation process during the
2683 startup. Shared libraries not already prelinked are always loaded at
2684 a randomly chosen address.
2686 Position independent executables (PIE) contain position independent code
2687 similar to the shared libraries and therefore such executables get loaded at
2688 a randomly chosen address upon startup. PIE executables always load even
2689 already prelinked shared libraries at a random address. You can build such
2690 executable using @command{gcc -fPIE -pie}.
2692 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2693 (as long as the randomization is enabled).
2695 @item show disable-randomization
2696 Show the current setting of the explicit disable of the native randomization of
2697 the virtual address space of the started program.
2702 @section Your Program's Arguments
2704 @cindex arguments (to your program)
2705 The arguments to your program can be specified by the arguments of the
2707 They are passed to a shell, which expands wildcard characters and
2708 performs redirection of I/O, and thence to your program. Your
2709 @code{SHELL} environment variable (if it exists) specifies what shell
2710 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2711 the default shell (@file{/bin/sh} on Unix).
2713 On non-Unix systems, the program is usually invoked directly by
2714 @value{GDBN}, which emulates I/O redirection via the appropriate system
2715 calls, and the wildcard characters are expanded by the startup code of
2716 the program, not by the shell.
2718 @code{run} with no arguments uses the same arguments used by the previous
2719 @code{run}, or those set by the @code{set args} command.
2724 Specify the arguments to be used the next time your program is run. If
2725 @code{set args} has no arguments, @code{run} executes your program
2726 with no arguments. Once you have run your program with arguments,
2727 using @code{set args} before the next @code{run} is the only way to run
2728 it again without arguments.
2732 Show the arguments to give your program when it is started.
2736 @section Your Program's Environment
2738 @cindex environment (of your program)
2739 The @dfn{environment} consists of a set of environment variables and
2740 their values. Environment variables conventionally record such things as
2741 your user name, your home directory, your terminal type, and your search
2742 path for programs to run. Usually you set up environment variables with
2743 the shell and they are inherited by all the other programs you run. When
2744 debugging, it can be useful to try running your program with a modified
2745 environment without having to start @value{GDBN} over again.
2749 @item path @var{directory}
2750 Add @var{directory} to the front of the @code{PATH} environment variable
2751 (the search path for executables) that will be passed to your program.
2752 The value of @code{PATH} used by @value{GDBN} does not change.
2753 You may specify several directory names, separated by whitespace or by a
2754 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2755 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2756 is moved to the front, so it is searched sooner.
2758 You can use the string @samp{$cwd} to refer to whatever is the current
2759 working directory at the time @value{GDBN} searches the path. If you
2760 use @samp{.} instead, it refers to the directory where you executed the
2761 @code{path} command. @value{GDBN} replaces @samp{.} in the
2762 @var{directory} argument (with the current path) before adding
2763 @var{directory} to the search path.
2764 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2765 @c document that, since repeating it would be a no-op.
2769 Display the list of search paths for executables (the @code{PATH}
2770 environment variable).
2772 @kindex show environment
2773 @item show environment @r{[}@var{varname}@r{]}
2774 Print the value of environment variable @var{varname} to be given to
2775 your program when it starts. If you do not supply @var{varname},
2776 print the names and values of all environment variables to be given to
2777 your program. You can abbreviate @code{environment} as @code{env}.
2779 @kindex set environment
2780 @anchor{set environment}
2781 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2782 Set environment variable @var{varname} to @var{value}. The value
2783 changes for your program (and the shell @value{GDBN} uses to launch
2784 it), not for @value{GDBN} itself. The @var{value} may be any string; the
2785 values of environment variables are just strings, and any
2786 interpretation is supplied by your program itself. The @var{value}
2787 parameter is optional; if it is eliminated, the variable is set to a
2789 @c "any string" here does not include leading, trailing
2790 @c blanks. Gnu asks: does anyone care?
2792 For example, this command:
2799 tells the debugged program, when subsequently run, that its user is named
2800 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2801 are not actually required.)
2803 Note that on Unix systems, @value{GDBN} runs your program via a shell,
2804 which also inherits the environment set with @code{set environment}.
2805 If necessary, you can avoid that by using the @samp{env} program as a
2806 wrapper instead of using @code{set environment}. @xref{set
2807 exec-wrapper}, for an example doing just that.
2809 Environment variables that are set by the user are also transmitted to
2810 @command{gdbserver} to be used when starting the remote inferior.
2811 @pxref{QEnvironmentHexEncoded}.
2813 @kindex unset environment
2814 @anchor{unset environment}
2815 @item unset environment @var{varname}
2816 Remove variable @var{varname} from the environment to be passed to your
2817 program. This is different from @samp{set env @var{varname} =};
2818 @code{unset environment} removes the variable from the environment,
2819 rather than assigning it an empty value.
2821 Environment variables that are unset by the user are also unset on
2822 @command{gdbserver} when starting the remote inferior.
2823 @pxref{QEnvironmentUnset}.
2826 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2827 the shell indicated by your @code{SHELL} environment variable if it
2828 exists (or @code{/bin/sh} if not). If your @code{SHELL} variable
2829 names a shell that runs an initialization file when started
2830 non-interactively---such as @file{.cshrc} for C-shell, $@file{.zshenv}
2831 for the Z shell, or the file specified in the @samp{BASH_ENV}
2832 environment variable for BASH---any variables you set in that file
2833 affect your program. You may wish to move setting of environment
2834 variables to files that are only run when you sign on, such as
2835 @file{.login} or @file{.profile}.
2837 @node Working Directory
2838 @section Your Program's Working Directory
2840 @cindex working directory (of your program)
2841 Each time you start your program with @code{run}, the inferior will be
2842 initialized with the current working directory specified by the
2843 @kbd{set cwd} command. If no directory has been specified by this
2844 command, then the inferior will inherit @value{GDBN}'s current working
2845 directory as its working directory if native debugging, or it will
2846 inherit the remote server's current working directory if remote
2851 @cindex change inferior's working directory
2852 @anchor{set cwd command}
2853 @item set cwd @r{[}@var{directory}@r{]}
2854 Set the inferior's working directory to @var{directory}, which will be
2855 @code{glob}-expanded in order to resolve tildes (@file{~}). If no
2856 argument has been specified, the command clears the setting and resets
2857 it to an empty state. This setting has no effect on @value{GDBN}'s
2858 working directory, and it only takes effect the next time you start
2859 the inferior. The @file{~} in @var{directory} is a short for the
2860 @dfn{home directory}, usually pointed to by the @env{HOME} environment
2861 variable. On MS-Windows, if @env{HOME} is not defined, @value{GDBN}
2862 uses the concatenation of @env{HOMEDRIVE} and @env{HOMEPATH} as
2865 You can also change @value{GDBN}'s current working directory by using
2866 the @code{cd} command.
2870 @cindex show inferior's working directory
2872 Show the inferior's working directory. If no directory has been
2873 specified by @kbd{set cwd}, then the default inferior's working
2874 directory is the same as @value{GDBN}'s working directory.
2877 @cindex change @value{GDBN}'s working directory
2879 @item cd @r{[}@var{directory}@r{]}
2880 Set the @value{GDBN} working directory to @var{directory}. If not
2881 given, @var{directory} uses @file{'~'}.
2883 The @value{GDBN} working directory serves as a default for the
2884 commands that specify files for @value{GDBN} to operate on.
2885 @xref{Files, ,Commands to Specify Files}.
2886 @xref{set cwd command}.
2890 Print the @value{GDBN} working directory.
2893 It is generally impossible to find the current working directory of
2894 the process being debugged (since a program can change its directory
2895 during its run). If you work on a system where @value{GDBN} supports
2896 the @code{info proc} command (@pxref{Process Information}), you can
2897 use the @code{info proc} command to find out the
2898 current working directory of the debuggee.
2901 @section Your Program's Input and Output
2906 By default, the program you run under @value{GDBN} does input and output to
2907 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2908 to its own terminal modes to interact with you, but it records the terminal
2909 modes your program was using and switches back to them when you continue
2910 running your program.
2913 @kindex info terminal
2915 Displays information recorded by @value{GDBN} about the terminal modes your
2919 You can redirect your program's input and/or output using shell
2920 redirection with the @code{run} command. For example,
2927 starts your program, diverting its output to the file @file{outfile}.
2930 @cindex controlling terminal
2931 Another way to specify where your program should do input and output is
2932 with the @code{tty} command. This command accepts a file name as
2933 argument, and causes this file to be the default for future @code{run}
2934 commands. It also resets the controlling terminal for the child
2935 process, for future @code{run} commands. For example,
2942 directs that processes started with subsequent @code{run} commands
2943 default to do input and output on the terminal @file{/dev/ttyb} and have
2944 that as their controlling terminal.
2946 An explicit redirection in @code{run} overrides the @code{tty} command's
2947 effect on the input/output device, but not its effect on the controlling
2950 When you use the @code{tty} command or redirect input in the @code{run}
2951 command, only the input @emph{for your program} is affected. The input
2952 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2953 for @code{set inferior-tty}.
2955 @cindex inferior tty
2956 @cindex set inferior controlling terminal
2957 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2958 display the name of the terminal that will be used for future runs of your
2962 @item set inferior-tty [ @var{tty} ]
2963 @kindex set inferior-tty
2964 Set the tty for the program being debugged to @var{tty}. Omitting @var{tty}
2965 restores the default behavior, which is to use the same terminal as
2968 @item show inferior-tty
2969 @kindex show inferior-tty
2970 Show the current tty for the program being debugged.
2974 @section Debugging an Already-running Process
2979 @item attach @var{process-id}
2980 This command attaches to a running process---one that was started
2981 outside @value{GDBN}. (@code{info files} shows your active
2982 targets.) The command takes as argument a process ID. The usual way to
2983 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2984 or with the @samp{jobs -l} shell command.
2986 @code{attach} does not repeat if you press @key{RET} a second time after
2987 executing the command.
2990 To use @code{attach}, your program must be running in an environment
2991 which supports processes; for example, @code{attach} does not work for
2992 programs on bare-board targets that lack an operating system. You must
2993 also have permission to send the process a signal.
2995 When you use @code{attach}, the debugger finds the program running in
2996 the process first by looking in the current working directory, then (if
2997 the program is not found) by using the source file search path
2998 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2999 the @code{file} command to load the program. @xref{Files, ,Commands to
3002 @anchor{set exec-file-mismatch}
3003 If the debugger can determine that the executable file running in the
3004 process it is attaching to does not match the current exec-file loaded
3005 by @value{GDBN}, the option @code{exec-file-mismatch} specifies how to
3006 handle the mismatch. @value{GDBN} tries to compare the files by
3007 comparing their build IDs (@pxref{build ID}), if available.
3010 @kindex exec-file-mismatch
3011 @cindex set exec-file-mismatch
3012 @item set exec-file-mismatch @samp{ask|warn|off}
3014 Whether to detect mismatch between the current executable file loaded
3015 by @value{GDBN} and the executable file used to start the process. If
3016 @samp{ask}, the default, display a warning and ask the user whether to
3017 load the process executable file; if @samp{warn}, just display a
3018 warning; if @samp{off}, don't attempt to detect a mismatch.
3020 @cindex show exec-file-mismatch
3021 @item show exec-file-mismatch
3022 Show the current value of @code{exec-file-mismatch}.
3026 The first thing @value{GDBN} does after arranging to debug the specified
3027 process is to stop it. You can examine and modify an attached process
3028 with all the @value{GDBN} commands that are ordinarily available when
3029 you start processes with @code{run}. You can insert breakpoints; you
3030 can step and continue; you can modify storage. If you would rather the
3031 process continue running, you may use the @code{continue} command after
3032 attaching @value{GDBN} to the process.
3037 When you have finished debugging the attached process, you can use the
3038 @code{detach} command to release it from @value{GDBN} control. Detaching
3039 the process continues its execution. After the @code{detach} command,
3040 that process and @value{GDBN} become completely independent once more, and you
3041 are ready to @code{attach} another process or start one with @code{run}.
3042 @code{detach} does not repeat if you press @key{RET} again after
3043 executing the command.
3046 If you exit @value{GDBN} while you have an attached process, you detach
3047 that process. If you use the @code{run} command, you kill that process.
3048 By default, @value{GDBN} asks for confirmation if you try to do either of these
3049 things; you can control whether or not you need to confirm by using the
3050 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
3054 @section Killing the Child Process
3059 Kill the child process in which your program is running under @value{GDBN}.
3062 This command is useful if you wish to debug a core dump instead of a
3063 running process. @value{GDBN} ignores any core dump file while your program
3066 On some operating systems, a program cannot be executed outside @value{GDBN}
3067 while you have breakpoints set on it inside @value{GDBN}. You can use the
3068 @code{kill} command in this situation to permit running your program
3069 outside the debugger.
3071 The @code{kill} command is also useful if you wish to recompile and
3072 relink your program, since on many systems it is impossible to modify an
3073 executable file while it is running in a process. In this case, when you
3074 next type @code{run}, @value{GDBN} notices that the file has changed, and
3075 reads the symbol table again (while trying to preserve your current
3076 breakpoint settings).
3078 @node Inferiors Connections and Programs
3079 @section Debugging Multiple Inferiors Connections and Programs
3081 @value{GDBN} lets you run and debug multiple programs in a single
3082 session. In addition, @value{GDBN} on some systems may let you run
3083 several programs simultaneously (otherwise you have to exit from one
3084 before starting another). On some systems @value{GDBN} may even let
3085 you debug several programs simultaneously on different remote systems.
3086 In the most general case, you can have multiple threads of execution
3087 in each of multiple processes, launched from multiple executables,
3088 running on different machines.
3091 @value{GDBN} represents the state of each program execution with an
3092 object called an @dfn{inferior}. An inferior typically corresponds to
3093 a process, but is more general and applies also to targets that do not
3094 have processes. Inferiors may be created before a process runs, and
3095 may be retained after a process exits. Inferiors have unique
3096 identifiers that are different from process ids. Usually each
3097 inferior will also have its own distinct address space, although some
3098 embedded targets may have several inferiors running in different parts
3099 of a single address space. Each inferior may in turn have multiple
3100 threads running in it.
3102 To find out what inferiors exist at any moment, use @w{@code{info
3106 @kindex info inferiors [ @var{id}@dots{} ]
3107 @item info inferiors
3108 Print a list of all inferiors currently being managed by @value{GDBN}.
3109 By default all inferiors are printed, but the argument @var{id}@dots{}
3110 -- a space separated list of inferior numbers -- can be used to limit
3111 the display to just the requested inferiors.
3113 @value{GDBN} displays for each inferior (in this order):
3117 the inferior number assigned by @value{GDBN}
3120 the target system's inferior identifier
3123 the target connection the inferior is bound to, including the unique
3124 connection number assigned by @value{GDBN}, and the protocol used by
3128 the name of the executable the inferior is running.
3133 An asterisk @samp{*} preceding the @value{GDBN} inferior number
3134 indicates the current inferior.
3138 @c end table here to get a little more width for example
3141 (@value{GDBP}) info inferiors
3142 Num Description Connection Executable
3143 * 1 process 3401 1 (native) goodbye
3144 2 process 2307 2 (extended-remote host:10000) hello
3147 To find out what open target connections exist at any moment, use
3148 @w{@code{info connections}}:
3151 @kindex info connections [ @var{id}@dots{} ]
3152 @item info connections
3153 Print a list of all open target connections currently being managed by
3154 @value{GDBN}. By default all connections are printed, but the
3155 argument @var{id}@dots{} -- a space separated list of connections
3156 numbers -- can be used to limit the display to just the requested
3159 @value{GDBN} displays for each connection (in this order):
3163 the connection number assigned by @value{GDBN}.
3166 the protocol used by the connection.
3169 a textual description of the protocol used by the connection.
3174 An asterisk @samp{*} preceding the connection number indicates the
3175 connection of the current inferior.
3179 @c end table here to get a little more width for example
3182 (@value{GDBP}) info connections
3183 Num What Description
3184 * 1 extended-remote host:10000 Extended remote serial target in gdb-specific protocol
3185 2 native Native process
3186 3 core Local core dump file
3189 To switch focus between inferiors, use the @code{inferior} command:
3192 @kindex inferior @var{infno}
3193 @item inferior @var{infno}
3194 Make inferior number @var{infno} the current inferior. The argument
3195 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
3196 in the first field of the @samp{info inferiors} display.
3199 @vindex $_inferior@r{, convenience variable}
3200 The debugger convenience variable @samp{$_inferior} contains the
3201 number of the current inferior. You may find this useful in writing
3202 breakpoint conditional expressions, command scripts, and so forth.
3203 @xref{Convenience Vars,, Convenience Variables}, for general
3204 information on convenience variables.
3206 You can get multiple executables into a debugging session via the
3207 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
3208 systems @value{GDBN} can add inferiors to the debug session
3209 automatically by following calls to @code{fork} and @code{exec}. To
3210 remove inferiors from the debugging session use the
3211 @w{@code{remove-inferiors}} command.
3214 @kindex add-inferior
3215 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ] [-no-connection ]
3216 Adds @var{n} inferiors to be run using @var{executable} as the
3217 executable; @var{n} defaults to 1. If no executable is specified,
3218 the inferiors begins empty, with no program. You can still assign or
3219 change the program assigned to the inferior at any time by using the
3220 @code{file} command with the executable name as its argument.
3222 By default, the new inferior begins connected to the same target
3223 connection as the current inferior. For example, if the current
3224 inferior was connected to @code{gdbserver} with @code{target remote},
3225 then the new inferior will be connected to the same @code{gdbserver}
3226 instance. The @samp{-no-connection} option starts the new inferior
3227 with no connection yet. You can then for example use the @code{target
3228 remote} command to connect to some other @code{gdbserver} instance,
3229 use @code{run} to spawn a local program, etc.
3231 @kindex clone-inferior
3232 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
3233 Adds @var{n} inferiors ready to execute the same program as inferior
3234 @var{infno}; @var{n} defaults to 1, and @var{infno} defaults to the
3235 number of the current inferior. This is a convenient command when you
3236 want to run another instance of the inferior you are debugging.
3239 (@value{GDBP}) info inferiors
3240 Num Description Connection Executable
3241 * 1 process 29964 1 (native) helloworld
3242 (@value{GDBP}) clone-inferior
3245 (@value{GDBP}) info inferiors
3246 Num Description Connection Executable
3247 * 1 process 29964 1 (native) helloworld
3248 2 <null> 1 (native) helloworld
3251 You can now simply switch focus to inferior 2 and run it.
3253 @kindex remove-inferiors
3254 @item remove-inferiors @var{infno}@dots{}
3255 Removes the inferior or inferiors @var{infno}@dots{}. It is not
3256 possible to remove an inferior that is running with this command. For
3257 those, use the @code{kill} or @code{detach} command first.
3261 To quit debugging one of the running inferiors that is not the current
3262 inferior, you can either detach from it by using the @w{@code{detach
3263 inferior}} command (allowing it to run independently), or kill it
3264 using the @w{@code{kill inferiors}} command:
3267 @kindex detach inferiors @var{infno}@dots{}
3268 @item detach inferior @var{infno}@dots{}
3269 Detach from the inferior or inferiors identified by @value{GDBN}
3270 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
3271 still stays on the list of inferiors shown by @code{info inferiors},
3272 but its Description will show @samp{<null>}.
3274 @kindex kill inferiors @var{infno}@dots{}
3275 @item kill inferiors @var{infno}@dots{}
3276 Kill the inferior or inferiors identified by @value{GDBN} inferior
3277 number(s) @var{infno}@dots{}. Note that the inferior's entry still
3278 stays on the list of inferiors shown by @code{info inferiors}, but its
3279 Description will show @samp{<null>}.
3282 After the successful completion of a command such as @code{detach},
3283 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
3284 a normal process exit, the inferior is still valid and listed with
3285 @code{info inferiors}, ready to be restarted.
3288 To be notified when inferiors are started or exit under @value{GDBN}'s
3289 control use @w{@code{set print inferior-events}}:
3292 @kindex set print inferior-events
3293 @cindex print messages on inferior start and exit
3294 @item set print inferior-events
3295 @itemx set print inferior-events on
3296 @itemx set print inferior-events off
3297 The @code{set print inferior-events} command allows you to enable or
3298 disable printing of messages when @value{GDBN} notices that new
3299 inferiors have started or that inferiors have exited or have been
3300 detached. By default, these messages will not be printed.
3302 @kindex show print inferior-events
3303 @item show print inferior-events
3304 Show whether messages will be printed when @value{GDBN} detects that
3305 inferiors have started, exited or have been detached.
3308 Many commands will work the same with multiple programs as with a
3309 single program: e.g., @code{print myglobal} will simply display the
3310 value of @code{myglobal} in the current inferior.
3313 Occasionally, when debugging @value{GDBN} itself, it may be useful to
3314 get more info about the relationship of inferiors, programs, address
3315 spaces in a debug session. You can do that with the @w{@code{maint
3316 info program-spaces}} command.
3319 @kindex maint info program-spaces
3320 @item maint info program-spaces
3321 Print a list of all program spaces currently being managed by
3324 @value{GDBN} displays for each program space (in this order):
3328 the program space number assigned by @value{GDBN}
3331 the name of the executable loaded into the program space, with e.g.,
3332 the @code{file} command.
3337 An asterisk @samp{*} preceding the @value{GDBN} program space number
3338 indicates the current program space.
3340 In addition, below each program space line, @value{GDBN} prints extra
3341 information that isn't suitable to display in tabular form. For
3342 example, the list of inferiors bound to the program space.
3345 (@value{GDBP}) maint info program-spaces
3349 Bound inferiors: ID 1 (process 21561)
3352 Here we can see that no inferior is running the program @code{hello},
3353 while @code{process 21561} is running the program @code{goodbye}. On
3354 some targets, it is possible that multiple inferiors are bound to the
3355 same program space. The most common example is that of debugging both
3356 the parent and child processes of a @code{vfork} call. For example,
3359 (@value{GDBP}) maint info program-spaces
3362 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
3365 Here, both inferior 2 and inferior 1 are running in the same program
3366 space as a result of inferior 1 having executed a @code{vfork} call.
3370 @section Debugging Programs with Multiple Threads
3372 @cindex threads of execution
3373 @cindex multiple threads
3374 @cindex switching threads
3375 In some operating systems, such as GNU/Linux and Solaris, a single program
3376 may have more than one @dfn{thread} of execution. The precise semantics
3377 of threads differ from one operating system to another, but in general
3378 the threads of a single program are akin to multiple processes---except
3379 that they share one address space (that is, they can all examine and
3380 modify the same variables). On the other hand, each thread has its own
3381 registers and execution stack, and perhaps private memory.
3383 @value{GDBN} provides these facilities for debugging multi-thread
3387 @item automatic notification of new threads
3388 @item @samp{thread @var{thread-id}}, a command to switch among threads
3389 @item @samp{info threads}, a command to inquire about existing threads
3390 @item @samp{thread apply [@var{thread-id-list} | all] @var{args}},
3391 a command to apply a command to a list of threads
3392 @item thread-specific breakpoints
3393 @item @samp{set print thread-events}, which controls printing of
3394 messages on thread start and exit.
3395 @item @samp{set libthread-db-search-path @var{path}}, which lets
3396 the user specify which @code{libthread_db} to use if the default choice
3397 isn't compatible with the program.
3400 @cindex focus of debugging
3401 @cindex current thread
3402 The @value{GDBN} thread debugging facility allows you to observe all
3403 threads while your program runs---but whenever @value{GDBN} takes
3404 control, one thread in particular is always the focus of debugging.
3405 This thread is called the @dfn{current thread}. Debugging commands show
3406 program information from the perspective of the current thread.
3408 @cindex @code{New} @var{systag} message
3409 @cindex thread identifier (system)
3410 @c FIXME-implementors!! It would be more helpful if the [New...] message
3411 @c included GDB's numeric thread handle, so you could just go to that
3412 @c thread without first checking `info threads'.
3413 Whenever @value{GDBN} detects a new thread in your program, it displays
3414 the target system's identification for the thread with a message in the
3415 form @samp{[New @var{systag}]}, where @var{systag} is a thread identifier
3416 whose form varies depending on the particular system. For example, on
3417 @sc{gnu}/Linux, you might see
3420 [New Thread 0x41e02940 (LWP 25582)]
3424 when @value{GDBN} notices a new thread. In contrast, on other systems,
3425 the @var{systag} is simply something like @samp{process 368}, with no
3428 @c FIXME!! (1) Does the [New...] message appear even for the very first
3429 @c thread of a program, or does it only appear for the
3430 @c second---i.e.@: when it becomes obvious we have a multithread
3432 @c (2) *Is* there necessarily a first thread always? Or do some
3433 @c multithread systems permit starting a program with multiple
3434 @c threads ab initio?
3436 @anchor{thread numbers}
3437 @cindex thread number, per inferior
3438 @cindex thread identifier (GDB)
3439 For debugging purposes, @value{GDBN} associates its own thread number
3440 ---always a single integer---with each thread of an inferior. This
3441 number is unique between all threads of an inferior, but not unique
3442 between threads of different inferiors.
3444 @cindex qualified thread ID
3445 You can refer to a given thread in an inferior using the qualified
3446 @var{inferior-num}.@var{thread-num} syntax, also known as
3447 @dfn{qualified thread ID}, with @var{inferior-num} being the inferior
3448 number and @var{thread-num} being the thread number of the given
3449 inferior. For example, thread @code{2.3} refers to thread number 3 of
3450 inferior 2. If you omit @var{inferior-num} (e.g., @code{thread 3}),
3451 then @value{GDBN} infers you're referring to a thread of the current
3454 Until you create a second inferior, @value{GDBN} does not show the
3455 @var{inferior-num} part of thread IDs, even though you can always use
3456 the full @var{inferior-num}.@var{thread-num} form to refer to threads
3457 of inferior 1, the initial inferior.
3459 @anchor{thread ID lists}
3460 @cindex thread ID lists
3461 Some commands accept a space-separated @dfn{thread ID list} as
3462 argument. A list element can be:
3466 A thread ID as shown in the first field of the @samp{info threads}
3467 display, with or without an inferior qualifier. E.g., @samp{2.1} or
3471 A range of thread numbers, again with or without an inferior
3472 qualifier, as in @var{inf}.@var{thr1}-@var{thr2} or
3473 @var{thr1}-@var{thr2}. E.g., @samp{1.2-4} or @samp{2-4}.
3476 All threads of an inferior, specified with a star wildcard, with or
3477 without an inferior qualifier, as in @var{inf}.@code{*} (e.g.,
3478 @samp{1.*}) or @code{*}. The former refers to all threads of the
3479 given inferior, and the latter form without an inferior qualifier
3480 refers to all threads of the current inferior.
3484 For example, if the current inferior is 1, and inferior 7 has one
3485 thread with ID 7.1, the thread list @samp{1 2-3 4.5 6.7-9 7.*}
3486 includes threads 1 to 3 of inferior 1, thread 5 of inferior 4, threads
3487 7 to 9 of inferior 6 and all threads of inferior 7. That is, in
3488 expanded qualified form, the same as @samp{1.1 1.2 1.3 4.5 6.7 6.8 6.9
3492 @anchor{global thread numbers}
3493 @cindex global thread number
3494 @cindex global thread identifier (GDB)
3495 In addition to a @emph{per-inferior} number, each thread is also
3496 assigned a unique @emph{global} number, also known as @dfn{global
3497 thread ID}, a single integer. Unlike the thread number component of
3498 the thread ID, no two threads have the same global ID, even when
3499 you're debugging multiple inferiors.
3501 From @value{GDBN}'s perspective, a process always has at least one
3502 thread. In other words, @value{GDBN} assigns a thread number to the
3503 program's ``main thread'' even if the program is not multi-threaded.
3505 @vindex $_thread@r{, convenience variable}
3506 @vindex $_gthread@r{, convenience variable}
3507 The debugger convenience variables @samp{$_thread} and
3508 @samp{$_gthread} contain, respectively, the per-inferior thread number
3509 and the global thread number of the current thread. You may find this
3510 useful in writing breakpoint conditional expressions, command scripts,
3511 and so forth. @xref{Convenience Vars,, Convenience Variables}, for
3512 general information on convenience variables.
3514 If @value{GDBN} detects the program is multi-threaded, it augments the
3515 usual message about stopping at a breakpoint with the ID and name of
3516 the thread that hit the breakpoint.
3519 Thread 2 "client" hit Breakpoint 1, send_message () at client.c:68
3522 Likewise when the program receives a signal:
3525 Thread 1 "main" received signal SIGINT, Interrupt.
3529 @kindex info threads
3530 @item info threads @r{[}@var{thread-id-list}@r{]}
3532 Display information about one or more threads. With no arguments
3533 displays information about all threads. You can specify the list of
3534 threads that you want to display using the thread ID list syntax
3535 (@pxref{thread ID lists}).
3537 @value{GDBN} displays for each thread (in this order):
3541 the per-inferior thread number assigned by @value{GDBN}
3544 the global thread number assigned by @value{GDBN}, if the @samp{-gid}
3545 option was specified
3548 the target system's thread identifier (@var{systag})
3551 the thread's name, if one is known. A thread can either be named by
3552 the user (see @code{thread name}, below), or, in some cases, by the
3556 the current stack frame summary for that thread
3560 An asterisk @samp{*} to the left of the @value{GDBN} thread number
3561 indicates the current thread.
3565 @c end table here to get a little more width for example
3568 (@value{GDBP}) info threads
3570 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3571 2 process 35 thread 23 0x34e5 in sigpause ()
3572 3 process 35 thread 27 0x34e5 in sigpause ()
3576 If you're debugging multiple inferiors, @value{GDBN} displays thread
3577 IDs using the qualified @var{inferior-num}.@var{thread-num} format.
3578 Otherwise, only @var{thread-num} is shown.
3580 If you specify the @samp{-gid} option, @value{GDBN} displays a column
3581 indicating each thread's global thread ID:
3584 (@value{GDBP}) info threads
3585 Id GId Target Id Frame
3586 1.1 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3587 1.2 3 process 35 thread 23 0x34e5 in sigpause ()
3588 1.3 4 process 35 thread 27 0x34e5 in sigpause ()
3589 * 2.1 2 process 65 thread 1 main (argc=1, argv=0x7ffffff8)
3592 On Solaris, you can display more information about user threads with a
3593 Solaris-specific command:
3596 @item maint info sol-threads
3597 @kindex maint info sol-threads
3598 @cindex thread info (Solaris)
3599 Display info on Solaris user threads.
3603 @kindex thread @var{thread-id}
3604 @item thread @var{thread-id}
3605 Make thread ID @var{thread-id} the current thread. The command
3606 argument @var{thread-id} is the @value{GDBN} thread ID, as shown in
3607 the first field of the @samp{info threads} display, with or without an
3608 inferior qualifier (e.g., @samp{2.1} or @samp{1}).
3610 @value{GDBN} responds by displaying the system identifier of the
3611 thread you selected, and its current stack frame summary:
3614 (@value{GDBP}) thread 2
3615 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
3616 #0 some_function (ignore=0x0) at example.c:8
3617 8 printf ("hello\n");
3621 As with the @samp{[New @dots{}]} message, the form of the text after
3622 @samp{Switching to} depends on your system's conventions for identifying
3625 @anchor{thread apply all}
3626 @kindex thread apply
3627 @cindex apply command to several threads
3628 @item thread apply [@var{thread-id-list} | all [-ascending]] [@var{flag}]@dots{} @var{command}
3629 The @code{thread apply} command allows you to apply the named
3630 @var{command} to one or more threads. Specify the threads that you
3631 want affected using the thread ID list syntax (@pxref{thread ID
3632 lists}), or specify @code{all} to apply to all threads. To apply a
3633 command to all threads in descending order, type @kbd{thread apply all
3634 @var{command}}. To apply a command to all threads in ascending order,
3635 type @kbd{thread apply all -ascending @var{command}}.
3637 The @var{flag} arguments control what output to produce and how to handle
3638 errors raised when applying @var{command} to a thread. @var{flag}
3639 must start with a @code{-} directly followed by one letter in
3640 @code{qcs}. If several flags are provided, they must be given
3641 individually, such as @code{-c -q}.
3643 By default, @value{GDBN} displays some thread information before the
3644 output produced by @var{command}, and an error raised during the
3645 execution of a @var{command} will abort @code{thread apply}. The
3646 following flags can be used to fine-tune this behavior:
3650 The flag @code{-c}, which stands for @samp{continue}, causes any
3651 errors in @var{command} to be displayed, and the execution of
3652 @code{thread apply} then continues.
3654 The flag @code{-s}, which stands for @samp{silent}, causes any errors
3655 or empty output produced by a @var{command} to be silently ignored.
3656 That is, the execution continues, but the thread information and errors
3659 The flag @code{-q} (@samp{quiet}) disables printing the thread
3663 Flags @code{-c} and @code{-s} cannot be used together.
3666 @cindex apply command to all threads (ignoring errors and empty output)
3667 @item taas [@var{option}]@dots{} @var{command}
3668 Shortcut for @code{thread apply all -s [@var{option}]@dots{} @var{command}}.
3669 Applies @var{command} on all threads, ignoring errors and empty output.
3671 The @code{taas} command accepts the same options as the @code{thread
3672 apply all} command. @xref{thread apply all}.
3675 @cindex apply a command to all frames of all threads (ignoring errors and empty output)
3676 @item tfaas [@var{option}]@dots{} @var{command}
3677 Shortcut for @code{thread apply all -s -- frame apply all -s [@var{option}]@dots{} @var{command}}.
3678 Applies @var{command} on all frames of all threads, ignoring errors
3679 and empty output. Note that the flag @code{-s} is specified twice:
3680 The first @code{-s} ensures that @code{thread apply} only shows the thread
3681 information of the threads for which @code{frame apply} produces
3682 some output. The second @code{-s} is needed to ensure that @code{frame
3683 apply} shows the frame information of a frame only if the
3684 @var{command} successfully produced some output.
3686 It can for example be used to print a local variable or a function
3687 argument without knowing the thread or frame where this variable or argument
3690 (@value{GDBP}) tfaas p some_local_var_i_do_not_remember_where_it_is
3693 The @code{tfaas} command accepts the same options as the @code{frame
3694 apply} command. @xref{frame apply}.
3697 @cindex name a thread
3698 @item thread name [@var{name}]
3699 This command assigns a name to the current thread. If no argument is
3700 given, any existing user-specified name is removed. The thread name
3701 appears in the @samp{info threads} display.
3703 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
3704 determine the name of the thread as given by the OS. On these
3705 systems, a name specified with @samp{thread name} will override the
3706 system-give name, and removing the user-specified name will cause
3707 @value{GDBN} to once again display the system-specified name.
3710 @cindex search for a thread
3711 @item thread find [@var{regexp}]
3712 Search for and display thread ids whose name or @var{systag}
3713 matches the supplied regular expression.
3715 As well as being the complement to the @samp{thread name} command,
3716 this command also allows you to identify a thread by its target
3717 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
3721 (@value{GDBN}) thread find 26688
3722 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
3723 (@value{GDBN}) info thread 4
3725 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
3728 @kindex set print thread-events
3729 @cindex print messages on thread start and exit
3730 @item set print thread-events
3731 @itemx set print thread-events on
3732 @itemx set print thread-events off
3733 The @code{set print thread-events} command allows you to enable or
3734 disable printing of messages when @value{GDBN} notices that new threads have
3735 started or that threads have exited. By default, these messages will
3736 be printed if detection of these events is supported by the target.
3737 Note that these messages cannot be disabled on all targets.
3739 @kindex show print thread-events
3740 @item show print thread-events
3741 Show whether messages will be printed when @value{GDBN} detects that threads
3742 have started and exited.
3745 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
3746 more information about how @value{GDBN} behaves when you stop and start
3747 programs with multiple threads.
3749 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
3750 watchpoints in programs with multiple threads.
3752 @anchor{set libthread-db-search-path}
3754 @kindex set libthread-db-search-path
3755 @cindex search path for @code{libthread_db}
3756 @item set libthread-db-search-path @r{[}@var{path}@r{]}
3757 If this variable is set, @var{path} is a colon-separated list of
3758 directories @value{GDBN} will use to search for @code{libthread_db}.
3759 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
3760 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
3761 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
3764 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
3765 @code{libthread_db} library to obtain information about threads in the
3766 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
3767 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
3768 specific thread debugging library loading is enabled
3769 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
3771 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
3772 refers to the default system directories that are
3773 normally searched for loading shared libraries. The @samp{$sdir} entry
3774 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
3775 (@pxref{libthread_db.so.1 file}).
3777 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
3778 refers to the directory from which @code{libpthread}
3779 was loaded in the inferior process.
3781 For any @code{libthread_db} library @value{GDBN} finds in above directories,
3782 @value{GDBN} attempts to initialize it with the current inferior process.
3783 If this initialization fails (which could happen because of a version
3784 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
3785 will unload @code{libthread_db}, and continue with the next directory.
3786 If none of @code{libthread_db} libraries initialize successfully,
3787 @value{GDBN} will issue a warning and thread debugging will be disabled.
3789 Setting @code{libthread-db-search-path} is currently implemented
3790 only on some platforms.
3792 @kindex show libthread-db-search-path
3793 @item show libthread-db-search-path
3794 Display current libthread_db search path.
3796 @kindex set debug libthread-db
3797 @kindex show debug libthread-db
3798 @cindex debugging @code{libthread_db}
3799 @item set debug libthread-db
3800 @itemx show debug libthread-db
3801 Turns on or off display of @code{libthread_db}-related events.
3802 Use @code{1} to enable, @code{0} to disable.
3806 @section Debugging Forks
3808 @cindex fork, debugging programs which call
3809 @cindex multiple processes
3810 @cindex processes, multiple
3811 On most systems, @value{GDBN} has no special support for debugging
3812 programs which create additional processes using the @code{fork}
3813 function. When a program forks, @value{GDBN} will continue to debug the
3814 parent process and the child process will run unimpeded. If you have
3815 set a breakpoint in any code which the child then executes, the child
3816 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3817 will cause it to terminate.
3819 However, if you want to debug the child process there is a workaround
3820 which isn't too painful. Put a call to @code{sleep} in the code which
3821 the child process executes after the fork. It may be useful to sleep
3822 only if a certain environment variable is set, or a certain file exists,
3823 so that the delay need not occur when you don't want to run @value{GDBN}
3824 on the child. While the child is sleeping, use the @code{ps} program to
3825 get its process ID. Then tell @value{GDBN} (a new invocation of
3826 @value{GDBN} if you are also debugging the parent process) to attach to
3827 the child process (@pxref{Attach}). From that point on you can debug
3828 the child process just like any other process which you attached to.
3830 On some systems, @value{GDBN} provides support for debugging programs
3831 that create additional processes using the @code{fork} or @code{vfork}
3832 functions. On @sc{gnu}/Linux platforms, this feature is supported
3833 with kernel version 2.5.46 and later.
3835 The fork debugging commands are supported in native mode and when
3836 connected to @code{gdbserver} in either @code{target remote} mode or
3837 @code{target extended-remote} mode.
3839 By default, when a program forks, @value{GDBN} will continue to debug
3840 the parent process and the child process will run unimpeded.
3842 If you want to follow the child process instead of the parent process,
3843 use the command @w{@code{set follow-fork-mode}}.
3846 @kindex set follow-fork-mode
3847 @item set follow-fork-mode @var{mode}
3848 Set the debugger response to a program call of @code{fork} or
3849 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3850 process. The @var{mode} argument can be:
3854 The original process is debugged after a fork. The child process runs
3855 unimpeded. This is the default.
3858 The new process is debugged after a fork. The parent process runs
3863 @kindex show follow-fork-mode
3864 @item show follow-fork-mode
3865 Display the current debugger response to a @code{fork} or @code{vfork} call.
3868 @cindex debugging multiple processes
3869 On Linux, if you want to debug both the parent and child processes, use the
3870 command @w{@code{set detach-on-fork}}.
3873 @kindex set detach-on-fork
3874 @item set detach-on-fork @var{mode}
3875 Tells gdb whether to detach one of the processes after a fork, or
3876 retain debugger control over them both.
3880 The child process (or parent process, depending on the value of
3881 @code{follow-fork-mode}) will be detached and allowed to run
3882 independently. This is the default.
3885 Both processes will be held under the control of @value{GDBN}.
3886 One process (child or parent, depending on the value of
3887 @code{follow-fork-mode}) is debugged as usual, while the other
3892 @kindex show detach-on-fork
3893 @item show detach-on-fork
3894 Show whether detach-on-fork mode is on/off.
3897 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3898 will retain control of all forked processes (including nested forks).
3899 You can list the forked processes under the control of @value{GDBN} by
3900 using the @w{@code{info inferiors}} command, and switch from one fork
3901 to another by using the @code{inferior} command (@pxref{Inferiors Connections and
3902 Programs, ,Debugging Multiple Inferiors Connections and Programs}).
3904 To quit debugging one of the forked processes, you can either detach
3905 from it by using the @w{@code{detach inferiors}} command (allowing it
3906 to run independently), or kill it using the @w{@code{kill inferiors}}
3907 command. @xref{Inferiors Connections and Programs, ,Debugging
3908 Multiple Inferiors Connections and Programs}.
3910 If you ask to debug a child process and a @code{vfork} is followed by an
3911 @code{exec}, @value{GDBN} executes the new target up to the first
3912 breakpoint in the new target. If you have a breakpoint set on
3913 @code{main} in your original program, the breakpoint will also be set on
3914 the child process's @code{main}.
3916 On some systems, when a child process is spawned by @code{vfork}, you
3917 cannot debug the child or parent until an @code{exec} call completes.
3919 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3920 call executes, the new target restarts. To restart the parent
3921 process, use the @code{file} command with the parent executable name
3922 as its argument. By default, after an @code{exec} call executes,
3923 @value{GDBN} discards the symbols of the previous executable image.
3924 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3928 @kindex set follow-exec-mode
3929 @item set follow-exec-mode @var{mode}
3931 Set debugger response to a program call of @code{exec}. An
3932 @code{exec} call replaces the program image of a process.
3934 @code{follow-exec-mode} can be:
3938 @value{GDBN} creates a new inferior and rebinds the process to this
3939 new inferior. The program the process was running before the
3940 @code{exec} call can be restarted afterwards by restarting the
3946 (@value{GDBP}) info inferiors
3948 Id Description Executable
3951 process 12020 is executing new program: prog2
3952 Program exited normally.
3953 (@value{GDBP}) info inferiors
3954 Id Description Executable
3960 @value{GDBN} keeps the process bound to the same inferior. The new
3961 executable image replaces the previous executable loaded in the
3962 inferior. Restarting the inferior after the @code{exec} call, with
3963 e.g., the @code{run} command, restarts the executable the process was
3964 running after the @code{exec} call. This is the default mode.
3969 (@value{GDBP}) info inferiors
3970 Id Description Executable
3973 process 12020 is executing new program: prog2
3974 Program exited normally.
3975 (@value{GDBP}) info inferiors
3976 Id Description Executable
3983 @code{follow-exec-mode} is supported in native mode and
3984 @code{target extended-remote} mode.
3986 You can use the @code{catch} command to make @value{GDBN} stop whenever
3987 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3988 Catchpoints, ,Setting Catchpoints}.
3990 @node Checkpoint/Restart
3991 @section Setting a @emph{Bookmark} to Return to Later
3996 @cindex snapshot of a process
3997 @cindex rewind program state
3999 On certain operating systems@footnote{Currently, only
4000 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
4001 program's state, called a @dfn{checkpoint}, and come back to it
4004 Returning to a checkpoint effectively undoes everything that has
4005 happened in the program since the @code{checkpoint} was saved. This
4006 includes changes in memory, registers, and even (within some limits)
4007 system state. Effectively, it is like going back in time to the
4008 moment when the checkpoint was saved.
4010 Thus, if you're stepping thru a program and you think you're
4011 getting close to the point where things go wrong, you can save
4012 a checkpoint. Then, if you accidentally go too far and miss
4013 the critical statement, instead of having to restart your program
4014 from the beginning, you can just go back to the checkpoint and
4015 start again from there.
4017 This can be especially useful if it takes a lot of time or
4018 steps to reach the point where you think the bug occurs.
4020 To use the @code{checkpoint}/@code{restart} method of debugging:
4025 Save a snapshot of the debugged program's current execution state.
4026 The @code{checkpoint} command takes no arguments, but each checkpoint
4027 is assigned a small integer id, similar to a breakpoint id.
4029 @kindex info checkpoints
4030 @item info checkpoints
4031 List the checkpoints that have been saved in the current debugging
4032 session. For each checkpoint, the following information will be
4039 @item Source line, or label
4042 @kindex restart @var{checkpoint-id}
4043 @item restart @var{checkpoint-id}
4044 Restore the program state that was saved as checkpoint number
4045 @var{checkpoint-id}. All program variables, registers, stack frames
4046 etc.@: will be returned to the values that they had when the checkpoint
4047 was saved. In essence, gdb will ``wind back the clock'' to the point
4048 in time when the checkpoint was saved.
4050 Note that breakpoints, @value{GDBN} variables, command history etc.
4051 are not affected by restoring a checkpoint. In general, a checkpoint
4052 only restores things that reside in the program being debugged, not in
4055 @kindex delete checkpoint @var{checkpoint-id}
4056 @item delete checkpoint @var{checkpoint-id}
4057 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
4061 Returning to a previously saved checkpoint will restore the user state
4062 of the program being debugged, plus a significant subset of the system
4063 (OS) state, including file pointers. It won't ``un-write'' data from
4064 a file, but it will rewind the file pointer to the previous location,
4065 so that the previously written data can be overwritten. For files
4066 opened in read mode, the pointer will also be restored so that the
4067 previously read data can be read again.
4069 Of course, characters that have been sent to a printer (or other
4070 external device) cannot be ``snatched back'', and characters received
4071 from eg.@: a serial device can be removed from internal program buffers,
4072 but they cannot be ``pushed back'' into the serial pipeline, ready to
4073 be received again. Similarly, the actual contents of files that have
4074 been changed cannot be restored (at this time).
4076 However, within those constraints, you actually can ``rewind'' your
4077 program to a previously saved point in time, and begin debugging it
4078 again --- and you can change the course of events so as to debug a
4079 different execution path this time.
4081 @cindex checkpoints and process id
4082 Finally, there is one bit of internal program state that will be
4083 different when you return to a checkpoint --- the program's process
4084 id. Each checkpoint will have a unique process id (or @var{pid}),
4085 and each will be different from the program's original @var{pid}.
4086 If your program has saved a local copy of its process id, this could
4087 potentially pose a problem.
4089 @subsection A Non-obvious Benefit of Using Checkpoints
4091 On some systems such as @sc{gnu}/Linux, address space randomization
4092 is performed on new processes for security reasons. This makes it
4093 difficult or impossible to set a breakpoint, or watchpoint, on an
4094 absolute address if you have to restart the program, since the
4095 absolute location of a symbol will change from one execution to the
4098 A checkpoint, however, is an @emph{identical} copy of a process.
4099 Therefore if you create a checkpoint at (eg.@:) the start of main,
4100 and simply return to that checkpoint instead of restarting the
4101 process, you can avoid the effects of address randomization and
4102 your symbols will all stay in the same place.
4105 @chapter Stopping and Continuing
4107 The principal purposes of using a debugger are so that you can stop your
4108 program before it terminates; or so that, if your program runs into
4109 trouble, you can investigate and find out why.
4111 Inside @value{GDBN}, your program may stop for any of several reasons,
4112 such as a signal, a breakpoint, or reaching a new line after a
4113 @value{GDBN} command such as @code{step}. You may then examine and
4114 change variables, set new breakpoints or remove old ones, and then
4115 continue execution. Usually, the messages shown by @value{GDBN} provide
4116 ample explanation of the status of your program---but you can also
4117 explicitly request this information at any time.
4120 @kindex info program
4122 Display information about the status of your program: whether it is
4123 running or not, what process it is, and why it stopped.
4127 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
4128 * Continuing and Stepping:: Resuming execution
4129 * Skipping Over Functions and Files::
4130 Skipping over functions and files
4132 * Thread Stops:: Stopping and starting multi-thread programs
4136 @section Breakpoints, Watchpoints, and Catchpoints
4139 A @dfn{breakpoint} makes your program stop whenever a certain point in
4140 the program is reached. For each breakpoint, you can add conditions to
4141 control in finer detail whether your program stops. You can set
4142 breakpoints with the @code{break} command and its variants (@pxref{Set
4143 Breaks, ,Setting Breakpoints}), to specify the place where your program
4144 should stop by line number, function name or exact address in the
4147 On some systems, you can set breakpoints in shared libraries before
4148 the executable is run.
4151 @cindex data breakpoints
4152 @cindex memory tracing
4153 @cindex breakpoint on memory address
4154 @cindex breakpoint on variable modification
4155 A @dfn{watchpoint} is a special breakpoint that stops your program
4156 when the value of an expression changes. The expression may be a value
4157 of a variable, or it could involve values of one or more variables
4158 combined by operators, such as @samp{a + b}. This is sometimes called
4159 @dfn{data breakpoints}. You must use a different command to set
4160 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
4161 from that, you can manage a watchpoint like any other breakpoint: you
4162 enable, disable, and delete both breakpoints and watchpoints using the
4165 You can arrange to have values from your program displayed automatically
4166 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
4170 @cindex breakpoint on events
4171 A @dfn{catchpoint} is another special breakpoint that stops your program
4172 when a certain kind of event occurs, such as the throwing of a C@t{++}
4173 exception or the loading of a library. As with watchpoints, you use a
4174 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
4175 Catchpoints}), but aside from that, you can manage a catchpoint like any
4176 other breakpoint. (To stop when your program receives a signal, use the
4177 @code{handle} command; see @ref{Signals, ,Signals}.)
4179 @cindex breakpoint numbers
4180 @cindex numbers for breakpoints
4181 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
4182 catchpoint when you create it; these numbers are successive integers
4183 starting with one. In many of the commands for controlling various
4184 features of breakpoints you use the breakpoint number to say which
4185 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
4186 @dfn{disabled}; if disabled, it has no effect on your program until you
4189 @cindex breakpoint ranges
4190 @cindex breakpoint lists
4191 @cindex ranges of breakpoints
4192 @cindex lists of breakpoints
4193 Some @value{GDBN} commands accept a space-separated list of breakpoints
4194 on which to operate. A list element can be either a single breakpoint number,
4195 like @samp{5}, or a range of such numbers, like @samp{5-7}.
4196 When a breakpoint list is given to a command, all breakpoints in that list
4200 * Set Breaks:: Setting breakpoints
4201 * Set Watchpoints:: Setting watchpoints
4202 * Set Catchpoints:: Setting catchpoints
4203 * Delete Breaks:: Deleting breakpoints
4204 * Disabling:: Disabling breakpoints
4205 * Conditions:: Break conditions
4206 * Break Commands:: Breakpoint command lists
4207 * Dynamic Printf:: Dynamic printf
4208 * Save Breakpoints:: How to save breakpoints in a file
4209 * Static Probe Points:: Listing static probe points
4210 * Error in Breakpoints:: ``Cannot insert breakpoints''
4211 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
4215 @subsection Setting Breakpoints
4217 @c FIXME LMB what does GDB do if no code on line of breakpt?
4218 @c consider in particular declaration with/without initialization.
4220 @c FIXME 2 is there stuff on this already? break at fun start, already init?
4223 @kindex b @r{(@code{break})}
4224 @vindex $bpnum@r{, convenience variable}
4225 @cindex latest breakpoint
4226 Breakpoints are set with the @code{break} command (abbreviated
4227 @code{b}). The debugger convenience variable @samp{$bpnum} records the
4228 number of the breakpoint you've set most recently; see @ref{Convenience
4229 Vars,, Convenience Variables}, for a discussion of what you can do with
4230 convenience variables.
4233 @item break @var{location}
4234 Set a breakpoint at the given @var{location}, which can specify a
4235 function name, a line number, or an address of an instruction.
4236 (@xref{Specify Location}, for a list of all the possible ways to
4237 specify a @var{location}.) The breakpoint will stop your program just
4238 before it executes any of the code in the specified @var{location}.
4240 When using source languages that permit overloading of symbols, such as
4241 C@t{++}, a function name may refer to more than one possible place to break.
4242 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
4245 It is also possible to insert a breakpoint that will stop the program
4246 only if a specific thread (@pxref{Thread-Specific Breakpoints})
4247 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
4250 When called without any arguments, @code{break} sets a breakpoint at
4251 the next instruction to be executed in the selected stack frame
4252 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
4253 innermost, this makes your program stop as soon as control
4254 returns to that frame. This is similar to the effect of a
4255 @code{finish} command in the frame inside the selected frame---except
4256 that @code{finish} does not leave an active breakpoint. If you use
4257 @code{break} without an argument in the innermost frame, @value{GDBN} stops
4258 the next time it reaches the current location; this may be useful
4261 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
4262 least one instruction has been executed. If it did not do this, you
4263 would be unable to proceed past a breakpoint without first disabling the
4264 breakpoint. This rule applies whether or not the breakpoint already
4265 existed when your program stopped.
4267 @item break @dots{} if @var{cond}
4268 Set a breakpoint with condition @var{cond}; evaluate the expression
4269 @var{cond} each time the breakpoint is reached, and stop only if the
4270 value is nonzero---that is, if @var{cond} evaluates as true.
4271 @samp{@dots{}} stands for one of the possible arguments described
4272 above (or no argument) specifying where to break. @xref{Conditions,
4273 ,Break Conditions}, for more information on breakpoint conditions.
4276 @item tbreak @var{args}
4277 Set a breakpoint enabled only for one stop. The @var{args} are the
4278 same as for the @code{break} command, and the breakpoint is set in the same
4279 way, but the breakpoint is automatically deleted after the first time your
4280 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
4283 @cindex hardware breakpoints
4284 @item hbreak @var{args}
4285 Set a hardware-assisted breakpoint. The @var{args} are the same as for the
4286 @code{break} command and the breakpoint is set in the same way, but the
4287 breakpoint requires hardware support and some target hardware may not
4288 have this support. The main purpose of this is EPROM/ROM code
4289 debugging, so you can set a breakpoint at an instruction without
4290 changing the instruction. This can be used with the new trap-generation
4291 provided by SPARClite DSU and most x86-based targets. These targets
4292 will generate traps when a program accesses some data or instruction
4293 address that is assigned to the debug registers. However the hardware
4294 breakpoint registers can take a limited number of breakpoints. For
4295 example, on the DSU, only two data breakpoints can be set at a time, and
4296 @value{GDBN} will reject this command if more than two are used. Delete
4297 or disable unused hardware breakpoints before setting new ones
4298 (@pxref{Disabling, ,Disabling Breakpoints}).
4299 @xref{Conditions, ,Break Conditions}.
4300 For remote targets, you can restrict the number of hardware
4301 breakpoints @value{GDBN} will use, see @ref{set remote
4302 hardware-breakpoint-limit}.
4305 @item thbreak @var{args}
4306 Set a hardware-assisted breakpoint enabled only for one stop. The @var{args}
4307 are the same as for the @code{hbreak} command and the breakpoint is set in
4308 the same way. However, like the @code{tbreak} command,
4309 the breakpoint is automatically deleted after the
4310 first time your program stops there. Also, like the @code{hbreak}
4311 command, the breakpoint requires hardware support and some target hardware
4312 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
4313 See also @ref{Conditions, ,Break Conditions}.
4316 @cindex regular expression
4317 @cindex breakpoints at functions matching a regexp
4318 @cindex set breakpoints in many functions
4319 @item rbreak @var{regex}
4320 Set breakpoints on all functions matching the regular expression
4321 @var{regex}. This command sets an unconditional breakpoint on all
4322 matches, printing a list of all breakpoints it set. Once these
4323 breakpoints are set, they are treated just like the breakpoints set with
4324 the @code{break} command. You can delete them, disable them, or make
4325 them conditional the same way as any other breakpoint.
4327 In programs using different languages, @value{GDBN} chooses the syntax
4328 to print the list of all breakpoints it sets according to the
4329 @samp{set language} value: using @samp{set language auto}
4330 (see @ref{Automatically, ,Set Language Automatically}) means to use the
4331 language of the breakpoint's function, other values mean to use
4332 the manually specified language (see @ref{Manually, ,Set Language Manually}).
4334 The syntax of the regular expression is the standard one used with tools
4335 like @file{grep}. Note that this is different from the syntax used by
4336 shells, so for instance @code{foo*} matches all functions that include
4337 an @code{fo} followed by zero or more @code{o}s. There is an implicit
4338 @code{.*} leading and trailing the regular expression you supply, so to
4339 match only functions that begin with @code{foo}, use @code{^foo}.
4341 @cindex non-member C@t{++} functions, set breakpoint in
4342 When debugging C@t{++} programs, @code{rbreak} is useful for setting
4343 breakpoints on overloaded functions that are not members of any special
4346 @cindex set breakpoints on all functions
4347 The @code{rbreak} command can be used to set breakpoints in
4348 @strong{all} the functions in a program, like this:
4351 (@value{GDBP}) rbreak .
4354 @item rbreak @var{file}:@var{regex}
4355 If @code{rbreak} is called with a filename qualification, it limits
4356 the search for functions matching the given regular expression to the
4357 specified @var{file}. This can be used, for example, to set breakpoints on
4358 every function in a given file:
4361 (@value{GDBP}) rbreak file.c:.
4364 The colon separating the filename qualifier from the regex may
4365 optionally be surrounded by spaces.
4367 @kindex info breakpoints
4368 @cindex @code{$_} and @code{info breakpoints}
4369 @item info breakpoints @r{[}@var{list}@dots{}@r{]}
4370 @itemx info break @r{[}@var{list}@dots{}@r{]}
4371 Print a table of all breakpoints, watchpoints, and catchpoints set and
4372 not deleted. Optional argument @var{n} means print information only
4373 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
4374 For each breakpoint, following columns are printed:
4377 @item Breakpoint Numbers
4379 Breakpoint, watchpoint, or catchpoint.
4381 Whether the breakpoint is marked to be disabled or deleted when hit.
4382 @item Enabled or Disabled
4383 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
4384 that are not enabled.
4386 Where the breakpoint is in your program, as a memory address. For a
4387 pending breakpoint whose address is not yet known, this field will
4388 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
4389 library that has the symbol or line referred by breakpoint is loaded.
4390 See below for details. A breakpoint with several locations will
4391 have @samp{<MULTIPLE>} in this field---see below for details.
4393 Where the breakpoint is in the source for your program, as a file and
4394 line number. For a pending breakpoint, the original string passed to
4395 the breakpoint command will be listed as it cannot be resolved until
4396 the appropriate shared library is loaded in the future.
4400 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
4401 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
4402 @value{GDBN} on the host's side. If it is ``target'', then the condition
4403 is evaluated by the target. The @code{info break} command shows
4404 the condition on the line following the affected breakpoint, together with
4405 its condition evaluation mode in between parentheses.
4407 Breakpoint commands, if any, are listed after that. A pending breakpoint is
4408 allowed to have a condition specified for it. The condition is not parsed for
4409 validity until a shared library is loaded that allows the pending
4410 breakpoint to resolve to a valid location.
4413 @code{info break} with a breakpoint
4414 number @var{n} as argument lists only that breakpoint. The
4415 convenience variable @code{$_} and the default examining-address for
4416 the @code{x} command are set to the address of the last breakpoint
4417 listed (@pxref{Memory, ,Examining Memory}).
4420 @code{info break} displays a count of the number of times the breakpoint
4421 has been hit. This is especially useful in conjunction with the
4422 @code{ignore} command. You can ignore a large number of breakpoint
4423 hits, look at the breakpoint info to see how many times the breakpoint
4424 was hit, and then run again, ignoring one less than that number. This
4425 will get you quickly to the last hit of that breakpoint.
4428 For a breakpoints with an enable count (xref) greater than 1,
4429 @code{info break} also displays that count.
4433 @value{GDBN} allows you to set any number of breakpoints at the same place in
4434 your program. There is nothing silly or meaningless about this. When
4435 the breakpoints are conditional, this is even useful
4436 (@pxref{Conditions, ,Break Conditions}).
4438 @cindex multiple locations, breakpoints
4439 @cindex breakpoints, multiple locations
4440 It is possible that a breakpoint corresponds to several locations
4441 in your program. Examples of this situation are:
4445 Multiple functions in the program may have the same name.
4448 For a C@t{++} constructor, the @value{NGCC} compiler generates several
4449 instances of the function body, used in different cases.
4452 For a C@t{++} template function, a given line in the function can
4453 correspond to any number of instantiations.
4456 For an inlined function, a given source line can correspond to
4457 several places where that function is inlined.
4460 In all those cases, @value{GDBN} will insert a breakpoint at all
4461 the relevant locations.
4463 A breakpoint with multiple locations is displayed in the breakpoint
4464 table using several rows---one header row, followed by one row for
4465 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
4466 address column. The rows for individual locations contain the actual
4467 addresses for locations, and show the functions to which those
4468 locations belong. The number column for a location is of the form
4469 @var{breakpoint-number}.@var{location-number}.
4474 Num Type Disp Enb Address What
4475 1 breakpoint keep y <MULTIPLE>
4477 breakpoint already hit 1 time
4478 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
4479 1.2 y 0x080486ca in void foo<double>() at t.cc:8
4482 You cannot delete the individual locations from a breakpoint. However,
4483 each location can be individually enabled or disabled by passing
4484 @var{breakpoint-number}.@var{location-number} as argument to the
4485 @code{enable} and @code{disable} commands. It's also possible to
4486 @code{enable} and @code{disable} a range of @var{location-number}
4487 locations using a @var{breakpoint-number} and two @var{location-number}s,
4488 in increasing order, separated by a hyphen, like
4489 @kbd{@var{breakpoint-number}.@var{location-number1}-@var{location-number2}},
4490 in which case @value{GDBN} acts on all the locations in the range (inclusive).
4491 Disabling or enabling the parent breakpoint (@pxref{Disabling}) affects
4492 all of the locations that belong to that breakpoint.
4494 @cindex pending breakpoints
4495 It's quite common to have a breakpoint inside a shared library.
4496 Shared libraries can be loaded and unloaded explicitly,
4497 and possibly repeatedly, as the program is executed. To support
4498 this use case, @value{GDBN} updates breakpoint locations whenever
4499 any shared library is loaded or unloaded. Typically, you would
4500 set a breakpoint in a shared library at the beginning of your
4501 debugging session, when the library is not loaded, and when the
4502 symbols from the library are not available. When you try to set
4503 breakpoint, @value{GDBN} will ask you if you want to set
4504 a so called @dfn{pending breakpoint}---breakpoint whose address
4505 is not yet resolved.
4507 After the program is run, whenever a new shared library is loaded,
4508 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
4509 shared library contains the symbol or line referred to by some
4510 pending breakpoint, that breakpoint is resolved and becomes an
4511 ordinary breakpoint. When a library is unloaded, all breakpoints
4512 that refer to its symbols or source lines become pending again.
4514 This logic works for breakpoints with multiple locations, too. For
4515 example, if you have a breakpoint in a C@t{++} template function, and
4516 a newly loaded shared library has an instantiation of that template,
4517 a new location is added to the list of locations for the breakpoint.
4519 Except for having unresolved address, pending breakpoints do not
4520 differ from regular breakpoints. You can set conditions or commands,
4521 enable and disable them and perform other breakpoint operations.
4523 @value{GDBN} provides some additional commands for controlling what
4524 happens when the @samp{break} command cannot resolve breakpoint
4525 address specification to an address:
4527 @kindex set breakpoint pending
4528 @kindex show breakpoint pending
4530 @item set breakpoint pending auto
4531 This is the default behavior. When @value{GDBN} cannot find the breakpoint
4532 location, it queries you whether a pending breakpoint should be created.
4534 @item set breakpoint pending on
4535 This indicates that an unrecognized breakpoint location should automatically
4536 result in a pending breakpoint being created.
4538 @item set breakpoint pending off
4539 This indicates that pending breakpoints are not to be created. Any
4540 unrecognized breakpoint location results in an error. This setting does
4541 not affect any pending breakpoints previously created.
4543 @item show breakpoint pending
4544 Show the current behavior setting for creating pending breakpoints.
4547 The settings above only affect the @code{break} command and its
4548 variants. Once breakpoint is set, it will be automatically updated
4549 as shared libraries are loaded and unloaded.
4551 @cindex automatic hardware breakpoints
4552 For some targets, @value{GDBN} can automatically decide if hardware or
4553 software breakpoints should be used, depending on whether the
4554 breakpoint address is read-only or read-write. This applies to
4555 breakpoints set with the @code{break} command as well as to internal
4556 breakpoints set by commands like @code{next} and @code{finish}. For
4557 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
4560 You can control this automatic behaviour with the following commands:
4562 @kindex set breakpoint auto-hw
4563 @kindex show breakpoint auto-hw
4565 @item set breakpoint auto-hw on
4566 This is the default behavior. When @value{GDBN} sets a breakpoint, it
4567 will try to use the target memory map to decide if software or hardware
4568 breakpoint must be used.
4570 @item set breakpoint auto-hw off
4571 This indicates @value{GDBN} should not automatically select breakpoint
4572 type. If the target provides a memory map, @value{GDBN} will warn when
4573 trying to set software breakpoint at a read-only address.
4576 @value{GDBN} normally implements breakpoints by replacing the program code
4577 at the breakpoint address with a special instruction, which, when
4578 executed, given control to the debugger. By default, the program
4579 code is so modified only when the program is resumed. As soon as
4580 the program stops, @value{GDBN} restores the original instructions. This
4581 behaviour guards against leaving breakpoints inserted in the
4582 target should gdb abrubptly disconnect. However, with slow remote
4583 targets, inserting and removing breakpoint can reduce the performance.
4584 This behavior can be controlled with the following commands::
4586 @kindex set breakpoint always-inserted
4587 @kindex show breakpoint always-inserted
4589 @item set breakpoint always-inserted off
4590 All breakpoints, including newly added by the user, are inserted in
4591 the target only when the target is resumed. All breakpoints are
4592 removed from the target when it stops. This is the default mode.
4594 @item set breakpoint always-inserted on
4595 Causes all breakpoints to be inserted in the target at all times. If
4596 the user adds a new breakpoint, or changes an existing breakpoint, the
4597 breakpoints in the target are updated immediately. A breakpoint is
4598 removed from the target only when breakpoint itself is deleted.
4601 @value{GDBN} handles conditional breakpoints by evaluating these conditions
4602 when a breakpoint breaks. If the condition is true, then the process being
4603 debugged stops, otherwise the process is resumed.
4605 If the target supports evaluating conditions on its end, @value{GDBN} may
4606 download the breakpoint, together with its conditions, to it.
4608 This feature can be controlled via the following commands:
4610 @kindex set breakpoint condition-evaluation
4611 @kindex show breakpoint condition-evaluation
4613 @item set breakpoint condition-evaluation host
4614 This option commands @value{GDBN} to evaluate the breakpoint
4615 conditions on the host's side. Unconditional breakpoints are sent to
4616 the target which in turn receives the triggers and reports them back to GDB
4617 for condition evaluation. This is the standard evaluation mode.
4619 @item set breakpoint condition-evaluation target
4620 This option commands @value{GDBN} to download breakpoint conditions
4621 to the target at the moment of their insertion. The target
4622 is responsible for evaluating the conditional expression and reporting
4623 breakpoint stop events back to @value{GDBN} whenever the condition
4624 is true. Due to limitations of target-side evaluation, some conditions
4625 cannot be evaluated there, e.g., conditions that depend on local data
4626 that is only known to the host. Examples include
4627 conditional expressions involving convenience variables, complex types
4628 that cannot be handled by the agent expression parser and expressions
4629 that are too long to be sent over to the target, specially when the
4630 target is a remote system. In these cases, the conditions will be
4631 evaluated by @value{GDBN}.
4633 @item set breakpoint condition-evaluation auto
4634 This is the default mode. If the target supports evaluating breakpoint
4635 conditions on its end, @value{GDBN} will download breakpoint conditions to
4636 the target (limitations mentioned previously apply). If the target does
4637 not support breakpoint condition evaluation, then @value{GDBN} will fallback
4638 to evaluating all these conditions on the host's side.
4642 @cindex negative breakpoint numbers
4643 @cindex internal @value{GDBN} breakpoints
4644 @value{GDBN} itself sometimes sets breakpoints in your program for
4645 special purposes, such as proper handling of @code{longjmp} (in C
4646 programs). These internal breakpoints are assigned negative numbers,
4647 starting with @code{-1}; @samp{info breakpoints} does not display them.
4648 You can see these breakpoints with the @value{GDBN} maintenance command
4649 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
4652 @node Set Watchpoints
4653 @subsection Setting Watchpoints
4655 @cindex setting watchpoints
4656 You can use a watchpoint to stop execution whenever the value of an
4657 expression changes, without having to predict a particular place where
4658 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
4659 The expression may be as simple as the value of a single variable, or
4660 as complex as many variables combined by operators. Examples include:
4664 A reference to the value of a single variable.
4667 An address cast to an appropriate data type. For example,
4668 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
4669 address (assuming an @code{int} occupies 4 bytes).
4672 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
4673 expression can use any operators valid in the program's native
4674 language (@pxref{Languages}).
4677 You can set a watchpoint on an expression even if the expression can
4678 not be evaluated yet. For instance, you can set a watchpoint on
4679 @samp{*global_ptr} before @samp{global_ptr} is initialized.
4680 @value{GDBN} will stop when your program sets @samp{global_ptr} and
4681 the expression produces a valid value. If the expression becomes
4682 valid in some other way than changing a variable (e.g.@: if the memory
4683 pointed to by @samp{*global_ptr} becomes readable as the result of a
4684 @code{malloc} call), @value{GDBN} may not stop until the next time
4685 the expression changes.
4687 @cindex software watchpoints
4688 @cindex hardware watchpoints
4689 Depending on your system, watchpoints may be implemented in software or
4690 hardware. @value{GDBN} does software watchpointing by single-stepping your
4691 program and testing the variable's value each time, which is hundreds of
4692 times slower than normal execution. (But this may still be worth it, to
4693 catch errors where you have no clue what part of your program is the
4696 On some systems, such as most PowerPC or x86-based targets,
4697 @value{GDBN} includes support for hardware watchpoints, which do not
4698 slow down the running of your program.
4702 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4703 Set a watchpoint for an expression. @value{GDBN} will break when the
4704 expression @var{expr} is written into by the program and its value
4705 changes. The simplest (and the most popular) use of this command is
4706 to watch the value of a single variable:
4709 (@value{GDBP}) watch foo
4712 If the command includes a @code{@r{[}thread @var{thread-id}@r{]}}
4713 argument, @value{GDBN} breaks only when the thread identified by
4714 @var{thread-id} changes the value of @var{expr}. If any other threads
4715 change the value of @var{expr}, @value{GDBN} will not break. Note
4716 that watchpoints restricted to a single thread in this way only work
4717 with Hardware Watchpoints.
4719 Ordinarily a watchpoint respects the scope of variables in @var{expr}
4720 (see below). The @code{-location} argument tells @value{GDBN} to
4721 instead watch the memory referred to by @var{expr}. In this case,
4722 @value{GDBN} will evaluate @var{expr}, take the address of the result,
4723 and watch the memory at that address. The type of the result is used
4724 to determine the size of the watched memory. If the expression's
4725 result does not have an address, then @value{GDBN} will print an
4728 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
4729 of masked watchpoints, if the current architecture supports this
4730 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
4731 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
4732 to an address to watch. The mask specifies that some bits of an address
4733 (the bits which are reset in the mask) should be ignored when matching
4734 the address accessed by the inferior against the watchpoint address.
4735 Thus, a masked watchpoint watches many addresses simultaneously---those
4736 addresses whose unmasked bits are identical to the unmasked bits in the
4737 watchpoint address. The @code{mask} argument implies @code{-location}.
4741 (@value{GDBP}) watch foo mask 0xffff00ff
4742 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
4746 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4747 Set a watchpoint that will break when the value of @var{expr} is read
4751 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4752 Set a watchpoint that will break when @var{expr} is either read from
4753 or written into by the program.
4755 @kindex info watchpoints @r{[}@var{list}@dots{}@r{]}
4756 @item info watchpoints @r{[}@var{list}@dots{}@r{]}
4757 This command prints a list of watchpoints, using the same format as
4758 @code{info break} (@pxref{Set Breaks}).
4761 If you watch for a change in a numerically entered address you need to
4762 dereference it, as the address itself is just a constant number which will
4763 never change. @value{GDBN} refuses to create a watchpoint that watches
4764 a never-changing value:
4767 (@value{GDBP}) watch 0x600850
4768 Cannot watch constant value 0x600850.
4769 (@value{GDBP}) watch *(int *) 0x600850
4770 Watchpoint 1: *(int *) 6293584
4773 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
4774 watchpoints execute very quickly, and the debugger reports a change in
4775 value at the exact instruction where the change occurs. If @value{GDBN}
4776 cannot set a hardware watchpoint, it sets a software watchpoint, which
4777 executes more slowly and reports the change in value at the next
4778 @emph{statement}, not the instruction, after the change occurs.
4780 @cindex use only software watchpoints
4781 You can force @value{GDBN} to use only software watchpoints with the
4782 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
4783 zero, @value{GDBN} will never try to use hardware watchpoints, even if
4784 the underlying system supports them. (Note that hardware-assisted
4785 watchpoints that were set @emph{before} setting
4786 @code{can-use-hw-watchpoints} to zero will still use the hardware
4787 mechanism of watching expression values.)
4790 @item set can-use-hw-watchpoints
4791 @kindex set can-use-hw-watchpoints
4792 Set whether or not to use hardware watchpoints.
4794 @item show can-use-hw-watchpoints
4795 @kindex show can-use-hw-watchpoints
4796 Show the current mode of using hardware watchpoints.
4799 For remote targets, you can restrict the number of hardware
4800 watchpoints @value{GDBN} will use, see @ref{set remote
4801 hardware-breakpoint-limit}.
4803 When you issue the @code{watch} command, @value{GDBN} reports
4806 Hardware watchpoint @var{num}: @var{expr}
4810 if it was able to set a hardware watchpoint.
4812 Currently, the @code{awatch} and @code{rwatch} commands can only set
4813 hardware watchpoints, because accesses to data that don't change the
4814 value of the watched expression cannot be detected without examining
4815 every instruction as it is being executed, and @value{GDBN} does not do
4816 that currently. If @value{GDBN} finds that it is unable to set a
4817 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
4818 will print a message like this:
4821 Expression cannot be implemented with read/access watchpoint.
4824 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4825 data type of the watched expression is wider than what a hardware
4826 watchpoint on the target machine can handle. For example, some systems
4827 can only watch regions that are up to 4 bytes wide; on such systems you
4828 cannot set hardware watchpoints for an expression that yields a
4829 double-precision floating-point number (which is typically 8 bytes
4830 wide). As a work-around, it might be possible to break the large region
4831 into a series of smaller ones and watch them with separate watchpoints.
4833 If you set too many hardware watchpoints, @value{GDBN} might be unable
4834 to insert all of them when you resume the execution of your program.
4835 Since the precise number of active watchpoints is unknown until such
4836 time as the program is about to be resumed, @value{GDBN} might not be
4837 able to warn you about this when you set the watchpoints, and the
4838 warning will be printed only when the program is resumed:
4841 Hardware watchpoint @var{num}: Could not insert watchpoint
4845 If this happens, delete or disable some of the watchpoints.
4847 Watching complex expressions that reference many variables can also
4848 exhaust the resources available for hardware-assisted watchpoints.
4849 That's because @value{GDBN} needs to watch every variable in the
4850 expression with separately allocated resources.
4852 If you call a function interactively using @code{print} or @code{call},
4853 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4854 kind of breakpoint or the call completes.
4856 @value{GDBN} automatically deletes watchpoints that watch local
4857 (automatic) variables, or expressions that involve such variables, when
4858 they go out of scope, that is, when the execution leaves the block in
4859 which these variables were defined. In particular, when the program
4860 being debugged terminates, @emph{all} local variables go out of scope,
4861 and so only watchpoints that watch global variables remain set. If you
4862 rerun the program, you will need to set all such watchpoints again. One
4863 way of doing that would be to set a code breakpoint at the entry to the
4864 @code{main} function and when it breaks, set all the watchpoints.
4866 @cindex watchpoints and threads
4867 @cindex threads and watchpoints
4868 In multi-threaded programs, watchpoints will detect changes to the
4869 watched expression from every thread.
4872 @emph{Warning:} In multi-threaded programs, software watchpoints
4873 have only limited usefulness. If @value{GDBN} creates a software
4874 watchpoint, it can only watch the value of an expression @emph{in a
4875 single thread}. If you are confident that the expression can only
4876 change due to the current thread's activity (and if you are also
4877 confident that no other thread can become current), then you can use
4878 software watchpoints as usual. However, @value{GDBN} may not notice
4879 when a non-current thread's activity changes the expression. (Hardware
4880 watchpoints, in contrast, watch an expression in all threads.)
4883 @xref{set remote hardware-watchpoint-limit}.
4885 @node Set Catchpoints
4886 @subsection Setting Catchpoints
4887 @cindex catchpoints, setting
4888 @cindex exception handlers
4889 @cindex event handling
4891 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4892 kinds of program events, such as C@t{++} exceptions or the loading of a
4893 shared library. Use the @code{catch} command to set a catchpoint.
4897 @item catch @var{event}
4898 Stop when @var{event} occurs. The @var{event} can be any of the following:
4901 @item throw @r{[}@var{regexp}@r{]}
4902 @itemx rethrow @r{[}@var{regexp}@r{]}
4903 @itemx catch @r{[}@var{regexp}@r{]}
4905 @kindex catch rethrow
4907 @cindex stop on C@t{++} exceptions
4908 The throwing, re-throwing, or catching of a C@t{++} exception.
4910 If @var{regexp} is given, then only exceptions whose type matches the
4911 regular expression will be caught.
4913 @vindex $_exception@r{, convenience variable}
4914 The convenience variable @code{$_exception} is available at an
4915 exception-related catchpoint, on some systems. This holds the
4916 exception being thrown.
4918 There are currently some limitations to C@t{++} exception handling in
4923 The support for these commands is system-dependent. Currently, only
4924 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
4928 The regular expression feature and the @code{$_exception} convenience
4929 variable rely on the presence of some SDT probes in @code{libstdc++}.
4930 If these probes are not present, then these features cannot be used.
4931 These probes were first available in the GCC 4.8 release, but whether
4932 or not they are available in your GCC also depends on how it was
4936 The @code{$_exception} convenience variable is only valid at the
4937 instruction at which an exception-related catchpoint is set.
4940 When an exception-related catchpoint is hit, @value{GDBN} stops at a
4941 location in the system library which implements runtime exception
4942 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
4943 (@pxref{Selection}) to get to your code.
4946 If you call a function interactively, @value{GDBN} normally returns
4947 control to you when the function has finished executing. If the call
4948 raises an exception, however, the call may bypass the mechanism that
4949 returns control to you and cause your program either to abort or to
4950 simply continue running until it hits a breakpoint, catches a signal
4951 that @value{GDBN} is listening for, or exits. This is the case even if
4952 you set a catchpoint for the exception; catchpoints on exceptions are
4953 disabled within interactive calls. @xref{Calling}, for information on
4954 controlling this with @code{set unwind-on-terminating-exception}.
4957 You cannot raise an exception interactively.
4960 You cannot install an exception handler interactively.
4963 @item exception @r{[}@var{name}@r{]}
4964 @kindex catch exception
4965 @cindex Ada exception catching
4966 @cindex catch Ada exceptions
4967 An Ada exception being raised. If an exception name is specified
4968 at the end of the command (eg @code{catch exception Program_Error}),
4969 the debugger will stop only when this specific exception is raised.
4970 Otherwise, the debugger stops execution when any Ada exception is raised.
4972 When inserting an exception catchpoint on a user-defined exception whose
4973 name is identical to one of the exceptions defined by the language, the
4974 fully qualified name must be used as the exception name. Otherwise,
4975 @value{GDBN} will assume that it should stop on the pre-defined exception
4976 rather than the user-defined one. For instance, assuming an exception
4977 called @code{Constraint_Error} is defined in package @code{Pck}, then
4978 the command to use to catch such exceptions is @kbd{catch exception
4979 Pck.Constraint_Error}.
4981 @vindex $_ada_exception@r{, convenience variable}
4982 The convenience variable @code{$_ada_exception} holds the address of
4983 the exception being thrown. This can be useful when setting a
4984 condition for such a catchpoint.
4986 @item exception unhandled
4987 @kindex catch exception unhandled
4988 An exception that was raised but is not handled by the program. The
4989 convenience variable @code{$_ada_exception} is set as for @code{catch
4992 @item handlers @r{[}@var{name}@r{]}
4993 @kindex catch handlers
4994 @cindex Ada exception handlers catching
4995 @cindex catch Ada exceptions when handled
4996 An Ada exception being handled. If an exception name is
4997 specified at the end of the command
4998 (eg @kbd{catch handlers Program_Error}), the debugger will stop
4999 only when this specific exception is handled.
5000 Otherwise, the debugger stops execution when any Ada exception is handled.
5002 When inserting a handlers catchpoint on a user-defined
5003 exception whose name is identical to one of the exceptions
5004 defined by the language, the fully qualified name must be used
5005 as the exception name. Otherwise, @value{GDBN} will assume that it
5006 should stop on the pre-defined exception rather than the
5007 user-defined one. For instance, assuming an exception called
5008 @code{Constraint_Error} is defined in package @code{Pck}, then the
5009 command to use to catch such exceptions handling is
5010 @kbd{catch handlers Pck.Constraint_Error}.
5012 The convenience variable @code{$_ada_exception} is set as for
5013 @code{catch exception}.
5016 @kindex catch assert
5017 A failed Ada assertion. Note that the convenience variable
5018 @code{$_ada_exception} is @emph{not} set by this catchpoint.
5022 @cindex break on fork/exec
5023 A call to @code{exec}.
5025 @anchor{catch syscall}
5027 @itemx syscall @r{[}@var{name} @r{|} @var{number} @r{|} @r{group:}@var{groupname} @r{|} @r{g:}@var{groupname}@r{]} @dots{}
5028 @kindex catch syscall
5029 @cindex break on a system call.
5030 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
5031 syscall is a mechanism for application programs to request a service
5032 from the operating system (OS) or one of the OS system services.
5033 @value{GDBN} can catch some or all of the syscalls issued by the
5034 debuggee, and show the related information for each syscall. If no
5035 argument is specified, calls to and returns from all system calls
5038 @var{name} can be any system call name that is valid for the
5039 underlying OS. Just what syscalls are valid depends on the OS. On
5040 GNU and Unix systems, you can find the full list of valid syscall
5041 names on @file{/usr/include/asm/unistd.h}.
5043 @c For MS-Windows, the syscall names and the corresponding numbers
5044 @c can be found, e.g., on this URL:
5045 @c http://www.metasploit.com/users/opcode/syscalls.html
5046 @c but we don't support Windows syscalls yet.
5048 Normally, @value{GDBN} knows in advance which syscalls are valid for
5049 each OS, so you can use the @value{GDBN} command-line completion
5050 facilities (@pxref{Completion,, command completion}) to list the
5053 You may also specify the system call numerically. A syscall's
5054 number is the value passed to the OS's syscall dispatcher to
5055 identify the requested service. When you specify the syscall by its
5056 name, @value{GDBN} uses its database of syscalls to convert the name
5057 into the corresponding numeric code, but using the number directly
5058 may be useful if @value{GDBN}'s database does not have the complete
5059 list of syscalls on your system (e.g., because @value{GDBN} lags
5060 behind the OS upgrades).
5062 You may specify a group of related syscalls to be caught at once using
5063 the @code{group:} syntax (@code{g:} is a shorter equivalent). For
5064 instance, on some platforms @value{GDBN} allows you to catch all
5065 network related syscalls, by passing the argument @code{group:network}
5066 to @code{catch syscall}. Note that not all syscall groups are
5067 available in every system. You can use the command completion
5068 facilities (@pxref{Completion,, command completion}) to list the
5069 syscall groups available on your environment.
5071 The example below illustrates how this command works if you don't provide
5075 (@value{GDBP}) catch syscall
5076 Catchpoint 1 (syscall)
5078 Starting program: /tmp/catch-syscall
5080 Catchpoint 1 (call to syscall 'close'), \
5081 0xffffe424 in __kernel_vsyscall ()
5085 Catchpoint 1 (returned from syscall 'close'), \
5086 0xffffe424 in __kernel_vsyscall ()
5090 Here is an example of catching a system call by name:
5093 (@value{GDBP}) catch syscall chroot
5094 Catchpoint 1 (syscall 'chroot' [61])
5096 Starting program: /tmp/catch-syscall
5098 Catchpoint 1 (call to syscall 'chroot'), \
5099 0xffffe424 in __kernel_vsyscall ()
5103 Catchpoint 1 (returned from syscall 'chroot'), \
5104 0xffffe424 in __kernel_vsyscall ()
5108 An example of specifying a system call numerically. In the case
5109 below, the syscall number has a corresponding entry in the XML
5110 file, so @value{GDBN} finds its name and prints it:
5113 (@value{GDBP}) catch syscall 252
5114 Catchpoint 1 (syscall(s) 'exit_group')
5116 Starting program: /tmp/catch-syscall
5118 Catchpoint 1 (call to syscall 'exit_group'), \
5119 0xffffe424 in __kernel_vsyscall ()
5123 Program exited normally.
5127 Here is an example of catching a syscall group:
5130 (@value{GDBP}) catch syscall group:process
5131 Catchpoint 1 (syscalls 'exit' [1] 'fork' [2] 'waitpid' [7]
5132 'execve' [11] 'wait4' [114] 'clone' [120] 'vfork' [190]
5133 'exit_group' [252] 'waitid' [284] 'unshare' [310])
5135 Starting program: /tmp/catch-syscall
5137 Catchpoint 1 (call to syscall fork), 0x00007ffff7df4e27 in open64 ()
5138 from /lib64/ld-linux-x86-64.so.2
5144 However, there can be situations when there is no corresponding name
5145 in XML file for that syscall number. In this case, @value{GDBN} prints
5146 a warning message saying that it was not able to find the syscall name,
5147 but the catchpoint will be set anyway. See the example below:
5150 (@value{GDBP}) catch syscall 764
5151 warning: The number '764' does not represent a known syscall.
5152 Catchpoint 2 (syscall 764)
5156 If you configure @value{GDBN} using the @samp{--without-expat} option,
5157 it will not be able to display syscall names. Also, if your
5158 architecture does not have an XML file describing its system calls,
5159 you will not be able to see the syscall names. It is important to
5160 notice that these two features are used for accessing the syscall
5161 name database. In either case, you will see a warning like this:
5164 (@value{GDBP}) catch syscall
5165 warning: Could not open "syscalls/i386-linux.xml"
5166 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
5167 GDB will not be able to display syscall names.
5168 Catchpoint 1 (syscall)
5172 Of course, the file name will change depending on your architecture and system.
5174 Still using the example above, you can also try to catch a syscall by its
5175 number. In this case, you would see something like:
5178 (@value{GDBP}) catch syscall 252
5179 Catchpoint 1 (syscall(s) 252)
5182 Again, in this case @value{GDBN} would not be able to display syscall's names.
5186 A call to @code{fork}.
5190 A call to @code{vfork}.
5192 @item load @r{[}@var{regexp}@r{]}
5193 @itemx unload @r{[}@var{regexp}@r{]}
5195 @kindex catch unload
5196 The loading or unloading of a shared library. If @var{regexp} is
5197 given, then the catchpoint will stop only if the regular expression
5198 matches one of the affected libraries.
5200 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5201 @kindex catch signal
5202 The delivery of a signal.
5204 With no arguments, this catchpoint will catch any signal that is not
5205 used internally by @value{GDBN}, specifically, all signals except
5206 @samp{SIGTRAP} and @samp{SIGINT}.
5208 With the argument @samp{all}, all signals, including those used by
5209 @value{GDBN}, will be caught. This argument cannot be used with other
5212 Otherwise, the arguments are a list of signal names as given to
5213 @code{handle} (@pxref{Signals}). Only signals specified in this list
5216 One reason that @code{catch signal} can be more useful than
5217 @code{handle} is that you can attach commands and conditions to the
5220 When a signal is caught by a catchpoint, the signal's @code{stop} and
5221 @code{print} settings, as specified by @code{handle}, are ignored.
5222 However, whether the signal is still delivered to the inferior depends
5223 on the @code{pass} setting; this can be changed in the catchpoint's
5228 @item tcatch @var{event}
5230 Set a catchpoint that is enabled only for one stop. The catchpoint is
5231 automatically deleted after the first time the event is caught.
5235 Use the @code{info break} command to list the current catchpoints.
5239 @subsection Deleting Breakpoints
5241 @cindex clearing breakpoints, watchpoints, catchpoints
5242 @cindex deleting breakpoints, watchpoints, catchpoints
5243 It is often necessary to eliminate a breakpoint, watchpoint, or
5244 catchpoint once it has done its job and you no longer want your program
5245 to stop there. This is called @dfn{deleting} the breakpoint. A
5246 breakpoint that has been deleted no longer exists; it is forgotten.
5248 With the @code{clear} command you can delete breakpoints according to
5249 where they are in your program. With the @code{delete} command you can
5250 delete individual breakpoints, watchpoints, or catchpoints by specifying
5251 their breakpoint numbers.
5253 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
5254 automatically ignores breakpoints on the first instruction to be executed
5255 when you continue execution without changing the execution address.
5260 Delete any breakpoints at the next instruction to be executed in the
5261 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
5262 the innermost frame is selected, this is a good way to delete a
5263 breakpoint where your program just stopped.
5265 @item clear @var{location}
5266 Delete any breakpoints set at the specified @var{location}.
5267 @xref{Specify Location}, for the various forms of @var{location}; the
5268 most useful ones are listed below:
5271 @item clear @var{function}
5272 @itemx clear @var{filename}:@var{function}
5273 Delete any breakpoints set at entry to the named @var{function}.
5275 @item clear @var{linenum}
5276 @itemx clear @var{filename}:@var{linenum}
5277 Delete any breakpoints set at or within the code of the specified
5278 @var{linenum} of the specified @var{filename}.
5281 @cindex delete breakpoints
5283 @kindex d @r{(@code{delete})}
5284 @item delete @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
5285 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
5286 list specified as argument. If no argument is specified, delete all
5287 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
5288 confirm off}). You can abbreviate this command as @code{d}.
5292 @subsection Disabling Breakpoints
5294 @cindex enable/disable a breakpoint
5295 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
5296 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
5297 it had been deleted, but remembers the information on the breakpoint so
5298 that you can @dfn{enable} it again later.
5300 You disable and enable breakpoints, watchpoints, and catchpoints with
5301 the @code{enable} and @code{disable} commands, optionally specifying
5302 one or more breakpoint numbers as arguments. Use @code{info break} to
5303 print a list of all breakpoints, watchpoints, and catchpoints if you
5304 do not know which numbers to use.
5306 Disabling and enabling a breakpoint that has multiple locations
5307 affects all of its locations.
5309 A breakpoint, watchpoint, or catchpoint can have any of several
5310 different states of enablement:
5314 Enabled. The breakpoint stops your program. A breakpoint set
5315 with the @code{break} command starts out in this state.
5317 Disabled. The breakpoint has no effect on your program.
5319 Enabled once. The breakpoint stops your program, but then becomes
5322 Enabled for a count. The breakpoint stops your program for the next
5323 N times, then becomes disabled.
5325 Enabled for deletion. The breakpoint stops your program, but
5326 immediately after it does so it is deleted permanently. A breakpoint
5327 set with the @code{tbreak} command starts out in this state.
5330 You can use the following commands to enable or disable breakpoints,
5331 watchpoints, and catchpoints:
5335 @kindex dis @r{(@code{disable})}
5336 @item disable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
5337 Disable the specified breakpoints---or all breakpoints, if none are
5338 listed. A disabled breakpoint has no effect but is not forgotten. All
5339 options such as ignore-counts, conditions and commands are remembered in
5340 case the breakpoint is enabled again later. You may abbreviate
5341 @code{disable} as @code{dis}.
5344 @item enable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
5345 Enable the specified breakpoints (or all defined breakpoints). They
5346 become effective once again in stopping your program.
5348 @item enable @r{[}breakpoints@r{]} once @var{list}@dots{}
5349 Enable the specified breakpoints temporarily. @value{GDBN} disables any
5350 of these breakpoints immediately after stopping your program.
5352 @item enable @r{[}breakpoints@r{]} count @var{count} @var{list}@dots{}
5353 Enable the specified breakpoints temporarily. @value{GDBN} records
5354 @var{count} with each of the specified breakpoints, and decrements a
5355 breakpoint's count when it is hit. When any count reaches 0,
5356 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
5357 count (@pxref{Conditions, ,Break Conditions}), that will be
5358 decremented to 0 before @var{count} is affected.
5360 @item enable @r{[}breakpoints@r{]} delete @var{list}@dots{}
5361 Enable the specified breakpoints to work once, then die. @value{GDBN}
5362 deletes any of these breakpoints as soon as your program stops there.
5363 Breakpoints set by the @code{tbreak} command start out in this state.
5366 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
5367 @c confusing: tbreak is also initially enabled.
5368 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
5369 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
5370 subsequently, they become disabled or enabled only when you use one of
5371 the commands above. (The command @code{until} can set and delete a
5372 breakpoint of its own, but it does not change the state of your other
5373 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
5377 @subsection Break Conditions
5378 @cindex conditional breakpoints
5379 @cindex breakpoint conditions
5381 @c FIXME what is scope of break condition expr? Context where wanted?
5382 @c in particular for a watchpoint?
5383 The simplest sort of breakpoint breaks every time your program reaches a
5384 specified place. You can also specify a @dfn{condition} for a
5385 breakpoint. A condition is just a Boolean expression in your
5386 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
5387 a condition evaluates the expression each time your program reaches it,
5388 and your program stops only if the condition is @emph{true}.
5390 This is the converse of using assertions for program validation; in that
5391 situation, you want to stop when the assertion is violated---that is,
5392 when the condition is false. In C, if you want to test an assertion expressed
5393 by the condition @var{assert}, you should set the condition
5394 @samp{! @var{assert}} on the appropriate breakpoint.
5396 Conditions are also accepted for watchpoints; you may not need them,
5397 since a watchpoint is inspecting the value of an expression anyhow---but
5398 it might be simpler, say, to just set a watchpoint on a variable name,
5399 and specify a condition that tests whether the new value is an interesting
5402 Break conditions can have side effects, and may even call functions in
5403 your program. This can be useful, for example, to activate functions
5404 that log program progress, or to use your own print functions to
5405 format special data structures. The effects are completely predictable
5406 unless there is another enabled breakpoint at the same address. (In
5407 that case, @value{GDBN} might see the other breakpoint first and stop your
5408 program without checking the condition of this one.) Note that
5409 breakpoint commands are usually more convenient and flexible than break
5411 purpose of performing side effects when a breakpoint is reached
5412 (@pxref{Break Commands, ,Breakpoint Command Lists}).
5414 Breakpoint conditions can also be evaluated on the target's side if
5415 the target supports it. Instead of evaluating the conditions locally,
5416 @value{GDBN} encodes the expression into an agent expression
5417 (@pxref{Agent Expressions}) suitable for execution on the target,
5418 independently of @value{GDBN}. Global variables become raw memory
5419 locations, locals become stack accesses, and so forth.
5421 In this case, @value{GDBN} will only be notified of a breakpoint trigger
5422 when its condition evaluates to true. This mechanism may provide faster
5423 response times depending on the performance characteristics of the target
5424 since it does not need to keep @value{GDBN} informed about
5425 every breakpoint trigger, even those with false conditions.
5427 Break conditions can be specified when a breakpoint is set, by using
5428 @samp{if} in the arguments to the @code{break} command. @xref{Set
5429 Breaks, ,Setting Breakpoints}. They can also be changed at any time
5430 with the @code{condition} command.
5432 You can also use the @code{if} keyword with the @code{watch} command.
5433 The @code{catch} command does not recognize the @code{if} keyword;
5434 @code{condition} is the only way to impose a further condition on a
5439 @item condition @var{bnum} @var{expression}
5440 Specify @var{expression} as the break condition for breakpoint,
5441 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
5442 breakpoint @var{bnum} stops your program only if the value of
5443 @var{expression} is true (nonzero, in C). When you use
5444 @code{condition}, @value{GDBN} checks @var{expression} immediately for
5445 syntactic correctness, and to determine whether symbols in it have
5446 referents in the context of your breakpoint. If @var{expression} uses
5447 symbols not referenced in the context of the breakpoint, @value{GDBN}
5448 prints an error message:
5451 No symbol "foo" in current context.
5456 not actually evaluate @var{expression} at the time the @code{condition}
5457 command (or a command that sets a breakpoint with a condition, like
5458 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
5460 @item condition @var{bnum}
5461 Remove the condition from breakpoint number @var{bnum}. It becomes
5462 an ordinary unconditional breakpoint.
5465 @cindex ignore count (of breakpoint)
5466 A special case of a breakpoint condition is to stop only when the
5467 breakpoint has been reached a certain number of times. This is so
5468 useful that there is a special way to do it, using the @dfn{ignore
5469 count} of the breakpoint. Every breakpoint has an ignore count, which
5470 is an integer. Most of the time, the ignore count is zero, and
5471 therefore has no effect. But if your program reaches a breakpoint whose
5472 ignore count is positive, then instead of stopping, it just decrements
5473 the ignore count by one and continues. As a result, if the ignore count
5474 value is @var{n}, the breakpoint does not stop the next @var{n} times
5475 your program reaches it.
5479 @item ignore @var{bnum} @var{count}
5480 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
5481 The next @var{count} times the breakpoint is reached, your program's
5482 execution does not stop; other than to decrement the ignore count, @value{GDBN}
5485 To make the breakpoint stop the next time it is reached, specify
5488 When you use @code{continue} to resume execution of your program from a
5489 breakpoint, you can specify an ignore count directly as an argument to
5490 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
5491 Stepping,,Continuing and Stepping}.
5493 If a breakpoint has a positive ignore count and a condition, the
5494 condition is not checked. Once the ignore count reaches zero,
5495 @value{GDBN} resumes checking the condition.
5497 You could achieve the effect of the ignore count with a condition such
5498 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
5499 is decremented each time. @xref{Convenience Vars, ,Convenience
5503 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
5506 @node Break Commands
5507 @subsection Breakpoint Command Lists
5509 @cindex breakpoint commands
5510 You can give any breakpoint (or watchpoint or catchpoint) a series of
5511 commands to execute when your program stops due to that breakpoint. For
5512 example, you might want to print the values of certain expressions, or
5513 enable other breakpoints.
5517 @kindex end@r{ (breakpoint commands)}
5518 @item commands @r{[}@var{list}@dots{}@r{]}
5519 @itemx @dots{} @var{command-list} @dots{}
5521 Specify a list of commands for the given breakpoints. The commands
5522 themselves appear on the following lines. Type a line containing just
5523 @code{end} to terminate the commands.
5525 To remove all commands from a breakpoint, type @code{commands} and
5526 follow it immediately with @code{end}; that is, give no commands.
5528 With no argument, @code{commands} refers to the last breakpoint,
5529 watchpoint, or catchpoint set (not to the breakpoint most recently
5530 encountered). If the most recent breakpoints were set with a single
5531 command, then the @code{commands} will apply to all the breakpoints
5532 set by that command. This applies to breakpoints set by
5533 @code{rbreak}, and also applies when a single @code{break} command
5534 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
5538 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
5539 disabled within a @var{command-list}.
5541 You can use breakpoint commands to start your program up again. Simply
5542 use the @code{continue} command, or @code{step}, or any other command
5543 that resumes execution.
5545 Any other commands in the command list, after a command that resumes
5546 execution, are ignored. This is because any time you resume execution
5547 (even with a simple @code{next} or @code{step}), you may encounter
5548 another breakpoint---which could have its own command list, leading to
5549 ambiguities about which list to execute.
5552 If the first command you specify in a command list is @code{silent}, the
5553 usual message about stopping at a breakpoint is not printed. This may
5554 be desirable for breakpoints that are to print a specific message and
5555 then continue. If none of the remaining commands print anything, you
5556 see no sign that the breakpoint was reached. @code{silent} is
5557 meaningful only at the beginning of a breakpoint command list.
5559 The commands @code{echo}, @code{output}, and @code{printf} allow you to
5560 print precisely controlled output, and are often useful in silent
5561 breakpoints. @xref{Output, ,Commands for Controlled Output}.
5563 For example, here is how you could use breakpoint commands to print the
5564 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
5570 printf "x is %d\n",x
5575 One application for breakpoint commands is to compensate for one bug so
5576 you can test for another. Put a breakpoint just after the erroneous line
5577 of code, give it a condition to detect the case in which something
5578 erroneous has been done, and give it commands to assign correct values
5579 to any variables that need them. End with the @code{continue} command
5580 so that your program does not stop, and start with the @code{silent}
5581 command so that no output is produced. Here is an example:
5592 @node Dynamic Printf
5593 @subsection Dynamic Printf
5595 @cindex dynamic printf
5597 The dynamic printf command @code{dprintf} combines a breakpoint with
5598 formatted printing of your program's data to give you the effect of
5599 inserting @code{printf} calls into your program on-the-fly, without
5600 having to recompile it.
5602 In its most basic form, the output goes to the GDB console. However,
5603 you can set the variable @code{dprintf-style} for alternate handling.
5604 For instance, you can ask to format the output by calling your
5605 program's @code{printf} function. This has the advantage that the
5606 characters go to the program's output device, so they can recorded in
5607 redirects to files and so forth.
5609 If you are doing remote debugging with a stub or agent, you can also
5610 ask to have the printf handled by the remote agent. In addition to
5611 ensuring that the output goes to the remote program's device along
5612 with any other output the program might produce, you can also ask that
5613 the dprintf remain active even after disconnecting from the remote
5614 target. Using the stub/agent is also more efficient, as it can do
5615 everything without needing to communicate with @value{GDBN}.
5619 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
5620 Whenever execution reaches @var{location}, print the values of one or
5621 more @var{expressions} under the control of the string @var{template}.
5622 To print several values, separate them with commas.
5624 @item set dprintf-style @var{style}
5625 Set the dprintf output to be handled in one of several different
5626 styles enumerated below. A change of style affects all existing
5627 dynamic printfs immediately. (If you need individual control over the
5628 print commands, simply define normal breakpoints with
5629 explicitly-supplied command lists.)
5633 @kindex dprintf-style gdb
5634 Handle the output using the @value{GDBN} @code{printf} command.
5637 @kindex dprintf-style call
5638 Handle the output by calling a function in your program (normally
5642 @kindex dprintf-style agent
5643 Have the remote debugging agent (such as @code{gdbserver}) handle
5644 the output itself. This style is only available for agents that
5645 support running commands on the target.
5648 @item set dprintf-function @var{function}
5649 Set the function to call if the dprintf style is @code{call}. By
5650 default its value is @code{printf}. You may set it to any expression.
5651 that @value{GDBN} can evaluate to a function, as per the @code{call}
5654 @item set dprintf-channel @var{channel}
5655 Set a ``channel'' for dprintf. If set to a non-empty value,
5656 @value{GDBN} will evaluate it as an expression and pass the result as
5657 a first argument to the @code{dprintf-function}, in the manner of
5658 @code{fprintf} and similar functions. Otherwise, the dprintf format
5659 string will be the first argument, in the manner of @code{printf}.
5661 As an example, if you wanted @code{dprintf} output to go to a logfile
5662 that is a standard I/O stream assigned to the variable @code{mylog},
5663 you could do the following:
5666 (gdb) set dprintf-style call
5667 (gdb) set dprintf-function fprintf
5668 (gdb) set dprintf-channel mylog
5669 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
5670 Dprintf 1 at 0x123456: file main.c, line 25.
5672 1 dprintf keep y 0x00123456 in main at main.c:25
5673 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
5678 Note that the @code{info break} displays the dynamic printf commands
5679 as normal breakpoint commands; you can thus easily see the effect of
5680 the variable settings.
5682 @item set disconnected-dprintf on
5683 @itemx set disconnected-dprintf off
5684 @kindex set disconnected-dprintf
5685 Choose whether @code{dprintf} commands should continue to run if
5686 @value{GDBN} has disconnected from the target. This only applies
5687 if the @code{dprintf-style} is @code{agent}.
5689 @item show disconnected-dprintf off
5690 @kindex show disconnected-dprintf
5691 Show the current choice for disconnected @code{dprintf}.
5695 @value{GDBN} does not check the validity of function and channel,
5696 relying on you to supply values that are meaningful for the contexts
5697 in which they are being used. For instance, the function and channel
5698 may be the values of local variables, but if that is the case, then
5699 all enabled dynamic prints must be at locations within the scope of
5700 those locals. If evaluation fails, @value{GDBN} will report an error.
5702 @node Save Breakpoints
5703 @subsection How to save breakpoints to a file
5705 To save breakpoint definitions to a file use the @w{@code{save
5706 breakpoints}} command.
5709 @kindex save breakpoints
5710 @cindex save breakpoints to a file for future sessions
5711 @item save breakpoints [@var{filename}]
5712 This command saves all current breakpoint definitions together with
5713 their commands and ignore counts, into a file @file{@var{filename}}
5714 suitable for use in a later debugging session. This includes all
5715 types of breakpoints (breakpoints, watchpoints, catchpoints,
5716 tracepoints). To read the saved breakpoint definitions, use the
5717 @code{source} command (@pxref{Command Files}). Note that watchpoints
5718 with expressions involving local variables may fail to be recreated
5719 because it may not be possible to access the context where the
5720 watchpoint is valid anymore. Because the saved breakpoint definitions
5721 are simply a sequence of @value{GDBN} commands that recreate the
5722 breakpoints, you can edit the file in your favorite editing program,
5723 and remove the breakpoint definitions you're not interested in, or
5724 that can no longer be recreated.
5727 @node Static Probe Points
5728 @subsection Static Probe Points
5730 @cindex static probe point, SystemTap
5731 @cindex static probe point, DTrace
5732 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
5733 for Statically Defined Tracing, and the probes are designed to have a tiny
5734 runtime code and data footprint, and no dynamic relocations.
5736 Currently, the following types of probes are supported on
5737 ELF-compatible systems:
5741 @item @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
5742 @acronym{SDT} probes@footnote{See
5743 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
5744 for more information on how to add @code{SystemTap} @acronym{SDT}
5745 probes in your applications.}. @code{SystemTap} probes are usable
5746 from assembly, C and C@t{++} languages@footnote{See
5747 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
5748 for a good reference on how the @acronym{SDT} probes are implemented.}.
5750 @item @code{DTrace} (@uref{http://oss.oracle.com/projects/DTrace})
5751 @acronym{USDT} probes. @code{DTrace} probes are usable from C and
5755 @cindex semaphores on static probe points
5756 Some @code{SystemTap} probes have an associated semaphore variable;
5757 for instance, this happens automatically if you defined your probe
5758 using a DTrace-style @file{.d} file. If your probe has a semaphore,
5759 @value{GDBN} will automatically enable it when you specify a
5760 breakpoint using the @samp{-probe-stap} notation. But, if you put a
5761 breakpoint at a probe's location by some other method (e.g.,
5762 @code{break file:line}), then @value{GDBN} will not automatically set
5763 the semaphore. @code{DTrace} probes do not support semaphores.
5765 You can examine the available static static probes using @code{info
5766 probes}, with optional arguments:
5770 @item info probes @r{[}@var{type}@r{]} @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5771 If given, @var{type} is either @code{stap} for listing
5772 @code{SystemTap} probes or @code{dtrace} for listing @code{DTrace}
5773 probes. If omitted all probes are listed regardless of their types.
5775 If given, @var{provider} is a regular expression used to match against provider
5776 names when selecting which probes to list. If omitted, probes by all
5777 probes from all providers are listed.
5779 If given, @var{name} is a regular expression to match against probe names
5780 when selecting which probes to list. If omitted, probe names are not
5781 considered when deciding whether to display them.
5783 If given, @var{objfile} is a regular expression used to select which
5784 object files (executable or shared libraries) to examine. If not
5785 given, all object files are considered.
5787 @item info probes all
5788 List the available static probes, from all types.
5791 @cindex enabling and disabling probes
5792 Some probe points can be enabled and/or disabled. The effect of
5793 enabling or disabling a probe depends on the type of probe being
5794 handled. Some @code{DTrace} probes can be enabled or
5795 disabled, but @code{SystemTap} probes cannot be disabled.
5797 You can enable (or disable) one or more probes using the following
5798 commands, with optional arguments:
5801 @kindex enable probes
5802 @item enable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5803 If given, @var{provider} is a regular expression used to match against
5804 provider names when selecting which probes to enable. If omitted,
5805 all probes from all providers are enabled.
5807 If given, @var{name} is a regular expression to match against probe
5808 names when selecting which probes to enable. If omitted, probe names
5809 are not considered when deciding whether to enable them.
5811 If given, @var{objfile} is a regular expression used to select which
5812 object files (executable or shared libraries) to examine. If not
5813 given, all object files are considered.
5815 @kindex disable probes
5816 @item disable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5817 See the @code{enable probes} command above for a description of the
5818 optional arguments accepted by this command.
5821 @vindex $_probe_arg@r{, convenience variable}
5822 A probe may specify up to twelve arguments. These are available at the
5823 point at which the probe is defined---that is, when the current PC is
5824 at the probe's location. The arguments are available using the
5825 convenience variables (@pxref{Convenience Vars})
5826 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. In @code{SystemTap}
5827 probes each probe argument is an integer of the appropriate size;
5828 types are not preserved. In @code{DTrace} probes types are preserved
5829 provided that they are recognized as such by @value{GDBN}; otherwise
5830 the value of the probe argument will be a long integer. The
5831 convenience variable @code{$_probe_argc} holds the number of arguments
5832 at the current probe point.
5834 These variables are always available, but attempts to access them at
5835 any location other than a probe point will cause @value{GDBN} to give
5839 @c @ifclear BARETARGET
5840 @node Error in Breakpoints
5841 @subsection ``Cannot insert breakpoints''
5843 If you request too many active hardware-assisted breakpoints and
5844 watchpoints, you will see this error message:
5846 @c FIXME: the precise wording of this message may change; the relevant
5847 @c source change is not committed yet (Sep 3, 1999).
5849 Stopped; cannot insert breakpoints.
5850 You may have requested too many hardware breakpoints and watchpoints.
5854 This message is printed when you attempt to resume the program, since
5855 only then @value{GDBN} knows exactly how many hardware breakpoints and
5856 watchpoints it needs to insert.
5858 When this message is printed, you need to disable or remove some of the
5859 hardware-assisted breakpoints and watchpoints, and then continue.
5861 @node Breakpoint-related Warnings
5862 @subsection ``Breakpoint address adjusted...''
5863 @cindex breakpoint address adjusted
5865 Some processor architectures place constraints on the addresses at
5866 which breakpoints may be placed. For architectures thus constrained,
5867 @value{GDBN} will attempt to adjust the breakpoint's address to comply
5868 with the constraints dictated by the architecture.
5870 One example of such an architecture is the Fujitsu FR-V. The FR-V is
5871 a VLIW architecture in which a number of RISC-like instructions may be
5872 bundled together for parallel execution. The FR-V architecture
5873 constrains the location of a breakpoint instruction within such a
5874 bundle to the instruction with the lowest address. @value{GDBN}
5875 honors this constraint by adjusting a breakpoint's address to the
5876 first in the bundle.
5878 It is not uncommon for optimized code to have bundles which contain
5879 instructions from different source statements, thus it may happen that
5880 a breakpoint's address will be adjusted from one source statement to
5881 another. Since this adjustment may significantly alter @value{GDBN}'s
5882 breakpoint related behavior from what the user expects, a warning is
5883 printed when the breakpoint is first set and also when the breakpoint
5886 A warning like the one below is printed when setting a breakpoint
5887 that's been subject to address adjustment:
5890 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
5893 Such warnings are printed both for user settable and @value{GDBN}'s
5894 internal breakpoints. If you see one of these warnings, you should
5895 verify that a breakpoint set at the adjusted address will have the
5896 desired affect. If not, the breakpoint in question may be removed and
5897 other breakpoints may be set which will have the desired behavior.
5898 E.g., it may be sufficient to place the breakpoint at a later
5899 instruction. A conditional breakpoint may also be useful in some
5900 cases to prevent the breakpoint from triggering too often.
5902 @value{GDBN} will also issue a warning when stopping at one of these
5903 adjusted breakpoints:
5906 warning: Breakpoint 1 address previously adjusted from 0x00010414
5910 When this warning is encountered, it may be too late to take remedial
5911 action except in cases where the breakpoint is hit earlier or more
5912 frequently than expected.
5914 @node Continuing and Stepping
5915 @section Continuing and Stepping
5919 @cindex resuming execution
5920 @dfn{Continuing} means resuming program execution until your program
5921 completes normally. In contrast, @dfn{stepping} means executing just
5922 one more ``step'' of your program, where ``step'' may mean either one
5923 line of source code, or one machine instruction (depending on what
5924 particular command you use). Either when continuing or when stepping,
5925 your program may stop even sooner, due to a breakpoint or a signal. (If
5926 it stops due to a signal, you may want to use @code{handle}, or use
5927 @samp{signal 0} to resume execution (@pxref{Signals, ,Signals}),
5928 or you may step into the signal's handler (@pxref{stepping and signal
5933 @kindex c @r{(@code{continue})}
5934 @kindex fg @r{(resume foreground execution)}
5935 @item continue @r{[}@var{ignore-count}@r{]}
5936 @itemx c @r{[}@var{ignore-count}@r{]}
5937 @itemx fg @r{[}@var{ignore-count}@r{]}
5938 Resume program execution, at the address where your program last stopped;
5939 any breakpoints set at that address are bypassed. The optional argument
5940 @var{ignore-count} allows you to specify a further number of times to
5941 ignore a breakpoint at this location; its effect is like that of
5942 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
5944 The argument @var{ignore-count} is meaningful only when your program
5945 stopped due to a breakpoint. At other times, the argument to
5946 @code{continue} is ignored.
5948 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
5949 debugged program is deemed to be the foreground program) are provided
5950 purely for convenience, and have exactly the same behavior as
5954 To resume execution at a different place, you can use @code{return}
5955 (@pxref{Returning, ,Returning from a Function}) to go back to the
5956 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
5957 Different Address}) to go to an arbitrary location in your program.
5959 A typical technique for using stepping is to set a breakpoint
5960 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
5961 beginning of the function or the section of your program where a problem
5962 is believed to lie, run your program until it stops at that breakpoint,
5963 and then step through the suspect area, examining the variables that are
5964 interesting, until you see the problem happen.
5968 @kindex s @r{(@code{step})}
5970 Continue running your program until control reaches a different source
5971 line, then stop it and return control to @value{GDBN}. This command is
5972 abbreviated @code{s}.
5975 @c "without debugging information" is imprecise; actually "without line
5976 @c numbers in the debugging information". (gcc -g1 has debugging info but
5977 @c not line numbers). But it seems complex to try to make that
5978 @c distinction here.
5979 @emph{Warning:} If you use the @code{step} command while control is
5980 within a function that was compiled without debugging information,
5981 execution proceeds until control reaches a function that does have
5982 debugging information. Likewise, it will not step into a function which
5983 is compiled without debugging information. To step through functions
5984 without debugging information, use the @code{stepi} command, described
5988 The @code{step} command only stops at the first instruction of a source
5989 line. This prevents the multiple stops that could otherwise occur in
5990 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5991 to stop if a function that has debugging information is called within
5992 the line. In other words, @code{step} @emph{steps inside} any functions
5993 called within the line.
5995 Also, the @code{step} command only enters a function if there is line
5996 number information for the function. Otherwise it acts like the
5997 @code{next} command. This avoids problems when using @code{cc -gl}
5998 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5999 was any debugging information about the routine.
6001 @item step @var{count}
6002 Continue running as in @code{step}, but do so @var{count} times. If a
6003 breakpoint is reached, or a signal not related to stepping occurs before
6004 @var{count} steps, stepping stops right away.
6007 @kindex n @r{(@code{next})}
6008 @item next @r{[}@var{count}@r{]}
6009 Continue to the next source line in the current (innermost) stack frame.
6010 This is similar to @code{step}, but function calls that appear within
6011 the line of code are executed without stopping. Execution stops when
6012 control reaches a different line of code at the original stack level
6013 that was executing when you gave the @code{next} command. This command
6014 is abbreviated @code{n}.
6016 An argument @var{count} is a repeat count, as for @code{step}.
6019 @c FIX ME!! Do we delete this, or is there a way it fits in with
6020 @c the following paragraph? --- Vctoria
6022 @c @code{next} within a function that lacks debugging information acts like
6023 @c @code{step}, but any function calls appearing within the code of the
6024 @c function are executed without stopping.
6026 The @code{next} command only stops at the first instruction of a
6027 source line. This prevents multiple stops that could otherwise occur in
6028 @code{switch} statements, @code{for} loops, etc.
6030 @kindex set step-mode
6032 @cindex functions without line info, and stepping
6033 @cindex stepping into functions with no line info
6034 @itemx set step-mode on
6035 The @code{set step-mode on} command causes the @code{step} command to
6036 stop at the first instruction of a function which contains no debug line
6037 information rather than stepping over it.
6039 This is useful in cases where you may be interested in inspecting the
6040 machine instructions of a function which has no symbolic info and do not
6041 want @value{GDBN} to automatically skip over this function.
6043 @item set step-mode off
6044 Causes the @code{step} command to step over any functions which contains no
6045 debug information. This is the default.
6047 @item show step-mode
6048 Show whether @value{GDBN} will stop in or step over functions without
6049 source line debug information.
6052 @kindex fin @r{(@code{finish})}
6054 Continue running until just after function in the selected stack frame
6055 returns. Print the returned value (if any). This command can be
6056 abbreviated as @code{fin}.
6058 Contrast this with the @code{return} command (@pxref{Returning,
6059 ,Returning from a Function}).
6061 @kindex set print finish
6062 @kindex show print finish
6063 @item set print finish @r{[}on|off@r{]}
6064 @itemx show print finish
6065 By default the @code{finish} command will show the value that is
6066 returned by the function. This can be disabled using @code{set print
6067 finish off}. When disabled, the value is still entered into the value
6068 history (@pxref{Value History}), but not displayed.
6071 @kindex u @r{(@code{until})}
6072 @cindex run until specified location
6075 Continue running until a source line past the current line, in the
6076 current stack frame, is reached. This command is used to avoid single
6077 stepping through a loop more than once. It is like the @code{next}
6078 command, except that when @code{until} encounters a jump, it
6079 automatically continues execution until the program counter is greater
6080 than the address of the jump.
6082 This means that when you reach the end of a loop after single stepping
6083 though it, @code{until} makes your program continue execution until it
6084 exits the loop. In contrast, a @code{next} command at the end of a loop
6085 simply steps back to the beginning of the loop, which forces you to step
6086 through the next iteration.
6088 @code{until} always stops your program if it attempts to exit the current
6091 @code{until} may produce somewhat counterintuitive results if the order
6092 of machine code does not match the order of the source lines. For
6093 example, in the following excerpt from a debugging session, the @code{f}
6094 (@code{frame}) command shows that execution is stopped at line
6095 @code{206}; yet when we use @code{until}, we get to line @code{195}:
6099 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
6101 (@value{GDBP}) until
6102 195 for ( ; argc > 0; NEXTARG) @{
6105 This happened because, for execution efficiency, the compiler had
6106 generated code for the loop closure test at the end, rather than the
6107 start, of the loop---even though the test in a C @code{for}-loop is
6108 written before the body of the loop. The @code{until} command appeared
6109 to step back to the beginning of the loop when it advanced to this
6110 expression; however, it has not really gone to an earlier
6111 statement---not in terms of the actual machine code.
6113 @code{until} with no argument works by means of single
6114 instruction stepping, and hence is slower than @code{until} with an
6117 @item until @var{location}
6118 @itemx u @var{location}
6119 Continue running your program until either the specified @var{location} is
6120 reached, or the current stack frame returns. The location is any of
6121 the forms described in @ref{Specify Location}.
6122 This form of the command uses temporary breakpoints, and
6123 hence is quicker than @code{until} without an argument. The specified
6124 location is actually reached only if it is in the current frame. This
6125 implies that @code{until} can be used to skip over recursive function
6126 invocations. For instance in the code below, if the current location is
6127 line @code{96}, issuing @code{until 99} will execute the program up to
6128 line @code{99} in the same invocation of factorial, i.e., after the inner
6129 invocations have returned.
6132 94 int factorial (int value)
6134 96 if (value > 1) @{
6135 97 value *= factorial (value - 1);
6142 @kindex advance @var{location}
6143 @item advance @var{location}
6144 Continue running the program up to the given @var{location}. An argument is
6145 required, which should be of one of the forms described in
6146 @ref{Specify Location}.
6147 Execution will also stop upon exit from the current stack
6148 frame. This command is similar to @code{until}, but @code{advance} will
6149 not skip over recursive function calls, and the target location doesn't
6150 have to be in the same frame as the current one.
6154 @kindex si @r{(@code{stepi})}
6156 @itemx stepi @var{arg}
6158 Execute one machine instruction, then stop and return to the debugger.
6160 It is often useful to do @samp{display/i $pc} when stepping by machine
6161 instructions. This makes @value{GDBN} automatically display the next
6162 instruction to be executed, each time your program stops. @xref{Auto
6163 Display,, Automatic Display}.
6165 An argument is a repeat count, as in @code{step}.
6169 @kindex ni @r{(@code{nexti})}
6171 @itemx nexti @var{arg}
6173 Execute one machine instruction, but if it is a function call,
6174 proceed until the function returns.
6176 An argument is a repeat count, as in @code{next}.
6180 @anchor{range stepping}
6181 @cindex range stepping
6182 @cindex target-assisted range stepping
6183 By default, and if available, @value{GDBN} makes use of
6184 target-assisted @dfn{range stepping}. In other words, whenever you
6185 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
6186 tells the target to step the corresponding range of instruction
6187 addresses instead of issuing multiple single-steps. This speeds up
6188 line stepping, particularly for remote targets. Ideally, there should
6189 be no reason you would want to turn range stepping off. However, it's
6190 possible that a bug in the debug info, a bug in the remote stub (for
6191 remote targets), or even a bug in @value{GDBN} could make line
6192 stepping behave incorrectly when target-assisted range stepping is
6193 enabled. You can use the following command to turn off range stepping
6197 @kindex set range-stepping
6198 @kindex show range-stepping
6199 @item set range-stepping
6200 @itemx show range-stepping
6201 Control whether range stepping is enabled.
6203 If @code{on}, and the target supports it, @value{GDBN} tells the
6204 target to step a range of addresses itself, instead of issuing
6205 multiple single-steps. If @code{off}, @value{GDBN} always issues
6206 single-steps, even if range stepping is supported by the target. The
6207 default is @code{on}.
6211 @node Skipping Over Functions and Files
6212 @section Skipping Over Functions and Files
6213 @cindex skipping over functions and files
6215 The program you are debugging may contain some functions which are
6216 uninteresting to debug. The @code{skip} command lets you tell @value{GDBN} to
6217 skip a function, all functions in a file or a particular function in
6218 a particular file when stepping.
6220 For example, consider the following C function:
6231 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
6232 are not interested in stepping through @code{boring}. If you run @code{step}
6233 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
6234 step over both @code{foo} and @code{boring}!
6236 One solution is to @code{step} into @code{boring} and use the @code{finish}
6237 command to immediately exit it. But this can become tedious if @code{boring}
6238 is called from many places.
6240 A more flexible solution is to execute @kbd{skip boring}. This instructs
6241 @value{GDBN} never to step into @code{boring}. Now when you execute
6242 @code{step} at line 103, you'll step over @code{boring} and directly into
6245 Functions may be skipped by providing either a function name, linespec
6246 (@pxref{Specify Location}), regular expression that matches the function's
6247 name, file name or a @code{glob}-style pattern that matches the file name.
6249 On Posix systems the form of the regular expression is
6250 ``Extended Regular Expressions''. See for example @samp{man 7 regex}
6251 on @sc{gnu}/Linux systems. On non-Posix systems the form of the regular
6252 expression is whatever is provided by the @code{regcomp} function of
6253 the underlying system.
6254 See for example @samp{man 7 glob} on @sc{gnu}/Linux systems for a
6255 description of @code{glob}-style patterns.
6259 @item skip @r{[}@var{options}@r{]}
6260 The basic form of the @code{skip} command takes zero or more options
6261 that specify what to skip.
6262 The @var{options} argument is any useful combination of the following:
6265 @item -file @var{file}
6266 @itemx -fi @var{file}
6267 Functions in @var{file} will be skipped over when stepping.
6269 @item -gfile @var{file-glob-pattern}
6270 @itemx -gfi @var{file-glob-pattern}
6271 @cindex skipping over files via glob-style patterns
6272 Functions in files matching @var{file-glob-pattern} will be skipped
6276 (gdb) skip -gfi utils/*.c
6279 @item -function @var{linespec}
6280 @itemx -fu @var{linespec}
6281 Functions named by @var{linespec} or the function containing the line
6282 named by @var{linespec} will be skipped over when stepping.
6283 @xref{Specify Location}.
6285 @item -rfunction @var{regexp}
6286 @itemx -rfu @var{regexp}
6287 @cindex skipping over functions via regular expressions
6288 Functions whose name matches @var{regexp} will be skipped over when stepping.
6290 This form is useful for complex function names.
6291 For example, there is generally no need to step into C@t{++} @code{std::string}
6292 constructors or destructors. Plus with C@t{++} templates it can be hard to
6293 write out the full name of the function, and often it doesn't matter what
6294 the template arguments are. Specifying the function to be skipped as a
6295 regular expression makes this easier.
6298 (gdb) skip -rfu ^std::(allocator|basic_string)<.*>::~?\1 *\(
6301 If you want to skip every templated C@t{++} constructor and destructor
6302 in the @code{std} namespace you can do:
6305 (gdb) skip -rfu ^std::([a-zA-z0-9_]+)<.*>::~?\1 *\(
6309 If no options are specified, the function you're currently debugging
6312 @kindex skip function
6313 @item skip function @r{[}@var{linespec}@r{]}
6314 After running this command, the function named by @var{linespec} or the
6315 function containing the line named by @var{linespec} will be skipped over when
6316 stepping. @xref{Specify Location}.
6318 If you do not specify @var{linespec}, the function you're currently debugging
6321 (If you have a function called @code{file} that you want to skip, use
6322 @kbd{skip function file}.)
6325 @item skip file @r{[}@var{filename}@r{]}
6326 After running this command, any function whose source lives in @var{filename}
6327 will be skipped over when stepping.
6330 (gdb) skip file boring.c
6331 File boring.c will be skipped when stepping.
6334 If you do not specify @var{filename}, functions whose source lives in the file
6335 you're currently debugging will be skipped.
6338 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
6339 These are the commands for managing your list of skips:
6343 @item info skip @r{[}@var{range}@r{]}
6344 Print details about the specified skip(s). If @var{range} is not specified,
6345 print a table with details about all functions and files marked for skipping.
6346 @code{info skip} prints the following information about each skip:
6350 A number identifying this skip.
6351 @item Enabled or Disabled
6352 Enabled skips are marked with @samp{y}.
6353 Disabled skips are marked with @samp{n}.
6355 If the file name is a @samp{glob} pattern this is @samp{y}.
6356 Otherwise it is @samp{n}.
6358 The name or @samp{glob} pattern of the file to be skipped.
6359 If no file is specified this is @samp{<none>}.
6361 If the function name is a @samp{regular expression} this is @samp{y}.
6362 Otherwise it is @samp{n}.
6364 The name or regular expression of the function to skip.
6365 If no function is specified this is @samp{<none>}.
6369 @item skip delete @r{[}@var{range}@r{]}
6370 Delete the specified skip(s). If @var{range} is not specified, delete all
6374 @item skip enable @r{[}@var{range}@r{]}
6375 Enable the specified skip(s). If @var{range} is not specified, enable all
6378 @kindex skip disable
6379 @item skip disable @r{[}@var{range}@r{]}
6380 Disable the specified skip(s). If @var{range} is not specified, disable all
6383 @kindex set debug skip
6384 @item set debug skip @r{[}on|off@r{]}
6385 Set whether to print the debug output about skipping files and functions.
6387 @kindex show debug skip
6388 @item show debug skip
6389 Show whether the debug output about skipping files and functions is printed.
6397 A signal is an asynchronous event that can happen in a program. The
6398 operating system defines the possible kinds of signals, and gives each
6399 kind a name and a number. For example, in Unix @code{SIGINT} is the
6400 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
6401 @code{SIGSEGV} is the signal a program gets from referencing a place in
6402 memory far away from all the areas in use; @code{SIGALRM} occurs when
6403 the alarm clock timer goes off (which happens only if your program has
6404 requested an alarm).
6406 @cindex fatal signals
6407 Some signals, including @code{SIGALRM}, are a normal part of the
6408 functioning of your program. Others, such as @code{SIGSEGV}, indicate
6409 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
6410 program has not specified in advance some other way to handle the signal.
6411 @code{SIGINT} does not indicate an error in your program, but it is normally
6412 fatal so it can carry out the purpose of the interrupt: to kill the program.
6414 @value{GDBN} has the ability to detect any occurrence of a signal in your
6415 program. You can tell @value{GDBN} in advance what to do for each kind of
6418 @cindex handling signals
6419 Normally, @value{GDBN} is set up to let the non-erroneous signals like
6420 @code{SIGALRM} be silently passed to your program
6421 (so as not to interfere with their role in the program's functioning)
6422 but to stop your program immediately whenever an error signal happens.
6423 You can change these settings with the @code{handle} command.
6426 @kindex info signals
6430 Print a table of all the kinds of signals and how @value{GDBN} has been told to
6431 handle each one. You can use this to see the signal numbers of all
6432 the defined types of signals.
6434 @item info signals @var{sig}
6435 Similar, but print information only about the specified signal number.
6437 @code{info handle} is an alias for @code{info signals}.
6439 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
6440 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
6441 for details about this command.
6444 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
6445 Change the way @value{GDBN} handles signal @var{signal}. The @var{signal}
6446 can be the number of a signal or its name (with or without the
6447 @samp{SIG} at the beginning); a list of signal numbers of the form
6448 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
6449 known signals. Optional arguments @var{keywords}, described below,
6450 say what change to make.
6454 The keywords allowed by the @code{handle} command can be abbreviated.
6455 Their full names are:
6459 @value{GDBN} should not stop your program when this signal happens. It may
6460 still print a message telling you that the signal has come in.
6463 @value{GDBN} should stop your program when this signal happens. This implies
6464 the @code{print} keyword as well.
6467 @value{GDBN} should print a message when this signal happens.
6470 @value{GDBN} should not mention the occurrence of the signal at all. This
6471 implies the @code{nostop} keyword as well.
6475 @value{GDBN} should allow your program to see this signal; your program
6476 can handle the signal, or else it may terminate if the signal is fatal
6477 and not handled. @code{pass} and @code{noignore} are synonyms.
6481 @value{GDBN} should not allow your program to see this signal.
6482 @code{nopass} and @code{ignore} are synonyms.
6486 When a signal stops your program, the signal is not visible to the
6488 continue. Your program sees the signal then, if @code{pass} is in
6489 effect for the signal in question @emph{at that time}. In other words,
6490 after @value{GDBN} reports a signal, you can use the @code{handle}
6491 command with @code{pass} or @code{nopass} to control whether your
6492 program sees that signal when you continue.
6494 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
6495 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
6496 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
6499 You can also use the @code{signal} command to prevent your program from
6500 seeing a signal, or cause it to see a signal it normally would not see,
6501 or to give it any signal at any time. For example, if your program stopped
6502 due to some sort of memory reference error, you might store correct
6503 values into the erroneous variables and continue, hoping to see more
6504 execution; but your program would probably terminate immediately as
6505 a result of the fatal signal once it saw the signal. To prevent this,
6506 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
6509 @cindex stepping and signal handlers
6510 @anchor{stepping and signal handlers}
6512 @value{GDBN} optimizes for stepping the mainline code. If a signal
6513 that has @code{handle nostop} and @code{handle pass} set arrives while
6514 a stepping command (e.g., @code{stepi}, @code{step}, @code{next}) is
6515 in progress, @value{GDBN} lets the signal handler run and then resumes
6516 stepping the mainline code once the signal handler returns. In other
6517 words, @value{GDBN} steps over the signal handler. This prevents
6518 signals that you've specified as not interesting (with @code{handle
6519 nostop}) from changing the focus of debugging unexpectedly. Note that
6520 the signal handler itself may still hit a breakpoint, stop for another
6521 signal that has @code{handle stop} in effect, or for any other event
6522 that normally results in stopping the stepping command sooner. Also
6523 note that @value{GDBN} still informs you that the program received a
6524 signal if @code{handle print} is set.
6526 @anchor{stepping into signal handlers}
6528 If you set @code{handle pass} for a signal, and your program sets up a
6529 handler for it, then issuing a stepping command, such as @code{step}
6530 or @code{stepi}, when your program is stopped due to the signal will
6531 step @emph{into} the signal handler (if the target supports that).
6533 Likewise, if you use the @code{queue-signal} command to queue a signal
6534 to be delivered to the current thread when execution of the thread
6535 resumes (@pxref{Signaling, ,Giving your Program a Signal}), then a
6536 stepping command will step into the signal handler.
6538 Here's an example, using @code{stepi} to step to the first instruction
6539 of @code{SIGUSR1}'s handler:
6542 (@value{GDBP}) handle SIGUSR1
6543 Signal Stop Print Pass to program Description
6544 SIGUSR1 Yes Yes Yes User defined signal 1
6548 Program received signal SIGUSR1, User defined signal 1.
6549 main () sigusr1.c:28
6552 sigusr1_handler () at sigusr1.c:9
6556 The same, but using @code{queue-signal} instead of waiting for the
6557 program to receive the signal first:
6562 (@value{GDBP}) queue-signal SIGUSR1
6564 sigusr1_handler () at sigusr1.c:9
6569 @cindex extra signal information
6570 @anchor{extra signal information}
6572 On some targets, @value{GDBN} can inspect extra signal information
6573 associated with the intercepted signal, before it is actually
6574 delivered to the program being debugged. This information is exported
6575 by the convenience variable @code{$_siginfo}, and consists of data
6576 that is passed by the kernel to the signal handler at the time of the
6577 receipt of a signal. The data type of the information itself is
6578 target dependent. You can see the data type using the @code{ptype
6579 $_siginfo} command. On Unix systems, it typically corresponds to the
6580 standard @code{siginfo_t} type, as defined in the @file{signal.h}
6583 Here's an example, on a @sc{gnu}/Linux system, printing the stray
6584 referenced address that raised a segmentation fault.
6588 (@value{GDBP}) continue
6589 Program received signal SIGSEGV, Segmentation fault.
6590 0x0000000000400766 in main ()
6592 (@value{GDBP}) ptype $_siginfo
6599 struct @{...@} _kill;
6600 struct @{...@} _timer;
6602 struct @{...@} _sigchld;
6603 struct @{...@} _sigfault;
6604 struct @{...@} _sigpoll;
6607 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
6611 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
6612 $1 = (void *) 0x7ffff7ff7000
6616 Depending on target support, @code{$_siginfo} may also be writable.
6618 @cindex Intel MPX boundary violations
6619 @cindex boundary violations, Intel MPX
6620 On some targets, a @code{SIGSEGV} can be caused by a boundary
6621 violation, i.e., accessing an address outside of the allowed range.
6622 In those cases @value{GDBN} may displays additional information,
6623 depending on how @value{GDBN} has been told to handle the signal.
6624 With @code{handle stop SIGSEGV}, @value{GDBN} displays the violation
6625 kind: "Upper" or "Lower", the memory address accessed and the
6626 bounds, while with @code{handle nostop SIGSEGV} no additional
6627 information is displayed.
6629 The usual output of a segfault is:
6631 Program received signal SIGSEGV, Segmentation fault
6632 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6633 68 value = *(p + len);
6636 While a bound violation is presented as:
6638 Program received signal SIGSEGV, Segmentation fault
6639 Upper bound violation while accessing address 0x7fffffffc3b3
6640 Bounds: [lower = 0x7fffffffc390, upper = 0x7fffffffc3a3]
6641 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6642 68 value = *(p + len);
6646 @section Stopping and Starting Multi-thread Programs
6648 @cindex stopped threads
6649 @cindex threads, stopped
6651 @cindex continuing threads
6652 @cindex threads, continuing
6654 @value{GDBN} supports debugging programs with multiple threads
6655 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
6656 are two modes of controlling execution of your program within the
6657 debugger. In the default mode, referred to as @dfn{all-stop mode},
6658 when any thread in your program stops (for example, at a breakpoint
6659 or while being stepped), all other threads in the program are also stopped by
6660 @value{GDBN}. On some targets, @value{GDBN} also supports
6661 @dfn{non-stop mode}, in which other threads can continue to run freely while
6662 you examine the stopped thread in the debugger.
6665 * All-Stop Mode:: All threads stop when GDB takes control
6666 * Non-Stop Mode:: Other threads continue to execute
6667 * Background Execution:: Running your program asynchronously
6668 * Thread-Specific Breakpoints:: Controlling breakpoints
6669 * Interrupted System Calls:: GDB may interfere with system calls
6670 * Observer Mode:: GDB does not alter program behavior
6674 @subsection All-Stop Mode
6676 @cindex all-stop mode
6678 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
6679 @emph{all} threads of execution stop, not just the current thread. This
6680 allows you to examine the overall state of the program, including
6681 switching between threads, without worrying that things may change
6684 Conversely, whenever you restart the program, @emph{all} threads start
6685 executing. @emph{This is true even when single-stepping} with commands
6686 like @code{step} or @code{next}.
6688 In particular, @value{GDBN} cannot single-step all threads in lockstep.
6689 Since thread scheduling is up to your debugging target's operating
6690 system (not controlled by @value{GDBN}), other threads may
6691 execute more than one statement while the current thread completes a
6692 single step. Moreover, in general other threads stop in the middle of a
6693 statement, rather than at a clean statement boundary, when the program
6696 You might even find your program stopped in another thread after
6697 continuing or even single-stepping. This happens whenever some other
6698 thread runs into a breakpoint, a signal, or an exception before the
6699 first thread completes whatever you requested.
6701 @cindex automatic thread selection
6702 @cindex switching threads automatically
6703 @cindex threads, automatic switching
6704 Whenever @value{GDBN} stops your program, due to a breakpoint or a
6705 signal, it automatically selects the thread where that breakpoint or
6706 signal happened. @value{GDBN} alerts you to the context switch with a
6707 message such as @samp{[Switching to Thread @var{n}]} to identify the
6710 On some OSes, you can modify @value{GDBN}'s default behavior by
6711 locking the OS scheduler to allow only a single thread to run.
6714 @item set scheduler-locking @var{mode}
6715 @cindex scheduler locking mode
6716 @cindex lock scheduler
6717 Set the scheduler locking mode. It applies to normal execution,
6718 record mode, and replay mode. If it is @code{off}, then there is no
6719 locking and any thread may run at any time. If @code{on}, then only
6720 the current thread may run when the inferior is resumed. The
6721 @code{step} mode optimizes for single-stepping; it prevents other
6722 threads from preempting the current thread while you are stepping, so
6723 that the focus of debugging does not change unexpectedly. Other
6724 threads never get a chance to run when you step, and they are
6725 completely free to run when you use commands like @samp{continue},
6726 @samp{until}, or @samp{finish}. However, unless another thread hits a
6727 breakpoint during its timeslice, @value{GDBN} does not change the
6728 current thread away from the thread that you are debugging. The
6729 @code{replay} mode behaves like @code{off} in record mode and like
6730 @code{on} in replay mode.
6732 @item show scheduler-locking
6733 Display the current scheduler locking mode.
6736 @cindex resume threads of multiple processes simultaneously
6737 By default, when you issue one of the execution commands such as
6738 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
6739 threads of the current inferior to run. For example, if @value{GDBN}
6740 is attached to two inferiors, each with two threads, the
6741 @code{continue} command resumes only the two threads of the current
6742 inferior. This is useful, for example, when you debug a program that
6743 forks and you want to hold the parent stopped (so that, for instance,
6744 it doesn't run to exit), while you debug the child. In other
6745 situations, you may not be interested in inspecting the current state
6746 of any of the processes @value{GDBN} is attached to, and you may want
6747 to resume them all until some breakpoint is hit. In the latter case,
6748 you can instruct @value{GDBN} to allow all threads of all the
6749 inferiors to run with the @w{@code{set schedule-multiple}} command.
6752 @kindex set schedule-multiple
6753 @item set schedule-multiple
6754 Set the mode for allowing threads of multiple processes to be resumed
6755 when an execution command is issued. When @code{on}, all threads of
6756 all processes are allowed to run. When @code{off}, only the threads
6757 of the current process are resumed. The default is @code{off}. The
6758 @code{scheduler-locking} mode takes precedence when set to @code{on},
6759 or while you are stepping and set to @code{step}.
6761 @item show schedule-multiple
6762 Display the current mode for resuming the execution of threads of
6767 @subsection Non-Stop Mode
6769 @cindex non-stop mode
6771 @c This section is really only a place-holder, and needs to be expanded
6772 @c with more details.
6774 For some multi-threaded targets, @value{GDBN} supports an optional
6775 mode of operation in which you can examine stopped program threads in
6776 the debugger while other threads continue to execute freely. This
6777 minimizes intrusion when debugging live systems, such as programs
6778 where some threads have real-time constraints or must continue to
6779 respond to external events. This is referred to as @dfn{non-stop} mode.
6781 In non-stop mode, when a thread stops to report a debugging event,
6782 @emph{only} that thread is stopped; @value{GDBN} does not stop other
6783 threads as well, in contrast to the all-stop mode behavior. Additionally,
6784 execution commands such as @code{continue} and @code{step} apply by default
6785 only to the current thread in non-stop mode, rather than all threads as
6786 in all-stop mode. This allows you to control threads explicitly in
6787 ways that are not possible in all-stop mode --- for example, stepping
6788 one thread while allowing others to run freely, stepping
6789 one thread while holding all others stopped, or stepping several threads
6790 independently and simultaneously.
6792 To enter non-stop mode, use this sequence of commands before you run
6793 or attach to your program:
6796 # If using the CLI, pagination breaks non-stop.
6799 # Finally, turn it on!
6803 You can use these commands to manipulate the non-stop mode setting:
6806 @kindex set non-stop
6807 @item set non-stop on
6808 Enable selection of non-stop mode.
6809 @item set non-stop off
6810 Disable selection of non-stop mode.
6811 @kindex show non-stop
6813 Show the current non-stop enablement setting.
6816 Note these commands only reflect whether non-stop mode is enabled,
6817 not whether the currently-executing program is being run in non-stop mode.
6818 In particular, the @code{set non-stop} preference is only consulted when
6819 @value{GDBN} starts or connects to the target program, and it is generally
6820 not possible to switch modes once debugging has started. Furthermore,
6821 since not all targets support non-stop mode, even when you have enabled
6822 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
6825 In non-stop mode, all execution commands apply only to the current thread
6826 by default. That is, @code{continue} only continues one thread.
6827 To continue all threads, issue @code{continue -a} or @code{c -a}.
6829 You can use @value{GDBN}'s background execution commands
6830 (@pxref{Background Execution}) to run some threads in the background
6831 while you continue to examine or step others from @value{GDBN}.
6832 The MI execution commands (@pxref{GDB/MI Program Execution}) are
6833 always executed asynchronously in non-stop mode.
6835 Suspending execution is done with the @code{interrupt} command when
6836 running in the background, or @kbd{Ctrl-c} during foreground execution.
6837 In all-stop mode, this stops the whole process;
6838 but in non-stop mode the interrupt applies only to the current thread.
6839 To stop the whole program, use @code{interrupt -a}.
6841 Other execution commands do not currently support the @code{-a} option.
6843 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
6844 that thread current, as it does in all-stop mode. This is because the
6845 thread stop notifications are asynchronous with respect to @value{GDBN}'s
6846 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
6847 changed to a different thread just as you entered a command to operate on the
6848 previously current thread.
6850 @node Background Execution
6851 @subsection Background Execution
6853 @cindex foreground execution
6854 @cindex background execution
6855 @cindex asynchronous execution
6856 @cindex execution, foreground, background and asynchronous
6858 @value{GDBN}'s execution commands have two variants: the normal
6859 foreground (synchronous) behavior, and a background
6860 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
6861 the program to report that some thread has stopped before prompting for
6862 another command. In background execution, @value{GDBN} immediately gives
6863 a command prompt so that you can issue other commands while your program runs.
6865 If the target doesn't support async mode, @value{GDBN} issues an error
6866 message if you attempt to use the background execution commands.
6868 @cindex @code{&}, background execution of commands
6869 To specify background execution, add a @code{&} to the command. For example,
6870 the background form of the @code{continue} command is @code{continue&}, or
6871 just @code{c&}. The execution commands that accept background execution
6877 @xref{Starting, , Starting your Program}.
6881 @xref{Attach, , Debugging an Already-running Process}.
6885 @xref{Continuing and Stepping, step}.
6889 @xref{Continuing and Stepping, stepi}.
6893 @xref{Continuing and Stepping, next}.
6897 @xref{Continuing and Stepping, nexti}.
6901 @xref{Continuing and Stepping, continue}.
6905 @xref{Continuing and Stepping, finish}.
6909 @xref{Continuing and Stepping, until}.
6913 Background execution is especially useful in conjunction with non-stop
6914 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
6915 However, you can also use these commands in the normal all-stop mode with
6916 the restriction that you cannot issue another execution command until the
6917 previous one finishes. Examples of commands that are valid in all-stop
6918 mode while the program is running include @code{help} and @code{info break}.
6920 You can interrupt your program while it is running in the background by
6921 using the @code{interrupt} command.
6928 Suspend execution of the running program. In all-stop mode,
6929 @code{interrupt} stops the whole process, but in non-stop mode, it stops
6930 only the current thread. To stop the whole program in non-stop mode,
6931 use @code{interrupt -a}.
6934 @node Thread-Specific Breakpoints
6935 @subsection Thread-Specific Breakpoints
6937 When your program has multiple threads (@pxref{Threads,, Debugging
6938 Programs with Multiple Threads}), you can choose whether to set
6939 breakpoints on all threads, or on a particular thread.
6942 @cindex breakpoints and threads
6943 @cindex thread breakpoints
6944 @kindex break @dots{} thread @var{thread-id}
6945 @item break @var{location} thread @var{thread-id}
6946 @itemx break @var{location} thread @var{thread-id} if @dots{}
6947 @var{location} specifies source lines; there are several ways of
6948 writing them (@pxref{Specify Location}), but the effect is always to
6949 specify some source line.
6951 Use the qualifier @samp{thread @var{thread-id}} with a breakpoint command
6952 to specify that you only want @value{GDBN} to stop the program when a
6953 particular thread reaches this breakpoint. The @var{thread-id} specifier
6954 is one of the thread identifiers assigned by @value{GDBN}, shown
6955 in the first column of the @samp{info threads} display.
6957 If you do not specify @samp{thread @var{thread-id}} when you set a
6958 breakpoint, the breakpoint applies to @emph{all} threads of your
6961 You can use the @code{thread} qualifier on conditional breakpoints as
6962 well; in this case, place @samp{thread @var{thread-id}} before or
6963 after the breakpoint condition, like this:
6966 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
6971 Thread-specific breakpoints are automatically deleted when
6972 @value{GDBN} detects the corresponding thread is no longer in the
6973 thread list. For example:
6977 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
6980 There are several ways for a thread to disappear, such as a regular
6981 thread exit, but also when you detach from the process with the
6982 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
6983 Process}), or if @value{GDBN} loses the remote connection
6984 (@pxref{Remote Debugging}), etc. Note that with some targets,
6985 @value{GDBN} is only able to detect a thread has exited when the user
6986 explictly asks for the thread list with the @code{info threads}
6989 @node Interrupted System Calls
6990 @subsection Interrupted System Calls
6992 @cindex thread breakpoints and system calls
6993 @cindex system calls and thread breakpoints
6994 @cindex premature return from system calls
6995 There is an unfortunate side effect when using @value{GDBN} to debug
6996 multi-threaded programs. If one thread stops for a
6997 breakpoint, or for some other reason, and another thread is blocked in a
6998 system call, then the system call may return prematurely. This is a
6999 consequence of the interaction between multiple threads and the signals
7000 that @value{GDBN} uses to implement breakpoints and other events that
7003 To handle this problem, your program should check the return value of
7004 each system call and react appropriately. This is good programming
7007 For example, do not write code like this:
7013 The call to @code{sleep} will return early if a different thread stops
7014 at a breakpoint or for some other reason.
7016 Instead, write this:
7021 unslept = sleep (unslept);
7024 A system call is allowed to return early, so the system is still
7025 conforming to its specification. But @value{GDBN} does cause your
7026 multi-threaded program to behave differently than it would without
7029 Also, @value{GDBN} uses internal breakpoints in the thread library to
7030 monitor certain events such as thread creation and thread destruction.
7031 When such an event happens, a system call in another thread may return
7032 prematurely, even though your program does not appear to stop.
7035 @subsection Observer Mode
7037 If you want to build on non-stop mode and observe program behavior
7038 without any chance of disruption by @value{GDBN}, you can set
7039 variables to disable all of the debugger's attempts to modify state,
7040 whether by writing memory, inserting breakpoints, etc. These operate
7041 at a low level, intercepting operations from all commands.
7043 When all of these are set to @code{off}, then @value{GDBN} is said to
7044 be @dfn{observer mode}. As a convenience, the variable
7045 @code{observer} can be set to disable these, plus enable non-stop
7048 Note that @value{GDBN} will not prevent you from making nonsensical
7049 combinations of these settings. For instance, if you have enabled
7050 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
7051 then breakpoints that work by writing trap instructions into the code
7052 stream will still not be able to be placed.
7057 @item set observer on
7058 @itemx set observer off
7059 When set to @code{on}, this disables all the permission variables
7060 below (except for @code{insert-fast-tracepoints}), plus enables
7061 non-stop debugging. Setting this to @code{off} switches back to
7062 normal debugging, though remaining in non-stop mode.
7065 Show whether observer mode is on or off.
7067 @kindex may-write-registers
7068 @item set may-write-registers on
7069 @itemx set may-write-registers off
7070 This controls whether @value{GDBN} will attempt to alter the values of
7071 registers, such as with assignment expressions in @code{print}, or the
7072 @code{jump} command. It defaults to @code{on}.
7074 @item show may-write-registers
7075 Show the current permission to write registers.
7077 @kindex may-write-memory
7078 @item set may-write-memory on
7079 @itemx set may-write-memory off
7080 This controls whether @value{GDBN} will attempt to alter the contents
7081 of memory, such as with assignment expressions in @code{print}. It
7082 defaults to @code{on}.
7084 @item show may-write-memory
7085 Show the current permission to write memory.
7087 @kindex may-insert-breakpoints
7088 @item set may-insert-breakpoints on
7089 @itemx set may-insert-breakpoints off
7090 This controls whether @value{GDBN} will attempt to insert breakpoints.
7091 This affects all breakpoints, including internal breakpoints defined
7092 by @value{GDBN}. It defaults to @code{on}.
7094 @item show may-insert-breakpoints
7095 Show the current permission to insert breakpoints.
7097 @kindex may-insert-tracepoints
7098 @item set may-insert-tracepoints on
7099 @itemx set may-insert-tracepoints off
7100 This controls whether @value{GDBN} will attempt to insert (regular)
7101 tracepoints at the beginning of a tracing experiment. It affects only
7102 non-fast tracepoints, fast tracepoints being under the control of
7103 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
7105 @item show may-insert-tracepoints
7106 Show the current permission to insert tracepoints.
7108 @kindex may-insert-fast-tracepoints
7109 @item set may-insert-fast-tracepoints on
7110 @itemx set may-insert-fast-tracepoints off
7111 This controls whether @value{GDBN} will attempt to insert fast
7112 tracepoints at the beginning of a tracing experiment. It affects only
7113 fast tracepoints, regular (non-fast) tracepoints being under the
7114 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
7116 @item show may-insert-fast-tracepoints
7117 Show the current permission to insert fast tracepoints.
7119 @kindex may-interrupt
7120 @item set may-interrupt on
7121 @itemx set may-interrupt off
7122 This controls whether @value{GDBN} will attempt to interrupt or stop
7123 program execution. When this variable is @code{off}, the
7124 @code{interrupt} command will have no effect, nor will
7125 @kbd{Ctrl-c}. It defaults to @code{on}.
7127 @item show may-interrupt
7128 Show the current permission to interrupt or stop the program.
7132 @node Reverse Execution
7133 @chapter Running programs backward
7134 @cindex reverse execution
7135 @cindex running programs backward
7137 When you are debugging a program, it is not unusual to realize that
7138 you have gone too far, and some event of interest has already happened.
7139 If the target environment supports it, @value{GDBN} can allow you to
7140 ``rewind'' the program by running it backward.
7142 A target environment that supports reverse execution should be able
7143 to ``undo'' the changes in machine state that have taken place as the
7144 program was executing normally. Variables, registers etc.@: should
7145 revert to their previous values. Obviously this requires a great
7146 deal of sophistication on the part of the target environment; not
7147 all target environments can support reverse execution.
7149 When a program is executed in reverse, the instructions that
7150 have most recently been executed are ``un-executed'', in reverse
7151 order. The program counter runs backward, following the previous
7152 thread of execution in reverse. As each instruction is ``un-executed'',
7153 the values of memory and/or registers that were changed by that
7154 instruction are reverted to their previous states. After executing
7155 a piece of source code in reverse, all side effects of that code
7156 should be ``undone'', and all variables should be returned to their
7157 prior values@footnote{
7158 Note that some side effects are easier to undo than others. For instance,
7159 memory and registers are relatively easy, but device I/O is hard. Some
7160 targets may be able undo things like device I/O, and some may not.
7162 The contract between @value{GDBN} and the reverse executing target
7163 requires only that the target do something reasonable when
7164 @value{GDBN} tells it to execute backwards, and then report the
7165 results back to @value{GDBN}. Whatever the target reports back to
7166 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
7167 assumes that the memory and registers that the target reports are in a
7168 consistent state, but @value{GDBN} accepts whatever it is given.
7171 On some platforms, @value{GDBN} has built-in support for reverse
7172 execution, activated with the @code{record} or @code{record btrace}
7173 commands. @xref{Process Record and Replay}. Some remote targets,
7174 typically full system emulators, support reverse execution directly
7175 without requiring any special command.
7177 If you are debugging in a target environment that supports
7178 reverse execution, @value{GDBN} provides the following commands.
7181 @kindex reverse-continue
7182 @kindex rc @r{(@code{reverse-continue})}
7183 @item reverse-continue @r{[}@var{ignore-count}@r{]}
7184 @itemx rc @r{[}@var{ignore-count}@r{]}
7185 Beginning at the point where your program last stopped, start executing
7186 in reverse. Reverse execution will stop for breakpoints and synchronous
7187 exceptions (signals), just like normal execution. Behavior of
7188 asynchronous signals depends on the target environment.
7190 @kindex reverse-step
7191 @kindex rs @r{(@code{step})}
7192 @item reverse-step @r{[}@var{count}@r{]}
7193 Run the program backward until control reaches the start of a
7194 different source line; then stop it, and return control to @value{GDBN}.
7196 Like the @code{step} command, @code{reverse-step} will only stop
7197 at the beginning of a source line. It ``un-executes'' the previously
7198 executed source line. If the previous source line included calls to
7199 debuggable functions, @code{reverse-step} will step (backward) into
7200 the called function, stopping at the beginning of the @emph{last}
7201 statement in the called function (typically a return statement).
7203 Also, as with the @code{step} command, if non-debuggable functions are
7204 called, @code{reverse-step} will run thru them backward without stopping.
7206 @kindex reverse-stepi
7207 @kindex rsi @r{(@code{reverse-stepi})}
7208 @item reverse-stepi @r{[}@var{count}@r{]}
7209 Reverse-execute one machine instruction. Note that the instruction
7210 to be reverse-executed is @emph{not} the one pointed to by the program
7211 counter, but the instruction executed prior to that one. For instance,
7212 if the last instruction was a jump, @code{reverse-stepi} will take you
7213 back from the destination of the jump to the jump instruction itself.
7215 @kindex reverse-next
7216 @kindex rn @r{(@code{reverse-next})}
7217 @item reverse-next @r{[}@var{count}@r{]}
7218 Run backward to the beginning of the previous line executed in
7219 the current (innermost) stack frame. If the line contains function
7220 calls, they will be ``un-executed'' without stopping. Starting from
7221 the first line of a function, @code{reverse-next} will take you back
7222 to the caller of that function, @emph{before} the function was called,
7223 just as the normal @code{next} command would take you from the last
7224 line of a function back to its return to its caller
7225 @footnote{Unless the code is too heavily optimized.}.
7227 @kindex reverse-nexti
7228 @kindex rni @r{(@code{reverse-nexti})}
7229 @item reverse-nexti @r{[}@var{count}@r{]}
7230 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
7231 in reverse, except that called functions are ``un-executed'' atomically.
7232 That is, if the previously executed instruction was a return from
7233 another function, @code{reverse-nexti} will continue to execute
7234 in reverse until the call to that function (from the current stack
7237 @kindex reverse-finish
7238 @item reverse-finish
7239 Just as the @code{finish} command takes you to the point where the
7240 current function returns, @code{reverse-finish} takes you to the point
7241 where it was called. Instead of ending up at the end of the current
7242 function invocation, you end up at the beginning.
7244 @kindex set exec-direction
7245 @item set exec-direction
7246 Set the direction of target execution.
7247 @item set exec-direction reverse
7248 @cindex execute forward or backward in time
7249 @value{GDBN} will perform all execution commands in reverse, until the
7250 exec-direction mode is changed to ``forward''. Affected commands include
7251 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
7252 command cannot be used in reverse mode.
7253 @item set exec-direction forward
7254 @value{GDBN} will perform all execution commands in the normal fashion.
7255 This is the default.
7259 @node Process Record and Replay
7260 @chapter Recording Inferior's Execution and Replaying It
7261 @cindex process record and replay
7262 @cindex recording inferior's execution and replaying it
7264 On some platforms, @value{GDBN} provides a special @dfn{process record
7265 and replay} target that can record a log of the process execution, and
7266 replay it later with both forward and reverse execution commands.
7269 When this target is in use, if the execution log includes the record
7270 for the next instruction, @value{GDBN} will debug in @dfn{replay
7271 mode}. In the replay mode, the inferior does not really execute code
7272 instructions. Instead, all the events that normally happen during
7273 code execution are taken from the execution log. While code is not
7274 really executed in replay mode, the values of registers (including the
7275 program counter register) and the memory of the inferior are still
7276 changed as they normally would. Their contents are taken from the
7280 If the record for the next instruction is not in the execution log,
7281 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
7282 inferior executes normally, and @value{GDBN} records the execution log
7285 The process record and replay target supports reverse execution
7286 (@pxref{Reverse Execution}), even if the platform on which the
7287 inferior runs does not. However, the reverse execution is limited in
7288 this case by the range of the instructions recorded in the execution
7289 log. In other words, reverse execution on platforms that don't
7290 support it directly can only be done in the replay mode.
7292 When debugging in the reverse direction, @value{GDBN} will work in
7293 replay mode as long as the execution log includes the record for the
7294 previous instruction; otherwise, it will work in record mode, if the
7295 platform supports reverse execution, or stop if not.
7297 Currently, process record and replay is supported on ARM, Aarch64,
7298 Moxie, PowerPC, PowerPC64, S/390, and x86 (i386/amd64) running
7299 GNU/Linux. Process record and replay can be used both when native
7300 debugging, and when remote debugging via @code{gdbserver}.
7302 For architecture environments that support process record and replay,
7303 @value{GDBN} provides the following commands:
7306 @kindex target record
7307 @kindex target record-full
7308 @kindex target record-btrace
7311 @kindex record btrace
7312 @kindex record btrace bts
7313 @kindex record btrace pt
7319 @kindex rec btrace bts
7320 @kindex rec btrace pt
7323 @item record @var{method}
7324 This command starts the process record and replay target. The
7325 recording method can be specified as parameter. Without a parameter
7326 the command uses the @code{full} recording method. The following
7327 recording methods are available:
7331 Full record/replay recording using @value{GDBN}'s software record and
7332 replay implementation. This method allows replaying and reverse
7335 @item btrace @var{format}
7336 Hardware-supported instruction recording, supported on Intel
7337 processors. This method does not record data. Further, the data is
7338 collected in a ring buffer so old data will be overwritten when the
7339 buffer is full. It allows limited reverse execution. Variables and
7340 registers are not available during reverse execution. In remote
7341 debugging, recording continues on disconnect. Recorded data can be
7342 inspected after reconnecting. The recording may be stopped using
7345 The recording format can be specified as parameter. Without a parameter
7346 the command chooses the recording format. The following recording
7347 formats are available:
7351 @cindex branch trace store
7352 Use the @dfn{Branch Trace Store} (@acronym{BTS}) recording format. In
7353 this format, the processor stores a from/to record for each executed
7354 branch in the btrace ring buffer.
7357 @cindex Intel Processor Trace
7358 Use the @dfn{Intel Processor Trace} recording format. In this
7359 format, the processor stores the execution trace in a compressed form
7360 that is afterwards decoded by @value{GDBN}.
7362 The trace can be recorded with very low overhead. The compressed
7363 trace format also allows small trace buffers to already contain a big
7364 number of instructions compared to @acronym{BTS}.
7366 Decoding the recorded execution trace, on the other hand, is more
7367 expensive than decoding @acronym{BTS} trace. This is mostly due to the
7368 increased number of instructions to process. You should increase the
7369 buffer-size with care.
7372 Not all recording formats may be available on all processors.
7375 The process record and replay target can only debug a process that is
7376 already running. Therefore, you need first to start the process with
7377 the @kbd{run} or @kbd{start} commands, and then start the recording
7378 with the @kbd{record @var{method}} command.
7380 @cindex displaced stepping, and process record and replay
7381 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
7382 will be automatically disabled when process record and replay target
7383 is started. That's because the process record and replay target
7384 doesn't support displaced stepping.
7386 @cindex non-stop mode, and process record and replay
7387 @cindex asynchronous execution, and process record and replay
7388 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
7389 the asynchronous execution mode (@pxref{Background Execution}), not
7390 all recording methods are available. The @code{full} recording method
7391 does not support these two modes.
7396 Stop the process record and replay target. When process record and
7397 replay target stops, the entire execution log will be deleted and the
7398 inferior will either be terminated, or will remain in its final state.
7400 When you stop the process record and replay target in record mode (at
7401 the end of the execution log), the inferior will be stopped at the
7402 next instruction that would have been recorded. In other words, if
7403 you record for a while and then stop recording, the inferior process
7404 will be left in the same state as if the recording never happened.
7406 On the other hand, if the process record and replay target is stopped
7407 while in replay mode (that is, not at the end of the execution log,
7408 but at some earlier point), the inferior process will become ``live''
7409 at that earlier state, and it will then be possible to continue the
7410 usual ``live'' debugging of the process from that state.
7412 When the inferior process exits, or @value{GDBN} detaches from it,
7413 process record and replay target will automatically stop itself.
7417 Go to a specific location in the execution log. There are several
7418 ways to specify the location to go to:
7421 @item record goto begin
7422 @itemx record goto start
7423 Go to the beginning of the execution log.
7425 @item record goto end
7426 Go to the end of the execution log.
7428 @item record goto @var{n}
7429 Go to instruction number @var{n} in the execution log.
7433 @item record save @var{filename}
7434 Save the execution log to a file @file{@var{filename}}.
7435 Default filename is @file{gdb_record.@var{process_id}}, where
7436 @var{process_id} is the process ID of the inferior.
7438 This command may not be available for all recording methods.
7440 @kindex record restore
7441 @item record restore @var{filename}
7442 Restore the execution log from a file @file{@var{filename}}.
7443 File must have been created with @code{record save}.
7445 @kindex set record full
7446 @item set record full insn-number-max @var{limit}
7447 @itemx set record full insn-number-max unlimited
7448 Set the limit of instructions to be recorded for the @code{full}
7449 recording method. Default value is 200000.
7451 If @var{limit} is a positive number, then @value{GDBN} will start
7452 deleting instructions from the log once the number of the record
7453 instructions becomes greater than @var{limit}. For every new recorded
7454 instruction, @value{GDBN} will delete the earliest recorded
7455 instruction to keep the number of recorded instructions at the limit.
7456 (Since deleting recorded instructions loses information, @value{GDBN}
7457 lets you control what happens when the limit is reached, by means of
7458 the @code{stop-at-limit} option, described below.)
7460 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
7461 delete recorded instructions from the execution log. The number of
7462 recorded instructions is limited only by the available memory.
7464 @kindex show record full
7465 @item show record full insn-number-max
7466 Show the limit of instructions to be recorded with the @code{full}
7469 @item set record full stop-at-limit
7470 Control the behavior of the @code{full} recording method when the
7471 number of recorded instructions reaches the limit. If ON (the
7472 default), @value{GDBN} will stop when the limit is reached for the
7473 first time and ask you whether you want to stop the inferior or
7474 continue running it and recording the execution log. If you decide
7475 to continue recording, each new recorded instruction will cause the
7476 oldest one to be deleted.
7478 If this option is OFF, @value{GDBN} will automatically delete the
7479 oldest record to make room for each new one, without asking.
7481 @item show record full stop-at-limit
7482 Show the current setting of @code{stop-at-limit}.
7484 @item set record full memory-query
7485 Control the behavior when @value{GDBN} is unable to record memory
7486 changes caused by an instruction for the @code{full} recording method.
