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 @vindex $_ada_exception@r{, convenience variable}
4792 The convenience variable @code{$_ada_exception} holds the address of
4793 the exception being thrown. This can be useful when setting a
4794 condition for such a catchpoint.
4796 @item exception unhandled
4797 @kindex catch exception unhandled
4798 An exception that was raised but is not handled by the program. The
4799 convenience variable @code{$_ada_exception} is set as for @code{catch
4802 @item handlers @r{[}@var{name}@r{]}
4803 @kindex catch handlers
4804 @cindex Ada exception handlers catching
4805 @cindex catch Ada exceptions when handled
4806 An Ada exception being handled. If an exception name is
4807 specified at the end of the command
4808 (eg @kbd{catch handlers Program_Error}), the debugger will stop
4809 only when this specific exception is handled.
4810 Otherwise, the debugger stops execution when any Ada exception is handled.
4812 When inserting a handlers catchpoint on a user-defined
4813 exception whose name is identical to one of the exceptions
4814 defined by the language, the fully qualified name must be used
4815 as the exception name. Otherwise, @value{GDBN} will assume that it
4816 should stop on the pre-defined exception rather than the
4817 user-defined one. For instance, assuming an exception called
4818 @code{Constraint_Error} is defined in package @code{Pck}, then the
4819 command to use to catch such exceptions handling is
4820 @kbd{catch handlers Pck.Constraint_Error}.
4822 The convenience variable @code{$_ada_exception} is set as for
4823 @code{catch exception}.
4826 @kindex catch assert
4827 A failed Ada assertion. Note that the convenience variable
4828 @code{$_ada_exception} is @emph{not} set by this catchpoint.
4832 @cindex break on fork/exec
4833 A call to @code{exec}.
4835 @anchor{catch syscall}
4837 @itemx syscall @r{[}@var{name} @r{|} @var{number} @r{|} @r{group:}@var{groupname} @r{|} @r{g:}@var{groupname}@r{]} @dots{}
4838 @kindex catch syscall
4839 @cindex break on a system call.
4840 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4841 syscall is a mechanism for application programs to request a service
4842 from the operating system (OS) or one of the OS system services.
4843 @value{GDBN} can catch some or all of the syscalls issued by the
4844 debuggee, and show the related information for each syscall. If no
4845 argument is specified, calls to and returns from all system calls
4848 @var{name} can be any system call name that is valid for the
4849 underlying OS. Just what syscalls are valid depends on the OS. On
4850 GNU and Unix systems, you can find the full list of valid syscall
4851 names on @file{/usr/include/asm/unistd.h}.
4853 @c For MS-Windows, the syscall names and the corresponding numbers
4854 @c can be found, e.g., on this URL:
4855 @c http://www.metasploit.com/users/opcode/syscalls.html
4856 @c but we don't support Windows syscalls yet.
4858 Normally, @value{GDBN} knows in advance which syscalls are valid for
4859 each OS, so you can use the @value{GDBN} command-line completion
4860 facilities (@pxref{Completion,, command completion}) to list the
4863 You may also specify the system call numerically. A syscall's
4864 number is the value passed to the OS's syscall dispatcher to
4865 identify the requested service. When you specify the syscall by its
4866 name, @value{GDBN} uses its database of syscalls to convert the name
4867 into the corresponding numeric code, but using the number directly
4868 may be useful if @value{GDBN}'s database does not have the complete
4869 list of syscalls on your system (e.g., because @value{GDBN} lags
4870 behind the OS upgrades).
4872 You may specify a group of related syscalls to be caught at once using
4873 the @code{group:} syntax (@code{g:} is a shorter equivalent). For
4874 instance, on some platforms @value{GDBN} allows you to catch all
4875 network related syscalls, by passing the argument @code{group:network}
4876 to @code{catch syscall}. Note that not all syscall groups are
4877 available in every system. You can use the command completion
4878 facilities (@pxref{Completion,, command completion}) to list the
4879 syscall groups available on your environment.
4881 The example below illustrates how this command works if you don't provide
4885 (@value{GDBP}) catch syscall
4886 Catchpoint 1 (syscall)
4888 Starting program: /tmp/catch-syscall
4890 Catchpoint 1 (call to syscall 'close'), \
4891 0xffffe424 in __kernel_vsyscall ()
4895 Catchpoint 1 (returned from syscall 'close'), \
4896 0xffffe424 in __kernel_vsyscall ()
4900 Here is an example of catching a system call by name:
4903 (@value{GDBP}) catch syscall chroot
4904 Catchpoint 1 (syscall 'chroot' [61])
4906 Starting program: /tmp/catch-syscall
4908 Catchpoint 1 (call to syscall 'chroot'), \
4909 0xffffe424 in __kernel_vsyscall ()
4913 Catchpoint 1 (returned from syscall 'chroot'), \
4914 0xffffe424 in __kernel_vsyscall ()
4918 An example of specifying a system call numerically. In the case
4919 below, the syscall number has a corresponding entry in the XML
4920 file, so @value{GDBN} finds its name and prints it:
4923 (@value{GDBP}) catch syscall 252
4924 Catchpoint 1 (syscall(s) 'exit_group')
4926 Starting program: /tmp/catch-syscall
4928 Catchpoint 1 (call to syscall 'exit_group'), \
4929 0xffffe424 in __kernel_vsyscall ()
4933 Program exited normally.
4937 Here is an example of catching a syscall group:
4940 (@value{GDBP}) catch syscall group:process
4941 Catchpoint 1 (syscalls 'exit' [1] 'fork' [2] 'waitpid' [7]
4942 'execve' [11] 'wait4' [114] 'clone' [120] 'vfork' [190]
4943 'exit_group' [252] 'waitid' [284] 'unshare' [310])
4945 Starting program: /tmp/catch-syscall
4947 Catchpoint 1 (call to syscall fork), 0x00007ffff7df4e27 in open64 ()
4948 from /lib64/ld-linux-x86-64.so.2
4954 However, there can be situations when there is no corresponding name
4955 in XML file for that syscall number. In this case, @value{GDBN} prints
4956 a warning message saying that it was not able to find the syscall name,
4957 but the catchpoint will be set anyway. See the example below:
4960 (@value{GDBP}) catch syscall 764
4961 warning: The number '764' does not represent a known syscall.
4962 Catchpoint 2 (syscall 764)
4966 If you configure @value{GDBN} using the @samp{--without-expat} option,
4967 it will not be able to display syscall names. Also, if your
4968 architecture does not have an XML file describing its system calls,
4969 you will not be able to see the syscall names. It is important to
4970 notice that these two features are used for accessing the syscall
4971 name database. In either case, you will see a warning like this:
4974 (@value{GDBP}) catch syscall
4975 warning: Could not open "syscalls/i386-linux.xml"
4976 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4977 GDB will not be able to display syscall names.
4978 Catchpoint 1 (syscall)
4982 Of course, the file name will change depending on your architecture and system.
4984 Still using the example above, you can also try to catch a syscall by its
4985 number. In this case, you would see something like:
4988 (@value{GDBP}) catch syscall 252
4989 Catchpoint 1 (syscall(s) 252)
4992 Again, in this case @value{GDBN} would not be able to display syscall's names.
4996 A call to @code{fork}.
5000 A call to @code{vfork}.
5002 @item load @r{[}@var{regexp}@r{]}
5003 @itemx unload @r{[}@var{regexp}@r{]}
5005 @kindex catch unload
5006 The loading or unloading of a shared library. If @var{regexp} is
5007 given, then the catchpoint will stop only if the regular expression
5008 matches one of the affected libraries.
5010 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5011 @kindex catch signal
5012 The delivery of a signal.
5014 With no arguments, this catchpoint will catch any signal that is not
5015 used internally by @value{GDBN}, specifically, all signals except
5016 @samp{SIGTRAP} and @samp{SIGINT}.
5018 With the argument @samp{all}, all signals, including those used by
5019 @value{GDBN}, will be caught. This argument cannot be used with other
5022 Otherwise, the arguments are a list of signal names as given to
5023 @code{handle} (@pxref{Signals}). Only signals specified in this list
5026 One reason that @code{catch signal} can be more useful than
5027 @code{handle} is that you can attach commands and conditions to the
5030 When a signal is caught by a catchpoint, the signal's @code{stop} and
5031 @code{print} settings, as specified by @code{handle}, are ignored.
5032 However, whether the signal is still delivered to the inferior depends
5033 on the @code{pass} setting; this can be changed in the catchpoint's
5038 @item tcatch @var{event}
5040 Set a catchpoint that is enabled only for one stop. The catchpoint is
5041 automatically deleted after the first time the event is caught.
5045 Use the @code{info break} command to list the current catchpoints.
5049 @subsection Deleting Breakpoints
5051 @cindex clearing breakpoints, watchpoints, catchpoints
5052 @cindex deleting breakpoints, watchpoints, catchpoints
5053 It is often necessary to eliminate a breakpoint, watchpoint, or
5054 catchpoint once it has done its job and you no longer want your program
5055 to stop there. This is called @dfn{deleting} the breakpoint. A
5056 breakpoint that has been deleted no longer exists; it is forgotten.
5058 With the @code{clear} command you can delete breakpoints according to
5059 where they are in your program. With the @code{delete} command you can
5060 delete individual breakpoints, watchpoints, or catchpoints by specifying
5061 their breakpoint numbers.
5063 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
5064 automatically ignores breakpoints on the first instruction to be executed
5065 when you continue execution without changing the execution address.
5070 Delete any breakpoints at the next instruction to be executed in the
5071 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
5072 the innermost frame is selected, this is a good way to delete a
5073 breakpoint where your program just stopped.
5075 @item clear @var{location}
5076 Delete any breakpoints set at the specified @var{location}.
5077 @xref{Specify Location}, for the various forms of @var{location}; the
5078 most useful ones are listed below:
5081 @item clear @var{function}
5082 @itemx clear @var{filename}:@var{function}
5083 Delete any breakpoints set at entry to the named @var{function}.
5085 @item clear @var{linenum}
5086 @itemx clear @var{filename}:@var{linenum}
5087 Delete any breakpoints set at or within the code of the specified
5088 @var{linenum} of the specified @var{filename}.
5091 @cindex delete breakpoints
5093 @kindex d @r{(@code{delete})}
5094 @item delete @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
5095 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
5096 list specified as argument. If no argument is specified, delete all
5097 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
5098 confirm off}). You can abbreviate this command as @code{d}.
5102 @subsection Disabling Breakpoints
5104 @cindex enable/disable a breakpoint
5105 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
5106 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
5107 it had been deleted, but remembers the information on the breakpoint so
5108 that you can @dfn{enable} it again later.
5110 You disable and enable breakpoints, watchpoints, and catchpoints with
5111 the @code{enable} and @code{disable} commands, optionally specifying
5112 one or more breakpoint numbers as arguments. Use @code{info break} to
5113 print a list of all breakpoints, watchpoints, and catchpoints if you
5114 do not know which numbers to use.
5116 Disabling and enabling a breakpoint that has multiple locations
5117 affects all of its locations.
5119 A breakpoint, watchpoint, or catchpoint can have any of several
5120 different states of enablement:
5124 Enabled. The breakpoint stops your program. A breakpoint set
5125 with the @code{break} command starts out in this state.
5127 Disabled. The breakpoint has no effect on your program.
5129 Enabled once. The breakpoint stops your program, but then becomes
5132 Enabled for a count. The breakpoint stops your program for the next
5133 N times, then becomes disabled.
5135 Enabled for deletion. The breakpoint stops your program, but
5136 immediately after it does so it is deleted permanently. A breakpoint
5137 set with the @code{tbreak} command starts out in this state.
5140 You can use the following commands to enable or disable breakpoints,
5141 watchpoints, and catchpoints:
5145 @kindex dis @r{(@code{disable})}
5146 @item disable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
5147 Disable the specified breakpoints---or all breakpoints, if none are
5148 listed. A disabled breakpoint has no effect but is not forgotten. All
5149 options such as ignore-counts, conditions and commands are remembered in
5150 case the breakpoint is enabled again later. You may abbreviate
5151 @code{disable} as @code{dis}.
5154 @item enable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
5155 Enable the specified breakpoints (or all defined breakpoints). They
5156 become effective once again in stopping your program.
5158 @item enable @r{[}breakpoints@r{]} once @var{list}@dots{}
5159 Enable the specified breakpoints temporarily. @value{GDBN} disables any
5160 of these breakpoints immediately after stopping your program.
5162 @item enable @r{[}breakpoints@r{]} count @var{count} @var{list}@dots{}
5163 Enable the specified breakpoints temporarily. @value{GDBN} records
5164 @var{count} with each of the specified breakpoints, and decrements a
5165 breakpoint's count when it is hit. When any count reaches 0,
5166 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
5167 count (@pxref{Conditions, ,Break Conditions}), that will be
5168 decremented to 0 before @var{count} is affected.
5170 @item enable @r{[}breakpoints@r{]} delete @var{list}@dots{}
5171 Enable the specified breakpoints to work once, then die. @value{GDBN}
5172 deletes any of these breakpoints as soon as your program stops there.
5173 Breakpoints set by the @code{tbreak} command start out in this state.
5176 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
5177 @c confusing: tbreak is also initially enabled.
5178 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
5179 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
5180 subsequently, they become disabled or enabled only when you use one of
5181 the commands above. (The command @code{until} can set and delete a
5182 breakpoint of its own, but it does not change the state of your other
5183 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
5187 @subsection Break Conditions
5188 @cindex conditional breakpoints
5189 @cindex breakpoint conditions
5191 @c FIXME what is scope of break condition expr? Context where wanted?
5192 @c in particular for a watchpoint?
5193 The simplest sort of breakpoint breaks every time your program reaches a
5194 specified place. You can also specify a @dfn{condition} for a
5195 breakpoint. A condition is just a Boolean expression in your
5196 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
5197 a condition evaluates the expression each time your program reaches it,
5198 and your program stops only if the condition is @emph{true}.
5200 This is the converse of using assertions for program validation; in that
5201 situation, you want to stop when the assertion is violated---that is,
5202 when the condition is false. In C, if you want to test an assertion expressed
5203 by the condition @var{assert}, you should set the condition
5204 @samp{! @var{assert}} on the appropriate breakpoint.
5206 Conditions are also accepted for watchpoints; you may not need them,
5207 since a watchpoint is inspecting the value of an expression anyhow---but
5208 it might be simpler, say, to just set a watchpoint on a variable name,
5209 and specify a condition that tests whether the new value is an interesting
5212 Break conditions can have side effects, and may even call functions in
5213 your program. This can be useful, for example, to activate functions
5214 that log program progress, or to use your own print functions to
5215 format special data structures. The effects are completely predictable
5216 unless there is another enabled breakpoint at the same address. (In
5217 that case, @value{GDBN} might see the other breakpoint first and stop your
5218 program without checking the condition of this one.) Note that
5219 breakpoint commands are usually more convenient and flexible than break
5221 purpose of performing side effects when a breakpoint is reached
5222 (@pxref{Break Commands, ,Breakpoint Command Lists}).
5224 Breakpoint conditions can also be evaluated on the target's side if
5225 the target supports it. Instead of evaluating the conditions locally,
5226 @value{GDBN} encodes the expression into an agent expression
5227 (@pxref{Agent Expressions}) suitable for execution on the target,
5228 independently of @value{GDBN}. Global variables become raw memory
5229 locations, locals become stack accesses, and so forth.
5231 In this case, @value{GDBN} will only be notified of a breakpoint trigger
5232 when its condition evaluates to true. This mechanism may provide faster
5233 response times depending on the performance characteristics of the target
5234 since it does not need to keep @value{GDBN} informed about
5235 every breakpoint trigger, even those with false conditions.
5237 Break conditions can be specified when a breakpoint is set, by using
5238 @samp{if} in the arguments to the @code{break} command. @xref{Set
5239 Breaks, ,Setting Breakpoints}. They can also be changed at any time
5240 with the @code{condition} command.
5242 You can also use the @code{if} keyword with the @code{watch} command.
5243 The @code{catch} command does not recognize the @code{if} keyword;
5244 @code{condition} is the only way to impose a further condition on a
5249 @item condition @var{bnum} @var{expression}
5250 Specify @var{expression} as the break condition for breakpoint,
5251 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
5252 breakpoint @var{bnum} stops your program only if the value of
5253 @var{expression} is true (nonzero, in C). When you use
5254 @code{condition}, @value{GDBN} checks @var{expression} immediately for
5255 syntactic correctness, and to determine whether symbols in it have
5256 referents in the context of your breakpoint. If @var{expression} uses
5257 symbols not referenced in the context of the breakpoint, @value{GDBN}
5258 prints an error message:
5261 No symbol "foo" in current context.
5266 not actually evaluate @var{expression} at the time the @code{condition}
5267 command (or a command that sets a breakpoint with a condition, like
5268 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
5270 @item condition @var{bnum}
5271 Remove the condition from breakpoint number @var{bnum}. It becomes
5272 an ordinary unconditional breakpoint.
5275 @cindex ignore count (of breakpoint)
5276 A special case of a breakpoint condition is to stop only when the
5277 breakpoint has been reached a certain number of times. This is so
5278 useful that there is a special way to do it, using the @dfn{ignore
5279 count} of the breakpoint. Every breakpoint has an ignore count, which
5280 is an integer. Most of the time, the ignore count is zero, and
5281 therefore has no effect. But if your program reaches a breakpoint whose
5282 ignore count is positive, then instead of stopping, it just decrements
5283 the ignore count by one and continues. As a result, if the ignore count
5284 value is @var{n}, the breakpoint does not stop the next @var{n} times
5285 your program reaches it.
5289 @item ignore @var{bnum} @var{count}
5290 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
5291 The next @var{count} times the breakpoint is reached, your program's
5292 execution does not stop; other than to decrement the ignore count, @value{GDBN}
5295 To make the breakpoint stop the next time it is reached, specify
5298 When you use @code{continue} to resume execution of your program from a
5299 breakpoint, you can specify an ignore count directly as an argument to
5300 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
5301 Stepping,,Continuing and Stepping}.
5303 If a breakpoint has a positive ignore count and a condition, the
5304 condition is not checked. Once the ignore count reaches zero,
5305 @value{GDBN} resumes checking the condition.
5307 You could achieve the effect of the ignore count with a condition such
5308 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
5309 is decremented each time. @xref{Convenience Vars, ,Convenience
5313 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
5316 @node Break Commands
5317 @subsection Breakpoint Command Lists
5319 @cindex breakpoint commands
5320 You can give any breakpoint (or watchpoint or catchpoint) a series of
5321 commands to execute when your program stops due to that breakpoint. For
5322 example, you might want to print the values of certain expressions, or
5323 enable other breakpoints.
5327 @kindex end@r{ (breakpoint commands)}
5328 @item commands @r{[}@var{list}@dots{}@r{]}
5329 @itemx @dots{} @var{command-list} @dots{}
5331 Specify a list of commands for the given breakpoints. The commands
5332 themselves appear on the following lines. Type a line containing just
5333 @code{end} to terminate the commands.
5335 To remove all commands from a breakpoint, type @code{commands} and
5336 follow it immediately with @code{end}; that is, give no commands.
5338 With no argument, @code{commands} refers to the last breakpoint,
5339 watchpoint, or catchpoint set (not to the breakpoint most recently
5340 encountered). If the most recent breakpoints were set with a single
5341 command, then the @code{commands} will apply to all the breakpoints
5342 set by that command. This applies to breakpoints set by
5343 @code{rbreak}, and also applies when a single @code{break} command
5344 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
5348 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
5349 disabled within a @var{command-list}.
5351 You can use breakpoint commands to start your program up again. Simply
5352 use the @code{continue} command, or @code{step}, or any other command
5353 that resumes execution.
5355 Any other commands in the command list, after a command that resumes
5356 execution, are ignored. This is because any time you resume execution
5357 (even with a simple @code{next} or @code{step}), you may encounter
5358 another breakpoint---which could have its own command list, leading to
5359 ambiguities about which list to execute.
5362 If the first command you specify in a command list is @code{silent}, the
5363 usual message about stopping at a breakpoint is not printed. This may
5364 be desirable for breakpoints that are to print a specific message and
5365 then continue. If none of the remaining commands print anything, you
5366 see no sign that the breakpoint was reached. @code{silent} is
5367 meaningful only at the beginning of a breakpoint command list.
5369 The commands @code{echo}, @code{output}, and @code{printf} allow you to
5370 print precisely controlled output, and are often useful in silent
5371 breakpoints. @xref{Output, ,Commands for Controlled Output}.
5373 For example, here is how you could use breakpoint commands to print the
5374 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
5380 printf "x is %d\n",x
5385 One application for breakpoint commands is to compensate for one bug so
5386 you can test for another. Put a breakpoint just after the erroneous line
5387 of code, give it a condition to detect the case in which something
5388 erroneous has been done, and give it commands to assign correct values
5389 to any variables that need them. End with the @code{continue} command
5390 so that your program does not stop, and start with the @code{silent}
5391 command so that no output is produced. Here is an example:
5402 @node Dynamic Printf
5403 @subsection Dynamic Printf
5405 @cindex dynamic printf
5407 The dynamic printf command @code{dprintf} combines a breakpoint with
5408 formatted printing of your program's data to give you the effect of
5409 inserting @code{printf} calls into your program on-the-fly, without
5410 having to recompile it.
5412 In its most basic form, the output goes to the GDB console. However,
5413 you can set the variable @code{dprintf-style} for alternate handling.
5414 For instance, you can ask to format the output by calling your
5415 program's @code{printf} function. This has the advantage that the
5416 characters go to the program's output device, so they can recorded in
5417 redirects to files and so forth.
5419 If you are doing remote debugging with a stub or agent, you can also
5420 ask to have the printf handled by the remote agent. In addition to
5421 ensuring that the output goes to the remote program's device along
5422 with any other output the program might produce, you can also ask that
5423 the dprintf remain active even after disconnecting from the remote
5424 target. Using the stub/agent is also more efficient, as it can do
5425 everything without needing to communicate with @value{GDBN}.
5429 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
5430 Whenever execution reaches @var{location}, print the values of one or
5431 more @var{expressions} under the control of the string @var{template}.
5432 To print several values, separate them with commas.
5434 @item set dprintf-style @var{style}
5435 Set the dprintf output to be handled in one of several different
5436 styles enumerated below. A change of style affects all existing
5437 dynamic printfs immediately. (If you need individual control over the
5438 print commands, simply define normal breakpoints with
5439 explicitly-supplied command lists.)
5443 @kindex dprintf-style gdb
5444 Handle the output using the @value{GDBN} @code{printf} command.
5447 @kindex dprintf-style call
5448 Handle the output by calling a function in your program (normally
5452 @kindex dprintf-style agent
5453 Have the remote debugging agent (such as @code{gdbserver}) handle
5454 the output itself. This style is only available for agents that
5455 support running commands on the target.
5458 @item set dprintf-function @var{function}
5459 Set the function to call if the dprintf style is @code{call}. By
5460 default its value is @code{printf}. You may set it to any expression.
5461 that @value{GDBN} can evaluate to a function, as per the @code{call}
5464 @item set dprintf-channel @var{channel}
5465 Set a ``channel'' for dprintf. If set to a non-empty value,
5466 @value{GDBN} will evaluate it as an expression and pass the result as
5467 a first argument to the @code{dprintf-function}, in the manner of
5468 @code{fprintf} and similar functions. Otherwise, the dprintf format
5469 string will be the first argument, in the manner of @code{printf}.
5471 As an example, if you wanted @code{dprintf} output to go to a logfile
5472 that is a standard I/O stream assigned to the variable @code{mylog},
5473 you could do the following:
5476 (gdb) set dprintf-style call
5477 (gdb) set dprintf-function fprintf
5478 (gdb) set dprintf-channel mylog
5479 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
5480 Dprintf 1 at 0x123456: file main.c, line 25.
5482 1 dprintf keep y 0x00123456 in main at main.c:25
5483 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
5488 Note that the @code{info break} displays the dynamic printf commands
5489 as normal breakpoint commands; you can thus easily see the effect of
5490 the variable settings.
5492 @item set disconnected-dprintf on
5493 @itemx set disconnected-dprintf off
5494 @kindex set disconnected-dprintf
5495 Choose whether @code{dprintf} commands should continue to run if
5496 @value{GDBN} has disconnected from the target. This only applies
5497 if the @code{dprintf-style} is @code{agent}.
5499 @item show disconnected-dprintf off
5500 @kindex show disconnected-dprintf
5501 Show the current choice for disconnected @code{dprintf}.
5505 @value{GDBN} does not check the validity of function and channel,
5506 relying on you to supply values that are meaningful for the contexts
5507 in which they are being used. For instance, the function and channel
5508 may be the values of local variables, but if that is the case, then
5509 all enabled dynamic prints must be at locations within the scope of
5510 those locals. If evaluation fails, @value{GDBN} will report an error.
5512 @node Save Breakpoints
5513 @subsection How to save breakpoints to a file
5515 To save breakpoint definitions to a file use the @w{@code{save
5516 breakpoints}} command.
5519 @kindex save breakpoints
5520 @cindex save breakpoints to a file for future sessions
5521 @item save breakpoints [@var{filename}]
5522 This command saves all current breakpoint definitions together with
5523 their commands and ignore counts, into a file @file{@var{filename}}
5524 suitable for use in a later debugging session. This includes all
5525 types of breakpoints (breakpoints, watchpoints, catchpoints,
5526 tracepoints). To read the saved breakpoint definitions, use the
5527 @code{source} command (@pxref{Command Files}). Note that watchpoints
5528 with expressions involving local variables may fail to be recreated
5529 because it may not be possible to access the context where the
5530 watchpoint is valid anymore. Because the saved breakpoint definitions
5531 are simply a sequence of @value{GDBN} commands that recreate the
5532 breakpoints, you can edit the file in your favorite editing program,
5533 and remove the breakpoint definitions you're not interested in, or
5534 that can no longer be recreated.
5537 @node Static Probe Points
5538 @subsection Static Probe Points
5540 @cindex static probe point, SystemTap
5541 @cindex static probe point, DTrace
5542 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
5543 for Statically Defined Tracing, and the probes are designed to have a tiny
5544 runtime code and data footprint, and no dynamic relocations.
5546 Currently, the following types of probes are supported on
5547 ELF-compatible systems:
5551 @item @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
5552 @acronym{SDT} probes@footnote{See
5553 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
5554 for more information on how to add @code{SystemTap} @acronym{SDT}
5555 probes in your applications.}. @code{SystemTap} probes are usable
5556 from assembly, C and C@t{++} languages@footnote{See
5557 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
5558 for a good reference on how the @acronym{SDT} probes are implemented.}.
5560 @item @code{DTrace} (@uref{http://oss.oracle.com/projects/DTrace})
5561 @acronym{USDT} probes. @code{DTrace} probes are usable from C and
5565 @cindex semaphores on static probe points
5566 Some @code{SystemTap} probes have an associated semaphore variable;
5567 for instance, this happens automatically if you defined your probe
5568 using a DTrace-style @file{.d} file. If your probe has a semaphore,
5569 @value{GDBN} will automatically enable it when you specify a
5570 breakpoint using the @samp{-probe-stap} notation. But, if you put a
5571 breakpoint at a probe's location by some other method (e.g.,
5572 @code{break file:line}), then @value{GDBN} will not automatically set
5573 the semaphore. @code{DTrace} probes do not support semaphores.
5575 You can examine the available static static probes using @code{info
5576 probes}, with optional arguments:
5580 @item info probes @r{[}@var{type}@r{]} @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5581 If given, @var{type} is either @code{stap} for listing
5582 @code{SystemTap} probes or @code{dtrace} for listing @code{DTrace}
5583 probes. If omitted all probes are listed regardless of their types.
5585 If given, @var{provider} is a regular expression used to match against provider
5586 names when selecting which probes to list. If omitted, probes by all
5587 probes from all providers are listed.
5589 If given, @var{name} is a regular expression to match against probe names
5590 when selecting which probes to list. If omitted, probe names are not
5591 considered when deciding whether to display them.
5593 If given, @var{objfile} is a regular expression used to select which
5594 object files (executable or shared libraries) to examine. If not
5595 given, all object files are considered.
5597 @item info probes all
5598 List the available static probes, from all types.
5601 @cindex enabling and disabling probes
5602 Some probe points can be enabled and/or disabled. The effect of
5603 enabling or disabling a probe depends on the type of probe being
5604 handled. Some @code{DTrace} probes can be enabled or
5605 disabled, but @code{SystemTap} probes cannot be disabled.
5607 You can enable (or disable) one or more probes using the following
5608 commands, with optional arguments:
5611 @kindex enable probes
5612 @item enable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5613 If given, @var{provider} is a regular expression used to match against
5614 provider names when selecting which probes to enable. If omitted,
5615 all probes from all providers are enabled.
5617 If given, @var{name} is a regular expression to match against probe
5618 names when selecting which probes to enable. If omitted, probe names
5619 are not considered when deciding whether to enable them.
5621 If given, @var{objfile} is a regular expression used to select which
5622 object files (executable or shared libraries) to examine. If not
5623 given, all object files are considered.
5625 @kindex disable probes
5626 @item disable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5627 See the @code{enable probes} command above for a description of the
5628 optional arguments accepted by this command.
5631 @vindex $_probe_arg@r{, convenience variable}
5632 A probe may specify up to twelve arguments. These are available at the
5633 point at which the probe is defined---that is, when the current PC is
5634 at the probe's location. The arguments are available using the
5635 convenience variables (@pxref{Convenience Vars})
5636 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. In @code{SystemTap}
5637 probes each probe argument is an integer of the appropriate size;
5638 types are not preserved. In @code{DTrace} probes types are preserved
5639 provided that they are recognized as such by @value{GDBN}; otherwise
5640 the value of the probe argument will be a long integer. The
5641 convenience variable @code{$_probe_argc} holds the number of arguments
5642 at the current probe point.
5644 These variables are always available, but attempts to access them at
5645 any location other than a probe point will cause @value{GDBN} to give
5649 @c @ifclear BARETARGET
5650 @node Error in Breakpoints
5651 @subsection ``Cannot insert breakpoints''
5653 If you request too many active hardware-assisted breakpoints and
5654 watchpoints, you will see this error message:
5656 @c FIXME: the precise wording of this message may change; the relevant
5657 @c source change is not committed yet (Sep 3, 1999).
5659 Stopped; cannot insert breakpoints.
5660 You may have requested too many hardware breakpoints and watchpoints.
5664 This message is printed when you attempt to resume the program, since
5665 only then @value{GDBN} knows exactly how many hardware breakpoints and
5666 watchpoints it needs to insert.
5668 When this message is printed, you need to disable or remove some of the
5669 hardware-assisted breakpoints and watchpoints, and then continue.
5671 @node Breakpoint-related Warnings
5672 @subsection ``Breakpoint address adjusted...''
5673 @cindex breakpoint address adjusted
5675 Some processor architectures place constraints on the addresses at
5676 which breakpoints may be placed. For architectures thus constrained,
5677 @value{GDBN} will attempt to adjust the breakpoint's address to comply
5678 with the constraints dictated by the architecture.
5680 One example of such an architecture is the Fujitsu FR-V. The FR-V is
5681 a VLIW architecture in which a number of RISC-like instructions may be
5682 bundled together for parallel execution. The FR-V architecture
5683 constrains the location of a breakpoint instruction within such a
5684 bundle to the instruction with the lowest address. @value{GDBN}
5685 honors this constraint by adjusting a breakpoint's address to the
5686 first in the bundle.
5688 It is not uncommon for optimized code to have bundles which contain
5689 instructions from different source statements, thus it may happen that
5690 a breakpoint's address will be adjusted from one source statement to
5691 another. Since this adjustment may significantly alter @value{GDBN}'s
5692 breakpoint related behavior from what the user expects, a warning is
5693 printed when the breakpoint is first set and also when the breakpoint
5696 A warning like the one below is printed when setting a breakpoint
5697 that's been subject to address adjustment:
5700 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
5703 Such warnings are printed both for user settable and @value{GDBN}'s
5704 internal breakpoints. If you see one of these warnings, you should
5705 verify that a breakpoint set at the adjusted address will have the
5706 desired affect. If not, the breakpoint in question may be removed and
5707 other breakpoints may be set which will have the desired behavior.
5708 E.g., it may be sufficient to place the breakpoint at a later
5709 instruction. A conditional breakpoint may also be useful in some
5710 cases to prevent the breakpoint from triggering too often.
5712 @value{GDBN} will also issue a warning when stopping at one of these
5713 adjusted breakpoints:
5716 warning: Breakpoint 1 address previously adjusted from 0x00010414
5720 When this warning is encountered, it may be too late to take remedial
5721 action except in cases where the breakpoint is hit earlier or more
5722 frequently than expected.
5724 @node Continuing and Stepping
5725 @section Continuing and Stepping
5729 @cindex resuming execution
5730 @dfn{Continuing} means resuming program execution until your program
5731 completes normally. In contrast, @dfn{stepping} means executing just
5732 one more ``step'' of your program, where ``step'' may mean either one
5733 line of source code, or one machine instruction (depending on what
5734 particular command you use). Either when continuing or when stepping,
5735 your program may stop even sooner, due to a breakpoint or a signal. (If
5736 it stops due to a signal, you may want to use @code{handle}, or use
5737 @samp{signal 0} to resume execution (@pxref{Signals, ,Signals}),
5738 or you may step into the signal's handler (@pxref{stepping and signal
5743 @kindex c @r{(@code{continue})}
5744 @kindex fg @r{(resume foreground execution)}
5745 @item continue @r{[}@var{ignore-count}@r{]}
5746 @itemx c @r{[}@var{ignore-count}@r{]}
5747 @itemx fg @r{[}@var{ignore-count}@r{]}
5748 Resume program execution, at the address where your program last stopped;
5749 any breakpoints set at that address are bypassed. The optional argument
5750 @var{ignore-count} allows you to specify a further number of times to
5751 ignore a breakpoint at this location; its effect is like that of
5752 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
5754 The argument @var{ignore-count} is meaningful only when your program
5755 stopped due to a breakpoint. At other times, the argument to
5756 @code{continue} is ignored.
5758 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
5759 debugged program is deemed to be the foreground program) are provided
5760 purely for convenience, and have exactly the same behavior as
5764 To resume execution at a different place, you can use @code{return}
5765 (@pxref{Returning, ,Returning from a Function}) to go back to the
5766 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
5767 Different Address}) to go to an arbitrary location in your program.
5769 A typical technique for using stepping is to set a breakpoint
5770 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
5771 beginning of the function or the section of your program where a problem
5772 is believed to lie, run your program until it stops at that breakpoint,
5773 and then step through the suspect area, examining the variables that are
5774 interesting, until you see the problem happen.
5778 @kindex s @r{(@code{step})}
5780 Continue running your program until control reaches a different source
5781 line, then stop it and return control to @value{GDBN}. This command is
5782 abbreviated @code{s}.
5785 @c "without debugging information" is imprecise; actually "without line
5786 @c numbers in the debugging information". (gcc -g1 has debugging info but
5787 @c not line numbers). But it seems complex to try to make that
5788 @c distinction here.
5789 @emph{Warning:} If you use the @code{step} command while control is
5790 within a function that was compiled without debugging information,
5791 execution proceeds until control reaches a function that does have
5792 debugging information. Likewise, it will not step into a function which
5793 is compiled without debugging information. To step through functions
5794 without debugging information, use the @code{stepi} command, described
5798 The @code{step} command only stops at the first instruction of a source
5799 line. This prevents the multiple stops that could otherwise occur in
5800 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5801 to stop if a function that has debugging information is called within
5802 the line. In other words, @code{step} @emph{steps inside} any functions
5803 called within the line.
5805 Also, the @code{step} command only enters a function if there is line
5806 number information for the function. Otherwise it acts like the
5807 @code{next} command. This avoids problems when using @code{cc -gl}
5808 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5809 was any debugging information about the routine.
5811 @item step @var{count}
5812 Continue running as in @code{step}, but do so @var{count} times. If a
5813 breakpoint is reached, or a signal not related to stepping occurs before
5814 @var{count} steps, stepping stops right away.
5817 @kindex n @r{(@code{next})}
5818 @item next @r{[}@var{count}@r{]}
5819 Continue to the next source line in the current (innermost) stack frame.
5820 This is similar to @code{step}, but function calls that appear within
5821 the line of code are executed without stopping. Execution stops when
5822 control reaches a different line of code at the original stack level
5823 that was executing when you gave the @code{next} command. This command
5824 is abbreviated @code{n}.
5826 An argument @var{count} is a repeat count, as for @code{step}.
5829 @c FIX ME!! Do we delete this, or is there a way it fits in with
5830 @c the following paragraph? --- Vctoria
5832 @c @code{next} within a function that lacks debugging information acts like
5833 @c @code{step}, but any function calls appearing within the code of the
5834 @c function are executed without stopping.
5836 The @code{next} command only stops at the first instruction of a
5837 source line. This prevents multiple stops that could otherwise occur in
5838 @code{switch} statements, @code{for} loops, etc.
5840 @kindex set step-mode
5842 @cindex functions without line info, and stepping
5843 @cindex stepping into functions with no line info
5844 @itemx set step-mode on
5845 The @code{set step-mode on} command causes the @code{step} command to
5846 stop at the first instruction of a function which contains no debug line
5847 information rather than stepping over it.
5849 This is useful in cases where you may be interested in inspecting the
5850 machine instructions of a function which has no symbolic info and do not
5851 want @value{GDBN} to automatically skip over this function.
5853 @item set step-mode off
5854 Causes the @code{step} command to step over any functions which contains no
5855 debug information. This is the default.
5857 @item show step-mode
5858 Show whether @value{GDBN} will stop in or step over functions without
5859 source line debug information.
5862 @kindex fin @r{(@code{finish})}
5864 Continue running until just after function in the selected stack frame
5865 returns. Print the returned value (if any). This command can be
5866 abbreviated as @code{fin}.
5868 Contrast this with the @code{return} command (@pxref{Returning,
5869 ,Returning from a Function}).
5871 @kindex set print finish
5872 @kindex show print finish
5873 @item set print finish @r{[}on|off@r{]}
5874 @itemx show print finish
5875 By default the @code{finish} command will show the value that is
5876 returned by the function. This can be disabled using @code{set print
5877 finish off}. When disabled, the value is still entered into the value
5878 history (@pxref{Value History}), but not displayed.
5881 @kindex u @r{(@code{until})}
5882 @cindex run until specified location
5885 Continue running until a source line past the current line, in the
5886 current stack frame, is reached. This command is used to avoid single
5887 stepping through a loop more than once. It is like the @code{next}
5888 command, except that when @code{until} encounters a jump, it
5889 automatically continues execution until the program counter is greater
5890 than the address of the jump.
5892 This means that when you reach the end of a loop after single stepping
5893 though it, @code{until} makes your program continue execution until it
5894 exits the loop. In contrast, a @code{next} command at the end of a loop
5895 simply steps back to the beginning of the loop, which forces you to step
5896 through the next iteration.
5898 @code{until} always stops your program if it attempts to exit the current
5901 @code{until} may produce somewhat counterintuitive results if the order
5902 of machine code does not match the order of the source lines. For
5903 example, in the following excerpt from a debugging session, the @code{f}
5904 (@code{frame}) command shows that execution is stopped at line
5905 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5909 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5911 (@value{GDBP}) until
5912 195 for ( ; argc > 0; NEXTARG) @{
5915 This happened because, for execution efficiency, the compiler had
5916 generated code for the loop closure test at the end, rather than the
5917 start, of the loop---even though the test in a C @code{for}-loop is
5918 written before the body of the loop. The @code{until} command appeared
5919 to step back to the beginning of the loop when it advanced to this
5920 expression; however, it has not really gone to an earlier
5921 statement---not in terms of the actual machine code.
5923 @code{until} with no argument works by means of single
5924 instruction stepping, and hence is slower than @code{until} with an
5927 @item until @var{location}
5928 @itemx u @var{location}
5929 Continue running your program until either the specified @var{location} is
5930 reached, or the current stack frame returns. The location is any of
5931 the forms described in @ref{Specify Location}.
5932 This form of the command uses temporary breakpoints, and
5933 hence is quicker than @code{until} without an argument. The specified
5934 location is actually reached only if it is in the current frame. This
5935 implies that @code{until} can be used to skip over recursive function
5936 invocations. For instance in the code below, if the current location is
5937 line @code{96}, issuing @code{until 99} will execute the program up to
5938 line @code{99} in the same invocation of factorial, i.e., after the inner
5939 invocations have returned.
5942 94 int factorial (int value)
5944 96 if (value > 1) @{
5945 97 value *= factorial (value - 1);
5952 @kindex advance @var{location}
5953 @item advance @var{location}
5954 Continue running the program up to the given @var{location}. An argument is
5955 required, which should be of one of the forms described in
5956 @ref{Specify Location}.
5957 Execution will also stop upon exit from the current stack
5958 frame. This command is similar to @code{until}, but @code{advance} will
5959 not skip over recursive function calls, and the target location doesn't
5960 have to be in the same frame as the current one.
5964 @kindex si @r{(@code{stepi})}
5966 @itemx stepi @var{arg}
5968 Execute one machine instruction, then stop and return to the debugger.
5970 It is often useful to do @samp{display/i $pc} when stepping by machine
5971 instructions. This makes @value{GDBN} automatically display the next
5972 instruction to be executed, each time your program stops. @xref{Auto
5973 Display,, Automatic Display}.
5975 An argument is a repeat count, as in @code{step}.
5979 @kindex ni @r{(@code{nexti})}
5981 @itemx nexti @var{arg}
5983 Execute one machine instruction, but if it is a function call,
5984 proceed until the function returns.
5986 An argument is a repeat count, as in @code{next}.
5990 @anchor{range stepping}
5991 @cindex range stepping
5992 @cindex target-assisted range stepping
5993 By default, and if available, @value{GDBN} makes use of
5994 target-assisted @dfn{range stepping}. In other words, whenever you
5995 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
5996 tells the target to step the corresponding range of instruction
5997 addresses instead of issuing multiple single-steps. This speeds up
5998 line stepping, particularly for remote targets. Ideally, there should
5999 be no reason you would want to turn range stepping off. However, it's
6000 possible that a bug in the debug info, a bug in the remote stub (for
6001 remote targets), or even a bug in @value{GDBN} could make line
6002 stepping behave incorrectly when target-assisted range stepping is
6003 enabled. You can use the following command to turn off range stepping
6007 @kindex set range-stepping
6008 @kindex show range-stepping
6009 @item set range-stepping
6010 @itemx show range-stepping
6011 Control whether range stepping is enabled.
6013 If @code{on}, and the target supports it, @value{GDBN} tells the
6014 target to step a range of addresses itself, instead of issuing
6015 multiple single-steps. If @code{off}, @value{GDBN} always issues
6016 single-steps, even if range stepping is supported by the target. The
6017 default is @code{on}.
6021 @node Skipping Over Functions and Files
6022 @section Skipping Over Functions and Files
6023 @cindex skipping over functions and files
6025 The program you are debugging may contain some functions which are
6026 uninteresting to debug. The @code{skip} command lets you tell @value{GDBN} to
6027 skip a function, all functions in a file or a particular function in
6028 a particular file when stepping.
6030 For example, consider the following C function:
6041 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
6042 are not interested in stepping through @code{boring}. If you run @code{step}
6043 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
6044 step over both @code{foo} and @code{boring}!
6046 One solution is to @code{step} into @code{boring} and use the @code{finish}
6047 command to immediately exit it. But this can become tedious if @code{boring}
6048 is called from many places.
6050 A more flexible solution is to execute @kbd{skip boring}. This instructs
6051 @value{GDBN} never to step into @code{boring}. Now when you execute
6052 @code{step} at line 103, you'll step over @code{boring} and directly into
6055 Functions may be skipped by providing either a function name, linespec
6056 (@pxref{Specify Location}), regular expression that matches the function's
6057 name, file name or a @code{glob}-style pattern that matches the file name.
6059 On Posix systems the form of the regular expression is
6060 ``Extended Regular Expressions''. See for example @samp{man 7 regex}
6061 on @sc{gnu}/Linux systems. On non-Posix systems the form of the regular
6062 expression is whatever is provided by the @code{regcomp} function of
6063 the underlying system.
6064 See for example @samp{man 7 glob} on @sc{gnu}/Linux systems for a
6065 description of @code{glob}-style patterns.
6069 @item skip @r{[}@var{options}@r{]}
6070 The basic form of the @code{skip} command takes zero or more options
6071 that specify what to skip.
6072 The @var{options} argument is any useful combination of the following:
6075 @item -file @var{file}
6076 @itemx -fi @var{file}
6077 Functions in @var{file} will be skipped over when stepping.
6079 @item -gfile @var{file-glob-pattern}
6080 @itemx -gfi @var{file-glob-pattern}
6081 @cindex skipping over files via glob-style patterns
6082 Functions in files matching @var{file-glob-pattern} will be skipped
6086 (gdb) skip -gfi utils/*.c
6089 @item -function @var{linespec}
6090 @itemx -fu @var{linespec}
6091 Functions named by @var{linespec} or the function containing the line
6092 named by @var{linespec} will be skipped over when stepping.
6093 @xref{Specify Location}.
6095 @item -rfunction @var{regexp}
6096 @itemx -rfu @var{regexp}
6097 @cindex skipping over functions via regular expressions
6098 Functions whose name matches @var{regexp} will be skipped over when stepping.
6100 This form is useful for complex function names.
6101 For example, there is generally no need to step into C@t{++} @code{std::string}
6102 constructors or destructors. Plus with C@t{++} templates it can be hard to
6103 write out the full name of the function, and often it doesn't matter what
6104 the template arguments are. Specifying the function to be skipped as a
6105 regular expression makes this easier.
6108 (gdb) skip -rfu ^std::(allocator|basic_string)<.*>::~?\1 *\(
6111 If you want to skip every templated C@t{++} constructor and destructor
6112 in the @code{std} namespace you can do:
6115 (gdb) skip -rfu ^std::([a-zA-z0-9_]+)<.*>::~?\1 *\(
6119 If no options are specified, the function you're currently debugging
6122 @kindex skip function
6123 @item skip function @r{[}@var{linespec}@r{]}
6124 After running this command, the function named by @var{linespec} or the
6125 function containing the line named by @var{linespec} will be skipped over when
6126 stepping. @xref{Specify Location}.
6128 If you do not specify @var{linespec}, the function you're currently debugging
6131 (If you have a function called @code{file} that you want to skip, use
6132 @kbd{skip function file}.)
6135 @item skip file @r{[}@var{filename}@r{]}
6136 After running this command, any function whose source lives in @var{filename}
6137 will be skipped over when stepping.
6140 (gdb) skip file boring.c
6141 File boring.c will be skipped when stepping.
6144 If you do not specify @var{filename}, functions whose source lives in the file
6145 you're currently debugging will be skipped.
6148 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
6149 These are the commands for managing your list of skips:
6153 @item info skip @r{[}@var{range}@r{]}
6154 Print details about the specified skip(s). If @var{range} is not specified,
6155 print a table with details about all functions and files marked for skipping.
6156 @code{info skip} prints the following information about each skip:
6160 A number identifying this skip.
6161 @item Enabled or Disabled
6162 Enabled skips are marked with @samp{y}.
6163 Disabled skips are marked with @samp{n}.
6165 If the file name is a @samp{glob} pattern this is @samp{y}.
6166 Otherwise it is @samp{n}.
6168 The name or @samp{glob} pattern of the file to be skipped.
6169 If no file is specified this is @samp{<none>}.
6171 If the function name is a @samp{regular expression} this is @samp{y}.
6172 Otherwise it is @samp{n}.
6174 The name or regular expression of the function to skip.
6175 If no function is specified this is @samp{<none>}.
6179 @item skip delete @r{[}@var{range}@r{]}
6180 Delete the specified skip(s). If @var{range} is not specified, delete all
6184 @item skip enable @r{[}@var{range}@r{]}
6185 Enable the specified skip(s). If @var{range} is not specified, enable all
6188 @kindex skip disable
6189 @item skip disable @r{[}@var{range}@r{]}
6190 Disable the specified skip(s). If @var{range} is not specified, disable all
6193 @kindex set debug skip
6194 @item set debug skip @r{[}on|off@r{]}
6195 Set whether to print the debug output about skipping files and functions.
6197 @kindex show debug skip
6198 @item show debug skip
6199 Show whether the debug output about skipping files and functions is printed.
6207 A signal is an asynchronous event that can happen in a program. The
6208 operating system defines the possible kinds of signals, and gives each
6209 kind a name and a number. For example, in Unix @code{SIGINT} is the
6210 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
6211 @code{SIGSEGV} is the signal a program gets from referencing a place in
6212 memory far away from all the areas in use; @code{SIGALRM} occurs when
6213 the alarm clock timer goes off (which happens only if your program has
6214 requested an alarm).
6216 @cindex fatal signals
6217 Some signals, including @code{SIGALRM}, are a normal part of the
6218 functioning of your program. Others, such as @code{SIGSEGV}, indicate
6219 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
6220 program has not specified in advance some other way to handle the signal.
6221 @code{SIGINT} does not indicate an error in your program, but it is normally
6222 fatal so it can carry out the purpose of the interrupt: to kill the program.
6224 @value{GDBN} has the ability to detect any occurrence of a signal in your
6225 program. You can tell @value{GDBN} in advance what to do for each kind of
6228 @cindex handling signals
6229 Normally, @value{GDBN} is set up to let the non-erroneous signals like
6230 @code{SIGALRM} be silently passed to your program
6231 (so as not to interfere with their role in the program's functioning)
6232 but to stop your program immediately whenever an error signal happens.
6233 You can change these settings with the @code{handle} command.
6236 @kindex info signals
6240 Print a table of all the kinds of signals and how @value{GDBN} has been told to
6241 handle each one. You can use this to see the signal numbers of all
6242 the defined types of signals.
6244 @item info signals @var{sig}
6245 Similar, but print information only about the specified signal number.
6247 @code{info handle} is an alias for @code{info signals}.
6249 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
6250 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
6251 for details about this command.
6254 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
6255 Change the way @value{GDBN} handles signal @var{signal}. The @var{signal}
6256 can be the number of a signal or its name (with or without the
6257 @samp{SIG} at the beginning); a list of signal numbers of the form
6258 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
6259 known signals. Optional arguments @var{keywords}, described below,
6260 say what change to make.
6264 The keywords allowed by the @code{handle} command can be abbreviated.
6265 Their full names are:
6269 @value{GDBN} should not stop your program when this signal happens. It may
6270 still print a message telling you that the signal has come in.
6273 @value{GDBN} should stop your program when this signal happens. This implies
6274 the @code{print} keyword as well.
6277 @value{GDBN} should print a message when this signal happens.
6280 @value{GDBN} should not mention the occurrence of the signal at all. This
6281 implies the @code{nostop} keyword as well.
6285 @value{GDBN} should allow your program to see this signal; your program
6286 can handle the signal, or else it may terminate if the signal is fatal
6287 and not handled. @code{pass} and @code{noignore} are synonyms.
6291 @value{GDBN} should not allow your program to see this signal.
6292 @code{nopass} and @code{ignore} are synonyms.
6296 When a signal stops your program, the signal is not visible to the
6298 continue. Your program sees the signal then, if @code{pass} is in
6299 effect for the signal in question @emph{at that time}. In other words,
6300 after @value{GDBN} reports a signal, you can use the @code{handle}
6301 command with @code{pass} or @code{nopass} to control whether your
6302 program sees that signal when you continue.
6304 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
6305 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
6306 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
6309 You can also use the @code{signal} command to prevent your program from
6310 seeing a signal, or cause it to see a signal it normally would not see,
6311 or to give it any signal at any time. For example, if your program stopped
6312 due to some sort of memory reference error, you might store correct
6313 values into the erroneous variables and continue, hoping to see more
6314 execution; but your program would probably terminate immediately as
6315 a result of the fatal signal once it saw the signal. To prevent this,
6316 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
6319 @cindex stepping and signal handlers
6320 @anchor{stepping and signal handlers}
6322 @value{GDBN} optimizes for stepping the mainline code. If a signal
6323 that has @code{handle nostop} and @code{handle pass} set arrives while
6324 a stepping command (e.g., @code{stepi}, @code{step}, @code{next}) is
6325 in progress, @value{GDBN} lets the signal handler run and then resumes
6326 stepping the mainline code once the signal handler returns. In other
6327 words, @value{GDBN} steps over the signal handler. This prevents
6328 signals that you've specified as not interesting (with @code{handle
6329 nostop}) from changing the focus of debugging unexpectedly. Note that
6330 the signal handler itself may still hit a breakpoint, stop for another
6331 signal that has @code{handle stop} in effect, or for any other event
6332 that normally results in stopping the stepping command sooner. Also
6333 note that @value{GDBN} still informs you that the program received a
6334 signal if @code{handle print} is set.
6336 @anchor{stepping into signal handlers}
6338 If you set @code{handle pass} for a signal, and your program sets up a
6339 handler for it, then issuing a stepping command, such as @code{step}
6340 or @code{stepi}, when your program is stopped due to the signal will
6341 step @emph{into} the signal handler (if the target supports that).
6343 Likewise, if you use the @code{queue-signal} command to queue a signal
6344 to be delivered to the current thread when execution of the thread
6345 resumes (@pxref{Signaling, ,Giving your Program a Signal}), then a
6346 stepping command will step into the signal handler.
6348 Here's an example, using @code{stepi} to step to the first instruction
6349 of @code{SIGUSR1}'s handler:
6352 (@value{GDBP}) handle SIGUSR1
6353 Signal Stop Print Pass to program Description
6354 SIGUSR1 Yes Yes Yes User defined signal 1
6358 Program received signal SIGUSR1, User defined signal 1.
6359 main () sigusr1.c:28
6362 sigusr1_handler () at sigusr1.c:9
6366 The same, but using @code{queue-signal} instead of waiting for the
6367 program to receive the signal first:
6372 (@value{GDBP}) queue-signal SIGUSR1
6374 sigusr1_handler () at sigusr1.c:9
6379 @cindex extra signal information
6380 @anchor{extra signal information}
6382 On some targets, @value{GDBN} can inspect extra signal information
6383 associated with the intercepted signal, before it is actually
6384 delivered to the program being debugged. This information is exported
6385 by the convenience variable @code{$_siginfo}, and consists of data
6386 that is passed by the kernel to the signal handler at the time of the
6387 receipt of a signal. The data type of the information itself is
6388 target dependent. You can see the data type using the @code{ptype
6389 $_siginfo} command. On Unix systems, it typically corresponds to the
6390 standard @code{siginfo_t} type, as defined in the @file{signal.h}
6393 Here's an example, on a @sc{gnu}/Linux system, printing the stray
6394 referenced address that raised a segmentation fault.
6398 (@value{GDBP}) continue
6399 Program received signal SIGSEGV, Segmentation fault.
6400 0x0000000000400766 in main ()
6402 (@value{GDBP}) ptype $_siginfo
6409 struct @{...@} _kill;
6410 struct @{...@} _timer;
6412 struct @{...@} _sigchld;
6413 struct @{...@} _sigfault;
6414 struct @{...@} _sigpoll;
6417 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
6421 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
6422 $1 = (void *) 0x7ffff7ff7000
6426 Depending on target support, @code{$_siginfo} may also be writable.
6428 @cindex Intel MPX boundary violations
6429 @cindex boundary violations, Intel MPX
6430 On some targets, a @code{SIGSEGV} can be caused by a boundary
6431 violation, i.e., accessing an address outside of the allowed range.
6432 In those cases @value{GDBN} may displays additional information,
6433 depending on how @value{GDBN} has been told to handle the signal.
6434 With @code{handle stop SIGSEGV}, @value{GDBN} displays the violation
6435 kind: "Upper" or "Lower", the memory address accessed and the
6436 bounds, while with @code{handle nostop SIGSEGV} no additional
6437 information is displayed.
6439 The usual output of a segfault is:
6441 Program received signal SIGSEGV, Segmentation fault
6442 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6443 68 value = *(p + len);
6446 While a bound violation is presented as:
6448 Program received signal SIGSEGV, Segmentation fault
6449 Upper bound violation while accessing address 0x7fffffffc3b3
6450 Bounds: [lower = 0x7fffffffc390, upper = 0x7fffffffc3a3]
6451 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6452 68 value = *(p + len);
6456 @section Stopping and Starting Multi-thread Programs
6458 @cindex stopped threads
6459 @cindex threads, stopped
6461 @cindex continuing threads
6462 @cindex threads, continuing
6464 @value{GDBN} supports debugging programs with multiple threads
6465 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
6466 are two modes of controlling execution of your program within the
6467 debugger. In the default mode, referred to as @dfn{all-stop mode},
6468 when any thread in your program stops (for example, at a breakpoint
6469 or while being stepped), all other threads in the program are also stopped by
6470 @value{GDBN}. On some targets, @value{GDBN} also supports
6471 @dfn{non-stop mode}, in which other threads can continue to run freely while
6472 you examine the stopped thread in the debugger.
6475 * All-Stop Mode:: All threads stop when GDB takes control
6476 * Non-Stop Mode:: Other threads continue to execute
6477 * Background Execution:: Running your program asynchronously
6478 * Thread-Specific Breakpoints:: Controlling breakpoints
6479 * Interrupted System Calls:: GDB may interfere with system calls
6480 * Observer Mode:: GDB does not alter program behavior
6484 @subsection All-Stop Mode
6486 @cindex all-stop mode
6488 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
6489 @emph{all} threads of execution stop, not just the current thread. This
6490 allows you to examine the overall state of the program, including
6491 switching between threads, without worrying that things may change
6494 Conversely, whenever you restart the program, @emph{all} threads start
6495 executing. @emph{This is true even when single-stepping} with commands
6496 like @code{step} or @code{next}.
6498 In particular, @value{GDBN} cannot single-step all threads in lockstep.
6499 Since thread scheduling is up to your debugging target's operating
6500 system (not controlled by @value{GDBN}), other threads may
6501 execute more than one statement while the current thread completes a
6502 single step. Moreover, in general other threads stop in the middle of a
6503 statement, rather than at a clean statement boundary, when the program
6506 You might even find your program stopped in another thread after
6507 continuing or even single-stepping. This happens whenever some other
6508 thread runs into a breakpoint, a signal, or an exception before the
6509 first thread completes whatever you requested.
6511 @cindex automatic thread selection
6512 @cindex switching threads automatically
6513 @cindex threads, automatic switching
6514 Whenever @value{GDBN} stops your program, due to a breakpoint or a
6515 signal, it automatically selects the thread where that breakpoint or
6516 signal happened. @value{GDBN} alerts you to the context switch with a
6517 message such as @samp{[Switching to Thread @var{n}]} to identify the
6520 On some OSes, you can modify @value{GDBN}'s default behavior by
6521 locking the OS scheduler to allow only a single thread to run.
6524 @item set scheduler-locking @var{mode}
6525 @cindex scheduler locking mode
6526 @cindex lock scheduler
6527 Set the scheduler locking mode. It applies to normal execution,
6528 record mode, and replay mode. If it is @code{off}, then there is no
6529 locking and any thread may run at any time. If @code{on}, then only
6530 the current thread may run when the inferior is resumed. The
6531 @code{step} mode optimizes for single-stepping; it prevents other
6532 threads from preempting the current thread while you are stepping, so
6533 that the focus of debugging does not change unexpectedly. Other
6534 threads never get a chance to run when you step, and they are
6535 completely free to run when you use commands like @samp{continue},
6536 @samp{until}, or @samp{finish}. However, unless another thread hits a
6537 breakpoint during its timeslice, @value{GDBN} does not change the
6538 current thread away from the thread that you are debugging. The
6539 @code{replay} mode behaves like @code{off} in record mode and like
6540 @code{on} in replay mode.
6542 @item show scheduler-locking
6543 Display the current scheduler locking mode.
6546 @cindex resume threads of multiple processes simultaneously
6547 By default, when you issue one of the execution commands such as
6548 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
6549 threads of the current inferior to run. For example, if @value{GDBN}
6550 is attached to two inferiors, each with two threads, the
6551 @code{continue} command resumes only the two threads of the current
6552 inferior. This is useful, for example, when you debug a program that
6553 forks and you want to hold the parent stopped (so that, for instance,
6554 it doesn't run to exit), while you debug the child. In other
6555 situations, you may not be interested in inspecting the current state
6556 of any of the processes @value{GDBN} is attached to, and you may want
6557 to resume them all until some breakpoint is hit. In the latter case,
6558 you can instruct @value{GDBN} to allow all threads of all the
6559 inferiors to run with the @w{@code{set schedule-multiple}} command.
6562 @kindex set schedule-multiple
6563 @item set schedule-multiple
6564 Set the mode for allowing threads of multiple processes to be resumed
6565 when an execution command is issued. When @code{on}, all threads of
6566 all processes are allowed to run. When @code{off}, only the threads
6567 of the current process are resumed. The default is @code{off}. The
6568 @code{scheduler-locking} mode takes precedence when set to @code{on},
6569 or while you are stepping and set to @code{step}.
6571 @item show schedule-multiple
6572 Display the current mode for resuming the execution of threads of
6577 @subsection Non-Stop Mode
6579 @cindex non-stop mode
6581 @c This section is really only a place-holder, and needs to be expanded
6582 @c with more details.
6584 For some multi-threaded targets, @value{GDBN} supports an optional
6585 mode of operation in which you can examine stopped program threads in
6586 the debugger while other threads continue to execute freely. This
6587 minimizes intrusion when debugging live systems, such as programs
6588 where some threads have real-time constraints or must continue to
6589 respond to external events. This is referred to as @dfn{non-stop} mode.
6591 In non-stop mode, when a thread stops to report a debugging event,
6592 @emph{only} that thread is stopped; @value{GDBN} does not stop other
6593 threads as well, in contrast to the all-stop mode behavior. Additionally,
6594 execution commands such as @code{continue} and @code{step} apply by default
6595 only to the current thread in non-stop mode, rather than all threads as
6596 in all-stop mode. This allows you to control threads explicitly in
6597 ways that are not possible in all-stop mode --- for example, stepping
6598 one thread while allowing others to run freely, stepping
6599 one thread while holding all others stopped, or stepping several threads
6600 independently and simultaneously.
6602 To enter non-stop mode, use this sequence of commands before you run
6603 or attach to your program:
6606 # If using the CLI, pagination breaks non-stop.
6609 # Finally, turn it on!
6613 You can use these commands to manipulate the non-stop mode setting:
6616 @kindex set non-stop
6617 @item set non-stop on
6618 Enable selection of non-stop mode.
6619 @item set non-stop off
6620 Disable selection of non-stop mode.
6621 @kindex show non-stop
6623 Show the current non-stop enablement setting.
6626 Note these commands only reflect whether non-stop mode is enabled,
6627 not whether the currently-executing program is being run in non-stop mode.
6628 In particular, the @code{set non-stop} preference is only consulted when
6629 @value{GDBN} starts or connects to the target program, and it is generally
6630 not possible to switch modes once debugging has started. Furthermore,
6631 since not all targets support non-stop mode, even when you have enabled
6632 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
6635 In non-stop mode, all execution commands apply only to the current thread
6636 by default. That is, @code{continue} only continues one thread.
6637 To continue all threads, issue @code{continue -a} or @code{c -a}.
6639 You can use @value{GDBN}'s background execution commands
6640 (@pxref{Background Execution}) to run some threads in the background
6641 while you continue to examine or step others from @value{GDBN}.
6642 The MI execution commands (@pxref{GDB/MI Program Execution}) are
6643 always executed asynchronously in non-stop mode.
6645 Suspending execution is done with the @code{interrupt} command when
6646 running in the background, or @kbd{Ctrl-c} during foreground execution.
6647 In all-stop mode, this stops the whole process;
6648 but in non-stop mode the interrupt applies only to the current thread.
6649 To stop the whole program, use @code{interrupt -a}.
6651 Other execution commands do not currently support the @code{-a} option.
6653 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
6654 that thread current, as it does in all-stop mode. This is because the
6655 thread stop notifications are asynchronous with respect to @value{GDBN}'s
6656 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
6657 changed to a different thread just as you entered a command to operate on the
6658 previously current thread.
6660 @node Background Execution
6661 @subsection Background Execution
6663 @cindex foreground execution
6664 @cindex background execution
6665 @cindex asynchronous execution
6666 @cindex execution, foreground, background and asynchronous
6668 @value{GDBN}'s execution commands have two variants: the normal
6669 foreground (synchronous) behavior, and a background
6670 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
6671 the program to report that some thread has stopped before prompting for
6672 another command. In background execution, @value{GDBN} immediately gives
6673 a command prompt so that you can issue other commands while your program runs.
6675 If the target doesn't support async mode, @value{GDBN} issues an error
6676 message if you attempt to use the background execution commands.
6678 @cindex @code{&}, background execution of commands
6679 To specify background execution, add a @code{&} to the command. For example,
6680 the background form of the @code{continue} command is @code{continue&}, or
6681 just @code{c&}. The execution commands that accept background execution
6687 @xref{Starting, , Starting your Program}.
6691 @xref{Attach, , Debugging an Already-running Process}.
6695 @xref{Continuing and Stepping, step}.
6699 @xref{Continuing and Stepping, stepi}.
6703 @xref{Continuing and Stepping, next}.
6707 @xref{Continuing and Stepping, nexti}.
6711 @xref{Continuing and Stepping, continue}.
6715 @xref{Continuing and Stepping, finish}.
6719 @xref{Continuing and Stepping, until}.
6723 Background execution is especially useful in conjunction with non-stop
6724 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
6725 However, you can also use these commands in the normal all-stop mode with
6726 the restriction that you cannot issue another execution command until the
6727 previous one finishes. Examples of commands that are valid in all-stop
6728 mode while the program is running include @code{help} and @code{info break}.
6730 You can interrupt your program while it is running in the background by
6731 using the @code{interrupt} command.
6738 Suspend execution of the running program. In all-stop mode,
6739 @code{interrupt} stops the whole process, but in non-stop mode, it stops
6740 only the current thread. To stop the whole program in non-stop mode,
6741 use @code{interrupt -a}.
6744 @node Thread-Specific Breakpoints
6745 @subsection Thread-Specific Breakpoints
6747 When your program has multiple threads (@pxref{Threads,, Debugging
6748 Programs with Multiple Threads}), you can choose whether to set
6749 breakpoints on all threads, or on a particular thread.
6752 @cindex breakpoints and threads
6753 @cindex thread breakpoints
6754 @kindex break @dots{} thread @var{thread-id}
6755 @item break @var{location} thread @var{thread-id}
6756 @itemx break @var{location} thread @var{thread-id} if @dots{}
6757 @var{location} specifies source lines; there are several ways of
6758 writing them (@pxref{Specify Location}), but the effect is always to
6759 specify some source line.
6761 Use the qualifier @samp{thread @var{thread-id}} with a breakpoint command
6762 to specify that you only want @value{GDBN} to stop the program when a
6763 particular thread reaches this breakpoint. The @var{thread-id} specifier
6764 is one of the thread identifiers assigned by @value{GDBN}, shown
6765 in the first column of the @samp{info threads} display.
