1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988-2019 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{} 1988-2019 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 @*
111 @node Top, Summary, (dir), (dir)
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) 1988-2019 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{~/.gdbinit}
1087 This is the init file in your home directory.
1088 It is loaded next, after @file{system.gdbinit}, and before
1089 command options have been processed.
1090 @item @file{./.gdbinit}
1091 This is the init file in the current directory.
1092 It is loaded last, after command line options other than @code{-x} and
1093 @code{-ex} have been processed. Command line options @code{-x} and
1094 @code{-ex} are processed last, after @file{./.gdbinit} has been loaded.
1097 For further documentation on startup processing, @xref{Startup}.
1098 For documentation on how to write command files,
1099 @xref{Command Files,,Command Files}.
1104 Do not execute commands found in @file{~/.gdbinit}, the init file
1105 in your home directory.
1111 @cindex @code{--quiet}
1112 @cindex @code{--silent}
1114 ``Quiet''. Do not print the introductory and copyright messages. These
1115 messages are also suppressed in batch mode.
1118 @cindex @code{--batch}
1119 Run in batch mode. Exit with status @code{0} after processing all the
1120 command files specified with @samp{-x} (and all commands from
1121 initialization files, if not inhibited with @samp{-n}). Exit with
1122 nonzero status if an error occurs in executing the @value{GDBN} commands
1123 in the command files. Batch mode also disables pagination, sets unlimited
1124 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1125 off} were in effect (@pxref{Messages/Warnings}).
1127 Batch mode may be useful for running @value{GDBN} as a filter, for
1128 example to download and run a program on another computer; in order to
1129 make this more useful, the message
1132 Program exited normally.
1136 (which is ordinarily issued whenever a program running under
1137 @value{GDBN} control terminates) is not issued when running in batch
1141 @cindex @code{--batch-silent}
1142 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1143 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1144 unaffected). This is much quieter than @samp{-silent} and would be useless
1145 for an interactive session.
1147 This is particularly useful when using targets that give @samp{Loading section}
1148 messages, for example.
1150 Note that targets that give their output via @value{GDBN}, as opposed to
1151 writing directly to @code{stdout}, will also be made silent.
1153 @item -return-child-result
1154 @cindex @code{--return-child-result}
1155 The return code from @value{GDBN} will be the return code from the child
1156 process (the process being debugged), with the following exceptions:
1160 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1161 internal error. In this case the exit code is the same as it would have been
1162 without @samp{-return-child-result}.
1164 The user quits with an explicit value. E.g., @samp{quit 1}.
1166 The child process never runs, or is not allowed to terminate, in which case
1167 the exit code will be -1.
1170 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1171 when @value{GDBN} is being used as a remote program loader or simulator
1176 @cindex @code{--nowindows}
1178 ``No windows''. If @value{GDBN} comes with a graphical user interface
1179 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1180 interface. If no GUI is available, this option has no effect.
1184 @cindex @code{--windows}
1186 If @value{GDBN} includes a GUI, then this option requires it to be
1189 @item -cd @var{directory}
1191 Run @value{GDBN} using @var{directory} as its working directory,
1192 instead of the current directory.
1194 @item -data-directory @var{directory}
1195 @itemx -D @var{directory}
1196 @cindex @code{--data-directory}
1198 Run @value{GDBN} using @var{directory} as its data directory.
1199 The data directory is where @value{GDBN} searches for its
1200 auxiliary files. @xref{Data Files}.
1204 @cindex @code{--fullname}
1206 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1207 subprocess. It tells @value{GDBN} to output the full file name and line
1208 number in a standard, recognizable fashion each time a stack frame is
1209 displayed (which includes each time your program stops). This
1210 recognizable format looks like two @samp{\032} characters, followed by
1211 the file name, line number and character position separated by colons,
1212 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1213 @samp{\032} characters as a signal to display the source code for the
1216 @item -annotate @var{level}
1217 @cindex @code{--annotate}
1218 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1219 effect is identical to using @samp{set annotate @var{level}}
1220 (@pxref{Annotations}). The annotation @var{level} controls how much
1221 information @value{GDBN} prints together with its prompt, values of
1222 expressions, source lines, and other types of output. Level 0 is the
1223 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1224 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1225 that control @value{GDBN}, and level 2 has been deprecated.
1227 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1231 @cindex @code{--args}
1232 Change interpretation of command line so that arguments following the
1233 executable file are passed as command line arguments to the inferior.
1234 This option stops option processing.
1236 @item -baud @var{bps}
1238 @cindex @code{--baud}
1240 Set the line speed (baud rate or bits per second) of any serial
1241 interface used by @value{GDBN} for remote debugging.
1243 @item -l @var{timeout}
1245 Set the timeout (in seconds) of any communication used by @value{GDBN}
1246 for remote debugging.
1248 @item -tty @var{device}
1249 @itemx -t @var{device}
1250 @cindex @code{--tty}
1252 Run using @var{device} for your program's standard input and output.
1253 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1255 @c resolve the situation of these eventually
1257 @cindex @code{--tui}
1258 Activate the @dfn{Text User Interface} when starting. The Text User
1259 Interface manages several text windows on the terminal, showing
1260 source, assembly, registers and @value{GDBN} command outputs
1261 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1262 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1263 Using @value{GDBN} under @sc{gnu} Emacs}).
1265 @item -interpreter @var{interp}
1266 @cindex @code{--interpreter}
1267 Use the interpreter @var{interp} for interface with the controlling
1268 program or device. This option is meant to be set by programs which
1269 communicate with @value{GDBN} using it as a back end.
1270 @xref{Interpreters, , Command Interpreters}.
1272 @samp{--interpreter=mi} (or @samp{--interpreter=mi3}) causes
1273 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} version 3 (@pxref{GDB/MI, ,
1274 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 9.1. @sc{gdb/mi}
1275 version 2 (@code{mi2}), included in @value{GDBN} 6.0 and version 1 (@code{mi1}),
1276 included in @value{GDBN} 5.3, are also available. Earlier @sc{gdb/mi}
1277 interfaces are no longer supported.
1280 @cindex @code{--write}
1281 Open the executable and core files for both reading and writing. This
1282 is equivalent to the @samp{set write on} command inside @value{GDBN}
1286 @cindex @code{--statistics}
1287 This option causes @value{GDBN} to print statistics about time and
1288 memory usage after it completes each command and returns to the prompt.
1291 @cindex @code{--version}
1292 This option causes @value{GDBN} to print its version number and
1293 no-warranty blurb, and exit.
1295 @item -configuration
1296 @cindex @code{--configuration}
1297 This option causes @value{GDBN} to print details about its build-time
1298 configuration parameters, and then exit. These details can be
1299 important when reporting @value{GDBN} bugs (@pxref{GDB Bugs}).
1304 @subsection What @value{GDBN} Does During Startup
1305 @cindex @value{GDBN} startup
1307 Here's the description of what @value{GDBN} does during session startup:
1311 Sets up the command interpreter as specified by the command line
1312 (@pxref{Mode Options, interpreter}).
1316 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1317 used when building @value{GDBN}; @pxref{System-wide configuration,
1318 ,System-wide configuration and settings}) and executes all the commands in
1321 @anchor{Home Directory Init File}
1323 Reads the init file (if any) in your home directory@footnote{On
1324 DOS/Windows systems, the home directory is the one pointed to by the
1325 @code{HOME} environment variable.} and executes all the commands in
1328 @anchor{Option -init-eval-command}
1330 Executes commands and command files specified by the @samp{-iex} and
1331 @samp{-ix} options in their specified order. Usually you should use the
1332 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1333 settings before @value{GDBN} init files get executed and before inferior
1337 Processes command line options and operands.
1339 @anchor{Init File in the Current Directory during Startup}
1341 Reads and executes the commands from init file (if any) in the current
1342 working directory as long as @samp{set auto-load local-gdbinit} is set to
1343 @samp{on} (@pxref{Init File in the Current Directory}).
1344 This is only done if the current directory is
1345 different from your home directory. Thus, you can have more than one
1346 init file, one generic in your home directory, and another, specific
1347 to the program you are debugging, in the directory where you invoke
1351 If the command line specified a program to debug, or a process to
1352 attach to, or a core file, @value{GDBN} loads any auto-loaded
1353 scripts provided for the program or for its loaded shared libraries.
1354 @xref{Auto-loading}.
1356 If you wish to disable the auto-loading during startup,
1357 you must do something like the following:
1360 $ gdb -iex "set auto-load python-scripts off" myprogram
1363 Option @samp{-ex} does not work because the auto-loading is then turned
1367 Executes commands and command files specified by the @samp{-ex} and
1368 @samp{-x} options in their specified order. @xref{Command Files}, for
1369 more details about @value{GDBN} command files.
1372 Reads the command history recorded in the @dfn{history file}.
1373 @xref{Command History}, for more details about the command history and the
1374 files where @value{GDBN} records it.
1377 Init files use the same syntax as @dfn{command files} (@pxref{Command
1378 Files}) and are processed by @value{GDBN} in the same way. The init
1379 file in your home directory can set options (such as @samp{set
1380 complaints}) that affect subsequent processing of command line options
1381 and operands. Init files are not executed if you use the @samp{-nx}
1382 option (@pxref{Mode Options, ,Choosing Modes}).
1384 To display the list of init files loaded by gdb at startup, you
1385 can use @kbd{gdb --help}.
1387 @cindex init file name
1388 @cindex @file{.gdbinit}
1389 @cindex @file{gdb.ini}
1390 The @value{GDBN} init files are normally called @file{.gdbinit}.
1391 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1392 the limitations of file names imposed by DOS filesystems. The Windows
1393 port of @value{GDBN} uses the standard name, but if it finds a
1394 @file{gdb.ini} file in your home directory, it warns you about that
1395 and suggests to rename the file to the standard name.
1399 @section Quitting @value{GDBN}
1400 @cindex exiting @value{GDBN}
1401 @cindex leaving @value{GDBN}
1404 @kindex quit @r{[}@var{expression}@r{]}
1405 @kindex q @r{(@code{quit})}
1406 @item quit @r{[}@var{expression}@r{]}
1408 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1409 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1410 do not supply @var{expression}, @value{GDBN} will terminate normally;
1411 otherwise it will terminate using the result of @var{expression} as the
1416 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1417 terminates the action of any @value{GDBN} command that is in progress and
1418 returns to @value{GDBN} command level. It is safe to type the interrupt
1419 character at any time because @value{GDBN} does not allow it to take effect
1420 until a time when it is safe.
1422 If you have been using @value{GDBN} to control an attached process or
1423 device, you can release it with the @code{detach} command
1424 (@pxref{Attach, ,Debugging an Already-running Process}).
1426 @node Shell Commands
1427 @section Shell Commands
1429 If you need to execute occasional shell commands during your
1430 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1431 just use the @code{shell} command.
1436 @cindex shell escape
1437 @item shell @var{command-string}
1438 @itemx !@var{command-string}
1439 Invoke a standard shell to execute @var{command-string}.
1440 Note that no space is needed between @code{!} and @var{command-string}.
1441 If it exists, the environment variable @code{SHELL} determines which
1442 shell to run. Otherwise @value{GDBN} uses the default shell
1443 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1446 The utility @code{make} is often needed in development environments.
1447 You do not have to use the @code{shell} command for this purpose in
1452 @cindex calling make
1453 @item make @var{make-args}
1454 Execute the @code{make} program with the specified
1455 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1461 @cindex send the output of a gdb command to a shell command
1463 @item pipe [@var{command}] | @var{shell_command}
1464 @itemx | [@var{command}] | @var{shell_command}
1465 @itemx pipe -d @var{delim} @var{command} @var{delim} @var{shell_command}
1466 @itemx | -d @var{delim} @var{command} @var{delim} @var{shell_command}
1467 Executes @var{command} and sends its output to @var{shell_command}.
1468 Note that no space is needed around @code{|}.
1469 If no @var{command} is provided, the last command executed is repeated.
1471 In case the @var{command} contains a @code{|}, the option @code{-d @var{delim}}
1472 can be used to specify an alternate delimiter string @var{delim} that separates
1473 the @var{command} from the @var{shell_command}.
1506 (gdb) | -d ! echo this contains a | char\n ! sed -e 's/|/PIPE/'
1507 this contains a PIPE char
1508 (gdb) | -d xxx echo this contains a | char!\n xxx sed -e 's/|/PIPE/'
1509 this contains a PIPE char!
1515 The convenience variables @code{$_shell_exitcode} and @code{$_shell_exitsignal}
1516 can be used to examine the exit status of the last shell command launched
1517 by @code{shell}, @code{make}, @code{pipe} and @code{|}.
1518 @xref{Convenience Vars,, Convenience Variables}.
1520 @node Logging Output
1521 @section Logging Output
1522 @cindex logging @value{GDBN} output
1523 @cindex save @value{GDBN} output to a file
1525 You may want to save the output of @value{GDBN} commands to a file.
1526 There are several commands to control @value{GDBN}'s logging.
1530 @item set logging on
1532 @item set logging off
1534 @cindex logging file name
1535 @item set logging file @var{file}
1536 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1537 @item set logging overwrite [on|off]
1538 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1539 you want @code{set logging on} to overwrite the logfile instead.
1540 @item set logging redirect [on|off]
1541 By default, @value{GDBN} output will go to both the terminal and the logfile.
1542 Set @code{redirect} if you want output to go only to the log file.
1543 @item set logging debugredirect [on|off]
1544 By default, @value{GDBN} debug output will go to both the terminal and the logfile.
1545 Set @code{debugredirect} if you want debug output to go only to the log file.
1546 @kindex show logging
1548 Show the current values of the logging settings.
1551 You can also redirect the output of a @value{GDBN} command to a
1552 shell command. @xref{pipe}.
1554 @chapter @value{GDBN} Commands
1556 You can abbreviate a @value{GDBN} command to the first few letters of the command
1557 name, if that abbreviation is unambiguous; and you can repeat certain
1558 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1559 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1560 show you the alternatives available, if there is more than one possibility).
1563 * Command Syntax:: How to give commands to @value{GDBN}
1564 * Command Settings:: How to change default behavior of commands
1565 * Completion:: Command completion
1566 * Command Options:: Command options
1567 * Help:: How to ask @value{GDBN} for help
1570 @node Command Syntax
1571 @section Command Syntax
1573 A @value{GDBN} command is a single line of input. There is no limit on
1574 how long it can be. It starts with a command name, which is followed by
1575 arguments whose meaning depends on the command name. For example, the
1576 command @code{step} accepts an argument which is the number of times to
1577 step, as in @samp{step 5}. You can also use the @code{step} command
1578 with no arguments. Some commands do not allow any arguments.
1580 @cindex abbreviation
1581 @value{GDBN} command names may always be truncated if that abbreviation is
1582 unambiguous. Other possible command abbreviations are listed in the
1583 documentation for individual commands. In some cases, even ambiguous
1584 abbreviations are allowed; for example, @code{s} is specially defined as
1585 equivalent to @code{step} even though there are other commands whose
1586 names start with @code{s}. You can test abbreviations by using them as
1587 arguments to the @code{help} command.
1589 @cindex repeating commands
1590 @kindex RET @r{(repeat last command)}
1591 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1592 repeat the previous command. Certain commands (for example, @code{run})
1593 will not repeat this way; these are commands whose unintentional
1594 repetition might cause trouble and which you are unlikely to want to
1595 repeat. User-defined commands can disable this feature; see
1596 @ref{Define, dont-repeat}.
1598 The @code{list} and @code{x} commands, when you repeat them with
1599 @key{RET}, construct new arguments rather than repeating
1600 exactly as typed. This permits easy scanning of source or memory.
1602 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1603 output, in a way similar to the common utility @code{more}
1604 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1605 @key{RET} too many in this situation, @value{GDBN} disables command
1606 repetition after any command that generates this sort of display.
1608 @kindex # @r{(a comment)}
1610 Any text from a @kbd{#} to the end of the line is a comment; it does
1611 nothing. This is useful mainly in command files (@pxref{Command
1612 Files,,Command Files}).
1614 @cindex repeating command sequences
1615 @kindex Ctrl-o @r{(operate-and-get-next)}
1616 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1617 commands. This command accepts the current line, like @key{RET}, and
1618 then fetches the next line relative to the current line from the history
1622 @node Command Settings
1623 @section Command Settings
1624 @cindex default behavior of commands, changing
1625 @cindex default settings, changing
1627 Many commands change their behavior according to command-specific
1628 variables or settings. These settings can be changed with the
1629 @code{set} subcommands. For example, the @code{print} command
1630 (@pxref{Data, ,Examining Data}) prints arrays differently depending on
1631 settings changeable with the commands @code{set print elements
1632 NUMBER-OF-ELEMENTS} and @code{set print array-indexes}, among others.
1634 You can change these settings to your preference in the gdbinit files
1635 loaded at @value{GDBN} startup. @xref{Startup}.
1637 The settings can also be changed interactively during the debugging
1638 session. For example, to change the limit of array elements to print,
1639 you can do the following:
1641 (@value{GDBN}) set print elements 10
1642 (@value{GDBN}) print some_array
1643 $1 = @{0, 10, 20, 30, 40, 50, 60, 70, 80, 90...@}
1646 The above @code{set print elements 10} command changes the number of
1647 elements to print from the default of 200 to 10. If you only intend
1648 this limit of 10 to be used for printing @code{some_array}, then you
1649 must restore the limit back to 200, with @code{set print elements
1652 Some commands allow overriding settings with command options. For
1653 example, the @code{print} command supports a number of options that
1654 allow overriding relevant global print settings as set by @code{set
1655 print} subcommands. @xref{print options}. The example above could be
1658 (@value{GDBN}) print -elements 10 -- some_array
1659 $1 = @{0, 10, 20, 30, 40, 50, 60, 70, 80, 90...@}
1662 Alternatively, you can use the @code{with} command to change a setting
1663 temporarily, for the duration of a command invocation.
1666 @kindex with command
1667 @kindex w @r{(@code{with})}
1669 @cindex temporarily change settings
1670 @item with @var{setting} [@var{value}] [-- @var{command}]
1671 @itemx w @var{setting} [@var{value}] [-- @var{command}]
1672 Temporarily set @var{setting} to @var{value} for the duration of
1675 @var{setting} is any setting you can change with the @code{set}
1676 subcommands. @var{value} is the value to assign to @code{setting}
1677 while running @code{command}.
1679 If no @var{command} is provided, the last command executed is
1682 If a @var{command} is provided, it must be preceded by a double dash
1683 (@code{--}) separator. This is required because some settings accept
1684 free-form arguments, such as expressions or filenames.
1686 For example, the command
1688 (@value{GDBN}) with print array on -- print some_array
1691 is equivalent to the following 3 commands:
1693 (@value{GDBN}) set print array on
1694 (@value{GDBN}) print some_array
1695 (@value{GDBN}) set print array off
1698 The @code{with} command is particularly useful when you want to
1699 override a setting while running user-defined commands, or commands
1700 defined in Python or Guile. @xref{Extending GDB,, Extending GDB}.
1703 (@value{GDBN}) with print pretty on -- my_complex_command
1706 To change several settings for the same command, you can nest
1707 @code{with} commands. For example, @code{with language ada -- with
1708 print elements 10} temporarily changes the language to Ada and sets a
1709 limit of 10 elements to print for arrays and strings.
1714 @section Command Completion
1717 @cindex word completion
1718 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1719 only one possibility; it can also show you what the valid possibilities
1720 are for the next word in a command, at any time. This works for @value{GDBN}
1721 commands, @value{GDBN} subcommands, command options, and the names of symbols
1724 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1725 of a word. If there is only one possibility, @value{GDBN} fills in the
1726 word, and waits for you to finish the command (or press @key{RET} to
1727 enter it). For example, if you type
1729 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1730 @c complete accuracy in these examples; space introduced for clarity.
1731 @c If texinfo enhancements make it unnecessary, it would be nice to
1732 @c replace " @key" by "@key" in the following...
1734 (@value{GDBP}) info bre @key{TAB}
1738 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1739 the only @code{info} subcommand beginning with @samp{bre}:
1742 (@value{GDBP}) info breakpoints
1746 You can either press @key{RET} at this point, to run the @code{info
1747 breakpoints} command, or backspace and enter something else, if
1748 @samp{breakpoints} does not look like the command you expected. (If you
1749 were sure you wanted @code{info breakpoints} in the first place, you
1750 might as well just type @key{RET} immediately after @samp{info bre},
1751 to exploit command abbreviations rather than command completion).
1753 If there is more than one possibility for the next word when you press
1754 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1755 characters and try again, or just press @key{TAB} a second time;
1756 @value{GDBN} displays all the possible completions for that word. For
1757 example, you might want to set a breakpoint on a subroutine whose name
1758 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1759 just sounds the bell. Typing @key{TAB} again displays all the
1760 function names in your program that begin with those characters, for
1764 (@value{GDBP}) b make_ @key{TAB}
1765 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1766 make_a_section_from_file make_environ
1767 make_abs_section make_function_type
1768 make_blockvector make_pointer_type
1769 make_cleanup make_reference_type
1770 make_command make_symbol_completion_list
1771 (@value{GDBP}) b make_
1775 After displaying the available possibilities, @value{GDBN} copies your
1776 partial input (@samp{b make_} in the example) so you can finish the
1779 If you just want to see the list of alternatives in the first place, you
1780 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1781 means @kbd{@key{META} ?}. You can type this either by holding down a
1782 key designated as the @key{META} shift on your keyboard (if there is
1783 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1785 If the number of possible completions is large, @value{GDBN} will
1786 print as much of the list as it has collected, as well as a message
1787 indicating that the list may be truncated.
1790 (@value{GDBP}) b m@key{TAB}@key{TAB}
1792 <... the rest of the possible completions ...>
1793 *** List may be truncated, max-completions reached. ***
1798 This behavior can be controlled with the following commands:
1801 @kindex set max-completions
1802 @item set max-completions @var{limit}
1803 @itemx set max-completions unlimited
1804 Set the maximum number of completion candidates. @value{GDBN} will
1805 stop looking for more completions once it collects this many candidates.
1806 This is useful when completing on things like function names as collecting
1807 all the possible candidates can be time consuming.
1808 The default value is 200. A value of zero disables tab-completion.
1809 Note that setting either no limit or a very large limit can make
1811 @kindex show max-completions
1812 @item show max-completions
1813 Show the maximum number of candidates that @value{GDBN} will collect and show
1817 @cindex quotes in commands
1818 @cindex completion of quoted strings
1819 Sometimes the string you need, while logically a ``word'', may contain
1820 parentheses or other characters that @value{GDBN} normally excludes from
1821 its notion of a word. To permit word completion to work in this
1822 situation, you may enclose words in @code{'} (single quote marks) in
1823 @value{GDBN} commands.
1825 A likely situation where you might need this is in typing an
1826 expression that involves a C@t{++} symbol name with template
1827 parameters. This is because when completing expressions, GDB treats
1828 the @samp{<} character as word delimiter, assuming that it's the
1829 less-than comparison operator (@pxref{C Operators, , C and C@t{++}
1832 For example, when you want to call a C@t{++} template function
1833 interactively using the @code{print} or @code{call} commands, you may
1834 need to distinguish whether you mean the version of @code{name} that
1835 was specialized for @code{int}, @code{name<int>()}, or the version
1836 that was specialized for @code{float}, @code{name<float>()}. To use
1837 the word-completion facilities in this situation, type a single quote
1838 @code{'} at the beginning of the function name. This alerts
1839 @value{GDBN} that it may need to consider more information than usual
1840 when you press @key{TAB} or @kbd{M-?} to request word completion:
1843 (@value{GDBP}) p 'func< @kbd{M-?}
1844 func<int>() func<float>()
1845 (@value{GDBP}) p 'func<
1848 When setting breakpoints however (@pxref{Specify Location}), you don't
1849 usually need to type a quote before the function name, because
1850 @value{GDBN} understands that you want to set a breakpoint on a
1854 (@value{GDBP}) b func< @kbd{M-?}
1855 func<int>() func<float>()
1856 (@value{GDBP}) b func<
1859 This is true even in the case of typing the name of C@t{++} overloaded
1860 functions (multiple definitions of the same function, distinguished by
1861 argument type). For example, when you want to set a breakpoint you
1862 don't need to distinguish whether you mean the version of @code{name}
1863 that takes an @code{int} parameter, @code{name(int)}, or the version
1864 that takes a @code{float} parameter, @code{name(float)}.
1867 (@value{GDBP}) b bubble( @kbd{M-?}
1868 bubble(int) bubble(double)
1869 (@value{GDBP}) b bubble(dou @kbd{M-?}
1873 See @ref{quoting names} for a description of other scenarios that
1876 For more information about overloaded functions, see @ref{C Plus Plus
1877 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1878 overload-resolution off} to disable overload resolution;
1879 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1881 @cindex completion of structure field names
1882 @cindex structure field name completion
1883 @cindex completion of union field names
1884 @cindex union field name completion
1885 When completing in an expression which looks up a field in a
1886 structure, @value{GDBN} also tries@footnote{The completer can be
1887 confused by certain kinds of invalid expressions. Also, it only
1888 examines the static type of the expression, not the dynamic type.} to
1889 limit completions to the field names available in the type of the
1893 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1894 magic to_fputs to_rewind
1895 to_data to_isatty to_write
1896 to_delete to_put to_write_async_safe
1901 This is because the @code{gdb_stdout} is a variable of the type
1902 @code{struct ui_file} that is defined in @value{GDBN} sources as
1909 ui_file_flush_ftype *to_flush;
1910 ui_file_write_ftype *to_write;
1911 ui_file_write_async_safe_ftype *to_write_async_safe;
1912 ui_file_fputs_ftype *to_fputs;
1913 ui_file_read_ftype *to_read;
1914 ui_file_delete_ftype *to_delete;
1915 ui_file_isatty_ftype *to_isatty;
1916 ui_file_rewind_ftype *to_rewind;
1917 ui_file_put_ftype *to_put;
1922 @node Command Options
1923 @section Command options
1925 @cindex command options
1926 Some commands accept options starting with a leading dash. For
1927 example, @code{print -pretty}. Similarly to command names, you can
1928 abbreviate a @value{GDBN} option to the first few letters of the
1929 option name, if that abbreviation is unambiguous, and you can also use
1930 the @key{TAB} key to get @value{GDBN} to fill out the rest of a word
1931 in an option (or to show you the alternatives available, if there is
1932 more than one possibility).
1934 @cindex command options, raw input
1935 Some commands take raw input as argument. For example, the print
1936 command processes arbitrary expressions in any of the languages
1937 supported by @value{GDBN}. With such commands, because raw input may
1938 start with a leading dash that would be confused with an option or any
1939 of its abbreviations, e.g.@: @code{print -r} (short for @code{print
1940 -raw} or printing negative @code{r}?), if you specify any command
1941 option, then you must use a double-dash (@code{--}) delimiter to
1942 indicate the end of options.
1944 @cindex command options, boolean
1946 Some options are described as accepting an argument which can be
1947 either @code{on} or @code{off}. These are known as @dfn{boolean
1948 options}. Similarly to boolean settings commands---@code{on} and
1949 @code{off} are the typical values, but any of @code{1}, @code{yes} and
1950 @code{enable} can also be used as ``true'' value, and any of @code{0},
1951 @code{no} and @code{disable} can also be used as ``false'' value. You
1952 can also omit a ``true'' value, as it is implied by default.
1954 For example, these are equivalent:
1957 (@value{GDBP}) print -object on -pretty off -element unlimited -- *myptr
1958 (@value{GDBP}) p -o -p 0 -e u -- *myptr
1961 You can discover the set of options some command accepts by completing
1962 on @code{-} after the command name. For example:
1965 (@value{GDBP}) print -@key{TAB}@key{TAB}
1966 -address -max-depth -repeats -vtbl
1967 -array -null-stop -static-members
1968 -array-indexes -object -symbol
1969 -elements -pretty -union
1972 Completion will in some cases guide you with a suggestion of what kind
1973 of argument an option expects. For example:
1976 (@value{GDBP}) print -elements @key{TAB}@key{TAB}
1980 Here, the option expects a number (e.g., @code{100}), not literal
1981 @code{NUMBER}. Such metasyntactical arguments are always presented in
1984 (For more on using the @code{print} command, see @ref{Data, ,Examining
1988 @section Getting Help
1989 @cindex online documentation
1992 You can always ask @value{GDBN} itself for information on its commands,
1993 using the command @code{help}.
1996 @kindex h @r{(@code{help})}
1999 You can use @code{help} (abbreviated @code{h}) with no arguments to
2000 display a short list of named classes of commands:
2004 List of classes of commands:
2006 aliases -- Aliases of other commands
2007 breakpoints -- Making program stop at certain points
2008 data -- Examining data
2009 files -- Specifying and examining files
2010 internals -- Maintenance commands
2011 obscure -- Obscure features
2012 running -- Running the program
2013 stack -- Examining the stack
2014 status -- Status inquiries
2015 support -- Support facilities
2016 tracepoints -- Tracing of program execution without
2017 stopping the program
2018 user-defined -- User-defined commands
2020 Type "help" followed by a class name for a list of
2021 commands in that class.
2022 Type "help" followed by command name for full
2024 Command name abbreviations are allowed if unambiguous.
2027 @c the above line break eliminates huge line overfull...
2029 @item help @var{class}
2030 Using one of the general help classes as an argument, you can get a
2031 list of the individual commands in that class. For example, here is the
2032 help display for the class @code{status}:
2035 (@value{GDBP}) help status
2040 @c Line break in "show" line falsifies real output, but needed
2041 @c to fit in smallbook page size.
2042 info -- Generic command for showing things
2043 about the program being debugged
2044 show -- Generic command for showing things
2047 Type "help" followed by command name for full
2049 Command name abbreviations are allowed if unambiguous.
2053 @item help @var{command}
2054 With a command name as @code{help} argument, @value{GDBN} displays a
2055 short paragraph on how to use that command.
2058 @item apropos [-v] @var{regexp}
2059 The @code{apropos} command searches through all of the @value{GDBN}
2060 commands, and their documentation, for the regular expression specified in
2061 @var{args}. It prints out all matches found. The optional flag @samp{-v},
2062 which stands for @samp{verbose}, indicates to output the full documentation
2063 of the matching commands and highlight the parts of the documentation
2064 matching @var{regexp}. For example:
2075 alias -- Define a new command that is an alias of an existing command
2076 aliases -- Aliases of other commands
2077 d -- Delete some breakpoints or auto-display expressions
2078 del -- Delete some breakpoints or auto-display expressions
2079 delete -- Delete some breakpoints or auto-display expressions
2087 apropos -v cut.*thread apply
2091 results in the below output, where @samp{cut for 'thread apply}
2092 is highlighted if styling is enabled.
2096 taas -- Apply a command to all threads (ignoring errors
2099 shortcut for 'thread apply all -s COMMAND'
2101 tfaas -- Apply a command to all frames of all threads
2102 (ignoring errors and empty output).
2103 Usage: tfaas COMMAND
2104 shortcut for 'thread apply all -s frame apply all -s COMMAND'
2109 @item complete @var{args}
2110 The @code{complete @var{args}} command lists all the possible completions
2111 for the beginning of a command. Use @var{args} to specify the beginning of the
2112 command you want completed. For example:
2118 @noindent results in:
2129 @noindent This is intended for use by @sc{gnu} Emacs.
2132 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
2133 and @code{show} to inquire about the state of your program, or the state
2134 of @value{GDBN} itself. Each command supports many topics of inquiry; this
2135 manual introduces each of them in the appropriate context. The listings
2136 under @code{info} and under @code{show} in the Command, Variable, and
2137 Function Index point to all the sub-commands. @xref{Command and Variable
2143 @kindex i @r{(@code{info})}
2145 This command (abbreviated @code{i}) is for describing the state of your
2146 program. For example, you can show the arguments passed to a function
2147 with @code{info args}, list the registers currently in use with @code{info
2148 registers}, or list the breakpoints you have set with @code{info breakpoints}.
2149 You can get a complete list of the @code{info} sub-commands with
2150 @w{@code{help info}}.
2154 You can assign the result of an expression to an environment variable with
2155 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
2156 @code{set prompt $}.
2160 In contrast to @code{info}, @code{show} is for describing the state of
2161 @value{GDBN} itself.
2162 You can change most of the things you can @code{show}, by using the
2163 related command @code{set}; for example, you can control what number
2164 system is used for displays with @code{set radix}, or simply inquire
2165 which is currently in use with @code{show radix}.
2168 To display all the settable parameters and their current
2169 values, you can use @code{show} with no arguments; you may also use
2170 @code{info set}. Both commands produce the same display.
2171 @c FIXME: "info set" violates the rule that "info" is for state of
2172 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
2173 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
2177 Here are several miscellaneous @code{show} subcommands, all of which are
2178 exceptional in lacking corresponding @code{set} commands:
2181 @kindex show version
2182 @cindex @value{GDBN} version number
2184 Show what version of @value{GDBN} is running. You should include this
2185 information in @value{GDBN} bug-reports. If multiple versions of
2186 @value{GDBN} are in use at your site, you may need to determine which
2187 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
2188 commands are introduced, and old ones may wither away. Also, many
2189 system vendors ship variant versions of @value{GDBN}, and there are
2190 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
2191 The version number is the same as the one announced when you start
2194 @kindex show copying
2195 @kindex info copying
2196 @cindex display @value{GDBN} copyright
2199 Display information about permission for copying @value{GDBN}.
2201 @kindex show warranty
2202 @kindex info warranty
2204 @itemx info warranty
2205 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
2206 if your version of @value{GDBN} comes with one.
2208 @kindex show configuration
2209 @item show configuration
2210 Display detailed information about the way @value{GDBN} was configured
2211 when it was built. This displays the optional arguments passed to the
2212 @file{configure} script and also configuration parameters detected
2213 automatically by @command{configure}. When reporting a @value{GDBN}
2214 bug (@pxref{GDB Bugs}), it is important to include this information in
2220 @chapter Running Programs Under @value{GDBN}
2222 When you run a program under @value{GDBN}, you must first generate
2223 debugging information when you compile it.
2225 You may start @value{GDBN} with its arguments, if any, in an environment
2226 of your choice. If you are doing native debugging, you may redirect
2227 your program's input and output, debug an already running process, or
2228 kill a child process.
2231 * Compilation:: Compiling for debugging
2232 * Starting:: Starting your program
2233 * Arguments:: Your program's arguments
2234 * Environment:: Your program's environment
2236 * Working Directory:: Your program's working directory
2237 * Input/Output:: Your program's input and output
2238 * Attach:: Debugging an already-running process
2239 * Kill Process:: Killing the child process
2241 * Inferiors and Programs:: Debugging multiple inferiors and programs
2242 * Threads:: Debugging programs with multiple threads
2243 * Forks:: Debugging forks
2244 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
2248 @section Compiling for Debugging
2250 In order to debug a program effectively, you need to generate
2251 debugging information when you compile it. This debugging information
2252 is stored in the object file; it describes the data type of each
2253 variable or function and the correspondence between source line numbers
2254 and addresses in the executable code.
2256 To request debugging information, specify the @samp{-g} option when you run
2259 Programs that are to be shipped to your customers are compiled with
2260 optimizations, using the @samp{-O} compiler option. However, some
2261 compilers are unable to handle the @samp{-g} and @samp{-O} options
2262 together. Using those compilers, you cannot generate optimized
2263 executables containing debugging information.
2265 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
2266 without @samp{-O}, making it possible to debug optimized code. We
2267 recommend that you @emph{always} use @samp{-g} whenever you compile a
2268 program. You may think your program is correct, but there is no sense
2269 in pushing your luck. For more information, see @ref{Optimized Code}.
2271 Older versions of the @sc{gnu} C compiler permitted a variant option
2272 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
2273 format; if your @sc{gnu} C compiler has this option, do not use it.
2275 @value{GDBN} knows about preprocessor macros and can show you their
2276 expansion (@pxref{Macros}). Most compilers do not include information
2277 about preprocessor macros in the debugging information if you specify
2278 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
2279 the @sc{gnu} C compiler, provides macro information if you are using
2280 the DWARF debugging format, and specify the option @option{-g3}.
2282 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
2283 gcc, Using the @sc{gnu} Compiler Collection (GCC)}, for more
2284 information on @value{NGCC} options affecting debug information.
2286 You will have the best debugging experience if you use the latest
2287 version of the DWARF debugging format that your compiler supports.
2288 DWARF is currently the most expressive and best supported debugging
2289 format in @value{GDBN}.
2293 @section Starting your Program
2299 @kindex r @r{(@code{run})}
2302 Use the @code{run} command to start your program under @value{GDBN}.
2303 You must first specify the program name with an argument to
2304 @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
2305 @value{GDBN}}), or by using the @code{file} or @code{exec-file}
2306 command (@pxref{Files, ,Commands to Specify Files}).
2310 If you are running your program in an execution environment that
2311 supports processes, @code{run} creates an inferior process and makes
2312 that process run your program. In some environments without processes,
2313 @code{run} jumps to the start of your program. Other targets,
2314 like @samp{remote}, are always running. If you get an error
2315 message like this one:
2318 The "remote" target does not support "run".
2319 Try "help target" or "continue".
2323 then use @code{continue} to run your program. You may need @code{load}
2324 first (@pxref{load}).
2326 The execution of a program is affected by certain information it
2327 receives from its superior. @value{GDBN} provides ways to specify this
2328 information, which you must do @emph{before} starting your program. (You
2329 can change it after starting your program, but such changes only affect
2330 your program the next time you start it.) This information may be
2331 divided into four categories:
2334 @item The @emph{arguments.}
2335 Specify the arguments to give your program as the arguments of the
2336 @code{run} command. If a shell is available on your target, the shell
2337 is used to pass the arguments, so that you may use normal conventions
2338 (such as wildcard expansion or variable substitution) in describing
2340 In Unix systems, you can control which shell is used with the
2341 @code{SHELL} environment variable. If you do not define @code{SHELL},
2342 @value{GDBN} uses the default shell (@file{/bin/sh}). You can disable
2343 use of any shell with the @code{set startup-with-shell} command (see
2346 @item The @emph{environment.}
2347 Your program normally inherits its environment from @value{GDBN}, but you can
2348 use the @value{GDBN} commands @code{set environment} and @code{unset
2349 environment} to change parts of the environment that affect
2350 your program. @xref{Environment, ,Your Program's Environment}.
2352 @item The @emph{working directory.}
2353 You can set your program's working directory with the command
2354 @kbd{set cwd}. If you do not set any working directory with this
2355 command, your program will inherit @value{GDBN}'s working directory if
2356 native debugging, or the remote server's working directory if remote
2357 debugging. @xref{Working Directory, ,Your Program's Working
2360 @item The @emph{standard input and output.}
2361 Your program normally uses the same device for standard input and
2362 standard output as @value{GDBN} is using. You can redirect input and output
2363 in the @code{run} command line, or you can use the @code{tty} command to
2364 set a different device for your program.
2365 @xref{Input/Output, ,Your Program's Input and Output}.
2368 @emph{Warning:} While input and output redirection work, you cannot use
2369 pipes to pass the output of the program you are debugging to another
2370 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2374 When you issue the @code{run} command, your program begins to execute
2375 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2376 of how to arrange for your program to stop. Once your program has
2377 stopped, you may call functions in your program, using the @code{print}
2378 or @code{call} commands. @xref{Data, ,Examining Data}.
2380 If the modification time of your symbol file has changed since the last
2381 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2382 table, and reads it again. When it does this, @value{GDBN} tries to retain
2383 your current breakpoints.
2388 @cindex run to main procedure
2389 The name of the main procedure can vary from language to language.
2390 With C or C@t{++}, the main procedure name is always @code{main}, but
2391 other languages such as Ada do not require a specific name for their
2392 main procedure. The debugger provides a convenient way to start the
2393 execution of the program and to stop at the beginning of the main
2394 procedure, depending on the language used.
2396 The @samp{start} command does the equivalent of setting a temporary
2397 breakpoint at the beginning of the main procedure and then invoking
2398 the @samp{run} command.
2400 @cindex elaboration phase
2401 Some programs contain an @dfn{elaboration} phase where some startup code is
2402 executed before the main procedure is called. This depends on the
2403 languages used to write your program. In C@t{++}, for instance,
2404 constructors for static and global objects are executed before
2405 @code{main} is called. It is therefore possible that the debugger stops
2406 before reaching the main procedure. However, the temporary breakpoint
2407 will remain to halt execution.
2409 Specify the arguments to give to your program as arguments to the
2410 @samp{start} command. These arguments will be given verbatim to the
2411 underlying @samp{run} command. Note that the same arguments will be
2412 reused if no argument is provided during subsequent calls to
2413 @samp{start} or @samp{run}.
2415 It is sometimes necessary to debug the program during elaboration. In
2416 these cases, using the @code{start} command would stop the execution
2417 of your program too late, as the program would have already completed
2418 the elaboration phase. Under these circumstances, either insert
2419 breakpoints in your elaboration code before running your program or
2420 use the @code{starti} command.
2424 @cindex run to first instruction
2425 The @samp{starti} command does the equivalent of setting a temporary
2426 breakpoint at the first instruction of a program's execution and then
2427 invoking the @samp{run} command. For programs containing an
2428 elaboration phase, the @code{starti} command will stop execution at
2429 the start of the elaboration phase.
2431 @anchor{set exec-wrapper}
2432 @kindex set exec-wrapper
2433 @item set exec-wrapper @var{wrapper}
2434 @itemx show exec-wrapper
2435 @itemx unset exec-wrapper
2436 When @samp{exec-wrapper} is set, the specified wrapper is used to
2437 launch programs for debugging. @value{GDBN} starts your program
2438 with a shell command of the form @kbd{exec @var{wrapper}
2439 @var{program}}. Quoting is added to @var{program} and its
2440 arguments, but not to @var{wrapper}, so you should add quotes if
2441 appropriate for your shell. The wrapper runs until it executes
2442 your program, and then @value{GDBN} takes control.
2444 You can use any program that eventually calls @code{execve} with
2445 its arguments as a wrapper. Several standard Unix utilities do
2446 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2447 with @code{exec "$@@"} will also work.
2449 For example, you can use @code{env} to pass an environment variable to
2450 the debugged program, without setting the variable in your shell's
2454 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2458 This command is available when debugging locally on most targets, excluding
2459 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2461 @kindex set startup-with-shell
2462 @anchor{set startup-with-shell}
2463 @item set startup-with-shell
2464 @itemx set startup-with-shell on
2465 @itemx set startup-with-shell off
2466 @itemx show startup-with-shell
2467 On Unix systems, by default, if a shell is available on your target,
2468 @value{GDBN}) uses it to start your program. Arguments of the
2469 @code{run} command are passed to the shell, which does variable
2470 substitution, expands wildcard characters and performs redirection of
2471 I/O. In some circumstances, it may be useful to disable such use of a
2472 shell, for example, when debugging the shell itself or diagnosing
2473 startup failures such as:
2477 Starting program: ./a.out
2478 During startup program terminated with signal SIGSEGV, Segmentation fault.
2482 which indicates the shell or the wrapper specified with
2483 @samp{exec-wrapper} crashed, not your program. Most often, this is
2484 caused by something odd in your shell's non-interactive mode
2485 initialization file---such as @file{.cshrc} for C-shell,
2486 $@file{.zshenv} for the Z shell, or the file specified in the
2487 @samp{BASH_ENV} environment variable for BASH.
2489 @anchor{set auto-connect-native-target}
2490 @kindex set auto-connect-native-target
2491 @item set auto-connect-native-target
2492 @itemx set auto-connect-native-target on
2493 @itemx set auto-connect-native-target off
2494 @itemx show auto-connect-native-target
2496 By default, if not connected to any target yet (e.g., with
2497 @code{target remote}), the @code{run} command starts your program as a
2498 native process under @value{GDBN}, on your local machine. If you're
2499 sure you don't want to debug programs on your local machine, you can
2500 tell @value{GDBN} to not connect to the native target automatically
2501 with the @code{set auto-connect-native-target off} command.
2503 If @code{on}, which is the default, and if @value{GDBN} is not
2504 connected to a target already, the @code{run} command automaticaly
2505 connects to the native target, if one is available.
2507 If @code{off}, and if @value{GDBN} is not connected to a target
2508 already, the @code{run} command fails with an error:
2512 Don't know how to run. Try "help target".
2515 If @value{GDBN} is already connected to a target, @value{GDBN} always
2516 uses it with the @code{run} command.
2518 In any case, you can explicitly connect to the native target with the
2519 @code{target native} command. For example,
2522 (@value{GDBP}) set auto-connect-native-target off
2524 Don't know how to run. Try "help target".
2525 (@value{GDBP}) target native
2527 Starting program: ./a.out
2528 [Inferior 1 (process 10421) exited normally]
2531 In case you connected explicitly to the @code{native} target,
2532 @value{GDBN} remains connected even if all inferiors exit, ready for
2533 the next @code{run} command. Use the @code{disconnect} command to
2536 Examples of other commands that likewise respect the
2537 @code{auto-connect-native-target} setting: @code{attach}, @code{info
2538 proc}, @code{info os}.
2540 @kindex set disable-randomization
2541 @item set disable-randomization
2542 @itemx set disable-randomization on
2543 This option (enabled by default in @value{GDBN}) will turn off the native
2544 randomization of the virtual address space of the started program. This option
2545 is useful for multiple debugging sessions to make the execution better
2546 reproducible and memory addresses reusable across debugging sessions.
2548 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2549 On @sc{gnu}/Linux you can get the same behavior using
2552 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2555 @item set disable-randomization off
2556 Leave the behavior of the started executable unchanged. Some bugs rear their
2557 ugly heads only when the program is loaded at certain addresses. If your bug
2558 disappears when you run the program under @value{GDBN}, that might be because
2559 @value{GDBN} by default disables the address randomization on platforms, such
2560 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2561 disable-randomization off} to try to reproduce such elusive bugs.
2563 On targets where it is available, virtual address space randomization
2564 protects the programs against certain kinds of security attacks. In these
2565 cases the attacker needs to know the exact location of a concrete executable
2566 code. Randomizing its location makes it impossible to inject jumps misusing
2567 a code at its expected addresses.
2569 Prelinking shared libraries provides a startup performance advantage but it
2570 makes addresses in these libraries predictable for privileged processes by
2571 having just unprivileged access at the target system. Reading the shared
2572 library binary gives enough information for assembling the malicious code
2573 misusing it. Still even a prelinked shared library can get loaded at a new
2574 random address just requiring the regular relocation process during the
2575 startup. Shared libraries not already prelinked are always loaded at
2576 a randomly chosen address.
2578 Position independent executables (PIE) contain position independent code
2579 similar to the shared libraries and therefore such executables get loaded at
2580 a randomly chosen address upon startup. PIE executables always load even
2581 already prelinked shared libraries at a random address. You can build such
2582 executable using @command{gcc -fPIE -pie}.
2584 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2585 (as long as the randomization is enabled).
2587 @item show disable-randomization
2588 Show the current setting of the explicit disable of the native randomization of
2589 the virtual address space of the started program.
2594 @section Your Program's Arguments
2596 @cindex arguments (to your program)
2597 The arguments to your program can be specified by the arguments of the
2599 They are passed to a shell, which expands wildcard characters and
2600 performs redirection of I/O, and thence to your program. Your
2601 @code{SHELL} environment variable (if it exists) specifies what shell
2602 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2603 the default shell (@file{/bin/sh} on Unix).
2605 On non-Unix systems, the program is usually invoked directly by
2606 @value{GDBN}, which emulates I/O redirection via the appropriate system
2607 calls, and the wildcard characters are expanded by the startup code of
2608 the program, not by the shell.
2610 @code{run} with no arguments uses the same arguments used by the previous
2611 @code{run}, or those set by the @code{set args} command.
2616 Specify the arguments to be used the next time your program is run. If
2617 @code{set args} has no arguments, @code{run} executes your program
2618 with no arguments. Once you have run your program with arguments,
2619 using @code{set args} before the next @code{run} is the only way to run
2620 it again without arguments.
2624 Show the arguments to give your program when it is started.
2628 @section Your Program's Environment
2630 @cindex environment (of your program)
2631 The @dfn{environment} consists of a set of environment variables and
2632 their values. Environment variables conventionally record such things as
2633 your user name, your home directory, your terminal type, and your search
2634 path for programs to run. Usually you set up environment variables with
2635 the shell and they are inherited by all the other programs you run. When
2636 debugging, it can be useful to try running your program with a modified
2637 environment without having to start @value{GDBN} over again.
2641 @item path @var{directory}
2642 Add @var{directory} to the front of the @code{PATH} environment variable
2643 (the search path for executables) that will be passed to your program.
2644 The value of @code{PATH} used by @value{GDBN} does not change.
2645 You may specify several directory names, separated by whitespace or by a
2646 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2647 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2648 is moved to the front, so it is searched sooner.
2650 You can use the string @samp{$cwd} to refer to whatever is the current
2651 working directory at the time @value{GDBN} searches the path. If you
2652 use @samp{.} instead, it refers to the directory where you executed the
2653 @code{path} command. @value{GDBN} replaces @samp{.} in the
2654 @var{directory} argument (with the current path) before adding
2655 @var{directory} to the search path.
2656 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2657 @c document that, since repeating it would be a no-op.
2661 Display the list of search paths for executables (the @code{PATH}
2662 environment variable).
2664 @kindex show environment
2665 @item show environment @r{[}@var{varname}@r{]}
2666 Print the value of environment variable @var{varname} to be given to
2667 your program when it starts. If you do not supply @var{varname},
2668 print the names and values of all environment variables to be given to
2669 your program. You can abbreviate @code{environment} as @code{env}.
2671 @kindex set environment
2672 @anchor{set environment}
2673 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2674 Set environment variable @var{varname} to @var{value}. The value
2675 changes for your program (and the shell @value{GDBN} uses to launch
2676 it), not for @value{GDBN} itself. The @var{value} may be any string; the
2677 values of environment variables are just strings, and any
2678 interpretation is supplied by your program itself. The @var{value}
2679 parameter is optional; if it is eliminated, the variable is set to a
2681 @c "any string" here does not include leading, trailing
2682 @c blanks. Gnu asks: does anyone care?
2684 For example, this command:
2691 tells the debugged program, when subsequently run, that its user is named
2692 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2693 are not actually required.)
2695 Note that on Unix systems, @value{GDBN} runs your program via a shell,
2696 which also inherits the environment set with @code{set environment}.
2697 If necessary, you can avoid that by using the @samp{env} program as a
2698 wrapper instead of using @code{set environment}. @xref{set
2699 exec-wrapper}, for an example doing just that.
2701 Environment variables that are set by the user are also transmitted to
2702 @command{gdbserver} to be used when starting the remote inferior.
2703 @pxref{QEnvironmentHexEncoded}.
2705 @kindex unset environment
2706 @anchor{unset environment}
2707 @item unset environment @var{varname}
2708 Remove variable @var{varname} from the environment to be passed to your
2709 program. This is different from @samp{set env @var{varname} =};
2710 @code{unset environment} removes the variable from the environment,
2711 rather than assigning it an empty value.
2713 Environment variables that are unset by the user are also unset on
2714 @command{gdbserver} when starting the remote inferior.
2715 @pxref{QEnvironmentUnset}.
2718 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2719 the shell indicated by your @code{SHELL} environment variable if it
2720 exists (or @code{/bin/sh} if not). If your @code{SHELL} variable
2721 names a shell that runs an initialization file when started
2722 non-interactively---such as @file{.cshrc} for C-shell, $@file{.zshenv}
2723 for the Z shell, or the file specified in the @samp{BASH_ENV}
2724 environment variable for BASH---any variables you set in that file
2725 affect your program. You may wish to move setting of environment
2726 variables to files that are only run when you sign on, such as
2727 @file{.login} or @file{.profile}.
2729 @node Working Directory
2730 @section Your Program's Working Directory
2732 @cindex working directory (of your program)
2733 Each time you start your program with @code{run}, the inferior will be
2734 initialized with the current working directory specified by the
2735 @kbd{set cwd} command. If no directory has been specified by this
2736 command, then the inferior will inherit @value{GDBN}'s current working
2737 directory as its working directory if native debugging, or it will
2738 inherit the remote server's current working directory if remote
2743 @cindex change inferior's working directory
2744 @anchor{set cwd command}
2745 @item set cwd @r{[}@var{directory}@r{]}
2746 Set the inferior's working directory to @var{directory}, which will be
2747 @code{glob}-expanded in order to resolve tildes (@file{~}). If no
2748 argument has been specified, the command clears the setting and resets
2749 it to an empty state. This setting has no effect on @value{GDBN}'s
2750 working directory, and it only takes effect the next time you start
2751 the inferior. The @file{~} in @var{directory} is a short for the
2752 @dfn{home directory}, usually pointed to by the @env{HOME} environment
2753 variable. On MS-Windows, if @env{HOME} is not defined, @value{GDBN}
2754 uses the concatenation of @env{HOMEDRIVE} and @env{HOMEPATH} as
2757 You can also change @value{GDBN}'s current working directory by using
2758 the @code{cd} command.
2762 @cindex show inferior's working directory
2764 Show the inferior's working directory. If no directory has been
2765 specified by @kbd{set cwd}, then the default inferior's working
2766 directory is the same as @value{GDBN}'s working directory.
2769 @cindex change @value{GDBN}'s working directory
2771 @item cd @r{[}@var{directory}@r{]}
2772 Set the @value{GDBN} working directory to @var{directory}. If not
2773 given, @var{directory} uses @file{'~'}.
2775 The @value{GDBN} working directory serves as a default for the
2776 commands that specify files for @value{GDBN} to operate on.
2777 @xref{Files, ,Commands to Specify Files}.
2778 @xref{set cwd command}.
2782 Print the @value{GDBN} working directory.
2785 It is generally impossible to find the current working directory of
2786 the process being debugged (since a program can change its directory
2787 during its run). If you work on a system where @value{GDBN} supports
2788 the @code{info proc} command (@pxref{Process Information}), you can
2789 use the @code{info proc} command to find out the
2790 current working directory of the debuggee.
2793 @section Your Program's Input and Output
2798 By default, the program you run under @value{GDBN} does input and output to
2799 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2800 to its own terminal modes to interact with you, but it records the terminal
2801 modes your program was using and switches back to them when you continue
2802 running your program.
2805 @kindex info terminal
2807 Displays information recorded by @value{GDBN} about the terminal modes your
2811 You can redirect your program's input and/or output using shell
2812 redirection with the @code{run} command. For example,
2819 starts your program, diverting its output to the file @file{outfile}.
2822 @cindex controlling terminal
2823 Another way to specify where your program should do input and output is
2824 with the @code{tty} command. This command accepts a file name as
2825 argument, and causes this file to be the default for future @code{run}
2826 commands. It also resets the controlling terminal for the child
2827 process, for future @code{run} commands. For example,
2834 directs that processes started with subsequent @code{run} commands
2835 default to do input and output on the terminal @file{/dev/ttyb} and have
2836 that as their controlling terminal.
2838 An explicit redirection in @code{run} overrides the @code{tty} command's
2839 effect on the input/output device, but not its effect on the controlling
2842 When you use the @code{tty} command or redirect input in the @code{run}
2843 command, only the input @emph{for your program} is affected. The input
2844 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2845 for @code{set inferior-tty}.
2847 @cindex inferior tty
2848 @cindex set inferior controlling terminal
2849 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2850 display the name of the terminal that will be used for future runs of your
2854 @item set inferior-tty [ @var{tty} ]
2855 @kindex set inferior-tty
2856 Set the tty for the program being debugged to @var{tty}. Omitting @var{tty}
2857 restores the default behavior, which is to use the same terminal as
2860 @item show inferior-tty
2861 @kindex show inferior-tty
2862 Show the current tty for the program being debugged.
2866 @section Debugging an Already-running Process
2871 @item attach @var{process-id}
2872 This command attaches to a running process---one that was started
2873 outside @value{GDBN}. (@code{info files} shows your active
2874 targets.) The command takes as argument a process ID. The usual way to
2875 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2876 or with the @samp{jobs -l} shell command.
2878 @code{attach} does not repeat if you press @key{RET} a second time after
2879 executing the command.
2882 To use @code{attach}, your program must be running in an environment
2883 which supports processes; for example, @code{attach} does not work for
2884 programs on bare-board targets that lack an operating system. You must
2885 also have permission to send the process a signal.
2887 When you use @code{attach}, the debugger finds the program running in
2888 the process first by looking in the current working directory, then (if
2889 the program is not found) by using the source file search path
2890 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2891 the @code{file} command to load the program. @xref{Files, ,Commands to
2894 The first thing @value{GDBN} does after arranging to debug the specified
2895 process is to stop it. You can examine and modify an attached process
2896 with all the @value{GDBN} commands that are ordinarily available when
2897 you start processes with @code{run}. You can insert breakpoints; you
2898 can step and continue; you can modify storage. If you would rather the
2899 process continue running, you may use the @code{continue} command after
2900 attaching @value{GDBN} to the process.
2905 When you have finished debugging the attached process, you can use the
2906 @code{detach} command to release it from @value{GDBN} control. Detaching
2907 the process continues its execution. After the @code{detach} command,
2908 that process and @value{GDBN} become completely independent once more, and you
2909 are ready to @code{attach} another process or start one with @code{run}.
2910 @code{detach} does not repeat if you press @key{RET} again after
2911 executing the command.
2914 If you exit @value{GDBN} while you have an attached process, you detach
2915 that process. If you use the @code{run} command, you kill that process.
2916 By default, @value{GDBN} asks for confirmation if you try to do either of these
2917 things; you can control whether or not you need to confirm by using the
2918 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2922 @section Killing the Child Process
2927 Kill the child process in which your program is running under @value{GDBN}.
2930 This command is useful if you wish to debug a core dump instead of a
2931 running process. @value{GDBN} ignores any core dump file while your program
2934 On some operating systems, a program cannot be executed outside @value{GDBN}
2935 while you have breakpoints set on it inside @value{GDBN}. You can use the
2936 @code{kill} command in this situation to permit running your program
2937 outside the debugger.
2939 The @code{kill} command is also useful if you wish to recompile and
2940 relink your program, since on many systems it is impossible to modify an
2941 executable file while it is running in a process. In this case, when you
2942 next type @code{run}, @value{GDBN} notices that the file has changed, and
2943 reads the symbol table again (while trying to preserve your current
2944 breakpoint settings).
2946 @node Inferiors and Programs
2947 @section Debugging Multiple Inferiors and Programs
2949 @value{GDBN} lets you run and debug multiple programs in a single
2950 session. In addition, @value{GDBN} on some systems may let you run
2951 several programs simultaneously (otherwise you have to exit from one
2952 before starting another). In the most general case, you can have
2953 multiple threads of execution in each of multiple processes, launched
2954 from multiple executables.
2957 @value{GDBN} represents the state of each program execution with an
2958 object called an @dfn{inferior}. An inferior typically corresponds to
2959 a process, but is more general and applies also to targets that do not
2960 have processes. Inferiors may be created before a process runs, and
2961 may be retained after a process exits. Inferiors have unique
2962 identifiers that are different from process ids. Usually each
2963 inferior will also have its own distinct address space, although some
2964 embedded targets may have several inferiors running in different parts
2965 of a single address space. Each inferior may in turn have multiple
2966 threads running in it.
2968 To find out what inferiors exist at any moment, use @w{@code{info
2972 @kindex info inferiors [ @var{id}@dots{} ]
2973 @item info inferiors
2974 Print a list of all inferiors currently being managed by @value{GDBN}.
2975 By default all inferiors are printed, but the argument @var{id}@dots{}
2976 -- a space separated list of inferior numbers -- can be used to limit
2977 the display to just the requested inferiors.
2979 @value{GDBN} displays for each inferior (in this order):
2983 the inferior number assigned by @value{GDBN}
2986 the target system's inferior identifier
2989 the name of the executable the inferior is running.
2994 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2995 indicates the current inferior.
2999 @c end table here to get a little more width for example
3002 (@value{GDBP}) info inferiors
3003 Num Description Executable
3004 2 process 2307 hello
3005 * 1 process 3401 goodbye
3008 To switch focus between inferiors, use the @code{inferior} command:
3011 @kindex inferior @var{infno}
3012 @item inferior @var{infno}
3013 Make inferior number @var{infno} the current inferior. The argument
3014 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
3015 in the first field of the @samp{info inferiors} display.
3018 @vindex $_inferior@r{, convenience variable}
3019 The debugger convenience variable @samp{$_inferior} contains the
3020 number of the current inferior. You may find this useful in writing
3021 breakpoint conditional expressions, command scripts, and so forth.
3022 @xref{Convenience Vars,, Convenience Variables}, for general
3023 information on convenience variables.
3025 You can get multiple executables into a debugging session via the
3026 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
3027 systems @value{GDBN} can add inferiors to the debug session
3028 automatically by following calls to @code{fork} and @code{exec}. To
3029 remove inferiors from the debugging session use the
3030 @w{@code{remove-inferiors}} command.
3033 @kindex add-inferior
3034 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
3035 Adds @var{n} inferiors to be run using @var{executable} as the
3036 executable; @var{n} defaults to 1. If no executable is specified,
3037 the inferiors begins empty, with no program. You can still assign or
3038 change the program assigned to the inferior at any time by using the
3039 @code{file} command with the executable name as its argument.
3041 @kindex clone-inferior
3042 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
3043 Adds @var{n} inferiors ready to execute the same program as inferior
3044 @var{infno}; @var{n} defaults to 1, and @var{infno} defaults to the
3045 number of the current inferior. This is a convenient command when you
3046 want to run another instance of the inferior you are debugging.
3049 (@value{GDBP}) info inferiors
3050 Num Description Executable
3051 * 1 process 29964 helloworld
3052 (@value{GDBP}) clone-inferior
3055 (@value{GDBP}) info inferiors
3056 Num Description Executable
3058 * 1 process 29964 helloworld
3061 You can now simply switch focus to inferior 2 and run it.
3063 @kindex remove-inferiors
3064 @item remove-inferiors @var{infno}@dots{}
3065 Removes the inferior or inferiors @var{infno}@dots{}. It is not
3066 possible to remove an inferior that is running with this command. For
3067 those, use the @code{kill} or @code{detach} command first.
3071 To quit debugging one of the running inferiors that is not the current
3072 inferior, you can either detach from it by using the @w{@code{detach
3073 inferior}} command (allowing it to run independently), or kill it
3074 using the @w{@code{kill inferiors}} command:
3077 @kindex detach inferiors @var{infno}@dots{}
3078 @item detach inferior @var{infno}@dots{}
3079 Detach from the inferior or inferiors identified by @value{GDBN}
3080 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
3081 still stays on the list of inferiors shown by @code{info inferiors},
3082 but its Description will show @samp{<null>}.
3084 @kindex kill inferiors @var{infno}@dots{}
3085 @item kill inferiors @var{infno}@dots{}
3086 Kill the inferior or inferiors identified by @value{GDBN} inferior
3087 number(s) @var{infno}@dots{}. Note that the inferior's entry still
3088 stays on the list of inferiors shown by @code{info inferiors}, but its
3089 Description will show @samp{<null>}.
3092 After the successful completion of a command such as @code{detach},
3093 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
3094 a normal process exit, the inferior is still valid and listed with
3095 @code{info inferiors}, ready to be restarted.
3098 To be notified when inferiors are started or exit under @value{GDBN}'s
3099 control use @w{@code{set print inferior-events}}:
3102 @kindex set print inferior-events
3103 @cindex print messages on inferior start and exit
3104 @item set print inferior-events
3105 @itemx set print inferior-events on
3106 @itemx set print inferior-events off
3107 The @code{set print inferior-events} command allows you to enable or
3108 disable printing of messages when @value{GDBN} notices that new
3109 inferiors have started or that inferiors have exited or have been
3110 detached. By default, these messages will not be printed.
3112 @kindex show print inferior-events
3113 @item show print inferior-events
3114 Show whether messages will be printed when @value{GDBN} detects that
3115 inferiors have started, exited or have been detached.
3118 Many commands will work the same with multiple programs as with a
3119 single program: e.g., @code{print myglobal} will simply display the
3120 value of @code{myglobal} in the current inferior.
3123 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
3124 get more info about the relationship of inferiors, programs, address
3125 spaces in a debug session. You can do that with the @w{@code{maint
3126 info program-spaces}} command.
3129 @kindex maint info program-spaces
3130 @item maint info program-spaces
3131 Print a list of all program spaces currently being managed by
3134 @value{GDBN} displays for each program space (in this order):
3138 the program space number assigned by @value{GDBN}
3141 the name of the executable loaded into the program space, with e.g.,
3142 the @code{file} command.
3147 An asterisk @samp{*} preceding the @value{GDBN} program space number
3148 indicates the current program space.
3150 In addition, below each program space line, @value{GDBN} prints extra
3151 information that isn't suitable to display in tabular form. For
3152 example, the list of inferiors bound to the program space.
3155 (@value{GDBP}) maint info program-spaces
3159 Bound inferiors: ID 1 (process 21561)
3162 Here we can see that no inferior is running the program @code{hello},
3163 while @code{process 21561} is running the program @code{goodbye}. On
3164 some targets, it is possible that multiple inferiors are bound to the
3165 same program space. The most common example is that of debugging both
3166 the parent and child processes of a @code{vfork} call. For example,
3169 (@value{GDBP}) maint info program-spaces
3172 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
3175 Here, both inferior 2 and inferior 1 are running in the same program
3176 space as a result of inferior 1 having executed a @code{vfork} call.
3180 @section Debugging Programs with Multiple Threads
3182 @cindex threads of execution
3183 @cindex multiple threads
3184 @cindex switching threads
3185 In some operating systems, such as GNU/Linux and Solaris, a single program
3186 may have more than one @dfn{thread} of execution. The precise semantics
3187 of threads differ from one operating system to another, but in general
3188 the threads of a single program are akin to multiple processes---except
3189 that they share one address space (that is, they can all examine and
3190 modify the same variables). On the other hand, each thread has its own
3191 registers and execution stack, and perhaps private memory.
3193 @value{GDBN} provides these facilities for debugging multi-thread
3197 @item automatic notification of new threads
3198 @item @samp{thread @var{thread-id}}, a command to switch among threads
3199 @item @samp{info threads}, a command to inquire about existing threads
3200 @item @samp{thread apply [@var{thread-id-list} | all] @var{args}},
3201 a command to apply a command to a list of threads
3202 @item thread-specific breakpoints
3203 @item @samp{set print thread-events}, which controls printing of
3204 messages on thread start and exit.
3205 @item @samp{set libthread-db-search-path @var{path}}, which lets
3206 the user specify which @code{libthread_db} to use if the default choice
3207 isn't compatible with the program.
3210 @cindex focus of debugging
3211 @cindex current thread
3212 The @value{GDBN} thread debugging facility allows you to observe all
3213 threads while your program runs---but whenever @value{GDBN} takes
3214 control, one thread in particular is always the focus of debugging.
3215 This thread is called the @dfn{current thread}. Debugging commands show
3216 program information from the perspective of the current thread.
3218 @cindex @code{New} @var{systag} message
3219 @cindex thread identifier (system)
3220 @c FIXME-implementors!! It would be more helpful if the [New...] message
3221 @c included GDB's numeric thread handle, so you could just go to that
3222 @c thread without first checking `info threads'.
3223 Whenever @value{GDBN} detects a new thread in your program, it displays
3224 the target system's identification for the thread with a message in the
3225 form @samp{[New @var{systag}]}, where @var{systag} is a thread identifier
3226 whose form varies depending on the particular system. For example, on
3227 @sc{gnu}/Linux, you might see
3230 [New Thread 0x41e02940 (LWP 25582)]
3234 when @value{GDBN} notices a new thread. In contrast, on other systems,
3235 the @var{systag} is simply something like @samp{process 368}, with no
3238 @c FIXME!! (1) Does the [New...] message appear even for the very first
3239 @c thread of a program, or does it only appear for the
3240 @c second---i.e.@: when it becomes obvious we have a multithread
3242 @c (2) *Is* there necessarily a first thread always? Or do some
3243 @c multithread systems permit starting a program with multiple
3244 @c threads ab initio?
3246 @anchor{thread numbers}
3247 @cindex thread number, per inferior
3248 @cindex thread identifier (GDB)
3249 For debugging purposes, @value{GDBN} associates its own thread number
3250 ---always a single integer---with each thread of an inferior. This
3251 number is unique between all threads of an inferior, but not unique
3252 between threads of different inferiors.
3254 @cindex qualified thread ID
3255 You can refer to a given thread in an inferior using the qualified
3256 @var{inferior-num}.@var{thread-num} syntax, also known as
3257 @dfn{qualified thread ID}, with @var{inferior-num} being the inferior
3258 number and @var{thread-num} being the thread number of the given
3259 inferior. For example, thread @code{2.3} refers to thread number 3 of
3260 inferior 2. If you omit @var{inferior-num} (e.g., @code{thread 3}),
3261 then @value{GDBN} infers you're referring to a thread of the current
3264 Until you create a second inferior, @value{GDBN} does not show the
3265 @var{inferior-num} part of thread IDs, even though you can always use
3266 the full @var{inferior-num}.@var{thread-num} form to refer to threads
3267 of inferior 1, the initial inferior.
3269 @anchor{thread ID lists}
3270 @cindex thread ID lists
3271 Some commands accept a space-separated @dfn{thread ID list} as
3272 argument. A list element can be:
3276 A thread ID as shown in the first field of the @samp{info threads}
3277 display, with or without an inferior qualifier. E.g., @samp{2.1} or
3281 A range of thread numbers, again with or without an inferior
3282 qualifier, as in @var{inf}.@var{thr1}-@var{thr2} or
3283 @var{thr1}-@var{thr2}. E.g., @samp{1.2-4} or @samp{2-4}.
3286 All threads of an inferior, specified with a star wildcard, with or
3287 without an inferior qualifier, as in @var{inf}.@code{*} (e.g.,
3288 @samp{1.*}) or @code{*}. The former refers to all threads of the
3289 given inferior, and the latter form without an inferior qualifier
3290 refers to all threads of the current inferior.
3294 For example, if the current inferior is 1, and inferior 7 has one
3295 thread with ID 7.1, the thread list @samp{1 2-3 4.5 6.7-9 7.*}
3296 includes threads 1 to 3 of inferior 1, thread 5 of inferior 4, threads
3297 7 to 9 of inferior 6 and all threads of inferior 7. That is, in
3298 expanded qualified form, the same as @samp{1.1 1.2 1.3 4.5 6.7 6.8 6.9
3302 @anchor{global thread numbers}
3303 @cindex global thread number
3304 @cindex global thread identifier (GDB)
3305 In addition to a @emph{per-inferior} number, each thread is also
3306 assigned a unique @emph{global} number, also known as @dfn{global
3307 thread ID}, a single integer. Unlike the thread number component of
3308 the thread ID, no two threads have the same global ID, even when
3309 you're debugging multiple inferiors.
3311 From @value{GDBN}'s perspective, a process always has at least one
3312 thread. In other words, @value{GDBN} assigns a thread number to the
3313 program's ``main thread'' even if the program is not multi-threaded.
3315 @vindex $_thread@r{, convenience variable}
3316 @vindex $_gthread@r{, convenience variable}
3317 The debugger convenience variables @samp{$_thread} and
3318 @samp{$_gthread} contain, respectively, the per-inferior thread number
3319 and the global thread number of the current thread. You may find this
3320 useful in writing breakpoint conditional expressions, command scripts,
3321 and so forth. @xref{Convenience Vars,, Convenience Variables}, for
3322 general information on convenience variables.
3324 If @value{GDBN} detects the program is multi-threaded, it augments the
3325 usual message about stopping at a breakpoint with the ID and name of
3326 the thread that hit the breakpoint.
3329 Thread 2 "client" hit Breakpoint 1, send_message () at client.c:68
3332 Likewise when the program receives a signal:
3335 Thread 1 "main" received signal SIGINT, Interrupt.
3339 @kindex info threads
3340 @item info threads @r{[}@var{thread-id-list}@r{]}
3342 Display information about one or more threads. With no arguments
3343 displays information about all threads. You can specify the list of
3344 threads that you want to display using the thread ID list syntax
3345 (@pxref{thread ID lists}).
3347 @value{GDBN} displays for each thread (in this order):
3351 the per-inferior thread number assigned by @value{GDBN}
3354 the global thread number assigned by @value{GDBN}, if the @samp{-gid}
3355 option was specified
3358 the target system's thread identifier (@var{systag})
3361 the thread's name, if one is known. A thread can either be named by
3362 the user (see @code{thread name}, below), or, in some cases, by the
3366 the current stack frame summary for that thread
3370 An asterisk @samp{*} to the left of the @value{GDBN} thread number
3371 indicates the current thread.
3375 @c end table here to get a little more width for example
3378 (@value{GDBP}) info threads
3380 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3381 2 process 35 thread 23 0x34e5 in sigpause ()
3382 3 process 35 thread 27 0x34e5 in sigpause ()
3386 If you're debugging multiple inferiors, @value{GDBN} displays thread
3387 IDs using the qualified @var{inferior-num}.@var{thread-num} format.
3388 Otherwise, only @var{thread-num} is shown.
3390 If you specify the @samp{-gid} option, @value{GDBN} displays a column
3391 indicating each thread's global thread ID:
3394 (@value{GDBP}) info threads
3395 Id GId Target Id Frame
3396 1.1 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3397 1.2 3 process 35 thread 23 0x34e5 in sigpause ()
3398 1.3 4 process 35 thread 27 0x34e5 in sigpause ()
3399 * 2.1 2 process 65 thread 1 main (argc=1, argv=0x7ffffff8)
3402 On Solaris, you can display more information about user threads with a
3403 Solaris-specific command:
3406 @item maint info sol-threads
3407 @kindex maint info sol-threads
3408 @cindex thread info (Solaris)
3409 Display info on Solaris user threads.
3413 @kindex thread @var{thread-id}
3414 @item thread @var{thread-id}
3415 Make thread ID @var{thread-id} the current thread. The command
3416 argument @var{thread-id} is the @value{GDBN} thread ID, as shown in
3417 the first field of the @samp{info threads} display, with or without an
3418 inferior qualifier (e.g., @samp{2.1} or @samp{1}).
3420 @value{GDBN} responds by displaying the system identifier of the
3421 thread you selected, and its current stack frame summary:
3424 (@value{GDBP}) thread 2
3425 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
3426 #0 some_function (ignore=0x0) at example.c:8
3427 8 printf ("hello\n");
3431 As with the @samp{[New @dots{}]} message, the form of the text after
3432 @samp{Switching to} depends on your system's conventions for identifying
3435 @anchor{thread apply all}
3436 @kindex thread apply
3437 @cindex apply command to several threads
3438 @item thread apply [@var{thread-id-list} | all [-ascending]] [@var{flag}]@dots{} @var{command}
3439 The @code{thread apply} command allows you to apply the named
3440 @var{command} to one or more threads. Specify the threads that you
3441 want affected using the thread ID list syntax (@pxref{thread ID
3442 lists}), or specify @code{all} to apply to all threads. To apply a
3443 command to all threads in descending order, type @kbd{thread apply all
3444 @var{command}}. To apply a command to all threads in ascending order,
3445 type @kbd{thread apply all -ascending @var{command}}.
3447 The @var{flag} arguments control what output to produce and how to handle
3448 errors raised when applying @var{command} to a thread. @var{flag}
3449 must start with a @code{-} directly followed by one letter in
3450 @code{qcs}. If several flags are provided, they must be given
3451 individually, such as @code{-c -q}.
3453 By default, @value{GDBN} displays some thread information before the
3454 output produced by @var{command}, and an error raised during the
3455 execution of a @var{command} will abort @code{thread apply}. The
3456 following flags can be used to fine-tune this behavior:
3460 The flag @code{-c}, which stands for @samp{continue}, causes any
3461 errors in @var{command} to be displayed, and the execution of
3462 @code{thread apply} then continues.
3464 The flag @code{-s}, which stands for @samp{silent}, causes any errors
3465 or empty output produced by a @var{command} to be silently ignored.
3466 That is, the execution continues, but the thread information and errors
3469 The flag @code{-q} (@samp{quiet}) disables printing the thread
3473 Flags @code{-c} and @code{-s} cannot be used together.
3476 @cindex apply command to all threads (ignoring errors and empty output)
3477 @item taas [@var{option}]@dots{} @var{command}
3478 Shortcut for @code{thread apply all -s [@var{option}]@dots{} @var{command}}.
3479 Applies @var{command} on all threads, ignoring errors and empty output.
3481 The @code{taas} command accepts the same options as the @code{thread
3482 apply all} command. @xref{thread apply all}.
3485 @cindex apply a command to all frames of all threads (ignoring errors and empty output)
3486 @item tfaas [@var{option}]@dots{} @var{command}
3487 Shortcut for @code{thread apply all -s -- frame apply all -s [@var{option}]@dots{} @var{command}}.
3488 Applies @var{command} on all frames of all threads, ignoring errors
3489 and empty output. Note that the flag @code{-s} is specified twice:
3490 The first @code{-s} ensures that @code{thread apply} only shows the thread
3491 information of the threads for which @code{frame apply} produces
3492 some output. The second @code{-s} is needed to ensure that @code{frame
3493 apply} shows the frame information of a frame only if the
3494 @var{command} successfully produced some output.
3496 It can for example be used to print a local variable or a function
3497 argument without knowing the thread or frame where this variable or argument
3500 (@value{GDBP}) tfaas p some_local_var_i_do_not_remember_where_it_is
3503 The @code{tfaas} command accepts the same options as the @code{frame
3504 apply} command. @xref{frame apply}.
3507 @cindex name a thread
3508 @item thread name [@var{name}]
3509 This command assigns a name to the current thread. If no argument is
3510 given, any existing user-specified name is removed. The thread name
3511 appears in the @samp{info threads} display.
3513 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
3514 determine the name of the thread as given by the OS. On these
3515 systems, a name specified with @samp{thread name} will override the
3516 system-give name, and removing the user-specified name will cause
3517 @value{GDBN} to once again display the system-specified name.
3520 @cindex search for a thread
3521 @item thread find [@var{regexp}]
3522 Search for and display thread ids whose name or @var{systag}
3523 matches the supplied regular expression.
3525 As well as being the complement to the @samp{thread name} command,
3526 this command also allows you to identify a thread by its target
3527 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
3531 (@value{GDBN}) thread find 26688
3532 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
3533 (@value{GDBN}) info thread 4
3535 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
3538 @kindex set print thread-events
3539 @cindex print messages on thread start and exit
3540 @item set print thread-events
3541 @itemx set print thread-events on
3542 @itemx set print thread-events off
3543 The @code{set print thread-events} command allows you to enable or
3544 disable printing of messages when @value{GDBN} notices that new threads have
3545 started or that threads have exited. By default, these messages will
3546 be printed if detection of these events is supported by the target.
3547 Note that these messages cannot be disabled on all targets.
3549 @kindex show print thread-events
3550 @item show print thread-events
3551 Show whether messages will be printed when @value{GDBN} detects that threads
3552 have started and exited.
3555 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
3556 more information about how @value{GDBN} behaves when you stop and start
3557 programs with multiple threads.
3559 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
3560 watchpoints in programs with multiple threads.
3562 @anchor{set libthread-db-search-path}
3564 @kindex set libthread-db-search-path
3565 @cindex search path for @code{libthread_db}
3566 @item set libthread-db-search-path @r{[}@var{path}@r{]}
3567 If this variable is set, @var{path} is a colon-separated list of
3568 directories @value{GDBN} will use to search for @code{libthread_db}.
3569 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
3570 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
3571 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
3574 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
3575 @code{libthread_db} library to obtain information about threads in the
3576 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
3577 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
3578 specific thread debugging library loading is enabled
3579 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
3581 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
3582 refers to the default system directories that are
3583 normally searched for loading shared libraries. The @samp{$sdir} entry
3584 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
3585 (@pxref{libthread_db.so.1 file}).
3587 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
3588 refers to the directory from which @code{libpthread}
3589 was loaded in the inferior process.
3591 For any @code{libthread_db} library @value{GDBN} finds in above directories,
3592 @value{GDBN} attempts to initialize it with the current inferior process.
3593 If this initialization fails (which could happen because of a version
3594 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
3595 will unload @code{libthread_db}, and continue with the next directory.
3596 If none of @code{libthread_db} libraries initialize successfully,
3597 @value{GDBN} will issue a warning and thread debugging will be disabled.
3599 Setting @code{libthread-db-search-path} is currently implemented
3600 only on some platforms.
3602 @kindex show libthread-db-search-path
3603 @item show libthread-db-search-path
3604 Display current libthread_db search path.
3606 @kindex set debug libthread-db
3607 @kindex show debug libthread-db
3608 @cindex debugging @code{libthread_db}
3609 @item set debug libthread-db
3610 @itemx show debug libthread-db
3611 Turns on or off display of @code{libthread_db}-related events.
3612 Use @code{1} to enable, @code{0} to disable.
3616 @section Debugging Forks
3618 @cindex fork, debugging programs which call
3619 @cindex multiple processes
3620 @cindex processes, multiple
3621 On most systems, @value{GDBN} has no special support for debugging
3622 programs which create additional processes using the @code{fork}
3623 function. When a program forks, @value{GDBN} will continue to debug the
3624 parent process and the child process will run unimpeded. If you have
3625 set a breakpoint in any code which the child then executes, the child
3626 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3627 will cause it to terminate.
3629 However, if you want to debug the child process there is a workaround
3630 which isn't too painful. Put a call to @code{sleep} in the code which
3631 the child process executes after the fork. It may be useful to sleep
3632 only if a certain environment variable is set, or a certain file exists,
3633 so that the delay need not occur when you don't want to run @value{GDBN}
3634 on the child. While the child is sleeping, use the @code{ps} program to
3635 get its process ID. Then tell @value{GDBN} (a new invocation of
3636 @value{GDBN} if you are also debugging the parent process) to attach to
3637 the child process (@pxref{Attach}). From that point on you can debug
3638 the child process just like any other process which you attached to.
3640 On some systems, @value{GDBN} provides support for debugging programs
3641 that create additional processes using the @code{fork} or @code{vfork}
3642 functions. On @sc{gnu}/Linux platforms, this feature is supported
3643 with kernel version 2.5.46 and later.
3645 The fork debugging commands are supported in native mode and when
3646 connected to @code{gdbserver} in either @code{target remote} mode or
3647 @code{target extended-remote} mode.
3649 By default, when a program forks, @value{GDBN} will continue to debug
3650 the parent process and the child process will run unimpeded.
3652 If you want to follow the child process instead of the parent process,
3653 use the command @w{@code{set follow-fork-mode}}.
3656 @kindex set follow-fork-mode
3657 @item set follow-fork-mode @var{mode}
3658 Set the debugger response to a program call of @code{fork} or
3659 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3660 process. The @var{mode} argument can be:
3664 The original process is debugged after a fork. The child process runs
3665 unimpeded. This is the default.
3668 The new process is debugged after a fork. The parent process runs
3673 @kindex show follow-fork-mode
3674 @item show follow-fork-mode
3675 Display the current debugger response to a @code{fork} or @code{vfork} call.
3678 @cindex debugging multiple processes
3679 On Linux, if you want to debug both the parent and child processes, use the
3680 command @w{@code{set detach-on-fork}}.
3683 @kindex set detach-on-fork
3684 @item set detach-on-fork @var{mode}
3685 Tells gdb whether to detach one of the processes after a fork, or
3686 retain debugger control over them both.
3690 The child process (or parent process, depending on the value of
3691 @code{follow-fork-mode}) will be detached and allowed to run
3692 independently. This is the default.
3695 Both processes will be held under the control of @value{GDBN}.
3696 One process (child or parent, depending on the value of
3697 @code{follow-fork-mode}) is debugged as usual, while the other
3702 @kindex show detach-on-fork
3703 @item show detach-on-fork
3704 Show whether detach-on-fork mode is on/off.
3707 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3708 will retain control of all forked processes (including nested forks).
3709 You can list the forked processes under the control of @value{GDBN} by
3710 using the @w{@code{info inferiors}} command, and switch from one fork
3711 to another by using the @code{inferior} command (@pxref{Inferiors and
3712 Programs, ,Debugging Multiple Inferiors and Programs}).
3714 To quit debugging one of the forked processes, you can either detach
3715 from it by using the @w{@code{detach inferiors}} command (allowing it
3716 to run independently), or kill it using the @w{@code{kill inferiors}}
3717 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3720 If you ask to debug a child process and a @code{vfork} is followed by an
3721 @code{exec}, @value{GDBN} executes the new target up to the first
3722 breakpoint in the new target. If you have a breakpoint set on
3723 @code{main} in your original program, the breakpoint will also be set on
3724 the child process's @code{main}.
3726 On some systems, when a child process is spawned by @code{vfork}, you
3727 cannot debug the child or parent until an @code{exec} call completes.
3729 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3730 call executes, the new target restarts. To restart the parent
3731 process, use the @code{file} command with the parent executable name
3732 as its argument. By default, after an @code{exec} call executes,
3733 @value{GDBN} discards the symbols of the previous executable image.
3734 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3738 @kindex set follow-exec-mode
3739 @item set follow-exec-mode @var{mode}
3741 Set debugger response to a program call of @code{exec}. An
3742 @code{exec} call replaces the program image of a process.
3744 @code{follow-exec-mode} can be:
3748 @value{GDBN} creates a new inferior and rebinds the process to this
3749 new inferior. The program the process was running before the
3750 @code{exec} call can be restarted afterwards by restarting the
3756 (@value{GDBP}) info inferiors
3758 Id Description Executable
3761 process 12020 is executing new program: prog2
3762 Program exited normally.
3763 (@value{GDBP}) info inferiors
3764 Id Description Executable
3770 @value{GDBN} keeps the process bound to the same inferior. The new
3771 executable image replaces the previous executable loaded in the
3772 inferior. Restarting the inferior after the @code{exec} call, with
3773 e.g., the @code{run} command, restarts the executable the process was
3774 running after the @code{exec} call. This is the default mode.
3779 (@value{GDBP}) info inferiors
3780 Id Description Executable
3783 process 12020 is executing new program: prog2
3784 Program exited normally.
3785 (@value{GDBP}) info inferiors
3786 Id Description Executable
3793 @code{follow-exec-mode} is supported in native mode and
3794 @code{target extended-remote} mode.
3796 You can use the @code{catch} command to make @value{GDBN} stop whenever
3797 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3798 Catchpoints, ,Setting Catchpoints}.
3800 @node Checkpoint/Restart
3801 @section Setting a @emph{Bookmark} to Return to Later
3806 @cindex snapshot of a process
3807 @cindex rewind program state
3809 On certain operating systems@footnote{Currently, only
3810 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3811 program's state, called a @dfn{checkpoint}, and come back to it
3814 Returning to a checkpoint effectively undoes everything that has
3815 happened in the program since the @code{checkpoint} was saved. This
3816 includes changes in memory, registers, and even (within some limits)
3817 system state. Effectively, it is like going back in time to the
3818 moment when the checkpoint was saved.
3820 Thus, if you're stepping thru a program and you think you're
3821 getting close to the point where things go wrong, you can save
3822 a checkpoint. Then, if you accidentally go too far and miss
3823 the critical statement, instead of having to restart your program
3824 from the beginning, you can just go back to the checkpoint and
3825 start again from there.
3827 This can be especially useful if it takes a lot of time or
3828 steps to reach the point where you think the bug occurs.
3830 To use the @code{checkpoint}/@code{restart} method of debugging:
3835 Save a snapshot of the debugged program's current execution state.
3836 The @code{checkpoint} command takes no arguments, but each checkpoint
3837 is assigned a small integer id, similar to a breakpoint id.
3839 @kindex info checkpoints
3840 @item info checkpoints
3841 List the checkpoints that have been saved in the current debugging
3842 session. For each checkpoint, the following information will be
3849 @item Source line, or label
3852 @kindex restart @var{checkpoint-id}
3853 @item restart @var{checkpoint-id}
3854 Restore the program state that was saved as checkpoint number
3855 @var{checkpoint-id}. All program variables, registers, stack frames
3856 etc.@: will be returned to the values that they had when the checkpoint
3857 was saved. In essence, gdb will ``wind back the clock'' to the point
3858 in time when the checkpoint was saved.
3860 Note that breakpoints, @value{GDBN} variables, command history etc.
3861 are not affected by restoring a checkpoint. In general, a checkpoint
3862 only restores things that reside in the program being debugged, not in
3865 @kindex delete checkpoint @var{checkpoint-id}
3866 @item delete checkpoint @var{checkpoint-id}
3867 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3871 Returning to a previously saved checkpoint will restore the user state
3872 of the program being debugged, plus a significant subset of the system
3873 (OS) state, including file pointers. It won't ``un-write'' data from
3874 a file, but it will rewind the file pointer to the previous location,
3875 so that the previously written data can be overwritten. For files
3876 opened in read mode, the pointer will also be restored so that the
3877 previously read data can be read again.
3879 Of course, characters that have been sent to a printer (or other
3880 external device) cannot be ``snatched back'', and characters received
3881 from eg.@: a serial device can be removed from internal program buffers,
3882 but they cannot be ``pushed back'' into the serial pipeline, ready to
3883 be received again. Similarly, the actual contents of files that have
3884 been changed cannot be restored (at this time).
3886 However, within those constraints, you actually can ``rewind'' your
3887 program to a previously saved point in time, and begin debugging it
3888 again --- and you can change the course of events so as to debug a
3889 different execution path this time.
3891 @cindex checkpoints and process id
3892 Finally, there is one bit of internal program state that will be
3893 different when you return to a checkpoint --- the program's process
3894 id. Each checkpoint will have a unique process id (or @var{pid}),
3895 and each will be different from the program's original @var{pid}.
3896 If your program has saved a local copy of its process id, this could
3897 potentially pose a problem.
3899 @subsection A Non-obvious Benefit of Using Checkpoints
3901 On some systems such as @sc{gnu}/Linux, address space randomization
3902 is performed on new processes for security reasons. This makes it
3903 difficult or impossible to set a breakpoint, or watchpoint, on an
3904 absolute address if you have to restart the program, since the
3905 absolute location of a symbol will change from one execution to the
3908 A checkpoint, however, is an @emph{identical} copy of a process.
3909 Therefore if you create a checkpoint at (eg.@:) the start of main,
3910 and simply return to that checkpoint instead of restarting the
3911 process, you can avoid the effects of address randomization and
3912 your symbols will all stay in the same place.
3915 @chapter Stopping and Continuing
3917 The principal purposes of using a debugger are so that you can stop your
3918 program before it terminates; or so that, if your program runs into
3919 trouble, you can investigate and find out why.
3921 Inside @value{GDBN}, your program may stop for any of several reasons,
3922 such as a signal, a breakpoint, or reaching a new line after a
3923 @value{GDBN} command such as @code{step}. You may then examine and
3924 change variables, set new breakpoints or remove old ones, and then
3925 continue execution. Usually, the messages shown by @value{GDBN} provide
3926 ample explanation of the status of your program---but you can also
3927 explicitly request this information at any time.
3930 @kindex info program
3932 Display information about the status of your program: whether it is
3933 running or not, what process it is, and why it stopped.
3937 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3938 * Continuing and Stepping:: Resuming execution
3939 * Skipping Over Functions and Files::
3940 Skipping over functions and files
3942 * Thread Stops:: Stopping and starting multi-thread programs
3946 @section Breakpoints, Watchpoints, and Catchpoints
3949 A @dfn{breakpoint} makes your program stop whenever a certain point in
3950 the program is reached. For each breakpoint, you can add conditions to
3951 control in finer detail whether your program stops. You can set
3952 breakpoints with the @code{break} command and its variants (@pxref{Set
3953 Breaks, ,Setting Breakpoints}), to specify the place where your program
3954 should stop by line number, function name or exact address in the
3957 On some systems, you can set breakpoints in shared libraries before
3958 the executable is run.
3961 @cindex data breakpoints
3962 @cindex memory tracing
3963 @cindex breakpoint on memory address
3964 @cindex breakpoint on variable modification
3965 A @dfn{watchpoint} is a special breakpoint that stops your program
3966 when the value of an expression changes. The expression may be a value
3967 of a variable, or it could involve values of one or more variables
3968 combined by operators, such as @samp{a + b}. This is sometimes called
3969 @dfn{data breakpoints}. You must use a different command to set
3970 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3971 from that, you can manage a watchpoint like any other breakpoint: you
3972 enable, disable, and delete both breakpoints and watchpoints using the
3975 You can arrange to have values from your program displayed automatically
3976 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3980 @cindex breakpoint on events
3981 A @dfn{catchpoint} is another special breakpoint that stops your program
3982 when a certain kind of event occurs, such as the throwing of a C@t{++}
3983 exception or the loading of a library. As with watchpoints, you use a
3984 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3985 Catchpoints}), but aside from that, you can manage a catchpoint like any
3986 other breakpoint. (To stop when your program receives a signal, use the
3987 @code{handle} command; see @ref{Signals, ,Signals}.)
3989 @cindex breakpoint numbers
3990 @cindex numbers for breakpoints
3991 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3992 catchpoint when you create it; these numbers are successive integers
3993 starting with one. In many of the commands for controlling various
3994 features of breakpoints you use the breakpoint number to say which
3995 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3996 @dfn{disabled}; if disabled, it has no effect on your program until you
3999 @cindex breakpoint ranges
4000 @cindex breakpoint lists
4001 @cindex ranges of breakpoints
4002 @cindex lists of breakpoints
4003 Some @value{GDBN} commands accept a space-separated list of breakpoints
4004 on which to operate. A list element can be either a single breakpoint number,
4005 like @samp{5}, or a range of such numbers, like @samp{5-7}.
4006 When a breakpoint list is given to a command, all breakpoints in that list
4010 * Set Breaks:: Setting breakpoints
4011 * Set Watchpoints:: Setting watchpoints
4012 * Set Catchpoints:: Setting catchpoints
4013 * Delete Breaks:: Deleting breakpoints
4014 * Disabling:: Disabling breakpoints
4015 * Conditions:: Break conditions
4016 * Break Commands:: Breakpoint command lists
4017 * Dynamic Printf:: Dynamic printf
4018 * Save Breakpoints:: How to save breakpoints in a file
4019 * Static Probe Points:: Listing static probe points
4020 * Error in Breakpoints:: ``Cannot insert breakpoints''
4021 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
4025 @subsection Setting Breakpoints
4027 @c FIXME LMB what does GDB do if no code on line of breakpt?
4028 @c consider in particular declaration with/without initialization.
4030 @c FIXME 2 is there stuff on this already? break at fun start, already init?
4033 @kindex b @r{(@code{break})}
4034 @vindex $bpnum@r{, convenience variable}
4035 @cindex latest breakpoint
4036 Breakpoints are set with the @code{break} command (abbreviated
4037 @code{b}). The debugger convenience variable @samp{$bpnum} records the
4038 number of the breakpoint you've set most recently; see @ref{Convenience
4039 Vars,, Convenience Variables}, for a discussion of what you can do with
4040 convenience variables.
4043 @item break @var{location}
4044 Set a breakpoint at the given @var{location}, which can specify a
4045 function name, a line number, or an address of an instruction.
4046 (@xref{Specify Location}, for a list of all the possible ways to
4047 specify a @var{location}.) The breakpoint will stop your program just
4048 before it executes any of the code in the specified @var{location}.
4050 When using source languages that permit overloading of symbols, such as
4051 C@t{++}, a function name may refer to more than one possible place to break.
4052 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
4055 It is also possible to insert a breakpoint that will stop the program
4056 only if a specific thread (@pxref{Thread-Specific Breakpoints})
4057 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
4060 When called without any arguments, @code{break} sets a breakpoint at
4061 the next instruction to be executed in the selected stack frame
4062 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
4063 innermost, this makes your program stop as soon as control
4064 returns to that frame. This is similar to the effect of a
4065 @code{finish} command in the frame inside the selected frame---except
4066 that @code{finish} does not leave an active breakpoint. If you use
4067 @code{break} without an argument in the innermost frame, @value{GDBN} stops
4068 the next time it reaches the current location; this may be useful
4071 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
4072 least one instruction has been executed. If it did not do this, you
4073 would be unable to proceed past a breakpoint without first disabling the
4074 breakpoint. This rule applies whether or not the breakpoint already
4075 existed when your program stopped.
4077 @item break @dots{} if @var{cond}
4078 Set a breakpoint with condition @var{cond}; evaluate the expression
4079 @var{cond} each time the breakpoint is reached, and stop only if the
4080 value is nonzero---that is, if @var{cond} evaluates as true.
4081 @samp{@dots{}} stands for one of the possible arguments described
4082 above (or no argument) specifying where to break. @xref{Conditions,
4083 ,Break Conditions}, for more information on breakpoint conditions.
4086 @item tbreak @var{args}
4087 Set a breakpoint enabled only for one stop. The @var{args} are the
4088 same as for the @code{break} command, and the breakpoint is set in the same
4089 way, but the breakpoint is automatically deleted after the first time your
4090 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
4093 @cindex hardware breakpoints
4094 @item hbreak @var{args}
4095 Set a hardware-assisted breakpoint. The @var{args} are the same as for the
4096 @code{break} command and the breakpoint is set in the same way, but the
4097 breakpoint requires hardware support and some target hardware may not
4098 have this support. The main purpose of this is EPROM/ROM code
4099 debugging, so you can set a breakpoint at an instruction without
4100 changing the instruction. This can be used with the new trap-generation
4101 provided by SPARClite DSU and most x86-based targets. These targets
4102 will generate traps when a program accesses some data or instruction
4103 address that is assigned to the debug registers. However the hardware
4104 breakpoint registers can take a limited number of breakpoints. For
4105 example, on the DSU, only two data breakpoints can be set at a time, and
4106 @value{GDBN} will reject this command if more than two are used. Delete
4107 or disable unused hardware breakpoints before setting new ones
4108 (@pxref{Disabling, ,Disabling Breakpoints}).
4109 @xref{Conditions, ,Break Conditions}.
4110 For remote targets, you can restrict the number of hardware
4111 breakpoints @value{GDBN} will use, see @ref{set remote
4112 hardware-breakpoint-limit}.
4115 @item thbreak @var{args}
4116 Set a hardware-assisted breakpoint enabled only for one stop. The @var{args}
4117 are the same as for the @code{hbreak} command and the breakpoint is set in
4118 the same way. However, like the @code{tbreak} command,
4119 the breakpoint is automatically deleted after the
4120 first time your program stops there. Also, like the @code{hbreak}
4121 command, the breakpoint requires hardware support and some target hardware
4122 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
4123 See also @ref{Conditions, ,Break Conditions}.
4126 @cindex regular expression
4127 @cindex breakpoints at functions matching a regexp
4128 @cindex set breakpoints in many functions
4129 @item rbreak @var{regex}
4130 Set breakpoints on all functions matching the regular expression
4131 @var{regex}. This command sets an unconditional breakpoint on all
4132 matches, printing a list of all breakpoints it set. Once these
4133 breakpoints are set, they are treated just like the breakpoints set with
4134 the @code{break} command. You can delete them, disable them, or make
4135 them conditional the same way as any other breakpoint.
4137 In programs using different languages, @value{GDBN} chooses the syntax
4138 to print the list of all breakpoints it sets according to the
4139 @samp{set language} value: using @samp{set language auto}
4140 (see @ref{Automatically, ,Set Language Automatically}) means to use the
4141 language of the breakpoint's function, other values mean to use
4142 the manually specified language (see @ref{Manually, ,Set Language Manually}).
4144 The syntax of the regular expression is the standard one used with tools
4145 like @file{grep}. Note that this is different from the syntax used by
4146 shells, so for instance @code{foo*} matches all functions that include
4147 an @code{fo} followed by zero or more @code{o}s. There is an implicit
4148 @code{.*} leading and trailing the regular expression you supply, so to
4149 match only functions that begin with @code{foo}, use @code{^foo}.
4151 @cindex non-member C@t{++} functions, set breakpoint in
4152 When debugging C@t{++} programs, @code{rbreak} is useful for setting
4153 breakpoints on overloaded functions that are not members of any special
4156 @cindex set breakpoints on all functions
4157 The @code{rbreak} command can be used to set breakpoints in
4158 @strong{all} the functions in a program, like this:
4161 (@value{GDBP}) rbreak .
4164 @item rbreak @var{file}:@var{regex}
4165 If @code{rbreak} is called with a filename qualification, it limits
4166 the search for functions matching the given regular expression to the
4167 specified @var{file}. This can be used, for example, to set breakpoints on
4168 every function in a given file:
4171 (@value{GDBP}) rbreak file.c:.
4174 The colon separating the filename qualifier from the regex may
4175 optionally be surrounded by spaces.
4177 @kindex info breakpoints
4178 @cindex @code{$_} and @code{info breakpoints}
4179 @item info breakpoints @r{[}@var{list}@dots{}@r{]}
4180 @itemx info break @r{[}@var{list}@dots{}@r{]}
4181 Print a table of all breakpoints, watchpoints, and catchpoints set and
4182 not deleted. Optional argument @var{n} means print information only
4183 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
4184 For each breakpoint, following columns are printed:
4187 @item Breakpoint Numbers
4189 Breakpoint, watchpoint, or catchpoint.
4191 Whether the breakpoint is marked to be disabled or deleted when hit.
4192 @item Enabled or Disabled
4193 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
4194 that are not enabled.
4196 Where the breakpoint is in your program, as a memory address. For a
4197 pending breakpoint whose address is not yet known, this field will
4198 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
4199 library that has the symbol or line referred by breakpoint is loaded.
4200 See below for details. A breakpoint with several locations will
4201 have @samp{<MULTIPLE>} in this field---see below for details.
4203 Where the breakpoint is in the source for your program, as a file and
4204 line number. For a pending breakpoint, the original string passed to
4205 the breakpoint command will be listed as it cannot be resolved until
4206 the appropriate shared library is loaded in the future.
4210 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
4211 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
4212 @value{GDBN} on the host's side. If it is ``target'', then the condition
4213 is evaluated by the target. The @code{info break} command shows
4214 the condition on the line following the affected breakpoint, together with
4215 its condition evaluation mode in between parentheses.
4217 Breakpoint commands, if any, are listed after that. A pending breakpoint is
4218 allowed to have a condition specified for it. The condition is not parsed for
4219 validity until a shared library is loaded that allows the pending
4220 breakpoint to resolve to a valid location.
4223 @code{info break} with a breakpoint
4224 number @var{n} as argument lists only that breakpoint. The
4225 convenience variable @code{$_} and the default examining-address for
4226 the @code{x} command are set to the address of the last breakpoint
4227 listed (@pxref{Memory, ,Examining Memory}).
4230 @code{info break} displays a count of the number of times the breakpoint
4231 has been hit. This is especially useful in conjunction with the
4232 @code{ignore} command. You can ignore a large number of breakpoint
4233 hits, look at the breakpoint info to see how many times the breakpoint
4234 was hit, and then run again, ignoring one less than that number. This
4235 will get you quickly to the last hit of that breakpoint.
4238 For a breakpoints with an enable count (xref) greater than 1,
4239 @code{info break} also displays that count.
4243 @value{GDBN} allows you to set any number of breakpoints at the same place in
4244 your program. There is nothing silly or meaningless about this. When
4245 the breakpoints are conditional, this is even useful
4246 (@pxref{Conditions, ,Break Conditions}).
4248 @cindex multiple locations, breakpoints
4249 @cindex breakpoints, multiple locations
4250 It is possible that a breakpoint corresponds to several locations
4251 in your program. Examples of this situation are:
4255 Multiple functions in the program may have the same name.
4258 For a C@t{++} constructor, the @value{NGCC} compiler generates several
4259 instances of the function body, used in different cases.
4262 For a C@t{++} template function, a given line in the function can
4263 correspond to any number of instantiations.
4266 For an inlined function, a given source line can correspond to
4267 several places where that function is inlined.
4270 In all those cases, @value{GDBN} will insert a breakpoint at all
4271 the relevant locations.
4273 A breakpoint with multiple locations is displayed in the breakpoint
4274 table using several rows---one header row, followed by one row for
4275 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
4276 address column. The rows for individual locations contain the actual
4277 addresses for locations, and show the functions to which those
4278 locations belong. The number column for a location is of the form
4279 @var{breakpoint-number}.@var{location-number}.
4284 Num Type Disp Enb Address What
4285 1 breakpoint keep y <MULTIPLE>
4287 breakpoint already hit 1 time
4288 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
4289 1.2 y 0x080486ca in void foo<double>() at t.cc:8
4292 You cannot delete the individual locations from a breakpoint. However,
4293 each location can be individually enabled or disabled by passing
4294 @var{breakpoint-number}.@var{location-number} as argument to the
4295 @code{enable} and @code{disable} commands. It's also possible to
4296 @code{enable} and @code{disable} a range of @var{location-number}
4297 locations using a @var{breakpoint-number} and two @var{location-number}s,
4298 in increasing order, separated by a hyphen, like
4299 @kbd{@var{breakpoint-number}.@var{location-number1}-@var{location-number2}},
4300 in which case @value{GDBN} acts on all the locations in the range (inclusive).
4301 Disabling or enabling the parent breakpoint (@pxref{Disabling}) affects
4302 all of the locations that belong to that breakpoint.
4304 @cindex pending breakpoints
4305 It's quite common to have a breakpoint inside a shared library.
4306 Shared libraries can be loaded and unloaded explicitly,
4307 and possibly repeatedly, as the program is executed. To support
4308 this use case, @value{GDBN} updates breakpoint locations whenever
4309 any shared library is loaded or unloaded. Typically, you would
4310 set a breakpoint in a shared library at the beginning of your
4311 debugging session, when the library is not loaded, and when the
4312 symbols from the library are not available. When you try to set
4313 breakpoint, @value{GDBN} will ask you if you want to set
4314 a so called @dfn{pending breakpoint}---breakpoint whose address
4315 is not yet resolved.
4317 After the program is run, whenever a new shared library is loaded,
4318 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
4319 shared library contains the symbol or line referred to by some
4320 pending breakpoint, that breakpoint is resolved and becomes an
4321 ordinary breakpoint. When a library is unloaded, all breakpoints
4322 that refer to its symbols or source lines become pending again.
4324 This logic works for breakpoints with multiple locations, too. For
4325 example, if you have a breakpoint in a C@t{++} template function, and
4326 a newly loaded shared library has an instantiation of that template,
4327 a new location is added to the list of locations for the breakpoint.
4329 Except for having unresolved address, pending breakpoints do not
4330 differ from regular breakpoints. You can set conditions or commands,
4331 enable and disable them and perform other breakpoint operations.
4333 @value{GDBN} provides some additional commands for controlling what
4334 happens when the @samp{break} command cannot resolve breakpoint
4335 address specification to an address:
4337 @kindex set breakpoint pending
4338 @kindex show breakpoint pending
4340 @item set breakpoint pending auto
4341 This is the default behavior. When @value{GDBN} cannot find the breakpoint
4342 location, it queries you whether a pending breakpoint should be created.
4344 @item set breakpoint pending on
4345 This indicates that an unrecognized breakpoint location should automatically
4346 result in a pending breakpoint being created.
4348 @item set breakpoint pending off
4349 This indicates that pending breakpoints are not to be created. Any
4350 unrecognized breakpoint location results in an error. This setting does
4351 not affect any pending breakpoints previously created.
4353 @item show breakpoint pending
4354 Show the current behavior setting for creating pending breakpoints.
4357 The settings above only affect the @code{break} command and its
4358 variants. Once breakpoint is set, it will be automatically updated
4359 as shared libraries are loaded and unloaded.
4361 @cindex automatic hardware breakpoints
4362 For some targets, @value{GDBN} can automatically decide if hardware or
4363 software breakpoints should be used, depending on whether the
4364 breakpoint address is read-only or read-write. This applies to
4365 breakpoints set with the @code{break} command as well as to internal
4366 breakpoints set by commands like @code{next} and @code{finish}. For
4367 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
4370 You can control this automatic behaviour with the following commands:
4372 @kindex set breakpoint auto-hw
4373 @kindex show breakpoint auto-hw
4375 @item set breakpoint auto-hw on
4376 This is the default behavior. When @value{GDBN} sets a breakpoint, it
4377 will try to use the target memory map to decide if software or hardware
4378 breakpoint must be used.
4380 @item set breakpoint auto-hw off
4381 This indicates @value{GDBN} should not automatically select breakpoint
4382 type. If the target provides a memory map, @value{GDBN} will warn when
4383 trying to set software breakpoint at a read-only address.
4386 @value{GDBN} normally implements breakpoints by replacing the program code
4387 at the breakpoint address with a special instruction, which, when
4388 executed, given control to the debugger. By default, the program
4389 code is so modified only when the program is resumed. As soon as
4390 the program stops, @value{GDBN} restores the original instructions. This
4391 behaviour guards against leaving breakpoints inserted in the
4392 target should gdb abrubptly disconnect. However, with slow remote
4393 targets, inserting and removing breakpoint can reduce the performance.
4394 This behavior can be controlled with the following commands::
4396 @kindex set breakpoint always-inserted
4397 @kindex show breakpoint always-inserted
4399 @item set breakpoint always-inserted off
4400 All breakpoints, including newly added by the user, are inserted in
4401 the target only when the target is resumed. All breakpoints are
4402 removed from the target when it stops. This is the default mode.
4404 @item set breakpoint always-inserted on
4405 Causes all breakpoints to be inserted in the target at all times. If
4406 the user adds a new breakpoint, or changes an existing breakpoint, the
4407 breakpoints in the target are updated immediately. A breakpoint is
4408 removed from the target only when breakpoint itself is deleted.
4411 @value{GDBN} handles conditional breakpoints by evaluating these conditions
4412 when a breakpoint breaks. If the condition is true, then the process being
4413 debugged stops, otherwise the process is resumed.
4415 If the target supports evaluating conditions on its end, @value{GDBN} may
4416 download the breakpoint, together with its conditions, to it.
4418 This feature can be controlled via the following commands:
4420 @kindex set breakpoint condition-evaluation
4421 @kindex show breakpoint condition-evaluation
4423 @item set breakpoint condition-evaluation host
4424 This option commands @value{GDBN} to evaluate the breakpoint
4425 conditions on the host's side. Unconditional breakpoints are sent to
4426 the target which in turn receives the triggers and reports them back to GDB
4427 for condition evaluation. This is the standard evaluation mode.
4429 @item set breakpoint condition-evaluation target
4430 This option commands @value{GDBN} to download breakpoint conditions
4431 to the target at the moment of their insertion. The target
4432 is responsible for evaluating the conditional expression and reporting
4433 breakpoint stop events back to @value{GDBN} whenever the condition
4434 is true. Due to limitations of target-side evaluation, some conditions
4435 cannot be evaluated there, e.g., conditions that depend on local data
4436 that is only known to the host. Examples include
4437 conditional expressions involving convenience variables, complex types
4438 that cannot be handled by the agent expression parser and expressions
4439 that are too long to be sent over to the target, specially when the
4440 target is a remote system. In these cases, the conditions will be
4441 evaluated by @value{GDBN}.
4443 @item set breakpoint condition-evaluation auto
4444 This is the default mode. If the target supports evaluating breakpoint
4445 conditions on its end, @value{GDBN} will download breakpoint conditions to
4446 the target (limitations mentioned previously apply). If the target does
4447 not support breakpoint condition evaluation, then @value{GDBN} will fallback
4448 to evaluating all these conditions on the host's side.
4452 @cindex negative breakpoint numbers
4453 @cindex internal @value{GDBN} breakpoints
4454 @value{GDBN} itself sometimes sets breakpoints in your program for
4455 special purposes, such as proper handling of @code{longjmp} (in C
4456 programs). These internal breakpoints are assigned negative numbers,
4457 starting with @code{-1}; @samp{info breakpoints} does not display them.
4458 You can see these breakpoints with the @value{GDBN} maintenance command
4459 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
4462 @node Set Watchpoints
4463 @subsection Setting Watchpoints
4465 @cindex setting watchpoints
4466 You can use a watchpoint to stop execution whenever the value of an
4467 expression changes, without having to predict a particular place where
4468 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
4469 The expression may be as simple as the value of a single variable, or
4470 as complex as many variables combined by operators. Examples include:
4474 A reference to the value of a single variable.
4477 An address cast to an appropriate data type. For example,
4478 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
4479 address (assuming an @code{int} occupies 4 bytes).
4482 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
4483 expression can use any operators valid in the program's native
4484 language (@pxref{Languages}).
4487 You can set a watchpoint on an expression even if the expression can
4488 not be evaluated yet. For instance, you can set a watchpoint on
4489 @samp{*global_ptr} before @samp{global_ptr} is initialized.
4490 @value{GDBN} will stop when your program sets @samp{global_ptr} and
4491 the expression produces a valid value. If the expression becomes
4492 valid in some other way than changing a variable (e.g.@: if the memory
4493 pointed to by @samp{*global_ptr} becomes readable as the result of a
4494 @code{malloc} call), @value{GDBN} may not stop until the next time
4495 the expression changes.
4497 @cindex software watchpoints
4498 @cindex hardware watchpoints
4499 Depending on your system, watchpoints may be implemented in software or
4500 hardware. @value{GDBN} does software watchpointing by single-stepping your
4501 program and testing the variable's value each time, which is hundreds of
4502 times slower than normal execution. (But this may still be worth it, to
4503 catch errors where you have no clue what part of your program is the
4506 On some systems, such as most PowerPC or x86-based targets,
4507 @value{GDBN} includes support for hardware watchpoints, which do not
4508 slow down the running of your program.
4512 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4513 Set a watchpoint for an expression. @value{GDBN} will break when the
4514 expression @var{expr} is written into by the program and its value
4515 changes. The simplest (and the most popular) use of this command is
4516 to watch the value of a single variable:
4519 (@value{GDBP}) watch foo
4522 If the command includes a @code{@r{[}thread @var{thread-id}@r{]}}
4523 argument, @value{GDBN} breaks only when the thread identified by
4524 @var{thread-id} changes the value of @var{expr}. If any other threads
4525 change the value of @var{expr}, @value{GDBN} will not break. Note
4526 that watchpoints restricted to a single thread in this way only work
4527 with Hardware Watchpoints.
4529 Ordinarily a watchpoint respects the scope of variables in @var{expr}
4530 (see below). The @code{-location} argument tells @value{GDBN} to
4531 instead watch the memory referred to by @var{expr}. In this case,
4532 @value{GDBN} will evaluate @var{expr}, take the address of the result,
4533 and watch the memory at that address. The type of the result is used
4534 to determine the size of the watched memory. If the expression's
4535 result does not have an address, then @value{GDBN} will print an
4538 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
4539 of masked watchpoints, if the current architecture supports this
4540 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
4541 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
4542 to an address to watch. The mask specifies that some bits of an address
4543 (the bits which are reset in the mask) should be ignored when matching
4544 the address accessed by the inferior against the watchpoint address.
4545 Thus, a masked watchpoint watches many addresses simultaneously---those
4546 addresses whose unmasked bits are identical to the unmasked bits in the
4547 watchpoint address. The @code{mask} argument implies @code{-location}.
4551 (@value{GDBP}) watch foo mask 0xffff00ff
4552 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
4556 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4557 Set a watchpoint that will break when the value of @var{expr} is read
4561 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4562 Set a watchpoint that will break when @var{expr} is either read from
4563 or written into by the program.
4565 @kindex info watchpoints @r{[}@var{list}@dots{}@r{]}
4566 @item info watchpoints @r{[}@var{list}@dots{}@r{]}
4567 This command prints a list of watchpoints, using the same format as
4568 @code{info break} (@pxref{Set Breaks}).
4571 If you watch for a change in a numerically entered address you need to
4572 dereference it, as the address itself is just a constant number which will
4573 never change. @value{GDBN} refuses to create a watchpoint that watches
4574 a never-changing value:
4577 (@value{GDBP}) watch 0x600850
4578 Cannot watch constant value 0x600850.
4579 (@value{GDBP}) watch *(int *) 0x600850
4580 Watchpoint 1: *(int *) 6293584
4583 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
4584 watchpoints execute very quickly, and the debugger reports a change in
4585 value at the exact instruction where the change occurs. If @value{GDBN}
4586 cannot set a hardware watchpoint, it sets a software watchpoint, which
4587 executes more slowly and reports the change in value at the next
4588 @emph{statement}, not the instruction, after the change occurs.
4590 @cindex use only software watchpoints
4591 You can force @value{GDBN} to use only software watchpoints with the
4592 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
4593 zero, @value{GDBN} will never try to use hardware watchpoints, even if
4594 the underlying system supports them. (Note that hardware-assisted
4595 watchpoints that were set @emph{before} setting
4596 @code{can-use-hw-watchpoints} to zero will still use the hardware
4597 mechanism of watching expression values.)
4600 @item set can-use-hw-watchpoints
4601 @kindex set can-use-hw-watchpoints
4602 Set whether or not to use hardware watchpoints.
4604 @item show can-use-hw-watchpoints
4605 @kindex show can-use-hw-watchpoints
4606 Show the current mode of using hardware watchpoints.
4609 For remote targets, you can restrict the number of hardware
4610 watchpoints @value{GDBN} will use, see @ref{set remote
4611 hardware-breakpoint-limit}.
4613 When you issue the @code{watch} command, @value{GDBN} reports
4616 Hardware watchpoint @var{num}: @var{expr}
4620 if it was able to set a hardware watchpoint.
4622 Currently, the @code{awatch} and @code{rwatch} commands can only set
4623 hardware watchpoints, because accesses to data that don't change the
4624 value of the watched expression cannot be detected without examining
4625 every instruction as it is being executed, and @value{GDBN} does not do
4626 that currently. If @value{GDBN} finds that it is unable to set a
4627 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
4628 will print a message like this:
4631 Expression cannot be implemented with read/access watchpoint.
4634 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4635 data type of the watched expression is wider than what a hardware
4636 watchpoint on the target machine can handle. For example, some systems
4637 can only watch regions that are up to 4 bytes wide; on such systems you
4638 cannot set hardware watchpoints for an expression that yields a
4639 double-precision floating-point number (which is typically 8 bytes
4640 wide). As a work-around, it might be possible to break the large region
4641 into a series of smaller ones and watch them with separate watchpoints.
4643 If you set too many hardware watchpoints, @value{GDBN} might be unable
4644 to insert all of them when you resume the execution of your program.
4645 Since the precise number of active watchpoints is unknown until such
4646 time as the program is about to be resumed, @value{GDBN} might not be
4647 able to warn you about this when you set the watchpoints, and the
4648 warning will be printed only when the program is resumed:
4651 Hardware watchpoint @var{num}: Could not insert watchpoint
4655 If this happens, delete or disable some of the watchpoints.
4657 Watching complex expressions that reference many variables can also
4658 exhaust the resources available for hardware-assisted watchpoints.
4659 That's because @value{GDBN} needs to watch every variable in the
4660 expression with separately allocated resources.
4662 If you call a function interactively using @code{print} or @code{call},
4663 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4664 kind of breakpoint or the call completes.
4666 @value{GDBN} automatically deletes watchpoints that watch local
4667 (automatic) variables, or expressions that involve such variables, when
4668 they go out of scope, that is, when the execution leaves the block in
4669 which these variables were defined. In particular, when the program
4670 being debugged terminates, @emph{all} local variables go out of scope,
4671 and so only watchpoints that watch global variables remain set. If you
4672 rerun the program, you will need to set all such watchpoints again. One
4673 way of doing that would be to set a code breakpoint at the entry to the
4674 @code{main} function and when it breaks, set all the watchpoints.
4676 @cindex watchpoints and threads
4677 @cindex threads and watchpoints
4678 In multi-threaded programs, watchpoints will detect changes to the
4679 watched expression from every thread.
4682 @emph{Warning:} In multi-threaded programs, software watchpoints
4683 have only limited usefulness. If @value{GDBN} creates a software
4684 watchpoint, it can only watch the value of an expression @emph{in a
4685 single thread}. If you are confident that the expression can only
4686 change due to the current thread's activity (and if you are also
4687 confident that no other thread can become current), then you can use
4688 software watchpoints as usual. However, @value{GDBN} may not notice
4689 when a non-current thread's activity changes the expression. (Hardware
4690 watchpoints, in contrast, watch an expression in all threads.)
4693 @xref{set remote hardware-watchpoint-limit}.
4695 @node Set Catchpoints
4696 @subsection Setting Catchpoints
4697 @cindex catchpoints, setting
4698 @cindex exception handlers
4699 @cindex event handling
4701 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4702 kinds of program events, such as C@t{++} exceptions or the loading of a
4703 shared library. Use the @code{catch} command to set a catchpoint.
4707 @item catch @var{event}
4708 Stop when @var{event} occurs. The @var{event} can be any of the following:
4711 @item throw @r{[}@var{regexp}@r{]}
4712 @itemx rethrow @r{[}@var{regexp}@r{]}
4713 @itemx catch @r{[}@var{regexp}@r{]}
4715 @kindex catch rethrow
4717 @cindex stop on C@t{++} exceptions
4718 The throwing, re-throwing, or catching of a C@t{++} exception.
4720 If @var{regexp} is given, then only exceptions whose type matches the
4721 regular expression will be caught.
4723 @vindex $_exception@r{, convenience variable}
4724 The convenience variable @code{$_exception} is available at an
4725 exception-related catchpoint, on some systems. This holds the
4726 exception being thrown.
4728 There are currently some limitations to C@t{++} exception handling in
4733 The support for these commands is system-dependent. Currently, only
4734 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
4738 The regular expression feature and the @code{$_exception} convenience
4739 variable rely on the presence of some SDT probes in @code{libstdc++}.
4740 If these probes are not present, then these features cannot be used.
4741 These probes were first available in the GCC 4.8 release, but whether
4742 or not they are available in your GCC also depends on how it was
4746 The @code{$_exception} convenience variable is only valid at the
4747 instruction at which an exception-related catchpoint is set.
4750 When an exception-related catchpoint is hit, @value{GDBN} stops at a
4751 location in the system library which implements runtime exception
4752 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
4753 (@pxref{Selection}) to get to your code.
4756 If you call a function interactively, @value{GDBN} normally returns
4757 control to you when the function has finished executing. If the call
4758 raises an exception, however, the call may bypass the mechanism that
4759 returns control to you and cause your program either to abort or to
4760 simply continue running until it hits a breakpoint, catches a signal
4761 that @value{GDBN} is listening for, or exits. This is the case even if
4762 you set a catchpoint for the exception; catchpoints on exceptions are
4763 disabled within interactive calls. @xref{Calling}, for information on
4764 controlling this with @code{set unwind-on-terminating-exception}.
4767 You cannot raise an exception interactively.
4770 You cannot install an exception handler interactively.
4773 @item exception @r{[}@var{name}@r{]}
4774 @kindex catch exception
4775 @cindex Ada exception catching
4776 @cindex catch Ada exceptions
4777 An Ada exception being raised. If an exception name is specified
4778 at the end of the command (eg @code{catch exception Program_Error}),
4779 the debugger will stop only when this specific exception is raised.
4780 Otherwise, the debugger stops execution when any Ada exception is raised.
4782 When inserting an exception catchpoint on a user-defined exception whose
4783 name is identical to one of the exceptions defined by the language, the
4784 fully qualified name must be used as the exception name. Otherwise,
4785 @value{GDBN} will assume that it should stop on the pre-defined exception
4786 rather than the user-defined one. For instance, assuming an exception
4787 called @code{Constraint_Error} is defined in package @code{Pck}, then
4788 the command to use to catch such exceptions is @kbd{catch exception
4789 Pck.Constraint_Error}.
4791 @item exception unhandled
4792 @kindex catch exception unhandled
4793 An exception that was raised but is not handled by the program.
4795 @item handlers @r{[}@var{name}@r{]}
4796 @kindex catch handlers
4797 @cindex Ada exception handlers catching
4798 @cindex catch Ada exceptions when handled
4799 An Ada exception being handled. If an exception name is
4800 specified at the end of the command
4801 (eg @kbd{catch handlers Program_Error}), the debugger will stop
4802 only when this specific exception is handled.
4803 Otherwise, the debugger stops execution when any Ada exception is handled.
4805 When inserting a handlers catchpoint on a user-defined
4806 exception whose name is identical to one of the exceptions
4807 defined by the language, the fully qualified name must be used
4808 as the exception name. Otherwise, @value{GDBN} will assume that it
4809 should stop on the pre-defined exception rather than the
4810 user-defined one. For instance, assuming an exception called
4811 @code{Constraint_Error} is defined in package @code{Pck}, then the
4812 command to use to catch such exceptions handling is
4813 @kbd{catch handlers Pck.Constraint_Error}.
4816 @kindex catch assert
4817 A failed Ada assertion.
4821 @cindex break on fork/exec
4822 A call to @code{exec}.
4824 @anchor{catch syscall}
4826 @itemx syscall @r{[}@var{name} @r{|} @var{number} @r{|} @r{group:}@var{groupname} @r{|} @r{g:}@var{groupname}@r{]} @dots{}
4827 @kindex catch syscall
4828 @cindex break on a system call.
4829 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4830 syscall is a mechanism for application programs to request a service
4831 from the operating system (OS) or one of the OS system services.
4832 @value{GDBN} can catch some or all of the syscalls issued by the
4833 debuggee, and show the related information for each syscall. If no
4834 argument is specified, calls to and returns from all system calls
4837 @var{name} can be any system call name that is valid for the
4838 underlying OS. Just what syscalls are valid depends on the OS. On
4839 GNU and Unix systems, you can find the full list of valid syscall
4840 names on @file{/usr/include/asm/unistd.h}.
4842 @c For MS-Windows, the syscall names and the corresponding numbers
4843 @c can be found, e.g., on this URL:
4844 @c http://www.metasploit.com/users/opcode/syscalls.html
4845 @c but we don't support Windows syscalls yet.
4847 Normally, @value{GDBN} knows in advance which syscalls are valid for
4848 each OS, so you can use the @value{GDBN} command-line completion
4849 facilities (@pxref{Completion,, command completion}) to list the
4852 You may also specify the system call numerically. A syscall's
4853 number is the value passed to the OS's syscall dispatcher to
4854 identify the requested service. When you specify the syscall by its
4855 name, @value{GDBN} uses its database of syscalls to convert the name
4856 into the corresponding numeric code, but using the number directly
4857 may be useful if @value{GDBN}'s database does not have the complete
4858 list of syscalls on your system (e.g., because @value{GDBN} lags
4859 behind the OS upgrades).
4861 You may specify a group of related syscalls to be caught at once using
4862 the @code{group:} syntax (@code{g:} is a shorter equivalent). For
4863 instance, on some platforms @value{GDBN} allows you to catch all
4864 network related syscalls, by passing the argument @code{group:network}
4865 to @code{catch syscall}. Note that not all syscall groups are
4866 available in every system. You can use the command completion
4867 facilities (@pxref{Completion,, command completion}) to list the
4868 syscall groups available on your environment.
4870 The example below illustrates how this command works if you don't provide
4874 (@value{GDBP}) catch syscall
4875 Catchpoint 1 (syscall)
4877 Starting program: /tmp/catch-syscall
4879 Catchpoint 1 (call to syscall 'close'), \
4880 0xffffe424 in __kernel_vsyscall ()
4884 Catchpoint 1 (returned from syscall 'close'), \
4885 0xffffe424 in __kernel_vsyscall ()
4889 Here is an example of catching a system call by name:
4892 (@value{GDBP}) catch syscall chroot
4893 Catchpoint 1 (syscall 'chroot' [61])
4895 Starting program: /tmp/catch-syscall
4897 Catchpoint 1 (call to syscall 'chroot'), \
4898 0xffffe424 in __kernel_vsyscall ()
4902 Catchpoint 1 (returned from syscall 'chroot'), \
4903 0xffffe424 in __kernel_vsyscall ()
4907 An example of specifying a system call numerically. In the case
4908 below, the syscall number has a corresponding entry in the XML
4909 file, so @value{GDBN} finds its name and prints it:
4912 (@value{GDBP}) catch syscall 252
4913 Catchpoint 1 (syscall(s) 'exit_group')
4915 Starting program: /tmp/catch-syscall
4917 Catchpoint 1 (call to syscall 'exit_group'), \
4918 0xffffe424 in __kernel_vsyscall ()
4922 Program exited normally.
4926 Here is an example of catching a syscall group:
4929 (@value{GDBP}) catch syscall group:process
4930 Catchpoint 1 (syscalls 'exit' [1] 'fork' [2] 'waitpid' [7]
4931 'execve' [11] 'wait4' [114] 'clone' [120] 'vfork' [190]
4932 'exit_group' [252] 'waitid' [284] 'unshare' [310])
4934 Starting program: /tmp/catch-syscall
4936 Catchpoint 1 (call to syscall fork), 0x00007ffff7df4e27 in open64 ()
4937 from /lib64/ld-linux-x86-64.so.2
4943 However, there can be situations when there is no corresponding name
4944 in XML file for that syscall number. In this case, @value{GDBN} prints
4945 a warning message saying that it was not able to find the syscall name,
4946 but the catchpoint will be set anyway. See the example below:
4949 (@value{GDBP}) catch syscall 764
4950 warning: The number '764' does not represent a known syscall.
4951 Catchpoint 2 (syscall 764)
4955 If you configure @value{GDBN} using the @samp{--without-expat} option,
4956 it will not be able to display syscall names. Also, if your
4957 architecture does not have an XML file describing its system calls,
4958 you will not be able to see the syscall names. It is important to
4959 notice that these two features are used for accessing the syscall
4960 name database. In either case, you will see a warning like this:
4963 (@value{GDBP}) catch syscall
4964 warning: Could not open "syscalls/i386-linux.xml"
4965 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4966 GDB will not be able to display syscall names.
4967 Catchpoint 1 (syscall)
4971 Of course, the file name will change depending on your architecture and system.
4973 Still using the example above, you can also try to catch a syscall by its
4974 number. In this case, you would see something like:
4977 (@value{GDBP}) catch syscall 252
4978 Catchpoint 1 (syscall(s) 252)
4981 Again, in this case @value{GDBN} would not be able to display syscall's names.
4985 A call to @code{fork}.
4989 A call to @code{vfork}.
4991 @item load @r{[}@var{regexp}@r{]}
4992 @itemx unload @r{[}@var{regexp}@r{]}
4994 @kindex catch unload
4995 The loading or unloading of a shared library. If @var{regexp} is
4996 given, then the catchpoint will stop only if the regular expression
4997 matches one of the affected libraries.
4999 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5000 @kindex catch signal
5001 The delivery of a signal.
5003 With no arguments, this catchpoint will catch any signal that is not
5004 used internally by @value{GDBN}, specifically, all signals except
5005 @samp{SIGTRAP} and @samp{SIGINT}.
5007 With the argument @samp{all}, all signals, including those used by
5008 @value{GDBN}, will be caught. This argument cannot be used with other
5011 Otherwise, the arguments are a list of signal names as given to
5012 @code{handle} (@pxref{Signals}). Only signals specified in this list
5015 One reason that @code{catch signal} can be more useful than
5016 @code{handle} is that you can attach commands and conditions to the
5019 When a signal is caught by a catchpoint, the signal's @code{stop} and
5020 @code{print} settings, as specified by @code{handle}, are ignored.
5021 However, whether the signal is still delivered to the inferior depends
5022 on the @code{pass} setting; this can be changed in the catchpoint's
5027 @item tcatch @var{event}
5029 Set a catchpoint that is enabled only for one stop. The catchpoint is
5030 automatically deleted after the first time the event is caught.
5034 Use the @code{info break} command to list the current catchpoints.
5038 @subsection Deleting Breakpoints
5040 @cindex clearing breakpoints, watchpoints, catchpoints
5041 @cindex deleting breakpoints, watchpoints, catchpoints
5042 It is often necessary to eliminate a breakpoint, watchpoint, or
5043 catchpoint once it has done its job and you no longer want your program
5044 to stop there. This is called @dfn{deleting} the breakpoint. A
5045 breakpoint that has been deleted no longer exists; it is forgotten.
5047 With the @code{clear} command you can delete breakpoints according to
5048 where they are in your program. With the @code{delete} command you can
5049 delete individual breakpoints, watchpoints, or catchpoints by specifying
5050 their breakpoint numbers.
5052 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
5053 automatically ignores breakpoints on the first instruction to be executed
5054 when you continue execution without changing the execution address.
5059 Delete any breakpoints at the next instruction to be executed in the
5060 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
5061 the innermost frame is selected, this is a good way to delete a
5062 breakpoint where your program just stopped.
5064 @item clear @var{location}
5065 Delete any breakpoints set at the specified @var{location}.
5066 @xref{Specify Location}, for the various forms of @var{location}; the
5067 most useful ones are listed below:
5070 @item clear @var{function}
5071 @itemx clear @var{filename}:@var{function}
5072 Delete any breakpoints set at entry to the named @var{function}.
5074 @item clear @var{linenum}
5075 @itemx clear @var{filename}:@var{linenum}
5076 Delete any breakpoints set at or within the code of the specified
5077 @var{linenum} of the specified @var{filename}.
5080 @cindex delete breakpoints
5082 @kindex d @r{(@code{delete})}
5083 @item delete @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
5084 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
5085 list specified as argument. If no argument is specified, delete all
5086 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
5087 confirm off}). You can abbreviate this command as @code{d}.
5091 @subsection Disabling Breakpoints
5093 @cindex enable/disable a breakpoint
5094 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
5095 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
5096 it had been deleted, but remembers the information on the breakpoint so
5097 that you can @dfn{enable} it again later.
5099 You disable and enable breakpoints, watchpoints, and catchpoints with
5100 the @code{enable} and @code{disable} commands, optionally specifying
5101 one or more breakpoint numbers as arguments. Use @code{info break} to
5102 print a list of all breakpoints, watchpoints, and catchpoints if you
5103 do not know which numbers to use.
5105 Disabling and enabling a breakpoint that has multiple locations
5106 affects all of its locations.
5108 A breakpoint, watchpoint, or catchpoint can have any of several
5109 different states of enablement:
5113 Enabled. The breakpoint stops your program. A breakpoint set
5114 with the @code{break} command starts out in this state.
5116 Disabled. The breakpoint has no effect on your program.
5118 Enabled once. The breakpoint stops your program, but then becomes
5121 Enabled for a count. The breakpoint stops your program for the next
5122 N times, then becomes disabled.
5124 Enabled for deletion. The breakpoint stops your program, but
5125 immediately after it does so it is deleted permanently. A breakpoint
5126 set with the @code{tbreak} command starts out in this state.
5129 You can use the following commands to enable or disable breakpoints,
5130 watchpoints, and catchpoints:
5134 @kindex dis @r{(@code{disable})}
5135 @item disable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
5136 Disable the specified breakpoints---or all breakpoints, if none are
5137 listed. A disabled breakpoint has no effect but is not forgotten. All
5138 options such as ignore-counts, conditions and commands are remembered in
5139 case the breakpoint is enabled again later. You may abbreviate
5140 @code{disable} as @code{dis}.
5143 @item enable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
5144 Enable the specified breakpoints (or all defined breakpoints). They
5145 become effective once again in stopping your program.
5147 @item enable @r{[}breakpoints@r{]} once @var{list}@dots{}
5148 Enable the specified breakpoints temporarily. @value{GDBN} disables any
5149 of these breakpoints immediately after stopping your program.
5151 @item enable @r{[}breakpoints@r{]} count @var{count} @var{list}@dots{}
5152 Enable the specified breakpoints temporarily. @value{GDBN} records
5153 @var{count} with each of the specified breakpoints, and decrements a
5154 breakpoint's count when it is hit. When any count reaches 0,
5155 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
5156 count (@pxref{Conditions, ,Break Conditions}), that will be
5157 decremented to 0 before @var{count} is affected.
5159 @item enable @r{[}breakpoints@r{]} delete @var{list}@dots{}
5160 Enable the specified breakpoints to work once, then die. @value{GDBN}
5161 deletes any of these breakpoints as soon as your program stops there.
5162 Breakpoints set by the @code{tbreak} command start out in this state.
5165 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
5166 @c confusing: tbreak is also initially enabled.
5167 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
5168 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
5169 subsequently, they become disabled or enabled only when you use one of
5170 the commands above. (The command @code{until} can set and delete a
5171 breakpoint of its own, but it does not change the state of your other
5172 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
5176 @subsection Break Conditions
5177 @cindex conditional breakpoints
5178 @cindex breakpoint conditions
5180 @c FIXME what is scope of break condition expr? Context where wanted?
5181 @c in particular for a watchpoint?
5182 The simplest sort of breakpoint breaks every time your program reaches a
5183 specified place. You can also specify a @dfn{condition} for a
5184 breakpoint. A condition is just a Boolean expression in your
5185 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
5186 a condition evaluates the expression each time your program reaches it,
5187 and your program stops only if the condition is @emph{true}.
5189 This is the converse of using assertions for program validation; in that
5190 situation, you want to stop when the assertion is violated---that is,
5191 when the condition is false. In C, if you want to test an assertion expressed
5192 by the condition @var{assert}, you should set the condition
5193 @samp{! @var{assert}} on the appropriate breakpoint.
5195 Conditions are also accepted for watchpoints; you may not need them,
5196 since a watchpoint is inspecting the value of an expression anyhow---but
5197 it might be simpler, say, to just set a watchpoint on a variable name,
5198 and specify a condition that tests whether the new value is an interesting
5201 Break conditions can have side effects, and may even call functions in
5202 your program. This can be useful, for example, to activate functions
5203 that log program progress, or to use your own print functions to
5204 format special data structures. The effects are completely predictable
5205 unless there is another enabled breakpoint at the same address. (In
5206 that case, @value{GDBN} might see the other breakpoint first and stop your
5207 program without checking the condition of this one.) Note that
5208 breakpoint commands are usually more convenient and flexible than break
5210 purpose of performing side effects when a breakpoint is reached
5211 (@pxref{Break Commands, ,Breakpoint Command Lists}).
5213 Breakpoint conditions can also be evaluated on the target's side if
5214 the target supports it. Instead of evaluating the conditions locally,
5215 @value{GDBN} encodes the expression into an agent expression
5216 (@pxref{Agent Expressions}) suitable for execution on the target,
5217 independently of @value{GDBN}. Global variables become raw memory
5218 locations, locals become stack accesses, and so forth.
5220 In this case, @value{GDBN} will only be notified of a breakpoint trigger
5221 when its condition evaluates to true. This mechanism may provide faster
5222 response times depending on the performance characteristics of the target
5223 since it does not need to keep @value{GDBN} informed about
5224 every breakpoint trigger, even those with false conditions.
5226 Break conditions can be specified when a breakpoint is set, by using
5227 @samp{if} in the arguments to the @code{break} command. @xref{Set
5228 Breaks, ,Setting Breakpoints}. They can also be changed at any time
5229 with the @code{condition} command.
5231 You can also use the @code{if} keyword with the @code{watch} command.
5232 The @code{catch} command does not recognize the @code{if} keyword;
5233 @code{condition} is the only way to impose a further condition on a
5238 @item condition @var{bnum} @var{expression}
5239 Specify @var{expression} as the break condition for breakpoint,
5240 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
5241 breakpoint @var{bnum} stops your program only if the value of
5242 @var{expression} is true (nonzero, in C). When you use
5243 @code{condition}, @value{GDBN} checks @var{expression} immediately for
5244 syntactic correctness, and to determine whether symbols in it have
5245 referents in the context of your breakpoint. If @var{expression} uses
5246 symbols not referenced in the context of the breakpoint, @value{GDBN}
5247 prints an error message:
5250 No symbol "foo" in current context.
5255 not actually evaluate @var{expression} at the time the @code{condition}
5256 command (or a command that sets a breakpoint with a condition, like
5257 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
5259 @item condition @var{bnum}
5260 Remove the condition from breakpoint number @var{bnum}. It becomes
5261 an ordinary unconditional breakpoint.
5264 @cindex ignore count (of breakpoint)
5265 A special case of a breakpoint condition is to stop only when the
5266 breakpoint has been reached a certain number of times. This is so
5267 useful that there is a special way to do it, using the @dfn{ignore
5268 count} of the breakpoint. Every breakpoint has an ignore count, which
5269 is an integer. Most of the time, the ignore count is zero, and
5270 therefore has no effect. But if your program reaches a breakpoint whose
5271 ignore count is positive, then instead of stopping, it just decrements
5272 the ignore count by one and continues. As a result, if the ignore count
5273 value is @var{n}, the breakpoint does not stop the next @var{n} times
5274 your program reaches it.
5278 @item ignore @var{bnum} @var{count}
5279 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
5280 The next @var{count} times the breakpoint is reached, your program's
5281 execution does not stop; other than to decrement the ignore count, @value{GDBN}
5284 To make the breakpoint stop the next time it is reached, specify
5287 When you use @code{continue} to resume execution of your program from a
5288 breakpoint, you can specify an ignore count directly as an argument to
5289 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
5290 Stepping,,Continuing and Stepping}.
5292 If a breakpoint has a positive ignore count and a condition, the
5293 condition is not checked. Once the ignore count reaches zero,
5294 @value{GDBN} resumes checking the condition.
5296 You could achieve the effect of the ignore count with a condition such
5297 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
5298 is decremented each time. @xref{Convenience Vars, ,Convenience
5302 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
5305 @node Break Commands
5306 @subsection Breakpoint Command Lists
5308 @cindex breakpoint commands
5309 You can give any breakpoint (or watchpoint or catchpoint) a series of
5310 commands to execute when your program stops due to that breakpoint. For
5311 example, you might want to print the values of certain expressions, or
5312 enable other breakpoints.
5316 @kindex end@r{ (breakpoint commands)}
5317 @item commands @r{[}@var{list}@dots{}@r{]}
5318 @itemx @dots{} @var{command-list} @dots{}
5320 Specify a list of commands for the given breakpoints. The commands
5321 themselves appear on the following lines. Type a line containing just
5322 @code{end} to terminate the commands.
5324 To remove all commands from a breakpoint, type @code{commands} and
5325 follow it immediately with @code{end}; that is, give no commands.
5327 With no argument, @code{commands} refers to the last breakpoint,
5328 watchpoint, or catchpoint set (not to the breakpoint most recently
5329 encountered). If the most recent breakpoints were set with a single
5330 command, then the @code{commands} will apply to all the breakpoints
5331 set by that command. This applies to breakpoints set by
5332 @code{rbreak}, and also applies when a single @code{break} command
5333 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
5337 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
5338 disabled within a @var{command-list}.
5340 You can use breakpoint commands to start your program up again. Simply
5341 use the @code{continue} command, or @code{step}, or any other command
5342 that resumes execution.
5344 Any other commands in the command list, after a command that resumes
5345 execution, are ignored. This is because any time you resume execution
5346 (even with a simple @code{next} or @code{step}), you may encounter
5347 another breakpoint---which could have its own command list, leading to
5348 ambiguities about which list to execute.
5351 If the first command you specify in a command list is @code{silent}, the
5352 usual message about stopping at a breakpoint is not printed. This may
5353 be desirable for breakpoints that are to print a specific message and
5354 then continue. If none of the remaining commands print anything, you
5355 see no sign that the breakpoint was reached. @code{silent} is
5356 meaningful only at the beginning of a breakpoint command list.
5358 The commands @code{echo}, @code{output}, and @code{printf} allow you to
5359 print precisely controlled output, and are often useful in silent
5360 breakpoints. @xref{Output, ,Commands for Controlled Output}.
5362 For example, here is how you could use breakpoint commands to print the
5363 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
5369 printf "x is %d\n",x
5374 One application for breakpoint commands is to compensate for one bug so
5375 you can test for another. Put a breakpoint just after the erroneous line
5376 of code, give it a condition to detect the case in which something
5377 erroneous has been done, and give it commands to assign correct values
5378 to any variables that need them. End with the @code{continue} command
5379 so that your program does not stop, and start with the @code{silent}
5380 command so that no output is produced. Here is an example:
5391 @node Dynamic Printf
5392 @subsection Dynamic Printf
5394 @cindex dynamic printf
5396 The dynamic printf command @code{dprintf} combines a breakpoint with
5397 formatted printing of your program's data to give you the effect of
5398 inserting @code{printf} calls into your program on-the-fly, without
5399 having to recompile it.
5401 In its most basic form, the output goes to the GDB console. However,
5402 you can set the variable @code{dprintf-style} for alternate handling.
5403 For instance, you can ask to format the output by calling your
5404 program's @code{printf} function. This has the advantage that the
5405 characters go to the program's output device, so they can recorded in
5406 redirects to files and so forth.
5408 If you are doing remote debugging with a stub or agent, you can also
5409 ask to have the printf handled by the remote agent. In addition to
5410 ensuring that the output goes to the remote program's device along
5411 with any other output the program might produce, you can also ask that
5412 the dprintf remain active even after disconnecting from the remote
5413 target. Using the stub/agent is also more efficient, as it can do
5414 everything without needing to communicate with @value{GDBN}.
5418 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
5419 Whenever execution reaches @var{location}, print the values of one or
5420 more @var{expressions} under the control of the string @var{template}.
5421 To print several values, separate them with commas.
5423 @item set dprintf-style @var{style}
5424 Set the dprintf output to be handled in one of several different
5425 styles enumerated below. A change of style affects all existing
5426 dynamic printfs immediately. (If you need individual control over the
5427 print commands, simply define normal breakpoints with
5428 explicitly-supplied command lists.)
5432 @kindex dprintf-style gdb
5433 Handle the output using the @value{GDBN} @code{printf} command.
5436 @kindex dprintf-style call
5437 Handle the output by calling a function in your program (normally
5441 @kindex dprintf-style agent
5442 Have the remote debugging agent (such as @code{gdbserver}) handle
5443 the output itself. This style is only available for agents that
5444 support running commands on the target.
5447 @item set dprintf-function @var{function}
5448 Set the function to call if the dprintf style is @code{call}. By
5449 default its value is @code{printf}. You may set it to any expression.
5450 that @value{GDBN} can evaluate to a function, as per the @code{call}
5453 @item set dprintf-channel @var{channel}
5454 Set a ``channel'' for dprintf. If set to a non-empty value,
5455 @value{GDBN} will evaluate it as an expression and pass the result as
5456 a first argument to the @code{dprintf-function}, in the manner of
5457 @code{fprintf} and similar functions. Otherwise, the dprintf format
5458 string will be the first argument, in the manner of @code{printf}.
5460 As an example, if you wanted @code{dprintf} output to go to a logfile
5461 that is a standard I/O stream assigned to the variable @code{mylog},
5462 you could do the following:
5465 (gdb) set dprintf-style call
5466 (gdb) set dprintf-function fprintf
5467 (gdb) set dprintf-channel mylog
5468 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
5469 Dprintf 1 at 0x123456: file main.c, line 25.
5471 1 dprintf keep y 0x00123456 in main at main.c:25
5472 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
5477 Note that the @code{info break} displays the dynamic printf commands
5478 as normal breakpoint commands; you can thus easily see the effect of
5479 the variable settings.
5481 @item set disconnected-dprintf on
5482 @itemx set disconnected-dprintf off
5483 @kindex set disconnected-dprintf
5484 Choose whether @code{dprintf} commands should continue to run if
5485 @value{GDBN} has disconnected from the target. This only applies
5486 if the @code{dprintf-style} is @code{agent}.
5488 @item show disconnected-dprintf off
5489 @kindex show disconnected-dprintf
5490 Show the current choice for disconnected @code{dprintf}.
5494 @value{GDBN} does not check the validity of function and channel,
5495 relying on you to supply values that are meaningful for the contexts
5496 in which they are being used. For instance, the function and channel
5497 may be the values of local variables, but if that is the case, then
5498 all enabled dynamic prints must be at locations within the scope of
5499 those locals. If evaluation fails, @value{GDBN} will report an error.
5501 @node Save Breakpoints
5502 @subsection How to save breakpoints to a file
5504 To save breakpoint definitions to a file use the @w{@code{save
5505 breakpoints}} command.
5508 @kindex save breakpoints
5509 @cindex save breakpoints to a file for future sessions
5510 @item save breakpoints [@var{filename}]
5511 This command saves all current breakpoint definitions together with
5512 their commands and ignore counts, into a file @file{@var{filename}}
5513 suitable for use in a later debugging session. This includes all
5514 types of breakpoints (breakpoints, watchpoints, catchpoints,
5515 tracepoints). To read the saved breakpoint definitions, use the
5516 @code{source} command (@pxref{Command Files}). Note that watchpoints
5517 with expressions involving local variables may fail to be recreated
5518 because it may not be possible to access the context where the
5519 watchpoint is valid anymore. Because the saved breakpoint definitions
5520 are simply a sequence of @value{GDBN} commands that recreate the
5521 breakpoints, you can edit the file in your favorite editing program,
5522 and remove the breakpoint definitions you're not interested in, or
5523 that can no longer be recreated.
5526 @node Static Probe Points
5527 @subsection Static Probe Points
5529 @cindex static probe point, SystemTap
5530 @cindex static probe point, DTrace
5531 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
5532 for Statically Defined Tracing, and the probes are designed to have a tiny
5533 runtime code and data footprint, and no dynamic relocations.
5535 Currently, the following types of probes are supported on
5536 ELF-compatible systems:
5540 @item @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
5541 @acronym{SDT} probes@footnote{See
5542 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
5543 for more information on how to add @code{SystemTap} @acronym{SDT}
5544 probes in your applications.}. @code{SystemTap} probes are usable
5545 from assembly, C and C@t{++} languages@footnote{See
5546 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
5547 for a good reference on how the @acronym{SDT} probes are implemented.}.
5549 @item @code{DTrace} (@uref{http://oss.oracle.com/projects/DTrace})
5550 @acronym{USDT} probes. @code{DTrace} probes are usable from C and
5554 @cindex semaphores on static probe points
5555 Some @code{SystemTap} probes have an associated semaphore variable;
5556 for instance, this happens automatically if you defined your probe
5557 using a DTrace-style @file{.d} file. If your probe has a semaphore,
5558 @value{GDBN} will automatically enable it when you specify a
5559 breakpoint using the @samp{-probe-stap} notation. But, if you put a
5560 breakpoint at a probe's location by some other method (e.g.,
5561 @code{break file:line}), then @value{GDBN} will not automatically set
5562 the semaphore. @code{DTrace} probes do not support semaphores.
5564 You can examine the available static static probes using @code{info
5565 probes}, with optional arguments:
5569 @item info probes @r{[}@var{type}@r{]} @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5570 If given, @var{type} is either @code{stap} for listing
5571 @code{SystemTap} probes or @code{dtrace} for listing @code{DTrace}
5572 probes. If omitted all probes are listed regardless of their types.
5574 If given, @var{provider} is a regular expression used to match against provider
5575 names when selecting which probes to list. If omitted, probes by all
5576 probes from all providers are listed.
5578 If given, @var{name} is a regular expression to match against probe names
5579 when selecting which probes to list. If omitted, probe names are not
5580 considered when deciding whether to display them.
5582 If given, @var{objfile} is a regular expression used to select which
5583 object files (executable or shared libraries) to examine. If not
5584 given, all object files are considered.
5586 @item info probes all
5587 List the available static probes, from all types.
5590 @cindex enabling and disabling probes
5591 Some probe points can be enabled and/or disabled. The effect of
5592 enabling or disabling a probe depends on the type of probe being
5593 handled. Some @code{DTrace} probes can be enabled or
5594 disabled, but @code{SystemTap} probes cannot be disabled.
5596 You can enable (or disable) one or more probes using the following
5597 commands, with optional arguments:
5600 @kindex enable probes
5601 @item enable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5602 If given, @var{provider} is a regular expression used to match against
5603 provider names when selecting which probes to enable. If omitted,
5604 all probes from all providers are enabled.
5606 If given, @var{name} is a regular expression to match against probe
5607 names when selecting which probes to enable. If omitted, probe names
5608 are not considered when deciding whether to enable them.
5610 If given, @var{objfile} is a regular expression used to select which
5611 object files (executable or shared libraries) to examine. If not
5612 given, all object files are considered.
5614 @kindex disable probes
5615 @item disable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5616 See the @code{enable probes} command above for a description of the
5617 optional arguments accepted by this command.
5620 @vindex $_probe_arg@r{, convenience variable}
5621 A probe may specify up to twelve arguments. These are available at the
5622 point at which the probe is defined---that is, when the current PC is
5623 at the probe's location. The arguments are available using the
5624 convenience variables (@pxref{Convenience Vars})
5625 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. In @code{SystemTap}
5626 probes each probe argument is an integer of the appropriate size;
5627 types are not preserved. In @code{DTrace} probes types are preserved
5628 provided that they are recognized as such by @value{GDBN}; otherwise
5629 the value of the probe argument will be a long integer. The
5630 convenience variable @code{$_probe_argc} holds the number of arguments
5631 at the current probe point.
5633 These variables are always available, but attempts to access them at
5634 any location other than a probe point will cause @value{GDBN} to give
5638 @c @ifclear BARETARGET
5639 @node Error in Breakpoints
5640 @subsection ``Cannot insert breakpoints''
5642 If you request too many active hardware-assisted breakpoints and
5643 watchpoints, you will see this error message:
5645 @c FIXME: the precise wording of this message may change; the relevant
5646 @c source change is not committed yet (Sep 3, 1999).
5648 Stopped; cannot insert breakpoints.
5649 You may have requested too many hardware breakpoints and watchpoints.
5653 This message is printed when you attempt to resume the program, since
5654 only then @value{GDBN} knows exactly how many hardware breakpoints and
5655 watchpoints it needs to insert.
5657 When this message is printed, you need to disable or remove some of the
5658 hardware-assisted breakpoints and watchpoints, and then continue.
5660 @node Breakpoint-related Warnings
5661 @subsection ``Breakpoint address adjusted...''
5662 @cindex breakpoint address adjusted
5664 Some processor architectures place constraints on the addresses at
5665 which breakpoints may be placed. For architectures thus constrained,
5666 @value{GDBN} will attempt to adjust the breakpoint's address to comply
5667 with the constraints dictated by the architecture.
5669 One example of such an architecture is the Fujitsu FR-V. The FR-V is
5670 a VLIW architecture in which a number of RISC-like instructions may be
5671 bundled together for parallel execution. The FR-V architecture
5672 constrains the location of a breakpoint instruction within such a
5673 bundle to the instruction with the lowest address. @value{GDBN}
5674 honors this constraint by adjusting a breakpoint's address to the
5675 first in the bundle.
5677 It is not uncommon for optimized code to have bundles which contain
5678 instructions from different source statements, thus it may happen that
5679 a breakpoint's address will be adjusted from one source statement to
5680 another. Since this adjustment may significantly alter @value{GDBN}'s
5681 breakpoint related behavior from what the user expects, a warning is
5682 printed when the breakpoint is first set and also when the breakpoint
5685 A warning like the one below is printed when setting a breakpoint
5686 that's been subject to address adjustment:
5689 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
5692 Such warnings are printed both for user settable and @value{GDBN}'s
5693 internal breakpoints. If you see one of these warnings, you should
5694 verify that a breakpoint set at the adjusted address will have the
5695 desired affect. If not, the breakpoint in question may be removed and
5696 other breakpoints may be set which will have the desired behavior.
5697 E.g., it may be sufficient to place the breakpoint at a later
5698 instruction. A conditional breakpoint may also be useful in some
5699 cases to prevent the breakpoint from triggering too often.
5701 @value{GDBN} will also issue a warning when stopping at one of these
5702 adjusted breakpoints:
5705 warning: Breakpoint 1 address previously adjusted from 0x00010414
5709 When this warning is encountered, it may be too late to take remedial
5710 action except in cases where the breakpoint is hit earlier or more
5711 frequently than expected.
5713 @node Continuing and Stepping
5714 @section Continuing and Stepping
5718 @cindex resuming execution
5719 @dfn{Continuing} means resuming program execution until your program
5720 completes normally. In contrast, @dfn{stepping} means executing just
5721 one more ``step'' of your program, where ``step'' may mean either one
5722 line of source code, or one machine instruction (depending on what
5723 particular command you use). Either when continuing or when stepping,
5724 your program may stop even sooner, due to a breakpoint or a signal. (If
5725 it stops due to a signal, you may want to use @code{handle}, or use
5726 @samp{signal 0} to resume execution (@pxref{Signals, ,Signals}),
5727 or you may step into the signal's handler (@pxref{stepping and signal
5732 @kindex c @r{(@code{continue})}
5733 @kindex fg @r{(resume foreground execution)}
5734 @item continue @r{[}@var{ignore-count}@r{]}
5735 @itemx c @r{[}@var{ignore-count}@r{]}
5736 @itemx fg @r{[}@var{ignore-count}@r{]}
5737 Resume program execution, at the address where your program last stopped;
5738 any breakpoints set at that address are bypassed. The optional argument
5739 @var{ignore-count} allows you to specify a further number of times to
5740 ignore a breakpoint at this location; its effect is like that of
5741 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
5743 The argument @var{ignore-count} is meaningful only when your program
5744 stopped due to a breakpoint. At other times, the argument to
5745 @code{continue} is ignored.
5747 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
5748 debugged program is deemed to be the foreground program) are provided
5749 purely for convenience, and have exactly the same behavior as
5753 To resume execution at a different place, you can use @code{return}
5754 (@pxref{Returning, ,Returning from a Function}) to go back to the
5755 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
5756 Different Address}) to go to an arbitrary location in your program.
5758 A typical technique for using stepping is to set a breakpoint
5759 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
5760 beginning of the function or the section of your program where a problem
5761 is believed to lie, run your program until it stops at that breakpoint,
5762 and then step through the suspect area, examining the variables that are
5763 interesting, until you see the problem happen.
5767 @kindex s @r{(@code{step})}
5769 Continue running your program until control reaches a different source
5770 line, then stop it and return control to @value{GDBN}. This command is
5771 abbreviated @code{s}.
5774 @c "without debugging information" is imprecise; actually "without line
5775 @c numbers in the debugging information". (gcc -g1 has debugging info but
5776 @c not line numbers). But it seems complex to try to make that
5777 @c distinction here.
5778 @emph{Warning:} If you use the @code{step} command while control is
5779 within a function that was compiled without debugging information,
5780 execution proceeds until control reaches a function that does have
5781 debugging information. Likewise, it will not step into a function which
5782 is compiled without debugging information. To step through functions
5783 without debugging information, use the @code{stepi} command, described
5787 The @code{step} command only stops at the first instruction of a source
5788 line. This prevents the multiple stops that could otherwise occur in
5789 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5790 to stop if a function that has debugging information is called within
5791 the line. In other words, @code{step} @emph{steps inside} any functions
5792 called within the line.
5794 Also, the @code{step} command only enters a function if there is line
5795 number information for the function. Otherwise it acts like the
5796 @code{next} command. This avoids problems when using @code{cc -gl}
5797 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5798 was any debugging information about the routine.
5800 @item step @var{count}
5801 Continue running as in @code{step}, but do so @var{count} times. If a
5802 breakpoint is reached, or a signal not related to stepping occurs before
5803 @var{count} steps, stepping stops right away.
5806 @kindex n @r{(@code{next})}
5807 @item next @r{[}@var{count}@r{]}
5808 Continue to the next source line in the current (innermost) stack frame.
5809 This is similar to @code{step}, but function calls that appear within
5810 the line of code are executed without stopping. Execution stops when
5811 control reaches a different line of code at the original stack level
5812 that was executing when you gave the @code{next} command. This command
5813 is abbreviated @code{n}.
5815 An argument @var{count} is a repeat count, as for @code{step}.
5818 @c FIX ME!! Do we delete this, or is there a way it fits in with
5819 @c the following paragraph? --- Vctoria
5821 @c @code{next} within a function that lacks debugging information acts like
5822 @c @code{step}, but any function calls appearing within the code of the
5823 @c function are executed without stopping.
5825 The @code{next} command only stops at the first instruction of a
5826 source line. This prevents multiple stops that could otherwise occur in
5827 @code{switch} statements, @code{for} loops, etc.
5829 @kindex set step-mode
5831 @cindex functions without line info, and stepping
5832 @cindex stepping into functions with no line info
5833 @itemx set step-mode on
5834 The @code{set step-mode on} command causes the @code{step} command to
5835 stop at the first instruction of a function which contains no debug line
5836 information rather than stepping over it.
5838 This is useful in cases where you may be interested in inspecting the
5839 machine instructions of a function which has no symbolic info and do not
5840 want @value{GDBN} to automatically skip over this function.
5842 @item set step-mode off
5843 Causes the @code{step} command to step over any functions which contains no
5844 debug information. This is the default.
5846 @item show step-mode
5847 Show whether @value{GDBN} will stop in or step over functions without
5848 source line debug information.
5851 @kindex fin @r{(@code{finish})}
5853 Continue running until just after function in the selected stack frame
5854 returns. Print the returned value (if any). This command can be
5855 abbreviated as @code{fin}.
5857 Contrast this with the @code{return} command (@pxref{Returning,
5858 ,Returning from a Function}).
5860 @kindex set print finish
5861 @kindex show print finish
5862 @item set print finish @r{[}on|off@r{]}
5863 @itemx show print finish
5864 By default the @code{finish} command will show the value that is
5865 returned by the function. This can be disabled using @code{set print
5866 finish off}. When disabled, the value is still entered into the value
5867 history (@pxref{Value History}), but not displayed.
5870 @kindex u @r{(@code{until})}
5871 @cindex run until specified location
5874 Continue running until a source line past the current line, in the
5875 current stack frame, is reached. This command is used to avoid single
5876 stepping through a loop more than once. It is like the @code{next}
5877 command, except that when @code{until} encounters a jump, it
5878 automatically continues execution until the program counter is greater
5879 than the address of the jump.
5881 This means that when you reach the end of a loop after single stepping
5882 though it, @code{until} makes your program continue execution until it
5883 exits the loop. In contrast, a @code{next} command at the end of a loop
5884 simply steps back to the beginning of the loop, which forces you to step
5885 through the next iteration.
5887 @code{until} always stops your program if it attempts to exit the current
5890 @code{until} may produce somewhat counterintuitive results if the order
5891 of machine code does not match the order of the source lines. For
5892 example, in the following excerpt from a debugging session, the @code{f}
5893 (@code{frame}) command shows that execution is stopped at line
5894 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5898 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5900 (@value{GDBP}) until
5901 195 for ( ; argc > 0; NEXTARG) @{
5904 This happened because, for execution efficiency, the compiler had
5905 generated code for the loop closure test at the end, rather than the
5906 start, of the loop---even though the test in a C @code{for}-loop is
5907 written before the body of the loop. The @code{until} command appeared
5908 to step back to the beginning of the loop when it advanced to this
5909 expression; however, it has not really gone to an earlier
5910 statement---not in terms of the actual machine code.
5912 @code{until} with no argument works by means of single
5913 instruction stepping, and hence is slower than @code{until} with an
5916 @item until @var{location}
5917 @itemx u @var{location}
5918 Continue running your program until either the specified @var{location} is
5919 reached, or the current stack frame returns. The location is any of
5920 the forms described in @ref{Specify Location}.
5921 This form of the command uses temporary breakpoints, and
5922 hence is quicker than @code{until} without an argument. The specified
5923 location is actually reached only if it is in the current frame. This
5924 implies that @code{until} can be used to skip over recursive function
5925 invocations. For instance in the code below, if the current location is
5926 line @code{96}, issuing @code{until 99} will execute the program up to
5927 line @code{99} in the same invocation of factorial, i.e., after the inner
5928 invocations have returned.
5931 94 int factorial (int value)
5933 96 if (value > 1) @{
5934 97 value *= factorial (value - 1);
5941 @kindex advance @var{location}
5942 @item advance @var{location}
5943 Continue running the program up to the given @var{location}. An argument is
5944 required, which should be of one of the forms described in
5945 @ref{Specify Location}.
5946 Execution will also stop upon exit from the current stack
5947 frame. This command is similar to @code{until}, but @code{advance} will
5948 not skip over recursive function calls, and the target location doesn't
5949 have to be in the same frame as the current one.
5953 @kindex si @r{(@code{stepi})}
5955 @itemx stepi @var{arg}
5957 Execute one machine instruction, then stop and return to the debugger.
5959 It is often useful to do @samp{display/i $pc} when stepping by machine
5960 instructions. This makes @value{GDBN} automatically display the next
5961 instruction to be executed, each time your program stops. @xref{Auto
5962 Display,, Automatic Display}.
5964 An argument is a repeat count, as in @code{step}.
5968 @kindex ni @r{(@code{nexti})}
5970 @itemx nexti @var{arg}
5972 Execute one machine instruction, but if it is a function call,
5973 proceed until the function returns.
5975 An argument is a repeat count, as in @code{next}.
5979 @anchor{range stepping}
5980 @cindex range stepping
5981 @cindex target-assisted range stepping
5982 By default, and if available, @value{GDBN} makes use of
5983 target-assisted @dfn{range stepping}. In other words, whenever you
5984 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
5985 tells the target to step the corresponding range of instruction
5986 addresses instead of issuing multiple single-steps. This speeds up
5987 line stepping, particularly for remote targets. Ideally, there should
5988 be no reason you would want to turn range stepping off. However, it's
5989 possible that a bug in the debug info, a bug in the remote stub (for
5990 remote targets), or even a bug in @value{GDBN} could make line
5991 stepping behave incorrectly when target-assisted range stepping is
5992 enabled. You can use the following command to turn off range stepping
5996 @kindex set range-stepping
5997 @kindex show range-stepping
5998 @item set range-stepping
5999 @itemx show range-stepping
6000 Control whether range stepping is enabled.
6002 If @code{on}, and the target supports it, @value{GDBN} tells the
6003 target to step a range of addresses itself, instead of issuing
6004 multiple single-steps. If @code{off}, @value{GDBN} always issues
6005 single-steps, even if range stepping is supported by the target. The
6006 default is @code{on}.
6010 @node Skipping Over Functions and Files
6011 @section Skipping Over Functions and Files
6012 @cindex skipping over functions and files
6014 The program you are debugging may contain some functions which are
6015 uninteresting to debug. The @code{skip} command lets you tell @value{GDBN} to
6016 skip a function, all functions in a file or a particular function in
6017 a particular file when stepping.
6019 For example, consider the following C function:
6030 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
6031 are not interested in stepping through @code{boring}. If you run @code{step}
6032 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
6033 step over both @code{foo} and @code{boring}!
6035 One solution is to @code{step} into @code{boring} and use the @code{finish}
6036 command to immediately exit it. But this can become tedious if @code{boring}
6037 is called from many places.
6039 A more flexible solution is to execute @kbd{skip boring}. This instructs
6040 @value{GDBN} never to step into @code{boring}. Now when you execute
6041 @code{step} at line 103, you'll step over @code{boring} and directly into
6044 Functions may be skipped by providing either a function name, linespec
6045 (@pxref{Specify Location}), regular expression that matches the function's
6046 name, file name or a @code{glob}-style pattern that matches the file name.