7487 If ON, @value{GDBN} will query whether to stop the inferior in that
7490 If this option is OFF (the default), @value{GDBN} will automatically
7491 ignore the effect of such instructions on memory. Later, when
7492 @value{GDBN} replays this execution log, it will mark the log of this
7493 instruction as not accessible, and it will not affect the replay
7496 @item show record full memory-query
7497 Show the current setting of @code{memory-query}.
7499 @kindex set record btrace
7500 The @code{btrace} record target does not trace data. As a
7501 convenience, when replaying, @value{GDBN} reads read-only memory off
7502 the live program directly, assuming that the addresses of the
7503 read-only areas don't change. This for example makes it possible to
7504 disassemble code while replaying, but not to print variables.
7505 In some cases, being able to inspect variables might be useful.
7506 You can use the following command for that:
7508 @item set record btrace replay-memory-access
7509 Control the behavior of the @code{btrace} recording method when
7510 accessing memory during replay. If @code{read-only} (the default),
7511 @value{GDBN} will only allow accesses to read-only memory.
7512 If @code{read-write}, @value{GDBN} will allow accesses to read-only
7513 and to read-write memory. Beware that the accessed memory corresponds
7514 to the live target and not necessarily to the current replay
7517 @item set record btrace cpu @var{identifier}
7518 Set the processor to be used for enabling workarounds for processor
7519 errata when decoding the trace.
7521 Processor errata are defects in processor operation, caused by its
7522 design or manufacture. They can cause a trace not to match the
7523 specification. This, in turn, may cause trace decode to fail.
7524 @value{GDBN} can detect erroneous trace packets and correct them, thus
7525 avoiding the decoding failures. These corrections are known as
7526 @dfn{errata workarounds}, and are enabled based on the processor on
7527 which the trace was recorded.
7529 By default, @value{GDBN} attempts to detect the processor
7530 automatically, and apply the necessary workarounds for it. However,
7531 you may need to specify the processor if @value{GDBN} does not yet
7532 support it. This command allows you to do that, and also allows to
7533 disable the workarounds.
7535 The argument @var{identifier} identifies the @sc{cpu} and is of the
7536 form: @code{@var{vendor}:@var{processor identifier}}. In addition,
7537 there are two special identifiers, @code{none} and @code{auto}
7540 The following vendor identifiers and corresponding processor
7541 identifiers are currently supported:
7543 @multitable @columnfractions .1 .9
7546 @tab @var{family}/@var{model}[/@var{stepping}]
7550 On GNU/Linux systems, the processor @var{family}, @var{model}, and
7551 @var{stepping} can be obtained from @code{/proc/cpuinfo}.
7553 If @var{identifier} is @code{auto}, enable errata workarounds for the
7554 processor on which the trace was recorded. If @var{identifier} is
7555 @code{none}, errata workarounds are disabled.
7557 For example, when using an old @value{GDBN} on a new system, decode
7558 may fail because @value{GDBN} does not support the new processor. It
7559 often suffices to specify an older processor that @value{GDBN}
7564 Active record target: record-btrace
7565 Recording format: Intel Processor Trace.
7567 Failed to configure the Intel Processor Trace decoder: unknown cpu.
7568 (gdb) set record btrace cpu intel:6/158
7570 Active record target: record-btrace
7571 Recording format: Intel Processor Trace.
7573 Recorded 84872 instructions in 3189 functions (0 gaps) for thread 1 (...).
7576 @kindex show record btrace
7577 @item show record btrace replay-memory-access
7578 Show the current setting of @code{replay-memory-access}.
7580 @item show record btrace cpu
7581 Show the processor to be used for enabling trace decode errata
7584 @kindex set record btrace bts
7585 @item set record btrace bts buffer-size @var{size}
7586 @itemx set record btrace bts buffer-size unlimited
7587 Set the requested ring buffer size for branch tracing in @acronym{BTS}
7588 format. Default is 64KB.
7590 If @var{size} is a positive number, then @value{GDBN} will try to
7591 allocate a buffer of at least @var{size} bytes for each new thread
7592 that uses the btrace recording method and the @acronym{BTS} format.
7593 The actually obtained buffer size may differ from the requested
7594 @var{size}. Use the @code{info record} command to see the actual
7595 buffer size for each thread that uses the btrace recording method and
7596 the @acronym{BTS} format.
7598 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
7599 allocate a buffer of 4MB.
7601 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
7602 also need longer to process the branch trace data before it can be used.
7604 @item show record btrace bts buffer-size @var{size}
7605 Show the current setting of the requested ring buffer size for branch
7606 tracing in @acronym{BTS} format.
7608 @kindex set record btrace pt
7609 @item set record btrace pt buffer-size @var{size}
7610 @itemx set record btrace pt buffer-size unlimited
7611 Set the requested ring buffer size for branch tracing in Intel
7612 Processor Trace format. Default is 16KB.
7614 If @var{size} is a positive number, then @value{GDBN} will try to
7615 allocate a buffer of at least @var{size} bytes for each new thread
7616 that uses the btrace recording method and the Intel Processor Trace
7617 format. The actually obtained buffer size may differ from the
7618 requested @var{size}. Use the @code{info record} command to see the
7619 actual buffer size for each thread.
7621 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
7622 allocate a buffer of 4MB.
7624 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
7625 also need longer to process the branch trace data before it can be used.
7627 @item show record btrace pt buffer-size @var{size}
7628 Show the current setting of the requested ring buffer size for branch
7629 tracing in Intel Processor Trace format.
7633 Show various statistics about the recording depending on the recording
7638 For the @code{full} recording method, it shows the state of process
7639 record and its in-memory execution log buffer, including:
7643 Whether in record mode or replay mode.
7645 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
7647 Highest recorded instruction number.
7649 Current instruction about to be replayed (if in replay mode).
7651 Number of instructions contained in the execution log.
7653 Maximum number of instructions that may be contained in the execution log.
7657 For the @code{btrace} recording method, it shows:
7663 Number of instructions that have been recorded.
7665 Number of blocks of sequential control-flow formed by the recorded
7668 Whether in record mode or replay mode.
7671 For the @code{bts} recording format, it also shows:
7674 Size of the perf ring buffer.
7677 For the @code{pt} recording format, it also shows:
7680 Size of the perf ring buffer.
7684 @kindex record delete
7687 When record target runs in replay mode (``in the past''), delete the
7688 subsequent execution log and begin to record a new execution log starting
7689 from the current address. This means you will abandon the previously
7690 recorded ``future'' and begin recording a new ``future''.
7692 @kindex record instruction-history
7693 @kindex rec instruction-history
7694 @item record instruction-history
7695 Disassembles instructions from the recorded execution log. By
7696 default, ten instructions are disassembled. This can be changed using
7697 the @code{set record instruction-history-size} command. Instructions
7698 are printed in execution order.
7700 It can also print mixed source+disassembly if you specify the the
7701 @code{/m} or @code{/s} modifier, and print the raw instructions in hex
7702 as well as in symbolic form by specifying the @code{/r} modifier.
7704 The current position marker is printed for the instruction at the
7705 current program counter value. This instruction can appear multiple
7706 times in the trace and the current position marker will be printed
7707 every time. To omit the current position marker, specify the
7710 To better align the printed instructions when the trace contains
7711 instructions from more than one function, the function name may be
7712 omitted by specifying the @code{/f} modifier.
7714 Speculatively executed instructions are prefixed with @samp{?}. This
7715 feature is not available for all recording formats.
7717 There are several ways to specify what part of the execution log to
7721 @item record instruction-history @var{insn}
7722 Disassembles ten instructions starting from instruction number
7725 @item record instruction-history @var{insn}, +/-@var{n}
7726 Disassembles @var{n} instructions around instruction number
7727 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
7728 @var{n} instructions after instruction number @var{insn}. If
7729 @var{n} is preceded with @code{-}, disassembles @var{n}
7730 instructions before instruction number @var{insn}.
7732 @item record instruction-history
7733 Disassembles ten more instructions after the last disassembly.
7735 @item record instruction-history -
7736 Disassembles ten more instructions before the last disassembly.
7738 @item record instruction-history @var{begin}, @var{end}
7739 Disassembles instructions beginning with instruction number
7740 @var{begin} until instruction number @var{end}. The instruction
7741 number @var{end} is included.
7744 This command may not be available for all recording methods.
7747 @item set record instruction-history-size @var{size}
7748 @itemx set record instruction-history-size unlimited
7749 Define how many instructions to disassemble in the @code{record
7750 instruction-history} command. The default value is 10.
7751 A @var{size} of @code{unlimited} means unlimited instructions.
7754 @item show record instruction-history-size
7755 Show how many instructions to disassemble in the @code{record
7756 instruction-history} command.
7758 @kindex record function-call-history
7759 @kindex rec function-call-history
7760 @item record function-call-history
7761 Prints the execution history at function granularity. It prints one
7762 line for each sequence of instructions that belong to the same
7763 function giving the name of that function, the source lines
7764 for this instruction sequence (if the @code{/l} modifier is
7765 specified), and the instructions numbers that form the sequence (if
7766 the @code{/i} modifier is specified). The function names are indented
7767 to reflect the call stack depth if the @code{/c} modifier is
7768 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be
7772 (@value{GDBP}) @b{list 1, 10}
7783 (@value{GDBP}) @b{record function-call-history /ilc}
7784 1 bar inst 1,4 at foo.c:6,8
7785 2 foo inst 5,10 at foo.c:2,3
7786 3 bar inst 11,13 at foo.c:9,10
7789 By default, ten lines are printed. This can be changed using the
7790 @code{set record function-call-history-size} command. Functions are
7791 printed in execution order. There are several ways to specify what
7795 @item record function-call-history @var{func}
7796 Prints ten functions starting from function number @var{func}.
7798 @item record function-call-history @var{func}, +/-@var{n}
7799 Prints @var{n} functions around function number @var{func}. If
7800 @var{n} is preceded with @code{+}, prints @var{n} functions after
7801 function number @var{func}. If @var{n} is preceded with @code{-},
7802 prints @var{n} functions before function number @var{func}.
7804 @item record function-call-history
7805 Prints ten more functions after the last ten-line print.
7807 @item record function-call-history -
7808 Prints ten more functions before the last ten-line print.
7810 @item record function-call-history @var{begin}, @var{end}
7811 Prints functions beginning with function number @var{begin} until
7812 function number @var{end}. The function number @var{end} is included.
7815 This command may not be available for all recording methods.
7817 @item set record function-call-history-size @var{size}
7818 @itemx set record function-call-history-size unlimited
7819 Define how many lines to print in the
7820 @code{record function-call-history} command. The default value is 10.
7821 A size of @code{unlimited} means unlimited lines.
7823 @item show record function-call-history-size
7824 Show how many lines to print in the
7825 @code{record function-call-history} command.
7830 @chapter Examining the Stack
7832 When your program has stopped, the first thing you need to know is where it
7833 stopped and how it got there.
7836 Each time your program performs a function call, information about the call
7838 That information includes the location of the call in your program,
7839 the arguments of the call,
7840 and the local variables of the function being called.
7841 The information is saved in a block of data called a @dfn{stack frame}.
7842 The stack frames are allocated in a region of memory called the @dfn{call
7845 When your program stops, the @value{GDBN} commands for examining the
7846 stack allow you to see all of this information.
7848 @cindex selected frame
7849 One of the stack frames is @dfn{selected} by @value{GDBN} and many
7850 @value{GDBN} commands refer implicitly to the selected frame. In
7851 particular, whenever you ask @value{GDBN} for the value of a variable in
7852 your program, the value is found in the selected frame. There are
7853 special @value{GDBN} commands to select whichever frame you are
7854 interested in. @xref{Selection, ,Selecting a Frame}.
7856 When your program stops, @value{GDBN} automatically selects the
7857 currently executing frame and describes it briefly, similar to the
7858 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
7861 * Frames:: Stack frames
7862 * Backtrace:: Backtraces
7863 * Selection:: Selecting a frame
7864 * Frame Info:: Information on a frame
7865 * Frame Apply:: Applying a command to several frames
7866 * Frame Filter Management:: Managing frame filters
7871 @section Stack Frames
7873 @cindex frame, definition
7875 The call stack is divided up into contiguous pieces called @dfn{stack
7876 frames}, or @dfn{frames} for short; each frame is the data associated
7877 with one call to one function. The frame contains the arguments given
7878 to the function, the function's local variables, and the address at
7879 which the function is executing.
7881 @cindex initial frame
7882 @cindex outermost frame
7883 @cindex innermost frame
7884 When your program is started, the stack has only one frame, that of the
7885 function @code{main}. This is called the @dfn{initial} frame or the
7886 @dfn{outermost} frame. Each time a function is called, a new frame is
7887 made. Each time a function returns, the frame for that function invocation
7888 is eliminated. If a function is recursive, there can be many frames for
7889 the same function. The frame for the function in which execution is
7890 actually occurring is called the @dfn{innermost} frame. This is the most
7891 recently created of all the stack frames that still exist.
7893 @cindex frame pointer
7894 Inside your program, stack frames are identified by their addresses. A
7895 stack frame consists of many bytes, each of which has its own address; each
7896 kind of computer has a convention for choosing one byte whose
7897 address serves as the address of the frame. Usually this address is kept
7898 in a register called the @dfn{frame pointer register}
7899 (@pxref{Registers, $fp}) while execution is going on in that frame.
7902 @cindex frame number
7903 @value{GDBN} labels each existing stack frame with a @dfn{level}, a
7904 number that is zero for the innermost frame, one for the frame that
7905 called it, and so on upward. These level numbers give you a way of
7906 designating stack frames in @value{GDBN} commands. The terms
7907 @dfn{frame number} and @dfn{frame level} can be used interchangeably to
7908 describe this number.
7910 @c The -fomit-frame-pointer below perennially causes hbox overflow
7911 @c underflow problems.
7912 @cindex frameless execution
7913 Some compilers provide a way to compile functions so that they operate
7914 without stack frames. (For example, the @value{NGCC} option
7916 @samp{-fomit-frame-pointer}
7918 generates functions without a frame.)
7919 This is occasionally done with heavily used library functions to save
7920 the frame setup time. @value{GDBN} has limited facilities for dealing
7921 with these function invocations. If the innermost function invocation
7922 has no stack frame, @value{GDBN} nevertheless regards it as though
7923 it had a separate frame, which is numbered zero as usual, allowing
7924 correct tracing of the function call chain. However, @value{GDBN} has
7925 no provision for frameless functions elsewhere in the stack.
7931 @cindex call stack traces
7932 A backtrace is a summary of how your program got where it is. It shows one
7933 line per frame, for many frames, starting with the currently executing
7934 frame (frame zero), followed by its caller (frame one), and on up the
7937 @anchor{backtrace-command}
7939 @kindex bt @r{(@code{backtrace})}
7940 To print a backtrace of the entire stack, use the @code{backtrace}
7941 command, or its alias @code{bt}. This command will print one line per
7942 frame for frames in the stack. By default, all stack frames are
7943 printed. You can stop the backtrace at any time by typing the system
7944 interrupt character, normally @kbd{Ctrl-c}.
7947 @item backtrace [@var{option}]@dots{} [@var{qualifier}]@dots{} [@var{count}]
7948 @itemx bt [@var{option}]@dots{} [@var{qualifier}]@dots{} [@var{count}]
7949 Print the backtrace of the entire stack.
7951 The optional @var{count} can be one of the following:
7956 Print only the innermost @var{n} frames, where @var{n} is a positive
7961 Print only the outermost @var{n} frames, where @var{n} is a positive
7969 Print the values of the local variables also. This can be combined
7970 with the optional @var{count} to limit the number of frames shown.
7973 Do not run Python frame filters on this backtrace. @xref{Frame
7974 Filter API}, for more information. Additionally use @ref{disable
7975 frame-filter all} to turn off all frame filters. This is only
7976 relevant when @value{GDBN} has been configured with @code{Python}
7980 A Python frame filter might decide to ``elide'' some frames. Normally
7981 such elided frames are still printed, but they are indented relative
7982 to the filtered frames that cause them to be elided. The @code{-hide}
7983 option causes elided frames to not be printed at all.
7986 The @code{backtrace} command also supports a number of options that
7987 allow overriding relevant global print settings as set by @code{set
7988 backtrace} and @code{set print} subcommands:
7991 @item -past-main [@code{on}|@code{off}]
7992 Set whether backtraces should continue past @code{main}. Related setting:
7993 @ref{set backtrace past-main}.
7995 @item -past-entry [@code{on}|@code{off}]
7996 Set whether backtraces should continue past the entry point of a program.
7997 Related setting: @ref{set backtrace past-entry}.
7999 @item -entry-values @code{no}|@code{only}|@code{preferred}|@code{if-needed}|@code{both}|@code{compact}|@code{default}
8000 Set printing of function arguments at function entry.
8001 Related setting: @ref{set print entry-values}.
8003 @item -frame-arguments @code{all}|@code{scalars}|@code{none}
8004 Set printing of non-scalar frame arguments.
8005 Related setting: @ref{set print frame-arguments}.
8007 @item -raw-frame-arguments [@code{on}|@code{off}]
8008 Set whether to print frame arguments in raw form.
8009 Related setting: @ref{set print raw-frame-arguments}.
8011 @item -frame-info @code{auto}|@code{source-line}|@code{location}|@code{source-and-location}|@code{location-and-address}|@code{short-location}
8012 Set printing of frame information.
8013 Related setting: @ref{set print frame-info}.
8016 The optional @var{qualifier} is maintained for backward compatibility.
8017 It can be one of the following:
8021 Equivalent to the @code{-full} option.
8024 Equivalent to the @code{-no-filters} option.
8027 Equivalent to the @code{-hide} option.
8034 The names @code{where} and @code{info stack} (abbreviated @code{info s})
8035 are additional aliases for @code{backtrace}.
8037 @cindex multiple threads, backtrace
8038 In a multi-threaded program, @value{GDBN} by default shows the
8039 backtrace only for the current thread. To display the backtrace for
8040 several or all of the threads, use the command @code{thread apply}
8041 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
8042 apply all backtrace}, @value{GDBN} will display the backtrace for all
8043 the threads; this is handy when you debug a core dump of a
8044 multi-threaded program.
8046 Each line in the backtrace shows the frame number and the function name.
8047 The program counter value is also shown---unless you use @code{set
8048 print address off}. The backtrace also shows the source file name and
8049 line number, as well as the arguments to the function. The program
8050 counter value is omitted if it is at the beginning of the code for that
8053 Here is an example of a backtrace. It was made with the command
8054 @samp{bt 3}, so it shows the innermost three frames.
8058 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
8060 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
8061 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
8063 (More stack frames follow...)
8068 The display for frame zero does not begin with a program counter
8069 value, indicating that your program has stopped at the beginning of the
8070 code for line @code{993} of @code{builtin.c}.
8073 The value of parameter @code{data} in frame 1 has been replaced by
8074 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
8075 only if it is a scalar (integer, pointer, enumeration, etc). See command
8076 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
8077 on how to configure the way function parameter values are printed.
8078 The command @kbd{set print frame-info} (@pxref{Print Settings}) controls
8079 what frame information is printed.
8081 @cindex optimized out, in backtrace
8082 @cindex function call arguments, optimized out
8083 If your program was compiled with optimizations, some compilers will
8084 optimize away arguments passed to functions if those arguments are
8085 never used after the call. Such optimizations generate code that
8086 passes arguments through registers, but doesn't store those arguments
8087 in the stack frame. @value{GDBN} has no way of displaying such
8088 arguments in stack frames other than the innermost one. Here's what
8089 such a backtrace might look like:
8093 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
8095 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
8096 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
8098 (More stack frames follow...)
8103 The values of arguments that were not saved in their stack frames are
8104 shown as @samp{<optimized out>}.
8106 If you need to display the values of such optimized-out arguments,
8107 either deduce that from other variables whose values depend on the one
8108 you are interested in, or recompile without optimizations.
8110 @cindex backtrace beyond @code{main} function
8111 @cindex program entry point
8112 @cindex startup code, and backtrace
8113 Most programs have a standard user entry point---a place where system
8114 libraries and startup code transition into user code. For C this is
8115 @code{main}@footnote{
8116 Note that embedded programs (the so-called ``free-standing''
8117 environment) are not required to have a @code{main} function as the
8118 entry point. They could even have multiple entry points.}.
8119 When @value{GDBN} finds the entry function in a backtrace
8120 it will terminate the backtrace, to avoid tracing into highly
8121 system-specific (and generally uninteresting) code.
8123 If you need to examine the startup code, or limit the number of levels
8124 in a backtrace, you can change this behavior:
8127 @item set backtrace past-main
8128 @itemx set backtrace past-main on
8129 @anchor{set backtrace past-main}
8130 @kindex set backtrace
8131 Backtraces will continue past the user entry point.
8133 @item set backtrace past-main off
8134 Backtraces will stop when they encounter the user entry point. This is the
8137 @item show backtrace past-main
8138 @kindex show backtrace
8139 Display the current user entry point backtrace policy.
8141 @item set backtrace past-entry
8142 @itemx set backtrace past-entry on
8143 @anchor{set backtrace past-entry}
8144 Backtraces will continue past the internal entry point of an application.
8145 This entry point is encoded by the linker when the application is built,
8146 and is likely before the user entry point @code{main} (or equivalent) is called.
8148 @item set backtrace past-entry off
8149 Backtraces will stop when they encounter the internal entry point of an
8150 application. This is the default.
8152 @item show backtrace past-entry
8153 Display the current internal entry point backtrace policy.
8155 @item set backtrace limit @var{n}
8156 @itemx set backtrace limit 0
8157 @itemx set backtrace limit unlimited
8158 @anchor{set backtrace limit}
8159 @cindex backtrace limit
8160 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
8161 or zero means unlimited levels.
8163 @item show backtrace limit
8164 Display the current limit on backtrace levels.
8167 You can control how file names are displayed.
8170 @item set filename-display
8171 @itemx set filename-display relative
8172 @cindex filename-display
8173 Display file names relative to the compilation directory. This is the default.
8175 @item set filename-display basename
8176 Display only basename of a filename.
8178 @item set filename-display absolute
8179 Display an absolute filename.
8181 @item show filename-display
8182 Show the current way to display filenames.
8186 @section Selecting a Frame
8188 Most commands for examining the stack and other data in your program work on
8189 whichever stack frame is selected at the moment. Here are the commands for
8190 selecting a stack frame; all of them finish by printing a brief description
8191 of the stack frame just selected.
8194 @kindex frame@r{, selecting}
8195 @kindex f @r{(@code{frame})}
8196 @item frame @r{[} @var{frame-selection-spec} @r{]}
8197 @item f @r{[} @var{frame-selection-spec} @r{]}
8198 The @command{frame} command allows different stack frames to be
8199 selected. The @var{frame-selection-spec} can be any of the following:
8204 @item level @var{num}
8205 Select frame level @var{num}. Recall that frame zero is the innermost
8206 (currently executing) frame, frame one is the frame that called the
8207 innermost one, and so on. The highest level frame is usually the one
8210 As this is the most common method of navigating the frame stack, the
8211 string @command{level} can be omitted. For example, the following two
8212 commands are equivalent:
8215 (@value{GDBP}) frame 3
8216 (@value{GDBP}) frame level 3
8219 @kindex frame address
8220 @item address @var{stack-address}
8221 Select the frame with stack address @var{stack-address}. The
8222 @var{stack-address} for a frame can be seen in the output of
8223 @command{info frame}, for example:
8227 Stack level 1, frame at 0x7fffffffda30:
8228 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
8229 tail call frame, caller of frame at 0x7fffffffda30
8230 source language c++.
8231 Arglist at unknown address.
8232 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
8235 The @var{stack-address} for this frame is @code{0x7fffffffda30} as
8236 indicated by the line:
8239 Stack level 1, frame at 0x7fffffffda30:
8242 @kindex frame function
8243 @item function @var{function-name}
8244 Select the stack frame for function @var{function-name}. If there are
8245 multiple stack frames for function @var{function-name} then the inner
8246 most stack frame is selected.
8249 @item view @var{stack-address} @r{[} @var{pc-addr} @r{]}
8250 View a frame that is not part of @value{GDBN}'s backtrace. The frame
8251 viewed has stack address @var{stack-addr}, and optionally, a program
8252 counter address of @var{pc-addr}.
8254 This is useful mainly if the chaining of stack frames has been
8255 damaged by a bug, making it impossible for @value{GDBN} to assign
8256 numbers properly to all frames. In addition, this can be useful
8257 when your program has multiple stacks and switches between them.
8259 When viewing a frame outside the current backtrace using
8260 @command{frame view} then you can always return to the original
8261 stack using one of the previous stack frame selection instructions,
8262 for example @command{frame level 0}.
8268 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
8269 numbers @var{n}, this advances toward the outermost frame, to higher
8270 frame numbers, to frames that have existed longer.
8273 @kindex do @r{(@code{down})}
8275 Move @var{n} frames down the stack; @var{n} defaults to 1. For
8276 positive numbers @var{n}, this advances toward the innermost frame, to
8277 lower frame numbers, to frames that were created more recently.
8278 You may abbreviate @code{down} as @code{do}.
8281 All of these commands end by printing two lines of output describing the
8282 frame. The first line shows the frame number, the function name, the
8283 arguments, and the source file and line number of execution in that
8284 frame. The second line shows the text of that source line.
8292 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
8294 10 read_input_file (argv[i]);
8298 After such a printout, the @code{list} command with no arguments
8299 prints ten lines centered on the point of execution in the frame.
8300 You can also edit the program at the point of execution with your favorite
8301 editing program by typing @code{edit}.
8302 @xref{List, ,Printing Source Lines},
8306 @kindex select-frame
8307 @item select-frame @r{[} @var{frame-selection-spec} @r{]}
8308 The @code{select-frame} command is a variant of @code{frame} that does
8309 not display the new frame after selecting it. This command is
8310 intended primarily for use in @value{GDBN} command scripts, where the
8311 output might be unnecessary and distracting. The
8312 @var{frame-selection-spec} is as for the @command{frame} command
8313 described in @ref{Selection, ,Selecting a Frame}.
8315 @kindex down-silently
8317 @item up-silently @var{n}
8318 @itemx down-silently @var{n}
8319 These two commands are variants of @code{up} and @code{down},
8320 respectively; they differ in that they do their work silently, without
8321 causing display of the new frame. They are intended primarily for use
8322 in @value{GDBN} command scripts, where the output might be unnecessary and
8327 @section Information About a Frame
8329 There are several other commands to print information about the selected
8335 When used without any argument, this command does not change which
8336 frame is selected, but prints a brief description of the currently
8337 selected stack frame. It can be abbreviated @code{f}. With an
8338 argument, this command is used to select a stack frame.
8339 @xref{Selection, ,Selecting a Frame}.
8342 @kindex info f @r{(@code{info frame})}
8345 This command prints a verbose description of the selected stack frame,
8350 the address of the frame
8352 the address of the next frame down (called by this frame)
8354 the address of the next frame up (caller of this frame)
8356 the language in which the source code corresponding to this frame is written
8358 the address of the frame's arguments
8360 the address of the frame's local variables
8362 the program counter saved in it (the address of execution in the caller frame)
8364 which registers were saved in the frame
8367 @noindent The verbose description is useful when
8368 something has gone wrong that has made the stack format fail to fit
8369 the usual conventions.
8371 @item info frame @r{[} @var{frame-selection-spec} @r{]}
8372 @itemx info f @r{[} @var{frame-selection-spec} @r{]}
8373 Print a verbose description of the frame selected by
8374 @var{frame-selection-spec}. The @var{frame-selection-spec} is the
8375 same as for the @command{frame} command (@pxref{Selection, ,Selecting
8376 a Frame}). The selected frame remains unchanged by this command.
8379 @item info args [-q]
8380 Print the arguments of the selected frame, each on a separate line.
8382 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
8383 printing header information and messages explaining why no argument
8386 @item info args [-q] [-t @var{type_regexp}] [@var{regexp}]
8387 Like @kbd{info args}, but only print the arguments selected
8388 with the provided regexp(s).
8390 If @var{regexp} is provided, print only the arguments whose names
8391 match the regular expression @var{regexp}.
8393 If @var{type_regexp} is provided, print only the arguments whose
8394 types, as printed by the @code{whatis} command, match
8395 the regular expression @var{type_regexp}.
8396 If @var{type_regexp} contains space(s), it should be enclosed in
8397 quote characters. If needed, use backslash to escape the meaning
8398 of special characters or quotes.
8400 If both @var{regexp} and @var{type_regexp} are provided, an argument
8401 is printed only if its name matches @var{regexp} and its type matches
8404 @item info locals [-q]
8406 Print the local variables of the selected frame, each on a separate
8407 line. These are all variables (declared either static or automatic)
8408 accessible at the point of execution of the selected frame.
8410 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
8411 printing header information and messages explaining why no local variables
8414 @item info locals [-q] [-t @var{type_regexp}] [@var{regexp}]
8415 Like @kbd{info locals}, but only print the local variables selected
8416 with the provided regexp(s).
8418 If @var{regexp} is provided, print only the local variables whose names
8419 match the regular expression @var{regexp}.
8421 If @var{type_regexp} is provided, print only the local variables whose
8422 types, as printed by the @code{whatis} command, match
8423 the regular expression @var{type_regexp}.
8424 If @var{type_regexp} contains space(s), it should be enclosed in
8425 quote characters. If needed, use backslash to escape the meaning
8426 of special characters or quotes.
8428 If both @var{regexp} and @var{type_regexp} are provided, a local variable
8429 is printed only if its name matches @var{regexp} and its type matches
8432 The command @kbd{info locals -q -t @var{type_regexp}} can usefully be
8433 combined with the commands @kbd{frame apply} and @kbd{thread apply}.
8434 For example, your program might use Resource Acquisition Is
8435 Initialization types (RAII) such as @code{lock_something_t}: each
8436 local variable of type @code{lock_something_t} automatically places a
8437 lock that is destroyed when the variable goes out of scope. You can
8438 then list all acquired locks in your program by doing
8440 thread apply all -s frame apply all -s info locals -q -t lock_something_t
8443 or the equivalent shorter form
8445 tfaas i lo -q -t lock_something_t
8451 @section Applying a Command to Several Frames.
8452 @anchor{frame apply}
8454 @cindex apply command to several frames
8456 @item frame apply [all | @var{count} | @var{-count} | level @var{level}@dots{}] [@var{option}]@dots{} @var{command}
8457 The @code{frame apply} command allows you to apply the named
8458 @var{command} to one or more frames.
8462 Specify @code{all} to apply @var{command} to all frames.
8465 Use @var{count} to apply @var{command} to the innermost @var{count}
8466 frames, where @var{count} is a positive number.
8469 Use @var{-count} to apply @var{command} to the outermost @var{count}
8470 frames, where @var{count} is a positive number.
8473 Use @code{level} to apply @var{command} to the set of frames identified
8474 by the @var{level} list. @var{level} is a frame level or a range of frame
8475 levels as @var{level1}-@var{level2}. The frame level is the number shown
8476 in the first field of the @samp{backtrace} command output.
8477 E.g., @samp{2-4 6-8 3} indicates to apply @var{command} for the frames
8478 at levels 2, 3, 4, 6, 7, 8, and then again on frame at level 3.
8482 Note that the frames on which @code{frame apply} applies a command are
8483 also influenced by the @code{set backtrace} settings such as @code{set
8484 backtrace past-main} and @code{set backtrace limit N}.
8485 @xref{Backtrace,,Backtraces}.
8487 The @code{frame apply} command also supports a number of options that
8488 allow overriding relevant @code{set backtrace} settings:
8491 @item -past-main [@code{on}|@code{off}]
8492 Whether backtraces should continue past @code{main}.
8493 Related setting: @ref{set backtrace past-main}.
8495 @item -past-entry [@code{on}|@code{off}]
8496 Whether backtraces should continue past the entry point of a program.
8497 Related setting: @ref{set backtrace past-entry}.
8500 By default, @value{GDBN} displays some frame information before the
8501 output produced by @var{command}, and an error raised during the
8502 execution of a @var{command} will abort @code{frame apply}. The
8503 following options can be used to fine-tune these behaviors:
8507 The flag @code{-c}, which stands for @samp{continue}, causes any
8508 errors in @var{command} to be displayed, and the execution of
8509 @code{frame apply} then continues.
8511 The flag @code{-s}, which stands for @samp{silent}, causes any errors
8512 or empty output produced by a @var{command} to be silently ignored.
8513 That is, the execution continues, but the frame information and errors
8516 The flag @code{-q} (@samp{quiet}) disables printing the frame
8520 The following example shows how the flags @code{-c} and @code{-s} are
8521 working when applying the command @code{p j} to all frames, where
8522 variable @code{j} can only be successfully printed in the outermost
8523 @code{#1 main} frame.
8527 (gdb) frame apply all p j
8528 #0 some_function (i=5) at fun.c:4
8529 No symbol "j" in current context.
8530 (gdb) frame apply all -c p j
8531 #0 some_function (i=5) at fun.c:4
8532 No symbol "j" in current context.
8533 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8535 (gdb) frame apply all -s p j
8536 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8542 By default, @samp{frame apply}, prints the frame location
8543 information before the command output:
8547 (gdb) frame apply all p $sp
8548 #0 some_function (i=5) at fun.c:4
8549 $4 = (void *) 0xffffd1e0
8550 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8551 $5 = (void *) 0xffffd1f0
8556 If the flag @code{-q} is given, no frame information is printed:
8559 (gdb) frame apply all -q p $sp
8560 $12 = (void *) 0xffffd1e0
8561 $13 = (void *) 0xffffd1f0
8571 @cindex apply a command to all frames (ignoring errors and empty output)
8572 @item faas @var{command}
8573 Shortcut for @code{frame apply all -s @var{command}}.
8574 Applies @var{command} on all frames, ignoring errors and empty output.
8576 It can for example be used to print a local variable or a function
8577 argument without knowing the frame where this variable or argument
8580 (@value{GDBP}) faas p some_local_var_i_do_not_remember_where_it_is
8583 The @code{faas} command accepts the same options as the @code{frame
8584 apply} command. @xref{frame apply}.
8586 Note that the command @code{tfaas @var{command}} applies @var{command}
8587 on all frames of all threads. See @xref{Threads,,Threads}.
8591 @node Frame Filter Management
8592 @section Management of Frame Filters.
8593 @cindex managing frame filters
8595 Frame filters are Python based utilities to manage and decorate the
8596 output of frames. @xref{Frame Filter API}, for further information.
8598 Managing frame filters is performed by several commands available
8599 within @value{GDBN}, detailed here.
8602 @kindex info frame-filter
8603 @item info frame-filter
8604 Print a list of installed frame filters from all dictionaries, showing
8605 their name, priority and enabled status.
8607 @kindex disable frame-filter
8608 @anchor{disable frame-filter all}
8609 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
8610 Disable a frame filter in the dictionary matching
8611 @var{filter-dictionary} and @var{filter-name}. The
8612 @var{filter-dictionary} may be @code{all}, @code{global},
8613 @code{progspace}, or the name of the object file where the frame filter
8614 dictionary resides. When @code{all} is specified, all frame filters
8615 across all dictionaries are disabled. The @var{filter-name} is the name
8616 of the frame filter and is used when @code{all} is not the option for
8617 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
8618 may be enabled again later.
8620 @kindex enable frame-filter
8621 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
8622 Enable a frame filter in the dictionary matching
8623 @var{filter-dictionary} and @var{filter-name}. The
8624 @var{filter-dictionary} may be @code{all}, @code{global},
8625 @code{progspace} or the name of the object file where the frame filter
8626 dictionary resides. When @code{all} is specified, all frame filters across
8627 all dictionaries are enabled. The @var{filter-name} is the name of the frame
8628 filter and is used when @code{all} is not the option for
8629 @var{filter-dictionary}.
8634 (gdb) info frame-filter
8636 global frame-filters:
8637 Priority Enabled Name
8638 1000 No PrimaryFunctionFilter
8641 progspace /build/test frame-filters:
8642 Priority Enabled Name
8643 100 Yes ProgspaceFilter
8645 objfile /build/test frame-filters:
8646 Priority Enabled Name
8647 999 Yes BuildProgramFilter
8649 (gdb) disable frame-filter /build/test BuildProgramFilter
8650 (gdb) info frame-filter
8652 global frame-filters:
8653 Priority Enabled Name
8654 1000 No PrimaryFunctionFilter
8657 progspace /build/test frame-filters:
8658 Priority Enabled Name
8659 100 Yes ProgspaceFilter
8661 objfile /build/test frame-filters:
8662 Priority Enabled Name
8663 999 No BuildProgramFilter
8665 (gdb) enable frame-filter global PrimaryFunctionFilter
8666 (gdb) info frame-filter
8668 global frame-filters:
8669 Priority Enabled Name
8670 1000 Yes PrimaryFunctionFilter
8673 progspace /build/test frame-filters:
8674 Priority Enabled Name
8675 100 Yes ProgspaceFilter
8677 objfile /build/test frame-filters:
8678 Priority Enabled Name
8679 999 No BuildProgramFilter
8682 @kindex set frame-filter priority
8683 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
8684 Set the @var{priority} of a frame filter in the dictionary matching
8685 @var{filter-dictionary}, and the frame filter name matching
8686 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
8687 @code{progspace} or the name of the object file where the frame filter
8688 dictionary resides. The @var{priority} is an integer.
8690 @kindex show frame-filter priority
8691 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
8692 Show the @var{priority} of a frame filter in the dictionary matching
8693 @var{filter-dictionary}, and the frame filter name matching
8694 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
8695 @code{progspace} or the name of the object file where the frame filter
8701 (gdb) info frame-filter
8703 global frame-filters:
8704 Priority Enabled Name
8705 1000 Yes PrimaryFunctionFilter
8708 progspace /build/test frame-filters:
8709 Priority Enabled Name
8710 100 Yes ProgspaceFilter
8712 objfile /build/test frame-filters:
8713 Priority Enabled Name
8714 999 No BuildProgramFilter
8716 (gdb) set frame-filter priority global Reverse 50
8717 (gdb) info frame-filter
8719 global frame-filters:
8720 Priority Enabled Name
8721 1000 Yes PrimaryFunctionFilter
8724 progspace /build/test frame-filters:
8725 Priority Enabled Name
8726 100 Yes ProgspaceFilter
8728 objfile /build/test frame-filters:
8729 Priority Enabled Name
8730 999 No BuildProgramFilter
8735 @chapter Examining Source Files
8737 @value{GDBN} can print parts of your program's source, since the debugging
8738 information recorded in the program tells @value{GDBN} what source files were
8739 used to build it. When your program stops, @value{GDBN} spontaneously prints
8740 the line where it stopped. Likewise, when you select a stack frame
8741 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
8742 execution in that frame has stopped. You can print other portions of
8743 source files by explicit command.
8745 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
8746 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
8747 @value{GDBN} under @sc{gnu} Emacs}.
8750 * List:: Printing source lines
8751 * Specify Location:: How to specify code locations
8752 * Edit:: Editing source files
8753 * Search:: Searching source files
8754 * Source Path:: Specifying source directories
8755 * Machine Code:: Source and machine code
8759 @section Printing Source Lines
8762 @kindex l @r{(@code{list})}
8763 To print lines from a source file, use the @code{list} command
8764 (abbreviated @code{l}). By default, ten lines are printed.
8765 There are several ways to specify what part of the file you want to
8766 print; see @ref{Specify Location}, for the full list.
8768 Here are the forms of the @code{list} command most commonly used:
8771 @item list @var{linenum}
8772 Print lines centered around line number @var{linenum} in the
8773 current source file.
8775 @item list @var{function}
8776 Print lines centered around the beginning of function
8780 Print more lines. If the last lines printed were printed with a
8781 @code{list} command, this prints lines following the last lines
8782 printed; however, if the last line printed was a solitary line printed
8783 as part of displaying a stack frame (@pxref{Stack, ,Examining the
8784 Stack}), this prints lines centered around that line.
8787 Print lines just before the lines last printed.
8790 @cindex @code{list}, how many lines to display
8791 By default, @value{GDBN} prints ten source lines with any of these forms of
8792 the @code{list} command. You can change this using @code{set listsize}:
8795 @kindex set listsize
8796 @item set listsize @var{count}
8797 @itemx set listsize unlimited
8798 Make the @code{list} command display @var{count} source lines (unless
8799 the @code{list} argument explicitly specifies some other number).
8800 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
8802 @kindex show listsize
8804 Display the number of lines that @code{list} prints.
8807 Repeating a @code{list} command with @key{RET} discards the argument,
8808 so it is equivalent to typing just @code{list}. This is more useful
8809 than listing the same lines again. An exception is made for an
8810 argument of @samp{-}; that argument is preserved in repetition so that
8811 each repetition moves up in the source file.
8813 In general, the @code{list} command expects you to supply zero, one or two
8814 @dfn{locations}. Locations specify source lines; there are several ways
8815 of writing them (@pxref{Specify Location}), but the effect is always
8816 to specify some source line.
8818 Here is a complete description of the possible arguments for @code{list}:
8821 @item list @var{location}
8822 Print lines centered around the line specified by @var{location}.
8824 @item list @var{first},@var{last}
8825 Print lines from @var{first} to @var{last}. Both arguments are
8826 locations. When a @code{list} command has two locations, and the
8827 source file of the second location is omitted, this refers to
8828 the same source file as the first location.
8830 @item list ,@var{last}
8831 Print lines ending with @var{last}.
8833 @item list @var{first},
8834 Print lines starting with @var{first}.
8837 Print lines just after the lines last printed.
8840 Print lines just before the lines last printed.
8843 As described in the preceding table.
8846 @node Specify Location
8847 @section Specifying a Location
8848 @cindex specifying location
8850 @cindex source location
8853 * Linespec Locations:: Linespec locations
8854 * Explicit Locations:: Explicit locations
8855 * Address Locations:: Address locations
8858 Several @value{GDBN} commands accept arguments that specify a location
8859 of your program's code. Since @value{GDBN} is a source-level
8860 debugger, a location usually specifies some line in the source code.
8861 Locations may be specified using three different formats:
8862 linespec locations, explicit locations, or address locations.
8864 @node Linespec Locations
8865 @subsection Linespec Locations
8866 @cindex linespec locations
8868 A @dfn{linespec} is a colon-separated list of source location parameters such
8869 as file name, function name, etc. Here are all the different ways of
8870 specifying a linespec:
8874 Specifies the line number @var{linenum} of the current source file.
8877 @itemx +@var{offset}
8878 Specifies the line @var{offset} lines before or after the @dfn{current
8879 line}. For the @code{list} command, the current line is the last one
8880 printed; for the breakpoint commands, this is the line at which
8881 execution stopped in the currently selected @dfn{stack frame}
8882 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
8883 used as the second of the two linespecs in a @code{list} command,
8884 this specifies the line @var{offset} lines up or down from the first
8887 @item @var{filename}:@var{linenum}
8888 Specifies the line @var{linenum} in the source file @var{filename}.
8889 If @var{filename} is a relative file name, then it will match any
8890 source file name with the same trailing components. For example, if
8891 @var{filename} is @samp{gcc/expr.c}, then it will match source file
8892 name of @file{/build/trunk/gcc/expr.c}, but not
8893 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
8895 @item @var{function}
8896 Specifies the line that begins the body of the function @var{function}.
8897 For example, in C, this is the line with the open brace.
8899 By default, in C@t{++} and Ada, @var{function} is interpreted as
8900 specifying all functions named @var{function} in all scopes. For
8901 C@t{++}, this means in all namespaces and classes. For Ada, this
8902 means in all packages.
8904 For example, assuming a program with C@t{++} symbols named
8905 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
8906 func}} and @w{@kbd{break B::func}} set a breakpoint on both symbols.
8908 Commands that accept a linespec let you override this with the
8909 @code{-qualified} option. For example, @w{@kbd{break -qualified
8910 func}} sets a breakpoint on a free-function named @code{func} ignoring
8911 any C@t{++} class methods and namespace functions called @code{func}.
8913 @xref{Explicit Locations}.
8915 @item @var{function}:@var{label}
8916 Specifies the line where @var{label} appears in @var{function}.
8918 @item @var{filename}:@var{function}
8919 Specifies the line that begins the body of the function @var{function}
8920 in the file @var{filename}. You only need the file name with a
8921 function name to avoid ambiguity when there are identically named
8922 functions in different source files.
8925 Specifies the line at which the label named @var{label} appears
8926 in the function corresponding to the currently selected stack frame.
8927 If there is no current selected stack frame (for instance, if the inferior
8928 is not running), then @value{GDBN} will not search for a label.
8930 @cindex breakpoint at static probe point
8931 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
8932 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
8933 applications to embed static probes. @xref{Static Probe Points}, for more
8934 information on finding and using static probes. This form of linespec
8935 specifies the location of such a static probe.
8937 If @var{objfile} is given, only probes coming from that shared library
8938 or executable matching @var{objfile} as a regular expression are considered.
8939 If @var{provider} is given, then only probes from that provider are considered.
8940 If several probes match the spec, @value{GDBN} will insert a breakpoint at
8941 each one of those probes.
8944 @node Explicit Locations
8945 @subsection Explicit Locations
8946 @cindex explicit locations
8948 @dfn{Explicit locations} allow the user to directly specify the source
8949 location's parameters using option-value pairs.
8951 Explicit locations are useful when several functions, labels, or
8952 file names have the same name (base name for files) in the program's
8953 sources. In these cases, explicit locations point to the source
8954 line you meant more accurately and unambiguously. Also, using
8955 explicit locations might be faster in large programs.
8957 For example, the linespec @samp{foo:bar} may refer to a function @code{bar}
8958 defined in the file named @file{foo} or the label @code{bar} in a function
8959 named @code{foo}. @value{GDBN} must search either the file system or
8960 the symbol table to know.
8962 The list of valid explicit location options is summarized in the
8966 @item -source @var{filename}
8967 The value specifies the source file name. To differentiate between
8968 files with the same base name, prepend as many directories as is necessary
8969 to uniquely identify the desired file, e.g., @file{foo/bar/baz.c}. Otherwise
8970 @value{GDBN} will use the first file it finds with the given base
8971 name. This option requires the use of either @code{-function} or @code{-line}.
8973 @item -function @var{function}
8974 The value specifies the name of a function. Operations
8975 on function locations unmodified by other options (such as @code{-label}
8976 or @code{-line}) refer to the line that begins the body of the function.
8977 In C, for example, this is the line with the open brace.
8979 By default, in C@t{++} and Ada, @var{function} is interpreted as
8980 specifying all functions named @var{function} in all scopes. For
8981 C@t{++}, this means in all namespaces and classes. For Ada, this
8982 means in all packages.
8984 For example, assuming a program with C@t{++} symbols named
8985 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
8986 -function func}} and @w{@kbd{break -function B::func}} set a
8987 breakpoint on both symbols.
8989 You can use the @kbd{-qualified} flag to override this (see below).
8993 This flag makes @value{GDBN} interpret a function name specified with
8994 @kbd{-function} as a complete fully-qualified name.
8996 For example, assuming a C@t{++} program with symbols named
8997 @code{A::B::func} and @code{B::func}, the @w{@kbd{break -qualified
8998 -function B::func}} command sets a breakpoint on @code{B::func}, only.
9000 (Note: the @kbd{-qualified} option can precede a linespec as well
9001 (@pxref{Linespec Locations}), so the particular example above could be
9002 simplified as @w{@kbd{break -qualified B::func}}.)
9004 @item -label @var{label}
9005 The value specifies the name of a label. When the function
9006 name is not specified, the label is searched in the function of the currently
9007 selected stack frame.
9009 @item -line @var{number}
9010 The value specifies a line offset for the location. The offset may either
9011 be absolute (@code{-line 3}) or relative (@code{-line +3}), depending on
9012 the command. When specified without any other options, the line offset is
9013 relative to the current line.
9016 Explicit location options may be abbreviated by omitting any non-unique
9017 trailing characters from the option name, e.g., @w{@kbd{break -s main.c -li 3}}.
9019 @node Address Locations
9020 @subsection Address Locations
9021 @cindex address locations
9023 @dfn{Address locations} indicate a specific program address. They have
9024 the generalized form *@var{address}.
9026 For line-oriented commands, such as @code{list} and @code{edit}, this
9027 specifies a source line that contains @var{address}. For @code{break} and
9028 other breakpoint-oriented commands, this can be used to set breakpoints in
9029 parts of your program which do not have debugging information or
9032 Here @var{address} may be any expression valid in the current working
9033 language (@pxref{Languages, working language}) that specifies a code
9034 address. In addition, as a convenience, @value{GDBN} extends the
9035 semantics of expressions used in locations to cover several situations
9036 that frequently occur during debugging. Here are the various forms
9040 @item @var{expression}
9041 Any expression valid in the current working language.
9043 @item @var{funcaddr}
9044 An address of a function or procedure derived from its name. In C,
9045 C@t{++}, Objective-C, Fortran, minimal, and assembly, this is
9046 simply the function's name @var{function} (and actually a special case
9047 of a valid expression). In Pascal and Modula-2, this is
9048 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
9049 (although the Pascal form also works).
9051 This form specifies the address of the function's first instruction,
9052 before the stack frame and arguments have been set up.
9054 @item '@var{filename}':@var{funcaddr}
9055 Like @var{funcaddr} above, but also specifies the name of the source
9056 file explicitly. This is useful if the name of the function does not
9057 specify the function unambiguously, e.g., if there are several
9058 functions with identical names in different source files.
9062 @section Editing Source Files
9063 @cindex editing source files
9066 @kindex e @r{(@code{edit})}
9067 To edit the lines in a source file, use the @code{edit} command.
9068 The editing program of your choice
9069 is invoked with the current line set to
9070 the active line in the program.
9071 Alternatively, there are several ways to specify what part of the file you
9072 want to print if you want to see other parts of the program:
9075 @item edit @var{location}
9076 Edit the source file specified by @code{location}. Editing starts at
9077 that @var{location}, e.g., at the specified source line of the
9078 specified file. @xref{Specify Location}, for all the possible forms
9079 of the @var{location} argument; here are the forms of the @code{edit}
9080 command most commonly used:
9083 @item edit @var{number}
9084 Edit the current source file with @var{number} as the active line number.
9086 @item edit @var{function}
9087 Edit the file containing @var{function} at the beginning of its definition.
9092 @subsection Choosing your Editor
9093 You can customize @value{GDBN} to use any editor you want
9095 The only restriction is that your editor (say @code{ex}), recognizes the
9096 following command-line syntax:
9098 ex +@var{number} file
9100 The optional numeric value +@var{number} specifies the number of the line in
9101 the file where to start editing.}.
9102 By default, it is @file{@value{EDITOR}}, but you can change this
9103 by setting the environment variable @code{EDITOR} before using
9104 @value{GDBN}. For example, to configure @value{GDBN} to use the
9105 @code{vi} editor, you could use these commands with the @code{sh} shell:
9111 or in the @code{csh} shell,
9113 setenv EDITOR /usr/bin/vi
9118 @section Searching Source Files
9119 @cindex searching source files
9121 There are two commands for searching through the current source file for a
9126 @kindex forward-search
9127 @kindex fo @r{(@code{forward-search})}
9128 @item forward-search @var{regexp}
9129 @itemx search @var{regexp}
9130 The command @samp{forward-search @var{regexp}} checks each line,
9131 starting with the one following the last line listed, for a match for
9132 @var{regexp}. It lists the line that is found. You can use the
9133 synonym @samp{search @var{regexp}} or abbreviate the command name as
9136 @kindex reverse-search
9137 @item reverse-search @var{regexp}
9138 The command @samp{reverse-search @var{regexp}} checks each line, starting
9139 with the one before the last line listed and going backward, for a match
9140 for @var{regexp}. It lists the line that is found. You can abbreviate
9141 this command as @code{rev}.
9145 @section Specifying Source Directories
9148 @cindex directories for source files
9149 Executable programs sometimes do not record the directories of the source
9150 files from which they were compiled, just the names. Even when they do,
9151 the directories could be moved between the compilation and your debugging
9152 session. @value{GDBN} has a list of directories to search for source files;
9153 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
9154 it tries all the directories in the list, in the order they are present
9155 in the list, until it finds a file with the desired name.
9157 For example, suppose an executable references the file
9158 @file{/usr/src/foo-1.0/lib/foo.c}, does not record a compilation
9159 directory, and the @dfn{source path} is @file{/mnt/cross}.
9160 @value{GDBN} would look for the source file in the following
9165 @item @file{/usr/src/foo-1.0/lib/foo.c}
9166 @item @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c}
9167 @item @file{/mnt/cross/foo.c}
9171 If the source file is not present at any of the above locations then
9172 an error is printed. @value{GDBN} does not look up the parts of the
9173 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
9174 Likewise, the subdirectories of the source path are not searched: if
9175 the source path is @file{/mnt/cross}, and the binary refers to
9176 @file{foo.c}, @value{GDBN} would not find it under
9177 @file{/mnt/cross/usr/src/foo-1.0/lib}.
9179 Plain file names, relative file names with leading directories, file
9180 names containing dots, etc.@: are all treated as described above,
9181 except that non-absolute file names are not looked up literally. If
9182 the @dfn{source path} is @file{/mnt/cross}, the source file is
9183 recorded as @file{../lib/foo.c}, and no compilation directory is
9184 recorded, then @value{GDBN} will search in the following locations:
9188 @item @file{/mnt/cross/../lib/foo.c}
9189 @item @file{/mnt/cross/foo.c}
9195 @vindex $cdir@r{, convenience variable}
9196 @vindex $cwd@r{, convenience variable}
9197 @cindex compilation directory
9198 @cindex current directory
9199 @cindex working directory
9200 @cindex directory, current
9201 @cindex directory, compilation
9202 The @dfn{source path} will always include two special entries
9203 @samp{$cdir} and @samp{$cwd}, these refer to the compilation directory
9204 (if one is recorded) and the current working directory respectively.
9206 @samp{$cdir} causes @value{GDBN} to search within the compilation
9207 directory, if one is recorded in the debug information. If no
9208 compilation directory is recorded in the debug information then
9209 @samp{$cdir} is ignored.
9211 @samp{$cwd} is not the same as @samp{.}---the former tracks the
9212 current working directory as it changes during your @value{GDBN}
9213 session, while the latter is immediately expanded to the current
9214 directory at the time you add an entry to the source path.
9216 If a compilation directory is recorded in the debug information, and
9217 @value{GDBN} has not found the source file after the first search
9218 using @dfn{source path}, then @value{GDBN} will combine the
9219 compilation directory and the filename, and then search for the source
9220 file again using the @dfn{source path}.
9222 For example, if the executable records the source file as
9223 @file{/usr/src/foo-1.0/lib/foo.c}, the compilation directory is
9224 recorded as @file{/project/build}, and the @dfn{source path} is
9225 @file{/mnt/cross:$cdir:$cwd} while the current working directory of
9226 the @value{GDBN} session is @file{/home/user}, then @value{GDBN} will
9227 search for the source file in the following locations:
9231 @item @file{/usr/src/foo-1.0/lib/foo.c}
9232 @item @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c}
9233 @item @file{/project/build/usr/src/foo-1.0/lib/foo.c}
9234 @item @file{/home/user/usr/src/foo-1.0/lib/foo.c}
9235 @item @file{/mnt/cross/project/build/usr/src/foo-1.0/lib/foo.c}
9236 @item @file{/project/build/project/build/usr/src/foo-1.0/lib/foo.c}
9237 @item @file{/home/user/project/build/usr/src/foo-1.0/lib/foo.c}
9238 @item @file{/mnt/cross/foo.c}
9239 @item @file{/project/build/foo.c}
9240 @item @file{/home/user/foo.c}
9244 If the file name in the previous example had been recorded in the
9245 executable as a relative path rather than an absolute path, then the
9246 first look up would not have occurred, but all of the remaining steps
9249 When searching for source files on MS-DOS and MS-Windows, where
9250 absolute paths start with a drive letter (e.g.
9251 @file{C:/project/foo.c}), @value{GDBN} will remove the drive letter
9252 from the file name before appending it to a search directory from
9253 @dfn{source path}; for instance if the executable references the
9254 source file @file{C:/project/foo.c} and @dfn{source path} is set to
9255 @file{D:/mnt/cross}, then @value{GDBN} will search in the following
9256 locations for the source file:
9260 @item @file{C:/project/foo.c}
9261 @item @file{D:/mnt/cross/project/foo.c}
9262 @item @file{D:/mnt/cross/foo.c}
9266 Note that the executable search path is @emph{not} used to locate the
9269 Whenever you reset or rearrange the source path, @value{GDBN} clears out
9270 any information it has cached about where source files are found and where
9271 each line is in the file.
9275 When you start @value{GDBN}, its source path includes only @samp{$cdir}
9276 and @samp{$cwd}, in that order.
9277 To add other directories, use the @code{directory} command.
9279 The search path is used to find both program source files and @value{GDBN}
9280 script files (read using the @samp{-command} option and @samp{source} command).
9282 In addition to the source path, @value{GDBN} provides a set of commands
9283 that manage a list of source path substitution rules. A @dfn{substitution
9284 rule} specifies how to rewrite source directories stored in the program's
9285 debug information in case the sources were moved to a different
9286 directory between compilation and debugging. A rule is made of
9287 two strings, the first specifying what needs to be rewritten in
9288 the path, and the second specifying how it should be rewritten.
9289 In @ref{set substitute-path}, we name these two parts @var{from} and
9290 @var{to} respectively. @value{GDBN} does a simple string replacement
9291 of @var{from} with @var{to} at the start of the directory part of the
9292 source file name, and uses that result instead of the original file
9293 name to look up the sources.
9295 Using the previous example, suppose the @file{foo-1.0} tree has been
9296 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
9297 @value{GDBN} to replace @file{/usr/src} in all source path names with
9298 @file{/mnt/cross}. The first lookup will then be
9299 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
9300 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
9301 substitution rule, use the @code{set substitute-path} command
9302 (@pxref{set substitute-path}).
9304 To avoid unexpected substitution results, a rule is applied only if the
9305 @var{from} part of the directory name ends at a directory separator.
9306 For instance, a rule substituting @file{/usr/source} into
9307 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
9308 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
9309 is applied only at the beginning of the directory name, this rule will
9310 not be applied to @file{/root/usr/source/baz.c} either.
9312 In many cases, you can achieve the same result using the @code{directory}
9313 command. However, @code{set substitute-path} can be more efficient in
9314 the case where the sources are organized in a complex tree with multiple
9315 subdirectories. With the @code{directory} command, you need to add each
9316 subdirectory of your project. If you moved the entire tree while
9317 preserving its internal organization, then @code{set substitute-path}
9318 allows you to direct the debugger to all the sources with one single
9321 @code{set substitute-path} is also more than just a shortcut command.
9322 The source path is only used if the file at the original location no
9323 longer exists. On the other hand, @code{set substitute-path} modifies
9324 the debugger behavior to look at the rewritten location instead. So, if
9325 for any reason a source file that is not relevant to your executable is
9326 located at the original location, a substitution rule is the only
9327 method available to point @value{GDBN} at the new location.
9329 @cindex @samp{--with-relocated-sources}
9330 @cindex default source path substitution
9331 You can configure a default source path substitution rule by
9332 configuring @value{GDBN} with the
9333 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
9334 should be the name of a directory under @value{GDBN}'s configured
9335 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
9336 directory names in debug information under @var{dir} will be adjusted
9337 automatically if the installed @value{GDBN} is moved to a new
9338 location. This is useful if @value{GDBN}, libraries or executables
9339 with debug information and corresponding source code are being moved
9343 @item directory @var{dirname} @dots{}
9344 @item dir @var{dirname} @dots{}
9345 Add directory @var{dirname} to the front of the source path. Several
9346 directory names may be given to this command, separated by @samp{:}
9347 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
9348 part of absolute file names) or
9349 whitespace. You may specify a directory that is already in the source
9350 path; this moves it forward, so @value{GDBN} searches it sooner.
9352 The special strings @samp{$cdir} (to refer to the compilation
9353 directory, if one is recorded), and @samp{$cwd} (to refer to the
9354 current working directory) can also be included in the list of
9355 directories @var{dirname}. Though these will already be in the source
9356 path they will be moved forward in the list so @value{GDBN} searches
9360 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
9362 @c RET-repeat for @code{directory} is explicitly disabled, but since
9363 @c repeating it would be a no-op we do not say that. (thanks to RMS)
9365 @item set directories @var{path-list}
9366 @kindex set directories
9367 Set the source path to @var{path-list}.
9368 @samp{$cdir:$cwd} are added if missing.
9370 @item show directories
9371 @kindex show directories
9372 Print the source path: show which directories it contains.
9374 @anchor{set substitute-path}
9375 @item set substitute-path @var{from} @var{to}
9376 @kindex set substitute-path
9377 Define a source path substitution rule, and add it at the end of the
9378 current list of existing substitution rules. If a rule with the same
9379 @var{from} was already defined, then the old rule is also deleted.
9381 For example, if the file @file{/foo/bar/baz.c} was moved to
9382 @file{/mnt/cross/baz.c}, then the command
9385 (@value{GDBP}) set substitute-path /foo/bar /mnt/cross
9389 will tell @value{GDBN} to replace @samp{/foo/bar} with
9390 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
9391 @file{baz.c} even though it was moved.
9393 In the case when more than one substitution rule have been defined,
9394 the rules are evaluated one by one in the order where they have been
9395 defined. The first one matching, if any, is selected to perform
9398 For instance, if we had entered the following commands:
9401 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
9402 (@value{GDBP}) set substitute-path /usr/src /mnt/src
9406 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
9407 @file{/mnt/include/defs.h} by using the first rule. However, it would
9408 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
9409 @file{/mnt/src/lib/foo.c}.
9412 @item unset substitute-path [path]
9413 @kindex unset substitute-path
9414 If a path is specified, search the current list of substitution rules
9415 for a rule that would rewrite that path. Delete that rule if found.
9416 A warning is emitted by the debugger if no rule could be found.
9418 If no path is specified, then all substitution rules are deleted.
9420 @item show substitute-path [path]
9421 @kindex show substitute-path
9422 If a path is specified, then print the source path substitution rule
9423 which would rewrite that path, if any.
9425 If no path is specified, then print all existing source path substitution
9430 If your source path is cluttered with directories that are no longer of
9431 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
9432 versions of source. You can correct the situation as follows:
9436 Use @code{directory} with no argument to reset the source path to its default value.
9439 Use @code{directory} with suitable arguments to reinstall the
9440 directories you want in the source path. You can add all the
9441 directories in one command.
9445 @section Source and Machine Code
9446 @cindex source line and its code address
9448 You can use the command @code{info line} to map source lines to program
9449 addresses (and vice versa), and the command @code{disassemble} to display
9450 a range of addresses as machine instructions. You can use the command
9451 @code{set disassemble-next-line} to set whether to disassemble next
9452 source line when execution stops. When run under @sc{gnu} Emacs
9453 mode, the @code{info line} command causes the arrow to point to the
9454 line specified. Also, @code{info line} prints addresses in symbolic form as
9460 @itemx info line @var{location}
9461 Print the starting and ending addresses of the compiled code for
9462 source line @var{location}. You can specify source lines in any of
9463 the ways documented in @ref{Specify Location}. With no @var{location}
9464 information about the current source line is printed.
9467 For example, we can use @code{info line} to discover the location of
9468 the object code for the first line of function
9469 @code{m4_changequote}:
9472 (@value{GDBP}) info line m4_changequote
9473 Line 895 of "builtin.c" starts at pc 0x634c <m4_changequote> and \
9474 ends at 0x6350 <m4_changequote+4>.
9478 @cindex code address and its source line
9479 We can also inquire (using @code{*@var{addr}} as the form for
9480 @var{location}) what source line covers a particular address:
9482 (@value{GDBP}) info line *0x63ff
9483 Line 926 of "builtin.c" starts at pc 0x63e4 <m4_changequote+152> and \
9484 ends at 0x6404 <m4_changequote+184>.
9487 @cindex @code{$_} and @code{info line}
9488 @cindex @code{x} command, default address
9489 @kindex x@r{(examine), and} info line
9490 After @code{info line}, the default address for the @code{x} command
9491 is changed to the starting address of the line, so that @samp{x/i} is
9492 sufficient to begin examining the machine code (@pxref{Memory,
9493 ,Examining Memory}). Also, this address is saved as the value of the
9494 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
9497 @cindex info line, repeated calls
9498 After @code{info line}, using @code{info line} again without
9499 specifying a location will display information about the next source
9504 @cindex assembly instructions
9505 @cindex instructions, assembly
9506 @cindex machine instructions
9507 @cindex listing machine instructions
9509 @itemx disassemble /m
9510 @itemx disassemble /s
9511 @itemx disassemble /r
9512 This specialized command dumps a range of memory as machine
9513 instructions. It can also print mixed source+disassembly by specifying
9514 the @code{/m} or @code{/s} modifier and print the raw instructions in hex
9515 as well as in symbolic form by specifying the @code{/r} modifier.
9516 The default memory range is the function surrounding the
9517 program counter of the selected frame. A single argument to this
9518 command is a program counter value; @value{GDBN} dumps the function
9519 surrounding this value. When two arguments are given, they should
9520 be separated by a comma, possibly surrounded by whitespace. The
9521 arguments specify a range of addresses to dump, in one of two forms:
9524 @item @var{start},@var{end}
9525 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
9526 @item @var{start},+@var{length}
9527 the addresses from @var{start} (inclusive) to
9528 @code{@var{start}+@var{length}} (exclusive).
9532 When 2 arguments are specified, the name of the function is also
9533 printed (since there could be several functions in the given range).
9535 The argument(s) can be any expression yielding a numeric value, such as
9536 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
9538 If the range of memory being disassembled contains current program counter,
9539 the instruction at that location is shown with a @code{=>} marker.
9542 The following example shows the disassembly of a range of addresses of
9543 HP PA-RISC 2.0 code:
9546 (@value{GDBP}) disas 0x32c4, 0x32e4
9547 Dump of assembler code from 0x32c4 to 0x32e4:
9548 0x32c4 <main+204>: addil 0,dp
9549 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
9550 0x32cc <main+212>: ldil 0x3000,r31
9551 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
9552 0x32d4 <main+220>: ldo 0(r31),rp
9553 0x32d8 <main+224>: addil -0x800,dp
9554 0x32dc <main+228>: ldo 0x588(r1),r26
9555 0x32e0 <main+232>: ldil 0x3000,r31
9556 End of assembler dump.
9559 Here is an example showing mixed source+assembly for Intel x86
9560 with @code{/m} or @code{/s}, when the program is stopped just after
9561 function prologue in a non-optimized function with no inline code.
9564 (@value{GDBP}) disas /m main
9565 Dump of assembler code for function main:
9567 0x08048330 <+0>: push %ebp
9568 0x08048331 <+1>: mov %esp,%ebp
9569 0x08048333 <+3>: sub $0x8,%esp
9570 0x08048336 <+6>: and $0xfffffff0,%esp
9571 0x08048339 <+9>: sub $0x10,%esp
9573 6 printf ("Hello.\n");
9574 => 0x0804833c <+12>: movl $0x8048440,(%esp)
9575 0x08048343 <+19>: call 0x8048284 <puts@@plt>
9579 0x08048348 <+24>: mov $0x0,%eax
9580 0x0804834d <+29>: leave
9581 0x0804834e <+30>: ret
9583 End of assembler dump.
9586 The @code{/m} option is deprecated as its output is not useful when
9587 there is either inlined code or re-ordered code.
9588 The @code{/s} option is the preferred choice.
9589 Here is an example for AMD x86-64 showing the difference between
9590 @code{/m} output and @code{/s} output.
9591 This example has one inline function defined in a header file,
9592 and the code is compiled with @samp{-O2} optimization.
9593 Note how the @code{/m} output is missing the disassembly of
9594 several instructions that are present in the @code{/s} output.
9624 (@value{GDBP}) disas /m main
9625 Dump of assembler code for function main:
9629 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
9630 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
9634 0x000000000040041d <+29>: xor %eax,%eax
9635 0x000000000040041f <+31>: retq
9636 0x0000000000400420 <+32>: add %eax,%eax
9637 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
9639 End of assembler dump.
9640 (@value{GDBP}) disas /s main
9641 Dump of assembler code for function main:
9645 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
9649 0x0000000000400406 <+6>: test %eax,%eax
9650 0x0000000000400408 <+8>: js 0x400420 <main+32>
9655 0x000000000040040a <+10>: lea 0xa(%rax),%edx
9656 0x000000000040040d <+13>: test %eax,%eax
9657 0x000000000040040f <+15>: mov $0x1,%eax
9658 0x0000000000400414 <+20>: cmovne %edx,%eax
9662 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
9666 0x000000000040041d <+29>: xor %eax,%eax
9667 0x000000000040041f <+31>: retq
9671 0x0000000000400420 <+32>: add %eax,%eax
9672 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
9673 End of assembler dump.
9676 Here is another example showing raw instructions in hex for AMD x86-64,
9679 (gdb) disas /r 0x400281,+10
9680 Dump of assembler code from 0x400281 to 0x40028b:
9681 0x0000000000400281: 38 36 cmp %dh,(%rsi)
9682 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
9683 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
9684 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
9685 End of assembler dump.
9688 Addresses cannot be specified as a location (@pxref{Specify Location}).
9689 So, for example, if you want to disassemble function @code{bar}
9690 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
9691 and not @samp{disassemble foo.c:bar}.
9693 Some architectures have more than one commonly-used set of instruction
9694 mnemonics or other syntax.
9696 For programs that were dynamically linked and use shared libraries,
9697 instructions that call functions or branch to locations in the shared
9698 libraries might show a seemingly bogus location---it's actually a
9699 location of the relocation table. On some architectures, @value{GDBN}
9700 might be able to resolve these to actual function names.
9703 @kindex set disassembler-options
9704 @cindex disassembler options
9705 @item set disassembler-options @var{option1}[,@var{option2}@dots{}]
9706 This command controls the passing of target specific information to
9707 the disassembler. For a list of valid options, please refer to the
9708 @code{-M}/@code{--disassembler-options} section of the @samp{objdump}
9709 manual and/or the output of @kbd{objdump --help}
9710 (@pxref{objdump,,objdump,binutils,The GNU Binary Utilities}).
9711 The default value is the empty string.
9713 If it is necessary to specify more than one disassembler option, then
9714 multiple options can be placed together into a comma separated list.
9715 Currently this command is only supported on targets ARM, MIPS, PowerPC
9718 @kindex show disassembler-options
9719 @item show disassembler-options
9720 Show the current setting of the disassembler options.
9724 @kindex set disassembly-flavor
9725 @cindex Intel disassembly flavor
9726 @cindex AT&T disassembly flavor
9727 @item set disassembly-flavor @var{instruction-set}
9728 Select the instruction set to use when disassembling the
9729 program via the @code{disassemble} or @code{x/i} commands.
9731 Currently this command is only defined for the Intel x86 family. You
9732 can set @var{instruction-set} to either @code{intel} or @code{att}.
9733 The default is @code{att}, the AT&T flavor used by default by Unix
9734 assemblers for x86-based targets.
9736 @kindex show disassembly-flavor
9737 @item show disassembly-flavor
9738 Show the current setting of the disassembly flavor.
9742 @kindex set disassemble-next-line
9743 @kindex show disassemble-next-line
9744 @item set disassemble-next-line
9745 @itemx show disassemble-next-line
9746 Control whether or not @value{GDBN} will disassemble the next source
9747 line or instruction when execution stops. If ON, @value{GDBN} will
9748 display disassembly of the next source line when execution of the
9749 program being debugged stops. This is @emph{in addition} to
9750 displaying the source line itself, which @value{GDBN} always does if
9751 possible. If the next source line cannot be displayed for some reason
9752 (e.g., if @value{GDBN} cannot find the source file, or there's no line
9753 info in the debug info), @value{GDBN} will display disassembly of the
9754 next @emph{instruction} instead of showing the next source line. If
9755 AUTO, @value{GDBN} will display disassembly of next instruction only
9756 if the source line cannot be displayed. This setting causes
9757 @value{GDBN} to display some feedback when you step through a function
9758 with no line info or whose source file is unavailable. The default is
9759 OFF, which means never display the disassembly of the next line or
9765 @chapter Examining Data
9767 @cindex printing data
9768 @cindex examining data
9771 The usual way to examine data in your program is with the @code{print}
9772 command (abbreviated @code{p}), or its synonym @code{inspect}. It
9773 evaluates and prints the value of an expression of the language your
9774 program is written in (@pxref{Languages, ,Using @value{GDBN} with
9775 Different Languages}). It may also print the expression using a
9776 Python-based pretty-printer (@pxref{Pretty Printing}).
9779 @item print [[@var{options}] --] @var{expr}
9780 @itemx print [[@var{options}] --] /@var{f} @var{expr}
9781 @var{expr} is an expression (in the source language). By default the
9782 value of @var{expr} is printed in a format appropriate to its data type;
9783 you can choose a different format by specifying @samp{/@var{f}}, where
9784 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
9787 @anchor{print options}
9788 The @code{print} command supports a number of options that allow
9789 overriding relevant global print settings as set by @code{set print}
9793 @item -address [@code{on}|@code{off}]
9794 Set printing of addresses.
9795 Related setting: @ref{set print address}.
9797 @item -array [@code{on}|@code{off}]
9798 Pretty formatting of arrays.
9799 Related setting: @ref{set print array}.
9801 @item -array-indexes [@code{on}|@code{off}]
9802 Set printing of array indexes.
9803 Related setting: @ref{set print array-indexes}.
9805 @item -elements @var{number-of-elements}|@code{unlimited}
9806 Set limit on string chars or array elements to print. The value
9807 @code{unlimited} causes there to be no limit. Related setting:
9808 @ref{set print elements}.
9810 @item -max-depth @var{depth}|@code{unlimited}
9811 Set the threshold after which nested structures are replaced with
9812 ellipsis. Related setting: @ref{set print max-depth}.
9814 @item -null-stop [@code{on}|@code{off}]
9815 Set printing of char arrays to stop at first null char. Related
9816 setting: @ref{set print null-stop}.
9818 @item -object [@code{on}|@code{off}]
9819 Set printing C@t{++} virtual function tables. Related setting:
9820 @ref{set print object}.
9822 @item -pretty [@code{on}|@code{off}]
9823 Set pretty formatting of structures. Related setting: @ref{set print
9826 @item -raw-values [@code{on}|@code{off}]
9827 Set whether to print values in raw form, bypassing any
9828 pretty-printers for that value. Related setting: @ref{set print
9831 @item -repeats @var{number-of-repeats}|@code{unlimited}
9832 Set threshold for repeated print elements. @code{unlimited} causes
9833 all elements to be individually printed. Related setting: @ref{set
9836 @item -static-members [@code{on}|@code{off}]
9837 Set printing C@t{++} static members. Related setting: @ref{set print
9840 @item -symbol [@code{on}|@code{off}]
9841 Set printing of symbol names when printing pointers. Related setting:
9842 @ref{set print symbol}.
9844 @item -union [@code{on}|@code{off}]
9845 Set printing of unions interior to structures. Related setting:
9846 @ref{set print union}.
9848 @item -vtbl [@code{on}|@code{off}]
9849 Set printing of C++ virtual function tables. Related setting:
9850 @ref{set print vtbl}.
9853 Because the @code{print} command accepts arbitrary expressions which
9854 may look like options (including abbreviations), if you specify any
9855 command option, then you must use a double dash (@code{--}) to mark
9856 the end of option processing.
9858 For example, this prints the value of the @code{-p} expression:
9861 (@value{GDBP}) print -p
9864 While this repeats the last value in the value history (see below)
9865 with the @code{-pretty} option in effect:
9868 (@value{GDBP}) print -p --
9871 Here is an example including both on option and an expression:
9875 (@value{GDBP}) print -pretty -- *myptr
9887 @item print [@var{options}]
9888 @itemx print [@var{options}] /@var{f}
9889 @cindex reprint the last value
9890 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
9891 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
9892 conveniently inspect the same value in an alternative format.
9895 A more low-level way of examining data is with the @code{x} command.
9896 It examines data in memory at a specified address and prints it in a
9897 specified format. @xref{Memory, ,Examining Memory}.
9899 If you are interested in information about types, or about how the
9900 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
9901 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
9904 @cindex exploring hierarchical data structures
9906 Another way of examining values of expressions and type information is
9907 through the Python extension command @code{explore} (available only if
9908 the @value{GDBN} build is configured with @code{--with-python}). It
9909 offers an interactive way to start at the highest level (or, the most
9910 abstract level) of the data type of an expression (or, the data type
9911 itself) and explore all the way down to leaf scalar values/fields
9912 embedded in the higher level data types.
9915 @item explore @var{arg}
9916 @var{arg} is either an expression (in the source language), or a type
9917 visible in the current context of the program being debugged.
9920 The working of the @code{explore} command can be illustrated with an
9921 example. If a data type @code{struct ComplexStruct} is defined in your
9931 struct ComplexStruct
9933 struct SimpleStruct *ss_p;
9939 followed by variable declarations as
9942 struct SimpleStruct ss = @{ 10, 1.11 @};
9943 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
9947 then, the value of the variable @code{cs} can be explored using the
9948 @code{explore} command as follows.
9952 The value of `cs' is a struct/class of type `struct ComplexStruct' with
9953 the following fields:
9955 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
9956 arr = <Enter 1 to explore this field of type `int [10]'>
9958 Enter the field number of choice:
9962 Since the fields of @code{cs} are not scalar values, you are being
9963 prompted to chose the field you want to explore. Let's say you choose
9964 the field @code{ss_p} by entering @code{0}. Then, since this field is a
9965 pointer, you will be asked if it is pointing to a single value. From
9966 the declaration of @code{cs} above, it is indeed pointing to a single
9967 value, hence you enter @code{y}. If you enter @code{n}, then you will
9968 be asked if it were pointing to an array of values, in which case this
9969 field will be explored as if it were an array.
9972 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
9973 Continue exploring it as a pointer to a single value [y/n]: y
9974 The value of `*(cs.ss_p)' is a struct/class of type `struct
9975 SimpleStruct' with the following fields:
9977 i = 10 .. (Value of type `int')
9978 d = 1.1100000000000001 .. (Value of type `double')
9980 Press enter to return to parent value:
9984 If the field @code{arr} of @code{cs} was chosen for exploration by
9985 entering @code{1} earlier, then since it is as array, you will be
9986 prompted to enter the index of the element in the array that you want
9990 `cs.arr' is an array of `int'.
9991 Enter the index of the element you want to explore in `cs.arr': 5
9993 `(cs.arr)[5]' is a scalar value of type `int'.
9997 Press enter to return to parent value:
10000 In general, at any stage of exploration, you can go deeper towards the
10001 leaf values by responding to the prompts appropriately, or hit the
10002 return key to return to the enclosing data structure (the @i{higher}
10003 level data structure).
10005 Similar to exploring values, you can use the @code{explore} command to
10006 explore types. Instead of specifying a value (which is typically a
10007 variable name or an expression valid in the current context of the
10008 program being debugged), you specify a type name. If you consider the
10009 same example as above, your can explore the type
10010 @code{struct ComplexStruct} by passing the argument
10011 @code{struct ComplexStruct} to the @code{explore} command.
10014 (gdb) explore struct ComplexStruct
10018 By responding to the prompts appropriately in the subsequent interactive
10019 session, you can explore the type @code{struct ComplexStruct} in a
10020 manner similar to how the value @code{cs} was explored in the above
10023 The @code{explore} command also has two sub-commands,
10024 @code{explore value} and @code{explore type}. The former sub-command is
10025 a way to explicitly specify that value exploration of the argument is
10026 being invoked, while the latter is a way to explicitly specify that type
10027 exploration of the argument is being invoked.
10030 @item explore value @var{expr}
10031 @cindex explore value
10032 This sub-command of @code{explore} explores the value of the
10033 expression @var{expr} (if @var{expr} is an expression valid in the
10034 current context of the program being debugged). The behavior of this
10035 command is identical to that of the behavior of the @code{explore}
10036 command being passed the argument @var{expr}.
10038 @item explore type @var{arg}
10039 @cindex explore type
10040 This sub-command of @code{explore} explores the type of @var{arg} (if
10041 @var{arg} is a type visible in the current context of program being
10042 debugged), or the type of the value/expression @var{arg} (if @var{arg}
10043 is an expression valid in the current context of the program being
10044 debugged). If @var{arg} is a type, then the behavior of this command is
10045 identical to that of the @code{explore} command being passed the
10046 argument @var{arg}. If @var{arg} is an expression, then the behavior of
10047 this command will be identical to that of the @code{explore} command
10048 being passed the type of @var{arg} as the argument.
10052 * Expressions:: Expressions
10053 * Ambiguous Expressions:: Ambiguous Expressions
10054 * Variables:: Program variables
10055 * Arrays:: Artificial arrays
10056 * Output Formats:: Output formats
10057 * Memory:: Examining memory
10058 * Auto Display:: Automatic display
10059 * Print Settings:: Print settings
10060 * Pretty Printing:: Python pretty printing
10061 * Value History:: Value history
10062 * Convenience Vars:: Convenience variables
10063 * Convenience Funs:: Convenience functions
10064 * Registers:: Registers
10065 * Floating Point Hardware:: Floating point hardware
10066 * Vector Unit:: Vector Unit
10067 * OS Information:: Auxiliary data provided by operating system
10068 * Memory Region Attributes:: Memory region attributes
10069 * Dump/Restore Files:: Copy between memory and a file
10070 * Core File Generation:: Cause a program dump its core
10071 * Character Sets:: Debugging programs that use a different
10072 character set than GDB does
10073 * Caching Target Data:: Data caching for targets
10074 * Searching Memory:: Searching memory for a sequence of bytes
10075 * Value Sizes:: Managing memory allocated for values
10079 @section Expressions
10081 @cindex expressions
10082 @code{print} and many other @value{GDBN} commands accept an expression and
10083 compute its value. Any kind of constant, variable or operator defined
10084 by the programming language you are using is valid in an expression in
10085 @value{GDBN}. This includes conditional expressions, function calls,
10086 casts, and string constants. It also includes preprocessor macros, if
10087 you compiled your program to include this information; see
10090 @cindex arrays in expressions
10091 @value{GDBN} supports array constants in expressions input by
10092 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
10093 you can use the command @code{print @{1, 2, 3@}} to create an array
10094 of three integers. If you pass an array to a function or assign it
10095 to a program variable, @value{GDBN} copies the array to memory that
10096 is @code{malloc}ed in the target program.
10098 Because C is so widespread, most of the expressions shown in examples in
10099 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
10100 Languages}, for information on how to use expressions in other
10103 In this section, we discuss operators that you can use in @value{GDBN}
10104 expressions regardless of your programming language.
10106 @cindex casts, in expressions
10107 Casts are supported in all languages, not just in C, because it is so
10108 useful to cast a number into a pointer in order to examine a structure
10109 at that address in memory.
10110 @c FIXME: casts supported---Mod2 true?
10112 @value{GDBN} supports these operators, in addition to those common
10113 to programming languages:
10117 @samp{@@} is a binary operator for treating parts of memory as arrays.
10118 @xref{Arrays, ,Artificial Arrays}, for more information.
10121 @samp{::} allows you to specify a variable in terms of the file or
10122 function where it is defined. @xref{Variables, ,Program Variables}.
10124 @cindex @{@var{type}@}
10125 @cindex type casting memory
10126 @cindex memory, viewing as typed object
10127 @cindex casts, to view memory
10128 @item @{@var{type}@} @var{addr}
10129 Refers to an object of type @var{type} stored at address @var{addr} in
10130 memory. The address @var{addr} may be any expression whose value is
10131 an integer or pointer (but parentheses are required around binary
10132 operators, just as in a cast). This construct is allowed regardless
10133 of what kind of data is normally supposed to reside at @var{addr}.
10136 @node Ambiguous Expressions
10137 @section Ambiguous Expressions
10138 @cindex ambiguous expressions
10140 Expressions can sometimes contain some ambiguous elements. For instance,
10141 some programming languages (notably Ada, C@t{++} and Objective-C) permit
10142 a single function name to be defined several times, for application in
10143 different contexts. This is called @dfn{overloading}. Another example
10144 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
10145 templates and is typically instantiated several times, resulting in
10146 the same function name being defined in different contexts.
10148 In some cases and depending on the language, it is possible to adjust
10149 the expression to remove the ambiguity. For instance in C@t{++}, you
10150 can specify the signature of the function you want to break on, as in
10151 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
10152 qualified name of your function often makes the expression unambiguous
10155 When an ambiguity that needs to be resolved is detected, the debugger
10156 has the capability to display a menu of numbered choices for each
10157 possibility, and then waits for the selection with the prompt @samp{>}.
10158 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
10159 aborts the current command. If the command in which the expression was
10160 used allows more than one choice to be selected, the next option in the
10161 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
10164 For example, the following session excerpt shows an attempt to set a
10165 breakpoint at the overloaded symbol @code{String::after}.
10166 We choose three particular definitions of that function name:
10168 @c FIXME! This is likely to change to show arg type lists, at least
10171 (@value{GDBP}) b String::after
10174 [2] file:String.cc; line number:867
10175 [3] file:String.cc; line number:860
10176 [4] file:String.cc; line number:875
10177 [5] file:String.cc; line number:853
10178 [6] file:String.cc; line number:846
10179 [7] file:String.cc; line number:735
10181 Breakpoint 1 at 0xb26c: file String.cc, line 867.
10182 Breakpoint 2 at 0xb344: file String.cc, line 875.
10183 Breakpoint 3 at 0xafcc: file String.cc, line 846.
10184 Multiple breakpoints were set.
10185 Use the "delete" command to delete unwanted
10192 @kindex set multiple-symbols
10193 @item set multiple-symbols @var{mode}
10194 @cindex multiple-symbols menu
10196 This option allows you to adjust the debugger behavior when an expression
10199 By default, @var{mode} is set to @code{all}. If the command with which
10200 the expression is used allows more than one choice, then @value{GDBN}
10201 automatically selects all possible choices. For instance, inserting
10202 a breakpoint on a function using an ambiguous name results in a breakpoint
10203 inserted on each possible match. However, if a unique choice must be made,
10204 then @value{GDBN} uses the menu to help you disambiguate the expression.
10205 For instance, printing the address of an overloaded function will result
10206 in the use of the menu.
10208 When @var{mode} is set to @code{ask}, the debugger always uses the menu
10209 when an ambiguity is detected.
10211 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
10212 an error due to the ambiguity and the command is aborted.
10214 @kindex show multiple-symbols
10215 @item show multiple-symbols
10216 Show the current value of the @code{multiple-symbols} setting.
10220 @section Program Variables
10222 The most common kind of expression to use is the name of a variable
10225 Variables in expressions are understood in the selected stack frame
10226 (@pxref{Selection, ,Selecting a Frame}); they must be either:
10230 global (or file-static)
10237 visible according to the scope rules of the
10238 programming language from the point of execution in that frame
10241 @noindent This means that in the function
10256 you can examine and use the variable @code{a} whenever your program is
10257 executing within the function @code{foo}, but you can only use or
10258 examine the variable @code{b} while your program is executing inside
10259 the block where @code{b} is declared.
10261 @cindex variable name conflict
10262 There is an exception: you can refer to a variable or function whose
10263 scope is a single source file even if the current execution point is not
10264 in this file. But it is possible to have more than one such variable or
10265 function with the same name (in different source files). If that
10266 happens, referring to that name has unpredictable effects. If you wish,
10267 you can specify a static variable in a particular function or file by
10268 using the colon-colon (@code{::}) notation:
10270 @cindex colon-colon, context for variables/functions
10272 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
10273 @cindex @code{::}, context for variables/functions
10276 @var{file}::@var{variable}
10277 @var{function}::@var{variable}
10281 Here @var{file} or @var{function} is the name of the context for the
10282 static @var{variable}. In the case of file names, you can use quotes to
10283 make sure @value{GDBN} parses the file name as a single word---for example,
10284 to print a global value of @code{x} defined in @file{f2.c}:
10287 (@value{GDBP}) p 'f2.c'::x
10290 The @code{::} notation is normally used for referring to
10291 static variables, since you typically disambiguate uses of local variables
10292 in functions by selecting the appropriate frame and using the
10293 simple name of the variable. However, you may also use this notation
10294 to refer to local variables in frames enclosing the selected frame:
10303 process (a); /* Stop here */
10314 For example, if there is a breakpoint at the commented line,
10315 here is what you might see
10316 when the program stops after executing the call @code{bar(0)}:
10321 (@value{GDBP}) p bar::a
10323 (@value{GDBP}) up 2
10324 #2 0x080483d0 in foo (a=5) at foobar.c:12
10327 (@value{GDBP}) p bar::a
10331 @cindex C@t{++} scope resolution
10332 These uses of @samp{::} are very rarely in conflict with the very
10333 similar use of the same notation in C@t{++}. When they are in
10334 conflict, the C@t{++} meaning takes precedence; however, this can be
10335 overridden by quoting the file or function name with single quotes.
10337 For example, suppose the program is stopped in a method of a class
10338 that has a field named @code{includefile}, and there is also an
10339 include file named @file{includefile} that defines a variable,
10340 @code{some_global}.
10343 (@value{GDBP}) p includefile
10345 (@value{GDBP}) p includefile::some_global
10346 A syntax error in expression, near `'.
10347 (@value{GDBP}) p 'includefile'::some_global
10351 @cindex wrong values
10352 @cindex variable values, wrong
10353 @cindex function entry/exit, wrong values of variables
10354 @cindex optimized code, wrong values of variables
10356 @emph{Warning:} Occasionally, a local variable may appear to have the
10357 wrong value at certain points in a function---just after entry to a new
10358 scope, and just before exit.
10360 You may see this problem when you are stepping by machine instructions.
10361 This is because, on most machines, it takes more than one instruction to
10362 set up a stack frame (including local variable definitions); if you are
10363 stepping by machine instructions, variables may appear to have the wrong
10364 values until the stack frame is completely built. On exit, it usually
10365 also takes more than one machine instruction to destroy a stack frame;
10366 after you begin stepping through that group of instructions, local
10367 variable definitions may be gone.
10369 This may also happen when the compiler does significant optimizations.
10370 To be sure of always seeing accurate values, turn off all optimization
10373 @cindex ``No symbol "foo" in current context''
10374 Another possible effect of compiler optimizations is to optimize
10375 unused variables out of existence, or assign variables to registers (as
10376 opposed to memory addresses). Depending on the support for such cases
10377 offered by the debug info format used by the compiler, @value{GDBN}
10378 might not be able to display values for such local variables. If that
10379 happens, @value{GDBN} will print a message like this:
10382 No symbol "foo" in current context.
10385 To solve such problems, either recompile without optimizations, or use a
10386 different debug info format, if the compiler supports several such
10387 formats. @xref{Compilation}, for more information on choosing compiler
10388 options. @xref{C, ,C and C@t{++}}, for more information about debug
10389 info formats that are best suited to C@t{++} programs.
10391 If you ask to print an object whose contents are unknown to
10392 @value{GDBN}, e.g., because its data type is not completely specified
10393 by the debug information, @value{GDBN} will say @samp{<incomplete
10394 type>}. @xref{Symbols, incomplete type}, for more about this.
10396 @cindex no debug info variables
10397 If you try to examine or use the value of a (global) variable for
10398 which @value{GDBN} has no type information, e.g., because the program
10399 includes no debug information, @value{GDBN} displays an error message.
10400 @xref{Symbols, unknown type}, for more about unknown types. If you
10401 cast the variable to its declared type, @value{GDBN} gets the
10402 variable's value using the cast-to type as the variable's type. For
10403 example, in a C program:
10406 (@value{GDBP}) p var
10407 'var' has unknown type; cast it to its declared type
10408 (@value{GDBP}) p (float) var
10412 If you append @kbd{@@entry} string to a function parameter name you get its
10413 value at the time the function got called. If the value is not available an
10414 error message is printed. Entry values are available only with some compilers.
10415 Entry values are normally also printed at the function parameter list according
10416 to @ref{set print entry-values}.
10419 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
10425 (gdb) print i@@entry
10429 Strings are identified as arrays of @code{char} values without specified
10430 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
10431 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
10432 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
10433 defines literal string type @code{"char"} as @code{char} without a sign.
10438 signed char var1[] = "A";
10441 You get during debugging
10446 $2 = @{65 'A', 0 '\0'@}
10450 @section Artificial Arrays
10452 @cindex artificial array
10454 @kindex @@@r{, referencing memory as an array}
10455 It is often useful to print out several successive objects of the
10456 same type in memory; a section of an array, or an array of
10457 dynamically determined size for which only a pointer exists in the
10460 You can do this by referring to a contiguous span of memory as an
10461 @dfn{artificial array}, using the binary operator @samp{@@}. The left
10462 operand of @samp{@@} should be the first element of the desired array
10463 and be an individual object. The right operand should be the desired length
10464 of the array. The result is an array value whose elements are all of
10465 the type of the left argument. The first element is actually the left
10466 argument; the second element comes from bytes of memory immediately
10467 following those that hold the first element, and so on. Here is an
10468 example. If a program says
10471 int *array = (int *) malloc (len * sizeof (int));
10475 you can print the contents of @code{array} with
10481 The left operand of @samp{@@} must reside in memory. Array values made
10482 with @samp{@@} in this way behave just like other arrays in terms of
10483 subscripting, and are coerced to pointers when used in expressions.
10484 Artificial arrays most often appear in expressions via the value history
10485 (@pxref{Value History, ,Value History}), after printing one out.
10487 Another way to create an artificial array is to use a cast.
10488 This re-interprets a value as if it were an array.
10489 The value need not be in memory:
10491 (@value{GDBP}) p/x (short[2])0x12345678
10492 $1 = @{0x1234, 0x5678@}
10495 As a convenience, if you leave the array length out (as in
10496 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
10497 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
10499 (@value{GDBP}) p/x (short[])0x12345678
10500 $2 = @{0x1234, 0x5678@}
10503 Sometimes the artificial array mechanism is not quite enough; in
10504 moderately complex data structures, the elements of interest may not
10505 actually be adjacent---for example, if you are interested in the values
10506 of pointers in an array. One useful work-around in this situation is
10507 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
10508 Variables}) as a counter in an expression that prints the first
10509 interesting value, and then repeat that expression via @key{RET}. For
10510 instance, suppose you have an array @code{dtab} of pointers to
10511 structures, and you are interested in the values of a field @code{fv}
10512 in each structure. Here is an example of what you might type:
10522 @node Output Formats
10523 @section Output Formats
10525 @cindex formatted output
10526 @cindex output formats
10527 By default, @value{GDBN} prints a value according to its data type. Sometimes
10528 this is not what you want. For example, you might want to print a number
10529 in hex, or a pointer in decimal. Or you might want to view data in memory
10530 at a certain address as a character string or as an instruction. To do
10531 these things, specify an @dfn{output format} when you print a value.
10533 The simplest use of output formats is to say how to print a value
10534 already computed. This is done by starting the arguments of the
10535 @code{print} command with a slash and a format letter. The format
10536 letters supported are:
10540 Regard the bits of the value as an integer, and print the integer in
10544 Print as integer in signed decimal.
10547 Print as integer in unsigned decimal.
10550 Print as integer in octal.
10553 Print as integer in binary. The letter @samp{t} stands for ``two''.
10554 @footnote{@samp{b} cannot be used because these format letters are also
10555 used with the @code{x} command, where @samp{b} stands for ``byte'';
10556 see @ref{Memory,,Examining Memory}.}
10559 @cindex unknown address, locating
10560 @cindex locate address
10561 Print as an address, both absolute in hexadecimal and as an offset from
10562 the nearest preceding symbol. You can use this format used to discover
10563 where (in what function) an unknown address is located:
10566 (@value{GDBP}) p/a 0x54320
10567 $3 = 0x54320 <_initialize_vx+396>
10571 The command @code{info symbol 0x54320} yields similar results.
10572 @xref{Symbols, info symbol}.
10575 Regard as an integer and print it as a character constant. This
10576 prints both the numerical value and its character representation. The
10577 character representation is replaced with the octal escape @samp{\nnn}
10578 for characters outside the 7-bit @sc{ascii} range.
10580 Without this format, @value{GDBN} displays @code{char},
10581 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
10582 constants. Single-byte members of vectors are displayed as integer
10586 Regard the bits of the value as a floating point number and print
10587 using typical floating point syntax.
10590 @cindex printing strings
10591 @cindex printing byte arrays
10592 Regard as a string, if possible. With this format, pointers to single-byte
10593 data are displayed as null-terminated strings and arrays of single-byte data
10594 are displayed as fixed-length strings. Other values are displayed in their
10597 Without this format, @value{GDBN} displays pointers to and arrays of
10598 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
10599 strings. Single-byte members of a vector are displayed as an integer
10603 Like @samp{x} formatting, the value is treated as an integer and
10604 printed as hexadecimal, but leading zeros are printed to pad the value
10605 to the size of the integer type.
10608 @cindex raw printing
10609 Print using the @samp{raw} formatting. By default, @value{GDBN} will
10610 use a Python-based pretty-printer, if one is available (@pxref{Pretty
10611 Printing}). This typically results in a higher-level display of the
10612 value's contents. The @samp{r} format bypasses any Python
10613 pretty-printer which might exist.
10616 For example, to print the program counter in hex (@pxref{Registers}), type
10623 Note that no space is required before the slash; this is because command
10624 names in @value{GDBN} cannot contain a slash.
10626 To reprint the last value in the value history with a different format,
10627 you can use the @code{print} command with just a format and no
10628 expression. For example, @samp{p/x} reprints the last value in hex.
10631 @section Examining Memory
10633 You can use the command @code{x} (for ``examine'') to examine memory in
10634 any of several formats, independently of your program's data types.
10636 @cindex examining memory
10638 @kindex x @r{(examine memory)}
10639 @item x/@var{nfu} @var{addr}
10640 @itemx x @var{addr}
10642 Use the @code{x} command to examine memory.
10645 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
10646 much memory to display and how to format it; @var{addr} is an
10647 expression giving the address where you want to start displaying memory.
10648 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
10649 Several commands set convenient defaults for @var{addr}.
10652 @item @var{n}, the repeat count
10653 The repeat count is a decimal integer; the default is 1. It specifies
10654 how much memory (counting by units @var{u}) to display. If a negative
10655 number is specified, memory is examined backward from @var{addr}.
10656 @c This really is **decimal**; unaffected by 'set radix' as of GDB
10659 @item @var{f}, the display format
10660 The display format is one of the formats used by @code{print}
10661 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
10662 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
10663 The default is @samp{x} (hexadecimal) initially. The default changes
10664 each time you use either @code{x} or @code{print}.
10666 @item @var{u}, the unit size
10667 The unit size is any of
10673 Halfwords (two bytes).
10675 Words (four bytes). This is the initial default.
10677 Giant words (eight bytes).
10680 Each time you specify a unit size with @code{x}, that size becomes the
10681 default unit the next time you use @code{x}. For the @samp{i} format,
10682 the unit size is ignored and is normally not written. For the @samp{s} format,
10683 the unit size defaults to @samp{b}, unless it is explicitly given.
10684 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
10685 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
10686 Note that the results depend on the programming language of the
10687 current compilation unit. If the language is C, the @samp{s}
10688 modifier will use the UTF-16 encoding while @samp{w} will use
10689 UTF-32. The encoding is set by the programming language and cannot
10692 @item @var{addr}, starting display address
10693 @var{addr} is the address where you want @value{GDBN} to begin displaying
10694 memory. The expression need not have a pointer value (though it may);
10695 it is always interpreted as an integer address of a byte of memory.
10696 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
10697 @var{addr} is usually just after the last address examined---but several
10698 other commands also set the default address: @code{info breakpoints} (to
10699 the address of the last breakpoint listed), @code{info line} (to the
10700 starting address of a line), and @code{print} (if you use it to display
10701 a value from memory).
10704 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
10705 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
10706 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
10707 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
10708 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
10710 You can also specify a negative repeat count to examine memory backward
10711 from the given address. For example, @samp{x/-3uh 0x54320} prints three
10712 halfwords (@code{h}) at @code{0x54314}, @code{0x54328}, and @code{0x5431c}.
10714 Since the letters indicating unit sizes are all distinct from the
10715 letters specifying output formats, you do not have to remember whether
10716 unit size or format comes first; either order works. The output
10717 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
10718 (However, the count @var{n} must come first; @samp{wx4} does not work.)
10720 Even though the unit size @var{u} is ignored for the formats @samp{s}
10721 and @samp{i}, you might still want to use a count @var{n}; for example,
10722 @samp{3i} specifies that you want to see three machine instructions,
10723 including any operands. For convenience, especially when used with
10724 the @code{display} command, the @samp{i} format also prints branch delay
10725 slot instructions, if any, beyond the count specified, which immediately
10726 follow the last instruction that is within the count. The command
10727 @code{disassemble} gives an alternative way of inspecting machine
10728 instructions; see @ref{Machine Code,,Source and Machine Code}.
10730 If a negative repeat count is specified for the formats @samp{s} or @samp{i},
10731 the command displays null-terminated strings or instructions before the given
10732 address as many as the absolute value of the given number. For the @samp{i}
10733 format, we use line number information in the debug info to accurately locate
10734 instruction boundaries while disassembling backward. If line info is not
10735 available, the command stops examining memory with an error message.
10737 All the defaults for the arguments to @code{x} are designed to make it
10738 easy to continue scanning memory with minimal specifications each time
10739 you use @code{x}. For example, after you have inspected three machine
10740 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
10741 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
10742 the repeat count @var{n} is used again; the other arguments default as
10743 for successive uses of @code{x}.
10745 When examining machine instructions, the instruction at current program
10746 counter is shown with a @code{=>} marker. For example:
10749 (@value{GDBP}) x/5i $pc-6
10750 0x804837f <main+11>: mov %esp,%ebp
10751 0x8048381 <main+13>: push %ecx
10752 0x8048382 <main+14>: sub $0x4,%esp
10753 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
10754 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
10757 @cindex @code{$_}, @code{$__}, and value history
10758 The addresses and contents printed by the @code{x} command are not saved
10759 in the value history because there is often too much of them and they
10760 would get in the way. Instead, @value{GDBN} makes these values available for
10761 subsequent use in expressions as values of the convenience variables
10762 @code{$_} and @code{$__}. After an @code{x} command, the last address
10763 examined is available for use in expressions in the convenience variable
10764 @code{$_}. The contents of that address, as examined, are available in
10765 the convenience variable @code{$__}.
10767 If the @code{x} command has a repeat count, the address and contents saved
10768 are from the last memory unit printed; this is not the same as the last
10769 address printed if several units were printed on the last line of output.
10771 @anchor{addressable memory unit}
10772 @cindex addressable memory unit
10773 Most targets have an addressable memory unit size of 8 bits. This means
10774 that to each memory address are associated 8 bits of data. Some
10775 targets, however, have other addressable memory unit sizes.
10776 Within @value{GDBN} and this document, the term
10777 @dfn{addressable memory unit} (or @dfn{memory unit} for short) is used
10778 when explicitly referring to a chunk of data of that size. The word
10779 @dfn{byte} is used to refer to a chunk of data of 8 bits, regardless of
10780 the addressable memory unit size of the target. For most systems,
10781 addressable memory unit is a synonym of byte.
10783 @cindex remote memory comparison
10784 @cindex target memory comparison
10785 @cindex verify remote memory image
10786 @cindex verify target memory image
10787 When you are debugging a program running on a remote target machine
10788 (@pxref{Remote Debugging}), you may wish to verify the program's image
10789 in the remote machine's memory against the executable file you
10790 downloaded to the target. Or, on any target, you may want to check
10791 whether the program has corrupted its own read-only sections. The
10792 @code{compare-sections} command is provided for such situations.
10795 @kindex compare-sections
10796 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
10797 Compare the data of a loadable section @var{section-name} in the
10798 executable file of the program being debugged with the same section in
10799 the target machine's memory, and report any mismatches. With no
10800 arguments, compares all loadable sections. With an argument of
10801 @code{-r}, compares all loadable read-only sections.
10803 Note: for remote targets, this command can be accelerated if the
10804 target supports computing the CRC checksum of a block of memory
10805 (@pxref{qCRC packet}).
10809 @section Automatic Display
10810 @cindex automatic display
10811 @cindex display of expressions
10813 If you find that you want to print the value of an expression frequently
10814 (to see how it changes), you might want to add it to the @dfn{automatic
10815 display list} so that @value{GDBN} prints its value each time your program stops.
10816 Each expression added to the list is given a number to identify it;
10817 to remove an expression from the list, you specify that number.
10818 The automatic display looks like this:
10822 3: bar[5] = (struct hack *) 0x3804
10826 This display shows item numbers, expressions and their current values. As with
10827 displays you request manually using @code{x} or @code{print}, you can
10828 specify the output format you prefer; in fact, @code{display} decides
10829 whether to use @code{print} or @code{x} depending your format
10830 specification---it uses @code{x} if you specify either the @samp{i}
10831 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
10835 @item display @var{expr}
10836 Add the expression @var{expr} to the list of expressions to display
10837 each time your program stops. @xref{Expressions, ,Expressions}.
10839 @code{display} does not repeat if you press @key{RET} again after using it.
10841 @item display/@var{fmt} @var{expr}
10842 For @var{fmt} specifying only a display format and not a size or
10843 count, add the expression @var{expr} to the auto-display list but
10844 arrange to display it each time in the specified format @var{fmt}.
10845 @xref{Output Formats,,Output Formats}.
10847 @item display/@var{fmt} @var{addr}
10848 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
10849 number of units, add the expression @var{addr} as a memory address to
10850 be examined each time your program stops. Examining means in effect
10851 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
10854 For example, @samp{display/i $pc} can be helpful, to see the machine
10855 instruction about to be executed each time execution stops (@samp{$pc}
10856 is a common name for the program counter; @pxref{Registers, ,Registers}).
10859 @kindex delete display
10861 @item undisplay @var{dnums}@dots{}
10862 @itemx delete display @var{dnums}@dots{}
10863 Remove items from the list of expressions to display. Specify the
10864 numbers of the displays that you want affected with the command
10865 argument @var{dnums}. It can be a single display number, one of the
10866 numbers shown in the first field of the @samp{info display} display;
10867 or it could be a range of display numbers, as in @code{2-4}.
10869 @code{undisplay} does not repeat if you press @key{RET} after using it.
10870 (Otherwise you would just get the error @samp{No display number @dots{}}.)
10872 @kindex disable display
10873 @item disable display @var{dnums}@dots{}
10874 Disable the display of item numbers @var{dnums}. A disabled display
10875 item is not printed automatically, but is not forgotten. It may be
10876 enabled again later. Specify the numbers of the displays that you
10877 want affected with the command argument @var{dnums}. It can be a
10878 single display number, one of the numbers shown in the first field of
10879 the @samp{info display} display; or it could be a range of display
10880 numbers, as in @code{2-4}.
10882 @kindex enable display
10883 @item enable display @var{dnums}@dots{}
10884 Enable display of item numbers @var{dnums}. It becomes effective once
10885 again in auto display of its expression, until you specify otherwise.
10886 Specify the numbers of the displays that you want affected with the
10887 command argument @var{dnums}. It can be a single display number, one
10888 of the numbers shown in the first field of the @samp{info display}
10889 display; or it could be a range of display numbers, as in @code{2-4}.
10892 Display the current values of the expressions on the list, just as is
10893 done when your program stops.
10895 @kindex info display
10897 Print the list of expressions previously set up to display
10898 automatically, each one with its item number, but without showing the
10899 values. This includes disabled expressions, which are marked as such.
10900 It also includes expressions which would not be displayed right now
10901 because they refer to automatic variables not currently available.
10904 @cindex display disabled out of scope
10905 If a display expression refers to local variables, then it does not make
10906 sense outside the lexical context for which it was set up. Such an
10907 expression is disabled when execution enters a context where one of its
10908 variables is not defined. For example, if you give the command
10909 @code{display last_char} while inside a function with an argument
10910 @code{last_char}, @value{GDBN} displays this argument while your program
10911 continues to stop inside that function. When it stops elsewhere---where
10912 there is no variable @code{last_char}---the display is disabled
10913 automatically. The next time your program stops where @code{last_char}
10914 is meaningful, you can enable the display expression once again.
10916 @node Print Settings
10917 @section Print Settings
10919 @cindex format options
10920 @cindex print settings
10921 @value{GDBN} provides the following ways to control how arrays, structures,
10922 and symbols are printed.
10925 These settings are useful for debugging programs in any language:
10929 @anchor{set print address}
10930 @item set print address
10931 @itemx set print address on
10932 @cindex print/don't print memory addresses
10933 @value{GDBN} prints memory addresses showing the location of stack
10934 traces, structure values, pointer values, breakpoints, and so forth,
10935 even when it also displays the contents of those addresses. The default
10936 is @code{on}. For example, this is what a stack frame display looks like with
10937 @code{set print address on}:
10942 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
10944 530 if (lquote != def_lquote)
10948 @item set print address off
10949 Do not print addresses when displaying their contents. For example,
10950 this is the same stack frame displayed with @code{set print address off}:
10954 (@value{GDBP}) set print addr off
10956 #0 set_quotes (lq="<<", rq=">>") at input.c:530
10957 530 if (lquote != def_lquote)
10961 You can use @samp{set print address off} to eliminate all machine
10962 dependent displays from the @value{GDBN} interface. For example, with
10963 @code{print address off}, you should get the same text for backtraces on
10964 all machines---whether or not they involve pointer arguments.
10967 @item show print address
10968 Show whether or not addresses are to be printed.
10971 When @value{GDBN} prints a symbolic address, it normally prints the
10972 closest earlier symbol plus an offset. If that symbol does not uniquely
10973 identify the address (for example, it is a name whose scope is a single
10974 source file), you may need to clarify. One way to do this is with
10975 @code{info line}, for example @samp{info line *0x4537}. Alternately,
10976 you can set @value{GDBN} to print the source file and line number when
10977 it prints a symbolic address:
10980 @item set print symbol-filename on
10981 @cindex source file and line of a symbol
10982 @cindex symbol, source file and line
10983 Tell @value{GDBN} to print the source file name and line number of a
10984 symbol in the symbolic form of an address.
10986 @item set print symbol-filename off
10987 Do not print source file name and line number of a symbol. This is the
10990 @item show print symbol-filename
10991 Show whether or not @value{GDBN} will print the source file name and
10992 line number of a symbol in the symbolic form of an address.
10995 Another situation where it is helpful to show symbol filenames and line
10996 numbers is when disassembling code; @value{GDBN} shows you the line
10997 number and source file that corresponds to each instruction.
10999 Also, you may wish to see the symbolic form only if the address being
11000 printed is reasonably close to the closest earlier symbol:
11003 @item set print max-symbolic-offset @var{max-offset}
11004 @itemx set print max-symbolic-offset unlimited
11005 @cindex maximum value for offset of closest symbol
11006 Tell @value{GDBN} to only display the symbolic form of an address if the
11007 offset between the closest earlier symbol and the address is less than
11008 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
11009 to always print the symbolic form of an address if any symbol precedes
11010 it. Zero is equivalent to @code{unlimited}.
11012 @item show print max-symbolic-offset
11013 Ask how large the maximum offset is that @value{GDBN} prints in a
11017 @cindex wild pointer, interpreting
11018 @cindex pointer, finding referent
11019 If you have a pointer and you are not sure where it points, try
11020 @samp{set print symbol-filename on}. Then you can determine the name
11021 and source file location of the variable where it points, using
11022 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
11023 For example, here @value{GDBN} shows that a variable @code{ptt} points
11024 at another variable @code{t}, defined in @file{hi2.c}:
11027 (@value{GDBP}) set print symbol-filename on
11028 (@value{GDBP}) p/a ptt
11029 $4 = 0xe008 <t in hi2.c>
11033 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
11034 does not show the symbol name and filename of the referent, even with
11035 the appropriate @code{set print} options turned on.
11038 You can also enable @samp{/a}-like formatting all the time using
11039 @samp{set print symbol on}:
11041 @anchor{set print symbol}
11043 @item set print symbol on
11044 Tell @value{GDBN} to print the symbol corresponding to an address, if
11047 @item set print symbol off
11048 Tell @value{GDBN} not to print the symbol corresponding to an
11049 address. In this mode, @value{GDBN} will still print the symbol
11050 corresponding to pointers to functions. This is the default.
11052 @item show print symbol
11053 Show whether @value{GDBN} will display the symbol corresponding to an
11057 Other settings control how different kinds of objects are printed:
11060 @anchor{set print array}
11061 @item set print array
11062 @itemx set print array on
11063 @cindex pretty print arrays
11064 Pretty print arrays. This format is more convenient to read,
11065 but uses more space. The default is off.
11067 @item set print array off
11068 Return to compressed format for arrays.
11070 @item show print array
11071 Show whether compressed or pretty format is selected for displaying
11074 @cindex print array indexes
11075 @anchor{set print array-indexes}
11076 @item set print array-indexes
11077 @itemx set print array-indexes on
11078 Print the index of each element when displaying arrays. May be more
11079 convenient to locate a given element in the array or quickly find the
11080 index of a given element in that printed array. The default is off.
11082 @item set print array-indexes off
11083 Stop printing element indexes when displaying arrays.
11085 @item show print array-indexes
11086 Show whether the index of each element is printed when displaying
11089 @anchor{set print elements}
11090 @item set print elements @var{number-of-elements}
11091 @itemx set print elements unlimited
11092 @cindex number of array elements to print
11093 @cindex limit on number of printed array elements
11094 Set a limit on how many elements of an array @value{GDBN} will print.
11095 If @value{GDBN} is printing a large array, it stops printing after it has
11096 printed the number of elements set by the @code{set print elements} command.
11097 This limit also applies to the display of strings.
11098 When @value{GDBN} starts, this limit is set to 200.
11099 Setting @var{number-of-elements} to @code{unlimited} or zero means
11100 that the number of elements to print is unlimited.
11102 @item show print elements
11103 Display the number of elements of a large array that @value{GDBN} will print.
11104 If the number is 0, then the printing is unlimited.
11106 @anchor{set print frame-arguments}
11107 @item set print frame-arguments @var{value}
11108 @kindex set print frame-arguments
11109 @cindex printing frame argument values
11110 @cindex print all frame argument values
11111 @cindex print frame argument values for scalars only
11112 @cindex do not print frame arguments
11113 This command allows to control how the values of arguments are printed
11114 when the debugger prints a frame (@pxref{Frames}). The possible
11119 The values of all arguments are printed.
11122 Print the value of an argument only if it is a scalar. The value of more
11123 complex arguments such as arrays, structures, unions, etc, is replaced
11124 by @code{@dots{}}. This is the default. Here is an example where
11125 only scalar arguments are shown:
11128 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
11133 None of the argument values are printed. Instead, the value of each argument
11134 is replaced by @code{@dots{}}. In this case, the example above now becomes:
11137 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
11142 Only the presence of arguments is indicated by @code{@dots{}}.
11143 The @code{@dots{}} are not printed for function without any arguments.
11144 None of the argument names and values are printed.
11145 In this case, the example above now becomes:
11148 #1 0x08048361 in call_me (@dots{}) at frame-args.c:23
11153 By default, only scalar arguments are printed. This command can be used
11154 to configure the debugger to print the value of all arguments, regardless
11155 of their type. However, it is often advantageous to not print the value
11156 of more complex parameters. For instance, it reduces the amount of
11157 information printed in each frame, making the backtrace more readable.
11158 Also, it improves performance when displaying Ada frames, because
11159 the computation of large arguments can sometimes be CPU-intensive,
11160 especially in large applications. Setting @code{print frame-arguments}
11161 to @code{scalars} (the default), @code{none} or @code{presence} avoids
11162 this computation, thus speeding up the display of each Ada frame.
11164 @item show print frame-arguments
11165 Show how the value of arguments should be displayed when printing a frame.
11167 @anchor{set print raw-frame-arguments}
11168 @item set print raw-frame-arguments on
11169 Print frame arguments in raw, non pretty-printed, form.
11171 @item set print raw-frame-arguments off
11172 Print frame arguments in pretty-printed form, if there is a pretty-printer
11173 for the value (@pxref{Pretty Printing}),
11174 otherwise print the value in raw form.
11175 This is the default.
11177 @item show print raw-frame-arguments
11178 Show whether to print frame arguments in raw form.
11180 @anchor{set print entry-values}
11181 @item set print entry-values @var{value}
11182 @kindex set print entry-values
11183 Set printing of frame argument values at function entry. In some cases
11184 @value{GDBN} can determine the value of function argument which was passed by
11185 the function caller, even if the value was modified inside the called function
11186 and therefore is different. With optimized code, the current value could be
11187 unavailable, but the entry value may still be known.
11189 The default value is @code{default} (see below for its description). Older
11190 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
11191 this feature will behave in the @code{default} setting the same way as with the
11194 This functionality is currently supported only by DWARF 2 debugging format and
11195 the compiler has to produce @samp{DW_TAG_call_site} tags. With
11196 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
11199 The @var{value} parameter can be one of the following:
11203 Print only actual parameter values, never print values from function entry
11207 #0 different (val=6)
11208 #0 lost (val=<optimized out>)
11210 #0 invalid (val=<optimized out>)
11214 Print only parameter values from function entry point. The actual parameter
11215 values are never printed.
11217 #0 equal (val@@entry=5)
11218 #0 different (val@@entry=5)
11219 #0 lost (val@@entry=5)
11220 #0 born (val@@entry=<optimized out>)
11221 #0 invalid (val@@entry=<optimized out>)
11225 Print only parameter values from function entry point. If value from function
11226 entry point is not known while the actual value is known, print the actual
11227 value for such parameter.
11229 #0 equal (val@@entry=5)
11230 #0 different (val@@entry=5)
11231 #0 lost (val@@entry=5)
11233 #0 invalid (val@@entry=<optimized out>)
11237 Print actual parameter values. If actual parameter value is not known while
11238 value from function entry point is known, print the entry point value for such
11242 #0 different (val=6)
11243 #0 lost (val@@entry=5)
11245 #0 invalid (val=<optimized out>)
11249 Always print both the actual parameter value and its value from function entry
11250 point, even if values of one or both are not available due to compiler
11253 #0 equal (val=5, val@@entry=5)
11254 #0 different (val=6, val@@entry=5)
11255 #0 lost (val=<optimized out>, val@@entry=5)
11256 #0 born (val=10, val@@entry=<optimized out>)
11257 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
11261 Print the actual parameter value if it is known and also its value from
11262 function entry point if it is known. If neither is known, print for the actual
11263 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
11264 values are known and identical, print the shortened
11265 @code{param=param@@entry=VALUE} notation.
11267 #0 equal (val=val@@entry=5)
11268 #0 different (val=6, val@@entry=5)
11269 #0 lost (val@@entry=5)
11271 #0 invalid (val=<optimized out>)
11275 Always print the actual parameter value. Print also its value from function
11276 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
11277 if both values are known and identical, print the shortened
11278 @code{param=param@@entry=VALUE} notation.
11280 #0 equal (val=val@@entry=5)
11281 #0 different (val=6, val@@entry=5)
11282 #0 lost (val=<optimized out>, val@@entry=5)
11284 #0 invalid (val=<optimized out>)
11288 For analysis messages on possible failures of frame argument values at function
11289 entry resolution see @ref{set debug entry-values}.
11291 @item show print entry-values
11292 Show the method being used for printing of frame argument values at function
11295 @anchor{set print frame-info}
11296 @item set print frame-info @var{value}
11297 @kindex set print frame-info
11298 @cindex printing frame information
11299 @cindex frame information, printing
11300 This command allows to control the information printed when
11301 the debugger prints a frame. See @ref{Frames}, @ref{Backtrace},
11302 for a general explanation about frames and frame information.
11303 Note that some other settings (such as @code{set print frame-arguments}
11304 and @code{set print address}) are also influencing if and how some frame
11305 information is displayed. In particular, the frame program counter is never
11306 printed if @code{set print address} is off.
11308 The possible values for @code{set print frame-info} are:
11310 @item short-location
11311 Print the frame level, the program counter (if not at the
11312 beginning of the location source line), the function, the function
11315 Same as @code{short-location} but also print the source file and source line
11317 @item location-and-address
11318 Same as @code{location} but print the program counter even if located at the
11319 beginning of the location source line.
11321 Print the program counter (if not at the beginning of the location
11322 source line), the line number and the source line.
11323 @item source-and-location
11324 Print what @code{location} and @code{source-line} are printing.
11326 The information printed for a frame is decided automatically
11327 by the @value{GDBN} command that prints a frame.
11328 For example, @code{frame} prints the information printed by
11329 @code{source-and-location} while @code{stepi} will switch between
11330 @code{source-line} and @code{source-and-location} depending on the program
11332 The default value is @code{auto}.
11335 @anchor{set print repeats}
11336 @item set print repeats @var{number-of-repeats}
11337 @itemx set print repeats unlimited
11338 @cindex repeated array elements
11339 Set the threshold for suppressing display of repeated array
11340 elements. When the number of consecutive identical elements of an
11341 array exceeds the threshold, @value{GDBN} prints the string
11342 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
11343 identical repetitions, instead of displaying the identical elements
11344 themselves. Setting the threshold to @code{unlimited} or zero will
11345 cause all elements to be individually printed. The default threshold
11348 @item show print repeats
11349 Display the current threshold for printing repeated identical
11352 @anchor{set print max-depth}
11353 @item set print max-depth @var{depth}
11354 @item set print max-depth unlimited
11355 @cindex printing nested structures
11356 Set the threshold after which nested structures are replaced with
11357 ellipsis, this can make visualising deeply nested structures easier.
11359 For example, given this C code
11362 typedef struct s1 @{ int a; @} s1;
11363 typedef struct s2 @{ s1 b; @} s2;
11364 typedef struct s3 @{ s2 c; @} s3;
11365 typedef struct s4 @{ s3 d; @} s4;
11367 s4 var = @{ @{ @{ @{ 3 @} @} @} @};
11370 The following table shows how different values of @var{depth} will
11371 effect how @code{var} is printed by @value{GDBN}:
11373 @multitable @columnfractions .3 .7
11374 @headitem @var{depth} setting @tab Result of @samp{p var}
11376 @tab @code{$1 = @{d = @{c = @{b = @{a = 3@}@}@}@}}
11378 @tab @code{$1 = @{...@}}
11380 @tab @code{$1 = @{d = @{...@}@}}
11382 @tab @code{$1 = @{d = @{c = @{...@}@}@}}
11384 @tab @code{$1 = @{d = @{c = @{b = @{...@}@}@}@}}
11386 @tab @code{$1 = @{d = @{c = @{b = @{a = 3@}@}@}@}}
11389 To see the contents of structures that have been hidden the user can
11390 either increase the print max-depth, or they can print the elements of
11391 the structure that are visible, for example
11394 (gdb) set print max-depth 2
11396 $1 = @{d = @{c = @{...@}@}@}
11398 $2 = @{c = @{b = @{...@}@}@}
11400 $3 = @{b = @{a = 3@}@}
11403 The pattern used to replace nested structures varies based on
11404 language, for most languages @code{@{...@}} is used, but Fortran uses
11407 @item show print max-depth
11408 Display the current threshold after which nested structures are
11409 replaces with ellipsis.
11411 @anchor{set print null-stop}
11412 @item set print null-stop
11413 @cindex @sc{null} elements in arrays
11414 Cause @value{GDBN} to stop printing the characters of an array when the first
11415 @sc{null} is encountered. This is useful when large arrays actually
11416 contain only short strings.
11417 The default is off.
11419 @item show print null-stop
11420 Show whether @value{GDBN} stops printing an array on the first
11421 @sc{null} character.
11423 @anchor{set print pretty}
11424 @item set print pretty on
11425 @cindex print structures in indented form
11426 @cindex indentation in structure display
11427 Cause @value{GDBN} to print structures in an indented format with one member
11428 per line, like this:
11443 @item set print pretty off
11444 Cause @value{GDBN} to print structures in a compact format, like this:
11448 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
11449 meat = 0x54 "Pork"@}
11454 This is the default format.
11456 @item show print pretty
11457 Show which format @value{GDBN} is using to print structures.
11459 @anchor{set print raw-values}
11460 @item set print raw-values on
11461 Print values in raw form, without applying the pretty
11462 printers for the value.
11464 @item set print raw-values off
11465 Print values in pretty-printed form, if there is a pretty-printer
11466 for the value (@pxref{Pretty Printing}),
11467 otherwise print the value in raw form.
11469 The default setting is ``off''.
11471 @item show print raw-values
11472 Show whether to print values in raw form.
11474 @item set print sevenbit-strings on
11475 @cindex eight-bit characters in strings
11476 @cindex octal escapes in strings
11477 Print using only seven-bit characters; if this option is set,
11478 @value{GDBN} displays any eight-bit characters (in strings or
11479 character values) using the notation @code{\}@var{nnn}. This setting is
11480 best if you are working in English (@sc{ascii}) and you use the
11481 high-order bit of characters as a marker or ``meta'' bit.
11483 @item set print sevenbit-strings off
11484 Print full eight-bit characters. This allows the use of more
11485 international character sets, and is the default.
11487 @item show print sevenbit-strings
11488 Show whether or not @value{GDBN} is printing only seven-bit characters.
11490 @anchor{set print union}
11491 @item set print union on
11492 @cindex unions in structures, printing
11493 Tell @value{GDBN} to print unions which are contained in structures
11494 and other unions. This is the default setting.
11496 @item set print union off
11497 Tell @value{GDBN} not to print unions which are contained in
11498 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
11501 @item show print union
11502 Ask @value{GDBN} whether or not it will print unions which are contained in
11503 structures and other unions.
11505 For example, given the declarations
11508 typedef enum @{Tree, Bug@} Species;
11509 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
11510 typedef enum @{Caterpillar, Cocoon, Butterfly@}
11521 struct thing foo = @{Tree, @{Acorn@}@};
11525 with @code{set print union on} in effect @samp{p foo} would print
11528 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
11532 and with @code{set print union off} in effect it would print
11535 $1 = @{it = Tree, form = @{...@}@}
11539 @code{set print union} affects programs written in C-like languages
11545 These settings are of interest when debugging C@t{++} programs:
11548 @cindex demangling C@t{++} names
11549 @item set print demangle
11550 @itemx set print demangle on
11551 Print C@t{++} names in their source form rather than in the encoded
11552 (``mangled'') form passed to the assembler and linker for type-safe
11553 linkage. The default is on.
11555 @item show print demangle
11556 Show whether C@t{++} names are printed in mangled or demangled form.
11558 @item set print asm-demangle
11559 @itemx set print asm-demangle on
11560 Print C@t{++} names in their source form rather than their mangled form, even
11561 in assembler code printouts such as instruction disassemblies.
11562 The default is off.
11564 @item show print asm-demangle
11565 Show whether C@t{++} names in assembly listings are printed in mangled
11568 @cindex C@t{++} symbol decoding style
11569 @cindex symbol decoding style, C@t{++}
11570 @kindex set demangle-style
11571 @item set demangle-style @var{style}
11572 Choose among several encoding schemes used by different compilers to represent
11573 C@t{++} names. If you omit @var{style}, you will see a list of possible
11574 formats. The default value is @var{auto}, which lets @value{GDBN} choose a
11575 decoding style by inspecting your program.
11577 @item show demangle-style
11578 Display the encoding style currently in use for decoding C@t{++} symbols.
11580 @anchor{set print object}
11581 @item set print object
11582 @itemx set print object on
11583 @cindex derived type of an object, printing
11584 @cindex display derived types
11585 When displaying a pointer to an object, identify the @emph{actual}
11586 (derived) type of the object rather than the @emph{declared} type, using
11587 the virtual function table. Note that the virtual function table is
11588 required---this feature can only work for objects that have run-time
11589 type identification; a single virtual method in the object's declared
11590 type is sufficient. Note that this setting is also taken into account when
11591 working with variable objects via MI (@pxref{GDB/MI}).
11593 @item set print object off
11594 Display only the declared type of objects, without reference to the
11595 virtual function table. This is the default setting.
11597 @item show print object
11598 Show whether actual, or declared, object types are displayed.
11600 @anchor{set print static-members}
11601 @item set print static-members
11602 @itemx set print static-members on
11603 @cindex static members of C@t{++} objects
11604 Print static members when displaying a C@t{++} object. The default is on.
11606 @item set print static-members off
11607 Do not print static members when displaying a C@t{++} object.
11609 @item show print static-members
11610 Show whether C@t{++} static members are printed or not.
11612 @item set print pascal_static-members
11613 @itemx set print pascal_static-members on
11614 @cindex static members of Pascal objects
11615 @cindex Pascal objects, static members display
11616 Print static members when displaying a Pascal object. The default is on.
11618 @item set print pascal_static-members off
11619 Do not print static members when displaying a Pascal object.
11621 @item show print pascal_static-members
11622 Show whether Pascal static members are printed or not.
11624 @c These don't work with HP ANSI C++ yet.
11625 @anchor{set print vtbl}
11626 @item set print vtbl
11627 @itemx set print vtbl on
11628 @cindex pretty print C@t{++} virtual function tables
11629 @cindex virtual functions (C@t{++}) display
11630 @cindex VTBL display
11631 Pretty print C@t{++} virtual function tables. The default is off.
11632 (The @code{vtbl} commands do not work on programs compiled with the HP
11633 ANSI C@t{++} compiler (@code{aCC}).)
11635 @item set print vtbl off
11636 Do not pretty print C@t{++} virtual function tables.
11638 @item show print vtbl
11639 Show whether C@t{++} virtual function tables are pretty printed, or not.
11642 @node Pretty Printing
11643 @section Pretty Printing
11645 @value{GDBN} provides a mechanism to allow pretty-printing of values using
11646 Python code. It greatly simplifies the display of complex objects. This
11647 mechanism works for both MI and the CLI.
11650 * Pretty-Printer Introduction:: Introduction to pretty-printers
11651 * Pretty-Printer Example:: An example pretty-printer
11652 * Pretty-Printer Commands:: Pretty-printer commands
11655 @node Pretty-Printer Introduction
11656 @subsection Pretty-Printer Introduction
11658 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
11659 registered for the value. If there is then @value{GDBN} invokes the
11660 pretty-printer to print the value. Otherwise the value is printed normally.
11662 Pretty-printers are normally named. This makes them easy to manage.
11663 The @samp{info pretty-printer} command will list all the installed
11664 pretty-printers with their names.
11665 If a pretty-printer can handle multiple data types, then its
11666 @dfn{subprinters} are the printers for the individual data types.
11667 Each such subprinter has its own name.
11668 The format of the name is @var{printer-name};@var{subprinter-name}.
11670 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
11671 Typically they are automatically loaded and registered when the corresponding
11672 debug information is loaded, thus making them available without having to
11673 do anything special.
11675 There are three places where a pretty-printer can be registered.
11679 Pretty-printers registered globally are available when debugging
11683 Pretty-printers registered with a program space are available only
11684 when debugging that program.
11685 @xref{Progspaces In Python}, for more details on program spaces in Python.
11688 Pretty-printers registered with an objfile are loaded and unloaded
11689 with the corresponding objfile (e.g., shared library).
11690 @xref{Objfiles In Python}, for more details on objfiles in Python.
11693 @xref{Selecting Pretty-Printers}, for further information on how
11694 pretty-printers are selected,
11696 @xref{Writing a Pretty-Printer}, for implementing pretty printers
11699 @node Pretty-Printer Example
11700 @subsection Pretty-Printer Example
11702 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
11705 (@value{GDBP}) print s
11707 static npos = 4294967295,
11709 <std::allocator<char>> = @{
11710 <__gnu_cxx::new_allocator<char>> = @{
11711 <No data fields>@}, <No data fields>
11713 members of std::basic_string<char, std::char_traits<char>,
11714 std::allocator<char> >::_Alloc_hider:
11715 _M_p = 0x804a014 "abcd"
11720 With a pretty-printer for @code{std::string} only the contents are printed:
11723 (@value{GDBP}) print s
11727 @node Pretty-Printer Commands
11728 @subsection Pretty-Printer Commands
11729 @cindex pretty-printer commands
11732 @kindex info pretty-printer
11733 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
11734 Print the list of installed pretty-printers.
11735 This includes disabled pretty-printers, which are marked as such.
11737 @var{object-regexp} is a regular expression matching the objects
11738 whose pretty-printers to list.
11739 Objects can be @code{global}, the program space's file
11740 (@pxref{Progspaces In Python}),
11741 and the object files within that program space (@pxref{Objfiles In Python}).
11742 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
11743 looks up a printer from these three objects.
11745 @var{name-regexp} is a regular expression matching the name of the printers
11748 @kindex disable pretty-printer
11749 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
11750 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
11751 A disabled pretty-printer is not forgotten, it may be enabled again later.
11753 @kindex enable pretty-printer
11754 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
11755 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
11760 Suppose we have three pretty-printers installed: one from library1.so
11761 named @code{foo} that prints objects of type @code{foo}, and
11762 another from library2.so named @code{bar} that prints two types of objects,
11763 @code{bar1} and @code{bar2}.
11766 (gdb) info pretty-printer
11773 (gdb) info pretty-printer library2
11778 (gdb) disable pretty-printer library1
11780 2 of 3 printers enabled
11781 (gdb) info pretty-printer
11788 (gdb) disable pretty-printer library2 bar;bar1
11790 1 of 3 printers enabled
11791 (gdb) info pretty-printer library2
11798 (gdb) disable pretty-printer library2 bar
11800 0 of 3 printers enabled
11801 (gdb) info pretty-printer library2
11810 Note that for @code{bar} the entire printer can be disabled,
11811 as can each individual subprinter.
11813 Printing values and frame arguments is done by default using
11814 the enabled pretty printers.
11816 The print option @code{-raw-values} and @value{GDBN} setting
11817 @code{set print raw-values} (@pxref{set print raw-values}) can be
11818 used to print values without applying the enabled pretty printers.
11820 Similarly, the backtrace option @code{-raw-frame-arguments} and
11821 @value{GDBN} setting @code{set print raw-frame-arguments}
11822 (@pxref{set print raw-frame-arguments}) can be used to ignore the
11823 enabled pretty printers when printing frame argument values.
11825 @node Value History
11826 @section Value History
11828 @cindex value history
11829 @cindex history of values printed by @value{GDBN}
11830 Values printed by the @code{print} command are saved in the @value{GDBN}
11831 @dfn{value history}. This allows you to refer to them in other expressions.
11832 Values are kept until the symbol table is re-read or discarded
11833 (for example with the @code{file} or @code{symbol-file} commands).
11834 When the symbol table changes, the value history is discarded,
11835 since the values may contain pointers back to the types defined in the
11840 @cindex history number
11841 The values printed are given @dfn{history numbers} by which you can
11842 refer to them. These are successive integers starting with one.
11843 @code{print} shows you the history number assigned to a value by
11844 printing @samp{$@var{num} = } before the value; here @var{num} is the
11847 To refer to any previous value, use @samp{$} followed by the value's
11848 history number. The way @code{print} labels its output is designed to
11849 remind you of this. Just @code{$} refers to the most recent value in
11850 the history, and @code{$$} refers to the value before that.
11851 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
11852 is the value just prior to @code{$$}, @code{$$1} is equivalent to
11853 @code{$$}, and @code{$$0} is equivalent to @code{$}.
11855 For example, suppose you have just printed a pointer to a structure and
11856 want to see the contents of the structure. It suffices to type
11862 If you have a chain of structures where the component @code{next} points
11863 to the next one, you can print the contents of the next one with this:
11870 You can print successive links in the chain by repeating this
11871 command---which you can do by just typing @key{RET}.
11873 Note that the history records values, not expressions. If the value of
11874 @code{x} is 4 and you type these commands:
11882 then the value recorded in the value history by the @code{print} command
11883 remains 4 even though the value of @code{x} has changed.
11886 @kindex show values
11888 Print the last ten values in the value history, with their item numbers.
11889 This is like @samp{p@ $$9} repeated ten times, except that @code{show
11890 values} does not change the history.
11892 @item show values @var{n}
11893 Print ten history values centered on history item number @var{n}.
11895 @item show values +
11896 Print ten history values just after the values last printed. If no more
11897 values are available, @code{show values +} produces no display.
11900 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
11901 same effect as @samp{show values +}.
11903 @node Convenience Vars
11904 @section Convenience Variables
11906 @cindex convenience variables
11907 @cindex user-defined variables
11908 @value{GDBN} provides @dfn{convenience variables} that you can use within
11909 @value{GDBN} to hold on to a value and refer to it later. These variables
11910 exist entirely within @value{GDBN}; they are not part of your program, and
11911 setting a convenience variable has no direct effect on further execution
11912 of your program. That is why you can use them freely.
11914 Convenience variables are prefixed with @samp{$}. Any name preceded by
11915 @samp{$} can be used for a convenience variable, unless it is one of
11916 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
11917 (Value history references, in contrast, are @emph{numbers} preceded
11918 by @samp{$}. @xref{Value History, ,Value History}.)
11920 You can save a value in a convenience variable with an assignment
11921 expression, just as you would set a variable in your program.
11925 set $foo = *object_ptr
11929 would save in @code{$foo} the value contained in the object pointed to by
11932 Using a convenience variable for the first time creates it, but its
11933 value is @code{void} until you assign a new value. You can alter the
11934 value with another assignment at any time.
11936 Convenience variables have no fixed types. You can assign a convenience
11937 variable any type of value, including structures and arrays, even if
11938 that variable already has a value of a different type. The convenience
11939 variable, when used as an expression, has the type of its current value.
11942 @kindex show convenience
11943 @cindex show all user variables and functions
11944 @item show convenience
11945 Print a list of convenience variables used so far, and their values,
11946 as well as a list of the convenience functions.
11947 Abbreviated @code{show conv}.
11949 @kindex init-if-undefined
11950 @cindex convenience variables, initializing
11951 @item init-if-undefined $@var{variable} = @var{expression}
11952 Set a convenience variable if it has not already been set. This is useful
11953 for user-defined commands that keep some state. It is similar, in concept,
11954 to using local static variables with initializers in C (except that
11955 convenience variables are global). It can also be used to allow users to
11956 override default values used in a command script.
11958 If the variable is already defined then the expression is not evaluated so
11959 any side-effects do not occur.
11962 One of the ways to use a convenience variable is as a counter to be
11963 incremented or a pointer to be advanced. For example, to print
11964 a field from successive elements of an array of structures:
11968 print bar[$i++]->contents
11972 Repeat that command by typing @key{RET}.
11974 Some convenience variables are created automatically by @value{GDBN} and given
11975 values likely to be useful.
11978 @vindex $_@r{, convenience variable}
11980 The variable @code{$_} is automatically set by the @code{x} command to
11981 the last address examined (@pxref{Memory, ,Examining Memory}). Other
11982 commands which provide a default address for @code{x} to examine also
11983 set @code{$_} to that address; these commands include @code{info line}
11984 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
11985 except when set by the @code{x} command, in which case it is a pointer
11986 to the type of @code{$__}.
11988 @vindex $__@r{, convenience variable}
11990 The variable @code{$__} is automatically set by the @code{x} command
11991 to the value found in the last address examined. Its type is chosen
11992 to match the format in which the data was printed.
11995 @vindex $_exitcode@r{, convenience variable}
11996 When the program being debugged terminates normally, @value{GDBN}
11997 automatically sets this variable to the exit code of the program, and
11998 resets @code{$_exitsignal} to @code{void}.
12001 @vindex $_exitsignal@r{, convenience variable}
12002 When the program being debugged dies due to an uncaught signal,
12003 @value{GDBN} automatically sets this variable to that signal's number,
12004 and resets @code{$_exitcode} to @code{void}.
12006 To distinguish between whether the program being debugged has exited
12007 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
12008 @code{$_exitsignal} is not @code{void}), the convenience function
12009 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
12010 Functions}). For example, considering the following source code:
12013 #include <signal.h>
12016 main (int argc, char *argv[])
12023 A valid way of telling whether the program being debugged has exited
12024 or signalled would be:
12027 (@value{GDBP}) define has_exited_or_signalled
12028 Type commands for definition of ``has_exited_or_signalled''.
12029 End with a line saying just ``end''.
12030 >if $_isvoid ($_exitsignal)
12031 >echo The program has exited\n
12033 >echo The program has signalled\n
12039 Program terminated with signal SIGALRM, Alarm clock.
12040 The program no longer exists.
12041 (@value{GDBP}) has_exited_or_signalled
12042 The program has signalled
12045 As can be seen, @value{GDBN} correctly informs that the program being
12046 debugged has signalled, since it calls @code{raise} and raises a
12047 @code{SIGALRM} signal. If the program being debugged had not called
12048 @code{raise}, then @value{GDBN} would report a normal exit:
12051 (@value{GDBP}) has_exited_or_signalled
12052 The program has exited
12056 The variable @code{$_exception} is set to the exception object being
12057 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
12059 @item $_ada_exception
12060 The variable @code{$_ada_exception} is set to the address of the
12061 exception being caught or thrown at an Ada exception-related
12062 catchpoint. @xref{Set Catchpoints}.
12065 @itemx $_probe_arg0@dots{}$_probe_arg11
12066 Arguments to a static probe. @xref{Static Probe Points}.
12069 @vindex $_sdata@r{, inspect, convenience variable}
12070 The variable @code{$_sdata} contains extra collected static tracepoint
12071 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
12072 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
12073 if extra static tracepoint data has not been collected.
12076 @vindex $_siginfo@r{, convenience variable}
12077 The variable @code{$_siginfo} contains extra signal information
12078 (@pxref{extra signal information}). Note that @code{$_siginfo}
12079 could be empty, if the application has not yet received any signals.
12080 For example, it will be empty before you execute the @code{run} command.
12083 @vindex $_tlb@r{, convenience variable}
12084 The variable @code{$_tlb} is automatically set when debugging
12085 applications running on MS-Windows in native mode or connected to
12086 gdbserver that supports the @code{qGetTIBAddr} request.
12087 @xref{General Query Packets}.
12088 This variable contains the address of the thread information block.
12091 The number of the current inferior. @xref{Inferiors Connections and
12092 Programs, ,Debugging Multiple Inferiors Connections and Programs}.
12095 The thread number of the current thread. @xref{thread numbers}.
12098 The global number of the current thread. @xref{global thread numbers}.
12102 @vindex $_gdb_major@r{, convenience variable}
12103 @vindex $_gdb_minor@r{, convenience variable}
12104 The major and minor version numbers of the running @value{GDBN}.
12105 Development snapshots and pretest versions have their minor version
12106 incremented by one; thus, @value{GDBN} pretest 9.11.90 will produce
12107 the value 12 for @code{$_gdb_minor}. These variables allow you to
12108 write scripts that work with different versions of @value{GDBN}
12109 without errors caused by features unavailable in some of those
12112 @item $_shell_exitcode
12113 @itemx $_shell_exitsignal
12114 @vindex $_shell_exitcode@r{, convenience variable}
12115 @vindex $_shell_exitsignal@r{, convenience variable}
12116 @cindex shell command, exit code
12117 @cindex shell command, exit signal
12118 @cindex exit status of shell commands
12119 @value{GDBN} commands such as @code{shell} and @code{|} are launching
12120 shell commands. When a launched command terminates, @value{GDBN}
12121 automatically maintains the variables @code{$_shell_exitcode}
12122 and @code{$_shell_exitsignal} according to the exit status of the last
12123 launched command. These variables are set and used similarly to
12124 the variables @code{$_exitcode} and @code{$_exitsignal}.
12128 @node Convenience Funs
12129 @section Convenience Functions
12131 @cindex convenience functions
12132 @value{GDBN} also supplies some @dfn{convenience functions}. These
12133 have a syntax similar to convenience variables. A convenience
12134 function can be used in an expression just like an ordinary function;
12135 however, a convenience function is implemented internally to
12138 These functions do not require @value{GDBN} to be configured with
12139 @code{Python} support, which means that they are always available.
12143 @item $_isvoid (@var{expr})
12144 @findex $_isvoid@r{, convenience function}
12145 Return one if the expression @var{expr} is @code{void}. Otherwise it
12148 A @code{void} expression is an expression where the type of the result
12149 is @code{void}. For example, you can examine a convenience variable
12150 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
12154 (@value{GDBP}) print $_exitcode
12156 (@value{GDBP}) print $_isvoid ($_exitcode)
12159 Starting program: ./a.out
12160 [Inferior 1 (process 29572) exited normally]
12161 (@value{GDBP}) print $_exitcode
12163 (@value{GDBP}) print $_isvoid ($_exitcode)
12167 In the example above, we used @code{$_isvoid} to check whether
12168 @code{$_exitcode} is @code{void} before and after the execution of the
12169 program being debugged. Before the execution there is no exit code to
12170 be examined, therefore @code{$_exitcode} is @code{void}. After the
12171 execution the program being debugged returned zero, therefore
12172 @code{$_exitcode} is zero, which means that it is not @code{void}
12175 The @code{void} expression can also be a call of a function from the
12176 program being debugged. For example, given the following function:
12185 The result of calling it inside @value{GDBN} is @code{void}:
12188 (@value{GDBP}) print foo ()
12190 (@value{GDBP}) print $_isvoid (foo ())
12192 (@value{GDBP}) set $v = foo ()
12193 (@value{GDBP}) print $v
12195 (@value{GDBP}) print $_isvoid ($v)
12199 @item $_gdb_setting_str (@var{setting})
12200 @findex $_gdb_setting_str@r{, convenience function}
12201 Return the value of the @value{GDBN} @var{setting} as a string.
12202 @var{setting} is any setting that can be used in a @code{set} or
12203 @code{show} command (@pxref{Controlling GDB}).
12206 (@value{GDBP}) show print frame-arguments
12207 Printing of non-scalar frame arguments is "scalars".
12208 (@value{GDBP}) p $_gdb_setting_str("print frame-arguments")
12210 (@value{GDBP}) p $_gdb_setting_str("height")
12215 @item $_gdb_setting (@var{setting})
12216 @findex $_gdb_setting@r{, convenience function}
12217 Return the value of the @value{GDBN} @var{setting}.
12218 The type of the returned value depends on the setting.
12220 The value type for boolean and auto boolean settings is @code{int}.
12221 The boolean values @code{off} and @code{on} are converted to
12222 the integer values @code{0} and @code{1}. The value @code{auto} is
12223 converted to the value @code{-1}.
12225 The value type for integer settings is either @code{unsigned int}
12226 or @code{int}, depending on the setting.
12228 Some integer settings accept an @code{unlimited} value.
12229 Depending on the setting, the @code{set} command also accepts
12230 the value @code{0} or the value @code{@minus{}1} as a synonym for
12232 For example, @code{set height unlimited} is equivalent to
12233 @code{set height 0}.
12235 Some other settings that accept the @code{unlimited} value
12236 use the value @code{0} to literally mean zero.
12237 For example, @code{set history size 0} indicates to not
12238 record any @value{GDBN} commands in the command history.
12239 For such settings, @code{@minus{}1} is the synonym
12240 for @code{unlimited}.
12242 See the documentation of the corresponding @code{set} command for
12243 the numerical value equivalent to @code{unlimited}.
12245 The @code{$_gdb_setting} function converts the unlimited value
12246 to a @code{0} or a @code{@minus{}1} value according to what the
12247 @code{set} command uses.
12251 (@value{GDBP}) p $_gdb_setting_str("height")
12253 (@value{GDBP}) p $_gdb_setting("height")
12255 (@value{GDBP}) set height unlimited
12256 (@value{GDBP}) p $_gdb_setting_str("height")
12258 (@value{GDBP}) p $_gdb_setting("height")
12262 (@value{GDBP}) p $_gdb_setting_str("history size")
12264 (@value{GDBP}) p $_gdb_setting("history size")
12266 (@value{GDBP}) p $_gdb_setting_str("disassemble-next-line")
12268 (@value{GDBP}) p $_gdb_setting("disassemble-next-line")
12274 Other setting types (enum, filename, optional filename, string, string noescape)
12275 are returned as string values.
12278 @item $_gdb_maint_setting_str (@var{setting})
12279 @findex $_gdb_maint_setting_str@r{, convenience function}
12280 Like the @code{$_gdb_setting_str} function, but works with
12281 @code{maintenance set} variables.
12283 @item $_gdb_maint_setting (@var{setting})
12284 @findex $_gdb_maint_setting@r{, convenience function}
12285 Like the @code{$_gdb_setting} function, but works with
12286 @code{maintenance set} variables.
12290 The following functions require @value{GDBN} to be configured with
12291 @code{Python} support.
12295 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
12296 @findex $_memeq@r{, convenience function}
12297 Returns one if the @var{length} bytes at the addresses given by
12298 @var{buf1} and @var{buf2} are equal.
12299 Otherwise it returns zero.
12301 @item $_regex(@var{str}, @var{regex})
12302 @findex $_regex@r{, convenience function}
12303 Returns one if the string @var{str} matches the regular expression
12304 @var{regex}. Otherwise it returns zero.
12305 The syntax of the regular expression is that specified by @code{Python}'s
12306 regular expression support.
12308 @item $_streq(@var{str1}, @var{str2})
12309 @findex $_streq@r{, convenience function}
12310 Returns one if the strings @var{str1} and @var{str2} are equal.
12311 Otherwise it returns zero.
12313 @item $_strlen(@var{str})
12314 @findex $_strlen@r{, convenience function}
12315 Returns the length of string @var{str}.
12317 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
12318 @findex $_caller_is@r{, convenience function}
12319 Returns one if the calling function's name is equal to @var{name}.
12320 Otherwise it returns zero.
12322 If the optional argument @var{number_of_frames} is provided,
12323 it is the number of frames up in the stack to look.
12331 at testsuite/gdb.python/py-caller-is.c:21
12332 #1 0x00000000004005a0 in middle_func ()
12333 at testsuite/gdb.python/py-caller-is.c:27
12334 #2 0x00000000004005ab in top_func ()
12335 at testsuite/gdb.python/py-caller-is.c:33
12336 #3 0x00000000004005b6 in main ()
12337 at testsuite/gdb.python/py-caller-is.c:39
12338 (gdb) print $_caller_is ("middle_func")
12340 (gdb) print $_caller_is ("top_func", 2)
12344 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
12345 @findex $_caller_matches@r{, convenience function}
12346 Returns one if the calling function's name matches the regular expression
12347 @var{regexp}. Otherwise it returns zero.
12349 If the optional argument @var{number_of_frames} is provided,
12350 it is the number of frames up in the stack to look.
12353 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
12354 @findex $_any_caller_is@r{, convenience function}
12355 Returns one if any calling function's name is equal to @var{name}.
12356 Otherwise it returns zero.
12358 If the optional argument @var{number_of_frames} is provided,
12359 it is the number of frames up in the stack to look.
12362 This function differs from @code{$_caller_is} in that this function
12363 checks all stack frames from the immediate caller to the frame specified
12364 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
12365 frame specified by @var{number_of_frames}.
12367 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
12368 @findex $_any_caller_matches@r{, convenience function}
12369 Returns one if any calling function's name matches the regular expression
12370 @var{regexp}. Otherwise it returns zero.
12372 If the optional argument @var{number_of_frames} is provided,
12373 it is the number of frames up in the stack to look.
12376 This function differs from @code{$_caller_matches} in that this function
12377 checks all stack frames from the immediate caller to the frame specified
12378 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
12379 frame specified by @var{number_of_frames}.
12381 @item $_as_string(@var{value})
12382 @findex $_as_string@r{, convenience function}
12383 Return the string representation of @var{value}.
12385 This function is useful to obtain the textual label (enumerator) of an
12386 enumeration value. For example, assuming the variable @var{node} is of
12387 an enumerated type:
12390 (gdb) printf "Visiting node of type %s\n", $_as_string(node)
12391 Visiting node of type NODE_INTEGER
12394 @item $_cimag(@var{value})
12395 @itemx $_creal(@var{value})
12396 @findex $_cimag@r{, convenience function}
12397 @findex $_creal@r{, convenience function}
12398 Return the imaginary (@code{$_cimag}) or real (@code{$_creal}) part of
12399 the complex number @var{value}.
12401 The type of the imaginary or real part depends on the type of the
12402 complex number, e.g., using @code{$_cimag} on a @code{float complex}
12403 will return an imaginary part of type @code{float}.
12407 @value{GDBN} provides the ability to list and get help on
12408 convenience functions.
12411 @item help function
12412 @kindex help function
12413 @cindex show all convenience functions
12414 Print a list of all convenience functions.
12421 You can refer to machine register contents, in expressions, as variables
12422 with names starting with @samp{$}. The names of registers are different
12423 for each machine; use @code{info registers} to see the names used on
12427 @kindex info registers
12428 @item info registers
12429 Print the names and values of all registers except floating-point
12430 and vector registers (in the selected stack frame).
12432 @kindex info all-registers
12433 @cindex floating point registers
12434 @item info all-registers
12435 Print the names and values of all registers, including floating-point
12436 and vector registers (in the selected stack frame).
12438 @item info registers @var{reggroup} @dots{}
12439 Print the name and value of the registers in each of the specified
12440 @var{reggroup}s. The @var{reggroup} can be any of those returned by
12441 @code{maint print reggroups} (@pxref{Maintenance Commands}).
12443 @item info registers @var{regname} @dots{}
12444 Print the @dfn{relativized} value of each specified register @var{regname}.
12445 As discussed in detail below, register values are normally relative to
12446 the selected stack frame. The @var{regname} may be any register name valid on
12447 the machine you are using, with or without the initial @samp{$}.
12450 @anchor{standard registers}
12451 @cindex stack pointer register
12452 @cindex program counter register
12453 @cindex process status register
12454 @cindex frame pointer register
12455 @cindex standard registers
12456 @value{GDBN} has four ``standard'' register names that are available (in
12457 expressions) on most machines---whenever they do not conflict with an
12458 architecture's canonical mnemonics for registers. The register names
12459 @code{$pc} and @code{$sp} are used for the program counter register and
12460 the stack pointer. @code{$fp} is used for a register that contains a
12461 pointer to the current stack frame, and @code{$ps} is used for a
12462 register that contains the processor status. For example,
12463 you could print the program counter in hex with
12470 or print the instruction to be executed next with
12477 or add four to the stack pointer@footnote{This is a way of removing
12478 one word from the stack, on machines where stacks grow downward in
12479 memory (most machines, nowadays). This assumes that the innermost
12480 stack frame is selected; setting @code{$sp} is not allowed when other
12481 stack frames are selected. To pop entire frames off the stack,
12482 regardless of machine architecture, use @code{return};
12483 see @ref{Returning, ,Returning from a Function}.} with
12489 Whenever possible, these four standard register names are available on
12490 your machine even though the machine has different canonical mnemonics,
12491 so long as there is no conflict. The @code{info registers} command
12492 shows the canonical names. For example, on the SPARC, @code{info
12493 registers} displays the processor status register as @code{$psr} but you
12494 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
12495 is an alias for the @sc{eflags} register.
12497 @value{GDBN} always considers the contents of an ordinary register as an
12498 integer when the register is examined in this way. Some machines have
12499 special registers which can hold nothing but floating point; these
12500 registers are considered to have floating point values. There is no way
12501 to refer to the contents of an ordinary register as floating point value
12502 (although you can @emph{print} it as a floating point value with
12503 @samp{print/f $@var{regname}}).
12505 Some registers have distinct ``raw'' and ``virtual'' data formats. This
12506 means that the data format in which the register contents are saved by
12507 the operating system is not the same one that your program normally
12508 sees. For example, the registers of the 68881 floating point
12509 coprocessor are always saved in ``extended'' (raw) format, but all C
12510 programs expect to work with ``double'' (virtual) format. In such
12511 cases, @value{GDBN} normally works with the virtual format only (the format
12512 that makes sense for your program), but the @code{info registers} command
12513 prints the data in both formats.
12515 @cindex SSE registers (x86)
12516 @cindex MMX registers (x86)
12517 Some machines have special registers whose contents can be interpreted
12518 in several different ways. For example, modern x86-based machines
12519 have SSE and MMX registers that can hold several values packed
12520 together in several different formats. @value{GDBN} refers to such
12521 registers in @code{struct} notation:
12524 (@value{GDBP}) print $xmm1
12526 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
12527 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
12528 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
12529 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
12530 v4_int32 = @{0, 20657912, 11, 13@},
12531 v2_int64 = @{88725056443645952, 55834574859@},
12532 uint128 = 0x0000000d0000000b013b36f800000000
12537 To set values of such registers, you need to tell @value{GDBN} which
12538 view of the register you wish to change, as if you were assigning
12539 value to a @code{struct} member:
12542 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
12545 Normally, register values are relative to the selected stack frame
12546 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
12547 value that the register would contain if all stack frames farther in
12548 were exited and their saved registers restored. In order to see the
12549 true contents of hardware registers, you must select the innermost
12550 frame (with @samp{frame 0}).
12552 @cindex caller-saved registers
12553 @cindex call-clobbered registers
12554 @cindex volatile registers
12555 @cindex <not saved> values
12556 Usually ABIs reserve some registers as not needed to be saved by the
12557 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
12558 registers). It may therefore not be possible for @value{GDBN} to know
12559 the value a register had before the call (in other words, in the outer
12560 frame), if the register value has since been changed by the callee.
12561 @value{GDBN} tries to deduce where the inner frame saved
12562 (``callee-saved'') registers, from the debug info, unwind info, or the
12563 machine code generated by your compiler. If some register is not
12564 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
12565 its own knowledge of the ABI, or because the debug/unwind info
12566 explicitly says the register's value is undefined), @value{GDBN}
12567 displays @w{@samp{<not saved>}} as the register's value. With targets
12568 that @value{GDBN} has no knowledge of the register saving convention,
12569 if a register was not saved by the callee, then its value and location
12570 in the outer frame are assumed to be the same of the inner frame.
12571 This is usually harmless, because if the register is call-clobbered,
12572 the caller either does not care what is in the register after the
12573 call, or has code to restore the value that it does care about. Note,
12574 however, that if you change such a register in the outer frame, you
12575 may also be affecting the inner frame. Also, the more ``outer'' the
12576 frame is you're looking at, the more likely a call-clobbered
12577 register's value is to be wrong, in the sense that it doesn't actually
12578 represent the value the register had just before the call.
12580 @node Floating Point Hardware
12581 @section Floating Point Hardware
12582 @cindex floating point
12584 Depending on the configuration, @value{GDBN} may be able to give
12585 you more information about the status of the floating point hardware.
12590 Display hardware-dependent information about the floating
12591 point unit. The exact contents and layout vary depending on the
12592 floating point chip. Currently, @samp{info float} is supported on
12593 the ARM and x86 machines.
12597 @section Vector Unit
12598 @cindex vector unit
12600 Depending on the configuration, @value{GDBN} may be able to give you
12601 more information about the status of the vector unit.
12604 @kindex info vector
12606 Display information about the vector unit. The exact contents and
12607 layout vary depending on the hardware.
12610 @node OS Information
12611 @section Operating System Auxiliary Information
12612 @cindex OS information
12614 @value{GDBN} provides interfaces to useful OS facilities that can help
12615 you debug your program.
12617 @cindex auxiliary vector
12618 @cindex vector, auxiliary
12619 Some operating systems supply an @dfn{auxiliary vector} to programs at
12620 startup. This is akin to the arguments and environment that you
12621 specify for a program, but contains a system-dependent variety of
12622 binary values that tell system libraries important details about the
12623 hardware, operating system, and process. Each value's purpose is
12624 identified by an integer tag; the meanings are well-known but system-specific.
12625 Depending on the configuration and operating system facilities,
12626 @value{GDBN} may be able to show you this information. For remote
12627 targets, this functionality may further depend on the remote stub's
12628 support of the @samp{qXfer:auxv:read} packet, see
12629 @ref{qXfer auxiliary vector read}.
12634 Display the auxiliary vector of the inferior, which can be either a
12635 live process or a core dump file. @value{GDBN} prints each tag value
12636 numerically, and also shows names and text descriptions for recognized
12637 tags. Some values in the vector are numbers, some bit masks, and some
12638 pointers to strings or other data. @value{GDBN} displays each value in the
12639 most appropriate form for a recognized tag, and in hexadecimal for
12640 an unrecognized tag.
12643 On some targets, @value{GDBN} can access operating system-specific
12644 information and show it to you. The types of information available
12645 will differ depending on the type of operating system running on the
12646 target. The mechanism used to fetch the data is described in
12647 @ref{Operating System Information}. For remote targets, this
12648 functionality depends on the remote stub's support of the
12649 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
12653 @item info os @var{infotype}
12655 Display OS information of the requested type.
12657 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
12659 @anchor{linux info os infotypes}
12661 @kindex info os cpus
12663 Display the list of all CPUs/cores. For each CPU/core, @value{GDBN} prints
12664 the available fields from /proc/cpuinfo. For each supported architecture
12665 different fields are available. Two common entries are processor which gives
12666 CPU number and bogomips; a system constant that is calculated during
12667 kernel initialization.
12669 @kindex info os files
12671 Display the list of open file descriptors on the target. For each
12672 file descriptor, @value{GDBN} prints the identifier of the process
12673 owning the descriptor, the command of the owning process, the value
12674 of the descriptor, and the target of the descriptor.
12676 @kindex info os modules
12678 Display the list of all loaded kernel modules on the target. For each
12679 module, @value{GDBN} prints the module name, the size of the module in
12680 bytes, the number of times the module is used, the dependencies of the
12681 module, the status of the module, and the address of the loaded module
12684 @kindex info os msg
12686 Display the list of all System V message queues on the target. For each
12687 message queue, @value{GDBN} prints the message queue key, the message
12688 queue identifier, the access permissions, the current number of bytes
12689 on the queue, the current number of messages on the queue, the processes
12690 that last sent and received a message on the queue, the user and group
12691 of the owner and creator of the message queue, the times at which a
12692 message was last sent and received on the queue, and the time at which
12693 the message queue was last changed.
12695 @kindex info os processes
12697 Display the list of processes on the target. For each process,
12698 @value{GDBN} prints the process identifier, the name of the user, the
12699 command corresponding to the process, and the list of processor cores
12700 that the process is currently running on. (To understand what these
12701 properties mean, for this and the following info types, please consult
12702 the general @sc{gnu}/Linux documentation.)
12704 @kindex info os procgroups
12706 Display the list of process groups on the target. For each process,
12707 @value{GDBN} prints the identifier of the process group that it belongs
12708 to, the command corresponding to the process group leader, the process
12709 identifier, and the command line of the process. The list is sorted
12710 first by the process group identifier, then by the process identifier,
12711 so that processes belonging to the same process group are grouped together
12712 and the process group leader is listed first.
12714 @kindex info os semaphores
12716 Display the list of all System V semaphore sets on the target. For each
12717 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
12718 set identifier, the access permissions, the number of semaphores in the
12719 set, the user and group of the owner and creator of the semaphore set,
12720 and the times at which the semaphore set was operated upon and changed.
12722 @kindex info os shm
12724 Display the list of all System V shared-memory regions on the target.
12725 For each shared-memory region, @value{GDBN} prints the region key,
12726 the shared-memory identifier, the access permissions, the size of the
12727 region, the process that created the region, the process that last
12728 attached to or detached from the region, the current number of live
12729 attaches to the region, and the times at which the region was last
12730 attached to, detach from, and changed.
12732 @kindex info os sockets
12734 Display the list of Internet-domain sockets on the target. For each
12735 socket, @value{GDBN} prints the address and port of the local and
12736 remote endpoints, the current state of the connection, the creator of
12737 the socket, the IP address family of the socket, and the type of the
12740 @kindex info os threads
12742 Display the list of threads running on the target. For each thread,
12743 @value{GDBN} prints the identifier of the process that the thread
12744 belongs to, the command of the process, the thread identifier, and the
12745 processor core that it is currently running on. The main thread of a
12746 process is not listed.
12750 If @var{infotype} is omitted, then list the possible values for
12751 @var{infotype} and the kind of OS information available for each
12752 @var{infotype}. If the target does not return a list of possible
12753 types, this command will report an error.
12756 @node Memory Region Attributes
12757 @section Memory Region Attributes
12758 @cindex memory region attributes
12760 @dfn{Memory region attributes} allow you to describe special handling
12761 required by regions of your target's memory. @value{GDBN} uses
12762 attributes to determine whether to allow certain types of memory
12763 accesses; whether to use specific width accesses; and whether to cache
12764 target memory. By default the description of memory regions is
12765 fetched from the target (if the current target supports this), but the
12766 user can override the fetched regions.
12768 Defined memory regions can be individually enabled and disabled. When a
12769 memory region is disabled, @value{GDBN} uses the default attributes when
12770 accessing memory in that region. Similarly, if no memory regions have
12771 been defined, @value{GDBN} uses the default attributes when accessing
12774 When a memory region is defined, it is given a number to identify it;
12775 to enable, disable, or remove a memory region, you specify that number.
12779 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
12780 Define a memory region bounded by @var{lower} and @var{upper} with
12781 attributes @var{attributes}@dots{}, and add it to the list of regions
12782 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
12783 case: it is treated as the target's maximum memory address.
12784 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
12787 Discard any user changes to the memory regions and use target-supplied
12788 regions, if available, or no regions if the target does not support.
12791 @item delete mem @var{nums}@dots{}
12792 Remove memory regions @var{nums}@dots{} from the list of regions
12793 monitored by @value{GDBN}.
12795 @kindex disable mem
12796 @item disable mem @var{nums}@dots{}
12797 Disable monitoring of memory regions @var{nums}@dots{}.
12798 A disabled memory region is not forgotten.
12799 It may be enabled again later.
12802 @item enable mem @var{nums}@dots{}
12803 Enable monitoring of memory regions @var{nums}@dots{}.
12807 Print a table of all defined memory regions, with the following columns
12811 @item Memory Region Number
12812 @item Enabled or Disabled.
12813 Enabled memory regions are marked with @samp{y}.
12814 Disabled memory regions are marked with @samp{n}.
12817 The address defining the inclusive lower bound of the memory region.
12820 The address defining the exclusive upper bound of the memory region.
12823 The list of attributes set for this memory region.
12828 @subsection Attributes
12830 @subsubsection Memory Access Mode
12831 The access mode attributes set whether @value{GDBN} may make read or
12832 write accesses to a memory region.