6767 If you do not specify @samp{thread @var{thread-id}} when you set a
6768 breakpoint, the breakpoint applies to @emph{all} threads of your
6771 You can use the @code{thread} qualifier on conditional breakpoints as
6772 well; in this case, place @samp{thread @var{thread-id}} before or
6773 after the breakpoint condition, like this:
6776 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
6781 Thread-specific breakpoints are automatically deleted when
6782 @value{GDBN} detects the corresponding thread is no longer in the
6783 thread list. For example:
6787 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
6790 There are several ways for a thread to disappear, such as a regular
6791 thread exit, but also when you detach from the process with the
6792 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
6793 Process}), or if @value{GDBN} loses the remote connection
6794 (@pxref{Remote Debugging}), etc. Note that with some targets,
6795 @value{GDBN} is only able to detect a thread has exited when the user
6796 explictly asks for the thread list with the @code{info threads}
6799 @node Interrupted System Calls
6800 @subsection Interrupted System Calls
6802 @cindex thread breakpoints and system calls
6803 @cindex system calls and thread breakpoints
6804 @cindex premature return from system calls
6805 There is an unfortunate side effect when using @value{GDBN} to debug
6806 multi-threaded programs. If one thread stops for a
6807 breakpoint, or for some other reason, and another thread is blocked in a
6808 system call, then the system call may return prematurely. This is a
6809 consequence of the interaction between multiple threads and the signals
6810 that @value{GDBN} uses to implement breakpoints and other events that
6813 To handle this problem, your program should check the return value of
6814 each system call and react appropriately. This is good programming
6817 For example, do not write code like this:
6823 The call to @code{sleep} will return early if a different thread stops
6824 at a breakpoint or for some other reason.
6826 Instead, write this:
6831 unslept = sleep (unslept);
6834 A system call is allowed to return early, so the system is still
6835 conforming to its specification. But @value{GDBN} does cause your
6836 multi-threaded program to behave differently than it would without
6839 Also, @value{GDBN} uses internal breakpoints in the thread library to
6840 monitor certain events such as thread creation and thread destruction.
6841 When such an event happens, a system call in another thread may return
6842 prematurely, even though your program does not appear to stop.
6845 @subsection Observer Mode
6847 If you want to build on non-stop mode and observe program behavior
6848 without any chance of disruption by @value{GDBN}, you can set
6849 variables to disable all of the debugger's attempts to modify state,
6850 whether by writing memory, inserting breakpoints, etc. These operate
6851 at a low level, intercepting operations from all commands.
6853 When all of these are set to @code{off}, then @value{GDBN} is said to
6854 be @dfn{observer mode}. As a convenience, the variable
6855 @code{observer} can be set to disable these, plus enable non-stop
6858 Note that @value{GDBN} will not prevent you from making nonsensical
6859 combinations of these settings. For instance, if you have enabled
6860 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
6861 then breakpoints that work by writing trap instructions into the code
6862 stream will still not be able to be placed.
6867 @item set observer on
6868 @itemx set observer off
6869 When set to @code{on}, this disables all the permission variables
6870 below (except for @code{insert-fast-tracepoints}), plus enables
6871 non-stop debugging. Setting this to @code{off} switches back to
6872 normal debugging, though remaining in non-stop mode.
6875 Show whether observer mode is on or off.
6877 @kindex may-write-registers
6878 @item set may-write-registers on
6879 @itemx set may-write-registers off
6880 This controls whether @value{GDBN} will attempt to alter the values of
6881 registers, such as with assignment expressions in @code{print}, or the
6882 @code{jump} command. It defaults to @code{on}.
6884 @item show may-write-registers
6885 Show the current permission to write registers.
6887 @kindex may-write-memory
6888 @item set may-write-memory on
6889 @itemx set may-write-memory off
6890 This controls whether @value{GDBN} will attempt to alter the contents
6891 of memory, such as with assignment expressions in @code{print}. It
6892 defaults to @code{on}.
6894 @item show may-write-memory
6895 Show the current permission to write memory.
6897 @kindex may-insert-breakpoints
6898 @item set may-insert-breakpoints on
6899 @itemx set may-insert-breakpoints off
6900 This controls whether @value{GDBN} will attempt to insert breakpoints.
6901 This affects all breakpoints, including internal breakpoints defined
6902 by @value{GDBN}. It defaults to @code{on}.
6904 @item show may-insert-breakpoints
6905 Show the current permission to insert breakpoints.
6907 @kindex may-insert-tracepoints
6908 @item set may-insert-tracepoints on
6909 @itemx set may-insert-tracepoints off
6910 This controls whether @value{GDBN} will attempt to insert (regular)
6911 tracepoints at the beginning of a tracing experiment. It affects only
6912 non-fast tracepoints, fast tracepoints being under the control of
6913 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
6915 @item show may-insert-tracepoints
6916 Show the current permission to insert tracepoints.
6918 @kindex may-insert-fast-tracepoints
6919 @item set may-insert-fast-tracepoints on
6920 @itemx set may-insert-fast-tracepoints off
6921 This controls whether @value{GDBN} will attempt to insert fast
6922 tracepoints at the beginning of a tracing experiment. It affects only
6923 fast tracepoints, regular (non-fast) tracepoints being under the
6924 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
6926 @item show may-insert-fast-tracepoints
6927 Show the current permission to insert fast tracepoints.
6929 @kindex may-interrupt
6930 @item set may-interrupt on
6931 @itemx set may-interrupt off
6932 This controls whether @value{GDBN} will attempt to interrupt or stop
6933 program execution. When this variable is @code{off}, the
6934 @code{interrupt} command will have no effect, nor will
6935 @kbd{Ctrl-c}. It defaults to @code{on}.
6937 @item show may-interrupt
6938 Show the current permission to interrupt or stop the program.
6942 @node Reverse Execution
6943 @chapter Running programs backward
6944 @cindex reverse execution
6945 @cindex running programs backward
6947 When you are debugging a program, it is not unusual to realize that
6948 you have gone too far, and some event of interest has already happened.
6949 If the target environment supports it, @value{GDBN} can allow you to
6950 ``rewind'' the program by running it backward.
6952 A target environment that supports reverse execution should be able
6953 to ``undo'' the changes in machine state that have taken place as the
6954 program was executing normally. Variables, registers etc.@: should
6955 revert to their previous values. Obviously this requires a great
6956 deal of sophistication on the part of the target environment; not
6957 all target environments can support reverse execution.
6959 When a program is executed in reverse, the instructions that
6960 have most recently been executed are ``un-executed'', in reverse
6961 order. The program counter runs backward, following the previous
6962 thread of execution in reverse. As each instruction is ``un-executed'',
6963 the values of memory and/or registers that were changed by that
6964 instruction are reverted to their previous states. After executing
6965 a piece of source code in reverse, all side effects of that code
6966 should be ``undone'', and all variables should be returned to their
6967 prior values@footnote{
6968 Note that some side effects are easier to undo than others. For instance,
6969 memory and registers are relatively easy, but device I/O is hard. Some
6970 targets may be able undo things like device I/O, and some may not.
6972 The contract between @value{GDBN} and the reverse executing target
6973 requires only that the target do something reasonable when
6974 @value{GDBN} tells it to execute backwards, and then report the
6975 results back to @value{GDBN}. Whatever the target reports back to
6976 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
6977 assumes that the memory and registers that the target reports are in a
6978 consistant state, but @value{GDBN} accepts whatever it is given.
6981 On some platforms, @value{GDBN} has built-in support for reverse
6982 execution, activated with the @code{record} or @code{record btrace}
6983 commands. @xref{Process Record and Replay}. Some remote targets,
6984 typically full system emulators, support reverse execution directly
6985 without requiring any special command.
6987 If you are debugging in a target environment that supports
6988 reverse execution, @value{GDBN} provides the following commands.
6991 @kindex reverse-continue
6992 @kindex rc @r{(@code{reverse-continue})}
6993 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6994 @itemx rc @r{[}@var{ignore-count}@r{]}
6995 Beginning at the point where your program last stopped, start executing
6996 in reverse. Reverse execution will stop for breakpoints and synchronous
6997 exceptions (signals), just like normal execution. Behavior of
6998 asynchronous signals depends on the target environment.
7000 @kindex reverse-step
7001 @kindex rs @r{(@code{step})}
7002 @item reverse-step @r{[}@var{count}@r{]}
7003 Run the program backward until control reaches the start of a
7004 different source line; then stop it, and return control to @value{GDBN}.
7006 Like the @code{step} command, @code{reverse-step} will only stop
7007 at the beginning of a source line. It ``un-executes'' the previously
7008 executed source line. If the previous source line included calls to
7009 debuggable functions, @code{reverse-step} will step (backward) into
7010 the called function, stopping at the beginning of the @emph{last}
7011 statement in the called function (typically a return statement).
7013 Also, as with the @code{step} command, if non-debuggable functions are
7014 called, @code{reverse-step} will run thru them backward without stopping.
7016 @kindex reverse-stepi
7017 @kindex rsi @r{(@code{reverse-stepi})}
7018 @item reverse-stepi @r{[}@var{count}@r{]}
7019 Reverse-execute one machine instruction. Note that the instruction
7020 to be reverse-executed is @emph{not} the one pointed to by the program
7021 counter, but the instruction executed prior to that one. For instance,
7022 if the last instruction was a jump, @code{reverse-stepi} will take you
7023 back from the destination of the jump to the jump instruction itself.
7025 @kindex reverse-next
7026 @kindex rn @r{(@code{reverse-next})}
7027 @item reverse-next @r{[}@var{count}@r{]}
7028 Run backward to the beginning of the previous line executed in
7029 the current (innermost) stack frame. If the line contains function
7030 calls, they will be ``un-executed'' without stopping. Starting from
7031 the first line of a function, @code{reverse-next} will take you back
7032 to the caller of that function, @emph{before} the function was called,
7033 just as the normal @code{next} command would take you from the last
7034 line of a function back to its return to its caller
7035 @footnote{Unless the code is too heavily optimized.}.
7037 @kindex reverse-nexti
7038 @kindex rni @r{(@code{reverse-nexti})}
7039 @item reverse-nexti @r{[}@var{count}@r{]}
7040 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
7041 in reverse, except that called functions are ``un-executed'' atomically.
7042 That is, if the previously executed instruction was a return from
7043 another function, @code{reverse-nexti} will continue to execute
7044 in reverse until the call to that function (from the current stack
7047 @kindex reverse-finish
7048 @item reverse-finish
7049 Just as the @code{finish} command takes you to the point where the
7050 current function returns, @code{reverse-finish} takes you to the point
7051 where it was called. Instead of ending up at the end of the current
7052 function invocation, you end up at the beginning.
7054 @kindex set exec-direction
7055 @item set exec-direction
7056 Set the direction of target execution.
7057 @item set exec-direction reverse
7058 @cindex execute forward or backward in time
7059 @value{GDBN} will perform all execution commands in reverse, until the
7060 exec-direction mode is changed to ``forward''. Affected commands include
7061 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
7062 command cannot be used in reverse mode.
7063 @item set exec-direction forward
7064 @value{GDBN} will perform all execution commands in the normal fashion.
7065 This is the default.
7069 @node Process Record and Replay
7070 @chapter Recording Inferior's Execution and Replaying It
7071 @cindex process record and replay
7072 @cindex recording inferior's execution and replaying it
7074 On some platforms, @value{GDBN} provides a special @dfn{process record
7075 and replay} target that can record a log of the process execution, and
7076 replay it later with both forward and reverse execution commands.
7079 When this target is in use, if the execution log includes the record
7080 for the next instruction, @value{GDBN} will debug in @dfn{replay
7081 mode}. In the replay mode, the inferior does not really execute code
7082 instructions. Instead, all the events that normally happen during
7083 code execution are taken from the execution log. While code is not
7084 really executed in replay mode, the values of registers (including the
7085 program counter register) and the memory of the inferior are still
7086 changed as they normally would. Their contents are taken from the
7090 If the record for the next instruction is not in the execution log,
7091 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
7092 inferior executes normally, and @value{GDBN} records the execution log
7095 The process record and replay target supports reverse execution
7096 (@pxref{Reverse Execution}), even if the platform on which the
7097 inferior runs does not. However, the reverse execution is limited in
7098 this case by the range of the instructions recorded in the execution
7099 log. In other words, reverse execution on platforms that don't
7100 support it directly can only be done in the replay mode.
7102 When debugging in the reverse direction, @value{GDBN} will work in
7103 replay mode as long as the execution log includes the record for the
7104 previous instruction; otherwise, it will work in record mode, if the
7105 platform supports reverse execution, or stop if not.
7107 Currently, process record and replay is supported on ARM, Aarch64,
7108 Moxie, PowerPC, PowerPC64, S/390, and x86 (i386/amd64) running
7109 GNU/Linux. Process record and replay can be used both when native
7110 debugging, and when remote debugging via @code{gdbserver}.
7112 For architecture environments that support process record and replay,
7113 @value{GDBN} provides the following commands:
7116 @kindex target record
7117 @kindex target record-full
7118 @kindex target record-btrace
7121 @kindex record btrace
7122 @kindex record btrace bts
7123 @kindex record btrace pt
7129 @kindex rec btrace bts
7130 @kindex rec btrace pt
7133 @item record @var{method}
7134 This command starts the process record and replay target. The
7135 recording method can be specified as parameter. Without a parameter
7136 the command uses the @code{full} recording method. The following
7137 recording methods are available:
7141 Full record/replay recording using @value{GDBN}'s software record and
7142 replay implementation. This method allows replaying and reverse
7145 @item btrace @var{format}
7146 Hardware-supported instruction recording, supported on Intel
7147 processors. This method does not record data. Further, the data is
7148 collected in a ring buffer so old data will be overwritten when the
7149 buffer is full. It allows limited reverse execution. Variables and
7150 registers are not available during reverse execution. In remote
7151 debugging, recording continues on disconnect. Recorded data can be
7152 inspected after reconnecting. The recording may be stopped using
7155 The recording format can be specified as parameter. Without a parameter
7156 the command chooses the recording format. The following recording
7157 formats are available:
7161 @cindex branch trace store
7162 Use the @dfn{Branch Trace Store} (@acronym{BTS}) recording format. In
7163 this format, the processor stores a from/to record for each executed
7164 branch in the btrace ring buffer.
7167 @cindex Intel Processor Trace
7168 Use the @dfn{Intel Processor Trace} recording format. In this
7169 format, the processor stores the execution trace in a compressed form
7170 that is afterwards decoded by @value{GDBN}.
7172 The trace can be recorded with very low overhead. The compressed
7173 trace format also allows small trace buffers to already contain a big
7174 number of instructions compared to @acronym{BTS}.
7176 Decoding the recorded execution trace, on the other hand, is more
7177 expensive than decoding @acronym{BTS} trace. This is mostly due to the
7178 increased number of instructions to process. You should increase the
7179 buffer-size with care.
7182 Not all recording formats may be available on all processors.
7185 The process record and replay target can only debug a process that is
7186 already running. Therefore, you need first to start the process with
7187 the @kbd{run} or @kbd{start} commands, and then start the recording
7188 with the @kbd{record @var{method}} command.
7190 @cindex displaced stepping, and process record and replay
7191 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
7192 will be automatically disabled when process record and replay target
7193 is started. That's because the process record and replay target
7194 doesn't support displaced stepping.
7196 @cindex non-stop mode, and process record and replay
7197 @cindex asynchronous execution, and process record and replay
7198 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
7199 the asynchronous execution mode (@pxref{Background Execution}), not
7200 all recording methods are available. The @code{full} recording method
7201 does not support these two modes.
7206 Stop the process record and replay target. When process record and
7207 replay target stops, the entire execution log will be deleted and the
7208 inferior will either be terminated, or will remain in its final state.
7210 When you stop the process record and replay target in record mode (at
7211 the end of the execution log), the inferior will be stopped at the
7212 next instruction that would have been recorded. In other words, if
7213 you record for a while and then stop recording, the inferior process
7214 will be left in the same state as if the recording never happened.
7216 On the other hand, if the process record and replay target is stopped
7217 while in replay mode (that is, not at the end of the execution log,
7218 but at some earlier point), the inferior process will become ``live''
7219 at that earlier state, and it will then be possible to continue the
7220 usual ``live'' debugging of the process from that state.
7222 When the inferior process exits, or @value{GDBN} detaches from it,
7223 process record and replay target will automatically stop itself.
7227 Go to a specific location in the execution log. There are several
7228 ways to specify the location to go to:
7231 @item record goto begin
7232 @itemx record goto start
7233 Go to the beginning of the execution log.
7235 @item record goto end
7236 Go to the end of the execution log.
7238 @item record goto @var{n}
7239 Go to instruction number @var{n} in the execution log.
7243 @item record save @var{filename}
7244 Save the execution log to a file @file{@var{filename}}.
7245 Default filename is @file{gdb_record.@var{process_id}}, where
7246 @var{process_id} is the process ID of the inferior.
7248 This command may not be available for all recording methods.
7250 @kindex record restore
7251 @item record restore @var{filename}
7252 Restore the execution log from a file @file{@var{filename}}.
7253 File must have been created with @code{record save}.
7255 @kindex set record full
7256 @item set record full insn-number-max @var{limit}
7257 @itemx set record full insn-number-max unlimited
7258 Set the limit of instructions to be recorded for the @code{full}
7259 recording method. Default value is 200000.
7261 If @var{limit} is a positive number, then @value{GDBN} will start
7262 deleting instructions from the log once the number of the record
7263 instructions becomes greater than @var{limit}. For every new recorded
7264 instruction, @value{GDBN} will delete the earliest recorded
7265 instruction to keep the number of recorded instructions at the limit.
7266 (Since deleting recorded instructions loses information, @value{GDBN}
7267 lets you control what happens when the limit is reached, by means of
7268 the @code{stop-at-limit} option, described below.)
7270 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
7271 delete recorded instructions from the execution log. The number of
7272 recorded instructions is limited only by the available memory.
7274 @kindex show record full
7275 @item show record full insn-number-max
7276 Show the limit of instructions to be recorded with the @code{full}
7279 @item set record full stop-at-limit
7280 Control the behavior of the @code{full} recording method when the
7281 number of recorded instructions reaches the limit. If ON (the
7282 default), @value{GDBN} will stop when the limit is reached for the
7283 first time and ask you whether you want to stop the inferior or
7284 continue running it and recording the execution log. If you decide
7285 to continue recording, each new recorded instruction will cause the
7286 oldest one to be deleted.
7288 If this option is OFF, @value{GDBN} will automatically delete the
7289 oldest record to make room for each new one, without asking.
7291 @item show record full stop-at-limit
7292 Show the current setting of @code{stop-at-limit}.
7294 @item set record full memory-query
7295 Control the behavior when @value{GDBN} is unable to record memory
7296 changes caused by an instruction for the @code{full} recording method.
7297 If ON, @value{GDBN} will query whether to stop the inferior in that
7300 If this option is OFF (the default), @value{GDBN} will automatically
7301 ignore the effect of such instructions on memory. Later, when
7302 @value{GDBN} replays this execution log, it will mark the log of this
7303 instruction as not accessible, and it will not affect the replay
7306 @item show record full memory-query
7307 Show the current setting of @code{memory-query}.
7309 @kindex set record btrace
7310 The @code{btrace} record target does not trace data. As a
7311 convenience, when replaying, @value{GDBN} reads read-only memory off
7312 the live program directly, assuming that the addresses of the
7313 read-only areas don't change. This for example makes it possible to
7314 disassemble code while replaying, but not to print variables.
7315 In some cases, being able to inspect variables might be useful.
7316 You can use the following command for that:
7318 @item set record btrace replay-memory-access
7319 Control the behavior of the @code{btrace} recording method when
7320 accessing memory during replay. If @code{read-only} (the default),
7321 @value{GDBN} will only allow accesses to read-only memory.
7322 If @code{read-write}, @value{GDBN} will allow accesses to read-only
7323 and to read-write memory. Beware that the accessed memory corresponds
7324 to the live target and not necessarily to the current replay
7327 @item set record btrace cpu @var{identifier}
7328 Set the processor to be used for enabling workarounds for processor
7329 errata when decoding the trace.
7331 Processor errata are defects in processor operation, caused by its
7332 design or manufacture. They can cause a trace not to match the
7333 specification. This, in turn, may cause trace decode to fail.
7334 @value{GDBN} can detect erroneous trace packets and correct them, thus
7335 avoiding the decoding failures. These corrections are known as
7336 @dfn{errata workarounds}, and are enabled based on the processor on
7337 which the trace was recorded.
7339 By default, @value{GDBN} attempts to detect the processor
7340 automatically, and apply the necessary workarounds for it. However,
7341 you may need to specify the processor if @value{GDBN} does not yet
7342 support it. This command allows you to do that, and also allows to
7343 disable the workarounds.
7345 The argument @var{identifier} identifies the @sc{cpu} and is of the
7346 form: @code{@var{vendor}:@var{procesor identifier}}. In addition,
7347 there are two special identifiers, @code{none} and @code{auto}
7350 The following vendor identifiers and corresponding processor
7351 identifiers are currently supported:
7353 @multitable @columnfractions .1 .9
7356 @tab @var{family}/@var{model}[/@var{stepping}]
7360 On GNU/Linux systems, the processor @var{family}, @var{model}, and
7361 @var{stepping} can be obtained from @code{/proc/cpuinfo}.
7363 If @var{identifier} is @code{auto}, enable errata workarounds for the
7364 processor on which the trace was recorded. If @var{identifier} is
7365 @code{none}, errata workarounds are disabled.
7367 For example, when using an old @value{GDBN} on a new system, decode
7368 may fail because @value{GDBN} does not support the new processor. It
7369 often suffices to specify an older processor that @value{GDBN}
7374 Active record target: record-btrace
7375 Recording format: Intel Processor Trace.
7377 Failed to configure the Intel Processor Trace decoder: unknown cpu.
7378 (gdb) set record btrace cpu intel:6/158
7380 Active record target: record-btrace
7381 Recording format: Intel Processor Trace.
7383 Recorded 84872 instructions in 3189 functions (0 gaps) for thread 1 (...).
7386 @kindex show record btrace
7387 @item show record btrace replay-memory-access
7388 Show the current setting of @code{replay-memory-access}.
7390 @item show record btrace cpu
7391 Show the processor to be used for enabling trace decode errata
7394 @kindex set record btrace bts
7395 @item set record btrace bts buffer-size @var{size}
7396 @itemx set record btrace bts buffer-size unlimited
7397 Set the requested ring buffer size for branch tracing in @acronym{BTS}
7398 format. Default is 64KB.
7400 If @var{size} is a positive number, then @value{GDBN} will try to
7401 allocate a buffer of at least @var{size} bytes for each new thread
7402 that uses the btrace recording method and the @acronym{BTS} format.
7403 The actually obtained buffer size may differ from the requested
7404 @var{size}. Use the @code{info record} command to see the actual
7405 buffer size for each thread that uses the btrace recording method and
7406 the @acronym{BTS} format.
7408 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
7409 allocate a buffer of 4MB.
7411 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
7412 also need longer to process the branch trace data before it can be used.
7414 @item show record btrace bts buffer-size @var{size}
7415 Show the current setting of the requested ring buffer size for branch
7416 tracing in @acronym{BTS} format.
7418 @kindex set record btrace pt
7419 @item set record btrace pt buffer-size @var{size}
7420 @itemx set record btrace pt buffer-size unlimited
7421 Set the requested ring buffer size for branch tracing in Intel
7422 Processor Trace format. Default is 16KB.
7424 If @var{size} is a positive number, then @value{GDBN} will try to
7425 allocate a buffer of at least @var{size} bytes for each new thread
7426 that uses the btrace recording method and the Intel Processor Trace
7427 format. The actually obtained buffer size may differ from the
7428 requested @var{size}. Use the @code{info record} command to see the
7429 actual buffer size for each thread.
7431 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
7432 allocate a buffer of 4MB.
7434 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
7435 also need longer to process the branch trace data before it can be used.
7437 @item show record btrace pt buffer-size @var{size}
7438 Show the current setting of the requested ring buffer size for branch
7439 tracing in Intel Processor Trace format.
7443 Show various statistics about the recording depending on the recording
7448 For the @code{full} recording method, it shows the state of process
7449 record and its in-memory execution log buffer, including:
7453 Whether in record mode or replay mode.
7455 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
7457 Highest recorded instruction number.
7459 Current instruction about to be replayed (if in replay mode).
7461 Number of instructions contained in the execution log.
7463 Maximum number of instructions that may be contained in the execution log.
7467 For the @code{btrace} recording method, it shows:
7473 Number of instructions that have been recorded.
7475 Number of blocks of sequential control-flow formed by the recorded
7478 Whether in record mode or replay mode.
7481 For the @code{bts} recording format, it also shows:
7484 Size of the perf ring buffer.
7487 For the @code{pt} recording format, it also shows:
7490 Size of the perf ring buffer.
7494 @kindex record delete
7497 When record target runs in replay mode (``in the past''), delete the
7498 subsequent execution log and begin to record a new execution log starting
7499 from the current address. This means you will abandon the previously
7500 recorded ``future'' and begin recording a new ``future''.
7502 @kindex record instruction-history
7503 @kindex rec instruction-history
7504 @item record instruction-history
7505 Disassembles instructions from the recorded execution log. By
7506 default, ten instructions are disassembled. This can be changed using
7507 the @code{set record instruction-history-size} command. Instructions
7508 are printed in execution order.
7510 It can also print mixed source+disassembly if you specify the the
7511 @code{/m} or @code{/s} modifier, and print the raw instructions in hex
7512 as well as in symbolic form by specifying the @code{/r} modifier.
7514 The current position marker is printed for the instruction at the
7515 current program counter value. This instruction can appear multiple
7516 times in the trace and the current position marker will be printed
7517 every time. To omit the current position marker, specify the
7520 To better align the printed instructions when the trace contains
7521 instructions from more than one function, the function name may be
7522 omitted by specifying the @code{/f} modifier.
7524 Speculatively executed instructions are prefixed with @samp{?}. This
7525 feature is not available for all recording formats.
7527 There are several ways to specify what part of the execution log to
7531 @item record instruction-history @var{insn}
7532 Disassembles ten instructions starting from instruction number
7535 @item record instruction-history @var{insn}, +/-@var{n}
7536 Disassembles @var{n} instructions around instruction number
7537 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
7538 @var{n} instructions after instruction number @var{insn}. If
7539 @var{n} is preceded with @code{-}, disassembles @var{n}
7540 instructions before instruction number @var{insn}.
7542 @item record instruction-history
7543 Disassembles ten more instructions after the last disassembly.
7545 @item record instruction-history -
7546 Disassembles ten more instructions before the last disassembly.
7548 @item record instruction-history @var{begin}, @var{end}
7549 Disassembles instructions beginning with instruction number
7550 @var{begin} until instruction number @var{end}. The instruction
7551 number @var{end} is included.
7554 This command may not be available for all recording methods.
7557 @item set record instruction-history-size @var{size}
7558 @itemx set record instruction-history-size unlimited
7559 Define how many instructions to disassemble in the @code{record
7560 instruction-history} command. The default value is 10.
7561 A @var{size} of @code{unlimited} means unlimited instructions.
7564 @item show record instruction-history-size
7565 Show how many instructions to disassemble in the @code{record
7566 instruction-history} command.
7568 @kindex record function-call-history
7569 @kindex rec function-call-history
7570 @item record function-call-history
7571 Prints the execution history at function granularity. It prints one
7572 line for each sequence of instructions that belong to the same
7573 function giving the name of that function, the source lines
7574 for this instruction sequence (if the @code{/l} modifier is
7575 specified), and the instructions numbers that form the sequence (if
7576 the @code{/i} modifier is specified). The function names are indented
7577 to reflect the call stack depth if the @code{/c} modifier is
7578 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be
7582 (@value{GDBP}) @b{list 1, 10}
7593 (@value{GDBP}) @b{record function-call-history /ilc}
7594 1 bar inst 1,4 at foo.c:6,8
7595 2 foo inst 5,10 at foo.c:2,3
7596 3 bar inst 11,13 at foo.c:9,10
7599 By default, ten lines are printed. This can be changed using the
7600 @code{set record function-call-history-size} command. Functions are
7601 printed in execution order. There are several ways to specify what
7605 @item record function-call-history @var{func}
7606 Prints ten functions starting from function number @var{func}.
7608 @item record function-call-history @var{func}, +/-@var{n}
7609 Prints @var{n} functions around function number @var{func}. If
7610 @var{n} is preceded with @code{+}, prints @var{n} functions after
7611 function number @var{func}. If @var{n} is preceded with @code{-},
7612 prints @var{n} functions before function number @var{func}.
7614 @item record function-call-history
7615 Prints ten more functions after the last ten-line print.
7617 @item record function-call-history -
7618 Prints ten more functions before the last ten-line print.
7620 @item record function-call-history @var{begin}, @var{end}
7621 Prints functions beginning with function number @var{begin} until
7622 function number @var{end}. The function number @var{end} is included.
7625 This command may not be available for all recording methods.
7627 @item set record function-call-history-size @var{size}
7628 @itemx set record function-call-history-size unlimited
7629 Define how many lines to print in the
7630 @code{record function-call-history} command. The default value is 10.
7631 A size of @code{unlimited} means unlimited lines.
7633 @item show record function-call-history-size
7634 Show how many lines to print in the
7635 @code{record function-call-history} command.
7640 @chapter Examining the Stack
7642 When your program has stopped, the first thing you need to know is where it
7643 stopped and how it got there.
7646 Each time your program performs a function call, information about the call
7648 That information includes the location of the call in your program,
7649 the arguments of the call,
7650 and the local variables of the function being called.
7651 The information is saved in a block of data called a @dfn{stack frame}.
7652 The stack frames are allocated in a region of memory called the @dfn{call
7655 When your program stops, the @value{GDBN} commands for examining the
7656 stack allow you to see all of this information.
7658 @cindex selected frame
7659 One of the stack frames is @dfn{selected} by @value{GDBN} and many
7660 @value{GDBN} commands refer implicitly to the selected frame. In
7661 particular, whenever you ask @value{GDBN} for the value of a variable in
7662 your program, the value is found in the selected frame. There are
7663 special @value{GDBN} commands to select whichever frame you are
7664 interested in. @xref{Selection, ,Selecting a Frame}.
7666 When your program stops, @value{GDBN} automatically selects the
7667 currently executing frame and describes it briefly, similar to the
7668 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
7671 * Frames:: Stack frames
7672 * Backtrace:: Backtraces
7673 * Selection:: Selecting a frame
7674 * Frame Info:: Information on a frame
7675 * Frame Apply:: Applying a command to several frames
7676 * Frame Filter Management:: Managing frame filters
7681 @section Stack Frames
7683 @cindex frame, definition
7685 The call stack is divided up into contiguous pieces called @dfn{stack
7686 frames}, or @dfn{frames} for short; each frame is the data associated
7687 with one call to one function. The frame contains the arguments given
7688 to the function, the function's local variables, and the address at
7689 which the function is executing.
7691 @cindex initial frame
7692 @cindex outermost frame
7693 @cindex innermost frame
7694 When your program is started, the stack has only one frame, that of the
7695 function @code{main}. This is called the @dfn{initial} frame or the
7696 @dfn{outermost} frame. Each time a function is called, a new frame is
7697 made. Each time a function returns, the frame for that function invocation
7698 is eliminated. If a function is recursive, there can be many frames for
7699 the same function. The frame for the function in which execution is
7700 actually occurring is called the @dfn{innermost} frame. This is the most
7701 recently created of all the stack frames that still exist.
7703 @cindex frame pointer
7704 Inside your program, stack frames are identified by their addresses. A
7705 stack frame consists of many bytes, each of which has its own address; each
7706 kind of computer has a convention for choosing one byte whose
7707 address serves as the address of the frame. Usually this address is kept
7708 in a register called the @dfn{frame pointer register}
7709 (@pxref{Registers, $fp}) while execution is going on in that frame.
7712 @cindex frame number
7713 @value{GDBN} labels each existing stack frame with a @dfn{level}, a
7714 number that is zero for the innermost frame, one for the frame that
7715 called it, and so on upward. These level numbers give you a way of
7716 designating stack frames in @value{GDBN} commands. The terms
7717 @dfn{frame number} and @dfn{frame level} can be used interchangeably to
7718 describe this number.
7720 @c The -fomit-frame-pointer below perennially causes hbox overflow
7721 @c underflow problems.
7722 @cindex frameless execution
7723 Some compilers provide a way to compile functions so that they operate
7724 without stack frames. (For example, the @value{NGCC} option
7726 @samp{-fomit-frame-pointer}
7728 generates functions without a frame.)
7729 This is occasionally done with heavily used library functions to save
7730 the frame setup time. @value{GDBN} has limited facilities for dealing
7731 with these function invocations. If the innermost function invocation
7732 has no stack frame, @value{GDBN} nevertheless regards it as though
7733 it had a separate frame, which is numbered zero as usual, allowing
7734 correct tracing of the function call chain. However, @value{GDBN} has
7735 no provision for frameless functions elsewhere in the stack.
7741 @cindex call stack traces
7742 A backtrace is a summary of how your program got where it is. It shows one
7743 line per frame, for many frames, starting with the currently executing
7744 frame (frame zero), followed by its caller (frame one), and on up the
7747 @anchor{backtrace-command}
7749 @kindex bt @r{(@code{backtrace})}
7750 To print a backtrace of the entire stack, use the @code{backtrace}
7751 command, or its alias @code{bt}. This command will print one line per
7752 frame for frames in the stack. By default, all stack frames are
7753 printed. You can stop the backtrace at any time by typing the system
7754 interrupt character, normally @kbd{Ctrl-c}.
7757 @item backtrace [@var{option}]@dots{} [@var{qualifier}]@dots{} [@var{count}]
7758 @itemx bt [@var{option}]@dots{} [@var{qualifier}]@dots{} [@var{count}]
7759 Print the backtrace of the entire stack.
7761 The optional @var{count} can be one of the following:
7766 Print only the innermost @var{n} frames, where @var{n} is a positive
7771 Print only the outermost @var{n} frames, where @var{n} is a positive
7779 Print the values of the local variables also. This can be combined
7780 with the optional @var{count} to limit the number of frames shown.
7783 Do not run Python frame filters on this backtrace. @xref{Frame
7784 Filter API}, for more information. Additionally use @ref{disable
7785 frame-filter all} to turn off all frame filters. This is only
7786 relevant when @value{GDBN} has been configured with @code{Python}
7790 A Python frame filter might decide to ``elide'' some frames. Normally
7791 such elided frames are still printed, but they are indented relative
7792 to the filtered frames that cause them to be elided. The @code{-hide}
7793 option causes elided frames to not be printed at all.
7796 The @code{backtrace} command also supports a number of options that
7797 allow overriding relevant global print settings as set by @code{set
7798 backtrace} and @code{set print} subcommands:
7801 @item -past-main [@code{on}|@code{off}]
7802 Set whether backtraces should continue past @code{main}. Related setting:
7803 @ref{set backtrace past-main}.
7805 @item -past-entry [@code{on}|@code{off}]
7806 Set whether backtraces should continue past the entry point of a program.
7807 Related setting: @ref{set backtrace past-entry}.
7809 @item -entry-values @code{no}|@code{only}|@code{preferred}|@code{if-needed}|@code{both}|@code{compact}|@code{default}
7810 Set printing of function arguments at function entry.
7811 Related setting: @ref{set print entry-values}.
7813 @item -frame-arguments @code{all}|@code{scalars}|@code{none}
7814 Set printing of non-scalar frame arguments.
7815 Related setting: @ref{set print frame-arguments}.
7817 @item -raw-frame-arguments [@code{on}|@code{off}]
7818 Set whether to print frame arguments in raw form.
7819 Related setting: @ref{set print raw-frame-arguments}.
7821 @item -frame-info @code{auto}|@code{source-line}|@code{location}|@code{source-and-location}|@code{location-and-address}|@code{short-location}
7822 Set printing of frame information.
7823 Related setting: @ref{set print frame-info}.
7826 The optional @var{qualifier} is maintained for backward compatibility.
7827 It can be one of the following:
7831 Equivalent to the @code{-full} option.
7834 Equivalent to the @code{-no-filters} option.
7837 Equivalent to the @code{-hide} option.
7844 The names @code{where} and @code{info stack} (abbreviated @code{info s})
7845 are additional aliases for @code{backtrace}.
7847 @cindex multiple threads, backtrace
7848 In a multi-threaded program, @value{GDBN} by default shows the
7849 backtrace only for the current thread. To display the backtrace for
7850 several or all of the threads, use the command @code{thread apply}
7851 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
7852 apply all backtrace}, @value{GDBN} will display the backtrace for all
7853 the threads; this is handy when you debug a core dump of a
7854 multi-threaded program.
7856 Each line in the backtrace shows the frame number and the function name.
7857 The program counter value is also shown---unless you use @code{set
7858 print address off}. The backtrace also shows the source file name and
7859 line number, as well as the arguments to the function. The program
7860 counter value is omitted if it is at the beginning of the code for that
7863 Here is an example of a backtrace. It was made with the command
7864 @samp{bt 3}, so it shows the innermost three frames.
7868 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7870 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
7871 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
7873 (More stack frames follow...)
7878 The display for frame zero does not begin with a program counter
7879 value, indicating that your program has stopped at the beginning of the
7880 code for line @code{993} of @code{builtin.c}.
7883 The value of parameter @code{data} in frame 1 has been replaced by
7884 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
7885 only if it is a scalar (integer, pointer, enumeration, etc). See command
7886 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
7887 on how to configure the way function parameter values are printed.
7888 The command @kbd{set print frame-info} (@pxref{Print Settings}) controls
7889 what frame information is printed.
7891 @cindex optimized out, in backtrace
7892 @cindex function call arguments, optimized out
7893 If your program was compiled with optimizations, some compilers will
7894 optimize away arguments passed to functions if those arguments are
7895 never used after the call. Such optimizations generate code that
7896 passes arguments through registers, but doesn't store those arguments
7897 in the stack frame. @value{GDBN} has no way of displaying such
7898 arguments in stack frames other than the innermost one. Here's what
7899 such a backtrace might look like:
7903 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7905 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
7906 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
7908 (More stack frames follow...)
7913 The values of arguments that were not saved in their stack frames are
7914 shown as @samp{<optimized out>}.
7916 If you need to display the values of such optimized-out arguments,
7917 either deduce that from other variables whose values depend on the one
7918 you are interested in, or recompile without optimizations.
7920 @cindex backtrace beyond @code{main} function
7921 @cindex program entry point
7922 @cindex startup code, and backtrace
7923 Most programs have a standard user entry point---a place where system
7924 libraries and startup code transition into user code. For C this is
7925 @code{main}@footnote{
7926 Note that embedded programs (the so-called ``free-standing''
7927 environment) are not required to have a @code{main} function as the
7928 entry point. They could even have multiple entry points.}.
7929 When @value{GDBN} finds the entry function in a backtrace
7930 it will terminate the backtrace, to avoid tracing into highly
7931 system-specific (and generally uninteresting) code.
7933 If you need to examine the startup code, or limit the number of levels
7934 in a backtrace, you can change this behavior:
7937 @item set backtrace past-main
7938 @itemx set backtrace past-main on
7939 @anchor{set backtrace past-main}
7940 @kindex set backtrace
7941 Backtraces will continue past the user entry point.
7943 @item set backtrace past-main off
7944 Backtraces will stop when they encounter the user entry point. This is the
7947 @item show backtrace past-main
7948 @kindex show backtrace
7949 Display the current user entry point backtrace policy.
7951 @item set backtrace past-entry
7952 @itemx set backtrace past-entry on
7953 @anchor{set backtrace past-entry}
7954 Backtraces will continue past the internal entry point of an application.
7955 This entry point is encoded by the linker when the application is built,
7956 and is likely before the user entry point @code{main} (or equivalent) is called.
7958 @item set backtrace past-entry off
7959 Backtraces will stop when they encounter the internal entry point of an
7960 application. This is the default.
7962 @item show backtrace past-entry
7963 Display the current internal entry point backtrace policy.
7965 @item set backtrace limit @var{n}
7966 @itemx set backtrace limit 0
7967 @itemx set backtrace limit unlimited
7968 @anchor{set backtrace limit}
7969 @cindex backtrace limit
7970 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
7971 or zero means unlimited levels.
7973 @item show backtrace limit
7974 Display the current limit on backtrace levels.
7977 You can control how file names are displayed.
7980 @item set filename-display
7981 @itemx set filename-display relative
7982 @cindex filename-display
7983 Display file names relative to the compilation directory. This is the default.
7985 @item set filename-display basename
7986 Display only basename of a filename.
7988 @item set filename-display absolute
7989 Display an absolute filename.
7991 @item show filename-display
7992 Show the current way to display filenames.
7996 @section Selecting a Frame
7998 Most commands for examining the stack and other data in your program work on
7999 whichever stack frame is selected at the moment. Here are the commands for
8000 selecting a stack frame; all of them finish by printing a brief description
8001 of the stack frame just selected.
8004 @kindex frame@r{, selecting}
8005 @kindex f @r{(@code{frame})}
8006 @item frame @r{[} @var{frame-selection-spec} @r{]}
8007 @item f @r{[} @var{frame-selection-spec} @r{]}
8008 The @command{frame} command allows different stack frames to be
8009 selected. The @var{frame-selection-spec} can be any of the following:
8014 @item level @var{num}
8015 Select frame level @var{num}. Recall that frame zero is the innermost
8016 (currently executing) frame, frame one is the frame that called the
8017 innermost one, and so on. The highest level frame is usually the one
8020 As this is the most common method of navigating the frame stack, the
8021 string @command{level} can be omitted. For example, the following two
8022 commands are equivalent:
8025 (@value{GDBP}) frame 3
8026 (@value{GDBP}) frame level 3
8029 @kindex frame address
8030 @item address @var{stack-address}
8031 Select the frame with stack address @var{stack-address}. The
8032 @var{stack-address} for a frame can be seen in the output of
8033 @command{info frame}, for example:
8037 Stack level 1, frame at 0x7fffffffda30:
8038 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
8039 tail call frame, caller of frame at 0x7fffffffda30
8040 source language c++.
8041 Arglist at unknown address.
8042 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
8045 The @var{stack-address} for this frame is @code{0x7fffffffda30} as
8046 indicated by the line:
8049 Stack level 1, frame at 0x7fffffffda30:
8052 @kindex frame function
8053 @item function @var{function-name}
8054 Select the stack frame for function @var{function-name}. If there are
8055 multiple stack frames for function @var{function-name} then the inner
8056 most stack frame is selected.
8059 @item view @var{stack-address} @r{[} @var{pc-addr} @r{]}
8060 View a frame that is not part of @value{GDBN}'s backtrace. The frame
8061 viewed has stack address @var{stack-addr}, and optionally, a program
8062 counter address of @var{pc-addr}.
8064 This is useful mainly if the chaining of stack frames has been
8065 damaged by a bug, making it impossible for @value{GDBN} to assign
8066 numbers properly to all frames. In addition, this can be useful
8067 when your program has multiple stacks and switches between them.
8069 When viewing a frame outside the current backtrace using
8070 @command{frame view} then you can always return to the original
8071 stack using one of the previous stack frame selection instructions,
8072 for example @command{frame level 0}.
8078 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
8079 numbers @var{n}, this advances toward the outermost frame, to higher
8080 frame numbers, to frames that have existed longer.
8083 @kindex do @r{(@code{down})}
8085 Move @var{n} frames down the stack; @var{n} defaults to 1. For
8086 positive numbers @var{n}, this advances toward the innermost frame, to
8087 lower frame numbers, to frames that were created more recently.
8088 You may abbreviate @code{down} as @code{do}.
8091 All of these commands end by printing two lines of output describing the
8092 frame. The first line shows the frame number, the function name, the
8093 arguments, and the source file and line number of execution in that
8094 frame. The second line shows the text of that source line.
8102 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
8104 10 read_input_file (argv[i]);
8108 After such a printout, the @code{list} command with no arguments
8109 prints ten lines centered on the point of execution in the frame.
8110 You can also edit the program at the point of execution with your favorite
8111 editing program by typing @code{edit}.
8112 @xref{List, ,Printing Source Lines},
8116 @kindex select-frame
8117 @item select-frame @r{[} @var{frame-selection-spec} @r{]}
8118 The @code{select-frame} command is a variant of @code{frame} that does
8119 not display the new frame after selecting it. This command is
8120 intended primarily for use in @value{GDBN} command scripts, where the
8121 output might be unnecessary and distracting. The
8122 @var{frame-selection-spec} is as for the @command{frame} command
8123 described in @ref{Selection, ,Selecting a Frame}.
8125 @kindex down-silently
8127 @item up-silently @var{n}
8128 @itemx down-silently @var{n}
8129 These two commands are variants of @code{up} and @code{down},
8130 respectively; they differ in that they do their work silently, without
8131 causing display of the new frame. They are intended primarily for use
8132 in @value{GDBN} command scripts, where the output might be unnecessary and
8137 @section Information About a Frame
8139 There are several other commands to print information about the selected
8145 When used without any argument, this command does not change which
8146 frame is selected, but prints a brief description of the currently
8147 selected stack frame. It can be abbreviated @code{f}. With an
8148 argument, this command is used to select a stack frame.
8149 @xref{Selection, ,Selecting a Frame}.
8152 @kindex info f @r{(@code{info frame})}
8155 This command prints a verbose description of the selected stack frame,
8160 the address of the frame
8162 the address of the next frame down (called by this frame)
8164 the address of the next frame up (caller of this frame)
8166 the language in which the source code corresponding to this frame is written
8168 the address of the frame's arguments
8170 the address of the frame's local variables
8172 the program counter saved in it (the address of execution in the caller frame)
8174 which registers were saved in the frame
8177 @noindent The verbose description is useful when
8178 something has gone wrong that has made the stack format fail to fit
8179 the usual conventions.
8181 @item info frame @r{[} @var{frame-selection-spec} @r{]}
8182 @itemx info f @r{[} @var{frame-selection-spec} @r{]}
8183 Print a verbose description of the frame selected by
8184 @var{frame-selection-spec}. The @var{frame-selection-spec} is the
8185 same as for the @command{frame} command (@pxref{Selection, ,Selecting
8186 a Frame}). The selected frame remains unchanged by this command.
8189 @item info args [-q]
8190 Print the arguments of the selected frame, each on a separate line.
8192 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
8193 printing header information and messages explaining why no argument
8196 @item info args [-q] [-t @var{type_regexp}] [@var{regexp}]
8197 Like @kbd{info args}, but only print the arguments selected
8198 with the provided regexp(s).
8200 If @var{regexp} is provided, print only the arguments whose names
8201 match the regular expression @var{regexp}.
8203 If @var{type_regexp} is provided, print only the arguments whose
8204 types, as printed by the @code{whatis} command, match
8205 the regular expression @var{type_regexp}.
8206 If @var{type_regexp} contains space(s), it should be enclosed in
8207 quote characters. If needed, use backslash to escape the meaning
8208 of special characters or quotes.
8210 If both @var{regexp} and @var{type_regexp} are provided, an argument
8211 is printed only if its name matches @var{regexp} and its type matches
8214 @item info locals [-q]
8216 Print the local variables of the selected frame, each on a separate
8217 line. These are all variables (declared either static or automatic)
8218 accessible at the point of execution of the selected frame.
8220 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
8221 printing header information and messages explaining why no local variables
8224 @item info locals [-q] [-t @var{type_regexp}] [@var{regexp}]
8225 Like @kbd{info locals}, but only print the local variables selected
8226 with the provided regexp(s).
8228 If @var{regexp} is provided, print only the local variables whose names
8229 match the regular expression @var{regexp}.
8231 If @var{type_regexp} is provided, print only the local variables whose
8232 types, as printed by the @code{whatis} command, match
8233 the regular expression @var{type_regexp}.
8234 If @var{type_regexp} contains space(s), it should be enclosed in
8235 quote characters. If needed, use backslash to escape the meaning
8236 of special characters or quotes.
8238 If both @var{regexp} and @var{type_regexp} are provided, a local variable
8239 is printed only if its name matches @var{regexp} and its type matches
8242 The command @kbd{info locals -q -t @var{type_regexp}} can usefully be
8243 combined with the commands @kbd{frame apply} and @kbd{thread apply}.
8244 For example, your program might use Resource Acquisition Is
8245 Initialization types (RAII) such as @code{lock_something_t}: each
8246 local variable of type @code{lock_something_t} automatically places a
8247 lock that is destroyed when the variable goes out of scope. You can
8248 then list all acquired locks in your program by doing
8250 thread apply all -s frame apply all -s info locals -q -t lock_something_t
8253 or the equivalent shorter form
8255 tfaas i lo -q -t lock_something_t
8261 @section Applying a Command to Several Frames.
8262 @anchor{frame apply}
8264 @cindex apply command to several frames
8266 @item frame apply [all | @var{count} | @var{-count} | level @var{level}@dots{}] [@var{option}]@dots{} @var{command}
8267 The @code{frame apply} command allows you to apply the named
8268 @var{command} to one or more frames.
8272 Specify @code{all} to apply @var{command} to all frames.
8275 Use @var{count} to apply @var{command} to the innermost @var{count}
8276 frames, where @var{count} is a positive number.
8279 Use @var{-count} to apply @var{command} to the outermost @var{count}
8280 frames, where @var{count} is a positive number.
8283 Use @code{level} to apply @var{command} to the set of frames identified
8284 by the @var{level} list. @var{level} is a frame level or a range of frame
8285 levels as @var{level1}-@var{level2}. The frame level is the number shown
8286 in the first field of the @samp{backtrace} command output.
8287 E.g., @samp{2-4 6-8 3} indicates to apply @var{command} for the frames
8288 at levels 2, 3, 4, 6, 7, 8, and then again on frame at level 3.
8292 Note that the frames on which @code{frame apply} applies a command are
8293 also influenced by the @code{set backtrace} settings such as @code{set
8294 backtrace past-main} and @code{set backtrace limit N}.
8295 @xref{Backtrace,,Backtraces}.
8297 The @code{frame apply} command also supports a number of options that
8298 allow overriding relevant @code{set backtrace} settings:
8301 @item -past-main [@code{on}|@code{off}]
8302 Whether backtraces should continue past @code{main}.
8303 Related setting: @ref{set backtrace past-main}.
8305 @item -past-entry [@code{on}|@code{off}]
8306 Whether backtraces should continue past the entry point of a program.
8307 Related setting: @ref{set backtrace past-entry}.
8310 By default, @value{GDBN} displays some frame information before the
8311 output produced by @var{command}, and an error raised during the
8312 execution of a @var{command} will abort @code{frame apply}. The
8313 following options can be used to fine-tune these behaviors:
8317 The flag @code{-c}, which stands for @samp{continue}, causes any
8318 errors in @var{command} to be displayed, and the execution of
8319 @code{frame apply} then continues.
8321 The flag @code{-s}, which stands for @samp{silent}, causes any errors
8322 or empty output produced by a @var{command} to be silently ignored.
8323 That is, the execution continues, but the frame information and errors
8326 The flag @code{-q} (@samp{quiet}) disables printing the frame
8330 The following example shows how the flags @code{-c} and @code{-s} are
8331 working when applying the command @code{p j} to all frames, where
8332 variable @code{j} can only be successfully printed in the outermost
8333 @code{#1 main} frame.
8337 (gdb) frame apply all p j
8338 #0 some_function (i=5) at fun.c:4
8339 No symbol "j" in current context.
8340 (gdb) frame apply all -c p j
8341 #0 some_function (i=5) at fun.c:4
8342 No symbol "j" in current context.
8343 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8345 (gdb) frame apply all -s p j
8346 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8352 By default, @samp{frame apply}, prints the frame location
8353 information before the command output:
8357 (gdb) frame apply all p $sp
8358 #0 some_function (i=5) at fun.c:4
8359 $4 = (void *) 0xffffd1e0
8360 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8361 $5 = (void *) 0xffffd1f0
8366 If the flag @code{-q} is given, no frame information is printed:
8369 (gdb) frame apply all -q p $sp
8370 $12 = (void *) 0xffffd1e0
8371 $13 = (void *) 0xffffd1f0
8381 @cindex apply a command to all frames (ignoring errors and empty output)
8382 @item faas @var{command}
8383 Shortcut for @code{frame apply all -s @var{command}}.
8384 Applies @var{command} on all frames, ignoring errors and empty output.
8386 It can for example be used to print a local variable or a function
8387 argument without knowing the frame where this variable or argument
8390 (@value{GDBP}) faas p some_local_var_i_do_not_remember_where_it_is
8393 The @code{faas} command accepts the same options as the @code{frame
8394 apply} command. @xref{frame apply}.
8396 Note that the command @code{tfaas @var{command}} applies @var{command}
8397 on all frames of all threads. See @xref{Threads,,Threads}.
8401 @node Frame Filter Management
8402 @section Management of Frame Filters.
8403 @cindex managing frame filters
8405 Frame filters are Python based utilities to manage and decorate the
8406 output of frames. @xref{Frame Filter API}, for further information.
8408 Managing frame filters is performed by several commands available
8409 within @value{GDBN}, detailed here.
8412 @kindex info frame-filter
8413 @item info frame-filter
8414 Print a list of installed frame filters from all dictionaries, showing
8415 their name, priority and enabled status.
8417 @kindex disable frame-filter
8418 @anchor{disable frame-filter all}
8419 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
8420 Disable a frame filter in the dictionary matching
8421 @var{filter-dictionary} and @var{filter-name}. The
8422 @var{filter-dictionary} may be @code{all}, @code{global},
8423 @code{progspace}, or the name of the object file where the frame filter
8424 dictionary resides. When @code{all} is specified, all frame filters
8425 across all dictionaries are disabled. The @var{filter-name} is the name
8426 of the frame filter and is used when @code{all} is not the option for
8427 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
8428 may be enabled again later.
8430 @kindex enable frame-filter
8431 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
8432 Enable a frame filter in the dictionary matching
8433 @var{filter-dictionary} and @var{filter-name}. The
8434 @var{filter-dictionary} may be @code{all}, @code{global},
8435 @code{progspace} or the name of the object file where the frame filter
8436 dictionary resides. When @code{all} is specified, all frame filters across
8437 all dictionaries are enabled. The @var{filter-name} is the name of the frame
8438 filter and is used when @code{all} is not the option for
8439 @var{filter-dictionary}.
8444 (gdb) info frame-filter
8446 global frame-filters:
8447 Priority Enabled Name
8448 1000 No PrimaryFunctionFilter
8451 progspace /build/test frame-filters:
8452 Priority Enabled Name
8453 100 Yes ProgspaceFilter
8455 objfile /build/test frame-filters:
8456 Priority Enabled Name
8457 999 Yes BuildProgra Filter
8459 (gdb) disable frame-filter /build/test BuildProgramFilter
8460 (gdb) info frame-filter
8462 global frame-filters:
8463 Priority Enabled Name
8464 1000 No PrimaryFunctionFilter
8467 progspace /build/test frame-filters:
8468 Priority Enabled Name
8469 100 Yes ProgspaceFilter
8471 objfile /build/test frame-filters:
8472 Priority Enabled Name
8473 999 No BuildProgramFilter
8475 (gdb) enable frame-filter global PrimaryFunctionFilter
8476 (gdb) info frame-filter
8478 global frame-filters:
8479 Priority Enabled Name
8480 1000 Yes PrimaryFunctionFilter
8483 progspace /build/test frame-filters:
8484 Priority Enabled Name
8485 100 Yes ProgspaceFilter
8487 objfile /build/test frame-filters:
8488 Priority Enabled Name
8489 999 No BuildProgramFilter
8492 @kindex set frame-filter priority
8493 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
8494 Set the @var{priority} of a frame filter in the dictionary matching
8495 @var{filter-dictionary}, and the frame filter name matching
8496 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
8497 @code{progspace} or the name of the object file where the frame filter
8498 dictionary resides. The @var{priority} is an integer.
8500 @kindex show frame-filter priority
8501 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
8502 Show the @var{priority} of a frame filter in the dictionary matching
8503 @var{filter-dictionary}, and the frame filter name matching
8504 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
8505 @code{progspace} or the name of the object file where the frame filter
8511 (gdb) info frame-filter
8513 global frame-filters:
8514 Priority Enabled Name
8515 1000 Yes PrimaryFunctionFilter
8518 progspace /build/test frame-filters:
8519 Priority Enabled Name
8520 100 Yes ProgspaceFilter
8522 objfile /build/test frame-filters:
8523 Priority Enabled Name
8524 999 No BuildProgramFilter
8526 (gdb) set frame-filter priority global Reverse 50
8527 (gdb) info frame-filter
8529 global frame-filters:
8530 Priority Enabled Name
8531 1000 Yes PrimaryFunctionFilter
8534 progspace /build/test frame-filters:
8535 Priority Enabled Name
8536 100 Yes ProgspaceFilter
8538 objfile /build/test frame-filters:
8539 Priority Enabled Name
8540 999 No BuildProgramFilter
8545 @chapter Examining Source Files
8547 @value{GDBN} can print parts of your program's source, since the debugging
8548 information recorded in the program tells @value{GDBN} what source files were
8549 used to build it. When your program stops, @value{GDBN} spontaneously prints
8550 the line where it stopped. Likewise, when you select a stack frame
8551 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
8552 execution in that frame has stopped. You can print other portions of
8553 source files by explicit command.
8555 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
8556 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
8557 @value{GDBN} under @sc{gnu} Emacs}.
8560 * List:: Printing source lines
8561 * Specify Location:: How to specify code locations
8562 * Edit:: Editing source files
8563 * Search:: Searching source files
8564 * Source Path:: Specifying source directories
8565 * Machine Code:: Source and machine code
8569 @section Printing Source Lines
8572 @kindex l @r{(@code{list})}
8573 To print lines from a source file, use the @code{list} command
8574 (abbreviated @code{l}). By default, ten lines are printed.
8575 There are several ways to specify what part of the file you want to
8576 print; see @ref{Specify Location}, for the full list.
8578 Here are the forms of the @code{list} command most commonly used:
8581 @item list @var{linenum}
8582 Print lines centered around line number @var{linenum} in the
8583 current source file.
8585 @item list @var{function}
8586 Print lines centered around the beginning of function
8590 Print more lines. If the last lines printed were printed with a
8591 @code{list} command, this prints lines following the last lines
8592 printed; however, if the last line printed was a solitary line printed
8593 as part of displaying a stack frame (@pxref{Stack, ,Examining the
8594 Stack}), this prints lines centered around that line.
8597 Print lines just before the lines last printed.
8600 @cindex @code{list}, how many lines to display
8601 By default, @value{GDBN} prints ten source lines with any of these forms of
8602 the @code{list} command. You can change this using @code{set listsize}:
8605 @kindex set listsize
8606 @item set listsize @var{count}
8607 @itemx set listsize unlimited
8608 Make the @code{list} command display @var{count} source lines (unless
8609 the @code{list} argument explicitly specifies some other number).
8610 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
8612 @kindex show listsize
8614 Display the number of lines that @code{list} prints.
8617 Repeating a @code{list} command with @key{RET} discards the argument,
8618 so it is equivalent to typing just @code{list}. This is more useful
8619 than listing the same lines again. An exception is made for an
8620 argument of @samp{-}; that argument is preserved in repetition so that
8621 each repetition moves up in the source file.
8623 In general, the @code{list} command expects you to supply zero, one or two
8624 @dfn{locations}. Locations specify source lines; there are several ways
8625 of writing them (@pxref{Specify Location}), but the effect is always
8626 to specify some source line.
8628 Here is a complete description of the possible arguments for @code{list}:
8631 @item list @var{location}
8632 Print lines centered around the line specified by @var{location}.
8634 @item list @var{first},@var{last}
8635 Print lines from @var{first} to @var{last}. Both arguments are
8636 locations. When a @code{list} command has two locations, and the
8637 source file of the second location is omitted, this refers to
8638 the same source file as the first location.
8640 @item list ,@var{last}
8641 Print lines ending with @var{last}.
8643 @item list @var{first},
8644 Print lines starting with @var{first}.
8647 Print lines just after the lines last printed.
8650 Print lines just before the lines last printed.
8653 As described in the preceding table.
8656 @node Specify Location
8657 @section Specifying a Location
8658 @cindex specifying location
8660 @cindex source location
8663 * Linespec Locations:: Linespec locations
8664 * Explicit Locations:: Explicit locations
8665 * Address Locations:: Address locations
8668 Several @value{GDBN} commands accept arguments that specify a location
8669 of your program's code. Since @value{GDBN} is a source-level
8670 debugger, a location usually specifies some line in the source code.
8671 Locations may be specified using three different formats:
8672 linespec locations, explicit locations, or address locations.
8674 @node Linespec Locations
8675 @subsection Linespec Locations
8676 @cindex linespec locations
8678 A @dfn{linespec} is a colon-separated list of source location parameters such
8679 as file name, function name, etc. Here are all the different ways of
8680 specifying a linespec:
8684 Specifies the line number @var{linenum} of the current source file.
8687 @itemx +@var{offset}
8688 Specifies the line @var{offset} lines before or after the @dfn{current
8689 line}. For the @code{list} command, the current line is the last one
8690 printed; for the breakpoint commands, this is the line at which
8691 execution stopped in the currently selected @dfn{stack frame}
8692 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
8693 used as the second of the two linespecs in a @code{list} command,
8694 this specifies the line @var{offset} lines up or down from the first
8697 @item @var{filename}:@var{linenum}
8698 Specifies the line @var{linenum} in the source file @var{filename}.
8699 If @var{filename} is a relative file name, then it will match any
8700 source file name with the same trailing components. For example, if
8701 @var{filename} is @samp{gcc/expr.c}, then it will match source file
8702 name of @file{/build/trunk/gcc/expr.c}, but not
8703 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
8705 @item @var{function}
8706 Specifies the line that begins the body of the function @var{function}.
8707 For example, in C, this is the line with the open brace.
8709 By default, in C@t{++} and Ada, @var{function} is interpreted as
8710 specifying all functions named @var{function} in all scopes. For
8711 C@t{++}, this means in all namespaces and classes. For Ada, this
8712 means in all packages.
8714 For example, assuming a program with C@t{++} symbols named
8715 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
8716 func}} and @w{@kbd{break B::func}} set a breakpoint on both symbols.
8718 Commands that accept a linespec let you override this with the
8719 @code{-qualified} option. For example, @w{@kbd{break -qualified
8720 func}} sets a breakpoint on a free-function named @code{func} ignoring
8721 any C@t{++} class methods and namespace functions called @code{func}.
8723 @xref{Explicit Locations}.
8725 @item @var{function}:@var{label}
8726 Specifies the line where @var{label} appears in @var{function}.
8728 @item @var{filename}:@var{function}
8729 Specifies the line that begins the body of the function @var{function}
8730 in the file @var{filename}. You only need the file name with a
8731 function name to avoid ambiguity when there are identically named
8732 functions in different source files.
8735 Specifies the line at which the label named @var{label} appears
8736 in the function corresponding to the currently selected stack frame.
8737 If there is no current selected stack frame (for instance, if the inferior
8738 is not running), then @value{GDBN} will not search for a label.
8740 @cindex breakpoint at static probe point
8741 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
8742 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
8743 applications to embed static probes. @xref{Static Probe Points}, for more
8744 information on finding and using static probes. This form of linespec
8745 specifies the location of such a static probe.
8747 If @var{objfile} is given, only probes coming from that shared library
8748 or executable matching @var{objfile} as a regular expression are considered.
8749 If @var{provider} is given, then only probes from that provider are considered.
8750 If several probes match the spec, @value{GDBN} will insert a breakpoint at
8751 each one of those probes.
8754 @node Explicit Locations
8755 @subsection Explicit Locations
8756 @cindex explicit locations
8758 @dfn{Explicit locations} allow the user to directly specify the source
8759 location's parameters using option-value pairs.
8761 Explicit locations are useful when several functions, labels, or
8762 file names have the same name (base name for files) in the program's
8763 sources. In these cases, explicit locations point to the source
8764 line you meant more accurately and unambiguously. Also, using
8765 explicit locations might be faster in large programs.
8767 For example, the linespec @samp{foo:bar} may refer to a function @code{bar}
8768 defined in the file named @file{foo} or the label @code{bar} in a function
8769 named @code{foo}. @value{GDBN} must search either the file system or
8770 the symbol table to know.
8772 The list of valid explicit location options is summarized in the
8776 @item -source @var{filename}
8777 The value specifies the source file name. To differentiate between
8778 files with the same base name, prepend as many directories as is necessary
8779 to uniquely identify the desired file, e.g., @file{foo/bar/baz.c}. Otherwise
8780 @value{GDBN} will use the first file it finds with the given base
8781 name. This option requires the use of either @code{-function} or @code{-line}.
8783 @item -function @var{function}
8784 The value specifies the name of a function. Operations
8785 on function locations unmodified by other options (such as @code{-label}
8786 or @code{-line}) refer to the line that begins the body of the function.
8787 In C, for example, this is the line with the open brace.
8789 By default, in C@t{++} and Ada, @var{function} is interpreted as
8790 specifying all functions named @var{function} in all scopes. For
8791 C@t{++}, this means in all namespaces and classes. For Ada, this
8792 means in all packages.
8794 For example, assuming a program with C@t{++} symbols named
8795 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
8796 -function func}} and @w{@kbd{break -function B::func}} set a
8797 breakpoint on both symbols.
8799 You can use the @kbd{-qualified} flag to override this (see below).
8803 This flag makes @value{GDBN} interpret a function name specified with
8804 @kbd{-function} as a complete fully-qualified name.
8806 For example, assuming a C@t{++} program with symbols named
8807 @code{A::B::func} and @code{B::func}, the @w{@kbd{break -qualified
8808 -function B::func}} command sets a breakpoint on @code{B::func}, only.
8810 (Note: the @kbd{-qualified} option can precede a linespec as well
8811 (@pxref{Linespec Locations}), so the particular example above could be
8812 simplified as @w{@kbd{break -qualified B::func}}.)
8814 @item -label @var{label}
8815 The value specifies the name of a label. When the function
8816 name is not specified, the label is searched in the function of the currently
8817 selected stack frame.
8819 @item -line @var{number}
8820 The value specifies a line offset for the location. The offset may either
8821 be absolute (@code{-line 3}) or relative (@code{-line +3}), depending on
8822 the command. When specified without any other options, the line offset is
8823 relative to the current line.
8826 Explicit location options may be abbreviated by omitting any non-unique
8827 trailing characters from the option name, e.g., @w{@kbd{break -s main.c -li 3}}.
8829 @node Address Locations
8830 @subsection Address Locations
8831 @cindex address locations
8833 @dfn{Address locations} indicate a specific program address. They have
8834 the generalized form *@var{address}.
8836 For line-oriented commands, such as @code{list} and @code{edit}, this
8837 specifies a source line that contains @var{address}. For @code{break} and
8838 other breakpoint-oriented commands, this can be used to set breakpoints in
8839 parts of your program which do not have debugging information or
8842 Here @var{address} may be any expression valid in the current working
8843 language (@pxref{Languages, working language}) that specifies a code
8844 address. In addition, as a convenience, @value{GDBN} extends the
8845 semantics of expressions used in locations to cover several situations
8846 that frequently occur during debugging. Here are the various forms
8850 @item @var{expression}
8851 Any expression valid in the current working language.
8853 @item @var{funcaddr}
8854 An address of a function or procedure derived from its name. In C,
8855 C@t{++}, Objective-C, Fortran, minimal, and assembly, this is
8856 simply the function's name @var{function} (and actually a special case
8857 of a valid expression). In Pascal and Modula-2, this is
8858 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
8859 (although the Pascal form also works).
8861 This form specifies the address of the function's first instruction,
8862 before the stack frame and arguments have been set up.
8864 @item '@var{filename}':@var{funcaddr}
8865 Like @var{funcaddr} above, but also specifies the name of the source
8866 file explicitly. This is useful if the name of the function does not
8867 specify the function unambiguously, e.g., if there are several
8868 functions with identical names in different source files.
8872 @section Editing Source Files
8873 @cindex editing source files
8876 @kindex e @r{(@code{edit})}
8877 To edit the lines in a source file, use the @code{edit} command.
8878 The editing program of your choice
8879 is invoked with the current line set to
8880 the active line in the program.