6048 On Posix systems the form of the regular expression is
6049 ``Extended Regular Expressions''. See for example @samp{man 7 regex}
6050 on @sc{gnu}/Linux systems. On non-Posix systems the form of the regular
6051 expression is whatever is provided by the @code{regcomp} function of
6052 the underlying system.
6053 See for example @samp{man 7 glob} on @sc{gnu}/Linux systems for a
6054 description of @code{glob}-style patterns.
6058 @item skip @r{[}@var{options}@r{]}
6059 The basic form of the @code{skip} command takes zero or more options
6060 that specify what to skip.
6061 The @var{options} argument is any useful combination of the following:
6064 @item -file @var{file}
6065 @itemx -fi @var{file}
6066 Functions in @var{file} will be skipped over when stepping.
6068 @item -gfile @var{file-glob-pattern}
6069 @itemx -gfi @var{file-glob-pattern}
6070 @cindex skipping over files via glob-style patterns
6071 Functions in files matching @var{file-glob-pattern} will be skipped
6075 (gdb) skip -gfi utils/*.c
6078 @item -function @var{linespec}
6079 @itemx -fu @var{linespec}
6080 Functions named by @var{linespec} or the function containing the line
6081 named by @var{linespec} will be skipped over when stepping.
6082 @xref{Specify Location}.
6084 @item -rfunction @var{regexp}
6085 @itemx -rfu @var{regexp}
6086 @cindex skipping over functions via regular expressions
6087 Functions whose name matches @var{regexp} will be skipped over when stepping.
6089 This form is useful for complex function names.
6090 For example, there is generally no need to step into C@t{++} @code{std::string}
6091 constructors or destructors. Plus with C@t{++} templates it can be hard to
6092 write out the full name of the function, and often it doesn't matter what
6093 the template arguments are. Specifying the function to be skipped as a
6094 regular expression makes this easier.
6097 (gdb) skip -rfu ^std::(allocator|basic_string)<.*>::~?\1 *\(
6100 If you want to skip every templated C@t{++} constructor and destructor
6101 in the @code{std} namespace you can do:
6104 (gdb) skip -rfu ^std::([a-zA-z0-9_]+)<.*>::~?\1 *\(
6108 If no options are specified, the function you're currently debugging
6111 @kindex skip function
6112 @item skip function @r{[}@var{linespec}@r{]}
6113 After running this command, the function named by @var{linespec} or the
6114 function containing the line named by @var{linespec} will be skipped over when
6115 stepping. @xref{Specify Location}.
6117 If you do not specify @var{linespec}, the function you're currently debugging
6120 (If you have a function called @code{file} that you want to skip, use
6121 @kbd{skip function file}.)
6124 @item skip file @r{[}@var{filename}@r{]}
6125 After running this command, any function whose source lives in @var{filename}
6126 will be skipped over when stepping.
6129 (gdb) skip file boring.c
6130 File boring.c will be skipped when stepping.
6133 If you do not specify @var{filename}, functions whose source lives in the file
6134 you're currently debugging will be skipped.
6137 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
6138 These are the commands for managing your list of skips:
6142 @item info skip @r{[}@var{range}@r{]}
6143 Print details about the specified skip(s). If @var{range} is not specified,
6144 print a table with details about all functions and files marked for skipping.
6145 @code{info skip} prints the following information about each skip:
6149 A number identifying this skip.
6150 @item Enabled or Disabled
6151 Enabled skips are marked with @samp{y}.
6152 Disabled skips are marked with @samp{n}.
6154 If the file name is a @samp{glob} pattern this is @samp{y}.
6155 Otherwise it is @samp{n}.
6157 The name or @samp{glob} pattern of the file to be skipped.
6158 If no file is specified this is @samp{<none>}.
6160 If the function name is a @samp{regular expression} this is @samp{y}.
6161 Otherwise it is @samp{n}.
6163 The name or regular expression of the function to skip.
6164 If no function is specified this is @samp{<none>}.
6168 @item skip delete @r{[}@var{range}@r{]}
6169 Delete the specified skip(s). If @var{range} is not specified, delete all
6173 @item skip enable @r{[}@var{range}@r{]}
6174 Enable the specified skip(s). If @var{range} is not specified, enable all
6177 @kindex skip disable
6178 @item skip disable @r{[}@var{range}@r{]}
6179 Disable the specified skip(s). If @var{range} is not specified, disable all
6182 @kindex set debug skip
6183 @item set debug skip @r{[}on|off@r{]}
6184 Set whether to print the debug output about skipping files and functions.
6186 @kindex show debug skip
6187 @item show debug skip
6188 Show whether the debug output about skipping files and functions is printed.
6196 A signal is an asynchronous event that can happen in a program. The
6197 operating system defines the possible kinds of signals, and gives each
6198 kind a name and a number. For example, in Unix @code{SIGINT} is the
6199 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
6200 @code{SIGSEGV} is the signal a program gets from referencing a place in
6201 memory far away from all the areas in use; @code{SIGALRM} occurs when
6202 the alarm clock timer goes off (which happens only if your program has
6203 requested an alarm).
6205 @cindex fatal signals
6206 Some signals, including @code{SIGALRM}, are a normal part of the
6207 functioning of your program. Others, such as @code{SIGSEGV}, indicate
6208 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
6209 program has not specified in advance some other way to handle the signal.
6210 @code{SIGINT} does not indicate an error in your program, but it is normally
6211 fatal so it can carry out the purpose of the interrupt: to kill the program.
6213 @value{GDBN} has the ability to detect any occurrence of a signal in your
6214 program. You can tell @value{GDBN} in advance what to do for each kind of
6217 @cindex handling signals
6218 Normally, @value{GDBN} is set up to let the non-erroneous signals like
6219 @code{SIGALRM} be silently passed to your program
6220 (so as not to interfere with their role in the program's functioning)
6221 but to stop your program immediately whenever an error signal happens.
6222 You can change these settings with the @code{handle} command.
6225 @kindex info signals
6229 Print a table of all the kinds of signals and how @value{GDBN} has been told to
6230 handle each one. You can use this to see the signal numbers of all
6231 the defined types of signals.
6233 @item info signals @var{sig}
6234 Similar, but print information only about the specified signal number.
6236 @code{info handle} is an alias for @code{info signals}.
6238 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
6239 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
6240 for details about this command.
6243 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
6244 Change the way @value{GDBN} handles signal @var{signal}. The @var{signal}
6245 can be the number of a signal or its name (with or without the
6246 @samp{SIG} at the beginning); a list of signal numbers of the form
6247 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
6248 known signals. Optional arguments @var{keywords}, described below,
6249 say what change to make.
6253 The keywords allowed by the @code{handle} command can be abbreviated.
6254 Their full names are:
6258 @value{GDBN} should not stop your program when this signal happens. It may
6259 still print a message telling you that the signal has come in.
6262 @value{GDBN} should stop your program when this signal happens. This implies
6263 the @code{print} keyword as well.
6266 @value{GDBN} should print a message when this signal happens.
6269 @value{GDBN} should not mention the occurrence of the signal at all. This
6270 implies the @code{nostop} keyword as well.
6274 @value{GDBN} should allow your program to see this signal; your program
6275 can handle the signal, or else it may terminate if the signal is fatal
6276 and not handled. @code{pass} and @code{noignore} are synonyms.
6280 @value{GDBN} should not allow your program to see this signal.
6281 @code{nopass} and @code{ignore} are synonyms.
6285 When a signal stops your program, the signal is not visible to the
6287 continue. Your program sees the signal then, if @code{pass} is in
6288 effect for the signal in question @emph{at that time}. In other words,
6289 after @value{GDBN} reports a signal, you can use the @code{handle}
6290 command with @code{pass} or @code{nopass} to control whether your
6291 program sees that signal when you continue.
6293 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
6294 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
6295 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
6298 You can also use the @code{signal} command to prevent your program from
6299 seeing a signal, or cause it to see a signal it normally would not see,
6300 or to give it any signal at any time. For example, if your program stopped
6301 due to some sort of memory reference error, you might store correct
6302 values into the erroneous variables and continue, hoping to see more
6303 execution; but your program would probably terminate immediately as
6304 a result of the fatal signal once it saw the signal. To prevent this,
6305 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
6308 @cindex stepping and signal handlers
6309 @anchor{stepping and signal handlers}
6311 @value{GDBN} optimizes for stepping the mainline code. If a signal
6312 that has @code{handle nostop} and @code{handle pass} set arrives while
6313 a stepping command (e.g., @code{stepi}, @code{step}, @code{next}) is
6314 in progress, @value{GDBN} lets the signal handler run and then resumes
6315 stepping the mainline code once the signal handler returns. In other
6316 words, @value{GDBN} steps over the signal handler. This prevents
6317 signals that you've specified as not interesting (with @code{handle
6318 nostop}) from changing the focus of debugging unexpectedly. Note that
6319 the signal handler itself may still hit a breakpoint, stop for another
6320 signal that has @code{handle stop} in effect, or for any other event
6321 that normally results in stopping the stepping command sooner. Also
6322 note that @value{GDBN} still informs you that the program received a
6323 signal if @code{handle print} is set.
6325 @anchor{stepping into signal handlers}
6327 If you set @code{handle pass} for a signal, and your program sets up a
6328 handler for it, then issuing a stepping command, such as @code{step}
6329 or @code{stepi}, when your program is stopped due to the signal will
6330 step @emph{into} the signal handler (if the target supports that).
6332 Likewise, if you use the @code{queue-signal} command to queue a signal
6333 to be delivered to the current thread when execution of the thread
6334 resumes (@pxref{Signaling, ,Giving your Program a Signal}), then a
6335 stepping command will step into the signal handler.
6337 Here's an example, using @code{stepi} to step to the first instruction
6338 of @code{SIGUSR1}'s handler:
6341 (@value{GDBP}) handle SIGUSR1
6342 Signal Stop Print Pass to program Description
6343 SIGUSR1 Yes Yes Yes User defined signal 1
6347 Program received signal SIGUSR1, User defined signal 1.
6348 main () sigusr1.c:28
6351 sigusr1_handler () at sigusr1.c:9
6355 The same, but using @code{queue-signal} instead of waiting for the
6356 program to receive the signal first:
6361 (@value{GDBP}) queue-signal SIGUSR1
6363 sigusr1_handler () at sigusr1.c:9
6368 @cindex extra signal information
6369 @anchor{extra signal information}
6371 On some targets, @value{GDBN} can inspect extra signal information
6372 associated with the intercepted signal, before it is actually
6373 delivered to the program being debugged. This information is exported
6374 by the convenience variable @code{$_siginfo}, and consists of data
6375 that is passed by the kernel to the signal handler at the time of the
6376 receipt of a signal. The data type of the information itself is
6377 target dependent. You can see the data type using the @code{ptype
6378 $_siginfo} command. On Unix systems, it typically corresponds to the
6379 standard @code{siginfo_t} type, as defined in the @file{signal.h}
6382 Here's an example, on a @sc{gnu}/Linux system, printing the stray
6383 referenced address that raised a segmentation fault.
6387 (@value{GDBP}) continue
6388 Program received signal SIGSEGV, Segmentation fault.
6389 0x0000000000400766 in main ()
6391 (@value{GDBP}) ptype $_siginfo
6398 struct @{...@} _kill;
6399 struct @{...@} _timer;
6401 struct @{...@} _sigchld;
6402 struct @{...@} _sigfault;
6403 struct @{...@} _sigpoll;
6406 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
6410 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
6411 $1 = (void *) 0x7ffff7ff7000
6415 Depending on target support, @code{$_siginfo} may also be writable.
6417 @cindex Intel MPX boundary violations
6418 @cindex boundary violations, Intel MPX
6419 On some targets, a @code{SIGSEGV} can be caused by a boundary
6420 violation, i.e., accessing an address outside of the allowed range.
6421 In those cases @value{GDBN} may displays additional information,
6422 depending on how @value{GDBN} has been told to handle the signal.
6423 With @code{handle stop SIGSEGV}, @value{GDBN} displays the violation
6424 kind: "Upper" or "Lower", the memory address accessed and the
6425 bounds, while with @code{handle nostop SIGSEGV} no additional
6426 information is displayed.
6428 The usual output of a segfault is:
6430 Program received signal SIGSEGV, Segmentation fault
6431 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6432 68 value = *(p + len);
6435 While a bound violation is presented as:
6437 Program received signal SIGSEGV, Segmentation fault
6438 Upper bound violation while accessing address 0x7fffffffc3b3
6439 Bounds: [lower = 0x7fffffffc390, upper = 0x7fffffffc3a3]
6440 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6441 68 value = *(p + len);
6445 @section Stopping and Starting Multi-thread Programs
6447 @cindex stopped threads
6448 @cindex threads, stopped
6450 @cindex continuing threads
6451 @cindex threads, continuing
6453 @value{GDBN} supports debugging programs with multiple threads
6454 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
6455 are two modes of controlling execution of your program within the
6456 debugger. In the default mode, referred to as @dfn{all-stop mode},
6457 when any thread in your program stops (for example, at a breakpoint
6458 or while being stepped), all other threads in the program are also stopped by
6459 @value{GDBN}. On some targets, @value{GDBN} also supports
6460 @dfn{non-stop mode}, in which other threads can continue to run freely while
6461 you examine the stopped thread in the debugger.
6464 * All-Stop Mode:: All threads stop when GDB takes control
6465 * Non-Stop Mode:: Other threads continue to execute
6466 * Background Execution:: Running your program asynchronously
6467 * Thread-Specific Breakpoints:: Controlling breakpoints
6468 * Interrupted System Calls:: GDB may interfere with system calls
6469 * Observer Mode:: GDB does not alter program behavior
6473 @subsection All-Stop Mode
6475 @cindex all-stop mode
6477 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
6478 @emph{all} threads of execution stop, not just the current thread. This
6479 allows you to examine the overall state of the program, including
6480 switching between threads, without worrying that things may change
6483 Conversely, whenever you restart the program, @emph{all} threads start
6484 executing. @emph{This is true even when single-stepping} with commands
6485 like @code{step} or @code{next}.
6487 In particular, @value{GDBN} cannot single-step all threads in lockstep.
6488 Since thread scheduling is up to your debugging target's operating
6489 system (not controlled by @value{GDBN}), other threads may
6490 execute more than one statement while the current thread completes a
6491 single step. Moreover, in general other threads stop in the middle of a
6492 statement, rather than at a clean statement boundary, when the program
6495 You might even find your program stopped in another thread after
6496 continuing or even single-stepping. This happens whenever some other
6497 thread runs into a breakpoint, a signal, or an exception before the
6498 first thread completes whatever you requested.
6500 @cindex automatic thread selection
6501 @cindex switching threads automatically
6502 @cindex threads, automatic switching
6503 Whenever @value{GDBN} stops your program, due to a breakpoint or a
6504 signal, it automatically selects the thread where that breakpoint or
6505 signal happened. @value{GDBN} alerts you to the context switch with a
6506 message such as @samp{[Switching to Thread @var{n}]} to identify the
6509 On some OSes, you can modify @value{GDBN}'s default behavior by
6510 locking the OS scheduler to allow only a single thread to run.
6513 @item set scheduler-locking @var{mode}
6514 @cindex scheduler locking mode
6515 @cindex lock scheduler
6516 Set the scheduler locking mode. It applies to normal execution,
6517 record mode, and replay mode. If it is @code{off}, then there is no
6518 locking and any thread may run at any time. If @code{on}, then only
6519 the current thread may run when the inferior is resumed. The
6520 @code{step} mode optimizes for single-stepping; it prevents other
6521 threads from preempting the current thread while you are stepping, so
6522 that the focus of debugging does not change unexpectedly. Other
6523 threads never get a chance to run when you step, and they are
6524 completely free to run when you use commands like @samp{continue},
6525 @samp{until}, or @samp{finish}. However, unless another thread hits a
6526 breakpoint during its timeslice, @value{GDBN} does not change the
6527 current thread away from the thread that you are debugging. The
6528 @code{replay} mode behaves like @code{off} in record mode and like
6529 @code{on} in replay mode.
6531 @item show scheduler-locking
6532 Display the current scheduler locking mode.
6535 @cindex resume threads of multiple processes simultaneously
6536 By default, when you issue one of the execution commands such as
6537 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
6538 threads of the current inferior to run. For example, if @value{GDBN}
6539 is attached to two inferiors, each with two threads, the
6540 @code{continue} command resumes only the two threads of the current
6541 inferior. This is useful, for example, when you debug a program that
6542 forks and you want to hold the parent stopped (so that, for instance,
6543 it doesn't run to exit), while you debug the child. In other
6544 situations, you may not be interested in inspecting the current state
6545 of any of the processes @value{GDBN} is attached to, and you may want
6546 to resume them all until some breakpoint is hit. In the latter case,
6547 you can instruct @value{GDBN} to allow all threads of all the
6548 inferiors to run with the @w{@code{set schedule-multiple}} command.
6551 @kindex set schedule-multiple
6552 @item set schedule-multiple
6553 Set the mode for allowing threads of multiple processes to be resumed
6554 when an execution command is issued. When @code{on}, all threads of
6555 all processes are allowed to run. When @code{off}, only the threads
6556 of the current process are resumed. The default is @code{off}. The
6557 @code{scheduler-locking} mode takes precedence when set to @code{on},
6558 or while you are stepping and set to @code{step}.
6560 @item show schedule-multiple
6561 Display the current mode for resuming the execution of threads of
6566 @subsection Non-Stop Mode
6568 @cindex non-stop mode
6570 @c This section is really only a place-holder, and needs to be expanded
6571 @c with more details.
6573 For some multi-threaded targets, @value{GDBN} supports an optional
6574 mode of operation in which you can examine stopped program threads in
6575 the debugger while other threads continue to execute freely. This
6576 minimizes intrusion when debugging live systems, such as programs
6577 where some threads have real-time constraints or must continue to
6578 respond to external events. This is referred to as @dfn{non-stop} mode.
6580 In non-stop mode, when a thread stops to report a debugging event,
6581 @emph{only} that thread is stopped; @value{GDBN} does not stop other
6582 threads as well, in contrast to the all-stop mode behavior. Additionally,
6583 execution commands such as @code{continue} and @code{step} apply by default
6584 only to the current thread in non-stop mode, rather than all threads as
6585 in all-stop mode. This allows you to control threads explicitly in
6586 ways that are not possible in all-stop mode --- for example, stepping
6587 one thread while allowing others to run freely, stepping
6588 one thread while holding all others stopped, or stepping several threads
6589 independently and simultaneously.
6591 To enter non-stop mode, use this sequence of commands before you run
6592 or attach to your program:
6595 # If using the CLI, pagination breaks non-stop.
6598 # Finally, turn it on!
6602 You can use these commands to manipulate the non-stop mode setting:
6605 @kindex set non-stop
6606 @item set non-stop on
6607 Enable selection of non-stop mode.
6608 @item set non-stop off
6609 Disable selection of non-stop mode.
6610 @kindex show non-stop
6612 Show the current non-stop enablement setting.
6615 Note these commands only reflect whether non-stop mode is enabled,
6616 not whether the currently-executing program is being run in non-stop mode.
6617 In particular, the @code{set non-stop} preference is only consulted when
6618 @value{GDBN} starts or connects to the target program, and it is generally
6619 not possible to switch modes once debugging has started. Furthermore,
6620 since not all targets support non-stop mode, even when you have enabled
6621 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
6624 In non-stop mode, all execution commands apply only to the current thread
6625 by default. That is, @code{continue} only continues one thread.
6626 To continue all threads, issue @code{continue -a} or @code{c -a}.
6628 You can use @value{GDBN}'s background execution commands
6629 (@pxref{Background Execution}) to run some threads in the background
6630 while you continue to examine or step others from @value{GDBN}.
6631 The MI execution commands (@pxref{GDB/MI Program Execution}) are
6632 always executed asynchronously in non-stop mode.
6634 Suspending execution is done with the @code{interrupt} command when
6635 running in the background, or @kbd{Ctrl-c} during foreground execution.
6636 In all-stop mode, this stops the whole process;
6637 but in non-stop mode the interrupt applies only to the current thread.
6638 To stop the whole program, use @code{interrupt -a}.
6640 Other execution commands do not currently support the @code{-a} option.
6642 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
6643 that thread current, as it does in all-stop mode. This is because the
6644 thread stop notifications are asynchronous with respect to @value{GDBN}'s
6645 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
6646 changed to a different thread just as you entered a command to operate on the
6647 previously current thread.
6649 @node Background Execution
6650 @subsection Background Execution
6652 @cindex foreground execution
6653 @cindex background execution
6654 @cindex asynchronous execution
6655 @cindex execution, foreground, background and asynchronous
6657 @value{GDBN}'s execution commands have two variants: the normal
6658 foreground (synchronous) behavior, and a background
6659 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
6660 the program to report that some thread has stopped before prompting for
6661 another command. In background execution, @value{GDBN} immediately gives
6662 a command prompt so that you can issue other commands while your program runs.
6664 If the target doesn't support async mode, @value{GDBN} issues an error
6665 message if you attempt to use the background execution commands.
6667 @cindex @code{&}, background execution of commands
6668 To specify background execution, add a @code{&} to the command. For example,
6669 the background form of the @code{continue} command is @code{continue&}, or
6670 just @code{c&}. The execution commands that accept background execution
6676 @xref{Starting, , Starting your Program}.
6680 @xref{Attach, , Debugging an Already-running Process}.
6684 @xref{Continuing and Stepping, step}.
6688 @xref{Continuing and Stepping, stepi}.
6692 @xref{Continuing and Stepping, next}.
6696 @xref{Continuing and Stepping, nexti}.
6700 @xref{Continuing and Stepping, continue}.
6704 @xref{Continuing and Stepping, finish}.
6708 @xref{Continuing and Stepping, until}.
6712 Background execution is especially useful in conjunction with non-stop
6713 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
6714 However, you can also use these commands in the normal all-stop mode with
6715 the restriction that you cannot issue another execution command until the
6716 previous one finishes. Examples of commands that are valid in all-stop
6717 mode while the program is running include @code{help} and @code{info break}.
6719 You can interrupt your program while it is running in the background by
6720 using the @code{interrupt} command.
6727 Suspend execution of the running program. In all-stop mode,
6728 @code{interrupt} stops the whole process, but in non-stop mode, it stops
6729 only the current thread. To stop the whole program in non-stop mode,
6730 use @code{interrupt -a}.
6733 @node Thread-Specific Breakpoints
6734 @subsection Thread-Specific Breakpoints
6736 When your program has multiple threads (@pxref{Threads,, Debugging
6737 Programs with Multiple Threads}), you can choose whether to set
6738 breakpoints on all threads, or on a particular thread.
6741 @cindex breakpoints and threads
6742 @cindex thread breakpoints
6743 @kindex break @dots{} thread @var{thread-id}
6744 @item break @var{location} thread @var{thread-id}
6745 @itemx break @var{location} thread @var{thread-id} if @dots{}
6746 @var{location} specifies source lines; there are several ways of
6747 writing them (@pxref{Specify Location}), but the effect is always to
6748 specify some source line.
6750 Use the qualifier @samp{thread @var{thread-id}} with a breakpoint command
6751 to specify that you only want @value{GDBN} to stop the program when a
6752 particular thread reaches this breakpoint. The @var{thread-id} specifier
6753 is one of the thread identifiers assigned by @value{GDBN}, shown
6754 in the first column of the @samp{info threads} display.
6756 If you do not specify @samp{thread @var{thread-id}} when you set a
6757 breakpoint, the breakpoint applies to @emph{all} threads of your
6760 You can use the @code{thread} qualifier on conditional breakpoints as
6761 well; in this case, place @samp{thread @var{thread-id}} before or
6762 after the breakpoint condition, like this:
6765 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
6770 Thread-specific breakpoints are automatically deleted when
6771 @value{GDBN} detects the corresponding thread is no longer in the
6772 thread list. For example:
6776 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
6779 There are several ways for a thread to disappear, such as a regular
6780 thread exit, but also when you detach from the process with the
6781 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
6782 Process}), or if @value{GDBN} loses the remote connection
6783 (@pxref{Remote Debugging}), etc. Note that with some targets,
6784 @value{GDBN} is only able to detect a thread has exited when the user
6785 explictly asks for the thread list with the @code{info threads}
6788 @node Interrupted System Calls
6789 @subsection Interrupted System Calls
6791 @cindex thread breakpoints and system calls
6792 @cindex system calls and thread breakpoints
6793 @cindex premature return from system calls
6794 There is an unfortunate side effect when using @value{GDBN} to debug
6795 multi-threaded programs. If one thread stops for a
6796 breakpoint, or for some other reason, and another thread is blocked in a
6797 system call, then the system call may return prematurely. This is a
6798 consequence of the interaction between multiple threads and the signals
6799 that @value{GDBN} uses to implement breakpoints and other events that
6802 To handle this problem, your program should check the return value of
6803 each system call and react appropriately. This is good programming
6806 For example, do not write code like this:
6812 The call to @code{sleep} will return early if a different thread stops
6813 at a breakpoint or for some other reason.
6815 Instead, write this:
6820 unslept = sleep (unslept);
6823 A system call is allowed to return early, so the system is still
6824 conforming to its specification. But @value{GDBN} does cause your
6825 multi-threaded program to behave differently than it would without
6828 Also, @value{GDBN} uses internal breakpoints in the thread library to
6829 monitor certain events such as thread creation and thread destruction.
6830 When such an event happens, a system call in another thread may return
6831 prematurely, even though your program does not appear to stop.
6834 @subsection Observer Mode
6836 If you want to build on non-stop mode and observe program behavior
6837 without any chance of disruption by @value{GDBN}, you can set
6838 variables to disable all of the debugger's attempts to modify state,
6839 whether by writing memory, inserting breakpoints, etc. These operate
6840 at a low level, intercepting operations from all commands.
6842 When all of these are set to @code{off}, then @value{GDBN} is said to
6843 be @dfn{observer mode}. As a convenience, the variable
6844 @code{observer} can be set to disable these, plus enable non-stop
6847 Note that @value{GDBN} will not prevent you from making nonsensical
6848 combinations of these settings. For instance, if you have enabled
6849 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
6850 then breakpoints that work by writing trap instructions into the code
6851 stream will still not be able to be placed.
6856 @item set observer on
6857 @itemx set observer off
6858 When set to @code{on}, this disables all the permission variables
6859 below (except for @code{insert-fast-tracepoints}), plus enables
6860 non-stop debugging. Setting this to @code{off} switches back to
6861 normal debugging, though remaining in non-stop mode.
6864 Show whether observer mode is on or off.
6866 @kindex may-write-registers
6867 @item set may-write-registers on
6868 @itemx set may-write-registers off
6869 This controls whether @value{GDBN} will attempt to alter the values of
6870 registers, such as with assignment expressions in @code{print}, or the
6871 @code{jump} command. It defaults to @code{on}.
6873 @item show may-write-registers
6874 Show the current permission to write registers.
6876 @kindex may-write-memory
6877 @item set may-write-memory on
6878 @itemx set may-write-memory off
6879 This controls whether @value{GDBN} will attempt to alter the contents
6880 of memory, such as with assignment expressions in @code{print}. It
6881 defaults to @code{on}.
6883 @item show may-write-memory
6884 Show the current permission to write memory.
6886 @kindex may-insert-breakpoints
6887 @item set may-insert-breakpoints on
6888 @itemx set may-insert-breakpoints off
6889 This controls whether @value{GDBN} will attempt to insert breakpoints.
6890 This affects all breakpoints, including internal breakpoints defined
6891 by @value{GDBN}. It defaults to @code{on}.
6893 @item show may-insert-breakpoints
6894 Show the current permission to insert breakpoints.
6896 @kindex may-insert-tracepoints
6897 @item set may-insert-tracepoints on
6898 @itemx set may-insert-tracepoints off
6899 This controls whether @value{GDBN} will attempt to insert (regular)
6900 tracepoints at the beginning of a tracing experiment. It affects only
6901 non-fast tracepoints, fast tracepoints being under the control of
6902 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
6904 @item show may-insert-tracepoints
6905 Show the current permission to insert tracepoints.
6907 @kindex may-insert-fast-tracepoints
6908 @item set may-insert-fast-tracepoints on
6909 @itemx set may-insert-fast-tracepoints off
6910 This controls whether @value{GDBN} will attempt to insert fast
6911 tracepoints at the beginning of a tracing experiment. It affects only
6912 fast tracepoints, regular (non-fast) tracepoints being under the
6913 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
6915 @item show may-insert-fast-tracepoints
6916 Show the current permission to insert fast tracepoints.
6918 @kindex may-interrupt
6919 @item set may-interrupt on
6920 @itemx set may-interrupt off
6921 This controls whether @value{GDBN} will attempt to interrupt or stop
6922 program execution. When this variable is @code{off}, the
6923 @code{interrupt} command will have no effect, nor will
6924 @kbd{Ctrl-c}. It defaults to @code{on}.
6926 @item show may-interrupt
6927 Show the current permission to interrupt or stop the program.
6931 @node Reverse Execution
6932 @chapter Running programs backward
6933 @cindex reverse execution
6934 @cindex running programs backward
6936 When you are debugging a program, it is not unusual to realize that
6937 you have gone too far, and some event of interest has already happened.
6938 If the target environment supports it, @value{GDBN} can allow you to
6939 ``rewind'' the program by running it backward.
6941 A target environment that supports reverse execution should be able
6942 to ``undo'' the changes in machine state that have taken place as the
6943 program was executing normally. Variables, registers etc.@: should
6944 revert to their previous values. Obviously this requires a great
6945 deal of sophistication on the part of the target environment; not
6946 all target environments can support reverse execution.
6948 When a program is executed in reverse, the instructions that
6949 have most recently been executed are ``un-executed'', in reverse
6950 order. The program counter runs backward, following the previous
6951 thread of execution in reverse. As each instruction is ``un-executed'',
6952 the values of memory and/or registers that were changed by that
6953 instruction are reverted to their previous states. After executing
6954 a piece of source code in reverse, all side effects of that code
6955 should be ``undone'', and all variables should be returned to their
6956 prior values@footnote{
6957 Note that some side effects are easier to undo than others. For instance,
6958 memory and registers are relatively easy, but device I/O is hard. Some
6959 targets may be able undo things like device I/O, and some may not.
6961 The contract between @value{GDBN} and the reverse executing target
6962 requires only that the target do something reasonable when
6963 @value{GDBN} tells it to execute backwards, and then report the
6964 results back to @value{GDBN}. Whatever the target reports back to
6965 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
6966 assumes that the memory and registers that the target reports are in a
6967 consistant state, but @value{GDBN} accepts whatever it is given.
6970 On some platforms, @value{GDBN} has built-in support for reverse
6971 execution, activated with the @code{record} or @code{record btrace}
6972 commands. @xref{Process Record and Replay}. Some remote targets,
6973 typically full system emulators, support reverse execution directly
6974 without requiring any special command.
6976 If you are debugging in a target environment that supports
6977 reverse execution, @value{GDBN} provides the following commands.
6980 @kindex reverse-continue
6981 @kindex rc @r{(@code{reverse-continue})}
6982 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6983 @itemx rc @r{[}@var{ignore-count}@r{]}
6984 Beginning at the point where your program last stopped, start executing
6985 in reverse. Reverse execution will stop for breakpoints and synchronous
6986 exceptions (signals), just like normal execution. Behavior of
6987 asynchronous signals depends on the target environment.
6989 @kindex reverse-step
6990 @kindex rs @r{(@code{step})}
6991 @item reverse-step @r{[}@var{count}@r{]}
6992 Run the program backward until control reaches the start of a
6993 different source line; then stop it, and return control to @value{GDBN}.
6995 Like the @code{step} command, @code{reverse-step} will only stop
6996 at the beginning of a source line. It ``un-executes'' the previously
6997 executed source line. If the previous source line included calls to
6998 debuggable functions, @code{reverse-step} will step (backward) into
6999 the called function, stopping at the beginning of the @emph{last}
7000 statement in the called function (typically a return statement).
7002 Also, as with the @code{step} command, if non-debuggable functions are
7003 called, @code{reverse-step} will run thru them backward without stopping.
7005 @kindex reverse-stepi
7006 @kindex rsi @r{(@code{reverse-stepi})}
7007 @item reverse-stepi @r{[}@var{count}@r{]}
7008 Reverse-execute one machine instruction. Note that the instruction
7009 to be reverse-executed is @emph{not} the one pointed to by the program
7010 counter, but the instruction executed prior to that one. For instance,
7011 if the last instruction was a jump, @code{reverse-stepi} will take you
7012 back from the destination of the jump to the jump instruction itself.
7014 @kindex reverse-next
7015 @kindex rn @r{(@code{reverse-next})}
7016 @item reverse-next @r{[}@var{count}@r{]}
7017 Run backward to the beginning of the previous line executed in
7018 the current (innermost) stack frame. If the line contains function
7019 calls, they will be ``un-executed'' without stopping. Starting from
7020 the first line of a function, @code{reverse-next} will take you back
7021 to the caller of that function, @emph{before} the function was called,
7022 just as the normal @code{next} command would take you from the last
7023 line of a function back to its return to its caller
7024 @footnote{Unless the code is too heavily optimized.}.
7026 @kindex reverse-nexti
7027 @kindex rni @r{(@code{reverse-nexti})}
7028 @item reverse-nexti @r{[}@var{count}@r{]}
7029 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
7030 in reverse, except that called functions are ``un-executed'' atomically.
7031 That is, if the previously executed instruction was a return from
7032 another function, @code{reverse-nexti} will continue to execute
7033 in reverse until the call to that function (from the current stack
7036 @kindex reverse-finish
7037 @item reverse-finish
7038 Just as the @code{finish} command takes you to the point where the
7039 current function returns, @code{reverse-finish} takes you to the point
7040 where it was called. Instead of ending up at the end of the current
7041 function invocation, you end up at the beginning.
7043 @kindex set exec-direction
7044 @item set exec-direction
7045 Set the direction of target execution.
7046 @item set exec-direction reverse
7047 @cindex execute forward or backward in time
7048 @value{GDBN} will perform all execution commands in reverse, until the
7049 exec-direction mode is changed to ``forward''. Affected commands include
7050 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
7051 command cannot be used in reverse mode.
7052 @item set exec-direction forward
7053 @value{GDBN} will perform all execution commands in the normal fashion.
7054 This is the default.
7058 @node Process Record and Replay
7059 @chapter Recording Inferior's Execution and Replaying It
7060 @cindex process record and replay
7061 @cindex recording inferior's execution and replaying it
7063 On some platforms, @value{GDBN} provides a special @dfn{process record
7064 and replay} target that can record a log of the process execution, and
7065 replay it later with both forward and reverse execution commands.
7068 When this target is in use, if the execution log includes the record
7069 for the next instruction, @value{GDBN} will debug in @dfn{replay
7070 mode}. In the replay mode, the inferior does not really execute code
7071 instructions. Instead, all the events that normally happen during
7072 code execution are taken from the execution log. While code is not
7073 really executed in replay mode, the values of registers (including the
7074 program counter register) and the memory of the inferior are still
7075 changed as they normally would. Their contents are taken from the
7079 If the record for the next instruction is not in the execution log,
7080 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
7081 inferior executes normally, and @value{GDBN} records the execution log
7084 The process record and replay target supports reverse execution
7085 (@pxref{Reverse Execution}), even if the platform on which the
7086 inferior runs does not. However, the reverse execution is limited in
7087 this case by the range of the instructions recorded in the execution
7088 log. In other words, reverse execution on platforms that don't
7089 support it directly can only be done in the replay mode.
7091 When debugging in the reverse direction, @value{GDBN} will work in
7092 replay mode as long as the execution log includes the record for the
7093 previous instruction; otherwise, it will work in record mode, if the
7094 platform supports reverse execution, or stop if not.
7096 Currently, process record and replay is supported on ARM, Aarch64,
7097 Moxie, PowerPC, PowerPC64, S/390, and x86 (i386/amd64) running
7098 GNU/Linux. Process record and replay can be used both when native
7099 debugging, and when remote debugging via @code{gdbserver}.
7101 For architecture environments that support process record and replay,
7102 @value{GDBN} provides the following commands:
7105 @kindex target record
7106 @kindex target record-full
7107 @kindex target record-btrace
7110 @kindex record btrace
7111 @kindex record btrace bts
7112 @kindex record btrace pt
7118 @kindex rec btrace bts
7119 @kindex rec btrace pt
7122 @item record @var{method}
7123 This command starts the process record and replay target. The
7124 recording method can be specified as parameter. Without a parameter
7125 the command uses the @code{full} recording method. The following
7126 recording methods are available:
7130 Full record/replay recording using @value{GDBN}'s software record and
7131 replay implementation. This method allows replaying and reverse
7134 @item btrace @var{format}
7135 Hardware-supported instruction recording, supported on Intel
7136 processors. This method does not record data. Further, the data is
7137 collected in a ring buffer so old data will be overwritten when the
7138 buffer is full. It allows limited reverse execution. Variables and
7139 registers are not available during reverse execution. In remote
7140 debugging, recording continues on disconnect. Recorded data can be
7141 inspected after reconnecting. The recording may be stopped using
7144 The recording format can be specified as parameter. Without a parameter
7145 the command chooses the recording format. The following recording
7146 formats are available:
7150 @cindex branch trace store
7151 Use the @dfn{Branch Trace Store} (@acronym{BTS}) recording format. In
7152 this format, the processor stores a from/to record for each executed
7153 branch in the btrace ring buffer.
7156 @cindex Intel Processor Trace
7157 Use the @dfn{Intel Processor Trace} recording format. In this
7158 format, the processor stores the execution trace in a compressed form
7159 that is afterwards decoded by @value{GDBN}.
7161 The trace can be recorded with very low overhead. The compressed
7162 trace format also allows small trace buffers to already contain a big
7163 number of instructions compared to @acronym{BTS}.
7165 Decoding the recorded execution trace, on the other hand, is more
7166 expensive than decoding @acronym{BTS} trace. This is mostly due to the
7167 increased number of instructions to process. You should increase the
7168 buffer-size with care.
7171 Not all recording formats may be available on all processors.
7174 The process record and replay target can only debug a process that is
7175 already running. Therefore, you need first to start the process with
7176 the @kbd{run} or @kbd{start} commands, and then start the recording
7177 with the @kbd{record @var{method}} command.
7179 @cindex displaced stepping, and process record and replay
7180 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
7181 will be automatically disabled when process record and replay target
7182 is started. That's because the process record and replay target
7183 doesn't support displaced stepping.
7185 @cindex non-stop mode, and process record and replay
7186 @cindex asynchronous execution, and process record and replay
7187 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
7188 the asynchronous execution mode (@pxref{Background Execution}), not
7189 all recording methods are available. The @code{full} recording method
7190 does not support these two modes.
7195 Stop the process record and replay target. When process record and
7196 replay target stops, the entire execution log will be deleted and the
7197 inferior will either be terminated, or will remain in its final state.
7199 When you stop the process record and replay target in record mode (at
7200 the end of the execution log), the inferior will be stopped at the
7201 next instruction that would have been recorded. In other words, if
7202 you record for a while and then stop recording, the inferior process
7203 will be left in the same state as if the recording never happened.
7205 On the other hand, if the process record and replay target is stopped
7206 while in replay mode (that is, not at the end of the execution log,
7207 but at some earlier point), the inferior process will become ``live''
7208 at that earlier state, and it will then be possible to continue the
7209 usual ``live'' debugging of the process from that state.
7211 When the inferior process exits, or @value{GDBN} detaches from it,
7212 process record and replay target will automatically stop itself.
7216 Go to a specific location in the execution log. There are several
7217 ways to specify the location to go to:
7220 @item record goto begin
7221 @itemx record goto start
7222 Go to the beginning of the execution log.
7224 @item record goto end
7225 Go to the end of the execution log.
7227 @item record goto @var{n}
7228 Go to instruction number @var{n} in the execution log.
7232 @item record save @var{filename}
7233 Save the execution log to a file @file{@var{filename}}.
7234 Default filename is @file{gdb_record.@var{process_id}}, where
7235 @var{process_id} is the process ID of the inferior.
7237 This command may not be available for all recording methods.
7239 @kindex record restore
7240 @item record restore @var{filename}
7241 Restore the execution log from a file @file{@var{filename}}.
7242 File must have been created with @code{record save}.
7244 @kindex set record full
7245 @item set record full insn-number-max @var{limit}
7246 @itemx set record full insn-number-max unlimited
7247 Set the limit of instructions to be recorded for the @code{full}
7248 recording method. Default value is 200000.
7250 If @var{limit} is a positive number, then @value{GDBN} will start
7251 deleting instructions from the log once the number of the record
7252 instructions becomes greater than @var{limit}. For every new recorded
7253 instruction, @value{GDBN} will delete the earliest recorded
7254 instruction to keep the number of recorded instructions at the limit.
7255 (Since deleting recorded instructions loses information, @value{GDBN}
7256 lets you control what happens when the limit is reached, by means of
7257 the @code{stop-at-limit} option, described below.)
7259 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
7260 delete recorded instructions from the execution log. The number of
7261 recorded instructions is limited only by the available memory.
7263 @kindex show record full
7264 @item show record full insn-number-max
7265 Show the limit of instructions to be recorded with the @code{full}
7268 @item set record full stop-at-limit
7269 Control the behavior of the @code{full} recording method when the
7270 number of recorded instructions reaches the limit. If ON (the
7271 default), @value{GDBN} will stop when the limit is reached for the
7272 first time and ask you whether you want to stop the inferior or
7273 continue running it and recording the execution log. If you decide
7274 to continue recording, each new recorded instruction will cause the
7275 oldest one to be deleted.
7277 If this option is OFF, @value{GDBN} will automatically delete the
7278 oldest record to make room for each new one, without asking.
7280 @item show record full stop-at-limit
7281 Show the current setting of @code{stop-at-limit}.
7283 @item set record full memory-query
7284 Control the behavior when @value{GDBN} is unable to record memory
7285 changes caused by an instruction for the @code{full} recording method.
7286 If ON, @value{GDBN} will query whether to stop the inferior in that
7289 If this option is OFF (the default), @value{GDBN} will automatically
7290 ignore the effect of such instructions on memory. Later, when
7291 @value{GDBN} replays this execution log, it will mark the log of this
7292 instruction as not accessible, and it will not affect the replay
7295 @item show record full memory-query
7296 Show the current setting of @code{memory-query}.
7298 @kindex set record btrace
7299 The @code{btrace} record target does not trace data. As a
7300 convenience, when replaying, @value{GDBN} reads read-only memory off
7301 the live program directly, assuming that the addresses of the
7302 read-only areas don't change. This for example makes it possible to
7303 disassemble code while replaying, but not to print variables.
7304 In some cases, being able to inspect variables might be useful.
7305 You can use the following command for that:
7307 @item set record btrace replay-memory-access
7308 Control the behavior of the @code{btrace} recording method when
7309 accessing memory during replay. If @code{read-only} (the default),
7310 @value{GDBN} will only allow accesses to read-only memory.
7311 If @code{read-write}, @value{GDBN} will allow accesses to read-only
7312 and to read-write memory. Beware that the accessed memory corresponds
7313 to the live target and not necessarily to the current replay
7316 @item set record btrace cpu @var{identifier}
7317 Set the processor to be used for enabling workarounds for processor
7318 errata when decoding the trace.
7320 Processor errata are defects in processor operation, caused by its
7321 design or manufacture. They can cause a trace not to match the
7322 specification. This, in turn, may cause trace decode to fail.
7323 @value{GDBN} can detect erroneous trace packets and correct them, thus
7324 avoiding the decoding failures. These corrections are known as
7325 @dfn{errata workarounds}, and are enabled based on the processor on
7326 which the trace was recorded.
7328 By default, @value{GDBN} attempts to detect the processor
7329 automatically, and apply the necessary workarounds for it. However,
7330 you may need to specify the processor if @value{GDBN} does not yet
7331 support it. This command allows you to do that, and also allows to
7332 disable the workarounds.
7334 The argument @var{identifier} identifies the @sc{cpu} and is of the
7335 form: @code{@var{vendor}:@var{procesor identifier}}. In addition,
7336 there are two special identifiers, @code{none} and @code{auto}
7339 The following vendor identifiers and corresponding processor
7340 identifiers are currently supported:
7342 @multitable @columnfractions .1 .9
7345 @tab @var{family}/@var{model}[/@var{stepping}]
7349 On GNU/Linux systems, the processor @var{family}, @var{model}, and
7350 @var{stepping} can be obtained from @code{/proc/cpuinfo}.
7352 If @var{identifier} is @code{auto}, enable errata workarounds for the
7353 processor on which the trace was recorded. If @var{identifier} is
7354 @code{none}, errata workarounds are disabled.
7356 For example, when using an old @value{GDBN} on a new system, decode
7357 may fail because @value{GDBN} does not support the new processor. It
7358 often suffices to specify an older processor that @value{GDBN}
7363 Active record target: record-btrace
7364 Recording format: Intel Processor Trace.
7366 Failed to configure the Intel Processor Trace decoder: unknown cpu.
7367 (gdb) set record btrace cpu intel:6/158
7369 Active record target: record-btrace
7370 Recording format: Intel Processor Trace.
7372 Recorded 84872 instructions in 3189 functions (0 gaps) for thread 1 (...).
7375 @kindex show record btrace
7376 @item show record btrace replay-memory-access
7377 Show the current setting of @code{replay-memory-access}.
7379 @item show record btrace cpu
7380 Show the processor to be used for enabling trace decode errata
7383 @kindex set record btrace bts
7384 @item set record btrace bts buffer-size @var{size}
7385 @itemx set record btrace bts buffer-size unlimited
7386 Set the requested ring buffer size for branch tracing in @acronym{BTS}
7387 format. Default is 64KB.
7389 If @var{size} is a positive number, then @value{GDBN} will try to
7390 allocate a buffer of at least @var{size} bytes for each new thread
7391 that uses the btrace recording method and the @acronym{BTS} format.
7392 The actually obtained buffer size may differ from the requested
7393 @var{size}. Use the @code{info record} command to see the actual
7394 buffer size for each thread that uses the btrace recording method and
7395 the @acronym{BTS} format.
7397 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
7398 allocate a buffer of 4MB.
7400 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
7401 also need longer to process the branch trace data before it can be used.
7403 @item show record btrace bts buffer-size @var{size}
7404 Show the current setting of the requested ring buffer size for branch
7405 tracing in @acronym{BTS} format.
7407 @kindex set record btrace pt
7408 @item set record btrace pt buffer-size @var{size}
7409 @itemx set record btrace pt buffer-size unlimited
7410 Set the requested ring buffer size for branch tracing in Intel
7411 Processor Trace format. Default is 16KB.
7413 If @var{size} is a positive number, then @value{GDBN} will try to
7414 allocate a buffer of at least @var{size} bytes for each new thread
7415 that uses the btrace recording method and the Intel Processor Trace
7416 format. The actually obtained buffer size may differ from the
7417 requested @var{size}. Use the @code{info record} command to see the
7418 actual buffer size for each thread.
7420 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
7421 allocate a buffer of 4MB.
7423 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
7424 also need longer to process the branch trace data before it can be used.
7426 @item show record btrace pt buffer-size @var{size}
7427 Show the current setting of the requested ring buffer size for branch
7428 tracing in Intel Processor Trace format.
7432 Show various statistics about the recording depending on the recording
7437 For the @code{full} recording method, it shows the state of process
7438 record and its in-memory execution log buffer, including:
7442 Whether in record mode or replay mode.
7444 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
7446 Highest recorded instruction number.
7448 Current instruction about to be replayed (if in replay mode).
7450 Number of instructions contained in the execution log.
7452 Maximum number of instructions that may be contained in the execution log.
7456 For the @code{btrace} recording method, it shows:
7462 Number of instructions that have been recorded.
7464 Number of blocks of sequential control-flow formed by the recorded
7467 Whether in record mode or replay mode.
7470 For the @code{bts} recording format, it also shows:
7473 Size of the perf ring buffer.
7476 For the @code{pt} recording format, it also shows:
7479 Size of the perf ring buffer.
7483 @kindex record delete
7486 When record target runs in replay mode (``in the past''), delete the
7487 subsequent execution log and begin to record a new execution log starting
7488 from the current address. This means you will abandon the previously
7489 recorded ``future'' and begin recording a new ``future''.
7491 @kindex record instruction-history
7492 @kindex rec instruction-history
7493 @item record instruction-history
7494 Disassembles instructions from the recorded execution log. By
7495 default, ten instructions are disassembled. This can be changed using
7496 the @code{set record instruction-history-size} command. Instructions
7497 are printed in execution order.
7499 It can also print mixed source+disassembly if you specify the the
7500 @code{/m} or @code{/s} modifier, and print the raw instructions in hex
7501 as well as in symbolic form by specifying the @code{/r} modifier.
7503 The current position marker is printed for the instruction at the
7504 current program counter value. This instruction can appear multiple
7505 times in the trace and the current position marker will be printed
7506 every time. To omit the current position marker, specify the
7509 To better align the printed instructions when the trace contains
7510 instructions from more than one function, the function name may be
7511 omitted by specifying the @code{/f} modifier.
7513 Speculatively executed instructions are prefixed with @samp{?}. This
7514 feature is not available for all recording formats.
7516 There are several ways to specify what part of the execution log to
7520 @item record instruction-history @var{insn}
7521 Disassembles ten instructions starting from instruction number
7524 @item record instruction-history @var{insn}, +/-@var{n}
7525 Disassembles @var{n} instructions around instruction number
7526 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
7527 @var{n} instructions after instruction number @var{insn}. If
7528 @var{n} is preceded with @code{-}, disassembles @var{n}
7529 instructions before instruction number @var{insn}.
7531 @item record instruction-history
7532 Disassembles ten more instructions after the last disassembly.
7534 @item record instruction-history -
7535 Disassembles ten more instructions before the last disassembly.
7537 @item record instruction-history @var{begin}, @var{end}
7538 Disassembles instructions beginning with instruction number
7539 @var{begin} until instruction number @var{end}. The instruction
7540 number @var{end} is included.
7543 This command may not be available for all recording methods.
7546 @item set record instruction-history-size @var{size}
7547 @itemx set record instruction-history-size unlimited
7548 Define how many instructions to disassemble in the @code{record
7549 instruction-history} command. The default value is 10.
7550 A @var{size} of @code{unlimited} means unlimited instructions.
7553 @item show record instruction-history-size
7554 Show how many instructions to disassemble in the @code{record
7555 instruction-history} command.
7557 @kindex record function-call-history
7558 @kindex rec function-call-history
7559 @item record function-call-history
7560 Prints the execution history at function granularity. It prints one
7561 line for each sequence of instructions that belong to the same
7562 function giving the name of that function, the source lines
7563 for this instruction sequence (if the @code{/l} modifier is
7564 specified), and the instructions numbers that form the sequence (if
7565 the @code{/i} modifier is specified). The function names are indented
7566 to reflect the call stack depth if the @code{/c} modifier is
7567 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be
7571 (@value{GDBP}) @b{list 1, 10}
7582 (@value{GDBP}) @b{record function-call-history /ilc}
7583 1 bar inst 1,4 at foo.c:6,8
7584 2 foo inst 5,10 at foo.c:2,3
7585 3 bar inst 11,13 at foo.c:9,10
7588 By default, ten lines are printed. This can be changed using the
7589 @code{set record function-call-history-size} command. Functions are
7590 printed in execution order. There are several ways to specify what
7594 @item record function-call-history @var{func}
7595 Prints ten functions starting from function number @var{func}.
7597 @item record function-call-history @var{func}, +/-@var{n}
7598 Prints @var{n} functions around function number @var{func}. If
7599 @var{n} is preceded with @code{+}, prints @var{n} functions after
7600 function number @var{func}. If @var{n} is preceded with @code{-},
7601 prints @var{n} functions before function number @var{func}.
7603 @item record function-call-history
7604 Prints ten more functions after the last ten-line print.
7606 @item record function-call-history -
7607 Prints ten more functions before the last ten-line print.
7609 @item record function-call-history @var{begin}, @var{end}
7610 Prints functions beginning with function number @var{begin} until
7611 function number @var{end}. The function number @var{end} is included.
7614 This command may not be available for all recording methods.
7616 @item set record function-call-history-size @var{size}
7617 @itemx set record function-call-history-size unlimited
7618 Define how many lines to print in the
7619 @code{record function-call-history} command. The default value is 10.
7620 A size of @code{unlimited} means unlimited lines.
7622 @item show record function-call-history-size
7623 Show how many lines to print in the
7624 @code{record function-call-history} command.
7629 @chapter Examining the Stack
7631 When your program has stopped, the first thing you need to know is where it
7632 stopped and how it got there.
7635 Each time your program performs a function call, information about the call
7637 That information includes the location of the call in your program,
7638 the arguments of the call,
7639 and the local variables of the function being called.
7640 The information is saved in a block of data called a @dfn{stack frame}.
7641 The stack frames are allocated in a region of memory called the @dfn{call
7644 When your program stops, the @value{GDBN} commands for examining the
7645 stack allow you to see all of this information.
7647 @cindex selected frame
7648 One of the stack frames is @dfn{selected} by @value{GDBN} and many
7649 @value{GDBN} commands refer implicitly to the selected frame. In
7650 particular, whenever you ask @value{GDBN} for the value of a variable in
7651 your program, the value is found in the selected frame. There are
7652 special @value{GDBN} commands to select whichever frame you are
7653 interested in. @xref{Selection, ,Selecting a Frame}.
7655 When your program stops, @value{GDBN} automatically selects the
7656 currently executing frame and describes it briefly, similar to the
7657 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
7660 * Frames:: Stack frames
7661 * Backtrace:: Backtraces
7662 * Selection:: Selecting a frame
7663 * Frame Info:: Information on a frame
7664 * Frame Apply:: Applying a command to several frames
7665 * Frame Filter Management:: Managing frame filters
7670 @section Stack Frames
7672 @cindex frame, definition
7674 The call stack is divided up into contiguous pieces called @dfn{stack
7675 frames}, or @dfn{frames} for short; each frame is the data associated
7676 with one call to one function. The frame contains the arguments given
7677 to the function, the function's local variables, and the address at
7678 which the function is executing.
7680 @cindex initial frame
7681 @cindex outermost frame
7682 @cindex innermost frame
7683 When your program is started, the stack has only one frame, that of the
7684 function @code{main}. This is called the @dfn{initial} frame or the
7685 @dfn{outermost} frame. Each time a function is called, a new frame is
7686 made. Each time a function returns, the frame for that function invocation
7687 is eliminated. If a function is recursive, there can be many frames for
7688 the same function. The frame for the function in which execution is
7689 actually occurring is called the @dfn{innermost} frame. This is the most
7690 recently created of all the stack frames that still exist.
7692 @cindex frame pointer
7693 Inside your program, stack frames are identified by their addresses. A
7694 stack frame consists of many bytes, each of which has its own address; each
7695 kind of computer has a convention for choosing one byte whose
7696 address serves as the address of the frame. Usually this address is kept
7697 in a register called the @dfn{frame pointer register}
7698 (@pxref{Registers, $fp}) while execution is going on in that frame.
7701 @cindex frame number
7702 @value{GDBN} labels each existing stack frame with a @dfn{level}, a
7703 number that is zero for the innermost frame, one for the frame that
7704 called it, and so on upward. These level numbers give you a way of
7705 designating stack frames in @value{GDBN} commands. The terms
7706 @dfn{frame number} and @dfn{frame level} can be used interchangeably to
7707 describe this number.
7709 @c The -fomit-frame-pointer below perennially causes hbox overflow
7710 @c underflow problems.
7711 @cindex frameless execution
7712 Some compilers provide a way to compile functions so that they operate
7713 without stack frames. (For example, the @value{NGCC} option
7715 @samp{-fomit-frame-pointer}
7717 generates functions without a frame.)
7718 This is occasionally done with heavily used library functions to save
7719 the frame setup time. @value{GDBN} has limited facilities for dealing
7720 with these function invocations. If the innermost function invocation
7721 has no stack frame, @value{GDBN} nevertheless regards it as though
7722 it had a separate frame, which is numbered zero as usual, allowing
7723 correct tracing of the function call chain. However, @value{GDBN} has
7724 no provision for frameless functions elsewhere in the stack.
7730 @cindex call stack traces
7731 A backtrace is a summary of how your program got where it is. It shows one
7732 line per frame, for many frames, starting with the currently executing
7733 frame (frame zero), followed by its caller (frame one), and on up the
7736 @anchor{backtrace-command}
7738 @kindex bt @r{(@code{backtrace})}
7739 To print a backtrace of the entire stack, use the @code{backtrace}
7740 command, or its alias @code{bt}. This command will print one line per
7741 frame for frames in the stack. By default, all stack frames are
7742 printed. You can stop the backtrace at any time by typing the system
7743 interrupt character, normally @kbd{Ctrl-c}.
7746 @item backtrace [@var{option}]@dots{} [@var{qualifier}]@dots{} [@var{count}]
7747 @itemx bt [@var{option}]@dots{} [@var{qualifier}]@dots{} [@var{count}]
7748 Print the backtrace of the entire stack.
7750 The optional @var{count} can be one of the following:
7755 Print only the innermost @var{n} frames, where @var{n} is a positive
7760 Print only the outermost @var{n} frames, where @var{n} is a positive
7768 Print the values of the local variables also. This can be combined
7769 with the optional @var{count} to limit the number of frames shown.
7772 Do not run Python frame filters on this backtrace. @xref{Frame
7773 Filter API}, for more information. Additionally use @ref{disable
7774 frame-filter all} to turn off all frame filters. This is only
7775 relevant when @value{GDBN} has been configured with @code{Python}
7779 A Python frame filter might decide to ``elide'' some frames. Normally
7780 such elided frames are still printed, but they are indented relative
7781 to the filtered frames that cause them to be elided. The @code{-hide}
7782 option causes elided frames to not be printed at all.
7785 The @code{backtrace} command also supports a number of options that
7786 allow overriding relevant global print settings as set by @code{set
7787 backtrace} and @code{set print} subcommands:
7790 @item -past-main [@code{on}|@code{off}]
7791 Set whether backtraces should continue past @code{main}. Related setting:
7792 @ref{set backtrace past-main}.
7794 @item -past-entry [@code{on}|@code{off}]
7795 Set whether backtraces should continue past the entry point of a program.
7796 Related setting: @ref{set backtrace past-entry}.
7798 @item -entry-values @code{no}|@code{only}|@code{preferred}|@code{if-needed}|@code{both}|@code{compact}|@code{default}
7799 Set printing of function arguments at function entry.
7800 Related setting: @ref{set print entry-values}.
7802 @item -frame-arguments @code{all}|@code{scalars}|@code{none}
7803 Set printing of non-scalar frame arguments.
7804 Related setting: @ref{set print frame-arguments}.
7806 @item -raw-frame-arguments [@code{on}|@code{off}]
7807 Set whether to print frame arguments in raw form.
7808 Related setting: @ref{set print raw-frame-arguments}.
7811 The optional @var{qualifier} is maintained for backward compatibility.
7812 It can be one of the following:
7816 Equivalent to the @code{-full} option.
7819 Equivalent to the @code{-no-filters} option.
7822 Equivalent to the @code{-hide} option.
7829 The names @code{where} and @code{info stack} (abbreviated @code{info s})
7830 are additional aliases for @code{backtrace}.
7832 @cindex multiple threads, backtrace
7833 In a multi-threaded program, @value{GDBN} by default shows the
7834 backtrace only for the current thread. To display the backtrace for
7835 several or all of the threads, use the command @code{thread apply}
7836 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
7837 apply all backtrace}, @value{GDBN} will display the backtrace for all
7838 the threads; this is handy when you debug a core dump of a
7839 multi-threaded program.
7841 Each line in the backtrace shows the frame number and the function name.
7842 The program counter value is also shown---unless you use @code{set
7843 print address off}. The backtrace also shows the source file name and
7844 line number, as well as the arguments to the function. The program
7845 counter value is omitted if it is at the beginning of the code for that
7848 Here is an example of a backtrace. It was made with the command
7849 @samp{bt 3}, so it shows the innermost three frames.
7853 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7855 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
7856 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
7858 (More stack frames follow...)
7863 The display for frame zero does not begin with a program counter
7864 value, indicating that your program has stopped at the beginning of the
7865 code for line @code{993} of @code{builtin.c}.
7868 The value of parameter @code{data} in frame 1 has been replaced by
7869 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
7870 only if it is a scalar (integer, pointer, enumeration, etc). See command
7871 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
7872 on how to configure the way function parameter values are printed.
7874 @cindex optimized out, in backtrace
7875 @cindex function call arguments, optimized out
7876 If your program was compiled with optimizations, some compilers will
7877 optimize away arguments passed to functions if those arguments are
7878 never used after the call. Such optimizations generate code that
7879 passes arguments through registers, but doesn't store those arguments
7880 in the stack frame. @value{GDBN} has no way of displaying such
7881 arguments in stack frames other than the innermost one. Here's what
7882 such a backtrace might look like:
7886 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7888 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
7889 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
7891 (More stack frames follow...)
7896 The values of arguments that were not saved in their stack frames are
7897 shown as @samp{<optimized out>}.
7899 If you need to display the values of such optimized-out arguments,
7900 either deduce that from other variables whose values depend on the one
7901 you are interested in, or recompile without optimizations.
7903 @cindex backtrace beyond @code{main} function
7904 @cindex program entry point
7905 @cindex startup code, and backtrace
7906 Most programs have a standard user entry point---a place where system
7907 libraries and startup code transition into user code. For C this is
7908 @code{main}@footnote{
7909 Note that embedded programs (the so-called ``free-standing''
7910 environment) are not required to have a @code{main} function as the
7911 entry point. They could even have multiple entry points.}.
7912 When @value{GDBN} finds the entry function in a backtrace
7913 it will terminate the backtrace, to avoid tracing into highly
7914 system-specific (and generally uninteresting) code.
7916 If you need to examine the startup code, or limit the number of levels
7917 in a backtrace, you can change this behavior:
7920 @item set backtrace past-main
7921 @itemx set backtrace past-main on
7922 @anchor{set backtrace past-main}
7923 @kindex set backtrace
7924 Backtraces will continue past the user entry point.
7926 @item set backtrace past-main off
7927 Backtraces will stop when they encounter the user entry point. This is the
7930 @item show backtrace past-main
7931 @kindex show backtrace
7932 Display the current user entry point backtrace policy.
7934 @item set backtrace past-entry
7935 @itemx set backtrace past-entry on
7936 @anchor{set backtrace past-entry}
7937 Backtraces will continue past the internal entry point of an application.
7938 This entry point is encoded by the linker when the application is built,
7939 and is likely before the user entry point @code{main} (or equivalent) is called.
7941 @item set backtrace past-entry off
7942 Backtraces will stop when they encounter the internal entry point of an
7943 application. This is the default.
7945 @item show backtrace past-entry
7946 Display the current internal entry point backtrace policy.
7948 @item set backtrace limit @var{n}
7949 @itemx set backtrace limit 0
7950 @itemx set backtrace limit unlimited
7951 @anchor{set backtrace limit}
7952 @cindex backtrace limit
7953 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
7954 or zero means unlimited levels.
7956 @item show backtrace limit
7957 Display the current limit on backtrace levels.
7960 You can control how file names are displayed.
7963 @item set filename-display
7964 @itemx set filename-display relative
7965 @cindex filename-display
7966 Display file names relative to the compilation directory. This is the default.
7968 @item set filename-display basename
7969 Display only basename of a filename.
7971 @item set filename-display absolute
7972 Display an absolute filename.
7974 @item show filename-display
7975 Show the current way to display filenames.
7979 @section Selecting a Frame
7981 Most commands for examining the stack and other data in your program work on
7982 whichever stack frame is selected at the moment. Here are the commands for
7983 selecting a stack frame; all of them finish by printing a brief description
7984 of the stack frame just selected.
7987 @kindex frame@r{, selecting}
7988 @kindex f @r{(@code{frame})}
7989 @item frame @r{[} @var{frame-selection-spec} @r{]}
7990 @item f @r{[} @var{frame-selection-spec} @r{]}
7991 The @command{frame} command allows different stack frames to be
7992 selected. The @var{frame-selection-spec} can be any of the following:
7997 @item level @var{num}
7998 Select frame level @var{num}. Recall that frame zero is the innermost
7999 (currently executing) frame, frame one is the frame that called the
8000 innermost one, and so on. The highest level frame is usually the one
8003 As this is the most common method of navigating the frame stack, the
8004 string @command{level} can be omitted. For example, the following two
8005 commands are equivalent:
8008 (@value{GDBP}) frame 3
8009 (@value{GDBP}) frame level 3
8012 @kindex frame address
8013 @item address @var{stack-address}
8014 Select the frame with stack address @var{stack-address}. The
8015 @var{stack-address} for a frame can be seen in the output of
8016 @command{info frame}, for example:
8020 Stack level 1, frame at 0x7fffffffda30:
8021 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
8022 tail call frame, caller of frame at 0x7fffffffda30
8023 source language c++.
8024 Arglist at unknown address.
8025 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
8028 The @var{stack-address} for this frame is @code{0x7fffffffda30} as
8029 indicated by the line:
8032 Stack level 1, frame at 0x7fffffffda30:
8035 @kindex frame function
8036 @item function @var{function-name}
8037 Select the stack frame for function @var{function-name}. If there are
8038 multiple stack frames for function @var{function-name} then the inner
8039 most stack frame is selected.
8042 @item view @var{stack-address} @r{[} @var{pc-addr} @r{]}
8043 View a frame that is not part of @value{GDBN}'s backtrace. The frame
8044 viewed has stack address @var{stack-addr}, and optionally, a program
8045 counter address of @var{pc-addr}.
8047 This is useful mainly if the chaining of stack frames has been
8048 damaged by a bug, making it impossible for @value{GDBN} to assign
8049 numbers properly to all frames. In addition, this can be useful
8050 when your program has multiple stacks and switches between them.
8052 When viewing a frame outside the current backtrace using
8053 @command{frame view} then you can always return to the original
8054 stack using one of the previous stack frame selection instructions,
8055 for example @command{frame level 0}.
8061 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
8062 numbers @var{n}, this advances toward the outermost frame, to higher
8063 frame numbers, to frames that have existed longer.
8066 @kindex do @r{(@code{down})}
8068 Move @var{n} frames down the stack; @var{n} defaults to 1. For
8069 positive numbers @var{n}, this advances toward the innermost frame, to
8070 lower frame numbers, to frames that were created more recently.
8071 You may abbreviate @code{down} as @code{do}.
8074 All of these commands end by printing two lines of output describing the
8075 frame. The first line shows the frame number, the function name, the
8076 arguments, and the source file and line number of execution in that
8077 frame. The second line shows the text of that source line.
8085 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
8087 10 read_input_file (argv[i]);
8091 After such a printout, the @code{list} command with no arguments
8092 prints ten lines centered on the point of execution in the frame.
8093 You can also edit the program at the point of execution with your favorite
8094 editing program by typing @code{edit}.
8095 @xref{List, ,Printing Source Lines},
8099 @kindex select-frame
8100 @item select-frame @r{[} @var{frame-selection-spec} @r{]}
8101 The @code{select-frame} command is a variant of @code{frame} that does
8102 not display the new frame after selecting it. This command is
8103 intended primarily for use in @value{GDBN} command scripts, where the
8104 output might be unnecessary and distracting. The
8105 @var{frame-selection-spec} is as for the @command{frame} command
8106 described in @ref{Selection, ,Selecting a Frame}.
8108 @kindex down-silently
8110 @item up-silently @var{n}
8111 @itemx down-silently @var{n}
8112 These two commands are variants of @code{up} and @code{down},
8113 respectively; they differ in that they do their work silently, without
8114 causing display of the new frame. They are intended primarily for use
8115 in @value{GDBN} command scripts, where the output might be unnecessary and
8120 @section Information About a Frame
8122 There are several other commands to print information about the selected
8128 When used without any argument, this command does not change which
8129 frame is selected, but prints a brief description of the currently
8130 selected stack frame. It can be abbreviated @code{f}. With an
8131 argument, this command is used to select a stack frame.
8132 @xref{Selection, ,Selecting a Frame}.
8135 @kindex info f @r{(@code{info frame})}
8138 This command prints a verbose description of the selected stack frame,
8143 the address of the frame
8145 the address of the next frame down (called by this frame)
8147 the address of the next frame up (caller of this frame)
8149 the language in which the source code corresponding to this frame is written
8151 the address of the frame's arguments
8153 the address of the frame's local variables
8155 the program counter saved in it (the address of execution in the caller frame)
8157 which registers were saved in the frame
8160 @noindent The verbose description is useful when
8161 something has gone wrong that has made the stack format fail to fit
8162 the usual conventions.
8164 @item info frame @r{[} @var{frame-selection-spec} @r{]}
8165 @itemx info f @r{[} @var{frame-selection-spec} @r{]}
8166 Print a verbose description of the frame selected by
8167 @var{frame-selection-spec}. The @var{frame-selection-spec} is the
8168 same as for the @command{frame} command (@pxref{Selection, ,Selecting
8169 a Frame}). The selected frame remains unchanged by this command.
8172 @item info args [-q]
8173 Print the arguments of the selected frame, each on a separate line.
8175 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
8176 printing header information and messages explaining why no argument
8179 @item info args [-q] [-t @var{type_regexp}] [@var{regexp}]
8180 Like @kbd{info args}, but only print the arguments selected
8181 with the provided regexp(s).
8183 If @var{regexp} is provided, print only the arguments whose names
8184 match the regular expression @var{regexp}.
8186 If @var{type_regexp} is provided, print only the arguments whose
8187 types, as printed by the @code{whatis} command, match
8188 the regular expression @var{type_regexp}.
8189 If @var{type_regexp} contains space(s), it should be enclosed in
8190 quote characters. If needed, use backslash to escape the meaning
8191 of special characters or quotes.
8193 If both @var{regexp} and @var{type_regexp} are provided, an argument
8194 is printed only if its name matches @var{regexp} and its type matches
8197 @item info locals [-q]
8199 Print the local variables of the selected frame, each on a separate
8200 line. These are all variables (declared either static or automatic)
8201 accessible at the point of execution of the selected frame.
8203 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
8204 printing header information and messages explaining why no local variables
8207 @item info locals [-q] [-t @var{type_regexp}] [@var{regexp}]
8208 Like @kbd{info locals}, but only print the local variables selected
8209 with the provided regexp(s).
8211 If @var{regexp} is provided, print only the local variables whose names
8212 match the regular expression @var{regexp}.
8214 If @var{type_regexp} is provided, print only the local variables whose
8215 types, as printed by the @code{whatis} command, match
8216 the regular expression @var{type_regexp}.
8217 If @var{type_regexp} contains space(s), it should be enclosed in
8218 quote characters. If needed, use backslash to escape the meaning
8219 of special characters or quotes.
8221 If both @var{regexp} and @var{type_regexp} are provided, a local variable
8222 is printed only if its name matches @var{regexp} and its type matches
8225 The command @kbd{info locals -q -t @var{type_regexp}} can usefully be
8226 combined with the commands @kbd{frame apply} and @kbd{thread apply}.
8227 For example, your program might use Resource Acquisition Is
8228 Initialization types (RAII) such as @code{lock_something_t}: each
8229 local variable of type @code{lock_something_t} automatically places a
8230 lock that is destroyed when the variable goes out of scope. You can
8231 then list all acquired locks in your program by doing
8233 thread apply all -s frame apply all -s info locals -q -t lock_something_t
8236 or the equivalent shorter form
8238 tfaas i lo -q -t lock_something_t
8244 @section Applying a Command to Several Frames.
8245 @anchor{frame apply}
8247 @cindex apply command to several frames
8249 @item frame apply [all | @var{count} | @var{-count} | level @var{level}@dots{}] [@var{option}]@dots{} @var{command}
8250 The @code{frame apply} command allows you to apply the named
8251 @var{command} to one or more frames.
8255 Specify @code{all} to apply @var{command} to all frames.
8258 Use @var{count} to apply @var{command} to the innermost @var{count}
8259 frames, where @var{count} is a positive number.
8262 Use @var{-count} to apply @var{command} to the outermost @var{count}
8263 frames, where @var{count} is a positive number.
8266 Use @code{level} to apply @var{command} to the set of frames identified
8267 by the @var{level} list. @var{level} is a frame level or a range of frame
8268 levels as @var{level1}-@var{level2}. The frame level is the number shown
8269 in the first field of the @samp{backtrace} command output.
8270 E.g., @samp{2-4 6-8 3} indicates to apply @var{command} for the frames
8271 at levels 2, 3, 4, 6, 7, 8, and then again on frame at level 3.
8275 Note that the frames on which @code{frame apply} applies a command are
8276 also influenced by the @code{set backtrace} settings such as @code{set
8277 backtrace past-main} and @code{set backtrace limit N}.
8278 @xref{Backtrace,,Backtraces}.
8280 The @code{frame apply} command also supports a number of options that
8281 allow overriding relevant @code{set backtrace} settings:
8284 @item -past-main [@code{on}|@code{off}]
8285 Whether backtraces should continue past @code{main}.
8286 Related setting: @ref{set backtrace past-main}.
8288 @item -past-entry [@code{on}|@code{off}]
8289 Whether backtraces should continue past the entry point of a program.
8290 Related setting: @ref{set backtrace past-entry}.
8293 By default, @value{GDBN} displays some frame information before the
8294 output produced by @var{command}, and an error raised during the
8295 execution of a @var{command} will abort @code{frame apply}. The
8296 following options can be used to fine-tune these behaviors:
8300 The flag @code{-c}, which stands for @samp{continue}, causes any
8301 errors in @var{command} to be displayed, and the execution of
8302 @code{frame apply} then continues.
8304 The flag @code{-s}, which stands for @samp{silent}, causes any errors
8305 or empty output produced by a @var{command} to be silently ignored.
8306 That is, the execution continues, but the frame information and errors
8309 The flag @code{-q} (@samp{quiet}) disables printing the frame
8313 The following example shows how the flags @code{-c} and @code{-s} are
8314 working when applying the command @code{p j} to all frames, where
8315 variable @code{j} can only be successfully printed in the outermost
8316 @code{#1 main} frame.
8320 (gdb) frame apply all p j
8321 #0 some_function (i=5) at fun.c:4
8322 No symbol "j" in current context.
8323 (gdb) frame apply all -c p j
8324 #0 some_function (i=5) at fun.c:4
8325 No symbol "j" in current context.
8326 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8328 (gdb) frame apply all -s p j
8329 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8335 By default, @samp{frame apply}, prints the frame location
8336 information before the command output:
8340 (gdb) frame apply all p $sp
8341 #0 some_function (i=5) at fun.c:4
8342 $4 = (void *) 0xffffd1e0
8343 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8344 $5 = (void *) 0xffffd1f0
8349 If the flag @code{-q} is given, no frame information is printed:
8352 (gdb) frame apply all -q p $sp
8353 $12 = (void *) 0xffffd1e0
8354 $13 = (void *) 0xffffd1f0
8364 @cindex apply a command to all frames (ignoring errors and empty output)
8365 @item faas @var{command}
8366 Shortcut for @code{frame apply all -s @var{command}}.
8367 Applies @var{command} on all frames, ignoring errors and empty output.
8369 It can for example be used to print a local variable or a function
8370 argument without knowing the frame where this variable or argument
8373 (@value{GDBP}) faas p some_local_var_i_do_not_remember_where_it_is
8376 The @code{faas} command accepts the same options as the @code{frame
8377 apply} command. @xref{frame apply}.
8379 Note that the command @code{tfaas @var{command}} applies @var{command}
8380 on all frames of all threads. See @xref{Threads,,Threads}.
8384 @node Frame Filter Management
8385 @section Management of Frame Filters.
8386 @cindex managing frame filters
8388 Frame filters are Python based utilities to manage and decorate the
8389 output of frames. @xref{Frame Filter API}, for further information.
8391 Managing frame filters is performed by several commands available
8392 within @value{GDBN}, detailed here.
8395 @kindex info frame-filter
8396 @item info frame-filter
8397 Print a list of installed frame filters from all dictionaries, showing
8398 their name, priority and enabled status.
8400 @kindex disable frame-filter
8401 @anchor{disable frame-filter all}
8402 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
8403 Disable a frame filter in the dictionary matching
8404 @var{filter-dictionary} and @var{filter-name}. The
8405 @var{filter-dictionary} may be @code{all}, @code{global},
8406 @code{progspace}, or the name of the object file where the frame filter
8407 dictionary resides. When @code{all} is specified, all frame filters
8408 across all dictionaries are disabled. The @var{filter-name} is the name
8409 of the frame filter and is used when @code{all} is not the option for
8410 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
8411 may be enabled again later.
8413 @kindex enable frame-filter
8414 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
8415 Enable a frame filter in the dictionary matching
8416 @var{filter-dictionary} and @var{filter-name}. The
8417 @var{filter-dictionary} may be @code{all}, @code{global},
8418 @code{progspace} or the name of the object file where the frame filter
8419 dictionary resides. When @code{all} is specified, all frame filters across
8420 all dictionaries are enabled. The @var{filter-name} is the name of the frame
8421 filter and is used when @code{all} is not the option for
8422 @var{filter-dictionary}.
8427 (gdb) info frame-filter
8429 global frame-filters:
8430 Priority Enabled Name
8431 1000 No PrimaryFunctionFilter
8434 progspace /build/test frame-filters:
8435 Priority Enabled Name
8436 100 Yes ProgspaceFilter
8438 objfile /build/test frame-filters:
8439 Priority Enabled Name
8440 999 Yes BuildProgra Filter
8442 (gdb) disable frame-filter /build/test BuildProgramFilter
8443 (gdb) info frame-filter
8445 global frame-filters:
8446 Priority Enabled Name
8447 1000 No PrimaryFunctionFilter
8450 progspace /build/test frame-filters:
8451 Priority Enabled Name
8452 100 Yes ProgspaceFilter
8454 objfile /build/test frame-filters:
8455 Priority Enabled Name
8456 999 No BuildProgramFilter
8458 (gdb) enable frame-filter global PrimaryFunctionFilter
8459 (gdb) info frame-filter
8461 global frame-filters:
8462 Priority Enabled Name
8463 1000 Yes PrimaryFunctionFilter
8466 progspace /build/test frame-filters:
8467 Priority Enabled Name
8468 100 Yes ProgspaceFilter
8470 objfile /build/test frame-filters:
8471 Priority Enabled Name
8472 999 No BuildProgramFilter
8475 @kindex set frame-filter priority
8476 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
8477 Set the @var{priority} of a frame filter in the dictionary matching
8478 @var{filter-dictionary}, and the frame filter name matching
8479 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
8480 @code{progspace} or the name of the object file where the frame filter
8481 dictionary resides. The @var{priority} is an integer.
8483 @kindex show frame-filter priority
8484 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
8485 Show the @var{priority} of a frame filter in the dictionary matching
8486 @var{filter-dictionary}, and the frame filter name matching
8487 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
8488 @code{progspace} or the name of the object file where the frame filter
8494 (gdb) info frame-filter
8496 global frame-filters:
8497 Priority Enabled Name
8498 1000 Yes PrimaryFunctionFilter
8501 progspace /build/test frame-filters:
8502 Priority Enabled Name
8503 100 Yes ProgspaceFilter
8505 objfile /build/test frame-filters:
8506 Priority Enabled Name
8507 999 No BuildProgramFilter
8509 (gdb) set frame-filter priority global Reverse 50
8510 (gdb) info frame-filter
8512 global frame-filters:
8513 Priority Enabled Name
8514 1000 Yes PrimaryFunctionFilter
8517 progspace /build/test frame-filters:
8518 Priority Enabled Name
8519 100 Yes ProgspaceFilter
8521 objfile /build/test frame-filters:
8522 Priority Enabled Name
8523 999 No BuildProgramFilter
8528 @chapter Examining Source Files
8530 @value{GDBN} can print parts of your program's source, since the debugging
8531 information recorded in the program tells @value{GDBN} what source files were
8532 used to build it. When your program stops, @value{GDBN} spontaneously prints
8533 the line where it stopped. Likewise, when you select a stack frame
8534 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
8535 execution in that frame has stopped. You can print other portions of
8536 source files by explicit command.
8538 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
8539 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
8540 @value{GDBN} under @sc{gnu} Emacs}.
8543 * List:: Printing source lines
8544 * Specify Location:: How to specify code locations
8545 * Edit:: Editing source files
8546 * Search:: Searching source files
8547 * Source Path:: Specifying source directories
8548 * Machine Code:: Source and machine code
8552 @section Printing Source Lines
8555 @kindex l @r{(@code{list})}
8556 To print lines from a source file, use the @code{list} command
8557 (abbreviated @code{l}). By default, ten lines are printed.
8558 There are several ways to specify what part of the file you want to
8559 print; see @ref{Specify Location}, for the full list.
8561 Here are the forms of the @code{list} command most commonly used:
8564 @item list @var{linenum}
8565 Print lines centered around line number @var{linenum} in the
8566 current source file.
8568 @item list @var{function}
8569 Print lines centered around the beginning of function
8573 Print more lines. If the last lines printed were printed with a
8574 @code{list} command, this prints lines following the last lines
8575 printed; however, if the last line printed was a solitary line printed
8576 as part of displaying a stack frame (@pxref{Stack, ,Examining the
8577 Stack}), this prints lines centered around that line.
8580 Print lines just before the lines last printed.
8583 @cindex @code{list}, how many lines to display
8584 By default, @value{GDBN} prints ten source lines with any of these forms of
8585 the @code{list} command. You can change this using @code{set listsize}:
8588 @kindex set listsize
8589 @item set listsize @var{count}
8590 @itemx set listsize unlimited
8591 Make the @code{list} command display @var{count} source lines (unless
8592 the @code{list} argument explicitly specifies some other number).
8593 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
8595 @kindex show listsize
8597 Display the number of lines that @code{list} prints.
8600 Repeating a @code{list} command with @key{RET} discards the argument,
8601 so it is equivalent to typing just @code{list}. This is more useful
8602 than listing the same lines again. An exception is made for an
8603 argument of @samp{-}; that argument is preserved in repetition so that
8604 each repetition moves up in the source file.
8606 In general, the @code{list} command expects you to supply zero, one or two
8607 @dfn{locations}. Locations specify source lines; there are several ways
8608 of writing them (@pxref{Specify Location}), but the effect is always
8609 to specify some source line.
8611 Here is a complete description of the possible arguments for @code{list}:
8614 @item list @var{location}
8615 Print lines centered around the line specified by @var{location}.
8617 @item list @var{first},@var{last}
8618 Print lines from @var{first} to @var{last}. Both arguments are
8619 locations. When a @code{list} command has two locations, and the
8620 source file of the second location is omitted, this refers to
8621 the same source file as the first location.
8623 @item list ,@var{last}
8624 Print lines ending with @var{last}.
8626 @item list @var{first},
8627 Print lines starting with @var{first}.
8630 Print lines just after the lines last printed.
8633 Print lines just before the lines last printed.
8636 As described in the preceding table.
8639 @node Specify Location
8640 @section Specifying a Location
8641 @cindex specifying location
8643 @cindex source location
8646 * Linespec Locations:: Linespec locations
8647 * Explicit Locations:: Explicit locations
8648 * Address Locations:: Address locations
8651 Several @value{GDBN} commands accept arguments that specify a location
8652 of your program's code. Since @value{GDBN} is a source-level
8653 debugger, a location usually specifies some line in the source code.
8654 Locations may be specified using three different formats:
8655 linespec locations, explicit locations, or address locations.
8657 @node Linespec Locations
8658 @subsection Linespec Locations
8659 @cindex linespec locations
8661 A @dfn{linespec} is a colon-separated list of source location parameters such
8662 as file name, function name, etc. Here are all the different ways of
8663 specifying a linespec:
8667 Specifies the line number @var{linenum} of the current source file.
8670 @itemx +@var{offset}
8671 Specifies the line @var{offset} lines before or after the @dfn{current
8672 line}. For the @code{list} command, the current line is the last one
8673 printed; for the breakpoint commands, this is the line at which
8674 execution stopped in the currently selected @dfn{stack frame}
8675 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
8676 used as the second of the two linespecs in a @code{list} command,
8677 this specifies the line @var{offset} lines up or down from the first
8680 @item @var{filename}:@var{linenum}
8681 Specifies the line @var{linenum} in the source file @var{filename}.
8682 If @var{filename} is a relative file name, then it will match any
8683 source file name with the same trailing components. For example, if
8684 @var{filename} is @samp{gcc/expr.c}, then it will match source file
8685 name of @file{/build/trunk/gcc/expr.c}, but not
8686 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
8688 @item @var{function}
8689 Specifies the line that begins the body of the function @var{function}.
8690 For example, in C, this is the line with the open brace.
8692 By default, in C@t{++} and Ada, @var{function} is interpreted as
8693 specifying all functions named @var{function} in all scopes. For
8694 C@t{++}, this means in all namespaces and classes. For Ada, this
8695 means in all packages.
8697 For example, assuming a program with C@t{++} symbols named
8698 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
8699 func}} and @w{@kbd{break B::func}} set a breakpoint on both symbols.
8701 Commands that accept a linespec let you override this with the
8702 @code{-qualified} option. For example, @w{@kbd{break -qualified
8703 func}} sets a breakpoint on a free-function named @code{func} ignoring
8704 any C@t{++} class methods and namespace functions called @code{func}.
8706 @xref{Explicit Locations}.
8708 @item @var{function}:@var{label}
8709 Specifies the line where @var{label} appears in @var{function}.
8711 @item @var{filename}:@var{function}
8712 Specifies the line that begins the body of the function @var{function}
8713 in the file @var{filename}. You only need the file name with a
8714 function name to avoid ambiguity when there are identically named
8715 functions in different source files.
8718 Specifies the line at which the label named @var{label} appears
8719 in the function corresponding to the currently selected stack frame.
8720 If there is no current selected stack frame (for instance, if the inferior
8721 is not running), then @value{GDBN} will not search for a label.
8723 @cindex breakpoint at static probe point
8724 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
8725 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
8726 applications to embed static probes. @xref{Static Probe Points}, for more
8727 information on finding and using static probes. This form of linespec
8728 specifies the location of such a static probe.
8730 If @var{objfile} is given, only probes coming from that shared library
8731 or executable matching @var{objfile} as a regular expression are considered.
8732 If @var{provider} is given, then only probes from that provider are considered.
8733 If several probes match the spec, @value{GDBN} will insert a breakpoint at
8734 each one of those probes.
8737 @node Explicit Locations
8738 @subsection Explicit Locations
8739 @cindex explicit locations
8741 @dfn{Explicit locations} allow the user to directly specify the source
8742 location's parameters using option-value pairs.
8744 Explicit locations are useful when several functions, labels, or
8745 file names have the same name (base name for files) in the program's
8746 sources. In these cases, explicit locations point to the source
8747 line you meant more accurately and unambiguously. Also, using
8748 explicit locations might be faster in large programs.
8750 For example, the linespec @samp{foo:bar} may refer to a function @code{bar}
8751 defined in the file named @file{foo} or the label @code{bar} in a function
8752 named @code{foo}. @value{GDBN} must search either the file system or
8753 the symbol table to know.
8755 The list of valid explicit location options is summarized in the
8759 @item -source @var{filename}
8760 The value specifies the source file name. To differentiate between
8761 files with the same base name, prepend as many directories as is necessary
8762 to uniquely identify the desired file, e.g., @file{foo/bar/baz.c}. Otherwise
8763 @value{GDBN} will use the first file it finds with the given base
8764 name. This option requires the use of either @code{-function} or @code{-line}.
8766 @item -function @var{function}
8767 The value specifies the name of a function. Operations
8768 on function locations unmodified by other options (such as @code{-label}
8769 or @code{-line}) refer to the line that begins the body of the function.
8770 In C, for example, this is the line with the open brace.
8772 By default, in C@t{++} and Ada, @var{function} is interpreted as
8773 specifying all functions named @var{function} in all scopes. For
8774 C@t{++}, this means in all namespaces and classes. For Ada, this
8775 means in all packages.
8777 For example, assuming a program with C@t{++} symbols named
8778 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
8779 -function func}} and @w{@kbd{break -function B::func}} set a
8780 breakpoint on both symbols.
8782 You can use the @kbd{-qualified} flag to override this (see below).
8786 This flag makes @value{GDBN} interpret a function name specified with
8787 @kbd{-function} as a complete fully-qualified name.
8789 For example, assuming a C@t{++} program with symbols named
8790 @code{A::B::func} and @code{B::func}, the @w{@kbd{break -qualified
8791 -function B::func}} command sets a breakpoint on @code{B::func}, only.
8793 (Note: the @kbd{-qualified} option can precede a linespec as well
8794 (@pxref{Linespec Locations}), so the particular example above could be
8795 simplified as @w{@kbd{break -qualified B::func}}.)
8797 @item -label @var{label}
8798 The value specifies the name of a label. When the function
8799 name is not specified, the label is searched in the function of the currently
8800 selected stack frame.
8802 @item -line @var{number}
8803 The value specifies a line offset for the location. The offset may either
8804 be absolute (@code{-line 3}) or relative (@code{-line +3}), depending on
8805 the command. When specified without any other options, the line offset is
8806 relative to the current line.
8809 Explicit location options may be abbreviated by omitting any non-unique
8810 trailing characters from the option name, e.g., @w{@kbd{break -s main.c -li 3}}.
8812 @node Address Locations
8813 @subsection Address Locations
8814 @cindex address locations
8816 @dfn{Address locations} indicate a specific program address. They have
8817 the generalized form *@var{address}.
8819 For line-oriented commands, such as @code{list} and @code{edit}, this
8820 specifies a source line that contains @var{address}. For @code{break} and
8821 other breakpoint-oriented commands, this can be used to set breakpoints in
8822 parts of your program which do not have debugging information or
8825 Here @var{address} may be any expression valid in the current working
8826 language (@pxref{Languages, working language}) that specifies a code
8827 address. In addition, as a convenience, @value{GDBN} extends the
8828 semantics of expressions used in locations to cover several situations
8829 that frequently occur during debugging. Here are the various forms
8833 @item @var{expression}
8834 Any expression valid in the current working language.
8836 @item @var{funcaddr}
8837 An address of a function or procedure derived from its name. In C,
8838 C@t{++}, Objective-C, Fortran, minimal, and assembly, this is
8839 simply the function's name @var{function} (and actually a special case
8840 of a valid expression). In Pascal and Modula-2, this is
8841 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
8842 (although the Pascal form also works).
8844 This form specifies the address of the function's first instruction,
8845 before the stack frame and arguments have been set up.
8847 @item '@var{filename}':@var{funcaddr}
8848 Like @var{funcaddr} above, but also specifies the name of the source
8849 file explicitly. This is useful if the name of the function does not
8850 specify the function unambiguously, e.g., if there are several
8851 functions with identical names in different source files.
8855 @section Editing Source Files
8856 @cindex editing source files
8859 @kindex e @r{(@code{edit})}
8860 To edit the lines in a source file, use the @code{edit} command.
8861 The editing program of your choice
8862 is invoked with the current line set to
8863 the active line in the program.
8864 Alternatively, there are several ways to specify what part of the file you
8865 want to print if you want to see other parts of the program:
8868 @item edit @var{location}
8869 Edit the source file specified by @code{location}. Editing starts at
8870 that @var{location}, e.g., at the specified source line of the
8871 specified file. @xref{Specify Location}, for all the possible forms
8872 of the @var{location} argument; here are the forms of the @code{edit}
8873 command most commonly used:
8876 @item edit @var{number}
8877 Edit the current source file with @var{number} as the active line number.
8879 @item edit @var{function}
8880 Edit the file containing @var{function} at the beginning of its definition.
8885 @subsection Choosing your Editor
8886 You can customize @value{GDBN} to use any editor you want
8888 The only restriction is that your editor (say @code{ex}), recognizes the
8889 following command-line syntax:
8891 ex +@var{number} file
8893 The optional numeric value +@var{number} specifies the number of the line in
8894 the file where to start editing.}.
8895 By default, it is @file{@value{EDITOR}}, but you can change this
8896 by setting the environment variable @code{EDITOR} before using
8897 @value{GDBN}. For example, to configure @value{GDBN} to use the
8898 @code{vi} editor, you could use these commands with the @code{sh} shell:
8904 or in the @code{csh} shell,
8906 setenv EDITOR /usr/bin/vi
8911 @section Searching Source Files
8912 @cindex searching source files
8914 There are two commands for searching through the current source file for a
8919 @kindex forward-search
8920 @kindex fo @r{(@code{forward-search})}
8921 @item forward-search @var{regexp}
8922 @itemx search @var{regexp}
8923 The command @samp{forward-search @var{regexp}} checks each line,
8924 starting with the one following the last line listed, for a match for
8925 @var{regexp}. It lists the line that is found. You can use the
8926 synonym @samp{search @var{regexp}} or abbreviate the command name as
8929 @kindex reverse-search
8930 @item reverse-search @var{regexp}
8931 The command @samp{reverse-search @var{regexp}} checks each line, starting
8932 with the one before the last line listed and going backward, for a match
8933 for @var{regexp}. It lists the line that is found. You can abbreviate
8934 this command as @code{rev}.
8938 @section Specifying Source Directories
8941 @cindex directories for source files
8942 Executable programs sometimes do not record the directories of the source
8943 files from which they were compiled, just the names. Even when they do,
8944 the directories could be moved between the compilation and your debugging
8945 session. @value{GDBN} has a list of directories to search for source files;
8946 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
8947 it tries all the directories in the list, in the order they are present
8948 in the list, until it finds a file with the desired name.
8950 For example, suppose an executable references the file
8951 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
8952 @file{/mnt/cross}. The file is first looked up literally; if this
8953 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
8954 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
8955 message is printed. @value{GDBN} does not look up the parts of the
8956 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
8957 Likewise, the subdirectories of the source path are not searched: if
8958 the source path is @file{/mnt/cross}, and the binary refers to
8959 @file{foo.c}, @value{GDBN} would not find it under
8960 @file{/mnt/cross/usr/src/foo-1.0/lib}.
8962 Plain file names, relative file names with leading directories, file
8963 names containing dots, etc.@: are all treated as described above; for
8964 instance, if the source path is @file{/mnt/cross}, and the source file
8965 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
8966 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
8967 that---@file{/mnt/cross/foo.c}.
8969 Note that the executable search path is @emph{not} used to locate the
8972 Whenever you reset or rearrange the source path, @value{GDBN} clears out
8973 any information it has cached about where source files are found and where
8974 each line is in the file.
8978 When you start @value{GDBN}, its source path includes only @samp{cdir}
8979 and @samp{cwd}, in that order.
8980 To add other directories, use the @code{directory} command.
8982 The search path is used to find both program source files and @value{GDBN}
8983 script files (read using the @samp{-command} option and @samp{source} command).
8985 In addition to the source path, @value{GDBN} provides a set of commands
8986 that manage a list of source path substitution rules. A @dfn{substitution
8987 rule} specifies how to rewrite source directories stored in the program's
8988 debug information in case the sources were moved to a different
8989 directory between compilation and debugging. A rule is made of
8990 two strings, the first specifying what needs to be rewritten in
8991 the path, and the second specifying how it should be rewritten.
8992 In @ref{set substitute-path}, we name these two parts @var{from} and
8993 @var{to} respectively. @value{GDBN} does a simple string replacement
8994 of @var{from} with @var{to} at the start of the directory part of the
8995 source file name, and uses that result instead of the original file
8996 name to look up the sources.
8998 Using the previous example, suppose the @file{foo-1.0} tree has been
8999 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
9000 @value{GDBN} to replace @file{/usr/src} in all source path names with
9001 @file{/mnt/cross}. The first lookup will then be
9002 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
9003 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
9004 substitution rule, use the @code{set substitute-path} command
9005 (@pxref{set substitute-path}).
9007 To avoid unexpected substitution results, a rule is applied only if the
9008 @var{from} part of the directory name ends at a directory separator.
9009 For instance, a rule substituting @file{/usr/source} into
9010 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
9011 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
9012 is applied only at the beginning of the directory name, this rule will
9013 not be applied to @file{/root/usr/source/baz.c} either.
9015 In many cases, you can achieve the same result using the @code{directory}
9016 command. However, @code{set substitute-path} can be more efficient in
9017 the case where the sources are organized in a complex tree with multiple
9018 subdirectories. With the @code{directory} command, you need to add each
9019 subdirectory of your project. If you moved the entire tree while
9020 preserving its internal organization, then @code{set substitute-path}
9021 allows you to direct the debugger to all the sources with one single
9024 @code{set substitute-path} is also more than just a shortcut command.
9025 The source path is only used if the file at the original location no
9026 longer exists. On the other hand, @code{set substitute-path} modifies
9027 the debugger behavior to look at the rewritten location instead. So, if
9028 for any reason a source file that is not relevant to your executable is
9029 located at the original location, a substitution rule is the only
9030 method available to point @value{GDBN} at the new location.
9032 @cindex @samp{--with-relocated-sources}
9033 @cindex default source path substitution
9034 You can configure a default source path substitution rule by
9035 configuring @value{GDBN} with the
9036 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
9037 should be the name of a directory under @value{GDBN}'s configured
9038 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
9039 directory names in debug information under @var{dir} will be adjusted
9040 automatically if the installed @value{GDBN} is moved to a new
9041 location. This is useful if @value{GDBN}, libraries or executables
9042 with debug information and corresponding source code are being moved
9046 @item directory @var{dirname} @dots{}
9047 @item dir @var{dirname} @dots{}
9048 Add directory @var{dirname} to the front of the source path. Several
9049 directory names may be given to this command, separated by @samp{:}
9050 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
9051 part of absolute file names) or
9052 whitespace. You may specify a directory that is already in the source
9053 path; this moves it forward, so @value{GDBN} searches it sooner.
9057 @vindex $cdir@r{, convenience variable}
9058 @vindex $cwd@r{, convenience variable}
9059 @cindex compilation directory
9060 @cindex current directory
9061 @cindex working directory
9062 @cindex directory, current
9063 @cindex directory, compilation
9064 You can use the string @samp{$cdir} to refer to the compilation
9065 directory (if one is recorded), and @samp{$cwd} to refer to the current
9066 working directory. @samp{$cwd} is not the same as @samp{.}---the former
9067 tracks the current working directory as it changes during your @value{GDBN}
9068 session, while the latter is immediately expanded to the current
9069 directory at the time you add an entry to the source path.
9072 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
9074 @c RET-repeat for @code{directory} is explicitly disabled, but since
9075 @c repeating it would be a no-op we do not say that. (thanks to RMS)
9077 @item set directories @var{path-list}
9078 @kindex set directories
9079 Set the source path to @var{path-list}.
9080 @samp{$cdir:$cwd} are added if missing.
9082 @item show directories
9083 @kindex show directories
9084 Print the source path: show which directories it contains.
9086 @anchor{set substitute-path}
9087 @item set substitute-path @var{from} @var{to}
9088 @kindex set substitute-path
9089 Define a source path substitution rule, and add it at the end of the
9090 current list of existing substitution rules. If a rule with the same
9091 @var{from} was already defined, then the old rule is also deleted.
9093 For example, if the file @file{/foo/bar/baz.c} was moved to
9094 @file{/mnt/cross/baz.c}, then the command
9097 (@value{GDBP}) set substitute-path /foo/bar /mnt/cross
9101 will tell @value{GDBN} to replace @samp{/foo/bar} with
9102 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
9103 @file{baz.c} even though it was moved.
9105 In the case when more than one substitution rule have been defined,
9106 the rules are evaluated one by one in the order where they have been
9107 defined. The first one matching, if any, is selected to perform
9110 For instance, if we had entered the following commands:
9113 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
9114 (@value{GDBP}) set substitute-path /usr/src /mnt/src
9118 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
9119 @file{/mnt/include/defs.h} by using the first rule. However, it would
9120 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
9121 @file{/mnt/src/lib/foo.c}.
9124 @item unset substitute-path [path]
9125 @kindex unset substitute-path
9126 If a path is specified, search the current list of substitution rules
9127 for a rule that would rewrite that path. Delete that rule if found.
9128 A warning is emitted by the debugger if no rule could be found.
9130 If no path is specified, then all substitution rules are deleted.
9132 @item show substitute-path [path]
9133 @kindex show substitute-path
9134 If a path is specified, then print the source path substitution rule
9135 which would rewrite that path, if any.
9137 If no path is specified, then print all existing source path substitution
9142 If your source path is cluttered with directories that are no longer of
9143 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
9144 versions of source. You can correct the situation as follows:
9148 Use @code{directory} with no argument to reset the source path to its default value.
9151 Use @code{directory} with suitable arguments to reinstall the
9152 directories you want in the source path. You can add all the
9153 directories in one command.
9157 @section Source and Machine Code
9158 @cindex source line and its code address
9160 You can use the command @code{info line} to map source lines to program
9161 addresses (and vice versa), and the command @code{disassemble} to display
9162 a range of addresses as machine instructions. You can use the command
9163 @code{set disassemble-next-line} to set whether to disassemble next
9164 source line when execution stops. When run under @sc{gnu} Emacs
9165 mode, the @code{info line} command causes the arrow to point to the
9166 line specified. Also, @code{info line} prints addresses in symbolic form as
9172 @itemx info line @var{location}
9173 Print the starting and ending addresses of the compiled code for
9174 source line @var{location}. You can specify source lines in any of
9175 the ways documented in @ref{Specify Location}. With no @var{location}
9176 information about the current source line is printed.
9179 For example, we can use @code{info line} to discover the location of
9180 the object code for the first line of function
9181 @code{m4_changequote}:
9184 (@value{GDBP}) info line m4_changequote
9185 Line 895 of "builtin.c" starts at pc 0x634c <m4_changequote> and \
9186 ends at 0x6350 <m4_changequote+4>.
9190 @cindex code address and its source line
9191 We can also inquire (using @code{*@var{addr}} as the form for
9192 @var{location}) what source line covers a particular address:
9194 (@value{GDBP}) info line *0x63ff
9195 Line 926 of "builtin.c" starts at pc 0x63e4 <m4_changequote+152> and \
9196 ends at 0x6404 <m4_changequote+184>.
9199 @cindex @code{$_} and @code{info line}
9200 @cindex @code{x} command, default address
9201 @kindex x@r{(examine), and} info line
9202 After @code{info line}, the default address for the @code{x} command
9203 is changed to the starting address of the line, so that @samp{x/i} is
9204 sufficient to begin examining the machine code (@pxref{Memory,
9205 ,Examining Memory}). Also, this address is saved as the value of the
9206 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
9209 @cindex info line, repeated calls
9210 After @code{info line}, using @code{info line} again without
9211 specifying a location will display information about the next source
9216 @cindex assembly instructions
9217 @cindex instructions, assembly
9218 @cindex machine instructions
9219 @cindex listing machine instructions
9221 @itemx disassemble /m
9222 @itemx disassemble /s
9223 @itemx disassemble /r
9224 This specialized command dumps a range of memory as machine
9225 instructions. It can also print mixed source+disassembly by specifying
9226 the @code{/m} or @code{/s} modifier and print the raw instructions in hex
9227 as well as in symbolic form by specifying the @code{/r} modifier.
9228 The default memory range is the function surrounding the
9229 program counter of the selected frame. A single argument to this
9230 command is a program counter value; @value{GDBN} dumps the function
9231 surrounding this value. When two arguments are given, they should
9232 be separated by a comma, possibly surrounded by whitespace. The
9233 arguments specify a range of addresses to dump, in one of two forms:
9236 @item @var{start},@var{end}
9237 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
9238 @item @var{start},+@var{length}
9239 the addresses from @var{start} (inclusive) to
9240 @code{@var{start}+@var{length}} (exclusive).
9244 When 2 arguments are specified, the name of the function is also
9245 printed (since there could be several functions in the given range).
9247 The argument(s) can be any expression yielding a numeric value, such as
9248 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
9250 If the range of memory being disassembled contains current program counter,
9251 the instruction at that location is shown with a @code{=>} marker.
9254 The following example shows the disassembly of a range of addresses of
9255 HP PA-RISC 2.0 code:
9258 (@value{GDBP}) disas 0x32c4, 0x32e4
9259 Dump of assembler code from 0x32c4 to 0x32e4:
9260 0x32c4 <main+204>: addil 0,dp
9261 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
9262 0x32cc <main+212>: ldil 0x3000,r31
9263 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
9264 0x32d4 <main+220>: ldo 0(r31),rp
9265 0x32d8 <main+224>: addil -0x800,dp
9266 0x32dc <main+228>: ldo 0x588(r1),r26
9267 0x32e0 <main+232>: ldil 0x3000,r31
9268 End of assembler dump.
9271 Here is an example showing mixed source+assembly for Intel x86
9272 with @code{/m} or @code{/s}, when the program is stopped just after
9273 function prologue in a non-optimized function with no inline code.
9276 (@value{GDBP}) disas /m main
9277 Dump of assembler code for function main:
9279 0x08048330 <+0>: push %ebp
9280 0x08048331 <+1>: mov %esp,%ebp
9281 0x08048333 <+3>: sub $0x8,%esp
9282 0x08048336 <+6>: and $0xfffffff0,%esp
9283 0x08048339 <+9>: sub $0x10,%esp
9285 6 printf ("Hello.\n");
9286 => 0x0804833c <+12>: movl $0x8048440,(%esp)
9287 0x08048343 <+19>: call 0x8048284 <puts@@plt>
9291 0x08048348 <+24>: mov $0x0,%eax
9292 0x0804834d <+29>: leave
9293 0x0804834e <+30>: ret
9295 End of assembler dump.
9298 The @code{/m} option is deprecated as its output is not useful when
9299 there is either inlined code or re-ordered code.
9300 The @code{/s} option is the preferred choice.
9301 Here is an example for AMD x86-64 showing the difference between
9302 @code{/m} output and @code{/s} output.
9303 This example has one inline function defined in a header file,
9304 and the code is compiled with @samp{-O2} optimization.
9305 Note how the @code{/m} output is missing the disassembly of
9306 several instructions that are present in the @code{/s} output.
9336 (@value{GDBP}) disas /m main
9337 Dump of assembler code for function main:
9341 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
9342 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
9346 0x000000000040041d <+29>: xor %eax,%eax
9347 0x000000000040041f <+31>: retq
9348 0x0000000000400420 <+32>: add %eax,%eax
9349 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
9351 End of assembler dump.
9352 (@value{GDBP}) disas /s main
9353 Dump of assembler code for function main:
9357 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
9361 0x0000000000400406 <+6>: test %eax,%eax
9362 0x0000000000400408 <+8>: js 0x400420 <main+32>
9367 0x000000000040040a <+10>: lea 0xa(%rax),%edx
9368 0x000000000040040d <+13>: test %eax,%eax
9369 0x000000000040040f <+15>: mov $0x1,%eax
9370 0x0000000000400414 <+20>: cmovne %edx,%eax
9374 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
9378 0x000000000040041d <+29>: xor %eax,%eax
9379 0x000000000040041f <+31>: retq
9383 0x0000000000400420 <+32>: add %eax,%eax
9384 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
9385 End of assembler dump.
9388 Here is another example showing raw instructions in hex for AMD x86-64,
9391 (gdb) disas /r 0x400281,+10
9392 Dump of assembler code from 0x400281 to 0x40028b:
9393 0x0000000000400281: 38 36 cmp %dh,(%rsi)
9394 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
9395 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
9396 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
9397 End of assembler dump.
9400 Addresses cannot be specified as a location (@pxref{Specify Location}).
9401 So, for example, if you want to disassemble function @code{bar}
9402 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
9403 and not @samp{disassemble foo.c:bar}.
9405 Some architectures have more than one commonly-used set of instruction
9406 mnemonics or other syntax.
9408 For programs that were dynamically linked and use shared libraries,
9409 instructions that call functions or branch to locations in the shared
9410 libraries might show a seemingly bogus location---it's actually a
9411 location of the relocation table. On some architectures, @value{GDBN}
9412 might be able to resolve these to actual function names.
9415 @kindex set disassembler-options
9416 @cindex disassembler options
9417 @item set disassembler-options @var{option1}[,@var{option2}@dots{}]
9418 This command controls the passing of target specific information to
9419 the disassembler. For a list of valid options, please refer to the
9420 @code{-M}/@code{--disassembler-options} section of the @samp{objdump}
9421 manual and/or the output of @kbd{objdump --help}
9422 (@pxref{objdump,,objdump,binutils,The GNU Binary Utilities}).
9423 The default value is the empty string.
9425 If it is necessary to specify more than one disassembler option, then
9426 multiple options can be placed together into a comma separated list.
9427 Currently this command is only supported on targets ARM, MIPS, PowerPC
9430 @kindex show disassembler-options
9431 @item show disassembler-options
9432 Show the current setting of the disassembler options.
9436 @kindex set disassembly-flavor
9437 @cindex Intel disassembly flavor
9438 @cindex AT&T disassembly flavor
9439 @item set disassembly-flavor @var{instruction-set}
9440 Select the instruction set to use when disassembling the
9441 program via the @code{disassemble} or @code{x/i} commands.
9443 Currently this command is only defined for the Intel x86 family. You
9444 can set @var{instruction-set} to either @code{intel} or @code{att}.
9445 The default is @code{att}, the AT&T flavor used by default by Unix
9446 assemblers for x86-based targets.
9448 @kindex show disassembly-flavor
9449 @item show disassembly-flavor
9450 Show the current setting of the disassembly flavor.
9454 @kindex set disassemble-next-line
9455 @kindex show disassemble-next-line
9456 @item set disassemble-next-line
9457 @itemx show disassemble-next-line
9458 Control whether or not @value{GDBN} will disassemble the next source
9459 line or instruction when execution stops. If ON, @value{GDBN} will
9460 display disassembly of the next source line when execution of the
9461 program being debugged stops. This is @emph{in addition} to
9462 displaying the source line itself, which @value{GDBN} always does if
9463 possible. If the next source line cannot be displayed for some reason
9464 (e.g., if @value{GDBN} cannot find the source file, or there's no line
9465 info in the debug info), @value{GDBN} will display disassembly of the
9466 next @emph{instruction} instead of showing the next source line. If
9467 AUTO, @value{GDBN} will display disassembly of next instruction only
9468 if the source line cannot be displayed. This setting causes
9469 @value{GDBN} to display some feedback when you step through a function
9470 with no line info or whose source file is unavailable. The default is
9471 OFF, which means never display the disassembly of the next line or
9477 @chapter Examining Data
9479 @cindex printing data
9480 @cindex examining data
9483 The usual way to examine data in your program is with the @code{print}
9484 command (abbreviated @code{p}), or its synonym @code{inspect}. It
9485 evaluates and prints the value of an expression of the language your
9486 program is written in (@pxref{Languages, ,Using @value{GDBN} with
9487 Different Languages}). It may also print the expression using a
9488 Python-based pretty-printer (@pxref{Pretty Printing}).
9491 @item print [[@var{options}] --] @var{expr}
9492 @itemx print [[@var{options}] --] /@var{f} @var{expr}
9493 @var{expr} is an expression (in the source language). By default the
9494 value of @var{expr} is printed in a format appropriate to its data type;
9495 you can choose a different format by specifying @samp{/@var{f}}, where
9496 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
9499 @anchor{print options}
9500 The @code{print} command supports a number of options that allow
9501 overriding relevant global print settings as set by @code{set print}
9505 @item -address [@code{on}|@code{off}]
9506 Set printing of addresses.
9507 Related setting: @ref{set print address}.
9509 @item -array [@code{on}|@code{off}]
9510 Pretty formatting of arrays.
9511 Related setting: @ref{set print array}.
9513 @item -array-indexes [@code{on}|@code{off}]
9514 Set printing of array indexes.
9515 Related setting: @ref{set print array-indexes}.
9517 @item -elements @var{number-of-elements}|@code{unlimited}
9518 Set limit on string chars or array elements to print. The value
9519 @code{unlimited} causes there to be no limit. Related setting:
9520 @ref{set print elements}.
9522 @item -max-depth @var{depth}|@code{unlimited}
9523 Set the threshold after which nested structures are replaced with
9524 ellipsis. Related setting: @ref{set print max-depth}.
9526 @item -null-stop [@code{on}|@code{off}]
9527 Set printing of char arrays to stop at first null char. Related
9528 setting: @ref{set print null-stop}.
9530 @item -object [@code{on}|@code{off}]
9531 Set printing C@t{++} virtual function tables. Related setting:
9532 @ref{set print object}.
9534 @item -pretty [@code{on}|@code{off}]
9535 Set pretty formatting of structures. Related setting: @ref{set print
9538 @item -repeats @var{number-of-repeats}|@code{unlimited}
9539 Set threshold for repeated print elements. @code{unlimited} causes
9540 all elements to be individually printed. Related setting: @ref{set
9543 @item -static-members [@code{on}|@code{off}]
9544 Set printing C@t{++} static members. Related setting: @ref{set print
9547 @item -symbol [@code{on}|@code{off}]
9548 Set printing of symbol names when printing pointers. Related setting:
9549 @ref{set print symbol}.
9551 @item -union [@code{on}|@code{off}]
9552 Set printing of unions interior to structures. Related setting:
9553 @ref{set print union}.
9555 @item -vtbl [@code{on}|@code{off}]
9556 Set printing of C++ virtual function tables. Related setting:
9557 @ref{set print vtbl}.
9560 Because the @code{print} command accepts arbitrary expressions which
9561 may look like options (including abbreviations), if you specify any
9562 command option, then you must use a double dash (@code{--}) to mark
9563 the end of option processing.
9565 For example, this prints the value of the @code{-r} expression:
9568 (@value{GDBP}) print -r
9571 While this repeats the last value in the value history (see below)
9572 with the @code{-raw} option in effect:
9575 (@value{GDBP}) print -r --
9578 Here is an example including both on option and an expression:
9582 (@value{GDBP}) print -pretty -- *myptr
9594 @item print [@var{options}]
9595 @itemx print [@var{options}] /@var{f}
9596 @cindex reprint the last value
9597 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
9598 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
9599 conveniently inspect the same value in an alternative format.
9602 A more low-level way of examining data is with the @code{x} command.
9603 It examines data in memory at a specified address and prints it in a
9604 specified format. @xref{Memory, ,Examining Memory}.
9606 If you are interested in information about types, or about how the
9607 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
9608 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
9611 @cindex exploring hierarchical data structures
9613 Another way of examining values of expressions and type information is
9614 through the Python extension command @code{explore} (available only if
9615 the @value{GDBN} build is configured with @code{--with-python}). It
9616 offers an interactive way to start at the highest level (or, the most
9617 abstract level) of the data type of an expression (or, the data type
9618 itself) and explore all the way down to leaf scalar values/fields
9619 embedded in the higher level data types.
9622 @item explore @var{arg}
9623 @var{arg} is either an expression (in the source language), or a type
9624 visible in the current context of the program being debugged.
9627 The working of the @code{explore} command can be illustrated with an
9628 example. If a data type @code{struct ComplexStruct} is defined in your
9638 struct ComplexStruct
9640 struct SimpleStruct *ss_p;
9646 followed by variable declarations as
9649 struct SimpleStruct ss = @{ 10, 1.11 @};
9650 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
9654 then, the value of the variable @code{cs} can be explored using the
9655 @code{explore} command as follows.
9659 The value of `cs' is a struct/class of type `struct ComplexStruct' with
9660 the following fields:
9662 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
9663 arr = <Enter 1 to explore this field of type `int [10]'>
9665 Enter the field number of choice:
9669 Since the fields of @code{cs} are not scalar values, you are being
9670 prompted to chose the field you want to explore. Let's say you choose
9671 the field @code{ss_p} by entering @code{0}. Then, since this field is a
9672 pointer, you will be asked if it is pointing to a single value. From
9673 the declaration of @code{cs} above, it is indeed pointing to a single
9674 value, hence you enter @code{y}. If you enter @code{n}, then you will
9675 be asked if it were pointing to an array of values, in which case this
9676 field will be explored as if it were an array.
9679 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
9680 Continue exploring it as a pointer to a single value [y/n]: y
9681 The value of `*(cs.ss_p)' is a struct/class of type `struct
9682 SimpleStruct' with the following fields:
9684 i = 10 .. (Value of type `int')
9685 d = 1.1100000000000001 .. (Value of type `double')
9687 Press enter to return to parent value:
9691 If the field @code{arr} of @code{cs} was chosen for exploration by
9692 entering @code{1} earlier, then since it is as array, you will be
9693 prompted to enter the index of the element in the array that you want
9697 `cs.arr' is an array of `int'.
9698 Enter the index of the element you want to explore in `cs.arr': 5
9700 `(cs.arr)[5]' is a scalar value of type `int'.
9704 Press enter to return to parent value:
9707 In general, at any stage of exploration, you can go deeper towards the
9708 leaf values by responding to the prompts appropriately, or hit the
9709 return key to return to the enclosing data structure (the @i{higher}
9710 level data structure).
9712 Similar to exploring values, you can use the @code{explore} command to
9713 explore types. Instead of specifying a value (which is typically a
9714 variable name or an expression valid in the current context of the
9715 program being debugged), you specify a type name. If you consider the
9716 same example as above, your can explore the type
9717 @code{struct ComplexStruct} by passing the argument
9718 @code{struct ComplexStruct} to the @code{explore} command.
9721 (gdb) explore struct ComplexStruct
9725 By responding to the prompts appropriately in the subsequent interactive
9726 session, you can explore the type @code{struct ComplexStruct} in a
9727 manner similar to how the value @code{cs} was explored in the above
9730 The @code{explore} command also has two sub-commands,
9731 @code{explore value} and @code{explore type}. The former sub-command is
9732 a way to explicitly specify that value exploration of the argument is
9733 being invoked, while the latter is a way to explicitly specify that type
9734 exploration of the argument is being invoked.
9737 @item explore value @var{expr}
9738 @cindex explore value
9739 This sub-command of @code{explore} explores the value of the
9740 expression @var{expr} (if @var{expr} is an expression valid in the
9741 current context of the program being debugged). The behavior of this
9742 command is identical to that of the behavior of the @code{explore}
9743 command being passed the argument @var{expr}.
9745 @item explore type @var{arg}
9746 @cindex explore type
9747 This sub-command of @code{explore} explores the type of @var{arg} (if
9748 @var{arg} is a type visible in the current context of program being
9749 debugged), or the type of the value/expression @var{arg} (if @var{arg}
9750 is an expression valid in the current context of the program being
9751 debugged). If @var{arg} is a type, then the behavior of this command is
9752 identical to that of the @code{explore} command being passed the
9753 argument @var{arg}. If @var{arg} is an expression, then the behavior of
9754 this command will be identical to that of the @code{explore} command
9755 being passed the type of @var{arg} as the argument.
9759 * Expressions:: Expressions
9760 * Ambiguous Expressions:: Ambiguous Expressions
9761 * Variables:: Program variables
9762 * Arrays:: Artificial arrays
9763 * Output Formats:: Output formats
9764 * Memory:: Examining memory
9765 * Auto Display:: Automatic display
9766 * Print Settings:: Print settings
9767 * Pretty Printing:: Python pretty printing
9768 * Value History:: Value history
9769 * Convenience Vars:: Convenience variables
9770 * Convenience Funs:: Convenience functions
9771 * Registers:: Registers
9772 * Floating Point Hardware:: Floating point hardware
9773 * Vector Unit:: Vector Unit
9774 * OS Information:: Auxiliary data provided by operating system
9775 * Memory Region Attributes:: Memory region attributes
9776 * Dump/Restore Files:: Copy between memory and a file
9777 * Core File Generation:: Cause a program dump its core
9778 * Character Sets:: Debugging programs that use a different
9779 character set than GDB does
9780 * Caching Target Data:: Data caching for targets
9781 * Searching Memory:: Searching memory for a sequence of bytes
9782 * Value Sizes:: Managing memory allocated for values
9786 @section Expressions
9789 @code{print} and many other @value{GDBN} commands accept an expression and
9790 compute its value. Any kind of constant, variable or operator defined
9791 by the programming language you are using is valid in an expression in
9792 @value{GDBN}. This includes conditional expressions, function calls,
9793 casts, and string constants. It also includes preprocessor macros, if
9794 you compiled your program to include this information; see
9797 @cindex arrays in expressions
9798 @value{GDBN} supports array constants in expressions input by
9799 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
9800 you can use the command @code{print @{1, 2, 3@}} to create an array
9801 of three integers. If you pass an array to a function or assign it
9802 to a program variable, @value{GDBN} copies the array to memory that
9803 is @code{malloc}ed in the target program.
9805 Because C is so widespread, most of the expressions shown in examples in
9806 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
9807 Languages}, for information on how to use expressions in other
9810 In this section, we discuss operators that you can use in @value{GDBN}
9811 expressions regardless of your programming language.
9813 @cindex casts, in expressions
9814 Casts are supported in all languages, not just in C, because it is so
9815 useful to cast a number into a pointer in order to examine a structure
9816 at that address in memory.
9817 @c FIXME: casts supported---Mod2 true?
9819 @value{GDBN} supports these operators, in addition to those common
9820 to programming languages:
9824 @samp{@@} is a binary operator for treating parts of memory as arrays.
9825 @xref{Arrays, ,Artificial Arrays}, for more information.
9828 @samp{::} allows you to specify a variable in terms of the file or
9829 function where it is defined. @xref{Variables, ,Program Variables}.
9831 @cindex @{@var{type}@}
9832 @cindex type casting memory
9833 @cindex memory, viewing as typed object
9834 @cindex casts, to view memory
9835 @item @{@var{type}@} @var{addr}
9836 Refers to an object of type @var{type} stored at address @var{addr} in
9837 memory. The address @var{addr} may be any expression whose value is
9838 an integer or pointer (but parentheses are required around binary
9839 operators, just as in a cast). This construct is allowed regardless
9840 of what kind of data is normally supposed to reside at @var{addr}.
9843 @node Ambiguous Expressions
9844 @section Ambiguous Expressions
9845 @cindex ambiguous expressions
9847 Expressions can sometimes contain some ambiguous elements. For instance,
9848 some programming languages (notably Ada, C@t{++} and Objective-C) permit
9849 a single function name to be defined several times, for application in
9850 different contexts. This is called @dfn{overloading}. Another example
9851 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
9852 templates and is typically instantiated several times, resulting in
9853 the same function name being defined in different contexts.
9855 In some cases and depending on the language, it is possible to adjust
9856 the expression to remove the ambiguity. For instance in C@t{++}, you
9857 can specify the signature of the function you want to break on, as in
9858 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
9859 qualified name of your function often makes the expression unambiguous
9862 When an ambiguity that needs to be resolved is detected, the debugger
9863 has the capability to display a menu of numbered choices for each
9864 possibility, and then waits for the selection with the prompt @samp{>}.
9865 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
9866 aborts the current command. If the command in which the expression was
9867 used allows more than one choice to be selected, the next option in the
9868 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
9871 For example, the following session excerpt shows an attempt to set a
9872 breakpoint at the overloaded symbol @code{String::after}.
9873 We choose three particular definitions of that function name:
9875 @c FIXME! This is likely to change to show arg type lists, at least
9878 (@value{GDBP}) b String::after
9881 [2] file:String.cc; line number:867
9882 [3] file:String.cc; line number:860
9883 [4] file:String.cc; line number:875
9884 [5] file:String.cc; line number:853
9885 [6] file:String.cc; line number:846
9886 [7] file:String.cc; line number:735
9888 Breakpoint 1 at 0xb26c: file String.cc, line 867.
9889 Breakpoint 2 at 0xb344: file String.cc, line 875.
9890 Breakpoint 3 at 0xafcc: file String.cc, line 846.
9891 Multiple breakpoints were set.
9892 Use the "delete" command to delete unwanted
9899 @kindex set multiple-symbols
9900 @item set multiple-symbols @var{mode}
9901 @cindex multiple-symbols menu
9903 This option allows you to adjust the debugger behavior when an expression
9906 By default, @var{mode} is set to @code{all}. If the command with which
9907 the expression is used allows more than one choice, then @value{GDBN}
9908 automatically selects all possible choices. For instance, inserting
9909 a breakpoint on a function using an ambiguous name results in a breakpoint
9910 inserted on each possible match. However, if a unique choice must be made,
9911 then @value{GDBN} uses the menu to help you disambiguate the expression.
9912 For instance, printing the address of an overloaded function will result
9913 in the use of the menu.
9915 When @var{mode} is set to @code{ask}, the debugger always uses the menu
9916 when an ambiguity is detected.
9918 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
9919 an error due to the ambiguity and the command is aborted.
9921 @kindex show multiple-symbols
9922 @item show multiple-symbols
9923 Show the current value of the @code{multiple-symbols} setting.
9927 @section Program Variables
9929 The most common kind of expression to use is the name of a variable
9932 Variables in expressions are understood in the selected stack frame
9933 (@pxref{Selection, ,Selecting a Frame}); they must be either:
9937 global (or file-static)
9944 visible according to the scope rules of the
9945 programming language from the point of execution in that frame
9948 @noindent This means that in the function
9963 you can examine and use the variable @code{a} whenever your program is
9964 executing within the function @code{foo}, but you can only use or
9965 examine the variable @code{b} while your program is executing inside
9966 the block where @code{b} is declared.
9968 @cindex variable name conflict
9969 There is an exception: you can refer to a variable or function whose
9970 scope is a single source file even if the current execution point is not
9971 in this file. But it is possible to have more than one such variable or
9972 function with the same name (in different source files). If that
9973 happens, referring to that name has unpredictable effects. If you wish,
9974 you can specify a static variable in a particular function or file by
9975 using the colon-colon (@code{::}) notation:
9977 @cindex colon-colon, context for variables/functions
9979 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
9980 @cindex @code{::}, context for variables/functions
9983 @var{file}::@var{variable}
9984 @var{function}::@var{variable}
9988 Here @var{file} or @var{function} is the name of the context for the
9989 static @var{variable}. In the case of file names, you can use quotes to
9990 make sure @value{GDBN} parses the file name as a single word---for example,
9991 to print a global value of @code{x} defined in @file{f2.c}:
9994 (@value{GDBP}) p 'f2.c'::x
9997 The @code{::} notation is normally used for referring to
9998 static variables, since you typically disambiguate uses of local variables
9999 in functions by selecting the appropriate frame and using the
10000 simple name of the variable. However, you may also use this notation
10001 to refer to local variables in frames enclosing the selected frame:
10010 process (a); /* Stop here */
10021 For example, if there is a breakpoint at the commented line,
10022 here is what you might see
10023 when the program stops after executing the call @code{bar(0)}:
10028 (@value{GDBP}) p bar::a
10030 (@value{GDBP}) up 2
10031 #2 0x080483d0 in foo (a=5) at foobar.c:12
10034 (@value{GDBP}) p bar::a
10038 @cindex C@t{++} scope resolution
10039 These uses of @samp{::} are very rarely in conflict with the very
10040 similar use of the same notation in C@t{++}. When they are in
10041 conflict, the C@t{++} meaning takes precedence; however, this can be
10042 overridden by quoting the file or function name with single quotes.
10044 For example, suppose the program is stopped in a method of a class
10045 that has a field named @code{includefile}, and there is also an
10046 include file named @file{includefile} that defines a variable,
10047 @code{some_global}.
10050 (@value{GDBP}) p includefile
10052 (@value{GDBP}) p includefile::some_global
10053 A syntax error in expression, near `'.
10054 (@value{GDBP}) p 'includefile'::some_global
10058 @cindex wrong values
10059 @cindex variable values, wrong
10060 @cindex function entry/exit, wrong values of variables
10061 @cindex optimized code, wrong values of variables
10063 @emph{Warning:} Occasionally, a local variable may appear to have the
10064 wrong value at certain points in a function---just after entry to a new
10065 scope, and just before exit.
10067 You may see this problem when you are stepping by machine instructions.
10068 This is because, on most machines, it takes more than one instruction to
10069 set up a stack frame (including local variable definitions); if you are
10070 stepping by machine instructions, variables may appear to have the wrong
10071 values until the stack frame is completely built. On exit, it usually
10072 also takes more than one machine instruction to destroy a stack frame;
10073 after you begin stepping through that group of instructions, local
10074 variable definitions may be gone.
10076 This may also happen when the compiler does significant optimizations.
10077 To be sure of always seeing accurate values, turn off all optimization
10080 @cindex ``No symbol "foo" in current context''
10081 Another possible effect of compiler optimizations is to optimize
10082 unused variables out of existence, or assign variables to registers (as
10083 opposed to memory addresses). Depending on the support for such cases
10084 offered by the debug info format used by the compiler, @value{GDBN}
10085 might not be able to display values for such local variables. If that
10086 happens, @value{GDBN} will print a message like this:
10089 No symbol "foo" in current context.
10092 To solve such problems, either recompile without optimizations, or use a
10093 different debug info format, if the compiler supports several such
10094 formats. @xref{Compilation}, for more information on choosing compiler
10095 options. @xref{C, ,C and C@t{++}}, for more information about debug
10096 info formats that are best suited to C@t{++} programs.
10098 If you ask to print an object whose contents are unknown to
10099 @value{GDBN}, e.g., because its data type is not completely specified
10100 by the debug information, @value{GDBN} will say @samp{<incomplete
10101 type>}. @xref{Symbols, incomplete type}, for more about this.
10103 @cindex no debug info variables
10104 If you try to examine or use the value of a (global) variable for
10105 which @value{GDBN} has no type information, e.g., because the program
10106 includes no debug information, @value{GDBN} displays an error message.
10107 @xref{Symbols, unknown type}, for more about unknown types. If you
10108 cast the variable to its declared type, @value{GDBN} gets the
10109 variable's value using the cast-to type as the variable's type. For
10110 example, in a C program:
10113 (@value{GDBP}) p var
10114 'var' has unknown type; cast it to its declared type
10115 (@value{GDBP}) p (float) var
10119 If you append @kbd{@@entry} string to a function parameter name you get its
10120 value at the time the function got called. If the value is not available an
10121 error message is printed. Entry values are available only with some compilers.
10122 Entry values are normally also printed at the function parameter list according
10123 to @ref{set print entry-values}.
10126 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
10132 (gdb) print i@@entry
10136 Strings are identified as arrays of @code{char} values without specified
10137 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
10138 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
10139 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
10140 defines literal string type @code{"char"} as @code{char} without a sign.
10145 signed char var1[] = "A";
10148 You get during debugging
10153 $2 = @{65 'A', 0 '\0'@}
10157 @section Artificial Arrays
10159 @cindex artificial array
10161 @kindex @@@r{, referencing memory as an array}
10162 It is often useful to print out several successive objects of the
10163 same type in memory; a section of an array, or an array of
10164 dynamically determined size for which only a pointer exists in the
10167 You can do this by referring to a contiguous span of memory as an
10168 @dfn{artificial array}, using the binary operator @samp{@@}. The left
10169 operand of @samp{@@} should be the first element of the desired array
10170 and be an individual object. The right operand should be the desired length
10171 of the array. The result is an array value whose elements are all of
10172 the type of the left argument. The first element is actually the left
10173 argument; the second element comes from bytes of memory immediately
10174 following those that hold the first element, and so on. Here is an
10175 example. If a program says
10178 int *array = (int *) malloc (len * sizeof (int));
10182 you can print the contents of @code{array} with
10188 The left operand of @samp{@@} must reside in memory. Array values made
10189 with @samp{@@} in this way behave just like other arrays in terms of
10190 subscripting, and are coerced to pointers when used in expressions.
10191 Artificial arrays most often appear in expressions via the value history
10192 (@pxref{Value History, ,Value History}), after printing one out.
10194 Another way to create an artificial array is to use a cast.
10195 This re-interprets a value as if it were an array.
10196 The value need not be in memory:
10198 (@value{GDBP}) p/x (short[2])0x12345678
10199 $1 = @{0x1234, 0x5678@}
10202 As a convenience, if you leave the array length out (as in
10203 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
10204 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
10206 (@value{GDBP}) p/x (short[])0x12345678
10207 $2 = @{0x1234, 0x5678@}
10210 Sometimes the artificial array mechanism is not quite enough; in
10211 moderately complex data structures, the elements of interest may not
10212 actually be adjacent---for example, if you are interested in the values
10213 of pointers in an array. One useful work-around in this situation is
10214 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
10215 Variables}) as a counter in an expression that prints the first
10216 interesting value, and then repeat that expression via @key{RET}. For
10217 instance, suppose you have an array @code{dtab} of pointers to
10218 structures, and you are interested in the values of a field @code{fv}
10219 in each structure. Here is an example of what you might type:
10229 @node Output Formats
10230 @section Output Formats
10232 @cindex formatted output
10233 @cindex output formats
10234 By default, @value{GDBN} prints a value according to its data type. Sometimes
10235 this is not what you want. For example, you might want to print a number
10236 in hex, or a pointer in decimal. Or you might want to view data in memory
10237 at a certain address as a character string or as an instruction. To do
10238 these things, specify an @dfn{output format} when you print a value.
10240 The simplest use of output formats is to say how to print a value
10241 already computed. This is done by starting the arguments of the
10242 @code{print} command with a slash and a format letter. The format
10243 letters supported are:
10247 Regard the bits of the value as an integer, and print the integer in
10251 Print as integer in signed decimal.
10254 Print as integer in unsigned decimal.
10257 Print as integer in octal.
10260 Print as integer in binary. The letter @samp{t} stands for ``two''.
10261 @footnote{@samp{b} cannot be used because these format letters are also
10262 used with the @code{x} command, where @samp{b} stands for ``byte'';
10263 see @ref{Memory,,Examining Memory}.}
10266 @cindex unknown address, locating
10267 @cindex locate address
10268 Print as an address, both absolute in hexadecimal and as an offset from
10269 the nearest preceding symbol. You can use this format used to discover
10270 where (in what function) an unknown address is located:
10273 (@value{GDBP}) p/a 0x54320
10274 $3 = 0x54320 <_initialize_vx+396>
10278 The command @code{info symbol 0x54320} yields similar results.
10279 @xref{Symbols, info symbol}.
10282 Regard as an integer and print it as a character constant. This
10283 prints both the numerical value and its character representation. The
10284 character representation is replaced with the octal escape @samp{\nnn}
10285 for characters outside the 7-bit @sc{ascii} range.
10287 Without this format, @value{GDBN} displays @code{char},
10288 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
10289 constants. Single-byte members of vectors are displayed as integer
10293 Regard the bits of the value as a floating point number and print
10294 using typical floating point syntax.
10297 @cindex printing strings
10298 @cindex printing byte arrays
10299 Regard as a string, if possible. With this format, pointers to single-byte
10300 data are displayed as null-terminated strings and arrays of single-byte data
10301 are displayed as fixed-length strings. Other values are displayed in their
10304 Without this format, @value{GDBN} displays pointers to and arrays of
10305 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
10306 strings. Single-byte members of a vector are displayed as an integer
10310 Like @samp{x} formatting, the value is treated as an integer and
10311 printed as hexadecimal, but leading zeros are printed to pad the value
10312 to the size of the integer type.
10315 @cindex raw printing
10316 Print using the @samp{raw} formatting. By default, @value{GDBN} will
10317 use a Python-based pretty-printer, if one is available (@pxref{Pretty
10318 Printing}). This typically results in a higher-level display of the
10319 value's contents. The @samp{r} format bypasses any Python
10320 pretty-printer which might exist.
10323 For example, to print the program counter in hex (@pxref{Registers}), type
10330 Note that no space is required before the slash; this is because command
10331 names in @value{GDBN} cannot contain a slash.
10333 To reprint the last value in the value history with a different format,
10334 you can use the @code{print} command with just a format and no
10335 expression. For example, @samp{p/x} reprints the last value in hex.
10338 @section Examining Memory
10340 You can use the command @code{x} (for ``examine'') to examine memory in
10341 any of several formats, independently of your program's data types.
10343 @cindex examining memory
10345 @kindex x @r{(examine memory)}
10346 @item x/@var{nfu} @var{addr}
10347 @itemx x @var{addr}
10349 Use the @code{x} command to examine memory.
10352 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
10353 much memory to display and how to format it; @var{addr} is an
10354 expression giving the address where you want to start displaying memory.
10355 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
10356 Several commands set convenient defaults for @var{addr}.
10359 @item @var{n}, the repeat count
10360 The repeat count is a decimal integer; the default is 1. It specifies
10361 how much memory (counting by units @var{u}) to display. If a negative
10362 number is specified, memory is examined backward from @var{addr}.
10363 @c This really is **decimal**; unaffected by 'set radix' as of GDB
10366 @item @var{f}, the display format
10367 The display format is one of the formats used by @code{print}
10368 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
10369 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
10370 The default is @samp{x} (hexadecimal) initially. The default changes
10371 each time you use either @code{x} or @code{print}.
10373 @item @var{u}, the unit size
10374 The unit size is any of
10380 Halfwords (two bytes).
10382 Words (four bytes). This is the initial default.
10384 Giant words (eight bytes).
10387 Each time you specify a unit size with @code{x}, that size becomes the
10388 default unit the next time you use @code{x}. For the @samp{i} format,
10389 the unit size is ignored and is normally not written. For the @samp{s} format,
10390 the unit size defaults to @samp{b}, unless it is explicitly given.
10391 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
10392 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
10393 Note that the results depend on the programming language of the
10394 current compilation unit. If the language is C, the @samp{s}
10395 modifier will use the UTF-16 encoding while @samp{w} will use
10396 UTF-32. The encoding is set by the programming language and cannot
10399 @item @var{addr}, starting display address
10400 @var{addr} is the address where you want @value{GDBN} to begin displaying
10401 memory. The expression need not have a pointer value (though it may);
10402 it is always interpreted as an integer address of a byte of memory.
10403 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
10404 @var{addr} is usually just after the last address examined---but several
10405 other commands also set the default address: @code{info breakpoints} (to
10406 the address of the last breakpoint listed), @code{info line} (to the
10407 starting address of a line), and @code{print} (if you use it to display
10408 a value from memory).
10411 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
10412 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
10413 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
10414 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
10415 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
10417 You can also specify a negative repeat count to examine memory backward
10418 from the given address. For example, @samp{x/-3uh 0x54320} prints three
10419 halfwords (@code{h}) at @code{0x54314}, @code{0x54328}, and @code{0x5431c}.
10421 Since the letters indicating unit sizes are all distinct from the
10422 letters specifying output formats, you do not have to remember whether
10423 unit size or format comes first; either order works. The output
10424 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
10425 (However, the count @var{n} must come first; @samp{wx4} does not work.)
10427 Even though the unit size @var{u} is ignored for the formats @samp{s}
10428 and @samp{i}, you might still want to use a count @var{n}; for example,
10429 @samp{3i} specifies that you want to see three machine instructions,
10430 including any operands. For convenience, especially when used with
10431 the @code{display} command, the @samp{i} format also prints branch delay
10432 slot instructions, if any, beyond the count specified, which immediately
10433 follow the last instruction that is within the count. The command
10434 @code{disassemble} gives an alternative way of inspecting machine
10435 instructions; see @ref{Machine Code,,Source and Machine Code}.
10437 If a negative repeat count is specified for the formats @samp{s} or @samp{i},
10438 the command displays null-terminated strings or instructions before the given
10439 address as many as the absolute value of the given number. For the @samp{i}
10440 format, we use line number information in the debug info to accurately locate
10441 instruction boundaries while disassembling backward. If line info is not
10442 available, the command stops examining memory with an error message.
10444 All the defaults for the arguments to @code{x} are designed to make it
10445 easy to continue scanning memory with minimal specifications each time
10446 you use @code{x}. For example, after you have inspected three machine
10447 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
10448 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
10449 the repeat count @var{n} is used again; the other arguments default as
10450 for successive uses of @code{x}.
10452 When examining machine instructions, the instruction at current program
10453 counter is shown with a @code{=>} marker. For example:
10456 (@value{GDBP}) x/5i $pc-6
10457 0x804837f <main+11>: mov %esp,%ebp
10458 0x8048381 <main+13>: push %ecx
10459 0x8048382 <main+14>: sub $0x4,%esp
10460 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
10461 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
10464 @cindex @code{$_}, @code{$__}, and value history
10465 The addresses and contents printed by the @code{x} command are not saved
10466 in the value history because there is often too much of them and they
10467 would get in the way. Instead, @value{GDBN} makes these values available for
10468 subsequent use in expressions as values of the convenience variables
10469 @code{$_} and @code{$__}. After an @code{x} command, the last address
10470 examined is available for use in expressions in the convenience variable
10471 @code{$_}. The contents of that address, as examined, are available in
10472 the convenience variable @code{$__}.
10474 If the @code{x} command has a repeat count, the address and contents saved
10475 are from the last memory unit printed; this is not the same as the last
10476 address printed if several units were printed on the last line of output.
10478 @anchor{addressable memory unit}
10479 @cindex addressable memory unit
10480 Most targets have an addressable memory unit size of 8 bits. This means
10481 that to each memory address are associated 8 bits of data. Some
10482 targets, however, have other addressable memory unit sizes.
10483 Within @value{GDBN} and this document, the term
10484 @dfn{addressable memory unit} (or @dfn{memory unit} for short) is used
10485 when explicitly referring to a chunk of data of that size. The word
10486 @dfn{byte} is used to refer to a chunk of data of 8 bits, regardless of
10487 the addressable memory unit size of the target. For most systems,
10488 addressable memory unit is a synonym of byte.
10490 @cindex remote memory comparison
10491 @cindex target memory comparison
10492 @cindex verify remote memory image
10493 @cindex verify target memory image
10494 When you are debugging a program running on a remote target machine
10495 (@pxref{Remote Debugging}), you may wish to verify the program's image
10496 in the remote machine's memory against the executable file you
10497 downloaded to the target. Or, on any target, you may want to check
10498 whether the program has corrupted its own read-only sections. The
10499 @code{compare-sections} command is provided for such situations.
10502 @kindex compare-sections
10503 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
10504 Compare the data of a loadable section @var{section-name} in the
10505 executable file of the program being debugged with the same section in
10506 the target machine's memory, and report any mismatches. With no
10507 arguments, compares all loadable sections. With an argument of
10508 @code{-r}, compares all loadable read-only sections.
10510 Note: for remote targets, this command can be accelerated if the
10511 target supports computing the CRC checksum of a block of memory
10512 (@pxref{qCRC packet}).
10516 @section Automatic Display
10517 @cindex automatic display
10518 @cindex display of expressions
10520 If you find that you want to print the value of an expression frequently
10521 (to see how it changes), you might want to add it to the @dfn{automatic
10522 display list} so that @value{GDBN} prints its value each time your program stops.
10523 Each expression added to the list is given a number to identify it;
10524 to remove an expression from the list, you specify that number.
10525 The automatic display looks like this:
10529 3: bar[5] = (struct hack *) 0x3804
10533 This display shows item numbers, expressions and their current values. As with
10534 displays you request manually using @code{x} or @code{print}, you can
10535 specify the output format you prefer; in fact, @code{display} decides
10536 whether to use @code{print} or @code{x} depending your format
10537 specification---it uses @code{x} if you specify either the @samp{i}
10538 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
10542 @item display @var{expr}
10543 Add the expression @var{expr} to the list of expressions to display
10544 each time your program stops. @xref{Expressions, ,Expressions}.
10546 @code{display} does not repeat if you press @key{RET} again after using it.
10548 @item display/@var{fmt} @var{expr}
10549 For @var{fmt} specifying only a display format and not a size or
10550 count, add the expression @var{expr} to the auto-display list but
10551 arrange to display it each time in the specified format @var{fmt}.
10552 @xref{Output Formats,,Output Formats}.
10554 @item display/@var{fmt} @var{addr}
10555 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
10556 number of units, add the expression @var{addr} as a memory address to
10557 be examined each time your program stops. Examining means in effect
10558 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
10561 For example, @samp{display/i $pc} can be helpful, to see the machine
10562 instruction about to be executed each time execution stops (@samp{$pc}
10563 is a common name for the program counter; @pxref{Registers, ,Registers}).
10566 @kindex delete display
10568 @item undisplay @var{dnums}@dots{}
10569 @itemx delete display @var{dnums}@dots{}
10570 Remove items from the list of expressions to display. Specify the
10571 numbers of the displays that you want affected with the command
10572 argument @var{dnums}. It can be a single display number, one of the
10573 numbers shown in the first field of the @samp{info display} display;
10574 or it could be a range of display numbers, as in @code{2-4}.
10576 @code{undisplay} does not repeat if you press @key{RET} after using it.
10577 (Otherwise you would just get the error @samp{No display number @dots{}}.)
10579 @kindex disable display
10580 @item disable display @var{dnums}@dots{}
10581 Disable the display of item numbers @var{dnums}. A disabled display
10582 item is not printed automatically, but is not forgotten. It may be
10583 enabled again later. Specify the numbers of the displays that you
10584 want affected with the command argument @var{dnums}. It can be a
10585 single display number, one of the numbers shown in the first field of
10586 the @samp{info display} display; or it could be a range of display
10587 numbers, as in @code{2-4}.
10589 @kindex enable display
10590 @item enable display @var{dnums}@dots{}
10591 Enable display of item numbers @var{dnums}. It becomes effective once
10592 again in auto display of its expression, until you specify otherwise.
10593 Specify the numbers of the displays that you want affected with the
10594 command argument @var{dnums}. It can be a single display number, one
10595 of the numbers shown in the first field of the @samp{info display}
10596 display; or it could be a range of display numbers, as in @code{2-4}.
10599 Display the current values of the expressions on the list, just as is
10600 done when your program stops.
10602 @kindex info display
10604 Print the list of expressions previously set up to display
10605 automatically, each one with its item number, but without showing the
10606 values. This includes disabled expressions, which are marked as such.
10607 It also includes expressions which would not be displayed right now
10608 because they refer to automatic variables not currently available.
10611 @cindex display disabled out of scope
10612 If a display expression refers to local variables, then it does not make
10613 sense outside the lexical context for which it was set up. Such an
10614 expression is disabled when execution enters a context where one of its
10615 variables is not defined. For example, if you give the command
10616 @code{display last_char} while inside a function with an argument
10617 @code{last_char}, @value{GDBN} displays this argument while your program
10618 continues to stop inside that function. When it stops elsewhere---where
10619 there is no variable @code{last_char}---the display is disabled
10620 automatically. The next time your program stops where @code{last_char}
10621 is meaningful, you can enable the display expression once again.
10623 @node Print Settings
10624 @section Print Settings
10626 @cindex format options
10627 @cindex print settings
10628 @value{GDBN} provides the following ways to control how arrays, structures,
10629 and symbols are printed.
10632 These settings are useful for debugging programs in any language:
10636 @anchor{set print address}
10637 @item set print address
10638 @itemx set print address on
10639 @cindex print/don't print memory addresses
10640 @value{GDBN} prints memory addresses showing the location of stack
10641 traces, structure values, pointer values, breakpoints, and so forth,
10642 even when it also displays the contents of those addresses. The default
10643 is @code{on}. For example, this is what a stack frame display looks like with
10644 @code{set print address on}:
10649 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
10651 530 if (lquote != def_lquote)
10655 @item set print address off
10656 Do not print addresses when displaying their contents. For example,
10657 this is the same stack frame displayed with @code{set print address off}:
10661 (@value{GDBP}) set print addr off
10663 #0 set_quotes (lq="<<", rq=">>") at input.c:530
10664 530 if (lquote != def_lquote)
10668 You can use @samp{set print address off} to eliminate all machine
10669 dependent displays from the @value{GDBN} interface. For example, with
10670 @code{print address off}, you should get the same text for backtraces on
10671 all machines---whether or not they involve pointer arguments.
10674 @item show print address
10675 Show whether or not addresses are to be printed.
10678 When @value{GDBN} prints a symbolic address, it normally prints the
10679 closest earlier symbol plus an offset. If that symbol does not uniquely
10680 identify the address (for example, it is a name whose scope is a single
10681 source file), you may need to clarify. One way to do this is with
10682 @code{info line}, for example @samp{info line *0x4537}. Alternately,
10683 you can set @value{GDBN} to print the source file and line number when
10684 it prints a symbolic address:
10687 @item set print symbol-filename on
10688 @cindex source file and line of a symbol
10689 @cindex symbol, source file and line
10690 Tell @value{GDBN} to print the source file name and line number of a
10691 symbol in the symbolic form of an address.
10693 @item set print symbol-filename off
10694 Do not print source file name and line number of a symbol. This is the
10697 @item show print symbol-filename
10698 Show whether or not @value{GDBN} will print the source file name and
10699 line number of a symbol in the symbolic form of an address.
10702 Another situation where it is helpful to show symbol filenames and line
10703 numbers is when disassembling code; @value{GDBN} shows you the line
10704 number and source file that corresponds to each instruction.
10706 Also, you may wish to see the symbolic form only if the address being
10707 printed is reasonably close to the closest earlier symbol:
10710 @item set print max-symbolic-offset @var{max-offset}
10711 @itemx set print max-symbolic-offset unlimited
10712 @cindex maximum value for offset of closest symbol
10713 Tell @value{GDBN} to only display the symbolic form of an address if the
10714 offset between the closest earlier symbol and the address is less than
10715 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
10716 to always print the symbolic form of an address if any symbol precedes
10717 it. Zero is equivalent to @code{unlimited}.
10719 @item show print max-symbolic-offset
10720 Ask how large the maximum offset is that @value{GDBN} prints in a
10724 @cindex wild pointer, interpreting
10725 @cindex pointer, finding referent
10726 If you have a pointer and you are not sure where it points, try
10727 @samp{set print symbol-filename on}. Then you can determine the name
10728 and source file location of the variable where it points, using
10729 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
10730 For example, here @value{GDBN} shows that a variable @code{ptt} points
10731 at another variable @code{t}, defined in @file{hi2.c}:
10734 (@value{GDBP}) set print symbol-filename on
10735 (@value{GDBP}) p/a ptt
10736 $4 = 0xe008 <t in hi2.c>
10740 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
10741 does not show the symbol name and filename of the referent, even with
10742 the appropriate @code{set print} options turned on.
10745 You can also enable @samp{/a}-like formatting all the time using
10746 @samp{set print symbol on}:
10748 @anchor{set print symbol}
10750 @item set print symbol on
10751 Tell @value{GDBN} to print the symbol corresponding to an address, if
10754 @item set print symbol off
10755 Tell @value{GDBN} not to print the symbol corresponding to an
10756 address. In this mode, @value{GDBN} will still print the symbol
10757 corresponding to pointers to functions. This is the default.
10759 @item show print symbol
10760 Show whether @value{GDBN} will display the symbol corresponding to an
10764 Other settings control how different kinds of objects are printed:
10767 @anchor{set print array}
10768 @item set print array
10769 @itemx set print array on
10770 @cindex pretty print arrays
10771 Pretty print arrays. This format is more convenient to read,
10772 but uses more space. The default is off.
10774 @item set print array off
10775 Return to compressed format for arrays.
10777 @item show print array
10778 Show whether compressed or pretty format is selected for displaying
10781 @cindex print array indexes
10782 @anchor{set print array-indexes}
10783 @item set print array-indexes
10784 @itemx set print array-indexes on
10785 Print the index of each element when displaying arrays. May be more
10786 convenient to locate a given element in the array or quickly find the
10787 index of a given element in that printed array. The default is off.
10789 @item set print array-indexes off
10790 Stop printing element indexes when displaying arrays.
10792 @item show print array-indexes
10793 Show whether the index of each element is printed when displaying
10796 @anchor{set print elements}
10797 @item set print elements @var{number-of-elements}
10798 @itemx set print elements unlimited
10799 @cindex number of array elements to print
10800 @cindex limit on number of printed array elements
10801 Set a limit on how many elements of an array @value{GDBN} will print.
10802 If @value{GDBN} is printing a large array, it stops printing after it has
10803 printed the number of elements set by the @code{set print elements} command.
10804 This limit also applies to the display of strings.
10805 When @value{GDBN} starts, this limit is set to 200.
10806 Setting @var{number-of-elements} to @code{unlimited} or zero means
10807 that the number of elements to print is unlimited.
10809 @item show print elements
10810 Display the number of elements of a large array that @value{GDBN} will print.
10811 If the number is 0, then the printing is unlimited.
10813 @anchor{set print frame-arguments}
10814 @item set print frame-arguments @var{value}
10815 @kindex set print frame-arguments
10816 @cindex printing frame argument values
10817 @cindex print all frame argument values
10818 @cindex print frame argument values for scalars only
10819 @cindex do not print frame argument values
10820 This command allows to control how the values of arguments are printed
10821 when the debugger prints a frame (@pxref{Frames}). The possible
10826 The values of all arguments are printed.
10829 Print the value of an argument only if it is a scalar. The value of more
10830 complex arguments such as arrays, structures, unions, etc, is replaced
10831 by @code{@dots{}}. This is the default. Here is an example where
10832 only scalar arguments are shown:
10835 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
10840 None of the argument values are printed. Instead, the value of each argument
10841 is replaced by @code{@dots{}}. In this case, the example above now becomes:
10844 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
10849 By default, only scalar arguments are printed. This command can be used
10850 to configure the debugger to print the value of all arguments, regardless
10851 of their type. However, it is often advantageous to not print the value
10852 of more complex parameters. For instance, it reduces the amount of
10853 information printed in each frame, making the backtrace more readable.
10854 Also, it improves performance when displaying Ada frames, because
10855 the computation of large arguments can sometimes be CPU-intensive,
10856 especially in large applications. Setting @code{print frame-arguments}
10857 to @code{scalars} (the default) or @code{none} avoids this computation,
10858 thus speeding up the display of each Ada frame.
10860 @item show print frame-arguments
10861 Show how the value of arguments should be displayed when printing a frame.
10863 @anchor{set print raw-frame-arguments}
10864 @item set print raw-frame-arguments on
10865 Print frame arguments in raw, non pretty-printed, form.
10867 @item set print raw-frame-arguments off
10868 Print frame arguments in pretty-printed form, if there is a pretty-printer
10869 for the value (@pxref{Pretty Printing}),
10870 otherwise print the value in raw form.
10871 This is the default.
10873 @item show print raw-frame-arguments
10874 Show whether to print frame arguments in raw form.
10876 @anchor{set print entry-values}
10877 @item set print entry-values @var{value}
10878 @kindex set print entry-values
10879 Set printing of frame argument values at function entry. In some cases
10880 @value{GDBN} can determine the value of function argument which was passed by
10881 the function caller, even if the value was modified inside the called function
10882 and therefore is different. With optimized code, the current value could be
10883 unavailable, but the entry value may still be known.
10885 The default value is @code{default} (see below for its description). Older
10886 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
10887 this feature will behave in the @code{default} setting the same way as with the
10890 This functionality is currently supported only by DWARF 2 debugging format and
10891 the compiler has to produce @samp{DW_TAG_call_site} tags. With
10892 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
10895 The @var{value} parameter can be one of the following:
10899 Print only actual parameter values, never print values from function entry
10903 #0 different (val=6)
10904 #0 lost (val=<optimized out>)
10906 #0 invalid (val=<optimized out>)
10910 Print only parameter values from function entry point. The actual parameter
10911 values are never printed.
10913 #0 equal (val@@entry=5)
10914 #0 different (val@@entry=5)
10915 #0 lost (val@@entry=5)
10916 #0 born (val@@entry=<optimized out>)
10917 #0 invalid (val@@entry=<optimized out>)
10921 Print only parameter values from function entry point. If value from function
10922 entry point is not known while the actual value is known, print the actual
10923 value for such parameter.
10925 #0 equal (val@@entry=5)
10926 #0 different (val@@entry=5)
10927 #0 lost (val@@entry=5)
10929 #0 invalid (val@@entry=<optimized out>)
10933 Print actual parameter values. If actual parameter value is not known while
10934 value from function entry point is known, print the entry point value for such
10938 #0 different (val=6)
10939 #0 lost (val@@entry=5)
10941 #0 invalid (val=<optimized out>)
10945 Always print both the actual parameter value and its value from function entry
10946 point, even if values of one or both are not available due to compiler
10949 #0 equal (val=5, val@@entry=5)
10950 #0 different (val=6, val@@entry=5)
10951 #0 lost (val=<optimized out>, val@@entry=5)
10952 #0 born (val=10, val@@entry=<optimized out>)
10953 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
10957 Print the actual parameter value if it is known and also its value from
10958 function entry point if it is known. If neither is known, print for the actual
10959 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
10960 values are known and identical, print the shortened
10961 @code{param=param@@entry=VALUE} notation.
10963 #0 equal (val=val@@entry=5)
10964 #0 different (val=6, val@@entry=5)
10965 #0 lost (val@@entry=5)
10967 #0 invalid (val=<optimized out>)
10971 Always print the actual parameter value. Print also its value from function
10972 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
10973 if both values are known and identical, print the shortened
10974 @code{param=param@@entry=VALUE} notation.
10976 #0 equal (val=val@@entry=5)
10977 #0 different (val=6, val@@entry=5)
10978 #0 lost (val=<optimized out>, val@@entry=5)
10980 #0 invalid (val=<optimized out>)
10984 For analysis messages on possible failures of frame argument values at function
10985 entry resolution see @ref{set debug entry-values}.
10987 @item show print entry-values
10988 Show the method being used for printing of frame argument values at function
10991 @anchor{set print repeats}
10992 @item set print repeats @var{number-of-repeats}
10993 @itemx set print repeats unlimited
10994 @cindex repeated array elements
10995 Set the threshold for suppressing display of repeated array
10996 elements. When the number of consecutive identical elements of an
10997 array exceeds the threshold, @value{GDBN} prints the string
10998 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
10999 identical repetitions, instead of displaying the identical elements
11000 themselves. Setting the threshold to @code{unlimited} or zero will
11001 cause all elements to be individually printed. The default threshold
11004 @item show print repeats
11005 Display the current threshold for printing repeated identical
11008 @anchor{set print max-depth}
11009 @item set print max-depth @var{depth}
11010 @item set print max-depth unlimited
11011 @cindex printing nested structures
11012 Set the threshold after which nested structures are replaced with
11013 ellipsis, this can make visualising deeply nested structures easier.
11015 For example, given this C code
11018 typedef struct s1 @{ int a; @} s1;
11019 typedef struct s2 @{ s1 b; @} s2;
11020 typedef struct s3 @{ s2 c; @} s3;
11021 typedef struct s4 @{ s3 d; @} s4;
11023 s4 var = @{ @{ @{ @{ 3 @} @} @} @};
11026 The following table shows how different values of @var{depth} will
11027 effect how @code{var} is printed by @value{GDBN}:
11029 @multitable @columnfractions .3 .7
11030 @headitem @var{depth} setting @tab Result of @samp{p var}
11032 @tab @code{$1 = @{d = @{c = @{b = @{a = 3@}@}@}@}}
11034 @tab @code{$1 = @{...@}}
11036 @tab @code{$1 = @{d = @{...@}@}}
11038 @tab @code{$1 = @{d = @{c = @{...@}@}@}}
11040 @tab @code{$1 = @{d = @{c = @{b = @{...@}@}@}@}}
11042 @tab @code{$1 = @{d = @{c = @{b = @{a = 3@}@}@}@}}
11045 To see the contents of structures that have been hidden the user can
11046 either increase the print max-depth, or they can print the elements of
11047 the structure that are visible, for example
11050 (gdb) set print max-depth 2
11052 $1 = @{d = @{c = @{...@}@}@}
11054 $2 = @{c = @{b = @{...@}@}@}
11056 $3 = @{b = @{a = 3@}@}
11059 The pattern used to replace nested structures varies based on
11060 language, for most languages @code{@{...@}} is used, but Fortran uses
11063 @item show print max-depth
11064 Display the current threshold after which nested structures are
11065 replaces with ellipsis.
11067 @anchor{set print null-stop}
11068 @item set print null-stop
11069 @cindex @sc{null} elements in arrays
11070 Cause @value{GDBN} to stop printing the characters of an array when the first
11071 @sc{null} is encountered. This is useful when large arrays actually
11072 contain only short strings.
11073 The default is off.
11075 @item show print null-stop
11076 Show whether @value{GDBN} stops printing an array on the first
11077 @sc{null} character.
11079 @anchor{set print pretty}
11080 @item set print pretty on
11081 @cindex print structures in indented form
11082 @cindex indentation in structure display
11083 Cause @value{GDBN} to print structures in an indented format with one member
11084 per line, like this:
11099 @item set print pretty off
11100 Cause @value{GDBN} to print structures in a compact format, like this:
11104 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
11105 meat = 0x54 "Pork"@}
11110 This is the default format.
11112 @item show print pretty
11113 Show which format @value{GDBN} is using to print structures.
11115 @item set print sevenbit-strings on
11116 @cindex eight-bit characters in strings
11117 @cindex octal escapes in strings
11118 Print using only seven-bit characters; if this option is set,
11119 @value{GDBN} displays any eight-bit characters (in strings or
11120 character values) using the notation @code{\}@var{nnn}. This setting is
11121 best if you are working in English (@sc{ascii}) and you use the
11122 high-order bit of characters as a marker or ``meta'' bit.
11124 @item set print sevenbit-strings off
11125 Print full eight-bit characters. This allows the use of more
11126 international character sets, and is the default.
11128 @item show print sevenbit-strings
11129 Show whether or not @value{GDBN} is printing only seven-bit characters.
11131 @anchor{set print union}
11132 @item set print union on
11133 @cindex unions in structures, printing
11134 Tell @value{GDBN} to print unions which are contained in structures
11135 and other unions. This is the default setting.
11137 @item set print union off
11138 Tell @value{GDBN} not to print unions which are contained in
11139 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
11142 @item show print union
11143 Ask @value{GDBN} whether or not it will print unions which are contained in
11144 structures and other unions.
11146 For example, given the declarations
11149 typedef enum @{Tree, Bug@} Species;
11150 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
11151 typedef enum @{Caterpillar, Cocoon, Butterfly@}
11162 struct thing foo = @{Tree, @{Acorn@}@};
11166 with @code{set print union on} in effect @samp{p foo} would print
11169 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
11173 and with @code{set print union off} in effect it would print
11176 $1 = @{it = Tree, form = @{...@}@}
11180 @code{set print union} affects programs written in C-like languages
11186 These settings are of interest when debugging C@t{++} programs:
11189 @cindex demangling C@t{++} names
11190 @item set print demangle
11191 @itemx set print demangle on
11192 Print C@t{++} names in their source form rather than in the encoded
11193 (``mangled'') form passed to the assembler and linker for type-safe
11194 linkage. The default is on.
11196 @item show print demangle
11197 Show whether C@t{++} names are printed in mangled or demangled form.
11199 @item set print asm-demangle
11200 @itemx set print asm-demangle on
11201 Print C@t{++} names in their source form rather than their mangled form, even
11202 in assembler code printouts such as instruction disassemblies.
11203 The default is off.
11205 @item show print asm-demangle
11206 Show whether C@t{++} names in assembly listings are printed in mangled
11209 @cindex C@t{++} symbol decoding style
11210 @cindex symbol decoding style, C@t{++}
11211 @kindex set demangle-style
11212 @item set demangle-style @var{style}
11213 Choose among several encoding schemes used by different compilers to represent
11214 C@t{++} names. If you omit @var{style}, you will see a list of possible
11215 formats. The default value is @var{auto}, which lets @value{GDBN} choose a
11216 decoding style by inspecting your program.
11218 @item show demangle-style
11219 Display the encoding style currently in use for decoding C@t{++} symbols.
11221 @anchor{set print object}
11222 @item set print object
11223 @itemx set print object on
11224 @cindex derived type of an object, printing
11225 @cindex display derived types
11226 When displaying a pointer to an object, identify the @emph{actual}
11227 (derived) type of the object rather than the @emph{declared} type, using
11228 the virtual function table. Note that the virtual function table is
11229 required---this feature can only work for objects that have run-time
11230 type identification; a single virtual method in the object's declared
11231 type is sufficient. Note that this setting is also taken into account when
11232 working with variable objects via MI (@pxref{GDB/MI}).
11234 @item set print object off
11235 Display only the declared type of objects, without reference to the
11236 virtual function table. This is the default setting.
11238 @item show print object
11239 Show whether actual, or declared, object types are displayed.
11241 @anchor{set print static-members}
11242 @item set print static-members
11243 @itemx set print static-members on
11244 @cindex static members of C@t{++} objects
11245 Print static members when displaying a C@t{++} object. The default is on.
11247 @item set print static-members off
11248 Do not print static members when displaying a C@t{++} object.
11250 @item show print static-members
11251 Show whether C@t{++} static members are printed or not.
11253 @item set print pascal_static-members
11254 @itemx set print pascal_static-members on
11255 @cindex static members of Pascal objects
11256 @cindex Pascal objects, static members display
11257 Print static members when displaying a Pascal object. The default is on.
11259 @item set print pascal_static-members off
11260 Do not print static members when displaying a Pascal object.
11262 @item show print pascal_static-members
11263 Show whether Pascal static members are printed or not.
11265 @c These don't work with HP ANSI C++ yet.
11266 @anchor{set print vtbl}
11267 @item set print vtbl
11268 @itemx set print vtbl on
11269 @cindex pretty print C@t{++} virtual function tables
11270 @cindex virtual functions (C@t{++}) display
11271 @cindex VTBL display
11272 Pretty print C@t{++} virtual function tables. The default is off.
11273 (The @code{vtbl} commands do not work on programs compiled with the HP
11274 ANSI C@t{++} compiler (@code{aCC}).)
11276 @item set print vtbl off
11277 Do not pretty print C@t{++} virtual function tables.
11279 @item show print vtbl
11280 Show whether C@t{++} virtual function tables are pretty printed, or not.
11283 @node Pretty Printing
11284 @section Pretty Printing
11286 @value{GDBN} provides a mechanism to allow pretty-printing of values using
11287 Python code. It greatly simplifies the display of complex objects. This
11288 mechanism works for both MI and the CLI.
11291 * Pretty-Printer Introduction:: Introduction to pretty-printers
11292 * Pretty-Printer Example:: An example pretty-printer
11293 * Pretty-Printer Commands:: Pretty-printer commands
11296 @node Pretty-Printer Introduction
11297 @subsection Pretty-Printer Introduction
11299 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
11300 registered for the value. If there is then @value{GDBN} invokes the
11301 pretty-printer to print the value. Otherwise the value is printed normally.
11303 Pretty-printers are normally named. This makes them easy to manage.
11304 The @samp{info pretty-printer} command will list all the installed
11305 pretty-printers with their names.
11306 If a pretty-printer can handle multiple data types, then its
11307 @dfn{subprinters} are the printers for the individual data types.