12834 While these attributes prevent @value{GDBN} from performing invalid
12835 memory accesses, they do nothing to prevent the target system, I/O DMA,
12836 etc.@: from accessing memory.
12840 Memory is read only.
12842 Memory is write only.
12844 Memory is read/write. This is the default.
12847 @subsubsection Memory Access Size
12848 The access size attribute tells @value{GDBN} to use specific sized
12849 accesses in the memory region. Often memory mapped device registers
12850 require specific sized accesses. If no access size attribute is
12851 specified, @value{GDBN} may use accesses of any size.
12855 Use 8 bit memory accesses.
12857 Use 16 bit memory accesses.
12859 Use 32 bit memory accesses.
12861 Use 64 bit memory accesses.
12864 @c @subsubsection Hardware/Software Breakpoints
12865 @c The hardware/software breakpoint attributes set whether @value{GDBN}
12866 @c will use hardware or software breakpoints for the internal breakpoints
12867 @c used by the step, next, finish, until, etc. commands.
12871 @c Always use hardware breakpoints
12872 @c @item swbreak (default)
12875 @subsubsection Data Cache
12876 The data cache attributes set whether @value{GDBN} will cache target
12877 memory. While this generally improves performance by reducing debug
12878 protocol overhead, it can lead to incorrect results because @value{GDBN}
12879 does not know about volatile variables or memory mapped device
12884 Enable @value{GDBN} to cache target memory.
12886 Disable @value{GDBN} from caching target memory. This is the default.
12889 @subsection Memory Access Checking
12890 @value{GDBN} can be instructed to refuse accesses to memory that is
12891 not explicitly described. This can be useful if accessing such
12892 regions has undesired effects for a specific target, or to provide
12893 better error checking. The following commands control this behaviour.
12896 @kindex set mem inaccessible-by-default
12897 @item set mem inaccessible-by-default [on|off]
12898 If @code{on} is specified, make @value{GDBN} treat memory not
12899 explicitly described by the memory ranges as non-existent and refuse accesses
12900 to such memory. The checks are only performed if there's at least one
12901 memory range defined. If @code{off} is specified, make @value{GDBN}
12902 treat the memory not explicitly described by the memory ranges as RAM.
12903 The default value is @code{on}.
12904 @kindex show mem inaccessible-by-default
12905 @item show mem inaccessible-by-default
12906 Show the current handling of accesses to unknown memory.
12910 @c @subsubsection Memory Write Verification
12911 @c The memory write verification attributes set whether @value{GDBN}
12912 @c will re-reads data after each write to verify the write was successful.
12916 @c @item noverify (default)
12919 @node Dump/Restore Files
12920 @section Copy Between Memory and a File
12921 @cindex dump/restore files
12922 @cindex append data to a file
12923 @cindex dump data to a file
12924 @cindex restore data from a file
12926 You can use the commands @code{dump}, @code{append}, and
12927 @code{restore} to copy data between target memory and a file. The
12928 @code{dump} and @code{append} commands write data to a file, and the
12929 @code{restore} command reads data from a file back into the inferior's
12930 memory. Files may be in binary, Motorola S-record, Intel hex,
12931 Tektronix Hex, or Verilog Hex format; however, @value{GDBN} can only
12932 append to binary files, and cannot read from Verilog Hex files.
12937 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
12938 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
12939 Dump the contents of memory from @var{start_addr} to @var{end_addr},
12940 or the value of @var{expr}, to @var{filename} in the given format.
12942 The @var{format} parameter may be any one of:
12949 Motorola S-record format.
12951 Tektronix Hex format.
12953 Verilog Hex format.
12956 @value{GDBN} uses the same definitions of these formats as the
12957 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
12958 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
12962 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
12963 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
12964 Append the contents of memory from @var{start_addr} to @var{end_addr},
12965 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
12966 (@value{GDBN} can only append data to files in raw binary form.)
12969 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
12970 Restore the contents of file @var{filename} into memory. The
12971 @code{restore} command can automatically recognize any known @sc{bfd}
12972 file format, except for raw binary. To restore a raw binary file you
12973 must specify the optional keyword @code{binary} after the filename.
12975 If @var{bias} is non-zero, its value will be added to the addresses
12976 contained in the file. Binary files always start at address zero, so
12977 they will be restored at address @var{bias}. Other bfd files have
12978 a built-in location; they will be restored at offset @var{bias}
12979 from that location.
12981 If @var{start} and/or @var{end} are non-zero, then only data between
12982 file offset @var{start} and file offset @var{end} will be restored.
12983 These offsets are relative to the addresses in the file, before
12984 the @var{bias} argument is applied.
12988 @node Core File Generation
12989 @section How to Produce a Core File from Your Program
12990 @cindex dump core from inferior
12992 A @dfn{core file} or @dfn{core dump} is a file that records the memory
12993 image of a running process and its process status (register values
12994 etc.). Its primary use is post-mortem debugging of a program that
12995 crashed while it ran outside a debugger. A program that crashes
12996 automatically produces a core file, unless this feature is disabled by
12997 the user. @xref{Files}, for information on invoking @value{GDBN} in
12998 the post-mortem debugging mode.
13000 Occasionally, you may wish to produce a core file of the program you
13001 are debugging in order to preserve a snapshot of its state.
13002 @value{GDBN} has a special command for that.
13006 @kindex generate-core-file
13007 @item generate-core-file [@var{file}]
13008 @itemx gcore [@var{file}]
13009 Produce a core dump of the inferior process. The optional argument
13010 @var{file} specifies the file name where to put the core dump. If not
13011 specified, the file name defaults to @file{core.@var{pid}}, where
13012 @var{pid} is the inferior process ID.
13014 Note that this command is implemented only for some systems (as of
13015 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
13017 On @sc{gnu}/Linux, this command can take into account the value of the
13018 file @file{/proc/@var{pid}/coredump_filter} when generating the core
13019 dump (@pxref{set use-coredump-filter}), and by default honors the
13020 @code{VM_DONTDUMP} flag for mappings where it is present in the file
13021 @file{/proc/@var{pid}/smaps} (@pxref{set dump-excluded-mappings}).
13023 @kindex set use-coredump-filter
13024 @anchor{set use-coredump-filter}
13025 @item set use-coredump-filter on
13026 @itemx set use-coredump-filter off
13027 Enable or disable the use of the file
13028 @file{/proc/@var{pid}/coredump_filter} when generating core dump
13029 files. This file is used by the Linux kernel to decide what types of
13030 memory mappings will be dumped or ignored when generating a core dump
13031 file. @var{pid} is the process ID of a currently running process.
13033 To make use of this feature, you have to write in the
13034 @file{/proc/@var{pid}/coredump_filter} file a value, in hexadecimal,
13035 which is a bit mask representing the memory mapping types. If a bit
13036 is set in the bit mask, then the memory mappings of the corresponding
13037 types will be dumped; otherwise, they will be ignored. This
13038 configuration is inherited by child processes. For more information
13039 about the bits that can be set in the
13040 @file{/proc/@var{pid}/coredump_filter} file, please refer to the
13041 manpage of @code{core(5)}.
13043 By default, this option is @code{on}. If this option is turned
13044 @code{off}, @value{GDBN} does not read the @file{coredump_filter} file
13045 and instead uses the same default value as the Linux kernel in order
13046 to decide which pages will be dumped in the core dump file. This
13047 value is currently @code{0x33}, which means that bits @code{0}
13048 (anonymous private mappings), @code{1} (anonymous shared mappings),
13049 @code{4} (ELF headers) and @code{5} (private huge pages) are active.
13050 This will cause these memory mappings to be dumped automatically.
13052 @kindex set dump-excluded-mappings
13053 @anchor{set dump-excluded-mappings}
13054 @item set dump-excluded-mappings on
13055 @itemx set dump-excluded-mappings off
13056 If @code{on} is specified, @value{GDBN} will dump memory mappings
13057 marked with the @code{VM_DONTDUMP} flag. This flag is represented in
13058 the file @file{/proc/@var{pid}/smaps} with the acronym @code{dd}.
13060 The default value is @code{off}.
13063 @node Character Sets
13064 @section Character Sets
13065 @cindex character sets
13067 @cindex translating between character sets
13068 @cindex host character set
13069 @cindex target character set
13071 If the program you are debugging uses a different character set to
13072 represent characters and strings than the one @value{GDBN} uses itself,
13073 @value{GDBN} can automatically translate between the character sets for
13074 you. The character set @value{GDBN} uses we call the @dfn{host
13075 character set}; the one the inferior program uses we call the
13076 @dfn{target character set}.
13078 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
13079 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
13080 remote protocol (@pxref{Remote Debugging}) to debug a program
13081 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
13082 then the host character set is Latin-1, and the target character set is
13083 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
13084 target-charset EBCDIC-US}, then @value{GDBN} translates between
13085 @sc{ebcdic} and Latin 1 as you print character or string values, or use
13086 character and string literals in expressions.
13088 @value{GDBN} has no way to automatically recognize which character set
13089 the inferior program uses; you must tell it, using the @code{set
13090 target-charset} command, described below.
13092 Here are the commands for controlling @value{GDBN}'s character set
13096 @item set target-charset @var{charset}
13097 @kindex set target-charset
13098 Set the current target character set to @var{charset}. To display the
13099 list of supported target character sets, type
13100 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
13102 @item set host-charset @var{charset}
13103 @kindex set host-charset
13104 Set the current host character set to @var{charset}.
13106 By default, @value{GDBN} uses a host character set appropriate to the
13107 system it is running on; you can override that default using the
13108 @code{set host-charset} command. On some systems, @value{GDBN} cannot
13109 automatically determine the appropriate host character set. In this
13110 case, @value{GDBN} uses @samp{UTF-8}.
13112 @value{GDBN} can only use certain character sets as its host character
13113 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
13114 @value{GDBN} will list the host character sets it supports.
13116 @item set charset @var{charset}
13117 @kindex set charset
13118 Set the current host and target character sets to @var{charset}. As
13119 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
13120 @value{GDBN} will list the names of the character sets that can be used
13121 for both host and target.
13124 @kindex show charset
13125 Show the names of the current host and target character sets.
13127 @item show host-charset
13128 @kindex show host-charset
13129 Show the name of the current host character set.
13131 @item show target-charset
13132 @kindex show target-charset
13133 Show the name of the current target character set.
13135 @item set target-wide-charset @var{charset}
13136 @kindex set target-wide-charset
13137 Set the current target's wide character set to @var{charset}. This is
13138 the character set used by the target's @code{wchar_t} type. To
13139 display the list of supported wide character sets, type
13140 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
13142 @item show target-wide-charset
13143 @kindex show target-wide-charset
13144 Show the name of the current target's wide character set.
13147 Here is an example of @value{GDBN}'s character set support in action.
13148 Assume that the following source code has been placed in the file
13149 @file{charset-test.c}:
13155 = @{72, 101, 108, 108, 111, 44, 32, 119,
13156 111, 114, 108, 100, 33, 10, 0@};
13157 char ibm1047_hello[]
13158 = @{200, 133, 147, 147, 150, 107, 64, 166,
13159 150, 153, 147, 132, 90, 37, 0@};
13163 printf ("Hello, world!\n");
13167 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
13168 containing the string @samp{Hello, world!} followed by a newline,
13169 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
13171 We compile the program, and invoke the debugger on it:
13174 $ gcc -g charset-test.c -o charset-test
13175 $ gdb -nw charset-test
13176 GNU gdb 2001-12-19-cvs
13177 Copyright 2001 Free Software Foundation, Inc.
13182 We can use the @code{show charset} command to see what character sets
13183 @value{GDBN} is currently using to interpret and display characters and
13187 (@value{GDBP}) show charset
13188 The current host and target character set is `ISO-8859-1'.
13192 For the sake of printing this manual, let's use @sc{ascii} as our
13193 initial character set:
13195 (@value{GDBP}) set charset ASCII
13196 (@value{GDBP}) show charset
13197 The current host and target character set is `ASCII'.
13201 Let's assume that @sc{ascii} is indeed the correct character set for our
13202 host system --- in other words, let's assume that if @value{GDBN} prints
13203 characters using the @sc{ascii} character set, our terminal will display
13204 them properly. Since our current target character set is also
13205 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
13208 (@value{GDBP}) print ascii_hello
13209 $1 = 0x401698 "Hello, world!\n"
13210 (@value{GDBP}) print ascii_hello[0]
13215 @value{GDBN} uses the target character set for character and string
13216 literals you use in expressions:
13219 (@value{GDBP}) print '+'
13224 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
13227 @value{GDBN} relies on the user to tell it which character set the
13228 target program uses. If we print @code{ibm1047_hello} while our target
13229 character set is still @sc{ascii}, we get jibberish:
13232 (@value{GDBP}) print ibm1047_hello
13233 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
13234 (@value{GDBP}) print ibm1047_hello[0]
13239 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
13240 @value{GDBN} tells us the character sets it supports:
13243 (@value{GDBP}) set target-charset
13244 ASCII EBCDIC-US IBM1047 ISO-8859-1
13245 (@value{GDBP}) set target-charset
13248 We can select @sc{ibm1047} as our target character set, and examine the
13249 program's strings again. Now the @sc{ascii} string is wrong, but
13250 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
13251 target character set, @sc{ibm1047}, to the host character set,
13252 @sc{ascii}, and they display correctly:
13255 (@value{GDBP}) set target-charset IBM1047
13256 (@value{GDBP}) show charset
13257 The current host character set is `ASCII'.
13258 The current target character set is `IBM1047'.
13259 (@value{GDBP}) print ascii_hello
13260 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
13261 (@value{GDBP}) print ascii_hello[0]
13263 (@value{GDBP}) print ibm1047_hello
13264 $8 = 0x4016a8 "Hello, world!\n"
13265 (@value{GDBP}) print ibm1047_hello[0]
13270 As above, @value{GDBN} uses the target character set for character and
13271 string literals you use in expressions:
13274 (@value{GDBP}) print '+'
13279 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
13282 @node Caching Target Data
13283 @section Caching Data of Targets
13284 @cindex caching data of targets
13286 @value{GDBN} caches data exchanged between the debugger and a target.
13287 Each cache is associated with the address space of the inferior.
13288 @xref{Inferiors Connections and Programs}, about inferior and address space.
13289 Such caching generally improves performance in remote debugging
13290 (@pxref{Remote Debugging}), because it reduces the overhead of the
13291 remote protocol by bundling memory reads and writes into large chunks.
13292 Unfortunately, simply caching everything would lead to incorrect results,
13293 since @value{GDBN} does not necessarily know anything about volatile
13294 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
13295 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
13297 Therefore, by default, @value{GDBN} only caches data
13298 known to be on the stack@footnote{In non-stop mode, it is moderately
13299 rare for a running thread to modify the stack of a stopped thread
13300 in a way that would interfere with a backtrace, and caching of
13301 stack reads provides a significant speed up of remote backtraces.} or
13302 in the code segment.
13303 Other regions of memory can be explicitly marked as
13304 cacheable; @pxref{Memory Region Attributes}.
13307 @kindex set remotecache
13308 @item set remotecache on
13309 @itemx set remotecache off
13310 This option no longer does anything; it exists for compatibility
13313 @kindex show remotecache
13314 @item show remotecache
13315 Show the current state of the obsolete remotecache flag.
13317 @kindex set stack-cache
13318 @item set stack-cache on
13319 @itemx set stack-cache off
13320 Enable or disable caching of stack accesses. When @code{on}, use
13321 caching. By default, this option is @code{on}.
13323 @kindex show stack-cache
13324 @item show stack-cache
13325 Show the current state of data caching for memory accesses.
13327 @kindex set code-cache
13328 @item set code-cache on
13329 @itemx set code-cache off
13330 Enable or disable caching of code segment accesses. When @code{on},
13331 use caching. By default, this option is @code{on}. This improves
13332 performance of disassembly in remote debugging.
13334 @kindex show code-cache
13335 @item show code-cache
13336 Show the current state of target memory cache for code segment
13339 @kindex info dcache
13340 @item info dcache @r{[}line@r{]}
13341 Print the information about the performance of data cache of the
13342 current inferior's address space. The information displayed
13343 includes the dcache width and depth, and for each cache line, its
13344 number, address, and how many times it was referenced. This
13345 command is useful for debugging the data cache operation.
13347 If a line number is specified, the contents of that line will be
13350 @item set dcache size @var{size}
13351 @cindex dcache size
13352 @kindex set dcache size
13353 Set maximum number of entries in dcache (dcache depth above).
13355 @item set dcache line-size @var{line-size}
13356 @cindex dcache line-size
13357 @kindex set dcache line-size
13358 Set number of bytes each dcache entry caches (dcache width above).
13359 Must be a power of 2.
13361 @item show dcache size
13362 @kindex show dcache size
13363 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
13365 @item show dcache line-size
13366 @kindex show dcache line-size
13367 Show default size of dcache lines.
13371 @node Searching Memory
13372 @section Search Memory
13373 @cindex searching memory
13375 Memory can be searched for a particular sequence of bytes with the
13376 @code{find} command.
13380 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
13381 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
13382 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
13383 etc. The search begins at address @var{start_addr} and continues for either
13384 @var{len} bytes or through to @var{end_addr} inclusive.
13387 @var{s} and @var{n} are optional parameters.
13388 They may be specified in either order, apart or together.
13391 @item @var{s}, search query size
13392 The size of each search query value.
13398 halfwords (two bytes)
13402 giant words (eight bytes)
13405 All values are interpreted in the current language.
13406 This means, for example, that if the current source language is C/C@t{++}
13407 then searching for the string ``hello'' includes the trailing '\0'.
13408 The null terminator can be removed from searching by using casts,
13409 e.g.: @samp{@{char[5]@}"hello"}.
13411 If the value size is not specified, it is taken from the
13412 value's type in the current language.
13413 This is useful when one wants to specify the search
13414 pattern as a mixture of types.
13415 Note that this means, for example, that in the case of C-like languages
13416 a search for an untyped 0x42 will search for @samp{(int) 0x42}
13417 which is typically four bytes.
13419 @item @var{n}, maximum number of finds
13420 The maximum number of matches to print. The default is to print all finds.
13423 You can use strings as search values. Quote them with double-quotes
13425 The string value is copied into the search pattern byte by byte,
13426 regardless of the endianness of the target and the size specification.
13428 The address of each match found is printed as well as a count of the
13429 number of matches found.
13431 The address of the last value found is stored in convenience variable
13433 A count of the number of matches is stored in @samp{$numfound}.
13435 For example, if stopped at the @code{printf} in this function:
13441 static char hello[] = "hello-hello";
13442 static struct @{ char c; short s; int i; @}
13443 __attribute__ ((packed)) mixed
13444 = @{ 'c', 0x1234, 0x87654321 @};
13445 printf ("%s\n", hello);
13450 you get during debugging:
13453 (gdb) find &hello[0], +sizeof(hello), "hello"
13454 0x804956d <hello.1620+6>
13456 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
13457 0x8049567 <hello.1620>
13458 0x804956d <hello.1620+6>
13460 (gdb) find &hello[0], +sizeof(hello), @{char[5]@}"hello"
13461 0x8049567 <hello.1620>
13462 0x804956d <hello.1620+6>
13464 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
13465 0x8049567 <hello.1620>
13467 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
13468 0x8049560 <mixed.1625>
13470 (gdb) print $numfound
13473 $2 = (void *) 0x8049560
13477 @section Value Sizes
13479 Whenever @value{GDBN} prints a value memory will be allocated within
13480 @value{GDBN} to hold the contents of the value. It is possible in
13481 some languages with dynamic typing systems, that an invalid program
13482 may indicate a value that is incorrectly large, this in turn may cause
13483 @value{GDBN} to try and allocate an overly large amount of memory.
13486 @kindex set max-value-size
13487 @item set max-value-size @var{bytes}
13488 @itemx set max-value-size unlimited
13489 Set the maximum size of memory that @value{GDBN} will allocate for the
13490 contents of a value to @var{bytes}, trying to display a value that
13491 requires more memory than that will result in an error.
13493 Setting this variable does not effect values that have already been
13494 allocated within @value{GDBN}, only future allocations.
13496 There's a minimum size that @code{max-value-size} can be set to in
13497 order that @value{GDBN} can still operate correctly, this minimum is
13498 currently 16 bytes.
13500 The limit applies to the results of some subexpressions as well as to
13501 complete expressions. For example, an expression denoting a simple
13502 integer component, such as @code{x.y.z}, may fail if the size of
13503 @var{x.y} is dynamic and exceeds @var{bytes}. On the other hand,
13504 @value{GDBN} is sometimes clever; the expression @code{A[i]}, where
13505 @var{A} is an array variable with non-constant size, will generally
13506 succeed regardless of the bounds on @var{A}, as long as the component
13507 size is less than @var{bytes}.
13509 The default value of @code{max-value-size} is currently 64k.
13511 @kindex show max-value-size
13512 @item show max-value-size
13513 Show the maximum size of memory, in bytes, that @value{GDBN} will
13514 allocate for the contents of a value.
13517 @node Optimized Code
13518 @chapter Debugging Optimized Code
13519 @cindex optimized code, debugging
13520 @cindex debugging optimized code
13522 Almost all compilers support optimization. With optimization
13523 disabled, the compiler generates assembly code that corresponds
13524 directly to your source code, in a simplistic way. As the compiler
13525 applies more powerful optimizations, the generated assembly code
13526 diverges from your original source code. With help from debugging
13527 information generated by the compiler, @value{GDBN} can map from
13528 the running program back to constructs from your original source.
13530 @value{GDBN} is more accurate with optimization disabled. If you
13531 can recompile without optimization, it is easier to follow the
13532 progress of your program during debugging. But, there are many cases
13533 where you may need to debug an optimized version.
13535 When you debug a program compiled with @samp{-g -O}, remember that the
13536 optimizer has rearranged your code; the debugger shows you what is
13537 really there. Do not be too surprised when the execution path does not
13538 exactly match your source file! An extreme example: if you define a
13539 variable, but never use it, @value{GDBN} never sees that
13540 variable---because the compiler optimizes it out of existence.
13542 Some things do not work as well with @samp{-g -O} as with just
13543 @samp{-g}, particularly on machines with instruction scheduling. If in
13544 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
13545 please report it to us as a bug (including a test case!).
13546 @xref{Variables}, for more information about debugging optimized code.
13549 * Inline Functions:: How @value{GDBN} presents inlining
13550 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
13553 @node Inline Functions
13554 @section Inline Functions
13555 @cindex inline functions, debugging
13557 @dfn{Inlining} is an optimization that inserts a copy of the function
13558 body directly at each call site, instead of jumping to a shared
13559 routine. @value{GDBN} displays inlined functions just like
13560 non-inlined functions. They appear in backtraces. You can view their
13561 arguments and local variables, step into them with @code{step}, skip
13562 them with @code{next}, and escape from them with @code{finish}.
13563 You can check whether a function was inlined by using the
13564 @code{info frame} command.
13566 For @value{GDBN} to support inlined functions, the compiler must
13567 record information about inlining in the debug information ---
13568 @value{NGCC} using the @sc{dwarf 2} format does this, and several
13569 other compilers do also. @value{GDBN} only supports inlined functions
13570 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
13571 do not emit two required attributes (@samp{DW_AT_call_file} and
13572 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
13573 function calls with earlier versions of @value{NGCC}. It instead
13574 displays the arguments and local variables of inlined functions as
13575 local variables in the caller.
13577 The body of an inlined function is directly included at its call site;
13578 unlike a non-inlined function, there are no instructions devoted to
13579 the call. @value{GDBN} still pretends that the call site and the
13580 start of the inlined function are different instructions. Stepping to
13581 the call site shows the call site, and then stepping again shows
13582 the first line of the inlined function, even though no additional
13583 instructions are executed.
13585 This makes source-level debugging much clearer; you can see both the
13586 context of the call and then the effect of the call. Only stepping by
13587 a single instruction using @code{stepi} or @code{nexti} does not do
13588 this; single instruction steps always show the inlined body.
13590 There are some ways that @value{GDBN} does not pretend that inlined
13591 function calls are the same as normal calls:
13595 Setting breakpoints at the call site of an inlined function may not
13596 work, because the call site does not contain any code. @value{GDBN}
13597 may incorrectly move the breakpoint to the next line of the enclosing
13598 function, after the call. This limitation will be removed in a future
13599 version of @value{GDBN}; until then, set a breakpoint on an earlier line
13600 or inside the inlined function instead.
13603 @value{GDBN} cannot locate the return value of inlined calls after
13604 using the @code{finish} command. This is a limitation of compiler-generated
13605 debugging information; after @code{finish}, you can step to the next line
13606 and print a variable where your program stored the return value.
13610 @node Tail Call Frames
13611 @section Tail Call Frames
13612 @cindex tail call frames, debugging
13614 Function @code{B} can call function @code{C} in its very last statement. In
13615 unoptimized compilation the call of @code{C} is immediately followed by return
13616 instruction at the end of @code{B} code. Optimizing compiler may replace the
13617 call and return in function @code{B} into one jump to function @code{C}
13618 instead. Such use of a jump instruction is called @dfn{tail call}.
13620 During execution of function @code{C}, there will be no indication in the
13621 function call stack frames that it was tail-called from @code{B}. If function
13622 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
13623 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
13624 some cases @value{GDBN} can determine that @code{C} was tail-called from
13625 @code{B}, and it will then create fictitious call frame for that, with the
13626 return address set up as if @code{B} called @code{C} normally.
13628 This functionality is currently supported only by DWARF 2 debugging format and
13629 the compiler has to produce @samp{DW_TAG_call_site} tags. With
13630 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
13633 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
13634 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
13638 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
13640 Stack level 1, frame at 0x7fffffffda30:
13641 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
13642 tail call frame, caller of frame at 0x7fffffffda30
13643 source language c++.
13644 Arglist at unknown address.
13645 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
13648 The detection of all the possible code path executions can find them ambiguous.
13649 There is no execution history stored (possible @ref{Reverse Execution} is never
13650 used for this purpose) and the last known caller could have reached the known
13651 callee by multiple different jump sequences. In such case @value{GDBN} still
13652 tries to show at least all the unambiguous top tail callers and all the
13653 unambiguous bottom tail calees, if any.
13656 @anchor{set debug entry-values}
13657 @item set debug entry-values
13658 @kindex set debug entry-values
13659 When set to on, enables printing of analysis messages for both frame argument
13660 values at function entry and tail calls. It will show all the possible valid
13661 tail calls code paths it has considered. It will also print the intersection
13662 of them with the final unambiguous (possibly partial or even empty) code path
13665 @item show debug entry-values
13666 @kindex show debug entry-values
13667 Show the current state of analysis messages printing for both frame argument
13668 values at function entry and tail calls.
13671 The analysis messages for tail calls can for example show why the virtual tail
13672 call frame for function @code{c} has not been recognized (due to the indirect
13673 reference by variable @code{x}):
13676 static void __attribute__((noinline, noclone)) c (void);
13677 void (*x) (void) = c;
13678 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
13679 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
13680 int main (void) @{ x (); return 0; @}
13682 Breakpoint 1, DW_OP_entry_value resolving cannot find
13683 DW_TAG_call_site 0x40039a in main
13685 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
13688 #1 0x000000000040039a in main () at t.c:5
13691 Another possibility is an ambiguous virtual tail call frames resolution:
13695 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
13696 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
13697 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
13698 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
13699 static void __attribute__((noinline, noclone)) b (void)
13700 @{ if (i) c (); else e (); @}
13701 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
13702 int main (void) @{ a (); return 0; @}
13704 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
13705 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
13706 tailcall: reduced: 0x4004d2(a) |
13709 #1 0x00000000004004d2 in a () at t.c:8
13710 #2 0x0000000000400395 in main () at t.c:9
13713 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
13714 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
13716 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
13717 @ifset HAVE_MAKEINFO_CLICK
13718 @set ARROW @click{}
13719 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
13720 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
13722 @ifclear HAVE_MAKEINFO_CLICK
13724 @set CALLSEQ1B @value{CALLSEQ1A}
13725 @set CALLSEQ2B @value{CALLSEQ2A}
13728 Frames #0 and #2 are real, #1 is a virtual tail call frame.
13729 The code can have possible execution paths @value{CALLSEQ1B} or
13730 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
13732 @code{initial:} state shows some random possible calling sequence @value{GDBN}
13733 has found. It then finds another possible calling sequence - that one is
13734 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
13735 printed as the @code{reduced:} calling sequence. That one could have many
13736 further @code{compare:} and @code{reduced:} statements as long as there remain
13737 any non-ambiguous sequence entries.
13739 For the frame of function @code{b} in both cases there are different possible
13740 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
13741 also ambiguous. The only non-ambiguous frame is the one for function @code{a},
13742 therefore this one is displayed to the user while the ambiguous frames are
13745 There can be also reasons why printing of frame argument values at function
13750 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
13751 static void __attribute__((noinline, noclone)) a (int i);
13752 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
13753 static void __attribute__((noinline, noclone)) a (int i)
13754 @{ if (i) b (i - 1); else c (0); @}
13755 int main (void) @{ a (5); return 0; @}
13758 #0 c (i=i@@entry=0) at t.c:2
13759 #1 0x0000000000400428 in a (DW_OP_entry_value resolving has found
13760 function "a" at 0x400420 can call itself via tail calls
13761 i=<optimized out>) at t.c:6
13762 #2 0x000000000040036e in main () at t.c:7
13765 @value{GDBN} cannot find out from the inferior state if and how many times did
13766 function @code{a} call itself (via function @code{b}) as these calls would be
13767 tail calls. Such tail calls would modify the @code{i} variable, therefore
13768 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
13769 prints @code{<optimized out>} instead.
13772 @chapter C Preprocessor Macros
13774 Some languages, such as C and C@t{++}, provide a way to define and invoke
13775 ``preprocessor macros'' which expand into strings of tokens.
13776 @value{GDBN} can evaluate expressions containing macro invocations, show
13777 the result of macro expansion, and show a macro's definition, including
13778 where it was defined.
13780 You may need to compile your program specially to provide @value{GDBN}
13781 with information about preprocessor macros. Most compilers do not
13782 include macros in their debugging information, even when you compile
13783 with the @option{-g} flag. @xref{Compilation}.
13785 A program may define a macro at one point, remove that definition later,
13786 and then provide a different definition after that. Thus, at different
13787 points in the program, a macro may have different definitions, or have
13788 no definition at all. If there is a current stack frame, @value{GDBN}
13789 uses the macros in scope at that frame's source code line. Otherwise,
13790 @value{GDBN} uses the macros in scope at the current listing location;
13793 Whenever @value{GDBN} evaluates an expression, it always expands any
13794 macro invocations present in the expression. @value{GDBN} also provides
13795 the following commands for working with macros explicitly.
13799 @kindex macro expand
13800 @cindex macro expansion, showing the results of preprocessor
13801 @cindex preprocessor macro expansion, showing the results of
13802 @cindex expanding preprocessor macros
13803 @item macro expand @var{expression}
13804 @itemx macro exp @var{expression}
13805 Show the results of expanding all preprocessor macro invocations in
13806 @var{expression}. Since @value{GDBN} simply expands macros, but does
13807 not parse the result, @var{expression} need not be a valid expression;
13808 it can be any string of tokens.
13811 @item macro expand-once @var{expression}
13812 @itemx macro exp1 @var{expression}
13813 @cindex expand macro once
13814 @i{(This command is not yet implemented.)} Show the results of
13815 expanding those preprocessor macro invocations that appear explicitly in
13816 @var{expression}. Macro invocations appearing in that expansion are
13817 left unchanged. This command allows you to see the effect of a
13818 particular macro more clearly, without being confused by further
13819 expansions. Since @value{GDBN} simply expands macros, but does not
13820 parse the result, @var{expression} need not be a valid expression; it
13821 can be any string of tokens.
13824 @cindex macro definition, showing
13825 @cindex definition of a macro, showing
13826 @cindex macros, from debug info
13827 @item info macro [-a|-all] [--] @var{macro}
13828 Show the current definition or all definitions of the named @var{macro},
13829 and describe the source location or compiler command-line where that
13830 definition was established. The optional double dash is to signify the end of
13831 argument processing and the beginning of @var{macro} for non C-like macros where
13832 the macro may begin with a hyphen.
13834 @kindex info macros
13835 @item info macros @var{location}
13836 Show all macro definitions that are in effect at the location specified
13837 by @var{location}, and describe the source location or compiler
13838 command-line where those definitions were established.
13840 @kindex macro define
13841 @cindex user-defined macros
13842 @cindex defining macros interactively
13843 @cindex macros, user-defined
13844 @item macro define @var{macro} @var{replacement-list}
13845 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
13846 Introduce a definition for a preprocessor macro named @var{macro},
13847 invocations of which are replaced by the tokens given in
13848 @var{replacement-list}. The first form of this command defines an
13849 ``object-like'' macro, which takes no arguments; the second form
13850 defines a ``function-like'' macro, which takes the arguments given in
13853 A definition introduced by this command is in scope in every
13854 expression evaluated in @value{GDBN}, until it is removed with the
13855 @code{macro undef} command, described below. The definition overrides
13856 all definitions for @var{macro} present in the program being debugged,
13857 as well as any previous user-supplied definition.
13859 @kindex macro undef
13860 @item macro undef @var{macro}
13861 Remove any user-supplied definition for the macro named @var{macro}.
13862 This command only affects definitions provided with the @code{macro
13863 define} command, described above; it cannot remove definitions present
13864 in the program being debugged.
13868 List all the macros defined using the @code{macro define} command.
13871 @cindex macros, example of debugging with
13872 Here is a transcript showing the above commands in action. First, we
13873 show our source files:
13878 #include "sample.h"
13881 #define ADD(x) (M + x)
13886 printf ("Hello, world!\n");
13888 printf ("We're so creative.\n");
13890 printf ("Goodbye, world!\n");
13897 Now, we compile the program using the @sc{gnu} C compiler,
13898 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
13899 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
13900 and @option{-gdwarf-4}; we recommend always choosing the most recent
13901 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
13902 includes information about preprocessor macros in the debugging
13906 $ gcc -gdwarf-2 -g3 sample.c -o sample
13910 Now, we start @value{GDBN} on our sample program:
13914 GNU gdb 2002-05-06-cvs
13915 Copyright 2002 Free Software Foundation, Inc.
13916 GDB is free software, @dots{}
13920 We can expand macros and examine their definitions, even when the
13921 program is not running. @value{GDBN} uses the current listing position
13922 to decide which macro definitions are in scope:
13925 (@value{GDBP}) list main
13928 5 #define ADD(x) (M + x)
13933 10 printf ("Hello, world!\n");
13935 12 printf ("We're so creative.\n");
13936 (@value{GDBP}) info macro ADD
13937 Defined at /home/jimb/gdb/macros/play/sample.c:5
13938 #define ADD(x) (M + x)
13939 (@value{GDBP}) info macro Q
13940 Defined at /home/jimb/gdb/macros/play/sample.h:1
13941 included at /home/jimb/gdb/macros/play/sample.c:2
13943 (@value{GDBP}) macro expand ADD(1)
13944 expands to: (42 + 1)
13945 (@value{GDBP}) macro expand-once ADD(1)
13946 expands to: once (M + 1)
13950 In the example above, note that @code{macro expand-once} expands only
13951 the macro invocation explicit in the original text --- the invocation of
13952 @code{ADD} --- but does not expand the invocation of the macro @code{M},
13953 which was introduced by @code{ADD}.
13955 Once the program is running, @value{GDBN} uses the macro definitions in
13956 force at the source line of the current stack frame:
13959 (@value{GDBP}) break main
13960 Breakpoint 1 at 0x8048370: file sample.c, line 10.
13962 Starting program: /home/jimb/gdb/macros/play/sample
13964 Breakpoint 1, main () at sample.c:10
13965 10 printf ("Hello, world!\n");
13969 At line 10, the definition of the macro @code{N} at line 9 is in force:
13972 (@value{GDBP}) info macro N
13973 Defined at /home/jimb/gdb/macros/play/sample.c:9
13975 (@value{GDBP}) macro expand N Q M
13976 expands to: 28 < 42
13977 (@value{GDBP}) print N Q M
13982 As we step over directives that remove @code{N}'s definition, and then
13983 give it a new definition, @value{GDBN} finds the definition (or lack
13984 thereof) in force at each point:
13987 (@value{GDBP}) next
13989 12 printf ("We're so creative.\n");
13990 (@value{GDBP}) info macro N
13991 The symbol `N' has no definition as a C/C++ preprocessor macro
13992 at /home/jimb/gdb/macros/play/sample.c:12
13993 (@value{GDBP}) next
13995 14 printf ("Goodbye, world!\n");
13996 (@value{GDBP}) info macro N
13997 Defined at /home/jimb/gdb/macros/play/sample.c:13
13999 (@value{GDBP}) macro expand N Q M
14000 expands to: 1729 < 42
14001 (@value{GDBP}) print N Q M
14006 In addition to source files, macros can be defined on the compilation command
14007 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
14008 such a way, @value{GDBN} displays the location of their definition as line zero
14009 of the source file submitted to the compiler.
14012 (@value{GDBP}) info macro __STDC__
14013 Defined at /home/jimb/gdb/macros/play/sample.c:0
14020 @chapter Tracepoints
14021 @c This chapter is based on the documentation written by Michael
14022 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
14024 @cindex tracepoints
14025 In some applications, it is not feasible for the debugger to interrupt
14026 the program's execution long enough for the developer to learn
14027 anything helpful about its behavior. If the program's correctness
14028 depends on its real-time behavior, delays introduced by a debugger
14029 might cause the program to change its behavior drastically, or perhaps
14030 fail, even when the code itself is correct. It is useful to be able
14031 to observe the program's behavior without interrupting it.
14033 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
14034 specify locations in the program, called @dfn{tracepoints}, and
14035 arbitrary expressions to evaluate when those tracepoints are reached.
14036 Later, using the @code{tfind} command, you can examine the values
14037 those expressions had when the program hit the tracepoints. The
14038 expressions may also denote objects in memory---structures or arrays,
14039 for example---whose values @value{GDBN} should record; while visiting
14040 a particular tracepoint, you may inspect those objects as if they were
14041 in memory at that moment. However, because @value{GDBN} records these
14042 values without interacting with you, it can do so quickly and
14043 unobtrusively, hopefully not disturbing the program's behavior.
14045 The tracepoint facility is currently available only for remote
14046 targets. @xref{Targets}. In addition, your remote target must know
14047 how to collect trace data. This functionality is implemented in the
14048 remote stub; however, none of the stubs distributed with @value{GDBN}
14049 support tracepoints as of this writing. The format of the remote
14050 packets used to implement tracepoints are described in @ref{Tracepoint
14053 It is also possible to get trace data from a file, in a manner reminiscent
14054 of corefiles; you specify the filename, and use @code{tfind} to search
14055 through the file. @xref{Trace Files}, for more details.
14057 This chapter describes the tracepoint commands and features.
14060 * Set Tracepoints::
14061 * Analyze Collected Data::
14062 * Tracepoint Variables::
14066 @node Set Tracepoints
14067 @section Commands to Set Tracepoints
14069 Before running such a @dfn{trace experiment}, an arbitrary number of
14070 tracepoints can be set. A tracepoint is actually a special type of
14071 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
14072 standard breakpoint commands. For instance, as with breakpoints,
14073 tracepoint numbers are successive integers starting from one, and many
14074 of the commands associated with tracepoints take the tracepoint number
14075 as their argument, to identify which tracepoint to work on.
14077 For each tracepoint, you can specify, in advance, some arbitrary set
14078 of data that you want the target to collect in the trace buffer when
14079 it hits that tracepoint. The collected data can include registers,
14080 local variables, or global data. Later, you can use @value{GDBN}
14081 commands to examine the values these data had at the time the
14082 tracepoint was hit.
14084 Tracepoints do not support every breakpoint feature. Ignore counts on
14085 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
14086 commands when they are hit. Tracepoints may not be thread-specific
14089 @cindex fast tracepoints
14090 Some targets may support @dfn{fast tracepoints}, which are inserted in
14091 a different way (such as with a jump instead of a trap), that is
14092 faster but possibly restricted in where they may be installed.
14094 @cindex static tracepoints
14095 @cindex markers, static tracepoints
14096 @cindex probing markers, static tracepoints
14097 Regular and fast tracepoints are dynamic tracing facilities, meaning
14098 that they can be used to insert tracepoints at (almost) any location
14099 in the target. Some targets may also support controlling @dfn{static
14100 tracepoints} from @value{GDBN}. With static tracing, a set of
14101 instrumentation points, also known as @dfn{markers}, are embedded in
14102 the target program, and can be activated or deactivated by name or
14103 address. These are usually placed at locations which facilitate
14104 investigating what the target is actually doing. @value{GDBN}'s
14105 support for static tracing includes being able to list instrumentation
14106 points, and attach them with @value{GDBN} defined high level
14107 tracepoints that expose the whole range of convenience of
14108 @value{GDBN}'s tracepoints support. Namely, support for collecting
14109 registers values and values of global or local (to the instrumentation
14110 point) variables; tracepoint conditions and trace state variables.
14111 The act of installing a @value{GDBN} static tracepoint on an
14112 instrumentation point, or marker, is referred to as @dfn{probing} a
14113 static tracepoint marker.
14115 @code{gdbserver} supports tracepoints on some target systems.
14116 @xref{Server,,Tracepoints support in @code{gdbserver}}.
14118 This section describes commands to set tracepoints and associated
14119 conditions and actions.
14122 * Create and Delete Tracepoints::
14123 * Enable and Disable Tracepoints::
14124 * Tracepoint Passcounts::
14125 * Tracepoint Conditions::
14126 * Trace State Variables::
14127 * Tracepoint Actions::
14128 * Listing Tracepoints::
14129 * Listing Static Tracepoint Markers::
14130 * Starting and Stopping Trace Experiments::
14131 * Tracepoint Restrictions::
14134 @node Create and Delete Tracepoints
14135 @subsection Create and Delete Tracepoints
14138 @cindex set tracepoint
14140 @item trace @var{location}
14141 The @code{trace} command is very similar to the @code{break} command.
14142 Its argument @var{location} can be any valid location.
14143 @xref{Specify Location}. The @code{trace} command defines a tracepoint,
14144 which is a point in the target program where the debugger will briefly stop,
14145 collect some data, and then allow the program to continue. Setting a tracepoint
14146 or changing its actions takes effect immediately if the remote stub
14147 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
14149 If remote stub doesn't support the @samp{InstallInTrace} feature, all
14150 these changes don't take effect until the next @code{tstart}
14151 command, and once a trace experiment is running, further changes will
14152 not have any effect until the next trace experiment starts. In addition,
14153 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
14154 address is not yet resolved. (This is similar to pending breakpoints.)
14155 Pending tracepoints are not downloaded to the target and not installed
14156 until they are resolved. The resolution of pending tracepoints requires
14157 @value{GDBN} support---when debugging with the remote target, and
14158 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
14159 tracing}), pending tracepoints can not be resolved (and downloaded to
14160 the remote stub) while @value{GDBN} is disconnected.
14162 Here are some examples of using the @code{trace} command:
14165 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
14167 (@value{GDBP}) @b{trace +2} // 2 lines forward
14169 (@value{GDBP}) @b{trace my_function} // first source line of function
14171 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
14173 (@value{GDBP}) @b{trace *0x2117c4} // an address
14177 You can abbreviate @code{trace} as @code{tr}.
14179 @item trace @var{location} if @var{cond}
14180 Set a tracepoint with condition @var{cond}; evaluate the expression
14181 @var{cond} each time the tracepoint is reached, and collect data only
14182 if the value is nonzero---that is, if @var{cond} evaluates as true.
14183 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
14184 information on tracepoint conditions.
14186 @item ftrace @var{location} [ if @var{cond} ]
14187 @cindex set fast tracepoint
14188 @cindex fast tracepoints, setting
14190 The @code{ftrace} command sets a fast tracepoint. For targets that
14191 support them, fast tracepoints will use a more efficient but possibly
14192 less general technique to trigger data collection, such as a jump
14193 instruction instead of a trap, or some sort of hardware support. It
14194 may not be possible to create a fast tracepoint at the desired
14195 location, in which case the command will exit with an explanatory
14198 @value{GDBN} handles arguments to @code{ftrace} exactly as for
14201 On 32-bit x86-architecture systems, fast tracepoints normally need to
14202 be placed at an instruction that is 5 bytes or longer, but can be
14203 placed at 4-byte instructions if the low 64K of memory of the target
14204 program is available to install trampolines. Some Unix-type systems,
14205 such as @sc{gnu}/Linux, exclude low addresses from the program's
14206 address space; but for instance with the Linux kernel it is possible
14207 to let @value{GDBN} use this area by doing a @command{sysctl} command
14208 to set the @code{mmap_min_addr} kernel parameter, as in
14211 sudo sysctl -w vm.mmap_min_addr=32768
14215 which sets the low address to 32K, which leaves plenty of room for
14216 trampolines. The minimum address should be set to a page boundary.
14218 @item strace @var{location} [ if @var{cond} ]
14219 @cindex set static tracepoint
14220 @cindex static tracepoints, setting
14221 @cindex probe static tracepoint marker
14223 The @code{strace} command sets a static tracepoint. For targets that
14224 support it, setting a static tracepoint probes a static
14225 instrumentation point, or marker, found at @var{location}. It may not
14226 be possible to set a static tracepoint at the desired location, in
14227 which case the command will exit with an explanatory message.
14229 @value{GDBN} handles arguments to @code{strace} exactly as for
14230 @code{trace}, with the addition that the user can also specify
14231 @code{-m @var{marker}} as @var{location}. This probes the marker
14232 identified by the @var{marker} string identifier. This identifier
14233 depends on the static tracepoint backend library your program is
14234 using. You can find all the marker identifiers in the @samp{ID} field
14235 of the @code{info static-tracepoint-markers} command output.
14236 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
14237 Markers}. For example, in the following small program using the UST
14243 trace_mark(ust, bar33, "str %s", "FOOBAZ");
14248 the marker id is composed of joining the first two arguments to the
14249 @code{trace_mark} call with a slash, which translates to:
14252 (@value{GDBP}) info static-tracepoint-markers
14253 Cnt Enb ID Address What
14254 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
14260 so you may probe the marker above with:
14263 (@value{GDBP}) strace -m ust/bar33
14266 Static tracepoints accept an extra collect action --- @code{collect
14267 $_sdata}. This collects arbitrary user data passed in the probe point
14268 call to the tracing library. In the UST example above, you'll see
14269 that the third argument to @code{trace_mark} is a printf-like format
14270 string. The user data is then the result of running that formatting
14271 string against the following arguments. Note that @code{info
14272 static-tracepoint-markers} command output lists that format string in
14273 the @samp{Data:} field.
14275 You can inspect this data when analyzing the trace buffer, by printing
14276 the $_sdata variable like any other variable available to
14277 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
14280 @cindex last tracepoint number
14281 @cindex recent tracepoint number
14282 @cindex tracepoint number
14283 The convenience variable @code{$tpnum} records the tracepoint number
14284 of the most recently set tracepoint.
14286 @kindex delete tracepoint
14287 @cindex tracepoint deletion
14288 @item delete tracepoint @r{[}@var{num}@r{]}
14289 Permanently delete one or more tracepoints. With no argument, the
14290 default is to delete all tracepoints. Note that the regular
14291 @code{delete} command can remove tracepoints also.
14296 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
14298 (@value{GDBP}) @b{delete trace} // remove all tracepoints
14302 You can abbreviate this command as @code{del tr}.
14305 @node Enable and Disable Tracepoints
14306 @subsection Enable and Disable Tracepoints
14308 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
14311 @kindex disable tracepoint
14312 @item disable tracepoint @r{[}@var{num}@r{]}
14313 Disable tracepoint @var{num}, or all tracepoints if no argument
14314 @var{num} is given. A disabled tracepoint will have no effect during
14315 a trace experiment, but it is not forgotten. You can re-enable
14316 a disabled tracepoint using the @code{enable tracepoint} command.
14317 If the command is issued during a trace experiment and the debug target
14318 has support for disabling tracepoints during a trace experiment, then the
14319 change will be effective immediately. Otherwise, it will be applied to the
14320 next trace experiment.
14322 @kindex enable tracepoint
14323 @item enable tracepoint @r{[}@var{num}@r{]}
14324 Enable tracepoint @var{num}, or all tracepoints. If this command is
14325 issued during a trace experiment and the debug target supports enabling
14326 tracepoints during a trace experiment, then the enabled tracepoints will
14327 become effective immediately. Otherwise, they will become effective the
14328 next time a trace experiment is run.
14331 @node Tracepoint Passcounts
14332 @subsection Tracepoint Passcounts
14336 @cindex tracepoint pass count
14337 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
14338 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
14339 automatically stop a trace experiment. If a tracepoint's passcount is
14340 @var{n}, then the trace experiment will be automatically stopped on
14341 the @var{n}'th time that tracepoint is hit. If the tracepoint number
14342 @var{num} is not specified, the @code{passcount} command sets the
14343 passcount of the most recently defined tracepoint. If no passcount is
14344 given, the trace experiment will run until stopped explicitly by the
14350 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
14351 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
14353 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
14354 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
14355 (@value{GDBP}) @b{trace foo}
14356 (@value{GDBP}) @b{pass 3}
14357 (@value{GDBP}) @b{trace bar}
14358 (@value{GDBP}) @b{pass 2}
14359 (@value{GDBP}) @b{trace baz}
14360 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
14361 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
14362 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
14363 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
14367 @node Tracepoint Conditions
14368 @subsection Tracepoint Conditions
14369 @cindex conditional tracepoints
14370 @cindex tracepoint conditions
14372 The simplest sort of tracepoint collects data every time your program
14373 reaches a specified place. You can also specify a @dfn{condition} for
14374 a tracepoint. A condition is just a Boolean expression in your
14375 programming language (@pxref{Expressions, ,Expressions}). A
14376 tracepoint with a condition evaluates the expression each time your
14377 program reaches it, and data collection happens only if the condition
14380 Tracepoint conditions can be specified when a tracepoint is set, by
14381 using @samp{if} in the arguments to the @code{trace} command.
14382 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
14383 also be set or changed at any time with the @code{condition} command,
14384 just as with breakpoints.
14386 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
14387 the conditional expression itself. Instead, @value{GDBN} encodes the
14388 expression into an agent expression (@pxref{Agent Expressions})
14389 suitable for execution on the target, independently of @value{GDBN}.
14390 Global variables become raw memory locations, locals become stack
14391 accesses, and so forth.
14393 For instance, suppose you have a function that is usually called
14394 frequently, but should not be called after an error has occurred. You
14395 could use the following tracepoint command to collect data about calls
14396 of that function that happen while the error code is propagating
14397 through the program; an unconditional tracepoint could end up
14398 collecting thousands of useless trace frames that you would have to
14402 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
14405 @node Trace State Variables
14406 @subsection Trace State Variables
14407 @cindex trace state variables
14409 A @dfn{trace state variable} is a special type of variable that is
14410 created and managed by target-side code. The syntax is the same as
14411 that for GDB's convenience variables (a string prefixed with ``$''),
14412 but they are stored on the target. They must be created explicitly,
14413 using a @code{tvariable} command. They are always 64-bit signed
14416 Trace state variables are remembered by @value{GDBN}, and downloaded
14417 to the target along with tracepoint information when the trace
14418 experiment starts. There are no intrinsic limits on the number of
14419 trace state variables, beyond memory limitations of the target.
14421 @cindex convenience variables, and trace state variables
14422 Although trace state variables are managed by the target, you can use
14423 them in print commands and expressions as if they were convenience
14424 variables; @value{GDBN} will get the current value from the target
14425 while the trace experiment is running. Trace state variables share
14426 the same namespace as other ``$'' variables, which means that you
14427 cannot have trace state variables with names like @code{$23} or
14428 @code{$pc}, nor can you have a trace state variable and a convenience
14429 variable with the same name.
14433 @item tvariable $@var{name} [ = @var{expression} ]
14435 The @code{tvariable} command creates a new trace state variable named
14436 @code{$@var{name}}, and optionally gives it an initial value of
14437 @var{expression}. The @var{expression} is evaluated when this command is
14438 entered; the result will be converted to an integer if possible,
14439 otherwise @value{GDBN} will report an error. A subsequent
14440 @code{tvariable} command specifying the same name does not create a
14441 variable, but instead assigns the supplied initial value to the
14442 existing variable of that name, overwriting any previous initial
14443 value. The default initial value is 0.
14445 @item info tvariables
14446 @kindex info tvariables
14447 List all the trace state variables along with their initial values.
14448 Their current values may also be displayed, if the trace experiment is
14451 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
14452 @kindex delete tvariable
14453 Delete the given trace state variables, or all of them if no arguments
14458 @node Tracepoint Actions
14459 @subsection Tracepoint Action Lists
14463 @cindex tracepoint actions
14464 @item actions @r{[}@var{num}@r{]}
14465 This command will prompt for a list of actions to be taken when the
14466 tracepoint is hit. If the tracepoint number @var{num} is not
14467 specified, this command sets the actions for the one that was most
14468 recently defined (so that you can define a tracepoint and then say
14469 @code{actions} without bothering about its number). You specify the
14470 actions themselves on the following lines, one action at a time, and
14471 terminate the actions list with a line containing just @code{end}. So
14472 far, the only defined actions are @code{collect}, @code{teval}, and
14473 @code{while-stepping}.
14475 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
14476 Commands, ,Breakpoint Command Lists}), except that only the defined
14477 actions are allowed; any other @value{GDBN} command is rejected.
14479 @cindex remove actions from a tracepoint
14480 To remove all actions from a tracepoint, type @samp{actions @var{num}}
14481 and follow it immediately with @samp{end}.
14484 (@value{GDBP}) @b{collect @var{data}} // collect some data
14486 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
14488 (@value{GDBP}) @b{end} // signals the end of actions.
14491 In the following example, the action list begins with @code{collect}
14492 commands indicating the things to be collected when the tracepoint is
14493 hit. Then, in order to single-step and collect additional data
14494 following the tracepoint, a @code{while-stepping} command is used,
14495 followed by the list of things to be collected after each step in a
14496 sequence of single steps. The @code{while-stepping} command is
14497 terminated by its own separate @code{end} command. Lastly, the action
14498 list is terminated by an @code{end} command.
14501 (@value{GDBP}) @b{trace foo}
14502 (@value{GDBP}) @b{actions}
14503 Enter actions for tracepoint 1, one per line:
14506 > while-stepping 12
14507 > collect $pc, arr[i]
14512 @kindex collect @r{(tracepoints)}
14513 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
14514 Collect values of the given expressions when the tracepoint is hit.
14515 This command accepts a comma-separated list of any valid expressions.
14516 In addition to global, static, or local variables, the following
14517 special arguments are supported:
14521 Collect all registers.
14524 Collect all function arguments.
14527 Collect all local variables.
14530 Collect the return address. This is helpful if you want to see more
14533 @emph{Note:} The return address location can not always be reliably
14534 determined up front, and the wrong address / registers may end up
14535 collected instead. On some architectures the reliability is higher
14536 for tracepoints at function entry, while on others it's the opposite.
14537 When this happens, backtracing will stop because the return address is
14538 found unavailable (unless another collect rule happened to match it).
14541 Collects the number of arguments from the static probe at which the
14542 tracepoint is located.
14543 @xref{Static Probe Points}.
14545 @item $_probe_arg@var{n}
14546 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
14547 from the static probe at which the tracepoint is located.
14548 @xref{Static Probe Points}.
14551 @vindex $_sdata@r{, collect}
14552 Collect static tracepoint marker specific data. Only available for
14553 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
14554 Lists}. On the UST static tracepoints library backend, an
14555 instrumentation point resembles a @code{printf} function call. The
14556 tracing library is able to collect user specified data formatted to a
14557 character string using the format provided by the programmer that
14558 instrumented the program. Other backends have similar mechanisms.
14559 Here's an example of a UST marker call:
14562 const char master_name[] = "$your_name";
14563 trace_mark(channel1, marker1, "hello %s", master_name)
14566 In this case, collecting @code{$_sdata} collects the string
14567 @samp{hello $yourname}. When analyzing the trace buffer, you can
14568 inspect @samp{$_sdata} like any other variable available to
14572 You can give several consecutive @code{collect} commands, each one
14573 with a single argument, or one @code{collect} command with several
14574 arguments separated by commas; the effect is the same.
14576 The optional @var{mods} changes the usual handling of the arguments.
14577 @code{s} requests that pointers to chars be handled as strings, in
14578 particular collecting the contents of the memory being pointed at, up
14579 to the first zero. The upper bound is by default the value of the
14580 @code{print elements} variable; if @code{s} is followed by a decimal
14581 number, that is the upper bound instead. So for instance
14582 @samp{collect/s25 mystr} collects as many as 25 characters at
14585 The command @code{info scope} (@pxref{Symbols, info scope}) is
14586 particularly useful for figuring out what data to collect.
14588 @kindex teval @r{(tracepoints)}
14589 @item teval @var{expr1}, @var{expr2}, @dots{}
14590 Evaluate the given expressions when the tracepoint is hit. This
14591 command accepts a comma-separated list of expressions. The results
14592 are discarded, so this is mainly useful for assigning values to trace
14593 state variables (@pxref{Trace State Variables}) without adding those
14594 values to the trace buffer, as would be the case if the @code{collect}
14597 @kindex while-stepping @r{(tracepoints)}
14598 @item while-stepping @var{n}
14599 Perform @var{n} single-step instruction traces after the tracepoint,
14600 collecting new data after each step. The @code{while-stepping}
14601 command is followed by the list of what to collect while stepping
14602 (followed by its own @code{end} command):
14605 > while-stepping 12
14606 > collect $regs, myglobal
14612 Note that @code{$pc} is not automatically collected by
14613 @code{while-stepping}; you need to explicitly collect that register if
14614 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
14617 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
14618 @kindex set default-collect
14619 @cindex default collection action
14620 This variable is a list of expressions to collect at each tracepoint
14621 hit. It is effectively an additional @code{collect} action prepended
14622 to every tracepoint action list. The expressions are parsed
14623 individually for each tracepoint, so for instance a variable named
14624 @code{xyz} may be interpreted as a global for one tracepoint, and a
14625 local for another, as appropriate to the tracepoint's location.
14627 @item show default-collect
14628 @kindex show default-collect
14629 Show the list of expressions that are collected by default at each
14634 @node Listing Tracepoints
14635 @subsection Listing Tracepoints
14638 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
14639 @kindex info tp @r{[}@var{n}@dots{}@r{]}
14640 @cindex information about tracepoints
14641 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
14642 Display information about the tracepoint @var{num}. If you don't
14643 specify a tracepoint number, displays information about all the
14644 tracepoints defined so far. The format is similar to that used for
14645 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
14646 command, simply restricting itself to tracepoints.
14648 A tracepoint's listing may include additional information specific to
14653 its passcount as given by the @code{passcount @var{n}} command
14656 the state about installed on target of each location
14660 (@value{GDBP}) @b{info trace}
14661 Num Type Disp Enb Address What
14662 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
14664 collect globfoo, $regs
14669 2 tracepoint keep y <MULTIPLE>
14671 2.1 y 0x0804859c in func4 at change-loc.h:35
14672 installed on target
14673 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
14674 installed on target
14675 2.3 y <PENDING> set_tracepoint
14676 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
14677 not installed on target
14682 This command can be abbreviated @code{info tp}.
14685 @node Listing Static Tracepoint Markers
14686 @subsection Listing Static Tracepoint Markers
14689 @kindex info static-tracepoint-markers
14690 @cindex information about static tracepoint markers
14691 @item info static-tracepoint-markers
14692 Display information about all static tracepoint markers defined in the
14695 For each marker, the following columns are printed:
14699 An incrementing counter, output to help readability. This is not a
14702 The marker ID, as reported by the target.
14703 @item Enabled or Disabled
14704 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
14705 that are not enabled.
14707 Where the marker is in your program, as a memory address.
14709 Where the marker is in the source for your program, as a file and line
14710 number. If the debug information included in the program does not
14711 allow @value{GDBN} to locate the source of the marker, this column
14712 will be left blank.
14716 In addition, the following information may be printed for each marker:
14720 User data passed to the tracing library by the marker call. In the
14721 UST backend, this is the format string passed as argument to the
14723 @item Static tracepoints probing the marker
14724 The list of static tracepoints attached to the marker.
14728 (@value{GDBP}) info static-tracepoint-markers
14729 Cnt ID Enb Address What
14730 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
14731 Data: number1 %d number2 %d
14732 Probed by static tracepoints: #2
14733 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
14739 @node Starting and Stopping Trace Experiments
14740 @subsection Starting and Stopping Trace Experiments
14743 @kindex tstart [ @var{notes} ]
14744 @cindex start a new trace experiment
14745 @cindex collected data discarded
14747 This command starts the trace experiment, and begins collecting data.
14748 It has the side effect of discarding all the data collected in the
14749 trace buffer during the previous trace experiment. If any arguments
14750 are supplied, they are taken as a note and stored with the trace
14751 experiment's state. The notes may be arbitrary text, and are
14752 especially useful with disconnected tracing in a multi-user context;
14753 the notes can explain what the trace is doing, supply user contact
14754 information, and so forth.
14756 @kindex tstop [ @var{notes} ]
14757 @cindex stop a running trace experiment
14759 This command stops the trace experiment. If any arguments are
14760 supplied, they are recorded with the experiment as a note. This is
14761 useful if you are stopping a trace started by someone else, for
14762 instance if the trace is interfering with the system's behavior and
14763 needs to be stopped quickly.
14765 @strong{Note}: a trace experiment and data collection may stop
14766 automatically if any tracepoint's passcount is reached
14767 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
14770 @cindex status of trace data collection
14771 @cindex trace experiment, status of
14773 This command displays the status of the current trace data
14777 Here is an example of the commands we described so far:
14780 (@value{GDBP}) @b{trace gdb_c_test}
14781 (@value{GDBP}) @b{actions}
14782 Enter actions for tracepoint #1, one per line.
14783 > collect $regs,$locals,$args
14784 > while-stepping 11
14788 (@value{GDBP}) @b{tstart}
14789 [time passes @dots{}]
14790 (@value{GDBP}) @b{tstop}
14793 @anchor{disconnected tracing}
14794 @cindex disconnected tracing
14795 You can choose to continue running the trace experiment even if
14796 @value{GDBN} disconnects from the target, voluntarily or
14797 involuntarily. For commands such as @code{detach}, the debugger will
14798 ask what you want to do with the trace. But for unexpected
14799 terminations (@value{GDBN} crash, network outage), it would be
14800 unfortunate to lose hard-won trace data, so the variable
14801 @code{disconnected-tracing} lets you decide whether the trace should
14802 continue running without @value{GDBN}.
14805 @item set disconnected-tracing on
14806 @itemx set disconnected-tracing off
14807 @kindex set disconnected-tracing
14808 Choose whether a tracing run should continue to run if @value{GDBN}
14809 has disconnected from the target. Note that @code{detach} or
14810 @code{quit} will ask you directly what to do about a running trace no
14811 matter what this variable's setting, so the variable is mainly useful
14812 for handling unexpected situations, such as loss of the network.
14814 @item show disconnected-tracing
14815 @kindex show disconnected-tracing
14816 Show the current choice for disconnected tracing.
14820 When you reconnect to the target, the trace experiment may or may not
14821 still be running; it might have filled the trace buffer in the
14822 meantime, or stopped for one of the other reasons. If it is running,
14823 it will continue after reconnection.
14825 Upon reconnection, the target will upload information about the
14826 tracepoints in effect. @value{GDBN} will then compare that
14827 information to the set of tracepoints currently defined, and attempt
14828 to match them up, allowing for the possibility that the numbers may
14829 have changed due to creation and deletion in the meantime. If one of
14830 the target's tracepoints does not match any in @value{GDBN}, the
14831 debugger will create a new tracepoint, so that you have a number with
14832 which to specify that tracepoint. This matching-up process is
14833 necessarily heuristic, and it may result in useless tracepoints being
14834 created; you may simply delete them if they are of no use.
14836 @cindex circular trace buffer
14837 If your target agent supports a @dfn{circular trace buffer}, then you
14838 can run a trace experiment indefinitely without filling the trace
14839 buffer; when space runs out, the agent deletes already-collected trace
14840 frames, oldest first, until there is enough room to continue
14841 collecting. This is especially useful if your tracepoints are being
14842 hit too often, and your trace gets terminated prematurely because the
14843 buffer is full. To ask for a circular trace buffer, simply set
14844 @samp{circular-trace-buffer} to on. You can set this at any time,
14845 including during tracing; if the agent can do it, it will change
14846 buffer handling on the fly, otherwise it will not take effect until
14850 @item set circular-trace-buffer on
14851 @itemx set circular-trace-buffer off
14852 @kindex set circular-trace-buffer
14853 Choose whether a tracing run should use a linear or circular buffer
14854 for trace data. A linear buffer will not lose any trace data, but may
14855 fill up prematurely, while a circular buffer will discard old trace
14856 data, but it will have always room for the latest tracepoint hits.
14858 @item show circular-trace-buffer
14859 @kindex show circular-trace-buffer
14860 Show the current choice for the trace buffer. Note that this may not
14861 match the agent's current buffer handling, nor is it guaranteed to
14862 match the setting that might have been in effect during a past run,
14863 for instance if you are looking at frames from a trace file.
14868 @item set trace-buffer-size @var{n}
14869 @itemx set trace-buffer-size unlimited
14870 @kindex set trace-buffer-size
14871 Request that the target use a trace buffer of @var{n} bytes. Not all
14872 targets will honor the request; they may have a compiled-in size for
14873 the trace buffer, or some other limitation. Set to a value of
14874 @code{unlimited} or @code{-1} to let the target use whatever size it
14875 likes. This is also the default.
14877 @item show trace-buffer-size
14878 @kindex show trace-buffer-size
14879 Show the current requested size for the trace buffer. Note that this
14880 will only match the actual size if the target supports size-setting,
14881 and was able to handle the requested size. For instance, if the
14882 target can only change buffer size between runs, this variable will
14883 not reflect the change until the next run starts. Use @code{tstatus}
14884 to get a report of the actual buffer size.
14888 @item set trace-user @var{text}
14889 @kindex set trace-user
14891 @item show trace-user
14892 @kindex show trace-user
14894 @item set trace-notes @var{text}
14895 @kindex set trace-notes
14896 Set the trace run's notes.
14898 @item show trace-notes
14899 @kindex show trace-notes
14900 Show the trace run's notes.
14902 @item set trace-stop-notes @var{text}
14903 @kindex set trace-stop-notes
14904 Set the trace run's stop notes. The handling of the note is as for
14905 @code{tstop} arguments; the set command is convenient way to fix a
14906 stop note that is mistaken or incomplete.
14908 @item show trace-stop-notes
14909 @kindex show trace-stop-notes
14910 Show the trace run's stop notes.
14914 @node Tracepoint Restrictions
14915 @subsection Tracepoint Restrictions
14917 @cindex tracepoint restrictions
14918 There are a number of restrictions on the use of tracepoints. As
14919 described above, tracepoint data gathering occurs on the target
14920 without interaction from @value{GDBN}. Thus the full capabilities of
14921 the debugger are not available during data gathering, and then at data
14922 examination time, you will be limited by only having what was
14923 collected. The following items describe some common problems, but it
14924 is not exhaustive, and you may run into additional difficulties not
14930 Tracepoint expressions are intended to gather objects (lvalues). Thus
14931 the full flexibility of GDB's expression evaluator is not available.
14932 You cannot call functions, cast objects to aggregate types, access
14933 convenience variables or modify values (except by assignment to trace
14934 state variables). Some language features may implicitly call
14935 functions (for instance Objective-C fields with accessors), and therefore
14936 cannot be collected either.
14939 Collection of local variables, either individually or in bulk with
14940 @code{$locals} or @code{$args}, during @code{while-stepping} may
14941 behave erratically. The stepping action may enter a new scope (for
14942 instance by stepping into a function), or the location of the variable
14943 may change (for instance it is loaded into a register). The
14944 tracepoint data recorded uses the location information for the
14945 variables that is correct for the tracepoint location. When the
14946 tracepoint is created, it is not possible, in general, to determine
14947 where the steps of a @code{while-stepping} sequence will advance the
14948 program---particularly if a conditional branch is stepped.
14951 Collection of an incompletely-initialized or partially-destroyed object
14952 may result in something that @value{GDBN} cannot display, or displays
14953 in a misleading way.
14956 When @value{GDBN} displays a pointer to character it automatically
14957 dereferences the pointer to also display characters of the string
14958 being pointed to. However, collecting the pointer during tracing does
14959 not automatically collect the string. You need to explicitly
14960 dereference the pointer and provide size information if you want to
14961 collect not only the pointer, but the memory pointed to. For example,
14962 @code{*ptr@@50} can be used to collect the 50 element array pointed to
14966 It is not possible to collect a complete stack backtrace at a
14967 tracepoint. Instead, you may collect the registers and a few hundred
14968 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
14969 (adjust to use the name of the actual stack pointer register on your
14970 target architecture, and the amount of stack you wish to capture).
14971 Then the @code{backtrace} command will show a partial backtrace when
14972 using a trace frame. The number of stack frames that can be examined
14973 depends on the sizes of the frames in the collected stack. Note that
14974 if you ask for a block so large that it goes past the bottom of the
14975 stack, the target agent may report an error trying to read from an
14979 If you do not collect registers at a tracepoint, @value{GDBN} can
14980 infer that the value of @code{$pc} must be the same as the address of
14981 the tracepoint and use that when you are looking at a trace frame
14982 for that tracepoint. However, this cannot work if the tracepoint has
14983 multiple locations (for instance if it was set in a function that was
14984 inlined), or if it has a @code{while-stepping} loop. In those cases
14985 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
14990 @node Analyze Collected Data
14991 @section Using the Collected Data
14993 After the tracepoint experiment ends, you use @value{GDBN} commands
14994 for examining the trace data. The basic idea is that each tracepoint
14995 collects a trace @dfn{snapshot} every time it is hit and another
14996 snapshot every time it single-steps. All these snapshots are
14997 consecutively numbered from zero and go into a buffer, and you can
14998 examine them later. The way you examine them is to @dfn{focus} on a
14999 specific trace snapshot. When the remote stub is focused on a trace
15000 snapshot, it will respond to all @value{GDBN} requests for memory and
15001 registers by reading from the buffer which belongs to that snapshot,
15002 rather than from @emph{real} memory or registers of the program being
15003 debugged. This means that @strong{all} @value{GDBN} commands
15004 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
15005 behave as if we were currently debugging the program state as it was
15006 when the tracepoint occurred. Any requests for data that are not in
15007 the buffer will fail.
15010 * tfind:: How to select a trace snapshot
15011 * tdump:: How to display all data for a snapshot
15012 * save tracepoints:: How to save tracepoints for a future run
15016 @subsection @code{tfind @var{n}}
15019 @cindex select trace snapshot
15020 @cindex find trace snapshot
15021 The basic command for selecting a trace snapshot from the buffer is
15022 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
15023 counting from zero. If no argument @var{n} is given, the next
15024 snapshot is selected.
15026 Here are the various forms of using the @code{tfind} command.
15030 Find the first snapshot in the buffer. This is a synonym for
15031 @code{tfind 0} (since 0 is the number of the first snapshot).
15034 Stop debugging trace snapshots, resume @emph{live} debugging.
15037 Same as @samp{tfind none}.
15040 No argument means find the next trace snapshot or find the first
15041 one if no trace snapshot is selected.
15044 Find the previous trace snapshot before the current one. This permits
15045 retracing earlier steps.
15047 @item tfind tracepoint @var{num}
15048 Find the next snapshot associated with tracepoint @var{num}. Search
15049 proceeds forward from the last examined trace snapshot. If no
15050 argument @var{num} is given, it means find the next snapshot collected
15051 for the same tracepoint as the current snapshot.
15053 @item tfind pc @var{addr}
15054 Find the next snapshot associated with the value @var{addr} of the
15055 program counter. Search proceeds forward from the last examined trace
15056 snapshot. If no argument @var{addr} is given, it means find the next
15057 snapshot with the same value of PC as the current snapshot.
15059 @item tfind outside @var{addr1}, @var{addr2}
15060 Find the next snapshot whose PC is outside the given range of
15061 addresses (exclusive).
15063 @item tfind range @var{addr1}, @var{addr2}
15064 Find the next snapshot whose PC is between @var{addr1} and
15065 @var{addr2} (inclusive).
15067 @item tfind line @r{[}@var{file}:@r{]}@var{n}
15068 Find the next snapshot associated with the source line @var{n}. If
15069 the optional argument @var{file} is given, refer to line @var{n} in
15070 that source file. Search proceeds forward from the last examined
15071 trace snapshot. If no argument @var{n} is given, it means find the
15072 next line other than the one currently being examined; thus saying
15073 @code{tfind line} repeatedly can appear to have the same effect as
15074 stepping from line to line in a @emph{live} debugging session.
15077 The default arguments for the @code{tfind} commands are specifically
15078 designed to make it easy to scan through the trace buffer. For
15079 instance, @code{tfind} with no argument selects the next trace
15080 snapshot, and @code{tfind -} with no argument selects the previous
15081 trace snapshot. So, by giving one @code{tfind} command, and then
15082 simply hitting @key{RET} repeatedly you can examine all the trace
15083 snapshots in order. Or, by saying @code{tfind -} and then hitting
15084 @key{RET} repeatedly you can examine the snapshots in reverse order.
15085 The @code{tfind line} command with no argument selects the snapshot
15086 for the next source line executed. The @code{tfind pc} command with
15087 no argument selects the next snapshot with the same program counter
15088 (PC) as the current frame. The @code{tfind tracepoint} command with
15089 no argument selects the next trace snapshot collected by the same
15090 tracepoint as the current one.
15092 In addition to letting you scan through the trace buffer manually,
15093 these commands make it easy to construct @value{GDBN} scripts that
15094 scan through the trace buffer and print out whatever collected data
15095 you are interested in. Thus, if we want to examine the PC, FP, and SP
15096 registers from each trace frame in the buffer, we can say this:
15099 (@value{GDBP}) @b{tfind start}
15100 (@value{GDBP}) @b{while ($trace_frame != -1)}
15101 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
15102 $trace_frame, $pc, $sp, $fp
15106 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
15107 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
15108 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
15109 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
15110 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
15111 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
15112 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
15113 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
15114 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
15115 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
15116 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
15119 Or, if we want to examine the variable @code{X} at each source line in
15123 (@value{GDBP}) @b{tfind start}
15124 (@value{GDBP}) @b{while ($trace_frame != -1)}
15125 > printf "Frame %d, X == %d\n", $trace_frame, X
15135 @subsection @code{tdump}
15137 @cindex dump all data collected at tracepoint
15138 @cindex tracepoint data, display
15140 This command takes no arguments. It prints all the data collected at
15141 the current trace snapshot.
15144 (@value{GDBP}) @b{trace 444}
15145 (@value{GDBP}) @b{actions}
15146 Enter actions for tracepoint #2, one per line:
15147 > collect $regs, $locals, $args, gdb_long_test
15150 (@value{GDBP}) @b{tstart}
15152 (@value{GDBP}) @b{tfind line 444}
15153 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
15155 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
15157 (@value{GDBP}) @b{tdump}
15158 Data collected at tracepoint 2, trace frame 1:
15159 d0 0xc4aa0085 -995491707
15163 d4 0x71aea3d 119204413
15166 d7 0x380035 3670069
15167 a0 0x19e24a 1696330
15168 a1 0x3000668 50333288
15170 a3 0x322000 3284992
15171 a4 0x3000698 50333336
15172 a5 0x1ad3cc 1758156
15173 fp 0x30bf3c 0x30bf3c
15174 sp 0x30bf34 0x30bf34
15176 pc 0x20b2c8 0x20b2c8
15180 p = 0x20e5b4 "gdb-test"
15187 gdb_long_test = 17 '\021'
15192 @code{tdump} works by scanning the tracepoint's current collection
15193 actions and printing the value of each expression listed. So
15194 @code{tdump} can fail, if after a run, you change the tracepoint's
15195 actions to mention variables that were not collected during the run.
15197 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
15198 uses the collected value of @code{$pc} to distinguish between trace
15199 frames that were collected at the tracepoint hit, and frames that were
15200 collected while stepping. This allows it to correctly choose whether
15201 to display the basic list of collections, or the collections from the
15202 body of the while-stepping loop. However, if @code{$pc} was not collected,
15203 then @code{tdump} will always attempt to dump using the basic collection
15204 list, and may fail if a while-stepping frame does not include all the
15205 same data that is collected at the tracepoint hit.
15206 @c This is getting pretty arcane, example would be good.
15208 @node save tracepoints
15209 @subsection @code{save tracepoints @var{filename}}
15210 @kindex save tracepoints
15211 @kindex save-tracepoints
15212 @cindex save tracepoints for future sessions
15214 This command saves all current tracepoint definitions together with
15215 their actions and passcounts, into a file @file{@var{filename}}
15216 suitable for use in a later debugging session. To read the saved
15217 tracepoint definitions, use the @code{source} command (@pxref{Command
15218 Files}). The @w{@code{save-tracepoints}} command is a deprecated
15219 alias for @w{@code{save tracepoints}}
15221 @node Tracepoint Variables
15222 @section Convenience Variables for Tracepoints
15223 @cindex tracepoint variables
15224 @cindex convenience variables for tracepoints
15227 @vindex $trace_frame
15228 @item (int) $trace_frame
15229 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
15230 snapshot is selected.
15232 @vindex $tracepoint
15233 @item (int) $tracepoint
15234 The tracepoint for the current trace snapshot.
15236 @vindex $trace_line
15237 @item (int) $trace_line
15238 The line number for the current trace snapshot.
15240 @vindex $trace_file
15241 @item (char []) $trace_file
15242 The source file for the current trace snapshot.
15244 @vindex $trace_func
15245 @item (char []) $trace_func
15246 The name of the function containing @code{$tracepoint}.
15249 Note: @code{$trace_file} is not suitable for use in @code{printf},
15250 use @code{output} instead.
15252 Here's a simple example of using these convenience variables for
15253 stepping through all the trace snapshots and printing some of their
15254 data. Note that these are not the same as trace state variables,
15255 which are managed by the target.
15258 (@value{GDBP}) @b{tfind start}
15260 (@value{GDBP}) @b{while $trace_frame != -1}
15261 > output $trace_file
15262 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
15268 @section Using Trace Files
15269 @cindex trace files
15271 In some situations, the target running a trace experiment may no
15272 longer be available; perhaps it crashed, or the hardware was needed
15273 for a different activity. To handle these cases, you can arrange to
15274 dump the trace data into a file, and later use that file as a source
15275 of trace data, via the @code{target tfile} command.
15280 @item tsave [ -r ] @var{filename}
15281 @itemx tsave [-ctf] @var{dirname}
15282 Save the trace data to @var{filename}. By default, this command
15283 assumes that @var{filename} refers to the host filesystem, so if
15284 necessary @value{GDBN} will copy raw trace data up from the target and
15285 then save it. If the target supports it, you can also supply the
15286 optional argument @code{-r} (``remote'') to direct the target to save
15287 the data directly into @var{filename} in its own filesystem, which may be
15288 more efficient if the trace buffer is very large. (Note, however, that
15289 @code{target tfile} can only read from files accessible to the host.)
15290 By default, this command will save trace frame in tfile format.
15291 You can supply the optional argument @code{-ctf} to save data in CTF
15292 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
15293 that can be shared by multiple debugging and tracing tools. Please go to
15294 @indicateurl{http://www.efficios.com/ctf} to get more information.
15296 @kindex target tfile
15300 @item target tfile @var{filename}
15301 @itemx target ctf @var{dirname}
15302 Use the file named @var{filename} or directory named @var{dirname} as
15303 a source of trace data. Commands that examine data work as they do with
15304 a live target, but it is not possible to run any new trace experiments.
15305 @code{tstatus} will report the state of the trace run at the moment
15306 the data was saved, as well as the current trace frame you are examining.
15307 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
15311 (@value{GDBP}) target ctf ctf.ctf
15312 (@value{GDBP}) tfind
15313 Found trace frame 0, tracepoint 2
15314 39 ++a; /* set tracepoint 1 here */
15315 (@value{GDBP}) tdump
15316 Data collected at tracepoint 2, trace frame 0:
15320 c = @{"123", "456", "789", "123", "456", "789"@}
15321 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
15329 @chapter Debugging Programs That Use Overlays
15332 If your program is too large to fit completely in your target system's
15333 memory, you can sometimes use @dfn{overlays} to work around this
15334 problem. @value{GDBN} provides some support for debugging programs that
15338 * How Overlays Work:: A general explanation of overlays.
15339 * Overlay Commands:: Managing overlays in @value{GDBN}.
15340 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
15341 mapped by asking the inferior.
15342 * Overlay Sample Program:: A sample program using overlays.
15345 @node How Overlays Work
15346 @section How Overlays Work
15347 @cindex mapped overlays
15348 @cindex unmapped overlays
15349 @cindex load address, overlay's
15350 @cindex mapped address
15351 @cindex overlay area
15353 Suppose you have a computer whose instruction address space is only 64
15354 kilobytes long, but which has much more memory which can be accessed by
15355 other means: special instructions, segment registers, or memory
15356 management hardware, for example. Suppose further that you want to
15357 adapt a program which is larger than 64 kilobytes to run on this system.
15359 One solution is to identify modules of your program which are relatively
15360 independent, and need not call each other directly; call these modules
15361 @dfn{overlays}. Separate the overlays from the main program, and place
15362 their machine code in the larger memory. Place your main program in
15363 instruction memory, but leave at least enough space there to hold the
15364 largest overlay as well.
15366 Now, to call a function located in an overlay, you must first copy that
15367 overlay's machine code from the large memory into the space set aside
15368 for it in the instruction memory, and then jump to its entry point
15371 @c NB: In the below the mapped area's size is greater or equal to the
15372 @c size of all overlays. This is intentional to remind the developer
15373 @c that overlays don't necessarily need to be the same size.
15377 Data Instruction Larger
15378 Address Space Address Space Address Space
15379 +-----------+ +-----------+ +-----------+
15381 +-----------+ +-----------+ +-----------+<-- overlay 1
15382 | program | | main | .----| overlay 1 | load address
15383 | variables | | program | | +-----------+
15384 | and heap | | | | | |
15385 +-----------+ | | | +-----------+<-- overlay 2
15386 | | +-----------+ | | | load address
15387 +-----------+ | | | .-| overlay 2 |
15389 mapped --->+-----------+ | | +-----------+
15390 address | | | | | |
15391 | overlay | <-' | | |
15392 | area | <---' +-----------+<-- overlay 3
15393 | | <---. | | load address
15394 +-----------+ `--| overlay 3 |
15401 @anchor{A code overlay}A code overlay
15405 The diagram (@pxref{A code overlay}) shows a system with separate data
15406 and instruction address spaces. To map an overlay, the program copies
15407 its code from the larger address space to the instruction address space.
15408 Since the overlays shown here all use the same mapped address, only one
15409 may be mapped at a time. For a system with a single address space for
15410 data and instructions, the diagram would be similar, except that the
15411 program variables and heap would share an address space with the main
15412 program and the overlay area.
15414 An overlay loaded into instruction memory and ready for use is called a
15415 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
15416 instruction memory. An overlay not present (or only partially present)
15417 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
15418 is its address in the larger memory. The mapped address is also called
15419 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
15420 called the @dfn{load memory address}, or @dfn{LMA}.
15422 Unfortunately, overlays are not a completely transparent way to adapt a
15423 program to limited instruction memory. They introduce a new set of
15424 global constraints you must keep in mind as you design your program:
15429 Before calling or returning to a function in an overlay, your program
15430 must make sure that overlay is actually mapped. Otherwise, the call or
15431 return will transfer control to the right address, but in the wrong
15432 overlay, and your program will probably crash.
15435 If the process of mapping an overlay is expensive on your system, you
15436 will need to choose your overlays carefully to minimize their effect on
15437 your program's performance.
15440 The executable file you load onto your system must contain each
15441 overlay's instructions, appearing at the overlay's load address, not its
15442 mapped address. However, each overlay's instructions must be relocated
15443 and its symbols defined as if the overlay were at its mapped address.
15444 You can use GNU linker scripts to specify different load and relocation
15445 addresses for pieces of your program; see @ref{Overlay Description,,,
15446 ld.info, Using ld: the GNU linker}.
15449 The procedure for loading executable files onto your system must be able
15450 to load their contents into the larger address space as well as the
15451 instruction and data spaces.
15455 The overlay system described above is rather simple, and could be
15456 improved in many ways:
15461 If your system has suitable bank switch registers or memory management
15462 hardware, you could use those facilities to make an overlay's load area
15463 contents simply appear at their mapped address in instruction space.
15464 This would probably be faster than copying the overlay to its mapped
15465 area in the usual way.
15468 If your overlays are small enough, you could set aside more than one
15469 overlay area, and have more than one overlay mapped at a time.
15472 You can use overlays to manage data, as well as instructions. In
15473 general, data overlays are even less transparent to your design than
15474 code overlays: whereas code overlays only require care when you call or
15475 return to functions, data overlays require care every time you access
15476 the data. Also, if you change the contents of a data overlay, you
15477 must copy its contents back out to its load address before you can copy a
15478 different data overlay into the same mapped area.
15483 @node Overlay Commands
15484 @section Overlay Commands
15486 To use @value{GDBN}'s overlay support, each overlay in your program must
15487 correspond to a separate section of the executable file. The section's
15488 virtual memory address and load memory address must be the overlay's
15489 mapped and load addresses. Identifying overlays with sections allows
15490 @value{GDBN} to determine the appropriate address of a function or
15491 variable, depending on whether the overlay is mapped or not.
15493 @value{GDBN}'s overlay commands all start with the word @code{overlay};
15494 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
15499 Disable @value{GDBN}'s overlay support. When overlay support is
15500 disabled, @value{GDBN} assumes that all functions and variables are
15501 always present at their mapped addresses. By default, @value{GDBN}'s
15502 overlay support is disabled.
15504 @item overlay manual
15505 @cindex manual overlay debugging
15506 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
15507 relies on you to tell it which overlays are mapped, and which are not,
15508 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
15509 commands described below.
15511 @item overlay map-overlay @var{overlay}
15512 @itemx overlay map @var{overlay}
15513 @cindex map an overlay
15514 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
15515 be the name of the object file section containing the overlay. When an
15516 overlay is mapped, @value{GDBN} assumes it can find the overlay's
15517 functions and variables at their mapped addresses. @value{GDBN} assumes
15518 that any other overlays whose mapped ranges overlap that of
15519 @var{overlay} are now unmapped.
15521 @item overlay unmap-overlay @var{overlay}
15522 @itemx overlay unmap @var{overlay}
15523 @cindex unmap an overlay
15524 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
15525 must be the name of the object file section containing the overlay.
15526 When an overlay is unmapped, @value{GDBN} assumes it can find the
15527 overlay's functions and variables at their load addresses.
15530 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
15531 consults a data structure the overlay manager maintains in the inferior
15532 to see which overlays are mapped. For details, see @ref{Automatic
15533 Overlay Debugging}.
15535 @item overlay load-target
15536 @itemx overlay load
15537 @cindex reloading the overlay table
15538 Re-read the overlay table from the inferior. Normally, @value{GDBN}
15539 re-reads the table @value{GDBN} automatically each time the inferior
15540 stops, so this command should only be necessary if you have changed the
15541 overlay mapping yourself using @value{GDBN}. This command is only
15542 useful when using automatic overlay debugging.
15544 @item overlay list-overlays
15545 @itemx overlay list
15546 @cindex listing mapped overlays
15547 Display a list of the overlays currently mapped, along with their mapped
15548 addresses, load addresses, and sizes.
15552 Normally, when @value{GDBN} prints a code address, it includes the name
15553 of the function the address falls in:
15556 (@value{GDBP}) print main
15557 $3 = @{int ()@} 0x11a0 <main>
15560 When overlay debugging is enabled, @value{GDBN} recognizes code in
15561 unmapped overlays, and prints the names of unmapped functions with
15562 asterisks around them. For example, if @code{foo} is a function in an
15563 unmapped overlay, @value{GDBN} prints it this way:
15566 (@value{GDBP}) overlay list
15567 No sections are mapped.
15568 (@value{GDBP}) print foo
15569 $5 = @{int (int)@} 0x100000 <*foo*>
15572 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
15576 (@value{GDBP}) overlay list
15577 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
15578 mapped at 0x1016 - 0x104a
15579 (@value{GDBP}) print foo
15580 $6 = @{int (int)@} 0x1016 <foo>
15583 When overlay debugging is enabled, @value{GDBN} can find the correct
15584 address for functions and variables in an overlay, whether or not the
15585 overlay is mapped. This allows most @value{GDBN} commands, like
15586 @code{break} and @code{disassemble}, to work normally, even on unmapped
15587 code. However, @value{GDBN}'s breakpoint support has some limitations:
15591 @cindex breakpoints in overlays
15592 @cindex overlays, setting breakpoints in
15593 You can set breakpoints in functions in unmapped overlays, as long as
15594 @value{GDBN} can write to the overlay at its load address.
15596 @value{GDBN} can not set hardware or simulator-based breakpoints in
15597 unmapped overlays. However, if you set a breakpoint at the end of your
15598 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
15599 you are using manual overlay management), @value{GDBN} will re-set its
15600 breakpoints properly.
15604 @node Automatic Overlay Debugging
15605 @section Automatic Overlay Debugging
15606 @cindex automatic overlay debugging
15608 @value{GDBN} can automatically track which overlays are mapped and which
15609 are not, given some simple co-operation from the overlay manager in the
15610 inferior. If you enable automatic overlay debugging with the
15611 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
15612 looks in the inferior's memory for certain variables describing the
15613 current state of the overlays.
15615 Here are the variables your overlay manager must define to support
15616 @value{GDBN}'s automatic overlay debugging:
15620 @item @code{_ovly_table}:
15621 This variable must be an array of the following structures:
15626 /* The overlay's mapped address. */
15629 /* The size of the overlay, in bytes. */
15630 unsigned long size;
15632 /* The overlay's load address. */
15635 /* Non-zero if the overlay is currently mapped;
15637 unsigned long mapped;
15641 @item @code{_novlys}:
15642 This variable must be a four-byte signed integer, holding the total
15643 number of elements in @code{_ovly_table}.
15647 To decide whether a particular overlay is mapped or not, @value{GDBN}
15648 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
15649 @code{lma} members equal the VMA and LMA of the overlay's section in the
15650 executable file. When @value{GDBN} finds a matching entry, it consults
15651 the entry's @code{mapped} member to determine whether the overlay is
15654 In addition, your overlay manager may define a function called
15655 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
15656 will silently set a breakpoint there. If the overlay manager then
15657 calls this function whenever it has changed the overlay table, this
15658 will enable @value{GDBN} to accurately keep track of which overlays
15659 are in program memory, and update any breakpoints that may be set
15660 in overlays. This will allow breakpoints to work even if the
15661 overlays are kept in ROM or other non-writable memory while they
15662 are not being executed.
15664 @node Overlay Sample Program
15665 @section Overlay Sample Program
15666 @cindex overlay example program
15668 When linking a program which uses overlays, you must place the overlays
15669 at their load addresses, while relocating them to run at their mapped
15670 addresses. To do this, you must write a linker script (@pxref{Overlay
15671 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
15672 since linker scripts are specific to a particular host system, target
15673 architecture, and target memory layout, this manual cannot provide
15674 portable sample code demonstrating @value{GDBN}'s overlay support.
15676 However, the @value{GDBN} source distribution does contain an overlaid
15677 program, with linker scripts for a few systems, as part of its test
15678 suite. The program consists of the following files from
15679 @file{gdb/testsuite/gdb.base}:
15683 The main program file.
15685 A simple overlay manager, used by @file{overlays.c}.
15690 Overlay modules, loaded and used by @file{overlays.c}.
15693 Linker scripts for linking the test program on the @code{d10v-elf}
15694 and @code{m32r-elf} targets.
15697 You can build the test program using the @code{d10v-elf} GCC
15698 cross-compiler like this:
15701 $ d10v-elf-gcc -g -c overlays.c
15702 $ d10v-elf-gcc -g -c ovlymgr.c
15703 $ d10v-elf-gcc -g -c foo.c
15704 $ d10v-elf-gcc -g -c bar.c
15705 $ d10v-elf-gcc -g -c baz.c
15706 $ d10v-elf-gcc -g -c grbx.c
15707 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
15708 baz.o grbx.o -Wl,-Td10v.ld -o overlays
15711 The build process is identical for any other architecture, except that
15712 you must substitute the appropriate compiler and linker script for the
15713 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
15717 @chapter Using @value{GDBN} with Different Languages
15720 Although programming languages generally have common aspects, they are
15721 rarely expressed in the same manner. For instance, in ANSI C,
15722 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
15723 Modula-2, it is accomplished by @code{p^}. Values can also be
15724 represented (and displayed) differently. Hex numbers in C appear as
15725 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
15727 @cindex working language
15728 Language-specific information is built into @value{GDBN} for some languages,
15729 allowing you to express operations like the above in your program's
15730 native language, and allowing @value{GDBN} to output values in a manner
15731 consistent with the syntax of your program's native language. The
15732 language you use to build expressions is called the @dfn{working
15736 * Setting:: Switching between source languages
15737 * Show:: Displaying the language
15738 * Checks:: Type and range checks
15739 * Supported Languages:: Supported languages
15740 * Unsupported Languages:: Unsupported languages
15744 @section Switching Between Source Languages
15746 There are two ways to control the working language---either have @value{GDBN}
15747 set it automatically, or select it manually yourself. You can use the
15748 @code{set language} command for either purpose. On startup, @value{GDBN}
15749 defaults to setting the language automatically. The working language is
15750 used to determine how expressions you type are interpreted, how values
15753 In addition to the working language, every source file that
15754 @value{GDBN} knows about has its own working language. For some object
15755 file formats, the compiler might indicate which language a particular
15756 source file is in. However, most of the time @value{GDBN} infers the
15757 language from the name of the file. The language of a source file
15758 controls whether C@t{++} names are demangled---this way @code{backtrace} can
15759 show each frame appropriately for its own language. There is no way to
15760 set the language of a source file from within @value{GDBN}, but you can
15761 set the language associated with a filename extension. @xref{Show, ,
15762 Displaying the Language}.
15764 This is most commonly a problem when you use a program, such
15765 as @code{cfront} or @code{f2c}, that generates C but is written in
15766 another language. In that case, make the
15767 program use @code{#line} directives in its C output; that way
15768 @value{GDBN} will know the correct language of the source code of the original
15769 program, and will display that source code, not the generated C code.
15772 * Filenames:: Filename extensions and languages.
15773 * Manually:: Setting the working language manually
15774 * Automatically:: Having @value{GDBN} infer the source language
15778 @subsection List of Filename Extensions and Languages
15780 If a source file name ends in one of the following extensions, then
15781 @value{GDBN} infers that its language is the one indicated.
15799 C@t{++} source file
15805 Objective-C source file
15809 Fortran source file
15812 Modula-2 source file
15816 Assembler source file. This actually behaves almost like C, but
15817 @value{GDBN} does not skip over function prologues when stepping.
15820 In addition, you may set the language associated with a filename
15821 extension. @xref{Show, , Displaying the Language}.
15824 @subsection Setting the Working Language
15826 If you allow @value{GDBN} to set the language automatically,
15827 expressions are interpreted the same way in your debugging session and
15830 @kindex set language
15831 If you wish, you may set the language manually. To do this, issue the
15832 command @samp{set language @var{lang}}, where @var{lang} is the name of
15833 a language, such as
15834 @code{c} or @code{modula-2}.
15835 For a list of the supported languages, type @samp{set language}.
15837 Setting the language manually prevents @value{GDBN} from updating the working
15838 language automatically. This can lead to confusion if you try
15839 to debug a program when the working language is not the same as the
15840 source language, when an expression is acceptable to both
15841 languages---but means different things. For instance, if the current
15842 source file were written in C, and @value{GDBN} was parsing Modula-2, a
15850 might not have the effect you intended. In C, this means to add
15851 @code{b} and @code{c} and place the result in @code{a}. The result
15852 printed would be the value of @code{a}. In Modula-2, this means to compare
15853 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
15855 @node Automatically
15856 @subsection Having @value{GDBN} Infer the Source Language
15858 To have @value{GDBN} set the working language automatically, use
15859 @samp{set language local} or @samp{set language auto}. @value{GDBN}
15860 then infers the working language. That is, when your program stops in a
15861 frame (usually by encountering a breakpoint), @value{GDBN} sets the
15862 working language to the language recorded for the function in that
15863 frame. If the language for a frame is unknown (that is, if the function
15864 or block corresponding to the frame was defined in a source file that
15865 does not have a recognized extension), the current working language is
15866 not changed, and @value{GDBN} issues a warning.
15868 This may not seem necessary for most programs, which are written
15869 entirely in one source language. However, program modules and libraries
15870 written in one source language can be used by a main program written in
15871 a different source language. Using @samp{set language auto} in this
15872 case frees you from having to set the working language manually.
15875 @section Displaying the Language
15877 The following commands help you find out which language is the
15878 working language, and also what language source files were written in.
15881 @item show language
15882 @anchor{show language}
15883 @kindex show language
15884 Display the current working language. This is the
15885 language you can use with commands such as @code{print} to
15886 build and compute expressions that may involve variables in your program.
15889 @kindex info frame@r{, show the source language}
15890 Display the source language for this frame. This language becomes the
15891 working language if you use an identifier from this frame.
15892 @xref{Frame Info, ,Information about a Frame}, to identify the other
15893 information listed here.
15896 @kindex info source@r{, show the source language}
15897 Display the source language of this source file.
15898 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
15899 information listed here.
15902 In unusual circumstances, you may have source files with extensions
15903 not in the standard list. You can then set the extension associated
15904 with a language explicitly:
15907 @item set extension-language @var{ext} @var{language}
15908 @kindex set extension-language
15909 Tell @value{GDBN} that source files with extension @var{ext} are to be
15910 assumed as written in the source language @var{language}.
15912 @item info extensions
15913 @kindex info extensions
15914 List all the filename extensions and the associated languages.
15918 @section Type and Range Checking
15920 Some languages are designed to guard you against making seemingly common
15921 errors through a series of compile- and run-time checks. These include
15922 checking the type of arguments to functions and operators and making
15923 sure mathematical overflows are caught at run time. Checks such as
15924 these help to ensure a program's correctness once it has been compiled
15925 by eliminating type mismatches and providing active checks for range
15926 errors when your program is running.
15928 By default @value{GDBN} checks for these errors according to the
15929 rules of the current source language. Although @value{GDBN} does not check
15930 the statements in your program, it can check expressions entered directly
15931 into @value{GDBN} for evaluation via the @code{print} command, for example.
15934 * Type Checking:: An overview of type checking
15935 * Range Checking:: An overview of range checking
15938 @cindex type checking
15939 @cindex checks, type
15940 @node Type Checking
15941 @subsection An Overview of Type Checking
15943 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
15944 arguments to operators and functions have to be of the correct type,
15945 otherwise an error occurs. These checks prevent type mismatch
15946 errors from ever causing any run-time problems. For example,
15949 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
15951 (@value{GDBP}) print obj.my_method (0)
15954 (@value{GDBP}) print obj.my_method (0x1234)
15955 Cannot resolve method klass::my_method to any overloaded instance
15958 The second example fails because in C@t{++} the integer constant
15959 @samp{0x1234} is not type-compatible with the pointer parameter type.
15961 For the expressions you use in @value{GDBN} commands, you can tell
15962 @value{GDBN} to not enforce strict type checking or
15963 to treat any mismatches as errors and abandon the expression;
15964 When type checking is disabled, @value{GDBN} successfully evaluates
15965 expressions like the second example above.
15967 Even if type checking is off, there may be other reasons
15968 related to type that prevent @value{GDBN} from evaluating an expression.
15969 For instance, @value{GDBN} does not know how to add an @code{int} and
15970 a @code{struct foo}. These particular type errors have nothing to do
15971 with the language in use and usually arise from expressions which make
15972 little sense to evaluate anyway.
15974 @value{GDBN} provides some additional commands for controlling type checking:
15976 @kindex set check type
15977 @kindex show check type
15979 @item set check type on
15980 @itemx set check type off
15981 Set strict type checking on or off. If any type mismatches occur in
15982 evaluating an expression while type checking is on, @value{GDBN} prints a
15983 message and aborts evaluation of the expression.
15985 @item show check type
15986 Show the current setting of type checking and whether @value{GDBN}
15987 is enforcing strict type checking rules.
15990 @cindex range checking
15991 @cindex checks, range
15992 @node Range Checking
15993 @subsection An Overview of Range Checking
15995 In some languages (such as Modula-2), it is an error to exceed the
15996 bounds of a type; this is enforced with run-time checks. Such range
15997 checking is meant to ensure program correctness by making sure
15998 computations do not overflow, or indices on an array element access do
15999 not exceed the bounds of the array.
16001 For expressions you use in @value{GDBN} commands, you can tell
16002 @value{GDBN} to treat range errors in one of three ways: ignore them,
16003 always treat them as errors and abandon the expression, or issue
16004 warnings but evaluate the expression anyway.
16006 A range error can result from numerical overflow, from exceeding an
16007 array index bound, or when you type a constant that is not a member
16008 of any type. Some languages, however, do not treat overflows as an
16009 error. In many implementations of C, mathematical overflow causes the
16010 result to ``wrap around'' to lower values---for example, if @var{m} is
16011 the largest integer value, and @var{s} is the smallest, then
16014 @var{m} + 1 @result{} @var{s}
16017 This, too, is specific to individual languages, and in some cases
16018 specific to individual compilers or machines. @xref{Supported Languages, ,
16019 Supported Languages}, for further details on specific languages.
16021 @value{GDBN} provides some additional commands for controlling the range checker:
16023 @kindex set check range
16024 @kindex show check range
16026 @item set check range auto
16027 Set range checking on or off based on the current working language.
16028 @xref{Supported Languages, ,Supported Languages}, for the default settings for
16031 @item set check range on
16032 @itemx set check range off
16033 Set range checking on or off, overriding the default setting for the
16034 current working language. A warning is issued if the setting does not
16035 match the language default. If a range error occurs and range checking is on,
16036 then a message is printed and evaluation of the expression is aborted.
16038 @item set check range warn
16039 Output messages when the @value{GDBN} range checker detects a range error,
16040 but attempt to evaluate the expression anyway. Evaluating the
16041 expression may still be impossible for other reasons, such as accessing
16042 memory that the process does not own (a typical example from many Unix
16046 Show the current setting of the range checker, and whether or not it is
16047 being set automatically by @value{GDBN}.
16050 @node Supported Languages
16051 @section Supported Languages
16053 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran,
16054 OpenCL C, Pascal, Rust, assembly, Modula-2, and Ada.
16055 @c This is false ...
16056 Some @value{GDBN} features may be used in expressions regardless of the
16057 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
16058 and the @samp{@{type@}addr} construct (@pxref{Expressions,
16059 ,Expressions}) can be used with the constructs of any supported
16062 The following sections detail to what degree each source language is
16063 supported by @value{GDBN}. These sections are not meant to be language
16064 tutorials or references, but serve only as a reference guide to what the
16065 @value{GDBN} expression parser accepts, and what input and output
16066 formats should look like for different languages. There are many good
16067 books written on each of these languages; please look to these for a
16068 language reference or tutorial.
16071 * C:: C and C@t{++}
16074 * Objective-C:: Objective-C
16075 * OpenCL C:: OpenCL C
16076 * Fortran:: Fortran
16079 * Modula-2:: Modula-2
16084 @subsection C and C@t{++}
16086 @cindex C and C@t{++}
16087 @cindex expressions in C or C@t{++}
16089 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
16090 to both languages. Whenever this is the case, we discuss those languages
16094 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
16095 @cindex @sc{gnu} C@t{++}
16096 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
16097 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
16098 effectively, you must compile your C@t{++} programs with a supported
16099 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
16100 compiler (@code{aCC}).
16103 * C Operators:: C and C@t{++} operators
16104 * C Constants:: C and C@t{++} constants
16105 * C Plus Plus Expressions:: C@t{++} expressions
16106 * C Defaults:: Default settings for C and C@t{++}
16107 * C Checks:: C and C@t{++} type and range checks
16108 * Debugging C:: @value{GDBN} and C
16109 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
16110 * Decimal Floating Point:: Numbers in Decimal Floating Point format
16114 @subsubsection C and C@t{++} Operators
16116 @cindex C and C@t{++} operators
16118 Operators must be defined on values of specific types. For instance,
16119 @code{+} is defined on numbers, but not on structures. Operators are
16120 often defined on groups of types.
16122 For the purposes of C and C@t{++}, the following definitions hold:
16127 @emph{Integral types} include @code{int} with any of its storage-class
16128 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
16131 @emph{Floating-point types} include @code{float}, @code{double}, and
16132 @code{long double} (if supported by the target platform).
16135 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
16138 @emph{Scalar types} include all of the above.
16143 The following operators are supported. They are listed here
16144 in order of increasing precedence:
16148 The comma or sequencing operator. Expressions in a comma-separated list
16149 are evaluated from left to right, with the result of the entire
16150 expression being the last expression evaluated.
16153 Assignment. The value of an assignment expression is the value
16154 assigned. Defined on scalar types.
16157 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
16158 and translated to @w{@code{@var{a} = @var{a op b}}}.
16159 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
16160 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
16161 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
16164 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
16165 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
16166 should be of an integral type.
16169 Logical @sc{or}. Defined on integral types.
16172 Logical @sc{and}. Defined on integral types.
16175 Bitwise @sc{or}. Defined on integral types.
16178 Bitwise exclusive-@sc{or}. Defined on integral types.
16181 Bitwise @sc{and}. Defined on integral types.
16184 Equality and inequality. Defined on scalar types. The value of these
16185 expressions is 0 for false and non-zero for true.
16187 @item <@r{, }>@r{, }<=@r{, }>=
16188 Less than, greater than, less than or equal, greater than or equal.
16189 Defined on scalar types. The value of these expressions is 0 for false
16190 and non-zero for true.
16193 left shift, and right shift. Defined on integral types.
16196 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
16199 Addition and subtraction. Defined on integral types, floating-point types and
16202 @item *@r{, }/@r{, }%
16203 Multiplication, division, and modulus. Multiplication and division are
16204 defined on integral and floating-point types. Modulus is defined on
16208 Increment and decrement. When appearing before a variable, the
16209 operation is performed before the variable is used in an expression;
16210 when appearing after it, the variable's value is used before the
16211 operation takes place.
16214 Pointer dereferencing. Defined on pointer types. Same precedence as
16218 Address operator. Defined on variables. Same precedence as @code{++}.
16220 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
16221 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
16222 to examine the address
16223 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
16227 Negative. Defined on integral and floating-point types. Same
16228 precedence as @code{++}.
16231 Logical negation. Defined on integral types. Same precedence as
16235 Bitwise complement operator. Defined on integral types. Same precedence as
16240 Structure member, and pointer-to-structure member. For convenience,
16241 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
16242 pointer based on the stored type information.
16243 Defined on @code{struct} and @code{union} data.
16246 Dereferences of pointers to members.
16249 Array indexing. @code{@var{a}[@var{i}]} is defined as
16250 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
16253 Function parameter list. Same precedence as @code{->}.
16256 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
16257 and @code{class} types.
16260 Doubled colons also represent the @value{GDBN} scope operator
16261 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
16265 If an operator is redefined in the user code, @value{GDBN} usually
16266 attempts to invoke the redefined version instead of using the operator's
16267 predefined meaning.
16270 @subsubsection C and C@t{++} Constants
16272 @cindex C and C@t{++} constants
16274 @value{GDBN} allows you to express the constants of C and C@t{++} in the
16279 Integer constants are a sequence of digits. Octal constants are
16280 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
16281 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
16282 @samp{l}, specifying that the constant should be treated as a
16286 Floating point constants are a sequence of digits, followed by a decimal
16287 point, followed by a sequence of digits, and optionally followed by an
16288 exponent. An exponent is of the form:
16289 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
16290 sequence of digits. The @samp{+} is optional for positive exponents.
16291 A floating-point constant may also end with a letter @samp{f} or
16292 @samp{F}, specifying that the constant should be treated as being of
16293 the @code{float} (as opposed to the default @code{double}) type; or with
16294 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
16298 Enumerated constants consist of enumerated identifiers, or their
16299 integral equivalents.
16302 Character constants are a single character surrounded by single quotes
16303 (@code{'}), or a number---the ordinal value of the corresponding character
16304 (usually its @sc{ascii} value). Within quotes, the single character may
16305 be represented by a letter or by @dfn{escape sequences}, which are of
16306 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
16307 of the character's ordinal value; or of the form @samp{\@var{x}}, where
16308 @samp{@var{x}} is a predefined special character---for example,
16309 @samp{\n} for newline.
16311 Wide character constants can be written by prefixing a character
16312 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
16313 form of @samp{x}. The target wide character set is used when
16314 computing the value of this constant (@pxref{Character Sets}).
16317 String constants are a sequence of character constants surrounded by
16318 double quotes (@code{"}). Any valid character constant (as described
16319 above) may appear. Double quotes within the string must be preceded by
16320 a backslash, so for instance @samp{"a\"b'c"} is a string of five
16323 Wide string constants can be written by prefixing a string constant
16324 with @samp{L}, as in C. The target wide character set is used when
16325 computing the value of this constant (@pxref{Character Sets}).
16328 Pointer constants are an integral value. You can also write pointers
16329 to constants using the C operator @samp{&}.
16332 Array constants are comma-separated lists surrounded by braces @samp{@{}
16333 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
16334 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
16335 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
16338 @node C Plus Plus Expressions
16339 @subsubsection C@t{++} Expressions
16341 @cindex expressions in C@t{++}
16342 @value{GDBN} expression handling can interpret most C@t{++} expressions.
16344 @cindex debugging C@t{++} programs
16345 @cindex C@t{++} compilers
16346 @cindex debug formats and C@t{++}
16347 @cindex @value{NGCC} and C@t{++}
16349 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
16350 the proper compiler and the proper debug format. Currently,
16351 @value{GDBN} works best when debugging C@t{++} code that is compiled
16352 with the most recent version of @value{NGCC} possible. The DWARF
16353 debugging format is preferred; @value{NGCC} defaults to this on most
16354 popular platforms. Other compilers and/or debug formats are likely to
16355 work badly or not at all when using @value{GDBN} to debug C@t{++}
16356 code. @xref{Compilation}.
16361 @cindex member functions
16363 Member function calls are allowed; you can use expressions like
16366 count = aml->GetOriginal(x, y)
16369 @vindex this@r{, inside C@t{++} member functions}
16370 @cindex namespace in C@t{++}
16372 While a member function is active (in the selected stack frame), your
16373 expressions have the same namespace available as the member function;
16374 that is, @value{GDBN} allows implicit references to the class instance
16375 pointer @code{this} following the same rules as C@t{++}. @code{using}
16376 declarations in the current scope are also respected by @value{GDBN}.
16378 @cindex call overloaded functions
16379 @cindex overloaded functions, calling
16380 @cindex type conversions in C@t{++}
16382 You can call overloaded functions; @value{GDBN} resolves the function
16383 call to the right definition, with some restrictions. @value{GDBN} does not
16384 perform overload resolution involving user-defined type conversions,
16385 calls to constructors, or instantiations of templates that do not exist
16386 in the program. It also cannot handle ellipsis argument lists or
16389 It does perform integral conversions and promotions, floating-point
16390 promotions, arithmetic conversions, pointer conversions, conversions of
16391 class objects to base classes, and standard conversions such as those of
16392 functions or arrays to pointers; it requires an exact match on the
16393 number of function arguments.
16395 Overload resolution is always performed, unless you have specified
16396 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
16397 ,@value{GDBN} Features for C@t{++}}.
16399 You must specify @code{set overload-resolution off} in order to use an
16400 explicit function signature to call an overloaded function, as in
16402 p 'foo(char,int)'('x', 13)
16405 The @value{GDBN} command-completion facility can simplify this;
16406 see @ref{Completion, ,Command Completion}.
16408 @cindex reference declarations
16410 @value{GDBN} understands variables declared as C@t{++} lvalue or rvalue
16411 references; you can use them in expressions just as you do in C@t{++}
16412 source---they are automatically dereferenced.
16414 In the parameter list shown when @value{GDBN} displays a frame, the values of
16415 reference variables are not displayed (unlike other variables); this
16416 avoids clutter, since references are often used for large structures.
16417 The @emph{address} of a reference variable is always shown, unless
16418 you have specified @samp{set print address off}.
16421 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
16422 expressions can use it just as expressions in your program do. Since
16423 one scope may be defined in another, you can use @code{::} repeatedly if
16424 necessary, for example in an expression like
16425 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
16426 resolving name scope by reference to source files, in both C and C@t{++}
16427 debugging (@pxref{Variables, ,Program Variables}).
16430 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
16435 @subsubsection C and C@t{++} Defaults
16437 @cindex C and C@t{++} defaults
16439 If you allow @value{GDBN} to set range checking automatically, it
16440 defaults to @code{off} whenever the working language changes to
16441 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
16442 selects the working language.
16444 If you allow @value{GDBN} to set the language automatically, it
16445 recognizes source files whose names end with @file{.c}, @file{.C}, or
16446 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
16447 these files, it sets the working language to C or C@t{++}.
16448 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
16449 for further details.
16452 @subsubsection C and C@t{++} Type and Range Checks
16454 @cindex C and C@t{++} checks
16456 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
16457 checking is used. However, if you turn type checking off, @value{GDBN}
16458 will allow certain non-standard conversions, such as promoting integer
16459 constants to pointers.
16461 Range checking, if turned on, is done on mathematical operations. Array
16462 indices are not checked, since they are often used to index a pointer
16463 that is not itself an array.
16466 @subsubsection @value{GDBN} and C
16468 The @code{set print union} and @code{show print union} commands apply to
16469 the @code{union} type. When set to @samp{on}, any @code{union} that is
16470 inside a @code{struct} or @code{class} is also printed. Otherwise, it
16471 appears as @samp{@{...@}}.
16473 The @code{@@} operator aids in the debugging of dynamic arrays, formed
16474 with pointers and a memory allocation function. @xref{Expressions,
16477 @node Debugging C Plus Plus
16478 @subsubsection @value{GDBN} Features for C@t{++}
16480 @cindex commands for C@t{++}
16482 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
16483 designed specifically for use with C@t{++}. Here is a summary:
16486 @cindex break in overloaded functions
16487 @item @r{breakpoint menus}
16488 When you want a breakpoint in a function whose name is overloaded,
16489 @value{GDBN} has the capability to display a menu of possible breakpoint
16490 locations to help you specify which function definition you want.
16491 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
16493 @cindex overloading in C@t{++}
16494 @item rbreak @var{regex}
16495 Setting breakpoints using regular expressions is helpful for setting
16496 breakpoints on overloaded functions that are not members of any special
16498 @xref{Set Breaks, ,Setting Breakpoints}.
16500 @cindex C@t{++} exception handling
16502 @itemx catch rethrow
16504 Debug C@t{++} exception handling using these commands. @xref{Set
16505 Catchpoints, , Setting Catchpoints}.
16507 @cindex inheritance
16508 @item ptype @var{typename}
16509 Print inheritance relationships as well as other information for type
16511 @xref{Symbols, ,Examining the Symbol Table}.
16513 @item info vtbl @var{expression}.
16514 The @code{info vtbl} command can be used to display the virtual
16515 method tables of the object computed by @var{expression}. This shows
16516 one entry per virtual table; there may be multiple virtual tables when
16517 multiple inheritance is in use.
16519 @cindex C@t{++} demangling
16520 @item demangle @var{name}
16521 Demangle @var{name}.
16522 @xref{Symbols}, for a more complete description of the @code{demangle} command.
16524 @cindex C@t{++} symbol display
16525 @item set print demangle
16526 @itemx show print demangle
16527 @itemx set print asm-demangle
16528 @itemx show print asm-demangle
16529 Control whether C@t{++} symbols display in their source form, both when
16530 displaying code as C@t{++} source and when displaying disassemblies.
16531 @xref{Print Settings, ,Print Settings}.
16533 @item set print object
16534 @itemx show print object
16535 Choose whether to print derived (actual) or declared types of objects.
16536 @xref{Print Settings, ,Print Settings}.
16538 @item set print vtbl
16539 @itemx show print vtbl
16540 Control the format for printing virtual function tables.
16541 @xref{Print Settings, ,Print Settings}.
16542 (The @code{vtbl} commands do not work on programs compiled with the HP
16543 ANSI C@t{++} compiler (@code{aCC}).)
16545 @kindex set overload-resolution
16546 @cindex overloaded functions, overload resolution
16547 @item set overload-resolution on
16548 Enable overload resolution for C@t{++} expression evaluation. The default
16549 is on. For overloaded functions, @value{GDBN} evaluates the arguments
16550 and searches for a function whose signature matches the argument types,
16551 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
16552 Expressions, ,C@t{++} Expressions}, for details).
16553 If it cannot find a match, it emits a message.
16555 @item set overload-resolution off
16556 Disable overload resolution for C@t{++} expression evaluation. For
16557 overloaded functions that are not class member functions, @value{GDBN}
16558 chooses the first function of the specified name that it finds in the
16559 symbol table, whether or not its arguments are of the correct type. For
16560 overloaded functions that are class member functions, @value{GDBN}
16561 searches for a function whose signature @emph{exactly} matches the
16564 @kindex show overload-resolution
16565 @item show overload-resolution
16566 Show the current setting of overload resolution.
16568 @item @r{Overloaded symbol names}
16569 You can specify a particular definition of an overloaded symbol, using
16570 the same notation that is used to declare such symbols in C@t{++}: type
16571 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
16572 also use the @value{GDBN} command-line word completion facilities to list the
16573 available choices, or to finish the type list for you.
16574 @xref{Completion,, Command Completion}, for details on how to do this.
16576 @item @r{Breakpoints in functions with ABI tags}
16578 The GNU C@t{++} compiler introduced the notion of ABI ``tags'', which
16579 correspond to changes in the ABI of a type, function, or variable that
16580 would not otherwise be reflected in a mangled name. See
16581 @url{https://developers.redhat.com/blog/2015/02/05/gcc5-and-the-c11-abi/}
16584 The ABI tags are visible in C@t{++} demangled names. For example, a
16585 function that returns a std::string:
16588 std::string function(int);
16592 when compiled for the C++11 ABI is marked with the @code{cxx11} ABI
16593 tag, and @value{GDBN} displays the symbol like this:
16596 function[abi:cxx11](int)
16599 You can set a breakpoint on such functions simply as if they had no
16603 (gdb) b function(int)
16604 Breakpoint 2 at 0x40060d: file main.cc, line 10.
16605 (gdb) info breakpoints
16606 Num Type Disp Enb Address What
16607 1 breakpoint keep y 0x0040060d in function[abi:cxx11](int)
16611 On the rare occasion you need to disambiguate between different ABI
16612 tags, you can do so by simply including the ABI tag in the function
16616 (@value{GDBP}) b ambiguous[abi:other_tag](int)
16620 @node Decimal Floating Point
16621 @subsubsection Decimal Floating Point format
16622 @cindex decimal floating point format
16624 @value{GDBN} can examine, set and perform computations with numbers in
16625 decimal floating point format, which in the C language correspond to the
16626 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
16627 specified by the extension to support decimal floating-point arithmetic.
16629 There are two encodings in use, depending on the architecture: BID (Binary
16630 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
16631 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
16634 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
16635 to manipulate decimal floating point numbers, it is not possible to convert
16636 (using a cast, for example) integers wider than 32-bit to decimal float.
16638 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
16639 point computations, error checking in decimal float operations ignores
16640 underflow, overflow and divide by zero exceptions.
16642 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
16643 to inspect @code{_Decimal128} values stored in floating point registers.
16644 See @ref{PowerPC,,PowerPC} for more details.
16650 @value{GDBN} can be used to debug programs written in D and compiled with
16651 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
16652 specific feature --- dynamic arrays.
16657 @cindex Go (programming language)
16658 @value{GDBN} can be used to debug programs written in Go and compiled with
16659 @file{gccgo} or @file{6g} compilers.
16661 Here is a summary of the Go-specific features and restrictions:
16664 @cindex current Go package
16665 @item The current Go package
16666 The name of the current package does not need to be specified when
16667 specifying global variables and functions.
16669 For example, given the program:
16673 var myglob = "Shall we?"
16679 When stopped inside @code{main} either of these work:
16683 (gdb) p main.myglob
16686 @cindex builtin Go types
16687 @item Builtin Go types
16688 The @code{string} type is recognized by @value{GDBN} and is printed
16691 @cindex builtin Go functions
16692 @item Builtin Go functions
16693 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
16694 function and handles it internally.
16696 @cindex restrictions on Go expressions
16697 @item Restrictions on Go expressions
16698 All Go operators are supported except @code{&^}.
16699 The Go @code{_} ``blank identifier'' is not supported.
16700 Automatic dereferencing of pointers is not supported.
16704 @subsection Objective-C
16706 @cindex Objective-C
16707 This section provides information about some commands and command
16708 options that are useful for debugging Objective-C code. See also
16709 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
16710 few more commands specific to Objective-C support.
16713 * Method Names in Commands::
16714 * The Print Command with Objective-C::
16717 @node Method Names in Commands
16718 @subsubsection Method Names in Commands
16720 The following commands have been extended to accept Objective-C method
16721 names as line specifications:
16723 @kindex clear@r{, and Objective-C}
16724 @kindex break@r{, and Objective-C}
16725 @kindex info line@r{, and Objective-C}
16726 @kindex jump@r{, and Objective-C}
16727 @kindex list@r{, and Objective-C}
16731 @item @code{info line}
16736 A fully qualified Objective-C method name is specified as
16739 -[@var{Class} @var{methodName}]
16742 where the minus sign is used to indicate an instance method and a
16743 plus sign (not shown) is used to indicate a class method. The class
16744 name @var{Class} and method name @var{methodName} are enclosed in
16745 brackets, similar to the way messages are specified in Objective-C
16746 source code. For example, to set a breakpoint at the @code{create}
16747 instance method of class @code{Fruit} in the program currently being
16751 break -[Fruit create]
16754 To list ten program lines around the @code{initialize} class method,
16758 list +[NSText initialize]
16761 In the current version of @value{GDBN}, the plus or minus sign is
16762 required. In future versions of @value{GDBN}, the plus or minus
16763 sign will be optional, but you can use it to narrow the search. It
16764 is also possible to specify just a method name:
16770 You must specify the complete method name, including any colons. If
16771 your program's source files contain more than one @code{create} method,
16772 you'll be presented with a numbered list of classes that implement that
16773 method. Indicate your choice by number, or type @samp{0} to exit if
16776 As another example, to clear a breakpoint established at the
16777 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
16780 clear -[NSWindow makeKeyAndOrderFront:]
16783 @node The Print Command with Objective-C
16784 @subsubsection The Print Command With Objective-C
16785 @cindex Objective-C, print objects
16786 @kindex print-object
16787 @kindex po @r{(@code{print-object})}
16789 The print command has also been extended to accept methods. For example:
16792 print -[@var{object} hash]
16795 @cindex print an Objective-C object description
16796 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
16798 will tell @value{GDBN} to send the @code{hash} message to @var{object}
16799 and print the result. Also, an additional command has been added,
16800 @code{print-object} or @code{po} for short, which is meant to print
16801 the description of an object. However, this command may only work
16802 with certain Objective-C libraries that have a particular hook
16803 function, @code{_NSPrintForDebugger}, defined.
16806 @subsection OpenCL C
16809 This section provides information about @value{GDBN}s OpenCL C support.
16812 * OpenCL C Datatypes::
16813 * OpenCL C Expressions::
16814 * OpenCL C Operators::
16817 @node OpenCL C Datatypes
16818 @subsubsection OpenCL C Datatypes
16820 @cindex OpenCL C Datatypes
16821 @value{GDBN} supports the builtin scalar and vector datatypes specified
16822 by OpenCL 1.1. In addition the half- and double-precision floating point
16823 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
16824 extensions are also known to @value{GDBN}.
16826 @node OpenCL C Expressions
16827 @subsubsection OpenCL C Expressions
16829 @cindex OpenCL C Expressions
16830 @value{GDBN} supports accesses to vector components including the access as
16831 lvalue where possible. Since OpenCL C is based on C99 most C expressions
16832 supported by @value{GDBN} can be used as well.
16834 @node OpenCL C Operators
16835 @subsubsection OpenCL C Operators
16837 @cindex OpenCL C Operators
16838 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
16842 @subsection Fortran
16843 @cindex Fortran-specific support in @value{GDBN}
16845 @value{GDBN} can be used to debug programs written in Fortran, but it
16846 currently supports only the features of Fortran 77 language.
16848 @cindex trailing underscore, in Fortran symbols
16849 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
16850 among them) append an underscore to the names of variables and
16851 functions. When you debug programs compiled by those compilers, you
16852 will need to refer to variables and functions with a trailing
16856 * Fortran Operators:: Fortran operators and expressions
16857 * Fortran Defaults:: Default settings for Fortran
16858 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
16861 @node Fortran Operators
16862 @subsubsection Fortran Operators and Expressions
16864 @cindex Fortran operators and expressions
16866 Operators must be defined on values of specific types. For instance,
16867 @code{+} is defined on numbers, but not on characters or other non-
16868 arithmetic types. Operators are often defined on groups of types.
16872 The exponentiation operator. It raises the first operand to the power
16876 The range operator. Normally used in the form of array(low:high) to
16877 represent a section of array.
16880 The access component operator. Normally used to access elements in derived
16881 types. Also suitable for unions. As unions aren't part of regular Fortran,
16882 this can only happen when accessing a register that uses a gdbarch-defined
16885 The scope operator. Normally used to access variables in modules or
16886 to set breakpoints on subroutines nested in modules or in other
16887 subroutines (internal subroutines).
16890 @node Fortran Defaults
16891 @subsubsection Fortran Defaults
16893 @cindex Fortran Defaults
16895 Fortran symbols are usually case-insensitive, so @value{GDBN} by
16896 default uses case-insensitive matches for Fortran symbols. You can
16897 change that with the @samp{set case-insensitive} command, see
16898 @ref{Symbols}, for the details.
16900 @node Special Fortran Commands
16901 @subsubsection Special Fortran Commands
16903 @cindex Special Fortran commands
16905 @value{GDBN} has some commands to support Fortran-specific features,
16906 such as displaying common blocks.
16909 @cindex @code{COMMON} blocks, Fortran
16910 @kindex info common
16911 @item info common @r{[}@var{common-name}@r{]}
16912 This command prints the values contained in the Fortran @code{COMMON}
16913 block whose name is @var{common-name}. With no argument, the names of
16914 all @code{COMMON} blocks visible at the current program location are
16921 @cindex Pascal support in @value{GDBN}, limitations
16922 Debugging Pascal programs which use sets, subranges, file variables, or
16923 nested functions does not currently work. @value{GDBN} does not support
16924 entering expressions, printing values, or similar features using Pascal
16927 The Pascal-specific command @code{set print pascal_static-members}
16928 controls whether static members of Pascal objects are displayed.
16929 @xref{Print Settings, pascal_static-members}.
16934 @value{GDBN} supports the @url{https://www.rust-lang.org/, Rust
16935 Programming Language}. Type- and value-printing, and expression
16936 parsing, are reasonably complete. However, there are a few
16937 peculiarities and holes to be aware of.
16941 Linespecs (@pxref{Specify Location}) are never relative to the current
16942 crate. Instead, they act as if there were a global namespace of
16943 crates, somewhat similar to the way @code{extern crate} behaves.
16945 That is, if @value{GDBN} is stopped at a breakpoint in a function in
16946 crate @samp{A}, module @samp{B}, then @code{break B::f} will attempt
16947 to set a breakpoint in a function named @samp{f} in a crate named
16950 As a consequence of this approach, linespecs also cannot refer to
16951 items using @samp{self::} or @samp{super::}.
16954 Because @value{GDBN} implements Rust name-lookup semantics in
16955 expressions, it will sometimes prepend the current crate to a name.
16956 For example, if @value{GDBN} is stopped at a breakpoint in the crate
16957 @samp{K}, then @code{print ::x::y} will try to find the symbol
16960 However, since it is useful to be able to refer to other crates when
16961 debugging, @value{GDBN} provides the @code{extern} extension to
16962 circumvent this. To use the extension, just put @code{extern} before
16963 a path expression to refer to the otherwise unavailable ``global''
16966 In the above example, if you wanted to refer to the symbol @samp{y} in
16967 the crate @samp{x}, you would use @code{print extern x::y}.
16970 The Rust expression evaluator does not support ``statement-like''
16971 expressions such as @code{if} or @code{match}, or lambda expressions.
16974 Tuple expressions are not implemented.
16977 The Rust expression evaluator does not currently implement the
16978 @code{Drop} trait. Objects that may be created by the evaluator will
16979 never be destroyed.
16982 @value{GDBN} does not implement type inference for generics. In order
16983 to call generic functions or otherwise refer to generic items, you
16984 will have to specify the type parameters manually.
16987 @value{GDBN} currently uses the C@t{++} demangler for Rust. In most
16988 cases this does not cause any problems. However, in an expression
16989 context, completing a generic function name will give syntactically
16990 invalid results. This happens because Rust requires the @samp{::}
16991 operator between the function name and its generic arguments. For
16992 example, @value{GDBN} might provide a completion like
16993 @code{crate::f<u32>}, where the parser would require
16994 @code{crate::f::<u32>}.
16997 As of this writing, the Rust compiler (version 1.8) has a few holes in
16998 the debugging information it generates. These holes prevent certain
16999 features from being implemented by @value{GDBN}:
17003 Method calls cannot be made via traits.
17006 Operator overloading is not implemented.
17009 When debugging in a monomorphized function, you cannot use the generic
17013 The type @code{Self} is not available.
17016 @code{use} statements are not available, so some names may not be
17017 available in the crate.
17022 @subsection Modula-2
17024 @cindex Modula-2, @value{GDBN} support
17026 The extensions made to @value{GDBN} to support Modula-2 only support
17027 output from the @sc{gnu} Modula-2 compiler (which is currently being
17028 developed). Other Modula-2 compilers are not currently supported, and
17029 attempting to debug executables produced by them is most likely
17030 to give an error as @value{GDBN} reads in the executable's symbol
17033 @cindex expressions in Modula-2
17035 * M2 Operators:: Built-in operators
17036 * Built-In Func/Proc:: Built-in functions and procedures
17037 * M2 Constants:: Modula-2 constants
17038 * M2 Types:: Modula-2 types
17039 * M2 Defaults:: Default settings for Modula-2
17040 * Deviations:: Deviations from standard Modula-2
17041 * M2 Checks:: Modula-2 type and range checks
17042 * M2 Scope:: The scope operators @code{::} and @code{.}
17043 * GDB/M2:: @value{GDBN} and Modula-2
17047 @subsubsection Operators
17048 @cindex Modula-2 operators
17050 Operators must be defined on values of specific types. For instance,
17051 @code{+} is defined on numbers, but not on structures. Operators are
17052 often defined on groups of types. For the purposes of Modula-2, the
17053 following definitions hold:
17058 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
17062 @emph{Character types} consist of @code{CHAR} and its subranges.
17065 @emph{Floating-point types} consist of @code{REAL}.
17068 @emph{Pointer types} consist of anything declared as @code{POINTER TO
17072 @emph{Scalar types} consist of all of the above.
17075 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
17078 @emph{Boolean types} consist of @code{BOOLEAN}.
17082 The following operators are supported, and appear in order of
17083 increasing precedence:
17087 Function argument or array index separator.
17090 Assignment. The value of @var{var} @code{:=} @var{value} is
17094 Less than, greater than on integral, floating-point, or enumerated
17098 Less than or equal to, greater than or equal to
17099 on integral, floating-point and enumerated types, or set inclusion on
17100 set types. Same precedence as @code{<}.
17102 @item =@r{, }<>@r{, }#
17103 Equality and two ways of expressing inequality, valid on scalar types.
17104 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
17105 available for inequality, since @code{#} conflicts with the script
17109 Set membership. Defined on set types and the types of their members.
17110 Same precedence as @code{<}.
17113 Boolean disjunction. Defined on boolean types.
17116 Boolean conjunction. Defined on boolean types.
17119 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
17122 Addition and subtraction on integral and floating-point types, or union
17123 and difference on set types.
17126 Multiplication on integral and floating-point types, or set intersection
17130 Division on floating-point types, or symmetric set difference on set
17131 types. Same precedence as @code{*}.
17134 Integer division and remainder. Defined on integral types. Same
17135 precedence as @code{*}.
17138 Negative. Defined on @code{INTEGER} and @code{REAL} data.
17141 Pointer dereferencing. Defined on pointer types.
17144 Boolean negation. Defined on boolean types. Same precedence as
17148 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
17149 precedence as @code{^}.
17152 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
17155 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
17159 @value{GDBN} and Modula-2 scope operators.
17163 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
17164 treats the use of the operator @code{IN}, or the use of operators
17165 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
17166 @code{<=}, and @code{>=} on sets as an error.
17170 @node Built-In Func/Proc
17171 @subsubsection Built-in Functions and Procedures
17172 @cindex Modula-2 built-ins
17174 Modula-2 also makes available several built-in procedures and functions.
17175 In describing these, the following metavariables are used:
17180 represents an @code{ARRAY} variable.
17183 represents a @code{CHAR} constant or variable.
17186 represents a variable or constant of integral type.
17189 represents an identifier that belongs to a set. Generally used in the
17190 same function with the metavariable @var{s}. The type of @var{s} should
17191 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
17194 represents a variable or constant of integral or floating-point type.
17197 represents a variable or constant of floating-point type.
17203 represents a variable.
17206 represents a variable or constant of one of many types. See the
17207 explanation of the function for details.
17210 All Modula-2 built-in procedures also return a result, described below.
17214 Returns the absolute value of @var{n}.
17217 If @var{c} is a lower case letter, it returns its upper case
17218 equivalent, otherwise it returns its argument.
17221 Returns the character whose ordinal value is @var{i}.
17224 Decrements the value in the variable @var{v} by one. Returns the new value.
17226 @item DEC(@var{v},@var{i})
17227 Decrements the value in the variable @var{v} by @var{i}. Returns the
17230 @item EXCL(@var{m},@var{s})
17231 Removes the element @var{m} from the set @var{s}. Returns the new
17234 @item FLOAT(@var{i})
17235 Returns the floating point equivalent of the integer @var{i}.
17237 @item HIGH(@var{a})
17238 Returns the index of the last member of @var{a}.
17241 Increments the value in the variable @var{v} by one. Returns the new value.
17243 @item INC(@var{v},@var{i})
17244 Increments the value in the variable @var{v} by @var{i}. Returns the
17247 @item INCL(@var{m},@var{s})
17248 Adds the element @var{m} to the set @var{s} if it is not already
17249 there. Returns the new set.
17252 Returns the maximum value of the type @var{t}.
17255 Returns the minimum value of the type @var{t}.
17258 Returns boolean TRUE if @var{i} is an odd number.
17261 Returns the ordinal value of its argument. For example, the ordinal
17262 value of a character is its @sc{ascii} value (on machines supporting
17263 the @sc{ascii} character set). The argument @var{x} must be of an
17264 ordered type, which include integral, character and enumerated types.
17266 @item SIZE(@var{x})
17267 Returns the size of its argument. The argument @var{x} can be a
17268 variable or a type.
17270 @item TRUNC(@var{r})
17271 Returns the integral part of @var{r}.
17273 @item TSIZE(@var{x})
17274 Returns the size of its argument. The argument @var{x} can be a
17275 variable or a type.
17277 @item VAL(@var{t},@var{i})
17278 Returns the member of the type @var{t} whose ordinal value is @var{i}.
17282 @emph{Warning:} Sets and their operations are not yet supported, so
17283 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
17287 @cindex Modula-2 constants
17289 @subsubsection Constants
17291 @value{GDBN} allows you to express the constants of Modula-2 in the following
17297 Integer constants are simply a sequence of digits. When used in an
17298 expression, a constant is interpreted to be type-compatible with the
17299 rest of the expression. Hexadecimal integers are specified by a
17300 trailing @samp{H}, and octal integers by a trailing @samp{B}.
17303 Floating point constants appear as a sequence of digits, followed by a
17304 decimal point and another sequence of digits. An optional exponent can
17305 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
17306 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
17307 digits of the floating point constant must be valid decimal (base 10)
17311 Character constants consist of a single character enclosed by a pair of
17312 like quotes, either single (@code{'}) or double (@code{"}). They may
17313 also be expressed by their ordinal value (their @sc{ascii} value, usually)
17314 followed by a @samp{C}.
17317 String constants consist of a sequence of characters enclosed by a
17318 pair of like quotes, either single (@code{'}) or double (@code{"}).
17319 Escape sequences in the style of C are also allowed. @xref{C
17320 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
17324 Enumerated constants consist of an enumerated identifier.
17327 Boolean constants consist of the identifiers @code{TRUE} and
17331 Pointer constants consist of integral values only.
17334 Set constants are not yet supported.
17338 @subsubsection Modula-2 Types
17339 @cindex Modula-2 types
17341 Currently @value{GDBN} can print the following data types in Modula-2
17342 syntax: array types, record types, set types, pointer types, procedure
17343 types, enumerated types, subrange types and base types. You can also
17344 print the contents of variables declared using these type.
17345 This section gives a number of simple source code examples together with
17346 sample @value{GDBN} sessions.
17348 The first example contains the following section of code:
17357 and you can request @value{GDBN} to interrogate the type and value of
17358 @code{r} and @code{s}.
17361 (@value{GDBP}) print s
17363 (@value{GDBP}) ptype s
17365 (@value{GDBP}) print r
17367 (@value{GDBP}) ptype r
17372 Likewise if your source code declares @code{s} as:
17376 s: SET ['A'..'Z'] ;
17380 then you may query the type of @code{s} by:
17383 (@value{GDBP}) ptype s
17384 type = SET ['A'..'Z']
17388 Note that at present you cannot interactively manipulate set
17389 expressions using the debugger.
17391 The following example shows how you might declare an array in Modula-2
17392 and how you can interact with @value{GDBN} to print its type and contents:
17396 s: ARRAY [-10..10] OF CHAR ;
17400 (@value{GDBP}) ptype s
17401 ARRAY [-10..10] OF CHAR
17404 Note that the array handling is not yet complete and although the type
17405 is printed correctly, expression handling still assumes that all
17406 arrays have a lower bound of zero and not @code{-10} as in the example
17409 Here are some more type related Modula-2 examples:
17413 colour = (blue, red, yellow, green) ;
17414 t = [blue..yellow] ;
17422 The @value{GDBN} interaction shows how you can query the data type
17423 and value of a variable.
17426 (@value{GDBP}) print s
17428 (@value{GDBP}) ptype t
17429 type = [blue..yellow]
17433 In this example a Modula-2 array is declared and its contents
17434 displayed. Observe that the contents are written in the same way as
17435 their @code{C} counterparts.
17439 s: ARRAY [1..5] OF CARDINAL ;
17445 (@value{GDBP}) print s
17446 $1 = @{1, 0, 0, 0, 0@}
17447 (@value{GDBP}) ptype s
17448 type = ARRAY [1..5] OF CARDINAL
17451 The Modula-2 language interface to @value{GDBN} also understands
17452 pointer types as shown in this example:
17456 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
17463 and you can request that @value{GDBN} describes the type of @code{s}.
17466 (@value{GDBP}) ptype s
17467 type = POINTER TO ARRAY [1..5] OF CARDINAL
17470 @value{GDBN} handles compound types as we can see in this example.
17471 Here we combine array types, record types, pointer types and subrange
17482 myarray = ARRAY myrange OF CARDINAL ;
17483 myrange = [-2..2] ;
17485 s: POINTER TO ARRAY myrange OF foo ;
17489 and you can ask @value{GDBN} to describe the type of @code{s} as shown
17493 (@value{GDBP}) ptype s
17494 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
17497 f3 : ARRAY [-2..2] OF CARDINAL;
17502 @subsubsection Modula-2 Defaults
17503 @cindex Modula-2 defaults
17505 If type and range checking are set automatically by @value{GDBN}, they
17506 both default to @code{on} whenever the working language changes to
17507 Modula-2. This happens regardless of whether you or @value{GDBN}
17508 selected the working language.
17510 If you allow @value{GDBN} to set the language automatically, then entering
17511 code compiled from a file whose name ends with @file{.mod} sets the
17512 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
17513 Infer the Source Language}, for further details.
17516 @subsubsection Deviations from Standard Modula-2
17517 @cindex Modula-2, deviations from
17519 A few changes have been made to make Modula-2 programs easier to debug.
17520 This is done primarily via loosening its type strictness:
17524 Unlike in standard Modula-2, pointer constants can be formed by
17525 integers. This allows you to modify pointer variables during
17526 debugging. (In standard Modula-2, the actual address contained in a
17527 pointer variable is hidden from you; it can only be modified
17528 through direct assignment to another pointer variable or expression that
17529 returned a pointer.)
17532 C escape sequences can be used in strings and characters to represent
17533 non-printable characters. @value{GDBN} prints out strings with these
17534 escape sequences embedded. Single non-printable characters are
17535 printed using the @samp{CHR(@var{nnn})} format.
17538 The assignment operator (@code{:=}) returns the value of its right-hand
17542 All built-in procedures both modify @emph{and} return their argument.
17546 @subsubsection Modula-2 Type and Range Checks
17547 @cindex Modula-2 checks
17550 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
17553 @c FIXME remove warning when type/range checks added
17555 @value{GDBN} considers two Modula-2 variables type equivalent if:
17559 They are of types that have been declared equivalent via a @code{TYPE
17560 @var{t1} = @var{t2}} statement
17563 They have been declared on the same line. (Note: This is true of the
17564 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
17567 As long as type checking is enabled, any attempt to combine variables
17568 whose types are not equivalent is an error.
17570 Range checking is done on all mathematical operations, assignment, array
17571 index bounds, and all built-in functions and procedures.
17574 @subsubsection The Scope Operators @code{::} and @code{.}
17576 @cindex @code{.}, Modula-2 scope operator
17577 @cindex colon, doubled as scope operator
17579 @vindex colon-colon@r{, in Modula-2}
17580 @c Info cannot handle :: but TeX can.
17583 @vindex ::@r{, in Modula-2}
17586 There are a few subtle differences between the Modula-2 scope operator
17587 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
17592 @var{module} . @var{id}
17593 @var{scope} :: @var{id}
17597 where @var{scope} is the name of a module or a procedure,
17598 @var{module} the name of a module, and @var{id} is any declared
17599 identifier within your program, except another module.
17601 Using the @code{::} operator makes @value{GDBN} search the scope
17602 specified by @var{scope} for the identifier @var{id}. If it is not
17603 found in the specified scope, then @value{GDBN} searches all scopes
17604 enclosing the one specified by @var{scope}.
17606 Using the @code{.} operator makes @value{GDBN} search the current scope for
17607 the identifier specified by @var{id} that was imported from the
17608 definition module specified by @var{module}. With this operator, it is
17609 an error if the identifier @var{id} was not imported from definition
17610 module @var{module}, or if @var{id} is not an identifier in
17614 @subsubsection @value{GDBN} and Modula-2
17616 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
17617 Five subcommands of @code{set print} and @code{show print} apply
17618 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
17619 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
17620 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
17621 analogue in Modula-2.
17623 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
17624 with any language, is not useful with Modula-2. Its
17625 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
17626 created in Modula-2 as they can in C or C@t{++}. However, because an
17627 address can be specified by an integral constant, the construct
17628 @samp{@{@var{type}@}@var{adrexp}} is still useful.
17630 @cindex @code{#} in Modula-2
17631 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
17632 interpreted as the beginning of a comment. Use @code{<>} instead.
17638 The extensions made to @value{GDBN} for Ada only support
17639 output from the @sc{gnu} Ada (GNAT) compiler.
17640 Other Ada compilers are not currently supported, and
17641 attempting to debug executables produced by them is most likely
17645 @cindex expressions in Ada
17647 * Ada Mode Intro:: General remarks on the Ada syntax
17648 and semantics supported by Ada mode
17650 * Omissions from Ada:: Restrictions on the Ada expression syntax.
17651 * Additions to Ada:: Extensions of the Ada expression syntax.
17652 * Overloading support for Ada:: Support for expressions involving overloaded
17654 * Stopping Before Main Program:: Debugging the program during elaboration.
17655 * Ada Exceptions:: Ada Exceptions
17656 * Ada Tasks:: Listing and setting breakpoints in tasks.
17657 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
17658 * Ravenscar Profile:: Tasking Support when using the Ravenscar
17660 * Ada Settings:: New settable GDB parameters for Ada.
17661 * Ada Glitches:: Known peculiarities of Ada mode.
17664 @node Ada Mode Intro
17665 @subsubsection Introduction
17666 @cindex Ada mode, general
17668 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
17669 syntax, with some extensions.
17670 The philosophy behind the design of this subset is
17674 That @value{GDBN} should provide basic literals and access to operations for
17675 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
17676 leaving more sophisticated computations to subprograms written into the
17677 program (which therefore may be called from @value{GDBN}).
17680 That type safety and strict adherence to Ada language restrictions
17681 are not particularly important to the @value{GDBN} user.
17684 That brevity is important to the @value{GDBN} user.
17687 Thus, for brevity, the debugger acts as if all names declared in
17688 user-written packages are directly visible, even if they are not visible
17689 according to Ada rules, thus making it unnecessary to fully qualify most
17690 names with their packages, regardless of context. Where this causes
17691 ambiguity, @value{GDBN} asks the user's intent.
17693 The debugger will start in Ada mode if it detects an Ada main program.
17694 As for other languages, it will enter Ada mode when stopped in a program that
17695 was translated from an Ada source file.
17697 While in Ada mode, you may use `@t{--}' for comments. This is useful
17698 mostly for documenting command files. The standard @value{GDBN} comment
17699 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
17700 middle (to allow based literals).
17702 @node Omissions from Ada
17703 @subsubsection Omissions from Ada
17704 @cindex Ada, omissions from
17706 Here are the notable omissions from the subset:
17710 Only a subset of the attributes are supported:
17714 @t{'First}, @t{'Last}, and @t{'Length}
17715 on array objects (not on types and subtypes).
17718 @t{'Min} and @t{'Max}.
17721 @t{'Pos} and @t{'Val}.
17727 @t{'Range} on array objects (not subtypes), but only as the right
17728 operand of the membership (@code{in}) operator.
17731 @t{'Access}, @t{'Unchecked_Access}, and
17732 @t{'Unrestricted_Access} (a GNAT extension).
17740 @code{Characters.Latin_1} are not available and
17741 concatenation is not implemented. Thus, escape characters in strings are
17742 not currently available.
17745 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
17746 equality of representations. They will generally work correctly
17747 for strings and arrays whose elements have integer or enumeration types.
17748 They may not work correctly for arrays whose element
17749 types have user-defined equality, for arrays of real values
17750 (in particular, IEEE-conformant floating point, because of negative
17751 zeroes and NaNs), and for arrays whose elements contain unused bits with
17752 indeterminate values.
17755 The other component-by-component array operations (@code{and}, @code{or},
17756 @code{xor}, @code{not}, and relational tests other than equality)
17757 are not implemented.
17760 @cindex array aggregates (Ada)
17761 @cindex record aggregates (Ada)
17762 @cindex aggregates (Ada)
17763 There is limited support for array and record aggregates. They are
17764 permitted only on the right sides of assignments, as in these examples:
17767 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
17768 (@value{GDBP}) set An_Array := (1, others => 0)
17769 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
17770 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
17771 (@value{GDBP}) set A_Record := (1, "Peter", True);
17772 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
17776 discriminant's value by assigning an aggregate has an
17777 undefined effect if that discriminant is used within the record.
17778 However, you can first modify discriminants by directly assigning to
17779 them (which normally would not be allowed in Ada), and then performing an
17780 aggregate assignment. For example, given a variable @code{A_Rec}
17781 declared to have a type such as:
17784 type Rec (Len : Small_Integer := 0) is record
17786 Vals : IntArray (1 .. Len);
17790 you can assign a value with a different size of @code{Vals} with two
17794 (@value{GDBP}) set A_Rec.Len := 4
17795 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
17798 As this example also illustrates, @value{GDBN} is very loose about the usual
17799 rules concerning aggregates. You may leave out some of the
17800 components of an array or record aggregate (such as the @code{Len}
17801 component in the assignment to @code{A_Rec} above); they will retain their
17802 original values upon assignment. You may freely use dynamic values as
17803 indices in component associations. You may even use overlapping or
17804 redundant component associations, although which component values are
17805 assigned in such cases is not defined.
17808 Calls to dispatching subprograms are not implemented.
17811 The overloading algorithm is much more limited (i.e., less selective)
17812 than that of real Ada. It makes only limited use of the context in
17813 which a subexpression appears to resolve its meaning, and it is much
17814 looser in its rules for allowing type matches. As a result, some
17815 function calls will be ambiguous, and the user will be asked to choose
17816 the proper resolution.
17819 The @code{new} operator is not implemented.
17822 Entry calls are not implemented.
17825 Aside from printing, arithmetic operations on the native VAX floating-point
17826 formats are not supported.
17829 It is not possible to slice a packed array.
17832 The names @code{True} and @code{False}, when not part of a qualified name,
17833 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
17835 Should your program
17836 redefine these names in a package or procedure (at best a dubious practice),
17837 you will have to use fully qualified names to access their new definitions.
17840 @node Additions to Ada
17841 @subsubsection Additions to Ada
17842 @cindex Ada, deviations from
17844 As it does for other languages, @value{GDBN} makes certain generic
17845 extensions to Ada (@pxref{Expressions}):
17849 If the expression @var{E} is a variable residing in memory (typically
17850 a local variable or array element) and @var{N} is a positive integer,
17851 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
17852 @var{N}-1 adjacent variables following it in memory as an array. In
17853 Ada, this operator is generally not necessary, since its prime use is
17854 in displaying parts of an array, and slicing will usually do this in
17855 Ada. However, there are occasional uses when debugging programs in
17856 which certain debugging information has been optimized away.
17859 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
17860 appears in function or file @var{B}.'' When @var{B} is a file name,
17861 you must typically surround it in single quotes.
17864 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
17865 @var{type} that appears at address @var{addr}.''
17868 A name starting with @samp{$} is a convenience variable
17869 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
17872 In addition, @value{GDBN} provides a few other shortcuts and outright
17873 additions specific to Ada:
17877 The assignment statement is allowed as an expression, returning
17878 its right-hand operand as its value. Thus, you may enter
17881 (@value{GDBP}) set x := y + 3
17882 (@value{GDBP}) print A(tmp := y + 1)
17886 The semicolon is allowed as an ``operator,'' returning as its value
17887 the value of its right-hand operand.
17888 This allows, for example,
17889 complex conditional breaks:
17892 (@value{GDBP}) break f
17893 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
17897 Rather than use catenation and symbolic character names to introduce special
17898 characters into strings, one may instead use a special bracket notation,
17899 which is also used to print strings. A sequence of characters of the form
17900 @samp{["@var{XX}"]} within a string or character literal denotes the
17901 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
17902 sequence of characters @samp{["""]} also denotes a single quotation mark
17903 in strings. For example,
17905 "One line.["0a"]Next line.["0a"]"
17908 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
17912 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
17913 @t{'Max} is optional (and is ignored in any case). For example, it is valid
17917 (@value{GDBP}) print 'max(x, y)
17921 When printing arrays, @value{GDBN} uses positional notation when the
17922 array has a lower bound of 1, and uses a modified named notation otherwise.
17923 For example, a one-dimensional array of three integers with a lower bound
17924 of 3 might print as
17931 That is, in contrast to valid Ada, only the first component has a @code{=>}
17935 You may abbreviate attributes in expressions with any unique,
17936 multi-character subsequence of
17937 their names (an exact match gets preference).
17938 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
17939 in place of @t{a'length}.
17942 @cindex quoting Ada internal identifiers
17943 Since Ada is case-insensitive, the debugger normally maps identifiers you type
17944 to lower case. The GNAT compiler uses upper-case characters for
17945 some of its internal identifiers, which are normally of no interest to users.
17946 For the rare occasions when you actually have to look at them,
17947 enclose them in angle brackets to avoid the lower-case mapping.
17950 (@value{GDBP}) print <JMPBUF_SAVE>[0]
17954 Printing an object of class-wide type or dereferencing an
17955 access-to-class-wide value will display all the components of the object's
17956 specific type (as indicated by its run-time tag). Likewise, component
17957 selection on such a value will operate on the specific type of the
17962 @node Overloading support for Ada
17963 @subsubsection Overloading support for Ada
17964 @cindex overloading, Ada
17966 The debugger supports limited overloading. Given a subprogram call in which
17967 the function symbol has multiple definitions, it will use the number of
17968 actual parameters and some information about their types to attempt to narrow
17969 the set of definitions. It also makes very limited use of context, preferring
17970 procedures to functions in the context of the @code{call} command, and
17971 functions to procedures elsewhere.
17973 If, after narrowing, the set of matching definitions still contains more than
17974 one definition, @value{GDBN} will display a menu to query which one it should
17978 (@value{GDBP}) print f(1)
17979 Multiple matches for f
17981 [1] foo.f (integer) return boolean at foo.adb:23
17982 [2] foo.f (foo.new_integer) return boolean at foo.adb:28
17986 In this case, just select one menu entry either to cancel expression evaluation
17987 (type @kbd{0} and press @key{RET}) or to continue evaluation with a specific
17988 instance (type the corresponding number and press @key{RET}).
17990 Here are a couple of commands to customize @value{GDBN}'s behavior in this
17995 @kindex set ada print-signatures
17996 @item set ada print-signatures
17997 Control whether parameter types and return types are displayed in overloads
17998 selection menus. It is @code{on} by default.
17999 @xref{Overloading support for Ada}.
18001 @kindex show ada print-signatures
18002 @item show ada print-signatures
18003 Show the current setting for displaying parameter types and return types in
18004 overloads selection menu.
18005 @xref{Overloading support for Ada}.
18009 @node Stopping Before Main Program
18010 @subsubsection Stopping at the Very Beginning
18012 @cindex breakpointing Ada elaboration code
18013 It is sometimes necessary to debug the program during elaboration, and
18014 before reaching the main procedure.
18015 As defined in the Ada Reference
18016 Manual, the elaboration code is invoked from a procedure called
18017 @code{adainit}. To run your program up to the beginning of
18018 elaboration, simply use the following two commands:
18019 @code{tbreak adainit} and @code{run}.
18021 @node Ada Exceptions
18022 @subsubsection Ada Exceptions
18024 A command is provided to list all Ada exceptions:
18027 @kindex info exceptions
18028 @item info exceptions
18029 @itemx info exceptions @var{regexp}
18030 The @code{info exceptions} command allows you to list all Ada exceptions
18031 defined within the program being debugged, as well as their addresses.
18032 With a regular expression, @var{regexp}, as argument, only those exceptions
18033 whose names match @var{regexp} are listed.
18036 Below is a small example, showing how the command can be used, first
18037 without argument, and next with a regular expression passed as an
18041 (@value{GDBP}) info exceptions
18042 All defined Ada exceptions:
18043 constraint_error: 0x613da0
18044 program_error: 0x613d20
18045 storage_error: 0x613ce0
18046 tasking_error: 0x613ca0
18047 const.aint_global_e: 0x613b00
18048 (@value{GDBP}) info exceptions const.aint
18049 All Ada exceptions matching regular expression "const.aint":
18050 constraint_error: 0x613da0
18051 const.aint_global_e: 0x613b00
18054 It is also possible to ask @value{GDBN} to stop your program's execution
18055 when an exception is raised. For more details, see @ref{Set Catchpoints}.
18058 @subsubsection Extensions for Ada Tasks
18059 @cindex Ada, tasking
18061 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
18062 @value{GDBN} provides the following task-related commands:
18067 This command shows a list of current Ada tasks, as in the following example:
18074 (@value{GDBP}) info tasks
18075 ID TID P-ID Pri State Name
18076 1 8088000 0 15 Child Activation Wait main_task
18077 2 80a4000 1 15 Accept Statement b
18078 3 809a800 1 15 Child Activation Wait a
18079 * 4 80ae800 3 15 Runnable c
18084 In this listing, the asterisk before the last task indicates it to be the
18085 task currently being inspected.
18089 Represents @value{GDBN}'s internal task number.
18095 The parent's task ID (@value{GDBN}'s internal task number).
18098 The base priority of the task.
18101 Current state of the task.
18105 The task has been created but has not been activated. It cannot be
18109 The task is not blocked for any reason known to Ada. (It may be waiting
18110 for a mutex, though.) It is conceptually "executing" in normal mode.
18113 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
18114 that were waiting on terminate alternatives have been awakened and have
18115 terminated themselves.
18117 @item Child Activation Wait
18118 The task is waiting for created tasks to complete activation.
18120 @item Accept Statement
18121 The task is waiting on an accept or selective wait statement.
18123 @item Waiting on entry call
18124 The task is waiting on an entry call.
18126 @item Async Select Wait
18127 The task is waiting to start the abortable part of an asynchronous
18131 The task is waiting on a select statement with only a delay
18134 @item Child Termination Wait
18135 The task is sleeping having completed a master within itself, and is
18136 waiting for the tasks dependent on that master to become terminated or
18137 waiting on a terminate Phase.
18139 @item Wait Child in Term Alt
18140 The task is sleeping waiting for tasks on terminate alternatives to
18141 finish terminating.
18143 @item Accepting RV with @var{taskno}
18144 The task is accepting a rendez-vous with the task @var{taskno}.
18148 Name of the task in the program.
18152 @kindex info task @var{taskno}
18153 @item info task @var{taskno}
18154 This command shows detailed informations on the specified task, as in
18155 the following example:
18160 (@value{GDBP}) info tasks
18161 ID TID P-ID Pri State Name
18162 1 8077880 0 15 Child Activation Wait main_task
18163 * 2 807c468 1 15 Runnable task_1
18164 (@value{GDBP}) info task 2
18165 Ada Task: 0x807c468
18169 Parent: 1 ("main_task")
18175 @kindex task@r{ (Ada)}
18176 @cindex current Ada task ID
18177 This command prints the ID and name of the current task.
18183 (@value{GDBP}) info tasks
18184 ID TID P-ID Pri State Name
18185 1 8077870 0 15 Child Activation Wait main_task
18186 * 2 807c458 1 15 Runnable some_task
18187 (@value{GDBP}) task
18188 [Current task is 2 "some_task"]
18191 @item task @var{taskno}
18192 @cindex Ada task switching
18193 This command is like the @code{thread @var{thread-id}}
18194 command (@pxref{Threads}). It switches the context of debugging
18195 from the current task to the given task.
18201 (@value{GDBP}) info tasks
18202 ID TID P-ID Pri State Name
18203 1 8077870 0 15 Child Activation Wait main_task
18204 * 2 807c458 1 15 Runnable some_task
18205 (@value{GDBP}) task 1
18206 [Switching to task 1 "main_task"]
18207 #0 0x8067726 in pthread_cond_wait ()
18209 #0 0x8067726 in pthread_cond_wait ()
18210 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
18211 #2 0x805cb63 in system.task_primitives.operations.sleep ()
18212 #3 0x806153e in system.tasking.stages.activate_tasks ()
18213 #4 0x804aacc in un () at un.adb:5
18216 @item break @var{location} task @var{taskno}
18217 @itemx break @var{location} task @var{taskno} if @dots{}
18218 @cindex breakpoints and tasks, in Ada
18219 @cindex task breakpoints, in Ada
18220 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
18221 These commands are like the @code{break @dots{} thread @dots{}}
18222 command (@pxref{Thread Stops}). The
18223 @var{location} argument specifies source lines, as described
18224 in @ref{Specify Location}.
18226 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
18227 to specify that you only want @value{GDBN} to stop the program when a
18228 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
18229 numeric task identifiers assigned by @value{GDBN}, shown in the first
18230 column of the @samp{info tasks} display.
18232 If you do not specify @samp{task @var{taskno}} when you set a
18233 breakpoint, the breakpoint applies to @emph{all} tasks of your
18236 You can use the @code{task} qualifier on conditional breakpoints as
18237 well; in this case, place @samp{task @var{taskno}} before the
18238 breakpoint condition (before the @code{if}).
18246 (@value{GDBP}) info tasks
18247 ID TID P-ID Pri State Name
18248 1 140022020 0 15 Child Activation Wait main_task
18249 2 140045060 1 15 Accept/Select Wait t2
18250 3 140044840 1 15 Runnable t1
18251 * 4 140056040 1 15 Runnable t3
18252 (@value{GDBP}) b 15 task 2
18253 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
18254 (@value{GDBP}) cont
18259 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
18261 (@value{GDBP}) info tasks
18262 ID TID P-ID Pri State Name
18263 1 140022020 0 15 Child Activation Wait main_task
18264 * 2 140045060 1 15 Runnable t2
18265 3 140044840 1 15 Runnable t1
18266 4 140056040 1 15 Delay Sleep t3
18270 @node Ada Tasks and Core Files
18271 @subsubsection Tasking Support when Debugging Core Files
18272 @cindex Ada tasking and core file debugging
18274 When inspecting a core file, as opposed to debugging a live program,
18275 tasking support may be limited or even unavailable, depending on
18276 the platform being used.
18277 For instance, on x86-linux, the list of tasks is available, but task
18278 switching is not supported.
18280 On certain platforms, the debugger needs to perform some
18281 memory writes in order to provide Ada tasking support. When inspecting
18282 a core file, this means that the core file must be opened with read-write
18283 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
18284 Under these circumstances, you should make a backup copy of the core
18285 file before inspecting it with @value{GDBN}.
18287 @node Ravenscar Profile
18288 @subsubsection Tasking Support when using the Ravenscar Profile
18289 @cindex Ravenscar Profile
18291 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
18292 specifically designed for systems with safety-critical real-time
18296 @kindex set ravenscar task-switching on
18297 @cindex task switching with program using Ravenscar Profile
18298 @item set ravenscar task-switching on
18299 Allows task switching when debugging a program that uses the Ravenscar
18300 Profile. This is the default.
18302 @kindex set ravenscar task-switching off
18303 @item set ravenscar task-switching off
18304 Turn off task switching when debugging a program that uses the Ravenscar
18305 Profile. This is mostly intended to disable the code that adds support
18306 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
18307 the Ravenscar runtime is preventing @value{GDBN} from working properly.
18308 To be effective, this command should be run before the program is started.
18310 @kindex show ravenscar task-switching
18311 @item show ravenscar task-switching
18312 Show whether it is possible to switch from task to task in a program
18313 using the Ravenscar Profile.
18318 @subsubsection Ada Settings
18319 @cindex Ada settings
18322 @kindex set varsize-limit
18323 @item set varsize-limit @var{size}
18324 Prevent @value{GDBN} from attempting to evaluate objects whose size
18325 is above the given limit (@var{size}) when those sizes are computed
18326 from run-time quantities. This is typically the case when the object
18327 has a variable size, such as an array whose bounds are not known at
18328 compile time for example. Setting @var{size} to @code{unlimited}
18329 removes the size limitation. By default, the limit is about 65KB.
18331 The purpose of having such a limit is to prevent @value{GDBN} from
18332 trying to grab enormous chunks of virtual memory when asked to evaluate
18333 a quantity whose bounds have been corrupted or have not yet been fully
18334 initialized. The limit applies to the results of some subexpressions
18335 as well as to complete expressions. For example, an expression denoting
18336 a simple integer component, such as @code{x.y.z}, may fail if the size of
18337 @code{x.y} is variable and exceeds @code{size}. On the other hand,
18338 @value{GDBN} is sometimes clever; the expression @code{A(i)}, where
18339 @code{A} is an array variable with non-constant size, will generally
18340 succeed regardless of the bounds on @code{A}, as long as the component
18341 size is less than @var{size}.
18343 @kindex show varsize-limit
18344 @item show varsize-limit
18345 Show the limit on types whose size is determined by run-time quantities.
18349 @subsubsection Known Peculiarities of Ada Mode
18350 @cindex Ada, problems
18352 Besides the omissions listed previously (@pxref{Omissions from Ada}),
18353 we know of several problems with and limitations of Ada mode in
18355 some of which will be fixed with planned future releases of the debugger
18356 and the GNU Ada compiler.
18360 Static constants that the compiler chooses not to materialize as objects in
18361 storage are invisible to the debugger.
18364 Named parameter associations in function argument lists are ignored (the
18365 argument lists are treated as positional).
18368 Many useful library packages are currently invisible to the debugger.
18371 Fixed-point arithmetic, conversions, input, and output is carried out using
18372 floating-point arithmetic, and may give results that only approximate those on
18376 The GNAT compiler never generates the prefix @code{Standard} for any of
18377 the standard symbols defined by the Ada language. @value{GDBN} knows about
18378 this: it will strip the prefix from names when you use it, and will never
18379 look for a name you have so qualified among local symbols, nor match against
18380 symbols in other packages or subprograms. If you have
18381 defined entities anywhere in your program other than parameters and
18382 local variables whose simple names match names in @code{Standard},
18383 GNAT's lack of qualification here can cause confusion. When this happens,
18384 you can usually resolve the confusion
18385 by qualifying the problematic names with package
18386 @code{Standard} explicitly.
18389 Older versions of the compiler sometimes generate erroneous debugging
18390 information, resulting in the debugger incorrectly printing the value
18391 of affected entities. In some cases, the debugger is able to work
18392 around an issue automatically. In other cases, the debugger is able
18393 to work around the issue, but the work-around has to be specifically
18396 @kindex set ada trust-PAD-over-XVS
18397 @kindex show ada trust-PAD-over-XVS
18400 @item set ada trust-PAD-over-XVS on
18401 Configure GDB to strictly follow the GNAT encoding when computing the
18402 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
18403 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
18404 a complete description of the encoding used by the GNAT compiler).