8881 Alternatively, there are several ways to specify what part of the file you
8882 want to print if you want to see other parts of the program:
8885 @item edit @var{location}
8886 Edit the source file specified by @code{location}. Editing starts at
8887 that @var{location}, e.g., at the specified source line of the
8888 specified file. @xref{Specify Location}, for all the possible forms
8889 of the @var{location} argument; here are the forms of the @code{edit}
8890 command most commonly used:
8893 @item edit @var{number}
8894 Edit the current source file with @var{number} as the active line number.
8896 @item edit @var{function}
8897 Edit the file containing @var{function} at the beginning of its definition.
8902 @subsection Choosing your Editor
8903 You can customize @value{GDBN} to use any editor you want
8905 The only restriction is that your editor (say @code{ex}), recognizes the
8906 following command-line syntax:
8908 ex +@var{number} file
8910 The optional numeric value +@var{number} specifies the number of the line in
8911 the file where to start editing.}.
8912 By default, it is @file{@value{EDITOR}}, but you can change this
8913 by setting the environment variable @code{EDITOR} before using
8914 @value{GDBN}. For example, to configure @value{GDBN} to use the
8915 @code{vi} editor, you could use these commands with the @code{sh} shell:
8921 or in the @code{csh} shell,
8923 setenv EDITOR /usr/bin/vi
8928 @section Searching Source Files
8929 @cindex searching source files
8931 There are two commands for searching through the current source file for a
8936 @kindex forward-search
8937 @kindex fo @r{(@code{forward-search})}
8938 @item forward-search @var{regexp}
8939 @itemx search @var{regexp}
8940 The command @samp{forward-search @var{regexp}} checks each line,
8941 starting with the one following the last line listed, for a match for
8942 @var{regexp}. It lists the line that is found. You can use the
8943 synonym @samp{search @var{regexp}} or abbreviate the command name as
8946 @kindex reverse-search
8947 @item reverse-search @var{regexp}
8948 The command @samp{reverse-search @var{regexp}} checks each line, starting
8949 with the one before the last line listed and going backward, for a match
8950 for @var{regexp}. It lists the line that is found. You can abbreviate
8951 this command as @code{rev}.
8955 @section Specifying Source Directories
8958 @cindex directories for source files
8959 Executable programs sometimes do not record the directories of the source
8960 files from which they were compiled, just the names. Even when they do,
8961 the directories could be moved between the compilation and your debugging
8962 session. @value{GDBN} has a list of directories to search for source files;
8963 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
8964 it tries all the directories in the list, in the order they are present
8965 in the list, until it finds a file with the desired name.
8967 For example, suppose an executable references the file
8968 @file{/usr/src/foo-1.0/lib/foo.c}, does not record a compilation
8969 directory, and the @dfn{source path} is @file{/mnt/cross}.
8970 @value{GDBN} would look for the source file in the following
8975 @item @file{/usr/src/foo-1.0/lib/foo.c}
8976 @item @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c}
8977 @item @file{/mnt/cross/foo.c}
8981 If the source file is not present at any of the above locations then
8982 an error is printed. @value{GDBN} does not look up the parts of the
8983 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
8984 Likewise, the subdirectories of the source path are not searched: if
8985 the source path is @file{/mnt/cross}, and the binary refers to
8986 @file{foo.c}, @value{GDBN} would not find it under
8987 @file{/mnt/cross/usr/src/foo-1.0/lib}.
8989 Plain file names, relative file names with leading directories, file
8990 names containing dots, etc.@: are all treated as described above,
8991 except that non-absolute file names are not looked up literally. If
8992 the @dfn{source path} is @file{/mnt/cross}, the source file is
8993 recorded as @file{../lib/foo.c}, and no compilation directory is
8994 recorded, then @value{GDBN} will search in the following locations:
8998 @item @file{/mnt/cross/../lib/foo.c}
8999 @item @file{/mnt/cross/foo.c}
9005 @vindex $cdir@r{, convenience variable}
9006 @vindex $cwd@r{, convenience variable}
9007 @cindex compilation directory
9008 @cindex current directory
9009 @cindex working directory
9010 @cindex directory, current
9011 @cindex directory, compilation
9012 The @dfn{source path} will always include two special entries
9013 @samp{$cdir} and @samp{$cwd}, these refer to the compilation directory
9014 (if one is recorded) and the current working directory respectively.
9016 @samp{$cdir} causes @value{GDBN} to search within the compilation
9017 directory, if one is recorded in the debug information. If no
9018 compilation directory is recorded in the debug information then
9019 @samp{$cdir} is ignored.
9021 @samp{$cwd} is not the same as @samp{.}---the former tracks the
9022 current working directory as it changes during your @value{GDBN}
9023 session, while the latter is immediately expanded to the current
9024 directory at the time you add an entry to the source path.
9026 If a compilation directory is recorded in the debug information, and
9027 @value{GDBN} has not found the source file after the first search
9028 using @dfn{source path}, then @value{GDBN} will combine the
9029 compilation directory and the filename, and then search for the source
9030 file again using the @dfn{source path}.
9032 For example, if the executable records the source file as
9033 @file{/usr/src/foo-1.0/lib/foo.c}, the compilation directory is
9034 recorded as @file{/project/build}, and the @dfn{source path} is
9035 @file{/mnt/cross:$cdir:$cwd} while the current working directory of
9036 the @value{GDBN} session is @file{/home/user}, then @value{GDBN} will
9037 search for the source file in the following loctions:
9041 @item @file{/usr/src/foo-1.0/lib/foo.c}
9042 @item @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c}
9043 @item @file{/project/build/usr/src/foo-1.0/lib/foo.c}
9044 @item @file{/home/user/usr/src/foo-1.0/lib/foo.c}
9045 @item @file{/mnt/cross/project/build/usr/src/foo-1.0/lib/foo.c}
9046 @item @file{/project/build/project/build/usr/src/foo-1.0/lib/foo.c}
9047 @item @file{/home/user/project/build/usr/src/foo-1.0/lib/foo.c}
9048 @item @file{/mnt/cross/foo.c}
9049 @item @file{/project/build/foo.c}
9050 @item @file{/home/user/foo.c}
9054 If the file name in the previous example had been recorded in the
9055 executable as a relative path rather than an absolute path, then the
9056 first look up would not have occurred, but all of the remaining steps
9059 When searching for source files on MS-DOS and MS-Windows, where
9060 absolute paths start with a drive letter (e.g.
9061 @file{C:/project/foo.c}), @value{GDBN} will remove the drive letter
9062 from the file name before appending it to a search directory from
9063 @dfn{source path}; for instance if the executable references the
9064 source file @file{C:/project/foo.c} and @dfn{source path} is set to
9065 @file{D:/mnt/cross}, then @value{GDBN} will search in the following
9066 locations for the source file:
9070 @item @file{C:/project/foo.c}
9071 @item @file{D:/mnt/cross/project/foo.c}
9072 @item @file{D:/mnt/cross/foo.c}
9076 Note that the executable search path is @emph{not} used to locate the
9079 Whenever you reset or rearrange the source path, @value{GDBN} clears out
9080 any information it has cached about where source files are found and where
9081 each line is in the file.
9085 When you start @value{GDBN}, its source path includes only @samp{$cdir}
9086 and @samp{$cwd}, in that order.
9087 To add other directories, use the @code{directory} command.
9089 The search path is used to find both program source files and @value{GDBN}
9090 script files (read using the @samp{-command} option and @samp{source} command).
9092 In addition to the source path, @value{GDBN} provides a set of commands
9093 that manage a list of source path substitution rules. A @dfn{substitution
9094 rule} specifies how to rewrite source directories stored in the program's
9095 debug information in case the sources were moved to a different
9096 directory between compilation and debugging. A rule is made of
9097 two strings, the first specifying what needs to be rewritten in
9098 the path, and the second specifying how it should be rewritten.
9099 In @ref{set substitute-path}, we name these two parts @var{from} and
9100 @var{to} respectively. @value{GDBN} does a simple string replacement
9101 of @var{from} with @var{to} at the start of the directory part of the
9102 source file name, and uses that result instead of the original file
9103 name to look up the sources.
9105 Using the previous example, suppose the @file{foo-1.0} tree has been
9106 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
9107 @value{GDBN} to replace @file{/usr/src} in all source path names with
9108 @file{/mnt/cross}. The first lookup will then be
9109 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
9110 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
9111 substitution rule, use the @code{set substitute-path} command
9112 (@pxref{set substitute-path}).
9114 To avoid unexpected substitution results, a rule is applied only if the
9115 @var{from} part of the directory name ends at a directory separator.
9116 For instance, a rule substituting @file{/usr/source} into
9117 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
9118 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
9119 is applied only at the beginning of the directory name, this rule will
9120 not be applied to @file{/root/usr/source/baz.c} either.
9122 In many cases, you can achieve the same result using the @code{directory}
9123 command. However, @code{set substitute-path} can be more efficient in
9124 the case where the sources are organized in a complex tree with multiple
9125 subdirectories. With the @code{directory} command, you need to add each
9126 subdirectory of your project. If you moved the entire tree while
9127 preserving its internal organization, then @code{set substitute-path}
9128 allows you to direct the debugger to all the sources with one single
9131 @code{set substitute-path} is also more than just a shortcut command.
9132 The source path is only used if the file at the original location no
9133 longer exists. On the other hand, @code{set substitute-path} modifies
9134 the debugger behavior to look at the rewritten location instead. So, if
9135 for any reason a source file that is not relevant to your executable is
9136 located at the original location, a substitution rule is the only
9137 method available to point @value{GDBN} at the new location.
9139 @cindex @samp{--with-relocated-sources}
9140 @cindex default source path substitution
9141 You can configure a default source path substitution rule by
9142 configuring @value{GDBN} with the
9143 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
9144 should be the name of a directory under @value{GDBN}'s configured
9145 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
9146 directory names in debug information under @var{dir} will be adjusted
9147 automatically if the installed @value{GDBN} is moved to a new
9148 location. This is useful if @value{GDBN}, libraries or executables
9149 with debug information and corresponding source code are being moved
9153 @item directory @var{dirname} @dots{}
9154 @item dir @var{dirname} @dots{}
9155 Add directory @var{dirname} to the front of the source path. Several
9156 directory names may be given to this command, separated by @samp{:}
9157 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
9158 part of absolute file names) or
9159 whitespace. You may specify a directory that is already in the source
9160 path; this moves it forward, so @value{GDBN} searches it sooner.
9162 The special strings @samp{$cdir} (to refer to the compilation
9163 directory, if one is recorded), and @samp{$cwd} (to refer to the
9164 current working directory) can also be included in the list of
9165 directories @var{dirname}. Though these will already be in the source
9166 path they will be moved forward in the list so @value{GDBN} searches
9170 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
9172 @c RET-repeat for @code{directory} is explicitly disabled, but since
9173 @c repeating it would be a no-op we do not say that. (thanks to RMS)
9175 @item set directories @var{path-list}
9176 @kindex set directories
9177 Set the source path to @var{path-list}.
9178 @samp{$cdir:$cwd} are added if missing.
9180 @item show directories
9181 @kindex show directories
9182 Print the source path: show which directories it contains.
9184 @anchor{set substitute-path}
9185 @item set substitute-path @var{from} @var{to}
9186 @kindex set substitute-path
9187 Define a source path substitution rule, and add it at the end of the
9188 current list of existing substitution rules. If a rule with the same
9189 @var{from} was already defined, then the old rule is also deleted.
9191 For example, if the file @file{/foo/bar/baz.c} was moved to
9192 @file{/mnt/cross/baz.c}, then the command
9195 (@value{GDBP}) set substitute-path /foo/bar /mnt/cross
9199 will tell @value{GDBN} to replace @samp{/foo/bar} with
9200 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
9201 @file{baz.c} even though it was moved.
9203 In the case when more than one substitution rule have been defined,
9204 the rules are evaluated one by one in the order where they have been
9205 defined. The first one matching, if any, is selected to perform
9208 For instance, if we had entered the following commands:
9211 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
9212 (@value{GDBP}) set substitute-path /usr/src /mnt/src
9216 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
9217 @file{/mnt/include/defs.h} by using the first rule. However, it would
9218 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
9219 @file{/mnt/src/lib/foo.c}.
9222 @item unset substitute-path [path]
9223 @kindex unset substitute-path
9224 If a path is specified, search the current list of substitution rules
9225 for a rule that would rewrite that path. Delete that rule if found.
9226 A warning is emitted by the debugger if no rule could be found.
9228 If no path is specified, then all substitution rules are deleted.
9230 @item show substitute-path [path]
9231 @kindex show substitute-path
9232 If a path is specified, then print the source path substitution rule
9233 which would rewrite that path, if any.
9235 If no path is specified, then print all existing source path substitution
9240 If your source path is cluttered with directories that are no longer of
9241 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
9242 versions of source. You can correct the situation as follows:
9246 Use @code{directory} with no argument to reset the source path to its default value.
9249 Use @code{directory} with suitable arguments to reinstall the
9250 directories you want in the source path. You can add all the
9251 directories in one command.
9255 @section Source and Machine Code
9256 @cindex source line and its code address
9258 You can use the command @code{info line} to map source lines to program
9259 addresses (and vice versa), and the command @code{disassemble} to display
9260 a range of addresses as machine instructions. You can use the command
9261 @code{set disassemble-next-line} to set whether to disassemble next
9262 source line when execution stops. When run under @sc{gnu} Emacs
9263 mode, the @code{info line} command causes the arrow to point to the
9264 line specified. Also, @code{info line} prints addresses in symbolic form as
9270 @itemx info line @var{location}
9271 Print the starting and ending addresses of the compiled code for
9272 source line @var{location}. You can specify source lines in any of
9273 the ways documented in @ref{Specify Location}. With no @var{location}
9274 information about the current source line is printed.
9277 For example, we can use @code{info line} to discover the location of
9278 the object code for the first line of function
9279 @code{m4_changequote}:
9282 (@value{GDBP}) info line m4_changequote
9283 Line 895 of "builtin.c" starts at pc 0x634c <m4_changequote> and \
9284 ends at 0x6350 <m4_changequote+4>.
9288 @cindex code address and its source line
9289 We can also inquire (using @code{*@var{addr}} as the form for
9290 @var{location}) what source line covers a particular address:
9292 (@value{GDBP}) info line *0x63ff
9293 Line 926 of "builtin.c" starts at pc 0x63e4 <m4_changequote+152> and \
9294 ends at 0x6404 <m4_changequote+184>.
9297 @cindex @code{$_} and @code{info line}
9298 @cindex @code{x} command, default address
9299 @kindex x@r{(examine), and} info line
9300 After @code{info line}, the default address for the @code{x} command
9301 is changed to the starting address of the line, so that @samp{x/i} is
9302 sufficient to begin examining the machine code (@pxref{Memory,
9303 ,Examining Memory}). Also, this address is saved as the value of the
9304 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
9307 @cindex info line, repeated calls
9308 After @code{info line}, using @code{info line} again without
9309 specifying a location will display information about the next source
9314 @cindex assembly instructions
9315 @cindex instructions, assembly
9316 @cindex machine instructions
9317 @cindex listing machine instructions
9319 @itemx disassemble /m
9320 @itemx disassemble /s
9321 @itemx disassemble /r
9322 This specialized command dumps a range of memory as machine
9323 instructions. It can also print mixed source+disassembly by specifying
9324 the @code{/m} or @code{/s} modifier and print the raw instructions in hex
9325 as well as in symbolic form by specifying the @code{/r} modifier.
9326 The default memory range is the function surrounding the
9327 program counter of the selected frame. A single argument to this
9328 command is a program counter value; @value{GDBN} dumps the function
9329 surrounding this value. When two arguments are given, they should
9330 be separated by a comma, possibly surrounded by whitespace. The
9331 arguments specify a range of addresses to dump, in one of two forms:
9334 @item @var{start},@var{end}
9335 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
9336 @item @var{start},+@var{length}
9337 the addresses from @var{start} (inclusive) to
9338 @code{@var{start}+@var{length}} (exclusive).
9342 When 2 arguments are specified, the name of the function is also
9343 printed (since there could be several functions in the given range).
9345 The argument(s) can be any expression yielding a numeric value, such as
9346 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
9348 If the range of memory being disassembled contains current program counter,
9349 the instruction at that location is shown with a @code{=>} marker.
9352 The following example shows the disassembly of a range of addresses of
9353 HP PA-RISC 2.0 code:
9356 (@value{GDBP}) disas 0x32c4, 0x32e4
9357 Dump of assembler code from 0x32c4 to 0x32e4:
9358 0x32c4 <main+204>: addil 0,dp
9359 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
9360 0x32cc <main+212>: ldil 0x3000,r31
9361 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
9362 0x32d4 <main+220>: ldo 0(r31),rp
9363 0x32d8 <main+224>: addil -0x800,dp
9364 0x32dc <main+228>: ldo 0x588(r1),r26
9365 0x32e0 <main+232>: ldil 0x3000,r31
9366 End of assembler dump.
9369 Here is an example showing mixed source+assembly for Intel x86
9370 with @code{/m} or @code{/s}, when the program is stopped just after
9371 function prologue in a non-optimized function with no inline code.
9374 (@value{GDBP}) disas /m main
9375 Dump of assembler code for function main:
9377 0x08048330 <+0>: push %ebp
9378 0x08048331 <+1>: mov %esp,%ebp
9379 0x08048333 <+3>: sub $0x8,%esp
9380 0x08048336 <+6>: and $0xfffffff0,%esp
9381 0x08048339 <+9>: sub $0x10,%esp
9383 6 printf ("Hello.\n");
9384 => 0x0804833c <+12>: movl $0x8048440,(%esp)
9385 0x08048343 <+19>: call 0x8048284 <puts@@plt>
9389 0x08048348 <+24>: mov $0x0,%eax
9390 0x0804834d <+29>: leave
9391 0x0804834e <+30>: ret
9393 End of assembler dump.
9396 The @code{/m} option is deprecated as its output is not useful when
9397 there is either inlined code or re-ordered code.
9398 The @code{/s} option is the preferred choice.
9399 Here is an example for AMD x86-64 showing the difference between
9400 @code{/m} output and @code{/s} output.
9401 This example has one inline function defined in a header file,
9402 and the code is compiled with @samp{-O2} optimization.
9403 Note how the @code{/m} output is missing the disassembly of
9404 several instructions that are present in the @code{/s} output.
9434 (@value{GDBP}) disas /m main
9435 Dump of assembler code for function main:
9439 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
9440 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
9444 0x000000000040041d <+29>: xor %eax,%eax
9445 0x000000000040041f <+31>: retq
9446 0x0000000000400420 <+32>: add %eax,%eax
9447 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
9449 End of assembler dump.
9450 (@value{GDBP}) disas /s main
9451 Dump of assembler code for function main:
9455 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
9459 0x0000000000400406 <+6>: test %eax,%eax
9460 0x0000000000400408 <+8>: js 0x400420 <main+32>
9465 0x000000000040040a <+10>: lea 0xa(%rax),%edx
9466 0x000000000040040d <+13>: test %eax,%eax
9467 0x000000000040040f <+15>: mov $0x1,%eax
9468 0x0000000000400414 <+20>: cmovne %edx,%eax
9472 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
9476 0x000000000040041d <+29>: xor %eax,%eax
9477 0x000000000040041f <+31>: retq
9481 0x0000000000400420 <+32>: add %eax,%eax
9482 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
9483 End of assembler dump.
9486 Here is another example showing raw instructions in hex for AMD x86-64,
9489 (gdb) disas /r 0x400281,+10
9490 Dump of assembler code from 0x400281 to 0x40028b:
9491 0x0000000000400281: 38 36 cmp %dh,(%rsi)
9492 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
9493 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
9494 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
9495 End of assembler dump.
9498 Addresses cannot be specified as a location (@pxref{Specify Location}).
9499 So, for example, if you want to disassemble function @code{bar}
9500 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
9501 and not @samp{disassemble foo.c:bar}.
9503 Some architectures have more than one commonly-used set of instruction
9504 mnemonics or other syntax.
9506 For programs that were dynamically linked and use shared libraries,
9507 instructions that call functions or branch to locations in the shared
9508 libraries might show a seemingly bogus location---it's actually a
9509 location of the relocation table. On some architectures, @value{GDBN}
9510 might be able to resolve these to actual function names.
9513 @kindex set disassembler-options
9514 @cindex disassembler options
9515 @item set disassembler-options @var{option1}[,@var{option2}@dots{}]
9516 This command controls the passing of target specific information to
9517 the disassembler. For a list of valid options, please refer to the
9518 @code{-M}/@code{--disassembler-options} section of the @samp{objdump}
9519 manual and/or the output of @kbd{objdump --help}
9520 (@pxref{objdump,,objdump,binutils,The GNU Binary Utilities}).
9521 The default value is the empty string.
9523 If it is necessary to specify more than one disassembler option, then
9524 multiple options can be placed together into a comma separated list.
9525 Currently this command is only supported on targets ARM, MIPS, PowerPC
9528 @kindex show disassembler-options
9529 @item show disassembler-options
9530 Show the current setting of the disassembler options.
9534 @kindex set disassembly-flavor
9535 @cindex Intel disassembly flavor
9536 @cindex AT&T disassembly flavor
9537 @item set disassembly-flavor @var{instruction-set}
9538 Select the instruction set to use when disassembling the
9539 program via the @code{disassemble} or @code{x/i} commands.
9541 Currently this command is only defined for the Intel x86 family. You
9542 can set @var{instruction-set} to either @code{intel} or @code{att}.
9543 The default is @code{att}, the AT&T flavor used by default by Unix
9544 assemblers for x86-based targets.
9546 @kindex show disassembly-flavor
9547 @item show disassembly-flavor
9548 Show the current setting of the disassembly flavor.
9552 @kindex set disassemble-next-line
9553 @kindex show disassemble-next-line
9554 @item set disassemble-next-line
9555 @itemx show disassemble-next-line
9556 Control whether or not @value{GDBN} will disassemble the next source
9557 line or instruction when execution stops. If ON, @value{GDBN} will
9558 display disassembly of the next source line when execution of the
9559 program being debugged stops. This is @emph{in addition} to
9560 displaying the source line itself, which @value{GDBN} always does if
9561 possible. If the next source line cannot be displayed for some reason
9562 (e.g., if @value{GDBN} cannot find the source file, or there's no line
9563 info in the debug info), @value{GDBN} will display disassembly of the
9564 next @emph{instruction} instead of showing the next source line. If
9565 AUTO, @value{GDBN} will display disassembly of next instruction only
9566 if the source line cannot be displayed. This setting causes
9567 @value{GDBN} to display some feedback when you step through a function
9568 with no line info or whose source file is unavailable. The default is
9569 OFF, which means never display the disassembly of the next line or
9575 @chapter Examining Data
9577 @cindex printing data
9578 @cindex examining data
9581 The usual way to examine data in your program is with the @code{print}
9582 command (abbreviated @code{p}), or its synonym @code{inspect}. It
9583 evaluates and prints the value of an expression of the language your
9584 program is written in (@pxref{Languages, ,Using @value{GDBN} with
9585 Different Languages}). It may also print the expression using a
9586 Python-based pretty-printer (@pxref{Pretty Printing}).
9589 @item print [[@var{options}] --] @var{expr}
9590 @itemx print [[@var{options}] --] /@var{f} @var{expr}
9591 @var{expr} is an expression (in the source language). By default the
9592 value of @var{expr} is printed in a format appropriate to its data type;
9593 you can choose a different format by specifying @samp{/@var{f}}, where
9594 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
9597 @anchor{print options}
9598 The @code{print} command supports a number of options that allow
9599 overriding relevant global print settings as set by @code{set print}
9603 @item -address [@code{on}|@code{off}]
9604 Set printing of addresses.
9605 Related setting: @ref{set print address}.
9607 @item -array [@code{on}|@code{off}]
9608 Pretty formatting of arrays.
9609 Related setting: @ref{set print array}.
9611 @item -array-indexes [@code{on}|@code{off}]
9612 Set printing of array indexes.
9613 Related setting: @ref{set print array-indexes}.
9615 @item -elements @var{number-of-elements}|@code{unlimited}
9616 Set limit on string chars or array elements to print. The value
9617 @code{unlimited} causes there to be no limit. Related setting:
9618 @ref{set print elements}.
9620 @item -max-depth @var{depth}|@code{unlimited}
9621 Set the threshold after which nested structures are replaced with
9622 ellipsis. Related setting: @ref{set print max-depth}.
9624 @item -null-stop [@code{on}|@code{off}]
9625 Set printing of char arrays to stop at first null char. Related
9626 setting: @ref{set print null-stop}.
9628 @item -object [@code{on}|@code{off}]
9629 Set printing C@t{++} virtual function tables. Related setting:
9630 @ref{set print object}.
9632 @item -pretty [@code{on}|@code{off}]
9633 Set pretty formatting of structures. Related setting: @ref{set print
9636 @item -repeats @var{number-of-repeats}|@code{unlimited}
9637 Set threshold for repeated print elements. @code{unlimited} causes
9638 all elements to be individually printed. Related setting: @ref{set
9641 @item -static-members [@code{on}|@code{off}]
9642 Set printing C@t{++} static members. Related setting: @ref{set print
9645 @item -symbol [@code{on}|@code{off}]
9646 Set printing of symbol names when printing pointers. Related setting:
9647 @ref{set print symbol}.
9649 @item -union [@code{on}|@code{off}]
9650 Set printing of unions interior to structures. Related setting:
9651 @ref{set print union}.
9653 @item -vtbl [@code{on}|@code{off}]
9654 Set printing of C++ virtual function tables. Related setting:
9655 @ref{set print vtbl}.
9658 Because the @code{print} command accepts arbitrary expressions which
9659 may look like options (including abbreviations), if you specify any
9660 command option, then you must use a double dash (@code{--}) to mark
9661 the end of option processing.
9663 For example, this prints the value of the @code{-r} expression:
9666 (@value{GDBP}) print -r
9669 While this repeats the last value in the value history (see below)
9670 with the @code{-raw} option in effect:
9673 (@value{GDBP}) print -r --
9676 Here is an example including both on option and an expression:
9680 (@value{GDBP}) print -pretty -- *myptr
9692 @item print [@var{options}]
9693 @itemx print [@var{options}] /@var{f}
9694 @cindex reprint the last value
9695 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
9696 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
9697 conveniently inspect the same value in an alternative format.
9700 A more low-level way of examining data is with the @code{x} command.
9701 It examines data in memory at a specified address and prints it in a
9702 specified format. @xref{Memory, ,Examining Memory}.
9704 If you are interested in information about types, or about how the
9705 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
9706 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
9709 @cindex exploring hierarchical data structures
9711 Another way of examining values of expressions and type information is
9712 through the Python extension command @code{explore} (available only if
9713 the @value{GDBN} build is configured with @code{--with-python}). It
9714 offers an interactive way to start at the highest level (or, the most
9715 abstract level) of the data type of an expression (or, the data type
9716 itself) and explore all the way down to leaf scalar values/fields
9717 embedded in the higher level data types.
9720 @item explore @var{arg}
9721 @var{arg} is either an expression (in the source language), or a type
9722 visible in the current context of the program being debugged.
9725 The working of the @code{explore} command can be illustrated with an
9726 example. If a data type @code{struct ComplexStruct} is defined in your
9736 struct ComplexStruct
9738 struct SimpleStruct *ss_p;
9744 followed by variable declarations as
9747 struct SimpleStruct ss = @{ 10, 1.11 @};
9748 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
9752 then, the value of the variable @code{cs} can be explored using the
9753 @code{explore} command as follows.
9757 The value of `cs' is a struct/class of type `struct ComplexStruct' with
9758 the following fields:
9760 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
9761 arr = <Enter 1 to explore this field of type `int [10]'>
9763 Enter the field number of choice:
9767 Since the fields of @code{cs} are not scalar values, you are being
9768 prompted to chose the field you want to explore. Let's say you choose
9769 the field @code{ss_p} by entering @code{0}. Then, since this field is a
9770 pointer, you will be asked if it is pointing to a single value. From
9771 the declaration of @code{cs} above, it is indeed pointing to a single
9772 value, hence you enter @code{y}. If you enter @code{n}, then you will
9773 be asked if it were pointing to an array of values, in which case this
9774 field will be explored as if it were an array.
9777 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
9778 Continue exploring it as a pointer to a single value [y/n]: y
9779 The value of `*(cs.ss_p)' is a struct/class of type `struct
9780 SimpleStruct' with the following fields:
9782 i = 10 .. (Value of type `int')
9783 d = 1.1100000000000001 .. (Value of type `double')
9785 Press enter to return to parent value:
9789 If the field @code{arr} of @code{cs} was chosen for exploration by
9790 entering @code{1} earlier, then since it is as array, you will be
9791 prompted to enter the index of the element in the array that you want
9795 `cs.arr' is an array of `int'.
9796 Enter the index of the element you want to explore in `cs.arr': 5
9798 `(cs.arr)[5]' is a scalar value of type `int'.
9802 Press enter to return to parent value:
9805 In general, at any stage of exploration, you can go deeper towards the
9806 leaf values by responding to the prompts appropriately, or hit the
9807 return key to return to the enclosing data structure (the @i{higher}
9808 level data structure).
9810 Similar to exploring values, you can use the @code{explore} command to
9811 explore types. Instead of specifying a value (which is typically a
9812 variable name or an expression valid in the current context of the
9813 program being debugged), you specify a type name. If you consider the
9814 same example as above, your can explore the type
9815 @code{struct ComplexStruct} by passing the argument
9816 @code{struct ComplexStruct} to the @code{explore} command.
9819 (gdb) explore struct ComplexStruct
9823 By responding to the prompts appropriately in the subsequent interactive
9824 session, you can explore the type @code{struct ComplexStruct} in a
9825 manner similar to how the value @code{cs} was explored in the above
9828 The @code{explore} command also has two sub-commands,
9829 @code{explore value} and @code{explore type}. The former sub-command is
9830 a way to explicitly specify that value exploration of the argument is
9831 being invoked, while the latter is a way to explicitly specify that type
9832 exploration of the argument is being invoked.
9835 @item explore value @var{expr}
9836 @cindex explore value
9837 This sub-command of @code{explore} explores the value of the
9838 expression @var{expr} (if @var{expr} is an expression valid in the
9839 current context of the program being debugged). The behavior of this
9840 command is identical to that of the behavior of the @code{explore}
9841 command being passed the argument @var{expr}.
9843 @item explore type @var{arg}
9844 @cindex explore type
9845 This sub-command of @code{explore} explores the type of @var{arg} (if
9846 @var{arg} is a type visible in the current context of program being
9847 debugged), or the type of the value/expression @var{arg} (if @var{arg}
9848 is an expression valid in the current context of the program being
9849 debugged). If @var{arg} is a type, then the behavior of this command is
9850 identical to that of the @code{explore} command being passed the
9851 argument @var{arg}. If @var{arg} is an expression, then the behavior of
9852 this command will be identical to that of the @code{explore} command
9853 being passed the type of @var{arg} as the argument.
9857 * Expressions:: Expressions
9858 * Ambiguous Expressions:: Ambiguous Expressions
9859 * Variables:: Program variables
9860 * Arrays:: Artificial arrays
9861 * Output Formats:: Output formats
9862 * Memory:: Examining memory
9863 * Auto Display:: Automatic display
9864 * Print Settings:: Print settings
9865 * Pretty Printing:: Python pretty printing
9866 * Value History:: Value history
9867 * Convenience Vars:: Convenience variables
9868 * Convenience Funs:: Convenience functions
9869 * Registers:: Registers
9870 * Floating Point Hardware:: Floating point hardware
9871 * Vector Unit:: Vector Unit
9872 * OS Information:: Auxiliary data provided by operating system
9873 * Memory Region Attributes:: Memory region attributes
9874 * Dump/Restore Files:: Copy between memory and a file
9875 * Core File Generation:: Cause a program dump its core
9876 * Character Sets:: Debugging programs that use a different
9877 character set than GDB does
9878 * Caching Target Data:: Data caching for targets
9879 * Searching Memory:: Searching memory for a sequence of bytes
9880 * Value Sizes:: Managing memory allocated for values
9884 @section Expressions
9887 @code{print} and many other @value{GDBN} commands accept an expression and
9888 compute its value. Any kind of constant, variable or operator defined
9889 by the programming language you are using is valid in an expression in
9890 @value{GDBN}. This includes conditional expressions, function calls,
9891 casts, and string constants. It also includes preprocessor macros, if
9892 you compiled your program to include this information; see
9895 @cindex arrays in expressions
9896 @value{GDBN} supports array constants in expressions input by
9897 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
9898 you can use the command @code{print @{1, 2, 3@}} to create an array
9899 of three integers. If you pass an array to a function or assign it
9900 to a program variable, @value{GDBN} copies the array to memory that
9901 is @code{malloc}ed in the target program.
9903 Because C is so widespread, most of the expressions shown in examples in
9904 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
9905 Languages}, for information on how to use expressions in other
9908 In this section, we discuss operators that you can use in @value{GDBN}
9909 expressions regardless of your programming language.
9911 @cindex casts, in expressions
9912 Casts are supported in all languages, not just in C, because it is so
9913 useful to cast a number into a pointer in order to examine a structure
9914 at that address in memory.
9915 @c FIXME: casts supported---Mod2 true?
9917 @value{GDBN} supports these operators, in addition to those common
9918 to programming languages:
9922 @samp{@@} is a binary operator for treating parts of memory as arrays.
9923 @xref{Arrays, ,Artificial Arrays}, for more information.
9926 @samp{::} allows you to specify a variable in terms of the file or
9927 function where it is defined. @xref{Variables, ,Program Variables}.
9929 @cindex @{@var{type}@}
9930 @cindex type casting memory
9931 @cindex memory, viewing as typed object
9932 @cindex casts, to view memory
9933 @item @{@var{type}@} @var{addr}
9934 Refers to an object of type @var{type} stored at address @var{addr} in
9935 memory. The address @var{addr} may be any expression whose value is
9936 an integer or pointer (but parentheses are required around binary
9937 operators, just as in a cast). This construct is allowed regardless
9938 of what kind of data is normally supposed to reside at @var{addr}.
9941 @node Ambiguous Expressions
9942 @section Ambiguous Expressions
9943 @cindex ambiguous expressions
9945 Expressions can sometimes contain some ambiguous elements. For instance,
9946 some programming languages (notably Ada, C@t{++} and Objective-C) permit
9947 a single function name to be defined several times, for application in
9948 different contexts. This is called @dfn{overloading}. Another example
9949 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
9950 templates and is typically instantiated several times, resulting in
9951 the same function name being defined in different contexts.
9953 In some cases and depending on the language, it is possible to adjust
9954 the expression to remove the ambiguity. For instance in C@t{++}, you
9955 can specify the signature of the function you want to break on, as in
9956 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
9957 qualified name of your function often makes the expression unambiguous
9960 When an ambiguity that needs to be resolved is detected, the debugger
9961 has the capability to display a menu of numbered choices for each
9962 possibility, and then waits for the selection with the prompt @samp{>}.
9963 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
9964 aborts the current command. If the command in which the expression was
9965 used allows more than one choice to be selected, the next option in the
9966 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
9969 For example, the following session excerpt shows an attempt to set a
9970 breakpoint at the overloaded symbol @code{String::after}.
9971 We choose three particular definitions of that function name:
9973 @c FIXME! This is likely to change to show arg type lists, at least
9976 (@value{GDBP}) b String::after
9979 [2] file:String.cc; line number:867
9980 [3] file:String.cc; line number:860
9981 [4] file:String.cc; line number:875
9982 [5] file:String.cc; line number:853
9983 [6] file:String.cc; line number:846
9984 [7] file:String.cc; line number:735
9986 Breakpoint 1 at 0xb26c: file String.cc, line 867.
9987 Breakpoint 2 at 0xb344: file String.cc, line 875.
9988 Breakpoint 3 at 0xafcc: file String.cc, line 846.
9989 Multiple breakpoints were set.
9990 Use the "delete" command to delete unwanted
9997 @kindex set multiple-symbols
9998 @item set multiple-symbols @var{mode}
9999 @cindex multiple-symbols menu
10001 This option allows you to adjust the debugger behavior when an expression
10004 By default, @var{mode} is set to @code{all}. If the command with which
10005 the expression is used allows more than one choice, then @value{GDBN}
10006 automatically selects all possible choices. For instance, inserting
10007 a breakpoint on a function using an ambiguous name results in a breakpoint
10008 inserted on each possible match. However, if a unique choice must be made,
10009 then @value{GDBN} uses the menu to help you disambiguate the expression.
10010 For instance, printing the address of an overloaded function will result
10011 in the use of the menu.
10013 When @var{mode} is set to @code{ask}, the debugger always uses the menu
10014 when an ambiguity is detected.
10016 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
10017 an error due to the ambiguity and the command is aborted.
10019 @kindex show multiple-symbols
10020 @item show multiple-symbols
10021 Show the current value of the @code{multiple-symbols} setting.
10025 @section Program Variables
10027 The most common kind of expression to use is the name of a variable
10030 Variables in expressions are understood in the selected stack frame
10031 (@pxref{Selection, ,Selecting a Frame}); they must be either:
10035 global (or file-static)
10042 visible according to the scope rules of the
10043 programming language from the point of execution in that frame
10046 @noindent This means that in the function
10061 you can examine and use the variable @code{a} whenever your program is
10062 executing within the function @code{foo}, but you can only use or
10063 examine the variable @code{b} while your program is executing inside
10064 the block where @code{b} is declared.
10066 @cindex variable name conflict
10067 There is an exception: you can refer to a variable or function whose
10068 scope is a single source file even if the current execution point is not
10069 in this file. But it is possible to have more than one such variable or
10070 function with the same name (in different source files). If that
10071 happens, referring to that name has unpredictable effects. If you wish,
10072 you can specify a static variable in a particular function or file by
10073 using the colon-colon (@code{::}) notation:
10075 @cindex colon-colon, context for variables/functions
10077 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
10078 @cindex @code{::}, context for variables/functions
10081 @var{file}::@var{variable}
10082 @var{function}::@var{variable}
10086 Here @var{file} or @var{function} is the name of the context for the
10087 static @var{variable}. In the case of file names, you can use quotes to
10088 make sure @value{GDBN} parses the file name as a single word---for example,
10089 to print a global value of @code{x} defined in @file{f2.c}:
10092 (@value{GDBP}) p 'f2.c'::x
10095 The @code{::} notation is normally used for referring to
10096 static variables, since you typically disambiguate uses of local variables
10097 in functions by selecting the appropriate frame and using the
10098 simple name of the variable. However, you may also use this notation
10099 to refer to local variables in frames enclosing the selected frame:
10108 process (a); /* Stop here */
10119 For example, if there is a breakpoint at the commented line,
10120 here is what you might see
10121 when the program stops after executing the call @code{bar(0)}:
10126 (@value{GDBP}) p bar::a
10128 (@value{GDBP}) up 2
10129 #2 0x080483d0 in foo (a=5) at foobar.c:12
10132 (@value{GDBP}) p bar::a
10136 @cindex C@t{++} scope resolution
10137 These uses of @samp{::} are very rarely in conflict with the very
10138 similar use of the same notation in C@t{++}. When they are in
10139 conflict, the C@t{++} meaning takes precedence; however, this can be
10140 overridden by quoting the file or function name with single quotes.
10142 For example, suppose the program is stopped in a method of a class
10143 that has a field named @code{includefile}, and there is also an
10144 include file named @file{includefile} that defines a variable,
10145 @code{some_global}.
10148 (@value{GDBP}) p includefile
10150 (@value{GDBP}) p includefile::some_global
10151 A syntax error in expression, near `'.
10152 (@value{GDBP}) p 'includefile'::some_global
10156 @cindex wrong values
10157 @cindex variable values, wrong
10158 @cindex function entry/exit, wrong values of variables
10159 @cindex optimized code, wrong values of variables
10161 @emph{Warning:} Occasionally, a local variable may appear to have the
10162 wrong value at certain points in a function---just after entry to a new
10163 scope, and just before exit.
10165 You may see this problem when you are stepping by machine instructions.
10166 This is because, on most machines, it takes more than one instruction to
10167 set up a stack frame (including local variable definitions); if you are
10168 stepping by machine instructions, variables may appear to have the wrong
10169 values until the stack frame is completely built. On exit, it usually
10170 also takes more than one machine instruction to destroy a stack frame;
10171 after you begin stepping through that group of instructions, local
10172 variable definitions may be gone.
10174 This may also happen when the compiler does significant optimizations.
10175 To be sure of always seeing accurate values, turn off all optimization
10178 @cindex ``No symbol "foo" in current context''
10179 Another possible effect of compiler optimizations is to optimize
10180 unused variables out of existence, or assign variables to registers (as
10181 opposed to memory addresses). Depending on the support for such cases
10182 offered by the debug info format used by the compiler, @value{GDBN}
10183 might not be able to display values for such local variables. If that
10184 happens, @value{GDBN} will print a message like this:
10187 No symbol "foo" in current context.
10190 To solve such problems, either recompile without optimizations, or use a
10191 different debug info format, if the compiler supports several such
10192 formats. @xref{Compilation}, for more information on choosing compiler
10193 options. @xref{C, ,C and C@t{++}}, for more information about debug
10194 info formats that are best suited to C@t{++} programs.
10196 If you ask to print an object whose contents are unknown to
10197 @value{GDBN}, e.g., because its data type is not completely specified
10198 by the debug information, @value{GDBN} will say @samp{<incomplete
10199 type>}. @xref{Symbols, incomplete type}, for more about this.
10201 @cindex no debug info variables
10202 If you try to examine or use the value of a (global) variable for
10203 which @value{GDBN} has no type information, e.g., because the program
10204 includes no debug information, @value{GDBN} displays an error message.
10205 @xref{Symbols, unknown type}, for more about unknown types. If you
10206 cast the variable to its declared type, @value{GDBN} gets the
10207 variable's value using the cast-to type as the variable's type. For
10208 example, in a C program:
10211 (@value{GDBP}) p var
10212 'var' has unknown type; cast it to its declared type
10213 (@value{GDBP}) p (float) var
10217 If you append @kbd{@@entry} string to a function parameter name you get its
10218 value at the time the function got called. If the value is not available an
10219 error message is printed. Entry values are available only with some compilers.
10220 Entry values are normally also printed at the function parameter list according
10221 to @ref{set print entry-values}.
10224 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
10230 (gdb) print i@@entry
10234 Strings are identified as arrays of @code{char} values without specified
10235 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
10236 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
10237 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
10238 defines literal string type @code{"char"} as @code{char} without a sign.
10243 signed char var1[] = "A";
10246 You get during debugging
10251 $2 = @{65 'A', 0 '\0'@}
10255 @section Artificial Arrays
10257 @cindex artificial array
10259 @kindex @@@r{, referencing memory as an array}
10260 It is often useful to print out several successive objects of the
10261 same type in memory; a section of an array, or an array of
10262 dynamically determined size for which only a pointer exists in the
10265 You can do this by referring to a contiguous span of memory as an
10266 @dfn{artificial array}, using the binary operator @samp{@@}. The left
10267 operand of @samp{@@} should be the first element of the desired array
10268 and be an individual object. The right operand should be the desired length
10269 of the array. The result is an array value whose elements are all of
10270 the type of the left argument. The first element is actually the left
10271 argument; the second element comes from bytes of memory immediately
10272 following those that hold the first element, and so on. Here is an
10273 example. If a program says
10276 int *array = (int *) malloc (len * sizeof (int));
10280 you can print the contents of @code{array} with
10286 The left operand of @samp{@@} must reside in memory. Array values made
10287 with @samp{@@} in this way behave just like other arrays in terms of
10288 subscripting, and are coerced to pointers when used in expressions.
10289 Artificial arrays most often appear in expressions via the value history
10290 (@pxref{Value History, ,Value History}), after printing one out.
10292 Another way to create an artificial array is to use a cast.
10293 This re-interprets a value as if it were an array.
10294 The value need not be in memory:
10296 (@value{GDBP}) p/x (short[2])0x12345678
10297 $1 = @{0x1234, 0x5678@}
10300 As a convenience, if you leave the array length out (as in
10301 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
10302 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
10304 (@value{GDBP}) p/x (short[])0x12345678
10305 $2 = @{0x1234, 0x5678@}
10308 Sometimes the artificial array mechanism is not quite enough; in
10309 moderately complex data structures, the elements of interest may not
10310 actually be adjacent---for example, if you are interested in the values
10311 of pointers in an array. One useful work-around in this situation is
10312 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
10313 Variables}) as a counter in an expression that prints the first
10314 interesting value, and then repeat that expression via @key{RET}. For
10315 instance, suppose you have an array @code{dtab} of pointers to
10316 structures, and you are interested in the values of a field @code{fv}
10317 in each structure. Here is an example of what you might type:
10327 @node Output Formats
10328 @section Output Formats
10330 @cindex formatted output
10331 @cindex output formats
10332 By default, @value{GDBN} prints a value according to its data type. Sometimes
10333 this is not what you want. For example, you might want to print a number
10334 in hex, or a pointer in decimal. Or you might want to view data in memory
10335 at a certain address as a character string or as an instruction. To do
10336 these things, specify an @dfn{output format} when you print a value.
10338 The simplest use of output formats is to say how to print a value
10339 already computed. This is done by starting the arguments of the
10340 @code{print} command with a slash and a format letter. The format
10341 letters supported are:
10345 Regard the bits of the value as an integer, and print the integer in
10349 Print as integer in signed decimal.
10352 Print as integer in unsigned decimal.
10355 Print as integer in octal.
10358 Print as integer in binary. The letter @samp{t} stands for ``two''.
10359 @footnote{@samp{b} cannot be used because these format letters are also
10360 used with the @code{x} command, where @samp{b} stands for ``byte'';
10361 see @ref{Memory,,Examining Memory}.}
10364 @cindex unknown address, locating
10365 @cindex locate address
10366 Print as an address, both absolute in hexadecimal and as an offset from
10367 the nearest preceding symbol. You can use this format used to discover
10368 where (in what function) an unknown address is located:
10371 (@value{GDBP}) p/a 0x54320
10372 $3 = 0x54320 <_initialize_vx+396>
10376 The command @code{info symbol 0x54320} yields similar results.
10377 @xref{Symbols, info symbol}.
10380 Regard as an integer and print it as a character constant. This
10381 prints both the numerical value and its character representation. The
10382 character representation is replaced with the octal escape @samp{\nnn}
10383 for characters outside the 7-bit @sc{ascii} range.
10385 Without this format, @value{GDBN} displays @code{char},
10386 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
10387 constants. Single-byte members of vectors are displayed as integer
10391 Regard the bits of the value as a floating point number and print
10392 using typical floating point syntax.
10395 @cindex printing strings
10396 @cindex printing byte arrays
10397 Regard as a string, if possible. With this format, pointers to single-byte
10398 data are displayed as null-terminated strings and arrays of single-byte data
10399 are displayed as fixed-length strings. Other values are displayed in their
10402 Without this format, @value{GDBN} displays pointers to and arrays of
10403 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
10404 strings. Single-byte members of a vector are displayed as an integer
10408 Like @samp{x} formatting, the value is treated as an integer and
10409 printed as hexadecimal, but leading zeros are printed to pad the value
10410 to the size of the integer type.
10413 @cindex raw printing
10414 Print using the @samp{raw} formatting. By default, @value{GDBN} will
10415 use a Python-based pretty-printer, if one is available (@pxref{Pretty
10416 Printing}). This typically results in a higher-level display of the
10417 value's contents. The @samp{r} format bypasses any Python
10418 pretty-printer which might exist.
10421 For example, to print the program counter in hex (@pxref{Registers}), type
10428 Note that no space is required before the slash; this is because command
10429 names in @value{GDBN} cannot contain a slash.
10431 To reprint the last value in the value history with a different format,
10432 you can use the @code{print} command with just a format and no
10433 expression. For example, @samp{p/x} reprints the last value in hex.
10436 @section Examining Memory
10438 You can use the command @code{x} (for ``examine'') to examine memory in
10439 any of several formats, independently of your program's data types.
10441 @cindex examining memory
10443 @kindex x @r{(examine memory)}
10444 @item x/@var{nfu} @var{addr}
10445 @itemx x @var{addr}
10447 Use the @code{x} command to examine memory.
10450 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
10451 much memory to display and how to format it; @var{addr} is an
10452 expression giving the address where you want to start displaying memory.
10453 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
10454 Several commands set convenient defaults for @var{addr}.
10457 @item @var{n}, the repeat count
10458 The repeat count is a decimal integer; the default is 1. It specifies
10459 how much memory (counting by units @var{u}) to display. If a negative
10460 number is specified, memory is examined backward from @var{addr}.
10461 @c This really is **decimal**; unaffected by 'set radix' as of GDB
10464 @item @var{f}, the display format
10465 The display format is one of the formats used by @code{print}
10466 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
10467 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
10468 The default is @samp{x} (hexadecimal) initially. The default changes
10469 each time you use either @code{x} or @code{print}.
10471 @item @var{u}, the unit size
10472 The unit size is any of
10478 Halfwords (two bytes).
10480 Words (four bytes). This is the initial default.
10482 Giant words (eight bytes).
10485 Each time you specify a unit size with @code{x}, that size becomes the
10486 default unit the next time you use @code{x}. For the @samp{i} format,
10487 the unit size is ignored and is normally not written. For the @samp{s} format,
10488 the unit size defaults to @samp{b}, unless it is explicitly given.
10489 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
10490 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
10491 Note that the results depend on the programming language of the
10492 current compilation unit. If the language is C, the @samp{s}
10493 modifier will use the UTF-16 encoding while @samp{w} will use
10494 UTF-32. The encoding is set by the programming language and cannot
10497 @item @var{addr}, starting display address
10498 @var{addr} is the address where you want @value{GDBN} to begin displaying
10499 memory. The expression need not have a pointer value (though it may);
10500 it is always interpreted as an integer address of a byte of memory.
10501 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
10502 @var{addr} is usually just after the last address examined---but several
10503 other commands also set the default address: @code{info breakpoints} (to
10504 the address of the last breakpoint listed), @code{info line} (to the
10505 starting address of a line), and @code{print} (if you use it to display
10506 a value from memory).
10509 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
10510 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
10511 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
10512 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
10513 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
10515 You can also specify a negative repeat count to examine memory backward
10516 from the given address. For example, @samp{x/-3uh 0x54320} prints three
10517 halfwords (@code{h}) at @code{0x54314}, @code{0x54328}, and @code{0x5431c}.
10519 Since the letters indicating unit sizes are all distinct from the
10520 letters specifying output formats, you do not have to remember whether
10521 unit size or format comes first; either order works. The output
10522 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
10523 (However, the count @var{n} must come first; @samp{wx4} does not work.)
10525 Even though the unit size @var{u} is ignored for the formats @samp{s}
10526 and @samp{i}, you might still want to use a count @var{n}; for example,
10527 @samp{3i} specifies that you want to see three machine instructions,
10528 including any operands. For convenience, especially when used with
10529 the @code{display} command, the @samp{i} format also prints branch delay
10530 slot instructions, if any, beyond the count specified, which immediately
10531 follow the last instruction that is within the count. The command
10532 @code{disassemble} gives an alternative way of inspecting machine
10533 instructions; see @ref{Machine Code,,Source and Machine Code}.
10535 If a negative repeat count is specified for the formats @samp{s} or @samp{i},
10536 the command displays null-terminated strings or instructions before the given
10537 address as many as the absolute value of the given number. For the @samp{i}
10538 format, we use line number information in the debug info to accurately locate
10539 instruction boundaries while disassembling backward. If line info is not
10540 available, the command stops examining memory with an error message.
10542 All the defaults for the arguments to @code{x} are designed to make it
10543 easy to continue scanning memory with minimal specifications each time
10544 you use @code{x}. For example, after you have inspected three machine
10545 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
10546 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
10547 the repeat count @var{n} is used again; the other arguments default as
10548 for successive uses of @code{x}.
10550 When examining machine instructions, the instruction at current program
10551 counter is shown with a @code{=>} marker. For example:
10554 (@value{GDBP}) x/5i $pc-6
10555 0x804837f <main+11>: mov %esp,%ebp
10556 0x8048381 <main+13>: push %ecx
10557 0x8048382 <main+14>: sub $0x4,%esp
10558 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
10559 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
10562 @cindex @code{$_}, @code{$__}, and value history
10563 The addresses and contents printed by the @code{x} command are not saved
10564 in the value history because there is often too much of them and they
10565 would get in the way. Instead, @value{GDBN} makes these values available for
10566 subsequent use in expressions as values of the convenience variables
10567 @code{$_} and @code{$__}. After an @code{x} command, the last address
10568 examined is available for use in expressions in the convenience variable
10569 @code{$_}. The contents of that address, as examined, are available in
10570 the convenience variable @code{$__}.
10572 If the @code{x} command has a repeat count, the address and contents saved
10573 are from the last memory unit printed; this is not the same as the last
10574 address printed if several units were printed on the last line of output.
10576 @anchor{addressable memory unit}
10577 @cindex addressable memory unit
10578 Most targets have an addressable memory unit size of 8 bits. This means
10579 that to each memory address are associated 8 bits of data. Some
10580 targets, however, have other addressable memory unit sizes.
10581 Within @value{GDBN} and this document, the term
10582 @dfn{addressable memory unit} (or @dfn{memory unit} for short) is used
10583 when explicitly referring to a chunk of data of that size. The word
10584 @dfn{byte} is used to refer to a chunk of data of 8 bits, regardless of
10585 the addressable memory unit size of the target. For most systems,
10586 addressable memory unit is a synonym of byte.
10588 @cindex remote memory comparison
10589 @cindex target memory comparison
10590 @cindex verify remote memory image
10591 @cindex verify target memory image
10592 When you are debugging a program running on a remote target machine
10593 (@pxref{Remote Debugging}), you may wish to verify the program's image
10594 in the remote machine's memory against the executable file you
10595 downloaded to the target. Or, on any target, you may want to check
10596 whether the program has corrupted its own read-only sections. The
10597 @code{compare-sections} command is provided for such situations.
10600 @kindex compare-sections
10601 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
10602 Compare the data of a loadable section @var{section-name} in the
10603 executable file of the program being debugged with the same section in
10604 the target machine's memory, and report any mismatches. With no
10605 arguments, compares all loadable sections. With an argument of
10606 @code{-r}, compares all loadable read-only sections.
10608 Note: for remote targets, this command can be accelerated if the
10609 target supports computing the CRC checksum of a block of memory
10610 (@pxref{qCRC packet}).
10614 @section Automatic Display
10615 @cindex automatic display
10616 @cindex display of expressions
10618 If you find that you want to print the value of an expression frequently
10619 (to see how it changes), you might want to add it to the @dfn{automatic
10620 display list} so that @value{GDBN} prints its value each time your program stops.
10621 Each expression added to the list is given a number to identify it;
10622 to remove an expression from the list, you specify that number.
10623 The automatic display looks like this:
10627 3: bar[5] = (struct hack *) 0x3804
10631 This display shows item numbers, expressions and their current values. As with
10632 displays you request manually using @code{x} or @code{print}, you can
10633 specify the output format you prefer; in fact, @code{display} decides
10634 whether to use @code{print} or @code{x} depending your format
10635 specification---it uses @code{x} if you specify either the @samp{i}
10636 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
10640 @item display @var{expr}
10641 Add the expression @var{expr} to the list of expressions to display
10642 each time your program stops. @xref{Expressions, ,Expressions}.
10644 @code{display} does not repeat if you press @key{RET} again after using it.
10646 @item display/@var{fmt} @var{expr}
10647 For @var{fmt} specifying only a display format and not a size or
10648 count, add the expression @var{expr} to the auto-display list but
10649 arrange to display it each time in the specified format @var{fmt}.
10650 @xref{Output Formats,,Output Formats}.
10652 @item display/@var{fmt} @var{addr}
10653 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
10654 number of units, add the expression @var{addr} as a memory address to
10655 be examined each time your program stops. Examining means in effect
10656 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
10659 For example, @samp{display/i $pc} can be helpful, to see the machine
10660 instruction about to be executed each time execution stops (@samp{$pc}
10661 is a common name for the program counter; @pxref{Registers, ,Registers}).
10664 @kindex delete display
10666 @item undisplay @var{dnums}@dots{}
10667 @itemx delete display @var{dnums}@dots{}
10668 Remove items from the list of expressions to display. Specify the
10669 numbers of the displays that you want affected with the command
10670 argument @var{dnums}. It can be a single display number, one of the
10671 numbers shown in the first field of the @samp{info display} display;
10672 or it could be a range of display numbers, as in @code{2-4}.
10674 @code{undisplay} does not repeat if you press @key{RET} after using it.
10675 (Otherwise you would just get the error @samp{No display number @dots{}}.)
10677 @kindex disable display
10678 @item disable display @var{dnums}@dots{}
10679 Disable the display of item numbers @var{dnums}. A disabled display
10680 item is not printed automatically, but is not forgotten. It may be
10681 enabled again later. Specify the numbers of the displays that you
10682 want affected with the command argument @var{dnums}. It can be a
10683 single display number, one of the numbers shown in the first field of
10684 the @samp{info display} display; or it could be a range of display
10685 numbers, as in @code{2-4}.
10687 @kindex enable display
10688 @item enable display @var{dnums}@dots{}
10689 Enable display of item numbers @var{dnums}. It becomes effective once
10690 again in auto display of its expression, until you specify otherwise.
10691 Specify the numbers of the displays that you want affected with the
10692 command argument @var{dnums}. It can be a single display number, one
10693 of the numbers shown in the first field of the @samp{info display}
10694 display; or it could be a range of display numbers, as in @code{2-4}.
10697 Display the current values of the expressions on the list, just as is
10698 done when your program stops.
10700 @kindex info display
10702 Print the list of expressions previously set up to display
10703 automatically, each one with its item number, but without showing the
10704 values. This includes disabled expressions, which are marked as such.
10705 It also includes expressions which would not be displayed right now
10706 because they refer to automatic variables not currently available.
10709 @cindex display disabled out of scope
10710 If a display expression refers to local variables, then it does not make
10711 sense outside the lexical context for which it was set up. Such an
10712 expression is disabled when execution enters a context where one of its
10713 variables is not defined. For example, if you give the command
10714 @code{display last_char} while inside a function with an argument
10715 @code{last_char}, @value{GDBN} displays this argument while your program
10716 continues to stop inside that function. When it stops elsewhere---where
10717 there is no variable @code{last_char}---the display is disabled
10718 automatically. The next time your program stops where @code{last_char}
10719 is meaningful, you can enable the display expression once again.
10721 @node Print Settings
10722 @section Print Settings
10724 @cindex format options
10725 @cindex print settings
10726 @value{GDBN} provides the following ways to control how arrays, structures,
10727 and symbols are printed.
10730 These settings are useful for debugging programs in any language:
10734 @anchor{set print address}
10735 @item set print address
10736 @itemx set print address on
10737 @cindex print/don't print memory addresses
10738 @value{GDBN} prints memory addresses showing the location of stack
10739 traces, structure values, pointer values, breakpoints, and so forth,
10740 even when it also displays the contents of those addresses. The default
10741 is @code{on}. For example, this is what a stack frame display looks like with
10742 @code{set print address on}:
10747 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
10749 530 if (lquote != def_lquote)
10753 @item set print address off
10754 Do not print addresses when displaying their contents. For example,
10755 this is the same stack frame displayed with @code{set print address off}:
10759 (@value{GDBP}) set print addr off
10761 #0 set_quotes (lq="<<", rq=">>") at input.c:530
10762 530 if (lquote != def_lquote)
10766 You can use @samp{set print address off} to eliminate all machine
10767 dependent displays from the @value{GDBN} interface. For example, with
10768 @code{print address off}, you should get the same text for backtraces on
10769 all machines---whether or not they involve pointer arguments.
10772 @item show print address
10773 Show whether or not addresses are to be printed.
10776 When @value{GDBN} prints a symbolic address, it normally prints the
10777 closest earlier symbol plus an offset. If that symbol does not uniquely
10778 identify the address (for example, it is a name whose scope is a single
10779 source file), you may need to clarify. One way to do this is with
10780 @code{info line}, for example @samp{info line *0x4537}. Alternately,
10781 you can set @value{GDBN} to print the source file and line number when
10782 it prints a symbolic address:
10785 @item set print symbol-filename on
10786 @cindex source file and line of a symbol
10787 @cindex symbol, source file and line
10788 Tell @value{GDBN} to print the source file name and line number of a
10789 symbol in the symbolic form of an address.
10791 @item set print symbol-filename off
10792 Do not print source file name and line number of a symbol. This is the
10795 @item show print symbol-filename
10796 Show whether or not @value{GDBN} will print the source file name and
10797 line number of a symbol in the symbolic form of an address.
10800 Another situation where it is helpful to show symbol filenames and line
10801 numbers is when disassembling code; @value{GDBN} shows you the line
10802 number and source file that corresponds to each instruction.
10804 Also, you may wish to see the symbolic form only if the address being
10805 printed is reasonably close to the closest earlier symbol:
10808 @item set print max-symbolic-offset @var{max-offset}
10809 @itemx set print max-symbolic-offset unlimited
10810 @cindex maximum value for offset of closest symbol
10811 Tell @value{GDBN} to only display the symbolic form of an address if the
10812 offset between the closest earlier symbol and the address is less than
10813 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
10814 to always print the symbolic form of an address if any symbol precedes
10815 it. Zero is equivalent to @code{unlimited}.
10817 @item show print max-symbolic-offset
10818 Ask how large the maximum offset is that @value{GDBN} prints in a
10822 @cindex wild pointer, interpreting
10823 @cindex pointer, finding referent
10824 If you have a pointer and you are not sure where it points, try
10825 @samp{set print symbol-filename on}. Then you can determine the name
10826 and source file location of the variable where it points, using
10827 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
10828 For example, here @value{GDBN} shows that a variable @code{ptt} points
10829 at another variable @code{t}, defined in @file{hi2.c}:
10832 (@value{GDBP}) set print symbol-filename on
10833 (@value{GDBP}) p/a ptt
10834 $4 = 0xe008 <t in hi2.c>
10838 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
10839 does not show the symbol name and filename of the referent, even with
10840 the appropriate @code{set print} options turned on.
10843 You can also enable @samp{/a}-like formatting all the time using
10844 @samp{set print symbol on}:
10846 @anchor{set print symbol}
10848 @item set print symbol on
10849 Tell @value{GDBN} to print the symbol corresponding to an address, if
10852 @item set print symbol off
10853 Tell @value{GDBN} not to print the symbol corresponding to an
10854 address. In this mode, @value{GDBN} will still print the symbol
10855 corresponding to pointers to functions. This is the default.
10857 @item show print symbol
10858 Show whether @value{GDBN} will display the symbol corresponding to an
10862 Other settings control how different kinds of objects are printed:
10865 @anchor{set print array}
10866 @item set print array
10867 @itemx set print array on
10868 @cindex pretty print arrays
10869 Pretty print arrays. This format is more convenient to read,
10870 but uses more space. The default is off.
10872 @item set print array off
10873 Return to compressed format for arrays.
10875 @item show print array
10876 Show whether compressed or pretty format is selected for displaying
10879 @cindex print array indexes
10880 @anchor{set print array-indexes}
10881 @item set print array-indexes
10882 @itemx set print array-indexes on
10883 Print the index of each element when displaying arrays. May be more
10884 convenient to locate a given element in the array or quickly find the
10885 index of a given element in that printed array. The default is off.
10887 @item set print array-indexes off
10888 Stop printing element indexes when displaying arrays.
10890 @item show print array-indexes
10891 Show whether the index of each element is printed when displaying
10894 @anchor{set print elements}
10895 @item set print elements @var{number-of-elements}
10896 @itemx set print elements unlimited
10897 @cindex number of array elements to print
10898 @cindex limit on number of printed array elements
10899 Set a limit on how many elements of an array @value{GDBN} will print.
10900 If @value{GDBN} is printing a large array, it stops printing after it has
10901 printed the number of elements set by the @code{set print elements} command.
10902 This limit also applies to the display of strings.
10903 When @value{GDBN} starts, this limit is set to 200.
10904 Setting @var{number-of-elements} to @code{unlimited} or zero means
10905 that the number of elements to print is unlimited.
10907 @item show print elements
10908 Display the number of elements of a large array that @value{GDBN} will print.
10909 If the number is 0, then the printing is unlimited.
10911 @anchor{set print frame-arguments}
10912 @item set print frame-arguments @var{value}
10913 @kindex set print frame-arguments
10914 @cindex printing frame argument values
10915 @cindex print all frame argument values
10916 @cindex print frame argument values for scalars only
10917 @cindex do not print frame arguments
10918 This command allows to control how the values of arguments are printed
10919 when the debugger prints a frame (@pxref{Frames}). The possible
10924 The values of all arguments are printed.
10927 Print the value of an argument only if it is a scalar. The value of more
10928 complex arguments such as arrays, structures, unions, etc, is replaced
10929 by @code{@dots{}}. This is the default. Here is an example where
10930 only scalar arguments are shown:
10933 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
10938 None of the argument values are printed. Instead, the value of each argument
10939 is replaced by @code{@dots{}}. In this case, the example above now becomes:
10942 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
10947 Only the presence of arguments is indicated by @code{@dots{}}.
10948 The @code{@dots{}} are not printed for function without any arguments.
10949 None of the argument names and values are printed.
10950 In this case, the example above now becomes:
10953 #1 0x08048361 in call_me (@dots{}) at frame-args.c:23
10958 By default, only scalar arguments are printed. This command can be used
10959 to configure the debugger to print the value of all arguments, regardless
10960 of their type. However, it is often advantageous to not print the value
10961 of more complex parameters. For instance, it reduces the amount of
10962 information printed in each frame, making the backtrace more readable.
10963 Also, it improves performance when displaying Ada frames, because
10964 the computation of large arguments can sometimes be CPU-intensive,
10965 especially in large applications. Setting @code{print frame-arguments}
10966 to @code{scalars} (the default), @code{none} or @code{presence} avoids
10967 this computation, thus speeding up the display of each Ada frame.
10969 @item show print frame-arguments
10970 Show how the value of arguments should be displayed when printing a frame.
10972 @anchor{set print raw-frame-arguments}
10973 @item set print raw-frame-arguments on
10974 Print frame arguments in raw, non pretty-printed, form.
10976 @item set print raw-frame-arguments off
10977 Print frame arguments in pretty-printed form, if there is a pretty-printer
10978 for the value (@pxref{Pretty Printing}),
10979 otherwise print the value in raw form.
10980 This is the default.
10982 @item show print raw-frame-arguments
10983 Show whether to print frame arguments in raw form.
10985 @anchor{set print entry-values}
10986 @item set print entry-values @var{value}
10987 @kindex set print entry-values
10988 Set printing of frame argument values at function entry. In some cases
10989 @value{GDBN} can determine the value of function argument which was passed by
10990 the function caller, even if the value was modified inside the called function
10991 and therefore is different. With optimized code, the current value could be
10992 unavailable, but the entry value may still be known.
10994 The default value is @code{default} (see below for its description). Older
10995 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
10996 this feature will behave in the @code{default} setting the same way as with the
10999 This functionality is currently supported only by DWARF 2 debugging format and
11000 the compiler has to produce @samp{DW_TAG_call_site} tags. With
11001 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
11004 The @var{value} parameter can be one of the following:
11008 Print only actual parameter values, never print values from function entry
11012 #0 different (val=6)
11013 #0 lost (val=<optimized out>)
11015 #0 invalid (val=<optimized out>)
11019 Print only parameter values from function entry point. The actual parameter
11020 values are never printed.
11022 #0 equal (val@@entry=5)
11023 #0 different (val@@entry=5)
11024 #0 lost (val@@entry=5)
11025 #0 born (val@@entry=<optimized out>)
11026 #0 invalid (val@@entry=<optimized out>)
11030 Print only parameter values from function entry point. If value from function
11031 entry point is not known while the actual value is known, print the actual
11032 value for such parameter.