11308 Each such subprinter has its own name.
11309 The format of the name is @var{printer-name};@var{subprinter-name}.
11311 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
11312 Typically they are automatically loaded and registered when the corresponding
11313 debug information is loaded, thus making them available without having to
11314 do anything special.
11316 There are three places where a pretty-printer can be registered.
11320 Pretty-printers registered globally are available when debugging
11324 Pretty-printers registered with a program space are available only
11325 when debugging that program.
11326 @xref{Progspaces In Python}, for more details on program spaces in Python.
11329 Pretty-printers registered with an objfile are loaded and unloaded
11330 with the corresponding objfile (e.g., shared library).
11331 @xref{Objfiles In Python}, for more details on objfiles in Python.
11334 @xref{Selecting Pretty-Printers}, for further information on how
11335 pretty-printers are selected,
11337 @xref{Writing a Pretty-Printer}, for implementing pretty printers
11340 @node Pretty-Printer Example
11341 @subsection Pretty-Printer Example
11343 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
11346 (@value{GDBP}) print s
11348 static npos = 4294967295,
11350 <std::allocator<char>> = @{
11351 <__gnu_cxx::new_allocator<char>> = @{
11352 <No data fields>@}, <No data fields>
11354 members of std::basic_string<char, std::char_traits<char>,
11355 std::allocator<char> >::_Alloc_hider:
11356 _M_p = 0x804a014 "abcd"
11361 With a pretty-printer for @code{std::string} only the contents are printed:
11364 (@value{GDBP}) print s
11368 @node Pretty-Printer Commands
11369 @subsection Pretty-Printer Commands
11370 @cindex pretty-printer commands
11373 @kindex info pretty-printer
11374 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
11375 Print the list of installed pretty-printers.
11376 This includes disabled pretty-printers, which are marked as such.
11378 @var{object-regexp} is a regular expression matching the objects
11379 whose pretty-printers to list.
11380 Objects can be @code{global}, the program space's file
11381 (@pxref{Progspaces In Python}),
11382 and the object files within that program space (@pxref{Objfiles In Python}).
11383 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
11384 looks up a printer from these three objects.
11386 @var{name-regexp} is a regular expression matching the name of the printers
11389 @kindex disable pretty-printer
11390 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
11391 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
11392 A disabled pretty-printer is not forgotten, it may be enabled again later.
11394 @kindex enable pretty-printer
11395 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
11396 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
11401 Suppose we have three pretty-printers installed: one from library1.so
11402 named @code{foo} that prints objects of type @code{foo}, and
11403 another from library2.so named @code{bar} that prints two types of objects,
11404 @code{bar1} and @code{bar2}.
11407 (gdb) info pretty-printer
11414 (gdb) info pretty-printer library2
11419 (gdb) disable pretty-printer library1
11421 2 of 3 printers enabled
11422 (gdb) info pretty-printer
11429 (gdb) disable pretty-printer library2 bar;bar1
11431 1 of 3 printers enabled
11432 (gdb) info pretty-printer library2
11439 (gdb) disable pretty-printer library2 bar
11441 0 of 3 printers enabled
11442 (gdb) info pretty-printer library2
11451 Note that for @code{bar} the entire printer can be disabled,
11452 as can each individual subprinter.
11454 @node Value History
11455 @section Value History
11457 @cindex value history
11458 @cindex history of values printed by @value{GDBN}
11459 Values printed by the @code{print} command are saved in the @value{GDBN}
11460 @dfn{value history}. This allows you to refer to them in other expressions.
11461 Values are kept until the symbol table is re-read or discarded
11462 (for example with the @code{file} or @code{symbol-file} commands).
11463 When the symbol table changes, the value history is discarded,
11464 since the values may contain pointers back to the types defined in the
11469 @cindex history number
11470 The values printed are given @dfn{history numbers} by which you can
11471 refer to them. These are successive integers starting with one.
11472 @code{print} shows you the history number assigned to a value by
11473 printing @samp{$@var{num} = } before the value; here @var{num} is the
11476 To refer to any previous value, use @samp{$} followed by the value's
11477 history number. The way @code{print} labels its output is designed to
11478 remind you of this. Just @code{$} refers to the most recent value in
11479 the history, and @code{$$} refers to the value before that.
11480 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
11481 is the value just prior to @code{$$}, @code{$$1} is equivalent to
11482 @code{$$}, and @code{$$0} is equivalent to @code{$}.
11484 For example, suppose you have just printed a pointer to a structure and
11485 want to see the contents of the structure. It suffices to type
11491 If you have a chain of structures where the component @code{next} points
11492 to the next one, you can print the contents of the next one with this:
11499 You can print successive links in the chain by repeating this
11500 command---which you can do by just typing @key{RET}.
11502 Note that the history records values, not expressions. If the value of
11503 @code{x} is 4 and you type these commands:
11511 then the value recorded in the value history by the @code{print} command
11512 remains 4 even though the value of @code{x} has changed.
11515 @kindex show values
11517 Print the last ten values in the value history, with their item numbers.
11518 This is like @samp{p@ $$9} repeated ten times, except that @code{show
11519 values} does not change the history.
11521 @item show values @var{n}
11522 Print ten history values centered on history item number @var{n}.
11524 @item show values +
11525 Print ten history values just after the values last printed. If no more
11526 values are available, @code{show values +} produces no display.
11529 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
11530 same effect as @samp{show values +}.
11532 @node Convenience Vars
11533 @section Convenience Variables
11535 @cindex convenience variables
11536 @cindex user-defined variables
11537 @value{GDBN} provides @dfn{convenience variables} that you can use within
11538 @value{GDBN} to hold on to a value and refer to it later. These variables
11539 exist entirely within @value{GDBN}; they are not part of your program, and
11540 setting a convenience variable has no direct effect on further execution
11541 of your program. That is why you can use them freely.
11543 Convenience variables are prefixed with @samp{$}. Any name preceded by
11544 @samp{$} can be used for a convenience variable, unless it is one of
11545 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
11546 (Value history references, in contrast, are @emph{numbers} preceded
11547 by @samp{$}. @xref{Value History, ,Value History}.)
11549 You can save a value in a convenience variable with an assignment
11550 expression, just as you would set a variable in your program.
11554 set $foo = *object_ptr
11558 would save in @code{$foo} the value contained in the object pointed to by
11561 Using a convenience variable for the first time creates it, but its
11562 value is @code{void} until you assign a new value. You can alter the
11563 value with another assignment at any time.
11565 Convenience variables have no fixed types. You can assign a convenience
11566 variable any type of value, including structures and arrays, even if
11567 that variable already has a value of a different type. The convenience
11568 variable, when used as an expression, has the type of its current value.
11571 @kindex show convenience
11572 @cindex show all user variables and functions
11573 @item show convenience
11574 Print a list of convenience variables used so far, and their values,
11575 as well as a list of the convenience functions.
11576 Abbreviated @code{show conv}.
11578 @kindex init-if-undefined
11579 @cindex convenience variables, initializing
11580 @item init-if-undefined $@var{variable} = @var{expression}
11581 Set a convenience variable if it has not already been set. This is useful
11582 for user-defined commands that keep some state. It is similar, in concept,
11583 to using local static variables with initializers in C (except that
11584 convenience variables are global). It can also be used to allow users to
11585 override default values used in a command script.
11587 If the variable is already defined then the expression is not evaluated so
11588 any side-effects do not occur.
11591 One of the ways to use a convenience variable is as a counter to be
11592 incremented or a pointer to be advanced. For example, to print
11593 a field from successive elements of an array of structures:
11597 print bar[$i++]->contents
11601 Repeat that command by typing @key{RET}.
11603 Some convenience variables are created automatically by @value{GDBN} and given
11604 values likely to be useful.
11607 @vindex $_@r{, convenience variable}
11609 The variable @code{$_} is automatically set by the @code{x} command to
11610 the last address examined (@pxref{Memory, ,Examining Memory}). Other
11611 commands which provide a default address for @code{x} to examine also
11612 set @code{$_} to that address; these commands include @code{info line}
11613 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
11614 except when set by the @code{x} command, in which case it is a pointer
11615 to the type of @code{$__}.
11617 @vindex $__@r{, convenience variable}
11619 The variable @code{$__} is automatically set by the @code{x} command
11620 to the value found in the last address examined. Its type is chosen
11621 to match the format in which the data was printed.
11624 @vindex $_exitcode@r{, convenience variable}
11625 When the program being debugged terminates normally, @value{GDBN}
11626 automatically sets this variable to the exit code of the program, and
11627 resets @code{$_exitsignal} to @code{void}.
11630 @vindex $_exitsignal@r{, convenience variable}
11631 When the program being debugged dies due to an uncaught signal,
11632 @value{GDBN} automatically sets this variable to that signal's number,
11633 and resets @code{$_exitcode} to @code{void}.
11635 To distinguish between whether the program being debugged has exited
11636 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
11637 @code{$_exitsignal} is not @code{void}), the convenience function
11638 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
11639 Functions}). For example, considering the following source code:
11642 #include <signal.h>
11645 main (int argc, char *argv[])
11652 A valid way of telling whether the program being debugged has exited
11653 or signalled would be:
11656 (@value{GDBP}) define has_exited_or_signalled
11657 Type commands for definition of ``has_exited_or_signalled''.
11658 End with a line saying just ``end''.
11659 >if $_isvoid ($_exitsignal)
11660 >echo The program has exited\n
11662 >echo The program has signalled\n
11668 Program terminated with signal SIGALRM, Alarm clock.
11669 The program no longer exists.
11670 (@value{GDBP}) has_exited_or_signalled
11671 The program has signalled
11674 As can be seen, @value{GDBN} correctly informs that the program being
11675 debugged has signalled, since it calls @code{raise} and raises a
11676 @code{SIGALRM} signal. If the program being debugged had not called
11677 @code{raise}, then @value{GDBN} would report a normal exit:
11680 (@value{GDBP}) has_exited_or_signalled
11681 The program has exited
11685 The variable @code{$_exception} is set to the exception object being
11686 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
11689 @itemx $_probe_arg0@dots{}$_probe_arg11
11690 Arguments to a static probe. @xref{Static Probe Points}.
11693 @vindex $_sdata@r{, inspect, convenience variable}
11694 The variable @code{$_sdata} contains extra collected static tracepoint
11695 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
11696 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
11697 if extra static tracepoint data has not been collected.
11700 @vindex $_siginfo@r{, convenience variable}
11701 The variable @code{$_siginfo} contains extra signal information
11702 (@pxref{extra signal information}). Note that @code{$_siginfo}
11703 could be empty, if the application has not yet received any signals.
11704 For example, it will be empty before you execute the @code{run} command.
11707 @vindex $_tlb@r{, convenience variable}
11708 The variable @code{$_tlb} is automatically set when debugging
11709 applications running on MS-Windows in native mode or connected to
11710 gdbserver that supports the @code{qGetTIBAddr} request.
11711 @xref{General Query Packets}.
11712 This variable contains the address of the thread information block.
11715 The number of the current inferior. @xref{Inferiors and
11716 Programs, ,Debugging Multiple Inferiors and Programs}.
11719 The thread number of the current thread. @xref{thread numbers}.
11722 The global number of the current thread. @xref{global thread numbers}.
11726 @vindex $_gdb_major@r{, convenience variable}
11727 @vindex $_gdb_minor@r{, convenience variable}
11728 The major and minor version numbers of the running @value{GDBN}.
11729 Development snapshots and pretest versions have their minor version
11730 incremented by one; thus, @value{GDBN} pretest 9.11.90 will produce
11731 the value 12 for @code{$_gdb_minor}. These variables allow you to
11732 write scripts that work with different versions of @value{GDBN}
11733 without errors caused by features unavailable in some of those
11736 @item $_shell_exitcode
11737 @itemx $_shell_exitsignal
11738 @vindex $_shell_exitcode@r{, convenience variable}
11739 @vindex $_shell_exitsignal@r{, convenience variable}
11740 @cindex shell command, exit code
11741 @cindex shell command, exit signal
11742 @cindex exit status of shell commands
11743 @value{GDBN} commands such as @code{shell} and @code{|} are launching
11744 shell commands. When a launched command terminates, @value{GDBN}
11745 automatically maintains the variables @code{$_shell_exitcode}
11746 and @code{$_shell_exitsignal} according to the exit status of the last
11747 launched command. These variables are set and used similarly to
11748 the variables @code{$_exitcode} and @code{$_exitsignal}.
11752 @node Convenience Funs
11753 @section Convenience Functions
11755 @cindex convenience functions
11756 @value{GDBN} also supplies some @dfn{convenience functions}. These
11757 have a syntax similar to convenience variables. A convenience
11758 function can be used in an expression just like an ordinary function;
11759 however, a convenience function is implemented internally to
11762 These functions do not require @value{GDBN} to be configured with
11763 @code{Python} support, which means that they are always available.
11767 @item $_isvoid (@var{expr})
11768 @findex $_isvoid@r{, convenience function}
11769 Return one if the expression @var{expr} is @code{void}. Otherwise it
11772 A @code{void} expression is an expression where the type of the result
11773 is @code{void}. For example, you can examine a convenience variable
11774 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
11778 (@value{GDBP}) print $_exitcode
11780 (@value{GDBP}) print $_isvoid ($_exitcode)
11783 Starting program: ./a.out
11784 [Inferior 1 (process 29572) exited normally]
11785 (@value{GDBP}) print $_exitcode
11787 (@value{GDBP}) print $_isvoid ($_exitcode)
11791 In the example above, we used @code{$_isvoid} to check whether
11792 @code{$_exitcode} is @code{void} before and after the execution of the
11793 program being debugged. Before the execution there is no exit code to
11794 be examined, therefore @code{$_exitcode} is @code{void}. After the
11795 execution the program being debugged returned zero, therefore
11796 @code{$_exitcode} is zero, which means that it is not @code{void}
11799 The @code{void} expression can also be a call of a function from the
11800 program being debugged. For example, given the following function:
11809 The result of calling it inside @value{GDBN} is @code{void}:
11812 (@value{GDBP}) print foo ()
11814 (@value{GDBP}) print $_isvoid (foo ())
11816 (@value{GDBP}) set $v = foo ()
11817 (@value{GDBP}) print $v
11819 (@value{GDBP}) print $_isvoid ($v)
11825 These functions require @value{GDBN} to be configured with
11826 @code{Python} support.
11830 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
11831 @findex $_memeq@r{, convenience function}
11832 Returns one if the @var{length} bytes at the addresses given by
11833 @var{buf1} and @var{buf2} are equal.
11834 Otherwise it returns zero.
11836 @item $_regex(@var{str}, @var{regex})
11837 @findex $_regex@r{, convenience function}
11838 Returns one if the string @var{str} matches the regular expression
11839 @var{regex}. Otherwise it returns zero.
11840 The syntax of the regular expression is that specified by @code{Python}'s
11841 regular expression support.
11843 @item $_streq(@var{str1}, @var{str2})
11844 @findex $_streq@r{, convenience function}
11845 Returns one if the strings @var{str1} and @var{str2} are equal.
11846 Otherwise it returns zero.
11848 @item $_strlen(@var{str})
11849 @findex $_strlen@r{, convenience function}
11850 Returns the length of string @var{str}.
11852 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
11853 @findex $_caller_is@r{, convenience function}
11854 Returns one if the calling function's name is equal to @var{name}.
11855 Otherwise it returns zero.
11857 If the optional argument @var{number_of_frames} is provided,
11858 it is the number of frames up in the stack to look.
11866 at testsuite/gdb.python/py-caller-is.c:21
11867 #1 0x00000000004005a0 in middle_func ()
11868 at testsuite/gdb.python/py-caller-is.c:27
11869 #2 0x00000000004005ab in top_func ()
11870 at testsuite/gdb.python/py-caller-is.c:33
11871 #3 0x00000000004005b6 in main ()
11872 at testsuite/gdb.python/py-caller-is.c:39
11873 (gdb) print $_caller_is ("middle_func")
11875 (gdb) print $_caller_is ("top_func", 2)
11879 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
11880 @findex $_caller_matches@r{, convenience function}
11881 Returns one if the calling function's name matches the regular expression
11882 @var{regexp}. Otherwise it returns zero.
11884 If the optional argument @var{number_of_frames} is provided,
11885 it is the number of frames up in the stack to look.
11888 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
11889 @findex $_any_caller_is@r{, convenience function}
11890 Returns one if any calling function's name is equal to @var{name}.
11891 Otherwise it returns zero.
11893 If the optional argument @var{number_of_frames} is provided,
11894 it is the number of frames up in the stack to look.
11897 This function differs from @code{$_caller_is} in that this function
11898 checks all stack frames from the immediate caller to the frame specified
11899 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
11900 frame specified by @var{number_of_frames}.
11902 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
11903 @findex $_any_caller_matches@r{, convenience function}
11904 Returns one if any calling function's name matches the regular expression
11905 @var{regexp}. Otherwise it returns zero.
11907 If the optional argument @var{number_of_frames} is provided,
11908 it is the number of frames up in the stack to look.
11911 This function differs from @code{$_caller_matches} in that this function
11912 checks all stack frames from the immediate caller to the frame specified
11913 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
11914 frame specified by @var{number_of_frames}.
11916 @item $_as_string(@var{value})
11917 @findex $_as_string@r{, convenience function}
11918 Return the string representation of @var{value}.
11920 This function is useful to obtain the textual label (enumerator) of an
11921 enumeration value. For example, assuming the variable @var{node} is of
11922 an enumerated type:
11925 (gdb) printf "Visiting node of type %s\n", $_as_string(node)
11926 Visiting node of type NODE_INTEGER
11929 @item $_cimag(@var{value})
11930 @itemx $_creal(@var{value})
11931 @findex $_cimag@r{, convenience function}
11932 @findex $_creal@r{, convenience function}
11933 Return the imaginary (@code{$_cimag}) or real (@code{$_creal}) part of
11934 the complex number @var{value}.
11936 The type of the imaginary or real part depends on the type of the
11937 complex number, e.g., using @code{$_cimag} on a @code{float complex}
11938 will return an imaginary part of type @code{float}.
11942 @value{GDBN} provides the ability to list and get help on
11943 convenience functions.
11946 @item help function
11947 @kindex help function
11948 @cindex show all convenience functions
11949 Print a list of all convenience functions.
11956 You can refer to machine register contents, in expressions, as variables
11957 with names starting with @samp{$}. The names of registers are different
11958 for each machine; use @code{info registers} to see the names used on
11962 @kindex info registers
11963 @item info registers
11964 Print the names and values of all registers except floating-point
11965 and vector registers (in the selected stack frame).
11967 @kindex info all-registers
11968 @cindex floating point registers
11969 @item info all-registers
11970 Print the names and values of all registers, including floating-point
11971 and vector registers (in the selected stack frame).
11973 @item info registers @var{reggroup} @dots{}
11974 Print the name and value of the registers in each of the specified
11975 @var{reggroup}s. The @var{reggoup} can be any of those returned by
11976 @code{maint print reggroups} (@pxref{Maintenance Commands}).
11978 @item info registers @var{regname} @dots{}
11979 Print the @dfn{relativized} value of each specified register @var{regname}.
11980 As discussed in detail below, register values are normally relative to
11981 the selected stack frame. The @var{regname} may be any register name valid on
11982 the machine you are using, with or without the initial @samp{$}.
11985 @anchor{standard registers}
11986 @cindex stack pointer register
11987 @cindex program counter register
11988 @cindex process status register
11989 @cindex frame pointer register
11990 @cindex standard registers
11991 @value{GDBN} has four ``standard'' register names that are available (in
11992 expressions) on most machines---whenever they do not conflict with an
11993 architecture's canonical mnemonics for registers. The register names
11994 @code{$pc} and @code{$sp} are used for the program counter register and
11995 the stack pointer. @code{$fp} is used for a register that contains a
11996 pointer to the current stack frame, and @code{$ps} is used for a
11997 register that contains the processor status. For example,
11998 you could print the program counter in hex with
12005 or print the instruction to be executed next with
12012 or add four to the stack pointer@footnote{This is a way of removing
12013 one word from the stack, on machines where stacks grow downward in
12014 memory (most machines, nowadays). This assumes that the innermost
12015 stack frame is selected; setting @code{$sp} is not allowed when other
12016 stack frames are selected. To pop entire frames off the stack,
12017 regardless of machine architecture, use @code{return};
12018 see @ref{Returning, ,Returning from a Function}.} with
12024 Whenever possible, these four standard register names are available on
12025 your machine even though the machine has different canonical mnemonics,
12026 so long as there is no conflict. The @code{info registers} command
12027 shows the canonical names. For example, on the SPARC, @code{info
12028 registers} displays the processor status register as @code{$psr} but you
12029 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
12030 is an alias for the @sc{eflags} register.
12032 @value{GDBN} always considers the contents of an ordinary register as an
12033 integer when the register is examined in this way. Some machines have
12034 special registers which can hold nothing but floating point; these
12035 registers are considered to have floating point values. There is no way
12036 to refer to the contents of an ordinary register as floating point value
12037 (although you can @emph{print} it as a floating point value with
12038 @samp{print/f $@var{regname}}).
12040 Some registers have distinct ``raw'' and ``virtual'' data formats. This
12041 means that the data format in which the register contents are saved by
12042 the operating system is not the same one that your program normally
12043 sees. For example, the registers of the 68881 floating point
12044 coprocessor are always saved in ``extended'' (raw) format, but all C
12045 programs expect to work with ``double'' (virtual) format. In such
12046 cases, @value{GDBN} normally works with the virtual format only (the format
12047 that makes sense for your program), but the @code{info registers} command
12048 prints the data in both formats.
12050 @cindex SSE registers (x86)
12051 @cindex MMX registers (x86)
12052 Some machines have special registers whose contents can be interpreted
12053 in several different ways. For example, modern x86-based machines
12054 have SSE and MMX registers that can hold several values packed
12055 together in several different formats. @value{GDBN} refers to such
12056 registers in @code{struct} notation:
12059 (@value{GDBP}) print $xmm1
12061 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
12062 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
12063 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
12064 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
12065 v4_int32 = @{0, 20657912, 11, 13@},
12066 v2_int64 = @{88725056443645952, 55834574859@},
12067 uint128 = 0x0000000d0000000b013b36f800000000
12072 To set values of such registers, you need to tell @value{GDBN} which
12073 view of the register you wish to change, as if you were assigning
12074 value to a @code{struct} member:
12077 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
12080 Normally, register values are relative to the selected stack frame
12081 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
12082 value that the register would contain if all stack frames farther in
12083 were exited and their saved registers restored. In order to see the
12084 true contents of hardware registers, you must select the innermost
12085 frame (with @samp{frame 0}).
12087 @cindex caller-saved registers
12088 @cindex call-clobbered registers
12089 @cindex volatile registers
12090 @cindex <not saved> values
12091 Usually ABIs reserve some registers as not needed to be saved by the
12092 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
12093 registers). It may therefore not be possible for @value{GDBN} to know
12094 the value a register had before the call (in other words, in the outer
12095 frame), if the register value has since been changed by the callee.
12096 @value{GDBN} tries to deduce where the inner frame saved
12097 (``callee-saved'') registers, from the debug info, unwind info, or the
12098 machine code generated by your compiler. If some register is not
12099 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
12100 its own knowledge of the ABI, or because the debug/unwind info
12101 explicitly says the register's value is undefined), @value{GDBN}
12102 displays @w{@samp{<not saved>}} as the register's value. With targets
12103 that @value{GDBN} has no knowledge of the register saving convention,
12104 if a register was not saved by the callee, then its value and location
12105 in the outer frame are assumed to be the same of the inner frame.
12106 This is usually harmless, because if the register is call-clobbered,
12107 the caller either does not care what is in the register after the
12108 call, or has code to restore the value that it does care about. Note,
12109 however, that if you change such a register in the outer frame, you
12110 may also be affecting the inner frame. Also, the more ``outer'' the
12111 frame is you're looking at, the more likely a call-clobbered
12112 register's value is to be wrong, in the sense that it doesn't actually
12113 represent the value the register had just before the call.
12115 @node Floating Point Hardware
12116 @section Floating Point Hardware
12117 @cindex floating point
12119 Depending on the configuration, @value{GDBN} may be able to give
12120 you more information about the status of the floating point hardware.
12125 Display hardware-dependent information about the floating
12126 point unit. The exact contents and layout vary depending on the
12127 floating point chip. Currently, @samp{info float} is supported on
12128 the ARM and x86 machines.
12132 @section Vector Unit
12133 @cindex vector unit
12135 Depending on the configuration, @value{GDBN} may be able to give you
12136 more information about the status of the vector unit.
12139 @kindex info vector
12141 Display information about the vector unit. The exact contents and
12142 layout vary depending on the hardware.
12145 @node OS Information
12146 @section Operating System Auxiliary Information
12147 @cindex OS information
12149 @value{GDBN} provides interfaces to useful OS facilities that can help
12150 you debug your program.
12152 @cindex auxiliary vector
12153 @cindex vector, auxiliary
12154 Some operating systems supply an @dfn{auxiliary vector} to programs at
12155 startup. This is akin to the arguments and environment that you
12156 specify for a program, but contains a system-dependent variety of
12157 binary values that tell system libraries important details about the
12158 hardware, operating system, and process. Each value's purpose is
12159 identified by an integer tag; the meanings are well-known but system-specific.
12160 Depending on the configuration and operating system facilities,
12161 @value{GDBN} may be able to show you this information. For remote
12162 targets, this functionality may further depend on the remote stub's
12163 support of the @samp{qXfer:auxv:read} packet, see
12164 @ref{qXfer auxiliary vector read}.
12169 Display the auxiliary vector of the inferior, which can be either a
12170 live process or a core dump file. @value{GDBN} prints each tag value
12171 numerically, and also shows names and text descriptions for recognized
12172 tags. Some values in the vector are numbers, some bit masks, and some
12173 pointers to strings or other data. @value{GDBN} displays each value in the
12174 most appropriate form for a recognized tag, and in hexadecimal for
12175 an unrecognized tag.
12178 On some targets, @value{GDBN} can access operating system-specific
12179 information and show it to you. The types of information available
12180 will differ depending on the type of operating system running on the
12181 target. The mechanism used to fetch the data is described in
12182 @ref{Operating System Information}. For remote targets, this
12183 functionality depends on the remote stub's support of the
12184 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
12188 @item info os @var{infotype}
12190 Display OS information of the requested type.
12192 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
12194 @anchor{linux info os infotypes}
12196 @kindex info os cpus
12198 Display the list of all CPUs/cores. For each CPU/core, @value{GDBN} prints
12199 the available fields from /proc/cpuinfo. For each supported architecture
12200 different fields are available. Two common entries are processor which gives
12201 CPU number and bogomips; a system constant that is calculated during
12202 kernel initialization.
12204 @kindex info os files
12206 Display the list of open file descriptors on the target. For each
12207 file descriptor, @value{GDBN} prints the identifier of the process
12208 owning the descriptor, the command of the owning process, the value
12209 of the descriptor, and the target of the descriptor.
12211 @kindex info os modules
12213 Display the list of all loaded kernel modules on the target. For each
12214 module, @value{GDBN} prints the module name, the size of the module in
12215 bytes, the number of times the module is used, the dependencies of the
12216 module, the status of the module, and the address of the loaded module
12219 @kindex info os msg
12221 Display the list of all System V message queues on the target. For each
12222 message queue, @value{GDBN} prints the message queue key, the message
12223 queue identifier, the access permissions, the current number of bytes
12224 on the queue, the current number of messages on the queue, the processes
12225 that last sent and received a message on the queue, the user and group
12226 of the owner and creator of the message queue, the times at which a
12227 message was last sent and received on the queue, and the time at which
12228 the message queue was last changed.
12230 @kindex info os processes
12232 Display the list of processes on the target. For each process,
12233 @value{GDBN} prints the process identifier, the name of the user, the
12234 command corresponding to the process, and the list of processor cores
12235 that the process is currently running on. (To understand what these
12236 properties mean, for this and the following info types, please consult
12237 the general @sc{gnu}/Linux documentation.)
12239 @kindex info os procgroups
12241 Display the list of process groups on the target. For each process,
12242 @value{GDBN} prints the identifier of the process group that it belongs
12243 to, the command corresponding to the process group leader, the process
12244 identifier, and the command line of the process. The list is sorted
12245 first by the process group identifier, then by the process identifier,
12246 so that processes belonging to the same process group are grouped together
12247 and the process group leader is listed first.
12249 @kindex info os semaphores
12251 Display the list of all System V semaphore sets on the target. For each
12252 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
12253 set identifier, the access permissions, the number of semaphores in the
12254 set, the user and group of the owner and creator of the semaphore set,
12255 and the times at which the semaphore set was operated upon and changed.
12257 @kindex info os shm
12259 Display the list of all System V shared-memory regions on the target.
12260 For each shared-memory region, @value{GDBN} prints the region key,
12261 the shared-memory identifier, the access permissions, the size of the
12262 region, the process that created the region, the process that last
12263 attached to or detached from the region, the current number of live
12264 attaches to the region, and the times at which the region was last
12265 attached to, detach from, and changed.
12267 @kindex info os sockets
12269 Display the list of Internet-domain sockets on the target. For each
12270 socket, @value{GDBN} prints the address and port of the local and
12271 remote endpoints, the current state of the connection, the creator of
12272 the socket, the IP address family of the socket, and the type of the
12275 @kindex info os threads
12277 Display the list of threads running on the target. For each thread,
12278 @value{GDBN} prints the identifier of the process that the thread
12279 belongs to, the command of the process, the thread identifier, and the
12280 processor core that it is currently running on. The main thread of a
12281 process is not listed.
12285 If @var{infotype} is omitted, then list the possible values for
12286 @var{infotype} and the kind of OS information available for each
12287 @var{infotype}. If the target does not return a list of possible
12288 types, this command will report an error.
12291 @node Memory Region Attributes
12292 @section Memory Region Attributes
12293 @cindex memory region attributes
12295 @dfn{Memory region attributes} allow you to describe special handling
12296 required by regions of your target's memory. @value{GDBN} uses
12297 attributes to determine whether to allow certain types of memory
12298 accesses; whether to use specific width accesses; and whether to cache
12299 target memory. By default the description of memory regions is
12300 fetched from the target (if the current target supports this), but the
12301 user can override the fetched regions.
12303 Defined memory regions can be individually enabled and disabled. When a
12304 memory region is disabled, @value{GDBN} uses the default attributes when
12305 accessing memory in that region. Similarly, if no memory regions have
12306 been defined, @value{GDBN} uses the default attributes when accessing
12309 When a memory region is defined, it is given a number to identify it;
12310 to enable, disable, or remove a memory region, you specify that number.
12314 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
12315 Define a memory region bounded by @var{lower} and @var{upper} with
12316 attributes @var{attributes}@dots{}, and add it to the list of regions
12317 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
12318 case: it is treated as the target's maximum memory address.
12319 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
12322 Discard any user changes to the memory regions and use target-supplied
12323 regions, if available, or no regions if the target does not support.
12326 @item delete mem @var{nums}@dots{}
12327 Remove memory regions @var{nums}@dots{} from the list of regions
12328 monitored by @value{GDBN}.
12330 @kindex disable mem
12331 @item disable mem @var{nums}@dots{}
12332 Disable monitoring of memory regions @var{nums}@dots{}.
12333 A disabled memory region is not forgotten.
12334 It may be enabled again later.
12337 @item enable mem @var{nums}@dots{}
12338 Enable monitoring of memory regions @var{nums}@dots{}.
12342 Print a table of all defined memory regions, with the following columns
12346 @item Memory Region Number
12347 @item Enabled or Disabled.
12348 Enabled memory regions are marked with @samp{y}.
12349 Disabled memory regions are marked with @samp{n}.
12352 The address defining the inclusive lower bound of the memory region.
12355 The address defining the exclusive upper bound of the memory region.
12358 The list of attributes set for this memory region.
12363 @subsection Attributes
12365 @subsubsection Memory Access Mode
12366 The access mode attributes set whether @value{GDBN} may make read or
12367 write accesses to a memory region.
12369 While these attributes prevent @value{GDBN} from performing invalid
12370 memory accesses, they do nothing to prevent the target system, I/O DMA,
12371 etc.@: from accessing memory.
12375 Memory is read only.
12377 Memory is write only.
12379 Memory is read/write. This is the default.
12382 @subsubsection Memory Access Size
12383 The access size attribute tells @value{GDBN} to use specific sized
12384 accesses in the memory region. Often memory mapped device registers
12385 require specific sized accesses. If no access size attribute is
12386 specified, @value{GDBN} may use accesses of any size.
12390 Use 8 bit memory accesses.
12392 Use 16 bit memory accesses.
12394 Use 32 bit memory accesses.
12396 Use 64 bit memory accesses.
12399 @c @subsubsection Hardware/Software Breakpoints
12400 @c The hardware/software breakpoint attributes set whether @value{GDBN}
12401 @c will use hardware or software breakpoints for the internal breakpoints
12402 @c used by the step, next, finish, until, etc. commands.
12406 @c Always use hardware breakpoints
12407 @c @item swbreak (default)
12410 @subsubsection Data Cache
12411 The data cache attributes set whether @value{GDBN} will cache target
12412 memory. While this generally improves performance by reducing debug
12413 protocol overhead, it can lead to incorrect results because @value{GDBN}
12414 does not know about volatile variables or memory mapped device
12419 Enable @value{GDBN} to cache target memory.
12421 Disable @value{GDBN} from caching target memory. This is the default.
12424 @subsection Memory Access Checking
12425 @value{GDBN} can be instructed to refuse accesses to memory that is
12426 not explicitly described. This can be useful if accessing such
12427 regions has undesired effects for a specific target, or to provide
12428 better error checking. The following commands control this behaviour.
12431 @kindex set mem inaccessible-by-default
12432 @item set mem inaccessible-by-default [on|off]
12433 If @code{on} is specified, make @value{GDBN} treat memory not
12434 explicitly described by the memory ranges as non-existent and refuse accesses
12435 to such memory. The checks are only performed if there's at least one
12436 memory range defined. If @code{off} is specified, make @value{GDBN}
12437 treat the memory not explicitly described by the memory ranges as RAM.
12438 The default value is @code{on}.
12439 @kindex show mem inaccessible-by-default
12440 @item show mem inaccessible-by-default
12441 Show the current handling of accesses to unknown memory.
12445 @c @subsubsection Memory Write Verification
12446 @c The memory write verification attributes set whether @value{GDBN}
12447 @c will re-reads data after each write to verify the write was successful.
12451 @c @item noverify (default)
12454 @node Dump/Restore Files
12455 @section Copy Between Memory and a File
12456 @cindex dump/restore files
12457 @cindex append data to a file
12458 @cindex dump data to a file
12459 @cindex restore data from a file
12461 You can use the commands @code{dump}, @code{append}, and
12462 @code{restore} to copy data between target memory and a file. The
12463 @code{dump} and @code{append} commands write data to a file, and the
12464 @code{restore} command reads data from a file back into the inferior's
12465 memory. Files may be in binary, Motorola S-record, Intel hex,
12466 Tektronix Hex, or Verilog Hex format; however, @value{GDBN} can only
12467 append to binary files, and cannot read from Verilog Hex files.
12472 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
12473 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
12474 Dump the contents of memory from @var{start_addr} to @var{end_addr},
12475 or the value of @var{expr}, to @var{filename} in the given format.
12477 The @var{format} parameter may be any one of:
12484 Motorola S-record format.
12486 Tektronix Hex format.
12488 Verilog Hex format.
12491 @value{GDBN} uses the same definitions of these formats as the
12492 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
12493 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
12497 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
12498 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
12499 Append the contents of memory from @var{start_addr} to @var{end_addr},
12500 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
12501 (@value{GDBN} can only append data to files in raw binary form.)
12504 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
12505 Restore the contents of file @var{filename} into memory. The
12506 @code{restore} command can automatically recognize any known @sc{bfd}
12507 file format, except for raw binary. To restore a raw binary file you
12508 must specify the optional keyword @code{binary} after the filename.
12510 If @var{bias} is non-zero, its value will be added to the addresses
12511 contained in the file. Binary files always start at address zero, so
12512 they will be restored at address @var{bias}. Other bfd files have
12513 a built-in location; they will be restored at offset @var{bias}
12514 from that location.
12516 If @var{start} and/or @var{end} are non-zero, then only data between
12517 file offset @var{start} and file offset @var{end} will be restored.
12518 These offsets are relative to the addresses in the file, before
12519 the @var{bias} argument is applied.
12523 @node Core File Generation
12524 @section How to Produce a Core File from Your Program
12525 @cindex dump core from inferior
12527 A @dfn{core file} or @dfn{core dump} is a file that records the memory
12528 image of a running process and its process status (register values
12529 etc.). Its primary use is post-mortem debugging of a program that
12530 crashed while it ran outside a debugger. A program that crashes
12531 automatically produces a core file, unless this feature is disabled by
12532 the user. @xref{Files}, for information on invoking @value{GDBN} in
12533 the post-mortem debugging mode.
12535 Occasionally, you may wish to produce a core file of the program you
12536 are debugging in order to preserve a snapshot of its state.
12537 @value{GDBN} has a special command for that.
12541 @kindex generate-core-file
12542 @item generate-core-file [@var{file}]
12543 @itemx gcore [@var{file}]
12544 Produce a core dump of the inferior process. The optional argument
12545 @var{file} specifies the file name where to put the core dump. If not
12546 specified, the file name defaults to @file{core.@var{pid}}, where
12547 @var{pid} is the inferior process ID.
12549 Note that this command is implemented only for some systems (as of
12550 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
12552 On @sc{gnu}/Linux, this command can take into account the value of the
12553 file @file{/proc/@var{pid}/coredump_filter} when generating the core
12554 dump (@pxref{set use-coredump-filter}), and by default honors the
12555 @code{VM_DONTDUMP} flag for mappings where it is present in the file
12556 @file{/proc/@var{pid}/smaps} (@pxref{set dump-excluded-mappings}).
12558 @kindex set use-coredump-filter
12559 @anchor{set use-coredump-filter}
12560 @item set use-coredump-filter on
12561 @itemx set use-coredump-filter off
12562 Enable or disable the use of the file
12563 @file{/proc/@var{pid}/coredump_filter} when generating core dump
12564 files. This file is used by the Linux kernel to decide what types of
12565 memory mappings will be dumped or ignored when generating a core dump
12566 file. @var{pid} is the process ID of a currently running process.
12568 To make use of this feature, you have to write in the
12569 @file{/proc/@var{pid}/coredump_filter} file a value, in hexadecimal,
12570 which is a bit mask representing the memory mapping types. If a bit
12571 is set in the bit mask, then the memory mappings of the corresponding
12572 types will be dumped; otherwise, they will be ignored. This
12573 configuration is inherited by child processes. For more information
12574 about the bits that can be set in the
12575 @file{/proc/@var{pid}/coredump_filter} file, please refer to the
12576 manpage of @code{core(5)}.
12578 By default, this option is @code{on}. If this option is turned
12579 @code{off}, @value{GDBN} does not read the @file{coredump_filter} file
12580 and instead uses the same default value as the Linux kernel in order
12581 to decide which pages will be dumped in the core dump file. This
12582 value is currently @code{0x33}, which means that bits @code{0}
12583 (anonymous private mappings), @code{1} (anonymous shared mappings),
12584 @code{4} (ELF headers) and @code{5} (private huge pages) are active.
12585 This will cause these memory mappings to be dumped automatically.
12587 @kindex set dump-excluded-mappings
12588 @anchor{set dump-excluded-mappings}
12589 @item set dump-excluded-mappings on
12590 @itemx set dump-excluded-mappings off
12591 If @code{on} is specified, @value{GDBN} will dump memory mappings
12592 marked with the @code{VM_DONTDUMP} flag. This flag is represented in
12593 the file @file{/proc/@var{pid}/smaps} with the acronym @code{dd}.
12595 The default value is @code{off}.
12598 @node Character Sets
12599 @section Character Sets
12600 @cindex character sets
12602 @cindex translating between character sets
12603 @cindex host character set
12604 @cindex target character set
12606 If the program you are debugging uses a different character set to
12607 represent characters and strings than the one @value{GDBN} uses itself,
12608 @value{GDBN} can automatically translate between the character sets for
12609 you. The character set @value{GDBN} uses we call the @dfn{host
12610 character set}; the one the inferior program uses we call the
12611 @dfn{target character set}.
12613 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
12614 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
12615 remote protocol (@pxref{Remote Debugging}) to debug a program
12616 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
12617 then the host character set is Latin-1, and the target character set is
12618 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
12619 target-charset EBCDIC-US}, then @value{GDBN} translates between
12620 @sc{ebcdic} and Latin 1 as you print character or string values, or use
12621 character and string literals in expressions.
12623 @value{GDBN} has no way to automatically recognize which character set
12624 the inferior program uses; you must tell it, using the @code{set
12625 target-charset} command, described below.
12627 Here are the commands for controlling @value{GDBN}'s character set
12631 @item set target-charset @var{charset}
12632 @kindex set target-charset
12633 Set the current target character set to @var{charset}. To display the
12634 list of supported target character sets, type
12635 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
12637 @item set host-charset @var{charset}
12638 @kindex set host-charset
12639 Set the current host character set to @var{charset}.
12641 By default, @value{GDBN} uses a host character set appropriate to the
12642 system it is running on; you can override that default using the
12643 @code{set host-charset} command. On some systems, @value{GDBN} cannot
12644 automatically determine the appropriate host character set. In this
12645 case, @value{GDBN} uses @samp{UTF-8}.
12647 @value{GDBN} can only use certain character sets as its host character
12648 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
12649 @value{GDBN} will list the host character sets it supports.
12651 @item set charset @var{charset}
12652 @kindex set charset
12653 Set the current host and target character sets to @var{charset}. As
12654 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
12655 @value{GDBN} will list the names of the character sets that can be used
12656 for both host and target.
12659 @kindex show charset
12660 Show the names of the current host and target character sets.
12662 @item show host-charset
12663 @kindex show host-charset
12664 Show the name of the current host character set.
12666 @item show target-charset
12667 @kindex show target-charset
12668 Show the name of the current target character set.
12670 @item set target-wide-charset @var{charset}
12671 @kindex set target-wide-charset
12672 Set the current target's wide character set to @var{charset}. This is
12673 the character set used by the target's @code{wchar_t} type. To
12674 display the list of supported wide character sets, type
12675 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
12677 @item show target-wide-charset
12678 @kindex show target-wide-charset
12679 Show the name of the current target's wide character set.
12682 Here is an example of @value{GDBN}'s character set support in action.
12683 Assume that the following source code has been placed in the file
12684 @file{charset-test.c}:
12690 = @{72, 101, 108, 108, 111, 44, 32, 119,
12691 111, 114, 108, 100, 33, 10, 0@};
12692 char ibm1047_hello[]
12693 = @{200, 133, 147, 147, 150, 107, 64, 166,
12694 150, 153, 147, 132, 90, 37, 0@};
12698 printf ("Hello, world!\n");
12702 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
12703 containing the string @samp{Hello, world!} followed by a newline,
12704 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
12706 We compile the program, and invoke the debugger on it:
12709 $ gcc -g charset-test.c -o charset-test
12710 $ gdb -nw charset-test
12711 GNU gdb 2001-12-19-cvs
12712 Copyright 2001 Free Software Foundation, Inc.
12717 We can use the @code{show charset} command to see what character sets
12718 @value{GDBN} is currently using to interpret and display characters and
12722 (@value{GDBP}) show charset
12723 The current host and target character set is `ISO-8859-1'.
12727 For the sake of printing this manual, let's use @sc{ascii} as our
12728 initial character set:
12730 (@value{GDBP}) set charset ASCII
12731 (@value{GDBP}) show charset
12732 The current host and target character set is `ASCII'.
12736 Let's assume that @sc{ascii} is indeed the correct character set for our
12737 host system --- in other words, let's assume that if @value{GDBN} prints
12738 characters using the @sc{ascii} character set, our terminal will display
12739 them properly. Since our current target character set is also
12740 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
12743 (@value{GDBP}) print ascii_hello
12744 $1 = 0x401698 "Hello, world!\n"
12745 (@value{GDBP}) print ascii_hello[0]
12750 @value{GDBN} uses the target character set for character and string
12751 literals you use in expressions:
12754 (@value{GDBP}) print '+'
12759 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
12762 @value{GDBN} relies on the user to tell it which character set the
12763 target program uses. If we print @code{ibm1047_hello} while our target
12764 character set is still @sc{ascii}, we get jibberish:
12767 (@value{GDBP}) print ibm1047_hello
12768 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
12769 (@value{GDBP}) print ibm1047_hello[0]
12774 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
12775 @value{GDBN} tells us the character sets it supports:
12778 (@value{GDBP}) set target-charset
12779 ASCII EBCDIC-US IBM1047 ISO-8859-1
12780 (@value{GDBP}) set target-charset
12783 We can select @sc{ibm1047} as our target character set, and examine the
12784 program's strings again. Now the @sc{ascii} string is wrong, but
12785 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
12786 target character set, @sc{ibm1047}, to the host character set,
12787 @sc{ascii}, and they display correctly:
12790 (@value{GDBP}) set target-charset IBM1047
12791 (@value{GDBP}) show charset
12792 The current host character set is `ASCII'.
12793 The current target character set is `IBM1047'.
12794 (@value{GDBP}) print ascii_hello
12795 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
12796 (@value{GDBP}) print ascii_hello[0]
12798 (@value{GDBP}) print ibm1047_hello
12799 $8 = 0x4016a8 "Hello, world!\n"
12800 (@value{GDBP}) print ibm1047_hello[0]
12805 As above, @value{GDBN} uses the target character set for character and
12806 string literals you use in expressions:
12809 (@value{GDBP}) print '+'
12814 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
12817 @node Caching Target Data
12818 @section Caching Data of Targets
12819 @cindex caching data of targets
12821 @value{GDBN} caches data exchanged between the debugger and a target.
12822 Each cache is associated with the address space of the inferior.
12823 @xref{Inferiors and Programs}, about inferior and address space.
12824 Such caching generally improves performance in remote debugging
12825 (@pxref{Remote Debugging}), because it reduces the overhead of the
12826 remote protocol by bundling memory reads and writes into large chunks.
12827 Unfortunately, simply caching everything would lead to incorrect results,
12828 since @value{GDBN} does not necessarily know anything about volatile
12829 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
12830 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
12832 Therefore, by default, @value{GDBN} only caches data
12833 known to be on the stack@footnote{In non-stop mode, it is moderately
12834 rare for a running thread to modify the stack of a stopped thread
12835 in a way that would interfere with a backtrace, and caching of
12836 stack reads provides a significant speed up of remote backtraces.} or
12837 in the code segment.
12838 Other regions of memory can be explicitly marked as
12839 cacheable; @pxref{Memory Region Attributes}.
12842 @kindex set remotecache
12843 @item set remotecache on
12844 @itemx set remotecache off
12845 This option no longer does anything; it exists for compatibility
12848 @kindex show remotecache
12849 @item show remotecache
12850 Show the current state of the obsolete remotecache flag.
12852 @kindex set stack-cache
12853 @item set stack-cache on
12854 @itemx set stack-cache off
12855 Enable or disable caching of stack accesses. When @code{on}, use
12856 caching. By default, this option is @code{on}.
12858 @kindex show stack-cache
12859 @item show stack-cache
12860 Show the current state of data caching for memory accesses.
12862 @kindex set code-cache
12863 @item set code-cache on
12864 @itemx set code-cache off
12865 Enable or disable caching of code segment accesses. When @code{on},
12866 use caching. By default, this option is @code{on}. This improves
12867 performance of disassembly in remote debugging.
12869 @kindex show code-cache
12870 @item show code-cache
12871 Show the current state of target memory cache for code segment
12874 @kindex info dcache
12875 @item info dcache @r{[}line@r{]}
12876 Print the information about the performance of data cache of the
12877 current inferior's address space. The information displayed
12878 includes the dcache width and depth, and for each cache line, its
12879 number, address, and how many times it was referenced. This
12880 command is useful for debugging the data cache operation.
12882 If a line number is specified, the contents of that line will be
12885 @item set dcache size @var{size}
12886 @cindex dcache size
12887 @kindex set dcache size
12888 Set maximum number of entries in dcache (dcache depth above).
12890 @item set dcache line-size @var{line-size}
12891 @cindex dcache line-size
12892 @kindex set dcache line-size
12893 Set number of bytes each dcache entry caches (dcache width above).
12894 Must be a power of 2.
12896 @item show dcache size
12897 @kindex show dcache size
12898 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
12900 @item show dcache line-size
12901 @kindex show dcache line-size
12902 Show default size of dcache lines.
12906 @node Searching Memory
12907 @section Search Memory
12908 @cindex searching memory
12910 Memory can be searched for a particular sequence of bytes with the
12911 @code{find} command.
12915 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
12916 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
12917 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
12918 etc. The search begins at address @var{start_addr} and continues for either
12919 @var{len} bytes or through to @var{end_addr} inclusive.
12922 @var{s} and @var{n} are optional parameters.
12923 They may be specified in either order, apart or together.
12926 @item @var{s}, search query size
12927 The size of each search query value.
12933 halfwords (two bytes)
12937 giant words (eight bytes)
12940 All values are interpreted in the current language.
12941 This means, for example, that if the current source language is C/C@t{++}
12942 then searching for the string ``hello'' includes the trailing '\0'.
12943 The null terminator can be removed from searching by using casts,
12944 e.g.: @samp{@{char[5]@}"hello"}.
12946 If the value size is not specified, it is taken from the
12947 value's type in the current language.
12948 This is useful when one wants to specify the search
12949 pattern as a mixture of types.
12950 Note that this means, for example, that in the case of C-like languages
12951 a search for an untyped 0x42 will search for @samp{(int) 0x42}
12952 which is typically four bytes.
12954 @item @var{n}, maximum number of finds
12955 The maximum number of matches to print. The default is to print all finds.
12958 You can use strings as search values. Quote them with double-quotes
12960 The string value is copied into the search pattern byte by byte,
12961 regardless of the endianness of the target and the size specification.
12963 The address of each match found is printed as well as a count of the
12964 number of matches found.
12966 The address of the last value found is stored in convenience variable
12968 A count of the number of matches is stored in @samp{$numfound}.
12970 For example, if stopped at the @code{printf} in this function:
12976 static char hello[] = "hello-hello";
12977 static struct @{ char c; short s; int i; @}
12978 __attribute__ ((packed)) mixed
12979 = @{ 'c', 0x1234, 0x87654321 @};
12980 printf ("%s\n", hello);
12985 you get during debugging:
12988 (gdb) find &hello[0], +sizeof(hello), "hello"
12989 0x804956d <hello.1620+6>
12991 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
12992 0x8049567 <hello.1620>
12993 0x804956d <hello.1620+6>
12995 (gdb) find &hello[0], +sizeof(hello), @{char[5]@}"hello"
12996 0x8049567 <hello.1620>
12997 0x804956d <hello.1620+6>
12999 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
13000 0x8049567 <hello.1620>
13002 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
13003 0x8049560 <mixed.1625>
13005 (gdb) print $numfound
13008 $2 = (void *) 0x8049560
13012 @section Value Sizes
13014 Whenever @value{GDBN} prints a value memory will be allocated within
13015 @value{GDBN} to hold the contents of the value. It is possible in
13016 some languages with dynamic typing systems, that an invalid program
13017 may indicate a value that is incorrectly large, this in turn may cause
13018 @value{GDBN} to try and allocate an overly large ammount of memory.
13021 @kindex set max-value-size
13022 @item set max-value-size @var{bytes}
13023 @itemx set max-value-size unlimited
13024 Set the maximum size of memory that @value{GDBN} will allocate for the
13025 contents of a value to @var{bytes}, trying to display a value that
13026 requires more memory than that will result in an error.
13028 Setting this variable does not effect values that have already been
13029 allocated within @value{GDBN}, only future allocations.
13031 There's a minimum size that @code{max-value-size} can be set to in
13032 order that @value{GDBN} can still operate correctly, this minimum is
13033 currently 16 bytes.
13035 The limit applies to the results of some subexpressions as well as to
13036 complete expressions. For example, an expression denoting a simple
13037 integer component, such as @code{x.y.z}, may fail if the size of
13038 @var{x.y} is dynamic and exceeds @var{bytes}. On the other hand,
13039 @value{GDBN} is sometimes clever; the expression @code{A[i]}, where
13040 @var{A} is an array variable with non-constant size, will generally
13041 succeed regardless of the bounds on @var{A}, as long as the component
13042 size is less than @var{bytes}.
13044 The default value of @code{max-value-size} is currently 64k.
13046 @kindex show max-value-size
13047 @item show max-value-size
13048 Show the maximum size of memory, in bytes, that @value{GDBN} will
13049 allocate for the contents of a value.
13052 @node Optimized Code
13053 @chapter Debugging Optimized Code
13054 @cindex optimized code, debugging
13055 @cindex debugging optimized code
13057 Almost all compilers support optimization. With optimization
13058 disabled, the compiler generates assembly code that corresponds
13059 directly to your source code, in a simplistic way. As the compiler
13060 applies more powerful optimizations, the generated assembly code
13061 diverges from your original source code. With help from debugging
13062 information generated by the compiler, @value{GDBN} can map from
13063 the running program back to constructs from your original source.
13065 @value{GDBN} is more accurate with optimization disabled. If you
13066 can recompile without optimization, it is easier to follow the
13067 progress of your program during debugging. But, there are many cases
13068 where you may need to debug an optimized version.
13070 When you debug a program compiled with @samp{-g -O}, remember that the
13071 optimizer has rearranged your code; the debugger shows you what is
13072 really there. Do not be too surprised when the execution path does not
13073 exactly match your source file! An extreme example: if you define a
13074 variable, but never use it, @value{GDBN} never sees that
13075 variable---because the compiler optimizes it out of existence.
13077 Some things do not work as well with @samp{-g -O} as with just
13078 @samp{-g}, particularly on machines with instruction scheduling. If in
13079 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
13080 please report it to us as a bug (including a test case!).
13081 @xref{Variables}, for more information about debugging optimized code.
13084 * Inline Functions:: How @value{GDBN} presents inlining
13085 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
13088 @node Inline Functions
13089 @section Inline Functions
13090 @cindex inline functions, debugging
13092 @dfn{Inlining} is an optimization that inserts a copy of the function
13093 body directly at each call site, instead of jumping to a shared
13094 routine. @value{GDBN} displays inlined functions just like
13095 non-inlined functions. They appear in backtraces. You can view their
13096 arguments and local variables, step into them with @code{step}, skip
13097 them with @code{next}, and escape from them with @code{finish}.
13098 You can check whether a function was inlined by using the
13099 @code{info frame} command.
13101 For @value{GDBN} to support inlined functions, the compiler must
13102 record information about inlining in the debug information ---
13103 @value{NGCC} using the @sc{dwarf 2} format does this, and several
13104 other compilers do also. @value{GDBN} only supports inlined functions
13105 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
13106 do not emit two required attributes (@samp{DW_AT_call_file} and
13107 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
13108 function calls with earlier versions of @value{NGCC}. It instead
13109 displays the arguments and local variables of inlined functions as
13110 local variables in the caller.
13112 The body of an inlined function is directly included at its call site;
13113 unlike a non-inlined function, there are no instructions devoted to
13114 the call. @value{GDBN} still pretends that the call site and the
13115 start of the inlined function are different instructions. Stepping to
13116 the call site shows the call site, and then stepping again shows
13117 the first line of the inlined function, even though no additional
13118 instructions are executed.
13120 This makes source-level debugging much clearer; you can see both the
13121 context of the call and then the effect of the call. Only stepping by
13122 a single instruction using @code{stepi} or @code{nexti} does not do
13123 this; single instruction steps always show the inlined body.
13125 There are some ways that @value{GDBN} does not pretend that inlined
13126 function calls are the same as normal calls:
13130 Setting breakpoints at the call site of an inlined function may not
13131 work, because the call site does not contain any code. @value{GDBN}
13132 may incorrectly move the breakpoint to the next line of the enclosing
13133 function, after the call. This limitation will be removed in a future
13134 version of @value{GDBN}; until then, set a breakpoint on an earlier line
13135 or inside the inlined function instead.
13138 @value{GDBN} cannot locate the return value of inlined calls after
13139 using the @code{finish} command. This is a limitation of compiler-generated
13140 debugging information; after @code{finish}, you can step to the next line
13141 and print a variable where your program stored the return value.
13145 @node Tail Call Frames
13146 @section Tail Call Frames
13147 @cindex tail call frames, debugging
13149 Function @code{B} can call function @code{C} in its very last statement. In
13150 unoptimized compilation the call of @code{C} is immediately followed by return
13151 instruction at the end of @code{B} code. Optimizing compiler may replace the
13152 call and return in function @code{B} into one jump to function @code{C}
13153 instead. Such use of a jump instruction is called @dfn{tail call}.
13155 During execution of function @code{C}, there will be no indication in the
13156 function call stack frames that it was tail-called from @code{B}. If function
13157 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
13158 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
13159 some cases @value{GDBN} can determine that @code{C} was tail-called from
13160 @code{B}, and it will then create fictitious call frame for that, with the
13161 return address set up as if @code{B} called @code{C} normally.
13163 This functionality is currently supported only by DWARF 2 debugging format and
13164 the compiler has to produce @samp{DW_TAG_call_site} tags. With
13165 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
13168 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
13169 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
13173 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
13175 Stack level 1, frame at 0x7fffffffda30:
13176 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
13177 tail call frame, caller of frame at 0x7fffffffda30
13178 source language c++.
13179 Arglist at unknown address.
13180 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
13183 The detection of all the possible code path executions can find them ambiguous.
13184 There is no execution history stored (possible @ref{Reverse Execution} is never
13185 used for this purpose) and the last known caller could have reached the known
13186 callee by multiple different jump sequences. In such case @value{GDBN} still
13187 tries to show at least all the unambiguous top tail callers and all the
13188 unambiguous bottom tail calees, if any.
13191 @anchor{set debug entry-values}
13192 @item set debug entry-values
13193 @kindex set debug entry-values
13194 When set to on, enables printing of analysis messages for both frame argument
13195 values at function entry and tail calls. It will show all the possible valid
13196 tail calls code paths it has considered. It will also print the intersection
13197 of them with the final unambiguous (possibly partial or even empty) code path
13200 @item show debug entry-values
13201 @kindex show debug entry-values
13202 Show the current state of analysis messages printing for both frame argument
13203 values at function entry and tail calls.
13206 The analysis messages for tail calls can for example show why the virtual tail
13207 call frame for function @code{c} has not been recognized (due to the indirect
13208 reference by variable @code{x}):
13211 static void __attribute__((noinline, noclone)) c (void);
13212 void (*x) (void) = c;
13213 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
13214 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
13215 int main (void) @{ x (); return 0; @}
13217 Breakpoint 1, DW_OP_entry_value resolving cannot find
13218 DW_TAG_call_site 0x40039a in main
13220 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
13223 #1 0x000000000040039a in main () at t.c:5
13226 Another possibility is an ambiguous virtual tail call frames resolution:
13230 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
13231 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
13232 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
13233 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
13234 static void __attribute__((noinline, noclone)) b (void)
13235 @{ if (i) c (); else e (); @}
13236 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
13237 int main (void) @{ a (); return 0; @}
13239 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
13240 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
13241 tailcall: reduced: 0x4004d2(a) |
13244 #1 0x00000000004004d2 in a () at t.c:8
13245 #2 0x0000000000400395 in main () at t.c:9
13248 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
13249 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
13251 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
13252 @ifset HAVE_MAKEINFO_CLICK
13253 @set ARROW @click{}
13254 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
13255 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
13257 @ifclear HAVE_MAKEINFO_CLICK
13259 @set CALLSEQ1B @value{CALLSEQ1A}
13260 @set CALLSEQ2B @value{CALLSEQ2A}
13263 Frames #0 and #2 are real, #1 is a virtual tail call frame.
13264 The code can have possible execution paths @value{CALLSEQ1B} or
13265 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
13267 @code{initial:} state shows some random possible calling sequence @value{GDBN}
13268 has found. It then finds another possible calling sequcen - that one is
13269 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
13270 printed as the @code{reduced:} calling sequence. That one could have many
13271 futher @code{compare:} and @code{reduced:} statements as long as there remain
13272 any non-ambiguous sequence entries.
13274 For the frame of function @code{b} in both cases there are different possible
13275 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
13276 also ambigous. The only non-ambiguous frame is the one for function @code{a},
13277 therefore this one is displayed to the user while the ambiguous frames are
13280 There can be also reasons why printing of frame argument values at function
13285 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
13286 static void __attribute__((noinline, noclone)) a (int i);
13287 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
13288 static void __attribute__((noinline, noclone)) a (int i)
13289 @{ if (i) b (i - 1); else c (0); @}
13290 int main (void) @{ a (5); return 0; @}
13293 #0 c (i=i@@entry=0) at t.c:2
13294 #1 0x0000000000400428 in a (DW_OP_entry_value resolving has found
13295 function "a" at 0x400420 can call itself via tail calls
13296 i=<optimized out>) at t.c:6
13297 #2 0x000000000040036e in main () at t.c:7
13300 @value{GDBN} cannot find out from the inferior state if and how many times did
13301 function @code{a} call itself (via function @code{b}) as these calls would be
13302 tail calls. Such tail calls would modify thue @code{i} variable, therefore
13303 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
13304 prints @code{<optimized out>} instead.
13307 @chapter C Preprocessor Macros
13309 Some languages, such as C and C@t{++}, provide a way to define and invoke
13310 ``preprocessor macros'' which expand into strings of tokens.
13311 @value{GDBN} can evaluate expressions containing macro invocations, show
13312 the result of macro expansion, and show a macro's definition, including
13313 where it was defined.
13315 You may need to compile your program specially to provide @value{GDBN}
13316 with information about preprocessor macros. Most compilers do not
13317 include macros in their debugging information, even when you compile
13318 with the @option{-g} flag. @xref{Compilation}.
13320 A program may define a macro at one point, remove that definition later,
13321 and then provide a different definition after that. Thus, at different
13322 points in the program, a macro may have different definitions, or have
13323 no definition at all. If there is a current stack frame, @value{GDBN}
13324 uses the macros in scope at that frame's source code line. Otherwise,
13325 @value{GDBN} uses the macros in scope at the current listing location;
13328 Whenever @value{GDBN} evaluates an expression, it always expands any
13329 macro invocations present in the expression. @value{GDBN} also provides
13330 the following commands for working with macros explicitly.
13334 @kindex macro expand
13335 @cindex macro expansion, showing the results of preprocessor
13336 @cindex preprocessor macro expansion, showing the results of
13337 @cindex expanding preprocessor macros
13338 @item macro expand @var{expression}
13339 @itemx macro exp @var{expression}
13340 Show the results of expanding all preprocessor macro invocations in
13341 @var{expression}. Since @value{GDBN} simply expands macros, but does
13342 not parse the result, @var{expression} need not be a valid expression;
13343 it can be any string of tokens.
13346 @item macro expand-once @var{expression}
13347 @itemx macro exp1 @var{expression}
13348 @cindex expand macro once
13349 @i{(This command is not yet implemented.)} Show the results of
13350 expanding those preprocessor macro invocations that appear explicitly in
13351 @var{expression}. Macro invocations appearing in that expansion are
13352 left unchanged. This command allows you to see the effect of a
13353 particular macro more clearly, without being confused by further
13354 expansions. Since @value{GDBN} simply expands macros, but does not
13355 parse the result, @var{expression} need not be a valid expression; it
13356 can be any string of tokens.
13359 @cindex macro definition, showing
13360 @cindex definition of a macro, showing
13361 @cindex macros, from debug info
13362 @item info macro [-a|-all] [--] @var{macro}
13363 Show the current definition or all definitions of the named @var{macro},
13364 and describe the source location or compiler command-line where that
13365 definition was established. The optional double dash is to signify the end of
13366 argument processing and the beginning of @var{macro} for non C-like macros where
13367 the macro may begin with a hyphen.
13369 @kindex info macros
13370 @item info macros @var{location}
13371 Show all macro definitions that are in effect at the location specified
13372 by @var{location}, and describe the source location or compiler
13373 command-line where those definitions were established.
13375 @kindex macro define
13376 @cindex user-defined macros
13377 @cindex defining macros interactively
13378 @cindex macros, user-defined
13379 @item macro define @var{macro} @var{replacement-list}
13380 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
13381 Introduce a definition for a preprocessor macro named @var{macro},
13382 invocations of which are replaced by the tokens given in
13383 @var{replacement-list}. The first form of this command defines an
13384 ``object-like'' macro, which takes no arguments; the second form
13385 defines a ``function-like'' macro, which takes the arguments given in
13388 A definition introduced by this command is in scope in every
13389 expression evaluated in @value{GDBN}, until it is removed with the
13390 @code{macro undef} command, described below. The definition overrides
13391 all definitions for @var{macro} present in the program being debugged,
13392 as well as any previous user-supplied definition.
13394 @kindex macro undef
13395 @item macro undef @var{macro}
13396 Remove any user-supplied definition for the macro named @var{macro}.
13397 This command only affects definitions provided with the @code{macro
13398 define} command, described above; it cannot remove definitions present
13399 in the program being debugged.
13403 List all the macros defined using the @code{macro define} command.
13406 @cindex macros, example of debugging with
13407 Here is a transcript showing the above commands in action. First, we
13408 show our source files:
13413 #include "sample.h"
13416 #define ADD(x) (M + x)
13421 printf ("Hello, world!\n");
13423 printf ("We're so creative.\n");
13425 printf ("Goodbye, world!\n");
13432 Now, we compile the program using the @sc{gnu} C compiler,
13433 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
13434 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
13435 and @option{-gdwarf-4}; we recommend always choosing the most recent
13436 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
13437 includes information about preprocessor macros in the debugging
13441 $ gcc -gdwarf-2 -g3 sample.c -o sample
13445 Now, we start @value{GDBN} on our sample program:
13449 GNU gdb 2002-05-06-cvs
13450 Copyright 2002 Free Software Foundation, Inc.
13451 GDB is free software, @dots{}
13455 We can expand macros and examine their definitions, even when the
13456 program is not running. @value{GDBN} uses the current listing position
13457 to decide which macro definitions are in scope:
13460 (@value{GDBP}) list main
13463 5 #define ADD(x) (M + x)
13468 10 printf ("Hello, world!\n");
13470 12 printf ("We're so creative.\n");
13471 (@value{GDBP}) info macro ADD
13472 Defined at /home/jimb/gdb/macros/play/sample.c:5
13473 #define ADD(x) (M + x)
13474 (@value{GDBP}) info macro Q
13475 Defined at /home/jimb/gdb/macros/play/sample.h:1
13476 included at /home/jimb/gdb/macros/play/sample.c:2
13478 (@value{GDBP}) macro expand ADD(1)
13479 expands to: (42 + 1)
13480 (@value{GDBP}) macro expand-once ADD(1)
13481 expands to: once (M + 1)
13485 In the example above, note that @code{macro expand-once} expands only
13486 the macro invocation explicit in the original text --- the invocation of
13487 @code{ADD} --- but does not expand the invocation of the macro @code{M},
13488 which was introduced by @code{ADD}.
13490 Once the program is running, @value{GDBN} uses the macro definitions in
13491 force at the source line of the current stack frame:
13494 (@value{GDBP}) break main
13495 Breakpoint 1 at 0x8048370: file sample.c, line 10.
13497 Starting program: /home/jimb/gdb/macros/play/sample
13499 Breakpoint 1, main () at sample.c:10
13500 10 printf ("Hello, world!\n");
13504 At line 10, the definition of the macro @code{N} at line 9 is in force:
13507 (@value{GDBP}) info macro N
13508 Defined at /home/jimb/gdb/macros/play/sample.c:9
13510 (@value{GDBP}) macro expand N Q M
13511 expands to: 28 < 42
13512 (@value{GDBP}) print N Q M
13517 As we step over directives that remove @code{N}'s definition, and then
13518 give it a new definition, @value{GDBN} finds the definition (or lack
13519 thereof) in force at each point:
13522 (@value{GDBP}) next
13524 12 printf ("We're so creative.\n");
13525 (@value{GDBP}) info macro N
13526 The symbol `N' has no definition as a C/C++ preprocessor macro
13527 at /home/jimb/gdb/macros/play/sample.c:12
13528 (@value{GDBP}) next
13530 14 printf ("Goodbye, world!\n");
13531 (@value{GDBP}) info macro N
13532 Defined at /home/jimb/gdb/macros/play/sample.c:13
13534 (@value{GDBP}) macro expand N Q M
13535 expands to: 1729 < 42
13536 (@value{GDBP}) print N Q M
13541 In addition to source files, macros can be defined on the compilation command
13542 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
13543 such a way, @value{GDBN} displays the location of their definition as line zero
13544 of the source file submitted to the compiler.
13547 (@value{GDBP}) info macro __STDC__
13548 Defined at /home/jimb/gdb/macros/play/sample.c:0
13555 @chapter Tracepoints
13556 @c This chapter is based on the documentation written by Michael
13557 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
13559 @cindex tracepoints
13560 In some applications, it is not feasible for the debugger to interrupt
13561 the program's execution long enough for the developer to learn
13562 anything helpful about its behavior. If the program's correctness
13563 depends on its real-time behavior, delays introduced by a debugger
13564 might cause the program to change its behavior drastically, or perhaps
13565 fail, even when the code itself is correct. It is useful to be able
13566 to observe the program's behavior without interrupting it.
13568 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
13569 specify locations in the program, called @dfn{tracepoints}, and
13570 arbitrary expressions to evaluate when those tracepoints are reached.
13571 Later, using the @code{tfind} command, you can examine the values
13572 those expressions had when the program hit the tracepoints. The
13573 expressions may also denote objects in memory---structures or arrays,
13574 for example---whose values @value{GDBN} should record; while visiting
13575 a particular tracepoint, you may inspect those objects as if they were
13576 in memory at that moment. However, because @value{GDBN} records these
13577 values without interacting with you, it can do so quickly and
13578 unobtrusively, hopefully not disturbing the program's behavior.
13580 The tracepoint facility is currently available only for remote
13581 targets. @xref{Targets}. In addition, your remote target must know
13582 how to collect trace data. This functionality is implemented in the
13583 remote stub; however, none of the stubs distributed with @value{GDBN}
13584 support tracepoints as of this writing. The format of the remote
13585 packets used to implement tracepoints are described in @ref{Tracepoint
13588 It is also possible to get trace data from a file, in a manner reminiscent
13589 of corefiles; you specify the filename, and use @code{tfind} to search
13590 through the file. @xref{Trace Files}, for more details.
13592 This chapter describes the tracepoint commands and features.
13595 * Set Tracepoints::
13596 * Analyze Collected Data::
13597 * Tracepoint Variables::
13601 @node Set Tracepoints
13602 @section Commands to Set Tracepoints
13604 Before running such a @dfn{trace experiment}, an arbitrary number of
13605 tracepoints can be set. A tracepoint is actually a special type of
13606 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
13607 standard breakpoint commands. For instance, as with breakpoints,
13608 tracepoint numbers are successive integers starting from one, and many
13609 of the commands associated with tracepoints take the tracepoint number
13610 as their argument, to identify which tracepoint to work on.
13612 For each tracepoint, you can specify, in advance, some arbitrary set
13613 of data that you want the target to collect in the trace buffer when
13614 it hits that tracepoint. The collected data can include registers,
13615 local variables, or global data. Later, you can use @value{GDBN}
13616 commands to examine the values these data had at the time the
13617 tracepoint was hit.
13619 Tracepoints do not support every breakpoint feature. Ignore counts on
13620 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
13621 commands when they are hit. Tracepoints may not be thread-specific
13624 @cindex fast tracepoints
13625 Some targets may support @dfn{fast tracepoints}, which are inserted in
13626 a different way (such as with a jump instead of a trap), that is
13627 faster but possibly restricted in where they may be installed.
13629 @cindex static tracepoints
13630 @cindex markers, static tracepoints
13631 @cindex probing markers, static tracepoints
13632 Regular and fast tracepoints are dynamic tracing facilities, meaning
13633 that they can be used to insert tracepoints at (almost) any location
13634 in the target. Some targets may also support controlling @dfn{static
13635 tracepoints} from @value{GDBN}. With static tracing, a set of
13636 instrumentation points, also known as @dfn{markers}, are embedded in
13637 the target program, and can be activated or deactivated by name or
13638 address. These are usually placed at locations which facilitate
13639 investigating what the target is actually doing. @value{GDBN}'s
13640 support for static tracing includes being able to list instrumentation
13641 points, and attach them with @value{GDBN} defined high level
13642 tracepoints that expose the whole range of convenience of
13643 @value{GDBN}'s tracepoints support. Namely, support for collecting
13644 registers values and values of global or local (to the instrumentation
13645 point) variables; tracepoint conditions and trace state variables.
13646 The act of installing a @value{GDBN} static tracepoint on an
13647 instrumentation point, or marker, is referred to as @dfn{probing} a
13648 static tracepoint marker.
13650 @code{gdbserver} supports tracepoints on some target systems.
13651 @xref{Server,,Tracepoints support in @code{gdbserver}}.
13653 This section describes commands to set tracepoints and associated
13654 conditions and actions.
13657 * Create and Delete Tracepoints::
13658 * Enable and Disable Tracepoints::
13659 * Tracepoint Passcounts::
13660 * Tracepoint Conditions::
13661 * Trace State Variables::
13662 * Tracepoint Actions::
13663 * Listing Tracepoints::
13664 * Listing Static Tracepoint Markers::
13665 * Starting and Stopping Trace Experiments::
13666 * Tracepoint Restrictions::
13669 @node Create and Delete Tracepoints
13670 @subsection Create and Delete Tracepoints
13673 @cindex set tracepoint
13675 @item trace @var{location}
13676 The @code{trace} command is very similar to the @code{break} command.
13677 Its argument @var{location} can be any valid location.
13678 @xref{Specify Location}. The @code{trace} command defines a tracepoint,
13679 which is a point in the target program where the debugger will briefly stop,
13680 collect some data, and then allow the program to continue. Setting a tracepoint
13681 or changing its actions takes effect immediately if the remote stub
13682 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
13684 If remote stub doesn't support the @samp{InstallInTrace} feature, all
13685 these changes don't take effect until the next @code{tstart}
13686 command, and once a trace experiment is running, further changes will
13687 not have any effect until the next trace experiment starts. In addition,
13688 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
13689 address is not yet resolved. (This is similar to pending breakpoints.)
13690 Pending tracepoints are not downloaded to the target and not installed
13691 until they are resolved. The resolution of pending tracepoints requires
13692 @value{GDBN} support---when debugging with the remote target, and
13693 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
13694 tracing}), pending tracepoints can not be resolved (and downloaded to
13695 the remote stub) while @value{GDBN} is disconnected.
13697 Here are some examples of using the @code{trace} command:
13700 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
13702 (@value{GDBP}) @b{trace +2} // 2 lines forward
13704 (@value{GDBP}) @b{trace my_function} // first source line of function
13706 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
13708 (@value{GDBP}) @b{trace *0x2117c4} // an address
13712 You can abbreviate @code{trace} as @code{tr}.
13714 @item trace @var{location} if @var{cond}
13715 Set a tracepoint with condition @var{cond}; evaluate the expression
13716 @var{cond} each time the tracepoint is reached, and collect data only
13717 if the value is nonzero---that is, if @var{cond} evaluates as true.
13718 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
13719 information on tracepoint conditions.
13721 @item ftrace @var{location} [ if @var{cond} ]
13722 @cindex set fast tracepoint
13723 @cindex fast tracepoints, setting
13725 The @code{ftrace} command sets a fast tracepoint. For targets that
13726 support them, fast tracepoints will use a more efficient but possibly
13727 less general technique to trigger data collection, such as a jump
13728 instruction instead of a trap, or some sort of hardware support. It
13729 may not be possible to create a fast tracepoint at the desired
13730 location, in which case the command will exit with an explanatory
13733 @value{GDBN} handles arguments to @code{ftrace} exactly as for
13736 On 32-bit x86-architecture systems, fast tracepoints normally need to
13737 be placed at an instruction that is 5 bytes or longer, but can be
13738 placed at 4-byte instructions if the low 64K of memory of the target
13739 program is available to install trampolines. Some Unix-type systems,
13740 such as @sc{gnu}/Linux, exclude low addresses from the program's
13741 address space; but for instance with the Linux kernel it is possible
13742 to let @value{GDBN} use this area by doing a @command{sysctl} command
13743 to set the @code{mmap_min_addr} kernel parameter, as in
13746 sudo sysctl -w vm.mmap_min_addr=32768
13750 which sets the low address to 32K, which leaves plenty of room for
13751 trampolines. The minimum address should be set to a page boundary.
13753 @item strace @var{location} [ if @var{cond} ]
13754 @cindex set static tracepoint
13755 @cindex static tracepoints, setting
13756 @cindex probe static tracepoint marker
13758 The @code{strace} command sets a static tracepoint. For targets that
13759 support it, setting a static tracepoint probes a static
13760 instrumentation point, or marker, found at @var{location}. It may not
13761 be possible to set a static tracepoint at the desired location, in
13762 which case the command will exit with an explanatory message.
13764 @value{GDBN} handles arguments to @code{strace} exactly as for
13765 @code{trace}, with the addition that the user can also specify
13766 @code{-m @var{marker}} as @var{location}. This probes the marker
13767 identified by the @var{marker} string identifier. This identifier
13768 depends on the static tracepoint backend library your program is
13769 using. You can find all the marker identifiers in the @samp{ID} field
13770 of the @code{info static-tracepoint-markers} command output.
13771 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
13772 Markers}. For example, in the following small program using the UST
13778 trace_mark(ust, bar33, "str %s", "FOOBAZ");
13783 the marker id is composed of joining the first two arguments to the
13784 @code{trace_mark} call with a slash, which translates to:
13787 (@value{GDBP}) info static-tracepoint-markers
13788 Cnt Enb ID Address What
13789 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
13795 so you may probe the marker above with:
13798 (@value{GDBP}) strace -m ust/bar33
13801 Static tracepoints accept an extra collect action --- @code{collect
13802 $_sdata}. This collects arbitrary user data passed in the probe point
13803 call to the tracing library. In the UST example above, you'll see
13804 that the third argument to @code{trace_mark} is a printf-like format
13805 string. The user data is then the result of running that formating
13806 string against the following arguments. Note that @code{info
13807 static-tracepoint-markers} command output lists that format string in
13808 the @samp{Data:} field.
13810 You can inspect this data when analyzing the trace buffer, by printing
13811 the $_sdata variable like any other variable available to
13812 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
13815 @cindex last tracepoint number
13816 @cindex recent tracepoint number
13817 @cindex tracepoint number
13818 The convenience variable @code{$tpnum} records the tracepoint number
13819 of the most recently set tracepoint.
13821 @kindex delete tracepoint
13822 @cindex tracepoint deletion
13823 @item delete tracepoint @r{[}@var{num}@r{]}
13824 Permanently delete one or more tracepoints. With no argument, the
13825 default is to delete all tracepoints. Note that the regular
13826 @code{delete} command can remove tracepoints also.
13831 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
13833 (@value{GDBP}) @b{delete trace} // remove all tracepoints
13837 You can abbreviate this command as @code{del tr}.
13840 @node Enable and Disable Tracepoints
13841 @subsection Enable and Disable Tracepoints
13843 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
13846 @kindex disable tracepoint
13847 @item disable tracepoint @r{[}@var{num}@r{]}
13848 Disable tracepoint @var{num}, or all tracepoints if no argument
13849 @var{num} is given. A disabled tracepoint will have no effect during
13850 a trace experiment, but it is not forgotten. You can re-enable
13851 a disabled tracepoint using the @code{enable tracepoint} command.
13852 If the command is issued during a trace experiment and the debug target
13853 has support for disabling tracepoints during a trace experiment, then the
13854 change will be effective immediately. Otherwise, it will be applied to the
13855 next trace experiment.
13857 @kindex enable tracepoint
13858 @item enable tracepoint @r{[}@var{num}@r{]}
13859 Enable tracepoint @var{num}, or all tracepoints. If this command is
13860 issued during a trace experiment and the debug target supports enabling
13861 tracepoints during a trace experiment, then the enabled tracepoints will
13862 become effective immediately. Otherwise, they will become effective the
13863 next time a trace experiment is run.
13866 @node Tracepoint Passcounts
13867 @subsection Tracepoint Passcounts
13871 @cindex tracepoint pass count
13872 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
13873 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
13874 automatically stop a trace experiment. If a tracepoint's passcount is
13875 @var{n}, then the trace experiment will be automatically stopped on
13876 the @var{n}'th time that tracepoint is hit. If the tracepoint number
13877 @var{num} is not specified, the @code{passcount} command sets the
13878 passcount of the most recently defined tracepoint. If no passcount is
13879 given, the trace experiment will run until stopped explicitly by the
13885 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
13886 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
13888 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
13889 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
13890 (@value{GDBP}) @b{trace foo}
13891 (@value{GDBP}) @b{pass 3}
13892 (@value{GDBP}) @b{trace bar}
13893 (@value{GDBP}) @b{pass 2}
13894 (@value{GDBP}) @b{trace baz}
13895 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
13896 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
13897 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
13898 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
13902 @node Tracepoint Conditions
13903 @subsection Tracepoint Conditions
13904 @cindex conditional tracepoints
13905 @cindex tracepoint conditions
13907 The simplest sort of tracepoint collects data every time your program
13908 reaches a specified place. You can also specify a @dfn{condition} for
13909 a tracepoint. A condition is just a Boolean expression in your
13910 programming language (@pxref{Expressions, ,Expressions}). A
13911 tracepoint with a condition evaluates the expression each time your
13912 program reaches it, and data collection happens only if the condition
13915 Tracepoint conditions can be specified when a tracepoint is set, by
13916 using @samp{if} in the arguments to the @code{trace} command.
13917 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
13918 also be set or changed at any time with the @code{condition} command,
13919 just as with breakpoints.
13921 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
13922 the conditional expression itself. Instead, @value{GDBN} encodes the
13923 expression into an agent expression (@pxref{Agent Expressions})
13924 suitable for execution on the target, independently of @value{GDBN}.
13925 Global variables become raw memory locations, locals become stack
13926 accesses, and so forth.
13928 For instance, suppose you have a function that is usually called
13929 frequently, but should not be called after an error has occurred. You
13930 could use the following tracepoint command to collect data about calls
13931 of that function that happen while the error code is propagating
13932 through the program; an unconditional tracepoint could end up
13933 collecting thousands of useless trace frames that you would have to
13937 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
13940 @node Trace State Variables
13941 @subsection Trace State Variables
13942 @cindex trace state variables
13944 A @dfn{trace state variable} is a special type of variable that is
13945 created and managed by target-side code. The syntax is the same as
13946 that for GDB's convenience variables (a string prefixed with ``$''),
13947 but they are stored on the target. They must be created explicitly,
13948 using a @code{tvariable} command. They are always 64-bit signed
13951 Trace state variables are remembered by @value{GDBN}, and downloaded
13952 to the target along with tracepoint information when the trace
13953 experiment starts. There are no intrinsic limits on the number of
13954 trace state variables, beyond memory limitations of the target.
13956 @cindex convenience variables, and trace state variables
13957 Although trace state variables are managed by the target, you can use
13958 them in print commands and expressions as if they were convenience
13959 variables; @value{GDBN} will get the current value from the target
13960 while the trace experiment is running. Trace state variables share
13961 the same namespace as other ``$'' variables, which means that you
13962 cannot have trace state variables with names like @code{$23} or
13963 @code{$pc}, nor can you have a trace state variable and a convenience
13964 variable with the same name.
13968 @item tvariable $@var{name} [ = @var{expression} ]
13970 The @code{tvariable} command creates a new trace state variable named
13971 @code{$@var{name}}, and optionally gives it an initial value of
13972 @var{expression}. The @var{expression} is evaluated when this command is
13973 entered; the result will be converted to an integer if possible,
13974 otherwise @value{GDBN} will report an error. A subsequent
13975 @code{tvariable} command specifying the same name does not create a
13976 variable, but instead assigns the supplied initial value to the
13977 existing variable of that name, overwriting any previous initial
13978 value. The default initial value is 0.
13980 @item info tvariables
13981 @kindex info tvariables
13982 List all the trace state variables along with their initial values.
13983 Their current values may also be displayed, if the trace experiment is
13986 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
13987 @kindex delete tvariable
13988 Delete the given trace state variables, or all of them if no arguments
13993 @node Tracepoint Actions
13994 @subsection Tracepoint Action Lists
13998 @cindex tracepoint actions
13999 @item actions @r{[}@var{num}@r{]}
14000 This command will prompt for a list of actions to be taken when the
14001 tracepoint is hit. If the tracepoint number @var{num} is not
14002 specified, this command sets the actions for the one that was most
14003 recently defined (so that you can define a tracepoint and then say
14004 @code{actions} without bothering about its number). You specify the
14005 actions themselves on the following lines, one action at a time, and
14006 terminate the actions list with a line containing just @code{end}. So
14007 far, the only defined actions are @code{collect}, @code{teval}, and
14008 @code{while-stepping}.
14010 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
14011 Commands, ,Breakpoint Command Lists}), except that only the defined
14012 actions are allowed; any other @value{GDBN} command is rejected.
14014 @cindex remove actions from a tracepoint
14015 To remove all actions from a tracepoint, type @samp{actions @var{num}}
14016 and follow it immediately with @samp{end}.
14019 (@value{GDBP}) @b{collect @var{data}} // collect some data
14021 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
14023 (@value{GDBP}) @b{end} // signals the end of actions.
14026 In the following example, the action list begins with @code{collect}
14027 commands indicating the things to be collected when the tracepoint is
14028 hit. Then, in order to single-step and collect additional data
14029 following the tracepoint, a @code{while-stepping} command is used,
14030 followed by the list of things to be collected after each step in a
14031 sequence of single steps. The @code{while-stepping} command is
14032 terminated by its own separate @code{end} command. Lastly, the action
14033 list is terminated by an @code{end} command.
14036 (@value{GDBP}) @b{trace foo}
14037 (@value{GDBP}) @b{actions}
14038 Enter actions for tracepoint 1, one per line:
14041 > while-stepping 12
14042 > collect $pc, arr[i]
14047 @kindex collect @r{(tracepoints)}
14048 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
14049 Collect values of the given expressions when the tracepoint is hit.
14050 This command accepts a comma-separated list of any valid expressions.
14051 In addition to global, static, or local variables, the following
14052 special arguments are supported:
14056 Collect all registers.
14059 Collect all function arguments.
14062 Collect all local variables.
14065 Collect the return address. This is helpful if you want to see more
14068 @emph{Note:} The return address location can not always be reliably
14069 determined up front, and the wrong address / registers may end up
14070 collected instead. On some architectures the reliability is higher
14071 for tracepoints at function entry, while on others it's the opposite.
14072 When this happens, backtracing will stop because the return address is
14073 found unavailable (unless another collect rule happened to match it).
14076 Collects the number of arguments from the static probe at which the
14077 tracepoint is located.
14078 @xref{Static Probe Points}.
14080 @item $_probe_arg@var{n}
14081 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
14082 from the static probe at which the tracepoint is located.
14083 @xref{Static Probe Points}.
14086 @vindex $_sdata@r{, collect}
14087 Collect static tracepoint marker specific data. Only available for
14088 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
14089 Lists}. On the UST static tracepoints library backend, an
14090 instrumentation point resembles a @code{printf} function call. The
14091 tracing library is able to collect user specified data formatted to a
14092 character string using the format provided by the programmer that
14093 instrumented the program. Other backends have similar mechanisms.
14094 Here's an example of a UST marker call:
14097 const char master_name[] = "$your_name";
14098 trace_mark(channel1, marker1, "hello %s", master_name)
14101 In this case, collecting @code{$_sdata} collects the string
14102 @samp{hello $yourname}. When analyzing the trace buffer, you can
14103 inspect @samp{$_sdata} like any other variable available to
14107 You can give several consecutive @code{collect} commands, each one
14108 with a single argument, or one @code{collect} command with several
14109 arguments separated by commas; the effect is the same.
14111 The optional @var{mods} changes the usual handling of the arguments.
14112 @code{s} requests that pointers to chars be handled as strings, in
14113 particular collecting the contents of the memory being pointed at, up
14114 to the first zero. The upper bound is by default the value of the
14115 @code{print elements} variable; if @code{s} is followed by a decimal
14116 number, that is the upper bound instead. So for instance
14117 @samp{collect/s25 mystr} collects as many as 25 characters at
14120 The command @code{info scope} (@pxref{Symbols, info scope}) is
14121 particularly useful for figuring out what data to collect.
14123 @kindex teval @r{(tracepoints)}
14124 @item teval @var{expr1}, @var{expr2}, @dots{}
14125 Evaluate the given expressions when the tracepoint is hit. This
14126 command accepts a comma-separated list of expressions. The results
14127 are discarded, so this is mainly useful for assigning values to trace
14128 state variables (@pxref{Trace State Variables}) without adding those
14129 values to the trace buffer, as would be the case if the @code{collect}
14132 @kindex while-stepping @r{(tracepoints)}
14133 @item while-stepping @var{n}
14134 Perform @var{n} single-step instruction traces after the tracepoint,
14135 collecting new data after each step. The @code{while-stepping}
14136 command is followed by the list of what to collect while stepping
14137 (followed by its own @code{end} command):
14140 > while-stepping 12
14141 > collect $regs, myglobal
14147 Note that @code{$pc} is not automatically collected by
14148 @code{while-stepping}; you need to explicitly collect that register if
14149 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
14152 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
14153 @kindex set default-collect
14154 @cindex default collection action
14155 This variable is a list of expressions to collect at each tracepoint
14156 hit. It is effectively an additional @code{collect} action prepended
14157 to every tracepoint action list. The expressions are parsed
14158 individually for each tracepoint, so for instance a variable named
14159 @code{xyz} may be interpreted as a global for one tracepoint, and a
14160 local for another, as appropriate to the tracepoint's location.
14162 @item show default-collect
14163 @kindex show default-collect
14164 Show the list of expressions that are collected by default at each
14169 @node Listing Tracepoints
14170 @subsection Listing Tracepoints
14173 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
14174 @kindex info tp @r{[}@var{n}@dots{}@r{]}
14175 @cindex information about tracepoints
14176 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
14177 Display information about the tracepoint @var{num}. If you don't
14178 specify a tracepoint number, displays information about all the
14179 tracepoints defined so far. The format is similar to that used for
14180 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
14181 command, simply restricting itself to tracepoints.
14183 A tracepoint's listing may include additional information specific to
14188 its passcount as given by the @code{passcount @var{n}} command
14191 the state about installed on target of each location
14195 (@value{GDBP}) @b{info trace}
14196 Num Type Disp Enb Address What
14197 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
14199 collect globfoo, $regs
14204 2 tracepoint keep y <MULTIPLE>
14206 2.1 y 0x0804859c in func4 at change-loc.h:35
14207 installed on target
14208 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
14209 installed on target
14210 2.3 y <PENDING> set_tracepoint
14211 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
14212 not installed on target
14217 This command can be abbreviated @code{info tp}.
14220 @node Listing Static Tracepoint Markers
14221 @subsection Listing Static Tracepoint Markers
14224 @kindex info static-tracepoint-markers
14225 @cindex information about static tracepoint markers
14226 @item info static-tracepoint-markers
14227 Display information about all static tracepoint markers defined in the
14230 For each marker, the following columns are printed:
14234 An incrementing counter, output to help readability. This is not a
14237 The marker ID, as reported by the target.
14238 @item Enabled or Disabled
14239 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
14240 that are not enabled.
14242 Where the marker is in your program, as a memory address.
14244 Where the marker is in the source for your program, as a file and line
14245 number. If the debug information included in the program does not
14246 allow @value{GDBN} to locate the source of the marker, this column
14247 will be left blank.
14251 In addition, the following information may be printed for each marker:
14255 User data passed to the tracing library by the marker call. In the
14256 UST backend, this is the format string passed as argument to the
14258 @item Static tracepoints probing the marker
14259 The list of static tracepoints attached to the marker.
14263 (@value{GDBP}) info static-tracepoint-markers
14264 Cnt ID Enb Address What
14265 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
14266 Data: number1 %d number2 %d
14267 Probed by static tracepoints: #2
14268 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
14274 @node Starting and Stopping Trace Experiments
14275 @subsection Starting and Stopping Trace Experiments
14278 @kindex tstart [ @var{notes} ]
14279 @cindex start a new trace experiment
14280 @cindex collected data discarded
14282 This command starts the trace experiment, and begins collecting data.
14283 It has the side effect of discarding all the data collected in the
14284 trace buffer during the previous trace experiment. If any arguments
14285 are supplied, they are taken as a note and stored with the trace
14286 experiment's state. The notes may be arbitrary text, and are
14287 especially useful with disconnected tracing in a multi-user context;
14288 the notes can explain what the trace is doing, supply user contact
14289 information, and so forth.
14291 @kindex tstop [ @var{notes} ]
14292 @cindex stop a running trace experiment
14294 This command stops the trace experiment. If any arguments are
14295 supplied, they are recorded with the experiment as a note. This is
14296 useful if you are stopping a trace started by someone else, for
14297 instance if the trace is interfering with the system's behavior and
14298 needs to be stopped quickly.
14300 @strong{Note}: a trace experiment and data collection may stop
14301 automatically if any tracepoint's passcount is reached
14302 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
14305 @cindex status of trace data collection
14306 @cindex trace experiment, status of
14308 This command displays the status of the current trace data
14312 Here is an example of the commands we described so far:
14315 (@value{GDBP}) @b{trace gdb_c_test}
14316 (@value{GDBP}) @b{actions}
14317 Enter actions for tracepoint #1, one per line.
14318 > collect $regs,$locals,$args
14319 > while-stepping 11
14323 (@value{GDBP}) @b{tstart}
14324 [time passes @dots{}]
14325 (@value{GDBP}) @b{tstop}
14328 @anchor{disconnected tracing}
14329 @cindex disconnected tracing
14330 You can choose to continue running the trace experiment even if
14331 @value{GDBN} disconnects from the target, voluntarily or
14332 involuntarily. For commands such as @code{detach}, the debugger will
14333 ask what you want to do with the trace. But for unexpected
14334 terminations (@value{GDBN} crash, network outage), it would be
14335 unfortunate to lose hard-won trace data, so the variable
14336 @code{disconnected-tracing} lets you decide whether the trace should
14337 continue running without @value{GDBN}.
14340 @item set disconnected-tracing on
14341 @itemx set disconnected-tracing off
14342 @kindex set disconnected-tracing
14343 Choose whether a tracing run should continue to run if @value{GDBN}
14344 has disconnected from the target. Note that @code{detach} or
14345 @code{quit} will ask you directly what to do about a running trace no
14346 matter what this variable's setting, so the variable is mainly useful
14347 for handling unexpected situations, such as loss of the network.
14349 @item show disconnected-tracing
14350 @kindex show disconnected-tracing
14351 Show the current choice for disconnected tracing.
14355 When you reconnect to the target, the trace experiment may or may not
14356 still be running; it might have filled the trace buffer in the
14357 meantime, or stopped for one of the other reasons. If it is running,
14358 it will continue after reconnection.
14360 Upon reconnection, the target will upload information about the
14361 tracepoints in effect. @value{GDBN} will then compare that
14362 information to the set of tracepoints currently defined, and attempt
14363 to match them up, allowing for the possibility that the numbers may
14364 have changed due to creation and deletion in the meantime. If one of
14365 the target's tracepoints does not match any in @value{GDBN}, the
14366 debugger will create a new tracepoint, so that you have a number with
14367 which to specify that tracepoint. This matching-up process is
14368 necessarily heuristic, and it may result in useless tracepoints being
14369 created; you may simply delete them if they are of no use.
14371 @cindex circular trace buffer
14372 If your target agent supports a @dfn{circular trace buffer}, then you
14373 can run a trace experiment indefinitely without filling the trace
14374 buffer; when space runs out, the agent deletes already-collected trace
14375 frames, oldest first, until there is enough room to continue
14376 collecting. This is especially useful if your tracepoints are being
14377 hit too often, and your trace gets terminated prematurely because the
14378 buffer is full. To ask for a circular trace buffer, simply set
14379 @samp{circular-trace-buffer} to on. You can set this at any time,
14380 including during tracing; if the agent can do it, it will change
14381 buffer handling on the fly, otherwise it will not take effect until
14385 @item set circular-trace-buffer on
14386 @itemx set circular-trace-buffer off
14387 @kindex set circular-trace-buffer
14388 Choose whether a tracing run should use a linear or circular buffer
14389 for trace data. A linear buffer will not lose any trace data, but may
14390 fill up prematurely, while a circular buffer will discard old trace
14391 data, but it will have always room for the latest tracepoint hits.
14393 @item show circular-trace-buffer
14394 @kindex show circular-trace-buffer
14395 Show the current choice for the trace buffer. Note that this may not
14396 match the agent's current buffer handling, nor is it guaranteed to
14397 match the setting that might have been in effect during a past run,
14398 for instance if you are looking at frames from a trace file.
14403 @item set trace-buffer-size @var{n}
14404 @itemx set trace-buffer-size unlimited
14405 @kindex set trace-buffer-size
14406 Request that the target use a trace buffer of @var{n} bytes. Not all
14407 targets will honor the request; they may have a compiled-in size for
14408 the trace buffer, or some other limitation. Set to a value of
14409 @code{unlimited} or @code{-1} to let the target use whatever size it
14410 likes. This is also the default.
14412 @item show trace-buffer-size
14413 @kindex show trace-buffer-size
14414 Show the current requested size for the trace buffer. Note that this
14415 will only match the actual size if the target supports size-setting,
14416 and was able to handle the requested size. For instance, if the
14417 target can only change buffer size between runs, this variable will
14418 not reflect the change until the next run starts. Use @code{tstatus}
14419 to get a report of the actual buffer size.
14423 @item set trace-user @var{text}
14424 @kindex set trace-user
14426 @item show trace-user
14427 @kindex show trace-user
14429 @item set trace-notes @var{text}
14430 @kindex set trace-notes
14431 Set the trace run's notes.
14433 @item show trace-notes
14434 @kindex show trace-notes
14435 Show the trace run's notes.
14437 @item set trace-stop-notes @var{text}
14438 @kindex set trace-stop-notes
14439 Set the trace run's stop notes. The handling of the note is as for
14440 @code{tstop} arguments; the set command is convenient way to fix a
14441 stop note that is mistaken or incomplete.
14443 @item show trace-stop-notes
14444 @kindex show trace-stop-notes
14445 Show the trace run's stop notes.
14449 @node Tracepoint Restrictions
14450 @subsection Tracepoint Restrictions
14452 @cindex tracepoint restrictions
14453 There are a number of restrictions on the use of tracepoints. As
14454 described above, tracepoint data gathering occurs on the target
14455 without interaction from @value{GDBN}. Thus the full capabilities of
14456 the debugger are not available during data gathering, and then at data
14457 examination time, you will be limited by only having what was
14458 collected. The following items describe some common problems, but it
14459 is not exhaustive, and you may run into additional difficulties not
14465 Tracepoint expressions are intended to gather objects (lvalues). Thus
14466 the full flexibility of GDB's expression evaluator is not available.
14467 You cannot call functions, cast objects to aggregate types, access
14468 convenience variables or modify values (except by assignment to trace
14469 state variables). Some language features may implicitly call
14470 functions (for instance Objective-C fields with accessors), and therefore
14471 cannot be collected either.
14474 Collection of local variables, either individually or in bulk with
14475 @code{$locals} or @code{$args}, during @code{while-stepping} may
14476 behave erratically. The stepping action may enter a new scope (for
14477 instance by stepping into a function), or the location of the variable
14478 may change (for instance it is loaded into a register). The
14479 tracepoint data recorded uses the location information for the
14480 variables that is correct for the tracepoint location. When the
14481 tracepoint is created, it is not possible, in general, to determine
14482 where the steps of a @code{while-stepping} sequence will advance the
14483 program---particularly if a conditional branch is stepped.
14486 Collection of an incompletely-initialized or partially-destroyed object
14487 may result in something that @value{GDBN} cannot display, or displays
14488 in a misleading way.
14491 When @value{GDBN} displays a pointer to character it automatically
14492 dereferences the pointer to also display characters of the string
14493 being pointed to. However, collecting the pointer during tracing does
14494 not automatically collect the string. You need to explicitly
14495 dereference the pointer and provide size information if you want to
14496 collect not only the pointer, but the memory pointed to. For example,
14497 @code{*ptr@@50} can be used to collect the 50 element array pointed to
14501 It is not possible to collect a complete stack backtrace at a
14502 tracepoint. Instead, you may collect the registers and a few hundred
14503 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
14504 (adjust to use the name of the actual stack pointer register on your
14505 target architecture, and the amount of stack you wish to capture).
14506 Then the @code{backtrace} command will show a partial backtrace when
14507 using a trace frame. The number of stack frames that can be examined
14508 depends on the sizes of the frames in the collected stack. Note that
14509 if you ask for a block so large that it goes past the bottom of the
14510 stack, the target agent may report an error trying to read from an
14514 If you do not collect registers at a tracepoint, @value{GDBN} can
14515 infer that the value of @code{$pc} must be the same as the address of
14516 the tracepoint and use that when you are looking at a trace frame
14517 for that tracepoint. However, this cannot work if the tracepoint has
14518 multiple locations (for instance if it was set in a function that was
14519 inlined), or if it has a @code{while-stepping} loop. In those cases
14520 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
14525 @node Analyze Collected Data
14526 @section Using the Collected Data
14528 After the tracepoint experiment ends, you use @value{GDBN} commands
14529 for examining the trace data. The basic idea is that each tracepoint
14530 collects a trace @dfn{snapshot} every time it is hit and another
14531 snapshot every time it single-steps. All these snapshots are
14532 consecutively numbered from zero and go into a buffer, and you can
14533 examine them later. The way you examine them is to @dfn{focus} on a
14534 specific trace snapshot. When the remote stub is focused on a trace
14535 snapshot, it will respond to all @value{GDBN} requests for memory and
14536 registers by reading from the buffer which belongs to that snapshot,
14537 rather than from @emph{real} memory or registers of the program being
14538 debugged. This means that @strong{all} @value{GDBN} commands
14539 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
14540 behave as if we were currently debugging the program state as it was
14541 when the tracepoint occurred. Any requests for data that are not in
14542 the buffer will fail.
14545 * tfind:: How to select a trace snapshot
14546 * tdump:: How to display all data for a snapshot
14547 * save tracepoints:: How to save tracepoints for a future run
14551 @subsection @code{tfind @var{n}}
14554 @cindex select trace snapshot
14555 @cindex find trace snapshot
14556 The basic command for selecting a trace snapshot from the buffer is
14557 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
14558 counting from zero. If no argument @var{n} is given, the next
14559 snapshot is selected.
14561 Here are the various forms of using the @code{tfind} command.
14565 Find the first snapshot in the buffer. This is a synonym for
14566 @code{tfind 0} (since 0 is the number of the first snapshot).
14569 Stop debugging trace snapshots, resume @emph{live} debugging.
14572 Same as @samp{tfind none}.
14575 No argument means find the next trace snapshot or find the first
14576 one if no trace snapshot is selected.
14579 Find the previous trace snapshot before the current one. This permits
14580 retracing earlier steps.
14582 @item tfind tracepoint @var{num}
14583 Find the next snapshot associated with tracepoint @var{num}. Search
14584 proceeds forward from the last examined trace snapshot. If no
14585 argument @var{num} is given, it means find the next snapshot collected
14586 for the same tracepoint as the current snapshot.
14588 @item tfind pc @var{addr}
14589 Find the next snapshot associated with the value @var{addr} of the
14590 program counter. Search proceeds forward from the last examined trace
14591 snapshot. If no argument @var{addr} is given, it means find the next
14592 snapshot with the same value of PC as the current snapshot.
14594 @item tfind outside @var{addr1}, @var{addr2}
14595 Find the next snapshot whose PC is outside the given range of
14596 addresses (exclusive).
14598 @item tfind range @var{addr1}, @var{addr2}
14599 Find the next snapshot whose PC is between @var{addr1} and
14600 @var{addr2} (inclusive).
14602 @item tfind line @r{[}@var{file}:@r{]}@var{n}
14603 Find the next snapshot associated with the source line @var{n}. If
14604 the optional argument @var{file} is given, refer to line @var{n} in
14605 that source file. Search proceeds forward from the last examined
14606 trace snapshot. If no argument @var{n} is given, it means find the
14607 next line other than the one currently being examined; thus saying
14608 @code{tfind line} repeatedly can appear to have the same effect as
14609 stepping from line to line in a @emph{live} debugging session.
14612 The default arguments for the @code{tfind} commands are specifically
14613 designed to make it easy to scan through the trace buffer. For
14614 instance, @code{tfind} with no argument selects the next trace
14615 snapshot, and @code{tfind -} with no argument selects the previous
14616 trace snapshot. So, by giving one @code{tfind} command, and then
14617 simply hitting @key{RET} repeatedly you can examine all the trace
14618 snapshots in order. Or, by saying @code{tfind -} and then hitting
14619 @key{RET} repeatedly you can examine the snapshots in reverse order.
14620 The @code{tfind line} command with no argument selects the snapshot
14621 for the next source line executed. The @code{tfind pc} command with
14622 no argument selects the next snapshot with the same program counter
14623 (PC) as the current frame. The @code{tfind tracepoint} command with
14624 no argument selects the next trace snapshot collected by the same
14625 tracepoint as the current one.
14627 In addition to letting you scan through the trace buffer manually,
14628 these commands make it easy to construct @value{GDBN} scripts that
14629 scan through the trace buffer and print out whatever collected data
14630 you are interested in. Thus, if we want to examine the PC, FP, and SP
14631 registers from each trace frame in the buffer, we can say this:
14634 (@value{GDBP}) @b{tfind start}
14635 (@value{GDBP}) @b{while ($trace_frame != -1)}
14636 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
14637 $trace_frame, $pc, $sp, $fp
14641 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
14642 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
14643 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
14644 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
14645 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
14646 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
14647 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
14648 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
14649 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
14650 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
14651 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
14654 Or, if we want to examine the variable @code{X} at each source line in
14658 (@value{GDBP}) @b{tfind start}
14659 (@value{GDBP}) @b{while ($trace_frame != -1)}
14660 > printf "Frame %d, X == %d\n", $trace_frame, X
14670 @subsection @code{tdump}
14672 @cindex dump all data collected at tracepoint
14673 @cindex tracepoint data, display
14675 This command takes no arguments. It prints all the data collected at
14676 the current trace snapshot.
14679 (@value{GDBP}) @b{trace 444}
14680 (@value{GDBP}) @b{actions}
14681 Enter actions for tracepoint #2, one per line:
14682 > collect $regs, $locals, $args, gdb_long_test
14685 (@value{GDBP}) @b{tstart}
14687 (@value{GDBP}) @b{tfind line 444}
14688 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
14690 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
14692 (@value{GDBP}) @b{tdump}
14693 Data collected at tracepoint 2, trace frame 1:
14694 d0 0xc4aa0085 -995491707
14698 d4 0x71aea3d 119204413
14701 d7 0x380035 3670069
14702 a0 0x19e24a 1696330
14703 a1 0x3000668 50333288
14705 a3 0x322000 3284992
14706 a4 0x3000698 50333336
14707 a5 0x1ad3cc 1758156
14708 fp 0x30bf3c 0x30bf3c
14709 sp 0x30bf34 0x30bf34
14711 pc 0x20b2c8 0x20b2c8
14715 p = 0x20e5b4 "gdb-test"
14722 gdb_long_test = 17 '\021'
14727 @code{tdump} works by scanning the tracepoint's current collection
14728 actions and printing the value of each expression listed. So
14729 @code{tdump} can fail, if after a run, you change the tracepoint's
14730 actions to mention variables that were not collected during the run.
14732 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
14733 uses the collected value of @code{$pc} to distinguish between trace
14734 frames that were collected at the tracepoint hit, and frames that were
14735 collected while stepping. This allows it to correctly choose whether
14736 to display the basic list of collections, or the collections from the
14737 body of the while-stepping loop. However, if @code{$pc} was not collected,
14738 then @code{tdump} will always attempt to dump using the basic collection
14739 list, and may fail if a while-stepping frame does not include all the
14740 same data that is collected at the tracepoint hit.
14741 @c This is getting pretty arcane, example would be good.
14743 @node save tracepoints
14744 @subsection @code{save tracepoints @var{filename}}
14745 @kindex save tracepoints
14746 @kindex save-tracepoints
14747 @cindex save tracepoints for future sessions
14749 This command saves all current tracepoint definitions together with
14750 their actions and passcounts, into a file @file{@var{filename}}
14751 suitable for use in a later debugging session. To read the saved
14752 tracepoint definitions, use the @code{source} command (@pxref{Command
14753 Files}). The @w{@code{save-tracepoints}} command is a deprecated
14754 alias for @w{@code{save tracepoints}}
14756 @node Tracepoint Variables
14757 @section Convenience Variables for Tracepoints
14758 @cindex tracepoint variables
14759 @cindex convenience variables for tracepoints
14762 @vindex $trace_frame
14763 @item (int) $trace_frame
14764 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
14765 snapshot is selected.
14767 @vindex $tracepoint
14768 @item (int) $tracepoint
14769 The tracepoint for the current trace snapshot.
14771 @vindex $trace_line
14772 @item (int) $trace_line
14773 The line number for the current trace snapshot.
14775 @vindex $trace_file
14776 @item (char []) $trace_file
14777 The source file for the current trace snapshot.
14779 @vindex $trace_func
14780 @item (char []) $trace_func
14781 The name of the function containing @code{$tracepoint}.
14784 Note: @code{$trace_file} is not suitable for use in @code{printf},
14785 use @code{output} instead.
14787 Here's a simple example of using these convenience variables for
14788 stepping through all the trace snapshots and printing some of their
14789 data. Note that these are not the same as trace state variables,
14790 which are managed by the target.
14793 (@value{GDBP}) @b{tfind start}
14795 (@value{GDBP}) @b{while $trace_frame != -1}
14796 > output $trace_file
14797 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
14803 @section Using Trace Files
14804 @cindex trace files
14806 In some situations, the target running a trace experiment may no
14807 longer be available; perhaps it crashed, or the hardware was needed
14808 for a different activity. To handle these cases, you can arrange to
14809 dump the trace data into a file, and later use that file as a source
14810 of trace data, via the @code{target tfile} command.
14815 @item tsave [ -r ] @var{filename}
14816 @itemx tsave [-ctf] @var{dirname}
14817 Save the trace data to @var{filename}. By default, this command
14818 assumes that @var{filename} refers to the host filesystem, so if
14819 necessary @value{GDBN} will copy raw trace data up from the target and
14820 then save it. If the target supports it, you can also supply the
14821 optional argument @code{-r} (``remote'') to direct the target to save
14822 the data directly into @var{filename} in its own filesystem, which may be
14823 more efficient if the trace buffer is very large. (Note, however, that
14824 @code{target tfile} can only read from files accessible to the host.)
14825 By default, this command will save trace frame in tfile format.
14826 You can supply the optional argument @code{-ctf} to save data in CTF
14827 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
14828 that can be shared by multiple debugging and tracing tools. Please go to
14829 @indicateurl{http://www.efficios.com/ctf} to get more information.
14831 @kindex target tfile
14835 @item target tfile @var{filename}
14836 @itemx target ctf @var{dirname}
14837 Use the file named @var{filename} or directory named @var{dirname} as
14838 a source of trace data. Commands that examine data work as they do with
14839 a live target, but it is not possible to run any new trace experiments.
14840 @code{tstatus} will report the state of the trace run at the moment
14841 the data was saved, as well as the current trace frame you are examining.
14842 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
14846 (@value{GDBP}) target ctf ctf.ctf
14847 (@value{GDBP}) tfind
14848 Found trace frame 0, tracepoint 2
14849 39 ++a; /* set tracepoint 1 here */
14850 (@value{GDBP}) tdump
14851 Data collected at tracepoint 2, trace frame 0:
14855 c = @{"123", "456", "789", "123", "456", "789"@}
14856 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
14864 @chapter Debugging Programs That Use Overlays
14867 If your program is too large to fit completely in your target system's
14868 memory, you can sometimes use @dfn{overlays} to work around this
14869 problem. @value{GDBN} provides some support for debugging programs that
14873 * How Overlays Work:: A general explanation of overlays.
14874 * Overlay Commands:: Managing overlays in @value{GDBN}.
14875 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
14876 mapped by asking the inferior.
14877 * Overlay Sample Program:: A sample program using overlays.
14880 @node How Overlays Work
14881 @section How Overlays Work
14882 @cindex mapped overlays
14883 @cindex unmapped overlays
14884 @cindex load address, overlay's
14885 @cindex mapped address
14886 @cindex overlay area
14888 Suppose you have a computer whose instruction address space is only 64
14889 kilobytes long, but which has much more memory which can be accessed by
14890 other means: special instructions, segment registers, or memory
14891 management hardware, for example. Suppose further that you want to
14892 adapt a program which is larger than 64 kilobytes to run on this system.
14894 One solution is to identify modules of your program which are relatively
14895 independent, and need not call each other directly; call these modules
14896 @dfn{overlays}. Separate the overlays from the main program, and place
14897 their machine code in the larger memory. Place your main program in
14898 instruction memory, but leave at least enough space there to hold the
14899 largest overlay as well.
14901 Now, to call a function located in an overlay, you must first copy that
14902 overlay's machine code from the large memory into the space set aside
14903 for it in the instruction memory, and then jump to its entry point
14906 @c NB: In the below the mapped area's size is greater or equal to the
14907 @c size of all overlays. This is intentional to remind the developer
14908 @c that overlays don't necessarily need to be the same size.
14912 Data Instruction Larger
14913 Address Space Address Space Address Space
14914 +-----------+ +-----------+ +-----------+
14916 +-----------+ +-----------+ +-----------+<-- overlay 1
14917 | program | | main | .----| overlay 1 | load address
14918 | variables | | program | | +-----------+
14919 | and heap | | | | | |
14920 +-----------+ | | | +-----------+<-- overlay 2
14921 | | +-----------+ | | | load address
14922 +-----------+ | | | .-| overlay 2 |
14924 mapped --->+-----------+ | | +-----------+
14925 address | | | | | |
14926 | overlay | <-' | | |
14927 | area | <---' +-----------+<-- overlay 3
14928 | | <---. | | load address
14929 +-----------+ `--| overlay 3 |
14936 @anchor{A code overlay}A code overlay
14940 The diagram (@pxref{A code overlay}) shows a system with separate data
14941 and instruction address spaces. To map an overlay, the program copies
14942 its code from the larger address space to the instruction address space.
14943 Since the overlays shown here all use the same mapped address, only one
14944 may be mapped at a time. For a system with a single address space for
14945 data and instructions, the diagram would be similar, except that the
14946 program variables and heap would share an address space with the main
14947 program and the overlay area.
14949 An overlay loaded into instruction memory and ready for use is called a
14950 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
14951 instruction memory. An overlay not present (or only partially present)
14952 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
14953 is its address in the larger memory. The mapped address is also called
14954 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
14955 called the @dfn{load memory address}, or @dfn{LMA}.
14957 Unfortunately, overlays are not a completely transparent way to adapt a
14958 program to limited instruction memory. They introduce a new set of
14959 global constraints you must keep in mind as you design your program:
14964 Before calling or returning to a function in an overlay, your program
14965 must make sure that overlay is actually mapped. Otherwise, the call or
14966 return will transfer control to the right address, but in the wrong
14967 overlay, and your program will probably crash.
14970 If the process of mapping an overlay is expensive on your system, you
14971 will need to choose your overlays carefully to minimize their effect on
14972 your program's performance.
14975 The executable file you load onto your system must contain each
14976 overlay's instructions, appearing at the overlay's load address, not its
14977 mapped address. However, each overlay's instructions must be relocated
14978 and its symbols defined as if the overlay were at its mapped address.
14979 You can use GNU linker scripts to specify different load and relocation
14980 addresses for pieces of your program; see @ref{Overlay Description,,,
14981 ld.info, Using ld: the GNU linker}.
14984 The procedure for loading executable files onto your system must be able
14985 to load their contents into the larger address space as well as the
14986 instruction and data spaces.
14990 The overlay system described above is rather simple, and could be
14991 improved in many ways:
14996 If your system has suitable bank switch registers or memory management
14997 hardware, you could use those facilities to make an overlay's load area
14998 contents simply appear at their mapped address in instruction space.
14999 This would probably be faster than copying the overlay to its mapped
15000 area in the usual way.
15003 If your overlays are small enough, you could set aside more than one
15004 overlay area, and have more than one overlay mapped at a time.
15007 You can use overlays to manage data, as well as instructions. In
15008 general, data overlays are even less transparent to your design than
15009 code overlays: whereas code overlays only require care when you call or
15010 return to functions, data overlays require care every time you access
15011 the data. Also, if you change the contents of a data overlay, you
15012 must copy its contents back out to its load address before you can copy a
15013 different data overlay into the same mapped area.
15018 @node Overlay Commands
15019 @section Overlay Commands
15021 To use @value{GDBN}'s overlay support, each overlay in your program must
15022 correspond to a separate section of the executable file. The section's
15023 virtual memory address and load memory address must be the overlay's
15024 mapped and load addresses. Identifying overlays with sections allows
15025 @value{GDBN} to determine the appropriate address of a function or
15026 variable, depending on whether the overlay is mapped or not.
15028 @value{GDBN}'s overlay commands all start with the word @code{overlay};
15029 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
15034 Disable @value{GDBN}'s overlay support. When overlay support is
15035 disabled, @value{GDBN} assumes that all functions and variables are
15036 always present at their mapped addresses. By default, @value{GDBN}'s
15037 overlay support is disabled.
15039 @item overlay manual
15040 @cindex manual overlay debugging
15041 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
15042 relies on you to tell it which overlays are mapped, and which are not,
15043 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
15044 commands described below.
15046 @item overlay map-overlay @var{overlay}
15047 @itemx overlay map @var{overlay}
15048 @cindex map an overlay
15049 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
15050 be the name of the object file section containing the overlay. When an
15051 overlay is mapped, @value{GDBN} assumes it can find the overlay's
15052 functions and variables at their mapped addresses. @value{GDBN} assumes
15053 that any other overlays whose mapped ranges overlap that of
15054 @var{overlay} are now unmapped.
15056 @item overlay unmap-overlay @var{overlay}
15057 @itemx overlay unmap @var{overlay}
15058 @cindex unmap an overlay
15059 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
15060 must be the name of the object file section containing the overlay.
15061 When an overlay is unmapped, @value{GDBN} assumes it can find the
15062 overlay's functions and variables at their load addresses.
15065 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
15066 consults a data structure the overlay manager maintains in the inferior
15067 to see which overlays are mapped. For details, see @ref{Automatic
15068 Overlay Debugging}.
15070 @item overlay load-target
15071 @itemx overlay load
15072 @cindex reloading the overlay table
15073 Re-read the overlay table from the inferior. Normally, @value{GDBN}
15074 re-reads the table @value{GDBN} automatically each time the inferior
15075 stops, so this command should only be necessary if you have changed the
15076 overlay mapping yourself using @value{GDBN}. This command is only
15077 useful when using automatic overlay debugging.
15079 @item overlay list-overlays
15080 @itemx overlay list
15081 @cindex listing mapped overlays
15082 Display a list of the overlays currently mapped, along with their mapped
15083 addresses, load addresses, and sizes.
15087 Normally, when @value{GDBN} prints a code address, it includes the name
15088 of the function the address falls in:
15091 (@value{GDBP}) print main
15092 $3 = @{int ()@} 0x11a0 <main>
15095 When overlay debugging is enabled, @value{GDBN} recognizes code in
15096 unmapped overlays, and prints the names of unmapped functions with
15097 asterisks around them. For example, if @code{foo} is a function in an
15098 unmapped overlay, @value{GDBN} prints it this way:
15101 (@value{GDBP}) overlay list
15102 No sections are mapped.
15103 (@value{GDBP}) print foo
15104 $5 = @{int (int)@} 0x100000 <*foo*>
15107 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
15111 (@value{GDBP}) overlay list
15112 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
15113 mapped at 0x1016 - 0x104a
15114 (@value{GDBP}) print foo
15115 $6 = @{int (int)@} 0x1016 <foo>
15118 When overlay debugging is enabled, @value{GDBN} can find the correct
15119 address for functions and variables in an overlay, whether or not the
15120 overlay is mapped. This allows most @value{GDBN} commands, like
15121 @code{break} and @code{disassemble}, to work normally, even on unmapped
15122 code. However, @value{GDBN}'s breakpoint support has some limitations:
15126 @cindex breakpoints in overlays
15127 @cindex overlays, setting breakpoints in
15128 You can set breakpoints in functions in unmapped overlays, as long as
15129 @value{GDBN} can write to the overlay at its load address.
15131 @value{GDBN} can not set hardware or simulator-based breakpoints in
15132 unmapped overlays. However, if you set a breakpoint at the end of your
15133 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
15134 you are using manual overlay management), @value{GDBN} will re-set its
15135 breakpoints properly.
15139 @node Automatic Overlay Debugging
15140 @section Automatic Overlay Debugging
15141 @cindex automatic overlay debugging
15143 @value{GDBN} can automatically track which overlays are mapped and which
15144 are not, given some simple co-operation from the overlay manager in the
15145 inferior. If you enable automatic overlay debugging with the
15146 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
15147 looks in the inferior's memory for certain variables describing the
15148 current state of the overlays.
15150 Here are the variables your overlay manager must define to support
15151 @value{GDBN}'s automatic overlay debugging:
15155 @item @code{_ovly_table}:
15156 This variable must be an array of the following structures:
15161 /* The overlay's mapped address. */
15164 /* The size of the overlay, in bytes. */
15165 unsigned long size;
15167 /* The overlay's load address. */
15170 /* Non-zero if the overlay is currently mapped;
15172 unsigned long mapped;
15176 @item @code{_novlys}:
15177 This variable must be a four-byte signed integer, holding the total
15178 number of elements in @code{_ovly_table}.
15182 To decide whether a particular overlay is mapped or not, @value{GDBN}
15183 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
15184 @code{lma} members equal the VMA and LMA of the overlay's section in the
15185 executable file. When @value{GDBN} finds a matching entry, it consults
15186 the entry's @code{mapped} member to determine whether the overlay is
15189 In addition, your overlay manager may define a function called
15190 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
15191 will silently set a breakpoint there. If the overlay manager then
15192 calls this function whenever it has changed the overlay table, this
15193 will enable @value{GDBN} to accurately keep track of which overlays
15194 are in program memory, and update any breakpoints that may be set
15195 in overlays. This will allow breakpoints to work even if the
15196 overlays are kept in ROM or other non-writable memory while they
15197 are not being executed.
15199 @node Overlay Sample Program
15200 @section Overlay Sample Program
15201 @cindex overlay example program
15203 When linking a program which uses overlays, you must place the overlays
15204 at their load addresses, while relocating them to run at their mapped
15205 addresses. To do this, you must write a linker script (@pxref{Overlay
15206 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
15207 since linker scripts are specific to a particular host system, target
15208 architecture, and target memory layout, this manual cannot provide
15209 portable sample code demonstrating @value{GDBN}'s overlay support.
15211 However, the @value{GDBN} source distribution does contain an overlaid
15212 program, with linker scripts for a few systems, as part of its test
15213 suite. The program consists of the following files from
15214 @file{gdb/testsuite/gdb.base}:
15218 The main program file.
15220 A simple overlay manager, used by @file{overlays.c}.
15225 Overlay modules, loaded and used by @file{overlays.c}.
15228 Linker scripts for linking the test program on the @code{d10v-elf}
15229 and @code{m32r-elf} targets.
15232 You can build the test program using the @code{d10v-elf} GCC
15233 cross-compiler like this:
15236 $ d10v-elf-gcc -g -c overlays.c
15237 $ d10v-elf-gcc -g -c ovlymgr.c
15238 $ d10v-elf-gcc -g -c foo.c
15239 $ d10v-elf-gcc -g -c bar.c
15240 $ d10v-elf-gcc -g -c baz.c
15241 $ d10v-elf-gcc -g -c grbx.c
15242 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
15243 baz.o grbx.o -Wl,-Td10v.ld -o overlays
15246 The build process is identical for any other architecture, except that
15247 you must substitute the appropriate compiler and linker script for the
15248 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
15252 @chapter Using @value{GDBN} with Different Languages
15255 Although programming languages generally have common aspects, they are
15256 rarely expressed in the same manner. For instance, in ANSI C,
15257 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
15258 Modula-2, it is accomplished by @code{p^}. Values can also be
15259 represented (and displayed) differently. Hex numbers in C appear as
15260 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
15262 @cindex working language
15263 Language-specific information is built into @value{GDBN} for some languages,
15264 allowing you to express operations like the above in your program's
15265 native language, and allowing @value{GDBN} to output values in a manner
15266 consistent with the syntax of your program's native language. The
15267 language you use to build expressions is called the @dfn{working
15271 * Setting:: Switching between source languages
15272 * Show:: Displaying the language
15273 * Checks:: Type and range checks
15274 * Supported Languages:: Supported languages
15275 * Unsupported Languages:: Unsupported languages
15279 @section Switching Between Source Languages
15281 There are two ways to control the working language---either have @value{GDBN}
15282 set it automatically, or select it manually yourself. You can use the
15283 @code{set language} command for either purpose. On startup, @value{GDBN}
15284 defaults to setting the language automatically. The working language is
15285 used to determine how expressions you type are interpreted, how values
15288 In addition to the working language, every source file that
15289 @value{GDBN} knows about has its own working language. For some object
15290 file formats, the compiler might indicate which language a particular
15291 source file is in. However, most of the time @value{GDBN} infers the
15292 language from the name of the file. The language of a source file
15293 controls whether C@t{++} names are demangled---this way @code{backtrace} can
15294 show each frame appropriately for its own language. There is no way to
15295 set the language of a source file from within @value{GDBN}, but you can
15296 set the language associated with a filename extension. @xref{Show, ,
15297 Displaying the Language}.
15299 This is most commonly a problem when you use a program, such
15300 as @code{cfront} or @code{f2c}, that generates C but is written in
15301 another language. In that case, make the
15302 program use @code{#line} directives in its C output; that way
15303 @value{GDBN} will know the correct language of the source code of the original
15304 program, and will display that source code, not the generated C code.
15307 * Filenames:: Filename extensions and languages.
15308 * Manually:: Setting the working language manually
15309 * Automatically:: Having @value{GDBN} infer the source language
15313 @subsection List of Filename Extensions and Languages
15315 If a source file name ends in one of the following extensions, then
15316 @value{GDBN} infers that its language is the one indicated.
15334 C@t{++} source file
15340 Objective-C source file
15344 Fortran source file
15347 Modula-2 source file
15351 Assembler source file. This actually behaves almost like C, but
15352 @value{GDBN} does not skip over function prologues when stepping.
15355 In addition, you may set the language associated with a filename
15356 extension. @xref{Show, , Displaying the Language}.
15359 @subsection Setting the Working Language
15361 If you allow @value{GDBN} to set the language automatically,
15362 expressions are interpreted the same way in your debugging session and
15365 @kindex set language
15366 If you wish, you may set the language manually. To do this, issue the
15367 command @samp{set language @var{lang}}, where @var{lang} is the name of
15368 a language, such as
15369 @code{c} or @code{modula-2}.
15370 For a list of the supported languages, type @samp{set language}.
15372 Setting the language manually prevents @value{GDBN} from updating the working
15373 language automatically. This can lead to confusion if you try
15374 to debug a program when the working language is not the same as the
15375 source language, when an expression is acceptable to both
15376 languages---but means different things. For instance, if the current
15377 source file were written in C, and @value{GDBN} was parsing Modula-2, a
15385 might not have the effect you intended. In C, this means to add
15386 @code{b} and @code{c} and place the result in @code{a}. The result
15387 printed would be the value of @code{a}. In Modula-2, this means to compare
15388 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
15390 @node Automatically
15391 @subsection Having @value{GDBN} Infer the Source Language
15393 To have @value{GDBN} set the working language automatically, use
15394 @samp{set language local} or @samp{set language auto}. @value{GDBN}
15395 then infers the working language. That is, when your program stops in a
15396 frame (usually by encountering a breakpoint), @value{GDBN} sets the
15397 working language to the language recorded for the function in that
15398 frame. If the language for a frame is unknown (that is, if the function
15399 or block corresponding to the frame was defined in a source file that
15400 does not have a recognized extension), the current working language is
15401 not changed, and @value{GDBN} issues a warning.
15403 This may not seem necessary for most programs, which are written
15404 entirely in one source language. However, program modules and libraries
15405 written in one source language can be used by a main program written in
15406 a different source language. Using @samp{set language auto} in this
15407 case frees you from having to set the working language manually.
15410 @section Displaying the Language
15412 The following commands help you find out which language is the
15413 working language, and also what language source files were written in.
15416 @item show language
15417 @anchor{show language}
15418 @kindex show language
15419 Display the current working language. This is the
15420 language you can use with commands such as @code{print} to
15421 build and compute expressions that may involve variables in your program.
15424 @kindex info frame@r{, show the source language}
15425 Display the source language for this frame. This language becomes the
15426 working language if you use an identifier from this frame.
15427 @xref{Frame Info, ,Information about a Frame}, to identify the other
15428 information listed here.
15431 @kindex info source@r{, show the source language}
15432 Display the source language of this source file.
15433 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
15434 information listed here.
15437 In unusual circumstances, you may have source files with extensions
15438 not in the standard list. You can then set the extension associated
15439 with a language explicitly:
15442 @item set extension-language @var{ext} @var{language}
15443 @kindex set extension-language
15444 Tell @value{GDBN} that source files with extension @var{ext} are to be
15445 assumed as written in the source language @var{language}.
15447 @item info extensions
15448 @kindex info extensions
15449 List all the filename extensions and the associated languages.
15453 @section Type and Range Checking
15455 Some languages are designed to guard you against making seemingly common
15456 errors through a series of compile- and run-time checks. These include
15457 checking the type of arguments to functions and operators and making
15458 sure mathematical overflows are caught at run time. Checks such as
15459 these help to ensure a program's correctness once it has been compiled
15460 by eliminating type mismatches and providing active checks for range
15461 errors when your program is running.
15463 By default @value{GDBN} checks for these errors according to the
15464 rules of the current source language. Although @value{GDBN} does not check
15465 the statements in your program, it can check expressions entered directly
15466 into @value{GDBN} for evaluation via the @code{print} command, for example.
15469 * Type Checking:: An overview of type checking
15470 * Range Checking:: An overview of range checking
15473 @cindex type checking
15474 @cindex checks, type
15475 @node Type Checking
15476 @subsection An Overview of Type Checking
15478 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
15479 arguments to operators and functions have to be of the correct type,
15480 otherwise an error occurs. These checks prevent type mismatch
15481 errors from ever causing any run-time problems. For example,
15484 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
15486 (@value{GDBP}) print obj.my_method (0)
15489 (@value{GDBP}) print obj.my_method (0x1234)
15490 Cannot resolve method klass::my_method to any overloaded instance
15493 The second example fails because in C@t{++} the integer constant
15494 @samp{0x1234} is not type-compatible with the pointer parameter type.
15496 For the expressions you use in @value{GDBN} commands, you can tell
15497 @value{GDBN} to not enforce strict type checking or
15498 to treat any mismatches as errors and abandon the expression;
15499 When type checking is disabled, @value{GDBN} successfully evaluates
15500 expressions like the second example above.
15502 Even if type checking is off, there may be other reasons
15503 related to type that prevent @value{GDBN} from evaluating an expression.
15504 For instance, @value{GDBN} does not know how to add an @code{int} and
15505 a @code{struct foo}. These particular type errors have nothing to do
15506 with the language in use and usually arise from expressions which make
15507 little sense to evaluate anyway.
15509 @value{GDBN} provides some additional commands for controlling type checking:
15511 @kindex set check type
15512 @kindex show check type
15514 @item set check type on
15515 @itemx set check type off
15516 Set strict type checking on or off. If any type mismatches occur in
15517 evaluating an expression while type checking is on, @value{GDBN} prints a
15518 message and aborts evaluation of the expression.
15520 @item show check type
15521 Show the current setting of type checking and whether @value{GDBN}
15522 is enforcing strict type checking rules.
15525 @cindex range checking
15526 @cindex checks, range
15527 @node Range Checking
15528 @subsection An Overview of Range Checking
15530 In some languages (such as Modula-2), it is an error to exceed the
15531 bounds of a type; this is enforced with run-time checks. Such range
15532 checking is meant to ensure program correctness by making sure
15533 computations do not overflow, or indices on an array element access do
15534 not exceed the bounds of the array.
15536 For expressions you use in @value{GDBN} commands, you can tell
15537 @value{GDBN} to treat range errors in one of three ways: ignore them,
15538 always treat them as errors and abandon the expression, or issue
15539 warnings but evaluate the expression anyway.
15541 A range error can result from numerical overflow, from exceeding an
15542 array index bound, or when you type a constant that is not a member
15543 of any type. Some languages, however, do not treat overflows as an
15544 error. In many implementations of C, mathematical overflow causes the
15545 result to ``wrap around'' to lower values---for example, if @var{m} is
15546 the largest integer value, and @var{s} is the smallest, then
15549 @var{m} + 1 @result{} @var{s}
15552 This, too, is specific to individual languages, and in some cases
15553 specific to individual compilers or machines. @xref{Supported Languages, ,
15554 Supported Languages}, for further details on specific languages.
15556 @value{GDBN} provides some additional commands for controlling the range checker:
15558 @kindex set check range
15559 @kindex show check range
15561 @item set check range auto
15562 Set range checking on or off based on the current working language.
15563 @xref{Supported Languages, ,Supported Languages}, for the default settings for
15566 @item set check range on
15567 @itemx set check range off
15568 Set range checking on or off, overriding the default setting for the
15569 current working language. A warning is issued if the setting does not
15570 match the language default. If a range error occurs and range checking is on,
15571 then a message is printed and evaluation of the expression is aborted.
15573 @item set check range warn
15574 Output messages when the @value{GDBN} range checker detects a range error,
15575 but attempt to evaluate the expression anyway. Evaluating the
15576 expression may still be impossible for other reasons, such as accessing
15577 memory that the process does not own (a typical example from many Unix
15581 Show the current setting of the range checker, and whether or not it is
15582 being set automatically by @value{GDBN}.
15585 @node Supported Languages
15586 @section Supported Languages
15588 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran,
15589 OpenCL C, Pascal, Rust, assembly, Modula-2, and Ada.
15590 @c This is false ...
15591 Some @value{GDBN} features may be used in expressions regardless of the
15592 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
15593 and the @samp{@{type@}addr} construct (@pxref{Expressions,
15594 ,Expressions}) can be used with the constructs of any supported
15597 The following sections detail to what degree each source language is
15598 supported by @value{GDBN}. These sections are not meant to be language
15599 tutorials or references, but serve only as a reference guide to what the
15600 @value{GDBN} expression parser accepts, and what input and output
15601 formats should look like for different languages. There are many good
15602 books written on each of these languages; please look to these for a
15603 language reference or tutorial.
15606 * C:: C and C@t{++}
15609 * Objective-C:: Objective-C
15610 * OpenCL C:: OpenCL C
15611 * Fortran:: Fortran
15614 * Modula-2:: Modula-2
15619 @subsection C and C@t{++}
15621 @cindex C and C@t{++}
15622 @cindex expressions in C or C@t{++}
15624 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
15625 to both languages. Whenever this is the case, we discuss those languages
15629 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
15630 @cindex @sc{gnu} C@t{++}
15631 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
15632 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
15633 effectively, you must compile your C@t{++} programs with a supported
15634 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
15635 compiler (@code{aCC}).
15638 * C Operators:: C and C@t{++} operators
15639 * C Constants:: C and C@t{++} constants
15640 * C Plus Plus Expressions:: C@t{++} expressions
15641 * C Defaults:: Default settings for C and C@t{++}
15642 * C Checks:: C and C@t{++} type and range checks
15643 * Debugging C:: @value{GDBN} and C
15644 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
15645 * Decimal Floating Point:: Numbers in Decimal Floating Point format
15649 @subsubsection C and C@t{++} Operators
15651 @cindex C and C@t{++} operators
15653 Operators must be defined on values of specific types. For instance,
15654 @code{+} is defined on numbers, but not on structures. Operators are
15655 often defined on groups of types.
15657 For the purposes of C and C@t{++}, the following definitions hold:
15662 @emph{Integral types} include @code{int} with any of its storage-class
15663 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
15666 @emph{Floating-point types} include @code{float}, @code{double}, and
15667 @code{long double} (if supported by the target platform).
15670 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
15673 @emph{Scalar types} include all of the above.
15678 The following operators are supported. They are listed here
15679 in order of increasing precedence:
15683 The comma or sequencing operator. Expressions in a comma-separated list
15684 are evaluated from left to right, with the result of the entire
15685 expression being the last expression evaluated.
15688 Assignment. The value of an assignment expression is the value
15689 assigned. Defined on scalar types.
15692 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
15693 and translated to @w{@code{@var{a} = @var{a op b}}}.
15694 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
15695 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
15696 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
15699 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
15700 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
15701 should be of an integral type.
15704 Logical @sc{or}. Defined on integral types.
15707 Logical @sc{and}. Defined on integral types.
15710 Bitwise @sc{or}. Defined on integral types.
15713 Bitwise exclusive-@sc{or}. Defined on integral types.
15716 Bitwise @sc{and}. Defined on integral types.
15719 Equality and inequality. Defined on scalar types. The value of these
15720 expressions is 0 for false and non-zero for true.
15722 @item <@r{, }>@r{, }<=@r{, }>=
15723 Less than, greater than, less than or equal, greater than or equal.
15724 Defined on scalar types. The value of these expressions is 0 for false
15725 and non-zero for true.
15728 left shift, and right shift. Defined on integral types.
15731 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
15734 Addition and subtraction. Defined on integral types, floating-point types and
15737 @item *@r{, }/@r{, }%
15738 Multiplication, division, and modulus. Multiplication and division are
15739 defined on integral and floating-point types. Modulus is defined on
15743 Increment and decrement. When appearing before a variable, the
15744 operation is performed before the variable is used in an expression;
15745 when appearing after it, the variable's value is used before the
15746 operation takes place.
15749 Pointer dereferencing. Defined on pointer types. Same precedence as
15753 Address operator. Defined on variables. Same precedence as @code{++}.
15755 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
15756 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
15757 to examine the address
15758 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
15762 Negative. Defined on integral and floating-point types. Same
15763 precedence as @code{++}.
15766 Logical negation. Defined on integral types. Same precedence as
15770 Bitwise complement operator. Defined on integral types. Same precedence as
15775 Structure member, and pointer-to-structure member. For convenience,
15776 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
15777 pointer based on the stored type information.
15778 Defined on @code{struct} and @code{union} data.
15781 Dereferences of pointers to members.
15784 Array indexing. @code{@var{a}[@var{i}]} is defined as
15785 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
15788 Function parameter list. Same precedence as @code{->}.
15791 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
15792 and @code{class} types.
15795 Doubled colons also represent the @value{GDBN} scope operator
15796 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
15800 If an operator is redefined in the user code, @value{GDBN} usually
15801 attempts to invoke the redefined version instead of using the operator's
15802 predefined meaning.
15805 @subsubsection C and C@t{++} Constants
15807 @cindex C and C@t{++} constants
15809 @value{GDBN} allows you to express the constants of C and C@t{++} in the
15814 Integer constants are a sequence of digits. Octal constants are
15815 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
15816 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
15817 @samp{l}, specifying that the constant should be treated as a
15821 Floating point constants are a sequence of digits, followed by a decimal
15822 point, followed by a sequence of digits, and optionally followed by an
15823 exponent. An exponent is of the form:
15824 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
15825 sequence of digits. The @samp{+} is optional for positive exponents.
15826 A floating-point constant may also end with a letter @samp{f} or
15827 @samp{F}, specifying that the constant should be treated as being of
15828 the @code{float} (as opposed to the default @code{double}) type; or with
15829 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
15833 Enumerated constants consist of enumerated identifiers, or their
15834 integral equivalents.
15837 Character constants are a single character surrounded by single quotes
15838 (@code{'}), or a number---the ordinal value of the corresponding character
15839 (usually its @sc{ascii} value). Within quotes, the single character may
15840 be represented by a letter or by @dfn{escape sequences}, which are of
15841 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
15842 of the character's ordinal value; or of the form @samp{\@var{x}}, where
15843 @samp{@var{x}} is a predefined special character---for example,
15844 @samp{\n} for newline.
15846 Wide character constants can be written by prefixing a character
15847 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
15848 form of @samp{x}. The target wide character set is used when
15849 computing the value of this constant (@pxref{Character Sets}).
15852 String constants are a sequence of character constants surrounded by
15853 double quotes (@code{"}). Any valid character constant (as described
15854 above) may appear. Double quotes within the string must be preceded by
15855 a backslash, so for instance @samp{"a\"b'c"} is a string of five
15858 Wide string constants can be written by prefixing a string constant
15859 with @samp{L}, as in C. The target wide character set is used when
15860 computing the value of this constant (@pxref{Character Sets}).
15863 Pointer constants are an integral value. You can also write pointers
15864 to constants using the C operator @samp{&}.
15867 Array constants are comma-separated lists surrounded by braces @samp{@{}
15868 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
15869 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
15870 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
15873 @node C Plus Plus Expressions
15874 @subsubsection C@t{++} Expressions
15876 @cindex expressions in C@t{++}
15877 @value{GDBN} expression handling can interpret most C@t{++} expressions.
15879 @cindex debugging C@t{++} programs
15880 @cindex C@t{++} compilers
15881 @cindex debug formats and C@t{++}
15882 @cindex @value{NGCC} and C@t{++}
15884 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
15885 the proper compiler and the proper debug format. Currently,
15886 @value{GDBN} works best when debugging C@t{++} code that is compiled
15887 with the most recent version of @value{NGCC} possible. The DWARF
15888 debugging format is preferred; @value{NGCC} defaults to this on most
15889 popular platforms. Other compilers and/or debug formats are likely to
15890 work badly or not at all when using @value{GDBN} to debug C@t{++}
15891 code. @xref{Compilation}.
15896 @cindex member functions
15898 Member function calls are allowed; you can use expressions like
15901 count = aml->GetOriginal(x, y)
15904 @vindex this@r{, inside C@t{++} member functions}
15905 @cindex namespace in C@t{++}
15907 While a member function is active (in the selected stack frame), your
15908 expressions have the same namespace available as the member function;
15909 that is, @value{GDBN} allows implicit references to the class instance
15910 pointer @code{this} following the same rules as C@t{++}. @code{using}
15911 declarations in the current scope are also respected by @value{GDBN}.
15913 @cindex call overloaded functions
15914 @cindex overloaded functions, calling
15915 @cindex type conversions in C@t{++}
15917 You can call overloaded functions; @value{GDBN} resolves the function
15918 call to the right definition, with some restrictions. @value{GDBN} does not
15919 perform overload resolution involving user-defined type conversions,
15920 calls to constructors, or instantiations of templates that do not exist
15921 in the program. It also cannot handle ellipsis argument lists or
15924 It does perform integral conversions and promotions, floating-point
15925 promotions, arithmetic conversions, pointer conversions, conversions of
15926 class objects to base classes, and standard conversions such as those of
15927 functions or arrays to pointers; it requires an exact match on the
15928 number of function arguments.
15930 Overload resolution is always performed, unless you have specified
15931 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
15932 ,@value{GDBN} Features for C@t{++}}.
15934 You must specify @code{set overload-resolution off} in order to use an
15935 explicit function signature to call an overloaded function, as in
15937 p 'foo(char,int)'('x', 13)
15940 The @value{GDBN} command-completion facility can simplify this;
15941 see @ref{Completion, ,Command Completion}.
15943 @cindex reference declarations
15945 @value{GDBN} understands variables declared as C@t{++} lvalue or rvalue
15946 references; you can use them in expressions just as you do in C@t{++}
15947 source---they are automatically dereferenced.
15949 In the parameter list shown when @value{GDBN} displays a frame, the values of
15950 reference variables are not displayed (unlike other variables); this
15951 avoids clutter, since references are often used for large structures.
15952 The @emph{address} of a reference variable is always shown, unless
15953 you have specified @samp{set print address off}.
15956 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
15957 expressions can use it just as expressions in your program do. Since
15958 one scope may be defined in another, you can use @code{::} repeatedly if
15959 necessary, for example in an expression like
15960 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
15961 resolving name scope by reference to source files, in both C and C@t{++}
15962 debugging (@pxref{Variables, ,Program Variables}).
15965 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
15970 @subsubsection C and C@t{++} Defaults
15972 @cindex C and C@t{++} defaults
15974 If you allow @value{GDBN} to set range checking automatically, it
15975 defaults to @code{off} whenever the working language changes to
15976 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
15977 selects the working language.
15979 If you allow @value{GDBN} to set the language automatically, it
15980 recognizes source files whose names end with @file{.c}, @file{.C}, or
15981 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
15982 these files, it sets the working language to C or C@t{++}.
15983 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
15984 for further details.
15987 @subsubsection C and C@t{++} Type and Range Checks
15989 @cindex C and C@t{++} checks
15991 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
15992 checking is used. However, if you turn type checking off, @value{GDBN}
15993 will allow certain non-standard conversions, such as promoting integer
15994 constants to pointers.
15996 Range checking, if turned on, is done on mathematical operations. Array
15997 indices are not checked, since they are often used to index a pointer
15998 that is not itself an array.
16001 @subsubsection @value{GDBN} and C
16003 The @code{set print union} and @code{show print union} commands apply to
16004 the @code{union} type. When set to @samp{on}, any @code{union} that is
16005 inside a @code{struct} or @code{class} is also printed. Otherwise, it
16006 appears as @samp{@{...@}}.
16008 The @code{@@} operator aids in the debugging of dynamic arrays, formed
16009 with pointers and a memory allocation function. @xref{Expressions,
16012 @node Debugging C Plus Plus
16013 @subsubsection @value{GDBN} Features for C@t{++}
16015 @cindex commands for C@t{++}
16017 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
16018 designed specifically for use with C@t{++}. Here is a summary:
16021 @cindex break in overloaded functions
16022 @item @r{breakpoint menus}
16023 When you want a breakpoint in a function whose name is overloaded,
16024 @value{GDBN} has the capability to display a menu of possible breakpoint
16025 locations to help you specify which function definition you want.
16026 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
16028 @cindex overloading in C@t{++}
16029 @item rbreak @var{regex}
16030 Setting breakpoints using regular expressions is helpful for setting
16031 breakpoints on overloaded functions that are not members of any special
16033 @xref{Set Breaks, ,Setting Breakpoints}.
16035 @cindex C@t{++} exception handling
16037 @itemx catch rethrow
16039 Debug C@t{++} exception handling using these commands. @xref{Set
16040 Catchpoints, , Setting Catchpoints}.
16042 @cindex inheritance
16043 @item ptype @var{typename}
16044 Print inheritance relationships as well as other information for type
16046 @xref{Symbols, ,Examining the Symbol Table}.
16048 @item info vtbl @var{expression}.
16049 The @code{info vtbl} command can be used to display the virtual
16050 method tables of the object computed by @var{expression}. This shows
16051 one entry per virtual table; there may be multiple virtual tables when
16052 multiple inheritance is in use.
16054 @cindex C@t{++} demangling
16055 @item demangle @var{name}
16056 Demangle @var{name}.
16057 @xref{Symbols}, for a more complete description of the @code{demangle} command.
16059 @cindex C@t{++} symbol display
16060 @item set print demangle
16061 @itemx show print demangle
16062 @itemx set print asm-demangle
16063 @itemx show print asm-demangle
16064 Control whether C@t{++} symbols display in their source form, both when
16065 displaying code as C@t{++} source and when displaying disassemblies.
16066 @xref{Print Settings, ,Print Settings}.
16068 @item set print object
16069 @itemx show print object
16070 Choose whether to print derived (actual) or declared types of objects.
16071 @xref{Print Settings, ,Print Settings}.
16073 @item set print vtbl
16074 @itemx show print vtbl
16075 Control the format for printing virtual function tables.
16076 @xref{Print Settings, ,Print Settings}.
16077 (The @code{vtbl} commands do not work on programs compiled with the HP
16078 ANSI C@t{++} compiler (@code{aCC}).)
16080 @kindex set overload-resolution
16081 @cindex overloaded functions, overload resolution
16082 @item set overload-resolution on
16083 Enable overload resolution for C@t{++} expression evaluation. The default
16084 is on. For overloaded functions, @value{GDBN} evaluates the arguments
16085 and searches for a function whose signature matches the argument types,
16086 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
16087 Expressions, ,C@t{++} Expressions}, for details).
16088 If it cannot find a match, it emits a message.
16090 @item set overload-resolution off
16091 Disable overload resolution for C@t{++} expression evaluation. For
16092 overloaded functions that are not class member functions, @value{GDBN}
16093 chooses the first function of the specified name that it finds in the
16094 symbol table, whether or not its arguments are of the correct type. For
16095 overloaded functions that are class member functions, @value{GDBN}
16096 searches for a function whose signature @emph{exactly} matches the
16099 @kindex show overload-resolution
16100 @item show overload-resolution
16101 Show the current setting of overload resolution.
16103 @item @r{Overloaded symbol names}
16104 You can specify a particular definition of an overloaded symbol, using
16105 the same notation that is used to declare such symbols in C@t{++}: type
16106 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
16107 also use the @value{GDBN} command-line word completion facilities to list the
16108 available choices, or to finish the type list for you.
16109 @xref{Completion,, Command Completion}, for details on how to do this.
16111 @item @r{Breakpoints in functions with ABI tags}
16113 The GNU C@t{++} compiler introduced the notion of ABI ``tags'', which
16114 correspond to changes in the ABI of a type, function, or variable that
16115 would not otherwise be reflected in a mangled name. See
16116 @url{https://developers.redhat.com/blog/2015/02/05/gcc5-and-the-c11-abi/}
16119 The ABI tags are visible in C@t{++} demangled names. For example, a
16120 function that returns a std::string:
16123 std::string function(int);
16127 when compiled for the C++11 ABI is marked with the @code{cxx11} ABI
16128 tag, and @value{GDBN} displays the symbol like this:
16131 function[abi:cxx11](int)
16134 You can set a breakpoint on such functions simply as if they had no
16138 (gdb) b function(int)
16139 Breakpoint 2 at 0x40060d: file main.cc, line 10.
16140 (gdb) info breakpoints
16141 Num Type Disp Enb Address What
16142 1 breakpoint keep y 0x0040060d in function[abi:cxx11](int)
16146 On the rare occasion you need to disambiguate between different ABI
16147 tags, you can do so by simply including the ABI tag in the function
16151 (@value{GDBP}) b ambiguous[abi:other_tag](int)
16155 @node Decimal Floating Point
16156 @subsubsection Decimal Floating Point format
16157 @cindex decimal floating point format
16159 @value{GDBN} can examine, set and perform computations with numbers in
16160 decimal floating point format, which in the C language correspond to the
16161 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
16162 specified by the extension to support decimal floating-point arithmetic.
16164 There are two encodings in use, depending on the architecture: BID (Binary
16165 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
16166 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
16169 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
16170 to manipulate decimal floating point numbers, it is not possible to convert
16171 (using a cast, for example) integers wider than 32-bit to decimal float.
16173 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
16174 point computations, error checking in decimal float operations ignores
16175 underflow, overflow and divide by zero exceptions.
16177 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
16178 to inspect @code{_Decimal128} values stored in floating point registers.
16179 See @ref{PowerPC,,PowerPC} for more details.
16185 @value{GDBN} can be used to debug programs written in D and compiled with
16186 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
16187 specific feature --- dynamic arrays.
16192 @cindex Go (programming language)
16193 @value{GDBN} can be used to debug programs written in Go and compiled with
16194 @file{gccgo} or @file{6g} compilers.
16196 Here is a summary of the Go-specific features and restrictions:
16199 @cindex current Go package
16200 @item The current Go package
16201 The name of the current package does not need to be specified when
16202 specifying global variables and functions.
16204 For example, given the program:
16208 var myglob = "Shall we?"
16214 When stopped inside @code{main} either of these work:
16218 (gdb) p main.myglob
16221 @cindex builtin Go types
16222 @item Builtin Go types
16223 The @code{string} type is recognized by @value{GDBN} and is printed
16226 @cindex builtin Go functions
16227 @item Builtin Go functions
16228 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
16229 function and handles it internally.
16231 @cindex restrictions on Go expressions
16232 @item Restrictions on Go expressions
16233 All Go operators are supported except @code{&^}.
16234 The Go @code{_} ``blank identifier'' is not supported.
16235 Automatic dereferencing of pointers is not supported.
16239 @subsection Objective-C
16241 @cindex Objective-C
16242 This section provides information about some commands and command
16243 options that are useful for debugging Objective-C code. See also
16244 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
16245 few more commands specific to Objective-C support.
16248 * Method Names in Commands::
16249 * The Print Command with Objective-C::
16252 @node Method Names in Commands
16253 @subsubsection Method Names in Commands
16255 The following commands have been extended to accept Objective-C method
16256 names as line specifications:
16258 @kindex clear@r{, and Objective-C}
16259 @kindex break@r{, and Objective-C}
16260 @kindex info line@r{, and Objective-C}
16261 @kindex jump@r{, and Objective-C}
16262 @kindex list@r{, and Objective-C}
16266 @item @code{info line}
16271 A fully qualified Objective-C method name is specified as
16274 -[@var{Class} @var{methodName}]
16277 where the minus sign is used to indicate an instance method and a
16278 plus sign (not shown) is used to indicate a class method. The class
16279 name @var{Class} and method name @var{methodName} are enclosed in
16280 brackets, similar to the way messages are specified in Objective-C
16281 source code. For example, to set a breakpoint at the @code{create}
16282 instance method of class @code{Fruit} in the program currently being
16286 break -[Fruit create]
16289 To list ten program lines around the @code{initialize} class method,
16293 list +[NSText initialize]
16296 In the current version of @value{GDBN}, the plus or minus sign is
16297 required. In future versions of @value{GDBN}, the plus or minus
16298 sign will be optional, but you can use it to narrow the search. It
16299 is also possible to specify just a method name:
16305 You must specify the complete method name, including any colons. If
16306 your program's source files contain more than one @code{create} method,
16307 you'll be presented with a numbered list of classes that implement that
16308 method. Indicate your choice by number, or type @samp{0} to exit if
16311 As another example, to clear a breakpoint established at the
16312 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
16315 clear -[NSWindow makeKeyAndOrderFront:]
16318 @node The Print Command with Objective-C
16319 @subsubsection The Print Command With Objective-C
16320 @cindex Objective-C, print objects
16321 @kindex print-object
16322 @kindex po @r{(@code{print-object})}
16324 The print command has also been extended to accept methods. For example:
16327 print -[@var{object} hash]
16330 @cindex print an Objective-C object description
16331 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
16333 will tell @value{GDBN} to send the @code{hash} message to @var{object}
16334 and print the result. Also, an additional command has been added,
16335 @code{print-object} or @code{po} for short, which is meant to print
16336 the description of an object. However, this command may only work
16337 with certain Objective-C libraries that have a particular hook
16338 function, @code{_NSPrintForDebugger}, defined.
16341 @subsection OpenCL C
16344 This section provides information about @value{GDBN}s OpenCL C support.
16347 * OpenCL C Datatypes::
16348 * OpenCL C Expressions::
16349 * OpenCL C Operators::
16352 @node OpenCL C Datatypes
16353 @subsubsection OpenCL C Datatypes
16355 @cindex OpenCL C Datatypes
16356 @value{GDBN} supports the builtin scalar and vector datatypes specified
16357 by OpenCL 1.1. In addition the half- and double-precision floating point
16358 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
16359 extensions are also known to @value{GDBN}.
16361 @node OpenCL C Expressions
16362 @subsubsection OpenCL C Expressions
16364 @cindex OpenCL C Expressions
16365 @value{GDBN} supports accesses to vector components including the access as
16366 lvalue where possible. Since OpenCL C is based on C99 most C expressions
16367 supported by @value{GDBN} can be used as well.
16369 @node OpenCL C Operators
16370 @subsubsection OpenCL C Operators
16372 @cindex OpenCL C Operators
16373 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
16377 @subsection Fortran
16378 @cindex Fortran-specific support in @value{GDBN}
16380 @value{GDBN} can be used to debug programs written in Fortran, but it
16381 currently supports only the features of Fortran 77 language.
16383 @cindex trailing underscore, in Fortran symbols
16384 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
16385 among them) append an underscore to the names of variables and
16386 functions. When you debug programs compiled by those compilers, you
16387 will need to refer to variables and functions with a trailing
16391 * Fortran Operators:: Fortran operators and expressions
16392 * Fortran Defaults:: Default settings for Fortran
16393 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
16396 @node Fortran Operators
16397 @subsubsection Fortran Operators and Expressions
16399 @cindex Fortran operators and expressions
16401 Operators must be defined on values of specific types. For instance,
16402 @code{+} is defined on numbers, but not on characters or other non-
16403 arithmetic types. Operators are often defined on groups of types.
16407 The exponentiation operator. It raises the first operand to the power
16411 The range operator. Normally used in the form of array(low:high) to
16412 represent a section of array.
16415 The access component operator. Normally used to access elements in derived
16416 types. Also suitable for unions. As unions aren't part of regular Fortran,
16417 this can only happen when accessing a register that uses a gdbarch-defined
16421 @node Fortran Defaults
16422 @subsubsection Fortran Defaults
16424 @cindex Fortran Defaults
16426 Fortran symbols are usually case-insensitive, so @value{GDBN} by
16427 default uses case-insensitive matches for Fortran symbols. You can
16428 change that with the @samp{set case-insensitive} command, see
16429 @ref{Symbols}, for the details.
16431 @node Special Fortran Commands
16432 @subsubsection Special Fortran Commands
16434 @cindex Special Fortran commands
16436 @value{GDBN} has some commands to support Fortran-specific features,
16437 such as displaying common blocks.
16440 @cindex @code{COMMON} blocks, Fortran
16441 @kindex info common
16442 @item info common @r{[}@var{common-name}@r{]}
16443 This command prints the values contained in the Fortran @code{COMMON}
16444 block whose name is @var{common-name}. With no argument, the names of
16445 all @code{COMMON} blocks visible at the current program location are
16452 @cindex Pascal support in @value{GDBN}, limitations
16453 Debugging Pascal programs which use sets, subranges, file variables, or
16454 nested functions does not currently work. @value{GDBN} does not support
16455 entering expressions, printing values, or similar features using Pascal
16458 The Pascal-specific command @code{set print pascal_static-members}
16459 controls whether static members of Pascal objects are displayed.
16460 @xref{Print Settings, pascal_static-members}.
16465 @value{GDBN} supports the @url{https://www.rust-lang.org/, Rust
16466 Programming Language}. Type- and value-printing, and expression
16467 parsing, are reasonably complete. However, there are a few
16468 peculiarities and holes to be aware of.
16472 Linespecs (@pxref{Specify Location}) are never relative to the current
16473 crate. Instead, they act as if there were a global namespace of
16474 crates, somewhat similar to the way @code{extern crate} behaves.
16476 That is, if @value{GDBN} is stopped at a breakpoint in a function in
16477 crate @samp{A}, module @samp{B}, then @code{break B::f} will attempt
16478 to set a breakpoint in a function named @samp{f} in a crate named
16481 As a consequence of this approach, linespecs also cannot refer to
16482 items using @samp{self::} or @samp{super::}.
16485 Because @value{GDBN} implements Rust name-lookup semantics in
16486 expressions, it will sometimes prepend the current crate to a name.
16487 For example, if @value{GDBN} is stopped at a breakpoint in the crate
16488 @samp{K}, then @code{print ::x::y} will try to find the symbol
16491 However, since it is useful to be able to refer to other crates when
16492 debugging, @value{GDBN} provides the @code{extern} extension to
16493 circumvent this. To use the extension, just put @code{extern} before
16494 a path expression to refer to the otherwise unavailable ``global''
16497 In the above example, if you wanted to refer to the symbol @samp{y} in
16498 the crate @samp{x}, you would use @code{print extern x::y}.
16501 The Rust expression evaluator does not support ``statement-like''
16502 expressions such as @code{if} or @code{match}, or lambda expressions.
16505 Tuple expressions are not implemented.
16508 The Rust expression evaluator does not currently implement the
16509 @code{Drop} trait. Objects that may be created by the evaluator will
16510 never be destroyed.
16513 @value{GDBN} does not implement type inference for generics. In order
16514 to call generic functions or otherwise refer to generic items, you
16515 will have to specify the type parameters manually.
16518 @value{GDBN} currently uses the C@t{++} demangler for Rust. In most
16519 cases this does not cause any problems. However, in an expression
16520 context, completing a generic function name will give syntactically
16521 invalid results. This happens because Rust requires the @samp{::}
16522 operator between the function name and its generic arguments. For
16523 example, @value{GDBN} might provide a completion like
16524 @code{crate::f<u32>}, where the parser would require
16525 @code{crate::f::<u32>}.
16528 As of this writing, the Rust compiler (version 1.8) has a few holes in
16529 the debugging information it generates. These holes prevent certain
16530 features from being implemented by @value{GDBN}:
16534 Method calls cannot be made via traits.
16537 Operator overloading is not implemented.
16540 When debugging in a monomorphized function, you cannot use the generic
16544 The type @code{Self} is not available.
16547 @code{use} statements are not available, so some names may not be
16548 available in the crate.
16553 @subsection Modula-2
16555 @cindex Modula-2, @value{GDBN} support
16557 The extensions made to @value{GDBN} to support Modula-2 only support
16558 output from the @sc{gnu} Modula-2 compiler (which is currently being
16559 developed). Other Modula-2 compilers are not currently supported, and
16560 attempting to debug executables produced by them is most likely
16561 to give an error as @value{GDBN} reads in the executable's symbol
16564 @cindex expressions in Modula-2
16566 * M2 Operators:: Built-in operators
16567 * Built-In Func/Proc:: Built-in functions and procedures
16568 * M2 Constants:: Modula-2 constants
16569 * M2 Types:: Modula-2 types
16570 * M2 Defaults:: Default settings for Modula-2
16571 * Deviations:: Deviations from standard Modula-2
16572 * M2 Checks:: Modula-2 type and range checks
16573 * M2 Scope:: The scope operators @code{::} and @code{.}
16574 * GDB/M2:: @value{GDBN} and Modula-2
16578 @subsubsection Operators
16579 @cindex Modula-2 operators
16581 Operators must be defined on values of specific types. For instance,
16582 @code{+} is defined on numbers, but not on structures. Operators are
16583 often defined on groups of types. For the purposes of Modula-2, the
16584 following definitions hold:
16589 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
16593 @emph{Character types} consist of @code{CHAR} and its subranges.
16596 @emph{Floating-point types} consist of @code{REAL}.
16599 @emph{Pointer types} consist of anything declared as @code{POINTER TO
16603 @emph{Scalar types} consist of all of the above.
16606 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
16609 @emph{Boolean types} consist of @code{BOOLEAN}.
16613 The following operators are supported, and appear in order of
16614 increasing precedence:
16618 Function argument or array index separator.
16621 Assignment. The value of @var{var} @code{:=} @var{value} is
16625 Less than, greater than on integral, floating-point, or enumerated
16629 Less than or equal to, greater than or equal to
16630 on integral, floating-point and enumerated types, or set inclusion on
16631 set types. Same precedence as @code{<}.
16633 @item =@r{, }<>@r{, }#
16634 Equality and two ways of expressing inequality, valid on scalar types.
16635 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
16636 available for inequality, since @code{#} conflicts with the script
16640 Set membership. Defined on set types and the types of their members.
16641 Same precedence as @code{<}.
16644 Boolean disjunction. Defined on boolean types.
16647 Boolean conjunction. Defined on boolean types.
16650 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
16653 Addition and subtraction on integral and floating-point types, or union
16654 and difference on set types.
16657 Multiplication on integral and floating-point types, or set intersection
16661 Division on floating-point types, or symmetric set difference on set
16662 types. Same precedence as @code{*}.
16665 Integer division and remainder. Defined on integral types. Same
16666 precedence as @code{*}.
16669 Negative. Defined on @code{INTEGER} and @code{REAL} data.
16672 Pointer dereferencing. Defined on pointer types.
16675 Boolean negation. Defined on boolean types. Same precedence as
16679 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
16680 precedence as @code{^}.
16683 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
16686 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
16690 @value{GDBN} and Modula-2 scope operators.
16694 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
16695 treats the use of the operator @code{IN}, or the use of operators
16696 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
16697 @code{<=}, and @code{>=} on sets as an error.
16701 @node Built-In Func/Proc
16702 @subsubsection Built-in Functions and Procedures
16703 @cindex Modula-2 built-ins
16705 Modula-2 also makes available several built-in procedures and functions.
16706 In describing these, the following metavariables are used:
16711 represents an @code{ARRAY} variable.
16714 represents a @code{CHAR} constant or variable.
16717 represents a variable or constant of integral type.
16720 represents an identifier that belongs to a set. Generally used in the
16721 same function with the metavariable @var{s}. The type of @var{s} should
16722 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
16725 represents a variable or constant of integral or floating-point type.
16728 represents a variable or constant of floating-point type.
16734 represents a variable.
16737 represents a variable or constant of one of many types. See the
16738 explanation of the function for details.
16741 All Modula-2 built-in procedures also return a result, described below.
16745 Returns the absolute value of @var{n}.
16748 If @var{c} is a lower case letter, it returns its upper case
16749 equivalent, otherwise it returns its argument.
16752 Returns the character whose ordinal value is @var{i}.
16755 Decrements the value in the variable @var{v} by one. Returns the new value.
16757 @item DEC(@var{v},@var{i})
16758 Decrements the value in the variable @var{v} by @var{i}. Returns the
16761 @item EXCL(@var{m},@var{s})
16762 Removes the element @var{m} from the set @var{s}. Returns the new
16765 @item FLOAT(@var{i})
16766 Returns the floating point equivalent of the integer @var{i}.
16768 @item HIGH(@var{a})
16769 Returns the index of the last member of @var{a}.
16772 Increments the value in the variable @var{v} by one. Returns the new value.
16774 @item INC(@var{v},@var{i})
16775 Increments the value in the variable @var{v} by @var{i}. Returns the
16778 @item INCL(@var{m},@var{s})
16779 Adds the element @var{m} to the set @var{s} if it is not already
16780 there. Returns the new set.