18405 This is the default.
18407 @item set ada trust-PAD-over-XVS off
18408 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
18409 sometimes prints the wrong value for certain entities, changing @code{ada
18410 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
18411 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
18412 @code{off}, but this incurs a slight performance penalty, so it is
18413 recommended to leave this setting to @code{on} unless necessary.
18417 @cindex GNAT descriptive types
18418 @cindex GNAT encoding
18419 Internally, the debugger also relies on the compiler following a number
18420 of conventions known as the @samp{GNAT Encoding}, all documented in
18421 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
18422 how the debugging information should be generated for certain types.
18423 In particular, this convention makes use of @dfn{descriptive types},
18424 which are artificial types generated purely to help the debugger.
18426 These encodings were defined at a time when the debugging information
18427 format used was not powerful enough to describe some of the more complex
18428 types available in Ada. Since DWARF allows us to express nearly all
18429 Ada features, the long-term goal is to slowly replace these descriptive
18430 types by their pure DWARF equivalent. To facilitate that transition,
18431 a new maintenance option is available to force the debugger to ignore
18432 those descriptive types. It allows the user to quickly evaluate how
18433 well @value{GDBN} works without them.
18437 @kindex maint ada set ignore-descriptive-types
18438 @item maintenance ada set ignore-descriptive-types [on|off]
18439 Control whether the debugger should ignore descriptive types.
18440 The default is not to ignore descriptives types (@code{off}).
18442 @kindex maint ada show ignore-descriptive-types
18443 @item maintenance ada show ignore-descriptive-types
18444 Show if descriptive types are ignored by @value{GDBN}.
18448 @node Unsupported Languages
18449 @section Unsupported Languages
18451 @cindex unsupported languages
18452 @cindex minimal language
18453 In addition to the other fully-supported programming languages,
18454 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
18455 It does not represent a real programming language, but provides a set
18456 of capabilities close to what the C or assembly languages provide.
18457 This should allow most simple operations to be performed while debugging
18458 an application that uses a language currently not supported by @value{GDBN}.
18460 If the language is set to @code{auto}, @value{GDBN} will automatically
18461 select this language if the current frame corresponds to an unsupported
18465 @chapter Examining the Symbol Table
18467 The commands described in this chapter allow you to inquire about the
18468 symbols (names of variables, functions and types) defined in your
18469 program. This information is inherent in the text of your program and
18470 does not change as your program executes. @value{GDBN} finds it in your
18471 program's symbol table, in the file indicated when you started @value{GDBN}
18472 (@pxref{File Options, ,Choosing Files}), or by one of the
18473 file-management commands (@pxref{Files, ,Commands to Specify Files}).
18475 @cindex symbol names
18476 @cindex names of symbols
18477 @cindex quoting names
18478 @anchor{quoting names}
18479 Occasionally, you may need to refer to symbols that contain unusual
18480 characters, which @value{GDBN} ordinarily treats as word delimiters. The
18481 most frequent case is in referring to static variables in other
18482 source files (@pxref{Variables,,Program Variables}). File names
18483 are recorded in object files as debugging symbols, but @value{GDBN} would
18484 ordinarily parse a typical file name, like @file{foo.c}, as the three words
18485 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
18486 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
18493 looks up the value of @code{x} in the scope of the file @file{foo.c}.
18496 @cindex case-insensitive symbol names
18497 @cindex case sensitivity in symbol names
18498 @kindex set case-sensitive
18499 @item set case-sensitive on
18500 @itemx set case-sensitive off
18501 @itemx set case-sensitive auto
18502 Normally, when @value{GDBN} looks up symbols, it matches their names
18503 with case sensitivity determined by the current source language.
18504 Occasionally, you may wish to control that. The command @code{set
18505 case-sensitive} lets you do that by specifying @code{on} for
18506 case-sensitive matches or @code{off} for case-insensitive ones. If
18507 you specify @code{auto}, case sensitivity is reset to the default
18508 suitable for the source language. The default is case-sensitive
18509 matches for all languages except for Fortran, for which the default is
18510 case-insensitive matches.
18512 @kindex show case-sensitive
18513 @item show case-sensitive
18514 This command shows the current setting of case sensitivity for symbols
18517 @kindex set print type methods
18518 @item set print type methods
18519 @itemx set print type methods on
18520 @itemx set print type methods off
18521 Normally, when @value{GDBN} prints a class, it displays any methods
18522 declared in that class. You can control this behavior either by
18523 passing the appropriate flag to @code{ptype}, or using @command{set
18524 print type methods}. Specifying @code{on} will cause @value{GDBN} to
18525 display the methods; this is the default. Specifying @code{off} will
18526 cause @value{GDBN} to omit the methods.
18528 @kindex show print type methods
18529 @item show print type methods
18530 This command shows the current setting of method display when printing
18533 @kindex set print type nested-type-limit
18534 @item set print type nested-type-limit @var{limit}
18535 @itemx set print type nested-type-limit unlimited
18536 Set the limit of displayed nested types that the type printer will
18537 show. A @var{limit} of @code{unlimited} or @code{-1} will show all
18538 nested definitions. By default, the type printer will not show any nested
18539 types defined in classes.
18541 @kindex show print type nested-type-limit
18542 @item show print type nested-type-limit
18543 This command shows the current display limit of nested types when
18546 @kindex set print type typedefs
18547 @item set print type typedefs
18548 @itemx set print type typedefs on
18549 @itemx set print type typedefs off
18551 Normally, when @value{GDBN} prints a class, it displays any typedefs
18552 defined in that class. You can control this behavior either by
18553 passing the appropriate flag to @code{ptype}, or using @command{set
18554 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
18555 display the typedef definitions; this is the default. Specifying
18556 @code{off} will cause @value{GDBN} to omit the typedef definitions.
18557 Note that this controls whether the typedef definition itself is
18558 printed, not whether typedef names are substituted when printing other
18561 @kindex show print type typedefs
18562 @item show print type typedefs
18563 This command shows the current setting of typedef display when
18566 @kindex info address
18567 @cindex address of a symbol
18568 @item info address @var{symbol}
18569 Describe where the data for @var{symbol} is stored. For a register
18570 variable, this says which register it is kept in. For a non-register
18571 local variable, this prints the stack-frame offset at which the variable
18574 Note the contrast with @samp{print &@var{symbol}}, which does not work
18575 at all for a register variable, and for a stack local variable prints
18576 the exact address of the current instantiation of the variable.
18578 @kindex info symbol
18579 @cindex symbol from address
18580 @cindex closest symbol and offset for an address
18581 @item info symbol @var{addr}
18582 Print the name of a symbol which is stored at the address @var{addr}.
18583 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
18584 nearest symbol and an offset from it:
18587 (@value{GDBP}) info symbol 0x54320
18588 _initialize_vx + 396 in section .text
18592 This is the opposite of the @code{info address} command. You can use
18593 it to find out the name of a variable or a function given its address.
18595 For dynamically linked executables, the name of executable or shared
18596 library containing the symbol is also printed:
18599 (@value{GDBP}) info symbol 0x400225
18600 _start + 5 in section .text of /tmp/a.out
18601 (@value{GDBP}) info symbol 0x2aaaac2811cf
18602 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
18607 @item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
18608 Demangle @var{name}.
18609 If @var{language} is provided it is the name of the language to demangle
18610 @var{name} in. Otherwise @var{name} is demangled in the current language.
18612 The @samp{--} option specifies the end of options,
18613 and is useful when @var{name} begins with a dash.
18615 The parameter @code{demangle-style} specifies how to interpret the kind
18616 of mangling used. @xref{Print Settings}.
18619 @item whatis[/@var{flags}] [@var{arg}]
18620 Print the data type of @var{arg}, which can be either an expression
18621 or a name of a data type. With no argument, print the data type of
18622 @code{$}, the last value in the value history.
18624 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
18625 is not actually evaluated, and any side-effecting operations (such as
18626 assignments or function calls) inside it do not take place.
18628 If @var{arg} is a variable or an expression, @code{whatis} prints its
18629 literal type as it is used in the source code. If the type was
18630 defined using a @code{typedef}, @code{whatis} will @emph{not} print
18631 the data type underlying the @code{typedef}. If the type of the
18632 variable or the expression is a compound data type, such as
18633 @code{struct} or @code{class}, @code{whatis} never prints their
18634 fields or methods. It just prints the @code{struct}/@code{class}
18635 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
18636 such a compound data type, use @code{ptype}.
18638 If @var{arg} is a type name that was defined using @code{typedef},
18639 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
18640 Unrolling means that @code{whatis} will show the underlying type used
18641 in the @code{typedef} declaration of @var{arg}. However, if that
18642 underlying type is also a @code{typedef}, @code{whatis} will not
18645 For C code, the type names may also have the form @samp{class
18646 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
18647 @var{union-tag}} or @samp{enum @var{enum-tag}}.
18649 @var{flags} can be used to modify how the type is displayed.
18650 Available flags are:
18654 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
18655 parameters and typedefs defined in a class when printing the class'
18656 members. The @code{/r} flag disables this.
18659 Do not print methods defined in the class.
18662 Print methods defined in the class. This is the default, but the flag
18663 exists in case you change the default with @command{set print type methods}.
18666 Do not print typedefs defined in the class. Note that this controls
18667 whether the typedef definition itself is printed, not whether typedef
18668 names are substituted when printing other types.
18671 Print typedefs defined in the class. This is the default, but the flag
18672 exists in case you change the default with @command{set print type typedefs}.
18675 Print the offsets and sizes of fields in a struct, similar to what the
18676 @command{pahole} tool does. This option implies the @code{/tm} flags.
18678 For example, given the following declarations:
18714 Issuing a @kbd{ptype /o struct tuv} command would print:
18717 (@value{GDBP}) ptype /o struct tuv
18718 /* offset | size */ type = struct tuv @{
18719 /* 0 | 4 */ int a1;
18720 /* XXX 4-byte hole */
18721 /* 8 | 8 */ char *a2;
18722 /* 16 | 4 */ int a3;
18724 /* total size (bytes): 24 */
18728 Notice the format of the first column of comments. There, you can
18729 find two parts separated by the @samp{|} character: the @emph{offset},
18730 which indicates where the field is located inside the struct, in
18731 bytes, and the @emph{size} of the field. Another interesting line is
18732 the marker of a @emph{hole} in the struct, indicating that it may be
18733 possible to pack the struct and make it use less space by reorganizing
18736 It is also possible to print offsets inside an union:
18739 (@value{GDBP}) ptype /o union qwe
18740 /* offset | size */ type = union qwe @{
18741 /* 24 */ struct tuv @{
18742 /* 0 | 4 */ int a1;
18743 /* XXX 4-byte hole */
18744 /* 8 | 8 */ char *a2;
18745 /* 16 | 4 */ int a3;
18747 /* total size (bytes): 24 */
18749 /* 40 */ struct xyz @{
18750 /* 0 | 4 */ int f1;
18751 /* 4 | 1 */ char f2;
18752 /* XXX 3-byte hole */
18753 /* 8 | 8 */ void *f3;
18754 /* 16 | 24 */ struct tuv @{
18755 /* 16 | 4 */ int a1;
18756 /* XXX 4-byte hole */
18757 /* 24 | 8 */ char *a2;
18758 /* 32 | 4 */ int a3;
18760 /* total size (bytes): 24 */
18763 /* total size (bytes): 40 */
18766 /* total size (bytes): 40 */
18770 In this case, since @code{struct tuv} and @code{struct xyz} occupy the
18771 same space (because we are dealing with an union), the offset is not
18772 printed for them. However, you can still examine the offset of each
18773 of these structures' fields.
18775 Another useful scenario is printing the offsets of a struct containing
18779 (@value{GDBP}) ptype /o struct tyu
18780 /* offset | size */ type = struct tyu @{
18781 /* 0:31 | 4 */ int a1 : 1;
18782 /* 0:28 | 4 */ int a2 : 3;
18783 /* 0: 5 | 4 */ int a3 : 23;
18784 /* 3: 3 | 1 */ signed char a4 : 2;
18785 /* XXX 3-bit hole */
18786 /* XXX 4-byte hole */
18787 /* 8 | 8 */ int64_t a5;
18788 /* 16: 0 | 4 */ int a6 : 5;
18789 /* 16: 5 | 8 */ int64_t a7 : 3;
18790 "/* XXX 7-byte padding */
18792 /* total size (bytes): 24 */
18796 Note how the offset information is now extended to also include the
18797 first bit of the bitfield.
18801 @item ptype[/@var{flags}] [@var{arg}]
18802 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
18803 detailed description of the type, instead of just the name of the type.
18804 @xref{Expressions, ,Expressions}.
18806 Contrary to @code{whatis}, @code{ptype} always unrolls any
18807 @code{typedef}s in its argument declaration, whether the argument is
18808 a variable, expression, or a data type. This means that @code{ptype}
18809 of a variable or an expression will not print literally its type as
18810 present in the source code---use @code{whatis} for that. @code{typedef}s at
18811 the pointer or reference targets are also unrolled. Only @code{typedef}s of
18812 fields, methods and inner @code{class typedef}s of @code{struct}s,
18813 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
18815 For example, for this variable declaration:
18818 typedef double real_t;
18819 struct complex @{ real_t real; double imag; @};
18820 typedef struct complex complex_t;
18822 real_t *real_pointer_var;
18826 the two commands give this output:
18830 (@value{GDBP}) whatis var
18832 (@value{GDBP}) ptype var
18833 type = struct complex @{
18837 (@value{GDBP}) whatis complex_t
18838 type = struct complex
18839 (@value{GDBP}) whatis struct complex
18840 type = struct complex
18841 (@value{GDBP}) ptype struct complex
18842 type = struct complex @{
18846 (@value{GDBP}) whatis real_pointer_var
18848 (@value{GDBP}) ptype real_pointer_var
18854 As with @code{whatis}, using @code{ptype} without an argument refers to
18855 the type of @code{$}, the last value in the value history.
18857 @cindex incomplete type
18858 Sometimes, programs use opaque data types or incomplete specifications
18859 of complex data structure. If the debug information included in the
18860 program does not allow @value{GDBN} to display a full declaration of
18861 the data type, it will say @samp{<incomplete type>}. For example,
18862 given these declarations:
18866 struct foo *fooptr;
18870 but no definition for @code{struct foo} itself, @value{GDBN} will say:
18873 (@value{GDBP}) ptype foo
18874 $1 = <incomplete type>
18878 ``Incomplete type'' is C terminology for data types that are not
18879 completely specified.
18881 @cindex unknown type
18882 Othertimes, information about a variable's type is completely absent
18883 from the debug information included in the program. This most often
18884 happens when the program or library where the variable is defined
18885 includes no debug information at all. @value{GDBN} knows the variable
18886 exists from inspecting the linker/loader symbol table (e.g., the ELF
18887 dynamic symbol table), but such symbols do not contain type
18888 information. Inspecting the type of a (global) variable for which
18889 @value{GDBN} has no type information shows:
18892 (@value{GDBP}) ptype var
18893 type = <data variable, no debug info>
18896 @xref{Variables, no debug info variables}, for how to print the values
18900 @item info types [-q] [@var{regexp}]
18901 Print a brief description of all types whose names match the regular
18902 expression @var{regexp} (or all types in your program, if you supply
18903 no argument). Each complete typename is matched as though it were a
18904 complete line; thus, @samp{i type value} gives information on all
18905 types in your program whose names include the string @code{value}, but
18906 @samp{i type ^value$} gives information only on types whose complete
18907 name is @code{value}.
18909 In programs using different languages, @value{GDBN} chooses the syntax
18910 to print the type description according to the
18911 @samp{set language} value: using @samp{set language auto}
18912 (see @ref{Automatically, ,Set Language Automatically}) means to use the
18913 language of the type, other values mean to use
18914 the manually specified language (see @ref{Manually, ,Set Language Manually}).
18916 This command differs from @code{ptype} in two ways: first, like
18917 @code{whatis}, it does not print a detailed description; second, it
18918 lists all source files and line numbers where a type is defined.
18920 The output from @samp{into types} is proceeded with a header line
18921 describing what types are being listed. The optional flag @samp{-q},
18922 which stands for @samp{quiet}, disables printing this header
18925 @kindex info type-printers
18926 @item info type-printers
18927 Versions of @value{GDBN} that ship with Python scripting enabled may
18928 have ``type printers'' available. When using @command{ptype} or
18929 @command{whatis}, these printers are consulted when the name of a type
18930 is needed. @xref{Type Printing API}, for more information on writing
18933 @code{info type-printers} displays all the available type printers.
18935 @kindex enable type-printer
18936 @kindex disable type-printer
18937 @item enable type-printer @var{name}@dots{}
18938 @item disable type-printer @var{name}@dots{}
18939 These commands can be used to enable or disable type printers.
18942 @cindex local variables
18943 @item info scope @var{location}
18944 List all the variables local to a particular scope. This command
18945 accepts a @var{location} argument---a function name, a source line, or
18946 an address preceded by a @samp{*}, and prints all the variables local
18947 to the scope defined by that location. (@xref{Specify Location}, for
18948 details about supported forms of @var{location}.) For example:
18951 (@value{GDBP}) @b{info scope command_line_handler}
18952 Scope for command_line_handler:
18953 Symbol rl is an argument at stack/frame offset 8, length 4.
18954 Symbol linebuffer is in static storage at address 0x150a18, length 4.
18955 Symbol linelength is in static storage at address 0x150a1c, length 4.
18956 Symbol p is a local variable in register $esi, length 4.
18957 Symbol p1 is a local variable in register $ebx, length 4.
18958 Symbol nline is a local variable in register $edx, length 4.
18959 Symbol repeat is a local variable at frame offset -8, length 4.
18963 This command is especially useful for determining what data to collect
18964 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
18967 @kindex info source
18969 Show information about the current source file---that is, the source file for
18970 the function containing the current point of execution:
18973 the name of the source file, and the directory containing it,
18975 the directory it was compiled in,
18977 its length, in lines,
18979 which programming language it is written in,
18981 if the debug information provides it, the program that compiled the file
18982 (which may include, e.g., the compiler version and command line arguments),
18984 whether the executable includes debugging information for that file, and
18985 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
18987 whether the debugging information includes information about
18988 preprocessor macros.
18992 @kindex info sources
18994 Print the names of all source files in your program for which there is
18995 debugging information, organized into two lists: files whose symbols
18996 have already been read, and files whose symbols will be read when needed.
18998 @item info sources [-dirname | -basename] [--] [@var{regexp}]
18999 Like @samp{info sources}, but only print the names of the files
19000 matching the provided @var{regexp}.
19001 By default, the @var{regexp} is used to match anywhere in the filename.
19002 If @code{-dirname}, only files having a dirname matching @var{regexp} are shown.
19003 If @code{-basename}, only files having a basename matching @var{regexp}
19005 The matching is case-sensitive, except on operating systems that
19006 have case-insensitive filesystem (e.g., MS-Windows).
19008 @kindex info functions
19009 @item info functions [-q] [-n]
19010 Print the names and data types of all defined functions.
19011 Similarly to @samp{info types}, this command groups its output by source
19012 files and annotates each function definition with its source line
19015 In programs using different languages, @value{GDBN} chooses the syntax
19016 to print the function name and type according to the
19017 @samp{set language} value: using @samp{set language auto}
19018 (see @ref{Automatically, ,Set Language Automatically}) means to use the
19019 language of the function, other values mean to use
19020 the manually specified language (see @ref{Manually, ,Set Language Manually}).
19022 The @samp{-n} flag excludes @dfn{non-debugging symbols} from the
19023 results. A non-debugging symbol is a symbol that comes from the
19024 executable's symbol table, not from the debug information (for
19025 example, DWARF) associated with the executable.
19027 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
19028 printing header information and messages explaining why no functions
19031 @item info functions [-q] [-n] [-t @var{type_regexp}] [@var{regexp}]
19032 Like @samp{info functions}, but only print the names and data types
19033 of the functions selected with the provided regexp(s).
19035 If @var{regexp} is provided, print only the functions whose names
19036 match the regular expression @var{regexp}.
19037 Thus, @samp{info fun step} finds all functions whose
19038 names include @code{step}; @samp{info fun ^step} finds those whose names
19039 start with @code{step}. If a function name contains characters that
19040 conflict with the regular expression language (e.g.@:
19041 @samp{operator*()}), they may be quoted with a backslash.
19043 If @var{type_regexp} is provided, print only the functions whose
19044 types, as printed by the @code{whatis} command, match
19045 the regular expression @var{type_regexp}.
19046 If @var{type_regexp} contains space(s), it should be enclosed in
19047 quote characters. If needed, use backslash to escape the meaning
19048 of special characters or quotes.
19049 Thus, @samp{info fun -t '^int ('} finds the functions that return
19050 an integer; @samp{info fun -t '(.*int.*'} finds the functions that
19051 have an argument type containing int; @samp{info fun -t '^int (' ^step}
19052 finds the functions whose names start with @code{step} and that return
19055 If both @var{regexp} and @var{type_regexp} are provided, a function
19056 is printed only if its name matches @var{regexp} and its type matches
19060 @kindex info variables
19061 @item info variables [-q] [-n]
19062 Print the names and data types of all variables that are defined
19063 outside of functions (i.e.@: excluding local variables).
19064 The printed variables are grouped by source files and annotated with
19065 their respective source line numbers.
19067 In programs using different languages, @value{GDBN} chooses the syntax
19068 to print the variable name and type according to the
19069 @samp{set language} value: using @samp{set language auto}
19070 (see @ref{Automatically, ,Set Language Automatically}) means to use the
19071 language of the variable, other values mean to use
19072 the manually specified language (see @ref{Manually, ,Set Language Manually}).
19074 The @samp{-n} flag excludes non-debugging symbols from the results.
19076 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
19077 printing header information and messages explaining why no variables
19080 @item info variables [-q] [-n] [-t @var{type_regexp}] [@var{regexp}]
19081 Like @kbd{info variables}, but only print the variables selected
19082 with the provided regexp(s).
19084 If @var{regexp} is provided, print only the variables whose names
19085 match the regular expression @var{regexp}.
19087 If @var{type_regexp} is provided, print only the variables whose
19088 types, as printed by the @code{whatis} command, match
19089 the regular expression @var{type_regexp}.
19090 If @var{type_regexp} contains space(s), it should be enclosed in
19091 quote characters. If needed, use backslash to escape the meaning
19092 of special characters or quotes.
19094 If both @var{regexp} and @var{type_regexp} are provided, an argument
19095 is printed only if its name matches @var{regexp} and its type matches
19098 @kindex info modules
19100 @item info modules @r{[}-q@r{]} @r{[}@var{regexp}@r{]}
19101 List all Fortran modules in the program, or all modules matching the
19102 optional regular expression @var{regexp}.
19104 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
19105 printing header information and messages explaining why no modules
19108 @kindex info module
19109 @cindex Fortran modules, information about
19110 @cindex functions and variables by Fortran module
19111 @cindex module functions and variables
19112 @item info module functions @r{[}-q@r{]} @r{[}-m @var{module-regexp}@r{]} @r{[}-t @var{type-regexp}@r{]} @r{[}@var{regexp}@r{]}
19113 @itemx info module variables @r{[}-q@r{]} @r{[}-m @var{module-regexp}@r{]} @r{[}-t @var{type-regexp}@r{]} @r{[}@var{regexp}@r{]}
19114 List all functions or variables within all Fortran modules. The set
19115 of functions or variables listed can be limited by providing some or
19116 all of the optional regular expressions. If @var{module-regexp} is
19117 provided, then only Fortran modules matching @var{module-regexp} will
19118 be searched. Only functions or variables whose type matches the
19119 optional regular expression @var{type-regexp} will be listed. And
19120 only functions or variables whose name matches the optional regular
19121 expression @var{regexp} will be listed.
19123 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
19124 printing header information and messages explaining why no functions
19125 or variables have been printed.
19127 @kindex info classes
19128 @cindex Objective-C, classes and selectors
19130 @itemx info classes @var{regexp}
19131 Display all Objective-C classes in your program, or
19132 (with the @var{regexp} argument) all those matching a particular regular
19135 @kindex info selectors
19136 @item info selectors
19137 @itemx info selectors @var{regexp}
19138 Display all Objective-C selectors in your program, or
19139 (with the @var{regexp} argument) all those matching a particular regular
19143 This was never implemented.
19144 @kindex info methods
19146 @itemx info methods @var{regexp}
19147 The @code{info methods} command permits the user to examine all defined
19148 methods within C@t{++} program, or (with the @var{regexp} argument) a
19149 specific set of methods found in the various C@t{++} classes. Many
19150 C@t{++} classes provide a large number of methods. Thus, the output
19151 from the @code{ptype} command can be overwhelming and hard to use. The
19152 @code{info-methods} command filters the methods, printing only those
19153 which match the regular-expression @var{regexp}.
19156 @cindex opaque data types
19157 @kindex set opaque-type-resolution
19158 @item set opaque-type-resolution on
19159 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
19160 declared as a pointer to a @code{struct}, @code{class}, or
19161 @code{union}---for example, @code{struct MyType *}---that is used in one
19162 source file although the full declaration of @code{struct MyType} is in
19163 another source file. The default is on.
19165 A change in the setting of this subcommand will not take effect until
19166 the next time symbols for a file are loaded.
19168 @item set opaque-type-resolution off
19169 Tell @value{GDBN} not to resolve opaque types. In this case, the type
19170 is printed as follows:
19172 @{<no data fields>@}
19175 @kindex show opaque-type-resolution
19176 @item show opaque-type-resolution
19177 Show whether opaque types are resolved or not.
19179 @kindex set print symbol-loading
19180 @cindex print messages when symbols are loaded
19181 @item set print symbol-loading
19182 @itemx set print symbol-loading full
19183 @itemx set print symbol-loading brief
19184 @itemx set print symbol-loading off
19185 The @code{set print symbol-loading} command allows you to control the
19186 printing of messages when @value{GDBN} loads symbol information.
19187 By default a message is printed for the executable and one for each
19188 shared library, and normally this is what you want. However, when
19189 debugging apps with large numbers of shared libraries these messages
19191 When set to @code{brief} a message is printed for each executable,
19192 and when @value{GDBN} loads a collection of shared libraries at once
19193 it will only print one message regardless of the number of shared
19194 libraries. When set to @code{off} no messages are printed.
19196 @kindex show print symbol-loading
19197 @item show print symbol-loading
19198 Show whether messages will be printed when a @value{GDBN} command
19199 entered from the keyboard causes symbol information to be loaded.
19201 @kindex maint print symbols
19202 @cindex symbol dump
19203 @kindex maint print psymbols
19204 @cindex partial symbol dump
19205 @kindex maint print msymbols
19206 @cindex minimal symbol dump
19207 @item maint print symbols @r{[}-pc @var{address}@r{]} @r{[}@var{filename}@r{]}
19208 @itemx maint print symbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
19209 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-pc @var{address}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
19210 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
19211 @itemx maint print msymbols @r{[}-objfile @var{objfile}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
19212 Write a dump of debugging symbol data into the file @var{filename} or
19213 the terminal if @var{filename} is unspecified.
19214 If @code{-objfile @var{objfile}} is specified, only dump symbols for
19216 If @code{-pc @var{address}} is specified, only dump symbols for the file
19217 with code at that address. Note that @var{address} may be a symbol like
19219 If @code{-source @var{source}} is specified, only dump symbols for that
19222 These commands are used to debug the @value{GDBN} symbol-reading code.
19223 These commands do not modify internal @value{GDBN} state, therefore
19224 @samp{maint print symbols} will only print symbols for already expanded symbol
19226 You can use the command @code{info sources} to find out which files these are.
19227 If you use @samp{maint print psymbols} instead, the dump shows information
19228 about symbols that @value{GDBN} only knows partially---that is, symbols
19229 defined in files that @value{GDBN} has skimmed, but not yet read completely.
19230 Finally, @samp{maint print msymbols} just dumps ``minimal symbols'', e.g.,
19233 @xref{Files, ,Commands to Specify Files}, for a discussion of how
19234 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
19236 @kindex maint info symtabs
19237 @kindex maint info psymtabs
19238 @cindex listing @value{GDBN}'s internal symbol tables
19239 @cindex symbol tables, listing @value{GDBN}'s internal
19240 @cindex full symbol tables, listing @value{GDBN}'s internal
19241 @cindex partial symbol tables, listing @value{GDBN}'s internal
19242 @item maint info symtabs @r{[} @var{regexp} @r{]}
19243 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
19245 List the @code{struct symtab} or @code{struct partial_symtab}
19246 structures whose names match @var{regexp}. If @var{regexp} is not
19247 given, list them all. The output includes expressions which you can
19248 copy into a @value{GDBN} debugging this one to examine a particular
19249 structure in more detail. For example:
19252 (@value{GDBP}) maint info psymtabs dwarf2read
19253 @{ objfile /home/gnu/build/gdb/gdb
19254 ((struct objfile *) 0x82e69d0)
19255 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
19256 ((struct partial_symtab *) 0x8474b10)
19259 text addresses 0x814d3c8 -- 0x8158074
19260 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
19261 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
19262 dependencies (none)
19265 (@value{GDBP}) maint info symtabs
19269 We see that there is one partial symbol table whose filename contains
19270 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
19271 and we see that @value{GDBN} has not read in any symtabs yet at all.
19272 If we set a breakpoint on a function, that will cause @value{GDBN} to
19273 read the symtab for the compilation unit containing that function:
19276 (@value{GDBP}) break dwarf2_psymtab_to_symtab
19277 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
19279 (@value{GDBP}) maint info symtabs
19280 @{ objfile /home/gnu/build/gdb/gdb
19281 ((struct objfile *) 0x82e69d0)
19282 @{ symtab /home/gnu/src/gdb/dwarf2read.c
19283 ((struct symtab *) 0x86c1f38)
19286 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
19287 linetable ((struct linetable *) 0x8370fa0)
19288 debugformat DWARF 2
19294 @kindex maint info line-table
19295 @cindex listing @value{GDBN}'s internal line tables
19296 @cindex line tables, listing @value{GDBN}'s internal
19297 @item maint info line-table @r{[} @var{regexp} @r{]}
19299 List the @code{struct linetable} from all @code{struct symtab}
19300 instances whose name matches @var{regexp}. If @var{regexp} is not
19301 given, list the @code{struct linetable} from all @code{struct symtab}.
19303 @kindex maint set symbol-cache-size
19304 @cindex symbol cache size
19305 @item maint set symbol-cache-size @var{size}
19306 Set the size of the symbol cache to @var{size}.
19307 The default size is intended to be good enough for debugging
19308 most applications. This option exists to allow for experimenting
19309 with different sizes.
19311 @kindex maint show symbol-cache-size
19312 @item maint show symbol-cache-size
19313 Show the size of the symbol cache.
19315 @kindex maint print symbol-cache
19316 @cindex symbol cache, printing its contents
19317 @item maint print symbol-cache
19318 Print the contents of the symbol cache.
19319 This is useful when debugging symbol cache issues.
19321 @kindex maint print symbol-cache-statistics
19322 @cindex symbol cache, printing usage statistics
19323 @item maint print symbol-cache-statistics
19324 Print symbol cache usage statistics.
19325 This helps determine how well the cache is being utilized.
19327 @kindex maint flush-symbol-cache
19328 @cindex symbol cache, flushing
19329 @item maint flush-symbol-cache
19330 Flush the contents of the symbol cache, all entries are removed.
19331 This command is useful when debugging the symbol cache.
19332 It is also useful when collecting performance data.
19337 @chapter Altering Execution
19339 Once you think you have found an error in your program, you might want to
19340 find out for certain whether correcting the apparent error would lead to
19341 correct results in the rest of the run. You can find the answer by
19342 experiment, using the @value{GDBN} features for altering execution of the
19345 For example, you can store new values into variables or memory
19346 locations, give your program a signal, restart it at a different
19347 address, or even return prematurely from a function.
19350 * Assignment:: Assignment to variables
19351 * Jumping:: Continuing at a different address
19352 * Signaling:: Giving your program a signal
19353 * Returning:: Returning from a function
19354 * Calling:: Calling your program's functions
19355 * Patching:: Patching your program
19356 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
19360 @section Assignment to Variables
19363 @cindex setting variables
19364 To alter the value of a variable, evaluate an assignment expression.
19365 @xref{Expressions, ,Expressions}. For example,
19372 stores the value 4 into the variable @code{x}, and then prints the
19373 value of the assignment expression (which is 4).
19374 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
19375 information on operators in supported languages.
19377 @kindex set variable
19378 @cindex variables, setting
19379 If you are not interested in seeing the value of the assignment, use the
19380 @code{set} command instead of the @code{print} command. @code{set} is
19381 really the same as @code{print} except that the expression's value is
19382 not printed and is not put in the value history (@pxref{Value History,
19383 ,Value History}). The expression is evaluated only for its effects.
19385 If the beginning of the argument string of the @code{set} command
19386 appears identical to a @code{set} subcommand, use the @code{set
19387 variable} command instead of just @code{set}. This command is identical
19388 to @code{set} except for its lack of subcommands. For example, if your
19389 program has a variable @code{width}, you get an error if you try to set
19390 a new value with just @samp{set width=13}, because @value{GDBN} has the
19391 command @code{set width}:
19394 (@value{GDBP}) whatis width
19396 (@value{GDBP}) p width
19398 (@value{GDBP}) set width=47
19399 Invalid syntax in expression.
19403 The invalid expression, of course, is @samp{=47}. In
19404 order to actually set the program's variable @code{width}, use
19407 (@value{GDBP}) set var width=47
19410 Because the @code{set} command has many subcommands that can conflict
19411 with the names of program variables, it is a good idea to use the
19412 @code{set variable} command instead of just @code{set}. For example, if
19413 your program has a variable @code{g}, you run into problems if you try
19414 to set a new value with just @samp{set g=4}, because @value{GDBN} has
19415 the command @code{set gnutarget}, abbreviated @code{set g}:
19419 (@value{GDBP}) whatis g
19423 (@value{GDBP}) set g=4
19427 The program being debugged has been started already.
19428 Start it from the beginning? (y or n) y
19429 Starting program: /home/smith/cc_progs/a.out
19430 "/home/smith/cc_progs/a.out": can't open to read symbols:
19431 Invalid bfd target.
19432 (@value{GDBP}) show g
19433 The current BFD target is "=4".
19438 The program variable @code{g} did not change, and you silently set the
19439 @code{gnutarget} to an invalid value. In order to set the variable
19443 (@value{GDBP}) set var g=4
19446 @value{GDBN} allows more implicit conversions in assignments than C; you can
19447 freely store an integer value into a pointer variable or vice versa,
19448 and you can convert any structure to any other structure that is the
19449 same length or shorter.
19450 @comment FIXME: how do structs align/pad in these conversions?
19451 @comment /doc@cygnus.com 18dec1990
19453 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
19454 construct to generate a value of specified type at a specified address
19455 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
19456 to memory location @code{0x83040} as an integer (which implies a certain size
19457 and representation in memory), and
19460 set @{int@}0x83040 = 4
19464 stores the value 4 into that memory location.
19467 @section Continuing at a Different Address
19469 Ordinarily, when you continue your program, you do so at the place where
19470 it stopped, with the @code{continue} command. You can instead continue at
19471 an address of your own choosing, with the following commands:
19475 @kindex j @r{(@code{jump})}
19476 @item jump @var{location}
19477 @itemx j @var{location}
19478 Resume execution at @var{location}. Execution stops again immediately
19479 if there is a breakpoint there. @xref{Specify Location}, for a description
19480 of the different forms of @var{location}. It is common
19481 practice to use the @code{tbreak} command in conjunction with
19482 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
19484 The @code{jump} command does not change the current stack frame, or
19485 the stack pointer, or the contents of any memory location or any
19486 register other than the program counter. If @var{location} is in
19487 a different function from the one currently executing, the results may
19488 be bizarre if the two functions expect different patterns of arguments or
19489 of local variables. For this reason, the @code{jump} command requests
19490 confirmation if the specified line is not in the function currently
19491 executing. However, even bizarre results are predictable if you are
19492 well acquainted with the machine-language code of your program.
19495 On many systems, you can get much the same effect as the @code{jump}
19496 command by storing a new value into the register @code{$pc}. The
19497 difference is that this does not start your program running; it only
19498 changes the address of where it @emph{will} run when you continue. For
19506 makes the next @code{continue} command or stepping command execute at
19507 address @code{0x485}, rather than at the address where your program stopped.
19508 @xref{Continuing and Stepping, ,Continuing and Stepping}.
19510 The most common occasion to use the @code{jump} command is to back
19511 up---perhaps with more breakpoints set---over a portion of a program
19512 that has already executed, in order to examine its execution in more
19517 @section Giving your Program a Signal
19518 @cindex deliver a signal to a program
19522 @item signal @var{signal}
19523 Resume execution where your program is stopped, but immediately give it the
19524 signal @var{signal}. The @var{signal} can be the name or the number of a
19525 signal. For example, on many systems @code{signal 2} and @code{signal
19526 SIGINT} are both ways of sending an interrupt signal.
19528 Alternatively, if @var{signal} is zero, continue execution without
19529 giving a signal. This is useful when your program stopped on account of
19530 a signal and would ordinarily see the signal when resumed with the
19531 @code{continue} command; @samp{signal 0} causes it to resume without a
19534 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
19535 delivered to the currently selected thread, not the thread that last
19536 reported a stop. This includes the situation where a thread was
19537 stopped due to a signal. So if you want to continue execution
19538 suppressing the signal that stopped a thread, you should select that
19539 same thread before issuing the @samp{signal 0} command. If you issue
19540 the @samp{signal 0} command with another thread as the selected one,
19541 @value{GDBN} detects that and asks for confirmation.
19543 Invoking the @code{signal} command is not the same as invoking the
19544 @code{kill} utility from the shell. Sending a signal with @code{kill}
19545 causes @value{GDBN} to decide what to do with the signal depending on
19546 the signal handling tables (@pxref{Signals}). The @code{signal} command
19547 passes the signal directly to your program.
19549 @code{signal} does not repeat when you press @key{RET} a second time
19550 after executing the command.
19552 @kindex queue-signal
19553 @item queue-signal @var{signal}
19554 Queue @var{signal} to be delivered immediately to the current thread
19555 when execution of the thread resumes. The @var{signal} can be the name or
19556 the number of a signal. For example, on many systems @code{signal 2} and
19557 @code{signal SIGINT} are both ways of sending an interrupt signal.
19558 The handling of the signal must be set to pass the signal to the program,
19559 otherwise @value{GDBN} will report an error.
19560 You can control the handling of signals from @value{GDBN} with the
19561 @code{handle} command (@pxref{Signals}).
19563 Alternatively, if @var{signal} is zero, any currently queued signal
19564 for the current thread is discarded and when execution resumes no signal
19565 will be delivered. This is useful when your program stopped on account
19566 of a signal and would ordinarily see the signal when resumed with the
19567 @code{continue} command.
19569 This command differs from the @code{signal} command in that the signal
19570 is just queued, execution is not resumed. And @code{queue-signal} cannot
19571 be used to pass a signal whose handling state has been set to @code{nopass}
19576 @xref{stepping into signal handlers}, for information on how stepping
19577 commands behave when the thread has a signal queued.
19580 @section Returning from a Function
19583 @cindex returning from a function
19586 @itemx return @var{expression}
19587 You can cancel execution of a function call with the @code{return}
19588 command. If you give an
19589 @var{expression} argument, its value is used as the function's return
19593 When you use @code{return}, @value{GDBN} discards the selected stack frame
19594 (and all frames within it). You can think of this as making the
19595 discarded frame return prematurely. If you wish to specify a value to
19596 be returned, give that value as the argument to @code{return}.
19598 This pops the selected stack frame (@pxref{Selection, ,Selecting a
19599 Frame}), and any other frames inside of it, leaving its caller as the
19600 innermost remaining frame. That frame becomes selected. The
19601 specified value is stored in the registers used for returning values
19604 The @code{return} command does not resume execution; it leaves the
19605 program stopped in the state that would exist if the function had just
19606 returned. In contrast, the @code{finish} command (@pxref{Continuing
19607 and Stepping, ,Continuing and Stepping}) resumes execution until the
19608 selected stack frame returns naturally.
19610 @value{GDBN} needs to know how the @var{expression} argument should be set for
19611 the inferior. The concrete registers assignment depends on the OS ABI and the
19612 type being returned by the selected stack frame. For example it is common for
19613 OS ABI to return floating point values in FPU registers while integer values in
19614 CPU registers. Still some ABIs return even floating point values in CPU
19615 registers. Larger integer widths (such as @code{long long int}) also have
19616 specific placement rules. @value{GDBN} already knows the OS ABI from its
19617 current target so it needs to find out also the type being returned to make the
19618 assignment into the right register(s).
19620 Normally, the selected stack frame has debug info. @value{GDBN} will always
19621 use the debug info instead of the implicit type of @var{expression} when the
19622 debug info is available. For example, if you type @kbd{return -1}, and the
19623 function in the current stack frame is declared to return a @code{long long
19624 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
19625 into a @code{long long int}:
19628 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
19630 (@value{GDBP}) return -1
19631 Make func return now? (y or n) y
19632 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
19633 43 printf ("result=%lld\n", func ());
19637 However, if the selected stack frame does not have a debug info, e.g., if the
19638 function was compiled without debug info, @value{GDBN} has to find out the type
19639 to return from user. Specifying a different type by mistake may set the value
19640 in different inferior registers than the caller code expects. For example,
19641 typing @kbd{return -1} with its implicit type @code{int} would set only a part
19642 of a @code{long long int} result for a debug info less function (on 32-bit
19643 architectures). Therefore the user is required to specify the return type by
19644 an appropriate cast explicitly:
19647 Breakpoint 2, 0x0040050b in func ()
19648 (@value{GDBP}) return -1
19649 Return value type not available for selected stack frame.
19650 Please use an explicit cast of the value to return.
19651 (@value{GDBP}) return (long long int) -1
19652 Make selected stack frame return now? (y or n) y
19653 #0 0x00400526 in main ()
19658 @section Calling Program Functions
19661 @cindex calling functions
19662 @cindex inferior functions, calling
19663 @item print @var{expr}
19664 Evaluate the expression @var{expr} and display the resulting value.
19665 The expression may include calls to functions in the program being
19669 @item call @var{expr}
19670 Evaluate the expression @var{expr} without displaying @code{void}
19673 You can use this variant of the @code{print} command if you want to
19674 execute a function from your program that does not return anything
19675 (a.k.a.@: @dfn{a void function}), but without cluttering the output
19676 with @code{void} returned values that @value{GDBN} will otherwise
19677 print. If the result is not void, it is printed and saved in the
19681 It is possible for the function you call via the @code{print} or
19682 @code{call} command to generate a signal (e.g., if there's a bug in
19683 the function, or if you passed it incorrect arguments). What happens
19684 in that case is controlled by the @code{set unwindonsignal} command.
19686 Similarly, with a C@t{++} program it is possible for the function you
19687 call via the @code{print} or @code{call} command to generate an
19688 exception that is not handled due to the constraints of the dummy
19689 frame. In this case, any exception that is raised in the frame, but has
19690 an out-of-frame exception handler will not be found. GDB builds a
19691 dummy-frame for the inferior function call, and the unwinder cannot
19692 seek for exception handlers outside of this dummy-frame. What happens
19693 in that case is controlled by the
19694 @code{set unwind-on-terminating-exception} command.
19697 @item set unwindonsignal
19698 @kindex set unwindonsignal
19699 @cindex unwind stack in called functions
19700 @cindex call dummy stack unwinding
19701 Set unwinding of the stack if a signal is received while in a function
19702 that @value{GDBN} called in the program being debugged. If set to on,
19703 @value{GDBN} unwinds the stack it created for the call and restores
19704 the context to what it was before the call. If set to off (the
19705 default), @value{GDBN} stops in the frame where the signal was
19708 @item show unwindonsignal
19709 @kindex show unwindonsignal
19710 Show the current setting of stack unwinding in the functions called by
19713 @item set unwind-on-terminating-exception
19714 @kindex set unwind-on-terminating-exception
19715 @cindex unwind stack in called functions with unhandled exceptions
19716 @cindex call dummy stack unwinding on unhandled exception.
19717 Set unwinding of the stack if a C@t{++} exception is raised, but left
19718 unhandled while in a function that @value{GDBN} called in the program being
19719 debugged. If set to on (the default), @value{GDBN} unwinds the stack
19720 it created for the call and restores the context to what it was before
19721 the call. If set to off, @value{GDBN} the exception is delivered to
19722 the default C@t{++} exception handler and the inferior terminated.
19724 @item show unwind-on-terminating-exception
19725 @kindex show unwind-on-terminating-exception
19726 Show the current setting of stack unwinding in the functions called by
19729 @item set may-call-functions
19730 @kindex set may-call-functions
19731 @cindex disabling calling functions in the program
19732 @cindex calling functions in the program, disabling
19733 Set permission to call functions in the program.
19734 This controls whether @value{GDBN} will attempt to call functions in
19735 the program, such as with expressions in the @code{print} command. It
19736 defaults to @code{on}.
19738 To call a function in the program, @value{GDBN} has to temporarily
19739 modify the state of the inferior. This has potentially undesired side
19740 effects. Also, having @value{GDBN} call nested functions is likely to
19741 be erroneous and may even crash the program being debugged. You can
19742 avoid such hazards by forbidding @value{GDBN} from calling functions
19743 in the program being debugged. If calling functions in the program
19744 is forbidden, GDB will throw an error when a command (such as printing
19745 an expression) starts a function call in the program.
19747 @item show may-call-functions
19748 @kindex show may-call-functions
19749 Show permission to call functions in the program.
19753 @subsection Calling functions with no debug info
19755 @cindex no debug info functions
19756 Sometimes, a function you wish to call is missing debug information.
19757 In such case, @value{GDBN} does not know the type of the function,
19758 including the types of the function's parameters. To avoid calling
19759 the inferior function incorrectly, which could result in the called
19760 function functioning erroneously and even crash, @value{GDBN} refuses
19761 to call the function unless you tell it the type of the function.
19763 For prototyped (i.e.@: ANSI/ISO style) functions, there are two ways
19764 to do that. The simplest is to cast the call to the function's
19765 declared return type. For example:
19768 (@value{GDBP}) p getenv ("PATH")
19769 'getenv' has unknown return type; cast the call to its declared return type
19770 (@value{GDBP}) p (char *) getenv ("PATH")
19771 $1 = 0x7fffffffe7ba "/usr/local/bin:/"...
19774 Casting the return type of a no-debug function is equivalent to
19775 casting the function to a pointer to a prototyped function that has a
19776 prototype that matches the types of the passed-in arguments, and
19777 calling that. I.e., the call above is equivalent to:
19780 (@value{GDBP}) p ((char * (*) (const char *)) getenv) ("PATH")
19784 and given this prototyped C or C++ function with float parameters:
19787 float multiply (float v1, float v2) @{ return v1 * v2; @}
19791 these calls are equivalent:
19794 (@value{GDBP}) p (float) multiply (2.0f, 3.0f)
19795 (@value{GDBP}) p ((float (*) (float, float)) multiply) (2.0f, 3.0f)
19798 If the function you wish to call is declared as unprototyped (i.e.@:
19799 old K&R style), you must use the cast-to-function-pointer syntax, so
19800 that @value{GDBN} knows that it needs to apply default argument
19801 promotions (promote float arguments to double). @xref{ABI, float
19802 promotion}. For example, given this unprototyped C function with
19803 float parameters, and no debug info:
19807 multiply_noproto (v1, v2)
19815 you call it like this:
19818 (@value{GDBP}) p ((float (*) ()) multiply_noproto) (2.0f, 3.0f)
19822 @section Patching Programs
19824 @cindex patching binaries
19825 @cindex writing into executables
19826 @cindex writing into corefiles
19828 By default, @value{GDBN} opens the file containing your program's
19829 executable code (or the corefile) read-only. This prevents accidental
19830 alterations to machine code; but it also prevents you from intentionally
19831 patching your program's binary.
19833 If you'd like to be able to patch the binary, you can specify that
19834 explicitly with the @code{set write} command. For example, you might
19835 want to turn on internal debugging flags, or even to make emergency
19841 @itemx set write off
19842 If you specify @samp{set write on}, @value{GDBN} opens executable and
19843 core files for both reading and writing; if you specify @kbd{set write
19844 off} (the default), @value{GDBN} opens them read-only.
19846 If you have already loaded a file, you must load it again (using the
19847 @code{exec-file} or @code{core-file} command) after changing @code{set
19848 write}, for your new setting to take effect.
19852 Display whether executable files and core files are opened for writing
19853 as well as reading.
19856 @node Compiling and Injecting Code
19857 @section Compiling and injecting code in @value{GDBN}
19858 @cindex injecting code
19859 @cindex writing into executables
19860 @cindex compiling code
19862 @value{GDBN} supports on-demand compilation and code injection into
19863 programs running under @value{GDBN}. GCC 5.0 or higher built with
19864 @file{libcc1.so} must be installed for this functionality to be enabled.
19865 This functionality is implemented with the following commands.
19868 @kindex compile code
19869 @item compile code @var{source-code}
19870 @itemx compile code -raw @var{--} @var{source-code}
19871 Compile @var{source-code} with the compiler language found as the current
19872 language in @value{GDBN} (@pxref{Languages}). If compilation and
19873 injection is not supported with the current language specified in
19874 @value{GDBN}, or the compiler does not support this feature, an error
19875 message will be printed. If @var{source-code} compiles and links
19876 successfully, @value{GDBN} will load the object-code emitted,
19877 and execute it within the context of the currently selected inferior.
19878 It is important to note that the compiled code is executed immediately.
19879 After execution, the compiled code is removed from @value{GDBN} and any
19880 new types or variables you have defined will be deleted.
19882 The command allows you to specify @var{source-code} in two ways.
19883 The simplest method is to provide a single line of code to the command.
19887 compile code printf ("hello world\n");
19890 If you specify options on the command line as well as source code, they
19891 may conflict. The @samp{--} delimiter can be used to separate options
19892 from actual source code. E.g.:
19895 compile code -r -- printf ("hello world\n");
19898 Alternatively you can enter source code as multiple lines of text. To
19899 enter this mode, invoke the @samp{compile code} command without any text
19900 following the command. This will start the multiple-line editor and
19901 allow you to type as many lines of source code as required. When you
19902 have completed typing, enter @samp{end} on its own line to exit the
19907 >printf ("hello\n");
19908 >printf ("world\n");
19912 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
19913 provided @var{source-code} in a callable scope. In this case, you must
19914 specify the entry point of the code by defining a function named
19915 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
19916 inferior. Using @samp{-raw} option may be needed for example when
19917 @var{source-code} requires @samp{#include} lines which may conflict with
19918 inferior symbols otherwise.
19920 @kindex compile file
19921 @item compile file @var{filename}
19922 @itemx compile file -raw @var{filename}
19923 Like @code{compile code}, but take the source code from @var{filename}.
19926 compile file /home/user/example.c
19931 @item compile print [[@var{options}] --] @var{expr}
19932 @itemx compile print [[@var{options}] --] /@var{f} @var{expr}
19933 Compile and execute @var{expr} with the compiler language found as the
19934 current language in @value{GDBN} (@pxref{Languages}). By default the
19935 value of @var{expr} is printed in a format appropriate to its data type;
19936 you can choose a different format by specifying @samp{/@var{f}}, where
19937 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
19938 Formats}. The @code{compile print} command accepts the same options
19939 as the @code{print} command; see @ref{print options}.
19941 @item compile print [[@var{options}] --]
19942 @itemx compile print [[@var{options}] --] /@var{f}
19943 @cindex reprint the last value
19944 Alternatively you can enter the expression (source code producing it) as
19945 multiple lines of text. To enter this mode, invoke the @samp{compile print}
19946 command without any text following the command. This will start the
19947 multiple-line editor.
19951 The process of compiling and injecting the code can be inspected using:
19954 @anchor{set debug compile}
19955 @item set debug compile
19956 @cindex compile command debugging info
19957 Turns on or off display of @value{GDBN} process of compiling and
19958 injecting the code. The default is off.
19960 @item show debug compile
19961 Displays the current state of displaying @value{GDBN} process of
19962 compiling and injecting the code.
19964 @anchor{set debug compile-cplus-types}
19965 @item set debug compile-cplus-types
19966 @cindex compile C@t{++} type conversion
19967 Turns on or off the display of C@t{++} type conversion debugging information.
19968 The default is off.
19970 @item show debug compile-cplus-types
19971 Displays the current state of displaying debugging information for
19972 C@t{++} type conversion.
19975 @subsection Compilation options for the @code{compile} command
19977 @value{GDBN} needs to specify the right compilation options for the code
19978 to be injected, in part to make its ABI compatible with the inferior
19979 and in part to make the injected code compatible with @value{GDBN}'s
19983 The options used, in increasing precedence:
19986 @item target architecture and OS options (@code{gdbarch})
19987 These options depend on target processor type and target operating
19988 system, usually they specify at least 32-bit (@code{-m32}) or 64-bit
19989 (@code{-m64}) compilation option.
19991 @item compilation options recorded in the target
19992 @value{NGCC} (since version 4.7) stores the options used for compilation
19993 into @code{DW_AT_producer} part of DWARF debugging information according
19994 to the @value{NGCC} option @code{-grecord-gcc-switches}. One has to
19995 explicitly specify @code{-g} during inferior compilation otherwise
19996 @value{NGCC} produces no DWARF. This feature is only relevant for
19997 platforms where @code{-g} produces DWARF by default, otherwise one may
19998 try to enforce DWARF by using @code{-gdwarf-4}.
20000 @item compilation options set by @code{set compile-args}
20004 You can override compilation options using the following command:
20007 @item set compile-args
20008 @cindex compile command options override
20009 Set compilation options used for compiling and injecting code with the
20010 @code{compile} commands. These options override any conflicting ones
20011 from the target architecture and/or options stored during inferior
20014 @item show compile-args
20015 Displays the current state of compilation options override.
20016 This does not show all the options actually used during compilation,
20017 use @ref{set debug compile} for that.
20020 @subsection Caveats when using the @code{compile} command
20022 There are a few caveats to keep in mind when using the @code{compile}
20023 command. As the caveats are different per language, the table below
20024 highlights specific issues on a per language basis.
20027 @item C code examples and caveats
20028 When the language in @value{GDBN} is set to @samp{C}, the compiler will
20029 attempt to compile the source code with a @samp{C} compiler. The source
20030 code provided to the @code{compile} command will have much the same
20031 access to variables and types as it normally would if it were part of
20032 the program currently being debugged in @value{GDBN}.
20034 Below is a sample program that forms the basis of the examples that
20035 follow. This program has been compiled and loaded into @value{GDBN},
20036 much like any other normal debugging session.
20039 void function1 (void)
20042 printf ("function 1\n");
20045 void function2 (void)
20060 For the purposes of the examples in this section, the program above has
20061 been compiled, loaded into @value{GDBN}, stopped at the function
20062 @code{main}, and @value{GDBN} is awaiting input from the user.
20064 To access variables and types for any program in @value{GDBN}, the
20065 program must be compiled and packaged with debug information. The
20066 @code{compile} command is not an exception to this rule. Without debug
20067 information, you can still use the @code{compile} command, but you will
20068 be very limited in what variables and types you can access.
20070 So with that in mind, the example above has been compiled with debug
20071 information enabled. The @code{compile} command will have access to
20072 all variables and types (except those that may have been optimized
20073 out). Currently, as @value{GDBN} has stopped the program in the
20074 @code{main} function, the @code{compile} command would have access to
20075 the variable @code{k}. You could invoke the @code{compile} command
20076 and type some source code to set the value of @code{k}. You can also
20077 read it, or do anything with that variable you would normally do in
20078 @code{C}. Be aware that changes to inferior variables in the
20079 @code{compile} command are persistent. In the following example:
20082 compile code k = 3;
20086 the variable @code{k} is now 3. It will retain that value until
20087 something else in the example program changes it, or another
20088 @code{compile} command changes it.
20090 Normal scope and access rules apply to source code compiled and
20091 injected by the @code{compile} command. In the example, the variables
20092 @code{j} and @code{k} are not accessible yet, because the program is
20093 currently stopped in the @code{main} function, where these variables
20094 are not in scope. Therefore, the following command
20097 compile code j = 3;
20101 will result in a compilation error message.
20103 Once the program is continued, execution will bring these variables in
20104 scope, and they will become accessible; then the code you specify via
20105 the @code{compile} command will be able to access them.
20107 You can create variables and types with the @code{compile} command as
20108 part of your source code. Variables and types that are created as part
20109 of the @code{compile} command are not visible to the rest of the program for
20110 the duration of its run. This example is valid:
20113 compile code int ff = 5; printf ("ff is %d\n", ff);
20116 However, if you were to type the following into @value{GDBN} after that
20117 command has completed:
20120 compile code printf ("ff is %d\n'', ff);
20124 a compiler error would be raised as the variable @code{ff} no longer
20125 exists. Object code generated and injected by the @code{compile}
20126 command is removed when its execution ends. Caution is advised
20127 when assigning to program variables values of variables created by the
20128 code submitted to the @code{compile} command. This example is valid:
20131 compile code int ff = 5; k = ff;
20134 The value of the variable @code{ff} is assigned to @code{k}. The variable
20135 @code{k} does not require the existence of @code{ff} to maintain the value
20136 it has been assigned. However, pointers require particular care in
20137 assignment. If the source code compiled with the @code{compile} command
20138 changed the address of a pointer in the example program, perhaps to a
20139 variable created in the @code{compile} command, that pointer would point
20140 to an invalid location when the command exits. The following example
20141 would likely cause issues with your debugged program:
20144 compile code int ff = 5; p = &ff;
20147 In this example, @code{p} would point to @code{ff} when the
20148 @code{compile} command is executing the source code provided to it.
20149 However, as variables in the (example) program persist with their
20150 assigned values, the variable @code{p} would point to an invalid
20151 location when the command exists. A general rule should be followed
20152 in that you should either assign @code{NULL} to any assigned pointers,
20153 or restore a valid location to the pointer before the command exits.
20155 Similar caution must be exercised with any structs, unions, and typedefs
20156 defined in @code{compile} command. Types defined in the @code{compile}
20157 command will no longer be available in the next @code{compile} command.
20158 Therefore, if you cast a variable to a type defined in the
20159 @code{compile} command, care must be taken to ensure that any future
20160 need to resolve the type can be achieved.
20163 (gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
20164 (gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
20165 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
20166 Compilation failed.
20167 (gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
20171 Variables that have been optimized away by the compiler are not
20172 accessible to the code submitted to the @code{compile} command.
20173 Access to those variables will generate a compiler error which @value{GDBN}
20174 will print to the console.
20177 @subsection Compiler search for the @code{compile} command
20179 @value{GDBN} needs to find @value{NGCC} for the inferior being debugged
20180 which may not be obvious for remote targets of different architecture
20181 than where @value{GDBN} is running. Environment variable @code{PATH} on
20182 @value{GDBN} host is searched for @value{NGCC} binary matching the
20183 target architecture and operating system. This search can be overriden
20184 by @code{set compile-gcc} @value{GDBN} command below. @code{PATH} is
20185 taken from shell that executed @value{GDBN}, it is not the value set by
20186 @value{GDBN} command @code{set environment}). @xref{Environment}.
20189 Specifically @code{PATH} is searched for binaries matching regular expression
20190 @code{@var{arch}(-[^-]*)?-@var{os}-gcc} according to the inferior target being
20191 debugged. @var{arch} is processor name --- multiarch is supported, so for
20192 example both @code{i386} and @code{x86_64} targets look for pattern
20193 @code{(x86_64|i.86)} and both @code{s390} and @code{s390x} targets look
20194 for pattern @code{s390x?}. @var{os} is currently supported only for
20195 pattern @code{linux(-gnu)?}.
20197 On Posix hosts the compiler driver @value{GDBN} needs to find also
20198 shared library @file{libcc1.so} from the compiler. It is searched in
20199 default shared library search path (overridable with usual environment
20200 variable @code{LD_LIBRARY_PATH}), unrelated to @code{PATH} or @code{set
20201 compile-gcc} settings. Contrary to it @file{libcc1plugin.so} is found
20202 according to the installation of the found compiler --- as possibly
20203 specified by the @code{set compile-gcc} command.
20206 @item set compile-gcc
20207 @cindex compile command driver filename override
20208 Set compilation command used for compiling and injecting code with the
20209 @code{compile} commands. If this option is not set (it is set to
20210 an empty string), the search described above will occur --- that is the
20213 @item show compile-gcc
20214 Displays the current compile command @value{NGCC} driver filename.
20215 If set, it is the main command @command{gcc}, found usually for example
20216 under name @file{x86_64-linux-gnu-gcc}.
20220 @chapter @value{GDBN} Files
20222 @value{GDBN} needs to know the file name of the program to be debugged,
20223 both in order to read its symbol table and in order to start your
20224 program. To debug a core dump of a previous run, you must also tell
20225 @value{GDBN} the name of the core dump file.
20228 * Files:: Commands to specify files
20229 * File Caching:: Information about @value{GDBN}'s file caching
20230 * Separate Debug Files:: Debugging information in separate files
20231 * MiniDebugInfo:: Debugging information in a special section
20232 * Index Files:: Index files speed up GDB
20233 * Symbol Errors:: Errors reading symbol files
20234 * Data Files:: GDB data files
20238 @section Commands to Specify Files
20240 @cindex symbol table
20241 @cindex core dump file
20243 You may want to specify executable and core dump file names. The usual
20244 way to do this is at start-up time, using the arguments to
20245 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
20246 Out of @value{GDBN}}).
20248 Occasionally it is necessary to change to a different file during a
20249 @value{GDBN} session. Or you may run @value{GDBN} and forget to
20250 specify a file you want to use. Or you are debugging a remote target
20251 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
20252 Program}). In these situations the @value{GDBN} commands to specify
20253 new files are useful.
20256 @cindex executable file
20258 @item file @var{filename}
20259 Use @var{filename} as the program to be debugged. It is read for its
20260 symbols and for the contents of pure memory. It is also the program
20261 executed when you use the @code{run} command. If you do not specify a
20262 directory and the file is not found in the @value{GDBN} working directory,
20263 @value{GDBN} uses the environment variable @code{PATH} as a list of
20264 directories to search, just as the shell does when looking for a program
20265 to run. You can change the value of this variable, for both @value{GDBN}
20266 and your program, using the @code{path} command.
20268 @cindex unlinked object files
20269 @cindex patching object files
20270 You can load unlinked object @file{.o} files into @value{GDBN} using
20271 the @code{file} command. You will not be able to ``run'' an object
20272 file, but you can disassemble functions and inspect variables. Also,
20273 if the underlying BFD functionality supports it, you could use
20274 @kbd{gdb -write} to patch object files using this technique. Note
20275 that @value{GDBN} can neither interpret nor modify relocations in this
20276 case, so branches and some initialized variables will appear to go to
20277 the wrong place. But this feature is still handy from time to time.
20280 @code{file} with no argument makes @value{GDBN} discard any information it
20281 has on both executable file and the symbol table.
20284 @item exec-file @r{[} @var{filename} @r{]}
20285 Specify that the program to be run (but not the symbol table) is found
20286 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
20287 if necessary to locate your program. Omitting @var{filename} means to
20288 discard information on the executable file.
20290 @kindex symbol-file
20291 @item symbol-file @r{[} @var{filename} @r{[} -o @var{offset} @r{]]}
20292 Read symbol table information from file @var{filename}. @code{PATH} is
20293 searched when necessary. Use the @code{file} command to get both symbol
20294 table and program to run from the same file.
20296 If an optional @var{offset} is specified, it is added to the start
20297 address of each section in the symbol file. This is useful if the
20298 program is relocated at runtime, such as the Linux kernel with kASLR
20301 @code{symbol-file} with no argument clears out @value{GDBN} information on your
20302 program's symbol table.
20304 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
20305 some breakpoints and auto-display expressions. This is because they may
20306 contain pointers to the internal data recording symbols and data types,
20307 which are part of the old symbol table data being discarded inside
20310 @code{symbol-file} does not repeat if you press @key{RET} again after
20313 When @value{GDBN} is configured for a particular environment, it
20314 understands debugging information in whatever format is the standard
20315 generated for that environment; you may use either a @sc{gnu} compiler, or
20316 other compilers that adhere to the local conventions.
20317 Best results are usually obtained from @sc{gnu} compilers; for example,
20318 using @code{@value{NGCC}} you can generate debugging information for
20321 For most kinds of object files, with the exception of old SVR3 systems
20322 using COFF, the @code{symbol-file} command does not normally read the
20323 symbol table in full right away. Instead, it scans the symbol table
20324 quickly to find which source files and which symbols are present. The
20325 details are read later, one source file at a time, as they are needed.
20327 The purpose of this two-stage reading strategy is to make @value{GDBN}
20328 start up faster. For the most part, it is invisible except for
20329 occasional pauses while the symbol table details for a particular source
20330 file are being read. (The @code{set verbose} command can turn these
20331 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
20332 Warnings and Messages}.)
20334 We have not implemented the two-stage strategy for COFF yet. When the
20335 symbol table is stored in COFF format, @code{symbol-file} reads the
20336 symbol table data in full right away. Note that ``stabs-in-COFF''
20337 still does the two-stage strategy, since the debug info is actually
20341 @cindex reading symbols immediately
20342 @cindex symbols, reading immediately
20343 @item symbol-file @r{[} -readnow @r{]} @var{filename}
20344 @itemx file @r{[} -readnow @r{]} @var{filename}
20345 You can override the @value{GDBN} two-stage strategy for reading symbol
20346 tables by using the @samp{-readnow} option with any of the commands that
20347 load symbol table information, if you want to be sure @value{GDBN} has the
20348 entire symbol table available.
20350 @cindex @code{-readnever}, option for symbol-file command
20351 @cindex never read symbols
20352 @cindex symbols, never read
20353 @item symbol-file @r{[} -readnever @r{]} @var{filename}
20354 @itemx file @r{[} -readnever @r{]} @var{filename}
20355 You can instruct @value{GDBN} to never read the symbolic information
20356 contained in @var{filename} by using the @samp{-readnever} option.
20357 @xref{--readnever}.
20359 @c FIXME: for now no mention of directories, since this seems to be in
20360 @c flux. 13mar1992 status is that in theory GDB would look either in
20361 @c current dir or in same dir as myprog; but issues like competing
20362 @c GDB's, or clutter in system dirs, mean that in practice right now
20363 @c only current dir is used. FFish says maybe a special GDB hierarchy
20364 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
20368 @item core-file @r{[}@var{filename}@r{]}
20370 Specify the whereabouts of a core dump file to be used as the ``contents
20371 of memory''. Traditionally, core files contain only some parts of the
20372 address space of the process that generated them; @value{GDBN} can access the
20373 executable file itself for other parts.
20375 @code{core-file} with no argument specifies that no core file is
20378 Note that the core file is ignored when your program is actually running
20379 under @value{GDBN}. So, if you have been running your program and you
20380 wish to debug a core file instead, you must kill the subprocess in which
20381 the program is running. To do this, use the @code{kill} command
20382 (@pxref{Kill Process, ,Killing the Child Process}).
20384 @kindex add-symbol-file
20385 @cindex dynamic linking
20386 @item add-symbol-file @var{filename} @r{[} -readnow @r{|} -readnever @r{]} @r{[} -o @var{offset} @r{]} @r{[} @var{textaddress} @r{]} @r{[} -s @var{section} @var{address} @dots{} @r{]}
20387 The @code{add-symbol-file} command reads additional symbol table
20388 information from the file @var{filename}. You would use this command
20389 when @var{filename} has been dynamically loaded (by some other means)
20390 into the program that is running. The @var{textaddress} parameter gives
20391 the memory address at which the file's text section has been loaded.
20392 You can additionally specify the base address of other sections using
20393 an arbitrary number of @samp{-s @var{section} @var{address}} pairs.
20394 If a section is omitted, @value{GDBN} will use its default addresses
20395 as found in @var{filename}. Any @var{address} or @var{textaddress}
20396 can be given as an expression.
20398 If an optional @var{offset} is specified, it is added to the start
20399 address of each section, except those for which the address was
20400 specified explicitly.
20402 The symbol table of the file @var{filename} is added to the symbol table
20403 originally read with the @code{symbol-file} command. You can use the
20404 @code{add-symbol-file} command any number of times; the new symbol data
20405 thus read is kept in addition to the old.
20407 Changes can be reverted using the command @code{remove-symbol-file}.
20409 @cindex relocatable object files, reading symbols from
20410 @cindex object files, relocatable, reading symbols from
20411 @cindex reading symbols from relocatable object files
20412 @cindex symbols, reading from relocatable object files
20413 @cindex @file{.o} files, reading symbols from
20414 Although @var{filename} is typically a shared library file, an
20415 executable file, or some other object file which has been fully
20416 relocated for loading into a process, you can also load symbolic
20417 information from relocatable @file{.o} files, as long as:
20421 the file's symbolic information refers only to linker symbols defined in
20422 that file, not to symbols defined by other object files,
20424 every section the file's symbolic information refers to has actually
20425 been loaded into the inferior, as it appears in the file, and
20427 you can determine the address at which every section was loaded, and
20428 provide these to the @code{add-symbol-file} command.
20432 Some embedded operating systems, like Sun Chorus and VxWorks, can load
20433 relocatable files into an already running program; such systems
20434 typically make the requirements above easy to meet. However, it's
20435 important to recognize that many native systems use complex link
20436 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
20437 assembly, for example) that make the requirements difficult to meet. In
20438 general, one cannot assume that using @code{add-symbol-file} to read a
20439 relocatable object file's symbolic information will have the same effect
20440 as linking the relocatable object file into the program in the normal
20443 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
20445 @kindex remove-symbol-file
20446 @item remove-symbol-file @var{filename}
20447 @item remove-symbol-file -a @var{address}
20448 Remove a symbol file added via the @code{add-symbol-file} command. The
20449 file to remove can be identified by its @var{filename} or by an @var{address}
20450 that lies within the boundaries of this symbol file in memory. Example:
20453 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
20454 add symbol table from file "/home/user/gdb/mylib.so" at
20455 .text_addr = 0x7ffff7ff9480
20457 Reading symbols from /home/user/gdb/mylib.so...
20458 (gdb) remove-symbol-file -a 0x7ffff7ff9480
20459 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
20464 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
20466 @kindex add-symbol-file-from-memory
20467 @cindex @code{syscall DSO}
20468 @cindex load symbols from memory
20469 @item add-symbol-file-from-memory @var{address}
20470 Load symbols from the given @var{address} in a dynamically loaded
20471 object file whose image is mapped directly into the inferior's memory.
20472 For example, the Linux kernel maps a @code{syscall DSO} into each
20473 process's address space; this DSO provides kernel-specific code for
20474 some system calls. The argument can be any expression whose
20475 evaluation yields the address of the file's shared object file header.
20476 For this command to work, you must have used @code{symbol-file} or
20477 @code{exec-file} commands in advance.
20480 @item section @var{section} @var{addr}
20481 The @code{section} command changes the base address of the named
20482 @var{section} of the exec file to @var{addr}. This can be used if the
20483 exec file does not contain section addresses, (such as in the
20484 @code{a.out} format), or when the addresses specified in the file
20485 itself are wrong. Each section must be changed separately. The
20486 @code{info files} command, described below, lists all the sections and
20490 @kindex info target
20493 @code{info files} and @code{info target} are synonymous; both print the
20494 current target (@pxref{Targets, ,Specifying a Debugging Target}),
20495 including the names of the executable and core dump files currently in
20496 use by @value{GDBN}, and the files from which symbols were loaded. The
20497 command @code{help target} lists all possible targets rather than
20500 @kindex maint info sections
20501 @item maint info sections
20502 Another command that can give you extra information about program sections
20503 is @code{maint info sections}. In addition to the section information
20504 displayed by @code{info files}, this command displays the flags and file
20505 offset of each section in the executable and core dump files. In addition,
20506 @code{maint info sections} provides the following command options (which
20507 may be arbitrarily combined):
20511 Display sections for all loaded object files, including shared libraries.
20512 @item @var{sections}
20513 Display info only for named @var{sections}.
20514 @item @var{section-flags}
20515 Display info only for sections for which @var{section-flags} are true.
20516 The section flags that @value{GDBN} currently knows about are:
20519 Section will have space allocated in the process when loaded.
20520 Set for all sections except those containing debug information.
20522 Section will be loaded from the file into the child process memory.
20523 Set for pre-initialized code and data, clear for @code{.bss} sections.
20525 Section needs to be relocated before loading.
20527 Section cannot be modified by the child process.
20529 Section contains executable code only.
20531 Section contains data only (no executable code).
20533 Section will reside in ROM.
20535 Section contains data for constructor/destructor lists.
20537 Section is not empty.
20539 An instruction to the linker to not output the section.
20540 @item COFF_SHARED_LIBRARY
20541 A notification to the linker that the section contains
20542 COFF shared library information.
20544 Section contains common symbols.
20547 @kindex set trust-readonly-sections
20548 @cindex read-only sections
20549 @item set trust-readonly-sections on
20550 Tell @value{GDBN} that readonly sections in your object file
20551 really are read-only (i.e.@: that their contents will not change).
20552 In that case, @value{GDBN} can fetch values from these sections
20553 out of the object file, rather than from the target program.
20554 For some targets (notably embedded ones), this can be a significant
20555 enhancement to debugging performance.
20557 The default is off.
20559 @item set trust-readonly-sections off
20560 Tell @value{GDBN} not to trust readonly sections. This means that
20561 the contents of the section might change while the program is running,
20562 and must therefore be fetched from the target when needed.
20564 @item show trust-readonly-sections
20565 Show the current setting of trusting readonly sections.
20568 All file-specifying commands allow both absolute and relative file names
20569 as arguments. @value{GDBN} always converts the file name to an absolute file
20570 name and remembers it that way.
20572 @cindex shared libraries
20573 @anchor{Shared Libraries}
20574 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, SunOS,
20575 Darwin/Mach-O, SVr4, IBM RS/6000 AIX, QNX Neutrino, FDPIC (FR-V), and
20576 DSBT (TIC6X) shared libraries.
20578 On MS-Windows @value{GDBN} must be linked with the Expat library to support
20579 shared libraries. @xref{Expat}.
20581 @value{GDBN} automatically loads symbol definitions from shared libraries
20582 when you use the @code{run} command, or when you examine a core file.
20583 (Before you issue the @code{run} command, @value{GDBN} does not understand
20584 references to a function in a shared library, however---unless you are
20585 debugging a core file).
20587 @c FIXME: some @value{GDBN} release may permit some refs to undef
20588 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
20589 @c FIXME...lib; check this from time to time when updating manual
20591 There are times, however, when you may wish to not automatically load
20592 symbol definitions from shared libraries, such as when they are
20593 particularly large or there are many of them.
20595 To control the automatic loading of shared library symbols, use the
20599 @kindex set auto-solib-add
20600 @item set auto-solib-add @var{mode}
20601 If @var{mode} is @code{on}, symbols from all shared object libraries
20602 will be loaded automatically when the inferior begins execution, you
20603 attach to an independently started inferior, or when the dynamic linker
20604 informs @value{GDBN} that a new library has been loaded. If @var{mode}
20605 is @code{off}, symbols must be loaded manually, using the
20606 @code{sharedlibrary} command. The default value is @code{on}.
20608 @cindex memory used for symbol tables
20609 If your program uses lots of shared libraries with debug info that
20610 takes large amounts of memory, you can decrease the @value{GDBN}
20611 memory footprint by preventing it from automatically loading the
20612 symbols from shared libraries. To that end, type @kbd{set
20613 auto-solib-add off} before running the inferior, then load each
20614 library whose debug symbols you do need with @kbd{sharedlibrary
20615 @var{regexp}}, where @var{regexp} is a regular expression that matches
20616 the libraries whose symbols you want to be loaded.
20618 @kindex show auto-solib-add
20619 @item show auto-solib-add
20620 Display the current autoloading mode.
20623 @cindex load shared library
20624 To explicitly load shared library symbols, use the @code{sharedlibrary}
20628 @kindex info sharedlibrary
20630 @item info share @var{regex}
20631 @itemx info sharedlibrary @var{regex}
20632 Print the names of the shared libraries which are currently loaded
20633 that match @var{regex}. If @var{regex} is omitted then print
20634 all shared libraries that are loaded.
20637 @item info dll @var{regex}
20638 This is an alias of @code{info sharedlibrary}.
20640 @kindex sharedlibrary
20642 @item sharedlibrary @var{regex}
20643 @itemx share @var{regex}
20644 Load shared object library symbols for files matching a
20645 Unix regular expression.
20646 As with files loaded automatically, it only loads shared libraries
20647 required by your program for a core file or after typing @code{run}. If
20648 @var{regex} is omitted all shared libraries required by your program are
20651 @item nosharedlibrary
20652 @kindex nosharedlibrary
20653 @cindex unload symbols from shared libraries
20654 Unload all shared object library symbols. This discards all symbols
20655 that have been loaded from all shared libraries. Symbols from shared
20656 libraries that were loaded by explicit user requests are not
20660 Sometimes you may wish that @value{GDBN} stops and gives you control
20661 when any of shared library events happen. The best way to do this is
20662 to use @code{catch load} and @code{catch unload} (@pxref{Set
20665 @value{GDBN} also supports the @code{set stop-on-solib-events}
20666 command for this. This command exists for historical reasons. It is
20667 less useful than setting a catchpoint, because it does not allow for
20668 conditions or commands as a catchpoint does.
20671 @item set stop-on-solib-events
20672 @kindex set stop-on-solib-events
20673 This command controls whether @value{GDBN} should give you control
20674 when the dynamic linker notifies it about some shared library event.
20675 The most common event of interest is loading or unloading of a new
20678 @item show stop-on-solib-events
20679 @kindex show stop-on-solib-events
20680 Show whether @value{GDBN} stops and gives you control when shared
20681 library events happen.
20684 Shared libraries are also supported in many cross or remote debugging
20685 configurations. @value{GDBN} needs to have access to the target's libraries;
20686 this can be accomplished either by providing copies of the libraries
20687 on the host system, or by asking @value{GDBN} to automatically retrieve the
20688 libraries from the target. If copies of the target libraries are
20689 provided, they need to be the same as the target libraries, although the
20690 copies on the target can be stripped as long as the copies on the host are
20693 @cindex where to look for shared libraries
20694 For remote debugging, you need to tell @value{GDBN} where the target
20695 libraries are, so that it can load the correct copies---otherwise, it
20696 may try to load the host's libraries. @value{GDBN} has two variables
20697 to specify the search directories for target libraries.
20700 @cindex prefix for executable and shared library file names
20701 @cindex system root, alternate
20702 @kindex set solib-absolute-prefix
20703 @kindex set sysroot
20704 @item set sysroot @var{path}
20705 Use @var{path} as the system root for the program being debugged. Any
20706 absolute shared library paths will be prefixed with @var{path}; many
20707 runtime loaders store the absolute paths to the shared library in the
20708 target program's memory. When starting processes remotely, and when
20709 attaching to already-running processes (local or remote), their
20710 executable filenames will be prefixed with @var{path} if reported to
20711 @value{GDBN} as absolute by the operating system. If you use
20712 @code{set sysroot} to find executables and shared libraries, they need
20713 to be laid out in the same way that they are on the target, with
20714 e.g.@: a @file{/bin}, @file{/lib} and @file{/usr/lib} hierarchy under
20717 If @var{path} starts with the sequence @file{target:} and the target
20718 system is remote then @value{GDBN} will retrieve the target binaries
20719 from the remote system. This is only supported when using a remote
20720 target that supports the @code{remote get} command (@pxref{File
20721 Transfer,,Sending files to a remote system}). The part of @var{path}
20722 following the initial @file{target:} (if present) is used as system
20723 root prefix on the remote file system. If @var{path} starts with the
20724 sequence @file{remote:} this is converted to the sequence
20725 @file{target:} by @code{set sysroot}@footnote{Historically the
20726 functionality to retrieve binaries from the remote system was
20727 provided by prefixing @var{path} with @file{remote:}}. If you want
20728 to specify a local system root using a directory that happens to be
20729 named @file{target:} or @file{remote:}, you need to use some
20730 equivalent variant of the name like @file{./target:}.
20732 For targets with an MS-DOS based filesystem, such as MS-Windows and
20733 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
20734 absolute file name with @var{path}. But first, on Unix hosts,
20735 @value{GDBN} converts all backslash directory separators into forward
20736 slashes, because the backslash is not a directory separator on Unix:
20739 c:\foo\bar.dll @result{} c:/foo/bar.dll
20742 Then, @value{GDBN} attempts prefixing the target file name with
20743 @var{path}, and looks for the resulting file name in the host file
20747 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
20750 If that does not find the binary, @value{GDBN} tries removing
20751 the @samp{:} character from the drive spec, both for convenience, and,
20752 for the case of the host file system not supporting file names with
20756 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
20759 This makes it possible to have a system root that mirrors a target
20760 with more than one drive. E.g., you may want to setup your local
20761 copies of the target system shared libraries like so (note @samp{c} vs
20765 @file{/path/to/sysroot/c/sys/bin/foo.dll}
20766 @file{/path/to/sysroot/c/sys/bin/bar.dll}
20767 @file{/path/to/sysroot/z/sys/bin/bar.dll}
20771 and point the system root at @file{/path/to/sysroot}, so that
20772 @value{GDBN} can find the correct copies of both
20773 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
20775 If that still does not find the binary, @value{GDBN} tries
20776 removing the whole drive spec from the target file name:
20779 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
20782 This last lookup makes it possible to not care about the drive name,
20783 if you don't want or need to.
20785 The @code{set solib-absolute-prefix} command is an alias for @code{set
20788 @cindex default system root
20789 @cindex @samp{--with-sysroot}
20790 You can set the default system root by using the configure-time
20791 @samp{--with-sysroot} option. If the system root is inside
20792 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
20793 @samp{--exec-prefix}), then the default system root will be updated
20794 automatically if the installed @value{GDBN} is moved to a new
20797 @kindex show sysroot
20799 Display the current executable and shared library prefix.
20801 @kindex set solib-search-path
20802 @item set solib-search-path @var{path}
20803 If this variable is set, @var{path} is a colon-separated list of
20804 directories to search for shared libraries. @samp{solib-search-path}
20805 is used after @samp{sysroot} fails to locate the library, or if the
20806 path to the library is relative instead of absolute. If you want to
20807 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
20808 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
20809 finding your host's libraries. @samp{sysroot} is preferred; setting
20810 it to a nonexistent directory may interfere with automatic loading
20811 of shared library symbols.
20813 @kindex show solib-search-path
20814 @item show solib-search-path
20815 Display the current shared library search path.
20817 @cindex DOS file-name semantics of file names.
20818 @kindex set target-file-system-kind (unix|dos-based|auto)
20819 @kindex show target-file-system-kind
20820 @item set target-file-system-kind @var{kind}
20821 Set assumed file system kind for target reported file names.
20823 Shared library file names as reported by the target system may not
20824 make sense as is on the system @value{GDBN} is running on. For
20825 example, when remote debugging a target that has MS-DOS based file
20826 system semantics, from a Unix host, the target may be reporting to
20827 @value{GDBN} a list of loaded shared libraries with file names such as
20828 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
20829 drive letters, so the @samp{c:\} prefix is not normally understood as
20830 indicating an absolute file name, and neither is the backslash
20831 normally considered a directory separator character. In that case,
20832 the native file system would interpret this whole absolute file name
20833 as a relative file name with no directory components. This would make
20834 it impossible to point @value{GDBN} at a copy of the remote target's
20835 shared libraries on the host using @code{set sysroot}, and impractical
20836 with @code{set solib-search-path}. Setting
20837 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
20838 to interpret such file names similarly to how the target would, and to
20839 map them to file names valid on @value{GDBN}'s native file system
20840 semantics. The value of @var{kind} can be @code{"auto"}, in addition
20841 to one of the supported file system kinds. In that case, @value{GDBN}
20842 tries to determine the appropriate file system variant based on the
20843 current target's operating system (@pxref{ABI, ,Configuring the
20844 Current ABI}). The supported file system settings are:
20848 Instruct @value{GDBN} to assume the target file system is of Unix
20849 kind. Only file names starting the forward slash (@samp{/}) character
20850 are considered absolute, and the directory separator character is also
20854 Instruct @value{GDBN} to assume the target file system is DOS based.
20855 File names starting with either a forward slash, or a drive letter
20856 followed by a colon (e.g., @samp{c:}), are considered absolute, and
20857 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
20858 considered directory separators.
20861 Instruct @value{GDBN} to use the file system kind associated with the
20862 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
20863 This is the default.
20867 @cindex file name canonicalization
20868 @cindex base name differences
20869 When processing file names provided by the user, @value{GDBN}
20870 frequently needs to compare them to the file names recorded in the
20871 program's debug info. Normally, @value{GDBN} compares just the
20872 @dfn{base names} of the files as strings, which is reasonably fast
20873 even for very large programs. (The base name of a file is the last
20874 portion of its name, after stripping all the leading directories.)
20875 This shortcut in comparison is based upon the assumption that files
20876 cannot have more than one base name. This is usually true, but
20877 references to files that use symlinks or similar filesystem
20878 facilities violate that assumption. If your program records files
20879 using such facilities, or if you provide file names to @value{GDBN}
20880 using symlinks etc., you can set @code{basenames-may-differ} to
20881 @code{true} to instruct @value{GDBN} to completely canonicalize each
20882 pair of file names it needs to compare. This will make file-name
20883 comparisons accurate, but at a price of a significant slowdown.
20886 @item set basenames-may-differ
20887 @kindex set basenames-may-differ
20888 Set whether a source file may have multiple base names.
20890 @item show basenames-may-differ
20891 @kindex show basenames-may-differ
20892 Show whether a source file may have multiple base names.
20896 @section File Caching
20897 @cindex caching of opened files
20898 @cindex caching of bfd objects
20900 To speed up file loading, and reduce memory usage, @value{GDBN} will
20901 reuse the @code{bfd} objects used to track open files. @xref{Top, ,
20902 BFD, bfd, The Binary File Descriptor Library}. The following commands
20903 allow visibility and control of the caching behavior.
20906 @kindex maint info bfds
20907 @item maint info bfds
20908 This prints information about each @code{bfd} object that is known to
20911 @kindex maint set bfd-sharing
20912 @kindex maint show bfd-sharing
20913 @kindex bfd caching
20914 @item maint set bfd-sharing
20915 @item maint show bfd-sharing
20916 Control whether @code{bfd} objects can be shared. When sharing is
20917 enabled @value{GDBN} reuses already open @code{bfd} objects rather
20918 than reopening the same file. Turning sharing off does not cause
20919 already shared @code{bfd} objects to be unshared, but all future files
20920 that are opened will create a new @code{bfd} object. Similarly,
20921 re-enabling sharing does not cause multiple existing @code{bfd}
20922 objects to be collapsed into a single shared @code{bfd} object.
20924 @kindex set debug bfd-cache @var{level}
20925 @kindex bfd caching
20926 @item set debug bfd-cache @var{level}
20927 Turns on debugging of the bfd cache, setting the level to @var{level}.
20929 @kindex show debug bfd-cache
20930 @kindex bfd caching
20931 @item show debug bfd-cache
20932 Show the current debugging level of the bfd cache.
20935 @node Separate Debug Files
20936 @section Debugging Information in Separate Files
20937 @cindex separate debugging information files
20938 @cindex debugging information in separate files
20939 @cindex @file{.debug} subdirectories
20940 @cindex debugging information directory, global
20941 @cindex global debugging information directories
20942 @cindex build ID, and separate debugging files
20943 @cindex @file{.build-id} directory
20945 @value{GDBN} allows you to put a program's debugging information in a
20946 file separate from the executable itself, in a way that allows
20947 @value{GDBN} to find and load the debugging information automatically.
20948 Since debugging information can be very large---sometimes larger
20949 than the executable code itself---some systems distribute debugging
20950 information for their executables in separate files, which users can
20951 install only when they need to debug a problem.
20953 @value{GDBN} supports two ways of specifying the separate debug info
20958 The executable contains a @dfn{debug link} that specifies the name of
20959 the separate debug info file. The separate debug file's name is
20960 usually @file{@var{executable}.debug}, where @var{executable} is the
20961 name of the corresponding executable file without leading directories
20962 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
20963 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
20964 checksum for the debug file, which @value{GDBN} uses to validate that
20965 the executable and the debug file came from the same build.
20969 The executable contains a @dfn{build ID}, a unique bit string that is
20970 also present in the corresponding debug info file. (This is supported
20971 only on some operating systems, when using the ELF or PE file formats
20972 for binary files and the @sc{gnu} Binutils.) For more details about
20973 this feature, see the description of the @option{--build-id}
20974 command-line option in @ref{Options, , Command Line Options, ld,
20975 The GNU Linker}. The debug info file's name is not specified
20976 explicitly by the build ID, but can be computed from the build ID, see
20980 Depending on the way the debug info file is specified, @value{GDBN}
20981 uses two different methods of looking for the debug file:
20985 For the ``debug link'' method, @value{GDBN} looks up the named file in
20986 the directory of the executable file, then in a subdirectory of that
20987 directory named @file{.debug}, and finally under each one of the
20988 global debug directories, in a subdirectory whose name is identical to
20989 the leading directories of the executable's absolute file name. (On
20990 MS-Windows/MS-DOS, the drive letter of the executable's leading
20991 directories is converted to a one-letter subdirectory, i.e.@:
20992 @file{d:/usr/bin/} is converted to @file{/d/usr/bin/}, because Windows
20993 filesystems disallow colons in file names.)
20996 For the ``build ID'' method, @value{GDBN} looks in the
20997 @file{.build-id} subdirectory of each one of the global debug directories for
20998 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
20999 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
21000 are the rest of the bit string. (Real build ID strings are 32 or more
21001 hex characters, not 10.)
21004 So, for example, suppose you ask @value{GDBN} to debug
21005 @file{/usr/bin/ls}, which has a debug link that specifies the
21006 file @file{ls.debug}, and a build ID whose value in hex is
21007 @code{abcdef1234}. If the list of the global debug directories includes
21008 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
21009 debug information files, in the indicated order:
21013 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
21015 @file{/usr/bin/ls.debug}
21017 @file{/usr/bin/.debug/ls.debug}
21019 @file{/usr/lib/debug/usr/bin/ls.debug}.
21022 @anchor{debug-file-directory}
21023 Global debugging info directories default to what is set by @value{GDBN}
21024 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
21025 you can also set the global debugging info directories, and view the list
21026 @value{GDBN} is currently using.
21030 @kindex set debug-file-directory
21031 @item set debug-file-directory @var{directories}
21032 Set the directories which @value{GDBN} searches for separate debugging
21033 information files to @var{directory}. Multiple path components can be set
21034 concatenating them by a path separator.
21036 @kindex show debug-file-directory
21037 @item show debug-file-directory
21038 Show the directories @value{GDBN} searches for separate debugging
21043 @cindex @code{.gnu_debuglink} sections
21044 @cindex debug link sections
21045 A debug link is a special section of the executable file named
21046 @code{.gnu_debuglink}. The section must contain:
21050 A filename, with any leading directory components removed, followed by
21053 zero to three bytes of padding, as needed to reach the next four-byte
21054 boundary within the section, and
21056 a four-byte CRC checksum, stored in the same endianness used for the
21057 executable file itself. The checksum is computed on the debugging
21058 information file's full contents by the function given below, passing
21059 zero as the @var{crc} argument.
21062 Any executable file format can carry a debug link, as long as it can
21063 contain a section named @code{.gnu_debuglink} with the contents
21066 @cindex @code{.note.gnu.build-id} sections
21067 @cindex build ID sections
21068 The build ID is a special section in the executable file (and in other
21069 ELF binary files that @value{GDBN} may consider). This section is
21070 often named @code{.note.gnu.build-id}, but that name is not mandatory.
21071 It contains unique identification for the built files---the ID remains
21072 the same across multiple builds of the same build tree. The default
21073 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
21074 content for the build ID string. The same section with an identical
21075 value is present in the original built binary with symbols, in its
21076 stripped variant, and in the separate debugging information file.
21078 The debugging information file itself should be an ordinary
21079 executable, containing a full set of linker symbols, sections, and
21080 debugging information. The sections of the debugging information file
21081 should have the same names, addresses, and sizes as the original file,
21082 but they need not contain any data---much like a @code{.bss} section
21083 in an ordinary executable.
21085 The @sc{gnu} binary utilities (Binutils) package includes the
21086 @samp{objcopy} utility that can produce
21087 the separated executable / debugging information file pairs using the
21088 following commands:
21091 @kbd{objcopy --only-keep-debug foo foo.debug}
21096 These commands remove the debugging
21097 information from the executable file @file{foo} and place it in the file
21098 @file{foo.debug}. You can use the first, second or both methods to link the
21103 The debug link method needs the following additional command to also leave
21104 behind a debug link in @file{foo}:
21107 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
21110 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
21111 a version of the @code{strip} command such that the command @kbd{strip foo -f
21112 foo.debug} has the same functionality as the two @code{objcopy} commands and
21113 the @code{ln -s} command above, together.
21116 Build ID gets embedded into the main executable using @code{ld --build-id} or
21117 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
21118 compatibility fixes for debug files separation are present in @sc{gnu} binary
21119 utilities (Binutils) package since version 2.18.
21124 @cindex CRC algorithm definition
21125 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
21126 IEEE 802.3 using the polynomial:
21128 @c TexInfo requires naked braces for multi-digit exponents for Tex
21129 @c output, but this causes HTML output to barf. HTML has to be set using
21130 @c raw commands. So we end up having to specify this equation in 2
21135 <em>x</em><sup>32</sup> + <em>x</em><sup>26</sup> + <em>x</em><sup>23</sup> + <em>x</em><sup>22</sup> + <em>x</em><sup>16</sup> + <em>x</em><sup>12</sup> + <em>x</em><sup>11</sup>
21136 + <em>x</em><sup>10</sup> + <em>x</em><sup>8</sup> + <em>x</em><sup>7</sup> + <em>x</em><sup>5</sup> + <em>x</em><sup>4</sup> + <em>x</em><sup>2</sup> + <em>x</em> + 1
21142 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
21143 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
21147 The function is computed byte at a time, taking the least
21148 significant bit of each byte first. The initial pattern
21149 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
21150 the final result is inverted to ensure trailing zeros also affect the
21153 @emph{Note:} This is the same CRC polynomial as used in handling the
21154 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
21155 However in the case of the Remote Serial Protocol, the CRC is computed
21156 @emph{most} significant bit first, and the result is not inverted, so
21157 trailing zeros have no effect on the CRC value.
21159 To complete the description, we show below the code of the function
21160 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
21161 initially supplied @code{crc} argument means that an initial call to
21162 this function passing in zero will start computing the CRC using
21165 @kindex gnu_debuglink_crc32
21168 gnu_debuglink_crc32 (unsigned long crc,
21169 unsigned char *buf, size_t len)
21171 static const unsigned long crc32_table[256] =
21173 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
21174 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
21175 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
21176 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
21177 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
21178 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
21179 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
21180 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
21181 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
21182 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
21183 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
21184 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
21185 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
21186 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
21187 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
21188 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
21189 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
21190 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
21191 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
21192 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
21193 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
21194 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
21195 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
21196 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
21197 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
21198 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
21199 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
21200 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
21201 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
21202 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
21203 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
21204 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
21205 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
21206 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
21207 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
21208 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
21209 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
21210 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
21211 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
21212 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
21213 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
21214 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
21215 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
21216 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
21217 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
21218 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
21219 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
21220 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
21221 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
21222 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
21223 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
21226 unsigned char *end;
21228 crc = ~crc & 0xffffffff;
21229 for (end = buf + len; buf < end; ++buf)
21230 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
21231 return ~crc & 0xffffffff;
21236 This computation does not apply to the ``build ID'' method.
21238 @node MiniDebugInfo
21239 @section Debugging information in a special section
21240 @cindex separate debug sections
21241 @cindex @samp{.gnu_debugdata} section
21243 Some systems ship pre-built executables and libraries that have a
21244 special @samp{.gnu_debugdata} section. This feature is called
21245 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
21246 is used to supply extra symbols for backtraces.
21248 The intent of this section is to provide extra minimal debugging
21249 information for use in simple backtraces. It is not intended to be a
21250 replacement for full separate debugging information (@pxref{Separate
21251 Debug Files}). The example below shows the intended use; however,
21252 @value{GDBN} does not currently put restrictions on what sort of
21253 debugging information might be included in the section.
21255 @value{GDBN} has support for this extension. If the section exists,
21256 then it is used provided that no other source of debugging information
21257 can be found, and that @value{GDBN} was configured with LZMA support.
21259 This section can be easily created using @command{objcopy} and other
21260 standard utilities:
21263 # Extract the dynamic symbols from the main binary, there is no need
21264 # to also have these in the normal symbol table.
21265 nm -D @var{binary} --format=posix --defined-only \
21266 | awk '@{ print $1 @}' | sort > dynsyms
21268 # Extract all the text (i.e. function) symbols from the debuginfo.
21269 # (Note that we actually also accept "D" symbols, for the benefit
21270 # of platforms like PowerPC64 that use function descriptors.)
21271 nm @var{binary} --format=posix --defined-only \
21272 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
21275 # Keep all the function symbols not already in the dynamic symbol
21277 comm -13 dynsyms funcsyms > keep_symbols
21279 # Separate full debug info into debug binary.
21280 objcopy --only-keep-debug @var{binary} debug
21282 # Copy the full debuginfo, keeping only a minimal set of symbols and
21283 # removing some unnecessary sections.
21284 objcopy -S --remove-section .gdb_index --remove-section .comment \
21285 --keep-symbols=keep_symbols debug mini_debuginfo
21287 # Drop the full debug info from the original binary.
21288 strip --strip-all -R .comment @var{binary}
21290 # Inject the compressed data into the .gnu_debugdata section of the
21293 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
21297 @section Index Files Speed Up @value{GDBN}
21298 @cindex index files
21299 @cindex @samp{.gdb_index} section
21301 When @value{GDBN} finds a symbol file, it scans the symbols in the
21302 file in order to construct an internal symbol table. This lets most
21303 @value{GDBN} operations work quickly---at the cost of a delay early
21304 on. For large programs, this delay can be quite lengthy, so
21305 @value{GDBN} provides a way to build an index, which speeds up
21308 For convenience, @value{GDBN} comes with a program,
21309 @command{gdb-add-index}, which can be used to add the index to a
21310 symbol file. It takes the symbol file as its only argument:
21313 $ gdb-add-index symfile
21316 @xref{gdb-add-index}.
21318 It is also possible to do the work manually. Here is what
21319 @command{gdb-add-index} does behind the curtains.
21321 The index is stored as a section in the symbol file. @value{GDBN} can
21322 write the index to a file, then you can put it into the symbol file
21323 using @command{objcopy}.
21325 To create an index file, use the @code{save gdb-index} command:
21328 @item save gdb-index [-dwarf-5] @var{directory}
21329 @kindex save gdb-index
21330 Create index files for all symbol files currently known by
21331 @value{GDBN}. For each known @var{symbol-file}, this command by
21332 default creates it produces a single file
21333 @file{@var{symbol-file}.gdb-index}. If you invoke this command with
21334 the @option{-dwarf-5} option, it produces 2 files:
21335 @file{@var{symbol-file}.debug_names} and
21336 @file{@var{symbol-file}.debug_str}. The files are created in the
21337 given @var{directory}.
21340 Once you have created an index file you can merge it into your symbol
21341 file, here named @file{symfile}, using @command{objcopy}:
21344 $ objcopy --add-section .gdb_index=symfile.gdb-index \
21345 --set-section-flags .gdb_index=readonly symfile symfile
21348 Or for @code{-dwarf-5}:
21351 $ objcopy --dump-section .debug_str=symfile.debug_str.new symfile
21352 $ cat symfile.debug_str >>symfile.debug_str.new
21353 $ objcopy --add-section .debug_names=symfile.gdb-index \
21354 --set-section-flags .debug_names=readonly \
21355 --update-section .debug_str=symfile.debug_str.new symfile symfile
21358 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
21359 sections that have been deprecated. Usually they are deprecated because
21360 they are missing a new feature or have performance issues.
21361 To tell @value{GDBN} to use a deprecated index section anyway
21362 specify @code{set use-deprecated-index-sections on}.
21363 The default is @code{off}.
21364 This can speed up startup, but may result in some functionality being lost.
21365 @xref{Index Section Format}.
21367 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
21368 must be done before gdb reads the file. The following will not work:
21371 $ gdb -ex "set use-deprecated-index-sections on" <program>
21374 Instead you must do, for example,
21377 $ gdb -iex "set use-deprecated-index-sections on" <program>
21380 Indices only work when using DWARF debugging information, not stabs.
21382 @subsection Automatic symbol index cache
21384 @cindex automatic symbol index cache
21385 It is possible for @value{GDBN} to automatically save a copy of this index in a
21386 cache on disk and retrieve it from there when loading the same binary in the
21387 future. This feature can be turned on with @kbd{set index-cache on}. The
21388 following commands can be used to tweak the behavior of the index cache.
21392 @kindex set index-cache
21393 @item set index-cache on
21394 @itemx set index-cache off
21395 Enable or disable the use of the symbol index cache.
21397 @item set index-cache directory @var{directory}
21398 @kindex show index-cache
21399 @itemx show index-cache directory
21400 Set/show the directory where index files will be saved.
21402 The default value for this directory depends on the host platform. On
21403 most systems, the index is cached in the @file{gdb} subdirectory of
21404 the directory pointed to by the @env{XDG_CACHE_HOME} environment
21405 variable, if it is defined, else in the @file{.cache/gdb} subdirectory
21406 of your home directory. However, on some systems, the default may
21407 differ according to local convention.
21409 There is no limit on the disk space used by index cache. It is perfectly safe
21410 to delete the content of that directory to free up disk space.
21412 @item show index-cache stats
21413 Print the number of cache hits and misses since the launch of @value{GDBN}.
21417 @node Symbol Errors
21418 @section Errors Reading Symbol Files
21420 While reading a symbol file, @value{GDBN} occasionally encounters problems,
21421 such as symbol types it does not recognize, or known bugs in compiler
21422 output. By default, @value{GDBN} does not notify you of such problems, since
21423 they are relatively common and primarily of interest to people
21424 debugging compilers. If you are interested in seeing information
21425 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
21426 only one message about each such type of problem, no matter how many
21427 times the problem occurs; or you can ask @value{GDBN} to print more messages,
21428 to see how many times the problems occur, with the @code{set
21429 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
21432 The messages currently printed, and their meanings, include:
21435 @item inner block not inside outer block in @var{symbol}
21437 The symbol information shows where symbol scopes begin and end
21438 (such as at the start of a function or a block of statements). This
21439 error indicates that an inner scope block is not fully contained
21440 in its outer scope blocks.
21442 @value{GDBN} circumvents the problem by treating the inner block as if it had
21443 the same scope as the outer block. In the error message, @var{symbol}
21444 may be shown as ``@code{(don't know)}'' if the outer block is not a
21447 @item block at @var{address} out of order
21449 The symbol information for symbol scope blocks should occur in
21450 order of increasing addresses. This error indicates that it does not
21453 @value{GDBN} does not circumvent this problem, and has trouble
21454 locating symbols in the source file whose symbols it is reading. (You
21455 can often determine what source file is affected by specifying
21456 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
21459 @item bad block start address patched
21461 The symbol information for a symbol scope block has a start address
21462 smaller than the address of the preceding source line. This is known
21463 to occur in the SunOS 4.1.1 (and earlier) C compiler.
21465 @value{GDBN} circumvents the problem by treating the symbol scope block as
21466 starting on the previous source line.
21468 @item bad string table offset in symbol @var{n}
21471 Symbol number @var{n} contains a pointer into the string table which is
21472 larger than the size of the string table.
21474 @value{GDBN} circumvents the problem by considering the symbol to have the
21475 name @code{foo}, which may cause other problems if many symbols end up
21478 @item unknown symbol type @code{0x@var{nn}}
21480 The symbol information contains new data types that @value{GDBN} does
21481 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
21482 uncomprehended information, in hexadecimal.
21484 @value{GDBN} circumvents the error by ignoring this symbol information.
21485 This usually allows you to debug your program, though certain symbols
21486 are not accessible. If you encounter such a problem and feel like
21487 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
21488 on @code{complain}, then go up to the function @code{read_dbx_symtab}
21489 and examine @code{*bufp} to see the symbol.
21491 @item stub type has NULL name
21493 @value{GDBN} could not find the full definition for a struct or class.
21495 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
21496 The symbol information for a C@t{++} member function is missing some
21497 information that recent versions of the compiler should have output for
21500 @item info mismatch between compiler and debugger
21502 @value{GDBN} could not parse a type specification output by the compiler.
21507 @section GDB Data Files
21509 @cindex prefix for data files
21510 @value{GDBN} will sometimes read an auxiliary data file. These files
21511 are kept in a directory known as the @dfn{data directory}.
21513 You can set the data directory's name, and view the name @value{GDBN}
21514 is currently using.
21517 @kindex set data-directory
21518 @item set data-directory @var{directory}
21519 Set the directory which @value{GDBN} searches for auxiliary data files
21520 to @var{directory}.
21522 @kindex show data-directory
21523 @item show data-directory
21524 Show the directory @value{GDBN} searches for auxiliary data files.
21527 @cindex default data directory
21528 @cindex @samp{--with-gdb-datadir}
21529 You can set the default data directory by using the configure-time
21530 @samp{--with-gdb-datadir} option. If the data directory is inside
21531 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
21532 @samp{--exec-prefix}), then the default data directory will be updated
21533 automatically if the installed @value{GDBN} is moved to a new
21536 The data directory may also be specified with the
21537 @code{--data-directory} command line option.
21538 @xref{Mode Options}.
21541 @chapter Specifying a Debugging Target
21543 @cindex debugging target
21544 A @dfn{target} is the execution environment occupied by your program.
21546 Often, @value{GDBN} runs in the same host environment as your program;
21547 in that case, the debugging target is specified as a side effect when
21548 you use the @code{file} or @code{core} commands. When you need more
21549 flexibility---for example, running @value{GDBN} on a physically separate
21550 host, or controlling a standalone system over a serial port or a
21551 realtime system over a TCP/IP connection---you can use the @code{target}
21552 command to specify one of the target types configured for @value{GDBN}
21553 (@pxref{Target Commands, ,Commands for Managing Targets}).
21555 @cindex target architecture
21556 It is possible to build @value{GDBN} for several different @dfn{target
21557 architectures}. When @value{GDBN} is built like that, you can choose
21558 one of the available architectures with the @kbd{set architecture}
21562 @kindex set architecture
21563 @kindex show architecture
21564 @item set architecture @var{arch}
21565 This command sets the current target architecture to @var{arch}. The
21566 value of @var{arch} can be @code{"auto"}, in addition to one of the
21567 supported architectures.
21569 @item show architecture
21570 Show the current target architecture.
21572 @item set processor
21574 @kindex set processor
21575 @kindex show processor
21576 These are alias commands for, respectively, @code{set architecture}
21577 and @code{show architecture}.
21581 * Active Targets:: Active targets
21582 * Target Commands:: Commands for managing targets
21583 * Byte Order:: Choosing target byte order
21586 @node Active Targets
21587 @section Active Targets
21589 @cindex stacking targets
21590 @cindex active targets
21591 @cindex multiple targets
21593 There are multiple classes of targets such as: processes, executable files or
21594 recording sessions. Core files belong to the process class, making core file
21595 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
21596 on multiple active targets, one in each class. This allows you to (for
21597 example) start a process and inspect its activity, while still having access to
21598 the executable file after the process finishes. Or if you start process
21599 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
21600 presented a virtual layer of the recording target, while the process target
21601 remains stopped at the chronologically last point of the process execution.
21603 Use the @code{core-file} and @code{exec-file} commands to select a new core
21604 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
21605 specify as a target a process that is already running, use the @code{attach}
21606 command (@pxref{Attach, ,Debugging an Already-running Process}).
21608 @node Target Commands
21609 @section Commands for Managing Targets
21612 @item target @var{type} @var{parameters}
21613 Connects the @value{GDBN} host environment to a target machine or
21614 process. A target is typically a protocol for talking to debugging
21615 facilities. You use the argument @var{type} to specify the type or
21616 protocol of the target machine.
21618 Further @var{parameters} are interpreted by the target protocol, but
21619 typically include things like device names or host names to connect
21620 with, process numbers, and baud rates.
21622 The @code{target} command does not repeat if you press @key{RET} again
21623 after executing the command.
21625 @kindex help target
21627 Displays the names of all targets available. To display targets
21628 currently selected, use either @code{info target} or @code{info files}
21629 (@pxref{Files, ,Commands to Specify Files}).
21631 @item help target @var{name}
21632 Describe a particular target, including any parameters necessary to
21635 @kindex set gnutarget
21636 @item set gnutarget @var{args}
21637 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
21638 knows whether it is reading an @dfn{executable},
21639 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
21640 with the @code{set gnutarget} command. Unlike most @code{target} commands,
21641 with @code{gnutarget} the @code{target} refers to a program, not a machine.
21644 @emph{Warning:} To specify a file format with @code{set gnutarget},
21645 you must know the actual BFD name.
21649 @xref{Files, , Commands to Specify Files}.
21651 @kindex show gnutarget
21652 @item show gnutarget
21653 Use the @code{show gnutarget} command to display what file format
21654 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
21655 @value{GDBN} will determine the file format for each file automatically,
21656 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
21659 @cindex common targets
21660 Here are some common targets (available, or not, depending on the GDB
21665 @item target exec @var{program}
21666 @cindex executable file target
21667 An executable file. @samp{target exec @var{program}} is the same as
21668 @samp{exec-file @var{program}}.
21670 @item target core @var{filename}
21671 @cindex core dump file target
21672 A core dump file. @samp{target core @var{filename}} is the same as
21673 @samp{core-file @var{filename}}.
21675 @item target remote @var{medium}
21676 @cindex remote target
21677 A remote system connected to @value{GDBN} via a serial line or network
21678 connection. This command tells @value{GDBN} to use its own remote
21679 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
21681 For example, if you have a board connected to @file{/dev/ttya} on the
21682 machine running @value{GDBN}, you could say:
21685 target remote /dev/ttya
21688 @code{target remote} supports the @code{load} command. This is only
21689 useful if you have some other way of getting the stub to the target
21690 system, and you can put it somewhere in memory where it won't get
21691 clobbered by the download.
21693 @item target sim @r{[}@var{simargs}@r{]} @dots{}
21694 @cindex built-in simulator target
21695 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
21703 works; however, you cannot assume that a specific memory map, device
21704 drivers, or even basic I/O is available, although some simulators do
21705 provide these. For info about any processor-specific simulator details,
21706 see the appropriate section in @ref{Embedded Processors, ,Embedded
21709 @item target native
21710 @cindex native target
21711 Setup for local/native process debugging. Useful to make the
21712 @code{run} command spawn native processes (likewise @code{attach},
21713 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
21714 (@pxref{set auto-connect-native-target}).
21718 Different targets are available on different configurations of @value{GDBN};
21719 your configuration may have more or fewer targets.
21721 Many remote targets require you to download the executable's code once
21722 you've successfully established a connection. You may wish to control
21723 various aspects of this process.
21728 @kindex set hash@r{, for remote monitors}
21729 @cindex hash mark while downloading
21730 This command controls whether a hash mark @samp{#} is displayed while
21731 downloading a file to the remote monitor. If on, a hash mark is
21732 displayed after each S-record is successfully downloaded to the
21736 @kindex show hash@r{, for remote monitors}
21737 Show the current status of displaying the hash mark.
21739 @item set debug monitor
21740 @kindex set debug monitor
21741 @cindex display remote monitor communications
21742 Enable or disable display of communications messages between
21743 @value{GDBN} and the remote monitor.
21745 @item show debug monitor
21746 @kindex show debug monitor
21747 Show the current status of displaying communications between
21748 @value{GDBN} and the remote monitor.
21753 @kindex load @var{filename} @var{offset}
21754 @item load @var{filename} @var{offset}
21756 Depending on what remote debugging facilities are configured into
21757 @value{GDBN}, the @code{load} command may be available. Where it exists, it
21758 is meant to make @var{filename} (an executable) available for debugging
21759 on the remote system---by downloading, or dynamic linking, for example.
21760 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
21761 the @code{add-symbol-file} command.
21763 If your @value{GDBN} does not have a @code{load} command, attempting to
21764 execute it gets the error message ``@code{You can't do that when your
21765 target is @dots{}}''
21767 The file is loaded at whatever address is specified in the executable.
21768 For some object file formats, you can specify the load address when you
21769 link the program; for other formats, like a.out, the object file format
21770 specifies a fixed address.
21771 @c FIXME! This would be a good place for an xref to the GNU linker doc.
21773 It is also possible to tell @value{GDBN} to load the executable file at a
21774 specific offset described by the optional argument @var{offset}. When
21775 @var{offset} is provided, @var{filename} must also be provided.
21777 Depending on the remote side capabilities, @value{GDBN} may be able to
21778 load programs into flash memory.
21780 @code{load} does not repeat if you press @key{RET} again after using it.
21785 @kindex flash-erase
21787 @anchor{flash-erase}
21789 Erases all known flash memory regions on the target.
21794 @section Choosing Target Byte Order
21796 @cindex choosing target byte order
21797 @cindex target byte order
21799 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
21800 offer the ability to run either big-endian or little-endian byte
21801 orders. Usually the executable or symbol will include a bit to
21802 designate the endian-ness, and you will not need to worry about
21803 which to use. However, you may still find it useful to adjust
21804 @value{GDBN}'s idea of processor endian-ness manually.
21808 @item set endian big
21809 Instruct @value{GDBN} to assume the target is big-endian.
21811 @item set endian little
21812 Instruct @value{GDBN} to assume the target is little-endian.
21814 @item set endian auto
21815 Instruct @value{GDBN} to use the byte order associated with the
21819 Display @value{GDBN}'s current idea of the target byte order.
21823 If the @code{set endian auto} mode is in effect and no executable has
21824 been selected, then the endianness used is the last one chosen either
21825 by one of the @code{set endian big} and @code{set endian little}
21826 commands or by inferring from the last executable used. If no
21827 endianness has been previously chosen, then the default for this mode
21828 is inferred from the target @value{GDBN} has been built for, and is
21829 @code{little} if the name of the target CPU has an @code{el} suffix
21830 and @code{big} otherwise.
21832 Note that these commands merely adjust interpretation of symbolic
21833 data on the host, and that they have absolutely no effect on the
21837 @node Remote Debugging
21838 @chapter Debugging Remote Programs
21839 @cindex remote debugging
21841 If you are trying to debug a program running on a machine that cannot run
21842 @value{GDBN} in the usual way, it is often useful to use remote debugging.
21843 For example, you might use remote debugging on an operating system kernel,
21844 or on a small system which does not have a general purpose operating system
21845 powerful enough to run a full-featured debugger.
21847 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
21848 to make this work with particular debugging targets. In addition,
21849 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
21850 but not specific to any particular target system) which you can use if you
21851 write the remote stubs---the code that runs on the remote system to
21852 communicate with @value{GDBN}.
21854 Other remote targets may be available in your
21855 configuration of @value{GDBN}; use @code{help target} to list them.
21858 * Connecting:: Connecting to a remote target
21859 * File Transfer:: Sending files to a remote system
21860 * Server:: Using the gdbserver program
21861 * Remote Configuration:: Remote configuration
21862 * Remote Stub:: Implementing a remote stub
21866 @section Connecting to a Remote Target
21867 @cindex remote debugging, connecting
21868 @cindex @code{gdbserver}, connecting
21869 @cindex remote debugging, types of connections
21870 @cindex @code{gdbserver}, types of connections
21871 @cindex @code{gdbserver}, @code{target remote} mode
21872 @cindex @code{gdbserver}, @code{target extended-remote} mode
21874 This section describes how to connect to a remote target, including the
21875 types of connections and their differences, how to set up executable and
21876 symbol files on the host and target, and the commands used for
21877 connecting to and disconnecting from the remote target.
21879 @subsection Types of Remote Connections
21881 @value{GDBN} supports two types of remote connections, @code{target remote}
21882 mode and @code{target extended-remote} mode. Note that many remote targets
21883 support only @code{target remote} mode. There are several major
21884 differences between the two types of connections, enumerated here:
21888 @cindex remote debugging, detach and program exit
21889 @item Result of detach or program exit
21890 @strong{With target remote mode:} When the debugged program exits or you
21891 detach from it, @value{GDBN} disconnects from the target. When using
21892 @code{gdbserver}, @code{gdbserver} will exit.
21894 @strong{With target extended-remote mode:} When the debugged program exits or
21895 you detach from it, @value{GDBN} remains connected to the target, even
21896 though no program is running. You can rerun the program, attach to a
21897 running program, or use @code{monitor} commands specific to the target.
21899 When using @code{gdbserver} in this case, it does not exit unless it was
21900 invoked using the @option{--once} option. If the @option{--once} option
21901 was not used, you can ask @code{gdbserver} to exit using the
21902 @code{monitor exit} command (@pxref{Monitor Commands for gdbserver}).
21904 @item Specifying the program to debug
21905 For both connection types you use the @code{file} command to specify the
21906 program on the host system. If you are using @code{gdbserver} there are
21907 some differences in how to specify the location of the program on the
21910 @strong{With target remote mode:} You must either specify the program to debug
21911 on the @code{gdbserver} command line or use the @option{--attach} option
21912 (@pxref{Attaching to a program,,Attaching to a Running Program}).
21914 @cindex @option{--multi}, @code{gdbserver} option
21915 @strong{With target extended-remote mode:} You may specify the program to debug
21916 on the @code{gdbserver} command line, or you can load the program or attach
21917 to it using @value{GDBN} commands after connecting to @code{gdbserver}.
21919 @anchor{--multi Option in Types of Remote Connnections}
21920 You can start @code{gdbserver} without supplying an initial command to run
21921 or process ID to attach. To do this, use the @option{--multi} command line
21922 option. Then you can connect using @code{target extended-remote} and start
21923 the program you want to debug (see below for details on using the
21924 @code{run} command in this scenario). Note that the conditions under which
21925 @code{gdbserver} terminates depend on how @value{GDBN} connects to it
21926 (@code{target remote} or @code{target extended-remote}). The
21927 @option{--multi} option to @code{gdbserver} has no influence on that.
21929 @item The @code{run} command
21930 @strong{With target remote mode:} The @code{run} command is not
21931 supported. Once a connection has been established, you can use all
21932 the usual @value{GDBN} commands to examine and change data. The
21933 remote program is already running, so you can use commands like
21934 @kbd{step} and @kbd{continue}.
21936 @strong{With target extended-remote mode:} The @code{run} command is
21937 supported. The @code{run} command uses the value set by
21938 @code{set remote exec-file} (@pxref{set remote exec-file}) to select
21939 the program to run. Command line arguments are supported, except for
21940 wildcard expansion and I/O redirection (@pxref{Arguments}).
21942 If you specify the program to debug on the command line, then the
21943 @code{run} command is not required to start execution, and you can
21944 resume using commands like @kbd{step} and @kbd{continue} as with
21945 @code{target remote} mode.
21947 @anchor{Attaching in Types of Remote Connections}
21949 @strong{With target remote mode:} The @value{GDBN} command @code{attach} is
21950 not supported. To attach to a running program using @code{gdbserver}, you
21951 must use the @option{--attach} option (@pxref{Running gdbserver}).
21953 @strong{With target extended-remote mode:} To attach to a running program,
21954 you may use the @code{attach} command after the connection has been
21955 established. If you are using @code{gdbserver}, you may also invoke
21956 @code{gdbserver} using the @option{--attach} option
21957 (@pxref{Running gdbserver}).
21959 Some remote targets allow @value{GDBN} to determine the executable file running
21960 in the process the debugger is attaching to. In such a case, @value{GDBN}
21961 uses the value of @code{exec-file-mismatch} to handle a possible mismatch
21962 between the executable file name running in the process and the name of the
21963 current exec-file loaded by @value{GDBN} (@pxref{set exec-file-mismatch}).
21967 @anchor{Host and target files}
21968 @subsection Host and Target Files
21969 @cindex remote debugging, symbol files
21970 @cindex symbol files, remote debugging
21972 @value{GDBN}, running on the host, needs access to symbol and debugging
21973 information for your program running on the target. This requires
21974 access to an unstripped copy of your program, and possibly any associated
21975 symbol files. Note that this section applies equally to both @code{target
21976 remote} mode and @code{target extended-remote} mode.
21978 Some remote targets (@pxref{qXfer executable filename read}, and
21979 @pxref{Host I/O Packets}) allow @value{GDBN} to access program files over
21980 the same connection used to communicate with @value{GDBN}. With such a
21981 target, if the remote program is unstripped, the only command you need is
21982 @code{target remote} (or @code{target extended-remote}).
21984 If the remote program is stripped, or the target does not support remote
21985 program file access, start up @value{GDBN} using the name of the local
21986 unstripped copy of your program as the first argument, or use the
21987 @code{file} command. Use @code{set sysroot} to specify the location (on
21988 the host) of target libraries (unless your @value{GDBN} was compiled with
21989 the correct sysroot using @code{--with-sysroot}). Alternatively, you
21990 may use @code{set solib-search-path} to specify how @value{GDBN} locates
21993 The symbol file and target libraries must exactly match the executable
21994 and libraries on the target, with one exception: the files on the host
21995 system should not be stripped, even if the files on the target system
21996 are. Mismatched or missing files will lead to confusing results
21997 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
21998 files may also prevent @code{gdbserver} from debugging multi-threaded
22001 @subsection Remote Connection Commands
22002 @cindex remote connection commands
22003 @value{GDBN} can communicate with the target over a serial line, a
22004 local Unix domain socket, or
22005 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
22006 each case, @value{GDBN} uses the same protocol for debugging your
22007 program; only the medium carrying the debugging packets varies. The
22008 @code{target remote} and @code{target extended-remote} commands
22009 establish a connection to the target. Both commands accept the same
22010 arguments, which indicate the medium to use:
22014 @item target remote @var{serial-device}
22015 @itemx target extended-remote @var{serial-device}
22016 @cindex serial line, @code{target remote}
22017 Use @var{serial-device} to communicate with the target. For example,
22018 to use a serial line connected to the device named @file{/dev/ttyb}:
22021 target remote /dev/ttyb
22024 If you're using a serial line, you may want to give @value{GDBN} the
22025 @samp{--baud} option, or use the @code{set serial baud} command
22026 (@pxref{Remote Configuration, set serial baud}) before the
22027 @code{target} command.
22029 @item target remote @var{local-socket}
22030 @itemx target extended-remote @var{local-socket}
22031 @cindex local socket, @code{target remote}
22032 @cindex Unix domain socket
22033 Use @var{local-socket} to communicate with the target. For example,
22034 to use a local Unix domain socket bound to the file system entry @file{/tmp/gdb-socket0}:
22037 target remote /tmp/gdb-socket0
22040 Note that this command has the same form as the command to connect
22041 to a serial line. @value{GDBN} will automatically determine which
22042 kind of file you have specified and will make the appropriate kind
22044 This feature is not available if the host system does not support
22045 Unix domain sockets.
22047 @item target remote @code{@var{host}:@var{port}}
22048 @itemx target remote @code{[@var{host}]:@var{port}}
22049 @itemx target remote @code{tcp:@var{host}:@var{port}}
22050 @itemx target remote @code{tcp:[@var{host}]:@var{port}}
22051 @itemx target remote @code{tcp4:@var{host}:@var{port}}
22052 @itemx target remote @code{tcp6:@var{host}:@var{port}}
22053 @itemx target remote @code{tcp6:[@var{host}]:@var{port}}
22054 @itemx target extended-remote @code{@var{host}:@var{port}}
22055 @itemx target extended-remote @code{[@var{host}]:@var{port}}
22056 @itemx target extended-remote @code{tcp:@var{host}:@var{port}}
22057 @itemx target extended-remote @code{tcp:[@var{host}]:@var{port}}
22058 @itemx target extended-remote @code{tcp4:@var{host}:@var{port}}
22059 @itemx target extended-remote @code{tcp6:@var{host}:@var{port}}
22060 @itemx target extended-remote @code{tcp6:[@var{host}]:@var{port}}
22061 @cindex @acronym{TCP} port, @code{target remote}
22062 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
22063 The @var{host} may be either a host name, a numeric @acronym{IPv4}
22064 address, or a numeric @acronym{IPv6} address (with or without the
22065 square brackets to separate the address from the port); @var{port}
22066 must be a decimal number. The @var{host} could be the target machine
22067 itself, if it is directly connected to the net, or it might be a
22068 terminal server which in turn has a serial line to the target.
22070 For example, to connect to port 2828 on a terminal server named
22074 target remote manyfarms:2828
22077 To connect to port 2828 on a terminal server whose address is
22078 @code{2001:0db8:85a3:0000:0000:8a2e:0370:7334}, you can either use the
22079 square bracket syntax:
22082 target remote [2001:0db8:85a3:0000:0000:8a2e:0370:7334]:2828
22086 or explicitly specify the @acronym{IPv6} protocol:
22089 target remote tcp6:2001:0db8:85a3:0000:0000:8a2e:0370:7334:2828
22092 This last example may be confusing to the reader, because there is no
22093 visible separation between the hostname and the port number.
22094 Therefore, we recommend the user to provide @acronym{IPv6} addresses
22095 using square brackets for clarity. However, it is important to
22096 mention that for @value{GDBN} there is no ambiguity: the number after
22097 the last colon is considered to be the port number.
22099 If your remote target is actually running on the same machine as your
22100 debugger session (e.g.@: a simulator for your target running on the
22101 same host), you can omit the hostname. For example, to connect to
22102 port 1234 on your local machine:
22105 target remote :1234
22109 Note that the colon is still required here.
22111 @item target remote @code{udp:@var{host}:@var{port}}
22112 @itemx target remote @code{udp:[@var{host}]:@var{port}}
22113 @itemx target remote @code{udp4:@var{host}:@var{port}}
22114 @itemx target remote @code{udp6:[@var{host}]:@var{port}}
22115 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
22116 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
22117 @itemx target extended-remote @code{udp:[@var{host}]:@var{port}}
22118 @itemx target extended-remote @code{udp4:@var{host}:@var{port}}
22119 @itemx target extended-remote @code{udp6:@var{host}:@var{port}}
22120 @itemx target extended-remote @code{udp6:[@var{host}]:@var{port}}
22121 @cindex @acronym{UDP} port, @code{target remote}
22122 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
22123 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
22126 target remote udp:manyfarms:2828
22129 When using a @acronym{UDP} connection for remote debugging, you should
22130 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
22131 can silently drop packets on busy or unreliable networks, which will
22132 cause havoc with your debugging session.
22134 @item target remote | @var{command}
22135 @itemx target extended-remote | @var{command}
22136 @cindex pipe, @code{target remote} to
22137 Run @var{command} in the background and communicate with it using a
22138 pipe. The @var{command} is a shell command, to be parsed and expanded
22139 by the system's command shell, @code{/bin/sh}; it should expect remote
22140 protocol packets on its standard input, and send replies on its
22141 standard output. You could use this to run a stand-alone simulator
22142 that speaks the remote debugging protocol, to make net connections
22143 using programs like @code{ssh}, or for other similar tricks.
22145 If @var{command} closes its standard output (perhaps by exiting),
22146 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
22147 program has already exited, this will have no effect.)
22151 @cindex interrupting remote programs
22152 @cindex remote programs, interrupting
22153 Whenever @value{GDBN} is waiting for the remote program, if you type the
22154 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
22155 program. This may or may not succeed, depending in part on the hardware
22156 and the serial drivers the remote system uses. If you type the
22157 interrupt character once again, @value{GDBN} displays this prompt:
22160 Interrupted while waiting for the program.
22161 Give up (and stop debugging it)? (y or n)
22164 In @code{target remote} mode, if you type @kbd{y}, @value{GDBN} abandons
22165 the remote debugging session. (If you decide you want to try again later,
22166 you can use @kbd{target remote} again to connect once more.) If you type
22167 @kbd{n}, @value{GDBN} goes back to waiting.
22169 In @code{target extended-remote} mode, typing @kbd{n} will leave
22170 @value{GDBN} connected to the target.
22173 @kindex detach (remote)
22175 When you have finished debugging the remote program, you can use the
22176 @code{detach} command to release it from @value{GDBN} control.
22177 Detaching from the target normally resumes its execution, but the results
22178 will depend on your particular remote stub. After the @code{detach}
22179 command in @code{target remote} mode, @value{GDBN} is free to connect to
22180 another target. In @code{target extended-remote} mode, @value{GDBN} is
22181 still connected to the target.
22185 The @code{disconnect} command closes the connection to the target, and
22186 the target is generally not resumed. It will wait for @value{GDBN}
22187 (this instance or another one) to connect and continue debugging. After
22188 the @code{disconnect} command, @value{GDBN} is again free to connect to
22191 @cindex send command to remote monitor
22192 @cindex extend @value{GDBN} for remote targets
22193 @cindex add new commands for external monitor
22195 @item monitor @var{cmd}
22196 This command allows you to send arbitrary commands directly to the
22197 remote monitor. Since @value{GDBN} doesn't care about the commands it
22198 sends like this, this command is the way to extend @value{GDBN}---you
22199 can add new commands that only the external monitor will understand
22203 @node File Transfer
22204 @section Sending files to a remote system
22205 @cindex remote target, file transfer
22206 @cindex file transfer
22207 @cindex sending files to remote systems
22209 Some remote targets offer the ability to transfer files over the same
22210 connection used to communicate with @value{GDBN}. This is convenient
22211 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
22212 running @code{gdbserver} over a network interface. For other targets,
22213 e.g.@: embedded devices with only a single serial port, this may be
22214 the only way to upload or download files.
22216 Not all remote targets support these commands.
22220 @item remote put @var{hostfile} @var{targetfile}
22221 Copy file @var{hostfile} from the host system (the machine running
22222 @value{GDBN}) to @var{targetfile} on the target system.
22225 @item remote get @var{targetfile} @var{hostfile}
22226 Copy file @var{targetfile} from the target system to @var{hostfile}
22227 on the host system.
22229 @kindex remote delete
22230 @item remote delete @var{targetfile}
22231 Delete @var{targetfile} from the target system.
22236 @section Using the @code{gdbserver} Program
22239 @cindex remote connection without stubs
22240 @code{gdbserver} is a control program for Unix-like systems, which
22241 allows you to connect your program with a remote @value{GDBN} via
22242 @code{target remote} or @code{target extended-remote}---but without
22243 linking in the usual debugging stub.
22245 @code{gdbserver} is not a complete replacement for the debugging stubs,
22246 because it requires essentially the same operating-system facilities
22247 that @value{GDBN} itself does. In fact, a system that can run
22248 @code{gdbserver} to connect to a remote @value{GDBN} could also run
22249 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
22250 because it is a much smaller program than @value{GDBN} itself. It is
22251 also easier to port than all of @value{GDBN}, so you may be able to get
22252 started more quickly on a new system by using @code{gdbserver}.
22253 Finally, if you develop code for real-time systems, you may find that
22254 the tradeoffs involved in real-time operation make it more convenient to
22255 do as much development work as possible on another system, for example
22256 by cross-compiling. You can use @code{gdbserver} to make a similar
22257 choice for debugging.
22259 @value{GDBN} and @code{gdbserver} communicate via either a serial line
22260 or a TCP connection, using the standard @value{GDBN} remote serial
22264 @emph{Warning:} @code{gdbserver} does not have any built-in security.
22265 Do not run @code{gdbserver} connected to any public network; a
22266 @value{GDBN} connection to @code{gdbserver} provides access to the
22267 target system with the same privileges as the user running
22271 @anchor{Running gdbserver}
22272 @subsection Running @code{gdbserver}
22273 @cindex arguments, to @code{gdbserver}
22274 @cindex @code{gdbserver}, command-line arguments
22276 Run @code{gdbserver} on the target system. You need a copy of the
22277 program you want to debug, including any libraries it requires.
22278 @code{gdbserver} does not need your program's symbol table, so you can
22279 strip the program if necessary to save space. @value{GDBN} on the host
22280 system does all the symbol handling.
22282 To use the server, you must tell it how to communicate with @value{GDBN};
22283 the name of your program; and the arguments for your program. The usual
22287 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
22290 @var{comm} is either a device name (to use a serial line), or a TCP
22291 hostname and portnumber, or @code{-} or @code{stdio} to use
22292 stdin/stdout of @code{gdbserver}.
22293 For example, to debug Emacs with the argument
22294 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
22298 target> gdbserver /dev/com1 emacs foo.txt
22301 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
22304 To use a TCP connection instead of a serial line:
22307 target> gdbserver host:2345 emacs foo.txt
22310 The only difference from the previous example is the first argument,
22311 specifying that you are communicating with the host @value{GDBN} via
22312 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
22313 expect a TCP connection from machine @samp{host} to local TCP port 2345.
22314 (Currently, the @samp{host} part is ignored.) You can choose any number
22315 you want for the port number as long as it does not conflict with any
22316 TCP ports already in use on the target system (for example, @code{23} is
22317 reserved for @code{telnet}).@footnote{If you choose a port number that
22318 conflicts with another service, @code{gdbserver} prints an error message
22319 and exits.} You must use the same port number with the host @value{GDBN}
22320 @code{target remote} command.
22322 The @code{stdio} connection is useful when starting @code{gdbserver}
22326 (gdb) target remote | ssh -T hostname gdbserver - hello
22329 The @samp{-T} option to ssh is provided because we don't need a remote pty,
22330 and we don't want escape-character handling. Ssh does this by default when
22331 a command is provided, the flag is provided to make it explicit.
22332 You could elide it if you want to.
22334 Programs started with stdio-connected gdbserver have @file{/dev/null} for
22335 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
22336 display through a pipe connected to gdbserver.
22337 Both @code{stdout} and @code{stderr} use the same pipe.
22339 @anchor{Attaching to a program}
22340 @subsubsection Attaching to a Running Program
22341 @cindex attach to a program, @code{gdbserver}
22342 @cindex @option{--attach}, @code{gdbserver} option
22344 On some targets, @code{gdbserver} can also attach to running programs.
22345 This is accomplished via the @code{--attach} argument. The syntax is:
22348 target> gdbserver --attach @var{comm} @var{pid}
22351 @var{pid} is the process ID of a currently running process. It isn't
22352 necessary to point @code{gdbserver} at a binary for the running process.
22354 In @code{target extended-remote} mode, you can also attach using the
22355 @value{GDBN} attach command
22356 (@pxref{Attaching in Types of Remote Connections}).
22359 You can debug processes by name instead of process ID if your target has the
22360 @code{pidof} utility:
22363 target> gdbserver --attach @var{comm} `pidof @var{program}`
22366 In case more than one copy of @var{program} is running, or @var{program}
22367 has multiple threads, most versions of @code{pidof} support the
22368 @code{-s} option to only return the first process ID.
22370 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
22372 This section applies only when @code{gdbserver} is run to listen on a TCP
22375 @code{gdbserver} normally terminates after all of its debugged processes have
22376 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
22377 extended-remote}, @code{gdbserver} stays running even with no processes left.
22378 @value{GDBN} normally terminates the spawned debugged process on its exit,
22379 which normally also terminates @code{gdbserver} in the @kbd{target remote}
22380 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
22381 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
22382 stays running even in the @kbd{target remote} mode.
22384 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
22385 Such reconnecting is useful for features like @ref{disconnected tracing}. For
22386 completeness, at most one @value{GDBN} can be connected at a time.
22388 @cindex @option{--once}, @code{gdbserver} option
22389 By default, @code{gdbserver} keeps the listening TCP port open, so that
22390 subsequent connections are possible. However, if you start @code{gdbserver}
22391 with the @option{--once} option, it will stop listening for any further
22392 connection attempts after connecting to the first @value{GDBN} session. This
22393 means no further connections to @code{gdbserver} will be possible after the
22394 first one. It also means @code{gdbserver} will terminate after the first
22395 connection with remote @value{GDBN} has closed, even for unexpectedly closed
22396 connections and even in the @kbd{target extended-remote} mode. The
22397 @option{--once} option allows reusing the same port number for connecting to
22398 multiple instances of @code{gdbserver} running on the same host, since each
22399 instance closes its port after the first connection.
22401 @anchor{Other Command-Line Arguments for gdbserver}
22402 @subsubsection Other Command-Line Arguments for @code{gdbserver}
22404 You can use the @option{--multi} option to start @code{gdbserver} without
22405 specifying a program to debug or a process to attach to. Then you can
22406 attach in @code{target extended-remote} mode and run or attach to a
22407 program. For more information,
22408 @pxref{--multi Option in Types of Remote Connnections}.
22410 @cindex @option{--debug}, @code{gdbserver} option
22411 The @option{--debug} option tells @code{gdbserver} to display extra
22412 status information about the debugging process.
22413 @cindex @option{--remote-debug}, @code{gdbserver} option
22414 The @option{--remote-debug} option tells @code{gdbserver} to display
22415 remote protocol debug output.
22416 @cindex @option{--debug-file}, @code{gdbserver} option
22417 @cindex @code{gdbserver}, send all debug output to a single file
22418 The @option{--debug-file=@var{filename}} option tells @code{gdbserver} to
22419 write any debug output to the given @var{filename}. These options are intended
22420 for @code{gdbserver} development and for bug reports to the developers.
22422 @cindex @option{--debug-format}, @code{gdbserver} option
22423 The @option{--debug-format=option1[,option2,...]} option tells
22424 @code{gdbserver} to include additional information in each output.
22425 Possible options are:
22429 Turn off all extra information in debugging output.
22431 Turn on all extra information in debugging output.
22433 Include a timestamp in each line of debugging output.
22436 Options are processed in order. Thus, for example, if @option{none}
22437 appears last then no additional information is added to debugging output.
22439 @cindex @option{--wrapper}, @code{gdbserver} option
22440 The @option{--wrapper} option specifies a wrapper to launch programs
22441 for debugging. The option should be followed by the name of the
22442 wrapper, then any command-line arguments to pass to the wrapper, then
22443 @kbd{--} indicating the end of the wrapper arguments.
22445 @code{gdbserver} runs the specified wrapper program with a combined
22446 command line including the wrapper arguments, then the name of the
22447 program to debug, then any arguments to the program. The wrapper
22448 runs until it executes your program, and then @value{GDBN} gains control.
22450 You can use any program that eventually calls @code{execve} with
22451 its arguments as a wrapper. Several standard Unix utilities do
22452 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
22453 with @code{exec "$@@"} will also work.
22455 For example, you can use @code{env} to pass an environment variable to
22456 the debugged program, without setting the variable in @code{gdbserver}'s
22460 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
22463 @cindex @option{--selftest}
22464 The @option{--selftest} option runs the self tests in @code{gdbserver}:
22467 $ gdbserver --selftest
22468 Ran 2 unit tests, 0 failed
22471 These tests are disabled in release.
22472 @subsection Connecting to @code{gdbserver}
22474 The basic procedure for connecting to the remote target is:
22478 Run @value{GDBN} on the host system.
22481 Make sure you have the necessary symbol files
22482 (@pxref{Host and target files}).
22483 Load symbols for your application using the @code{file} command before you
22484 connect. Use @code{set sysroot} to locate target libraries (unless your
22485 @value{GDBN} was compiled with the correct sysroot using
22486 @code{--with-sysroot}).
22489 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
22490 For TCP connections, you must start up @code{gdbserver} prior to using
22491 the @code{target} command. Otherwise you may get an error whose
22492 text depends on the host system, but which usually looks something like
22493 @samp{Connection refused}. Don't use the @code{load}
22494 command in @value{GDBN} when using @code{target remote} mode, since the
22495 program is already on the target.
22499 @anchor{Monitor Commands for gdbserver}
22500 @subsection Monitor Commands for @code{gdbserver}
22501 @cindex monitor commands, for @code{gdbserver}
22503 During a @value{GDBN} session using @code{gdbserver}, you can use the
22504 @code{monitor} command to send special requests to @code{gdbserver}.
22505 Here are the available commands.
22509 List the available monitor commands.
22511 @item monitor set debug 0
22512 @itemx monitor set debug 1
22513 Disable or enable general debugging messages.
22515 @item monitor set remote-debug 0
22516 @itemx monitor set remote-debug 1
22517 Disable or enable specific debugging messages associated with the remote
22518 protocol (@pxref{Remote Protocol}).
22520 @item monitor set debug-file filename
22521 @itemx monitor set debug-file
22522 Send any debug output to the given file, or to stderr.
22524 @item monitor set debug-format option1@r{[},option2,...@r{]}
22525 Specify additional text to add to debugging messages.
22526 Possible options are:
22530 Turn off all extra information in debugging output.
22532 Turn on all extra information in debugging output.
22534 Include a timestamp in each line of debugging output.
22537 Options are processed in order. Thus, for example, if @option{none}
22538 appears last then no additional information is added to debugging output.
22540 @item monitor set libthread-db-search-path [PATH]
22541 @cindex gdbserver, search path for @code{libthread_db}
22542 When this command is issued, @var{path} is a colon-separated list of
22543 directories to search for @code{libthread_db} (@pxref{Threads,,set
22544 libthread-db-search-path}). If you omit @var{path},
22545 @samp{libthread-db-search-path} will be reset to its default value.
22547 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
22548 not supported in @code{gdbserver}.
22551 Tell gdbserver to exit immediately. This command should be followed by
22552 @code{disconnect} to close the debugging session. @code{gdbserver} will
22553 detach from any attached processes and kill any processes it created.
22554 Use @code{monitor exit} to terminate @code{gdbserver} at the end
22555 of a multi-process mode debug session.
22559 @subsection Tracepoints support in @code{gdbserver}
22560 @cindex tracepoints support in @code{gdbserver}
22562 On some targets, @code{gdbserver} supports tracepoints, fast
22563 tracepoints and static tracepoints.
22565 For fast or static tracepoints to work, a special library called the
22566 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
22567 This library is built and distributed as an integral part of
22568 @code{gdbserver}. In addition, support for static tracepoints
22569 requires building the in-process agent library with static tracepoints
22570 support. At present, the UST (LTTng Userspace Tracer,
22571 @url{http://lttng.org/ust}) tracing engine is supported. This support
22572 is automatically available if UST development headers are found in the
22573 standard include path when @code{gdbserver} is built, or if
22574 @code{gdbserver} was explicitly configured using @option{--with-ust}
22575 to point at such headers. You can explicitly disable the support
22576 using @option{--with-ust=no}.
22578 There are several ways to load the in-process agent in your program:
22581 @item Specifying it as dependency at link time
22583 You can link your program dynamically with the in-process agent
22584 library. On most systems, this is accomplished by adding
22585 @code{-linproctrace} to the link command.
22587 @item Using the system's preloading mechanisms
22589 You can force loading the in-process agent at startup time by using
22590 your system's support for preloading shared libraries. Many Unixes
22591 support the concept of preloading user defined libraries. In most
22592 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
22593 in the environment. See also the description of @code{gdbserver}'s
22594 @option{--wrapper} command line option.
22596 @item Using @value{GDBN} to force loading the agent at run time
22598 On some systems, you can force the inferior to load a shared library,
22599 by calling a dynamic loader function in the inferior that takes care
22600 of dynamically looking up and loading a shared library. On most Unix
22601 systems, the function is @code{dlopen}. You'll use the @code{call}
22602 command for that. For example:
22605 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
22608 Note that on most Unix systems, for the @code{dlopen} function to be
22609 available, the program needs to be linked with @code{-ldl}.
22612 On systems that have a userspace dynamic loader, like most Unix
22613 systems, when you connect to @code{gdbserver} using @code{target
22614 remote}, you'll find that the program is stopped at the dynamic
22615 loader's entry point, and no shared library has been loaded in the
22616 program's address space yet, including the in-process agent. In that
22617 case, before being able to use any of the fast or static tracepoints
22618 features, you need to let the loader run and load the shared
22619 libraries. The simplest way to do that is to run the program to the
22620 main procedure. E.g., if debugging a C or C@t{++} program, start
22621 @code{gdbserver} like so:
22624 $ gdbserver :9999 myprogram
22627 Start GDB and connect to @code{gdbserver} like so, and run to main:
22631 (@value{GDBP}) target remote myhost:9999
22632 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
22633 (@value{GDBP}) b main
22634 (@value{GDBP}) continue
22637 The in-process tracing agent library should now be loaded into the
22638 process; you can confirm it with the @code{info sharedlibrary}
22639 command, which will list @file{libinproctrace.so} as loaded in the
22640 process. You are now ready to install fast tracepoints, list static
22641 tracepoint markers, probe static tracepoints markers, and start
22644 @node Remote Configuration
22645 @section Remote Configuration
22648 @kindex show remote
22649 This section documents the configuration options available when
22650 debugging remote programs. For the options related to the File I/O
22651 extensions of the remote protocol, see @ref{system,
22652 system-call-allowed}.
22655 @item set remoteaddresssize @var{bits}
22656 @cindex address size for remote targets
22657 @cindex bits in remote address
22658 Set the maximum size of address in a memory packet to the specified
22659 number of bits. @value{GDBN} will mask off the address bits above
22660 that number, when it passes addresses to the remote target. The
22661 default value is the number of bits in the target's address.
22663 @item show remoteaddresssize
22664 Show the current value of remote address size in bits.
22666 @item set serial baud @var{n}
22667 @cindex baud rate for remote targets
22668 Set the baud rate for the remote serial I/O to @var{n} baud. The
22669 value is used to set the speed of the serial port used for debugging
22672 @item show serial baud
22673 Show the current speed of the remote connection.
22675 @item set serial parity @var{parity}
22676 Set the parity for the remote serial I/O. Supported values of @var{parity} are:
22677 @code{even}, @code{none}, and @code{odd}. The default is @code{none}.
22679 @item show serial parity
22680 Show the current parity of the serial port.
22682 @item set remotebreak
22683 @cindex interrupt remote programs
22684 @cindex BREAK signal instead of Ctrl-C
22685 @anchor{set remotebreak}
22686 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
22687 when you type @kbd{Ctrl-c} to interrupt the program running
22688 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
22689 character instead. The default is off, since most remote systems
22690 expect to see @samp{Ctrl-C} as the interrupt signal.
22692 @item show remotebreak
22693 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
22694 interrupt the remote program.
22696 @item set remoteflow on
22697 @itemx set remoteflow off
22698 @kindex set remoteflow
22699 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
22700 on the serial port used to communicate to the remote target.
22702 @item show remoteflow
22703 @kindex show remoteflow
22704 Show the current setting of hardware flow control.
22706 @item set remotelogbase @var{base}
22707 Set the base (a.k.a.@: radix) of logging serial protocol
22708 communications to @var{base}. Supported values of @var{base} are:
22709 @code{ascii}, @code{octal}, and @code{hex}. The default is
22712 @item show remotelogbase
22713 Show the current setting of the radix for logging remote serial
22716 @item set remotelogfile @var{file}
22717 @cindex record serial communications on file
22718 Record remote serial communications on the named @var{file}. The
22719 default is not to record at all.
22721 @item show remotelogfile
22722 Show the current setting of the file name on which to record the
22723 serial communications.
22725 @item set remotetimeout @var{num}
22726 @cindex timeout for serial communications
22727 @cindex remote timeout
22728 Set the timeout limit to wait for the remote target to respond to
22729 @var{num} seconds. The default is 2 seconds.
22731 @item show remotetimeout
22732 Show the current number of seconds to wait for the remote target
22735 @cindex limit hardware breakpoints and watchpoints
22736 @cindex remote target, limit break- and watchpoints
22737 @anchor{set remote hardware-watchpoint-limit}
22738 @anchor{set remote hardware-breakpoint-limit}
22739 @item set remote hardware-watchpoint-limit @var{limit}
22740 @itemx set remote hardware-breakpoint-limit @var{limit}
22741 Restrict @value{GDBN} to using @var{limit} remote hardware watchpoints
22742 or breakpoints. The @var{limit} can be set to 0 to disable hardware
22743 watchpoints or breakpoints, and @code{unlimited} for unlimited
22744 watchpoints or breakpoints.
22746 @item show remote hardware-watchpoint-limit
22747 @itemx show remote hardware-breakpoint-limit
22748 Show the current limit for the number of hardware watchpoints or
22749 breakpoints that @value{GDBN} can use.
22751 @cindex limit hardware watchpoints length
22752 @cindex remote target, limit watchpoints length
22753 @anchor{set remote hardware-watchpoint-length-limit}
22754 @item set remote hardware-watchpoint-length-limit @var{limit}
22755 Restrict @value{GDBN} to using @var{limit} bytes for the maximum
22756 length of a remote hardware watchpoint. A @var{limit} of 0 disables
22757 hardware watchpoints and @code{unlimited} allows watchpoints of any
22760 @item show remote hardware-watchpoint-length-limit
22761 Show the current limit (in bytes) of the maximum length of
22762 a remote hardware watchpoint.
22764 @item set remote exec-file @var{filename}
22765 @itemx show remote exec-file
22766 @anchor{set remote exec-file}
22767 @cindex executable file, for remote target
22768 Select the file used for @code{run} with @code{target
22769 extended-remote}. This should be set to a filename valid on the
22770 target system. If it is not set, the target will use a default
22771 filename (e.g.@: the last program run).
22773 @item set remote interrupt-sequence
22774 @cindex interrupt remote programs
22775 @cindex select Ctrl-C, BREAK or BREAK-g
22776 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
22777 @samp{BREAK-g} as the
22778 sequence to the remote target in order to interrupt the execution.
22779 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
22780 is high level of serial line for some certain time.
22781 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
22782 It is @code{BREAK} signal followed by character @code{g}.
22784 @item show interrupt-sequence
22785 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
22786 is sent by @value{GDBN} to interrupt the remote program.
22787 @code{BREAK-g} is BREAK signal followed by @code{g} and
22788 also known as Magic SysRq g.
22790 @item set remote interrupt-on-connect
22791 @cindex send interrupt-sequence on start
22792 Specify whether interrupt-sequence is sent to remote target when
22793 @value{GDBN} connects to it. This is mostly needed when you debug
22794 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
22795 which is known as Magic SysRq g in order to connect @value{GDBN}.
22797 @item show interrupt-on-connect
22798 Show whether interrupt-sequence is sent
22799 to remote target when @value{GDBN} connects to it.
22803 @item set tcp auto-retry on
22804 @cindex auto-retry, for remote TCP target
22805 Enable auto-retry for remote TCP connections. This is useful if the remote
22806 debugging agent is launched in parallel with @value{GDBN}; there is a race
22807 condition because the agent may not become ready to accept the connection
22808 before @value{GDBN} attempts to connect. When auto-retry is
22809 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
22810 to establish the connection using the timeout specified by
22811 @code{set tcp connect-timeout}.
22813 @item set tcp auto-retry off
22814 Do not auto-retry failed TCP connections.
22816 @item show tcp auto-retry
22817 Show the current auto-retry setting.
22819 @item set tcp connect-timeout @var{seconds}
22820 @itemx set tcp connect-timeout unlimited
22821 @cindex connection timeout, for remote TCP target
22822 @cindex timeout, for remote target connection
22823 Set the timeout for establishing a TCP connection to the remote target to
22824 @var{seconds}. The timeout affects both polling to retry failed connections
22825 (enabled by @code{set tcp auto-retry on}) and waiting for connections
22826 that are merely slow to complete, and represents an approximate cumulative
22827 value. If @var{seconds} is @code{unlimited}, there is no timeout and
22828 @value{GDBN} will keep attempting to establish a connection forever,
22829 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
22831 @item show tcp connect-timeout
22832 Show the current connection timeout setting.
22835 @cindex remote packets, enabling and disabling
22836 The @value{GDBN} remote protocol autodetects the packets supported by
22837 your debugging stub. If you need to override the autodetection, you
22838 can use these commands to enable or disable individual packets. Each
22839 packet can be set to @samp{on} (the remote target supports this
22840 packet), @samp{off} (the remote target does not support this packet),
22841 or @samp{auto} (detect remote target support for this packet). They
22842 all default to @samp{auto}. For more information about each packet,
22843 see @ref{Remote Protocol}.
22845 During normal use, you should not have to use any of these commands.
22846 If you do, that may be a bug in your remote debugging stub, or a bug
22847 in @value{GDBN}. You may want to report the problem to the
22848 @value{GDBN} developers.
22850 For each packet @var{name}, the command to enable or disable the
22851 packet is @code{set remote @var{name}-packet}. The available settings
22854 @multitable @columnfractions 0.28 0.32 0.25
22857 @tab Related Features
22859 @item @code{fetch-register}
22861 @tab @code{info registers}
22863 @item @code{set-register}
22867 @item @code{binary-download}
22869 @tab @code{load}, @code{set}
22871 @item @code{read-aux-vector}
22872 @tab @code{qXfer:auxv:read}
22873 @tab @code{info auxv}
22875 @item @code{symbol-lookup}
22876 @tab @code{qSymbol}
22877 @tab Detecting multiple threads
22879 @item @code{attach}
22880 @tab @code{vAttach}
22883 @item @code{verbose-resume}
22885 @tab Stepping or resuming multiple threads
22891 @item @code{software-breakpoint}
22895 @item @code{hardware-breakpoint}
22899 @item @code{write-watchpoint}
22903 @item @code{read-watchpoint}
22907 @item @code{access-watchpoint}
22911 @item @code{pid-to-exec-file}
22912 @tab @code{qXfer:exec-file:read}
22913 @tab @code{attach}, @code{run}
22915 @item @code{target-features}
22916 @tab @code{qXfer:features:read}
22917 @tab @code{set architecture}
22919 @item @code{library-info}
22920 @tab @code{qXfer:libraries:read}
22921 @tab @code{info sharedlibrary}
22923 @item @code{memory-map}
22924 @tab @code{qXfer:memory-map:read}
22925 @tab @code{info mem}
22927 @item @code{read-sdata-object}
22928 @tab @code{qXfer:sdata:read}
22929 @tab @code{print $_sdata}
22931 @item @code{read-siginfo-object}
22932 @tab @code{qXfer:siginfo:read}
22933 @tab @code{print $_siginfo}
22935 @item @code{write-siginfo-object}
22936 @tab @code{qXfer:siginfo:write}
22937 @tab @code{set $_siginfo}
22939 @item @code{threads}
22940 @tab @code{qXfer:threads:read}
22941 @tab @code{info threads}
22943 @item @code{get-thread-local-@*storage-address}
22944 @tab @code{qGetTLSAddr}
22945 @tab Displaying @code{__thread} variables
22947 @item @code{get-thread-information-block-address}
22948 @tab @code{qGetTIBAddr}
22949 @tab Display MS-Windows Thread Information Block.
22951 @item @code{search-memory}
22952 @tab @code{qSearch:memory}
22955 @item @code{supported-packets}
22956 @tab @code{qSupported}
22957 @tab Remote communications parameters
22959 @item @code{catch-syscalls}
22960 @tab @code{QCatchSyscalls}
22961 @tab @code{catch syscall}
22963 @item @code{pass-signals}
22964 @tab @code{QPassSignals}
22965 @tab @code{handle @var{signal}}
22967 @item @code{program-signals}
22968 @tab @code{QProgramSignals}
22969 @tab @code{handle @var{signal}}
22971 @item @code{hostio-close-packet}
22972 @tab @code{vFile:close}
22973 @tab @code{remote get}, @code{remote put}
22975 @item @code{hostio-open-packet}
22976 @tab @code{vFile:open}
22977 @tab @code{remote get}, @code{remote put}
22979 @item @code{hostio-pread-packet}
22980 @tab @code{vFile:pread}
22981 @tab @code{remote get}, @code{remote put}
22983 @item @code{hostio-pwrite-packet}
22984 @tab @code{vFile:pwrite}
22985 @tab @code{remote get}, @code{remote put}
22987 @item @code{hostio-unlink-packet}
22988 @tab @code{vFile:unlink}
22989 @tab @code{remote delete}
22991 @item @code{hostio-readlink-packet}
22992 @tab @code{vFile:readlink}
22995 @item @code{hostio-fstat-packet}
22996 @tab @code{vFile:fstat}
22999 @item @code{hostio-setfs-packet}
23000 @tab @code{vFile:setfs}
23003 @item @code{noack-packet}
23004 @tab @code{QStartNoAckMode}
23005 @tab Packet acknowledgment
23007 @item @code{osdata}
23008 @tab @code{qXfer:osdata:read}
23009 @tab @code{info os}
23011 @item @code{query-attached}
23012 @tab @code{qAttached}
23013 @tab Querying remote process attach state.
23015 @item @code{trace-buffer-size}
23016 @tab @code{QTBuffer:size}
23017 @tab @code{set trace-buffer-size}
23019 @item @code{trace-status}
23020 @tab @code{qTStatus}
23021 @tab @code{tstatus}
23023 @item @code{traceframe-info}
23024 @tab @code{qXfer:traceframe-info:read}
23025 @tab Traceframe info
23027 @item @code{install-in-trace}
23028 @tab @code{InstallInTrace}
23029 @tab Install tracepoint in tracing
23031 @item @code{disable-randomization}
23032 @tab @code{QDisableRandomization}
23033 @tab @code{set disable-randomization}
23035 @item @code{startup-with-shell}
23036 @tab @code{QStartupWithShell}
23037 @tab @code{set startup-with-shell}
23039 @item @code{environment-hex-encoded}
23040 @tab @code{QEnvironmentHexEncoded}
23041 @tab @code{set environment}
23043 @item @code{environment-unset}
23044 @tab @code{QEnvironmentUnset}
23045 @tab @code{unset environment}
23047 @item @code{environment-reset}
23048 @tab @code{QEnvironmentReset}
23049 @tab @code{Reset the inferior environment (i.e., unset user-set variables)}
23051 @item @code{set-working-dir}
23052 @tab @code{QSetWorkingDir}
23053 @tab @code{set cwd}
23055 @item @code{conditional-breakpoints-packet}
23056 @tab @code{Z0 and Z1}
23057 @tab @code{Support for target-side breakpoint condition evaluation}
23059 @item @code{multiprocess-extensions}
23060 @tab @code{multiprocess extensions}
23061 @tab Debug multiple processes and remote process PID awareness
23063 @item @code{swbreak-feature}
23064 @tab @code{swbreak stop reason}
23067 @item @code{hwbreak-feature}
23068 @tab @code{hwbreak stop reason}
23071 @item @code{fork-event-feature}
23072 @tab @code{fork stop reason}
23075 @item @code{vfork-event-feature}
23076 @tab @code{vfork stop reason}
23079 @item @code{exec-event-feature}
23080 @tab @code{exec stop reason}
23083 @item @code{thread-events}
23084 @tab @code{QThreadEvents}
23085 @tab Tracking thread lifetime.
23087 @item @code{no-resumed-stop-reply}
23088 @tab @code{no resumed thread left stop reply}
23089 @tab Tracking thread lifetime.
23094 @section Implementing a Remote Stub
23096 @cindex debugging stub, example
23097 @cindex remote stub, example
23098 @cindex stub example, remote debugging
23099 The stub files provided with @value{GDBN} implement the target side of the
23100 communication protocol, and the @value{GDBN} side is implemented in the
23101 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
23102 these subroutines to communicate, and ignore the details. (If you're
23103 implementing your own stub file, you can still ignore the details: start
23104 with one of the existing stub files. @file{sparc-stub.c} is the best
23105 organized, and therefore the easiest to read.)
23107 @cindex remote serial debugging, overview
23108 To debug a program running on another machine (the debugging
23109 @dfn{target} machine), you must first arrange for all the usual
23110 prerequisites for the program to run by itself. For example, for a C
23115 A startup routine to set up the C runtime environment; these usually
23116 have a name like @file{crt0}. The startup routine may be supplied by
23117 your hardware supplier, or you may have to write your own.
23120 A C subroutine library to support your program's
23121 subroutine calls, notably managing input and output.
23124 A way of getting your program to the other machine---for example, a
23125 download program. These are often supplied by the hardware
23126 manufacturer, but you may have to write your own from hardware
23130 The next step is to arrange for your program to use a serial port to
23131 communicate with the machine where @value{GDBN} is running (the @dfn{host}
23132 machine). In general terms, the scheme looks like this:
23136 @value{GDBN} already understands how to use this protocol; when everything
23137 else is set up, you can simply use the @samp{target remote} command
23138 (@pxref{Targets,,Specifying a Debugging Target}).
23140 @item On the target,
23141 you must link with your program a few special-purpose subroutines that
23142 implement the @value{GDBN} remote serial protocol. The file containing these
23143 subroutines is called a @dfn{debugging stub}.
23145 On certain remote targets, you can use an auxiliary program
23146 @code{gdbserver} instead of linking a stub into your program.
23147 @xref{Server,,Using the @code{gdbserver} Program}, for details.
23150 The debugging stub is specific to the architecture of the remote
23151 machine; for example, use @file{sparc-stub.c} to debug programs on
23154 @cindex remote serial stub list
23155 These working remote stubs are distributed with @value{GDBN}:
23160 @cindex @file{i386-stub.c}
23163 For Intel 386 and compatible architectures.
23166 @cindex @file{m68k-stub.c}
23167 @cindex Motorola 680x0
23169 For Motorola 680x0 architectures.
23172 @cindex @file{sh-stub.c}
23175 For Renesas SH architectures.
23178 @cindex @file{sparc-stub.c}
23180 For @sc{sparc} architectures.
23182 @item sparcl-stub.c
23183 @cindex @file{sparcl-stub.c}
23186 For Fujitsu @sc{sparclite} architectures.
23190 The @file{README} file in the @value{GDBN} distribution may list other
23191 recently added stubs.
23194 * Stub Contents:: What the stub can do for you
23195 * Bootstrapping:: What you must do for the stub
23196 * Debug Session:: Putting it all together
23199 @node Stub Contents
23200 @subsection What the Stub Can Do for You
23202 @cindex remote serial stub
23203 The debugging stub for your architecture supplies these three
23207 @item set_debug_traps
23208 @findex set_debug_traps
23209 @cindex remote serial stub, initialization
23210 This routine arranges for @code{handle_exception} to run when your
23211 program stops. You must call this subroutine explicitly in your
23212 program's startup code.
23214 @item handle_exception
23215 @findex handle_exception
23216 @cindex remote serial stub, main routine
23217 This is the central workhorse, but your program never calls it
23218 explicitly---the setup code arranges for @code{handle_exception} to
23219 run when a trap is triggered.
23221 @code{handle_exception} takes control when your program stops during
23222 execution (for example, on a breakpoint), and mediates communications
23223 with @value{GDBN} on the host machine. This is where the communications
23224 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
23225 representative on the target machine. It begins by sending summary
23226 information on the state of your program, then continues to execute,
23227 retrieving and transmitting any information @value{GDBN} needs, until you
23228 execute a @value{GDBN} command that makes your program resume; at that point,
23229 @code{handle_exception} returns control to your own code on the target
23233 @cindex @code{breakpoint} subroutine, remote
23234 Use this auxiliary subroutine to make your program contain a
23235 breakpoint. Depending on the particular situation, this may be the only
23236 way for @value{GDBN} to get control. For instance, if your target
23237 machine has some sort of interrupt button, you won't need to call this;
23238 pressing the interrupt button transfers control to
23239 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
23240 simply receiving characters on the serial port may also trigger a trap;
23241 again, in that situation, you don't need to call @code{breakpoint} from
23242 your own program---simply running @samp{target remote} from the host
23243 @value{GDBN} session gets control.
23245 Call @code{breakpoint} if none of these is true, or if you simply want
23246 to make certain your program stops at a predetermined point for the
23247 start of your debugging session.
23250 @node Bootstrapping
23251 @subsection What You Must Do for the Stub
23253 @cindex remote stub, support routines
23254 The debugging stubs that come with @value{GDBN} are set up for a particular
23255 chip architecture, but they have no information about the rest of your
23256 debugging target machine.
23258 First of all you need to tell the stub how to communicate with the
23262 @item int getDebugChar()
23263 @findex getDebugChar
23264 Write this subroutine to read a single character from the serial port.
23265 It may be identical to @code{getchar} for your target system; a
23266 different name is used to allow you to distinguish the two if you wish.
23268 @item void putDebugChar(int)
23269 @findex putDebugChar
23270 Write this subroutine to write a single character to the serial port.
23271 It may be identical to @code{putchar} for your target system; a
23272 different name is used to allow you to distinguish the two if you wish.
23275 @cindex control C, and remote debugging
23276 @cindex interrupting remote targets
23277 If you want @value{GDBN} to be able to stop your program while it is
23278 running, you need to use an interrupt-driven serial driver, and arrange
23279 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
23280 character). That is the character which @value{GDBN} uses to tell the
23281 remote system to stop.
23283 Getting the debugging target to return the proper status to @value{GDBN}
23284 probably requires changes to the standard stub; one quick and dirty way
23285 is to just execute a breakpoint instruction (the ``dirty'' part is that
23286 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
23288 Other routines you need to supply are:
23291 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
23292 @findex exceptionHandler
23293 Write this function to install @var{exception_address} in the exception
23294 handling tables. You need to do this because the stub does not have any
23295 way of knowing what the exception handling tables on your target system
23296 are like (for example, the processor's table might be in @sc{rom},
23297 containing entries which point to a table in @sc{ram}).
23298 The @var{exception_number} specifies the exception which should be changed;
23299 its meaning is architecture-dependent (for example, different numbers
23300 might represent divide by zero, misaligned access, etc). When this
23301 exception occurs, control should be transferred directly to
23302 @var{exception_address}, and the processor state (stack, registers,
23303 and so on) should be just as it is when a processor exception occurs. So if
23304 you want to use a jump instruction to reach @var{exception_address}, it
23305 should be a simple jump, not a jump to subroutine.
23307 For the 386, @var{exception_address} should be installed as an interrupt
23308 gate so that interrupts are masked while the handler runs. The gate
23309 should be at privilege level 0 (the most privileged level). The
23310 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
23311 help from @code{exceptionHandler}.