11034 #0 equal (val@@entry=5)
11035 #0 different (val@@entry=5)
11036 #0 lost (val@@entry=5)
11038 #0 invalid (val@@entry=<optimized out>)
11042 Print actual parameter values. If actual parameter value is not known while
11043 value from function entry point is known, print the entry point value for such
11047 #0 different (val=6)
11048 #0 lost (val@@entry=5)
11050 #0 invalid (val=<optimized out>)
11054 Always print both the actual parameter value and its value from function entry
11055 point, even if values of one or both are not available due to compiler
11058 #0 equal (val=5, val@@entry=5)
11059 #0 different (val=6, val@@entry=5)
11060 #0 lost (val=<optimized out>, val@@entry=5)
11061 #0 born (val=10, val@@entry=<optimized out>)
11062 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
11066 Print the actual parameter value if it is known and also its value from
11067 function entry point if it is known. If neither is known, print for the actual
11068 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
11069 values are known and identical, print the shortened
11070 @code{param=param@@entry=VALUE} notation.
11072 #0 equal (val=val@@entry=5)
11073 #0 different (val=6, val@@entry=5)
11074 #0 lost (val@@entry=5)
11076 #0 invalid (val=<optimized out>)
11080 Always print the actual parameter value. Print also its value from function
11081 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
11082 if both values are known and identical, print the shortened
11083 @code{param=param@@entry=VALUE} notation.
11085 #0 equal (val=val@@entry=5)
11086 #0 different (val=6, val@@entry=5)
11087 #0 lost (val=<optimized out>, val@@entry=5)
11089 #0 invalid (val=<optimized out>)
11093 For analysis messages on possible failures of frame argument values at function
11094 entry resolution see @ref{set debug entry-values}.
11096 @item show print entry-values
11097 Show the method being used for printing of frame argument values at function
11100 @anchor{set print frame-info}
11101 @item set print frame-info @var{value}
11102 @kindex set print frame-info
11103 @cindex printing frame information
11104 @cindex frame information, printing
11105 This command allows to control the information printed when
11106 the debugger prints a frame. See @ref{Frames}, @ref{Backtrace},
11107 for a general explanation about frames and frame information.
11108 Note that some other settings (such as @code{set print frame-arguments}
11109 and @code{set print address}) are also influencing if and how some frame
11110 information is displayed. In particular, the frame program counter is never
11111 printed if @code{set print address} is off.
11113 The possible values for @code{set print frame-info} are:
11115 @item short-location
11116 Print the frame level, the program counter (if not at the
11117 beginning of the location source line), the function, the function
11120 Same as @code{short-location} but also print the source file and source line
11122 @item location-and-address
11123 Same as @code{location} but print the program counter even if located at the
11124 beginning of the location source line.
11126 Print the program counter (if not at the beginning of the location
11127 source line), the line number and the source line.
11128 @item source-and-location
11129 Print what @code{location} and @code{source-line} are printing.
11131 The information printed for a frame is decided automatically
11132 by the @value{GDBN} command that prints a frame.
11133 For example, @code{frame} prints the information printed by
11134 @code{source-and-location} while @code{stepi} will switch between
11135 @code{source-line} and @code{source-and-location} depending on the program
11137 The default value is @code{auto}.
11140 @anchor{set print repeats}
11141 @item set print repeats @var{number-of-repeats}
11142 @itemx set print repeats unlimited
11143 @cindex repeated array elements
11144 Set the threshold for suppressing display of repeated array
11145 elements. When the number of consecutive identical elements of an
11146 array exceeds the threshold, @value{GDBN} prints the string
11147 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
11148 identical repetitions, instead of displaying the identical elements
11149 themselves. Setting the threshold to @code{unlimited} or zero will
11150 cause all elements to be individually printed. The default threshold
11153 @item show print repeats
11154 Display the current threshold for printing repeated identical
11157 @anchor{set print max-depth}
11158 @item set print max-depth @var{depth}
11159 @item set print max-depth unlimited
11160 @cindex printing nested structures
11161 Set the threshold after which nested structures are replaced with
11162 ellipsis, this can make visualising deeply nested structures easier.
11164 For example, given this C code
11167 typedef struct s1 @{ int a; @} s1;
11168 typedef struct s2 @{ s1 b; @} s2;
11169 typedef struct s3 @{ s2 c; @} s3;
11170 typedef struct s4 @{ s3 d; @} s4;
11172 s4 var = @{ @{ @{ @{ 3 @} @} @} @};
11175 The following table shows how different values of @var{depth} will
11176 effect how @code{var} is printed by @value{GDBN}:
11178 @multitable @columnfractions .3 .7
11179 @headitem @var{depth} setting @tab Result of @samp{p var}
11181 @tab @code{$1 = @{d = @{c = @{b = @{a = 3@}@}@}@}}
11183 @tab @code{$1 = @{...@}}
11185 @tab @code{$1 = @{d = @{...@}@}}
11187 @tab @code{$1 = @{d = @{c = @{...@}@}@}}
11189 @tab @code{$1 = @{d = @{c = @{b = @{...@}@}@}@}}
11191 @tab @code{$1 = @{d = @{c = @{b = @{a = 3@}@}@}@}}
11194 To see the contents of structures that have been hidden the user can
11195 either increase the print max-depth, or they can print the elements of
11196 the structure that are visible, for example
11199 (gdb) set print max-depth 2
11201 $1 = @{d = @{c = @{...@}@}@}
11203 $2 = @{c = @{b = @{...@}@}@}
11205 $3 = @{b = @{a = 3@}@}
11208 The pattern used to replace nested structures varies based on
11209 language, for most languages @code{@{...@}} is used, but Fortran uses
11212 @item show print max-depth
11213 Display the current threshold after which nested structures are
11214 replaces with ellipsis.
11216 @anchor{set print null-stop}
11217 @item set print null-stop
11218 @cindex @sc{null} elements in arrays
11219 Cause @value{GDBN} to stop printing the characters of an array when the first
11220 @sc{null} is encountered. This is useful when large arrays actually
11221 contain only short strings.
11222 The default is off.
11224 @item show print null-stop
11225 Show whether @value{GDBN} stops printing an array on the first
11226 @sc{null} character.
11228 @anchor{set print pretty}
11229 @item set print pretty on
11230 @cindex print structures in indented form
11231 @cindex indentation in structure display
11232 Cause @value{GDBN} to print structures in an indented format with one member
11233 per line, like this:
11248 @item set print pretty off
11249 Cause @value{GDBN} to print structures in a compact format, like this:
11253 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
11254 meat = 0x54 "Pork"@}
11259 This is the default format.
11261 @item show print pretty
11262 Show which format @value{GDBN} is using to print structures.
11264 @item set print sevenbit-strings on
11265 @cindex eight-bit characters in strings
11266 @cindex octal escapes in strings
11267 Print using only seven-bit characters; if this option is set,
11268 @value{GDBN} displays any eight-bit characters (in strings or
11269 character values) using the notation @code{\}@var{nnn}. This setting is
11270 best if you are working in English (@sc{ascii}) and you use the
11271 high-order bit of characters as a marker or ``meta'' bit.
11273 @item set print sevenbit-strings off
11274 Print full eight-bit characters. This allows the use of more
11275 international character sets, and is the default.
11277 @item show print sevenbit-strings
11278 Show whether or not @value{GDBN} is printing only seven-bit characters.
11280 @anchor{set print union}
11281 @item set print union on
11282 @cindex unions in structures, printing
11283 Tell @value{GDBN} to print unions which are contained in structures
11284 and other unions. This is the default setting.
11286 @item set print union off
11287 Tell @value{GDBN} not to print unions which are contained in
11288 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
11291 @item show print union
11292 Ask @value{GDBN} whether or not it will print unions which are contained in
11293 structures and other unions.
11295 For example, given the declarations
11298 typedef enum @{Tree, Bug@} Species;
11299 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
11300 typedef enum @{Caterpillar, Cocoon, Butterfly@}
11311 struct thing foo = @{Tree, @{Acorn@}@};
11315 with @code{set print union on} in effect @samp{p foo} would print
11318 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
11322 and with @code{set print union off} in effect it would print
11325 $1 = @{it = Tree, form = @{...@}@}
11329 @code{set print union} affects programs written in C-like languages
11335 These settings are of interest when debugging C@t{++} programs:
11338 @cindex demangling C@t{++} names
11339 @item set print demangle
11340 @itemx set print demangle on
11341 Print C@t{++} names in their source form rather than in the encoded
11342 (``mangled'') form passed to the assembler and linker for type-safe
11343 linkage. The default is on.
11345 @item show print demangle
11346 Show whether C@t{++} names are printed in mangled or demangled form.
11348 @item set print asm-demangle
11349 @itemx set print asm-demangle on
11350 Print C@t{++} names in their source form rather than their mangled form, even
11351 in assembler code printouts such as instruction disassemblies.
11352 The default is off.
11354 @item show print asm-demangle
11355 Show whether C@t{++} names in assembly listings are printed in mangled
11358 @cindex C@t{++} symbol decoding style
11359 @cindex symbol decoding style, C@t{++}
11360 @kindex set demangle-style
11361 @item set demangle-style @var{style}
11362 Choose among several encoding schemes used by different compilers to represent
11363 C@t{++} names. If you omit @var{style}, you will see a list of possible
11364 formats. The default value is @var{auto}, which lets @value{GDBN} choose a
11365 decoding style by inspecting your program.
11367 @item show demangle-style
11368 Display the encoding style currently in use for decoding C@t{++} symbols.
11370 @anchor{set print object}
11371 @item set print object
11372 @itemx set print object on
11373 @cindex derived type of an object, printing
11374 @cindex display derived types
11375 When displaying a pointer to an object, identify the @emph{actual}
11376 (derived) type of the object rather than the @emph{declared} type, using
11377 the virtual function table. Note that the virtual function table is
11378 required---this feature can only work for objects that have run-time
11379 type identification; a single virtual method in the object's declared
11380 type is sufficient. Note that this setting is also taken into account when
11381 working with variable objects via MI (@pxref{GDB/MI}).
11383 @item set print object off
11384 Display only the declared type of objects, without reference to the
11385 virtual function table. This is the default setting.
11387 @item show print object
11388 Show whether actual, or declared, object types are displayed.
11390 @anchor{set print static-members}
11391 @item set print static-members
11392 @itemx set print static-members on
11393 @cindex static members of C@t{++} objects
11394 Print static members when displaying a C@t{++} object. The default is on.
11396 @item set print static-members off
11397 Do not print static members when displaying a C@t{++} object.
11399 @item show print static-members
11400 Show whether C@t{++} static members are printed or not.
11402 @item set print pascal_static-members
11403 @itemx set print pascal_static-members on
11404 @cindex static members of Pascal objects
11405 @cindex Pascal objects, static members display
11406 Print static members when displaying a Pascal object. The default is on.
11408 @item set print pascal_static-members off
11409 Do not print static members when displaying a Pascal object.
11411 @item show print pascal_static-members
11412 Show whether Pascal static members are printed or not.
11414 @c These don't work with HP ANSI C++ yet.
11415 @anchor{set print vtbl}
11416 @item set print vtbl
11417 @itemx set print vtbl on
11418 @cindex pretty print C@t{++} virtual function tables
11419 @cindex virtual functions (C@t{++}) display
11420 @cindex VTBL display
11421 Pretty print C@t{++} virtual function tables. The default is off.
11422 (The @code{vtbl} commands do not work on programs compiled with the HP
11423 ANSI C@t{++} compiler (@code{aCC}).)
11425 @item set print vtbl off
11426 Do not pretty print C@t{++} virtual function tables.
11428 @item show print vtbl
11429 Show whether C@t{++} virtual function tables are pretty printed, or not.
11432 @node Pretty Printing
11433 @section Pretty Printing
11435 @value{GDBN} provides a mechanism to allow pretty-printing of values using
11436 Python code. It greatly simplifies the display of complex objects. This
11437 mechanism works for both MI and the CLI.
11440 * Pretty-Printer Introduction:: Introduction to pretty-printers
11441 * Pretty-Printer Example:: An example pretty-printer
11442 * Pretty-Printer Commands:: Pretty-printer commands
11445 @node Pretty-Printer Introduction
11446 @subsection Pretty-Printer Introduction
11448 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
11449 registered for the value. If there is then @value{GDBN} invokes the
11450 pretty-printer to print the value. Otherwise the value is printed normally.
11452 Pretty-printers are normally named. This makes them easy to manage.
11453 The @samp{info pretty-printer} command will list all the installed
11454 pretty-printers with their names.
11455 If a pretty-printer can handle multiple data types, then its
11456 @dfn{subprinters} are the printers for the individual data types.
11457 Each such subprinter has its own name.
11458 The format of the name is @var{printer-name};@var{subprinter-name}.
11460 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
11461 Typically they are automatically loaded and registered when the corresponding
11462 debug information is loaded, thus making them available without having to
11463 do anything special.
11465 There are three places where a pretty-printer can be registered.
11469 Pretty-printers registered globally are available when debugging
11473 Pretty-printers registered with a program space are available only
11474 when debugging that program.
11475 @xref{Progspaces In Python}, for more details on program spaces in Python.
11478 Pretty-printers registered with an objfile are loaded and unloaded
11479 with the corresponding objfile (e.g., shared library).
11480 @xref{Objfiles In Python}, for more details on objfiles in Python.
11483 @xref{Selecting Pretty-Printers}, for further information on how
11484 pretty-printers are selected,
11486 @xref{Writing a Pretty-Printer}, for implementing pretty printers
11489 @node Pretty-Printer Example
11490 @subsection Pretty-Printer Example
11492 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
11495 (@value{GDBP}) print s
11497 static npos = 4294967295,
11499 <std::allocator<char>> = @{
11500 <__gnu_cxx::new_allocator<char>> = @{
11501 <No data fields>@}, <No data fields>
11503 members of std::basic_string<char, std::char_traits<char>,
11504 std::allocator<char> >::_Alloc_hider:
11505 _M_p = 0x804a014 "abcd"
11510 With a pretty-printer for @code{std::string} only the contents are printed:
11513 (@value{GDBP}) print s
11517 @node Pretty-Printer Commands
11518 @subsection Pretty-Printer Commands
11519 @cindex pretty-printer commands
11522 @kindex info pretty-printer
11523 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
11524 Print the list of installed pretty-printers.
11525 This includes disabled pretty-printers, which are marked as such.
11527 @var{object-regexp} is a regular expression matching the objects
11528 whose pretty-printers to list.
11529 Objects can be @code{global}, the program space's file
11530 (@pxref{Progspaces In Python}),
11531 and the object files within that program space (@pxref{Objfiles In Python}).
11532 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
11533 looks up a printer from these three objects.
11535 @var{name-regexp} is a regular expression matching the name of the printers
11538 @kindex disable pretty-printer
11539 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
11540 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
11541 A disabled pretty-printer is not forgotten, it may be enabled again later.
11543 @kindex enable pretty-printer
11544 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
11545 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
11550 Suppose we have three pretty-printers installed: one from library1.so
11551 named @code{foo} that prints objects of type @code{foo}, and
11552 another from library2.so named @code{bar} that prints two types of objects,
11553 @code{bar1} and @code{bar2}.
11556 (gdb) info pretty-printer
11563 (gdb) info pretty-printer library2
11568 (gdb) disable pretty-printer library1
11570 2 of 3 printers enabled
11571 (gdb) info pretty-printer
11578 (gdb) disable pretty-printer library2 bar;bar1
11580 1 of 3 printers enabled
11581 (gdb) info pretty-printer library2
11588 (gdb) disable pretty-printer library2 bar
11590 0 of 3 printers enabled
11591 (gdb) info pretty-printer library2
11600 Note that for @code{bar} the entire printer can be disabled,
11601 as can each individual subprinter.
11603 @node Value History
11604 @section Value History
11606 @cindex value history
11607 @cindex history of values printed by @value{GDBN}
11608 Values printed by the @code{print} command are saved in the @value{GDBN}
11609 @dfn{value history}. This allows you to refer to them in other expressions.
11610 Values are kept until the symbol table is re-read or discarded
11611 (for example with the @code{file} or @code{symbol-file} commands).
11612 When the symbol table changes, the value history is discarded,
11613 since the values may contain pointers back to the types defined in the
11618 @cindex history number
11619 The values printed are given @dfn{history numbers} by which you can
11620 refer to them. These are successive integers starting with one.
11621 @code{print} shows you the history number assigned to a value by
11622 printing @samp{$@var{num} = } before the value; here @var{num} is the
11625 To refer to any previous value, use @samp{$} followed by the value's
11626 history number. The way @code{print} labels its output is designed to
11627 remind you of this. Just @code{$} refers to the most recent value in
11628 the history, and @code{$$} refers to the value before that.
11629 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
11630 is the value just prior to @code{$$}, @code{$$1} is equivalent to
11631 @code{$$}, and @code{$$0} is equivalent to @code{$}.
11633 For example, suppose you have just printed a pointer to a structure and
11634 want to see the contents of the structure. It suffices to type
11640 If you have a chain of structures where the component @code{next} points
11641 to the next one, you can print the contents of the next one with this:
11648 You can print successive links in the chain by repeating this
11649 command---which you can do by just typing @key{RET}.
11651 Note that the history records values, not expressions. If the value of
11652 @code{x} is 4 and you type these commands:
11660 then the value recorded in the value history by the @code{print} command
11661 remains 4 even though the value of @code{x} has changed.
11664 @kindex show values
11666 Print the last ten values in the value history, with their item numbers.
11667 This is like @samp{p@ $$9} repeated ten times, except that @code{show
11668 values} does not change the history.
11670 @item show values @var{n}
11671 Print ten history values centered on history item number @var{n}.
11673 @item show values +
11674 Print ten history values just after the values last printed. If no more
11675 values are available, @code{show values +} produces no display.
11678 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
11679 same effect as @samp{show values +}.
11681 @node Convenience Vars
11682 @section Convenience Variables
11684 @cindex convenience variables
11685 @cindex user-defined variables
11686 @value{GDBN} provides @dfn{convenience variables} that you can use within
11687 @value{GDBN} to hold on to a value and refer to it later. These variables
11688 exist entirely within @value{GDBN}; they are not part of your program, and
11689 setting a convenience variable has no direct effect on further execution
11690 of your program. That is why you can use them freely.
11692 Convenience variables are prefixed with @samp{$}. Any name preceded by
11693 @samp{$} can be used for a convenience variable, unless it is one of
11694 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
11695 (Value history references, in contrast, are @emph{numbers} preceded
11696 by @samp{$}. @xref{Value History, ,Value History}.)
11698 You can save a value in a convenience variable with an assignment
11699 expression, just as you would set a variable in your program.
11703 set $foo = *object_ptr
11707 would save in @code{$foo} the value contained in the object pointed to by
11710 Using a convenience variable for the first time creates it, but its
11711 value is @code{void} until you assign a new value. You can alter the
11712 value with another assignment at any time.
11714 Convenience variables have no fixed types. You can assign a convenience
11715 variable any type of value, including structures and arrays, even if
11716 that variable already has a value of a different type. The convenience
11717 variable, when used as an expression, has the type of its current value.
11720 @kindex show convenience
11721 @cindex show all user variables and functions
11722 @item show convenience
11723 Print a list of convenience variables used so far, and their values,
11724 as well as a list of the convenience functions.
11725 Abbreviated @code{show conv}.
11727 @kindex init-if-undefined
11728 @cindex convenience variables, initializing
11729 @item init-if-undefined $@var{variable} = @var{expression}
11730 Set a convenience variable if it has not already been set. This is useful
11731 for user-defined commands that keep some state. It is similar, in concept,
11732 to using local static variables with initializers in C (except that
11733 convenience variables are global). It can also be used to allow users to
11734 override default values used in a command script.
11736 If the variable is already defined then the expression is not evaluated so
11737 any side-effects do not occur.
11740 One of the ways to use a convenience variable is as a counter to be
11741 incremented or a pointer to be advanced. For example, to print
11742 a field from successive elements of an array of structures:
11746 print bar[$i++]->contents
11750 Repeat that command by typing @key{RET}.
11752 Some convenience variables are created automatically by @value{GDBN} and given
11753 values likely to be useful.
11756 @vindex $_@r{, convenience variable}
11758 The variable @code{$_} is automatically set by the @code{x} command to
11759 the last address examined (@pxref{Memory, ,Examining Memory}). Other
11760 commands which provide a default address for @code{x} to examine also
11761 set @code{$_} to that address; these commands include @code{info line}
11762 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
11763 except when set by the @code{x} command, in which case it is a pointer
11764 to the type of @code{$__}.
11766 @vindex $__@r{, convenience variable}
11768 The variable @code{$__} is automatically set by the @code{x} command
11769 to the value found in the last address examined. Its type is chosen
11770 to match the format in which the data was printed.
11773 @vindex $_exitcode@r{, convenience variable}
11774 When the program being debugged terminates normally, @value{GDBN}
11775 automatically sets this variable to the exit code of the program, and
11776 resets @code{$_exitsignal} to @code{void}.
11779 @vindex $_exitsignal@r{, convenience variable}
11780 When the program being debugged dies due to an uncaught signal,
11781 @value{GDBN} automatically sets this variable to that signal's number,
11782 and resets @code{$_exitcode} to @code{void}.
11784 To distinguish between whether the program being debugged has exited
11785 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
11786 @code{$_exitsignal} is not @code{void}), the convenience function
11787 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
11788 Functions}). For example, considering the following source code:
11791 #include <signal.h>
11794 main (int argc, char *argv[])
11801 A valid way of telling whether the program being debugged has exited
11802 or signalled would be:
11805 (@value{GDBP}) define has_exited_or_signalled
11806 Type commands for definition of ``has_exited_or_signalled''.
11807 End with a line saying just ``end''.
11808 >if $_isvoid ($_exitsignal)
11809 >echo The program has exited\n
11811 >echo The program has signalled\n
11817 Program terminated with signal SIGALRM, Alarm clock.
11818 The program no longer exists.
11819 (@value{GDBP}) has_exited_or_signalled
11820 The program has signalled
11823 As can be seen, @value{GDBN} correctly informs that the program being
11824 debugged has signalled, since it calls @code{raise} and raises a
11825 @code{SIGALRM} signal. If the program being debugged had not called
11826 @code{raise}, then @value{GDBN} would report a normal exit:
11829 (@value{GDBP}) has_exited_or_signalled
11830 The program has exited
11834 The variable @code{$_exception} is set to the exception object being
11835 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
11837 @item $_ada_exception
11838 The variable @code{$_ada_exception} is set to the address of the
11839 exception being caught or thrown at an Ada exception-related
11840 catchpoint. @xref{Set Catchpoints}.
11843 @itemx $_probe_arg0@dots{}$_probe_arg11
11844 Arguments to a static probe. @xref{Static Probe Points}.
11847 @vindex $_sdata@r{, inspect, convenience variable}
11848 The variable @code{$_sdata} contains extra collected static tracepoint
11849 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
11850 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
11851 if extra static tracepoint data has not been collected.
11854 @vindex $_siginfo@r{, convenience variable}
11855 The variable @code{$_siginfo} contains extra signal information
11856 (@pxref{extra signal information}). Note that @code{$_siginfo}
11857 could be empty, if the application has not yet received any signals.
11858 For example, it will be empty before you execute the @code{run} command.
11861 @vindex $_tlb@r{, convenience variable}
11862 The variable @code{$_tlb} is automatically set when debugging
11863 applications running on MS-Windows in native mode or connected to
11864 gdbserver that supports the @code{qGetTIBAddr} request.
11865 @xref{General Query Packets}.
11866 This variable contains the address of the thread information block.
11869 The number of the current inferior. @xref{Inferiors and
11870 Programs, ,Debugging Multiple Inferiors and Programs}.
11873 The thread number of the current thread. @xref{thread numbers}.
11876 The global number of the current thread. @xref{global thread numbers}.
11880 @vindex $_gdb_major@r{, convenience variable}
11881 @vindex $_gdb_minor@r{, convenience variable}
11882 The major and minor version numbers of the running @value{GDBN}.
11883 Development snapshots and pretest versions have their minor version
11884 incremented by one; thus, @value{GDBN} pretest 9.11.90 will produce
11885 the value 12 for @code{$_gdb_minor}. These variables allow you to
11886 write scripts that work with different versions of @value{GDBN}
11887 without errors caused by features unavailable in some of those
11890 @item $_shell_exitcode
11891 @itemx $_shell_exitsignal
11892 @vindex $_shell_exitcode@r{, convenience variable}
11893 @vindex $_shell_exitsignal@r{, convenience variable}
11894 @cindex shell command, exit code
11895 @cindex shell command, exit signal
11896 @cindex exit status of shell commands
11897 @value{GDBN} commands such as @code{shell} and @code{|} are launching
11898 shell commands. When a launched command terminates, @value{GDBN}
11899 automatically maintains the variables @code{$_shell_exitcode}
11900 and @code{$_shell_exitsignal} according to the exit status of the last
11901 launched command. These variables are set and used similarly to
11902 the variables @code{$_exitcode} and @code{$_exitsignal}.
11906 @node Convenience Funs
11907 @section Convenience Functions
11909 @cindex convenience functions
11910 @value{GDBN} also supplies some @dfn{convenience functions}. These
11911 have a syntax similar to convenience variables. A convenience
11912 function can be used in an expression just like an ordinary function;
11913 however, a convenience function is implemented internally to
11916 These functions do not require @value{GDBN} to be configured with
11917 @code{Python} support, which means that they are always available.
11921 @item $_isvoid (@var{expr})
11922 @findex $_isvoid@r{, convenience function}
11923 Return one if the expression @var{expr} is @code{void}. Otherwise it
11926 A @code{void} expression is an expression where the type of the result
11927 is @code{void}. For example, you can examine a convenience variable
11928 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
11932 (@value{GDBP}) print $_exitcode
11934 (@value{GDBP}) print $_isvoid ($_exitcode)
11937 Starting program: ./a.out
11938 [Inferior 1 (process 29572) exited normally]
11939 (@value{GDBP}) print $_exitcode
11941 (@value{GDBP}) print $_isvoid ($_exitcode)
11945 In the example above, we used @code{$_isvoid} to check whether
11946 @code{$_exitcode} is @code{void} before and after the execution of the
11947 program being debugged. Before the execution there is no exit code to
11948 be examined, therefore @code{$_exitcode} is @code{void}. After the
11949 execution the program being debugged returned zero, therefore
11950 @code{$_exitcode} is zero, which means that it is not @code{void}
11953 The @code{void} expression can also be a call of a function from the
11954 program being debugged. For example, given the following function:
11963 The result of calling it inside @value{GDBN} is @code{void}:
11966 (@value{GDBP}) print foo ()
11968 (@value{GDBP}) print $_isvoid (foo ())
11970 (@value{GDBP}) set $v = foo ()
11971 (@value{GDBP}) print $v
11973 (@value{GDBP}) print $_isvoid ($v)
11979 These functions require @value{GDBN} to be configured with
11980 @code{Python} support.
11984 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
11985 @findex $_memeq@r{, convenience function}
11986 Returns one if the @var{length} bytes at the addresses given by
11987 @var{buf1} and @var{buf2} are equal.
11988 Otherwise it returns zero.
11990 @item $_regex(@var{str}, @var{regex})
11991 @findex $_regex@r{, convenience function}
11992 Returns one if the string @var{str} matches the regular expression
11993 @var{regex}. Otherwise it returns zero.
11994 The syntax of the regular expression is that specified by @code{Python}'s
11995 regular expression support.
11997 @item $_streq(@var{str1}, @var{str2})
11998 @findex $_streq@r{, convenience function}
11999 Returns one if the strings @var{str1} and @var{str2} are equal.
12000 Otherwise it returns zero.
12002 @item $_strlen(@var{str})
12003 @findex $_strlen@r{, convenience function}
12004 Returns the length of string @var{str}.
12006 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
12007 @findex $_caller_is@r{, convenience function}
12008 Returns one if the calling function's name is equal to @var{name}.
12009 Otherwise it returns zero.
12011 If the optional argument @var{number_of_frames} is provided,
12012 it is the number of frames up in the stack to look.
12020 at testsuite/gdb.python/py-caller-is.c:21
12021 #1 0x00000000004005a0 in middle_func ()
12022 at testsuite/gdb.python/py-caller-is.c:27
12023 #2 0x00000000004005ab in top_func ()
12024 at testsuite/gdb.python/py-caller-is.c:33
12025 #3 0x00000000004005b6 in main ()
12026 at testsuite/gdb.python/py-caller-is.c:39
12027 (gdb) print $_caller_is ("middle_func")
12029 (gdb) print $_caller_is ("top_func", 2)
12033 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
12034 @findex $_caller_matches@r{, convenience function}
12035 Returns one if the calling function's name matches the regular expression
12036 @var{regexp}. Otherwise it returns zero.
12038 If the optional argument @var{number_of_frames} is provided,
12039 it is the number of frames up in the stack to look.
12042 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
12043 @findex $_any_caller_is@r{, convenience function}
12044 Returns one if any calling function's name is equal to @var{name}.
12045 Otherwise it returns zero.
12047 If the optional argument @var{number_of_frames} is provided,
12048 it is the number of frames up in the stack to look.
12051 This function differs from @code{$_caller_is} in that this function
12052 checks all stack frames from the immediate caller to the frame specified
12053 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
12054 frame specified by @var{number_of_frames}.
12056 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
12057 @findex $_any_caller_matches@r{, convenience function}
12058 Returns one if any calling function's name matches the regular expression
12059 @var{regexp}. Otherwise it returns zero.
12061 If the optional argument @var{number_of_frames} is provided,
12062 it is the number of frames up in the stack to look.
12065 This function differs from @code{$_caller_matches} in that this function
12066 checks all stack frames from the immediate caller to the frame specified
12067 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
12068 frame specified by @var{number_of_frames}.
12070 @item $_as_string(@var{value})
12071 @findex $_as_string@r{, convenience function}
12072 Return the string representation of @var{value}.
12074 This function is useful to obtain the textual label (enumerator) of an
12075 enumeration value. For example, assuming the variable @var{node} is of
12076 an enumerated type:
12079 (gdb) printf "Visiting node of type %s\n", $_as_string(node)
12080 Visiting node of type NODE_INTEGER
12083 @item $_cimag(@var{value})
12084 @itemx $_creal(@var{value})
12085 @findex $_cimag@r{, convenience function}
12086 @findex $_creal@r{, convenience function}
12087 Return the imaginary (@code{$_cimag}) or real (@code{$_creal}) part of
12088 the complex number @var{value}.
12090 The type of the imaginary or real part depends on the type of the
12091 complex number, e.g., using @code{$_cimag} on a @code{float complex}
12092 will return an imaginary part of type @code{float}.
12096 @value{GDBN} provides the ability to list and get help on
12097 convenience functions.
12100 @item help function
12101 @kindex help function
12102 @cindex show all convenience functions
12103 Print a list of all convenience functions.
12110 You can refer to machine register contents, in expressions, as variables
12111 with names starting with @samp{$}. The names of registers are different
12112 for each machine; use @code{info registers} to see the names used on
12116 @kindex info registers
12117 @item info registers
12118 Print the names and values of all registers except floating-point
12119 and vector registers (in the selected stack frame).
12121 @kindex info all-registers
12122 @cindex floating point registers
12123 @item info all-registers
12124 Print the names and values of all registers, including floating-point
12125 and vector registers (in the selected stack frame).
12127 @item info registers @var{reggroup} @dots{}
12128 Print the name and value of the registers in each of the specified
12129 @var{reggroup}s. The @var{reggoup} can be any of those returned by
12130 @code{maint print reggroups} (@pxref{Maintenance Commands}).
12132 @item info registers @var{regname} @dots{}
12133 Print the @dfn{relativized} value of each specified register @var{regname}.
12134 As discussed in detail below, register values are normally relative to
12135 the selected stack frame. The @var{regname} may be any register name valid on
12136 the machine you are using, with or without the initial @samp{$}.
12139 @anchor{standard registers}
12140 @cindex stack pointer register
12141 @cindex program counter register
12142 @cindex process status register
12143 @cindex frame pointer register
12144 @cindex standard registers
12145 @value{GDBN} has four ``standard'' register names that are available (in
12146 expressions) on most machines---whenever they do not conflict with an
12147 architecture's canonical mnemonics for registers. The register names
12148 @code{$pc} and @code{$sp} are used for the program counter register and
12149 the stack pointer. @code{$fp} is used for a register that contains a
12150 pointer to the current stack frame, and @code{$ps} is used for a
12151 register that contains the processor status. For example,
12152 you could print the program counter in hex with
12159 or print the instruction to be executed next with
12166 or add four to the stack pointer@footnote{This is a way of removing
12167 one word from the stack, on machines where stacks grow downward in
12168 memory (most machines, nowadays). This assumes that the innermost
12169 stack frame is selected; setting @code{$sp} is not allowed when other
12170 stack frames are selected. To pop entire frames off the stack,
12171 regardless of machine architecture, use @code{return};
12172 see @ref{Returning, ,Returning from a Function}.} with
12178 Whenever possible, these four standard register names are available on
12179 your machine even though the machine has different canonical mnemonics,
12180 so long as there is no conflict. The @code{info registers} command
12181 shows the canonical names. For example, on the SPARC, @code{info
12182 registers} displays the processor status register as @code{$psr} but you
12183 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
12184 is an alias for the @sc{eflags} register.
12186 @value{GDBN} always considers the contents of an ordinary register as an
12187 integer when the register is examined in this way. Some machines have
12188 special registers which can hold nothing but floating point; these
12189 registers are considered to have floating point values. There is no way
12190 to refer to the contents of an ordinary register as floating point value
12191 (although you can @emph{print} it as a floating point value with
12192 @samp{print/f $@var{regname}}).
12194 Some registers have distinct ``raw'' and ``virtual'' data formats. This
12195 means that the data format in which the register contents are saved by
12196 the operating system is not the same one that your program normally
12197 sees. For example, the registers of the 68881 floating point
12198 coprocessor are always saved in ``extended'' (raw) format, but all C
12199 programs expect to work with ``double'' (virtual) format. In such
12200 cases, @value{GDBN} normally works with the virtual format only (the format
12201 that makes sense for your program), but the @code{info registers} command
12202 prints the data in both formats.
12204 @cindex SSE registers (x86)
12205 @cindex MMX registers (x86)
12206 Some machines have special registers whose contents can be interpreted
12207 in several different ways. For example, modern x86-based machines
12208 have SSE and MMX registers that can hold several values packed
12209 together in several different formats. @value{GDBN} refers to such
12210 registers in @code{struct} notation:
12213 (@value{GDBP}) print $xmm1
12215 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
12216 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
12217 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
12218 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
12219 v4_int32 = @{0, 20657912, 11, 13@},
12220 v2_int64 = @{88725056443645952, 55834574859@},
12221 uint128 = 0x0000000d0000000b013b36f800000000
12226 To set values of such registers, you need to tell @value{GDBN} which
12227 view of the register you wish to change, as if you were assigning
12228 value to a @code{struct} member:
12231 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
12234 Normally, register values are relative to the selected stack frame
12235 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
12236 value that the register would contain if all stack frames farther in
12237 were exited and their saved registers restored. In order to see the
12238 true contents of hardware registers, you must select the innermost
12239 frame (with @samp{frame 0}).
12241 @cindex caller-saved registers
12242 @cindex call-clobbered registers
12243 @cindex volatile registers
12244 @cindex <not saved> values
12245 Usually ABIs reserve some registers as not needed to be saved by the
12246 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
12247 registers). It may therefore not be possible for @value{GDBN} to know
12248 the value a register had before the call (in other words, in the outer
12249 frame), if the register value has since been changed by the callee.
12250 @value{GDBN} tries to deduce where the inner frame saved
12251 (``callee-saved'') registers, from the debug info, unwind info, or the
12252 machine code generated by your compiler. If some register is not
12253 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
12254 its own knowledge of the ABI, or because the debug/unwind info
12255 explicitly says the register's value is undefined), @value{GDBN}
12256 displays @w{@samp{<not saved>}} as the register's value. With targets
12257 that @value{GDBN} has no knowledge of the register saving convention,
12258 if a register was not saved by the callee, then its value and location
12259 in the outer frame are assumed to be the same of the inner frame.
12260 This is usually harmless, because if the register is call-clobbered,
12261 the caller either does not care what is in the register after the
12262 call, or has code to restore the value that it does care about. Note,
12263 however, that if you change such a register in the outer frame, you
12264 may also be affecting the inner frame. Also, the more ``outer'' the
12265 frame is you're looking at, the more likely a call-clobbered
12266 register's value is to be wrong, in the sense that it doesn't actually
12267 represent the value the register had just before the call.
12269 @node Floating Point Hardware
12270 @section Floating Point Hardware
12271 @cindex floating point
12273 Depending on the configuration, @value{GDBN} may be able to give
12274 you more information about the status of the floating point hardware.
12279 Display hardware-dependent information about the floating
12280 point unit. The exact contents and layout vary depending on the
12281 floating point chip. Currently, @samp{info float} is supported on
12282 the ARM and x86 machines.
12286 @section Vector Unit
12287 @cindex vector unit
12289 Depending on the configuration, @value{GDBN} may be able to give you
12290 more information about the status of the vector unit.
12293 @kindex info vector
12295 Display information about the vector unit. The exact contents and
12296 layout vary depending on the hardware.
12299 @node OS Information
12300 @section Operating System Auxiliary Information
12301 @cindex OS information
12303 @value{GDBN} provides interfaces to useful OS facilities that can help
12304 you debug your program.
12306 @cindex auxiliary vector
12307 @cindex vector, auxiliary
12308 Some operating systems supply an @dfn{auxiliary vector} to programs at
12309 startup. This is akin to the arguments and environment that you
12310 specify for a program, but contains a system-dependent variety of
12311 binary values that tell system libraries important details about the
12312 hardware, operating system, and process. Each value's purpose is
12313 identified by an integer tag; the meanings are well-known but system-specific.
12314 Depending on the configuration and operating system facilities,
12315 @value{GDBN} may be able to show you this information. For remote
12316 targets, this functionality may further depend on the remote stub's
12317 support of the @samp{qXfer:auxv:read} packet, see
12318 @ref{qXfer auxiliary vector read}.
12323 Display the auxiliary vector of the inferior, which can be either a
12324 live process or a core dump file. @value{GDBN} prints each tag value
12325 numerically, and also shows names and text descriptions for recognized
12326 tags. Some values in the vector are numbers, some bit masks, and some
12327 pointers to strings or other data. @value{GDBN} displays each value in the
12328 most appropriate form for a recognized tag, and in hexadecimal for
12329 an unrecognized tag.
12332 On some targets, @value{GDBN} can access operating system-specific
12333 information and show it to you. The types of information available
12334 will differ depending on the type of operating system running on the
12335 target. The mechanism used to fetch the data is described in
12336 @ref{Operating System Information}. For remote targets, this
12337 functionality depends on the remote stub's support of the
12338 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
12342 @item info os @var{infotype}
12344 Display OS information of the requested type.
12346 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
12348 @anchor{linux info os infotypes}
12350 @kindex info os cpus
12352 Display the list of all CPUs/cores. For each CPU/core, @value{GDBN} prints
12353 the available fields from /proc/cpuinfo. For each supported architecture
12354 different fields are available. Two common entries are processor which gives
12355 CPU number and bogomips; a system constant that is calculated during
12356 kernel initialization.
12358 @kindex info os files
12360 Display the list of open file descriptors on the target. For each
12361 file descriptor, @value{GDBN} prints the identifier of the process
12362 owning the descriptor, the command of the owning process, the value
12363 of the descriptor, and the target of the descriptor.
12365 @kindex info os modules
12367 Display the list of all loaded kernel modules on the target. For each
12368 module, @value{GDBN} prints the module name, the size of the module in
12369 bytes, the number of times the module is used, the dependencies of the
12370 module, the status of the module, and the address of the loaded module
12373 @kindex info os msg
12375 Display the list of all System V message queues on the target. For each
12376 message queue, @value{GDBN} prints the message queue key, the message
12377 queue identifier, the access permissions, the current number of bytes
12378 on the queue, the current number of messages on the queue, the processes
12379 that last sent and received a message on the queue, the user and group
12380 of the owner and creator of the message queue, the times at which a
12381 message was last sent and received on the queue, and the time at which
12382 the message queue was last changed.
12384 @kindex info os processes
12386 Display the list of processes on the target. For each process,
12387 @value{GDBN} prints the process identifier, the name of the user, the
12388 command corresponding to the process, and the list of processor cores
12389 that the process is currently running on. (To understand what these
12390 properties mean, for this and the following info types, please consult
12391 the general @sc{gnu}/Linux documentation.)
12393 @kindex info os procgroups
12395 Display the list of process groups on the target. For each process,
12396 @value{GDBN} prints the identifier of the process group that it belongs
12397 to, the command corresponding to the process group leader, the process
12398 identifier, and the command line of the process. The list is sorted
12399 first by the process group identifier, then by the process identifier,
12400 so that processes belonging to the same process group are grouped together
12401 and the process group leader is listed first.
12403 @kindex info os semaphores
12405 Display the list of all System V semaphore sets on the target. For each
12406 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
12407 set identifier, the access permissions, the number of semaphores in the
12408 set, the user and group of the owner and creator of the semaphore set,
12409 and the times at which the semaphore set was operated upon and changed.
12411 @kindex info os shm
12413 Display the list of all System V shared-memory regions on the target.
12414 For each shared-memory region, @value{GDBN} prints the region key,
12415 the shared-memory identifier, the access permissions, the size of the
12416 region, the process that created the region, the process that last
12417 attached to or detached from the region, the current number of live
12418 attaches to the region, and the times at which the region was last
12419 attached to, detach from, and changed.
12421 @kindex info os sockets
12423 Display the list of Internet-domain sockets on the target. For each
12424 socket, @value{GDBN} prints the address and port of the local and
12425 remote endpoints, the current state of the connection, the creator of
12426 the socket, the IP address family of the socket, and the type of the
12429 @kindex info os threads
12431 Display the list of threads running on the target. For each thread,
12432 @value{GDBN} prints the identifier of the process that the thread
12433 belongs to, the command of the process, the thread identifier, and the
12434 processor core that it is currently running on. The main thread of a
12435 process is not listed.
12439 If @var{infotype} is omitted, then list the possible values for
12440 @var{infotype} and the kind of OS information available for each
12441 @var{infotype}. If the target does not return a list of possible
12442 types, this command will report an error.
12445 @node Memory Region Attributes
12446 @section Memory Region Attributes
12447 @cindex memory region attributes
12449 @dfn{Memory region attributes} allow you to describe special handling
12450 required by regions of your target's memory. @value{GDBN} uses
12451 attributes to determine whether to allow certain types of memory
12452 accesses; whether to use specific width accesses; and whether to cache
12453 target memory. By default the description of memory regions is
12454 fetched from the target (if the current target supports this), but the
12455 user can override the fetched regions.
12457 Defined memory regions can be individually enabled and disabled. When a
12458 memory region is disabled, @value{GDBN} uses the default attributes when
12459 accessing memory in that region. Similarly, if no memory regions have
12460 been defined, @value{GDBN} uses the default attributes when accessing
12463 When a memory region is defined, it is given a number to identify it;
12464 to enable, disable, or remove a memory region, you specify that number.
12468 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
12469 Define a memory region bounded by @var{lower} and @var{upper} with
12470 attributes @var{attributes}@dots{}, and add it to the list of regions
12471 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
12472 case: it is treated as the target's maximum memory address.
12473 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
12476 Discard any user changes to the memory regions and use target-supplied
12477 regions, if available, or no regions if the target does not support.
12480 @item delete mem @var{nums}@dots{}
12481 Remove memory regions @var{nums}@dots{} from the list of regions
12482 monitored by @value{GDBN}.
12484 @kindex disable mem
12485 @item disable mem @var{nums}@dots{}
12486 Disable monitoring of memory regions @var{nums}@dots{}.
12487 A disabled memory region is not forgotten.
12488 It may be enabled again later.
12491 @item enable mem @var{nums}@dots{}
12492 Enable monitoring of memory regions @var{nums}@dots{}.
12496 Print a table of all defined memory regions, with the following columns
12500 @item Memory Region Number
12501 @item Enabled or Disabled.
12502 Enabled memory regions are marked with @samp{y}.
12503 Disabled memory regions are marked with @samp{n}.
12506 The address defining the inclusive lower bound of the memory region.
12509 The address defining the exclusive upper bound of the memory region.
12512 The list of attributes set for this memory region.
12517 @subsection Attributes
12519 @subsubsection Memory Access Mode
12520 The access mode attributes set whether @value{GDBN} may make read or
12521 write accesses to a memory region.
12523 While these attributes prevent @value{GDBN} from performing invalid
12524 memory accesses, they do nothing to prevent the target system, I/O DMA,
12525 etc.@: from accessing memory.
12529 Memory is read only.
12531 Memory is write only.
12533 Memory is read/write. This is the default.
12536 @subsubsection Memory Access Size
12537 The access size attribute tells @value{GDBN} to use specific sized
12538 accesses in the memory region. Often memory mapped device registers
12539 require specific sized accesses. If no access size attribute is
12540 specified, @value{GDBN} may use accesses of any size.
12544 Use 8 bit memory accesses.
12546 Use 16 bit memory accesses.
12548 Use 32 bit memory accesses.
12550 Use 64 bit memory accesses.
12553 @c @subsubsection Hardware/Software Breakpoints
12554 @c The hardware/software breakpoint attributes set whether @value{GDBN}
12555 @c will use hardware or software breakpoints for the internal breakpoints
12556 @c used by the step, next, finish, until, etc. commands.
12560 @c Always use hardware breakpoints
12561 @c @item swbreak (default)
12564 @subsubsection Data Cache
12565 The data cache attributes set whether @value{GDBN} will cache target
12566 memory. While this generally improves performance by reducing debug
12567 protocol overhead, it can lead to incorrect results because @value{GDBN}
12568 does not know about volatile variables or memory mapped device
12573 Enable @value{GDBN} to cache target memory.
12575 Disable @value{GDBN} from caching target memory. This is the default.
12578 @subsection Memory Access Checking
12579 @value{GDBN} can be instructed to refuse accesses to memory that is
12580 not explicitly described. This can be useful if accessing such
12581 regions has undesired effects for a specific target, or to provide
12582 better error checking. The following commands control this behaviour.
12585 @kindex set mem inaccessible-by-default
12586 @item set mem inaccessible-by-default [on|off]
12587 If @code{on} is specified, make @value{GDBN} treat memory not
12588 explicitly described by the memory ranges as non-existent and refuse accesses
12589 to such memory. The checks are only performed if there's at least one
12590 memory range defined. If @code{off} is specified, make @value{GDBN}
12591 treat the memory not explicitly described by the memory ranges as RAM.
12592 The default value is @code{on}.
12593 @kindex show mem inaccessible-by-default
12594 @item show mem inaccessible-by-default
12595 Show the current handling of accesses to unknown memory.
12599 @c @subsubsection Memory Write Verification
12600 @c The memory write verification attributes set whether @value{GDBN}
12601 @c will re-reads data after each write to verify the write was successful.
12605 @c @item noverify (default)
12608 @node Dump/Restore Files
12609 @section Copy Between Memory and a File
12610 @cindex dump/restore files
12611 @cindex append data to a file
12612 @cindex dump data to a file
12613 @cindex restore data from a file
12615 You can use the commands @code{dump}, @code{append}, and
12616 @code{restore} to copy data between target memory and a file. The
12617 @code{dump} and @code{append} commands write data to a file, and the
12618 @code{restore} command reads data from a file back into the inferior's
12619 memory. Files may be in binary, Motorola S-record, Intel hex,
12620 Tektronix Hex, or Verilog Hex format; however, @value{GDBN} can only
12621 append to binary files, and cannot read from Verilog Hex files.
12626 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
12627 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
12628 Dump the contents of memory from @var{start_addr} to @var{end_addr},
12629 or the value of @var{expr}, to @var{filename} in the given format.
12631 The @var{format} parameter may be any one of:
12638 Motorola S-record format.
12640 Tektronix Hex format.
12642 Verilog Hex format.
12645 @value{GDBN} uses the same definitions of these formats as the
12646 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
12647 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
12651 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
12652 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
12653 Append the contents of memory from @var{start_addr} to @var{end_addr},
12654 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
12655 (@value{GDBN} can only append data to files in raw binary form.)
12658 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
12659 Restore the contents of file @var{filename} into memory. The
12660 @code{restore} command can automatically recognize any known @sc{bfd}
12661 file format, except for raw binary. To restore a raw binary file you
12662 must specify the optional keyword @code{binary} after the filename.
12664 If @var{bias} is non-zero, its value will be added to the addresses
12665 contained in the file. Binary files always start at address zero, so
12666 they will be restored at address @var{bias}. Other bfd files have
12667 a built-in location; they will be restored at offset @var{bias}
12668 from that location.
12670 If @var{start} and/or @var{end} are non-zero, then only data between
12671 file offset @var{start} and file offset @var{end} will be restored.
12672 These offsets are relative to the addresses in the file, before
12673 the @var{bias} argument is applied.
12677 @node Core File Generation
12678 @section How to Produce a Core File from Your Program
12679 @cindex dump core from inferior
12681 A @dfn{core file} or @dfn{core dump} is a file that records the memory
12682 image of a running process and its process status (register values
12683 etc.). Its primary use is post-mortem debugging of a program that
12684 crashed while it ran outside a debugger. A program that crashes
12685 automatically produces a core file, unless this feature is disabled by
12686 the user. @xref{Files}, for information on invoking @value{GDBN} in
12687 the post-mortem debugging mode.
12689 Occasionally, you may wish to produce a core file of the program you
12690 are debugging in order to preserve a snapshot of its state.
12691 @value{GDBN} has a special command for that.
12695 @kindex generate-core-file
12696 @item generate-core-file [@var{file}]
12697 @itemx gcore [@var{file}]
12698 Produce a core dump of the inferior process. The optional argument
12699 @var{file} specifies the file name where to put the core dump. If not
12700 specified, the file name defaults to @file{core.@var{pid}}, where
12701 @var{pid} is the inferior process ID.
12703 Note that this command is implemented only for some systems (as of
12704 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
12706 On @sc{gnu}/Linux, this command can take into account the value of the
12707 file @file{/proc/@var{pid}/coredump_filter} when generating the core
12708 dump (@pxref{set use-coredump-filter}), and by default honors the
12709 @code{VM_DONTDUMP} flag for mappings where it is present in the file
12710 @file{/proc/@var{pid}/smaps} (@pxref{set dump-excluded-mappings}).
12712 @kindex set use-coredump-filter
12713 @anchor{set use-coredump-filter}
12714 @item set use-coredump-filter on
12715 @itemx set use-coredump-filter off
12716 Enable or disable the use of the file
12717 @file{/proc/@var{pid}/coredump_filter} when generating core dump
12718 files. This file is used by the Linux kernel to decide what types of
12719 memory mappings will be dumped or ignored when generating a core dump
12720 file. @var{pid} is the process ID of a currently running process.
12722 To make use of this feature, you have to write in the
12723 @file{/proc/@var{pid}/coredump_filter} file a value, in hexadecimal,
12724 which is a bit mask representing the memory mapping types. If a bit
12725 is set in the bit mask, then the memory mappings of the corresponding
12726 types will be dumped; otherwise, they will be ignored. This
12727 configuration is inherited by child processes. For more information
12728 about the bits that can be set in the
12729 @file{/proc/@var{pid}/coredump_filter} file, please refer to the
12730 manpage of @code{core(5)}.
12732 By default, this option is @code{on}. If this option is turned
12733 @code{off}, @value{GDBN} does not read the @file{coredump_filter} file
12734 and instead uses the same default value as the Linux kernel in order
12735 to decide which pages will be dumped in the core dump file. This
12736 value is currently @code{0x33}, which means that bits @code{0}
12737 (anonymous private mappings), @code{1} (anonymous shared mappings),
12738 @code{4} (ELF headers) and @code{5} (private huge pages) are active.
12739 This will cause these memory mappings to be dumped automatically.
12741 @kindex set dump-excluded-mappings
12742 @anchor{set dump-excluded-mappings}
12743 @item set dump-excluded-mappings on
12744 @itemx set dump-excluded-mappings off
12745 If @code{on} is specified, @value{GDBN} will dump memory mappings
12746 marked with the @code{VM_DONTDUMP} flag. This flag is represented in
12747 the file @file{/proc/@var{pid}/smaps} with the acronym @code{dd}.
12749 The default value is @code{off}.
12752 @node Character Sets
12753 @section Character Sets
12754 @cindex character sets
12756 @cindex translating between character sets
12757 @cindex host character set
12758 @cindex target character set
12760 If the program you are debugging uses a different character set to
12761 represent characters and strings than the one @value{GDBN} uses itself,
12762 @value{GDBN} can automatically translate between the character sets for
12763 you. The character set @value{GDBN} uses we call the @dfn{host
12764 character set}; the one the inferior program uses we call the
12765 @dfn{target character set}.
12767 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
12768 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
12769 remote protocol (@pxref{Remote Debugging}) to debug a program
12770 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
12771 then the host character set is Latin-1, and the target character set is
12772 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
12773 target-charset EBCDIC-US}, then @value{GDBN} translates between
12774 @sc{ebcdic} and Latin 1 as you print character or string values, or use
12775 character and string literals in expressions.
12777 @value{GDBN} has no way to automatically recognize which character set
12778 the inferior program uses; you must tell it, using the @code{set
12779 target-charset} command, described below.
12781 Here are the commands for controlling @value{GDBN}'s character set
12785 @item set target-charset @var{charset}
12786 @kindex set target-charset
12787 Set the current target character set to @var{charset}. To display the
12788 list of supported target character sets, type
12789 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
12791 @item set host-charset @var{charset}
12792 @kindex set host-charset
12793 Set the current host character set to @var{charset}.
12795 By default, @value{GDBN} uses a host character set appropriate to the
12796 system it is running on; you can override that default using the
12797 @code{set host-charset} command. On some systems, @value{GDBN} cannot
12798 automatically determine the appropriate host character set. In this
12799 case, @value{GDBN} uses @samp{UTF-8}.
12801 @value{GDBN} can only use certain character sets as its host character
12802 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
12803 @value{GDBN} will list the host character sets it supports.
12805 @item set charset @var{charset}
12806 @kindex set charset
12807 Set the current host and target character sets to @var{charset}. As
12808 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
12809 @value{GDBN} will list the names of the character sets that can be used
12810 for both host and target.
12813 @kindex show charset
12814 Show the names of the current host and target character sets.
12816 @item show host-charset
12817 @kindex show host-charset
12818 Show the name of the current host character set.
12820 @item show target-charset
12821 @kindex show target-charset
12822 Show the name of the current target character set.
12824 @item set target-wide-charset @var{charset}
12825 @kindex set target-wide-charset
12826 Set the current target's wide character set to @var{charset}. This is
12827 the character set used by the target's @code{wchar_t} type. To
12828 display the list of supported wide character sets, type
12829 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
12831 @item show target-wide-charset
12832 @kindex show target-wide-charset
12833 Show the name of the current target's wide character set.
12836 Here is an example of @value{GDBN}'s character set support in action.
12837 Assume that the following source code has been placed in the file
12838 @file{charset-test.c}:
12844 = @{72, 101, 108, 108, 111, 44, 32, 119,
12845 111, 114, 108, 100, 33, 10, 0@};
12846 char ibm1047_hello[]
12847 = @{200, 133, 147, 147, 150, 107, 64, 166,
12848 150, 153, 147, 132, 90, 37, 0@};
12852 printf ("Hello, world!\n");
12856 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
12857 containing the string @samp{Hello, world!} followed by a newline,
12858 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
12860 We compile the program, and invoke the debugger on it:
12863 $ gcc -g charset-test.c -o charset-test
12864 $ gdb -nw charset-test
12865 GNU gdb 2001-12-19-cvs
12866 Copyright 2001 Free Software Foundation, Inc.
12871 We can use the @code{show charset} command to see what character sets
12872 @value{GDBN} is currently using to interpret and display characters and
12876 (@value{GDBP}) show charset
12877 The current host and target character set is `ISO-8859-1'.
12881 For the sake of printing this manual, let's use @sc{ascii} as our
12882 initial character set:
12884 (@value{GDBP}) set charset ASCII
12885 (@value{GDBP}) show charset
12886 The current host and target character set is `ASCII'.
12890 Let's assume that @sc{ascii} is indeed the correct character set for our
12891 host system --- in other words, let's assume that if @value{GDBN} prints
12892 characters using the @sc{ascii} character set, our terminal will display
12893 them properly. Since our current target character set is also
12894 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
12897 (@value{GDBP}) print ascii_hello
12898 $1 = 0x401698 "Hello, world!\n"
12899 (@value{GDBP}) print ascii_hello[0]
12904 @value{GDBN} uses the target character set for character and string
12905 literals you use in expressions:
12908 (@value{GDBP}) print '+'
12913 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
12916 @value{GDBN} relies on the user to tell it which character set the
12917 target program uses. If we print @code{ibm1047_hello} while our target
12918 character set is still @sc{ascii}, we get jibberish:
12921 (@value{GDBP}) print ibm1047_hello
12922 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
12923 (@value{GDBP}) print ibm1047_hello[0]
12928 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
12929 @value{GDBN} tells us the character sets it supports:
12932 (@value{GDBP}) set target-charset
12933 ASCII EBCDIC-US IBM1047 ISO-8859-1
12934 (@value{GDBP}) set target-charset
12937 We can select @sc{ibm1047} as our target character set, and examine the
12938 program's strings again. Now the @sc{ascii} string is wrong, but
12939 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
12940 target character set, @sc{ibm1047}, to the host character set,
12941 @sc{ascii}, and they display correctly:
12944 (@value{GDBP}) set target-charset IBM1047
12945 (@value{GDBP}) show charset
12946 The current host character set is `ASCII'.
12947 The current target character set is `IBM1047'.
12948 (@value{GDBP}) print ascii_hello
12949 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
12950 (@value{GDBP}) print ascii_hello[0]
12952 (@value{GDBP}) print ibm1047_hello
12953 $8 = 0x4016a8 "Hello, world!\n"
12954 (@value{GDBP}) print ibm1047_hello[0]
12959 As above, @value{GDBN} uses the target character set for character and
12960 string literals you use in expressions:
12963 (@value{GDBP}) print '+'
12968 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
12971 @node Caching Target Data
12972 @section Caching Data of Targets
12973 @cindex caching data of targets
12975 @value{GDBN} caches data exchanged between the debugger and a target.
12976 Each cache is associated with the address space of the inferior.
12977 @xref{Inferiors and Programs}, about inferior and address space.
12978 Such caching generally improves performance in remote debugging
12979 (@pxref{Remote Debugging}), because it reduces the overhead of the
12980 remote protocol by bundling memory reads and writes into large chunks.
12981 Unfortunately, simply caching everything would lead to incorrect results,
12982 since @value{GDBN} does not necessarily know anything about volatile
12983 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
12984 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
12986 Therefore, by default, @value{GDBN} only caches data
12987 known to be on the stack@footnote{In non-stop mode, it is moderately
12988 rare for a running thread to modify the stack of a stopped thread
12989 in a way that would interfere with a backtrace, and caching of
12990 stack reads provides a significant speed up of remote backtraces.} or
12991 in the code segment.
12992 Other regions of memory can be explicitly marked as
12993 cacheable; @pxref{Memory Region Attributes}.
12996 @kindex set remotecache
12997 @item set remotecache on
12998 @itemx set remotecache off
12999 This option no longer does anything; it exists for compatibility
13002 @kindex show remotecache
13003 @item show remotecache
13004 Show the current state of the obsolete remotecache flag.
13006 @kindex set stack-cache
13007 @item set stack-cache on
13008 @itemx set stack-cache off
13009 Enable or disable caching of stack accesses. When @code{on}, use
13010 caching. By default, this option is @code{on}.
13012 @kindex show stack-cache
13013 @item show stack-cache
13014 Show the current state of data caching for memory accesses.
13016 @kindex set code-cache
13017 @item set code-cache on
13018 @itemx set code-cache off
13019 Enable or disable caching of code segment accesses. When @code{on},
13020 use caching. By default, this option is @code{on}. This improves
13021 performance of disassembly in remote debugging.
13023 @kindex show code-cache
13024 @item show code-cache
13025 Show the current state of target memory cache for code segment
13028 @kindex info dcache
13029 @item info dcache @r{[}line@r{]}
13030 Print the information about the performance of data cache of the
13031 current inferior's address space. The information displayed
13032 includes the dcache width and depth, and for each cache line, its
13033 number, address, and how many times it was referenced. This
13034 command is useful for debugging the data cache operation.
13036 If a line number is specified, the contents of that line will be
13039 @item set dcache size @var{size}
13040 @cindex dcache size
13041 @kindex set dcache size
13042 Set maximum number of entries in dcache (dcache depth above).
13044 @item set dcache line-size @var{line-size}
13045 @cindex dcache line-size
13046 @kindex set dcache line-size
13047 Set number of bytes each dcache entry caches (dcache width above).
13048 Must be a power of 2.
13050 @item show dcache size
13051 @kindex show dcache size
13052 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
13054 @item show dcache line-size
13055 @kindex show dcache line-size
13056 Show default size of dcache lines.
13060 @node Searching Memory
13061 @section Search Memory
13062 @cindex searching memory
13064 Memory can be searched for a particular sequence of bytes with the
13065 @code{find} command.
13069 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
13070 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
13071 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
13072 etc. The search begins at address @var{start_addr} and continues for either
13073 @var{len} bytes or through to @var{end_addr} inclusive.
13076 @var{s} and @var{n} are optional parameters.
13077 They may be specified in either order, apart or together.
13080 @item @var{s}, search query size
13081 The size of each search query value.
13087 halfwords (two bytes)
13091 giant words (eight bytes)
13094 All values are interpreted in the current language.
13095 This means, for example, that if the current source language is C/C@t{++}
13096 then searching for the string ``hello'' includes the trailing '\0'.
13097 The null terminator can be removed from searching by using casts,
13098 e.g.: @samp{@{char[5]@}"hello"}.
13100 If the value size is not specified, it is taken from the
13101 value's type in the current language.
13102 This is useful when one wants to specify the search
13103 pattern as a mixture of types.
13104 Note that this means, for example, that in the case of C-like languages
13105 a search for an untyped 0x42 will search for @samp{(int) 0x42}
13106 which is typically four bytes.
13108 @item @var{n}, maximum number of finds
13109 The maximum number of matches to print. The default is to print all finds.
13112 You can use strings as search values. Quote them with double-quotes
13114 The string value is copied into the search pattern byte by byte,
13115 regardless of the endianness of the target and the size specification.
13117 The address of each match found is printed as well as a count of the
13118 number of matches found.
13120 The address of the last value found is stored in convenience variable
13122 A count of the number of matches is stored in @samp{$numfound}.
13124 For example, if stopped at the @code{printf} in this function:
13130 static char hello[] = "hello-hello";
13131 static struct @{ char c; short s; int i; @}
13132 __attribute__ ((packed)) mixed
13133 = @{ 'c', 0x1234, 0x87654321 @};
13134 printf ("%s\n", hello);
13139 you get during debugging:
13142 (gdb) find &hello[0], +sizeof(hello), "hello"
13143 0x804956d <hello.1620+6>
13145 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
13146 0x8049567 <hello.1620>
13147 0x804956d <hello.1620+6>
13149 (gdb) find &hello[0], +sizeof(hello), @{char[5]@}"hello"
13150 0x8049567 <hello.1620>
13151 0x804956d <hello.1620+6>
13153 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
13154 0x8049567 <hello.1620>
13156 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
13157 0x8049560 <mixed.1625>
13159 (gdb) print $numfound
13162 $2 = (void *) 0x8049560
13166 @section Value Sizes
13168 Whenever @value{GDBN} prints a value memory will be allocated within
13169 @value{GDBN} to hold the contents of the value. It is possible in
13170 some languages with dynamic typing systems, that an invalid program
13171 may indicate a value that is incorrectly large, this in turn may cause
13172 @value{GDBN} to try and allocate an overly large ammount of memory.
13175 @kindex set max-value-size
13176 @item set max-value-size @var{bytes}
13177 @itemx set max-value-size unlimited
13178 Set the maximum size of memory that @value{GDBN} will allocate for the
13179 contents of a value to @var{bytes}, trying to display a value that
13180 requires more memory than that will result in an error.
13182 Setting this variable does not effect values that have already been
13183 allocated within @value{GDBN}, only future allocations.
13185 There's a minimum size that @code{max-value-size} can be set to in
13186 order that @value{GDBN} can still operate correctly, this minimum is
13187 currently 16 bytes.
13189 The limit applies to the results of some subexpressions as well as to
13190 complete expressions. For example, an expression denoting a simple
13191 integer component, such as @code{x.y.z}, may fail if the size of
13192 @var{x.y} is dynamic and exceeds @var{bytes}. On the other hand,
13193 @value{GDBN} is sometimes clever; the expression @code{A[i]}, where
13194 @var{A} is an array variable with non-constant size, will generally
13195 succeed regardless of the bounds on @var{A}, as long as the component
13196 size is less than @var{bytes}.
13198 The default value of @code{max-value-size} is currently 64k.
13200 @kindex show max-value-size
13201 @item show max-value-size
13202 Show the maximum size of memory, in bytes, that @value{GDBN} will
13203 allocate for the contents of a value.
13206 @node Optimized Code
13207 @chapter Debugging Optimized Code
13208 @cindex optimized code, debugging
13209 @cindex debugging optimized code
13211 Almost all compilers support optimization. With optimization
13212 disabled, the compiler generates assembly code that corresponds
13213 directly to your source code, in a simplistic way. As the compiler
13214 applies more powerful optimizations, the generated assembly code
13215 diverges from your original source code. With help from debugging
13216 information generated by the compiler, @value{GDBN} can map from
13217 the running program back to constructs from your original source.
13219 @value{GDBN} is more accurate with optimization disabled. If you
13220 can recompile without optimization, it is easier to follow the
13221 progress of your program during debugging. But, there are many cases
13222 where you may need to debug an optimized version.
13224 When you debug a program compiled with @samp{-g -O}, remember that the
13225 optimizer has rearranged your code; the debugger shows you what is
13226 really there. Do not be too surprised when the execution path does not
13227 exactly match your source file! An extreme example: if you define a
13228 variable, but never use it, @value{GDBN} never sees that
13229 variable---because the compiler optimizes it out of existence.
13231 Some things do not work as well with @samp{-g -O} as with just
13232 @samp{-g}, particularly on machines with instruction scheduling. If in
13233 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
13234 please report it to us as a bug (including a test case!).
13235 @xref{Variables}, for more information about debugging optimized code.
13238 * Inline Functions:: How @value{GDBN} presents inlining
13239 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
13242 @node Inline Functions
13243 @section Inline Functions
13244 @cindex inline functions, debugging
13246 @dfn{Inlining} is an optimization that inserts a copy of the function
13247 body directly at each call site, instead of jumping to a shared
13248 routine. @value{GDBN} displays inlined functions just like
13249 non-inlined functions. They appear in backtraces. You can view their
13250 arguments and local variables, step into them with @code{step}, skip
13251 them with @code{next}, and escape from them with @code{finish}.
13252 You can check whether a function was inlined by using the
13253 @code{info frame} command.
13255 For @value{GDBN} to support inlined functions, the compiler must
13256 record information about inlining in the debug information ---
13257 @value{NGCC} using the @sc{dwarf 2} format does this, and several
13258 other compilers do also. @value{GDBN} only supports inlined functions
13259 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
13260 do not emit two required attributes (@samp{DW_AT_call_file} and
13261 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
13262 function calls with earlier versions of @value{NGCC}. It instead
13263 displays the arguments and local variables of inlined functions as
13264 local variables in the caller.
13266 The body of an inlined function is directly included at its call site;
13267 unlike a non-inlined function, there are no instructions devoted to
13268 the call. @value{GDBN} still pretends that the call site and the
13269 start of the inlined function are different instructions. Stepping to
13270 the call site shows the call site, and then stepping again shows
13271 the first line of the inlined function, even though no additional
13272 instructions are executed.