16783 Returns the maximum value of the type @var{t}.
16786 Returns the minimum value of the type @var{t}.
16789 Returns boolean TRUE if @var{i} is an odd number.
16792 Returns the ordinal value of its argument. For example, the ordinal
16793 value of a character is its @sc{ascii} value (on machines supporting
16794 the @sc{ascii} character set). The argument @var{x} must be of an
16795 ordered type, which include integral, character and enumerated types.
16797 @item SIZE(@var{x})
16798 Returns the size of its argument. The argument @var{x} can be a
16799 variable or a type.
16801 @item TRUNC(@var{r})
16802 Returns the integral part of @var{r}.
16804 @item TSIZE(@var{x})
16805 Returns the size of its argument. The argument @var{x} can be a
16806 variable or a type.
16808 @item VAL(@var{t},@var{i})
16809 Returns the member of the type @var{t} whose ordinal value is @var{i}.
16813 @emph{Warning:} Sets and their operations are not yet supported, so
16814 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
16818 @cindex Modula-2 constants
16820 @subsubsection Constants
16822 @value{GDBN} allows you to express the constants of Modula-2 in the following
16828 Integer constants are simply a sequence of digits. When used in an
16829 expression, a constant is interpreted to be type-compatible with the
16830 rest of the expression. Hexadecimal integers are specified by a
16831 trailing @samp{H}, and octal integers by a trailing @samp{B}.
16834 Floating point constants appear as a sequence of digits, followed by a
16835 decimal point and another sequence of digits. An optional exponent can
16836 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
16837 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
16838 digits of the floating point constant must be valid decimal (base 10)
16842 Character constants consist of a single character enclosed by a pair of
16843 like quotes, either single (@code{'}) or double (@code{"}). They may
16844 also be expressed by their ordinal value (their @sc{ascii} value, usually)
16845 followed by a @samp{C}.
16848 String constants consist of a sequence of characters enclosed by a
16849 pair of like quotes, either single (@code{'}) or double (@code{"}).
16850 Escape sequences in the style of C are also allowed. @xref{C
16851 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
16855 Enumerated constants consist of an enumerated identifier.
16858 Boolean constants consist of the identifiers @code{TRUE} and
16862 Pointer constants consist of integral values only.
16865 Set constants are not yet supported.
16869 @subsubsection Modula-2 Types
16870 @cindex Modula-2 types
16872 Currently @value{GDBN} can print the following data types in Modula-2
16873 syntax: array types, record types, set types, pointer types, procedure
16874 types, enumerated types, subrange types and base types. You can also
16875 print the contents of variables declared using these type.
16876 This section gives a number of simple source code examples together with
16877 sample @value{GDBN} sessions.
16879 The first example contains the following section of code:
16888 and you can request @value{GDBN} to interrogate the type and value of
16889 @code{r} and @code{s}.
16892 (@value{GDBP}) print s
16894 (@value{GDBP}) ptype s
16896 (@value{GDBP}) print r
16898 (@value{GDBP}) ptype r
16903 Likewise if your source code declares @code{s} as:
16907 s: SET ['A'..'Z'] ;
16911 then you may query the type of @code{s} by:
16914 (@value{GDBP}) ptype s
16915 type = SET ['A'..'Z']
16919 Note that at present you cannot interactively manipulate set
16920 expressions using the debugger.
16922 The following example shows how you might declare an array in Modula-2
16923 and how you can interact with @value{GDBN} to print its type and contents:
16927 s: ARRAY [-10..10] OF CHAR ;
16931 (@value{GDBP}) ptype s
16932 ARRAY [-10..10] OF CHAR
16935 Note that the array handling is not yet complete and although the type
16936 is printed correctly, expression handling still assumes that all
16937 arrays have a lower bound of zero and not @code{-10} as in the example
16940 Here are some more type related Modula-2 examples:
16944 colour = (blue, red, yellow, green) ;
16945 t = [blue..yellow] ;
16953 The @value{GDBN} interaction shows how you can query the data type
16954 and value of a variable.
16957 (@value{GDBP}) print s
16959 (@value{GDBP}) ptype t
16960 type = [blue..yellow]
16964 In this example a Modula-2 array is declared and its contents
16965 displayed. Observe that the contents are written in the same way as
16966 their @code{C} counterparts.
16970 s: ARRAY [1..5] OF CARDINAL ;
16976 (@value{GDBP}) print s
16977 $1 = @{1, 0, 0, 0, 0@}
16978 (@value{GDBP}) ptype s
16979 type = ARRAY [1..5] OF CARDINAL
16982 The Modula-2 language interface to @value{GDBN} also understands
16983 pointer types as shown in this example:
16987 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
16994 and you can request that @value{GDBN} describes the type of @code{s}.
16997 (@value{GDBP}) ptype s
16998 type = POINTER TO ARRAY [1..5] OF CARDINAL
17001 @value{GDBN} handles compound types as we can see in this example.
17002 Here we combine array types, record types, pointer types and subrange
17013 myarray = ARRAY myrange OF CARDINAL ;
17014 myrange = [-2..2] ;
17016 s: POINTER TO ARRAY myrange OF foo ;
17020 and you can ask @value{GDBN} to describe the type of @code{s} as shown
17024 (@value{GDBP}) ptype s
17025 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
17028 f3 : ARRAY [-2..2] OF CARDINAL;
17033 @subsubsection Modula-2 Defaults
17034 @cindex Modula-2 defaults
17036 If type and range checking are set automatically by @value{GDBN}, they
17037 both default to @code{on} whenever the working language changes to
17038 Modula-2. This happens regardless of whether you or @value{GDBN}
17039 selected the working language.
17041 If you allow @value{GDBN} to set the language automatically, then entering
17042 code compiled from a file whose name ends with @file{.mod} sets the
17043 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
17044 Infer the Source Language}, for further details.
17047 @subsubsection Deviations from Standard Modula-2
17048 @cindex Modula-2, deviations from
17050 A few changes have been made to make Modula-2 programs easier to debug.
17051 This is done primarily via loosening its type strictness:
17055 Unlike in standard Modula-2, pointer constants can be formed by
17056 integers. This allows you to modify pointer variables during
17057 debugging. (In standard Modula-2, the actual address contained in a
17058 pointer variable is hidden from you; it can only be modified
17059 through direct assignment to another pointer variable or expression that
17060 returned a pointer.)
17063 C escape sequences can be used in strings and characters to represent
17064 non-printable characters. @value{GDBN} prints out strings with these
17065 escape sequences embedded. Single non-printable characters are
17066 printed using the @samp{CHR(@var{nnn})} format.
17069 The assignment operator (@code{:=}) returns the value of its right-hand
17073 All built-in procedures both modify @emph{and} return their argument.
17077 @subsubsection Modula-2 Type and Range Checks
17078 @cindex Modula-2 checks
17081 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
17084 @c FIXME remove warning when type/range checks added
17086 @value{GDBN} considers two Modula-2 variables type equivalent if:
17090 They are of types that have been declared equivalent via a @code{TYPE
17091 @var{t1} = @var{t2}} statement
17094 They have been declared on the same line. (Note: This is true of the
17095 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
17098 As long as type checking is enabled, any attempt to combine variables
17099 whose types are not equivalent is an error.
17101 Range checking is done on all mathematical operations, assignment, array
17102 index bounds, and all built-in functions and procedures.
17105 @subsubsection The Scope Operators @code{::} and @code{.}
17107 @cindex @code{.}, Modula-2 scope operator
17108 @cindex colon, doubled as scope operator
17110 @vindex colon-colon@r{, in Modula-2}
17111 @c Info cannot handle :: but TeX can.
17114 @vindex ::@r{, in Modula-2}
17117 There are a few subtle differences between the Modula-2 scope operator
17118 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
17123 @var{module} . @var{id}
17124 @var{scope} :: @var{id}
17128 where @var{scope} is the name of a module or a procedure,
17129 @var{module} the name of a module, and @var{id} is any declared
17130 identifier within your program, except another module.
17132 Using the @code{::} operator makes @value{GDBN} search the scope
17133 specified by @var{scope} for the identifier @var{id}. If it is not
17134 found in the specified scope, then @value{GDBN} searches all scopes
17135 enclosing the one specified by @var{scope}.
17137 Using the @code{.} operator makes @value{GDBN} search the current scope for
17138 the identifier specified by @var{id} that was imported from the
17139 definition module specified by @var{module}. With this operator, it is
17140 an error if the identifier @var{id} was not imported from definition
17141 module @var{module}, or if @var{id} is not an identifier in
17145 @subsubsection @value{GDBN} and Modula-2
17147 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
17148 Five subcommands of @code{set print} and @code{show print} apply
17149 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
17150 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
17151 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
17152 analogue in Modula-2.
17154 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
17155 with any language, is not useful with Modula-2. Its
17156 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
17157 created in Modula-2 as they can in C or C@t{++}. However, because an
17158 address can be specified by an integral constant, the construct
17159 @samp{@{@var{type}@}@var{adrexp}} is still useful.
17161 @cindex @code{#} in Modula-2
17162 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
17163 interpreted as the beginning of a comment. Use @code{<>} instead.
17169 The extensions made to @value{GDBN} for Ada only support
17170 output from the @sc{gnu} Ada (GNAT) compiler.
17171 Other Ada compilers are not currently supported, and
17172 attempting to debug executables produced by them is most likely
17176 @cindex expressions in Ada
17178 * Ada Mode Intro:: General remarks on the Ada syntax
17179 and semantics supported by Ada mode
17181 * Omissions from Ada:: Restrictions on the Ada expression syntax.
17182 * Additions to Ada:: Extensions of the Ada expression syntax.
17183 * Overloading support for Ada:: Support for expressions involving overloaded
17185 * Stopping Before Main Program:: Debugging the program during elaboration.
17186 * Ada Exceptions:: Ada Exceptions
17187 * Ada Tasks:: Listing and setting breakpoints in tasks.
17188 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
17189 * Ravenscar Profile:: Tasking Support when using the Ravenscar
17191 * Ada Settings:: New settable GDB parameters for Ada.
17192 * Ada Glitches:: Known peculiarities of Ada mode.
17195 @node Ada Mode Intro
17196 @subsubsection Introduction
17197 @cindex Ada mode, general
17199 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
17200 syntax, with some extensions.
17201 The philosophy behind the design of this subset is
17205 That @value{GDBN} should provide basic literals and access to operations for
17206 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
17207 leaving more sophisticated computations to subprograms written into the
17208 program (which therefore may be called from @value{GDBN}).
17211 That type safety and strict adherence to Ada language restrictions
17212 are not particularly important to the @value{GDBN} user.
17215 That brevity is important to the @value{GDBN} user.
17218 Thus, for brevity, the debugger acts as if all names declared in
17219 user-written packages are directly visible, even if they are not visible
17220 according to Ada rules, thus making it unnecessary to fully qualify most
17221 names with their packages, regardless of context. Where this causes
17222 ambiguity, @value{GDBN} asks the user's intent.
17224 The debugger will start in Ada mode if it detects an Ada main program.
17225 As for other languages, it will enter Ada mode when stopped in a program that
17226 was translated from an Ada source file.
17228 While in Ada mode, you may use `@t{--}' for comments. This is useful
17229 mostly for documenting command files. The standard @value{GDBN} comment
17230 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
17231 middle (to allow based literals).
17233 @node Omissions from Ada
17234 @subsubsection Omissions from Ada
17235 @cindex Ada, omissions from
17237 Here are the notable omissions from the subset:
17241 Only a subset of the attributes are supported:
17245 @t{'First}, @t{'Last}, and @t{'Length}
17246 on array objects (not on types and subtypes).
17249 @t{'Min} and @t{'Max}.
17252 @t{'Pos} and @t{'Val}.
17258 @t{'Range} on array objects (not subtypes), but only as the right
17259 operand of the membership (@code{in}) operator.
17262 @t{'Access}, @t{'Unchecked_Access}, and
17263 @t{'Unrestricted_Access} (a GNAT extension).
17271 @code{Characters.Latin_1} are not available and
17272 concatenation is not implemented. Thus, escape characters in strings are
17273 not currently available.
17276 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
17277 equality of representations. They will generally work correctly
17278 for strings and arrays whose elements have integer or enumeration types.
17279 They may not work correctly for arrays whose element
17280 types have user-defined equality, for arrays of real values
17281 (in particular, IEEE-conformant floating point, because of negative
17282 zeroes and NaNs), and for arrays whose elements contain unused bits with
17283 indeterminate values.
17286 The other component-by-component array operations (@code{and}, @code{or},
17287 @code{xor}, @code{not}, and relational tests other than equality)
17288 are not implemented.
17291 @cindex array aggregates (Ada)
17292 @cindex record aggregates (Ada)
17293 @cindex aggregates (Ada)
17294 There is limited support for array and record aggregates. They are
17295 permitted only on the right sides of assignments, as in these examples:
17298 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
17299 (@value{GDBP}) set An_Array := (1, others => 0)
17300 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
17301 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
17302 (@value{GDBP}) set A_Record := (1, "Peter", True);
17303 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
17307 discriminant's value by assigning an aggregate has an
17308 undefined effect if that discriminant is used within the record.
17309 However, you can first modify discriminants by directly assigning to
17310 them (which normally would not be allowed in Ada), and then performing an
17311 aggregate assignment. For example, given a variable @code{A_Rec}
17312 declared to have a type such as:
17315 type Rec (Len : Small_Integer := 0) is record
17317 Vals : IntArray (1 .. Len);
17321 you can assign a value with a different size of @code{Vals} with two
17325 (@value{GDBP}) set A_Rec.Len := 4
17326 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
17329 As this example also illustrates, @value{GDBN} is very loose about the usual
17330 rules concerning aggregates. You may leave out some of the
17331 components of an array or record aggregate (such as the @code{Len}
17332 component in the assignment to @code{A_Rec} above); they will retain their
17333 original values upon assignment. You may freely use dynamic values as
17334 indices in component associations. You may even use overlapping or
17335 redundant component associations, although which component values are
17336 assigned in such cases is not defined.
17339 Calls to dispatching subprograms are not implemented.
17342 The overloading algorithm is much more limited (i.e., less selective)
17343 than that of real Ada. It makes only limited use of the context in
17344 which a subexpression appears to resolve its meaning, and it is much
17345 looser in its rules for allowing type matches. As a result, some
17346 function calls will be ambiguous, and the user will be asked to choose
17347 the proper resolution.
17350 The @code{new} operator is not implemented.
17353 Entry calls are not implemented.
17356 Aside from printing, arithmetic operations on the native VAX floating-point
17357 formats are not supported.
17360 It is not possible to slice a packed array.
17363 The names @code{True} and @code{False}, when not part of a qualified name,
17364 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
17366 Should your program
17367 redefine these names in a package or procedure (at best a dubious practice),
17368 you will have to use fully qualified names to access their new definitions.
17371 @node Additions to Ada
17372 @subsubsection Additions to Ada
17373 @cindex Ada, deviations from
17375 As it does for other languages, @value{GDBN} makes certain generic
17376 extensions to Ada (@pxref{Expressions}):
17380 If the expression @var{E} is a variable residing in memory (typically
17381 a local variable or array element) and @var{N} is a positive integer,
17382 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
17383 @var{N}-1 adjacent variables following it in memory as an array. In
17384 Ada, this operator is generally not necessary, since its prime use is
17385 in displaying parts of an array, and slicing will usually do this in
17386 Ada. However, there are occasional uses when debugging programs in
17387 which certain debugging information has been optimized away.
17390 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
17391 appears in function or file @var{B}.'' When @var{B} is a file name,
17392 you must typically surround it in single quotes.
17395 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
17396 @var{type} that appears at address @var{addr}.''
17399 A name starting with @samp{$} is a convenience variable
17400 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
17403 In addition, @value{GDBN} provides a few other shortcuts and outright
17404 additions specific to Ada:
17408 The assignment statement is allowed as an expression, returning
17409 its right-hand operand as its value. Thus, you may enter
17412 (@value{GDBP}) set x := y + 3
17413 (@value{GDBP}) print A(tmp := y + 1)
17417 The semicolon is allowed as an ``operator,'' returning as its value
17418 the value of its right-hand operand.
17419 This allows, for example,
17420 complex conditional breaks:
17423 (@value{GDBP}) break f
17424 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
17428 Rather than use catenation and symbolic character names to introduce special
17429 characters into strings, one may instead use a special bracket notation,
17430 which is also used to print strings. A sequence of characters of the form
17431 @samp{["@var{XX}"]} within a string or character literal denotes the
17432 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
17433 sequence of characters @samp{["""]} also denotes a single quotation mark
17434 in strings. For example,
17436 "One line.["0a"]Next line.["0a"]"
17439 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
17443 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
17444 @t{'Max} is optional (and is ignored in any case). For example, it is valid
17448 (@value{GDBP}) print 'max(x, y)
17452 When printing arrays, @value{GDBN} uses positional notation when the
17453 array has a lower bound of 1, and uses a modified named notation otherwise.
17454 For example, a one-dimensional array of three integers with a lower bound
17455 of 3 might print as
17462 That is, in contrast to valid Ada, only the first component has a @code{=>}
17466 You may abbreviate attributes in expressions with any unique,
17467 multi-character subsequence of
17468 their names (an exact match gets preference).
17469 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
17470 in place of @t{a'length}.
17473 @cindex quoting Ada internal identifiers
17474 Since Ada is case-insensitive, the debugger normally maps identifiers you type
17475 to lower case. The GNAT compiler uses upper-case characters for
17476 some of its internal identifiers, which are normally of no interest to users.
17477 For the rare occasions when you actually have to look at them,
17478 enclose them in angle brackets to avoid the lower-case mapping.
17481 (@value{GDBP}) print <JMPBUF_SAVE>[0]
17485 Printing an object of class-wide type or dereferencing an
17486 access-to-class-wide value will display all the components of the object's
17487 specific type (as indicated by its run-time tag). Likewise, component
17488 selection on such a value will operate on the specific type of the
17493 @node Overloading support for Ada
17494 @subsubsection Overloading support for Ada
17495 @cindex overloading, Ada
17497 The debugger supports limited overloading. Given a subprogram call in which
17498 the function symbol has multiple definitions, it will use the number of
17499 actual parameters and some information about their types to attempt to narrow
17500 the set of definitions. It also makes very limited use of context, preferring
17501 procedures to functions in the context of the @code{call} command, and
17502 functions to procedures elsewhere.
17504 If, after narrowing, the set of matching definitions still contains more than
17505 one definition, @value{GDBN} will display a menu to query which one it should
17509 (@value{GDBP}) print f(1)
17510 Multiple matches for f
17512 [1] foo.f (integer) return boolean at foo.adb:23
17513 [2] foo.f (foo.new_integer) return boolean at foo.adb:28
17517 In this case, just select one menu entry either to cancel expression evaluation
17518 (type @kbd{0} and press @key{RET}) or to continue evaluation with a specific
17519 instance (type the corresponding number and press @key{RET}).
17521 Here are a couple of commands to customize @value{GDBN}'s behavior in this
17526 @kindex set ada print-signatures
17527 @item set ada print-signatures
17528 Control whether parameter types and return types are displayed in overloads
17529 selection menus. It is @code{on} by default.
17530 @xref{Overloading support for Ada}.
17532 @kindex show ada print-signatures
17533 @item show ada print-signatures
17534 Show the current setting for displaying parameter types and return types in
17535 overloads selection menu.
17536 @xref{Overloading support for Ada}.
17540 @node Stopping Before Main Program
17541 @subsubsection Stopping at the Very Beginning
17543 @cindex breakpointing Ada elaboration code
17544 It is sometimes necessary to debug the program during elaboration, and
17545 before reaching the main procedure.
17546 As defined in the Ada Reference
17547 Manual, the elaboration code is invoked from a procedure called
17548 @code{adainit}. To run your program up to the beginning of
17549 elaboration, simply use the following two commands:
17550 @code{tbreak adainit} and @code{run}.
17552 @node Ada Exceptions
17553 @subsubsection Ada Exceptions
17555 A command is provided to list all Ada exceptions:
17558 @kindex info exceptions
17559 @item info exceptions
17560 @itemx info exceptions @var{regexp}
17561 The @code{info exceptions} command allows you to list all Ada exceptions
17562 defined within the program being debugged, as well as their addresses.
17563 With a regular expression, @var{regexp}, as argument, only those exceptions
17564 whose names match @var{regexp} are listed.
17567 Below is a small example, showing how the command can be used, first
17568 without argument, and next with a regular expression passed as an
17572 (@value{GDBP}) info exceptions
17573 All defined Ada exceptions:
17574 constraint_error: 0x613da0
17575 program_error: 0x613d20
17576 storage_error: 0x613ce0
17577 tasking_error: 0x613ca0
17578 const.aint_global_e: 0x613b00
17579 (@value{GDBP}) info exceptions const.aint
17580 All Ada exceptions matching regular expression "const.aint":
17581 constraint_error: 0x613da0
17582 const.aint_global_e: 0x613b00
17585 It is also possible to ask @value{GDBN} to stop your program's execution
17586 when an exception is raised. For more details, see @ref{Set Catchpoints}.
17589 @subsubsection Extensions for Ada Tasks
17590 @cindex Ada, tasking
17592 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
17593 @value{GDBN} provides the following task-related commands:
17598 This command shows a list of current Ada tasks, as in the following example:
17605 (@value{GDBP}) info tasks
17606 ID TID P-ID Pri State Name
17607 1 8088000 0 15 Child Activation Wait main_task
17608 2 80a4000 1 15 Accept Statement b
17609 3 809a800 1 15 Child Activation Wait a
17610 * 4 80ae800 3 15 Runnable c
17615 In this listing, the asterisk before the last task indicates it to be the
17616 task currently being inspected.
17620 Represents @value{GDBN}'s internal task number.
17626 The parent's task ID (@value{GDBN}'s internal task number).
17629 The base priority of the task.
17632 Current state of the task.
17636 The task has been created but has not been activated. It cannot be
17640 The task is not blocked for any reason known to Ada. (It may be waiting
17641 for a mutex, though.) It is conceptually "executing" in normal mode.
17644 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
17645 that were waiting on terminate alternatives have been awakened and have
17646 terminated themselves.
17648 @item Child Activation Wait
17649 The task is waiting for created tasks to complete activation.
17651 @item Accept Statement
17652 The task is waiting on an accept or selective wait statement.
17654 @item Waiting on entry call
17655 The task is waiting on an entry call.
17657 @item Async Select Wait
17658 The task is waiting to start the abortable part of an asynchronous
17662 The task is waiting on a select statement with only a delay
17665 @item Child Termination Wait
17666 The task is sleeping having completed a master within itself, and is
17667 waiting for the tasks dependent on that master to become terminated or
17668 waiting on a terminate Phase.
17670 @item Wait Child in Term Alt
17671 The task is sleeping waiting for tasks on terminate alternatives to
17672 finish terminating.
17674 @item Accepting RV with @var{taskno}
17675 The task is accepting a rendez-vous with the task @var{taskno}.
17679 Name of the task in the program.
17683 @kindex info task @var{taskno}
17684 @item info task @var{taskno}
17685 This command shows detailled informations on the specified task, as in
17686 the following example:
17691 (@value{GDBP}) info tasks
17692 ID TID P-ID Pri State Name
17693 1 8077880 0 15 Child Activation Wait main_task
17694 * 2 807c468 1 15 Runnable task_1
17695 (@value{GDBP}) info task 2
17696 Ada Task: 0x807c468
17700 Parent: 1 (main_task)
17706 @kindex task@r{ (Ada)}
17707 @cindex current Ada task ID
17708 This command prints the ID of the current task.
17714 (@value{GDBP}) info tasks
17715 ID TID P-ID Pri State Name
17716 1 8077870 0 15 Child Activation Wait main_task
17717 * 2 807c458 1 15 Runnable t
17718 (@value{GDBP}) task
17719 [Current task is 2]
17722 @item task @var{taskno}
17723 @cindex Ada task switching
17724 This command is like the @code{thread @var{thread-id}}
17725 command (@pxref{Threads}). It switches the context of debugging
17726 from the current task to the given task.
17732 (@value{GDBP}) info tasks
17733 ID TID P-ID Pri State Name
17734 1 8077870 0 15 Child Activation Wait main_task
17735 * 2 807c458 1 15 Runnable t
17736 (@value{GDBP}) task 1
17737 [Switching to task 1]
17738 #0 0x8067726 in pthread_cond_wait ()
17740 #0 0x8067726 in pthread_cond_wait ()
17741 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
17742 #2 0x805cb63 in system.task_primitives.operations.sleep ()
17743 #3 0x806153e in system.tasking.stages.activate_tasks ()
17744 #4 0x804aacc in un () at un.adb:5
17747 @item break @var{location} task @var{taskno}
17748 @itemx break @var{location} task @var{taskno} if @dots{}
17749 @cindex breakpoints and tasks, in Ada
17750 @cindex task breakpoints, in Ada
17751 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
17752 These commands are like the @code{break @dots{} thread @dots{}}
17753 command (@pxref{Thread Stops}). The
17754 @var{location} argument specifies source lines, as described
17755 in @ref{Specify Location}.
17757 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
17758 to specify that you only want @value{GDBN} to stop the program when a
17759 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
17760 numeric task identifiers assigned by @value{GDBN}, shown in the first
17761 column of the @samp{info tasks} display.
17763 If you do not specify @samp{task @var{taskno}} when you set a
17764 breakpoint, the breakpoint applies to @emph{all} tasks of your
17767 You can use the @code{task} qualifier on conditional breakpoints as
17768 well; in this case, place @samp{task @var{taskno}} before the
17769 breakpoint condition (before the @code{if}).
17777 (@value{GDBP}) info tasks
17778 ID TID P-ID Pri State Name
17779 1 140022020 0 15 Child Activation Wait main_task
17780 2 140045060 1 15 Accept/Select Wait t2
17781 3 140044840 1 15 Runnable t1
17782 * 4 140056040 1 15 Runnable t3
17783 (@value{GDBP}) b 15 task 2
17784 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
17785 (@value{GDBP}) cont
17790 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
17792 (@value{GDBP}) info tasks
17793 ID TID P-ID Pri State Name
17794 1 140022020 0 15 Child Activation Wait main_task
17795 * 2 140045060 1 15 Runnable t2
17796 3 140044840 1 15 Runnable t1
17797 4 140056040 1 15 Delay Sleep t3
17801 @node Ada Tasks and Core Files
17802 @subsubsection Tasking Support when Debugging Core Files
17803 @cindex Ada tasking and core file debugging
17805 When inspecting a core file, as opposed to debugging a live program,
17806 tasking support may be limited or even unavailable, depending on
17807 the platform being used.
17808 For instance, on x86-linux, the list of tasks is available, but task
17809 switching is not supported.
17811 On certain platforms, the debugger needs to perform some
17812 memory writes in order to provide Ada tasking support. When inspecting
17813 a core file, this means that the core file must be opened with read-write
17814 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
17815 Under these circumstances, you should make a backup copy of the core
17816 file before inspecting it with @value{GDBN}.
17818 @node Ravenscar Profile
17819 @subsubsection Tasking Support when using the Ravenscar Profile
17820 @cindex Ravenscar Profile
17822 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
17823 specifically designed for systems with safety-critical real-time
17827 @kindex set ravenscar task-switching on
17828 @cindex task switching with program using Ravenscar Profile
17829 @item set ravenscar task-switching on
17830 Allows task switching when debugging a program that uses the Ravenscar
17831 Profile. This is the default.
17833 @kindex set ravenscar task-switching off
17834 @item set ravenscar task-switching off
17835 Turn off task switching when debugging a program that uses the Ravenscar
17836 Profile. This is mostly intended to disable the code that adds support
17837 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
17838 the Ravenscar runtime is preventing @value{GDBN} from working properly.
17839 To be effective, this command should be run before the program is started.
17841 @kindex show ravenscar task-switching
17842 @item show ravenscar task-switching
17843 Show whether it is possible to switch from task to task in a program
17844 using the Ravenscar Profile.
17849 @subsubsection Ada Settings
17850 @cindex Ada settings
17853 @kindex set varsize-limit
17854 @item set varsize-limit @var{size}
17855 Prevent @value{GDBN} from attempting to evaluate objects whose size
17856 is above the given limit (@var{size}) when those sizes are computed
17857 from run-time quantities. This is typically the case when the object
17858 has a variable size, such as an array whose bounds are not known at
17859 compile time for example. Setting @var{size} to @code{unlimited}
17860 removes the size limitation. By default, the limit is about 65KB.
17862 The purpose of having such a limit is to prevent @value{GDBN} from
17863 trying to grab enormous chunks of virtual memory when asked to evaluate
17864 a quantity whose bounds have been corrupted or have not yet been fully
17865 initialized. The limit applies to the results of some subexpressions
17866 as well as to complete expressions. For example, an expression denoting
17867 a simple integer component, such as @code{x.y.z}, may fail if the size of
17868 @code{x.y} is variable and exceeds @code{size}. On the other hand,
17869 @value{GDBN} is sometimes clever; the expression @code{A(i)}, where
17870 @code{A} is an array variable with non-constant size, will generally
17871 succeed regardless of the bounds on @code{A}, as long as the component
17872 size is less than @var{size}.
17874 @kindex show varsize-limit
17875 @item show varsize-limit
17876 Show the limit on types whose size is determined by run-time quantities.
17880 @subsubsection Known Peculiarities of Ada Mode
17881 @cindex Ada, problems
17883 Besides the omissions listed previously (@pxref{Omissions from Ada}),
17884 we know of several problems with and limitations of Ada mode in
17886 some of which will be fixed with planned future releases of the debugger
17887 and the GNU Ada compiler.
17891 Static constants that the compiler chooses not to materialize as objects in
17892 storage are invisible to the debugger.
17895 Named parameter associations in function argument lists are ignored (the
17896 argument lists are treated as positional).
17899 Many useful library packages are currently invisible to the debugger.
17902 Fixed-point arithmetic, conversions, input, and output is carried out using
17903 floating-point arithmetic, and may give results that only approximate those on
17907 The GNAT compiler never generates the prefix @code{Standard} for any of
17908 the standard symbols defined by the Ada language. @value{GDBN} knows about
17909 this: it will strip the prefix from names when you use it, and will never
17910 look for a name you have so qualified among local symbols, nor match against
17911 symbols in other packages or subprograms. If you have
17912 defined entities anywhere in your program other than parameters and
17913 local variables whose simple names match names in @code{Standard},
17914 GNAT's lack of qualification here can cause confusion. When this happens,
17915 you can usually resolve the confusion
17916 by qualifying the problematic names with package
17917 @code{Standard} explicitly.
17920 Older versions of the compiler sometimes generate erroneous debugging
17921 information, resulting in the debugger incorrectly printing the value
17922 of affected entities. In some cases, the debugger is able to work
17923 around an issue automatically. In other cases, the debugger is able
17924 to work around the issue, but the work-around has to be specifically
17927 @kindex set ada trust-PAD-over-XVS
17928 @kindex show ada trust-PAD-over-XVS
17931 @item set ada trust-PAD-over-XVS on
17932 Configure GDB to strictly follow the GNAT encoding when computing the
17933 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
17934 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
17935 a complete description of the encoding used by the GNAT compiler).
17936 This is the default.
17938 @item set ada trust-PAD-over-XVS off
17939 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
17940 sometimes prints the wrong value for certain entities, changing @code{ada
17941 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
17942 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
17943 @code{off}, but this incurs a slight performance penalty, so it is
17944 recommended to leave this setting to @code{on} unless necessary.
17948 @cindex GNAT descriptive types
17949 @cindex GNAT encoding
17950 Internally, the debugger also relies on the compiler following a number
17951 of conventions known as the @samp{GNAT Encoding}, all documented in
17952 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
17953 how the debugging information should be generated for certain types.
17954 In particular, this convention makes use of @dfn{descriptive types},
17955 which are artificial types generated purely to help the debugger.
17957 These encodings were defined at a time when the debugging information
17958 format used was not powerful enough to describe some of the more complex
17959 types available in Ada. Since DWARF allows us to express nearly all
17960 Ada features, the long-term goal is to slowly replace these descriptive
17961 types by their pure DWARF equivalent. To facilitate that transition,
17962 a new maintenance option is available to force the debugger to ignore
17963 those descriptive types. It allows the user to quickly evaluate how
17964 well @value{GDBN} works without them.
17968 @kindex maint ada set ignore-descriptive-types
17969 @item maintenance ada set ignore-descriptive-types [on|off]
17970 Control whether the debugger should ignore descriptive types.
17971 The default is not to ignore descriptives types (@code{off}).
17973 @kindex maint ada show ignore-descriptive-types
17974 @item maintenance ada show ignore-descriptive-types
17975 Show if descriptive types are ignored by @value{GDBN}.
17979 @node Unsupported Languages
17980 @section Unsupported Languages
17982 @cindex unsupported languages
17983 @cindex minimal language
17984 In addition to the other fully-supported programming languages,
17985 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
17986 It does not represent a real programming language, but provides a set
17987 of capabilities close to what the C or assembly languages provide.
17988 This should allow most simple operations to be performed while debugging
17989 an application that uses a language currently not supported by @value{GDBN}.
17991 If the language is set to @code{auto}, @value{GDBN} will automatically
17992 select this language if the current frame corresponds to an unsupported
17996 @chapter Examining the Symbol Table
17998 The commands described in this chapter allow you to inquire about the
17999 symbols (names of variables, functions and types) defined in your
18000 program. This information is inherent in the text of your program and
18001 does not change as your program executes. @value{GDBN} finds it in your
18002 program's symbol table, in the file indicated when you started @value{GDBN}
18003 (@pxref{File Options, ,Choosing Files}), or by one of the
18004 file-management commands (@pxref{Files, ,Commands to Specify Files}).
18006 @cindex symbol names
18007 @cindex names of symbols
18008 @cindex quoting names
18009 @anchor{quoting names}
18010 Occasionally, you may need to refer to symbols that contain unusual
18011 characters, which @value{GDBN} ordinarily treats as word delimiters. The
18012 most frequent case is in referring to static variables in other
18013 source files (@pxref{Variables,,Program Variables}). File names
18014 are recorded in object files as debugging symbols, but @value{GDBN} would
18015 ordinarily parse a typical file name, like @file{foo.c}, as the three words
18016 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
18017 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
18024 looks up the value of @code{x} in the scope of the file @file{foo.c}.
18027 @cindex case-insensitive symbol names
18028 @cindex case sensitivity in symbol names
18029 @kindex set case-sensitive
18030 @item set case-sensitive on
18031 @itemx set case-sensitive off
18032 @itemx set case-sensitive auto
18033 Normally, when @value{GDBN} looks up symbols, it matches their names
18034 with case sensitivity determined by the current source language.
18035 Occasionally, you may wish to control that. The command @code{set
18036 case-sensitive} lets you do that by specifying @code{on} for
18037 case-sensitive matches or @code{off} for case-insensitive ones. If
18038 you specify @code{auto}, case sensitivity is reset to the default
18039 suitable for the source language. The default is case-sensitive
18040 matches for all languages except for Fortran, for which the default is
18041 case-insensitive matches.
18043 @kindex show case-sensitive
18044 @item show case-sensitive
18045 This command shows the current setting of case sensitivity for symbols
18048 @kindex set print type methods
18049 @item set print type methods
18050 @itemx set print type methods on
18051 @itemx set print type methods off
18052 Normally, when @value{GDBN} prints a class, it displays any methods
18053 declared in that class. You can control this behavior either by
18054 passing the appropriate flag to @code{ptype}, or using @command{set
18055 print type methods}. Specifying @code{on} will cause @value{GDBN} to
18056 display the methods; this is the default. Specifying @code{off} will
18057 cause @value{GDBN} to omit the methods.
18059 @kindex show print type methods
18060 @item show print type methods
18061 This command shows the current setting of method display when printing
18064 @kindex set print type nested-type-limit
18065 @item set print type nested-type-limit @var{limit}
18066 @itemx set print type nested-type-limit unlimited
18067 Set the limit of displayed nested types that the type printer will
18068 show. A @var{limit} of @code{unlimited} or @code{-1} will show all
18069 nested definitions. By default, the type printer will not show any nested
18070 types defined in classes.
18072 @kindex show print type nested-type-limit
18073 @item show print type nested-type-limit
18074 This command shows the current display limit of nested types when
18077 @kindex set print type typedefs
18078 @item set print type typedefs
18079 @itemx set print type typedefs on
18080 @itemx set print type typedefs off
18082 Normally, when @value{GDBN} prints a class, it displays any typedefs
18083 defined in that class. You can control this behavior either by
18084 passing the appropriate flag to @code{ptype}, or using @command{set
18085 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
18086 display the typedef definitions; this is the default. Specifying
18087 @code{off} will cause @value{GDBN} to omit the typedef definitions.
18088 Note that this controls whether the typedef definition itself is
18089 printed, not whether typedef names are substituted when printing other
18092 @kindex show print type typedefs
18093 @item show print type typedefs
18094 This command shows the current setting of typedef display when
18097 @kindex info address
18098 @cindex address of a symbol
18099 @item info address @var{symbol}
18100 Describe where the data for @var{symbol} is stored. For a register
18101 variable, this says which register it is kept in. For a non-register
18102 local variable, this prints the stack-frame offset at which the variable
18105 Note the contrast with @samp{print &@var{symbol}}, which does not work
18106 at all for a register variable, and for a stack local variable prints
18107 the exact address of the current instantiation of the variable.
18109 @kindex info symbol
18110 @cindex symbol from address
18111 @cindex closest symbol and offset for an address
18112 @item info symbol @var{addr}
18113 Print the name of a symbol which is stored at the address @var{addr}.
18114 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
18115 nearest symbol and an offset from it:
18118 (@value{GDBP}) info symbol 0x54320
18119 _initialize_vx + 396 in section .text
18123 This is the opposite of the @code{info address} command. You can use
18124 it to find out the name of a variable or a function given its address.
18126 For dynamically linked executables, the name of executable or shared
18127 library containing the symbol is also printed:
18130 (@value{GDBP}) info symbol 0x400225
18131 _start + 5 in section .text of /tmp/a.out
18132 (@value{GDBP}) info symbol 0x2aaaac2811cf
18133 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
18138 @item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
18139 Demangle @var{name}.
18140 If @var{language} is provided it is the name of the language to demangle
18141 @var{name} in. Otherwise @var{name} is demangled in the current language.
18143 The @samp{--} option specifies the end of options,
18144 and is useful when @var{name} begins with a dash.
18146 The parameter @code{demangle-style} specifies how to interpret the kind
18147 of mangling used. @xref{Print Settings}.
18150 @item whatis[/@var{flags}] [@var{arg}]
18151 Print the data type of @var{arg}, which can be either an expression
18152 or a name of a data type. With no argument, print the data type of
18153 @code{$}, the last value in the value history.
18155 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
18156 is not actually evaluated, and any side-effecting operations (such as
18157 assignments or function calls) inside it do not take place.
18159 If @var{arg} is a variable or an expression, @code{whatis} prints its
18160 literal type as it is used in the source code. If the type was
18161 defined using a @code{typedef}, @code{whatis} will @emph{not} print
18162 the data type underlying the @code{typedef}. If the type of the
18163 variable or the expression is a compound data type, such as
18164 @code{struct} or @code{class}, @code{whatis} never prints their
18165 fields or methods. It just prints the @code{struct}/@code{class}
18166 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
18167 such a compound data type, use @code{ptype}.
18169 If @var{arg} is a type name that was defined using @code{typedef},
18170 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
18171 Unrolling means that @code{whatis} will show the underlying type used
18172 in the @code{typedef} declaration of @var{arg}. However, if that
18173 underlying type is also a @code{typedef}, @code{whatis} will not
18176 For C code, the type names may also have the form @samp{class
18177 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
18178 @var{union-tag}} or @samp{enum @var{enum-tag}}.
18180 @var{flags} can be used to modify how the type is displayed.
18181 Available flags are:
18185 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
18186 parameters and typedefs defined in a class when printing the class'
18187 members. The @code{/r} flag disables this.
18190 Do not print methods defined in the class.
18193 Print methods defined in the class. This is the default, but the flag
18194 exists in case you change the default with @command{set print type methods}.
18197 Do not print typedefs defined in the class. Note that this controls
18198 whether the typedef definition itself is printed, not whether typedef
18199 names are substituted when printing other types.
18202 Print typedefs defined in the class. This is the default, but the flag
18203 exists in case you change the default with @command{set print type typedefs}.
18206 Print the offsets and sizes of fields in a struct, similar to what the
18207 @command{pahole} tool does. This option implies the @code{/tm} flags.
18209 For example, given the following declarations:
18245 Issuing a @kbd{ptype /o struct tuv} command would print:
18248 (@value{GDBP}) ptype /o struct tuv
18249 /* offset | size */ type = struct tuv @{
18250 /* 0 | 4 */ int a1;
18251 /* XXX 4-byte hole */
18252 /* 8 | 8 */ char *a2;
18253 /* 16 | 4 */ int a3;
18255 /* total size (bytes): 24 */
18259 Notice the format of the first column of comments. There, you can
18260 find two parts separated by the @samp{|} character: the @emph{offset},
18261 which indicates where the field is located inside the struct, in
18262 bytes, and the @emph{size} of the field. Another interesting line is
18263 the marker of a @emph{hole} in the struct, indicating that it may be
18264 possible to pack the struct and make it use less space by reorganizing
18267 It is also possible to print offsets inside an union:
18270 (@value{GDBP}) ptype /o union qwe
18271 /* offset | size */ type = union qwe @{
18272 /* 24 */ struct tuv @{
18273 /* 0 | 4 */ int a1;
18274 /* XXX 4-byte hole */
18275 /* 8 | 8 */ char *a2;
18276 /* 16 | 4 */ int a3;
18278 /* total size (bytes): 24 */
18280 /* 40 */ struct xyz @{
18281 /* 0 | 4 */ int f1;
18282 /* 4 | 1 */ char f2;
18283 /* XXX 3-byte hole */
18284 /* 8 | 8 */ void *f3;
18285 /* 16 | 24 */ struct tuv @{
18286 /* 16 | 4 */ int a1;
18287 /* XXX 4-byte hole */
18288 /* 24 | 8 */ char *a2;
18289 /* 32 | 4 */ int a3;
18291 /* total size (bytes): 24 */
18294 /* total size (bytes): 40 */
18297 /* total size (bytes): 40 */
18301 In this case, since @code{struct tuv} and @code{struct xyz} occupy the
18302 same space (because we are dealing with an union), the offset is not
18303 printed for them. However, you can still examine the offset of each
18304 of these structures' fields.
18306 Another useful scenario is printing the offsets of a struct containing
18310 (@value{GDBP}) ptype /o struct tyu
18311 /* offset | size */ type = struct tyu @{
18312 /* 0:31 | 4 */ int a1 : 1;
18313 /* 0:28 | 4 */ int a2 : 3;
18314 /* 0: 5 | 4 */ int a3 : 23;
18315 /* 3: 3 | 1 */ signed char a4 : 2;
18316 /* XXX 3-bit hole */
18317 /* XXX 4-byte hole */
18318 /* 8 | 8 */ int64_t a5;
18319 /* 16: 0 | 4 */ int a6 : 5;
18320 /* 16: 5 | 8 */ int64_t a7 : 3;
18321 "/* XXX 7-byte padding */
18323 /* total size (bytes): 24 */
18327 Note how the offset information is now extended to also include the
18328 first bit of the bitfield.
18332 @item ptype[/@var{flags}] [@var{arg}]
18333 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
18334 detailed description of the type, instead of just the name of the type.
18335 @xref{Expressions, ,Expressions}.
18337 Contrary to @code{whatis}, @code{ptype} always unrolls any
18338 @code{typedef}s in its argument declaration, whether the argument is
18339 a variable, expression, or a data type. This means that @code{ptype}
18340 of a variable or an expression will not print literally its type as
18341 present in the source code---use @code{whatis} for that. @code{typedef}s at
18342 the pointer or reference targets are also unrolled. Only @code{typedef}s of
18343 fields, methods and inner @code{class typedef}s of @code{struct}s,
18344 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
18346 For example, for this variable declaration:
18349 typedef double real_t;
18350 struct complex @{ real_t real; double imag; @};
18351 typedef struct complex complex_t;
18353 real_t *real_pointer_var;
18357 the two commands give this output:
18361 (@value{GDBP}) whatis var
18363 (@value{GDBP}) ptype var
18364 type = struct complex @{
18368 (@value{GDBP}) whatis complex_t
18369 type = struct complex
18370 (@value{GDBP}) whatis struct complex
18371 type = struct complex
18372 (@value{GDBP}) ptype struct complex
18373 type = struct complex @{
18377 (@value{GDBP}) whatis real_pointer_var
18379 (@value{GDBP}) ptype real_pointer_var
18385 As with @code{whatis}, using @code{ptype} without an argument refers to
18386 the type of @code{$}, the last value in the value history.
18388 @cindex incomplete type
18389 Sometimes, programs use opaque data types or incomplete specifications
18390 of complex data structure. If the debug information included in the
18391 program does not allow @value{GDBN} to display a full declaration of
18392 the data type, it will say @samp{<incomplete type>}. For example,
18393 given these declarations:
18397 struct foo *fooptr;
18401 but no definition for @code{struct foo} itself, @value{GDBN} will say:
18404 (@value{GDBP}) ptype foo
18405 $1 = <incomplete type>
18409 ``Incomplete type'' is C terminology for data types that are not
18410 completely specified.
18412 @cindex unknown type
18413 Othertimes, information about a variable's type is completely absent
18414 from the debug information included in the program. This most often
18415 happens when the program or library where the variable is defined
18416 includes no debug information at all. @value{GDBN} knows the variable
18417 exists from inspecting the linker/loader symbol table (e.g., the ELF
18418 dynamic symbol table), but such symbols do not contain type
18419 information. Inspecting the type of a (global) variable for which
18420 @value{GDBN} has no type information shows:
18423 (@value{GDBP}) ptype var
18424 type = <data variable, no debug info>
18427 @xref{Variables, no debug info variables}, for how to print the values
18431 @item info types @var{regexp}
18433 Print a brief description of all types whose names match the regular
18434 expression @var{regexp} (or all types in your program, if you supply
18435 no argument). Each complete typename is matched as though it were a
18436 complete line; thus, @samp{i type value} gives information on all
18437 types in your program whose names include the string @code{value}, but
18438 @samp{i type ^value$} gives information only on types whose complete
18439 name is @code{value}.
18441 In programs using different languages, @value{GDBN} chooses the syntax
18442 to print the type description according to the
18443 @samp{set language} value: using @samp{set language auto}
18444 (see @ref{Automatically, ,Set Language Automatically}) means to use the
18445 language of the type, other values mean to use
18446 the manually specified language (see @ref{Manually, ,Set Language Manually}).
18448 This command differs from @code{ptype} in two ways: first, like
18449 @code{whatis}, it does not print a detailed description; second, it
18450 lists all source files and line numbers where a type is defined.
18452 @kindex info type-printers
18453 @item info type-printers
18454 Versions of @value{GDBN} that ship with Python scripting enabled may
18455 have ``type printers'' available. When using @command{ptype} or
18456 @command{whatis}, these printers are consulted when the name of a type
18457 is needed. @xref{Type Printing API}, for more information on writing
18460 @code{info type-printers} displays all the available type printers.
18462 @kindex enable type-printer
18463 @kindex disable type-printer
18464 @item enable type-printer @var{name}@dots{}
18465 @item disable type-printer @var{name}@dots{}
18466 These commands can be used to enable or disable type printers.
18469 @cindex local variables
18470 @item info scope @var{location}
18471 List all the variables local to a particular scope. This command
18472 accepts a @var{location} argument---a function name, a source line, or
18473 an address preceded by a @samp{*}, and prints all the variables local
18474 to the scope defined by that location. (@xref{Specify Location}, for
18475 details about supported forms of @var{location}.) For example:
18478 (@value{GDBP}) @b{info scope command_line_handler}
18479 Scope for command_line_handler:
18480 Symbol rl is an argument at stack/frame offset 8, length 4.
18481 Symbol linebuffer is in static storage at address 0x150a18, length 4.
18482 Symbol linelength is in static storage at address 0x150a1c, length 4.
18483 Symbol p is a local variable in register $esi, length 4.
18484 Symbol p1 is a local variable in register $ebx, length 4.
18485 Symbol nline is a local variable in register $edx, length 4.
18486 Symbol repeat is a local variable at frame offset -8, length 4.
18490 This command is especially useful for determining what data to collect
18491 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
18494 @kindex info source
18496 Show information about the current source file---that is, the source file for
18497 the function containing the current point of execution:
18500 the name of the source file, and the directory containing it,
18502 the directory it was compiled in,
18504 its length, in lines,
18506 which programming language it is written in,
18508 if the debug information provides it, the program that compiled the file
18509 (which may include, e.g., the compiler version and command line arguments),
18511 whether the executable includes debugging information for that file, and
18512 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
18514 whether the debugging information includes information about
18515 preprocessor macros.
18519 @kindex info sources
18521 Print the names of all source files in your program for which there is
18522 debugging information, organized into two lists: files whose symbols
18523 have already been read, and files whose symbols will be read when needed.
18525 @kindex info functions
18526 @item info functions [-q]
18527 Print the names and data types of all defined functions.
18528 Similarly to @samp{info types}, this command groups its output by source
18529 files and annotates each function definition with its source line
18532 In programs using different languages, @value{GDBN} chooses the syntax
18533 to print the function name and type according to the
18534 @samp{set language} value: using @samp{set language auto}
18535 (see @ref{Automatically, ,Set Language Automatically}) means to use the
18536 language of the function, other values mean to use
18537 the manually specified language (see @ref{Manually, ,Set Language Manually}).
18539 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
18540 printing header information and messages explaining why no functions
18543 @item info functions [-q] [-t @var{type_regexp}] [@var{regexp}]
18544 Like @samp{info functions}, but only print the names and data types
18545 of the functions selected with the provided regexp(s).
18547 If @var{regexp} is provided, print only the functions whose names
18548 match the regular expression @var{regexp}.
18549 Thus, @samp{info fun step} finds all functions whose
18550 names include @code{step}; @samp{info fun ^step} finds those whose names
18551 start with @code{step}. If a function name contains characters that
18552 conflict with the regular expression language (e.g.@:
18553 @samp{operator*()}), they may be quoted with a backslash.
18555 If @var{type_regexp} is provided, print only the functions whose
18556 types, as printed by the @code{whatis} command, match
18557 the regular expression @var{type_regexp}.
18558 If @var{type_regexp} contains space(s), it should be enclosed in
18559 quote characters. If needed, use backslash to escape the meaning
18560 of special characters or quotes.
18561 Thus, @samp{info fun -t '^int ('} finds the functions that return
18562 an integer; @samp{info fun -t '(.*int.*'} finds the functions that
18563 have an argument type containing int; @samp{info fun -t '^int (' ^step}
18564 finds the functions whose names start with @code{step} and that return
18567 If both @var{regexp} and @var{type_regexp} are provided, a function
18568 is printed only if its name matches @var{regexp} and its type matches
18572 @kindex info variables
18573 @item info variables [-q]
18574 Print the names and data types of all variables that are defined
18575 outside of functions (i.e.@: excluding local variables).
18576 The printed variables are grouped by source files and annotated with
18577 their respective source line numbers.
18579 In programs using different languages, @value{GDBN} chooses the syntax
18580 to print the variable name and type according to the
18581 @samp{set language} value: using @samp{set language auto}
18582 (see @ref{Automatically, ,Set Language Automatically}) means to use the
18583 language of the variable, other values mean to use
18584 the manually specified language (see @ref{Manually, ,Set Language Manually}).
18586 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
18587 printing header information and messages explaining why no variables
18590 @item info variables [-q] [-t @var{type_regexp}] [@var{regexp}]
18591 Like @kbd{info variables}, but only print the variables selected
18592 with the provided regexp(s).
18594 If @var{regexp} is provided, print only the variables whose names
18595 match the regular expression @var{regexp}.
18597 If @var{type_regexp} is provided, print only the variables whose
18598 types, as printed by the @code{whatis} command, match
18599 the regular expression @var{type_regexp}.
18600 If @var{type_regexp} contains space(s), it should be enclosed in
18601 quote characters. If needed, use backslash to escape the meaning
18602 of special characters or quotes.
18604 If both @var{regexp} and @var{type_regexp} are provided, an argument
18605 is printed only if its name matches @var{regexp} and its type matches
18608 @kindex info classes
18609 @cindex Objective-C, classes and selectors
18611 @itemx info classes @var{regexp}
18612 Display all Objective-C classes in your program, or
18613 (with the @var{regexp} argument) all those matching a particular regular
18616 @kindex info selectors
18617 @item info selectors
18618 @itemx info selectors @var{regexp}
18619 Display all Objective-C selectors in your program, or
18620 (with the @var{regexp} argument) all those matching a particular regular
18624 This was never implemented.
18625 @kindex info methods
18627 @itemx info methods @var{regexp}
18628 The @code{info methods} command permits the user to examine all defined
18629 methods within C@t{++} program, or (with the @var{regexp} argument) a
18630 specific set of methods found in the various C@t{++} classes. Many
18631 C@t{++} classes provide a large number of methods. Thus, the output
18632 from the @code{ptype} command can be overwhelming and hard to use. The
18633 @code{info-methods} command filters the methods, printing only those
18634 which match the regular-expression @var{regexp}.
18637 @cindex opaque data types
18638 @kindex set opaque-type-resolution
18639 @item set opaque-type-resolution on
18640 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
18641 declared as a pointer to a @code{struct}, @code{class}, or
18642 @code{union}---for example, @code{struct MyType *}---that is used in one
18643 source file although the full declaration of @code{struct MyType} is in
18644 another source file. The default is on.
18646 A change in the setting of this subcommand will not take effect until
18647 the next time symbols for a file are loaded.
18649 @item set opaque-type-resolution off
18650 Tell @value{GDBN} not to resolve opaque types. In this case, the type
18651 is printed as follows:
18653 @{<no data fields>@}
18656 @kindex show opaque-type-resolution
18657 @item show opaque-type-resolution
18658 Show whether opaque types are resolved or not.
18660 @kindex set print symbol-loading
18661 @cindex print messages when symbols are loaded
18662 @item set print symbol-loading
18663 @itemx set print symbol-loading full
18664 @itemx set print symbol-loading brief
18665 @itemx set print symbol-loading off
18666 The @code{set print symbol-loading} command allows you to control the
18667 printing of messages when @value{GDBN} loads symbol information.
18668 By default a message is printed for the executable and one for each
18669 shared library, and normally this is what you want. However, when
18670 debugging apps with large numbers of shared libraries these messages
18672 When set to @code{brief} a message is printed for each executable,
18673 and when @value{GDBN} loads a collection of shared libraries at once
18674 it will only print one message regardless of the number of shared
18675 libraries. When set to @code{off} no messages are printed.
18677 @kindex show print symbol-loading
18678 @item show print symbol-loading
18679 Show whether messages will be printed when a @value{GDBN} command
18680 entered from the keyboard causes symbol information to be loaded.
18682 @kindex maint print symbols
18683 @cindex symbol dump
18684 @kindex maint print psymbols
18685 @cindex partial symbol dump
18686 @kindex maint print msymbols
18687 @cindex minimal symbol dump
18688 @item maint print symbols @r{[}-pc @var{address}@r{]} @r{[}@var{filename}@r{]}
18689 @itemx maint print symbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
18690 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-pc @var{address}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
18691 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
18692 @itemx maint print msymbols @r{[}-objfile @var{objfile}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
18693 Write a dump of debugging symbol data into the file @var{filename} or
18694 the terminal if @var{filename} is unspecified.
18695 If @code{-objfile @var{objfile}} is specified, only dump symbols for
18697 If @code{-pc @var{address}} is specified, only dump symbols for the file
18698 with code at that address. Note that @var{address} may be a symbol like
18700 If @code{-source @var{source}} is specified, only dump symbols for that
18703 These commands are used to debug the @value{GDBN} symbol-reading code.
18704 These commands do not modify internal @value{GDBN} state, therefore
18705 @samp{maint print symbols} will only print symbols for already expanded symbol
18707 You can use the command @code{info sources} to find out which files these are.
18708 If you use @samp{maint print psymbols} instead, the dump shows information
18709 about symbols that @value{GDBN} only knows partially---that is, symbols
18710 defined in files that @value{GDBN} has skimmed, but not yet read completely.
18711 Finally, @samp{maint print msymbols} just dumps ``minimal symbols'', e.g.,
18714 @xref{Files, ,Commands to Specify Files}, for a discussion of how
18715 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
18717 @kindex maint info symtabs
18718 @kindex maint info psymtabs
18719 @cindex listing @value{GDBN}'s internal symbol tables
18720 @cindex symbol tables, listing @value{GDBN}'s internal
18721 @cindex full symbol tables, listing @value{GDBN}'s internal
18722 @cindex partial symbol tables, listing @value{GDBN}'s internal
18723 @item maint info symtabs @r{[} @var{regexp} @r{]}
18724 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
18726 List the @code{struct symtab} or @code{struct partial_symtab}
18727 structures whose names match @var{regexp}. If @var{regexp} is not
18728 given, list them all. The output includes expressions which you can
18729 copy into a @value{GDBN} debugging this one to examine a particular
18730 structure in more detail. For example:
18733 (@value{GDBP}) maint info psymtabs dwarf2read
18734 @{ objfile /home/gnu/build/gdb/gdb
18735 ((struct objfile *) 0x82e69d0)
18736 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
18737 ((struct partial_symtab *) 0x8474b10)
18740 text addresses 0x814d3c8 -- 0x8158074
18741 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
18742 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
18743 dependencies (none)
18746 (@value{GDBP}) maint info symtabs
18750 We see that there is one partial symbol table whose filename contains
18751 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
18752 and we see that @value{GDBN} has not read in any symtabs yet at all.
18753 If we set a breakpoint on a function, that will cause @value{GDBN} to
18754 read the symtab for the compilation unit containing that function:
18757 (@value{GDBP}) break dwarf2_psymtab_to_symtab
18758 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
18760 (@value{GDBP}) maint info symtabs
18761 @{ objfile /home/gnu/build/gdb/gdb
18762 ((struct objfile *) 0x82e69d0)
18763 @{ symtab /home/gnu/src/gdb/dwarf2read.c
18764 ((struct symtab *) 0x86c1f38)
18767 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
18768 linetable ((struct linetable *) 0x8370fa0)
18769 debugformat DWARF 2
18775 @kindex maint info line-table
18776 @cindex listing @value{GDBN}'s internal line tables
18777 @cindex line tables, listing @value{GDBN}'s internal
18778 @item maint info line-table @r{[} @var{regexp} @r{]}
18780 List the @code{struct linetable} from all @code{struct symtab}
18781 instances whose name matches @var{regexp}. If @var{regexp} is not
18782 given, list the @code{struct linetable} from all @code{struct symtab}.
18784 @kindex maint set symbol-cache-size
18785 @cindex symbol cache size
18786 @item maint set symbol-cache-size @var{size}
18787 Set the size of the symbol cache to @var{size}.
18788 The default size is intended to be good enough for debugging
18789 most applications. This option exists to allow for experimenting
18790 with different sizes.
18792 @kindex maint show symbol-cache-size
18793 @item maint show symbol-cache-size
18794 Show the size of the symbol cache.
18796 @kindex maint print symbol-cache
18797 @cindex symbol cache, printing its contents
18798 @item maint print symbol-cache
18799 Print the contents of the symbol cache.
18800 This is useful when debugging symbol cache issues.
18802 @kindex maint print symbol-cache-statistics
18803 @cindex symbol cache, printing usage statistics
18804 @item maint print symbol-cache-statistics
18805 Print symbol cache usage statistics.
18806 This helps determine how well the cache is being utilized.
18808 @kindex maint flush-symbol-cache
18809 @cindex symbol cache, flushing
18810 @item maint flush-symbol-cache
18811 Flush the contents of the symbol cache, all entries are removed.
18812 This command is useful when debugging the symbol cache.
18813 It is also useful when collecting performance data.
18818 @chapter Altering Execution
18820 Once you think you have found an error in your program, you might want to
18821 find out for certain whether correcting the apparent error would lead to
18822 correct results in the rest of the run. You can find the answer by
18823 experiment, using the @value{GDBN} features for altering execution of the
18826 For example, you can store new values into variables or memory
18827 locations, give your program a signal, restart it at a different
18828 address, or even return prematurely from a function.
18831 * Assignment:: Assignment to variables
18832 * Jumping:: Continuing at a different address
18833 * Signaling:: Giving your program a signal
18834 * Returning:: Returning from a function
18835 * Calling:: Calling your program's functions
18836 * Patching:: Patching your program
18837 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
18841 @section Assignment to Variables
18844 @cindex setting variables
18845 To alter the value of a variable, evaluate an assignment expression.
18846 @xref{Expressions, ,Expressions}. For example,
18853 stores the value 4 into the variable @code{x}, and then prints the
18854 value of the assignment expression (which is 4).
18855 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
18856 information on operators in supported languages.
18858 @kindex set variable
18859 @cindex variables, setting
18860 If you are not interested in seeing the value of the assignment, use the
18861 @code{set} command instead of the @code{print} command. @code{set} is
18862 really the same as @code{print} except that the expression's value is
18863 not printed and is not put in the value history (@pxref{Value History,
18864 ,Value History}). The expression is evaluated only for its effects.
18866 If the beginning of the argument string of the @code{set} command
18867 appears identical to a @code{set} subcommand, use the @code{set
18868 variable} command instead of just @code{set}. This command is identical
18869 to @code{set} except for its lack of subcommands. For example, if your
18870 program has a variable @code{width}, you get an error if you try to set
18871 a new value with just @samp{set width=13}, because @value{GDBN} has the
18872 command @code{set width}:
18875 (@value{GDBP}) whatis width
18877 (@value{GDBP}) p width
18879 (@value{GDBP}) set width=47
18880 Invalid syntax in expression.
18884 The invalid expression, of course, is @samp{=47}. In
18885 order to actually set the program's variable @code{width}, use
18888 (@value{GDBP}) set var width=47
18891 Because the @code{set} command has many subcommands that can conflict
18892 with the names of program variables, it is a good idea to use the
18893 @code{set variable} command instead of just @code{set}. For example, if
18894 your program has a variable @code{g}, you run into problems if you try
18895 to set a new value with just @samp{set g=4}, because @value{GDBN} has
18896 the command @code{set gnutarget}, abbreviated @code{set g}:
18900 (@value{GDBP}) whatis g
18904 (@value{GDBP}) set g=4
18908 The program being debugged has been started already.
18909 Start it from the beginning? (y or n) y
18910 Starting program: /home/smith/cc_progs/a.out
18911 "/home/smith/cc_progs/a.out": can't open to read symbols:
18912 Invalid bfd target.
18913 (@value{GDBP}) show g
18914 The current BFD target is "=4".
18919 The program variable @code{g} did not change, and you silently set the
18920 @code{gnutarget} to an invalid value. In order to set the variable
18924 (@value{GDBP}) set var g=4
18927 @value{GDBN} allows more implicit conversions in assignments than C; you can
18928 freely store an integer value into a pointer variable or vice versa,
18929 and you can convert any structure to any other structure that is the
18930 same length or shorter.
18931 @comment FIXME: how do structs align/pad in these conversions?
18932 @comment /doc@cygnus.com 18dec1990
18934 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
18935 construct to generate a value of specified type at a specified address
18936 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
18937 to memory location @code{0x83040} as an integer (which implies a certain size
18938 and representation in memory), and
18941 set @{int@}0x83040 = 4
18945 stores the value 4 into that memory location.
18948 @section Continuing at a Different Address
18950 Ordinarily, when you continue your program, you do so at the place where
18951 it stopped, with the @code{continue} command. You can instead continue at
18952 an address of your own choosing, with the following commands:
18956 @kindex j @r{(@code{jump})}
18957 @item jump @var{location}
18958 @itemx j @var{location}
18959 Resume execution at @var{location}. Execution stops again immediately
18960 if there is a breakpoint there. @xref{Specify Location}, for a description
18961 of the different forms of @var{location}. It is common
18962 practice to use the @code{tbreak} command in conjunction with
18963 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
18965 The @code{jump} command does not change the current stack frame, or
18966 the stack pointer, or the contents of any memory location or any
18967 register other than the program counter. If @var{location} is in
18968 a different function from the one currently executing, the results may
18969 be bizarre if the two functions expect different patterns of arguments or
18970 of local variables. For this reason, the @code{jump} command requests
18971 confirmation if the specified line is not in the function currently
18972 executing. However, even bizarre results are predictable if you are
18973 well acquainted with the machine-language code of your program.
18976 On many systems, you can get much the same effect as the @code{jump}
18977 command by storing a new value into the register @code{$pc}. The
18978 difference is that this does not start your program running; it only
18979 changes the address of where it @emph{will} run when you continue. For
18987 makes the next @code{continue} command or stepping command execute at
18988 address @code{0x485}, rather than at the address where your program stopped.
18989 @xref{Continuing and Stepping, ,Continuing and Stepping}.
18991 The most common occasion to use the @code{jump} command is to back
18992 up---perhaps with more breakpoints set---over a portion of a program
18993 that has already executed, in order to examine its execution in more
18998 @section Giving your Program a Signal
18999 @cindex deliver a signal to a program
19003 @item signal @var{signal}
19004 Resume execution where your program is stopped, but immediately give it the
19005 signal @var{signal}. The @var{signal} can be the name or the number of a
19006 signal. For example, on many systems @code{signal 2} and @code{signal
19007 SIGINT} are both ways of sending an interrupt signal.
19009 Alternatively, if @var{signal} is zero, continue execution without
19010 giving a signal. This is useful when your program stopped on account of
19011 a signal and would ordinarily see the signal when resumed with the
19012 @code{continue} command; @samp{signal 0} causes it to resume without a
19015 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
19016 delivered to the currently selected thread, not the thread that last
19017 reported a stop. This includes the situation where a thread was
19018 stopped due to a signal. So if you want to continue execution
19019 suppressing the signal that stopped a thread, you should select that
19020 same thread before issuing the @samp{signal 0} command. If you issue
19021 the @samp{signal 0} command with another thread as the selected one,
19022 @value{GDBN} detects that and asks for confirmation.
19024 Invoking the @code{signal} command is not the same as invoking the
19025 @code{kill} utility from the shell. Sending a signal with @code{kill}
19026 causes @value{GDBN} to decide what to do with the signal depending on
19027 the signal handling tables (@pxref{Signals}). The @code{signal} command
19028 passes the signal directly to your program.
19030 @code{signal} does not repeat when you press @key{RET} a second time
19031 after executing the command.
19033 @kindex queue-signal
19034 @item queue-signal @var{signal}
19035 Queue @var{signal} to be delivered immediately to the current thread
19036 when execution of the thread resumes. The @var{signal} can be the name or
19037 the number of a signal. For example, on many systems @code{signal 2} and
19038 @code{signal SIGINT} are both ways of sending an interrupt signal.
19039 The handling of the signal must be set to pass the signal to the program,
19040 otherwise @value{GDBN} will report an error.
19041 You can control the handling of signals from @value{GDBN} with the
19042 @code{handle} command (@pxref{Signals}).
19044 Alternatively, if @var{signal} is zero, any currently queued signal
19045 for the current thread is discarded and when execution resumes no signal
19046 will be delivered. This is useful when your program stopped on account
19047 of a signal and would ordinarily see the signal when resumed with the
19048 @code{continue} command.
19050 This command differs from the @code{signal} command in that the signal
19051 is just queued, execution is not resumed. And @code{queue-signal} cannot
19052 be used to pass a signal whose handling state has been set to @code{nopass}
19057 @xref{stepping into signal handlers}, for information on how stepping
19058 commands behave when the thread has a signal queued.
19061 @section Returning from a Function
19064 @cindex returning from a function
19067 @itemx return @var{expression}
19068 You can cancel execution of a function call with the @code{return}
19069 command. If you give an
19070 @var{expression} argument, its value is used as the function's return
19074 When you use @code{return}, @value{GDBN} discards the selected stack frame
19075 (and all frames within it). You can think of this as making the
19076 discarded frame return prematurely. If you wish to specify a value to
19077 be returned, give that value as the argument to @code{return}.
19079 This pops the selected stack frame (@pxref{Selection, ,Selecting a
19080 Frame}), and any other frames inside of it, leaving its caller as the
19081 innermost remaining frame. That frame becomes selected. The
19082 specified value is stored in the registers used for returning values
19085 The @code{return} command does not resume execution; it leaves the
19086 program stopped in the state that would exist if the function had just
19087 returned. In contrast, the @code{finish} command (@pxref{Continuing
19088 and Stepping, ,Continuing and Stepping}) resumes execution until the
19089 selected stack frame returns naturally.
19091 @value{GDBN} needs to know how the @var{expression} argument should be set for
19092 the inferior. The concrete registers assignment depends on the OS ABI and the
19093 type being returned by the selected stack frame. For example it is common for
19094 OS ABI to return floating point values in FPU registers while integer values in
19095 CPU registers. Still some ABIs return even floating point values in CPU
19096 registers. Larger integer widths (such as @code{long long int}) also have
19097 specific placement rules. @value{GDBN} already knows the OS ABI from its
19098 current target so it needs to find out also the type being returned to make the
19099 assignment into the right register(s).
19101 Normally, the selected stack frame has debug info. @value{GDBN} will always
19102 use the debug info instead of the implicit type of @var{expression} when the
19103 debug info is available. For example, if you type @kbd{return -1}, and the
19104 function in the current stack frame is declared to return a @code{long long
19105 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
19106 into a @code{long long int}:
19109 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
19111 (@value{GDBP}) return -1
19112 Make func return now? (y or n) y
19113 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
19114 43 printf ("result=%lld\n", func ());
19118 However, if the selected stack frame does not have a debug info, e.g., if the
19119 function was compiled without debug info, @value{GDBN} has to find out the type
19120 to return from user. Specifying a different type by mistake may set the value
19121 in different inferior registers than the caller code expects. For example,
19122 typing @kbd{return -1} with its implicit type @code{int} would set only a part
19123 of a @code{long long int} result for a debug info less function (on 32-bit
19124 architectures). Therefore the user is required to specify the return type by
19125 an appropriate cast explicitly:
19128 Breakpoint 2, 0x0040050b in func ()
19129 (@value{GDBP}) return -1
19130 Return value type not available for selected stack frame.
19131 Please use an explicit cast of the value to return.
19132 (@value{GDBP}) return (long long int) -1
19133 Make selected stack frame return now? (y or n) y
19134 #0 0x00400526 in main ()
19139 @section Calling Program Functions
19142 @cindex calling functions
19143 @cindex inferior functions, calling
19144 @item print @var{expr}
19145 Evaluate the expression @var{expr} and display the resulting value.
19146 The expression may include calls to functions in the program being
19150 @item call @var{expr}
19151 Evaluate the expression @var{expr} without displaying @code{void}
19154 You can use this variant of the @code{print} command if you want to
19155 execute a function from your program that does not return anything
19156 (a.k.a.@: @dfn{a void function}), but without cluttering the output
19157 with @code{void} returned values that @value{GDBN} will otherwise
19158 print. If the result is not void, it is printed and saved in the
19162 It is possible for the function you call via the @code{print} or
19163 @code{call} command to generate a signal (e.g., if there's a bug in
19164 the function, or if you passed it incorrect arguments). What happens
19165 in that case is controlled by the @code{set unwindonsignal} command.
19167 Similarly, with a C@t{++} program it is possible for the function you
19168 call via the @code{print} or @code{call} command to generate an
19169 exception that is not handled due to the constraints of the dummy
19170 frame. In this case, any exception that is raised in the frame, but has
19171 an out-of-frame exception handler will not be found. GDB builds a
19172 dummy-frame for the inferior function call, and the unwinder cannot
19173 seek for exception handlers outside of this dummy-frame. What happens
19174 in that case is controlled by the
19175 @code{set unwind-on-terminating-exception} command.
19178 @item set unwindonsignal
19179 @kindex set unwindonsignal
19180 @cindex unwind stack in called functions
19181 @cindex call dummy stack unwinding
19182 Set unwinding of the stack if a signal is received while in a function
19183 that @value{GDBN} called in the program being debugged. If set to on,
19184 @value{GDBN} unwinds the stack it created for the call and restores
19185 the context to what it was before the call. If set to off (the
19186 default), @value{GDBN} stops in the frame where the signal was
19189 @item show unwindonsignal
19190 @kindex show unwindonsignal
19191 Show the current setting of stack unwinding in the functions called by
19194 @item set unwind-on-terminating-exception
19195 @kindex set unwind-on-terminating-exception
19196 @cindex unwind stack in called functions with unhandled exceptions
19197 @cindex call dummy stack unwinding on unhandled exception.
19198 Set unwinding of the stack if a C@t{++} exception is raised, but left
19199 unhandled while in a function that @value{GDBN} called in the program being
19200 debugged. If set to on (the default), @value{GDBN} unwinds the stack
19201 it created for the call and restores the context to what it was before
19202 the call. If set to off, @value{GDBN} the exception is delivered to
19203 the default C@t{++} exception handler and the inferior terminated.
19205 @item show unwind-on-terminating-exception
19206 @kindex show unwind-on-terminating-exception
19207 Show the current setting of stack unwinding in the functions called by
19210 @item set may-call-functions
19211 @kindex set may-call-functions
19212 @cindex disabling calling functions in the program
19213 @cindex calling functions in the program, disabling
19214 Set permission to call functions in the program.
19215 This controls whether @value{GDBN} will attempt to call functions in
19216 the program, such as with expressions in the @code{print} command. It
19217 defaults to @code{on}.
19219 To call a function in the program, @value{GDBN} has to temporarily
19220 modify the state of the inferior. This has potentially undesired side
19221 effects. Also, having @value{GDBN} call nested functions is likely to
19222 be erroneous and may even crash the program being debugged. You can
19223 avoid such hazards by forbidding @value{GDBN} from calling functions
19224 in the program being debugged. If calling functions in the program
19225 is forbidden, GDB will throw an error when a command (such as printing
19226 an expression) starts a function call in the program.
19228 @item show may-call-functions
19229 @kindex show may-call-functions
19230 Show permission to call functions in the program.
19234 @subsection Calling functions with no debug info
19236 @cindex no debug info functions
19237 Sometimes, a function you wish to call is missing debug information.
19238 In such case, @value{GDBN} does not know the type of the function,
19239 including the types of the function's parameters. To avoid calling
19240 the inferior function incorrectly, which could result in the called
19241 function functioning erroneously and even crash, @value{GDBN} refuses
19242 to call the function unless you tell it the type of the function.
19244 For prototyped (i.e.@: ANSI/ISO style) functions, there are two ways
19245 to do that. The simplest is to cast the call to the function's
19246 declared return type. For example:
19249 (@value{GDBP}) p getenv ("PATH")
19250 'getenv' has unknown return type; cast the call to its declared return type
19251 (@value{GDBP}) p (char *) getenv ("PATH")
19252 $1 = 0x7fffffffe7ba "/usr/local/bin:/"...
19255 Casting the return type of a no-debug function is equivalent to
19256 casting the function to a pointer to a prototyped function that has a
19257 prototype that matches the types of the passed-in arguments, and
19258 calling that. I.e., the call above is equivalent to:
19261 (@value{GDBP}) p ((char * (*) (const char *)) getenv) ("PATH")
19265 and given this prototyped C or C++ function with float parameters:
19268 float multiply (float v1, float v2) @{ return v1 * v2; @}
19272 these calls are equivalent:
19275 (@value{GDBP}) p (float) multiply (2.0f, 3.0f)
19276 (@value{GDBP}) p ((float (*) (float, float)) multiply) (2.0f, 3.0f)
19279 If the function you wish to call is declared as unprototyped (i.e.@:
19280 old K&R style), you must use the cast-to-function-pointer syntax, so
19281 that @value{GDBN} knows that it needs to apply default argument
19282 promotions (promote float arguments to double). @xref{ABI, float
19283 promotion}. For example, given this unprototyped C function with
19284 float parameters, and no debug info:
19288 multiply_noproto (v1, v2)
19296 you call it like this:
19299 (@value{GDBP}) p ((float (*) ()) multiply_noproto) (2.0f, 3.0f)
19303 @section Patching Programs
19305 @cindex patching binaries
19306 @cindex writing into executables
19307 @cindex writing into corefiles
19309 By default, @value{GDBN} opens the file containing your program's
19310 executable code (or the corefile) read-only. This prevents accidental
19311 alterations to machine code; but it also prevents you from intentionally
19312 patching your program's binary.
19314 If you'd like to be able to patch the binary, you can specify that
19315 explicitly with the @code{set write} command. For example, you might
19316 want to turn on internal debugging flags, or even to make emergency
19322 @itemx set write off
19323 If you specify @samp{set write on}, @value{GDBN} opens executable and
19324 core files for both reading and writing; if you specify @kbd{set write
19325 off} (the default), @value{GDBN} opens them read-only.
19327 If you have already loaded a file, you must load it again (using the
19328 @code{exec-file} or @code{core-file} command) after changing @code{set
19329 write}, for your new setting to take effect.
19333 Display whether executable files and core files are opened for writing
19334 as well as reading.
19337 @node Compiling and Injecting Code
19338 @section Compiling and injecting code in @value{GDBN}
19339 @cindex injecting code
19340 @cindex writing into executables
19341 @cindex compiling code
19343 @value{GDBN} supports on-demand compilation and code injection into
19344 programs running under @value{GDBN}. GCC 5.0 or higher built with
19345 @file{libcc1.so} must be installed for this functionality to be enabled.
19346 This functionality is implemented with the following commands.
19349 @kindex compile code
19350 @item compile code @var{source-code}
19351 @itemx compile code -raw @var{--} @var{source-code}
19352 Compile @var{source-code} with the compiler language found as the current
19353 language in @value{GDBN} (@pxref{Languages}). If compilation and
19354 injection is not supported with the current language specified in
19355 @value{GDBN}, or the compiler does not support this feature, an error
19356 message will be printed. If @var{source-code} compiles and links
19357 successfully, @value{GDBN} will load the object-code emitted,
19358 and execute it within the context of the currently selected inferior.
19359 It is important to note that the compiled code is executed immediately.
19360 After execution, the compiled code is removed from @value{GDBN} and any
19361 new types or variables you have defined will be deleted.
19363 The command allows you to specify @var{source-code} in two ways.
19364 The simplest method is to provide a single line of code to the command.
19368 compile code printf ("hello world\n");
19371 If you specify options on the command line as well as source code, they
19372 may conflict. The @samp{--} delimiter can be used to separate options
19373 from actual source code. E.g.:
19376 compile code -r -- printf ("hello world\n");
19379 Alternatively you can enter source code as multiple lines of text. To
19380 enter this mode, invoke the @samp{compile code} command without any text
19381 following the command. This will start the multiple-line editor and
19382 allow you to type as many lines of source code as required. When you
19383 have completed typing, enter @samp{end} on its own line to exit the
19388 >printf ("hello\n");
19389 >printf ("world\n");
19393 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
19394 provided @var{source-code} in a callable scope. In this case, you must
19395 specify the entry point of the code by defining a function named
19396 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
19397 inferior. Using @samp{-raw} option may be needed for example when
19398 @var{source-code} requires @samp{#include} lines which may conflict with
19399 inferior symbols otherwise.
19401 @kindex compile file
19402 @item compile file @var{filename}
19403 @itemx compile file -raw @var{filename}
19404 Like @code{compile code}, but take the source code from @var{filename}.
19407 compile file /home/user/example.c
19412 @item compile print [[@var{options}] --] @var{expr}
19413 @itemx compile print [[@var{options}] --] /@var{f} @var{expr}
19414 Compile and execute @var{expr} with the compiler language found as the
19415 current language in @value{GDBN} (@pxref{Languages}). By default the
19416 value of @var{expr} is printed in a format appropriate to its data type;
19417 you can choose a different format by specifying @samp{/@var{f}}, where
19418 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
19419 Formats}. The @code{compile print} command accepts the same options
19420 as the @code{print} command; see @ref{print options}.
19422 @item compile print [[@var{options}] --]
19423 @itemx compile print [[@var{options}] --] /@var{f}
19424 @cindex reprint the last value
19425 Alternatively you can enter the expression (source code producing it) as
19426 multiple lines of text. To enter this mode, invoke the @samp{compile print}
19427 command without any text following the command. This will start the
19428 multiple-line editor.
19432 The process of compiling and injecting the code can be inspected using:
19435 @anchor{set debug compile}
19436 @item set debug compile
19437 @cindex compile command debugging info
19438 Turns on or off display of @value{GDBN} process of compiling and
19439 injecting the code. The default is off.
19441 @item show debug compile
19442 Displays the current state of displaying @value{GDBN} process of
19443 compiling and injecting the code.
19445 @anchor{set debug compile-cplus-types}
19446 @item set debug compile-cplus-types
19447 @cindex compile C@t{++} type conversion
19448 Turns on or off the display of C@t{++} type conversion debugging information.
19449 The default is off.
19451 @item show debug compile-cplus-types
19452 Displays the current state of displaying debugging information for
19453 C@t{++} type conversion.
19456 @subsection Compilation options for the @code{compile} command
19458 @value{GDBN} needs to specify the right compilation options for the code
19459 to be injected, in part to make its ABI compatible with the inferior
19460 and in part to make the injected code compatible with @value{GDBN}'s
19464 The options used, in increasing precedence:
19467 @item target architecture and OS options (@code{gdbarch})
19468 These options depend on target processor type and target operating
19469 system, usually they specify at least 32-bit (@code{-m32}) or 64-bit
19470 (@code{-m64}) compilation option.
19472 @item compilation options recorded in the target
19473 @value{NGCC} (since version 4.7) stores the options used for compilation
19474 into @code{DW_AT_producer} part of DWARF debugging information according
19475 to the @value{NGCC} option @code{-grecord-gcc-switches}. One has to
19476 explicitly specify @code{-g} during inferior compilation otherwise
19477 @value{NGCC} produces no DWARF. This feature is only relevant for
19478 platforms where @code{-g} produces DWARF by default, otherwise one may
19479 try to enforce DWARF by using @code{-gdwarf-4}.
19481 @item compilation options set by @code{set compile-args}
19485 You can override compilation options using the following command:
19488 @item set compile-args
19489 @cindex compile command options override
19490 Set compilation options used for compiling and injecting code with the
19491 @code{compile} commands. These options override any conflicting ones
19492 from the target architecture and/or options stored during inferior
19495 @item show compile-args
19496 Displays the current state of compilation options override.
19497 This does not show all the options actually used during compilation,
19498 use @ref{set debug compile} for that.
19501 @subsection Caveats when using the @code{compile} command
19503 There are a few caveats to keep in mind when using the @code{compile}
19504 command. As the caveats are different per language, the table below
19505 highlights specific issues on a per language basis.
19508 @item C code examples and caveats
19509 When the language in @value{GDBN} is set to @samp{C}, the compiler will
19510 attempt to compile the source code with a @samp{C} compiler. The source
19511 code provided to the @code{compile} command will have much the same
19512 access to variables and types as it normally would if it were part of
19513 the program currently being debugged in @value{GDBN}.
19515 Below is a sample program that forms the basis of the examples that
19516 follow. This program has been compiled and loaded into @value{GDBN},
19517 much like any other normal debugging session.
19520 void function1 (void)
19523 printf ("function 1\n");
19526 void function2 (void)
19541 For the purposes of the examples in this section, the program above has
19542 been compiled, loaded into @value{GDBN}, stopped at the function
19543 @code{main}, and @value{GDBN} is awaiting input from the user.
19545 To access variables and types for any program in @value{GDBN}, the
19546 program must be compiled and packaged with debug information. The
19547 @code{compile} command is not an exception to this rule. Without debug
19548 information, you can still use the @code{compile} command, but you will
19549 be very limited in what variables and types you can access.
19551 So with that in mind, the example above has been compiled with debug
19552 information enabled. The @code{compile} command will have access to
19553 all variables and types (except those that may have been optimized
19554 out). Currently, as @value{GDBN} has stopped the program in the
19555 @code{main} function, the @code{compile} command would have access to
19556 the variable @code{k}. You could invoke the @code{compile} command
19557 and type some source code to set the value of @code{k}. You can also
19558 read it, or do anything with that variable you would normally do in
19559 @code{C}. Be aware that changes to inferior variables in the
19560 @code{compile} command are persistent. In the following example:
19563 compile code k = 3;
19567 the variable @code{k} is now 3. It will retain that value until
19568 something else in the example program changes it, or another
19569 @code{compile} command changes it.
19571 Normal scope and access rules apply to source code compiled and
19572 injected by the @code{compile} command. In the example, the variables
19573 @code{j} and @code{k} are not accessible yet, because the program is
19574 currently stopped in the @code{main} function, where these variables
19575 are not in scope. Therefore, the following command
19578 compile code j = 3;
19582 will result in a compilation error message.
19584 Once the program is continued, execution will bring these variables in
19585 scope, and they will become accessible; then the code you specify via
19586 the @code{compile} command will be able to access them.
19588 You can create variables and types with the @code{compile} command as
19589 part of your source code. Variables and types that are created as part
19590 of the @code{compile} command are not visible to the rest of the program for
19591 the duration of its run. This example is valid:
19594 compile code int ff = 5; printf ("ff is %d\n", ff);
19597 However, if you were to type the following into @value{GDBN} after that
19598 command has completed:
19601 compile code printf ("ff is %d\n'', ff);
19605 a compiler error would be raised as the variable @code{ff} no longer
19606 exists. Object code generated and injected by the @code{compile}
19607 command is removed when its execution ends. Caution is advised
19608 when assigning to program variables values of variables created by the
19609 code submitted to the @code{compile} command. This example is valid:
19612 compile code int ff = 5; k = ff;
19615 The value of the variable @code{ff} is assigned to @code{k}. The variable
19616 @code{k} does not require the existence of @code{ff} to maintain the value
19617 it has been assigned. However, pointers require particular care in
19618 assignment. If the source code compiled with the @code{compile} command
19619 changed the address of a pointer in the example program, perhaps to a
19620 variable created in the @code{compile} command, that pointer would point
19621 to an invalid location when the command exits. The following example
19622 would likely cause issues with your debugged program:
19625 compile code int ff = 5; p = &ff;
19628 In this example, @code{p} would point to @code{ff} when the
19629 @code{compile} command is executing the source code provided to it.
19630 However, as variables in the (example) program persist with their
19631 assigned values, the variable @code{p} would point to an invalid
19632 location when the command exists. A general rule should be followed
19633 in that you should either assign @code{NULL} to any assigned pointers,
19634 or restore a valid location to the pointer before the command exits.
19636 Similar caution must be exercised with any structs, unions, and typedefs
19637 defined in @code{compile} command. Types defined in the @code{compile}
19638 command will no longer be available in the next @code{compile} command.
19639 Therefore, if you cast a variable to a type defined in the
19640 @code{compile} command, care must be taken to ensure that any future
19641 need to resolve the type can be achieved.
19644 (gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
19645 (gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
19646 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
19647 Compilation failed.
19648 (gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
19652 Variables that have been optimized away by the compiler are not
19653 accessible to the code submitted to the @code{compile} command.
19654 Access to those variables will generate a compiler error which @value{GDBN}
19655 will print to the console.
19658 @subsection Compiler search for the @code{compile} command
19660 @value{GDBN} needs to find @value{NGCC} for the inferior being debugged
19661 which may not be obvious for remote targets of different architecture
19662 than where @value{GDBN} is running. Environment variable @code{PATH} on
19663 @value{GDBN} host is searched for @value{NGCC} binary matching the
19664 target architecture and operating system. This search can be overriden
19665 by @code{set compile-gcc} @value{GDBN} command below. @code{PATH} is
19666 taken from shell that executed @value{GDBN}, it is not the value set by
19667 @value{GDBN} command @code{set environment}). @xref{Environment}.
19670 Specifically @code{PATH} is searched for binaries matching regular expression
19671 @code{@var{arch}(-[^-]*)?-@var{os}-gcc} according to the inferior target being
19672 debugged. @var{arch} is processor name --- multiarch is supported, so for
19673 example both @code{i386} and @code{x86_64} targets look for pattern
19674 @code{(x86_64|i.86)} and both @code{s390} and @code{s390x} targets look
19675 for pattern @code{s390x?}. @var{os} is currently supported only for
19676 pattern @code{linux(-gnu)?}.
19678 On Posix hosts the compiler driver @value{GDBN} needs to find also
19679 shared library @file{libcc1.so} from the compiler. It is searched in
19680 default shared library search path (overridable with usual environment
19681 variable @code{LD_LIBRARY_PATH}), unrelated to @code{PATH} or @code{set
19682 compile-gcc} settings. Contrary to it @file{libcc1plugin.so} is found
19683 according to the installation of the found compiler --- as possibly
19684 specified by the @code{set compile-gcc} command.
19687 @item set compile-gcc
19688 @cindex compile command driver filename override
19689 Set compilation command used for compiling and injecting code with the
19690 @code{compile} commands. If this option is not set (it is set to
19691 an empty string), the search described above will occur --- that is the
19694 @item show compile-gcc
19695 Displays the current compile command @value{NGCC} driver filename.
19696 If set, it is the main command @command{gcc}, found usually for example
19697 under name @file{x86_64-linux-gnu-gcc}.
19701 @chapter @value{GDBN} Files
19703 @value{GDBN} needs to know the file name of the program to be debugged,
19704 both in order to read its symbol table and in order to start your
19705 program. To debug a core dump of a previous run, you must also tell
19706 @value{GDBN} the name of the core dump file.
19709 * Files:: Commands to specify files
19710 * File Caching:: Information about @value{GDBN}'s file caching
19711 * Separate Debug Files:: Debugging information in separate files
19712 * MiniDebugInfo:: Debugging information in a special section
19713 * Index Files:: Index files speed up GDB
19714 * Symbol Errors:: Errors reading symbol files
19715 * Data Files:: GDB data files
19719 @section Commands to Specify Files
19721 @cindex symbol table
19722 @cindex core dump file
19724 You may want to specify executable and core dump file names. The usual
19725 way to do this is at start-up time, using the arguments to
19726 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
19727 Out of @value{GDBN}}).
19729 Occasionally it is necessary to change to a different file during a
19730 @value{GDBN} session. Or you may run @value{GDBN} and forget to
19731 specify a file you want to use. Or you are debugging a remote target
19732 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
19733 Program}). In these situations the @value{GDBN} commands to specify
19734 new files are useful.
19737 @cindex executable file
19739 @item file @var{filename}
19740 Use @var{filename} as the program to be debugged. It is read for its
19741 symbols and for the contents of pure memory. It is also the program
19742 executed when you use the @code{run} command. If you do not specify a
19743 directory and the file is not found in the @value{GDBN} working directory,
19744 @value{GDBN} uses the environment variable @code{PATH} as a list of
19745 directories to search, just as the shell does when looking for a program
19746 to run. You can change the value of this variable, for both @value{GDBN}
19747 and your program, using the @code{path} command.
19749 @cindex unlinked object files
19750 @cindex patching object files
19751 You can load unlinked object @file{.o} files into @value{GDBN} using
19752 the @code{file} command. You will not be able to ``run'' an object
19753 file, but you can disassemble functions and inspect variables. Also,
19754 if the underlying BFD functionality supports it, you could use
19755 @kbd{gdb -write} to patch object files using this technique. Note
19756 that @value{GDBN} can neither interpret nor modify relocations in this
19757 case, so branches and some initialized variables will appear to go to
19758 the wrong place. But this feature is still handy from time to time.
19761 @code{file} with no argument makes @value{GDBN} discard any information it
19762 has on both executable file and the symbol table.
19765 @item exec-file @r{[} @var{filename} @r{]}
19766 Specify that the program to be run (but not the symbol table) is found
19767 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
19768 if necessary to locate your program. Omitting @var{filename} means to
19769 discard information on the executable file.
19771 @kindex symbol-file
19772 @item symbol-file @r{[} @var{filename} @r{[} -o @var{offset} @r{]]}
19773 Read symbol table information from file @var{filename}. @code{PATH} is
19774 searched when necessary. Use the @code{file} command to get both symbol
19775 table and program to run from the same file.
19777 If an optional @var{offset} is specified, it is added to the start
19778 address of each section in the symbol file. This is useful if the
19779 program is relocated at runtime, such as the Linux kernel with kASLR
19782 @code{symbol-file} with no argument clears out @value{GDBN} information on your
19783 program's symbol table.
19785 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
19786 some breakpoints and auto-display expressions. This is because they may
19787 contain pointers to the internal data recording symbols and data types,
19788 which are part of the old symbol table data being discarded inside
19791 @code{symbol-file} does not repeat if you press @key{RET} again after
19794 When @value{GDBN} is configured for a particular environment, it
19795 understands debugging information in whatever format is the standard
19796 generated for that environment; you may use either a @sc{gnu} compiler, or
19797 other compilers that adhere to the local conventions.
19798 Best results are usually obtained from @sc{gnu} compilers; for example,
19799 using @code{@value{NGCC}} you can generate debugging information for
19802 For most kinds of object files, with the exception of old SVR3 systems
19803 using COFF, the @code{symbol-file} command does not normally read the
19804 symbol table in full right away. Instead, it scans the symbol table
19805 quickly to find which source files and which symbols are present. The
19806 details are read later, one source file at a time, as they are needed.
19808 The purpose of this two-stage reading strategy is to make @value{GDBN}
19809 start up faster. For the most part, it is invisible except for
19810 occasional pauses while the symbol table details for a particular source
19811 file are being read. (The @code{set verbose} command can turn these
19812 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
19813 Warnings and Messages}.)
19815 We have not implemented the two-stage strategy for COFF yet. When the
19816 symbol table is stored in COFF format, @code{symbol-file} reads the
19817 symbol table data in full right away. Note that ``stabs-in-COFF''
19818 still does the two-stage strategy, since the debug info is actually
19822 @cindex reading symbols immediately
19823 @cindex symbols, reading immediately
19824 @item symbol-file @r{[} -readnow @r{]} @var{filename}
19825 @itemx file @r{[} -readnow @r{]} @var{filename}
19826 You can override the @value{GDBN} two-stage strategy for reading symbol
19827 tables by using the @samp{-readnow} option with any of the commands that
19828 load symbol table information, if you want to be sure @value{GDBN} has the
19829 entire symbol table available.
19831 @cindex @code{-readnever}, option for symbol-file command
19832 @cindex never read symbols
19833 @cindex symbols, never read
19834 @item symbol-file @r{[} -readnever @r{]} @var{filename}
19835 @itemx file @r{[} -readnever @r{]} @var{filename}
19836 You can instruct @value{GDBN} to never read the symbolic information
19837 contained in @var{filename} by using the @samp{-readnever} option.
19838 @xref{--readnever}.
19840 @c FIXME: for now no mention of directories, since this seems to be in
19841 @c flux. 13mar1992 status is that in theory GDB would look either in
19842 @c current dir or in same dir as myprog; but issues like competing
19843 @c GDB's, or clutter in system dirs, mean that in practice right now
19844 @c only current dir is used. FFish says maybe a special GDB hierarchy
19845 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
19849 @item core-file @r{[}@var{filename}@r{]}
19851 Specify the whereabouts of a core dump file to be used as the ``contents
19852 of memory''. Traditionally, core files contain only some parts of the
19853 address space of the process that generated them; @value{GDBN} can access the
19854 executable file itself for other parts.
19856 @code{core-file} with no argument specifies that no core file is
19859 Note that the core file is ignored when your program is actually running
19860 under @value{GDBN}. So, if you have been running your program and you
19861 wish to debug a core file instead, you must kill the subprocess in which
19862 the program is running. To do this, use the @code{kill} command
19863 (@pxref{Kill Process, ,Killing the Child Process}).
19865 @kindex add-symbol-file
19866 @cindex dynamic linking
19867 @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{]}
19868 The @code{add-symbol-file} command reads additional symbol table
19869 information from the file @var{filename}. You would use this command
19870 when @var{filename} has been dynamically loaded (by some other means)
19871 into the program that is running. The @var{textaddress} parameter gives
19872 the memory address at which the file's text section has been loaded.
19873 You can additionally specify the base address of other sections using
19874 an arbitrary number of @samp{-s @var{section} @var{address}} pairs.
19875 If a section is omitted, @value{GDBN} will use its default addresses
19876 as found in @var{filename}. Any @var{address} or @var{textaddress}
19877 can be given as an expression.
19879 If an optional @var{offset} is specified, it is added to the start
19880 address of each section, except those for which the address was
19881 specified explicitly.
19883 The symbol table of the file @var{filename} is added to the symbol table
19884 originally read with the @code{symbol-file} command. You can use the
19885 @code{add-symbol-file} command any number of times; the new symbol data
19886 thus read is kept in addition to the old.
19888 Changes can be reverted using the command @code{remove-symbol-file}.
19890 @cindex relocatable object files, reading symbols from
19891 @cindex object files, relocatable, reading symbols from
19892 @cindex reading symbols from relocatable object files
19893 @cindex symbols, reading from relocatable object files
19894 @cindex @file{.o} files, reading symbols from
19895 Although @var{filename} is typically a shared library file, an
19896 executable file, or some other object file which has been fully
19897 relocated for loading into a process, you can also load symbolic
19898 information from relocatable @file{.o} files, as long as:
19902 the file's symbolic information refers only to linker symbols defined in
19903 that file, not to symbols defined by other object files,
19905 every section the file's symbolic information refers to has actually
19906 been loaded into the inferior, as it appears in the file, and
19908 you can determine the address at which every section was loaded, and
19909 provide these to the @code{add-symbol-file} command.
19913 Some embedded operating systems, like Sun Chorus and VxWorks, can load
19914 relocatable files into an already running program; such systems
19915 typically make the requirements above easy to meet. However, it's
19916 important to recognize that many native systems use complex link
19917 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
19918 assembly, for example) that make the requirements difficult to meet. In
19919 general, one cannot assume that using @code{add-symbol-file} to read a
19920 relocatable object file's symbolic information will have the same effect
19921 as linking the relocatable object file into the program in the normal
19924 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
19926 @kindex remove-symbol-file
19927 @item remove-symbol-file @var{filename}
19928 @item remove-symbol-file -a @var{address}
19929 Remove a symbol file added via the @code{add-symbol-file} command. The
19930 file to remove can be identified by its @var{filename} or by an @var{address}
19931 that lies within the boundaries of this symbol file in memory. Example:
19934 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
19935 add symbol table from file "/home/user/gdb/mylib.so" at
19936 .text_addr = 0x7ffff7ff9480
19938 Reading symbols from /home/user/gdb/mylib.so...done.
19939 (gdb) remove-symbol-file -a 0x7ffff7ff9480
19940 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
19945 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
19947 @kindex add-symbol-file-from-memory
19948 @cindex @code{syscall DSO}
19949 @cindex load symbols from memory
19950 @item add-symbol-file-from-memory @var{address}
19951 Load symbols from the given @var{address} in a dynamically loaded
19952 object file whose image is mapped directly into the inferior's memory.
19953 For example, the Linux kernel maps a @code{syscall DSO} into each
19954 process's address space; this DSO provides kernel-specific code for
19955 some system calls. The argument can be any expression whose
19956 evaluation yields the address of the file's shared object file header.
19957 For this command to work, you must have used @code{symbol-file} or
19958 @code{exec-file} commands in advance.
19961 @item section @var{section} @var{addr}
19962 The @code{section} command changes the base address of the named
19963 @var{section} of the exec file to @var{addr}. This can be used if the
19964 exec file does not contain section addresses, (such as in the
19965 @code{a.out} format), or when the addresses specified in the file
19966 itself are wrong. Each section must be changed separately. The
19967 @code{info files} command, described below, lists all the sections and
19971 @kindex info target
19974 @code{info files} and @code{info target} are synonymous; both print the
19975 current target (@pxref{Targets, ,Specifying a Debugging Target}),
19976 including the names of the executable and core dump files currently in
19977 use by @value{GDBN}, and the files from which symbols were loaded. The
19978 command @code{help target} lists all possible targets rather than
19981 @kindex maint info sections
19982 @item maint info sections
19983 Another command that can give you extra information about program sections
19984 is @code{maint info sections}. In addition to the section information
19985 displayed by @code{info files}, this command displays the flags and file
19986 offset of each section in the executable and core dump files. In addition,
19987 @code{maint info sections} provides the following command options (which
19988 may be arbitrarily combined):
19992 Display sections for all loaded object files, including shared libraries.
19993 @item @var{sections}
19994 Display info only for named @var{sections}.
19995 @item @var{section-flags}
19996 Display info only for sections for which @var{section-flags} are true.
19997 The section flags that @value{GDBN} currently knows about are:
20000 Section will have space allocated in the process when loaded.
20001 Set for all sections except those containing debug information.
20003 Section will be loaded from the file into the child process memory.
20004 Set for pre-initialized code and data, clear for @code{.bss} sections.
20006 Section needs to be relocated before loading.
20008 Section cannot be modified by the child process.
20010 Section contains executable code only.
20012 Section contains data only (no executable code).
20014 Section will reside in ROM.
20016 Section contains data for constructor/destructor lists.
20018 Section is not empty.
20020 An instruction to the linker to not output the section.
20021 @item COFF_SHARED_LIBRARY
20022 A notification to the linker that the section contains
20023 COFF shared library information.
20025 Section contains common symbols.
20028 @kindex set trust-readonly-sections
20029 @cindex read-only sections
20030 @item set trust-readonly-sections on
20031 Tell @value{GDBN} that readonly sections in your object file
20032 really are read-only (i.e.@: that their contents will not change).
20033 In that case, @value{GDBN} can fetch values from these sections
20034 out of the object file, rather than from the target program.
20035 For some targets (notably embedded ones), this can be a significant
20036 enhancement to debugging performance.
20038 The default is off.
20040 @item set trust-readonly-sections off
20041 Tell @value{GDBN} not to trust readonly sections. This means that
20042 the contents of the section might change while the program is running,
20043 and must therefore be fetched from the target when needed.
20045 @item show trust-readonly-sections
20046 Show the current setting of trusting readonly sections.
20049 All file-specifying commands allow both absolute and relative file names
20050 as arguments. @value{GDBN} always converts the file name to an absolute file
20051 name and remembers it that way.
20053 @cindex shared libraries
20054 @anchor{Shared Libraries}
20055 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, SunOS,
20056 Darwin/Mach-O, SVr4, IBM RS/6000 AIX, QNX Neutrino, FDPIC (FR-V), and
20057 DSBT (TIC6X) shared libraries.
20059 On MS-Windows @value{GDBN} must be linked with the Expat library to support
20060 shared libraries. @xref{Expat}.
20062 @value{GDBN} automatically loads symbol definitions from shared libraries
20063 when you use the @code{run} command, or when you examine a core file.
20064 (Before you issue the @code{run} command, @value{GDBN} does not understand
20065 references to a function in a shared library, however---unless you are
20066 debugging a core file).
20068 @c FIXME: some @value{GDBN} release may permit some refs to undef
20069 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
20070 @c FIXME...lib; check this from time to time when updating manual
20072 There are times, however, when you may wish to not automatically load
20073 symbol definitions from shared libraries, such as when they are
20074 particularly large or there are many of them.
20076 To control the automatic loading of shared library symbols, use the
20080 @kindex set auto-solib-add
20081 @item set auto-solib-add @var{mode}
20082 If @var{mode} is @code{on}, symbols from all shared object libraries
20083 will be loaded automatically when the inferior begins execution, you
20084 attach to an independently started inferior, or when the dynamic linker
20085 informs @value{GDBN} that a new library has been loaded. If @var{mode}
20086 is @code{off}, symbols must be loaded manually, using the
20087 @code{sharedlibrary} command. The default value is @code{on}.
20089 @cindex memory used for symbol tables
20090 If your program uses lots of shared libraries with debug info that
20091 takes large amounts of memory, you can decrease the @value{GDBN}
20092 memory footprint by preventing it from automatically loading the
20093 symbols from shared libraries. To that end, type @kbd{set
20094 auto-solib-add off} before running the inferior, then load each
20095 library whose debug symbols you do need with @kbd{sharedlibrary
20096 @var{regexp}}, where @var{regexp} is a regular expression that matches
20097 the libraries whose symbols you want to be loaded.
20099 @kindex show auto-solib-add
20100 @item show auto-solib-add
20101 Display the current autoloading mode.
20104 @cindex load shared library
20105 To explicitly load shared library symbols, use the @code{sharedlibrary}
20109 @kindex info sharedlibrary
20111 @item info share @var{regex}
20112 @itemx info sharedlibrary @var{regex}
20113 Print the names of the shared libraries which are currently loaded
20114 that match @var{regex}. If @var{regex} is omitted then print
20115 all shared libraries that are loaded.
20118 @item info dll @var{regex}
20119 This is an alias of @code{info sharedlibrary}.
20121 @kindex sharedlibrary
20123 @item sharedlibrary @var{regex}
20124 @itemx share @var{regex}
20125 Load shared object library symbols for files matching a
20126 Unix regular expression.
20127 As with files loaded automatically, it only loads shared libraries
20128 required by your program for a core file or after typing @code{run}. If
20129 @var{regex} is omitted all shared libraries required by your program are
20132 @item nosharedlibrary
20133 @kindex nosharedlibrary
20134 @cindex unload symbols from shared libraries
20135 Unload all shared object library symbols. This discards all symbols
20136 that have been loaded from all shared libraries. Symbols from shared
20137 libraries that were loaded by explicit user requests are not
20141 Sometimes you may wish that @value{GDBN} stops and gives you control
20142 when any of shared library events happen. The best way to do this is
20143 to use @code{catch load} and @code{catch unload} (@pxref{Set
20146 @value{GDBN} also supports the the @code{set stop-on-solib-events}
20147 command for this. This command exists for historical reasons. It is
20148 less useful than setting a catchpoint, because it does not allow for
20149 conditions or commands as a catchpoint does.
20152 @item set stop-on-solib-events
20153 @kindex set stop-on-solib-events
20154 This command controls whether @value{GDBN} should give you control
20155 when the dynamic linker notifies it about some shared library event.
20156 The most common event of interest is loading or unloading of a new
20159 @item show stop-on-solib-events
20160 @kindex show stop-on-solib-events
20161 Show whether @value{GDBN} stops and gives you control when shared
20162 library events happen.
20165 Shared libraries are also supported in many cross or remote debugging
20166 configurations. @value{GDBN} needs to have access to the target's libraries;
20167 this can be accomplished either by providing copies of the libraries
20168 on the host system, or by asking @value{GDBN} to automatically retrieve the
20169 libraries from the target. If copies of the target libraries are
20170 provided, they need to be the same as the target libraries, although the
20171 copies on the target can be stripped as long as the copies on the host are
20174 @cindex where to look for shared libraries
20175 For remote debugging, you need to tell @value{GDBN} where the target
20176 libraries are, so that it can load the correct copies---otherwise, it
20177 may try to load the host's libraries. @value{GDBN} has two variables
20178 to specify the search directories for target libraries.
20181 @cindex prefix for executable and shared library file names
20182 @cindex system root, alternate
20183 @kindex set solib-absolute-prefix
20184 @kindex set sysroot
20185 @item set sysroot @var{path}
20186 Use @var{path} as the system root for the program being debugged. Any
20187 absolute shared library paths will be prefixed with @var{path}; many
20188 runtime loaders store the absolute paths to the shared library in the
20189 target program's memory. When starting processes remotely, and when
20190 attaching to already-running processes (local or remote), their
20191 executable filenames will be prefixed with @var{path} if reported to
20192 @value{GDBN} as absolute by the operating system. If you use
20193 @code{set sysroot} to find executables and shared libraries, they need
20194 to be laid out in the same way that they are on the target, with
20195 e.g.@: a @file{/bin}, @file{/lib} and @file{/usr/lib} hierarchy under
20198 If @var{path} starts with the sequence @file{target:} and the target
20199 system is remote then @value{GDBN} will retrieve the target binaries
20200 from the remote system. This is only supported when using a remote
20201 target that supports the @code{remote get} command (@pxref{File
20202 Transfer,,Sending files to a remote system}). The part of @var{path}
20203 following the initial @file{target:} (if present) is used as system
20204 root prefix on the remote file system. If @var{path} starts with the
20205 sequence @file{remote:} this is converted to the sequence
20206 @file{target:} by @code{set sysroot}@footnote{Historically the
20207 functionality to retrieve binaries from the remote system was
20208 provided by prefixing @var{path} with @file{remote:}}. If you want
20209 to specify a local system root using a directory that happens to be
20210 named @file{target:} or @file{remote:}, you need to use some
20211 equivalent variant of the name like @file{./target:}.
20213 For targets with an MS-DOS based filesystem, such as MS-Windows and
20214 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
20215 absolute file name with @var{path}. But first, on Unix hosts,
20216 @value{GDBN} converts all backslash directory separators into forward
20217 slashes, because the backslash is not a directory separator on Unix:
20220 c:\foo\bar.dll @result{} c:/foo/bar.dll
20223 Then, @value{GDBN} attempts prefixing the target file name with
20224 @var{path}, and looks for the resulting file name in the host file
20228 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
20231 If that does not find the binary, @value{GDBN} tries removing
20232 the @samp{:} character from the drive spec, both for convenience, and,
20233 for the case of the host file system not supporting file names with
20237 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
20240 This makes it possible to have a system root that mirrors a target
20241 with more than one drive. E.g., you may want to setup your local
20242 copies of the target system shared libraries like so (note @samp{c} vs
20246 @file{/path/to/sysroot/c/sys/bin/foo.dll}
20247 @file{/path/to/sysroot/c/sys/bin/bar.dll}
20248 @file{/path/to/sysroot/z/sys/bin/bar.dll}
20252 and point the system root at @file{/path/to/sysroot}, so that
20253 @value{GDBN} can find the correct copies of both
20254 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
20256 If that still does not find the binary, @value{GDBN} tries
20257 removing the whole drive spec from the target file name:
20260 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
20263 This last lookup makes it possible to not care about the drive name,
20264 if you don't want or need to.
20266 The @code{set solib-absolute-prefix} command is an alias for @code{set
20269 @cindex default system root
20270 @cindex @samp{--with-sysroot}
20271 You can set the default system root by using the configure-time
20272 @samp{--with-sysroot} option. If the system root is inside
20273 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
20274 @samp{--exec-prefix}), then the default system root will be updated
20275 automatically if the installed @value{GDBN} is moved to a new
20278 @kindex show sysroot
20280 Display the current executable and shared library prefix.
20282 @kindex set solib-search-path
20283 @item set solib-search-path @var{path}
20284 If this variable is set, @var{path} is a colon-separated list of
20285 directories to search for shared libraries. @samp{solib-search-path}
20286 is used after @samp{sysroot} fails to locate the library, or if the
20287 path to the library is relative instead of absolute. If you want to
20288 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
20289 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
20290 finding your host's libraries. @samp{sysroot} is preferred; setting
20291 it to a nonexistent directory may interfere with automatic loading
20292 of shared library symbols.
20294 @kindex show solib-search-path
20295 @item show solib-search-path
20296 Display the current shared library search path.
20298 @cindex DOS file-name semantics of file names.
20299 @kindex set target-file-system-kind (unix|dos-based|auto)
20300 @kindex show target-file-system-kind
20301 @item set target-file-system-kind @var{kind}
20302 Set assumed file system kind for target reported file names.
20304 Shared library file names as reported by the target system may not
20305 make sense as is on the system @value{GDBN} is running on. For
20306 example, when remote debugging a target that has MS-DOS based file
20307 system semantics, from a Unix host, the target may be reporting to
20308 @value{GDBN} a list of loaded shared libraries with file names such as
20309 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
20310 drive letters, so the @samp{c:\} prefix is not normally understood as
20311 indicating an absolute file name, and neither is the backslash
20312 normally considered a directory separator character. In that case,
20313 the native file system would interpret this whole absolute file name
20314 as a relative file name with no directory components. This would make
20315 it impossible to point @value{GDBN} at a copy of the remote target's
20316 shared libraries on the host using @code{set sysroot}, and impractical
20317 with @code{set solib-search-path}. Setting
20318 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
20319 to interpret such file names similarly to how the target would, and to
20320 map them to file names valid on @value{GDBN}'s native file system
20321 semantics. The value of @var{kind} can be @code{"auto"}, in addition
20322 to one of the supported file system kinds. In that case, @value{GDBN}
20323 tries to determine the appropriate file system variant based on the
20324 current target's operating system (@pxref{ABI, ,Configuring the
20325 Current ABI}). The supported file system settings are:
20329 Instruct @value{GDBN} to assume the target file system is of Unix
20330 kind. Only file names starting the forward slash (@samp{/}) character
20331 are considered absolute, and the directory separator character is also
20335 Instruct @value{GDBN} to assume the target file system is DOS based.
20336 File names starting with either a forward slash, or a drive letter
20337 followed by a colon (e.g., @samp{c:}), are considered absolute, and
20338 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
20339 considered directory separators.
20342 Instruct @value{GDBN} to use the file system kind associated with the
20343 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
20344 This is the default.
20348 @cindex file name canonicalization
20349 @cindex base name differences
20350 When processing file names provided by the user, @value{GDBN}
20351 frequently needs to compare them to the file names recorded in the
20352 program's debug info. Normally, @value{GDBN} compares just the
20353 @dfn{base names} of the files as strings, which is reasonably fast
20354 even for very large programs. (The base name of a file is the last
20355 portion of its name, after stripping all the leading directories.)
20356 This shortcut in comparison is based upon the assumption that files
20357 cannot have more than one base name. This is usually true, but
20358 references to files that use symlinks or similar filesystem
20359 facilities violate that assumption. If your program records files
20360 using such facilities, or if you provide file names to @value{GDBN}
20361 using symlinks etc., you can set @code{basenames-may-differ} to
20362 @code{true} to instruct @value{GDBN} to completely canonicalize each
20363 pair of file names it needs to compare. This will make file-name
20364 comparisons accurate, but at a price of a significant slowdown.
20367 @item set basenames-may-differ
20368 @kindex set basenames-may-differ
20369 Set whether a source file may have multiple base names.
20371 @item show basenames-may-differ
20372 @kindex show basenames-may-differ
20373 Show whether a source file may have multiple base names.
20377 @section File Caching
20378 @cindex caching of opened files
20379 @cindex caching of bfd objects
20381 To speed up file loading, and reduce memory usage, @value{GDBN} will
20382 reuse the @code{bfd} objects used to track open files. @xref{Top, ,
20383 BFD, bfd, The Binary File Descriptor Library}. The following commands
20384 allow visibility and control of the caching behavior.
20387 @kindex maint info bfds
20388 @item maint info bfds
20389 This prints information about each @code{bfd} object that is known to
20392 @kindex maint set bfd-sharing
20393 @kindex maint show bfd-sharing
20394 @kindex bfd caching
20395 @item maint set bfd-sharing
20396 @item maint show bfd-sharing
20397 Control whether @code{bfd} objects can be shared. When sharing is
20398 enabled @value{GDBN} reuses already open @code{bfd} objects rather
20399 than reopening the same file. Turning sharing off does not cause
20400 already shared @code{bfd} objects to be unshared, but all future files
20401 that are opened will create a new @code{bfd} object. Similarly,
20402 re-enabling sharing does not cause multiple existing @code{bfd}
20403 objects to be collapsed into a single shared @code{bfd} object.
20405 @kindex set debug bfd-cache @var{level}
20406 @kindex bfd caching
20407 @item set debug bfd-cache @var{level}
20408 Turns on debugging of the bfd cache, setting the level to @var{level}.
20410 @kindex show debug bfd-cache
20411 @kindex bfd caching
20412 @item show debug bfd-cache
20413 Show the current debugging level of the bfd cache.
20416 @node Separate Debug Files
20417 @section Debugging Information in Separate Files
20418 @cindex separate debugging information files
20419 @cindex debugging information in separate files
20420 @cindex @file{.debug} subdirectories
20421 @cindex debugging information directory, global
20422 @cindex global debugging information directories
20423 @cindex build ID, and separate debugging files
20424 @cindex @file{.build-id} directory
20426 @value{GDBN} allows you to put a program's debugging information in a
20427 file separate from the executable itself, in a way that allows
20428 @value{GDBN} to find and load the debugging information automatically.
20429 Since debugging information can be very large---sometimes larger
20430 than the executable code itself---some systems distribute debugging
20431 information for their executables in separate files, which users can
20432 install only when they need to debug a problem.
20434 @value{GDBN} supports two ways of specifying the separate debug info
20439 The executable contains a @dfn{debug link} that specifies the name of
20440 the separate debug info file. The separate debug file's name is
20441 usually @file{@var{executable}.debug}, where @var{executable} is the
20442 name of the corresponding executable file without leading directories
20443 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
20444 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
20445 checksum for the debug file, which @value{GDBN} uses to validate that
20446 the executable and the debug file came from the same build.
20449 The executable contains a @dfn{build ID}, a unique bit string that is
20450 also present in the corresponding debug info file. (This is supported
20451 only on some operating systems, when using the ELF or PE file formats
20452 for binary files and the @sc{gnu} Binutils.) For more details about
20453 this feature, see the description of the @option{--build-id}
20454 command-line option in @ref{Options, , Command Line Options, ld,
20455 The GNU Linker}. The debug info file's name is not specified
20456 explicitly by the build ID, but can be computed from the build ID, see
20460 Depending on the way the debug info file is specified, @value{GDBN}
20461 uses two different methods of looking for the debug file:
20465 For the ``debug link'' method, @value{GDBN} looks up the named file in
20466 the directory of the executable file, then in a subdirectory of that
20467 directory named @file{.debug}, and finally under each one of the
20468 global debug directories, in a subdirectory whose name is identical to
20469 the leading directories of the executable's absolute file name. (On
20470 MS-Windows/MS-DOS, the drive letter of the executable's leading
20471 directories is converted to a one-letter subdirectory, i.e.@:
20472 @file{d:/usr/bin/} is converted to @file{/d/usr/bin/}, because Windows
20473 filesystems disallow colons in file names.)
20476 For the ``build ID'' method, @value{GDBN} looks in the
20477 @file{.build-id} subdirectory of each one of the global debug directories for
20478 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
20479 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
20480 are the rest of the bit string. (Real build ID strings are 32 or more
20481 hex characters, not 10.)
20484 So, for example, suppose you ask @value{GDBN} to debug
20485 @file{/usr/bin/ls}, which has a debug link that specifies the
20486 file @file{ls.debug}, and a build ID whose value in hex is
20487 @code{abcdef1234}. If the list of the global debug directories includes
20488 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
20489 debug information files, in the indicated order:
20493 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
20495 @file{/usr/bin/ls.debug}
20497 @file{/usr/bin/.debug/ls.debug}
20499 @file{/usr/lib/debug/usr/bin/ls.debug}.
20502 @anchor{debug-file-directory}
20503 Global debugging info directories default to what is set by @value{GDBN}
20504 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
20505 you can also set the global debugging info directories, and view the list
20506 @value{GDBN} is currently using.
20510 @kindex set debug-file-directory
20511 @item set debug-file-directory @var{directories}
20512 Set the directories which @value{GDBN} searches for separate debugging
20513 information files to @var{directory}. Multiple path components can be set
20514 concatenating them by a path separator.
20516 @kindex show debug-file-directory
20517 @item show debug-file-directory
20518 Show the directories @value{GDBN} searches for separate debugging
20523 @cindex @code{.gnu_debuglink} sections
20524 @cindex debug link sections
20525 A debug link is a special section of the executable file named
20526 @code{.gnu_debuglink}. The section must contain:
20530 A filename, with any leading directory components removed, followed by
20533 zero to three bytes of padding, as needed to reach the next four-byte
20534 boundary within the section, and
20536 a four-byte CRC checksum, stored in the same endianness used for the
20537 executable file itself. The checksum is computed on the debugging
20538 information file's full contents by the function given below, passing
20539 zero as the @var{crc} argument.
20542 Any executable file format can carry a debug link, as long as it can
20543 contain a section named @code{.gnu_debuglink} with the contents
20546 @cindex @code{.note.gnu.build-id} sections
20547 @cindex build ID sections
20548 The build ID is a special section in the executable file (and in other
20549 ELF binary files that @value{GDBN} may consider). This section is
20550 often named @code{.note.gnu.build-id}, but that name is not mandatory.
20551 It contains unique identification for the built files---the ID remains
20552 the same across multiple builds of the same build tree. The default
20553 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
20554 content for the build ID string. The same section with an identical
20555 value is present in the original built binary with symbols, in its
20556 stripped variant, and in the separate debugging information file.
20558 The debugging information file itself should be an ordinary
20559 executable, containing a full set of linker symbols, sections, and
20560 debugging information. The sections of the debugging information file
20561 should have the same names, addresses, and sizes as the original file,
20562 but they need not contain any data---much like a @code{.bss} section
20563 in an ordinary executable.
20565 The @sc{gnu} binary utilities (Binutils) package includes the
20566 @samp{objcopy} utility that can produce
20567 the separated executable / debugging information file pairs using the
20568 following commands:
20571 @kbd{objcopy --only-keep-debug foo foo.debug}
20576 These commands remove the debugging
20577 information from the executable file @file{foo} and place it in the file
20578 @file{foo.debug}. You can use the first, second or both methods to link the
20583 The debug link method needs the following additional command to also leave
20584 behind a debug link in @file{foo}:
20587 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
20590 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
20591 a version of the @code{strip} command such that the command @kbd{strip foo -f
20592 foo.debug} has the same functionality as the two @code{objcopy} commands and
20593 the @code{ln -s} command above, together.
20596 Build ID gets embedded into the main executable using @code{ld --build-id} or
20597 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
20598 compatibility fixes for debug files separation are present in @sc{gnu} binary
20599 utilities (Binutils) package since version 2.18.
20604 @cindex CRC algorithm definition
20605 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
20606 IEEE 802.3 using the polynomial:
20608 @c TexInfo requires naked braces for multi-digit exponents for Tex
20609 @c output, but this causes HTML output to barf. HTML has to be set using
20610 @c raw commands. So we end up having to specify this equation in 2
20615 <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>
20616 + <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
20622 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
20623 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
20627 The function is computed byte at a time, taking the least
20628 significant bit of each byte first. The initial pattern
20629 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
20630 the final result is inverted to ensure trailing zeros also affect the
20633 @emph{Note:} This is the same CRC polynomial as used in handling the
20634 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
20635 However in the case of the Remote Serial Protocol, the CRC is computed
20636 @emph{most} significant bit first, and the result is not inverted, so
20637 trailing zeros have no effect on the CRC value.
20639 To complete the description, we show below the code of the function
20640 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
20641 initially supplied @code{crc} argument means that an initial call to
20642 this function passing in zero will start computing the CRC using
20645 @kindex gnu_debuglink_crc32
20648 gnu_debuglink_crc32 (unsigned long crc,
20649 unsigned char *buf, size_t len)
20651 static const unsigned long crc32_table[256] =
20653 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
20654 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
20655 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
20656 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
20657 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
20658 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
20659 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
20660 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
20661 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
20662 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
20663 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
20664 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
20665 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
20666 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
20667 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
20668 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
20669 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
20670 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
20671 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
20672 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
20673 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
20674 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
20675 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
20676 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
20677 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
20678 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
20679 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
20680 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
20681 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
20682 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
20683 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
20684 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
20685 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
20686 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
20687 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
20688 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
20689 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
20690 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
20691 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
20692 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
20693 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
20694 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
20695 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
20696 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
20697 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
20698 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
20699 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
20700 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
20701 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
20702 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
20703 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
20706 unsigned char *end;
20708 crc = ~crc & 0xffffffff;
20709 for (end = buf + len; buf < end; ++buf)
20710 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
20711 return ~crc & 0xffffffff;
20716 This computation does not apply to the ``build ID'' method.
20718 @node MiniDebugInfo
20719 @section Debugging information in a special section
20720 @cindex separate debug sections
20721 @cindex @samp{.gnu_debugdata} section
20723 Some systems ship pre-built executables and libraries that have a
20724 special @samp{.gnu_debugdata} section. This feature is called
20725 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
20726 is used to supply extra symbols for backtraces.
20728 The intent of this section is to provide extra minimal debugging
20729 information for use in simple backtraces. It is not intended to be a
20730 replacement for full separate debugging information (@pxref{Separate
20731 Debug Files}). The example below shows the intended use; however,
20732 @value{GDBN} does not currently put restrictions on what sort of
20733 debugging information might be included in the section.
20735 @value{GDBN} has support for this extension. If the section exists,
20736 then it is used provided that no other source of debugging information
20737 can be found, and that @value{GDBN} was configured with LZMA support.
20739 This section can be easily created using @command{objcopy} and other
20740 standard utilities:
20743 # Extract the dynamic symbols from the main binary, there is no need
20744 # to also have these in the normal symbol table.
20745 nm -D @var{binary} --format=posix --defined-only \
20746 | awk '@{ print $1 @}' | sort > dynsyms
20748 # Extract all the text (i.e. function) symbols from the debuginfo.
20749 # (Note that we actually also accept "D" symbols, for the benefit
20750 # of platforms like PowerPC64 that use function descriptors.)
20751 nm @var{binary} --format=posix --defined-only \
20752 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
20755 # Keep all the function symbols not already in the dynamic symbol
20757 comm -13 dynsyms funcsyms > keep_symbols
20759 # Separate full debug info into debug binary.
20760 objcopy --only-keep-debug @var{binary} debug
20762 # Copy the full debuginfo, keeping only a minimal set of symbols and
20763 # removing some unnecessary sections.
20764 objcopy -S --remove-section .gdb_index --remove-section .comment \
20765 --keep-symbols=keep_symbols debug mini_debuginfo
20767 # Drop the full debug info from the original binary.
20768 strip --strip-all -R .comment @var{binary}
20770 # Inject the compressed data into the .gnu_debugdata section of the
20773 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
20777 @section Index Files Speed Up @value{GDBN}
20778 @cindex index files
20779 @cindex @samp{.gdb_index} section
20781 When @value{GDBN} finds a symbol file, it scans the symbols in the
20782 file in order to construct an internal symbol table. This lets most
20783 @value{GDBN} operations work quickly---at the cost of a delay early
20784 on. For large programs, this delay can be quite lengthy, so
20785 @value{GDBN} provides a way to build an index, which speeds up
20788 For convenience, @value{GDBN} comes with a program,
20789 @command{gdb-add-index}, which can be used to add the index to a
20790 symbol file. It takes the symbol file as its only argument:
20793 $ gdb-add-index symfile
20796 @xref{gdb-add-index}.
20798 It is also possible to do the work manually. Here is what
20799 @command{gdb-add-index} does behind the curtains.
20801 The index is stored as a section in the symbol file. @value{GDBN} can
20802 write the index to a file, then you can put it into the symbol file
20803 using @command{objcopy}.
20805 To create an index file, use the @code{save gdb-index} command:
20808 @item save gdb-index [-dwarf-5] @var{directory}
20809 @kindex save gdb-index
20810 Create index files for all symbol files currently known by
20811 @value{GDBN}. For each known @var{symbol-file}, this command by
20812 default creates it produces a single file
20813 @file{@var{symbol-file}.gdb-index}. If you invoke this command with
20814 the @option{-dwarf-5} option, it produces 2 files:
20815 @file{@var{symbol-file}.debug_names} and
20816 @file{@var{symbol-file}.debug_str}. The files are created in the
20817 given @var{directory}.
20820 Once you have created an index file you can merge it into your symbol
20821 file, here named @file{symfile}, using @command{objcopy}:
20824 $ objcopy --add-section .gdb_index=symfile.gdb-index \
20825 --set-section-flags .gdb_index=readonly symfile symfile
20828 Or for @code{-dwarf-5}:
20831 $ objcopy --dump-section .debug_str=symfile.debug_str.new symfile
20832 $ cat symfile.debug_str >>symfile.debug_str.new
20833 $ objcopy --add-section .debug_names=symfile.gdb-index \
20834 --set-section-flags .debug_names=readonly \
20835 --update-section .debug_str=symfile.debug_str.new symfile symfile
20838 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
20839 sections that have been deprecated. Usually they are deprecated because
20840 they are missing a new feature or have performance issues.
20841 To tell @value{GDBN} to use a deprecated index section anyway
20842 specify @code{set use-deprecated-index-sections on}.
20843 The default is @code{off}.
20844 This can speed up startup, but may result in some functionality being lost.
20845 @xref{Index Section Format}.
20847 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
20848 must be done before gdb reads the file. The following will not work:
20851 $ gdb -ex "set use-deprecated-index-sections on" <program>
20854 Instead you must do, for example,
20857 $ gdb -iex "set use-deprecated-index-sections on" <program>
20860 There are currently some limitation on indices. They only work when
20861 for DWARF debugging information, not stabs. And, they do not
20862 currently work for programs using Ada.
20864 @subsection Automatic symbol index cache
20866 @cindex automatic symbol index cache
20867 It is possible for @value{GDBN} to automatically save a copy of this index in a
20868 cache on disk and retrieve it from there when loading the same binary in the
20869 future. This feature can be turned on with @kbd{set index-cache on}. The
20870 following commands can be used to tweak the behavior of the index cache.
20874 @kindex set index-cache
20875 @item set index-cache on
20876 @itemx set index-cache off
20877 Enable or disable the use of the symbol index cache.
20879 @item set index-cache directory @var{directory}
20880 @kindex show index-cache
20881 @itemx show index-cache directory
20882 Set/show the directory where index files will be saved.
20884 The default value for this directory depends on the host platform. On
20885 most systems, the index is cached in the @file{gdb} subdirectory of
20886 the directory pointed to by the @env{XDG_CACHE_HOME} environment
20887 variable, if it is defined, else in the @file{.cache/gdb} subdirectory
20888 of your home directory. However, on some systems, the default may
20889 differ according to local convention.
20891 There is no limit on the disk space used by index cache. It is perfectly safe
20892 to delete the content of that directory to free up disk space.
20894 @item show index-cache stats
20895 Print the number of cache hits and misses since the launch of @value{GDBN}.
20899 @node Symbol Errors
20900 @section Errors Reading Symbol Files
20902 While reading a symbol file, @value{GDBN} occasionally encounters problems,
20903 such as symbol types it does not recognize, or known bugs in compiler
20904 output. By default, @value{GDBN} does not notify you of such problems, since
20905 they are relatively common and primarily of interest to people
20906 debugging compilers. If you are interested in seeing information
20907 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
20908 only one message about each such type of problem, no matter how many
20909 times the problem occurs; or you can ask @value{GDBN} to print more messages,
20910 to see how many times the problems occur, with the @code{set
20911 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
20914 The messages currently printed, and their meanings, include:
20917 @item inner block not inside outer block in @var{symbol}
20919 The symbol information shows where symbol scopes begin and end
20920 (such as at the start of a function or a block of statements). This
20921 error indicates that an inner scope block is not fully contained
20922 in its outer scope blocks.
20924 @value{GDBN} circumvents the problem by treating the inner block as if it had
20925 the same scope as the outer block. In the error message, @var{symbol}
20926 may be shown as ``@code{(don't know)}'' if the outer block is not a
20929 @item block at @var{address} out of order
20931 The symbol information for symbol scope blocks should occur in
20932 order of increasing addresses. This error indicates that it does not
20935 @value{GDBN} does not circumvent this problem, and has trouble
20936 locating symbols in the source file whose symbols it is reading. (You
20937 can often determine what source file is affected by specifying
20938 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
20941 @item bad block start address patched
20943 The symbol information for a symbol scope block has a start address
20944 smaller than the address of the preceding source line. This is known
20945 to occur in the SunOS 4.1.1 (and earlier) C compiler.
20947 @value{GDBN} circumvents the problem by treating the symbol scope block as
20948 starting on the previous source line.
20950 @item bad string table offset in symbol @var{n}
20953 Symbol number @var{n} contains a pointer into the string table which is
20954 larger than the size of the string table.
20956 @value{GDBN} circumvents the problem by considering the symbol to have the
20957 name @code{foo}, which may cause other problems if many symbols end up
20960 @item unknown symbol type @code{0x@var{nn}}
20962 The symbol information contains new data types that @value{GDBN} does
20963 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
20964 uncomprehended information, in hexadecimal.
20966 @value{GDBN} circumvents the error by ignoring this symbol information.
20967 This usually allows you to debug your program, though certain symbols
20968 are not accessible. If you encounter such a problem and feel like
20969 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
20970 on @code{complain}, then go up to the function @code{read_dbx_symtab}
20971 and examine @code{*bufp} to see the symbol.
20973 @item stub type has NULL name
20975 @value{GDBN} could not find the full definition for a struct or class.
20977 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
20978 The symbol information for a C@t{++} member function is missing some
20979 information that recent versions of the compiler should have output for
20982 @item info mismatch between compiler and debugger
20984 @value{GDBN} could not parse a type specification output by the compiler.
20989 @section GDB Data Files
20991 @cindex prefix for data files
20992 @value{GDBN} will sometimes read an auxiliary data file. These files
20993 are kept in a directory known as the @dfn{data directory}.
20995 You can set the data directory's name, and view the name @value{GDBN}
20996 is currently using.
20999 @kindex set data-directory
21000 @item set data-directory @var{directory}
21001 Set the directory which @value{GDBN} searches for auxiliary data files
21002 to @var{directory}.
21004 @kindex show data-directory
21005 @item show data-directory
21006 Show the directory @value{GDBN} searches for auxiliary data files.
21009 @cindex default data directory
21010 @cindex @samp{--with-gdb-datadir}
21011 You can set the default data directory by using the configure-time
21012 @samp{--with-gdb-datadir} option. If the data directory is inside
21013 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
21014 @samp{--exec-prefix}), then the default data directory will be updated
21015 automatically if the installed @value{GDBN} is moved to a new
21018 The data directory may also be specified with the
21019 @code{--data-directory} command line option.
21020 @xref{Mode Options}.
21023 @chapter Specifying a Debugging Target
21025 @cindex debugging target
21026 A @dfn{target} is the execution environment occupied by your program.
21028 Often, @value{GDBN} runs in the same host environment as your program;
21029 in that case, the debugging target is specified as a side effect when
21030 you use the @code{file} or @code{core} commands. When you need more
21031 flexibility---for example, running @value{GDBN} on a physically separate
21032 host, or controlling a standalone system over a serial port or a
21033 realtime system over a TCP/IP connection---you can use the @code{target}
21034 command to specify one of the target types configured for @value{GDBN}
21035 (@pxref{Target Commands, ,Commands for Managing Targets}).
21037 @cindex target architecture
21038 It is possible to build @value{GDBN} for several different @dfn{target
21039 architectures}. When @value{GDBN} is built like that, you can choose
21040 one of the available architectures with the @kbd{set architecture}
21044 @kindex set architecture
21045 @kindex show architecture
21046 @item set architecture @var{arch}
21047 This command sets the current target architecture to @var{arch}. The
21048 value of @var{arch} can be @code{"auto"}, in addition to one of the
21049 supported architectures.
21051 @item show architecture
21052 Show the current target architecture.
21054 @item set processor
21056 @kindex set processor
21057 @kindex show processor
21058 These are alias commands for, respectively, @code{set architecture}
21059 and @code{show architecture}.
21063 * Active Targets:: Active targets
21064 * Target Commands:: Commands for managing targets
21065 * Byte Order:: Choosing target byte order
21068 @node Active Targets
21069 @section Active Targets
21071 @cindex stacking targets
21072 @cindex active targets
21073 @cindex multiple targets
21075 There are multiple classes of targets such as: processes, executable files or
21076 recording sessions. Core files belong to the process class, making core file
21077 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
21078 on multiple active targets, one in each class. This allows you to (for
21079 example) start a process and inspect its activity, while still having access to
21080 the executable file after the process finishes. Or if you start process
21081 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
21082 presented a virtual layer of the recording target, while the process target
21083 remains stopped at the chronologically last point of the process execution.
21085 Use the @code{core-file} and @code{exec-file} commands to select a new core
21086 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
21087 specify as a target a process that is already running, use the @code{attach}
21088 command (@pxref{Attach, ,Debugging an Already-running Process}).
21090 @node Target Commands
21091 @section Commands for Managing Targets
21094 @item target @var{type} @var{parameters}
21095 Connects the @value{GDBN} host environment to a target machine or
21096 process. A target is typically a protocol for talking to debugging
21097 facilities. You use the argument @var{type} to specify the type or
21098 protocol of the target machine.
21100 Further @var{parameters} are interpreted by the target protocol, but
21101 typically include things like device names or host names to connect
21102 with, process numbers, and baud rates.
21104 The @code{target} command does not repeat if you press @key{RET} again
21105 after executing the command.
21107 @kindex help target
21109 Displays the names of all targets available. To display targets
21110 currently selected, use either @code{info target} or @code{info files}
21111 (@pxref{Files, ,Commands to Specify Files}).
21113 @item help target @var{name}
21114 Describe a particular target, including any parameters necessary to
21117 @kindex set gnutarget
21118 @item set gnutarget @var{args}
21119 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
21120 knows whether it is reading an @dfn{executable},
21121 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
21122 with the @code{set gnutarget} command. Unlike most @code{target} commands,
21123 with @code{gnutarget} the @code{target} refers to a program, not a machine.
21126 @emph{Warning:} To specify a file format with @code{set gnutarget},
21127 you must know the actual BFD name.
21131 @xref{Files, , Commands to Specify Files}.
21133 @kindex show gnutarget
21134 @item show gnutarget
21135 Use the @code{show gnutarget} command to display what file format
21136 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
21137 @value{GDBN} will determine the file format for each file automatically,
21138 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
21141 @cindex common targets
21142 Here are some common targets (available, or not, depending on the GDB
21147 @item target exec @var{program}
21148 @cindex executable file target
21149 An executable file. @samp{target exec @var{program}} is the same as
21150 @samp{exec-file @var{program}}.
21152 @item target core @var{filename}
21153 @cindex core dump file target
21154 A core dump file. @samp{target core @var{filename}} is the same as
21155 @samp{core-file @var{filename}}.
21157 @item target remote @var{medium}
21158 @cindex remote target
21159 A remote system connected to @value{GDBN} via a serial line or network
21160 connection. This command tells @value{GDBN} to use its own remote
21161 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
21163 For example, if you have a board connected to @file{/dev/ttya} on the
21164 machine running @value{GDBN}, you could say:
21167 target remote /dev/ttya
21170 @code{target remote} supports the @code{load} command. This is only
21171 useful if you have some other way of getting the stub to the target
21172 system, and you can put it somewhere in memory where it won't get
21173 clobbered by the download.
21175 @item target sim @r{[}@var{simargs}@r{]} @dots{}
21176 @cindex built-in simulator target
21177 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
21185 works; however, you cannot assume that a specific memory map, device
21186 drivers, or even basic I/O is available, although some simulators do
21187 provide these. For info about any processor-specific simulator details,
21188 see the appropriate section in @ref{Embedded Processors, ,Embedded
21191 @item target native
21192 @cindex native target
21193 Setup for local/native process debugging. Useful to make the
21194 @code{run} command spawn native processes (likewise @code{attach},
21195 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
21196 (@pxref{set auto-connect-native-target}).
21200 Different targets are available on different configurations of @value{GDBN};
21201 your configuration may have more or fewer targets.
21203 Many remote targets require you to download the executable's code once
21204 you've successfully established a connection. You may wish to control
21205 various aspects of this process.
21210 @kindex set hash@r{, for remote monitors}
21211 @cindex hash mark while downloading
21212 This command controls whether a hash mark @samp{#} is displayed while
21213 downloading a file to the remote monitor. If on, a hash mark is
21214 displayed after each S-record is successfully downloaded to the
21218 @kindex show hash@r{, for remote monitors}
21219 Show the current status of displaying the hash mark.
21221 @item set debug monitor
21222 @kindex set debug monitor
21223 @cindex display remote monitor communications
21224 Enable or disable display of communications messages between
21225 @value{GDBN} and the remote monitor.
21227 @item show debug monitor
21228 @kindex show debug monitor
21229 Show the current status of displaying communications between
21230 @value{GDBN} and the remote monitor.
21235 @kindex load @var{filename} @var{offset}
21236 @item load @var{filename} @var{offset}
21238 Depending on what remote debugging facilities are configured into
21239 @value{GDBN}, the @code{load} command may be available. Where it exists, it
21240 is meant to make @var{filename} (an executable) available for debugging
21241 on the remote system---by downloading, or dynamic linking, for example.
21242 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
21243 the @code{add-symbol-file} command.
21245 If your @value{GDBN} does not have a @code{load} command, attempting to
21246 execute it gets the error message ``@code{You can't do that when your
21247 target is @dots{}}''
21249 The file is loaded at whatever address is specified in the executable.
21250 For some object file formats, you can specify the load address when you
21251 link the program; for other formats, like a.out, the object file format
21252 specifies a fixed address.
21253 @c FIXME! This would be a good place for an xref to the GNU linker doc.
21255 It is also possible to tell @value{GDBN} to load the executable file at a
21256 specific offset described by the optional argument @var{offset}. When
21257 @var{offset} is provided, @var{filename} must also be provided.
21259 Depending on the remote side capabilities, @value{GDBN} may be able to
21260 load programs into flash memory.
21262 @code{load} does not repeat if you press @key{RET} again after using it.
21267 @kindex flash-erase
21269 @anchor{flash-erase}
21271 Erases all known flash memory regions on the target.
21276 @section Choosing Target Byte Order
21278 @cindex choosing target byte order
21279 @cindex target byte order
21281 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
21282 offer the ability to run either big-endian or little-endian byte
21283 orders. Usually the executable or symbol will include a bit to
21284 designate the endian-ness, and you will not need to worry about
21285 which to use. However, you may still find it useful to adjust
21286 @value{GDBN}'s idea of processor endian-ness manually.
21290 @item set endian big
21291 Instruct @value{GDBN} to assume the target is big-endian.
21293 @item set endian little
21294 Instruct @value{GDBN} to assume the target is little-endian.
21296 @item set endian auto
21297 Instruct @value{GDBN} to use the byte order associated with the
21301 Display @value{GDBN}'s current idea of the target byte order.
21305 If the @code{set endian auto} mode is in effect and no executable has
21306 been selected, then the endianness used is the last one chosen either
21307 by one of the @code{set endian big} and @code{set endian little}
21308 commands or by inferring from the last executable used. If no
21309 endianness has been previously chosen, then the default for this mode
21310 is inferred from the target @value{GDBN} has been built for, and is
21311 @code{little} if the name of the target CPU has an @code{el} suffix
21312 and @code{big} otherwise.
21314 Note that these commands merely adjust interpretation of symbolic
21315 data on the host, and that they have absolutely no effect on the
21319 @node Remote Debugging
21320 @chapter Debugging Remote Programs
21321 @cindex remote debugging
21323 If you are trying to debug a program running on a machine that cannot run
21324 @value{GDBN} in the usual way, it is often useful to use remote debugging.
21325 For example, you might use remote debugging on an operating system kernel,
21326 or on a small system which does not have a general purpose operating system
21327 powerful enough to run a full-featured debugger.
21329 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
21330 to make this work with particular debugging targets. In addition,
21331 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
21332 but not specific to any particular target system) which you can use if you
21333 write the remote stubs---the code that runs on the remote system to
21334 communicate with @value{GDBN}.
21336 Other remote targets may be available in your
21337 configuration of @value{GDBN}; use @code{help target} to list them.
21340 * Connecting:: Connecting to a remote target
21341 * File Transfer:: Sending files to a remote system
21342 * Server:: Using the gdbserver program
21343 * Remote Configuration:: Remote configuration
21344 * Remote Stub:: Implementing a remote stub
21348 @section Connecting to a Remote Target
21349 @cindex remote debugging, connecting
21350 @cindex @code{gdbserver}, connecting
21351 @cindex remote debugging, types of connections
21352 @cindex @code{gdbserver}, types of connections
21353 @cindex @code{gdbserver}, @code{target remote} mode
21354 @cindex @code{gdbserver}, @code{target extended-remote} mode
21356 This section describes how to connect to a remote target, including the
21357 types of connections and their differences, how to set up executable and
21358 symbol files on the host and target, and the commands used for
21359 connecting to and disconnecting from the remote target.
21361 @subsection Types of Remote Connections
21363 @value{GDBN} supports two types of remote connections, @code{target remote}
21364 mode and @code{target extended-remote} mode. Note that many remote targets
21365 support only @code{target remote} mode. There are several major
21366 differences between the two types of connections, enumerated here:
21370 @cindex remote debugging, detach and program exit
21371 @item Result of detach or program exit
21372 @strong{With target remote mode:} When the debugged program exits or you
21373 detach from it, @value{GDBN} disconnects from the target. When using
21374 @code{gdbserver}, @code{gdbserver} will exit.
21376 @strong{With target extended-remote mode:} When the debugged program exits or
21377 you detach from it, @value{GDBN} remains connected to the target, even
21378 though no program is running. You can rerun the program, attach to a
21379 running program, or use @code{monitor} commands specific to the target.
21381 When using @code{gdbserver} in this case, it does not exit unless it was
21382 invoked using the @option{--once} option. If the @option{--once} option
21383 was not used, you can ask @code{gdbserver} to exit using the
21384 @code{monitor exit} command (@pxref{Monitor Commands for gdbserver}).
21386 @item Specifying the program to debug
21387 For both connection types you use the @code{file} command to specify the
21388 program on the host system. If you are using @code{gdbserver} there are
21389 some differences in how to specify the location of the program on the
21392 @strong{With target remote mode:} You must either specify the program to debug
21393 on the @code{gdbserver} command line or use the @option{--attach} option
21394 (@pxref{Attaching to a program,,Attaching to a Running Program}).
21396 @cindex @option{--multi}, @code{gdbserver} option
21397 @strong{With target extended-remote mode:} You may specify the program to debug
21398 on the @code{gdbserver} command line, or you can load the program or attach
21399 to it using @value{GDBN} commands after connecting to @code{gdbserver}.
21401 @anchor{--multi Option in Types of Remote Connnections}
21402 You can start @code{gdbserver} without supplying an initial command to run
21403 or process ID to attach. To do this, use the @option{--multi} command line
21404 option. Then you can connect using @code{target extended-remote} and start
21405 the program you want to debug (see below for details on using the
21406 @code{run} command in this scenario). Note that the conditions under which
21407 @code{gdbserver} terminates depend on how @value{GDBN} connects to it
21408 (@code{target remote} or @code{target extended-remote}). The
21409 @option{--multi} option to @code{gdbserver} has no influence on that.
21411 @item The @code{run} command
21412 @strong{With target remote mode:} The @code{run} command is not
21413 supported. Once a connection has been established, you can use all
21414 the usual @value{GDBN} commands to examine and change data. The
21415 remote program is already running, so you can use commands like
21416 @kbd{step} and @kbd{continue}.
21418 @strong{With target extended-remote mode:} The @code{run} command is
21419 supported. The @code{run} command uses the value set by
21420 @code{set remote exec-file} (@pxref{set remote exec-file}) to select
21421 the program to run. Command line arguments are supported, except for
21422 wildcard expansion and I/O redirection (@pxref{Arguments}).
21424 If you specify the program to debug on the command line, then the
21425 @code{run} command is not required to start execution, and you can
21426 resume using commands like @kbd{step} and @kbd{continue} as with
21427 @code{target remote} mode.
21429 @anchor{Attaching in Types of Remote Connections}
21431 @strong{With target remote mode:} The @value{GDBN} command @code{attach} is
21432 not supported. To attach to a running program using @code{gdbserver}, you
21433 must use the @option{--attach} option (@pxref{Running gdbserver}).
21435 @strong{With target extended-remote mode:} To attach to a running program,
21436 you may use the @code{attach} command after the connection has been
21437 established. If you are using @code{gdbserver}, you may also invoke
21438 @code{gdbserver} using the @option{--attach} option
21439 (@pxref{Running gdbserver}).
21443 @anchor{Host and target files}
21444 @subsection Host and Target Files
21445 @cindex remote debugging, symbol files
21446 @cindex symbol files, remote debugging
21448 @value{GDBN}, running on the host, needs access to symbol and debugging
21449 information for your program running on the target. This requires
21450 access to an unstripped copy of your program, and possibly any associated
21451 symbol files. Note that this section applies equally to both @code{target
21452 remote} mode and @code{target extended-remote} mode.
21454 Some remote targets (@pxref{qXfer executable filename read}, and
21455 @pxref{Host I/O Packets}) allow @value{GDBN} to access program files over
21456 the same connection used to communicate with @value{GDBN}. With such a
21457 target, if the remote program is unstripped, the only command you need is
21458 @code{target remote} (or @code{target extended-remote}).
21460 If the remote program is stripped, or the target does not support remote
21461 program file access, start up @value{GDBN} using the name of the local
21462 unstripped copy of your program as the first argument, or use the
21463 @code{file} command. Use @code{set sysroot} to specify the location (on
21464 the host) of target libraries (unless your @value{GDBN} was compiled with
21465 the correct sysroot using @code{--with-sysroot}). Alternatively, you
21466 may use @code{set solib-search-path} to specify how @value{GDBN} locates
21469 The symbol file and target libraries must exactly match the executable
21470 and libraries on the target, with one exception: the files on the host
21471 system should not be stripped, even if the files on the target system
21472 are. Mismatched or missing files will lead to confusing results
21473 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
21474 files may also prevent @code{gdbserver} from debugging multi-threaded
21477 @subsection Remote Connection Commands
21478 @cindex remote connection commands
21479 @value{GDBN} can communicate with the target over a serial line, a
21480 local Unix domain socket, or
21481 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
21482 each case, @value{GDBN} uses the same protocol for debugging your
21483 program; only the medium carrying the debugging packets varies. The
21484 @code{target remote} and @code{target extended-remote} commands
21485 establish a connection to the target. Both commands accept the same
21486 arguments, which indicate the medium to use:
21490 @item target remote @var{serial-device}
21491 @itemx target extended-remote @var{serial-device}
21492 @cindex serial line, @code{target remote}
21493 Use @var{serial-device} to communicate with the target. For example,
21494 to use a serial line connected to the device named @file{/dev/ttyb}:
21497 target remote /dev/ttyb
21500 If you're using a serial line, you may want to give @value{GDBN} the
21501 @samp{--baud} option, or use the @code{set serial baud} command
21502 (@pxref{Remote Configuration, set serial baud}) before the
21503 @code{target} command.
21505 @item target remote @var{local-socket}
21506 @itemx target extended-remote @var{local-socket}
21507 @cindex local socket, @code{target remote}
21508 @cindex Unix domain socket
21509 Use @var{local-socket} to communicate with the target. For example,
21510 to use a local Unix domain socket bound to the file system entry @file{/tmp/gdb-socket0}:
21513 target remote /tmp/gdb-socket0
21516 Note that this command has the same form as the command to connect
21517 to a serial line. @value{GDBN} will automatically determine which
21518 kind of file you have specified and will make the appropriate kind
21520 This feature is not available if the host system does not support
21521 Unix domain sockets.
21523 @item target remote @code{@var{host}:@var{port}}
21524 @itemx target remote @code{@var{[host]}:@var{port}}
21525 @itemx target remote @code{tcp:@var{host}:@var{port}}
21526 @itemx target remote @code{tcp:@var{[host]}:@var{port}}
21527 @itemx target remote @code{tcp4:@var{host}:@var{port}}
21528 @itemx target remote @code{tcp6:@var{host}:@var{port}}
21529 @itemx target remote @code{tcp6:@var{[host]}:@var{port}}
21530 @itemx target extended-remote @code{@var{host}:@var{port}}
21531 @itemx target extended-remote @code{@var{[host]}:@var{port}}
21532 @itemx target extended-remote @code{tcp:@var{host}:@var{port}}
21533 @itemx target extended-remote @code{tcp:@var{[host]}:@var{port}}
21534 @itemx target extended-remote @code{tcp4:@var{host}:@var{port}}
21535 @itemx target extended-remote @code{tcp6:@var{host}:@var{port}}
21536 @itemx target extended-remote @code{tcp6:@var{[host]}:@var{port}}
21537 @cindex @acronym{TCP} port, @code{target remote}
21538 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
21539 The @var{host} may be either a host name, a numeric @acronym{IPv4}
21540 address, or a numeric @acronym{IPv6} address (with or without the
21541 square brackets to separate the address from the port); @var{port}
21542 must be a decimal number. The @var{host} could be the target machine
21543 itself, if it is directly connected to the net, or it might be a
21544 terminal server which in turn has a serial line to the target.
21546 For example, to connect to port 2828 on a terminal server named
21550 target remote manyfarms:2828
21553 To connect to port 2828 on a terminal server whose address is
21554 @code{2001:0db8:85a3:0000:0000:8a2e:0370:7334}, you can either use the
21555 square bracket syntax:
21558 target remote [2001:0db8:85a3:0000:0000:8a2e:0370:7334]:2828
21562 or explicitly specify the @acronym{IPv6} protocol:
21565 target remote tcp6:2001:0db8:85a3:0000:0000:8a2e:0370:7334:2828
21568 This last example may be confusing to the reader, because there is no
21569 visible separation between the hostname and the port number.
21570 Therefore, we recommend the user to provide @acronym{IPv6} addresses
21571 using square brackets for clarity. However, it is important to
21572 mention that for @value{GDBN} there is no ambiguity: the number after
21573 the last colon is considered to be the port number.
21575 If your remote target is actually running on the same machine as your
21576 debugger session (e.g.@: a simulator for your target running on the
21577 same host), you can omit the hostname. For example, to connect to
21578 port 1234 on your local machine:
21581 target remote :1234
21585 Note that the colon is still required here.
21587 @item target remote @code{udp:@var{host}:@var{port}}
21588 @itemx target remote @code{udp:@var{[host]}:@var{port}}
21589 @itemx target remote @code{udp4:@var{host}:@var{port}}
21590 @itemx target remote @code{udp6:@var{[host]}:@var{port}}
21591 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
21592 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
21593 @itemx target extended-remote @code{udp:@var{[host]}:@var{port}}
21594 @itemx target extended-remote @code{udp4:@var{host}:@var{port}}
21595 @itemx target extended-remote @code{udp6:@var{host}:@var{port}}
21596 @itemx target extended-remote @code{udp6:@var{[host]}:@var{port}}
21597 @cindex @acronym{UDP} port, @code{target remote}
21598 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
21599 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
21602 target remote udp:manyfarms:2828
21605 When using a @acronym{UDP} connection for remote debugging, you should
21606 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
21607 can silently drop packets on busy or unreliable networks, which will
21608 cause havoc with your debugging session.
21610 @item target remote | @var{command}
21611 @itemx target extended-remote | @var{command}
21612 @cindex pipe, @code{target remote} to
21613 Run @var{command} in the background and communicate with it using a
21614 pipe. The @var{command} is a shell command, to be parsed and expanded
21615 by the system's command shell, @code{/bin/sh}; it should expect remote
21616 protocol packets on its standard input, and send replies on its
21617 standard output. You could use this to run a stand-alone simulator
21618 that speaks the remote debugging protocol, to make net connections
21619 using programs like @code{ssh}, or for other similar tricks.
21621 If @var{command} closes its standard output (perhaps by exiting),
21622 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
21623 program has already exited, this will have no effect.)
21627 @cindex interrupting remote programs
21628 @cindex remote programs, interrupting
21629 Whenever @value{GDBN} is waiting for the remote program, if you type the
21630 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
21631 program. This may or may not succeed, depending in part on the hardware
21632 and the serial drivers the remote system uses. If you type the
21633 interrupt character once again, @value{GDBN} displays this prompt:
21636 Interrupted while waiting for the program.
21637 Give up (and stop debugging it)? (y or n)
21640 In @code{target remote} mode, if you type @kbd{y}, @value{GDBN} abandons
21641 the remote debugging session. (If you decide you want to try again later,
21642 you can use @kbd{target remote} again to connect once more.) If you type
21643 @kbd{n}, @value{GDBN} goes back to waiting.
21645 In @code{target extended-remote} mode, typing @kbd{n} will leave
21646 @value{GDBN} connected to the target.
21649 @kindex detach (remote)
21651 When you have finished debugging the remote program, you can use the
21652 @code{detach} command to release it from @value{GDBN} control.
21653 Detaching from the target normally resumes its execution, but the results
21654 will depend on your particular remote stub. After the @code{detach}
21655 command in @code{target remote} mode, @value{GDBN} is free to connect to
21656 another target. In @code{target extended-remote} mode, @value{GDBN} is
21657 still connected to the target.
21661 The @code{disconnect} command closes the connection to the target, and
21662 the target is generally not resumed. It will wait for @value{GDBN}
21663 (this instance or another one) to connect and continue debugging. After
21664 the @code{disconnect} command, @value{GDBN} is again free to connect to
21667 @cindex send command to remote monitor
21668 @cindex extend @value{GDBN} for remote targets
21669 @cindex add new commands for external monitor
21671 @item monitor @var{cmd}
21672 This command allows you to send arbitrary commands directly to the
21673 remote monitor. Since @value{GDBN} doesn't care about the commands it
21674 sends like this, this command is the way to extend @value{GDBN}---you
21675 can add new commands that only the external monitor will understand
21679 @node File Transfer
21680 @section Sending files to a remote system
21681 @cindex remote target, file transfer
21682 @cindex file transfer
21683 @cindex sending files to remote systems
21685 Some remote targets offer the ability to transfer files over the same
21686 connection used to communicate with @value{GDBN}. This is convenient
21687 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
21688 running @code{gdbserver} over a network interface. For other targets,
21689 e.g.@: embedded devices with only a single serial port, this may be
21690 the only way to upload or download files.
21692 Not all remote targets support these commands.
21696 @item remote put @var{hostfile} @var{targetfile}
21697 Copy file @var{hostfile} from the host system (the machine running
21698 @value{GDBN}) to @var{targetfile} on the target system.
21701 @item remote get @var{targetfile} @var{hostfile}
21702 Copy file @var{targetfile} from the target system to @var{hostfile}
21703 on the host system.
21705 @kindex remote delete
21706 @item remote delete @var{targetfile}
21707 Delete @var{targetfile} from the target system.
21712 @section Using the @code{gdbserver} Program
21715 @cindex remote connection without stubs
21716 @code{gdbserver} is a control program for Unix-like systems, which
21717 allows you to connect your program with a remote @value{GDBN} via
21718 @code{target remote} or @code{target extended-remote}---but without
21719 linking in the usual debugging stub.
21721 @code{gdbserver} is not a complete replacement for the debugging stubs,
21722 because it requires essentially the same operating-system facilities
21723 that @value{GDBN} itself does. In fact, a system that can run
21724 @code{gdbserver} to connect to a remote @value{GDBN} could also run
21725 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
21726 because it is a much smaller program than @value{GDBN} itself. It is
21727 also easier to port than all of @value{GDBN}, so you may be able to get
21728 started more quickly on a new system by using @code{gdbserver}.
21729 Finally, if you develop code for real-time systems, you may find that
21730 the tradeoffs involved in real-time operation make it more convenient to
21731 do as much development work as possible on another system, for example
21732 by cross-compiling. You can use @code{gdbserver} to make a similar
21733 choice for debugging.
21735 @value{GDBN} and @code{gdbserver} communicate via either a serial line
21736 or a TCP connection, using the standard @value{GDBN} remote serial
21740 @emph{Warning:} @code{gdbserver} does not have any built-in security.
21741 Do not run @code{gdbserver} connected to any public network; a
21742 @value{GDBN} connection to @code{gdbserver} provides access to the
21743 target system with the same privileges as the user running
21747 @anchor{Running gdbserver}
21748 @subsection Running @code{gdbserver}
21749 @cindex arguments, to @code{gdbserver}
21750 @cindex @code{gdbserver}, command-line arguments
21752 Run @code{gdbserver} on the target system. You need a copy of the
21753 program you want to debug, including any libraries it requires.
21754 @code{gdbserver} does not need your program's symbol table, so you can
21755 strip the program if necessary to save space. @value{GDBN} on the host
21756 system does all the symbol handling.
21758 To use the server, you must tell it how to communicate with @value{GDBN};
21759 the name of your program; and the arguments for your program. The usual
21763 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
21766 @var{comm} is either a device name (to use a serial line), or a TCP
21767 hostname and portnumber, or @code{-} or @code{stdio} to use
21768 stdin/stdout of @code{gdbserver}.
21769 For example, to debug Emacs with the argument
21770 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
21774 target> gdbserver /dev/com1 emacs foo.txt
21777 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
21780 To use a TCP connection instead of a serial line:
21783 target> gdbserver host:2345 emacs foo.txt
21786 The only difference from the previous example is the first argument,
21787 specifying that you are communicating with the host @value{GDBN} via
21788 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
21789 expect a TCP connection from machine @samp{host} to local TCP port 2345.
21790 (Currently, the @samp{host} part is ignored.) You can choose any number
21791 you want for the port number as long as it does not conflict with any
21792 TCP ports already in use on the target system (for example, @code{23} is
21793 reserved for @code{telnet}).@footnote{If you choose a port number that
21794 conflicts with another service, @code{gdbserver} prints an error message
21795 and exits.} You must use the same port number with the host @value{GDBN}
21796 @code{target remote} command.
21798 The @code{stdio} connection is useful when starting @code{gdbserver}
21802 (gdb) target remote | ssh -T hostname gdbserver - hello
21805 The @samp{-T} option to ssh is provided because we don't need a remote pty,
21806 and we don't want escape-character handling. Ssh does this by default when
21807 a command is provided, the flag is provided to make it explicit.
21808 You could elide it if you want to.
21810 Programs started with stdio-connected gdbserver have @file{/dev/null} for
21811 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
21812 display through a pipe connected to gdbserver.
21813 Both @code{stdout} and @code{stderr} use the same pipe.
21815 @anchor{Attaching to a program}
21816 @subsubsection Attaching to a Running Program
21817 @cindex attach to a program, @code{gdbserver}
21818 @cindex @option{--attach}, @code{gdbserver} option
21820 On some targets, @code{gdbserver} can also attach to running programs.
21821 This is accomplished via the @code{--attach} argument. The syntax is:
21824 target> gdbserver --attach @var{comm} @var{pid}
21827 @var{pid} is the process ID of a currently running process. It isn't
21828 necessary to point @code{gdbserver} at a binary for the running process.
21830 In @code{target extended-remote} mode, you can also attach using the
21831 @value{GDBN} attach command
21832 (@pxref{Attaching in Types of Remote Connections}).
21835 You can debug processes by name instead of process ID if your target has the
21836 @code{pidof} utility:
21839 target> gdbserver --attach @var{comm} `pidof @var{program}`
21842 In case more than one copy of @var{program} is running, or @var{program}
21843 has multiple threads, most versions of @code{pidof} support the
21844 @code{-s} option to only return the first process ID.
21846 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
21848 This section applies only when @code{gdbserver} is run to listen on a TCP
21851 @code{gdbserver} normally terminates after all of its debugged processes have
21852 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
21853 extended-remote}, @code{gdbserver} stays running even with no processes left.
21854 @value{GDBN} normally terminates the spawned debugged process on its exit,
21855 which normally also terminates @code{gdbserver} in the @kbd{target remote}
21856 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
21857 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
21858 stays running even in the @kbd{target remote} mode.
21860 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
21861 Such reconnecting is useful for features like @ref{disconnected tracing}. For
21862 completeness, at most one @value{GDBN} can be connected at a time.
21864 @cindex @option{--once}, @code{gdbserver} option
21865 By default, @code{gdbserver} keeps the listening TCP port open, so that
21866 subsequent connections are possible. However, if you start @code{gdbserver}
21867 with the @option{--once} option, it will stop listening for any further
21868 connection attempts after connecting to the first @value{GDBN} session. This
21869 means no further connections to @code{gdbserver} will be possible after the
21870 first one. It also means @code{gdbserver} will terminate after the first
21871 connection with remote @value{GDBN} has closed, even for unexpectedly closed
21872 connections and even in the @kbd{target extended-remote} mode. The
21873 @option{--once} option allows reusing the same port number for connecting to
21874 multiple instances of @code{gdbserver} running on the same host, since each
21875 instance closes its port after the first connection.
21877 @anchor{Other Command-Line Arguments for gdbserver}
21878 @subsubsection Other Command-Line Arguments for @code{gdbserver}
21880 You can use the @option{--multi} option to start @code{gdbserver} without
21881 specifying a program to debug or a process to attach to. Then you can
21882 attach in @code{target extended-remote} mode and run or attach to a
21883 program. For more information,
21884 @pxref{--multi Option in Types of Remote Connnections}.
21886 @cindex @option{--debug}, @code{gdbserver} option
21887 The @option{--debug} option tells @code{gdbserver} to display extra
21888 status information about the debugging process.
21889 @cindex @option{--remote-debug}, @code{gdbserver} option
21890 The @option{--remote-debug} option tells @code{gdbserver} to display
21891 remote protocol debug output.
21892 @cindex @option{--debug-file}, @code{gdbserver} option
21893 @cindex @code{gdbserver}, send all debug output to a single file
21894 The @option{--debug-file=@var{filename}} option tells @code{gdbserver} to
21895 write any debug output to the given @var{filename}. These options are intended
21896 for @code{gdbserver} development and for bug reports to the developers.
21898 @cindex @option{--debug-format}, @code{gdbserver} option
21899 The @option{--debug-format=option1[,option2,...]} option tells
21900 @code{gdbserver} to include additional information in each output.
21901 Possible options are:
21905 Turn off all extra information in debugging output.
21907 Turn on all extra information in debugging output.
21909 Include a timestamp in each line of debugging output.
21912 Options are processed in order. Thus, for example, if @option{none}
21913 appears last then no additional information is added to debugging output.
21915 @cindex @option{--wrapper}, @code{gdbserver} option
21916 The @option{--wrapper} option specifies a wrapper to launch programs
21917 for debugging. The option should be followed by the name of the
21918 wrapper, then any command-line arguments to pass to the wrapper, then
21919 @kbd{--} indicating the end of the wrapper arguments.
21921 @code{gdbserver} runs the specified wrapper program with a combined
21922 command line including the wrapper arguments, then the name of the
21923 program to debug, then any arguments to the program. The wrapper
21924 runs until it executes your program, and then @value{GDBN} gains control.
21926 You can use any program that eventually calls @code{execve} with
21927 its arguments as a wrapper. Several standard Unix utilities do
21928 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
21929 with @code{exec "$@@"} will also work.
21931 For example, you can use @code{env} to pass an environment variable to
21932 the debugged program, without setting the variable in @code{gdbserver}'s
21936 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
21939 @cindex @option{--selftest}
21940 The @option{--selftest} option runs the self tests in @code{gdbserver}:
21943 $ gdbserver --selftest
21944 Ran 2 unit tests, 0 failed
21947 These tests are disabled in release.
21948 @subsection Connecting to @code{gdbserver}
21950 The basic procedure for connecting to the remote target is:
21954 Run @value{GDBN} on the host system.
21957 Make sure you have the necessary symbol files
21958 (@pxref{Host and target files}).