23313 @item void flush_i_cache()
23314 @findex flush_i_cache
23315 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
23316 instruction cache, if any, on your target machine. If there is no
23317 instruction cache, this subroutine may be a no-op.
23319 On target machines that have instruction caches, @value{GDBN} requires this
23320 function to make certain that the state of your program is stable.
23324 You must also make sure this library routine is available:
23327 @item void *memset(void *, int, int)
23329 This is the standard library function @code{memset} that sets an area of
23330 memory to a known value. If you have one of the free versions of
23331 @code{libc.a}, @code{memset} can be found there; otherwise, you must
23332 either obtain it from your hardware manufacturer, or write your own.
23335 If you do not use the GNU C compiler, you may need other standard
23336 library subroutines as well; this varies from one stub to another,
23337 but in general the stubs are likely to use any of the common library
23338 subroutines which @code{@value{NGCC}} generates as inline code.
23341 @node Debug Session
23342 @subsection Putting it All Together
23344 @cindex remote serial debugging summary
23345 In summary, when your program is ready to debug, you must follow these
23350 Make sure you have defined the supporting low-level routines
23351 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
23353 @code{getDebugChar}, @code{putDebugChar},
23354 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
23358 Insert these lines in your program's startup code, before the main
23359 procedure is called:
23366 On some machines, when a breakpoint trap is raised, the hardware
23367 automatically makes the PC point to the instruction after the
23368 breakpoint. If your machine doesn't do that, you may need to adjust
23369 @code{handle_exception} to arrange for it to return to the instruction
23370 after the breakpoint on this first invocation, so that your program
23371 doesn't keep hitting the initial breakpoint instead of making
23375 For the 680x0 stub only, you need to provide a variable called
23376 @code{exceptionHook}. Normally you just use:
23379 void (*exceptionHook)() = 0;
23383 but if before calling @code{set_debug_traps}, you set it to point to a
23384 function in your program, that function is called when
23385 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
23386 error). The function indicated by @code{exceptionHook} is called with
23387 one parameter: an @code{int} which is the exception number.
23390 Compile and link together: your program, the @value{GDBN} debugging stub for
23391 your target architecture, and the supporting subroutines.
23394 Make sure you have a serial connection between your target machine and
23395 the @value{GDBN} host, and identify the serial port on the host.
23398 @c The "remote" target now provides a `load' command, so we should
23399 @c document that. FIXME.
23400 Download your program to your target machine (or get it there by
23401 whatever means the manufacturer provides), and start it.
23404 Start @value{GDBN} on the host, and connect to the target
23405 (@pxref{Connecting,,Connecting to a Remote Target}).
23409 @node Configurations
23410 @chapter Configuration-Specific Information
23412 While nearly all @value{GDBN} commands are available for all native and
23413 cross versions of the debugger, there are some exceptions. This chapter
23414 describes things that are only available in certain configurations.
23416 There are three major categories of configurations: native
23417 configurations, where the host and target are the same, embedded
23418 operating system configurations, which are usually the same for several
23419 different processor architectures, and bare embedded processors, which
23420 are quite different from each other.
23425 * Embedded Processors::
23432 This section describes details specific to particular native
23436 * BSD libkvm Interface:: Debugging BSD kernel memory images
23437 * Process Information:: Process information
23438 * DJGPP Native:: Features specific to the DJGPP port
23439 * Cygwin Native:: Features specific to the Cygwin port
23440 * Hurd Native:: Features specific to @sc{gnu} Hurd
23441 * Darwin:: Features specific to Darwin
23442 * FreeBSD:: Features specific to FreeBSD
23445 @node BSD libkvm Interface
23446 @subsection BSD libkvm Interface
23449 @cindex kernel memory image
23450 @cindex kernel crash dump
23452 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
23453 interface that provides a uniform interface for accessing kernel virtual
23454 memory images, including live systems and crash dumps. @value{GDBN}
23455 uses this interface to allow you to debug live kernels and kernel crash
23456 dumps on many native BSD configurations. This is implemented as a
23457 special @code{kvm} debugging target. For debugging a live system, load
23458 the currently running kernel into @value{GDBN} and connect to the
23462 (@value{GDBP}) @b{target kvm}
23465 For debugging crash dumps, provide the file name of the crash dump as an
23469 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
23472 Once connected to the @code{kvm} target, the following commands are
23478 Set current context from the @dfn{Process Control Block} (PCB) address.
23481 Set current context from proc address. This command isn't available on
23482 modern FreeBSD systems.
23485 @node Process Information
23486 @subsection Process Information
23488 @cindex examine process image
23489 @cindex process info via @file{/proc}
23491 Some operating systems provide interfaces to fetch additional
23492 information about running processes beyond memory and per-thread
23493 register state. If @value{GDBN} is configured for an operating system
23494 with a supported interface, the command @code{info proc} is available
23495 to report information about the process running your program, or about
23496 any process running on your system.
23498 One supported interface is a facility called @samp{/proc} that can be
23499 used to examine the image of a running process using file-system
23500 subroutines. This facility is supported on @sc{gnu}/Linux and Solaris
23503 On FreeBSD and NetBSD systems, system control nodes are used to query
23504 process information.
23506 In addition, some systems may provide additional process information
23507 in core files. Note that a core file may include a subset of the
23508 information available from a live process. Process information is
23509 currently available from cores created on @sc{gnu}/Linux and FreeBSD
23516 @itemx info proc @var{process-id}
23517 Summarize available information about a process. If a
23518 process ID is specified by @var{process-id}, display information about
23519 that process; otherwise display information about the program being
23520 debugged. The summary includes the debugged process ID, the command
23521 line used to invoke it, its current working directory, and its
23522 executable file's absolute file name.
23524 On some systems, @var{process-id} can be of the form
23525 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
23526 within a process. If the optional @var{pid} part is missing, it means
23527 a thread from the process being debugged (the leading @samp{/} still
23528 needs to be present, or else @value{GDBN} will interpret the number as
23529 a process ID rather than a thread ID).
23531 @item info proc cmdline
23532 @cindex info proc cmdline
23533 Show the original command line of the process. This command is
23534 supported on @sc{gnu}/Linux, FreeBSD and NetBSD.
23536 @item info proc cwd
23537 @cindex info proc cwd
23538 Show the current working directory of the process. This command is
23539 supported on @sc{gnu}/Linux, FreeBSD and NetBSD.
23541 @item info proc exe
23542 @cindex info proc exe
23543 Show the name of executable of the process. This command is supported
23544 on @sc{gnu}/Linux, FreeBSD and NetBSD.
23546 @item info proc files
23547 @cindex info proc files
23548 Show the file descriptors open by the process. For each open file
23549 descriptor, @value{GDBN} shows its number, type (file, directory,
23550 character device, socket), file pointer offset, and the name of the
23551 resource open on the descriptor. The resource name can be a file name
23552 (for files, directories, and devices) or a protocol followed by socket
23553 address (for network connections). This command is supported on
23556 This example shows the open file descriptors for a process using a
23557 tty for standard input and output as well as two network sockets:
23560 (gdb) info proc files 22136
23564 FD Type Offset Flags Name
23565 text file - r-------- /usr/bin/ssh
23566 ctty chr - rw------- /dev/pts/20
23567 cwd dir - r-------- /usr/home/john
23568 root dir - r-------- /
23569 0 chr 0x32933a4 rw------- /dev/pts/20
23570 1 chr 0x32933a4 rw------- /dev/pts/20
23571 2 chr 0x32933a4 rw------- /dev/pts/20
23572 3 socket 0x0 rw----n-- tcp4 10.0.1.2:53014 -> 10.0.1.10:22
23573 4 socket 0x0 rw------- unix stream:/tmp/ssh-FIt89oAzOn5f/agent.2456
23576 @item info proc mappings
23577 @cindex memory address space mappings
23578 Report the memory address space ranges accessible in a process. On
23579 Solaris, FreeBSD and NetBSD systems, each memory range includes information
23580 on whether the process has read, write, or execute access rights to each
23581 range. On @sc{gnu}/Linux, FreeBSD and NetBSD systems, each memory range
23582 includes the object file which is mapped to that range.
23584 @item info proc stat
23585 @itemx info proc status
23586 @cindex process detailed status information
23587 Show additional process-related information, including the user ID and
23588 group ID; virtual memory usage; the signals that are pending, blocked,
23589 and ignored; its TTY; its consumption of system and user time; its
23590 stack size; its @samp{nice} value; etc. These commands are supported
23591 on @sc{gnu}/Linux, FreeBSD and NetBSD.
23593 For @sc{gnu}/Linux systems, see the @samp{proc} man page for more
23594 information (type @kbd{man 5 proc} from your shell prompt).
23596 For FreeBSD and NetBSD systems, @code{info proc stat} is an alias for
23597 @code{info proc status}.
23599 @item info proc all
23600 Show all the information about the process described under all of the
23601 above @code{info proc} subcommands.
23604 @comment These sub-options of 'info proc' were not included when
23605 @comment procfs.c was re-written. Keep their descriptions around
23606 @comment against the day when someone finds the time to put them back in.
23607 @kindex info proc times
23608 @item info proc times
23609 Starting time, user CPU time, and system CPU time for your program and
23612 @kindex info proc id
23614 Report on the process IDs related to your program: its own process ID,
23615 the ID of its parent, the process group ID, and the session ID.
23618 @item set procfs-trace
23619 @kindex set procfs-trace
23620 @cindex @code{procfs} API calls
23621 This command enables and disables tracing of @code{procfs} API calls.
23623 @item show procfs-trace
23624 @kindex show procfs-trace
23625 Show the current state of @code{procfs} API call tracing.
23627 @item set procfs-file @var{file}
23628 @kindex set procfs-file
23629 Tell @value{GDBN} to write @code{procfs} API trace to the named
23630 @var{file}. @value{GDBN} appends the trace info to the previous
23631 contents of the file. The default is to display the trace on the
23634 @item show procfs-file
23635 @kindex show procfs-file
23636 Show the file to which @code{procfs} API trace is written.
23638 @item proc-trace-entry
23639 @itemx proc-trace-exit
23640 @itemx proc-untrace-entry
23641 @itemx proc-untrace-exit
23642 @kindex proc-trace-entry
23643 @kindex proc-trace-exit
23644 @kindex proc-untrace-entry
23645 @kindex proc-untrace-exit
23646 These commands enable and disable tracing of entries into and exits
23647 from the @code{syscall} interface.
23650 @kindex info pidlist
23651 @cindex process list, QNX Neutrino
23652 For QNX Neutrino only, this command displays the list of all the
23653 processes and all the threads within each process.
23656 @kindex info meminfo
23657 @cindex mapinfo list, QNX Neutrino
23658 For QNX Neutrino only, this command displays the list of all mapinfos.
23662 @subsection Features for Debugging @sc{djgpp} Programs
23663 @cindex @sc{djgpp} debugging
23664 @cindex native @sc{djgpp} debugging
23665 @cindex MS-DOS-specific commands
23668 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
23669 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
23670 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
23671 top of real-mode DOS systems and their emulations.
23673 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
23674 defines a few commands specific to the @sc{djgpp} port. This
23675 subsection describes those commands.
23680 This is a prefix of @sc{djgpp}-specific commands which print
23681 information about the target system and important OS structures.
23684 @cindex MS-DOS system info
23685 @cindex free memory information (MS-DOS)
23686 @item info dos sysinfo
23687 This command displays assorted information about the underlying
23688 platform: the CPU type and features, the OS version and flavor, the
23689 DPMI version, and the available conventional and DPMI memory.
23694 @cindex segment descriptor tables
23695 @cindex descriptor tables display
23697 @itemx info dos ldt
23698 @itemx info dos idt
23699 These 3 commands display entries from, respectively, Global, Local,
23700 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
23701 tables are data structures which store a descriptor for each segment
23702 that is currently in use. The segment's selector is an index into a
23703 descriptor table; the table entry for that index holds the
23704 descriptor's base address and limit, and its attributes and access
23707 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
23708 segment (used for both data and the stack), and a DOS segment (which
23709 allows access to DOS/BIOS data structures and absolute addresses in
23710 conventional memory). However, the DPMI host will usually define
23711 additional segments in order to support the DPMI environment.
23713 @cindex garbled pointers
23714 These commands allow to display entries from the descriptor tables.
23715 Without an argument, all entries from the specified table are
23716 displayed. An argument, which should be an integer expression, means
23717 display a single entry whose index is given by the argument. For
23718 example, here's a convenient way to display information about the
23719 debugged program's data segment:
23722 @exdent @code{(@value{GDBP}) info dos ldt $ds}
23723 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
23727 This comes in handy when you want to see whether a pointer is outside
23728 the data segment's limit (i.e.@: @dfn{garbled}).
23730 @cindex page tables display (MS-DOS)
23732 @itemx info dos pte
23733 These two commands display entries from, respectively, the Page
23734 Directory and the Page Tables. Page Directories and Page Tables are
23735 data structures which control how virtual memory addresses are mapped
23736 into physical addresses. A Page Table includes an entry for every
23737 page of memory that is mapped into the program's address space; there
23738 may be several Page Tables, each one holding up to 4096 entries. A
23739 Page Directory has up to 4096 entries, one each for every Page Table
23740 that is currently in use.
23742 Without an argument, @kbd{info dos pde} displays the entire Page
23743 Directory, and @kbd{info dos pte} displays all the entries in all of
23744 the Page Tables. An argument, an integer expression, given to the
23745 @kbd{info dos pde} command means display only that entry from the Page
23746 Directory table. An argument given to the @kbd{info dos pte} command
23747 means display entries from a single Page Table, the one pointed to by
23748 the specified entry in the Page Directory.
23750 @cindex direct memory access (DMA) on MS-DOS
23751 These commands are useful when your program uses @dfn{DMA} (Direct
23752 Memory Access), which needs physical addresses to program the DMA
23755 These commands are supported only with some DPMI servers.
23757 @cindex physical address from linear address
23758 @item info dos address-pte @var{addr}
23759 This command displays the Page Table entry for a specified linear
23760 address. The argument @var{addr} is a linear address which should
23761 already have the appropriate segment's base address added to it,
23762 because this command accepts addresses which may belong to @emph{any}
23763 segment. For example, here's how to display the Page Table entry for
23764 the page where a variable @code{i} is stored:
23767 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
23768 @exdent @code{Page Table entry for address 0x11a00d30:}
23769 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
23773 This says that @code{i} is stored at offset @code{0xd30} from the page
23774 whose physical base address is @code{0x02698000}, and shows all the
23775 attributes of that page.
23777 Note that you must cast the addresses of variables to a @code{char *},
23778 since otherwise the value of @code{__djgpp_base_address}, the base
23779 address of all variables and functions in a @sc{djgpp} program, will
23780 be added using the rules of C pointer arithmetics: if @code{i} is
23781 declared an @code{int}, @value{GDBN} will add 4 times the value of
23782 @code{__djgpp_base_address} to the address of @code{i}.
23784 Here's another example, it displays the Page Table entry for the
23788 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
23789 @exdent @code{Page Table entry for address 0x29110:}
23790 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
23794 (The @code{+ 3} offset is because the transfer buffer's address is the
23795 3rd member of the @code{_go32_info_block} structure.) The output
23796 clearly shows that this DPMI server maps the addresses in conventional
23797 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
23798 linear (@code{0x29110}) addresses are identical.
23800 This command is supported only with some DPMI servers.
23803 @cindex DOS serial data link, remote debugging
23804 In addition to native debugging, the DJGPP port supports remote
23805 debugging via a serial data link. The following commands are specific
23806 to remote serial debugging in the DJGPP port of @value{GDBN}.
23809 @kindex set com1base
23810 @kindex set com1irq
23811 @kindex set com2base
23812 @kindex set com2irq
23813 @kindex set com3base
23814 @kindex set com3irq
23815 @kindex set com4base
23816 @kindex set com4irq
23817 @item set com1base @var{addr}
23818 This command sets the base I/O port address of the @file{COM1} serial
23821 @item set com1irq @var{irq}
23822 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
23823 for the @file{COM1} serial port.
23825 There are similar commands @samp{set com2base}, @samp{set com3irq},
23826 etc.@: for setting the port address and the @code{IRQ} lines for the
23829 @kindex show com1base
23830 @kindex show com1irq
23831 @kindex show com2base
23832 @kindex show com2irq
23833 @kindex show com3base
23834 @kindex show com3irq
23835 @kindex show com4base
23836 @kindex show com4irq
23837 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
23838 display the current settings of the base address and the @code{IRQ}
23839 lines used by the COM ports.
23842 @kindex info serial
23843 @cindex DOS serial port status
23844 This command prints the status of the 4 DOS serial ports. For each
23845 port, it prints whether it's active or not, its I/O base address and
23846 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
23847 counts of various errors encountered so far.
23851 @node Cygwin Native
23852 @subsection Features for Debugging MS Windows PE Executables
23853 @cindex MS Windows debugging
23854 @cindex native Cygwin debugging
23855 @cindex Cygwin-specific commands
23857 @value{GDBN} supports native debugging of MS Windows programs, including
23858 DLLs with and without symbolic debugging information.
23860 @cindex Ctrl-BREAK, MS-Windows
23861 @cindex interrupt debuggee on MS-Windows
23862 MS-Windows programs that call @code{SetConsoleMode} to switch off the
23863 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
23864 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
23865 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
23866 sequence, which can be used to interrupt the debuggee even if it
23869 There are various additional Cygwin-specific commands, described in
23870 this section. Working with DLLs that have no debugging symbols is
23871 described in @ref{Non-debug DLL Symbols}.
23876 This is a prefix of MS Windows-specific commands which print
23877 information about the target system and important OS structures.
23879 @item info w32 selector
23880 This command displays information returned by
23881 the Win32 API @code{GetThreadSelectorEntry} function.
23882 It takes an optional argument that is evaluated to
23883 a long value to give the information about this given selector.
23884 Without argument, this command displays information
23885 about the six segment registers.
23887 @item info w32 thread-information-block
23888 This command displays thread specific information stored in the
23889 Thread Information Block (readable on the X86 CPU family using @code{$fs}
23890 selector for 32-bit programs and @code{$gs} for 64-bit programs).
23892 @kindex signal-event
23893 @item signal-event @var{id}
23894 This command signals an event with user-provided @var{id}. Used to resume
23895 crashing process when attached to it using MS-Windows JIT debugging (AeDebug).
23897 To use it, create or edit the following keys in
23898 @code{HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AeDebug} and/or
23899 @code{HKLM\SOFTWARE\Wow6432Node\Microsoft\Windows NT\CurrentVersion\AeDebug}
23900 (for x86_64 versions):
23904 @code{Debugger} (REG_SZ) --- a command to launch the debugger.
23905 Suggested command is: @code{@var{fully-qualified-path-to-gdb.exe} -ex
23906 "attach %ld" -ex "signal-event %ld" -ex "continue"}.
23908 The first @code{%ld} will be replaced by the process ID of the
23909 crashing process, the second @code{%ld} will be replaced by the ID of
23910 the event that blocks the crashing process, waiting for @value{GDBN}
23914 @code{Auto} (REG_SZ) --- either @code{1} or @code{0}. @code{1} will
23915 make the system run debugger specified by the Debugger key
23916 automatically, @code{0} will cause a dialog box with ``OK'' and
23917 ``Cancel'' buttons to appear, which allows the user to either
23918 terminate the crashing process (OK) or debug it (Cancel).
23921 @kindex set cygwin-exceptions
23922 @cindex debugging the Cygwin DLL
23923 @cindex Cygwin DLL, debugging
23924 @item set cygwin-exceptions @var{mode}
23925 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
23926 happen inside the Cygwin DLL. If @var{mode} is @code{off},
23927 @value{GDBN} will delay recognition of exceptions, and may ignore some
23928 exceptions which seem to be caused by internal Cygwin DLL
23929 ``bookkeeping''. This option is meant primarily for debugging the
23930 Cygwin DLL itself; the default value is @code{off} to avoid annoying
23931 @value{GDBN} users with false @code{SIGSEGV} signals.
23933 @kindex show cygwin-exceptions
23934 @item show cygwin-exceptions
23935 Displays whether @value{GDBN} will break on exceptions that happen
23936 inside the Cygwin DLL itself.
23938 @kindex set new-console
23939 @item set new-console @var{mode}
23940 If @var{mode} is @code{on} the debuggee will
23941 be started in a new console on next start.
23942 If @var{mode} is @code{off}, the debuggee will
23943 be started in the same console as the debugger.
23945 @kindex show new-console
23946 @item show new-console
23947 Displays whether a new console is used
23948 when the debuggee is started.
23950 @kindex set new-group
23951 @item set new-group @var{mode}
23952 This boolean value controls whether the debuggee should
23953 start a new group or stay in the same group as the debugger.
23954 This affects the way the Windows OS handles
23957 @kindex show new-group
23958 @item show new-group
23959 Displays current value of new-group boolean.
23961 @kindex set debugevents
23962 @item set debugevents
23963 This boolean value adds debug output concerning kernel events related
23964 to the debuggee seen by the debugger. This includes events that
23965 signal thread and process creation and exit, DLL loading and
23966 unloading, console interrupts, and debugging messages produced by the
23967 Windows @code{OutputDebugString} API call.
23969 @kindex set debugexec
23970 @item set debugexec
23971 This boolean value adds debug output concerning execute events
23972 (such as resume thread) seen by the debugger.
23974 @kindex set debugexceptions
23975 @item set debugexceptions
23976 This boolean value adds debug output concerning exceptions in the
23977 debuggee seen by the debugger.
23979 @kindex set debugmemory
23980 @item set debugmemory
23981 This boolean value adds debug output concerning debuggee memory reads
23982 and writes by the debugger.
23986 This boolean values specifies whether the debuggee is called
23987 via a shell or directly (default value is on).
23991 Displays if the debuggee will be started with a shell.
23996 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
23999 @node Non-debug DLL Symbols
24000 @subsubsection Support for DLLs without Debugging Symbols
24001 @cindex DLLs with no debugging symbols
24002 @cindex Minimal symbols and DLLs
24004 Very often on windows, some of the DLLs that your program relies on do
24005 not include symbolic debugging information (for example,
24006 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
24007 symbols in a DLL, it relies on the minimal amount of symbolic
24008 information contained in the DLL's export table. This section
24009 describes working with such symbols, known internally to @value{GDBN} as
24010 ``minimal symbols''.
24012 Note that before the debugged program has started execution, no DLLs
24013 will have been loaded. The easiest way around this problem is simply to
24014 start the program --- either by setting a breakpoint or letting the
24015 program run once to completion.
24017 @subsubsection DLL Name Prefixes
24019 In keeping with the naming conventions used by the Microsoft debugging
24020 tools, DLL export symbols are made available with a prefix based on the
24021 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
24022 also entered into the symbol table, so @code{CreateFileA} is often
24023 sufficient. In some cases there will be name clashes within a program
24024 (particularly if the executable itself includes full debugging symbols)
24025 necessitating the use of the fully qualified name when referring to the
24026 contents of the DLL. Use single-quotes around the name to avoid the
24027 exclamation mark (``!'') being interpreted as a language operator.
24029 Note that the internal name of the DLL may be all upper-case, even
24030 though the file name of the DLL is lower-case, or vice-versa. Since
24031 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
24032 some confusion. If in doubt, try the @code{info functions} and
24033 @code{info variables} commands or even @code{maint print msymbols}
24034 (@pxref{Symbols}). Here's an example:
24037 (@value{GDBP}) info function CreateFileA
24038 All functions matching regular expression "CreateFileA":
24040 Non-debugging symbols:
24041 0x77e885f4 CreateFileA
24042 0x77e885f4 KERNEL32!CreateFileA
24046 (@value{GDBP}) info function !
24047 All functions matching regular expression "!":
24049 Non-debugging symbols:
24050 0x6100114c cygwin1!__assert
24051 0x61004034 cygwin1!_dll_crt0@@0
24052 0x61004240 cygwin1!dll_crt0(per_process *)
24056 @subsubsection Working with Minimal Symbols
24058 Symbols extracted from a DLL's export table do not contain very much
24059 type information. All that @value{GDBN} can do is guess whether a symbol
24060 refers to a function or variable depending on the linker section that
24061 contains the symbol. Also note that the actual contents of the memory
24062 contained in a DLL are not available unless the program is running. This
24063 means that you cannot examine the contents of a variable or disassemble
24064 a function within a DLL without a running program.
24066 Variables are generally treated as pointers and dereferenced
24067 automatically. For this reason, it is often necessary to prefix a
24068 variable name with the address-of operator (``&'') and provide explicit
24069 type information in the command. Here's an example of the type of
24073 (@value{GDBP}) print 'cygwin1!__argv'
24074 'cygwin1!__argv' has unknown type; cast it to its declared type
24078 (@value{GDBP}) x 'cygwin1!__argv'
24079 'cygwin1!__argv' has unknown type; cast it to its declared type
24082 And two possible solutions:
24085 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
24086 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
24090 (@value{GDBP}) x/2x &'cygwin1!__argv'
24091 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
24092 (@value{GDBP}) x/x 0x10021608
24093 0x10021608: 0x0022fd98
24094 (@value{GDBP}) x/s 0x0022fd98
24095 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
24098 Setting a break point within a DLL is possible even before the program
24099 starts execution. However, under these circumstances, @value{GDBN} can't
24100 examine the initial instructions of the function in order to skip the
24101 function's frame set-up code. You can work around this by using ``*&''
24102 to set the breakpoint at a raw memory address:
24105 (@value{GDBP}) break *&'python22!PyOS_Readline'
24106 Breakpoint 1 at 0x1e04eff0
24109 The author of these extensions is not entirely convinced that setting a
24110 break point within a shared DLL like @file{kernel32.dll} is completely
24114 @subsection Commands Specific to @sc{gnu} Hurd Systems
24115 @cindex @sc{gnu} Hurd debugging
24117 This subsection describes @value{GDBN} commands specific to the
24118 @sc{gnu} Hurd native debugging.
24123 @kindex set signals@r{, Hurd command}
24124 @kindex set sigs@r{, Hurd command}
24125 This command toggles the state of inferior signal interception by
24126 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
24127 affected by this command. @code{sigs} is a shorthand alias for
24132 @kindex show signals@r{, Hurd command}
24133 @kindex show sigs@r{, Hurd command}
24134 Show the current state of intercepting inferior's signals.
24136 @item set signal-thread
24137 @itemx set sigthread
24138 @kindex set signal-thread
24139 @kindex set sigthread
24140 This command tells @value{GDBN} which thread is the @code{libc} signal
24141 thread. That thread is run when a signal is delivered to a running
24142 process. @code{set sigthread} is the shorthand alias of @code{set
24145 @item show signal-thread
24146 @itemx show sigthread
24147 @kindex show signal-thread
24148 @kindex show sigthread
24149 These two commands show which thread will run when the inferior is
24150 delivered a signal.
24153 @kindex set stopped@r{, Hurd command}
24154 This commands tells @value{GDBN} that the inferior process is stopped,
24155 as with the @code{SIGSTOP} signal. The stopped process can be
24156 continued by delivering a signal to it.
24159 @kindex show stopped@r{, Hurd command}
24160 This command shows whether @value{GDBN} thinks the debuggee is
24163 @item set exceptions
24164 @kindex set exceptions@r{, Hurd command}
24165 Use this command to turn off trapping of exceptions in the inferior.
24166 When exception trapping is off, neither breakpoints nor
24167 single-stepping will work. To restore the default, set exception
24170 @item show exceptions
24171 @kindex show exceptions@r{, Hurd command}
24172 Show the current state of trapping exceptions in the inferior.
24174 @item set task pause
24175 @kindex set task@r{, Hurd commands}
24176 @cindex task attributes (@sc{gnu} Hurd)
24177 @cindex pause current task (@sc{gnu} Hurd)
24178 This command toggles task suspension when @value{GDBN} has control.
24179 Setting it to on takes effect immediately, and the task is suspended
24180 whenever @value{GDBN} gets control. Setting it to off will take
24181 effect the next time the inferior is continued. If this option is set
24182 to off, you can use @code{set thread default pause on} or @code{set
24183 thread pause on} (see below) to pause individual threads.
24185 @item show task pause
24186 @kindex show task@r{, Hurd commands}
24187 Show the current state of task suspension.
24189 @item set task detach-suspend-count
24190 @cindex task suspend count
24191 @cindex detach from task, @sc{gnu} Hurd
24192 This command sets the suspend count the task will be left with when
24193 @value{GDBN} detaches from it.
24195 @item show task detach-suspend-count
24196 Show the suspend count the task will be left with when detaching.
24198 @item set task exception-port
24199 @itemx set task excp
24200 @cindex task exception port, @sc{gnu} Hurd
24201 This command sets the task exception port to which @value{GDBN} will
24202 forward exceptions. The argument should be the value of the @dfn{send
24203 rights} of the task. @code{set task excp} is a shorthand alias.
24205 @item set noninvasive
24206 @cindex noninvasive task options
24207 This command switches @value{GDBN} to a mode that is the least
24208 invasive as far as interfering with the inferior is concerned. This
24209 is the same as using @code{set task pause}, @code{set exceptions}, and
24210 @code{set signals} to values opposite to the defaults.
24212 @item info send-rights
24213 @itemx info receive-rights
24214 @itemx info port-rights
24215 @itemx info port-sets
24216 @itemx info dead-names
24219 @cindex send rights, @sc{gnu} Hurd
24220 @cindex receive rights, @sc{gnu} Hurd
24221 @cindex port rights, @sc{gnu} Hurd
24222 @cindex port sets, @sc{gnu} Hurd
24223 @cindex dead names, @sc{gnu} Hurd
24224 These commands display information about, respectively, send rights,
24225 receive rights, port rights, port sets, and dead names of a task.
24226 There are also shorthand aliases: @code{info ports} for @code{info
24227 port-rights} and @code{info psets} for @code{info port-sets}.
24229 @item set thread pause
24230 @kindex set thread@r{, Hurd command}
24231 @cindex thread properties, @sc{gnu} Hurd
24232 @cindex pause current thread (@sc{gnu} Hurd)
24233 This command toggles current thread suspension when @value{GDBN} has
24234 control. Setting it to on takes effect immediately, and the current
24235 thread is suspended whenever @value{GDBN} gets control. Setting it to
24236 off will take effect the next time the inferior is continued.
24237 Normally, this command has no effect, since when @value{GDBN} has
24238 control, the whole task is suspended. However, if you used @code{set
24239 task pause off} (see above), this command comes in handy to suspend
24240 only the current thread.
24242 @item show thread pause
24243 @kindex show thread@r{, Hurd command}
24244 This command shows the state of current thread suspension.
24246 @item set thread run
24247 This command sets whether the current thread is allowed to run.
24249 @item show thread run
24250 Show whether the current thread is allowed to run.
24252 @item set thread detach-suspend-count
24253 @cindex thread suspend count, @sc{gnu} Hurd
24254 @cindex detach from thread, @sc{gnu} Hurd
24255 This command sets the suspend count @value{GDBN} will leave on a
24256 thread when detaching. This number is relative to the suspend count
24257 found by @value{GDBN} when it notices the thread; use @code{set thread
24258 takeover-suspend-count} to force it to an absolute value.
24260 @item show thread detach-suspend-count
24261 Show the suspend count @value{GDBN} will leave on the thread when
24264 @item set thread exception-port
24265 @itemx set thread excp
24266 Set the thread exception port to which to forward exceptions. This
24267 overrides the port set by @code{set task exception-port} (see above).
24268 @code{set thread excp} is the shorthand alias.
24270 @item set thread takeover-suspend-count
24271 Normally, @value{GDBN}'s thread suspend counts are relative to the
24272 value @value{GDBN} finds when it notices each thread. This command
24273 changes the suspend counts to be absolute instead.
24275 @item set thread default
24276 @itemx show thread default
24277 @cindex thread default settings, @sc{gnu} Hurd
24278 Each of the above @code{set thread} commands has a @code{set thread
24279 default} counterpart (e.g., @code{set thread default pause}, @code{set
24280 thread default exception-port}, etc.). The @code{thread default}
24281 variety of commands sets the default thread properties for all
24282 threads; you can then change the properties of individual threads with
24283 the non-default commands.
24290 @value{GDBN} provides the following commands specific to the Darwin target:
24293 @item set debug darwin @var{num}
24294 @kindex set debug darwin
24295 When set to a non zero value, enables debugging messages specific to
24296 the Darwin support. Higher values produce more verbose output.
24298 @item show debug darwin
24299 @kindex show debug darwin
24300 Show the current state of Darwin messages.
24302 @item set debug mach-o @var{num}
24303 @kindex set debug mach-o
24304 When set to a non zero value, enables debugging messages while
24305 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
24306 file format used on Darwin for object and executable files.) Higher
24307 values produce more verbose output. This is a command to diagnose
24308 problems internal to @value{GDBN} and should not be needed in normal
24311 @item show debug mach-o
24312 @kindex show debug mach-o
24313 Show the current state of Mach-O file messages.
24315 @item set mach-exceptions on
24316 @itemx set mach-exceptions off
24317 @kindex set mach-exceptions
24318 On Darwin, faults are first reported as a Mach exception and are then
24319 mapped to a Posix signal. Use this command to turn on trapping of
24320 Mach exceptions in the inferior. This might be sometimes useful to
24321 better understand the cause of a fault. The default is off.
24323 @item show mach-exceptions
24324 @kindex show mach-exceptions
24325 Show the current state of exceptions trapping.
24329 @subsection FreeBSD
24332 When the ABI of a system call is changed in the FreeBSD kernel, this
24333 is implemented by leaving a compatibility system call using the old
24334 ABI at the existing number and allocating a new system call number for
24335 the version using the new ABI. As a convenience, when a system call
24336 is caught by name (@pxref{catch syscall}), compatibility system calls
24339 For example, FreeBSD 12 introduced a new variant of the @code{kevent}
24340 system call and catching the @code{kevent} system call by name catches
24344 (@value{GDBP}) catch syscall kevent
24345 Catchpoint 1 (syscalls 'freebsd11_kevent' [363] 'kevent' [560])
24351 @section Embedded Operating Systems
24353 This section describes configurations involving the debugging of
24354 embedded operating systems that are available for several different
24357 @value{GDBN} includes the ability to debug programs running on
24358 various real-time operating systems.
24360 @node Embedded Processors
24361 @section Embedded Processors
24363 This section goes into details specific to particular embedded
24366 @cindex send command to simulator
24367 Whenever a specific embedded processor has a simulator, @value{GDBN}
24368 allows to send an arbitrary command to the simulator.
24371 @item sim @var{command}
24372 @kindex sim@r{, a command}
24373 Send an arbitrary @var{command} string to the simulator. Consult the
24374 documentation for the specific simulator in use for information about
24375 acceptable commands.
24380 * ARC:: Synopsys ARC
24382 * M68K:: Motorola M68K
24383 * MicroBlaze:: Xilinx MicroBlaze
24384 * MIPS Embedded:: MIPS Embedded
24385 * OpenRISC 1000:: OpenRISC 1000 (or1k)
24386 * PowerPC Embedded:: PowerPC Embedded
24389 * Super-H:: Renesas Super-H
24393 @subsection Synopsys ARC
24394 @cindex Synopsys ARC
24395 @cindex ARC specific commands
24401 @value{GDBN} provides the following ARC-specific commands:
24404 @item set debug arc
24405 @kindex set debug arc
24406 Control the level of ARC specific debug messages. Use 0 for no messages (the
24407 default), 1 for debug messages, and 2 for even more debug messages.
24409 @item show debug arc
24410 @kindex show debug arc
24411 Show the level of ARC specific debugging in operation.
24413 @item maint print arc arc-instruction @var{address}
24414 @kindex maint print arc arc-instruction
24415 Print internal disassembler information about instruction at a given address.
24422 @value{GDBN} provides the following ARM-specific commands:
24425 @item set arm disassembler
24427 This commands selects from a list of disassembly styles. The
24428 @code{"std"} style is the standard style.
24430 @item show arm disassembler
24432 Show the current disassembly style.
24434 @item set arm apcs32
24435 @cindex ARM 32-bit mode
24436 This command toggles ARM operation mode between 32-bit and 26-bit.
24438 @item show arm apcs32
24439 Display the current usage of the ARM 32-bit mode.
24441 @item set arm fpu @var{fputype}
24442 This command sets the ARM floating-point unit (FPU) type. The
24443 argument @var{fputype} can be one of these:
24447 Determine the FPU type by querying the OS ABI.
24449 Software FPU, with mixed-endian doubles on little-endian ARM
24452 GCC-compiled FPA co-processor.
24454 Software FPU with pure-endian doubles.
24460 Show the current type of the FPU.
24463 This command forces @value{GDBN} to use the specified ABI.
24466 Show the currently used ABI.
24468 @item set arm fallback-mode (arm|thumb|auto)
24469 @value{GDBN} uses the symbol table, when available, to determine
24470 whether instructions are ARM or Thumb. This command controls
24471 @value{GDBN}'s default behavior when the symbol table is not
24472 available. The default is @samp{auto}, which causes @value{GDBN} to
24473 use the current execution mode (from the @code{T} bit in the @code{CPSR}
24476 @item show arm fallback-mode
24477 Show the current fallback instruction mode.
24479 @item set arm force-mode (arm|thumb|auto)
24480 This command overrides use of the symbol table to determine whether
24481 instructions are ARM or Thumb. The default is @samp{auto}, which
24482 causes @value{GDBN} to use the symbol table and then the setting
24483 of @samp{set arm fallback-mode}.
24485 @item show arm force-mode
24486 Show the current forced instruction mode.
24488 @item set debug arm
24489 Toggle whether to display ARM-specific debugging messages from the ARM
24490 target support subsystem.
24492 @item show debug arm
24493 Show whether ARM-specific debugging messages are enabled.
24497 @item target sim @r{[}@var{simargs}@r{]} @dots{}
24498 The @value{GDBN} ARM simulator accepts the following optional arguments.
24501 @item --swi-support=@var{type}
24502 Tell the simulator which SWI interfaces to support. The argument
24503 @var{type} may be a comma separated list of the following values.
24504 The default value is @code{all}.
24519 The Motorola m68k configuration includes ColdFire support.
24522 @subsection MicroBlaze
24523 @cindex Xilinx MicroBlaze
24524 @cindex XMD, Xilinx Microprocessor Debugger
24526 The MicroBlaze is a soft-core processor supported on various Xilinx
24527 FPGAs, such as Spartan or Virtex series. Boards with these processors
24528 usually have JTAG ports which connect to a host system running the Xilinx
24529 Embedded Development Kit (EDK) or Software Development Kit (SDK).
24530 This host system is used to download the configuration bitstream to
24531 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
24532 communicates with the target board using the JTAG interface and
24533 presents a @code{gdbserver} interface to the board. By default
24534 @code{xmd} uses port @code{1234}. (While it is possible to change
24535 this default port, it requires the use of undocumented @code{xmd}
24536 commands. Contact Xilinx support if you need to do this.)
24538 Use these GDB commands to connect to the MicroBlaze target processor.
24541 @item target remote :1234
24542 Use this command to connect to the target if you are running @value{GDBN}
24543 on the same system as @code{xmd}.
24545 @item target remote @var{xmd-host}:1234
24546 Use this command to connect to the target if it is connected to @code{xmd}
24547 running on a different system named @var{xmd-host}.
24550 Use this command to download a program to the MicroBlaze target.
24552 @item set debug microblaze @var{n}
24553 Enable MicroBlaze-specific debugging messages if non-zero.
24555 @item show debug microblaze @var{n}
24556 Show MicroBlaze-specific debugging level.
24559 @node MIPS Embedded
24560 @subsection @acronym{MIPS} Embedded
24563 @value{GDBN} supports these special commands for @acronym{MIPS} targets:
24566 @item set mipsfpu double
24567 @itemx set mipsfpu single
24568 @itemx set mipsfpu none
24569 @itemx set mipsfpu auto
24570 @itemx show mipsfpu
24571 @kindex set mipsfpu
24572 @kindex show mipsfpu
24573 @cindex @acronym{MIPS} remote floating point
24574 @cindex floating point, @acronym{MIPS} remote
24575 If your target board does not support the @acronym{MIPS} floating point
24576 coprocessor, you should use the command @samp{set mipsfpu none} (if you
24577 need this, you may wish to put the command in your @value{GDBN} init
24578 file). This tells @value{GDBN} how to find the return value of
24579 functions which return floating point values. It also allows
24580 @value{GDBN} to avoid saving the floating point registers when calling
24581 functions on the board. If you are using a floating point coprocessor
24582 with only single precision floating point support, as on the @sc{r4650}
24583 processor, use the command @samp{set mipsfpu single}. The default
24584 double precision floating point coprocessor may be selected using
24585 @samp{set mipsfpu double}.
24587 In previous versions the only choices were double precision or no
24588 floating point, so @samp{set mipsfpu on} will select double precision
24589 and @samp{set mipsfpu off} will select no floating point.
24591 As usual, you can inquire about the @code{mipsfpu} variable with
24592 @samp{show mipsfpu}.
24595 @node OpenRISC 1000
24596 @subsection OpenRISC 1000
24597 @cindex OpenRISC 1000
24600 The OpenRISC 1000 provides a free RISC instruction set architecture. It is
24601 mainly provided as a soft-core which can run on Xilinx, Altera and other
24604 @value{GDBN} for OpenRISC supports the below commands when connecting to
24612 Runs the builtin CPU simulator which can run very basic
24613 programs but does not support most hardware functions like MMU.
24614 For more complex use cases the user is advised to run an external
24615 target, and connect using @samp{target remote}.
24617 Example: @code{target sim}
24619 @item set debug or1k
24620 Toggle whether to display OpenRISC-specific debugging messages from the
24621 OpenRISC target support subsystem.
24623 @item show debug or1k
24624 Show whether OpenRISC-specific debugging messages are enabled.
24627 @node PowerPC Embedded
24628 @subsection PowerPC Embedded
24630 @cindex DVC register
24631 @value{GDBN} supports using the DVC (Data Value Compare) register to
24632 implement in hardware simple hardware watchpoint conditions of the form:
24635 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
24636 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
24639 The DVC register will be automatically used when @value{GDBN} detects
24640 such pattern in a condition expression, and the created watchpoint uses one
24641 debug register (either the @code{exact-watchpoints} option is on and the
24642 variable is scalar, or the variable has a length of one byte). This feature
24643 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
24646 When running on PowerPC embedded processors, @value{GDBN} automatically uses
24647 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
24648 in which case watchpoints using only one debug register are created when
24649 watching variables of scalar types.
24651 You can create an artificial array to watch an arbitrary memory
24652 region using one of the following commands (@pxref{Expressions}):
24655 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
24656 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
24659 PowerPC embedded processors support masked watchpoints. See the discussion
24660 about the @code{mask} argument in @ref{Set Watchpoints}.
24662 @cindex ranged breakpoint
24663 PowerPC embedded processors support hardware accelerated
24664 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
24665 the inferior whenever it executes an instruction at any address within
24666 the range it specifies. To set a ranged breakpoint in @value{GDBN},
24667 use the @code{break-range} command.
24669 @value{GDBN} provides the following PowerPC-specific commands:
24672 @kindex break-range
24673 @item break-range @var{start-location}, @var{end-location}
24674 Set a breakpoint for an address range given by
24675 @var{start-location} and @var{end-location}, which can specify a function name,
24676 a line number, an offset of lines from the current line or from the start
24677 location, or an address of an instruction (see @ref{Specify Location},
24678 for a list of all the possible ways to specify a @var{location}.)
24679 The breakpoint will stop execution of the inferior whenever it
24680 executes an instruction at any address within the specified range,
24681 (including @var{start-location} and @var{end-location}.)
24683 @kindex set powerpc
24684 @item set powerpc soft-float
24685 @itemx show powerpc soft-float
24686 Force @value{GDBN} to use (or not use) a software floating point calling
24687 convention. By default, @value{GDBN} selects the calling convention based
24688 on the selected architecture and the provided executable file.
24690 @item set powerpc vector-abi
24691 @itemx show powerpc vector-abi
24692 Force @value{GDBN} to use the specified calling convention for vector
24693 arguments and return values. The valid options are @samp{auto};
24694 @samp{generic}, to avoid vector registers even if they are present;
24695 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
24696 registers. By default, @value{GDBN} selects the calling convention
24697 based on the selected architecture and the provided executable file.
24699 @item set powerpc exact-watchpoints
24700 @itemx show powerpc exact-watchpoints
24701 Allow @value{GDBN} to use only one debug register when watching a variable
24702 of scalar type, thus assuming that the variable is accessed through the
24703 address of its first byte.
24708 @subsection Atmel AVR
24711 When configured for debugging the Atmel AVR, @value{GDBN} supports the
24712 following AVR-specific commands:
24715 @item info io_registers
24716 @kindex info io_registers@r{, AVR}
24717 @cindex I/O registers (Atmel AVR)
24718 This command displays information about the AVR I/O registers. For
24719 each register, @value{GDBN} prints its number and value.
24726 When configured for debugging CRIS, @value{GDBN} provides the
24727 following CRIS-specific commands:
24730 @item set cris-version @var{ver}
24731 @cindex CRIS version
24732 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
24733 The CRIS version affects register names and sizes. This command is useful in
24734 case autodetection of the CRIS version fails.
24736 @item show cris-version
24737 Show the current CRIS version.
24739 @item set cris-dwarf2-cfi
24740 @cindex DWARF-2 CFI and CRIS
24741 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
24742 Change to @samp{off} when using @code{gcc-cris} whose version is below
24745 @item show cris-dwarf2-cfi
24746 Show the current state of using DWARF-2 CFI.
24748 @item set cris-mode @var{mode}
24750 Set the current CRIS mode to @var{mode}. It should only be changed when
24751 debugging in guru mode, in which case it should be set to
24752 @samp{guru} (the default is @samp{normal}).
24754 @item show cris-mode
24755 Show the current CRIS mode.
24759 @subsection Renesas Super-H
24762 For the Renesas Super-H processor, @value{GDBN} provides these
24766 @item set sh calling-convention @var{convention}
24767 @kindex set sh calling-convention
24768 Set the calling-convention used when calling functions from @value{GDBN}.
24769 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
24770 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
24771 convention. If the DWARF-2 information of the called function specifies
24772 that the function follows the Renesas calling convention, the function
24773 is called using the Renesas calling convention. If the calling convention
24774 is set to @samp{renesas}, the Renesas calling convention is always used,
24775 regardless of the DWARF-2 information. This can be used to override the
24776 default of @samp{gcc} if debug information is missing, or the compiler
24777 does not emit the DWARF-2 calling convention entry for a function.
24779 @item show sh calling-convention
24780 @kindex show sh calling-convention
24781 Show the current calling convention setting.
24786 @node Architectures
24787 @section Architectures
24789 This section describes characteristics of architectures that affect
24790 all uses of @value{GDBN} with the architecture, both native and cross.
24797 * HPPA:: HP PA architecture
24805 @subsection AArch64
24806 @cindex AArch64 support
24808 When @value{GDBN} is debugging the AArch64 architecture, it provides the
24809 following special commands:
24812 @item set debug aarch64
24813 @kindex set debug aarch64
24814 This command determines whether AArch64 architecture-specific debugging
24815 messages are to be displayed.
24817 @item show debug aarch64
24818 Show whether AArch64 debugging messages are displayed.
24822 @subsubsection AArch64 SVE.
24823 @cindex AArch64 SVE.
24825 When @value{GDBN} is debugging the AArch64 architecture, if the Scalable Vector
24826 Extension (SVE) is present, then @value{GDBN} will provide the vector registers
24827 @code{$z0} through @code{$z31}, vector predicate registers @code{$p0} through
24828 @code{$p15}, and the @code{$ffr} register. In addition, the pseudo register
24829 @code{$vg} will be provided. This is the vector granule for the current thread
24830 and represents the number of 64-bit chunks in an SVE @code{z} register.
24832 If the vector length changes, then the @code{$vg} register will be updated,
24833 but the lengths of the @code{z} and @code{p} registers will not change. This
24834 is a known limitation of @value{GDBN} and does not affect the execution of the
24837 @subsubsection AArch64 Pointer Authentication.
24838 @cindex AArch64 Pointer Authentication.
24840 When @value{GDBN} is debugging the AArch64 architecture, and the program is
24841 using the v8.3-A feature Pointer Authentication (PAC), then whenever the link
24842 register @code{$lr} is pointing to an PAC function its value will be masked.
24843 When GDB prints a backtrace, any addresses that required unmasking will be
24844 postfixed with the marker [PAC]. When using the MI, this is printed as part
24845 of the @code{addr_flags} field.
24848 @subsection x86 Architecture-specific Issues
24851 @item set struct-convention @var{mode}
24852 @kindex set struct-convention
24853 @cindex struct return convention
24854 @cindex struct/union returned in registers
24855 Set the convention used by the inferior to return @code{struct}s and
24856 @code{union}s from functions to @var{mode}. Possible values of
24857 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
24858 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
24859 are returned on the stack, while @code{"reg"} means that a
24860 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
24861 be returned in a register.
24863 @item show struct-convention
24864 @kindex show struct-convention
24865 Show the current setting of the convention to return @code{struct}s
24870 @subsubsection Intel @dfn{Memory Protection Extensions} (MPX).
24871 @cindex Intel Memory Protection Extensions (MPX).
24873 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
24874 @footnote{The register named with capital letters represent the architecture
24875 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
24876 which are the lower bound and upper bound. Bounds are effective addresses or
24877 memory locations. The upper bounds are architecturally represented in 1's
24878 complement form. A bound having lower bound = 0, and upper bound = 0
24879 (1's complement of all bits set) will allow access to the entire address space.
24881 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
24882 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
24883 display the upper bound performing the complement of one operation on the
24884 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
24885 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
24886 can also be noted that the upper bounds are inclusive.
24888 As an example, assume that the register BND0 holds bounds for a pointer having
24889 access allowed for the range between 0x32 and 0x71. The values present on
24890 bnd0raw and bnd registers are presented as follows:
24893 bnd0raw = @{0x32, 0xffffffff8e@}
24894 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
24897 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
24898 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
24899 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
24900 Python, the display includes the memory size, in bits, accessible to
24903 Bounds can also be stored in bounds tables, which are stored in
24904 application memory. These tables store bounds for pointers by specifying
24905 the bounds pointer's value along with its bounds. Evaluating and changing
24906 bounds located in bound tables is therefore interesting while investigating
24907 bugs on MPX context. @value{GDBN} provides commands for this purpose:
24910 @item show mpx bound @var{pointer}
24911 @kindex show mpx bound
24912 Display bounds of the given @var{pointer}.
24914 @item set mpx bound @var{pointer}, @var{lbound}, @var{ubound}
24915 @kindex set mpx bound
24916 Set the bounds of a pointer in the bound table.
24917 This command takes three parameters: @var{pointer} is the pointers
24918 whose bounds are to be changed, @var{lbound} and @var{ubound} are new values
24919 for lower and upper bounds respectively.
24922 When you call an inferior function on an Intel MPX enabled program,
24923 GDB sets the inferior's bound registers to the init (disabled) state
24924 before calling the function. As a consequence, bounds checks for the
24925 pointer arguments passed to the function will always pass.
24927 This is necessary because when you call an inferior function, the
24928 program is usually in the middle of the execution of other function.
24929 Since at that point bound registers are in an arbitrary state, not
24930 clearing them would lead to random bound violations in the called
24933 You can still examine the influence of the bound registers on the
24934 execution of the called function by stopping the execution of the
24935 called function at its prologue, setting bound registers, and
24936 continuing the execution. For example:
24940 Breakpoint 2 at 0x4009de: file i386-mpx-call.c, line 47.
24941 $ print upper (a, b, c, d, 1)
24942 Breakpoint 2, upper (a=0x0, b=0x6e0000005b, c=0x0, d=0x0, len=48)....
24944 @{lbound = 0x0, ubound = ffffffff@} : size -1
24947 At this last step the value of bnd0 can be changed for investigation of bound
24948 violations caused along the execution of the call. In order to know how to
24949 set the bound registers or bound table for the call consult the ABI.
24954 See the following section.
24957 @subsection @acronym{MIPS}
24959 @cindex stack on Alpha
24960 @cindex stack on @acronym{MIPS}
24961 @cindex Alpha stack
24962 @cindex @acronym{MIPS} stack
24963 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
24964 sometimes requires @value{GDBN} to search backward in the object code to
24965 find the beginning of a function.
24967 @cindex response time, @acronym{MIPS} debugging
24968 To improve response time (especially for embedded applications, where
24969 @value{GDBN} may be restricted to a slow serial line for this search)
24970 you may want to limit the size of this search, using one of these
24974 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
24975 @item set heuristic-fence-post @var{limit}
24976 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
24977 search for the beginning of a function. A value of @var{0} (the
24978 default) means there is no limit. However, except for @var{0}, the
24979 larger the limit the more bytes @code{heuristic-fence-post} must search
24980 and therefore the longer it takes to run. You should only need to use
24981 this command when debugging a stripped executable.
24983 @item show heuristic-fence-post
24984 Display the current limit.
24988 These commands are available @emph{only} when @value{GDBN} is configured
24989 for debugging programs on Alpha or @acronym{MIPS} processors.
24991 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
24995 @item set mips abi @var{arg}
24996 @kindex set mips abi
24997 @cindex set ABI for @acronym{MIPS}
24998 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
24999 values of @var{arg} are:
25003 The default ABI associated with the current binary (this is the
25013 @item show mips abi
25014 @kindex show mips abi
25015 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
25017 @item set mips compression @var{arg}
25018 @kindex set mips compression
25019 @cindex code compression, @acronym{MIPS}
25020 Tell @value{GDBN} which @acronym{MIPS} compressed
25021 @acronym{ISA, Instruction Set Architecture} encoding is used by the
25022 inferior. @value{GDBN} uses this for code disassembly and other
25023 internal interpretation purposes. This setting is only referred to
25024 when no executable has been associated with the debugging session or
25025 the executable does not provide information about the encoding it uses.
25026 Otherwise this setting is automatically updated from information
25027 provided by the executable.
25029 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
25030 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
25031 executables containing @acronym{MIPS16} code frequently are not
25032 identified as such.
25034 This setting is ``sticky''; that is, it retains its value across
25035 debugging sessions until reset either explicitly with this command or
25036 implicitly from an executable.
25038 The compiler and/or assembler typically add symbol table annotations to
25039 identify functions compiled for the @acronym{MIPS16} or
25040 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
25041 are present, @value{GDBN} uses them in preference to the global
25042 compressed @acronym{ISA} encoding setting.
25044 @item show mips compression
25045 @kindex show mips compression
25046 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
25047 @value{GDBN} to debug the inferior.
25050 @itemx show mipsfpu
25051 @xref{MIPS Embedded, set mipsfpu}.
25053 @item set mips mask-address @var{arg}
25054 @kindex set mips mask-address
25055 @cindex @acronym{MIPS} addresses, masking
25056 This command determines whether the most-significant 32 bits of 64-bit
25057 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
25058 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
25059 setting, which lets @value{GDBN} determine the correct value.
25061 @item show mips mask-address
25062 @kindex show mips mask-address
25063 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
25066 @item set remote-mips64-transfers-32bit-regs
25067 @kindex set remote-mips64-transfers-32bit-regs
25068 This command controls compatibility with 64-bit @acronym{MIPS} targets that
25069 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
25070 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
25071 and 64 bits for other registers, set this option to @samp{on}.
25073 @item show remote-mips64-transfers-32bit-regs
25074 @kindex show remote-mips64-transfers-32bit-regs
25075 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
25077 @item set debug mips
25078 @kindex set debug mips
25079 This command turns on and off debugging messages for the @acronym{MIPS}-specific
25080 target code in @value{GDBN}.
25082 @item show debug mips
25083 @kindex show debug mips
25084 Show the current setting of @acronym{MIPS} debugging messages.
25090 @cindex HPPA support
25092 When @value{GDBN} is debugging the HP PA architecture, it provides the
25093 following special commands:
25096 @item set debug hppa
25097 @kindex set debug hppa
25098 This command determines whether HPPA architecture-specific debugging
25099 messages are to be displayed.
25101 @item show debug hppa
25102 Show whether HPPA debugging messages are displayed.
25104 @item maint print unwind @var{address}
25105 @kindex maint print unwind@r{, HPPA}
25106 This command displays the contents of the unwind table entry at the
25107 given @var{address}.
25113 @subsection PowerPC
25114 @cindex PowerPC architecture
25116 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
25117 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
25118 numbers stored in the floating point registers. These values must be stored
25119 in two consecutive registers, always starting at an even register like
25120 @code{f0} or @code{f2}.
25122 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
25123 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
25124 @code{f2} and @code{f3} for @code{$dl1} and so on.
25126 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
25127 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
25130 @subsection Nios II
25131 @cindex Nios II architecture
25133 When @value{GDBN} is debugging the Nios II architecture,
25134 it provides the following special commands:
25138 @item set debug nios2
25139 @kindex set debug nios2
25140 This command turns on and off debugging messages for the Nios II
25141 target code in @value{GDBN}.
25143 @item show debug nios2
25144 @kindex show debug nios2
25145 Show the current setting of Nios II debugging messages.
25149 @subsection Sparc64
25150 @cindex Sparc64 support
25151 @cindex Application Data Integrity
25152 @subsubsection ADI Support
25154 The M7 processor supports an Application Data Integrity (ADI) feature that
25155 detects invalid data accesses. When software allocates memory and enables
25156 ADI on the allocated memory, it chooses a 4-bit version number, sets the
25157 version in the upper 4 bits of the 64-bit pointer to that data, and stores
25158 the 4-bit version in every cacheline of that data. Hardware saves the latter
25159 in spare bits in the cache and memory hierarchy. On each load and store,
25160 the processor compares the upper 4 VA (virtual address) bits to the
25161 cacheline's version. If there is a mismatch, the processor generates a
25162 version mismatch trap which can be either precise or disrupting. The trap
25163 is an error condition which the kernel delivers to the process as a SIGSEGV
25166 Note that only 64-bit applications can use ADI and need to be built with
25169 Values of the ADI version tags, which are in granularity of a
25170 cacheline (64 bytes), can be viewed or modified.
25174 @kindex adi examine
25175 @item adi (examine | x) [ / @var{n} ] @var{addr}
25177 The @code{adi examine} command displays the value of one ADI version tag per
25180 @var{n} is a decimal integer specifying the number in bytes; the default
25181 is 1. It specifies how much ADI version information, at the ratio of 1:ADI
25182 block size, to display.
25184 @var{addr} is the address in user address space where you want @value{GDBN}
25185 to begin displaying the ADI version tags.
25187 Below is an example of displaying ADI versions of variable "shmaddr".
25190 (@value{GDBP}) adi x/100 shmaddr
25191 0xfff800010002c000: 0 0
25195 @item adi (assign | a) [ / @var{n} ] @var{addr} = @var{tag}
25197 The @code{adi assign} command is used to assign new ADI version tag
25200 @var{n} is a decimal integer specifying the number in bytes;
25201 the default is 1. It specifies how much ADI version information, at the
25202 ratio of 1:ADI block size, to modify.
25204 @var{addr} is the address in user address space where you want @value{GDBN}
25205 to begin modifying the ADI version tags.
25207 @var{tag} is the new ADI version tag.
25209 For example, do the following to modify then verify ADI versions of
25210 variable "shmaddr":
25213 (@value{GDBP}) adi a/100 shmaddr = 7
25214 (@value{GDBP}) adi x/100 shmaddr
25215 0xfff800010002c000: 7 7
25222 @cindex S12Z support
25224 When @value{GDBN} is debugging the S12Z architecture,
25225 it provides the following special command:
25228 @item maint info bdccsr
25229 @kindex maint info bdccsr@r{, S12Z}
25230 This command displays the current value of the microprocessor's
25235 @node Controlling GDB
25236 @chapter Controlling @value{GDBN}
25238 You can alter the way @value{GDBN} interacts with you by using the
25239 @code{set} command. For commands controlling how @value{GDBN} displays
25240 data, see @ref{Print Settings, ,Print Settings}. Other settings are
25245 * Editing:: Command editing
25246 * Command History:: Command history
25247 * Screen Size:: Screen size
25248 * Output Styling:: Output styling
25249 * Numbers:: Numbers
25250 * ABI:: Configuring the current ABI
25251 * Auto-loading:: Automatically loading associated files
25252 * Messages/Warnings:: Optional warnings and messages
25253 * Debugging Output:: Optional messages about internal happenings
25254 * Other Misc Settings:: Other Miscellaneous Settings
25262 @value{GDBN} indicates its readiness to read a command by printing a string
25263 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
25264 can change the prompt string with the @code{set prompt} command. For
25265 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
25266 the prompt in one of the @value{GDBN} sessions so that you can always tell
25267 which one you are talking to.
25269 @emph{Note:} @code{set prompt} does not add a space for you after the
25270 prompt you set. This allows you to set a prompt which ends in a space
25271 or a prompt that does not.
25275 @item set prompt @var{newprompt}
25276 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
25278 @kindex show prompt
25280 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
25283 Versions of @value{GDBN} that ship with Python scripting enabled have
25284 prompt extensions. The commands for interacting with these extensions
25288 @kindex set extended-prompt
25289 @item set extended-prompt @var{prompt}
25290 Set an extended prompt that allows for substitutions.
25291 @xref{gdb.prompt}, for a list of escape sequences that can be used for
25292 substitution. Any escape sequences specified as part of the prompt
25293 string are replaced with the corresponding strings each time the prompt
25299 set extended-prompt Current working directory: \w (gdb)
25302 Note that when an extended-prompt is set, it takes control of the
25303 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
25305 @kindex show extended-prompt
25306 @item show extended-prompt
25307 Prints the extended prompt. Any escape sequences specified as part of
25308 the prompt string with @code{set extended-prompt}, are replaced with the
25309 corresponding strings each time the prompt is displayed.
25313 @section Command Editing
25315 @cindex command line editing
25317 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
25318 @sc{gnu} library provides consistent behavior for programs which provide a
25319 command line interface to the user. Advantages are @sc{gnu} Emacs-style
25320 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
25321 substitution, and a storage and recall of command history across
25322 debugging sessions.
25324 You may control the behavior of command line editing in @value{GDBN} with the
25325 command @code{set}.
25328 @kindex set editing
25331 @itemx set editing on
25332 Enable command line editing (enabled by default).
25334 @item set editing off
25335 Disable command line editing.
25337 @kindex show editing
25339 Show whether command line editing is enabled.
25342 @ifset SYSTEM_READLINE
25343 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
25345 @ifclear SYSTEM_READLINE
25346 @xref{Command Line Editing},
25348 for more details about the Readline
25349 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
25350 encouraged to read that chapter.
25352 @cindex Readline application name
25353 @value{GDBN} sets the Readline application name to @samp{gdb}. This
25354 is useful for conditions in @file{.inputrc}.
25356 @cindex operate-and-get-next
25357 @value{GDBN} defines a bindable Readline command,
25358 @code{operate-and-get-next}. This is bound to @kbd{C-o} by default.
25359 This command accepts the current line for execution and fetches the
25360 next line relative to the current line from the history for editing.
25361 Any argument is ignored.
25363 @node Command History
25364 @section Command History
25365 @cindex command history
25367 @value{GDBN} can keep track of the commands you type during your
25368 debugging sessions, so that you can be certain of precisely what
25369 happened. Use these commands to manage the @value{GDBN} command
25372 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
25373 package, to provide the history facility.
25374 @ifset SYSTEM_READLINE
25375 @xref{Using History Interactively, , , history, GNU History Library},
25377 @ifclear SYSTEM_READLINE
25378 @xref{Using History Interactively},
25380 for the detailed description of the History library.
25382 To issue a command to @value{GDBN} without affecting certain aspects of
25383 the state which is seen by users, prefix it with @samp{server }
25384 (@pxref{Server Prefix}). This
25385 means that this command will not affect the command history, nor will it
25386 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
25387 pressed on a line by itself.
25389 @cindex @code{server}, command prefix
25390 The server prefix does not affect the recording of values into the value
25391 history; to print a value without recording it into the value history,
25392 use the @code{output} command instead of the @code{print} command.
25394 Here is the description of @value{GDBN} commands related to command
25398 @cindex history substitution
25399 @cindex history file
25400 @kindex set history filename
25401 @cindex @env{GDBHISTFILE}, environment variable
25402 @item set history filename @r{[}@var{fname}@r{]}
25403 Set the name of the @value{GDBN} command history file to @var{fname}.
25404 This is the file where @value{GDBN} reads an initial command history
25405 list, and where it writes the command history from this session when it
25406 exits. You can access this list through history expansion or through
25407 the history command editing characters listed below. This file defaults
25408 to the value of the environment variable @code{GDBHISTFILE}, or to
25409 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
25412 The @code{GDBHISTFILE} environment variable is read after processing
25413 any @value{GDBN} initialization files (@pxref{Startup}) and after
25414 processing any commands passed using command line options (for
25415 example, @code{-ex}).
25417 If the @var{fname} argument is not given, or if the @code{GDBHISTFILE}
25418 is the empty string then @value{GDBN} will neither try to load an
25419 existing history file, nor will it try to save the history on exit.
25421 @cindex save command history
25422 @kindex set history save
25423 @item set history save
25424 @itemx set history save on
25425 Record command history in a file, whose name may be specified with the
25426 @code{set history filename} command. By default, this option is
25427 disabled. The command history will be recorded when @value{GDBN}
25428 exits. If @code{set history filename} is set to the empty string then
25429 history saving is disabled, even when @code{set history save} is
25432 @item set history save off
25433 Don't record the command history into the file specified by @code{set
25434 history filename} when @value{GDBN} exits.
25436 @cindex history size
25437 @kindex set history size
25438 @cindex @env{GDBHISTSIZE}, environment variable
25439 @item set history size @var{size}
25440 @itemx set history size unlimited
25441 Set the number of commands which @value{GDBN} keeps in its history list.
25442 This defaults to the value of the environment variable @env{GDBHISTSIZE}, or
25443 to 256 if this variable is not set. Non-numeric values of @env{GDBHISTSIZE}
25444 are ignored. If @var{size} is @code{unlimited} or if @env{GDBHISTSIZE} is
25445 either a negative number or the empty string, then the number of commands
25446 @value{GDBN} keeps in the history list is unlimited.
25448 The @code{GDBHISTSIZE} environment variable is read after processing
25449 any @value{GDBN} initialization files (@pxref{Startup}) and after
25450 processing any commands passed using command line options (for
25451 example, @code{-ex}).
25453 @cindex remove duplicate history
25454 @kindex set history remove-duplicates
25455 @item set history remove-duplicates @var{count}
25456 @itemx set history remove-duplicates unlimited
25457 Control the removal of duplicate history entries in the command history list.
25458 If @var{count} is non-zero, @value{GDBN} will look back at the last @var{count}
25459 history entries and remove the first entry that is a duplicate of the current
25460 entry being added to the command history list. If @var{count} is
25461 @code{unlimited} then this lookbehind is unbounded. If @var{count} is 0, then
25462 removal of duplicate history entries is disabled.
25464 Only history entries added during the current session are considered for
25465 removal. This option is set to 0 by default.
25469 History expansion assigns special meaning to the character @kbd{!}.
25470 @ifset SYSTEM_READLINE
25471 @xref{Event Designators, , , history, GNU History Library},
25473 @ifclear SYSTEM_READLINE
25474 @xref{Event Designators},
25478 @cindex history expansion, turn on/off
25479 Since @kbd{!} is also the logical not operator in C, history expansion
25480 is off by default. If you decide to enable history expansion with the
25481 @code{set history expansion on} command, you may sometimes need to
25482 follow @kbd{!} (when it is used as logical not, in an expression) with
25483 a space or a tab to prevent it from being expanded. The readline
25484 history facilities do not attempt substitution on the strings
25485 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
25487 The commands to control history expansion are:
25490 @item set history expansion on
25491 @itemx set history expansion
25492 @kindex set history expansion
25493 Enable history expansion. History expansion is off by default.
25495 @item set history expansion off
25496 Disable history expansion.
25499 @kindex show history
25501 @itemx show history filename
25502 @itemx show history save
25503 @itemx show history size
25504 @itemx show history expansion
25505 These commands display the state of the @value{GDBN} history parameters.
25506 @code{show history} by itself displays all four states.
25511 @kindex show commands
25512 @cindex show last commands
25513 @cindex display command history
25514 @item show commands
25515 Display the last ten commands in the command history.
25517 @item show commands @var{n}
25518 Print ten commands centered on command number @var{n}.
25520 @item show commands +
25521 Print ten commands just after the commands last printed.
25525 @section Screen Size
25526 @cindex size of screen
25527 @cindex screen size
25530 @cindex pauses in output
25532 Certain commands to @value{GDBN} may produce large amounts of
25533 information output to the screen. To help you read all of it,
25534 @value{GDBN} pauses and asks you for input at the end of each page of
25535 output. Type @key{RET} when you want to see one more page of output,
25536 @kbd{q} to discard the remaining output, or @kbd{c} to continue
25537 without paging for the rest of the current command. Also, the screen
25538 width setting determines when to wrap lines of output. Depending on
25539 what is being printed, @value{GDBN} tries to break the line at a
25540 readable place, rather than simply letting it overflow onto the
25543 Normally @value{GDBN} knows the size of the screen from the terminal
25544 driver software. For example, on Unix @value{GDBN} uses the termcap data base
25545 together with the value of the @code{TERM} environment variable and the
25546 @code{stty rows} and @code{stty cols} settings. If this is not correct,
25547 you can override it with the @code{set height} and @code{set
25554 @kindex show height
25555 @item set height @var{lpp}
25556 @itemx set height unlimited
25558 @itemx set width @var{cpl}
25559 @itemx set width unlimited
25561 These @code{set} commands specify a screen height of @var{lpp} lines and
25562 a screen width of @var{cpl} characters. The associated @code{show}
25563 commands display the current settings.
25565 If you specify a height of either @code{unlimited} or zero lines,
25566 @value{GDBN} does not pause during output no matter how long the
25567 output is. This is useful if output is to a file or to an editor
25570 Likewise, you can specify @samp{set width unlimited} or @samp{set
25571 width 0} to prevent @value{GDBN} from wrapping its output.
25573 @item set pagination on
25574 @itemx set pagination off
25575 @kindex set pagination
25576 Turn the output pagination on or off; the default is on. Turning
25577 pagination off is the alternative to @code{set height unlimited}. Note that
25578 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
25579 Options, -batch}) also automatically disables pagination.
25581 @item show pagination
25582 @kindex show pagination
25583 Show the current pagination mode.
25586 @node Output Styling
25587 @section Output Styling
25593 @value{GDBN} can style its output on a capable terminal. This is
25594 enabled by default on most systems, but disabled by default when in
25595 batch mode (@pxref{Mode Options}). Various style settings are available;
25596 and styles can also be disabled entirely.
25599 @item set style enabled @samp{on|off}
25600 Enable or disable all styling. The default is host-dependent, with
25601 most hosts defaulting to @samp{on}.
25603 @item show style enabled
25604 Show the current state of styling.
25606 @item set style sources @samp{on|off}
25607 Enable or disable source code styling. This affects whether source
25608 code, such as the output of the @code{list} command, is styled. Note
25609 that source styling only works if styling in general is enabled, and
25610 if @value{GDBN} was linked with the GNU Source Highlight library. The
25611 default is @samp{on}.
25613 @item show style sources
25614 Show the current state of source code styling.
25617 Subcommands of @code{set style} control specific forms of styling.
25618 These subcommands all follow the same pattern: each style-able object
25619 can be styled with a foreground color, a background color, and an
25622 For example, the style of file names can be controlled using the
25623 @code{set style filename} group of commands:
25626 @item set style filename background @var{color}
25627 Set the background to @var{color}. Valid colors are @samp{none}
25628 (meaning the terminal's default color), @samp{black}, @samp{red},
25629 @samp{green}, @samp{yellow}, @samp{blue}, @samp{magenta}, @samp{cyan},
25632 @item set style filename foreground @var{color}
25633 Set the foreground to @var{color}. Valid colors are @samp{none}
25634 (meaning the terminal's default color), @samp{black}, @samp{red},
25635 @samp{green}, @samp{yellow}, @samp{blue}, @samp{magenta}, @samp{cyan},
25638 @item set style filename intensity @var{value}
25639 Set the intensity to @var{value}. Valid intensities are @samp{normal}
25640 (the default), @samp{bold}, and @samp{dim}.
25643 The @code{show style} command and its subcommands are styling
25644 a style name in their output using its own style.
25645 So, use @command{show style} to see the complete list of styles,
25646 their characteristics and the visual aspect of each style.
25648 The style-able objects are:
25651 Control the styling of file names. By default, this style's
25652 foreground color is green.
25655 Control the styling of function names. These are managed with the
25656 @code{set style function} family of commands. By default, this
25657 style's foreground color is yellow.
25660 Control the styling of variable names. These are managed with the
25661 @code{set style variable} family of commands. By default, this style's
25662 foreground color is cyan.
25665 Control the styling of addresses. These are managed with the
25666 @code{set style address} family of commands. By default, this style's
25667 foreground color is blue.
25670 Control the styling of titles. These are managed with the
25671 @code{set style title} family of commands. By default, this style's
25672 intensity is bold. Commands are using the title style to improve
25673 the readability of large output. For example, the commands
25674 @command{apropos} and @command{help} are using the title style
25675 for the command names.
25678 Control the styling of highlightings. These are managed with the
25679 @code{set style highlight} family of commands. By default, this style's
25680 foreground color is red. Commands are using the highlight style to draw
25681 the user attention to some specific parts of their output. For example,
25682 the command @command{apropos -v REGEXP} uses the highlight style to
25683 mark the documentation parts matching @var{regexp}.
25686 Control the styling of the TUI border. Note that, unlike other
25687 styling options, only the color of the border can be controlled via
25688 @code{set style}. This was done for compatibility reasons, as TUI
25689 controls to set the border's intensity predated the addition of
25690 general styling to @value{GDBN}. @xref{TUI Configuration}.
25692 @item tui-active-border
25693 Control the styling of the active TUI border; that is, the TUI window
25694 that has the focus.
25700 @cindex number representation
25701 @cindex entering numbers
25703 You can always enter numbers in octal, decimal, or hexadecimal in
25704 @value{GDBN} by the usual conventions: octal numbers begin with
25705 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
25706 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
25707 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
25708 10; likewise, the default display for numbers---when no particular
25709 format is specified---is base 10. You can change the default base for
25710 both input and output with the commands described below.
25713 @kindex set input-radix
25714 @item set input-radix @var{base}
25715 Set the default base for numeric input. Supported choices
25716 for @var{base} are decimal 8, 10, or 16. The base must itself be
25717 specified either unambiguously or using the current input radix; for
25721 set input-radix 012
25722 set input-radix 10.
25723 set input-radix 0xa
25727 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
25728 leaves the input radix unchanged, no matter what it was, since
25729 @samp{10}, being without any leading or trailing signs of its base, is
25730 interpreted in the current radix. Thus, if the current radix is 16,
25731 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
25734 @kindex set output-radix
25735 @item set output-radix @var{base}
25736 Set the default base for numeric display. Supported choices
25737 for @var{base} are decimal 8, 10, or 16. The base must itself be
25738 specified either unambiguously or using the current input radix.
25740 @kindex show input-radix
25741 @item show input-radix
25742 Display the current default base for numeric input.
25744 @kindex show output-radix
25745 @item show output-radix
25746 Display the current default base for numeric display.
25748 @item set radix @r{[}@var{base}@r{]}
25752 These commands set and show the default base for both input and output
25753 of numbers. @code{set radix} sets the radix of input and output to
25754 the same base; without an argument, it resets the radix back to its
25755 default value of 10.
25760 @section Configuring the Current ABI
25762 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
25763 application automatically. However, sometimes you need to override its
25764 conclusions. Use these commands to manage @value{GDBN}'s view of the
25770 @cindex Newlib OS ABI and its influence on the longjmp handling
25772 One @value{GDBN} configuration can debug binaries for multiple operating
25773 system targets, either via remote debugging or native emulation.
25774 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
25775 but you can override its conclusion using the @code{set osabi} command.
25776 One example where this is useful is in debugging of binaries which use
25777 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
25778 not have the same identifying marks that the standard C library for your
25781 When @value{GDBN} is debugging the AArch64 architecture, it provides a
25782 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
25783 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
25784 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
25788 Show the OS ABI currently in use.
25791 With no argument, show the list of registered available OS ABI's.
25793 @item set osabi @var{abi}
25794 Set the current OS ABI to @var{abi}.
25797 @cindex float promotion
25799 Generally, the way that an argument of type @code{float} is passed to a
25800 function depends on whether the function is prototyped. For a prototyped
25801 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
25802 according to the architecture's convention for @code{float}. For unprototyped
25803 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
25804 @code{double} and then passed.
25806 Unfortunately, some forms of debug information do not reliably indicate whether
25807 a function is prototyped. If @value{GDBN} calls a function that is not marked
25808 as prototyped, it consults @kbd{set coerce-float-to-double}.
25811 @kindex set coerce-float-to-double
25812 @item set coerce-float-to-double
25813 @itemx set coerce-float-to-double on
25814 Arguments of type @code{float} will be promoted to @code{double} when passed
25815 to an unprototyped function. This is the default setting.
25817 @item set coerce-float-to-double off
25818 Arguments of type @code{float} will be passed directly to unprototyped
25821 @kindex show coerce-float-to-double
25822 @item show coerce-float-to-double
25823 Show the current setting of promoting @code{float} to @code{double}.
25827 @kindex show cp-abi
25828 @value{GDBN} needs to know the ABI used for your program's C@t{++}
25829 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
25830 used to build your application. @value{GDBN} only fully supports
25831 programs with a single C@t{++} ABI; if your program contains code using
25832 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
25833 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
25834 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
25835 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
25836 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
25837 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
25842 Show the C@t{++} ABI currently in use.
25845 With no argument, show the list of supported C@t{++} ABI's.
25847 @item set cp-abi @var{abi}
25848 @itemx set cp-abi auto
25849 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
25853 @section Automatically loading associated files
25854 @cindex auto-loading
25856 @value{GDBN} sometimes reads files with commands and settings automatically,
25857 without being explicitly told so by the user. We call this feature
25858 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
25859 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
25860 results or introduce security risks (e.g., if the file comes from untrusted
25864 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
25865 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
25867 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
25868 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
25871 There are various kinds of files @value{GDBN} can automatically load.
25872 In addition to these files, @value{GDBN} supports auto-loading code written
25873 in various extension languages. @xref{Auto-loading extensions}.
25875 Note that loading of these associated files (including the local @file{.gdbinit}
25876 file) requires accordingly configured @code{auto-load safe-path}
25877 (@pxref{Auto-loading safe path}).
25879 For these reasons, @value{GDBN} includes commands and options to let you
25880 control when to auto-load files and which files should be auto-loaded.
25883 @anchor{set auto-load off}
25884 @kindex set auto-load off
25885 @item set auto-load off
25886 Globally disable loading of all auto-loaded files.
25887 You may want to use this command with the @samp{-iex} option
25888 (@pxref{Option -init-eval-command}) such as:
25890 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
25893 Be aware that system init file (@pxref{System-wide configuration})
25894 and init files from your home directory (@pxref{Home Directory Init File})
25895 still get read (as they come from generally trusted directories).
25896 To prevent @value{GDBN} from auto-loading even those init files, use the
25897 @option{-nx} option (@pxref{Mode Options}), in addition to
25898 @code{set auto-load no}.
25900 @anchor{show auto-load}
25901 @kindex show auto-load
25902 @item show auto-load
25903 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
25907 (gdb) show auto-load
25908 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
25909 libthread-db: Auto-loading of inferior specific libthread_db is on.
25910 local-gdbinit: Auto-loading of .gdbinit script from current directory
25912 python-scripts: Auto-loading of Python scripts is on.
25913 safe-path: List of directories from which it is safe to auto-load files
25914 is $debugdir:$datadir/auto-load.
25915 scripts-directory: List of directories from which to load auto-loaded scripts
25916 is $debugdir:$datadir/auto-load.
25919 @anchor{info auto-load}
25920 @kindex info auto-load
25921 @item info auto-load
25922 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
25926 (gdb) info auto-load
25929 Yes /home/user/gdb/gdb-gdb.gdb
25930 libthread-db: No auto-loaded libthread-db.
25931 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
25935 Yes /home/user/gdb/gdb-gdb.py
25939 These are @value{GDBN} control commands for the auto-loading:
25941 @multitable @columnfractions .5 .5
25942 @item @xref{set auto-load off}.
25943 @tab Disable auto-loading globally.
25944 @item @xref{show auto-load}.
25945 @tab Show setting of all kinds of files.
25946 @item @xref{info auto-load}.
25947 @tab Show state of all kinds of files.
25948 @item @xref{set auto-load gdb-scripts}.
25949 @tab Control for @value{GDBN} command scripts.
25950 @item @xref{show auto-load gdb-scripts}.
25951 @tab Show setting of @value{GDBN} command scripts.
25952 @item @xref{info auto-load gdb-scripts}.
25953 @tab Show state of @value{GDBN} command scripts.
25954 @item @xref{set auto-load python-scripts}.
25955 @tab Control for @value{GDBN} Python scripts.
25956 @item @xref{show auto-load python-scripts}.
25957 @tab Show setting of @value{GDBN} Python scripts.
25958 @item @xref{info auto-load python-scripts}.
25959 @tab Show state of @value{GDBN} Python scripts.
25960 @item @xref{set auto-load guile-scripts}.
25961 @tab Control for @value{GDBN} Guile scripts.
25962 @item @xref{show auto-load guile-scripts}.
25963 @tab Show setting of @value{GDBN} Guile scripts.
25964 @item @xref{info auto-load guile-scripts}.
25965 @tab Show state of @value{GDBN} Guile scripts.
25966 @item @xref{set auto-load scripts-directory}.
25967 @tab Control for @value{GDBN} auto-loaded scripts location.
25968 @item @xref{show auto-load scripts-directory}.
25969 @tab Show @value{GDBN} auto-loaded scripts location.
25970 @item @xref{add-auto-load-scripts-directory}.
25971 @tab Add directory for auto-loaded scripts location list.
25972 @item @xref{set auto-load local-gdbinit}.
25973 @tab Control for init file in the current directory.
25974 @item @xref{show auto-load local-gdbinit}.
25975 @tab Show setting of init file in the current directory.
25976 @item @xref{info auto-load local-gdbinit}.
25977 @tab Show state of init file in the current directory.
25978 @item @xref{set auto-load libthread-db}.
25979 @tab Control for thread debugging library.
25980 @item @xref{show auto-load libthread-db}.
25981 @tab Show setting of thread debugging library.
25982 @item @xref{info auto-load libthread-db}.
25983 @tab Show state of thread debugging library.
25984 @item @xref{set auto-load safe-path}.
25985 @tab Control directories trusted for automatic loading.
25986 @item @xref{show auto-load safe-path}.
25987 @tab Show directories trusted for automatic loading.
25988 @item @xref{add-auto-load-safe-path}.
25989 @tab Add directory trusted for automatic loading.
25992 @node Init File in the Current Directory
25993 @subsection Automatically loading init file in the current directory
25994 @cindex auto-loading init file in the current directory
25996 By default, @value{GDBN} reads and executes the canned sequences of commands
25997 from init file (if any) in the current working directory,
25998 see @ref{Init File in the Current Directory during Startup}.
26000 Note that loading of this local @file{.gdbinit} file also requires accordingly
26001 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26004 @anchor{set auto-load local-gdbinit}
26005 @kindex set auto-load local-gdbinit
26006 @item set auto-load local-gdbinit [on|off]
26007 Enable or disable the auto-loading of canned sequences of commands
26008 (@pxref{Sequences}) found in init file in the current directory.
26010 @anchor{show auto-load local-gdbinit}
26011 @kindex show auto-load local-gdbinit
26012 @item show auto-load local-gdbinit
26013 Show whether auto-loading of canned sequences of commands from init file in the
26014 current directory is enabled or disabled.
26016 @anchor{info auto-load local-gdbinit}
26017 @kindex info auto-load local-gdbinit
26018 @item info auto-load local-gdbinit
26019 Print whether canned sequences of commands from init file in the
26020 current directory have been auto-loaded.
26023 @node libthread_db.so.1 file
26024 @subsection Automatically loading thread debugging library
26025 @cindex auto-loading libthread_db.so.1
26027 This feature is currently present only on @sc{gnu}/Linux native hosts.
26029 @value{GDBN} reads in some cases thread debugging library from places specific
26030 to the inferior (@pxref{set libthread-db-search-path}).
26032 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
26033 without checking this @samp{set auto-load libthread-db} switch as system
26034 libraries have to be trusted in general. In all other cases of
26035 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
26036 auto-load libthread-db} is enabled before trying to open such thread debugging
26039 Note that loading of this debugging library also requires accordingly configured
26040 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26043 @anchor{set auto-load libthread-db}
26044 @kindex set auto-load libthread-db
26045 @item set auto-load libthread-db [on|off]
26046 Enable or disable the auto-loading of inferior specific thread debugging library.
26048 @anchor{show auto-load libthread-db}
26049 @kindex show auto-load libthread-db
26050 @item show auto-load libthread-db
26051 Show whether auto-loading of inferior specific thread debugging library is
26052 enabled or disabled.
26054 @anchor{info auto-load libthread-db}
26055 @kindex info auto-load libthread-db
26056 @item info auto-load libthread-db
26057 Print the list of all loaded inferior specific thread debugging libraries and
26058 for each such library print list of inferior @var{pid}s using it.
26061 @node Auto-loading safe path
26062 @subsection Security restriction for auto-loading
26063 @cindex auto-loading safe-path
26065 As the files of inferior can come from untrusted source (such as submitted by
26066 an application user) @value{GDBN} does not always load any files automatically.
26067 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
26068 directories trusted for loading files not explicitly requested by user.
26069 Each directory can also be a shell wildcard pattern.
26071 If the path is not set properly you will see a warning and the file will not
26076 Reading symbols from /home/user/gdb/gdb...
26077 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
26078 declined by your `auto-load safe-path' set
26079 to "$debugdir:$datadir/auto-load".
26080 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
26081 declined by your `auto-load safe-path' set
26082 to "$debugdir:$datadir/auto-load".
26086 To instruct @value{GDBN} to go ahead and use the init files anyway,
26087 invoke @value{GDBN} like this:
26090 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
26093 The list of trusted directories is controlled by the following commands:
26096 @anchor{set auto-load safe-path}
26097 @kindex set auto-load safe-path
26098 @item set auto-load safe-path @r{[}@var{directories}@r{]}
26099 Set the list of directories (and their subdirectories) trusted for automatic
26100 loading and execution of scripts. You can also enter a specific trusted file.
26101 Each directory can also be a shell wildcard pattern; wildcards do not match
26102 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
26103 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
26104 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
26105 its default value as specified during @value{GDBN} compilation.
26107 The list of directories uses path separator (@samp{:} on GNU and Unix
26108 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
26109 to the @env{PATH} environment variable.
26111 @anchor{show auto-load safe-path}
26112 @kindex show auto-load safe-path
26113 @item show auto-load safe-path
26114 Show the list of directories trusted for automatic loading and execution of
26117 @anchor{add-auto-load-safe-path}
26118 @kindex add-auto-load-safe-path
26119 @item add-auto-load-safe-path
26120 Add an entry (or list of entries) to the list of directories trusted for
26121 automatic loading and execution of scripts. Multiple entries may be delimited
26122 by the host platform path separator in use.
26125 This variable defaults to what @code{--with-auto-load-dir} has been configured
26126 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
26127 substitution applies the same as for @ref{set auto-load scripts-directory}.
26128 The default @code{set auto-load safe-path} value can be also overriden by
26129 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
26131 Setting this variable to @file{/} disables this security protection,
26132 corresponding @value{GDBN} configuration option is
26133 @option{--without-auto-load-safe-path}.
26134 This variable is supposed to be set to the system directories writable by the
26135 system superuser only. Users can add their source directories in init files in
26136 their home directories (@pxref{Home Directory Init File}). See also deprecated
26137 init file in the current directory
26138 (@pxref{Init File in the Current Directory during Startup}).
26140 To force @value{GDBN} to load the files it declined to load in the previous
26141 example, you could use one of the following ways:
26144 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
26145 Specify this trusted directory (or a file) as additional component of the list.
26146 You have to specify also any existing directories displayed by
26147 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
26149 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
26150 Specify this directory as in the previous case but just for a single
26151 @value{GDBN} session.
26153 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
26154 Disable auto-loading safety for a single @value{GDBN} session.
26155 This assumes all the files you debug during this @value{GDBN} session will come
26156 from trusted sources.
26158 @item @kbd{./configure --without-auto-load-safe-path}
26159 During compilation of @value{GDBN} you may disable any auto-loading safety.
26160 This assumes all the files you will ever debug with this @value{GDBN} come from
26164 On the other hand you can also explicitly forbid automatic files loading which
26165 also suppresses any such warning messages:
26168 @item @kbd{gdb -iex "set auto-load no" @dots{}}
26169 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
26171 @item @file{~/.gdbinit}: @samp{set auto-load no}
26172 Disable auto-loading globally for the user
26173 (@pxref{Home Directory Init File}). While it is improbable, you could also
26174 use system init file instead (@pxref{System-wide configuration}).
26177 This setting applies to the file names as entered by user. If no entry matches
26178 @value{GDBN} tries as a last resort to also resolve all the file names into
26179 their canonical form (typically resolving symbolic links) and compare the
26180 entries again. @value{GDBN} already canonicalizes most of the filenames on its
26181 own before starting the comparison so a canonical form of directories is
26182 recommended to be entered.
26184 @node Auto-loading verbose mode
26185 @subsection Displaying files tried for auto-load
26186 @cindex auto-loading verbose mode
26188 For better visibility of all the file locations where you can place scripts to
26189 be auto-loaded with inferior --- or to protect yourself against accidental
26190 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
26191 all the files attempted to be loaded. Both existing and non-existing files may
26194 For example the list of directories from which it is safe to auto-load files
26195 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
26196 may not be too obvious while setting it up.
26199 (gdb) set debug auto-load on
26200 (gdb) file ~/src/t/true
26201 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
26202 for objfile "/tmp/true".
26203 auto-load: Updating directories of "/usr:/opt".
26204 auto-load: Using directory "/usr".
26205 auto-load: Using directory "/opt".
26206 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
26207 by your `auto-load safe-path' set to "/usr:/opt".
26211 @anchor{set debug auto-load}
26212 @kindex set debug auto-load
26213 @item set debug auto-load [on|off]
26214 Set whether to print the filenames attempted to be auto-loaded.
26216 @anchor{show debug auto-load}
26217 @kindex show debug auto-load
26218 @item show debug auto-load
26219 Show whether printing of the filenames attempted to be auto-loaded is turned
26223 @node Messages/Warnings
26224 @section Optional Warnings and Messages
26226 @cindex verbose operation
26227 @cindex optional warnings
26228 By default, @value{GDBN} is silent about its inner workings. If you are
26229 running on a slow machine, you may want to use the @code{set verbose}
26230 command. This makes @value{GDBN} tell you when it does a lengthy
26231 internal operation, so you will not think it has crashed.
26233 Currently, the messages controlled by @code{set verbose} are those
26234 which announce that the symbol table for a source file is being read;
26235 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
26238 @kindex set verbose
26239 @item set verbose on
26240 Enables @value{GDBN} output of certain informational messages.
26242 @item set verbose off
26243 Disables @value{GDBN} output of certain informational messages.
26245 @kindex show verbose
26247 Displays whether @code{set verbose} is on or off.
26250 By default, if @value{GDBN} encounters bugs in the symbol table of an
26251 object file, it is silent; but if you are debugging a compiler, you may
26252 find this information useful (@pxref{Symbol Errors, ,Errors Reading
26257 @kindex set complaints
26258 @item set complaints @var{limit}
26259 Permits @value{GDBN} to output @var{limit} complaints about each type of
26260 unusual symbols before becoming silent about the problem. Set
26261 @var{limit} to zero to suppress all complaints; set it to a large number
26262 to prevent complaints from being suppressed.
26264 @kindex show complaints
26265 @item show complaints
26266 Displays how many symbol complaints @value{GDBN} is permitted to produce.
26270 @anchor{confirmation requests}
26271 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
26272 lot of stupid questions to confirm certain commands. For example, if
26273 you try to run a program which is already running:
26277 The program being debugged has been started already.
26278 Start it from the beginning? (y or n)
26281 If you are willing to unflinchingly face the consequences of your own
26282 commands, you can disable this ``feature'':
26286 @kindex set confirm
26288 @cindex confirmation
26289 @cindex stupid questions
26290 @item set confirm off
26291 Disables confirmation requests. Note that running @value{GDBN} with
26292 the @option{--batch} option (@pxref{Mode Options, -batch}) also
26293 automatically disables confirmation requests.
26295 @item set confirm on
26296 Enables confirmation requests (the default).
26298 @kindex show confirm
26300 Displays state of confirmation requests.
26304 @cindex command tracing
26305 If you need to debug user-defined commands or sourced files you may find it
26306 useful to enable @dfn{command tracing}. In this mode each command will be
26307 printed as it is executed, prefixed with one or more @samp{+} symbols, the
26308 quantity denoting the call depth of each command.
26311 @kindex set trace-commands
26312 @cindex command scripts, debugging
26313 @item set trace-commands on
26314 Enable command tracing.
26315 @item set trace-commands off
26316 Disable command tracing.
26317 @item show trace-commands
26318 Display the current state of command tracing.
26321 @node Debugging Output
26322 @section Optional Messages about Internal Happenings
26323 @cindex optional debugging messages
26325 @value{GDBN} has commands that enable optional debugging messages from
26326 various @value{GDBN} subsystems; normally these commands are of
26327 interest to @value{GDBN} maintainers, or when reporting a bug. This
26328 section documents those commands.
26331 @kindex set exec-done-display
26332 @item set exec-done-display
26333 Turns on or off the notification of asynchronous commands'
26334 completion. When on, @value{GDBN} will print a message when an
26335 asynchronous command finishes its execution. The default is off.
26336 @kindex show exec-done-display
26337 @item show exec-done-display
26338 Displays the current setting of asynchronous command completion
26341 @cindex ARM AArch64
26342 @item set debug aarch64
26343 Turns on or off display of debugging messages related to ARM AArch64.
26344 The default is off.
26346 @item show debug aarch64
26347 Displays the current state of displaying debugging messages related to
26349 @cindex gdbarch debugging info
26350 @cindex architecture debugging info
26351 @item set debug arch
26352 Turns on or off display of gdbarch debugging info. The default is off
26353 @item show debug arch
26354 Displays the current state of displaying gdbarch debugging info.
26355 @item set debug aix-solib
26356 @cindex AIX shared library debugging
26357 Control display of debugging messages from the AIX shared library
26358 support module. The default is off.
26359 @item show debug aix-thread
26360 Show the current state of displaying AIX shared library debugging messages.
26361 @item set debug aix-thread
26362 @cindex AIX threads
26363 Display debugging messages about inner workings of the AIX thread
26365 @item show debug aix-thread
26366 Show the current state of AIX thread debugging info display.
26367 @item set debug check-physname
26369 Check the results of the ``physname'' computation. When reading DWARF
26370 debugging information for C@t{++}, @value{GDBN} attempts to compute
26371 each entity's name. @value{GDBN} can do this computation in two
26372 different ways, depending on exactly what information is present.
26373 When enabled, this setting causes @value{GDBN} to compute the names
26374 both ways and display any discrepancies.
26375 @item show debug check-physname
26376 Show the current state of ``physname'' checking.
26377 @item set debug coff-pe-read
26378 @cindex COFF/PE exported symbols
26379 Control display of debugging messages related to reading of COFF/PE
26380 exported symbols. The default is off.
26381 @item show debug coff-pe-read
26382 Displays the current state of displaying debugging messages related to
26383 reading of COFF/PE exported symbols.
26384 @item set debug dwarf-die
26386 Dump DWARF DIEs after they are read in.
26387 The value is the number of nesting levels to print.
26388 A value of zero turns off the display.
26389 @item show debug dwarf-die
26390 Show the current state of DWARF DIE debugging.
26391 @item set debug dwarf-line
26392 @cindex DWARF Line Tables
26393 Turns on or off display of debugging messages related to reading
26394 DWARF line tables. The default is 0 (off).
26395 A value of 1 provides basic information.
26396 A value greater than 1 provides more verbose information.
26397 @item show debug dwarf-line
26398 Show the current state of DWARF line table debugging.
26399 @item set debug dwarf-read
26400 @cindex DWARF Reading
26401 Turns on or off display of debugging messages related to reading
26402 DWARF debug info. The default is 0 (off).
26403 A value of 1 provides basic information.
26404 A value greater than 1 provides more verbose information.
26405 @item show debug dwarf-read
26406 Show the current state of DWARF reader debugging.
26407 @item set debug displaced
26408 @cindex displaced stepping debugging info
26409 Turns on or off display of @value{GDBN} debugging info for the
26410 displaced stepping support. The default is off.
26411 @item show debug displaced
26412 Displays the current state of displaying @value{GDBN} debugging info
26413 related to displaced stepping.
26414 @item set debug event
26415 @cindex event debugging info
26416 Turns on or off display of @value{GDBN} event debugging info. The
26418 @item show debug event
26419 Displays the current state of displaying @value{GDBN} event debugging
26421 @item set debug expression
26422 @cindex expression debugging info
26423 Turns on or off display of debugging info about @value{GDBN}
26424 expression parsing. The default is off.
26425 @item show debug expression
26426 Displays the current state of displaying debugging info about
26427 @value{GDBN} expression parsing.
26428 @item set debug fbsd-lwp
26429 @cindex FreeBSD LWP debug messages
26430 Turns on or off debugging messages from the FreeBSD LWP debug support.
26431 @item show debug fbsd-lwp
26432 Show the current state of FreeBSD LWP debugging messages.
26433 @item set debug fbsd-nat
26434 @cindex FreeBSD native target debug messages
26435 Turns on or off debugging messages from the FreeBSD native target.
26436 @item show debug fbsd-nat
26437 Show the current state of FreeBSD native target debugging messages.
26438 @item set debug frame
26439 @cindex frame debugging info
26440 Turns on or off display of @value{GDBN} frame debugging info. The
26442 @item show debug frame
26443 Displays the current state of displaying @value{GDBN} frame debugging
26445 @item set debug gnu-nat
26446 @cindex @sc{gnu}/Hurd debug messages
26447 Turn on or off debugging messages from the @sc{gnu}/Hurd debug support.
26448 @item show debug gnu-nat
26449 Show the current state of @sc{gnu}/Hurd debugging messages.
26450 @item set debug infrun
26451 @cindex inferior debugging info
26452 Turns on or off display of @value{GDBN} debugging info for running the inferior.
26453 The default is off. @file{infrun.c} contains GDB's runtime state machine used
26454 for implementing operations such as single-stepping the inferior.
26455 @item show debug infrun
26456 Displays the current state of @value{GDBN} inferior debugging.
26457 @item set debug jit
26458 @cindex just-in-time compilation, debugging messages
26459 Turn on or off debugging messages from JIT debug support.
26460 @item show debug jit
26461 Displays the current state of @value{GDBN} JIT debugging.
26462 @item set debug lin-lwp
26463 @cindex @sc{gnu}/Linux LWP debug messages
26464 @cindex Linux lightweight processes
26465 Turn on or off debugging messages from the Linux LWP debug support.
26466 @item show debug lin-lwp
26467 Show the current state of Linux LWP debugging messages.
26468 @item set debug linux-namespaces
26469 @cindex @sc{gnu}/Linux namespaces debug messages
26470 Turn on or off debugging messages from the Linux namespaces debug support.
26471 @item show debug linux-namespaces
26472 Show the current state of Linux namespaces debugging messages.
26473 @item set debug mach-o
26474 @cindex Mach-O symbols processing
26475 Control display of debugging messages related to Mach-O symbols
26476 processing. The default is off.
26477 @item show debug mach-o
26478 Displays the current state of displaying debugging messages related to
26479 reading of COFF/PE exported symbols.
26480 @item set debug notification
26481 @cindex remote async notification debugging info
26482 Turn on or off debugging messages about remote async notification.
26483 The default is off.
26484 @item show debug notification
26485 Displays the current state of remote async notification debugging messages.
26486 @item set debug observer
26487 @cindex observer debugging info
26488 Turns on or off display of @value{GDBN} observer debugging. This
26489 includes info such as the notification of observable events.
26490 @item show debug observer
26491 Displays the current state of observer debugging.
26492 @item set debug overload
26493 @cindex C@t{++} overload debugging info
26494 Turns on or off display of @value{GDBN} C@t{++} overload debugging
26495 info. This includes info such as ranking of functions, etc. The default
26497 @item show debug overload
26498 Displays the current state of displaying @value{GDBN} C@t{++} overload
26500 @cindex expression parser, debugging info
26501 @cindex debug expression parser
26502 @item set debug parser
26503 Turns on or off the display of expression parser debugging output.
26504 Internally, this sets the @code{yydebug} variable in the expression
26505 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
26506 details. The default is off.
26507 @item show debug parser
26508 Show the current state of expression parser debugging.
26509 @cindex packets, reporting on stdout
26510 @cindex serial connections, debugging
26511 @cindex debug remote protocol
26512 @cindex remote protocol debugging
26513 @cindex display remote packets
26514 @item set debug remote
26515 Turns on or off display of reports on all packets sent back and forth across
26516 the serial line to the remote machine. The info is printed on the
26517 @value{GDBN} standard output stream. The default is off.
26518 @item show debug remote
26519 Displays the state of display of remote packets.
26521 @item set debug remote-packet-max-chars
26522 Sets the maximum number of characters to display for each remote packet when
26523 @code{set debug remote} is on. This is useful to prevent @value{GDBN} from
26524 displaying lengthy remote packets and polluting the console.
26526 The default value is @code{512}, which means @value{GDBN} will truncate each
26527 remote packet after 512 bytes.
26529 Setting this option to @code{unlimited} will disable truncation and will output
26530 the full length of the remote packets.
26531 @item show debug remote-packet-max-chars
26532 Displays the number of bytes to output for remote packet debugging.
26534 @item set debug separate-debug-file
26535 Turns on or off display of debug output about separate debug file search.
26536 @item show debug separate-debug-file
26537 Displays the state of separate debug file search debug output.
26539 @item set debug serial
26540 Turns on or off display of @value{GDBN} serial debugging info. The
26542 @item show debug serial
26543 Displays the current state of displaying @value{GDBN} serial debugging
26545 @item set debug solib-frv
26546 @cindex FR-V shared-library debugging
26547 Turn on or off debugging messages for FR-V shared-library code.
26548 @item show debug solib-frv
26549 Display the current state of FR-V shared-library code debugging
26551 @item set debug symbol-lookup
26552 @cindex symbol lookup
26553 Turns on or off display of debugging messages related to symbol lookup.
26554 The default is 0 (off).
26555 A value of 1 provides basic information.
26556 A value greater than 1 provides more verbose information.
26557 @item show debug symbol-lookup
26558 Show the current state of symbol lookup debugging messages.
26559 @item set debug symfile
26560 @cindex symbol file functions
26561 Turns on or off display of debugging messages related to symbol file functions.
26562 The default is off. @xref{Files}.
26563 @item show debug symfile
26564 Show the current state of symbol file debugging messages.
26565 @item set debug symtab-create
26566 @cindex symbol table creation
26567 Turns on or off display of debugging messages related to symbol table creation.
26568 The default is 0 (off).
26569 A value of 1 provides basic information.
26570 A value greater than 1 provides more verbose information.
26571 @item show debug symtab-create
26572 Show the current state of symbol table creation debugging.
26573 @item set debug target
26574 @cindex target debugging info
26575 Turns on or off display of @value{GDBN} target debugging info. This info
26576 includes what is going on at the target level of GDB, as it happens. The
26577 default is 0. Set it to 1 to track events, and to 2 to also track the
26578 value of large memory transfers.
26579 @item show debug target
26580 Displays the current state of displaying @value{GDBN} target debugging
26582 @item set debug timestamp
26583 @cindex timestamping debugging info
26584 Turns on or off display of timestamps with @value{GDBN} debugging info.
26585 When enabled, seconds and microseconds are displayed before each debugging
26587 @item show debug timestamp
26588 Displays the current state of displaying timestamps with @value{GDBN}
26590 @item set debug varobj
26591 @cindex variable object debugging info
26592 Turns on or off display of @value{GDBN} variable object debugging
26593 info. The default is off.
26594 @item show debug varobj
26595 Displays the current state of displaying @value{GDBN} variable object
26597 @item set debug xml
26598 @cindex XML parser debugging
26599 Turn on or off debugging messages for built-in XML parsers.
26600 @item show debug xml
26601 Displays the current state of XML debugging messages.
26604 @node Other Misc Settings
26605 @section Other Miscellaneous Settings
26606 @cindex miscellaneous settings
26609 @kindex set interactive-mode
26610 @item set interactive-mode
26611 If @code{on}, forces @value{GDBN} to assume that GDB was started
26612 in a terminal. In practice, this means that @value{GDBN} should wait
26613 for the user to answer queries generated by commands entered at
26614 the command prompt. If @code{off}, forces @value{GDBN} to operate
26615 in the opposite mode, and it uses the default answers to all queries.
26616 If @code{auto} (the default), @value{GDBN} tries to determine whether
26617 its standard input is a terminal, and works in interactive-mode if it
26618 is, non-interactively otherwise.
26620 In the vast majority of cases, the debugger should be able to guess
26621 correctly which mode should be used. But this setting can be useful
26622 in certain specific cases, such as running a MinGW @value{GDBN}
26623 inside a cygwin window.
26625 @kindex show interactive-mode
26626 @item show interactive-mode
26627 Displays whether the debugger is operating in interactive mode or not.
26630 @node Extending GDB
26631 @chapter Extending @value{GDBN}
26632 @cindex extending GDB
26634 @value{GDBN} provides several mechanisms for extension.
26635 @value{GDBN} also provides the ability to automatically load
26636 extensions when it reads a file for debugging. This allows the
26637 user to automatically customize @value{GDBN} for the program
26641 * Sequences:: Canned Sequences of @value{GDBN} Commands
26642 * Python:: Extending @value{GDBN} using Python
26643 * Guile:: Extending @value{GDBN} using Guile
26644 * Auto-loading extensions:: Automatically loading extensions
26645 * Multiple Extension Languages:: Working with multiple extension languages
26646 * Aliases:: Creating new spellings of existing commands
26649 To facilitate the use of extension languages, @value{GDBN} is capable
26650 of evaluating the contents of a file. When doing so, @value{GDBN}
26651 can recognize which extension language is being used by looking at
26652 the filename extension. Files with an unrecognized filename extension
26653 are always treated as a @value{GDBN} Command Files.
26654 @xref{Command Files,, Command files}.
26656 You can control how @value{GDBN} evaluates these files with the following
26660 @kindex set script-extension
26661 @kindex show script-extension
26662 @item set script-extension off
26663 All scripts are always evaluated as @value{GDBN} Command Files.
26665 @item set script-extension soft
26666 The debugger determines the scripting language based on filename
26667 extension. If this scripting language is supported, @value{GDBN}
26668 evaluates the script using that language. Otherwise, it evaluates
26669 the file as a @value{GDBN} Command File.
26671 @item set script-extension strict
26672 The debugger determines the scripting language based on filename
26673 extension, and evaluates the script using that language. If the
26674 language is not supported, then the evaluation fails.
26676 @item show script-extension
26677 Display the current value of the @code{script-extension} option.
26681 @ifset SYSTEM_GDBINIT_DIR
26682 This setting is not used for files in the system-wide gdbinit directory.
26683 Files in that directory must have an extension matching their language,
26684 or have a @file{.gdb} extension to be interpreted as regular @value{GDBN}
26685 commands. @xref{Startup}.
26689 @section Canned Sequences of Commands
26691 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
26692 Command Lists}), @value{GDBN} provides two ways to store sequences of
26693 commands for execution as a unit: user-defined commands and command
26697 * Define:: How to define your own commands
26698 * Hooks:: Hooks for user-defined commands
26699 * Command Files:: How to write scripts of commands to be stored in a file
26700 * Output:: Commands for controlled output
26701 * Auto-loading sequences:: Controlling auto-loaded command files
26705 @subsection User-defined Commands
26707 @cindex user-defined command
26708 @cindex arguments, to user-defined commands
26709 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
26710 which you assign a new name as a command. This is done with the
26711 @code{define} command. User commands may accept an unlimited number of arguments
26712 separated by whitespace. Arguments are accessed within the user command
26713 via @code{$arg0@dots{}$argN}. A trivial example:
26717 print $arg0 + $arg1 + $arg2
26722 To execute the command use:
26729 This defines the command @code{adder}, which prints the sum of
26730 its three arguments. Note the arguments are text substitutions, so they may
26731 reference variables, use complex expressions, or even perform inferior
26734 @cindex argument count in user-defined commands
26735 @cindex how many arguments (user-defined commands)
26736 In addition, @code{$argc} may be used to find out how many arguments have
26742 print $arg0 + $arg1
26745 print $arg0 + $arg1 + $arg2
26750 Combining with the @code{eval} command (@pxref{eval}) makes it easier
26751 to process a variable number of arguments:
26758 eval "set $sum = $sum + $arg%d", $i
26768 @item define @var{commandname}
26769 Define a command named @var{commandname}. If there is already a command
26770 by that name, you are asked to confirm that you want to redefine it.
26771 The argument @var{commandname} may be a bare command name consisting of letters,
26772 numbers, dashes, dots, and underscores. It may also start with any
26773 predefined or user-defined prefix command.
26774 For example, @samp{define target my-target} creates
26775 a user-defined @samp{target my-target} command.
26777 The definition of the command is made up of other @value{GDBN} command lines,
26778 which are given following the @code{define} command. The end of these
26779 commands is marked by a line containing @code{end}.
26782 @kindex end@r{ (user-defined commands)}
26783 @item document @var{commandname}
26784 Document the user-defined command @var{commandname}, so that it can be
26785 accessed by @code{help}. The command @var{commandname} must already be
26786 defined. This command reads lines of documentation just as @code{define}
26787 reads the lines of the command definition, ending with @code{end}.
26788 After the @code{document} command is finished, @code{help} on command
26789 @var{commandname} displays the documentation you have written.
26791 You may use the @code{document} command again to change the
26792 documentation of a command. Redefining the command with @code{define}
26793 does not change the documentation.
26795 @kindex define-prefix
26796 @item define-prefix @var{commandname}
26797 Define or mark the command @var{commandname} as a user-defined prefix
26798 command. Once marked, @var{commandname} can be used as prefix command
26799 by the @code{define} command.
26800 Note that @code{define-prefix} can be used with a not yet defined
26801 @var{commandname}. In such a case, @var{commandname} is defined as
26802 an empty user-defined command.
26803 In case you redefine a command that was marked as a user-defined
26804 prefix command, the subcommands of the redefined command are kept
26805 (and @value{GDBN} indicates so to the user).
26809 (gdb) define-prefix abc
26810 (gdb) define-prefix abc def
26811 (gdb) define abc def
26812 Type commands for definition of "abc def".
26813 End with a line saying just "end".
26814 >echo command initial def\n
26816 (gdb) define abc def ghi
26817 Type commands for definition of "abc def ghi".
26818 End with a line saying just "end".
26819 >echo command ghi\n
26821 (gdb) define abc def
26822 Keeping subcommands of prefix command "def".
26823 Redefine command "def"? (y or n) y
26824 Type commands for definition of "abc def".
26825 End with a line saying just "end".
26826 >echo command def\n
26835 @kindex dont-repeat
26836 @cindex don't repeat command
26838 Used inside a user-defined command, this tells @value{GDBN} that this
26839 command should not be repeated when the user hits @key{RET}
26840 (@pxref{Command Syntax, repeat last command}).
26842 @kindex help user-defined
26843 @item help user-defined
26844 List all user-defined commands and all python commands defined in class
26845 COMMAND_USER. The first line of the documentation or docstring is
26850 @itemx show user @var{commandname}
26851 Display the @value{GDBN} commands used to define @var{commandname} (but
26852 not its documentation). If no @var{commandname} is given, display the
26853 definitions for all user-defined commands.
26854 This does not work for user-defined python commands.
26856 @cindex infinite recursion in user-defined commands
26857 @kindex show max-user-call-depth
26858 @kindex set max-user-call-depth
26859 @item show max-user-call-depth
26860 @itemx set max-user-call-depth
26861 The value of @code{max-user-call-depth} controls how many recursion
26862 levels are allowed in user-defined commands before @value{GDBN} suspects an
26863 infinite recursion and aborts the command.
26864 This does not apply to user-defined python commands.
26867 In addition to the above commands, user-defined commands frequently
26868 use control flow commands, described in @ref{Command Files}.
26870 When user-defined commands are executed, the
26871 commands of the definition are not printed. An error in any command
26872 stops execution of the user-defined command.
26874 If used interactively, commands that would ask for confirmation proceed
26875 without asking when used inside a user-defined command. Many @value{GDBN}
26876 commands that normally print messages to say what they are doing omit the
26877 messages when used in a user-defined command.
26880 @subsection User-defined Command Hooks
26881 @cindex command hooks
26882 @cindex hooks, for commands
26883 @cindex hooks, pre-command
26886 You may define @dfn{hooks}, which are a special kind of user-defined
26887 command. Whenever you run the command @samp{foo}, if the user-defined
26888 command @samp{hook-foo} exists, it is executed (with no arguments)
26889 before that command.
26891 @cindex hooks, post-command
26893 A hook may also be defined which is run after the command you executed.
26894 Whenever you run the command @samp{foo}, if the user-defined command
26895 @samp{hookpost-foo} exists, it is executed (with no arguments) after
26896 that command. Post-execution hooks may exist simultaneously with
26897 pre-execution hooks, for the same command.
26899 It is valid for a hook to call the command which it hooks. If this
26900 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
26902 @c It would be nice if hookpost could be passed a parameter indicating
26903 @c if the command it hooks executed properly or not. FIXME!
26905 @kindex stop@r{, a pseudo-command}
26906 In addition, a pseudo-command, @samp{stop} exists. Defining
26907 (@samp{hook-stop}) makes the associated commands execute every time
26908 execution stops in your program: before breakpoint commands are run,
26909 displays are printed, or the stack frame is printed.
26911 For example, to ignore @code{SIGALRM} signals while
26912 single-stepping, but treat them normally during normal execution,
26917 handle SIGALRM nopass
26921 handle SIGALRM pass
26924 define hook-continue
26925 handle SIGALRM pass
26929 As a further example, to hook at the beginning and end of the @code{echo}
26930 command, and to add extra text to the beginning and end of the message,
26938 define hookpost-echo
26942 (@value{GDBP}) echo Hello World
26943 <<<---Hello World--->>>
26948 You can define a hook for any single-word command in @value{GDBN}, but
26949 not for command aliases; you should define a hook for the basic command
26950 name, e.g.@: @code{backtrace} rather than @code{bt}.
26951 @c FIXME! So how does Joe User discover whether a command is an alias
26953 You can hook a multi-word command by adding @code{hook-} or
26954 @code{hookpost-} to the last word of the command, e.g.@:
26955 @samp{define target hook-remote} to add a hook to @samp{target remote}.
26957 If an error occurs during the execution of your hook, execution of
26958 @value{GDBN} commands stops and @value{GDBN} issues a prompt
26959 (before the command that you actually typed had a chance to run).
26961 If you try to define a hook which does not match any known command, you
26962 get a warning from the @code{define} command.
26964 @node Command Files
26965 @subsection Command Files
26967 @cindex command files
26968 @cindex scripting commands
26969 A command file for @value{GDBN} is a text file made of lines that are
26970 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
26971 also be included. An empty line in a command file does nothing; it
26972 does not mean to repeat the last command, as it would from the
26975 You can request the execution of a command file with the @code{source}
26976 command. Note that the @code{source} command is also used to evaluate
26977 scripts that are not Command Files. The exact behavior can be configured
26978 using the @code{script-extension} setting.
26979 @xref{Extending GDB,, Extending GDB}.
26983 @cindex execute commands from a file
26984 @item source [-s] [-v] @var{filename}
26985 Execute the command file @var{filename}.
26988 The lines in a command file are generally executed sequentially,
26989 unless the order of execution is changed by one of the
26990 @emph{flow-control commands} described below. The commands are not
26991 printed as they are executed. An error in any command terminates
26992 execution of the command file and control is returned to the console.
26994 @value{GDBN} first searches for @var{filename} in the current directory.
26995 If the file is not found there, and @var{filename} does not specify a
26996 directory, then @value{GDBN} also looks for the file on the source search path
26997 (specified with the @samp{directory} command);
26998 except that @file{$cdir} is not searched because the compilation directory
26999 is not relevant to scripts.
27001 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
27002 on the search path even if @var{filename} specifies a directory.
27003 The search is done by appending @var{filename} to each element of the
27004 search path. So, for example, if @var{filename} is @file{mylib/myscript}
27005 and the search path contains @file{/home/user} then @value{GDBN} will
27006 look for the script @file{/home/user/mylib/myscript}.
27007 The search is also done if @var{filename} is an absolute path.
27008 For example, if @var{filename} is @file{/tmp/myscript} and
27009 the search path contains @file{/home/user} then @value{GDBN} will
27010 look for the script @file{/home/user/tmp/myscript}.
27011 For DOS-like systems, if @var{filename} contains a drive specification,
27012 it is stripped before concatenation. For example, if @var{filename} is
27013 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
27014 will look for the script @file{c:/tmp/myscript}.
27016 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
27017 each command as it is executed. The option must be given before
27018 @var{filename}, and is interpreted as part of the filename anywhere else.
27020 Commands that would ask for confirmation if used interactively proceed
27021 without asking when used in a command file. Many @value{GDBN} commands that
27022 normally print messages to say what they are doing omit the messages
27023 when called from command files.
27025 @value{GDBN} also accepts command input from standard input. In this
27026 mode, normal output goes to standard output and error output goes to
27027 standard error. Errors in a command file supplied on standard input do
27028 not terminate execution of the command file---execution continues with
27032 gdb < cmds > log 2>&1
27035 (The syntax above will vary depending on the shell used.) This example
27036 will execute commands from the file @file{cmds}. All output and errors
27037 would be directed to @file{log}.
27039 Since commands stored on command files tend to be more general than
27040 commands typed interactively, they frequently need to deal with
27041 complicated situations, such as different or unexpected values of
27042 variables and symbols, changes in how the program being debugged is
27043 built, etc. @value{GDBN} provides a set of flow-control commands to
27044 deal with these complexities. Using these commands, you can write
27045 complex scripts that loop over data structures, execute commands
27046 conditionally, etc.
27053 This command allows to include in your script conditionally executed
27054 commands. The @code{if} command takes a single argument, which is an
27055 expression to evaluate. It is followed by a series of commands that
27056 are executed only if the expression is true (its value is nonzero).
27057 There can then optionally be an @code{else} line, followed by a series
27058 of commands that are only executed if the expression was false. The
27059 end of the list is marked by a line containing @code{end}.
27063 This command allows to write loops. Its syntax is similar to
27064 @code{if}: the command takes a single argument, which is an expression
27065 to evaluate, and must be followed by the commands to execute, one per
27066 line, terminated by an @code{end}. These commands are called the
27067 @dfn{body} of the loop. The commands in the body of @code{while} are
27068 executed repeatedly as long as the expression evaluates to true.
27072 This command exits the @code{while} loop in whose body it is included.
27073 Execution of the script continues after that @code{while}s @code{end}
27076 @kindex loop_continue
27077 @item loop_continue
27078 This command skips the execution of the rest of the body of commands
27079 in the @code{while} loop in whose body it is included. Execution
27080 branches to the beginning of the @code{while} loop, where it evaluates
27081 the controlling expression.
27083 @kindex end@r{ (if/else/while commands)}
27085 Terminate the block of commands that are the body of @code{if},
27086 @code{else}, or @code{while} flow-control commands.
27091 @subsection Commands for Controlled Output
27093 During the execution of a command file or a user-defined command, normal
27094 @value{GDBN} output is suppressed; the only output that appears is what is
27095 explicitly printed by the commands in the definition. This section
27096 describes three commands useful for generating exactly the output you
27101 @item echo @var{text}
27102 @c I do not consider backslash-space a standard C escape sequence
27103 @c because it is not in ANSI.
27104 Print @var{text}. Nonprinting characters can be included in
27105 @var{text} using C escape sequences, such as @samp{\n} to print a
27106 newline. @strong{No newline is printed unless you specify one.}
27107 In addition to the standard C escape sequences, a backslash followed
27108 by a space stands for a space. This is useful for displaying a
27109 string with spaces at the beginning or the end, since leading and
27110 trailing spaces are otherwise trimmed from all arguments.
27111 To print @samp{@w{ }and foo =@w{ }}, use the command
27112 @samp{echo \@w{ }and foo = \@w{ }}.
27114 A backslash at the end of @var{text} can be used, as in C, to continue
27115 the command onto subsequent lines. For example,
27118 echo This is some text\n\
27119 which is continued\n\
27120 onto several lines.\n
27123 produces the same output as
27126 echo This is some text\n
27127 echo which is continued\n
27128 echo onto several lines.\n
27132 @item output @var{expression}
27133 Print the value of @var{expression} and nothing but that value: no
27134 newlines, no @samp{$@var{nn} = }. The value is not entered in the
27135 value history either. @xref{Expressions, ,Expressions}, for more information
27138 @item output/@var{fmt} @var{expression}
27139 Print the value of @var{expression} in format @var{fmt}. You can use
27140 the same formats as for @code{print}. @xref{Output Formats,,Output
27141 Formats}, for more information.
27144 @item printf @var{template}, @var{expressions}@dots{}
27145 Print the values of one or more @var{expressions} under the control of
27146 the string @var{template}. To print several values, make
27147 @var{expressions} be a comma-separated list of individual expressions,
27148 which may be either numbers or pointers. Their values are printed as
27149 specified by @var{template}, exactly as a C program would do by
27150 executing the code below:
27153 printf (@var{template}, @var{expressions}@dots{});
27156 As in @code{C} @code{printf}, ordinary characters in @var{template}
27157 are printed verbatim, while @dfn{conversion specification} introduced
27158 by the @samp{%} character cause subsequent @var{expressions} to be
27159 evaluated, their values converted and formatted according to type and
27160 style information encoded in the conversion specifications, and then
27163 For example, you can print two values in hex like this:
27166 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
27169 @code{printf} supports all the standard @code{C} conversion
27170 specifications, including the flags and modifiers between the @samp{%}
27171 character and the conversion letter, with the following exceptions:
27175 The argument-ordering modifiers, such as @samp{2$}, are not supported.
27178 The modifier @samp{*} is not supported for specifying precision or
27182 The @samp{'} flag (for separation of digits into groups according to
27183 @code{LC_NUMERIC'}) is not supported.
27186 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
27190 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
27193 The conversion letters @samp{a} and @samp{A} are not supported.
27197 Note that the @samp{ll} type modifier is supported only if the
27198 underlying @code{C} implementation used to build @value{GDBN} supports
27199 the @code{long long int} type, and the @samp{L} type modifier is
27200 supported only if @code{long double} type is available.
27202 As in @code{C}, @code{printf} supports simple backslash-escape
27203 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
27204 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
27205 single character. Octal and hexadecimal escape sequences are not
27208 Additionally, @code{printf} supports conversion specifications for DFP
27209 (@dfn{Decimal Floating Point}) types using the following length modifiers
27210 together with a floating point specifier.
27215 @samp{H} for printing @code{Decimal32} types.
27218 @samp{D} for printing @code{Decimal64} types.
27221 @samp{DD} for printing @code{Decimal128} types.
27224 If the underlying @code{C} implementation used to build @value{GDBN} has
27225 support for the three length modifiers for DFP types, other modifiers
27226 such as width and precision will also be available for @value{GDBN} to use.
27228 In case there is no such @code{C} support, no additional modifiers will be
27229 available and the value will be printed in the standard way.
27231 Here's an example of printing DFP types using the above conversion letters:
27233 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
27238 @item eval @var{template}, @var{expressions}@dots{}
27239 Convert the values of one or more @var{expressions} under the control of
27240 the string @var{template} to a command line, and call it.
27244 @node Auto-loading sequences
27245 @subsection Controlling auto-loading native @value{GDBN} scripts
27246 @cindex native script auto-loading
27248 When a new object file is read (for example, due to the @code{file}
27249 command, or because the inferior has loaded a shared library),
27250 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
27251 @xref{Auto-loading extensions}.
27253 Auto-loading can be enabled or disabled,
27254 and the list of auto-loaded scripts can be printed.
27257 @anchor{set auto-load gdb-scripts}
27258 @kindex set auto-load gdb-scripts
27259 @item set auto-load gdb-scripts [on|off]
27260 Enable or disable the auto-loading of canned sequences of commands scripts.
27262 @anchor{show auto-load gdb-scripts}
27263 @kindex show auto-load gdb-scripts
27264 @item show auto-load gdb-scripts
27265 Show whether auto-loading of canned sequences of commands scripts is enabled or
27268 @anchor{info auto-load gdb-scripts}
27269 @kindex info auto-load gdb-scripts
27270 @cindex print list of auto-loaded canned sequences of commands scripts
27271 @item info auto-load gdb-scripts [@var{regexp}]
27272 Print the list of all canned sequences of commands scripts that @value{GDBN}
27276 If @var{regexp} is supplied only canned sequences of commands scripts with
27277 matching names are printed.
27279 @c Python docs live in a separate file.
27280 @include python.texi
27282 @c Guile docs live in a separate file.
27283 @include guile.texi
27285 @node Auto-loading extensions
27286 @section Auto-loading extensions
27287 @cindex auto-loading extensions
27289 @value{GDBN} provides two mechanisms for automatically loading extensions
27290 when a new object file is read (for example, due to the @code{file}
27291 command, or because the inferior has loaded a shared library):
27292 @file{@var{objfile}-gdb.@var{ext}} and the @code{.debug_gdb_scripts}
27293 section of modern file formats like ELF.
27296 * objfile-gdb.ext file: objfile-gdbdotext file. The @file{@var{objfile}-gdb.@var{ext}} file
27297 * .debug_gdb_scripts section: dotdebug_gdb_scripts section. The @code{.debug_gdb_scripts} section
27298 * Which flavor to choose?::
27301 The auto-loading feature is useful for supplying application-specific
27302 debugging commands and features.
27304 Auto-loading can be enabled or disabled,
27305 and the list of auto-loaded scripts can be printed.
27306 See the @samp{auto-loading} section of each extension language
27307 for more information.
27308 For @value{GDBN} command files see @ref{Auto-loading sequences}.
27309 For Python files see @ref{Python Auto-loading}.
27311 Note that loading of this script file also requires accordingly configured
27312 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
27314 @node objfile-gdbdotext file
27315 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
27316 @cindex @file{@var{objfile}-gdb.gdb}
27317 @cindex @file{@var{objfile}-gdb.py}
27318 @cindex @file{@var{objfile}-gdb.scm}
27320 When a new object file is read, @value{GDBN} looks for a file named
27321 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
27322 where @var{objfile} is the object file's name and
27323 where @var{ext} is the file extension for the extension language:
27326 @item @file{@var{objfile}-gdb.gdb}
27327 GDB's own command language
27328 @item @file{@var{objfile}-gdb.py}
27330 @item @file{@var{objfile}-gdb.scm}
27334 @var{script-name} is formed by ensuring that the file name of @var{objfile}
27335 is absolute, following all symlinks, and resolving @code{.} and @code{..}
27336 components, and appending the @file{-gdb.@var{ext}} suffix.
27337 If this file exists and is readable, @value{GDBN} will evaluate it as a
27338 script in the specified extension language.
27340 If this file does not exist, then @value{GDBN} will look for
27341 @var{script-name} file in all of the directories as specified below.
27343 Note that loading of these files requires an accordingly configured
27344 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
27346 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
27347 scripts normally according to its @file{.exe} filename. But if no scripts are
27348 found @value{GDBN} also tries script filenames matching the object file without
27349 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
27350 is attempted on any platform. This makes the script filenames compatible
27351 between Unix and MS-Windows hosts.
27354 @anchor{set auto-load scripts-directory}
27355 @kindex set auto-load scripts-directory
27356 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
27357 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
27358 may be delimited by the host platform path separator in use
27359 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
27361 Each entry here needs to be covered also by the security setting
27362 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
27364 @anchor{with-auto-load-dir}
27365 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
27366 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
27367 configuration option @option{--with-auto-load-dir}.
27369 Any reference to @file{$debugdir} will get replaced by
27370 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
27371 reference to @file{$datadir} will get replaced by @var{data-directory} which is
27372 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
27373 @file{$datadir} must be placed as a directory component --- either alone or
27374 delimited by @file{/} or @file{\} directory separators, depending on the host
27377 The list of directories uses path separator (@samp{:} on GNU and Unix
27378 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
27379 to the @env{PATH} environment variable.
27381 @anchor{show auto-load scripts-directory}
27382 @kindex show auto-load scripts-directory
27383 @item show auto-load scripts-directory
27384 Show @value{GDBN} auto-loaded scripts location.
27386 @anchor{add-auto-load-scripts-directory}
27387 @kindex add-auto-load-scripts-directory
27388 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
27389 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
27390 Multiple entries may be delimited by the host platform path separator in use.
27393 @value{GDBN} does not track which files it has already auto-loaded this way.
27394 @value{GDBN} will load the associated script every time the corresponding
27395 @var{objfile} is opened.
27396 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
27397 is evaluated more than once.
27399 @node dotdebug_gdb_scripts section
27400 @subsection The @code{.debug_gdb_scripts} section
27401 @cindex @code{.debug_gdb_scripts} section
27403 For systems using file formats like ELF and COFF,
27404 when @value{GDBN} loads a new object file
27405 it will look for a special section named @code{.debug_gdb_scripts}.
27406 If this section exists, its contents is a list of null-terminated entries
27407 specifying scripts to load. Each entry begins with a non-null prefix byte that
27408 specifies the kind of entry, typically the extension language and whether the
27409 script is in a file or inlined in @code{.debug_gdb_scripts}.
27411 The following entries are supported:
27414 @item SECTION_SCRIPT_ID_PYTHON_FILE = 1
27415 @item SECTION_SCRIPT_ID_SCHEME_FILE = 3
27416 @item SECTION_SCRIPT_ID_PYTHON_TEXT = 4
27417 @item SECTION_SCRIPT_ID_SCHEME_TEXT = 6
27420 @subsubsection Script File Entries
27422 If the entry specifies a file, @value{GDBN} will look for the file first
27423 in the current directory and then along the source search path
27424 (@pxref{Source Path, ,Specifying Source Directories}),
27425 except that @file{$cdir} is not searched, since the compilation
27426 directory is not relevant to scripts.
27428 File entries can be placed in section @code{.debug_gdb_scripts} with,
27429 for example, this GCC macro for Python scripts.
27432 /* Note: The "MS" section flags are to remove duplicates. */
27433 #define DEFINE_GDB_PY_SCRIPT(script_name) \
27435 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
27436 .byte 1 /* Python */\n\
27437 .asciz \"" script_name "\"\n\
27443 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
27444 Then one can reference the macro in a header or source file like this:
27447 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
27450 The script name may include directories if desired.
27452 Note that loading of this script file also requires accordingly configured
27453 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
27455 If the macro invocation is put in a header, any application or library
27456 using this header will get a reference to the specified script,
27457 and with the use of @code{"MS"} attributes on the section, the linker
27458 will remove duplicates.
27460 @subsubsection Script Text Entries
27462 Script text entries allow to put the executable script in the entry
27463 itself instead of loading it from a file.
27464 The first line of the entry, everything after the prefix byte and up to
27465 the first newline (@code{0xa}) character, is the script name, and must not
27466 contain any kind of space character, e.g., spaces or tabs.
27467 The rest of the entry, up to the trailing null byte, is the script to
27468 execute in the specified language. The name needs to be unique among
27469 all script names, as @value{GDBN} executes each script only once based
27472 Here is an example from file @file{py-section-script.c} in the @value{GDBN}
27476 #include "symcat.h"
27477 #include "gdb/section-scripts.h"
27479 ".pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n"
27480 ".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
27481 ".ascii \"gdb.inlined-script\\n\"\n"
27482 ".ascii \"class test_cmd (gdb.Command):\\n\"\n"
27483 ".ascii \" def __init__ (self):\\n\"\n"
27484 ".ascii \" super (test_cmd, self).__init__ ("
27485 "\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
27486 ".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
27487 ".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
27488 ".ascii \"test_cmd ()\\n\"\n"
27494 Loading of inlined scripts requires a properly configured
27495 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
27496 The path to specify in @code{auto-load safe-path} is the path of the file
27497 containing the @code{.debug_gdb_scripts} section.
27499 @node Which flavor to choose?
27500 @subsection Which flavor to choose?
27502 Given the multiple ways of auto-loading extensions, it might not always
27503 be clear which one to choose. This section provides some guidance.
27506 Benefits of the @file{-gdb.@var{ext}} way:
27510 Can be used with file formats that don't support multiple sections.
27513 Ease of finding scripts for public libraries.
27515 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
27516 in the source search path.
27517 For publicly installed libraries, e.g., @file{libstdc++}, there typically
27518 isn't a source directory in which to find the script.
27521 Doesn't require source code additions.
27525 Benefits of the @code{.debug_gdb_scripts} way:
27529 Works with static linking.
27531 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
27532 trigger their loading. When an application is statically linked the only
27533 objfile available is the executable, and it is cumbersome to attach all the
27534 scripts from all the input libraries to the executable's
27535 @file{-gdb.@var{ext}} script.
27538 Works with classes that are entirely inlined.
27540 Some classes can be entirely inlined, and thus there may not be an associated
27541 shared library to attach a @file{-gdb.@var{ext}} script to.
27544 Scripts needn't be copied out of the source tree.
27546 In some circumstances, apps can be built out of large collections of internal
27547 libraries, and the build infrastructure necessary to install the
27548 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
27549 cumbersome. It may be easier to specify the scripts in the
27550 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
27551 top of the source tree to the source search path.
27554 @node Multiple Extension Languages
27555 @section Multiple Extension Languages
27557 The Guile and Python extension languages do not share any state,
27558 and generally do not interfere with each other.
27559 There are some things to be aware of, however.
27561 @subsection Python comes first
27563 Python was @value{GDBN}'s first extension language, and to avoid breaking
27564 existing behaviour Python comes first. This is generally solved by the
27565 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
27566 extension languages, and when it makes a call to an extension language,
27567 (say to pretty-print a value), it tries each in turn until an extension
27568 language indicates it has performed the request (e.g., has returned the
27569 pretty-printed form of a value).
27570 This extends to errors while performing such requests: If an error happens
27571 while, for example, trying to pretty-print an object then the error is
27572 reported and any following extension languages are not tried.
27575 @section Creating new spellings of existing commands
27576 @cindex aliases for commands
27578 It is often useful to define alternate spellings of existing commands.
27579 For example, if a new @value{GDBN} command defined in Python has
27580 a long name to type, it is handy to have an abbreviated version of it
27581 that involves less typing.
27583 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
27584 of the @samp{step} command even though it is otherwise an ambiguous
27585 abbreviation of other commands like @samp{set} and @samp{show}.
27587 Aliases are also used to provide shortened or more common versions
27588 of multi-word commands. For example, @value{GDBN} provides the
27589 @samp{tty} alias of the @samp{set inferior-tty} command.
27591 You can define a new alias with the @samp{alias} command.
27596 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND} [DEFAULT-ARGS...]
27600 @var{ALIAS} specifies the name of the new alias.
27601 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
27604 @var{COMMAND} specifies the name of an existing command
27605 that is being aliased.
27607 @var{COMMAND} can also be the name of an existing alias. In this case,
27608 @var{COMMAND} cannot be an alias that has default arguments.
27610 The @samp{-a} option specifies that the new alias is an abbreviation
27611 of the command. Abbreviations are not used in command completion.
27613 The @samp{--} option specifies the end of options,
27614 and is useful when @var{ALIAS} begins with a dash.
27616 You can specify @var{default-args} for your alias.
27617 These @var{default-args} will be automatically added before the alias
27618 arguments typed explicitly on the command line.
27620 For example, the below defines an alias @code{btfullall} that shows all local
27621 variables and all frame arguments:
27623 (@value{GDBP}) alias btfullall = backtrace -full -frame-arguments all
27626 For more information about @var{default-args}, see @ref{Command aliases default args,
27627 ,Automatically prepend default arguments to user-defined aliases}.
27629 Here is a simple example showing how to make an abbreviation
27630 of a command so that there is less to type.
27631 Suppose you were tired of typing @samp{disas}, the current
27632 shortest unambiguous abbreviation of the @samp{disassemble} command
27633 and you wanted an even shorter version named @samp{di}.
27634 The following will accomplish this.
27637 (gdb) alias -a di = disas
27640 Note that aliases are different from user-defined commands.
27641 With a user-defined command, you also need to write documentation
27642 for it with the @samp{document} command.
27643 An alias automatically picks up the documentation of the existing command.
27645 Here is an example where we make @samp{elms} an abbreviation of
27646 @samp{elements} in the @samp{set print elements} command.
27647 This is to show that you can make an abbreviation of any part
27651 (gdb) alias -a set print elms = set print elements
27652 (gdb) alias -a show print elms = show print elements
27653 (gdb) set p elms 20
27655 Limit on string chars or array elements to print is 200.
27658 Note that if you are defining an alias of a @samp{set} command,
27659 and you want to have an alias for the corresponding @samp{show}
27660 command, then you need to define the latter separately.
27662 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
27663 @var{ALIAS}, just as they are normally.
27666 (gdb) alias -a set pr elms = set p ele
27669 Finally, here is an example showing the creation of a one word
27670 alias for a more complex command.
27671 This creates alias @samp{spe} of the command @samp{set print elements}.
27674 (gdb) alias spe = set print elements
27679 @chapter Command Interpreters
27680 @cindex command interpreters
27682 @value{GDBN} supports multiple command interpreters, and some command
27683 infrastructure to allow users or user interface writers to switch
27684 between interpreters or run commands in other interpreters.
27686 @value{GDBN} currently supports two command interpreters, the console
27687 interpreter (sometimes called the command-line interpreter or @sc{cli})
27688 and the machine interface interpreter (or @sc{gdb/mi}). This manual
27689 describes both of these interfaces in great detail.
27691 By default, @value{GDBN} will start with the console interpreter.
27692 However, the user may choose to start @value{GDBN} with another
27693 interpreter by specifying the @option{-i} or @option{--interpreter}
27694 startup options. Defined interpreters include:
27698 @cindex console interpreter
27699 The traditional console or command-line interpreter. This is the most often
27700 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
27701 @value{GDBN} will use this interpreter.
27704 @cindex mi interpreter
27705 The newest @sc{gdb/mi} interface (currently @code{mi3}). Used primarily
27706 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
27707 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
27711 @cindex mi3 interpreter
27712 The @sc{gdb/mi} interface introduced in @value{GDBN} 9.1.
27715 @cindex mi2 interpreter
27716 The @sc{gdb/mi} interface introduced in @value{GDBN} 6.0.
27719 @cindex mi1 interpreter
27720 The @sc{gdb/mi} interface introduced in @value{GDBN} 5.1.
27724 @cindex invoke another interpreter
27726 @kindex interpreter-exec
27727 You may execute commands in any interpreter from the current
27728 interpreter using the appropriate command. If you are running the
27729 console interpreter, simply use the @code{interpreter-exec} command:
27732 interpreter-exec mi "-data-list-register-names"
27735 @sc{gdb/mi} has a similar command, although it is only available in versions of
27736 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
27738 Note that @code{interpreter-exec} only changes the interpreter for the
27739 duration of the specified command. It does not change the interpreter
27742 @cindex start a new independent interpreter
27744 Although you may only choose a single interpreter at startup, it is
27745 possible to run an independent interpreter on a specified input/output
27746 device (usually a tty).
27748 For example, consider a debugger GUI or IDE that wants to provide a
27749 @value{GDBN} console view. It may do so by embedding a terminal
27750 emulator widget in its GUI, starting @value{GDBN} in the traditional
27751 command-line mode with stdin/stdout/stderr redirected to that
27752 terminal, and then creating an MI interpreter running on a specified
27753 input/output device. The console interpreter created by @value{GDBN}
27754 at startup handles commands the user types in the terminal widget,
27755 while the GUI controls and synchronizes state with @value{GDBN} using
27756 the separate MI interpreter.
27758 To start a new secondary @dfn{user interface} running MI, use the
27759 @code{new-ui} command:
27762 @cindex new user interface
27764 new-ui @var{interpreter} @var{tty}
27767 The @var{interpreter} parameter specifies the interpreter to run.
27768 This accepts the same values as the @code{interpreter-exec} command.
27769 For example, @samp{console}, @samp{mi}, @samp{mi2}, etc. The
27770 @var{tty} parameter specifies the name of the bidirectional file the
27771 interpreter uses for input/output, usually the name of a
27772 pseudoterminal slave on Unix systems. For example:
27775 (@value{GDBP}) new-ui mi /dev/pts/9
27779 runs an MI interpreter on @file{/dev/pts/9}.
27782 @chapter @value{GDBN} Text User Interface
27784 @cindex Text User Interface
27787 * TUI Overview:: TUI overview
27788 * TUI Keys:: TUI key bindings
27789 * TUI Single Key Mode:: TUI single key mode
27790 * TUI Commands:: TUI-specific commands
27791 * TUI Configuration:: TUI configuration variables
27794 The @value{GDBN} Text User Interface (TUI) is a terminal
27795 interface which uses the @code{curses} library to show the source
27796 file, the assembly output, the program registers and @value{GDBN}
27797 commands in separate text windows. The TUI mode is supported only
27798 on platforms where a suitable version of the @code{curses} library
27801 The TUI mode is enabled by default when you invoke @value{GDBN} as
27802 @samp{@value{GDBP} -tui}.
27803 You can also switch in and out of TUI mode while @value{GDBN} runs by
27804 using various TUI commands and key bindings, such as @command{tui
27805 enable} or @kbd{C-x C-a}. @xref{TUI Commands, ,TUI Commands}, and
27806 @ref{TUI Keys, ,TUI Key Bindings}.
27809 @section TUI Overview
27811 In TUI mode, @value{GDBN} can display several text windows:
27815 This window is the @value{GDBN} command window with the @value{GDBN}
27816 prompt and the @value{GDBN} output. The @value{GDBN} input is still
27817 managed using readline.
27820 The source window shows the source file of the program. The current
27821 line and active breakpoints are displayed in this window.
27824 The assembly window shows the disassembly output of the program.
27827 This window shows the processor registers. Registers are highlighted
27828 when their values change.
27831 The source and assembly windows show the current program position
27832 by highlighting the current line and marking it with a @samp{>} marker.
27833 Breakpoints are indicated with two markers. The first marker
27834 indicates the breakpoint type:
27838 Breakpoint which was hit at least once.
27841 Breakpoint which was never hit.
27844 Hardware breakpoint which was hit at least once.
27847 Hardware breakpoint which was never hit.
27850 The second marker indicates whether the breakpoint is enabled or not:
27854 Breakpoint is enabled.
27857 Breakpoint is disabled.
27860 The source, assembly and register windows are updated when the current
27861 thread changes, when the frame changes, or when the program counter
27864 These windows are not all visible at the same time. The command
27865 window is always visible. The others can be arranged in several
27876 source and assembly,
27879 source and registers, or
27882 assembly and registers.
27885 These are the standard layouts, but other layouts can be defined.
27887 A status line above the command window shows the following information:
27891 Indicates the current @value{GDBN} target.
27892 (@pxref{Targets, ,Specifying a Debugging Target}).
27895 Gives the current process or thread number.
27896 When no process is being debugged, this field is set to @code{No process}.
27899 Gives the current function name for the selected frame.
27900 The name is demangled if demangling is turned on (@pxref{Print Settings}).
27901 When there is no symbol corresponding to the current program counter,
27902 the string @code{??} is displayed.
27905 Indicates the current line number for the selected frame.
27906 When the current line number is not known, the string @code{??} is displayed.
27909 Indicates the current program counter address.
27913 @section TUI Key Bindings
27914 @cindex TUI key bindings
27916 The TUI installs several key bindings in the readline keymaps
27917 @ifset SYSTEM_READLINE
27918 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
27920 @ifclear SYSTEM_READLINE
27921 (@pxref{Command Line Editing}).
27923 The following key bindings are installed for both TUI mode and the
27924 @value{GDBN} standard mode.
27933 Enter or leave the TUI mode. When leaving the TUI mode,
27934 the curses window management stops and @value{GDBN} operates using
27935 its standard mode, writing on the terminal directly. When reentering
27936 the TUI mode, control is given back to the curses windows.
27937 The screen is then refreshed.
27939 This key binding uses the bindable Readline function
27940 @code{tui-switch-mode}.
27944 Use a TUI layout with only one window. The layout will
27945 either be @samp{source} or @samp{assembly}. When the TUI mode
27946 is not active, it will switch to the TUI mode.
27948 Think of this key binding as the Emacs @kbd{C-x 1} binding.
27950 This key binding uses the bindable Readline function
27951 @code{tui-delete-other-windows}.
27955 Use a TUI layout with at least two windows. When the current
27956 layout already has two windows, the next layout with two windows is used.
27957 When a new layout is chosen, one window will always be common to the
27958 previous layout and the new one.
27960 Think of it as the Emacs @kbd{C-x 2} binding.
27962 This key binding uses the bindable Readline function
27963 @code{tui-change-windows}.
27967 Change the active window. The TUI associates several key bindings
27968 (like scrolling and arrow keys) with the active window. This command
27969 gives the focus to the next TUI window.
27971 Think of it as the Emacs @kbd{C-x o} binding.
27973 This key binding uses the bindable Readline function
27974 @code{tui-other-window}.
27978 Switch in and out of the TUI SingleKey mode that binds single
27979 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
27981 This key binding uses the bindable Readline function
27982 @code{next-keymap}.
27985 The following key bindings only work in the TUI mode:
27990 Scroll the active window one page up.
27994 Scroll the active window one page down.
27998 Scroll the active window one line up.
28002 Scroll the active window one line down.
28006 Scroll the active window one column left.
28010 Scroll the active window one column right.
28014 Refresh the screen.
28017 Because the arrow keys scroll the active window in the TUI mode, they
28018 are not available for their normal use by readline unless the command
28019 window has the focus. When another window is active, you must use
28020 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
28021 and @kbd{C-f} to control the command window.
28023 @node TUI Single Key Mode
28024 @section TUI Single Key Mode
28025 @cindex TUI single key mode
28027 The TUI also provides a @dfn{SingleKey} mode, which binds several
28028 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
28029 switch into this mode, where the following key bindings are used:
28032 @kindex c @r{(SingleKey TUI key)}
28036 @kindex d @r{(SingleKey TUI key)}
28040 @kindex f @r{(SingleKey TUI key)}
28044 @kindex n @r{(SingleKey TUI key)}
28048 @kindex o @r{(SingleKey TUI key)}
28050 nexti. The shortcut letter @samp{o} stands for ``step Over''.
28052 @kindex q @r{(SingleKey TUI key)}
28054 exit the SingleKey mode.
28056 @kindex r @r{(SingleKey TUI key)}
28060 @kindex s @r{(SingleKey TUI key)}
28064 @kindex i @r{(SingleKey TUI key)}
28066 stepi. The shortcut letter @samp{i} stands for ``step Into''.
28068 @kindex u @r{(SingleKey TUI key)}
28072 @kindex v @r{(SingleKey TUI key)}
28076 @kindex w @r{(SingleKey TUI key)}
28081 Other keys temporarily switch to the @value{GDBN} command prompt.
28082 The key that was pressed is inserted in the editing buffer so that
28083 it is possible to type most @value{GDBN} commands without interaction
28084 with the TUI SingleKey mode. Once the command is entered the TUI
28085 SingleKey mode is restored. The only way to permanently leave
28086 this mode is by typing @kbd{q} or @kbd{C-x s}.
28088 @cindex SingleKey keymap name
28089 If @value{GDBN} was built with Readline 8.0 or later, the TUI
28090 SingleKey keymap will be named @samp{SingleKey}. This can be used in
28091 @file{.inputrc} to add additional bindings to this keymap.
28094 @section TUI-specific Commands
28095 @cindex TUI commands
28097 The TUI has specific commands to control the text windows.
28098 These commands are always available, even when @value{GDBN} is not in
28099 the TUI mode. When @value{GDBN} is in the standard mode, most
28100 of these commands will automatically switch to the TUI mode.
28102 Note that if @value{GDBN}'s @code{stdout} is not connected to a
28103 terminal, or @value{GDBN} has been started with the machine interface
28104 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
28105 these commands will fail with an error, because it would not be
28106 possible or desirable to enable curses window management.
28111 Activate TUI mode. The last active TUI window layout will be used if
28112 TUI mode has previously been used in the current debugging session,
28113 otherwise a default layout is used.
28116 @kindex tui disable
28117 Disable TUI mode, returning to the console interpreter.
28121 List and give the size of all displayed windows.
28123 @item tui new-layout @var{name} @var{window} @var{weight} @r{[}@var{window} @var{weight}@dots{}@r{]}
28124 @kindex tui new-layout
28125 Create a new TUI layout. The new layout will be named @var{name}, and
28126 can be accessed using the @code{layout} command (see below).
28128 Each @var{window} parameter is either the name of a window to display,
28129 or a window description. The windows will be displayed from top to
28130 bottom in the order listed.
28132 The names of the windows are the same as the ones given to the
28133 @code{focus} command (see below); additional, the @code{status}
28134 window can be specified. Note that, because it is of fixed height,
28135 the weight assigned to the status window is of no importance. It is
28136 conventional to use @samp{0} here.
28138 A window description looks a bit like an invocation of @code{tui
28139 new-layout}, and is of the form
28140 @{@r{[}@code{-horizontal}@r{]}@var{window} @var{weight} @r{[}@var{window} @var{weight}@dots{}@r{]}@}.
28142 This specifies a sub-layout. If @code{-horizontal} is given, the
28143 windows in this description will be arranged side-by-side, rather than
28146 Each @var{weight} is an integer. It is the weight of this window
28147 relative to all the other windows in the layout. These numbers are
28148 used to calculate how much of the screen is given to each window.
28153 (gdb) tui new-layout example src 1 regs 1 status 0 cmd 1
28156 Here, the new layout is called @samp{example}. It shows the source
28157 and register windows, followed by the status window, and then finally
28158 the command window. The non-status windows all have the same weight,
28159 so the terminal will be split into three roughly equal sections.
28161 Here is a more complex example, showing a horizontal layout:
28164 (gdb) tui new-layout example @{-horizontal src 1 asm 1@} 2 status 0 cmd 1
28167 This will result in side-by-side source and assembly windows; with the
28168 status and command window being beneath these, filling the entire
28169 width of the terminal. Because they have weight 2, the source and
28170 assembly windows will be twice the height of the command window.
28172 @item layout @var{name}
28174 Changes which TUI windows are displayed. The @var{name} parameter
28175 controls which layout is shown. It can be either one of the built-in
28176 layout names, or the name of a layout defined by the user using
28177 @code{tui new-layout}.
28179 The built-in layouts are as follows:
28183 Display the next layout.
28186 Display the previous layout.
28189 Display the source and command windows.
28192 Display the assembly and command windows.
28195 Display the source, assembly, and command windows.
28198 When in @code{src} layout display the register, source, and command
28199 windows. When in @code{asm} or @code{split} layout display the
28200 register, assembler, and command windows.
28203 @item focus @var{name}
28205 Changes which TUI window is currently active for scrolling. The
28206 @var{name} parameter can be any of the following:
28210 Make the next window active for scrolling.
28213 Make the previous window active for scrolling.
28216 Make the source window active for scrolling.
28219 Make the assembly window active for scrolling.
28222 Make the register window active for scrolling.
28225 Make the command window active for scrolling.
28230 Refresh the screen. This is similar to typing @kbd{C-L}.
28232 @item tui reg @var{group}
28234 Changes the register group displayed in the tui register window to
28235 @var{group}. If the register window is not currently displayed this
28236 command will cause the register window to be displayed. The list of
28237 register groups, as well as their order is target specific. The
28238 following groups are available on most targets:
28241 Repeatedly selecting this group will cause the display to cycle
28242 through all of the available register groups.
28245 Repeatedly selecting this group will cause the display to cycle
28246 through all of the available register groups in the reverse order to
28250 Display the general registers.
28252 Display the floating point registers.
28254 Display the system registers.
28256 Display the vector registers.
28258 Display all registers.
28263 Update the source window and the current execution point.
28265 @item winheight @var{name} +@var{count}
28266 @itemx winheight @var{name} -@var{count}
28268 Change the height of the window @var{name} by @var{count}
28269 lines. Positive counts increase the height, while negative counts
28270 decrease it. The @var{name} parameter can be one of @code{src} (the
28271 source window), @code{cmd} (the command window), @code{asm} (the
28272 disassembly window), or @code{regs} (the register display window).
28275 @node TUI Configuration
28276 @section TUI Configuration Variables
28277 @cindex TUI configuration variables
28279 Several configuration variables control the appearance of TUI windows.
28282 @item set tui border-kind @var{kind}
28283 @kindex set tui border-kind
28284 Select the border appearance for the source, assembly and register windows.
28285 The possible values are the following:
28288 Use a space character to draw the border.
28291 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
28294 Use the Alternate Character Set to draw the border. The border is
28295 drawn using character line graphics if the terminal supports them.
28298 @item set tui border-mode @var{mode}
28299 @kindex set tui border-mode
28300 @itemx set tui active-border-mode @var{mode}
28301 @kindex set tui active-border-mode
28302 Select the display attributes for the borders of the inactive windows
28303 or the active window. The @var{mode} can be one of the following:
28306 Use normal attributes to display the border.
28312 Use reverse video mode.
28315 Use half bright mode.
28317 @item half-standout
28318 Use half bright and standout mode.
28321 Use extra bright or bold mode.
28323 @item bold-standout
28324 Use extra bright or bold and standout mode.
28327 @item set tui tab-width @var{nchars}
28328 @kindex set tui tab-width
28330 Set the width of tab stops to be @var{nchars} characters. This
28331 setting affects the display of TAB characters in the source and
28334 @item set tui compact-source @r{[}on@r{|}off@r{]}
28335 @kindex set tui compact-source
28336 Set whether the TUI source window is displayed in ``compact'' form.
28337 The default display uses more space for line numbers and starts the
28338 source text at the next tab stop; the compact display uses only as
28339 much space as is needed for the line numbers in the current file, and
28340 only a single space to separate the line numbers from the source.
28343 Note that the colors of the TUI borders can be controlled using the
28344 appropriate @code{set style} commands. @xref{Output Styling}.
28347 @chapter Using @value{GDBN} under @sc{gnu} Emacs
28350 @cindex @sc{gnu} Emacs
28351 A special interface allows you to use @sc{gnu} Emacs to view (and
28352 edit) the source files for the program you are debugging with
28355 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
28356 executable file you want to debug as an argument. This command starts
28357 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
28358 created Emacs buffer.
28359 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
28361 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
28366 All ``terminal'' input and output goes through an Emacs buffer, called
28369 This applies both to @value{GDBN} commands and their output, and to the input
28370 and output done by the program you are debugging.
28372 This is useful because it means that you can copy the text of previous
28373 commands and input them again; you can even use parts of the output
28376 All the facilities of Emacs' Shell mode are available for interacting
28377 with your program. In particular, you can send signals the usual
28378 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
28382 @value{GDBN} displays source code through Emacs.
28384 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
28385 source file for that frame and puts an arrow (@samp{=>}) at the
28386 left margin of the current line. Emacs uses a separate buffer for
28387 source display, and splits the screen to show both your @value{GDBN} session
28390 Explicit @value{GDBN} @code{list} or search commands still produce output as
28391 usual, but you probably have no reason to use them from Emacs.
28394 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
28395 a graphical mode, enabled by default, which provides further buffers
28396 that can control the execution and describe the state of your program.
28397 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
28399 If you specify an absolute file name when prompted for the @kbd{M-x
28400 gdb} argument, then Emacs sets your current working directory to where
28401 your program resides. If you only specify the file name, then Emacs
28402 sets your current working directory to the directory associated
28403 with the previous buffer. In this case, @value{GDBN} may find your
28404 program by searching your environment's @code{PATH} variable, but on
28405 some operating systems it might not find the source. So, although the
28406 @value{GDBN} input and output session proceeds normally, the auxiliary
28407 buffer does not display the current source and line of execution.
28409 The initial working directory of @value{GDBN} is printed on the top
28410 line of the GUD buffer and this serves as a default for the commands
28411 that specify files for @value{GDBN} to operate on. @xref{Files,
28412 ,Commands to Specify Files}.
28414 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
28415 need to call @value{GDBN} by a different name (for example, if you
28416 keep several configurations around, with different names) you can
28417 customize the Emacs variable @code{gud-gdb-command-name} to run the
28420 In the GUD buffer, you can use these special Emacs commands in
28421 addition to the standard Shell mode commands:
28425 Describe the features of Emacs' GUD Mode.
28428 Execute to another source line, like the @value{GDBN} @code{step} command; also
28429 update the display window to show the current file and location.
28432 Execute to next source line in this function, skipping all function
28433 calls, like the @value{GDBN} @code{next} command. Then update the display window
28434 to show the current file and location.
28437 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
28438 display window accordingly.
28441 Execute until exit from the selected stack frame, like the @value{GDBN}
28442 @code{finish} command.
28445 Continue execution of your program, like the @value{GDBN} @code{continue}
28449 Go up the number of frames indicated by the numeric argument
28450 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
28451 like the @value{GDBN} @code{up} command.
28454 Go down the number of frames indicated by the numeric argument, like the
28455 @value{GDBN} @code{down} command.
28458 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
28459 tells @value{GDBN} to set a breakpoint on the source line point is on.
28461 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
28462 separate frame which shows a backtrace when the GUD buffer is current.
28463 Move point to any frame in the stack and type @key{RET} to make it
28464 become the current frame and display the associated source in the
28465 source buffer. Alternatively, click @kbd{Mouse-2} to make the
28466 selected frame become the current one. In graphical mode, the
28467 speedbar displays watch expressions.
28469 If you accidentally delete the source-display buffer, an easy way to get
28470 it back is to type the command @code{f} in the @value{GDBN} buffer, to
28471 request a frame display; when you run under Emacs, this recreates
28472 the source buffer if necessary to show you the context of the current
28475 The source files displayed in Emacs are in ordinary Emacs buffers
28476 which are visiting the source files in the usual way. You can edit
28477 the files with these buffers if you wish; but keep in mind that @value{GDBN}
28478 communicates with Emacs in terms of line numbers. If you add or
28479 delete lines from the text, the line numbers that @value{GDBN} knows cease
28480 to correspond properly with the code.
28482 A more detailed description of Emacs' interaction with @value{GDBN} is
28483 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
28487 @chapter The @sc{gdb/mi} Interface
28489 @unnumberedsec Function and Purpose
28491 @cindex @sc{gdb/mi}, its purpose
28492 @sc{gdb/mi} is a line based machine oriented text interface to
28493 @value{GDBN} and is activated by specifying using the
28494 @option{--interpreter} command line option (@pxref{Mode Options}). It
28495 is specifically intended to support the development of systems which
28496 use the debugger as just one small component of a larger system.
28498 This chapter is a specification of the @sc{gdb/mi} interface. It is written
28499 in the form of a reference manual.
28501 Note that @sc{gdb/mi} is still under construction, so some of the
28502 features described below are incomplete and subject to change
28503 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
28505 @unnumberedsec Notation and Terminology
28507 @cindex notational conventions, for @sc{gdb/mi}
28508 This chapter uses the following notation:
28512 @code{|} separates two alternatives.
28515 @code{[ @var{something} ]} indicates that @var{something} is optional:
28516 it may or may not be given.
28519 @code{( @var{group} )*} means that @var{group} inside the parentheses
28520 may repeat zero or more times.
28523 @code{( @var{group} )+} means that @var{group} inside the parentheses
28524 may repeat one or more times.
28527 @code{"@var{string}"} means a literal @var{string}.
28531 @heading Dependencies
28535 * GDB/MI General Design::
28536 * GDB/MI Command Syntax::
28537 * GDB/MI Compatibility with CLI::
28538 * GDB/MI Development and Front Ends::
28539 * GDB/MI Output Records::
28540 * GDB/MI Simple Examples::
28541 * GDB/MI Command Description Format::
28542 * GDB/MI Breakpoint Commands::
28543 * GDB/MI Catchpoint Commands::
28544 * GDB/MI Program Context::
28545 * GDB/MI Thread Commands::
28546 * GDB/MI Ada Tasking Commands::
28547 * GDB/MI Program Execution::
28548 * GDB/MI Stack Manipulation::
28549 * GDB/MI Variable Objects::
28550 * GDB/MI Data Manipulation::
28551 * GDB/MI Tracepoint Commands::
28552 * GDB/MI Symbol Query::
28553 * GDB/MI File Commands::
28555 * GDB/MI Kod Commands::
28556 * GDB/MI Memory Overlay Commands::
28557 * GDB/MI Signal Handling Commands::
28559 * GDB/MI Target Manipulation::
28560 * GDB/MI File Transfer Commands::
28561 * GDB/MI Ada Exceptions Commands::
28562 * GDB/MI Support Commands::
28563 * GDB/MI Miscellaneous Commands::
28566 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28567 @node GDB/MI General Design
28568 @section @sc{gdb/mi} General Design
28569 @cindex GDB/MI General Design
28571 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
28572 parts---commands sent to @value{GDBN}, responses to those commands
28573 and notifications. Each command results in exactly one response,
28574 indicating either successful completion of the command, or an error.
28575 For the commands that do not resume the target, the response contains the
28576 requested information. For the commands that resume the target, the
28577 response only indicates whether the target was successfully resumed.
28578 Notifications is the mechanism for reporting changes in the state of the
28579 target, or in @value{GDBN} state, that cannot conveniently be associated with
28580 a command and reported as part of that command response.
28582 The important examples of notifications are:
28586 Exec notifications. These are used to report changes in
28587 target state---when a target is resumed, or stopped. It would not
28588 be feasible to include this information in response of resuming
28589 commands, because one resume commands can result in multiple events in
28590 different threads. Also, quite some time may pass before any event
28591 happens in the target, while a frontend needs to know whether the resuming
28592 command itself was successfully executed.
28595 Console output, and status notifications. Console output
28596 notifications are used to report output of CLI commands, as well as
28597 diagnostics for other commands. Status notifications are used to
28598 report the progress of a long-running operation. Naturally, including
28599 this information in command response would mean no output is produced
28600 until the command is finished, which is undesirable.
28603 General notifications. Commands may have various side effects on
28604 the @value{GDBN} or target state beyond their official purpose. For example,
28605 a command may change the selected thread. Although such changes can
28606 be included in command response, using notification allows for more
28607 orthogonal frontend design.
28611 There's no guarantee that whenever an MI command reports an error,
28612 @value{GDBN} or the target are in any specific state, and especially,
28613 the state is not reverted to the state before the MI command was
28614 processed. Therefore, whenever an MI command results in an error,
28615 we recommend that the frontend refreshes all the information shown in
28616 the user interface.
28620 * Context management::
28621 * Asynchronous and non-stop modes::
28625 @node Context management
28626 @subsection Context management
28628 @subsubsection Threads and Frames
28630 In most cases when @value{GDBN} accesses the target, this access is
28631 done in context of a specific thread and frame (@pxref{Frames}).
28632 Often, even when accessing global data, the target requires that a thread
28633 be specified. The CLI interface maintains the selected thread and frame,
28634 and supplies them to target on each command. This is convenient,
28635 because a command line user would not want to specify that information
28636 explicitly on each command, and because user interacts with
28637 @value{GDBN} via a single terminal, so no confusion is possible as
28638 to what thread and frame are the current ones.
28640 In the case of MI, the concept of selected thread and frame is less
28641 useful. First, a frontend can easily remember this information
28642 itself. Second, a graphical frontend can have more than one window,
28643 each one used for debugging a different thread, and the frontend might
28644 want to access additional threads for internal purposes. This
28645 increases the risk that by relying on implicitly selected thread, the
28646 frontend may be operating on a wrong one. Therefore, each MI command
28647 should explicitly specify which thread and frame to operate on. To
28648 make it possible, each MI command accepts the @samp{--thread} and
28649 @samp{--frame} options, the value to each is @value{GDBN} global
28650 identifier for thread and frame to operate on.
28652 Usually, each top-level window in a frontend allows the user to select
28653 a thread and a frame, and remembers the user selection for further
28654 operations. However, in some cases @value{GDBN} may suggest that the
28655 current thread or frame be changed. For example, when stopping on a
28656 breakpoint it is reasonable to switch to the thread where breakpoint is
28657 hit. For another example, if the user issues the CLI @samp{thread} or
28658 @samp{frame} commands via the frontend, it is desirable to change the
28659 frontend's selection to the one specified by user. @value{GDBN}
28660 communicates the suggestion to change current thread and frame using the
28661 @samp{=thread-selected} notification.
28663 Note that historically, MI shares the selected thread with CLI, so
28664 frontends used the @code{-thread-select} to execute commands in the
28665 right context. However, getting this to work right is cumbersome. The
28666 simplest way is for frontend to emit @code{-thread-select} command
28667 before every command. This doubles the number of commands that need
28668 to be sent. The alternative approach is to suppress @code{-thread-select}
28669 if the selected thread in @value{GDBN} is supposed to be identical to the
28670 thread the frontend wants to operate on. However, getting this
28671 optimization right can be tricky. In particular, if the frontend
28672 sends several commands to @value{GDBN}, and one of the commands changes the
28673 selected thread, then the behaviour of subsequent commands will
28674 change. So, a frontend should either wait for response from such
28675 problematic commands, or explicitly add @code{-thread-select} for
28676 all subsequent commands. No frontend is known to do this exactly
28677 right, so it is suggested to just always pass the @samp{--thread} and
28678 @samp{--frame} options.