13274 This makes source-level debugging much clearer; you can see both the
13275 context of the call and then the effect of the call. Only stepping by
13276 a single instruction using @code{stepi} or @code{nexti} does not do
13277 this; single instruction steps always show the inlined body.
13279 There are some ways that @value{GDBN} does not pretend that inlined
13280 function calls are the same as normal calls:
13284 Setting breakpoints at the call site of an inlined function may not
13285 work, because the call site does not contain any code. @value{GDBN}
13286 may incorrectly move the breakpoint to the next line of the enclosing
13287 function, after the call. This limitation will be removed in a future
13288 version of @value{GDBN}; until then, set a breakpoint on an earlier line
13289 or inside the inlined function instead.
13292 @value{GDBN} cannot locate the return value of inlined calls after
13293 using the @code{finish} command. This is a limitation of compiler-generated
13294 debugging information; after @code{finish}, you can step to the next line
13295 and print a variable where your program stored the return value.
13299 @node Tail Call Frames
13300 @section Tail Call Frames
13301 @cindex tail call frames, debugging
13303 Function @code{B} can call function @code{C} in its very last statement. In
13304 unoptimized compilation the call of @code{C} is immediately followed by return
13305 instruction at the end of @code{B} code. Optimizing compiler may replace the
13306 call and return in function @code{B} into one jump to function @code{C}
13307 instead. Such use of a jump instruction is called @dfn{tail call}.
13309 During execution of function @code{C}, there will be no indication in the
13310 function call stack frames that it was tail-called from @code{B}. If function
13311 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
13312 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
13313 some cases @value{GDBN} can determine that @code{C} was tail-called from
13314 @code{B}, and it will then create fictitious call frame for that, with the
13315 return address set up as if @code{B} called @code{C} normally.
13317 This functionality is currently supported only by DWARF 2 debugging format and
13318 the compiler has to produce @samp{DW_TAG_call_site} tags. With
13319 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
13322 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
13323 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
13327 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
13329 Stack level 1, frame at 0x7fffffffda30:
13330 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
13331 tail call frame, caller of frame at 0x7fffffffda30
13332 source language c++.
13333 Arglist at unknown address.
13334 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
13337 The detection of all the possible code path executions can find them ambiguous.
13338 There is no execution history stored (possible @ref{Reverse Execution} is never
13339 used for this purpose) and the last known caller could have reached the known
13340 callee by multiple different jump sequences. In such case @value{GDBN} still
13341 tries to show at least all the unambiguous top tail callers and all the
13342 unambiguous bottom tail calees, if any.
13345 @anchor{set debug entry-values}
13346 @item set debug entry-values
13347 @kindex set debug entry-values
13348 When set to on, enables printing of analysis messages for both frame argument
13349 values at function entry and tail calls. It will show all the possible valid
13350 tail calls code paths it has considered. It will also print the intersection
13351 of them with the final unambiguous (possibly partial or even empty) code path
13354 @item show debug entry-values
13355 @kindex show debug entry-values
13356 Show the current state of analysis messages printing for both frame argument
13357 values at function entry and tail calls.
13360 The analysis messages for tail calls can for example show why the virtual tail
13361 call frame for function @code{c} has not been recognized (due to the indirect
13362 reference by variable @code{x}):
13365 static void __attribute__((noinline, noclone)) c (void);
13366 void (*x) (void) = c;
13367 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
13368 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
13369 int main (void) @{ x (); return 0; @}
13371 Breakpoint 1, DW_OP_entry_value resolving cannot find
13372 DW_TAG_call_site 0x40039a in main
13374 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
13377 #1 0x000000000040039a in main () at t.c:5
13380 Another possibility is an ambiguous virtual tail call frames resolution:
13384 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
13385 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
13386 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
13387 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
13388 static void __attribute__((noinline, noclone)) b (void)
13389 @{ if (i) c (); else e (); @}
13390 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
13391 int main (void) @{ a (); return 0; @}
13393 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
13394 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
13395 tailcall: reduced: 0x4004d2(a) |
13398 #1 0x00000000004004d2 in a () at t.c:8
13399 #2 0x0000000000400395 in main () at t.c:9
13402 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
13403 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
13405 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
13406 @ifset HAVE_MAKEINFO_CLICK
13407 @set ARROW @click{}
13408 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
13409 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
13411 @ifclear HAVE_MAKEINFO_CLICK
13413 @set CALLSEQ1B @value{CALLSEQ1A}
13414 @set CALLSEQ2B @value{CALLSEQ2A}
13417 Frames #0 and #2 are real, #1 is a virtual tail call frame.
13418 The code can have possible execution paths @value{CALLSEQ1B} or
13419 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
13421 @code{initial:} state shows some random possible calling sequence @value{GDBN}
13422 has found. It then finds another possible calling sequcen - that one is
13423 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
13424 printed as the @code{reduced:} calling sequence. That one could have many
13425 futher @code{compare:} and @code{reduced:} statements as long as there remain
13426 any non-ambiguous sequence entries.
13428 For the frame of function @code{b} in both cases there are different possible
13429 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
13430 also ambigous. The only non-ambiguous frame is the one for function @code{a},
13431 therefore this one is displayed to the user while the ambiguous frames are
13434 There can be also reasons why printing of frame argument values at function
13439 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
13440 static void __attribute__((noinline, noclone)) a (int i);
13441 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
13442 static void __attribute__((noinline, noclone)) a (int i)
13443 @{ if (i) b (i - 1); else c (0); @}
13444 int main (void) @{ a (5); return 0; @}
13447 #0 c (i=i@@entry=0) at t.c:2
13448 #1 0x0000000000400428 in a (DW_OP_entry_value resolving has found
13449 function "a" at 0x400420 can call itself via tail calls
13450 i=<optimized out>) at t.c:6
13451 #2 0x000000000040036e in main () at t.c:7
13454 @value{GDBN} cannot find out from the inferior state if and how many times did
13455 function @code{a} call itself (via function @code{b}) as these calls would be
13456 tail calls. Such tail calls would modify thue @code{i} variable, therefore
13457 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
13458 prints @code{<optimized out>} instead.
13461 @chapter C Preprocessor Macros
13463 Some languages, such as C and C@t{++}, provide a way to define and invoke
13464 ``preprocessor macros'' which expand into strings of tokens.
13465 @value{GDBN} can evaluate expressions containing macro invocations, show
13466 the result of macro expansion, and show a macro's definition, including
13467 where it was defined.
13469 You may need to compile your program specially to provide @value{GDBN}
13470 with information about preprocessor macros. Most compilers do not
13471 include macros in their debugging information, even when you compile
13472 with the @option{-g} flag. @xref{Compilation}.
13474 A program may define a macro at one point, remove that definition later,
13475 and then provide a different definition after that. Thus, at different
13476 points in the program, a macro may have different definitions, or have
13477 no definition at all. If there is a current stack frame, @value{GDBN}
13478 uses the macros in scope at that frame's source code line. Otherwise,
13479 @value{GDBN} uses the macros in scope at the current listing location;
13482 Whenever @value{GDBN} evaluates an expression, it always expands any
13483 macro invocations present in the expression. @value{GDBN} also provides
13484 the following commands for working with macros explicitly.
13488 @kindex macro expand
13489 @cindex macro expansion, showing the results of preprocessor
13490 @cindex preprocessor macro expansion, showing the results of
13491 @cindex expanding preprocessor macros
13492 @item macro expand @var{expression}
13493 @itemx macro exp @var{expression}
13494 Show the results of expanding all preprocessor macro invocations in
13495 @var{expression}. Since @value{GDBN} simply expands macros, but does
13496 not parse the result, @var{expression} need not be a valid expression;
13497 it can be any string of tokens.
13500 @item macro expand-once @var{expression}
13501 @itemx macro exp1 @var{expression}
13502 @cindex expand macro once
13503 @i{(This command is not yet implemented.)} Show the results of
13504 expanding those preprocessor macro invocations that appear explicitly in
13505 @var{expression}. Macro invocations appearing in that expansion are
13506 left unchanged. This command allows you to see the effect of a
13507 particular macro more clearly, without being confused by further
13508 expansions. Since @value{GDBN} simply expands macros, but does not
13509 parse the result, @var{expression} need not be a valid expression; it
13510 can be any string of tokens.
13513 @cindex macro definition, showing
13514 @cindex definition of a macro, showing
13515 @cindex macros, from debug info
13516 @item info macro [-a|-all] [--] @var{macro}
13517 Show the current definition or all definitions of the named @var{macro},
13518 and describe the source location or compiler command-line where that
13519 definition was established. The optional double dash is to signify the end of
13520 argument processing and the beginning of @var{macro} for non C-like macros where
13521 the macro may begin with a hyphen.
13523 @kindex info macros
13524 @item info macros @var{location}
13525 Show all macro definitions that are in effect at the location specified
13526 by @var{location}, and describe the source location or compiler
13527 command-line where those definitions were established.
13529 @kindex macro define
13530 @cindex user-defined macros
13531 @cindex defining macros interactively
13532 @cindex macros, user-defined
13533 @item macro define @var{macro} @var{replacement-list}
13534 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
13535 Introduce a definition for a preprocessor macro named @var{macro},
13536 invocations of which are replaced by the tokens given in
13537 @var{replacement-list}. The first form of this command defines an
13538 ``object-like'' macro, which takes no arguments; the second form
13539 defines a ``function-like'' macro, which takes the arguments given in
13542 A definition introduced by this command is in scope in every
13543 expression evaluated in @value{GDBN}, until it is removed with the
13544 @code{macro undef} command, described below. The definition overrides
13545 all definitions for @var{macro} present in the program being debugged,
13546 as well as any previous user-supplied definition.
13548 @kindex macro undef
13549 @item macro undef @var{macro}
13550 Remove any user-supplied definition for the macro named @var{macro}.
13551 This command only affects definitions provided with the @code{macro
13552 define} command, described above; it cannot remove definitions present
13553 in the program being debugged.
13557 List all the macros defined using the @code{macro define} command.
13560 @cindex macros, example of debugging with
13561 Here is a transcript showing the above commands in action. First, we
13562 show our source files:
13567 #include "sample.h"
13570 #define ADD(x) (M + x)
13575 printf ("Hello, world!\n");
13577 printf ("We're so creative.\n");
13579 printf ("Goodbye, world!\n");
13586 Now, we compile the program using the @sc{gnu} C compiler,
13587 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
13588 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
13589 and @option{-gdwarf-4}; we recommend always choosing the most recent
13590 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
13591 includes information about preprocessor macros in the debugging
13595 $ gcc -gdwarf-2 -g3 sample.c -o sample
13599 Now, we start @value{GDBN} on our sample program:
13603 GNU gdb 2002-05-06-cvs
13604 Copyright 2002 Free Software Foundation, Inc.
13605 GDB is free software, @dots{}
13609 We can expand macros and examine their definitions, even when the
13610 program is not running. @value{GDBN} uses the current listing position
13611 to decide which macro definitions are in scope:
13614 (@value{GDBP}) list main
13617 5 #define ADD(x) (M + x)
13622 10 printf ("Hello, world!\n");
13624 12 printf ("We're so creative.\n");
13625 (@value{GDBP}) info macro ADD
13626 Defined at /home/jimb/gdb/macros/play/sample.c:5
13627 #define ADD(x) (M + x)
13628 (@value{GDBP}) info macro Q
13629 Defined at /home/jimb/gdb/macros/play/sample.h:1
13630 included at /home/jimb/gdb/macros/play/sample.c:2
13632 (@value{GDBP}) macro expand ADD(1)
13633 expands to: (42 + 1)
13634 (@value{GDBP}) macro expand-once ADD(1)
13635 expands to: once (M + 1)
13639 In the example above, note that @code{macro expand-once} expands only
13640 the macro invocation explicit in the original text --- the invocation of
13641 @code{ADD} --- but does not expand the invocation of the macro @code{M},
13642 which was introduced by @code{ADD}.
13644 Once the program is running, @value{GDBN} uses the macro definitions in
13645 force at the source line of the current stack frame:
13648 (@value{GDBP}) break main
13649 Breakpoint 1 at 0x8048370: file sample.c, line 10.
13651 Starting program: /home/jimb/gdb/macros/play/sample
13653 Breakpoint 1, main () at sample.c:10
13654 10 printf ("Hello, world!\n");
13658 At line 10, the definition of the macro @code{N} at line 9 is in force:
13661 (@value{GDBP}) info macro N
13662 Defined at /home/jimb/gdb/macros/play/sample.c:9
13664 (@value{GDBP}) macro expand N Q M
13665 expands to: 28 < 42
13666 (@value{GDBP}) print N Q M
13671 As we step over directives that remove @code{N}'s definition, and then
13672 give it a new definition, @value{GDBN} finds the definition (or lack
13673 thereof) in force at each point:
13676 (@value{GDBP}) next
13678 12 printf ("We're so creative.\n");
13679 (@value{GDBP}) info macro N
13680 The symbol `N' has no definition as a C/C++ preprocessor macro
13681 at /home/jimb/gdb/macros/play/sample.c:12
13682 (@value{GDBP}) next
13684 14 printf ("Goodbye, world!\n");
13685 (@value{GDBP}) info macro N
13686 Defined at /home/jimb/gdb/macros/play/sample.c:13
13688 (@value{GDBP}) macro expand N Q M
13689 expands to: 1729 < 42
13690 (@value{GDBP}) print N Q M
13695 In addition to source files, macros can be defined on the compilation command
13696 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
13697 such a way, @value{GDBN} displays the location of their definition as line zero
13698 of the source file submitted to the compiler.
13701 (@value{GDBP}) info macro __STDC__
13702 Defined at /home/jimb/gdb/macros/play/sample.c:0
13709 @chapter Tracepoints
13710 @c This chapter is based on the documentation written by Michael
13711 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
13713 @cindex tracepoints
13714 In some applications, it is not feasible for the debugger to interrupt
13715 the program's execution long enough for the developer to learn
13716 anything helpful about its behavior. If the program's correctness
13717 depends on its real-time behavior, delays introduced by a debugger
13718 might cause the program to change its behavior drastically, or perhaps
13719 fail, even when the code itself is correct. It is useful to be able
13720 to observe the program's behavior without interrupting it.
13722 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
13723 specify locations in the program, called @dfn{tracepoints}, and
13724 arbitrary expressions to evaluate when those tracepoints are reached.
13725 Later, using the @code{tfind} command, you can examine the values
13726 those expressions had when the program hit the tracepoints. The
13727 expressions may also denote objects in memory---structures or arrays,
13728 for example---whose values @value{GDBN} should record; while visiting
13729 a particular tracepoint, you may inspect those objects as if they were
13730 in memory at that moment. However, because @value{GDBN} records these
13731 values without interacting with you, it can do so quickly and
13732 unobtrusively, hopefully not disturbing the program's behavior.
13734 The tracepoint facility is currently available only for remote
13735 targets. @xref{Targets}. In addition, your remote target must know
13736 how to collect trace data. This functionality is implemented in the
13737 remote stub; however, none of the stubs distributed with @value{GDBN}
13738 support tracepoints as of this writing. The format of the remote
13739 packets used to implement tracepoints are described in @ref{Tracepoint
13742 It is also possible to get trace data from a file, in a manner reminiscent
13743 of corefiles; you specify the filename, and use @code{tfind} to search
13744 through the file. @xref{Trace Files}, for more details.
13746 This chapter describes the tracepoint commands and features.
13749 * Set Tracepoints::
13750 * Analyze Collected Data::
13751 * Tracepoint Variables::
13755 @node Set Tracepoints
13756 @section Commands to Set Tracepoints
13758 Before running such a @dfn{trace experiment}, an arbitrary number of
13759 tracepoints can be set. A tracepoint is actually a special type of
13760 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
13761 standard breakpoint commands. For instance, as with breakpoints,
13762 tracepoint numbers are successive integers starting from one, and many
13763 of the commands associated with tracepoints take the tracepoint number
13764 as their argument, to identify which tracepoint to work on.
13766 For each tracepoint, you can specify, in advance, some arbitrary set
13767 of data that you want the target to collect in the trace buffer when
13768 it hits that tracepoint. The collected data can include registers,
13769 local variables, or global data. Later, you can use @value{GDBN}
13770 commands to examine the values these data had at the time the
13771 tracepoint was hit.
13773 Tracepoints do not support every breakpoint feature. Ignore counts on
13774 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
13775 commands when they are hit. Tracepoints may not be thread-specific
13778 @cindex fast tracepoints
13779 Some targets may support @dfn{fast tracepoints}, which are inserted in
13780 a different way (such as with a jump instead of a trap), that is
13781 faster but possibly restricted in where they may be installed.
13783 @cindex static tracepoints
13784 @cindex markers, static tracepoints
13785 @cindex probing markers, static tracepoints
13786 Regular and fast tracepoints are dynamic tracing facilities, meaning
13787 that they can be used to insert tracepoints at (almost) any location
13788 in the target. Some targets may also support controlling @dfn{static
13789 tracepoints} from @value{GDBN}. With static tracing, a set of
13790 instrumentation points, also known as @dfn{markers}, are embedded in
13791 the target program, and can be activated or deactivated by name or
13792 address. These are usually placed at locations which facilitate
13793 investigating what the target is actually doing. @value{GDBN}'s
13794 support for static tracing includes being able to list instrumentation
13795 points, and attach them with @value{GDBN} defined high level
13796 tracepoints that expose the whole range of convenience of
13797 @value{GDBN}'s tracepoints support. Namely, support for collecting
13798 registers values and values of global or local (to the instrumentation
13799 point) variables; tracepoint conditions and trace state variables.
13800 The act of installing a @value{GDBN} static tracepoint on an
13801 instrumentation point, or marker, is referred to as @dfn{probing} a
13802 static tracepoint marker.
13804 @code{gdbserver} supports tracepoints on some target systems.
13805 @xref{Server,,Tracepoints support in @code{gdbserver}}.
13807 This section describes commands to set tracepoints and associated
13808 conditions and actions.
13811 * Create and Delete Tracepoints::
13812 * Enable and Disable Tracepoints::
13813 * Tracepoint Passcounts::
13814 * Tracepoint Conditions::
13815 * Trace State Variables::
13816 * Tracepoint Actions::
13817 * Listing Tracepoints::
13818 * Listing Static Tracepoint Markers::
13819 * Starting and Stopping Trace Experiments::
13820 * Tracepoint Restrictions::
13823 @node Create and Delete Tracepoints
13824 @subsection Create and Delete Tracepoints
13827 @cindex set tracepoint
13829 @item trace @var{location}
13830 The @code{trace} command is very similar to the @code{break} command.
13831 Its argument @var{location} can be any valid location.
13832 @xref{Specify Location}. The @code{trace} command defines a tracepoint,
13833 which is a point in the target program where the debugger will briefly stop,
13834 collect some data, and then allow the program to continue. Setting a tracepoint
13835 or changing its actions takes effect immediately if the remote stub
13836 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
13838 If remote stub doesn't support the @samp{InstallInTrace} feature, all
13839 these changes don't take effect until the next @code{tstart}
13840 command, and once a trace experiment is running, further changes will
13841 not have any effect until the next trace experiment starts. In addition,
13842 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
13843 address is not yet resolved. (This is similar to pending breakpoints.)
13844 Pending tracepoints are not downloaded to the target and not installed
13845 until they are resolved. The resolution of pending tracepoints requires
13846 @value{GDBN} support---when debugging with the remote target, and
13847 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
13848 tracing}), pending tracepoints can not be resolved (and downloaded to
13849 the remote stub) while @value{GDBN} is disconnected.
13851 Here are some examples of using the @code{trace} command:
13854 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
13856 (@value{GDBP}) @b{trace +2} // 2 lines forward
13858 (@value{GDBP}) @b{trace my_function} // first source line of function
13860 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
13862 (@value{GDBP}) @b{trace *0x2117c4} // an address
13866 You can abbreviate @code{trace} as @code{tr}.
13868 @item trace @var{location} if @var{cond}
13869 Set a tracepoint with condition @var{cond}; evaluate the expression
13870 @var{cond} each time the tracepoint is reached, and collect data only
13871 if the value is nonzero---that is, if @var{cond} evaluates as true.
13872 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
13873 information on tracepoint conditions.
13875 @item ftrace @var{location} [ if @var{cond} ]
13876 @cindex set fast tracepoint
13877 @cindex fast tracepoints, setting
13879 The @code{ftrace} command sets a fast tracepoint. For targets that
13880 support them, fast tracepoints will use a more efficient but possibly
13881 less general technique to trigger data collection, such as a jump
13882 instruction instead of a trap, or some sort of hardware support. It
13883 may not be possible to create a fast tracepoint at the desired
13884 location, in which case the command will exit with an explanatory
13887 @value{GDBN} handles arguments to @code{ftrace} exactly as for
13890 On 32-bit x86-architecture systems, fast tracepoints normally need to
13891 be placed at an instruction that is 5 bytes or longer, but can be
13892 placed at 4-byte instructions if the low 64K of memory of the target
13893 program is available to install trampolines. Some Unix-type systems,
13894 such as @sc{gnu}/Linux, exclude low addresses from the program's
13895 address space; but for instance with the Linux kernel it is possible
13896 to let @value{GDBN} use this area by doing a @command{sysctl} command
13897 to set the @code{mmap_min_addr} kernel parameter, as in
13900 sudo sysctl -w vm.mmap_min_addr=32768
13904 which sets the low address to 32K, which leaves plenty of room for
13905 trampolines. The minimum address should be set to a page boundary.
13907 @item strace @var{location} [ if @var{cond} ]
13908 @cindex set static tracepoint
13909 @cindex static tracepoints, setting
13910 @cindex probe static tracepoint marker
13912 The @code{strace} command sets a static tracepoint. For targets that
13913 support it, setting a static tracepoint probes a static
13914 instrumentation point, or marker, found at @var{location}. It may not
13915 be possible to set a static tracepoint at the desired location, in
13916 which case the command will exit with an explanatory message.
13918 @value{GDBN} handles arguments to @code{strace} exactly as for
13919 @code{trace}, with the addition that the user can also specify
13920 @code{-m @var{marker}} as @var{location}. This probes the marker
13921 identified by the @var{marker} string identifier. This identifier
13922 depends on the static tracepoint backend library your program is
13923 using. You can find all the marker identifiers in the @samp{ID} field
13924 of the @code{info static-tracepoint-markers} command output.
13925 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
13926 Markers}. For example, in the following small program using the UST
13932 trace_mark(ust, bar33, "str %s", "FOOBAZ");
13937 the marker id is composed of joining the first two arguments to the
13938 @code{trace_mark} call with a slash, which translates to:
13941 (@value{GDBP}) info static-tracepoint-markers
13942 Cnt Enb ID Address What
13943 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
13949 so you may probe the marker above with:
13952 (@value{GDBP}) strace -m ust/bar33
13955 Static tracepoints accept an extra collect action --- @code{collect
13956 $_sdata}. This collects arbitrary user data passed in the probe point
13957 call to the tracing library. In the UST example above, you'll see
13958 that the third argument to @code{trace_mark} is a printf-like format
13959 string. The user data is then the result of running that formating
13960 string against the following arguments. Note that @code{info
13961 static-tracepoint-markers} command output lists that format string in
13962 the @samp{Data:} field.
13964 You can inspect this data when analyzing the trace buffer, by printing
13965 the $_sdata variable like any other variable available to
13966 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
13969 @cindex last tracepoint number
13970 @cindex recent tracepoint number
13971 @cindex tracepoint number
13972 The convenience variable @code{$tpnum} records the tracepoint number
13973 of the most recently set tracepoint.
13975 @kindex delete tracepoint
13976 @cindex tracepoint deletion
13977 @item delete tracepoint @r{[}@var{num}@r{]}
13978 Permanently delete one or more tracepoints. With no argument, the
13979 default is to delete all tracepoints. Note that the regular
13980 @code{delete} command can remove tracepoints also.
13985 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
13987 (@value{GDBP}) @b{delete trace} // remove all tracepoints
13991 You can abbreviate this command as @code{del tr}.
13994 @node Enable and Disable Tracepoints
13995 @subsection Enable and Disable Tracepoints
13997 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
14000 @kindex disable tracepoint
14001 @item disable tracepoint @r{[}@var{num}@r{]}
14002 Disable tracepoint @var{num}, or all tracepoints if no argument
14003 @var{num} is given. A disabled tracepoint will have no effect during
14004 a trace experiment, but it is not forgotten. You can re-enable
14005 a disabled tracepoint using the @code{enable tracepoint} command.
14006 If the command is issued during a trace experiment and the debug target
14007 has support for disabling tracepoints during a trace experiment, then the
14008 change will be effective immediately. Otherwise, it will be applied to the
14009 next trace experiment.
14011 @kindex enable tracepoint
14012 @item enable tracepoint @r{[}@var{num}@r{]}
14013 Enable tracepoint @var{num}, or all tracepoints. If this command is
14014 issued during a trace experiment and the debug target supports enabling
14015 tracepoints during a trace experiment, then the enabled tracepoints will
14016 become effective immediately. Otherwise, they will become effective the
14017 next time a trace experiment is run.
14020 @node Tracepoint Passcounts
14021 @subsection Tracepoint Passcounts
14025 @cindex tracepoint pass count
14026 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
14027 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
14028 automatically stop a trace experiment. If a tracepoint's passcount is
14029 @var{n}, then the trace experiment will be automatically stopped on
14030 the @var{n}'th time that tracepoint is hit. If the tracepoint number
14031 @var{num} is not specified, the @code{passcount} command sets the
14032 passcount of the most recently defined tracepoint. If no passcount is
14033 given, the trace experiment will run until stopped explicitly by the
14039 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
14040 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
14042 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
14043 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
14044 (@value{GDBP}) @b{trace foo}
14045 (@value{GDBP}) @b{pass 3}
14046 (@value{GDBP}) @b{trace bar}
14047 (@value{GDBP}) @b{pass 2}
14048 (@value{GDBP}) @b{trace baz}
14049 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
14050 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
14051 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
14052 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
14056 @node Tracepoint Conditions
14057 @subsection Tracepoint Conditions
14058 @cindex conditional tracepoints
14059 @cindex tracepoint conditions
14061 The simplest sort of tracepoint collects data every time your program
14062 reaches a specified place. You can also specify a @dfn{condition} for
14063 a tracepoint. A condition is just a Boolean expression in your
14064 programming language (@pxref{Expressions, ,Expressions}). A
14065 tracepoint with a condition evaluates the expression each time your
14066 program reaches it, and data collection happens only if the condition
14069 Tracepoint conditions can be specified when a tracepoint is set, by
14070 using @samp{if} in the arguments to the @code{trace} command.
14071 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
14072 also be set or changed at any time with the @code{condition} command,
14073 just as with breakpoints.
14075 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
14076 the conditional expression itself. Instead, @value{GDBN} encodes the
14077 expression into an agent expression (@pxref{Agent Expressions})
14078 suitable for execution on the target, independently of @value{GDBN}.
14079 Global variables become raw memory locations, locals become stack
14080 accesses, and so forth.
14082 For instance, suppose you have a function that is usually called
14083 frequently, but should not be called after an error has occurred. You
14084 could use the following tracepoint command to collect data about calls
14085 of that function that happen while the error code is propagating
14086 through the program; an unconditional tracepoint could end up
14087 collecting thousands of useless trace frames that you would have to
14091 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
14094 @node Trace State Variables
14095 @subsection Trace State Variables
14096 @cindex trace state variables
14098 A @dfn{trace state variable} is a special type of variable that is
14099 created and managed by target-side code. The syntax is the same as
14100 that for GDB's convenience variables (a string prefixed with ``$''),
14101 but they are stored on the target. They must be created explicitly,
14102 using a @code{tvariable} command. They are always 64-bit signed
14105 Trace state variables are remembered by @value{GDBN}, and downloaded
14106 to the target along with tracepoint information when the trace
14107 experiment starts. There are no intrinsic limits on the number of
14108 trace state variables, beyond memory limitations of the target.
14110 @cindex convenience variables, and trace state variables
14111 Although trace state variables are managed by the target, you can use
14112 them in print commands and expressions as if they were convenience
14113 variables; @value{GDBN} will get the current value from the target
14114 while the trace experiment is running. Trace state variables share
14115 the same namespace as other ``$'' variables, which means that you
14116 cannot have trace state variables with names like @code{$23} or
14117 @code{$pc}, nor can you have a trace state variable and a convenience
14118 variable with the same name.
14122 @item tvariable $@var{name} [ = @var{expression} ]
14124 The @code{tvariable} command creates a new trace state variable named
14125 @code{$@var{name}}, and optionally gives it an initial value of
14126 @var{expression}. The @var{expression} is evaluated when this command is
14127 entered; the result will be converted to an integer if possible,
14128 otherwise @value{GDBN} will report an error. A subsequent
14129 @code{tvariable} command specifying the same name does not create a
14130 variable, but instead assigns the supplied initial value to the
14131 existing variable of that name, overwriting any previous initial
14132 value. The default initial value is 0.
14134 @item info tvariables
14135 @kindex info tvariables
14136 List all the trace state variables along with their initial values.
14137 Their current values may also be displayed, if the trace experiment is
14140 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
14141 @kindex delete tvariable
14142 Delete the given trace state variables, or all of them if no arguments
14147 @node Tracepoint Actions
14148 @subsection Tracepoint Action Lists
14152 @cindex tracepoint actions
14153 @item actions @r{[}@var{num}@r{]}
14154 This command will prompt for a list of actions to be taken when the
14155 tracepoint is hit. If the tracepoint number @var{num} is not
14156 specified, this command sets the actions for the one that was most
14157 recently defined (so that you can define a tracepoint and then say
14158 @code{actions} without bothering about its number). You specify the
14159 actions themselves on the following lines, one action at a time, and
14160 terminate the actions list with a line containing just @code{end}. So
14161 far, the only defined actions are @code{collect}, @code{teval}, and
14162 @code{while-stepping}.
14164 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
14165 Commands, ,Breakpoint Command Lists}), except that only the defined
14166 actions are allowed; any other @value{GDBN} command is rejected.
14168 @cindex remove actions from a tracepoint
14169 To remove all actions from a tracepoint, type @samp{actions @var{num}}
14170 and follow it immediately with @samp{end}.
14173 (@value{GDBP}) @b{collect @var{data}} // collect some data
14175 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
14177 (@value{GDBP}) @b{end} // signals the end of actions.
14180 In the following example, the action list begins with @code{collect}
14181 commands indicating the things to be collected when the tracepoint is
14182 hit. Then, in order to single-step and collect additional data
14183 following the tracepoint, a @code{while-stepping} command is used,
14184 followed by the list of things to be collected after each step in a
14185 sequence of single steps. The @code{while-stepping} command is
14186 terminated by its own separate @code{end} command. Lastly, the action
14187 list is terminated by an @code{end} command.
14190 (@value{GDBP}) @b{trace foo}
14191 (@value{GDBP}) @b{actions}
14192 Enter actions for tracepoint 1, one per line:
14195 > while-stepping 12
14196 > collect $pc, arr[i]
14201 @kindex collect @r{(tracepoints)}
14202 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
14203 Collect values of the given expressions when the tracepoint is hit.
14204 This command accepts a comma-separated list of any valid expressions.
14205 In addition to global, static, or local variables, the following
14206 special arguments are supported:
14210 Collect all registers.
14213 Collect all function arguments.
14216 Collect all local variables.
14219 Collect the return address. This is helpful if you want to see more
14222 @emph{Note:} The return address location can not always be reliably
14223 determined up front, and the wrong address / registers may end up
14224 collected instead. On some architectures the reliability is higher
14225 for tracepoints at function entry, while on others it's the opposite.
14226 When this happens, backtracing will stop because the return address is
14227 found unavailable (unless another collect rule happened to match it).
14230 Collects the number of arguments from the static probe at which the
14231 tracepoint is located.
14232 @xref{Static Probe Points}.
14234 @item $_probe_arg@var{n}
14235 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
14236 from the static probe at which the tracepoint is located.
14237 @xref{Static Probe Points}.
14240 @vindex $_sdata@r{, collect}
14241 Collect static tracepoint marker specific data. Only available for
14242 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
14243 Lists}. On the UST static tracepoints library backend, an
14244 instrumentation point resembles a @code{printf} function call. The
14245 tracing library is able to collect user specified data formatted to a
14246 character string using the format provided by the programmer that
14247 instrumented the program. Other backends have similar mechanisms.
14248 Here's an example of a UST marker call:
14251 const char master_name[] = "$your_name";
14252 trace_mark(channel1, marker1, "hello %s", master_name)
14255 In this case, collecting @code{$_sdata} collects the string
14256 @samp{hello $yourname}. When analyzing the trace buffer, you can
14257 inspect @samp{$_sdata} like any other variable available to
14261 You can give several consecutive @code{collect} commands, each one
14262 with a single argument, or one @code{collect} command with several
14263 arguments separated by commas; the effect is the same.
14265 The optional @var{mods} changes the usual handling of the arguments.
14266 @code{s} requests that pointers to chars be handled as strings, in
14267 particular collecting the contents of the memory being pointed at, up
14268 to the first zero. The upper bound is by default the value of the
14269 @code{print elements} variable; if @code{s} is followed by a decimal
14270 number, that is the upper bound instead. So for instance
14271 @samp{collect/s25 mystr} collects as many as 25 characters at
14274 The command @code{info scope} (@pxref{Symbols, info scope}) is
14275 particularly useful for figuring out what data to collect.
14277 @kindex teval @r{(tracepoints)}
14278 @item teval @var{expr1}, @var{expr2}, @dots{}
14279 Evaluate the given expressions when the tracepoint is hit. This
14280 command accepts a comma-separated list of expressions. The results
14281 are discarded, so this is mainly useful for assigning values to trace
14282 state variables (@pxref{Trace State Variables}) without adding those
14283 values to the trace buffer, as would be the case if the @code{collect}
14286 @kindex while-stepping @r{(tracepoints)}
14287 @item while-stepping @var{n}
14288 Perform @var{n} single-step instruction traces after the tracepoint,
14289 collecting new data after each step. The @code{while-stepping}
14290 command is followed by the list of what to collect while stepping
14291 (followed by its own @code{end} command):
14294 > while-stepping 12
14295 > collect $regs, myglobal
14301 Note that @code{$pc} is not automatically collected by
14302 @code{while-stepping}; you need to explicitly collect that register if
14303 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
14306 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
14307 @kindex set default-collect
14308 @cindex default collection action
14309 This variable is a list of expressions to collect at each tracepoint
14310 hit. It is effectively an additional @code{collect} action prepended
14311 to every tracepoint action list. The expressions are parsed
14312 individually for each tracepoint, so for instance a variable named
14313 @code{xyz} may be interpreted as a global for one tracepoint, and a
14314 local for another, as appropriate to the tracepoint's location.
14316 @item show default-collect
14317 @kindex show default-collect
14318 Show the list of expressions that are collected by default at each
14323 @node Listing Tracepoints
14324 @subsection Listing Tracepoints
14327 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
14328 @kindex info tp @r{[}@var{n}@dots{}@r{]}
14329 @cindex information about tracepoints
14330 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
14331 Display information about the tracepoint @var{num}. If you don't
14332 specify a tracepoint number, displays information about all the
14333 tracepoints defined so far. The format is similar to that used for
14334 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
14335 command, simply restricting itself to tracepoints.
14337 A tracepoint's listing may include additional information specific to
14342 its passcount as given by the @code{passcount @var{n}} command
14345 the state about installed on target of each location
14349 (@value{GDBP}) @b{info trace}
14350 Num Type Disp Enb Address What
14351 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
14353 collect globfoo, $regs
14358 2 tracepoint keep y <MULTIPLE>
14360 2.1 y 0x0804859c in func4 at change-loc.h:35
14361 installed on target
14362 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
14363 installed on target
14364 2.3 y <PENDING> set_tracepoint
14365 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
14366 not installed on target
14371 This command can be abbreviated @code{info tp}.
14374 @node Listing Static Tracepoint Markers
14375 @subsection Listing Static Tracepoint Markers
14378 @kindex info static-tracepoint-markers
14379 @cindex information about static tracepoint markers
14380 @item info static-tracepoint-markers
14381 Display information about all static tracepoint markers defined in the
14384 For each marker, the following columns are printed:
14388 An incrementing counter, output to help readability. This is not a
14391 The marker ID, as reported by the target.
14392 @item Enabled or Disabled
14393 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
14394 that are not enabled.
14396 Where the marker is in your program, as a memory address.
14398 Where the marker is in the source for your program, as a file and line
14399 number. If the debug information included in the program does not
14400 allow @value{GDBN} to locate the source of the marker, this column
14401 will be left blank.
14405 In addition, the following information may be printed for each marker:
14409 User data passed to the tracing library by the marker call. In the
14410 UST backend, this is the format string passed as argument to the
14412 @item Static tracepoints probing the marker
14413 The list of static tracepoints attached to the marker.
14417 (@value{GDBP}) info static-tracepoint-markers
14418 Cnt ID Enb Address What
14419 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
14420 Data: number1 %d number2 %d
14421 Probed by static tracepoints: #2
14422 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
14428 @node Starting and Stopping Trace Experiments
14429 @subsection Starting and Stopping Trace Experiments
14432 @kindex tstart [ @var{notes} ]
14433 @cindex start a new trace experiment
14434 @cindex collected data discarded
14436 This command starts the trace experiment, and begins collecting data.
14437 It has the side effect of discarding all the data collected in the
14438 trace buffer during the previous trace experiment. If any arguments
14439 are supplied, they are taken as a note and stored with the trace
14440 experiment's state. The notes may be arbitrary text, and are
14441 especially useful with disconnected tracing in a multi-user context;
14442 the notes can explain what the trace is doing, supply user contact
14443 information, and so forth.
14445 @kindex tstop [ @var{notes} ]
14446 @cindex stop a running trace experiment
14448 This command stops the trace experiment. If any arguments are
14449 supplied, they are recorded with the experiment as a note. This is
14450 useful if you are stopping a trace started by someone else, for
14451 instance if the trace is interfering with the system's behavior and
14452 needs to be stopped quickly.
14454 @strong{Note}: a trace experiment and data collection may stop
14455 automatically if any tracepoint's passcount is reached
14456 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
14459 @cindex status of trace data collection
14460 @cindex trace experiment, status of
14462 This command displays the status of the current trace data
14466 Here is an example of the commands we described so far:
14469 (@value{GDBP}) @b{trace gdb_c_test}
14470 (@value{GDBP}) @b{actions}
14471 Enter actions for tracepoint #1, one per line.
14472 > collect $regs,$locals,$args
14473 > while-stepping 11
14477 (@value{GDBP}) @b{tstart}
14478 [time passes @dots{}]
14479 (@value{GDBP}) @b{tstop}
14482 @anchor{disconnected tracing}
14483 @cindex disconnected tracing
14484 You can choose to continue running the trace experiment even if
14485 @value{GDBN} disconnects from the target, voluntarily or
14486 involuntarily. For commands such as @code{detach}, the debugger will
14487 ask what you want to do with the trace. But for unexpected
14488 terminations (@value{GDBN} crash, network outage), it would be
14489 unfortunate to lose hard-won trace data, so the variable
14490 @code{disconnected-tracing} lets you decide whether the trace should
14491 continue running without @value{GDBN}.
14494 @item set disconnected-tracing on
14495 @itemx set disconnected-tracing off
14496 @kindex set disconnected-tracing
14497 Choose whether a tracing run should continue to run if @value{GDBN}
14498 has disconnected from the target. Note that @code{detach} or
14499 @code{quit} will ask you directly what to do about a running trace no
14500 matter what this variable's setting, so the variable is mainly useful
14501 for handling unexpected situations, such as loss of the network.
14503 @item show disconnected-tracing
14504 @kindex show disconnected-tracing
14505 Show the current choice for disconnected tracing.
14509 When you reconnect to the target, the trace experiment may or may not
14510 still be running; it might have filled the trace buffer in the
14511 meantime, or stopped for one of the other reasons. If it is running,
14512 it will continue after reconnection.
14514 Upon reconnection, the target will upload information about the
14515 tracepoints in effect. @value{GDBN} will then compare that
14516 information to the set of tracepoints currently defined, and attempt
14517 to match them up, allowing for the possibility that the numbers may
14518 have changed due to creation and deletion in the meantime. If one of
14519 the target's tracepoints does not match any in @value{GDBN}, the
14520 debugger will create a new tracepoint, so that you have a number with
14521 which to specify that tracepoint. This matching-up process is
14522 necessarily heuristic, and it may result in useless tracepoints being
14523 created; you may simply delete them if they are of no use.
14525 @cindex circular trace buffer
14526 If your target agent supports a @dfn{circular trace buffer}, then you
14527 can run a trace experiment indefinitely without filling the trace
14528 buffer; when space runs out, the agent deletes already-collected trace
14529 frames, oldest first, until there is enough room to continue
14530 collecting. This is especially useful if your tracepoints are being
14531 hit too often, and your trace gets terminated prematurely because the
14532 buffer is full. To ask for a circular trace buffer, simply set
14533 @samp{circular-trace-buffer} to on. You can set this at any time,
14534 including during tracing; if the agent can do it, it will change
14535 buffer handling on the fly, otherwise it will not take effect until
14539 @item set circular-trace-buffer on
14540 @itemx set circular-trace-buffer off
14541 @kindex set circular-trace-buffer
14542 Choose whether a tracing run should use a linear or circular buffer
14543 for trace data. A linear buffer will not lose any trace data, but may
14544 fill up prematurely, while a circular buffer will discard old trace
14545 data, but it will have always room for the latest tracepoint hits.
14547 @item show circular-trace-buffer
14548 @kindex show circular-trace-buffer
14549 Show the current choice for the trace buffer. Note that this may not
14550 match the agent's current buffer handling, nor is it guaranteed to
14551 match the setting that might have been in effect during a past run,
14552 for instance if you are looking at frames from a trace file.
14557 @item set trace-buffer-size @var{n}
14558 @itemx set trace-buffer-size unlimited
14559 @kindex set trace-buffer-size
14560 Request that the target use a trace buffer of @var{n} bytes. Not all
14561 targets will honor the request; they may have a compiled-in size for
14562 the trace buffer, or some other limitation. Set to a value of
14563 @code{unlimited} or @code{-1} to let the target use whatever size it
14564 likes. This is also the default.
14566 @item show trace-buffer-size
14567 @kindex show trace-buffer-size
14568 Show the current requested size for the trace buffer. Note that this
14569 will only match the actual size if the target supports size-setting,
14570 and was able to handle the requested size. For instance, if the
14571 target can only change buffer size between runs, this variable will
14572 not reflect the change until the next run starts. Use @code{tstatus}
14573 to get a report of the actual buffer size.
14577 @item set trace-user @var{text}
14578 @kindex set trace-user
14580 @item show trace-user
14581 @kindex show trace-user
14583 @item set trace-notes @var{text}
14584 @kindex set trace-notes
14585 Set the trace run's notes.
14587 @item show trace-notes
14588 @kindex show trace-notes
14589 Show the trace run's notes.
14591 @item set trace-stop-notes @var{text}
14592 @kindex set trace-stop-notes
14593 Set the trace run's stop notes. The handling of the note is as for
14594 @code{tstop} arguments; the set command is convenient way to fix a
14595 stop note that is mistaken or incomplete.
14597 @item show trace-stop-notes
14598 @kindex show trace-stop-notes
14599 Show the trace run's stop notes.
14603 @node Tracepoint Restrictions
14604 @subsection Tracepoint Restrictions
14606 @cindex tracepoint restrictions
14607 There are a number of restrictions on the use of tracepoints. As
14608 described above, tracepoint data gathering occurs on the target
14609 without interaction from @value{GDBN}. Thus the full capabilities of
14610 the debugger are not available during data gathering, and then at data
14611 examination time, you will be limited by only having what was
14612 collected. The following items describe some common problems, but it
14613 is not exhaustive, and you may run into additional difficulties not
14619 Tracepoint expressions are intended to gather objects (lvalues). Thus
14620 the full flexibility of GDB's expression evaluator is not available.
14621 You cannot call functions, cast objects to aggregate types, access
14622 convenience variables or modify values (except by assignment to trace
14623 state variables). Some language features may implicitly call
14624 functions (for instance Objective-C fields with accessors), and therefore
14625 cannot be collected either.
14628 Collection of local variables, either individually or in bulk with
14629 @code{$locals} or @code{$args}, during @code{while-stepping} may
14630 behave erratically. The stepping action may enter a new scope (for
14631 instance by stepping into a function), or the location of the variable
14632 may change (for instance it is loaded into a register). The
14633 tracepoint data recorded uses the location information for the
14634 variables that is correct for the tracepoint location. When the
14635 tracepoint is created, it is not possible, in general, to determine
14636 where the steps of a @code{while-stepping} sequence will advance the
14637 program---particularly if a conditional branch is stepped.
14640 Collection of an incompletely-initialized or partially-destroyed object
14641 may result in something that @value{GDBN} cannot display, or displays
14642 in a misleading way.
14645 When @value{GDBN} displays a pointer to character it automatically
14646 dereferences the pointer to also display characters of the string
14647 being pointed to. However, collecting the pointer during tracing does
14648 not automatically collect the string. You need to explicitly
14649 dereference the pointer and provide size information if you want to
14650 collect not only the pointer, but the memory pointed to. For example,
14651 @code{*ptr@@50} can be used to collect the 50 element array pointed to
14655 It is not possible to collect a complete stack backtrace at a
14656 tracepoint. Instead, you may collect the registers and a few hundred
14657 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
14658 (adjust to use the name of the actual stack pointer register on your
14659 target architecture, and the amount of stack you wish to capture).
14660 Then the @code{backtrace} command will show a partial backtrace when
14661 using a trace frame. The number of stack frames that can be examined
14662 depends on the sizes of the frames in the collected stack. Note that
14663 if you ask for a block so large that it goes past the bottom of the
14664 stack, the target agent may report an error trying to read from an
14668 If you do not collect registers at a tracepoint, @value{GDBN} can
14669 infer that the value of @code{$pc} must be the same as the address of
14670 the tracepoint and use that when you are looking at a trace frame
14671 for that tracepoint. However, this cannot work if the tracepoint has
14672 multiple locations (for instance if it was set in a function that was
14673 inlined), or if it has a @code{while-stepping} loop. In those cases
14674 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
14679 @node Analyze Collected Data
14680 @section Using the Collected Data
14682 After the tracepoint experiment ends, you use @value{GDBN} commands
14683 for examining the trace data. The basic idea is that each tracepoint
14684 collects a trace @dfn{snapshot} every time it is hit and another
14685 snapshot every time it single-steps. All these snapshots are
14686 consecutively numbered from zero and go into a buffer, and you can
14687 examine them later. The way you examine them is to @dfn{focus} on a
14688 specific trace snapshot. When the remote stub is focused on a trace
14689 snapshot, it will respond to all @value{GDBN} requests for memory and
14690 registers by reading from the buffer which belongs to that snapshot,
14691 rather than from @emph{real} memory or registers of the program being
14692 debugged. This means that @strong{all} @value{GDBN} commands
14693 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
14694 behave as if we were currently debugging the program state as it was
14695 when the tracepoint occurred. Any requests for data that are not in
14696 the buffer will fail.
14699 * tfind:: How to select a trace snapshot
14700 * tdump:: How to display all data for a snapshot
14701 * save tracepoints:: How to save tracepoints for a future run
14705 @subsection @code{tfind @var{n}}
14708 @cindex select trace snapshot
14709 @cindex find trace snapshot
14710 The basic command for selecting a trace snapshot from the buffer is
14711 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
14712 counting from zero. If no argument @var{n} is given, the next
14713 snapshot is selected.
14715 Here are the various forms of using the @code{tfind} command.
14719 Find the first snapshot in the buffer. This is a synonym for
14720 @code{tfind 0} (since 0 is the number of the first snapshot).
14723 Stop debugging trace snapshots, resume @emph{live} debugging.
14726 Same as @samp{tfind none}.
14729 No argument means find the next trace snapshot or find the first
14730 one if no trace snapshot is selected.
14733 Find the previous trace snapshot before the current one. This permits
14734 retracing earlier steps.
14736 @item tfind tracepoint @var{num}
14737 Find the next snapshot associated with tracepoint @var{num}. Search
14738 proceeds forward from the last examined trace snapshot. If no
14739 argument @var{num} is given, it means find the next snapshot collected
14740 for the same tracepoint as the current snapshot.
14742 @item tfind pc @var{addr}
14743 Find the next snapshot associated with the value @var{addr} of the
14744 program counter. Search proceeds forward from the last examined trace
14745 snapshot. If no argument @var{addr} is given, it means find the next
14746 snapshot with the same value of PC as the current snapshot.
14748 @item tfind outside @var{addr1}, @var{addr2}
14749 Find the next snapshot whose PC is outside the given range of
14750 addresses (exclusive).
14752 @item tfind range @var{addr1}, @var{addr2}
14753 Find the next snapshot whose PC is between @var{addr1} and
14754 @var{addr2} (inclusive).
14756 @item tfind line @r{[}@var{file}:@r{]}@var{n}
14757 Find the next snapshot associated with the source line @var{n}. If
14758 the optional argument @var{file} is given, refer to line @var{n} in
14759 that source file. Search proceeds forward from the last examined
14760 trace snapshot. If no argument @var{n} is given, it means find the
14761 next line other than the one currently being examined; thus saying
14762 @code{tfind line} repeatedly can appear to have the same effect as
14763 stepping from line to line in a @emph{live} debugging session.
14766 The default arguments for the @code{tfind} commands are specifically
14767 designed to make it easy to scan through the trace buffer. For
14768 instance, @code{tfind} with no argument selects the next trace
14769 snapshot, and @code{tfind -} with no argument selects the previous
14770 trace snapshot. So, by giving one @code{tfind} command, and then
14771 simply hitting @key{RET} repeatedly you can examine all the trace
14772 snapshots in order. Or, by saying @code{tfind -} and then hitting
14773 @key{RET} repeatedly you can examine the snapshots in reverse order.
14774 The @code{tfind line} command with no argument selects the snapshot
14775 for the next source line executed. The @code{tfind pc} command with
14776 no argument selects the next snapshot with the same program counter
14777 (PC) as the current frame. The @code{tfind tracepoint} command with
14778 no argument selects the next trace snapshot collected by the same
14779 tracepoint as the current one.
14781 In addition to letting you scan through the trace buffer manually,
14782 these commands make it easy to construct @value{GDBN} scripts that
14783 scan through the trace buffer and print out whatever collected data
14784 you are interested in. Thus, if we want to examine the PC, FP, and SP
14785 registers from each trace frame in the buffer, we can say this:
14788 (@value{GDBP}) @b{tfind start}
14789 (@value{GDBP}) @b{while ($trace_frame != -1)}
14790 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
14791 $trace_frame, $pc, $sp, $fp
14795 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
14796 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
14797 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
14798 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
14799 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
14800 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
14801 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
14802 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
14803 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
14804 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
14805 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
14808 Or, if we want to examine the variable @code{X} at each source line in
14812 (@value{GDBP}) @b{tfind start}
14813 (@value{GDBP}) @b{while ($trace_frame != -1)}
14814 > printf "Frame %d, X == %d\n", $trace_frame, X
14824 @subsection @code{tdump}
14826 @cindex dump all data collected at tracepoint
14827 @cindex tracepoint data, display
14829 This command takes no arguments. It prints all the data collected at
14830 the current trace snapshot.
14833 (@value{GDBP}) @b{trace 444}
14834 (@value{GDBP}) @b{actions}
14835 Enter actions for tracepoint #2, one per line:
14836 > collect $regs, $locals, $args, gdb_long_test
14839 (@value{GDBP}) @b{tstart}
14841 (@value{GDBP}) @b{tfind line 444}
14842 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
14844 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
14846 (@value{GDBP}) @b{tdump}
14847 Data collected at tracepoint 2, trace frame 1:
14848 d0 0xc4aa0085 -995491707
14852 d4 0x71aea3d 119204413
14855 d7 0x380035 3670069
14856 a0 0x19e24a 1696330
14857 a1 0x3000668 50333288
14859 a3 0x322000 3284992
14860 a4 0x3000698 50333336
14861 a5 0x1ad3cc 1758156
14862 fp 0x30bf3c 0x30bf3c
14863 sp 0x30bf34 0x30bf34
14865 pc 0x20b2c8 0x20b2c8
14869 p = 0x20e5b4 "gdb-test"
14876 gdb_long_test = 17 '\021'
14881 @code{tdump} works by scanning the tracepoint's current collection
14882 actions and printing the value of each expression listed. So
14883 @code{tdump} can fail, if after a run, you change the tracepoint's
14884 actions to mention variables that were not collected during the run.
14886 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
14887 uses the collected value of @code{$pc} to distinguish between trace
14888 frames that were collected at the tracepoint hit, and frames that were
14889 collected while stepping. This allows it to correctly choose whether
14890 to display the basic list of collections, or the collections from the
14891 body of the while-stepping loop. However, if @code{$pc} was not collected,
14892 then @code{tdump} will always attempt to dump using the basic collection
14893 list, and may fail if a while-stepping frame does not include all the
14894 same data that is collected at the tracepoint hit.
14895 @c This is getting pretty arcane, example would be good.
14897 @node save tracepoints
14898 @subsection @code{save tracepoints @var{filename}}
14899 @kindex save tracepoints
14900 @kindex save-tracepoints
14901 @cindex save tracepoints for future sessions
14903 This command saves all current tracepoint definitions together with
14904 their actions and passcounts, into a file @file{@var{filename}}
14905 suitable for use in a later debugging session. To read the saved
14906 tracepoint definitions, use the @code{source} command (@pxref{Command
14907 Files}). The @w{@code{save-tracepoints}} command is a deprecated
14908 alias for @w{@code{save tracepoints}}
14910 @node Tracepoint Variables
14911 @section Convenience Variables for Tracepoints
14912 @cindex tracepoint variables
14913 @cindex convenience variables for tracepoints
14916 @vindex $trace_frame
14917 @item (int) $trace_frame
14918 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
14919 snapshot is selected.
14921 @vindex $tracepoint
14922 @item (int) $tracepoint
14923 The tracepoint for the current trace snapshot.
14925 @vindex $trace_line
14926 @item (int) $trace_line
14927 The line number for the current trace snapshot.
14929 @vindex $trace_file
14930 @item (char []) $trace_file
14931 The source file for the current trace snapshot.
14933 @vindex $trace_func
14934 @item (char []) $trace_func
14935 The name of the function containing @code{$tracepoint}.
14938 Note: @code{$trace_file} is not suitable for use in @code{printf},
14939 use @code{output} instead.
14941 Here's a simple example of using these convenience variables for
14942 stepping through all the trace snapshots and printing some of their
14943 data. Note that these are not the same as trace state variables,
14944 which are managed by the target.
14947 (@value{GDBP}) @b{tfind start}
14949 (@value{GDBP}) @b{while $trace_frame != -1}
14950 > output $trace_file
14951 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
14957 @section Using Trace Files
14958 @cindex trace files
14960 In some situations, the target running a trace experiment may no
14961 longer be available; perhaps it crashed, or the hardware was needed
14962 for a different activity. To handle these cases, you can arrange to
14963 dump the trace data into a file, and later use that file as a source
14964 of trace data, via the @code{target tfile} command.
14969 @item tsave [ -r ] @var{filename}
14970 @itemx tsave [-ctf] @var{dirname}
14971 Save the trace data to @var{filename}. By default, this command
14972 assumes that @var{filename} refers to the host filesystem, so if
14973 necessary @value{GDBN} will copy raw trace data up from the target and
14974 then save it. If the target supports it, you can also supply the
14975 optional argument @code{-r} (``remote'') to direct the target to save
14976 the data directly into @var{filename} in its own filesystem, which may be
14977 more efficient if the trace buffer is very large. (Note, however, that
14978 @code{target tfile} can only read from files accessible to the host.)
14979 By default, this command will save trace frame in tfile format.
14980 You can supply the optional argument @code{-ctf} to save data in CTF
14981 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
14982 that can be shared by multiple debugging and tracing tools. Please go to
14983 @indicateurl{http://www.efficios.com/ctf} to get more information.
14985 @kindex target tfile
14989 @item target tfile @var{filename}
14990 @itemx target ctf @var{dirname}
14991 Use the file named @var{filename} or directory named @var{dirname} as
14992 a source of trace data. Commands that examine data work as they do with
14993 a live target, but it is not possible to run any new trace experiments.
14994 @code{tstatus} will report the state of the trace run at the moment
14995 the data was saved, as well as the current trace frame you are examining.
14996 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
15000 (@value{GDBP}) target ctf ctf.ctf
15001 (@value{GDBP}) tfind
15002 Found trace frame 0, tracepoint 2
15003 39 ++a; /* set tracepoint 1 here */
15004 (@value{GDBP}) tdump
15005 Data collected at tracepoint 2, trace frame 0:
15009 c = @{"123", "456", "789", "123", "456", "789"@}
15010 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
15018 @chapter Debugging Programs That Use Overlays
15021 If your program is too large to fit completely in your target system's
15022 memory, you can sometimes use @dfn{overlays} to work around this
15023 problem. @value{GDBN} provides some support for debugging programs that
15027 * How Overlays Work:: A general explanation of overlays.
15028 * Overlay Commands:: Managing overlays in @value{GDBN}.
15029 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
15030 mapped by asking the inferior.
15031 * Overlay Sample Program:: A sample program using overlays.
15034 @node How Overlays Work
15035 @section How Overlays Work
15036 @cindex mapped overlays
15037 @cindex unmapped overlays
15038 @cindex load address, overlay's
15039 @cindex mapped address
15040 @cindex overlay area
15042 Suppose you have a computer whose instruction address space is only 64
15043 kilobytes long, but which has much more memory which can be accessed by
15044 other means: special instructions, segment registers, or memory
15045 management hardware, for example. Suppose further that you want to
15046 adapt a program which is larger than 64 kilobytes to run on this system.
15048 One solution is to identify modules of your program which are relatively
15049 independent, and need not call each other directly; call these modules
15050 @dfn{overlays}. Separate the overlays from the main program, and place
15051 their machine code in the larger memory. Place your main program in
15052 instruction memory, but leave at least enough space there to hold the
15053 largest overlay as well.
15055 Now, to call a function located in an overlay, you must first copy that
15056 overlay's machine code from the large memory into the space set aside
15057 for it in the instruction memory, and then jump to its entry point
15060 @c NB: In the below the mapped area's size is greater or equal to the
15061 @c size of all overlays. This is intentional to remind the developer
15062 @c that overlays don't necessarily need to be the same size.
15066 Data Instruction Larger
15067 Address Space Address Space Address Space
15068 +-----------+ +-----------+ +-----------+
15070 +-----------+ +-----------+ +-----------+<-- overlay 1
15071 | program | | main | .----| overlay 1 | load address
15072 | variables | | program | | +-----------+
15073 | and heap | | | | | |
15074 +-----------+ | | | +-----------+<-- overlay 2
15075 | | +-----------+ | | | load address
15076 +-----------+ | | | .-| overlay 2 |
15078 mapped --->+-----------+ | | +-----------+
15079 address | | | | | |
15080 | overlay | <-' | | |
15081 | area | <---' +-----------+<-- overlay 3
15082 | | <---. | | load address
15083 +-----------+ `--| overlay 3 |
15090 @anchor{A code overlay}A code overlay
15094 The diagram (@pxref{A code overlay}) shows a system with separate data
15095 and instruction address spaces. To map an overlay, the program copies
15096 its code from the larger address space to the instruction address space.
15097 Since the overlays shown here all use the same mapped address, only one
15098 may be mapped at a time. For a system with a single address space for
15099 data and instructions, the diagram would be similar, except that the
15100 program variables and heap would share an address space with the main
15101 program and the overlay area.
15103 An overlay loaded into instruction memory and ready for use is called a
15104 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
15105 instruction memory. An overlay not present (or only partially present)
15106 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
15107 is its address in the larger memory. The mapped address is also called
15108 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
15109 called the @dfn{load memory address}, or @dfn{LMA}.
15111 Unfortunately, overlays are not a completely transparent way to adapt a
15112 program to limited instruction memory. They introduce a new set of
15113 global constraints you must keep in mind as you design your program:
15118 Before calling or returning to a function in an overlay, your program
15119 must make sure that overlay is actually mapped. Otherwise, the call or
15120 return will transfer control to the right address, but in the wrong
15121 overlay, and your program will probably crash.
15124 If the process of mapping an overlay is expensive on your system, you
15125 will need to choose your overlays carefully to minimize their effect on
15126 your program's performance.
15129 The executable file you load onto your system must contain each
15130 overlay's instructions, appearing at the overlay's load address, not its
15131 mapped address. However, each overlay's instructions must be relocated
15132 and its symbols defined as if the overlay were at its mapped address.
15133 You can use GNU linker scripts to specify different load and relocation
15134 addresses for pieces of your program; see @ref{Overlay Description,,,
15135 ld.info, Using ld: the GNU linker}.
15138 The procedure for loading executable files onto your system must be able
15139 to load their contents into the larger address space as well as the
15140 instruction and data spaces.
15144 The overlay system described above is rather simple, and could be
15145 improved in many ways:
15150 If your system has suitable bank switch registers or memory management
15151 hardware, you could use those facilities to make an overlay's load area
15152 contents simply appear at their mapped address in instruction space.
15153 This would probably be faster than copying the overlay to its mapped
15154 area in the usual way.
15157 If your overlays are small enough, you could set aside more than one
15158 overlay area, and have more than one overlay mapped at a time.
15161 You can use overlays to manage data, as well as instructions. In
15162 general, data overlays are even less transparent to your design than
15163 code overlays: whereas code overlays only require care when you call or
15164 return to functions, data overlays require care every time you access
15165 the data. Also, if you change the contents of a data overlay, you
15166 must copy its contents back out to its load address before you can copy a
15167 different data overlay into the same mapped area.
15172 @node Overlay Commands
15173 @section Overlay Commands
15175 To use @value{GDBN}'s overlay support, each overlay in your program must
15176 correspond to a separate section of the executable file. The section's
15177 virtual memory address and load memory address must be the overlay's
15178 mapped and load addresses. Identifying overlays with sections allows
15179 @value{GDBN} to determine the appropriate address of a function or
15180 variable, depending on whether the overlay is mapped or not.
15182 @value{GDBN}'s overlay commands all start with the word @code{overlay};
15183 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
15188 Disable @value{GDBN}'s overlay support. When overlay support is
15189 disabled, @value{GDBN} assumes that all functions and variables are
15190 always present at their mapped addresses. By default, @value{GDBN}'s
15191 overlay support is disabled.
15193 @item overlay manual
15194 @cindex manual overlay debugging
15195 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
15196 relies on you to tell it which overlays are mapped, and which are not,
15197 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
15198 commands described below.
15200 @item overlay map-overlay @var{overlay}
15201 @itemx overlay map @var{overlay}
15202 @cindex map an overlay
15203 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
15204 be the name of the object file section containing the overlay. When an
15205 overlay is mapped, @value{GDBN} assumes it can find the overlay's
15206 functions and variables at their mapped addresses. @value{GDBN} assumes
15207 that any other overlays whose mapped ranges overlap that of
15208 @var{overlay} are now unmapped.
15210 @item overlay unmap-overlay @var{overlay}
15211 @itemx overlay unmap @var{overlay}
15212 @cindex unmap an overlay
15213 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
15214 must be the name of the object file section containing the overlay.
15215 When an overlay is unmapped, @value{GDBN} assumes it can find the
15216 overlay's functions and variables at their load addresses.
15219 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
15220 consults a data structure the overlay manager maintains in the inferior
15221 to see which overlays are mapped. For details, see @ref{Automatic
15222 Overlay Debugging}.
15224 @item overlay load-target
15225 @itemx overlay load
15226 @cindex reloading the overlay table
15227 Re-read the overlay table from the inferior. Normally, @value{GDBN}
15228 re-reads the table @value{GDBN} automatically each time the inferior
15229 stops, so this command should only be necessary if you have changed the
15230 overlay mapping yourself using @value{GDBN}. This command is only
15231 useful when using automatic overlay debugging.
15233 @item overlay list-overlays
15234 @itemx overlay list
15235 @cindex listing mapped overlays
15236 Display a list of the overlays currently mapped, along with their mapped
15237 addresses, load addresses, and sizes.
15241 Normally, when @value{GDBN} prints a code address, it includes the name
15242 of the function the address falls in:
15245 (@value{GDBP}) print main
15246 $3 = @{int ()@} 0x11a0 <main>
15249 When overlay debugging is enabled, @value{GDBN} recognizes code in
15250 unmapped overlays, and prints the names of unmapped functions with
15251 asterisks around them. For example, if @code{foo} is a function in an
15252 unmapped overlay, @value{GDBN} prints it this way:
15255 (@value{GDBP}) overlay list
15256 No sections are mapped.
15257 (@value{GDBP}) print foo
15258 $5 = @{int (int)@} 0x100000 <*foo*>
15261 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
15265 (@value{GDBP}) overlay list
15266 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
15267 mapped at 0x1016 - 0x104a
15268 (@value{GDBP}) print foo
15269 $6 = @{int (int)@} 0x1016 <foo>
15272 When overlay debugging is enabled, @value{GDBN} can find the correct
15273 address for functions and variables in an overlay, whether or not the
15274 overlay is mapped. This allows most @value{GDBN} commands, like
15275 @code{break} and @code{disassemble}, to work normally, even on unmapped
15276 code. However, @value{GDBN}'s breakpoint support has some limitations:
15280 @cindex breakpoints in overlays
15281 @cindex overlays, setting breakpoints in
15282 You can set breakpoints in functions in unmapped overlays, as long as
15283 @value{GDBN} can write to the overlay at its load address.
15285 @value{GDBN} can not set hardware or simulator-based breakpoints in
15286 unmapped overlays. However, if you set a breakpoint at the end of your
15287 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
15288 you are using manual overlay management), @value{GDBN} will re-set its
15289 breakpoints properly.
15293 @node Automatic Overlay Debugging
15294 @section Automatic Overlay Debugging
15295 @cindex automatic overlay debugging
15297 @value{GDBN} can automatically track which overlays are mapped and which
15298 are not, given some simple co-operation from the overlay manager in the
15299 inferior. If you enable automatic overlay debugging with the
15300 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
15301 looks in the inferior's memory for certain variables describing the
15302 current state of the overlays.
15304 Here are the variables your overlay manager must define to support
15305 @value{GDBN}'s automatic overlay debugging:
15309 @item @code{_ovly_table}:
15310 This variable must be an array of the following structures:
15315 /* The overlay's mapped address. */
15318 /* The size of the overlay, in bytes. */
15319 unsigned long size;
15321 /* The overlay's load address. */
15324 /* Non-zero if the overlay is currently mapped;
15326 unsigned long mapped;
15330 @item @code{_novlys}:
15331 This variable must be a four-byte signed integer, holding the total
15332 number of elements in @code{_ovly_table}.
15336 To decide whether a particular overlay is mapped or not, @value{GDBN}
15337 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
15338 @code{lma} members equal the VMA and LMA of the overlay's section in the
15339 executable file. When @value{GDBN} finds a matching entry, it consults
15340 the entry's @code{mapped} member to determine whether the overlay is
15343 In addition, your overlay manager may define a function called
15344 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
15345 will silently set a breakpoint there. If the overlay manager then
15346 calls this function whenever it has changed the overlay table, this
15347 will enable @value{GDBN} to accurately keep track of which overlays
15348 are in program memory, and update any breakpoints that may be set
15349 in overlays. This will allow breakpoints to work even if the
15350 overlays are kept in ROM or other non-writable memory while they
15351 are not being executed.
15353 @node Overlay Sample Program
15354 @section Overlay Sample Program
15355 @cindex overlay example program
15357 When linking a program which uses overlays, you must place the overlays
15358 at their load addresses, while relocating them to run at their mapped
15359 addresses. To do this, you must write a linker script (@pxref{Overlay
15360 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
15361 since linker scripts are specific to a particular host system, target
15362 architecture, and target memory layout, this manual cannot provide
15363 portable sample code demonstrating @value{GDBN}'s overlay support.