21959 Load symbols for your application using the @code{file} command before you
21960 connect. Use @code{set sysroot} to locate target libraries (unless your
21961 @value{GDBN} was compiled with the correct sysroot using
21962 @code{--with-sysroot}).
21965 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
21966 For TCP connections, you must start up @code{gdbserver} prior to using
21967 the @code{target} command. Otherwise you may get an error whose
21968 text depends on the host system, but which usually looks something like
21969 @samp{Connection refused}. Don't use the @code{load}
21970 command in @value{GDBN} when using @code{target remote} mode, since the
21971 program is already on the target.
21975 @anchor{Monitor Commands for gdbserver}
21976 @subsection Monitor Commands for @code{gdbserver}
21977 @cindex monitor commands, for @code{gdbserver}
21979 During a @value{GDBN} session using @code{gdbserver}, you can use the
21980 @code{monitor} command to send special requests to @code{gdbserver}.
21981 Here are the available commands.
21985 List the available monitor commands.
21987 @item monitor set debug 0
21988 @itemx monitor set debug 1
21989 Disable or enable general debugging messages.
21991 @item monitor set remote-debug 0
21992 @itemx monitor set remote-debug 1
21993 Disable or enable specific debugging messages associated with the remote
21994 protocol (@pxref{Remote Protocol}).
21996 @item monitor set debug-file filename
21997 @itemx monitor set debug-file
21998 Send any debug output to the given file, or to stderr.
22000 @item monitor set debug-format option1@r{[},option2,...@r{]}
22001 Specify additional text to add to debugging messages.
22002 Possible options are:
22006 Turn off all extra information in debugging output.
22008 Turn on all extra information in debugging output.
22010 Include a timestamp in each line of debugging output.
22013 Options are processed in order. Thus, for example, if @option{none}
22014 appears last then no additional information is added to debugging output.
22016 @item monitor set libthread-db-search-path [PATH]
22017 @cindex gdbserver, search path for @code{libthread_db}
22018 When this command is issued, @var{path} is a colon-separated list of
22019 directories to search for @code{libthread_db} (@pxref{Threads,,set
22020 libthread-db-search-path}). If you omit @var{path},
22021 @samp{libthread-db-search-path} will be reset to its default value.
22023 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
22024 not supported in @code{gdbserver}.
22027 Tell gdbserver to exit immediately. This command should be followed by
22028 @code{disconnect} to close the debugging session. @code{gdbserver} will
22029 detach from any attached processes and kill any processes it created.
22030 Use @code{monitor exit} to terminate @code{gdbserver} at the end
22031 of a multi-process mode debug session.
22035 @subsection Tracepoints support in @code{gdbserver}
22036 @cindex tracepoints support in @code{gdbserver}
22038 On some targets, @code{gdbserver} supports tracepoints, fast
22039 tracepoints and static tracepoints.
22041 For fast or static tracepoints to work, a special library called the
22042 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
22043 This library is built and distributed as an integral part of
22044 @code{gdbserver}. In addition, support for static tracepoints
22045 requires building the in-process agent library with static tracepoints
22046 support. At present, the UST (LTTng Userspace Tracer,
22047 @url{http://lttng.org/ust}) tracing engine is supported. This support
22048 is automatically available if UST development headers are found in the
22049 standard include path when @code{gdbserver} is built, or if
22050 @code{gdbserver} was explicitly configured using @option{--with-ust}
22051 to point at such headers. You can explicitly disable the support
22052 using @option{--with-ust=no}.
22054 There are several ways to load the in-process agent in your program:
22057 @item Specifying it as dependency at link time
22059 You can link your program dynamically with the in-process agent
22060 library. On most systems, this is accomplished by adding
22061 @code{-linproctrace} to the link command.
22063 @item Using the system's preloading mechanisms
22065 You can force loading the in-process agent at startup time by using
22066 your system's support for preloading shared libraries. Many Unixes
22067 support the concept of preloading user defined libraries. In most
22068 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
22069 in the environment. See also the description of @code{gdbserver}'s
22070 @option{--wrapper} command line option.
22072 @item Using @value{GDBN} to force loading the agent at run time
22074 On some systems, you can force the inferior to load a shared library,
22075 by calling a dynamic loader function in the inferior that takes care
22076 of dynamically looking up and loading a shared library. On most Unix
22077 systems, the function is @code{dlopen}. You'll use the @code{call}
22078 command for that. For example:
22081 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
22084 Note that on most Unix systems, for the @code{dlopen} function to be
22085 available, the program needs to be linked with @code{-ldl}.
22088 On systems that have a userspace dynamic loader, like most Unix
22089 systems, when you connect to @code{gdbserver} using @code{target
22090 remote}, you'll find that the program is stopped at the dynamic
22091 loader's entry point, and no shared library has been loaded in the
22092 program's address space yet, including the in-process agent. In that
22093 case, before being able to use any of the fast or static tracepoints
22094 features, you need to let the loader run and load the shared
22095 libraries. The simplest way to do that is to run the program to the
22096 main procedure. E.g., if debugging a C or C@t{++} program, start
22097 @code{gdbserver} like so:
22100 $ gdbserver :9999 myprogram
22103 Start GDB and connect to @code{gdbserver} like so, and run to main:
22107 (@value{GDBP}) target remote myhost:9999
22108 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
22109 (@value{GDBP}) b main
22110 (@value{GDBP}) continue
22113 The in-process tracing agent library should now be loaded into the
22114 process; you can confirm it with the @code{info sharedlibrary}
22115 command, which will list @file{libinproctrace.so} as loaded in the
22116 process. You are now ready to install fast tracepoints, list static
22117 tracepoint markers, probe static tracepoints markers, and start
22120 @node Remote Configuration
22121 @section Remote Configuration
22124 @kindex show remote
22125 This section documents the configuration options available when
22126 debugging remote programs. For the options related to the File I/O
22127 extensions of the remote protocol, see @ref{system,
22128 system-call-allowed}.
22131 @item set remoteaddresssize @var{bits}
22132 @cindex address size for remote targets
22133 @cindex bits in remote address
22134 Set the maximum size of address in a memory packet to the specified
22135 number of bits. @value{GDBN} will mask off the address bits above
22136 that number, when it passes addresses to the remote target. The
22137 default value is the number of bits in the target's address.
22139 @item show remoteaddresssize
22140 Show the current value of remote address size in bits.
22142 @item set serial baud @var{n}
22143 @cindex baud rate for remote targets
22144 Set the baud rate for the remote serial I/O to @var{n} baud. The
22145 value is used to set the speed of the serial port used for debugging
22148 @item show serial baud
22149 Show the current speed of the remote connection.
22151 @item set serial parity @var{parity}
22152 Set the parity for the remote serial I/O. Supported values of @var{parity} are:
22153 @code{even}, @code{none}, and @code{odd}. The default is @code{none}.
22155 @item show serial parity
22156 Show the current parity of the serial port.
22158 @item set remotebreak
22159 @cindex interrupt remote programs
22160 @cindex BREAK signal instead of Ctrl-C
22161 @anchor{set remotebreak}
22162 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
22163 when you type @kbd{Ctrl-c} to interrupt the program running
22164 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
22165 character instead. The default is off, since most remote systems
22166 expect to see @samp{Ctrl-C} as the interrupt signal.
22168 @item show remotebreak
22169 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
22170 interrupt the remote program.
22172 @item set remoteflow on
22173 @itemx set remoteflow off
22174 @kindex set remoteflow
22175 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
22176 on the serial port used to communicate to the remote target.
22178 @item show remoteflow
22179 @kindex show remoteflow
22180 Show the current setting of hardware flow control.
22182 @item set remotelogbase @var{base}
22183 Set the base (a.k.a.@: radix) of logging serial protocol
22184 communications to @var{base}. Supported values of @var{base} are:
22185 @code{ascii}, @code{octal}, and @code{hex}. The default is
22188 @item show remotelogbase
22189 Show the current setting of the radix for logging remote serial
22192 @item set remotelogfile @var{file}
22193 @cindex record serial communications on file
22194 Record remote serial communications on the named @var{file}. The
22195 default is not to record at all.
22197 @item show remotelogfile
22198 Show the current setting of the file name on which to record the
22199 serial communications.
22201 @item set remotetimeout @var{num}
22202 @cindex timeout for serial communications
22203 @cindex remote timeout
22204 Set the timeout limit to wait for the remote target to respond to
22205 @var{num} seconds. The default is 2 seconds.
22207 @item show remotetimeout
22208 Show the current number of seconds to wait for the remote target
22211 @cindex limit hardware breakpoints and watchpoints
22212 @cindex remote target, limit break- and watchpoints
22213 @anchor{set remote hardware-watchpoint-limit}
22214 @anchor{set remote hardware-breakpoint-limit}
22215 @item set remote hardware-watchpoint-limit @var{limit}
22216 @itemx set remote hardware-breakpoint-limit @var{limit}
22217 Restrict @value{GDBN} to using @var{limit} remote hardware watchpoints
22218 or breakpoints. The @var{limit} can be set to 0 to disable hardware
22219 watchpoints or breakpoints, and @code{unlimited} for unlimited
22220 watchpoints or breakpoints.
22222 @item show remote hardware-watchpoint-limit
22223 @itemx show remote hardware-breakpoint-limit
22224 Show the current limit for the number of hardware watchpoints or
22225 breakpoints that @value{GDBN} can use.
22227 @cindex limit hardware watchpoints length
22228 @cindex remote target, limit watchpoints length
22229 @anchor{set remote hardware-watchpoint-length-limit}
22230 @item set remote hardware-watchpoint-length-limit @var{limit}
22231 Restrict @value{GDBN} to using @var{limit} bytes for the maximum
22232 length of a remote hardware watchpoint. A @var{limit} of 0 disables
22233 hardware watchpoints and @code{unlimited} allows watchpoints of any
22236 @item show remote hardware-watchpoint-length-limit
22237 Show the current limit (in bytes) of the maximum length of
22238 a remote hardware watchpoint.
22240 @item set remote exec-file @var{filename}
22241 @itemx show remote exec-file
22242 @anchor{set remote exec-file}
22243 @cindex executable file, for remote target
22244 Select the file used for @code{run} with @code{target
22245 extended-remote}. This should be set to a filename valid on the
22246 target system. If it is not set, the target will use a default
22247 filename (e.g.@: the last program run).
22249 @item set remote interrupt-sequence
22250 @cindex interrupt remote programs
22251 @cindex select Ctrl-C, BREAK or BREAK-g
22252 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
22253 @samp{BREAK-g} as the
22254 sequence to the remote target in order to interrupt the execution.
22255 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
22256 is high level of serial line for some certain time.
22257 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
22258 It is @code{BREAK} signal followed by character @code{g}.
22260 @item show interrupt-sequence
22261 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
22262 is sent by @value{GDBN} to interrupt the remote program.
22263 @code{BREAK-g} is BREAK signal followed by @code{g} and
22264 also known as Magic SysRq g.
22266 @item set remote interrupt-on-connect
22267 @cindex send interrupt-sequence on start
22268 Specify whether interrupt-sequence is sent to remote target when
22269 @value{GDBN} connects to it. This is mostly needed when you debug
22270 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
22271 which is known as Magic SysRq g in order to connect @value{GDBN}.
22273 @item show interrupt-on-connect
22274 Show whether interrupt-sequence is sent
22275 to remote target when @value{GDBN} connects to it.
22279 @item set tcp auto-retry on
22280 @cindex auto-retry, for remote TCP target
22281 Enable auto-retry for remote TCP connections. This is useful if the remote
22282 debugging agent is launched in parallel with @value{GDBN}; there is a race
22283 condition because the agent may not become ready to accept the connection
22284 before @value{GDBN} attempts to connect. When auto-retry is
22285 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
22286 to establish the connection using the timeout specified by
22287 @code{set tcp connect-timeout}.
22289 @item set tcp auto-retry off
22290 Do not auto-retry failed TCP connections.
22292 @item show tcp auto-retry
22293 Show the current auto-retry setting.
22295 @item set tcp connect-timeout @var{seconds}
22296 @itemx set tcp connect-timeout unlimited
22297 @cindex connection timeout, for remote TCP target
22298 @cindex timeout, for remote target connection
22299 Set the timeout for establishing a TCP connection to the remote target to
22300 @var{seconds}. The timeout affects both polling to retry failed connections
22301 (enabled by @code{set tcp auto-retry on}) and waiting for connections
22302 that are merely slow to complete, and represents an approximate cumulative
22303 value. If @var{seconds} is @code{unlimited}, there is no timeout and
22304 @value{GDBN} will keep attempting to establish a connection forever,
22305 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
22307 @item show tcp connect-timeout
22308 Show the current connection timeout setting.
22311 @cindex remote packets, enabling and disabling
22312 The @value{GDBN} remote protocol autodetects the packets supported by
22313 your debugging stub. If you need to override the autodetection, you
22314 can use these commands to enable or disable individual packets. Each
22315 packet can be set to @samp{on} (the remote target supports this
22316 packet), @samp{off} (the remote target does not support this packet),
22317 or @samp{auto} (detect remote target support for this packet). They
22318 all default to @samp{auto}. For more information about each packet,
22319 see @ref{Remote Protocol}.
22321 During normal use, you should not have to use any of these commands.
22322 If you do, that may be a bug in your remote debugging stub, or a bug
22323 in @value{GDBN}. You may want to report the problem to the
22324 @value{GDBN} developers.
22326 For each packet @var{name}, the command to enable or disable the
22327 packet is @code{set remote @var{name}-packet}. The available settings
22330 @multitable @columnfractions 0.28 0.32 0.25
22333 @tab Related Features
22335 @item @code{fetch-register}
22337 @tab @code{info registers}
22339 @item @code{set-register}
22343 @item @code{binary-download}
22345 @tab @code{load}, @code{set}
22347 @item @code{read-aux-vector}
22348 @tab @code{qXfer:auxv:read}
22349 @tab @code{info auxv}
22351 @item @code{symbol-lookup}
22352 @tab @code{qSymbol}
22353 @tab Detecting multiple threads
22355 @item @code{attach}
22356 @tab @code{vAttach}
22359 @item @code{verbose-resume}
22361 @tab Stepping or resuming multiple threads
22367 @item @code{software-breakpoint}
22371 @item @code{hardware-breakpoint}
22375 @item @code{write-watchpoint}
22379 @item @code{read-watchpoint}
22383 @item @code{access-watchpoint}
22387 @item @code{pid-to-exec-file}
22388 @tab @code{qXfer:exec-file:read}
22389 @tab @code{attach}, @code{run}
22391 @item @code{target-features}
22392 @tab @code{qXfer:features:read}
22393 @tab @code{set architecture}
22395 @item @code{library-info}
22396 @tab @code{qXfer:libraries:read}
22397 @tab @code{info sharedlibrary}
22399 @item @code{memory-map}
22400 @tab @code{qXfer:memory-map:read}
22401 @tab @code{info mem}
22403 @item @code{read-sdata-object}
22404 @tab @code{qXfer:sdata:read}
22405 @tab @code{print $_sdata}
22407 @item @code{read-spu-object}
22408 @tab @code{qXfer:spu:read}
22409 @tab @code{info spu}
22411 @item @code{write-spu-object}
22412 @tab @code{qXfer:spu:write}
22413 @tab @code{info spu}
22415 @item @code{read-siginfo-object}
22416 @tab @code{qXfer:siginfo:read}
22417 @tab @code{print $_siginfo}
22419 @item @code{write-siginfo-object}
22420 @tab @code{qXfer:siginfo:write}
22421 @tab @code{set $_siginfo}
22423 @item @code{threads}
22424 @tab @code{qXfer:threads:read}
22425 @tab @code{info threads}
22427 @item @code{get-thread-local-@*storage-address}
22428 @tab @code{qGetTLSAddr}
22429 @tab Displaying @code{__thread} variables
22431 @item @code{get-thread-information-block-address}
22432 @tab @code{qGetTIBAddr}
22433 @tab Display MS-Windows Thread Information Block.
22435 @item @code{search-memory}
22436 @tab @code{qSearch:memory}
22439 @item @code{supported-packets}
22440 @tab @code{qSupported}
22441 @tab Remote communications parameters
22443 @item @code{catch-syscalls}
22444 @tab @code{QCatchSyscalls}
22445 @tab @code{catch syscall}
22447 @item @code{pass-signals}
22448 @tab @code{QPassSignals}
22449 @tab @code{handle @var{signal}}
22451 @item @code{program-signals}
22452 @tab @code{QProgramSignals}
22453 @tab @code{handle @var{signal}}
22455 @item @code{hostio-close-packet}
22456 @tab @code{vFile:close}
22457 @tab @code{remote get}, @code{remote put}
22459 @item @code{hostio-open-packet}
22460 @tab @code{vFile:open}
22461 @tab @code{remote get}, @code{remote put}
22463 @item @code{hostio-pread-packet}
22464 @tab @code{vFile:pread}
22465 @tab @code{remote get}, @code{remote put}
22467 @item @code{hostio-pwrite-packet}
22468 @tab @code{vFile:pwrite}
22469 @tab @code{remote get}, @code{remote put}
22471 @item @code{hostio-unlink-packet}
22472 @tab @code{vFile:unlink}
22473 @tab @code{remote delete}
22475 @item @code{hostio-readlink-packet}
22476 @tab @code{vFile:readlink}
22479 @item @code{hostio-fstat-packet}
22480 @tab @code{vFile:fstat}
22483 @item @code{hostio-setfs-packet}
22484 @tab @code{vFile:setfs}
22487 @item @code{noack-packet}
22488 @tab @code{QStartNoAckMode}
22489 @tab Packet acknowledgment
22491 @item @code{osdata}
22492 @tab @code{qXfer:osdata:read}
22493 @tab @code{info os}
22495 @item @code{query-attached}
22496 @tab @code{qAttached}
22497 @tab Querying remote process attach state.
22499 @item @code{trace-buffer-size}
22500 @tab @code{QTBuffer:size}
22501 @tab @code{set trace-buffer-size}
22503 @item @code{trace-status}
22504 @tab @code{qTStatus}
22505 @tab @code{tstatus}
22507 @item @code{traceframe-info}
22508 @tab @code{qXfer:traceframe-info:read}
22509 @tab Traceframe info
22511 @item @code{install-in-trace}
22512 @tab @code{InstallInTrace}
22513 @tab Install tracepoint in tracing
22515 @item @code{disable-randomization}
22516 @tab @code{QDisableRandomization}
22517 @tab @code{set disable-randomization}
22519 @item @code{startup-with-shell}
22520 @tab @code{QStartupWithShell}
22521 @tab @code{set startup-with-shell}
22523 @item @code{environment-hex-encoded}
22524 @tab @code{QEnvironmentHexEncoded}
22525 @tab @code{set environment}
22527 @item @code{environment-unset}
22528 @tab @code{QEnvironmentUnset}
22529 @tab @code{unset environment}
22531 @item @code{environment-reset}
22532 @tab @code{QEnvironmentReset}
22533 @tab @code{Reset the inferior environment (i.e., unset user-set variables)}
22535 @item @code{set-working-dir}
22536 @tab @code{QSetWorkingDir}
22537 @tab @code{set cwd}
22539 @item @code{conditional-breakpoints-packet}
22540 @tab @code{Z0 and Z1}
22541 @tab @code{Support for target-side breakpoint condition evaluation}
22543 @item @code{multiprocess-extensions}
22544 @tab @code{multiprocess extensions}
22545 @tab Debug multiple processes and remote process PID awareness
22547 @item @code{swbreak-feature}
22548 @tab @code{swbreak stop reason}
22551 @item @code{hwbreak-feature}
22552 @tab @code{hwbreak stop reason}
22555 @item @code{fork-event-feature}
22556 @tab @code{fork stop reason}
22559 @item @code{vfork-event-feature}
22560 @tab @code{vfork stop reason}
22563 @item @code{exec-event-feature}
22564 @tab @code{exec stop reason}
22567 @item @code{thread-events}
22568 @tab @code{QThreadEvents}
22569 @tab Tracking thread lifetime.
22571 @item @code{no-resumed-stop-reply}
22572 @tab @code{no resumed thread left stop reply}
22573 @tab Tracking thread lifetime.
22578 @section Implementing a Remote Stub
22580 @cindex debugging stub, example
22581 @cindex remote stub, example
22582 @cindex stub example, remote debugging
22583 The stub files provided with @value{GDBN} implement the target side of the
22584 communication protocol, and the @value{GDBN} side is implemented in the
22585 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
22586 these subroutines to communicate, and ignore the details. (If you're
22587 implementing your own stub file, you can still ignore the details: start
22588 with one of the existing stub files. @file{sparc-stub.c} is the best
22589 organized, and therefore the easiest to read.)
22591 @cindex remote serial debugging, overview
22592 To debug a program running on another machine (the debugging
22593 @dfn{target} machine), you must first arrange for all the usual
22594 prerequisites for the program to run by itself. For example, for a C
22599 A startup routine to set up the C runtime environment; these usually
22600 have a name like @file{crt0}. The startup routine may be supplied by
22601 your hardware supplier, or you may have to write your own.
22604 A C subroutine library to support your program's
22605 subroutine calls, notably managing input and output.
22608 A way of getting your program to the other machine---for example, a
22609 download program. These are often supplied by the hardware
22610 manufacturer, but you may have to write your own from hardware
22614 The next step is to arrange for your program to use a serial port to
22615 communicate with the machine where @value{GDBN} is running (the @dfn{host}
22616 machine). In general terms, the scheme looks like this:
22620 @value{GDBN} already understands how to use this protocol; when everything
22621 else is set up, you can simply use the @samp{target remote} command
22622 (@pxref{Targets,,Specifying a Debugging Target}).
22624 @item On the target,
22625 you must link with your program a few special-purpose subroutines that
22626 implement the @value{GDBN} remote serial protocol. The file containing these
22627 subroutines is called a @dfn{debugging stub}.
22629 On certain remote targets, you can use an auxiliary program
22630 @code{gdbserver} instead of linking a stub into your program.
22631 @xref{Server,,Using the @code{gdbserver} Program}, for details.
22634 The debugging stub is specific to the architecture of the remote
22635 machine; for example, use @file{sparc-stub.c} to debug programs on
22638 @cindex remote serial stub list
22639 These working remote stubs are distributed with @value{GDBN}:
22644 @cindex @file{i386-stub.c}
22647 For Intel 386 and compatible architectures.
22650 @cindex @file{m68k-stub.c}
22651 @cindex Motorola 680x0
22653 For Motorola 680x0 architectures.
22656 @cindex @file{sh-stub.c}
22659 For Renesas SH architectures.
22662 @cindex @file{sparc-stub.c}
22664 For @sc{sparc} architectures.
22666 @item sparcl-stub.c
22667 @cindex @file{sparcl-stub.c}
22670 For Fujitsu @sc{sparclite} architectures.
22674 The @file{README} file in the @value{GDBN} distribution may list other
22675 recently added stubs.
22678 * Stub Contents:: What the stub can do for you
22679 * Bootstrapping:: What you must do for the stub
22680 * Debug Session:: Putting it all together
22683 @node Stub Contents
22684 @subsection What the Stub Can Do for You
22686 @cindex remote serial stub
22687 The debugging stub for your architecture supplies these three
22691 @item set_debug_traps
22692 @findex set_debug_traps
22693 @cindex remote serial stub, initialization
22694 This routine arranges for @code{handle_exception} to run when your
22695 program stops. You must call this subroutine explicitly in your
22696 program's startup code.
22698 @item handle_exception
22699 @findex handle_exception
22700 @cindex remote serial stub, main routine
22701 This is the central workhorse, but your program never calls it
22702 explicitly---the setup code arranges for @code{handle_exception} to
22703 run when a trap is triggered.
22705 @code{handle_exception} takes control when your program stops during
22706 execution (for example, on a breakpoint), and mediates communications
22707 with @value{GDBN} on the host machine. This is where the communications
22708 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
22709 representative on the target machine. It begins by sending summary
22710 information on the state of your program, then continues to execute,
22711 retrieving and transmitting any information @value{GDBN} needs, until you
22712 execute a @value{GDBN} command that makes your program resume; at that point,
22713 @code{handle_exception} returns control to your own code on the target
22717 @cindex @code{breakpoint} subroutine, remote
22718 Use this auxiliary subroutine to make your program contain a
22719 breakpoint. Depending on the particular situation, this may be the only
22720 way for @value{GDBN} to get control. For instance, if your target
22721 machine has some sort of interrupt button, you won't need to call this;
22722 pressing the interrupt button transfers control to
22723 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
22724 simply receiving characters on the serial port may also trigger a trap;
22725 again, in that situation, you don't need to call @code{breakpoint} from
22726 your own program---simply running @samp{target remote} from the host
22727 @value{GDBN} session gets control.
22729 Call @code{breakpoint} if none of these is true, or if you simply want
22730 to make certain your program stops at a predetermined point for the
22731 start of your debugging session.
22734 @node Bootstrapping
22735 @subsection What You Must Do for the Stub
22737 @cindex remote stub, support routines
22738 The debugging stubs that come with @value{GDBN} are set up for a particular
22739 chip architecture, but they have no information about the rest of your
22740 debugging target machine.
22742 First of all you need to tell the stub how to communicate with the
22746 @item int getDebugChar()
22747 @findex getDebugChar
22748 Write this subroutine to read a single character from the serial port.
22749 It may be identical to @code{getchar} for your target system; a
22750 different name is used to allow you to distinguish the two if you wish.
22752 @item void putDebugChar(int)
22753 @findex putDebugChar
22754 Write this subroutine to write a single character to the serial port.
22755 It may be identical to @code{putchar} for your target system; a
22756 different name is used to allow you to distinguish the two if you wish.
22759 @cindex control C, and remote debugging
22760 @cindex interrupting remote targets
22761 If you want @value{GDBN} to be able to stop your program while it is
22762 running, you need to use an interrupt-driven serial driver, and arrange
22763 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
22764 character). That is the character which @value{GDBN} uses to tell the
22765 remote system to stop.
22767 Getting the debugging target to return the proper status to @value{GDBN}
22768 probably requires changes to the standard stub; one quick and dirty way
22769 is to just execute a breakpoint instruction (the ``dirty'' part is that
22770 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
22772 Other routines you need to supply are:
22775 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
22776 @findex exceptionHandler
22777 Write this function to install @var{exception_address} in the exception
22778 handling tables. You need to do this because the stub does not have any
22779 way of knowing what the exception handling tables on your target system
22780 are like (for example, the processor's table might be in @sc{rom},
22781 containing entries which point to a table in @sc{ram}).
22782 The @var{exception_number} specifies the exception which should be changed;
22783 its meaning is architecture-dependent (for example, different numbers
22784 might represent divide by zero, misaligned access, etc). When this
22785 exception occurs, control should be transferred directly to
22786 @var{exception_address}, and the processor state (stack, registers,
22787 and so on) should be just as it is when a processor exception occurs. So if
22788 you want to use a jump instruction to reach @var{exception_address}, it
22789 should be a simple jump, not a jump to subroutine.
22791 For the 386, @var{exception_address} should be installed as an interrupt
22792 gate so that interrupts are masked while the handler runs. The gate
22793 should be at privilege level 0 (the most privileged level). The
22794 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
22795 help from @code{exceptionHandler}.
22797 @item void flush_i_cache()
22798 @findex flush_i_cache
22799 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
22800 instruction cache, if any, on your target machine. If there is no
22801 instruction cache, this subroutine may be a no-op.
22803 On target machines that have instruction caches, @value{GDBN} requires this
22804 function to make certain that the state of your program is stable.
22808 You must also make sure this library routine is available:
22811 @item void *memset(void *, int, int)
22813 This is the standard library function @code{memset} that sets an area of
22814 memory to a known value. If you have one of the free versions of
22815 @code{libc.a}, @code{memset} can be found there; otherwise, you must
22816 either obtain it from your hardware manufacturer, or write your own.
22819 If you do not use the GNU C compiler, you may need other standard
22820 library subroutines as well; this varies from one stub to another,
22821 but in general the stubs are likely to use any of the common library
22822 subroutines which @code{@value{NGCC}} generates as inline code.
22825 @node Debug Session
22826 @subsection Putting it All Together
22828 @cindex remote serial debugging summary
22829 In summary, when your program is ready to debug, you must follow these
22834 Make sure you have defined the supporting low-level routines
22835 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
22837 @code{getDebugChar}, @code{putDebugChar},
22838 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
22842 Insert these lines in your program's startup code, before the main
22843 procedure is called:
22850 On some machines, when a breakpoint trap is raised, the hardware
22851 automatically makes the PC point to the instruction after the
22852 breakpoint. If your machine doesn't do that, you may need to adjust
22853 @code{handle_exception} to arrange for it to return to the instruction
22854 after the breakpoint on this first invocation, so that your program
22855 doesn't keep hitting the initial breakpoint instead of making
22859 For the 680x0 stub only, you need to provide a variable called
22860 @code{exceptionHook}. Normally you just use:
22863 void (*exceptionHook)() = 0;
22867 but if before calling @code{set_debug_traps}, you set it to point to a
22868 function in your program, that function is called when
22869 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
22870 error). The function indicated by @code{exceptionHook} is called with
22871 one parameter: an @code{int} which is the exception number.
22874 Compile and link together: your program, the @value{GDBN} debugging stub for
22875 your target architecture, and the supporting subroutines.
22878 Make sure you have a serial connection between your target machine and
22879 the @value{GDBN} host, and identify the serial port on the host.
22882 @c The "remote" target now provides a `load' command, so we should
22883 @c document that. FIXME.
22884 Download your program to your target machine (or get it there by
22885 whatever means the manufacturer provides), and start it.
22888 Start @value{GDBN} on the host, and connect to the target
22889 (@pxref{Connecting,,Connecting to a Remote Target}).
22893 @node Configurations
22894 @chapter Configuration-Specific Information
22896 While nearly all @value{GDBN} commands are available for all native and
22897 cross versions of the debugger, there are some exceptions. This chapter
22898 describes things that are only available in certain configurations.
22900 There are three major categories of configurations: native
22901 configurations, where the host and target are the same, embedded
22902 operating system configurations, which are usually the same for several
22903 different processor architectures, and bare embedded processors, which
22904 are quite different from each other.
22909 * Embedded Processors::
22916 This section describes details specific to particular native
22920 * BSD libkvm Interface:: Debugging BSD kernel memory images
22921 * Process Information:: Process information
22922 * DJGPP Native:: Features specific to the DJGPP port
22923 * Cygwin Native:: Features specific to the Cygwin port
22924 * Hurd Native:: Features specific to @sc{gnu} Hurd
22925 * Darwin:: Features specific to Darwin
22926 * FreeBSD:: Features specific to FreeBSD
22929 @node BSD libkvm Interface
22930 @subsection BSD libkvm Interface
22933 @cindex kernel memory image
22934 @cindex kernel crash dump
22936 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
22937 interface that provides a uniform interface for accessing kernel virtual
22938 memory images, including live systems and crash dumps. @value{GDBN}
22939 uses this interface to allow you to debug live kernels and kernel crash
22940 dumps on many native BSD configurations. This is implemented as a
22941 special @code{kvm} debugging target. For debugging a live system, load
22942 the currently running kernel into @value{GDBN} and connect to the
22946 (@value{GDBP}) @b{target kvm}
22949 For debugging crash dumps, provide the file name of the crash dump as an
22953 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
22956 Once connected to the @code{kvm} target, the following commands are
22962 Set current context from the @dfn{Process Control Block} (PCB) address.
22965 Set current context from proc address. This command isn't available on
22966 modern FreeBSD systems.
22969 @node Process Information
22970 @subsection Process Information
22972 @cindex examine process image
22973 @cindex process info via @file{/proc}
22975 Some operating systems provide interfaces to fetch additional
22976 information about running processes beyond memory and per-thread
22977 register state. If @value{GDBN} is configured for an operating system
22978 with a supported interface, the command @code{info proc} is available
22979 to report information about the process running your program, or about
22980 any process running on your system.
22982 One supported interface is a facility called @samp{/proc} that can be
22983 used to examine the image of a running process using file-system
22984 subroutines. This facility is supported on @sc{gnu}/Linux and Solaris
22987 On FreeBSD systems, system control nodes are used to query process
22990 In addition, some systems may provide additional process information
22991 in core files. Note that a core file may include a subset of the
22992 information available from a live process. Process information is
22993 currently avaiable from cores created on @sc{gnu}/Linux and FreeBSD
23000 @itemx info proc @var{process-id}
23001 Summarize available information about a process. If a
23002 process ID is specified by @var{process-id}, display information about
23003 that process; otherwise display information about the program being
23004 debugged. The summary includes the debugged process ID, the command
23005 line used to invoke it, its current working directory, and its
23006 executable file's absolute file name.
23008 On some systems, @var{process-id} can be of the form
23009 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
23010 within a process. If the optional @var{pid} part is missing, it means
23011 a thread from the process being debugged (the leading @samp{/} still
23012 needs to be present, or else @value{GDBN} will interpret the number as
23013 a process ID rather than a thread ID).
23015 @item info proc cmdline
23016 @cindex info proc cmdline
23017 Show the original command line of the process. This command is
23018 supported on @sc{gnu}/Linux and FreeBSD.
23020 @item info proc cwd
23021 @cindex info proc cwd
23022 Show the current working directory of the process. This command is
23023 supported on @sc{gnu}/Linux and FreeBSD.
23025 @item info proc exe
23026 @cindex info proc exe
23027 Show the name of executable of the process. This command is supported
23028 on @sc{gnu}/Linux and FreeBSD.
23030 @item info proc files
23031 @cindex info proc files
23032 Show the file descriptors open by the process. For each open file
23033 descriptor, @value{GDBN} shows its number, type (file, directory,
23034 character device, socket), file pointer offset, and the name of the
23035 resource open on the descriptor. The resource name can be a file name
23036 (for files, directories, and devices) or a protocol followed by socket
23037 address (for network connections). This command is supported on
23040 This example shows the open file descriptors for a process using a
23041 tty for standard input and output as well as two network sockets:
23044 (gdb) info proc files 22136
23048 FD Type Offset Flags Name
23049 text file - r-------- /usr/bin/ssh
23050 ctty chr - rw------- /dev/pts/20
23051 cwd dir - r-------- /usr/home/john
23052 root dir - r-------- /
23053 0 chr 0x32933a4 rw------- /dev/pts/20
23054 1 chr 0x32933a4 rw------- /dev/pts/20
23055 2 chr 0x32933a4 rw------- /dev/pts/20
23056 3 socket 0x0 rw----n-- tcp4 10.0.1.2:53014 -> 10.0.1.10:22
23057 4 socket 0x0 rw------- unix stream:/tmp/ssh-FIt89oAzOn5f/agent.2456
23060 @item info proc mappings
23061 @cindex memory address space mappings
23062 Report the memory address space ranges accessible in a process. On
23063 Solaris and FreeBSD systems, each memory range includes information on
23064 whether the process has read, write, or execute access rights to each
23065 range. On @sc{gnu}/Linux and FreeBSD systems, each memory range
23066 includes the object file which is mapped to that range.
23068 @item info proc stat
23069 @itemx info proc status
23070 @cindex process detailed status information
23071 Show additional process-related information, including the user ID and
23072 group ID; virtual memory usage; the signals that are pending, blocked,
23073 and ignored; its TTY; its consumption of system and user time; its
23074 stack size; its @samp{nice} value; etc. These commands are supported
23075 on @sc{gnu}/Linux and FreeBSD.
23077 For @sc{gnu}/Linux systems, see the @samp{proc} man page for more
23078 information (type @kbd{man 5 proc} from your shell prompt).
23080 For FreeBSD systems, @code{info proc stat} is an alias for @code{info
23083 @item info proc all
23084 Show all the information about the process described under all of the
23085 above @code{info proc} subcommands.
23088 @comment These sub-options of 'info proc' were not included when
23089 @comment procfs.c was re-written. Keep their descriptions around
23090 @comment against the day when someone finds the time to put them back in.
23091 @kindex info proc times
23092 @item info proc times
23093 Starting time, user CPU time, and system CPU time for your program and
23096 @kindex info proc id
23098 Report on the process IDs related to your program: its own process ID,
23099 the ID of its parent, the process group ID, and the session ID.
23102 @item set procfs-trace
23103 @kindex set procfs-trace
23104 @cindex @code{procfs} API calls
23105 This command enables and disables tracing of @code{procfs} API calls.
23107 @item show procfs-trace
23108 @kindex show procfs-trace
23109 Show the current state of @code{procfs} API call tracing.
23111 @item set procfs-file @var{file}
23112 @kindex set procfs-file
23113 Tell @value{GDBN} to write @code{procfs} API trace to the named
23114 @var{file}. @value{GDBN} appends the trace info to the previous
23115 contents of the file. The default is to display the trace on the
23118 @item show procfs-file
23119 @kindex show procfs-file
23120 Show the file to which @code{procfs} API trace is written.
23122 @item proc-trace-entry
23123 @itemx proc-trace-exit
23124 @itemx proc-untrace-entry
23125 @itemx proc-untrace-exit
23126 @kindex proc-trace-entry
23127 @kindex proc-trace-exit
23128 @kindex proc-untrace-entry
23129 @kindex proc-untrace-exit
23130 These commands enable and disable tracing of entries into and exits
23131 from the @code{syscall} interface.
23134 @kindex info pidlist
23135 @cindex process list, QNX Neutrino
23136 For QNX Neutrino only, this command displays the list of all the
23137 processes and all the threads within each process.
23140 @kindex info meminfo
23141 @cindex mapinfo list, QNX Neutrino
23142 For QNX Neutrino only, this command displays the list of all mapinfos.
23146 @subsection Features for Debugging @sc{djgpp} Programs
23147 @cindex @sc{djgpp} debugging
23148 @cindex native @sc{djgpp} debugging
23149 @cindex MS-DOS-specific commands
23152 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
23153 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
23154 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
23155 top of real-mode DOS systems and their emulations.
23157 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
23158 defines a few commands specific to the @sc{djgpp} port. This
23159 subsection describes those commands.
23164 This is a prefix of @sc{djgpp}-specific commands which print
23165 information about the target system and important OS structures.
23168 @cindex MS-DOS system info
23169 @cindex free memory information (MS-DOS)
23170 @item info dos sysinfo
23171 This command displays assorted information about the underlying
23172 platform: the CPU type and features, the OS version and flavor, the
23173 DPMI version, and the available conventional and DPMI memory.
23178 @cindex segment descriptor tables
23179 @cindex descriptor tables display
23181 @itemx info dos ldt
23182 @itemx info dos idt
23183 These 3 commands display entries from, respectively, Global, Local,
23184 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
23185 tables are data structures which store a descriptor for each segment
23186 that is currently in use. The segment's selector is an index into a
23187 descriptor table; the table entry for that index holds the
23188 descriptor's base address and limit, and its attributes and access
23191 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
23192 segment (used for both data and the stack), and a DOS segment (which
23193 allows access to DOS/BIOS data structures and absolute addresses in
23194 conventional memory). However, the DPMI host will usually define
23195 additional segments in order to support the DPMI environment.
23197 @cindex garbled pointers
23198 These commands allow to display entries from the descriptor tables.
23199 Without an argument, all entries from the specified table are
23200 displayed. An argument, which should be an integer expression, means
23201 display a single entry whose index is given by the argument. For
23202 example, here's a convenient way to display information about the
23203 debugged program's data segment:
23206 @exdent @code{(@value{GDBP}) info dos ldt $ds}
23207 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
23211 This comes in handy when you want to see whether a pointer is outside
23212 the data segment's limit (i.e.@: @dfn{garbled}).
23214 @cindex page tables display (MS-DOS)
23216 @itemx info dos pte
23217 These two commands display entries from, respectively, the Page
23218 Directory and the Page Tables. Page Directories and Page Tables are
23219 data structures which control how virtual memory addresses are mapped
23220 into physical addresses. A Page Table includes an entry for every
23221 page of memory that is mapped into the program's address space; there
23222 may be several Page Tables, each one holding up to 4096 entries. A
23223 Page Directory has up to 4096 entries, one each for every Page Table
23224 that is currently in use.
23226 Without an argument, @kbd{info dos pde} displays the entire Page
23227 Directory, and @kbd{info dos pte} displays all the entries in all of
23228 the Page Tables. An argument, an integer expression, given to the
23229 @kbd{info dos pde} command means display only that entry from the Page
23230 Directory table. An argument given to the @kbd{info dos pte} command
23231 means display entries from a single Page Table, the one pointed to by
23232 the specified entry in the Page Directory.
23234 @cindex direct memory access (DMA) on MS-DOS
23235 These commands are useful when your program uses @dfn{DMA} (Direct
23236 Memory Access), which needs physical addresses to program the DMA
23239 These commands are supported only with some DPMI servers.
23241 @cindex physical address from linear address
23242 @item info dos address-pte @var{addr}
23243 This command displays the Page Table entry for a specified linear
23244 address. The argument @var{addr} is a linear address which should
23245 already have the appropriate segment's base address added to it,
23246 because this command accepts addresses which may belong to @emph{any}
23247 segment. For example, here's how to display the Page Table entry for
23248 the page where a variable @code{i} is stored:
23251 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
23252 @exdent @code{Page Table entry for address 0x11a00d30:}
23253 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
23257 This says that @code{i} is stored at offset @code{0xd30} from the page
23258 whose physical base address is @code{0x02698000}, and shows all the
23259 attributes of that page.
23261 Note that you must cast the addresses of variables to a @code{char *},
23262 since otherwise the value of @code{__djgpp_base_address}, the base
23263 address of all variables and functions in a @sc{djgpp} program, will
23264 be added using the rules of C pointer arithmetics: if @code{i} is
23265 declared an @code{int}, @value{GDBN} will add 4 times the value of
23266 @code{__djgpp_base_address} to the address of @code{i}.
23268 Here's another example, it displays the Page Table entry for the
23272 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
23273 @exdent @code{Page Table entry for address 0x29110:}
23274 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
23278 (The @code{+ 3} offset is because the transfer buffer's address is the
23279 3rd member of the @code{_go32_info_block} structure.) The output
23280 clearly shows that this DPMI server maps the addresses in conventional
23281 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
23282 linear (@code{0x29110}) addresses are identical.
23284 This command is supported only with some DPMI servers.
23287 @cindex DOS serial data link, remote debugging
23288 In addition to native debugging, the DJGPP port supports remote
23289 debugging via a serial data link. The following commands are specific
23290 to remote serial debugging in the DJGPP port of @value{GDBN}.
23293 @kindex set com1base
23294 @kindex set com1irq
23295 @kindex set com2base
23296 @kindex set com2irq
23297 @kindex set com3base
23298 @kindex set com3irq
23299 @kindex set com4base
23300 @kindex set com4irq
23301 @item set com1base @var{addr}
23302 This command sets the base I/O port address of the @file{COM1} serial
23305 @item set com1irq @var{irq}
23306 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
23307 for the @file{COM1} serial port.
23309 There are similar commands @samp{set com2base}, @samp{set com3irq},
23310 etc.@: for setting the port address and the @code{IRQ} lines for the
23313 @kindex show com1base
23314 @kindex show com1irq
23315 @kindex show com2base
23316 @kindex show com2irq
23317 @kindex show com3base
23318 @kindex show com3irq
23319 @kindex show com4base
23320 @kindex show com4irq
23321 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
23322 display the current settings of the base address and the @code{IRQ}
23323 lines used by the COM ports.
23326 @kindex info serial
23327 @cindex DOS serial port status
23328 This command prints the status of the 4 DOS serial ports. For each
23329 port, it prints whether it's active or not, its I/O base address and
23330 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
23331 counts of various errors encountered so far.
23335 @node Cygwin Native
23336 @subsection Features for Debugging MS Windows PE Executables
23337 @cindex MS Windows debugging
23338 @cindex native Cygwin debugging
23339 @cindex Cygwin-specific commands
23341 @value{GDBN} supports native debugging of MS Windows programs, including
23342 DLLs with and without symbolic debugging information.
23344 @cindex Ctrl-BREAK, MS-Windows
23345 @cindex interrupt debuggee on MS-Windows
23346 MS-Windows programs that call @code{SetConsoleMode} to switch off the
23347 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
23348 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
23349 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
23350 sequence, which can be used to interrupt the debuggee even if it
23353 There are various additional Cygwin-specific commands, described in
23354 this section. Working with DLLs that have no debugging symbols is
23355 described in @ref{Non-debug DLL Symbols}.
23360 This is a prefix of MS Windows-specific commands which print
23361 information about the target system and important OS structures.
23363 @item info w32 selector
23364 This command displays information returned by
23365 the Win32 API @code{GetThreadSelectorEntry} function.
23366 It takes an optional argument that is evaluated to
23367 a long value to give the information about this given selector.
23368 Without argument, this command displays information
23369 about the six segment registers.
23371 @item info w32 thread-information-block
23372 This command displays thread specific information stored in the
23373 Thread Information Block (readable on the X86 CPU family using @code{$fs}
23374 selector for 32-bit programs and @code{$gs} for 64-bit programs).
23376 @kindex signal-event
23377 @item signal-event @var{id}
23378 This command signals an event with user-provided @var{id}. Used to resume
23379 crashing process when attached to it using MS-Windows JIT debugging (AeDebug).
23381 To use it, create or edit the following keys in
23382 @code{HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AeDebug} and/or
23383 @code{HKLM\SOFTWARE\Wow6432Node\Microsoft\Windows NT\CurrentVersion\AeDebug}
23384 (for x86_64 versions):
23388 @code{Debugger} (REG_SZ) --- a command to launch the debugger.
23389 Suggested command is: @code{@var{fully-qualified-path-to-gdb.exe} -ex
23390 "attach %ld" -ex "signal-event %ld" -ex "continue"}.
23392 The first @code{%ld} will be replaced by the process ID of the
23393 crashing process, the second @code{%ld} will be replaced by the ID of
23394 the event that blocks the crashing process, waiting for @value{GDBN}
23398 @code{Auto} (REG_SZ) --- either @code{1} or @code{0}. @code{1} will
23399 make the system run debugger specified by the Debugger key
23400 automatically, @code{0} will cause a dialog box with ``OK'' and
23401 ``Cancel'' buttons to appear, which allows the user to either
23402 terminate the crashing process (OK) or debug it (Cancel).
23405 @kindex set cygwin-exceptions
23406 @cindex debugging the Cygwin DLL
23407 @cindex Cygwin DLL, debugging
23408 @item set cygwin-exceptions @var{mode}
23409 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
23410 happen inside the Cygwin DLL. If @var{mode} is @code{off},
23411 @value{GDBN} will delay recognition of exceptions, and may ignore some
23412 exceptions which seem to be caused by internal Cygwin DLL
23413 ``bookkeeping''. This option is meant primarily for debugging the
23414 Cygwin DLL itself; the default value is @code{off} to avoid annoying
23415 @value{GDBN} users with false @code{SIGSEGV} signals.
23417 @kindex show cygwin-exceptions
23418 @item show cygwin-exceptions
23419 Displays whether @value{GDBN} will break on exceptions that happen
23420 inside the Cygwin DLL itself.
23422 @kindex set new-console
23423 @item set new-console @var{mode}
23424 If @var{mode} is @code{on} the debuggee will
23425 be started in a new console on next start.
23426 If @var{mode} is @code{off}, the debuggee will
23427 be started in the same console as the debugger.
23429 @kindex show new-console
23430 @item show new-console
23431 Displays whether a new console is used
23432 when the debuggee is started.
23434 @kindex set new-group
23435 @item set new-group @var{mode}
23436 This boolean value controls whether the debuggee should
23437 start a new group or stay in the same group as the debugger.
23438 This affects the way the Windows OS handles
23441 @kindex show new-group
23442 @item show new-group
23443 Displays current value of new-group boolean.
23445 @kindex set debugevents
23446 @item set debugevents
23447 This boolean value adds debug output concerning kernel events related
23448 to the debuggee seen by the debugger. This includes events that
23449 signal thread and process creation and exit, DLL loading and
23450 unloading, console interrupts, and debugging messages produced by the
23451 Windows @code{OutputDebugString} API call.
23453 @kindex set debugexec
23454 @item set debugexec
23455 This boolean value adds debug output concerning execute events
23456 (such as resume thread) seen by the debugger.
23458 @kindex set debugexceptions
23459 @item set debugexceptions
23460 This boolean value adds debug output concerning exceptions in the
23461 debuggee seen by the debugger.
23463 @kindex set debugmemory
23464 @item set debugmemory
23465 This boolean value adds debug output concerning debuggee memory reads
23466 and writes by the debugger.
23470 This boolean values specifies whether the debuggee is called
23471 via a shell or directly (default value is on).
23475 Displays if the debuggee will be started with a shell.
23480 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
23483 @node Non-debug DLL Symbols
23484 @subsubsection Support for DLLs without Debugging Symbols
23485 @cindex DLLs with no debugging symbols
23486 @cindex Minimal symbols and DLLs
23488 Very often on windows, some of the DLLs that your program relies on do
23489 not include symbolic debugging information (for example,
23490 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
23491 symbols in a DLL, it relies on the minimal amount of symbolic
23492 information contained in the DLL's export table. This section
23493 describes working with such symbols, known internally to @value{GDBN} as
23494 ``minimal symbols''.
23496 Note that before the debugged program has started execution, no DLLs
23497 will have been loaded. The easiest way around this problem is simply to
23498 start the program --- either by setting a breakpoint or letting the
23499 program run once to completion.
23501 @subsubsection DLL Name Prefixes
23503 In keeping with the naming conventions used by the Microsoft debugging
23504 tools, DLL export symbols are made available with a prefix based on the
23505 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
23506 also entered into the symbol table, so @code{CreateFileA} is often
23507 sufficient. In some cases there will be name clashes within a program
23508 (particularly if the executable itself includes full debugging symbols)
23509 necessitating the use of the fully qualified name when referring to the
23510 contents of the DLL. Use single-quotes around the name to avoid the
23511 exclamation mark (``!'') being interpreted as a language operator.
23513 Note that the internal name of the DLL may be all upper-case, even
23514 though the file name of the DLL is lower-case, or vice-versa. Since
23515 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
23516 some confusion. If in doubt, try the @code{info functions} and
23517 @code{info variables} commands or even @code{maint print msymbols}
23518 (@pxref{Symbols}). Here's an example:
23521 (@value{GDBP}) info function CreateFileA
23522 All functions matching regular expression "CreateFileA":
23524 Non-debugging symbols:
23525 0x77e885f4 CreateFileA
23526 0x77e885f4 KERNEL32!CreateFileA
23530 (@value{GDBP}) info function !
23531 All functions matching regular expression "!":
23533 Non-debugging symbols:
23534 0x6100114c cygwin1!__assert
23535 0x61004034 cygwin1!_dll_crt0@@0
23536 0x61004240 cygwin1!dll_crt0(per_process *)
23540 @subsubsection Working with Minimal Symbols
23542 Symbols extracted from a DLL's export table do not contain very much
23543 type information. All that @value{GDBN} can do is guess whether a symbol
23544 refers to a function or variable depending on the linker section that
23545 contains the symbol. Also note that the actual contents of the memory
23546 contained in a DLL are not available unless the program is running. This
23547 means that you cannot examine the contents of a variable or disassemble
23548 a function within a DLL without a running program.
23550 Variables are generally treated as pointers and dereferenced
23551 automatically. For this reason, it is often necessary to prefix a
23552 variable name with the address-of operator (``&'') and provide explicit
23553 type information in the command. Here's an example of the type of
23557 (@value{GDBP}) print 'cygwin1!__argv'
23558 'cygwin1!__argv' has unknown type; cast it to its declared type
23562 (@value{GDBP}) x 'cygwin1!__argv'
23563 'cygwin1!__argv' has unknown type; cast it to its declared type
23566 And two possible solutions:
23569 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
23570 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
23574 (@value{GDBP}) x/2x &'cygwin1!__argv'
23575 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
23576 (@value{GDBP}) x/x 0x10021608
23577 0x10021608: 0x0022fd98
23578 (@value{GDBP}) x/s 0x0022fd98
23579 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
23582 Setting a break point within a DLL is possible even before the program
23583 starts execution. However, under these circumstances, @value{GDBN} can't
23584 examine the initial instructions of the function in order to skip the
23585 function's frame set-up code. You can work around this by using ``*&''
23586 to set the breakpoint at a raw memory address:
23589 (@value{GDBP}) break *&'python22!PyOS_Readline'
23590 Breakpoint 1 at 0x1e04eff0
23593 The author of these extensions is not entirely convinced that setting a
23594 break point within a shared DLL like @file{kernel32.dll} is completely
23598 @subsection Commands Specific to @sc{gnu} Hurd Systems
23599 @cindex @sc{gnu} Hurd debugging
23601 This subsection describes @value{GDBN} commands specific to the
23602 @sc{gnu} Hurd native debugging.
23607 @kindex set signals@r{, Hurd command}
23608 @kindex set sigs@r{, Hurd command}
23609 This command toggles the state of inferior signal interception by
23610 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
23611 affected by this command. @code{sigs} is a shorthand alias for
23616 @kindex show signals@r{, Hurd command}
23617 @kindex show sigs@r{, Hurd command}
23618 Show the current state of intercepting inferior's signals.
23620 @item set signal-thread
23621 @itemx set sigthread
23622 @kindex set signal-thread
23623 @kindex set sigthread
23624 This command tells @value{GDBN} which thread is the @code{libc} signal
23625 thread. That thread is run when a signal is delivered to a running
23626 process. @code{set sigthread} is the shorthand alias of @code{set
23629 @item show signal-thread
23630 @itemx show sigthread
23631 @kindex show signal-thread
23632 @kindex show sigthread
23633 These two commands show which thread will run when the inferior is
23634 delivered a signal.
23637 @kindex set stopped@r{, Hurd command}
23638 This commands tells @value{GDBN} that the inferior process is stopped,
23639 as with the @code{SIGSTOP} signal. The stopped process can be
23640 continued by delivering a signal to it.
23643 @kindex show stopped@r{, Hurd command}
23644 This command shows whether @value{GDBN} thinks the debuggee is
23647 @item set exceptions
23648 @kindex set exceptions@r{, Hurd command}
23649 Use this command to turn off trapping of exceptions in the inferior.
23650 When exception trapping is off, neither breakpoints nor
23651 single-stepping will work. To restore the default, set exception
23654 @item show exceptions
23655 @kindex show exceptions@r{, Hurd command}
23656 Show the current state of trapping exceptions in the inferior.
23658 @item set task pause
23659 @kindex set task@r{, Hurd commands}
23660 @cindex task attributes (@sc{gnu} Hurd)
23661 @cindex pause current task (@sc{gnu} Hurd)
23662 This command toggles task suspension when @value{GDBN} has control.
23663 Setting it to on takes effect immediately, and the task is suspended
23664 whenever @value{GDBN} gets control. Setting it to off will take
23665 effect the next time the inferior is continued. If this option is set
23666 to off, you can use @code{set thread default pause on} or @code{set
23667 thread pause on} (see below) to pause individual threads.
23669 @item show task pause
23670 @kindex show task@r{, Hurd commands}
23671 Show the current state of task suspension.
23673 @item set task detach-suspend-count
23674 @cindex task suspend count
23675 @cindex detach from task, @sc{gnu} Hurd
23676 This command sets the suspend count the task will be left with when
23677 @value{GDBN} detaches from it.
23679 @item show task detach-suspend-count
23680 Show the suspend count the task will be left with when detaching.
23682 @item set task exception-port
23683 @itemx set task excp
23684 @cindex task exception port, @sc{gnu} Hurd
23685 This command sets the task exception port to which @value{GDBN} will
23686 forward exceptions. The argument should be the value of the @dfn{send
23687 rights} of the task. @code{set task excp} is a shorthand alias.
23689 @item set noninvasive
23690 @cindex noninvasive task options
23691 This command switches @value{GDBN} to a mode that is the least
23692 invasive as far as interfering with the inferior is concerned. This
23693 is the same as using @code{set task pause}, @code{set exceptions}, and
23694 @code{set signals} to values opposite to the defaults.
23696 @item info send-rights
23697 @itemx info receive-rights
23698 @itemx info port-rights
23699 @itemx info port-sets
23700 @itemx info dead-names
23703 @cindex send rights, @sc{gnu} Hurd
23704 @cindex receive rights, @sc{gnu} Hurd
23705 @cindex port rights, @sc{gnu} Hurd
23706 @cindex port sets, @sc{gnu} Hurd
23707 @cindex dead names, @sc{gnu} Hurd
23708 These commands display information about, respectively, send rights,
23709 receive rights, port rights, port sets, and dead names of a task.
23710 There are also shorthand aliases: @code{info ports} for @code{info
23711 port-rights} and @code{info psets} for @code{info port-sets}.
23713 @item set thread pause
23714 @kindex set thread@r{, Hurd command}
23715 @cindex thread properties, @sc{gnu} Hurd
23716 @cindex pause current thread (@sc{gnu} Hurd)
23717 This command toggles current thread suspension when @value{GDBN} has
23718 control. Setting it to on takes effect immediately, and the current
23719 thread is suspended whenever @value{GDBN} gets control. Setting it to
23720 off will take effect the next time the inferior is continued.
23721 Normally, this command has no effect, since when @value{GDBN} has
23722 control, the whole task is suspended. However, if you used @code{set
23723 task pause off} (see above), this command comes in handy to suspend
23724 only the current thread.
23726 @item show thread pause
23727 @kindex show thread@r{, Hurd command}
23728 This command shows the state of current thread suspension.
23730 @item set thread run
23731 This command sets whether the current thread is allowed to run.
23733 @item show thread run
23734 Show whether the current thread is allowed to run.
23736 @item set thread detach-suspend-count
23737 @cindex thread suspend count, @sc{gnu} Hurd
23738 @cindex detach from thread, @sc{gnu} Hurd
23739 This command sets the suspend count @value{GDBN} will leave on a
23740 thread when detaching. This number is relative to the suspend count
23741 found by @value{GDBN} when it notices the thread; use @code{set thread
23742 takeover-suspend-count} to force it to an absolute value.
23744 @item show thread detach-suspend-count
23745 Show the suspend count @value{GDBN} will leave on the thread when
23748 @item set thread exception-port
23749 @itemx set thread excp
23750 Set the thread exception port to which to forward exceptions. This
23751 overrides the port set by @code{set task exception-port} (see above).
23752 @code{set thread excp} is the shorthand alias.
23754 @item set thread takeover-suspend-count
23755 Normally, @value{GDBN}'s thread suspend counts are relative to the
23756 value @value{GDBN} finds when it notices each thread. This command
23757 changes the suspend counts to be absolute instead.
23759 @item set thread default
23760 @itemx show thread default
23761 @cindex thread default settings, @sc{gnu} Hurd
23762 Each of the above @code{set thread} commands has a @code{set thread
23763 default} counterpart (e.g., @code{set thread default pause}, @code{set
23764 thread default exception-port}, etc.). The @code{thread default}
23765 variety of commands sets the default thread properties for all
23766 threads; you can then change the properties of individual threads with
23767 the non-default commands.
23774 @value{GDBN} provides the following commands specific to the Darwin target:
23777 @item set debug darwin @var{num}
23778 @kindex set debug darwin
23779 When set to a non zero value, enables debugging messages specific to
23780 the Darwin support. Higher values produce more verbose output.
23782 @item show debug darwin
23783 @kindex show debug darwin
23784 Show the current state of Darwin messages.
23786 @item set debug mach-o @var{num}
23787 @kindex set debug mach-o
23788 When set to a non zero value, enables debugging messages while
23789 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
23790 file format used on Darwin for object and executable files.) Higher
23791 values produce more verbose output. This is a command to diagnose
23792 problems internal to @value{GDBN} and should not be needed in normal
23795 @item show debug mach-o
23796 @kindex show debug mach-o
23797 Show the current state of Mach-O file messages.
23799 @item set mach-exceptions on
23800 @itemx set mach-exceptions off
23801 @kindex set mach-exceptions
23802 On Darwin, faults are first reported as a Mach exception and are then
23803 mapped to a Posix signal. Use this command to turn on trapping of
23804 Mach exceptions in the inferior. This might be sometimes useful to
23805 better understand the cause of a fault. The default is off.
23807 @item show mach-exceptions
23808 @kindex show mach-exceptions
23809 Show the current state of exceptions trapping.
23813 @subsection FreeBSD
23816 When the ABI of a system call is changed in the FreeBSD kernel, this
23817 is implemented by leaving a compatibility system call using the old
23818 ABI at the existing number and allocating a new system call number for
23819 the version using the new ABI. As a convenience, when a system call
23820 is caught by name (@pxref{catch syscall}), compatibility system calls
23823 For example, FreeBSD 12 introduced a new variant of the @code{kevent}
23824 system call and catching the @code{kevent} system call by name catches
23828 (@value{GDBP}) catch syscall kevent
23829 Catchpoint 1 (syscalls 'freebsd11_kevent' [363] 'kevent' [560])
23835 @section Embedded Operating Systems
23837 This section describes configurations involving the debugging of
23838 embedded operating systems that are available for several different
23841 @value{GDBN} includes the ability to debug programs running on
23842 various real-time operating systems.
23844 @node Embedded Processors
23845 @section Embedded Processors
23847 This section goes into details specific to particular embedded
23850 @cindex send command to simulator
23851 Whenever a specific embedded processor has a simulator, @value{GDBN}
23852 allows to send an arbitrary command to the simulator.
23855 @item sim @var{command}
23856 @kindex sim@r{, a command}
23857 Send an arbitrary @var{command} string to the simulator. Consult the
23858 documentation for the specific simulator in use for information about
23859 acceptable commands.
23864 * ARC:: Synopsys ARC
23866 * M68K:: Motorola M68K
23867 * MicroBlaze:: Xilinx MicroBlaze
23868 * MIPS Embedded:: MIPS Embedded
23869 * OpenRISC 1000:: OpenRISC 1000 (or1k)
23870 * PowerPC Embedded:: PowerPC Embedded
23873 * Super-H:: Renesas Super-H
23877 @subsection Synopsys ARC
23878 @cindex Synopsys ARC
23879 @cindex ARC specific commands
23885 @value{GDBN} provides the following ARC-specific commands:
23888 @item set debug arc
23889 @kindex set debug arc
23890 Control the level of ARC specific debug messages. Use 0 for no messages (the
23891 default), 1 for debug messages, and 2 for even more debug messages.
23893 @item show debug arc
23894 @kindex show debug arc
23895 Show the level of ARC specific debugging in operation.
23897 @item maint print arc arc-instruction @var{address}
23898 @kindex maint print arc arc-instruction
23899 Print internal disassembler information about instruction at a given address.
23906 @value{GDBN} provides the following ARM-specific commands:
23909 @item set arm disassembler
23911 This commands selects from a list of disassembly styles. The
23912 @code{"std"} style is the standard style.
23914 @item show arm disassembler
23916 Show the current disassembly style.
23918 @item set arm apcs32
23919 @cindex ARM 32-bit mode
23920 This command toggles ARM operation mode between 32-bit and 26-bit.
23922 @item show arm apcs32
23923 Display the current usage of the ARM 32-bit mode.
23925 @item set arm fpu @var{fputype}
23926 This command sets the ARM floating-point unit (FPU) type. The
23927 argument @var{fputype} can be one of these:
23931 Determine the FPU type by querying the OS ABI.
23933 Software FPU, with mixed-endian doubles on little-endian ARM
23936 GCC-compiled FPA co-processor.
23938 Software FPU with pure-endian doubles.
23944 Show the current type of the FPU.
23947 This command forces @value{GDBN} to use the specified ABI.
23950 Show the currently used ABI.
23952 @item set arm fallback-mode (arm|thumb|auto)
23953 @value{GDBN} uses the symbol table, when available, to determine
23954 whether instructions are ARM or Thumb. This command controls
23955 @value{GDBN}'s default behavior when the symbol table is not
23956 available. The default is @samp{auto}, which causes @value{GDBN} to
23957 use the current execution mode (from the @code{T} bit in the @code{CPSR}
23960 @item show arm fallback-mode
23961 Show the current fallback instruction mode.
23963 @item set arm force-mode (arm|thumb|auto)
23964 This command overrides use of the symbol table to determine whether
23965 instructions are ARM or Thumb. The default is @samp{auto}, which
23966 causes @value{GDBN} to use the symbol table and then the setting
23967 of @samp{set arm fallback-mode}.
23969 @item show arm force-mode
23970 Show the current forced instruction mode.
23972 @item set debug arm
23973 Toggle whether to display ARM-specific debugging messages from the ARM
23974 target support subsystem.
23976 @item show debug arm
23977 Show whether ARM-specific debugging messages are enabled.
23981 @item target sim @r{[}@var{simargs}@r{]} @dots{}
23982 The @value{GDBN} ARM simulator accepts the following optional arguments.
23985 @item --swi-support=@var{type}
23986 Tell the simulator which SWI interfaces to support. The argument
23987 @var{type} may be a comma separated list of the following values.
23988 The default value is @code{all}.
24003 The Motorola m68k configuration includes ColdFire support.
24006 @subsection MicroBlaze
24007 @cindex Xilinx MicroBlaze
24008 @cindex XMD, Xilinx Microprocessor Debugger
24010 The MicroBlaze is a soft-core processor supported on various Xilinx
24011 FPGAs, such as Spartan or Virtex series. Boards with these processors
24012 usually have JTAG ports which connect to a host system running the Xilinx
24013 Embedded Development Kit (EDK) or Software Development Kit (SDK).
24014 This host system is used to download the configuration bitstream to
24015 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
24016 communicates with the target board using the JTAG interface and
24017 presents a @code{gdbserver} interface to the board. By default
24018 @code{xmd} uses port @code{1234}. (While it is possible to change
24019 this default port, it requires the use of undocumented @code{xmd}
24020 commands. Contact Xilinx support if you need to do this.)
24022 Use these GDB commands to connect to the MicroBlaze target processor.
24025 @item target remote :1234
24026 Use this command to connect to the target if you are running @value{GDBN}
24027 on the same system as @code{xmd}.
24029 @item target remote @var{xmd-host}:1234
24030 Use this command to connect to the target if it is connected to @code{xmd}
24031 running on a different system named @var{xmd-host}.
24034 Use this command to download a program to the MicroBlaze target.
24036 @item set debug microblaze @var{n}
24037 Enable MicroBlaze-specific debugging messages if non-zero.
24039 @item show debug microblaze @var{n}
24040 Show MicroBlaze-specific debugging level.
24043 @node MIPS Embedded
24044 @subsection @acronym{MIPS} Embedded
24047 @value{GDBN} supports these special commands for @acronym{MIPS} targets:
24050 @item set mipsfpu double
24051 @itemx set mipsfpu single
24052 @itemx set mipsfpu none
24053 @itemx set mipsfpu auto
24054 @itemx show mipsfpu
24055 @kindex set mipsfpu
24056 @kindex show mipsfpu
24057 @cindex @acronym{MIPS} remote floating point
24058 @cindex floating point, @acronym{MIPS} remote
24059 If your target board does not support the @acronym{MIPS} floating point
24060 coprocessor, you should use the command @samp{set mipsfpu none} (if you
24061 need this, you may wish to put the command in your @value{GDBN} init
24062 file). This tells @value{GDBN} how to find the return value of
24063 functions which return floating point values. It also allows
24064 @value{GDBN} to avoid saving the floating point registers when calling
24065 functions on the board. If you are using a floating point coprocessor
24066 with only single precision floating point support, as on the @sc{r4650}
24067 processor, use the command @samp{set mipsfpu single}. The default
24068 double precision floating point coprocessor may be selected using
24069 @samp{set mipsfpu double}.
24071 In previous versions the only choices were double precision or no
24072 floating point, so @samp{set mipsfpu on} will select double precision
24073 and @samp{set mipsfpu off} will select no floating point.
24075 As usual, you can inquire about the @code{mipsfpu} variable with
24076 @samp{show mipsfpu}.
24079 @node OpenRISC 1000
24080 @subsection OpenRISC 1000
24081 @cindex OpenRISC 1000
24084 The OpenRISC 1000 provides a free RISC instruction set architecture. It is
24085 mainly provided as a soft-core which can run on Xilinx, Altera and other
24088 @value{GDBN} for OpenRISC supports the below commands when connecting to
24096 Runs the builtin CPU simulator which can run very basic
24097 programs but does not support most hardware functions like MMU.
24098 For more complex use cases the user is advised to run an external
24099 target, and connect using @samp{target remote}.
24101 Example: @code{target sim}
24103 @item set debug or1k
24104 Toggle whether to display OpenRISC-specific debugging messages from the
24105 OpenRISC target support subsystem.
24107 @item show debug or1k
24108 Show whether OpenRISC-specific debugging messages are enabled.
24111 @node PowerPC Embedded
24112 @subsection PowerPC Embedded
24114 @cindex DVC register
24115 @value{GDBN} supports using the DVC (Data Value Compare) register to
24116 implement in hardware simple hardware watchpoint conditions of the form:
24119 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
24120 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
24123 The DVC register will be automatically used when @value{GDBN} detects
24124 such pattern in a condition expression, and the created watchpoint uses one
24125 debug register (either the @code{exact-watchpoints} option is on and the
24126 variable is scalar, or the variable has a length of one byte). This feature
24127 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
24130 When running on PowerPC embedded processors, @value{GDBN} automatically uses
24131 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
24132 in which case watchpoints using only one debug register are created when
24133 watching variables of scalar types.
24135 You can create an artificial array to watch an arbitrary memory
24136 region using one of the following commands (@pxref{Expressions}):
24139 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
24140 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
24143 PowerPC embedded processors support masked watchpoints. See the discussion
24144 about the @code{mask} argument in @ref{Set Watchpoints}.
24146 @cindex ranged breakpoint
24147 PowerPC embedded processors support hardware accelerated
24148 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
24149 the inferior whenever it executes an instruction at any address within
24150 the range it specifies. To set a ranged breakpoint in @value{GDBN},
24151 use the @code{break-range} command.
24153 @value{GDBN} provides the following PowerPC-specific commands:
24156 @kindex break-range
24157 @item break-range @var{start-location}, @var{end-location}
24158 Set a breakpoint for an address range given by
24159 @var{start-location} and @var{end-location}, which can specify a function name,
24160 a line number, an offset of lines from the current line or from the start
24161 location, or an address of an instruction (see @ref{Specify Location},
24162 for a list of all the possible ways to specify a @var{location}.)
24163 The breakpoint will stop execution of the inferior whenever it
24164 executes an instruction at any address within the specified range,
24165 (including @var{start-location} and @var{end-location}.)
24167 @kindex set powerpc
24168 @item set powerpc soft-float
24169 @itemx show powerpc soft-float
24170 Force @value{GDBN} to use (or not use) a software floating point calling
24171 convention. By default, @value{GDBN} selects the calling convention based
24172 on the selected architecture and the provided executable file.
24174 @item set powerpc vector-abi
24175 @itemx show powerpc vector-abi
24176 Force @value{GDBN} to use the specified calling convention for vector
24177 arguments and return values. The valid options are @samp{auto};
24178 @samp{generic}, to avoid vector registers even if they are present;
24179 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
24180 registers. By default, @value{GDBN} selects the calling convention
24181 based on the selected architecture and the provided executable file.
24183 @item set powerpc exact-watchpoints
24184 @itemx show powerpc exact-watchpoints
24185 Allow @value{GDBN} to use only one debug register when watching a variable
24186 of scalar type, thus assuming that the variable is accessed through the
24187 address of its first byte.
24192 @subsection Atmel AVR
24195 When configured for debugging the Atmel AVR, @value{GDBN} supports the
24196 following AVR-specific commands:
24199 @item info io_registers
24200 @kindex info io_registers@r{, AVR}
24201 @cindex I/O registers (Atmel AVR)
24202 This command displays information about the AVR I/O registers. For
24203 each register, @value{GDBN} prints its number and value.
24210 When configured for debugging CRIS, @value{GDBN} provides the
24211 following CRIS-specific commands:
24214 @item set cris-version @var{ver}
24215 @cindex CRIS version
24216 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
24217 The CRIS version affects register names and sizes. This command is useful in
24218 case autodetection of the CRIS version fails.
24220 @item show cris-version
24221 Show the current CRIS version.
24223 @item set cris-dwarf2-cfi
24224 @cindex DWARF-2 CFI and CRIS
24225 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
24226 Change to @samp{off} when using @code{gcc-cris} whose version is below
24229 @item show cris-dwarf2-cfi
24230 Show the current state of using DWARF-2 CFI.
24232 @item set cris-mode @var{mode}
24234 Set the current CRIS mode to @var{mode}. It should only be changed when
24235 debugging in guru mode, in which case it should be set to
24236 @samp{guru} (the default is @samp{normal}).
24238 @item show cris-mode
24239 Show the current CRIS mode.
24243 @subsection Renesas Super-H
24246 For the Renesas Super-H processor, @value{GDBN} provides these
24250 @item set sh calling-convention @var{convention}
24251 @kindex set sh calling-convention
24252 Set the calling-convention used when calling functions from @value{GDBN}.
24253 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
24254 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
24255 convention. If the DWARF-2 information of the called function specifies
24256 that the function follows the Renesas calling convention, the function
24257 is called using the Renesas calling convention. If the calling convention
24258 is set to @samp{renesas}, the Renesas calling convention is always used,
24259 regardless of the DWARF-2 information. This can be used to override the
24260 default of @samp{gcc} if debug information is missing, or the compiler
24261 does not emit the DWARF-2 calling convention entry for a function.
24263 @item show sh calling-convention
24264 @kindex show sh calling-convention
24265 Show the current calling convention setting.
24270 @node Architectures
24271 @section Architectures
24273 This section describes characteristics of architectures that affect
24274 all uses of @value{GDBN} with the architecture, both native and cross.
24281 * HPPA:: HP PA architecture
24282 * SPU:: Cell Broadband Engine SPU architecture
24290 @subsection AArch64
24291 @cindex AArch64 support
24293 When @value{GDBN} is debugging the AArch64 architecture, it provides the
24294 following special commands:
24297 @item set debug aarch64
24298 @kindex set debug aarch64
24299 This command determines whether AArch64 architecture-specific debugging
24300 messages are to be displayed.
24302 @item show debug aarch64
24303 Show whether AArch64 debugging messages are displayed.
24307 @subsubsection AArch64 SVE.
24308 @cindex AArch64 SVE.
24310 When @value{GDBN} is debugging the AArch64 architecture, if the Scalable Vector
24311 Extension (SVE) is present, then @value{GDBN} will provide the vector registers
24312 @code{$z0} through @code{$z31}, vector predicate registers @code{$p0} through
24313 @code{$p15}, and the @code{$ffr} register. In addition, the pseudo register
24314 @code{$vg} will be provided. This is the vector granule for the current thread
24315 and represents the number of 64-bit chunks in an SVE @code{z} register.
24317 If the vector length changes, then the @code{$vg} register will be updated,
24318 but the lengths of the @code{z} and @code{p} registers will not change. This
24319 is a known limitation of @value{GDBN} and does not affect the execution of the
24324 @subsection x86 Architecture-specific Issues
24327 @item set struct-convention @var{mode}
24328 @kindex set struct-convention
24329 @cindex struct return convention
24330 @cindex struct/union returned in registers
24331 Set the convention used by the inferior to return @code{struct}s and
24332 @code{union}s from functions to @var{mode}. Possible values of
24333 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
24334 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
24335 are returned on the stack, while @code{"reg"} means that a
24336 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
24337 be returned in a register.
24339 @item show struct-convention
24340 @kindex show struct-convention
24341 Show the current setting of the convention to return @code{struct}s
24346 @subsubsection Intel @dfn{Memory Protection Extensions} (MPX).
24347 @cindex Intel Memory Protection Extensions (MPX).
24349 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
24350 @footnote{The register named with capital letters represent the architecture
24351 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
24352 which are the lower bound and upper bound. Bounds are effective addresses or
24353 memory locations. The upper bounds are architecturally represented in 1's
24354 complement form. A bound having lower bound = 0, and upper bound = 0
24355 (1's complement of all bits set) will allow access to the entire address space.
24357 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
24358 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
24359 display the upper bound performing the complement of one operation on the
24360 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
24361 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
24362 can also be noted that the upper bounds are inclusive.
24364 As an example, assume that the register BND0 holds bounds for a pointer having
24365 access allowed for the range between 0x32 and 0x71. The values present on
24366 bnd0raw and bnd registers are presented as follows:
24369 bnd0raw = @{0x32, 0xffffffff8e@}
24370 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
24373 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
24374 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
24375 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
24376 Python, the display includes the memory size, in bits, accessible to
24379 Bounds can also be stored in bounds tables, which are stored in
24380 application memory. These tables store bounds for pointers by specifying
24381 the bounds pointer's value along with its bounds. Evaluating and changing
24382 bounds located in bound tables is therefore interesting while investigating
24383 bugs on MPX context. @value{GDBN} provides commands for this purpose:
24386 @item show mpx bound @var{pointer}
24387 @kindex show mpx bound
24388 Display bounds of the given @var{pointer}.
24390 @item set mpx bound @var{pointer}, @var{lbound}, @var{ubound}
24391 @kindex set mpx bound
24392 Set the bounds of a pointer in the bound table.
24393 This command takes three parameters: @var{pointer} is the pointers
24394 whose bounds are to be changed, @var{lbound} and @var{ubound} are new values
24395 for lower and upper bounds respectively.
24398 When you call an inferior function on an Intel MPX enabled program,
24399 GDB sets the inferior's bound registers to the init (disabled) state
24400 before calling the function. As a consequence, bounds checks for the
24401 pointer arguments passed to the function will always pass.
24403 This is necessary because when you call an inferior function, the
24404 program is usually in the middle of the execution of other function.
24405 Since at that point bound registers are in an arbitrary state, not
24406 clearing them would lead to random bound violations in the called
24409 You can still examine the influence of the bound registers on the
24410 execution of the called function by stopping the execution of the
24411 called function at its prologue, setting bound registers, and
24412 continuing the execution. For example:
24416 Breakpoint 2 at 0x4009de: file i386-mpx-call.c, line 47.
24417 $ print upper (a, b, c, d, 1)
24418 Breakpoint 2, upper (a=0x0, b=0x6e0000005b, c=0x0, d=0x0, len=48)....
24420 @{lbound = 0x0, ubound = ffffffff@} : size -1
24423 At this last step the value of bnd0 can be changed for investigation of bound
24424 violations caused along the execution of the call. In order to know how to
24425 set the bound registers or bound table for the call consult the ABI.
24430 See the following section.
24433 @subsection @acronym{MIPS}
24435 @cindex stack on Alpha
24436 @cindex stack on @acronym{MIPS}
24437 @cindex Alpha stack
24438 @cindex @acronym{MIPS} stack
24439 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
24440 sometimes requires @value{GDBN} to search backward in the object code to
24441 find the beginning of a function.
24443 @cindex response time, @acronym{MIPS} debugging
24444 To improve response time (especially for embedded applications, where
24445 @value{GDBN} may be restricted to a slow serial line for this search)
24446 you may want to limit the size of this search, using one of these
24450 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
24451 @item set heuristic-fence-post @var{limit}
24452 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
24453 search for the beginning of a function. A value of @var{0} (the
24454 default) means there is no limit. However, except for @var{0}, the
24455 larger the limit the more bytes @code{heuristic-fence-post} must search
24456 and therefore the longer it takes to run. You should only need to use
24457 this command when debugging a stripped executable.
24459 @item show heuristic-fence-post
24460 Display the current limit.
24464 These commands are available @emph{only} when @value{GDBN} is configured
24465 for debugging programs on Alpha or @acronym{MIPS} processors.
24467 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
24471 @item set mips abi @var{arg}
24472 @kindex set mips abi
24473 @cindex set ABI for @acronym{MIPS}
24474 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
24475 values of @var{arg} are:
24479 The default ABI associated with the current binary (this is the
24489 @item show mips abi
24490 @kindex show mips abi
24491 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
24493 @item set mips compression @var{arg}
24494 @kindex set mips compression
24495 @cindex code compression, @acronym{MIPS}
24496 Tell @value{GDBN} which @acronym{MIPS} compressed
24497 @acronym{ISA, Instruction Set Architecture} encoding is used by the
24498 inferior. @value{GDBN} uses this for code disassembly and other
24499 internal interpretation purposes. This setting is only referred to
24500 when no executable has been associated with the debugging session or
24501 the executable does not provide information about the encoding it uses.
24502 Otherwise this setting is automatically updated from information
24503 provided by the executable.
24505 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
24506 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
24507 executables containing @acronym{MIPS16} code frequently are not
24508 identified as such.
24510 This setting is ``sticky''; that is, it retains its value across
24511 debugging sessions until reset either explicitly with this command or
24512 implicitly from an executable.
24514 The compiler and/or assembler typically add symbol table annotations to
24515 identify functions compiled for the @acronym{MIPS16} or
24516 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
24517 are present, @value{GDBN} uses them in preference to the global
24518 compressed @acronym{ISA} encoding setting.
24520 @item show mips compression
24521 @kindex show mips compression
24522 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
24523 @value{GDBN} to debug the inferior.
24526 @itemx show mipsfpu
24527 @xref{MIPS Embedded, set mipsfpu}.
24529 @item set mips mask-address @var{arg}
24530 @kindex set mips mask-address
24531 @cindex @acronym{MIPS} addresses, masking
24532 This command determines whether the most-significant 32 bits of 64-bit
24533 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
24534 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
24535 setting, which lets @value{GDBN} determine the correct value.
24537 @item show mips mask-address
24538 @kindex show mips mask-address
24539 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
24542 @item set remote-mips64-transfers-32bit-regs
24543 @kindex set remote-mips64-transfers-32bit-regs
24544 This command controls compatibility with 64-bit @acronym{MIPS} targets that
24545 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
24546 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
24547 and 64 bits for other registers, set this option to @samp{on}.
24549 @item show remote-mips64-transfers-32bit-regs
24550 @kindex show remote-mips64-transfers-32bit-regs
24551 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
24553 @item set debug mips
24554 @kindex set debug mips
24555 This command turns on and off debugging messages for the @acronym{MIPS}-specific
24556 target code in @value{GDBN}.
24558 @item show debug mips
24559 @kindex show debug mips
24560 Show the current setting of @acronym{MIPS} debugging messages.
24566 @cindex HPPA support
24568 When @value{GDBN} is debugging the HP PA architecture, it provides the
24569 following special commands:
24572 @item set debug hppa
24573 @kindex set debug hppa
24574 This command determines whether HPPA architecture-specific debugging
24575 messages are to be displayed.
24577 @item show debug hppa
24578 Show whether HPPA debugging messages are displayed.
24580 @item maint print unwind @var{address}
24581 @kindex maint print unwind@r{, HPPA}
24582 This command displays the contents of the unwind table entry at the
24583 given @var{address}.
24589 @subsection Cell Broadband Engine SPU architecture
24590 @cindex Cell Broadband Engine
24593 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
24594 it provides the following special commands:
24597 @item info spu event
24599 Display SPU event facility status. Shows current event mask
24600 and pending event status.
24602 @item info spu signal
24603 Display SPU signal notification facility status. Shows pending
24604 signal-control word and signal notification mode of both signal
24605 notification channels.
24607 @item info spu mailbox
24608 Display SPU mailbox facility status. Shows all pending entries,
24609 in order of processing, in each of the SPU Write Outbound,
24610 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
24613 Display MFC DMA status. Shows all pending commands in the MFC
24614 DMA queue. For each entry, opcode, tag, class IDs, effective
24615 and local store addresses and transfer size are shown.
24617 @item info spu proxydma
24618 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
24619 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
24620 and local store addresses and transfer size are shown.
24624 When @value{GDBN} is debugging a combined PowerPC/SPU application
24625 on the Cell Broadband Engine, it provides in addition the following
24629 @item set spu stop-on-load @var{arg}
24631 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
24632 will give control to the user when a new SPE thread enters its @code{main}
24633 function. The default is @code{off}.
24635 @item show spu stop-on-load
24637 Show whether to stop for new SPE threads.
24639 @item set spu auto-flush-cache @var{arg}
24640 Set whether to automatically flush the software-managed cache. When set to
24641 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
24642 cache to be flushed whenever SPE execution stops. This provides a consistent
24643 view of PowerPC memory that is accessed via the cache. If an application
24644 does not use the software-managed cache, this option has no effect.
24646 @item show spu auto-flush-cache
24647 Show whether to automatically flush the software-managed cache.
24652 @subsection PowerPC
24653 @cindex PowerPC architecture
24655 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
24656 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
24657 numbers stored in the floating point registers. These values must be stored
24658 in two consecutive registers, always starting at an even register like
24659 @code{f0} or @code{f2}.
24661 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
24662 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
24663 @code{f2} and @code{f3} for @code{$dl1} and so on.
24665 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
24666 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
24669 @subsection Nios II
24670 @cindex Nios II architecture
24672 When @value{GDBN} is debugging the Nios II architecture,
24673 it provides the following special commands:
24677 @item set debug nios2
24678 @kindex set debug nios2
24679 This command turns on and off debugging messages for the Nios II
24680 target code in @value{GDBN}.
24682 @item show debug nios2
24683 @kindex show debug nios2
24684 Show the current setting of Nios II debugging messages.
24688 @subsection Sparc64
24689 @cindex Sparc64 support
24690 @cindex Application Data Integrity
24691 @subsubsection ADI Support
24693 The M7 processor supports an Application Data Integrity (ADI) feature that
24694 detects invalid data accesses. When software allocates memory and enables
24695 ADI on the allocated memory, it chooses a 4-bit version number, sets the
24696 version in the upper 4 bits of the 64-bit pointer to that data, and stores
24697 the 4-bit version in every cacheline of that data. Hardware saves the latter
24698 in spare bits in the cache and memory hierarchy. On each load and store,
24699 the processor compares the upper 4 VA (virtual address) bits to the
24700 cacheline's version. If there is a mismatch, the processor generates a
24701 version mismatch trap which can be either precise or disrupting. The trap
24702 is an error condition which the kernel delivers to the process as a SIGSEGV
24705 Note that only 64-bit applications can use ADI and need to be built with
24708 Values of the ADI version tags, which are in granularity of a
24709 cacheline (64 bytes), can be viewed or modified.
24713 @kindex adi examine
24714 @item adi (examine | x) [ / @var{n} ] @var{addr}
24716 The @code{adi examine} command displays the value of one ADI version tag per
24719 @var{n} is a decimal integer specifying the number in bytes; the default
24720 is 1. It specifies how much ADI version information, at the ratio of 1:ADI
24721 block size, to display.
24723 @var{addr} is the address in user address space where you want @value{GDBN}
24724 to begin displaying the ADI version tags.
24726 Below is an example of displaying ADI versions of variable "shmaddr".
24729 (@value{GDBP}) adi x/100 shmaddr
24730 0xfff800010002c000: 0 0
24734 @item adi (assign | a) [ / @var{n} ] @var{addr} = @var{tag}
24736 The @code{adi assign} command is used to assign new ADI version tag
24739 @var{n} is a decimal integer specifying the number in bytes;
24740 the default is 1. It specifies how much ADI version information, at the
24741 ratio of 1:ADI block size, to modify.
24743 @var{addr} is the address in user address space where you want @value{GDBN}
24744 to begin modifying the ADI version tags.
24746 @var{tag} is the new ADI version tag.
24748 For example, do the following to modify then verify ADI versions of
24749 variable "shmaddr":
24752 (@value{GDBP}) adi a/100 shmaddr = 7
24753 (@value{GDBP}) adi x/100 shmaddr
24754 0xfff800010002c000: 7 7
24761 @cindex S12Z support
24763 When @value{GDBN} is debugging the S12Z architecture,
24764 it provides the following special command:
24767 @item maint info bdccsr
24768 @kindex maint info bdccsr@r{, S12Z}
24769 This command displays the current value of the microprocessor's
24774 @node Controlling GDB
24775 @chapter Controlling @value{GDBN}
24777 You can alter the way @value{GDBN} interacts with you by using the
24778 @code{set} command. For commands controlling how @value{GDBN} displays
24779 data, see @ref{Print Settings, ,Print Settings}. Other settings are
24784 * Editing:: Command editing
24785 * Command History:: Command history
24786 * Screen Size:: Screen size
24787 * Output Styling:: Output styling
24788 * Numbers:: Numbers
24789 * ABI:: Configuring the current ABI
24790 * Auto-loading:: Automatically loading associated files
24791 * Messages/Warnings:: Optional warnings and messages
24792 * Debugging Output:: Optional messages about internal happenings
24793 * Other Misc Settings:: Other Miscellaneous Settings
24801 @value{GDBN} indicates its readiness to read a command by printing a string
24802 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
24803 can change the prompt string with the @code{set prompt} command. For
24804 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
24805 the prompt in one of the @value{GDBN} sessions so that you can always tell
24806 which one you are talking to.
24808 @emph{Note:} @code{set prompt} does not add a space for you after the
24809 prompt you set. This allows you to set a prompt which ends in a space
24810 or a prompt that does not.
24814 @item set prompt @var{newprompt}
24815 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
24817 @kindex show prompt
24819 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
24822 Versions of @value{GDBN} that ship with Python scripting enabled have
24823 prompt extensions. The commands for interacting with these extensions
24827 @kindex set extended-prompt
24828 @item set extended-prompt @var{prompt}
24829 Set an extended prompt that allows for substitutions.
24830 @xref{gdb.prompt}, for a list of escape sequences that can be used for
24831 substitution. Any escape sequences specified as part of the prompt
24832 string are replaced with the corresponding strings each time the prompt
24838 set extended-prompt Current working directory: \w (gdb)
24841 Note that when an extended-prompt is set, it takes control of the
24842 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
24844 @kindex show extended-prompt
24845 @item show extended-prompt
24846 Prints the extended prompt. Any escape sequences specified as part of
24847 the prompt string with @code{set extended-prompt}, are replaced with the
24848 corresponding strings each time the prompt is displayed.
24852 @section Command Editing
24854 @cindex command line editing
24856 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
24857 @sc{gnu} library provides consistent behavior for programs which provide a
24858 command line interface to the user. Advantages are @sc{gnu} Emacs-style
24859 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
24860 substitution, and a storage and recall of command history across
24861 debugging sessions.
24863 You may control the behavior of command line editing in @value{GDBN} with the
24864 command @code{set}.
24867 @kindex set editing
24870 @itemx set editing on
24871 Enable command line editing (enabled by default).
24873 @item set editing off
24874 Disable command line editing.
24876 @kindex show editing
24878 Show whether command line editing is enabled.
24881 @ifset SYSTEM_READLINE
24882 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
24884 @ifclear SYSTEM_READLINE
24885 @xref{Command Line Editing},
24887 for more details about the Readline
24888 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
24889 encouraged to read that chapter.
24891 @node Command History
24892 @section Command History
24893 @cindex command history
24895 @value{GDBN} can keep track of the commands you type during your
24896 debugging sessions, so that you can be certain of precisely what
24897 happened. Use these commands to manage the @value{GDBN} command
24900 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
24901 package, to provide the history facility.
24902 @ifset SYSTEM_READLINE
24903 @xref{Using History Interactively, , , history, GNU History Library},
24905 @ifclear SYSTEM_READLINE
24906 @xref{Using History Interactively},
24908 for the detailed description of the History library.
24910 To issue a command to @value{GDBN} without affecting certain aspects of
24911 the state which is seen by users, prefix it with @samp{server }
24912 (@pxref{Server Prefix}). This
24913 means that this command will not affect the command history, nor will it
24914 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
24915 pressed on a line by itself.
24917 @cindex @code{server}, command prefix
24918 The server prefix does not affect the recording of values into the value
24919 history; to print a value without recording it into the value history,
24920 use the @code{output} command instead of the @code{print} command.
24922 Here is the description of @value{GDBN} commands related to command
24926 @cindex history substitution
24927 @cindex history file
24928 @kindex set history filename
24929 @cindex @env{GDBHISTFILE}, environment variable
24930 @item set history filename @var{fname}
24931 Set the name of the @value{GDBN} command history file to @var{fname}.
24932 This is the file where @value{GDBN} reads an initial command history
24933 list, and where it writes the command history from this session when it
24934 exits. You can access this list through history expansion or through
24935 the history command editing characters listed below. This file defaults
24936 to the value of the environment variable @code{GDBHISTFILE}, or to
24937 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
24940 @cindex save command history
24941 @kindex set history save
24942 @item set history save
24943 @itemx set history save on
24944 Record command history in a file, whose name may be specified with the
24945 @code{set history filename} command. By default, this option is disabled.
24947 @item set history save off
24948 Stop recording command history in a file.
24950 @cindex history size
24951 @kindex set history size
24952 @cindex @env{GDBHISTSIZE}, environment variable
24953 @item set history size @var{size}
24954 @itemx set history size unlimited
24955 Set the number of commands which @value{GDBN} keeps in its history list.
24956 This defaults to the value of the environment variable @env{GDBHISTSIZE}, or
24957 to 256 if this variable is not set. Non-numeric values of @env{GDBHISTSIZE}
24958 are ignored. If @var{size} is @code{unlimited} or if @env{GDBHISTSIZE} is
24959 either a negative number or the empty string, then the number of commands
24960 @value{GDBN} keeps in the history list is unlimited.
24962 @cindex remove duplicate history
24963 @kindex set history remove-duplicates
24964 @item set history remove-duplicates @var{count}
24965 @itemx set history remove-duplicates unlimited
24966 Control the removal of duplicate history entries in the command history list.
24967 If @var{count} is non-zero, @value{GDBN} will look back at the last @var{count}
24968 history entries and remove the first entry that is a duplicate of the current
24969 entry being added to the command history list. If @var{count} is
24970 @code{unlimited} then this lookbehind is unbounded. If @var{count} is 0, then
24971 removal of duplicate history entries is disabled.
24973 Only history entries added during the current session are considered for
24974 removal. This option is set to 0 by default.
24978 History expansion assigns special meaning to the character @kbd{!}.
24979 @ifset SYSTEM_READLINE
24980 @xref{Event Designators, , , history, GNU History Library},
24982 @ifclear SYSTEM_READLINE
24983 @xref{Event Designators},
24987 @cindex history expansion, turn on/off
24988 Since @kbd{!} is also the logical not operator in C, history expansion
24989 is off by default. If you decide to enable history expansion with the
24990 @code{set history expansion on} command, you may sometimes need to
24991 follow @kbd{!} (when it is used as logical not, in an expression) with
24992 a space or a tab to prevent it from being expanded. The readline
24993 history facilities do not attempt substitution on the strings
24994 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
24996 The commands to control history expansion are:
24999 @item set history expansion on
25000 @itemx set history expansion
25001 @kindex set history expansion
25002 Enable history expansion. History expansion is off by default.
25004 @item set history expansion off
25005 Disable history expansion.
25008 @kindex show history
25010 @itemx show history filename
25011 @itemx show history save
25012 @itemx show history size
25013 @itemx show history expansion
25014 These commands display the state of the @value{GDBN} history parameters.
25015 @code{show history} by itself displays all four states.
25020 @kindex show commands
25021 @cindex show last commands
25022 @cindex display command history
25023 @item show commands
25024 Display the last ten commands in the command history.
25026 @item show commands @var{n}
25027 Print ten commands centered on command number @var{n}.
25029 @item show commands +
25030 Print ten commands just after the commands last printed.
25034 @section Screen Size
25035 @cindex size of screen
25036 @cindex screen size
25039 @cindex pauses in output
25041 Certain commands to @value{GDBN} may produce large amounts of
25042 information output to the screen. To help you read all of it,
25043 @value{GDBN} pauses and asks you for input at the end of each page of
25044 output. Type @key{RET} when you want to see one more page of output,
25045 @kbd{q} to discard the remaining output, or @kbd{c} to continue
25046 without paging for the rest of the current command. Also, the screen
25047 width setting determines when to wrap lines of output. Depending on
25048 what is being printed, @value{GDBN} tries to break the line at a
25049 readable place, rather than simply letting it overflow onto the
25052 Normally @value{GDBN} knows the size of the screen from the terminal
25053 driver software. For example, on Unix @value{GDBN} uses the termcap data base
25054 together with the value of the @code{TERM} environment variable and the
25055 @code{stty rows} and @code{stty cols} settings. If this is not correct,
25056 you can override it with the @code{set height} and @code{set
25063 @kindex show height
25064 @item set height @var{lpp}
25065 @itemx set height unlimited
25067 @itemx set width @var{cpl}
25068 @itemx set width unlimited
25070 These @code{set} commands specify a screen height of @var{lpp} lines and
25071 a screen width of @var{cpl} characters. The associated @code{show}
25072 commands display the current settings.
25074 If you specify a height of either @code{unlimited} or zero lines,
25075 @value{GDBN} does not pause during output no matter how long the
25076 output is. This is useful if output is to a file or to an editor
25079 Likewise, you can specify @samp{set width unlimited} or @samp{set
25080 width 0} to prevent @value{GDBN} from wrapping its output.
25082 @item set pagination on
25083 @itemx set pagination off
25084 @kindex set pagination
25085 Turn the output pagination on or off; the default is on. Turning
25086 pagination off is the alternative to @code{set height unlimited}. Note that
25087 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
25088 Options, -batch}) also automatically disables pagination.
25090 @item show pagination
25091 @kindex show pagination
25092 Show the current pagination mode.
25095 @node Output Styling
25096 @section Output Styling
25102 @value{GDBN} can style its output on a capable terminal. This is
25103 enabled by default on most systems, but disabled by default when in
25104 batch mode (@pxref{Mode Options}). Various style settings are available;
25105 and styles can also be disabled entirely.
25108 @item set style enabled @samp{on|off}
25109 Enable or disable all styling. The default is host-dependent, with
25110 most hosts defaulting to @samp{on}.
25112 @item show style enabled
25113 Show the current state of styling.
25115 @item set style sources @samp{on|off}
25116 Enable or disable source code styling. This affects whether source
25117 code, such as the output of the @code{list} command, is styled. Note
25118 that source styling only works if styling in general is enabled, and
25119 if @value{GDBN} was linked with the GNU Source Highlight library. The
25120 default is @samp{on}.
25122 @item show style sources
25123 Show the current state of source code styling.
25126 Subcommands of @code{set style} control specific forms of styling.
25127 These subcommands all follow the same pattern: each style-able object
25128 can be styled with a foreground color, a background color, and an
25131 For example, the style of file names can be controlled using the
25132 @code{set style filename} group of commands:
25135 @item set style filename background @var{color}
25136 Set the background to @var{color}. Valid colors are @samp{none}
25137 (meaning the terminal's default color), @samp{black}, @samp{red},
25138 @samp{green}, @samp{yellow}, @samp{blue}, @samp{magenta}, @samp{cyan},
25141 @item set style filename foreground @var{color}
25142 Set the foreground to @var{color}. Valid colors are @samp{none}
25143 (meaning the terminal's default color), @samp{black}, @samp{red},
25144 @samp{green}, @samp{yellow}, @samp{blue}, @samp{magenta}, @samp{cyan},
25147 @item set style filename intensity @var{value}
25148 Set the intensity to @var{value}. Valid intensities are @samp{normal}
25149 (the default), @samp{bold}, and @samp{dim}.
25152 The @code{show style} command and its subcommands are styling
25153 a style name in their output using its own style.
25154 So, use @command{show style} to see the complete list of styles,
25155 their characteristics and the visual aspect of each style.
25157 The style-able objects are:
25160 Control the styling of file names. By default, this style's
25161 foreground color is green.
25164 Control the styling of function names. These are managed with the
25165 @code{set style function} family of commands. By default, this
25166 style's foreground color is yellow.
25169 Control the styling of variable names. These are managed with the
25170 @code{set style variable} family of commands. By default, this style's
25171 foreground color is cyan.
25174 Control the styling of addresses. These are managed with the
25175 @code{set style address} family of commands. By default, this style's
25176 foreground color is blue.
25179 Control the styling of titles. These are managed with the
25180 @code{set style title} family of commands. By default, this style's
25181 intensity is bold. Commands are using the title style to improve
25182 the readibility of large output. For example, the commands
25183 @command{apropos} and @command{help} are using the title style
25184 for the command names.
25187 Control the styling of highlightings. These are managed with the
25188 @code{set style highlight} family of commands. By default, this style's
25189 foreground color is red. Commands are using the highlight style to draw
25190 the user attention to some specific parts of their output. For example,
25191 the command @command{apropos -v REGEXP} uses the highlight style to
25192 mark the documentation parts matching @var{regexp}.
25198 @cindex number representation
25199 @cindex entering numbers
25201 You can always enter numbers in octal, decimal, or hexadecimal in
25202 @value{GDBN} by the usual conventions: octal numbers begin with
25203 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
25204 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
25205 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
25206 10; likewise, the default display for numbers---when no particular
25207 format is specified---is base 10. You can change the default base for
25208 both input and output with the commands described below.
25211 @kindex set input-radix
25212 @item set input-radix @var{base}
25213 Set the default base for numeric input. Supported choices
25214 for @var{base} are decimal 8, 10, or 16. The base must itself be
25215 specified either unambiguously or using the current input radix; for
25219 set input-radix 012
25220 set input-radix 10.
25221 set input-radix 0xa
25225 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
25226 leaves the input radix unchanged, no matter what it was, since
25227 @samp{10}, being without any leading or trailing signs of its base, is
25228 interpreted in the current radix. Thus, if the current radix is 16,
25229 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
25232 @kindex set output-radix
25233 @item set output-radix @var{base}
25234 Set the default base for numeric display. Supported choices
25235 for @var{base} are decimal 8, 10, or 16. The base must itself be
25236 specified either unambiguously or using the current input radix.
25238 @kindex show input-radix
25239 @item show input-radix
25240 Display the current default base for numeric input.
25242 @kindex show output-radix
25243 @item show output-radix
25244 Display the current default base for numeric display.
25246 @item set radix @r{[}@var{base}@r{]}
25250 These commands set and show the default base for both input and output
25251 of numbers. @code{set radix} sets the radix of input and output to
25252 the same base; without an argument, it resets the radix back to its
25253 default value of 10.
25258 @section Configuring the Current ABI
25260 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
25261 application automatically. However, sometimes you need to override its
25262 conclusions. Use these commands to manage @value{GDBN}'s view of the
25268 @cindex Newlib OS ABI and its influence on the longjmp handling
25270 One @value{GDBN} configuration can debug binaries for multiple operating
25271 system targets, either via remote debugging or native emulation.
25272 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
25273 but you can override its conclusion using the @code{set osabi} command.
25274 One example where this is useful is in debugging of binaries which use
25275 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
25276 not have the same identifying marks that the standard C library for your
25279 When @value{GDBN} is debugging the AArch64 architecture, it provides a
25280 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
25281 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
25282 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
25286 Show the OS ABI currently in use.
25289 With no argument, show the list of registered available OS ABI's.
25291 @item set osabi @var{abi}
25292 Set the current OS ABI to @var{abi}.
25295 @cindex float promotion
25297 Generally, the way that an argument of type @code{float} is passed to a
25298 function depends on whether the function is prototyped. For a prototyped
25299 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
25300 according to the architecture's convention for @code{float}. For unprototyped
25301 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
25302 @code{double} and then passed.
25304 Unfortunately, some forms of debug information do not reliably indicate whether
25305 a function is prototyped. If @value{GDBN} calls a function that is not marked
25306 as prototyped, it consults @kbd{set coerce-float-to-double}.
25309 @kindex set coerce-float-to-double
25310 @item set coerce-float-to-double
25311 @itemx set coerce-float-to-double on
25312 Arguments of type @code{float} will be promoted to @code{double} when passed
25313 to an unprototyped function. This is the default setting.
25315 @item set coerce-float-to-double off
25316 Arguments of type @code{float} will be passed directly to unprototyped
25319 @kindex show coerce-float-to-double
25320 @item show coerce-float-to-double
25321 Show the current setting of promoting @code{float} to @code{double}.
25325 @kindex show cp-abi
25326 @value{GDBN} needs to know the ABI used for your program's C@t{++}
25327 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
25328 used to build your application. @value{GDBN} only fully supports
25329 programs with a single C@t{++} ABI; if your program contains code using
25330 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
25331 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
25332 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
25333 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
25334 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
25335 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
25340 Show the C@t{++} ABI currently in use.
25343 With no argument, show the list of supported C@t{++} ABI's.
25345 @item set cp-abi @var{abi}
25346 @itemx set cp-abi auto
25347 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
25351 @section Automatically loading associated files
25352 @cindex auto-loading
25354 @value{GDBN} sometimes reads files with commands and settings automatically,
25355 without being explicitly told so by the user. We call this feature
25356 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
25357 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
25358 results or introduce security risks (e.g., if the file comes from untrusted
25362 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
25363 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
25365 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
25366 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
25369 There are various kinds of files @value{GDBN} can automatically load.
25370 In addition to these files, @value{GDBN} supports auto-loading code written
25371 in various extension languages. @xref{Auto-loading extensions}.
25373 Note that loading of these associated files (including the local @file{.gdbinit}
25374 file) requires accordingly configured @code{auto-load safe-path}
25375 (@pxref{Auto-loading safe path}).
25377 For these reasons, @value{GDBN} includes commands and options to let you
25378 control when to auto-load files and which files should be auto-loaded.
25381 @anchor{set auto-load off}
25382 @kindex set auto-load off
25383 @item set auto-load off
25384 Globally disable loading of all auto-loaded files.
25385 You may want to use this command with the @samp{-iex} option
25386 (@pxref{Option -init-eval-command}) such as:
25388 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
25391 Be aware that system init file (@pxref{System-wide configuration})
25392 and init files from your home directory (@pxref{Home Directory Init File})
25393 still get read (as they come from generally trusted directories).
25394 To prevent @value{GDBN} from auto-loading even those init files, use the
25395 @option{-nx} option (@pxref{Mode Options}), in addition to
25396 @code{set auto-load no}.
25398 @anchor{show auto-load}
25399 @kindex show auto-load
25400 @item show auto-load
25401 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
25405 (gdb) show auto-load
25406 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
25407 libthread-db: Auto-loading of inferior specific libthread_db is on.
25408 local-gdbinit: Auto-loading of .gdbinit script from current directory
25410 python-scripts: Auto-loading of Python scripts is on.
25411 safe-path: List of directories from which it is safe to auto-load files
25412 is $debugdir:$datadir/auto-load.
25413 scripts-directory: List of directories from which to load auto-loaded scripts
25414 is $debugdir:$datadir/auto-load.
25417 @anchor{info auto-load}
25418 @kindex info auto-load
25419 @item info auto-load
25420 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
25424 (gdb) info auto-load
25427 Yes /home/user/gdb/gdb-gdb.gdb
25428 libthread-db: No auto-loaded libthread-db.
25429 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
25433 Yes /home/user/gdb/gdb-gdb.py
25437 These are @value{GDBN} control commands for the auto-loading:
25439 @multitable @columnfractions .5 .5
25440 @item @xref{set auto-load off}.
25441 @tab Disable auto-loading globally.
25442 @item @xref{show auto-load}.
25443 @tab Show setting of all kinds of files.
25444 @item @xref{info auto-load}.
25445 @tab Show state of all kinds of files.
25446 @item @xref{set auto-load gdb-scripts}.
25447 @tab Control for @value{GDBN} command scripts.
25448 @item @xref{show auto-load gdb-scripts}.
25449 @tab Show setting of @value{GDBN} command scripts.
25450 @item @xref{info auto-load gdb-scripts}.
25451 @tab Show state of @value{GDBN} command scripts.
25452 @item @xref{set auto-load python-scripts}.
25453 @tab Control for @value{GDBN} Python scripts.
25454 @item @xref{show auto-load python-scripts}.
25455 @tab Show setting of @value{GDBN} Python scripts.
25456 @item @xref{info auto-load python-scripts}.
25457 @tab Show state of @value{GDBN} Python scripts.
25458 @item @xref{set auto-load guile-scripts}.
25459 @tab Control for @value{GDBN} Guile scripts.
25460 @item @xref{show auto-load guile-scripts}.
25461 @tab Show setting of @value{GDBN} Guile scripts.
25462 @item @xref{info auto-load guile-scripts}.
25463 @tab Show state of @value{GDBN} Guile scripts.
25464 @item @xref{set auto-load scripts-directory}.
25465 @tab Control for @value{GDBN} auto-loaded scripts location.
25466 @item @xref{show auto-load scripts-directory}.
25467 @tab Show @value{GDBN} auto-loaded scripts location.
25468 @item @xref{add-auto-load-scripts-directory}.
25469 @tab Add directory for auto-loaded scripts location list.
25470 @item @xref{set auto-load local-gdbinit}.
25471 @tab Control for init file in the current directory.
25472 @item @xref{show auto-load local-gdbinit}.
25473 @tab Show setting of init file in the current directory.
25474 @item @xref{info auto-load local-gdbinit}.
25475 @tab Show state of init file in the current directory.
25476 @item @xref{set auto-load libthread-db}.
25477 @tab Control for thread debugging library.
25478 @item @xref{show auto-load libthread-db}.
25479 @tab Show setting of thread debugging library.
25480 @item @xref{info auto-load libthread-db}.
25481 @tab Show state of thread debugging library.
25482 @item @xref{set auto-load safe-path}.
25483 @tab Control directories trusted for automatic loading.
25484 @item @xref{show auto-load safe-path}.
25485 @tab Show directories trusted for automatic loading.
25486 @item @xref{add-auto-load-safe-path}.
25487 @tab Add directory trusted for automatic loading.
25490 @node Init File in the Current Directory
25491 @subsection Automatically loading init file in the current directory
25492 @cindex auto-loading init file in the current directory
25494 By default, @value{GDBN} reads and executes the canned sequences of commands
25495 from init file (if any) in the current working directory,
25496 see @ref{Init File in the Current Directory during Startup}.
25498 Note that loading of this local @file{.gdbinit} file also requires accordingly
25499 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25502 @anchor{set auto-load local-gdbinit}
25503 @kindex set auto-load local-gdbinit
25504 @item set auto-load local-gdbinit [on|off]
25505 Enable or disable the auto-loading of canned sequences of commands
25506 (@pxref{Sequences}) found in init file in the current directory.
25508 @anchor{show auto-load local-gdbinit}
25509 @kindex show auto-load local-gdbinit
25510 @item show auto-load local-gdbinit
25511 Show whether auto-loading of canned sequences of commands from init file in the
25512 current directory is enabled or disabled.
25514 @anchor{info auto-load local-gdbinit}
25515 @kindex info auto-load local-gdbinit
25516 @item info auto-load local-gdbinit
25517 Print whether canned sequences of commands from init file in the
25518 current directory have been auto-loaded.
25521 @node libthread_db.so.1 file
25522 @subsection Automatically loading thread debugging library
25523 @cindex auto-loading libthread_db.so.1
25525 This feature is currently present only on @sc{gnu}/Linux native hosts.
25527 @value{GDBN} reads in some cases thread debugging library from places specific
25528 to the inferior (@pxref{set libthread-db-search-path}).
25530 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
25531 without checking this @samp{set auto-load libthread-db} switch as system
25532 libraries have to be trusted in general. In all other cases of
25533 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
25534 auto-load libthread-db} is enabled before trying to open such thread debugging
25537 Note that loading of this debugging library also requires accordingly configured
25538 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25541 @anchor{set auto-load libthread-db}
25542 @kindex set auto-load libthread-db
25543 @item set auto-load libthread-db [on|off]
25544 Enable or disable the auto-loading of inferior specific thread debugging library.
25546 @anchor{show auto-load libthread-db}
25547 @kindex show auto-load libthread-db
25548 @item show auto-load libthread-db
25549 Show whether auto-loading of inferior specific thread debugging library is
25550 enabled or disabled.
25552 @anchor{info auto-load libthread-db}
25553 @kindex info auto-load libthread-db
25554 @item info auto-load libthread-db
25555 Print the list of all loaded inferior specific thread debugging libraries and
25556 for each such library print list of inferior @var{pid}s using it.
25559 @node Auto-loading safe path
25560 @subsection Security restriction for auto-loading
25561 @cindex auto-loading safe-path
25563 As the files of inferior can come from untrusted source (such as submitted by
25564 an application user) @value{GDBN} does not always load any files automatically.
25565 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
25566 directories trusted for loading files not explicitly requested by user.
25567 Each directory can also be a shell wildcard pattern.
25569 If the path is not set properly you will see a warning and the file will not
25574 Reading symbols from /home/user/gdb/gdb...done.
25575 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
25576 declined by your `auto-load safe-path' set
25577 to "$debugdir:$datadir/auto-load".
25578 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
25579 declined by your `auto-load safe-path' set
25580 to "$debugdir:$datadir/auto-load".
25584 To instruct @value{GDBN} to go ahead and use the init files anyway,
25585 invoke @value{GDBN} like this:
25588 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
25591 The list of trusted directories is controlled by the following commands:
25594 @anchor{set auto-load safe-path}
25595 @kindex set auto-load safe-path
25596 @item set auto-load safe-path @r{[}@var{directories}@r{]}
25597 Set the list of directories (and their subdirectories) trusted for automatic
25598 loading and execution of scripts. You can also enter a specific trusted file.
25599 Each directory can also be a shell wildcard pattern; wildcards do not match
25600 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
25601 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
25602 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
25603 its default value as specified during @value{GDBN} compilation.
25605 The list of directories uses path separator (@samp{:} on GNU and Unix
25606 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
25607 to the @env{PATH} environment variable.
25609 @anchor{show auto-load safe-path}
25610 @kindex show auto-load safe-path
25611 @item show auto-load safe-path
25612 Show the list of directories trusted for automatic loading and execution of
25615 @anchor{add-auto-load-safe-path}
25616 @kindex add-auto-load-safe-path
25617 @item add-auto-load-safe-path
25618 Add an entry (or list of entries) to the list of directories trusted for
25619 automatic loading and execution of scripts. Multiple entries may be delimited
25620 by the host platform path separator in use.
25623 This variable defaults to what @code{--with-auto-load-dir} has been configured
25624 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
25625 substitution applies the same as for @ref{set auto-load scripts-directory}.
25626 The default @code{set auto-load safe-path} value can be also overriden by
25627 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
25629 Setting this variable to @file{/} disables this security protection,
25630 corresponding @value{GDBN} configuration option is
25631 @option{--without-auto-load-safe-path}.
25632 This variable is supposed to be set to the system directories writable by the
25633 system superuser only. Users can add their source directories in init files in
25634 their home directories (@pxref{Home Directory Init File}). See also deprecated
25635 init file in the current directory
25636 (@pxref{Init File in the Current Directory during Startup}).
25638 To force @value{GDBN} to load the files it declined to load in the previous
25639 example, you could use one of the following ways:
25642 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
25643 Specify this trusted directory (or a file) as additional component of the list.
25644 You have to specify also any existing directories displayed by
25645 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
25647 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
25648 Specify this directory as in the previous case but just for a single
25649 @value{GDBN} session.
25651 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
25652 Disable auto-loading safety for a single @value{GDBN} session.
25653 This assumes all the files you debug during this @value{GDBN} session will come
25654 from trusted sources.
25656 @item @kbd{./configure --without-auto-load-safe-path}
25657 During compilation of @value{GDBN} you may disable any auto-loading safety.
25658 This assumes all the files you will ever debug with this @value{GDBN} come from
25662 On the other hand you can also explicitly forbid automatic files loading which
25663 also suppresses any such warning messages:
25666 @item @kbd{gdb -iex "set auto-load no" @dots{}}
25667 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
25669 @item @file{~/.gdbinit}: @samp{set auto-load no}
25670 Disable auto-loading globally for the user
25671 (@pxref{Home Directory Init File}). While it is improbable, you could also
25672 use system init file instead (@pxref{System-wide configuration}).
25675 This setting applies to the file names as entered by user. If no entry matches
25676 @value{GDBN} tries as a last resort to also resolve all the file names into
25677 their canonical form (typically resolving symbolic links) and compare the
25678 entries again. @value{GDBN} already canonicalizes most of the filenames on its
25679 own before starting the comparison so a canonical form of directories is
25680 recommended to be entered.
25682 @node Auto-loading verbose mode
25683 @subsection Displaying files tried for auto-load
25684 @cindex auto-loading verbose mode
25686 For better visibility of all the file locations where you can place scripts to
25687 be auto-loaded with inferior --- or to protect yourself against accidental
25688 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
25689 all the files attempted to be loaded. Both existing and non-existing files may
25692 For example the list of directories from which it is safe to auto-load files
25693 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
25694 may not be too obvious while setting it up.
25697 (gdb) set debug auto-load on
25698 (gdb) file ~/src/t/true
25699 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
25700 for objfile "/tmp/true".
25701 auto-load: Updating directories of "/usr:/opt".
25702 auto-load: Using directory "/usr".
25703 auto-load: Using directory "/opt".
25704 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
25705 by your `auto-load safe-path' set to "/usr:/opt".
25709 @anchor{set debug auto-load}
25710 @kindex set debug auto-load
25711 @item set debug auto-load [on|off]
25712 Set whether to print the filenames attempted to be auto-loaded.
25714 @anchor{show debug auto-load}
25715 @kindex show debug auto-load
25716 @item show debug auto-load
25717 Show whether printing of the filenames attempted to be auto-loaded is turned
25721 @node Messages/Warnings
25722 @section Optional Warnings and Messages
25724 @cindex verbose operation
25725 @cindex optional warnings
25726 By default, @value{GDBN} is silent about its inner workings. If you are
25727 running on a slow machine, you may want to use the @code{set verbose}
25728 command. This makes @value{GDBN} tell you when it does a lengthy
25729 internal operation, so you will not think it has crashed.
25731 Currently, the messages controlled by @code{set verbose} are those
25732 which announce that the symbol table for a source file is being read;
25733 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
25736 @kindex set verbose
25737 @item set verbose on
25738 Enables @value{GDBN} output of certain informational messages.
25740 @item set verbose off
25741 Disables @value{GDBN} output of certain informational messages.
25743 @kindex show verbose
25745 Displays whether @code{set verbose} is on or off.
25748 By default, if @value{GDBN} encounters bugs in the symbol table of an
25749 object file, it is silent; but if you are debugging a compiler, you may
25750 find this information useful (@pxref{Symbol Errors, ,Errors Reading
25755 @kindex set complaints
25756 @item set complaints @var{limit}
25757 Permits @value{GDBN} to output @var{limit} complaints about each type of
25758 unusual symbols before becoming silent about the problem. Set
25759 @var{limit} to zero to suppress all complaints; set it to a large number
25760 to prevent complaints from being suppressed.
25762 @kindex show complaints
25763 @item show complaints
25764 Displays how many symbol complaints @value{GDBN} is permitted to produce.
25768 @anchor{confirmation requests}
25769 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
25770 lot of stupid questions to confirm certain commands. For example, if
25771 you try to run a program which is already running:
25775 The program being debugged has been started already.
25776 Start it from the beginning? (y or n)
25779 If you are willing to unflinchingly face the consequences of your own
25780 commands, you can disable this ``feature'':
25784 @kindex set confirm
25786 @cindex confirmation
25787 @cindex stupid questions
25788 @item set confirm off
25789 Disables confirmation requests. Note that running @value{GDBN} with
25790 the @option{--batch} option (@pxref{Mode Options, -batch}) also
25791 automatically disables confirmation requests.
25793 @item set confirm on
25794 Enables confirmation requests (the default).
25796 @kindex show confirm
25798 Displays state of confirmation requests.
25802 @cindex command tracing
25803 If you need to debug user-defined commands or sourced files you may find it
25804 useful to enable @dfn{command tracing}. In this mode each command will be
25805 printed as it is executed, prefixed with one or more @samp{+} symbols, the
25806 quantity denoting the call depth of each command.
25809 @kindex set trace-commands
25810 @cindex command scripts, debugging
25811 @item set trace-commands on
25812 Enable command tracing.
25813 @item set trace-commands off
25814 Disable command tracing.
25815 @item show trace-commands
25816 Display the current state of command tracing.
25819 @node Debugging Output
25820 @section Optional Messages about Internal Happenings
25821 @cindex optional debugging messages
25823 @value{GDBN} has commands that enable optional debugging messages from
25824 various @value{GDBN} subsystems; normally these commands are of
25825 interest to @value{GDBN} maintainers, or when reporting a bug. This
25826 section documents those commands.
25829 @kindex set exec-done-display
25830 @item set exec-done-display
25831 Turns on or off the notification of asynchronous commands'
25832 completion. When on, @value{GDBN} will print a message when an
25833 asynchronous command finishes its execution. The default is off.
25834 @kindex show exec-done-display
25835 @item show exec-done-display
25836 Displays the current setting of asynchronous command completion
25839 @cindex ARM AArch64
25840 @item set debug aarch64
25841 Turns on or off display of debugging messages related to ARM AArch64.
25842 The default is off.
25844 @item show debug aarch64
25845 Displays the current state of displaying debugging messages related to
25847 @cindex gdbarch debugging info
25848 @cindex architecture debugging info
25849 @item set debug arch
25850 Turns on or off display of gdbarch debugging info. The default is off
25851 @item show debug arch
25852 Displays the current state of displaying gdbarch debugging info.
25853 @item set debug aix-solib
25854 @cindex AIX shared library debugging
25855 Control display of debugging messages from the AIX shared library
25856 support module. The default is off.
25857 @item show debug aix-thread
25858 Show the current state of displaying AIX shared library debugging messages.
25859 @item set debug aix-thread
25860 @cindex AIX threads
25861 Display debugging messages about inner workings of the AIX thread
25863 @item show debug aix-thread
25864 Show the current state of AIX thread debugging info display.
25865 @item set debug check-physname
25867 Check the results of the ``physname'' computation. When reading DWARF
25868 debugging information for C@t{++}, @value{GDBN} attempts to compute
25869 each entity's name. @value{GDBN} can do this computation in two
25870 different ways, depending on exactly what information is present.
25871 When enabled, this setting causes @value{GDBN} to compute the names
25872 both ways and display any discrepancies.
25873 @item show debug check-physname
25874 Show the current state of ``physname'' checking.
25875 @item set debug coff-pe-read
25876 @cindex COFF/PE exported symbols
25877 Control display of debugging messages related to reading of COFF/PE
25878 exported symbols. The default is off.
25879 @item show debug coff-pe-read
25880 Displays the current state of displaying debugging messages related to
25881 reading of COFF/PE exported symbols.
25882 @item set debug dwarf-die
25884 Dump DWARF DIEs after they are read in.
25885 The value is the number of nesting levels to print.
25886 A value of zero turns off the display.
25887 @item show debug dwarf-die
25888 Show the current state of DWARF DIE debugging.
25889 @item set debug dwarf-line
25890 @cindex DWARF Line Tables
25891 Turns on or off display of debugging messages related to reading
25892 DWARF line tables. The default is 0 (off).
25893 A value of 1 provides basic information.
25894 A value greater than 1 provides more verbose information.
25895 @item show debug dwarf-line
25896 Show the current state of DWARF line table debugging.
25897 @item set debug dwarf-read
25898 @cindex DWARF Reading
25899 Turns on or off display of debugging messages related to reading
25900 DWARF debug info. The default is 0 (off).
25901 A value of 1 provides basic information.
25902 A value greater than 1 provides more verbose information.
25903 @item show debug dwarf-read
25904 Show the current state of DWARF reader debugging.
25905 @item set debug displaced
25906 @cindex displaced stepping debugging info
25907 Turns on or off display of @value{GDBN} debugging info for the
25908 displaced stepping support. The default is off.
25909 @item show debug displaced
25910 Displays the current state of displaying @value{GDBN} debugging info
25911 related to displaced stepping.
25912 @item set debug event
25913 @cindex event debugging info
25914 Turns on or off display of @value{GDBN} event debugging info. The
25916 @item show debug event
25917 Displays the current state of displaying @value{GDBN} event debugging
25919 @item set debug expression
25920 @cindex expression debugging info
25921 Turns on or off display of debugging info about @value{GDBN}
25922 expression parsing. The default is off.
25923 @item show debug expression
25924 Displays the current state of displaying debugging info about
25925 @value{GDBN} expression parsing.
25926 @item set debug fbsd-lwp
25927 @cindex FreeBSD LWP debug messages
25928 Turns on or off debugging messages from the FreeBSD LWP debug support.
25929 @item show debug fbsd-lwp
25930 Show the current state of FreeBSD LWP debugging messages.
25931 @item set debug fbsd-nat
25932 @cindex FreeBSD native target debug messages
25933 Turns on or off debugging messages from the FreeBSD native target.
25934 @item show debug fbsd-nat
25935 Show the current state of FreeBSD native target debugging messages.
25936 @item set debug frame
25937 @cindex frame debugging info
25938 Turns on or off display of @value{GDBN} frame debugging info. The
25940 @item show debug frame
25941 Displays the current state of displaying @value{GDBN} frame debugging
25943 @item set debug gnu-nat
25944 @cindex @sc{gnu}/Hurd debug messages
25945 Turn on or off debugging messages from the @sc{gnu}/Hurd debug support.
25946 @item show debug gnu-nat
25947 Show the current state of @sc{gnu}/Hurd debugging messages.
25948 @item set debug infrun
25949 @cindex inferior debugging info
25950 Turns on or off display of @value{GDBN} debugging info for running the inferior.
25951 The default is off. @file{infrun.c} contains GDB's runtime state machine used
25952 for implementing operations such as single-stepping the inferior.
25953 @item show debug infrun
25954 Displays the current state of @value{GDBN} inferior debugging.
25955 @item set debug jit
25956 @cindex just-in-time compilation, debugging messages
25957 Turn on or off debugging messages from JIT debug support.
25958 @item show debug jit
25959 Displays the current state of @value{GDBN} JIT debugging.
25960 @item set debug lin-lwp
25961 @cindex @sc{gnu}/Linux LWP debug messages
25962 @cindex Linux lightweight processes
25963 Turn on or off debugging messages from the Linux LWP debug support.
25964 @item show debug lin-lwp
25965 Show the current state of Linux LWP debugging messages.
25966 @item set debug linux-namespaces
25967 @cindex @sc{gnu}/Linux namespaces debug messages
25968 Turn on or off debugging messages from the Linux namespaces debug support.
25969 @item show debug linux-namespaces
25970 Show the current state of Linux namespaces debugging messages.
25971 @item set debug mach-o
25972 @cindex Mach-O symbols processing
25973 Control display of debugging messages related to Mach-O symbols
25974 processing. The default is off.
25975 @item show debug mach-o
25976 Displays the current state of displaying debugging messages related to
25977 reading of COFF/PE exported symbols.
25978 @item set debug notification
25979 @cindex remote async notification debugging info
25980 Turn on or off debugging messages about remote async notification.
25981 The default is off.
25982 @item show debug notification
25983 Displays the current state of remote async notification debugging messages.
25984 @item set debug observer
25985 @cindex observer debugging info
25986 Turns on or off display of @value{GDBN} observer debugging. This
25987 includes info such as the notification of observable events.
25988 @item show debug observer
25989 Displays the current state of observer debugging.
25990 @item set debug overload
25991 @cindex C@t{++} overload debugging info
25992 Turns on or off display of @value{GDBN} C@t{++} overload debugging
25993 info. This includes info such as ranking of functions, etc. The default
25995 @item show debug overload
25996 Displays the current state of displaying @value{GDBN} C@t{++} overload
25998 @cindex expression parser, debugging info
25999 @cindex debug expression parser
26000 @item set debug parser
26001 Turns on or off the display of expression parser debugging output.
26002 Internally, this sets the @code{yydebug} variable in the expression
26003 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
26004 details. The default is off.
26005 @item show debug parser
26006 Show the current state of expression parser debugging.
26007 @cindex packets, reporting on stdout
26008 @cindex serial connections, debugging
26009 @cindex debug remote protocol
26010 @cindex remote protocol debugging
26011 @cindex display remote packets
26012 @item set debug remote
26013 Turns on or off display of reports on all packets sent back and forth across
26014 the serial line to the remote machine. The info is printed on the
26015 @value{GDBN} standard output stream. The default is off.
26016 @item show debug remote
26017 Displays the state of display of remote packets.
26019 @item set debug separate-debug-file
26020 Turns on or off display of debug output about separate debug file search.
26021 @item show debug separate-debug-file
26022 Displays the state of separate debug file search debug output.
26024 @item set debug serial
26025 Turns on or off display of @value{GDBN} serial debugging info. The
26027 @item show debug serial
26028 Displays the current state of displaying @value{GDBN} serial debugging
26030 @item set debug solib-frv
26031 @cindex FR-V shared-library debugging
26032 Turn on or off debugging messages for FR-V shared-library code.
26033 @item show debug solib-frv
26034 Display the current state of FR-V shared-library code debugging
26036 @item set debug symbol-lookup
26037 @cindex symbol lookup
26038 Turns on or off display of debugging messages related to symbol lookup.
26039 The default is 0 (off).
26040 A value of 1 provides basic information.
26041 A value greater than 1 provides more verbose information.
26042 @item show debug symbol-lookup
26043 Show the current state of symbol lookup debugging messages.
26044 @item set debug symfile
26045 @cindex symbol file functions
26046 Turns on or off display of debugging messages related to symbol file functions.
26047 The default is off. @xref{Files}.
26048 @item show debug symfile
26049 Show the current state of symbol file debugging messages.
26050 @item set debug symtab-create
26051 @cindex symbol table creation
26052 Turns on or off display of debugging messages related to symbol table creation.
26053 The default is 0 (off).
26054 A value of 1 provides basic information.
26055 A value greater than 1 provides more verbose information.
26056 @item show debug symtab-create
26057 Show the current state of symbol table creation debugging.
26058 @item set debug target
26059 @cindex target debugging info
26060 Turns on or off display of @value{GDBN} target debugging info. This info
26061 includes what is going on at the target level of GDB, as it happens. The
26062 default is 0. Set it to 1 to track events, and to 2 to also track the
26063 value of large memory transfers.
26064 @item show debug target
26065 Displays the current state of displaying @value{GDBN} target debugging
26067 @item set debug timestamp
26068 @cindex timestampping debugging info
26069 Turns on or off display of timestamps with @value{GDBN} debugging info.
26070 When enabled, seconds and microseconds are displayed before each debugging
26072 @item show debug timestamp
26073 Displays the current state of displaying timestamps with @value{GDBN}
26075 @item set debug varobj
26076 @cindex variable object debugging info
26077 Turns on or off display of @value{GDBN} variable object debugging
26078 info. The default is off.
26079 @item show debug varobj
26080 Displays the current state of displaying @value{GDBN} variable object
26082 @item set debug xml
26083 @cindex XML parser debugging
26084 Turn on or off debugging messages for built-in XML parsers.
26085 @item show debug xml
26086 Displays the current state of XML debugging messages.
26089 @node Other Misc Settings
26090 @section Other Miscellaneous Settings
26091 @cindex miscellaneous settings
26094 @kindex set interactive-mode
26095 @item set interactive-mode
26096 If @code{on}, forces @value{GDBN} to assume that GDB was started
26097 in a terminal. In practice, this means that @value{GDBN} should wait
26098 for the user to answer queries generated by commands entered at
26099 the command prompt. If @code{off}, forces @value{GDBN} to operate
26100 in the opposite mode, and it uses the default answers to all queries.
26101 If @code{auto} (the default), @value{GDBN} tries to determine whether
26102 its standard input is a terminal, and works in interactive-mode if it
26103 is, non-interactively otherwise.
26105 In the vast majority of cases, the debugger should be able to guess
26106 correctly which mode should be used. But this setting can be useful
26107 in certain specific cases, such as running a MinGW @value{GDBN}
26108 inside a cygwin window.
26110 @kindex show interactive-mode
26111 @item show interactive-mode
26112 Displays whether the debugger is operating in interactive mode or not.
26115 @node Extending GDB
26116 @chapter Extending @value{GDBN}
26117 @cindex extending GDB
26119 @value{GDBN} provides several mechanisms for extension.
26120 @value{GDBN} also provides the ability to automatically load
26121 extensions when it reads a file for debugging. This allows the
26122 user to automatically customize @value{GDBN} for the program
26126 * Sequences:: Canned Sequences of @value{GDBN} Commands
26127 * Python:: Extending @value{GDBN} using Python
26128 * Guile:: Extending @value{GDBN} using Guile
26129 * Auto-loading extensions:: Automatically loading extensions
26130 * Multiple Extension Languages:: Working with multiple extension languages
26131 * Aliases:: Creating new spellings of existing commands
26134 To facilitate the use of extension languages, @value{GDBN} is capable
26135 of evaluating the contents of a file. When doing so, @value{GDBN}
26136 can recognize which extension language is being used by looking at
26137 the filename extension. Files with an unrecognized filename extension
26138 are always treated as a @value{GDBN} Command Files.
26139 @xref{Command Files,, Command files}.
26141 You can control how @value{GDBN} evaluates these files with the following
26145 @kindex set script-extension
26146 @kindex show script-extension
26147 @item set script-extension off
26148 All scripts are always evaluated as @value{GDBN} Command Files.
26150 @item set script-extension soft
26151 The debugger determines the scripting language based on filename
26152 extension. If this scripting language is supported, @value{GDBN}
26153 evaluates the script using that language. Otherwise, it evaluates
26154 the file as a @value{GDBN} Command File.
26156 @item set script-extension strict
26157 The debugger determines the scripting language based on filename
26158 extension, and evaluates the script using that language. If the
26159 language is not supported, then the evaluation fails.
26161 @item show script-extension
26162 Display the current value of the @code{script-extension} option.
26167 @section Canned Sequences of Commands
26169 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
26170 Command Lists}), @value{GDBN} provides two ways to store sequences of
26171 commands for execution as a unit: user-defined commands and command
26175 * Define:: How to define your own commands
26176 * Hooks:: Hooks for user-defined commands
26177 * Command Files:: How to write scripts of commands to be stored in a file
26178 * Output:: Commands for controlled output
26179 * Auto-loading sequences:: Controlling auto-loaded command files
26183 @subsection User-defined Commands
26185 @cindex user-defined command
26186 @cindex arguments, to user-defined commands
26187 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
26188 which you assign a new name as a command. This is done with the
26189 @code{define} command. User commands may accept an unlimited number of arguments
26190 separated by whitespace. Arguments are accessed within the user command
26191 via @code{$arg0@dots{}$argN}. A trivial example:
26195 print $arg0 + $arg1 + $arg2
26200 To execute the command use:
26207 This defines the command @code{adder}, which prints the sum of
26208 its three arguments. Note the arguments are text substitutions, so they may
26209 reference variables, use complex expressions, or even perform inferior
26212 @cindex argument count in user-defined commands
26213 @cindex how many arguments (user-defined commands)
26214 In addition, @code{$argc} may be used to find out how many arguments have
26220 print $arg0 + $arg1
26223 print $arg0 + $arg1 + $arg2
26228 Combining with the @code{eval} command (@pxref{eval}) makes it easier
26229 to process a variable number of arguments:
26236 eval "set $sum = $sum + $arg%d", $i
26246 @item define @var{commandname}
26247 Define a command named @var{commandname}. If there is already a command
26248 by that name, you are asked to confirm that you want to redefine it.
26249 The argument @var{commandname} may be a bare command name consisting of letters,
26250 numbers, dashes, and underscores. It may also start with any predefined
26251 prefix command. For example, @samp{define target my-target} creates
26252 a user-defined @samp{target my-target} command.
26254 The definition of the command is made up of other @value{GDBN} command lines,
26255 which are given following the @code{define} command. The end of these
26256 commands is marked by a line containing @code{end}.
26259 @kindex end@r{ (user-defined commands)}
26260 @item document @var{commandname}
26261 Document the user-defined command @var{commandname}, so that it can be
26262 accessed by @code{help}. The command @var{commandname} must already be
26263 defined. This command reads lines of documentation just as @code{define}
26264 reads the lines of the command definition, ending with @code{end}.
26265 After the @code{document} command is finished, @code{help} on command
26266 @var{commandname} displays the documentation you have written.
26268 You may use the @code{document} command again to change the
26269 documentation of a command. Redefining the command with @code{define}
26270 does not change the documentation.
26272 @kindex dont-repeat
26273 @cindex don't repeat command
26275 Used inside a user-defined command, this tells @value{GDBN} that this
26276 command should not be repeated when the user hits @key{RET}
26277 (@pxref{Command Syntax, repeat last command}).
26279 @kindex help user-defined
26280 @item help user-defined
26281 List all user-defined commands and all python commands defined in class
26282 COMAND_USER. The first line of the documentation or docstring is
26287 @itemx show user @var{commandname}
26288 Display the @value{GDBN} commands used to define @var{commandname} (but
26289 not its documentation). If no @var{commandname} is given, display the
26290 definitions for all user-defined commands.
26291 This does not work for user-defined python commands.
26293 @cindex infinite recursion in user-defined commands
26294 @kindex show max-user-call-depth
26295 @kindex set max-user-call-depth
26296 @item show max-user-call-depth
26297 @itemx set max-user-call-depth
26298 The value of @code{max-user-call-depth} controls how many recursion
26299 levels are allowed in user-defined commands before @value{GDBN} suspects an
26300 infinite recursion and aborts the command.
26301 This does not apply to user-defined python commands.
26304 In addition to the above commands, user-defined commands frequently
26305 use control flow commands, described in @ref{Command Files}.
26307 When user-defined commands are executed, the
26308 commands of the definition are not printed. An error in any command
26309 stops execution of the user-defined command.
26311 If used interactively, commands that would ask for confirmation proceed
26312 without asking when used inside a user-defined command. Many @value{GDBN}
26313 commands that normally print messages to say what they are doing omit the
26314 messages when used in a user-defined command.
26317 @subsection User-defined Command Hooks
26318 @cindex command hooks
26319 @cindex hooks, for commands
26320 @cindex hooks, pre-command
26323 You may define @dfn{hooks}, which are a special kind of user-defined
26324 command. Whenever you run the command @samp{foo}, if the user-defined
26325 command @samp{hook-foo} exists, it is executed (with no arguments)
26326 before that command.
26328 @cindex hooks, post-command
26330 A hook may also be defined which is run after the command you executed.
26331 Whenever you run the command @samp{foo}, if the user-defined command
26332 @samp{hookpost-foo} exists, it is executed (with no arguments) after
26333 that command. Post-execution hooks may exist simultaneously with
26334 pre-execution hooks, for the same command.
26336 It is valid for a hook to call the command which it hooks. If this
26337 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
26339 @c It would be nice if hookpost could be passed a parameter indicating
26340 @c if the command it hooks executed properly or not. FIXME!
26342 @kindex stop@r{, a pseudo-command}
26343 In addition, a pseudo-command, @samp{stop} exists. Defining
26344 (@samp{hook-stop}) makes the associated commands execute every time
26345 execution stops in your program: before breakpoint commands are run,
26346 displays are printed, or the stack frame is printed.
26348 For example, to ignore @code{SIGALRM} signals while
26349 single-stepping, but treat them normally during normal execution,
26354 handle SIGALRM nopass
26358 handle SIGALRM pass
26361 define hook-continue
26362 handle SIGALRM pass
26366 As a further example, to hook at the beginning and end of the @code{echo}
26367 command, and to add extra text to the beginning and end of the message,
26375 define hookpost-echo
26379 (@value{GDBP}) echo Hello World
26380 <<<---Hello World--->>>
26385 You can define a hook for any single-word command in @value{GDBN}, but
26386 not for command aliases; you should define a hook for the basic command
26387 name, e.g.@: @code{backtrace} rather than @code{bt}.
26388 @c FIXME! So how does Joe User discover whether a command is an alias
26390 You can hook a multi-word command by adding @code{hook-} or
26391 @code{hookpost-} to the last word of the command, e.g.@:
26392 @samp{define target hook-remote} to add a hook to @samp{target remote}.
26394 If an error occurs during the execution of your hook, execution of
26395 @value{GDBN} commands stops and @value{GDBN} issues a prompt
26396 (before the command that you actually typed had a chance to run).
26398 If you try to define a hook which does not match any known command, you
26399 get a warning from the @code{define} command.
26401 @node Command Files
26402 @subsection Command Files
26404 @cindex command files
26405 @cindex scripting commands
26406 A command file for @value{GDBN} is a text file made of lines that are
26407 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
26408 also be included. An empty line in a command file does nothing; it
26409 does not mean to repeat the last command, as it would from the
26412 You can request the execution of a command file with the @code{source}
26413 command. Note that the @code{source} command is also used to evaluate
26414 scripts that are not Command Files. The exact behavior can be configured
26415 using the @code{script-extension} setting.
26416 @xref{Extending GDB,, Extending GDB}.
26420 @cindex execute commands from a file
26421 @item source [-s] [-v] @var{filename}
26422 Execute the command file @var{filename}.
26425 The lines in a command file are generally executed sequentially,
26426 unless the order of execution is changed by one of the
26427 @emph{flow-control commands} described below. The commands are not
26428 printed as they are executed. An error in any command terminates
26429 execution of the command file and control is returned to the console.
26431 @value{GDBN} first searches for @var{filename} in the current directory.
26432 If the file is not found there, and @var{filename} does not specify a
26433 directory, then @value{GDBN} also looks for the file on the source search path
26434 (specified with the @samp{directory} command);
26435 except that @file{$cdir} is not searched because the compilation directory
26436 is not relevant to scripts.
26438 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
26439 on the search path even if @var{filename} specifies a directory.
26440 The search is done by appending @var{filename} to each element of the
26441 search path. So, for example, if @var{filename} is @file{mylib/myscript}
26442 and the search path contains @file{/home/user} then @value{GDBN} will
26443 look for the script @file{/home/user/mylib/myscript}.
26444 The search is also done if @var{filename} is an absolute path.
26445 For example, if @var{filename} is @file{/tmp/myscript} and
26446 the search path contains @file{/home/user} then @value{GDBN} will
26447 look for the script @file{/home/user/tmp/myscript}.
26448 For DOS-like systems, if @var{filename} contains a drive specification,
26449 it is stripped before concatenation. For example, if @var{filename} is
26450 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
26451 will look for the script @file{c:/tmp/myscript}.
26453 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
26454 each command as it is executed. The option must be given before
26455 @var{filename}, and is interpreted as part of the filename anywhere else.
26457 Commands that would ask for confirmation if used interactively proceed
26458 without asking when used in a command file. Many @value{GDBN} commands that
26459 normally print messages to say what they are doing omit the messages
26460 when called from command files.
26462 @value{GDBN} also accepts command input from standard input. In this
26463 mode, normal output goes to standard output and error output goes to
26464 standard error. Errors in a command file supplied on standard input do
26465 not terminate execution of the command file---execution continues with
26469 gdb < cmds > log 2>&1
26472 (The syntax above will vary depending on the shell used.) This example
26473 will execute commands from the file @file{cmds}. All output and errors
26474 would be directed to @file{log}.
26476 Since commands stored on command files tend to be more general than
26477 commands typed interactively, they frequently need to deal with
26478 complicated situations, such as different or unexpected values of
26479 variables and symbols, changes in how the program being debugged is
26480 built, etc. @value{GDBN} provides a set of flow-control commands to
26481 deal with these complexities. Using these commands, you can write
26482 complex scripts that loop over data structures, execute commands
26483 conditionally, etc.
26490 This command allows to include in your script conditionally executed
26491 commands. The @code{if} command takes a single argument, which is an
26492 expression to evaluate. It is followed by a series of commands that
26493 are executed only if the expression is true (its value is nonzero).
26494 There can then optionally be an @code{else} line, followed by a series
26495 of commands that are only executed if the expression was false. The
26496 end of the list is marked by a line containing @code{end}.
26500 This command allows to write loops. Its syntax is similar to
26501 @code{if}: the command takes a single argument, which is an expression
26502 to evaluate, and must be followed by the commands to execute, one per
26503 line, terminated by an @code{end}. These commands are called the
26504 @dfn{body} of the loop. The commands in the body of @code{while} are
26505 executed repeatedly as long as the expression evaluates to true.
26509 This command exits the @code{while} loop in whose body it is included.
26510 Execution of the script continues after that @code{while}s @code{end}
26513 @kindex loop_continue
26514 @item loop_continue
26515 This command skips the execution of the rest of the body of commands
26516 in the @code{while} loop in whose body it is included. Execution
26517 branches to the beginning of the @code{while} loop, where it evaluates
26518 the controlling expression.
26520 @kindex end@r{ (if/else/while commands)}
26522 Terminate the block of commands that are the body of @code{if},
26523 @code{else}, or @code{while} flow-control commands.
26528 @subsection Commands for Controlled Output
26530 During the execution of a command file or a user-defined command, normal
26531 @value{GDBN} output is suppressed; the only output that appears is what is
26532 explicitly printed by the commands in the definition. This section
26533 describes three commands useful for generating exactly the output you
26538 @item echo @var{text}
26539 @c I do not consider backslash-space a standard C escape sequence
26540 @c because it is not in ANSI.
26541 Print @var{text}. Nonprinting characters can be included in
26542 @var{text} using C escape sequences, such as @samp{\n} to print a
26543 newline. @strong{No newline is printed unless you specify one.}
26544 In addition to the standard C escape sequences, a backslash followed
26545 by a space stands for a space. This is useful for displaying a
26546 string with spaces at the beginning or the end, since leading and
26547 trailing spaces are otherwise trimmed from all arguments.
26548 To print @samp{@w{ }and foo =@w{ }}, use the command
26549 @samp{echo \@w{ }and foo = \@w{ }}.
26551 A backslash at the end of @var{text} can be used, as in C, to continue
26552 the command onto subsequent lines. For example,
26555 echo This is some text\n\
26556 which is continued\n\
26557 onto several lines.\n
26560 produces the same output as
26563 echo This is some text\n
26564 echo which is continued\n
26565 echo onto several lines.\n
26569 @item output @var{expression}
26570 Print the value of @var{expression} and nothing but that value: no
26571 newlines, no @samp{$@var{nn} = }. The value is not entered in the
26572 value history either. @xref{Expressions, ,Expressions}, for more information
26575 @item output/@var{fmt} @var{expression}
26576 Print the value of @var{expression} in format @var{fmt}. You can use
26577 the same formats as for @code{print}. @xref{Output Formats,,Output
26578 Formats}, for more information.
26581 @item printf @var{template}, @var{expressions}@dots{}
26582 Print the values of one or more @var{expressions} under the control of
26583 the string @var{template}. To print several values, make
26584 @var{expressions} be a comma-separated list of individual expressions,
26585 which may be either numbers or pointers. Their values are printed as
26586 specified by @var{template}, exactly as a C program would do by
26587 executing the code below:
26590 printf (@var{template}, @var{expressions}@dots{});
26593 As in @code{C} @code{printf}, ordinary characters in @var{template}
26594 are printed verbatim, while @dfn{conversion specification} introduced
26595 by the @samp{%} character cause subsequent @var{expressions} to be
26596 evaluated, their values converted and formatted according to type and
26597 style information encoded in the conversion specifications, and then
26600 For example, you can print two values in hex like this:
26603 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
26606 @code{printf} supports all the standard @code{C} conversion
26607 specifications, including the flags and modifiers between the @samp{%}
26608 character and the conversion letter, with the following exceptions:
26612 The argument-ordering modifiers, such as @samp{2$}, are not supported.
26615 The modifier @samp{*} is not supported for specifying precision or
26619 The @samp{'} flag (for separation of digits into groups according to
26620 @code{LC_NUMERIC'}) is not supported.
26623 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
26627 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
26630 The conversion letters @samp{a} and @samp{A} are not supported.
26634 Note that the @samp{ll} type modifier is supported only if the
26635 underlying @code{C} implementation used to build @value{GDBN} supports
26636 the @code{long long int} type, and the @samp{L} type modifier is
26637 supported only if @code{long double} type is available.
26639 As in @code{C}, @code{printf} supports simple backslash-escape
26640 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
26641 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
26642 single character. Octal and hexadecimal escape sequences are not
26645 Additionally, @code{printf} supports conversion specifications for DFP
26646 (@dfn{Decimal Floating Point}) types using the following length modifiers
26647 together with a floating point specifier.
26652 @samp{H} for printing @code{Decimal32} types.
26655 @samp{D} for printing @code{Decimal64} types.
26658 @samp{DD} for printing @code{Decimal128} types.
26661 If the underlying @code{C} implementation used to build @value{GDBN} has
26662 support for the three length modifiers for DFP types, other modifiers
26663 such as width and precision will also be available for @value{GDBN} to use.
26665 In case there is no such @code{C} support, no additional modifiers will be
26666 available and the value will be printed in the standard way.
26668 Here's an example of printing DFP types using the above conversion letters:
26670 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
26675 @item eval @var{template}, @var{expressions}@dots{}
26676 Convert the values of one or more @var{expressions} under the control of
26677 the string @var{template} to a command line, and call it.
26681 @node Auto-loading sequences
26682 @subsection Controlling auto-loading native @value{GDBN} scripts
26683 @cindex native script auto-loading
26685 When a new object file is read (for example, due to the @code{file}
26686 command, or because the inferior has loaded a shared library),
26687 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
26688 @xref{Auto-loading extensions}.
26690 Auto-loading can be enabled or disabled,
26691 and the list of auto-loaded scripts can be printed.
26694 @anchor{set auto-load gdb-scripts}
26695 @kindex set auto-load gdb-scripts
26696 @item set auto-load gdb-scripts [on|off]
26697 Enable or disable the auto-loading of canned sequences of commands scripts.
26699 @anchor{show auto-load gdb-scripts}
26700 @kindex show auto-load gdb-scripts
26701 @item show auto-load gdb-scripts
26702 Show whether auto-loading of canned sequences of commands scripts is enabled or
26705 @anchor{info auto-load gdb-scripts}
26706 @kindex info auto-load gdb-scripts
26707 @cindex print list of auto-loaded canned sequences of commands scripts
26708 @item info auto-load gdb-scripts [@var{regexp}]
26709 Print the list of all canned sequences of commands scripts that @value{GDBN}
26713 If @var{regexp} is supplied only canned sequences of commands scripts with
26714 matching names are printed.
26716 @c Python docs live in a separate file.
26717 @include python.texi
26719 @c Guile docs live in a separate file.
26720 @include guile.texi
26722 @node Auto-loading extensions
26723 @section Auto-loading extensions
26724 @cindex auto-loading extensions
26726 @value{GDBN} provides two mechanisms for automatically loading extensions
26727 when a new object file is read (for example, due to the @code{file}
26728 command, or because the inferior has loaded a shared library):
26729 @file{@var{objfile}-gdb.@var{ext}} and the @code{.debug_gdb_scripts}
26730 section of modern file formats like ELF.
26733 * objfile-gdb.ext file: objfile-gdbdotext file. The @file{@var{objfile}-gdb.@var{ext}} file
26734 * .debug_gdb_scripts section: dotdebug_gdb_scripts section. The @code{.debug_gdb_scripts} section
26735 * Which flavor to choose?::
26738 The auto-loading feature is useful for supplying application-specific
26739 debugging commands and features.
26741 Auto-loading can be enabled or disabled,
26742 and the list of auto-loaded scripts can be printed.
26743 See the @samp{auto-loading} section of each extension language
26744 for more information.
26745 For @value{GDBN} command files see @ref{Auto-loading sequences}.
26746 For Python files see @ref{Python Auto-loading}.
26748 Note that loading of this script file also requires accordingly configured
26749 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26751 @node objfile-gdbdotext file
26752 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
26753 @cindex @file{@var{objfile}-gdb.gdb}
26754 @cindex @file{@var{objfile}-gdb.py}
26755 @cindex @file{@var{objfile}-gdb.scm}
26757 When a new object file is read, @value{GDBN} looks for a file named
26758 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
26759 where @var{objfile} is the object file's name and
26760 where @var{ext} is the file extension for the extension language:
26763 @item @file{@var{objfile}-gdb.gdb}
26764 GDB's own command language
26765 @item @file{@var{objfile}-gdb.py}
26767 @item @file{@var{objfile}-gdb.scm}
26771 @var{script-name} is formed by ensuring that the file name of @var{objfile}
26772 is absolute, following all symlinks, and resolving @code{.} and @code{..}
26773 components, and appending the @file{-gdb.@var{ext}} suffix.
26774 If this file exists and is readable, @value{GDBN} will evaluate it as a
26775 script in the specified extension language.
26777 If this file does not exist, then @value{GDBN} will look for
26778 @var{script-name} file in all of the directories as specified below.
26780 Note that loading of these files requires an accordingly configured
26781 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26783 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
26784 scripts normally according to its @file{.exe} filename. But if no scripts are
26785 found @value{GDBN} also tries script filenames matching the object file without
26786 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
26787 is attempted on any platform. This makes the script filenames compatible
26788 between Unix and MS-Windows hosts.
26791 @anchor{set auto-load scripts-directory}
26792 @kindex set auto-load scripts-directory
26793 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
26794 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
26795 may be delimited by the host platform path separator in use
26796 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
26798 Each entry here needs to be covered also by the security setting
26799 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
26801 @anchor{with-auto-load-dir}
26802 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
26803 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
26804 configuration option @option{--with-auto-load-dir}.
26806 Any reference to @file{$debugdir} will get replaced by
26807 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
26808 reference to @file{$datadir} will get replaced by @var{data-directory} which is
26809 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
26810 @file{$datadir} must be placed as a directory component --- either alone or
26811 delimited by @file{/} or @file{\} directory separators, depending on the host
26814 The list of directories uses path separator (@samp{:} on GNU and Unix
26815 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
26816 to the @env{PATH} environment variable.
26818 @anchor{show auto-load scripts-directory}
26819 @kindex show auto-load scripts-directory
26820 @item show auto-load scripts-directory
26821 Show @value{GDBN} auto-loaded scripts location.
26823 @anchor{add-auto-load-scripts-directory}
26824 @kindex add-auto-load-scripts-directory
26825 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
26826 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
26827 Multiple entries may be delimited by the host platform path separator in use.
26830 @value{GDBN} does not track which files it has already auto-loaded this way.
26831 @value{GDBN} will load the associated script every time the corresponding
26832 @var{objfile} is opened.
26833 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
26834 is evaluated more than once.
26836 @node dotdebug_gdb_scripts section
26837 @subsection The @code{.debug_gdb_scripts} section
26838 @cindex @code{.debug_gdb_scripts} section
26840 For systems using file formats like ELF and COFF,
26841 when @value{GDBN} loads a new object file
26842 it will look for a special section named @code{.debug_gdb_scripts}.
26843 If this section exists, its contents is a list of null-terminated entries
26844 specifying scripts to load. Each entry begins with a non-null prefix byte that
26845 specifies the kind of entry, typically the extension language and whether the
26846 script is in a file or inlined in @code{.debug_gdb_scripts}.
26848 The following entries are supported:
26851 @item SECTION_SCRIPT_ID_PYTHON_FILE = 1
26852 @item SECTION_SCRIPT_ID_SCHEME_FILE = 3
26853 @item SECTION_SCRIPT_ID_PYTHON_TEXT = 4
26854 @item SECTION_SCRIPT_ID_SCHEME_TEXT = 6
26857 @subsubsection Script File Entries
26859 If the entry specifies a file, @value{GDBN} will look for the file first
26860 in the current directory and then along the source search path
26861 (@pxref{Source Path, ,Specifying Source Directories}),
26862 except that @file{$cdir} is not searched, since the compilation
26863 directory is not relevant to scripts.
26865 File entries can be placed in section @code{.debug_gdb_scripts} with,
26866 for example, this GCC macro for Python scripts.
26869 /* Note: The "MS" section flags are to remove duplicates. */
26870 #define DEFINE_GDB_PY_SCRIPT(script_name) \
26872 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
26873 .byte 1 /* Python */\n\
26874 .asciz \"" script_name "\"\n\
26880 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
26881 Then one can reference the macro in a header or source file like this:
26884 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
26887 The script name may include directories if desired.
26889 Note that loading of this script file also requires accordingly configured
26890 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26892 If the macro invocation is put in a header, any application or library
26893 using this header will get a reference to the specified script,
26894 and with the use of @code{"MS"} attributes on the section, the linker
26895 will remove duplicates.
26897 @subsubsection Script Text Entries
26899 Script text entries allow to put the executable script in the entry
26900 itself instead of loading it from a file.
26901 The first line of the entry, everything after the prefix byte and up to
26902 the first newline (@code{0xa}) character, is the script name, and must not
26903 contain any kind of space character, e.g., spaces or tabs.
26904 The rest of the entry, up to the trailing null byte, is the script to
26905 execute in the specified language. The name needs to be unique among
26906 all script names, as @value{GDBN} executes each script only once based
26909 Here is an example from file @file{py-section-script.c} in the @value{GDBN}
26913 #include "symcat.h"
26914 #include "gdb/section-scripts.h"
26916 ".pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n"
26917 ".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
26918 ".ascii \"gdb.inlined-script\\n\"\n"
26919 ".ascii \"class test_cmd (gdb.Command):\\n\"\n"
26920 ".ascii \" def __init__ (self):\\n\"\n"
26921 ".ascii \" super (test_cmd, self).__init__ ("
26922 "\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
26923 ".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
26924 ".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
26925 ".ascii \"test_cmd ()\\n\"\n"
26931 Loading of inlined scripts requires a properly configured
26932 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26933 The path to specify in @code{auto-load safe-path} is the path of the file
26934 containing the @code{.debug_gdb_scripts} section.
26936 @node Which flavor to choose?
26937 @subsection Which flavor to choose?
26939 Given the multiple ways of auto-loading extensions, it might not always
26940 be clear which one to choose. This section provides some guidance.
26943 Benefits of the @file{-gdb.@var{ext}} way:
26947 Can be used with file formats that don't support multiple sections.
26950 Ease of finding scripts for public libraries.
26952 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
26953 in the source search path.
26954 For publicly installed libraries, e.g., @file{libstdc++}, there typically
26955 isn't a source directory in which to find the script.
26958 Doesn't require source code additions.
26962 Benefits of the @code{.debug_gdb_scripts} way:
26966 Works with static linking.
26968 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
26969 trigger their loading. When an application is statically linked the only
26970 objfile available is the executable, and it is cumbersome to attach all the
26971 scripts from all the input libraries to the executable's
26972 @file{-gdb.@var{ext}} script.
26975 Works with classes that are entirely inlined.
26977 Some classes can be entirely inlined, and thus there may not be an associated
26978 shared library to attach a @file{-gdb.@var{ext}} script to.
26981 Scripts needn't be copied out of the source tree.
26983 In some circumstances, apps can be built out of large collections of internal
26984 libraries, and the build infrastructure necessary to install the
26985 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
26986 cumbersome. It may be easier to specify the scripts in the
26987 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
26988 top of the source tree to the source search path.
26991 @node Multiple Extension Languages
26992 @section Multiple Extension Languages
26994 The Guile and Python extension languages do not share any state,
26995 and generally do not interfere with each other.
26996 There are some things to be aware of, however.
26998 @subsection Python comes first
27000 Python was @value{GDBN}'s first extension language, and to avoid breaking
27001 existing behaviour Python comes first. This is generally solved by the
27002 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
27003 extension languages, and when it makes a call to an extension language,
27004 (say to pretty-print a value), it tries each in turn until an extension
27005 language indicates it has performed the request (e.g., has returned the
27006 pretty-printed form of a value).
27007 This extends to errors while performing such requests: If an error happens
27008 while, for example, trying to pretty-print an object then the error is
27009 reported and any following extension languages are not tried.
27012 @section Creating new spellings of existing commands
27013 @cindex aliases for commands
27015 It is often useful to define alternate spellings of existing commands.
27016 For example, if a new @value{GDBN} command defined in Python has
27017 a long name to type, it is handy to have an abbreviated version of it
27018 that involves less typing.
27020 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
27021 of the @samp{step} command even though it is otherwise an ambiguous
27022 abbreviation of other commands like @samp{set} and @samp{show}.
27024 Aliases are also used to provide shortened or more common versions
27025 of multi-word commands. For example, @value{GDBN} provides the
27026 @samp{tty} alias of the @samp{set inferior-tty} command.
27028 You can define a new alias with the @samp{alias} command.
27033 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
27037 @var{ALIAS} specifies the name of the new alias.
27038 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
27041 @var{COMMAND} specifies the name of an existing command
27042 that is being aliased.
27044 The @samp{-a} option specifies that the new alias is an abbreviation
27045 of the command. Abbreviations are not shown in command
27046 lists displayed by the @samp{help} command.
27048 The @samp{--} option specifies the end of options,
27049 and is useful when @var{ALIAS} begins with a dash.
27051 Here is a simple example showing how to make an abbreviation
27052 of a command so that there is less to type.
27053 Suppose you were tired of typing @samp{disas}, the current
27054 shortest unambiguous abbreviation of the @samp{disassemble} command
27055 and you wanted an even shorter version named @samp{di}.
27056 The following will accomplish this.
27059 (gdb) alias -a di = disas
27062 Note that aliases are different from user-defined commands.
27063 With a user-defined command, you also need to write documentation
27064 for it with the @samp{document} command.
27065 An alias automatically picks up the documentation of the existing command.
27067 Here is an example where we make @samp{elms} an abbreviation of
27068 @samp{elements} in the @samp{set print elements} command.
27069 This is to show that you can make an abbreviation of any part
27073 (gdb) alias -a set print elms = set print elements
27074 (gdb) alias -a show print elms = show print elements
27075 (gdb) set p elms 20
27077 Limit on string chars or array elements to print is 200.
27080 Note that if you are defining an alias of a @samp{set} command,
27081 and you want to have an alias for the corresponding @samp{show}
27082 command, then you need to define the latter separately.
27084 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
27085 @var{ALIAS}, just as they are normally.
27088 (gdb) alias -a set pr elms = set p ele
27091 Finally, here is an example showing the creation of a one word
27092 alias for a more complex command.
27093 This creates alias @samp{spe} of the command @samp{set print elements}.
27096 (gdb) alias spe = set print elements
27101 @chapter Command Interpreters
27102 @cindex command interpreters
27104 @value{GDBN} supports multiple command interpreters, and some command
27105 infrastructure to allow users or user interface writers to switch
27106 between interpreters or run commands in other interpreters.
27108 @value{GDBN} currently supports two command interpreters, the console
27109 interpreter (sometimes called the command-line interpreter or @sc{cli})
27110 and the machine interface interpreter (or @sc{gdb/mi}). This manual
27111 describes both of these interfaces in great detail.
27113 By default, @value{GDBN} will start with the console interpreter.
27114 However, the user may choose to start @value{GDBN} with another
27115 interpreter by specifying the @option{-i} or @option{--interpreter}
27116 startup options. Defined interpreters include:
27120 @cindex console interpreter
27121 The traditional console or command-line interpreter. This is the most often
27122 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
27123 @value{GDBN} will use this interpreter.
27126 @cindex mi interpreter
27127 The newest @sc{gdb/mi} interface (currently @code{mi3}). Used primarily
27128 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
27129 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
27133 @cindex mi3 interpreter
27134 The @sc{gdb/mi} interface introduced in @value{GDBN} 9.1.
27137 @cindex mi2 interpreter
27138 The @sc{gdb/mi} interface introduced in @value{GDBN} 6.0.
27141 @cindex mi1 interpreter
27142 The @sc{gdb/mi} interface introduced in @value{GDBN} 5.1.
27146 @cindex invoke another interpreter
27148 @kindex interpreter-exec
27149 You may execute commands in any interpreter from the current
27150 interpreter using the appropriate command. If you are running the
27151 console interpreter, simply use the @code{interpreter-exec} command:
27154 interpreter-exec mi "-data-list-register-names"
27157 @sc{gdb/mi} has a similar command, although it is only available in versions of
27158 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
27160 Note that @code{interpreter-exec} only changes the interpreter for the
27161 duration of the specified command. It does not change the interpreter
27164 @cindex start a new independent interpreter
27166 Although you may only choose a single interpreter at startup, it is
27167 possible to run an independent interpreter on a specified input/output
27168 device (usually a tty).
27170 For example, consider a debugger GUI or IDE that wants to provide a
27171 @value{GDBN} console view. It may do so by embedding a terminal
27172 emulator widget in its GUI, starting @value{GDBN} in the traditional
27173 command-line mode with stdin/stdout/stderr redirected to that
27174 terminal, and then creating an MI interpreter running on a specified
27175 input/output device. The console interpreter created by @value{GDBN}
27176 at startup handles commands the user types in the terminal widget,
27177 while the GUI controls and synchronizes state with @value{GDBN} using
27178 the separate MI interpreter.
27180 To start a new secondary @dfn{user interface} running MI, use the
27181 @code{new-ui} command:
27184 @cindex new user interface
27186 new-ui @var{interpreter} @var{tty}
27189 The @var{interpreter} parameter specifies the interpreter to run.
27190 This accepts the same values as the @code{interpreter-exec} command.
27191 For example, @samp{console}, @samp{mi}, @samp{mi2}, etc. The
27192 @var{tty} parameter specifies the name of the bidirectional file the
27193 interpreter uses for input/output, usually the name of a
27194 pseudoterminal slave on Unix systems. For example:
27197 (@value{GDBP}) new-ui mi /dev/pts/9
27201 runs an MI interpreter on @file{/dev/pts/9}.
27204 @chapter @value{GDBN} Text User Interface
27206 @cindex Text User Interface
27209 * TUI Overview:: TUI overview
27210 * TUI Keys:: TUI key bindings
27211 * TUI Single Key Mode:: TUI single key mode
27212 * TUI Commands:: TUI-specific commands
27213 * TUI Configuration:: TUI configuration variables
27216 The @value{GDBN} Text User Interface (TUI) is a terminal
27217 interface which uses the @code{curses} library to show the source
27218 file, the assembly output, the program registers and @value{GDBN}
27219 commands in separate text windows. The TUI mode is supported only
27220 on platforms where a suitable version of the @code{curses} library
27223 The TUI mode is enabled by default when you invoke @value{GDBN} as
27224 @samp{@value{GDBP} -tui}.
27225 You can also switch in and out of TUI mode while @value{GDBN} runs by
27226 using various TUI commands and key bindings, such as @command{tui
27227 enable} or @kbd{C-x C-a}. @xref{TUI Commands, ,TUI Commands}, and
27228 @ref{TUI Keys, ,TUI Key Bindings}.
27231 @section TUI Overview
27233 In TUI mode, @value{GDBN} can display several text windows:
27237 This window is the @value{GDBN} command window with the @value{GDBN}
27238 prompt and the @value{GDBN} output. The @value{GDBN} input is still
27239 managed using readline.
27242 The source window shows the source file of the program. The current
27243 line and active breakpoints are displayed in this window.
27246 The assembly window shows the disassembly output of the program.
27249 This window shows the processor registers. Registers are highlighted
27250 when their values change.