28680 @subsubsection Language
28682 The execution of several commands depends on which language is selected.
28683 By default, the current language (@pxref{show language}) is used.
28684 But for commands known to be language-sensitive, it is recommended
28685 to use the @samp{--language} option. This option takes one argument,
28686 which is the name of the language to use while executing the command.
28690 -data-evaluate-expression --language c "sizeof (void*)"
28695 The valid language names are the same names accepted by the
28696 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
28697 @samp{local} or @samp{unknown}.
28699 @node Asynchronous and non-stop modes
28700 @subsection Asynchronous command execution and non-stop mode
28702 On some targets, @value{GDBN} is capable of processing MI commands
28703 even while the target is running. This is called @dfn{asynchronous
28704 command execution} (@pxref{Background Execution}). The frontend may
28705 specify a preference for asynchronous execution using the
28706 @code{-gdb-set mi-async 1} command, which should be emitted before
28707 either running the executable or attaching to the target. After the
28708 frontend has started the executable or attached to the target, it can
28709 find if asynchronous execution is enabled using the
28710 @code{-list-target-features} command.
28713 @item -gdb-set mi-async on
28714 @item -gdb-set mi-async off
28715 Set whether MI is in asynchronous mode.
28717 When @code{off}, which is the default, MI execution commands (e.g.,
28718 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
28719 for the program to stop before processing further commands.
28721 When @code{on}, MI execution commands are background execution
28722 commands (e.g., @code{-exec-continue} becomes the equivalent of the
28723 @code{c&} CLI command), and so @value{GDBN} is capable of processing
28724 MI commands even while the target is running.
28726 @item -gdb-show mi-async
28727 Show whether MI asynchronous mode is enabled.
28730 Note: In @value{GDBN} version 7.7 and earlier, this option was called
28731 @code{target-async} instead of @code{mi-async}, and it had the effect
28732 of both putting MI in asynchronous mode and making CLI background
28733 commands possible. CLI background commands are now always possible
28734 ``out of the box'' if the target supports them. The old spelling is
28735 kept as a deprecated alias for backwards compatibility.
28737 Even if @value{GDBN} can accept a command while target is running,
28738 many commands that access the target do not work when the target is
28739 running. Therefore, asynchronous command execution is most useful
28740 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
28741 it is possible to examine the state of one thread, while other threads
28744 When a given thread is running, MI commands that try to access the
28745 target in the context of that thread may not work, or may work only on
28746 some targets. In particular, commands that try to operate on thread's
28747 stack will not work, on any target. Commands that read memory, or
28748 modify breakpoints, may work or not work, depending on the target. Note
28749 that even commands that operate on global state, such as @code{print},
28750 @code{set}, and breakpoint commands, still access the target in the
28751 context of a specific thread, so frontend should try to find a
28752 stopped thread and perform the operation on that thread (using the
28753 @samp{--thread} option).
28755 Which commands will work in the context of a running thread is
28756 highly target dependent. However, the two commands
28757 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
28758 to find the state of a thread, will always work.
28760 @node Thread groups
28761 @subsection Thread groups
28762 @value{GDBN} may be used to debug several processes at the same time.
28763 On some platforms, @value{GDBN} may support debugging of several
28764 hardware systems, each one having several cores with several different
28765 processes running on each core. This section describes the MI
28766 mechanism to support such debugging scenarios.
28768 The key observation is that regardless of the structure of the
28769 target, MI can have a global list of threads, because most commands that
28770 accept the @samp{--thread} option do not need to know what process that
28771 thread belongs to. Therefore, it is not necessary to introduce
28772 neither additional @samp{--process} option, nor an notion of the
28773 current process in the MI interface. The only strictly new feature
28774 that is required is the ability to find how the threads are grouped
28777 To allow the user to discover such grouping, and to support arbitrary
28778 hierarchy of machines/cores/processes, MI introduces the concept of a
28779 @dfn{thread group}. Thread group is a collection of threads and other
28780 thread groups. A thread group always has a string identifier, a type,
28781 and may have additional attributes specific to the type. A new
28782 command, @code{-list-thread-groups}, returns the list of top-level
28783 thread groups, which correspond to processes that @value{GDBN} is
28784 debugging at the moment. By passing an identifier of a thread group
28785 to the @code{-list-thread-groups} command, it is possible to obtain
28786 the members of specific thread group.
28788 To allow the user to easily discover processes, and other objects, he
28789 wishes to debug, a concept of @dfn{available thread group} is
28790 introduced. Available thread group is an thread group that
28791 @value{GDBN} is not debugging, but that can be attached to, using the
28792 @code{-target-attach} command. The list of available top-level thread
28793 groups can be obtained using @samp{-list-thread-groups --available}.
28794 In general, the content of a thread group may be only retrieved only
28795 after attaching to that thread group.
28797 Thread groups are related to inferiors (@pxref{Inferiors Connections and
28798 Programs}). Each inferior corresponds to a thread group of a special
28799 type @samp{process}, and some additional operations are permitted on
28800 such thread groups.
28802 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28803 @node GDB/MI Command Syntax
28804 @section @sc{gdb/mi} Command Syntax
28807 * GDB/MI Input Syntax::
28808 * GDB/MI Output Syntax::
28811 @node GDB/MI Input Syntax
28812 @subsection @sc{gdb/mi} Input Syntax
28814 @cindex input syntax for @sc{gdb/mi}
28815 @cindex @sc{gdb/mi}, input syntax
28817 @item @var{command} @expansion{}
28818 @code{@var{cli-command} | @var{mi-command}}
28820 @item @var{cli-command} @expansion{}
28821 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
28822 @var{cli-command} is any existing @value{GDBN} CLI command.
28824 @item @var{mi-command} @expansion{}
28825 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
28826 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
28828 @item @var{token} @expansion{}
28829 "any sequence of digits"
28831 @item @var{option} @expansion{}
28832 @code{"-" @var{parameter} [ " " @var{parameter} ]}
28834 @item @var{parameter} @expansion{}
28835 @code{@var{non-blank-sequence} | @var{c-string}}
28837 @item @var{operation} @expansion{}
28838 @emph{any of the operations described in this chapter}
28840 @item @var{non-blank-sequence} @expansion{}
28841 @emph{anything, provided it doesn't contain special characters such as
28842 "-", @var{nl}, """ and of course " "}
28844 @item @var{c-string} @expansion{}
28845 @code{""" @var{seven-bit-iso-c-string-content} """}
28847 @item @var{nl} @expansion{}
28856 The CLI commands are still handled by the @sc{mi} interpreter; their
28857 output is described below.
28860 The @code{@var{token}}, when present, is passed back when the command
28864 Some @sc{mi} commands accept optional arguments as part of the parameter
28865 list. Each option is identified by a leading @samp{-} (dash) and may be
28866 followed by an optional argument parameter. Options occur first in the
28867 parameter list and can be delimited from normal parameters using
28868 @samp{--} (this is useful when some parameters begin with a dash).
28875 We want easy access to the existing CLI syntax (for debugging).
28878 We want it to be easy to spot a @sc{mi} operation.
28881 @node GDB/MI Output Syntax
28882 @subsection @sc{gdb/mi} Output Syntax
28884 @cindex output syntax of @sc{gdb/mi}
28885 @cindex @sc{gdb/mi}, output syntax
28886 The output from @sc{gdb/mi} consists of zero or more out-of-band records
28887 followed, optionally, by a single result record. This result record
28888 is for the most recent command. The sequence of output records is
28889 terminated by @samp{(gdb)}.
28891 If an input command was prefixed with a @code{@var{token}} then the
28892 corresponding output for that command will also be prefixed by that same
28896 @item @var{output} @expansion{}
28897 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
28899 @item @var{result-record} @expansion{}
28900 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
28902 @item @var{out-of-band-record} @expansion{}
28903 @code{@var{async-record} | @var{stream-record}}
28905 @item @var{async-record} @expansion{}
28906 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
28908 @item @var{exec-async-output} @expansion{}
28909 @code{[ @var{token} ] "*" @var{async-output nl}}
28911 @item @var{status-async-output} @expansion{}
28912 @code{[ @var{token} ] "+" @var{async-output nl}}
28914 @item @var{notify-async-output} @expansion{}
28915 @code{[ @var{token} ] "=" @var{async-output nl}}
28917 @item @var{async-output} @expansion{}
28918 @code{@var{async-class} ( "," @var{result} )*}
28920 @item @var{result-class} @expansion{}
28921 @code{"done" | "running" | "connected" | "error" | "exit"}
28923 @item @var{async-class} @expansion{}
28924 @code{"stopped" | @var{others}} (where @var{others} will be added
28925 depending on the needs---this is still in development).
28927 @item @var{result} @expansion{}
28928 @code{ @var{variable} "=" @var{value}}
28930 @item @var{variable} @expansion{}
28931 @code{ @var{string} }
28933 @item @var{value} @expansion{}
28934 @code{ @var{const} | @var{tuple} | @var{list} }
28936 @item @var{const} @expansion{}
28937 @code{@var{c-string}}
28939 @item @var{tuple} @expansion{}
28940 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
28942 @item @var{list} @expansion{}
28943 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
28944 @var{result} ( "," @var{result} )* "]" }
28946 @item @var{stream-record} @expansion{}
28947 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
28949 @item @var{console-stream-output} @expansion{}
28950 @code{"~" @var{c-string nl}}
28952 @item @var{target-stream-output} @expansion{}
28953 @code{"@@" @var{c-string nl}}
28955 @item @var{log-stream-output} @expansion{}
28956 @code{"&" @var{c-string nl}}
28958 @item @var{nl} @expansion{}
28961 @item @var{token} @expansion{}
28962 @emph{any sequence of digits}.
28970 All output sequences end in a single line containing a period.
28973 The @code{@var{token}} is from the corresponding request. Note that
28974 for all async output, while the token is allowed by the grammar and
28975 may be output by future versions of @value{GDBN} for select async
28976 output messages, it is generally omitted. Frontends should treat
28977 all async output as reporting general changes in the state of the
28978 target and there should be no need to associate async output to any
28982 @cindex status output in @sc{gdb/mi}
28983 @var{status-async-output} contains on-going status information about the
28984 progress of a slow operation. It can be discarded. All status output is
28985 prefixed by @samp{+}.
28988 @cindex async output in @sc{gdb/mi}
28989 @var{exec-async-output} contains asynchronous state change on the target
28990 (stopped, started, disappeared). All async output is prefixed by
28994 @cindex notify output in @sc{gdb/mi}
28995 @var{notify-async-output} contains supplementary information that the
28996 client should handle (e.g., a new breakpoint information). All notify
28997 output is prefixed by @samp{=}.
29000 @cindex console output in @sc{gdb/mi}
29001 @var{console-stream-output} is output that should be displayed as is in the
29002 console. It is the textual response to a CLI command. All the console
29003 output is prefixed by @samp{~}.
29006 @cindex target output in @sc{gdb/mi}
29007 @var{target-stream-output} is the output produced by the target program.
29008 All the target output is prefixed by @samp{@@}.
29011 @cindex log output in @sc{gdb/mi}
29012 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
29013 instance messages that should be displayed as part of an error log. All
29014 the log output is prefixed by @samp{&}.
29017 @cindex list output in @sc{gdb/mi}
29018 New @sc{gdb/mi} commands should only output @var{lists} containing
29024 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
29025 details about the various output records.
29027 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29028 @node GDB/MI Compatibility with CLI
29029 @section @sc{gdb/mi} Compatibility with CLI
29031 @cindex compatibility, @sc{gdb/mi} and CLI
29032 @cindex @sc{gdb/mi}, compatibility with CLI
29034 For the developers convenience CLI commands can be entered directly,
29035 but there may be some unexpected behaviour. For example, commands
29036 that query the user will behave as if the user replied yes, breakpoint
29037 command lists are not executed and some CLI commands, such as
29038 @code{if}, @code{when} and @code{define}, prompt for further input with
29039 @samp{>}, which is not valid MI output.
29041 This feature may be removed at some stage in the future and it is
29042 recommended that front ends use the @code{-interpreter-exec} command
29043 (@pxref{-interpreter-exec}).
29045 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29046 @node GDB/MI Development and Front Ends
29047 @section @sc{gdb/mi} Development and Front Ends
29048 @cindex @sc{gdb/mi} development
29050 The application which takes the MI output and presents the state of the
29051 program being debugged to the user is called a @dfn{front end}.
29053 Since @sc{gdb/mi} is used by a variety of front ends to @value{GDBN}, changes
29054 to the MI interface may break existing usage. This section describes how the
29055 protocol changes and how to request previous version of the protocol when it
29058 Some changes in MI need not break a carefully designed front end, and
29059 for these the MI version will remain unchanged. The following is a
29060 list of changes that may occur within one level, so front ends should
29061 parse MI output in a way that can handle them:
29065 New MI commands may be added.
29068 New fields may be added to the output of any MI command.
29071 The range of values for fields with specified values, e.g.,
29072 @code{in_scope} (@pxref{-var-update}) may be extended.
29074 @c The format of field's content e.g type prefix, may change so parse it
29075 @c at your own risk. Yes, in general?
29077 @c The order of fields may change? Shouldn't really matter but it might
29078 @c resolve inconsistencies.
29081 If the changes are likely to break front ends, the MI version level
29082 will be increased by one. The new versions of the MI protocol are not compatible
29083 with the old versions. Old versions of MI remain available, allowing front ends
29084 to keep using them until they are modified to use the latest MI version.
29086 Since @code{--interpreter=mi} always points to the latest MI version, it is
29087 recommended that front ends request a specific version of MI when launching
29088 @value{GDBN} (e.g. @code{--interpreter=mi2}) to make sure they get an
29089 interpreter with the MI version they expect.
29091 The following table gives a summary of the released versions of the MI
29092 interface: the version number, the version of GDB in which it first appeared
29093 and the breaking changes compared to the previous version.
29095 @multitable @columnfractions .05 .05 .9
29096 @headitem MI version @tab GDB version @tab Breaking changes
29113 The @code{-environment-pwd}, @code{-environment-directory} and
29114 @code{-environment-path} commands now returns values using the MI output
29115 syntax, rather than CLI output syntax.
29118 @code{-var-list-children}'s @code{children} result field is now a list, rather
29122 @code{-var-update}'s @code{changelist} result field is now a list, rather than
29134 The output of information about multi-location breakpoints has changed in the
29135 responses to the @code{-break-insert} and @code{-break-info} commands, as well
29136 as in the @code{=breakpoint-created} and @code{=breakpoint-modified} events.
29137 The multiple locations are now placed in a @code{locations} field, whose value
29143 If your front end cannot yet migrate to a more recent version of the
29144 MI protocol, you can nevertheless selectively enable specific features
29145 available in those recent MI versions, using the following commands:
29149 @item -fix-multi-location-breakpoint-output
29150 Use the output for multi-location breakpoints which was introduced by
29151 MI 3, even when using MI versions 2 or 1. This command has no
29152 effect when using MI version 3 or later.
29156 The best way to avoid unexpected changes in MI that might break your front
29157 end is to make your project known to @value{GDBN} developers and
29158 follow development on @email{gdb@@sourceware.org} and
29159 @email{gdb-patches@@sourceware.org}.
29160 @cindex mailing lists
29162 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29163 @node GDB/MI Output Records
29164 @section @sc{gdb/mi} Output Records
29167 * GDB/MI Result Records::
29168 * GDB/MI Stream Records::
29169 * GDB/MI Async Records::
29170 * GDB/MI Breakpoint Information::
29171 * GDB/MI Frame Information::
29172 * GDB/MI Thread Information::
29173 * GDB/MI Ada Exception Information::
29176 @node GDB/MI Result Records
29177 @subsection @sc{gdb/mi} Result Records
29179 @cindex result records in @sc{gdb/mi}
29180 @cindex @sc{gdb/mi}, result records
29181 In addition to a number of out-of-band notifications, the response to a
29182 @sc{gdb/mi} command includes one of the following result indications:
29186 @item "^done" [ "," @var{results} ]
29187 The synchronous operation was successful, @code{@var{results}} are the return
29192 This result record is equivalent to @samp{^done}. Historically, it
29193 was output instead of @samp{^done} if the command has resumed the
29194 target. This behaviour is maintained for backward compatibility, but
29195 all frontends should treat @samp{^done} and @samp{^running}
29196 identically and rely on the @samp{*running} output record to determine
29197 which threads are resumed.
29201 @value{GDBN} has connected to a remote target.
29203 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
29205 The operation failed. The @code{msg=@var{c-string}} variable contains
29206 the corresponding error message.
29208 If present, the @code{code=@var{c-string}} variable provides an error
29209 code on which consumers can rely on to detect the corresponding
29210 error condition. At present, only one error code is defined:
29213 @item "undefined-command"
29214 Indicates that the command causing the error does not exist.
29219 @value{GDBN} has terminated.
29223 @node GDB/MI Stream Records
29224 @subsection @sc{gdb/mi} Stream Records
29226 @cindex @sc{gdb/mi}, stream records
29227 @cindex stream records in @sc{gdb/mi}
29228 @value{GDBN} internally maintains a number of output streams: the console, the
29229 target, and the log. The output intended for each of these streams is
29230 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
29232 Each stream record begins with a unique @dfn{prefix character} which
29233 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
29234 Syntax}). In addition to the prefix, each stream record contains a
29235 @code{@var{string-output}}. This is either raw text (with an implicit new
29236 line) or a quoted C string (which does not contain an implicit newline).
29239 @item "~" @var{string-output}
29240 The console output stream contains text that should be displayed in the
29241 CLI console window. It contains the textual responses to CLI commands.
29243 @item "@@" @var{string-output}
29244 The target output stream contains any textual output from the running
29245 target. This is only present when GDB's event loop is truly
29246 asynchronous, which is currently only the case for remote targets.
29248 @item "&" @var{string-output}
29249 The log stream contains debugging messages being produced by @value{GDBN}'s
29253 @node GDB/MI Async Records
29254 @subsection @sc{gdb/mi} Async Records
29256 @cindex async records in @sc{gdb/mi}
29257 @cindex @sc{gdb/mi}, async records
29258 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
29259 additional changes that have occurred. Those changes can either be a
29260 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
29261 target activity (e.g., target stopped).
29263 The following is the list of possible async records:
29267 @item *running,thread-id="@var{thread}"
29268 The target is now running. The @var{thread} field can be the global
29269 thread ID of the thread that is now running, and it can be
29270 @samp{all} if all threads are running. The frontend should assume
29271 that no interaction with a running thread is possible after this
29272 notification is produced. The frontend should not assume that this
29273 notification is output only once for any command. @value{GDBN} may
29274 emit this notification several times, either for different threads,
29275 because it cannot resume all threads together, or even for a single
29276 thread, if the thread must be stepped though some code before letting
29279 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
29280 The target has stopped. The @var{reason} field can have one of the
29284 @item breakpoint-hit
29285 A breakpoint was reached.
29286 @item watchpoint-trigger
29287 A watchpoint was triggered.
29288 @item read-watchpoint-trigger
29289 A read watchpoint was triggered.
29290 @item access-watchpoint-trigger
29291 An access watchpoint was triggered.
29292 @item function-finished
29293 An -exec-finish or similar CLI command was accomplished.
29294 @item location-reached
29295 An -exec-until or similar CLI command was accomplished.
29296 @item watchpoint-scope
29297 A watchpoint has gone out of scope.
29298 @item end-stepping-range
29299 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
29300 similar CLI command was accomplished.
29301 @item exited-signalled
29302 The inferior exited because of a signal.
29304 The inferior exited.
29305 @item exited-normally
29306 The inferior exited normally.
29307 @item signal-received
29308 A signal was received by the inferior.
29310 The inferior has stopped due to a library being loaded or unloaded.
29311 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
29312 set or when a @code{catch load} or @code{catch unload} catchpoint is
29313 in use (@pxref{Set Catchpoints}).
29315 The inferior has forked. This is reported when @code{catch fork}
29316 (@pxref{Set Catchpoints}) has been used.
29318 The inferior has vforked. This is reported in when @code{catch vfork}
29319 (@pxref{Set Catchpoints}) has been used.
29320 @item syscall-entry
29321 The inferior entered a system call. This is reported when @code{catch
29322 syscall} (@pxref{Set Catchpoints}) has been used.
29323 @item syscall-return
29324 The inferior returned from a system call. This is reported when
29325 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
29327 The inferior called @code{exec}. This is reported when @code{catch exec}
29328 (@pxref{Set Catchpoints}) has been used.
29331 The @var{id} field identifies the global thread ID of the thread
29332 that directly caused the stop -- for example by hitting a breakpoint.
29333 Depending on whether all-stop
29334 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
29335 stop all threads, or only the thread that directly triggered the stop.
29336 If all threads are stopped, the @var{stopped} field will have the
29337 value of @code{"all"}. Otherwise, the value of the @var{stopped}
29338 field will be a list of thread identifiers. Presently, this list will
29339 always include a single thread, but frontend should be prepared to see
29340 several threads in the list. The @var{core} field reports the
29341 processor core on which the stop event has happened. This field may be absent
29342 if such information is not available.
29344 @item =thread-group-added,id="@var{id}"
29345 @itemx =thread-group-removed,id="@var{id}"
29346 A thread group was either added or removed. The @var{id} field
29347 contains the @value{GDBN} identifier of the thread group. When a thread
29348 group is added, it generally might not be associated with a running
29349 process. When a thread group is removed, its id becomes invalid and
29350 cannot be used in any way.
29352 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
29353 A thread group became associated with a running program,
29354 either because the program was just started or the thread group
29355 was attached to a program. The @var{id} field contains the
29356 @value{GDBN} identifier of the thread group. The @var{pid} field
29357 contains process identifier, specific to the operating system.
29359 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
29360 A thread group is no longer associated with a running program,
29361 either because the program has exited, or because it was detached
29362 from. The @var{id} field contains the @value{GDBN} identifier of the
29363 thread group. The @var{code} field is the exit code of the inferior; it exists
29364 only when the inferior exited with some code.
29366 @item =thread-created,id="@var{id}",group-id="@var{gid}"
29367 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
29368 A thread either was created, or has exited. The @var{id} field
29369 contains the global @value{GDBN} identifier of the thread. The @var{gid}
29370 field identifies the thread group this thread belongs to.
29372 @item =thread-selected,id="@var{id}"[,frame="@var{frame}"]
29373 Informs that the selected thread or frame were changed. This notification
29374 is not emitted as result of the @code{-thread-select} or
29375 @code{-stack-select-frame} commands, but is emitted whenever an MI command
29376 that is not documented to change the selected thread and frame actually
29377 changes them. In particular, invoking, directly or indirectly
29378 (via user-defined command), the CLI @code{thread} or @code{frame} commands,
29379 will generate this notification. Changing the thread or frame from another
29380 user interface (see @ref{Interpreters}) will also generate this notification.
29382 The @var{frame} field is only present if the newly selected thread is
29383 stopped. See @ref{GDB/MI Frame Information} for the format of its value.
29385 We suggest that in response to this notification, front ends
29386 highlight the selected thread and cause subsequent commands to apply to
29389 @item =library-loaded,...
29390 Reports that a new library file was loaded by the program. This
29391 notification has 5 fields---@var{id}, @var{target-name},
29392 @var{host-name}, @var{symbols-loaded} and @var{ranges}. The @var{id} field is an
29393 opaque identifier of the library. For remote debugging case,
29394 @var{target-name} and @var{host-name} fields give the name of the
29395 library file on the target, and on the host respectively. For native
29396 debugging, both those fields have the same value. The
29397 @var{symbols-loaded} field is emitted only for backward compatibility
29398 and should not be relied on to convey any useful information. The
29399 @var{thread-group} field, if present, specifies the id of the thread
29400 group in whose context the library was loaded. If the field is
29401 absent, it means the library was loaded in the context of all present
29402 thread groups. The @var{ranges} field specifies the ranges of addresses belonging
29405 @item =library-unloaded,...
29406 Reports that a library was unloaded by the program. This notification
29407 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
29408 the same meaning as for the @code{=library-loaded} notification.
29409 The @var{thread-group} field, if present, specifies the id of the
29410 thread group in whose context the library was unloaded. If the field is
29411 absent, it means the library was unloaded in the context of all present
29414 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
29415 @itemx =traceframe-changed,end
29416 Reports that the trace frame was changed and its new number is
29417 @var{tfnum}. The number of the tracepoint associated with this trace
29418 frame is @var{tpnum}.
29420 @item =tsv-created,name=@var{name},initial=@var{initial}
29421 Reports that the new trace state variable @var{name} is created with
29422 initial value @var{initial}.
29424 @item =tsv-deleted,name=@var{name}
29425 @itemx =tsv-deleted
29426 Reports that the trace state variable @var{name} is deleted or all
29427 trace state variables are deleted.
29429 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
29430 Reports that the trace state variable @var{name} is modified with
29431 the initial value @var{initial}. The current value @var{current} of
29432 trace state variable is optional and is reported if the current
29433 value of trace state variable is known.
29435 @item =breakpoint-created,bkpt=@{...@}
29436 @itemx =breakpoint-modified,bkpt=@{...@}
29437 @itemx =breakpoint-deleted,id=@var{number}
29438 Reports that a breakpoint was created, modified, or deleted,
29439 respectively. Only user-visible breakpoints are reported to the MI
29442 The @var{bkpt} argument is of the same form as returned by the various
29443 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
29444 @var{number} is the ordinal number of the breakpoint.
29446 Note that if a breakpoint is emitted in the result record of a
29447 command, then it will not also be emitted in an async record.
29449 @item =record-started,thread-group="@var{id}",method="@var{method}"[,format="@var{format}"]
29450 @itemx =record-stopped,thread-group="@var{id}"
29451 Execution log recording was either started or stopped on an
29452 inferior. The @var{id} is the @value{GDBN} identifier of the thread
29453 group corresponding to the affected inferior.
29455 The @var{method} field indicates the method used to record execution. If the
29456 method in use supports multiple recording formats, @var{format} will be present
29457 and contain the currently used format. @xref{Process Record and Replay},
29458 for existing method and format values.
29460 @item =cmd-param-changed,param=@var{param},value=@var{value}
29461 Reports that a parameter of the command @code{set @var{param}} is
29462 changed to @var{value}. In the multi-word @code{set} command,
29463 the @var{param} is the whole parameter list to @code{set} command.
29464 For example, In command @code{set check type on}, @var{param}
29465 is @code{check type} and @var{value} is @code{on}.
29467 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
29468 Reports that bytes from @var{addr} to @var{data} + @var{len} were
29469 written in an inferior. The @var{id} is the identifier of the
29470 thread group corresponding to the affected inferior. The optional
29471 @code{type="code"} part is reported if the memory written to holds
29475 @node GDB/MI Breakpoint Information
29476 @subsection @sc{gdb/mi} Breakpoint Information
29478 When @value{GDBN} reports information about a breakpoint, a
29479 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
29484 The breakpoint number.
29487 The type of the breakpoint. For ordinary breakpoints this will be
29488 @samp{breakpoint}, but many values are possible.
29491 If the type of the breakpoint is @samp{catchpoint}, then this
29492 indicates the exact type of catchpoint.
29495 This is the breakpoint disposition---either @samp{del}, meaning that
29496 the breakpoint will be deleted at the next stop, or @samp{keep},
29497 meaning that the breakpoint will not be deleted.
29500 This indicates whether the breakpoint is enabled, in which case the
29501 value is @samp{y}, or disabled, in which case the value is @samp{n}.
29502 Note that this is not the same as the field @code{enable}.
29505 The address of the breakpoint. This may be a hexidecimal number,
29506 giving the address; or the string @samp{<PENDING>}, for a pending
29507 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
29508 multiple locations. This field will not be present if no address can
29509 be determined. For example, a watchpoint does not have an address.
29512 Optional field containing any flags related to the address. These flags are
29513 architecture-dependent; see @ref{Architectures} for their meaning for a
29517 If known, the function in which the breakpoint appears.
29518 If not known, this field is not present.
29521 The name of the source file which contains this function, if known.
29522 If not known, this field is not present.
29525 The full file name of the source file which contains this function, if
29526 known. If not known, this field is not present.
29529 The line number at which this breakpoint appears, if known.
29530 If not known, this field is not present.
29533 If the source file is not known, this field may be provided. If
29534 provided, this holds the address of the breakpoint, possibly followed
29538 If this breakpoint is pending, this field is present and holds the
29539 text used to set the breakpoint, as entered by the user.
29542 Where this breakpoint's condition is evaluated, either @samp{host} or
29546 If this is a thread-specific breakpoint, then this identifies the
29547 thread in which the breakpoint can trigger.
29550 If this breakpoint is restricted to a particular Ada task, then this
29551 field will hold the task identifier.
29554 If the breakpoint is conditional, this is the condition expression.
29557 The ignore count of the breakpoint.
29560 The enable count of the breakpoint.
29562 @item traceframe-usage
29565 @item static-tracepoint-marker-string-id
29566 For a static tracepoint, the name of the static tracepoint marker.
29569 For a masked watchpoint, this is the mask.
29572 A tracepoint's pass count.
29574 @item original-location
29575 The location of the breakpoint as originally specified by the user.
29576 This field is optional.
29579 The number of times the breakpoint has been hit.
29582 This field is only given for tracepoints. This is either @samp{y},
29583 meaning that the tracepoint is installed, or @samp{n}, meaning that it
29587 Some extra data, the exact contents of which are type-dependent.
29590 This field is present if the breakpoint has multiple locations. It is also
29591 exceptionally present if the breakpoint is enabled and has a single, disabled
29594 The value is a list of locations. The format of a location is described below.
29598 A location in a multi-location breakpoint is represented as a tuple with the
29604 The location number as a dotted pair, like @samp{1.2}. The first digit is the
29605 number of the parent breakpoint. The second digit is the number of the
29606 location within that breakpoint.
29609 This indicates whether the location is enabled, in which case the
29610 value is @samp{y}, or disabled, in which case the value is @samp{n}.
29611 Note that this is not the same as the field @code{enable}.
29614 The address of this location as an hexidecimal number.
29617 Optional field containing any flags related to the address. These flags are
29618 architecture-dependent; see @ref{Architectures} for their meaning for a
29622 If known, the function in which the location appears.
29623 If not known, this field is not present.
29626 The name of the source file which contains this location, if known.
29627 If not known, this field is not present.
29630 The full file name of the source file which contains this location, if
29631 known. If not known, this field is not present.
29634 The line number at which this location appears, if known.
29635 If not known, this field is not present.
29637 @item thread-groups
29638 The thread groups this location is in.
29642 For example, here is what the output of @code{-break-insert}
29643 (@pxref{GDB/MI Breakpoint Commands}) might be:
29646 -> -break-insert main
29647 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
29648 enabled="y",addr="0x08048564",func="main",file="myprog.c",
29649 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
29654 @node GDB/MI Frame Information
29655 @subsection @sc{gdb/mi} Frame Information
29657 Response from many MI commands includes an information about stack
29658 frame. This information is a tuple that may have the following
29663 The level of the stack frame. The innermost frame has the level of
29664 zero. This field is always present.
29667 The name of the function corresponding to the frame. This field may
29668 be absent if @value{GDBN} is unable to determine the function name.
29671 The code address for the frame. This field is always present.
29674 Optional field containing any flags related to the address. These flags are
29675 architecture-dependent; see @ref{Architectures} for their meaning for a
29679 The name of the source files that correspond to the frame's code
29680 address. This field may be absent.
29683 The source line corresponding to the frames' code address. This field
29687 The name of the binary file (either executable or shared library) the
29688 corresponds to the frame's code address. This field may be absent.
29692 @node GDB/MI Thread Information
29693 @subsection @sc{gdb/mi} Thread Information
29695 Whenever @value{GDBN} has to report an information about a thread, it
29696 uses a tuple with the following fields. The fields are always present unless
29701 The global numeric id assigned to the thread by @value{GDBN}.
29704 The target-specific string identifying the thread.
29707 Additional information about the thread provided by the target.
29708 It is supposed to be human-readable and not interpreted by the
29709 frontend. This field is optional.
29712 The name of the thread. If the user specified a name using the
29713 @code{thread name} command, then this name is given. Otherwise, if
29714 @value{GDBN} can extract the thread name from the target, then that
29715 name is given. If @value{GDBN} cannot find the thread name, then this
29719 The execution state of the thread, either @samp{stopped} or @samp{running},
29720 depending on whether the thread is presently running.
29723 The stack frame currently executing in the thread. This field is only present
29724 if the thread is stopped. Its format is documented in
29725 @ref{GDB/MI Frame Information}.
29728 The value of this field is an integer number of the processor core the
29729 thread was last seen on. This field is optional.
29732 @node GDB/MI Ada Exception Information
29733 @subsection @sc{gdb/mi} Ada Exception Information
29735 Whenever a @code{*stopped} record is emitted because the program
29736 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
29737 @value{GDBN} provides the name of the exception that was raised via
29738 the @code{exception-name} field. Also, for exceptions that were raised
29739 with an exception message, @value{GDBN} provides that message via
29740 the @code{exception-message} field.
29742 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29743 @node GDB/MI Simple Examples
29744 @section Simple Examples of @sc{gdb/mi} Interaction
29745 @cindex @sc{gdb/mi}, simple examples
29747 This subsection presents several simple examples of interaction using
29748 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
29749 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
29750 the output received from @sc{gdb/mi}.
29752 Note the line breaks shown in the examples are here only for
29753 readability, they don't appear in the real output.
29755 @subheading Setting a Breakpoint
29757 Setting a breakpoint generates synchronous output which contains detailed
29758 information of the breakpoint.
29761 -> -break-insert main
29762 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
29763 enabled="y",addr="0x08048564",func="main",file="myprog.c",
29764 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
29769 @subheading Program Execution
29771 Program execution generates asynchronous records and MI gives the
29772 reason that execution stopped.
29778 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
29779 frame=@{addr="0x08048564",func="main",
29780 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
29781 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68",
29782 arch="i386:x86_64"@}
29787 <- *stopped,reason="exited-normally"
29791 @subheading Quitting @value{GDBN}
29793 Quitting @value{GDBN} just prints the result class @samp{^exit}.
29801 Please note that @samp{^exit} is printed immediately, but it might
29802 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
29803 performs necessary cleanups, including killing programs being debugged
29804 or disconnecting from debug hardware, so the frontend should wait till
29805 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
29806 fails to exit in reasonable time.
29808 @subheading A Bad Command
29810 Here's what happens if you pass a non-existent command:
29814 <- ^error,msg="Undefined MI command: rubbish"
29819 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29820 @node GDB/MI Command Description Format
29821 @section @sc{gdb/mi} Command Description Format
29823 The remaining sections describe blocks of commands. Each block of
29824 commands is laid out in a fashion similar to this section.
29826 @subheading Motivation
29828 The motivation for this collection of commands.
29830 @subheading Introduction
29832 A brief introduction to this collection of commands as a whole.
29834 @subheading Commands
29836 For each command in the block, the following is described:
29838 @subsubheading Synopsis
29841 -command @var{args}@dots{}
29844 @subsubheading Result
29846 @subsubheading @value{GDBN} Command
29848 The corresponding @value{GDBN} CLI command(s), if any.
29850 @subsubheading Example
29852 Example(s) formatted for readability. Some of the described commands have
29853 not been implemented yet and these are labeled N.A.@: (not available).
29856 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29857 @node GDB/MI Breakpoint Commands
29858 @section @sc{gdb/mi} Breakpoint Commands
29860 @cindex breakpoint commands for @sc{gdb/mi}
29861 @cindex @sc{gdb/mi}, breakpoint commands
29862 This section documents @sc{gdb/mi} commands for manipulating
29865 @subheading The @code{-break-after} Command
29866 @findex -break-after
29868 @subsubheading Synopsis
29871 -break-after @var{number} @var{count}
29874 The breakpoint number @var{number} is not in effect until it has been
29875 hit @var{count} times. To see how this is reflected in the output of
29876 the @samp{-break-list} command, see the description of the
29877 @samp{-break-list} command below.
29879 @subsubheading @value{GDBN} Command
29881 The corresponding @value{GDBN} command is @samp{ignore}.
29883 @subsubheading Example
29888 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
29889 enabled="y",addr="0x000100d0",func="main",file="hello.c",
29890 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
29898 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
29899 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29900 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29901 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29902 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29903 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29904 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29905 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29906 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
29907 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
29912 @subheading The @code{-break-catch} Command
29913 @findex -break-catch
29916 @subheading The @code{-break-commands} Command
29917 @findex -break-commands
29919 @subsubheading Synopsis
29922 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
29925 Specifies the CLI commands that should be executed when breakpoint
29926 @var{number} is hit. The parameters @var{command1} to @var{commandN}
29927 are the commands. If no command is specified, any previously-set
29928 commands are cleared. @xref{Break Commands}. Typical use of this
29929 functionality is tracing a program, that is, printing of values of
29930 some variables whenever breakpoint is hit and then continuing.
29932 @subsubheading @value{GDBN} Command
29934 The corresponding @value{GDBN} command is @samp{commands}.
29936 @subsubheading Example
29941 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
29942 enabled="y",addr="0x000100d0",func="main",file="hello.c",
29943 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
29946 -break-commands 1 "print v" "continue"
29951 @subheading The @code{-break-condition} Command
29952 @findex -break-condition
29954 @subsubheading Synopsis
29957 -break-condition @var{number} @var{expr}
29960 Breakpoint @var{number} will stop the program only if the condition in
29961 @var{expr} is true. The condition becomes part of the
29962 @samp{-break-list} output (see the description of the @samp{-break-list}
29965 @subsubheading @value{GDBN} Command
29967 The corresponding @value{GDBN} command is @samp{condition}.
29969 @subsubheading Example
29973 -break-condition 1 1
29977 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
29978 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29979 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29980 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29981 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29982 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29983 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29984 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29985 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
29986 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
29990 @subheading The @code{-break-delete} Command
29991 @findex -break-delete
29993 @subsubheading Synopsis
29996 -break-delete ( @var{breakpoint} )+
29999 Delete the breakpoint(s) whose number(s) are specified in the argument
30000 list. This is obviously reflected in the breakpoint list.
30002 @subsubheading @value{GDBN} Command
30004 The corresponding @value{GDBN} command is @samp{delete}.
30006 @subsubheading Example
30014 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
30015 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30016 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30017 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30018 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30019 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30020 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30025 @subheading The @code{-break-disable} Command
30026 @findex -break-disable
30028 @subsubheading Synopsis
30031 -break-disable ( @var{breakpoint} )+
30034 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
30035 break list is now set to @samp{n} for the named @var{breakpoint}(s).
30037 @subsubheading @value{GDBN} Command
30039 The corresponding @value{GDBN} command is @samp{disable}.
30041 @subsubheading Example
30049 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30050 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30051 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30052 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30053 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30054 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30055 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30056 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
30057 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
30058 line="5",thread-groups=["i1"],times="0"@}]@}
30062 @subheading The @code{-break-enable} Command
30063 @findex -break-enable
30065 @subsubheading Synopsis
30068 -break-enable ( @var{breakpoint} )+
30071 Enable (previously disabled) @var{breakpoint}(s).
30073 @subsubheading @value{GDBN} Command
30075 The corresponding @value{GDBN} command is @samp{enable}.
30077 @subsubheading Example
30085 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30086 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30087 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30088 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30089 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30090 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30091 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30092 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
30093 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
30094 line="5",thread-groups=["i1"],times="0"@}]@}
30098 @subheading The @code{-break-info} Command
30099 @findex -break-info
30101 @subsubheading Synopsis
30104 -break-info @var{breakpoint}
30108 Get information about a single breakpoint.
30110 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
30111 Information}, for details on the format of each breakpoint in the
30114 @subsubheading @value{GDBN} Command
30116 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
30118 @subsubheading Example
30121 @subheading The @code{-break-insert} Command
30122 @findex -break-insert
30123 @anchor{-break-insert}
30125 @subsubheading Synopsis
30128 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
30129 [ -c @var{condition} ] [ -i @var{ignore-count} ]
30130 [ -p @var{thread-id} ] [ @var{location} ]
30134 If specified, @var{location}, can be one of:
30137 @item linespec location
30138 A linespec location. @xref{Linespec Locations}.
30140 @item explicit location
30141 An explicit location. @sc{gdb/mi} explicit locations are
30142 analogous to the CLI's explicit locations using the option names
30143 listed below. @xref{Explicit Locations}.
30146 @item --source @var{filename}
30147 The source file name of the location. This option requires the use
30148 of either @samp{--function} or @samp{--line}.
30150 @item --function @var{function}
30151 The name of a function or method.
30153 @item --label @var{label}
30154 The name of a label.
30156 @item --line @var{lineoffset}
30157 An absolute or relative line offset from the start of the location.
30160 @item address location
30161 An address location, *@var{address}. @xref{Address Locations}.
30165 The possible optional parameters of this command are:
30169 Insert a temporary breakpoint.
30171 Insert a hardware breakpoint.
30173 If @var{location} cannot be parsed (for example if it
30174 refers to unknown files or functions), create a pending
30175 breakpoint. Without this flag, @value{GDBN} will report
30176 an error, and won't create a breakpoint, if @var{location}
30179 Create a disabled breakpoint.
30181 Create a tracepoint. @xref{Tracepoints}. When this parameter
30182 is used together with @samp{-h}, a fast tracepoint is created.
30183 @item -c @var{condition}
30184 Make the breakpoint conditional on @var{condition}.
30185 @item -i @var{ignore-count}
30186 Initialize the @var{ignore-count}.
30187 @item -p @var{thread-id}
30188 Restrict the breakpoint to the thread with the specified global
30192 @subsubheading Result
30194 @xref{GDB/MI Breakpoint Information}, for details on the format of the
30195 resulting breakpoint.
30197 Note: this format is open to change.
30198 @c An out-of-band breakpoint instead of part of the result?
30200 @subsubheading @value{GDBN} Command
30202 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
30203 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
30205 @subsubheading Example
30210 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
30211 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
30214 -break-insert -t foo
30215 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
30216 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
30220 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30221 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30222 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30223 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30224 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30225 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30226 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30227 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30228 addr="0x0001072c", func="main",file="recursive2.c",
30229 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
30231 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
30232 addr="0x00010774",func="foo",file="recursive2.c",
30233 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
30236 @c -break-insert -r foo.*
30237 @c ~int foo(int, int);
30238 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
30239 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
30244 @subheading The @code{-dprintf-insert} Command
30245 @findex -dprintf-insert
30247 @subsubheading Synopsis
30250 -dprintf-insert [ -t ] [ -f ] [ -d ]
30251 [ -c @var{condition} ] [ -i @var{ignore-count} ]
30252 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
30257 If supplied, @var{location} may be specified the same way as for
30258 the @code{-break-insert} command. @xref{-break-insert}.
30260 The possible optional parameters of this command are:
30264 Insert a temporary breakpoint.
30266 If @var{location} cannot be parsed (for example, if it
30267 refers to unknown files or functions), create a pending
30268 breakpoint. Without this flag, @value{GDBN} will report
30269 an error, and won't create a breakpoint, if @var{location}
30272 Create a disabled breakpoint.
30273 @item -c @var{condition}
30274 Make the breakpoint conditional on @var{condition}.
30275 @item -i @var{ignore-count}
30276 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
30277 to @var{ignore-count}.
30278 @item -p @var{thread-id}
30279 Restrict the breakpoint to the thread with the specified global
30283 @subsubheading Result
30285 @xref{GDB/MI Breakpoint Information}, for details on the format of the
30286 resulting breakpoint.
30288 @c An out-of-band breakpoint instead of part of the result?
30290 @subsubheading @value{GDBN} Command
30292 The corresponding @value{GDBN} command is @samp{dprintf}.
30294 @subsubheading Example
30298 4-dprintf-insert foo "At foo entry\n"
30299 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
30300 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
30301 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
30302 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
30303 original-location="foo"@}
30305 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
30306 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
30307 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
30308 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
30309 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
30310 original-location="mi-dprintf.c:26"@}
30314 @subheading The @code{-break-list} Command
30315 @findex -break-list
30317 @subsubheading Synopsis
30323 Displays the list of inserted breakpoints, showing the following fields:
30327 number of the breakpoint
30329 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
30331 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
30334 is the breakpoint enabled or no: @samp{y} or @samp{n}
30336 memory location at which the breakpoint is set
30338 logical location of the breakpoint, expressed by function name, file
30340 @item Thread-groups
30341 list of thread groups to which this breakpoint applies
30343 number of times the breakpoint has been hit
30346 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
30347 @code{body} field is an empty list.
30349 @subsubheading @value{GDBN} Command
30351 The corresponding @value{GDBN} command is @samp{info break}.
30353 @subsubheading Example
30358 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30359 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30360 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30361 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30362 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30363 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30364 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30365 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30366 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
30368 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
30369 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
30370 line="13",thread-groups=["i1"],times="0"@}]@}
30374 Here's an example of the result when there are no breakpoints:
30379 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
30380 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30381 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30382 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30383 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30384 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30385 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30390 @subheading The @code{-break-passcount} Command
30391 @findex -break-passcount
30393 @subsubheading Synopsis
30396 -break-passcount @var{tracepoint-number} @var{passcount}
30399 Set the passcount for tracepoint @var{tracepoint-number} to
30400 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
30401 is not a tracepoint, error is emitted. This corresponds to CLI
30402 command @samp{passcount}.
30404 @subheading The @code{-break-watch} Command
30405 @findex -break-watch
30407 @subsubheading Synopsis
30410 -break-watch [ -a | -r ]
30413 Create a watchpoint. With the @samp{-a} option it will create an
30414 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
30415 read from or on a write to the memory location. With the @samp{-r}
30416 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
30417 trigger only when the memory location is accessed for reading. Without
30418 either of the options, the watchpoint created is a regular watchpoint,
30419 i.e., it will trigger when the memory location is accessed for writing.
30420 @xref{Set Watchpoints, , Setting Watchpoints}.
30422 Note that @samp{-break-list} will report a single list of watchpoints and
30423 breakpoints inserted.
30425 @subsubheading @value{GDBN} Command
30427 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
30430 @subsubheading Example
30432 Setting a watchpoint on a variable in the @code{main} function:
30437 ^done,wpt=@{number="2",exp="x"@}
30442 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
30443 value=@{old="-268439212",new="55"@},
30444 frame=@{func="main",args=[],file="recursive2.c",
30445 fullname="/home/foo/bar/recursive2.c",line="5",arch="i386:x86_64"@}
30449 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
30450 the program execution twice: first for the variable changing value, then
30451 for the watchpoint going out of scope.
30456 ^done,wpt=@{number="5",exp="C"@}
30461 *stopped,reason="watchpoint-trigger",
30462 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
30463 frame=@{func="callee4",args=[],
30464 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30465 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13",
30466 arch="i386:x86_64"@}
30471 *stopped,reason="watchpoint-scope",wpnum="5",
30472 frame=@{func="callee3",args=[@{name="strarg",
30473 value="0x11940 \"A string argument.\""@}],
30474 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30475 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
30476 arch="i386:x86_64"@}
30480 Listing breakpoints and watchpoints, at different points in the program
30481 execution. Note that once the watchpoint goes out of scope, it is
30487 ^done,wpt=@{number="2",exp="C"@}
30490 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30491 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30492 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30493 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30494 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30495 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30496 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30497 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30498 addr="0x00010734",func="callee4",
30499 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30500 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
30502 bkpt=@{number="2",type="watchpoint",disp="keep",
30503 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
30508 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
30509 value=@{old="-276895068",new="3"@},
30510 frame=@{func="callee4",args=[],
30511 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30512 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13",
30513 arch="i386:x86_64"@}
30516 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30517 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30518 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30519 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30520 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30521 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30522 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30523 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30524 addr="0x00010734",func="callee4",
30525 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30526 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
30528 bkpt=@{number="2",type="watchpoint",disp="keep",
30529 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
30533 ^done,reason="watchpoint-scope",wpnum="2",
30534 frame=@{func="callee3",args=[@{name="strarg",
30535 value="0x11940 \"A string argument.\""@}],
30536 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30537 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
30538 arch="i386:x86_64"@}
30541 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30542 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30543 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30544 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30545 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30546 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30547 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30548 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30549 addr="0x00010734",func="callee4",
30550 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30551 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
30552 thread-groups=["i1"],times="1"@}]@}
30557 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30558 @node GDB/MI Catchpoint Commands
30559 @section @sc{gdb/mi} Catchpoint Commands
30561 This section documents @sc{gdb/mi} commands for manipulating
30565 * Shared Library GDB/MI Catchpoint Commands::
30566 * Ada Exception GDB/MI Catchpoint Commands::
30567 * C++ Exception GDB/MI Catchpoint Commands::
30570 @node Shared Library GDB/MI Catchpoint Commands
30571 @subsection Shared Library @sc{gdb/mi} Catchpoints
30573 @subheading The @code{-catch-load} Command
30574 @findex -catch-load
30576 @subsubheading Synopsis
30579 -catch-load [ -t ] [ -d ] @var{regexp}
30582 Add a catchpoint for library load events. If the @samp{-t} option is used,
30583 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
30584 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
30585 in a disabled state. The @samp{regexp} argument is a regular
30586 expression used to match the name of the loaded library.
30589 @subsubheading @value{GDBN} Command
30591 The corresponding @value{GDBN} command is @samp{catch load}.
30593 @subsubheading Example
30596 -catch-load -t foo.so
30597 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
30598 what="load of library matching foo.so",catch-type="load",times="0"@}
30603 @subheading The @code{-catch-unload} Command
30604 @findex -catch-unload
30606 @subsubheading Synopsis
30609 -catch-unload [ -t ] [ -d ] @var{regexp}
30612 Add a catchpoint for library unload events. If the @samp{-t} option is
30613 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
30614 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
30615 created in a disabled state. The @samp{regexp} argument is a regular
30616 expression used to match the name of the unloaded library.
30618 @subsubheading @value{GDBN} Command
30620 The corresponding @value{GDBN} command is @samp{catch unload}.
30622 @subsubheading Example
30625 -catch-unload -d bar.so
30626 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
30627 what="load of library matching bar.so",catch-type="unload",times="0"@}
30631 @node Ada Exception GDB/MI Catchpoint Commands
30632 @subsection Ada Exception @sc{gdb/mi} Catchpoints
30634 The following @sc{gdb/mi} commands can be used to create catchpoints
30635 that stop the execution when Ada exceptions are being raised.
30637 @subheading The @code{-catch-assert} Command
30638 @findex -catch-assert
30640 @subsubheading Synopsis
30643 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
30646 Add a catchpoint for failed Ada assertions.
30648 The possible optional parameters for this command are:
30651 @item -c @var{condition}
30652 Make the catchpoint conditional on @var{condition}.
30654 Create a disabled catchpoint.
30656 Create a temporary catchpoint.
30659 @subsubheading @value{GDBN} Command
30661 The corresponding @value{GDBN} command is @samp{catch assert}.
30663 @subsubheading Example
30667 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
30668 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
30669 thread-groups=["i1"],times="0",
30670 original-location="__gnat_debug_raise_assert_failure"@}
30674 @subheading The @code{-catch-exception} Command
30675 @findex -catch-exception
30677 @subsubheading Synopsis
30680 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
30684 Add a catchpoint stopping when Ada exceptions are raised.
30685 By default, the command stops the program when any Ada exception
30686 gets raised. But it is also possible, by using some of the
30687 optional parameters described below, to create more selective
30690 The possible optional parameters for this command are:
30693 @item -c @var{condition}
30694 Make the catchpoint conditional on @var{condition}.
30696 Create a disabled catchpoint.
30697 @item -e @var{exception-name}
30698 Only stop when @var{exception-name} is raised. This option cannot
30699 be used combined with @samp{-u}.
30701 Create a temporary catchpoint.
30703 Stop only when an unhandled exception gets raised. This option
30704 cannot be used combined with @samp{-e}.
30707 @subsubheading @value{GDBN} Command
30709 The corresponding @value{GDBN} commands are @samp{catch exception}
30710 and @samp{catch exception unhandled}.
30712 @subsubheading Example
30715 -catch-exception -e Program_Error
30716 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
30717 enabled="y",addr="0x0000000000404874",
30718 what="`Program_Error' Ada exception", thread-groups=["i1"],
30719 times="0",original-location="__gnat_debug_raise_exception"@}
30723 @subheading The @code{-catch-handlers} Command
30724 @findex -catch-handlers
30726 @subsubheading Synopsis
30729 -catch-handlers [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
30733 Add a catchpoint stopping when Ada exceptions are handled.
30734 By default, the command stops the program when any Ada exception
30735 gets handled. But it is also possible, by using some of the
30736 optional parameters described below, to create more selective
30739 The possible optional parameters for this command are:
30742 @item -c @var{condition}
30743 Make the catchpoint conditional on @var{condition}.
30745 Create a disabled catchpoint.
30746 @item -e @var{exception-name}
30747 Only stop when @var{exception-name} is handled.
30749 Create a temporary catchpoint.
30752 @subsubheading @value{GDBN} Command
30754 The corresponding @value{GDBN} command is @samp{catch handlers}.
30756 @subsubheading Example
30759 -catch-handlers -e Constraint_Error
30760 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
30761 enabled="y",addr="0x0000000000402f68",
30762 what="`Constraint_Error' Ada exception handlers",thread-groups=["i1"],
30763 times="0",original-location="__gnat_begin_handler"@}
30767 @node C++ Exception GDB/MI Catchpoint Commands
30768 @subsection C@t{++} Exception @sc{gdb/mi} Catchpoints
30770 The following @sc{gdb/mi} commands can be used to create catchpoints
30771 that stop the execution when C@t{++} exceptions are being throw, rethrown,
30774 @subheading The @code{-catch-throw} Command
30775 @findex -catch-throw
30777 @subsubheading Synopsis
30780 -catch-throw [ -t ] [ -r @var{regexp}]
30783 Stop when the debuggee throws a C@t{++} exception. If @var{regexp} is
30784 given, then only exceptions whose type matches the regular expression
30787 If @samp{-t} is given, then the catchpoint is enabled only for one
30788 stop, the catchpoint is automatically deleted after stopping once for
30791 @subsubheading @value{GDBN} Command
30793 The corresponding @value{GDBN} commands are @samp{catch throw}
30794 and @samp{tcatch throw} (@pxref{Set Catchpoints}).
30796 @subsubheading Example
30799 -catch-throw -r exception_type
30800 ^done,bkpt=@{number="1",type="catchpoint",disp="keep",enabled="y",
30801 what="exception throw",catch-type="throw",
30802 thread-groups=["i1"],
30803 regexp="exception_type",times="0"@}
30809 ~"Catchpoint 1 (exception thrown), 0x00007ffff7ae00ed
30810 in __cxa_throw () from /lib64/libstdc++.so.6\n"
30811 *stopped,bkptno="1",reason="breakpoint-hit",disp="keep",
30812 frame=@{addr="0x00007ffff7ae00ed",func="__cxa_throw",
30813 args=[],from="/lib64/libstdc++.so.6",arch="i386:x86-64"@},
30814 thread-id="1",stopped-threads="all",core="6"
30818 @subheading The @code{-catch-rethrow} Command
30819 @findex -catch-rethrow
30821 @subsubheading Synopsis
30824 -catch-rethrow [ -t ] [ -r @var{regexp}]
30827 Stop when a C@t{++} exception is re-thrown. If @var{regexp} is given,
30828 then only exceptions whose type matches the regular expression will be
30831 If @samp{-t} is given, then the catchpoint is enabled only for one
30832 stop, the catchpoint is automatically deleted after the first event is
30835 @subsubheading @value{GDBN} Command
30837 The corresponding @value{GDBN} commands are @samp{catch rethrow}
30838 and @samp{tcatch rethrow} (@pxref{Set Catchpoints}).
30840 @subsubheading Example
30843 -catch-rethrow -r exception_type
30844 ^done,bkpt=@{number="1",type="catchpoint",disp="keep",enabled="y",
30845 what="exception rethrow",catch-type="rethrow",
30846 thread-groups=["i1"],
30847 regexp="exception_type",times="0"@}
30853 ~"Catchpoint 1 (exception rethrown), 0x00007ffff7ae00ed
30854 in __cxa_rethrow () from /lib64/libstdc++.so.6\n"
30855 *stopped,bkptno="1",reason="breakpoint-hit",disp="keep",
30856 frame=@{addr="0x00007ffff7ae00ed",func="__cxa_rethrow",
30857 args=[],from="/lib64/libstdc++.so.6",arch="i386:x86-64"@},
30858 thread-id="1",stopped-threads="all",core="6"
30862 @subheading The @code{-catch-catch} Command
30863 @findex -catch-catch
30865 @subsubheading Synopsis
30868 -catch-catch [ -t ] [ -r @var{regexp}]
30871 Stop when the debuggee catches a C@t{++} exception. If @var{regexp}
30872 is given, then only exceptions whose type matches the regular
30873 expression will be caught.
30875 If @samp{-t} is given, then the catchpoint is enabled only for one
30876 stop, the catchpoint is automatically deleted after the first event is
30879 @subsubheading @value{GDBN} Command
30881 The corresponding @value{GDBN} commands are @samp{catch catch}
30882 and @samp{tcatch catch} (@pxref{Set Catchpoints}).
30884 @subsubheading Example
30887 -catch-catch -r exception_type
30888 ^done,bkpt=@{number="1",type="catchpoint",disp="keep",enabled="y",
30889 what="exception catch",catch-type="catch",
30890 thread-groups=["i1"],
30891 regexp="exception_type",times="0"@}
30897 ~"Catchpoint 1 (exception caught), 0x00007ffff7ae00ed
30898 in __cxa_begin_catch () from /lib64/libstdc++.so.6\n"
30899 *stopped,bkptno="1",reason="breakpoint-hit",disp="keep",
30900 frame=@{addr="0x00007ffff7ae00ed",func="__cxa_begin_catch",
30901 args=[],from="/lib64/libstdc++.so.6",arch="i386:x86-64"@},
30902 thread-id="1",stopped-threads="all",core="6"
30906 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30907 @node GDB/MI Program Context
30908 @section @sc{gdb/mi} Program Context
30910 @subheading The @code{-exec-arguments} Command
30911 @findex -exec-arguments
30914 @subsubheading Synopsis
30917 -exec-arguments @var{args}
30920 Set the inferior program arguments, to be used in the next
30923 @subsubheading @value{GDBN} Command
30925 The corresponding @value{GDBN} command is @samp{set args}.
30927 @subsubheading Example
30931 -exec-arguments -v word
30938 @subheading The @code{-exec-show-arguments} Command
30939 @findex -exec-show-arguments
30941 @subsubheading Synopsis
30944 -exec-show-arguments
30947 Print the arguments of the program.
30949 @subsubheading @value{GDBN} Command
30951 The corresponding @value{GDBN} command is @samp{show args}.
30953 @subsubheading Example
30958 @subheading The @code{-environment-cd} Command
30959 @findex -environment-cd
30961 @subsubheading Synopsis
30964 -environment-cd @var{pathdir}
30967 Set @value{GDBN}'s working directory.
30969 @subsubheading @value{GDBN} Command
30971 The corresponding @value{GDBN} command is @samp{cd}.
30973 @subsubheading Example
30977 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
30983 @subheading The @code{-environment-directory} Command
30984 @findex -environment-directory
30986 @subsubheading Synopsis
30989 -environment-directory [ -r ] [ @var{pathdir} ]+
30992 Add directories @var{pathdir} to beginning of search path for source files.
30993 If the @samp{-r} option is used, the search path is reset to the default
30994 search path. If directories @var{pathdir} are supplied in addition to the
30995 @samp{-r} option, the search path is first reset and then addition
30997 Multiple directories may be specified, separated by blanks. Specifying
30998 multiple directories in a single command
30999 results in the directories added to the beginning of the
31000 search path in the same order they were presented in the command.
31001 If blanks are needed as
31002 part of a directory name, double-quotes should be used around
31003 the name. In the command output, the path will show up separated
31004 by the system directory-separator character. The directory-separator
31005 character must not be used
31006 in any directory name.
31007 If no directories are specified, the current search path is displayed.
31009 @subsubheading @value{GDBN} Command
31011 The corresponding @value{GDBN} command is @samp{dir}.
31013 @subsubheading Example
31017 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
31018 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
31020 -environment-directory ""
31021 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
31023 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
31024 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
31026 -environment-directory -r
31027 ^done,source-path="$cdir:$cwd"
31032 @subheading The @code{-environment-path} Command
31033 @findex -environment-path
31035 @subsubheading Synopsis
31038 -environment-path [ -r ] [ @var{pathdir} ]+
31041 Add directories @var{pathdir} to beginning of search path for object files.
31042 If the @samp{-r} option is used, the search path is reset to the original
31043 search path that existed at gdb start-up. If directories @var{pathdir} are
31044 supplied in addition to the
31045 @samp{-r} option, the search path is first reset and then addition
31047 Multiple directories may be specified, separated by blanks. Specifying
31048 multiple directories in a single command
31049 results in the directories added to the beginning of the
31050 search path in the same order they were presented in the command.
31051 If blanks are needed as
31052 part of a directory name, double-quotes should be used around
31053 the name. In the command output, the path will show up separated
31054 by the system directory-separator character. The directory-separator
31055 character must not be used
31056 in any directory name.
31057 If no directories are specified, the current path is displayed.
31060 @subsubheading @value{GDBN} Command
31062 The corresponding @value{GDBN} command is @samp{path}.
31064 @subsubheading Example
31069 ^done,path="/usr/bin"
31071 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
31072 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
31074 -environment-path -r /usr/local/bin
31075 ^done,path="/usr/local/bin:/usr/bin"
31080 @subheading The @code{-environment-pwd} Command
31081 @findex -environment-pwd
31083 @subsubheading Synopsis
31089 Show the current working directory.
31091 @subsubheading @value{GDBN} Command
31093 The corresponding @value{GDBN} command is @samp{pwd}.
31095 @subsubheading Example
31100 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
31104 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31105 @node GDB/MI Thread Commands
31106 @section @sc{gdb/mi} Thread Commands
31109 @subheading The @code{-thread-info} Command
31110 @findex -thread-info
31112 @subsubheading Synopsis
31115 -thread-info [ @var{thread-id} ]
31118 Reports information about either a specific thread, if the
31119 @var{thread-id} parameter is present, or about all threads.
31120 @var{thread-id} is the thread's global thread ID. When printing
31121 information about all threads, also reports the global ID of the
31124 @subsubheading @value{GDBN} Command
31126 The @samp{info thread} command prints the same information
31129 @subsubheading Result
31131 The result contains the following attributes:
31135 A list of threads. The format of the elements of the list is described in
31136 @ref{GDB/MI Thread Information}.
31138 @item current-thread-id
31139 The global id of the currently selected thread. This field is omitted if there
31140 is no selected thread (for example, when the selected inferior is not running,
31141 and therefore has no threads) or if a @var{thread-id} argument was passed to
31146 @subsubheading Example
31151 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
31152 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
31153 args=[]@},state="running"@},
31154 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
31155 frame=@{level="0",addr="0x0804891f",func="foo",
31156 args=[@{name="i",value="10"@}],
31157 file="/tmp/a.c",fullname="/tmp/a.c",line="158",arch="i386:x86_64"@},
31158 state="running"@}],
31159 current-thread-id="1"
31163 @subheading The @code{-thread-list-ids} Command
31164 @findex -thread-list-ids
31166 @subsubheading Synopsis
31172 Produces a list of the currently known global @value{GDBN} thread ids.
31173 At the end of the list it also prints the total number of such
31176 This command is retained for historical reasons, the
31177 @code{-thread-info} command should be used instead.
31179 @subsubheading @value{GDBN} Command
31181 Part of @samp{info threads} supplies the same information.
31183 @subsubheading Example
31188 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
31189 current-thread-id="1",number-of-threads="3"
31194 @subheading The @code{-thread-select} Command
31195 @findex -thread-select
31197 @subsubheading Synopsis
31200 -thread-select @var{thread-id}
31203 Make thread with global thread number @var{thread-id} the current
31204 thread. It prints the number of the new current thread, and the
31205 topmost frame for that thread.
31207 This command is deprecated in favor of explicitly using the
31208 @samp{--thread} option to each command.
31210 @subsubheading @value{GDBN} Command
31212 The corresponding @value{GDBN} command is @samp{thread}.
31214 @subsubheading Example
31221 *stopped,reason="end-stepping-range",thread-id="2",line="187",
31222 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
31226 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
31227 number-of-threads="3"
31230 ^done,new-thread-id="3",
31231 frame=@{level="0",func="vprintf",
31232 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
31233 @{name="arg",value="0x2"@}],file="vprintf.c",line="31",arch="i386:x86_64"@}
31237 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31238 @node GDB/MI Ada Tasking Commands
31239 @section @sc{gdb/mi} Ada Tasking Commands
31241 @subheading The @code{-ada-task-info} Command
31242 @findex -ada-task-info
31244 @subsubheading Synopsis
31247 -ada-task-info [ @var{task-id} ]
31250 Reports information about either a specific Ada task, if the
31251 @var{task-id} parameter is present, or about all Ada tasks.
31253 @subsubheading @value{GDBN} Command
31255 The @samp{info tasks} command prints the same information
31256 about all Ada tasks (@pxref{Ada Tasks}).
31258 @subsubheading Result
31260 The result is a table of Ada tasks. The following columns are
31261 defined for each Ada task:
31265 This field exists only for the current thread. It has the value @samp{*}.
31268 The identifier that @value{GDBN} uses to refer to the Ada task.
31271 The identifier that the target uses to refer to the Ada task.
31274 The global thread identifier of the thread corresponding to the Ada
31277 This field should always exist, as Ada tasks are always implemented
31278 on top of a thread. But if @value{GDBN} cannot find this corresponding
31279 thread for any reason, the field is omitted.
31282 This field exists only when the task was created by another task.
31283 In this case, it provides the ID of the parent task.
31286 The base priority of the task.
31289 The current state of the task. For a detailed description of the
31290 possible states, see @ref{Ada Tasks}.
31293 The name of the task.
31297 @subsubheading Example
31301 ^done,tasks=@{nr_rows="3",nr_cols="8",
31302 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
31303 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
31304 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
31305 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
31306 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
31307 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
31308 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
31309 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
31310 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
31311 state="Child Termination Wait",name="main_task"@}]@}
31315 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31316 @node GDB/MI Program Execution
31317 @section @sc{gdb/mi} Program Execution
31319 These are the asynchronous commands which generate the out-of-band
31320 record @samp{*stopped}. Currently @value{GDBN} only really executes
31321 asynchronously with remote targets and this interaction is mimicked in
31324 @subheading The @code{-exec-continue} Command
31325 @findex -exec-continue
31327 @subsubheading Synopsis
31330 -exec-continue [--reverse] [--all|--thread-group N]
31333 Resumes the execution of the inferior program, which will continue
31334 to execute until it reaches a debugger stop event. If the
31335 @samp{--reverse} option is specified, execution resumes in reverse until
31336 it reaches a stop event. Stop events may include
31339 breakpoints or watchpoints
31341 signals or exceptions
31343 the end of the process (or its beginning under @samp{--reverse})
31345 the end or beginning of a replay log if one is being used.
31347 In all-stop mode (@pxref{All-Stop
31348 Mode}), may resume only one thread, or all threads, depending on the
31349 value of the @samp{scheduler-locking} variable. If @samp{--all} is
31350 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
31351 ignored in all-stop mode. If the @samp{--thread-group} options is
31352 specified, then all threads in that thread group are resumed.
31354 @subsubheading @value{GDBN} Command
31356 The corresponding @value{GDBN} corresponding is @samp{continue}.
31358 @subsubheading Example
31365 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
31366 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
31367 line="13",arch="i386:x86_64"@}
31372 @subheading The @code{-exec-finish} Command
31373 @findex -exec-finish
31375 @subsubheading Synopsis
31378 -exec-finish [--reverse]
31381 Resumes the execution of the inferior program until the current
31382 function is exited. Displays the results returned by the function.
31383 If the @samp{--reverse} option is specified, resumes the reverse
31384 execution of the inferior program until the point where current
31385 function was called.
31387 @subsubheading @value{GDBN} Command
31389 The corresponding @value{GDBN} command is @samp{finish}.
31391 @subsubheading Example
31393 Function returning @code{void}.
31400 *stopped,reason="function-finished",frame=@{func="main",args=[],
31401 file="hello.c",fullname="/home/foo/bar/hello.c",line="7",arch="i386:x86_64"@}
31405 Function returning other than @code{void}. The name of the internal
31406 @value{GDBN} variable storing the result is printed, together with the
31413 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
31414 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
31415 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
31416 arch="i386:x86_64"@},
31417 gdb-result-var="$1",return-value="0"
31422 @subheading The @code{-exec-interrupt} Command
31423 @findex -exec-interrupt
31425 @subsubheading Synopsis
31428 -exec-interrupt [--all|--thread-group N]
31431 Interrupts the background execution of the target. Note how the token
31432 associated with the stop message is the one for the execution command
31433 that has been interrupted. The token for the interrupt itself only
31434 appears in the @samp{^done} output. If the user is trying to
31435 interrupt a non-running program, an error message will be printed.
31437 Note that when asynchronous execution is enabled, this command is
31438 asynchronous just like other execution commands. That is, first the
31439 @samp{^done} response will be printed, and the target stop will be
31440 reported after that using the @samp{*stopped} notification.
31442 In non-stop mode, only the context thread is interrupted by default.
31443 All threads (in all inferiors) will be interrupted if the
31444 @samp{--all} option is specified. If the @samp{--thread-group}
31445 option is specified, all threads in that group will be interrupted.
31447 @subsubheading @value{GDBN} Command
31449 The corresponding @value{GDBN} command is @samp{interrupt}.
31451 @subsubheading Example
31462 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
31463 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
31464 fullname="/home/foo/bar/try.c",line="13",arch="i386:x86_64"@}
31469 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
31473 @subheading The @code{-exec-jump} Command
31476 @subsubheading Synopsis
31479 -exec-jump @var{location}
31482 Resumes execution of the inferior program at the location specified by
31483 parameter. @xref{Specify Location}, for a description of the
31484 different forms of @var{location}.
31486 @subsubheading @value{GDBN} Command
31488 The corresponding @value{GDBN} command is @samp{jump}.
31490 @subsubheading Example
31493 -exec-jump foo.c:10
31494 *running,thread-id="all"
31499 @subheading The @code{-exec-next} Command
31502 @subsubheading Synopsis
31505 -exec-next [--reverse]
31508 Resumes execution of the inferior program, stopping when the beginning
31509 of the next source line is reached.
31511 If the @samp{--reverse} option is specified, resumes reverse execution
31512 of the inferior program, stopping at the beginning of the previous
31513 source line. If you issue this command on the first line of a
31514 function, it will take you back to the caller of that function, to the
31515 source line where the function was called.
31518 @subsubheading @value{GDBN} Command
31520 The corresponding @value{GDBN} command is @samp{next}.
31522 @subsubheading Example
31528 *stopped,reason="end-stepping-range",line="8",file="hello.c"
31533 @subheading The @code{-exec-next-instruction} Command
31534 @findex -exec-next-instruction
31536 @subsubheading Synopsis
31539 -exec-next-instruction [--reverse]
31542 Executes one machine instruction. If the instruction is a function
31543 call, continues until the function returns. If the program stops at an
31544 instruction in the middle of a source line, the address will be
31547 If the @samp{--reverse} option is specified, resumes reverse execution
31548 of the inferior program, stopping at the previous instruction. If the
31549 previously executed instruction was a return from another function,
31550 it will continue to execute in reverse until the call to that function
31551 (from the current stack frame) is reached.
31553 @subsubheading @value{GDBN} Command
31555 The corresponding @value{GDBN} command is @samp{nexti}.
31557 @subsubheading Example
31561 -exec-next-instruction
31565 *stopped,reason="end-stepping-range",
31566 addr="0x000100d4",line="5",file="hello.c"
31571 @subheading The @code{-exec-return} Command
31572 @findex -exec-return
31574 @subsubheading Synopsis
31580 Makes current function return immediately. Doesn't execute the inferior.
31581 Displays the new current frame.
31583 @subsubheading @value{GDBN} Command
31585 The corresponding @value{GDBN} command is @samp{return}.
31587 @subsubheading Example
31591 200-break-insert callee4
31592 200^done,bkpt=@{number="1",addr="0x00010734",
31593 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
31598 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
31599 frame=@{func="callee4",args=[],
31600 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31601 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
31602 arch="i386:x86_64"@}
31608 111^done,frame=@{level="0",func="callee3",
31609 args=[@{name="strarg",
31610 value="0x11940 \"A string argument.\""@}],
31611 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31612 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
31613 arch="i386:x86_64"@}
31618 @subheading The @code{-exec-run} Command
31621 @subsubheading Synopsis
31624 -exec-run [ --all | --thread-group N ] [ --start ]
31627 Starts execution of the inferior from the beginning. The inferior
31628 executes until either a breakpoint is encountered or the program
31629 exits. In the latter case the output will include an exit code, if
31630 the program has exited exceptionally.
31632 When neither the @samp{--all} nor the @samp{--thread-group} option
31633 is specified, the current inferior is started. If the
31634 @samp{--thread-group} option is specified, it should refer to a thread
31635 group of type @samp{process}, and that thread group will be started.
31636 If the @samp{--all} option is specified, then all inferiors will be started.
31638 Using the @samp{--start} option instructs the debugger to stop
31639 the execution at the start of the inferior's main subprogram,
31640 following the same behavior as the @code{start} command
31641 (@pxref{Starting}).
31643 @subsubheading @value{GDBN} Command
31645 The corresponding @value{GDBN} command is @samp{run}.
31647 @subsubheading Examples
31652 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
31657 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
31658 frame=@{func="main",args=[],file="recursive2.c",
31659 fullname="/home/foo/bar/recursive2.c",line="4",arch="i386:x86_64"@}
31664 Program exited normally:
31672 *stopped,reason="exited-normally"
31677 Program exited exceptionally:
31685 *stopped,reason="exited",exit-code="01"
31689 Another way the program can terminate is if it receives a signal such as
31690 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
31694 *stopped,reason="exited-signalled",signal-name="SIGINT",
31695 signal-meaning="Interrupt"
31699 @c @subheading -exec-signal
31702 @subheading The @code{-exec-step} Command
31705 @subsubheading Synopsis
31708 -exec-step [--reverse]
31711 Resumes execution of the inferior program, stopping when the beginning
31712 of the next source line is reached, if the next source line is not a
31713 function call. If it is, stop at the first instruction of the called
31714 function. If the @samp{--reverse} option is specified, resumes reverse
31715 execution of the inferior program, stopping at the beginning of the
31716 previously executed source line.
31718 @subsubheading @value{GDBN} Command
31720 The corresponding @value{GDBN} command is @samp{step}.
31722 @subsubheading Example
31724 Stepping into a function:
31730 *stopped,reason="end-stepping-range",
31731 frame=@{func="foo",args=[@{name="a",value="10"@},
31732 @{name="b",value="0"@}],file="recursive2.c",
31733 fullname="/home/foo/bar/recursive2.c",line="11",arch="i386:x86_64"@}
31743 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
31748 @subheading The @code{-exec-step-instruction} Command
31749 @findex -exec-step-instruction
31751 @subsubheading Synopsis
31754 -exec-step-instruction [--reverse]
31757 Resumes the inferior which executes one machine instruction. If the
31758 @samp{--reverse} option is specified, resumes reverse execution of the
31759 inferior program, stopping at the previously executed instruction.
31760 The output, once @value{GDBN} has stopped, will vary depending on
31761 whether we have stopped in the middle of a source line or not. In the
31762 former case, the address at which the program stopped will be printed
31765 @subsubheading @value{GDBN} Command
31767 The corresponding @value{GDBN} command is @samp{stepi}.
31769 @subsubheading Example
31773 -exec-step-instruction
31777 *stopped,reason="end-stepping-range",
31778 frame=@{func="foo",args=[],file="try.c",
31779 fullname="/home/foo/bar/try.c",line="10",arch="i386:x86_64"@}
31781 -exec-step-instruction
31785 *stopped,reason="end-stepping-range",
31786 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
31787 fullname="/home/foo/bar/try.c",line="10",arch="i386:x86_64"@}
31792 @subheading The @code{-exec-until} Command
31793 @findex -exec-until
31795 @subsubheading Synopsis
31798 -exec-until [ @var{location} ]
31801 Executes the inferior until the @var{location} specified in the
31802 argument is reached. If there is no argument, the inferior executes
31803 until a source line greater than the current one is reached. The
31804 reason for stopping in this case will be @samp{location-reached}.
31806 @subsubheading @value{GDBN} Command
31808 The corresponding @value{GDBN} command is @samp{until}.
31810 @subsubheading Example
31814 -exec-until recursive2.c:6
31818 *stopped,reason="location-reached",frame=@{func="main",args=[],
31819 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6",
31820 arch="i386:x86_64"@}
31825 @subheading -file-clear
31826 Is this going away????
31829 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31830 @node GDB/MI Stack Manipulation
31831 @section @sc{gdb/mi} Stack Manipulation Commands
31833 @subheading The @code{-enable-frame-filters} Command
31834 @findex -enable-frame-filters
31837 -enable-frame-filters
31840 @value{GDBN} allows Python-based frame filters to affect the output of
31841 the MI commands relating to stack traces. As there is no way to
31842 implement this in a fully backward-compatible way, a front end must
31843 request that this functionality be enabled.
31845 Once enabled, this feature cannot be disabled.
31847 Note that if Python support has not been compiled into @value{GDBN},
31848 this command will still succeed (and do nothing).
31850 @subheading The @code{-stack-info-frame} Command
31851 @findex -stack-info-frame
31853 @subsubheading Synopsis
31859 Get info on the selected frame.
31861 @subsubheading @value{GDBN} Command
31863 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
31864 (without arguments).
31866 @subsubheading Example
31871 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
31872 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31873 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17",
31874 arch="i386:x86_64"@}
31878 @subheading The @code{-stack-info-depth} Command
31879 @findex -stack-info-depth
31881 @subsubheading Synopsis
31884 -stack-info-depth [ @var{max-depth} ]
31887 Return the depth of the stack. If the integer argument @var{max-depth}
31888 is specified, do not count beyond @var{max-depth} frames.
31890 @subsubheading @value{GDBN} Command
31892 There's no equivalent @value{GDBN} command.
31894 @subsubheading Example
31896 For a stack with frame levels 0 through 11:
31903 -stack-info-depth 4
31906 -stack-info-depth 12
31909 -stack-info-depth 11
31912 -stack-info-depth 13
31917 @anchor{-stack-list-arguments}
31918 @subheading The @code{-stack-list-arguments} Command
31919 @findex -stack-list-arguments
31921 @subsubheading Synopsis
31924 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
31925 [ @var{low-frame} @var{high-frame} ]
31928 Display a list of the arguments for the frames between @var{low-frame}
31929 and @var{high-frame} (inclusive). If @var{low-frame} and
31930 @var{high-frame} are not provided, list the arguments for the whole
31931 call stack. If the two arguments are equal, show the single frame
31932 at the corresponding level. It is an error if @var{low-frame} is
31933 larger than the actual number of frames. On the other hand,
31934 @var{high-frame} may be larger than the actual number of frames, in
31935 which case only existing frames will be returned.
31937 If @var{print-values} is 0 or @code{--no-values}, print only the names of
31938 the variables; if it is 1 or @code{--all-values}, print also their
31939 values; and if it is 2 or @code{--simple-values}, print the name,
31940 type and value for simple data types, and the name and type for arrays,
31941 structures and unions. If the option @code{--no-frame-filters} is
31942 supplied, then Python frame filters will not be executed.
31944 If the @code{--skip-unavailable} option is specified, arguments that
31945 are not available are not listed. Partially available arguments
31946 are still displayed, however.
31948 Use of this command to obtain arguments in a single frame is
31949 deprecated in favor of the @samp{-stack-list-variables} command.
31951 @subsubheading @value{GDBN} Command
31953 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
31954 @samp{gdb_get_args} command which partially overlaps with the
31955 functionality of @samp{-stack-list-arguments}.
31957 @subsubheading Example
31964 frame=@{level="0",addr="0x00010734",func="callee4",
31965 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31966 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
31967 arch="i386:x86_64"@},
31968 frame=@{level="1",addr="0x0001076c",func="callee3",
31969 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31970 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17",
31971 arch="i386:x86_64"@},
31972 frame=@{level="2",addr="0x0001078c",func="callee2",
31973 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31974 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22",
31975 arch="i386:x86_64"@},
31976 frame=@{level="3",addr="0x000107b4",func="callee1",
31977 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31978 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27",
31979 arch="i386:x86_64"@},
31980 frame=@{level="4",addr="0x000107e0",func="main",
31981 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31982 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32",
31983 arch="i386:x86_64"@}]
31985 -stack-list-arguments 0
31988 frame=@{level="0",args=[]@},
31989 frame=@{level="1",args=[name="strarg"]@},
31990 frame=@{level="2",args=[name="intarg",name="strarg"]@},
31991 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
31992 frame=@{level="4",args=[]@}]
31994 -stack-list-arguments 1
31997 frame=@{level="0",args=[]@},
31999 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
32000 frame=@{level="2",args=[
32001 @{name="intarg",value="2"@},
32002 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
32003 @{frame=@{level="3",args=[
32004 @{name="intarg",value="2"@},
32005 @{name="strarg",value="0x11940 \"A string argument.\""@},
32006 @{name="fltarg",value="3.5"@}]@},
32007 frame=@{level="4",args=[]@}]
32009 -stack-list-arguments 0 2 2
32010 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
32012 -stack-list-arguments 1 2 2
32013 ^done,stack-args=[frame=@{level="2",
32014 args=[@{name="intarg",value="2"@},
32015 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
32019 @c @subheading -stack-list-exception-handlers
32022 @anchor{-stack-list-frames}
32023 @subheading The @code{-stack-list-frames} Command
32024 @findex -stack-list-frames
32026 @subsubheading Synopsis
32029 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
32032 List the frames currently on the stack. For each frame it displays the
32037 The frame number, 0 being the topmost frame, i.e., the innermost function.
32039 The @code{$pc} value for that frame.
32043 File name of the source file where the function lives.
32044 @item @var{fullname}
32045 The full file name of the source file where the function lives.
32047 Line number corresponding to the @code{$pc}.
32049 The shared library where this function is defined. This is only given
32050 if the frame's function is not known.
32052 Frame's architecture.
32055 If invoked without arguments, this command prints a backtrace for the
32056 whole stack. If given two integer arguments, it shows the frames whose
32057 levels are between the two arguments (inclusive). If the two arguments
32058 are equal, it shows the single frame at the corresponding level. It is
32059 an error if @var{low-frame} is larger than the actual number of
32060 frames. On the other hand, @var{high-frame} may be larger than the
32061 actual number of frames, in which case only existing frames will be
32062 returned. If the option @code{--no-frame-filters} is supplied, then
32063 Python frame filters will not be executed.
32065 @subsubheading @value{GDBN} Command
32067 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
32069 @subsubheading Example
32071 Full stack backtrace:
32077 [frame=@{level="0",addr="0x0001076c",func="foo",
32078 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11",
32079 arch="i386:x86_64"@},
32080 frame=@{level="1",addr="0x000107a4",func="foo",
32081 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32082 arch="i386:x86_64"@},
32083 frame=@{level="2",addr="0x000107a4",func="foo",
32084 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32085 arch="i386:x86_64"@},
32086 frame=@{level="3",addr="0x000107a4",func="foo",
32087 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32088 arch="i386:x86_64"@},
32089 frame=@{level="4",addr="0x000107a4",func="foo",
32090 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32091 arch="i386:x86_64"@},
32092 frame=@{level="5",addr="0x000107a4",func="foo",
32093 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32094 arch="i386:x86_64"@},
32095 frame=@{level="6",addr="0x000107a4",func="foo",
32096 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32097 arch="i386:x86_64"@},
32098 frame=@{level="7",addr="0x000107a4",func="foo",
32099 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32100 arch="i386:x86_64"@},
32101 frame=@{level="8",addr="0x000107a4",func="foo",
32102 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32103 arch="i386:x86_64"@},
32104 frame=@{level="9",addr="0x000107a4",func="foo",
32105 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32106 arch="i386:x86_64"@},
32107 frame=@{level="10",addr="0x000107a4",func="foo",
32108 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32109 arch="i386:x86_64"@},
32110 frame=@{level="11",addr="0x00010738",func="main",
32111 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4",
32112 arch="i386:x86_64"@}]
32116 Show frames between @var{low_frame} and @var{high_frame}:
32120 -stack-list-frames 3 5
32122 [frame=@{level="3",addr="0x000107a4",func="foo",
32123 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32124 arch="i386:x86_64"@},
32125 frame=@{level="4",addr="0x000107a4",func="foo",
32126 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32127 arch="i386:x86_64"@},
32128 frame=@{level="5",addr="0x000107a4",func="foo",
32129 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32130 arch="i386:x86_64"@}]
32134 Show a single frame:
32138 -stack-list-frames 3 3
32140 [frame=@{level="3",addr="0x000107a4",func="foo",
32141 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32142 arch="i386:x86_64"@}]
32147 @subheading The @code{-stack-list-locals} Command
32148 @findex -stack-list-locals
32149 @anchor{-stack-list-locals}
32151 @subsubheading Synopsis
32154 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
32157 Display the local variable names for the selected frame. If
32158 @var{print-values} is 0 or @code{--no-values}, print only the names of
32159 the variables; if it is 1 or @code{--all-values}, print also their
32160 values; and if it is 2 or @code{--simple-values}, print the name,
32161 type and value for simple data types, and the name and type for arrays,
32162 structures and unions. In this last case, a frontend can immediately
32163 display the value of simple data types and create variable objects for
32164 other data types when the user wishes to explore their values in
32165 more detail. If the option @code{--no-frame-filters} is supplied, then
32166 Python frame filters will not be executed.
32168 If the @code{--skip-unavailable} option is specified, local variables
32169 that are not available are not listed. Partially available local
32170 variables are still displayed, however.
32172 This command is deprecated in favor of the
32173 @samp{-stack-list-variables} command.
32175 @subsubheading @value{GDBN} Command
32177 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
32179 @subsubheading Example
32183 -stack-list-locals 0
32184 ^done,locals=[name="A",name="B",name="C"]
32186 -stack-list-locals --all-values
32187 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
32188 @{name="C",value="@{1, 2, 3@}"@}]
32189 -stack-list-locals --simple-values
32190 ^done,locals=[@{name="A",type="int",value="1"@},
32191 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
32195 @anchor{-stack-list-variables}
32196 @subheading The @code{-stack-list-variables} Command
32197 @findex -stack-list-variables
32199 @subsubheading Synopsis
32202 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
32205 Display the names of local variables and function arguments for the selected frame. If
32206 @var{print-values} is 0 or @code{--no-values}, print only the names of
32207 the variables; if it is 1 or @code{--all-values}, print also their
32208 values; and if it is 2 or @code{--simple-values}, print the name,
32209 type and value for simple data types, and the name and type for arrays,
32210 structures and unions. If the option @code{--no-frame-filters} is
32211 supplied, then Python frame filters will not be executed.
32213 If the @code{--skip-unavailable} option is specified, local variables
32214 and arguments that are not available are not listed. Partially
32215 available arguments and local variables are still displayed, however.
32217 @subsubheading Example
32221 -stack-list-variables --thread 1 --frame 0 --all-values
32222 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
32227 @subheading The @code{-stack-select-frame} Command
32228 @findex -stack-select-frame
32230 @subsubheading Synopsis
32233 -stack-select-frame @var{framenum}
32236 Change the selected frame. Select a different frame @var{framenum} on
32239 This command in deprecated in favor of passing the @samp{--frame}
32240 option to every command.
32242 @subsubheading @value{GDBN} Command
32244 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
32245 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
32247 @subsubheading Example
32251 -stack-select-frame 2
32256 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32257 @node GDB/MI Variable Objects
32258 @section @sc{gdb/mi} Variable Objects
32262 @subheading Motivation for Variable Objects in @sc{gdb/mi}
32264 For the implementation of a variable debugger window (locals, watched
32265 expressions, etc.), we are proposing the adaptation of the existing code
32266 used by @code{Insight}.
32268 The two main reasons for that are:
32272 It has been proven in practice (it is already on its second generation).
32275 It will shorten development time (needless to say how important it is
32279 The original interface was designed to be used by Tcl code, so it was
32280 slightly changed so it could be used through @sc{gdb/mi}. This section
32281 describes the @sc{gdb/mi} operations that will be available and gives some
32282 hints about their use.
32284 @emph{Note}: In addition to the set of operations described here, we
32285 expect the @sc{gui} implementation of a variable window to require, at
32286 least, the following operations:
32289 @item @code{-gdb-show} @code{output-radix}
32290 @item @code{-stack-list-arguments}
32291 @item @code{-stack-list-locals}
32292 @item @code{-stack-select-frame}
32297 @subheading Introduction to Variable Objects
32299 @cindex variable objects in @sc{gdb/mi}
32301 Variable objects are "object-oriented" MI interface for examining and
32302 changing values of expressions. Unlike some other MI interfaces that
32303 work with expressions, variable objects are specifically designed for
32304 simple and efficient presentation in the frontend. A variable object
32305 is identified by string name. When a variable object is created, the
32306 frontend specifies the expression for that variable object. The
32307 expression can be a simple variable, or it can be an arbitrary complex
32308 expression, and can even involve CPU registers. After creating a
32309 variable object, the frontend can invoke other variable object
32310 operations---for example to obtain or change the value of a variable
32311 object, or to change display format.
32313 Variable objects have hierarchical tree structure. Any variable object
32314 that corresponds to a composite type, such as structure in C, has
32315 a number of child variable objects, for example corresponding to each
32316 element of a structure. A child variable object can itself have
32317 children, recursively. Recursion ends when we reach
32318 leaf variable objects, which always have built-in types. Child variable
32319 objects are created only by explicit request, so if a frontend
32320 is not interested in the children of a particular variable object, no
32321 child will be created.
32323 For a leaf variable object it is possible to obtain its value as a
32324 string, or set the value from a string. String value can be also
32325 obtained for a non-leaf variable object, but it's generally a string
32326 that only indicates the type of the object, and does not list its
32327 contents. Assignment to a non-leaf variable object is not allowed.
32329 A frontend does not need to read the values of all variable objects each time
32330 the program stops. Instead, MI provides an update command that lists all
32331 variable objects whose values has changed since the last update
32332 operation. This considerably reduces the amount of data that must
32333 be transferred to the frontend. As noted above, children variable
32334 objects are created on demand, and only leaf variable objects have a
32335 real value. As result, gdb will read target memory only for leaf
32336 variables that frontend has created.
32338 The automatic update is not always desirable. For example, a frontend
32339 might want to keep a value of some expression for future reference,
32340 and never update it. For another example, fetching memory is
32341 relatively slow for embedded targets, so a frontend might want
32342 to disable automatic update for the variables that are either not
32343 visible on the screen, or ``closed''. This is possible using so
32344 called ``frozen variable objects''. Such variable objects are never
32345 implicitly updated.
32347 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
32348 fixed variable object, the expression is parsed when the variable
32349 object is created, including associating identifiers to specific
32350 variables. The meaning of expression never changes. For a floating
32351 variable object the values of variables whose names appear in the
32352 expressions are re-evaluated every time in the context of the current
32353 frame. Consider this example:
32358 struct work_state state;
32365 If a fixed variable object for the @code{state} variable is created in
32366 this function, and we enter the recursive call, the variable
32367 object will report the value of @code{state} in the top-level
32368 @code{do_work} invocation. On the other hand, a floating variable
32369 object will report the value of @code{state} in the current frame.
32371 If an expression specified when creating a fixed variable object
32372 refers to a local variable, the variable object becomes bound to the
32373 thread and frame in which the variable object is created. When such
32374 variable object is updated, @value{GDBN} makes sure that the
32375 thread/frame combination the variable object is bound to still exists,
32376 and re-evaluates the variable object in context of that thread/frame.
32378 The following is the complete set of @sc{gdb/mi} operations defined to
32379 access this functionality:
32381 @multitable @columnfractions .4 .6
32382 @item @strong{Operation}
32383 @tab @strong{Description}
32385 @item @code{-enable-pretty-printing}
32386 @tab enable Python-based pretty-printing
32387 @item @code{-var-create}
32388 @tab create a variable object
32389 @item @code{-var-delete}
32390 @tab delete the variable object and/or its children
32391 @item @code{-var-set-format}
32392 @tab set the display format of this variable
32393 @item @code{-var-show-format}
32394 @tab show the display format of this variable
32395 @item @code{-var-info-num-children}
32396 @tab tells how many children this object has
32397 @item @code{-var-list-children}
32398 @tab return a list of the object's children
32399 @item @code{-var-info-type}
32400 @tab show the type of this variable object
32401 @item @code{-var-info-expression}
32402 @tab print parent-relative expression that this variable object represents
32403 @item @code{-var-info-path-expression}
32404 @tab print full expression that this variable object represents
32405 @item @code{-var-show-attributes}
32406 @tab is this variable editable? does it exist here?
32407 @item @code{-var-evaluate-expression}
32408 @tab get the value of this variable
32409 @item @code{-var-assign}
32410 @tab set the value of this variable
32411 @item @code{-var-update}
32412 @tab update the variable and its children
32413 @item @code{-var-set-frozen}
32414 @tab set frozenness attribute
32415 @item @code{-var-set-update-range}
32416 @tab set range of children to display on update
32419 In the next subsection we describe each operation in detail and suggest
32420 how it can be used.
32422 @subheading Description And Use of Operations on Variable Objects
32424 @subheading The @code{-enable-pretty-printing} Command
32425 @findex -enable-pretty-printing
32428 -enable-pretty-printing
32431 @value{GDBN} allows Python-based visualizers to affect the output of the
32432 MI variable object commands. However, because there was no way to
32433 implement this in a fully backward-compatible way, a front end must
32434 request that this functionality be enabled.
32436 Once enabled, this feature cannot be disabled.
32438 Note that if Python support has not been compiled into @value{GDBN},
32439 this command will still succeed (and do nothing).
32441 This feature is currently (as of @value{GDBN} 7.0) experimental, and
32442 may work differently in future versions of @value{GDBN}.
32444 @subheading The @code{-var-create} Command
32445 @findex -var-create
32447 @subsubheading Synopsis
32450 -var-create @{@var{name} | "-"@}
32451 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
32454 This operation creates a variable object, which allows the monitoring of
32455 a variable, the result of an expression, a memory cell or a CPU
32458 The @var{name} parameter is the string by which the object can be
32459 referenced. It must be unique. If @samp{-} is specified, the varobj
32460 system will generate a string ``varNNNNNN'' automatically. It will be
32461 unique provided that one does not specify @var{name} of that format.
32462 The command fails if a duplicate name is found.
32464 The frame under which the expression should be evaluated can be
32465 specified by @var{frame-addr}. A @samp{*} indicates that the current
32466 frame should be used. A @samp{@@} indicates that a floating variable
32467 object must be created.
32469 @var{expression} is any expression valid on the current language set (must not
32470 begin with a @samp{*}), or one of the following:
32474 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
32477 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
32480 @samp{$@var{regname}} --- a CPU register name
32483 @cindex dynamic varobj
32484 A varobj's contents may be provided by a Python-based pretty-printer. In this
32485 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
32486 have slightly different semantics in some cases. If the
32487 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
32488 will never create a dynamic varobj. This ensures backward
32489 compatibility for existing clients.
32491 @subsubheading Result
32493 This operation returns attributes of the newly-created varobj. These
32498 The name of the varobj.
32501 The number of children of the varobj. This number is not necessarily
32502 reliable for a dynamic varobj. Instead, you must examine the
32503 @samp{has_more} attribute.
32506 The varobj's scalar value. For a varobj whose type is some sort of
32507 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
32508 will not be interesting.
32511 The varobj's type. This is a string representation of the type, as
32512 would be printed by the @value{GDBN} CLI. If @samp{print object}
32513 (@pxref{Print Settings, set print object}) is set to @code{on}, the
32514 @emph{actual} (derived) type of the object is shown rather than the
32515 @emph{declared} one.
32518 If a variable object is bound to a specific thread, then this is the
32519 thread's global identifier.
32522 For a dynamic varobj, this indicates whether there appear to be any
32523 children available. For a non-dynamic varobj, this will be 0.
32526 This attribute will be present and have the value @samp{1} if the
32527 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
32528 then this attribute will not be present.
32531 A dynamic varobj can supply a display hint to the front end. The
32532 value comes directly from the Python pretty-printer object's
32533 @code{display_hint} method. @xref{Pretty Printing API}.
32536 Typical output will look like this:
32539 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
32540 has_more="@var{has_more}"
32544 @subheading The @code{-var-delete} Command
32545 @findex -var-delete
32547 @subsubheading Synopsis
32550 -var-delete [ -c ] @var{name}
32553 Deletes a previously created variable object and all of its children.
32554 With the @samp{-c} option, just deletes the children.
32556 Returns an error if the object @var{name} is not found.
32559 @subheading The @code{-var-set-format} Command
32560 @findex -var-set-format
32562 @subsubheading Synopsis
32565 -var-set-format @var{name} @var{format-spec}
32568 Sets the output format for the value of the object @var{name} to be
32571 @anchor{-var-set-format}
32572 The syntax for the @var{format-spec} is as follows:
32575 @var{format-spec} @expansion{}
32576 @{binary | decimal | hexadecimal | octal | natural | zero-hexadecimal@}
32579 The natural format is the default format choosen automatically
32580 based on the variable type (like decimal for an @code{int}, hex
32581 for pointers, etc.).
32583 The zero-hexadecimal format has a representation similar to hexadecimal
32584 but with padding zeroes to the left of the value. For example, a 32-bit
32585 hexadecimal value of 0x1234 would be represented as 0x00001234 in the
32586 zero-hexadecimal format.
32588 For a variable with children, the format is set only on the
32589 variable itself, and the children are not affected.
32591 @subheading The @code{-var-show-format} Command
32592 @findex -var-show-format
32594 @subsubheading Synopsis
32597 -var-show-format @var{name}
32600 Returns the format used to display the value of the object @var{name}.
32603 @var{format} @expansion{}
32608 @subheading The @code{-var-info-num-children} Command
32609 @findex -var-info-num-children
32611 @subsubheading Synopsis
32614 -var-info-num-children @var{name}
32617 Returns the number of children of a variable object @var{name}:
32623 Note that this number is not completely reliable for a dynamic varobj.
32624 It will return the current number of children, but more children may
32628 @subheading The @code{-var-list-children} Command
32629 @findex -var-list-children
32631 @subsubheading Synopsis
32634 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
32636 @anchor{-var-list-children}
32638 Return a list of the children of the specified variable object and
32639 create variable objects for them, if they do not already exist. With
32640 a single argument or if @var{print-values} has a value of 0 or
32641 @code{--no-values}, print only the names of the variables; if
32642 @var{print-values} is 1 or @code{--all-values}, also print their
32643 values; and if it is 2 or @code{--simple-values} print the name and
32644 value for simple data types and just the name for arrays, structures
32647 @var{from} and @var{to}, if specified, indicate the range of children
32648 to report. If @var{from} or @var{to} is less than zero, the range is
32649 reset and all children will be reported. Otherwise, children starting
32650 at @var{from} (zero-based) and up to and excluding @var{to} will be
32653 If a child range is requested, it will only affect the current call to
32654 @code{-var-list-children}, but not future calls to @code{-var-update}.
32655 For this, you must instead use @code{-var-set-update-range}. The
32656 intent of this approach is to enable a front end to implement any
32657 update approach it likes; for example, scrolling a view may cause the
32658 front end to request more children with @code{-var-list-children}, and
32659 then the front end could call @code{-var-set-update-range} with a
32660 different range to ensure that future updates are restricted to just
32663 For each child the following results are returned:
32668 Name of the variable object created for this child.
32671 The expression to be shown to the user by the front end to designate this child.
32672 For example this may be the name of a structure member.
32674 For a dynamic varobj, this value cannot be used to form an
32675 expression. There is no way to do this at all with a dynamic varobj.
32677 For C/C@t{++} structures there are several pseudo children returned to
32678 designate access qualifiers. For these pseudo children @var{exp} is
32679 @samp{public}, @samp{private}, or @samp{protected}. In this case the
32680 type and value are not present.
32682 A dynamic varobj will not report the access qualifying
32683 pseudo-children, regardless of the language. This information is not
32684 available at all with a dynamic varobj.
32687 Number of children this child has. For a dynamic varobj, this will be
32691 The type of the child. If @samp{print object}
32692 (@pxref{Print Settings, set print object}) is set to @code{on}, the
32693 @emph{actual} (derived) type of the object is shown rather than the
32694 @emph{declared} one.
32697 If values were requested, this is the value.
32700 If this variable object is associated with a thread, this is the
32701 thread's global thread id. Otherwise this result is not present.
32704 If the variable object is frozen, this variable will be present with a value of 1.
32707 A dynamic varobj can supply a display hint to the front end. The
32708 value comes directly from the Python pretty-printer object's
32709 @code{display_hint} method. @xref{Pretty Printing API}.
32712 This attribute will be present and have the value @samp{1} if the
32713 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
32714 then this attribute will not be present.
32718 The result may have its own attributes:
32722 A dynamic varobj can supply a display hint to the front end. The
32723 value comes directly from the Python pretty-printer object's
32724 @code{display_hint} method. @xref{Pretty Printing API}.
32727 This is an integer attribute which is nonzero if there are children
32728 remaining after the end of the selected range.
32731 @subsubheading Example
32735 -var-list-children n
32736 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
32737 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
32739 -var-list-children --all-values n
32740 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
32741 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
32745 @subheading The @code{-var-info-type} Command
32746 @findex -var-info-type
32748 @subsubheading Synopsis
32751 -var-info-type @var{name}
32754 Returns the type of the specified variable @var{name}. The type is
32755 returned as a string in the same format as it is output by the
32759 type=@var{typename}
32763 @subheading The @code{-var-info-expression} Command
32764 @findex -var-info-expression
32766 @subsubheading Synopsis
32769 -var-info-expression @var{name}
32772 Returns a string that is suitable for presenting this
32773 variable object in user interface. The string is generally
32774 not valid expression in the current language, and cannot be evaluated.
32776 For example, if @code{a} is an array, and variable object
32777 @code{A} was created for @code{a}, then we'll get this output:
32780 (gdb) -var-info-expression A.1
32781 ^done,lang="C",exp="1"
32785 Here, the value of @code{lang} is the language name, which can be
32786 found in @ref{Supported Languages}.
32788 Note that the output of the @code{-var-list-children} command also
32789 includes those expressions, so the @code{-var-info-expression} command
32792 @subheading The @code{-var-info-path-expression} Command
32793 @findex -var-info-path-expression
32795 @subsubheading Synopsis
32798 -var-info-path-expression @var{name}
32801 Returns an expression that can be evaluated in the current
32802 context and will yield the same value that a variable object has.
32803 Compare this with the @code{-var-info-expression} command, which
32804 result can be used only for UI presentation. Typical use of
32805 the @code{-var-info-path-expression} command is creating a
32806 watchpoint from a variable object.
32808 This command is currently not valid for children of a dynamic varobj,
32809 and will give an error when invoked on one.
32811 For example, suppose @code{C} is a C@t{++} class, derived from class
32812 @code{Base}, and that the @code{Base} class has a member called
32813 @code{m_size}. Assume a variable @code{c} is has the type of
32814 @code{C} and a variable object @code{C} was created for variable
32815 @code{c}. Then, we'll get this output:
32817 (gdb) -var-info-path-expression C.Base.public.m_size
32818 ^done,path_expr=((Base)c).m_size)
32821 @subheading The @code{-var-show-attributes} Command
32822 @findex -var-show-attributes
32824 @subsubheading Synopsis
32827 -var-show-attributes @var{name}
32830 List attributes of the specified variable object @var{name}:
32833 status=@var{attr} [ ( ,@var{attr} )* ]
32837 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
32839 @subheading The @code{-var-evaluate-expression} Command
32840 @findex -var-evaluate-expression
32842 @subsubheading Synopsis
32845 -var-evaluate-expression [-f @var{format-spec}] @var{name}
32848 Evaluates the expression that is represented by the specified variable
32849 object and returns its value as a string. The format of the string
32850 can be specified with the @samp{-f} option. The possible values of
32851 this option are the same as for @code{-var-set-format}
32852 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
32853 the current display format will be used. The current display format
32854 can be changed using the @code{-var-set-format} command.
32860 Note that one must invoke @code{-var-list-children} for a variable
32861 before the value of a child variable can be evaluated.
32863 @subheading The @code{-var-assign} Command
32864 @findex -var-assign
32866 @subsubheading Synopsis
32869 -var-assign @var{name} @var{expression}
32872 Assigns the value of @var{expression} to the variable object specified
32873 by @var{name}. The object must be @samp{editable}. If the variable's
32874 value is altered by the assign, the variable will show up in any
32875 subsequent @code{-var-update} list.
32877 @subsubheading Example
32885 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
32889 @subheading The @code{-var-update} Command
32890 @findex -var-update
32892 @subsubheading Synopsis
32895 -var-update [@var{print-values}] @{@var{name} | "*"@}
32898 Reevaluate the expressions corresponding to the variable object
32899 @var{name} and all its direct and indirect children, and return the
32900 list of variable objects whose values have changed; @var{name} must
32901 be a root variable object. Here, ``changed'' means that the result of
32902 @code{-var-evaluate-expression} before and after the
32903 @code{-var-update} is different. If @samp{*} is used as the variable
32904 object names, all existing variable objects are updated, except
32905 for frozen ones (@pxref{-var-set-frozen}). The option
32906 @var{print-values} determines whether both names and values, or just
32907 names are printed. The possible values of this option are the same
32908 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
32909 recommended to use the @samp{--all-values} option, to reduce the
32910 number of MI commands needed on each program stop.
32912 With the @samp{*} parameter, if a variable object is bound to a
32913 currently running thread, it will not be updated, without any
32916 If @code{-var-set-update-range} was previously used on a varobj, then
32917 only the selected range of children will be reported.
32919 @code{-var-update} reports all the changed varobjs in a tuple named
32922 Each item in the change list is itself a tuple holding:
32926 The name of the varobj.
32929 If values were requested for this update, then this field will be
32930 present and will hold the value of the varobj.
32933 @anchor{-var-update}
32934 This field is a string which may take one of three values:
32938 The variable object's current value is valid.
32941 The variable object does not currently hold a valid value but it may
32942 hold one in the future if its associated expression comes back into
32946 The variable object no longer holds a valid value.
32947 This can occur when the executable file being debugged has changed,
32948 either through recompilation or by using the @value{GDBN} @code{file}
32949 command. The front end should normally choose to delete these variable
32953 In the future new values may be added to this list so the front should
32954 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
32957 This is only present if the varobj is still valid. If the type
32958 changed, then this will be the string @samp{true}; otherwise it will
32961 When a varobj's type changes, its children are also likely to have
32962 become incorrect. Therefore, the varobj's children are automatically
32963 deleted when this attribute is @samp{true}. Also, the varobj's update
32964 range, when set using the @code{-var-set-update-range} command, is
32968 If the varobj's type changed, then this field will be present and will
32971 @item new_num_children
32972 For a dynamic varobj, if the number of children changed, or if the
32973 type changed, this will be the new number of children.
32975 The @samp{numchild} field in other varobj responses is generally not
32976 valid for a dynamic varobj -- it will show the number of children that
32977 @value{GDBN} knows about, but because dynamic varobjs lazily
32978 instantiate their children, this will not reflect the number of
32979 children which may be available.
32981 The @samp{new_num_children} attribute only reports changes to the
32982 number of children known by @value{GDBN}. This is the only way to
32983 detect whether an update has removed children (which necessarily can
32984 only happen at the end of the update range).
32987 The display hint, if any.
32990 This is an integer value, which will be 1 if there are more children
32991 available outside the varobj's update range.
32994 This attribute will be present and have the value @samp{1} if the
32995 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
32996 then this attribute will not be present.
32999 If new children were added to a dynamic varobj within the selected
33000 update range (as set by @code{-var-set-update-range}), then they will
33001 be listed in this attribute.
33004 @subsubheading Example
33011 -var-update --all-values var1
33012 ^done,changelist=[@{name="var1",value="3",in_scope="true",
33013 type_changed="false"@}]
33017 @subheading The @code{-var-set-frozen} Command
33018 @findex -var-set-frozen
33019 @anchor{-var-set-frozen}
33021 @subsubheading Synopsis
33024 -var-set-frozen @var{name} @var{flag}
33027 Set the frozenness flag on the variable object @var{name}. The
33028 @var{flag} parameter should be either @samp{1} to make the variable
33029 frozen or @samp{0} to make it unfrozen. If a variable object is
33030 frozen, then neither itself, nor any of its children, are
33031 implicitly updated by @code{-var-update} of
33032 a parent variable or by @code{-var-update *}. Only
33033 @code{-var-update} of the variable itself will update its value and
33034 values of its children. After a variable object is unfrozen, it is
33035 implicitly updated by all subsequent @code{-var-update} operations.
33036 Unfreezing a variable does not update it, only subsequent
33037 @code{-var-update} does.
33039 @subsubheading Example
33043 -var-set-frozen V 1
33048 @subheading The @code{-var-set-update-range} command
33049 @findex -var-set-update-range
33050 @anchor{-var-set-update-range}
33052 @subsubheading Synopsis
33055 -var-set-update-range @var{name} @var{from} @var{to}
33058 Set the range of children to be returned by future invocations of
33059 @code{-var-update}.
33061 @var{from} and @var{to} indicate the range of children to report. If
33062 @var{from} or @var{to} is less than zero, the range is reset and all
33063 children will be reported. Otherwise, children starting at @var{from}
33064 (zero-based) and up to and excluding @var{to} will be reported.
33066 @subsubheading Example
33070 -var-set-update-range V 1 2
33074 @subheading The @code{-var-set-visualizer} command
33075 @findex -var-set-visualizer
33076 @anchor{-var-set-visualizer}
33078 @subsubheading Synopsis
33081 -var-set-visualizer @var{name} @var{visualizer}
33084 Set a visualizer for the variable object @var{name}.
33086 @var{visualizer} is the visualizer to use. The special value
33087 @samp{None} means to disable any visualizer in use.
33089 If not @samp{None}, @var{visualizer} must be a Python expression.
33090 This expression must evaluate to a callable object which accepts a
33091 single argument. @value{GDBN} will call this object with the value of
33092 the varobj @var{name} as an argument (this is done so that the same
33093 Python pretty-printing code can be used for both the CLI and MI).
33094 When called, this object must return an object which conforms to the
33095 pretty-printing interface (@pxref{Pretty Printing API}).
33097 The pre-defined function @code{gdb.default_visualizer} may be used to
33098 select a visualizer by following the built-in process
33099 (@pxref{Selecting Pretty-Printers}). This is done automatically when
33100 a varobj is created, and so ordinarily is not needed.
33102 This feature is only available if Python support is enabled. The MI
33103 command @code{-list-features} (@pxref{GDB/MI Support Commands})
33104 can be used to check this.
33106 @subsubheading Example
33108 Resetting the visualizer:
33112 -var-set-visualizer V None
33116 Reselecting the default (type-based) visualizer:
33120 -var-set-visualizer V gdb.default_visualizer
33124 Suppose @code{SomeClass} is a visualizer class. A lambda expression
33125 can be used to instantiate this class for a varobj:
33129 -var-set-visualizer V "lambda val: SomeClass()"
33133 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33134 @node GDB/MI Data Manipulation
33135 @section @sc{gdb/mi} Data Manipulation
33137 @cindex data manipulation, in @sc{gdb/mi}
33138 @cindex @sc{gdb/mi}, data manipulation
33139 This section describes the @sc{gdb/mi} commands that manipulate data:
33140 examine memory and registers, evaluate expressions, etc.
33142 For details about what an addressable memory unit is,
33143 @pxref{addressable memory unit}.
33145 @c REMOVED FROM THE INTERFACE.
33146 @c @subheading -data-assign
33147 @c Change the value of a program variable. Plenty of side effects.
33148 @c @subsubheading GDB Command
33150 @c @subsubheading Example
33153 @subheading The @code{-data-disassemble} Command
33154 @findex -data-disassemble
33156 @subsubheading Synopsis
33160 [ -s @var{start-addr} -e @var{end-addr} ]
33161 | [ -a @var{addr} ]
33162 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
33170 @item @var{start-addr}
33171 is the beginning address (or @code{$pc})
33172 @item @var{end-addr}
33175 is an address anywhere within (or the name of) the function to
33176 disassemble. If an address is specified, the whole function
33177 surrounding that address will be disassembled. If a name is
33178 specified, the whole function with that name will be disassembled.
33179 @item @var{filename}
33180 is the name of the file to disassemble
33181 @item @var{linenum}
33182 is the line number to disassemble around
33184 is the number of disassembly lines to be produced. If it is -1,
33185 the whole function will be disassembled, in case no @var{end-addr} is
33186 specified. If @var{end-addr} is specified as a non-zero value, and
33187 @var{lines} is lower than the number of disassembly lines between
33188 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
33189 displayed; if @var{lines} is higher than the number of lines between
33190 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
33195 @item 0 disassembly only
33196 @item 1 mixed source and disassembly (deprecated)
33197 @item 2 disassembly with raw opcodes
33198 @item 3 mixed source and disassembly with raw opcodes (deprecated)
33199 @item 4 mixed source and disassembly
33200 @item 5 mixed source and disassembly with raw opcodes
33203 Modes 1 and 3 are deprecated. The output is ``source centric''
33204 which hasn't proved useful in practice.
33205 @xref{Machine Code}, for a discussion of the difference between
33206 @code{/m} and @code{/s} output of the @code{disassemble} command.
33209 @subsubheading Result
33211 The result of the @code{-data-disassemble} command will be a list named
33212 @samp{asm_insns}, the contents of this list depend on the @var{mode}
33213 used with the @code{-data-disassemble} command.
33215 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
33220 The address at which this instruction was disassembled.
33223 The name of the function this instruction is within.
33226 The decimal offset in bytes from the start of @samp{func-name}.
33229 The text disassembly for this @samp{address}.
33232 This field is only present for modes 2, 3 and 5. This contains the raw opcode
33233 bytes for the @samp{inst} field.
33237 For modes 1, 3, 4 and 5 the @samp{asm_insns} list contains tuples named
33238 @samp{src_and_asm_line}, each of which has the following fields:
33242 The line number within @samp{file}.
33245 The file name from the compilation unit. This might be an absolute
33246 file name or a relative file name depending on the compile command
33250 Absolute file name of @samp{file}. It is converted to a canonical form
33251 using the source file search path
33252 (@pxref{Source Path, ,Specifying Source Directories})
33253 and after resolving all the symbolic links.
33255 If the source file is not found this field will contain the path as
33256 present in the debug information.
33258 @item line_asm_insn
33259 This is a list of tuples containing the disassembly for @samp{line} in
33260 @samp{file}. The fields of each tuple are the same as for
33261 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
33262 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
33267 Note that whatever included in the @samp{inst} field, is not
33268 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
33271 @subsubheading @value{GDBN} Command
33273 The corresponding @value{GDBN} command is @samp{disassemble}.
33275 @subsubheading Example
33277 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
33281 -data-disassemble -s $pc -e "$pc + 20" -- 0
33284 @{address="0x000107c0",func-name="main",offset="4",
33285 inst="mov 2, %o0"@},
33286 @{address="0x000107c4",func-name="main",offset="8",
33287 inst="sethi %hi(0x11800), %o2"@},
33288 @{address="0x000107c8",func-name="main",offset="12",
33289 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
33290 @{address="0x000107cc",func-name="main",offset="16",
33291 inst="sethi %hi(0x11800), %o2"@},
33292 @{address="0x000107d0",func-name="main",offset="20",
33293 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
33297 Disassemble the whole @code{main} function. Line 32 is part of
33301 -data-disassemble -f basics.c -l 32 -- 0
33303 @{address="0x000107bc",func-name="main",offset="0",
33304 inst="save %sp, -112, %sp"@},
33305 @{address="0x000107c0",func-name="main",offset="4",
33306 inst="mov 2, %o0"@},
33307 @{address="0x000107c4",func-name="main",offset="8",
33308 inst="sethi %hi(0x11800), %o2"@},
33310 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
33311 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
33315 Disassemble 3 instructions from the start of @code{main}:
33319 -data-disassemble -f basics.c -l 32 -n 3 -- 0
33321 @{address="0x000107bc",func-name="main",offset="0",
33322 inst="save %sp, -112, %sp"@},
33323 @{address="0x000107c0",func-name="main",offset="4",
33324 inst="mov 2, %o0"@},
33325 @{address="0x000107c4",func-name="main",offset="8",
33326 inst="sethi %hi(0x11800), %o2"@}]
33330 Disassemble 3 instructions from the start of @code{main} in mixed mode:
33334 -data-disassemble -f basics.c -l 32 -n 3 -- 1
33336 src_and_asm_line=@{line="31",
33337 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
33338 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
33339 line_asm_insn=[@{address="0x000107bc",
33340 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
33341 src_and_asm_line=@{line="32",
33342 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
33343 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
33344 line_asm_insn=[@{address="0x000107c0",
33345 func-name="main",offset="4",inst="mov 2, %o0"@},
33346 @{address="0x000107c4",func-name="main",offset="8",
33347 inst="sethi %hi(0x11800), %o2"@}]@}]
33352 @subheading The @code{-data-evaluate-expression} Command
33353 @findex -data-evaluate-expression
33355 @subsubheading Synopsis
33358 -data-evaluate-expression @var{expr}
33361 Evaluate @var{expr} as an expression. The expression could contain an
33362 inferior function call. The function call will execute synchronously.
33363 If the expression contains spaces, it must be enclosed in double quotes.
33365 @subsubheading @value{GDBN} Command
33367 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
33368 @samp{call}. In @code{gdbtk} only, there's a corresponding
33369 @samp{gdb_eval} command.
33371 @subsubheading Example
33373 In the following example, the numbers that precede the commands are the
33374 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
33375 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
33379 211-data-evaluate-expression A
33382 311-data-evaluate-expression &A
33383 311^done,value="0xefffeb7c"
33385 411-data-evaluate-expression A+3
33388 511-data-evaluate-expression "A + 3"
33394 @subheading The @code{-data-list-changed-registers} Command
33395 @findex -data-list-changed-registers
33397 @subsubheading Synopsis
33400 -data-list-changed-registers
33403 Display a list of the registers that have changed.
33405 @subsubheading @value{GDBN} Command
33407 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
33408 has the corresponding command @samp{gdb_changed_register_list}.
33410 @subsubheading Example
33412 On a PPC MBX board:
33420 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
33421 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
33422 line="5",arch="powerpc"@}
33424 -data-list-changed-registers
33425 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
33426 "10","11","13","14","15","16","17","18","19","20","21","22","23",
33427 "24","25","26","27","28","30","31","64","65","66","67","69"]
33432 @subheading The @code{-data-list-register-names} Command
33433 @findex -data-list-register-names
33435 @subsubheading Synopsis
33438 -data-list-register-names [ ( @var{regno} )+ ]
33441 Show a list of register names for the current target. If no arguments
33442 are given, it shows a list of the names of all the registers. If
33443 integer numbers are given as arguments, it will print a list of the
33444 names of the registers corresponding to the arguments. To ensure
33445 consistency between a register name and its number, the output list may
33446 include empty register names.
33448 @subsubheading @value{GDBN} Command
33450 @value{GDBN} does not have a command which corresponds to
33451 @samp{-data-list-register-names}. In @code{gdbtk} there is a
33452 corresponding command @samp{gdb_regnames}.
33454 @subsubheading Example
33456 For the PPC MBX board:
33459 -data-list-register-names
33460 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
33461 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
33462 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
33463 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
33464 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
33465 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
33466 "", "pc","ps","cr","lr","ctr","xer"]
33468 -data-list-register-names 1 2 3
33469 ^done,register-names=["r1","r2","r3"]
33473 @subheading The @code{-data-list-register-values} Command
33474 @findex -data-list-register-values
33476 @subsubheading Synopsis
33479 -data-list-register-values
33480 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
33483 Display the registers' contents. The format according to which the
33484 registers' contents are to be returned is given by @var{fmt}, followed
33485 by an optional list of numbers specifying the registers to display. A
33486 missing list of numbers indicates that the contents of all the
33487 registers must be returned. The @code{--skip-unavailable} option
33488 indicates that only the available registers are to be returned.
33490 Allowed formats for @var{fmt} are:
33507 @subsubheading @value{GDBN} Command
33509 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
33510 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
33512 @subsubheading Example
33514 For a PPC MBX board (note: line breaks are for readability only, they
33515 don't appear in the actual output):
33519 -data-list-register-values r 64 65
33520 ^done,register-values=[@{number="64",value="0xfe00a300"@},
33521 @{number="65",value="0x00029002"@}]
33523 -data-list-register-values x
33524 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
33525 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
33526 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
33527 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
33528 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
33529 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
33530 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
33531 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
33532 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
33533 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
33534 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
33535 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
33536 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
33537 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
33538 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
33539 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
33540 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
33541 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
33542 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
33543 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
33544 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
33545 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
33546 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
33547 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
33548 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
33549 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
33550 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
33551 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
33552 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
33553 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
33554 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
33555 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
33556 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
33557 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
33558 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
33559 @{number="69",value="0x20002b03"@}]
33564 @subheading The @code{-data-read-memory} Command
33565 @findex -data-read-memory
33567 This command is deprecated, use @code{-data-read-memory-bytes} instead.
33569 @subsubheading Synopsis
33572 -data-read-memory [ -o @var{byte-offset} ]
33573 @var{address} @var{word-format} @var{word-size}
33574 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
33581 @item @var{address}
33582 An expression specifying the address of the first memory word to be
33583 read. Complex expressions containing embedded white space should be
33584 quoted using the C convention.
33586 @item @var{word-format}
33587 The format to be used to print the memory words. The notation is the
33588 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
33591 @item @var{word-size}
33592 The size of each memory word in bytes.
33594 @item @var{nr-rows}
33595 The number of rows in the output table.
33597 @item @var{nr-cols}
33598 The number of columns in the output table.
33601 If present, indicates that each row should include an @sc{ascii} dump. The
33602 value of @var{aschar} is used as a padding character when a byte is not a
33603 member of the printable @sc{ascii} character set (printable @sc{ascii}
33604 characters are those whose code is between 32 and 126, inclusively).
33606 @item @var{byte-offset}
33607 An offset to add to the @var{address} before fetching memory.
33610 This command displays memory contents as a table of @var{nr-rows} by
33611 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
33612 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
33613 (returned as @samp{total-bytes}). Should less than the requested number
33614 of bytes be returned by the target, the missing words are identified
33615 using @samp{N/A}. The number of bytes read from the target is returned
33616 in @samp{nr-bytes} and the starting address used to read memory in
33619 The address of the next/previous row or page is available in
33620 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
33623 @subsubheading @value{GDBN} Command
33625 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
33626 @samp{gdb_get_mem} memory read command.
33628 @subsubheading Example
33630 Read six bytes of memory starting at @code{bytes+6} but then offset by
33631 @code{-6} bytes. Format as three rows of two columns. One byte per
33632 word. Display each word in hex.
33636 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
33637 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
33638 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
33639 prev-page="0x0000138a",memory=[
33640 @{addr="0x00001390",data=["0x00","0x01"]@},
33641 @{addr="0x00001392",data=["0x02","0x03"]@},
33642 @{addr="0x00001394",data=["0x04","0x05"]@}]
33646 Read two bytes of memory starting at address @code{shorts + 64} and
33647 display as a single word formatted in decimal.
33651 5-data-read-memory shorts+64 d 2 1 1
33652 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
33653 next-row="0x00001512",prev-row="0x0000150e",
33654 next-page="0x00001512",prev-page="0x0000150e",memory=[
33655 @{addr="0x00001510",data=["128"]@}]
33659 Read thirty two bytes of memory starting at @code{bytes+16} and format
33660 as eight rows of four columns. Include a string encoding with @samp{x}
33661 used as the non-printable character.
33665 4-data-read-memory bytes+16 x 1 8 4 x
33666 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
33667 next-row="0x000013c0",prev-row="0x0000139c",
33668 next-page="0x000013c0",prev-page="0x00001380",memory=[
33669 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
33670 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
33671 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
33672 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
33673 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
33674 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
33675 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
33676 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
33680 @subheading The @code{-data-read-memory-bytes} Command
33681 @findex -data-read-memory-bytes
33683 @subsubheading Synopsis
33686 -data-read-memory-bytes [ -o @var{offset} ]
33687 @var{address} @var{count}
33694 @item @var{address}
33695 An expression specifying the address of the first addressable memory unit
33696 to be read. Complex expressions containing embedded white space should be
33697 quoted using the C convention.
33700 The number of addressable memory units to read. This should be an integer
33704 The offset relative to @var{address} at which to start reading. This
33705 should be an integer literal. This option is provided so that a frontend
33706 is not required to first evaluate address and then perform address
33707 arithmetics itself.
33711 This command attempts to read all accessible memory regions in the
33712 specified range. First, all regions marked as unreadable in the memory
33713 map (if one is defined) will be skipped. @xref{Memory Region
33714 Attributes}. Second, @value{GDBN} will attempt to read the remaining
33715 regions. For each one, if reading full region results in an errors,
33716 @value{GDBN} will try to read a subset of the region.
33718 In general, every single memory unit in the region may be readable or not,
33719 and the only way to read every readable unit is to try a read at
33720 every address, which is not practical. Therefore, @value{GDBN} will
33721 attempt to read all accessible memory units at either beginning or the end
33722 of the region, using a binary division scheme. This heuristic works
33723 well for reading across a memory map boundary. Note that if a region
33724 has a readable range that is neither at the beginning or the end,
33725 @value{GDBN} will not read it.
33727 The result record (@pxref{GDB/MI Result Records}) that is output of
33728 the command includes a field named @samp{memory} whose content is a
33729 list of tuples. Each tuple represent a successfully read memory block
33730 and has the following fields:
33734 The start address of the memory block, as hexadecimal literal.
33737 The end address of the memory block, as hexadecimal literal.
33740 The offset of the memory block, as hexadecimal literal, relative to
33741 the start address passed to @code{-data-read-memory-bytes}.
33744 The contents of the memory block, in hex.
33750 @subsubheading @value{GDBN} Command
33752 The corresponding @value{GDBN} command is @samp{x}.
33754 @subsubheading Example
33758 -data-read-memory-bytes &a 10
33759 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
33761 contents="01000000020000000300"@}]
33766 @subheading The @code{-data-write-memory-bytes} Command
33767 @findex -data-write-memory-bytes
33769 @subsubheading Synopsis
33772 -data-write-memory-bytes @var{address} @var{contents}
33773 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
33780 @item @var{address}
33781 An expression specifying the address of the first addressable memory unit
33782 to be written. Complex expressions containing embedded white space should
33783 be quoted using the C convention.
33785 @item @var{contents}
33786 The hex-encoded data to write. It is an error if @var{contents} does
33787 not represent an integral number of addressable memory units.
33790 Optional argument indicating the number of addressable memory units to be
33791 written. If @var{count} is greater than @var{contents}' length,
33792 @value{GDBN} will repeatedly write @var{contents} until it fills
33793 @var{count} memory units.
33797 @subsubheading @value{GDBN} Command
33799 There's no corresponding @value{GDBN} command.
33801 @subsubheading Example
33805 -data-write-memory-bytes &a "aabbccdd"
33812 -data-write-memory-bytes &a "aabbccdd" 16e
33817 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33818 @node GDB/MI Tracepoint Commands
33819 @section @sc{gdb/mi} Tracepoint Commands
33821 The commands defined in this section implement MI support for
33822 tracepoints. For detailed introduction, see @ref{Tracepoints}.
33824 @subheading The @code{-trace-find} Command
33825 @findex -trace-find
33827 @subsubheading Synopsis
33830 -trace-find @var{mode} [@var{parameters}@dots{}]
33833 Find a trace frame using criteria defined by @var{mode} and
33834 @var{parameters}. The following table lists permissible
33835 modes and their parameters. For details of operation, see @ref{tfind}.
33840 No parameters are required. Stops examining trace frames.
33843 An integer is required as parameter. Selects tracepoint frame with
33846 @item tracepoint-number
33847 An integer is required as parameter. Finds next
33848 trace frame that corresponds to tracepoint with the specified number.
33851 An address is required as parameter. Finds
33852 next trace frame that corresponds to any tracepoint at the specified
33855 @item pc-inside-range
33856 Two addresses are required as parameters. Finds next trace
33857 frame that corresponds to a tracepoint at an address inside the
33858 specified range. Both bounds are considered to be inside the range.
33860 @item pc-outside-range
33861 Two addresses are required as parameters. Finds
33862 next trace frame that corresponds to a tracepoint at an address outside
33863 the specified range. Both bounds are considered to be inside the range.
33866 Line specification is required as parameter. @xref{Specify Location}.
33867 Finds next trace frame that corresponds to a tracepoint at
33868 the specified location.
33872 If @samp{none} was passed as @var{mode}, the response does not
33873 have fields. Otherwise, the response may have the following fields:
33877 This field has either @samp{0} or @samp{1} as the value, depending
33878 on whether a matching tracepoint was found.
33881 The index of the found traceframe. This field is present iff
33882 the @samp{found} field has value of @samp{1}.
33885 The index of the found tracepoint. This field is present iff
33886 the @samp{found} field has value of @samp{1}.
33889 The information about the frame corresponding to the found trace
33890 frame. This field is present only if a trace frame was found.
33891 @xref{GDB/MI Frame Information}, for description of this field.
33895 @subsubheading @value{GDBN} Command
33897 The corresponding @value{GDBN} command is @samp{tfind}.
33899 @subheading -trace-define-variable
33900 @findex -trace-define-variable
33902 @subsubheading Synopsis
33905 -trace-define-variable @var{name} [ @var{value} ]
33908 Create trace variable @var{name} if it does not exist. If
33909 @var{value} is specified, sets the initial value of the specified
33910 trace variable to that value. Note that the @var{name} should start
33911 with the @samp{$} character.
33913 @subsubheading @value{GDBN} Command
33915 The corresponding @value{GDBN} command is @samp{tvariable}.
33917 @subheading The @code{-trace-frame-collected} Command
33918 @findex -trace-frame-collected
33920 @subsubheading Synopsis
33923 -trace-frame-collected
33924 [--var-print-values @var{var_pval}]
33925 [--comp-print-values @var{comp_pval}]
33926 [--registers-format @var{regformat}]
33927 [--memory-contents]
33930 This command returns the set of collected objects, register names,
33931 trace state variable names, memory ranges and computed expressions
33932 that have been collected at a particular trace frame. The optional
33933 parameters to the command affect the output format in different ways.
33934 See the output description table below for more details.
33936 The reported names can be used in the normal manner to create
33937 varobjs and inspect the objects themselves. The items returned by
33938 this command are categorized so that it is clear which is a variable,
33939 which is a register, which is a trace state variable, which is a
33940 memory range and which is a computed expression.
33942 For instance, if the actions were
33944 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
33945 collect *(int*)0xaf02bef0@@40
33949 the object collected in its entirety would be @code{myVar}. The
33950 object @code{myArray} would be partially collected, because only the
33951 element at index @code{myIndex} would be collected. The remaining
33952 objects would be computed expressions.
33954 An example output would be:
33958 -trace-frame-collected
33960 explicit-variables=[@{name="myVar",value="1"@}],
33961 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
33962 @{name="myObj.field",value="0"@},
33963 @{name="myPtr->field",value="1"@},
33964 @{name="myCount + 2",value="3"@},
33965 @{name="$tvar1 + 1",value="43970027"@}],
33966 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
33967 @{number="1",value="0x0"@},
33968 @{number="2",value="0x4"@},
33970 @{number="125",value="0x0"@}],
33971 tvars=[@{name="$tvar1",current="43970026"@}],
33972 memory=[@{address="0x0000000000602264",length="4"@},
33973 @{address="0x0000000000615bc0",length="4"@}]
33980 @item explicit-variables
33981 The set of objects that have been collected in their entirety (as
33982 opposed to collecting just a few elements of an array or a few struct
33983 members). For each object, its name and value are printed.
33984 The @code{--var-print-values} option affects how or whether the value
33985 field is output. If @var{var_pval} is 0, then print only the names;
33986 if it is 1, print also their values; and if it is 2, print the name,
33987 type and value for simple data types, and the name and type for
33988 arrays, structures and unions.
33990 @item computed-expressions
33991 The set of computed expressions that have been collected at the
33992 current trace frame. The @code{--comp-print-values} option affects
33993 this set like the @code{--var-print-values} option affects the
33994 @code{explicit-variables} set. See above.
33997 The registers that have been collected at the current trace frame.
33998 For each register collected, the name and current value are returned.
33999 The value is formatted according to the @code{--registers-format}
34000 option. See the @command{-data-list-register-values} command for a
34001 list of the allowed formats. The default is @samp{x}.
34004 The trace state variables that have been collected at the current
34005 trace frame. For each trace state variable collected, the name and
34006 current value are returned.
34009 The set of memory ranges that have been collected at the current trace
34010 frame. Its content is a list of tuples. Each tuple represents a
34011 collected memory range and has the following fields:
34015 The start address of the memory range, as hexadecimal literal.
34018 The length of the memory range, as decimal literal.
34021 The contents of the memory block, in hex. This field is only present
34022 if the @code{--memory-contents} option is specified.
34028 @subsubheading @value{GDBN} Command
34030 There is no corresponding @value{GDBN} command.
34032 @subsubheading Example
34034 @subheading -trace-list-variables
34035 @findex -trace-list-variables
34037 @subsubheading Synopsis
34040 -trace-list-variables
34043 Return a table of all defined trace variables. Each element of the
34044 table has the following fields:
34048 The name of the trace variable. This field is always present.
34051 The initial value. This is a 64-bit signed integer. This
34052 field is always present.
34055 The value the trace variable has at the moment. This is a 64-bit
34056 signed integer. This field is absent iff current value is
34057 not defined, for example if the trace was never run, or is
34062 @subsubheading @value{GDBN} Command
34064 The corresponding @value{GDBN} command is @samp{tvariables}.
34066 @subsubheading Example
34070 -trace-list-variables
34071 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
34072 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
34073 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
34074 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
34075 body=[variable=@{name="$trace_timestamp",initial="0"@}
34076 variable=@{name="$foo",initial="10",current="15"@}]@}
34080 @subheading -trace-save
34081 @findex -trace-save
34083 @subsubheading Synopsis
34086 -trace-save [ -r ] [ -ctf ] @var{filename}
34089 Saves the collected trace data to @var{filename}. Without the
34090 @samp{-r} option, the data is downloaded from the target and saved
34091 in a local file. With the @samp{-r} option the target is asked
34092 to perform the save.
34094 By default, this command will save the trace in the tfile format. You can
34095 supply the optional @samp{-ctf} argument to save it the CTF format. See
34096 @ref{Trace Files} for more information about CTF.
34098 @subsubheading @value{GDBN} Command
34100 The corresponding @value{GDBN} command is @samp{tsave}.
34103 @subheading -trace-start
34104 @findex -trace-start
34106 @subsubheading Synopsis
34112 Starts a tracing experiment. The result of this command does not
34115 @subsubheading @value{GDBN} Command
34117 The corresponding @value{GDBN} command is @samp{tstart}.
34119 @subheading -trace-status
34120 @findex -trace-status
34122 @subsubheading Synopsis
34128 Obtains the status of a tracing experiment. The result may include
34129 the following fields:
34134 May have a value of either @samp{0}, when no tracing operations are
34135 supported, @samp{1}, when all tracing operations are supported, or
34136 @samp{file} when examining trace file. In the latter case, examining
34137 of trace frame is possible but new tracing experiement cannot be
34138 started. This field is always present.
34141 May have a value of either @samp{0} or @samp{1} depending on whether
34142 tracing experiement is in progress on target. This field is present
34143 if @samp{supported} field is not @samp{0}.
34146 Report the reason why the tracing was stopped last time. This field
34147 may be absent iff tracing was never stopped on target yet. The
34148 value of @samp{request} means the tracing was stopped as result of
34149 the @code{-trace-stop} command. The value of @samp{overflow} means
34150 the tracing buffer is full. The value of @samp{disconnection} means
34151 tracing was automatically stopped when @value{GDBN} has disconnected.
34152 The value of @samp{passcount} means tracing was stopped when a
34153 tracepoint was passed a maximal number of times for that tracepoint.
34154 This field is present if @samp{supported} field is not @samp{0}.
34156 @item stopping-tracepoint
34157 The number of tracepoint whose passcount as exceeded. This field is
34158 present iff the @samp{stop-reason} field has the value of
34162 @itemx frames-created
34163 The @samp{frames} field is a count of the total number of trace frames
34164 in the trace buffer, while @samp{frames-created} is the total created
34165 during the run, including ones that were discarded, such as when a
34166 circular trace buffer filled up. Both fields are optional.
34170 These fields tell the current size of the tracing buffer and the
34171 remaining space. These fields are optional.
34174 The value of the circular trace buffer flag. @code{1} means that the
34175 trace buffer is circular and old trace frames will be discarded if
34176 necessary to make room, @code{0} means that the trace buffer is linear
34180 The value of the disconnected tracing flag. @code{1} means that
34181 tracing will continue after @value{GDBN} disconnects, @code{0} means
34182 that the trace run will stop.
34185 The filename of the trace file being examined. This field is
34186 optional, and only present when examining a trace file.
34190 @subsubheading @value{GDBN} Command
34192 The corresponding @value{GDBN} command is @samp{tstatus}.
34194 @subheading -trace-stop
34195 @findex -trace-stop
34197 @subsubheading Synopsis
34203 Stops a tracing experiment. The result of this command has the same
34204 fields as @code{-trace-status}, except that the @samp{supported} and
34205 @samp{running} fields are not output.
34207 @subsubheading @value{GDBN} Command
34209 The corresponding @value{GDBN} command is @samp{tstop}.
34212 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34213 @node GDB/MI Symbol Query
34214 @section @sc{gdb/mi} Symbol Query Commands
34218 @subheading The @code{-symbol-info-address} Command
34219 @findex -symbol-info-address
34221 @subsubheading Synopsis
34224 -symbol-info-address @var{symbol}
34227 Describe where @var{symbol} is stored.
34229 @subsubheading @value{GDBN} Command
34231 The corresponding @value{GDBN} command is @samp{info address}.
34233 @subsubheading Example
34237 @subheading The @code{-symbol-info-file} Command
34238 @findex -symbol-info-file
34240 @subsubheading Synopsis
34246 Show the file for the symbol.
34248 @subsubheading @value{GDBN} Command
34250 There's no equivalent @value{GDBN} command. @code{gdbtk} has
34251 @samp{gdb_find_file}.
34253 @subsubheading Example
34257 @subheading The @code{-symbol-info-functions} Command
34258 @findex -symbol-info-functions
34259 @anchor{-symbol-info-functions}
34261 @subsubheading Synopsis
34264 -symbol-info-functions [--include-nondebug]
34265 [--type @var{type_regexp}]
34266 [--name @var{name_regexp}]
34267 [--max-results @var{limit}]
34271 Return a list containing the names and types for all global functions
34272 taken from the debug information. The functions are grouped by source
34273 file, and shown with the line number on which each function is
34276 The @code{--include-nondebug} option causes the output to include
34277 code symbols from the symbol table.
34279 The options @code{--type} and @code{--name} allow the symbols returned
34280 to be filtered based on either the name of the function, or the type
34281 signature of the function.
34283 The option @code{--max-results} restricts the command to return no
34284 more than @var{limit} results. If exactly @var{limit} results are
34285 returned then there might be additional results available if a higher
34288 @subsubheading @value{GDBN} Command
34290 The corresponding @value{GDBN} command is @samp{info functions}.
34292 @subsubheading Example
34296 -symbol-info-functions
34299 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34300 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34301 symbols=[@{line="36", name="f4", type="void (int *)",
34302 description="void f4(int *);"@},
34303 @{line="42", name="main", type="int ()",
34304 description="int main();"@},
34305 @{line="30", name="f1", type="my_int_t (int, int)",
34306 description="static my_int_t f1(int, int);"@}]@},
34307 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
34308 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
34309 symbols=[@{line="33", name="f2", type="float (another_float_t)",
34310 description="float f2(another_float_t);"@},
34311 @{line="39", name="f3", type="int (another_int_t)",
34312 description="int f3(another_int_t);"@},
34313 @{line="27", name="f1", type="another_float_t (int)",
34314 description="static another_float_t f1(int);"@}]@}]@}
34318 -symbol-info-functions --name f1
34321 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34322 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34323 symbols=[@{line="30", name="f1", type="my_int_t (int, int)",
34324 description="static my_int_t f1(int, int);"@}]@},
34325 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
34326 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
34327 symbols=[@{line="27", name="f1", type="another_float_t (int)",
34328 description="static another_float_t f1(int);"@}]@}]@}
34332 -symbol-info-functions --type void
34335 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34336 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34337 symbols=[@{line="36", name="f4", type="void (int *)",
34338 description="void f4(int *);"@}]@}]@}
34342 -symbol-info-functions --include-nondebug
34345 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34346 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34347 symbols=[@{line="36", name="f4", type="void (int *)",
34348 description="void f4(int *);"@},
34349 @{line="42", name="main", type="int ()",
34350 description="int main();"@},
34351 @{line="30", name="f1", type="my_int_t (int, int)",
34352 description="static my_int_t f1(int, int);"@}]@},
34353 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
34354 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
34355 symbols=[@{line="33", name="f2", type="float (another_float_t)",
34356 description="float f2(another_float_t);"@},
34357 @{line="39", name="f3", type="int (another_int_t)",
34358 description="int f3(another_int_t);"@},
34359 @{line="27", name="f1", type="another_float_t (int)",
34360 description="static another_float_t f1(int);"@}]@}],
34362 [@{address="0x0000000000400398",name="_init"@},
34363 @{address="0x00000000004003b0",name="_start"@},
34369 @subheading The @code{-symbol-info-module-functions} Command
34370 @findex -symbol-info-module-functions
34371 @anchor{-symbol-info-module-functions}
34373 @subsubheading Synopsis
34376 -symbol-info-module-functions [--module @var{module_regexp}]
34377 [--name @var{name_regexp}]
34378 [--type @var{type_regexp}]
34382 Return a list containing the names of all known functions within all
34383 know Fortran modules. The functions are grouped by source file and
34384 containing module, and shown with the line number on which each
34385 function is defined.
34387 The option @code{--module} only returns results for modules matching
34388 @var{module_regexp}. The option @code{--name} only returns functions
34389 whose name matches @var{name_regexp}, and @code{--type} only returns
34390 functions whose type matches @var{type_regexp}.
34392 @subsubheading @value{GDBN} Command
34394 The corresponding @value{GDBN} command is @samp{info module functions}.
34396 @subsubheading Example
34401 -symbol-info-module-functions
34404 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
34405 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
34406 symbols=[@{line="21",name="mod1::check_all",type="void (void)",
34407 description="void mod1::check_all(void);"@}]@}]@},
34409 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
34410 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
34411 symbols=[@{line="30",name="mod2::check_var_i",type="void (void)",
34412 description="void mod2::check_var_i(void);"@}]@}]@},
34414 files=[@{filename="/projec/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
34415 fullname="/projec/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
34416 symbols=[@{line="21",name="mod3::check_all",type="void (void)",
34417 description="void mod3::check_all(void);"@},
34418 @{line="27",name="mod3::check_mod2",type="void (void)",
34419 description="void mod3::check_mod2(void);"@}]@}]@},
34420 @{module="modmany",
34421 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
34422 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
34423 symbols=[@{line="35",name="modmany::check_some",type="void (void)",
34424 description="void modmany::check_some(void);"@}]@}]@},
34426 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
34427 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
34428 symbols=[@{line="44",name="moduse::check_all",type="void (void)",
34429 description="void moduse::check_all(void);"@},
34430 @{line="49",name="moduse::check_var_x",type="void (void)",
34431 description="void moduse::check_var_x(void);"@}]@}]@}]
34435 @subheading The @code{-symbol-info-module-variables} Command
34436 @findex -symbol-info-module-variables
34437 @anchor{-symbol-info-module-variables}
34439 @subsubheading Synopsis
34442 -symbol-info-module-variables [--module @var{module_regexp}]
34443 [--name @var{name_regexp}]
34444 [--type @var{type_regexp}]
34448 Return a list containing the names of all known variables within all
34449 know Fortran modules. The variables are grouped by source file and
34450 containing module, and shown with the line number on which each
34451 variable is defined.
34453 The option @code{--module} only returns results for modules matching
34454 @var{module_regexp}. The option @code{--name} only returns variables
34455 whose name matches @var{name_regexp}, and @code{--type} only returns
34456 variables whose type matches @var{type_regexp}.
34458 @subsubheading @value{GDBN} Command
34460 The corresponding @value{GDBN} command is @samp{info module variables}.
34462 @subsubheading Example
34467 -symbol-info-module-variables
34470 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
34471 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
34472 symbols=[@{line="18",name="mod1::var_const",type="integer(kind=4)",
34473 description="integer(kind=4) mod1::var_const;"@},
34474 @{line="17",name="mod1::var_i",type="integer(kind=4)",
34475 description="integer(kind=4) mod1::var_i;"@}]@}]@},
34477 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
34478 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
34479 symbols=[@{line="28",name="mod2::var_i",type="integer(kind=4)",
34480 description="integer(kind=4) mod2::var_i;"@}]@}]@},
34482 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
34483 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
34484 symbols=[@{line="18",name="mod3::mod1",type="integer(kind=4)",
34485 description="integer(kind=4) mod3::mod1;"@},
34486 @{line="17",name="mod3::mod2",type="integer(kind=4)",
34487 description="integer(kind=4) mod3::mod2;"@},
34488 @{line="19",name="mod3::var_i",type="integer(kind=4)",
34489 description="integer(kind=4) mod3::var_i;"@}]@}]@},
34490 @{module="modmany",
34491 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
34492 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
34493 symbols=[@{line="33",name="modmany::var_a",type="integer(kind=4)",
34494 description="integer(kind=4) modmany::var_a;"@},
34495 @{line="33",name="modmany::var_b",type="integer(kind=4)",
34496 description="integer(kind=4) modmany::var_b;"@},
34497 @{line="33",name="modmany::var_c",type="integer(kind=4)",
34498 description="integer(kind=4) modmany::var_c;"@},
34499 @{line="33",name="modmany::var_i",type="integer(kind=4)",
34500 description="integer(kind=4) modmany::var_i;"@}]@}]@},
34502 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
34503 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
34504 symbols=[@{line="42",name="moduse::var_x",type="integer(kind=4)",
34505 description="integer(kind=4) moduse::var_x;"@},
34506 @{line="42",name="moduse::var_y",type="integer(kind=4)",
34507 description="integer(kind=4) moduse::var_y;"@}]@}]@}]
34511 @subheading The @code{-symbol-info-modules} Command
34512 @findex -symbol-info-modules
34513 @anchor{-symbol-info-modules}
34515 @subsubheading Synopsis
34518 -symbol-info-modules [--name @var{name_regexp}]
34519 [--max-results @var{limit}]
34524 Return a list containing the names of all known Fortran modules. The
34525 modules are grouped by source file, and shown with the line number on
34526 which each modules is defined.
34528 The option @code{--name} allows the modules returned to be filtered
34529 based the name of the module.
34531 The option @code{--max-results} restricts the command to return no
34532 more than @var{limit} results. If exactly @var{limit} results are
34533 returned then there might be additional results available if a higher
34536 @subsubheading @value{GDBN} Command
34538 The corresponding @value{GDBN} command is @samp{info modules}.
34540 @subsubheading Example
34544 -symbol-info-modules
34547 [@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
34548 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
34549 symbols=[@{line="16",name="mod1"@},
34550 @{line="22",name="mod2"@}]@},
34551 @{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
34552 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
34553 symbols=[@{line="16",name="mod3"@},
34554 @{line="22",name="modmany"@},
34555 @{line="26",name="moduse"@}]@}]@}
34559 -symbol-info-modules --name mod[123]
34562 [@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
34563 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
34564 symbols=[@{line="16",name="mod1"@},
34565 @{line="22",name="mod2"@}]@},
34566 @{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
34567 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
34568 symbols=[@{line="16",name="mod3"@}]@}]@}
34572 @subheading The @code{-symbol-info-types} Command
34573 @findex -symbol-info-types
34574 @anchor{-symbol-info-types}
34576 @subsubheading Synopsis
34579 -symbol-info-types [--name @var{name_regexp}]
34580 [--max-results @var{limit}]
34585 Return a list of all defined types. The types are grouped by source
34586 file, and shown with the line number on which each user defined type
34587 is defined. Some base types are not defined in the source code but
34588 are added to the debug information by the compiler, for example
34589 @code{int}, @code{float}, etc.; these types do not have an associated
34592 The option @code{--name} allows the list of types returned to be
34595 The option @code{--max-results} restricts the command to return no
34596 more than @var{limit} results. If exactly @var{limit} results are
34597 returned then there might be additional results available if a higher
34600 @subsubheading @value{GDBN} Command
34602 The corresponding @value{GDBN} command is @samp{info types}.
34604 @subsubheading Example
34611 [@{filename="gdb.mi/mi-sym-info-1.c",
34612 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34613 symbols=[@{name="float"@},
34615 @{line="27",name="typedef int my_int_t;"@}]@},
34616 @{filename="gdb.mi/mi-sym-info-2.c",
34617 fullname="/project/gdb.mi/mi-sym-info-2.c",
34618 symbols=[@{line="24",name="typedef float another_float_t;"@},
34619 @{line="23",name="typedef int another_int_t;"@},
34621 @{name="int"@}]@}]@}
34625 -symbol-info-types --name _int_
34628 [@{filename="gdb.mi/mi-sym-info-1.c",
34629 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34630 symbols=[@{line="27",name="typedef int my_int_t;"@}]@},
34631 @{filename="gdb.mi/mi-sym-info-2.c",
34632 fullname="/project/gdb.mi/mi-sym-info-2.c",
34633 symbols=[@{line="23",name="typedef int another_int_t;"@}]@}]@}
34637 @subheading The @code{-symbol-info-variables} Command
34638 @findex -symbol-info-variables
34639 @anchor{-symbol-info-variables}
34641 @subsubheading Synopsis
34644 -symbol-info-variables [--include-nondebug]
34645 [--type @var{type_regexp}]
34646 [--name @var{name_regexp}]
34647 [--max-results @var{limit}]
34652 Return a list containing the names and types for all global variables
34653 taken from the debug information. The variables are grouped by source
34654 file, and shown with the line number on which each variable is
34657 The @code{--include-nondebug} option causes the output to include
34658 data symbols from the symbol table.
34660 The options @code{--type} and @code{--name} allow the symbols returned
34661 to be filtered based on either the name of the variable, or the type
34664 The option @code{--max-results} restricts the command to return no
34665 more than @var{limit} results. If exactly @var{limit} results are
34666 returned then there might be additional results available if a higher
34669 @subsubheading @value{GDBN} Command
34671 The corresponding @value{GDBN} command is @samp{info variables}.
34673 @subsubheading Example
34677 -symbol-info-variables
34680 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34681 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34682 symbols=[@{line="25",name="global_f1",type="float",
34683 description="static float global_f1;"@},
34684 @{line="24",name="global_i1",type="int",
34685 description="static int global_i1;"@}]@},
34686 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
34687 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
34688 symbols=[@{line="21",name="global_f2",type="int",
34689 description="int global_f2;"@},
34690 @{line="20",name="global_i2",type="int",
34691 description="int global_i2;"@},
34692 @{line="19",name="global_f1",type="float",
34693 description="static float global_f1;"@},
34694 @{line="18",name="global_i1",type="int",
34695 description="static int global_i1;"@}]@}]@}
34699 -symbol-info-variables --name f1
34702 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34703 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34704 symbols=[@{line="25",name="global_f1",type="float",
34705 description="static float global_f1;"@}]@},
34706 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
34707 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
34708 symbols=[@{line="19",name="global_f1",type="float",
34709 description="static float global_f1;"@}]@}]@}
34713 -symbol-info-variables --type float
34716 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34717 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34718 symbols=[@{line="25",name="global_f1",type="float",
34719 description="static float global_f1;"@}]@},
34720 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
34721 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
34722 symbols=[@{line="19",name="global_f1",type="float",
34723 description="static float global_f1;"@}]@}]@}
34727 -symbol-info-variables --include-nondebug
34730 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34731 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34732 symbols=[@{line="25",name="global_f1",type="float",
34733 description="static float global_f1;"@},
34734 @{line="24",name="global_i1",type="int",
34735 description="static int global_i1;"@}]@},
34736 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
34737 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
34738 symbols=[@{line="21",name="global_f2",type="int",
34739 description="int global_f2;"@},
34740 @{line="20",name="global_i2",type="int",
34741 description="int global_i2;"@},
34742 @{line="19",name="global_f1",type="float",
34743 description="static float global_f1;"@},
34744 @{line="18",name="global_i1",type="int",
34745 description="static int global_i1;"@}]@}],
34747 [@{address="0x00000000004005d0",name="_IO_stdin_used"@},
34748 @{address="0x00000000004005d8",name="__dso_handle"@}
34755 @subheading The @code{-symbol-info-line} Command
34756 @findex -symbol-info-line
34758 @subsubheading Synopsis
34764 Show the core addresses of the code for a source line.
34766 @subsubheading @value{GDBN} Command
34768 The corresponding @value{GDBN} command is @samp{info line}.
34769 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
34771 @subsubheading Example
34775 @subheading The @code{-symbol-info-symbol} Command
34776 @findex -symbol-info-symbol
34778 @subsubheading Synopsis
34781 -symbol-info-symbol @var{addr}
34784 Describe what symbol is at location @var{addr}.
34786 @subsubheading @value{GDBN} Command
34788 The corresponding @value{GDBN} command is @samp{info symbol}.
34790 @subsubheading Example
34794 @subheading The @code{-symbol-list-functions} Command
34795 @findex -symbol-list-functions
34797 @subsubheading Synopsis
34800 -symbol-list-functions
34803 List the functions in the executable.
34805 @subsubheading @value{GDBN} Command
34807 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
34808 @samp{gdb_search} in @code{gdbtk}.
34810 @subsubheading Example
34815 @subheading The @code{-symbol-list-lines} Command
34816 @findex -symbol-list-lines
34818 @subsubheading Synopsis
34821 -symbol-list-lines @var{filename}
34824 Print the list of lines that contain code and their associated program
34825 addresses for the given source filename. The entries are sorted in
34826 ascending PC order.
34828 @subsubheading @value{GDBN} Command
34830 There is no corresponding @value{GDBN} command.
34832 @subsubheading Example
34835 -symbol-list-lines basics.c
34836 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
34842 @subheading The @code{-symbol-list-types} Command
34843 @findex -symbol-list-types
34845 @subsubheading Synopsis
34851 List all the type names.
34853 @subsubheading @value{GDBN} Command
34855 The corresponding commands are @samp{info types} in @value{GDBN},
34856 @samp{gdb_search} in @code{gdbtk}.
34858 @subsubheading Example
34862 @subheading The @code{-symbol-list-variables} Command
34863 @findex -symbol-list-variables
34865 @subsubheading Synopsis
34868 -symbol-list-variables
34871 List all the global and static variable names.
34873 @subsubheading @value{GDBN} Command
34875 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
34877 @subsubheading Example
34881 @subheading The @code{-symbol-locate} Command
34882 @findex -symbol-locate
34884 @subsubheading Synopsis
34890 @subsubheading @value{GDBN} Command
34892 @samp{gdb_loc} in @code{gdbtk}.
34894 @subsubheading Example
34898 @subheading The @code{-symbol-type} Command
34899 @findex -symbol-type
34901 @subsubheading Synopsis
34904 -symbol-type @var{variable}
34907 Show type of @var{variable}.
34909 @subsubheading @value{GDBN} Command
34911 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
34912 @samp{gdb_obj_variable}.
34914 @subsubheading Example
34919 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34920 @node GDB/MI File Commands
34921 @section @sc{gdb/mi} File Commands
34923 This section describes the GDB/MI commands to specify executable file names
34924 and to read in and obtain symbol table information.
34926 @subheading The @code{-file-exec-and-symbols} Command
34927 @findex -file-exec-and-symbols
34929 @subsubheading Synopsis
34932 -file-exec-and-symbols @var{file}
34935 Specify the executable file to be debugged. This file is the one from
34936 which the symbol table is also read. If no file is specified, the
34937 command clears the executable and symbol information. If breakpoints
34938 are set when using this command with no arguments, @value{GDBN} will produce
34939 error messages. Otherwise, no output is produced, except a completion
34942 @subsubheading @value{GDBN} Command
34944 The corresponding @value{GDBN} command is @samp{file}.
34946 @subsubheading Example
34950 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
34956 @subheading The @code{-file-exec-file} Command
34957 @findex -file-exec-file
34959 @subsubheading Synopsis
34962 -file-exec-file @var{file}
34965 Specify the executable file to be debugged. Unlike
34966 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
34967 from this file. If used without argument, @value{GDBN} clears the information
34968 about the executable file. No output is produced, except a completion
34971 @subsubheading @value{GDBN} Command
34973 The corresponding @value{GDBN} command is @samp{exec-file}.
34975 @subsubheading Example
34979 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
34986 @subheading The @code{-file-list-exec-sections} Command
34987 @findex -file-list-exec-sections
34989 @subsubheading Synopsis
34992 -file-list-exec-sections
34995 List the sections of the current executable file.
34997 @subsubheading @value{GDBN} Command
34999 The @value{GDBN} command @samp{info file} shows, among the rest, the same
35000 information as this command. @code{gdbtk} has a corresponding command
35001 @samp{gdb_load_info}.
35003 @subsubheading Example
35008 @subheading The @code{-file-list-exec-source-file} Command
35009 @findex -file-list-exec-source-file
35011 @subsubheading Synopsis
35014 -file-list-exec-source-file
35017 List the line number, the current source file, and the absolute path
35018 to the current source file for the current executable. The macro
35019 information field has a value of @samp{1} or @samp{0} depending on
35020 whether or not the file includes preprocessor macro information.
35022 @subsubheading @value{GDBN} Command
35024 The @value{GDBN} equivalent is @samp{info source}
35026 @subsubheading Example
35030 123-file-list-exec-source-file
35031 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
35036 @subheading The @code{-file-list-exec-source-files} Command
35037 @findex -file-list-exec-source-files
35039 @subsubheading Synopsis
35042 -file-list-exec-source-files
35045 List the source files for the current executable.
35047 It will always output both the filename and fullname (absolute file
35048 name) of a source file.
35050 @subsubheading @value{GDBN} Command
35052 The @value{GDBN} equivalent is @samp{info sources}.
35053 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
35055 @subsubheading Example
35058 -file-list-exec-source-files
35060 @{file=foo.c,fullname=/home/foo.c@},
35061 @{file=/home/bar.c,fullname=/home/bar.c@},
35062 @{file=gdb_could_not_find_fullpath.c@}]
35066 @subheading The @code{-file-list-shared-libraries} Command
35067 @findex -file-list-shared-libraries
35069 @subsubheading Synopsis
35072 -file-list-shared-libraries [ @var{regexp} ]
35075 List the shared libraries in the program.
35076 With a regular expression @var{regexp}, only those libraries whose
35077 names match @var{regexp} are listed.
35079 @subsubheading @value{GDBN} Command
35081 The corresponding @value{GDBN} command is @samp{info shared}. The fields
35082 have a similar meaning to the @code{=library-loaded} notification.
35083 The @code{ranges} field specifies the multiple segments belonging to this
35084 library. Each range has the following fields:
35088 The address defining the inclusive lower bound of the segment.
35090 The address defining the exclusive upper bound of the segment.
35093 @subsubheading Example
35096 -file-list-exec-source-files
35097 ^done,shared-libraries=[
35098 @{id="/lib/libfoo.so",target-name="/lib/libfoo.so",host-name="/lib/libfoo.so",symbols-loaded="1",thread-group="i1",ranges=[@{from="0x72815989",to="0x728162c0"@}]@},
35099 @{id="/lib/libbar.so",target-name="/lib/libbar.so",host-name="/lib/libbar.so",symbols-loaded="1",thread-group="i1",ranges=[@{from="0x76ee48c0",to="0x76ee9160"@}]@}]
35105 @subheading The @code{-file-list-symbol-files} Command
35106 @findex -file-list-symbol-files
35108 @subsubheading Synopsis
35111 -file-list-symbol-files
35116 @subsubheading @value{GDBN} Command
35118 The corresponding @value{GDBN} command is @samp{info file} (part of it).
35120 @subsubheading Example
35125 @subheading The @code{-file-symbol-file} Command
35126 @findex -file-symbol-file
35128 @subsubheading Synopsis
35131 -file-symbol-file @var{file}
35134 Read symbol table info from the specified @var{file} argument. When
35135 used without arguments, clears @value{GDBN}'s symbol table info. No output is
35136 produced, except for a completion notification.
35138 @subsubheading @value{GDBN} Command
35140 The corresponding @value{GDBN} command is @samp{symbol-file}.
35142 @subsubheading Example
35146 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
35152 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35153 @node GDB/MI Memory Overlay Commands
35154 @section @sc{gdb/mi} Memory Overlay Commands
35156 The memory overlay commands are not implemented.
35158 @c @subheading -overlay-auto
35160 @c @subheading -overlay-list-mapping-state
35162 @c @subheading -overlay-list-overlays
35164 @c @subheading -overlay-map
35166 @c @subheading -overlay-off
35168 @c @subheading -overlay-on
35170 @c @subheading -overlay-unmap
35172 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35173 @node GDB/MI Signal Handling Commands
35174 @section @sc{gdb/mi} Signal Handling Commands
35176 Signal handling commands are not implemented.
35178 @c @subheading -signal-handle
35180 @c @subheading -signal-list-handle-actions
35182 @c @subheading -signal-list-signal-types
35186 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35187 @node GDB/MI Target Manipulation
35188 @section @sc{gdb/mi} Target Manipulation Commands
35191 @subheading The @code{-target-attach} Command
35192 @findex -target-attach
35194 @subsubheading Synopsis
35197 -target-attach @var{pid} | @var{gid} | @var{file}
35200 Attach to a process @var{pid} or a file @var{file} outside of
35201 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
35202 group, the id previously returned by
35203 @samp{-list-thread-groups --available} must be used.
35205 @subsubheading @value{GDBN} Command
35207 The corresponding @value{GDBN} command is @samp{attach}.
35209 @subsubheading Example
35213 =thread-created,id="1"
35214 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
35220 @subheading The @code{-target-compare-sections} Command
35221 @findex -target-compare-sections
35223 @subsubheading Synopsis
35226 -target-compare-sections [ @var{section} ]
35229 Compare data of section @var{section} on target to the exec file.
35230 Without the argument, all sections are compared.
35232 @subsubheading @value{GDBN} Command
35234 The @value{GDBN} equivalent is @samp{compare-sections}.
35236 @subsubheading Example
35241 @subheading The @code{-target-detach} Command
35242 @findex -target-detach
35244 @subsubheading Synopsis
35247 -target-detach [ @var{pid} | @var{gid} ]
35250 Detach from the remote target which normally resumes its execution.
35251 If either @var{pid} or @var{gid} is specified, detaches from either
35252 the specified process, or specified thread group. There's no output.
35254 @subsubheading @value{GDBN} Command
35256 The corresponding @value{GDBN} command is @samp{detach}.
35258 @subsubheading Example
35268 @subheading The @code{-target-disconnect} Command
35269 @findex -target-disconnect
35271 @subsubheading Synopsis
35277 Disconnect from the remote target. There's no output and the target is
35278 generally not resumed.
35280 @subsubheading @value{GDBN} Command
35282 The corresponding @value{GDBN} command is @samp{disconnect}.
35284 @subsubheading Example
35294 @subheading The @code{-target-download} Command
35295 @findex -target-download
35297 @subsubheading Synopsis
35303 Loads the executable onto the remote target.
35304 It prints out an update message every half second, which includes the fields:
35308 The name of the section.
35310 The size of what has been sent so far for that section.
35312 The size of the section.
35314 The total size of what was sent so far (the current and the previous sections).
35316 The size of the overall executable to download.
35320 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
35321 @sc{gdb/mi} Output Syntax}).
35323 In addition, it prints the name and size of the sections, as they are
35324 downloaded. These messages include the following fields:
35328 The name of the section.
35330 The size of the section.
35332 The size of the overall executable to download.
35336 At the end, a summary is printed.
35338 @subsubheading @value{GDBN} Command
35340 The corresponding @value{GDBN} command is @samp{load}.
35342 @subsubheading Example
35344 Note: each status message appears on a single line. Here the messages
35345 have been broken down so that they can fit onto a page.