15365 However, the @value{GDBN} source distribution does contain an overlaid
15366 program, with linker scripts for a few systems, as part of its test
15367 suite. The program consists of the following files from
15368 @file{gdb/testsuite/gdb.base}:
15372 The main program file.
15374 A simple overlay manager, used by @file{overlays.c}.
15379 Overlay modules, loaded and used by @file{overlays.c}.
15382 Linker scripts for linking the test program on the @code{d10v-elf}
15383 and @code{m32r-elf} targets.
15386 You can build the test program using the @code{d10v-elf} GCC
15387 cross-compiler like this:
15390 $ d10v-elf-gcc -g -c overlays.c
15391 $ d10v-elf-gcc -g -c ovlymgr.c
15392 $ d10v-elf-gcc -g -c foo.c
15393 $ d10v-elf-gcc -g -c bar.c
15394 $ d10v-elf-gcc -g -c baz.c
15395 $ d10v-elf-gcc -g -c grbx.c
15396 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
15397 baz.o grbx.o -Wl,-Td10v.ld -o overlays
15400 The build process is identical for any other architecture, except that
15401 you must substitute the appropriate compiler and linker script for the
15402 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
15406 @chapter Using @value{GDBN} with Different Languages
15409 Although programming languages generally have common aspects, they are
15410 rarely expressed in the same manner. For instance, in ANSI C,
15411 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
15412 Modula-2, it is accomplished by @code{p^}. Values can also be
15413 represented (and displayed) differently. Hex numbers in C appear as
15414 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
15416 @cindex working language
15417 Language-specific information is built into @value{GDBN} for some languages,
15418 allowing you to express operations like the above in your program's
15419 native language, and allowing @value{GDBN} to output values in a manner
15420 consistent with the syntax of your program's native language. The
15421 language you use to build expressions is called the @dfn{working
15425 * Setting:: Switching between source languages
15426 * Show:: Displaying the language
15427 * Checks:: Type and range checks
15428 * Supported Languages:: Supported languages
15429 * Unsupported Languages:: Unsupported languages
15433 @section Switching Between Source Languages
15435 There are two ways to control the working language---either have @value{GDBN}
15436 set it automatically, or select it manually yourself. You can use the
15437 @code{set language} command for either purpose. On startup, @value{GDBN}
15438 defaults to setting the language automatically. The working language is
15439 used to determine how expressions you type are interpreted, how values
15442 In addition to the working language, every source file that
15443 @value{GDBN} knows about has its own working language. For some object
15444 file formats, the compiler might indicate which language a particular
15445 source file is in. However, most of the time @value{GDBN} infers the
15446 language from the name of the file. The language of a source file
15447 controls whether C@t{++} names are demangled---this way @code{backtrace} can
15448 show each frame appropriately for its own language. There is no way to
15449 set the language of a source file from within @value{GDBN}, but you can
15450 set the language associated with a filename extension. @xref{Show, ,
15451 Displaying the Language}.
15453 This is most commonly a problem when you use a program, such
15454 as @code{cfront} or @code{f2c}, that generates C but is written in
15455 another language. In that case, make the
15456 program use @code{#line} directives in its C output; that way
15457 @value{GDBN} will know the correct language of the source code of the original
15458 program, and will display that source code, not the generated C code.
15461 * Filenames:: Filename extensions and languages.
15462 * Manually:: Setting the working language manually
15463 * Automatically:: Having @value{GDBN} infer the source language
15467 @subsection List of Filename Extensions and Languages
15469 If a source file name ends in one of the following extensions, then
15470 @value{GDBN} infers that its language is the one indicated.
15488 C@t{++} source file
15494 Objective-C source file
15498 Fortran source file
15501 Modula-2 source file
15505 Assembler source file. This actually behaves almost like C, but
15506 @value{GDBN} does not skip over function prologues when stepping.
15509 In addition, you may set the language associated with a filename
15510 extension. @xref{Show, , Displaying the Language}.
15513 @subsection Setting the Working Language
15515 If you allow @value{GDBN} to set the language automatically,
15516 expressions are interpreted the same way in your debugging session and
15519 @kindex set language
15520 If you wish, you may set the language manually. To do this, issue the
15521 command @samp{set language @var{lang}}, where @var{lang} is the name of
15522 a language, such as
15523 @code{c} or @code{modula-2}.
15524 For a list of the supported languages, type @samp{set language}.
15526 Setting the language manually prevents @value{GDBN} from updating the working
15527 language automatically. This can lead to confusion if you try
15528 to debug a program when the working language is not the same as the
15529 source language, when an expression is acceptable to both
15530 languages---but means different things. For instance, if the current
15531 source file were written in C, and @value{GDBN} was parsing Modula-2, a
15539 might not have the effect you intended. In C, this means to add
15540 @code{b} and @code{c} and place the result in @code{a}. The result
15541 printed would be the value of @code{a}. In Modula-2, this means to compare
15542 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
15544 @node Automatically
15545 @subsection Having @value{GDBN} Infer the Source Language
15547 To have @value{GDBN} set the working language automatically, use
15548 @samp{set language local} or @samp{set language auto}. @value{GDBN}
15549 then infers the working language. That is, when your program stops in a
15550 frame (usually by encountering a breakpoint), @value{GDBN} sets the
15551 working language to the language recorded for the function in that
15552 frame. If the language for a frame is unknown (that is, if the function
15553 or block corresponding to the frame was defined in a source file that
15554 does not have a recognized extension), the current working language is
15555 not changed, and @value{GDBN} issues a warning.
15557 This may not seem necessary for most programs, which are written
15558 entirely in one source language. However, program modules and libraries
15559 written in one source language can be used by a main program written in
15560 a different source language. Using @samp{set language auto} in this
15561 case frees you from having to set the working language manually.
15564 @section Displaying the Language
15566 The following commands help you find out which language is the
15567 working language, and also what language source files were written in.
15570 @item show language
15571 @anchor{show language}
15572 @kindex show language
15573 Display the current working language. This is the
15574 language you can use with commands such as @code{print} to
15575 build and compute expressions that may involve variables in your program.
15578 @kindex info frame@r{, show the source language}
15579 Display the source language for this frame. This language becomes the
15580 working language if you use an identifier from this frame.
15581 @xref{Frame Info, ,Information about a Frame}, to identify the other
15582 information listed here.
15585 @kindex info source@r{, show the source language}
15586 Display the source language of this source file.
15587 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
15588 information listed here.
15591 In unusual circumstances, you may have source files with extensions
15592 not in the standard list. You can then set the extension associated
15593 with a language explicitly:
15596 @item set extension-language @var{ext} @var{language}
15597 @kindex set extension-language
15598 Tell @value{GDBN} that source files with extension @var{ext} are to be
15599 assumed as written in the source language @var{language}.
15601 @item info extensions
15602 @kindex info extensions
15603 List all the filename extensions and the associated languages.
15607 @section Type and Range Checking
15609 Some languages are designed to guard you against making seemingly common
15610 errors through a series of compile- and run-time checks. These include
15611 checking the type of arguments to functions and operators and making
15612 sure mathematical overflows are caught at run time. Checks such as
15613 these help to ensure a program's correctness once it has been compiled
15614 by eliminating type mismatches and providing active checks for range
15615 errors when your program is running.
15617 By default @value{GDBN} checks for these errors according to the
15618 rules of the current source language. Although @value{GDBN} does not check
15619 the statements in your program, it can check expressions entered directly
15620 into @value{GDBN} for evaluation via the @code{print} command, for example.
15623 * Type Checking:: An overview of type checking
15624 * Range Checking:: An overview of range checking
15627 @cindex type checking
15628 @cindex checks, type
15629 @node Type Checking
15630 @subsection An Overview of Type Checking
15632 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
15633 arguments to operators and functions have to be of the correct type,
15634 otherwise an error occurs. These checks prevent type mismatch
15635 errors from ever causing any run-time problems. For example,
15638 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
15640 (@value{GDBP}) print obj.my_method (0)
15643 (@value{GDBP}) print obj.my_method (0x1234)
15644 Cannot resolve method klass::my_method to any overloaded instance
15647 The second example fails because in C@t{++} the integer constant
15648 @samp{0x1234} is not type-compatible with the pointer parameter type.
15650 For the expressions you use in @value{GDBN} commands, you can tell
15651 @value{GDBN} to not enforce strict type checking or
15652 to treat any mismatches as errors and abandon the expression;
15653 When type checking is disabled, @value{GDBN} successfully evaluates
15654 expressions like the second example above.
15656 Even if type checking is off, there may be other reasons
15657 related to type that prevent @value{GDBN} from evaluating an expression.
15658 For instance, @value{GDBN} does not know how to add an @code{int} and
15659 a @code{struct foo}. These particular type errors have nothing to do
15660 with the language in use and usually arise from expressions which make
15661 little sense to evaluate anyway.
15663 @value{GDBN} provides some additional commands for controlling type checking:
15665 @kindex set check type
15666 @kindex show check type
15668 @item set check type on
15669 @itemx set check type off
15670 Set strict type checking on or off. If any type mismatches occur in
15671 evaluating an expression while type checking is on, @value{GDBN} prints a
15672 message and aborts evaluation of the expression.
15674 @item show check type
15675 Show the current setting of type checking and whether @value{GDBN}
15676 is enforcing strict type checking rules.
15679 @cindex range checking
15680 @cindex checks, range
15681 @node Range Checking
15682 @subsection An Overview of Range Checking
15684 In some languages (such as Modula-2), it is an error to exceed the
15685 bounds of a type; this is enforced with run-time checks. Such range
15686 checking is meant to ensure program correctness by making sure
15687 computations do not overflow, or indices on an array element access do
15688 not exceed the bounds of the array.
15690 For expressions you use in @value{GDBN} commands, you can tell
15691 @value{GDBN} to treat range errors in one of three ways: ignore them,
15692 always treat them as errors and abandon the expression, or issue
15693 warnings but evaluate the expression anyway.
15695 A range error can result from numerical overflow, from exceeding an
15696 array index bound, or when you type a constant that is not a member
15697 of any type. Some languages, however, do not treat overflows as an
15698 error. In many implementations of C, mathematical overflow causes the
15699 result to ``wrap around'' to lower values---for example, if @var{m} is
15700 the largest integer value, and @var{s} is the smallest, then
15703 @var{m} + 1 @result{} @var{s}
15706 This, too, is specific to individual languages, and in some cases
15707 specific to individual compilers or machines. @xref{Supported Languages, ,
15708 Supported Languages}, for further details on specific languages.
15710 @value{GDBN} provides some additional commands for controlling the range checker:
15712 @kindex set check range
15713 @kindex show check range
15715 @item set check range auto
15716 Set range checking on or off based on the current working language.
15717 @xref{Supported Languages, ,Supported Languages}, for the default settings for
15720 @item set check range on
15721 @itemx set check range off
15722 Set range checking on or off, overriding the default setting for the
15723 current working language. A warning is issued if the setting does not
15724 match the language default. If a range error occurs and range checking is on,
15725 then a message is printed and evaluation of the expression is aborted.
15727 @item set check range warn
15728 Output messages when the @value{GDBN} range checker detects a range error,
15729 but attempt to evaluate the expression anyway. Evaluating the
15730 expression may still be impossible for other reasons, such as accessing
15731 memory that the process does not own (a typical example from many Unix
15735 Show the current setting of the range checker, and whether or not it is
15736 being set automatically by @value{GDBN}.
15739 @node Supported Languages
15740 @section Supported Languages
15742 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran,
15743 OpenCL C, Pascal, Rust, assembly, Modula-2, and Ada.
15744 @c This is false ...
15745 Some @value{GDBN} features may be used in expressions regardless of the
15746 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
15747 and the @samp{@{type@}addr} construct (@pxref{Expressions,
15748 ,Expressions}) can be used with the constructs of any supported
15751 The following sections detail to what degree each source language is
15752 supported by @value{GDBN}. These sections are not meant to be language
15753 tutorials or references, but serve only as a reference guide to what the
15754 @value{GDBN} expression parser accepts, and what input and output
15755 formats should look like for different languages. There are many good
15756 books written on each of these languages; please look to these for a
15757 language reference or tutorial.
15760 * C:: C and C@t{++}
15763 * Objective-C:: Objective-C
15764 * OpenCL C:: OpenCL C
15765 * Fortran:: Fortran
15768 * Modula-2:: Modula-2
15773 @subsection C and C@t{++}
15775 @cindex C and C@t{++}
15776 @cindex expressions in C or C@t{++}
15778 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
15779 to both languages. Whenever this is the case, we discuss those languages
15783 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
15784 @cindex @sc{gnu} C@t{++}
15785 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
15786 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
15787 effectively, you must compile your C@t{++} programs with a supported
15788 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
15789 compiler (@code{aCC}).
15792 * C Operators:: C and C@t{++} operators
15793 * C Constants:: C and C@t{++} constants
15794 * C Plus Plus Expressions:: C@t{++} expressions
15795 * C Defaults:: Default settings for C and C@t{++}
15796 * C Checks:: C and C@t{++} type and range checks
15797 * Debugging C:: @value{GDBN} and C
15798 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
15799 * Decimal Floating Point:: Numbers in Decimal Floating Point format
15803 @subsubsection C and C@t{++} Operators
15805 @cindex C and C@t{++} operators
15807 Operators must be defined on values of specific types. For instance,
15808 @code{+} is defined on numbers, but not on structures. Operators are
15809 often defined on groups of types.
15811 For the purposes of C and C@t{++}, the following definitions hold:
15816 @emph{Integral types} include @code{int} with any of its storage-class
15817 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
15820 @emph{Floating-point types} include @code{float}, @code{double}, and
15821 @code{long double} (if supported by the target platform).
15824 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
15827 @emph{Scalar types} include all of the above.
15832 The following operators are supported. They are listed here
15833 in order of increasing precedence:
15837 The comma or sequencing operator. Expressions in a comma-separated list
15838 are evaluated from left to right, with the result of the entire
15839 expression being the last expression evaluated.
15842 Assignment. The value of an assignment expression is the value
15843 assigned. Defined on scalar types.
15846 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
15847 and translated to @w{@code{@var{a} = @var{a op b}}}.
15848 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
15849 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
15850 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
15853 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
15854 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
15855 should be of an integral type.
15858 Logical @sc{or}. Defined on integral types.
15861 Logical @sc{and}. Defined on integral types.
15864 Bitwise @sc{or}. Defined on integral types.
15867 Bitwise exclusive-@sc{or}. Defined on integral types.
15870 Bitwise @sc{and}. Defined on integral types.
15873 Equality and inequality. Defined on scalar types. The value of these
15874 expressions is 0 for false and non-zero for true.
15876 @item <@r{, }>@r{, }<=@r{, }>=
15877 Less than, greater than, less than or equal, greater than or equal.
15878 Defined on scalar types. The value of these expressions is 0 for false
15879 and non-zero for true.
15882 left shift, and right shift. Defined on integral types.
15885 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
15888 Addition and subtraction. Defined on integral types, floating-point types and
15891 @item *@r{, }/@r{, }%
15892 Multiplication, division, and modulus. Multiplication and division are
15893 defined on integral and floating-point types. Modulus is defined on
15897 Increment and decrement. When appearing before a variable, the
15898 operation is performed before the variable is used in an expression;
15899 when appearing after it, the variable's value is used before the
15900 operation takes place.
15903 Pointer dereferencing. Defined on pointer types. Same precedence as
15907 Address operator. Defined on variables. Same precedence as @code{++}.
15909 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
15910 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
15911 to examine the address
15912 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
15916 Negative. Defined on integral and floating-point types. Same
15917 precedence as @code{++}.
15920 Logical negation. Defined on integral types. Same precedence as
15924 Bitwise complement operator. Defined on integral types. Same precedence as
15929 Structure member, and pointer-to-structure member. For convenience,
15930 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
15931 pointer based on the stored type information.
15932 Defined on @code{struct} and @code{union} data.
15935 Dereferences of pointers to members.
15938 Array indexing. @code{@var{a}[@var{i}]} is defined as
15939 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
15942 Function parameter list. Same precedence as @code{->}.
15945 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
15946 and @code{class} types.
15949 Doubled colons also represent the @value{GDBN} scope operator
15950 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
15954 If an operator is redefined in the user code, @value{GDBN} usually
15955 attempts to invoke the redefined version instead of using the operator's
15956 predefined meaning.
15959 @subsubsection C and C@t{++} Constants
15961 @cindex C and C@t{++} constants
15963 @value{GDBN} allows you to express the constants of C and C@t{++} in the
15968 Integer constants are a sequence of digits. Octal constants are
15969 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
15970 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
15971 @samp{l}, specifying that the constant should be treated as a
15975 Floating point constants are a sequence of digits, followed by a decimal
15976 point, followed by a sequence of digits, and optionally followed by an
15977 exponent. An exponent is of the form:
15978 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
15979 sequence of digits. The @samp{+} is optional for positive exponents.
15980 A floating-point constant may also end with a letter @samp{f} or
15981 @samp{F}, specifying that the constant should be treated as being of
15982 the @code{float} (as opposed to the default @code{double}) type; or with
15983 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
15987 Enumerated constants consist of enumerated identifiers, or their
15988 integral equivalents.
15991 Character constants are a single character surrounded by single quotes
15992 (@code{'}), or a number---the ordinal value of the corresponding character
15993 (usually its @sc{ascii} value). Within quotes, the single character may
15994 be represented by a letter or by @dfn{escape sequences}, which are of
15995 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
15996 of the character's ordinal value; or of the form @samp{\@var{x}}, where
15997 @samp{@var{x}} is a predefined special character---for example,
15998 @samp{\n} for newline.
16000 Wide character constants can be written by prefixing a character
16001 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
16002 form of @samp{x}. The target wide character set is used when
16003 computing the value of this constant (@pxref{Character Sets}).
16006 String constants are a sequence of character constants surrounded by
16007 double quotes (@code{"}). Any valid character constant (as described
16008 above) may appear. Double quotes within the string must be preceded by
16009 a backslash, so for instance @samp{"a\"b'c"} is a string of five
16012 Wide string constants can be written by prefixing a string constant
16013 with @samp{L}, as in C. The target wide character set is used when
16014 computing the value of this constant (@pxref{Character Sets}).
16017 Pointer constants are an integral value. You can also write pointers
16018 to constants using the C operator @samp{&}.
16021 Array constants are comma-separated lists surrounded by braces @samp{@{}
16022 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
16023 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
16024 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
16027 @node C Plus Plus Expressions
16028 @subsubsection C@t{++} Expressions
16030 @cindex expressions in C@t{++}
16031 @value{GDBN} expression handling can interpret most C@t{++} expressions.
16033 @cindex debugging C@t{++} programs
16034 @cindex C@t{++} compilers
16035 @cindex debug formats and C@t{++}
16036 @cindex @value{NGCC} and C@t{++}
16038 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
16039 the proper compiler and the proper debug format. Currently,
16040 @value{GDBN} works best when debugging C@t{++} code that is compiled
16041 with the most recent version of @value{NGCC} possible. The DWARF
16042 debugging format is preferred; @value{NGCC} defaults to this on most
16043 popular platforms. Other compilers and/or debug formats are likely to
16044 work badly or not at all when using @value{GDBN} to debug C@t{++}
16045 code. @xref{Compilation}.
16050 @cindex member functions
16052 Member function calls are allowed; you can use expressions like
16055 count = aml->GetOriginal(x, y)
16058 @vindex this@r{, inside C@t{++} member functions}
16059 @cindex namespace in C@t{++}
16061 While a member function is active (in the selected stack frame), your
16062 expressions have the same namespace available as the member function;
16063 that is, @value{GDBN} allows implicit references to the class instance
16064 pointer @code{this} following the same rules as C@t{++}. @code{using}
16065 declarations in the current scope are also respected by @value{GDBN}.
16067 @cindex call overloaded functions
16068 @cindex overloaded functions, calling
16069 @cindex type conversions in C@t{++}
16071 You can call overloaded functions; @value{GDBN} resolves the function
16072 call to the right definition, with some restrictions. @value{GDBN} does not
16073 perform overload resolution involving user-defined type conversions,
16074 calls to constructors, or instantiations of templates that do not exist
16075 in the program. It also cannot handle ellipsis argument lists or
16078 It does perform integral conversions and promotions, floating-point
16079 promotions, arithmetic conversions, pointer conversions, conversions of
16080 class objects to base classes, and standard conversions such as those of
16081 functions or arrays to pointers; it requires an exact match on the
16082 number of function arguments.
16084 Overload resolution is always performed, unless you have specified
16085 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
16086 ,@value{GDBN} Features for C@t{++}}.
16088 You must specify @code{set overload-resolution off} in order to use an
16089 explicit function signature to call an overloaded function, as in
16091 p 'foo(char,int)'('x', 13)
16094 The @value{GDBN} command-completion facility can simplify this;
16095 see @ref{Completion, ,Command Completion}.
16097 @cindex reference declarations
16099 @value{GDBN} understands variables declared as C@t{++} lvalue or rvalue
16100 references; you can use them in expressions just as you do in C@t{++}
16101 source---they are automatically dereferenced.
16103 In the parameter list shown when @value{GDBN} displays a frame, the values of
16104 reference variables are not displayed (unlike other variables); this
16105 avoids clutter, since references are often used for large structures.
16106 The @emph{address} of a reference variable is always shown, unless
16107 you have specified @samp{set print address off}.
16110 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
16111 expressions can use it just as expressions in your program do. Since
16112 one scope may be defined in another, you can use @code{::} repeatedly if
16113 necessary, for example in an expression like
16114 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
16115 resolving name scope by reference to source files, in both C and C@t{++}
16116 debugging (@pxref{Variables, ,Program Variables}).
16119 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
16124 @subsubsection C and C@t{++} Defaults
16126 @cindex C and C@t{++} defaults
16128 If you allow @value{GDBN} to set range checking automatically, it
16129 defaults to @code{off} whenever the working language changes to
16130 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
16131 selects the working language.
16133 If you allow @value{GDBN} to set the language automatically, it
16134 recognizes source files whose names end with @file{.c}, @file{.C}, or
16135 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
16136 these files, it sets the working language to C or C@t{++}.
16137 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
16138 for further details.
16141 @subsubsection C and C@t{++} Type and Range Checks
16143 @cindex C and C@t{++} checks
16145 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
16146 checking is used. However, if you turn type checking off, @value{GDBN}
16147 will allow certain non-standard conversions, such as promoting integer
16148 constants to pointers.
16150 Range checking, if turned on, is done on mathematical operations. Array
16151 indices are not checked, since they are often used to index a pointer
16152 that is not itself an array.
16155 @subsubsection @value{GDBN} and C
16157 The @code{set print union} and @code{show print union} commands apply to
16158 the @code{union} type. When set to @samp{on}, any @code{union} that is
16159 inside a @code{struct} or @code{class} is also printed. Otherwise, it
16160 appears as @samp{@{...@}}.
16162 The @code{@@} operator aids in the debugging of dynamic arrays, formed
16163 with pointers and a memory allocation function. @xref{Expressions,
16166 @node Debugging C Plus Plus
16167 @subsubsection @value{GDBN} Features for C@t{++}
16169 @cindex commands for C@t{++}
16171 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
16172 designed specifically for use with C@t{++}. Here is a summary:
16175 @cindex break in overloaded functions
16176 @item @r{breakpoint menus}
16177 When you want a breakpoint in a function whose name is overloaded,
16178 @value{GDBN} has the capability to display a menu of possible breakpoint
16179 locations to help you specify which function definition you want.
16180 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
16182 @cindex overloading in C@t{++}
16183 @item rbreak @var{regex}
16184 Setting breakpoints using regular expressions is helpful for setting
16185 breakpoints on overloaded functions that are not members of any special
16187 @xref{Set Breaks, ,Setting Breakpoints}.
16189 @cindex C@t{++} exception handling
16191 @itemx catch rethrow
16193 Debug C@t{++} exception handling using these commands. @xref{Set
16194 Catchpoints, , Setting Catchpoints}.
16196 @cindex inheritance
16197 @item ptype @var{typename}
16198 Print inheritance relationships as well as other information for type
16200 @xref{Symbols, ,Examining the Symbol Table}.
16202 @item info vtbl @var{expression}.
16203 The @code{info vtbl} command can be used to display the virtual
16204 method tables of the object computed by @var{expression}. This shows
16205 one entry per virtual table; there may be multiple virtual tables when
16206 multiple inheritance is in use.
16208 @cindex C@t{++} demangling
16209 @item demangle @var{name}
16210 Demangle @var{name}.
16211 @xref{Symbols}, for a more complete description of the @code{demangle} command.
16213 @cindex C@t{++} symbol display
16214 @item set print demangle
16215 @itemx show print demangle
16216 @itemx set print asm-demangle
16217 @itemx show print asm-demangle
16218 Control whether C@t{++} symbols display in their source form, both when
16219 displaying code as C@t{++} source and when displaying disassemblies.
16220 @xref{Print Settings, ,Print Settings}.
16222 @item set print object
16223 @itemx show print object
16224 Choose whether to print derived (actual) or declared types of objects.
16225 @xref{Print Settings, ,Print Settings}.
16227 @item set print vtbl
16228 @itemx show print vtbl
16229 Control the format for printing virtual function tables.
16230 @xref{Print Settings, ,Print Settings}.
16231 (The @code{vtbl} commands do not work on programs compiled with the HP
16232 ANSI C@t{++} compiler (@code{aCC}).)
16234 @kindex set overload-resolution
16235 @cindex overloaded functions, overload resolution
16236 @item set overload-resolution on
16237 Enable overload resolution for C@t{++} expression evaluation. The default
16238 is on. For overloaded functions, @value{GDBN} evaluates the arguments
16239 and searches for a function whose signature matches the argument types,
16240 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
16241 Expressions, ,C@t{++} Expressions}, for details).
16242 If it cannot find a match, it emits a message.
16244 @item set overload-resolution off
16245 Disable overload resolution for C@t{++} expression evaluation. For
16246 overloaded functions that are not class member functions, @value{GDBN}
16247 chooses the first function of the specified name that it finds in the
16248 symbol table, whether or not its arguments are of the correct type. For
16249 overloaded functions that are class member functions, @value{GDBN}
16250 searches for a function whose signature @emph{exactly} matches the
16253 @kindex show overload-resolution
16254 @item show overload-resolution
16255 Show the current setting of overload resolution.
16257 @item @r{Overloaded symbol names}
16258 You can specify a particular definition of an overloaded symbol, using
16259 the same notation that is used to declare such symbols in C@t{++}: type
16260 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
16261 also use the @value{GDBN} command-line word completion facilities to list the
16262 available choices, or to finish the type list for you.
16263 @xref{Completion,, Command Completion}, for details on how to do this.
16265 @item @r{Breakpoints in functions with ABI tags}
16267 The GNU C@t{++} compiler introduced the notion of ABI ``tags'', which
16268 correspond to changes in the ABI of a type, function, or variable that
16269 would not otherwise be reflected in a mangled name. See
16270 @url{https://developers.redhat.com/blog/2015/02/05/gcc5-and-the-c11-abi/}
16273 The ABI tags are visible in C@t{++} demangled names. For example, a
16274 function that returns a std::string:
16277 std::string function(int);
16281 when compiled for the C++11 ABI is marked with the @code{cxx11} ABI
16282 tag, and @value{GDBN} displays the symbol like this:
16285 function[abi:cxx11](int)
16288 You can set a breakpoint on such functions simply as if they had no
16292 (gdb) b function(int)
16293 Breakpoint 2 at 0x40060d: file main.cc, line 10.
16294 (gdb) info breakpoints
16295 Num Type Disp Enb Address What
16296 1 breakpoint keep y 0x0040060d in function[abi:cxx11](int)
16300 On the rare occasion you need to disambiguate between different ABI
16301 tags, you can do so by simply including the ABI tag in the function
16305 (@value{GDBP}) b ambiguous[abi:other_tag](int)
16309 @node Decimal Floating Point
16310 @subsubsection Decimal Floating Point format
16311 @cindex decimal floating point format
16313 @value{GDBN} can examine, set and perform computations with numbers in
16314 decimal floating point format, which in the C language correspond to the
16315 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
16316 specified by the extension to support decimal floating-point arithmetic.
16318 There are two encodings in use, depending on the architecture: BID (Binary
16319 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
16320 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
16323 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
16324 to manipulate decimal floating point numbers, it is not possible to convert
16325 (using a cast, for example) integers wider than 32-bit to decimal float.
16327 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
16328 point computations, error checking in decimal float operations ignores
16329 underflow, overflow and divide by zero exceptions.
16331 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
16332 to inspect @code{_Decimal128} values stored in floating point registers.
16333 See @ref{PowerPC,,PowerPC} for more details.
16339 @value{GDBN} can be used to debug programs written in D and compiled with
16340 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
16341 specific feature --- dynamic arrays.
16346 @cindex Go (programming language)
16347 @value{GDBN} can be used to debug programs written in Go and compiled with
16348 @file{gccgo} or @file{6g} compilers.
16350 Here is a summary of the Go-specific features and restrictions:
16353 @cindex current Go package
16354 @item The current Go package
16355 The name of the current package does not need to be specified when
16356 specifying global variables and functions.
16358 For example, given the program:
16362 var myglob = "Shall we?"
16368 When stopped inside @code{main} either of these work:
16372 (gdb) p main.myglob
16375 @cindex builtin Go types
16376 @item Builtin Go types
16377 The @code{string} type is recognized by @value{GDBN} and is printed
16380 @cindex builtin Go functions
16381 @item Builtin Go functions
16382 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
16383 function and handles it internally.
16385 @cindex restrictions on Go expressions
16386 @item Restrictions on Go expressions
16387 All Go operators are supported except @code{&^}.
16388 The Go @code{_} ``blank identifier'' is not supported.
16389 Automatic dereferencing of pointers is not supported.
16393 @subsection Objective-C
16395 @cindex Objective-C
16396 This section provides information about some commands and command
16397 options that are useful for debugging Objective-C code. See also
16398 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
16399 few more commands specific to Objective-C support.
16402 * Method Names in Commands::
16403 * The Print Command with Objective-C::
16406 @node Method Names in Commands
16407 @subsubsection Method Names in Commands
16409 The following commands have been extended to accept Objective-C method
16410 names as line specifications:
16412 @kindex clear@r{, and Objective-C}
16413 @kindex break@r{, and Objective-C}
16414 @kindex info line@r{, and Objective-C}
16415 @kindex jump@r{, and Objective-C}
16416 @kindex list@r{, and Objective-C}
16420 @item @code{info line}
16425 A fully qualified Objective-C method name is specified as
16428 -[@var{Class} @var{methodName}]
16431 where the minus sign is used to indicate an instance method and a
16432 plus sign (not shown) is used to indicate a class method. The class
16433 name @var{Class} and method name @var{methodName} are enclosed in
16434 brackets, similar to the way messages are specified in Objective-C
16435 source code. For example, to set a breakpoint at the @code{create}
16436 instance method of class @code{Fruit} in the program currently being
16440 break -[Fruit create]
16443 To list ten program lines around the @code{initialize} class method,
16447 list +[NSText initialize]
16450 In the current version of @value{GDBN}, the plus or minus sign is
16451 required. In future versions of @value{GDBN}, the plus or minus
16452 sign will be optional, but you can use it to narrow the search. It
16453 is also possible to specify just a method name:
16459 You must specify the complete method name, including any colons. If
16460 your program's source files contain more than one @code{create} method,
16461 you'll be presented with a numbered list of classes that implement that
16462 method. Indicate your choice by number, or type @samp{0} to exit if
16465 As another example, to clear a breakpoint established at the
16466 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
16469 clear -[NSWindow makeKeyAndOrderFront:]
16472 @node The Print Command with Objective-C
16473 @subsubsection The Print Command With Objective-C
16474 @cindex Objective-C, print objects
16475 @kindex print-object
16476 @kindex po @r{(@code{print-object})}
16478 The print command has also been extended to accept methods. For example:
16481 print -[@var{object} hash]
16484 @cindex print an Objective-C object description
16485 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
16487 will tell @value{GDBN} to send the @code{hash} message to @var{object}
16488 and print the result. Also, an additional command has been added,
16489 @code{print-object} or @code{po} for short, which is meant to print
16490 the description of an object. However, this command may only work
16491 with certain Objective-C libraries that have a particular hook
16492 function, @code{_NSPrintForDebugger}, defined.
16495 @subsection OpenCL C
16498 This section provides information about @value{GDBN}s OpenCL C support.
16501 * OpenCL C Datatypes::
16502 * OpenCL C Expressions::
16503 * OpenCL C Operators::
16506 @node OpenCL C Datatypes
16507 @subsubsection OpenCL C Datatypes
16509 @cindex OpenCL C Datatypes
16510 @value{GDBN} supports the builtin scalar and vector datatypes specified
16511 by OpenCL 1.1. In addition the half- and double-precision floating point
16512 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
16513 extensions are also known to @value{GDBN}.
16515 @node OpenCL C Expressions
16516 @subsubsection OpenCL C Expressions
16518 @cindex OpenCL C Expressions
16519 @value{GDBN} supports accesses to vector components including the access as
16520 lvalue where possible. Since OpenCL C is based on C99 most C expressions
16521 supported by @value{GDBN} can be used as well.
16523 @node OpenCL C Operators
16524 @subsubsection OpenCL C Operators
16526 @cindex OpenCL C Operators
16527 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
16531 @subsection Fortran
16532 @cindex Fortran-specific support in @value{GDBN}
16534 @value{GDBN} can be used to debug programs written in Fortran, but it
16535 currently supports only the features of Fortran 77 language.
16537 @cindex trailing underscore, in Fortran symbols
16538 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
16539 among them) append an underscore to the names of variables and
16540 functions. When you debug programs compiled by those compilers, you
16541 will need to refer to variables and functions with a trailing
16545 * Fortran Operators:: Fortran operators and expressions
16546 * Fortran Defaults:: Default settings for Fortran
16547 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
16550 @node Fortran Operators
16551 @subsubsection Fortran Operators and Expressions
16553 @cindex Fortran operators and expressions
16555 Operators must be defined on values of specific types. For instance,
16556 @code{+} is defined on numbers, but not on characters or other non-
16557 arithmetic types. Operators are often defined on groups of types.
16561 The exponentiation operator. It raises the first operand to the power
16565 The range operator. Normally used in the form of array(low:high) to
16566 represent a section of array.
16569 The access component operator. Normally used to access elements in derived
16570 types. Also suitable for unions. As unions aren't part of regular Fortran,
16571 this can only happen when accessing a register that uses a gdbarch-defined
16575 @node Fortran Defaults
16576 @subsubsection Fortran Defaults
16578 @cindex Fortran Defaults
16580 Fortran symbols are usually case-insensitive, so @value{GDBN} by
16581 default uses case-insensitive matches for Fortran symbols. You can
16582 change that with the @samp{set case-insensitive} command, see
16583 @ref{Symbols}, for the details.
16585 @node Special Fortran Commands
16586 @subsubsection Special Fortran Commands
16588 @cindex Special Fortran commands
16590 @value{GDBN} has some commands to support Fortran-specific features,
16591 such as displaying common blocks.
16594 @cindex @code{COMMON} blocks, Fortran
16595 @kindex info common
16596 @item info common @r{[}@var{common-name}@r{]}
16597 This command prints the values contained in the Fortran @code{COMMON}
16598 block whose name is @var{common-name}. With no argument, the names of
16599 all @code{COMMON} blocks visible at the current program location are
16606 @cindex Pascal support in @value{GDBN}, limitations
16607 Debugging Pascal programs which use sets, subranges, file variables, or
16608 nested functions does not currently work. @value{GDBN} does not support
16609 entering expressions, printing values, or similar features using Pascal
16612 The Pascal-specific command @code{set print pascal_static-members}
16613 controls whether static members of Pascal objects are displayed.
16614 @xref{Print Settings, pascal_static-members}.
16619 @value{GDBN} supports the @url{https://www.rust-lang.org/, Rust
16620 Programming Language}. Type- and value-printing, and expression
16621 parsing, are reasonably complete. However, there are a few
16622 peculiarities and holes to be aware of.
16626 Linespecs (@pxref{Specify Location}) are never relative to the current
16627 crate. Instead, they act as if there were a global namespace of
16628 crates, somewhat similar to the way @code{extern crate} behaves.
16630 That is, if @value{GDBN} is stopped at a breakpoint in a function in
16631 crate @samp{A}, module @samp{B}, then @code{break B::f} will attempt
16632 to set a breakpoint in a function named @samp{f} in a crate named
16635 As a consequence of this approach, linespecs also cannot refer to
16636 items using @samp{self::} or @samp{super::}.
16639 Because @value{GDBN} implements Rust name-lookup semantics in
16640 expressions, it will sometimes prepend the current crate to a name.
16641 For example, if @value{GDBN} is stopped at a breakpoint in the crate
16642 @samp{K}, then @code{print ::x::y} will try to find the symbol
16645 However, since it is useful to be able to refer to other crates when
16646 debugging, @value{GDBN} provides the @code{extern} extension to
16647 circumvent this. To use the extension, just put @code{extern} before
16648 a path expression to refer to the otherwise unavailable ``global''
16651 In the above example, if you wanted to refer to the symbol @samp{y} in
16652 the crate @samp{x}, you would use @code{print extern x::y}.
16655 The Rust expression evaluator does not support ``statement-like''
16656 expressions such as @code{if} or @code{match}, or lambda expressions.
16659 Tuple expressions are not implemented.
16662 The Rust expression evaluator does not currently implement the
16663 @code{Drop} trait. Objects that may be created by the evaluator will
16664 never be destroyed.
16667 @value{GDBN} does not implement type inference for generics. In order
16668 to call generic functions or otherwise refer to generic items, you
16669 will have to specify the type parameters manually.
16672 @value{GDBN} currently uses the C@t{++} demangler for Rust. In most
16673 cases this does not cause any problems. However, in an expression
16674 context, completing a generic function name will give syntactically
16675 invalid results. This happens because Rust requires the @samp{::}
16676 operator between the function name and its generic arguments. For
16677 example, @value{GDBN} might provide a completion like
16678 @code{crate::f<u32>}, where the parser would require
16679 @code{crate::f::<u32>}.
16682 As of this writing, the Rust compiler (version 1.8) has a few holes in
16683 the debugging information it generates. These holes prevent certain
16684 features from being implemented by @value{GDBN}:
16688 Method calls cannot be made via traits.
16691 Operator overloading is not implemented.
16694 When debugging in a monomorphized function, you cannot use the generic
16698 The type @code{Self} is not available.
16701 @code{use} statements are not available, so some names may not be
16702 available in the crate.
16707 @subsection Modula-2
16709 @cindex Modula-2, @value{GDBN} support
16711 The extensions made to @value{GDBN} to support Modula-2 only support
16712 output from the @sc{gnu} Modula-2 compiler (which is currently being
16713 developed). Other Modula-2 compilers are not currently supported, and
16714 attempting to debug executables produced by them is most likely
16715 to give an error as @value{GDBN} reads in the executable's symbol
16718 @cindex expressions in Modula-2
16720 * M2 Operators:: Built-in operators
16721 * Built-In Func/Proc:: Built-in functions and procedures
16722 * M2 Constants:: Modula-2 constants
16723 * M2 Types:: Modula-2 types
16724 * M2 Defaults:: Default settings for Modula-2
16725 * Deviations:: Deviations from standard Modula-2
16726 * M2 Checks:: Modula-2 type and range checks
16727 * M2 Scope:: The scope operators @code{::} and @code{.}
16728 * GDB/M2:: @value{GDBN} and Modula-2
16732 @subsubsection Operators
16733 @cindex Modula-2 operators
16735 Operators must be defined on values of specific types. For instance,
16736 @code{+} is defined on numbers, but not on structures. Operators are
16737 often defined on groups of types. For the purposes of Modula-2, the
16738 following definitions hold:
16743 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
16747 @emph{Character types} consist of @code{CHAR} and its subranges.
16750 @emph{Floating-point types} consist of @code{REAL}.
16753 @emph{Pointer types} consist of anything declared as @code{POINTER TO
16757 @emph{Scalar types} consist of all of the above.
16760 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
16763 @emph{Boolean types} consist of @code{BOOLEAN}.
16767 The following operators are supported, and appear in order of
16768 increasing precedence:
16772 Function argument or array index separator.
16775 Assignment. The value of @var{var} @code{:=} @var{value} is
16779 Less than, greater than on integral, floating-point, or enumerated
16783 Less than or equal to, greater than or equal to
16784 on integral, floating-point and enumerated types, or set inclusion on
16785 set types. Same precedence as @code{<}.
16787 @item =@r{, }<>@r{, }#
16788 Equality and two ways of expressing inequality, valid on scalar types.
16789 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
16790 available for inequality, since @code{#} conflicts with the script
16794 Set membership. Defined on set types and the types of their members.
16795 Same precedence as @code{<}.
16798 Boolean disjunction. Defined on boolean types.
16801 Boolean conjunction. Defined on boolean types.
16804 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
16807 Addition and subtraction on integral and floating-point types, or union
16808 and difference on set types.
16811 Multiplication on integral and floating-point types, or set intersection
16815 Division on floating-point types, or symmetric set difference on set
16816 types. Same precedence as @code{*}.
16819 Integer division and remainder. Defined on integral types. Same
16820 precedence as @code{*}.
16823 Negative. Defined on @code{INTEGER} and @code{REAL} data.
16826 Pointer dereferencing. Defined on pointer types.
16829 Boolean negation. Defined on boolean types. Same precedence as
16833 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
16834 precedence as @code{^}.
16837 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
16840 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
16844 @value{GDBN} and Modula-2 scope operators.
16848 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
16849 treats the use of the operator @code{IN}, or the use of operators
16850 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
16851 @code{<=}, and @code{>=} on sets as an error.
16855 @node Built-In Func/Proc
16856 @subsubsection Built-in Functions and Procedures
16857 @cindex Modula-2 built-ins
16859 Modula-2 also makes available several built-in procedures and functions.
16860 In describing these, the following metavariables are used:
16865 represents an @code{ARRAY} variable.
16868 represents a @code{CHAR} constant or variable.
16871 represents a variable or constant of integral type.
16874 represents an identifier that belongs to a set. Generally used in the
16875 same function with the metavariable @var{s}. The type of @var{s} should
16876 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
16879 represents a variable or constant of integral or floating-point type.
16882 represents a variable or constant of floating-point type.
16888 represents a variable.
16891 represents a variable or constant of one of many types. See the
16892 explanation of the function for details.
16895 All Modula-2 built-in procedures also return a result, described below.
16899 Returns the absolute value of @var{n}.
16902 If @var{c} is a lower case letter, it returns its upper case
16903 equivalent, otherwise it returns its argument.
16906 Returns the character whose ordinal value is @var{i}.
16909 Decrements the value in the variable @var{v} by one. Returns the new value.
16911 @item DEC(@var{v},@var{i})
16912 Decrements the value in the variable @var{v} by @var{i}. Returns the
16915 @item EXCL(@var{m},@var{s})
16916 Removes the element @var{m} from the set @var{s}. Returns the new
16919 @item FLOAT(@var{i})
16920 Returns the floating point equivalent of the integer @var{i}.
16922 @item HIGH(@var{a})
16923 Returns the index of the last member of @var{a}.
16926 Increments the value in the variable @var{v} by one. Returns the new value.
16928 @item INC(@var{v},@var{i})
16929 Increments the value in the variable @var{v} by @var{i}. Returns the
16932 @item INCL(@var{m},@var{s})
16933 Adds the element @var{m} to the set @var{s} if it is not already
16934 there. Returns the new set.
16937 Returns the maximum value of the type @var{t}.
16940 Returns the minimum value of the type @var{t}.
16943 Returns boolean TRUE if @var{i} is an odd number.
16946 Returns the ordinal value of its argument. For example, the ordinal
16947 value of a character is its @sc{ascii} value (on machines supporting
16948 the @sc{ascii} character set). The argument @var{x} must be of an
16949 ordered type, which include integral, character and enumerated types.
16951 @item SIZE(@var{x})
16952 Returns the size of its argument. The argument @var{x} can be a
16953 variable or a type.
16955 @item TRUNC(@var{r})
16956 Returns the integral part of @var{r}.
16958 @item TSIZE(@var{x})
16959 Returns the size of its argument. The argument @var{x} can be a
16960 variable or a type.
16962 @item VAL(@var{t},@var{i})
16963 Returns the member of the type @var{t} whose ordinal value is @var{i}.
16967 @emph{Warning:} Sets and their operations are not yet supported, so
16968 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
16972 @cindex Modula-2 constants
16974 @subsubsection Constants
16976 @value{GDBN} allows you to express the constants of Modula-2 in the following
16982 Integer constants are simply a sequence of digits. When used in an
16983 expression, a constant is interpreted to be type-compatible with the
16984 rest of the expression. Hexadecimal integers are specified by a
16985 trailing @samp{H}, and octal integers by a trailing @samp{B}.
16988 Floating point constants appear as a sequence of digits, followed by a
16989 decimal point and another sequence of digits. An optional exponent can
16990 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
16991 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
16992 digits of the floating point constant must be valid decimal (base 10)
16996 Character constants consist of a single character enclosed by a pair of
16997 like quotes, either single (@code{'}) or double (@code{"}). They may
16998 also be expressed by their ordinal value (their @sc{ascii} value, usually)
16999 followed by a @samp{C}.
17002 String constants consist of a sequence of characters enclosed by a
17003 pair of like quotes, either single (@code{'}) or double (@code{"}).
17004 Escape sequences in the style of C are also allowed. @xref{C
17005 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
17009 Enumerated constants consist of an enumerated identifier.
17012 Boolean constants consist of the identifiers @code{TRUE} and
17016 Pointer constants consist of integral values only.
17019 Set constants are not yet supported.
17023 @subsubsection Modula-2 Types
17024 @cindex Modula-2 types
17026 Currently @value{GDBN} can print the following data types in Modula-2
17027 syntax: array types, record types, set types, pointer types, procedure
17028 types, enumerated types, subrange types and base types. You can also
17029 print the contents of variables declared using these type.
17030 This section gives a number of simple source code examples together with
17031 sample @value{GDBN} sessions.
17033 The first example contains the following section of code:
17042 and you can request @value{GDBN} to interrogate the type and value of
17043 @code{r} and @code{s}.
17046 (@value{GDBP}) print s
17048 (@value{GDBP}) ptype s
17050 (@value{GDBP}) print r
17052 (@value{GDBP}) ptype r
17057 Likewise if your source code declares @code{s} as:
17061 s: SET ['A'..'Z'] ;
17065 then you may query the type of @code{s} by:
17068 (@value{GDBP}) ptype s
17069 type = SET ['A'..'Z']
17073 Note that at present you cannot interactively manipulate set
17074 expressions using the debugger.
17076 The following example shows how you might declare an array in Modula-2
17077 and how you can interact with @value{GDBN} to print its type and contents:
17081 s: ARRAY [-10..10] OF CHAR ;
17085 (@value{GDBP}) ptype s
17086 ARRAY [-10..10] OF CHAR
17089 Note that the array handling is not yet complete and although the type
17090 is printed correctly, expression handling still assumes that all
17091 arrays have a lower bound of zero and not @code{-10} as in the example
17094 Here are some more type related Modula-2 examples:
17098 colour = (blue, red, yellow, green) ;
17099 t = [blue..yellow] ;
17107 The @value{GDBN} interaction shows how you can query the data type
17108 and value of a variable.
17111 (@value{GDBP}) print s
17113 (@value{GDBP}) ptype t
17114 type = [blue..yellow]
17118 In this example a Modula-2 array is declared and its contents
17119 displayed. Observe that the contents are written in the same way as
17120 their @code{C} counterparts.
17124 s: ARRAY [1..5] OF CARDINAL ;
17130 (@value{GDBP}) print s
17131 $1 = @{1, 0, 0, 0, 0@}
17132 (@value{GDBP}) ptype s
17133 type = ARRAY [1..5] OF CARDINAL
17136 The Modula-2 language interface to @value{GDBN} also understands
17137 pointer types as shown in this example:
17141 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
17148 and you can request that @value{GDBN} describes the type of @code{s}.
17151 (@value{GDBP}) ptype s
17152 type = POINTER TO ARRAY [1..5] OF CARDINAL
17155 @value{GDBN} handles compound types as we can see in this example.
17156 Here we combine array types, record types, pointer types and subrange
17167 myarray = ARRAY myrange OF CARDINAL ;
17168 myrange = [-2..2] ;
17170 s: POINTER TO ARRAY myrange OF foo ;
17174 and you can ask @value{GDBN} to describe the type of @code{s} as shown
17178 (@value{GDBP}) ptype s
17179 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
17182 f3 : ARRAY [-2..2] OF CARDINAL;
17187 @subsubsection Modula-2 Defaults
17188 @cindex Modula-2 defaults
17190 If type and range checking are set automatically by @value{GDBN}, they
17191 both default to @code{on} whenever the working language changes to
17192 Modula-2. This happens regardless of whether you or @value{GDBN}
17193 selected the working language.
17195 If you allow @value{GDBN} to set the language automatically, then entering
17196 code compiled from a file whose name ends with @file{.mod} sets the
17197 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
17198 Infer the Source Language}, for further details.
17201 @subsubsection Deviations from Standard Modula-2
17202 @cindex Modula-2, deviations from
17204 A few changes have been made to make Modula-2 programs easier to debug.
17205 This is done primarily via loosening its type strictness:
17209 Unlike in standard Modula-2, pointer constants can be formed by
17210 integers. This allows you to modify pointer variables during
17211 debugging. (In standard Modula-2, the actual address contained in a
17212 pointer variable is hidden from you; it can only be modified
17213 through direct assignment to another pointer variable or expression that
17214 returned a pointer.)
17217 C escape sequences can be used in strings and characters to represent
17218 non-printable characters. @value{GDBN} prints out strings with these
17219 escape sequences embedded. Single non-printable characters are
17220 printed using the @samp{CHR(@var{nnn})} format.
17223 The assignment operator (@code{:=}) returns the value of its right-hand
17227 All built-in procedures both modify @emph{and} return their argument.
17231 @subsubsection Modula-2 Type and Range Checks
17232 @cindex Modula-2 checks
17235 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
17238 @c FIXME remove warning when type/range checks added
17240 @value{GDBN} considers two Modula-2 variables type equivalent if:
17244 They are of types that have been declared equivalent via a @code{TYPE
17245 @var{t1} = @var{t2}} statement
17248 They have been declared on the same line. (Note: This is true of the
17249 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
17252 As long as type checking is enabled, any attempt to combine variables
17253 whose types are not equivalent is an error.
17255 Range checking is done on all mathematical operations, assignment, array
17256 index bounds, and all built-in functions and procedures.
17259 @subsubsection The Scope Operators @code{::} and @code{.}
17261 @cindex @code{.}, Modula-2 scope operator
17262 @cindex colon, doubled as scope operator
17264 @vindex colon-colon@r{, in Modula-2}
17265 @c Info cannot handle :: but TeX can.
17268 @vindex ::@r{, in Modula-2}
17271 There are a few subtle differences between the Modula-2 scope operator
17272 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
17277 @var{module} . @var{id}
17278 @var{scope} :: @var{id}
17282 where @var{scope} is the name of a module or a procedure,
17283 @var{module} the name of a module, and @var{id} is any declared
17284 identifier within your program, except another module.
17286 Using the @code{::} operator makes @value{GDBN} search the scope
17287 specified by @var{scope} for the identifier @var{id}. If it is not
17288 found in the specified scope, then @value{GDBN} searches all scopes
17289 enclosing the one specified by @var{scope}.
17291 Using the @code{.} operator makes @value{GDBN} search the current scope for
17292 the identifier specified by @var{id} that was imported from the
17293 definition module specified by @var{module}. With this operator, it is
17294 an error if the identifier @var{id} was not imported from definition
17295 module @var{module}, or if @var{id} is not an identifier in
17299 @subsubsection @value{GDBN} and Modula-2
17301 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
17302 Five subcommands of @code{set print} and @code{show print} apply
17303 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
17304 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
17305 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
17306 analogue in Modula-2.
17308 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
17309 with any language, is not useful with Modula-2. Its
17310 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
17311 created in Modula-2 as they can in C or C@t{++}. However, because an
17312 address can be specified by an integral constant, the construct
17313 @samp{@{@var{type}@}@var{adrexp}} is still useful.
17315 @cindex @code{#} in Modula-2
17316 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
17317 interpreted as the beginning of a comment. Use @code{<>} instead.
17323 The extensions made to @value{GDBN} for Ada only support
17324 output from the @sc{gnu} Ada (GNAT) compiler.
17325 Other Ada compilers are not currently supported, and
17326 attempting to debug executables produced by them is most likely
17330 @cindex expressions in Ada
17332 * Ada Mode Intro:: General remarks on the Ada syntax
17333 and semantics supported by Ada mode
17335 * Omissions from Ada:: Restrictions on the Ada expression syntax.
17336 * Additions to Ada:: Extensions of the Ada expression syntax.
17337 * Overloading support for Ada:: Support for expressions involving overloaded
17339 * Stopping Before Main Program:: Debugging the program during elaboration.
17340 * Ada Exceptions:: Ada Exceptions
17341 * Ada Tasks:: Listing and setting breakpoints in tasks.
17342 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
17343 * Ravenscar Profile:: Tasking Support when using the Ravenscar
17345 * Ada Settings:: New settable GDB parameters for Ada.
17346 * Ada Glitches:: Known peculiarities of Ada mode.
17349 @node Ada Mode Intro
17350 @subsubsection Introduction
17351 @cindex Ada mode, general
17353 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
17354 syntax, with some extensions.
17355 The philosophy behind the design of this subset is
17359 That @value{GDBN} should provide basic literals and access to operations for
17360 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
17361 leaving more sophisticated computations to subprograms written into the
17362 program (which therefore may be called from @value{GDBN}).
17365 That type safety and strict adherence to Ada language restrictions
17366 are not particularly important to the @value{GDBN} user.
17369 That brevity is important to the @value{GDBN} user.
17372 Thus, for brevity, the debugger acts as if all names declared in
17373 user-written packages are directly visible, even if they are not visible
17374 according to Ada rules, thus making it unnecessary to fully qualify most
17375 names with their packages, regardless of context. Where this causes
17376 ambiguity, @value{GDBN} asks the user's intent.
17378 The debugger will start in Ada mode if it detects an Ada main program.
17379 As for other languages, it will enter Ada mode when stopped in a program that
17380 was translated from an Ada source file.
17382 While in Ada mode, you may use `@t{--}' for comments. This is useful
17383 mostly for documenting command files. The standard @value{GDBN} comment
17384 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
17385 middle (to allow based literals).
17387 @node Omissions from Ada
17388 @subsubsection Omissions from Ada
17389 @cindex Ada, omissions from
17391 Here are the notable omissions from the subset:
17395 Only a subset of the attributes are supported:
17399 @t{'First}, @t{'Last}, and @t{'Length}
17400 on array objects (not on types and subtypes).
17403 @t{'Min} and @t{'Max}.
17406 @t{'Pos} and @t{'Val}.
17412 @t{'Range} on array objects (not subtypes), but only as the right
17413 operand of the membership (@code{in}) operator.
17416 @t{'Access}, @t{'Unchecked_Access}, and
17417 @t{'Unrestricted_Access} (a GNAT extension).
17425 @code{Characters.Latin_1} are not available and
17426 concatenation is not implemented. Thus, escape characters in strings are
17427 not currently available.
17430 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
17431 equality of representations. They will generally work correctly
17432 for strings and arrays whose elements have integer or enumeration types.
17433 They may not work correctly for arrays whose element
17434 types have user-defined equality, for arrays of real values
17435 (in particular, IEEE-conformant floating point, because of negative
17436 zeroes and NaNs), and for arrays whose elements contain unused bits with
17437 indeterminate values.
17440 The other component-by-component array operations (@code{and}, @code{or},
17441 @code{xor}, @code{not}, and relational tests other than equality)
17442 are not implemented.
17445 @cindex array aggregates (Ada)
17446 @cindex record aggregates (Ada)
17447 @cindex aggregates (Ada)
17448 There is limited support for array and record aggregates. They are
17449 permitted only on the right sides of assignments, as in these examples:
17452 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
17453 (@value{GDBP}) set An_Array := (1, others => 0)
17454 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
17455 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
17456 (@value{GDBP}) set A_Record := (1, "Peter", True);
17457 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
17461 discriminant's value by assigning an aggregate has an
17462 undefined effect if that discriminant is used within the record.
17463 However, you can first modify discriminants by directly assigning to
17464 them (which normally would not be allowed in Ada), and then performing an
17465 aggregate assignment. For example, given a variable @code{A_Rec}
17466 declared to have a type such as:
17469 type Rec (Len : Small_Integer := 0) is record
17471 Vals : IntArray (1 .. Len);
17475 you can assign a value with a different size of @code{Vals} with two
17479 (@value{GDBP}) set A_Rec.Len := 4
17480 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
17483 As this example also illustrates, @value{GDBN} is very loose about the usual
17484 rules concerning aggregates. You may leave out some of the
17485 components of an array or record aggregate (such as the @code{Len}
17486 component in the assignment to @code{A_Rec} above); they will retain their
17487 original values upon assignment. You may freely use dynamic values as
17488 indices in component associations. You may even use overlapping or
17489 redundant component associations, although which component values are
17490 assigned in such cases is not defined.
17493 Calls to dispatching subprograms are not implemented.
17496 The overloading algorithm is much more limited (i.e., less selective)
17497 than that of real Ada. It makes only limited use of the context in
17498 which a subexpression appears to resolve its meaning, and it is much
17499 looser in its rules for allowing type matches. As a result, some
17500 function calls will be ambiguous, and the user will be asked to choose
17501 the proper resolution.
17504 The @code{new} operator is not implemented.
17507 Entry calls are not implemented.
17510 Aside from printing, arithmetic operations on the native VAX floating-point
17511 formats are not supported.
17514 It is not possible to slice a packed array.
17517 The names @code{True} and @code{False}, when not part of a qualified name,
17518 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
17520 Should your program
17521 redefine these names in a package or procedure (at best a dubious practice),
17522 you will have to use fully qualified names to access their new definitions.
17525 @node Additions to Ada
17526 @subsubsection Additions to Ada
17527 @cindex Ada, deviations from
17529 As it does for other languages, @value{GDBN} makes certain generic
17530 extensions to Ada (@pxref{Expressions}):
17534 If the expression @var{E} is a variable residing in memory (typically
17535 a local variable or array element) and @var{N} is a positive integer,
17536 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
17537 @var{N}-1 adjacent variables following it in memory as an array. In
17538 Ada, this operator is generally not necessary, since its prime use is
17539 in displaying parts of an array, and slicing will usually do this in
17540 Ada. However, there are occasional uses when debugging programs in
17541 which certain debugging information has been optimized away.
17544 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
17545 appears in function or file @var{B}.'' When @var{B} is a file name,
17546 you must typically surround it in single quotes.
17549 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
17550 @var{type} that appears at address @var{addr}.''
17553 A name starting with @samp{$} is a convenience variable
17554 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
17557 In addition, @value{GDBN} provides a few other shortcuts and outright
17558 additions specific to Ada:
17562 The assignment statement is allowed as an expression, returning
17563 its right-hand operand as its value. Thus, you may enter
17566 (@value{GDBP}) set x := y + 3
17567 (@value{GDBP}) print A(tmp := y + 1)
17571 The semicolon is allowed as an ``operator,'' returning as its value
17572 the value of its right-hand operand.
17573 This allows, for example,
17574 complex conditional breaks:
17577 (@value{GDBP}) break f
17578 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
17582 Rather than use catenation and symbolic character names to introduce special
17583 characters into strings, one may instead use a special bracket notation,
17584 which is also used to print strings. A sequence of characters of the form
17585 @samp{["@var{XX}"]} within a string or character literal denotes the
17586 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
17587 sequence of characters @samp{["""]} also denotes a single quotation mark
17588 in strings. For example,
17590 "One line.["0a"]Next line.["0a"]"
17593 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
17597 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
17598 @t{'Max} is optional (and is ignored in any case). For example, it is valid
17602 (@value{GDBP}) print 'max(x, y)
17606 When printing arrays, @value{GDBN} uses positional notation when the
17607 array has a lower bound of 1, and uses a modified named notation otherwise.
17608 For example, a one-dimensional array of three integers with a lower bound
17609 of 3 might print as
17616 That is, in contrast to valid Ada, only the first component has a @code{=>}
17620 You may abbreviate attributes in expressions with any unique,
17621 multi-character subsequence of
17622 their names (an exact match gets preference).
17623 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
17624 in place of @t{a'length}.
17627 @cindex quoting Ada internal identifiers
17628 Since Ada is case-insensitive, the debugger normally maps identifiers you type
17629 to lower case. The GNAT compiler uses upper-case characters for
17630 some of its internal identifiers, which are normally of no interest to users.
17631 For the rare occasions when you actually have to look at them,
17632 enclose them in angle brackets to avoid the lower-case mapping.
17635 (@value{GDBP}) print <JMPBUF_SAVE>[0]
17639 Printing an object of class-wide type or dereferencing an
17640 access-to-class-wide value will display all the components of the object's
17641 specific type (as indicated by its run-time tag). Likewise, component
17642 selection on such a value will operate on the specific type of the
17647 @node Overloading support for Ada
17648 @subsubsection Overloading support for Ada
17649 @cindex overloading, Ada
17651 The debugger supports limited overloading. Given a subprogram call in which
17652 the function symbol has multiple definitions, it will use the number of
17653 actual parameters and some information about their types to attempt to narrow
17654 the set of definitions. It also makes very limited use of context, preferring
17655 procedures to functions in the context of the @code{call} command, and
17656 functions to procedures elsewhere.
17658 If, after narrowing, the set of matching definitions still contains more than
17659 one definition, @value{GDBN} will display a menu to query which one it should
17663 (@value{GDBP}) print f(1)
17664 Multiple matches for f
17666 [1] foo.f (integer) return boolean at foo.adb:23
17667 [2] foo.f (foo.new_integer) return boolean at foo.adb:28
17671 In this case, just select one menu entry either to cancel expression evaluation
17672 (type @kbd{0} and press @key{RET}) or to continue evaluation with a specific
17673 instance (type the corresponding number and press @key{RET}).
17675 Here are a couple of commands to customize @value{GDBN}'s behavior in this
17680 @kindex set ada print-signatures
17681 @item set ada print-signatures
17682 Control whether parameter types and return types are displayed in overloads
17683 selection menus. It is @code{on} by default.
17684 @xref{Overloading support for Ada}.
17686 @kindex show ada print-signatures
17687 @item show ada print-signatures
17688 Show the current setting for displaying parameter types and return types in
17689 overloads selection menu.
17690 @xref{Overloading support for Ada}.
17694 @node Stopping Before Main Program
17695 @subsubsection Stopping at the Very Beginning
17697 @cindex breakpointing Ada elaboration code
17698 It is sometimes necessary to debug the program during elaboration, and
17699 before reaching the main procedure.
17700 As defined in the Ada Reference
17701 Manual, the elaboration code is invoked from a procedure called
17702 @code{adainit}. To run your program up to the beginning of
17703 elaboration, simply use the following two commands:
17704 @code{tbreak adainit} and @code{run}.
17706 @node Ada Exceptions
17707 @subsubsection Ada Exceptions
17709 A command is provided to list all Ada exceptions:
17712 @kindex info exceptions
17713 @item info exceptions
17714 @itemx info exceptions @var{regexp}
17715 The @code{info exceptions} command allows you to list all Ada exceptions
17716 defined within the program being debugged, as well as their addresses.
17717 With a regular expression, @var{regexp}, as argument, only those exceptions
17718 whose names match @var{regexp} are listed.
17721 Below is a small example, showing how the command can be used, first
17722 without argument, and next with a regular expression passed as an
17726 (@value{GDBP}) info exceptions
17727 All defined Ada exceptions:
17728 constraint_error: 0x613da0
17729 program_error: 0x613d20
17730 storage_error: 0x613ce0
17731 tasking_error: 0x613ca0
17732 const.aint_global_e: 0x613b00
17733 (@value{GDBP}) info exceptions const.aint
17734 All Ada exceptions matching regular expression "const.aint":
17735 constraint_error: 0x613da0
17736 const.aint_global_e: 0x613b00
17739 It is also possible to ask @value{GDBN} to stop your program's execution
17740 when an exception is raised. For more details, see @ref{Set Catchpoints}.
17743 @subsubsection Extensions for Ada Tasks
17744 @cindex Ada, tasking
17746 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
17747 @value{GDBN} provides the following task-related commands:
17752 This command shows a list of current Ada tasks, as in the following example:
17759 (@value{GDBP}) info tasks
17760 ID TID P-ID Pri State Name
17761 1 8088000 0 15 Child Activation Wait main_task
17762 2 80a4000 1 15 Accept Statement b
17763 3 809a800 1 15 Child Activation Wait a
17764 * 4 80ae800 3 15 Runnable c
17769 In this listing, the asterisk before the last task indicates it to be the
17770 task currently being inspected.
17774 Represents @value{GDBN}'s internal task number.
17780 The parent's task ID (@value{GDBN}'s internal task number).
17783 The base priority of the task.
17786 Current state of the task.
17790 The task has been created but has not been activated. It cannot be
17794 The task is not blocked for any reason known to Ada. (It may be waiting
17795 for a mutex, though.) It is conceptually "executing" in normal mode.
17798 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
17799 that were waiting on terminate alternatives have been awakened and have
17800 terminated themselves.
17802 @item Child Activation Wait
17803 The task is waiting for created tasks to complete activation.
17805 @item Accept Statement
17806 The task is waiting on an accept or selective wait statement.
17808 @item Waiting on entry call
17809 The task is waiting on an entry call.
17811 @item Async Select Wait
17812 The task is waiting to start the abortable part of an asynchronous
17816 The task is waiting on a select statement with only a delay
17819 @item Child Termination Wait
17820 The task is sleeping having completed a master within itself, and is
17821 waiting for the tasks dependent on that master to become terminated or
17822 waiting on a terminate Phase.
17824 @item Wait Child in Term Alt
17825 The task is sleeping waiting for tasks on terminate alternatives to
17826 finish terminating.
17828 @item Accepting RV with @var{taskno}
17829 The task is accepting a rendez-vous with the task @var{taskno}.
17833 Name of the task in the program.
17837 @kindex info task @var{taskno}
17838 @item info task @var{taskno}
17839 This command shows detailled informations on the specified task, as in
17840 the following example:
17845 (@value{GDBP}) info tasks
17846 ID TID P-ID Pri State Name
17847 1 8077880 0 15 Child Activation Wait main_task
17848 * 2 807c468 1 15 Runnable task_1
17849 (@value{GDBP}) info task 2
17850 Ada Task: 0x807c468
17854 Parent: 1 ("main_task")
17860 @kindex task@r{ (Ada)}
17861 @cindex current Ada task ID
17862 This command prints the ID and name of the current task.
17868 (@value{GDBP}) info tasks
17869 ID TID P-ID Pri State Name
17870 1 8077870 0 15 Child Activation Wait main_task
17871 * 2 807c458 1 15 Runnable some_task
17872 (@value{GDBP}) task
17873 [Current task is 2 "some_task"]
17876 @item task @var{taskno}
17877 @cindex Ada task switching
17878 This command is like the @code{thread @var{thread-id}}
17879 command (@pxref{Threads}). It switches the context of debugging
17880 from the current task to the given task.