27253 The source and assembly windows show the current program position
27254 by highlighting the current line and marking it with a @samp{>} marker.
27255 Breakpoints are indicated with two markers. The first marker
27256 indicates the breakpoint type:
27260 Breakpoint which was hit at least once.
27263 Breakpoint which was never hit.
27266 Hardware breakpoint which was hit at least once.
27269 Hardware breakpoint which was never hit.
27272 The second marker indicates whether the breakpoint is enabled or not:
27276 Breakpoint is enabled.
27279 Breakpoint is disabled.
27282 The source, assembly and register windows are updated when the current
27283 thread changes, when the frame changes, or when the program counter
27286 These windows are not all visible at the same time. The command
27287 window is always visible. The others can be arranged in several
27298 source and assembly,
27301 source and registers, or
27304 assembly and registers.
27307 A status line above the command window shows the following information:
27311 Indicates the current @value{GDBN} target.
27312 (@pxref{Targets, ,Specifying a Debugging Target}).
27315 Gives the current process or thread number.
27316 When no process is being debugged, this field is set to @code{No process}.
27319 Gives the current function name for the selected frame.
27320 The name is demangled if demangling is turned on (@pxref{Print Settings}).
27321 When there is no symbol corresponding to the current program counter,
27322 the string @code{??} is displayed.
27325 Indicates the current line number for the selected frame.
27326 When the current line number is not known, the string @code{??} is displayed.
27329 Indicates the current program counter address.
27333 @section TUI Key Bindings
27334 @cindex TUI key bindings
27336 The TUI installs several key bindings in the readline keymaps
27337 @ifset SYSTEM_READLINE
27338 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
27340 @ifclear SYSTEM_READLINE
27341 (@pxref{Command Line Editing}).
27343 The following key bindings are installed for both TUI mode and the
27344 @value{GDBN} standard mode.
27353 Enter or leave the TUI mode. When leaving the TUI mode,
27354 the curses window management stops and @value{GDBN} operates using
27355 its standard mode, writing on the terminal directly. When reentering
27356 the TUI mode, control is given back to the curses windows.
27357 The screen is then refreshed.
27361 Use a TUI layout with only one window. The layout will
27362 either be @samp{source} or @samp{assembly}. When the TUI mode
27363 is not active, it will switch to the TUI mode.
27365 Think of this key binding as the Emacs @kbd{C-x 1} binding.
27369 Use a TUI layout with at least two windows. When the current
27370 layout already has two windows, the next layout with two windows is used.
27371 When a new layout is chosen, one window will always be common to the
27372 previous layout and the new one.
27374 Think of it as the Emacs @kbd{C-x 2} binding.
27378 Change the active window. The TUI associates several key bindings
27379 (like scrolling and arrow keys) with the active window. This command
27380 gives the focus to the next TUI window.
27382 Think of it as the Emacs @kbd{C-x o} binding.
27386 Switch in and out of the TUI SingleKey mode that binds single
27387 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
27390 The following key bindings only work in the TUI mode:
27395 Scroll the active window one page up.
27399 Scroll the active window one page down.
27403 Scroll the active window one line up.
27407 Scroll the active window one line down.
27411 Scroll the active window one column left.
27415 Scroll the active window one column right.
27419 Refresh the screen.
27422 Because the arrow keys scroll the active window in the TUI mode, they
27423 are not available for their normal use by readline unless the command
27424 window has the focus. When another window is active, you must use
27425 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
27426 and @kbd{C-f} to control the command window.
27428 @node TUI Single Key Mode
27429 @section TUI Single Key Mode
27430 @cindex TUI single key mode
27432 The TUI also provides a @dfn{SingleKey} mode, which binds several
27433 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
27434 switch into this mode, where the following key bindings are used:
27437 @kindex c @r{(SingleKey TUI key)}
27441 @kindex d @r{(SingleKey TUI key)}
27445 @kindex f @r{(SingleKey TUI key)}
27449 @kindex n @r{(SingleKey TUI key)}
27453 @kindex o @r{(SingleKey TUI key)}
27455 nexti. The shortcut letter @samp{o} stands for ``step Over''.
27457 @kindex q @r{(SingleKey TUI key)}
27459 exit the SingleKey mode.
27461 @kindex r @r{(SingleKey TUI key)}
27465 @kindex s @r{(SingleKey TUI key)}
27469 @kindex i @r{(SingleKey TUI key)}
27471 stepi. The shortcut letter @samp{i} stands for ``step Into''.
27473 @kindex u @r{(SingleKey TUI key)}
27477 @kindex v @r{(SingleKey TUI key)}
27481 @kindex w @r{(SingleKey TUI key)}
27486 Other keys temporarily switch to the @value{GDBN} command prompt.
27487 The key that was pressed is inserted in the editing buffer so that
27488 it is possible to type most @value{GDBN} commands without interaction
27489 with the TUI SingleKey mode. Once the command is entered the TUI
27490 SingleKey mode is restored. The only way to permanently leave
27491 this mode is by typing @kbd{q} or @kbd{C-x s}.
27495 @section TUI-specific Commands
27496 @cindex TUI commands
27498 The TUI has specific commands to control the text windows.
27499 These commands are always available, even when @value{GDBN} is not in
27500 the TUI mode. When @value{GDBN} is in the standard mode, most
27501 of these commands will automatically switch to the TUI mode.
27503 Note that if @value{GDBN}'s @code{stdout} is not connected to a
27504 terminal, or @value{GDBN} has been started with the machine interface
27505 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
27506 these commands will fail with an error, because it would not be
27507 possible or desirable to enable curses window management.
27512 Activate TUI mode. The last active TUI window layout will be used if
27513 TUI mode has prevsiouly been used in the current debugging session,
27514 otherwise a default layout is used.
27517 @kindex tui disable
27518 Disable TUI mode, returning to the console interpreter.
27522 List and give the size of all displayed windows.
27524 @item layout @var{name}
27526 Changes which TUI windows are displayed. In each layout the command
27527 window is always displayed, the @var{name} parameter controls which
27528 additional windows are displayed, and can be any of the following:
27532 Display the next layout.
27535 Display the previous layout.
27538 Display the source and command windows.
27541 Display the assembly and command windows.
27544 Display the source, assembly, and command windows.
27547 When in @code{src} layout display the register, source, and command
27548 windows. When in @code{asm} or @code{split} layout display the
27549 register, assembler, and command windows.
27552 @item focus @var{name}
27554 Changes which TUI window is currently active for scrolling. The
27555 @var{name} parameter can be any of the following:
27559 Make the next window active for scrolling.
27562 Make the previous window active for scrolling.
27565 Make the source window active for scrolling.
27568 Make the assembly window active for scrolling.
27571 Make the register window active for scrolling.
27574 Make the command window active for scrolling.
27579 Refresh the screen. This is similar to typing @kbd{C-L}.
27581 @item tui reg @var{group}
27583 Changes the register group displayed in the tui register window to
27584 @var{group}. If the register window is not currently displayed this
27585 command will cause the register window to be displayed. The list of
27586 register groups, as well as their order is target specific. The
27587 following groups are available on most targets:
27590 Repeatedly selecting this group will cause the display to cycle
27591 through all of the available register groups.
27594 Repeatedly selecting this group will cause the display to cycle
27595 through all of the available register groups in the reverse order to
27599 Display the general registers.
27601 Display the floating point registers.
27603 Display the system registers.
27605 Display the vector registers.
27607 Display all registers.
27612 Update the source window and the current execution point.
27614 @item winheight @var{name} +@var{count}
27615 @itemx winheight @var{name} -@var{count}
27617 Change the height of the window @var{name} by @var{count}
27618 lines. Positive counts increase the height, while negative counts
27619 decrease it. The @var{name} parameter can be one of @code{src} (the
27620 source window), @code{cmd} (the command window), @code{asm} (the
27621 disassembly window), or @code{regs} (the register display window).
27624 @node TUI Configuration
27625 @section TUI Configuration Variables
27626 @cindex TUI configuration variables
27628 Several configuration variables control the appearance of TUI windows.
27631 @item set tui border-kind @var{kind}
27632 @kindex set tui border-kind
27633 Select the border appearance for the source, assembly and register windows.
27634 The possible values are the following:
27637 Use a space character to draw the border.
27640 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
27643 Use the Alternate Character Set to draw the border. The border is
27644 drawn using character line graphics if the terminal supports them.
27647 @item set tui border-mode @var{mode}
27648 @kindex set tui border-mode
27649 @itemx set tui active-border-mode @var{mode}
27650 @kindex set tui active-border-mode
27651 Select the display attributes for the borders of the inactive windows
27652 or the active window. The @var{mode} can be one of the following:
27655 Use normal attributes to display the border.
27661 Use reverse video mode.
27664 Use half bright mode.
27666 @item half-standout
27667 Use half bright and standout mode.
27670 Use extra bright or bold mode.
27672 @item bold-standout
27673 Use extra bright or bold and standout mode.
27676 @item set tui tab-width @var{nchars}
27677 @kindex set tui tab-width
27679 Set the width of tab stops to be @var{nchars} characters. This
27680 setting affects the display of TAB characters in the source and
27685 @chapter Using @value{GDBN} under @sc{gnu} Emacs
27688 @cindex @sc{gnu} Emacs
27689 A special interface allows you to use @sc{gnu} Emacs to view (and
27690 edit) the source files for the program you are debugging with
27693 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
27694 executable file you want to debug as an argument. This command starts
27695 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
27696 created Emacs buffer.
27697 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
27699 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
27704 All ``terminal'' input and output goes through an Emacs buffer, called
27707 This applies both to @value{GDBN} commands and their output, and to the input
27708 and output done by the program you are debugging.
27710 This is useful because it means that you can copy the text of previous
27711 commands and input them again; you can even use parts of the output
27714 All the facilities of Emacs' Shell mode are available for interacting
27715 with your program. In particular, you can send signals the usual
27716 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
27720 @value{GDBN} displays source code through Emacs.
27722 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
27723 source file for that frame and puts an arrow (@samp{=>}) at the
27724 left margin of the current line. Emacs uses a separate buffer for
27725 source display, and splits the screen to show both your @value{GDBN} session
27728 Explicit @value{GDBN} @code{list} or search commands still produce output as
27729 usual, but you probably have no reason to use them from Emacs.
27732 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
27733 a graphical mode, enabled by default, which provides further buffers
27734 that can control the execution and describe the state of your program.
27735 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
27737 If you specify an absolute file name when prompted for the @kbd{M-x
27738 gdb} argument, then Emacs sets your current working directory to where
27739 your program resides. If you only specify the file name, then Emacs
27740 sets your current working directory to the directory associated
27741 with the previous buffer. In this case, @value{GDBN} may find your
27742 program by searching your environment's @code{PATH} variable, but on
27743 some operating systems it might not find the source. So, although the
27744 @value{GDBN} input and output session proceeds normally, the auxiliary
27745 buffer does not display the current source and line of execution.
27747 The initial working directory of @value{GDBN} is printed on the top
27748 line of the GUD buffer and this serves as a default for the commands
27749 that specify files for @value{GDBN} to operate on. @xref{Files,
27750 ,Commands to Specify Files}.
27752 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
27753 need to call @value{GDBN} by a different name (for example, if you
27754 keep several configurations around, with different names) you can
27755 customize the Emacs variable @code{gud-gdb-command-name} to run the
27758 In the GUD buffer, you can use these special Emacs commands in
27759 addition to the standard Shell mode commands:
27763 Describe the features of Emacs' GUD Mode.
27766 Execute to another source line, like the @value{GDBN} @code{step} command; also
27767 update the display window to show the current file and location.
27770 Execute to next source line in this function, skipping all function
27771 calls, like the @value{GDBN} @code{next} command. Then update the display window
27772 to show the current file and location.
27775 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
27776 display window accordingly.
27779 Execute until exit from the selected stack frame, like the @value{GDBN}
27780 @code{finish} command.
27783 Continue execution of your program, like the @value{GDBN} @code{continue}
27787 Go up the number of frames indicated by the numeric argument
27788 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
27789 like the @value{GDBN} @code{up} command.
27792 Go down the number of frames indicated by the numeric argument, like the
27793 @value{GDBN} @code{down} command.
27796 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
27797 tells @value{GDBN} to set a breakpoint on the source line point is on.
27799 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
27800 separate frame which shows a backtrace when the GUD buffer is current.
27801 Move point to any frame in the stack and type @key{RET} to make it
27802 become the current frame and display the associated source in the
27803 source buffer. Alternatively, click @kbd{Mouse-2} to make the
27804 selected frame become the current one. In graphical mode, the
27805 speedbar displays watch expressions.
27807 If you accidentally delete the source-display buffer, an easy way to get
27808 it back is to type the command @code{f} in the @value{GDBN} buffer, to
27809 request a frame display; when you run under Emacs, this recreates
27810 the source buffer if necessary to show you the context of the current
27813 The source files displayed in Emacs are in ordinary Emacs buffers
27814 which are visiting the source files in the usual way. You can edit
27815 the files with these buffers if you wish; but keep in mind that @value{GDBN}
27816 communicates with Emacs in terms of line numbers. If you add or
27817 delete lines from the text, the line numbers that @value{GDBN} knows cease
27818 to correspond properly with the code.
27820 A more detailed description of Emacs' interaction with @value{GDBN} is
27821 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
27825 @chapter The @sc{gdb/mi} Interface
27827 @unnumberedsec Function and Purpose
27829 @cindex @sc{gdb/mi}, its purpose
27830 @sc{gdb/mi} is a line based machine oriented text interface to
27831 @value{GDBN} and is activated by specifying using the
27832 @option{--interpreter} command line option (@pxref{Mode Options}). It
27833 is specifically intended to support the development of systems which
27834 use the debugger as just one small component of a larger system.
27836 This chapter is a specification of the @sc{gdb/mi} interface. It is written
27837 in the form of a reference manual.
27839 Note that @sc{gdb/mi} is still under construction, so some of the
27840 features described below are incomplete and subject to change
27841 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
27843 @unnumberedsec Notation and Terminology
27845 @cindex notational conventions, for @sc{gdb/mi}
27846 This chapter uses the following notation:
27850 @code{|} separates two alternatives.
27853 @code{[ @var{something} ]} indicates that @var{something} is optional:
27854 it may or may not be given.
27857 @code{( @var{group} )*} means that @var{group} inside the parentheses
27858 may repeat zero or more times.
27861 @code{( @var{group} )+} means that @var{group} inside the parentheses
27862 may repeat one or more times.
27865 @code{"@var{string}"} means a literal @var{string}.
27869 @heading Dependencies
27873 * GDB/MI General Design::
27874 * GDB/MI Command Syntax::
27875 * GDB/MI Compatibility with CLI::
27876 * GDB/MI Development and Front Ends::
27877 * GDB/MI Output Records::
27878 * GDB/MI Simple Examples::
27879 * GDB/MI Command Description Format::
27880 * GDB/MI Breakpoint Commands::
27881 * GDB/MI Catchpoint Commands::
27882 * GDB/MI Program Context::
27883 * GDB/MI Thread Commands::
27884 * GDB/MI Ada Tasking Commands::
27885 * GDB/MI Program Execution::
27886 * GDB/MI Stack Manipulation::
27887 * GDB/MI Variable Objects::
27888 * GDB/MI Data Manipulation::
27889 * GDB/MI Tracepoint Commands::
27890 * GDB/MI Symbol Query::
27891 * GDB/MI File Commands::
27893 * GDB/MI Kod Commands::
27894 * GDB/MI Memory Overlay Commands::
27895 * GDB/MI Signal Handling Commands::
27897 * GDB/MI Target Manipulation::
27898 * GDB/MI File Transfer Commands::
27899 * GDB/MI Ada Exceptions Commands::
27900 * GDB/MI Support Commands::
27901 * GDB/MI Miscellaneous Commands::
27904 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27905 @node GDB/MI General Design
27906 @section @sc{gdb/mi} General Design
27907 @cindex GDB/MI General Design
27909 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
27910 parts---commands sent to @value{GDBN}, responses to those commands
27911 and notifications. Each command results in exactly one response,
27912 indicating either successful completion of the command, or an error.
27913 For the commands that do not resume the target, the response contains the
27914 requested information. For the commands that resume the target, the
27915 response only indicates whether the target was successfully resumed.
27916 Notifications is the mechanism for reporting changes in the state of the
27917 target, or in @value{GDBN} state, that cannot conveniently be associated with
27918 a command and reported as part of that command response.
27920 The important examples of notifications are:
27924 Exec notifications. These are used to report changes in
27925 target state---when a target is resumed, or stopped. It would not
27926 be feasible to include this information in response of resuming
27927 commands, because one resume commands can result in multiple events in
27928 different threads. Also, quite some time may pass before any event
27929 happens in the target, while a frontend needs to know whether the resuming
27930 command itself was successfully executed.
27933 Console output, and status notifications. Console output
27934 notifications are used to report output of CLI commands, as well as
27935 diagnostics for other commands. Status notifications are used to
27936 report the progress of a long-running operation. Naturally, including
27937 this information in command response would mean no output is produced
27938 until the command is finished, which is undesirable.
27941 General notifications. Commands may have various side effects on
27942 the @value{GDBN} or target state beyond their official purpose. For example,
27943 a command may change the selected thread. Although such changes can
27944 be included in command response, using notification allows for more
27945 orthogonal frontend design.
27949 There's no guarantee that whenever an MI command reports an error,
27950 @value{GDBN} or the target are in any specific state, and especially,
27951 the state is not reverted to the state before the MI command was
27952 processed. Therefore, whenever an MI command results in an error,
27953 we recommend that the frontend refreshes all the information shown in
27954 the user interface.
27958 * Context management::
27959 * Asynchronous and non-stop modes::
27963 @node Context management
27964 @subsection Context management
27966 @subsubsection Threads and Frames
27968 In most cases when @value{GDBN} accesses the target, this access is
27969 done in context of a specific thread and frame (@pxref{Frames}).
27970 Often, even when accessing global data, the target requires that a thread
27971 be specified. The CLI interface maintains the selected thread and frame,
27972 and supplies them to target on each command. This is convenient,
27973 because a command line user would not want to specify that information
27974 explicitly on each command, and because user interacts with
27975 @value{GDBN} via a single terminal, so no confusion is possible as
27976 to what thread and frame are the current ones.
27978 In the case of MI, the concept of selected thread and frame is less
27979 useful. First, a frontend can easily remember this information
27980 itself. Second, a graphical frontend can have more than one window,
27981 each one used for debugging a different thread, and the frontend might
27982 want to access additional threads for internal purposes. This
27983 increases the risk that by relying on implicitly selected thread, the
27984 frontend may be operating on a wrong one. Therefore, each MI command
27985 should explicitly specify which thread and frame to operate on. To
27986 make it possible, each MI command accepts the @samp{--thread} and
27987 @samp{--frame} options, the value to each is @value{GDBN} global
27988 identifier for thread and frame to operate on.
27990 Usually, each top-level window in a frontend allows the user to select
27991 a thread and a frame, and remembers the user selection for further
27992 operations. However, in some cases @value{GDBN} may suggest that the
27993 current thread or frame be changed. For example, when stopping on a
27994 breakpoint it is reasonable to switch to the thread where breakpoint is
27995 hit. For another example, if the user issues the CLI @samp{thread} or
27996 @samp{frame} commands via the frontend, it is desirable to change the
27997 frontend's selection to the one specified by user. @value{GDBN}
27998 communicates the suggestion to change current thread and frame using the
27999 @samp{=thread-selected} notification.
28001 Note that historically, MI shares the selected thread with CLI, so
28002 frontends used the @code{-thread-select} to execute commands in the
28003 right context. However, getting this to work right is cumbersome. The
28004 simplest way is for frontend to emit @code{-thread-select} command
28005 before every command. This doubles the number of commands that need
28006 to be sent. The alternative approach is to suppress @code{-thread-select}
28007 if the selected thread in @value{GDBN} is supposed to be identical to the
28008 thread the frontend wants to operate on. However, getting this
28009 optimization right can be tricky. In particular, if the frontend
28010 sends several commands to @value{GDBN}, and one of the commands changes the
28011 selected thread, then the behaviour of subsequent commands will
28012 change. So, a frontend should either wait for response from such
28013 problematic commands, or explicitly add @code{-thread-select} for
28014 all subsequent commands. No frontend is known to do this exactly
28015 right, so it is suggested to just always pass the @samp{--thread} and
28016 @samp{--frame} options.
28018 @subsubsection Language
28020 The execution of several commands depends on which language is selected.
28021 By default, the current language (@pxref{show language}) is used.
28022 But for commands known to be language-sensitive, it is recommended
28023 to use the @samp{--language} option. This option takes one argument,
28024 which is the name of the language to use while executing the command.
28028 -data-evaluate-expression --language c "sizeof (void*)"
28033 The valid language names are the same names accepted by the
28034 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
28035 @samp{local} or @samp{unknown}.
28037 @node Asynchronous and non-stop modes
28038 @subsection Asynchronous command execution and non-stop mode
28040 On some targets, @value{GDBN} is capable of processing MI commands
28041 even while the target is running. This is called @dfn{asynchronous
28042 command execution} (@pxref{Background Execution}). The frontend may
28043 specify a preferrence for asynchronous execution using the
28044 @code{-gdb-set mi-async 1} command, which should be emitted before
28045 either running the executable or attaching to the target. After the
28046 frontend has started the executable or attached to the target, it can
28047 find if asynchronous execution is enabled using the
28048 @code{-list-target-features} command.
28051 @item -gdb-set mi-async on
28052 @item -gdb-set mi-async off
28053 Set whether MI is in asynchronous mode.
28055 When @code{off}, which is the default, MI execution commands (e.g.,
28056 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
28057 for the program to stop before processing further commands.
28059 When @code{on}, MI execution commands are background execution
28060 commands (e.g., @code{-exec-continue} becomes the equivalent of the
28061 @code{c&} CLI command), and so @value{GDBN} is capable of processing
28062 MI commands even while the target is running.
28064 @item -gdb-show mi-async
28065 Show whether MI asynchronous mode is enabled.
28068 Note: In @value{GDBN} version 7.7 and earlier, this option was called
28069 @code{target-async} instead of @code{mi-async}, and it had the effect
28070 of both putting MI in asynchronous mode and making CLI background
28071 commands possible. CLI background commands are now always possible
28072 ``out of the box'' if the target supports them. The old spelling is
28073 kept as a deprecated alias for backwards compatibility.
28075 Even if @value{GDBN} can accept a command while target is running,
28076 many commands that access the target do not work when the target is
28077 running. Therefore, asynchronous command execution is most useful
28078 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
28079 it is possible to examine the state of one thread, while other threads
28082 When a given thread is running, MI commands that try to access the
28083 target in the context of that thread may not work, or may work only on
28084 some targets. In particular, commands that try to operate on thread's
28085 stack will not work, on any target. Commands that read memory, or
28086 modify breakpoints, may work or not work, depending on the target. Note
28087 that even commands that operate on global state, such as @code{print},
28088 @code{set}, and breakpoint commands, still access the target in the
28089 context of a specific thread, so frontend should try to find a
28090 stopped thread and perform the operation on that thread (using the
28091 @samp{--thread} option).
28093 Which commands will work in the context of a running thread is
28094 highly target dependent. However, the two commands
28095 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
28096 to find the state of a thread, will always work.
28098 @node Thread groups
28099 @subsection Thread groups
28100 @value{GDBN} may be used to debug several processes at the same time.
28101 On some platfroms, @value{GDBN} may support debugging of several
28102 hardware systems, each one having several cores with several different
28103 processes running on each core. This section describes the MI
28104 mechanism to support such debugging scenarios.
28106 The key observation is that regardless of the structure of the
28107 target, MI can have a global list of threads, because most commands that
28108 accept the @samp{--thread} option do not need to know what process that
28109 thread belongs to. Therefore, it is not necessary to introduce
28110 neither additional @samp{--process} option, nor an notion of the
28111 current process in the MI interface. The only strictly new feature
28112 that is required is the ability to find how the threads are grouped
28115 To allow the user to discover such grouping, and to support arbitrary
28116 hierarchy of machines/cores/processes, MI introduces the concept of a
28117 @dfn{thread group}. Thread group is a collection of threads and other
28118 thread groups. A thread group always has a string identifier, a type,
28119 and may have additional attributes specific to the type. A new
28120 command, @code{-list-thread-groups}, returns the list of top-level
28121 thread groups, which correspond to processes that @value{GDBN} is
28122 debugging at the moment. By passing an identifier of a thread group
28123 to the @code{-list-thread-groups} command, it is possible to obtain
28124 the members of specific thread group.
28126 To allow the user to easily discover processes, and other objects, he
28127 wishes to debug, a concept of @dfn{available thread group} is
28128 introduced. Available thread group is an thread group that
28129 @value{GDBN} is not debugging, but that can be attached to, using the
28130 @code{-target-attach} command. The list of available top-level thread
28131 groups can be obtained using @samp{-list-thread-groups --available}.
28132 In general, the content of a thread group may be only retrieved only
28133 after attaching to that thread group.
28135 Thread groups are related to inferiors (@pxref{Inferiors and
28136 Programs}). Each inferior corresponds to a thread group of a special
28137 type @samp{process}, and some additional operations are permitted on
28138 such thread groups.
28140 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28141 @node GDB/MI Command Syntax
28142 @section @sc{gdb/mi} Command Syntax
28145 * GDB/MI Input Syntax::
28146 * GDB/MI Output Syntax::
28149 @node GDB/MI Input Syntax
28150 @subsection @sc{gdb/mi} Input Syntax
28152 @cindex input syntax for @sc{gdb/mi}
28153 @cindex @sc{gdb/mi}, input syntax
28155 @item @var{command} @expansion{}
28156 @code{@var{cli-command} | @var{mi-command}}
28158 @item @var{cli-command} @expansion{}
28159 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
28160 @var{cli-command} is any existing @value{GDBN} CLI command.
28162 @item @var{mi-command} @expansion{}
28163 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
28164 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
28166 @item @var{token} @expansion{}
28167 "any sequence of digits"
28169 @item @var{option} @expansion{}
28170 @code{"-" @var{parameter} [ " " @var{parameter} ]}
28172 @item @var{parameter} @expansion{}
28173 @code{@var{non-blank-sequence} | @var{c-string}}
28175 @item @var{operation} @expansion{}
28176 @emph{any of the operations described in this chapter}
28178 @item @var{non-blank-sequence} @expansion{}
28179 @emph{anything, provided it doesn't contain special characters such as
28180 "-", @var{nl}, """ and of course " "}
28182 @item @var{c-string} @expansion{}
28183 @code{""" @var{seven-bit-iso-c-string-content} """}
28185 @item @var{nl} @expansion{}
28194 The CLI commands are still handled by the @sc{mi} interpreter; their
28195 output is described below.
28198 The @code{@var{token}}, when present, is passed back when the command
28202 Some @sc{mi} commands accept optional arguments as part of the parameter
28203 list. Each option is identified by a leading @samp{-} (dash) and may be
28204 followed by an optional argument parameter. Options occur first in the
28205 parameter list and can be delimited from normal parameters using
28206 @samp{--} (this is useful when some parameters begin with a dash).
28213 We want easy access to the existing CLI syntax (for debugging).
28216 We want it to be easy to spot a @sc{mi} operation.
28219 @node GDB/MI Output Syntax
28220 @subsection @sc{gdb/mi} Output Syntax
28222 @cindex output syntax of @sc{gdb/mi}
28223 @cindex @sc{gdb/mi}, output syntax
28224 The output from @sc{gdb/mi} consists of zero or more out-of-band records
28225 followed, optionally, by a single result record. This result record
28226 is for the most recent command. The sequence of output records is
28227 terminated by @samp{(gdb)}.
28229 If an input command was prefixed with a @code{@var{token}} then the
28230 corresponding output for that command will also be prefixed by that same
28234 @item @var{output} @expansion{}
28235 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
28237 @item @var{result-record} @expansion{}
28238 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
28240 @item @var{out-of-band-record} @expansion{}
28241 @code{@var{async-record} | @var{stream-record}}
28243 @item @var{async-record} @expansion{}
28244 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
28246 @item @var{exec-async-output} @expansion{}
28247 @code{[ @var{token} ] "*" @var{async-output nl}}
28249 @item @var{status-async-output} @expansion{}
28250 @code{[ @var{token} ] "+" @var{async-output nl}}
28252 @item @var{notify-async-output} @expansion{}
28253 @code{[ @var{token} ] "=" @var{async-output nl}}
28255 @item @var{async-output} @expansion{}
28256 @code{@var{async-class} ( "," @var{result} )*}
28258 @item @var{result-class} @expansion{}
28259 @code{"done" | "running" | "connected" | "error" | "exit"}
28261 @item @var{async-class} @expansion{}
28262 @code{"stopped" | @var{others}} (where @var{others} will be added
28263 depending on the needs---this is still in development).
28265 @item @var{result} @expansion{}
28266 @code{ @var{variable} "=" @var{value}}
28268 @item @var{variable} @expansion{}
28269 @code{ @var{string} }
28271 @item @var{value} @expansion{}
28272 @code{ @var{const} | @var{tuple} | @var{list} }
28274 @item @var{const} @expansion{}
28275 @code{@var{c-string}}
28277 @item @var{tuple} @expansion{}
28278 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
28280 @item @var{list} @expansion{}
28281 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
28282 @var{result} ( "," @var{result} )* "]" }
28284 @item @var{stream-record} @expansion{}
28285 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
28287 @item @var{console-stream-output} @expansion{}
28288 @code{"~" @var{c-string nl}}
28290 @item @var{target-stream-output} @expansion{}
28291 @code{"@@" @var{c-string nl}}
28293 @item @var{log-stream-output} @expansion{}
28294 @code{"&" @var{c-string nl}}
28296 @item @var{nl} @expansion{}
28299 @item @var{token} @expansion{}
28300 @emph{any sequence of digits}.
28308 All output sequences end in a single line containing a period.
28311 The @code{@var{token}} is from the corresponding request. Note that
28312 for all async output, while the token is allowed by the grammar and
28313 may be output by future versions of @value{GDBN} for select async
28314 output messages, it is generally omitted. Frontends should treat
28315 all async output as reporting general changes in the state of the
28316 target and there should be no need to associate async output to any
28320 @cindex status output in @sc{gdb/mi}
28321 @var{status-async-output} contains on-going status information about the
28322 progress of a slow operation. It can be discarded. All status output is
28323 prefixed by @samp{+}.
28326 @cindex async output in @sc{gdb/mi}
28327 @var{exec-async-output} contains asynchronous state change on the target
28328 (stopped, started, disappeared). All async output is prefixed by
28332 @cindex notify output in @sc{gdb/mi}
28333 @var{notify-async-output} contains supplementary information that the
28334 client should handle (e.g., a new breakpoint information). All notify
28335 output is prefixed by @samp{=}.
28338 @cindex console output in @sc{gdb/mi}
28339 @var{console-stream-output} is output that should be displayed as is in the
28340 console. It is the textual response to a CLI command. All the console
28341 output is prefixed by @samp{~}.
28344 @cindex target output in @sc{gdb/mi}
28345 @var{target-stream-output} is the output produced by the target program.
28346 All the target output is prefixed by @samp{@@}.
28349 @cindex log output in @sc{gdb/mi}
28350 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
28351 instance messages that should be displayed as part of an error log. All
28352 the log output is prefixed by @samp{&}.
28355 @cindex list output in @sc{gdb/mi}
28356 New @sc{gdb/mi} commands should only output @var{lists} containing
28362 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
28363 details about the various output records.
28365 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28366 @node GDB/MI Compatibility with CLI
28367 @section @sc{gdb/mi} Compatibility with CLI
28369 @cindex compatibility, @sc{gdb/mi} and CLI
28370 @cindex @sc{gdb/mi}, compatibility with CLI
28372 For the developers convenience CLI commands can be entered directly,
28373 but there may be some unexpected behaviour. For example, commands
28374 that query the user will behave as if the user replied yes, breakpoint
28375 command lists are not executed and some CLI commands, such as
28376 @code{if}, @code{when} and @code{define}, prompt for further input with
28377 @samp{>}, which is not valid MI output.
28379 This feature may be removed at some stage in the future and it is
28380 recommended that front ends use the @code{-interpreter-exec} command
28381 (@pxref{-interpreter-exec}).
28383 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28384 @node GDB/MI Development and Front Ends
28385 @section @sc{gdb/mi} Development and Front Ends
28386 @cindex @sc{gdb/mi} development
28388 The application which takes the MI output and presents the state of the
28389 program being debugged to the user is called a @dfn{front end}.
28391 Since @sc{gdb/mi} is used by a variety of front ends to @value{GDBN}, changes
28392 to the MI interface may break existing usage. This section describes how the
28393 protocol changes and how to request previous version of the protocol when it
28396 Some changes in MI need not break a carefully designed front end, and
28397 for these the MI version will remain unchanged. The following is a
28398 list of changes that may occur within one level, so front ends should
28399 parse MI output in a way that can handle them:
28403 New MI commands may be added.
28406 New fields may be added to the output of any MI command.
28409 The range of values for fields with specified values, e.g.,
28410 @code{in_scope} (@pxref{-var-update}) may be extended.
28412 @c The format of field's content e.g type prefix, may change so parse it
28413 @c at your own risk. Yes, in general?
28415 @c The order of fields may change? Shouldn't really matter but it might
28416 @c resolve inconsistencies.
28419 If the changes are likely to break front ends, the MI version level
28420 will be increased by one. The new versions of the MI protocol are not compatible
28421 with the old versions. Old versions of MI remain available, allowing front ends
28422 to keep using them until they are modified to use the latest MI version.
28424 Since @code{--interpreter=mi} always points to the latest MI version, it is
28425 recommended that front ends request a specific version of MI when launching
28426 @value{GDBN} (e.g. @code{--interpreter=mi2}) to make sure they get an
28427 interpreter with the MI version they expect.
28429 The following table gives a summary of the the released versions of the MI
28430 interface: the version number, the version of GDB in which it first appeared
28431 and the breaking changes compared to the previous version.
28433 @multitable @columnfractions .05 .05 .9
28434 @headitem MI version @tab GDB version @tab Breaking changes
28451 The @code{-environment-pwd}, @code{-environment-directory} and
28452 @code{-environment-path} commands now returns values using the MI output
28453 syntax, rather than CLI output syntax.
28456 @code{-var-list-children}'s @code{children} result field is now a list, rather
28460 @code{-var-update}'s @code{changelist} result field is now a list, rather than
28472 The output of information about multi-location breakpoints has changed in the
28473 responses to the @code{-break-insert} and @code{-break-info} commands, as well
28474 as in the @code{=breakpoint-created} and @code{=breakpoint-modified} events.
28475 The multiple locations are now placed in a @code{locations} field, whose value
28481 If your front end cannot yet migrate to a more recent version of the
28482 MI protocol, you can nevertheless selectively enable specific features
28483 available in those recent MI versions, using the following commands:
28487 @item -fix-multi-location-breakpoint-output
28488 Use the output for multi-location breakpoints which was introduced by
28489 MI 3, even when using MI versions 2 or 1. This command has no
28490 effect when using MI version 3 or later.
28494 The best way to avoid unexpected changes in MI that might break your front
28495 end is to make your project known to @value{GDBN} developers and
28496 follow development on @email{gdb@@sourceware.org} and
28497 @email{gdb-patches@@sourceware.org}.
28498 @cindex mailing lists
28500 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28501 @node GDB/MI Output Records
28502 @section @sc{gdb/mi} Output Records
28505 * GDB/MI Result Records::
28506 * GDB/MI Stream Records::
28507 * GDB/MI Async Records::
28508 * GDB/MI Breakpoint Information::
28509 * GDB/MI Frame Information::
28510 * GDB/MI Thread Information::
28511 * GDB/MI Ada Exception Information::
28514 @node GDB/MI Result Records
28515 @subsection @sc{gdb/mi} Result Records
28517 @cindex result records in @sc{gdb/mi}
28518 @cindex @sc{gdb/mi}, result records
28519 In addition to a number of out-of-band notifications, the response to a
28520 @sc{gdb/mi} command includes one of the following result indications:
28524 @item "^done" [ "," @var{results} ]
28525 The synchronous operation was successful, @code{@var{results}} are the return
28530 This result record is equivalent to @samp{^done}. Historically, it
28531 was output instead of @samp{^done} if the command has resumed the
28532 target. This behaviour is maintained for backward compatibility, but
28533 all frontends should treat @samp{^done} and @samp{^running}
28534 identically and rely on the @samp{*running} output record to determine
28535 which threads are resumed.
28539 @value{GDBN} has connected to a remote target.
28541 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
28543 The operation failed. The @code{msg=@var{c-string}} variable contains
28544 the corresponding error message.
28546 If present, the @code{code=@var{c-string}} variable provides an error
28547 code on which consumers can rely on to detect the corresponding
28548 error condition. At present, only one error code is defined:
28551 @item "undefined-command"
28552 Indicates that the command causing the error does not exist.
28557 @value{GDBN} has terminated.
28561 @node GDB/MI Stream Records
28562 @subsection @sc{gdb/mi} Stream Records
28564 @cindex @sc{gdb/mi}, stream records
28565 @cindex stream records in @sc{gdb/mi}
28566 @value{GDBN} internally maintains a number of output streams: the console, the
28567 target, and the log. The output intended for each of these streams is
28568 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
28570 Each stream record begins with a unique @dfn{prefix character} which
28571 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
28572 Syntax}). In addition to the prefix, each stream record contains a
28573 @code{@var{string-output}}. This is either raw text (with an implicit new
28574 line) or a quoted C string (which does not contain an implicit newline).
28577 @item "~" @var{string-output}
28578 The console output stream contains text that should be displayed in the
28579 CLI console window. It contains the textual responses to CLI commands.
28581 @item "@@" @var{string-output}
28582 The target output stream contains any textual output from the running
28583 target. This is only present when GDB's event loop is truly
28584 asynchronous, which is currently only the case for remote targets.
28586 @item "&" @var{string-output}
28587 The log stream contains debugging messages being produced by @value{GDBN}'s
28591 @node GDB/MI Async Records
28592 @subsection @sc{gdb/mi} Async Records
28594 @cindex async records in @sc{gdb/mi}
28595 @cindex @sc{gdb/mi}, async records
28596 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
28597 additional changes that have occurred. Those changes can either be a
28598 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
28599 target activity (e.g., target stopped).
28601 The following is the list of possible async records:
28605 @item *running,thread-id="@var{thread}"
28606 The target is now running. The @var{thread} field can be the global
28607 thread ID of the the thread that is now running, and it can be
28608 @samp{all} if all threads are running. The frontend should assume
28609 that no interaction with a running thread is possible after this
28610 notification is produced. The frontend should not assume that this
28611 notification is output only once for any command. @value{GDBN} may
28612 emit this notification several times, either for different threads,
28613 because it cannot resume all threads together, or even for a single
28614 thread, if the thread must be stepped though some code before letting
28617 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
28618 The target has stopped. The @var{reason} field can have one of the
28622 @item breakpoint-hit
28623 A breakpoint was reached.
28624 @item watchpoint-trigger
28625 A watchpoint was triggered.
28626 @item read-watchpoint-trigger
28627 A read watchpoint was triggered.
28628 @item access-watchpoint-trigger
28629 An access watchpoint was triggered.
28630 @item function-finished
28631 An -exec-finish or similar CLI command was accomplished.
28632 @item location-reached
28633 An -exec-until or similar CLI command was accomplished.
28634 @item watchpoint-scope
28635 A watchpoint has gone out of scope.
28636 @item end-stepping-range
28637 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
28638 similar CLI command was accomplished.
28639 @item exited-signalled
28640 The inferior exited because of a signal.
28642 The inferior exited.
28643 @item exited-normally
28644 The inferior exited normally.
28645 @item signal-received
28646 A signal was received by the inferior.
28648 The inferior has stopped due to a library being loaded or unloaded.
28649 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
28650 set or when a @code{catch load} or @code{catch unload} catchpoint is
28651 in use (@pxref{Set Catchpoints}).
28653 The inferior has forked. This is reported when @code{catch fork}
28654 (@pxref{Set Catchpoints}) has been used.
28656 The inferior has vforked. This is reported in when @code{catch vfork}
28657 (@pxref{Set Catchpoints}) has been used.
28658 @item syscall-entry
28659 The inferior entered a system call. This is reported when @code{catch
28660 syscall} (@pxref{Set Catchpoints}) has been used.
28661 @item syscall-return
28662 The inferior returned from a system call. This is reported when
28663 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
28665 The inferior called @code{exec}. This is reported when @code{catch exec}
28666 (@pxref{Set Catchpoints}) has been used.
28669 The @var{id} field identifies the global thread ID of the thread
28670 that directly caused the stop -- for example by hitting a breakpoint.
28671 Depending on whether all-stop
28672 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
28673 stop all threads, or only the thread that directly triggered the stop.
28674 If all threads are stopped, the @var{stopped} field will have the
28675 value of @code{"all"}. Otherwise, the value of the @var{stopped}
28676 field will be a list of thread identifiers. Presently, this list will
28677 always include a single thread, but frontend should be prepared to see
28678 several threads in the list. The @var{core} field reports the
28679 processor core on which the stop event has happened. This field may be absent
28680 if such information is not available.
28682 @item =thread-group-added,id="@var{id}"
28683 @itemx =thread-group-removed,id="@var{id}"
28684 A thread group was either added or removed. The @var{id} field
28685 contains the @value{GDBN} identifier of the thread group. When a thread
28686 group is added, it generally might not be associated with a running
28687 process. When a thread group is removed, its id becomes invalid and
28688 cannot be used in any way.
28690 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
28691 A thread group became associated with a running program,
28692 either because the program was just started or the thread group
28693 was attached to a program. The @var{id} field contains the
28694 @value{GDBN} identifier of the thread group. The @var{pid} field
28695 contains process identifier, specific to the operating system.
28697 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
28698 A thread group is no longer associated with a running program,
28699 either because the program has exited, or because it was detached
28700 from. The @var{id} field contains the @value{GDBN} identifier of the
28701 thread group. The @var{code} field is the exit code of the inferior; it exists
28702 only when the inferior exited with some code.
28704 @item =thread-created,id="@var{id}",group-id="@var{gid}"
28705 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
28706 A thread either was created, or has exited. The @var{id} field
28707 contains the global @value{GDBN} identifier of the thread. The @var{gid}
28708 field identifies the thread group this thread belongs to.
28710 @item =thread-selected,id="@var{id}"[,frame="@var{frame}"]
28711 Informs that the selected thread or frame were changed. This notification
28712 is not emitted as result of the @code{-thread-select} or
28713 @code{-stack-select-frame} commands, but is emitted whenever an MI command
28714 that is not documented to change the selected thread and frame actually
28715 changes them. In particular, invoking, directly or indirectly
28716 (via user-defined command), the CLI @code{thread} or @code{frame} commands,
28717 will generate this notification. Changing the thread or frame from another
28718 user interface (see @ref{Interpreters}) will also generate this notification.
28720 The @var{frame} field is only present if the newly selected thread is
28721 stopped. See @ref{GDB/MI Frame Information} for the format of its value.
28723 We suggest that in response to this notification, front ends
28724 highlight the selected thread and cause subsequent commands to apply to
28727 @item =library-loaded,...
28728 Reports that a new library file was loaded by the program. This
28729 notification has 5 fields---@var{id}, @var{target-name},
28730 @var{host-name}, @var{symbols-loaded} and @var{ranges}. The @var{id} field is an
28731 opaque identifier of the library. For remote debugging case,
28732 @var{target-name} and @var{host-name} fields give the name of the
28733 library file on the target, and on the host respectively. For native
28734 debugging, both those fields have the same value. The
28735 @var{symbols-loaded} field is emitted only for backward compatibility
28736 and should not be relied on to convey any useful information. The
28737 @var{thread-group} field, if present, specifies the id of the thread
28738 group in whose context the library was loaded. If the field is
28739 absent, it means the library was loaded in the context of all present
28740 thread groups. The @var{ranges} field specifies the ranges of addresses belonging
28743 @item =library-unloaded,...
28744 Reports that a library was unloaded by the program. This notification
28745 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
28746 the same meaning as for the @code{=library-loaded} notification.
28747 The @var{thread-group} field, if present, specifies the id of the
28748 thread group in whose context the library was unloaded. If the field is
28749 absent, it means the library was unloaded in the context of all present
28752 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
28753 @itemx =traceframe-changed,end
28754 Reports that the trace frame was changed and its new number is
28755 @var{tfnum}. The number of the tracepoint associated with this trace
28756 frame is @var{tpnum}.
28758 @item =tsv-created,name=@var{name},initial=@var{initial}
28759 Reports that the new trace state variable @var{name} is created with
28760 initial value @var{initial}.
28762 @item =tsv-deleted,name=@var{name}
28763 @itemx =tsv-deleted
28764 Reports that the trace state variable @var{name} is deleted or all
28765 trace state variables are deleted.
28767 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
28768 Reports that the trace state variable @var{name} is modified with
28769 the initial value @var{initial}. The current value @var{current} of
28770 trace state variable is optional and is reported if the current
28771 value of trace state variable is known.
28773 @item =breakpoint-created,bkpt=@{...@}
28774 @itemx =breakpoint-modified,bkpt=@{...@}
28775 @itemx =breakpoint-deleted,id=@var{number}
28776 Reports that a breakpoint was created, modified, or deleted,
28777 respectively. Only user-visible breakpoints are reported to the MI
28780 The @var{bkpt} argument is of the same form as returned by the various
28781 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
28782 @var{number} is the ordinal number of the breakpoint.
28784 Note that if a breakpoint is emitted in the result record of a
28785 command, then it will not also be emitted in an async record.
28787 @item =record-started,thread-group="@var{id}",method="@var{method}"[,format="@var{format}"]
28788 @itemx =record-stopped,thread-group="@var{id}"
28789 Execution log recording was either started or stopped on an
28790 inferior. The @var{id} is the @value{GDBN} identifier of the thread
28791 group corresponding to the affected inferior.
28793 The @var{method} field indicates the method used to record execution. If the
28794 method in use supports multiple recording formats, @var{format} will be present
28795 and contain the currently used format. @xref{Process Record and Replay},
28796 for existing method and format values.
28798 @item =cmd-param-changed,param=@var{param},value=@var{value}
28799 Reports that a parameter of the command @code{set @var{param}} is
28800 changed to @var{value}. In the multi-word @code{set} command,
28801 the @var{param} is the whole parameter list to @code{set} command.
28802 For example, In command @code{set check type on}, @var{param}
28803 is @code{check type} and @var{value} is @code{on}.
28805 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
28806 Reports that bytes from @var{addr} to @var{data} + @var{len} were
28807 written in an inferior. The @var{id} is the identifier of the
28808 thread group corresponding to the affected inferior. The optional
28809 @code{type="code"} part is reported if the memory written to holds
28813 @node GDB/MI Breakpoint Information
28814 @subsection @sc{gdb/mi} Breakpoint Information
28816 When @value{GDBN} reports information about a breakpoint, a
28817 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
28822 The breakpoint number.
28825 The type of the breakpoint. For ordinary breakpoints this will be
28826 @samp{breakpoint}, but many values are possible.
28829 If the type of the breakpoint is @samp{catchpoint}, then this
28830 indicates the exact type of catchpoint.
28833 This is the breakpoint disposition---either @samp{del}, meaning that
28834 the breakpoint will be deleted at the next stop, or @samp{keep},
28835 meaning that the breakpoint will not be deleted.
28838 This indicates whether the breakpoint is enabled, in which case the
28839 value is @samp{y}, or disabled, in which case the value is @samp{n}.
28840 Note that this is not the same as the field @code{enable}.
28843 The address of the breakpoint. This may be a hexidecimal number,
28844 giving the address; or the string @samp{<PENDING>}, for a pending
28845 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
28846 multiple locations. This field will not be present if no address can
28847 be determined. For example, a watchpoint does not have an address.
28850 If known, the function in which the breakpoint appears.
28851 If not known, this field is not present.
28854 The name of the source file which contains this function, if known.
28855 If not known, this field is not present.
28858 The full file name of the source file which contains this function, if
28859 known. If not known, this field is not present.
28862 The line number at which this breakpoint appears, if known.
28863 If not known, this field is not present.
28866 If the source file is not known, this field may be provided. If
28867 provided, this holds the address of the breakpoint, possibly followed
28871 If this breakpoint is pending, this field is present and holds the
28872 text used to set the breakpoint, as entered by the user.
28875 Where this breakpoint's condition is evaluated, either @samp{host} or
28879 If this is a thread-specific breakpoint, then this identifies the
28880 thread in which the breakpoint can trigger.
28883 If this breakpoint is restricted to a particular Ada task, then this
28884 field will hold the task identifier.
28887 If the breakpoint is conditional, this is the condition expression.
28890 The ignore count of the breakpoint.
28893 The enable count of the breakpoint.
28895 @item traceframe-usage
28898 @item static-tracepoint-marker-string-id
28899 For a static tracepoint, the name of the static tracepoint marker.
28902 For a masked watchpoint, this is the mask.
28905 A tracepoint's pass count.
28907 @item original-location
28908 The location of the breakpoint as originally specified by the user.
28909 This field is optional.
28912 The number of times the breakpoint has been hit.
28915 This field is only given for tracepoints. This is either @samp{y},
28916 meaning that the tracepoint is installed, or @samp{n}, meaning that it
28920 Some extra data, the exact contents of which are type-dependent.
28923 This field is present if the breakpoint has multiple locations. It is also
28924 exceptionally present if the breakpoint is enabled and has a single, disabled
28927 The value is a list of locations. The format of a location is decribed below.
28931 A location in a multi-location breakpoint is represented as a tuple with the
28937 The location number as a dotted pair, like @samp{1.2}. The first digit is the
28938 number of the parent breakpoint. The second digit is the number of the
28939 location within that breakpoint.
28942 This indicates whether the location is enabled, in which case the
28943 value is @samp{y}, or disabled, in which case the value is @samp{n}.
28944 Note that this is not the same as the field @code{enable}.
28947 The address of this location as an hexidecimal number.
28950 If known, the function in which the location appears.
28951 If not known, this field is not present.
28954 The name of the source file which contains this location, if known.
28955 If not known, this field is not present.
28958 The full file name of the source file which contains this location, if
28959 known. If not known, this field is not present.
28962 The line number at which this location appears, if known.
28963 If not known, this field is not present.
28965 @item thread-groups
28966 The thread groups this location is in.
28970 For example, here is what the output of @code{-break-insert}
28971 (@pxref{GDB/MI Breakpoint Commands}) might be:
28974 -> -break-insert main
28975 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28976 enabled="y",addr="0x08048564",func="main",file="myprog.c",
28977 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
28982 @node GDB/MI Frame Information
28983 @subsection @sc{gdb/mi} Frame Information
28985 Response from many MI commands includes an information about stack
28986 frame. This information is a tuple that may have the following
28991 The level of the stack frame. The innermost frame has the level of
28992 zero. This field is always present.
28995 The name of the function corresponding to the frame. This field may
28996 be absent if @value{GDBN} is unable to determine the function name.
28999 The code address for the frame. This field is always present.
29002 The name of the source files that correspond to the frame's code
29003 address. This field may be absent.
29006 The source line corresponding to the frames' code address. This field
29010 The name of the binary file (either executable or shared library) the
29011 corresponds to the frame's code address. This field may be absent.
29015 @node GDB/MI Thread Information
29016 @subsection @sc{gdb/mi} Thread Information
29018 Whenever @value{GDBN} has to report an information about a thread, it
29019 uses a tuple with the following fields. The fields are always present unless
29024 The global numeric id assigned to the thread by @value{GDBN}.
29027 The target-specific string identifying the thread.
29030 Additional information about the thread provided by the target.
29031 It is supposed to be human-readable and not interpreted by the
29032 frontend. This field is optional.
29035 The name of the thread. If the user specified a name using the
29036 @code{thread name} command, then this name is given. Otherwise, if
29037 @value{GDBN} can extract the thread name from the target, then that
29038 name is given. If @value{GDBN} cannot find the thread name, then this
29042 The execution state of the thread, either @samp{stopped} or @samp{running},
29043 depending on whether the thread is presently running.
29046 The stack frame currently executing in the thread. This field is only present
29047 if the thread is stopped. Its format is documented in
29048 @ref{GDB/MI Frame Information}.
29051 The value of this field is an integer number of the processor core the
29052 thread was last seen on. This field is optional.
29055 @node GDB/MI Ada Exception Information
29056 @subsection @sc{gdb/mi} Ada Exception Information
29058 Whenever a @code{*stopped} record is emitted because the program
29059 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
29060 @value{GDBN} provides the name of the exception that was raised via
29061 the @code{exception-name} field. Also, for exceptions that were raised
29062 with an exception message, @value{GDBN} provides that message via
29063 the @code{exception-message} field.
29065 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29066 @node GDB/MI Simple Examples
29067 @section Simple Examples of @sc{gdb/mi} Interaction
29068 @cindex @sc{gdb/mi}, simple examples
29070 This subsection presents several simple examples of interaction using
29071 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
29072 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
29073 the output received from @sc{gdb/mi}.
29075 Note the line breaks shown in the examples are here only for
29076 readability, they don't appear in the real output.
29078 @subheading Setting a Breakpoint
29080 Setting a breakpoint generates synchronous output which contains detailed
29081 information of the breakpoint.
29084 -> -break-insert main
29085 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
29086 enabled="y",addr="0x08048564",func="main",file="myprog.c",
29087 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
29092 @subheading Program Execution
29094 Program execution generates asynchronous records and MI gives the
29095 reason that execution stopped.
29101 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
29102 frame=@{addr="0x08048564",func="main",
29103 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
29104 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68",
29105 arch="i386:x86_64"@}
29110 <- *stopped,reason="exited-normally"
29114 @subheading Quitting @value{GDBN}
29116 Quitting @value{GDBN} just prints the result class @samp{^exit}.
29124 Please note that @samp{^exit} is printed immediately, but it might
29125 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
29126 performs necessary cleanups, including killing programs being debugged
29127 or disconnecting from debug hardware, so the frontend should wait till
29128 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
29129 fails to exit in reasonable time.
29131 @subheading A Bad Command
29133 Here's what happens if you pass a non-existent command:
29137 <- ^error,msg="Undefined MI command: rubbish"
29142 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29143 @node GDB/MI Command Description Format
29144 @section @sc{gdb/mi} Command Description Format
29146 The remaining sections describe blocks of commands. Each block of
29147 commands is laid out in a fashion similar to this section.
29149 @subheading Motivation
29151 The motivation for this collection of commands.
29153 @subheading Introduction
29155 A brief introduction to this collection of commands as a whole.
29157 @subheading Commands
29159 For each command in the block, the following is described:
29161 @subsubheading Synopsis
29164 -command @var{args}@dots{}
29167 @subsubheading Result
29169 @subsubheading @value{GDBN} Command
29171 The corresponding @value{GDBN} CLI command(s), if any.
29173 @subsubheading Example
29175 Example(s) formatted for readability. Some of the described commands have
29176 not been implemented yet and these are labeled N.A.@: (not available).
29179 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29180 @node GDB/MI Breakpoint Commands
29181 @section @sc{gdb/mi} Breakpoint Commands
29183 @cindex breakpoint commands for @sc{gdb/mi}
29184 @cindex @sc{gdb/mi}, breakpoint commands
29185 This section documents @sc{gdb/mi} commands for manipulating
29188 @subheading The @code{-break-after} Command
29189 @findex -break-after
29191 @subsubheading Synopsis
29194 -break-after @var{number} @var{count}
29197 The breakpoint number @var{number} is not in effect until it has been
29198 hit @var{count} times. To see how this is reflected in the output of
29199 the @samp{-break-list} command, see the description of the
29200 @samp{-break-list} command below.
29202 @subsubheading @value{GDBN} Command
29204 The corresponding @value{GDBN} command is @samp{ignore}.
29206 @subsubheading Example
29211 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
29212 enabled="y",addr="0x000100d0",func="main",file="hello.c",
29213 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
29221 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
29222 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29223 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29224 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29225 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29226 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29227 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29228 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29229 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
29230 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
29235 @subheading The @code{-break-catch} Command
29236 @findex -break-catch
29239 @subheading The @code{-break-commands} Command
29240 @findex -break-commands
29242 @subsubheading Synopsis
29245 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
29248 Specifies the CLI commands that should be executed when breakpoint
29249 @var{number} is hit. The parameters @var{command1} to @var{commandN}
29250 are the commands. If no command is specified, any previously-set
29251 commands are cleared. @xref{Break Commands}. Typical use of this
29252 functionality is tracing a program, that is, printing of values of
29253 some variables whenever breakpoint is hit and then continuing.
29255 @subsubheading @value{GDBN} Command
29257 The corresponding @value{GDBN} command is @samp{commands}.
29259 @subsubheading Example
29264 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
29265 enabled="y",addr="0x000100d0",func="main",file="hello.c",
29266 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
29269 -break-commands 1 "print v" "continue"
29274 @subheading The @code{-break-condition} Command
29275 @findex -break-condition
29277 @subsubheading Synopsis
29280 -break-condition @var{number} @var{expr}
29283 Breakpoint @var{number} will stop the program only if the condition in
29284 @var{expr} is true. The condition becomes part of the
29285 @samp{-break-list} output (see the description of the @samp{-break-list}
29288 @subsubheading @value{GDBN} Command
29290 The corresponding @value{GDBN} command is @samp{condition}.
29292 @subsubheading Example
29296 -break-condition 1 1
29300 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
29301 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29302 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29303 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29304 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29305 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29306 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29307 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29308 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
29309 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
29313 @subheading The @code{-break-delete} Command
29314 @findex -break-delete
29316 @subsubheading Synopsis
29319 -break-delete ( @var{breakpoint} )+
29322 Delete the breakpoint(s) whose number(s) are specified in the argument
29323 list. This is obviously reflected in the breakpoint list.
29325 @subsubheading @value{GDBN} Command
29327 The corresponding @value{GDBN} command is @samp{delete}.
29329 @subsubheading Example
29337 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
29338 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29339 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29340 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29341 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29342 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29343 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29348 @subheading The @code{-break-disable} Command
29349 @findex -break-disable
29351 @subsubheading Synopsis
29354 -break-disable ( @var{breakpoint} )+
29357 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
29358 break list is now set to @samp{n} for the named @var{breakpoint}(s).
29360 @subsubheading @value{GDBN} Command
29362 The corresponding @value{GDBN} command is @samp{disable}.
29364 @subsubheading Example
29372 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
29373 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29374 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29375 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29376 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29377 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29378 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29379 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
29380 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
29381 line="5",thread-groups=["i1"],times="0"@}]@}
29385 @subheading The @code{-break-enable} Command
29386 @findex -break-enable
29388 @subsubheading Synopsis
29391 -break-enable ( @var{breakpoint} )+
29394 Enable (previously disabled) @var{breakpoint}(s).
29396 @subsubheading @value{GDBN} Command
29398 The corresponding @value{GDBN} command is @samp{enable}.
29400 @subsubheading Example
29408 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
29409 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29410 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29411 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29412 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29413 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29414 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29415 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
29416 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
29417 line="5",thread-groups=["i1"],times="0"@}]@}
29421 @subheading The @code{-break-info} Command
29422 @findex -break-info
29424 @subsubheading Synopsis
29427 -break-info @var{breakpoint}
29431 Get information about a single breakpoint.
29433 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
29434 Information}, for details on the format of each breakpoint in the
29437 @subsubheading @value{GDBN} Command
29439 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
29441 @subsubheading Example
29444 @subheading The @code{-break-insert} Command
29445 @findex -break-insert
29446 @anchor{-break-insert}
29448 @subsubheading Synopsis
29451 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
29452 [ -c @var{condition} ] [ -i @var{ignore-count} ]
29453 [ -p @var{thread-id} ] [ @var{location} ]
29457 If specified, @var{location}, can be one of:
29460 @item linespec location
29461 A linespec location. @xref{Linespec Locations}.
29463 @item explicit location
29464 An explicit location. @sc{gdb/mi} explicit locations are
29465 analogous to the CLI's explicit locations using the option names
29466 listed below. @xref{Explicit Locations}.
29469 @item --source @var{filename}
29470 The source file name of the location. This option requires the use
29471 of either @samp{--function} or @samp{--line}.
29473 @item --function @var{function}
29474 The name of a function or method.
29476 @item --label @var{label}
29477 The name of a label.
29479 @item --line @var{lineoffset}
29480 An absolute or relative line offset from the start of the location.
29483 @item address location
29484 An address location, *@var{address}. @xref{Address Locations}.
29488 The possible optional parameters of this command are:
29492 Insert a temporary breakpoint.
29494 Insert a hardware breakpoint.
29496 If @var{location} cannot be parsed (for example if it
29497 refers to unknown files or functions), create a pending
29498 breakpoint. Without this flag, @value{GDBN} will report
29499 an error, and won't create a breakpoint, if @var{location}
29502 Create a disabled breakpoint.
29504 Create a tracepoint. @xref{Tracepoints}. When this parameter
29505 is used together with @samp{-h}, a fast tracepoint is created.
29506 @item -c @var{condition}
29507 Make the breakpoint conditional on @var{condition}.
29508 @item -i @var{ignore-count}
29509 Initialize the @var{ignore-count}.
29510 @item -p @var{thread-id}
29511 Restrict the breakpoint to the thread with the specified global
29515 @subsubheading Result
29517 @xref{GDB/MI Breakpoint Information}, for details on the format of the
29518 resulting breakpoint.
29520 Note: this format is open to change.
29521 @c An out-of-band breakpoint instead of part of the result?
29523 @subsubheading @value{GDBN} Command
29525 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
29526 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
29528 @subsubheading Example
29533 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
29534 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
29537 -break-insert -t foo
29538 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
29539 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
29543 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
29544 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29545 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29546 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29547 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29548 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29549 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29550 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29551 addr="0x0001072c", func="main",file="recursive2.c",
29552 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
29554 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
29555 addr="0x00010774",func="foo",file="recursive2.c",
29556 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
29559 @c -break-insert -r foo.*
29560 @c ~int foo(int, int);
29561 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
29562 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
29567 @subheading The @code{-dprintf-insert} Command
29568 @findex -dprintf-insert
29570 @subsubheading Synopsis
29573 -dprintf-insert [ -t ] [ -f ] [ -d ]
29574 [ -c @var{condition} ] [ -i @var{ignore-count} ]
29575 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
29580 If supplied, @var{location} may be specified the same way as for
29581 the @code{-break-insert} command. @xref{-break-insert}.
29583 The possible optional parameters of this command are:
29587 Insert a temporary breakpoint.
29589 If @var{location} cannot be parsed (for example, if it
29590 refers to unknown files or functions), create a pending
29591 breakpoint. Without this flag, @value{GDBN} will report
29592 an error, and won't create a breakpoint, if @var{location}
29595 Create a disabled breakpoint.
29596 @item -c @var{condition}
29597 Make the breakpoint conditional on @var{condition}.
29598 @item -i @var{ignore-count}
29599 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
29600 to @var{ignore-count}.
29601 @item -p @var{thread-id}
29602 Restrict the breakpoint to the thread with the specified global
29606 @subsubheading Result
29608 @xref{GDB/MI Breakpoint Information}, for details on the format of the
29609 resulting breakpoint.
29611 @c An out-of-band breakpoint instead of part of the result?
29613 @subsubheading @value{GDBN} Command
29615 The corresponding @value{GDBN} command is @samp{dprintf}.
29617 @subsubheading Example
29621 4-dprintf-insert foo "At foo entry\n"
29622 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
29623 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
29624 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
29625 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
29626 original-location="foo"@}
29628 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
29629 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
29630 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
29631 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
29632 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
29633 original-location="mi-dprintf.c:26"@}
29637 @subheading The @code{-break-list} Command
29638 @findex -break-list
29640 @subsubheading Synopsis
29646 Displays the list of inserted breakpoints, showing the following fields:
29650 number of the breakpoint
29652 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
29654 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
29657 is the breakpoint enabled or no: @samp{y} or @samp{n}
29659 memory location at which the breakpoint is set
29661 logical location of the breakpoint, expressed by function name, file
29663 @item Thread-groups
29664 list of thread groups to which this breakpoint applies
29666 number of times the breakpoint has been hit
29669 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
29670 @code{body} field is an empty list.
29672 @subsubheading @value{GDBN} Command
29674 The corresponding @value{GDBN} command is @samp{info break}.
29676 @subsubheading Example
29681 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
29682 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29683 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29684 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29685 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29686 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29687 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29688 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29689 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
29691 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
29692 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
29693 line="13",thread-groups=["i1"],times="0"@}]@}
29697 Here's an example of the result when there are no breakpoints:
29702 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
29703 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29704 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29705 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29706 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29707 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29708 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29713 @subheading The @code{-break-passcount} Command
29714 @findex -break-passcount
29716 @subsubheading Synopsis
29719 -break-passcount @var{tracepoint-number} @var{passcount}
29722 Set the passcount for tracepoint @var{tracepoint-number} to
29723 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
29724 is not a tracepoint, error is emitted. This corresponds to CLI
29725 command @samp{passcount}.
29727 @subheading The @code{-break-watch} Command
29728 @findex -break-watch
29730 @subsubheading Synopsis
29733 -break-watch [ -a | -r ]
29736 Create a watchpoint. With the @samp{-a} option it will create an
29737 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
29738 read from or on a write to the memory location. With the @samp{-r}
29739 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
29740 trigger only when the memory location is accessed for reading. Without
29741 either of the options, the watchpoint created is a regular watchpoint,
29742 i.e., it will trigger when the memory location is accessed for writing.
29743 @xref{Set Watchpoints, , Setting Watchpoints}.
29745 Note that @samp{-break-list} will report a single list of watchpoints and
29746 breakpoints inserted.
29748 @subsubheading @value{GDBN} Command
29750 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
29753 @subsubheading Example
29755 Setting a watchpoint on a variable in the @code{main} function:
29760 ^done,wpt=@{number="2",exp="x"@}
29765 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
29766 value=@{old="-268439212",new="55"@},
29767 frame=@{func="main",args=[],file="recursive2.c",
29768 fullname="/home/foo/bar/recursive2.c",line="5",arch="i386:x86_64"@}
29772 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
29773 the program execution twice: first for the variable changing value, then
29774 for the watchpoint going out of scope.
29779 ^done,wpt=@{number="5",exp="C"@}
29784 *stopped,reason="watchpoint-trigger",
29785 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
29786 frame=@{func="callee4",args=[],
29787 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29788 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13",
29789 arch="i386:x86_64"@}
29794 *stopped,reason="watchpoint-scope",wpnum="5",
29795 frame=@{func="callee3",args=[@{name="strarg",
29796 value="0x11940 \"A string argument.\""@}],
29797 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29798 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
29799 arch="i386:x86_64"@}
29803 Listing breakpoints and watchpoints, at different points in the program
29804 execution. Note that once the watchpoint goes out of scope, it is
29810 ^done,wpt=@{number="2",exp="C"@}
29813 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
29814 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29815 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29816 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29817 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29818 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29819 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29820 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29821 addr="0x00010734",func="callee4",
29822 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29823 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
29825 bkpt=@{number="2",type="watchpoint",disp="keep",
29826 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
29831 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
29832 value=@{old="-276895068",new="3"@},
29833 frame=@{func="callee4",args=[],
29834 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29835 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13",
29836 arch="i386:x86_64"@}
29839 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
29840 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29841 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29842 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29843 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29844 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29845 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29846 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29847 addr="0x00010734",func="callee4",
29848 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29849 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
29851 bkpt=@{number="2",type="watchpoint",disp="keep",
29852 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
29856 ^done,reason="watchpoint-scope",wpnum="2",
29857 frame=@{func="callee3",args=[@{name="strarg",
29858 value="0x11940 \"A string argument.\""@}],
29859 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29860 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
29861 arch="i386:x86_64"@}
29864 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
29865 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29866 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29867 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29868 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29869 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29870 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29871 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29872 addr="0x00010734",func="callee4",
29873 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29874 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
29875 thread-groups=["i1"],times="1"@}]@}
29880 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29881 @node GDB/MI Catchpoint Commands
29882 @section @sc{gdb/mi} Catchpoint Commands
29884 This section documents @sc{gdb/mi} commands for manipulating
29888 * Shared Library GDB/MI Catchpoint Commands::
29889 * Ada Exception GDB/MI Catchpoint Commands::
29890 * C++ Exception GDB/MI Catchpoint Commands::
29893 @node Shared Library GDB/MI Catchpoint Commands
29894 @subsection Shared Library @sc{gdb/mi} Catchpoints
29896 @subheading The @code{-catch-load} Command
29897 @findex -catch-load
29899 @subsubheading Synopsis
29902 -catch-load [ -t ] [ -d ] @var{regexp}
29905 Add a catchpoint for library load events. If the @samp{-t} option is used,
29906 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
29907 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
29908 in a disabled state. The @samp{regexp} argument is a regular
29909 expression used to match the name of the loaded library.
29912 @subsubheading @value{GDBN} Command
29914 The corresponding @value{GDBN} command is @samp{catch load}.
29916 @subsubheading Example
29919 -catch-load -t foo.so
29920 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
29921 what="load of library matching foo.so",catch-type="load",times="0"@}
29926 @subheading The @code{-catch-unload} Command
29927 @findex -catch-unload
29929 @subsubheading Synopsis
29932 -catch-unload [ -t ] [ -d ] @var{regexp}
29935 Add a catchpoint for library unload events. If the @samp{-t} option is
29936 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
29937 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
29938 created in a disabled state. The @samp{regexp} argument is a regular
29939 expression used to match the name of the unloaded library.
29941 @subsubheading @value{GDBN} Command
29943 The corresponding @value{GDBN} command is @samp{catch unload}.
29945 @subsubheading Example
29948 -catch-unload -d bar.so
29949 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
29950 what="load of library matching bar.so",catch-type="unload",times="0"@}
29954 @node Ada Exception GDB/MI Catchpoint Commands
29955 @subsection Ada Exception @sc{gdb/mi} Catchpoints
29957 The following @sc{gdb/mi} commands can be used to create catchpoints
29958 that stop the execution when Ada exceptions are being raised.
29960 @subheading The @code{-catch-assert} Command
29961 @findex -catch-assert
29963 @subsubheading Synopsis
29966 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
29969 Add a catchpoint for failed Ada assertions.
29971 The possible optional parameters for this command are:
29974 @item -c @var{condition}
29975 Make the catchpoint conditional on @var{condition}.
29977 Create a disabled catchpoint.
29979 Create a temporary catchpoint.
29982 @subsubheading @value{GDBN} Command
29984 The corresponding @value{GDBN} command is @samp{catch assert}.
29986 @subsubheading Example
29990 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
29991 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
29992 thread-groups=["i1"],times="0",
29993 original-location="__gnat_debug_raise_assert_failure"@}
29997 @subheading The @code{-catch-exception} Command
29998 @findex -catch-exception
30000 @subsubheading Synopsis
30003 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
30007 Add a catchpoint stopping when Ada exceptions are raised.
30008 By default, the command stops the program when any Ada exception
30009 gets raised. But it is also possible, by using some of the
30010 optional parameters described below, to create more selective
30013 The possible optional parameters for this command are:
30016 @item -c @var{condition}
30017 Make the catchpoint conditional on @var{condition}.
30019 Create a disabled catchpoint.
30020 @item -e @var{exception-name}
30021 Only stop when @var{exception-name} is raised. This option cannot
30022 be used combined with @samp{-u}.
30024 Create a temporary catchpoint.
30026 Stop only when an unhandled exception gets raised. This option
30027 cannot be used combined with @samp{-e}.
30030 @subsubheading @value{GDBN} Command
30032 The corresponding @value{GDBN} commands are @samp{catch exception}
30033 and @samp{catch exception unhandled}.
30035 @subsubheading Example
30038 -catch-exception -e Program_Error
30039 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
30040 enabled="y",addr="0x0000000000404874",
30041 what="`Program_Error' Ada exception", thread-groups=["i1"],
30042 times="0",original-location="__gnat_debug_raise_exception"@}
30046 @subheading The @code{-catch-handlers} Command
30047 @findex -catch-handlers
30049 @subsubheading Synopsis
30052 -catch-handlers [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
30056 Add a catchpoint stopping when Ada exceptions are handled.
30057 By default, the command stops the program when any Ada exception
30058 gets handled. But it is also possible, by using some of the
30059 optional parameters described below, to create more selective
30062 The possible optional parameters for this command are:
30065 @item -c @var{condition}
30066 Make the catchpoint conditional on @var{condition}.
30068 Create a disabled catchpoint.
30069 @item -e @var{exception-name}
30070 Only stop when @var{exception-name} is handled.
30072 Create a temporary catchpoint.
30075 @subsubheading @value{GDBN} Command
30077 The corresponding @value{GDBN} command is @samp{catch handlers}.
30079 @subsubheading Example
30082 -catch-handlers -e Constraint_Error
30083 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
30084 enabled="y",addr="0x0000000000402f68",
30085 what="`Constraint_Error' Ada exception handlers",thread-groups=["i1"],
30086 times="0",original-location="__gnat_begin_handler"@}
30090 @node C++ Exception GDB/MI Catchpoint Commands
30091 @subsection C@t{++} Exception @sc{gdb/mi} Catchpoints
30093 The following @sc{gdb/mi} commands can be used to create catchpoints
30094 that stop the execution when C@t{++} exceptions are being throw, rethrown,
30097 @subheading The @code{-catch-throw} Command
30098 @findex -catch-throw
30100 @subsubheading Synopsis
30103 -catch-throw [ -t ] [ -r @var{regexp}]
30106 Stop when the debuggee throws a C@t{++} exception. If @var{regexp} is
30107 given, then only exceptions whose type matches the regular expression
30110 If @samp{-t} is given, then the catchpoint is enabled only for one
30111 stop, the catchpoint is automatically deleted after stopping once for
30114 @subsubheading @value{GDBN} Command
30116 The corresponding @value{GDBN} commands are @samp{catch throw}
30117 and @samp{tcatch throw} (@pxref{Set Catchpoints}).
30119 @subsubheading Example
30122 -catch-throw -r exception_type
30123 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30124 addr="0x00000000004006c0",what="exception throw",
30125 catch-type="throw",thread-groups=["i1"],
30126 regexp="exception_type",times="0"@}
30132 ~"Catchpoint 1 (exception thrown), 0x00007ffff7ae00ed
30133 in __cxa_throw () from /lib64/libstdc++.so.6\n"
30134 *stopped,bkptno="1",reason="breakpoint-hit",disp="keep",
30135 frame=@{addr="0x00007ffff7ae00ed",func="__cxa_throw",
30136 args=[],from="/lib64/libstdc++.so.6",arch="i386:x86-64"@},
30137 thread-id="1",stopped-threads="all",core="6"
30141 @subheading The @code{-catch-rethrow} Command
30142 @findex -catch-rethrow
30144 @subsubheading Synopsis
30147 -catch-rethrow [ -t ] [ -r @var{regexp}]
30150 Stop when a C@t{++} exception is re-thrown. If @var{regexp} is given,
30151 then only exceptions whose type matches the regular expression will be
30154 If @samp{-t} is given, then the catchpoint is enabled only for one
30155 stop, the catchpoint is automatically deleted after the first event is
30158 @subsubheading @value{GDBN} Command
30160 The corresponding @value{GDBN} commands are @samp{catch rethrow}
30161 and @samp{tcatch rethrow} (@pxref{Set Catchpoints}).
30163 @subsubheading Example
30166 -catch-rethrow -r exception_type
30167 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30168 addr="0x00000000004006c0",what="exception rethrow",
30169 catch-type="rethrow",thread-groups=["i1"],
30170 regexp="exception_type",times="0"@}
30176 ~"Catchpoint 1 (exception rethrown), 0x00007ffff7ae00ed
30177 in __cxa_rethrow () from /lib64/libstdc++.so.6\n"
30178 *stopped,bkptno="1",reason="breakpoint-hit",disp="keep",
30179 frame=@{addr="0x00007ffff7ae00ed",func="__cxa_rethrow",
30180 args=[],from="/lib64/libstdc++.so.6",arch="i386:x86-64"@},
30181 thread-id="1",stopped-threads="all",core="6"
30185 @subheading The @code{-catch-catch} Command
30186 @findex -catch-catch
30188 @subsubheading Synopsis
30191 -catch-catch [ -t ] [ -r @var{regexp}]
30194 Stop when the debuggee catches a C@t{++} exception. If @var{regexp}
30195 is given, then only exceptions whose type matches the regular
30196 expression will be caught.
30198 If @samp{-t} is given, then the catchpoint is enabled only for one
30199 stop, the catchpoint is automatically deleted after the first event is
30202 @subsubheading @value{GDBN} Command
30204 The corresponding @value{GDBN} commands are @samp{catch catch}
30205 and @samp{tcatch catch} (@pxref{Set Catchpoints}).
30207 @subsubheading Example
30210 -catch-catch -r exception_type
30211 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30212 addr="0x00000000004006c0",what="exception catch",
30213 catch-type="catch",thread-groups=["i1"],
30214 regexp="exception_type",times="0"@}
30220 ~"Catchpoint 1 (exception caught), 0x00007ffff7ae00ed
30221 in __cxa_begin_catch () from /lib64/libstdc++.so.6\n"
30222 *stopped,bkptno="1",reason="breakpoint-hit",disp="keep",
30223 frame=@{addr="0x00007ffff7ae00ed",func="__cxa_begin_catch",
30224 args=[],from="/lib64/libstdc++.so.6",arch="i386:x86-64"@},
30225 thread-id="1",stopped-threads="all",core="6"
30229 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30230 @node GDB/MI Program Context
30231 @section @sc{gdb/mi} Program Context
30233 @subheading The @code{-exec-arguments} Command
30234 @findex -exec-arguments
30237 @subsubheading Synopsis
30240 -exec-arguments @var{args}
30243 Set the inferior program arguments, to be used in the next
30246 @subsubheading @value{GDBN} Command
30248 The corresponding @value{GDBN} command is @samp{set args}.
30250 @subsubheading Example
30254 -exec-arguments -v word
30261 @subheading The @code{-exec-show-arguments} Command
30262 @findex -exec-show-arguments
30264 @subsubheading Synopsis
30267 -exec-show-arguments
30270 Print the arguments of the program.
30272 @subsubheading @value{GDBN} Command
30274 The corresponding @value{GDBN} command is @samp{show args}.
30276 @subsubheading Example
30281 @subheading The @code{-environment-cd} Command
30282 @findex -environment-cd
30284 @subsubheading Synopsis
30287 -environment-cd @var{pathdir}
30290 Set @value{GDBN}'s working directory.
30292 @subsubheading @value{GDBN} Command
30294 The corresponding @value{GDBN} command is @samp{cd}.
30296 @subsubheading Example
30300 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
30306 @subheading The @code{-environment-directory} Command
30307 @findex -environment-directory
30309 @subsubheading Synopsis
30312 -environment-directory [ -r ] [ @var{pathdir} ]+
30315 Add directories @var{pathdir} to beginning of search path for source files.
30316 If the @samp{-r} option is used, the search path is reset to the default
30317 search path. If directories @var{pathdir} are supplied in addition to the
30318 @samp{-r} option, the search path is first reset and then addition
30320 Multiple directories may be specified, separated by blanks. Specifying
30321 multiple directories in a single command
30322 results in the directories added to the beginning of the
30323 search path in the same order they were presented in the command.
30324 If blanks are needed as
30325 part of a directory name, double-quotes should be used around
30326 the name. In the command output, the path will show up separated
30327 by the system directory-separator character. The directory-separator
30328 character must not be used
30329 in any directory name.
30330 If no directories are specified, the current search path is displayed.
30332 @subsubheading @value{GDBN} Command
30334 The corresponding @value{GDBN} command is @samp{dir}.
30336 @subsubheading Example
30340 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
30341 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
30343 -environment-directory ""
30344 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
30346 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
30347 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
30349 -environment-directory -r
30350 ^done,source-path="$cdir:$cwd"
30355 @subheading The @code{-environment-path} Command
30356 @findex -environment-path
30358 @subsubheading Synopsis
30361 -environment-path [ -r ] [ @var{pathdir} ]+
30364 Add directories @var{pathdir} to beginning of search path for object files.
30365 If the @samp{-r} option is used, the search path is reset to the original
30366 search path that existed at gdb start-up. If directories @var{pathdir} are
30367 supplied in addition to the
30368 @samp{-r} option, the search path is first reset and then addition
30370 Multiple directories may be specified, separated by blanks. Specifying
30371 multiple directories in a single command
30372 results in the directories added to the beginning of the
30373 search path in the same order they were presented in the command.
30374 If blanks are needed as
30375 part of a directory name, double-quotes should be used around
30376 the name. In the command output, the path will show up separated
30377 by the system directory-separator character. The directory-separator
30378 character must not be used
30379 in any directory name.
30380 If no directories are specified, the current path is displayed.
30383 @subsubheading @value{GDBN} Command
30385 The corresponding @value{GDBN} command is @samp{path}.
30387 @subsubheading Example
30392 ^done,path="/usr/bin"
30394 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
30395 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
30397 -environment-path -r /usr/local/bin
30398 ^done,path="/usr/local/bin:/usr/bin"
30403 @subheading The @code{-environment-pwd} Command
30404 @findex -environment-pwd
30406 @subsubheading Synopsis
30412 Show the current working directory.
30414 @subsubheading @value{GDBN} Command
30416 The corresponding @value{GDBN} command is @samp{pwd}.
30418 @subsubheading Example
30423 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
30427 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30428 @node GDB/MI Thread Commands
30429 @section @sc{gdb/mi} Thread Commands
30432 @subheading The @code{-thread-info} Command
30433 @findex -thread-info
30435 @subsubheading Synopsis
30438 -thread-info [ @var{thread-id} ]
30441 Reports information about either a specific thread, if the
30442 @var{thread-id} parameter is present, or about all threads.
30443 @var{thread-id} is the thread's global thread ID. When printing
30444 information about all threads, also reports the global ID of the
30447 @subsubheading @value{GDBN} Command
30449 The @samp{info thread} command prints the same information
30452 @subsubheading Result
30454 The result contains the following attributes:
30458 A list of threads. The format of the elements of the list is described in
30459 @ref{GDB/MI Thread Information}.
30461 @item current-thread-id
30462 The global id of the currently selected thread. This field is omitted if there
30463 is no selected thread (for example, when the selected inferior is not running,
30464 and therefore has no threads) or if a @var{thread-id} argument was passed to
30469 @subsubheading Example
30474 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
30475 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
30476 args=[]@},state="running"@},
30477 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
30478 frame=@{level="0",addr="0x0804891f",func="foo",
30479 args=[@{name="i",value="10"@}],
30480 file="/tmp/a.c",fullname="/tmp/a.c",line="158",arch="i386:x86_64"@},
30481 state="running"@}],
30482 current-thread-id="1"
30486 @subheading The @code{-thread-list-ids} Command
30487 @findex -thread-list-ids
30489 @subsubheading Synopsis
30495 Produces a list of the currently known global @value{GDBN} thread ids.
30496 At the end of the list it also prints the total number of such
30499 This command is retained for historical reasons, the
30500 @code{-thread-info} command should be used instead.
30502 @subsubheading @value{GDBN} Command
30504 Part of @samp{info threads} supplies the same information.
30506 @subsubheading Example
30511 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
30512 current-thread-id="1",number-of-threads="3"
30517 @subheading The @code{-thread-select} Command
30518 @findex -thread-select
30520 @subsubheading Synopsis
30523 -thread-select @var{thread-id}
30526 Make thread with global thread number @var{thread-id} the current
30527 thread. It prints the number of the new current thread, and the
30528 topmost frame for that thread.
30530 This command is deprecated in favor of explicitly using the
30531 @samp{--thread} option to each command.
30533 @subsubheading @value{GDBN} Command
30535 The corresponding @value{GDBN} command is @samp{thread}.
30537 @subsubheading Example
30544 *stopped,reason="end-stepping-range",thread-id="2",line="187",
30545 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
30549 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
30550 number-of-threads="3"
30553 ^done,new-thread-id="3",
30554 frame=@{level="0",func="vprintf",
30555 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
30556 @{name="arg",value="0x2"@}],file="vprintf.c",line="31",arch="i386:x86_64"@}
30560 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30561 @node GDB/MI Ada Tasking Commands
30562 @section @sc{gdb/mi} Ada Tasking Commands
30564 @subheading The @code{-ada-task-info} Command
30565 @findex -ada-task-info
30567 @subsubheading Synopsis
30570 -ada-task-info [ @var{task-id} ]
30573 Reports information about either a specific Ada task, if the
30574 @var{task-id} parameter is present, or about all Ada tasks.
30576 @subsubheading @value{GDBN} Command
30578 The @samp{info tasks} command prints the same information
30579 about all Ada tasks (@pxref{Ada Tasks}).
30581 @subsubheading Result
30583 The result is a table of Ada tasks. The following columns are
30584 defined for each Ada task:
30588 This field exists only for the current thread. It has the value @samp{*}.
30591 The identifier that @value{GDBN} uses to refer to the Ada task.
30594 The identifier that the target uses to refer to the Ada task.
30597 The global thread identifier of the thread corresponding to the Ada
30600 This field should always exist, as Ada tasks are always implemented
30601 on top of a thread. But if @value{GDBN} cannot find this corresponding
30602 thread for any reason, the field is omitted.
30605 This field exists only when the task was created by another task.
30606 In this case, it provides the ID of the parent task.
30609 The base priority of the task.
30612 The current state of the task. For a detailed description of the
30613 possible states, see @ref{Ada Tasks}.
30616 The name of the task.
30620 @subsubheading Example
30624 ^done,tasks=@{nr_rows="3",nr_cols="8",
30625 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
30626 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
30627 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
30628 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
30629 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
30630 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
30631 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
30632 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
30633 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
30634 state="Child Termination Wait",name="main_task"@}]@}
30638 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30639 @node GDB/MI Program Execution
30640 @section @sc{gdb/mi} Program Execution
30642 These are the asynchronous commands which generate the out-of-band
30643 record @samp{*stopped}. Currently @value{GDBN} only really executes
30644 asynchronously with remote targets and this interaction is mimicked in
30647 @subheading The @code{-exec-continue} Command
30648 @findex -exec-continue
30650 @subsubheading Synopsis
30653 -exec-continue [--reverse] [--all|--thread-group N]
30656 Resumes the execution of the inferior program, which will continue
30657 to execute until it reaches a debugger stop event. If the
30658 @samp{--reverse} option is specified, execution resumes in reverse until
30659 it reaches a stop event. Stop events may include
30662 breakpoints or watchpoints
30664 signals or exceptions
30666 the end of the process (or its beginning under @samp{--reverse})
30668 the end or beginning of a replay log if one is being used.
30670 In all-stop mode (@pxref{All-Stop
30671 Mode}), may resume only one thread, or all threads, depending on the
30672 value of the @samp{scheduler-locking} variable. If @samp{--all} is
30673 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
30674 ignored in all-stop mode. If the @samp{--thread-group} options is
30675 specified, then all threads in that thread group are resumed.
30677 @subsubheading @value{GDBN} Command
30679 The corresponding @value{GDBN} corresponding is @samp{continue}.
30681 @subsubheading Example
30688 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
30689 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
30690 line="13",arch="i386:x86_64"@}
30695 @subheading The @code{-exec-finish} Command
30696 @findex -exec-finish
30698 @subsubheading Synopsis
30701 -exec-finish [--reverse]
30704 Resumes the execution of the inferior program until the current
30705 function is exited. Displays the results returned by the function.
30706 If the @samp{--reverse} option is specified, resumes the reverse
30707 execution of the inferior program until the point where current
30708 function was called.
30710 @subsubheading @value{GDBN} Command
30712 The corresponding @value{GDBN} command is @samp{finish}.
30714 @subsubheading Example
30716 Function returning @code{void}.
30723 *stopped,reason="function-finished",frame=@{func="main",args=[],
30724 file="hello.c",fullname="/home/foo/bar/hello.c",line="7",arch="i386:x86_64"@}
30728 Function returning other than @code{void}. The name of the internal
30729 @value{GDBN} variable storing the result is printed, together with the
30736 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
30737 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
30738 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30739 arch="i386:x86_64"@},
30740 gdb-result-var="$1",return-value="0"
30745 @subheading The @code{-exec-interrupt} Command
30746 @findex -exec-interrupt
30748 @subsubheading Synopsis
30751 -exec-interrupt [--all|--thread-group N]
30754 Interrupts the background execution of the target. Note how the token
30755 associated with the stop message is the one for the execution command
30756 that has been interrupted. The token for the interrupt itself only
30757 appears in the @samp{^done} output. If the user is trying to
30758 interrupt a non-running program, an error message will be printed.
30760 Note that when asynchronous execution is enabled, this command is
30761 asynchronous just like other execution commands. That is, first the
30762 @samp{^done} response will be printed, and the target stop will be
30763 reported after that using the @samp{*stopped} notification.
30765 In non-stop mode, only the context thread is interrupted by default.
30766 All threads (in all inferiors) will be interrupted if the
30767 @samp{--all} option is specified. If the @samp{--thread-group}
30768 option is specified, all threads in that group will be interrupted.
30770 @subsubheading @value{GDBN} Command
30772 The corresponding @value{GDBN} command is @samp{interrupt}.
30774 @subsubheading Example
30785 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
30786 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
30787 fullname="/home/foo/bar/try.c",line="13",arch="i386:x86_64"@}
30792 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
30796 @subheading The @code{-exec-jump} Command
30799 @subsubheading Synopsis
30802 -exec-jump @var{location}
30805 Resumes execution of the inferior program at the location specified by
30806 parameter. @xref{Specify Location}, for a description of the
30807 different forms of @var{location}.
30809 @subsubheading @value{GDBN} Command
30811 The corresponding @value{GDBN} command is @samp{jump}.
30813 @subsubheading Example
30816 -exec-jump foo.c:10
30817 *running,thread-id="all"
30822 @subheading The @code{-exec-next} Command
30825 @subsubheading Synopsis
30828 -exec-next [--reverse]
30831 Resumes execution of the inferior program, stopping when the beginning
30832 of the next source line is reached.
30834 If the @samp{--reverse} option is specified, resumes reverse execution
30835 of the inferior program, stopping at the beginning of the previous
30836 source line. If you issue this command on the first line of a
30837 function, it will take you back to the caller of that function, to the
30838 source line where the function was called.
30841 @subsubheading @value{GDBN} Command
30843 The corresponding @value{GDBN} command is @samp{next}.
30845 @subsubheading Example
30851 *stopped,reason="end-stepping-range",line="8",file="hello.c"
30856 @subheading The @code{-exec-next-instruction} Command
30857 @findex -exec-next-instruction
30859 @subsubheading Synopsis
30862 -exec-next-instruction [--reverse]
30865 Executes one machine instruction. If the instruction is a function
30866 call, continues until the function returns. If the program stops at an
30867 instruction in the middle of a source line, the address will be
30870 If the @samp{--reverse} option is specified, resumes reverse execution
30871 of the inferior program, stopping at the previous instruction. If the
30872 previously executed instruction was a return from another function,
30873 it will continue to execute in reverse until the call to that function
30874 (from the current stack frame) is reached.
30876 @subsubheading @value{GDBN} Command
30878 The corresponding @value{GDBN} command is @samp{nexti}.
30880 @subsubheading Example
30884 -exec-next-instruction
30888 *stopped,reason="end-stepping-range",
30889 addr="0x000100d4",line="5",file="hello.c"
30894 @subheading The @code{-exec-return} Command
30895 @findex -exec-return
30897 @subsubheading Synopsis
30903 Makes current function return immediately. Doesn't execute the inferior.
30904 Displays the new current frame.
30906 @subsubheading @value{GDBN} Command
30908 The corresponding @value{GDBN} command is @samp{return}.
30910 @subsubheading Example
30914 200-break-insert callee4
30915 200^done,bkpt=@{number="1",addr="0x00010734",
30916 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
30921 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
30922 frame=@{func="callee4",args=[],
30923 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30924 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
30925 arch="i386:x86_64"@}
30931 111^done,frame=@{level="0",func="callee3",
30932 args=[@{name="strarg",
30933 value="0x11940 \"A string argument.\""@}],
30934 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30935 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
30936 arch="i386:x86_64"@}
30941 @subheading The @code{-exec-run} Command
30944 @subsubheading Synopsis
30947 -exec-run [ --all | --thread-group N ] [ --start ]
30950 Starts execution of the inferior from the beginning. The inferior
30951 executes until either a breakpoint is encountered or the program
30952 exits. In the latter case the output will include an exit code, if
30953 the program has exited exceptionally.
30955 When neither the @samp{--all} nor the @samp{--thread-group} option
30956 is specified, the current inferior is started. If the
30957 @samp{--thread-group} option is specified, it should refer to a thread
30958 group of type @samp{process}, and that thread group will be started.
30959 If the @samp{--all} option is specified, then all inferiors will be started.
30961 Using the @samp{--start} option instructs the debugger to stop
30962 the execution at the start of the inferior's main subprogram,
30963 following the same behavior as the @code{start} command
30964 (@pxref{Starting}).
30966 @subsubheading @value{GDBN} Command
30968 The corresponding @value{GDBN} command is @samp{run}.
30970 @subsubheading Examples
30975 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
30980 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
30981 frame=@{func="main",args=[],file="recursive2.c",
30982 fullname="/home/foo/bar/recursive2.c",line="4",arch="i386:x86_64"@}
30987 Program exited normally:
30995 *stopped,reason="exited-normally"
31000 Program exited exceptionally:
31008 *stopped,reason="exited",exit-code="01"
31012 Another way the program can terminate is if it receives a signal such as
31013 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
31017 *stopped,reason="exited-signalled",signal-name="SIGINT",
31018 signal-meaning="Interrupt"
31022 @c @subheading -exec-signal
31025 @subheading The @code{-exec-step} Command
31028 @subsubheading Synopsis
31031 -exec-step [--reverse]
31034 Resumes execution of the inferior program, stopping when the beginning
31035 of the next source line is reached, if the next source line is not a
31036 function call. If it is, stop at the first instruction of the called
31037 function. If the @samp{--reverse} option is specified, resumes reverse
31038 execution of the inferior program, stopping at the beginning of the
31039 previously executed source line.
31041 @subsubheading @value{GDBN} Command
31043 The corresponding @value{GDBN} command is @samp{step}.
31045 @subsubheading Example
31047 Stepping into a function:
31053 *stopped,reason="end-stepping-range",
31054 frame=@{func="foo",args=[@{name="a",value="10"@},
31055 @{name="b",value="0"@}],file="recursive2.c",
31056 fullname="/home/foo/bar/recursive2.c",line="11",arch="i386:x86_64"@}
31066 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
31071 @subheading The @code{-exec-step-instruction} Command
31072 @findex -exec-step-instruction
31074 @subsubheading Synopsis
31077 -exec-step-instruction [--reverse]
31080 Resumes the inferior which executes one machine instruction. If the
31081 @samp{--reverse} option is specified, resumes reverse execution of the
31082 inferior program, stopping at the previously executed instruction.
31083 The output, once @value{GDBN} has stopped, will vary depending on
31084 whether we have stopped in the middle of a source line or not. In the
31085 former case, the address at which the program stopped will be printed
31088 @subsubheading @value{GDBN} Command
31090 The corresponding @value{GDBN} command is @samp{stepi}.
31092 @subsubheading Example
31096 -exec-step-instruction
31100 *stopped,reason="end-stepping-range",
31101 frame=@{func="foo",args=[],file="try.c",
31102 fullname="/home/foo/bar/try.c",line="10",arch="i386:x86_64"@}
31104 -exec-step-instruction
31108 *stopped,reason="end-stepping-range",
31109 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
31110 fullname="/home/foo/bar/try.c",line="10",arch="i386:x86_64"@}
31115 @subheading The @code{-exec-until} Command
31116 @findex -exec-until
31118 @subsubheading Synopsis
31121 -exec-until [ @var{location} ]
31124 Executes the inferior until the @var{location} specified in the
31125 argument is reached. If there is no argument, the inferior executes
31126 until a source line greater than the current one is reached. The
31127 reason for stopping in this case will be @samp{location-reached}.
31129 @subsubheading @value{GDBN} Command
31131 The corresponding @value{GDBN} command is @samp{until}.
31133 @subsubheading Example
31137 -exec-until recursive2.c:6
31141 *stopped,reason="location-reached",frame=@{func="main",args=[],
31142 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6",
31143 arch="i386:x86_64"@}
31148 @subheading -file-clear
31149 Is this going away????
31152 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31153 @node GDB/MI Stack Manipulation
31154 @section @sc{gdb/mi} Stack Manipulation Commands
31156 @subheading The @code{-enable-frame-filters} Command
31157 @findex -enable-frame-filters
31160 -enable-frame-filters
31163 @value{GDBN} allows Python-based frame filters to affect the output of
31164 the MI commands relating to stack traces. As there is no way to
31165 implement this in a fully backward-compatible way, a front end must
31166 request that this functionality be enabled.
31168 Once enabled, this feature cannot be disabled.
31170 Note that if Python support has not been compiled into @value{GDBN},
31171 this command will still succeed (and do nothing).
31173 @subheading The @code{-stack-info-frame} Command
31174 @findex -stack-info-frame
31176 @subsubheading Synopsis
31182 Get info on the selected frame.
31184 @subsubheading @value{GDBN} Command
31186 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
31187 (without arguments).
31189 @subsubheading Example
31194 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
31195 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31196 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17",
31197 arch="i386:x86_64"@}
31201 @subheading The @code{-stack-info-depth} Command
31202 @findex -stack-info-depth
31204 @subsubheading Synopsis
31207 -stack-info-depth [ @var{max-depth} ]
31210 Return the depth of the stack. If the integer argument @var{max-depth}
31211 is specified, do not count beyond @var{max-depth} frames.
31213 @subsubheading @value{GDBN} Command
31215 There's no equivalent @value{GDBN} command.
31217 @subsubheading Example
31219 For a stack with frame levels 0 through 11:
31226 -stack-info-depth 4
31229 -stack-info-depth 12
31232 -stack-info-depth 11
31235 -stack-info-depth 13
31240 @anchor{-stack-list-arguments}
31241 @subheading The @code{-stack-list-arguments} Command
31242 @findex -stack-list-arguments
31244 @subsubheading Synopsis
31247 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
31248 [ @var{low-frame} @var{high-frame} ]
31251 Display a list of the arguments for the frames between @var{low-frame}
31252 and @var{high-frame} (inclusive). If @var{low-frame} and
31253 @var{high-frame} are not provided, list the arguments for the whole
31254 call stack. If the two arguments are equal, show the single frame
31255 at the corresponding level. It is an error if @var{low-frame} is
31256 larger than the actual number of frames. On the other hand,
31257 @var{high-frame} may be larger than the actual number of frames, in
31258 which case only existing frames will be returned.
31260 If @var{print-values} is 0 or @code{--no-values}, print only the names of
31261 the variables; if it is 1 or @code{--all-values}, print also their
31262 values; and if it is 2 or @code{--simple-values}, print the name,
31263 type and value for simple data types, and the name and type for arrays,
31264 structures and unions. If the option @code{--no-frame-filters} is
31265 supplied, then Python frame filters will not be executed.
31267 If the @code{--skip-unavailable} option is specified, arguments that
31268 are not available are not listed. Partially available arguments
31269 are still displayed, however.
31271 Use of this command to obtain arguments in a single frame is
31272 deprecated in favor of the @samp{-stack-list-variables} command.
31274 @subsubheading @value{GDBN} Command
31276 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
31277 @samp{gdb_get_args} command which partially overlaps with the
31278 functionality of @samp{-stack-list-arguments}.
31280 @subsubheading Example
31287 frame=@{level="0",addr="0x00010734",func="callee4",
31288 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31289 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
31290 arch="i386:x86_64"@},
31291 frame=@{level="1",addr="0x0001076c",func="callee3",
31292 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31293 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17",
31294 arch="i386:x86_64"@},
31295 frame=@{level="2",addr="0x0001078c",func="callee2",
31296 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31297 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22",
31298 arch="i386:x86_64"@},
31299 frame=@{level="3",addr="0x000107b4",func="callee1",
31300 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31301 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27",
31302 arch="i386:x86_64"@},
31303 frame=@{level="4",addr="0x000107e0",func="main",
31304 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31305 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32",
31306 arch="i386:x86_64"@}]
31308 -stack-list-arguments 0
31311 frame=@{level="0",args=[]@},
31312 frame=@{level="1",args=[name="strarg"]@},
31313 frame=@{level="2",args=[name="intarg",name="strarg"]@},
31314 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
31315 frame=@{level="4",args=[]@}]
31317 -stack-list-arguments 1
31320 frame=@{level="0",args=[]@},
31322 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
31323 frame=@{level="2",args=[
31324 @{name="intarg",value="2"@},
31325 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
31326 @{frame=@{level="3",args=[
31327 @{name="intarg",value="2"@},
31328 @{name="strarg",value="0x11940 \"A string argument.\""@},
31329 @{name="fltarg",value="3.5"@}]@},
31330 frame=@{level="4",args=[]@}]
31332 -stack-list-arguments 0 2 2
31333 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
31335 -stack-list-arguments 1 2 2
31336 ^done,stack-args=[frame=@{level="2",
31337 args=[@{name="intarg",value="2"@},
31338 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
31342 @c @subheading -stack-list-exception-handlers
31345 @anchor{-stack-list-frames}
31346 @subheading The @code{-stack-list-frames} Command
31347 @findex -stack-list-frames
31349 @subsubheading Synopsis
31352 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
31355 List the frames currently on the stack. For each frame it displays the
31360 The frame number, 0 being the topmost frame, i.e., the innermost function.
31362 The @code{$pc} value for that frame.
31366 File name of the source file where the function lives.
31367 @item @var{fullname}
31368 The full file name of the source file where the function lives.
31370 Line number corresponding to the @code{$pc}.
31372 The shared library where this function is defined. This is only given
31373 if the frame's function is not known.
31375 Frame's architecture.
31378 If invoked without arguments, this command prints a backtrace for the
31379 whole stack. If given two integer arguments, it shows the frames whose
31380 levels are between the two arguments (inclusive). If the two arguments
31381 are equal, it shows the single frame at the corresponding level. It is
31382 an error if @var{low-frame} is larger than the actual number of
31383 frames. On the other hand, @var{high-frame} may be larger than the
31384 actual number of frames, in which case only existing frames will be
31385 returned. If the option @code{--no-frame-filters} is supplied, then
31386 Python frame filters will not be executed.
31388 @subsubheading @value{GDBN} Command
31390 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
31392 @subsubheading Example
31394 Full stack backtrace:
31400 [frame=@{level="0",addr="0x0001076c",func="foo",
31401 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11",
31402 arch="i386:x86_64"@},
31403 frame=@{level="1",addr="0x000107a4",func="foo",
31404 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
31405 arch="i386:x86_64"@},
31406 frame=@{level="2",addr="0x000107a4",func="foo",
31407 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
31408 arch="i386:x86_64"@},
31409 frame=@{level="3",addr="0x000107a4",func="foo",
31410 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
31411 arch="i386:x86_64"@},
31412 frame=@{level="4",addr="0x000107a4",func="foo",
31413 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
31414 arch="i386:x86_64"@},
31415 frame=@{level="5",addr="0x000107a4",func="foo",
31416 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
31417 arch="i386:x86_64"@},
31418 frame=@{level="6",addr="0x000107a4",func="foo",
31419 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
31420 arch="i386:x86_64"@},
31421 frame=@{level="7",addr="0x000107a4",func="foo",
31422 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
31423 arch="i386:x86_64"@},
31424 frame=@{level="8",addr="0x000107a4",func="foo",
31425 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
31426 arch="i386:x86_64"@},
31427 frame=@{level="9",addr="0x000107a4",func="foo",
31428 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
31429 arch="i386:x86_64"@},
31430 frame=@{level="10",addr="0x000107a4",func="foo",
31431 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
31432 arch="i386:x86_64"@},
31433 frame=@{level="11",addr="0x00010738",func="main",
31434 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4",
31435 arch="i386:x86_64"@}]
31439 Show frames between @var{low_frame} and @var{high_frame}:
31443 -stack-list-frames 3 5
31445 [frame=@{level="3",addr="0x000107a4",func="foo",
31446 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
31447 arch="i386:x86_64"@},
31448 frame=@{level="4",addr="0x000107a4",func="foo",
31449 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
31450 arch="i386:x86_64"@},
31451 frame=@{level="5",addr="0x000107a4",func="foo",
31452 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
31453 arch="i386:x86_64"@}]
31457 Show a single frame:
31461 -stack-list-frames 3 3
31463 [frame=@{level="3",addr="0x000107a4",func="foo",
31464 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
31465 arch="i386:x86_64"@}]
31470 @subheading The @code{-stack-list-locals} Command
31471 @findex -stack-list-locals
31472 @anchor{-stack-list-locals}
31474 @subsubheading Synopsis
31477 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
31480 Display the local variable names for the selected frame. If
31481 @var{print-values} is 0 or @code{--no-values}, print only the names of
31482 the variables; if it is 1 or @code{--all-values}, print also their
31483 values; and if it is 2 or @code{--simple-values}, print the name,
31484 type and value for simple data types, and the name and type for arrays,
31485 structures and unions. In this last case, a frontend can immediately
31486 display the value of simple data types and create variable objects for
31487 other data types when the user wishes to explore their values in
31488 more detail. If the option @code{--no-frame-filters} is supplied, then
31489 Python frame filters will not be executed.
31491 If the @code{--skip-unavailable} option is specified, local variables
31492 that are not available are not listed. Partially available local
31493 variables are still displayed, however.
31495 This command is deprecated in favor of the
31496 @samp{-stack-list-variables} command.
31498 @subsubheading @value{GDBN} Command
31500 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
31502 @subsubheading Example
31506 -stack-list-locals 0
31507 ^done,locals=[name="A",name="B",name="C"]
31509 -stack-list-locals --all-values
31510 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
31511 @{name="C",value="@{1, 2, 3@}"@}]
31512 -stack-list-locals --simple-values
31513 ^done,locals=[@{name="A",type="int",value="1"@},
31514 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
31518 @anchor{-stack-list-variables}
31519 @subheading The @code{-stack-list-variables} Command
31520 @findex -stack-list-variables
31522 @subsubheading Synopsis
31525 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
31528 Display the names of local variables and function arguments for the selected frame. If
31529 @var{print-values} is 0 or @code{--no-values}, print only the names of
31530 the variables; if it is 1 or @code{--all-values}, print also their
31531 values; and if it is 2 or @code{--simple-values}, print the name,
31532 type and value for simple data types, and the name and type for arrays,
31533 structures and unions. If the option @code{--no-frame-filters} is
31534 supplied, then Python frame filters will not be executed.
31536 If the @code{--skip-unavailable} option is specified, local variables
31537 and arguments that are not available are not listed. Partially
31538 available arguments and local variables are still displayed, however.
31540 @subsubheading Example
31544 -stack-list-variables --thread 1 --frame 0 --all-values
31545 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
31550 @subheading The @code{-stack-select-frame} Command
31551 @findex -stack-select-frame
31553 @subsubheading Synopsis
31556 -stack-select-frame @var{framenum}
31559 Change the selected frame. Select a different frame @var{framenum} on
31562 This command in deprecated in favor of passing the @samp{--frame}
31563 option to every command.
31565 @subsubheading @value{GDBN} Command
31567 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
31568 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
31570 @subsubheading Example
31574 -stack-select-frame 2
31579 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31580 @node GDB/MI Variable Objects
31581 @section @sc{gdb/mi} Variable Objects
31585 @subheading Motivation for Variable Objects in @sc{gdb/mi}
31587 For the implementation of a variable debugger window (locals, watched
31588 expressions, etc.), we are proposing the adaptation of the existing code
31589 used by @code{Insight}.
31591 The two main reasons for that are:
31595 It has been proven in practice (it is already on its second generation).
31598 It will shorten development time (needless to say how important it is
31602 The original interface was designed to be used by Tcl code, so it was
31603 slightly changed so it could be used through @sc{gdb/mi}. This section
31604 describes the @sc{gdb/mi} operations that will be available and gives some
31605 hints about their use.
31607 @emph{Note}: In addition to the set of operations described here, we
31608 expect the @sc{gui} implementation of a variable window to require, at
31609 least, the following operations:
31612 @item @code{-gdb-show} @code{output-radix}
31613 @item @code{-stack-list-arguments}
31614 @item @code{-stack-list-locals}
31615 @item @code{-stack-select-frame}
31620 @subheading Introduction to Variable Objects
31622 @cindex variable objects in @sc{gdb/mi}
31624 Variable objects are "object-oriented" MI interface for examining and
31625 changing values of expressions. Unlike some other MI interfaces that
31626 work with expressions, variable objects are specifically designed for
31627 simple and efficient presentation in the frontend. A variable object
31628 is identified by string name. When a variable object is created, the
31629 frontend specifies the expression for that variable object. The
31630 expression can be a simple variable, or it can be an arbitrary complex
31631 expression, and can even involve CPU registers. After creating a
31632 variable object, the frontend can invoke other variable object
31633 operations---for example to obtain or change the value of a variable
31634 object, or to change display format.
31636 Variable objects have hierarchical tree structure. Any variable object
31637 that corresponds to a composite type, such as structure in C, has
31638 a number of child variable objects, for example corresponding to each
31639 element of a structure. A child variable object can itself have
31640 children, recursively. Recursion ends when we reach
31641 leaf variable objects, which always have built-in types. Child variable
31642 objects are created only by explicit request, so if a frontend
31643 is not interested in the children of a particular variable object, no
31644 child will be created.
31646 For a leaf variable object it is possible to obtain its value as a
31647 string, or set the value from a string. String value can be also
31648 obtained for a non-leaf variable object, but it's generally a string
31649 that only indicates the type of the object, and does not list its
31650 contents. Assignment to a non-leaf variable object is not allowed.
31652 A frontend does not need to read the values of all variable objects each time
31653 the program stops. Instead, MI provides an update command that lists all
31654 variable objects whose values has changed since the last update
31655 operation. This considerably reduces the amount of data that must
31656 be transferred to the frontend. As noted above, children variable
31657 objects are created on demand, and only leaf variable objects have a
31658 real value. As result, gdb will read target memory only for leaf
31659 variables that frontend has created.
31661 The automatic update is not always desirable. For example, a frontend
31662 might want to keep a value of some expression for future reference,
31663 and never update it. For another example, fetching memory is
31664 relatively slow for embedded targets, so a frontend might want
31665 to disable automatic update for the variables that are either not
31666 visible on the screen, or ``closed''. This is possible using so
31667 called ``frozen variable objects''. Such variable objects are never
31668 implicitly updated.
31670 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
31671 fixed variable object, the expression is parsed when the variable
31672 object is created, including associating identifiers to specific
31673 variables. The meaning of expression never changes. For a floating
31674 variable object the values of variables whose names appear in the
31675 expressions are re-evaluated every time in the context of the current
31676 frame. Consider this example:
31681 struct work_state state;
31688 If a fixed variable object for the @code{state} variable is created in
31689 this function, and we enter the recursive call, the variable
31690 object will report the value of @code{state} in the top-level
31691 @code{do_work} invocation. On the other hand, a floating variable
31692 object will report the value of @code{state} in the current frame.
31694 If an expression specified when creating a fixed variable object
31695 refers to a local variable, the variable object becomes bound to the
31696 thread and frame in which the variable object is created. When such
31697 variable object is updated, @value{GDBN} makes sure that the
31698 thread/frame combination the variable object is bound to still exists,
31699 and re-evaluates the variable object in context of that thread/frame.
31701 The following is the complete set of @sc{gdb/mi} operations defined to
31702 access this functionality:
31704 @multitable @columnfractions .4 .6
31705 @item @strong{Operation}
31706 @tab @strong{Description}
31708 @item @code{-enable-pretty-printing}
31709 @tab enable Python-based pretty-printing
31710 @item @code{-var-create}
31711 @tab create a variable object
31712 @item @code{-var-delete}
31713 @tab delete the variable object and/or its children
31714 @item @code{-var-set-format}
31715 @tab set the display format of this variable
31716 @item @code{-var-show-format}
31717 @tab show the display format of this variable
31718 @item @code{-var-info-num-children}
31719 @tab tells how many children this object has
31720 @item @code{-var-list-children}
31721 @tab return a list of the object's children
31722 @item @code{-var-info-type}
31723 @tab show the type of this variable object
31724 @item @code{-var-info-expression}
31725 @tab print parent-relative expression that this variable object represents
31726 @item @code{-var-info-path-expression}
31727 @tab print full expression that this variable object represents
31728 @item @code{-var-show-attributes}
31729 @tab is this variable editable? does it exist here?
31730 @item @code{-var-evaluate-expression}
31731 @tab get the value of this variable
31732 @item @code{-var-assign}
31733 @tab set the value of this variable
31734 @item @code{-var-update}
31735 @tab update the variable and its children
31736 @item @code{-var-set-frozen}
31737 @tab set frozeness attribute
31738 @item @code{-var-set-update-range}
31739 @tab set range of children to display on update
31742 In the next subsection we describe each operation in detail and suggest
31743 how it can be used.
31745 @subheading Description And Use of Operations on Variable Objects
31747 @subheading The @code{-enable-pretty-printing} Command
31748 @findex -enable-pretty-printing
31751 -enable-pretty-printing
31754 @value{GDBN} allows Python-based visualizers to affect the output of the
31755 MI variable object commands. However, because there was no way to
31756 implement this in a fully backward-compatible way, a front end must
31757 request that this functionality be enabled.
31759 Once enabled, this feature cannot be disabled.
31761 Note that if Python support has not been compiled into @value{GDBN},
31762 this command will still succeed (and do nothing).
31764 This feature is currently (as of @value{GDBN} 7.0) experimental, and
31765 may work differently in future versions of @value{GDBN}.
31767 @subheading The @code{-var-create} Command
31768 @findex -var-create
31770 @subsubheading Synopsis
31773 -var-create @{@var{name} | "-"@}
31774 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
31777 This operation creates a variable object, which allows the monitoring of
31778 a variable, the result of an expression, a memory cell or a CPU
31781 The @var{name} parameter is the string by which the object can be
31782 referenced. It must be unique. If @samp{-} is specified, the varobj
31783 system will generate a string ``varNNNNNN'' automatically. It will be
31784 unique provided that one does not specify @var{name} of that format.
31785 The command fails if a duplicate name is found.
31787 The frame under which the expression should be evaluated can be
31788 specified by @var{frame-addr}. A @samp{*} indicates that the current
31789 frame should be used. A @samp{@@} indicates that a floating variable
31790 object must be created.
31792 @var{expression} is any expression valid on the current language set (must not
31793 begin with a @samp{*}), or one of the following:
31797 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
31800 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
31803 @samp{$@var{regname}} --- a CPU register name
31806 @cindex dynamic varobj
31807 A varobj's contents may be provided by a Python-based pretty-printer. In this
31808 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
31809 have slightly different semantics in some cases. If the
31810 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
31811 will never create a dynamic varobj. This ensures backward
31812 compatibility for existing clients.
31814 @subsubheading Result
31816 This operation returns attributes of the newly-created varobj. These
31821 The name of the varobj.
31824 The number of children of the varobj. This number is not necessarily
31825 reliable for a dynamic varobj. Instead, you must examine the
31826 @samp{has_more} attribute.
31829 The varobj's scalar value. For a varobj whose type is some sort of
31830 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
31831 will not be interesting.
31834 The varobj's type. This is a string representation of the type, as
31835 would be printed by the @value{GDBN} CLI. If @samp{print object}
31836 (@pxref{Print Settings, set print object}) is set to @code{on}, the
31837 @emph{actual} (derived) type of the object is shown rather than the
31838 @emph{declared} one.
31841 If a variable object is bound to a specific thread, then this is the
31842 thread's global identifier.
31845 For a dynamic varobj, this indicates whether there appear to be any
31846 children available. For a non-dynamic varobj, this will be 0.
31849 This attribute will be present and have the value @samp{1} if the
31850 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
31851 then this attribute will not be present.
31854 A dynamic varobj can supply a display hint to the front end. The
31855 value comes directly from the Python pretty-printer object's
31856 @code{display_hint} method. @xref{Pretty Printing API}.
31859 Typical output will look like this:
31862 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
31863 has_more="@var{has_more}"
31867 @subheading The @code{-var-delete} Command
31868 @findex -var-delete
31870 @subsubheading Synopsis
31873 -var-delete [ -c ] @var{name}
31876 Deletes a previously created variable object and all of its children.
31877 With the @samp{-c} option, just deletes the children.
31879 Returns an error if the object @var{name} is not found.
31882 @subheading The @code{-var-set-format} Command
31883 @findex -var-set-format
31885 @subsubheading Synopsis
31888 -var-set-format @var{name} @var{format-spec}
31891 Sets the output format for the value of the object @var{name} to be
31894 @anchor{-var-set-format}
31895 The syntax for the @var{format-spec} is as follows:
31898 @var{format-spec} @expansion{}
31899 @{binary | decimal | hexadecimal | octal | natural | zero-hexadecimal@}
31902 The natural format is the default format choosen automatically
31903 based on the variable type (like decimal for an @code{int}, hex
31904 for pointers, etc.).
31906 The zero-hexadecimal format has a representation similar to hexadecimal
31907 but with padding zeroes to the left of the value. For example, a 32-bit
31908 hexadecimal value of 0x1234 would be represented as 0x00001234 in the
31909 zero-hexadecimal format.
31911 For a variable with children, the format is set only on the
31912 variable itself, and the children are not affected.
31914 @subheading The @code{-var-show-format} Command
31915 @findex -var-show-format
31917 @subsubheading Synopsis
31920 -var-show-format @var{name}
31923 Returns the format used to display the value of the object @var{name}.
31926 @var{format} @expansion{}
31931 @subheading The @code{-var-info-num-children} Command
31932 @findex -var-info-num-children
31934 @subsubheading Synopsis
31937 -var-info-num-children @var{name}
31940 Returns the number of children of a variable object @var{name}:
31946 Note that this number is not completely reliable for a dynamic varobj.
31947 It will return the current number of children, but more children may
31951 @subheading The @code{-var-list-children} Command
31952 @findex -var-list-children
31954 @subsubheading Synopsis
31957 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
31959 @anchor{-var-list-children}
31961 Return a list of the children of the specified variable object and
31962 create variable objects for them, if they do not already exist. With
31963 a single argument or if @var{print-values} has a value of 0 or
31964 @code{--no-values}, print only the names of the variables; if
31965 @var{print-values} is 1 or @code{--all-values}, also print their
31966 values; and if it is 2 or @code{--simple-values} print the name and
31967 value for simple data types and just the name for arrays, structures
31970 @var{from} and @var{to}, if specified, indicate the range of children
31971 to report. If @var{from} or @var{to} is less than zero, the range is
31972 reset and all children will be reported. Otherwise, children starting
31973 at @var{from} (zero-based) and up to and excluding @var{to} will be
31976 If a child range is requested, it will only affect the current call to
31977 @code{-var-list-children}, but not future calls to @code{-var-update}.
31978 For this, you must instead use @code{-var-set-update-range}. The
31979 intent of this approach is to enable a front end to implement any
31980 update approach it likes; for example, scrolling a view may cause the
31981 front end to request more children with @code{-var-list-children}, and
31982 then the front end could call @code{-var-set-update-range} with a
31983 different range to ensure that future updates are restricted to just
31986 For each child the following results are returned:
31991 Name of the variable object created for this child.
31994 The expression to be shown to the user by the front end to designate this child.
31995 For example this may be the name of a structure member.
31997 For a dynamic varobj, this value cannot be used to form an
31998 expression. There is no way to do this at all with a dynamic varobj.
32000 For C/C@t{++} structures there are several pseudo children returned to
32001 designate access qualifiers. For these pseudo children @var{exp} is
32002 @samp{public}, @samp{private}, or @samp{protected}. In this case the
32003 type and value are not present.
32005 A dynamic varobj will not report the access qualifying
32006 pseudo-children, regardless of the language. This information is not
32007 available at all with a dynamic varobj.
32010 Number of children this child has. For a dynamic varobj, this will be
32014 The type of the child. If @samp{print object}
32015 (@pxref{Print Settings, set print object}) is set to @code{on}, the
32016 @emph{actual} (derived) type of the object is shown rather than the
32017 @emph{declared} one.
32020 If values were requested, this is the value.
32023 If this variable object is associated with a thread, this is the
32024 thread's global thread id. Otherwise this result is not present.
32027 If the variable object is frozen, this variable will be present with a value of 1.
32030 A dynamic varobj can supply a display hint to the front end. The
32031 value comes directly from the Python pretty-printer object's
32032 @code{display_hint} method. @xref{Pretty Printing API}.
32035 This attribute will be present and have the value @samp{1} if the
32036 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
32037 then this attribute will not be present.
32041 The result may have its own attributes:
32045 A dynamic varobj can supply a display hint to the front end. The
32046 value comes directly from the Python pretty-printer object's
32047 @code{display_hint} method. @xref{Pretty Printing API}.
32050 This is an integer attribute which is nonzero if there are children
32051 remaining after the end of the selected range.
32054 @subsubheading Example
32058 -var-list-children n
32059 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
32060 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
32062 -var-list-children --all-values n
32063 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
32064 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
32068 @subheading The @code{-var-info-type} Command
32069 @findex -var-info-type
32071 @subsubheading Synopsis
32074 -var-info-type @var{name}
32077 Returns the type of the specified variable @var{name}. The type is
32078 returned as a string in the same format as it is output by the
32082 type=@var{typename}
32086 @subheading The @code{-var-info-expression} Command
32087 @findex -var-info-expression
32089 @subsubheading Synopsis
32092 -var-info-expression @var{name}
32095 Returns a string that is suitable for presenting this
32096 variable object in user interface. The string is generally
32097 not valid expression in the current language, and cannot be evaluated.
32099 For example, if @code{a} is an array, and variable object
32100 @code{A} was created for @code{a}, then we'll get this output:
32103 (gdb) -var-info-expression A.1
32104 ^done,lang="C",exp="1"
32108 Here, the value of @code{lang} is the language name, which can be
32109 found in @ref{Supported Languages}.
32111 Note that the output of the @code{-var-list-children} command also
32112 includes those expressions, so the @code{-var-info-expression} command
32115 @subheading The @code{-var-info-path-expression} Command
32116 @findex -var-info-path-expression
32118 @subsubheading Synopsis
32121 -var-info-path-expression @var{name}
32124 Returns an expression that can be evaluated in the current
32125 context and will yield the same value that a variable object has.
32126 Compare this with the @code{-var-info-expression} command, which
32127 result can be used only for UI presentation. Typical use of
32128 the @code{-var-info-path-expression} command is creating a
32129 watchpoint from a variable object.
32131 This command is currently not valid for children of a dynamic varobj,
32132 and will give an error when invoked on one.
32134 For example, suppose @code{C} is a C@t{++} class, derived from class
32135 @code{Base}, and that the @code{Base} class has a member called
32136 @code{m_size}. Assume a variable @code{c} is has the type of
32137 @code{C} and a variable object @code{C} was created for variable
32138 @code{c}. Then, we'll get this output:
32140 (gdb) -var-info-path-expression C.Base.public.m_size
32141 ^done,path_expr=((Base)c).m_size)
32144 @subheading The @code{-var-show-attributes} Command
32145 @findex -var-show-attributes
32147 @subsubheading Synopsis
32150 -var-show-attributes @var{name}
32153 List attributes of the specified variable object @var{name}:
32156 status=@var{attr} [ ( ,@var{attr} )* ]
32160 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
32162 @subheading The @code{-var-evaluate-expression} Command
32163 @findex -var-evaluate-expression
32165 @subsubheading Synopsis
32168 -var-evaluate-expression [-f @var{format-spec}] @var{name}
32171 Evaluates the expression that is represented by the specified variable
32172 object and returns its value as a string. The format of the string
32173 can be specified with the @samp{-f} option. The possible values of
32174 this option are the same as for @code{-var-set-format}
32175 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
32176 the current display format will be used. The current display format
32177 can be changed using the @code{-var-set-format} command.
32183 Note that one must invoke @code{-var-list-children} for a variable
32184 before the value of a child variable can be evaluated.
32186 @subheading The @code{-var-assign} Command
32187 @findex -var-assign
32189 @subsubheading Synopsis
32192 -var-assign @var{name} @var{expression}
32195 Assigns the value of @var{expression} to the variable object specified
32196 by @var{name}. The object must be @samp{editable}. If the variable's
32197 value is altered by the assign, the variable will show up in any
32198 subsequent @code{-var-update} list.
32200 @subsubheading Example
32208 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
32212 @subheading The @code{-var-update} Command
32213 @findex -var-update
32215 @subsubheading Synopsis
32218 -var-update [@var{print-values}] @{@var{name} | "*"@}
32221 Reevaluate the expressions corresponding to the variable object
32222 @var{name} and all its direct and indirect children, and return the
32223 list of variable objects whose values have changed; @var{name} must
32224 be a root variable object. Here, ``changed'' means that the result of
32225 @code{-var-evaluate-expression} before and after the
32226 @code{-var-update} is different. If @samp{*} is used as the variable
32227 object names, all existing variable objects are updated, except
32228 for frozen ones (@pxref{-var-set-frozen}). The option
32229 @var{print-values} determines whether both names and values, or just
32230 names are printed. The possible values of this option are the same
32231 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
32232 recommended to use the @samp{--all-values} option, to reduce the
32233 number of MI commands needed on each program stop.
32235 With the @samp{*} parameter, if a variable object is bound to a
32236 currently running thread, it will not be updated, without any
32239 If @code{-var-set-update-range} was previously used on a varobj, then
32240 only the selected range of children will be reported.
32242 @code{-var-update} reports all the changed varobjs in a tuple named
32245 Each item in the change list is itself a tuple holding:
32249 The name of the varobj.
32252 If values were requested for this update, then this field will be
32253 present and will hold the value of the varobj.
32256 @anchor{-var-update}
32257 This field is a string which may take one of three values:
32261 The variable object's current value is valid.
32264 The variable object does not currently hold a valid value but it may
32265 hold one in the future if its associated expression comes back into
32269 The variable object no longer holds a valid value.
32270 This can occur when the executable file being debugged has changed,
32271 either through recompilation or by using the @value{GDBN} @code{file}
32272 command. The front end should normally choose to delete these variable
32276 In the future new values may be added to this list so the front should
32277 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
32280 This is only present if the varobj is still valid. If the type
32281 changed, then this will be the string @samp{true}; otherwise it will
32284 When a varobj's type changes, its children are also likely to have
32285 become incorrect. Therefore, the varobj's children are automatically
32286 deleted when this attribute is @samp{true}. Also, the varobj's update
32287 range, when set using the @code{-var-set-update-range} command, is
32291 If the varobj's type changed, then this field will be present and will
32294 @item new_num_children
32295 For a dynamic varobj, if the number of children changed, or if the
32296 type changed, this will be the new number of children.
32298 The @samp{numchild} field in other varobj responses is generally not
32299 valid for a dynamic varobj -- it will show the number of children that
32300 @value{GDBN} knows about, but because dynamic varobjs lazily
32301 instantiate their children, this will not reflect the number of
32302 children which may be available.
32304 The @samp{new_num_children} attribute only reports changes to the
32305 number of children known by @value{GDBN}. This is the only way to
32306 detect whether an update has removed children (which necessarily can
32307 only happen at the end of the update range).
32310 The display hint, if any.
32313 This is an integer value, which will be 1 if there are more children
32314 available outside the varobj's update range.
32317 This attribute will be present and have the value @samp{1} if the
32318 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
32319 then this attribute will not be present.
32322 If new children were added to a dynamic varobj within the selected
32323 update range (as set by @code{-var-set-update-range}), then they will
32324 be listed in this attribute.
32327 @subsubheading Example
32334 -var-update --all-values var1
32335 ^done,changelist=[@{name="var1",value="3",in_scope="true",
32336 type_changed="false"@}]
32340 @subheading The @code{-var-set-frozen} Command
32341 @findex -var-set-frozen
32342 @anchor{-var-set-frozen}
32344 @subsubheading Synopsis
32347 -var-set-frozen @var{name} @var{flag}
32350 Set the frozenness flag on the variable object @var{name}. The
32351 @var{flag} parameter should be either @samp{1} to make the variable
32352 frozen or @samp{0} to make it unfrozen. If a variable object is
32353 frozen, then neither itself, nor any of its children, are
32354 implicitly updated by @code{-var-update} of
32355 a parent variable or by @code{-var-update *}. Only
32356 @code{-var-update} of the variable itself will update its value and
32357 values of its children. After a variable object is unfrozen, it is
32358 implicitly updated by all subsequent @code{-var-update} operations.
32359 Unfreezing a variable does not update it, only subsequent
32360 @code{-var-update} does.
32362 @subsubheading Example
32366 -var-set-frozen V 1
32371 @subheading The @code{-var-set-update-range} command
32372 @findex -var-set-update-range
32373 @anchor{-var-set-update-range}
32375 @subsubheading Synopsis
32378 -var-set-update-range @var{name} @var{from} @var{to}
32381 Set the range of children to be returned by future invocations of
32382 @code{-var-update}.
32384 @var{from} and @var{to} indicate the range of children to report. If
32385 @var{from} or @var{to} is less than zero, the range is reset and all
32386 children will be reported. Otherwise, children starting at @var{from}
32387 (zero-based) and up to and excluding @var{to} will be reported.
32389 @subsubheading Example
32393 -var-set-update-range V 1 2
32397 @subheading The @code{-var-set-visualizer} command
32398 @findex -var-set-visualizer
32399 @anchor{-var-set-visualizer}
32401 @subsubheading Synopsis
32404 -var-set-visualizer @var{name} @var{visualizer}
32407 Set a visualizer for the variable object @var{name}.
32409 @var{visualizer} is the visualizer to use. The special value
32410 @samp{None} means to disable any visualizer in use.
32412 If not @samp{None}, @var{visualizer} must be a Python expression.
32413 This expression must evaluate to a callable object which accepts a
32414 single argument. @value{GDBN} will call this object with the value of
32415 the varobj @var{name} as an argument (this is done so that the same
32416 Python pretty-printing code can be used for both the CLI and MI).
32417 When called, this object must return an object which conforms to the
32418 pretty-printing interface (@pxref{Pretty Printing API}).
32420 The pre-defined function @code{gdb.default_visualizer} may be used to
32421 select a visualizer by following the built-in process
32422 (@pxref{Selecting Pretty-Printers}). This is done automatically when
32423 a varobj is created, and so ordinarily is not needed.
32425 This feature is only available if Python support is enabled. The MI
32426 command @code{-list-features} (@pxref{GDB/MI Support Commands})
32427 can be used to check this.
32429 @subsubheading Example
32431 Resetting the visualizer:
32435 -var-set-visualizer V None
32439 Reselecting the default (type-based) visualizer:
32443 -var-set-visualizer V gdb.default_visualizer
32447 Suppose @code{SomeClass} is a visualizer class. A lambda expression
32448 can be used to instantiate this class for a varobj:
32452 -var-set-visualizer V "lambda val: SomeClass()"
32456 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32457 @node GDB/MI Data Manipulation
32458 @section @sc{gdb/mi} Data Manipulation
32460 @cindex data manipulation, in @sc{gdb/mi}
32461 @cindex @sc{gdb/mi}, data manipulation
32462 This section describes the @sc{gdb/mi} commands that manipulate data:
32463 examine memory and registers, evaluate expressions, etc.
32465 For details about what an addressable memory unit is,
32466 @pxref{addressable memory unit}.
32468 @c REMOVED FROM THE INTERFACE.
32469 @c @subheading -data-assign
32470 @c Change the value of a program variable. Plenty of side effects.
32471 @c @subsubheading GDB Command
32473 @c @subsubheading Example
32476 @subheading The @code{-data-disassemble} Command
32477 @findex -data-disassemble
32479 @subsubheading Synopsis
32483 [ -s @var{start-addr} -e @var{end-addr} ]
32484 | [ -a @var{addr} ]
32485 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
32493 @item @var{start-addr}
32494 is the beginning address (or @code{$pc})
32495 @item @var{end-addr}
32498 is an address anywhere within (or the name of) the function to
32499 disassemble. If an address is specified, the whole function
32500 surrounding that address will be disassembled. If a name is
32501 specified, the whole function with that name will be disassembled.
32502 @item @var{filename}
32503 is the name of the file to disassemble
32504 @item @var{linenum}
32505 is the line number to disassemble around
32507 is the number of disassembly lines to be produced. If it is -1,
32508 the whole function will be disassembled, in case no @var{end-addr} is
32509 specified. If @var{end-addr} is specified as a non-zero value, and
32510 @var{lines} is lower than the number of disassembly lines between
32511 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
32512 displayed; if @var{lines} is higher than the number of lines between
32513 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
32518 @item 0 disassembly only
32519 @item 1 mixed source and disassembly (deprecated)
32520 @item 2 disassembly with raw opcodes
32521 @item 3 mixed source and disassembly with raw opcodes (deprecated)
32522 @item 4 mixed source and disassembly
32523 @item 5 mixed source and disassembly with raw opcodes
32526 Modes 1 and 3 are deprecated. The output is ``source centric''
32527 which hasn't proved useful in practice.
32528 @xref{Machine Code}, for a discussion of the difference between
32529 @code{/m} and @code{/s} output of the @code{disassemble} command.
32532 @subsubheading Result
32534 The result of the @code{-data-disassemble} command will be a list named
32535 @samp{asm_insns}, the contents of this list depend on the @var{mode}
32536 used with the @code{-data-disassemble} command.
32538 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
32543 The address at which this instruction was disassembled.
32546 The name of the function this instruction is within.
32549 The decimal offset in bytes from the start of @samp{func-name}.
32552 The text disassembly for this @samp{address}.
32555 This field is only present for modes 2, 3 and 5. This contains the raw opcode
32556 bytes for the @samp{inst} field.
32560 For modes 1, 3, 4 and 5 the @samp{asm_insns} list contains tuples named
32561 @samp{src_and_asm_line}, each of which has the following fields:
32565 The line number within @samp{file}.
32568 The file name from the compilation unit. This might be an absolute
32569 file name or a relative file name depending on the compile command
32573 Absolute file name of @samp{file}. It is converted to a canonical form
32574 using the source file search path
32575 (@pxref{Source Path, ,Specifying Source Directories})
32576 and after resolving all the symbolic links.
32578 If the source file is not found this field will contain the path as
32579 present in the debug information.
32581 @item line_asm_insn
32582 This is a list of tuples containing the disassembly for @samp{line} in
32583 @samp{file}. The fields of each tuple are the same as for
32584 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
32585 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
32590 Note that whatever included in the @samp{inst} field, is not
32591 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
32594 @subsubheading @value{GDBN} Command
32596 The corresponding @value{GDBN} command is @samp{disassemble}.
32598 @subsubheading Example
32600 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
32604 -data-disassemble -s $pc -e "$pc + 20" -- 0
32607 @{address="0x000107c0",func-name="main",offset="4",
32608 inst="mov 2, %o0"@},
32609 @{address="0x000107c4",func-name="main",offset="8",
32610 inst="sethi %hi(0x11800), %o2"@},
32611 @{address="0x000107c8",func-name="main",offset="12",
32612 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
32613 @{address="0x000107cc",func-name="main",offset="16",
32614 inst="sethi %hi(0x11800), %o2"@},
32615 @{address="0x000107d0",func-name="main",offset="20",
32616 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
32620 Disassemble the whole @code{main} function. Line 32 is part of
32624 -data-disassemble -f basics.c -l 32 -- 0
32626 @{address="0x000107bc",func-name="main",offset="0",
32627 inst="save %sp, -112, %sp"@},
32628 @{address="0x000107c0",func-name="main",offset="4",
32629 inst="mov 2, %o0"@},
32630 @{address="0x000107c4",func-name="main",offset="8",
32631 inst="sethi %hi(0x11800), %o2"@},
32633 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
32634 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
32638 Disassemble 3 instructions from the start of @code{main}:
32642 -data-disassemble -f basics.c -l 32 -n 3 -- 0
32644 @{address="0x000107bc",func-name="main",offset="0",
32645 inst="save %sp, -112, %sp"@},
32646 @{address="0x000107c0",func-name="main",offset="4",
32647 inst="mov 2, %o0"@},
32648 @{address="0x000107c4",func-name="main",offset="8",
32649 inst="sethi %hi(0x11800), %o2"@}]
32653 Disassemble 3 instructions from the start of @code{main} in mixed mode:
32657 -data-disassemble -f basics.c -l 32 -n 3 -- 1
32659 src_and_asm_line=@{line="31",
32660 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
32661 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
32662 line_asm_insn=[@{address="0x000107bc",
32663 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
32664 src_and_asm_line=@{line="32",
32665 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
32666 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
32667 line_asm_insn=[@{address="0x000107c0",
32668 func-name="main",offset="4",inst="mov 2, %o0"@},
32669 @{address="0x000107c4",func-name="main",offset="8",
32670 inst="sethi %hi(0x11800), %o2"@}]@}]
32675 @subheading The @code{-data-evaluate-expression} Command
32676 @findex -data-evaluate-expression
32678 @subsubheading Synopsis
32681 -data-evaluate-expression @var{expr}
32684 Evaluate @var{expr} as an expression. The expression could contain an
32685 inferior function call. The function call will execute synchronously.
32686 If the expression contains spaces, it must be enclosed in double quotes.
32688 @subsubheading @value{GDBN} Command
32690 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
32691 @samp{call}. In @code{gdbtk} only, there's a corresponding
32692 @samp{gdb_eval} command.
32694 @subsubheading Example
32696 In the following example, the numbers that precede the commands are the
32697 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
32698 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
32702 211-data-evaluate-expression A
32705 311-data-evaluate-expression &A
32706 311^done,value="0xefffeb7c"
32708 411-data-evaluate-expression A+3
32711 511-data-evaluate-expression "A + 3"
32717 @subheading The @code{-data-list-changed-registers} Command
32718 @findex -data-list-changed-registers
32720 @subsubheading Synopsis
32723 -data-list-changed-registers
32726 Display a list of the registers that have changed.
32728 @subsubheading @value{GDBN} Command
32730 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
32731 has the corresponding command @samp{gdb_changed_register_list}.
32733 @subsubheading Example
32735 On a PPC MBX board:
32743 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
32744 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
32745 line="5",arch="powerpc"@}
32747 -data-list-changed-registers
32748 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
32749 "10","11","13","14","15","16","17","18","19","20","21","22","23",
32750 "24","25","26","27","28","30","31","64","65","66","67","69"]
32755 @subheading The @code{-data-list-register-names} Command
32756 @findex -data-list-register-names
32758 @subsubheading Synopsis
32761 -data-list-register-names [ ( @var{regno} )+ ]
32764 Show a list of register names for the current target. If no arguments
32765 are given, it shows a list of the names of all the registers. If
32766 integer numbers are given as arguments, it will print a list of the
32767 names of the registers corresponding to the arguments. To ensure
32768 consistency between a register name and its number, the output list may
32769 include empty register names.
32771 @subsubheading @value{GDBN} Command
32773 @value{GDBN} does not have a command which corresponds to
32774 @samp{-data-list-register-names}. In @code{gdbtk} there is a
32775 corresponding command @samp{gdb_regnames}.
32777 @subsubheading Example
32779 For the PPC MBX board:
32782 -data-list-register-names
32783 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
32784 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
32785 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
32786 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
32787 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
32788 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
32789 "", "pc","ps","cr","lr","ctr","xer"]
32791 -data-list-register-names 1 2 3
32792 ^done,register-names=["r1","r2","r3"]
32796 @subheading The @code{-data-list-register-values} Command
32797 @findex -data-list-register-values
32799 @subsubheading Synopsis
32802 -data-list-register-values
32803 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
32806 Display the registers' contents. The format according to which the
32807 registers' contents are to be returned is given by @var{fmt}, followed
32808 by an optional list of numbers specifying the registers to display. A
32809 missing list of numbers indicates that the contents of all the
32810 registers must be returned. The @code{--skip-unavailable} option
32811 indicates that only the available registers are to be returned.
32813 Allowed formats for @var{fmt} are:
32830 @subsubheading @value{GDBN} Command
32832 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
32833 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
32835 @subsubheading Example
32837 For a PPC MBX board (note: line breaks are for readability only, they
32838 don't appear in the actual output):
32842 -data-list-register-values r 64 65
32843 ^done,register-values=[@{number="64",value="0xfe00a300"@},
32844 @{number="65",value="0x00029002"@}]
32846 -data-list-register-values x
32847 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
32848 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
32849 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
32850 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
32851 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
32852 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
32853 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
32854 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
32855 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
32856 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
32857 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
32858 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
32859 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
32860 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
32861 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
32862 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
32863 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
32864 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
32865 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
32866 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
32867 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
32868 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
32869 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
32870 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
32871 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
32872 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
32873 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
32874 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
32875 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
32876 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
32877 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
32878 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
32879 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
32880 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
32881 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
32882 @{number="69",value="0x20002b03"@}]
32887 @subheading The @code{-data-read-memory} Command
32888 @findex -data-read-memory
32890 This command is deprecated, use @code{-data-read-memory-bytes} instead.
32892 @subsubheading Synopsis
32895 -data-read-memory [ -o @var{byte-offset} ]
32896 @var{address} @var{word-format} @var{word-size}
32897 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
32904 @item @var{address}
32905 An expression specifying the address of the first memory word to be
32906 read. Complex expressions containing embedded white space should be
32907 quoted using the C convention.
32909 @item @var{word-format}
32910 The format to be used to print the memory words. The notation is the
32911 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
32914 @item @var{word-size}
32915 The size of each memory word in bytes.
32917 @item @var{nr-rows}
32918 The number of rows in the output table.
32920 @item @var{nr-cols}
32921 The number of columns in the output table.
32924 If present, indicates that each row should include an @sc{ascii} dump. The
32925 value of @var{aschar} is used as a padding character when a byte is not a
32926 member of the printable @sc{ascii} character set (printable @sc{ascii}
32927 characters are those whose code is between 32 and 126, inclusively).
32929 @item @var{byte-offset}
32930 An offset to add to the @var{address} before fetching memory.
32933 This command displays memory contents as a table of @var{nr-rows} by
32934 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
32935 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
32936 (returned as @samp{total-bytes}). Should less than the requested number
32937 of bytes be returned by the target, the missing words are identified
32938 using @samp{N/A}. The number of bytes read from the target is returned
32939 in @samp{nr-bytes} and the starting address used to read memory in
32942 The address of the next/previous row or page is available in
32943 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
32946 @subsubheading @value{GDBN} Command
32948 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
32949 @samp{gdb_get_mem} memory read command.
32951 @subsubheading Example
32953 Read six bytes of memory starting at @code{bytes+6} but then offset by
32954 @code{-6} bytes. Format as three rows of two columns. One byte per
32955 word. Display each word in hex.
32959 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
32960 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
32961 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
32962 prev-page="0x0000138a",memory=[
32963 @{addr="0x00001390",data=["0x00","0x01"]@},
32964 @{addr="0x00001392",data=["0x02","0x03"]@},
32965 @{addr="0x00001394",data=["0x04","0x05"]@}]
32969 Read two bytes of memory starting at address @code{shorts + 64} and
32970 display as a single word formatted in decimal.
32974 5-data-read-memory shorts+64 d 2 1 1
32975 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
32976 next-row="0x00001512",prev-row="0x0000150e",
32977 next-page="0x00001512",prev-page="0x0000150e",memory=[
32978 @{addr="0x00001510",data=["128"]@}]
32982 Read thirty two bytes of memory starting at @code{bytes+16} and format
32983 as eight rows of four columns. Include a string encoding with @samp{x}
32984 used as the non-printable character.
32988 4-data-read-memory bytes+16 x 1 8 4 x
32989 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
32990 next-row="0x000013c0",prev-row="0x0000139c",
32991 next-page="0x000013c0",prev-page="0x00001380",memory=[
32992 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
32993 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
32994 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
32995 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
32996 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
32997 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
32998 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
32999 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
33003 @subheading The @code{-data-read-memory-bytes} Command
33004 @findex -data-read-memory-bytes
33006 @subsubheading Synopsis
33009 -data-read-memory-bytes [ -o @var{offset} ]
33010 @var{address} @var{count}
33017 @item @var{address}
33018 An expression specifying the address of the first addressable memory unit
33019 to be read. Complex expressions containing embedded white space should be
33020 quoted using the C convention.
33023 The number of addressable memory units to read. This should be an integer
33027 The offset relative to @var{address} at which to start reading. This
33028 should be an integer literal. This option is provided so that a frontend
33029 is not required to first evaluate address and then perform address
33030 arithmetics itself.
33034 This command attempts to read all accessible memory regions in the
33035 specified range. First, all regions marked as unreadable in the memory
33036 map (if one is defined) will be skipped. @xref{Memory Region
33037 Attributes}. Second, @value{GDBN} will attempt to read the remaining
33038 regions. For each one, if reading full region results in an errors,
33039 @value{GDBN} will try to read a subset of the region.
33041 In general, every single memory unit in the region may be readable or not,
33042 and the only way to read every readable unit is to try a read at
33043 every address, which is not practical. Therefore, @value{GDBN} will
33044 attempt to read all accessible memory units at either beginning or the end
33045 of the region, using a binary division scheme. This heuristic works
33046 well for reading accross a memory map boundary. Note that if a region
33047 has a readable range that is neither at the beginning or the end,
33048 @value{GDBN} will not read it.
33050 The result record (@pxref{GDB/MI Result Records}) that is output of
33051 the command includes a field named @samp{memory} whose content is a
33052 list of tuples. Each tuple represent a successfully read memory block
33053 and has the following fields:
33057 The start address of the memory block, as hexadecimal literal.
33060 The end address of the memory block, as hexadecimal literal.
33063 The offset of the memory block, as hexadecimal literal, relative to
33064 the start address passed to @code{-data-read-memory-bytes}.
33067 The contents of the memory block, in hex.
33073 @subsubheading @value{GDBN} Command
33075 The corresponding @value{GDBN} command is @samp{x}.
33077 @subsubheading Example
33081 -data-read-memory-bytes &a 10
33082 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
33084 contents="01000000020000000300"@}]
33089 @subheading The @code{-data-write-memory-bytes} Command
33090 @findex -data-write-memory-bytes
33092 @subsubheading Synopsis
33095 -data-write-memory-bytes @var{address} @var{contents}
33096 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
33103 @item @var{address}
33104 An expression specifying the address of the first addressable memory unit
33105 to be written. Complex expressions containing embedded white space should
33106 be quoted using the C convention.
33108 @item @var{contents}
33109 The hex-encoded data to write. It is an error if @var{contents} does
33110 not represent an integral number of addressable memory units.
33113 Optional argument indicating the number of addressable memory units to be
33114 written. If @var{count} is greater than @var{contents}' length,
33115 @value{GDBN} will repeatedly write @var{contents} until it fills
33116 @var{count} memory units.
33120 @subsubheading @value{GDBN} Command
33122 There's no corresponding @value{GDBN} command.
33124 @subsubheading Example
33128 -data-write-memory-bytes &a "aabbccdd"
33135 -data-write-memory-bytes &a "aabbccdd" 16e
33140 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33141 @node GDB/MI Tracepoint Commands
33142 @section @sc{gdb/mi} Tracepoint Commands
33144 The commands defined in this section implement MI support for
33145 tracepoints. For detailed introduction, see @ref{Tracepoints}.
33147 @subheading The @code{-trace-find} Command
33148 @findex -trace-find
33150 @subsubheading Synopsis
33153 -trace-find @var{mode} [@var{parameters}@dots{}]
33156 Find a trace frame using criteria defined by @var{mode} and
33157 @var{parameters}. The following table lists permissible
33158 modes and their parameters. For details of operation, see @ref{tfind}.
33163 No parameters are required. Stops examining trace frames.
33166 An integer is required as parameter. Selects tracepoint frame with
33169 @item tracepoint-number
33170 An integer is required as parameter. Finds next
33171 trace frame that corresponds to tracepoint with the specified number.
33174 An address is required as parameter. Finds
33175 next trace frame that corresponds to any tracepoint at the specified
33178 @item pc-inside-range
33179 Two addresses are required as parameters. Finds next trace
33180 frame that corresponds to a tracepoint at an address inside the
33181 specified range. Both bounds are considered to be inside the range.
33183 @item pc-outside-range
33184 Two addresses are required as parameters. Finds
33185 next trace frame that corresponds to a tracepoint at an address outside
33186 the specified range. Both bounds are considered to be inside the range.
33189 Line specification is required as parameter. @xref{Specify Location}.
33190 Finds next trace frame that corresponds to a tracepoint at
33191 the specified location.
33195 If @samp{none} was passed as @var{mode}, the response does not
33196 have fields. Otherwise, the response may have the following fields:
33200 This field has either @samp{0} or @samp{1} as the value, depending
33201 on whether a matching tracepoint was found.
33204 The index of the found traceframe. This field is present iff
33205 the @samp{found} field has value of @samp{1}.
33208 The index of the found tracepoint. This field is present iff
33209 the @samp{found} field has value of @samp{1}.
33212 The information about the frame corresponding to the found trace
33213 frame. This field is present only if a trace frame was found.
33214 @xref{GDB/MI Frame Information}, for description of this field.
33218 @subsubheading @value{GDBN} Command
33220 The corresponding @value{GDBN} command is @samp{tfind}.
33222 @subheading -trace-define-variable
33223 @findex -trace-define-variable
33225 @subsubheading Synopsis
33228 -trace-define-variable @var{name} [ @var{value} ]
33231 Create trace variable @var{name} if it does not exist. If
33232 @var{value} is specified, sets the initial value of the specified
33233 trace variable to that value. Note that the @var{name} should start
33234 with the @samp{$} character.
33236 @subsubheading @value{GDBN} Command
33238 The corresponding @value{GDBN} command is @samp{tvariable}.
33240 @subheading The @code{-trace-frame-collected} Command
33241 @findex -trace-frame-collected
33243 @subsubheading Synopsis
33246 -trace-frame-collected
33247 [--var-print-values @var{var_pval}]
33248 [--comp-print-values @var{comp_pval}]
33249 [--registers-format @var{regformat}]
33250 [--memory-contents]
33253 This command returns the set of collected objects, register names,
33254 trace state variable names, memory ranges and computed expressions
33255 that have been collected at a particular trace frame. The optional
33256 parameters to the command affect the output format in different ways.
33257 See the output description table below for more details.
33259 The reported names can be used in the normal manner to create
33260 varobjs and inspect the objects themselves. The items returned by
33261 this command are categorized so that it is clear which is a variable,
33262 which is a register, which is a trace state variable, which is a
33263 memory range and which is a computed expression.
33265 For instance, if the actions were
33267 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
33268 collect *(int*)0xaf02bef0@@40
33272 the object collected in its entirety would be @code{myVar}. The
33273 object @code{myArray} would be partially collected, because only the
33274 element at index @code{myIndex} would be collected. The remaining
33275 objects would be computed expressions.
33277 An example output would be:
33281 -trace-frame-collected
33283 explicit-variables=[@{name="myVar",value="1"@}],
33284 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
33285 @{name="myObj.field",value="0"@},
33286 @{name="myPtr->field",value="1"@},
33287 @{name="myCount + 2",value="3"@},
33288 @{name="$tvar1 + 1",value="43970027"@}],
33289 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
33290 @{number="1",value="0x0"@},
33291 @{number="2",value="0x4"@},
33293 @{number="125",value="0x0"@}],
33294 tvars=[@{name="$tvar1",current="43970026"@}],
33295 memory=[@{address="0x0000000000602264",length="4"@},
33296 @{address="0x0000000000615bc0",length="4"@}]
33303 @item explicit-variables
33304 The set of objects that have been collected in their entirety (as
33305 opposed to collecting just a few elements of an array or a few struct
33306 members). For each object, its name and value are printed.
33307 The @code{--var-print-values} option affects how or whether the value
33308 field is output. If @var{var_pval} is 0, then print only the names;
33309 if it is 1, print also their values; and if it is 2, print the name,
33310 type and value for simple data types, and the name and type for
33311 arrays, structures and unions.
33313 @item computed-expressions
33314 The set of computed expressions that have been collected at the
33315 current trace frame. The @code{--comp-print-values} option affects
33316 this set like the @code{--var-print-values} option affects the
33317 @code{explicit-variables} set. See above.
33320 The registers that have been collected at the current trace frame.
33321 For each register collected, the name and current value are returned.
33322 The value is formatted according to the @code{--registers-format}
33323 option. See the @command{-data-list-register-values} command for a
33324 list of the allowed formats. The default is @samp{x}.
33327 The trace state variables that have been collected at the current
33328 trace frame. For each trace state variable collected, the name and
33329 current value are returned.
33332 The set of memory ranges that have been collected at the current trace
33333 frame. Its content is a list of tuples. Each tuple represents a
33334 collected memory range and has the following fields:
33338 The start address of the memory range, as hexadecimal literal.
33341 The length of the memory range, as decimal literal.
33344 The contents of the memory block, in hex. This field is only present
33345 if the @code{--memory-contents} option is specified.
33351 @subsubheading @value{GDBN} Command
33353 There is no corresponding @value{GDBN} command.
33355 @subsubheading Example
33357 @subheading -trace-list-variables
33358 @findex -trace-list-variables
33360 @subsubheading Synopsis
33363 -trace-list-variables
33366 Return a table of all defined trace variables. Each element of the
33367 table has the following fields:
33371 The name of the trace variable. This field is always present.
33374 The initial value. This is a 64-bit signed integer. This
33375 field is always present.
33378 The value the trace variable has at the moment. This is a 64-bit
33379 signed integer. This field is absent iff current value is
33380 not defined, for example if the trace was never run, or is
33385 @subsubheading @value{GDBN} Command
33387 The corresponding @value{GDBN} command is @samp{tvariables}.
33389 @subsubheading Example
33393 -trace-list-variables
33394 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
33395 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
33396 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
33397 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
33398 body=[variable=@{name="$trace_timestamp",initial="0"@}
33399 variable=@{name="$foo",initial="10",current="15"@}]@}
33403 @subheading -trace-save
33404 @findex -trace-save
33406 @subsubheading Synopsis
33409 -trace-save [ -r ] [ -ctf ] @var{filename}
33412 Saves the collected trace data to @var{filename}. Without the
33413 @samp{-r} option, the data is downloaded from the target and saved
33414 in a local file. With the @samp{-r} option the target is asked
33415 to perform the save.
33417 By default, this command will save the trace in the tfile format. You can
33418 supply the optional @samp{-ctf} argument to save it the CTF format. See
33419 @ref{Trace Files} for more information about CTF.
33421 @subsubheading @value{GDBN} Command
33423 The corresponding @value{GDBN} command is @samp{tsave}.
33426 @subheading -trace-start
33427 @findex -trace-start
33429 @subsubheading Synopsis
33435 Starts a tracing experiment. The result of this command does not
33438 @subsubheading @value{GDBN} Command
33440 The corresponding @value{GDBN} command is @samp{tstart}.
33442 @subheading -trace-status
33443 @findex -trace-status
33445 @subsubheading Synopsis
33451 Obtains the status of a tracing experiment. The result may include
33452 the following fields:
33457 May have a value of either @samp{0}, when no tracing operations are
33458 supported, @samp{1}, when all tracing operations are supported, or
33459 @samp{file} when examining trace file. In the latter case, examining
33460 of trace frame is possible but new tracing experiement cannot be
33461 started. This field is always present.
33464 May have a value of either @samp{0} or @samp{1} depending on whether
33465 tracing experiement is in progress on target. This field is present
33466 if @samp{supported} field is not @samp{0}.
33469 Report the reason why the tracing was stopped last time. This field
33470 may be absent iff tracing was never stopped on target yet. The
33471 value of @samp{request} means the tracing was stopped as result of
33472 the @code{-trace-stop} command. The value of @samp{overflow} means
33473 the tracing buffer is full. The value of @samp{disconnection} means
33474 tracing was automatically stopped when @value{GDBN} has disconnected.
33475 The value of @samp{passcount} means tracing was stopped when a
33476 tracepoint was passed a maximal number of times for that tracepoint.
33477 This field is present if @samp{supported} field is not @samp{0}.
33479 @item stopping-tracepoint
33480 The number of tracepoint whose passcount as exceeded. This field is
33481 present iff the @samp{stop-reason} field has the value of
33485 @itemx frames-created
33486 The @samp{frames} field is a count of the total number of trace frames
33487 in the trace buffer, while @samp{frames-created} is the total created
33488 during the run, including ones that were discarded, such as when a
33489 circular trace buffer filled up. Both fields are optional.
33493 These fields tell the current size of the tracing buffer and the
33494 remaining space. These fields are optional.
33497 The value of the circular trace buffer flag. @code{1} means that the
33498 trace buffer is circular and old trace frames will be discarded if
33499 necessary to make room, @code{0} means that the trace buffer is linear
33503 The value of the disconnected tracing flag. @code{1} means that
33504 tracing will continue after @value{GDBN} disconnects, @code{0} means
33505 that the trace run will stop.
33508 The filename of the trace file being examined. This field is
33509 optional, and only present when examining a trace file.
33513 @subsubheading @value{GDBN} Command
33515 The corresponding @value{GDBN} command is @samp{tstatus}.
33517 @subheading -trace-stop
33518 @findex -trace-stop
33520 @subsubheading Synopsis
33526 Stops a tracing experiment. The result of this command has the same
33527 fields as @code{-trace-status}, except that the @samp{supported} and
33528 @samp{running} fields are not output.
33530 @subsubheading @value{GDBN} Command
33532 The corresponding @value{GDBN} command is @samp{tstop}.
33535 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33536 @node GDB/MI Symbol Query
33537 @section @sc{gdb/mi} Symbol Query Commands
33541 @subheading The @code{-symbol-info-address} Command
33542 @findex -symbol-info-address
33544 @subsubheading Synopsis
33547 -symbol-info-address @var{symbol}
33550 Describe where @var{symbol} is stored.
33552 @subsubheading @value{GDBN} Command
33554 The corresponding @value{GDBN} command is @samp{info address}.
33556 @subsubheading Example
33560 @subheading The @code{-symbol-info-file} Command
33561 @findex -symbol-info-file
33563 @subsubheading Synopsis
33569 Show the file for the symbol.
33571 @subsubheading @value{GDBN} Command
33573 There's no equivalent @value{GDBN} command. @code{gdbtk} has
33574 @samp{gdb_find_file}.
33576 @subsubheading Example
33580 @subheading The @code{-symbol-info-function} Command
33581 @findex -symbol-info-function
33583 @subsubheading Synopsis
33586 -symbol-info-function
33589 Show which function the symbol lives in.
33591 @subsubheading @value{GDBN} Command
33593 @samp{gdb_get_function} in @code{gdbtk}.
33595 @subsubheading Example
33599 @subheading The @code{-symbol-info-line} Command
33600 @findex -symbol-info-line
33602 @subsubheading Synopsis
33608 Show the core addresses of the code for a source line.
33610 @subsubheading @value{GDBN} Command
33612 The corresponding @value{GDBN} command is @samp{info line}.
33613 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
33615 @subsubheading Example
33619 @subheading The @code{-symbol-info-symbol} Command
33620 @findex -symbol-info-symbol
33622 @subsubheading Synopsis
33625 -symbol-info-symbol @var{addr}
33628 Describe what symbol is at location @var{addr}.
33630 @subsubheading @value{GDBN} Command
33632 The corresponding @value{GDBN} command is @samp{info symbol}.
33634 @subsubheading Example
33638 @subheading The @code{-symbol-list-functions} Command
33639 @findex -symbol-list-functions
33641 @subsubheading Synopsis
33644 -symbol-list-functions
33647 List the functions in the executable.
33649 @subsubheading @value{GDBN} Command
33651 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
33652 @samp{gdb_search} in @code{gdbtk}.
33654 @subsubheading Example
33659 @subheading The @code{-symbol-list-lines} Command
33660 @findex -symbol-list-lines
33662 @subsubheading Synopsis
33665 -symbol-list-lines @var{filename}
33668 Print the list of lines that contain code and their associated program
33669 addresses for the given source filename. The entries are sorted in
33670 ascending PC order.
33672 @subsubheading @value{GDBN} Command
33674 There is no corresponding @value{GDBN} command.
33676 @subsubheading Example
33679 -symbol-list-lines basics.c
33680 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
33686 @subheading The @code{-symbol-list-types} Command
33687 @findex -symbol-list-types
33689 @subsubheading Synopsis
33695 List all the type names.
33697 @subsubheading @value{GDBN} Command
33699 The corresponding commands are @samp{info types} in @value{GDBN},
33700 @samp{gdb_search} in @code{gdbtk}.
33702 @subsubheading Example
33706 @subheading The @code{-symbol-list-variables} Command
33707 @findex -symbol-list-variables
33709 @subsubheading Synopsis
33712 -symbol-list-variables
33715 List all the global and static variable names.
33717 @subsubheading @value{GDBN} Command
33719 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
33721 @subsubheading Example
33725 @subheading The @code{-symbol-locate} Command
33726 @findex -symbol-locate
33728 @subsubheading Synopsis
33734 @subsubheading @value{GDBN} Command
33736 @samp{gdb_loc} in @code{gdbtk}.
33738 @subsubheading Example
33742 @subheading The @code{-symbol-type} Command
33743 @findex -symbol-type
33745 @subsubheading Synopsis
33748 -symbol-type @var{variable}
33751 Show type of @var{variable}.
33753 @subsubheading @value{GDBN} Command
33755 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
33756 @samp{gdb_obj_variable}.
33758 @subsubheading Example
33763 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33764 @node GDB/MI File Commands
33765 @section @sc{gdb/mi} File Commands
33767 This section describes the GDB/MI commands to specify executable file names
33768 and to read in and obtain symbol table information.
33770 @subheading The @code{-file-exec-and-symbols} Command
33771 @findex -file-exec-and-symbols
33773 @subsubheading Synopsis
33776 -file-exec-and-symbols @var{file}
33779 Specify the executable file to be debugged. This file is the one from
33780 which the symbol table is also read. If no file is specified, the
33781 command clears the executable and symbol information. If breakpoints
33782 are set when using this command with no arguments, @value{GDBN} will produce
33783 error messages. Otherwise, no output is produced, except a completion
33786 @subsubheading @value{GDBN} Command
33788 The corresponding @value{GDBN} command is @samp{file}.
33790 @subsubheading Example
33794 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
33800 @subheading The @code{-file-exec-file} Command
33801 @findex -file-exec-file
33803 @subsubheading Synopsis
33806 -file-exec-file @var{file}
33809 Specify the executable file to be debugged. Unlike
33810 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
33811 from this file. If used without argument, @value{GDBN} clears the information
33812 about the executable file. No output is produced, except a completion
33815 @subsubheading @value{GDBN} Command
33817 The corresponding @value{GDBN} command is @samp{exec-file}.
33819 @subsubheading Example
33823 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
33830 @subheading The @code{-file-list-exec-sections} Command
33831 @findex -file-list-exec-sections
33833 @subsubheading Synopsis
33836 -file-list-exec-sections
33839 List the sections of the current executable file.
33841 @subsubheading @value{GDBN} Command
33843 The @value{GDBN} command @samp{info file} shows, among the rest, the same
33844 information as this command. @code{gdbtk} has a corresponding command
33845 @samp{gdb_load_info}.
33847 @subsubheading Example
33852 @subheading The @code{-file-list-exec-source-file} Command
33853 @findex -file-list-exec-source-file
33855 @subsubheading Synopsis
33858 -file-list-exec-source-file
33861 List the line number, the current source file, and the absolute path
33862 to the current source file for the current executable. The macro
33863 information field has a value of @samp{1} or @samp{0} depending on
33864 whether or not the file includes preprocessor macro information.
33866 @subsubheading @value{GDBN} Command
33868 The @value{GDBN} equivalent is @samp{info source}
33870 @subsubheading Example
33874 123-file-list-exec-source-file
33875 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
33880 @subheading The @code{-file-list-exec-source-files} Command
33881 @findex -file-list-exec-source-files
33883 @subsubheading Synopsis
33886 -file-list-exec-source-files
33889 List the source files for the current executable.
33891 It will always output both the filename and fullname (absolute file
33892 name) of a source file.
33894 @subsubheading @value{GDBN} Command
33896 The @value{GDBN} equivalent is @samp{info sources}.
33897 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
33899 @subsubheading Example
33902 -file-list-exec-source-files
33904 @{file=foo.c,fullname=/home/foo.c@},
33905 @{file=/home/bar.c,fullname=/home/bar.c@},
33906 @{file=gdb_could_not_find_fullpath.c@}]
33910 @subheading The @code{-file-list-shared-libraries} Command
33911 @findex -file-list-shared-libraries
33913 @subsubheading Synopsis
33916 -file-list-shared-libraries [ @var{regexp} ]
33919 List the shared libraries in the program.
33920 With a regular expression @var{regexp}, only those libraries whose
33921 names match @var{regexp} are listed.
33923 @subsubheading @value{GDBN} Command
33925 The corresponding @value{GDBN} command is @samp{info shared}. The fields
33926 have a similar meaning to the @code{=library-loaded} notification.
33927 The @code{ranges} field specifies the multiple segments belonging to this
33928 library. Each range has the following fields:
33932 The address defining the inclusive lower bound of the segment.
33934 The address defining the exclusive upper bound of the segment.
33937 @subsubheading Example
33940 -file-list-exec-source-files
33941 ^done,shared-libraries=[
33942 @{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"@}]@},
33943 @{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"@}]@}]
33949 @subheading The @code{-file-list-symbol-files} Command
33950 @findex -file-list-symbol-files
33952 @subsubheading Synopsis
33955 -file-list-symbol-files
33960 @subsubheading @value{GDBN} Command
33962 The corresponding @value{GDBN} command is @samp{info file} (part of it).
33964 @subsubheading Example
33969 @subheading The @code{-file-symbol-file} Command
33970 @findex -file-symbol-file
33972 @subsubheading Synopsis
33975 -file-symbol-file @var{file}
33978 Read symbol table info from the specified @var{file} argument. When
33979 used without arguments, clears @value{GDBN}'s symbol table info. No output is
33980 produced, except for a completion notification.