35350 +download,@{section=".text",section-size="6668",total-size="9880"@}
35351 +download,@{section=".text",section-sent="512",section-size="6668",
35352 total-sent="512",total-size="9880"@}
35353 +download,@{section=".text",section-sent="1024",section-size="6668",
35354 total-sent="1024",total-size="9880"@}
35355 +download,@{section=".text",section-sent="1536",section-size="6668",
35356 total-sent="1536",total-size="9880"@}
35357 +download,@{section=".text",section-sent="2048",section-size="6668",
35358 total-sent="2048",total-size="9880"@}
35359 +download,@{section=".text",section-sent="2560",section-size="6668",
35360 total-sent="2560",total-size="9880"@}
35361 +download,@{section=".text",section-sent="3072",section-size="6668",
35362 total-sent="3072",total-size="9880"@}
35363 +download,@{section=".text",section-sent="3584",section-size="6668",
35364 total-sent="3584",total-size="9880"@}
35365 +download,@{section=".text",section-sent="4096",section-size="6668",
35366 total-sent="4096",total-size="9880"@}
35367 +download,@{section=".text",section-sent="4608",section-size="6668",
35368 total-sent="4608",total-size="9880"@}
35369 +download,@{section=".text",section-sent="5120",section-size="6668",
35370 total-sent="5120",total-size="9880"@}
35371 +download,@{section=".text",section-sent="5632",section-size="6668",
35372 total-sent="5632",total-size="9880"@}
35373 +download,@{section=".text",section-sent="6144",section-size="6668",
35374 total-sent="6144",total-size="9880"@}
35375 +download,@{section=".text",section-sent="6656",section-size="6668",
35376 total-sent="6656",total-size="9880"@}
35377 +download,@{section=".init",section-size="28",total-size="9880"@}
35378 +download,@{section=".fini",section-size="28",total-size="9880"@}
35379 +download,@{section=".data",section-size="3156",total-size="9880"@}
35380 +download,@{section=".data",section-sent="512",section-size="3156",
35381 total-sent="7236",total-size="9880"@}
35382 +download,@{section=".data",section-sent="1024",section-size="3156",
35383 total-sent="7748",total-size="9880"@}
35384 +download,@{section=".data",section-sent="1536",section-size="3156",
35385 total-sent="8260",total-size="9880"@}
35386 +download,@{section=".data",section-sent="2048",section-size="3156",
35387 total-sent="8772",total-size="9880"@}
35388 +download,@{section=".data",section-sent="2560",section-size="3156",
35389 total-sent="9284",total-size="9880"@}
35390 +download,@{section=".data",section-sent="3072",section-size="3156",
35391 total-sent="9796",total-size="9880"@}
35392 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
35399 @subheading The @code{-target-exec-status} Command
35400 @findex -target-exec-status
35402 @subsubheading Synopsis
35405 -target-exec-status
35408 Provide information on the state of the target (whether it is running or
35409 not, for instance).
35411 @subsubheading @value{GDBN} Command
35413 There's no equivalent @value{GDBN} command.
35415 @subsubheading Example
35419 @subheading The @code{-target-list-available-targets} Command
35420 @findex -target-list-available-targets
35422 @subsubheading Synopsis
35425 -target-list-available-targets
35428 List the possible targets to connect to.
35430 @subsubheading @value{GDBN} Command
35432 The corresponding @value{GDBN} command is @samp{help target}.
35434 @subsubheading Example
35438 @subheading The @code{-target-list-current-targets} Command
35439 @findex -target-list-current-targets
35441 @subsubheading Synopsis
35444 -target-list-current-targets
35447 Describe the current target.
35449 @subsubheading @value{GDBN} Command
35451 The corresponding information is printed by @samp{info file} (among
35454 @subsubheading Example
35458 @subheading The @code{-target-list-parameters} Command
35459 @findex -target-list-parameters
35461 @subsubheading Synopsis
35464 -target-list-parameters
35470 @subsubheading @value{GDBN} Command
35474 @subsubheading Example
35477 @subheading The @code{-target-flash-erase} Command
35478 @findex -target-flash-erase
35480 @subsubheading Synopsis
35483 -target-flash-erase
35486 Erases all known flash memory regions on the target.
35488 The corresponding @value{GDBN} command is @samp{flash-erase}.
35490 The output is a list of flash regions that have been erased, with starting
35491 addresses and memory region sizes.
35495 -target-flash-erase
35496 ^done,erased-regions=@{address="0x0",size="0x40000"@}
35500 @subheading The @code{-target-select} Command
35501 @findex -target-select
35503 @subsubheading Synopsis
35506 -target-select @var{type} @var{parameters @dots{}}
35509 Connect @value{GDBN} to the remote target. This command takes two args:
35513 The type of target, for instance @samp{remote}, etc.
35514 @item @var{parameters}
35515 Device names, host names and the like. @xref{Target Commands, ,
35516 Commands for Managing Targets}, for more details.
35519 The output is a connection notification, followed by the address at
35520 which the target program is, in the following form:
35523 ^connected,addr="@var{address}",func="@var{function name}",
35524 args=[@var{arg list}]
35527 @subsubheading @value{GDBN} Command
35529 The corresponding @value{GDBN} command is @samp{target}.
35531 @subsubheading Example
35535 -target-select remote /dev/ttya
35536 ^connected,addr="0xfe00a300",func="??",args=[]
35540 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35541 @node GDB/MI File Transfer Commands
35542 @section @sc{gdb/mi} File Transfer Commands
35545 @subheading The @code{-target-file-put} Command
35546 @findex -target-file-put
35548 @subsubheading Synopsis
35551 -target-file-put @var{hostfile} @var{targetfile}
35554 Copy file @var{hostfile} from the host system (the machine running
35555 @value{GDBN}) to @var{targetfile} on the target system.
35557 @subsubheading @value{GDBN} Command
35559 The corresponding @value{GDBN} command is @samp{remote put}.
35561 @subsubheading Example
35565 -target-file-put localfile remotefile
35571 @subheading The @code{-target-file-get} Command
35572 @findex -target-file-get
35574 @subsubheading Synopsis
35577 -target-file-get @var{targetfile} @var{hostfile}
35580 Copy file @var{targetfile} from the target system to @var{hostfile}
35581 on the host system.
35583 @subsubheading @value{GDBN} Command
35585 The corresponding @value{GDBN} command is @samp{remote get}.
35587 @subsubheading Example
35591 -target-file-get remotefile localfile
35597 @subheading The @code{-target-file-delete} Command
35598 @findex -target-file-delete
35600 @subsubheading Synopsis
35603 -target-file-delete @var{targetfile}
35606 Delete @var{targetfile} from the target system.
35608 @subsubheading @value{GDBN} Command
35610 The corresponding @value{GDBN} command is @samp{remote delete}.
35612 @subsubheading Example
35616 -target-file-delete remotefile
35622 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35623 @node GDB/MI Ada Exceptions Commands
35624 @section Ada Exceptions @sc{gdb/mi} Commands
35626 @subheading The @code{-info-ada-exceptions} Command
35627 @findex -info-ada-exceptions
35629 @subsubheading Synopsis
35632 -info-ada-exceptions [ @var{regexp}]
35635 List all Ada exceptions defined within the program being debugged.
35636 With a regular expression @var{regexp}, only those exceptions whose
35637 names match @var{regexp} are listed.
35639 @subsubheading @value{GDBN} Command
35641 The corresponding @value{GDBN} command is @samp{info exceptions}.
35643 @subsubheading Result
35645 The result is a table of Ada exceptions. The following columns are
35646 defined for each exception:
35650 The name of the exception.
35653 The address of the exception.
35657 @subsubheading Example
35660 -info-ada-exceptions aint
35661 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
35662 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
35663 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
35664 body=[@{name="constraint_error",address="0x0000000000613da0"@},
35665 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
35668 @subheading Catching Ada Exceptions
35670 The commands describing how to ask @value{GDBN} to stop when a program
35671 raises an exception are described at @ref{Ada Exception GDB/MI
35672 Catchpoint Commands}.
35675 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35676 @node GDB/MI Support Commands
35677 @section @sc{gdb/mi} Support Commands
35679 Since new commands and features get regularly added to @sc{gdb/mi},
35680 some commands are available to help front-ends query the debugger
35681 about support for these capabilities. Similarly, it is also possible
35682 to query @value{GDBN} about target support of certain features.
35684 @subheading The @code{-info-gdb-mi-command} Command
35685 @cindex @code{-info-gdb-mi-command}
35686 @findex -info-gdb-mi-command
35688 @subsubheading Synopsis
35691 -info-gdb-mi-command @var{cmd_name}
35694 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
35696 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
35697 is technically not part of the command name (@pxref{GDB/MI Input
35698 Syntax}), and thus should be omitted in @var{cmd_name}. However,
35699 for ease of use, this command also accepts the form with the leading
35702 @subsubheading @value{GDBN} Command
35704 There is no corresponding @value{GDBN} command.
35706 @subsubheading Result
35708 The result is a tuple. There is currently only one field:
35712 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
35713 @code{"false"} otherwise.
35717 @subsubheading Example
35719 Here is an example where the @sc{gdb/mi} command does not exist:
35722 -info-gdb-mi-command unsupported-command
35723 ^done,command=@{exists="false"@}
35727 And here is an example where the @sc{gdb/mi} command is known
35731 -info-gdb-mi-command symbol-list-lines
35732 ^done,command=@{exists="true"@}
35735 @subheading The @code{-list-features} Command
35736 @findex -list-features
35737 @cindex supported @sc{gdb/mi} features, list
35739 Returns a list of particular features of the MI protocol that
35740 this version of gdb implements. A feature can be a command,
35741 or a new field in an output of some command, or even an
35742 important bugfix. While a frontend can sometimes detect presence
35743 of a feature at runtime, it is easier to perform detection at debugger
35746 The command returns a list of strings, with each string naming an
35747 available feature. Each returned string is just a name, it does not
35748 have any internal structure. The list of possible feature names
35754 (gdb) -list-features
35755 ^done,result=["feature1","feature2"]
35758 The current list of features is:
35761 @item frozen-varobjs
35762 Indicates support for the @code{-var-set-frozen} command, as well
35763 as possible presence of the @code{frozen} field in the output
35764 of @code{-varobj-create}.
35765 @item pending-breakpoints
35766 Indicates support for the @option{-f} option to the @code{-break-insert}
35769 Indicates Python scripting support, Python-based
35770 pretty-printing commands, and possible presence of the
35771 @samp{display_hint} field in the output of @code{-var-list-children}
35773 Indicates support for the @code{-thread-info} command.
35774 @item data-read-memory-bytes
35775 Indicates support for the @code{-data-read-memory-bytes} and the
35776 @code{-data-write-memory-bytes} commands.
35777 @item breakpoint-notifications
35778 Indicates that changes to breakpoints and breakpoints created via the
35779 CLI will be announced via async records.
35780 @item ada-task-info
35781 Indicates support for the @code{-ada-task-info} command.
35782 @item language-option
35783 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
35784 option (@pxref{Context management}).
35785 @item info-gdb-mi-command
35786 Indicates support for the @code{-info-gdb-mi-command} command.
35787 @item undefined-command-error-code
35788 Indicates support for the "undefined-command" error code in error result
35789 records, produced when trying to execute an undefined @sc{gdb/mi} command
35790 (@pxref{GDB/MI Result Records}).
35791 @item exec-run-start-option
35792 Indicates that the @code{-exec-run} command supports the @option{--start}
35793 option (@pxref{GDB/MI Program Execution}).
35794 @item data-disassemble-a-option
35795 Indicates that the @code{-data-disassemble} command supports the @option{-a}
35796 option (@pxref{GDB/MI Data Manipulation}).
35799 @subheading The @code{-list-target-features} Command
35800 @findex -list-target-features
35802 Returns a list of particular features that are supported by the
35803 target. Those features affect the permitted MI commands, but
35804 unlike the features reported by the @code{-list-features} command, the
35805 features depend on which target GDB is using at the moment. Whenever
35806 a target can change, due to commands such as @code{-target-select},
35807 @code{-target-attach} or @code{-exec-run}, the list of target features
35808 may change, and the frontend should obtain it again.
35812 (gdb) -list-target-features
35813 ^done,result=["async"]
35816 The current list of features is:
35820 Indicates that the target is capable of asynchronous command
35821 execution, which means that @value{GDBN} will accept further commands
35822 while the target is running.
35825 Indicates that the target is capable of reverse execution.
35826 @xref{Reverse Execution}, for more information.
35830 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35831 @node GDB/MI Miscellaneous Commands
35832 @section Miscellaneous @sc{gdb/mi} Commands
35834 @c @subheading -gdb-complete
35836 @subheading The @code{-gdb-exit} Command
35839 @subsubheading Synopsis
35845 Exit @value{GDBN} immediately.
35847 @subsubheading @value{GDBN} Command
35849 Approximately corresponds to @samp{quit}.
35851 @subsubheading Example
35861 @subheading The @code{-exec-abort} Command
35862 @findex -exec-abort
35864 @subsubheading Synopsis
35870 Kill the inferior running program.
35872 @subsubheading @value{GDBN} Command
35874 The corresponding @value{GDBN} command is @samp{kill}.
35876 @subsubheading Example
35881 @subheading The @code{-gdb-set} Command
35884 @subsubheading Synopsis
35890 Set an internal @value{GDBN} variable.
35891 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
35893 @subsubheading @value{GDBN} Command
35895 The corresponding @value{GDBN} command is @samp{set}.
35897 @subsubheading Example
35907 @subheading The @code{-gdb-show} Command
35910 @subsubheading Synopsis
35916 Show the current value of a @value{GDBN} variable.
35918 @subsubheading @value{GDBN} Command
35920 The corresponding @value{GDBN} command is @samp{show}.
35922 @subsubheading Example
35931 @c @subheading -gdb-source
35934 @subheading The @code{-gdb-version} Command
35935 @findex -gdb-version
35937 @subsubheading Synopsis
35943 Show version information for @value{GDBN}. Used mostly in testing.
35945 @subsubheading @value{GDBN} Command
35947 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
35948 default shows this information when you start an interactive session.
35950 @subsubheading Example
35952 @c This example modifies the actual output from GDB to avoid overfull
35958 ~Copyright 2000 Free Software Foundation, Inc.
35959 ~GDB is free software, covered by the GNU General Public License, and
35960 ~you are welcome to change it and/or distribute copies of it under
35961 ~ certain conditions.
35962 ~Type "show copying" to see the conditions.
35963 ~There is absolutely no warranty for GDB. Type "show warranty" for
35965 ~This GDB was configured as
35966 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
35971 @subheading The @code{-list-thread-groups} Command
35972 @findex -list-thread-groups
35974 @subheading Synopsis
35977 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
35980 Lists thread groups (@pxref{Thread groups}). When a single thread
35981 group is passed as the argument, lists the children of that group.
35982 When several thread group are passed, lists information about those
35983 thread groups. Without any parameters, lists information about all
35984 top-level thread groups.
35986 Normally, thread groups that are being debugged are reported.
35987 With the @samp{--available} option, @value{GDBN} reports thread groups
35988 available on the target.
35990 The output of this command may have either a @samp{threads} result or
35991 a @samp{groups} result. The @samp{thread} result has a list of tuples
35992 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
35993 Information}). The @samp{groups} result has a list of tuples as value,
35994 each tuple describing a thread group. If top-level groups are
35995 requested (that is, no parameter is passed), or when several groups
35996 are passed, the output always has a @samp{groups} result. The format
35997 of the @samp{group} result is described below.
35999 To reduce the number of roundtrips it's possible to list thread groups
36000 together with their children, by passing the @samp{--recurse} option
36001 and the recursion depth. Presently, only recursion depth of 1 is
36002 permitted. If this option is present, then every reported thread group
36003 will also include its children, either as @samp{group} or
36004 @samp{threads} field.
36006 In general, any combination of option and parameters is permitted, with
36007 the following caveats:
36011 When a single thread group is passed, the output will typically
36012 be the @samp{threads} result. Because threads may not contain
36013 anything, the @samp{recurse} option will be ignored.
36016 When the @samp{--available} option is passed, limited information may
36017 be available. In particular, the list of threads of a process might
36018 be inaccessible. Further, specifying specific thread groups might
36019 not give any performance advantage over listing all thread groups.
36020 The frontend should assume that @samp{-list-thread-groups --available}
36021 is always an expensive operation and cache the results.
36025 The @samp{groups} result is a list of tuples, where each tuple may
36026 have the following fields:
36030 Identifier of the thread group. This field is always present.
36031 The identifier is an opaque string; frontends should not try to
36032 convert it to an integer, even though it might look like one.
36035 The type of the thread group. At present, only @samp{process} is a
36039 The target-specific process identifier. This field is only present
36040 for thread groups of type @samp{process} and only if the process exists.
36043 The exit code of this group's last exited thread, formatted in octal.
36044 This field is only present for thread groups of type @samp{process} and
36045 only if the process is not running.
36048 The number of children this thread group has. This field may be
36049 absent for an available thread group.
36052 This field has a list of tuples as value, each tuple describing a
36053 thread. It may be present if the @samp{--recurse} option is
36054 specified, and it's actually possible to obtain the threads.
36057 This field is a list of integers, each identifying a core that one
36058 thread of the group is running on. This field may be absent if
36059 such information is not available.
36062 The name of the executable file that corresponds to this thread group.
36063 The field is only present for thread groups of type @samp{process},
36064 and only if there is a corresponding executable file.
36068 @subheading Example
36072 -list-thread-groups
36073 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
36074 -list-thread-groups 17
36075 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
36076 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
36077 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
36078 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
36079 file="/tmp/a.c",fullname="/tmp/a.c",line="158",arch="i386:x86_64"@},state="running"@}]]
36080 -list-thread-groups --available
36081 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
36082 -list-thread-groups --available --recurse 1
36083 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
36084 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
36085 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
36086 -list-thread-groups --available --recurse 1 17 18
36087 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
36088 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
36089 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
36092 @subheading The @code{-info-os} Command
36095 @subsubheading Synopsis
36098 -info-os [ @var{type} ]
36101 If no argument is supplied, the command returns a table of available
36102 operating-system-specific information types. If one of these types is
36103 supplied as an argument @var{type}, then the command returns a table
36104 of data of that type.
36106 The types of information available depend on the target operating
36109 @subsubheading @value{GDBN} Command
36111 The corresponding @value{GDBN} command is @samp{info os}.
36113 @subsubheading Example
36115 When run on a @sc{gnu}/Linux system, the output will look something
36121 ^done,OSDataTable=@{nr_rows="10",nr_cols="3",
36122 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
36123 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
36124 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
36125 body=[item=@{col0="cpus",col1="Listing of all cpus/cores on the system",
36127 item=@{col0="files",col1="Listing of all file descriptors",
36128 col2="File descriptors"@},
36129 item=@{col0="modules",col1="Listing of all loaded kernel modules",
36130 col2="Kernel modules"@},
36131 item=@{col0="msg",col1="Listing of all message queues",
36132 col2="Message queues"@},
36133 item=@{col0="processes",col1="Listing of all processes",
36134 col2="Processes"@},
36135 item=@{col0="procgroups",col1="Listing of all process groups",
36136 col2="Process groups"@},
36137 item=@{col0="semaphores",col1="Listing of all semaphores",
36138 col2="Semaphores"@},
36139 item=@{col0="shm",col1="Listing of all shared-memory regions",
36140 col2="Shared-memory regions"@},
36141 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
36143 item=@{col0="threads",col1="Listing of all threads",
36147 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
36148 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
36149 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
36150 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
36151 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
36152 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
36153 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
36154 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
36156 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
36157 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
36161 (Note that the MI output here includes a @code{"Title"} column that
36162 does not appear in command-line @code{info os}; this column is useful
36163 for MI clients that want to enumerate the types of data, such as in a
36164 popup menu, but is needless clutter on the command line, and
36165 @code{info os} omits it.)
36167 @subheading The @code{-add-inferior} Command
36168 @findex -add-inferior
36170 @subheading Synopsis
36176 Creates a new inferior (@pxref{Inferiors Connections and Programs}). The created
36177 inferior is not associated with any executable. Such association may
36178 be established with the @samp{-file-exec-and-symbols} command
36179 (@pxref{GDB/MI File Commands}). The command response has a single
36180 field, @samp{inferior}, whose value is the identifier of the
36181 thread group corresponding to the new inferior.
36183 @subheading Example
36188 ^done,inferior="i3"
36191 @subheading The @code{-interpreter-exec} Command
36192 @findex -interpreter-exec
36194 @subheading Synopsis
36197 -interpreter-exec @var{interpreter} @var{command}
36199 @anchor{-interpreter-exec}
36201 Execute the specified @var{command} in the given @var{interpreter}.
36203 @subheading @value{GDBN} Command
36205 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
36207 @subheading Example
36211 -interpreter-exec console "break main"
36212 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
36213 &"During symbol reading, bad structure-type format.\n"
36214 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
36219 @subheading The @code{-inferior-tty-set} Command
36220 @findex -inferior-tty-set
36222 @subheading Synopsis
36225 -inferior-tty-set /dev/pts/1
36228 Set terminal for future runs of the program being debugged.
36230 @subheading @value{GDBN} Command
36232 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
36234 @subheading Example
36238 -inferior-tty-set /dev/pts/1
36243 @subheading The @code{-inferior-tty-show} Command
36244 @findex -inferior-tty-show
36246 @subheading Synopsis
36252 Show terminal for future runs of program being debugged.
36254 @subheading @value{GDBN} Command
36256 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
36258 @subheading Example
36262 -inferior-tty-set /dev/pts/1
36266 ^done,inferior_tty_terminal="/dev/pts/1"
36270 @subheading The @code{-enable-timings} Command
36271 @findex -enable-timings
36273 @subheading Synopsis
36276 -enable-timings [yes | no]
36279 Toggle the printing of the wallclock, user and system times for an MI
36280 command as a field in its output. This command is to help frontend
36281 developers optimize the performance of their code. No argument is
36282 equivalent to @samp{yes}.
36284 @subheading @value{GDBN} Command
36288 @subheading Example
36296 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
36297 addr="0x080484ed",func="main",file="myprog.c",
36298 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
36300 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
36308 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
36309 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
36310 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
36311 fullname="/home/nickrob/myprog.c",line="73",arch="i386:x86_64"@}
36315 @subheading The @code{-complete} Command
36318 @subheading Synopsis
36321 -complete @var{command}
36324 Show a list of completions for partially typed CLI @var{command}.
36326 This command is intended for @sc{gdb/mi} frontends that cannot use two separate
36327 CLI and MI channels --- for example: because of lack of PTYs like on Windows or
36328 because @value{GDBN} is used remotely via a SSH connection.
36332 The result consists of two or three fields:
36336 This field contains the completed @var{command}. If @var{command}
36337 has no known completions, this field is omitted.
36340 This field contains a (possibly empty) array of matches. It is always present.
36342 @item max_completions_reached
36343 This field contains @code{1} if number of known completions is above
36344 @code{max-completions} limit (@pxref{Completion}), otherwise it contains
36345 @code{0}. It is always present.
36349 @subheading @value{GDBN} Command
36351 The corresponding @value{GDBN} command is @samp{complete}.
36353 @subheading Example
36358 ^done,completion="break",
36359 matches=["break","break-range"],
36360 max_completions_reached="0"
36363 ^done,completion="b ma",
36364 matches=["b madvise","b main"],max_completions_reached="0"
36366 -complete "b push_b"
36367 ^done,completion="b push_back(",
36369 "b A::push_back(void*)",
36370 "b std::string::push_back(char)",
36371 "b std::vector<int, std::allocator<int> >::push_back(int&&)"],
36372 max_completions_reached="0"
36374 -complete "nonexist"
36375 ^done,matches=[],max_completions_reached="0"
36381 @chapter @value{GDBN} Annotations
36383 This chapter describes annotations in @value{GDBN}. Annotations were
36384 designed to interface @value{GDBN} to graphical user interfaces or other
36385 similar programs which want to interact with @value{GDBN} at a
36386 relatively high level.
36388 The annotation mechanism has largely been superseded by @sc{gdb/mi}
36392 This is Edition @value{EDITION}, @value{DATE}.
36396 * Annotations Overview:: What annotations are; the general syntax.
36397 * Server Prefix:: Issuing a command without affecting user state.
36398 * Prompting:: Annotations marking @value{GDBN}'s need for input.
36399 * Errors:: Annotations for error messages.
36400 * Invalidation:: Some annotations describe things now invalid.
36401 * Annotations for Running::
36402 Whether the program is running, how it stopped, etc.
36403 * Source Annotations:: Annotations describing source code.
36406 @node Annotations Overview
36407 @section What is an Annotation?
36408 @cindex annotations
36410 Annotations start with a newline character, two @samp{control-z}
36411 characters, and the name of the annotation. If there is no additional
36412 information associated with this annotation, the name of the annotation
36413 is followed immediately by a newline. If there is additional
36414 information, the name of the annotation is followed by a space, the
36415 additional information, and a newline. The additional information
36416 cannot contain newline characters.
36418 Any output not beginning with a newline and two @samp{control-z}
36419 characters denotes literal output from @value{GDBN}. Currently there is
36420 no need for @value{GDBN} to output a newline followed by two
36421 @samp{control-z} characters, but if there was such a need, the
36422 annotations could be extended with an @samp{escape} annotation which
36423 means those three characters as output.
36425 The annotation @var{level}, which is specified using the
36426 @option{--annotate} command line option (@pxref{Mode Options}), controls
36427 how much information @value{GDBN} prints together with its prompt,
36428 values of expressions, source lines, and other types of output. Level 0
36429 is for no annotations, level 1 is for use when @value{GDBN} is run as a
36430 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
36431 for programs that control @value{GDBN}, and level 2 annotations have
36432 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
36433 Interface, annotate, GDB's Obsolete Annotations}).
36436 @kindex set annotate
36437 @item set annotate @var{level}
36438 The @value{GDBN} command @code{set annotate} sets the level of
36439 annotations to the specified @var{level}.
36441 @item show annotate
36442 @kindex show annotate
36443 Show the current annotation level.
36446 This chapter describes level 3 annotations.
36448 A simple example of starting up @value{GDBN} with annotations is:
36451 $ @kbd{gdb --annotate=3}
36453 Copyright 2003 Free Software Foundation, Inc.
36454 GDB is free software, covered by the GNU General Public License,
36455 and you are welcome to change it and/or distribute copies of it
36456 under certain conditions.
36457 Type "show copying" to see the conditions.
36458 There is absolutely no warranty for GDB. Type "show warranty"
36460 This GDB was configured as "i386-pc-linux-gnu"
36471 Here @samp{quit} is input to @value{GDBN}; the rest is output from
36472 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
36473 denotes a @samp{control-z} character) are annotations; the rest is
36474 output from @value{GDBN}.
36476 @node Server Prefix
36477 @section The Server Prefix
36478 @cindex server prefix
36480 If you prefix a command with @samp{server } then it will not affect
36481 the command history, nor will it affect @value{GDBN}'s notion of which
36482 command to repeat if @key{RET} is pressed on a line by itself. This
36483 means that commands can be run behind a user's back by a front-end in
36484 a transparent manner.
36486 The @code{server } prefix does not affect the recording of values into
36487 the value history; to print a value without recording it into the
36488 value history, use the @code{output} command instead of the
36489 @code{print} command.
36491 Using this prefix also disables confirmation requests
36492 (@pxref{confirmation requests}).
36495 @section Annotation for @value{GDBN} Input
36497 @cindex annotations for prompts
36498 When @value{GDBN} prompts for input, it annotates this fact so it is possible
36499 to know when to send output, when the output from a given command is
36502 Different kinds of input each have a different @dfn{input type}. Each
36503 input type has three annotations: a @code{pre-} annotation, which
36504 denotes the beginning of any prompt which is being output, a plain
36505 annotation, which denotes the end of the prompt, and then a @code{post-}
36506 annotation which denotes the end of any echo which may (or may not) be
36507 associated with the input. For example, the @code{prompt} input type
36508 features the following annotations:
36516 The input types are
36519 @findex pre-prompt annotation
36520 @findex prompt annotation
36521 @findex post-prompt annotation
36523 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
36525 @findex pre-commands annotation
36526 @findex commands annotation
36527 @findex post-commands annotation
36529 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
36530 command. The annotations are repeated for each command which is input.
36532 @findex pre-overload-choice annotation
36533 @findex overload-choice annotation
36534 @findex post-overload-choice annotation
36535 @item overload-choice
36536 When @value{GDBN} wants the user to select between various overloaded functions.
36538 @findex pre-query annotation
36539 @findex query annotation
36540 @findex post-query annotation
36542 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
36544 @findex pre-prompt-for-continue annotation
36545 @findex prompt-for-continue annotation
36546 @findex post-prompt-for-continue annotation
36547 @item prompt-for-continue
36548 When @value{GDBN} is asking the user to press return to continue. Note: Don't
36549 expect this to work well; instead use @code{set height 0} to disable
36550 prompting. This is because the counting of lines is buggy in the
36551 presence of annotations.
36556 @cindex annotations for errors, warnings and interrupts
36558 @findex quit annotation
36563 This annotation occurs right before @value{GDBN} responds to an interrupt.
36565 @findex error annotation
36570 This annotation occurs right before @value{GDBN} responds to an error.
36572 Quit and error annotations indicate that any annotations which @value{GDBN} was
36573 in the middle of may end abruptly. For example, if a
36574 @code{value-history-begin} annotation is followed by a @code{error}, one
36575 cannot expect to receive the matching @code{value-history-end}. One
36576 cannot expect not to receive it either, however; an error annotation
36577 does not necessarily mean that @value{GDBN} is immediately returning all the way
36580 @findex error-begin annotation
36581 A quit or error annotation may be preceded by
36587 Any output between that and the quit or error annotation is the error
36590 Warning messages are not yet annotated.
36591 @c If we want to change that, need to fix warning(), type_error(),
36592 @c range_error(), and possibly other places.
36595 @section Invalidation Notices
36597 @cindex annotations for invalidation messages
36598 The following annotations say that certain pieces of state may have
36602 @findex frames-invalid annotation
36603 @item ^Z^Zframes-invalid
36605 The frames (for example, output from the @code{backtrace} command) may
36608 @findex breakpoints-invalid annotation
36609 @item ^Z^Zbreakpoints-invalid
36611 The breakpoints may have changed. For example, the user just added or
36612 deleted a breakpoint.
36615 @node Annotations for Running
36616 @section Running the Program
36617 @cindex annotations for running programs
36619 @findex starting annotation
36620 @findex stopping annotation
36621 When the program starts executing due to a @value{GDBN} command such as
36622 @code{step} or @code{continue},
36628 is output. When the program stops,
36634 is output. Before the @code{stopped} annotation, a variety of
36635 annotations describe how the program stopped.
36638 @findex exited annotation
36639 @item ^Z^Zexited @var{exit-status}
36640 The program exited, and @var{exit-status} is the exit status (zero for
36641 successful exit, otherwise nonzero).
36643 @findex signalled annotation
36644 @findex signal-name annotation
36645 @findex signal-name-end annotation
36646 @findex signal-string annotation
36647 @findex signal-string-end annotation
36648 @item ^Z^Zsignalled
36649 The program exited with a signal. After the @code{^Z^Zsignalled}, the
36650 annotation continues:
36656 ^Z^Zsignal-name-end
36660 ^Z^Zsignal-string-end
36665 where @var{name} is the name of the signal, such as @code{SIGILL} or
36666 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
36667 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
36668 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
36669 user's benefit and have no particular format.
36671 @findex signal annotation
36673 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
36674 just saying that the program received the signal, not that it was
36675 terminated with it.
36677 @findex breakpoint annotation
36678 @item ^Z^Zbreakpoint @var{number}
36679 The program hit breakpoint number @var{number}.
36681 @findex watchpoint annotation
36682 @item ^Z^Zwatchpoint @var{number}
36683 The program hit watchpoint number @var{number}.
36686 @node Source Annotations
36687 @section Displaying Source
36688 @cindex annotations for source display
36690 @findex source annotation
36691 The following annotation is used instead of displaying source code:
36694 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
36697 where @var{filename} is an absolute file name indicating which source
36698 file, @var{line} is the line number within that file (where 1 is the
36699 first line in the file), @var{character} is the character position
36700 within the file (where 0 is the first character in the file) (for most
36701 debug formats this will necessarily point to the beginning of a line),
36702 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
36703 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
36704 @var{addr} is the address in the target program associated with the
36705 source which is being displayed. The @var{addr} is in the form @samp{0x}
36706 followed by one or more lowercase hex digits (note that this does not
36707 depend on the language).
36709 @node JIT Interface
36710 @chapter JIT Compilation Interface
36711 @cindex just-in-time compilation
36712 @cindex JIT compilation interface
36714 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
36715 interface. A JIT compiler is a program or library that generates native
36716 executable code at runtime and executes it, usually in order to achieve good
36717 performance while maintaining platform independence.
36719 Programs that use JIT compilation are normally difficult to debug because
36720 portions of their code are generated at runtime, instead of being loaded from
36721 object files, which is where @value{GDBN} normally finds the program's symbols
36722 and debug information. In order to debug programs that use JIT compilation,
36723 @value{GDBN} has an interface that allows the program to register in-memory
36724 symbol files with @value{GDBN} at runtime.
36726 If you are using @value{GDBN} to debug a program that uses this interface, then
36727 it should work transparently so long as you have not stripped the binary. If
36728 you are developing a JIT compiler, then the interface is documented in the rest
36729 of this chapter. At this time, the only known client of this interface is the
36732 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
36733 JIT compiler communicates with @value{GDBN} by writing data into a global
36734 variable and calling a function at a well-known symbol. When @value{GDBN}
36735 attaches, it reads a linked list of symbol files from the global variable to
36736 find existing code, and puts a breakpoint in the function so that it can find
36737 out about additional code.
36740 * Declarations:: Relevant C struct declarations
36741 * Registering Code:: Steps to register code
36742 * Unregistering Code:: Steps to unregister code
36743 * Custom Debug Info:: Emit debug information in a custom format
36747 @section JIT Declarations
36749 These are the relevant struct declarations that a C program should include to
36750 implement the interface:
36760 struct jit_code_entry
36762 struct jit_code_entry *next_entry;
36763 struct jit_code_entry *prev_entry;
36764 const char *symfile_addr;
36765 uint64_t symfile_size;
36768 struct jit_descriptor
36771 /* This type should be jit_actions_t, but we use uint32_t
36772 to be explicit about the bitwidth. */
36773 uint32_t action_flag;
36774 struct jit_code_entry *relevant_entry;
36775 struct jit_code_entry *first_entry;
36778 /* GDB puts a breakpoint in this function. */
36779 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
36781 /* Make sure to specify the version statically, because the
36782 debugger may check the version before we can set it. */
36783 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
36786 If the JIT is multi-threaded, then it is important that the JIT synchronize any
36787 modifications to this global data properly, which can easily be done by putting
36788 a global mutex around modifications to these structures.
36790 @node Registering Code
36791 @section Registering Code
36793 To register code with @value{GDBN}, the JIT should follow this protocol:
36797 Generate an object file in memory with symbols and other desired debug
36798 information. The file must include the virtual addresses of the sections.
36801 Create a code entry for the file, which gives the start and size of the symbol
36805 Add it to the linked list in the JIT descriptor.
36808 Point the relevant_entry field of the descriptor at the entry.
36811 Set @code{action_flag} to @code{JIT_REGISTER} and call
36812 @code{__jit_debug_register_code}.
36815 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
36816 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
36817 new code. However, the linked list must still be maintained in order to allow
36818 @value{GDBN} to attach to a running process and still find the symbol files.
36820 @node Unregistering Code
36821 @section Unregistering Code
36823 If code is freed, then the JIT should use the following protocol:
36827 Remove the code entry corresponding to the code from the linked list.
36830 Point the @code{relevant_entry} field of the descriptor at the code entry.
36833 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
36834 @code{__jit_debug_register_code}.
36837 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
36838 and the JIT will leak the memory used for the associated symbol files.
36840 @node Custom Debug Info
36841 @section Custom Debug Info
36842 @cindex custom JIT debug info
36843 @cindex JIT debug info reader
36845 Generating debug information in platform-native file formats (like ELF
36846 or COFF) may be an overkill for JIT compilers; especially if all the
36847 debug info is used for is displaying a meaningful backtrace. The
36848 issue can be resolved by having the JIT writers decide on a debug info
36849 format and also provide a reader that parses the debug info generated
36850 by the JIT compiler. This section gives a brief overview on writing
36851 such a parser. More specific details can be found in the source file
36852 @file{gdb/jit-reader.in}, which is also installed as a header at
36853 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
36855 The reader is implemented as a shared object (so this functionality is
36856 not available on platforms which don't allow loading shared objects at
36857 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
36858 @code{jit-reader-unload} are provided, to be used to load and unload
36859 the readers from a preconfigured directory. Once loaded, the shared
36860 object is used the parse the debug information emitted by the JIT
36864 * Using JIT Debug Info Readers:: How to use supplied readers correctly
36865 * Writing JIT Debug Info Readers:: Creating a debug-info reader
36868 @node Using JIT Debug Info Readers
36869 @subsection Using JIT Debug Info Readers
36870 @kindex jit-reader-load
36871 @kindex jit-reader-unload
36873 Readers can be loaded and unloaded using the @code{jit-reader-load}
36874 and @code{jit-reader-unload} commands.
36877 @item jit-reader-load @var{reader}
36878 Load the JIT reader named @var{reader}, which is a shared
36879 object specified as either an absolute or a relative file name. In
36880 the latter case, @value{GDBN} will try to load the reader from a
36881 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
36882 system (here @var{libdir} is the system library directory, often
36883 @file{/usr/local/lib}).
36885 Only one reader can be active at a time; trying to load a second
36886 reader when one is already loaded will result in @value{GDBN}
36887 reporting an error. A new JIT reader can be loaded by first unloading
36888 the current one using @code{jit-reader-unload} and then invoking
36889 @code{jit-reader-load}.
36891 @item jit-reader-unload
36892 Unload the currently loaded JIT reader.
36896 @node Writing JIT Debug Info Readers
36897 @subsection Writing JIT Debug Info Readers
36898 @cindex writing JIT debug info readers
36900 As mentioned, a reader is essentially a shared object conforming to a
36901 certain ABI. This ABI is described in @file{jit-reader.h}.
36903 @file{jit-reader.h} defines the structures, macros and functions
36904 required to write a reader. It is installed (along with
36905 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
36906 the system include directory.
36908 Readers need to be released under a GPL compatible license. A reader
36909 can be declared as released under such a license by placing the macro
36910 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
36912 The entry point for readers is the symbol @code{gdb_init_reader},
36913 which is expected to be a function with the prototype
36915 @findex gdb_init_reader
36917 extern struct gdb_reader_funcs *gdb_init_reader (void);
36920 @cindex @code{struct gdb_reader_funcs}
36922 @code{struct gdb_reader_funcs} contains a set of pointers to callback
36923 functions. These functions are executed to read the debug info
36924 generated by the JIT compiler (@code{read}), to unwind stack frames
36925 (@code{unwind}) and to create canonical frame IDs
36926 (@code{get_frame_id}). It also has a callback that is called when the
36927 reader is being unloaded (@code{destroy}). The struct looks like this
36930 struct gdb_reader_funcs
36932 /* Must be set to GDB_READER_INTERFACE_VERSION. */
36933 int reader_version;
36935 /* For use by the reader. */
36938 gdb_read_debug_info *read;
36939 gdb_unwind_frame *unwind;
36940 gdb_get_frame_id *get_frame_id;
36941 gdb_destroy_reader *destroy;
36945 @cindex @code{struct gdb_symbol_callbacks}
36946 @cindex @code{struct gdb_unwind_callbacks}
36948 The callbacks are provided with another set of callbacks by
36949 @value{GDBN} to do their job. For @code{read}, these callbacks are
36950 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
36951 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
36952 @code{struct gdb_symbol_callbacks} has callbacks to create new object
36953 files and new symbol tables inside those object files. @code{struct
36954 gdb_unwind_callbacks} has callbacks to read registers off the current
36955 frame and to write out the values of the registers in the previous
36956 frame. Both have a callback (@code{target_read}) to read bytes off the
36957 target's address space.
36959 @node In-Process Agent
36960 @chapter In-Process Agent
36961 @cindex debugging agent
36962 The traditional debugging model is conceptually low-speed, but works fine,
36963 because most bugs can be reproduced in debugging-mode execution. However,
36964 as multi-core or many-core processors are becoming mainstream, and
36965 multi-threaded programs become more and more popular, there should be more
36966 and more bugs that only manifest themselves at normal-mode execution, for
36967 example, thread races, because debugger's interference with the program's
36968 timing may conceal the bugs. On the other hand, in some applications,
36969 it is not feasible for the debugger to interrupt the program's execution
36970 long enough for the developer to learn anything helpful about its behavior.
36971 If the program's correctness depends on its real-time behavior, delays
36972 introduced by a debugger might cause the program to fail, even when the
36973 code itself is correct. It is useful to be able to observe the program's
36974 behavior without interrupting it.
36976 Therefore, traditional debugging model is too intrusive to reproduce
36977 some bugs. In order to reduce the interference with the program, we can
36978 reduce the number of operations performed by debugger. The
36979 @dfn{In-Process Agent}, a shared library, is running within the same
36980 process with inferior, and is able to perform some debugging operations
36981 itself. As a result, debugger is only involved when necessary, and
36982 performance of debugging can be improved accordingly. Note that
36983 interference with program can be reduced but can't be removed completely,
36984 because the in-process agent will still stop or slow down the program.
36986 The in-process agent can interpret and execute Agent Expressions
36987 (@pxref{Agent Expressions}) during performing debugging operations. The
36988 agent expressions can be used for different purposes, such as collecting
36989 data in tracepoints, and condition evaluation in breakpoints.
36991 @anchor{Control Agent}
36992 You can control whether the in-process agent is used as an aid for
36993 debugging with the following commands:
36996 @kindex set agent on
36998 Causes the in-process agent to perform some operations on behalf of the
36999 debugger. Just which operations requested by the user will be done
37000 by the in-process agent depends on the its capabilities. For example,
37001 if you request to evaluate breakpoint conditions in the in-process agent,
37002 and the in-process agent has such capability as well, then breakpoint
37003 conditions will be evaluated in the in-process agent.
37005 @kindex set agent off
37006 @item set agent off
37007 Disables execution of debugging operations by the in-process agent. All
37008 of the operations will be performed by @value{GDBN}.
37012 Display the current setting of execution of debugging operations by
37013 the in-process agent.
37017 * In-Process Agent Protocol::
37020 @node In-Process Agent Protocol
37021 @section In-Process Agent Protocol
37022 @cindex in-process agent protocol
37024 The in-process agent is able to communicate with both @value{GDBN} and
37025 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
37026 used for communications between @value{GDBN} or GDBserver and the IPA.
37027 In general, @value{GDBN} or GDBserver sends commands
37028 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
37029 in-process agent replies back with the return result of the command, or
37030 some other information. The data sent to in-process agent is composed
37031 of primitive data types, such as 4-byte or 8-byte type, and composite
37032 types, which are called objects (@pxref{IPA Protocol Objects}).
37035 * IPA Protocol Objects::
37036 * IPA Protocol Commands::
37039 @node IPA Protocol Objects
37040 @subsection IPA Protocol Objects
37041 @cindex ipa protocol objects
37043 The commands sent to and results received from agent may contain some
37044 complex data types called @dfn{objects}.
37046 The in-process agent is running on the same machine with @value{GDBN}
37047 or GDBserver, so it doesn't have to handle as much differences between
37048 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
37049 However, there are still some differences of two ends in two processes:
37053 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
37054 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
37056 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
37057 GDBserver is compiled with one, and in-process agent is compiled with
37061 Here are the IPA Protocol Objects:
37065 agent expression object. It represents an agent expression
37066 (@pxref{Agent Expressions}).
37067 @anchor{agent expression object}
37069 tracepoint action object. It represents a tracepoint action
37070 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
37071 memory, static trace data and to evaluate expression.
37072 @anchor{tracepoint action object}
37074 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
37075 @anchor{tracepoint object}
37079 The following table describes important attributes of each IPA protocol
37082 @multitable @columnfractions .30 .20 .50
37083 @headitem Name @tab Size @tab Description
37084 @item @emph{agent expression object} @tab @tab
37085 @item length @tab 4 @tab length of bytes code
37086 @item byte code @tab @var{length} @tab contents of byte code
37087 @item @emph{tracepoint action for collecting memory} @tab @tab
37088 @item 'M' @tab 1 @tab type of tracepoint action
37089 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
37090 address of the lowest byte to collect, otherwise @var{addr} is the offset
37091 of @var{basereg} for memory collecting.
37092 @item len @tab 8 @tab length of memory for collecting
37093 @item basereg @tab 4 @tab the register number containing the starting
37094 memory address for collecting.
37095 @item @emph{tracepoint action for collecting registers} @tab @tab
37096 @item 'R' @tab 1 @tab type of tracepoint action
37097 @item @emph{tracepoint action for collecting static trace data} @tab @tab
37098 @item 'L' @tab 1 @tab type of tracepoint action
37099 @item @emph{tracepoint action for expression evaluation} @tab @tab
37100 @item 'X' @tab 1 @tab type of tracepoint action
37101 @item agent expression @tab length of @tab @ref{agent expression object}
37102 @item @emph{tracepoint object} @tab @tab
37103 @item number @tab 4 @tab number of tracepoint
37104 @item address @tab 8 @tab address of tracepoint inserted on
37105 @item type @tab 4 @tab type of tracepoint
37106 @item enabled @tab 1 @tab enable or disable of tracepoint
37107 @item step_count @tab 8 @tab step
37108 @item pass_count @tab 8 @tab pass
37109 @item numactions @tab 4 @tab number of tracepoint actions
37110 @item hit count @tab 8 @tab hit count
37111 @item trace frame usage @tab 8 @tab trace frame usage
37112 @item compiled_cond @tab 8 @tab compiled condition
37113 @item orig_size @tab 8 @tab orig size
37114 @item condition @tab 4 if condition is NULL otherwise length of
37115 @ref{agent expression object}
37116 @tab zero if condition is NULL, otherwise is
37117 @ref{agent expression object}
37118 @item actions @tab variable
37119 @tab numactions number of @ref{tracepoint action object}
37122 @node IPA Protocol Commands
37123 @subsection IPA Protocol Commands
37124 @cindex ipa protocol commands
37126 The spaces in each command are delimiters to ease reading this commands
37127 specification. They don't exist in real commands.
37131 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
37132 Installs a new fast tracepoint described by @var{tracepoint_object}
37133 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
37134 head of @dfn{jumppad}, which is used to jump to data collection routine
37139 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
37140 @var{target_address} is address of tracepoint in the inferior.
37141 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
37142 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
37143 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
37144 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
37151 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
37152 is about to kill inferiors.
37160 @item probe_marker_at:@var{address}
37161 Asks in-process agent to probe the marker at @var{address}.
37168 @item unprobe_marker_at:@var{address}
37169 Asks in-process agent to unprobe the marker at @var{address}.
37173 @chapter Reporting Bugs in @value{GDBN}
37174 @cindex bugs in @value{GDBN}
37175 @cindex reporting bugs in @value{GDBN}
37177 Your bug reports play an essential role in making @value{GDBN} reliable.
37179 Reporting a bug may help you by bringing a solution to your problem, or it
37180 may not. But in any case the principal function of a bug report is to help
37181 the entire community by making the next version of @value{GDBN} work better. Bug
37182 reports are your contribution to the maintenance of @value{GDBN}.
37184 In order for a bug report to serve its purpose, you must include the
37185 information that enables us to fix the bug.
37188 * Bug Criteria:: Have you found a bug?
37189 * Bug Reporting:: How to report bugs
37193 @section Have You Found a Bug?
37194 @cindex bug criteria
37196 If you are not sure whether you have found a bug, here are some guidelines:
37199 @cindex fatal signal
37200 @cindex debugger crash
37201 @cindex crash of debugger
37203 If the debugger gets a fatal signal, for any input whatever, that is a
37204 @value{GDBN} bug. Reliable debuggers never crash.
37206 @cindex error on valid input
37208 If @value{GDBN} produces an error message for valid input, that is a
37209 bug. (Note that if you're cross debugging, the problem may also be
37210 somewhere in the connection to the target.)
37212 @cindex invalid input
37214 If @value{GDBN} does not produce an error message for invalid input,
37215 that is a bug. However, you should note that your idea of
37216 ``invalid input'' might be our idea of ``an extension'' or ``support
37217 for traditional practice''.
37220 If you are an experienced user of debugging tools, your suggestions
37221 for improvement of @value{GDBN} are welcome in any case.
37224 @node Bug Reporting
37225 @section How to Report Bugs
37226 @cindex bug reports
37227 @cindex @value{GDBN} bugs, reporting
37229 A number of companies and individuals offer support for @sc{gnu} products.
37230 If you obtained @value{GDBN} from a support organization, we recommend you
37231 contact that organization first.
37233 You can find contact information for many support companies and
37234 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
37236 @c should add a web page ref...
37239 @ifset BUGURL_DEFAULT
37240 In any event, we also recommend that you submit bug reports for
37241 @value{GDBN}. The preferred method is to submit them directly using
37242 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
37243 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
37246 @strong{Do not send bug reports to @samp{info-gdb}, or to
37247 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
37248 not want to receive bug reports. Those that do have arranged to receive
37251 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
37252 serves as a repeater. The mailing list and the newsgroup carry exactly
37253 the same messages. Often people think of posting bug reports to the
37254 newsgroup instead of mailing them. This appears to work, but it has one
37255 problem which can be crucial: a newsgroup posting often lacks a mail
37256 path back to the sender. Thus, if we need to ask for more information,
37257 we may be unable to reach you. For this reason, it is better to send
37258 bug reports to the mailing list.
37260 @ifclear BUGURL_DEFAULT
37261 In any event, we also recommend that you submit bug reports for
37262 @value{GDBN} to @value{BUGURL}.
37266 The fundamental principle of reporting bugs usefully is this:
37267 @strong{report all the facts}. If you are not sure whether to state a
37268 fact or leave it out, state it!
37270 Often people omit facts because they think they know what causes the
37271 problem and assume that some details do not matter. Thus, you might
37272 assume that the name of the variable you use in an example does not matter.
37273 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
37274 stray memory reference which happens to fetch from the location where that
37275 name is stored in memory; perhaps, if the name were different, the contents
37276 of that location would fool the debugger into doing the right thing despite
37277 the bug. Play it safe and give a specific, complete example. That is the
37278 easiest thing for you to do, and the most helpful.
37280 Keep in mind that the purpose of a bug report is to enable us to fix the
37281 bug. It may be that the bug has been reported previously, but neither
37282 you nor we can know that unless your bug report is complete and
37285 Sometimes people give a few sketchy facts and ask, ``Does this ring a
37286 bell?'' Those bug reports are useless, and we urge everyone to
37287 @emph{refuse to respond to them} except to chide the sender to report
37290 To enable us to fix the bug, you should include all these things:
37294 The version of @value{GDBN}. @value{GDBN} announces it if you start
37295 with no arguments; you can also print it at any time using @code{show
37298 Without this, we will not know whether there is any point in looking for
37299 the bug in the current version of @value{GDBN}.
37302 The type of machine you are using, and the operating system name and
37306 The details of the @value{GDBN} build-time configuration.
37307 @value{GDBN} shows these details if you invoke it with the
37308 @option{--configuration} command-line option, or if you type
37309 @code{show configuration} at @value{GDBN}'s prompt.
37312 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
37313 ``@value{GCC}--2.8.1''.
37316 What compiler (and its version) was used to compile the program you are
37317 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
37318 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
37319 to get this information; for other compilers, see the documentation for
37323 The command arguments you gave the compiler to compile your example and
37324 observe the bug. For example, did you use @samp{-O}? To guarantee
37325 you will not omit something important, list them all. A copy of the
37326 Makefile (or the output from make) is sufficient.
37328 If we were to try to guess the arguments, we would probably guess wrong
37329 and then we might not encounter the bug.
37332 A complete input script, and all necessary source files, that will
37336 A description of what behavior you observe that you believe is
37337 incorrect. For example, ``It gets a fatal signal.''
37339 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
37340 will certainly notice it. But if the bug is incorrect output, we might
37341 not notice unless it is glaringly wrong. You might as well not give us
37342 a chance to make a mistake.
37344 Even if the problem you experience is a fatal signal, you should still
37345 say so explicitly. Suppose something strange is going on, such as, your
37346 copy of @value{GDBN} is out of synch, or you have encountered a bug in
37347 the C library on your system. (This has happened!) Your copy might
37348 crash and ours would not. If you told us to expect a crash, then when
37349 ours fails to crash, we would know that the bug was not happening for
37350 us. If you had not told us to expect a crash, then we would not be able
37351 to draw any conclusion from our observations.
37354 @cindex recording a session script
37355 To collect all this information, you can use a session recording program
37356 such as @command{script}, which is available on many Unix systems.
37357 Just run your @value{GDBN} session inside @command{script} and then
37358 include the @file{typescript} file with your bug report.
37360 Another way to record a @value{GDBN} session is to run @value{GDBN}
37361 inside Emacs and then save the entire buffer to a file.
37364 If you wish to suggest changes to the @value{GDBN} source, send us context
37365 diffs. If you even discuss something in the @value{GDBN} source, refer to
37366 it by context, not by line number.
37368 The line numbers in our development sources will not match those in your
37369 sources. Your line numbers would convey no useful information to us.
37373 Here are some things that are not necessary:
37377 A description of the envelope of the bug.
37379 Often people who encounter a bug spend a lot of time investigating
37380 which changes to the input file will make the bug go away and which
37381 changes will not affect it.
37383 This is often time consuming and not very useful, because the way we
37384 will find the bug is by running a single example under the debugger
37385 with breakpoints, not by pure deduction from a series of examples.
37386 We recommend that you save your time for something else.
37388 Of course, if you can find a simpler example to report @emph{instead}
37389 of the original one, that is a convenience for us. Errors in the
37390 output will be easier to spot, running under the debugger will take
37391 less time, and so on.
37393 However, simplification is not vital; if you do not want to do this,
37394 report the bug anyway and send us the entire test case you used.
37397 A patch for the bug.
37399 A patch for the bug does help us if it is a good one. But do not omit
37400 the necessary information, such as the test case, on the assumption that
37401 a patch is all we need. We might see problems with your patch and decide
37402 to fix the problem another way, or we might not understand it at all.
37404 Sometimes with a program as complicated as @value{GDBN} it is very hard to
37405 construct an example that will make the program follow a certain path
37406 through the code. If you do not send us the example, we will not be able
37407 to construct one, so we will not be able to verify that the bug is fixed.
37409 And if we cannot understand what bug you are trying to fix, or why your
37410 patch should be an improvement, we will not install it. A test case will
37411 help us to understand.
37414 A guess about what the bug is or what it depends on.
37416 Such guesses are usually wrong. Even we cannot guess right about such
37417 things without first using the debugger to find the facts.
37420 @c The readline documentation is distributed with the readline code
37421 @c and consists of the two following files:
37424 @c Use -I with makeinfo to point to the appropriate directory,
37425 @c environment var TEXINPUTS with TeX.
37426 @ifclear SYSTEM_READLINE
37427 @include rluser.texi
37428 @include hsuser.texi
37432 @appendix In Memoriam
37434 The @value{GDBN} project mourns the loss of the following long-time
37439 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
37440 to Free Software in general. Outside of @value{GDBN}, he was known in
37441 the Amiga world for his series of Fish Disks, and the GeekGadget project.
37443 @item Michael Snyder
37444 Michael was one of the Global Maintainers of the @value{GDBN} project,
37445 with contributions recorded as early as 1996, until 2011. In addition
37446 to his day to day participation, he was a large driving force behind
37447 adding Reverse Debugging to @value{GDBN}.
37450 Beyond their technical contributions to the project, they were also
37451 enjoyable members of the Free Software Community. We will miss them.
37453 @node Formatting Documentation
37454 @appendix Formatting Documentation
37456 @cindex @value{GDBN} reference card
37457 @cindex reference card
37458 The @value{GDBN} 4 release includes an already-formatted reference card, ready
37459 for printing with PostScript or Ghostscript, in the @file{gdb}
37460 subdirectory of the main source directory@footnote{In
37461 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
37462 release.}. If you can use PostScript or Ghostscript with your printer,
37463 you can print the reference card immediately with @file{refcard.ps}.
37465 The release also includes the source for the reference card. You
37466 can format it, using @TeX{}, by typing:
37472 The @value{GDBN} reference card is designed to print in @dfn{landscape}
37473 mode on US ``letter'' size paper;
37474 that is, on a sheet 11 inches wide by 8.5 inches
37475 high. You will need to specify this form of printing as an option to
37476 your @sc{dvi} output program.
37478 @cindex documentation
37480 All the documentation for @value{GDBN} comes as part of the machine-readable
37481 distribution. The documentation is written in Texinfo format, which is
37482 a documentation system that uses a single source file to produce both
37483 on-line information and a printed manual. You can use one of the Info
37484 formatting commands to create the on-line version of the documentation
37485 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
37487 @value{GDBN} includes an already formatted copy of the on-line Info
37488 version of this manual in the @file{gdb} subdirectory. The main Info
37489 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
37490 subordinate files matching @samp{gdb.info*} in the same directory. If
37491 necessary, you can print out these files, or read them with any editor;
37492 but they are easier to read using the @code{info} subsystem in @sc{gnu}
37493 Emacs or the standalone @code{info} program, available as part of the
37494 @sc{gnu} Texinfo distribution.
37496 If you want to format these Info files yourself, you need one of the
37497 Info formatting programs, such as @code{texinfo-format-buffer} or
37500 If you have @code{makeinfo} installed, and are in the top level
37501 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
37502 version @value{GDBVN}), you can make the Info file by typing:
37509 If you want to typeset and print copies of this manual, you need @TeX{},
37510 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
37511 Texinfo definitions file.
37513 @TeX{} is a typesetting program; it does not print files directly, but
37514 produces output files called @sc{dvi} files. To print a typeset
37515 document, you need a program to print @sc{dvi} files. If your system
37516 has @TeX{} installed, chances are it has such a program. The precise
37517 command to use depends on your system; @kbd{lpr -d} is common; another
37518 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
37519 require a file name without any extension or a @samp{.dvi} extension.
37521 @TeX{} also requires a macro definitions file called
37522 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
37523 written in Texinfo format. On its own, @TeX{} cannot either read or
37524 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
37525 and is located in the @file{gdb-@var{version-number}/texinfo}
37528 If you have @TeX{} and a @sc{dvi} printer program installed, you can
37529 typeset and print this manual. First switch to the @file{gdb}
37530 subdirectory of the main source directory (for example, to
37531 @file{gdb-@value{GDBVN}/gdb}) and type:
37537 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
37539 @node Installing GDB
37540 @appendix Installing @value{GDBN}
37541 @cindex installation
37544 * Requirements:: Requirements for building @value{GDBN}
37545 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
37546 * Separate Objdir:: Compiling @value{GDBN} in another directory
37547 * Config Names:: Specifying names for hosts and targets
37548 * Configure Options:: Summary of options for configure
37549 * System-wide configuration:: Having a system-wide init file
37553 @section Requirements for Building @value{GDBN}
37554 @cindex building @value{GDBN}, requirements for
37556 Building @value{GDBN} requires various tools and packages to be available.
37557 Other packages will be used only if they are found.
37559 @heading Tools/Packages Necessary for Building @value{GDBN}
37561 @item C@t{++}11 compiler
37562 @value{GDBN} is written in C@t{++}11. It should be buildable with any
37563 recent C@t{++}11 compiler, e.g.@: GCC.
37566 @value{GDBN}'s build system relies on features only found in the GNU
37567 make program. Other variants of @code{make} will not work.
37570 @heading Tools/Packages Optional for Building @value{GDBN}
37574 @value{GDBN} can use the Expat XML parsing library. This library may be
37575 included with your operating system distribution; if it is not, you
37576 can get the latest version from @url{http://expat.sourceforge.net}.
37577 The @file{configure} script will search for this library in several
37578 standard locations; if it is installed in an unusual path, you can
37579 use the @option{--with-libexpat-prefix} option to specify its location.
37585 Remote protocol memory maps (@pxref{Memory Map Format})
37587 Target descriptions (@pxref{Target Descriptions})
37589 Remote shared library lists (@xref{Library List Format},
37590 or alternatively @pxref{Library List Format for SVR4 Targets})
37592 MS-Windows shared libraries (@pxref{Shared Libraries})
37594 Traceframe info (@pxref{Traceframe Info Format})
37596 Branch trace (@pxref{Branch Trace Format},
37597 @pxref{Branch Trace Configuration Format})
37601 @value{GDBN} can be scripted using GNU Guile. @xref{Guile}. By
37602 default, @value{GDBN} will be compiled if the Guile libraries are
37603 installed and are found by @file{configure}. You can use the
37604 @code{--with-guile} option to request Guile, and pass either the Guile
37605 version number or the file name of the relevant @code{pkg-config}
37606 program to choose a particular version of Guile.
37609 @value{GDBN}'s features related to character sets (@pxref{Character
37610 Sets}) require a functioning @code{iconv} implementation. If you are
37611 on a GNU system, then this is provided by the GNU C Library. Some
37612 other systems also provide a working @code{iconv}.
37614 If @value{GDBN} is using the @code{iconv} program which is installed
37615 in a non-standard place, you will need to tell @value{GDBN} where to
37616 find it. This is done with @option{--with-iconv-bin} which specifies
37617 the directory that contains the @code{iconv} program. This program is
37618 run in order to make a list of the available character sets.
37620 On systems without @code{iconv}, you can install GNU Libiconv. If
37621 Libiconv is installed in a standard place, @value{GDBN} will
37622 automatically use it if it is needed. If you have previously
37623 installed Libiconv in a non-standard place, you can use the
37624 @option{--with-libiconv-prefix} option to @file{configure}.
37626 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
37627 arrange to build Libiconv if a directory named @file{libiconv} appears
37628 in the top-most source directory. If Libiconv is built this way, and
37629 if the operating system does not provide a suitable @code{iconv}
37630 implementation, then the just-built library will automatically be used
37631 by @value{GDBN}. One easy way to set this up is to download GNU
37632 Libiconv, unpack it inside the top-level directory of the @value{GDBN}
37633 source tree, and then rename the directory holding the Libiconv source
37634 code to @samp{libiconv}.
37637 @value{GDBN} can support debugging sections that are compressed with
37638 the LZMA library. @xref{MiniDebugInfo}. If this library is not
37639 included with your operating system, you can find it in the xz package
37640 at @url{http://tukaani.org/xz/}. If the LZMA library is available in
37641 the usual place, then the @file{configure} script will use it
37642 automatically. If it is installed in an unusual path, you can use the
37643 @option{--with-lzma-prefix} option to specify its location.
37647 @value{GDBN} can use the GNU MPFR multiple-precision floating-point
37648 library. This library may be included with your operating system
37649 distribution; if it is not, you can get the latest version from
37650 @url{http://www.mpfr.org}. The @file{configure} script will search
37651 for this library in several standard locations; if it is installed
37652 in an unusual path, you can use the @option{--with-libmpfr-prefix}
37653 option to specify its location.
37655 GNU MPFR is used to emulate target floating-point arithmetic during
37656 expression evaluation when the target uses different floating-point
37657 formats than the host. If GNU MPFR it is not available, @value{GDBN}
37658 will fall back to using host floating-point arithmetic.
37661 @value{GDBN} can be scripted using Python language. @xref{Python}.
37662 By default, @value{GDBN} will be compiled if the Python libraries are
37663 installed and are found by @file{configure}. You can use the
37664 @code{--with-python} option to request Python, and pass either the
37665 file name of the relevant @code{python} executable, or the name of the
37666 directory in which Python is installed, to choose a particular
37667 installation of Python.
37670 @cindex compressed debug sections
37671 @value{GDBN} will use the @samp{zlib} library, if available, to read
37672 compressed debug sections. Some linkers, such as GNU gold, are capable
37673 of producing binaries with compressed debug sections. If @value{GDBN}
37674 is compiled with @samp{zlib}, it will be able to read the debug
37675 information in such binaries.
37677 The @samp{zlib} library is likely included with your operating system
37678 distribution; if it is not, you can get the latest version from
37679 @url{http://zlib.net}.
37682 @node Running Configure
37683 @section Invoking the @value{GDBN} @file{configure} Script
37684 @cindex configuring @value{GDBN}
37685 @value{GDBN} comes with a @file{configure} script that automates the process
37686 of preparing @value{GDBN} for installation; you can then use @code{make} to
37687 build the @code{gdb} program.
37689 @c irrelevant in info file; it's as current as the code it lives with.
37690 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
37691 look at the @file{README} file in the sources; we may have improved the
37692 installation procedures since publishing this manual.}
37695 The @value{GDBN} distribution includes all the source code you need for
37696 @value{GDBN} in a single directory, whose name is usually composed by
37697 appending the version number to @samp{gdb}.
37699 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
37700 @file{gdb-@value{GDBVN}} directory. That directory contains:
37703 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
37704 script for configuring @value{GDBN} and all its supporting libraries
37706 @item gdb-@value{GDBVN}/gdb
37707 the source specific to @value{GDBN} itself
37709 @item gdb-@value{GDBVN}/bfd
37710 source for the Binary File Descriptor library
37712 @item gdb-@value{GDBVN}/include
37713 @sc{gnu} include files
37715 @item gdb-@value{GDBVN}/libiberty
37716 source for the @samp{-liberty} free software library
37718 @item gdb-@value{GDBVN}/opcodes
37719 source for the library of opcode tables and disassemblers
37721 @item gdb-@value{GDBVN}/readline
37722 source for the @sc{gnu} command-line interface
37725 There may be other subdirectories as well.
37727 The simplest way to configure and build @value{GDBN} is to run @file{configure}
37728 from the @file{gdb-@var{version-number}} source directory, which in
37729 this example is the @file{gdb-@value{GDBVN}} directory.
37731 First switch to the @file{gdb-@var{version-number}} source directory
37732 if you are not already in it; then run @file{configure}. Pass the
37733 identifier for the platform on which @value{GDBN} will run as an
37739 cd gdb-@value{GDBVN}
37744 Running @samp{configure} and then running @code{make} builds the
37745 included supporting libraries, then @code{gdb} itself. The configured
37746 source files, and the binaries, are left in the corresponding source
37750 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
37751 system does not recognize this automatically when you run a different
37752 shell, you may need to run @code{sh} on it explicitly:
37758 You should run the @file{configure} script from the top directory in the
37759 source tree, the @file{gdb-@var{version-number}} directory. If you run
37760 @file{configure} from one of the subdirectories, you will configure only
37761 that subdirectory. That is usually not what you want. In particular,
37762 if you run the first @file{configure} from the @file{gdb} subdirectory
37763 of the @file{gdb-@var{version-number}} directory, you will omit the
37764 configuration of @file{bfd}, @file{readline}, and other sibling
37765 directories of the @file{gdb} subdirectory. This leads to build errors
37766 about missing include files such as @file{bfd/bfd.h}.
37768 You can install @code{@value{GDBN}} anywhere. The best way to do this
37769 is to pass the @code{--prefix} option to @code{configure}, and then
37770 install it with @code{make install}.
37772 @node Separate Objdir
37773 @section Compiling @value{GDBN} in Another Directory
37775 If you want to run @value{GDBN} versions for several host or target machines,
37776 you need a different @code{gdb} compiled for each combination of
37777 host and target. @file{configure} is designed to make this easy by
37778 allowing you to generate each configuration in a separate subdirectory,
37779 rather than in the source directory. If your @code{make} program
37780 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
37781 @code{make} in each of these directories builds the @code{gdb}
37782 program specified there.
37784 To build @code{gdb} in a separate directory, run @file{configure}
37785 with the @samp{--srcdir} option to specify where to find the source.
37786 (You also need to specify a path to find @file{configure}
37787 itself from your working directory. If the path to @file{configure}
37788 would be the same as the argument to @samp{--srcdir}, you can leave out
37789 the @samp{--srcdir} option; it is assumed.)
37791 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
37792 separate directory for a Sun 4 like this:
37796 cd gdb-@value{GDBVN}
37799 ../gdb-@value{GDBVN}/configure
37804 When @file{configure} builds a configuration using a remote source
37805 directory, it creates a tree for the binaries with the same structure
37806 (and using the same names) as the tree under the source directory. In
37807 the example, you'd find the Sun 4 library @file{libiberty.a} in the
37808 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
37809 @file{gdb-sun4/gdb}.
37811 Make sure that your path to the @file{configure} script has just one
37812 instance of @file{gdb} in it. If your path to @file{configure} looks
37813 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
37814 one subdirectory of @value{GDBN}, not the whole package. This leads to
37815 build errors about missing include files such as @file{bfd/bfd.h}.
37817 One popular reason to build several @value{GDBN} configurations in separate
37818 directories is to configure @value{GDBN} for cross-compiling (where
37819 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
37820 programs that run on another machine---the @dfn{target}).
37821 You specify a cross-debugging target by
37822 giving the @samp{--target=@var{target}} option to @file{configure}.
37824 When you run @code{make} to build a program or library, you must run
37825 it in a configured directory---whatever directory you were in when you
37826 called @file{configure} (or one of its subdirectories).
37828 The @code{Makefile} that @file{configure} generates in each source
37829 directory also runs recursively. If you type @code{make} in a source
37830 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
37831 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
37832 will build all the required libraries, and then build GDB.
37834 When you have multiple hosts or targets configured in separate
37835 directories, you can run @code{make} on them in parallel (for example,
37836 if they are NFS-mounted on each of the hosts); they will not interfere
37840 @section Specifying Names for Hosts and Targets
37842 The specifications used for hosts and targets in the @file{configure}
37843 script are based on a three-part naming scheme, but some short predefined
37844 aliases are also supported. The full naming scheme encodes three pieces
37845 of information in the following pattern:
37848 @var{architecture}-@var{vendor}-@var{os}
37851 For example, you can use the alias @code{sun4} as a @var{host} argument,
37852 or as the value for @var{target} in a @code{--target=@var{target}}
37853 option. The equivalent full name is @samp{sparc-sun-sunos4}.
37855 The @file{configure} script accompanying @value{GDBN} does not provide
37856 any query facility to list all supported host and target names or
37857 aliases. @file{configure} calls the Bourne shell script
37858 @code{config.sub} to map abbreviations to full names; you can read the
37859 script, if you wish, or you can use it to test your guesses on
37860 abbreviations---for example:
37863 % sh config.sub i386-linux
37865 % sh config.sub alpha-linux
37866 alpha-unknown-linux-gnu
37867 % sh config.sub hp9k700
37869 % sh config.sub sun4
37870 sparc-sun-sunos4.1.1
37871 % sh config.sub sun3
37872 m68k-sun-sunos4.1.1
37873 % sh config.sub i986v
37874 Invalid configuration `i986v': machine `i986v' not recognized
37878 @code{config.sub} is also distributed in the @value{GDBN} source
37879 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
37881 @node Configure Options
37882 @section @file{configure} Options
37884 Here is a summary of the @file{configure} options and arguments that
37885 are most often useful for building @value{GDBN}. @file{configure}
37886 also has several other options not listed here. @inforef{Running
37887 configure scripts,,autoconf.info}, for a full
37888 explanation of @file{configure}.
37891 configure @r{[}--help@r{]}
37892 @r{[}--prefix=@var{dir}@r{]}
37893 @r{[}--exec-prefix=@var{dir}@r{]}
37894 @r{[}--srcdir=@var{dirname}@r{]}
37895 @r{[}--target=@var{target}@r{]}
37899 You may introduce options with a single @samp{-} rather than
37900 @samp{--} if you prefer; but you may abbreviate option names if you use
37905 Display a quick summary of how to invoke @file{configure}.
37907 @item --prefix=@var{dir}
37908 Configure the source to install programs and files under directory
37911 @item --exec-prefix=@var{dir}
37912 Configure the source to install programs under directory
37915 @c avoid splitting the warning from the explanation:
37917 @item --srcdir=@var{dirname}
37918 Use this option to make configurations in directories separate from the
37919 @value{GDBN} source directories. Among other things, you can use this to
37920 build (or maintain) several configurations simultaneously, in separate
37921 directories. @file{configure} writes configuration-specific files in
37922 the current directory, but arranges for them to use the source in the
37923 directory @var{dirname}. @file{configure} creates directories under
37924 the working directory in parallel to the source directories below
37927 @item --target=@var{target}
37928 Configure @value{GDBN} for cross-debugging programs running on the specified
37929 @var{target}. Without this option, @value{GDBN} is configured to debug
37930 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
37932 There is no convenient way to generate a list of all available
37933 targets. Also see the @code{--enable-targets} option, below.
37936 There are many other options that are specific to @value{GDBN}. This
37937 lists just the most common ones; there are some very specialized
37938 options not described here.
37941 @item --enable-targets=@r{[}@var{target}@r{]}@dots{}
37942 @itemx --enable-targets=all
37943 Configure @value{GDBN} for cross-debugging programs running on the
37944 specified list of targets. The special value @samp{all} configures
37945 @value{GDBN} for debugging programs running on any target it supports.
37947 @item --with-gdb-datadir=@var{path}
37948 Set the @value{GDBN}-specific data directory. @value{GDBN} will look
37949 here for certain supporting files or scripts. This defaults to the
37950 @file{gdb} subdirectory of @samp{datadir} (which can be set using
37953 @item --with-relocated-sources=@var{dir}
37954 Sets up the default source path substitution rule so that directory
37955 names recorded in debug information will be automatically adjusted for
37956 any directory under @var{dir}. @var{dir} should be a subdirectory of
37957 @value{GDBN}'s configured prefix, the one mentioned in the
37958 @code{--prefix} or @code{--exec-prefix} options to configure. This
37959 option is useful if GDB is supposed to be moved to a different place
37962 @item --enable-64-bit-bfd
37963 Enable 64-bit support in BFD on 32-bit hosts.
37965 @item --disable-gdbmi
37966 Build @value{GDBN} without the GDB/MI machine interface
37970 Build @value{GDBN} with the text-mode full-screen user interface
37971 (TUI). Requires a curses library (ncurses and cursesX are also
37974 @item --with-curses
37975 Use the curses library instead of the termcap library, for text-mode
37976 terminal operations.
37978 @item --with-debuginfod
37979 Build @value{GDBN} with libdebuginfod, the debuginfod client library.
37980 Used to automatically fetch source files and separate debug files from
37981 debuginfod servers using the associated executable's build ID. Enabled
37982 by default if libdebuginfod is installed and found at configure time.
37983 debuginfod is packaged with elfutils, starting with version 0.178. You
37984 can get the latest version from `https://sourceware.org/elfutils/'.
37986 @item --with-libunwind-ia64
37987 Use the libunwind library for unwinding function call stack on ia64
37988 target platforms. See http://www.nongnu.org/libunwind/index.html for
37991 @item --with-system-readline
37992 Use the readline library installed on the host, rather than the
37993 library supplied as part of @value{GDBN}. Readline 7 or newer is
37994 required; this is enforced by the build system.
37996 @item --with-system-zlib
37997 Use the zlib library installed on the host, rather than the library
37998 supplied as part of @value{GDBN}.
38001 Build @value{GDBN} with Expat, a library for XML parsing. (Done by
38002 default if libexpat is installed and found at configure time.) This
38003 library is used to read XML files supplied with @value{GDBN}. If it
38004 is unavailable, some features, such as remote protocol memory maps,
38005 target descriptions, and shared library lists, that are based on XML
38006 files, will not be available in @value{GDBN}. If your host does not
38007 have libexpat installed, you can get the latest version from
38008 `http://expat.sourceforge.net'.
38010 @item --with-libiconv-prefix@r{[}=@var{dir}@r{]}
38012 Build @value{GDBN} with GNU libiconv, a character set encoding
38013 conversion library. This is not done by default, as on GNU systems
38014 the @code{iconv} that is built in to the C library is sufficient. If
38015 your host does not have a working @code{iconv}, you can get the latest
38016 version of GNU iconv from `https://www.gnu.org/software/libiconv/'.
38018 @value{GDBN}'s build system also supports building GNU libiconv as
38019 part of the overall build. @xref{Requirements}.
38022 Build @value{GDBN} with LZMA, a compression library. (Done by default
38023 if liblzma is installed and found at configure time.) LZMA is used by
38024 @value{GDBN}'s "mini debuginfo" feature, which is only useful on
38025 platforms using the ELF object file format. If your host does not
38026 have liblzma installed, you can get the latest version from
38027 `https://tukaani.org/xz/'.
38030 Build @value{GDBN} with GNU MPFR, a library for multiple-precision
38031 floating-point computation with correct rounding. (Done by default if
38032 GNU MPFR is installed and found at configure time.) This library is
38033 used to emulate target floating-point arithmetic during expression
38034 evaluation when the target uses different floating-point formats than
38035 the host. If GNU MPFR is not available, @value{GDBN} will fall back
38036 to using host floating-point arithmetic. If your host does not have
38037 GNU MPFR installed, you can get the latest version from
38038 `http://www.mpfr.org'.
38040 @item --with-python@r{[}=@var{python}@r{]}
38041 Build @value{GDBN} with Python scripting support. (Done by default if
38042 libpython is present and found at configure time.) Python makes
38043 @value{GDBN} scripting much more powerful than the restricted CLI
38044 scripting language. If your host does not have Python installed, you
38045 can find it on `http://www.python.org/download/'. The oldest version
38046 of Python supported by GDB is 2.6. The optional argument @var{python}
38047 is used to find the Python headers and libraries. It can be either
38048 the name of a Python executable, or the name of the directory in which
38049 Python is installed.
38051 @item --with-guile[=GUILE]'
38052 Build @value{GDBN} with GNU Guile scripting support. (Done by default
38053 if libguile is present and found at configure time.) If your host
38054 does not have Guile installed, you can find it at
38055 `https://www.gnu.org/software/guile/'. The optional argument GUILE
38056 can be a version number, which will cause @code{configure} to try to
38057 use that version of Guile; or the file name of a @code{pkg-config}
38058 executable, which will be queried to find the information needed to
38059 compile and link against Guile.
38061 @item --without-included-regex
38062 Don't use the regex library included with @value{GDBN} (as part of the
38063 libiberty library). This is the default on hosts with version 2 of
38066 @item --with-sysroot=@var{dir}
38067 Use @var{dir} as the default system root directory for libraries whose
38068 file names begin with @file{/lib}' or @file{/usr/lib'}. (The value of
38069 @var{dir} can be modified at run time by using the @command{set
38070 sysroot} command.) If @var{dir} is under the @value{GDBN} configured
38071 prefix (set with @code{--prefix} or @code{--exec-prefix options}, the
38072 default system root will be automatically adjusted if and when
38073 @value{GDBN} is moved to a different location.
38075 @item --with-system-gdbinit=@var{file}
38076 Configure @value{GDBN} to automatically load a system-wide init file.
38077 @var{file} should be an absolute file name. If @var{file} is in a
38078 directory under the configured prefix, and @value{GDBN} is moved to
38079 another location after being built, the location of the system-wide
38080 init file will be adjusted accordingly.
38082 @item --with-system-gdbinit-dir=@var{directory}
38083 Configure @value{GDBN} to automatically load init files from a
38084 system-wide directory. @var{directory} should be an absolute directory
38085 name. If @var{directory} is in a directory under the configured
38086 prefix, and @value{GDBN} is moved to another location after being
38087 built, the location of the system-wide init directory will be
38088 adjusted accordingly.
38090 @item --enable-build-warnings
38091 When building the @value{GDBN} sources, ask the compiler to warn about
38092 any code which looks even vaguely suspicious. It passes many
38093 different warning flags, depending on the exact version of the
38094 compiler you are using.
38096 @item --enable-werror
38097 Treat compiler warnings as werrors. It adds the @code{-Werror} flag
38098 to the compiler, which will fail the compilation if the compiler
38099 outputs any warning messages.
38101 @item --enable-ubsan
38102 Enable the GCC undefined behavior sanitizer. This is disabled by
38103 default, but passing @code{--enable-ubsan=yes} or
38104 @code{--enable-ubsan=auto} to @code{configure} will enable it. The
38105 undefined behavior sanitizer checks for C@t{++} undefined behavior.
38106 It has a performance cost, so if you are looking at @value{GDBN}'s
38107 performance, you should disable it. The undefined behavior sanitizer
38108 was first introduced in GCC 4.9.
38111 @node System-wide configuration
38112 @section System-wide configuration and settings
38113 @cindex system-wide init file
38115 @value{GDBN} can be configured to have a system-wide init file and a
38116 system-wide init file directory; this file and files in that directory
38117 (if they have a recognized file extension) will be read and executed at
38118 startup (@pxref{Startup, , What @value{GDBN} does during startup}).
38120 Here are the corresponding configure options:
38123 @item --with-system-gdbinit=@var{file}
38124 Specify that the default location of the system-wide init file is
38126 @item --with-system-gdbinit-dir=@var{directory}
38127 Specify that the default location of the system-wide init file directory
38128 is @var{directory}.
38131 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
38132 they may be subject to relocation. Two possible cases:
38136 If the default location of this init file/directory contains @file{$prefix},
38137 it will be subject to relocation. Suppose that the configure options
38138 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
38139 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
38140 init file is looked for as @file{$install/etc/gdbinit} instead of
38141 @file{$prefix/etc/gdbinit}.
38144 By contrast, if the default location does not contain the prefix,
38145 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
38146 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
38147 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
38148 wherever @value{GDBN} is installed.
38151 If the configured location of the system-wide init file (as given by the
38152 @option{--with-system-gdbinit} option at configure time) is in the
38153 data-directory (as specified by @option{--with-gdb-datadir} at configure
38154 time) or in one of its subdirectories, then @value{GDBN} will look for the
38155 system-wide init file in the directory specified by the
38156 @option{--data-directory} command-line option.
38157 Note that the system-wide init file is only read once, during @value{GDBN}
38158 initialization. If the data-directory is changed after @value{GDBN} has
38159 started with the @code{set data-directory} command, the file will not be
38162 This applies similarly to the system-wide directory specified in
38163 @option{--with-system-gdbinit-dir}.
38165 Any supported scripting language can be used for these init files, as long
38166 as the file extension matches the scripting language. To be interpreted
38167 as regular @value{GDBN} commands, the files needs to have a @file{.gdb}
38171 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
38174 @node System-wide Configuration Scripts
38175 @subsection Installed System-wide Configuration Scripts
38176 @cindex system-wide configuration scripts
38178 The @file{system-gdbinit} directory, located inside the data-directory
38179 (as specified by @option{--with-gdb-datadir} at configure time) contains
38180 a number of scripts which can be used as system-wide init files. To
38181 automatically source those scripts at startup, @value{GDBN} should be
38182 configured with @option{--with-system-gdbinit}. Otherwise, any user
38183 should be able to source them by hand as needed.
38185 The following scripts are currently available:
38188 @item @file{elinos.py}
38190 @cindex ELinOS system-wide configuration script
38191 This script is useful when debugging a program on an ELinOS target.
38192 It takes advantage of the environment variables defined in a standard
38193 ELinOS environment in order to determine the location of the system
38194 shared libraries, and then sets the @samp{solib-absolute-prefix}
38195 and @samp{solib-search-path} variables appropriately.
38197 @item @file{wrs-linux.py}
38198 @pindex wrs-linux.py
38199 @cindex Wind River Linux system-wide configuration script
38200 This script is useful when debugging a program on a target running
38201 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
38202 the host-side sysroot used by the target system.
38206 @node Maintenance Commands
38207 @appendix Maintenance Commands
38208 @cindex maintenance commands
38209 @cindex internal commands
38211 In addition to commands intended for @value{GDBN} users, @value{GDBN}
38212 includes a number of commands intended for @value{GDBN} developers,
38213 that are not documented elsewhere in this manual. These commands are
38214 provided here for reference. (For commands that turn on debugging
38215 messages, see @ref{Debugging Output}.)
38218 @kindex maint agent
38219 @kindex maint agent-eval
38220 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
38221 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
38222 Translate the given @var{expression} into remote agent bytecodes.
38223 This command is useful for debugging the Agent Expression mechanism
38224 (@pxref{Agent Expressions}). The @samp{agent} version produces an
38225 expression useful for data collection, such as by tracepoints, while
38226 @samp{maint agent-eval} produces an expression that evaluates directly
38227 to a result. For instance, a collection expression for @code{globa +
38228 globb} will include bytecodes to record four bytes of memory at each
38229 of the addresses of @code{globa} and @code{globb}, while discarding
38230 the result of the addition, while an evaluation expression will do the
38231 addition and return the sum.
38232 If @code{-at} is given, generate remote agent bytecode for @var{location}.
38233 If not, generate remote agent bytecode for current frame PC address.
38235 @kindex maint agent-printf
38236 @item maint agent-printf @var{format},@var{expr},...
38237 Translate the given format string and list of argument expressions
38238 into remote agent bytecodes and display them as a disassembled list.
38239 This command is useful for debugging the agent version of dynamic
38240 printf (@pxref{Dynamic Printf}).
38242 @kindex maint info breakpoints
38243 @item @anchor{maint info breakpoints}maint info breakpoints
38244 Using the same format as @samp{info breakpoints}, display both the
38245 breakpoints you've set explicitly, and those @value{GDBN} is using for
38246 internal purposes. Internal breakpoints are shown with negative
38247 breakpoint numbers. The type column identifies what kind of breakpoint
38252 Normal, explicitly set breakpoint.
38255 Normal, explicitly set watchpoint.
38258 Internal breakpoint, used to handle correctly stepping through
38259 @code{longjmp} calls.
38261 @item longjmp resume
38262 Internal breakpoint at the target of a @code{longjmp}.
38265 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
38268 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
38271 Shared library events.
38275 @kindex maint info btrace
38276 @item maint info btrace
38277 Pint information about raw branch tracing data.
38279 @kindex maint btrace packet-history
38280 @item maint btrace packet-history
38281 Print the raw branch trace packets that are used to compute the
38282 execution history for the @samp{record btrace} command. Both the
38283 information and the format in which it is printed depend on the btrace
38288 For the BTS recording format, print a list of blocks of sequential
38289 code. For each block, the following information is printed:
38293 Newer blocks have higher numbers. The oldest block has number zero.
38294 @item Lowest @samp{PC}
38295 @item Highest @samp{PC}
38299 For the Intel Processor Trace recording format, print a list of
38300 Intel Processor Trace packets. For each packet, the following
38301 information is printed:
38304 @item Packet number
38305 Newer packets have higher numbers. The oldest packet has number zero.
38307 The packet's offset in the trace stream.
38308 @item Packet opcode and payload
38312 @kindex maint btrace clear-packet-history
38313 @item maint btrace clear-packet-history
38314 Discards the cached packet history printed by the @samp{maint btrace
38315 packet-history} command. The history will be computed again when
38318 @kindex maint btrace clear
38319 @item maint btrace clear
38320 Discard the branch trace data. The data will be fetched anew and the
38321 branch trace will be recomputed when needed.
38323 This implicitly truncates the branch trace to a single branch trace
38324 buffer. When updating branch trace incrementally, the branch trace
38325 available to @value{GDBN} may be bigger than a single branch trace
38328 @kindex maint set btrace pt skip-pad
38329 @item maint set btrace pt skip-pad
38330 @kindex maint show btrace pt skip-pad
38331 @item maint show btrace pt skip-pad
38332 Control whether @value{GDBN} will skip PAD packets when computing the
38335 @kindex set displaced-stepping
38336 @kindex show displaced-stepping
38337 @cindex displaced stepping support
38338 @cindex out-of-line single-stepping
38339 @item set displaced-stepping
38340 @itemx show displaced-stepping
38341 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
38342 if the target supports it. Displaced stepping is a way to single-step
38343 over breakpoints without removing them from the inferior, by executing
38344 an out-of-line copy of the instruction that was originally at the
38345 breakpoint location. It is also known as out-of-line single-stepping.
38348 @item set displaced-stepping on
38349 If the target architecture supports it, @value{GDBN} will use
38350 displaced stepping to step over breakpoints.
38352 @item set displaced-stepping off
38353 @value{GDBN} will not use displaced stepping to step over breakpoints,
38354 even if such is supported by the target architecture.
38356 @cindex non-stop mode, and @samp{set displaced-stepping}
38357 @item set displaced-stepping auto
38358 This is the default mode. @value{GDBN} will use displaced stepping
38359 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
38360 architecture supports displaced stepping.
38363 @kindex maint check-psymtabs
38364 @item maint check-psymtabs
38365 Check the consistency of currently expanded psymtabs versus symtabs.
38366 Use this to check, for example, whether a symbol is in one but not the other.
38368 @kindex maint check-symtabs
38369 @item maint check-symtabs
38370 Check the consistency of currently expanded symtabs.
38372 @kindex maint expand-symtabs
38373 @item maint expand-symtabs [@var{regexp}]
38374 Expand symbol tables.
38375 If @var{regexp} is specified, only expand symbol tables for file
38376 names matching @var{regexp}.
38378 @kindex maint set catch-demangler-crashes
38379 @kindex maint show catch-demangler-crashes
38380 @cindex demangler crashes
38381 @item maint set catch-demangler-crashes [on|off]
38382 @itemx maint show catch-demangler-crashes
38383 Control whether @value{GDBN} should attempt to catch crashes in the
38384 symbol name demangler. The default is to attempt to catch crashes.
38385 If enabled, the first time a crash is caught, a core file is created,
38386 the offending symbol is displayed and the user is presented with the
38387 option to terminate the current session.
38389 @kindex maint cplus first_component
38390 @item maint cplus first_component @var{name}
38391 Print the first C@t{++} class/namespace component of @var{name}.
38393 @kindex maint cplus namespace
38394 @item maint cplus namespace
38395 Print the list of possible C@t{++} namespaces.
38397 @kindex maint deprecate
38398 @kindex maint undeprecate
38399 @cindex deprecated commands
38400 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
38401 @itemx maint undeprecate @var{command}
38402 Deprecate or undeprecate the named @var{command}. Deprecated commands
38403 cause @value{GDBN} to issue a warning when you use them. The optional
38404 argument @var{replacement} says which newer command should be used in
38405 favor of the deprecated one; if it is given, @value{GDBN} will mention
38406 the replacement as part of the warning.
38408 @kindex maint dump-me
38409 @item maint dump-me
38410 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
38411 Cause a fatal signal in the debugger and force it to dump its core.
38412 This is supported only on systems which support aborting a program
38413 with the @code{SIGQUIT} signal.
38415 @kindex maint internal-error
38416 @kindex maint internal-warning
38417 @kindex maint demangler-warning
38418 @cindex demangler crashes
38419 @item maint internal-error @r{[}@var{message-text}@r{]}
38420 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
38421 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
38423 Cause @value{GDBN} to call the internal function @code{internal_error},
38424 @code{internal_warning} or @code{demangler_warning} and hence behave
38425 as though an internal problem has been detected. In addition to
38426 reporting the internal problem, these functions give the user the
38427 opportunity to either quit @value{GDBN} or (for @code{internal_error}
38428 and @code{internal_warning}) create a core file of the current
38429 @value{GDBN} session.
38431 These commands take an optional parameter @var{message-text} that is
38432 used as the text of the error or warning message.
38434 Here's an example of using @code{internal-error}:
38437 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
38438 @dots{}/maint.c:121: internal-error: testing, 1, 2
38439 A problem internal to GDB has been detected. Further
38440 debugging may prove unreliable.
38441 Quit this debugging session? (y or n) @kbd{n}
38442 Create a core file? (y or n) @kbd{n}
38446 @cindex @value{GDBN} internal error
38447 @cindex internal errors, control of @value{GDBN} behavior
38448 @cindex demangler crashes
38450 @kindex maint set internal-error
38451 @kindex maint show internal-error
38452 @kindex maint set internal-warning
38453 @kindex maint show internal-warning
38454 @kindex maint set demangler-warning
38455 @kindex maint show demangler-warning
38456 @item maint set internal-error @var{action} [ask|yes|no]
38457 @itemx maint show internal-error @var{action}
38458 @itemx maint set internal-warning @var{action} [ask|yes|no]
38459 @itemx maint show internal-warning @var{action}
38460 @itemx maint set demangler-warning @var{action} [ask|yes|no]
38461 @itemx maint show demangler-warning @var{action}
38462 When @value{GDBN} reports an internal problem (error or warning) it
38463 gives the user the opportunity to both quit @value{GDBN} and create a
38464 core file of the current @value{GDBN} session. These commands let you
38465 override the default behaviour for each particular @var{action},
38466 described in the table below.
38470 You can specify that @value{GDBN} should always (yes) or never (no)
38471 quit. The default is to ask the user what to do.
38474 You can specify that @value{GDBN} should always (yes) or never (no)
38475 create a core file. The default is to ask the user what to do. Note
38476 that there is no @code{corefile} option for @code{demangler-warning}:
38477 demangler warnings always create a core file and this cannot be
38481 @kindex maint packet
38482 @item maint packet @var{text}
38483 If @value{GDBN} is talking to an inferior via the serial protocol,
38484 then this command sends the string @var{text} to the inferior, and
38485 displays the response packet. @value{GDBN} supplies the initial
38486 @samp{$} character, the terminating @samp{#} character, and the
38489 @kindex maint print architecture
38490 @item maint print architecture @r{[}@var{file}@r{]}
38491 Print the entire architecture configuration. The optional argument
38492 @var{file} names the file where the output goes.
38494 @kindex maint print c-tdesc @r{[}@var{file}@r{]}
38495 @item maint print c-tdesc
38496 Print the target description (@pxref{Target Descriptions}) as
38497 a C source file. By default, the target description is for the current
38498 target, but if the optional argument @var{file} is provided, that file
38499 is used to produce the description. The @var{file} should be an XML
38500 document, of the form described in @ref{Target Description Format}.
38501 The created source file is built into @value{GDBN} when @value{GDBN} is
38502 built again. This command is used by developers after they add or
38503 modify XML target descriptions.
38505 @kindex maint print xml-tdesc
38506 @item maint print xml-tdesc @r{[}@var{file}@r{]}
38507 Print the target description (@pxref{Target Descriptions}) as an XML
38508 file. By default print the target description for the current target,
38509 but if the optional argument @var{file} is provided, then that file is
38510 read in by GDB and then used to produce the description. The
38511 @var{file} should be an XML document, of the form described in
38512 @ref{Target Description Format}.
38514 @kindex maint check xml-descriptions
38515 @item maint check xml-descriptions @var{dir}
38516 Check that the target descriptions dynamically created by @value{GDBN}
38517 equal the descriptions created from XML files found in @var{dir}.
38519 @anchor{maint check libthread-db}
38520 @kindex maint check libthread-db
38521 @item maint check libthread-db
38522 Run integrity checks on the current inferior's thread debugging
38523 library. This exercises all @code{libthread_db} functionality used by
38524 @value{GDBN} on GNU/Linux systems, and by extension also exercises the
38525 @code{proc_service} functions provided by @value{GDBN} that
38526 @code{libthread_db} uses. Note that parts of the test may be skipped
38527 on some platforms when debugging core files.
38529 @kindex maint print dummy-frames
38530 @item maint print dummy-frames
38531 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
38534 (@value{GDBP}) @kbd{b add}
38536 (@value{GDBP}) @kbd{print add(2,3)}
38537 Breakpoint 2, add (a=2, b=3) at @dots{}
38539 The program being debugged stopped while in a function called from GDB.
38541 (@value{GDBP}) @kbd{maint print dummy-frames}
38542 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
38546 Takes an optional file parameter.
38548 @kindex maint print registers
38549 @kindex maint print raw-registers
38550 @kindex maint print cooked-registers
38551 @kindex maint print register-groups
38552 @kindex maint print remote-registers
38553 @item maint print registers @r{[}@var{file}@r{]}
38554 @itemx maint print raw-registers @r{[}@var{file}@r{]}
38555 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
38556 @itemx maint print register-groups @r{[}@var{file}@r{]}
38557 @itemx maint print remote-registers @r{[}@var{file}@r{]}
38558 Print @value{GDBN}'s internal register data structures.
38560 The command @code{maint print raw-registers} includes the contents of
38561 the raw register cache; the command @code{maint print
38562 cooked-registers} includes the (cooked) value of all registers,
38563 including registers which aren't available on the target nor visible
38564 to user; the command @code{maint print register-groups} includes the
38565 groups that each register is a member of; and the command @code{maint
38566 print remote-registers} includes the remote target's register numbers
38567 and offsets in the `G' packets.
38569 These commands take an optional parameter, a file name to which to
38570 write the information.
38572 @kindex maint print reggroups
38573 @item maint print reggroups @r{[}@var{file}@r{]}
38574 Print @value{GDBN}'s internal register group data structures. The
38575 optional argument @var{file} tells to what file to write the
38578 The register groups info looks like this:
38581 (@value{GDBP}) @kbd{maint print reggroups}
38594 This command forces @value{GDBN} to flush its internal register cache.
38596 @kindex maint print objfiles
38597 @cindex info for known object files
38598 @item maint print objfiles @r{[}@var{regexp}@r{]}
38599 Print a dump of all known object files.
38600 If @var{regexp} is specified, only print object files whose names
38601 match @var{regexp}. For each object file, this command prints its name,
38602 address in memory, and all of its psymtabs and symtabs.
38604 @kindex maint print user-registers
38605 @cindex user registers
38606 @item maint print user-registers
38607 List all currently available @dfn{user registers}. User registers
38608 typically provide alternate names for actual hardware registers. They
38609 include the four ``standard'' registers @code{$fp}, @code{$pc},
38610 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
38611 registers can be used in expressions in the same way as the canonical
38612 register names, but only the latter are listed by the @code{info
38613 registers} and @code{maint print registers} commands.
38615 @kindex maint print section-scripts
38616 @cindex info for known .debug_gdb_scripts-loaded scripts
38617 @item maint print section-scripts [@var{regexp}]
38618 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
38619 If @var{regexp} is specified, only print scripts loaded by object files
38620 matching @var{regexp}.
38621 For each script, this command prints its name as specified in the objfile,
38622 and the full path if known.
38623 @xref{dotdebug_gdb_scripts section}.
38625 @kindex maint print statistics
38626 @cindex bcache statistics
38627 @item maint print statistics
38628 This command prints, for each object file in the program, various data
38629 about that object file followed by the byte cache (@dfn{bcache})
38630 statistics for the object file. The objfile data includes the number
38631 of minimal, partial, full, and stabs symbols, the number of types
38632 defined by the objfile, the number of as yet unexpanded psym tables,
38633 the number of line tables and string tables, and the amount of memory
38634 used by the various tables. The bcache statistics include the counts,
38635 sizes, and counts of duplicates of all and unique objects, max,
38636 average, and median entry size, total memory used and its overhead and
38637 savings, and various measures of the hash table size and chain
38640 @kindex maint print target-stack
38641 @cindex target stack description
38642 @item maint print target-stack
38643 A @dfn{target} is an interface between the debugger and a particular
38644 kind of file or process. Targets can be stacked in @dfn{strata},
38645 so that more than one target can potentially respond to a request.
38646 In particular, memory accesses will walk down the stack of targets
38647 until they find a target that is interested in handling that particular
38650 This command prints a short description of each layer that was pushed on
38651 the @dfn{target stack}, starting from the top layer down to the bottom one.
38653 @kindex maint print type
38654 @cindex type chain of a data type
38655 @item maint print type @var{expr}
38656 Print the type chain for a type specified by @var{expr}. The argument
38657 can be either a type name or a symbol. If it is a symbol, the type of
38658 that symbol is described. The type chain produced by this command is
38659 a recursive definition of the data type as stored in @value{GDBN}'s
38660 data structures, including its flags and contained types.
38662 @kindex maint selftest
38664 @item maint selftest @r{[}@var{filter}@r{]}
38665 Run any self tests that were compiled in to @value{GDBN}. This will
38666 print a message showing how many tests were run, and how many failed.
38667 If a @var{filter} is passed, only the tests with @var{filter} in their
38670 @kindex maint info selftests
38672 @item maint info selftests
38673 List the selftests compiled in to @value{GDBN}.
38675 @kindex maint set dwarf always-disassemble
38676 @kindex maint show dwarf always-disassemble
38677 @item maint set dwarf always-disassemble
38678 @item maint show dwarf always-disassemble
38679 Control the behavior of @code{info address} when using DWARF debugging
38682 The default is @code{off}, which means that @value{GDBN} should try to
38683 describe a variable's location in an easily readable format. When
38684 @code{on}, @value{GDBN} will instead display the DWARF location
38685 expression in an assembly-like format. Note that some locations are
38686 too complex for @value{GDBN} to describe simply; in this case you will
38687 always see the disassembly form.
38689 Here is an example of the resulting disassembly:
38692 (gdb) info addr argc
38693 Symbol "argc" is a complex DWARF expression:
38697 For more information on these expressions, see
38698 @uref{http://www.dwarfstd.org/, the DWARF standard}.
38700 @kindex maint set dwarf max-cache-age
38701 @kindex maint show dwarf max-cache-age
38702 @item maint set dwarf max-cache-age
38703 @itemx maint show dwarf max-cache-age
38704 Control the DWARF compilation unit cache.
38706 @cindex DWARF compilation units cache
38707 In object files with inter-compilation-unit references, such as those
38708 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF
38709 reader needs to frequently refer to previously read compilation units.
38710 This setting controls how long a compilation unit will remain in the
38711 cache if it is not referenced. A higher limit means that cached
38712 compilation units will be stored in memory longer, and more total
38713 memory will be used. Setting it to zero disables caching, which will
38714 slow down @value{GDBN} startup, but reduce memory consumption.
38716 @kindex maint set dwarf unwinders
38717 @kindex maint show dwarf unwinders
38718 @item maint set dwarf unwinders
38719 @itemx maint show dwarf unwinders
38720 Control use of the DWARF frame unwinders.
38722 @cindex DWARF frame unwinders
38723 Many targets that support DWARF debugging use @value{GDBN}'s DWARF
38724 frame unwinders to build the backtrace. Many of these targets will
38725 also have a second mechanism for building the backtrace for use in
38726 cases where DWARF information is not available, this second mechanism
38727 is often an analysis of a function's prologue.
38729 In order to extend testing coverage of the second level stack
38730 unwinding mechanisms it is helpful to be able to disable the DWARF
38731 stack unwinders, this can be done with this switch.
38733 In normal use of @value{GDBN} disabling the DWARF unwinders is not
38734 advisable, there are cases that are better handled through DWARF than
38735 prologue analysis, and the debug experience is likely to be better
38736 with the DWARF frame unwinders enabled.
38738 If DWARF frame unwinders are not supported for a particular target
38739 architecture, then enabling this flag does not cause them to be used.
38741 @kindex maint set worker-threads
38742 @kindex maint show worker-threads
38743 @item maint set worker-threads
38744 @item maint show worker-threads
38745 Control the number of worker threads that may be used by @value{GDBN}.
38746 On capable hosts, @value{GDBN} may use multiple threads to speed up
38747 certain CPU-intensive operations, such as demangling symbol names.
38748 While the number of threads used by @value{GDBN} may vary, this
38749 command can be used to set an upper bound on this number. The default
38750 is @code{unlimited}, which lets @value{GDBN} choose a reasonable
38751 number. Note that this only controls worker threads started by
38752 @value{GDBN} itself; libraries used by @value{GDBN} may start threads
38755 @kindex maint set profile
38756 @kindex maint show profile
38757 @cindex profiling GDB
38758 @item maint set profile
38759 @itemx maint show profile
38760 Control profiling of @value{GDBN}.
38762 Profiling will be disabled until you use the @samp{maint set profile}
38763 command to enable it. When you enable profiling, the system will begin
38764 collecting timing and execution count data; when you disable profiling or
38765 exit @value{GDBN}, the results will be written to a log file. Remember that
38766 if you use profiling, @value{GDBN} will overwrite the profiling log file
38767 (often called @file{gmon.out}). If you have a record of important profiling
38768 data in a @file{gmon.out} file, be sure to move it to a safe location.
38770 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
38771 compiled with the @samp{-pg} compiler option.
38773 @kindex maint set show-debug-regs
38774 @kindex maint show show-debug-regs
38775 @cindex hardware debug registers
38776 @item maint set show-debug-regs
38777 @itemx maint show show-debug-regs
38778 Control whether to show variables that mirror the hardware debug
38779 registers. Use @code{on} to enable, @code{off} to disable. If
38780 enabled, the debug registers values are shown when @value{GDBN} inserts or
38781 removes a hardware breakpoint or watchpoint, and when the inferior
38782 triggers a hardware-assisted breakpoint or watchpoint.
38784 @kindex maint set show-all-tib
38785 @kindex maint show show-all-tib
38786 @item maint set show-all-tib
38787 @itemx maint show show-all-tib
38788 Control whether to show all non zero areas within a 1k block starting
38789 at thread local base, when using the @samp{info w32 thread-information-block}
38792 @kindex maint set target-async
38793 @kindex maint show target-async
38794 @item maint set target-async
38795 @itemx maint show target-async
38796 This controls whether @value{GDBN} targets operate in synchronous or
38797 asynchronous mode (@pxref{Background Execution}). Normally the
38798 default is asynchronous, if it is available; but this can be changed
38799 to more easily debug problems occurring only in synchronous mode.
38801 @kindex maint set target-non-stop @var{mode} [on|off|auto]
38802 @kindex maint show target-non-stop
38803 @item maint set target-non-stop
38804 @itemx maint show target-non-stop
38806 This controls whether @value{GDBN} targets always operate in non-stop
38807 mode even if @code{set non-stop} is @code{off} (@pxref{Non-Stop
38808 Mode}). The default is @code{auto}, meaning non-stop mode is enabled
38809 if supported by the target.
38812 @item maint set target-non-stop auto
38813 This is the default mode. @value{GDBN} controls the target in
38814 non-stop mode if the target supports it.
38816 @item maint set target-non-stop on
38817 @value{GDBN} controls the target in non-stop mode even if the target
38818 does not indicate support.
38820 @item maint set target-non-stop off
38821 @value{GDBN} does not control the target in non-stop mode even if the
38822 target supports it.
38825 @kindex maint set tui-resize-message
38826 @kindex maint show tui-resize-message
38827 @item maint set tui-resize-message
38828 @item maint show tui-resize-message
38829 Control whether @value{GDBN} displays a message each time the terminal
38830 is resized when in TUI mode. The default is @code{off}, which means
38831 that @value{GDBN} is silent during resizes. When @code{on},
38832 @value{GDBN} will display a message after a resize is completed; the
38833 message will include a number indicating how many times the terminal
38834 has been resized. This setting is intended for use by the test suite,
38835 where it would otherwise be difficult to determine when a resize and
38836 refresh has been completed.
38838 @kindex maint set per-command
38839 @kindex maint show per-command
38840 @item maint set per-command
38841 @itemx maint show per-command
38842 @cindex resources used by commands
38844 @value{GDBN} can display the resources used by each command.
38845 This is useful in debugging performance problems.
38848 @item maint set per-command space [on|off]
38849 @itemx maint show per-command space
38850 Enable or disable the printing of the memory used by GDB for each command.
38851 If enabled, @value{GDBN} will display how much memory each command
38852 took, following the command's own output.
38853 This can also be requested by invoking @value{GDBN} with the
38854 @option{--statistics} command-line switch (@pxref{Mode Options}).
38856 @item maint set per-command time [on|off]
38857 @itemx maint show per-command time
38858 Enable or disable the printing of the execution time of @value{GDBN}
38860 If enabled, @value{GDBN} will display how much time it
38861 took to execute each command, following the command's own output.
38862 Both CPU time and wallclock time are printed.
38863 Printing both is useful when trying to determine whether the cost is
38864 CPU or, e.g., disk/network latency.
38865 Note that the CPU time printed is for @value{GDBN} only, it does not include
38866 the execution time of the inferior because there's no mechanism currently
38867 to compute how much time was spent by @value{GDBN} and how much time was
38868 spent by the program been debugged.
38869 This can also be requested by invoking @value{GDBN} with the
38870 @option{--statistics} command-line switch (@pxref{Mode Options}).
38872 @item maint set per-command symtab [on|off]
38873 @itemx maint show per-command symtab
38874 Enable or disable the printing of basic symbol table statistics
38876 If enabled, @value{GDBN} will display the following information:
38880 number of symbol tables
38882 number of primary symbol tables
38884 number of blocks in the blockvector
38888 @kindex maint set check-libthread-db
38889 @kindex maint show check-libthread-db
38890 @item maint set check-libthread-db [on|off]
38891 @itemx maint show check-libthread-db
38892 Control whether @value{GDBN} should run integrity checks on inferior
38893 specific thread debugging libraries as they are loaded. The default
38894 is not to perform such checks. If any check fails @value{GDBN} will
38895 unload the library and continue searching for a suitable candidate as
38896 described in @ref{set libthread-db-search-path}. For more information
38897 about the tests, see @ref{maint check libthread-db}.
38899 @kindex maint space
38900 @cindex memory used by commands
38901 @item maint space @var{value}
38902 An alias for @code{maint set per-command space}.
38903 A non-zero value enables it, zero disables it.
38906 @cindex time of command execution
38907 @item maint time @var{value}
38908 An alias for @code{maint set per-command time}.
38909 A non-zero value enables it, zero disables it.
38911 @kindex maint translate-address
38912 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
38913 Find the symbol stored at the location specified by the address
38914 @var{addr} and an optional section name @var{section}. If found,
38915 @value{GDBN} prints the name of the closest symbol and an offset from
38916 the symbol's location to the specified address. This is similar to
38917 the @code{info address} command (@pxref{Symbols}), except that this
38918 command also allows to find symbols in other sections.
38920 If section was not specified, the section in which the symbol was found
38921 is also printed. For dynamically linked executables, the name of
38922 executable or shared library containing the symbol is printed as well.
38924 @kindex maint test-options
38925 @item maint test-options require-delimiter
38926 @itemx maint test-options unknown-is-error
38927 @itemx maint test-options unknown-is-operand
38928 These commands are used by the testsuite to validate the command
38929 options framework. The @code{require-delimiter} variant requires a
38930 double-dash delimiter to indicate end of options. The
38931 @code{unknown-is-error} and @code{unknown-is-operand} do not. The
38932 @code{unknown-is-error} variant throws an error on unknown option,
38933 while @code{unknown-is-operand} treats unknown options as the start of
38934 the command's operands. When run, the commands output the result of
38935 the processed options. When completed, the commands store the
38936 internal result of completion in a variable exposed by the @code{maint
38937 show test-options-completion-result} command.
38939 @kindex maint show test-options-completion-result
38940 @item maint show test-options-completion-result
38941 Shows the result of completing the @code{maint test-options}
38942 subcommands. This is used by the testsuite to validate completion
38943 support in the command options framework.
38945 @kindex maint set test-settings
38946 @kindex maint show test-settings
38947 @item maint set test-settings @var{kind}
38948 @itemx maint show test-settings @var{kind}
38949 These are representative commands for each @var{kind} of setting type
38950 @value{GDBN} supports. They are used by the testsuite for exercising
38951 the settings infrastructure.
38954 @item maint with @var{setting} [@var{value}] [-- @var{command}]
38955 Like the @code{with} command, but works with @code{maintenance set}
38956 variables. This is used by the testsuite to exercise the @code{with}
38957 command's infrastructure.
38961 The following command is useful for non-interactive invocations of
38962 @value{GDBN}, such as in the test suite.
38965 @item set watchdog @var{nsec}
38966 @kindex set watchdog
38967 @cindex watchdog timer
38968 @cindex timeout for commands
38969 Set the maximum number of seconds @value{GDBN} will wait for the
38970 target operation to finish. If this time expires, @value{GDBN}
38971 reports and error and the command is aborted.
38973 @item show watchdog
38974 Show the current setting of the target wait timeout.
38977 @node Remote Protocol
38978 @appendix @value{GDBN} Remote Serial Protocol
38983 * Stop Reply Packets::
38984 * General Query Packets::
38985 * Architecture-Specific Protocol Details::
38986 * Tracepoint Packets::
38987 * Host I/O Packets::
38989 * Notification Packets::
38990 * Remote Non-Stop::
38991 * Packet Acknowledgment::
38993 * File-I/O Remote Protocol Extension::
38994 * Library List Format::
38995 * Library List Format for SVR4 Targets::
38996 * Memory Map Format::
38997 * Thread List Format::
38998 * Traceframe Info Format::
38999 * Branch Trace Format::
39000 * Branch Trace Configuration Format::
39006 There may be occasions when you need to know something about the
39007 protocol---for example, if there is only one serial port to your target
39008 machine, you might want your program to do something special if it
39009 recognizes a packet meant for @value{GDBN}.
39011 In the examples below, @samp{->} and @samp{<-} are used to indicate
39012 transmitted and received data, respectively.
39014 @cindex protocol, @value{GDBN} remote serial
39015 @cindex serial protocol, @value{GDBN} remote
39016 @cindex remote serial protocol
39017 All @value{GDBN} commands and responses (other than acknowledgments
39018 and notifications, see @ref{Notification Packets}) are sent as a
39019 @var{packet}. A @var{packet} is introduced with the character
39020 @samp{$}, the actual @var{packet-data}, and the terminating character
39021 @samp{#} followed by a two-digit @var{checksum}:
39024 @code{$}@var{packet-data}@code{#}@var{checksum}
39028 @cindex checksum, for @value{GDBN} remote
39030 The two-digit @var{checksum} is computed as the modulo 256 sum of all
39031 characters between the leading @samp{$} and the trailing @samp{#} (an
39032 eight bit unsigned checksum).
39034 Implementors should note that prior to @value{GDBN} 5.0 the protocol
39035 specification also included an optional two-digit @var{sequence-id}:
39038 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
39041 @cindex sequence-id, for @value{GDBN} remote
39043 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
39044 has never output @var{sequence-id}s. Stubs that handle packets added
39045 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
39047 When either the host or the target machine receives a packet, the first
39048 response expected is an acknowledgment: either @samp{+} (to indicate
39049 the package was received correctly) or @samp{-} (to request
39053 -> @code{$}@var{packet-data}@code{#}@var{checksum}
39058 The @samp{+}/@samp{-} acknowledgments can be disabled
39059 once a connection is established.
39060 @xref{Packet Acknowledgment}, for details.
39062 The host (@value{GDBN}) sends @var{command}s, and the target (the
39063 debugging stub incorporated in your program) sends a @var{response}. In
39064 the case of step and continue @var{command}s, the response is only sent
39065 when the operation has completed, and the target has again stopped all
39066 threads in all attached processes. This is the default all-stop mode
39067 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
39068 execution mode; see @ref{Remote Non-Stop}, for details.
39070 @var{packet-data} consists of a sequence of characters with the
39071 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
39074 @cindex remote protocol, field separator
39075 Fields within the packet should be separated using @samp{,} @samp{;} or
39076 @samp{:}. Except where otherwise noted all numbers are represented in
39077 @sc{hex} with leading zeros suppressed.
39079 Implementors should note that prior to @value{GDBN} 5.0, the character
39080 @samp{:} could not appear as the third character in a packet (as it
39081 would potentially conflict with the @var{sequence-id}).
39083 @cindex remote protocol, binary data
39084 @anchor{Binary Data}
39085 Binary data in most packets is encoded either as two hexadecimal
39086 digits per byte of binary data. This allowed the traditional remote
39087 protocol to work over connections which were only seven-bit clean.
39088 Some packets designed more recently assume an eight-bit clean
39089 connection, and use a more efficient encoding to send and receive
39092 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
39093 as an escape character. Any escaped byte is transmitted as the escape
39094 character followed by the original character XORed with @code{0x20}.
39095 For example, the byte @code{0x7d} would be transmitted as the two
39096 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
39097 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
39098 @samp{@}}) must always be escaped. Responses sent by the stub
39099 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
39100 is not interpreted as the start of a run-length encoded sequence
39103 Response @var{data} can be run-length encoded to save space.
39104 Run-length encoding replaces runs of identical characters with one
39105 instance of the repeated character, followed by a @samp{*} and a
39106 repeat count. The repeat count is itself sent encoded, to avoid
39107 binary characters in @var{data}: a value of @var{n} is sent as
39108 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
39109 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
39110 code 32) for a repeat count of 3. (This is because run-length
39111 encoding starts to win for counts 3 or more.) Thus, for example,
39112 @samp{0* } is a run-length encoding of ``0000'': the space character
39113 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
39116 The printable characters @samp{#} and @samp{$} or with a numeric value
39117 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
39118 seven repeats (@samp{$}) can be expanded using a repeat count of only
39119 five (@samp{"}). For example, @samp{00000000} can be encoded as
39122 The error response returned for some packets includes a two character
39123 error number. That number is not well defined.
39125 @cindex empty response, for unsupported packets
39126 For any @var{command} not supported by the stub, an empty response
39127 (@samp{$#00}) should be returned. That way it is possible to extend the
39128 protocol. A newer @value{GDBN} can tell if a packet is supported based
39131 At a minimum, a stub is required to support the @samp{g} and @samp{G}
39132 commands for register access, and the @samp{m} and @samp{M} commands
39133 for memory access. Stubs that only control single-threaded targets
39134 can implement run control with the @samp{c} (continue), and @samp{s}
39135 (step) commands. Stubs that support multi-threading targets should
39136 support the @samp{vCont} command. All other commands are optional.
39141 The following table provides a complete list of all currently defined
39142 @var{command}s and their corresponding response @var{data}.
39143 @xref{File-I/O Remote Protocol Extension}, for details about the File
39144 I/O extension of the remote protocol.
39146 Each packet's description has a template showing the packet's overall
39147 syntax, followed by an explanation of the packet's meaning. We
39148 include spaces in some of the templates for clarity; these are not
39149 part of the packet's syntax. No @value{GDBN} packet uses spaces to
39150 separate its components. For example, a template like @samp{foo
39151 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
39152 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
39153 @var{baz}. @value{GDBN} does not transmit a space character between the
39154 @samp{foo} and the @var{bar}, or between the @var{bar} and the
39157 @cindex @var{thread-id}, in remote protocol
39158 @anchor{thread-id syntax}
39159 Several packets and replies include a @var{thread-id} field to identify
39160 a thread. Normally these are positive numbers with a target-specific
39161 interpretation, formatted as big-endian hex strings. A @var{thread-id}
39162 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
39165 In addition, the remote protocol supports a multiprocess feature in
39166 which the @var{thread-id} syntax is extended to optionally include both
39167 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
39168 The @var{pid} (process) and @var{tid} (thread) components each have the
39169 format described above: a positive number with target-specific
39170 interpretation formatted as a big-endian hex string, literal @samp{-1}
39171 to indicate all processes or threads (respectively), or @samp{0} to
39172 indicate an arbitrary process or thread. Specifying just a process, as
39173 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
39174 error to specify all processes but a specific thread, such as
39175 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
39176 for those packets and replies explicitly documented to include a process
39177 ID, rather than a @var{thread-id}.
39179 The multiprocess @var{thread-id} syntax extensions are only used if both
39180 @value{GDBN} and the stub report support for the @samp{multiprocess}
39181 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
39184 Note that all packet forms beginning with an upper- or lower-case
39185 letter, other than those described here, are reserved for future use.
39187 Here are the packet descriptions.
39192 @cindex @samp{!} packet
39193 @anchor{extended mode}
39194 Enable extended mode. In extended mode, the remote server is made
39195 persistent. The @samp{R} packet is used to restart the program being
39201 The remote target both supports and has enabled extended mode.
39205 @cindex @samp{?} packet
39207 Indicate the reason the target halted. The reply is the same as for
39208 step and continue. This packet has a special interpretation when the
39209 target is in non-stop mode; see @ref{Remote Non-Stop}.
39212 @xref{Stop Reply Packets}, for the reply specifications.
39214 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
39215 @cindex @samp{A} packet
39216 Initialized @code{argv[]} array passed into program. @var{arglen}
39217 specifies the number of bytes in the hex encoded byte stream
39218 @var{arg}. See @code{gdbserver} for more details.
39223 The arguments were set.
39229 @cindex @samp{b} packet
39230 (Don't use this packet; its behavior is not well-defined.)
39231 Change the serial line speed to @var{baud}.
39233 JTC: @emph{When does the transport layer state change? When it's
39234 received, or after the ACK is transmitted. In either case, there are
39235 problems if the command or the acknowledgment packet is dropped.}
39237 Stan: @emph{If people really wanted to add something like this, and get
39238 it working for the first time, they ought to modify ser-unix.c to send
39239 some kind of out-of-band message to a specially-setup stub and have the
39240 switch happen "in between" packets, so that from remote protocol's point
39241 of view, nothing actually happened.}
39243 @item B @var{addr},@var{mode}
39244 @cindex @samp{B} packet
39245 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
39246 breakpoint at @var{addr}.
39248 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
39249 (@pxref{insert breakpoint or watchpoint packet}).
39251 @cindex @samp{bc} packet
39254 Backward continue. Execute the target system in reverse. No parameter.
39255 @xref{Reverse Execution}, for more information.
39258 @xref{Stop Reply Packets}, for the reply specifications.
39260 @cindex @samp{bs} packet
39263 Backward single step. Execute one instruction in reverse. No parameter.
39264 @xref{Reverse Execution}, for more information.
39267 @xref{Stop Reply Packets}, for the reply specifications.
39269 @item c @r{[}@var{addr}@r{]}
39270 @cindex @samp{c} packet
39271 Continue at @var{addr}, which is the address to resume. If @var{addr}
39272 is omitted, resume at current address.
39274 This packet is deprecated for multi-threading support. @xref{vCont
39278 @xref{Stop Reply Packets}, for the reply specifications.
39280 @item C @var{sig}@r{[};@var{addr}@r{]}
39281 @cindex @samp{C} packet
39282 Continue with signal @var{sig} (hex signal number). If
39283 @samp{;@var{addr}} is omitted, resume at same address.
39285 This packet is deprecated for multi-threading support. @xref{vCont
39289 @xref{Stop Reply Packets}, for the reply specifications.
39292 @cindex @samp{d} packet
39295 Don't use this packet; instead, define a general set packet
39296 (@pxref{General Query Packets}).
39300 @cindex @samp{D} packet
39301 The first form of the packet is used to detach @value{GDBN} from the
39302 remote system. It is sent to the remote target
39303 before @value{GDBN} disconnects via the @code{detach} command.
39305 The second form, including a process ID, is used when multiprocess
39306 protocol extensions are enabled (@pxref{multiprocess extensions}), to
39307 detach only a specific process. The @var{pid} is specified as a
39308 big-endian hex string.
39318 @item F @var{RC},@var{EE},@var{CF};@var{XX}
39319 @cindex @samp{F} packet
39320 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
39321 This is part of the File-I/O protocol extension. @xref{File-I/O
39322 Remote Protocol Extension}, for the specification.
39325 @anchor{read registers packet}
39326 @cindex @samp{g} packet
39327 Read general registers.
39331 @item @var{XX@dots{}}
39332 Each byte of register data is described by two hex digits. The bytes
39333 with the register are transmitted in target byte order. The size of
39334 each register and their position within the @samp{g} packet are
39335 determined by the @value{GDBN} internal gdbarch functions
39336 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}.
39338 When reading registers from a trace frame (@pxref{Analyze Collected
39339 Data,,Using the Collected Data}), the stub may also return a string of
39340 literal @samp{x}'s in place of the register data digits, to indicate
39341 that the corresponding register has not been collected, thus its value
39342 is unavailable. For example, for an architecture with 4 registers of
39343 4 bytes each, the following reply indicates to @value{GDBN} that
39344 registers 0 and 2 have not been collected, while registers 1 and 3
39345 have been collected, and both have zero value:
39349 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
39356 @item G @var{XX@dots{}}
39357 @cindex @samp{G} packet
39358 Write general registers. @xref{read registers packet}, for a
39359 description of the @var{XX@dots{}} data.
39369 @item H @var{op} @var{thread-id}
39370 @cindex @samp{H} packet
39371 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
39372 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
39373 should be @samp{c} for step and continue operations (note that this
39374 is deprecated, supporting the @samp{vCont} command is a better
39375 option), and @samp{g} for other operations. The thread designator
39376 @var{thread-id} has the format and interpretation described in
39377 @ref{thread-id syntax}.
39388 @c 'H': How restrictive (or permissive) is the thread model. If a
39389 @c thread is selected and stopped, are other threads allowed
39390 @c to continue to execute? As I mentioned above, I think the
39391 @c semantics of each command when a thread is selected must be
39392 @c described. For example:
39394 @c 'g': If the stub supports threads and a specific thread is
39395 @c selected, returns the register block from that thread;
39396 @c otherwise returns current registers.
39398 @c 'G' If the stub supports threads and a specific thread is
39399 @c selected, sets the registers of the register block of
39400 @c that thread; otherwise sets current registers.
39402 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
39403 @anchor{cycle step packet}
39404 @cindex @samp{i} packet
39405 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
39406 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
39407 step starting at that address.
39410 @cindex @samp{I} packet
39411 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
39415 @cindex @samp{k} packet
39418 The exact effect of this packet is not specified.
39420 For a bare-metal target, it may power cycle or reset the target
39421 system. For that reason, the @samp{k} packet has no reply.
39423 For a single-process target, it may kill that process if possible.
39425 A multiple-process target may choose to kill just one process, or all
39426 that are under @value{GDBN}'s control. For more precise control, use
39427 the vKill packet (@pxref{vKill packet}).
39429 If the target system immediately closes the connection in response to
39430 @samp{k}, @value{GDBN} does not consider the lack of packet
39431 acknowledgment to be an error, and assumes the kill was successful.
39433 If connected using @kbd{target extended-remote}, and the target does
39434 not close the connection in response to a kill request, @value{GDBN}
39435 probes the target state as if a new connection was opened
39436 (@pxref{? packet}).
39438 @item m @var{addr},@var{length}
39439 @cindex @samp{m} packet
39440 Read @var{length} addressable memory units starting at address @var{addr}
39441 (@pxref{addressable memory unit}). Note that @var{addr} may not be aligned to
39442 any particular boundary.
39444 The stub need not use any particular size or alignment when gathering
39445 data from memory for the response; even if @var{addr} is word-aligned
39446 and @var{length} is a multiple of the word size, the stub is free to
39447 use byte accesses, or not. For this reason, this packet may not be
39448 suitable for accessing memory-mapped I/O devices.
39449 @cindex alignment of remote memory accesses
39450 @cindex size of remote memory accesses
39451 @cindex memory, alignment and size of remote accesses
39455 @item @var{XX@dots{}}
39456 Memory contents; each byte is transmitted as a two-digit hexadecimal number.
39457 The reply may contain fewer addressable memory units than requested if the
39458 server was able to read only part of the region of memory.
39463 @item M @var{addr},@var{length}:@var{XX@dots{}}
39464 @cindex @samp{M} packet
39465 Write @var{length} addressable memory units starting at address @var{addr}
39466 (@pxref{addressable memory unit}). The data is given by @var{XX@dots{}}; each
39467 byte is transmitted as a two-digit hexadecimal number.
39474 for an error (this includes the case where only part of the data was
39479 @cindex @samp{p} packet
39480 Read the value of register @var{n}; @var{n} is in hex.
39481 @xref{read registers packet}, for a description of how the returned
39482 register value is encoded.
39486 @item @var{XX@dots{}}
39487 the register's value
39491 Indicating an unrecognized @var{query}.
39494 @item P @var{n@dots{}}=@var{r@dots{}}
39495 @anchor{write register packet}
39496 @cindex @samp{P} packet
39497 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
39498 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
39499 digits for each byte in the register (target byte order).
39509 @item q @var{name} @var{params}@dots{}
39510 @itemx Q @var{name} @var{params}@dots{}
39511 @cindex @samp{q} packet
39512 @cindex @samp{Q} packet
39513 General query (@samp{q}) and set (@samp{Q}). These packets are
39514 described fully in @ref{General Query Packets}.
39517 @cindex @samp{r} packet
39518 Reset the entire system.
39520 Don't use this packet; use the @samp{R} packet instead.
39523 @cindex @samp{R} packet
39524 Restart the program being debugged. The @var{XX}, while needed, is ignored.
39525 This packet is only available in extended mode (@pxref{extended mode}).
39527 The @samp{R} packet has no reply.
39529 @item s @r{[}@var{addr}@r{]}
39530 @cindex @samp{s} packet
39531 Single step, resuming at @var{addr}. If
39532 @var{addr} is omitted, resume at same address.
39534 This packet is deprecated for multi-threading support. @xref{vCont
39538 @xref{Stop Reply Packets}, for the reply specifications.
39540 @item S @var{sig}@r{[};@var{addr}@r{]}
39541 @anchor{step with signal packet}
39542 @cindex @samp{S} packet
39543 Step with signal. This is analogous to the @samp{C} packet, but
39544 requests a single-step, rather than a normal resumption of execution.
39546 This packet is deprecated for multi-threading support. @xref{vCont
39550 @xref{Stop Reply Packets}, for the reply specifications.
39552 @item t @var{addr}:@var{PP},@var{MM}
39553 @cindex @samp{t} packet
39554 Search backwards starting at address @var{addr} for a match with pattern
39555 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
39556 There must be at least 3 digits in @var{addr}.
39558 @item T @var{thread-id}
39559 @cindex @samp{T} packet
39560 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
39565 thread is still alive
39571 Packets starting with @samp{v} are identified by a multi-letter name,
39572 up to the first @samp{;} or @samp{?} (or the end of the packet).
39574 @item vAttach;@var{pid}
39575 @cindex @samp{vAttach} packet
39576 Attach to a new process with the specified process ID @var{pid}.
39577 The process ID is a
39578 hexadecimal integer identifying the process. In all-stop mode, all
39579 threads in the attached process are stopped; in non-stop mode, it may be
39580 attached without being stopped if that is supported by the target.
39582 @c In non-stop mode, on a successful vAttach, the stub should set the
39583 @c current thread to a thread of the newly-attached process. After
39584 @c attaching, GDB queries for the attached process's thread ID with qC.
39585 @c Also note that, from a user perspective, whether or not the
39586 @c target is stopped on attach in non-stop mode depends on whether you
39587 @c use the foreground or background version of the attach command, not
39588 @c on what vAttach does; GDB does the right thing with respect to either
39589 @c stopping or restarting threads.
39591 This packet is only available in extended mode (@pxref{extended mode}).
39597 @item @r{Any stop packet}
39598 for success in all-stop mode (@pxref{Stop Reply Packets})
39600 for success in non-stop mode (@pxref{Remote Non-Stop})
39603 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
39604 @cindex @samp{vCont} packet
39605 @anchor{vCont packet}
39606 Resume the inferior, specifying different actions for each thread.
39608 For each inferior thread, the leftmost action with a matching
39609 @var{thread-id} is applied. Threads that don't match any action
39610 remain in their current state. Thread IDs are specified using the
39611 syntax described in @ref{thread-id syntax}. If multiprocess
39612 extensions (@pxref{multiprocess extensions}) are supported, actions
39613 can be specified to match all threads in a process by using the
39614 @samp{p@var{pid}.-1} form of the @var{thread-id}. An action with no
39615 @var{thread-id} matches all threads. Specifying no actions is an
39618 Currently supported actions are:
39624 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
39628 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
39631 @item r @var{start},@var{end}
39632 Step once, and then keep stepping as long as the thread stops at
39633 addresses between @var{start} (inclusive) and @var{end} (exclusive).
39634 The remote stub reports a stop reply when either the thread goes out
39635 of the range or is stopped due to an unrelated reason, such as hitting
39636 a breakpoint. @xref{range stepping}.
39638 If the range is empty (@var{start} == @var{end}), then the action
39639 becomes equivalent to the @samp{s} action. In other words,
39640 single-step once, and report the stop (even if the stepped instruction
39641 jumps to @var{start}).
39643 (A stop reply may be sent at any point even if the PC is still within
39644 the stepping range; for example, it is valid to implement this packet
39645 in a degenerate way as a single instruction step operation.)
39649 The optional argument @var{addr} normally associated with the
39650 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
39651 not supported in @samp{vCont}.
39653 The @samp{t} action is only relevant in non-stop mode
39654 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
39655 A stop reply should be generated for any affected thread not already stopped.
39656 When a thread is stopped by means of a @samp{t} action,
39657 the corresponding stop reply should indicate that the thread has stopped with
39658 signal @samp{0}, regardless of whether the target uses some other signal
39659 as an implementation detail.
39661 The server must ignore @samp{c}, @samp{C}, @samp{s}, @samp{S}, and
39662 @samp{r} actions for threads that are already running. Conversely,
39663 the server must ignore @samp{t} actions for threads that are already
39666 @emph{Note:} In non-stop mode, a thread is considered running until
39667 @value{GDBN} acknowledges an asynchronous stop notification for it with
39668 the @samp{vStopped} packet (@pxref{Remote Non-Stop}).
39670 The stub must support @samp{vCont} if it reports support for
39671 multiprocess extensions (@pxref{multiprocess extensions}).
39674 @xref{Stop Reply Packets}, for the reply specifications.
39677 @cindex @samp{vCont?} packet
39678 Request a list of actions supported by the @samp{vCont} packet.
39682 @item vCont@r{[};@var{action}@dots{}@r{]}
39683 The @samp{vCont} packet is supported. Each @var{action} is a supported
39684 command in the @samp{vCont} packet.
39686 The @samp{vCont} packet is not supported.
39689 @anchor{vCtrlC packet}
39691 @cindex @samp{vCtrlC} packet
39692 Interrupt remote target as if a control-C was pressed on the remote
39693 terminal. This is the equivalent to reacting to the @code{^C}
39694 (@samp{\003}, the control-C character) character in all-stop mode
39695 while the target is running, except this works in non-stop mode.
39696 @xref{interrupting remote targets}, for more info on the all-stop
39707 @item vFile:@var{operation}:@var{parameter}@dots{}
39708 @cindex @samp{vFile} packet
39709 Perform a file operation on the target system. For details,
39710 see @ref{Host I/O Packets}.
39712 @item vFlashErase:@var{addr},@var{length}
39713 @cindex @samp{vFlashErase} packet
39714 Direct the stub to erase @var{length} bytes of flash starting at
39715 @var{addr}. The region may enclose any number of flash blocks, but
39716 its start and end must fall on block boundaries, as indicated by the
39717 flash block size appearing in the memory map (@pxref{Memory Map
39718 Format}). @value{GDBN} groups flash memory programming operations
39719 together, and sends a @samp{vFlashDone} request after each group; the
39720 stub is allowed to delay erase operation until the @samp{vFlashDone}
39721 packet is received.
39731 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
39732 @cindex @samp{vFlashWrite} packet
39733 Direct the stub to write data to flash address @var{addr}. The data
39734 is passed in binary form using the same encoding as for the @samp{X}
39735 packet (@pxref{Binary Data}). The memory ranges specified by
39736 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
39737 not overlap, and must appear in order of increasing addresses
39738 (although @samp{vFlashErase} packets for higher addresses may already
39739 have been received; the ordering is guaranteed only between
39740 @samp{vFlashWrite} packets). If a packet writes to an address that was
39741 neither erased by a preceding @samp{vFlashErase} packet nor by some other
39742 target-specific method, the results are unpredictable.
39750 for vFlashWrite addressing non-flash memory
39756 @cindex @samp{vFlashDone} packet
39757 Indicate to the stub that flash programming operation is finished.
39758 The stub is permitted to delay or batch the effects of a group of
39759 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
39760 @samp{vFlashDone} packet is received. The contents of the affected
39761 regions of flash memory are unpredictable until the @samp{vFlashDone}
39762 request is completed.
39764 @item vKill;@var{pid}
39765 @cindex @samp{vKill} packet
39766 @anchor{vKill packet}
39767 Kill the process with the specified process ID @var{pid}, which is a
39768 hexadecimal integer identifying the process. This packet is used in
39769 preference to @samp{k} when multiprocess protocol extensions are
39770 supported; see @ref{multiprocess extensions}.
39780 @item vMustReplyEmpty
39781 @cindex @samp{vMustReplyEmpty} packet
39782 The correct reply to an unknown @samp{v} packet is to return the empty
39783 string, however, some older versions of @command{gdbserver} would
39784 incorrectly return @samp{OK} for unknown @samp{v} packets.
39786 The @samp{vMustReplyEmpty} is used as a feature test to check how
39787 @command{gdbserver} handles unknown packets, it is important that this
39788 packet be handled in the same way as other unknown @samp{v} packets.
39789 If this packet is handled differently to other unknown @samp{v}
39790 packets then it is possible that @value{GDBN} may run into problems in
39791 other areas, specifically around use of @samp{vFile:setfs:}.
39793 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
39794 @cindex @samp{vRun} packet
39795 Run the program @var{filename}, passing it each @var{argument} on its
39796 command line. The file and arguments are hex-encoded strings. If
39797 @var{filename} is an empty string, the stub may use a default program
39798 (e.g.@: the last program run). The program is created in the stopped
39801 @c FIXME: What about non-stop mode?
39803 This packet is only available in extended mode (@pxref{extended mode}).
39809 @item @r{Any stop packet}
39810 for success (@pxref{Stop Reply Packets})
39814 @cindex @samp{vStopped} packet
39815 @xref{Notification Packets}.
39817 @item X @var{addr},@var{length}:@var{XX@dots{}}
39819 @cindex @samp{X} packet
39820 Write data to memory, where the data is transmitted in binary.
39821 Memory is specified by its address @var{addr} and number of addressable memory
39822 units @var{length} (@pxref{addressable memory unit});
39823 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
39833 @item z @var{type},@var{addr},@var{kind}
39834 @itemx Z @var{type},@var{addr},@var{kind}
39835 @anchor{insert breakpoint or watchpoint packet}
39836 @cindex @samp{z} packet
39837 @cindex @samp{Z} packets
39838 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
39839 watchpoint starting at address @var{address} of kind @var{kind}.
39841 Each breakpoint and watchpoint packet @var{type} is documented
39844 @emph{Implementation notes: A remote target shall return an empty string
39845 for an unrecognized breakpoint or watchpoint packet @var{type}. A
39846 remote target shall support either both or neither of a given
39847 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
39848 avoid potential problems with duplicate packets, the operations should
39849 be implemented in an idempotent way.}
39851 @item z0,@var{addr},@var{kind}
39852 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
39853 @cindex @samp{z0} packet
39854 @cindex @samp{Z0} packet
39855 Insert (@samp{Z0}) or remove (@samp{z0}) a software breakpoint at address
39856 @var{addr} of type @var{kind}.
39858 A software breakpoint is implemented by replacing the instruction at
39859 @var{addr} with a software breakpoint or trap instruction. The
39860 @var{kind} is target-specific and typically indicates the size of the
39861 breakpoint in bytes that should be inserted. E.g., the @sc{arm} and
39862 @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
39863 architectures have additional meanings for @var{kind}
39864 (@pxref{Architecture-Specific Protocol Details}); if no
39865 architecture-specific value is being used, it should be @samp{0}.
39866 @var{kind} is hex-encoded. @var{cond_list} is an optional list of
39867 conditional expressions in bytecode form that should be evaluated on
39868 the target's side. These are the conditions that should be taken into
39869 consideration when deciding if the breakpoint trigger should be
39870 reported back to @value{GDBN}.
39872 See also the @samp{swbreak} stop reason (@pxref{swbreak stop reason})
39873 for how to best report a software breakpoint event to @value{GDBN}.
39875 The @var{cond_list} parameter is comprised of a series of expressions,
39876 concatenated without separators. Each expression has the following form:
39880 @item X @var{len},@var{expr}
39881 @var{len} is the length of the bytecode expression and @var{expr} is the
39882 actual conditional expression in bytecode form.
39886 The optional @var{cmd_list} parameter introduces commands that may be
39887 run on the target, rather than being reported back to @value{GDBN}.
39888 The parameter starts with a numeric flag @var{persist}; if the flag is
39889 nonzero, then the breakpoint may remain active and the commands
39890 continue to be run even when @value{GDBN} disconnects from the target.
39891 Following this flag is a series of expressions concatenated with no
39892 separators. Each expression has the following form:
39896 @item X @var{len},@var{expr}
39897 @var{len} is the length of the bytecode expression and @var{expr} is the
39898 actual commands expression in bytecode form.
39902 @emph{Implementation note: It is possible for a target to copy or move
39903 code that contains software breakpoints (e.g., when implementing
39904 overlays). The behavior of this packet, in the presence of such a
39905 target, is not defined.}
39917 @item z1,@var{addr},@var{kind}
39918 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
39919 @cindex @samp{z1} packet
39920 @cindex @samp{Z1} packet
39921 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
39922 address @var{addr}.
39924 A hardware breakpoint is implemented using a mechanism that is not
39925 dependent on being able to modify the target's memory. The
39926 @var{kind}, @var{cond_list}, and @var{cmd_list} arguments have the
39927 same meaning as in @samp{Z0} packets.
39929 @emph{Implementation note: A hardware breakpoint is not affected by code
39942 @item z2,@var{addr},@var{kind}
39943 @itemx Z2,@var{addr},@var{kind}
39944 @cindex @samp{z2} packet
39945 @cindex @samp{Z2} packet
39946 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
39947 The number of bytes to watch is specified by @var{kind}.
39959 @item z3,@var{addr},@var{kind}
39960 @itemx Z3,@var{addr},@var{kind}
39961 @cindex @samp{z3} packet
39962 @cindex @samp{Z3} packet
39963 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
39964 The number of bytes to watch is specified by @var{kind}.
39976 @item z4,@var{addr},@var{kind}
39977 @itemx Z4,@var{addr},@var{kind}
39978 @cindex @samp{z4} packet
39979 @cindex @samp{Z4} packet
39980 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
39981 The number of bytes to watch is specified by @var{kind}.
39995 @node Stop Reply Packets
39996 @section Stop Reply Packets
39997 @cindex stop reply packets
39999 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
40000 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
40001 receive any of the below as a reply. Except for @samp{?}
40002 and @samp{vStopped}, that reply is only returned
40003 when the target halts. In the below the exact meaning of @dfn{signal
40004 number} is defined by the header @file{include/gdb/signals.h} in the
40005 @value{GDBN} source code.
40007 In non-stop mode, the server will simply reply @samp{OK} to commands
40008 such as @samp{vCont}; any stop will be the subject of a future
40009 notification. @xref{Remote Non-Stop}.
40011 As in the description of request packets, we include spaces in the
40012 reply templates for clarity; these are not part of the reply packet's
40013 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
40019 The program received signal number @var{AA} (a two-digit hexadecimal
40020 number). This is equivalent to a @samp{T} response with no
40021 @var{n}:@var{r} pairs.
40023 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
40024 @cindex @samp{T} packet reply
40025 The program received signal number @var{AA} (a two-digit hexadecimal
40026 number). This is equivalent to an @samp{S} response, except that the
40027 @samp{@var{n}:@var{r}} pairs can carry values of important registers
40028 and other information directly in the stop reply packet, reducing
40029 round-trip latency. Single-step and breakpoint traps are reported
40030 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
40034 If @var{n} is a hexadecimal number, it is a register number, and the
40035 corresponding @var{r} gives that register's value. The data @var{r} is a
40036 series of bytes in target byte order, with each byte given by a
40037 two-digit hex number.
40040 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
40041 the stopped thread, as specified in @ref{thread-id syntax}.
40044 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
40045 the core on which the stop event was detected.
40048 If @var{n} is a recognized @dfn{stop reason}, it describes a more
40049 specific event that stopped the target. The currently defined stop
40050 reasons are listed below. The @var{aa} should be @samp{05}, the trap
40051 signal. At most one stop reason should be present.
40054 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
40055 and go on to the next; this allows us to extend the protocol in the
40059 The currently defined stop reasons are:
40065 The packet indicates a watchpoint hit, and @var{r} is the data address, in
40068 @item syscall_entry
40069 @itemx syscall_return
40070 The packet indicates a syscall entry or return, and @var{r} is the
40071 syscall number, in hex.
40073 @cindex shared library events, remote reply
40075 The packet indicates that the loaded libraries have changed.
40076 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
40077 list of loaded libraries. The @var{r} part is ignored.
40079 @cindex replay log events, remote reply
40081 The packet indicates that the target cannot continue replaying
40082 logged execution events, because it has reached the end (or the
40083 beginning when executing backward) of the log. The value of @var{r}
40084 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
40085 for more information.
40088 @anchor{swbreak stop reason}
40089 The packet indicates a software breakpoint instruction was executed,
40090 irrespective of whether it was @value{GDBN} that planted the
40091 breakpoint or the breakpoint is hardcoded in the program. The @var{r}
40092 part must be left empty.
40094 On some architectures, such as x86, at the architecture level, when a
40095 breakpoint instruction executes the program counter points at the
40096 breakpoint address plus an offset. On such targets, the stub is
40097 responsible for adjusting the PC to point back at the breakpoint
40100 This packet should not be sent by default; older @value{GDBN} versions
40101 did not support it. @value{GDBN} requests it, by supplying an
40102 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
40103 remote stub must also supply the appropriate @samp{qSupported} feature
40104 indicating support.
40106 This packet is required for correct non-stop mode operation.
40109 The packet indicates the target stopped for a hardware breakpoint.
40110 The @var{r} part must be left empty.
40112 The same remarks about @samp{qSupported} and non-stop mode above
40115 @cindex fork events, remote reply
40117 The packet indicates that @code{fork} was called, and @var{r}
40118 is the thread ID of the new child process. Refer to
40119 @ref{thread-id syntax} for the format of the @var{thread-id}
40120 field. This packet is only applicable to targets that support
40123 This packet should not be sent by default; older @value{GDBN} versions
40124 did not support it. @value{GDBN} requests it, by supplying an
40125 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
40126 remote stub must also supply the appropriate @samp{qSupported} feature
40127 indicating support.
40129 @cindex vfork events, remote reply
40131 The packet indicates that @code{vfork} was called, and @var{r}
40132 is the thread ID of the new child process. Refer to
40133 @ref{thread-id syntax} for the format of the @var{thread-id}
40134 field. This packet is only applicable to targets that support
40137 This packet should not be sent by default; older @value{GDBN} versions
40138 did not support it. @value{GDBN} requests it, by supplying an
40139 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
40140 remote stub must also supply the appropriate @samp{qSupported} feature
40141 indicating support.
40143 @cindex vforkdone events, remote reply
40145 The packet indicates that a child process created by a vfork
40146 has either called @code{exec} or terminated, so that the
40147 address spaces of the parent and child process are no longer
40148 shared. The @var{r} part is ignored. This packet is only
40149 applicable to targets that support vforkdone events.
40151 This packet should not be sent by default; older @value{GDBN} versions
40152 did not support it. @value{GDBN} requests it, by supplying an
40153 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
40154 remote stub must also supply the appropriate @samp{qSupported} feature
40155 indicating support.
40157 @cindex exec events, remote reply
40159 The packet indicates that @code{execve} was called, and @var{r}
40160 is the absolute pathname of the file that was executed, in hex.
40161 This packet is only applicable to targets that support exec events.
40163 This packet should not be sent by default; older @value{GDBN} versions
40164 did not support it. @value{GDBN} requests it, by supplying an
40165 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
40166 remote stub must also supply the appropriate @samp{qSupported} feature
40167 indicating support.
40169 @cindex thread create event, remote reply
40170 @anchor{thread create event}
40172 The packet indicates that the thread was just created. The new thread
40173 is stopped until @value{GDBN} sets it running with a resumption packet
40174 (@pxref{vCont packet}). This packet should not be sent by default;
40175 @value{GDBN} requests it with the @ref{QThreadEvents} packet. See
40176 also the @samp{w} (@pxref{thread exit event}) remote reply below. The
40177 @var{r} part is ignored.
40182 @itemx W @var{AA} ; process:@var{pid}
40183 The process exited, and @var{AA} is the exit status. This is only
40184 applicable to certain targets.
40186 The second form of the response, including the process ID of the
40187 exited process, can be used only when @value{GDBN} has reported
40188 support for multiprocess protocol extensions; see @ref{multiprocess
40189 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
40193 @itemx X @var{AA} ; process:@var{pid}
40194 The process terminated with signal @var{AA}.
40196 The second form of the response, including the process ID of the
40197 terminated process, can be used only when @value{GDBN} has reported
40198 support for multiprocess protocol extensions; see @ref{multiprocess
40199 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
40202 @anchor{thread exit event}
40203 @cindex thread exit event, remote reply
40204 @item w @var{AA} ; @var{tid}
40206 The thread exited, and @var{AA} is the exit status. This response
40207 should not be sent by default; @value{GDBN} requests it with the
40208 @ref{QThreadEvents} packet. See also @ref{thread create event} above.
40209 @var{AA} is formatted as a big-endian hex string.
40212 There are no resumed threads left in the target. In other words, even
40213 though the process is alive, the last resumed thread has exited. For
40214 example, say the target process has two threads: thread 1 and thread
40215 2. The client leaves thread 1 stopped, and resumes thread 2, which
40216 subsequently exits. At this point, even though the process is still
40217 alive, and thus no @samp{W} stop reply is sent, no thread is actually
40218 executing either. The @samp{N} stop reply thus informs the client
40219 that it can stop waiting for stop replies. This packet should not be
40220 sent by default; older @value{GDBN} versions did not support it.
40221 @value{GDBN} requests it, by supplying an appropriate
40222 @samp{qSupported} feature (@pxref{qSupported}). The remote stub must
40223 also supply the appropriate @samp{qSupported} feature indicating
40226 @item O @var{XX}@dots{}
40227 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
40228 written as the program's console output. This can happen at any time
40229 while the program is running and the debugger should continue to wait
40230 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
40232 @item F @var{call-id},@var{parameter}@dots{}
40233 @var{call-id} is the identifier which says which host system call should
40234 be called. This is just the name of the function. Translation into the
40235 correct system call is only applicable as it's defined in @value{GDBN}.
40236 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
40239 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
40240 this very system call.
40242 The target replies with this packet when it expects @value{GDBN} to
40243 call a host system call on behalf of the target. @value{GDBN} replies
40244 with an appropriate @samp{F} packet and keeps up waiting for the next
40245 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
40246 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
40247 Protocol Extension}, for more details.
40251 @node General Query Packets
40252 @section General Query Packets
40253 @cindex remote query requests
40255 Packets starting with @samp{q} are @dfn{general query packets};
40256 packets starting with @samp{Q} are @dfn{general set packets}. General
40257 query and set packets are a semi-unified form for retrieving and
40258 sending information to and from the stub.
40260 The initial letter of a query or set packet is followed by a name
40261 indicating what sort of thing the packet applies to. For example,
40262 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
40263 definitions with the stub. These packet names follow some
40268 The name must not contain commas, colons or semicolons.
40270 Most @value{GDBN} query and set packets have a leading upper case
40273 The names of custom vendor packets should use a company prefix, in
40274 lower case, followed by a period. For example, packets designed at
40275 the Acme Corporation might begin with @samp{qacme.foo} (for querying
40276 foos) or @samp{Qacme.bar} (for setting bars).
40279 The name of a query or set packet should be separated from any
40280 parameters by a @samp{:}; the parameters themselves should be
40281 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
40282 full packet name, and check for a separator or the end of the packet,
40283 in case two packet names share a common prefix. New packets should not begin
40284 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
40285 packets predate these conventions, and have arguments without any terminator
40286 for the packet name; we suspect they are in widespread use in places that
40287 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
40288 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
40291 Like the descriptions of the other packets, each description here
40292 has a template showing the packet's overall syntax, followed by an
40293 explanation of the packet's meaning. We include spaces in some of the
40294 templates for clarity; these are not part of the packet's syntax. No
40295 @value{GDBN} packet uses spaces to separate its components.
40297 Here are the currently defined query and set packets:
40303 Turn on or off the agent as a helper to perform some debugging operations
40304 delegated from @value{GDBN} (@pxref{Control Agent}).
40306 @item QAllow:@var{op}:@var{val}@dots{}
40307 @cindex @samp{QAllow} packet
40308 Specify which operations @value{GDBN} expects to request of the
40309 target, as a semicolon-separated list of operation name and value
40310 pairs. Possible values for @var{op} include @samp{WriteReg},
40311 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
40312 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
40313 indicating that @value{GDBN} will not request the operation, or 1,
40314 indicating that it may. (The target can then use this to set up its
40315 own internals optimally, for instance if the debugger never expects to
40316 insert breakpoints, it may not need to install its own trap handler.)
40319 @cindex current thread, remote request
40320 @cindex @samp{qC} packet
40321 Return the current thread ID.
40325 @item QC @var{thread-id}
40326 Where @var{thread-id} is a thread ID as documented in
40327 @ref{thread-id syntax}.
40328 @item @r{(anything else)}
40329 Any other reply implies the old thread ID.
40332 @item qCRC:@var{addr},@var{length}
40333 @cindex CRC of memory block, remote request
40334 @cindex @samp{qCRC} packet
40335 @anchor{qCRC packet}
40336 Compute the CRC checksum of a block of memory using CRC-32 defined in
40337 IEEE 802.3. The CRC is computed byte at a time, taking the most
40338 significant bit of each byte first. The initial pattern code
40339 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
40341 @emph{Note:} This is the same CRC used in validating separate debug
40342 files (@pxref{Separate Debug Files, , Debugging Information in Separate
40343 Files}). However the algorithm is slightly different. When validating
40344 separate debug files, the CRC is computed taking the @emph{least}
40345 significant bit of each byte first, and the final result is inverted to
40346 detect trailing zeros.
40351 An error (such as memory fault)
40352 @item C @var{crc32}
40353 The specified memory region's checksum is @var{crc32}.
40356 @item QDisableRandomization:@var{value}
40357 @cindex disable address space randomization, remote request
40358 @cindex @samp{QDisableRandomization} packet
40359 Some target operating systems will randomize the virtual address space
40360 of the inferior process as a security feature, but provide a feature
40361 to disable such randomization, e.g.@: to allow for a more deterministic
40362 debugging experience. On such systems, this packet with a @var{value}
40363 of 1 directs the target to disable address space randomization for
40364 processes subsequently started via @samp{vRun} packets, while a packet
40365 with a @var{value} of 0 tells the target to enable address space
40368 This packet is only available in extended mode (@pxref{extended mode}).
40373 The request succeeded.
40376 An error occurred. The error number @var{nn} is given as hex digits.
40379 An empty reply indicates that @samp{QDisableRandomization} is not supported
40383 This packet is not probed by default; the remote stub must request it,
40384 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40385 This should only be done on targets that actually support disabling
40386 address space randomization.
40388 @item QStartupWithShell:@var{value}
40389 @cindex startup with shell, remote request
40390 @cindex @samp{QStartupWithShell} packet
40391 On UNIX-like targets, it is possible to start the inferior using a
40392 shell program. This is the default behavior on both @value{GDBN} and
40393 @command{gdbserver} (@pxref{set startup-with-shell}). This packet is
40394 used to inform @command{gdbserver} whether it should start the
40395 inferior using a shell or not.
40397 If @var{value} is @samp{0}, @command{gdbserver} will not use a shell
40398 to start the inferior. If @var{value} is @samp{1},
40399 @command{gdbserver} will use a shell to start the inferior. All other
40400 values are considered an error.
40402 This packet is only available in extended mode (@pxref{extended
40408 The request succeeded.
40411 An error occurred. The error number @var{nn} is given as hex digits.
40414 This packet is not probed by default; the remote stub must request it,
40415 by supplying an appropriate @samp{qSupported} response
40416 (@pxref{qSupported}). This should only be done on targets that
40417 actually support starting the inferior using a shell.
40419 Use of this packet is controlled by the @code{set startup-with-shell}
40420 command; @pxref{set startup-with-shell}.
40422 @item QEnvironmentHexEncoded:@var{hex-value}
40423 @anchor{QEnvironmentHexEncoded}
40424 @cindex set environment variable, remote request
40425 @cindex @samp{QEnvironmentHexEncoded} packet
40426 On UNIX-like targets, it is possible to set environment variables that
40427 will be passed to the inferior during the startup process. This
40428 packet is used to inform @command{gdbserver} of an environment
40429 variable that has been defined by the user on @value{GDBN} (@pxref{set
40432 The packet is composed by @var{hex-value}, an hex encoded
40433 representation of the @var{name=value} format representing an
40434 environment variable. The name of the environment variable is
40435 represented by @var{name}, and the value to be assigned to the
40436 environment variable is represented by @var{value}. If the variable
40437 has no value (i.e., the value is @code{null}), then @var{value} will
40440 This packet is only available in extended mode (@pxref{extended
40446 The request succeeded.
40449 This packet is not probed by default; the remote stub must request it,
40450 by supplying an appropriate @samp{qSupported} response
40451 (@pxref{qSupported}). This should only be done on targets that
40452 actually support passing environment variables to the starting
40455 This packet is related to the @code{set environment} command;
40456 @pxref{set environment}.
40458 @item QEnvironmentUnset:@var{hex-value}
40459 @anchor{QEnvironmentUnset}
40460 @cindex unset environment variable, remote request
40461 @cindex @samp{QEnvironmentUnset} packet
40462 On UNIX-like targets, it is possible to unset environment variables
40463 before starting the inferior in the remote target. This packet is
40464 used to inform @command{gdbserver} of an environment variable that has
40465 been unset by the user on @value{GDBN} (@pxref{unset environment}).
40467 The packet is composed by @var{hex-value}, an hex encoded
40468 representation of the name of the environment variable to be unset.
40470 This packet is only available in extended mode (@pxref{extended
40476 The request succeeded.
40479 This packet is not probed by default; the remote stub must request it,
40480 by supplying an appropriate @samp{qSupported} response
40481 (@pxref{qSupported}). This should only be done on targets that
40482 actually support passing environment variables to the starting
40485 This packet is related to the @code{unset environment} command;
40486 @pxref{unset environment}.
40488 @item QEnvironmentReset
40489 @anchor{QEnvironmentReset}
40490 @cindex reset environment, remote request
40491 @cindex @samp{QEnvironmentReset} packet
40492 On UNIX-like targets, this packet is used to reset the state of
40493 environment variables in the remote target before starting the
40494 inferior. In this context, reset means unsetting all environment
40495 variables that were previously set by the user (i.e., were not
40496 initially present in the environment). It is sent to
40497 @command{gdbserver} before the @samp{QEnvironmentHexEncoded}
40498 (@pxref{QEnvironmentHexEncoded}) and the @samp{QEnvironmentUnset}
40499 (@pxref{QEnvironmentUnset}) packets.
40501 This packet is only available in extended mode (@pxref{extended
40507 The request succeeded.
40510 This packet is not probed by default; the remote stub must request it,
40511 by supplying an appropriate @samp{qSupported} response
40512 (@pxref{qSupported}). This should only be done on targets that
40513 actually support passing environment variables to the starting
40516 @item QSetWorkingDir:@r{[}@var{directory}@r{]}
40517 @anchor{QSetWorkingDir packet}
40518 @cindex set working directory, remote request
40519 @cindex @samp{QSetWorkingDir} packet
40520 This packet is used to inform the remote server of the intended
40521 current working directory for programs that are going to be executed.
40523 The packet is composed by @var{directory}, an hex encoded
40524 representation of the directory that the remote inferior will use as
40525 its current working directory. If @var{directory} is an empty string,
40526 the remote server should reset the inferior's current working
40527 directory to its original, empty value.
40529 This packet is only available in extended mode (@pxref{extended
40535 The request succeeded.
40539 @itemx qsThreadInfo
40540 @cindex list active threads, remote request
40541 @cindex @samp{qfThreadInfo} packet
40542 @cindex @samp{qsThreadInfo} packet
40543 Obtain a list of all active thread IDs from the target (OS). Since there
40544 may be too many active threads to fit into one reply packet, this query
40545 works iteratively: it may require more than one query/reply sequence to
40546 obtain the entire list of threads. The first query of the sequence will
40547 be the @samp{qfThreadInfo} query; subsequent queries in the
40548 sequence will be the @samp{qsThreadInfo} query.
40550 NOTE: This packet replaces the @samp{qL} query (see below).
40554 @item m @var{thread-id}
40556 @item m @var{thread-id},@var{thread-id}@dots{}
40557 a comma-separated list of thread IDs
40559 (lower case letter @samp{L}) denotes end of list.
40562 In response to each query, the target will reply with a list of one or
40563 more thread IDs, separated by commas.
40564 @value{GDBN} will respond to each reply with a request for more thread
40565 ids (using the @samp{qs} form of the query), until the target responds
40566 with @samp{l} (lower-case ell, for @dfn{last}).
40567 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
40570 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
40571 initial connection with the remote target, and the very first thread ID
40572 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
40573 message. Therefore, the stub should ensure that the first thread ID in
40574 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
40576 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
40577 @cindex get thread-local storage address, remote request
40578 @cindex @samp{qGetTLSAddr} packet
40579 Fetch the address associated with thread local storage specified
40580 by @var{thread-id}, @var{offset}, and @var{lm}.
40582 @var{thread-id} is the thread ID associated with the
40583 thread for which to fetch the TLS address. @xref{thread-id syntax}.
40585 @var{offset} is the (big endian, hex encoded) offset associated with the
40586 thread local variable. (This offset is obtained from the debug
40587 information associated with the variable.)
40589 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
40590 load module associated with the thread local storage. For example,
40591 a @sc{gnu}/Linux system will pass the link map address of the shared
40592 object associated with the thread local storage under consideration.
40593 Other operating environments may choose to represent the load module
40594 differently, so the precise meaning of this parameter will vary.
40598 @item @var{XX}@dots{}
40599 Hex encoded (big endian) bytes representing the address of the thread
40600 local storage requested.
40603 An error occurred. The error number @var{nn} is given as hex digits.
40606 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
40609 @item qGetTIBAddr:@var{thread-id}
40610 @cindex get thread information block address
40611 @cindex @samp{qGetTIBAddr} packet
40612 Fetch address of the Windows OS specific Thread Information Block.
40614 @var{thread-id} is the thread ID associated with the thread.
40618 @item @var{XX}@dots{}
40619 Hex encoded (big endian) bytes representing the linear address of the
40620 thread information block.
40623 An error occured. This means that either the thread was not found, or the
40624 address could not be retrieved.
40627 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
40630 @item qL @var{startflag} @var{threadcount} @var{nextthread}
40631 Obtain thread information from RTOS. Where: @var{startflag} (one hex
40632 digit) is one to indicate the first query and zero to indicate a
40633 subsequent query; @var{threadcount} (two hex digits) is the maximum
40634 number of threads the response packet can contain; and @var{nextthread}
40635 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
40636 returned in the response as @var{argthread}.
40638 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
40642 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
40643 Where: @var{count} (two hex digits) is the number of threads being
40644 returned; @var{done} (one hex digit) is zero to indicate more threads
40645 and one indicates no further threads; @var{argthreadid} (eight hex
40646 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
40647 is a sequence of thread IDs, @var{threadid} (eight hex
40648 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
40652 @cindex section offsets, remote request
40653 @cindex @samp{qOffsets} packet
40654 Get section offsets that the target used when relocating the downloaded
40659 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
40660 Relocate the @code{Text} section by @var{xxx} from its original address.
40661 Relocate the @code{Data} section by @var{yyy} from its original address.
40662 If the object file format provides segment information (e.g.@: @sc{elf}
40663 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
40664 segments by the supplied offsets.
40666 @emph{Note: while a @code{Bss} offset may be included in the response,
40667 @value{GDBN} ignores this and instead applies the @code{Data} offset
40668 to the @code{Bss} section.}
40670 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
40671 Relocate the first segment of the object file, which conventionally
40672 contains program code, to a starting address of @var{xxx}. If
40673 @samp{DataSeg} is specified, relocate the second segment, which
40674 conventionally contains modifiable data, to a starting address of
40675 @var{yyy}. @value{GDBN} will report an error if the object file
40676 does not contain segment information, or does not contain at least
40677 as many segments as mentioned in the reply. Extra segments are
40678 kept at fixed offsets relative to the last relocated segment.
40681 @item qP @var{mode} @var{thread-id}
40682 @cindex thread information, remote request
40683 @cindex @samp{qP} packet
40684 Returns information on @var{thread-id}. Where: @var{mode} is a hex
40685 encoded 32 bit mode; @var{thread-id} is a thread ID
40686 (@pxref{thread-id syntax}).
40688 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
40691 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
40695 @cindex non-stop mode, remote request
40696 @cindex @samp{QNonStop} packet
40698 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
40699 @xref{Remote Non-Stop}, for more information.
40704 The request succeeded.
40707 An error occurred. The error number @var{nn} is given as hex digits.
40710 An empty reply indicates that @samp{QNonStop} is not supported by
40714 This packet is not probed by default; the remote stub must request it,
40715 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40716 Use of this packet is controlled by the @code{set non-stop} command;
40717 @pxref{Non-Stop Mode}.
40719 @item QCatchSyscalls:1 @r{[};@var{sysno}@r{]}@dots{}
40720 @itemx QCatchSyscalls:0
40721 @cindex catch syscalls from inferior, remote request
40722 @cindex @samp{QCatchSyscalls} packet
40723 @anchor{QCatchSyscalls}
40724 Enable (@samp{QCatchSyscalls:1}) or disable (@samp{QCatchSyscalls:0})
40725 catching syscalls from the inferior process.
40727 For @samp{QCatchSyscalls:1}, each listed syscall @var{sysno} (encoded
40728 in hex) should be reported to @value{GDBN}. If no syscall @var{sysno}
40729 is listed, every system call should be reported.
40731 Note that if a syscall not in the list is reported, @value{GDBN} will
40732 still filter the event according to its own list from all corresponding
40733 @code{catch syscall} commands. However, it is more efficient to only
40734 report the requested syscalls.
40736 Multiple @samp{QCatchSyscalls:1} packets do not combine; any earlier
40737 @samp{QCatchSyscalls:1} list is completely replaced by the new list.
40739 If the inferior process execs, the state of @samp{QCatchSyscalls} is
40740 kept for the new process too. On targets where exec may affect syscall
40741 numbers, for example with exec between 32 and 64-bit processes, the
40742 client should send a new packet with the new syscall list.
40747 The request succeeded.
40750 An error occurred. @var{nn} are hex digits.
40753 An empty reply indicates that @samp{QCatchSyscalls} is not supported by
40757 Use of this packet is controlled by the @code{set remote catch-syscalls}
40758 command (@pxref{Remote Configuration, set remote catch-syscalls}).
40759 This packet is not probed by default; the remote stub must request it,
40760 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40762 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
40763 @cindex pass signals to inferior, remote request
40764 @cindex @samp{QPassSignals} packet
40765 @anchor{QPassSignals}
40766 Each listed @var{signal} should be passed directly to the inferior process.
40767 Signals are numbered identically to continue packets and stop replies
40768 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
40769 strictly greater than the previous item. These signals do not need to stop
40770 the inferior, or be reported to @value{GDBN}. All other signals should be
40771 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
40772 combine; any earlier @samp{QPassSignals} list is completely replaced by the
40773 new list. This packet improves performance when using @samp{handle
40774 @var{signal} nostop noprint pass}.
40779 The request succeeded.
40782 An error occurred. The error number @var{nn} is given as hex digits.
40785 An empty reply indicates that @samp{QPassSignals} is not supported by
40789 Use of this packet is controlled by the @code{set remote pass-signals}
40790 command (@pxref{Remote Configuration, set remote pass-signals}).