17886 (@value{GDBP}) info tasks
17887 ID TID P-ID Pri State Name
17888 1 8077870 0 15 Child Activation Wait main_task
17889 * 2 807c458 1 15 Runnable some_task
17890 (@value{GDBP}) task 1
17891 [Switching to task 1 "main_task"]
17892 #0 0x8067726 in pthread_cond_wait ()
17894 #0 0x8067726 in pthread_cond_wait ()
17895 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
17896 #2 0x805cb63 in system.task_primitives.operations.sleep ()
17897 #3 0x806153e in system.tasking.stages.activate_tasks ()
17898 #4 0x804aacc in un () at un.adb:5
17901 @item break @var{location} task @var{taskno}
17902 @itemx break @var{location} task @var{taskno} if @dots{}
17903 @cindex breakpoints and tasks, in Ada
17904 @cindex task breakpoints, in Ada
17905 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
17906 These commands are like the @code{break @dots{} thread @dots{}}
17907 command (@pxref{Thread Stops}). The
17908 @var{location} argument specifies source lines, as described
17909 in @ref{Specify Location}.
17911 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
17912 to specify that you only want @value{GDBN} to stop the program when a
17913 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
17914 numeric task identifiers assigned by @value{GDBN}, shown in the first
17915 column of the @samp{info tasks} display.
17917 If you do not specify @samp{task @var{taskno}} when you set a
17918 breakpoint, the breakpoint applies to @emph{all} tasks of your
17921 You can use the @code{task} qualifier on conditional breakpoints as
17922 well; in this case, place @samp{task @var{taskno}} before the
17923 breakpoint condition (before the @code{if}).
17931 (@value{GDBP}) info tasks
17932 ID TID P-ID Pri State Name
17933 1 140022020 0 15 Child Activation Wait main_task
17934 2 140045060 1 15 Accept/Select Wait t2
17935 3 140044840 1 15 Runnable t1
17936 * 4 140056040 1 15 Runnable t3
17937 (@value{GDBP}) b 15 task 2
17938 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
17939 (@value{GDBP}) cont
17944 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
17946 (@value{GDBP}) info tasks
17947 ID TID P-ID Pri State Name
17948 1 140022020 0 15 Child Activation Wait main_task
17949 * 2 140045060 1 15 Runnable t2
17950 3 140044840 1 15 Runnable t1
17951 4 140056040 1 15 Delay Sleep t3
17955 @node Ada Tasks and Core Files
17956 @subsubsection Tasking Support when Debugging Core Files
17957 @cindex Ada tasking and core file debugging
17959 When inspecting a core file, as opposed to debugging a live program,
17960 tasking support may be limited or even unavailable, depending on
17961 the platform being used.
17962 For instance, on x86-linux, the list of tasks is available, but task
17963 switching is not supported.
17965 On certain platforms, the debugger needs to perform some
17966 memory writes in order to provide Ada tasking support. When inspecting
17967 a core file, this means that the core file must be opened with read-write
17968 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
17969 Under these circumstances, you should make a backup copy of the core
17970 file before inspecting it with @value{GDBN}.
17972 @node Ravenscar Profile
17973 @subsubsection Tasking Support when using the Ravenscar Profile
17974 @cindex Ravenscar Profile
17976 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
17977 specifically designed for systems with safety-critical real-time
17981 @kindex set ravenscar task-switching on
17982 @cindex task switching with program using Ravenscar Profile
17983 @item set ravenscar task-switching on
17984 Allows task switching when debugging a program that uses the Ravenscar
17985 Profile. This is the default.
17987 @kindex set ravenscar task-switching off
17988 @item set ravenscar task-switching off
17989 Turn off task switching when debugging a program that uses the Ravenscar
17990 Profile. This is mostly intended to disable the code that adds support
17991 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
17992 the Ravenscar runtime is preventing @value{GDBN} from working properly.
17993 To be effective, this command should be run before the program is started.
17995 @kindex show ravenscar task-switching
17996 @item show ravenscar task-switching
17997 Show whether it is possible to switch from task to task in a program
17998 using the Ravenscar Profile.
18003 @subsubsection Ada Settings
18004 @cindex Ada settings
18007 @kindex set varsize-limit
18008 @item set varsize-limit @var{size}
18009 Prevent @value{GDBN} from attempting to evaluate objects whose size
18010 is above the given limit (@var{size}) when those sizes are computed
18011 from run-time quantities. This is typically the case when the object
18012 has a variable size, such as an array whose bounds are not known at
18013 compile time for example. Setting @var{size} to @code{unlimited}
18014 removes the size limitation. By default, the limit is about 65KB.
18016 The purpose of having such a limit is to prevent @value{GDBN} from
18017 trying to grab enormous chunks of virtual memory when asked to evaluate
18018 a quantity whose bounds have been corrupted or have not yet been fully
18019 initialized. The limit applies to the results of some subexpressions
18020 as well as to complete expressions. For example, an expression denoting
18021 a simple integer component, such as @code{x.y.z}, may fail if the size of
18022 @code{x.y} is variable and exceeds @code{size}. On the other hand,
18023 @value{GDBN} is sometimes clever; the expression @code{A(i)}, where
18024 @code{A} is an array variable with non-constant size, will generally
18025 succeed regardless of the bounds on @code{A}, as long as the component
18026 size is less than @var{size}.
18028 @kindex show varsize-limit
18029 @item show varsize-limit
18030 Show the limit on types whose size is determined by run-time quantities.
18034 @subsubsection Known Peculiarities of Ada Mode
18035 @cindex Ada, problems
18037 Besides the omissions listed previously (@pxref{Omissions from Ada}),
18038 we know of several problems with and limitations of Ada mode in
18040 some of which will be fixed with planned future releases of the debugger
18041 and the GNU Ada compiler.
18045 Static constants that the compiler chooses not to materialize as objects in
18046 storage are invisible to the debugger.
18049 Named parameter associations in function argument lists are ignored (the
18050 argument lists are treated as positional).
18053 Many useful library packages are currently invisible to the debugger.
18056 Fixed-point arithmetic, conversions, input, and output is carried out using
18057 floating-point arithmetic, and may give results that only approximate those on
18061 The GNAT compiler never generates the prefix @code{Standard} for any of
18062 the standard symbols defined by the Ada language. @value{GDBN} knows about
18063 this: it will strip the prefix from names when you use it, and will never
18064 look for a name you have so qualified among local symbols, nor match against
18065 symbols in other packages or subprograms. If you have
18066 defined entities anywhere in your program other than parameters and
18067 local variables whose simple names match names in @code{Standard},
18068 GNAT's lack of qualification here can cause confusion. When this happens,
18069 you can usually resolve the confusion
18070 by qualifying the problematic names with package
18071 @code{Standard} explicitly.
18074 Older versions of the compiler sometimes generate erroneous debugging
18075 information, resulting in the debugger incorrectly printing the value
18076 of affected entities. In some cases, the debugger is able to work
18077 around an issue automatically. In other cases, the debugger is able
18078 to work around the issue, but the work-around has to be specifically
18081 @kindex set ada trust-PAD-over-XVS
18082 @kindex show ada trust-PAD-over-XVS
18085 @item set ada trust-PAD-over-XVS on
18086 Configure GDB to strictly follow the GNAT encoding when computing the
18087 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
18088 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
18089 a complete description of the encoding used by the GNAT compiler).
18090 This is the default.
18092 @item set ada trust-PAD-over-XVS off
18093 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
18094 sometimes prints the wrong value for certain entities, changing @code{ada
18095 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
18096 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
18097 @code{off}, but this incurs a slight performance penalty, so it is
18098 recommended to leave this setting to @code{on} unless necessary.
18102 @cindex GNAT descriptive types
18103 @cindex GNAT encoding
18104 Internally, the debugger also relies on the compiler following a number
18105 of conventions known as the @samp{GNAT Encoding}, all documented in
18106 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
18107 how the debugging information should be generated for certain types.
18108 In particular, this convention makes use of @dfn{descriptive types},
18109 which are artificial types generated purely to help the debugger.
18111 These encodings were defined at a time when the debugging information
18112 format used was not powerful enough to describe some of the more complex
18113 types available in Ada. Since DWARF allows us to express nearly all
18114 Ada features, the long-term goal is to slowly replace these descriptive
18115 types by their pure DWARF equivalent. To facilitate that transition,
18116 a new maintenance option is available to force the debugger to ignore
18117 those descriptive types. It allows the user to quickly evaluate how
18118 well @value{GDBN} works without them.
18122 @kindex maint ada set ignore-descriptive-types
18123 @item maintenance ada set ignore-descriptive-types [on|off]
18124 Control whether the debugger should ignore descriptive types.
18125 The default is not to ignore descriptives types (@code{off}).
18127 @kindex maint ada show ignore-descriptive-types
18128 @item maintenance ada show ignore-descriptive-types
18129 Show if descriptive types are ignored by @value{GDBN}.
18133 @node Unsupported Languages
18134 @section Unsupported Languages
18136 @cindex unsupported languages
18137 @cindex minimal language
18138 In addition to the other fully-supported programming languages,
18139 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
18140 It does not represent a real programming language, but provides a set
18141 of capabilities close to what the C or assembly languages provide.
18142 This should allow most simple operations to be performed while debugging
18143 an application that uses a language currently not supported by @value{GDBN}.
18145 If the language is set to @code{auto}, @value{GDBN} will automatically
18146 select this language if the current frame corresponds to an unsupported
18150 @chapter Examining the Symbol Table
18152 The commands described in this chapter allow you to inquire about the
18153 symbols (names of variables, functions and types) defined in your
18154 program. This information is inherent in the text of your program and
18155 does not change as your program executes. @value{GDBN} finds it in your
18156 program's symbol table, in the file indicated when you started @value{GDBN}
18157 (@pxref{File Options, ,Choosing Files}), or by one of the
18158 file-management commands (@pxref{Files, ,Commands to Specify Files}).
18160 @cindex symbol names
18161 @cindex names of symbols
18162 @cindex quoting names
18163 @anchor{quoting names}
18164 Occasionally, you may need to refer to symbols that contain unusual
18165 characters, which @value{GDBN} ordinarily treats as word delimiters. The
18166 most frequent case is in referring to static variables in other
18167 source files (@pxref{Variables,,Program Variables}). File names
18168 are recorded in object files as debugging symbols, but @value{GDBN} would
18169 ordinarily parse a typical file name, like @file{foo.c}, as the three words
18170 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
18171 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
18178 looks up the value of @code{x} in the scope of the file @file{foo.c}.
18181 @cindex case-insensitive symbol names
18182 @cindex case sensitivity in symbol names
18183 @kindex set case-sensitive
18184 @item set case-sensitive on
18185 @itemx set case-sensitive off
18186 @itemx set case-sensitive auto
18187 Normally, when @value{GDBN} looks up symbols, it matches their names
18188 with case sensitivity determined by the current source language.
18189 Occasionally, you may wish to control that. The command @code{set
18190 case-sensitive} lets you do that by specifying @code{on} for
18191 case-sensitive matches or @code{off} for case-insensitive ones. If
18192 you specify @code{auto}, case sensitivity is reset to the default
18193 suitable for the source language. The default is case-sensitive
18194 matches for all languages except for Fortran, for which the default is
18195 case-insensitive matches.
18197 @kindex show case-sensitive
18198 @item show case-sensitive
18199 This command shows the current setting of case sensitivity for symbols
18202 @kindex set print type methods
18203 @item set print type methods
18204 @itemx set print type methods on
18205 @itemx set print type methods off
18206 Normally, when @value{GDBN} prints a class, it displays any methods
18207 declared in that class. You can control this behavior either by
18208 passing the appropriate flag to @code{ptype}, or using @command{set
18209 print type methods}. Specifying @code{on} will cause @value{GDBN} to
18210 display the methods; this is the default. Specifying @code{off} will
18211 cause @value{GDBN} to omit the methods.
18213 @kindex show print type methods
18214 @item show print type methods
18215 This command shows the current setting of method display when printing
18218 @kindex set print type nested-type-limit
18219 @item set print type nested-type-limit @var{limit}
18220 @itemx set print type nested-type-limit unlimited
18221 Set the limit of displayed nested types that the type printer will
18222 show. A @var{limit} of @code{unlimited} or @code{-1} will show all
18223 nested definitions. By default, the type printer will not show any nested
18224 types defined in classes.
18226 @kindex show print type nested-type-limit
18227 @item show print type nested-type-limit
18228 This command shows the current display limit of nested types when
18231 @kindex set print type typedefs
18232 @item set print type typedefs
18233 @itemx set print type typedefs on
18234 @itemx set print type typedefs off
18236 Normally, when @value{GDBN} prints a class, it displays any typedefs
18237 defined in that class. You can control this behavior either by
18238 passing the appropriate flag to @code{ptype}, or using @command{set
18239 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
18240 display the typedef definitions; this is the default. Specifying
18241 @code{off} will cause @value{GDBN} to omit the typedef definitions.
18242 Note that this controls whether the typedef definition itself is
18243 printed, not whether typedef names are substituted when printing other
18246 @kindex show print type typedefs
18247 @item show print type typedefs
18248 This command shows the current setting of typedef display when
18251 @kindex info address
18252 @cindex address of a symbol
18253 @item info address @var{symbol}
18254 Describe where the data for @var{symbol} is stored. For a register
18255 variable, this says which register it is kept in. For a non-register
18256 local variable, this prints the stack-frame offset at which the variable
18259 Note the contrast with @samp{print &@var{symbol}}, which does not work
18260 at all for a register variable, and for a stack local variable prints
18261 the exact address of the current instantiation of the variable.
18263 @kindex info symbol
18264 @cindex symbol from address
18265 @cindex closest symbol and offset for an address
18266 @item info symbol @var{addr}
18267 Print the name of a symbol which is stored at the address @var{addr}.
18268 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
18269 nearest symbol and an offset from it:
18272 (@value{GDBP}) info symbol 0x54320
18273 _initialize_vx + 396 in section .text
18277 This is the opposite of the @code{info address} command. You can use
18278 it to find out the name of a variable or a function given its address.
18280 For dynamically linked executables, the name of executable or shared
18281 library containing the symbol is also printed:
18284 (@value{GDBP}) info symbol 0x400225
18285 _start + 5 in section .text of /tmp/a.out
18286 (@value{GDBP}) info symbol 0x2aaaac2811cf
18287 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
18292 @item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
18293 Demangle @var{name}.
18294 If @var{language} is provided it is the name of the language to demangle
18295 @var{name} in. Otherwise @var{name} is demangled in the current language.
18297 The @samp{--} option specifies the end of options,
18298 and is useful when @var{name} begins with a dash.
18300 The parameter @code{demangle-style} specifies how to interpret the kind
18301 of mangling used. @xref{Print Settings}.
18304 @item whatis[/@var{flags}] [@var{arg}]
18305 Print the data type of @var{arg}, which can be either an expression
18306 or a name of a data type. With no argument, print the data type of
18307 @code{$}, the last value in the value history.
18309 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
18310 is not actually evaluated, and any side-effecting operations (such as
18311 assignments or function calls) inside it do not take place.
18313 If @var{arg} is a variable or an expression, @code{whatis} prints its
18314 literal type as it is used in the source code. If the type was
18315 defined using a @code{typedef}, @code{whatis} will @emph{not} print
18316 the data type underlying the @code{typedef}. If the type of the
18317 variable or the expression is a compound data type, such as
18318 @code{struct} or @code{class}, @code{whatis} never prints their
18319 fields or methods. It just prints the @code{struct}/@code{class}
18320 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
18321 such a compound data type, use @code{ptype}.
18323 If @var{arg} is a type name that was defined using @code{typedef},
18324 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
18325 Unrolling means that @code{whatis} will show the underlying type used
18326 in the @code{typedef} declaration of @var{arg}. However, if that
18327 underlying type is also a @code{typedef}, @code{whatis} will not
18330 For C code, the type names may also have the form @samp{class
18331 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
18332 @var{union-tag}} or @samp{enum @var{enum-tag}}.
18334 @var{flags} can be used to modify how the type is displayed.
18335 Available flags are:
18339 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
18340 parameters and typedefs defined in a class when printing the class'
18341 members. The @code{/r} flag disables this.
18344 Do not print methods defined in the class.
18347 Print methods defined in the class. This is the default, but the flag
18348 exists in case you change the default with @command{set print type methods}.
18351 Do not print typedefs defined in the class. Note that this controls
18352 whether the typedef definition itself is printed, not whether typedef
18353 names are substituted when printing other types.
18356 Print typedefs defined in the class. This is the default, but the flag
18357 exists in case you change the default with @command{set print type typedefs}.
18360 Print the offsets and sizes of fields in a struct, similar to what the
18361 @command{pahole} tool does. This option implies the @code{/tm} flags.
18363 For example, given the following declarations:
18399 Issuing a @kbd{ptype /o struct tuv} command would print:
18402 (@value{GDBP}) ptype /o struct tuv
18403 /* offset | size */ type = struct tuv @{
18404 /* 0 | 4 */ int a1;
18405 /* XXX 4-byte hole */
18406 /* 8 | 8 */ char *a2;
18407 /* 16 | 4 */ int a3;
18409 /* total size (bytes): 24 */
18413 Notice the format of the first column of comments. There, you can
18414 find two parts separated by the @samp{|} character: the @emph{offset},
18415 which indicates where the field is located inside the struct, in
18416 bytes, and the @emph{size} of the field. Another interesting line is
18417 the marker of a @emph{hole} in the struct, indicating that it may be
18418 possible to pack the struct and make it use less space by reorganizing
18421 It is also possible to print offsets inside an union:
18424 (@value{GDBP}) ptype /o union qwe
18425 /* offset | size */ type = union qwe @{
18426 /* 24 */ struct tuv @{
18427 /* 0 | 4 */ int a1;
18428 /* XXX 4-byte hole */
18429 /* 8 | 8 */ char *a2;
18430 /* 16 | 4 */ int a3;
18432 /* total size (bytes): 24 */
18434 /* 40 */ struct xyz @{
18435 /* 0 | 4 */ int f1;
18436 /* 4 | 1 */ char f2;
18437 /* XXX 3-byte hole */
18438 /* 8 | 8 */ void *f3;
18439 /* 16 | 24 */ struct tuv @{
18440 /* 16 | 4 */ int a1;
18441 /* XXX 4-byte hole */
18442 /* 24 | 8 */ char *a2;
18443 /* 32 | 4 */ int a3;
18445 /* total size (bytes): 24 */
18448 /* total size (bytes): 40 */
18451 /* total size (bytes): 40 */
18455 In this case, since @code{struct tuv} and @code{struct xyz} occupy the
18456 same space (because we are dealing with an union), the offset is not
18457 printed for them. However, you can still examine the offset of each
18458 of these structures' fields.
18460 Another useful scenario is printing the offsets of a struct containing
18464 (@value{GDBP}) ptype /o struct tyu
18465 /* offset | size */ type = struct tyu @{
18466 /* 0:31 | 4 */ int a1 : 1;
18467 /* 0:28 | 4 */ int a2 : 3;
18468 /* 0: 5 | 4 */ int a3 : 23;
18469 /* 3: 3 | 1 */ signed char a4 : 2;
18470 /* XXX 3-bit hole */
18471 /* XXX 4-byte hole */
18472 /* 8 | 8 */ int64_t a5;
18473 /* 16: 0 | 4 */ int a6 : 5;
18474 /* 16: 5 | 8 */ int64_t a7 : 3;
18475 "/* XXX 7-byte padding */
18477 /* total size (bytes): 24 */
18481 Note how the offset information is now extended to also include the
18482 first bit of the bitfield.
18486 @item ptype[/@var{flags}] [@var{arg}]
18487 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
18488 detailed description of the type, instead of just the name of the type.
18489 @xref{Expressions, ,Expressions}.
18491 Contrary to @code{whatis}, @code{ptype} always unrolls any
18492 @code{typedef}s in its argument declaration, whether the argument is
18493 a variable, expression, or a data type. This means that @code{ptype}
18494 of a variable or an expression will not print literally its type as
18495 present in the source code---use @code{whatis} for that. @code{typedef}s at
18496 the pointer or reference targets are also unrolled. Only @code{typedef}s of
18497 fields, methods and inner @code{class typedef}s of @code{struct}s,
18498 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
18500 For example, for this variable declaration:
18503 typedef double real_t;
18504 struct complex @{ real_t real; double imag; @};
18505 typedef struct complex complex_t;
18507 real_t *real_pointer_var;
18511 the two commands give this output:
18515 (@value{GDBP}) whatis var
18517 (@value{GDBP}) ptype var
18518 type = struct complex @{
18522 (@value{GDBP}) whatis complex_t
18523 type = struct complex
18524 (@value{GDBP}) whatis struct complex
18525 type = struct complex
18526 (@value{GDBP}) ptype struct complex
18527 type = struct complex @{
18531 (@value{GDBP}) whatis real_pointer_var
18533 (@value{GDBP}) ptype real_pointer_var
18539 As with @code{whatis}, using @code{ptype} without an argument refers to
18540 the type of @code{$}, the last value in the value history.
18542 @cindex incomplete type
18543 Sometimes, programs use opaque data types or incomplete specifications
18544 of complex data structure. If the debug information included in the
18545 program does not allow @value{GDBN} to display a full declaration of
18546 the data type, it will say @samp{<incomplete type>}. For example,
18547 given these declarations:
18551 struct foo *fooptr;
18555 but no definition for @code{struct foo} itself, @value{GDBN} will say:
18558 (@value{GDBP}) ptype foo
18559 $1 = <incomplete type>
18563 ``Incomplete type'' is C terminology for data types that are not
18564 completely specified.
18566 @cindex unknown type
18567 Othertimes, information about a variable's type is completely absent
18568 from the debug information included in the program. This most often
18569 happens when the program or library where the variable is defined
18570 includes no debug information at all. @value{GDBN} knows the variable
18571 exists from inspecting the linker/loader symbol table (e.g., the ELF
18572 dynamic symbol table), but such symbols do not contain type
18573 information. Inspecting the type of a (global) variable for which
18574 @value{GDBN} has no type information shows:
18577 (@value{GDBP}) ptype var
18578 type = <data variable, no debug info>
18581 @xref{Variables, no debug info variables}, for how to print the values
18585 @item info types [-q] [@var{regexp}]
18586 Print a brief description of all types whose names match the regular
18587 expression @var{regexp} (or all types in your program, if you supply
18588 no argument). Each complete typename is matched as though it were a
18589 complete line; thus, @samp{i type value} gives information on all
18590 types in your program whose names include the string @code{value}, but
18591 @samp{i type ^value$} gives information only on types whose complete
18592 name is @code{value}.
18594 In programs using different languages, @value{GDBN} chooses the syntax
18595 to print the type description according to the
18596 @samp{set language} value: using @samp{set language auto}
18597 (see @ref{Automatically, ,Set Language Automatically}) means to use the
18598 language of the type, other values mean to use
18599 the manually specified language (see @ref{Manually, ,Set Language Manually}).
18601 This command differs from @code{ptype} in two ways: first, like
18602 @code{whatis}, it does not print a detailed description; second, it
18603 lists all source files and line numbers where a type is defined.
18605 The output from @samp{into types} is proceeded with a header line
18606 describing what types are being listed. The optional flag @samp{-q},
18607 which stands for @samp{quiet}, disables printing this header
18610 @kindex info type-printers
18611 @item info type-printers
18612 Versions of @value{GDBN} that ship with Python scripting enabled may
18613 have ``type printers'' available. When using @command{ptype} or
18614 @command{whatis}, these printers are consulted when the name of a type
18615 is needed. @xref{Type Printing API}, for more information on writing
18618 @code{info type-printers} displays all the available type printers.
18620 @kindex enable type-printer
18621 @kindex disable type-printer
18622 @item enable type-printer @var{name}@dots{}
18623 @item disable type-printer @var{name}@dots{}
18624 These commands can be used to enable or disable type printers.
18627 @cindex local variables
18628 @item info scope @var{location}
18629 List all the variables local to a particular scope. This command
18630 accepts a @var{location} argument---a function name, a source line, or
18631 an address preceded by a @samp{*}, and prints all the variables local
18632 to the scope defined by that location. (@xref{Specify Location}, for
18633 details about supported forms of @var{location}.) For example:
18636 (@value{GDBP}) @b{info scope command_line_handler}
18637 Scope for command_line_handler:
18638 Symbol rl is an argument at stack/frame offset 8, length 4.
18639 Symbol linebuffer is in static storage at address 0x150a18, length 4.
18640 Symbol linelength is in static storage at address 0x150a1c, length 4.
18641 Symbol p is a local variable in register $esi, length 4.
18642 Symbol p1 is a local variable in register $ebx, length 4.
18643 Symbol nline is a local variable in register $edx, length 4.
18644 Symbol repeat is a local variable at frame offset -8, length 4.
18648 This command is especially useful for determining what data to collect
18649 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
18652 @kindex info source
18654 Show information about the current source file---that is, the source file for
18655 the function containing the current point of execution:
18658 the name of the source file, and the directory containing it,
18660 the directory it was compiled in,
18662 its length, in lines,
18664 which programming language it is written in,
18666 if the debug information provides it, the program that compiled the file
18667 (which may include, e.g., the compiler version and command line arguments),
18669 whether the executable includes debugging information for that file, and
18670 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
18672 whether the debugging information includes information about
18673 preprocessor macros.
18677 @kindex info sources
18679 Print the names of all source files in your program for which there is
18680 debugging information, organized into two lists: files whose symbols
18681 have already been read, and files whose symbols will be read when needed.
18683 @item info sources [-dirname | -basename] [--] [@var{regexp}]
18684 Like @samp{info sources}, but only print the names of the files
18685 matching the provided @var{regexp}.
18686 By default, the @var{regexp} is used to match anywhere in the filename.
18687 If @code{-dirname}, only files having a dirname matching @var{regexp} are shown.
18688 If @code{-basename}, only files having a basename matching @var{regexp}
18690 The matching is case-sensitive, except on operating systems that
18691 have case-insensitive filesystem (e.g., MS-Windows).
18693 @kindex info functions
18694 @item info functions [-q] [-n]
18695 Print the names and data types of all defined functions.
18696 Similarly to @samp{info types}, this command groups its output by source
18697 files and annotates each function definition with its source line
18700 In programs using different languages, @value{GDBN} chooses the syntax
18701 to print the function name and type according to the
18702 @samp{set language} value: using @samp{set language auto}
18703 (see @ref{Automatically, ,Set Language Automatically}) means to use the
18704 language of the function, other values mean to use
18705 the manually specified language (see @ref{Manually, ,Set Language Manually}).
18707 The @samp{-n} flag excludes @dfn{non-debugging symbols} from the
18708 results. A non-debugging symbol is a symbol that comes from the
18709 executable's symbol table, not from the debug information (for
18710 example, DWARF) associated with the executable.
18712 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
18713 printing header information and messages explaining why no functions
18716 @item info functions [-q] [-n] [-t @var{type_regexp}] [@var{regexp}]
18717 Like @samp{info functions}, but only print the names and data types
18718 of the functions selected with the provided regexp(s).
18720 If @var{regexp} is provided, print only the functions whose names
18721 match the regular expression @var{regexp}.
18722 Thus, @samp{info fun step} finds all functions whose
18723 names include @code{step}; @samp{info fun ^step} finds those whose names
18724 start with @code{step}. If a function name contains characters that
18725 conflict with the regular expression language (e.g.@:
18726 @samp{operator*()}), they may be quoted with a backslash.
18728 If @var{type_regexp} is provided, print only the functions whose
18729 types, as printed by the @code{whatis} command, match
18730 the regular expression @var{type_regexp}.
18731 If @var{type_regexp} contains space(s), it should be enclosed in
18732 quote characters. If needed, use backslash to escape the meaning
18733 of special characters or quotes.
18734 Thus, @samp{info fun -t '^int ('} finds the functions that return
18735 an integer; @samp{info fun -t '(.*int.*'} finds the functions that
18736 have an argument type containing int; @samp{info fun -t '^int (' ^step}
18737 finds the functions whose names start with @code{step} and that return
18740 If both @var{regexp} and @var{type_regexp} are provided, a function
18741 is printed only if its name matches @var{regexp} and its type matches
18745 @kindex info variables
18746 @item info variables [-q] [-n]
18747 Print the names and data types of all variables that are defined
18748 outside of functions (i.e.@: excluding local variables).
18749 The printed variables are grouped by source files and annotated with
18750 their respective source line numbers.
18752 In programs using different languages, @value{GDBN} chooses the syntax
18753 to print the variable name and type according to the
18754 @samp{set language} value: using @samp{set language auto}
18755 (see @ref{Automatically, ,Set Language Automatically}) means to use the
18756 language of the variable, other values mean to use
18757 the manually specified language (see @ref{Manually, ,Set Language Manually}).
18759 The @samp{-n} flag excludes non-debugging symbols from the results.
18761 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
18762 printing header information and messages explaining why no variables
18765 @item info variables [-q] [-n] [-t @var{type_regexp}] [@var{regexp}]
18766 Like @kbd{info variables}, but only print the variables selected
18767 with the provided regexp(s).
18769 If @var{regexp} is provided, print only the variables whose names
18770 match the regular expression @var{regexp}.
18772 If @var{type_regexp} is provided, print only the variables whose
18773 types, as printed by the @code{whatis} command, match
18774 the regular expression @var{type_regexp}.
18775 If @var{type_regexp} contains space(s), it should be enclosed in
18776 quote characters. If needed, use backslash to escape the meaning
18777 of special characters or quotes.
18779 If both @var{regexp} and @var{type_regexp} are provided, an argument
18780 is printed only if its name matches @var{regexp} and its type matches
18783 @kindex info classes
18784 @cindex Objective-C, classes and selectors
18786 @itemx info classes @var{regexp}
18787 Display all Objective-C classes in your program, or
18788 (with the @var{regexp} argument) all those matching a particular regular
18791 @kindex info selectors
18792 @item info selectors
18793 @itemx info selectors @var{regexp}
18794 Display all Objective-C selectors in your program, or
18795 (with the @var{regexp} argument) all those matching a particular regular
18799 This was never implemented.
18800 @kindex info methods
18802 @itemx info methods @var{regexp}
18803 The @code{info methods} command permits the user to examine all defined
18804 methods within C@t{++} program, or (with the @var{regexp} argument) a
18805 specific set of methods found in the various C@t{++} classes. Many
18806 C@t{++} classes provide a large number of methods. Thus, the output
18807 from the @code{ptype} command can be overwhelming and hard to use. The
18808 @code{info-methods} command filters the methods, printing only those
18809 which match the regular-expression @var{regexp}.
18812 @cindex opaque data types
18813 @kindex set opaque-type-resolution
18814 @item set opaque-type-resolution on
18815 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
18816 declared as a pointer to a @code{struct}, @code{class}, or
18817 @code{union}---for example, @code{struct MyType *}---that is used in one
18818 source file although the full declaration of @code{struct MyType} is in
18819 another source file. The default is on.
18821 A change in the setting of this subcommand will not take effect until
18822 the next time symbols for a file are loaded.
18824 @item set opaque-type-resolution off
18825 Tell @value{GDBN} not to resolve opaque types. In this case, the type
18826 is printed as follows:
18828 @{<no data fields>@}
18831 @kindex show opaque-type-resolution
18832 @item show opaque-type-resolution
18833 Show whether opaque types are resolved or not.
18835 @kindex set print symbol-loading
18836 @cindex print messages when symbols are loaded
18837 @item set print symbol-loading
18838 @itemx set print symbol-loading full
18839 @itemx set print symbol-loading brief
18840 @itemx set print symbol-loading off
18841 The @code{set print symbol-loading} command allows you to control the
18842 printing of messages when @value{GDBN} loads symbol information.
18843 By default a message is printed for the executable and one for each
18844 shared library, and normally this is what you want. However, when
18845 debugging apps with large numbers of shared libraries these messages
18847 When set to @code{brief} a message is printed for each executable,
18848 and when @value{GDBN} loads a collection of shared libraries at once
18849 it will only print one message regardless of the number of shared
18850 libraries. When set to @code{off} no messages are printed.
18852 @kindex show print symbol-loading
18853 @item show print symbol-loading
18854 Show whether messages will be printed when a @value{GDBN} command
18855 entered from the keyboard causes symbol information to be loaded.
18857 @kindex maint print symbols
18858 @cindex symbol dump
18859 @kindex maint print psymbols
18860 @cindex partial symbol dump
18861 @kindex maint print msymbols
18862 @cindex minimal symbol dump
18863 @item maint print symbols @r{[}-pc @var{address}@r{]} @r{[}@var{filename}@r{]}
18864 @itemx maint print symbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
18865 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-pc @var{address}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
18866 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
18867 @itemx maint print msymbols @r{[}-objfile @var{objfile}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
18868 Write a dump of debugging symbol data into the file @var{filename} or
18869 the terminal if @var{filename} is unspecified.
18870 If @code{-objfile @var{objfile}} is specified, only dump symbols for
18872 If @code{-pc @var{address}} is specified, only dump symbols for the file
18873 with code at that address. Note that @var{address} may be a symbol like
18875 If @code{-source @var{source}} is specified, only dump symbols for that
18878 These commands are used to debug the @value{GDBN} symbol-reading code.
18879 These commands do not modify internal @value{GDBN} state, therefore
18880 @samp{maint print symbols} will only print symbols for already expanded symbol
18882 You can use the command @code{info sources} to find out which files these are.
18883 If you use @samp{maint print psymbols} instead, the dump shows information
18884 about symbols that @value{GDBN} only knows partially---that is, symbols
18885 defined in files that @value{GDBN} has skimmed, but not yet read completely.
18886 Finally, @samp{maint print msymbols} just dumps ``minimal symbols'', e.g.,
18889 @xref{Files, ,Commands to Specify Files}, for a discussion of how
18890 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
18892 @kindex maint info symtabs
18893 @kindex maint info psymtabs
18894 @cindex listing @value{GDBN}'s internal symbol tables
18895 @cindex symbol tables, listing @value{GDBN}'s internal
18896 @cindex full symbol tables, listing @value{GDBN}'s internal
18897 @cindex partial symbol tables, listing @value{GDBN}'s internal
18898 @item maint info symtabs @r{[} @var{regexp} @r{]}
18899 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
18901 List the @code{struct symtab} or @code{struct partial_symtab}
18902 structures whose names match @var{regexp}. If @var{regexp} is not
18903 given, list them all. The output includes expressions which you can
18904 copy into a @value{GDBN} debugging this one to examine a particular
18905 structure in more detail. For example:
18908 (@value{GDBP}) maint info psymtabs dwarf2read
18909 @{ objfile /home/gnu/build/gdb/gdb
18910 ((struct objfile *) 0x82e69d0)
18911 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
18912 ((struct partial_symtab *) 0x8474b10)
18915 text addresses 0x814d3c8 -- 0x8158074
18916 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
18917 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
18918 dependencies (none)
18921 (@value{GDBP}) maint info symtabs
18925 We see that there is one partial symbol table whose filename contains
18926 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
18927 and we see that @value{GDBN} has not read in any symtabs yet at all.
18928 If we set a breakpoint on a function, that will cause @value{GDBN} to
18929 read the symtab for the compilation unit containing that function:
18932 (@value{GDBP}) break dwarf2_psymtab_to_symtab
18933 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
18935 (@value{GDBP}) maint info symtabs
18936 @{ objfile /home/gnu/build/gdb/gdb
18937 ((struct objfile *) 0x82e69d0)
18938 @{ symtab /home/gnu/src/gdb/dwarf2read.c
18939 ((struct symtab *) 0x86c1f38)
18942 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
18943 linetable ((struct linetable *) 0x8370fa0)
18944 debugformat DWARF 2
18950 @kindex maint info line-table
18951 @cindex listing @value{GDBN}'s internal line tables
18952 @cindex line tables, listing @value{GDBN}'s internal
18953 @item maint info line-table @r{[} @var{regexp} @r{]}
18955 List the @code{struct linetable} from all @code{struct symtab}
18956 instances whose name matches @var{regexp}. If @var{regexp} is not
18957 given, list the @code{struct linetable} from all @code{struct symtab}.
18959 @kindex maint set symbol-cache-size
18960 @cindex symbol cache size
18961 @item maint set symbol-cache-size @var{size}
18962 Set the size of the symbol cache to @var{size}.
18963 The default size is intended to be good enough for debugging
18964 most applications. This option exists to allow for experimenting
18965 with different sizes.
18967 @kindex maint show symbol-cache-size
18968 @item maint show symbol-cache-size
18969 Show the size of the symbol cache.
18971 @kindex maint print symbol-cache
18972 @cindex symbol cache, printing its contents
18973 @item maint print symbol-cache
18974 Print the contents of the symbol cache.
18975 This is useful when debugging symbol cache issues.
18977 @kindex maint print symbol-cache-statistics
18978 @cindex symbol cache, printing usage statistics
18979 @item maint print symbol-cache-statistics
18980 Print symbol cache usage statistics.
18981 This helps determine how well the cache is being utilized.
18983 @kindex maint flush-symbol-cache
18984 @cindex symbol cache, flushing
18985 @item maint flush-symbol-cache
18986 Flush the contents of the symbol cache, all entries are removed.
18987 This command is useful when debugging the symbol cache.
18988 It is also useful when collecting performance data.
18993 @chapter Altering Execution
18995 Once you think you have found an error in your program, you might want to
18996 find out for certain whether correcting the apparent error would lead to
18997 correct results in the rest of the run. You can find the answer by
18998 experiment, using the @value{GDBN} features for altering execution of the
19001 For example, you can store new values into variables or memory
19002 locations, give your program a signal, restart it at a different
19003 address, or even return prematurely from a function.
19006 * Assignment:: Assignment to variables
19007 * Jumping:: Continuing at a different address
19008 * Signaling:: Giving your program a signal
19009 * Returning:: Returning from a function
19010 * Calling:: Calling your program's functions
19011 * Patching:: Patching your program
19012 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
19016 @section Assignment to Variables
19019 @cindex setting variables
19020 To alter the value of a variable, evaluate an assignment expression.
19021 @xref{Expressions, ,Expressions}. For example,
19028 stores the value 4 into the variable @code{x}, and then prints the
19029 value of the assignment expression (which is 4).
19030 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
19031 information on operators in supported languages.
19033 @kindex set variable
19034 @cindex variables, setting
19035 If you are not interested in seeing the value of the assignment, use the
19036 @code{set} command instead of the @code{print} command. @code{set} is
19037 really the same as @code{print} except that the expression's value is
19038 not printed and is not put in the value history (@pxref{Value History,
19039 ,Value History}). The expression is evaluated only for its effects.
19041 If the beginning of the argument string of the @code{set} command
19042 appears identical to a @code{set} subcommand, use the @code{set
19043 variable} command instead of just @code{set}. This command is identical
19044 to @code{set} except for its lack of subcommands. For example, if your
19045 program has a variable @code{width}, you get an error if you try to set
19046 a new value with just @samp{set width=13}, because @value{GDBN} has the
19047 command @code{set width}:
19050 (@value{GDBP}) whatis width
19052 (@value{GDBP}) p width
19054 (@value{GDBP}) set width=47
19055 Invalid syntax in expression.
19059 The invalid expression, of course, is @samp{=47}. In
19060 order to actually set the program's variable @code{width}, use
19063 (@value{GDBP}) set var width=47
19066 Because the @code{set} command has many subcommands that can conflict
19067 with the names of program variables, it is a good idea to use the
19068 @code{set variable} command instead of just @code{set}. For example, if
19069 your program has a variable @code{g}, you run into problems if you try
19070 to set a new value with just @samp{set g=4}, because @value{GDBN} has
19071 the command @code{set gnutarget}, abbreviated @code{set g}:
19075 (@value{GDBP}) whatis g
19079 (@value{GDBP}) set g=4
19083 The program being debugged has been started already.
19084 Start it from the beginning? (y or n) y
19085 Starting program: /home/smith/cc_progs/a.out
19086 "/home/smith/cc_progs/a.out": can't open to read symbols:
19087 Invalid bfd target.
19088 (@value{GDBP}) show g
19089 The current BFD target is "=4".
19094 The program variable @code{g} did not change, and you silently set the
19095 @code{gnutarget} to an invalid value. In order to set the variable
19099 (@value{GDBP}) set var g=4
19102 @value{GDBN} allows more implicit conversions in assignments than C; you can
19103 freely store an integer value into a pointer variable or vice versa,
19104 and you can convert any structure to any other structure that is the
19105 same length or shorter.
19106 @comment FIXME: how do structs align/pad in these conversions?
19107 @comment /doc@cygnus.com 18dec1990
19109 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
19110 construct to generate a value of specified type at a specified address
19111 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
19112 to memory location @code{0x83040} as an integer (which implies a certain size
19113 and representation in memory), and
19116 set @{int@}0x83040 = 4
19120 stores the value 4 into that memory location.
19123 @section Continuing at a Different Address
19125 Ordinarily, when you continue your program, you do so at the place where
19126 it stopped, with the @code{continue} command. You can instead continue at
19127 an address of your own choosing, with the following commands:
19131 @kindex j @r{(@code{jump})}
19132 @item jump @var{location}
19133 @itemx j @var{location}
19134 Resume execution at @var{location}. Execution stops again immediately
19135 if there is a breakpoint there. @xref{Specify Location}, for a description
19136 of the different forms of @var{location}. It is common
19137 practice to use the @code{tbreak} command in conjunction with
19138 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
19140 The @code{jump} command does not change the current stack frame, or
19141 the stack pointer, or the contents of any memory location or any
19142 register other than the program counter. If @var{location} is in
19143 a different function from the one currently executing, the results may
19144 be bizarre if the two functions expect different patterns of arguments or
19145 of local variables. For this reason, the @code{jump} command requests
19146 confirmation if the specified line is not in the function currently
19147 executing. However, even bizarre results are predictable if you are
19148 well acquainted with the machine-language code of your program.
19151 On many systems, you can get much the same effect as the @code{jump}
19152 command by storing a new value into the register @code{$pc}. The
19153 difference is that this does not start your program running; it only
19154 changes the address of where it @emph{will} run when you continue. For
19162 makes the next @code{continue} command or stepping command execute at
19163 address @code{0x485}, rather than at the address where your program stopped.
19164 @xref{Continuing and Stepping, ,Continuing and Stepping}.
19166 The most common occasion to use the @code{jump} command is to back
19167 up---perhaps with more breakpoints set---over a portion of a program
19168 that has already executed, in order to examine its execution in more
19173 @section Giving your Program a Signal
19174 @cindex deliver a signal to a program
19178 @item signal @var{signal}
19179 Resume execution where your program is stopped, but immediately give it the
19180 signal @var{signal}. The @var{signal} can be the name or the number of a
19181 signal. For example, on many systems @code{signal 2} and @code{signal
19182 SIGINT} are both ways of sending an interrupt signal.
19184 Alternatively, if @var{signal} is zero, continue execution without
19185 giving a signal. This is useful when your program stopped on account of
19186 a signal and would ordinarily see the signal when resumed with the
19187 @code{continue} command; @samp{signal 0} causes it to resume without a
19190 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
19191 delivered to the currently selected thread, not the thread that last
19192 reported a stop. This includes the situation where a thread was
19193 stopped due to a signal. So if you want to continue execution
19194 suppressing the signal that stopped a thread, you should select that
19195 same thread before issuing the @samp{signal 0} command. If you issue
19196 the @samp{signal 0} command with another thread as the selected one,
19197 @value{GDBN} detects that and asks for confirmation.
19199 Invoking the @code{signal} command is not the same as invoking the
19200 @code{kill} utility from the shell. Sending a signal with @code{kill}
19201 causes @value{GDBN} to decide what to do with the signal depending on
19202 the signal handling tables (@pxref{Signals}). The @code{signal} command
19203 passes the signal directly to your program.
19205 @code{signal} does not repeat when you press @key{RET} a second time
19206 after executing the command.
19208 @kindex queue-signal
19209 @item queue-signal @var{signal}
19210 Queue @var{signal} to be delivered immediately to the current thread
19211 when execution of the thread resumes. The @var{signal} can be the name or
19212 the number of a signal. For example, on many systems @code{signal 2} and
19213 @code{signal SIGINT} are both ways of sending an interrupt signal.
19214 The handling of the signal must be set to pass the signal to the program,
19215 otherwise @value{GDBN} will report an error.
19216 You can control the handling of signals from @value{GDBN} with the
19217 @code{handle} command (@pxref{Signals}).
19219 Alternatively, if @var{signal} is zero, any currently queued signal
19220 for the current thread is discarded and when execution resumes no signal
19221 will be delivered. This is useful when your program stopped on account
19222 of a signal and would ordinarily see the signal when resumed with the
19223 @code{continue} command.
19225 This command differs from the @code{signal} command in that the signal
19226 is just queued, execution is not resumed. And @code{queue-signal} cannot
19227 be used to pass a signal whose handling state has been set to @code{nopass}
19232 @xref{stepping into signal handlers}, for information on how stepping
19233 commands behave when the thread has a signal queued.
19236 @section Returning from a Function
19239 @cindex returning from a function
19242 @itemx return @var{expression}
19243 You can cancel execution of a function call with the @code{return}
19244 command. If you give an
19245 @var{expression} argument, its value is used as the function's return
19249 When you use @code{return}, @value{GDBN} discards the selected stack frame
19250 (and all frames within it). You can think of this as making the
19251 discarded frame return prematurely. If you wish to specify a value to
19252 be returned, give that value as the argument to @code{return}.
19254 This pops the selected stack frame (@pxref{Selection, ,Selecting a
19255 Frame}), and any other frames inside of it, leaving its caller as the
19256 innermost remaining frame. That frame becomes selected. The
19257 specified value is stored in the registers used for returning values
19260 The @code{return} command does not resume execution; it leaves the
19261 program stopped in the state that would exist if the function had just
19262 returned. In contrast, the @code{finish} command (@pxref{Continuing
19263 and Stepping, ,Continuing and Stepping}) resumes execution until the
19264 selected stack frame returns naturally.
19266 @value{GDBN} needs to know how the @var{expression} argument should be set for
19267 the inferior. The concrete registers assignment depends on the OS ABI and the
19268 type being returned by the selected stack frame. For example it is common for
19269 OS ABI to return floating point values in FPU registers while integer values in
19270 CPU registers. Still some ABIs return even floating point values in CPU
19271 registers. Larger integer widths (such as @code{long long int}) also have
19272 specific placement rules. @value{GDBN} already knows the OS ABI from its
19273 current target so it needs to find out also the type being returned to make the
19274 assignment into the right register(s).
19276 Normally, the selected stack frame has debug info. @value{GDBN} will always
19277 use the debug info instead of the implicit type of @var{expression} when the
19278 debug info is available. For example, if you type @kbd{return -1}, and the
19279 function in the current stack frame is declared to return a @code{long long
19280 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
19281 into a @code{long long int}:
19284 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
19286 (@value{GDBP}) return -1
19287 Make func return now? (y or n) y
19288 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
19289 43 printf ("result=%lld\n", func ());
19293 However, if the selected stack frame does not have a debug info, e.g., if the
19294 function was compiled without debug info, @value{GDBN} has to find out the type
19295 to return from user. Specifying a different type by mistake may set the value
19296 in different inferior registers than the caller code expects. For example,
19297 typing @kbd{return -1} with its implicit type @code{int} would set only a part
19298 of a @code{long long int} result for a debug info less function (on 32-bit
19299 architectures). Therefore the user is required to specify the return type by
19300 an appropriate cast explicitly:
19303 Breakpoint 2, 0x0040050b in func ()
19304 (@value{GDBP}) return -1
19305 Return value type not available for selected stack frame.
19306 Please use an explicit cast of the value to return.
19307 (@value{GDBP}) return (long long int) -1
19308 Make selected stack frame return now? (y or n) y
19309 #0 0x00400526 in main ()
19314 @section Calling Program Functions
19317 @cindex calling functions
19318 @cindex inferior functions, calling
19319 @item print @var{expr}
19320 Evaluate the expression @var{expr} and display the resulting value.
19321 The expression may include calls to functions in the program being
19325 @item call @var{expr}
19326 Evaluate the expression @var{expr} without displaying @code{void}
19329 You can use this variant of the @code{print} command if you want to
19330 execute a function from your program that does not return anything
19331 (a.k.a.@: @dfn{a void function}), but without cluttering the output
19332 with @code{void} returned values that @value{GDBN} will otherwise
19333 print. If the result is not void, it is printed and saved in the
19337 It is possible for the function you call via the @code{print} or
19338 @code{call} command to generate a signal (e.g., if there's a bug in
19339 the function, or if you passed it incorrect arguments). What happens
19340 in that case is controlled by the @code{set unwindonsignal} command.
19342 Similarly, with a C@t{++} program it is possible for the function you
19343 call via the @code{print} or @code{call} command to generate an
19344 exception that is not handled due to the constraints of the dummy
19345 frame. In this case, any exception that is raised in the frame, but has
19346 an out-of-frame exception handler will not be found. GDB builds a
19347 dummy-frame for the inferior function call, and the unwinder cannot
19348 seek for exception handlers outside of this dummy-frame. What happens
19349 in that case is controlled by the
19350 @code{set unwind-on-terminating-exception} command.
19353 @item set unwindonsignal
19354 @kindex set unwindonsignal
19355 @cindex unwind stack in called functions
19356 @cindex call dummy stack unwinding
19357 Set unwinding of the stack if a signal is received while in a function
19358 that @value{GDBN} called in the program being debugged. If set to on,
19359 @value{GDBN} unwinds the stack it created for the call and restores
19360 the context to what it was before the call. If set to off (the
19361 default), @value{GDBN} stops in the frame where the signal was
19364 @item show unwindonsignal
19365 @kindex show unwindonsignal
19366 Show the current setting of stack unwinding in the functions called by
19369 @item set unwind-on-terminating-exception
19370 @kindex set unwind-on-terminating-exception
19371 @cindex unwind stack in called functions with unhandled exceptions
19372 @cindex call dummy stack unwinding on unhandled exception.
19373 Set unwinding of the stack if a C@t{++} exception is raised, but left
19374 unhandled while in a function that @value{GDBN} called in the program being
19375 debugged. If set to on (the default), @value{GDBN} unwinds the stack
19376 it created for the call and restores the context to what it was before
19377 the call. If set to off, @value{GDBN} the exception is delivered to
19378 the default C@t{++} exception handler and the inferior terminated.
19380 @item show unwind-on-terminating-exception
19381 @kindex show unwind-on-terminating-exception
19382 Show the current setting of stack unwinding in the functions called by
19385 @item set may-call-functions
19386 @kindex set may-call-functions
19387 @cindex disabling calling functions in the program
19388 @cindex calling functions in the program, disabling
19389 Set permission to call functions in the program.
19390 This controls whether @value{GDBN} will attempt to call functions in
19391 the program, such as with expressions in the @code{print} command. It
19392 defaults to @code{on}.
19394 To call a function in the program, @value{GDBN} has to temporarily
19395 modify the state of the inferior. This has potentially undesired side
19396 effects. Also, having @value{GDBN} call nested functions is likely to
19397 be erroneous and may even crash the program being debugged. You can
19398 avoid such hazards by forbidding @value{GDBN} from calling functions
19399 in the program being debugged. If calling functions in the program
19400 is forbidden, GDB will throw an error when a command (such as printing
19401 an expression) starts a function call in the program.
19403 @item show may-call-functions
19404 @kindex show may-call-functions
19405 Show permission to call functions in the program.
19409 @subsection Calling functions with no debug info
19411 @cindex no debug info functions
19412 Sometimes, a function you wish to call is missing debug information.
19413 In such case, @value{GDBN} does not know the type of the function,
19414 including the types of the function's parameters. To avoid calling
19415 the inferior function incorrectly, which could result in the called
19416 function functioning erroneously and even crash, @value{GDBN} refuses
19417 to call the function unless you tell it the type of the function.
19419 For prototyped (i.e.@: ANSI/ISO style) functions, there are two ways
19420 to do that. The simplest is to cast the call to the function's
19421 declared return type. For example:
19424 (@value{GDBP}) p getenv ("PATH")
19425 'getenv' has unknown return type; cast the call to its declared return type
19426 (@value{GDBP}) p (char *) getenv ("PATH")
19427 $1 = 0x7fffffffe7ba "/usr/local/bin:/"...
19430 Casting the return type of a no-debug function is equivalent to
19431 casting the function to a pointer to a prototyped function that has a
19432 prototype that matches the types of the passed-in arguments, and
19433 calling that. I.e., the call above is equivalent to:
19436 (@value{GDBP}) p ((char * (*) (const char *)) getenv) ("PATH")
19440 and given this prototyped C or C++ function with float parameters:
19443 float multiply (float v1, float v2) @{ return v1 * v2; @}
19447 these calls are equivalent:
19450 (@value{GDBP}) p (float) multiply (2.0f, 3.0f)
19451 (@value{GDBP}) p ((float (*) (float, float)) multiply) (2.0f, 3.0f)
19454 If the function you wish to call is declared as unprototyped (i.e.@:
19455 old K&R style), you must use the cast-to-function-pointer syntax, so
19456 that @value{GDBN} knows that it needs to apply default argument
19457 promotions (promote float arguments to double). @xref{ABI, float
19458 promotion}. For example, given this unprototyped C function with
19459 float parameters, and no debug info:
19463 multiply_noproto (v1, v2)
19471 you call it like this:
19474 (@value{GDBP}) p ((float (*) ()) multiply_noproto) (2.0f, 3.0f)
19478 @section Patching Programs
19480 @cindex patching binaries
19481 @cindex writing into executables
19482 @cindex writing into corefiles
19484 By default, @value{GDBN} opens the file containing your program's
19485 executable code (or the corefile) read-only. This prevents accidental
19486 alterations to machine code; but it also prevents you from intentionally
19487 patching your program's binary.
19489 If you'd like to be able to patch the binary, you can specify that
19490 explicitly with the @code{set write} command. For example, you might
19491 want to turn on internal debugging flags, or even to make emergency
19497 @itemx set write off
19498 If you specify @samp{set write on}, @value{GDBN} opens executable and
19499 core files for both reading and writing; if you specify @kbd{set write
19500 off} (the default), @value{GDBN} opens them read-only.
19502 If you have already loaded a file, you must load it again (using the
19503 @code{exec-file} or @code{core-file} command) after changing @code{set
19504 write}, for your new setting to take effect.
19508 Display whether executable files and core files are opened for writing
19509 as well as reading.
19512 @node Compiling and Injecting Code
19513 @section Compiling and injecting code in @value{GDBN}
19514 @cindex injecting code
19515 @cindex writing into executables
19516 @cindex compiling code
19518 @value{GDBN} supports on-demand compilation and code injection into
19519 programs running under @value{GDBN}. GCC 5.0 or higher built with
19520 @file{libcc1.so} must be installed for this functionality to be enabled.
19521 This functionality is implemented with the following commands.
19524 @kindex compile code
19525 @item compile code @var{source-code}
19526 @itemx compile code -raw @var{--} @var{source-code}
19527 Compile @var{source-code} with the compiler language found as the current
19528 language in @value{GDBN} (@pxref{Languages}). If compilation and
19529 injection is not supported with the current language specified in
19530 @value{GDBN}, or the compiler does not support this feature, an error
19531 message will be printed. If @var{source-code} compiles and links
19532 successfully, @value{GDBN} will load the object-code emitted,
19533 and execute it within the context of the currently selected inferior.
19534 It is important to note that the compiled code is executed immediately.
19535 After execution, the compiled code is removed from @value{GDBN} and any
19536 new types or variables you have defined will be deleted.
19538 The command allows you to specify @var{source-code} in two ways.
19539 The simplest method is to provide a single line of code to the command.
19543 compile code printf ("hello world\n");
19546 If you specify options on the command line as well as source code, they
19547 may conflict. The @samp{--} delimiter can be used to separate options
19548 from actual source code. E.g.:
19551 compile code -r -- printf ("hello world\n");
19554 Alternatively you can enter source code as multiple lines of text. To
19555 enter this mode, invoke the @samp{compile code} command without any text
19556 following the command. This will start the multiple-line editor and
19557 allow you to type as many lines of source code as required. When you
19558 have completed typing, enter @samp{end} on its own line to exit the
19563 >printf ("hello\n");
19564 >printf ("world\n");
19568 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
19569 provided @var{source-code} in a callable scope. In this case, you must
19570 specify the entry point of the code by defining a function named
19571 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
19572 inferior. Using @samp{-raw} option may be needed for example when
19573 @var{source-code} requires @samp{#include} lines which may conflict with
19574 inferior symbols otherwise.
19576 @kindex compile file
19577 @item compile file @var{filename}
19578 @itemx compile file -raw @var{filename}
19579 Like @code{compile code}, but take the source code from @var{filename}.
19582 compile file /home/user/example.c
19587 @item compile print [[@var{options}] --] @var{expr}
19588 @itemx compile print [[@var{options}] --] /@var{f} @var{expr}
19589 Compile and execute @var{expr} with the compiler language found as the
19590 current language in @value{GDBN} (@pxref{Languages}). By default the
19591 value of @var{expr} is printed in a format appropriate to its data type;
19592 you can choose a different format by specifying @samp{/@var{f}}, where
19593 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
19594 Formats}. The @code{compile print} command accepts the same options
19595 as the @code{print} command; see @ref{print options}.
19597 @item compile print [[@var{options}] --]
19598 @itemx compile print [[@var{options}] --] /@var{f}
19599 @cindex reprint the last value
19600 Alternatively you can enter the expression (source code producing it) as
19601 multiple lines of text. To enter this mode, invoke the @samp{compile print}
19602 command without any text following the command. This will start the
19603 multiple-line editor.
19607 The process of compiling and injecting the code can be inspected using:
19610 @anchor{set debug compile}
19611 @item set debug compile
19612 @cindex compile command debugging info
19613 Turns on or off display of @value{GDBN} process of compiling and
19614 injecting the code. The default is off.
19616 @item show debug compile
19617 Displays the current state of displaying @value{GDBN} process of
19618 compiling and injecting the code.
19620 @anchor{set debug compile-cplus-types}
19621 @item set debug compile-cplus-types
19622 @cindex compile C@t{++} type conversion
19623 Turns on or off the display of C@t{++} type conversion debugging information.
19624 The default is off.
19626 @item show debug compile-cplus-types
19627 Displays the current state of displaying debugging information for
19628 C@t{++} type conversion.
19631 @subsection Compilation options for the @code{compile} command
19633 @value{GDBN} needs to specify the right compilation options for the code
19634 to be injected, in part to make its ABI compatible with the inferior
19635 and in part to make the injected code compatible with @value{GDBN}'s
19639 The options used, in increasing precedence:
19642 @item target architecture and OS options (@code{gdbarch})
19643 These options depend on target processor type and target operating
19644 system, usually they specify at least 32-bit (@code{-m32}) or 64-bit
19645 (@code{-m64}) compilation option.
19647 @item compilation options recorded in the target
19648 @value{NGCC} (since version 4.7) stores the options used for compilation
19649 into @code{DW_AT_producer} part of DWARF debugging information according
19650 to the @value{NGCC} option @code{-grecord-gcc-switches}. One has to
19651 explicitly specify @code{-g} during inferior compilation otherwise
19652 @value{NGCC} produces no DWARF. This feature is only relevant for
19653 platforms where @code{-g} produces DWARF by default, otherwise one may
19654 try to enforce DWARF by using @code{-gdwarf-4}.
19656 @item compilation options set by @code{set compile-args}
19660 You can override compilation options using the following command:
19663 @item set compile-args
19664 @cindex compile command options override
19665 Set compilation options used for compiling and injecting code with the
19666 @code{compile} commands. These options override any conflicting ones
19667 from the target architecture and/or options stored during inferior
19670 @item show compile-args
19671 Displays the current state of compilation options override.
19672 This does not show all the options actually used during compilation,
19673 use @ref{set debug compile} for that.
19676 @subsection Caveats when using the @code{compile} command
19678 There are a few caveats to keep in mind when using the @code{compile}
19679 command. As the caveats are different per language, the table below
19680 highlights specific issues on a per language basis.
19683 @item C code examples and caveats
19684 When the language in @value{GDBN} is set to @samp{C}, the compiler will
19685 attempt to compile the source code with a @samp{C} compiler. The source
19686 code provided to the @code{compile} command will have much the same
19687 access to variables and types as it normally would if it were part of
19688 the program currently being debugged in @value{GDBN}.
19690 Below is a sample program that forms the basis of the examples that
19691 follow. This program has been compiled and loaded into @value{GDBN},
19692 much like any other normal debugging session.
19695 void function1 (void)
19698 printf ("function 1\n");
19701 void function2 (void)
19716 For the purposes of the examples in this section, the program above has
19717 been compiled, loaded into @value{GDBN}, stopped at the function
19718 @code{main}, and @value{GDBN} is awaiting input from the user.
19720 To access variables and types for any program in @value{GDBN}, the
19721 program must be compiled and packaged with debug information. The
19722 @code{compile} command is not an exception to this rule. Without debug
19723 information, you can still use the @code{compile} command, but you will
19724 be very limited in what variables and types you can access.
19726 So with that in mind, the example above has been compiled with debug
19727 information enabled. The @code{compile} command will have access to
19728 all variables and types (except those that may have been optimized
19729 out). Currently, as @value{GDBN} has stopped the program in the
19730 @code{main} function, the @code{compile} command would have access to
19731 the variable @code{k}. You could invoke the @code{compile} command
19732 and type some source code to set the value of @code{k}. You can also
19733 read it, or do anything with that variable you would normally do in
19734 @code{C}. Be aware that changes to inferior variables in the
19735 @code{compile} command are persistent. In the following example:
19738 compile code k = 3;
19742 the variable @code{k} is now 3. It will retain that value until
19743 something else in the example program changes it, or another
19744 @code{compile} command changes it.
19746 Normal scope and access rules apply to source code compiled and
19747 injected by the @code{compile} command. In the example, the variables
19748 @code{j} and @code{k} are not accessible yet, because the program is
19749 currently stopped in the @code{main} function, where these variables
19750 are not in scope. Therefore, the following command
19753 compile code j = 3;
19757 will result in a compilation error message.
19759 Once the program is continued, execution will bring these variables in
19760 scope, and they will become accessible; then the code you specify via
19761 the @code{compile} command will be able to access them.
19763 You can create variables and types with the @code{compile} command as
19764 part of your source code. Variables and types that are created as part
19765 of the @code{compile} command are not visible to the rest of the program for
19766 the duration of its run. This example is valid:
19769 compile code int ff = 5; printf ("ff is %d\n", ff);
19772 However, if you were to type the following into @value{GDBN} after that
19773 command has completed:
19776 compile code printf ("ff is %d\n'', ff);
19780 a compiler error would be raised as the variable @code{ff} no longer
19781 exists. Object code generated and injected by the @code{compile}
19782 command is removed when its execution ends. Caution is advised
19783 when assigning to program variables values of variables created by the
19784 code submitted to the @code{compile} command. This example is valid:
19787 compile code int ff = 5; k = ff;
19790 The value of the variable @code{ff} is assigned to @code{k}. The variable
19791 @code{k} does not require the existence of @code{ff} to maintain the value
19792 it has been assigned. However, pointers require particular care in
19793 assignment. If the source code compiled with the @code{compile} command
19794 changed the address of a pointer in the example program, perhaps to a
19795 variable created in the @code{compile} command, that pointer would point
19796 to an invalid location when the command exits. The following example
19797 would likely cause issues with your debugged program:
19800 compile code int ff = 5; p = &ff;
19803 In this example, @code{p} would point to @code{ff} when the
19804 @code{compile} command is executing the source code provided to it.
19805 However, as variables in the (example) program persist with their
19806 assigned values, the variable @code{p} would point to an invalid
19807 location when the command exists. A general rule should be followed
19808 in that you should either assign @code{NULL} to any assigned pointers,
19809 or restore a valid location to the pointer before the command exits.
19811 Similar caution must be exercised with any structs, unions, and typedefs
19812 defined in @code{compile} command. Types defined in the @code{compile}
19813 command will no longer be available in the next @code{compile} command.
19814 Therefore, if you cast a variable to a type defined in the
19815 @code{compile} command, care must be taken to ensure that any future
19816 need to resolve the type can be achieved.
19819 (gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
19820 (gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
19821 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
19822 Compilation failed.
19823 (gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
19827 Variables that have been optimized away by the compiler are not
19828 accessible to the code submitted to the @code{compile} command.
19829 Access to those variables will generate a compiler error which @value{GDBN}
19830 will print to the console.
19833 @subsection Compiler search for the @code{compile} command
19835 @value{GDBN} needs to find @value{NGCC} for the inferior being debugged
19836 which may not be obvious for remote targets of different architecture
19837 than where @value{GDBN} is running. Environment variable @code{PATH} on
19838 @value{GDBN} host is searched for @value{NGCC} binary matching the
19839 target architecture and operating system. This search can be overriden
19840 by @code{set compile-gcc} @value{GDBN} command below. @code{PATH} is
19841 taken from shell that executed @value{GDBN}, it is not the value set by
19842 @value{GDBN} command @code{set environment}). @xref{Environment}.
19845 Specifically @code{PATH} is searched for binaries matching regular expression
19846 @code{@var{arch}(-[^-]*)?-@var{os}-gcc} according to the inferior target being
19847 debugged. @var{arch} is processor name --- multiarch is supported, so for
19848 example both @code{i386} and @code{x86_64} targets look for pattern
19849 @code{(x86_64|i.86)} and both @code{s390} and @code{s390x} targets look
19850 for pattern @code{s390x?}. @var{os} is currently supported only for
19851 pattern @code{linux(-gnu)?}.
19853 On Posix hosts the compiler driver @value{GDBN} needs to find also
19854 shared library @file{libcc1.so} from the compiler. It is searched in
19855 default shared library search path (overridable with usual environment
19856 variable @code{LD_LIBRARY_PATH}), unrelated to @code{PATH} or @code{set
19857 compile-gcc} settings. Contrary to it @file{libcc1plugin.so} is found
19858 according to the installation of the found compiler --- as possibly
19859 specified by the @code{set compile-gcc} command.
19862 @item set compile-gcc
19863 @cindex compile command driver filename override
19864 Set compilation command used for compiling and injecting code with the
19865 @code{compile} commands. If this option is not set (it is set to
19866 an empty string), the search described above will occur --- that is the
19869 @item show compile-gcc
19870 Displays the current compile command @value{NGCC} driver filename.
19871 If set, it is the main command @command{gcc}, found usually for example
19872 under name @file{x86_64-linux-gnu-gcc}.
19876 @chapter @value{GDBN} Files
19878 @value{GDBN} needs to know the file name of the program to be debugged,
19879 both in order to read its symbol table and in order to start your
19880 program. To debug a core dump of a previous run, you must also tell
19881 @value{GDBN} the name of the core dump file.
19884 * Files:: Commands to specify files
19885 * File Caching:: Information about @value{GDBN}'s file caching
19886 * Separate Debug Files:: Debugging information in separate files
19887 * MiniDebugInfo:: Debugging information in a special section
19888 * Index Files:: Index files speed up GDB
19889 * Symbol Errors:: Errors reading symbol files
19890 * Data Files:: GDB data files
19894 @section Commands to Specify Files
19896 @cindex symbol table
19897 @cindex core dump file
19899 You may want to specify executable and core dump file names. The usual
19900 way to do this is at start-up time, using the arguments to
19901 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
19902 Out of @value{GDBN}}).
19904 Occasionally it is necessary to change to a different file during a
19905 @value{GDBN} session. Or you may run @value{GDBN} and forget to
19906 specify a file you want to use. Or you are debugging a remote target
19907 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
19908 Program}). In these situations the @value{GDBN} commands to specify
19909 new files are useful.
19912 @cindex executable file
19914 @item file @var{filename}
19915 Use @var{filename} as the program to be debugged. It is read for its
19916 symbols and for the contents of pure memory. It is also the program
19917 executed when you use the @code{run} command. If you do not specify a
19918 directory and the file is not found in the @value{GDBN} working directory,
19919 @value{GDBN} uses the environment variable @code{PATH} as a list of
19920 directories to search, just as the shell does when looking for a program
19921 to run. You can change the value of this variable, for both @value{GDBN}
19922 and your program, using the @code{path} command.