33982 @subsubheading @value{GDBN} Command
33984 The corresponding @value{GDBN} command is @samp{symbol-file}.
33986 @subsubheading Example
33990 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
33996 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33997 @node GDB/MI Memory Overlay Commands
33998 @section @sc{gdb/mi} Memory Overlay Commands
34000 The memory overlay commands are not implemented.
34002 @c @subheading -overlay-auto
34004 @c @subheading -overlay-list-mapping-state
34006 @c @subheading -overlay-list-overlays
34008 @c @subheading -overlay-map
34010 @c @subheading -overlay-off
34012 @c @subheading -overlay-on
34014 @c @subheading -overlay-unmap
34016 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34017 @node GDB/MI Signal Handling Commands
34018 @section @sc{gdb/mi} Signal Handling Commands
34020 Signal handling commands are not implemented.
34022 @c @subheading -signal-handle
34024 @c @subheading -signal-list-handle-actions
34026 @c @subheading -signal-list-signal-types
34030 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34031 @node GDB/MI Target Manipulation
34032 @section @sc{gdb/mi} Target Manipulation Commands
34035 @subheading The @code{-target-attach} Command
34036 @findex -target-attach
34038 @subsubheading Synopsis
34041 -target-attach @var{pid} | @var{gid} | @var{file}
34044 Attach to a process @var{pid} or a file @var{file} outside of
34045 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
34046 group, the id previously returned by
34047 @samp{-list-thread-groups --available} must be used.
34049 @subsubheading @value{GDBN} Command
34051 The corresponding @value{GDBN} command is @samp{attach}.
34053 @subsubheading Example
34057 =thread-created,id="1"
34058 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
34064 @subheading The @code{-target-compare-sections} Command
34065 @findex -target-compare-sections
34067 @subsubheading Synopsis
34070 -target-compare-sections [ @var{section} ]
34073 Compare data of section @var{section} on target to the exec file.
34074 Without the argument, all sections are compared.
34076 @subsubheading @value{GDBN} Command
34078 The @value{GDBN} equivalent is @samp{compare-sections}.
34080 @subsubheading Example
34085 @subheading The @code{-target-detach} Command
34086 @findex -target-detach
34088 @subsubheading Synopsis
34091 -target-detach [ @var{pid} | @var{gid} ]
34094 Detach from the remote target which normally resumes its execution.
34095 If either @var{pid} or @var{gid} is specified, detaches from either
34096 the specified process, or specified thread group. There's no output.
34098 @subsubheading @value{GDBN} Command
34100 The corresponding @value{GDBN} command is @samp{detach}.
34102 @subsubheading Example
34112 @subheading The @code{-target-disconnect} Command
34113 @findex -target-disconnect
34115 @subsubheading Synopsis
34121 Disconnect from the remote target. There's no output and the target is
34122 generally not resumed.
34124 @subsubheading @value{GDBN} Command
34126 The corresponding @value{GDBN} command is @samp{disconnect}.
34128 @subsubheading Example
34138 @subheading The @code{-target-download} Command
34139 @findex -target-download
34141 @subsubheading Synopsis
34147 Loads the executable onto the remote target.
34148 It prints out an update message every half second, which includes the fields:
34152 The name of the section.
34154 The size of what has been sent so far for that section.
34156 The size of the section.
34158 The total size of what was sent so far (the current and the previous sections).
34160 The size of the overall executable to download.
34164 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
34165 @sc{gdb/mi} Output Syntax}).
34167 In addition, it prints the name and size of the sections, as they are
34168 downloaded. These messages include the following fields:
34172 The name of the section.
34174 The size of the section.
34176 The size of the overall executable to download.
34180 At the end, a summary is printed.
34182 @subsubheading @value{GDBN} Command
34184 The corresponding @value{GDBN} command is @samp{load}.
34186 @subsubheading Example
34188 Note: each status message appears on a single line. Here the messages
34189 have been broken down so that they can fit onto a page.
34194 +download,@{section=".text",section-size="6668",total-size="9880"@}
34195 +download,@{section=".text",section-sent="512",section-size="6668",
34196 total-sent="512",total-size="9880"@}
34197 +download,@{section=".text",section-sent="1024",section-size="6668",
34198 total-sent="1024",total-size="9880"@}
34199 +download,@{section=".text",section-sent="1536",section-size="6668",
34200 total-sent="1536",total-size="9880"@}
34201 +download,@{section=".text",section-sent="2048",section-size="6668",
34202 total-sent="2048",total-size="9880"@}
34203 +download,@{section=".text",section-sent="2560",section-size="6668",
34204 total-sent="2560",total-size="9880"@}
34205 +download,@{section=".text",section-sent="3072",section-size="6668",
34206 total-sent="3072",total-size="9880"@}
34207 +download,@{section=".text",section-sent="3584",section-size="6668",
34208 total-sent="3584",total-size="9880"@}
34209 +download,@{section=".text",section-sent="4096",section-size="6668",
34210 total-sent="4096",total-size="9880"@}
34211 +download,@{section=".text",section-sent="4608",section-size="6668",
34212 total-sent="4608",total-size="9880"@}
34213 +download,@{section=".text",section-sent="5120",section-size="6668",
34214 total-sent="5120",total-size="9880"@}
34215 +download,@{section=".text",section-sent="5632",section-size="6668",
34216 total-sent="5632",total-size="9880"@}
34217 +download,@{section=".text",section-sent="6144",section-size="6668",
34218 total-sent="6144",total-size="9880"@}
34219 +download,@{section=".text",section-sent="6656",section-size="6668",
34220 total-sent="6656",total-size="9880"@}
34221 +download,@{section=".init",section-size="28",total-size="9880"@}
34222 +download,@{section=".fini",section-size="28",total-size="9880"@}
34223 +download,@{section=".data",section-size="3156",total-size="9880"@}
34224 +download,@{section=".data",section-sent="512",section-size="3156",
34225 total-sent="7236",total-size="9880"@}
34226 +download,@{section=".data",section-sent="1024",section-size="3156",
34227 total-sent="7748",total-size="9880"@}
34228 +download,@{section=".data",section-sent="1536",section-size="3156",
34229 total-sent="8260",total-size="9880"@}
34230 +download,@{section=".data",section-sent="2048",section-size="3156",
34231 total-sent="8772",total-size="9880"@}
34232 +download,@{section=".data",section-sent="2560",section-size="3156",
34233 total-sent="9284",total-size="9880"@}
34234 +download,@{section=".data",section-sent="3072",section-size="3156",
34235 total-sent="9796",total-size="9880"@}
34236 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
34243 @subheading The @code{-target-exec-status} Command
34244 @findex -target-exec-status
34246 @subsubheading Synopsis
34249 -target-exec-status
34252 Provide information on the state of the target (whether it is running or
34253 not, for instance).
34255 @subsubheading @value{GDBN} Command
34257 There's no equivalent @value{GDBN} command.
34259 @subsubheading Example
34263 @subheading The @code{-target-list-available-targets} Command
34264 @findex -target-list-available-targets
34266 @subsubheading Synopsis
34269 -target-list-available-targets
34272 List the possible targets to connect to.
34274 @subsubheading @value{GDBN} Command
34276 The corresponding @value{GDBN} command is @samp{help target}.
34278 @subsubheading Example
34282 @subheading The @code{-target-list-current-targets} Command
34283 @findex -target-list-current-targets
34285 @subsubheading Synopsis
34288 -target-list-current-targets
34291 Describe the current target.
34293 @subsubheading @value{GDBN} Command
34295 The corresponding information is printed by @samp{info file} (among
34298 @subsubheading Example
34302 @subheading The @code{-target-list-parameters} Command
34303 @findex -target-list-parameters
34305 @subsubheading Synopsis
34308 -target-list-parameters
34314 @subsubheading @value{GDBN} Command
34318 @subsubheading Example
34321 @subheading The @code{-target-flash-erase} Command
34322 @findex -target-flash-erase
34324 @subsubheading Synopsis
34327 -target-flash-erase
34330 Erases all known flash memory regions on the target.
34332 The corresponding @value{GDBN} command is @samp{flash-erase}.
34334 The output is a list of flash regions that have been erased, with starting
34335 addresses and memory region sizes.
34339 -target-flash-erase
34340 ^done,erased-regions=@{address="0x0",size="0x40000"@}
34344 @subheading The @code{-target-select} Command
34345 @findex -target-select
34347 @subsubheading Synopsis
34350 -target-select @var{type} @var{parameters @dots{}}
34353 Connect @value{GDBN} to the remote target. This command takes two args:
34357 The type of target, for instance @samp{remote}, etc.
34358 @item @var{parameters}
34359 Device names, host names and the like. @xref{Target Commands, ,
34360 Commands for Managing Targets}, for more details.
34363 The output is a connection notification, followed by the address at
34364 which the target program is, in the following form:
34367 ^connected,addr="@var{address}",func="@var{function name}",
34368 args=[@var{arg list}]
34371 @subsubheading @value{GDBN} Command
34373 The corresponding @value{GDBN} command is @samp{target}.
34375 @subsubheading Example
34379 -target-select remote /dev/ttya
34380 ^connected,addr="0xfe00a300",func="??",args=[]
34384 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34385 @node GDB/MI File Transfer Commands
34386 @section @sc{gdb/mi} File Transfer Commands
34389 @subheading The @code{-target-file-put} Command
34390 @findex -target-file-put
34392 @subsubheading Synopsis
34395 -target-file-put @var{hostfile} @var{targetfile}
34398 Copy file @var{hostfile} from the host system (the machine running
34399 @value{GDBN}) to @var{targetfile} on the target system.
34401 @subsubheading @value{GDBN} Command
34403 The corresponding @value{GDBN} command is @samp{remote put}.
34405 @subsubheading Example
34409 -target-file-put localfile remotefile
34415 @subheading The @code{-target-file-get} Command
34416 @findex -target-file-get
34418 @subsubheading Synopsis
34421 -target-file-get @var{targetfile} @var{hostfile}
34424 Copy file @var{targetfile} from the target system to @var{hostfile}
34425 on the host system.
34427 @subsubheading @value{GDBN} Command
34429 The corresponding @value{GDBN} command is @samp{remote get}.
34431 @subsubheading Example
34435 -target-file-get remotefile localfile
34441 @subheading The @code{-target-file-delete} Command
34442 @findex -target-file-delete
34444 @subsubheading Synopsis
34447 -target-file-delete @var{targetfile}
34450 Delete @var{targetfile} from the target system.
34452 @subsubheading @value{GDBN} Command
34454 The corresponding @value{GDBN} command is @samp{remote delete}.
34456 @subsubheading Example
34460 -target-file-delete remotefile
34466 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34467 @node GDB/MI Ada Exceptions Commands
34468 @section Ada Exceptions @sc{gdb/mi} Commands
34470 @subheading The @code{-info-ada-exceptions} Command
34471 @findex -info-ada-exceptions
34473 @subsubheading Synopsis
34476 -info-ada-exceptions [ @var{regexp}]
34479 List all Ada exceptions defined within the program being debugged.
34480 With a regular expression @var{regexp}, only those exceptions whose
34481 names match @var{regexp} are listed.
34483 @subsubheading @value{GDBN} Command
34485 The corresponding @value{GDBN} command is @samp{info exceptions}.
34487 @subsubheading Result
34489 The result is a table of Ada exceptions. The following columns are
34490 defined for each exception:
34494 The name of the exception.
34497 The address of the exception.
34501 @subsubheading Example
34504 -info-ada-exceptions aint
34505 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
34506 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
34507 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
34508 body=[@{name="constraint_error",address="0x0000000000613da0"@},
34509 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
34512 @subheading Catching Ada Exceptions
34514 The commands describing how to ask @value{GDBN} to stop when a program
34515 raises an exception are described at @ref{Ada Exception GDB/MI
34516 Catchpoint Commands}.
34519 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34520 @node GDB/MI Support Commands
34521 @section @sc{gdb/mi} Support Commands
34523 Since new commands and features get regularly added to @sc{gdb/mi},
34524 some commands are available to help front-ends query the debugger
34525 about support for these capabilities. Similarly, it is also possible
34526 to query @value{GDBN} about target support of certain features.
34528 @subheading The @code{-info-gdb-mi-command} Command
34529 @cindex @code{-info-gdb-mi-command}
34530 @findex -info-gdb-mi-command
34532 @subsubheading Synopsis
34535 -info-gdb-mi-command @var{cmd_name}
34538 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
34540 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
34541 is technically not part of the command name (@pxref{GDB/MI Input
34542 Syntax}), and thus should be omitted in @var{cmd_name}. However,
34543 for ease of use, this command also accepts the form with the leading
34546 @subsubheading @value{GDBN} Command
34548 There is no corresponding @value{GDBN} command.
34550 @subsubheading Result
34552 The result is a tuple. There is currently only one field:
34556 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
34557 @code{"false"} otherwise.
34561 @subsubheading Example
34563 Here is an example where the @sc{gdb/mi} command does not exist:
34566 -info-gdb-mi-command unsupported-command
34567 ^done,command=@{exists="false"@}
34571 And here is an example where the @sc{gdb/mi} command is known
34575 -info-gdb-mi-command symbol-list-lines
34576 ^done,command=@{exists="true"@}
34579 @subheading The @code{-list-features} Command
34580 @findex -list-features
34581 @cindex supported @sc{gdb/mi} features, list
34583 Returns a list of particular features of the MI protocol that
34584 this version of gdb implements. A feature can be a command,
34585 or a new field in an output of some command, or even an
34586 important bugfix. While a frontend can sometimes detect presence
34587 of a feature at runtime, it is easier to perform detection at debugger
34590 The command returns a list of strings, with each string naming an
34591 available feature. Each returned string is just a name, it does not
34592 have any internal structure. The list of possible feature names
34598 (gdb) -list-features
34599 ^done,result=["feature1","feature2"]
34602 The current list of features is:
34605 @item frozen-varobjs
34606 Indicates support for the @code{-var-set-frozen} command, as well
34607 as possible presense of the @code{frozen} field in the output
34608 of @code{-varobj-create}.
34609 @item pending-breakpoints
34610 Indicates support for the @option{-f} option to the @code{-break-insert}
34613 Indicates Python scripting support, Python-based
34614 pretty-printing commands, and possible presence of the
34615 @samp{display_hint} field in the output of @code{-var-list-children}
34617 Indicates support for the @code{-thread-info} command.
34618 @item data-read-memory-bytes
34619 Indicates support for the @code{-data-read-memory-bytes} and the
34620 @code{-data-write-memory-bytes} commands.
34621 @item breakpoint-notifications
34622 Indicates that changes to breakpoints and breakpoints created via the
34623 CLI will be announced via async records.
34624 @item ada-task-info
34625 Indicates support for the @code{-ada-task-info} command.
34626 @item language-option
34627 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
34628 option (@pxref{Context management}).
34629 @item info-gdb-mi-command
34630 Indicates support for the @code{-info-gdb-mi-command} command.
34631 @item undefined-command-error-code
34632 Indicates support for the "undefined-command" error code in error result
34633 records, produced when trying to execute an undefined @sc{gdb/mi} command
34634 (@pxref{GDB/MI Result Records}).
34635 @item exec-run-start-option
34636 Indicates that the @code{-exec-run} command supports the @option{--start}
34637 option (@pxref{GDB/MI Program Execution}).
34638 @item data-disassemble-a-option
34639 Indicates that the @code{-data-disassemble} command supports the @option{-a}
34640 option (@pxref{GDB/MI Data Manipulation}).
34643 @subheading The @code{-list-target-features} Command
34644 @findex -list-target-features
34646 Returns a list of particular features that are supported by the
34647 target. Those features affect the permitted MI commands, but
34648 unlike the features reported by the @code{-list-features} command, the
34649 features depend on which target GDB is using at the moment. Whenever
34650 a target can change, due to commands such as @code{-target-select},
34651 @code{-target-attach} or @code{-exec-run}, the list of target features
34652 may change, and the frontend should obtain it again.
34656 (gdb) -list-target-features
34657 ^done,result=["async"]
34660 The current list of features is:
34664 Indicates that the target is capable of asynchronous command
34665 execution, which means that @value{GDBN} will accept further commands
34666 while the target is running.
34669 Indicates that the target is capable of reverse execution.
34670 @xref{Reverse Execution}, for more information.
34674 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34675 @node GDB/MI Miscellaneous Commands
34676 @section Miscellaneous @sc{gdb/mi} Commands
34678 @c @subheading -gdb-complete
34680 @subheading The @code{-gdb-exit} Command
34683 @subsubheading Synopsis
34689 Exit @value{GDBN} immediately.
34691 @subsubheading @value{GDBN} Command
34693 Approximately corresponds to @samp{quit}.
34695 @subsubheading Example
34705 @subheading The @code{-exec-abort} Command
34706 @findex -exec-abort
34708 @subsubheading Synopsis
34714 Kill the inferior running program.
34716 @subsubheading @value{GDBN} Command
34718 The corresponding @value{GDBN} command is @samp{kill}.
34720 @subsubheading Example
34725 @subheading The @code{-gdb-set} Command
34728 @subsubheading Synopsis
34734 Set an internal @value{GDBN} variable.
34735 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
34737 @subsubheading @value{GDBN} Command
34739 The corresponding @value{GDBN} command is @samp{set}.
34741 @subsubheading Example
34751 @subheading The @code{-gdb-show} Command
34754 @subsubheading Synopsis
34760 Show the current value of a @value{GDBN} variable.
34762 @subsubheading @value{GDBN} Command
34764 The corresponding @value{GDBN} command is @samp{show}.
34766 @subsubheading Example
34775 @c @subheading -gdb-source
34778 @subheading The @code{-gdb-version} Command
34779 @findex -gdb-version
34781 @subsubheading Synopsis
34787 Show version information for @value{GDBN}. Used mostly in testing.
34789 @subsubheading @value{GDBN} Command
34791 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
34792 default shows this information when you start an interactive session.
34794 @subsubheading Example
34796 @c This example modifies the actual output from GDB to avoid overfull
34802 ~Copyright 2000 Free Software Foundation, Inc.
34803 ~GDB is free software, covered by the GNU General Public License, and
34804 ~you are welcome to change it and/or distribute copies of it under
34805 ~ certain conditions.
34806 ~Type "show copying" to see the conditions.
34807 ~There is absolutely no warranty for GDB. Type "show warranty" for
34809 ~This GDB was configured as
34810 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
34815 @subheading The @code{-list-thread-groups} Command
34816 @findex -list-thread-groups
34818 @subheading Synopsis
34821 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
34824 Lists thread groups (@pxref{Thread groups}). When a single thread
34825 group is passed as the argument, lists the children of that group.
34826 When several thread group are passed, lists information about those
34827 thread groups. Without any parameters, lists information about all
34828 top-level thread groups.
34830 Normally, thread groups that are being debugged are reported.
34831 With the @samp{--available} option, @value{GDBN} reports thread groups
34832 available on the target.
34834 The output of this command may have either a @samp{threads} result or
34835 a @samp{groups} result. The @samp{thread} result has a list of tuples
34836 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
34837 Information}). The @samp{groups} result has a list of tuples as value,
34838 each tuple describing a thread group. If top-level groups are
34839 requested (that is, no parameter is passed), or when several groups
34840 are passed, the output always has a @samp{groups} result. The format
34841 of the @samp{group} result is described below.
34843 To reduce the number of roundtrips it's possible to list thread groups
34844 together with their children, by passing the @samp{--recurse} option
34845 and the recursion depth. Presently, only recursion depth of 1 is
34846 permitted. If this option is present, then every reported thread group
34847 will also include its children, either as @samp{group} or
34848 @samp{threads} field.
34850 In general, any combination of option and parameters is permitted, with
34851 the following caveats:
34855 When a single thread group is passed, the output will typically
34856 be the @samp{threads} result. Because threads may not contain
34857 anything, the @samp{recurse} option will be ignored.
34860 When the @samp{--available} option is passed, limited information may
34861 be available. In particular, the list of threads of a process might
34862 be inaccessible. Further, specifying specific thread groups might
34863 not give any performance advantage over listing all thread groups.
34864 The frontend should assume that @samp{-list-thread-groups --available}
34865 is always an expensive operation and cache the results.
34869 The @samp{groups} result is a list of tuples, where each tuple may
34870 have the following fields:
34874 Identifier of the thread group. This field is always present.
34875 The identifier is an opaque string; frontends should not try to
34876 convert it to an integer, even though it might look like one.
34879 The type of the thread group. At present, only @samp{process} is a
34883 The target-specific process identifier. This field is only present
34884 for thread groups of type @samp{process} and only if the process exists.
34887 The exit code of this group's last exited thread, formatted in octal.
34888 This field is only present for thread groups of type @samp{process} and
34889 only if the process is not running.
34892 The number of children this thread group has. This field may be
34893 absent for an available thread group.
34896 This field has a list of tuples as value, each tuple describing a
34897 thread. It may be present if the @samp{--recurse} option is
34898 specified, and it's actually possible to obtain the threads.
34901 This field is a list of integers, each identifying a core that one
34902 thread of the group is running on. This field may be absent if
34903 such information is not available.
34906 The name of the executable file that corresponds to this thread group.
34907 The field is only present for thread groups of type @samp{process},
34908 and only if there is a corresponding executable file.
34912 @subheading Example
34916 -list-thread-groups
34917 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
34918 -list-thread-groups 17
34919 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
34920 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
34921 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
34922 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
34923 file="/tmp/a.c",fullname="/tmp/a.c",line="158",arch="i386:x86_64"@},state="running"@}]]
34924 -list-thread-groups --available
34925 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
34926 -list-thread-groups --available --recurse 1
34927 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
34928 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
34929 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
34930 -list-thread-groups --available --recurse 1 17 18
34931 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
34932 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
34933 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
34936 @subheading The @code{-info-os} Command
34939 @subsubheading Synopsis
34942 -info-os [ @var{type} ]
34945 If no argument is supplied, the command returns a table of available
34946 operating-system-specific information types. If one of these types is
34947 supplied as an argument @var{type}, then the command returns a table
34948 of data of that type.
34950 The types of information available depend on the target operating
34953 @subsubheading @value{GDBN} Command
34955 The corresponding @value{GDBN} command is @samp{info os}.
34957 @subsubheading Example
34959 When run on a @sc{gnu}/Linux system, the output will look something
34965 ^done,OSDataTable=@{nr_rows="10",nr_cols="3",
34966 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
34967 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
34968 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
34969 body=[item=@{col0="cpus",col1="Listing of all cpus/cores on the system",
34971 item=@{col0="files",col1="Listing of all file descriptors",
34972 col2="File descriptors"@},
34973 item=@{col0="modules",col1="Listing of all loaded kernel modules",
34974 col2="Kernel modules"@},
34975 item=@{col0="msg",col1="Listing of all message queues",
34976 col2="Message queues"@},
34977 item=@{col0="processes",col1="Listing of all processes",
34978 col2="Processes"@},
34979 item=@{col0="procgroups",col1="Listing of all process groups",
34980 col2="Process groups"@},
34981 item=@{col0="semaphores",col1="Listing of all semaphores",
34982 col2="Semaphores"@},
34983 item=@{col0="shm",col1="Listing of all shared-memory regions",
34984 col2="Shared-memory regions"@},
34985 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
34987 item=@{col0="threads",col1="Listing of all threads",
34991 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
34992 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
34993 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
34994 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
34995 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
34996 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
34997 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
34998 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
35000 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
35001 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
35005 (Note that the MI output here includes a @code{"Title"} column that
35006 does not appear in command-line @code{info os}; this column is useful
35007 for MI clients that want to enumerate the types of data, such as in a
35008 popup menu, but is needless clutter on the command line, and
35009 @code{info os} omits it.)
35011 @subheading The @code{-add-inferior} Command
35012 @findex -add-inferior
35014 @subheading Synopsis
35020 Creates a new inferior (@pxref{Inferiors and Programs}). The created
35021 inferior is not associated with any executable. Such association may
35022 be established with the @samp{-file-exec-and-symbols} command
35023 (@pxref{GDB/MI File Commands}). The command response has a single
35024 field, @samp{inferior}, whose value is the identifier of the
35025 thread group corresponding to the new inferior.
35027 @subheading Example
35032 ^done,inferior="i3"
35035 @subheading The @code{-interpreter-exec} Command
35036 @findex -interpreter-exec
35038 @subheading Synopsis
35041 -interpreter-exec @var{interpreter} @var{command}
35043 @anchor{-interpreter-exec}
35045 Execute the specified @var{command} in the given @var{interpreter}.
35047 @subheading @value{GDBN} Command
35049 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
35051 @subheading Example
35055 -interpreter-exec console "break main"
35056 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
35057 &"During symbol reading, bad structure-type format.\n"
35058 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
35063 @subheading The @code{-inferior-tty-set} Command
35064 @findex -inferior-tty-set
35066 @subheading Synopsis
35069 -inferior-tty-set /dev/pts/1
35072 Set terminal for future runs of the program being debugged.
35074 @subheading @value{GDBN} Command
35076 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
35078 @subheading Example
35082 -inferior-tty-set /dev/pts/1
35087 @subheading The @code{-inferior-tty-show} Command
35088 @findex -inferior-tty-show
35090 @subheading Synopsis
35096 Show terminal for future runs of program being debugged.
35098 @subheading @value{GDBN} Command
35100 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
35102 @subheading Example
35106 -inferior-tty-set /dev/pts/1
35110 ^done,inferior_tty_terminal="/dev/pts/1"
35114 @subheading The @code{-enable-timings} Command
35115 @findex -enable-timings
35117 @subheading Synopsis
35120 -enable-timings [yes | no]
35123 Toggle the printing of the wallclock, user and system times for an MI
35124 command as a field in its output. This command is to help frontend
35125 developers optimize the performance of their code. No argument is
35126 equivalent to @samp{yes}.
35128 @subheading @value{GDBN} Command
35132 @subheading Example
35140 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
35141 addr="0x080484ed",func="main",file="myprog.c",
35142 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
35144 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
35152 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
35153 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
35154 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
35155 fullname="/home/nickrob/myprog.c",line="73",arch="i386:x86_64"@}
35159 @subheading The @code{-complete} Command
35162 @subheading Synopsis
35165 -complete @var{command}
35168 Show a list of completions for partially typed CLI @var{command}.
35170 This command is intended for @sc{gdb/mi} frontends that cannot use two separate
35171 CLI and MI channels --- for example: because of lack of PTYs like on Windows or
35172 because @value{GDBN} is used remotely via a SSH connection.
35176 The result consists of two or three fields:
35180 This field contains the completed @var{command}. If @var{command}
35181 has no known completions, this field is omitted.
35184 This field contains a (possibly empty) array of matches. It is always present.
35186 @item max_completions_reached
35187 This field contains @code{1} if number of known completions is above
35188 @code{max-completions} limit (@pxref{Completion}), otherwise it contains
35189 @code{0}. It is always present.
35193 @subheading @value{GDBN} Command
35195 The corresponding @value{GDBN} command is @samp{complete}.
35197 @subheading Example
35202 ^done,completion="break",
35203 matches=["break","break-range"],
35204 max_completions_reached="0"
35207 ^done,completion="b ma",
35208 matches=["b madvise","b main"],max_completions_reached="0"
35210 -complete "b push_b"
35211 ^done,completion="b push_back(",
35213 "b A::push_back(void*)",
35214 "b std::string::push_back(char)",
35215 "b std::vector<int, std::allocator<int> >::push_back(int&&)"],
35216 max_completions_reached="0"
35218 -complete "nonexist"
35219 ^done,matches=[],max_completions_reached="0"
35225 @chapter @value{GDBN} Annotations
35227 This chapter describes annotations in @value{GDBN}. Annotations were
35228 designed to interface @value{GDBN} to graphical user interfaces or other
35229 similar programs which want to interact with @value{GDBN} at a
35230 relatively high level.
35232 The annotation mechanism has largely been superseded by @sc{gdb/mi}
35236 This is Edition @value{EDITION}, @value{DATE}.
35240 * Annotations Overview:: What annotations are; the general syntax.
35241 * Server Prefix:: Issuing a command without affecting user state.
35242 * Prompting:: Annotations marking @value{GDBN}'s need for input.
35243 * Errors:: Annotations for error messages.
35244 * Invalidation:: Some annotations describe things now invalid.
35245 * Annotations for Running::
35246 Whether the program is running, how it stopped, etc.
35247 * Source Annotations:: Annotations describing source code.
35250 @node Annotations Overview
35251 @section What is an Annotation?
35252 @cindex annotations
35254 Annotations start with a newline character, two @samp{control-z}
35255 characters, and the name of the annotation. If there is no additional
35256 information associated with this annotation, the name of the annotation
35257 is followed immediately by a newline. If there is additional
35258 information, the name of the annotation is followed by a space, the
35259 additional information, and a newline. The additional information
35260 cannot contain newline characters.
35262 Any output not beginning with a newline and two @samp{control-z}
35263 characters denotes literal output from @value{GDBN}. Currently there is
35264 no need for @value{GDBN} to output a newline followed by two
35265 @samp{control-z} characters, but if there was such a need, the
35266 annotations could be extended with an @samp{escape} annotation which
35267 means those three characters as output.
35269 The annotation @var{level}, which is specified using the
35270 @option{--annotate} command line option (@pxref{Mode Options}), controls
35271 how much information @value{GDBN} prints together with its prompt,
35272 values of expressions, source lines, and other types of output. Level 0
35273 is for no annotations, level 1 is for use when @value{GDBN} is run as a
35274 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
35275 for programs that control @value{GDBN}, and level 2 annotations have
35276 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
35277 Interface, annotate, GDB's Obsolete Annotations}).
35280 @kindex set annotate
35281 @item set annotate @var{level}
35282 The @value{GDBN} command @code{set annotate} sets the level of
35283 annotations to the specified @var{level}.
35285 @item show annotate
35286 @kindex show annotate
35287 Show the current annotation level.
35290 This chapter describes level 3 annotations.
35292 A simple example of starting up @value{GDBN} with annotations is:
35295 $ @kbd{gdb --annotate=3}
35297 Copyright 2003 Free Software Foundation, Inc.
35298 GDB is free software, covered by the GNU General Public License,
35299 and you are welcome to change it and/or distribute copies of it
35300 under certain conditions.
35301 Type "show copying" to see the conditions.
35302 There is absolutely no warranty for GDB. Type "show warranty"
35304 This GDB was configured as "i386-pc-linux-gnu"
35315 Here @samp{quit} is input to @value{GDBN}; the rest is output from
35316 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
35317 denotes a @samp{control-z} character) are annotations; the rest is
35318 output from @value{GDBN}.
35320 @node Server Prefix
35321 @section The Server Prefix
35322 @cindex server prefix
35324 If you prefix a command with @samp{server } then it will not affect
35325 the command history, nor will it affect @value{GDBN}'s notion of which
35326 command to repeat if @key{RET} is pressed on a line by itself. This
35327 means that commands can be run behind a user's back by a front-end in
35328 a transparent manner.
35330 The @code{server } prefix does not affect the recording of values into
35331 the value history; to print a value without recording it into the
35332 value history, use the @code{output} command instead of the
35333 @code{print} command.
35335 Using this prefix also disables confirmation requests
35336 (@pxref{confirmation requests}).
35339 @section Annotation for @value{GDBN} Input
35341 @cindex annotations for prompts
35342 When @value{GDBN} prompts for input, it annotates this fact so it is possible
35343 to know when to send output, when the output from a given command is
35346 Different kinds of input each have a different @dfn{input type}. Each
35347 input type has three annotations: a @code{pre-} annotation, which
35348 denotes the beginning of any prompt which is being output, a plain
35349 annotation, which denotes the end of the prompt, and then a @code{post-}
35350 annotation which denotes the end of any echo which may (or may not) be
35351 associated with the input. For example, the @code{prompt} input type
35352 features the following annotations:
35360 The input types are
35363 @findex pre-prompt annotation
35364 @findex prompt annotation
35365 @findex post-prompt annotation
35367 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
35369 @findex pre-commands annotation
35370 @findex commands annotation
35371 @findex post-commands annotation
35373 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
35374 command. The annotations are repeated for each command which is input.
35376 @findex pre-overload-choice annotation
35377 @findex overload-choice annotation
35378 @findex post-overload-choice annotation
35379 @item overload-choice
35380 When @value{GDBN} wants the user to select between various overloaded functions.
35382 @findex pre-query annotation
35383 @findex query annotation
35384 @findex post-query annotation
35386 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
35388 @findex pre-prompt-for-continue annotation
35389 @findex prompt-for-continue annotation
35390 @findex post-prompt-for-continue annotation
35391 @item prompt-for-continue
35392 When @value{GDBN} is asking the user to press return to continue. Note: Don't
35393 expect this to work well; instead use @code{set height 0} to disable
35394 prompting. This is because the counting of lines is buggy in the
35395 presence of annotations.
35400 @cindex annotations for errors, warnings and interrupts
35402 @findex quit annotation
35407 This annotation occurs right before @value{GDBN} responds to an interrupt.
35409 @findex error annotation
35414 This annotation occurs right before @value{GDBN} responds to an error.
35416 Quit and error annotations indicate that any annotations which @value{GDBN} was
35417 in the middle of may end abruptly. For example, if a
35418 @code{value-history-begin} annotation is followed by a @code{error}, one
35419 cannot expect to receive the matching @code{value-history-end}. One
35420 cannot expect not to receive it either, however; an error annotation
35421 does not necessarily mean that @value{GDBN} is immediately returning all the way
35424 @findex error-begin annotation
35425 A quit or error annotation may be preceded by
35431 Any output between that and the quit or error annotation is the error
35434 Warning messages are not yet annotated.
35435 @c If we want to change that, need to fix warning(), type_error(),
35436 @c range_error(), and possibly other places.
35439 @section Invalidation Notices
35441 @cindex annotations for invalidation messages
35442 The following annotations say that certain pieces of state may have
35446 @findex frames-invalid annotation
35447 @item ^Z^Zframes-invalid
35449 The frames (for example, output from the @code{backtrace} command) may
35452 @findex breakpoints-invalid annotation
35453 @item ^Z^Zbreakpoints-invalid
35455 The breakpoints may have changed. For example, the user just added or
35456 deleted a breakpoint.
35459 @node Annotations for Running
35460 @section Running the Program
35461 @cindex annotations for running programs
35463 @findex starting annotation
35464 @findex stopping annotation
35465 When the program starts executing due to a @value{GDBN} command such as
35466 @code{step} or @code{continue},
35472 is output. When the program stops,
35478 is output. Before the @code{stopped} annotation, a variety of
35479 annotations describe how the program stopped.
35482 @findex exited annotation
35483 @item ^Z^Zexited @var{exit-status}
35484 The program exited, and @var{exit-status} is the exit status (zero for
35485 successful exit, otherwise nonzero).
35487 @findex signalled annotation
35488 @findex signal-name annotation
35489 @findex signal-name-end annotation
35490 @findex signal-string annotation
35491 @findex signal-string-end annotation
35492 @item ^Z^Zsignalled
35493 The program exited with a signal. After the @code{^Z^Zsignalled}, the
35494 annotation continues:
35500 ^Z^Zsignal-name-end
35504 ^Z^Zsignal-string-end
35509 where @var{name} is the name of the signal, such as @code{SIGILL} or
35510 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
35511 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
35512 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
35513 user's benefit and have no particular format.
35515 @findex signal annotation
35517 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
35518 just saying that the program received the signal, not that it was
35519 terminated with it.
35521 @findex breakpoint annotation
35522 @item ^Z^Zbreakpoint @var{number}
35523 The program hit breakpoint number @var{number}.
35525 @findex watchpoint annotation
35526 @item ^Z^Zwatchpoint @var{number}
35527 The program hit watchpoint number @var{number}.
35530 @node Source Annotations
35531 @section Displaying Source
35532 @cindex annotations for source display
35534 @findex source annotation
35535 The following annotation is used instead of displaying source code:
35538 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
35541 where @var{filename} is an absolute file name indicating which source
35542 file, @var{line} is the line number within that file (where 1 is the
35543 first line in the file), @var{character} is the character position
35544 within the file (where 0 is the first character in the file) (for most
35545 debug formats this will necessarily point to the beginning of a line),
35546 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
35547 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
35548 @var{addr} is the address in the target program associated with the
35549 source which is being displayed. The @var{addr} is in the form @samp{0x}
35550 followed by one or more lowercase hex digits (note that this does not
35551 depend on the language).
35553 @node JIT Interface
35554 @chapter JIT Compilation Interface
35555 @cindex just-in-time compilation
35556 @cindex JIT compilation interface
35558 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
35559 interface. A JIT compiler is a program or library that generates native
35560 executable code at runtime and executes it, usually in order to achieve good
35561 performance while maintaining platform independence.
35563 Programs that use JIT compilation are normally difficult to debug because
35564 portions of their code are generated at runtime, instead of being loaded from
35565 object files, which is where @value{GDBN} normally finds the program's symbols
35566 and debug information. In order to debug programs that use JIT compilation,
35567 @value{GDBN} has an interface that allows the program to register in-memory
35568 symbol files with @value{GDBN} at runtime.
35570 If you are using @value{GDBN} to debug a program that uses this interface, then
35571 it should work transparently so long as you have not stripped the binary. If
35572 you are developing a JIT compiler, then the interface is documented in the rest
35573 of this chapter. At this time, the only known client of this interface is the
35576 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
35577 JIT compiler communicates with @value{GDBN} by writing data into a global
35578 variable and calling a fuction at a well-known symbol. When @value{GDBN}
35579 attaches, it reads a linked list of symbol files from the global variable to
35580 find existing code, and puts a breakpoint in the function so that it can find
35581 out about additional code.
35584 * Declarations:: Relevant C struct declarations
35585 * Registering Code:: Steps to register code
35586 * Unregistering Code:: Steps to unregister code
35587 * Custom Debug Info:: Emit debug information in a custom format
35591 @section JIT Declarations
35593 These are the relevant struct declarations that a C program should include to
35594 implement the interface:
35604 struct jit_code_entry
35606 struct jit_code_entry *next_entry;
35607 struct jit_code_entry *prev_entry;
35608 const char *symfile_addr;
35609 uint64_t symfile_size;
35612 struct jit_descriptor
35615 /* This type should be jit_actions_t, but we use uint32_t
35616 to be explicit about the bitwidth. */
35617 uint32_t action_flag;
35618 struct jit_code_entry *relevant_entry;
35619 struct jit_code_entry *first_entry;
35622 /* GDB puts a breakpoint in this function. */
35623 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
35625 /* Make sure to specify the version statically, because the
35626 debugger may check the version before we can set it. */
35627 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
35630 If the JIT is multi-threaded, then it is important that the JIT synchronize any
35631 modifications to this global data properly, which can easily be done by putting
35632 a global mutex around modifications to these structures.
35634 @node Registering Code
35635 @section Registering Code
35637 To register code with @value{GDBN}, the JIT should follow this protocol:
35641 Generate an object file in memory with symbols and other desired debug
35642 information. The file must include the virtual addresses of the sections.
35645 Create a code entry for the file, which gives the start and size of the symbol
35649 Add it to the linked list in the JIT descriptor.
35652 Point the relevant_entry field of the descriptor at the entry.
35655 Set @code{action_flag} to @code{JIT_REGISTER} and call
35656 @code{__jit_debug_register_code}.
35659 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
35660 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
35661 new code. However, the linked list must still be maintained in order to allow
35662 @value{GDBN} to attach to a running process and still find the symbol files.
35664 @node Unregistering Code
35665 @section Unregistering Code
35667 If code is freed, then the JIT should use the following protocol:
35671 Remove the code entry corresponding to the code from the linked list.
35674 Point the @code{relevant_entry} field of the descriptor at the code entry.
35677 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
35678 @code{__jit_debug_register_code}.
35681 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
35682 and the JIT will leak the memory used for the associated symbol files.
35684 @node Custom Debug Info
35685 @section Custom Debug Info
35686 @cindex custom JIT debug info
35687 @cindex JIT debug info reader
35689 Generating debug information in platform-native file formats (like ELF
35690 or COFF) may be an overkill for JIT compilers; especially if all the
35691 debug info is used for is displaying a meaningful backtrace. The
35692 issue can be resolved by having the JIT writers decide on a debug info
35693 format and also provide a reader that parses the debug info generated
35694 by the JIT compiler. This section gives a brief overview on writing
35695 such a parser. More specific details can be found in the source file
35696 @file{gdb/jit-reader.in}, which is also installed as a header at
35697 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
35699 The reader is implemented as a shared object (so this functionality is
35700 not available on platforms which don't allow loading shared objects at
35701 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
35702 @code{jit-reader-unload} are provided, to be used to load and unload
35703 the readers from a preconfigured directory. Once loaded, the shared
35704 object is used the parse the debug information emitted by the JIT
35708 * Using JIT Debug Info Readers:: How to use supplied readers correctly
35709 * Writing JIT Debug Info Readers:: Creating a debug-info reader
35712 @node Using JIT Debug Info Readers
35713 @subsection Using JIT Debug Info Readers
35714 @kindex jit-reader-load
35715 @kindex jit-reader-unload
35717 Readers can be loaded and unloaded using the @code{jit-reader-load}
35718 and @code{jit-reader-unload} commands.
35721 @item jit-reader-load @var{reader}
35722 Load the JIT reader named @var{reader}, which is a shared
35723 object specified as either an absolute or a relative file name. In
35724 the latter case, @value{GDBN} will try to load the reader from a
35725 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
35726 system (here @var{libdir} is the system library directory, often
35727 @file{/usr/local/lib}).
35729 Only one reader can be active at a time; trying to load a second
35730 reader when one is already loaded will result in @value{GDBN}
35731 reporting an error. A new JIT reader can be loaded by first unloading
35732 the current one using @code{jit-reader-unload} and then invoking
35733 @code{jit-reader-load}.
35735 @item jit-reader-unload
35736 Unload the currently loaded JIT reader.
35740 @node Writing JIT Debug Info Readers
35741 @subsection Writing JIT Debug Info Readers
35742 @cindex writing JIT debug info readers
35744 As mentioned, a reader is essentially a shared object conforming to a
35745 certain ABI. This ABI is described in @file{jit-reader.h}.
35747 @file{jit-reader.h} defines the structures, macros and functions
35748 required to write a reader. It is installed (along with
35749 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
35750 the system include directory.
35752 Readers need to be released under a GPL compatible license. A reader
35753 can be declared as released under such a license by placing the macro
35754 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
35756 The entry point for readers is the symbol @code{gdb_init_reader},
35757 which is expected to be a function with the prototype
35759 @findex gdb_init_reader
35761 extern struct gdb_reader_funcs *gdb_init_reader (void);
35764 @cindex @code{struct gdb_reader_funcs}
35766 @code{struct gdb_reader_funcs} contains a set of pointers to callback
35767 functions. These functions are executed to read the debug info
35768 generated by the JIT compiler (@code{read}), to unwind stack frames
35769 (@code{unwind}) and to create canonical frame IDs
35770 (@code{get_Frame_id}). It also has a callback that is called when the
35771 reader is being unloaded (@code{destroy}). The struct looks like this
35774 struct gdb_reader_funcs
35776 /* Must be set to GDB_READER_INTERFACE_VERSION. */
35777 int reader_version;
35779 /* For use by the reader. */
35782 gdb_read_debug_info *read;
35783 gdb_unwind_frame *unwind;
35784 gdb_get_frame_id *get_frame_id;
35785 gdb_destroy_reader *destroy;
35789 @cindex @code{struct gdb_symbol_callbacks}
35790 @cindex @code{struct gdb_unwind_callbacks}
35792 The callbacks are provided with another set of callbacks by
35793 @value{GDBN} to do their job. For @code{read}, these callbacks are
35794 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
35795 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
35796 @code{struct gdb_symbol_callbacks} has callbacks to create new object
35797 files and new symbol tables inside those object files. @code{struct
35798 gdb_unwind_callbacks} has callbacks to read registers off the current
35799 frame and to write out the values of the registers in the previous
35800 frame. Both have a callback (@code{target_read}) to read bytes off the
35801 target's address space.
35803 @node In-Process Agent
35804 @chapter In-Process Agent
35805 @cindex debugging agent
35806 The traditional debugging model is conceptually low-speed, but works fine,
35807 because most bugs can be reproduced in debugging-mode execution. However,
35808 as multi-core or many-core processors are becoming mainstream, and
35809 multi-threaded programs become more and more popular, there should be more
35810 and more bugs that only manifest themselves at normal-mode execution, for
35811 example, thread races, because debugger's interference with the program's
35812 timing may conceal the bugs. On the other hand, in some applications,
35813 it is not feasible for the debugger to interrupt the program's execution
35814 long enough for the developer to learn anything helpful about its behavior.
35815 If the program's correctness depends on its real-time behavior, delays
35816 introduced by a debugger might cause the program to fail, even when the
35817 code itself is correct. It is useful to be able to observe the program's
35818 behavior without interrupting it.
35820 Therefore, traditional debugging model is too intrusive to reproduce
35821 some bugs. In order to reduce the interference with the program, we can
35822 reduce the number of operations performed by debugger. The
35823 @dfn{In-Process Agent}, a shared library, is running within the same
35824 process with inferior, and is able to perform some debugging operations
35825 itself. As a result, debugger is only involved when necessary, and
35826 performance of debugging can be improved accordingly. Note that
35827 interference with program can be reduced but can't be removed completely,
35828 because the in-process agent will still stop or slow down the program.
35830 The in-process agent can interpret and execute Agent Expressions
35831 (@pxref{Agent Expressions}) during performing debugging operations. The
35832 agent expressions can be used for different purposes, such as collecting
35833 data in tracepoints, and condition evaluation in breakpoints.
35835 @anchor{Control Agent}
35836 You can control whether the in-process agent is used as an aid for
35837 debugging with the following commands:
35840 @kindex set agent on
35842 Causes the in-process agent to perform some operations on behalf of the
35843 debugger. Just which operations requested by the user will be done
35844 by the in-process agent depends on the its capabilities. For example,
35845 if you request to evaluate breakpoint conditions in the in-process agent,
35846 and the in-process agent has such capability as well, then breakpoint
35847 conditions will be evaluated in the in-process agent.
35849 @kindex set agent off
35850 @item set agent off
35851 Disables execution of debugging operations by the in-process agent. All
35852 of the operations will be performed by @value{GDBN}.
35856 Display the current setting of execution of debugging operations by
35857 the in-process agent.
35861 * In-Process Agent Protocol::
35864 @node In-Process Agent Protocol
35865 @section In-Process Agent Protocol
35866 @cindex in-process agent protocol
35868 The in-process agent is able to communicate with both @value{GDBN} and
35869 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
35870 used for communications between @value{GDBN} or GDBserver and the IPA.
35871 In general, @value{GDBN} or GDBserver sends commands
35872 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
35873 in-process agent replies back with the return result of the command, or
35874 some other information. The data sent to in-process agent is composed
35875 of primitive data types, such as 4-byte or 8-byte type, and composite
35876 types, which are called objects (@pxref{IPA Protocol Objects}).
35879 * IPA Protocol Objects::
35880 * IPA Protocol Commands::
35883 @node IPA Protocol Objects
35884 @subsection IPA Protocol Objects
35885 @cindex ipa protocol objects
35887 The commands sent to and results received from agent may contain some
35888 complex data types called @dfn{objects}.
35890 The in-process agent is running on the same machine with @value{GDBN}
35891 or GDBserver, so it doesn't have to handle as much differences between
35892 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
35893 However, there are still some differences of two ends in two processes:
35897 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
35898 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
35900 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
35901 GDBserver is compiled with one, and in-process agent is compiled with
35905 Here are the IPA Protocol Objects:
35909 agent expression object. It represents an agent expression
35910 (@pxref{Agent Expressions}).
35911 @anchor{agent expression object}
35913 tracepoint action object. It represents a tracepoint action
35914 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
35915 memory, static trace data and to evaluate expression.
35916 @anchor{tracepoint action object}
35918 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
35919 @anchor{tracepoint object}
35923 The following table describes important attributes of each IPA protocol
35926 @multitable @columnfractions .30 .20 .50
35927 @headitem Name @tab Size @tab Description
35928 @item @emph{agent expression object} @tab @tab
35929 @item length @tab 4 @tab length of bytes code
35930 @item byte code @tab @var{length} @tab contents of byte code
35931 @item @emph{tracepoint action for collecting memory} @tab @tab
35932 @item 'M' @tab 1 @tab type of tracepoint action
35933 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
35934 address of the lowest byte to collect, otherwise @var{addr} is the offset
35935 of @var{basereg} for memory collecting.
35936 @item len @tab 8 @tab length of memory for collecting
35937 @item basereg @tab 4 @tab the register number containing the starting
35938 memory address for collecting.
35939 @item @emph{tracepoint action for collecting registers} @tab @tab
35940 @item 'R' @tab 1 @tab type of tracepoint action
35941 @item @emph{tracepoint action for collecting static trace data} @tab @tab
35942 @item 'L' @tab 1 @tab type of tracepoint action
35943 @item @emph{tracepoint action for expression evaluation} @tab @tab
35944 @item 'X' @tab 1 @tab type of tracepoint action
35945 @item agent expression @tab length of @tab @ref{agent expression object}
35946 @item @emph{tracepoint object} @tab @tab
35947 @item number @tab 4 @tab number of tracepoint
35948 @item address @tab 8 @tab address of tracepoint inserted on
35949 @item type @tab 4 @tab type of tracepoint
35950 @item enabled @tab 1 @tab enable or disable of tracepoint
35951 @item step_count @tab 8 @tab step
35952 @item pass_count @tab 8 @tab pass
35953 @item numactions @tab 4 @tab number of tracepoint actions
35954 @item hit count @tab 8 @tab hit count
35955 @item trace frame usage @tab 8 @tab trace frame usage
35956 @item compiled_cond @tab 8 @tab compiled condition
35957 @item orig_size @tab 8 @tab orig size
35958 @item condition @tab 4 if condition is NULL otherwise length of
35959 @ref{agent expression object}
35960 @tab zero if condition is NULL, otherwise is
35961 @ref{agent expression object}
35962 @item actions @tab variable
35963 @tab numactions number of @ref{tracepoint action object}
35966 @node IPA Protocol Commands
35967 @subsection IPA Protocol Commands
35968 @cindex ipa protocol commands
35970 The spaces in each command are delimiters to ease reading this commands
35971 specification. They don't exist in real commands.
35975 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
35976 Installs a new fast tracepoint described by @var{tracepoint_object}
35977 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
35978 head of @dfn{jumppad}, which is used to jump to data collection routine
35983 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
35984 @var{target_address} is address of tracepoint in the inferior.
35985 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
35986 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
35987 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
35988 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
35995 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
35996 is about to kill inferiors.
36004 @item probe_marker_at:@var{address}
36005 Asks in-process agent to probe the marker at @var{address}.
36012 @item unprobe_marker_at:@var{address}
36013 Asks in-process agent to unprobe the marker at @var{address}.
36017 @chapter Reporting Bugs in @value{GDBN}
36018 @cindex bugs in @value{GDBN}
36019 @cindex reporting bugs in @value{GDBN}
36021 Your bug reports play an essential role in making @value{GDBN} reliable.
36023 Reporting a bug may help you by bringing a solution to your problem, or it
36024 may not. But in any case the principal function of a bug report is to help
36025 the entire community by making the next version of @value{GDBN} work better. Bug
36026 reports are your contribution to the maintenance of @value{GDBN}.
36028 In order for a bug report to serve its purpose, you must include the
36029 information that enables us to fix the bug.
36032 * Bug Criteria:: Have you found a bug?
36033 * Bug Reporting:: How to report bugs
36037 @section Have You Found a Bug?
36038 @cindex bug criteria
36040 If you are not sure whether you have found a bug, here are some guidelines:
36043 @cindex fatal signal
36044 @cindex debugger crash
36045 @cindex crash of debugger
36047 If the debugger gets a fatal signal, for any input whatever, that is a
36048 @value{GDBN} bug. Reliable debuggers never crash.
36050 @cindex error on valid input
36052 If @value{GDBN} produces an error message for valid input, that is a
36053 bug. (Note that if you're cross debugging, the problem may also be
36054 somewhere in the connection to the target.)
36056 @cindex invalid input
36058 If @value{GDBN} does not produce an error message for invalid input,
36059 that is a bug. However, you should note that your idea of
36060 ``invalid input'' might be our idea of ``an extension'' or ``support
36061 for traditional practice''.
36064 If you are an experienced user of debugging tools, your suggestions
36065 for improvement of @value{GDBN} are welcome in any case.
36068 @node Bug Reporting
36069 @section How to Report Bugs
36070 @cindex bug reports
36071 @cindex @value{GDBN} bugs, reporting
36073 A number of companies and individuals offer support for @sc{gnu} products.
36074 If you obtained @value{GDBN} from a support organization, we recommend you
36075 contact that organization first.
36077 You can find contact information for many support companies and
36078 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
36080 @c should add a web page ref...
36083 @ifset BUGURL_DEFAULT
36084 In any event, we also recommend that you submit bug reports for
36085 @value{GDBN}. The preferred method is to submit them directly using
36086 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
36087 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
36090 @strong{Do not send bug reports to @samp{info-gdb}, or to
36091 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
36092 not want to receive bug reports. Those that do have arranged to receive
36095 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
36096 serves as a repeater. The mailing list and the newsgroup carry exactly
36097 the same messages. Often people think of posting bug reports to the
36098 newsgroup instead of mailing them. This appears to work, but it has one
36099 problem which can be crucial: a newsgroup posting often lacks a mail
36100 path back to the sender. Thus, if we need to ask for more information,
36101 we may be unable to reach you. For this reason, it is better to send
36102 bug reports to the mailing list.
36104 @ifclear BUGURL_DEFAULT
36105 In any event, we also recommend that you submit bug reports for
36106 @value{GDBN} to @value{BUGURL}.
36110 The fundamental principle of reporting bugs usefully is this:
36111 @strong{report all the facts}. If you are not sure whether to state a
36112 fact or leave it out, state it!
36114 Often people omit facts because they think they know what causes the
36115 problem and assume that some details do not matter. Thus, you might
36116 assume that the name of the variable you use in an example does not matter.
36117 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
36118 stray memory reference which happens to fetch from the location where that
36119 name is stored in memory; perhaps, if the name were different, the contents
36120 of that location would fool the debugger into doing the right thing despite
36121 the bug. Play it safe and give a specific, complete example. That is the
36122 easiest thing for you to do, and the most helpful.
36124 Keep in mind that the purpose of a bug report is to enable us to fix the
36125 bug. It may be that the bug has been reported previously, but neither
36126 you nor we can know that unless your bug report is complete and
36129 Sometimes people give a few sketchy facts and ask, ``Does this ring a
36130 bell?'' Those bug reports are useless, and we urge everyone to
36131 @emph{refuse to respond to them} except to chide the sender to report
36134 To enable us to fix the bug, you should include all these things:
36138 The version of @value{GDBN}. @value{GDBN} announces it if you start
36139 with no arguments; you can also print it at any time using @code{show
36142 Without this, we will not know whether there is any point in looking for
36143 the bug in the current version of @value{GDBN}.
36146 The type of machine you are using, and the operating system name and
36150 The details of the @value{GDBN} build-time configuration.
36151 @value{GDBN} shows these details if you invoke it with the
36152 @option{--configuration} command-line option, or if you type
36153 @code{show configuration} at @value{GDBN}'s prompt.
36156 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
36157 ``@value{GCC}--2.8.1''.
36160 What compiler (and its version) was used to compile the program you are
36161 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
36162 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
36163 to get this information; for other compilers, see the documentation for
36167 The command arguments you gave the compiler to compile your example and
36168 observe the bug. For example, did you use @samp{-O}? To guarantee
36169 you will not omit something important, list them all. A copy of the
36170 Makefile (or the output from make) is sufficient.
36172 If we were to try to guess the arguments, we would probably guess wrong
36173 and then we might not encounter the bug.
36176 A complete input script, and all necessary source files, that will
36180 A description of what behavior you observe that you believe is
36181 incorrect. For example, ``It gets a fatal signal.''
36183 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
36184 will certainly notice it. But if the bug is incorrect output, we might
36185 not notice unless it is glaringly wrong. You might as well not give us
36186 a chance to make a mistake.
36188 Even if the problem you experience is a fatal signal, you should still
36189 say so explicitly. Suppose something strange is going on, such as, your
36190 copy of @value{GDBN} is out of synch, or you have encountered a bug in
36191 the C library on your system. (This has happened!) Your copy might
36192 crash and ours would not. If you told us to expect a crash, then when
36193 ours fails to crash, we would know that the bug was not happening for
36194 us. If you had not told us to expect a crash, then we would not be able
36195 to draw any conclusion from our observations.
36198 @cindex recording a session script
36199 To collect all this information, you can use a session recording program
36200 such as @command{script}, which is available on many Unix systems.
36201 Just run your @value{GDBN} session inside @command{script} and then
36202 include the @file{typescript} file with your bug report.
36204 Another way to record a @value{GDBN} session is to run @value{GDBN}
36205 inside Emacs and then save the entire buffer to a file.
36208 If you wish to suggest changes to the @value{GDBN} source, send us context
36209 diffs. If you even discuss something in the @value{GDBN} source, refer to
36210 it by context, not by line number.
36212 The line numbers in our development sources will not match those in your
36213 sources. Your line numbers would convey no useful information to us.
36217 Here are some things that are not necessary:
36221 A description of the envelope of the bug.
36223 Often people who encounter a bug spend a lot of time investigating
36224 which changes to the input file will make the bug go away and which
36225 changes will not affect it.
36227 This is often time consuming and not very useful, because the way we
36228 will find the bug is by running a single example under the debugger
36229 with breakpoints, not by pure deduction from a series of examples.
36230 We recommend that you save your time for something else.
36232 Of course, if you can find a simpler example to report @emph{instead}
36233 of the original one, that is a convenience for us. Errors in the
36234 output will be easier to spot, running under the debugger will take
36235 less time, and so on.
36237 However, simplification is not vital; if you do not want to do this,
36238 report the bug anyway and send us the entire test case you used.
36241 A patch for the bug.
36243 A patch for the bug does help us if it is a good one. But do not omit
36244 the necessary information, such as the test case, on the assumption that
36245 a patch is all we need. We might see problems with your patch and decide
36246 to fix the problem another way, or we might not understand it at all.
36248 Sometimes with a program as complicated as @value{GDBN} it is very hard to
36249 construct an example that will make the program follow a certain path
36250 through the code. If you do not send us the example, we will not be able
36251 to construct one, so we will not be able to verify that the bug is fixed.
36253 And if we cannot understand what bug you are trying to fix, or why your
36254 patch should be an improvement, we will not install it. A test case will
36255 help us to understand.
36258 A guess about what the bug is or what it depends on.
36260 Such guesses are usually wrong. Even we cannot guess right about such
36261 things without first using the debugger to find the facts.
36264 @c The readline documentation is distributed with the readline code
36265 @c and consists of the two following files:
36268 @c Use -I with makeinfo to point to the appropriate directory,
36269 @c environment var TEXINPUTS with TeX.
36270 @ifclear SYSTEM_READLINE
36271 @include rluser.texi
36272 @include hsuser.texi
36276 @appendix In Memoriam
36278 The @value{GDBN} project mourns the loss of the following long-time
36283 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
36284 to Free Software in general. Outside of @value{GDBN}, he was known in
36285 the Amiga world for his series of Fish Disks, and the GeekGadget project.
36287 @item Michael Snyder
36288 Michael was one of the Global Maintainers of the @value{GDBN} project,
36289 with contributions recorded as early as 1996, until 2011. In addition
36290 to his day to day participation, he was a large driving force behind
36291 adding Reverse Debugging to @value{GDBN}.
36294 Beyond their technical contributions to the project, they were also
36295 enjoyable members of the Free Software Community. We will miss them.
36297 @node Formatting Documentation
36298 @appendix Formatting Documentation
36300 @cindex @value{GDBN} reference card
36301 @cindex reference card
36302 The @value{GDBN} 4 release includes an already-formatted reference card, ready
36303 for printing with PostScript or Ghostscript, in the @file{gdb}
36304 subdirectory of the main source directory@footnote{In
36305 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
36306 release.}. If you can use PostScript or Ghostscript with your printer,
36307 you can print the reference card immediately with @file{refcard.ps}.
36309 The release also includes the source for the reference card. You
36310 can format it, using @TeX{}, by typing:
36316 The @value{GDBN} reference card is designed to print in @dfn{landscape}
36317 mode on US ``letter'' size paper;
36318 that is, on a sheet 11 inches wide by 8.5 inches
36319 high. You will need to specify this form of printing as an option to
36320 your @sc{dvi} output program.
36322 @cindex documentation
36324 All the documentation for @value{GDBN} comes as part of the machine-readable
36325 distribution. The documentation is written in Texinfo format, which is
36326 a documentation system that uses a single source file to produce both
36327 on-line information and a printed manual. You can use one of the Info
36328 formatting commands to create the on-line version of the documentation
36329 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
36331 @value{GDBN} includes an already formatted copy of the on-line Info
36332 version of this manual in the @file{gdb} subdirectory. The main Info
36333 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
36334 subordinate files matching @samp{gdb.info*} in the same directory. If
36335 necessary, you can print out these files, or read them with any editor;
36336 but they are easier to read using the @code{info} subsystem in @sc{gnu}
36337 Emacs or the standalone @code{info} program, available as part of the
36338 @sc{gnu} Texinfo distribution.
36340 If you want to format these Info files yourself, you need one of the
36341 Info formatting programs, such as @code{texinfo-format-buffer} or
36344 If you have @code{makeinfo} installed, and are in the top level
36345 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
36346 version @value{GDBVN}), you can make the Info file by typing:
36353 If you want to typeset and print copies of this manual, you need @TeX{},
36354 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
36355 Texinfo definitions file.
36357 @TeX{} is a typesetting program; it does not print files directly, but
36358 produces output files called @sc{dvi} files. To print a typeset
36359 document, you need a program to print @sc{dvi} files. If your system
36360 has @TeX{} installed, chances are it has such a program. The precise
36361 command to use depends on your system; @kbd{lpr -d} is common; another
36362 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
36363 require a file name without any extension or a @samp{.dvi} extension.
36365 @TeX{} also requires a macro definitions file called
36366 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
36367 written in Texinfo format. On its own, @TeX{} cannot either read or
36368 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
36369 and is located in the @file{gdb-@var{version-number}/texinfo}
36372 If you have @TeX{} and a @sc{dvi} printer program installed, you can
36373 typeset and print this manual. First switch to the @file{gdb}
36374 subdirectory of the main source directory (for example, to
36375 @file{gdb-@value{GDBVN}/gdb}) and type:
36381 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
36383 @node Installing GDB
36384 @appendix Installing @value{GDBN}
36385 @cindex installation
36388 * Requirements:: Requirements for building @value{GDBN}
36389 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
36390 * Separate Objdir:: Compiling @value{GDBN} in another directory
36391 * Config Names:: Specifying names for hosts and targets
36392 * Configure Options:: Summary of options for configure
36393 * System-wide configuration:: Having a system-wide init file
36397 @section Requirements for Building @value{GDBN}
36398 @cindex building @value{GDBN}, requirements for
36400 Building @value{GDBN} requires various tools and packages to be available.
36401 Other packages will be used only if they are found.
36403 @heading Tools/Packages Necessary for Building @value{GDBN}
36405 @item C@t{++}11 compiler
36406 @value{GDBN} is written in C@t{++}11. It should be buildable with any
36407 recent C@t{++}11 compiler, e.g.@: GCC.
36410 @value{GDBN}'s build system relies on features only found in the GNU
36411 make program. Other variants of @code{make} will not work.
36414 @heading Tools/Packages Optional for Building @value{GDBN}
36418 @value{GDBN} can use the Expat XML parsing library. This library may be
36419 included with your operating system distribution; if it is not, you
36420 can get the latest version from @url{http://expat.sourceforge.net}.
36421 The @file{configure} script will search for this library in several
36422 standard locations; if it is installed in an unusual path, you can
36423 use the @option{--with-libexpat-prefix} option to specify its location.
36429 Remote protocol memory maps (@pxref{Memory Map Format})
36431 Target descriptions (@pxref{Target Descriptions})
36433 Remote shared library lists (@xref{Library List Format},
36434 or alternatively @pxref{Library List Format for SVR4 Targets})
36436 MS-Windows shared libraries (@pxref{Shared Libraries})
36438 Traceframe info (@pxref{Traceframe Info Format})
36440 Branch trace (@pxref{Branch Trace Format},
36441 @pxref{Branch Trace Configuration Format})
36445 @value{GDBN} can be scripted using GNU Guile. @xref{Guile}. By
36446 default, @value{GDBN} will be compiled if the Guile libraries are
36447 installed and are found by @file{configure}. You can use the
36448 @code{--with-guile} option to request Guile, and pass either the Guile
36449 version number or the file name of the relevant @code{pkg-config}
36450 program to choose a particular version of Guile.
36453 @value{GDBN}'s features related to character sets (@pxref{Character
36454 Sets}) require a functioning @code{iconv} implementation. If you are
36455 on a GNU system, then this is provided by the GNU C Library. Some
36456 other systems also provide a working @code{iconv}.
36458 If @value{GDBN} is using the @code{iconv} program which is installed
36459 in a non-standard place, you will need to tell @value{GDBN} where to
36460 find it. This is done with @option{--with-iconv-bin} which specifies
36461 the directory that contains the @code{iconv} program. This program is
36462 run in order to make a list of the available character sets.
36464 On systems without @code{iconv}, you can install GNU Libiconv. If
36465 Libiconv is installed in a standard place, @value{GDBN} will
36466 automatically use it if it is needed. If you have previously
36467 installed Libiconv in a non-standard place, you can use the
36468 @option{--with-libiconv-prefix} option to @file{configure}.
36470 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
36471 arrange to build Libiconv if a directory named @file{libiconv} appears
36472 in the top-most source directory. If Libiconv is built this way, and
36473 if the operating system does not provide a suitable @code{iconv}
36474 implementation, then the just-built library will automatically be used
36475 by @value{GDBN}. One easy way to set this up is to download GNU
36476 Libiconv, unpack it inside the top-level directory of the @value{GDBN}
36477 source tree, and then rename the directory holding the Libiconv source
36478 code to @samp{libiconv}.
36481 @value{GDBN} can support debugging sections that are compressed with
36482 the LZMA library. @xref{MiniDebugInfo}. If this library is not
36483 included with your operating system, you can find it in the xz package
36484 at @url{http://tukaani.org/xz/}. If the LZMA library is available in
36485 the usual place, then the @file{configure} script will use it
36486 automatically. If it is installed in an unusual path, you can use the
36487 @option{--with-lzma-prefix} option to specify its location.
36491 @value{GDBN} can use the GNU MPFR multiple-precision floating-point
36492 library. This library may be included with your operating system
36493 distribution; if it is not, you can get the latest version from
36494 @url{http://www.mpfr.org}. The @file{configure} script will search
36495 for this library in several standard locations; if it is installed
36496 in an unusual path, you can use the @option{--with-libmpfr-prefix}
36497 option to specify its location.
36499 GNU MPFR is used to emulate target floating-point arithmetic during
36500 expression evaluation when the target uses different floating-point
36501 formats than the host. If GNU MPFR it is not available, @value{GDBN}
36502 will fall back to using host floating-point arithmetic.
36505 @value{GDBN} can be scripted using Python language. @xref{Python}.
36506 By default, @value{GDBN} will be compiled if the Python libraries are
36507 installed and are found by @file{configure}. You can use the
36508 @code{--with-python} option to request Python, and pass either the
36509 file name of the relevant @code{python} executable, or the name of the
36510 directory in which Python is installed, to choose a particular
36511 installation of Python.
36514 @cindex compressed debug sections
36515 @value{GDBN} will use the @samp{zlib} library, if available, to read
36516 compressed debug sections. Some linkers, such as GNU gold, are capable
36517 of producing binaries with compressed debug sections. If @value{GDBN}
36518 is compiled with @samp{zlib}, it will be able to read the debug
36519 information in such binaries.
36521 The @samp{zlib} library is likely included with your operating system
36522 distribution; if it is not, you can get the latest version from
36523 @url{http://zlib.net}.
36526 @node Running Configure
36527 @section Invoking the @value{GDBN} @file{configure} Script
36528 @cindex configuring @value{GDBN}
36529 @value{GDBN} comes with a @file{configure} script that automates the process
36530 of preparing @value{GDBN} for installation; you can then use @code{make} to
36531 build the @code{gdb} program.
36533 @c irrelevant in info file; it's as current as the code it lives with.
36534 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
36535 look at the @file{README} file in the sources; we may have improved the
36536 installation procedures since publishing this manual.}
36539 The @value{GDBN} distribution includes all the source code you need for
36540 @value{GDBN} in a single directory, whose name is usually composed by
36541 appending the version number to @samp{gdb}.
36543 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
36544 @file{gdb-@value{GDBVN}} directory. That directory contains:
36547 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
36548 script for configuring @value{GDBN} and all its supporting libraries
36550 @item gdb-@value{GDBVN}/gdb
36551 the source specific to @value{GDBN} itself
36553 @item gdb-@value{GDBVN}/bfd
36554 source for the Binary File Descriptor library
36556 @item gdb-@value{GDBVN}/include
36557 @sc{gnu} include files
36559 @item gdb-@value{GDBVN}/libiberty
36560 source for the @samp{-liberty} free software library
36562 @item gdb-@value{GDBVN}/opcodes
36563 source for the library of opcode tables and disassemblers
36565 @item gdb-@value{GDBVN}/readline
36566 source for the @sc{gnu} command-line interface
36569 There may be other subdirectories as well.
36571 The simplest way to configure and build @value{GDBN} is to run @file{configure}
36572 from the @file{gdb-@var{version-number}} source directory, which in
36573 this example is the @file{gdb-@value{GDBVN}} directory.
36575 First switch to the @file{gdb-@var{version-number}} source directory
36576 if you are not already in it; then run @file{configure}. Pass the
36577 identifier for the platform on which @value{GDBN} will run as an
36583 cd gdb-@value{GDBVN}
36588 Running @samp{configure} and then running @code{make} builds the
36589 included supporting libraries, then @code{gdb} itself. The configured
36590 source files, and the binaries, are left in the corresponding source
36594 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
36595 system does not recognize this automatically when you run a different
36596 shell, you may need to run @code{sh} on it explicitly:
36602 You should run the @file{configure} script from the top directory in the
36603 source tree, the @file{gdb-@var{version-number}} directory. If you run
36604 @file{configure} from one of the subdirectories, you will configure only
36605 that subdirectory. That is usually not what you want. In particular,
36606 if you run the first @file{configure} from the @file{gdb} subdirectory
36607 of the @file{gdb-@var{version-number}} directory, you will omit the
36608 configuration of @file{bfd}, @file{readline}, and other sibling
36609 directories of the @file{gdb} subdirectory. This leads to build errors
36610 about missing include files such as @file{bfd/bfd.h}.
36612 You can install @code{@value{GDBN}} anywhere. The best way to do this
36613 is to pass the @code{--prefix} option to @code{configure}, and then
36614 install it with @code{make install}.
36616 @node Separate Objdir
36617 @section Compiling @value{GDBN} in Another Directory
36619 If you want to run @value{GDBN} versions for several host or target machines,
36620 you need a different @code{gdb} compiled for each combination of
36621 host and target. @file{configure} is designed to make this easy by
36622 allowing you to generate each configuration in a separate subdirectory,
36623 rather than in the source directory. If your @code{make} program
36624 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
36625 @code{make} in each of these directories builds the @code{gdb}
36626 program specified there.
36628 To build @code{gdb} in a separate directory, run @file{configure}
36629 with the @samp{--srcdir} option to specify where to find the source.
36630 (You also need to specify a path to find @file{configure}
36631 itself from your working directory. If the path to @file{configure}
36632 would be the same as the argument to @samp{--srcdir}, you can leave out
36633 the @samp{--srcdir} option; it is assumed.)
36635 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
36636 separate directory for a Sun 4 like this:
36640 cd gdb-@value{GDBVN}
36643 ../gdb-@value{GDBVN}/configure
36648 When @file{configure} builds a configuration using a remote source
36649 directory, it creates a tree for the binaries with the same structure
36650 (and using the same names) as the tree under the source directory. In
36651 the example, you'd find the Sun 4 library @file{libiberty.a} in the
36652 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
36653 @file{gdb-sun4/gdb}.
36655 Make sure that your path to the @file{configure} script has just one
36656 instance of @file{gdb} in it. If your path to @file{configure} looks
36657 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
36658 one subdirectory of @value{GDBN}, not the whole package. This leads to
36659 build errors about missing include files such as @file{bfd/bfd.h}.
36661 One popular reason to build several @value{GDBN} configurations in separate
36662 directories is to configure @value{GDBN} for cross-compiling (where
36663 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
36664 programs that run on another machine---the @dfn{target}).
36665 You specify a cross-debugging target by
36666 giving the @samp{--target=@var{target}} option to @file{configure}.
36668 When you run @code{make} to build a program or library, you must run
36669 it in a configured directory---whatever directory you were in when you
36670 called @file{configure} (or one of its subdirectories).
36672 The @code{Makefile} that @file{configure} generates in each source
36673 directory also runs recursively. If you type @code{make} in a source
36674 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
36675 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
36676 will build all the required libraries, and then build GDB.
36678 When you have multiple hosts or targets configured in separate
36679 directories, you can run @code{make} on them in parallel (for example,
36680 if they are NFS-mounted on each of the hosts); they will not interfere
36684 @section Specifying Names for Hosts and Targets
36686 The specifications used for hosts and targets in the @file{configure}
36687 script are based on a three-part naming scheme, but some short predefined
36688 aliases are also supported. The full naming scheme encodes three pieces
36689 of information in the following pattern:
36692 @var{architecture}-@var{vendor}-@var{os}
36695 For example, you can use the alias @code{sun4} as a @var{host} argument,
36696 or as the value for @var{target} in a @code{--target=@var{target}}
36697 option. The equivalent full name is @samp{sparc-sun-sunos4}.
36699 The @file{configure} script accompanying @value{GDBN} does not provide
36700 any query facility to list all supported host and target names or
36701 aliases. @file{configure} calls the Bourne shell script
36702 @code{config.sub} to map abbreviations to full names; you can read the
36703 script, if you wish, or you can use it to test your guesses on
36704 abbreviations---for example:
36707 % sh config.sub i386-linux
36709 % sh config.sub alpha-linux
36710 alpha-unknown-linux-gnu
36711 % sh config.sub hp9k700
36713 % sh config.sub sun4
36714 sparc-sun-sunos4.1.1
36715 % sh config.sub sun3
36716 m68k-sun-sunos4.1.1
36717 % sh config.sub i986v
36718 Invalid configuration `i986v': machine `i986v' not recognized
36722 @code{config.sub} is also distributed in the @value{GDBN} source
36723 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
36725 @node Configure Options
36726 @section @file{configure} Options
36728 Here is a summary of the @file{configure} options and arguments that
36729 are most often useful for building @value{GDBN}. @file{configure}
36730 also has several other options not listed here. @inforef{Running
36731 configure scripts,,autoconf.info}, for a full
36732 explanation of @file{configure}.
36735 configure @r{[}--help@r{]}
36736 @r{[}--prefix=@var{dir}@r{]}
36737 @r{[}--exec-prefix=@var{dir}@r{]}
36738 @r{[}--srcdir=@var{dirname}@r{]}
36739 @r{[}--target=@var{target}@r{]}
36743 You may introduce options with a single @samp{-} rather than
36744 @samp{--} if you prefer; but you may abbreviate option names if you use
36749 Display a quick summary of how to invoke @file{configure}.
36751 @item --prefix=@var{dir}
36752 Configure the source to install programs and files under directory
36755 @item --exec-prefix=@var{dir}
36756 Configure the source to install programs under directory
36759 @c avoid splitting the warning from the explanation:
36761 @item --srcdir=@var{dirname}
36762 Use this option to make configurations in directories separate from the
36763 @value{GDBN} source directories. Among other things, you can use this to
36764 build (or maintain) several configurations simultaneously, in separate
36765 directories. @file{configure} writes configuration-specific files in
36766 the current directory, but arranges for them to use the source in the
36767 directory @var{dirname}. @file{configure} creates directories under
36768 the working directory in parallel to the source directories below
36771 @item --target=@var{target}
36772 Configure @value{GDBN} for cross-debugging programs running on the specified
36773 @var{target}. Without this option, @value{GDBN} is configured to debug
36774 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
36776 There is no convenient way to generate a list of all available
36777 targets. Also see the @code{--enable-targets} option, below.
36780 There are many other options that are specific to @value{GDBN}. This
36781 lists just the most common ones; there are some very specialized
36782 options not described here.
36785 @item --enable-targets=@r{[}@var{target}@r{]}@dots{}
36786 @itemx --enable-targets=all
36787 Configure @value{GDBN} for cross-debugging programs running on the
36788 specified list of targets. The special value @samp{all} configures
36789 @value{GDBN} for debugging programs running on any target it supports.
36791 @item --with-gdb-datadir=@var{path}
36792 Set the @value{GDBN}-specific data directory. @value{GDBN} will look
36793 here for certain supporting files or scripts. This defaults to the
36794 @file{gdb} subdirectory of @samp{datadi} (which can be set using
36797 @item --with-relocated-sources=@var{dir}
36798 Sets up the default source path substitution rule so that directory
36799 names recorded in debug information will be automatically adjusted for
36800 any directory under @var{dir}. @var{dir} should be a subdirectory of
36801 @value{GDBN}'s configured prefix, the one mentioned in the
36802 @code{--prefix} or @code{--exec-prefix} options to configure. This
36803 option is useful if GDB is supposed to be moved to a different place
36806 @item --enable-64-bit-bfd
36807 Enable 64-bit support in BFD on 32-bit hosts.
36809 @item --disable-gdbmi
36810 Build @value{GDBN} without the GDB/MI machine interface
36814 Build @value{GDBN} with the text-mode full-screen user interface
36815 (TUI). Requires a curses library (ncurses and cursesX are also
36818 @item --with-curses
36819 Use the curses library instead of the termcap library, for text-mode
36820 terminal operations.
36822 @item --with-libunwind-ia64
36823 Use the libunwind library for unwinding function call stack on ia64
36824 target platforms. See http://www.nongnu.org/libunwind/index.html for
36827 @item --with-system-readline
36828 Use the readline library installed on the host, rather than the
36829 library supplied as part of @value{GDBN}.
36831 @item --with-system-zlib
36832 Use the zlib library installed on the host, rather than the library
36833 supplied as part of @value{GDBN}.
36836 Build @value{GDBN} with Expat, a library for XML parsing. (Done by
36837 default if libexpat is installed and found at configure time.) This
36838 library is used to read XML files supplied with @value{GDBN}. If it
36839 is unavailable, some features, such as remote protocol memory maps,
36840 target descriptions, and shared library lists, that are based on XML
36841 files, will not be available in @value{GDBN}. If your host does not
36842 have libexpat installed, you can get the latest version from
36843 `http://expat.sourceforge.net'.
36845 @item --with-libiconv-prefix@r{[}=@var{dir}@r{]}
36847 Build @value{GDBN} with GNU libiconv, a character set encoding
36848 conversion library. This is not done by default, as on GNU systems
36849 the @code{iconv} that is built in to the C library is sufficient. If
36850 your host does not have a working @code{iconv}, you can get the latest
36851 version of GNU iconv from `https://www.gnu.org/software/libiconv/'.
36853 @value{GDBN}'s build system also supports building GNU libiconv as
36854 part of the overall build. @xref{Requirements}.
36857 Build @value{GDBN} with LZMA, a compression library. (Done by default
36858 if liblzma is installed and found at configure time.) LZMA is used by
36859 @value{GDBN}'s "mini debuginfo" feature, which is only useful on
36860 platforms using the ELF object file format. If your host does not
36861 have liblzma installed, you can get the latest version from
36862 `https://tukaani.org/xz/'.
36865 Build @value{GDBN} with GNU MPFR, a library for multiple-precision
36866 floating-point computation with correct rounding. (Done by default if
36867 GNU MPFR is installed and found at configure time.) This library is
36868 used to emulate target floating-point arithmetic during expression
36869 evaluation when the target uses different floating-point formats than
36870 the host. If GNU MPFR is not available, @value{GDBN} will fall back
36871 to using host floating-point arithmetic. If your host does not have
36872 GNU MPFR installed, you can get the latest version from
36873 `http://www.mpfr.org'.
36875 @item --with-python@r{[}=@var{python}@r{]}
36876 Build @value{GDBN} with Python scripting support. (Done by default if
36877 libpython is present and found at configure time.) Python makes
36878 @value{GDBN} scripting much more powerful than the restricted CLI
36879 scripting language. If your host does not have Python installed, you
36880 can find it on `http://www.python.org/download/'. The oldest version
36881 of Python supported by GDB is 2.6. The optional argument @var{python}
36882 is used to find the Python headers and libraries. It can be either
36883 the name of a Python executable, or the name of the directory in which
36884 Python is installed.
36886 @item --with-guile[=GUILE]'
36887 Build @value{GDBN} with GNU Guile scripting support. (Done by default
36888 if libguile is present and found at configure time.) If your host
36889 does not have Guile installed, you can find it at
36890 `https://www.gnu.org/software/guile/'. The optional argument GUILE
36891 can be a version number, which will cause @code{configure} to try to
36892 use that version of Guile; or the file name of a @code{pkg-config}
36893 executable, which will be queried to find the information needed to
36894 compile and link against Guile.
36896 @item --without-included-regex
36897 Don't use the regex library included with @value{GDBN} (as part of the
36898 libiberty library). This is the default on hosts with version 2 of
36901 @item --with-sysroot=@var{dir}
36902 Use @var{dir} as the default system root directory for libraries whose
36903 file names begin with @file{/lib}' or @file{/usr/lib'}. (The value of
36904 @var{dir} can be modified at run time by using the @command{set
36905 sysroot} command.) If @var{dir} is under the @value{GDBN} configured
36906 prefix (set with @code{--prefix} or @code{--exec-prefix options}, the
36907 default system root will be automatically adjusted if and when
36908 @value{GDBN} is moved to a different location.
36910 @item --with-system-gdbinit=@var{file}
36911 Configure @value{GDBN} to automatically load a system-wide init file.
36912 @var{file} should be an absolute file name. If @var{file} is in a
36913 directory under the configured prefix, and @value{GDBN} is moved to
36914 another location after being built, the location of the system-wide
36915 init file will be adjusted accordingly.
36917 @item --enable-build-warnings
36918 When building the @value{GDBN} sources, ask the compiler to warn about
36919 any code which looks even vaguely suspicious. It passes many
36920 different warning flags, depending on the exact version of the
36921 compiler you are using.
36923 @item --enable-werror
36924 Treat compiler warnings as werrors. It adds the @code{-Werror} flag
36925 to the compiler, which will fail the compilation if the compiler
36926 outputs any warning messages.
36928 @item --enable-ubsan
36929 Enable the GCC undefined behavior sanitizer. This is disabled by
36930 default, but passing @code{--enable-ubsan=yes} or
36931 @code{--enable-ubsan=auto} to @code{configure} will enable it. The
36932 undefined behavior sanitizer checks for C@t{++} undefined behavior.
36933 It has a performance cost, so if you are looking at @value{GDBN}'s
36934 performance, you should disable it. The undefined behavior sanitizer
36935 was first introduced in GCC 4.9.
36938 @node System-wide configuration
36939 @section System-wide configuration and settings
36940 @cindex system-wide init file
36942 @value{GDBN} can be configured to have a system-wide init file;
36943 this file will be read and executed at startup (@pxref{Startup, , What
36944 @value{GDBN} does during startup}).
36946 Here is the corresponding configure option:
36949 @item --with-system-gdbinit=@var{file}
36950 Specify that the default location of the system-wide init file is
36954 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
36955 it may be subject to relocation. Two possible cases:
36959 If the default location of this init file contains @file{$prefix},
36960 it will be subject to relocation. Suppose that the configure options
36961 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
36962 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
36963 init file is looked for as @file{$install/etc/gdbinit} instead of
36964 @file{$prefix/etc/gdbinit}.
36967 By contrast, if the default location does not contain the prefix,
36968 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
36969 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
36970 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
36971 wherever @value{GDBN} is installed.
36974 If the configured location of the system-wide init file (as given by the
36975 @option{--with-system-gdbinit} option at configure time) is in the
36976 data-directory (as specified by @option{--with-gdb-datadir} at configure
36977 time) or in one of its subdirectories, then @value{GDBN} will look for the
36978 system-wide init file in the directory specified by the
36979 @option{--data-directory} command-line option.
36980 Note that the system-wide init file is only read once, during @value{GDBN}
36981 initialization. If the data-directory is changed after @value{GDBN} has
36982 started with the @code{set data-directory} command, the file will not be
36986 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
36989 @node System-wide Configuration Scripts
36990 @subsection Installed System-wide Configuration Scripts
36991 @cindex system-wide configuration scripts
36993 The @file{system-gdbinit} directory, located inside the data-directory
36994 (as specified by @option{--with-gdb-datadir} at configure time) contains
36995 a number of scripts which can be used as system-wide init files. To
36996 automatically source those scripts at startup, @value{GDBN} should be
36997 configured with @option{--with-system-gdbinit}. Otherwise, any user
36998 should be able to source them by hand as needed.
37000 The following scripts are currently available:
37003 @item @file{elinos.py}
37005 @cindex ELinOS system-wide configuration script
37006 This script is useful when debugging a program on an ELinOS target.
37007 It takes advantage of the environment variables defined in a standard
37008 ELinOS environment in order to determine the location of the system
37009 shared libraries, and then sets the @samp{solib-absolute-prefix}
37010 and @samp{solib-search-path} variables appropriately.
37012 @item @file{wrs-linux.py}
37013 @pindex wrs-linux.py
37014 @cindex Wind River Linux system-wide configuration script
37015 This script is useful when debugging a program on a target running
37016 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
37017 the host-side sysroot used by the target system.
37021 @node Maintenance Commands
37022 @appendix Maintenance Commands
37023 @cindex maintenance commands
37024 @cindex internal commands
37026 In addition to commands intended for @value{GDBN} users, @value{GDBN}
37027 includes a number of commands intended for @value{GDBN} developers,
37028 that are not documented elsewhere in this manual. These commands are
37029 provided here for reference. (For commands that turn on debugging
37030 messages, see @ref{Debugging Output}.)
37033 @kindex maint agent
37034 @kindex maint agent-eval
37035 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
37036 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
37037 Translate the given @var{expression} into remote agent bytecodes.
37038 This command is useful for debugging the Agent Expression mechanism
37039 (@pxref{Agent Expressions}). The @samp{agent} version produces an
37040 expression useful for data collection, such as by tracepoints, while
37041 @samp{maint agent-eval} produces an expression that evaluates directly
37042 to a result. For instance, a collection expression for @code{globa +
37043 globb} will include bytecodes to record four bytes of memory at each
37044 of the addresses of @code{globa} and @code{globb}, while discarding
37045 the result of the addition, while an evaluation expression will do the
37046 addition and return the sum.
37047 If @code{-at} is given, generate remote agent bytecode for @var{location}.
37048 If not, generate remote agent bytecode for current frame PC address.
37050 @kindex maint agent-printf
37051 @item maint agent-printf @var{format},@var{expr},...
37052 Translate the given format string and list of argument expressions
37053 into remote agent bytecodes and display them as a disassembled list.
37054 This command is useful for debugging the agent version of dynamic
37055 printf (@pxref{Dynamic Printf}).
37057 @kindex maint info breakpoints
37058 @item @anchor{maint info breakpoints}maint info breakpoints
37059 Using the same format as @samp{info breakpoints}, display both the
37060 breakpoints you've set explicitly, and those @value{GDBN} is using for
37061 internal purposes. Internal breakpoints are shown with negative
37062 breakpoint numbers. The type column identifies what kind of breakpoint
37067 Normal, explicitly set breakpoint.
37070 Normal, explicitly set watchpoint.
37073 Internal breakpoint, used to handle correctly stepping through
37074 @code{longjmp} calls.
37076 @item longjmp resume
37077 Internal breakpoint at the target of a @code{longjmp}.
37080 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
37083 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
37086 Shared library events.
37090 @kindex maint info btrace
37091 @item maint info btrace
37092 Pint information about raw branch tracing data.
37094 @kindex maint btrace packet-history
37095 @item maint btrace packet-history
37096 Print the raw branch trace packets that are used to compute the
37097 execution history for the @samp{record btrace} command. Both the
37098 information and the format in which it is printed depend on the btrace
37103 For the BTS recording format, print a list of blocks of sequential
37104 code. For each block, the following information is printed:
37108 Newer blocks have higher numbers. The oldest block has number zero.
37109 @item Lowest @samp{PC}
37110 @item Highest @samp{PC}
37114 For the Intel Processor Trace recording format, print a list of
37115 Intel Processor Trace packets. For each packet, the following
37116 information is printed:
37119 @item Packet number
37120 Newer packets have higher numbers. The oldest packet has number zero.
37122 The packet's offset in the trace stream.
37123 @item Packet opcode and payload
37127 @kindex maint btrace clear-packet-history
37128 @item maint btrace clear-packet-history
37129 Discards the cached packet history printed by the @samp{maint btrace
37130 packet-history} command. The history will be computed again when
37133 @kindex maint btrace clear
37134 @item maint btrace clear
37135 Discard the branch trace data. The data will be fetched anew and the
37136 branch trace will be recomputed when needed.
37138 This implicitly truncates the branch trace to a single branch trace
37139 buffer. When updating branch trace incrementally, the branch trace
37140 available to @value{GDBN} may be bigger than a single branch trace
37143 @kindex maint set btrace pt skip-pad
37144 @item maint set btrace pt skip-pad
37145 @kindex maint show btrace pt skip-pad
37146 @item maint show btrace pt skip-pad
37147 Control whether @value{GDBN} will skip PAD packets when computing the
37150 @kindex set displaced-stepping
37151 @kindex show displaced-stepping
37152 @cindex displaced stepping support
37153 @cindex out-of-line single-stepping
37154 @item set displaced-stepping
37155 @itemx show displaced-stepping
37156 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
37157 if the target supports it. Displaced stepping is a way to single-step
37158 over breakpoints without removing them from the inferior, by executing
37159 an out-of-line copy of the instruction that was originally at the
37160 breakpoint location. It is also known as out-of-line single-stepping.
37163 @item set displaced-stepping on
37164 If the target architecture supports it, @value{GDBN} will use
37165 displaced stepping to step over breakpoints.
37167 @item set displaced-stepping off
37168 @value{GDBN} will not use displaced stepping to step over breakpoints,
37169 even if such is supported by the target architecture.
37171 @cindex non-stop mode, and @samp{set displaced-stepping}
37172 @item set displaced-stepping auto
37173 This is the default mode. @value{GDBN} will use displaced stepping
37174 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
37175 architecture supports displaced stepping.
37178 @kindex maint check-psymtabs
37179 @item maint check-psymtabs
37180 Check the consistency of currently expanded psymtabs versus symtabs.
37181 Use this to check, for example, whether a symbol is in one but not the other.
37183 @kindex maint check-symtabs
37184 @item maint check-symtabs
37185 Check the consistency of currently expanded symtabs.
37187 @kindex maint expand-symtabs
37188 @item maint expand-symtabs [@var{regexp}]
37189 Expand symbol tables.
37190 If @var{regexp} is specified, only expand symbol tables for file
37191 names matching @var{regexp}.
37193 @kindex maint set catch-demangler-crashes
37194 @kindex maint show catch-demangler-crashes
37195 @cindex demangler crashes
37196 @item maint set catch-demangler-crashes [on|off]
37197 @itemx maint show catch-demangler-crashes
37198 Control whether @value{GDBN} should attempt to catch crashes in the
37199 symbol name demangler. The default is to attempt to catch crashes.
37200 If enabled, the first time a crash is caught, a core file is created,
37201 the offending symbol is displayed and the user is presented with the
37202 option to terminate the current session.
37204 @kindex maint cplus first_component
37205 @item maint cplus first_component @var{name}
37206 Print the first C@t{++} class/namespace component of @var{name}.
37208 @kindex maint cplus namespace
37209 @item maint cplus namespace
37210 Print the list of possible C@t{++} namespaces.
37212 @kindex maint deprecate
37213 @kindex maint undeprecate
37214 @cindex deprecated commands
37215 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
37216 @itemx maint undeprecate @var{command}
37217 Deprecate or undeprecate the named @var{command}. Deprecated commands
37218 cause @value{GDBN} to issue a warning when you use them. The optional
37219 argument @var{replacement} says which newer command should be used in
37220 favor of the deprecated one; if it is given, @value{GDBN} will mention
37221 the replacement as part of the warning.
37223 @kindex maint dump-me
37224 @item maint dump-me
37225 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
37226 Cause a fatal signal in the debugger and force it to dump its core.
37227 This is supported only on systems which support aborting a program
37228 with the @code{SIGQUIT} signal.
37230 @kindex maint internal-error
37231 @kindex maint internal-warning
37232 @kindex maint demangler-warning
37233 @cindex demangler crashes
37234 @item maint internal-error @r{[}@var{message-text}@r{]}
37235 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
37236 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
37238 Cause @value{GDBN} to call the internal function @code{internal_error},
37239 @code{internal_warning} or @code{demangler_warning} and hence behave
37240 as though an internal problem has been detected. In addition to
37241 reporting the internal problem, these functions give the user the
37242 opportunity to either quit @value{GDBN} or (for @code{internal_error}
37243 and @code{internal_warning}) create a core file of the current
37244 @value{GDBN} session.
37246 These commands take an optional parameter @var{message-text} that is
37247 used as the text of the error or warning message.
37249 Here's an example of using @code{internal-error}:
37252 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
37253 @dots{}/maint.c:121: internal-error: testing, 1, 2
37254 A problem internal to GDB has been detected. Further
37255 debugging may prove unreliable.
37256 Quit this debugging session? (y or n) @kbd{n}
37257 Create a core file? (y or n) @kbd{n}
37261 @cindex @value{GDBN} internal error
37262 @cindex internal errors, control of @value{GDBN} behavior
37263 @cindex demangler crashes
37265 @kindex maint set internal-error
37266 @kindex maint show internal-error
37267 @kindex maint set internal-warning
37268 @kindex maint show internal-warning
37269 @kindex maint set demangler-warning
37270 @kindex maint show demangler-warning
37271 @item maint set internal-error @var{action} [ask|yes|no]
37272 @itemx maint show internal-error @var{action}
37273 @itemx maint set internal-warning @var{action} [ask|yes|no]
37274 @itemx maint show internal-warning @var{action}
37275 @itemx maint set demangler-warning @var{action} [ask|yes|no]
37276 @itemx maint show demangler-warning @var{action}
37277 When @value{GDBN} reports an internal problem (error or warning) it
37278 gives the user the opportunity to both quit @value{GDBN} and create a
37279 core file of the current @value{GDBN} session. These commands let you
37280 override the default behaviour for each particular @var{action},
37281 described in the table below.
37285 You can specify that @value{GDBN} should always (yes) or never (no)
37286 quit. The default is to ask the user what to do.
37289 You can specify that @value{GDBN} should always (yes) or never (no)
37290 create a core file. The default is to ask the user what to do. Note
37291 that there is no @code{corefile} option for @code{demangler-warning}:
37292 demangler warnings always create a core file and this cannot be
37296 @kindex maint packet
37297 @item maint packet @var{text}
37298 If @value{GDBN} is talking to an inferior via the serial protocol,
37299 then this command sends the string @var{text} to the inferior, and
37300 displays the response packet. @value{GDBN} supplies the initial
37301 @samp{$} character, the terminating @samp{#} character, and the
37304 @kindex maint print architecture
37305 @item maint print architecture @r{[}@var{file}@r{]}
37306 Print the entire architecture configuration. The optional argument
37307 @var{file} names the file where the output goes.
37309 @kindex maint print c-tdesc @r{[}@var{file}@r{]}
37310 @item maint print c-tdesc
37311 Print the target description (@pxref{Target Descriptions}) as
37312 a C source file. By default, the target description is for the current
37313 target, but if the optional argument @var{file} is provided, that file
37314 is used to produce the description. The @var{file} should be an XML
37315 document, of the form described in @ref{Target Description Format}.
37316 The created source file is built into @value{GDBN} when @value{GDBN} is
37317 built again. This command is used by developers after they add or
37318 modify XML target descriptions.
37320 @kindex maint check xml-descriptions
37321 @item maint check xml-descriptions @var{dir}
37322 Check that the target descriptions dynamically created by @value{GDBN}
37323 equal the descriptions created from XML files found in @var{dir}.
37325 @anchor{maint check libthread-db}
37326 @kindex maint check libthread-db
37327 @item maint check libthread-db
37328 Run integrity checks on the current inferior's thread debugging
37329 library. This exercises all @code{libthread_db} functionality used by
37330 @value{GDBN} on GNU/Linux systems, and by extension also exercises the
37331 @code{proc_service} functions provided by @value{GDBN} that
37332 @code{libthread_db} uses. Note that parts of the test may be skipped
37333 on some platforms when debugging core files.
37335 @kindex maint print dummy-frames
37336 @item maint print dummy-frames
37337 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
37340 (@value{GDBP}) @kbd{b add}
37342 (@value{GDBP}) @kbd{print add(2,3)}
37343 Breakpoint 2, add (a=2, b=3) at @dots{}
37345 The program being debugged stopped while in a function called from GDB.
37347 (@value{GDBP}) @kbd{maint print dummy-frames}
37348 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
37352 Takes an optional file parameter.
37354 @kindex maint print registers
37355 @kindex maint print raw-registers
37356 @kindex maint print cooked-registers
37357 @kindex maint print register-groups
37358 @kindex maint print remote-registers
37359 @item maint print registers @r{[}@var{file}@r{]}
37360 @itemx maint print raw-registers @r{[}@var{file}@r{]}
37361 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
37362 @itemx maint print register-groups @r{[}@var{file}@r{]}
37363 @itemx maint print remote-registers @r{[}@var{file}@r{]}
37364 Print @value{GDBN}'s internal register data structures.
37366 The command @code{maint print raw-registers} includes the contents of
37367 the raw register cache; the command @code{maint print
37368 cooked-registers} includes the (cooked) value of all registers,
37369 including registers which aren't available on the target nor visible
37370 to user; the command @code{maint print register-groups} includes the
37371 groups that each register is a member of; and the command @code{maint
37372 print remote-registers} includes the remote target's register numbers
37373 and offsets in the `G' packets.
37375 These commands take an optional parameter, a file name to which to
37376 write the information.
37378 @kindex maint print reggroups
37379 @item maint print reggroups @r{[}@var{file}@r{]}
37380 Print @value{GDBN}'s internal register group data structures. The
37381 optional argument @var{file} tells to what file to write the
37384 The register groups info looks like this:
37387 (@value{GDBP}) @kbd{maint print reggroups}
37400 This command forces @value{GDBN} to flush its internal register cache.
37402 @kindex maint print objfiles
37403 @cindex info for known object files
37404 @item maint print objfiles @r{[}@var{regexp}@r{]}
37405 Print a dump of all known object files.
37406 If @var{regexp} is specified, only print object files whose names
37407 match @var{regexp}. For each object file, this command prints its name,
37408 address in memory, and all of its psymtabs and symtabs.
37410 @kindex maint print user-registers
37411 @cindex user registers
37412 @item maint print user-registers
37413 List all currently available @dfn{user registers}. User registers
37414 typically provide alternate names for actual hardware registers. They
37415 include the four ``standard'' registers @code{$fp}, @code{$pc},
37416 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
37417 registers can be used in expressions in the same way as the canonical
37418 register names, but only the latter are listed by the @code{info
37419 registers} and @code{maint print registers} commands.
37421 @kindex maint print section-scripts
37422 @cindex info for known .debug_gdb_scripts-loaded scripts
37423 @item maint print section-scripts [@var{regexp}]
37424 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
37425 If @var{regexp} is specified, only print scripts loaded by object files
37426 matching @var{regexp}.
37427 For each script, this command prints its name as specified in the objfile,
37428 and the full path if known.
37429 @xref{dotdebug_gdb_scripts section}.
37431 @kindex maint print statistics
37432 @cindex bcache statistics
37433 @item maint print statistics
37434 This command prints, for each object file in the program, various data
37435 about that object file followed by the byte cache (@dfn{bcache})
37436 statistics for the object file. The objfile data includes the number
37437 of minimal, partial, full, and stabs symbols, the number of types
37438 defined by the objfile, the number of as yet unexpanded psym tables,
37439 the number of line tables and string tables, and the amount of memory
37440 used by the various tables. The bcache statistics include the counts,
37441 sizes, and counts of duplicates of all and unique objects, max,
37442 average, and median entry size, total memory used and its overhead and
37443 savings, and various measures of the hash table size and chain
37446 @kindex maint print target-stack
37447 @cindex target stack description
37448 @item maint print target-stack
37449 A @dfn{target} is an interface between the debugger and a particular
37450 kind of file or process. Targets can be stacked in @dfn{strata},
37451 so that more than one target can potentially respond to a request.
37452 In particular, memory accesses will walk down the stack of targets
37453 until they find a target that is interested in handling that particular
37456 This command prints a short description of each layer that was pushed on
37457 the @dfn{target stack}, starting from the top layer down to the bottom one.
37459 @kindex maint print type
37460 @cindex type chain of a data type
37461 @item maint print type @var{expr}
37462 Print the type chain for a type specified by @var{expr}. The argument
37463 can be either a type name or a symbol. If it is a symbol, the type of
37464 that symbol is described. The type chain produced by this command is
37465 a recursive definition of the data type as stored in @value{GDBN}'s
37466 data structures, including its flags and contained types.
37468 @kindex maint selftest
37470 @item maint selftest @r{[}@var{filter}@r{]}
37471 Run any self tests that were compiled in to @value{GDBN}. This will
37472 print a message showing how many tests were run, and how many failed.
37473 If a @var{filter} is passed, only the tests with @var{filter} in their
37476 @kindex maint info selftests
37478 @item maint info selftests
37479 List the selftests compiled in to @value{GDBN}.
37481 @kindex maint set dwarf always-disassemble
37482 @kindex maint show dwarf always-disassemble
37483 @item maint set dwarf always-disassemble
37484 @item maint show dwarf always-disassemble
37485 Control the behavior of @code{info address} when using DWARF debugging
37488 The default is @code{off}, which means that @value{GDBN} should try to
37489 describe a variable's location in an easily readable format. When
37490 @code{on}, @value{GDBN} will instead display the DWARF location
37491 expression in an assembly-like format. Note that some locations are
37492 too complex for @value{GDBN} to describe simply; in this case you will
37493 always see the disassembly form.
37495 Here is an example of the resulting disassembly:
37498 (gdb) info addr argc
37499 Symbol "argc" is a complex DWARF expression:
37503 For more information on these expressions, see
37504 @uref{http://www.dwarfstd.org/, the DWARF standard}.
37506 @kindex maint set dwarf max-cache-age
37507 @kindex maint show dwarf max-cache-age
37508 @item maint set dwarf max-cache-age
37509 @itemx maint show dwarf max-cache-age
37510 Control the DWARF compilation unit cache.
37512 @cindex DWARF compilation units cache
37513 In object files with inter-compilation-unit references, such as those
37514 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF
37515 reader needs to frequently refer to previously read compilation units.
37516 This setting controls how long a compilation unit will remain in the
37517 cache if it is not referenced. A higher limit means that cached
37518 compilation units will be stored in memory longer, and more total
37519 memory will be used. Setting it to zero disables caching, which will
37520 slow down @value{GDBN} startup, but reduce memory consumption.
37522 @kindex maint set dwarf unwinders
37523 @kindex maint show dwarf unwinders
37524 @item maint set dwarf unwinders
37525 @itemx maint show dwarf unwinders
37526 Control use of the DWARF frame unwinders.
37528 @cindex DWARF frame unwinders
37529 Many targets that support DWARF debugging use @value{GDBN}'s DWARF
37530 frame unwinders to build the backtrace. Many of these targets will
37531 also have a second mechanism for building the backtrace for use in
37532 cases where DWARF information is not available, this second mechanism
37533 is often an analysis of a function's prologue.
37535 In order to extend testing coverage of the second level stack
37536 unwinding mechanisms it is helpful to be able to disable the DWARF
37537 stack unwinders, this can be done with this switch.
37539 In normal use of @value{GDBN} disabling the DWARF unwinders is not
37540 advisable, there are cases that are better handled through DWARF than
37541 prologue analysis, and the debug experience is likely to be better
37542 with the DWARF frame unwinders enabled.
37544 If DWARF frame unwinders are not supported for a particular target
37545 architecture, then enabling this flag does not cause them to be used.
37546 @kindex maint set profile
37547 @kindex maint show profile
37548 @cindex profiling GDB
37549 @item maint set profile
37550 @itemx maint show profile
37551 Control profiling of @value{GDBN}.
37553 Profiling will be disabled until you use the @samp{maint set profile}
37554 command to enable it. When you enable profiling, the system will begin
37555 collecting timing and execution count data; when you disable profiling or
37556 exit @value{GDBN}, the results will be written to a log file. Remember that
37557 if you use profiling, @value{GDBN} will overwrite the profiling log file
37558 (often called @file{gmon.out}). If you have a record of important profiling
37559 data in a @file{gmon.out} file, be sure to move it to a safe location.
37561 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
37562 compiled with the @samp{-pg} compiler option.
37564 @kindex maint set show-debug-regs
37565 @kindex maint show show-debug-regs
37566 @cindex hardware debug registers
37567 @item maint set show-debug-regs
37568 @itemx maint show show-debug-regs
37569 Control whether to show variables that mirror the hardware debug
37570 registers. Use @code{on} to enable, @code{off} to disable. If
37571 enabled, the debug registers values are shown when @value{GDBN} inserts or
37572 removes a hardware breakpoint or watchpoint, and when the inferior
37573 triggers a hardware-assisted breakpoint or watchpoint.
37575 @kindex maint set show-all-tib
37576 @kindex maint show show-all-tib
37577 @item maint set show-all-tib
37578 @itemx maint show show-all-tib
37579 Control whether to show all non zero areas within a 1k block starting
37580 at thread local base, when using the @samp{info w32 thread-information-block}
37583 @kindex maint set target-async
37584 @kindex maint show target-async
37585 @item maint set target-async
37586 @itemx maint show target-async
37587 This controls whether @value{GDBN} targets operate in synchronous or
37588 asynchronous mode (@pxref{Background Execution}). Normally the
37589 default is asynchronous, if it is available; but this can be changed
37590 to more easily debug problems occurring only in synchronous mode.
37592 @kindex maint set target-non-stop @var{mode} [on|off|auto]
37593 @kindex maint show target-non-stop
37594 @item maint set target-non-stop
37595 @itemx maint show target-non-stop
37597 This controls whether @value{GDBN} targets always operate in non-stop
37598 mode even if @code{set non-stop} is @code{off} (@pxref{Non-Stop
37599 Mode}). The default is @code{auto}, meaning non-stop mode is enabled
37600 if supported by the target.
37603 @item maint set target-non-stop auto
37604 This is the default mode. @value{GDBN} controls the target in
37605 non-stop mode if the target supports it.
37607 @item maint set target-non-stop on
37608 @value{GDBN} controls the target in non-stop mode even if the target
37609 does not indicate support.
37611 @item maint set target-non-stop off
37612 @value{GDBN} does not control the target in non-stop mode even if the
37613 target supports it.
37616 @kindex maint set per-command
37617 @kindex maint show per-command
37618 @item maint set per-command
37619 @itemx maint show per-command
37620 @cindex resources used by commands
37622 @value{GDBN} can display the resources used by each command.
37623 This is useful in debugging performance problems.
37626 @item maint set per-command space [on|off]
37627 @itemx maint show per-command space
37628 Enable or disable the printing of the memory used by GDB for each command.
37629 If enabled, @value{GDBN} will display how much memory each command
37630 took, following the command's own output.
37631 This can also be requested by invoking @value{GDBN} with the
37632 @option{--statistics} command-line switch (@pxref{Mode Options}).
37634 @item maint set per-command time [on|off]
37635 @itemx maint show per-command time
37636 Enable or disable the printing of the execution time of @value{GDBN}
37638 If enabled, @value{GDBN} will display how much time it
37639 took to execute each command, following the command's own output.
37640 Both CPU time and wallclock time are printed.
37641 Printing both is useful when trying to determine whether the cost is
37642 CPU or, e.g., disk/network latency.
37643 Note that the CPU time printed is for @value{GDBN} only, it does not include
37644 the execution time of the inferior because there's no mechanism currently
37645 to compute how much time was spent by @value{GDBN} and how much time was
37646 spent by the program been debugged.
37647 This can also be requested by invoking @value{GDBN} with the
37648 @option{--statistics} command-line switch (@pxref{Mode Options}).
37650 @item maint set per-command symtab [on|off]
37651 @itemx maint show per-command symtab
37652 Enable or disable the printing of basic symbol table statistics
37654 If enabled, @value{GDBN} will display the following information:
37658 number of symbol tables
37660 number of primary symbol tables
37662 number of blocks in the blockvector
37666 @kindex maint set check-libthread-db
37667 @kindex maint show check-libthread-db
37668 @item maint set check-libthread-db [on|off]
37669 @itemx maint show check-libthread-db
37670 Control whether @value{GDBN} should run integrity checks on inferior
37671 specific thread debugging libraries as they are loaded. The default
37672 is not to perform such checks. If any check fails @value{GDBN} will
37673 unload the library and continue searching for a suitable candidate as
37674 described in @ref{set libthread-db-search-path}. For more information
37675 about the tests, see @ref{maint check libthread-db}.
37677 @kindex maint space
37678 @cindex memory used by commands
37679 @item maint space @var{value}
37680 An alias for @code{maint set per-command space}.
37681 A non-zero value enables it, zero disables it.
37684 @cindex time of command execution
37685 @item maint time @var{value}
37686 An alias for @code{maint set per-command time}.
37687 A non-zero value enables it, zero disables it.
37689 @kindex maint translate-address
37690 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
37691 Find the symbol stored at the location specified by the address
37692 @var{addr} and an optional section name @var{section}. If found,
37693 @value{GDBN} prints the name of the closest symbol and an offset from
37694 the symbol's location to the specified address. This is similar to
37695 the @code{info address} command (@pxref{Symbols}), except that this
37696 command also allows to find symbols in other sections.
37698 If section was not specified, the section in which the symbol was found
37699 is also printed. For dynamically linked executables, the name of
37700 executable or shared library containing the symbol is printed as well.
37702 @kindex maint test-options
37703 @item maint test-options require-delimiter
37704 @itemx maint test-options unknown-is-error
37705 @itemx maint test-options unknown-is-operand
37706 These commands are used by the testsuite to validate the command
37707 options framework. The @code{require-delimiter} variant requires a
37708 double-dash delimiter to indicate end of options. The
37709 @code{unknown-is-error} and @code{unknown-is-operand} do not. The
37710 @code{unknown-is-error} variant throws an error on unknown option,
37711 while @code{unknown-is-operand} treats unknown options as the start of
37712 the command's operands. When run, the commands output the result of
37713 the processed options. When completed, the commands store the
37714 internal result of completion in a variable exposed by the @code{maint
37715 show test-options-completion-result} command.
37717 @kindex maint show test-options-completion-result
37718 @item maint show test-options-completion-result
37719 Shows the result of completing the @code{maint test-options}
37720 subcommands. This is used by the testsuite to validate completion
37721 support in the command options framework.
37723 @kindex maint set test-settings
37724 @kindex maint show test-settings
37725 @item maint set test-settings @var{kind}
37726 @itemx maint show test-settings @var{kind}
37727 These are representative commands for each @var{kind} of setting type
37728 @value{GDBN} supports. They are used by the testsuite for exercising
37729 the settings infrastructure.
37732 @item maint with @var{setting} [@var{value}] [-- @var{command}]
37733 Like the @code{with} command, but works with @code{maintenance set}
37734 variables. This is used by the testsuite to exercise the @code{with}
37735 command's infrastructure.
37739 The following command is useful for non-interactive invocations of
37740 @value{GDBN}, such as in the test suite.
37743 @item set watchdog @var{nsec}
37744 @kindex set watchdog
37745 @cindex watchdog timer
37746 @cindex timeout for commands
37747 Set the maximum number of seconds @value{GDBN} will wait for the
37748 target operation to finish. If this time expires, @value{GDBN}
37749 reports and error and the command is aborted.
37751 @item show watchdog
37752 Show the current setting of the target wait timeout.
37755 @node Remote Protocol
37756 @appendix @value{GDBN} Remote Serial Protocol
37761 * Stop Reply Packets::
37762 * General Query Packets::
37763 * Architecture-Specific Protocol Details::
37764 * Tracepoint Packets::
37765 * Host I/O Packets::
37767 * Notification Packets::
37768 * Remote Non-Stop::
37769 * Packet Acknowledgment::
37771 * File-I/O Remote Protocol Extension::
37772 * Library List Format::
37773 * Library List Format for SVR4 Targets::
37774 * Memory Map Format::
37775 * Thread List Format::
37776 * Traceframe Info Format::
37777 * Branch Trace Format::
37778 * Branch Trace Configuration Format::
37784 There may be occasions when you need to know something about the
37785 protocol---for example, if there is only one serial port to your target
37786 machine, you might want your program to do something special if it
37787 recognizes a packet meant for @value{GDBN}.
37789 In the examples below, @samp{->} and @samp{<-} are used to indicate
37790 transmitted and received data, respectively.
37792 @cindex protocol, @value{GDBN} remote serial
37793 @cindex serial protocol, @value{GDBN} remote
37794 @cindex remote serial protocol
37795 All @value{GDBN} commands and responses (other than acknowledgments
37796 and notifications, see @ref{Notification Packets}) are sent as a
37797 @var{packet}. A @var{packet} is introduced with the character
37798 @samp{$}, the actual @var{packet-data}, and the terminating character
37799 @samp{#} followed by a two-digit @var{checksum}:
37802 @code{$}@var{packet-data}@code{#}@var{checksum}
37806 @cindex checksum, for @value{GDBN} remote
37808 The two-digit @var{checksum} is computed as the modulo 256 sum of all
37809 characters between the leading @samp{$} and the trailing @samp{#} (an
37810 eight bit unsigned checksum).
37812 Implementors should note that prior to @value{GDBN} 5.0 the protocol
37813 specification also included an optional two-digit @var{sequence-id}:
37816 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
37819 @cindex sequence-id, for @value{GDBN} remote
37821 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
37822 has never output @var{sequence-id}s. Stubs that handle packets added
37823 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
37825 When either the host or the target machine receives a packet, the first
37826 response expected is an acknowledgment: either @samp{+} (to indicate
37827 the package was received correctly) or @samp{-} (to request
37831 -> @code{$}@var{packet-data}@code{#}@var{checksum}
37836 The @samp{+}/@samp{-} acknowledgments can be disabled
37837 once a connection is established.
37838 @xref{Packet Acknowledgment}, for details.
37840 The host (@value{GDBN}) sends @var{command}s, and the target (the
37841 debugging stub incorporated in your program) sends a @var{response}. In
37842 the case of step and continue @var{command}s, the response is only sent
37843 when the operation has completed, and the target has again stopped all
37844 threads in all attached processes. This is the default all-stop mode
37845 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
37846 execution mode; see @ref{Remote Non-Stop}, for details.
37848 @var{packet-data} consists of a sequence of characters with the
37849 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
37852 @cindex remote protocol, field separator
37853 Fields within the packet should be separated using @samp{,} @samp{;} or
37854 @samp{:}. Except where otherwise noted all numbers are represented in
37855 @sc{hex} with leading zeros suppressed.
37857 Implementors should note that prior to @value{GDBN} 5.0, the character
37858 @samp{:} could not appear as the third character in a packet (as it
37859 would potentially conflict with the @var{sequence-id}).
37861 @cindex remote protocol, binary data
37862 @anchor{Binary Data}
37863 Binary data in most packets is encoded either as two hexadecimal
37864 digits per byte of binary data. This allowed the traditional remote
37865 protocol to work over connections which were only seven-bit clean.
37866 Some packets designed more recently assume an eight-bit clean
37867 connection, and use a more efficient encoding to send and receive
37870 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
37871 as an escape character. Any escaped byte is transmitted as the escape
37872 character followed by the original character XORed with @code{0x20}.
37873 For example, the byte @code{0x7d} would be transmitted as the two
37874 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
37875 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
37876 @samp{@}}) must always be escaped. Responses sent by the stub
37877 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
37878 is not interpreted as the start of a run-length encoded sequence
37881 Response @var{data} can be run-length encoded to save space.
37882 Run-length encoding replaces runs of identical characters with one
37883 instance of the repeated character, followed by a @samp{*} and a
37884 repeat count. The repeat count is itself sent encoded, to avoid
37885 binary characters in @var{data}: a value of @var{n} is sent as
37886 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
37887 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
37888 code 32) for a repeat count of 3. (This is because run-length
37889 encoding starts to win for counts 3 or more.) Thus, for example,
37890 @samp{0* } is a run-length encoding of ``0000'': the space character
37891 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
37894 The printable characters @samp{#} and @samp{$} or with a numeric value
37895 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
37896 seven repeats (@samp{$}) can be expanded using a repeat count of only
37897 five (@samp{"}). For example, @samp{00000000} can be encoded as
37900 The error response returned for some packets includes a two character
37901 error number. That number is not well defined.
37903 @cindex empty response, for unsupported packets
37904 For any @var{command} not supported by the stub, an empty response
37905 (@samp{$#00}) should be returned. That way it is possible to extend the
37906 protocol. A newer @value{GDBN} can tell if a packet is supported based
37909 At a minimum, a stub is required to support the @samp{g} and @samp{G}
37910 commands for register access, and the @samp{m} and @samp{M} commands
37911 for memory access. Stubs that only control single-threaded targets
37912 can implement run control with the @samp{c} (continue), and @samp{s}
37913 (step) commands. Stubs that support multi-threading targets should
37914 support the @samp{vCont} command. All other commands are optional.
37919 The following table provides a complete list of all currently defined
37920 @var{command}s and their corresponding response @var{data}.
37921 @xref{File-I/O Remote Protocol Extension}, for details about the File
37922 I/O extension of the remote protocol.
37924 Each packet's description has a template showing the packet's overall
37925 syntax, followed by an explanation of the packet's meaning. We
37926 include spaces in some of the templates for clarity; these are not
37927 part of the packet's syntax. No @value{GDBN} packet uses spaces to
37928 separate its components. For example, a template like @samp{foo
37929 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
37930 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
37931 @var{baz}. @value{GDBN} does not transmit a space character between the
37932 @samp{foo} and the @var{bar}, or between the @var{bar} and the
37935 @cindex @var{thread-id}, in remote protocol
37936 @anchor{thread-id syntax}
37937 Several packets and replies include a @var{thread-id} field to identify
37938 a thread. Normally these are positive numbers with a target-specific
37939 interpretation, formatted as big-endian hex strings. A @var{thread-id}
37940 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
37943 In addition, the remote protocol supports a multiprocess feature in
37944 which the @var{thread-id} syntax is extended to optionally include both
37945 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
37946 The @var{pid} (process) and @var{tid} (thread) components each have the
37947 format described above: a positive number with target-specific
37948 interpretation formatted as a big-endian hex string, literal @samp{-1}
37949 to indicate all processes or threads (respectively), or @samp{0} to
37950 indicate an arbitrary process or thread. Specifying just a process, as
37951 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
37952 error to specify all processes but a specific thread, such as
37953 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
37954 for those packets and replies explicitly documented to include a process
37955 ID, rather than a @var{thread-id}.
37957 The multiprocess @var{thread-id} syntax extensions are only used if both
37958 @value{GDBN} and the stub report support for the @samp{multiprocess}
37959 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
37962 Note that all packet forms beginning with an upper- or lower-case
37963 letter, other than those described here, are reserved for future use.
37965 Here are the packet descriptions.
37970 @cindex @samp{!} packet
37971 @anchor{extended mode}
37972 Enable extended mode. In extended mode, the remote server is made
37973 persistent. The @samp{R} packet is used to restart the program being
37979 The remote target both supports and has enabled extended mode.
37983 @cindex @samp{?} packet
37985 Indicate the reason the target halted. The reply is the same as for
37986 step and continue. This packet has a special interpretation when the
37987 target is in non-stop mode; see @ref{Remote Non-Stop}.
37990 @xref{Stop Reply Packets}, for the reply specifications.
37992 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
37993 @cindex @samp{A} packet
37994 Initialized @code{argv[]} array passed into program. @var{arglen}
37995 specifies the number of bytes in the hex encoded byte stream
37996 @var{arg}. See @code{gdbserver} for more details.
38001 The arguments were set.
38007 @cindex @samp{b} packet
38008 (Don't use this packet; its behavior is not well-defined.)
38009 Change the serial line speed to @var{baud}.
38011 JTC: @emph{When does the transport layer state change? When it's
38012 received, or after the ACK is transmitted. In either case, there are
38013 problems if the command or the acknowledgment packet is dropped.}
38015 Stan: @emph{If people really wanted to add something like this, and get
38016 it working for the first time, they ought to modify ser-unix.c to send
38017 some kind of out-of-band message to a specially-setup stub and have the
38018 switch happen "in between" packets, so that from remote protocol's point
38019 of view, nothing actually happened.}
38021 @item B @var{addr},@var{mode}
38022 @cindex @samp{B} packet
38023 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
38024 breakpoint at @var{addr}.
38026 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
38027 (@pxref{insert breakpoint or watchpoint packet}).
38029 @cindex @samp{bc} packet
38032 Backward continue. Execute the target system in reverse. No parameter.
38033 @xref{Reverse Execution}, for more information.
38036 @xref{Stop Reply Packets}, for the reply specifications.
38038 @cindex @samp{bs} packet
38041 Backward single step. Execute one instruction in reverse. No parameter.
38042 @xref{Reverse Execution}, for more information.
38045 @xref{Stop Reply Packets}, for the reply specifications.
38047 @item c @r{[}@var{addr}@r{]}
38048 @cindex @samp{c} packet
38049 Continue at @var{addr}, which is the address to resume. If @var{addr}
38050 is omitted, resume at current address.
38052 This packet is deprecated for multi-threading support. @xref{vCont
38056 @xref{Stop Reply Packets}, for the reply specifications.
38058 @item C @var{sig}@r{[};@var{addr}@r{]}
38059 @cindex @samp{C} packet
38060 Continue with signal @var{sig} (hex signal number). If
38061 @samp{;@var{addr}} is omitted, resume at same address.
38063 This packet is deprecated for multi-threading support. @xref{vCont
38067 @xref{Stop Reply Packets}, for the reply specifications.
38070 @cindex @samp{d} packet
38073 Don't use this packet; instead, define a general set packet
38074 (@pxref{General Query Packets}).
38078 @cindex @samp{D} packet
38079 The first form of the packet is used to detach @value{GDBN} from the
38080 remote system. It is sent to the remote target
38081 before @value{GDBN} disconnects via the @code{detach} command.
38083 The second form, including a process ID, is used when multiprocess
38084 protocol extensions are enabled (@pxref{multiprocess extensions}), to
38085 detach only a specific process. The @var{pid} is specified as a
38086 big-endian hex string.
38096 @item F @var{RC},@var{EE},@var{CF};@var{XX}
38097 @cindex @samp{F} packet
38098 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
38099 This is part of the File-I/O protocol extension. @xref{File-I/O
38100 Remote Protocol Extension}, for the specification.
38103 @anchor{read registers packet}
38104 @cindex @samp{g} packet
38105 Read general registers.
38109 @item @var{XX@dots{}}
38110 Each byte of register data is described by two hex digits. The bytes
38111 with the register are transmitted in target byte order. The size of
38112 each register and their position within the @samp{g} packet are
38113 determined by the @value{GDBN} internal gdbarch functions
38114 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}.
38116 When reading registers from a trace frame (@pxref{Analyze Collected
38117 Data,,Using the Collected Data}), the stub may also return a string of
38118 literal @samp{x}'s in place of the register data digits, to indicate
38119 that the corresponding register has not been collected, thus its value
38120 is unavailable. For example, for an architecture with 4 registers of
38121 4 bytes each, the following reply indicates to @value{GDBN} that
38122 registers 0 and 2 have not been collected, while registers 1 and 3
38123 have been collected, and both have zero value:
38127 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
38134 @item G @var{XX@dots{}}
38135 @cindex @samp{G} packet
38136 Write general registers. @xref{read registers packet}, for a
38137 description of the @var{XX@dots{}} data.
38147 @item H @var{op} @var{thread-id}
38148 @cindex @samp{H} packet
38149 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
38150 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
38151 should be @samp{c} for step and continue operations (note that this
38152 is deprecated, supporting the @samp{vCont} command is a better
38153 option), and @samp{g} for other operations. The thread designator
38154 @var{thread-id} has the format and interpretation described in
38155 @ref{thread-id syntax}.
38166 @c 'H': How restrictive (or permissive) is the thread model. If a
38167 @c thread is selected and stopped, are other threads allowed
38168 @c to continue to execute? As I mentioned above, I think the
38169 @c semantics of each command when a thread is selected must be
38170 @c described. For example:
38172 @c 'g': If the stub supports threads and a specific thread is
38173 @c selected, returns the register block from that thread;
38174 @c otherwise returns current registers.
38176 @c 'G' If the stub supports threads and a specific thread is
38177 @c selected, sets the registers of the register block of
38178 @c that thread; otherwise sets current registers.
38180 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
38181 @anchor{cycle step packet}
38182 @cindex @samp{i} packet
38183 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
38184 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
38185 step starting at that address.
38188 @cindex @samp{I} packet
38189 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
38193 @cindex @samp{k} packet
38196 The exact effect of this packet is not specified.
38198 For a bare-metal target, it may power cycle or reset the target
38199 system. For that reason, the @samp{k} packet has no reply.
38201 For a single-process target, it may kill that process if possible.
38203 A multiple-process target may choose to kill just one process, or all
38204 that are under @value{GDBN}'s control. For more precise control, use
38205 the vKill packet (@pxref{vKill packet}).
38207 If the target system immediately closes the connection in response to
38208 @samp{k}, @value{GDBN} does not consider the lack of packet
38209 acknowledgment to be an error, and assumes the kill was successful.
38211 If connected using @kbd{target extended-remote}, and the target does
38212 not close the connection in response to a kill request, @value{GDBN}
38213 probes the target state as if a new connection was opened
38214 (@pxref{? packet}).
38216 @item m @var{addr},@var{length}
38217 @cindex @samp{m} packet
38218 Read @var{length} addressable memory units starting at address @var{addr}
38219 (@pxref{addressable memory unit}). Note that @var{addr} may not be aligned to
38220 any particular boundary.
38222 The stub need not use any particular size or alignment when gathering
38223 data from memory for the response; even if @var{addr} is word-aligned
38224 and @var{length} is a multiple of the word size, the stub is free to
38225 use byte accesses, or not. For this reason, this packet may not be
38226 suitable for accessing memory-mapped I/O devices.
38227 @cindex alignment of remote memory accesses
38228 @cindex size of remote memory accesses
38229 @cindex memory, alignment and size of remote accesses
38233 @item @var{XX@dots{}}
38234 Memory contents; each byte is transmitted as a two-digit hexadecimal number.
38235 The reply may contain fewer addressable memory units than requested if the
38236 server was able to read only part of the region of memory.
38241 @item M @var{addr},@var{length}:@var{XX@dots{}}
38242 @cindex @samp{M} packet
38243 Write @var{length} addressable memory units starting at address @var{addr}
38244 (@pxref{addressable memory unit}). The data is given by @var{XX@dots{}}; each
38245 byte is transmitted as a two-digit hexadecimal number.
38252 for an error (this includes the case where only part of the data was
38257 @cindex @samp{p} packet
38258 Read the value of register @var{n}; @var{n} is in hex.
38259 @xref{read registers packet}, for a description of how the returned
38260 register value is encoded.
38264 @item @var{XX@dots{}}
38265 the register's value
38269 Indicating an unrecognized @var{query}.
38272 @item P @var{n@dots{}}=@var{r@dots{}}
38273 @anchor{write register packet}
38274 @cindex @samp{P} packet
38275 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
38276 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
38277 digits for each byte in the register (target byte order).
38287 @item q @var{name} @var{params}@dots{}
38288 @itemx Q @var{name} @var{params}@dots{}
38289 @cindex @samp{q} packet
38290 @cindex @samp{Q} packet
38291 General query (@samp{q}) and set (@samp{Q}). These packets are
38292 described fully in @ref{General Query Packets}.
38295 @cindex @samp{r} packet
38296 Reset the entire system.
38298 Don't use this packet; use the @samp{R} packet instead.
38301 @cindex @samp{R} packet
38302 Restart the program being debugged. The @var{XX}, while needed, is ignored.
38303 This packet is only available in extended mode (@pxref{extended mode}).
38305 The @samp{R} packet has no reply.
38307 @item s @r{[}@var{addr}@r{]}
38308 @cindex @samp{s} packet
38309 Single step, resuming at @var{addr}. If
38310 @var{addr} is omitted, resume at same address.
38312 This packet is deprecated for multi-threading support. @xref{vCont
38316 @xref{Stop Reply Packets}, for the reply specifications.
38318 @item S @var{sig}@r{[};@var{addr}@r{]}
38319 @anchor{step with signal packet}
38320 @cindex @samp{S} packet
38321 Step with signal. This is analogous to the @samp{C} packet, but
38322 requests a single-step, rather than a normal resumption of execution.
38324 This packet is deprecated for multi-threading support. @xref{vCont
38328 @xref{Stop Reply Packets}, for the reply specifications.
38330 @item t @var{addr}:@var{PP},@var{MM}
38331 @cindex @samp{t} packet
38332 Search backwards starting at address @var{addr} for a match with pattern
38333 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
38334 There must be at least 3 digits in @var{addr}.
38336 @item T @var{thread-id}
38337 @cindex @samp{T} packet
38338 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
38343 thread is still alive
38349 Packets starting with @samp{v} are identified by a multi-letter name,
38350 up to the first @samp{;} or @samp{?} (or the end of the packet).
38352 @item vAttach;@var{pid}
38353 @cindex @samp{vAttach} packet
38354 Attach to a new process with the specified process ID @var{pid}.
38355 The process ID is a
38356 hexadecimal integer identifying the process. In all-stop mode, all
38357 threads in the attached process are stopped; in non-stop mode, it may be
38358 attached without being stopped if that is supported by the target.
38360 @c In non-stop mode, on a successful vAttach, the stub should set the
38361 @c current thread to a thread of the newly-attached process. After
38362 @c attaching, GDB queries for the attached process's thread ID with qC.
38363 @c Also note that, from a user perspective, whether or not the
38364 @c target is stopped on attach in non-stop mode depends on whether you
38365 @c use the foreground or background version of the attach command, not
38366 @c on what vAttach does; GDB does the right thing with respect to either
38367 @c stopping or restarting threads.
38369 This packet is only available in extended mode (@pxref{extended mode}).
38375 @item @r{Any stop packet}
38376 for success in all-stop mode (@pxref{Stop Reply Packets})
38378 for success in non-stop mode (@pxref{Remote Non-Stop})
38381 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
38382 @cindex @samp{vCont} packet
38383 @anchor{vCont packet}
38384 Resume the inferior, specifying different actions for each thread.
38386 For each inferior thread, the leftmost action with a matching
38387 @var{thread-id} is applied. Threads that don't match any action
38388 remain in their current state. Thread IDs are specified using the
38389 syntax described in @ref{thread-id syntax}. If multiprocess
38390 extensions (@pxref{multiprocess extensions}) are supported, actions
38391 can be specified to match all threads in a process by using the
38392 @samp{p@var{pid}.-1} form of the @var{thread-id}. An action with no
38393 @var{thread-id} matches all threads. Specifying no actions is an
38396 Currently supported actions are:
38402 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
38406 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
38409 @item r @var{start},@var{end}
38410 Step once, and then keep stepping as long as the thread stops at
38411 addresses between @var{start} (inclusive) and @var{end} (exclusive).
38412 The remote stub reports a stop reply when either the thread goes out
38413 of the range or is stopped due to an unrelated reason, such as hitting
38414 a breakpoint. @xref{range stepping}.
38416 If the range is empty (@var{start} == @var{end}), then the action
38417 becomes equivalent to the @samp{s} action. In other words,
38418 single-step once, and report the stop (even if the stepped instruction
38419 jumps to @var{start}).
38421 (A stop reply may be sent at any point even if the PC is still within
38422 the stepping range; for example, it is valid to implement this packet
38423 in a degenerate way as a single instruction step operation.)
38427 The optional argument @var{addr} normally associated with the
38428 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
38429 not supported in @samp{vCont}.
38431 The @samp{t} action is only relevant in non-stop mode
38432 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
38433 A stop reply should be generated for any affected thread not already stopped.
38434 When a thread is stopped by means of a @samp{t} action,
38435 the corresponding stop reply should indicate that the thread has stopped with
38436 signal @samp{0}, regardless of whether the target uses some other signal
38437 as an implementation detail.
38439 The server must ignore @samp{c}, @samp{C}, @samp{s}, @samp{S}, and
38440 @samp{r} actions for threads that are already running. Conversely,
38441 the server must ignore @samp{t} actions for threads that are already
38444 @emph{Note:} In non-stop mode, a thread is considered running until
38445 @value{GDBN} acknowleges an asynchronous stop notification for it with
38446 the @samp{vStopped} packet (@pxref{Remote Non-Stop}).
38448 The stub must support @samp{vCont} if it reports support for
38449 multiprocess extensions (@pxref{multiprocess extensions}).
38452 @xref{Stop Reply Packets}, for the reply specifications.
38455 @cindex @samp{vCont?} packet
38456 Request a list of actions supported by the @samp{vCont} packet.
38460 @item vCont@r{[};@var{action}@dots{}@r{]}
38461 The @samp{vCont} packet is supported. Each @var{action} is a supported
38462 command in the @samp{vCont} packet.
38464 The @samp{vCont} packet is not supported.
38467 @anchor{vCtrlC packet}
38469 @cindex @samp{vCtrlC} packet
38470 Interrupt remote target as if a control-C was pressed on the remote
38471 terminal. This is the equivalent to reacting to the @code{^C}
38472 (@samp{\003}, the control-C character) character in all-stop mode
38473 while the target is running, except this works in non-stop mode.
38474 @xref{interrupting remote targets}, for more info on the all-stop
38485 @item vFile:@var{operation}:@var{parameter}@dots{}
38486 @cindex @samp{vFile} packet
38487 Perform a file operation on the target system. For details,
38488 see @ref{Host I/O Packets}.
38490 @item vFlashErase:@var{addr},@var{length}
38491 @cindex @samp{vFlashErase} packet
38492 Direct the stub to erase @var{length} bytes of flash starting at
38493 @var{addr}. The region may enclose any number of flash blocks, but
38494 its start and end must fall on block boundaries, as indicated by the
38495 flash block size appearing in the memory map (@pxref{Memory Map
38496 Format}). @value{GDBN} groups flash memory programming operations
38497 together, and sends a @samp{vFlashDone} request after each group; the
38498 stub is allowed to delay erase operation until the @samp{vFlashDone}
38499 packet is received.
38509 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
38510 @cindex @samp{vFlashWrite} packet
38511 Direct the stub to write data to flash address @var{addr}. The data
38512 is passed in binary form using the same encoding as for the @samp{X}
38513 packet (@pxref{Binary Data}). The memory ranges specified by
38514 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
38515 not overlap, and must appear in order of increasing addresses
38516 (although @samp{vFlashErase} packets for higher addresses may already
38517 have been received; the ordering is guaranteed only between
38518 @samp{vFlashWrite} packets). If a packet writes to an address that was
38519 neither erased by a preceding @samp{vFlashErase} packet nor by some other
38520 target-specific method, the results are unpredictable.
38528 for vFlashWrite addressing non-flash memory
38534 @cindex @samp{vFlashDone} packet
38535 Indicate to the stub that flash programming operation is finished.
38536 The stub is permitted to delay or batch the effects of a group of
38537 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
38538 @samp{vFlashDone} packet is received. The contents of the affected
38539 regions of flash memory are unpredictable until the @samp{vFlashDone}
38540 request is completed.
38542 @item vKill;@var{pid}
38543 @cindex @samp{vKill} packet
38544 @anchor{vKill packet}
38545 Kill the process with the specified process ID @var{pid}, which is a
38546 hexadecimal integer identifying the process. This packet is used in
38547 preference to @samp{k} when multiprocess protocol extensions are
38548 supported; see @ref{multiprocess extensions}.
38558 @item vMustReplyEmpty
38559 @cindex @samp{vMustReplyEmpty} packet
38560 The correct reply to an unknown @samp{v} packet is to return the empty
38561 string, however, some older versions of @command{gdbserver} would
38562 incorrectly return @samp{OK} for unknown @samp{v} packets.
38564 The @samp{vMustReplyEmpty} is used as a feature test to check how
38565 @command{gdbserver} handles unknown packets, it is important that this
38566 packet be handled in the same way as other unknown @samp{v} packets.
38567 If this packet is handled differently to other unknown @samp{v}
38568 packets then it is possile that @value{GDBN} may run into problems in
38569 other areas, specifically around use of @samp{vFile:setfs:}.
38571 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
38572 @cindex @samp{vRun} packet
38573 Run the program @var{filename}, passing it each @var{argument} on its
38574 command line. The file and arguments are hex-encoded strings. If
38575 @var{filename} is an empty string, the stub may use a default program
38576 (e.g.@: the last program run). The program is created in the stopped
38579 @c FIXME: What about non-stop mode?
38581 This packet is only available in extended mode (@pxref{extended mode}).
38587 @item @r{Any stop packet}
38588 for success (@pxref{Stop Reply Packets})
38592 @cindex @samp{vStopped} packet
38593 @xref{Notification Packets}.
38595 @item X @var{addr},@var{length}:@var{XX@dots{}}
38597 @cindex @samp{X} packet
38598 Write data to memory, where the data is transmitted in binary.
38599 Memory is specified by its address @var{addr} and number of addressable memory
38600 units @var{length} (@pxref{addressable memory unit});
38601 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
38611 @item z @var{type},@var{addr},@var{kind}
38612 @itemx Z @var{type},@var{addr},@var{kind}
38613 @anchor{insert breakpoint or watchpoint packet}
38614 @cindex @samp{z} packet
38615 @cindex @samp{Z} packets
38616 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
38617 watchpoint starting at address @var{address} of kind @var{kind}.
38619 Each breakpoint and watchpoint packet @var{type} is documented
38622 @emph{Implementation notes: A remote target shall return an empty string
38623 for an unrecognized breakpoint or watchpoint packet @var{type}. A
38624 remote target shall support either both or neither of a given
38625 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
38626 avoid potential problems with duplicate packets, the operations should
38627 be implemented in an idempotent way.}
38629 @item z0,@var{addr},@var{kind}
38630 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
38631 @cindex @samp{z0} packet
38632 @cindex @samp{Z0} packet
38633 Insert (@samp{Z0}) or remove (@samp{z0}) a software breakpoint at address
38634 @var{addr} of type @var{kind}.
38636 A software breakpoint is implemented by replacing the instruction at
38637 @var{addr} with a software breakpoint or trap instruction. The
38638 @var{kind} is target-specific and typically indicates the size of the
38639 breakpoint in bytes that should be inserted. E.g., the @sc{arm} and
38640 @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
38641 architectures have additional meanings for @var{kind}
38642 (@pxref{Architecture-Specific Protocol Details}); if no
38643 architecture-specific value is being used, it should be @samp{0}.
38644 @var{kind} is hex-encoded. @var{cond_list} is an optional list of
38645 conditional expressions in bytecode form that should be evaluated on
38646 the target's side. These are the conditions that should be taken into
38647 consideration when deciding if the breakpoint trigger should be
38648 reported back to @value{GDBN}.
38650 See also the @samp{swbreak} stop reason (@pxref{swbreak stop reason})
38651 for how to best report a software breakpoint event to @value{GDBN}.
38653 The @var{cond_list} parameter is comprised of a series of expressions,
38654 concatenated without separators. Each expression has the following form:
38658 @item X @var{len},@var{expr}
38659 @var{len} is the length of the bytecode expression and @var{expr} is the
38660 actual conditional expression in bytecode form.
38664 The optional @var{cmd_list} parameter introduces commands that may be
38665 run on the target, rather than being reported back to @value{GDBN}.
38666 The parameter starts with a numeric flag @var{persist}; if the flag is
38667 nonzero, then the breakpoint may remain active and the commands
38668 continue to be run even when @value{GDBN} disconnects from the target.
38669 Following this flag is a series of expressions concatenated with no
38670 separators. Each expression has the following form:
38674 @item X @var{len},@var{expr}
38675 @var{len} is the length of the bytecode expression and @var{expr} is the
38676 actual commands expression in bytecode form.
38680 @emph{Implementation note: It is possible for a target to copy or move
38681 code that contains software breakpoints (e.g., when implementing
38682 overlays). The behavior of this packet, in the presence of such a
38683 target, is not defined.}
38695 @item z1,@var{addr},@var{kind}
38696 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
38697 @cindex @samp{z1} packet
38698 @cindex @samp{Z1} packet
38699 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
38700 address @var{addr}.
38702 A hardware breakpoint is implemented using a mechanism that is not
38703 dependent on being able to modify the target's memory. The
38704 @var{kind}, @var{cond_list}, and @var{cmd_list} arguments have the
38705 same meaning as in @samp{Z0} packets.
38707 @emph{Implementation note: A hardware breakpoint is not affected by code
38720 @item z2,@var{addr},@var{kind}
38721 @itemx Z2,@var{addr},@var{kind}
38722 @cindex @samp{z2} packet
38723 @cindex @samp{Z2} packet
38724 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
38725 The number of bytes to watch is specified by @var{kind}.
38737 @item z3,@var{addr},@var{kind}
38738 @itemx Z3,@var{addr},@var{kind}
38739 @cindex @samp{z3} packet
38740 @cindex @samp{Z3} packet
38741 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
38742 The number of bytes to watch is specified by @var{kind}.
38754 @item z4,@var{addr},@var{kind}
38755 @itemx Z4,@var{addr},@var{kind}
38756 @cindex @samp{z4} packet
38757 @cindex @samp{Z4} packet
38758 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
38759 The number of bytes to watch is specified by @var{kind}.
38773 @node Stop Reply Packets
38774 @section Stop Reply Packets
38775 @cindex stop reply packets
38777 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
38778 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
38779 receive any of the below as a reply. Except for @samp{?}
38780 and @samp{vStopped}, that reply is only returned
38781 when the target halts. In the below the exact meaning of @dfn{signal
38782 number} is defined by the header @file{include/gdb/signals.h} in the
38783 @value{GDBN} source code.
38785 In non-stop mode, the server will simply reply @samp{OK} to commands
38786 such as @samp{vCont}; any stop will be the subject of a future
38787 notification. @xref{Remote Non-Stop}.
38789 As in the description of request packets, we include spaces in the
38790 reply templates for clarity; these are not part of the reply packet's
38791 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
38797 The program received signal number @var{AA} (a two-digit hexadecimal
38798 number). This is equivalent to a @samp{T} response with no
38799 @var{n}:@var{r} pairs.
38801 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
38802 @cindex @samp{T} packet reply
38803 The program received signal number @var{AA} (a two-digit hexadecimal
38804 number). This is equivalent to an @samp{S} response, except that the
38805 @samp{@var{n}:@var{r}} pairs can carry values of important registers
38806 and other information directly in the stop reply packet, reducing
38807 round-trip latency. Single-step and breakpoint traps are reported
38808 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
38812 If @var{n} is a hexadecimal number, it is a register number, and the
38813 corresponding @var{r} gives that register's value. The data @var{r} is a
38814 series of bytes in target byte order, with each byte given by a
38815 two-digit hex number.
38818 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
38819 the stopped thread, as specified in @ref{thread-id syntax}.
38822 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
38823 the core on which the stop event was detected.
38826 If @var{n} is a recognized @dfn{stop reason}, it describes a more
38827 specific event that stopped the target. The currently defined stop
38828 reasons are listed below. The @var{aa} should be @samp{05}, the trap
38829 signal. At most one stop reason should be present.
38832 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
38833 and go on to the next; this allows us to extend the protocol in the
38837 The currently defined stop reasons are:
38843 The packet indicates a watchpoint hit, and @var{r} is the data address, in
38846 @item syscall_entry
38847 @itemx syscall_return
38848 The packet indicates a syscall entry or return, and @var{r} is the
38849 syscall number, in hex.
38851 @cindex shared library events, remote reply
38853 The packet indicates that the loaded libraries have changed.
38854 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
38855 list of loaded libraries. The @var{r} part is ignored.
38857 @cindex replay log events, remote reply
38859 The packet indicates that the target cannot continue replaying
38860 logged execution events, because it has reached the end (or the
38861 beginning when executing backward) of the log. The value of @var{r}
38862 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
38863 for more information.
38866 @anchor{swbreak stop reason}
38867 The packet indicates a software breakpoint instruction was executed,
38868 irrespective of whether it was @value{GDBN} that planted the
38869 breakpoint or the breakpoint is hardcoded in the program. The @var{r}
38870 part must be left empty.
38872 On some architectures, such as x86, at the architecture level, when a
38873 breakpoint instruction executes the program counter points at the
38874 breakpoint address plus an offset. On such targets, the stub is
38875 responsible for adjusting the PC to point back at the breakpoint
38878 This packet should not be sent by default; older @value{GDBN} versions
38879 did not support it. @value{GDBN} requests it, by supplying an
38880 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
38881 remote stub must also supply the appropriate @samp{qSupported} feature
38882 indicating support.
38884 This packet is required for correct non-stop mode operation.
38887 The packet indicates the target stopped for a hardware breakpoint.
38888 The @var{r} part must be left empty.
38890 The same remarks about @samp{qSupported} and non-stop mode above
38893 @cindex fork events, remote reply
38895 The packet indicates that @code{fork} was called, and @var{r}
38896 is the thread ID of the new child process. Refer to
38897 @ref{thread-id syntax} for the format of the @var{thread-id}
38898 field. This packet is only applicable to targets that support
38901 This packet should not be sent by default; older @value{GDBN} versions
38902 did not support it. @value{GDBN} requests it, by supplying an
38903 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
38904 remote stub must also supply the appropriate @samp{qSupported} feature
38905 indicating support.
38907 @cindex vfork events, remote reply
38909 The packet indicates that @code{vfork} was called, and @var{r}
38910 is the thread ID of the new child process. Refer to
38911 @ref{thread-id syntax} for the format of the @var{thread-id}
38912 field. This packet is only applicable to targets that support
38915 This packet should not be sent by default; older @value{GDBN} versions
38916 did not support it. @value{GDBN} requests it, by supplying an
38917 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
38918 remote stub must also supply the appropriate @samp{qSupported} feature
38919 indicating support.
38921 @cindex vforkdone events, remote reply
38923 The packet indicates that a child process created by a vfork
38924 has either called @code{exec} or terminated, so that the
38925 address spaces of the parent and child process are no longer
38926 shared. The @var{r} part is ignored. This packet is only
38927 applicable to targets that support vforkdone events.
38929 This packet should not be sent by default; older @value{GDBN} versions
38930 did not support it. @value{GDBN} requests it, by supplying an
38931 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
38932 remote stub must also supply the appropriate @samp{qSupported} feature
38933 indicating support.
38935 @cindex exec events, remote reply
38937 The packet indicates that @code{execve} was called, and @var{r}
38938 is the absolute pathname of the file that was executed, in hex.
38939 This packet is only applicable to targets that support exec events.
38941 This packet should not be sent by default; older @value{GDBN} versions
38942 did not support it. @value{GDBN} requests it, by supplying an
38943 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
38944 remote stub must also supply the appropriate @samp{qSupported} feature
38945 indicating support.
38947 @cindex thread create event, remote reply
38948 @anchor{thread create event}
38950 The packet indicates that the thread was just created. The new thread
38951 is stopped until @value{GDBN} sets it running with a resumption packet
38952 (@pxref{vCont packet}). This packet should not be sent by default;
38953 @value{GDBN} requests it with the @ref{QThreadEvents} packet. See
38954 also the @samp{w} (@pxref{thread exit event}) remote reply below. The
38955 @var{r} part is ignored.
38960 @itemx W @var{AA} ; process:@var{pid}
38961 The process exited, and @var{AA} is the exit status. This is only
38962 applicable to certain targets.
38964 The second form of the response, including the process ID of the
38965 exited process, can be used only when @value{GDBN} has reported
38966 support for multiprocess protocol extensions; see @ref{multiprocess
38967 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
38971 @itemx X @var{AA} ; process:@var{pid}
38972 The process terminated with signal @var{AA}.
38974 The second form of the response, including the process ID of the
38975 terminated process, can be used only when @value{GDBN} has reported
38976 support for multiprocess protocol extensions; see @ref{multiprocess
38977 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
38980 @anchor{thread exit event}
38981 @cindex thread exit event, remote reply
38982 @item w @var{AA} ; @var{tid}
38984 The thread exited, and @var{AA} is the exit status. This response
38985 should not be sent by default; @value{GDBN} requests it with the
38986 @ref{QThreadEvents} packet. See also @ref{thread create event} above.
38987 @var{AA} is formatted as a big-endian hex string.
38990 There are no resumed threads left in the target. In other words, even
38991 though the process is alive, the last resumed thread has exited. For
38992 example, say the target process has two threads: thread 1 and thread
38993 2. The client leaves thread 1 stopped, and resumes thread 2, which
38994 subsequently exits. At this point, even though the process is still
38995 alive, and thus no @samp{W} stop reply is sent, no thread is actually
38996 executing either. The @samp{N} stop reply thus informs the client
38997 that it can stop waiting for stop replies. This packet should not be
38998 sent by default; older @value{GDBN} versions did not support it.
38999 @value{GDBN} requests it, by supplying an appropriate
39000 @samp{qSupported} feature (@pxref{qSupported}). The remote stub must
39001 also supply the appropriate @samp{qSupported} feature indicating
39004 @item O @var{XX}@dots{}
39005 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
39006 written as the program's console output. This can happen at any time
39007 while the program is running and the debugger should continue to wait
39008 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
39010 @item F @var{call-id},@var{parameter}@dots{}
39011 @var{call-id} is the identifier which says which host system call should
39012 be called. This is just the name of the function. Translation into the
39013 correct system call is only applicable as it's defined in @value{GDBN}.
39014 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
39017 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
39018 this very system call.
39020 The target replies with this packet when it expects @value{GDBN} to
39021 call a host system call on behalf of the target. @value{GDBN} replies
39022 with an appropriate @samp{F} packet and keeps up waiting for the next
39023 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
39024 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
39025 Protocol Extension}, for more details.
39029 @node General Query Packets
39030 @section General Query Packets
39031 @cindex remote query requests
39033 Packets starting with @samp{q} are @dfn{general query packets};
39034 packets starting with @samp{Q} are @dfn{general set packets}. General
39035 query and set packets are a semi-unified form for retrieving and
39036 sending information to and from the stub.
39038 The initial letter of a query or set packet is followed by a name
39039 indicating what sort of thing the packet applies to. For example,
39040 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
39041 definitions with the stub. These packet names follow some
39046 The name must not contain commas, colons or semicolons.
39048 Most @value{GDBN} query and set packets have a leading upper case
39051 The names of custom vendor packets should use a company prefix, in
39052 lower case, followed by a period. For example, packets designed at
39053 the Acme Corporation might begin with @samp{qacme.foo} (for querying
39054 foos) or @samp{Qacme.bar} (for setting bars).
39057 The name of a query or set packet should be separated from any
39058 parameters by a @samp{:}; the parameters themselves should be
39059 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
39060 full packet name, and check for a separator or the end of the packet,
39061 in case two packet names share a common prefix. New packets should not begin
39062 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
39063 packets predate these conventions, and have arguments without any terminator
39064 for the packet name; we suspect they are in widespread use in places that
39065 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
39066 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
39069 Like the descriptions of the other packets, each description here
39070 has a template showing the packet's overall syntax, followed by an
39071 explanation of the packet's meaning. We include spaces in some of the
39072 templates for clarity; these are not part of the packet's syntax. No
39073 @value{GDBN} packet uses spaces to separate its components.
39075 Here are the currently defined query and set packets:
39081 Turn on or off the agent as a helper to perform some debugging operations
39082 delegated from @value{GDBN} (@pxref{Control Agent}).
39084 @item QAllow:@var{op}:@var{val}@dots{}
39085 @cindex @samp{QAllow} packet
39086 Specify which operations @value{GDBN} expects to request of the
39087 target, as a semicolon-separated list of operation name and value
39088 pairs. Possible values for @var{op} include @samp{WriteReg},
39089 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
39090 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
39091 indicating that @value{GDBN} will not request the operation, or 1,
39092 indicating that it may. (The target can then use this to set up its
39093 own internals optimally, for instance if the debugger never expects to
39094 insert breakpoints, it may not need to install its own trap handler.)
39097 @cindex current thread, remote request
39098 @cindex @samp{qC} packet
39099 Return the current thread ID.
39103 @item QC @var{thread-id}
39104 Where @var{thread-id} is a thread ID as documented in
39105 @ref{thread-id syntax}.
39106 @item @r{(anything else)}
39107 Any other reply implies the old thread ID.
39110 @item qCRC:@var{addr},@var{length}
39111 @cindex CRC of memory block, remote request
39112 @cindex @samp{qCRC} packet
39113 @anchor{qCRC packet}
39114 Compute the CRC checksum of a block of memory using CRC-32 defined in
39115 IEEE 802.3. The CRC is computed byte at a time, taking the most
39116 significant bit of each byte first. The initial pattern code
39117 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
39119 @emph{Note:} This is the same CRC used in validating separate debug
39120 files (@pxref{Separate Debug Files, , Debugging Information in Separate
39121 Files}). However the algorithm is slightly different. When validating
39122 separate debug files, the CRC is computed taking the @emph{least}
39123 significant bit of each byte first, and the final result is inverted to
39124 detect trailing zeros.
39129 An error (such as memory fault)
39130 @item C @var{crc32}
39131 The specified memory region's checksum is @var{crc32}.
39134 @item QDisableRandomization:@var{value}
39135 @cindex disable address space randomization, remote request
39136 @cindex @samp{QDisableRandomization} packet
39137 Some target operating systems will randomize the virtual address space
39138 of the inferior process as a security feature, but provide a feature
39139 to disable such randomization, e.g.@: to allow for a more deterministic
39140 debugging experience. On such systems, this packet with a @var{value}
39141 of 1 directs the target to disable address space randomization for
39142 processes subsequently started via @samp{vRun} packets, while a packet
39143 with a @var{value} of 0 tells the target to enable address space
39146 This packet is only available in extended mode (@pxref{extended mode}).
39151 The request succeeded.
39154 An error occurred. The error number @var{nn} is given as hex digits.
39157 An empty reply indicates that @samp{QDisableRandomization} is not supported
39161 This packet is not probed by default; the remote stub must request it,
39162 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39163 This should only be done on targets that actually support disabling
39164 address space randomization.
39166 @item QStartupWithShell:@var{value}
39167 @cindex startup with shell, remote request
39168 @cindex @samp{QStartupWithShell} packet
39169 On UNIX-like targets, it is possible to start the inferior using a
39170 shell program. This is the default behavior on both @value{GDBN} and
39171 @command{gdbserver} (@pxref{set startup-with-shell}). This packet is
39172 used to inform @command{gdbserver} whether it should start the
39173 inferior using a shell or not.
39175 If @var{value} is @samp{0}, @command{gdbserver} will not use a shell
39176 to start the inferior. If @var{value} is @samp{1},
39177 @command{gdbserver} will use a shell to start the inferior. All other
39178 values are considered an error.
39180 This packet is only available in extended mode (@pxref{extended
39186 The request succeeded.
39189 An error occurred. The error number @var{nn} is given as hex digits.
39192 This packet is not probed by default; the remote stub must request it,
39193 by supplying an appropriate @samp{qSupported} response
39194 (@pxref{qSupported}). This should only be done on targets that
39195 actually support starting the inferior using a shell.
39197 Use of this packet is controlled by the @code{set startup-with-shell}
39198 command; @pxref{set startup-with-shell}.
39200 @item QEnvironmentHexEncoded:@var{hex-value}
39201 @anchor{QEnvironmentHexEncoded}
39202 @cindex set environment variable, remote request
39203 @cindex @samp{QEnvironmentHexEncoded} packet
39204 On UNIX-like targets, it is possible to set environment variables that
39205 will be passed to the inferior during the startup process. This
39206 packet is used to inform @command{gdbserver} of an environment
39207 variable that has been defined by the user on @value{GDBN} (@pxref{set
39210 The packet is composed by @var{hex-value}, an hex encoded
39211 representation of the @var{name=value} format representing an
39212 environment variable. The name of the environment variable is
39213 represented by @var{name}, and the value to be assigned to the
39214 environment variable is represented by @var{value}. If the variable
39215 has no value (i.e., the value is @code{null}), then @var{value} will
39218 This packet is only available in extended mode (@pxref{extended
39224 The request succeeded.
39227 This packet is not probed by default; the remote stub must request it,
39228 by supplying an appropriate @samp{qSupported} response
39229 (@pxref{qSupported}). This should only be done on targets that
39230 actually support passing environment variables to the starting
39233 This packet is related to the @code{set environment} command;
39234 @pxref{set environment}.
39236 @item QEnvironmentUnset:@var{hex-value}
39237 @anchor{QEnvironmentUnset}
39238 @cindex unset environment variable, remote request
39239 @cindex @samp{QEnvironmentUnset} packet
39240 On UNIX-like targets, it is possible to unset environment variables
39241 before starting the inferior in the remote target. This packet is
39242 used to inform @command{gdbserver} of an environment variable that has
39243 been unset by the user on @value{GDBN} (@pxref{unset environment}).
39245 The packet is composed by @var{hex-value}, an hex encoded
39246 representation of the name of the environment variable to be unset.
39248 This packet is only available in extended mode (@pxref{extended
39254 The request succeeded.
39257 This packet is not probed by default; the remote stub must request it,
39258 by supplying an appropriate @samp{qSupported} response
39259 (@pxref{qSupported}). This should only be done on targets that
39260 actually support passing environment variables to the starting
39263 This packet is related to the @code{unset environment} command;
39264 @pxref{unset environment}.
39266 @item QEnvironmentReset
39267 @anchor{QEnvironmentReset}
39268 @cindex reset environment, remote request
39269 @cindex @samp{QEnvironmentReset} packet
39270 On UNIX-like targets, this packet is used to reset the state of
39271 environment variables in the remote target before starting the
39272 inferior. In this context, reset means unsetting all environment
39273 variables that were previously set by the user (i.e., were not
39274 initially present in the environment). It is sent to
39275 @command{gdbserver} before the @samp{QEnvironmentHexEncoded}
39276 (@pxref{QEnvironmentHexEncoded}) and the @samp{QEnvironmentUnset}
39277 (@pxref{QEnvironmentUnset}) packets.
39279 This packet is only available in extended mode (@pxref{extended
39285 The request succeeded.
39288 This packet is not probed by default; the remote stub must request it,
39289 by supplying an appropriate @samp{qSupported} response
39290 (@pxref{qSupported}). This should only be done on targets that
39291 actually support passing environment variables to the starting
39294 @item QSetWorkingDir:@r{[}@var{directory}@r{]}
39295 @anchor{QSetWorkingDir packet}
39296 @cindex set working directory, remote request
39297 @cindex @samp{QSetWorkingDir} packet
39298 This packet is used to inform the remote server of the intended
39299 current working directory for programs that are going to be executed.
39301 The packet is composed by @var{directory}, an hex encoded
39302 representation of the directory that the remote inferior will use as
39303 its current working directory. If @var{directory} is an empty string,
39304 the remote server should reset the inferior's current working
39305 directory to its original, empty value.
39307 This packet is only available in extended mode (@pxref{extended
39313 The request succeeded.
39317 @itemx qsThreadInfo
39318 @cindex list active threads, remote request
39319 @cindex @samp{qfThreadInfo} packet
39320 @cindex @samp{qsThreadInfo} packet
39321 Obtain a list of all active thread IDs from the target (OS). Since there
39322 may be too many active threads to fit into one reply packet, this query
39323 works iteratively: it may require more than one query/reply sequence to
39324 obtain the entire list of threads. The first query of the sequence will
39325 be the @samp{qfThreadInfo} query; subsequent queries in the
39326 sequence will be the @samp{qsThreadInfo} query.
39328 NOTE: This packet replaces the @samp{qL} query (see below).
39332 @item m @var{thread-id}
39334 @item m @var{thread-id},@var{thread-id}@dots{}
39335 a comma-separated list of thread IDs
39337 (lower case letter @samp{L}) denotes end of list.
39340 In response to each query, the target will reply with a list of one or
39341 more thread IDs, separated by commas.
39342 @value{GDBN} will respond to each reply with a request for more thread
39343 ids (using the @samp{qs} form of the query), until the target responds
39344 with @samp{l} (lower-case ell, for @dfn{last}).
39345 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
39348 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
39349 initial connection with the remote target, and the very first thread ID
39350 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
39351 message. Therefore, the stub should ensure that the first thread ID in
39352 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
39354 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
39355 @cindex get thread-local storage address, remote request
39356 @cindex @samp{qGetTLSAddr} packet
39357 Fetch the address associated with thread local storage specified
39358 by @var{thread-id}, @var{offset}, and @var{lm}.
39360 @var{thread-id} is the thread ID associated with the
39361 thread for which to fetch the TLS address. @xref{thread-id syntax}.
39363 @var{offset} is the (big endian, hex encoded) offset associated with the
39364 thread local variable. (This offset is obtained from the debug
39365 information associated with the variable.)
39367 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
39368 load module associated with the thread local storage. For example,
39369 a @sc{gnu}/Linux system will pass the link map address of the shared
39370 object associated with the thread local storage under consideration.
39371 Other operating environments may choose to represent the load module
39372 differently, so the precise meaning of this parameter will vary.
39376 @item @var{XX}@dots{}
39377 Hex encoded (big endian) bytes representing the address of the thread
39378 local storage requested.
39381 An error occurred. The error number @var{nn} is given as hex digits.
39384 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
39387 @item qGetTIBAddr:@var{thread-id}
39388 @cindex get thread information block address
39389 @cindex @samp{qGetTIBAddr} packet
39390 Fetch address of the Windows OS specific Thread Information Block.
39392 @var{thread-id} is the thread ID associated with the thread.
39396 @item @var{XX}@dots{}
39397 Hex encoded (big endian) bytes representing the linear address of the
39398 thread information block.
39401 An error occured. This means that either the thread was not found, or the
39402 address could not be retrieved.
39405 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
39408 @item qL @var{startflag} @var{threadcount} @var{nextthread}
39409 Obtain thread information from RTOS. Where: @var{startflag} (one hex
39410 digit) is one to indicate the first query and zero to indicate a
39411 subsequent query; @var{threadcount} (two hex digits) is the maximum
39412 number of threads the response packet can contain; and @var{nextthread}
39413 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
39414 returned in the response as @var{argthread}.
39416 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
39420 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
39421 Where: @var{count} (two hex digits) is the number of threads being
39422 returned; @var{done} (one hex digit) is zero to indicate more threads
39423 and one indicates no further threads; @var{argthreadid} (eight hex
39424 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
39425 is a sequence of thread IDs, @var{threadid} (eight hex
39426 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
39430 @cindex section offsets, remote request
39431 @cindex @samp{qOffsets} packet
39432 Get section offsets that the target used when relocating the downloaded
39437 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
39438 Relocate the @code{Text} section by @var{xxx} from its original address.
39439 Relocate the @code{Data} section by @var{yyy} from its original address.
39440 If the object file format provides segment information (e.g.@: @sc{elf}
39441 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
39442 segments by the supplied offsets.
39444 @emph{Note: while a @code{Bss} offset may be included in the response,
39445 @value{GDBN} ignores this and instead applies the @code{Data} offset
39446 to the @code{Bss} section.}
39448 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
39449 Relocate the first segment of the object file, which conventionally
39450 contains program code, to a starting address of @var{xxx}. If
39451 @samp{DataSeg} is specified, relocate the second segment, which
39452 conventionally contains modifiable data, to a starting address of
39453 @var{yyy}. @value{GDBN} will report an error if the object file
39454 does not contain segment information, or does not contain at least
39455 as many segments as mentioned in the reply. Extra segments are
39456 kept at fixed offsets relative to the last relocated segment.
39459 @item qP @var{mode} @var{thread-id}
39460 @cindex thread information, remote request
39461 @cindex @samp{qP} packet
39462 Returns information on @var{thread-id}. Where: @var{mode} is a hex
39463 encoded 32 bit mode; @var{thread-id} is a thread ID
39464 (@pxref{thread-id syntax}).
39466 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
39469 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
39473 @cindex non-stop mode, remote request
39474 @cindex @samp{QNonStop} packet
39476 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
39477 @xref{Remote Non-Stop}, for more information.
39482 The request succeeded.
39485 An error occurred. The error number @var{nn} is given as hex digits.
39488 An empty reply indicates that @samp{QNonStop} is not supported by
39492 This packet is not probed by default; the remote stub must request it,
39493 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39494 Use of this packet is controlled by the @code{set non-stop} command;
39495 @pxref{Non-Stop Mode}.
39497 @item QCatchSyscalls:1 @r{[};@var{sysno}@r{]}@dots{}
39498 @itemx QCatchSyscalls:0
39499 @cindex catch syscalls from inferior, remote request
39500 @cindex @samp{QCatchSyscalls} packet
39501 @anchor{QCatchSyscalls}
39502 Enable (@samp{QCatchSyscalls:1}) or disable (@samp{QCatchSyscalls:0})
39503 catching syscalls from the inferior process.
39505 For @samp{QCatchSyscalls:1}, each listed syscall @var{sysno} (encoded
39506 in hex) should be reported to @value{GDBN}. If no syscall @var{sysno}
39507 is listed, every system call should be reported.
39509 Note that if a syscall not in the list is reported, @value{GDBN} will
39510 still filter the event according to its own list from all corresponding
39511 @code{catch syscall} commands. However, it is more efficient to only
39512 report the requested syscalls.
39514 Multiple @samp{QCatchSyscalls:1} packets do not combine; any earlier
39515 @samp{QCatchSyscalls:1} list is completely replaced by the new list.
39517 If the inferior process execs, the state of @samp{QCatchSyscalls} is
39518 kept for the new process too. On targets where exec may affect syscall
39519 numbers, for example with exec between 32 and 64-bit processes, the
39520 client should send a new packet with the new syscall list.
39525 The request succeeded.
39528 An error occurred. @var{nn} are hex digits.
39531 An empty reply indicates that @samp{QCatchSyscalls} is not supported by
39535 Use of this packet is controlled by the @code{set remote catch-syscalls}
39536 command (@pxref{Remote Configuration, set remote catch-syscalls}).