40791 This packet is not probed by default; the remote stub must request it,
40792 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40794 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
40795 @cindex signals the inferior may see, remote request
40796 @cindex @samp{QProgramSignals} packet
40797 @anchor{QProgramSignals}
40798 Each listed @var{signal} may be delivered to the inferior process.
40799 Others should be silently discarded.
40801 In some cases, the remote stub may need to decide whether to deliver a
40802 signal to the program or not without @value{GDBN} involvement. One
40803 example of that is while detaching --- the program's threads may have
40804 stopped for signals that haven't yet had a chance of being reported to
40805 @value{GDBN}, and so the remote stub can use the signal list specified
40806 by this packet to know whether to deliver or ignore those pending
40809 This does not influence whether to deliver a signal as requested by a
40810 resumption packet (@pxref{vCont packet}).
40812 Signals are numbered identically to continue packets and stop replies
40813 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
40814 strictly greater than the previous item. Multiple
40815 @samp{QProgramSignals} packets do not combine; any earlier
40816 @samp{QProgramSignals} list is completely replaced by the new list.
40821 The request succeeded.
40824 An error occurred. The error number @var{nn} is given as hex digits.
40827 An empty reply indicates that @samp{QProgramSignals} is not supported
40831 Use of this packet is controlled by the @code{set remote program-signals}
40832 command (@pxref{Remote Configuration, set remote program-signals}).
40833 This packet is not probed by default; the remote stub must request it,
40834 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40836 @anchor{QThreadEvents}
40837 @item QThreadEvents:1
40838 @itemx QThreadEvents:0
40839 @cindex thread create/exit events, remote request
40840 @cindex @samp{QThreadEvents} packet
40842 Enable (@samp{QThreadEvents:1}) or disable (@samp{QThreadEvents:0})
40843 reporting of thread create and exit events. @xref{thread create
40844 event}, for the reply specifications. For example, this is used in
40845 non-stop mode when @value{GDBN} stops a set of threads and
40846 synchronously waits for the their corresponding stop replies. Without
40847 exit events, if one of the threads exits, @value{GDBN} would hang
40848 forever not knowing that it should no longer expect a stop for that
40849 same thread. @value{GDBN} does not enable this feature unless the
40850 stub reports that it supports it by including @samp{QThreadEvents+} in
40851 its @samp{qSupported} reply.
40856 The request succeeded.
40859 An error occurred. The error number @var{nn} is given as hex digits.
40862 An empty reply indicates that @samp{QThreadEvents} is not supported by
40866 Use of this packet is controlled by the @code{set remote thread-events}
40867 command (@pxref{Remote Configuration, set remote thread-events}).
40869 @item qRcmd,@var{command}
40870 @cindex execute remote command, remote request
40871 @cindex @samp{qRcmd} packet
40872 @var{command} (hex encoded) is passed to the local interpreter for
40873 execution. Invalid commands should be reported using the output
40874 string. Before the final result packet, the target may also respond
40875 with a number of intermediate @samp{O@var{output}} console output
40876 packets. @emph{Implementors should note that providing access to a
40877 stubs's interpreter may have security implications}.
40882 A command response with no output.
40884 A command response with the hex encoded output string @var{OUTPUT}.
40886 Indicate a badly formed request.
40888 An empty reply indicates that @samp{qRcmd} is not recognized.
40891 (Note that the @code{qRcmd} packet's name is separated from the
40892 command by a @samp{,}, not a @samp{:}, contrary to the naming
40893 conventions above. Please don't use this packet as a model for new
40896 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
40897 @cindex searching memory, in remote debugging
40899 @cindex @samp{qSearch:memory} packet
40901 @cindex @samp{qSearch memory} packet
40902 @anchor{qSearch memory}
40903 Search @var{length} bytes at @var{address} for @var{search-pattern}.
40904 Both @var{address} and @var{length} are encoded in hex;
40905 @var{search-pattern} is a sequence of bytes, also hex encoded.
40910 The pattern was not found.
40912 The pattern was found at @var{address}.
40914 A badly formed request or an error was encountered while searching memory.
40916 An empty reply indicates that @samp{qSearch:memory} is not recognized.
40919 @item QStartNoAckMode
40920 @cindex @samp{QStartNoAckMode} packet
40921 @anchor{QStartNoAckMode}
40922 Request that the remote stub disable the normal @samp{+}/@samp{-}
40923 protocol acknowledgments (@pxref{Packet Acknowledgment}).
40928 The stub has switched to no-acknowledgment mode.
40929 @value{GDBN} acknowledges this response,
40930 but neither the stub nor @value{GDBN} shall send or expect further
40931 @samp{+}/@samp{-} acknowledgments in the current connection.
40933 An empty reply indicates that the stub does not support no-acknowledgment mode.
40936 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
40937 @cindex supported packets, remote query
40938 @cindex features of the remote protocol
40939 @cindex @samp{qSupported} packet
40940 @anchor{qSupported}
40941 Tell the remote stub about features supported by @value{GDBN}, and
40942 query the stub for features it supports. This packet allows
40943 @value{GDBN} and the remote stub to take advantage of each others'
40944 features. @samp{qSupported} also consolidates multiple feature probes
40945 at startup, to improve @value{GDBN} performance---a single larger
40946 packet performs better than multiple smaller probe packets on
40947 high-latency links. Some features may enable behavior which must not
40948 be on by default, e.g.@: because it would confuse older clients or
40949 stubs. Other features may describe packets which could be
40950 automatically probed for, but are not. These features must be
40951 reported before @value{GDBN} will use them. This ``default
40952 unsupported'' behavior is not appropriate for all packets, but it
40953 helps to keep the initial connection time under control with new
40954 versions of @value{GDBN} which support increasing numbers of packets.
40958 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
40959 The stub supports or does not support each returned @var{stubfeature},
40960 depending on the form of each @var{stubfeature} (see below for the
40963 An empty reply indicates that @samp{qSupported} is not recognized,
40964 or that no features needed to be reported to @value{GDBN}.
40967 The allowed forms for each feature (either a @var{gdbfeature} in the
40968 @samp{qSupported} packet, or a @var{stubfeature} in the response)
40972 @item @var{name}=@var{value}
40973 The remote protocol feature @var{name} is supported, and associated
40974 with the specified @var{value}. The format of @var{value} depends
40975 on the feature, but it must not include a semicolon.
40977 The remote protocol feature @var{name} is supported, and does not
40978 need an associated value.
40980 The remote protocol feature @var{name} is not supported.
40982 The remote protocol feature @var{name} may be supported, and
40983 @value{GDBN} should auto-detect support in some other way when it is
40984 needed. This form will not be used for @var{gdbfeature} notifications,
40985 but may be used for @var{stubfeature} responses.
40988 Whenever the stub receives a @samp{qSupported} request, the
40989 supplied set of @value{GDBN} features should override any previous
40990 request. This allows @value{GDBN} to put the stub in a known
40991 state, even if the stub had previously been communicating with
40992 a different version of @value{GDBN}.
40994 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
40999 This feature indicates whether @value{GDBN} supports multiprocess
41000 extensions to the remote protocol. @value{GDBN} does not use such
41001 extensions unless the stub also reports that it supports them by
41002 including @samp{multiprocess+} in its @samp{qSupported} reply.
41003 @xref{multiprocess extensions}, for details.
41006 This feature indicates that @value{GDBN} supports the XML target
41007 description. If the stub sees @samp{xmlRegisters=} with target
41008 specific strings separated by a comma, it will report register
41012 This feature indicates whether @value{GDBN} supports the
41013 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
41014 instruction reply packet}).
41017 This feature indicates whether @value{GDBN} supports the swbreak stop
41018 reason in stop replies. @xref{swbreak stop reason}, for details.
41021 This feature indicates whether @value{GDBN} supports the hwbreak stop
41022 reason in stop replies. @xref{swbreak stop reason}, for details.
41025 This feature indicates whether @value{GDBN} supports fork event
41026 extensions to the remote protocol. @value{GDBN} does not use such
41027 extensions unless the stub also reports that it supports them by
41028 including @samp{fork-events+} in its @samp{qSupported} reply.
41031 This feature indicates whether @value{GDBN} supports vfork event
41032 extensions to the remote protocol. @value{GDBN} does not use such
41033 extensions unless the stub also reports that it supports them by
41034 including @samp{vfork-events+} in its @samp{qSupported} reply.
41037 This feature indicates whether @value{GDBN} supports exec event
41038 extensions to the remote protocol. @value{GDBN} does not use such
41039 extensions unless the stub also reports that it supports them by
41040 including @samp{exec-events+} in its @samp{qSupported} reply.
41042 @item vContSupported
41043 This feature indicates whether @value{GDBN} wants to know the
41044 supported actions in the reply to @samp{vCont?} packet.
41047 Stubs should ignore any unknown values for
41048 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
41049 packet supports receiving packets of unlimited length (earlier
41050 versions of @value{GDBN} may reject overly long responses). Additional values
41051 for @var{gdbfeature} may be defined in the future to let the stub take
41052 advantage of new features in @value{GDBN}, e.g.@: incompatible
41053 improvements in the remote protocol---the @samp{multiprocess} feature is
41054 an example of such a feature. The stub's reply should be independent
41055 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
41056 describes all the features it supports, and then the stub replies with
41057 all the features it supports.
41059 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
41060 responses, as long as each response uses one of the standard forms.
41062 Some features are flags. A stub which supports a flag feature
41063 should respond with a @samp{+} form response. Other features
41064 require values, and the stub should respond with an @samp{=}
41067 Each feature has a default value, which @value{GDBN} will use if
41068 @samp{qSupported} is not available or if the feature is not mentioned
41069 in the @samp{qSupported} response. The default values are fixed; a
41070 stub is free to omit any feature responses that match the defaults.
41072 Not all features can be probed, but for those which can, the probing
41073 mechanism is useful: in some cases, a stub's internal
41074 architecture may not allow the protocol layer to know some information
41075 about the underlying target in advance. This is especially common in
41076 stubs which may be configured for multiple targets.
41078 These are the currently defined stub features and their properties:
41080 @multitable @columnfractions 0.35 0.2 0.12 0.2
41081 @c NOTE: The first row should be @headitem, but we do not yet require
41082 @c a new enough version of Texinfo (4.7) to use @headitem.
41084 @tab Value Required
41088 @item @samp{PacketSize}
41093 @item @samp{qXfer:auxv:read}
41098 @item @samp{qXfer:btrace:read}
41103 @item @samp{qXfer:btrace-conf:read}
41108 @item @samp{qXfer:exec-file:read}
41113 @item @samp{qXfer:features:read}
41118 @item @samp{qXfer:libraries:read}
41123 @item @samp{qXfer:libraries-svr4:read}
41128 @item @samp{augmented-libraries-svr4-read}
41133 @item @samp{qXfer:memory-map:read}
41138 @item @samp{qXfer:sdata:read}
41143 @item @samp{qXfer:siginfo:read}
41148 @item @samp{qXfer:siginfo:write}
41153 @item @samp{qXfer:threads:read}
41158 @item @samp{qXfer:traceframe-info:read}
41163 @item @samp{qXfer:uib:read}
41168 @item @samp{qXfer:fdpic:read}
41173 @item @samp{Qbtrace:off}
41178 @item @samp{Qbtrace:bts}
41183 @item @samp{Qbtrace:pt}
41188 @item @samp{Qbtrace-conf:bts:size}
41193 @item @samp{Qbtrace-conf:pt:size}
41198 @item @samp{QNonStop}
41203 @item @samp{QCatchSyscalls}
41208 @item @samp{QPassSignals}
41213 @item @samp{QStartNoAckMode}
41218 @item @samp{multiprocess}
41223 @item @samp{ConditionalBreakpoints}
41228 @item @samp{ConditionalTracepoints}
41233 @item @samp{ReverseContinue}
41238 @item @samp{ReverseStep}
41243 @item @samp{TracepointSource}
41248 @item @samp{QAgent}
41253 @item @samp{QAllow}
41258 @item @samp{QDisableRandomization}
41263 @item @samp{EnableDisableTracepoints}
41268 @item @samp{QTBuffer:size}
41273 @item @samp{tracenz}
41278 @item @samp{BreakpointCommands}
41283 @item @samp{swbreak}
41288 @item @samp{hwbreak}
41293 @item @samp{fork-events}
41298 @item @samp{vfork-events}
41303 @item @samp{exec-events}
41308 @item @samp{QThreadEvents}
41313 @item @samp{no-resumed}
41320 These are the currently defined stub features, in more detail:
41323 @cindex packet size, remote protocol
41324 @item PacketSize=@var{bytes}
41325 The remote stub can accept packets up to at least @var{bytes} in
41326 length. @value{GDBN} will send packets up to this size for bulk
41327 transfers, and will never send larger packets. This is a limit on the
41328 data characters in the packet, including the frame and checksum.
41329 There is no trailing NUL byte in a remote protocol packet; if the stub
41330 stores packets in a NUL-terminated format, it should allow an extra
41331 byte in its buffer for the NUL. If this stub feature is not supported,
41332 @value{GDBN} guesses based on the size of the @samp{g} packet response.
41334 @item qXfer:auxv:read
41335 The remote stub understands the @samp{qXfer:auxv:read} packet
41336 (@pxref{qXfer auxiliary vector read}).
41338 @item qXfer:btrace:read
41339 The remote stub understands the @samp{qXfer:btrace:read}
41340 packet (@pxref{qXfer btrace read}).
41342 @item qXfer:btrace-conf:read
41343 The remote stub understands the @samp{qXfer:btrace-conf:read}
41344 packet (@pxref{qXfer btrace-conf read}).
41346 @item qXfer:exec-file:read
41347 The remote stub understands the @samp{qXfer:exec-file:read} packet
41348 (@pxref{qXfer executable filename read}).
41350 @item qXfer:features:read
41351 The remote stub understands the @samp{qXfer:features:read} packet
41352 (@pxref{qXfer target description read}).
41354 @item qXfer:libraries:read
41355 The remote stub understands the @samp{qXfer:libraries:read} packet
41356 (@pxref{qXfer library list read}).
41358 @item qXfer:libraries-svr4:read
41359 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
41360 (@pxref{qXfer svr4 library list read}).
41362 @item augmented-libraries-svr4-read
41363 The remote stub understands the augmented form of the
41364 @samp{qXfer:libraries-svr4:read} packet
41365 (@pxref{qXfer svr4 library list read}).
41367 @item qXfer:memory-map:read
41368 The remote stub understands the @samp{qXfer:memory-map:read} packet
41369 (@pxref{qXfer memory map read}).
41371 @item qXfer:sdata:read
41372 The remote stub understands the @samp{qXfer:sdata:read} packet
41373 (@pxref{qXfer sdata read}).
41375 @item qXfer:siginfo:read
41376 The remote stub understands the @samp{qXfer:siginfo:read} packet
41377 (@pxref{qXfer siginfo read}).
41379 @item qXfer:siginfo:write
41380 The remote stub understands the @samp{qXfer:siginfo:write} packet
41381 (@pxref{qXfer siginfo write}).
41383 @item qXfer:threads:read
41384 The remote stub understands the @samp{qXfer:threads:read} packet
41385 (@pxref{qXfer threads read}).
41387 @item qXfer:traceframe-info:read
41388 The remote stub understands the @samp{qXfer:traceframe-info:read}
41389 packet (@pxref{qXfer traceframe info read}).
41391 @item qXfer:uib:read
41392 The remote stub understands the @samp{qXfer:uib:read}
41393 packet (@pxref{qXfer unwind info block}).
41395 @item qXfer:fdpic:read
41396 The remote stub understands the @samp{qXfer:fdpic:read}
41397 packet (@pxref{qXfer fdpic loadmap read}).
41400 The remote stub understands the @samp{QNonStop} packet
41401 (@pxref{QNonStop}).
41403 @item QCatchSyscalls
41404 The remote stub understands the @samp{QCatchSyscalls} packet
41405 (@pxref{QCatchSyscalls}).
41408 The remote stub understands the @samp{QPassSignals} packet
41409 (@pxref{QPassSignals}).
41411 @item QStartNoAckMode
41412 The remote stub understands the @samp{QStartNoAckMode} packet and
41413 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
41416 @anchor{multiprocess extensions}
41417 @cindex multiprocess extensions, in remote protocol
41418 The remote stub understands the multiprocess extensions to the remote
41419 protocol syntax. The multiprocess extensions affect the syntax of
41420 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
41421 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
41422 replies. Note that reporting this feature indicates support for the
41423 syntactic extensions only, not that the stub necessarily supports
41424 debugging of more than one process at a time. The stub must not use
41425 multiprocess extensions in packet replies unless @value{GDBN} has also
41426 indicated it supports them in its @samp{qSupported} request.
41428 @item qXfer:osdata:read
41429 The remote stub understands the @samp{qXfer:osdata:read} packet
41430 ((@pxref{qXfer osdata read}).
41432 @item ConditionalBreakpoints
41433 The target accepts and implements evaluation of conditional expressions
41434 defined for breakpoints. The target will only report breakpoint triggers
41435 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
41437 @item ConditionalTracepoints
41438 The remote stub accepts and implements conditional expressions defined
41439 for tracepoints (@pxref{Tracepoint Conditions}).
41441 @item ReverseContinue
41442 The remote stub accepts and implements the reverse continue packet
41446 The remote stub accepts and implements the reverse step packet
41449 @item TracepointSource
41450 The remote stub understands the @samp{QTDPsrc} packet that supplies
41451 the source form of tracepoint definitions.
41454 The remote stub understands the @samp{QAgent} packet.
41457 The remote stub understands the @samp{QAllow} packet.
41459 @item QDisableRandomization
41460 The remote stub understands the @samp{QDisableRandomization} packet.
41462 @item StaticTracepoint
41463 @cindex static tracepoints, in remote protocol
41464 The remote stub supports static tracepoints.
41466 @item InstallInTrace
41467 @anchor{install tracepoint in tracing}
41468 The remote stub supports installing tracepoint in tracing.
41470 @item EnableDisableTracepoints
41471 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
41472 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
41473 to be enabled and disabled while a trace experiment is running.
41475 @item QTBuffer:size
41476 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
41477 packet that allows to change the size of the trace buffer.
41480 @cindex string tracing, in remote protocol
41481 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
41482 See @ref{Bytecode Descriptions} for details about the bytecode.
41484 @item BreakpointCommands
41485 @cindex breakpoint commands, in remote protocol
41486 The remote stub supports running a breakpoint's command list itself,
41487 rather than reporting the hit to @value{GDBN}.
41490 The remote stub understands the @samp{Qbtrace:off} packet.
41493 The remote stub understands the @samp{Qbtrace:bts} packet.
41496 The remote stub understands the @samp{Qbtrace:pt} packet.
41498 @item Qbtrace-conf:bts:size
41499 The remote stub understands the @samp{Qbtrace-conf:bts:size} packet.
41501 @item Qbtrace-conf:pt:size
41502 The remote stub understands the @samp{Qbtrace-conf:pt:size} packet.
41505 The remote stub reports the @samp{swbreak} stop reason for memory
41509 The remote stub reports the @samp{hwbreak} stop reason for hardware
41513 The remote stub reports the @samp{fork} stop reason for fork events.
41516 The remote stub reports the @samp{vfork} stop reason for vfork events
41517 and vforkdone events.
41520 The remote stub reports the @samp{exec} stop reason for exec events.
41522 @item vContSupported
41523 The remote stub reports the supported actions in the reply to
41524 @samp{vCont?} packet.
41526 @item QThreadEvents
41527 The remote stub understands the @samp{QThreadEvents} packet.
41530 The remote stub reports the @samp{N} stop reply.
41535 @cindex symbol lookup, remote request
41536 @cindex @samp{qSymbol} packet
41537 Notify the target that @value{GDBN} is prepared to serve symbol lookup
41538 requests. Accept requests from the target for the values of symbols.
41543 The target does not need to look up any (more) symbols.
41544 @item qSymbol:@var{sym_name}
41545 The target requests the value of symbol @var{sym_name} (hex encoded).
41546 @value{GDBN} may provide the value by using the
41547 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
41551 @item qSymbol:@var{sym_value}:@var{sym_name}
41552 Set the value of @var{sym_name} to @var{sym_value}.
41554 @var{sym_name} (hex encoded) is the name of a symbol whose value the
41555 target has previously requested.
41557 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
41558 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
41564 The target does not need to look up any (more) symbols.
41565 @item qSymbol:@var{sym_name}
41566 The target requests the value of a new symbol @var{sym_name} (hex
41567 encoded). @value{GDBN} will continue to supply the values of symbols
41568 (if available), until the target ceases to request them.
41573 @itemx QTDisconnected
41580 @itemx qTMinFTPILen
41582 @xref{Tracepoint Packets}.
41584 @item qThreadExtraInfo,@var{thread-id}
41585 @cindex thread attributes info, remote request
41586 @cindex @samp{qThreadExtraInfo} packet
41587 Obtain from the target OS a printable string description of thread
41588 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
41589 for the forms of @var{thread-id}. This
41590 string may contain anything that the target OS thinks is interesting
41591 for @value{GDBN} to tell the user about the thread. The string is
41592 displayed in @value{GDBN}'s @code{info threads} display. Some
41593 examples of possible thread extra info strings are @samp{Runnable}, or
41594 @samp{Blocked on Mutex}.
41598 @item @var{XX}@dots{}
41599 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
41600 comprising the printable string containing the extra information about
41601 the thread's attributes.
41604 (Note that the @code{qThreadExtraInfo} packet's name is separated from
41605 the command by a @samp{,}, not a @samp{:}, contrary to the naming
41606 conventions above. Please don't use this packet as a model for new
41625 @xref{Tracepoint Packets}.
41627 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
41628 @cindex read special object, remote request
41629 @cindex @samp{qXfer} packet
41630 @anchor{qXfer read}
41631 Read uninterpreted bytes from the target's special data area
41632 identified by the keyword @var{object}. Request @var{length} bytes
41633 starting at @var{offset} bytes into the data. The content and
41634 encoding of @var{annex} is specific to @var{object}; it can supply
41635 additional details about what data to access.
41640 Data @var{data} (@pxref{Binary Data}) has been read from the
41641 target. There may be more data at a higher address (although
41642 it is permitted to return @samp{m} even for the last valid
41643 block of data, as long as at least one byte of data was read).
41644 It is possible for @var{data} to have fewer bytes than the @var{length} in the
41648 Data @var{data} (@pxref{Binary Data}) has been read from the target.
41649 There is no more data to be read. It is possible for @var{data} to
41650 have fewer bytes than the @var{length} in the request.
41653 The @var{offset} in the request is at the end of the data.
41654 There is no more data to be read.
41657 The request was malformed, or @var{annex} was invalid.
41660 The offset was invalid, or there was an error encountered reading the data.
41661 The @var{nn} part is a hex-encoded @code{errno} value.
41664 An empty reply indicates the @var{object} string was not recognized by
41665 the stub, or that the object does not support reading.
41668 Here are the specific requests of this form defined so far. All the
41669 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
41670 formats, listed above.
41673 @item qXfer:auxv:read::@var{offset},@var{length}
41674 @anchor{qXfer auxiliary vector read}
41675 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
41676 auxiliary vector}. Note @var{annex} must be empty.
41678 This packet is not probed by default; the remote stub must request it,
41679 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
41681 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
41682 @anchor{qXfer btrace read}
41684 Return a description of the current branch trace.
41685 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
41686 packet may have one of the following values:
41690 Returns all available branch trace.
41693 Returns all available branch trace if the branch trace changed since
41694 the last read request.
41697 Returns the new branch trace since the last read request. Adds a new
41698 block to the end of the trace that begins at zero and ends at the source
41699 location of the first branch in the trace buffer. This extra block is
41700 used to stitch traces together.
41702 If the trace buffer overflowed, returns an error indicating the overflow.
41705 This packet is not probed by default; the remote stub must request it
41706 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
41708 @item qXfer:btrace-conf:read::@var{offset},@var{length}
41709 @anchor{qXfer btrace-conf read}
41711 Return a description of the current branch trace configuration.
41712 @xref{Branch Trace Configuration Format}.
41714 This packet is not probed by default; the remote stub must request it
41715 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
41717 @item qXfer:exec-file:read:@var{annex}:@var{offset},@var{length}
41718 @anchor{qXfer executable filename read}
41719 Return the full absolute name of the file that was executed to create
41720 a process running on the remote system. The annex specifies the
41721 numeric process ID of the process to query, encoded as a hexadecimal
41722 number. If the annex part is empty the remote stub should return the
41723 filename corresponding to the currently executing process.
41725 This packet is not probed by default; the remote stub must request it,
41726 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
41728 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
41729 @anchor{qXfer target description read}
41730 Access the @dfn{target description}. @xref{Target Descriptions}. The
41731 annex specifies which XML document to access. The main description is
41732 always loaded from the @samp{target.xml} annex.
41734 This packet is not probed by default; the remote stub must request it,
41735 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
41737 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
41738 @anchor{qXfer library list read}
41739 Access the target's list of loaded libraries. @xref{Library List Format}.
41740 The annex part of the generic @samp{qXfer} packet must be empty
41741 (@pxref{qXfer read}).
41743 Targets which maintain a list of libraries in the program's memory do
41744 not need to implement this packet; it is designed for platforms where
41745 the operating system manages the list of loaded libraries.
41747 This packet is not probed by default; the remote stub must request it,
41748 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
41750 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
41751 @anchor{qXfer svr4 library list read}
41752 Access the target's list of loaded libraries when the target is an SVR4
41753 platform. @xref{Library List Format for SVR4 Targets}. The annex part
41754 of the generic @samp{qXfer} packet must be empty unless the remote
41755 stub indicated it supports the augmented form of this packet
41756 by supplying an appropriate @samp{qSupported} response
41757 (@pxref{qXfer read}, @ref{qSupported}).
41759 This packet is optional for better performance on SVR4 targets.
41760 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
41762 This packet is not probed by default; the remote stub must request it,
41763 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
41765 If the remote stub indicates it supports the augmented form of this
41766 packet then the annex part of the generic @samp{qXfer} packet may
41767 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
41768 arguments. The currently supported arguments are:
41771 @item start=@var{address}
41772 A hexadecimal number specifying the address of the @samp{struct
41773 link_map} to start reading the library list from. If unset or zero
41774 then the first @samp{struct link_map} in the library list will be
41775 chosen as the starting point.
41777 @item prev=@var{address}
41778 A hexadecimal number specifying the address of the @samp{struct
41779 link_map} immediately preceding the @samp{struct link_map}
41780 specified by the @samp{start} argument. If unset or zero then
41781 the remote stub will expect that no @samp{struct link_map}
41782 exists prior to the starting point.
41786 Arguments that are not understood by the remote stub will be silently
41789 @item qXfer:memory-map:read::@var{offset},@var{length}
41790 @anchor{qXfer memory map read}
41791 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
41792 annex part of the generic @samp{qXfer} packet must be empty
41793 (@pxref{qXfer read}).
41795 This packet is not probed by default; the remote stub must request it,
41796 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
41798 @item qXfer:sdata:read::@var{offset},@var{length}
41799 @anchor{qXfer sdata read}
41801 Read contents of the extra collected static tracepoint marker
41802 information. The annex part of the generic @samp{qXfer} packet must
41803 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
41806 This packet is not probed by default; the remote stub must request it,
41807 by supplying an appropriate @samp{qSupported} response
41808 (@pxref{qSupported}).
41810 @item qXfer:siginfo:read::@var{offset},@var{length}
41811 @anchor{qXfer siginfo read}
41812 Read contents of the extra signal information on the target
41813 system. The annex part of the generic @samp{qXfer} packet must be
41814 empty (@pxref{qXfer read}).
41816 This packet is not probed by default; the remote stub must request it,
41817 by supplying an appropriate @samp{qSupported} response
41818 (@pxref{qSupported}).
41820 @item qXfer:threads:read::@var{offset},@var{length}
41821 @anchor{qXfer threads read}
41822 Access the list of threads on target. @xref{Thread List Format}. The
41823 annex part of the generic @samp{qXfer} packet must be empty
41824 (@pxref{qXfer read}).
41826 This packet is not probed by default; the remote stub must request it,
41827 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
41829 @item qXfer:traceframe-info:read::@var{offset},@var{length}
41830 @anchor{qXfer traceframe info read}
41832 Return a description of the current traceframe's contents.
41833 @xref{Traceframe Info Format}. The annex part of the generic
41834 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
41836 This packet is not probed by default; the remote stub must request it,
41837 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
41839 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
41840 @anchor{qXfer unwind info block}
41842 Return the unwind information block for @var{pc}. This packet is used
41843 on OpenVMS/ia64 to ask the kernel unwind information.
41845 This packet is not probed by default.
41847 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
41848 @anchor{qXfer fdpic loadmap read}
41849 Read contents of @code{loadmap}s on the target system. The
41850 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
41851 executable @code{loadmap} or interpreter @code{loadmap} to read.
41853 This packet is not probed by default; the remote stub must request it,
41854 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
41856 @item qXfer:osdata:read::@var{offset},@var{length}
41857 @anchor{qXfer osdata read}
41858 Access the target's @dfn{operating system information}.
41859 @xref{Operating System Information}.
41863 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
41864 @cindex write data into object, remote request
41865 @anchor{qXfer write}
41866 Write uninterpreted bytes into the target's special data area
41867 identified by the keyword @var{object}, starting at @var{offset} bytes
41868 into the data. The binary-encoded data (@pxref{Binary Data}) to be
41869 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
41870 is specific to @var{object}; it can supply additional details about what data
41876 @var{nn} (hex encoded) is the number of bytes written.
41877 This may be fewer bytes than supplied in the request.
41880 The request was malformed, or @var{annex} was invalid.
41883 The offset was invalid, or there was an error encountered writing the data.
41884 The @var{nn} part is a hex-encoded @code{errno} value.
41887 An empty reply indicates the @var{object} string was not
41888 recognized by the stub, or that the object does not support writing.
41891 Here are the specific requests of this form defined so far. All the
41892 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
41893 formats, listed above.
41896 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
41897 @anchor{qXfer siginfo write}
41898 Write @var{data} to the extra signal information on the target system.
41899 The annex part of the generic @samp{qXfer} packet must be
41900 empty (@pxref{qXfer write}).
41902 This packet is not probed by default; the remote stub must request it,
41903 by supplying an appropriate @samp{qSupported} response
41904 (@pxref{qSupported}).
41907 @item qXfer:@var{object}:@var{operation}:@dots{}
41908 Requests of this form may be added in the future. When a stub does
41909 not recognize the @var{object} keyword, or its support for
41910 @var{object} does not recognize the @var{operation} keyword, the stub
41911 must respond with an empty packet.
41913 @item qAttached:@var{pid}
41914 @cindex query attached, remote request
41915 @cindex @samp{qAttached} packet
41916 Return an indication of whether the remote server attached to an
41917 existing process or created a new process. When the multiprocess
41918 protocol extensions are supported (@pxref{multiprocess extensions}),
41919 @var{pid} is an integer in hexadecimal format identifying the target
41920 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
41921 the query packet will be simplified as @samp{qAttached}.
41923 This query is used, for example, to know whether the remote process
41924 should be detached or killed when a @value{GDBN} session is ended with
41925 the @code{quit} command.
41930 The remote server attached to an existing process.
41932 The remote server created a new process.
41934 A badly formed request or an error was encountered.
41938 Enable branch tracing for the current thread using Branch Trace Store.
41943 Branch tracing has been enabled.
41945 A badly formed request or an error was encountered.
41949 Enable branch tracing for the current thread using Intel Processor Trace.
41954 Branch tracing has been enabled.
41956 A badly formed request or an error was encountered.
41960 Disable branch tracing for the current thread.
41965 Branch tracing has been disabled.
41967 A badly formed request or an error was encountered.
41970 @item Qbtrace-conf:bts:size=@var{value}
41971 Set the requested ring buffer size for new threads that use the
41972 btrace recording method in bts format.
41977 The ring buffer size has been set.
41979 A badly formed request or an error was encountered.
41982 @item Qbtrace-conf:pt:size=@var{value}
41983 Set the requested ring buffer size for new threads that use the
41984 btrace recording method in pt format.
41989 The ring buffer size has been set.
41991 A badly formed request or an error was encountered.
41996 @node Architecture-Specific Protocol Details
41997 @section Architecture-Specific Protocol Details
41999 This section describes how the remote protocol is applied to specific
42000 target architectures. Also see @ref{Standard Target Features}, for
42001 details of XML target descriptions for each architecture.
42004 * ARM-Specific Protocol Details::
42005 * MIPS-Specific Protocol Details::
42008 @node ARM-Specific Protocol Details
42009 @subsection @acronym{ARM}-specific Protocol Details
42012 * ARM Breakpoint Kinds::
42015 @node ARM Breakpoint Kinds
42016 @subsubsection @acronym{ARM} Breakpoint Kinds
42017 @cindex breakpoint kinds, @acronym{ARM}
42019 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
42024 16-bit Thumb mode breakpoint.
42027 32-bit Thumb mode (Thumb-2) breakpoint.
42030 32-bit @acronym{ARM} mode breakpoint.
42034 @node MIPS-Specific Protocol Details
42035 @subsection @acronym{MIPS}-specific Protocol Details
42038 * MIPS Register packet Format::
42039 * MIPS Breakpoint Kinds::
42042 @node MIPS Register packet Format
42043 @subsubsection @acronym{MIPS} Register Packet Format
42044 @cindex register packet format, @acronym{MIPS}
42046 The following @code{g}/@code{G} packets have previously been defined.
42047 In the below, some thirty-two bit registers are transferred as
42048 sixty-four bits. Those registers should be zero/sign extended (which?)
42049 to fill the space allocated. Register bytes are transferred in target
42050 byte order. The two nibbles within a register byte are transferred
42051 most-significant -- least-significant.
42056 All registers are transferred as thirty-two bit quantities in the order:
42057 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
42058 registers; fsr; fir; fp.
42061 All registers are transferred as sixty-four bit quantities (including
42062 thirty-two bit registers such as @code{sr}). The ordering is the same
42067 @node MIPS Breakpoint Kinds
42068 @subsubsection @acronym{MIPS} Breakpoint Kinds
42069 @cindex breakpoint kinds, @acronym{MIPS}
42071 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
42076 16-bit @acronym{MIPS16} mode breakpoint.
42079 16-bit @acronym{microMIPS} mode breakpoint.
42082 32-bit standard @acronym{MIPS} mode breakpoint.
42085 32-bit @acronym{microMIPS} mode breakpoint.
42089 @node Tracepoint Packets
42090 @section Tracepoint Packets
42091 @cindex tracepoint packets
42092 @cindex packets, tracepoint
42094 Here we describe the packets @value{GDBN} uses to implement
42095 tracepoints (@pxref{Tracepoints}).
42099 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
42100 @cindex @samp{QTDP} packet
42101 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
42102 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
42103 the tracepoint is disabled. The @var{step} gives the tracepoint's step
42104 count, and @var{pass} gives its pass count. If an @samp{F} is present,
42105 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
42106 the number of bytes that the target should copy elsewhere to make room
42107 for the tracepoint. If an @samp{X} is present, it introduces a
42108 tracepoint condition, which consists of a hexadecimal length, followed
42109 by a comma and hex-encoded bytes, in a manner similar to action
42110 encodings as described below. If the trailing @samp{-} is present,
42111 further @samp{QTDP} packets will follow to specify this tracepoint's
42117 The packet was understood and carried out.
42119 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
42121 The packet was not recognized.
42124 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
42125 Define actions to be taken when a tracepoint is hit. The @var{n} and
42126 @var{addr} must be the same as in the initial @samp{QTDP} packet for
42127 this tracepoint. This packet may only be sent immediately after
42128 another @samp{QTDP} packet that ended with a @samp{-}. If the
42129 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
42130 specifying more actions for this tracepoint.
42132 In the series of action packets for a given tracepoint, at most one
42133 can have an @samp{S} before its first @var{action}. If such a packet
42134 is sent, it and the following packets define ``while-stepping''
42135 actions. Any prior packets define ordinary actions --- that is, those
42136 taken when the tracepoint is first hit. If no action packet has an
42137 @samp{S}, then all the packets in the series specify ordinary
42138 tracepoint actions.
42140 The @samp{@var{action}@dots{}} portion of the packet is a series of
42141 actions, concatenated without separators. Each action has one of the
42147 Collect the registers whose bits are set in @var{mask},
42148 a hexadecimal number whose @var{i}'th bit is set if register number
42149 @var{i} should be collected. (The least significant bit is numbered
42150 zero.) Note that @var{mask} may be any number of digits long; it may
42151 not fit in a 32-bit word.
42153 @item M @var{basereg},@var{offset},@var{len}
42154 Collect @var{len} bytes of memory starting at the address in register
42155 number @var{basereg}, plus @var{offset}. If @var{basereg} is
42156 @samp{-1}, then the range has a fixed address: @var{offset} is the
42157 address of the lowest byte to collect. The @var{basereg},
42158 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
42159 values (the @samp{-1} value for @var{basereg} is a special case).
42161 @item X @var{len},@var{expr}
42162 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
42163 it directs. The agent expression @var{expr} is as described in
42164 @ref{Agent Expressions}. Each byte of the expression is encoded as a
42165 two-digit hex number in the packet; @var{len} is the number of bytes
42166 in the expression (and thus one-half the number of hex digits in the
42171 Any number of actions may be packed together in a single @samp{QTDP}
42172 packet, as long as the packet does not exceed the maximum packet
42173 length (400 bytes, for many stubs). There may be only one @samp{R}
42174 action per tracepoint, and it must precede any @samp{M} or @samp{X}
42175 actions. Any registers referred to by @samp{M} and @samp{X} actions
42176 must be collected by a preceding @samp{R} action. (The
42177 ``while-stepping'' actions are treated as if they were attached to a
42178 separate tracepoint, as far as these restrictions are concerned.)
42183 The packet was understood and carried out.
42185 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
42187 The packet was not recognized.
42190 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
42191 @cindex @samp{QTDPsrc} packet
42192 Specify a source string of tracepoint @var{n} at address @var{addr}.
42193 This is useful to get accurate reproduction of the tracepoints
42194 originally downloaded at the beginning of the trace run. The @var{type}
42195 is the name of the tracepoint part, such as @samp{cond} for the
42196 tracepoint's conditional expression (see below for a list of types), while
42197 @var{bytes} is the string, encoded in hexadecimal.
42199 @var{start} is the offset of the @var{bytes} within the overall source
42200 string, while @var{slen} is the total length of the source string.
42201 This is intended for handling source strings that are longer than will
42202 fit in a single packet.
42203 @c Add detailed example when this info is moved into a dedicated
42204 @c tracepoint descriptions section.
42206 The available string types are @samp{at} for the location,
42207 @samp{cond} for the conditional, and @samp{cmd} for an action command.
42208 @value{GDBN} sends a separate packet for each command in the action
42209 list, in the same order in which the commands are stored in the list.
42211 The target does not need to do anything with source strings except
42212 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
42215 Although this packet is optional, and @value{GDBN} will only send it
42216 if the target replies with @samp{TracepointSource} @xref{General
42217 Query Packets}, it makes both disconnected tracing and trace files
42218 much easier to use. Otherwise the user must be careful that the
42219 tracepoints in effect while looking at trace frames are identical to
42220 the ones in effect during the trace run; even a small discrepancy
42221 could cause @samp{tdump} not to work, or a particular trace frame not
42224 @item QTDV:@var{n}:@var{value}:@var{builtin}:@var{name}
42225 @cindex define trace state variable, remote request
42226 @cindex @samp{QTDV} packet
42227 Create a new trace state variable, number @var{n}, with an initial
42228 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
42229 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
42230 the option of not using this packet for initial values of zero; the
42231 target should simply create the trace state variables as they are
42232 mentioned in expressions. The value @var{builtin} should be 1 (one)
42233 if the trace state variable is builtin and 0 (zero) if it is not builtin.
42234 @value{GDBN} only sets @var{builtin} to 1 if a previous @samp{qTfV} or
42235 @samp{qTsV} packet had it set. The contents of @var{name} is the
42236 hex-encoded name (without the leading @samp{$}) of the trace state
42239 @item QTFrame:@var{n}
42240 @cindex @samp{QTFrame} packet
42241 Select the @var{n}'th tracepoint frame from the buffer, and use the
42242 register and memory contents recorded there to answer subsequent
42243 request packets from @value{GDBN}.
42245 A successful reply from the stub indicates that the stub has found the
42246 requested frame. The response is a series of parts, concatenated
42247 without separators, describing the frame we selected. Each part has
42248 one of the following forms:
42252 The selected frame is number @var{n} in the trace frame buffer;
42253 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
42254 was no frame matching the criteria in the request packet.
42257 The selected trace frame records a hit of tracepoint number @var{t};
42258 @var{t} is a hexadecimal number.
42262 @item QTFrame:pc:@var{addr}
42263 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
42264 currently selected frame whose PC is @var{addr};
42265 @var{addr} is a hexadecimal number.
42267 @item QTFrame:tdp:@var{t}
42268 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
42269 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
42270 is a hexadecimal number.
42272 @item QTFrame:range:@var{start}:@var{end}
42273 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
42274 currently selected frame whose PC is between @var{start} (inclusive)
42275 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
42278 @item QTFrame:outside:@var{start}:@var{end}
42279 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
42280 frame @emph{outside} the given range of addresses (exclusive).
42283 @cindex @samp{qTMinFTPILen} packet
42284 This packet requests the minimum length of instruction at which a fast
42285 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
42286 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
42287 it depends on the target system being able to create trampolines in
42288 the first 64K of memory, which might or might not be possible for that
42289 system. So the reply to this packet will be 4 if it is able to
42296 The minimum instruction length is currently unknown.
42298 The minimum instruction length is @var{length}, where @var{length}
42299 is a hexadecimal number greater or equal to 1. A reply
42300 of 1 means that a fast tracepoint may be placed on any instruction
42301 regardless of size.
42303 An error has occurred.
42305 An empty reply indicates that the request is not supported by the stub.
42309 @cindex @samp{QTStart} packet
42310 Begin the tracepoint experiment. Begin collecting data from
42311 tracepoint hits in the trace frame buffer. This packet supports the
42312 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
42313 instruction reply packet}).
42316 @cindex @samp{QTStop} packet
42317 End the tracepoint experiment. Stop collecting trace frames.
42319 @item QTEnable:@var{n}:@var{addr}
42321 @cindex @samp{QTEnable} packet
42322 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
42323 experiment. If the tracepoint was previously disabled, then collection
42324 of data from it will resume.
42326 @item QTDisable:@var{n}:@var{addr}
42328 @cindex @samp{QTDisable} packet
42329 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
42330 experiment. No more data will be collected from the tracepoint unless
42331 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
42334 @cindex @samp{QTinit} packet
42335 Clear the table of tracepoints, and empty the trace frame buffer.
42337 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
42338 @cindex @samp{QTro} packet
42339 Establish the given ranges of memory as ``transparent''. The stub
42340 will answer requests for these ranges from memory's current contents,
42341 if they were not collected as part of the tracepoint hit.
42343 @value{GDBN} uses this to mark read-only regions of memory, like those
42344 containing program code. Since these areas never change, they should
42345 still have the same contents they did when the tracepoint was hit, so
42346 there's no reason for the stub to refuse to provide their contents.
42348 @item QTDisconnected:@var{value}
42349 @cindex @samp{QTDisconnected} packet
42350 Set the choice to what to do with the tracing run when @value{GDBN}
42351 disconnects from the target. A @var{value} of 1 directs the target to
42352 continue the tracing run, while 0 tells the target to stop tracing if
42353 @value{GDBN} is no longer in the picture.
42356 @cindex @samp{qTStatus} packet
42357 Ask the stub if there is a trace experiment running right now.
42359 The reply has the form:
42363 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
42364 @var{running} is a single digit @code{1} if the trace is presently
42365 running, or @code{0} if not. It is followed by semicolon-separated
42366 optional fields that an agent may use to report additional status.
42370 If the trace is not running, the agent may report any of several
42371 explanations as one of the optional fields:
42376 No trace has been run yet.
42378 @item tstop[:@var{text}]:0
42379 The trace was stopped by a user-originated stop command. The optional
42380 @var{text} field is a user-supplied string supplied as part of the
42381 stop command (for instance, an explanation of why the trace was
42382 stopped manually). It is hex-encoded.
42385 The trace stopped because the trace buffer filled up.
42387 @item tdisconnected:0
42388 The trace stopped because @value{GDBN} disconnected from the target.
42390 @item tpasscount:@var{tpnum}
42391 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
42393 @item terror:@var{text}:@var{tpnum}
42394 The trace stopped because tracepoint @var{tpnum} had an error. The
42395 string @var{text} is available to describe the nature of the error
42396 (for instance, a divide by zero in the condition expression); it
42400 The trace stopped for some other reason.
42404 Additional optional fields supply statistical and other information.
42405 Although not required, they are extremely useful for users monitoring
42406 the progress of a trace run. If a trace has stopped, and these
42407 numbers are reported, they must reflect the state of the just-stopped
42412 @item tframes:@var{n}
42413 The number of trace frames in the buffer.
42415 @item tcreated:@var{n}
42416 The total number of trace frames created during the run. This may
42417 be larger than the trace frame count, if the buffer is circular.
42419 @item tsize:@var{n}
42420 The total size of the trace buffer, in bytes.
42422 @item tfree:@var{n}
42423 The number of bytes still unused in the buffer.
42425 @item circular:@var{n}
42426 The value of the circular trace buffer flag. @code{1} means that the
42427 trace buffer is circular and old trace frames will be discarded if
42428 necessary to make room, @code{0} means that the trace buffer is linear
42431 @item disconn:@var{n}
42432 The value of the disconnected tracing flag. @code{1} means that
42433 tracing will continue after @value{GDBN} disconnects, @code{0} means
42434 that the trace run will stop.
42438 @item qTP:@var{tp}:@var{addr}
42439 @cindex tracepoint status, remote request
42440 @cindex @samp{qTP} packet
42441 Ask the stub for the current state of tracepoint number @var{tp} at
42442 address @var{addr}.
42446 @item V@var{hits}:@var{usage}
42447 The tracepoint has been hit @var{hits} times so far during the trace
42448 run, and accounts for @var{usage} in the trace buffer. Note that
42449 @code{while-stepping} steps are not counted as separate hits, but the
42450 steps' space consumption is added into the usage number.
42454 @item qTV:@var{var}
42455 @cindex trace state variable value, remote request
42456 @cindex @samp{qTV} packet
42457 Ask the stub for the value of the trace state variable number @var{var}.
42462 The value of the variable is @var{value}. This will be the current
42463 value of the variable if the user is examining a running target, or a
42464 saved value if the variable was collected in the trace frame that the
42465 user is looking at. Note that multiple requests may result in
42466 different reply values, such as when requesting values while the
42467 program is running.
42470 The value of the variable is unknown. This would occur, for example,
42471 if the user is examining a trace frame in which the requested variable
42476 @cindex @samp{qTfP} packet
42478 @cindex @samp{qTsP} packet
42479 These packets request data about tracepoints that are being used by
42480 the target. @value{GDBN} sends @code{qTfP} to get the first piece
42481 of data, and multiple @code{qTsP} to get additional pieces. Replies
42482 to these packets generally take the form of the @code{QTDP} packets
42483 that define tracepoints. (FIXME add detailed syntax)
42486 @cindex @samp{qTfV} packet
42488 @cindex @samp{qTsV} packet
42489 These packets request data about trace state variables that are on the
42490 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
42491 and multiple @code{qTsV} to get additional variables. Replies to
42492 these packets follow the syntax of the @code{QTDV} packets that define
42493 trace state variables.
42499 @cindex @samp{qTfSTM} packet
42500 @cindex @samp{qTsSTM} packet
42501 These packets request data about static tracepoint markers that exist
42502 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
42503 first piece of data, and multiple @code{qTsSTM} to get additional
42504 pieces. Replies to these packets take the following form:
42508 @item m @var{address}:@var{id}:@var{extra}
42510 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
42511 a comma-separated list of markers
42513 (lower case letter @samp{L}) denotes end of list.
42515 An error occurred. The error number @var{nn} is given as hex digits.
42517 An empty reply indicates that the request is not supported by the
42521 The @var{address} is encoded in hex;
42522 @var{id} and @var{extra} are strings encoded in hex.
42524 In response to each query, the target will reply with a list of one or
42525 more markers, separated by commas. @value{GDBN} will respond to each
42526 reply with a request for more markers (using the @samp{qs} form of the
42527 query), until the target responds with @samp{l} (lower-case ell, for
42530 @item qTSTMat:@var{address}
42532 @cindex @samp{qTSTMat} packet
42533 This packets requests data about static tracepoint markers in the
42534 target program at @var{address}. Replies to this packet follow the
42535 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
42536 tracepoint markers.
42538 @item QTSave:@var{filename}
42539 @cindex @samp{QTSave} packet
42540 This packet directs the target to save trace data to the file name
42541 @var{filename} in the target's filesystem. The @var{filename} is encoded
42542 as a hex string; the interpretation of the file name (relative vs
42543 absolute, wild cards, etc) is up to the target.
42545 @item qTBuffer:@var{offset},@var{len}
42546 @cindex @samp{qTBuffer} packet
42547 Return up to @var{len} bytes of the current contents of trace buffer,
42548 starting at @var{offset}. The trace buffer is treated as if it were
42549 a contiguous collection of traceframes, as per the trace file format.
42550 The reply consists as many hex-encoded bytes as the target can deliver
42551 in a packet; it is not an error to return fewer than were asked for.
42552 A reply consisting of just @code{l} indicates that no bytes are
42555 @item QTBuffer:circular:@var{value}
42556 This packet directs the target to use a circular trace buffer if
42557 @var{value} is 1, or a linear buffer if the value is 0.
42559 @item QTBuffer:size:@var{size}
42560 @anchor{QTBuffer-size}
42561 @cindex @samp{QTBuffer size} packet
42562 This packet directs the target to make the trace buffer be of size
42563 @var{size} if possible. A value of @code{-1} tells the target to
42564 use whatever size it prefers.
42566 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
42567 @cindex @samp{QTNotes} packet
42568 This packet adds optional textual notes to the trace run. Allowable
42569 types include @code{user}, @code{notes}, and @code{tstop}, the
42570 @var{text} fields are arbitrary strings, hex-encoded.
42574 @subsection Relocate instruction reply packet
42575 When installing fast tracepoints in memory, the target may need to
42576 relocate the instruction currently at the tracepoint address to a
42577 different address in memory. For most instructions, a simple copy is
42578 enough, but, for example, call instructions that implicitly push the
42579 return address on the stack, and relative branches or other
42580 PC-relative instructions require offset adjustment, so that the effect
42581 of executing the instruction at a different address is the same as if
42582 it had executed in the original location.
42584 In response to several of the tracepoint packets, the target may also
42585 respond with a number of intermediate @samp{qRelocInsn} request
42586 packets before the final result packet, to have @value{GDBN} handle
42587 this relocation operation. If a packet supports this mechanism, its
42588 documentation will explicitly say so. See for example the above
42589 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
42590 format of the request is:
42593 @item qRelocInsn:@var{from};@var{to}
42595 This requests @value{GDBN} to copy instruction at address @var{from}
42596 to address @var{to}, possibly adjusted so that executing the
42597 instruction at @var{to} has the same effect as executing it at
42598 @var{from}. @value{GDBN} writes the adjusted instruction to target
42599 memory starting at @var{to}.
42604 @item qRelocInsn:@var{adjusted_size}
42605 Informs the stub the relocation is complete. The @var{adjusted_size} is
42606 the length in bytes of resulting relocated instruction sequence.
42608 A badly formed request was detected, or an error was encountered while
42609 relocating the instruction.
42612 @node Host I/O Packets
42613 @section Host I/O Packets
42614 @cindex Host I/O, remote protocol
42615 @cindex file transfer, remote protocol
42617 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
42618 operations on the far side of a remote link. For example, Host I/O is
42619 used to upload and download files to a remote target with its own
42620 filesystem. Host I/O uses the same constant values and data structure
42621 layout as the target-initiated File-I/O protocol. However, the
42622 Host I/O packets are structured differently. The target-initiated
42623 protocol relies on target memory to store parameters and buffers.
42624 Host I/O requests are initiated by @value{GDBN}, and the
42625 target's memory is not involved. @xref{File-I/O Remote Protocol
42626 Extension}, for more details on the target-initiated protocol.
42628 The Host I/O request packets all encode a single operation along with
42629 its arguments. They have this format:
42633 @item vFile:@var{operation}: @var{parameter}@dots{}
42634 @var{operation} is the name of the particular request; the target
42635 should compare the entire packet name up to the second colon when checking
42636 for a supported operation. The format of @var{parameter} depends on
42637 the operation. Numbers are always passed in hexadecimal. Negative
42638 numbers have an explicit minus sign (i.e.@: two's complement is not
42639 used). Strings (e.g.@: filenames) are encoded as a series of
42640 hexadecimal bytes. The last argument to a system call may be a
42641 buffer of escaped binary data (@pxref{Binary Data}).
42645 The valid responses to Host I/O packets are:
42649 @item F @var{result} [, @var{errno}] [; @var{attachment}]
42650 @var{result} is the integer value returned by this operation, usually
42651 non-negative for success and -1 for errors. If an error has occured,
42652 @var{errno} will be included in the result specifying a
42653 value defined by the File-I/O protocol (@pxref{Errno Values}). For
42654 operations which return data, @var{attachment} supplies the data as a
42655 binary buffer. Binary buffers in response packets are escaped in the
42656 normal way (@pxref{Binary Data}). See the individual packet
42657 documentation for the interpretation of @var{result} and
42661 An empty response indicates that this operation is not recognized.
42665 These are the supported Host I/O operations:
42668 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
42669 Open a file at @var{filename} and return a file descriptor for it, or
42670 return -1 if an error occurs. The @var{filename} is a string,
42671 @var{flags} is an integer indicating a mask of open flags
42672 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
42673 of mode bits to use if the file is created (@pxref{mode_t Values}).
42674 @xref{open}, for details of the open flags and mode values.
42676 @item vFile:close: @var{fd}
42677 Close the open file corresponding to @var{fd} and return 0, or
42678 -1 if an error occurs.
42680 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
42681 Read data from the open file corresponding to @var{fd}. Up to
42682 @var{count} bytes will be read from the file, starting at @var{offset}
42683 relative to the start of the file. The target may read fewer bytes;
42684 common reasons include packet size limits and an end-of-file
42685 condition. The number of bytes read is returned. Zero should only be
42686 returned for a successful read at the end of the file, or if
42687 @var{count} was zero.
42689 The data read should be returned as a binary attachment on success.
42690 If zero bytes were read, the response should include an empty binary
42691 attachment (i.e.@: a trailing semicolon). The return value is the
42692 number of target bytes read; the binary attachment may be longer if
42693 some characters were escaped.
42695 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
42696 Write @var{data} (a binary buffer) to the open file corresponding
42697 to @var{fd}. Start the write at @var{offset} from the start of the
42698 file. Unlike many @code{write} system calls, there is no
42699 separate @var{count} argument; the length of @var{data} in the
42700 packet is used. @samp{vFile:pwrite} returns the number of bytes written,
42701 which may be shorter than the length of @var{data}, or -1 if an
42704 @item vFile:fstat: @var{fd}
42705 Get information about the open file corresponding to @var{fd}.
42706 On success the information is returned as a binary attachment
42707 and the return value is the size of this attachment in bytes.
42708 If an error occurs the return value is -1. The format of the
42709 returned binary attachment is as described in @ref{struct stat}.
42711 @item vFile:unlink: @var{filename}
42712 Delete the file at @var{filename} on the target. Return 0,
42713 or -1 if an error occurs. The @var{filename} is a string.
42715 @item vFile:readlink: @var{filename}
42716 Read value of symbolic link @var{filename} on the target. Return
42717 the number of bytes read, or -1 if an error occurs.
42719 The data read should be returned as a binary attachment on success.
42720 If zero bytes were read, the response should include an empty binary
42721 attachment (i.e.@: a trailing semicolon). The return value is the
42722 number of target bytes read; the binary attachment may be longer if
42723 some characters were escaped.
42725 @item vFile:setfs: @var{pid}
42726 Select the filesystem on which @code{vFile} operations with
42727 @var{filename} arguments will operate. This is required for
42728 @value{GDBN} to be able to access files on remote targets where
42729 the remote stub does not share a common filesystem with the
42732 If @var{pid} is nonzero, select the filesystem as seen by process
42733 @var{pid}. If @var{pid} is zero, select the filesystem as seen by
42734 the remote stub. Return 0 on success, or -1 if an error occurs.
42735 If @code{vFile:setfs:} indicates success, the selected filesystem
42736 remains selected until the next successful @code{vFile:setfs:}
42742 @section Interrupts
42743 @cindex interrupts (remote protocol)
42744 @anchor{interrupting remote targets}
42746 In all-stop mode, when a program on the remote target is running,
42747 @value{GDBN} may attempt to interrupt it by sending a @samp{Ctrl-C},
42748 @code{BREAK} or a @code{BREAK} followed by @code{g}, control of which
42749 is specified via @value{GDBN}'s @samp{interrupt-sequence}.
42751 The precise meaning of @code{BREAK} is defined by the transport
42752 mechanism and may, in fact, be undefined. @value{GDBN} does not
42753 currently define a @code{BREAK} mechanism for any of the network
42754 interfaces except for TCP, in which case @value{GDBN} sends the
42755 @code{telnet} BREAK sequence.
42757 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
42758 transport mechanisms. It is represented by sending the single byte
42759 @code{0x03} without any of the usual packet overhead described in
42760 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
42761 transmitted as part of a packet, it is considered to be packet data
42762 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
42763 (@pxref{X packet}), used for binary downloads, may include an unescaped
42764 @code{0x03} as part of its packet.
42766 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
42767 When Linux kernel receives this sequence from serial port,
42768 it stops execution and connects to gdb.
42770 In non-stop mode, because packet resumptions are asynchronous
42771 (@pxref{vCont packet}), @value{GDBN} is always free to send a remote
42772 command to the remote stub, even when the target is running. For that
42773 reason, @value{GDBN} instead sends a regular packet (@pxref{vCtrlC
42774 packet}) with the usual packet framing instead of the single byte
42777 Stubs are not required to recognize these interrupt mechanisms and the
42778 precise meaning associated with receipt of the interrupt is
42779 implementation defined. If the target supports debugging of multiple
42780 threads and/or processes, it should attempt to interrupt all
42781 currently-executing threads and processes.
42782 If the stub is successful at interrupting the
42783 running program, it should send one of the stop
42784 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
42785 of successfully stopping the program in all-stop mode, and a stop reply
42786 for each stopped thread in non-stop mode.
42787 Interrupts received while the
42788 program is stopped are queued and the program will be interrupted when
42789 it is resumed next time.
42791 @node Notification Packets
42792 @section Notification Packets
42793 @cindex notification packets
42794 @cindex packets, notification
42796 The @value{GDBN} remote serial protocol includes @dfn{notifications},
42797 packets that require no acknowledgment. Both the GDB and the stub
42798 may send notifications (although the only notifications defined at
42799 present are sent by the stub). Notifications carry information
42800 without incurring the round-trip latency of an acknowledgment, and so
42801 are useful for low-impact communications where occasional packet loss
42804 A notification packet has the form @samp{% @var{data} #
42805 @var{checksum}}, where @var{data} is the content of the notification,
42806 and @var{checksum} is a checksum of @var{data}, computed and formatted
42807 as for ordinary @value{GDBN} packets. A notification's @var{data}
42808 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
42809 receiving a notification, the recipient sends no @samp{+} or @samp{-}
42810 to acknowledge the notification's receipt or to report its corruption.
42812 Every notification's @var{data} begins with a name, which contains no
42813 colon characters, followed by a colon character.
42815 Recipients should silently ignore corrupted notifications and
42816 notifications they do not understand. Recipients should restart
42817 timeout periods on receipt of a well-formed notification, whether or
42818 not they understand it.
42820 Senders should only send the notifications described here when this
42821 protocol description specifies that they are permitted. In the
42822 future, we may extend the protocol to permit existing notifications in
42823 new contexts; this rule helps older senders avoid confusing newer
42826 (Older versions of @value{GDBN} ignore bytes received until they see
42827 the @samp{$} byte that begins an ordinary packet, so new stubs may
42828 transmit notifications without fear of confusing older clients. There
42829 are no notifications defined for @value{GDBN} to send at the moment, but we
42830 assume that most older stubs would ignore them, as well.)
42832 Each notification is comprised of three parts:
42834 @item @var{name}:@var{event}
42835 The notification packet is sent by the side that initiates the
42836 exchange (currently, only the stub does that), with @var{event}
42837 carrying the specific information about the notification, and
42838 @var{name} specifying the name of the notification.
42840 The acknowledge sent by the other side, usually @value{GDBN}, to
42841 acknowledge the exchange and request the event.
42844 The purpose of an asynchronous notification mechanism is to report to
42845 @value{GDBN} that something interesting happened in the remote stub.
42847 The remote stub may send notification @var{name}:@var{event}
42848 at any time, but @value{GDBN} acknowledges the notification when
42849 appropriate. The notification event is pending before @value{GDBN}
42850 acknowledges. Only one notification at a time may be pending; if
42851 additional events occur before @value{GDBN} has acknowledged the
42852 previous notification, they must be queued by the stub for later
42853 synchronous transmission in response to @var{ack} packets from
42854 @value{GDBN}. Because the notification mechanism is unreliable,
42855 the stub is permitted to resend a notification if it believes
42856 @value{GDBN} may not have received it.
42858 Specifically, notifications may appear when @value{GDBN} is not
42859 otherwise reading input from the stub, or when @value{GDBN} is
42860 expecting to read a normal synchronous response or a
42861 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
42862 Notification packets are distinct from any other communication from
42863 the stub so there is no ambiguity.
42865 After receiving a notification, @value{GDBN} shall acknowledge it by
42866 sending a @var{ack} packet as a regular, synchronous request to the
42867 stub. Such acknowledgment is not required to happen immediately, as
42868 @value{GDBN} is permitted to send other, unrelated packets to the
42869 stub first, which the stub should process normally.
42871 Upon receiving a @var{ack} packet, if the stub has other queued
42872 events to report to @value{GDBN}, it shall respond by sending a
42873 normal @var{event}. @value{GDBN} shall then send another @var{ack}
42874 packet to solicit further responses; again, it is permitted to send
42875 other, unrelated packets as well which the stub should process
42878 If the stub receives a @var{ack} packet and there are no additional
42879 @var{event} to report, the stub shall return an @samp{OK} response.
42880 At this point, @value{GDBN} has finished processing a notification
42881 and the stub has completed sending any queued events. @value{GDBN}
42882 won't accept any new notifications until the final @samp{OK} is
42883 received . If further notification events occur, the stub shall send
42884 a new notification, @value{GDBN} shall accept the notification, and
42885 the process shall be repeated.
42887 The process of asynchronous notification can be illustrated by the
42890 <- @code{%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
42893 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
42895 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
42900 The following notifications are defined:
42901 @multitable @columnfractions 0.12 0.12 0.38 0.38
42910 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
42911 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
42912 for information on how these notifications are acknowledged by
42914 @tab Report an asynchronous stop event in non-stop mode.
42918 @node Remote Non-Stop
42919 @section Remote Protocol Support for Non-Stop Mode
42921 @value{GDBN}'s remote protocol supports non-stop debugging of
42922 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
42923 supports non-stop mode, it should report that to @value{GDBN} by including
42924 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
42926 @value{GDBN} typically sends a @samp{QNonStop} packet only when
42927 establishing a new connection with the stub. Entering non-stop mode
42928 does not alter the state of any currently-running threads, but targets
42929 must stop all threads in any already-attached processes when entering
42930 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
42931 probe the target state after a mode change.
42933 In non-stop mode, when an attached process encounters an event that
42934 would otherwise be reported with a stop reply, it uses the
42935 asynchronous notification mechanism (@pxref{Notification Packets}) to
42936 inform @value{GDBN}. In contrast to all-stop mode, where all threads
42937 in all processes are stopped when a stop reply is sent, in non-stop
42938 mode only the thread reporting the stop event is stopped. That is,
42939 when reporting a @samp{S} or @samp{T} response to indicate completion
42940 of a step operation, hitting a breakpoint, or a fault, only the
42941 affected thread is stopped; any other still-running threads continue
42942 to run. When reporting a @samp{W} or @samp{X} response, all running
42943 threads belonging to other attached processes continue to run.
42945 In non-stop mode, the target shall respond to the @samp{?} packet as
42946 follows. First, any incomplete stop reply notification/@samp{vStopped}
42947 sequence in progress is abandoned. The target must begin a new
42948 sequence reporting stop events for all stopped threads, whether or not
42949 it has previously reported those events to @value{GDBN}. The first
42950 stop reply is sent as a synchronous reply to the @samp{?} packet, and
42951 subsequent stop replies are sent as responses to @samp{vStopped} packets
42952 using the mechanism described above. The target must not send
42953 asynchronous stop reply notifications until the sequence is complete.
42954 If all threads are running when the target receives the @samp{?} packet,
42955 or if the target is not attached to any process, it shall respond
42958 If the stub supports non-stop mode, it should also support the
42959 @samp{swbreak} stop reason if software breakpoints are supported, and
42960 the @samp{hwbreak} stop reason if hardware breakpoints are supported
42961 (@pxref{swbreak stop reason}). This is because given the asynchronous
42962 nature of non-stop mode, between the time a thread hits a breakpoint
42963 and the time the event is finally processed by @value{GDBN}, the
42964 breakpoint may have already been removed from the target. Due to
42965 this, @value{GDBN} needs to be able to tell whether a trap stop was
42966 caused by a delayed breakpoint event, which should be ignored, as
42967 opposed to a random trap signal, which should be reported to the user.
42968 Note the @samp{swbreak} feature implies that the target is responsible
42969 for adjusting the PC when a software breakpoint triggers, if
42970 necessary, such as on the x86 architecture.
42972 @node Packet Acknowledgment
42973 @section Packet Acknowledgment
42975 @cindex acknowledgment, for @value{GDBN} remote
42976 @cindex packet acknowledgment, for @value{GDBN} remote
42977 By default, when either the host or the target machine receives a packet,
42978 the first response expected is an acknowledgment: either @samp{+} (to indicate
42979 the package was received correctly) or @samp{-} (to request retransmission).
42980 This mechanism allows the @value{GDBN} remote protocol to operate over
42981 unreliable transport mechanisms, such as a serial line.
42983 In cases where the transport mechanism is itself reliable (such as a pipe or
42984 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
42985 It may be desirable to disable them in that case to reduce communication
42986 overhead, or for other reasons. This can be accomplished by means of the
42987 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
42989 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
42990 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
42991 and response format still includes the normal checksum, as described in
42992 @ref{Overview}, but the checksum may be ignored by the receiver.
42994 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
42995 no-acknowledgment mode, it should report that to @value{GDBN}
42996 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
42997 @pxref{qSupported}.
42998 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
42999 disabled via the @code{set remote noack-packet off} command
43000 (@pxref{Remote Configuration}),
43001 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
43002 Only then may the stub actually turn off packet acknowledgments.
43003 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
43004 response, which can be safely ignored by the stub.
43006 Note that @code{set remote noack-packet} command only affects negotiation
43007 between @value{GDBN} and the stub when subsequent connections are made;
43008 it does not affect the protocol acknowledgment state for any current
43010 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
43011 new connection is established,
43012 there is also no protocol request to re-enable the acknowledgments
43013 for the current connection, once disabled.
43018 Example sequence of a target being re-started. Notice how the restart
43019 does not get any direct output:
43024 @emph{target restarts}
43027 <- @code{T001:1234123412341234}
43031 Example sequence of a target being stepped by a single instruction:
43034 -> @code{G1445@dots{}}
43039 <- @code{T001:1234123412341234}
43043 <- @code{1455@dots{}}
43047 @node File-I/O Remote Protocol Extension
43048 @section File-I/O Remote Protocol Extension
43049 @cindex File-I/O remote protocol extension
43052 * File-I/O Overview::
43053 * Protocol Basics::
43054 * The F Request Packet::
43055 * The F Reply Packet::
43056 * The Ctrl-C Message::
43058 * List of Supported Calls::
43059 * Protocol-specific Representation of Datatypes::
43061 * File-I/O Examples::
43064 @node File-I/O Overview
43065 @subsection File-I/O Overview
43066 @cindex file-i/o overview
43068 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
43069 target to use the host's file system and console I/O to perform various
43070 system calls. System calls on the target system are translated into a
43071 remote protocol packet to the host system, which then performs the needed
43072 actions and returns a response packet to the target system.
43073 This simulates file system operations even on targets that lack file systems.
43075 The protocol is defined to be independent of both the host and target systems.
43076 It uses its own internal representation of datatypes and values. Both
43077 @value{GDBN} and the target's @value{GDBN} stub are responsible for
43078 translating the system-dependent value representations into the internal
43079 protocol representations when data is transmitted.
43081 The communication is synchronous. A system call is possible only when
43082 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
43083 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
43084 the target is stopped to allow deterministic access to the target's
43085 memory. Therefore File-I/O is not interruptible by target signals. On
43086 the other hand, it is possible to interrupt File-I/O by a user interrupt
43087 (@samp{Ctrl-C}) within @value{GDBN}.
43089 The target's request to perform a host system call does not finish
43090 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
43091 after finishing the system call, the target returns to continuing the
43092 previous activity (continue, step). No additional continue or step
43093 request from @value{GDBN} is required.
43096 (@value{GDBP}) continue
43097 <- target requests 'system call X'
43098 target is stopped, @value{GDBN} executes system call
43099 -> @value{GDBN} returns result
43100 ... target continues, @value{GDBN} returns to wait for the target
43101 <- target hits breakpoint and sends a Txx packet
43104 The protocol only supports I/O on the console and to regular files on
43105 the host file system. Character or block special devices, pipes,
43106 named pipes, sockets or any other communication method on the host
43107 system are not supported by this protocol.
43109 File I/O is not supported in non-stop mode.
43111 @node Protocol Basics
43112 @subsection Protocol Basics
43113 @cindex protocol basics, file-i/o
43115 The File-I/O protocol uses the @code{F} packet as the request as well
43116 as reply packet. Since a File-I/O system call can only occur when
43117 @value{GDBN} is waiting for a response from the continuing or stepping target,
43118 the File-I/O request is a reply that @value{GDBN} has to expect as a result
43119 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
43120 This @code{F} packet contains all information needed to allow @value{GDBN}
43121 to call the appropriate host system call:
43125 A unique identifier for the requested system call.
43128 All parameters to the system call. Pointers are given as addresses
43129 in the target memory address space. Pointers to strings are given as
43130 pointer/length pair. Numerical values are given as they are.
43131 Numerical control flags are given in a protocol-specific representation.
43135 At this point, @value{GDBN} has to perform the following actions.
43139 If the parameters include pointer values to data needed as input to a
43140 system call, @value{GDBN} requests this data from the target with a
43141 standard @code{m} packet request. This additional communication has to be
43142 expected by the target implementation and is handled as any other @code{m}
43146 @value{GDBN} translates all value from protocol representation to host
43147 representation as needed. Datatypes are coerced into the host types.
43150 @value{GDBN} calls the system call.
43153 It then coerces datatypes back to protocol representation.
43156 If the system call is expected to return data in buffer space specified
43157 by pointer parameters to the call, the data is transmitted to the
43158 target using a @code{M} or @code{X} packet. This packet has to be expected
43159 by the target implementation and is handled as any other @code{M} or @code{X}
43164 Eventually @value{GDBN} replies with another @code{F} packet which contains all
43165 necessary information for the target to continue. This at least contains
43172 @code{errno}, if has been changed by the system call.
43179 After having done the needed type and value coercion, the target continues
43180 the latest continue or step action.
43182 @node The F Request Packet
43183 @subsection The @code{F} Request Packet
43184 @cindex file-i/o request packet
43185 @cindex @code{F} request packet
43187 The @code{F} request packet has the following format:
43190 @item F@var{call-id},@var{parameter@dots{}}
43192 @var{call-id} is the identifier to indicate the host system call to be called.
43193 This is just the name of the function.
43195 @var{parameter@dots{}} are the parameters to the system call.
43196 Parameters are hexadecimal integer values, either the actual values in case
43197 of scalar datatypes, pointers to target buffer space in case of compound
43198 datatypes and unspecified memory areas, or pointer/length pairs in case
43199 of string parameters. These are appended to the @var{call-id} as a
43200 comma-delimited list. All values are transmitted in ASCII
43201 string representation, pointer/length pairs separated by a slash.
43207 @node The F Reply Packet
43208 @subsection The @code{F} Reply Packet
43209 @cindex file-i/o reply packet
43210 @cindex @code{F} reply packet
43212 The @code{F} reply packet has the following format:
43216 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
43218 @var{retcode} is the return code of the system call as hexadecimal value.
43220 @var{errno} is the @code{errno} set by the call, in protocol-specific
43222 This parameter can be omitted if the call was successful.
43224 @var{Ctrl-C flag} is only sent if the user requested a break. In this
43225 case, @var{errno} must be sent as well, even if the call was successful.
43226 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
43233 or, if the call was interrupted before the host call has been performed:
43240 assuming 4 is the protocol-specific representation of @code{EINTR}.
43245 @node The Ctrl-C Message
43246 @subsection The @samp{Ctrl-C} Message
43247 @cindex ctrl-c message, in file-i/o protocol
43249 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
43250 reply packet (@pxref{The F Reply Packet}),
43251 the target should behave as if it had
43252 gotten a break message. The meaning for the target is ``system call
43253 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
43254 (as with a break message) and return to @value{GDBN} with a @code{T02}
43257 It's important for the target to know in which
43258 state the system call was interrupted. There are two possible cases:
43262 The system call hasn't been performed on the host yet.
43265 The system call on the host has been finished.
43269 These two states can be distinguished by the target by the value of the
43270 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
43271 call hasn't been performed. This is equivalent to the @code{EINTR} handling
43272 on POSIX systems. In any other case, the target may presume that the
43273 system call has been finished --- successfully or not --- and should behave
43274 as if the break message arrived right after the system call.
43276 @value{GDBN} must behave reliably. If the system call has not been called
43277 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
43278 @code{errno} in the packet. If the system call on the host has been finished
43279 before the user requests a break, the full action must be finished by
43280 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
43281 The @code{F} packet may only be sent when either nothing has happened
43282 or the full action has been completed.
43285 @subsection Console I/O
43286 @cindex console i/o as part of file-i/o
43288 By default and if not explicitly closed by the target system, the file
43289 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
43290 on the @value{GDBN} console is handled as any other file output operation
43291 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
43292 by @value{GDBN} so that after the target read request from file descriptor
43293 0 all following typing is buffered until either one of the following
43298 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
43300 system call is treated as finished.
43303 The user presses @key{RET}. This is treated as end of input with a trailing
43307 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
43308 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
43312 If the user has typed more characters than fit in the buffer given to
43313 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
43314 either another @code{read(0, @dots{})} is requested by the target, or debugging
43315 is stopped at the user's request.
43318 @node List of Supported Calls
43319 @subsection List of Supported Calls
43320 @cindex list of supported file-i/o calls
43337 @unnumberedsubsubsec open
43338 @cindex open, file-i/o system call
43343 int open(const char *pathname, int flags);
43344 int open(const char *pathname, int flags, mode_t mode);
43348 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
43351 @var{flags} is the bitwise @code{OR} of the following values:
43355 If the file does not exist it will be created. The host
43356 rules apply as far as file ownership and time stamps
43360 When used with @code{O_CREAT}, if the file already exists it is
43361 an error and open() fails.
43364 If the file already exists and the open mode allows
43365 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
43366 truncated to zero length.
43369 The file is opened in append mode.
43372 The file is opened for reading only.
43375 The file is opened for writing only.
43378 The file is opened for reading and writing.
43382 Other bits are silently ignored.
43386 @var{mode} is the bitwise @code{OR} of the following values:
43390 User has read permission.
43393 User has write permission.
43396 Group has read permission.
43399 Group has write permission.
43402 Others have read permission.
43405 Others have write permission.
43409 Other bits are silently ignored.
43412 @item Return value:
43413 @code{open} returns the new file descriptor or -1 if an error
43420 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
43423 @var{pathname} refers to a directory.
43426 The requested access is not allowed.
43429 @var{pathname} was too long.
43432 A directory component in @var{pathname} does not exist.
43435 @var{pathname} refers to a device, pipe, named pipe or socket.
43438 @var{pathname} refers to a file on a read-only filesystem and
43439 write access was requested.
43442 @var{pathname} is an invalid pointer value.
43445 No space on device to create the file.
43448 The process already has the maximum number of files open.
43451 The limit on the total number of files open on the system
43455 The call was interrupted by the user.
43461 @unnumberedsubsubsec close
43462 @cindex close, file-i/o system call
43471 @samp{Fclose,@var{fd}}
43473 @item Return value:
43474 @code{close} returns zero on success, or -1 if an error occurred.
43480 @var{fd} isn't a valid open file descriptor.
43483 The call was interrupted by the user.
43489 @unnumberedsubsubsec read
43490 @cindex read, file-i/o system call
43495 int read(int fd, void *buf, unsigned int count);
43499 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
43501 @item Return value:
43502 On success, the number of bytes read is returned.
43503 Zero indicates end of file. If count is zero, read
43504 returns zero as well. On error, -1 is returned.
43510 @var{fd} is not a valid file descriptor or is not open for
43514 @var{bufptr} is an invalid pointer value.
43517 The call was interrupted by the user.
43523 @unnumberedsubsubsec write
43524 @cindex write, file-i/o system call
43529 int write(int fd, const void *buf, unsigned int count);
43533 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
43535 @item Return value:
43536 On success, the number of bytes written are returned.
43537 Zero indicates nothing was written. On error, -1
43544 @var{fd} is not a valid file descriptor or is not open for
43548 @var{bufptr} is an invalid pointer value.
43551 An attempt was made to write a file that exceeds the
43552 host-specific maximum file size allowed.
43555 No space on device to write the data.
43558 The call was interrupted by the user.
43564 @unnumberedsubsubsec lseek
43565 @cindex lseek, file-i/o system call
43570 long lseek (int fd, long offset, int flag);
43574 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
43576 @var{flag} is one of:
43580 The offset is set to @var{offset} bytes.
43583 The offset is set to its current location plus @var{offset}
43587 The offset is set to the size of the file plus @var{offset}
43591 @item Return value:
43592 On success, the resulting unsigned offset in bytes from
43593 the beginning of the file is returned. Otherwise, a
43594 value of -1 is returned.
43600 @var{fd} is not a valid open file descriptor.
43603 @var{fd} is associated with the @value{GDBN} console.
43606 @var{flag} is not a proper value.
43609 The call was interrupted by the user.
43615 @unnumberedsubsubsec rename
43616 @cindex rename, file-i/o system call
43621 int rename(const char *oldpath, const char *newpath);
43625 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
43627 @item Return value:
43628 On success, zero is returned. On error, -1 is returned.
43634 @var{newpath} is an existing directory, but @var{oldpath} is not a
43638 @var{newpath} is a non-empty directory.
43641 @var{oldpath} or @var{newpath} is a directory that is in use by some
43645 An attempt was made to make a directory a subdirectory
43649 A component used as a directory in @var{oldpath} or new
43650 path is not a directory. Or @var{oldpath} is a directory
43651 and @var{newpath} exists but is not a directory.
43654 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
43657 No access to the file or the path of the file.
43661 @var{oldpath} or @var{newpath} was too long.
43664 A directory component in @var{oldpath} or @var{newpath} does not exist.
43667 The file is on a read-only filesystem.
43670 The device containing the file has no room for the new
43674 The call was interrupted by the user.
43680 @unnumberedsubsubsec unlink
43681 @cindex unlink, file-i/o system call
43686 int unlink(const char *pathname);
43690 @samp{Funlink,@var{pathnameptr}/@var{len}}
43692 @item Return value:
43693 On success, zero is returned. On error, -1 is returned.
43699 No access to the file or the path of the file.
43702 The system does not allow unlinking of directories.
43705 The file @var{pathname} cannot be unlinked because it's
43706 being used by another process.
43709 @var{pathnameptr} is an invalid pointer value.
43712 @var{pathname} was too long.
43715 A directory component in @var{pathname} does not exist.
43718 A component of the path is not a directory.
43721 The file is on a read-only filesystem.
43724 The call was interrupted by the user.
43730 @unnumberedsubsubsec stat/fstat
43731 @cindex fstat, file-i/o system call
43732 @cindex stat, file-i/o system call
43737 int stat(const char *pathname, struct stat *buf);
43738 int fstat(int fd, struct stat *buf);
43742 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
43743 @samp{Ffstat,@var{fd},@var{bufptr}}
43745 @item Return value:
43746 On success, zero is returned. On error, -1 is returned.
43752 @var{fd} is not a valid open file.
43755 A directory component in @var{pathname} does not exist or the
43756 path is an empty string.
43759 A component of the path is not a directory.
43762 @var{pathnameptr} is an invalid pointer value.
43765 No access to the file or the path of the file.
43768 @var{pathname} was too long.
43771 The call was interrupted by the user.
43777 @unnumberedsubsubsec gettimeofday
43778 @cindex gettimeofday, file-i/o system call
43783 int gettimeofday(struct timeval *tv, void *tz);
43787 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
43789 @item Return value:
43790 On success, 0 is returned, -1 otherwise.
43796 @var{tz} is a non-NULL pointer.
43799 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
43805 @unnumberedsubsubsec isatty
43806 @cindex isatty, file-i/o system call
43811 int isatty(int fd);
43815 @samp{Fisatty,@var{fd}}
43817 @item Return value:
43818 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
43824 The call was interrupted by the user.
43829 Note that the @code{isatty} call is treated as a special case: it returns
43830 1 to the target if the file descriptor is attached
43831 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
43832 would require implementing @code{ioctl} and would be more complex than
43837 @unnumberedsubsubsec system
43838 @cindex system, file-i/o system call
43843 int system(const char *command);
43847 @samp{Fsystem,@var{commandptr}/@var{len}}
43849 @item Return value:
43850 If @var{len} is zero, the return value indicates whether a shell is
43851 available. A zero return value indicates a shell is not available.
43852 For non-zero @var{len}, the value returned is -1 on error and the
43853 return status of the command otherwise. Only the exit status of the
43854 command is returned, which is extracted from the host's @code{system}
43855 return value by calling @code{WEXITSTATUS(retval)}. In case
43856 @file{/bin/sh} could not be executed, 127 is returned.
43862 The call was interrupted by the user.
43867 @value{GDBN} takes over the full task of calling the necessary host calls
43868 to perform the @code{system} call. The return value of @code{system} on
43869 the host is simplified before it's returned
43870 to the target. Any termination signal information from the child process
43871 is discarded, and the return value consists
43872 entirely of the exit status of the called command.
43874 Due to security concerns, the @code{system} call is by default refused
43875 by @value{GDBN}. The user has to allow this call explicitly with the
43876 @code{set remote system-call-allowed 1} command.
43879 @item set remote system-call-allowed
43880 @kindex set remote system-call-allowed
43881 Control whether to allow the @code{system} calls in the File I/O
43882 protocol for the remote target. The default is zero (disabled).
43884 @item show remote system-call-allowed
43885 @kindex show remote system-call-allowed
43886 Show whether the @code{system} calls are allowed in the File I/O
43890 @node Protocol-specific Representation of Datatypes
43891 @subsection Protocol-specific Representation of Datatypes
43892 @cindex protocol-specific representation of datatypes, in file-i/o protocol
43895 * Integral Datatypes::
43897 * Memory Transfer::
43902 @node Integral Datatypes
43903 @unnumberedsubsubsec Integral Datatypes
43904 @cindex integral datatypes, in file-i/o protocol
43906 The integral datatypes used in the system calls are @code{int},
43907 @code{unsigned int}, @code{long}, @code{unsigned long},
43908 @code{mode_t}, and @code{time_t}.
43910 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
43911 implemented as 32 bit values in this protocol.
43913 @code{long} and @code{unsigned long} are implemented as 64 bit types.
43915 @xref{Limits}, for corresponding MIN and MAX values (similar to those
43916 in @file{limits.h}) to allow range checking on host and target.
43918 @code{time_t} datatypes are defined as seconds since the Epoch.
43920 All integral datatypes transferred as part of a memory read or write of a
43921 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
43924 @node Pointer Values
43925 @unnumberedsubsubsec Pointer Values
43926 @cindex pointer values, in file-i/o protocol
43928 Pointers to target data are transmitted as they are. An exception
43929 is made for pointers to buffers for which the length isn't
43930 transmitted as part of the function call, namely strings. Strings
43931 are transmitted as a pointer/length pair, both as hex values, e.g.@:
43938 which is a pointer to data of length 18 bytes at position 0x1aaf.
43939 The length is defined as the full string length in bytes, including
43940 the trailing null byte. For example, the string @code{"hello world"}
43941 at address 0x123456 is transmitted as
43947 @node Memory Transfer
43948 @unnumberedsubsubsec Memory Transfer
43949 @cindex memory transfer, in file-i/o protocol
43951 Structured data which is transferred using a memory read or write (for
43952 example, a @code{struct stat}) is expected to be in a protocol-specific format
43953 with all scalar multibyte datatypes being big endian. Translation to
43954 this representation needs to be done both by the target before the @code{F}
43955 packet is sent, and by @value{GDBN} before
43956 it transfers memory to the target. Transferred pointers to structured
43957 data should point to the already-coerced data at any time.
43961 @unnumberedsubsubsec struct stat
43962 @cindex struct stat, in file-i/o protocol
43964 The buffer of type @code{struct stat} used by the target and @value{GDBN}
43965 is defined as follows:
43969 unsigned int st_dev; /* device */
43970 unsigned int st_ino; /* inode */
43971 mode_t st_mode; /* protection */
43972 unsigned int st_nlink; /* number of hard links */
43973 unsigned int st_uid; /* user ID of owner */
43974 unsigned int st_gid; /* group ID of owner */
43975 unsigned int st_rdev; /* device type (if inode device) */
43976 unsigned long st_size; /* total size, in bytes */
43977 unsigned long st_blksize; /* blocksize for filesystem I/O */
43978 unsigned long st_blocks; /* number of blocks allocated */
43979 time_t st_atime; /* time of last access */
43980 time_t st_mtime; /* time of last modification */
43981 time_t st_ctime; /* time of last change */
43985 The integral datatypes conform to the definitions given in the
43986 appropriate section (see @ref{Integral Datatypes}, for details) so this
43987 structure is of size 64 bytes.
43989 The values of several fields have a restricted meaning and/or
43995 A value of 0 represents a file, 1 the console.
43998 No valid meaning for the target. Transmitted unchanged.
44001 Valid mode bits are described in @ref{Constants}. Any other
44002 bits have currently no meaning for the target.
44007 No valid meaning for the target. Transmitted unchanged.
44012 These values have a host and file system dependent
44013 accuracy. Especially on Windows hosts, the file system may not
44014 support exact timing values.
44017 The target gets a @code{struct stat} of the above representation and is
44018 responsible for coercing it to the target representation before
44021 Note that due to size differences between the host, target, and protocol
44022 representations of @code{struct stat} members, these members could eventually
44023 get truncated on the target.
44025 @node struct timeval
44026 @unnumberedsubsubsec struct timeval
44027 @cindex struct timeval, in file-i/o protocol
44029 The buffer of type @code{struct timeval} used by the File-I/O protocol
44030 is defined as follows:
44034 time_t tv_sec; /* second */
44035 long tv_usec; /* microsecond */
44039 The integral datatypes conform to the definitions given in the
44040 appropriate section (see @ref{Integral Datatypes}, for details) so this
44041 structure is of size 8 bytes.
44044 @subsection Constants
44045 @cindex constants, in file-i/o protocol
44047 The following values are used for the constants inside of the
44048 protocol. @value{GDBN} and target are responsible for translating these
44049 values before and after the call as needed.
44060 @unnumberedsubsubsec Open Flags
44061 @cindex open flags, in file-i/o protocol
44063 All values are given in hexadecimal representation.
44075 @node mode_t Values
44076 @unnumberedsubsubsec mode_t Values
44077 @cindex mode_t values, in file-i/o protocol
44079 All values are given in octal representation.
44096 @unnumberedsubsubsec Errno Values
44097 @cindex errno values, in file-i/o protocol
44099 All values are given in decimal representation.
44124 @code{EUNKNOWN} is used as a fallback error value if a host system returns
44125 any error value not in the list of supported error numbers.
44128 @unnumberedsubsubsec Lseek Flags
44129 @cindex lseek flags, in file-i/o protocol
44138 @unnumberedsubsubsec Limits
44139 @cindex limits, in file-i/o protocol
44141 All values are given in decimal representation.
44144 INT_MIN -2147483648
44146 UINT_MAX 4294967295
44147 LONG_MIN -9223372036854775808
44148 LONG_MAX 9223372036854775807
44149 ULONG_MAX 18446744073709551615
44152 @node File-I/O Examples
44153 @subsection File-I/O Examples
44154 @cindex file-i/o examples
44156 Example sequence of a write call, file descriptor 3, buffer is at target
44157 address 0x1234, 6 bytes should be written:
44160 <- @code{Fwrite,3,1234,6}
44161 @emph{request memory read from target}
44164 @emph{return "6 bytes written"}
44168 Example sequence of a read call, file descriptor 3, buffer is at target
44169 address 0x1234, 6 bytes should be read:
44172 <- @code{Fread,3,1234,6}
44173 @emph{request memory write to target}
44174 -> @code{X1234,6:XXXXXX}
44175 @emph{return "6 bytes read"}
44179 Example sequence of a read call, call fails on the host due to invalid
44180 file descriptor (@code{EBADF}):
44183 <- @code{Fread,3,1234,6}
44187 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
44191 <- @code{Fread,3,1234,6}
44196 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
44200 <- @code{Fread,3,1234,6}
44201 -> @code{X1234,6:XXXXXX}
44205 @node Library List Format
44206 @section Library List Format
44207 @cindex library list format, remote protocol
44209 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
44210 same process as your application to manage libraries. In this case,
44211 @value{GDBN} can use the loader's symbol table and normal memory
44212 operations to maintain a list of shared libraries. On other
44213 platforms, the operating system manages loaded libraries.
44214 @value{GDBN} can not retrieve the list of currently loaded libraries
44215 through memory operations, so it uses the @samp{qXfer:libraries:read}
44216 packet (@pxref{qXfer library list read}) instead. The remote stub
44217 queries the target's operating system and reports which libraries
44220 The @samp{qXfer:libraries:read} packet returns an XML document which
44221 lists loaded libraries and their offsets. Each library has an
44222 associated name and one or more segment or section base addresses,
44223 which report where the library was loaded in memory.
44225 For the common case of libraries that are fully linked binaries, the
44226 library should have a list of segments. If the target supports
44227 dynamic linking of a relocatable object file, its library XML element
44228 should instead include a list of allocated sections. The segment or
44229 section bases are start addresses, not relocation offsets; they do not
44230 depend on the library's link-time base addresses.
44232 @value{GDBN} must be linked with the Expat library to support XML
44233 library lists. @xref{Expat}.
44235 A simple memory map, with one loaded library relocated by a single
44236 offset, looks like this:
44240 <library name="/lib/libc.so.6">
44241 <segment address="0x10000000"/>
44246 Another simple memory map, with one loaded library with three
44247 allocated sections (.text, .data, .bss), looks like this:
44251 <library name="sharedlib.o">
44252 <section address="0x10000000"/>
44253 <section address="0x20000000"/>
44254 <section address="0x30000000"/>
44259 The format of a library list is described by this DTD:
44262 <!-- library-list: Root element with versioning -->
44263 <!ELEMENT library-list (library)*>
44264 <!ATTLIST library-list version CDATA #FIXED "1.0">
44265 <!ELEMENT library (segment*, section*)>
44266 <!ATTLIST library name CDATA #REQUIRED>
44267 <!ELEMENT segment EMPTY>
44268 <!ATTLIST segment address CDATA #REQUIRED>
44269 <!ELEMENT section EMPTY>
44270 <!ATTLIST section address CDATA #REQUIRED>
44273 In addition, segments and section descriptors cannot be mixed within a
44274 single library element, and you must supply at least one segment or
44275 section for each library.
44277 @node Library List Format for SVR4 Targets
44278 @section Library List Format for SVR4 Targets
44279 @cindex library list format, remote protocol
44281 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
44282 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
44283 shared libraries. Still a special library list provided by this packet is
44284 more efficient for the @value{GDBN} remote protocol.
44286 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
44287 loaded libraries and their SVR4 linker parameters. For each library on SVR4
44288 target, the following parameters are reported:
44292 @code{name}, the absolute file name from the @code{l_name} field of
44293 @code{struct link_map}.
44295 @code{lm} with address of @code{struct link_map} used for TLS
44296 (Thread Local Storage) access.
44298 @code{l_addr}, the displacement as read from the field @code{l_addr} of
44299 @code{struct link_map}. For prelinked libraries this is not an absolute
44300 memory address. It is a displacement of absolute memory address against
44301 address the file was prelinked to during the library load.
44303 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
44306 Additionally the single @code{main-lm} attribute specifies address of
44307 @code{struct link_map} used for the main executable. This parameter is used
44308 for TLS access and its presence is optional.
44310 @value{GDBN} must be linked with the Expat library to support XML
44311 SVR4 library lists. @xref{Expat}.
44313 A simple memory map, with two loaded libraries (which do not use prelink),
44317 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
44318 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
44320 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
44322 </library-list-svr>
44325 The format of an SVR4 library list is described by this DTD:
44328 <!-- library-list-svr4: Root element with versioning -->
44329 <!ELEMENT library-list-svr4 (library)*>
44330 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
44331 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
44332 <!ELEMENT library EMPTY>
44333 <!ATTLIST library name CDATA #REQUIRED>
44334 <!ATTLIST library lm CDATA #REQUIRED>
44335 <!ATTLIST library l_addr CDATA #REQUIRED>
44336 <!ATTLIST library l_ld CDATA #REQUIRED>
44339 @node Memory Map Format
44340 @section Memory Map Format
44341 @cindex memory map format
44343 To be able to write into flash memory, @value{GDBN} needs to obtain a
44344 memory map from the target. This section describes the format of the
44347 The memory map is obtained using the @samp{qXfer:memory-map:read}
44348 (@pxref{qXfer memory map read}) packet and is an XML document that
44349 lists memory regions.
44351 @value{GDBN} must be linked with the Expat library to support XML
44352 memory maps. @xref{Expat}.
44354 The top-level structure of the document is shown below:
44357 <?xml version="1.0"?>
44358 <!DOCTYPE memory-map
44359 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
44360 "http://sourceware.org/gdb/gdb-memory-map.dtd">
44366 Each region can be either:
44371 A region of RAM starting at @var{addr} and extending for @var{length}
44375 <memory type="ram" start="@var{addr}" length="@var{length}"/>
44380 A region of read-only memory:
44383 <memory type="rom" start="@var{addr}" length="@var{length}"/>
44388 A region of flash memory, with erasure blocks @var{blocksize}
44392 <memory type="flash" start="@var{addr}" length="@var{length}">
44393 <property name="blocksize">@var{blocksize}</property>
44399 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
44400 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
44401 packets to write to addresses in such ranges.
44403 The formal DTD for memory map format is given below:
44406 <!-- ................................................... -->
44407 <!-- Memory Map XML DTD ................................ -->
44408 <!-- File: memory-map.dtd .............................. -->
44409 <!-- .................................... .............. -->
44410 <!-- memory-map.dtd -->
44411 <!-- memory-map: Root element with versioning -->
44412 <!ELEMENT memory-map (memory)*>
44413 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
44414 <!ELEMENT memory (property)*>
44415 <!-- memory: Specifies a memory region,
44416 and its type, or device. -->
44417 <!ATTLIST memory type (ram|rom|flash) #REQUIRED
44418 start CDATA #REQUIRED
44419 length CDATA #REQUIRED>
44420 <!-- property: Generic attribute tag -->
44421 <!ELEMENT property (#PCDATA | property)*>
44422 <!ATTLIST property name (blocksize) #REQUIRED>
44425 @node Thread List Format
44426 @section Thread List Format
44427 @cindex thread list format
44429 To efficiently update the list of threads and their attributes,
44430 @value{GDBN} issues the @samp{qXfer:threads:read} packet
44431 (@pxref{qXfer threads read}) and obtains the XML document with
44432 the following structure:
44435 <?xml version="1.0"?>
44437 <thread id="id" core="0" name="name">
44438 ... description ...
44443 Each @samp{thread} element must have the @samp{id} attribute that
44444 identifies the thread (@pxref{thread-id syntax}). The
44445 @samp{core} attribute, if present, specifies which processor core
44446 the thread was last executing on. The @samp{name} attribute, if
44447 present, specifies the human-readable name of the thread. The content
44448 of the of @samp{thread} element is interpreted as human-readable
44449 auxiliary information. The @samp{handle} attribute, if present,
44450 is a hex encoded representation of the thread handle.
44453 @node Traceframe Info Format
44454 @section Traceframe Info Format
44455 @cindex traceframe info format
44457 To be able to know which objects in the inferior can be examined when
44458 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
44459 memory ranges, registers and trace state variables that have been
44460 collected in a traceframe.
44462 This list is obtained using the @samp{qXfer:traceframe-info:read}
44463 (@pxref{qXfer traceframe info read}) packet and is an XML document.
44465 @value{GDBN} must be linked with the Expat library to support XML
44466 traceframe info discovery. @xref{Expat}.
44468 The top-level structure of the document is shown below:
44471 <?xml version="1.0"?>
44472 <!DOCTYPE traceframe-info
44473 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
44474 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
44480 Each traceframe block can be either:
44485 A region of collected memory starting at @var{addr} and extending for
44486 @var{length} bytes from there:
44489 <memory start="@var{addr}" length="@var{length}"/>
44493 A block indicating trace state variable numbered @var{number} has been
44497 <tvar id="@var{number}"/>
44502 The formal DTD for the traceframe info format is given below:
44505 <!ELEMENT traceframe-info (memory | tvar)* >
44506 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
44508 <!ELEMENT memory EMPTY>
44509 <!ATTLIST memory start CDATA #REQUIRED
44510 length CDATA #REQUIRED>
44512 <!ATTLIST tvar id CDATA #REQUIRED>
44515 @node Branch Trace Format
44516 @section Branch Trace Format
44517 @cindex branch trace format
44519 In order to display the branch trace of an inferior thread,
44520 @value{GDBN} needs to obtain the list of branches. This list is
44521 represented as list of sequential code blocks that are connected via
44522 branches. The code in each block has been executed sequentially.
44524 This list is obtained using the @samp{qXfer:btrace:read}
44525 (@pxref{qXfer btrace read}) packet and is an XML document.
44527 @value{GDBN} must be linked with the Expat library to support XML
44528 traceframe info discovery. @xref{Expat}.
44530 The top-level structure of the document is shown below:
44533 <?xml version="1.0"?>
44535 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
44536 "http://sourceware.org/gdb/gdb-btrace.dtd">
44545 A block of sequentially executed instructions starting at @var{begin}
44546 and ending at @var{end}:
44549 <block begin="@var{begin}" end="@var{end}"/>
44554 The formal DTD for the branch trace format is given below:
44557 <!ELEMENT btrace (block* | pt) >
44558 <!ATTLIST btrace version CDATA #FIXED "1.0">
44560 <!ELEMENT block EMPTY>
44561 <!ATTLIST block begin CDATA #REQUIRED
44562 end CDATA #REQUIRED>
44564 <!ELEMENT pt (pt-config?, raw?)>
44566 <!ELEMENT pt-config (cpu?)>
44568 <!ELEMENT cpu EMPTY>
44569 <!ATTLIST cpu vendor CDATA #REQUIRED
44570 family CDATA #REQUIRED
44571 model CDATA #REQUIRED
44572 stepping CDATA #REQUIRED>
44574 <!ELEMENT raw (#PCDATA)>
44577 @node Branch Trace Configuration Format
44578 @section Branch Trace Configuration Format
44579 @cindex branch trace configuration format
44581 For each inferior thread, @value{GDBN} can obtain the branch trace
44582 configuration using the @samp{qXfer:btrace-conf:read}
44583 (@pxref{qXfer btrace-conf read}) packet.
44585 The configuration describes the branch trace format and configuration
44586 settings for that format. The following information is described:
44590 This thread uses the @dfn{Branch Trace Store} (@acronym{BTS}) format.
44593 The size of the @acronym{BTS} ring buffer in bytes.
44596 This thread uses the @dfn{Intel Processor Trace} (@acronym{Intel
44600 The size of the @acronym{Intel PT} ring buffer in bytes.
44604 @value{GDBN} must be linked with the Expat library to support XML
44605 branch trace configuration discovery. @xref{Expat}.
44607 The formal DTD for the branch trace configuration format is given below:
44610 <!ELEMENT btrace-conf (bts?, pt?)>
44611 <!ATTLIST btrace-conf version CDATA #FIXED "1.0">
44613 <!ELEMENT bts EMPTY>
44614 <!ATTLIST bts size CDATA #IMPLIED>
44616 <!ELEMENT pt EMPTY>
44617 <!ATTLIST pt size CDATA #IMPLIED>
44620 @include agentexpr.texi
44622 @node Target Descriptions
44623 @appendix Target Descriptions
44624 @cindex target descriptions
44626 One of the challenges of using @value{GDBN} to debug embedded systems
44627 is that there are so many minor variants of each processor
44628 architecture in use. It is common practice for vendors to start with
44629 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
44630 and then make changes to adapt it to a particular market niche. Some
44631 architectures have hundreds of variants, available from dozens of
44632 vendors. This leads to a number of problems:
44636 With so many different customized processors, it is difficult for
44637 the @value{GDBN} maintainers to keep up with the changes.
44639 Since individual variants may have short lifetimes or limited
44640 audiences, it may not be worthwhile to carry information about every
44641 variant in the @value{GDBN} source tree.
44643 When @value{GDBN} does support the architecture of the embedded system
44644 at hand, the task of finding the correct architecture name to give the
44645 @command{set architecture} command can be error-prone.
44648 To address these problems, the @value{GDBN} remote protocol allows a
44649 target system to not only identify itself to @value{GDBN}, but to
44650 actually describe its own features. This lets @value{GDBN} support
44651 processor variants it has never seen before --- to the extent that the
44652 descriptions are accurate, and that @value{GDBN} understands them.
44654 @value{GDBN} must be linked with the Expat library to support XML
44655 target descriptions. @xref{Expat}.
44658 * Retrieving Descriptions:: How descriptions are fetched from a target.
44659 * Target Description Format:: The contents of a target description.
44660 * Predefined Target Types:: Standard types available for target
44662 * Enum Target Types:: How to define enum target types.
44663 * Standard Target Features:: Features @value{GDBN} knows about.
44666 @node Retrieving Descriptions
44667 @section Retrieving Descriptions
44669 Target descriptions can be read from the target automatically, or
44670 specified by the user manually. The default behavior is to read the
44671 description from the target. @value{GDBN} retrieves it via the remote
44672 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
44673 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
44674 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
44675 XML document, of the form described in @ref{Target Description
44678 Alternatively, you can specify a file to read for the target description.
44679 If a file is set, the target will not be queried. The commands to
44680 specify a file are:
44683 @cindex set tdesc filename
44684 @item set tdesc filename @var{path}
44685 Read the target description from @var{path}.
44687 @cindex unset tdesc filename
44688 @item unset tdesc filename
44689 Do not read the XML target description from a file. @value{GDBN}
44690 will use the description supplied by the current target.
44692 @cindex show tdesc filename
44693 @item show tdesc filename
44694 Show the filename to read for a target description, if any.
44698 @node Target Description Format
44699 @section Target Description Format
44700 @cindex target descriptions, XML format
44702 A target description annex is an @uref{http://www.w3.org/XML/, XML}
44703 document which complies with the Document Type Definition provided in
44704 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
44705 means you can use generally available tools like @command{xmllint} to
44706 check that your feature descriptions are well-formed and valid.
44707 However, to help people unfamiliar with XML write descriptions for
44708 their targets, we also describe the grammar here.
44710 Target descriptions can identify the architecture of the remote target
44711 and (for some architectures) provide information about custom register
44712 sets. They can also identify the OS ABI of the remote target.
44713 @value{GDBN} can use this information to autoconfigure for your
44714 target, or to warn you if you connect to an unsupported target.
44716 Here is a simple target description:
44719 <target version="1.0">
44720 <architecture>i386:x86-64</architecture>
44725 This minimal description only says that the target uses
44726 the x86-64 architecture.
44728 A target description has the following overall form, with [ ] marking
44729 optional elements and @dots{} marking repeatable elements. The elements
44730 are explained further below.
44733 <?xml version="1.0"?>
44734 <!DOCTYPE target SYSTEM "gdb-target.dtd">
44735 <target version="1.0">
44736 @r{[}@var{architecture}@r{]}
44737 @r{[}@var{osabi}@r{]}
44738 @r{[}@var{compatible}@r{]}
44739 @r{[}@var{feature}@dots{}@r{]}
44744 The description is generally insensitive to whitespace and line
44745 breaks, under the usual common-sense rules. The XML version
44746 declaration and document type declaration can generally be omitted
44747 (@value{GDBN} does not require them), but specifying them may be
44748 useful for XML validation tools. The @samp{version} attribute for
44749 @samp{<target>} may also be omitted, but we recommend
44750 including it; if future versions of @value{GDBN} use an incompatible
44751 revision of @file{gdb-target.dtd}, they will detect and report
44752 the version mismatch.
44754 @subsection Inclusion
44755 @cindex target descriptions, inclusion
44758 @cindex <xi:include>
44761 It can sometimes be valuable to split a target description up into
44762 several different annexes, either for organizational purposes, or to
44763 share files between different possible target descriptions. You can
44764 divide a description into multiple files by replacing any element of
44765 the target description with an inclusion directive of the form:
44768 <xi:include href="@var{document}"/>
44772 When @value{GDBN} encounters an element of this form, it will retrieve
44773 the named XML @var{document}, and replace the inclusion directive with
44774 the contents of that document. If the current description was read
44775 using @samp{qXfer}, then so will be the included document;
44776 @var{document} will be interpreted as the name of an annex. If the
44777 current description was read from a file, @value{GDBN} will look for
44778 @var{document} as a file in the same directory where it found the
44779 original description.
44781 @subsection Architecture
44782 @cindex <architecture>
44784 An @samp{<architecture>} element has this form:
44787 <architecture>@var{arch}</architecture>
44790 @var{arch} is one of the architectures from the set accepted by
44791 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
44794 @cindex @code{<osabi>}
44796 This optional field was introduced in @value{GDBN} version 7.0.
44797 Previous versions of @value{GDBN} ignore it.
44799 An @samp{<osabi>} element has this form:
44802 <osabi>@var{abi-name}</osabi>
44805 @var{abi-name} is an OS ABI name from the same selection accepted by
44806 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
44808 @subsection Compatible Architecture
44809 @cindex @code{<compatible>}
44811 This optional field was introduced in @value{GDBN} version 7.0.
44812 Previous versions of @value{GDBN} ignore it.
44814 A @samp{<compatible>} element has this form:
44817 <compatible>@var{arch}</compatible>
44820 @var{arch} is one of the architectures from the set accepted by
44821 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
44823 A @samp{<compatible>} element is used to specify that the target
44824 is able to run binaries in some other than the main target architecture
44825 given by the @samp{<architecture>} element. For example, on the
44826 Cell Broadband Engine, the main architecture is @code{powerpc:common}
44827 or @code{powerpc:common64}, but the system is able to run binaries
44828 in the @code{spu} architecture as well. The way to describe this
44829 capability with @samp{<compatible>} is as follows:
44832 <architecture>powerpc:common</architecture>
44833 <compatible>spu</compatible>
44836 @subsection Features
44839 Each @samp{<feature>} describes some logical portion of the target
44840 system. Features are currently used to describe available CPU
44841 registers and the types of their contents. A @samp{<feature>} element
44845 <feature name="@var{name}">
44846 @r{[}@var{type}@dots{}@r{]}
44852 Each feature's name should be unique within the description. The name
44853 of a feature does not matter unless @value{GDBN} has some special
44854 knowledge of the contents of that feature; if it does, the feature
44855 should have its standard name. @xref{Standard Target Features}.
44859 Any register's value is a collection of bits which @value{GDBN} must
44860 interpret. The default interpretation is a two's complement integer,
44861 but other types can be requested by name in the register description.
44862 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
44863 Target Types}), and the description can define additional composite
44866 Each type element must have an @samp{id} attribute, which gives
44867 a unique (within the containing @samp{<feature>}) name to the type.
44868 Types must be defined before they are used.
44871 Some targets offer vector registers, which can be treated as arrays
44872 of scalar elements. These types are written as @samp{<vector>} elements,
44873 specifying the array element type, @var{type}, and the number of elements,
44877 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
44881 If a register's value is usefully viewed in multiple ways, define it
44882 with a union type containing the useful representations. The
44883 @samp{<union>} element contains one or more @samp{<field>} elements,
44884 each of which has a @var{name} and a @var{type}:
44887 <union id="@var{id}">
44888 <field name="@var{name}" type="@var{type}"/>
44895 If a register's value is composed from several separate values, define
44896 it with either a structure type or a flags type.
44897 A flags type may only contain bitfields.
44898 A structure type may either contain only bitfields or contain no bitfields.
44899 If the value contains only bitfields, its total size in bytes must be
44902 Non-bitfield values have a @var{name} and @var{type}.
44905 <struct id="@var{id}">
44906 <field name="@var{name}" type="@var{type}"/>
44911 Both @var{name} and @var{type} values are required.
44912 No implicit padding is added.
44914 Bitfield values have a @var{name}, @var{start}, @var{end} and @var{type}.
44917 <struct id="@var{id}" size="@var{size}">
44918 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
44924 <flags id="@var{id}" size="@var{size}">
44925 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
44930 The @var{name} value is required.
44931 Bitfield values may be named with the empty string, @samp{""},
44932 in which case the field is ``filler'' and its value is not printed.
44933 Not all bits need to be specified, so ``filler'' fields are optional.
44935 The @var{start} and @var{end} values are required, and @var{type}
44937 The field's @var{start} must be less than or equal to its @var{end},
44938 and zero represents the least significant bit.
44940 The default value of @var{type} is @code{bool} for single bit fields,
44941 and an unsigned integer otherwise.
44943 Which to choose? Structures or flags?
44945 Registers defined with @samp{flags} have these advantages over
44946 defining them with @samp{struct}:
44950 Arithmetic may be performed on them as if they were integers.
44952 They are printed in a more readable fashion.
44955 Registers defined with @samp{struct} have one advantage over
44956 defining them with @samp{flags}:
44960 One can fetch individual fields like in @samp{C}.
44963 (gdb) print $my_struct_reg.field3
44969 @subsection Registers
44972 Each register is represented as an element with this form:
44975 <reg name="@var{name}"
44976 bitsize="@var{size}"
44977 @r{[}regnum="@var{num}"@r{]}
44978 @r{[}save-restore="@var{save-restore}"@r{]}
44979 @r{[}type="@var{type}"@r{]}
44980 @r{[}group="@var{group}"@r{]}/>
44984 The components are as follows:
44989 The register's name; it must be unique within the target description.
44992 The register's size, in bits.
44995 The register's number. If omitted, a register's number is one greater
44996 than that of the previous register (either in the current feature or in
44997 a preceding feature); the first register in the target description
44998 defaults to zero. This register number is used to read or write
44999 the register; e.g.@: it is used in the remote @code{p} and @code{P}
45000 packets, and registers appear in the @code{g} and @code{G} packets
45001 in order of increasing register number.
45004 Whether the register should be preserved across inferior function
45005 calls; this must be either @code{yes} or @code{no}. The default is
45006 @code{yes}, which is appropriate for most registers except for
45007 some system control registers; this is not related to the target's
45011 The type of the register. It may be a predefined type, a type
45012 defined in the current feature, or one of the special types @code{int}
45013 and @code{float}. @code{int} is an integer type of the correct size
45014 for @var{bitsize}, and @code{float} is a floating point type (in the
45015 architecture's normal floating point format) of the correct size for
45016 @var{bitsize}. The default is @code{int}.
45019 The register group to which this register belongs. It can be one of the
45020 standard register groups @code{general}, @code{float}, @code{vector} or an
45021 arbitrary string. Group names should be limited to alphanumeric characters.
45022 If a group name is made up of multiple words the words may be separated by
45023 hyphens; e.g.@: @code{special-group} or @code{ultra-special-group}. If no
45024 @var{group} is specified, @value{GDBN} will not display the register in
45025 @code{info registers}.
45029 @node Predefined Target Types
45030 @section Predefined Target Types
45031 @cindex target descriptions, predefined types
45033 Type definitions in the self-description can build up composite types
45034 from basic building blocks, but can not define fundamental types. Instead,
45035 standard identifiers are provided by @value{GDBN} for the fundamental
45036 types. The currently supported types are:
45041 Boolean type, occupying a single bit.
45049 Signed integer types holding the specified number of bits.
45057 Unsigned integer types holding the specified number of bits.
45061 Pointers to unspecified code and data. The program counter and
45062 any dedicated return address register may be marked as code
45063 pointers; printing a code pointer converts it into a symbolic
45064 address. The stack pointer and any dedicated address registers
45065 may be marked as data pointers.
45068 Single precision IEEE floating point.
45071 Double precision IEEE floating point.
45074 The 12-byte extended precision format used by ARM FPA registers.
45077 The 10-byte extended precision format used by x87 registers.
45080 32bit @sc{eflags} register used by x86.
45083 32bit @sc{mxcsr} register used by x86.
45087 @node Enum Target Types
45088 @section Enum Target Types
45089 @cindex target descriptions, enum types
45091 Enum target types are useful in @samp{struct} and @samp{flags}
45092 register descriptions. @xref{Target Description Format}.
45094 Enum types have a name, size and a list of name/value pairs.
45097 <enum id="@var{id}" size="@var{size}">
45098 <evalue name="@var{name}" value="@var{value}"/>
45103 Enums must be defined before they are used.
45106 <enum id="levels_type" size="4">
45107 <evalue name="low" value="0"/>
45108 <evalue name="high" value="1"/>
45110 <flags id="flags_type" size="4">
45111 <field name="X" start="0"/>
45112 <field name="LEVEL" start="1" end="1" type="levels_type"/>
45114 <reg name="flags" bitsize="32" type="flags_type"/>
45117 Given that description, a value of 3 for the @samp{flags} register
45118 would be printed as:
45121 (gdb) info register flags
45122 flags 0x3 [ X LEVEL=high ]
45125 @node Standard Target Features
45126 @section Standard Target Features
45127 @cindex target descriptions, standard features
45129 A target description must contain either no registers or all the
45130 target's registers. If the description contains no registers, then
45131 @value{GDBN} will assume a default register layout, selected based on
45132 the architecture. If the description contains any registers, the
45133 default layout will not be used; the standard registers must be
45134 described in the target description, in such a way that @value{GDBN}
45135 can recognize them.
45137 This is accomplished by giving specific names to feature elements
45138 which contain standard registers. @value{GDBN} will look for features
45139 with those names and verify that they contain the expected registers;
45140 if any known feature is missing required registers, or if any required
45141 feature is missing, @value{GDBN} will reject the target
45142 description. You can add additional registers to any of the
45143 standard features --- @value{GDBN} will display them just as if
45144 they were added to an unrecognized feature.
45146 This section lists the known features and their expected contents.
45147 Sample XML documents for these features are included in the
45148 @value{GDBN} source tree, in the directory @file{gdb/features}.
45150 Names recognized by @value{GDBN} should include the name of the
45151 company or organization which selected the name, and the overall
45152 architecture to which the feature applies; so e.g.@: the feature
45153 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
45155 The names of registers are not case sensitive for the purpose
45156 of recognizing standard features, but @value{GDBN} will only display
45157 registers using the capitalization used in the description.
45160 * AArch64 Features::
45164 * MicroBlaze Features::
45168 * Nios II Features::
45169 * OpenRISC 1000 Features::
45170 * PowerPC Features::
45171 * RISC-V Features::
45173 * S/390 and System z Features::
45179 @node AArch64 Features
45180 @subsection AArch64 Features
45181 @cindex target descriptions, AArch64 features
45183 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
45184 targets. It should contain registers @samp{x0} through @samp{x30},
45185 @samp{sp}, @samp{pc}, and @samp{cpsr}.
45187 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
45188 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
45191 The @samp{org.gnu.gdb.aarch64.sve} feature is optional. If present,
45192 it should contain registers @samp{z0} through @samp{z31}, @samp{p0}
45193 through @samp{p15}, @samp{ffr} and @samp{vg}.
45195 The @samp{org.gnu.gdb.aarch64.pauth} feature is optional. If present,
45196 it should contain registers @samp{pauth_dmask} and @samp{pauth_cmask}.
45199 @subsection ARC Features
45200 @cindex target descriptions, ARC Features
45202 ARC processors are highly configurable, so even core registers and their number
45203 are not completely predetermined. In addition flags and PC registers which are
45204 important to @value{GDBN} are not ``core'' registers in ARC. It is required
45205 that one of the core registers features is present.
45206 @samp{org.gnu.gdb.arc.aux-minimal} feature is mandatory.
45208 The @samp{org.gnu.gdb.arc.core.v2} feature is required for ARC EM and ARC HS
45209 targets with a normal register file. It should contain registers @samp{r0}
45210 through @samp{r25}, @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink},
45211 @samp{lp_count} and @samp{pcl}. This feature may contain register @samp{ilink}
45212 and any of extension core registers @samp{r32} through @samp{r59/acch}.
45213 @samp{ilink} and extension core registers are not available to read/write, when
45214 debugging GNU/Linux applications, thus @samp{ilink} is made optional.
45216 The @samp{org.gnu.gdb.arc.core-reduced.v2} feature is required for ARC EM and
45217 ARC HS targets with a reduced register file. It should contain registers
45218 @samp{r0} through @samp{r3}, @samp{r10} through @samp{r15}, @samp{gp},
45219 @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink}, @samp{lp_count} and @samp{pcl}.
45220 This feature may contain register @samp{ilink} and any of extension core
45221 registers @samp{r32} through @samp{r59/acch}.
45223 The @samp{org.gnu.gdb.arc.core.arcompact} feature is required for ARCompact
45224 targets with a normal register file. It should contain registers @samp{r0}
45225 through @samp{r25}, @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink},
45226 @samp{lp_count} and @samp{pcl}. This feature may contain registers
45227 @samp{ilink1}, @samp{ilink2} and any of extension core registers @samp{r32}
45228 through @samp{r59/acch}. @samp{ilink1} and @samp{ilink2} and extension core
45229 registers are not available when debugging GNU/Linux applications. The only
45230 difference with @samp{org.gnu.gdb.arc.core.v2} feature is in the names of
45231 @samp{ilink1} and @samp{ilink2} registers and that @samp{r30} is mandatory in
45232 ARC v2, but @samp{ilink2} is optional on ARCompact.
45234 The @samp{org.gnu.gdb.arc.aux-minimal} feature is required for all ARC
45235 targets. It should contain registers @samp{pc} and @samp{status32}.
45238 @subsection ARM Features
45239 @cindex target descriptions, ARM features
45241 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
45243 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
45244 @samp{lr}, @samp{pc}, and @samp{cpsr}.
45246 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
45247 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
45248 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
45251 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
45252 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
45254 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
45255 it should contain at least registers @samp{wR0} through @samp{wR15} and
45256 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
45257 @samp{wCSSF}, and @samp{wCASF} registers are optional.
45259 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
45260 should contain at least registers @samp{d0} through @samp{d15}. If
45261 they are present, @samp{d16} through @samp{d31} should also be included.
45262 @value{GDBN} will synthesize the single-precision registers from
45263 halves of the double-precision registers.
45265 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
45266 need to contain registers; it instructs @value{GDBN} to display the
45267 VFP double-precision registers as vectors and to synthesize the
45268 quad-precision registers from pairs of double-precision registers.
45269 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
45270 be present and include 32 double-precision registers.
45272 @node i386 Features
45273 @subsection i386 Features
45274 @cindex target descriptions, i386 features
45276 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
45277 targets. It should describe the following registers:
45281 @samp{eax} through @samp{edi} plus @samp{eip} for i386
45283 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
45285 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
45286 @samp{fs}, @samp{gs}
45288 @samp{st0} through @samp{st7}
45290 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
45291 @samp{foseg}, @samp{fooff} and @samp{fop}
45294 The register sets may be different, depending on the target.
45296 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
45297 describe registers:
45301 @samp{xmm0} through @samp{xmm7} for i386
45303 @samp{xmm0} through @samp{xmm15} for amd64
45308 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
45309 @samp{org.gnu.gdb.i386.sse} feature. It should
45310 describe the upper 128 bits of @sc{ymm} registers:
45314 @samp{ymm0h} through @samp{ymm7h} for i386
45316 @samp{ymm0h} through @samp{ymm15h} for amd64
45319 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel
45320 Memory Protection Extension (MPX). It should describe the following registers:
45324 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
45326 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
45329 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
45330 describe a single register, @samp{orig_eax}.
45332 The @samp{org.gnu.gdb.i386.segments} feature is optional. It should
45333 describe two system registers: @samp{fs_base} and @samp{gs_base}.
45335 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
45336 @samp{org.gnu.gdb.i386.avx} feature. It should
45337 describe additional @sc{xmm} registers:
45341 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
45344 It should describe the upper 128 bits of additional @sc{ymm} registers:
45348 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
45352 describe the upper 256 bits of @sc{zmm} registers:
45356 @samp{zmm0h} through @samp{zmm7h} for i386.
45358 @samp{zmm0h} through @samp{zmm15h} for amd64.
45362 describe the additional @sc{zmm} registers:
45366 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
45369 The @samp{org.gnu.gdb.i386.pkeys} feature is optional. It should
45370 describe a single register, @samp{pkru}. It is a 32-bit register
45371 valid for i386 and amd64.
45373 @node MicroBlaze Features
45374 @subsection MicroBlaze Features
45375 @cindex target descriptions, MicroBlaze features
45377 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
45378 targets. It should contain registers @samp{r0} through @samp{r31},
45379 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
45380 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
45381 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
45383 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
45384 If present, it should contain registers @samp{rshr} and @samp{rslr}
45386 @node MIPS Features
45387 @subsection @acronym{MIPS} Features
45388 @cindex target descriptions, @acronym{MIPS} features
45390 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
45391 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
45392 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
45395 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
45396 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
45397 registers. They may be 32-bit or 64-bit depending on the target.
45399 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
45400 it may be optional in a future version of @value{GDBN}. It should
45401 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
45402 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
45404 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
45405 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
45406 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
45407 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
45409 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
45410 contain a single register, @samp{restart}, which is used by the
45411 Linux kernel to control restartable syscalls.
45413 @node M68K Features
45414 @subsection M68K Features
45415 @cindex target descriptions, M68K features
45418 @item @samp{org.gnu.gdb.m68k.core}
45419 @itemx @samp{org.gnu.gdb.coldfire.core}
45420 @itemx @samp{org.gnu.gdb.fido.core}
45421 One of those features must be always present.
45422 The feature that is present determines which flavor of m68k is
45423 used. The feature that is present should contain registers
45424 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
45425 @samp{sp}, @samp{ps} and @samp{pc}.
45427 @item @samp{org.gnu.gdb.coldfire.fp}
45428 This feature is optional. If present, it should contain registers
45429 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
45432 Note that, despite the fact that this feature's name says
45433 @samp{coldfire}, it is used to describe any floating point registers.
45434 The size of the registers must match the main m68k flavor; so, for
45435 example, if the primary feature is reported as @samp{coldfire}, then
45436 64-bit floating point registers are required.
45439 @node NDS32 Features
45440 @subsection NDS32 Features
45441 @cindex target descriptions, NDS32 features
45443 The @samp{org.gnu.gdb.nds32.core} feature is required for NDS32
45444 targets. It should contain at least registers @samp{r0} through
45445 @samp{r10}, @samp{r15}, @samp{fp}, @samp{gp}, @samp{lp}, @samp{sp},
45448 The @samp{org.gnu.gdb.nds32.fpu} feature is optional. If present,
45449 it should contain 64-bit double-precision floating-point registers
45450 @samp{fd0} through @emph{fdN}, which should be @samp{fd3}, @samp{fd7},
45451 @samp{fd15}, or @samp{fd31} based on the FPU configuration implemented.
45453 @emph{Note:} The first sixteen 64-bit double-precision floating-point
45454 registers are overlapped with the thirty-two 32-bit single-precision
45455 floating-point registers. The 32-bit single-precision registers, if
45456 not being listed explicitly, will be synthesized from halves of the
45457 overlapping 64-bit double-precision registers. Listing 32-bit
45458 single-precision registers explicitly is deprecated, and the
45459 support to it could be totally removed some day.
45461 @node Nios II Features
45462 @subsection Nios II Features
45463 @cindex target descriptions, Nios II features
45465 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
45466 targets. It should contain the 32 core registers (@samp{zero},
45467 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
45468 @samp{pc}, and the 16 control registers (@samp{status} through
45471 @node OpenRISC 1000 Features
45472 @subsection Openrisc 1000 Features
45473 @cindex target descriptions, OpenRISC 1000 features
45475 The @samp{org.gnu.gdb.or1k.group0} feature is required for OpenRISC 1000
45476 targets. It should contain the 32 general purpose registers (@samp{r0}
45477 through @samp{r31}), @samp{ppc}, @samp{npc} and @samp{sr}.
45479 @node PowerPC Features
45480 @subsection PowerPC Features
45481 @cindex target descriptions, PowerPC features
45483 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
45484 targets. It should contain registers @samp{r0} through @samp{r31},
45485 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
45486 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
45488 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
45489 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
45491 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
45492 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr}, and
45493 @samp{vrsave}. @value{GDBN} will define pseudo-registers @samp{v0}
45494 through @samp{v31} as aliases for the corresponding @samp{vrX}
45497 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
45498 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN} will
45499 combine these registers with the floating point registers (@samp{f0}
45500 through @samp{f31}) and the altivec registers (@samp{vr0} through
45501 @samp{vr31}) to present the 128-bit wide registers @samp{vs0} through
45502 @samp{vs63}, the set of vector-scalar registers for POWER7.
45503 Therefore, this feature requires both @samp{org.gnu.gdb.power.fpu} and
45504 @samp{org.gnu.gdb.power.altivec}.
45506 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
45507 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
45508 @samp{spefscr}. SPE targets should provide 32-bit registers in
45509 @samp{org.gnu.gdb.power.core} and provide the upper halves in
45510 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
45511 these to present registers @samp{ev0} through @samp{ev31} to the
45514 The @samp{org.gnu.gdb.power.ppr} feature is optional. It should
45515 contain the 64-bit register @samp{ppr}.
45517 The @samp{org.gnu.gdb.power.dscr} feature is optional. It should
45518 contain the 64-bit register @samp{dscr}.
45520 The @samp{org.gnu.gdb.power.tar} feature is optional. It should
45521 contain the 64-bit register @samp{tar}.
45523 The @samp{org.gnu.gdb.power.ebb} feature is optional. It should
45524 contain registers @samp{bescr}, @samp{ebbhr} and @samp{ebbrr}, all
45527 The @samp{org.gnu.gdb.power.linux.pmu} feature is optional. It should
45528 contain registers @samp{mmcr0}, @samp{mmcr2}, @samp{siar}, @samp{sdar}
45529 and @samp{sier}, all 64-bit wide. This is the subset of the isa 2.07
45530 server PMU registers provided by @sc{gnu}/Linux.
45532 The @samp{org.gnu.gdb.power.htm.spr} feature is optional. It should
45533 contain registers @samp{tfhar}, @samp{texasr} and @samp{tfiar}, all
45536 The @samp{org.gnu.gdb.power.htm.core} feature is optional. It should
45537 contain the checkpointed general-purpose registers @samp{cr0} through
45538 @samp{cr31}, as well as the checkpointed registers @samp{clr} and
45539 @samp{cctr}. These registers may all be either 32-bit or 64-bit
45540 depending on the target. It should also contain the checkpointed
45541 registers @samp{ccr} and @samp{cxer}, which should both be 32-bit
45544 The @samp{org.gnu.gdb.power.htm.fpu} feature is optional. It should
45545 contain the checkpointed 64-bit floating-point registers @samp{cf0}
45546 through @samp{cf31}, as well as the checkpointed 64-bit register
45549 The @samp{org.gnu.gdb.power.htm.altivec} feature is optional. It
45550 should contain the checkpointed altivec registers @samp{cvr0} through
45551 @samp{cvr31}, all 128-bit wide. It should also contain the
45552 checkpointed registers @samp{cvscr} and @samp{cvrsave}, both 32-bit
45555 The @samp{org.gnu.gdb.power.htm.vsx} feature is optional. It should
45556 contain registers @samp{cvs0h} through @samp{cvs31h}. @value{GDBN}
45557 will combine these registers with the checkpointed floating point
45558 registers (@samp{cf0} through @samp{cf31}) and the checkpointed
45559 altivec registers (@samp{cvr0} through @samp{cvr31}) to present the
45560 128-bit wide checkpointed vector-scalar registers @samp{cvs0} through
45561 @samp{cvs63}. Therefore, this feature requires both
45562 @samp{org.gnu.gdb.power.htm.altivec} and
45563 @samp{org.gnu.gdb.power.htm.fpu}.
45565 The @samp{org.gnu.gdb.power.htm.ppr} feature is optional. It should
45566 contain the 64-bit checkpointed register @samp{cppr}.
45568 The @samp{org.gnu.gdb.power.htm.dscr} feature is optional. It should
45569 contain the 64-bit checkpointed register @samp{cdscr}.
45571 The @samp{org.gnu.gdb.power.htm.tar} feature is optional. It should
45572 contain the 64-bit checkpointed register @samp{ctar}.
45575 @node RISC-V Features
45576 @subsection RISC-V Features
45577 @cindex target descriptions, RISC-V Features
45579 The @samp{org.gnu.gdb.riscv.cpu} feature is required for RISC-V
45580 targets. It should contain the registers @samp{x0} through
45581 @samp{x31}, and @samp{pc}. Either the architectural names (@samp{x0},
45582 @samp{x1}, etc) can be used, or the ABI names (@samp{zero}, @samp{ra},
45585 The @samp{org.gnu.gdb.riscv.fpu} feature is optional. If present, it
45586 should contain registers @samp{f0} through @samp{f31}, @samp{fflags},
45587 @samp{frm}, and @samp{fcsr}. As with the cpu feature, either the
45588 architectural register names, or the ABI names can be used.
45590 The @samp{org.gnu.gdb.riscv.virtual} feature is optional. If present,
45591 it should contain registers that are not backed by real registers on
45592 the target, but are instead virtual, where the register value is
45593 derived from other target state. In many ways these are like
45594 @value{GDBN}s pseudo-registers, except implemented by the target.
45595 Currently the only register expected in this set is the one byte
45596 @samp{priv} register that contains the target's privilege level in the
45597 least significant two bits.
45599 The @samp{org.gnu.gdb.riscv.csr} feature is optional. If present, it
45600 should contain all of the target's standard CSRs. Standard CSRs are
45601 those defined in the RISC-V specification documents. There is some
45602 overlap between this feature and the fpu feature; the @samp{fflags},
45603 @samp{frm}, and @samp{fcsr} registers could be in either feature. The
45604 expectation is that these registers will be in the fpu feature if the
45605 target has floating point hardware, but can be moved into the csr
45606 feature if the target has the floating point control registers, but no
45607 other floating point hardware.
45610 @subsection RX Features
45611 @cindex target descriptions, RX Features
45613 The @samp{org.gnu.gdb.rx.core} feature is required for RX
45614 targets. It should contain the registers @samp{r0} through
45615 @samp{r15}, @samp{usp}, @samp{isp}, @samp{psw}, @samp{pc}, @samp{intb},
45616 @samp{bpsw}, @samp{bpc}, @samp{fintv}, @samp{fpsw}, and @samp{acc}.
45618 @node S/390 and System z Features
45619 @subsection S/390 and System z Features
45620 @cindex target descriptions, S/390 features
45621 @cindex target descriptions, System z features
45623 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
45624 System z targets. It should contain the PSW and the 16 general
45625 registers. In particular, System z targets should provide the 64-bit
45626 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
45627 S/390 targets should provide the 32-bit versions of these registers.
45628 A System z target that runs in 31-bit addressing mode should provide
45629 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
45630 register's upper halves @samp{r0h} through @samp{r15h}, and their
45631 lower halves @samp{r0l} through @samp{r15l}.
45633 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
45634 contain the 64-bit registers @samp{f0} through @samp{f15}, and
45637 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
45638 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
45640 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
45641 contain the register @samp{orig_r2}, which is 64-bit wide on System z
45642 targets and 32-bit otherwise. In addition, the feature may contain
45643 the @samp{last_break} register, whose width depends on the addressing
45644 mode, as well as the @samp{system_call} register, which is always
45647 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
45648 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
45649 @samp{atia}, and @samp{tr0} through @samp{tr15}.
45651 The @samp{org.gnu.gdb.s390.vx} feature is optional. It should contain
45652 64-bit wide registers @samp{v0l} through @samp{v15l}, which will be
45653 combined by @value{GDBN} with the floating point registers @samp{f0}
45654 through @samp{f15} to present the 128-bit wide vector registers
45655 @samp{v0} through @samp{v15}. In addition, this feature should
45656 contain the 128-bit wide vector registers @samp{v16} through
45659 The @samp{org.gnu.gdb.s390.gs} feature is optional. It should contain
45660 the 64-bit wide guarded-storage-control registers @samp{gsd},
45661 @samp{gssm}, and @samp{gsepla}.
45663 The @samp{org.gnu.gdb.s390.gsbc} feature is optional. It should contain
45664 the 64-bit wide guarded-storage broadcast control registers
45665 @samp{bc_gsd}, @samp{bc_gssm}, and @samp{bc_gsepla}.
45667 @node Sparc Features
45668 @subsection Sparc Features
45669 @cindex target descriptions, sparc32 features
45670 @cindex target descriptions, sparc64 features
45671 The @samp{org.gnu.gdb.sparc.cpu} feature is required for sparc32/sparc64
45672 targets. It should describe the following registers:
45676 @samp{g0} through @samp{g7}
45678 @samp{o0} through @samp{o7}
45680 @samp{l0} through @samp{l7}
45682 @samp{i0} through @samp{i7}
45685 They may be 32-bit or 64-bit depending on the target.
45687 Also the @samp{org.gnu.gdb.sparc.fpu} feature is required for sparc32/sparc64
45688 targets. It should describe the following registers:
45692 @samp{f0} through @samp{f31}
45694 @samp{f32} through @samp{f62} for sparc64
45697 The @samp{org.gnu.gdb.sparc.cp0} feature is required for sparc32/sparc64
45698 targets. It should describe the following registers:
45702 @samp{y}, @samp{psr}, @samp{wim}, @samp{tbr}, @samp{pc}, @samp{npc},
45703 @samp{fsr}, and @samp{csr} for sparc32
45705 @samp{pc}, @samp{npc}, @samp{state}, @samp{fsr}, @samp{fprs}, and @samp{y}
45709 @node TIC6x Features
45710 @subsection TMS320C6x Features
45711 @cindex target descriptions, TIC6x features
45712 @cindex target descriptions, TMS320C6x features
45713 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
45714 targets. It should contain registers @samp{A0} through @samp{A15},
45715 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
45717 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
45718 contain registers @samp{A16} through @samp{A31} and @samp{B16}
45719 through @samp{B31}.
45721 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
45722 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
45724 @node Operating System Information
45725 @appendix Operating System Information
45726 @cindex operating system information
45732 Users of @value{GDBN} often wish to obtain information about the state of
45733 the operating system running on the target---for example the list of
45734 processes, or the list of open files. This section describes the
45735 mechanism that makes it possible. This mechanism is similar to the
45736 target features mechanism (@pxref{Target Descriptions}), but focuses
45737 on a different aspect of target.
45739 Operating system information is retrieved from the target via the
45740 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
45741 read}). The object name in the request should be @samp{osdata}, and
45742 the @var{annex} identifies the data to be fetched.
45745 @appendixsection Process list
45746 @cindex operating system information, process list
45748 When requesting the process list, the @var{annex} field in the
45749 @samp{qXfer} request should be @samp{processes}. The returned data is
45750 an XML document. The formal syntax of this document is defined in
45751 @file{gdb/features/osdata.dtd}.
45753 An example document is:
45756 <?xml version="1.0"?>
45757 <!DOCTYPE target SYSTEM "osdata.dtd">
45758 <osdata type="processes">
45760 <column name="pid">1</column>
45761 <column name="user">root</column>
45762 <column name="command">/sbin/init</column>
45763 <column name="cores">1,2,3</column>
45768 Each item should include a column whose name is @samp{pid}. The value
45769 of that column should identify the process on the target. The
45770 @samp{user} and @samp{command} columns are optional, and will be
45771 displayed by @value{GDBN}. The @samp{cores} column, if present,
45772 should contain a comma-separated list of cores that this process
45773 is running on. Target may provide additional columns,
45774 which @value{GDBN} currently ignores.
45776 @node Trace File Format
45777 @appendix Trace File Format
45778 @cindex trace file format
45780 The trace file comes in three parts: a header, a textual description
45781 section, and a trace frame section with binary data.
45783 The header has the form @code{\x7fTRACE0\n}. The first byte is
45784 @code{0x7f} so as to indicate that the file contains binary data,
45785 while the @code{0} is a version number that may have different values
45788 The description section consists of multiple lines of @sc{ascii} text
45789 separated by newline characters (@code{0xa}). The lines may include a
45790 variety of optional descriptive or context-setting information, such
45791 as tracepoint definitions or register set size. @value{GDBN} will
45792 ignore any line that it does not recognize. An empty line marks the end
45797 Specifies the size of a register block in bytes. This is equal to the
45798 size of a @code{g} packet payload in the remote protocol. @var{size}
45799 is an ascii decimal number. There should be only one such line in
45800 a single trace file.
45802 @item status @var{status}
45803 Trace status. @var{status} has the same format as a @code{qTStatus}
45804 remote packet reply. There should be only one such line in a single trace
45807 @item tp @var{payload}
45808 Tracepoint definition. The @var{payload} has the same format as
45809 @code{qTfP}/@code{qTsP} remote packet reply payload. A single tracepoint
45810 may take multiple lines of definition, corresponding to the multiple
45813 @item tsv @var{payload}
45814 Trace state variable definition. The @var{payload} has the same format as
45815 @code{qTfV}/@code{qTsV} remote packet reply payload. A single variable
45816 may take multiple lines of definition, corresponding to the multiple
45819 @item tdesc @var{payload}
45820 Target description in XML format. The @var{payload} is a single line of
45821 the XML file. All such lines should be concatenated together to get
45822 the original XML file. This file is in the same format as @code{qXfer}
45823 @code{features} payload, and corresponds to the main @code{target.xml}
45824 file. Includes are not allowed.
45828 The trace frame section consists of a number of consecutive frames.
45829 Each frame begins with a two-byte tracepoint number, followed by a
45830 four-byte size giving the amount of data in the frame. The data in
45831 the frame consists of a number of blocks, each introduced by a
45832 character indicating its type (at least register, memory, and trace
45833 state variable). The data in this section is raw binary, not a
45834 hexadecimal or other encoding; its endianness matches the target's
45837 @c FIXME bi-arch may require endianness/arch info in description section
45840 @item R @var{bytes}
45841 Register block. The number and ordering of bytes matches that of a
45842 @code{g} packet in the remote protocol. Note that these are the
45843 actual bytes, in target order, not a hexadecimal encoding.
45845 @item M @var{address} @var{length} @var{bytes}...
45846 Memory block. This is a contiguous block of memory, at the 8-byte
45847 address @var{address}, with a 2-byte length @var{length}, followed by
45848 @var{length} bytes.
45850 @item V @var{number} @var{value}
45851 Trace state variable block. This records the 8-byte signed value
45852 @var{value} of trace state variable numbered @var{number}.
45856 Future enhancements of the trace file format may include additional types
45859 @node Index Section Format
45860 @appendix @code{.gdb_index} section format
45861 @cindex .gdb_index section format
45862 @cindex index section format
45864 This section documents the index section that is created by @code{save
45865 gdb-index} (@pxref{Index Files}). The index section is
45866 DWARF-specific; some knowledge of DWARF is assumed in this
45869 The mapped index file format is designed to be directly
45870 @code{mmap}able on any architecture. In most cases, a datum is
45871 represented using a little-endian 32-bit integer value, called an
45872 @code{offset_type}. Big endian machines must byte-swap the values
45873 before using them. Exceptions to this rule are noted. The data is
45874 laid out such that alignment is always respected.
45876 A mapped index consists of several areas, laid out in order.
45880 The file header. This is a sequence of values, of @code{offset_type}
45881 unless otherwise noted:
45885 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
45886 Version 4 uses a different hashing function from versions 5 and 6.
45887 Version 6 includes symbols for inlined functions, whereas versions 4
45888 and 5 do not. Version 7 adds attributes to the CU indices in the
45889 symbol table. Version 8 specifies that symbols from DWARF type units
45890 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
45891 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
45893 @value{GDBN} will only read version 4, 5, or 6 indices
45894 by specifying @code{set use-deprecated-index-sections on}.
45895 GDB has a workaround for potentially broken version 7 indices so it is
45896 currently not flagged as deprecated.
45899 The offset, from the start of the file, of the CU list.
45902 The offset, from the start of the file, of the types CU list. Note
45903 that this area can be empty, in which case this offset will be equal
45904 to the next offset.
45907 The offset, from the start of the file, of the address area.
45910 The offset, from the start of the file, of the symbol table.
45913 The offset, from the start of the file, of the constant pool.
45917 The CU list. This is a sequence of pairs of 64-bit little-endian
45918 values, sorted by the CU offset. The first element in each pair is
45919 the offset of a CU in the @code{.debug_info} section. The second
45920 element in each pair is the length of that CU. References to a CU
45921 elsewhere in the map are done using a CU index, which is just the
45922 0-based index into this table. Note that if there are type CUs, then
45923 conceptually CUs and type CUs form a single list for the purposes of
45927 The types CU list. This is a sequence of triplets of 64-bit
45928 little-endian values. In a triplet, the first value is the CU offset,
45929 the second value is the type offset in the CU, and the third value is
45930 the type signature. The types CU list is not sorted.
45933 The address area. The address area consists of a sequence of address
45934 entries. Each address entry has three elements:
45938 The low address. This is a 64-bit little-endian value.
45941 The high address. This is a 64-bit little-endian value. Like
45942 @code{DW_AT_high_pc}, the value is one byte beyond the end.
45945 The CU index. This is an @code{offset_type} value.
45949 The symbol table. This is an open-addressed hash table. The size of
45950 the hash table is always a power of 2.
45952 Each slot in the hash table consists of a pair of @code{offset_type}
45953 values. The first value is the offset of the symbol's name in the
45954 constant pool. The second value is the offset of the CU vector in the
45957 If both values are 0, then this slot in the hash table is empty. This
45958 is ok because while 0 is a valid constant pool index, it cannot be a
45959 valid index for both a string and a CU vector.
45961 The hash value for a table entry is computed by applying an
45962 iterative hash function to the symbol's name. Starting with an
45963 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
45964 the string is incorporated into the hash using the formula depending on the
45969 The formula is @code{r = r * 67 + c - 113}.
45971 @item Versions 5 to 7
45972 The formula is @code{r = r * 67 + tolower (c) - 113}.
45975 The terminating @samp{\0} is not incorporated into the hash.
45977 The step size used in the hash table is computed via
45978 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
45979 value, and @samp{size} is the size of the hash table. The step size
45980 is used to find the next candidate slot when handling a hash
45983 The names of C@t{++} symbols in the hash table are canonicalized. We
45984 don't currently have a simple description of the canonicalization
45985 algorithm; if you intend to create new index sections, you must read
45989 The constant pool. This is simply a bunch of bytes. It is organized
45990 so that alignment is correct: CU vectors are stored first, followed by
45993 A CU vector in the constant pool is a sequence of @code{offset_type}
45994 values. The first value is the number of CU indices in the vector.
45995 Each subsequent value is the index and symbol attributes of a CU in
45996 the CU list. This element in the hash table is used to indicate which
45997 CUs define the symbol and how the symbol is used.
45998 See below for the format of each CU index+attributes entry.
46000 A string in the constant pool is zero-terminated.
46003 Attributes were added to CU index values in @code{.gdb_index} version 7.
46004 If a symbol has multiple uses within a CU then there is one
46005 CU index+attributes value for each use.
46007 The format of each CU index+attributes entry is as follows
46013 This is the index of the CU in the CU list.
46015 These bits are reserved for future purposes and must be zero.
46017 The kind of the symbol in the CU.
46021 This value is reserved and should not be used.
46022 By reserving zero the full @code{offset_type} value is backwards compatible
46023 with previous versions of the index.
46025 The symbol is a type.
46027 The symbol is a variable or an enum value.
46029 The symbol is a function.
46031 Any other kind of symbol.
46033 These values are reserved.
46037 This bit is zero if the value is global and one if it is static.
46039 The determination of whether a symbol is global or static is complicated.
46040 The authorative reference is the file @file{dwarf2read.c} in
46041 @value{GDBN} sources.
46045 This pseudo-code describes the computation of a symbol's kind and
46046 global/static attributes in the index.
46049 is_external = get_attribute (die, DW_AT_external);
46050 language = get_attribute (cu_die, DW_AT_language);
46053 case DW_TAG_typedef:
46054 case DW_TAG_base_type:
46055 case DW_TAG_subrange_type:
46059 case DW_TAG_enumerator:
46061 is_static = language != CPLUS;
46063 case DW_TAG_subprogram:
46065 is_static = ! (is_external || language == ADA);
46067 case DW_TAG_constant:
46069 is_static = ! is_external;
46071 case DW_TAG_variable:
46073 is_static = ! is_external;
46075 case DW_TAG_namespace:
46079 case DW_TAG_class_type:
46080 case DW_TAG_interface_type:
46081 case DW_TAG_structure_type:
46082 case DW_TAG_union_type:
46083 case DW_TAG_enumeration_type:
46085 is_static = language != CPLUS;
46093 @appendix Manual pages
46097 * gdb man:: The GNU Debugger man page
46098 * gdbserver man:: Remote Server for the GNU Debugger man page
46099 * gcore man:: Generate a core file of a running program
46100 * gdbinit man:: gdbinit scripts
46101 * gdb-add-index man:: Add index files to speed up GDB
46107 @c man title gdb The GNU Debugger
46109 @c man begin SYNOPSIS gdb
46110 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
46111 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
46112 [@option{-b}@w{ }@var{bps}]
46113 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
46114 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
46115 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
46116 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
46117 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
46120 @c man begin DESCRIPTION gdb
46121 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
46122 going on ``inside'' another program while it executes -- or what another
46123 program was doing at the moment it crashed.
46125 @value{GDBN} can do four main kinds of things (plus other things in support of
46126 these) to help you catch bugs in the act:
46130 Start your program, specifying anything that might affect its behavior.
46133 Make your program stop on specified conditions.
46136 Examine what has happened, when your program has stopped.
46139 Change things in your program, so you can experiment with correcting the
46140 effects of one bug and go on to learn about another.
46143 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
46146 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
46147 commands from the terminal until you tell it to exit with the @value{GDBN}
46148 command @code{quit}. You can get online help from @value{GDBN} itself
46149 by using the command @code{help}.
46151 You can run @code{gdb} with no arguments or options; but the most
46152 usual way to start @value{GDBN} is with one argument or two, specifying an
46153 executable program as the argument:
46159 You can also start with both an executable program and a core file specified:
46165 You can, instead, specify a process ID as a second argument or use option
46166 @code{-p}, if you want to debug a running process:
46174 would attach @value{GDBN} to process @code{1234}. With option @option{-p} you
46175 can omit the @var{program} filename.
46177 Here are some of the most frequently needed @value{GDBN} commands:
46179 @c pod2man highlights the right hand side of the @item lines.
46181 @item break [@var{file}:]@var{function}
46182 Set a breakpoint at @var{function} (in @var{file}).
46184 @item run [@var{arglist}]
46185 Start your program (with @var{arglist}, if specified).
46188 Backtrace: display the program stack.
46190 @item print @var{expr}
46191 Display the value of an expression.
46194 Continue running your program (after stopping, e.g. at a breakpoint).
46197 Execute next program line (after stopping); step @emph{over} any
46198 function calls in the line.
46200 @item edit [@var{file}:]@var{function}
46201 look at the program line where it is presently stopped.
46203 @item list [@var{file}:]@var{function}
46204 type the text of the program in the vicinity of where it is presently stopped.
46207 Execute next program line (after stopping); step @emph{into} any
46208 function calls in the line.
46210 @item help [@var{name}]
46211 Show information about @value{GDBN} command @var{name}, or general information
46212 about using @value{GDBN}.
46215 Exit from @value{GDBN}.
46219 For full details on @value{GDBN},
46220 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
46221 by Richard M. Stallman and Roland H. Pesch. The same text is available online
46222 as the @code{gdb} entry in the @code{info} program.
46226 @c man begin OPTIONS gdb
46227 Any arguments other than options specify an executable
46228 file and core file (or process ID); that is, the first argument
46229 encountered with no
46230 associated option flag is equivalent to a @option{-se} option, and the second,
46231 if any, is equivalent to a @option{-c} option if it's the name of a file.
46233 both long and short forms; both are shown here. The long forms are also
46234 recognized if you truncate them, so long as enough of the option is
46235 present to be unambiguous. (If you prefer, you can flag option
46236 arguments with @option{+} rather than @option{-}, though we illustrate the
46237 more usual convention.)
46239 All the options and command line arguments you give are processed
46240 in sequential order. The order makes a difference when the @option{-x}
46246 List all options, with brief explanations.
46248 @item -symbols=@var{file}
46249 @itemx -s @var{file}
46250 Read symbol table from file @var{file}.
46253 Enable writing into executable and core files.
46255 @item -exec=@var{file}
46256 @itemx -e @var{file}
46257 Use file @var{file} as the executable file to execute when
46258 appropriate, and for examining pure data in conjunction with a core
46261 @item -se=@var{file}
46262 Read symbol table from file @var{file} and use it as the executable
46265 @item -core=@var{file}
46266 @itemx -c @var{file}
46267 Use file @var{file} as a core dump to examine.
46269 @item -command=@var{file}
46270 @itemx -x @var{file}
46271 Execute @value{GDBN} commands from file @var{file}.
46273 @item -ex @var{command}
46274 Execute given @value{GDBN} @var{command}.
46276 @item -directory=@var{directory}
46277 @itemx -d @var{directory}
46278 Add @var{directory} to the path to search for source files.
46281 Do not execute commands from @file{~/.gdbinit}.
46285 Do not execute commands from any @file{.gdbinit} initialization files.
46289 ``Quiet''. Do not print the introductory and copyright messages. These
46290 messages are also suppressed in batch mode.
46293 Run in batch mode. Exit with status @code{0} after processing all the command
46294 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
46295 Exit with nonzero status if an error occurs in executing the @value{GDBN}
46296 commands in the command files.
46298 Batch mode may be useful for running @value{GDBN} as a filter, for example to
46299 download and run a program on another computer; in order to make this
46300 more useful, the message
46303 Program exited normally.
46307 (which is ordinarily issued whenever a program running under @value{GDBN} control
46308 terminates) is not issued when running in batch mode.
46310 @item -cd=@var{directory}
46311 Run @value{GDBN} using @var{directory} as its working directory,
46312 instead of the current directory.
46316 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
46317 @value{GDBN} to output the full file name and line number in a standard,
46318 recognizable fashion each time a stack frame is displayed (which
46319 includes each time the program stops). This recognizable format looks
46320 like two @samp{\032} characters, followed by the file name, line number
46321 and character position separated by colons, and a newline. The
46322 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
46323 characters as a signal to display the source code for the frame.
46326 Set the line speed (baud rate or bits per second) of any serial
46327 interface used by @value{GDBN} for remote debugging.
46329 @item -tty=@var{device}
46330 Run using @var{device} for your program's standard input and output.
46334 @c man begin SEEALSO gdb
46336 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
46337 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
46338 documentation are properly installed at your site, the command
46345 should give you access to the complete manual.
46347 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
46348 Richard M. Stallman and Roland H. Pesch, July 1991.
46352 @node gdbserver man
46353 @heading gdbserver man
46355 @c man title gdbserver Remote Server for the GNU Debugger
46357 @c man begin SYNOPSIS gdbserver
46358 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
46360 gdbserver --attach @var{comm} @var{pid}
46362 gdbserver --multi @var{comm}
46366 @c man begin DESCRIPTION gdbserver
46367 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
46368 than the one which is running the program being debugged.
46371 @subheading Usage (server (target) side)
46374 Usage (server (target) side):
46377 First, you need to have a copy of the program you want to debug put onto
46378 the target system. The program can be stripped to save space if needed, as
46379 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
46380 the @value{GDBN} running on the host system.
46382 To use the server, you log on to the target system, and run the @command{gdbserver}
46383 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
46384 your program, and (c) its arguments. The general syntax is:
46387 target> gdbserver @var{comm} @var{program} [@var{args} ...]
46390 For example, using a serial port, you might say:
46394 @c @file would wrap it as F</dev/com1>.
46395 target> gdbserver /dev/com1 emacs foo.txt
46398 target> gdbserver @file{/dev/com1} emacs foo.txt
46402 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
46403 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
46404 waits patiently for the host @value{GDBN} to communicate with it.
46406 To use a TCP connection, you could say:
46409 target> gdbserver host:2345 emacs foo.txt
46412 This says pretty much the same thing as the last example, except that we are
46413 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
46414 that we are expecting to see a TCP connection from @code{host} to local TCP port
46415 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
46416 want for the port number as long as it does not conflict with any existing TCP
46417 ports on the target system. This same port number must be used in the host
46418 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
46419 you chose a port number that conflicts with another service, @command{gdbserver} will
46420 print an error message and exit.
46422 @command{gdbserver} can also attach to running programs.
46423 This is accomplished via the @option{--attach} argument. The syntax is:
46426 target> gdbserver --attach @var{comm} @var{pid}
46429 @var{pid} is the process ID of a currently running process. It isn't
46430 necessary to point @command{gdbserver} at a binary for the running process.
46432 To start @code{gdbserver} without supplying an initial command to run
46433 or process ID to attach, use the @option{--multi} command line option.
46434 In such case you should connect using @kbd{target extended-remote} to start
46435 the program you want to debug.
46438 target> gdbserver --multi @var{comm}
46442 @subheading Usage (host side)
46448 You need an unstripped copy of the target program on your host system, since
46449 @value{GDBN} needs to examine its symbol tables and such. Start up @value{GDBN} as you normally
46450 would, with the target program as the first argument. (You may need to use the
46451 @option{--baud} option if the serial line is running at anything except 9600 baud.)
46452 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
46453 new command you need to know about is @code{target remote}
46454 (or @code{target extended-remote}). Its argument is either
46455 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
46456 descriptor. For example:
46460 @c @file would wrap it as F</dev/ttyb>.
46461 (gdb) target remote /dev/ttyb
46464 (gdb) target remote @file{/dev/ttyb}
46469 communicates with the server via serial line @file{/dev/ttyb}, and:
46472 (gdb) target remote the-target:2345
46476 communicates via a TCP connection to port 2345 on host `the-target', where
46477 you previously started up @command{gdbserver} with the same port number. Note that for
46478 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
46479 command, otherwise you may get an error that looks something like
46480 `Connection refused'.
46482 @command{gdbserver} can also debug multiple inferiors at once,
46485 the @value{GDBN} manual in node @code{Inferiors Connections and Programs}
46486 -- shell command @code{info -f gdb -n 'Inferiors Connections and Programs'}.
46489 @ref{Inferiors Connections and Programs}.
46491 In such case use the @code{extended-remote} @value{GDBN} command variant:
46494 (gdb) target extended-remote the-target:2345
46497 The @command{gdbserver} option @option{--multi} may or may not be used in such
46501 @c man begin OPTIONS gdbserver
46502 There are three different modes for invoking @command{gdbserver}:
46507 Debug a specific program specified by its program name:
46510 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
46513 The @var{comm} parameter specifies how should the server communicate
46514 with @value{GDBN}; it is either a device name (to use a serial line),
46515 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
46516 stdin/stdout of @code{gdbserver}. Specify the name of the program to
46517 debug in @var{prog}. Any remaining arguments will be passed to the
46518 program verbatim. When the program exits, @value{GDBN} will close the
46519 connection, and @code{gdbserver} will exit.
46522 Debug a specific program by specifying the process ID of a running
46526 gdbserver --attach @var{comm} @var{pid}
46529 The @var{comm} parameter is as described above. Supply the process ID
46530 of a running program in @var{pid}; @value{GDBN} will do everything
46531 else. Like with the previous mode, when the process @var{pid} exits,
46532 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
46535 Multi-process mode -- debug more than one program/process:
46538 gdbserver --multi @var{comm}
46541 In this mode, @value{GDBN} can instruct @command{gdbserver} which
46542 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
46543 close the connection when a process being debugged exits, so you can
46544 debug several processes in the same session.
46547 In each of the modes you may specify these options:
46552 List all options, with brief explanations.
46555 This option causes @command{gdbserver} to print its version number and exit.
46558 @command{gdbserver} will attach to a running program. The syntax is:
46561 target> gdbserver --attach @var{comm} @var{pid}
46564 @var{pid} is the process ID of a currently running process. It isn't
46565 necessary to point @command{gdbserver} at a binary for the running process.
46568 To start @code{gdbserver} without supplying an initial command to run
46569 or process ID to attach, use this command line option.
46570 Then you can connect using @kbd{target extended-remote} and start
46571 the program you want to debug. The syntax is:
46574 target> gdbserver --multi @var{comm}
46578 Instruct @code{gdbserver} to display extra status information about the debugging
46580 This option is intended for @code{gdbserver} development and for bug reports to
46583 @item --remote-debug
46584 Instruct @code{gdbserver} to display remote protocol debug output.
46585 This option is intended for @code{gdbserver} development and for bug reports to
46588 @item --debug-file=@var{filename}
46589 Instruct @code{gdbserver} to send any debug output to the given @var{filename}.
46590 This option is intended for @code{gdbserver} development and for bug reports to
46593 @item --debug-format=option1@r{[},option2,...@r{]}
46594 Instruct @code{gdbserver} to include extra information in each line
46595 of debugging output.
46596 @xref{Other Command-Line Arguments for gdbserver}.
46599 Specify a wrapper to launch programs
46600 for debugging. The option should be followed by the name of the
46601 wrapper, then any command-line arguments to pass to the wrapper, then
46602 @kbd{--} indicating the end of the wrapper arguments.
46605 By default, @command{gdbserver} keeps the listening TCP port open, so that
46606 additional connections are possible. However, if you start @code{gdbserver}
46607 with the @option{--once} option, it will stop listening for any further
46608 connection attempts after connecting to the first @value{GDBN} session.
46610 @c --disable-packet is not documented for users.
46612 @c --disable-randomization and --no-disable-randomization are superseded by
46613 @c QDisableRandomization.
46618 @c man begin SEEALSO gdbserver
46620 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
46621 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
46622 documentation are properly installed at your site, the command
46628 should give you access to the complete manual.
46630 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
46631 Richard M. Stallman and Roland H. Pesch, July 1991.
46638 @c man title gcore Generate a core file of a running program
46641 @c man begin SYNOPSIS gcore
46642 gcore [-a] [-o @var{prefix}] @var{pid1} [@var{pid2}...@var{pidN}]
46646 @c man begin DESCRIPTION gcore
46647 Generate core dumps of one or more running programs with process IDs
46648 @var{pid1}, @var{pid2}, etc. A core file produced by @command{gcore}
46649 is equivalent to one produced by the kernel when the process crashes
46650 (and when @kbd{ulimit -c} was used to set up an appropriate core dump
46651 limit). However, unlike after a crash, after @command{gcore} finishes
46652 its job the program remains running without any change.
46655 @c man begin OPTIONS gcore
46658 Dump all memory mappings. The actual effect of this option depends on
46659 the Operating System. On @sc{gnu}/Linux, it will disable
46660 @code{use-coredump-filter} (@pxref{set use-coredump-filter}) and
46661 enable @code{dump-excluded-mappings} (@pxref{set
46662 dump-excluded-mappings}).
46664 @item -o @var{prefix}
46665 The optional argument @var{prefix} specifies the prefix to be used
46666 when composing the file names of the core dumps. The file name is
46667 composed as @file{@var{prefix}.@var{pid}}, where @var{pid} is the
46668 process ID of the running program being analyzed by @command{gcore}.
46669 If not specified, @var{prefix} defaults to @var{gcore}.
46673 @c man begin SEEALSO gcore
46675 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
46676 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
46677 documentation are properly installed at your site, the command
46684 should give you access to the complete manual.
46686 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
46687 Richard M. Stallman and Roland H. Pesch, July 1991.
46694 @c man title gdbinit GDB initialization scripts
46697 @c man begin SYNOPSIS gdbinit
46698 @ifset SYSTEM_GDBINIT
46699 @value{SYSTEM_GDBINIT}
46702 @ifset SYSTEM_GDBINIT_DIR
46703 @value{SYSTEM_GDBINIT_DIR}/*
46712 @c man begin DESCRIPTION gdbinit
46713 These files contain @value{GDBN} commands to automatically execute during
46714 @value{GDBN} startup. The lines of contents are canned sequences of commands,
46717 the @value{GDBN} manual in node @code{Sequences}
46718 -- shell command @code{info -f gdb -n Sequences}.
46724 Please read more in
46726 the @value{GDBN} manual in node @code{Startup}
46727 -- shell command @code{info -f gdb -n Startup}.
46734 @ifset SYSTEM_GDBINIT
46735 @item @value{SYSTEM_GDBINIT}
46737 @ifclear SYSTEM_GDBINIT
46738 @item (not enabled with @code{--with-system-gdbinit} during compilation)
46740 System-wide initialization file. It is executed unless user specified
46741 @value{GDBN} option @code{-nx} or @code{-n}.
46744 the @value{GDBN} manual in node @code{System-wide configuration}
46745 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
46747 @ifset SYSTEM_GDBINIT_DIR
46748 @item @value{SYSTEM_GDBINIT_DIR}
46750 @ifclear SYSTEM_GDBINIT_DIR
46751 @item (not enabled with @code{--with-system-gdbinit-dir} during compilation)
46753 System-wide initialization directory. All files in this directory are
46754 executed on startup unless user specified @value{GDBN} option @code{-nx} or
46755 @code{-n}, as long as they have a recognized file extension.
46758 the @value{GDBN} manual in node @code{System-wide configuration}
46759 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
46762 @ref{System-wide configuration}.
46766 User initialization file. It is executed unless user specified
46767 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
46770 Initialization file for current directory. It may need to be enabled with
46771 @value{GDBN} security command @code{set auto-load local-gdbinit}.
46774 the @value{GDBN} manual in node @code{Init File in the Current Directory}
46775 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
46778 @ref{Init File in the Current Directory}.
46783 @c man begin SEEALSO gdbinit
46785 gdb(1), @code{info -f gdb -n Startup}
46787 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
46788 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
46789 documentation are properly installed at your site, the command
46795 should give you access to the complete manual.
46797 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
46798 Richard M. Stallman and Roland H. Pesch, July 1991.
46802 @node gdb-add-index man
46803 @heading gdb-add-index
46804 @pindex gdb-add-index
46805 @anchor{gdb-add-index}
46807 @c man title gdb-add-index Add index files to speed up GDB
46809 @c man begin SYNOPSIS gdb-add-index
46810 gdb-add-index @var{filename}
46813 @c man begin DESCRIPTION gdb-add-index
46814 When @value{GDBN} finds a symbol file, it scans the symbols in the
46815 file in order to construct an internal symbol table. This lets most
46816 @value{GDBN} operations work quickly--at the cost of a delay early on.
46817 For large programs, this delay can be quite lengthy, so @value{GDBN}
46818 provides a way to build an index, which speeds up startup.
46820 To determine whether a file contains such an index, use the command
46821 @kbd{readelf -S filename}: the index is stored in a section named
46822 @code{.gdb_index}. The index file can only be produced on systems
46823 which use ELF binaries and DWARF debug information (i.e., sections
46824 named @code{.debug_*}).
46826 @command{gdb-add-index} uses @value{GDBN} and @command{objdump} found
46827 in the @env{PATH} environment variable. If you want to use different
46828 versions of these programs, you can specify them through the
46829 @env{GDB} and @env{OBJDUMP} environment variables.
46833 the @value{GDBN} manual in node @code{Index Files}
46834 -- shell command @kbd{info -f gdb -n "Index Files"}.
46841 @c man begin SEEALSO gdb-add-index
46843 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
46844 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
46845 documentation are properly installed at your site, the command
46851 should give you access to the complete manual.
46853 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
46854 Richard M. Stallman and Roland H. Pesch, July 1991.
46860 @node GNU Free Documentation License
46861 @appendix GNU Free Documentation License
46864 @node Concept Index
46865 @unnumbered Concept Index
46869 @node Command and Variable Index
46870 @unnumbered Command, Variable, and Function Index
46875 % I think something like @@colophon should be in texinfo. In the
46877 \long\def\colophon{\hbox to0pt{}\vfill
46878 \centerline{The body of this manual is set in}
46879 \centerline{\fontname\tenrm,}
46880 \centerline{with headings in {\bf\fontname\tenbf}}
46881 \centerline{and examples in {\tt\fontname\tentt}.}
46882 \centerline{{\it\fontname\tenit\/},}
46883 \centerline{{\bf\fontname\tenbf}, and}
46884 \centerline{{\sl\fontname\tensl\/}}
46885 \centerline{are used for emphasis.}\vfill}
46887 % Blame: doc@@cygnus.com, 1991.