39537 This packet is not probed by default; the remote stub must request it,
39538 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39540 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
39541 @cindex pass signals to inferior, remote request
39542 @cindex @samp{QPassSignals} packet
39543 @anchor{QPassSignals}
39544 Each listed @var{signal} should be passed directly to the inferior process.
39545 Signals are numbered identically to continue packets and stop replies
39546 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
39547 strictly greater than the previous item. These signals do not need to stop
39548 the inferior, or be reported to @value{GDBN}. All other signals should be
39549 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
39550 combine; any earlier @samp{QPassSignals} list is completely replaced by the
39551 new list. This packet improves performance when using @samp{handle
39552 @var{signal} nostop noprint pass}.
39557 The request succeeded.
39560 An error occurred. The error number @var{nn} is given as hex digits.
39563 An empty reply indicates that @samp{QPassSignals} is not supported by
39567 Use of this packet is controlled by the @code{set remote pass-signals}
39568 command (@pxref{Remote Configuration, set remote pass-signals}).
39569 This packet is not probed by default; the remote stub must request it,
39570 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39572 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
39573 @cindex signals the inferior may see, remote request
39574 @cindex @samp{QProgramSignals} packet
39575 @anchor{QProgramSignals}
39576 Each listed @var{signal} may be delivered to the inferior process.
39577 Others should be silently discarded.
39579 In some cases, the remote stub may need to decide whether to deliver a
39580 signal to the program or not without @value{GDBN} involvement. One
39581 example of that is while detaching --- the program's threads may have
39582 stopped for signals that haven't yet had a chance of being reported to
39583 @value{GDBN}, and so the remote stub can use the signal list specified
39584 by this packet to know whether to deliver or ignore those pending
39587 This does not influence whether to deliver a signal as requested by a
39588 resumption packet (@pxref{vCont packet}).
39590 Signals are numbered identically to continue packets and stop replies
39591 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
39592 strictly greater than the previous item. Multiple
39593 @samp{QProgramSignals} packets do not combine; any earlier
39594 @samp{QProgramSignals} list is completely replaced by the new list.
39599 The request succeeded.
39602 An error occurred. The error number @var{nn} is given as hex digits.
39605 An empty reply indicates that @samp{QProgramSignals} is not supported
39609 Use of this packet is controlled by the @code{set remote program-signals}
39610 command (@pxref{Remote Configuration, set remote program-signals}).
39611 This packet is not probed by default; the remote stub must request it,
39612 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39614 @anchor{QThreadEvents}
39615 @item QThreadEvents:1
39616 @itemx QThreadEvents:0
39617 @cindex thread create/exit events, remote request
39618 @cindex @samp{QThreadEvents} packet
39620 Enable (@samp{QThreadEvents:1}) or disable (@samp{QThreadEvents:0})
39621 reporting of thread create and exit events. @xref{thread create
39622 event}, for the reply specifications. For example, this is used in
39623 non-stop mode when @value{GDBN} stops a set of threads and
39624 synchronously waits for the their corresponding stop replies. Without
39625 exit events, if one of the threads exits, @value{GDBN} would hang
39626 forever not knowing that it should no longer expect a stop for that
39627 same thread. @value{GDBN} does not enable this feature unless the
39628 stub reports that it supports it by including @samp{QThreadEvents+} in
39629 its @samp{qSupported} reply.
39634 The request succeeded.
39637 An error occurred. The error number @var{nn} is given as hex digits.
39640 An empty reply indicates that @samp{QThreadEvents} is not supported by
39644 Use of this packet is controlled by the @code{set remote thread-events}
39645 command (@pxref{Remote Configuration, set remote thread-events}).
39647 @item qRcmd,@var{command}
39648 @cindex execute remote command, remote request
39649 @cindex @samp{qRcmd} packet
39650 @var{command} (hex encoded) is passed to the local interpreter for
39651 execution. Invalid commands should be reported using the output
39652 string. Before the final result packet, the target may also respond
39653 with a number of intermediate @samp{O@var{output}} console output
39654 packets. @emph{Implementors should note that providing access to a
39655 stubs's interpreter may have security implications}.
39660 A command response with no output.
39662 A command response with the hex encoded output string @var{OUTPUT}.
39664 Indicate a badly formed request.
39666 An empty reply indicates that @samp{qRcmd} is not recognized.
39669 (Note that the @code{qRcmd} packet's name is separated from the
39670 command by a @samp{,}, not a @samp{:}, contrary to the naming
39671 conventions above. Please don't use this packet as a model for new
39674 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
39675 @cindex searching memory, in remote debugging
39677 @cindex @samp{qSearch:memory} packet
39679 @cindex @samp{qSearch memory} packet
39680 @anchor{qSearch memory}
39681 Search @var{length} bytes at @var{address} for @var{search-pattern}.
39682 Both @var{address} and @var{length} are encoded in hex;
39683 @var{search-pattern} is a sequence of bytes, also hex encoded.
39688 The pattern was not found.
39690 The pattern was found at @var{address}.
39692 A badly formed request or an error was encountered while searching memory.
39694 An empty reply indicates that @samp{qSearch:memory} is not recognized.
39697 @item QStartNoAckMode
39698 @cindex @samp{QStartNoAckMode} packet
39699 @anchor{QStartNoAckMode}
39700 Request that the remote stub disable the normal @samp{+}/@samp{-}
39701 protocol acknowledgments (@pxref{Packet Acknowledgment}).
39706 The stub has switched to no-acknowledgment mode.
39707 @value{GDBN} acknowledges this reponse,
39708 but neither the stub nor @value{GDBN} shall send or expect further
39709 @samp{+}/@samp{-} acknowledgments in the current connection.
39711 An empty reply indicates that the stub does not support no-acknowledgment mode.
39714 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
39715 @cindex supported packets, remote query
39716 @cindex features of the remote protocol
39717 @cindex @samp{qSupported} packet
39718 @anchor{qSupported}
39719 Tell the remote stub about features supported by @value{GDBN}, and
39720 query the stub for features it supports. This packet allows
39721 @value{GDBN} and the remote stub to take advantage of each others'
39722 features. @samp{qSupported} also consolidates multiple feature probes
39723 at startup, to improve @value{GDBN} performance---a single larger
39724 packet performs better than multiple smaller probe packets on
39725 high-latency links. Some features may enable behavior which must not
39726 be on by default, e.g.@: because it would confuse older clients or
39727 stubs. Other features may describe packets which could be
39728 automatically probed for, but are not. These features must be
39729 reported before @value{GDBN} will use them. This ``default
39730 unsupported'' behavior is not appropriate for all packets, but it
39731 helps to keep the initial connection time under control with new
39732 versions of @value{GDBN} which support increasing numbers of packets.
39736 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
39737 The stub supports or does not support each returned @var{stubfeature},
39738 depending on the form of each @var{stubfeature} (see below for the
39741 An empty reply indicates that @samp{qSupported} is not recognized,
39742 or that no features needed to be reported to @value{GDBN}.
39745 The allowed forms for each feature (either a @var{gdbfeature} in the
39746 @samp{qSupported} packet, or a @var{stubfeature} in the response)
39750 @item @var{name}=@var{value}
39751 The remote protocol feature @var{name} is supported, and associated
39752 with the specified @var{value}. The format of @var{value} depends
39753 on the feature, but it must not include a semicolon.
39755 The remote protocol feature @var{name} is supported, and does not
39756 need an associated value.
39758 The remote protocol feature @var{name} is not supported.
39760 The remote protocol feature @var{name} may be supported, and
39761 @value{GDBN} should auto-detect support in some other way when it is
39762 needed. This form will not be used for @var{gdbfeature} notifications,
39763 but may be used for @var{stubfeature} responses.
39766 Whenever the stub receives a @samp{qSupported} request, the
39767 supplied set of @value{GDBN} features should override any previous
39768 request. This allows @value{GDBN} to put the stub in a known
39769 state, even if the stub had previously been communicating with
39770 a different version of @value{GDBN}.
39772 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
39777 This feature indicates whether @value{GDBN} supports multiprocess
39778 extensions to the remote protocol. @value{GDBN} does not use such
39779 extensions unless the stub also reports that it supports them by
39780 including @samp{multiprocess+} in its @samp{qSupported} reply.
39781 @xref{multiprocess extensions}, for details.
39784 This feature indicates that @value{GDBN} supports the XML target
39785 description. If the stub sees @samp{xmlRegisters=} with target
39786 specific strings separated by a comma, it will report register
39790 This feature indicates whether @value{GDBN} supports the
39791 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
39792 instruction reply packet}).
39795 This feature indicates whether @value{GDBN} supports the swbreak stop
39796 reason in stop replies. @xref{swbreak stop reason}, for details.
39799 This feature indicates whether @value{GDBN} supports the hwbreak stop
39800 reason in stop replies. @xref{swbreak stop reason}, for details.
39803 This feature indicates whether @value{GDBN} supports fork event
39804 extensions to the remote protocol. @value{GDBN} does not use such
39805 extensions unless the stub also reports that it supports them by
39806 including @samp{fork-events+} in its @samp{qSupported} reply.
39809 This feature indicates whether @value{GDBN} supports vfork event
39810 extensions to the remote protocol. @value{GDBN} does not use such
39811 extensions unless the stub also reports that it supports them by
39812 including @samp{vfork-events+} in its @samp{qSupported} reply.
39815 This feature indicates whether @value{GDBN} supports exec event
39816 extensions to the remote protocol. @value{GDBN} does not use such
39817 extensions unless the stub also reports that it supports them by
39818 including @samp{exec-events+} in its @samp{qSupported} reply.
39820 @item vContSupported
39821 This feature indicates whether @value{GDBN} wants to know the
39822 supported actions in the reply to @samp{vCont?} packet.
39825 Stubs should ignore any unknown values for
39826 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
39827 packet supports receiving packets of unlimited length (earlier
39828 versions of @value{GDBN} may reject overly long responses). Additional values
39829 for @var{gdbfeature} may be defined in the future to let the stub take
39830 advantage of new features in @value{GDBN}, e.g.@: incompatible
39831 improvements in the remote protocol---the @samp{multiprocess} feature is
39832 an example of such a feature. The stub's reply should be independent
39833 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
39834 describes all the features it supports, and then the stub replies with
39835 all the features it supports.
39837 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
39838 responses, as long as each response uses one of the standard forms.
39840 Some features are flags. A stub which supports a flag feature
39841 should respond with a @samp{+} form response. Other features
39842 require values, and the stub should respond with an @samp{=}
39845 Each feature has a default value, which @value{GDBN} will use if
39846 @samp{qSupported} is not available or if the feature is not mentioned
39847 in the @samp{qSupported} response. The default values are fixed; a
39848 stub is free to omit any feature responses that match the defaults.
39850 Not all features can be probed, but for those which can, the probing
39851 mechanism is useful: in some cases, a stub's internal
39852 architecture may not allow the protocol layer to know some information
39853 about the underlying target in advance. This is especially common in
39854 stubs which may be configured for multiple targets.
39856 These are the currently defined stub features and their properties:
39858 @multitable @columnfractions 0.35 0.2 0.12 0.2
39859 @c NOTE: The first row should be @headitem, but we do not yet require
39860 @c a new enough version of Texinfo (4.7) to use @headitem.
39862 @tab Value Required
39866 @item @samp{PacketSize}
39871 @item @samp{qXfer:auxv:read}
39876 @item @samp{qXfer:btrace:read}
39881 @item @samp{qXfer:btrace-conf:read}
39886 @item @samp{qXfer:exec-file:read}
39891 @item @samp{qXfer:features:read}
39896 @item @samp{qXfer:libraries:read}
39901 @item @samp{qXfer:libraries-svr4:read}
39906 @item @samp{augmented-libraries-svr4-read}
39911 @item @samp{qXfer:memory-map:read}
39916 @item @samp{qXfer:sdata:read}
39921 @item @samp{qXfer:spu:read}
39926 @item @samp{qXfer:spu:write}
39931 @item @samp{qXfer:siginfo:read}
39936 @item @samp{qXfer:siginfo:write}
39941 @item @samp{qXfer:threads:read}
39946 @item @samp{qXfer:traceframe-info:read}
39951 @item @samp{qXfer:uib:read}
39956 @item @samp{qXfer:fdpic:read}
39961 @item @samp{Qbtrace:off}
39966 @item @samp{Qbtrace:bts}
39971 @item @samp{Qbtrace:pt}
39976 @item @samp{Qbtrace-conf:bts:size}
39981 @item @samp{Qbtrace-conf:pt:size}
39986 @item @samp{QNonStop}
39991 @item @samp{QCatchSyscalls}
39996 @item @samp{QPassSignals}
40001 @item @samp{QStartNoAckMode}
40006 @item @samp{multiprocess}
40011 @item @samp{ConditionalBreakpoints}
40016 @item @samp{ConditionalTracepoints}
40021 @item @samp{ReverseContinue}
40026 @item @samp{ReverseStep}
40031 @item @samp{TracepointSource}
40036 @item @samp{QAgent}
40041 @item @samp{QAllow}
40046 @item @samp{QDisableRandomization}
40051 @item @samp{EnableDisableTracepoints}
40056 @item @samp{QTBuffer:size}
40061 @item @samp{tracenz}
40066 @item @samp{BreakpointCommands}
40071 @item @samp{swbreak}
40076 @item @samp{hwbreak}
40081 @item @samp{fork-events}
40086 @item @samp{vfork-events}
40091 @item @samp{exec-events}
40096 @item @samp{QThreadEvents}
40101 @item @samp{no-resumed}
40108 These are the currently defined stub features, in more detail:
40111 @cindex packet size, remote protocol
40112 @item PacketSize=@var{bytes}
40113 The remote stub can accept packets up to at least @var{bytes} in
40114 length. @value{GDBN} will send packets up to this size for bulk
40115 transfers, and will never send larger packets. This is a limit on the
40116 data characters in the packet, including the frame and checksum.
40117 There is no trailing NUL byte in a remote protocol packet; if the stub
40118 stores packets in a NUL-terminated format, it should allow an extra
40119 byte in its buffer for the NUL. If this stub feature is not supported,
40120 @value{GDBN} guesses based on the size of the @samp{g} packet response.
40122 @item qXfer:auxv:read
40123 The remote stub understands the @samp{qXfer:auxv:read} packet
40124 (@pxref{qXfer auxiliary vector read}).
40126 @item qXfer:btrace:read
40127 The remote stub understands the @samp{qXfer:btrace:read}
40128 packet (@pxref{qXfer btrace read}).
40130 @item qXfer:btrace-conf:read
40131 The remote stub understands the @samp{qXfer:btrace-conf:read}
40132 packet (@pxref{qXfer btrace-conf read}).
40134 @item qXfer:exec-file:read
40135 The remote stub understands the @samp{qXfer:exec-file:read} packet
40136 (@pxref{qXfer executable filename read}).
40138 @item qXfer:features:read
40139 The remote stub understands the @samp{qXfer:features:read} packet
40140 (@pxref{qXfer target description read}).
40142 @item qXfer:libraries:read
40143 The remote stub understands the @samp{qXfer:libraries:read} packet
40144 (@pxref{qXfer library list read}).
40146 @item qXfer:libraries-svr4:read
40147 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
40148 (@pxref{qXfer svr4 library list read}).
40150 @item augmented-libraries-svr4-read
40151 The remote stub understands the augmented form of the
40152 @samp{qXfer:libraries-svr4:read} packet
40153 (@pxref{qXfer svr4 library list read}).
40155 @item qXfer:memory-map:read
40156 The remote stub understands the @samp{qXfer:memory-map:read} packet
40157 (@pxref{qXfer memory map read}).
40159 @item qXfer:sdata:read
40160 The remote stub understands the @samp{qXfer:sdata:read} packet
40161 (@pxref{qXfer sdata read}).
40163 @item qXfer:spu:read
40164 The remote stub understands the @samp{qXfer:spu:read} packet
40165 (@pxref{qXfer spu read}).
40167 @item qXfer:spu:write
40168 The remote stub understands the @samp{qXfer:spu:write} packet
40169 (@pxref{qXfer spu write}).
40171 @item qXfer:siginfo:read
40172 The remote stub understands the @samp{qXfer:siginfo:read} packet
40173 (@pxref{qXfer siginfo read}).
40175 @item qXfer:siginfo:write
40176 The remote stub understands the @samp{qXfer:siginfo:write} packet
40177 (@pxref{qXfer siginfo write}).
40179 @item qXfer:threads:read
40180 The remote stub understands the @samp{qXfer:threads:read} packet
40181 (@pxref{qXfer threads read}).
40183 @item qXfer:traceframe-info:read
40184 The remote stub understands the @samp{qXfer:traceframe-info:read}
40185 packet (@pxref{qXfer traceframe info read}).
40187 @item qXfer:uib:read
40188 The remote stub understands the @samp{qXfer:uib:read}
40189 packet (@pxref{qXfer unwind info block}).
40191 @item qXfer:fdpic:read
40192 The remote stub understands the @samp{qXfer:fdpic:read}
40193 packet (@pxref{qXfer fdpic loadmap read}).
40196 The remote stub understands the @samp{QNonStop} packet
40197 (@pxref{QNonStop}).
40199 @item QCatchSyscalls
40200 The remote stub understands the @samp{QCatchSyscalls} packet
40201 (@pxref{QCatchSyscalls}).
40204 The remote stub understands the @samp{QPassSignals} packet
40205 (@pxref{QPassSignals}).
40207 @item QStartNoAckMode
40208 The remote stub understands the @samp{QStartNoAckMode} packet and
40209 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
40212 @anchor{multiprocess extensions}
40213 @cindex multiprocess extensions, in remote protocol
40214 The remote stub understands the multiprocess extensions to the remote
40215 protocol syntax. The multiprocess extensions affect the syntax of
40216 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
40217 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
40218 replies. Note that reporting this feature indicates support for the
40219 syntactic extensions only, not that the stub necessarily supports
40220 debugging of more than one process at a time. The stub must not use
40221 multiprocess extensions in packet replies unless @value{GDBN} has also
40222 indicated it supports them in its @samp{qSupported} request.
40224 @item qXfer:osdata:read
40225 The remote stub understands the @samp{qXfer:osdata:read} packet
40226 ((@pxref{qXfer osdata read}).
40228 @item ConditionalBreakpoints
40229 The target accepts and implements evaluation of conditional expressions
40230 defined for breakpoints. The target will only report breakpoint triggers
40231 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
40233 @item ConditionalTracepoints
40234 The remote stub accepts and implements conditional expressions defined
40235 for tracepoints (@pxref{Tracepoint Conditions}).
40237 @item ReverseContinue
40238 The remote stub accepts and implements the reverse continue packet
40242 The remote stub accepts and implements the reverse step packet
40245 @item TracepointSource
40246 The remote stub understands the @samp{QTDPsrc} packet that supplies
40247 the source form of tracepoint definitions.
40250 The remote stub understands the @samp{QAgent} packet.
40253 The remote stub understands the @samp{QAllow} packet.
40255 @item QDisableRandomization
40256 The remote stub understands the @samp{QDisableRandomization} packet.
40258 @item StaticTracepoint
40259 @cindex static tracepoints, in remote protocol
40260 The remote stub supports static tracepoints.
40262 @item InstallInTrace
40263 @anchor{install tracepoint in tracing}
40264 The remote stub supports installing tracepoint in tracing.
40266 @item EnableDisableTracepoints
40267 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
40268 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
40269 to be enabled and disabled while a trace experiment is running.
40271 @item QTBuffer:size
40272 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
40273 packet that allows to change the size of the trace buffer.
40276 @cindex string tracing, in remote protocol
40277 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
40278 See @ref{Bytecode Descriptions} for details about the bytecode.
40280 @item BreakpointCommands
40281 @cindex breakpoint commands, in remote protocol
40282 The remote stub supports running a breakpoint's command list itself,
40283 rather than reporting the hit to @value{GDBN}.
40286 The remote stub understands the @samp{Qbtrace:off} packet.
40289 The remote stub understands the @samp{Qbtrace:bts} packet.
40292 The remote stub understands the @samp{Qbtrace:pt} packet.
40294 @item Qbtrace-conf:bts:size
40295 The remote stub understands the @samp{Qbtrace-conf:bts:size} packet.
40297 @item Qbtrace-conf:pt:size
40298 The remote stub understands the @samp{Qbtrace-conf:pt:size} packet.
40301 The remote stub reports the @samp{swbreak} stop reason for memory
40305 The remote stub reports the @samp{hwbreak} stop reason for hardware
40309 The remote stub reports the @samp{fork} stop reason for fork events.
40312 The remote stub reports the @samp{vfork} stop reason for vfork events
40313 and vforkdone events.
40316 The remote stub reports the @samp{exec} stop reason for exec events.
40318 @item vContSupported
40319 The remote stub reports the supported actions in the reply to
40320 @samp{vCont?} packet.
40322 @item QThreadEvents
40323 The remote stub understands the @samp{QThreadEvents} packet.
40326 The remote stub reports the @samp{N} stop reply.
40331 @cindex symbol lookup, remote request
40332 @cindex @samp{qSymbol} packet
40333 Notify the target that @value{GDBN} is prepared to serve symbol lookup
40334 requests. Accept requests from the target for the values of symbols.
40339 The target does not need to look up any (more) symbols.
40340 @item qSymbol:@var{sym_name}
40341 The target requests the value of symbol @var{sym_name} (hex encoded).
40342 @value{GDBN} may provide the value by using the
40343 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
40347 @item qSymbol:@var{sym_value}:@var{sym_name}
40348 Set the value of @var{sym_name} to @var{sym_value}.
40350 @var{sym_name} (hex encoded) is the name of a symbol whose value the
40351 target has previously requested.
40353 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
40354 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
40360 The target does not need to look up any (more) symbols.
40361 @item qSymbol:@var{sym_name}
40362 The target requests the value of a new symbol @var{sym_name} (hex
40363 encoded). @value{GDBN} will continue to supply the values of symbols
40364 (if available), until the target ceases to request them.
40369 @itemx QTDisconnected
40376 @itemx qTMinFTPILen
40378 @xref{Tracepoint Packets}.
40380 @item qThreadExtraInfo,@var{thread-id}
40381 @cindex thread attributes info, remote request
40382 @cindex @samp{qThreadExtraInfo} packet
40383 Obtain from the target OS a printable string description of thread
40384 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
40385 for the forms of @var{thread-id}. This
40386 string may contain anything that the target OS thinks is interesting
40387 for @value{GDBN} to tell the user about the thread. The string is
40388 displayed in @value{GDBN}'s @code{info threads} display. Some
40389 examples of possible thread extra info strings are @samp{Runnable}, or
40390 @samp{Blocked on Mutex}.
40394 @item @var{XX}@dots{}
40395 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
40396 comprising the printable string containing the extra information about
40397 the thread's attributes.
40400 (Note that the @code{qThreadExtraInfo} packet's name is separated from
40401 the command by a @samp{,}, not a @samp{:}, contrary to the naming
40402 conventions above. Please don't use this packet as a model for new
40421 @xref{Tracepoint Packets}.
40423 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
40424 @cindex read special object, remote request
40425 @cindex @samp{qXfer} packet
40426 @anchor{qXfer read}
40427 Read uninterpreted bytes from the target's special data area
40428 identified by the keyword @var{object}. Request @var{length} bytes
40429 starting at @var{offset} bytes into the data. The content and
40430 encoding of @var{annex} is specific to @var{object}; it can supply
40431 additional details about what data to access.
40436 Data @var{data} (@pxref{Binary Data}) has been read from the
40437 target. There may be more data at a higher address (although
40438 it is permitted to return @samp{m} even for the last valid
40439 block of data, as long as at least one byte of data was read).
40440 It is possible for @var{data} to have fewer bytes than the @var{length} in the
40444 Data @var{data} (@pxref{Binary Data}) has been read from the target.
40445 There is no more data to be read. It is possible for @var{data} to
40446 have fewer bytes than the @var{length} in the request.
40449 The @var{offset} in the request is at the end of the data.
40450 There is no more data to be read.
40453 The request was malformed, or @var{annex} was invalid.
40456 The offset was invalid, or there was an error encountered reading the data.
40457 The @var{nn} part is a hex-encoded @code{errno} value.
40460 An empty reply indicates the @var{object} string was not recognized by
40461 the stub, or that the object does not support reading.
40464 Here are the specific requests of this form defined so far. All the
40465 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
40466 formats, listed above.
40469 @item qXfer:auxv:read::@var{offset},@var{length}
40470 @anchor{qXfer auxiliary vector read}
40471 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
40472 auxiliary vector}. Note @var{annex} must be empty.
40474 This packet is not probed by default; the remote stub must request it,
40475 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40477 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
40478 @anchor{qXfer btrace read}
40480 Return a description of the current branch trace.
40481 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
40482 packet may have one of the following values:
40486 Returns all available branch trace.
40489 Returns all available branch trace if the branch trace changed since
40490 the last read request.
40493 Returns the new branch trace since the last read request. Adds a new
40494 block to the end of the trace that begins at zero and ends at the source
40495 location of the first branch in the trace buffer. This extra block is
40496 used to stitch traces together.
40498 If the trace buffer overflowed, returns an error indicating the overflow.
40501 This packet is not probed by default; the remote stub must request it
40502 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40504 @item qXfer:btrace-conf:read::@var{offset},@var{length}
40505 @anchor{qXfer btrace-conf read}
40507 Return a description of the current branch trace configuration.
40508 @xref{Branch Trace Configuration Format}.
40510 This packet is not probed by default; the remote stub must request it
40511 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40513 @item qXfer:exec-file:read:@var{annex}:@var{offset},@var{length}
40514 @anchor{qXfer executable filename read}
40515 Return the full absolute name of the file that was executed to create
40516 a process running on the remote system. The annex specifies the
40517 numeric process ID of the process to query, encoded as a hexadecimal
40518 number. If the annex part is empty the remote stub should return the
40519 filename corresponding to the currently executing process.
40521 This packet is not probed by default; the remote stub must request it,
40522 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40524 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
40525 @anchor{qXfer target description read}
40526 Access the @dfn{target description}. @xref{Target Descriptions}. The
40527 annex specifies which XML document to access. The main description is
40528 always loaded from the @samp{target.xml} annex.
40530 This packet is not probed by default; the remote stub must request it,
40531 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40533 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
40534 @anchor{qXfer library list read}
40535 Access the target's list of loaded libraries. @xref{Library List Format}.
40536 The annex part of the generic @samp{qXfer} packet must be empty
40537 (@pxref{qXfer read}).
40539 Targets which maintain a list of libraries in the program's memory do
40540 not need to implement this packet; it is designed for platforms where
40541 the operating system manages the list of loaded libraries.
40543 This packet is not probed by default; the remote stub must request it,
40544 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40546 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
40547 @anchor{qXfer svr4 library list read}
40548 Access the target's list of loaded libraries when the target is an SVR4
40549 platform. @xref{Library List Format for SVR4 Targets}. The annex part
40550 of the generic @samp{qXfer} packet must be empty unless the remote
40551 stub indicated it supports the augmented form of this packet
40552 by supplying an appropriate @samp{qSupported} response
40553 (@pxref{qXfer read}, @ref{qSupported}).
40555 This packet is optional for better performance on SVR4 targets.
40556 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
40558 This packet is not probed by default; the remote stub must request it,
40559 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40561 If the remote stub indicates it supports the augmented form of this
40562 packet then the annex part of the generic @samp{qXfer} packet may
40563 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
40564 arguments. The currently supported arguments are:
40567 @item start=@var{address}
40568 A hexadecimal number specifying the address of the @samp{struct
40569 link_map} to start reading the library list from. If unset or zero
40570 then the first @samp{struct link_map} in the library list will be
40571 chosen as the starting point.
40573 @item prev=@var{address}
40574 A hexadecimal number specifying the address of the @samp{struct
40575 link_map} immediately preceding the @samp{struct link_map}
40576 specified by the @samp{start} argument. If unset or zero then
40577 the remote stub will expect that no @samp{struct link_map}
40578 exists prior to the starting point.
40582 Arguments that are not understood by the remote stub will be silently
40585 @item qXfer:memory-map:read::@var{offset},@var{length}
40586 @anchor{qXfer memory map read}
40587 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
40588 annex part of the generic @samp{qXfer} packet must be empty
40589 (@pxref{qXfer read}).
40591 This packet is not probed by default; the remote stub must request it,
40592 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40594 @item qXfer:sdata:read::@var{offset},@var{length}
40595 @anchor{qXfer sdata read}
40597 Read contents of the extra collected static tracepoint marker
40598 information. The annex part of the generic @samp{qXfer} packet must
40599 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
40602 This packet is not probed by default; the remote stub must request it,
40603 by supplying an appropriate @samp{qSupported} response
40604 (@pxref{qSupported}).
40606 @item qXfer:siginfo:read::@var{offset},@var{length}
40607 @anchor{qXfer siginfo read}
40608 Read contents of the extra signal information on the target
40609 system. The annex part of the generic @samp{qXfer} packet must be
40610 empty (@pxref{qXfer read}).
40612 This packet is not probed by default; the remote stub must request it,
40613 by supplying an appropriate @samp{qSupported} response
40614 (@pxref{qSupported}).
40616 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
40617 @anchor{qXfer spu read}
40618 Read contents of an @code{spufs} file on the target system. The
40619 annex specifies which file to read; it must be of the form
40620 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
40621 in the target process, and @var{name} identifes the @code{spufs} file
40622 in that context to be accessed.
40624 This packet is not probed by default; the remote stub must request it,
40625 by supplying an appropriate @samp{qSupported} response
40626 (@pxref{qSupported}).
40628 @item qXfer:threads:read::@var{offset},@var{length}
40629 @anchor{qXfer threads read}
40630 Access the list of threads on target. @xref{Thread List Format}. The
40631 annex part of the generic @samp{qXfer} packet must be empty
40632 (@pxref{qXfer read}).
40634 This packet is not probed by default; the remote stub must request it,
40635 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40637 @item qXfer:traceframe-info:read::@var{offset},@var{length}
40638 @anchor{qXfer traceframe info read}
40640 Return a description of the current traceframe's contents.
40641 @xref{Traceframe Info Format}. The annex part of the generic
40642 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
40644 This packet is not probed by default; the remote stub must request it,
40645 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40647 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
40648 @anchor{qXfer unwind info block}
40650 Return the unwind information block for @var{pc}. This packet is used
40651 on OpenVMS/ia64 to ask the kernel unwind information.
40653 This packet is not probed by default.
40655 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
40656 @anchor{qXfer fdpic loadmap read}
40657 Read contents of @code{loadmap}s on the target system. The
40658 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
40659 executable @code{loadmap} or interpreter @code{loadmap} to read.
40661 This packet is not probed by default; the remote stub must request it,
40662 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40664 @item qXfer:osdata:read::@var{offset},@var{length}
40665 @anchor{qXfer osdata read}
40666 Access the target's @dfn{operating system information}.
40667 @xref{Operating System Information}.
40671 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
40672 @cindex write data into object, remote request
40673 @anchor{qXfer write}
40674 Write uninterpreted bytes into the target's special data area
40675 identified by the keyword @var{object}, starting at @var{offset} bytes
40676 into the data. The binary-encoded data (@pxref{Binary Data}) to be
40677 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
40678 is specific to @var{object}; it can supply additional details about what data
40684 @var{nn} (hex encoded) is the number of bytes written.
40685 This may be fewer bytes than supplied in the request.
40688 The request was malformed, or @var{annex} was invalid.
40691 The offset was invalid, or there was an error encountered writing the data.
40692 The @var{nn} part is a hex-encoded @code{errno} value.
40695 An empty reply indicates the @var{object} string was not
40696 recognized by the stub, or that the object does not support writing.
40699 Here are the specific requests of this form defined so far. All the
40700 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
40701 formats, listed above.
40704 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
40705 @anchor{qXfer siginfo write}
40706 Write @var{data} to the extra signal information on the target system.
40707 The annex part of the generic @samp{qXfer} packet must be
40708 empty (@pxref{qXfer write}).
40710 This packet is not probed by default; the remote stub must request it,
40711 by supplying an appropriate @samp{qSupported} response
40712 (@pxref{qSupported}).
40714 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
40715 @anchor{qXfer spu write}
40716 Write @var{data} to an @code{spufs} file on the target system. The
40717 annex specifies which file to write; it must be of the form
40718 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
40719 in the target process, and @var{name} identifes the @code{spufs} file
40720 in that context to be accessed.
40722 This packet is not probed by default; the remote stub must request it,
40723 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40726 @item qXfer:@var{object}:@var{operation}:@dots{}
40727 Requests of this form may be added in the future. When a stub does
40728 not recognize the @var{object} keyword, or its support for
40729 @var{object} does not recognize the @var{operation} keyword, the stub
40730 must respond with an empty packet.
40732 @item qAttached:@var{pid}
40733 @cindex query attached, remote request
40734 @cindex @samp{qAttached} packet
40735 Return an indication of whether the remote server attached to an
40736 existing process or created a new process. When the multiprocess
40737 protocol extensions are supported (@pxref{multiprocess extensions}),
40738 @var{pid} is an integer in hexadecimal format identifying the target
40739 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
40740 the query packet will be simplified as @samp{qAttached}.
40742 This query is used, for example, to know whether the remote process
40743 should be detached or killed when a @value{GDBN} session is ended with
40744 the @code{quit} command.
40749 The remote server attached to an existing process.
40751 The remote server created a new process.
40753 A badly formed request or an error was encountered.
40757 Enable branch tracing for the current thread using Branch Trace Store.
40762 Branch tracing has been enabled.
40764 A badly formed request or an error was encountered.
40768 Enable branch tracing for the current thread using Intel Processor Trace.
40773 Branch tracing has been enabled.
40775 A badly formed request or an error was encountered.
40779 Disable branch tracing for the current thread.
40784 Branch tracing has been disabled.
40786 A badly formed request or an error was encountered.
40789 @item Qbtrace-conf:bts:size=@var{value}
40790 Set the requested ring buffer size for new threads that use the
40791 btrace recording method in bts format.
40796 The ring buffer size has been set.
40798 A badly formed request or an error was encountered.
40801 @item Qbtrace-conf:pt:size=@var{value}
40802 Set the requested ring buffer size for new threads that use the
40803 btrace recording method in pt format.
40808 The ring buffer size has been set.
40810 A badly formed request or an error was encountered.
40815 @node Architecture-Specific Protocol Details
40816 @section Architecture-Specific Protocol Details
40818 This section describes how the remote protocol is applied to specific
40819 target architectures. Also see @ref{Standard Target Features}, for
40820 details of XML target descriptions for each architecture.
40823 * ARM-Specific Protocol Details::
40824 * MIPS-Specific Protocol Details::
40827 @node ARM-Specific Protocol Details
40828 @subsection @acronym{ARM}-specific Protocol Details
40831 * ARM Breakpoint Kinds::
40834 @node ARM Breakpoint Kinds
40835 @subsubsection @acronym{ARM} Breakpoint Kinds
40836 @cindex breakpoint kinds, @acronym{ARM}
40838 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
40843 16-bit Thumb mode breakpoint.
40846 32-bit Thumb mode (Thumb-2) breakpoint.
40849 32-bit @acronym{ARM} mode breakpoint.
40853 @node MIPS-Specific Protocol Details
40854 @subsection @acronym{MIPS}-specific Protocol Details
40857 * MIPS Register packet Format::
40858 * MIPS Breakpoint Kinds::
40861 @node MIPS Register packet Format
40862 @subsubsection @acronym{MIPS} Register Packet Format
40863 @cindex register packet format, @acronym{MIPS}
40865 The following @code{g}/@code{G} packets have previously been defined.
40866 In the below, some thirty-two bit registers are transferred as
40867 sixty-four bits. Those registers should be zero/sign extended (which?)
40868 to fill the space allocated. Register bytes are transferred in target
40869 byte order. The two nibbles within a register byte are transferred
40870 most-significant -- least-significant.
40875 All registers are transferred as thirty-two bit quantities in the order:
40876 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
40877 registers; fsr; fir; fp.
40880 All registers are transferred as sixty-four bit quantities (including
40881 thirty-two bit registers such as @code{sr}). The ordering is the same
40886 @node MIPS Breakpoint Kinds
40887 @subsubsection @acronym{MIPS} Breakpoint Kinds
40888 @cindex breakpoint kinds, @acronym{MIPS}
40890 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
40895 16-bit @acronym{MIPS16} mode breakpoint.
40898 16-bit @acronym{microMIPS} mode breakpoint.
40901 32-bit standard @acronym{MIPS} mode breakpoint.
40904 32-bit @acronym{microMIPS} mode breakpoint.
40908 @node Tracepoint Packets
40909 @section Tracepoint Packets
40910 @cindex tracepoint packets
40911 @cindex packets, tracepoint
40913 Here we describe the packets @value{GDBN} uses to implement
40914 tracepoints (@pxref{Tracepoints}).
40918 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
40919 @cindex @samp{QTDP} packet
40920 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
40921 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
40922 the tracepoint is disabled. The @var{step} gives the tracepoint's step
40923 count, and @var{pass} gives its pass count. If an @samp{F} is present,
40924 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
40925 the number of bytes that the target should copy elsewhere to make room
40926 for the tracepoint. If an @samp{X} is present, it introduces a
40927 tracepoint condition, which consists of a hexadecimal length, followed
40928 by a comma and hex-encoded bytes, in a manner similar to action
40929 encodings as described below. If the trailing @samp{-} is present,
40930 further @samp{QTDP} packets will follow to specify this tracepoint's
40936 The packet was understood and carried out.
40938 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
40940 The packet was not recognized.
40943 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
40944 Define actions to be taken when a tracepoint is hit. The @var{n} and
40945 @var{addr} must be the same as in the initial @samp{QTDP} packet for
40946 this tracepoint. This packet may only be sent immediately after
40947 another @samp{QTDP} packet that ended with a @samp{-}. If the
40948 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
40949 specifying more actions for this tracepoint.
40951 In the series of action packets for a given tracepoint, at most one
40952 can have an @samp{S} before its first @var{action}. If such a packet
40953 is sent, it and the following packets define ``while-stepping''
40954 actions. Any prior packets define ordinary actions --- that is, those
40955 taken when the tracepoint is first hit. If no action packet has an
40956 @samp{S}, then all the packets in the series specify ordinary
40957 tracepoint actions.
40959 The @samp{@var{action}@dots{}} portion of the packet is a series of
40960 actions, concatenated without separators. Each action has one of the
40966 Collect the registers whose bits are set in @var{mask},
40967 a hexadecimal number whose @var{i}'th bit is set if register number
40968 @var{i} should be collected. (The least significant bit is numbered
40969 zero.) Note that @var{mask} may be any number of digits long; it may
40970 not fit in a 32-bit word.
40972 @item M @var{basereg},@var{offset},@var{len}
40973 Collect @var{len} bytes of memory starting at the address in register
40974 number @var{basereg}, plus @var{offset}. If @var{basereg} is
40975 @samp{-1}, then the range has a fixed address: @var{offset} is the
40976 address of the lowest byte to collect. The @var{basereg},
40977 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
40978 values (the @samp{-1} value for @var{basereg} is a special case).
40980 @item X @var{len},@var{expr}
40981 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
40982 it directs. The agent expression @var{expr} is as described in
40983 @ref{Agent Expressions}. Each byte of the expression is encoded as a
40984 two-digit hex number in the packet; @var{len} is the number of bytes
40985 in the expression (and thus one-half the number of hex digits in the
40990 Any number of actions may be packed together in a single @samp{QTDP}
40991 packet, as long as the packet does not exceed the maximum packet
40992 length (400 bytes, for many stubs). There may be only one @samp{R}
40993 action per tracepoint, and it must precede any @samp{M} or @samp{X}
40994 actions. Any registers referred to by @samp{M} and @samp{X} actions
40995 must be collected by a preceding @samp{R} action. (The
40996 ``while-stepping'' actions are treated as if they were attached to a
40997 separate tracepoint, as far as these restrictions are concerned.)
41002 The packet was understood and carried out.
41004 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
41006 The packet was not recognized.
41009 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
41010 @cindex @samp{QTDPsrc} packet
41011 Specify a source string of tracepoint @var{n} at address @var{addr}.
41012 This is useful to get accurate reproduction of the tracepoints
41013 originally downloaded at the beginning of the trace run. The @var{type}
41014 is the name of the tracepoint part, such as @samp{cond} for the
41015 tracepoint's conditional expression (see below for a list of types), while
41016 @var{bytes} is the string, encoded in hexadecimal.
41018 @var{start} is the offset of the @var{bytes} within the overall source
41019 string, while @var{slen} is the total length of the source string.
41020 This is intended for handling source strings that are longer than will
41021 fit in a single packet.
41022 @c Add detailed example when this info is moved into a dedicated
41023 @c tracepoint descriptions section.
41025 The available string types are @samp{at} for the location,
41026 @samp{cond} for the conditional, and @samp{cmd} for an action command.
41027 @value{GDBN} sends a separate packet for each command in the action
41028 list, in the same order in which the commands are stored in the list.
41030 The target does not need to do anything with source strings except
41031 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
41034 Although this packet is optional, and @value{GDBN} will only send it
41035 if the target replies with @samp{TracepointSource} @xref{General
41036 Query Packets}, it makes both disconnected tracing and trace files
41037 much easier to use. Otherwise the user must be careful that the
41038 tracepoints in effect while looking at trace frames are identical to
41039 the ones in effect during the trace run; even a small discrepancy
41040 could cause @samp{tdump} not to work, or a particular trace frame not
41043 @item QTDV:@var{n}:@var{value}:@var{builtin}:@var{name}
41044 @cindex define trace state variable, remote request
41045 @cindex @samp{QTDV} packet
41046 Create a new trace state variable, number @var{n}, with an initial
41047 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
41048 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
41049 the option of not using this packet for initial values of zero; the
41050 target should simply create the trace state variables as they are
41051 mentioned in expressions. The value @var{builtin} should be 1 (one)
41052 if the trace state variable is builtin and 0 (zero) if it is not builtin.
41053 @value{GDBN} only sets @var{builtin} to 1 if a previous @samp{qTfV} or
41054 @samp{qTsV} packet had it set. The contents of @var{name} is the
41055 hex-encoded name (without the leading @samp{$}) of the trace state
41058 @item QTFrame:@var{n}
41059 @cindex @samp{QTFrame} packet
41060 Select the @var{n}'th tracepoint frame from the buffer, and use the
41061 register and memory contents recorded there to answer subsequent
41062 request packets from @value{GDBN}.
41064 A successful reply from the stub indicates that the stub has found the
41065 requested frame. The response is a series of parts, concatenated
41066 without separators, describing the frame we selected. Each part has
41067 one of the following forms:
41071 The selected frame is number @var{n} in the trace frame buffer;
41072 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
41073 was no frame matching the criteria in the request packet.
41076 The selected trace frame records a hit of tracepoint number @var{t};
41077 @var{t} is a hexadecimal number.
41081 @item QTFrame:pc:@var{addr}
41082 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
41083 currently selected frame whose PC is @var{addr};
41084 @var{addr} is a hexadecimal number.
41086 @item QTFrame:tdp:@var{t}
41087 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
41088 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
41089 is a hexadecimal number.
41091 @item QTFrame:range:@var{start}:@var{end}
41092 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
41093 currently selected frame whose PC is between @var{start} (inclusive)
41094 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
41097 @item QTFrame:outside:@var{start}:@var{end}
41098 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
41099 frame @emph{outside} the given range of addresses (exclusive).
41102 @cindex @samp{qTMinFTPILen} packet
41103 This packet requests the minimum length of instruction at which a fast
41104 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
41105 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
41106 it depends on the target system being able to create trampolines in
41107 the first 64K of memory, which might or might not be possible for that
41108 system. So the reply to this packet will be 4 if it is able to
41115 The minimum instruction length is currently unknown.
41117 The minimum instruction length is @var{length}, where @var{length}
41118 is a hexadecimal number greater or equal to 1. A reply
41119 of 1 means that a fast tracepoint may be placed on any instruction
41120 regardless of size.
41122 An error has occurred.
41124 An empty reply indicates that the request is not supported by the stub.
41128 @cindex @samp{QTStart} packet
41129 Begin the tracepoint experiment. Begin collecting data from
41130 tracepoint hits in the trace frame buffer. This packet supports the
41131 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
41132 instruction reply packet}).
41135 @cindex @samp{QTStop} packet
41136 End the tracepoint experiment. Stop collecting trace frames.
41138 @item QTEnable:@var{n}:@var{addr}
41140 @cindex @samp{QTEnable} packet
41141 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
41142 experiment. If the tracepoint was previously disabled, then collection
41143 of data from it will resume.
41145 @item QTDisable:@var{n}:@var{addr}
41147 @cindex @samp{QTDisable} packet
41148 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
41149 experiment. No more data will be collected from the tracepoint unless
41150 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
41153 @cindex @samp{QTinit} packet
41154 Clear the table of tracepoints, and empty the trace frame buffer.
41156 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
41157 @cindex @samp{QTro} packet
41158 Establish the given ranges of memory as ``transparent''. The stub
41159 will answer requests for these ranges from memory's current contents,
41160 if they were not collected as part of the tracepoint hit.
41162 @value{GDBN} uses this to mark read-only regions of memory, like those
41163 containing program code. Since these areas never change, they should
41164 still have the same contents they did when the tracepoint was hit, so
41165 there's no reason for the stub to refuse to provide their contents.
41167 @item QTDisconnected:@var{value}
41168 @cindex @samp{QTDisconnected} packet
41169 Set the choice to what to do with the tracing run when @value{GDBN}
41170 disconnects from the target. A @var{value} of 1 directs the target to
41171 continue the tracing run, while 0 tells the target to stop tracing if
41172 @value{GDBN} is no longer in the picture.
41175 @cindex @samp{qTStatus} packet
41176 Ask the stub if there is a trace experiment running right now.
41178 The reply has the form:
41182 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
41183 @var{running} is a single digit @code{1} if the trace is presently
41184 running, or @code{0} if not. It is followed by semicolon-separated
41185 optional fields that an agent may use to report additional status.
41189 If the trace is not running, the agent may report any of several
41190 explanations as one of the optional fields:
41195 No trace has been run yet.
41197 @item tstop[:@var{text}]:0
41198 The trace was stopped by a user-originated stop command. The optional
41199 @var{text} field is a user-supplied string supplied as part of the
41200 stop command (for instance, an explanation of why the trace was
41201 stopped manually). It is hex-encoded.
41204 The trace stopped because the trace buffer filled up.
41206 @item tdisconnected:0
41207 The trace stopped because @value{GDBN} disconnected from the target.
41209 @item tpasscount:@var{tpnum}
41210 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
41212 @item terror:@var{text}:@var{tpnum}
41213 The trace stopped because tracepoint @var{tpnum} had an error. The
41214 string @var{text} is available to describe the nature of the error
41215 (for instance, a divide by zero in the condition expression); it
41219 The trace stopped for some other reason.
41223 Additional optional fields supply statistical and other information.
41224 Although not required, they are extremely useful for users monitoring
41225 the progress of a trace run. If a trace has stopped, and these
41226 numbers are reported, they must reflect the state of the just-stopped
41231 @item tframes:@var{n}
41232 The number of trace frames in the buffer.
41234 @item tcreated:@var{n}
41235 The total number of trace frames created during the run. This may
41236 be larger than the trace frame count, if the buffer is circular.
41238 @item tsize:@var{n}
41239 The total size of the trace buffer, in bytes.
41241 @item tfree:@var{n}
41242 The number of bytes still unused in the buffer.
41244 @item circular:@var{n}
41245 The value of the circular trace buffer flag. @code{1} means that the
41246 trace buffer is circular and old trace frames will be discarded if
41247 necessary to make room, @code{0} means that the trace buffer is linear
41250 @item disconn:@var{n}
41251 The value of the disconnected tracing flag. @code{1} means that
41252 tracing will continue after @value{GDBN} disconnects, @code{0} means
41253 that the trace run will stop.
41257 @item qTP:@var{tp}:@var{addr}
41258 @cindex tracepoint status, remote request
41259 @cindex @samp{qTP} packet
41260 Ask the stub for the current state of tracepoint number @var{tp} at
41261 address @var{addr}.
41265 @item V@var{hits}:@var{usage}
41266 The tracepoint has been hit @var{hits} times so far during the trace
41267 run, and accounts for @var{usage} in the trace buffer. Note that
41268 @code{while-stepping} steps are not counted as separate hits, but the
41269 steps' space consumption is added into the usage number.
41273 @item qTV:@var{var}
41274 @cindex trace state variable value, remote request
41275 @cindex @samp{qTV} packet
41276 Ask the stub for the value of the trace state variable number @var{var}.
41281 The value of the variable is @var{value}. This will be the current
41282 value of the variable if the user is examining a running target, or a
41283 saved value if the variable was collected in the trace frame that the
41284 user is looking at. Note that multiple requests may result in
41285 different reply values, such as when requesting values while the
41286 program is running.
41289 The value of the variable is unknown. This would occur, for example,
41290 if the user is examining a trace frame in which the requested variable
41295 @cindex @samp{qTfP} packet
41297 @cindex @samp{qTsP} packet
41298 These packets request data about tracepoints that are being used by
41299 the target. @value{GDBN} sends @code{qTfP} to get the first piece
41300 of data, and multiple @code{qTsP} to get additional pieces. Replies
41301 to these packets generally take the form of the @code{QTDP} packets
41302 that define tracepoints. (FIXME add detailed syntax)
41305 @cindex @samp{qTfV} packet
41307 @cindex @samp{qTsV} packet
41308 These packets request data about trace state variables that are on the
41309 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
41310 and multiple @code{qTsV} to get additional variables. Replies to
41311 these packets follow the syntax of the @code{QTDV} packets that define
41312 trace state variables.
41318 @cindex @samp{qTfSTM} packet
41319 @cindex @samp{qTsSTM} packet
41320 These packets request data about static tracepoint markers that exist
41321 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
41322 first piece of data, and multiple @code{qTsSTM} to get additional
41323 pieces. Replies to these packets take the following form:
41327 @item m @var{address}:@var{id}:@var{extra}
41329 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
41330 a comma-separated list of markers
41332 (lower case letter @samp{L}) denotes end of list.
41334 An error occurred. The error number @var{nn} is given as hex digits.
41336 An empty reply indicates that the request is not supported by the
41340 The @var{address} is encoded in hex;
41341 @var{id} and @var{extra} are strings encoded in hex.
41343 In response to each query, the target will reply with a list of one or
41344 more markers, separated by commas. @value{GDBN} will respond to each
41345 reply with a request for more markers (using the @samp{qs} form of the
41346 query), until the target responds with @samp{l} (lower-case ell, for
41349 @item qTSTMat:@var{address}
41351 @cindex @samp{qTSTMat} packet
41352 This packets requests data about static tracepoint markers in the
41353 target program at @var{address}. Replies to this packet follow the
41354 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
41355 tracepoint markers.
41357 @item QTSave:@var{filename}
41358 @cindex @samp{QTSave} packet
41359 This packet directs the target to save trace data to the file name
41360 @var{filename} in the target's filesystem. The @var{filename} is encoded
41361 as a hex string; the interpretation of the file name (relative vs
41362 absolute, wild cards, etc) is up to the target.
41364 @item qTBuffer:@var{offset},@var{len}
41365 @cindex @samp{qTBuffer} packet
41366 Return up to @var{len} bytes of the current contents of trace buffer,
41367 starting at @var{offset}. The trace buffer is treated as if it were
41368 a contiguous collection of traceframes, as per the trace file format.
41369 The reply consists as many hex-encoded bytes as the target can deliver
41370 in a packet; it is not an error to return fewer than were asked for.
41371 A reply consisting of just @code{l} indicates that no bytes are
41374 @item QTBuffer:circular:@var{value}
41375 This packet directs the target to use a circular trace buffer if
41376 @var{value} is 1, or a linear buffer if the value is 0.
41378 @item QTBuffer:size:@var{size}
41379 @anchor{QTBuffer-size}
41380 @cindex @samp{QTBuffer size} packet
41381 This packet directs the target to make the trace buffer be of size
41382 @var{size} if possible. A value of @code{-1} tells the target to
41383 use whatever size it prefers.
41385 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
41386 @cindex @samp{QTNotes} packet
41387 This packet adds optional textual notes to the trace run. Allowable
41388 types include @code{user}, @code{notes}, and @code{tstop}, the
41389 @var{text} fields are arbitrary strings, hex-encoded.
41393 @subsection Relocate instruction reply packet
41394 When installing fast tracepoints in memory, the target may need to
41395 relocate the instruction currently at the tracepoint address to a
41396 different address in memory. For most instructions, a simple copy is
41397 enough, but, for example, call instructions that implicitly push the
41398 return address on the stack, and relative branches or other
41399 PC-relative instructions require offset adjustment, so that the effect
41400 of executing the instruction at a different address is the same as if
41401 it had executed in the original location.
41403 In response to several of the tracepoint packets, the target may also
41404 respond with a number of intermediate @samp{qRelocInsn} request
41405 packets before the final result packet, to have @value{GDBN} handle
41406 this relocation operation. If a packet supports this mechanism, its
41407 documentation will explicitly say so. See for example the above
41408 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
41409 format of the request is:
41412 @item qRelocInsn:@var{from};@var{to}
41414 This requests @value{GDBN} to copy instruction at address @var{from}
41415 to address @var{to}, possibly adjusted so that executing the
41416 instruction at @var{to} has the same effect as executing it at
41417 @var{from}. @value{GDBN} writes the adjusted instruction to target
41418 memory starting at @var{to}.
41423 @item qRelocInsn:@var{adjusted_size}
41424 Informs the stub the relocation is complete. The @var{adjusted_size} is
41425 the length in bytes of resulting relocated instruction sequence.
41427 A badly formed request was detected, or an error was encountered while
41428 relocating the instruction.
41431 @node Host I/O Packets
41432 @section Host I/O Packets
41433 @cindex Host I/O, remote protocol
41434 @cindex file transfer, remote protocol
41436 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
41437 operations on the far side of a remote link. For example, Host I/O is
41438 used to upload and download files to a remote target with its own
41439 filesystem. Host I/O uses the same constant values and data structure
41440 layout as the target-initiated File-I/O protocol. However, the
41441 Host I/O packets are structured differently. The target-initiated
41442 protocol relies on target memory to store parameters and buffers.
41443 Host I/O requests are initiated by @value{GDBN}, and the
41444 target's memory is not involved. @xref{File-I/O Remote Protocol
41445 Extension}, for more details on the target-initiated protocol.
41447 The Host I/O request packets all encode a single operation along with
41448 its arguments. They have this format:
41452 @item vFile:@var{operation}: @var{parameter}@dots{}
41453 @var{operation} is the name of the particular request; the target
41454 should compare the entire packet name up to the second colon when checking
41455 for a supported operation. The format of @var{parameter} depends on
41456 the operation. Numbers are always passed in hexadecimal. Negative
41457 numbers have an explicit minus sign (i.e.@: two's complement is not
41458 used). Strings (e.g.@: filenames) are encoded as a series of
41459 hexadecimal bytes. The last argument to a system call may be a
41460 buffer of escaped binary data (@pxref{Binary Data}).
41464 The valid responses to Host I/O packets are:
41468 @item F @var{result} [, @var{errno}] [; @var{attachment}]
41469 @var{result} is the integer value returned by this operation, usually
41470 non-negative for success and -1 for errors. If an error has occured,
41471 @var{errno} will be included in the result specifying a
41472 value defined by the File-I/O protocol (@pxref{Errno Values}). For
41473 operations which return data, @var{attachment} supplies the data as a
41474 binary buffer. Binary buffers in response packets are escaped in the
41475 normal way (@pxref{Binary Data}). See the individual packet
41476 documentation for the interpretation of @var{result} and
41480 An empty response indicates that this operation is not recognized.
41484 These are the supported Host I/O operations:
41487 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
41488 Open a file at @var{filename} and return a file descriptor for it, or
41489 return -1 if an error occurs. The @var{filename} is a string,
41490 @var{flags} is an integer indicating a mask of open flags
41491 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
41492 of mode bits to use if the file is created (@pxref{mode_t Values}).
41493 @xref{open}, for details of the open flags and mode values.
41495 @item vFile:close: @var{fd}
41496 Close the open file corresponding to @var{fd} and return 0, or
41497 -1 if an error occurs.
41499 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
41500 Read data from the open file corresponding to @var{fd}. Up to
41501 @var{count} bytes will be read from the file, starting at @var{offset}
41502 relative to the start of the file. The target may read fewer bytes;
41503 common reasons include packet size limits and an end-of-file
41504 condition. The number of bytes read is returned. Zero should only be
41505 returned for a successful read at the end of the file, or if
41506 @var{count} was zero.
41508 The data read should be returned as a binary attachment on success.
41509 If zero bytes were read, the response should include an empty binary
41510 attachment (i.e.@: a trailing semicolon). The return value is the
41511 number of target bytes read; the binary attachment may be longer if
41512 some characters were escaped.
41514 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
41515 Write @var{data} (a binary buffer) to the open file corresponding
41516 to @var{fd}. Start the write at @var{offset} from the start of the
41517 file. Unlike many @code{write} system calls, there is no
41518 separate @var{count} argument; the length of @var{data} in the
41519 packet is used. @samp{vFile:write} returns the number of bytes written,
41520 which may be shorter than the length of @var{data}, or -1 if an
41523 @item vFile:fstat: @var{fd}
41524 Get information about the open file corresponding to @var{fd}.
41525 On success the information is returned as a binary attachment
41526 and the return value is the size of this attachment in bytes.
41527 If an error occurs the return value is -1. The format of the
41528 returned binary attachment is as described in @ref{struct stat}.
41530 @item vFile:unlink: @var{filename}
41531 Delete the file at @var{filename} on the target. Return 0,
41532 or -1 if an error occurs. The @var{filename} is a string.
41534 @item vFile:readlink: @var{filename}
41535 Read value of symbolic link @var{filename} on the target. Return
41536 the number of bytes read, or -1 if an error occurs.
41538 The data read should be returned as a binary attachment on success.
41539 If zero bytes were read, the response should include an empty binary
41540 attachment (i.e.@: a trailing semicolon). The return value is the
41541 number of target bytes read; the binary attachment may be longer if
41542 some characters were escaped.
41544 @item vFile:setfs: @var{pid}
41545 Select the filesystem on which @code{vFile} operations with
41546 @var{filename} arguments will operate. This is required for
41547 @value{GDBN} to be able to access files on remote targets where
41548 the remote stub does not share a common filesystem with the
41551 If @var{pid} is nonzero, select the filesystem as seen by process
41552 @var{pid}. If @var{pid} is zero, select the filesystem as seen by
41553 the remote stub. Return 0 on success, or -1 if an error occurs.
41554 If @code{vFile:setfs:} indicates success, the selected filesystem
41555 remains selected until the next successful @code{vFile:setfs:}
41561 @section Interrupts
41562 @cindex interrupts (remote protocol)
41563 @anchor{interrupting remote targets}
41565 In all-stop mode, when a program on the remote target is running,
41566 @value{GDBN} may attempt to interrupt it by sending a @samp{Ctrl-C},
41567 @code{BREAK} or a @code{BREAK} followed by @code{g}, control of which
41568 is specified via @value{GDBN}'s @samp{interrupt-sequence}.
41570 The precise meaning of @code{BREAK} is defined by the transport
41571 mechanism and may, in fact, be undefined. @value{GDBN} does not
41572 currently define a @code{BREAK} mechanism for any of the network
41573 interfaces except for TCP, in which case @value{GDBN} sends the
41574 @code{telnet} BREAK sequence.
41576 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
41577 transport mechanisms. It is represented by sending the single byte
41578 @code{0x03} without any of the usual packet overhead described in
41579 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
41580 transmitted as part of a packet, it is considered to be packet data
41581 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
41582 (@pxref{X packet}), used for binary downloads, may include an unescaped
41583 @code{0x03} as part of its packet.
41585 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
41586 When Linux kernel receives this sequence from serial port,
41587 it stops execution and connects to gdb.
41589 In non-stop mode, because packet resumptions are asynchronous
41590 (@pxref{vCont packet}), @value{GDBN} is always free to send a remote
41591 command to the remote stub, even when the target is running. For that
41592 reason, @value{GDBN} instead sends a regular packet (@pxref{vCtrlC
41593 packet}) with the usual packet framing instead of the single byte
41596 Stubs are not required to recognize these interrupt mechanisms and the
41597 precise meaning associated with receipt of the interrupt is
41598 implementation defined. If the target supports debugging of multiple
41599 threads and/or processes, it should attempt to interrupt all
41600 currently-executing threads and processes.
41601 If the stub is successful at interrupting the
41602 running program, it should send one of the stop
41603 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
41604 of successfully stopping the program in all-stop mode, and a stop reply
41605 for each stopped thread in non-stop mode.
41606 Interrupts received while the
41607 program is stopped are queued and the program will be interrupted when
41608 it is resumed next time.
41610 @node Notification Packets
41611 @section Notification Packets
41612 @cindex notification packets
41613 @cindex packets, notification
41615 The @value{GDBN} remote serial protocol includes @dfn{notifications},
41616 packets that require no acknowledgment. Both the GDB and the stub
41617 may send notifications (although the only notifications defined at
41618 present are sent by the stub). Notifications carry information
41619 without incurring the round-trip latency of an acknowledgment, and so
41620 are useful for low-impact communications where occasional packet loss
41623 A notification packet has the form @samp{% @var{data} #
41624 @var{checksum}}, where @var{data} is the content of the notification,
41625 and @var{checksum} is a checksum of @var{data}, computed and formatted
41626 as for ordinary @value{GDBN} packets. A notification's @var{data}
41627 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
41628 receiving a notification, the recipient sends no @samp{+} or @samp{-}
41629 to acknowledge the notification's receipt or to report its corruption.
41631 Every notification's @var{data} begins with a name, which contains no
41632 colon characters, followed by a colon character.
41634 Recipients should silently ignore corrupted notifications and
41635 notifications they do not understand. Recipients should restart
41636 timeout periods on receipt of a well-formed notification, whether or
41637 not they understand it.
41639 Senders should only send the notifications described here when this
41640 protocol description specifies that they are permitted. In the
41641 future, we may extend the protocol to permit existing notifications in
41642 new contexts; this rule helps older senders avoid confusing newer
41645 (Older versions of @value{GDBN} ignore bytes received until they see
41646 the @samp{$} byte that begins an ordinary packet, so new stubs may
41647 transmit notifications without fear of confusing older clients. There
41648 are no notifications defined for @value{GDBN} to send at the moment, but we
41649 assume that most older stubs would ignore them, as well.)
41651 Each notification is comprised of three parts:
41653 @item @var{name}:@var{event}
41654 The notification packet is sent by the side that initiates the
41655 exchange (currently, only the stub does that), with @var{event}
41656 carrying the specific information about the notification, and
41657 @var{name} specifying the name of the notification.
41659 The acknowledge sent by the other side, usually @value{GDBN}, to
41660 acknowledge the exchange and request the event.
41663 The purpose of an asynchronous notification mechanism is to report to
41664 @value{GDBN} that something interesting happened in the remote stub.
41666 The remote stub may send notification @var{name}:@var{event}
41667 at any time, but @value{GDBN} acknowledges the notification when
41668 appropriate. The notification event is pending before @value{GDBN}
41669 acknowledges. Only one notification at a time may be pending; if
41670 additional events occur before @value{GDBN} has acknowledged the
41671 previous notification, they must be queued by the stub for later
41672 synchronous transmission in response to @var{ack} packets from
41673 @value{GDBN}. Because the notification mechanism is unreliable,
41674 the stub is permitted to resend a notification if it believes
41675 @value{GDBN} may not have received it.
41677 Specifically, notifications may appear when @value{GDBN} is not
41678 otherwise reading input from the stub, or when @value{GDBN} is
41679 expecting to read a normal synchronous response or a
41680 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
41681 Notification packets are distinct from any other communication from
41682 the stub so there is no ambiguity.
41684 After receiving a notification, @value{GDBN} shall acknowledge it by
41685 sending a @var{ack} packet as a regular, synchronous request to the
41686 stub. Such acknowledgment is not required to happen immediately, as
41687 @value{GDBN} is permitted to send other, unrelated packets to the
41688 stub first, which the stub should process normally.
41690 Upon receiving a @var{ack} packet, if the stub has other queued
41691 events to report to @value{GDBN}, it shall respond by sending a
41692 normal @var{event}. @value{GDBN} shall then send another @var{ack}
41693 packet to solicit further responses; again, it is permitted to send
41694 other, unrelated packets as well which the stub should process
41697 If the stub receives a @var{ack} packet and there are no additional
41698 @var{event} to report, the stub shall return an @samp{OK} response.
41699 At this point, @value{GDBN} has finished processing a notification
41700 and the stub has completed sending any queued events. @value{GDBN}
41701 won't accept any new notifications until the final @samp{OK} is
41702 received . If further notification events occur, the stub shall send
41703 a new notification, @value{GDBN} shall accept the notification, and
41704 the process shall be repeated.
41706 The process of asynchronous notification can be illustrated by the
41709 <- @code{%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
41712 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
41714 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
41719 The following notifications are defined:
41720 @multitable @columnfractions 0.12 0.12 0.38 0.38
41729 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
41730 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
41731 for information on how these notifications are acknowledged by
41733 @tab Report an asynchronous stop event in non-stop mode.
41737 @node Remote Non-Stop
41738 @section Remote Protocol Support for Non-Stop Mode
41740 @value{GDBN}'s remote protocol supports non-stop debugging of
41741 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
41742 supports non-stop mode, it should report that to @value{GDBN} by including
41743 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
41745 @value{GDBN} typically sends a @samp{QNonStop} packet only when
41746 establishing a new connection with the stub. Entering non-stop mode
41747 does not alter the state of any currently-running threads, but targets
41748 must stop all threads in any already-attached processes when entering
41749 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
41750 probe the target state after a mode change.
41752 In non-stop mode, when an attached process encounters an event that
41753 would otherwise be reported with a stop reply, it uses the
41754 asynchronous notification mechanism (@pxref{Notification Packets}) to
41755 inform @value{GDBN}. In contrast to all-stop mode, where all threads
41756 in all processes are stopped when a stop reply is sent, in non-stop
41757 mode only the thread reporting the stop event is stopped. That is,
41758 when reporting a @samp{S} or @samp{T} response to indicate completion
41759 of a step operation, hitting a breakpoint, or a fault, only the
41760 affected thread is stopped; any other still-running threads continue
41761 to run. When reporting a @samp{W} or @samp{X} response, all running
41762 threads belonging to other attached processes continue to run.
41764 In non-stop mode, the target shall respond to the @samp{?} packet as
41765 follows. First, any incomplete stop reply notification/@samp{vStopped}
41766 sequence in progress is abandoned. The target must begin a new
41767 sequence reporting stop events for all stopped threads, whether or not
41768 it has previously reported those events to @value{GDBN}. The first
41769 stop reply is sent as a synchronous reply to the @samp{?} packet, and
41770 subsequent stop replies are sent as responses to @samp{vStopped} packets
41771 using the mechanism described above. The target must not send
41772 asynchronous stop reply notifications until the sequence is complete.
41773 If all threads are running when the target receives the @samp{?} packet,
41774 or if the target is not attached to any process, it shall respond
41777 If the stub supports non-stop mode, it should also support the
41778 @samp{swbreak} stop reason if software breakpoints are supported, and
41779 the @samp{hwbreak} stop reason if hardware breakpoints are supported
41780 (@pxref{swbreak stop reason}). This is because given the asynchronous
41781 nature of non-stop mode, between the time a thread hits a breakpoint
41782 and the time the event is finally processed by @value{GDBN}, the
41783 breakpoint may have already been removed from the target. Due to
41784 this, @value{GDBN} needs to be able to tell whether a trap stop was
41785 caused by a delayed breakpoint event, which should be ignored, as
41786 opposed to a random trap signal, which should be reported to the user.
41787 Note the @samp{swbreak} feature implies that the target is responsible
41788 for adjusting the PC when a software breakpoint triggers, if
41789 necessary, such as on the x86 architecture.
41791 @node Packet Acknowledgment
41792 @section Packet Acknowledgment
41794 @cindex acknowledgment, for @value{GDBN} remote
41795 @cindex packet acknowledgment, for @value{GDBN} remote
41796 By default, when either the host or the target machine receives a packet,
41797 the first response expected is an acknowledgment: either @samp{+} (to indicate
41798 the package was received correctly) or @samp{-} (to request retransmission).
41799 This mechanism allows the @value{GDBN} remote protocol to operate over
41800 unreliable transport mechanisms, such as a serial line.
41802 In cases where the transport mechanism is itself reliable (such as a pipe or
41803 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
41804 It may be desirable to disable them in that case to reduce communication
41805 overhead, or for other reasons. This can be accomplished by means of the
41806 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
41808 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
41809 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
41810 and response format still includes the normal checksum, as described in
41811 @ref{Overview}, but the checksum may be ignored by the receiver.
41813 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
41814 no-acknowledgment mode, it should report that to @value{GDBN}
41815 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
41816 @pxref{qSupported}.
41817 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
41818 disabled via the @code{set remote noack-packet off} command
41819 (@pxref{Remote Configuration}),
41820 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
41821 Only then may the stub actually turn off packet acknowledgments.
41822 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
41823 response, which can be safely ignored by the stub.
41825 Note that @code{set remote noack-packet} command only affects negotiation
41826 between @value{GDBN} and the stub when subsequent connections are made;
41827 it does not affect the protocol acknowledgment state for any current
41829 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
41830 new connection is established,
41831 there is also no protocol request to re-enable the acknowledgments
41832 for the current connection, once disabled.
41837 Example sequence of a target being re-started. Notice how the restart
41838 does not get any direct output:
41843 @emph{target restarts}
41846 <- @code{T001:1234123412341234}
41850 Example sequence of a target being stepped by a single instruction:
41853 -> @code{G1445@dots{}}
41858 <- @code{T001:1234123412341234}
41862 <- @code{1455@dots{}}
41866 @node File-I/O Remote Protocol Extension
41867 @section File-I/O Remote Protocol Extension
41868 @cindex File-I/O remote protocol extension
41871 * File-I/O Overview::
41872 * Protocol Basics::
41873 * The F Request Packet::
41874 * The F Reply Packet::
41875 * The Ctrl-C Message::
41877 * List of Supported Calls::
41878 * Protocol-specific Representation of Datatypes::
41880 * File-I/O Examples::
41883 @node File-I/O Overview
41884 @subsection File-I/O Overview
41885 @cindex file-i/o overview
41887 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
41888 target to use the host's file system and console I/O to perform various
41889 system calls. System calls on the target system are translated into a
41890 remote protocol packet to the host system, which then performs the needed
41891 actions and returns a response packet to the target system.
41892 This simulates file system operations even on targets that lack file systems.
41894 The protocol is defined to be independent of both the host and target systems.
41895 It uses its own internal representation of datatypes and values. Both
41896 @value{GDBN} and the target's @value{GDBN} stub are responsible for
41897 translating the system-dependent value representations into the internal
41898 protocol representations when data is transmitted.
41900 The communication is synchronous. A system call is possible only when
41901 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
41902 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
41903 the target is stopped to allow deterministic access to the target's
41904 memory. Therefore File-I/O is not interruptible by target signals. On
41905 the other hand, it is possible to interrupt File-I/O by a user interrupt
41906 (@samp{Ctrl-C}) within @value{GDBN}.
41908 The target's request to perform a host system call does not finish
41909 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
41910 after finishing the system call, the target returns to continuing the
41911 previous activity (continue, step). No additional continue or step
41912 request from @value{GDBN} is required.
41915 (@value{GDBP}) continue
41916 <- target requests 'system call X'
41917 target is stopped, @value{GDBN} executes system call
41918 -> @value{GDBN} returns result
41919 ... target continues, @value{GDBN} returns to wait for the target
41920 <- target hits breakpoint and sends a Txx packet
41923 The protocol only supports I/O on the console and to regular files on
41924 the host file system. Character or block special devices, pipes,
41925 named pipes, sockets or any other communication method on the host
41926 system are not supported by this protocol.
41928 File I/O is not supported in non-stop mode.
41930 @node Protocol Basics
41931 @subsection Protocol Basics
41932 @cindex protocol basics, file-i/o
41934 The File-I/O protocol uses the @code{F} packet as the request as well
41935 as reply packet. Since a File-I/O system call can only occur when
41936 @value{GDBN} is waiting for a response from the continuing or stepping target,
41937 the File-I/O request is a reply that @value{GDBN} has to expect as a result
41938 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
41939 This @code{F} packet contains all information needed to allow @value{GDBN}
41940 to call the appropriate host system call:
41944 A unique identifier for the requested system call.
41947 All parameters to the system call. Pointers are given as addresses
41948 in the target memory address space. Pointers to strings are given as
41949 pointer/length pair. Numerical values are given as they are.
41950 Numerical control flags are given in a protocol-specific representation.
41954 At this point, @value{GDBN} has to perform the following actions.
41958 If the parameters include pointer values to data needed as input to a
41959 system call, @value{GDBN} requests this data from the target with a
41960 standard @code{m} packet request. This additional communication has to be
41961 expected by the target implementation and is handled as any other @code{m}
41965 @value{GDBN} translates all value from protocol representation to host
41966 representation as needed. Datatypes are coerced into the host types.
41969 @value{GDBN} calls the system call.
41972 It then coerces datatypes back to protocol representation.
41975 If the system call is expected to return data in buffer space specified
41976 by pointer parameters to the call, the data is transmitted to the
41977 target using a @code{M} or @code{X} packet. This packet has to be expected
41978 by the target implementation and is handled as any other @code{M} or @code{X}
41983 Eventually @value{GDBN} replies with another @code{F} packet which contains all
41984 necessary information for the target to continue. This at least contains
41991 @code{errno}, if has been changed by the system call.
41998 After having done the needed type and value coercion, the target continues
41999 the latest continue or step action.
42001 @node The F Request Packet
42002 @subsection The @code{F} Request Packet
42003 @cindex file-i/o request packet
42004 @cindex @code{F} request packet
42006 The @code{F} request packet has the following format:
42009 @item F@var{call-id},@var{parameter@dots{}}
42011 @var{call-id} is the identifier to indicate the host system call to be called.
42012 This is just the name of the function.
42014 @var{parameter@dots{}} are the parameters to the system call.
42015 Parameters are hexadecimal integer values, either the actual values in case
42016 of scalar datatypes, pointers to target buffer space in case of compound
42017 datatypes and unspecified memory areas, or pointer/length pairs in case
42018 of string parameters. These are appended to the @var{call-id} as a
42019 comma-delimited list. All values are transmitted in ASCII
42020 string representation, pointer/length pairs separated by a slash.
42026 @node The F Reply Packet
42027 @subsection The @code{F} Reply Packet
42028 @cindex file-i/o reply packet
42029 @cindex @code{F} reply packet
42031 The @code{F} reply packet has the following format:
42035 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
42037 @var{retcode} is the return code of the system call as hexadecimal value.
42039 @var{errno} is the @code{errno} set by the call, in protocol-specific
42041 This parameter can be omitted if the call was successful.
42043 @var{Ctrl-C flag} is only sent if the user requested a break. In this
42044 case, @var{errno} must be sent as well, even if the call was successful.
42045 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
42052 or, if the call was interrupted before the host call has been performed:
42059 assuming 4 is the protocol-specific representation of @code{EINTR}.
42064 @node The Ctrl-C Message
42065 @subsection The @samp{Ctrl-C} Message
42066 @cindex ctrl-c message, in file-i/o protocol
42068 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
42069 reply packet (@pxref{The F Reply Packet}),
42070 the target should behave as if it had
42071 gotten a break message. The meaning for the target is ``system call
42072 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
42073 (as with a break message) and return to @value{GDBN} with a @code{T02}
42076 It's important for the target to know in which
42077 state the system call was interrupted. There are two possible cases:
42081 The system call hasn't been performed on the host yet.
42084 The system call on the host has been finished.
42088 These two states can be distinguished by the target by the value of the
42089 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
42090 call hasn't been performed. This is equivalent to the @code{EINTR} handling
42091 on POSIX systems. In any other case, the target may presume that the
42092 system call has been finished --- successfully or not --- and should behave
42093 as if the break message arrived right after the system call.
42095 @value{GDBN} must behave reliably. If the system call has not been called
42096 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
42097 @code{errno} in the packet. If the system call on the host has been finished
42098 before the user requests a break, the full action must be finished by
42099 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
42100 The @code{F} packet may only be sent when either nothing has happened
42101 or the full action has been completed.
42104 @subsection Console I/O
42105 @cindex console i/o as part of file-i/o
42107 By default and if not explicitly closed by the target system, the file
42108 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
42109 on the @value{GDBN} console is handled as any other file output operation
42110 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
42111 by @value{GDBN} so that after the target read request from file descriptor
42112 0 all following typing is buffered until either one of the following
42117 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
42119 system call is treated as finished.
42122 The user presses @key{RET}. This is treated as end of input with a trailing
42126 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
42127 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
42131 If the user has typed more characters than fit in the buffer given to
42132 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
42133 either another @code{read(0, @dots{})} is requested by the target, or debugging
42134 is stopped at the user's request.
42137 @node List of Supported Calls
42138 @subsection List of Supported Calls
42139 @cindex list of supported file-i/o calls
42156 @unnumberedsubsubsec open
42157 @cindex open, file-i/o system call
42162 int open(const char *pathname, int flags);
42163 int open(const char *pathname, int flags, mode_t mode);
42167 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
42170 @var{flags} is the bitwise @code{OR} of the following values:
42174 If the file does not exist it will be created. The host
42175 rules apply as far as file ownership and time stamps
42179 When used with @code{O_CREAT}, if the file already exists it is
42180 an error and open() fails.
42183 If the file already exists and the open mode allows
42184 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
42185 truncated to zero length.
42188 The file is opened in append mode.
42191 The file is opened for reading only.
42194 The file is opened for writing only.
42197 The file is opened for reading and writing.
42201 Other bits are silently ignored.
42205 @var{mode} is the bitwise @code{OR} of the following values:
42209 User has read permission.
42212 User has write permission.
42215 Group has read permission.
42218 Group has write permission.
42221 Others have read permission.
42224 Others have write permission.
42228 Other bits are silently ignored.
42231 @item Return value:
42232 @code{open} returns the new file descriptor or -1 if an error
42239 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
42242 @var{pathname} refers to a directory.
42245 The requested access is not allowed.
42248 @var{pathname} was too long.
42251 A directory component in @var{pathname} does not exist.
42254 @var{pathname} refers to a device, pipe, named pipe or socket.
42257 @var{pathname} refers to a file on a read-only filesystem and
42258 write access was requested.
42261 @var{pathname} is an invalid pointer value.
42264 No space on device to create the file.
42267 The process already has the maximum number of files open.
42270 The limit on the total number of files open on the system
42274 The call was interrupted by the user.
42280 @unnumberedsubsubsec close
42281 @cindex close, file-i/o system call
42290 @samp{Fclose,@var{fd}}
42292 @item Return value:
42293 @code{close} returns zero on success, or -1 if an error occurred.
42299 @var{fd} isn't a valid open file descriptor.
42302 The call was interrupted by the user.
42308 @unnumberedsubsubsec read
42309 @cindex read, file-i/o system call
42314 int read(int fd, void *buf, unsigned int count);
42318 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
42320 @item Return value:
42321 On success, the number of bytes read is returned.
42322 Zero indicates end of file. If count is zero, read
42323 returns zero as well. On error, -1 is returned.
42329 @var{fd} is not a valid file descriptor or is not open for
42333 @var{bufptr} is an invalid pointer value.
42336 The call was interrupted by the user.
42342 @unnumberedsubsubsec write
42343 @cindex write, file-i/o system call
42348 int write(int fd, const void *buf, unsigned int count);
42352 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
42354 @item Return value:
42355 On success, the number of bytes written are returned.
42356 Zero indicates nothing was written. On error, -1
42363 @var{fd} is not a valid file descriptor or is not open for
42367 @var{bufptr} is an invalid pointer value.
42370 An attempt was made to write a file that exceeds the
42371 host-specific maximum file size allowed.
42374 No space on device to write the data.
42377 The call was interrupted by the user.
42383 @unnumberedsubsubsec lseek
42384 @cindex lseek, file-i/o system call
42389 long lseek (int fd, long offset, int flag);
42393 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
42395 @var{flag} is one of:
42399 The offset is set to @var{offset} bytes.
42402 The offset is set to its current location plus @var{offset}
42406 The offset is set to the size of the file plus @var{offset}
42410 @item Return value:
42411 On success, the resulting unsigned offset in bytes from
42412 the beginning of the file is returned. Otherwise, a
42413 value of -1 is returned.
42419 @var{fd} is not a valid open file descriptor.
42422 @var{fd} is associated with the @value{GDBN} console.
42425 @var{flag} is not a proper value.
42428 The call was interrupted by the user.
42434 @unnumberedsubsubsec rename
42435 @cindex rename, file-i/o system call
42440 int rename(const char *oldpath, const char *newpath);
42444 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
42446 @item Return value:
42447 On success, zero is returned. On error, -1 is returned.
42453 @var{newpath} is an existing directory, but @var{oldpath} is not a
42457 @var{newpath} is a non-empty directory.
42460 @var{oldpath} or @var{newpath} is a directory that is in use by some
42464 An attempt was made to make a directory a subdirectory
42468 A component used as a directory in @var{oldpath} or new
42469 path is not a directory. Or @var{oldpath} is a directory
42470 and @var{newpath} exists but is not a directory.
42473 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
42476 No access to the file or the path of the file.
42480 @var{oldpath} or @var{newpath} was too long.
42483 A directory component in @var{oldpath} or @var{newpath} does not exist.
42486 The file is on a read-only filesystem.
42489 The device containing the file has no room for the new
42493 The call was interrupted by the user.
42499 @unnumberedsubsubsec unlink
42500 @cindex unlink, file-i/o system call
42505 int unlink(const char *pathname);
42509 @samp{Funlink,@var{pathnameptr}/@var{len}}
42511 @item Return value:
42512 On success, zero is returned. On error, -1 is returned.
42518 No access to the file or the path of the file.
42521 The system does not allow unlinking of directories.
42524 The file @var{pathname} cannot be unlinked because it's
42525 being used by another process.
42528 @var{pathnameptr} is an invalid pointer value.
42531 @var{pathname} was too long.
42534 A directory component in @var{pathname} does not exist.
42537 A component of the path is not a directory.
42540 The file is on a read-only filesystem.
42543 The call was interrupted by the user.
42549 @unnumberedsubsubsec stat/fstat
42550 @cindex fstat, file-i/o system call
42551 @cindex stat, file-i/o system call
42556 int stat(const char *pathname, struct stat *buf);
42557 int fstat(int fd, struct stat *buf);
42561 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
42562 @samp{Ffstat,@var{fd},@var{bufptr}}
42564 @item Return value:
42565 On success, zero is returned. On error, -1 is returned.
42571 @var{fd} is not a valid open file.
42574 A directory component in @var{pathname} does not exist or the
42575 path is an empty string.
42578 A component of the path is not a directory.
42581 @var{pathnameptr} is an invalid pointer value.
42584 No access to the file or the path of the file.
42587 @var{pathname} was too long.
42590 The call was interrupted by the user.
42596 @unnumberedsubsubsec gettimeofday
42597 @cindex gettimeofday, file-i/o system call
42602 int gettimeofday(struct timeval *tv, void *tz);
42606 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
42608 @item Return value:
42609 On success, 0 is returned, -1 otherwise.
42615 @var{tz} is a non-NULL pointer.
42618 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
42624 @unnumberedsubsubsec isatty
42625 @cindex isatty, file-i/o system call
42630 int isatty(int fd);
42634 @samp{Fisatty,@var{fd}}
42636 @item Return value:
42637 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
42643 The call was interrupted by the user.
42648 Note that the @code{isatty} call is treated as a special case: it returns
42649 1 to the target if the file descriptor is attached
42650 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
42651 would require implementing @code{ioctl} and would be more complex than
42656 @unnumberedsubsubsec system
42657 @cindex system, file-i/o system call
42662 int system(const char *command);
42666 @samp{Fsystem,@var{commandptr}/@var{len}}
42668 @item Return value:
42669 If @var{len} is zero, the return value indicates whether a shell is
42670 available. A zero return value indicates a shell is not available.
42671 For non-zero @var{len}, the value returned is -1 on error and the
42672 return status of the command otherwise. Only the exit status of the
42673 command is returned, which is extracted from the host's @code{system}
42674 return value by calling @code{WEXITSTATUS(retval)}. In case
42675 @file{/bin/sh} could not be executed, 127 is returned.
42681 The call was interrupted by the user.
42686 @value{GDBN} takes over the full task of calling the necessary host calls
42687 to perform the @code{system} call. The return value of @code{system} on
42688 the host is simplified before it's returned
42689 to the target. Any termination signal information from the child process
42690 is discarded, and the return value consists
42691 entirely of the exit status of the called command.
42693 Due to security concerns, the @code{system} call is by default refused
42694 by @value{GDBN}. The user has to allow this call explicitly with the
42695 @code{set remote system-call-allowed 1} command.
42698 @item set remote system-call-allowed
42699 @kindex set remote system-call-allowed
42700 Control whether to allow the @code{system} calls in the File I/O
42701 protocol for the remote target. The default is zero (disabled).
42703 @item show remote system-call-allowed
42704 @kindex show remote system-call-allowed
42705 Show whether the @code{system} calls are allowed in the File I/O
42709 @node Protocol-specific Representation of Datatypes
42710 @subsection Protocol-specific Representation of Datatypes
42711 @cindex protocol-specific representation of datatypes, in file-i/o protocol
42714 * Integral Datatypes::
42716 * Memory Transfer::
42721 @node Integral Datatypes
42722 @unnumberedsubsubsec Integral Datatypes
42723 @cindex integral datatypes, in file-i/o protocol
42725 The integral datatypes used in the system calls are @code{int},
42726 @code{unsigned int}, @code{long}, @code{unsigned long},
42727 @code{mode_t}, and @code{time_t}.
42729 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
42730 implemented as 32 bit values in this protocol.
42732 @code{long} and @code{unsigned long} are implemented as 64 bit types.
42734 @xref{Limits}, for corresponding MIN and MAX values (similar to those
42735 in @file{limits.h}) to allow range checking on host and target.
42737 @code{time_t} datatypes are defined as seconds since the Epoch.
42739 All integral datatypes transferred as part of a memory read or write of a
42740 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
42743 @node Pointer Values
42744 @unnumberedsubsubsec Pointer Values
42745 @cindex pointer values, in file-i/o protocol
42747 Pointers to target data are transmitted as they are. An exception
42748 is made for pointers to buffers for which the length isn't
42749 transmitted as part of the function call, namely strings. Strings
42750 are transmitted as a pointer/length pair, both as hex values, e.g.@:
42757 which is a pointer to data of length 18 bytes at position 0x1aaf.
42758 The length is defined as the full string length in bytes, including
42759 the trailing null byte. For example, the string @code{"hello world"}
42760 at address 0x123456 is transmitted as
42766 @node Memory Transfer
42767 @unnumberedsubsubsec Memory Transfer
42768 @cindex memory transfer, in file-i/o protocol
42770 Structured data which is transferred using a memory read or write (for
42771 example, a @code{struct stat}) is expected to be in a protocol-specific format
42772 with all scalar multibyte datatypes being big endian. Translation to
42773 this representation needs to be done both by the target before the @code{F}
42774 packet is sent, and by @value{GDBN} before
42775 it transfers memory to the target. Transferred pointers to structured
42776 data should point to the already-coerced data at any time.
42780 @unnumberedsubsubsec struct stat
42781 @cindex struct stat, in file-i/o protocol
42783 The buffer of type @code{struct stat} used by the target and @value{GDBN}
42784 is defined as follows:
42788 unsigned int st_dev; /* device */
42789 unsigned int st_ino; /* inode */
42790 mode_t st_mode; /* protection */
42791 unsigned int st_nlink; /* number of hard links */
42792 unsigned int st_uid; /* user ID of owner */
42793 unsigned int st_gid; /* group ID of owner */
42794 unsigned int st_rdev; /* device type (if inode device) */
42795 unsigned long st_size; /* total size, in bytes */
42796 unsigned long st_blksize; /* blocksize for filesystem I/O */
42797 unsigned long st_blocks; /* number of blocks allocated */
42798 time_t st_atime; /* time of last access */
42799 time_t st_mtime; /* time of last modification */
42800 time_t st_ctime; /* time of last change */
42804 The integral datatypes conform to the definitions given in the
42805 appropriate section (see @ref{Integral Datatypes}, for details) so this
42806 structure is of size 64 bytes.
42808 The values of several fields have a restricted meaning and/or
42814 A value of 0 represents a file, 1 the console.
42817 No valid meaning for the target. Transmitted unchanged.
42820 Valid mode bits are described in @ref{Constants}. Any other
42821 bits have currently no meaning for the target.
42826 No valid meaning for the target. Transmitted unchanged.
42831 These values have a host and file system dependent
42832 accuracy. Especially on Windows hosts, the file system may not
42833 support exact timing values.
42836 The target gets a @code{struct stat} of the above representation and is
42837 responsible for coercing it to the target representation before
42840 Note that due to size differences between the host, target, and protocol
42841 representations of @code{struct stat} members, these members could eventually
42842 get truncated on the target.
42844 @node struct timeval
42845 @unnumberedsubsubsec struct timeval
42846 @cindex struct timeval, in file-i/o protocol
42848 The buffer of type @code{struct timeval} used by the File-I/O protocol
42849 is defined as follows:
42853 time_t tv_sec; /* second */
42854 long tv_usec; /* microsecond */
42858 The integral datatypes conform to the definitions given in the
42859 appropriate section (see @ref{Integral Datatypes}, for details) so this
42860 structure is of size 8 bytes.
42863 @subsection Constants
42864 @cindex constants, in file-i/o protocol
42866 The following values are used for the constants inside of the
42867 protocol. @value{GDBN} and target are responsible for translating these
42868 values before and after the call as needed.
42879 @unnumberedsubsubsec Open Flags
42880 @cindex open flags, in file-i/o protocol
42882 All values are given in hexadecimal representation.
42894 @node mode_t Values
42895 @unnumberedsubsubsec mode_t Values
42896 @cindex mode_t values, in file-i/o protocol
42898 All values are given in octal representation.
42915 @unnumberedsubsubsec Errno Values
42916 @cindex errno values, in file-i/o protocol
42918 All values are given in decimal representation.
42943 @code{EUNKNOWN} is used as a fallback error value if a host system returns
42944 any error value not in the list of supported error numbers.
42947 @unnumberedsubsubsec Lseek Flags
42948 @cindex lseek flags, in file-i/o protocol
42957 @unnumberedsubsubsec Limits
42958 @cindex limits, in file-i/o protocol
42960 All values are given in decimal representation.
42963 INT_MIN -2147483648
42965 UINT_MAX 4294967295
42966 LONG_MIN -9223372036854775808
42967 LONG_MAX 9223372036854775807
42968 ULONG_MAX 18446744073709551615
42971 @node File-I/O Examples
42972 @subsection File-I/O Examples
42973 @cindex file-i/o examples
42975 Example sequence of a write call, file descriptor 3, buffer is at target
42976 address 0x1234, 6 bytes should be written:
42979 <- @code{Fwrite,3,1234,6}
42980 @emph{request memory read from target}
42983 @emph{return "6 bytes written"}
42987 Example sequence of a read call, file descriptor 3, buffer is at target
42988 address 0x1234, 6 bytes should be read:
42991 <- @code{Fread,3,1234,6}
42992 @emph{request memory write to target}
42993 -> @code{X1234,6:XXXXXX}
42994 @emph{return "6 bytes read"}
42998 Example sequence of a read call, call fails on the host due to invalid
42999 file descriptor (@code{EBADF}):
43002 <- @code{Fread,3,1234,6}
43006 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
43010 <- @code{Fread,3,1234,6}
43015 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
43019 <- @code{Fread,3,1234,6}
43020 -> @code{X1234,6:XXXXXX}
43024 @node Library List Format
43025 @section Library List Format
43026 @cindex library list format, remote protocol
43028 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
43029 same process as your application to manage libraries. In this case,
43030 @value{GDBN} can use the loader's symbol table and normal memory
43031 operations to maintain a list of shared libraries. On other
43032 platforms, the operating system manages loaded libraries.
43033 @value{GDBN} can not retrieve the list of currently loaded libraries
43034 through memory operations, so it uses the @samp{qXfer:libraries:read}
43035 packet (@pxref{qXfer library list read}) instead. The remote stub
43036 queries the target's operating system and reports which libraries
43039 The @samp{qXfer:libraries:read} packet returns an XML document which
43040 lists loaded libraries and their offsets. Each library has an
43041 associated name and one or more segment or section base addresses,
43042 which report where the library was loaded in memory.
43044 For the common case of libraries that are fully linked binaries, the
43045 library should have a list of segments. If the target supports
43046 dynamic linking of a relocatable object file, its library XML element
43047 should instead include a list of allocated sections. The segment or
43048 section bases are start addresses, not relocation offsets; they do not
43049 depend on the library's link-time base addresses.
43051 @value{GDBN} must be linked with the Expat library to support XML
43052 library lists. @xref{Expat}.
43054 A simple memory map, with one loaded library relocated by a single
43055 offset, looks like this:
43059 <library name="/lib/libc.so.6">
43060 <segment address="0x10000000"/>
43065 Another simple memory map, with one loaded library with three
43066 allocated sections (.text, .data, .bss), looks like this:
43070 <library name="sharedlib.o">
43071 <section address="0x10000000"/>
43072 <section address="0x20000000"/>
43073 <section address="0x30000000"/>
43078 The format of a library list is described by this DTD:
43081 <!-- library-list: Root element with versioning -->
43082 <!ELEMENT library-list (library)*>
43083 <!ATTLIST library-list version CDATA #FIXED "1.0">
43084 <!ELEMENT library (segment*, section*)>
43085 <!ATTLIST library name CDATA #REQUIRED>
43086 <!ELEMENT segment EMPTY>
43087 <!ATTLIST segment address CDATA #REQUIRED>
43088 <!ELEMENT section EMPTY>
43089 <!ATTLIST section address CDATA #REQUIRED>
43092 In addition, segments and section descriptors cannot be mixed within a
43093 single library element, and you must supply at least one segment or
43094 section for each library.
43096 @node Library List Format for SVR4 Targets
43097 @section Library List Format for SVR4 Targets
43098 @cindex library list format, remote protocol
43100 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
43101 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
43102 shared libraries. Still a special library list provided by this packet is
43103 more efficient for the @value{GDBN} remote protocol.
43105 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
43106 loaded libraries and their SVR4 linker parameters. For each library on SVR4
43107 target, the following parameters are reported:
43111 @code{name}, the absolute file name from the @code{l_name} field of
43112 @code{struct link_map}.
43114 @code{lm} with address of @code{struct link_map} used for TLS
43115 (Thread Local Storage) access.
43117 @code{l_addr}, the displacement as read from the field @code{l_addr} of
43118 @code{struct link_map}. For prelinked libraries this is not an absolute
43119 memory address. It is a displacement of absolute memory address against
43120 address the file was prelinked to during the library load.
43122 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
43125 Additionally the single @code{main-lm} attribute specifies address of
43126 @code{struct link_map} used for the main executable. This parameter is used
43127 for TLS access and its presence is optional.
43129 @value{GDBN} must be linked with the Expat library to support XML
43130 SVR4 library lists. @xref{Expat}.
43132 A simple memory map, with two loaded libraries (which do not use prelink),
43136 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
43137 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
43139 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
43141 </library-list-svr>
43144 The format of an SVR4 library list is described by this DTD:
43147 <!-- library-list-svr4: Root element with versioning -->
43148 <!ELEMENT library-list-svr4 (library)*>
43149 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
43150 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
43151 <!ELEMENT library EMPTY>
43152 <!ATTLIST library name CDATA #REQUIRED>
43153 <!ATTLIST library lm CDATA #REQUIRED>
43154 <!ATTLIST library l_addr CDATA #REQUIRED>
43155 <!ATTLIST library l_ld CDATA #REQUIRED>
43158 @node Memory Map Format
43159 @section Memory Map Format
43160 @cindex memory map format
43162 To be able to write into flash memory, @value{GDBN} needs to obtain a
43163 memory map from the target. This section describes the format of the
43166 The memory map is obtained using the @samp{qXfer:memory-map:read}
43167 (@pxref{qXfer memory map read}) packet and is an XML document that
43168 lists memory regions.
43170 @value{GDBN} must be linked with the Expat library to support XML
43171 memory maps. @xref{Expat}.
43173 The top-level structure of the document is shown below:
43176 <?xml version="1.0"?>
43177 <!DOCTYPE memory-map
43178 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
43179 "http://sourceware.org/gdb/gdb-memory-map.dtd">
43185 Each region can be either:
43190 A region of RAM starting at @var{addr} and extending for @var{length}
43194 <memory type="ram" start="@var{addr}" length="@var{length}"/>
43199 A region of read-only memory:
43202 <memory type="rom" start="@var{addr}" length="@var{length}"/>
43207 A region of flash memory, with erasure blocks @var{blocksize}
43211 <memory type="flash" start="@var{addr}" length="@var{length}">
43212 <property name="blocksize">@var{blocksize}</property>
43218 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
43219 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
43220 packets to write to addresses in such ranges.
43222 The formal DTD for memory map format is given below:
43225 <!-- ................................................... -->
43226 <!-- Memory Map XML DTD ................................ -->
43227 <!-- File: memory-map.dtd .............................. -->
43228 <!-- .................................... .............. -->
43229 <!-- memory-map.dtd -->
43230 <!-- memory-map: Root element with versioning -->
43231 <!ELEMENT memory-map (memory)*>
43232 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
43233 <!ELEMENT memory (property)*>
43234 <!-- memory: Specifies a memory region,
43235 and its type, or device. -->
43236 <!ATTLIST memory type (ram|rom|flash) #REQUIRED
43237 start CDATA #REQUIRED
43238 length CDATA #REQUIRED>
43239 <!-- property: Generic attribute tag -->
43240 <!ELEMENT property (#PCDATA | property)*>
43241 <!ATTLIST property name (blocksize) #REQUIRED>
43244 @node Thread List Format
43245 @section Thread List Format
43246 @cindex thread list format
43248 To efficiently update the list of threads and their attributes,
43249 @value{GDBN} issues the @samp{qXfer:threads:read} packet
43250 (@pxref{qXfer threads read}) and obtains the XML document with
43251 the following structure:
43254 <?xml version="1.0"?>
43256 <thread id="id" core="0" name="name">
43257 ... description ...
43262 Each @samp{thread} element must have the @samp{id} attribute that
43263 identifies the thread (@pxref{thread-id syntax}). The
43264 @samp{core} attribute, if present, specifies which processor core
43265 the thread was last executing on. The @samp{name} attribute, if
43266 present, specifies the human-readable name of the thread. The content
43267 of the of @samp{thread} element is interpreted as human-readable
43268 auxiliary information. The @samp{handle} attribute, if present,
43269 is a hex encoded representation of the thread handle.
43272 @node Traceframe Info Format
43273 @section Traceframe Info Format
43274 @cindex traceframe info format
43276 To be able to know which objects in the inferior can be examined when
43277 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
43278 memory ranges, registers and trace state variables that have been
43279 collected in a traceframe.
43281 This list is obtained using the @samp{qXfer:traceframe-info:read}
43282 (@pxref{qXfer traceframe info read}) packet and is an XML document.
43284 @value{GDBN} must be linked with the Expat library to support XML
43285 traceframe info discovery. @xref{Expat}.
43287 The top-level structure of the document is shown below:
43290 <?xml version="1.0"?>
43291 <!DOCTYPE traceframe-info
43292 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
43293 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
43299 Each traceframe block can be either:
43304 A region of collected memory starting at @var{addr} and extending for
43305 @var{length} bytes from there:
43308 <memory start="@var{addr}" length="@var{length}"/>
43312 A block indicating trace state variable numbered @var{number} has been
43316 <tvar id="@var{number}"/>
43321 The formal DTD for the traceframe info format is given below:
43324 <!ELEMENT traceframe-info (memory | tvar)* >
43325 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
43327 <!ELEMENT memory EMPTY>
43328 <!ATTLIST memory start CDATA #REQUIRED
43329 length CDATA #REQUIRED>
43331 <!ATTLIST tvar id CDATA #REQUIRED>
43334 @node Branch Trace Format
43335 @section Branch Trace Format
43336 @cindex branch trace format
43338 In order to display the branch trace of an inferior thread,
43339 @value{GDBN} needs to obtain the list of branches. This list is
43340 represented as list of sequential code blocks that are connected via
43341 branches. The code in each block has been executed sequentially.
43343 This list is obtained using the @samp{qXfer:btrace:read}
43344 (@pxref{qXfer btrace read}) packet and is an XML document.
43346 @value{GDBN} must be linked with the Expat library to support XML
43347 traceframe info discovery. @xref{Expat}.
43349 The top-level structure of the document is shown below:
43352 <?xml version="1.0"?>
43354 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
43355 "http://sourceware.org/gdb/gdb-btrace.dtd">
43364 A block of sequentially executed instructions starting at @var{begin}
43365 and ending at @var{end}:
43368 <block begin="@var{begin}" end="@var{end}"/>
43373 The formal DTD for the branch trace format is given below:
43376 <!ELEMENT btrace (block* | pt) >
43377 <!ATTLIST btrace version CDATA #FIXED "1.0">
43379 <!ELEMENT block EMPTY>
43380 <!ATTLIST block begin CDATA #REQUIRED
43381 end CDATA #REQUIRED>
43383 <!ELEMENT pt (pt-config?, raw?)>
43385 <!ELEMENT pt-config (cpu?)>
43387 <!ELEMENT cpu EMPTY>
43388 <!ATTLIST cpu vendor CDATA #REQUIRED
43389 family CDATA #REQUIRED
43390 model CDATA #REQUIRED
43391 stepping CDATA #REQUIRED>
43393 <!ELEMENT raw (#PCDATA)>
43396 @node Branch Trace Configuration Format
43397 @section Branch Trace Configuration Format
43398 @cindex branch trace configuration format
43400 For each inferior thread, @value{GDBN} can obtain the branch trace
43401 configuration using the @samp{qXfer:btrace-conf:read}
43402 (@pxref{qXfer btrace-conf read}) packet.
43404 The configuration describes the branch trace format and configuration
43405 settings for that format. The following information is described:
43409 This thread uses the @dfn{Branch Trace Store} (@acronym{BTS}) format.
43412 The size of the @acronym{BTS} ring buffer in bytes.
43415 This thread uses the @dfn{Intel Processor Trace} (@acronym{Intel
43419 The size of the @acronym{Intel PT} ring buffer in bytes.
43423 @value{GDBN} must be linked with the Expat library to support XML
43424 branch trace configuration discovery. @xref{Expat}.
43426 The formal DTD for the branch trace configuration format is given below:
43429 <!ELEMENT btrace-conf (bts?, pt?)>
43430 <!ATTLIST btrace-conf version CDATA #FIXED "1.0">
43432 <!ELEMENT bts EMPTY>
43433 <!ATTLIST bts size CDATA #IMPLIED>
43435 <!ELEMENT pt EMPTY>
43436 <!ATTLIST pt size CDATA #IMPLIED>
43439 @include agentexpr.texi
43441 @node Target Descriptions
43442 @appendix Target Descriptions
43443 @cindex target descriptions
43445 One of the challenges of using @value{GDBN} to debug embedded systems
43446 is that there are so many minor variants of each processor
43447 architecture in use. It is common practice for vendors to start with
43448 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
43449 and then make changes to adapt it to a particular market niche. Some
43450 architectures have hundreds of variants, available from dozens of
43451 vendors. This leads to a number of problems:
43455 With so many different customized processors, it is difficult for
43456 the @value{GDBN} maintainers to keep up with the changes.
43458 Since individual variants may have short lifetimes or limited
43459 audiences, it may not be worthwhile to carry information about every
43460 variant in the @value{GDBN} source tree.
43462 When @value{GDBN} does support the architecture of the embedded system
43463 at hand, the task of finding the correct architecture name to give the
43464 @command{set architecture} command can be error-prone.
43467 To address these problems, the @value{GDBN} remote protocol allows a
43468 target system to not only identify itself to @value{GDBN}, but to
43469 actually describe its own features. This lets @value{GDBN} support
43470 processor variants it has never seen before --- to the extent that the
43471 descriptions are accurate, and that @value{GDBN} understands them.
43473 @value{GDBN} must be linked with the Expat library to support XML
43474 target descriptions. @xref{Expat}.
43477 * Retrieving Descriptions:: How descriptions are fetched from a target.
43478 * Target Description Format:: The contents of a target description.
43479 * Predefined Target Types:: Standard types available for target
43481 * Enum Target Types:: How to define enum target types.
43482 * Standard Target Features:: Features @value{GDBN} knows about.
43485 @node Retrieving Descriptions
43486 @section Retrieving Descriptions
43488 Target descriptions can be read from the target automatically, or
43489 specified by the user manually. The default behavior is to read the
43490 description from the target. @value{GDBN} retrieves it via the remote
43491 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
43492 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
43493 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
43494 XML document, of the form described in @ref{Target Description
43497 Alternatively, you can specify a file to read for the target description.
43498 If a file is set, the target will not be queried. The commands to
43499 specify a file are:
43502 @cindex set tdesc filename
43503 @item set tdesc filename @var{path}
43504 Read the target description from @var{path}.
43506 @cindex unset tdesc filename
43507 @item unset tdesc filename
43508 Do not read the XML target description from a file. @value{GDBN}
43509 will use the description supplied by the current target.
43511 @cindex show tdesc filename
43512 @item show tdesc filename
43513 Show the filename to read for a target description, if any.
43517 @node Target Description Format
43518 @section Target Description Format
43519 @cindex target descriptions, XML format
43521 A target description annex is an @uref{http://www.w3.org/XML/, XML}
43522 document which complies with the Document Type Definition provided in
43523 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
43524 means you can use generally available tools like @command{xmllint} to
43525 check that your feature descriptions are well-formed and valid.
43526 However, to help people unfamiliar with XML write descriptions for
43527 their targets, we also describe the grammar here.
43529 Target descriptions can identify the architecture of the remote target
43530 and (for some architectures) provide information about custom register
43531 sets. They can also identify the OS ABI of the remote target.
43532 @value{GDBN} can use this information to autoconfigure for your
43533 target, or to warn you if you connect to an unsupported target.
43535 Here is a simple target description:
43538 <target version="1.0">
43539 <architecture>i386:x86-64</architecture>
43544 This minimal description only says that the target uses
43545 the x86-64 architecture.
43547 A target description has the following overall form, with [ ] marking
43548 optional elements and @dots{} marking repeatable elements. The elements
43549 are explained further below.
43552 <?xml version="1.0"?>
43553 <!DOCTYPE target SYSTEM "gdb-target.dtd">
43554 <target version="1.0">
43555 @r{[}@var{architecture}@r{]}
43556 @r{[}@var{osabi}@r{]}
43557 @r{[}@var{compatible}@r{]}
43558 @r{[}@var{feature}@dots{}@r{]}
43563 The description is generally insensitive to whitespace and line
43564 breaks, under the usual common-sense rules. The XML version
43565 declaration and document type declaration can generally be omitted
43566 (@value{GDBN} does not require them), but specifying them may be
43567 useful for XML validation tools. The @samp{version} attribute for
43568 @samp{<target>} may also be omitted, but we recommend
43569 including it; if future versions of @value{GDBN} use an incompatible
43570 revision of @file{gdb-target.dtd}, they will detect and report
43571 the version mismatch.
43573 @subsection Inclusion
43574 @cindex target descriptions, inclusion
43577 @cindex <xi:include>
43580 It can sometimes be valuable to split a target description up into
43581 several different annexes, either for organizational purposes, or to
43582 share files between different possible target descriptions. You can
43583 divide a description into multiple files by replacing any element of
43584 the target description with an inclusion directive of the form:
43587 <xi:include href="@var{document}"/>
43591 When @value{GDBN} encounters an element of this form, it will retrieve
43592 the named XML @var{document}, and replace the inclusion directive with
43593 the contents of that document. If the current description was read
43594 using @samp{qXfer}, then so will be the included document;
43595 @var{document} will be interpreted as the name of an annex. If the
43596 current description was read from a file, @value{GDBN} will look for
43597 @var{document} as a file in the same directory where it found the
43598 original description.
43600 @subsection Architecture
43601 @cindex <architecture>
43603 An @samp{<architecture>} element has this form:
43606 <architecture>@var{arch}</architecture>
43609 @var{arch} is one of the architectures from the set accepted by
43610 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
43613 @cindex @code{<osabi>}
43615 This optional field was introduced in @value{GDBN} version 7.0.
43616 Previous versions of @value{GDBN} ignore it.
43618 An @samp{<osabi>} element has this form:
43621 <osabi>@var{abi-name}</osabi>
43624 @var{abi-name} is an OS ABI name from the same selection accepted by
43625 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
43627 @subsection Compatible Architecture
43628 @cindex @code{<compatible>}
43630 This optional field was introduced in @value{GDBN} version 7.0.
43631 Previous versions of @value{GDBN} ignore it.
43633 A @samp{<compatible>} element has this form:
43636 <compatible>@var{arch}</compatible>
43639 @var{arch} is one of the architectures from the set accepted by
43640 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
43642 A @samp{<compatible>} element is used to specify that the target
43643 is able to run binaries in some other than the main target architecture
43644 given by the @samp{<architecture>} element. For example, on the
43645 Cell Broadband Engine, the main architecture is @code{powerpc:common}
43646 or @code{powerpc:common64}, but the system is able to run binaries
43647 in the @code{spu} architecture as well. The way to describe this
43648 capability with @samp{<compatible>} is as follows:
43651 <architecture>powerpc:common</architecture>
43652 <compatible>spu</compatible>
43655 @subsection Features
43658 Each @samp{<feature>} describes some logical portion of the target
43659 system. Features are currently used to describe available CPU
43660 registers and the types of their contents. A @samp{<feature>} element
43664 <feature name="@var{name}">
43665 @r{[}@var{type}@dots{}@r{]}
43671 Each feature's name should be unique within the description. The name
43672 of a feature does not matter unless @value{GDBN} has some special
43673 knowledge of the contents of that feature; if it does, the feature
43674 should have its standard name. @xref{Standard Target Features}.
43678 Any register's value is a collection of bits which @value{GDBN} must
43679 interpret. The default interpretation is a two's complement integer,
43680 but other types can be requested by name in the register description.
43681 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
43682 Target Types}), and the description can define additional composite
43685 Each type element must have an @samp{id} attribute, which gives
43686 a unique (within the containing @samp{<feature>}) name to the type.
43687 Types must be defined before they are used.
43690 Some targets offer vector registers, which can be treated as arrays
43691 of scalar elements. These types are written as @samp{<vector>} elements,
43692 specifying the array element type, @var{type}, and the number of elements,
43696 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
43700 If a register's value is usefully viewed in multiple ways, define it
43701 with a union type containing the useful representations. The
43702 @samp{<union>} element contains one or more @samp{<field>} elements,
43703 each of which has a @var{name} and a @var{type}:
43706 <union id="@var{id}">
43707 <field name="@var{name}" type="@var{type}"/>
43714 If a register's value is composed from several separate values, define
43715 it with either a structure type or a flags type.
43716 A flags type may only contain bitfields.
43717 A structure type may either contain only bitfields or contain no bitfields.
43718 If the value contains only bitfields, its total size in bytes must be
43721 Non-bitfield values have a @var{name} and @var{type}.
43724 <struct id="@var{id}">
43725 <field name="@var{name}" type="@var{type}"/>
43730 Both @var{name} and @var{type} values are required.
43731 No implicit padding is added.
43733 Bitfield values have a @var{name}, @var{start}, @var{end} and @var{type}.
43736 <struct id="@var{id}" size="@var{size}">
43737 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
43743 <flags id="@var{id}" size="@var{size}">
43744 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
43749 The @var{name} value is required.
43750 Bitfield values may be named with the empty string, @samp{""},
43751 in which case the field is ``filler'' and its value is not printed.
43752 Not all bits need to be specified, so ``filler'' fields are optional.
43754 The @var{start} and @var{end} values are required, and @var{type}
43756 The field's @var{start} must be less than or equal to its @var{end},
43757 and zero represents the least significant bit.
43759 The default value of @var{type} is @code{bool} for single bit fields,
43760 and an unsigned integer otherwise.
43762 Which to choose? Structures or flags?
43764 Registers defined with @samp{flags} have these advantages over
43765 defining them with @samp{struct}:
43769 Arithmetic may be performed on them as if they were integers.
43771 They are printed in a more readable fashion.
43774 Registers defined with @samp{struct} have one advantage over
43775 defining them with @samp{flags}:
43779 One can fetch individual fields like in @samp{C}.
43782 (gdb) print $my_struct_reg.field3
43788 @subsection Registers
43791 Each register is represented as an element with this form:
43794 <reg name="@var{name}"
43795 bitsize="@var{size}"
43796 @r{[}regnum="@var{num}"@r{]}
43797 @r{[}save-restore="@var{save-restore}"@r{]}
43798 @r{[}type="@var{type}"@r{]}
43799 @r{[}group="@var{group}"@r{]}/>
43803 The components are as follows:
43808 The register's name; it must be unique within the target description.
43811 The register's size, in bits.
43814 The register's number. If omitted, a register's number is one greater
43815 than that of the previous register (either in the current feature or in
43816 a preceding feature); the first register in the target description
43817 defaults to zero. This register number is used to read or write
43818 the register; e.g.@: it is used in the remote @code{p} and @code{P}
43819 packets, and registers appear in the @code{g} and @code{G} packets
43820 in order of increasing register number.
43823 Whether the register should be preserved across inferior function
43824 calls; this must be either @code{yes} or @code{no}. The default is
43825 @code{yes}, which is appropriate for most registers except for
43826 some system control registers; this is not related to the target's
43830 The type of the register. It may be a predefined type, a type
43831 defined in the current feature, or one of the special types @code{int}
43832 and @code{float}. @code{int} is an integer type of the correct size
43833 for @var{bitsize}, and @code{float} is a floating point type (in the
43834 architecture's normal floating point format) of the correct size for
43835 @var{bitsize}. The default is @code{int}.
43838 The register group to which this register belongs. It can be one of the
43839 standard register groups @code{general}, @code{float}, @code{vector} or an
43840 arbitrary string. Group names should be limited to alphanumeric characters.
43841 If a group name is made up of multiple words the words may be separated by
43842 hyphens; e.g.@: @code{special-group} or @code{ultra-special-group}. If no
43843 @var{group} is specified, @value{GDBN} will not display the register in
43844 @code{info registers}.
43848 @node Predefined Target Types
43849 @section Predefined Target Types
43850 @cindex target descriptions, predefined types
43852 Type definitions in the self-description can build up composite types
43853 from basic building blocks, but can not define fundamental types. Instead,
43854 standard identifiers are provided by @value{GDBN} for the fundamental
43855 types. The currently supported types are:
43860 Boolean type, occupying a single bit.
43868 Signed integer types holding the specified number of bits.
43876 Unsigned integer types holding the specified number of bits.
43880 Pointers to unspecified code and data. The program counter and
43881 any dedicated return address register may be marked as code
43882 pointers; printing a code pointer converts it into a symbolic
43883 address. The stack pointer and any dedicated address registers
43884 may be marked as data pointers.
43887 Single precision IEEE floating point.
43890 Double precision IEEE floating point.
43893 The 12-byte extended precision format used by ARM FPA registers.
43896 The 10-byte extended precision format used by x87 registers.
43899 32bit @sc{eflags} register used by x86.
43902 32bit @sc{mxcsr} register used by x86.
43906 @node Enum Target Types
43907 @section Enum Target Types
43908 @cindex target descriptions, enum types
43910 Enum target types are useful in @samp{struct} and @samp{flags}
43911 register descriptions. @xref{Target Description Format}.
43913 Enum types have a name, size and a list of name/value pairs.
43916 <enum id="@var{id}" size="@var{size}">
43917 <evalue name="@var{name}" value="@var{value}"/>
43922 Enums must be defined before they are used.
43925 <enum id="levels_type" size="4">
43926 <evalue name="low" value="0"/>
43927 <evalue name="high" value="1"/>
43929 <flags id="flags_type" size="4">
43930 <field name="X" start="0"/>
43931 <field name="LEVEL" start="1" end="1" type="levels_type"/>
43933 <reg name="flags" bitsize="32" type="flags_type"/>
43936 Given that description, a value of 3 for the @samp{flags} register
43937 would be printed as:
43940 (gdb) info register flags
43941 flags 0x3 [ X LEVEL=high ]
43944 @node Standard Target Features
43945 @section Standard Target Features
43946 @cindex target descriptions, standard features
43948 A target description must contain either no registers or all the
43949 target's registers. If the description contains no registers, then
43950 @value{GDBN} will assume a default register layout, selected based on
43951 the architecture. If the description contains any registers, the
43952 default layout will not be used; the standard registers must be
43953 described in the target description, in such a way that @value{GDBN}
43954 can recognize them.
43956 This is accomplished by giving specific names to feature elements
43957 which contain standard registers. @value{GDBN} will look for features
43958 with those names and verify that they contain the expected registers;
43959 if any known feature is missing required registers, or if any required
43960 feature is missing, @value{GDBN} will reject the target
43961 description. You can add additional registers to any of the
43962 standard features --- @value{GDBN} will display them just as if
43963 they were added to an unrecognized feature.
43965 This section lists the known features and their expected contents.
43966 Sample XML documents for these features are included in the
43967 @value{GDBN} source tree, in the directory @file{gdb/features}.
43969 Names recognized by @value{GDBN} should include the name of the
43970 company or organization which selected the name, and the overall
43971 architecture to which the feature applies; so e.g.@: the feature
43972 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
43974 The names of registers are not case sensitive for the purpose
43975 of recognizing standard features, but @value{GDBN} will only display
43976 registers using the capitalization used in the description.
43979 * AArch64 Features::
43983 * MicroBlaze Features::
43987 * Nios II Features::
43988 * OpenRISC 1000 Features::
43989 * PowerPC Features::
43990 * RISC-V Features::
43991 * S/390 and System z Features::
43997 @node AArch64 Features
43998 @subsection AArch64 Features
43999 @cindex target descriptions, AArch64 features
44001 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
44002 targets. It should contain registers @samp{x0} through @samp{x30},
44003 @samp{sp}, @samp{pc}, and @samp{cpsr}.
44005 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
44006 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
44009 The @samp{org.gnu.gdb.aarch64.sve} feature is optional. If present,
44010 it should contain registers @samp{z0} through @samp{z31}, @samp{p0}
44011 through @samp{p15}, @samp{ffr} and @samp{vg}.
44013 The @samp{org.gnu.gdb.aarch64.pauth} feature is optional. If present,
44014 it should contain registers @samp{pauth_dmask} and @samp{pauth_cmask}.
44017 @subsection ARC Features
44018 @cindex target descriptions, ARC Features
44020 ARC processors are highly configurable, so even core registers and their number
44021 are not completely predetermined. In addition flags and PC registers which are
44022 important to @value{GDBN} are not ``core'' registers in ARC. It is required
44023 that one of the core registers features is present.
44024 @samp{org.gnu.gdb.arc.aux-minimal} feature is mandatory.
44026 The @samp{org.gnu.gdb.arc.core.v2} feature is required for ARC EM and ARC HS
44027 targets with a normal register file. It should contain registers @samp{r0}
44028 through @samp{r25}, @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink},
44029 @samp{lp_count} and @samp{pcl}. This feature may contain register @samp{ilink}
44030 and any of extension core registers @samp{r32} through @samp{r59/acch}.
44031 @samp{ilink} and extension core registers are not available to read/write, when
44032 debugging GNU/Linux applications, thus @samp{ilink} is made optional.
44034 The @samp{org.gnu.gdb.arc.core-reduced.v2} feature is required for ARC EM and
44035 ARC HS targets with a reduced register file. It should contain registers
44036 @samp{r0} through @samp{r3}, @samp{r10} through @samp{r15}, @samp{gp},
44037 @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink}, @samp{lp_count} and @samp{pcl}.
44038 This feature may contain register @samp{ilink} and any of extension core
44039 registers @samp{r32} through @samp{r59/acch}.
44041 The @samp{org.gnu.gdb.arc.core.arcompact} feature is required for ARCompact
44042 targets with a normal register file. It should contain registers @samp{r0}
44043 through @samp{r25}, @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink},
44044 @samp{lp_count} and @samp{pcl}. This feature may contain registers
44045 @samp{ilink1}, @samp{ilink2} and any of extension core registers @samp{r32}
44046 through @samp{r59/acch}. @samp{ilink1} and @samp{ilink2} and extension core
44047 registers are not available when debugging GNU/Linux applications. The only
44048 difference with @samp{org.gnu.gdb.arc.core.v2} feature is in the names of
44049 @samp{ilink1} and @samp{ilink2} registers and that @samp{r30} is mandatory in
44050 ARC v2, but @samp{ilink2} is optional on ARCompact.
44052 The @samp{org.gnu.gdb.arc.aux-minimal} feature is required for all ARC
44053 targets. It should contain registers @samp{pc} and @samp{status32}.
44056 @subsection ARM Features
44057 @cindex target descriptions, ARM features
44059 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
44061 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
44062 @samp{lr}, @samp{pc}, and @samp{cpsr}.
44064 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
44065 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
44066 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
44069 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
44070 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
44072 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
44073 it should contain at least registers @samp{wR0} through @samp{wR15} and
44074 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
44075 @samp{wCSSF}, and @samp{wCASF} registers are optional.
44077 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
44078 should contain at least registers @samp{d0} through @samp{d15}. If
44079 they are present, @samp{d16} through @samp{d31} should also be included.
44080 @value{GDBN} will synthesize the single-precision registers from
44081 halves of the double-precision registers.
44083 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
44084 need to contain registers; it instructs @value{GDBN} to display the
44085 VFP double-precision registers as vectors and to synthesize the
44086 quad-precision registers from pairs of double-precision registers.
44087 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
44088 be present and include 32 double-precision registers.
44090 @node i386 Features
44091 @subsection i386 Features
44092 @cindex target descriptions, i386 features
44094 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
44095 targets. It should describe the following registers:
44099 @samp{eax} through @samp{edi} plus @samp{eip} for i386
44101 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
44103 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
44104 @samp{fs}, @samp{gs}
44106 @samp{st0} through @samp{st7}
44108 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
44109 @samp{foseg}, @samp{fooff} and @samp{fop}
44112 The register sets may be different, depending on the target.
44114 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
44115 describe registers:
44119 @samp{xmm0} through @samp{xmm7} for i386
44121 @samp{xmm0} through @samp{xmm15} for amd64
44126 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
44127 @samp{org.gnu.gdb.i386.sse} feature. It should
44128 describe the upper 128 bits of @sc{ymm} registers:
44132 @samp{ymm0h} through @samp{ymm7h} for i386
44134 @samp{ymm0h} through @samp{ymm15h} for amd64
44137 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel
44138 Memory Protection Extension (MPX). It should describe the following registers:
44142 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
44144 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
44147 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
44148 describe a single register, @samp{orig_eax}.
44150 The @samp{org.gnu.gdb.i386.segments} feature is optional. It should
44151 describe two system registers: @samp{fs_base} and @samp{gs_base}.
44153 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
44154 @samp{org.gnu.gdb.i386.avx} feature. It should
44155 describe additional @sc{xmm} registers:
44159 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
44162 It should describe the upper 128 bits of additional @sc{ymm} registers:
44166 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
44170 describe the upper 256 bits of @sc{zmm} registers:
44174 @samp{zmm0h} through @samp{zmm7h} for i386.
44176 @samp{zmm0h} through @samp{zmm15h} for amd64.
44180 describe the additional @sc{zmm} registers:
44184 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
44187 The @samp{org.gnu.gdb.i386.pkeys} feature is optional. It should
44188 describe a single register, @samp{pkru}. It is a 32-bit register
44189 valid for i386 and amd64.
44191 @node MicroBlaze Features
44192 @subsection MicroBlaze Features
44193 @cindex target descriptions, MicroBlaze features
44195 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
44196 targets. It should contain registers @samp{r0} through @samp{r31},
44197 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
44198 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
44199 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
44201 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
44202 If present, it should contain registers @samp{rshr} and @samp{rslr}
44204 @node MIPS Features
44205 @subsection @acronym{MIPS} Features
44206 @cindex target descriptions, @acronym{MIPS} features
44208 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
44209 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
44210 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
44213 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
44214 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
44215 registers. They may be 32-bit or 64-bit depending on the target.
44217 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
44218 it may be optional in a future version of @value{GDBN}. It should
44219 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
44220 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
44222 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
44223 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
44224 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
44225 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
44227 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
44228 contain a single register, @samp{restart}, which is used by the
44229 Linux kernel to control restartable syscalls.
44231 @node M68K Features
44232 @subsection M68K Features
44233 @cindex target descriptions, M68K features
44236 @item @samp{org.gnu.gdb.m68k.core}
44237 @itemx @samp{org.gnu.gdb.coldfire.core}
44238 @itemx @samp{org.gnu.gdb.fido.core}
44239 One of those features must be always present.
44240 The feature that is present determines which flavor of m68k is
44241 used. The feature that is present should contain registers
44242 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
44243 @samp{sp}, @samp{ps} and @samp{pc}.
44245 @item @samp{org.gnu.gdb.coldfire.fp}
44246 This feature is optional. If present, it should contain registers
44247 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
44251 @node NDS32 Features
44252 @subsection NDS32 Features
44253 @cindex target descriptions, NDS32 features
44255 The @samp{org.gnu.gdb.nds32.core} feature is required for NDS32
44256 targets. It should contain at least registers @samp{r0} through
44257 @samp{r10}, @samp{r15}, @samp{fp}, @samp{gp}, @samp{lp}, @samp{sp},
44260 The @samp{org.gnu.gdb.nds32.fpu} feature is optional. If present,
44261 it should contain 64-bit double-precision floating-point registers
44262 @samp{fd0} through @emph{fdN}, which should be @samp{fd3}, @samp{fd7},
44263 @samp{fd15}, or @samp{fd31} based on the FPU configuration implemented.
44265 @emph{Note:} The first sixteen 64-bit double-precision floating-point
44266 registers are overlapped with the thirty-two 32-bit single-precision
44267 floating-point registers. The 32-bit single-precision registers, if
44268 not being listed explicitly, will be synthesized from halves of the
44269 overlapping 64-bit double-precision registers. Listing 32-bit
44270 single-precision registers explicitly is deprecated, and the
44271 support to it could be totally removed some day.
44273 @node Nios II Features
44274 @subsection Nios II Features
44275 @cindex target descriptions, Nios II features
44277 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
44278 targets. It should contain the 32 core registers (@samp{zero},
44279 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
44280 @samp{pc}, and the 16 control registers (@samp{status} through
44283 @node OpenRISC 1000 Features
44284 @subsection Openrisc 1000 Features
44285 @cindex target descriptions, OpenRISC 1000 features
44287 The @samp{org.gnu.gdb.or1k.group0} feature is required for OpenRISC 1000
44288 targets. It should contain the 32 general purpose registers (@samp{r0}
44289 through @samp{r31}), @samp{ppc}, @samp{npc} and @samp{sr}.
44291 @node PowerPC Features
44292 @subsection PowerPC Features
44293 @cindex target descriptions, PowerPC features
44295 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
44296 targets. It should contain registers @samp{r0} through @samp{r31},
44297 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
44298 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
44300 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
44301 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
44303 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
44304 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr}, and
44305 @samp{vrsave}. @value{GDBN} will define pseudo-registers @samp{v0}
44306 through @samp{v31} as aliases for the corresponding @samp{vrX}
44309 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
44310 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN} will
44311 combine these registers with the floating point registers (@samp{f0}
44312 through @samp{f31}) and the altivec registers (@samp{vr0} through
44313 @samp{vr31}) to present the 128-bit wide registers @samp{vs0} through
44314 @samp{vs63}, the set of vector-scalar registers for POWER7.
44315 Therefore, this feature requires both @samp{org.gnu.gdb.power.fpu} and
44316 @samp{org.gnu.gdb.power.altivec}.
44318 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
44319 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
44320 @samp{spefscr}. SPE targets should provide 32-bit registers in
44321 @samp{org.gnu.gdb.power.core} and provide the upper halves in
44322 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
44323 these to present registers @samp{ev0} through @samp{ev31} to the
44326 The @samp{org.gnu.gdb.power.ppr} feature is optional. It should
44327 contain the 64-bit register @samp{ppr}.
44329 The @samp{org.gnu.gdb.power.dscr} feature is optional. It should
44330 contain the 64-bit register @samp{dscr}.
44332 The @samp{org.gnu.gdb.power.tar} feature is optional. It should
44333 contain the 64-bit register @samp{tar}.
44335 The @samp{org.gnu.gdb.power.ebb} feature is optional. It should
44336 contain registers @samp{bescr}, @samp{ebbhr} and @samp{ebbrr}, all
44339 The @samp{org.gnu.gdb.power.linux.pmu} feature is optional. It should
44340 contain registers @samp{mmcr0}, @samp{mmcr2}, @samp{siar}, @samp{sdar}
44341 and @samp{sier}, all 64-bit wide. This is the subset of the isa 2.07
44342 server PMU registers provided by @sc{gnu}/Linux.
44344 The @samp{org.gnu.gdb.power.htm.spr} feature is optional. It should
44345 contain registers @samp{tfhar}, @samp{texasr} and @samp{tfiar}, all
44348 The @samp{org.gnu.gdb.power.htm.core} feature is optional. It should
44349 contain the checkpointed general-purpose registers @samp{cr0} through
44350 @samp{cr31}, as well as the checkpointed registers @samp{clr} and
44351 @samp{cctr}. These registers may all be either 32-bit or 64-bit
44352 depending on the target. It should also contain the checkpointed
44353 registers @samp{ccr} and @samp{cxer}, which should both be 32-bit
44356 The @samp{org.gnu.gdb.power.htm.fpu} feature is optional. It should
44357 contain the checkpointed 64-bit floating-point registers @samp{cf0}
44358 through @samp{cf31}, as well as the checkpointed 64-bit register
44361 The @samp{org.gnu.gdb.power.htm.altivec} feature is optional. It
44362 should contain the checkpointed altivec registers @samp{cvr0} through
44363 @samp{cvr31}, all 128-bit wide. It should also contain the
44364 checkpointed registers @samp{cvscr} and @samp{cvrsave}, both 32-bit
44367 The @samp{org.gnu.gdb.power.htm.vsx} feature is optional. It should
44368 contain registers @samp{cvs0h} through @samp{cvs31h}. @value{GDBN}
44369 will combine these registers with the checkpointed floating point
44370 registers (@samp{cf0} through @samp{cf31}) and the checkpointed
44371 altivec registers (@samp{cvr0} through @samp{cvr31}) to present the
44372 128-bit wide checkpointed vector-scalar registers @samp{cvs0} through
44373 @samp{cvs63}. Therefore, this feature requires both
44374 @samp{org.gnu.gdb.power.htm.altivec} and
44375 @samp{org.gnu.gdb.power.htm.fpu}.
44377 The @samp{org.gnu.gdb.power.htm.ppr} feature is optional. It should
44378 contain the 64-bit checkpointed register @samp{cppr}.
44380 The @samp{org.gnu.gdb.power.htm.dscr} feature is optional. It should
44381 contain the 64-bit checkpointed register @samp{cdscr}.
44383 The @samp{org.gnu.gdb.power.htm.tar} feature is optional. It should
44384 contain the 64-bit checkpointed register @samp{ctar}.
44387 @node RISC-V Features
44388 @subsection RISC-V Features
44389 @cindex target descriptions, RISC-V Features
44391 The @samp{org.gnu.gdb.riscv.cpu} feature is required for RISC-V
44392 targets. It should contain the registers @samp{x0} through
44393 @samp{x31}, and @samp{pc}. Either the architectural names (@samp{x0},
44394 @samp{x1}, etc) can be used, or the ABI names (@samp{zero}, @samp{ra},
44397 The @samp{org.gnu.gdb.riscv.fpu} feature is optional. If present, it
44398 should contain registers @samp{f0} through @samp{f31}, @samp{fflags},
44399 @samp{frm}, and @samp{fcsr}. As with the cpu feature, either the
44400 architectural register names, or the ABI names can be used.
44402 The @samp{org.gnu.gdb.riscv.virtual} feature is optional. If present,
44403 it should contain registers that are not backed by real registers on
44404 the target, but are instead virtual, where the register value is
44405 derived from other target state. In many ways these are like
44406 @value{GDBN}s pseudo-registers, except implemented by the target.
44407 Currently the only register expected in this set is the one byte
44408 @samp{priv} register that contains the target's privilege level in the
44409 least significant two bits.
44411 The @samp{org.gnu.gdb.riscv.csr} feature is optional. If present, it
44412 should contain all of the target's standard CSRs. Standard CSRs are
44413 those defined in the RISC-V specification documents. There is some
44414 overlap between this feature and the fpu feature; the @samp{fflags},
44415 @samp{frm}, and @samp{fcsr} registers could be in either feature. The
44416 expectation is that these registers will be in the fpu feature if the
44417 target has floating point hardware, but can be moved into the csr
44418 feature if the target has the floating point control registers, but no
44419 other floating point hardware.
44421 @node S/390 and System z Features
44422 @subsection S/390 and System z Features
44423 @cindex target descriptions, S/390 features
44424 @cindex target descriptions, System z features
44426 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
44427 System z targets. It should contain the PSW and the 16 general
44428 registers. In particular, System z targets should provide the 64-bit
44429 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
44430 S/390 targets should provide the 32-bit versions of these registers.
44431 A System z target that runs in 31-bit addressing mode should provide
44432 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
44433 register's upper halves @samp{r0h} through @samp{r15h}, and their
44434 lower halves @samp{r0l} through @samp{r15l}.
44436 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
44437 contain the 64-bit registers @samp{f0} through @samp{f15}, and
44440 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
44441 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
44443 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
44444 contain the register @samp{orig_r2}, which is 64-bit wide on System z
44445 targets and 32-bit otherwise. In addition, the feature may contain
44446 the @samp{last_break} register, whose width depends on the addressing
44447 mode, as well as the @samp{system_call} register, which is always
44450 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
44451 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
44452 @samp{atia}, and @samp{tr0} through @samp{tr15}.
44454 The @samp{org.gnu.gdb.s390.vx} feature is optional. It should contain
44455 64-bit wide registers @samp{v0l} through @samp{v15l}, which will be
44456 combined by @value{GDBN} with the floating point registers @samp{f0}
44457 through @samp{f15} to present the 128-bit wide vector registers
44458 @samp{v0} through @samp{v15}. In addition, this feature should
44459 contain the 128-bit wide vector registers @samp{v16} through
44462 The @samp{org.gnu.gdb.s390.gs} feature is optional. It should contain
44463 the 64-bit wide guarded-storage-control registers @samp{gsd},
44464 @samp{gssm}, and @samp{gsepla}.
44466 The @samp{org.gnu.gdb.s390.gsbc} feature is optional. It should contain
44467 the 64-bit wide guarded-storage broadcast control registers
44468 @samp{bc_gsd}, @samp{bc_gssm}, and @samp{bc_gsepla}.
44470 @node Sparc Features
44471 @subsection Sparc Features
44472 @cindex target descriptions, sparc32 features
44473 @cindex target descriptions, sparc64 features
44474 The @samp{org.gnu.gdb.sparc.cpu} feature is required for sparc32/sparc64
44475 targets. It should describe the following registers:
44479 @samp{g0} through @samp{g7}
44481 @samp{o0} through @samp{o7}
44483 @samp{l0} through @samp{l7}
44485 @samp{i0} through @samp{i7}
44488 They may be 32-bit or 64-bit depending on the target.
44490 Also the @samp{org.gnu.gdb.sparc.fpu} feature is required for sparc32/sparc64
44491 targets. It should describe the following registers:
44495 @samp{f0} through @samp{f31}
44497 @samp{f32} through @samp{f62} for sparc64
44500 The @samp{org.gnu.gdb.sparc.cp0} feature is required for sparc32/sparc64
44501 targets. It should describe the following registers:
44505 @samp{y}, @samp{psr}, @samp{wim}, @samp{tbr}, @samp{pc}, @samp{npc},
44506 @samp{fsr}, and @samp{csr} for sparc32
44508 @samp{pc}, @samp{npc}, @samp{state}, @samp{fsr}, @samp{fprs}, and @samp{y}
44512 @node TIC6x Features
44513 @subsection TMS320C6x Features
44514 @cindex target descriptions, TIC6x features
44515 @cindex target descriptions, TMS320C6x features
44516 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
44517 targets. It should contain registers @samp{A0} through @samp{A15},
44518 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
44520 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
44521 contain registers @samp{A16} through @samp{A31} and @samp{B16}
44522 through @samp{B31}.
44524 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
44525 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
44527 @node Operating System Information
44528 @appendix Operating System Information
44529 @cindex operating system information
44535 Users of @value{GDBN} often wish to obtain information about the state of
44536 the operating system running on the target---for example the list of
44537 processes, or the list of open files. This section describes the
44538 mechanism that makes it possible. This mechanism is similar to the
44539 target features mechanism (@pxref{Target Descriptions}), but focuses
44540 on a different aspect of target.
44542 Operating system information is retrived from the target via the
44543 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
44544 read}). The object name in the request should be @samp{osdata}, and
44545 the @var{annex} identifies the data to be fetched.
44548 @appendixsection Process list
44549 @cindex operating system information, process list
44551 When requesting the process list, the @var{annex} field in the
44552 @samp{qXfer} request should be @samp{processes}. The returned data is
44553 an XML document. The formal syntax of this document is defined in
44554 @file{gdb/features/osdata.dtd}.
44556 An example document is:
44559 <?xml version="1.0"?>
44560 <!DOCTYPE target SYSTEM "osdata.dtd">
44561 <osdata type="processes">
44563 <column name="pid">1</column>
44564 <column name="user">root</column>
44565 <column name="command">/sbin/init</column>
44566 <column name="cores">1,2,3</column>
44571 Each item should include a column whose name is @samp{pid}. The value
44572 of that column should identify the process on the target. The
44573 @samp{user} and @samp{command} columns are optional, and will be
44574 displayed by @value{GDBN}. The @samp{cores} column, if present,
44575 should contain a comma-separated list of cores that this process
44576 is running on. Target may provide additional columns,
44577 which @value{GDBN} currently ignores.
44579 @node Trace File Format
44580 @appendix Trace File Format
44581 @cindex trace file format
44583 The trace file comes in three parts: a header, a textual description
44584 section, and a trace frame section with binary data.
44586 The header has the form @code{\x7fTRACE0\n}. The first byte is
44587 @code{0x7f} so as to indicate that the file contains binary data,
44588 while the @code{0} is a version number that may have different values
44591 The description section consists of multiple lines of @sc{ascii} text
44592 separated by newline characters (@code{0xa}). The lines may include a
44593 variety of optional descriptive or context-setting information, such
44594 as tracepoint definitions or register set size. @value{GDBN} will
44595 ignore any line that it does not recognize. An empty line marks the end
44600 Specifies the size of a register block in bytes. This is equal to the
44601 size of a @code{g} packet payload in the remote protocol. @var{size}
44602 is an ascii decimal number. There should be only one such line in
44603 a single trace file.
44605 @item status @var{status}
44606 Trace status. @var{status} has the same format as a @code{qTStatus}
44607 remote packet reply. There should be only one such line in a single trace
44610 @item tp @var{payload}
44611 Tracepoint definition. The @var{payload} has the same format as
44612 @code{qTfP}/@code{qTsP} remote packet reply payload. A single tracepoint
44613 may take multiple lines of definition, corresponding to the multiple
44616 @item tsv @var{payload}
44617 Trace state variable definition. The @var{payload} has the same format as
44618 @code{qTfV}/@code{qTsV} remote packet reply payload. A single variable
44619 may take multiple lines of definition, corresponding to the multiple
44622 @item tdesc @var{payload}
44623 Target description in XML format. The @var{payload} is a single line of
44624 the XML file. All such lines should be concatenated together to get
44625 the original XML file. This file is in the same format as @code{qXfer}
44626 @code{features} payload, and corresponds to the main @code{target.xml}
44627 file. Includes are not allowed.
44631 The trace frame section consists of a number of consecutive frames.
44632 Each frame begins with a two-byte tracepoint number, followed by a
44633 four-byte size giving the amount of data in the frame. The data in
44634 the frame consists of a number of blocks, each introduced by a
44635 character indicating its type (at least register, memory, and trace
44636 state variable). The data in this section is raw binary, not a
44637 hexadecimal or other encoding; its endianness matches the target's
44640 @c FIXME bi-arch may require endianness/arch info in description section
44643 @item R @var{bytes}
44644 Register block. The number and ordering of bytes matches that of a
44645 @code{g} packet in the remote protocol. Note that these are the
44646 actual bytes, in target order, not a hexadecimal encoding.
44648 @item M @var{address} @var{length} @var{bytes}...
44649 Memory block. This is a contiguous block of memory, at the 8-byte
44650 address @var{address}, with a 2-byte length @var{length}, followed by
44651 @var{length} bytes.
44653 @item V @var{number} @var{value}
44654 Trace state variable block. This records the 8-byte signed value
44655 @var{value} of trace state variable numbered @var{number}.
44659 Future enhancements of the trace file format may include additional types
44662 @node Index Section Format
44663 @appendix @code{.gdb_index} section format
44664 @cindex .gdb_index section format
44665 @cindex index section format
44667 This section documents the index section that is created by @code{save
44668 gdb-index} (@pxref{Index Files}). The index section is
44669 DWARF-specific; some knowledge of DWARF is assumed in this
44672 The mapped index file format is designed to be directly
44673 @code{mmap}able on any architecture. In most cases, a datum is
44674 represented using a little-endian 32-bit integer value, called an
44675 @code{offset_type}. Big endian machines must byte-swap the values
44676 before using them. Exceptions to this rule are noted. The data is
44677 laid out such that alignment is always respected.
44679 A mapped index consists of several areas, laid out in order.
44683 The file header. This is a sequence of values, of @code{offset_type}
44684 unless otherwise noted:
44688 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
44689 Version 4 uses a different hashing function from versions 5 and 6.
44690 Version 6 includes symbols for inlined functions, whereas versions 4
44691 and 5 do not. Version 7 adds attributes to the CU indices in the
44692 symbol table. Version 8 specifies that symbols from DWARF type units
44693 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
44694 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
44696 @value{GDBN} will only read version 4, 5, or 6 indices
44697 by specifying @code{set use-deprecated-index-sections on}.
44698 GDB has a workaround for potentially broken version 7 indices so it is
44699 currently not flagged as deprecated.
44702 The offset, from the start of the file, of the CU list.
44705 The offset, from the start of the file, of the types CU list. Note
44706 that this area can be empty, in which case this offset will be equal
44707 to the next offset.
44710 The offset, from the start of the file, of the address area.
44713 The offset, from the start of the file, of the symbol table.
44716 The offset, from the start of the file, of the constant pool.
44720 The CU list. This is a sequence of pairs of 64-bit little-endian
44721 values, sorted by the CU offset. The first element in each pair is
44722 the offset of a CU in the @code{.debug_info} section. The second
44723 element in each pair is the length of that CU. References to a CU
44724 elsewhere in the map are done using a CU index, which is just the
44725 0-based index into this table. Note that if there are type CUs, then
44726 conceptually CUs and type CUs form a single list for the purposes of
44730 The types CU list. This is a sequence of triplets of 64-bit
44731 little-endian values. In a triplet, the first value is the CU offset,
44732 the second value is the type offset in the CU, and the third value is
44733 the type signature. The types CU list is not sorted.
44736 The address area. The address area consists of a sequence of address
44737 entries. Each address entry has three elements:
44741 The low address. This is a 64-bit little-endian value.
44744 The high address. This is a 64-bit little-endian value. Like
44745 @code{DW_AT_high_pc}, the value is one byte beyond the end.
44748 The CU index. This is an @code{offset_type} value.
44752 The symbol table. This is an open-addressed hash table. The size of
44753 the hash table is always a power of 2.
44755 Each slot in the hash table consists of a pair of @code{offset_type}
44756 values. The first value is the offset of the symbol's name in the
44757 constant pool. The second value is the offset of the CU vector in the
44760 If both values are 0, then this slot in the hash table is empty. This
44761 is ok because while 0 is a valid constant pool index, it cannot be a
44762 valid index for both a string and a CU vector.
44764 The hash value for a table entry is computed by applying an
44765 iterative hash function to the symbol's name. Starting with an
44766 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
44767 the string is incorporated into the hash using the formula depending on the
44772 The formula is @code{r = r * 67 + c - 113}.
44774 @item Versions 5 to 7
44775 The formula is @code{r = r * 67 + tolower (c) - 113}.
44778 The terminating @samp{\0} is not incorporated into the hash.
44780 The step size used in the hash table is computed via
44781 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
44782 value, and @samp{size} is the size of the hash table. The step size
44783 is used to find the next candidate slot when handling a hash
44786 The names of C@t{++} symbols in the hash table are canonicalized. We
44787 don't currently have a simple description of the canonicalization
44788 algorithm; if you intend to create new index sections, you must read
44792 The constant pool. This is simply a bunch of bytes. It is organized
44793 so that alignment is correct: CU vectors are stored first, followed by
44796 A CU vector in the constant pool is a sequence of @code{offset_type}
44797 values. The first value is the number of CU indices in the vector.
44798 Each subsequent value is the index and symbol attributes of a CU in
44799 the CU list. This element in the hash table is used to indicate which
44800 CUs define the symbol and how the symbol is used.
44801 See below for the format of each CU index+attributes entry.
44803 A string in the constant pool is zero-terminated.
44806 Attributes were added to CU index values in @code{.gdb_index} version 7.
44807 If a symbol has multiple uses within a CU then there is one
44808 CU index+attributes value for each use.
44810 The format of each CU index+attributes entry is as follows
44816 This is the index of the CU in the CU list.
44818 These bits are reserved for future purposes and must be zero.
44820 The kind of the symbol in the CU.
44824 This value is reserved and should not be used.
44825 By reserving zero the full @code{offset_type} value is backwards compatible
44826 with previous versions of the index.
44828 The symbol is a type.
44830 The symbol is a variable or an enum value.
44832 The symbol is a function.
44834 Any other kind of symbol.
44836 These values are reserved.
44840 This bit is zero if the value is global and one if it is static.
44842 The determination of whether a symbol is global or static is complicated.
44843 The authorative reference is the file @file{dwarf2read.c} in
44844 @value{GDBN} sources.
44848 This pseudo-code describes the computation of a symbol's kind and
44849 global/static attributes in the index.
44852 is_external = get_attribute (die, DW_AT_external);
44853 language = get_attribute (cu_die, DW_AT_language);
44856 case DW_TAG_typedef:
44857 case DW_TAG_base_type:
44858 case DW_TAG_subrange_type:
44862 case DW_TAG_enumerator:
44864 is_static = language != CPLUS;
44866 case DW_TAG_subprogram:
44868 is_static = ! (is_external || language == ADA);
44870 case DW_TAG_constant:
44872 is_static = ! is_external;
44874 case DW_TAG_variable:
44876 is_static = ! is_external;
44878 case DW_TAG_namespace:
44882 case DW_TAG_class_type:
44883 case DW_TAG_interface_type:
44884 case DW_TAG_structure_type:
44885 case DW_TAG_union_type:
44886 case DW_TAG_enumeration_type:
44888 is_static = language != CPLUS;
44896 @appendix Manual pages
44900 * gdb man:: The GNU Debugger man page
44901 * gdbserver man:: Remote Server for the GNU Debugger man page
44902 * gcore man:: Generate a core file of a running program
44903 * gdbinit man:: gdbinit scripts
44904 * gdb-add-index man:: Add index files to speed up GDB
44910 @c man title gdb The GNU Debugger
44912 @c man begin SYNOPSIS gdb
44913 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
44914 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
44915 [@option{-b}@w{ }@var{bps}]
44916 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
44917 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
44918 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
44919 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
44920 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
44923 @c man begin DESCRIPTION gdb
44924 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
44925 going on ``inside'' another program while it executes -- or what another
44926 program was doing at the moment it crashed.
44928 @value{GDBN} can do four main kinds of things (plus other things in support of
44929 these) to help you catch bugs in the act:
44933 Start your program, specifying anything that might affect its behavior.
44936 Make your program stop on specified conditions.
44939 Examine what has happened, when your program has stopped.
44942 Change things in your program, so you can experiment with correcting the
44943 effects of one bug and go on to learn about another.
44946 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
44949 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
44950 commands from the terminal until you tell it to exit with the @value{GDBN}
44951 command @code{quit}. You can get online help from @value{GDBN} itself
44952 by using the command @code{help}.
44954 You can run @code{gdb} with no arguments or options; but the most
44955 usual way to start @value{GDBN} is with one argument or two, specifying an
44956 executable program as the argument:
44962 You can also start with both an executable program and a core file specified:
44968 You can, instead, specify a process ID as a second argument or use option
44969 @code{-p}, if you want to debug a running process:
44977 would attach @value{GDBN} to process @code{1234}. With option @option{-p} you
44978 can omit the @var{program} filename.
44980 Here are some of the most frequently needed @value{GDBN} commands:
44982 @c pod2man highlights the right hand side of the @item lines.
44984 @item break [@var{file}:]@var{function}
44985 Set a breakpoint at @var{function} (in @var{file}).
44987 @item run [@var{arglist}]
44988 Start your program (with @var{arglist}, if specified).
44991 Backtrace: display the program stack.
44993 @item print @var{expr}
44994 Display the value of an expression.
44997 Continue running your program (after stopping, e.g. at a breakpoint).
45000 Execute next program line (after stopping); step @emph{over} any
45001 function calls in the line.
45003 @item edit [@var{file}:]@var{function}
45004 look at the program line where it is presently stopped.
45006 @item list [@var{file}:]@var{function}
45007 type the text of the program in the vicinity of where it is presently stopped.
45010 Execute next program line (after stopping); step @emph{into} any
45011 function calls in the line.
45013 @item help [@var{name}]
45014 Show information about @value{GDBN} command @var{name}, or general information
45015 about using @value{GDBN}.
45018 Exit from @value{GDBN}.
45022 For full details on @value{GDBN},
45023 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
45024 by Richard M. Stallman and Roland H. Pesch. The same text is available online
45025 as the @code{gdb} entry in the @code{info} program.
45029 @c man begin OPTIONS gdb
45030 Any arguments other than options specify an executable
45031 file and core file (or process ID); that is, the first argument
45032 encountered with no
45033 associated option flag is equivalent to a @option{-se} option, and the second,
45034 if any, is equivalent to a @option{-c} option if it's the name of a file.
45036 both long and short forms; both are shown here. The long forms are also
45037 recognized if you truncate them, so long as enough of the option is
45038 present to be unambiguous. (If you prefer, you can flag option
45039 arguments with @option{+} rather than @option{-}, though we illustrate the
45040 more usual convention.)
45042 All the options and command line arguments you give are processed
45043 in sequential order. The order makes a difference when the @option{-x}
45049 List all options, with brief explanations.
45051 @item -symbols=@var{file}
45052 @itemx -s @var{file}
45053 Read symbol table from file @var{file}.
45056 Enable writing into executable and core files.
45058 @item -exec=@var{file}
45059 @itemx -e @var{file}
45060 Use file @var{file} as the executable file to execute when
45061 appropriate, and for examining pure data in conjunction with a core
45064 @item -se=@var{file}
45065 Read symbol table from file @var{file} and use it as the executable
45068 @item -core=@var{file}
45069 @itemx -c @var{file}
45070 Use file @var{file} as a core dump to examine.
45072 @item -command=@var{file}
45073 @itemx -x @var{file}
45074 Execute @value{GDBN} commands from file @var{file}.
45076 @item -ex @var{command}
45077 Execute given @value{GDBN} @var{command}.
45079 @item -directory=@var{directory}
45080 @itemx -d @var{directory}
45081 Add @var{directory} to the path to search for source files.
45084 Do not execute commands from @file{~/.gdbinit}.
45088 Do not execute commands from any @file{.gdbinit} initialization files.
45092 ``Quiet''. Do not print the introductory and copyright messages. These
45093 messages are also suppressed in batch mode.
45096 Run in batch mode. Exit with status @code{0} after processing all the command
45097 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
45098 Exit with nonzero status if an error occurs in executing the @value{GDBN}
45099 commands in the command files.
45101 Batch mode may be useful for running @value{GDBN} as a filter, for example to
45102 download and run a program on another computer; in order to make this
45103 more useful, the message
45106 Program exited normally.
45110 (which is ordinarily issued whenever a program running under @value{GDBN} control
45111 terminates) is not issued when running in batch mode.
45113 @item -cd=@var{directory}
45114 Run @value{GDBN} using @var{directory} as its working directory,
45115 instead of the current directory.
45119 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
45120 @value{GDBN} to output the full file name and line number in a standard,
45121 recognizable fashion each time a stack frame is displayed (which
45122 includes each time the program stops). This recognizable format looks
45123 like two @samp{\032} characters, followed by the file name, line number
45124 and character position separated by colons, and a newline. The
45125 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
45126 characters as a signal to display the source code for the frame.
45129 Set the line speed (baud rate or bits per second) of any serial
45130 interface used by @value{GDBN} for remote debugging.
45132 @item -tty=@var{device}
45133 Run using @var{device} for your program's standard input and output.
45137 @c man begin SEEALSO gdb
45139 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
45140 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
45141 documentation are properly installed at your site, the command
45148 should give you access to the complete manual.
45150 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
45151 Richard M. Stallman and Roland H. Pesch, July 1991.
45155 @node gdbserver man
45156 @heading gdbserver man
45158 @c man title gdbserver Remote Server for the GNU Debugger
45160 @c man begin SYNOPSIS gdbserver
45161 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
45163 gdbserver --attach @var{comm} @var{pid}
45165 gdbserver --multi @var{comm}
45169 @c man begin DESCRIPTION gdbserver
45170 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
45171 than the one which is running the program being debugged.
45174 @subheading Usage (server (target) side)
45177 Usage (server (target) side):
45180 First, you need to have a copy of the program you want to debug put onto
45181 the target system. The program can be stripped to save space if needed, as
45182 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
45183 the @value{GDBN} running on the host system.
45185 To use the server, you log on to the target system, and run the @command{gdbserver}
45186 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
45187 your program, and (c) its arguments. The general syntax is:
45190 target> gdbserver @var{comm} @var{program} [@var{args} ...]
45193 For example, using a serial port, you might say:
45197 @c @file would wrap it as F</dev/com1>.
45198 target> gdbserver /dev/com1 emacs foo.txt
45201 target> gdbserver @file{/dev/com1} emacs foo.txt
45205 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
45206 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
45207 waits patiently for the host @value{GDBN} to communicate with it.
45209 To use a TCP connection, you could say:
45212 target> gdbserver host:2345 emacs foo.txt
45215 This says pretty much the same thing as the last example, except that we are
45216 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
45217 that we are expecting to see a TCP connection from @code{host} to local TCP port
45218 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
45219 want for the port number as long as it does not conflict with any existing TCP
45220 ports on the target system. This same port number must be used in the host
45221 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
45222 you chose a port number that conflicts with another service, @command{gdbserver} will
45223 print an error message and exit.
45225 @command{gdbserver} can also attach to running programs.
45226 This is accomplished via the @option{--attach} argument. The syntax is:
45229 target> gdbserver --attach @var{comm} @var{pid}
45232 @var{pid} is the process ID of a currently running process. It isn't
45233 necessary to point @command{gdbserver} at a binary for the running process.
45235 To start @code{gdbserver} without supplying an initial command to run
45236 or process ID to attach, use the @option{--multi} command line option.
45237 In such case you should connect using @kbd{target extended-remote} to start
45238 the program you want to debug.
45241 target> gdbserver --multi @var{comm}
45245 @subheading Usage (host side)
45251 You need an unstripped copy of the target program on your host system, since
45252 @value{GDBN} needs to examine its symbol tables and such. Start up @value{GDBN} as you normally
45253 would, with the target program as the first argument. (You may need to use the
45254 @option{--baud} option if the serial line is running at anything except 9600 baud.)
45255 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
45256 new command you need to know about is @code{target remote}
45257 (or @code{target extended-remote}). Its argument is either
45258 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
45259 descriptor. For example:
45263 @c @file would wrap it as F</dev/ttyb>.
45264 (gdb) target remote /dev/ttyb
45267 (gdb) target remote @file{/dev/ttyb}
45272 communicates with the server via serial line @file{/dev/ttyb}, and:
45275 (gdb) target remote the-target:2345
45279 communicates via a TCP connection to port 2345 on host `the-target', where
45280 you previously started up @command{gdbserver} with the same port number. Note that for
45281 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
45282 command, otherwise you may get an error that looks something like
45283 `Connection refused'.
45285 @command{gdbserver} can also debug multiple inferiors at once,
45288 the @value{GDBN} manual in node @code{Inferiors and Programs}
45289 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
45292 @ref{Inferiors and Programs}.
45294 In such case use the @code{extended-remote} @value{GDBN} command variant:
45297 (gdb) target extended-remote the-target:2345
45300 The @command{gdbserver} option @option{--multi} may or may not be used in such
45304 @c man begin OPTIONS gdbserver
45305 There are three different modes for invoking @command{gdbserver}:
45310 Debug a specific program specified by its program name:
45313 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
45316 The @var{comm} parameter specifies how should the server communicate
45317 with @value{GDBN}; it is either a device name (to use a serial line),
45318 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
45319 stdin/stdout of @code{gdbserver}. Specify the name of the program to
45320 debug in @var{prog}. Any remaining arguments will be passed to the
45321 program verbatim. When the program exits, @value{GDBN} will close the
45322 connection, and @code{gdbserver} will exit.
45325 Debug a specific program by specifying the process ID of a running
45329 gdbserver --attach @var{comm} @var{pid}
45332 The @var{comm} parameter is as described above. Supply the process ID
45333 of a running program in @var{pid}; @value{GDBN} will do everything
45334 else. Like with the previous mode, when the process @var{pid} exits,
45335 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
45338 Multi-process mode -- debug more than one program/process:
45341 gdbserver --multi @var{comm}
45344 In this mode, @value{GDBN} can instruct @command{gdbserver} which
45345 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
45346 close the connection when a process being debugged exits, so you can
45347 debug several processes in the same session.
45350 In each of the modes you may specify these options:
45355 List all options, with brief explanations.
45358 This option causes @command{gdbserver} to print its version number and exit.
45361 @command{gdbserver} will attach to a running program. The syntax is:
45364 target> gdbserver --attach @var{comm} @var{pid}
45367 @var{pid} is the process ID of a currently running process. It isn't
45368 necessary to point @command{gdbserver} at a binary for the running process.
45371 To start @code{gdbserver} without supplying an initial command to run
45372 or process ID to attach, use this command line option.
45373 Then you can connect using @kbd{target extended-remote} and start
45374 the program you want to debug. The syntax is:
45377 target> gdbserver --multi @var{comm}
45381 Instruct @code{gdbserver} to display extra status information about the debugging
45383 This option is intended for @code{gdbserver} development and for bug reports to
45386 @item --remote-debug
45387 Instruct @code{gdbserver} to display remote protocol debug output.
45388 This option is intended for @code{gdbserver} development and for bug reports to
45391 @item --debug-file=@var{filename}
45392 Instruct @code{gdbserver} to send any debug output to the given @var{filename}.
45393 This option is intended for @code{gdbserver} development and for bug reports to
45396 @item --debug-format=option1@r{[},option2,...@r{]}
45397 Instruct @code{gdbserver} to include extra information in each line
45398 of debugging output.
45399 @xref{Other Command-Line Arguments for gdbserver}.
45402 Specify a wrapper to launch programs
45403 for debugging. The option should be followed by the name of the
45404 wrapper, then any command-line arguments to pass to the wrapper, then
45405 @kbd{--} indicating the end of the wrapper arguments.
45408 By default, @command{gdbserver} keeps the listening TCP port open, so that
45409 additional connections are possible. However, if you start @code{gdbserver}
45410 with the @option{--once} option, it will stop listening for any further
45411 connection attempts after connecting to the first @value{GDBN} session.
45413 @c --disable-packet is not documented for users.
45415 @c --disable-randomization and --no-disable-randomization are superseded by
45416 @c QDisableRandomization.
45421 @c man begin SEEALSO gdbserver
45423 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
45424 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
45425 documentation are properly installed at your site, the command
45431 should give you access to the complete manual.
45433 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
45434 Richard M. Stallman and Roland H. Pesch, July 1991.
45441 @c man title gcore Generate a core file of a running program
45444 @c man begin SYNOPSIS gcore
45445 gcore [-a] [-o @var{prefix}] @var{pid1} [@var{pid2}...@var{pidN}]
45449 @c man begin DESCRIPTION gcore
45450 Generate core dumps of one or more running programs with process IDs
45451 @var{pid1}, @var{pid2}, etc. A core file produced by @command{gcore}
45452 is equivalent to one produced by the kernel when the process crashes
45453 (and when @kbd{ulimit -c} was used to set up an appropriate core dump
45454 limit). However, unlike after a crash, after @command{gcore} finishes
45455 its job the program remains running without any change.
45458 @c man begin OPTIONS gcore
45461 Dump all memory mappings. The actual effect of this option depends on
45462 the Operating System. On @sc{gnu}/Linux, it will disable
45463 @code{use-coredump-filter} (@pxref{set use-coredump-filter}) and
45464 enable @code{dump-excluded-mappings} (@pxref{set
45465 dump-excluded-mappings}).
45467 @item -o @var{prefix}
45468 The optional argument @var{prefix} specifies the prefix to be used
45469 when composing the file names of the core dumps. The file name is
45470 composed as @file{@var{prefix}.@var{pid}}, where @var{pid} is the
45471 process ID of the running program being analyzed by @command{gcore}.
45472 If not specified, @var{prefix} defaults to @var{gcore}.
45476 @c man begin SEEALSO gcore
45478 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
45479 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
45480 documentation are properly installed at your site, the command
45487 should give you access to the complete manual.
45489 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
45490 Richard M. Stallman and Roland H. Pesch, July 1991.
45497 @c man title gdbinit GDB initialization scripts
45500 @c man begin SYNOPSIS gdbinit
45501 @ifset SYSTEM_GDBINIT
45502 @value{SYSTEM_GDBINIT}
45511 @c man begin DESCRIPTION gdbinit
45512 These files contain @value{GDBN} commands to automatically execute during
45513 @value{GDBN} startup. The lines of contents are canned sequences of commands,
45516 the @value{GDBN} manual in node @code{Sequences}
45517 -- shell command @code{info -f gdb -n Sequences}.
45523 Please read more in
45525 the @value{GDBN} manual in node @code{Startup}
45526 -- shell command @code{info -f gdb -n Startup}.
45533 @ifset SYSTEM_GDBINIT
45534 @item @value{SYSTEM_GDBINIT}
45536 @ifclear SYSTEM_GDBINIT
45537 @item (not enabled with @code{--with-system-gdbinit} during compilation)
45539 System-wide initialization file. It is executed unless user specified
45540 @value{GDBN} option @code{-nx} or @code{-n}.
45543 the @value{GDBN} manual in node @code{System-wide configuration}
45544 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
45547 @ref{System-wide configuration}.
45551 User initialization file. It is executed unless user specified
45552 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
45555 Initialization file for current directory. It may need to be enabled with
45556 @value{GDBN} security command @code{set auto-load local-gdbinit}.
45559 the @value{GDBN} manual in node @code{Init File in the Current Directory}
45560 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
45563 @ref{Init File in the Current Directory}.
45568 @c man begin SEEALSO gdbinit
45570 gdb(1), @code{info -f gdb -n Startup}
45572 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
45573 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
45574 documentation are properly installed at your site, the command
45580 should give you access to the complete manual.
45582 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
45583 Richard M. Stallman and Roland H. Pesch, July 1991.
45587 @node gdb-add-index man
45588 @heading gdb-add-index
45589 @pindex gdb-add-index
45590 @anchor{gdb-add-index}
45592 @c man title gdb-add-index Add index files to speed up GDB
45594 @c man begin SYNOPSIS gdb-add-index
45595 gdb-add-index @var{filename}
45598 @c man begin DESCRIPTION gdb-add-index
45599 When @value{GDBN} finds a symbol file, it scans the symbols in the
45600 file in order to construct an internal symbol table. This lets most
45601 @value{GDBN} operations work quickly--at the cost of a delay early on.
45602 For large programs, this delay can be quite lengthy, so @value{GDBN}
45603 provides a way to build an index, which speeds up startup.
45605 To determine whether a file contains such an index, use the command
45606 @kbd{readelf -S filename}: the index is stored in a section named
45607 @code{.gdb_index}. The index file can only be produced on systems
45608 which use ELF binaries and DWARF debug information (i.e., sections
45609 named @code{.debug_*}).
45611 @command{gdb-add-index} uses @value{GDBN} and @command{objdump} found
45612 in the @env{PATH} environment variable. If you want to use different
45613 versions of these programs, you can specify them through the
45614 @env{GDB} and @env{OBJDUMP} environment variables.
45618 the @value{GDBN} manual in node @code{Index Files}
45619 -- shell command @kbd{info -f gdb -n "Index Files"}.
45626 @c man begin SEEALSO gdb-add-index
45628 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
45629 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
45630 documentation are properly installed at your site, the command
45636 should give you access to the complete manual.
45638 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
45639 Richard M. Stallman and Roland H. Pesch, July 1991.
45645 @node GNU Free Documentation License
45646 @appendix GNU Free Documentation License
45649 @node Concept Index
45650 @unnumbered Concept Index
45654 @node Command and Variable Index
45655 @unnumbered Command, Variable, and Function Index
45660 % I think something like @@colophon should be in texinfo. In the
45662 \long\def\colophon{\hbox to0pt{}\vfill
45663 \centerline{The body of this manual is set in}
45664 \centerline{\fontname\tenrm,}
45665 \centerline{with headings in {\bf\fontname\tenbf}}
45666 \centerline{and examples in {\tt\fontname\tentt}.}
45667 \centerline{{\it\fontname\tenit\/},}
45668 \centerline{{\bf\fontname\tenbf}, and}
45669 \centerline{{\sl\fontname\tensl\/}}
45670 \centerline{are used for emphasis.}\vfill}
45672 % Blame: doc@@cygnus.com, 1991.