19924 @cindex unlinked object files
19925 @cindex patching object files
19926 You can load unlinked object @file{.o} files into @value{GDBN} using
19927 the @code{file} command. You will not be able to ``run'' an object
19928 file, but you can disassemble functions and inspect variables. Also,
19929 if the underlying BFD functionality supports it, you could use
19930 @kbd{gdb -write} to patch object files using this technique. Note
19931 that @value{GDBN} can neither interpret nor modify relocations in this
19932 case, so branches and some initialized variables will appear to go to
19933 the wrong place. But this feature is still handy from time to time.
19936 @code{file} with no argument makes @value{GDBN} discard any information it
19937 has on both executable file and the symbol table.
19940 @item exec-file @r{[} @var{filename} @r{]}
19941 Specify that the program to be run (but not the symbol table) is found
19942 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
19943 if necessary to locate your program. Omitting @var{filename} means to
19944 discard information on the executable file.
19946 @kindex symbol-file
19947 @item symbol-file @r{[} @var{filename} @r{[} -o @var{offset} @r{]]}
19948 Read symbol table information from file @var{filename}. @code{PATH} is
19949 searched when necessary. Use the @code{file} command to get both symbol
19950 table and program to run from the same file.
19952 If an optional @var{offset} is specified, it is added to the start
19953 address of each section in the symbol file. This is useful if the
19954 program is relocated at runtime, such as the Linux kernel with kASLR
19957 @code{symbol-file} with no argument clears out @value{GDBN} information on your
19958 program's symbol table.
19960 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
19961 some breakpoints and auto-display expressions. This is because they may
19962 contain pointers to the internal data recording symbols and data types,
19963 which are part of the old symbol table data being discarded inside
19966 @code{symbol-file} does not repeat if you press @key{RET} again after
19969 When @value{GDBN} is configured for a particular environment, it
19970 understands debugging information in whatever format is the standard
19971 generated for that environment; you may use either a @sc{gnu} compiler, or
19972 other compilers that adhere to the local conventions.
19973 Best results are usually obtained from @sc{gnu} compilers; for example,
19974 using @code{@value{NGCC}} you can generate debugging information for
19977 For most kinds of object files, with the exception of old SVR3 systems
19978 using COFF, the @code{symbol-file} command does not normally read the
19979 symbol table in full right away. Instead, it scans the symbol table
19980 quickly to find which source files and which symbols are present. The
19981 details are read later, one source file at a time, as they are needed.
19983 The purpose of this two-stage reading strategy is to make @value{GDBN}
19984 start up faster. For the most part, it is invisible except for
19985 occasional pauses while the symbol table details for a particular source
19986 file are being read. (The @code{set verbose} command can turn these
19987 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
19988 Warnings and Messages}.)
19990 We have not implemented the two-stage strategy for COFF yet. When the
19991 symbol table is stored in COFF format, @code{symbol-file} reads the
19992 symbol table data in full right away. Note that ``stabs-in-COFF''
19993 still does the two-stage strategy, since the debug info is actually
19997 @cindex reading symbols immediately
19998 @cindex symbols, reading immediately
19999 @item symbol-file @r{[} -readnow @r{]} @var{filename}
20000 @itemx file @r{[} -readnow @r{]} @var{filename}
20001 You can override the @value{GDBN} two-stage strategy for reading symbol
20002 tables by using the @samp{-readnow} option with any of the commands that
20003 load symbol table information, if you want to be sure @value{GDBN} has the
20004 entire symbol table available.
20006 @cindex @code{-readnever}, option for symbol-file command
20007 @cindex never read symbols
20008 @cindex symbols, never read
20009 @item symbol-file @r{[} -readnever @r{]} @var{filename}
20010 @itemx file @r{[} -readnever @r{]} @var{filename}
20011 You can instruct @value{GDBN} to never read the symbolic information
20012 contained in @var{filename} by using the @samp{-readnever} option.
20013 @xref{--readnever}.
20015 @c FIXME: for now no mention of directories, since this seems to be in
20016 @c flux. 13mar1992 status is that in theory GDB would look either in
20017 @c current dir or in same dir as myprog; but issues like competing
20018 @c GDB's, or clutter in system dirs, mean that in practice right now
20019 @c only current dir is used. FFish says maybe a special GDB hierarchy
20020 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
20024 @item core-file @r{[}@var{filename}@r{]}
20026 Specify the whereabouts of a core dump file to be used as the ``contents
20027 of memory''. Traditionally, core files contain only some parts of the
20028 address space of the process that generated them; @value{GDBN} can access the
20029 executable file itself for other parts.
20031 @code{core-file} with no argument specifies that no core file is
20034 Note that the core file is ignored when your program is actually running
20035 under @value{GDBN}. So, if you have been running your program and you
20036 wish to debug a core file instead, you must kill the subprocess in which
20037 the program is running. To do this, use the @code{kill} command
20038 (@pxref{Kill Process, ,Killing the Child Process}).
20040 @kindex add-symbol-file
20041 @cindex dynamic linking
20042 @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{]}
20043 The @code{add-symbol-file} command reads additional symbol table
20044 information from the file @var{filename}. You would use this command
20045 when @var{filename} has been dynamically loaded (by some other means)
20046 into the program that is running. The @var{textaddress} parameter gives
20047 the memory address at which the file's text section has been loaded.
20048 You can additionally specify the base address of other sections using
20049 an arbitrary number of @samp{-s @var{section} @var{address}} pairs.
20050 If a section is omitted, @value{GDBN} will use its default addresses
20051 as found in @var{filename}. Any @var{address} or @var{textaddress}
20052 can be given as an expression.
20054 If an optional @var{offset} is specified, it is added to the start
20055 address of each section, except those for which the address was
20056 specified explicitly.
20058 The symbol table of the file @var{filename} is added to the symbol table
20059 originally read with the @code{symbol-file} command. You can use the
20060 @code{add-symbol-file} command any number of times; the new symbol data
20061 thus read is kept in addition to the old.
20063 Changes can be reverted using the command @code{remove-symbol-file}.
20065 @cindex relocatable object files, reading symbols from
20066 @cindex object files, relocatable, reading symbols from
20067 @cindex reading symbols from relocatable object files
20068 @cindex symbols, reading from relocatable object files
20069 @cindex @file{.o} files, reading symbols from
20070 Although @var{filename} is typically a shared library file, an
20071 executable file, or some other object file which has been fully
20072 relocated for loading into a process, you can also load symbolic
20073 information from relocatable @file{.o} files, as long as:
20077 the file's symbolic information refers only to linker symbols defined in
20078 that file, not to symbols defined by other object files,
20080 every section the file's symbolic information refers to has actually
20081 been loaded into the inferior, as it appears in the file, and
20083 you can determine the address at which every section was loaded, and
20084 provide these to the @code{add-symbol-file} command.
20088 Some embedded operating systems, like Sun Chorus and VxWorks, can load
20089 relocatable files into an already running program; such systems
20090 typically make the requirements above easy to meet. However, it's
20091 important to recognize that many native systems use complex link
20092 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
20093 assembly, for example) that make the requirements difficult to meet. In
20094 general, one cannot assume that using @code{add-symbol-file} to read a
20095 relocatable object file's symbolic information will have the same effect
20096 as linking the relocatable object file into the program in the normal
20099 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
20101 @kindex remove-symbol-file
20102 @item remove-symbol-file @var{filename}
20103 @item remove-symbol-file -a @var{address}
20104 Remove a symbol file added via the @code{add-symbol-file} command. The
20105 file to remove can be identified by its @var{filename} or by an @var{address}
20106 that lies within the boundaries of this symbol file in memory. Example:
20109 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
20110 add symbol table from file "/home/user/gdb/mylib.so" at
20111 .text_addr = 0x7ffff7ff9480
20113 Reading symbols from /home/user/gdb/mylib.so...done.
20114 (gdb) remove-symbol-file -a 0x7ffff7ff9480
20115 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
20120 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
20122 @kindex add-symbol-file-from-memory
20123 @cindex @code{syscall DSO}
20124 @cindex load symbols from memory
20125 @item add-symbol-file-from-memory @var{address}
20126 Load symbols from the given @var{address} in a dynamically loaded
20127 object file whose image is mapped directly into the inferior's memory.
20128 For example, the Linux kernel maps a @code{syscall DSO} into each
20129 process's address space; this DSO provides kernel-specific code for
20130 some system calls. The argument can be any expression whose
20131 evaluation yields the address of the file's shared object file header.
20132 For this command to work, you must have used @code{symbol-file} or
20133 @code{exec-file} commands in advance.
20136 @item section @var{section} @var{addr}
20137 The @code{section} command changes the base address of the named
20138 @var{section} of the exec file to @var{addr}. This can be used if the
20139 exec file does not contain section addresses, (such as in the
20140 @code{a.out} format), or when the addresses specified in the file
20141 itself are wrong. Each section must be changed separately. The
20142 @code{info files} command, described below, lists all the sections and
20146 @kindex info target
20149 @code{info files} and @code{info target} are synonymous; both print the
20150 current target (@pxref{Targets, ,Specifying a Debugging Target}),
20151 including the names of the executable and core dump files currently in
20152 use by @value{GDBN}, and the files from which symbols were loaded. The
20153 command @code{help target} lists all possible targets rather than
20156 @kindex maint info sections
20157 @item maint info sections
20158 Another command that can give you extra information about program sections
20159 is @code{maint info sections}. In addition to the section information
20160 displayed by @code{info files}, this command displays the flags and file
20161 offset of each section in the executable and core dump files. In addition,
20162 @code{maint info sections} provides the following command options (which
20163 may be arbitrarily combined):
20167 Display sections for all loaded object files, including shared libraries.
20168 @item @var{sections}
20169 Display info only for named @var{sections}.
20170 @item @var{section-flags}
20171 Display info only for sections for which @var{section-flags} are true.
20172 The section flags that @value{GDBN} currently knows about are:
20175 Section will have space allocated in the process when loaded.
20176 Set for all sections except those containing debug information.
20178 Section will be loaded from the file into the child process memory.
20179 Set for pre-initialized code and data, clear for @code{.bss} sections.
20181 Section needs to be relocated before loading.
20183 Section cannot be modified by the child process.
20185 Section contains executable code only.
20187 Section contains data only (no executable code).
20189 Section will reside in ROM.
20191 Section contains data for constructor/destructor lists.
20193 Section is not empty.
20195 An instruction to the linker to not output the section.
20196 @item COFF_SHARED_LIBRARY
20197 A notification to the linker that the section contains
20198 COFF shared library information.
20200 Section contains common symbols.
20203 @kindex set trust-readonly-sections
20204 @cindex read-only sections
20205 @item set trust-readonly-sections on
20206 Tell @value{GDBN} that readonly sections in your object file
20207 really are read-only (i.e.@: that their contents will not change).
20208 In that case, @value{GDBN} can fetch values from these sections
20209 out of the object file, rather than from the target program.
20210 For some targets (notably embedded ones), this can be a significant
20211 enhancement to debugging performance.
20213 The default is off.
20215 @item set trust-readonly-sections off
20216 Tell @value{GDBN} not to trust readonly sections. This means that
20217 the contents of the section might change while the program is running,
20218 and must therefore be fetched from the target when needed.
20220 @item show trust-readonly-sections
20221 Show the current setting of trusting readonly sections.
20224 All file-specifying commands allow both absolute and relative file names
20225 as arguments. @value{GDBN} always converts the file name to an absolute file
20226 name and remembers it that way.
20228 @cindex shared libraries
20229 @anchor{Shared Libraries}
20230 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, SunOS,
20231 Darwin/Mach-O, SVr4, IBM RS/6000 AIX, QNX Neutrino, FDPIC (FR-V), and
20232 DSBT (TIC6X) shared libraries.
20234 On MS-Windows @value{GDBN} must be linked with the Expat library to support
20235 shared libraries. @xref{Expat}.
20237 @value{GDBN} automatically loads symbol definitions from shared libraries
20238 when you use the @code{run} command, or when you examine a core file.
20239 (Before you issue the @code{run} command, @value{GDBN} does not understand
20240 references to a function in a shared library, however---unless you are
20241 debugging a core file).
20243 @c FIXME: some @value{GDBN} release may permit some refs to undef
20244 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
20245 @c FIXME...lib; check this from time to time when updating manual
20247 There are times, however, when you may wish to not automatically load
20248 symbol definitions from shared libraries, such as when they are
20249 particularly large or there are many of them.
20251 To control the automatic loading of shared library symbols, use the
20255 @kindex set auto-solib-add
20256 @item set auto-solib-add @var{mode}
20257 If @var{mode} is @code{on}, symbols from all shared object libraries
20258 will be loaded automatically when the inferior begins execution, you
20259 attach to an independently started inferior, or when the dynamic linker
20260 informs @value{GDBN} that a new library has been loaded. If @var{mode}
20261 is @code{off}, symbols must be loaded manually, using the
20262 @code{sharedlibrary} command. The default value is @code{on}.
20264 @cindex memory used for symbol tables
20265 If your program uses lots of shared libraries with debug info that
20266 takes large amounts of memory, you can decrease the @value{GDBN}
20267 memory footprint by preventing it from automatically loading the
20268 symbols from shared libraries. To that end, type @kbd{set
20269 auto-solib-add off} before running the inferior, then load each
20270 library whose debug symbols you do need with @kbd{sharedlibrary
20271 @var{regexp}}, where @var{regexp} is a regular expression that matches
20272 the libraries whose symbols you want to be loaded.
20274 @kindex show auto-solib-add
20275 @item show auto-solib-add
20276 Display the current autoloading mode.
20279 @cindex load shared library
20280 To explicitly load shared library symbols, use the @code{sharedlibrary}
20284 @kindex info sharedlibrary
20286 @item info share @var{regex}
20287 @itemx info sharedlibrary @var{regex}
20288 Print the names of the shared libraries which are currently loaded
20289 that match @var{regex}. If @var{regex} is omitted then print
20290 all shared libraries that are loaded.
20293 @item info dll @var{regex}
20294 This is an alias of @code{info sharedlibrary}.
20296 @kindex sharedlibrary
20298 @item sharedlibrary @var{regex}
20299 @itemx share @var{regex}
20300 Load shared object library symbols for files matching a
20301 Unix regular expression.
20302 As with files loaded automatically, it only loads shared libraries
20303 required by your program for a core file or after typing @code{run}. If
20304 @var{regex} is omitted all shared libraries required by your program are
20307 @item nosharedlibrary
20308 @kindex nosharedlibrary
20309 @cindex unload symbols from shared libraries
20310 Unload all shared object library symbols. This discards all symbols
20311 that have been loaded from all shared libraries. Symbols from shared
20312 libraries that were loaded by explicit user requests are not
20316 Sometimes you may wish that @value{GDBN} stops and gives you control
20317 when any of shared library events happen. The best way to do this is
20318 to use @code{catch load} and @code{catch unload} (@pxref{Set
20321 @value{GDBN} also supports the the @code{set stop-on-solib-events}
20322 command for this. This command exists for historical reasons. It is
20323 less useful than setting a catchpoint, because it does not allow for
20324 conditions or commands as a catchpoint does.
20327 @item set stop-on-solib-events
20328 @kindex set stop-on-solib-events
20329 This command controls whether @value{GDBN} should give you control
20330 when the dynamic linker notifies it about some shared library event.
20331 The most common event of interest is loading or unloading of a new
20334 @item show stop-on-solib-events
20335 @kindex show stop-on-solib-events
20336 Show whether @value{GDBN} stops and gives you control when shared
20337 library events happen.
20340 Shared libraries are also supported in many cross or remote debugging
20341 configurations. @value{GDBN} needs to have access to the target's libraries;
20342 this can be accomplished either by providing copies of the libraries
20343 on the host system, or by asking @value{GDBN} to automatically retrieve the
20344 libraries from the target. If copies of the target libraries are
20345 provided, they need to be the same as the target libraries, although the
20346 copies on the target can be stripped as long as the copies on the host are
20349 @cindex where to look for shared libraries
20350 For remote debugging, you need to tell @value{GDBN} where the target
20351 libraries are, so that it can load the correct copies---otherwise, it
20352 may try to load the host's libraries. @value{GDBN} has two variables
20353 to specify the search directories for target libraries.
20356 @cindex prefix for executable and shared library file names
20357 @cindex system root, alternate
20358 @kindex set solib-absolute-prefix
20359 @kindex set sysroot
20360 @item set sysroot @var{path}
20361 Use @var{path} as the system root for the program being debugged. Any
20362 absolute shared library paths will be prefixed with @var{path}; many
20363 runtime loaders store the absolute paths to the shared library in the
20364 target program's memory. When starting processes remotely, and when
20365 attaching to already-running processes (local or remote), their
20366 executable filenames will be prefixed with @var{path} if reported to
20367 @value{GDBN} as absolute by the operating system. If you use
20368 @code{set sysroot} to find executables and shared libraries, they need
20369 to be laid out in the same way that they are on the target, with
20370 e.g.@: a @file{/bin}, @file{/lib} and @file{/usr/lib} hierarchy under
20373 If @var{path} starts with the sequence @file{target:} and the target
20374 system is remote then @value{GDBN} will retrieve the target binaries
20375 from the remote system. This is only supported when using a remote
20376 target that supports the @code{remote get} command (@pxref{File
20377 Transfer,,Sending files to a remote system}). The part of @var{path}
20378 following the initial @file{target:} (if present) is used as system
20379 root prefix on the remote file system. If @var{path} starts with the
20380 sequence @file{remote:} this is converted to the sequence
20381 @file{target:} by @code{set sysroot}@footnote{Historically the
20382 functionality to retrieve binaries from the remote system was
20383 provided by prefixing @var{path} with @file{remote:}}. If you want
20384 to specify a local system root using a directory that happens to be
20385 named @file{target:} or @file{remote:}, you need to use some
20386 equivalent variant of the name like @file{./target:}.
20388 For targets with an MS-DOS based filesystem, such as MS-Windows and
20389 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
20390 absolute file name with @var{path}. But first, on Unix hosts,
20391 @value{GDBN} converts all backslash directory separators into forward
20392 slashes, because the backslash is not a directory separator on Unix:
20395 c:\foo\bar.dll @result{} c:/foo/bar.dll
20398 Then, @value{GDBN} attempts prefixing the target file name with
20399 @var{path}, and looks for the resulting file name in the host file
20403 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
20406 If that does not find the binary, @value{GDBN} tries removing
20407 the @samp{:} character from the drive spec, both for convenience, and,
20408 for the case of the host file system not supporting file names with
20412 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
20415 This makes it possible to have a system root that mirrors a target
20416 with more than one drive. E.g., you may want to setup your local
20417 copies of the target system shared libraries like so (note @samp{c} vs
20421 @file{/path/to/sysroot/c/sys/bin/foo.dll}
20422 @file{/path/to/sysroot/c/sys/bin/bar.dll}
20423 @file{/path/to/sysroot/z/sys/bin/bar.dll}
20427 and point the system root at @file{/path/to/sysroot}, so that
20428 @value{GDBN} can find the correct copies of both
20429 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
20431 If that still does not find the binary, @value{GDBN} tries
20432 removing the whole drive spec from the target file name:
20435 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
20438 This last lookup makes it possible to not care about the drive name,
20439 if you don't want or need to.
20441 The @code{set solib-absolute-prefix} command is an alias for @code{set
20444 @cindex default system root
20445 @cindex @samp{--with-sysroot}
20446 You can set the default system root by using the configure-time
20447 @samp{--with-sysroot} option. If the system root is inside
20448 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
20449 @samp{--exec-prefix}), then the default system root will be updated
20450 automatically if the installed @value{GDBN} is moved to a new
20453 @kindex show sysroot
20455 Display the current executable and shared library prefix.
20457 @kindex set solib-search-path
20458 @item set solib-search-path @var{path}
20459 If this variable is set, @var{path} is a colon-separated list of
20460 directories to search for shared libraries. @samp{solib-search-path}
20461 is used after @samp{sysroot} fails to locate the library, or if the
20462 path to the library is relative instead of absolute. If you want to
20463 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
20464 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
20465 finding your host's libraries. @samp{sysroot} is preferred; setting
20466 it to a nonexistent directory may interfere with automatic loading
20467 of shared library symbols.
20469 @kindex show solib-search-path
20470 @item show solib-search-path
20471 Display the current shared library search path.
20473 @cindex DOS file-name semantics of file names.
20474 @kindex set target-file-system-kind (unix|dos-based|auto)
20475 @kindex show target-file-system-kind
20476 @item set target-file-system-kind @var{kind}
20477 Set assumed file system kind for target reported file names.
20479 Shared library file names as reported by the target system may not
20480 make sense as is on the system @value{GDBN} is running on. For
20481 example, when remote debugging a target that has MS-DOS based file
20482 system semantics, from a Unix host, the target may be reporting to
20483 @value{GDBN} a list of loaded shared libraries with file names such as
20484 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
20485 drive letters, so the @samp{c:\} prefix is not normally understood as
20486 indicating an absolute file name, and neither is the backslash
20487 normally considered a directory separator character. In that case,
20488 the native file system would interpret this whole absolute file name
20489 as a relative file name with no directory components. This would make
20490 it impossible to point @value{GDBN} at a copy of the remote target's
20491 shared libraries on the host using @code{set sysroot}, and impractical
20492 with @code{set solib-search-path}. Setting
20493 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
20494 to interpret such file names similarly to how the target would, and to
20495 map them to file names valid on @value{GDBN}'s native file system
20496 semantics. The value of @var{kind} can be @code{"auto"}, in addition
20497 to one of the supported file system kinds. In that case, @value{GDBN}
20498 tries to determine the appropriate file system variant based on the
20499 current target's operating system (@pxref{ABI, ,Configuring the
20500 Current ABI}). The supported file system settings are:
20504 Instruct @value{GDBN} to assume the target file system is of Unix
20505 kind. Only file names starting the forward slash (@samp{/}) character
20506 are considered absolute, and the directory separator character is also
20510 Instruct @value{GDBN} to assume the target file system is DOS based.
20511 File names starting with either a forward slash, or a drive letter
20512 followed by a colon (e.g., @samp{c:}), are considered absolute, and
20513 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
20514 considered directory separators.
20517 Instruct @value{GDBN} to use the file system kind associated with the
20518 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
20519 This is the default.
20523 @cindex file name canonicalization
20524 @cindex base name differences
20525 When processing file names provided by the user, @value{GDBN}
20526 frequently needs to compare them to the file names recorded in the
20527 program's debug info. Normally, @value{GDBN} compares just the
20528 @dfn{base names} of the files as strings, which is reasonably fast
20529 even for very large programs. (The base name of a file is the last
20530 portion of its name, after stripping all the leading directories.)
20531 This shortcut in comparison is based upon the assumption that files
20532 cannot have more than one base name. This is usually true, but
20533 references to files that use symlinks or similar filesystem
20534 facilities violate that assumption. If your program records files
20535 using such facilities, or if you provide file names to @value{GDBN}
20536 using symlinks etc., you can set @code{basenames-may-differ} to
20537 @code{true} to instruct @value{GDBN} to completely canonicalize each
20538 pair of file names it needs to compare. This will make file-name
20539 comparisons accurate, but at a price of a significant slowdown.
20542 @item set basenames-may-differ
20543 @kindex set basenames-may-differ
20544 Set whether a source file may have multiple base names.
20546 @item show basenames-may-differ
20547 @kindex show basenames-may-differ
20548 Show whether a source file may have multiple base names.
20552 @section File Caching
20553 @cindex caching of opened files
20554 @cindex caching of bfd objects
20556 To speed up file loading, and reduce memory usage, @value{GDBN} will
20557 reuse the @code{bfd} objects used to track open files. @xref{Top, ,
20558 BFD, bfd, The Binary File Descriptor Library}. The following commands
20559 allow visibility and control of the caching behavior.
20562 @kindex maint info bfds
20563 @item maint info bfds
20564 This prints information about each @code{bfd} object that is known to
20567 @kindex maint set bfd-sharing
20568 @kindex maint show bfd-sharing
20569 @kindex bfd caching
20570 @item maint set bfd-sharing
20571 @item maint show bfd-sharing
20572 Control whether @code{bfd} objects can be shared. When sharing is
20573 enabled @value{GDBN} reuses already open @code{bfd} objects rather
20574 than reopening the same file. Turning sharing off does not cause
20575 already shared @code{bfd} objects to be unshared, but all future files
20576 that are opened will create a new @code{bfd} object. Similarly,
20577 re-enabling sharing does not cause multiple existing @code{bfd}
20578 objects to be collapsed into a single shared @code{bfd} object.
20580 @kindex set debug bfd-cache @var{level}
20581 @kindex bfd caching
20582 @item set debug bfd-cache @var{level}
20583 Turns on debugging of the bfd cache, setting the level to @var{level}.
20585 @kindex show debug bfd-cache
20586 @kindex bfd caching
20587 @item show debug bfd-cache
20588 Show the current debugging level of the bfd cache.
20591 @node Separate Debug Files
20592 @section Debugging Information in Separate Files
20593 @cindex separate debugging information files
20594 @cindex debugging information in separate files
20595 @cindex @file{.debug} subdirectories
20596 @cindex debugging information directory, global
20597 @cindex global debugging information directories
20598 @cindex build ID, and separate debugging files
20599 @cindex @file{.build-id} directory
20601 @value{GDBN} allows you to put a program's debugging information in a
20602 file separate from the executable itself, in a way that allows
20603 @value{GDBN} to find and load the debugging information automatically.
20604 Since debugging information can be very large---sometimes larger
20605 than the executable code itself---some systems distribute debugging
20606 information for their executables in separate files, which users can
20607 install only when they need to debug a problem.
20609 @value{GDBN} supports two ways of specifying the separate debug info
20614 The executable contains a @dfn{debug link} that specifies the name of
20615 the separate debug info file. The separate debug file's name is
20616 usually @file{@var{executable}.debug}, where @var{executable} is the
20617 name of the corresponding executable file without leading directories
20618 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
20619 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
20620 checksum for the debug file, which @value{GDBN} uses to validate that
20621 the executable and the debug file came from the same build.
20624 The executable contains a @dfn{build ID}, a unique bit string that is
20625 also present in the corresponding debug info file. (This is supported
20626 only on some operating systems, when using the ELF or PE file formats
20627 for binary files and the @sc{gnu} Binutils.) For more details about
20628 this feature, see the description of the @option{--build-id}
20629 command-line option in @ref{Options, , Command Line Options, ld,
20630 The GNU Linker}. The debug info file's name is not specified
20631 explicitly by the build ID, but can be computed from the build ID, see
20635 Depending on the way the debug info file is specified, @value{GDBN}
20636 uses two different methods of looking for the debug file:
20640 For the ``debug link'' method, @value{GDBN} looks up the named file in
20641 the directory of the executable file, then in a subdirectory of that
20642 directory named @file{.debug}, and finally under each one of the
20643 global debug directories, in a subdirectory whose name is identical to
20644 the leading directories of the executable's absolute file name. (On
20645 MS-Windows/MS-DOS, the drive letter of the executable's leading
20646 directories is converted to a one-letter subdirectory, i.e.@:
20647 @file{d:/usr/bin/} is converted to @file{/d/usr/bin/}, because Windows
20648 filesystems disallow colons in file names.)
20651 For the ``build ID'' method, @value{GDBN} looks in the
20652 @file{.build-id} subdirectory of each one of the global debug directories for
20653 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
20654 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
20655 are the rest of the bit string. (Real build ID strings are 32 or more
20656 hex characters, not 10.)
20659 So, for example, suppose you ask @value{GDBN} to debug
20660 @file{/usr/bin/ls}, which has a debug link that specifies the
20661 file @file{ls.debug}, and a build ID whose value in hex is
20662 @code{abcdef1234}. If the list of the global debug directories includes
20663 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
20664 debug information files, in the indicated order:
20668 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
20670 @file{/usr/bin/ls.debug}
20672 @file{/usr/bin/.debug/ls.debug}
20674 @file{/usr/lib/debug/usr/bin/ls.debug}.
20677 @anchor{debug-file-directory}
20678 Global debugging info directories default to what is set by @value{GDBN}
20679 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
20680 you can also set the global debugging info directories, and view the list
20681 @value{GDBN} is currently using.
20685 @kindex set debug-file-directory
20686 @item set debug-file-directory @var{directories}
20687 Set the directories which @value{GDBN} searches for separate debugging
20688 information files to @var{directory}. Multiple path components can be set
20689 concatenating them by a path separator.
20691 @kindex show debug-file-directory
20692 @item show debug-file-directory
20693 Show the directories @value{GDBN} searches for separate debugging
20698 @cindex @code{.gnu_debuglink} sections
20699 @cindex debug link sections
20700 A debug link is a special section of the executable file named
20701 @code{.gnu_debuglink}. The section must contain:
20705 A filename, with any leading directory components removed, followed by
20708 zero to three bytes of padding, as needed to reach the next four-byte
20709 boundary within the section, and
20711 a four-byte CRC checksum, stored in the same endianness used for the
20712 executable file itself. The checksum is computed on the debugging
20713 information file's full contents by the function given below, passing
20714 zero as the @var{crc} argument.
20717 Any executable file format can carry a debug link, as long as it can
20718 contain a section named @code{.gnu_debuglink} with the contents
20721 @cindex @code{.note.gnu.build-id} sections
20722 @cindex build ID sections
20723 The build ID is a special section in the executable file (and in other
20724 ELF binary files that @value{GDBN} may consider). This section is
20725 often named @code{.note.gnu.build-id}, but that name is not mandatory.
20726 It contains unique identification for the built files---the ID remains
20727 the same across multiple builds of the same build tree. The default
20728 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
20729 content for the build ID string. The same section with an identical
20730 value is present in the original built binary with symbols, in its
20731 stripped variant, and in the separate debugging information file.
20733 The debugging information file itself should be an ordinary
20734 executable, containing a full set of linker symbols, sections, and
20735 debugging information. The sections of the debugging information file
20736 should have the same names, addresses, and sizes as the original file,
20737 but they need not contain any data---much like a @code{.bss} section
20738 in an ordinary executable.
20740 The @sc{gnu} binary utilities (Binutils) package includes the
20741 @samp{objcopy} utility that can produce
20742 the separated executable / debugging information file pairs using the
20743 following commands:
20746 @kbd{objcopy --only-keep-debug foo foo.debug}
20751 These commands remove the debugging
20752 information from the executable file @file{foo} and place it in the file
20753 @file{foo.debug}. You can use the first, second or both methods to link the
20758 The debug link method needs the following additional command to also leave
20759 behind a debug link in @file{foo}:
20762 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
20765 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
20766 a version of the @code{strip} command such that the command @kbd{strip foo -f
20767 foo.debug} has the same functionality as the two @code{objcopy} commands and
20768 the @code{ln -s} command above, together.
20771 Build ID gets embedded into the main executable using @code{ld --build-id} or
20772 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
20773 compatibility fixes for debug files separation are present in @sc{gnu} binary
20774 utilities (Binutils) package since version 2.18.
20779 @cindex CRC algorithm definition
20780 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
20781 IEEE 802.3 using the polynomial:
20783 @c TexInfo requires naked braces for multi-digit exponents for Tex
20784 @c output, but this causes HTML output to barf. HTML has to be set using
20785 @c raw commands. So we end up having to specify this equation in 2
20790 <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>
20791 + <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
20797 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
20798 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
20802 The function is computed byte at a time, taking the least
20803 significant bit of each byte first. The initial pattern
20804 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
20805 the final result is inverted to ensure trailing zeros also affect the
20808 @emph{Note:} This is the same CRC polynomial as used in handling the
20809 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
20810 However in the case of the Remote Serial Protocol, the CRC is computed
20811 @emph{most} significant bit first, and the result is not inverted, so
20812 trailing zeros have no effect on the CRC value.
20814 To complete the description, we show below the code of the function
20815 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
20816 initially supplied @code{crc} argument means that an initial call to
20817 this function passing in zero will start computing the CRC using
20820 @kindex gnu_debuglink_crc32
20823 gnu_debuglink_crc32 (unsigned long crc,
20824 unsigned char *buf, size_t len)
20826 static const unsigned long crc32_table[256] =
20828 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
20829 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
20830 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
20831 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
20832 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
20833 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
20834 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
20835 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
20836 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
20837 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
20838 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
20839 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
20840 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
20841 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
20842 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
20843 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
20844 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
20845 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
20846 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
20847 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
20848 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
20849 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
20850 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
20851 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
20852 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
20853 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
20854 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
20855 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
20856 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
20857 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
20858 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
20859 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
20860 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
20861 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
20862 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
20863 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
20864 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
20865 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
20866 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
20867 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
20868 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
20869 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
20870 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
20871 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
20872 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
20873 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
20874 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
20875 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
20876 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
20877 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
20878 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
20881 unsigned char *end;
20883 crc = ~crc & 0xffffffff;
20884 for (end = buf + len; buf < end; ++buf)
20885 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
20886 return ~crc & 0xffffffff;
20891 This computation does not apply to the ``build ID'' method.
20893 @node MiniDebugInfo
20894 @section Debugging information in a special section
20895 @cindex separate debug sections
20896 @cindex @samp{.gnu_debugdata} section
20898 Some systems ship pre-built executables and libraries that have a
20899 special @samp{.gnu_debugdata} section. This feature is called
20900 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
20901 is used to supply extra symbols for backtraces.
20903 The intent of this section is to provide extra minimal debugging
20904 information for use in simple backtraces. It is not intended to be a
20905 replacement for full separate debugging information (@pxref{Separate
20906 Debug Files}). The example below shows the intended use; however,
20907 @value{GDBN} does not currently put restrictions on what sort of
20908 debugging information might be included in the section.
20910 @value{GDBN} has support for this extension. If the section exists,
20911 then it is used provided that no other source of debugging information
20912 can be found, and that @value{GDBN} was configured with LZMA support.
20914 This section can be easily created using @command{objcopy} and other
20915 standard utilities:
20918 # Extract the dynamic symbols from the main binary, there is no need
20919 # to also have these in the normal symbol table.
20920 nm -D @var{binary} --format=posix --defined-only \
20921 | awk '@{ print $1 @}' | sort > dynsyms
20923 # Extract all the text (i.e. function) symbols from the debuginfo.
20924 # (Note that we actually also accept "D" symbols, for the benefit
20925 # of platforms like PowerPC64 that use function descriptors.)
20926 nm @var{binary} --format=posix --defined-only \
20927 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
20930 # Keep all the function symbols not already in the dynamic symbol
20932 comm -13 dynsyms funcsyms > keep_symbols
20934 # Separate full debug info into debug binary.
20935 objcopy --only-keep-debug @var{binary} debug
20937 # Copy the full debuginfo, keeping only a minimal set of symbols and
20938 # removing some unnecessary sections.
20939 objcopy -S --remove-section .gdb_index --remove-section .comment \
20940 --keep-symbols=keep_symbols debug mini_debuginfo
20942 # Drop the full debug info from the original binary.
20943 strip --strip-all -R .comment @var{binary}
20945 # Inject the compressed data into the .gnu_debugdata section of the
20948 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
20952 @section Index Files Speed Up @value{GDBN}
20953 @cindex index files
20954 @cindex @samp{.gdb_index} section
20956 When @value{GDBN} finds a symbol file, it scans the symbols in the
20957 file in order to construct an internal symbol table. This lets most
20958 @value{GDBN} operations work quickly---at the cost of a delay early
20959 on. For large programs, this delay can be quite lengthy, so
20960 @value{GDBN} provides a way to build an index, which speeds up
20963 For convenience, @value{GDBN} comes with a program,
20964 @command{gdb-add-index}, which can be used to add the index to a
20965 symbol file. It takes the symbol file as its only argument:
20968 $ gdb-add-index symfile
20971 @xref{gdb-add-index}.
20973 It is also possible to do the work manually. Here is what
20974 @command{gdb-add-index} does behind the curtains.
20976 The index is stored as a section in the symbol file. @value{GDBN} can
20977 write the index to a file, then you can put it into the symbol file
20978 using @command{objcopy}.
20980 To create an index file, use the @code{save gdb-index} command:
20983 @item save gdb-index [-dwarf-5] @var{directory}
20984 @kindex save gdb-index
20985 Create index files for all symbol files currently known by
20986 @value{GDBN}. For each known @var{symbol-file}, this command by
20987 default creates it produces a single file
20988 @file{@var{symbol-file}.gdb-index}. If you invoke this command with
20989 the @option{-dwarf-5} option, it produces 2 files:
20990 @file{@var{symbol-file}.debug_names} and
20991 @file{@var{symbol-file}.debug_str}. The files are created in the
20992 given @var{directory}.
20995 Once you have created an index file you can merge it into your symbol
20996 file, here named @file{symfile}, using @command{objcopy}:
20999 $ objcopy --add-section .gdb_index=symfile.gdb-index \
21000 --set-section-flags .gdb_index=readonly symfile symfile
21003 Or for @code{-dwarf-5}:
21006 $ objcopy --dump-section .debug_str=symfile.debug_str.new symfile
21007 $ cat symfile.debug_str >>symfile.debug_str.new
21008 $ objcopy --add-section .debug_names=symfile.gdb-index \
21009 --set-section-flags .debug_names=readonly \
21010 --update-section .debug_str=symfile.debug_str.new symfile symfile
21013 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
21014 sections that have been deprecated. Usually they are deprecated because
21015 they are missing a new feature or have performance issues.
21016 To tell @value{GDBN} to use a deprecated index section anyway
21017 specify @code{set use-deprecated-index-sections on}.
21018 The default is @code{off}.
21019 This can speed up startup, but may result in some functionality being lost.
21020 @xref{Index Section Format}.
21022 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
21023 must be done before gdb reads the file. The following will not work:
21026 $ gdb -ex "set use-deprecated-index-sections on" <program>
21029 Instead you must do, for example,
21032 $ gdb -iex "set use-deprecated-index-sections on" <program>
21035 There are currently some limitation on indices. They only work when
21036 using DWARF debugging information, not stabs. And, only the
21037 @code{-dwarf-5} index works for programs using Ada.
21039 @subsection Automatic symbol index cache
21041 @cindex automatic symbol index cache
21042 It is possible for @value{GDBN} to automatically save a copy of this index in a
21043 cache on disk and retrieve it from there when loading the same binary in the
21044 future. This feature can be turned on with @kbd{set index-cache on}. The
21045 following commands can be used to tweak the behavior of the index cache.
21049 @kindex set index-cache
21050 @item set index-cache on
21051 @itemx set index-cache off
21052 Enable or disable the use of the symbol index cache.
21054 @item set index-cache directory @var{directory}
21055 @kindex show index-cache
21056 @itemx show index-cache directory
21057 Set/show the directory where index files will be saved.
21059 The default value for this directory depends on the host platform. On
21060 most systems, the index is cached in the @file{gdb} subdirectory of
21061 the directory pointed to by the @env{XDG_CACHE_HOME} environment
21062 variable, if it is defined, else in the @file{.cache/gdb} subdirectory
21063 of your home directory. However, on some systems, the default may
21064 differ according to local convention.
21066 There is no limit on the disk space used by index cache. It is perfectly safe
21067 to delete the content of that directory to free up disk space.
21069 @item show index-cache stats
21070 Print the number of cache hits and misses since the launch of @value{GDBN}.
21074 @node Symbol Errors
21075 @section Errors Reading Symbol Files
21077 While reading a symbol file, @value{GDBN} occasionally encounters problems,
21078 such as symbol types it does not recognize, or known bugs in compiler
21079 output. By default, @value{GDBN} does not notify you of such problems, since
21080 they are relatively common and primarily of interest to people
21081 debugging compilers. If you are interested in seeing information
21082 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
21083 only one message about each such type of problem, no matter how many
21084 times the problem occurs; or you can ask @value{GDBN} to print more messages,
21085 to see how many times the problems occur, with the @code{set
21086 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
21089 The messages currently printed, and their meanings, include:
21092 @item inner block not inside outer block in @var{symbol}
21094 The symbol information shows where symbol scopes begin and end
21095 (such as at the start of a function or a block of statements). This
21096 error indicates that an inner scope block is not fully contained
21097 in its outer scope blocks.
21099 @value{GDBN} circumvents the problem by treating the inner block as if it had
21100 the same scope as the outer block. In the error message, @var{symbol}
21101 may be shown as ``@code{(don't know)}'' if the outer block is not a
21104 @item block at @var{address} out of order
21106 The symbol information for symbol scope blocks should occur in
21107 order of increasing addresses. This error indicates that it does not
21110 @value{GDBN} does not circumvent this problem, and has trouble
21111 locating symbols in the source file whose symbols it is reading. (You
21112 can often determine what source file is affected by specifying
21113 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
21116 @item bad block start address patched
21118 The symbol information for a symbol scope block has a start address
21119 smaller than the address of the preceding source line. This is known
21120 to occur in the SunOS 4.1.1 (and earlier) C compiler.
21122 @value{GDBN} circumvents the problem by treating the symbol scope block as
21123 starting on the previous source line.
21125 @item bad string table offset in symbol @var{n}
21128 Symbol number @var{n} contains a pointer into the string table which is
21129 larger than the size of the string table.
21131 @value{GDBN} circumvents the problem by considering the symbol to have the
21132 name @code{foo}, which may cause other problems if many symbols end up
21135 @item unknown symbol type @code{0x@var{nn}}
21137 The symbol information contains new data types that @value{GDBN} does
21138 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
21139 uncomprehended information, in hexadecimal.
21141 @value{GDBN} circumvents the error by ignoring this symbol information.
21142 This usually allows you to debug your program, though certain symbols
21143 are not accessible. If you encounter such a problem and feel like
21144 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
21145 on @code{complain}, then go up to the function @code{read_dbx_symtab}
21146 and examine @code{*bufp} to see the symbol.
21148 @item stub type has NULL name
21150 @value{GDBN} could not find the full definition for a struct or class.
21152 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
21153 The symbol information for a C@t{++} member function is missing some
21154 information that recent versions of the compiler should have output for
21157 @item info mismatch between compiler and debugger
21159 @value{GDBN} could not parse a type specification output by the compiler.
21164 @section GDB Data Files
21166 @cindex prefix for data files
21167 @value{GDBN} will sometimes read an auxiliary data file. These files
21168 are kept in a directory known as the @dfn{data directory}.
21170 You can set the data directory's name, and view the name @value{GDBN}
21171 is currently using.
21174 @kindex set data-directory
21175 @item set data-directory @var{directory}
21176 Set the directory which @value{GDBN} searches for auxiliary data files
21177 to @var{directory}.
21179 @kindex show data-directory
21180 @item show data-directory
21181 Show the directory @value{GDBN} searches for auxiliary data files.
21184 @cindex default data directory
21185 @cindex @samp{--with-gdb-datadir}
21186 You can set the default data directory by using the configure-time
21187 @samp{--with-gdb-datadir} option. If the data directory is inside
21188 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
21189 @samp{--exec-prefix}), then the default data directory will be updated
21190 automatically if the installed @value{GDBN} is moved to a new
21193 The data directory may also be specified with the
21194 @code{--data-directory} command line option.
21195 @xref{Mode Options}.
21198 @chapter Specifying a Debugging Target
21200 @cindex debugging target
21201 A @dfn{target} is the execution environment occupied by your program.
21203 Often, @value{GDBN} runs in the same host environment as your program;
21204 in that case, the debugging target is specified as a side effect when
21205 you use the @code{file} or @code{core} commands. When you need more
21206 flexibility---for example, running @value{GDBN} on a physically separate
21207 host, or controlling a standalone system over a serial port or a
21208 realtime system over a TCP/IP connection---you can use the @code{target}
21209 command to specify one of the target types configured for @value{GDBN}
21210 (@pxref{Target Commands, ,Commands for Managing Targets}).
21212 @cindex target architecture
21213 It is possible to build @value{GDBN} for several different @dfn{target
21214 architectures}. When @value{GDBN} is built like that, you can choose
21215 one of the available architectures with the @kbd{set architecture}
21219 @kindex set architecture
21220 @kindex show architecture
21221 @item set architecture @var{arch}
21222 This command sets the current target architecture to @var{arch}. The
21223 value of @var{arch} can be @code{"auto"}, in addition to one of the
21224 supported architectures.
21226 @item show architecture
21227 Show the current target architecture.
21229 @item set processor
21231 @kindex set processor
21232 @kindex show processor
21233 These are alias commands for, respectively, @code{set architecture}
21234 and @code{show architecture}.
21238 * Active Targets:: Active targets
21239 * Target Commands:: Commands for managing targets
21240 * Byte Order:: Choosing target byte order
21243 @node Active Targets
21244 @section Active Targets
21246 @cindex stacking targets
21247 @cindex active targets
21248 @cindex multiple targets
21250 There are multiple classes of targets such as: processes, executable files or
21251 recording sessions. Core files belong to the process class, making core file
21252 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
21253 on multiple active targets, one in each class. This allows you to (for
21254 example) start a process and inspect its activity, while still having access to
21255 the executable file after the process finishes. Or if you start process
21256 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
21257 presented a virtual layer of the recording target, while the process target
21258 remains stopped at the chronologically last point of the process execution.
21260 Use the @code{core-file} and @code{exec-file} commands to select a new core
21261 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
21262 specify as a target a process that is already running, use the @code{attach}
21263 command (@pxref{Attach, ,Debugging an Already-running Process}).
21265 @node Target Commands
21266 @section Commands for Managing Targets
21269 @item target @var{type} @var{parameters}
21270 Connects the @value{GDBN} host environment to a target machine or
21271 process. A target is typically a protocol for talking to debugging
21272 facilities. You use the argument @var{type} to specify the type or
21273 protocol of the target machine.
21275 Further @var{parameters} are interpreted by the target protocol, but
21276 typically include things like device names or host names to connect
21277 with, process numbers, and baud rates.
21279 The @code{target} command does not repeat if you press @key{RET} again
21280 after executing the command.
21282 @kindex help target
21284 Displays the names of all targets available. To display targets
21285 currently selected, use either @code{info target} or @code{info files}
21286 (@pxref{Files, ,Commands to Specify Files}).
21288 @item help target @var{name}
21289 Describe a particular target, including any parameters necessary to
21292 @kindex set gnutarget
21293 @item set gnutarget @var{args}
21294 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
21295 knows whether it is reading an @dfn{executable},
21296 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
21297 with the @code{set gnutarget} command. Unlike most @code{target} commands,
21298 with @code{gnutarget} the @code{target} refers to a program, not a machine.
21301 @emph{Warning:} To specify a file format with @code{set gnutarget},
21302 you must know the actual BFD name.
21306 @xref{Files, , Commands to Specify Files}.
21308 @kindex show gnutarget
21309 @item show gnutarget
21310 Use the @code{show gnutarget} command to display what file format
21311 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
21312 @value{GDBN} will determine the file format for each file automatically,
21313 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
21316 @cindex common targets
21317 Here are some common targets (available, or not, depending on the GDB
21322 @item target exec @var{program}
21323 @cindex executable file target
21324 An executable file. @samp{target exec @var{program}} is the same as
21325 @samp{exec-file @var{program}}.
21327 @item target core @var{filename}
21328 @cindex core dump file target
21329 A core dump file. @samp{target core @var{filename}} is the same as
21330 @samp{core-file @var{filename}}.
21332 @item target remote @var{medium}
21333 @cindex remote target
21334 A remote system connected to @value{GDBN} via a serial line or network
21335 connection. This command tells @value{GDBN} to use its own remote
21336 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
21338 For example, if you have a board connected to @file{/dev/ttya} on the
21339 machine running @value{GDBN}, you could say:
21342 target remote /dev/ttya
21345 @code{target remote} supports the @code{load} command. This is only
21346 useful if you have some other way of getting the stub to the target
21347 system, and you can put it somewhere in memory where it won't get
21348 clobbered by the download.
21350 @item target sim @r{[}@var{simargs}@r{]} @dots{}
21351 @cindex built-in simulator target
21352 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
21360 works; however, you cannot assume that a specific memory map, device
21361 drivers, or even basic I/O is available, although some simulators do
21362 provide these. For info about any processor-specific simulator details,
21363 see the appropriate section in @ref{Embedded Processors, ,Embedded
21366 @item target native
21367 @cindex native target
21368 Setup for local/native process debugging. Useful to make the
21369 @code{run} command spawn native processes (likewise @code{attach},
21370 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
21371 (@pxref{set auto-connect-native-target}).
21375 Different targets are available on different configurations of @value{GDBN};
21376 your configuration may have more or fewer targets.
21378 Many remote targets require you to download the executable's code once
21379 you've successfully established a connection. You may wish to control
21380 various aspects of this process.
21385 @kindex set hash@r{, for remote monitors}
21386 @cindex hash mark while downloading
21387 This command controls whether a hash mark @samp{#} is displayed while
21388 downloading a file to the remote monitor. If on, a hash mark is
21389 displayed after each S-record is successfully downloaded to the
21393 @kindex show hash@r{, for remote monitors}
21394 Show the current status of displaying the hash mark.
21396 @item set debug monitor
21397 @kindex set debug monitor
21398 @cindex display remote monitor communications
21399 Enable or disable display of communications messages between
21400 @value{GDBN} and the remote monitor.
21402 @item show debug monitor
21403 @kindex show debug monitor
21404 Show the current status of displaying communications between
21405 @value{GDBN} and the remote monitor.
21410 @kindex load @var{filename} @var{offset}
21411 @item load @var{filename} @var{offset}
21413 Depending on what remote debugging facilities are configured into
21414 @value{GDBN}, the @code{load} command may be available. Where it exists, it
21415 is meant to make @var{filename} (an executable) available for debugging
21416 on the remote system---by downloading, or dynamic linking, for example.
21417 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
21418 the @code{add-symbol-file} command.
21420 If your @value{GDBN} does not have a @code{load} command, attempting to
21421 execute it gets the error message ``@code{You can't do that when your
21422 target is @dots{}}''
21424 The file is loaded at whatever address is specified in the executable.
21425 For some object file formats, you can specify the load address when you
21426 link the program; for other formats, like a.out, the object file format
21427 specifies a fixed address.
21428 @c FIXME! This would be a good place for an xref to the GNU linker doc.
21430 It is also possible to tell @value{GDBN} to load the executable file at a
21431 specific offset described by the optional argument @var{offset}. When
21432 @var{offset} is provided, @var{filename} must also be provided.
21434 Depending on the remote side capabilities, @value{GDBN} may be able to
21435 load programs into flash memory.
21437 @code{load} does not repeat if you press @key{RET} again after using it.
21442 @kindex flash-erase
21444 @anchor{flash-erase}
21446 Erases all known flash memory regions on the target.
21451 @section Choosing Target Byte Order
21453 @cindex choosing target byte order
21454 @cindex target byte order
21456 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
21457 offer the ability to run either big-endian or little-endian byte
21458 orders. Usually the executable or symbol will include a bit to
21459 designate the endian-ness, and you will not need to worry about
21460 which to use. However, you may still find it useful to adjust
21461 @value{GDBN}'s idea of processor endian-ness manually.
21465 @item set endian big
21466 Instruct @value{GDBN} to assume the target is big-endian.
21468 @item set endian little
21469 Instruct @value{GDBN} to assume the target is little-endian.
21471 @item set endian auto
21472 Instruct @value{GDBN} to use the byte order associated with the
21476 Display @value{GDBN}'s current idea of the target byte order.
21480 If the @code{set endian auto} mode is in effect and no executable has
21481 been selected, then the endianness used is the last one chosen either
21482 by one of the @code{set endian big} and @code{set endian little}
21483 commands or by inferring from the last executable used. If no
21484 endianness has been previously chosen, then the default for this mode
21485 is inferred from the target @value{GDBN} has been built for, and is
21486 @code{little} if the name of the target CPU has an @code{el} suffix
21487 and @code{big} otherwise.
21489 Note that these commands merely adjust interpretation of symbolic
21490 data on the host, and that they have absolutely no effect on the
21494 @node Remote Debugging
21495 @chapter Debugging Remote Programs
21496 @cindex remote debugging
21498 If you are trying to debug a program running on a machine that cannot run
21499 @value{GDBN} in the usual way, it is often useful to use remote debugging.
21500 For example, you might use remote debugging on an operating system kernel,
21501 or on a small system which does not have a general purpose operating system
21502 powerful enough to run a full-featured debugger.
21504 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
21505 to make this work with particular debugging targets. In addition,
21506 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
21507 but not specific to any particular target system) which you can use if you
21508 write the remote stubs---the code that runs on the remote system to
21509 communicate with @value{GDBN}.
21511 Other remote targets may be available in your
21512 configuration of @value{GDBN}; use @code{help target} to list them.
21515 * Connecting:: Connecting to a remote target
21516 * File Transfer:: Sending files to a remote system
21517 * Server:: Using the gdbserver program
21518 * Remote Configuration:: Remote configuration
21519 * Remote Stub:: Implementing a remote stub
21523 @section Connecting to a Remote Target
21524 @cindex remote debugging, connecting
21525 @cindex @code{gdbserver}, connecting
21526 @cindex remote debugging, types of connections
21527 @cindex @code{gdbserver}, types of connections
21528 @cindex @code{gdbserver}, @code{target remote} mode
21529 @cindex @code{gdbserver}, @code{target extended-remote} mode
21531 This section describes how to connect to a remote target, including the
21532 types of connections and their differences, how to set up executable and
21533 symbol files on the host and target, and the commands used for
21534 connecting to and disconnecting from the remote target.
21536 @subsection Types of Remote Connections
21538 @value{GDBN} supports two types of remote connections, @code{target remote}
21539 mode and @code{target extended-remote} mode. Note that many remote targets
21540 support only @code{target remote} mode. There are several major
21541 differences between the two types of connections, enumerated here:
21545 @cindex remote debugging, detach and program exit
21546 @item Result of detach or program exit
21547 @strong{With target remote mode:} When the debugged program exits or you
21548 detach from it, @value{GDBN} disconnects from the target. When using
21549 @code{gdbserver}, @code{gdbserver} will exit.
21551 @strong{With target extended-remote mode:} When the debugged program exits or
21552 you detach from it, @value{GDBN} remains connected to the target, even
21553 though no program is running. You can rerun the program, attach to a
21554 running program, or use @code{monitor} commands specific to the target.
21556 When using @code{gdbserver} in this case, it does not exit unless it was
21557 invoked using the @option{--once} option. If the @option{--once} option
21558 was not used, you can ask @code{gdbserver} to exit using the
21559 @code{monitor exit} command (@pxref{Monitor Commands for gdbserver}).
21561 @item Specifying the program to debug
21562 For both connection types you use the @code{file} command to specify the
21563 program on the host system. If you are using @code{gdbserver} there are
21564 some differences in how to specify the location of the program on the
21567 @strong{With target remote mode:} You must either specify the program to debug
21568 on the @code{gdbserver} command line or use the @option{--attach} option
21569 (@pxref{Attaching to a program,,Attaching to a Running Program}).
21571 @cindex @option{--multi}, @code{gdbserver} option
21572 @strong{With target extended-remote mode:} You may specify the program to debug
21573 on the @code{gdbserver} command line, or you can load the program or attach
21574 to it using @value{GDBN} commands after connecting to @code{gdbserver}.
21576 @anchor{--multi Option in Types of Remote Connnections}
21577 You can start @code{gdbserver} without supplying an initial command to run
21578 or process ID to attach. To do this, use the @option{--multi} command line
21579 option. Then you can connect using @code{target extended-remote} and start
21580 the program you want to debug (see below for details on using the
21581 @code{run} command in this scenario). Note that the conditions under which
21582 @code{gdbserver} terminates depend on how @value{GDBN} connects to it
21583 (@code{target remote} or @code{target extended-remote}). The
21584 @option{--multi} option to @code{gdbserver} has no influence on that.
21586 @item The @code{run} command
21587 @strong{With target remote mode:} The @code{run} command is not
21588 supported. Once a connection has been established, you can use all
21589 the usual @value{GDBN} commands to examine and change data. The
21590 remote program is already running, so you can use commands like
21591 @kbd{step} and @kbd{continue}.
21593 @strong{With target extended-remote mode:} The @code{run} command is
21594 supported. The @code{run} command uses the value set by
21595 @code{set remote exec-file} (@pxref{set remote exec-file}) to select
21596 the program to run. Command line arguments are supported, except for
21597 wildcard expansion and I/O redirection (@pxref{Arguments}).
21599 If you specify the program to debug on the command line, then the
21600 @code{run} command is not required to start execution, and you can
21601 resume using commands like @kbd{step} and @kbd{continue} as with
21602 @code{target remote} mode.
21604 @anchor{Attaching in Types of Remote Connections}
21606 @strong{With target remote mode:} The @value{GDBN} command @code{attach} is
21607 not supported. To attach to a running program using @code{gdbserver}, you
21608 must use the @option{--attach} option (@pxref{Running gdbserver}).
21610 @strong{With target extended-remote mode:} To attach to a running program,
21611 you may use the @code{attach} command after the connection has been
21612 established. If you are using @code{gdbserver}, you may also invoke
21613 @code{gdbserver} using the @option{--attach} option
21614 (@pxref{Running gdbserver}).
21618 @anchor{Host and target files}
21619 @subsection Host and Target Files
21620 @cindex remote debugging, symbol files
21621 @cindex symbol files, remote debugging
21623 @value{GDBN}, running on the host, needs access to symbol and debugging
21624 information for your program running on the target. This requires
21625 access to an unstripped copy of your program, and possibly any associated
21626 symbol files. Note that this section applies equally to both @code{target
21627 remote} mode and @code{target extended-remote} mode.
21629 Some remote targets (@pxref{qXfer executable filename read}, and
21630 @pxref{Host I/O Packets}) allow @value{GDBN} to access program files over
21631 the same connection used to communicate with @value{GDBN}. With such a
21632 target, if the remote program is unstripped, the only command you need is
21633 @code{target remote} (or @code{target extended-remote}).
21635 If the remote program is stripped, or the target does not support remote
21636 program file access, start up @value{GDBN} using the name of the local
21637 unstripped copy of your program as the first argument, or use the
21638 @code{file} command. Use @code{set sysroot} to specify the location (on
21639 the host) of target libraries (unless your @value{GDBN} was compiled with
21640 the correct sysroot using @code{--with-sysroot}). Alternatively, you
21641 may use @code{set solib-search-path} to specify how @value{GDBN} locates
21644 The symbol file and target libraries must exactly match the executable
21645 and libraries on the target, with one exception: the files on the host
21646 system should not be stripped, even if the files on the target system
21647 are. Mismatched or missing files will lead to confusing results
21648 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
21649 files may also prevent @code{gdbserver} from debugging multi-threaded
21652 @subsection Remote Connection Commands
21653 @cindex remote connection commands
21654 @value{GDBN} can communicate with the target over a serial line, a
21655 local Unix domain socket, or
21656 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
21657 each case, @value{GDBN} uses the same protocol for debugging your
21658 program; only the medium carrying the debugging packets varies. The
21659 @code{target remote} and @code{target extended-remote} commands
21660 establish a connection to the target. Both commands accept the same
21661 arguments, which indicate the medium to use:
21665 @item target remote @var{serial-device}
21666 @itemx target extended-remote @var{serial-device}
21667 @cindex serial line, @code{target remote}
21668 Use @var{serial-device} to communicate with the target. For example,
21669 to use a serial line connected to the device named @file{/dev/ttyb}:
21672 target remote /dev/ttyb
21675 If you're using a serial line, you may want to give @value{GDBN} the
21676 @samp{--baud} option, or use the @code{set serial baud} command
21677 (@pxref{Remote Configuration, set serial baud}) before the
21678 @code{target} command.
21680 @item target remote @var{local-socket}
21681 @itemx target extended-remote @var{local-socket}
21682 @cindex local socket, @code{target remote}
21683 @cindex Unix domain socket
21684 Use @var{local-socket} to communicate with the target. For example,
21685 to use a local Unix domain socket bound to the file system entry @file{/tmp/gdb-socket0}:
21688 target remote /tmp/gdb-socket0
21691 Note that this command has the same form as the command to connect
21692 to a serial line. @value{GDBN} will automatically determine which
21693 kind of file you have specified and will make the appropriate kind
21695 This feature is not available if the host system does not support
21696 Unix domain sockets.
21698 @item target remote @code{@var{host}:@var{port}}
21699 @itemx target remote @code{@var{[host]}:@var{port}}
21700 @itemx target remote @code{tcp:@var{host}:@var{port}}
21701 @itemx target remote @code{tcp:@var{[host]}:@var{port}}
21702 @itemx target remote @code{tcp4:@var{host}:@var{port}}
21703 @itemx target remote @code{tcp6:@var{host}:@var{port}}
21704 @itemx target remote @code{tcp6:@var{[host]}:@var{port}}
21705 @itemx target extended-remote @code{@var{host}:@var{port}}
21706 @itemx target extended-remote @code{@var{[host]}:@var{port}}
21707 @itemx target extended-remote @code{tcp:@var{host}:@var{port}}
21708 @itemx target extended-remote @code{tcp:@var{[host]}:@var{port}}
21709 @itemx target extended-remote @code{tcp4:@var{host}:@var{port}}
21710 @itemx target extended-remote @code{tcp6:@var{host}:@var{port}}
21711 @itemx target extended-remote @code{tcp6:@var{[host]}:@var{port}}
21712 @cindex @acronym{TCP} port, @code{target remote}
21713 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
21714 The @var{host} may be either a host name, a numeric @acronym{IPv4}
21715 address, or a numeric @acronym{IPv6} address (with or without the
21716 square brackets to separate the address from the port); @var{port}
21717 must be a decimal number. The @var{host} could be the target machine
21718 itself, if it is directly connected to the net, or it might be a
21719 terminal server which in turn has a serial line to the target.
21721 For example, to connect to port 2828 on a terminal server named
21725 target remote manyfarms:2828
21728 To connect to port 2828 on a terminal server whose address is
21729 @code{2001:0db8:85a3:0000:0000:8a2e:0370:7334}, you can either use the
21730 square bracket syntax:
21733 target remote [2001:0db8:85a3:0000:0000:8a2e:0370:7334]:2828
21737 or explicitly specify the @acronym{IPv6} protocol:
21740 target remote tcp6:2001:0db8:85a3:0000:0000:8a2e:0370:7334:2828
21743 This last example may be confusing to the reader, because there is no
21744 visible separation between the hostname and the port number.
21745 Therefore, we recommend the user to provide @acronym{IPv6} addresses
21746 using square brackets for clarity. However, it is important to
21747 mention that for @value{GDBN} there is no ambiguity: the number after
21748 the last colon is considered to be the port number.
21750 If your remote target is actually running on the same machine as your
21751 debugger session (e.g.@: a simulator for your target running on the
21752 same host), you can omit the hostname. For example, to connect to
21753 port 1234 on your local machine:
21756 target remote :1234
21760 Note that the colon is still required here.
21762 @item target remote @code{udp:@var{host}:@var{port}}
21763 @itemx target remote @code{udp:@var{[host]}:@var{port}}
21764 @itemx target remote @code{udp4:@var{host}:@var{port}}
21765 @itemx target remote @code{udp6:@var{[host]}:@var{port}}
21766 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
21767 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
21768 @itemx target extended-remote @code{udp:@var{[host]}:@var{port}}
21769 @itemx target extended-remote @code{udp4:@var{host}:@var{port}}
21770 @itemx target extended-remote @code{udp6:@var{host}:@var{port}}
21771 @itemx target extended-remote @code{udp6:@var{[host]}:@var{port}}
21772 @cindex @acronym{UDP} port, @code{target remote}
21773 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
21774 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
21777 target remote udp:manyfarms:2828
21780 When using a @acronym{UDP} connection for remote debugging, you should
21781 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
21782 can silently drop packets on busy or unreliable networks, which will
21783 cause havoc with your debugging session.
21785 @item target remote | @var{command}
21786 @itemx target extended-remote | @var{command}
21787 @cindex pipe, @code{target remote} to
21788 Run @var{command} in the background and communicate with it using a
21789 pipe. The @var{command} is a shell command, to be parsed and expanded
21790 by the system's command shell, @code{/bin/sh}; it should expect remote
21791 protocol packets on its standard input, and send replies on its
21792 standard output. You could use this to run a stand-alone simulator
21793 that speaks the remote debugging protocol, to make net connections
21794 using programs like @code{ssh}, or for other similar tricks.
21796 If @var{command} closes its standard output (perhaps by exiting),
21797 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
21798 program has already exited, this will have no effect.)
21802 @cindex interrupting remote programs
21803 @cindex remote programs, interrupting
21804 Whenever @value{GDBN} is waiting for the remote program, if you type the
21805 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
21806 program. This may or may not succeed, depending in part on the hardware
21807 and the serial drivers the remote system uses. If you type the
21808 interrupt character once again, @value{GDBN} displays this prompt:
21811 Interrupted while waiting for the program.
21812 Give up (and stop debugging it)? (y or n)
21815 In @code{target remote} mode, if you type @kbd{y}, @value{GDBN} abandons
21816 the remote debugging session. (If you decide you want to try again later,
21817 you can use @kbd{target remote} again to connect once more.) If you type
21818 @kbd{n}, @value{GDBN} goes back to waiting.
21820 In @code{target extended-remote} mode, typing @kbd{n} will leave
21821 @value{GDBN} connected to the target.
21824 @kindex detach (remote)
21826 When you have finished debugging the remote program, you can use the
21827 @code{detach} command to release it from @value{GDBN} control.
21828 Detaching from the target normally resumes its execution, but the results
21829 will depend on your particular remote stub. After the @code{detach}
21830 command in @code{target remote} mode, @value{GDBN} is free to connect to
21831 another target. In @code{target extended-remote} mode, @value{GDBN} is
21832 still connected to the target.
21836 The @code{disconnect} command closes the connection to the target, and
21837 the target is generally not resumed. It will wait for @value{GDBN}
21838 (this instance or another one) to connect and continue debugging. After
21839 the @code{disconnect} command, @value{GDBN} is again free to connect to
21842 @cindex send command to remote monitor
21843 @cindex extend @value{GDBN} for remote targets
21844 @cindex add new commands for external monitor
21846 @item monitor @var{cmd}
21847 This command allows you to send arbitrary commands directly to the
21848 remote monitor. Since @value{GDBN} doesn't care about the commands it
21849 sends like this, this command is the way to extend @value{GDBN}---you
21850 can add new commands that only the external monitor will understand
21854 @node File Transfer
21855 @section Sending files to a remote system
21856 @cindex remote target, file transfer
21857 @cindex file transfer
21858 @cindex sending files to remote systems
21860 Some remote targets offer the ability to transfer files over the same
21861 connection used to communicate with @value{GDBN}. This is convenient
21862 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
21863 running @code{gdbserver} over a network interface. For other targets,
21864 e.g.@: embedded devices with only a single serial port, this may be
21865 the only way to upload or download files.
21867 Not all remote targets support these commands.
21871 @item remote put @var{hostfile} @var{targetfile}
21872 Copy file @var{hostfile} from the host system (the machine running
21873 @value{GDBN}) to @var{targetfile} on the target system.
21876 @item remote get @var{targetfile} @var{hostfile}
21877 Copy file @var{targetfile} from the target system to @var{hostfile}
21878 on the host system.
21880 @kindex remote delete
21881 @item remote delete @var{targetfile}
21882 Delete @var{targetfile} from the target system.
21887 @section Using the @code{gdbserver} Program
21890 @cindex remote connection without stubs
21891 @code{gdbserver} is a control program for Unix-like systems, which
21892 allows you to connect your program with a remote @value{GDBN} via
21893 @code{target remote} or @code{target extended-remote}---but without
21894 linking in the usual debugging stub.
21896 @code{gdbserver} is not a complete replacement for the debugging stubs,
21897 because it requires essentially the same operating-system facilities
21898 that @value{GDBN} itself does. In fact, a system that can run
21899 @code{gdbserver} to connect to a remote @value{GDBN} could also run
21900 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
21901 because it is a much smaller program than @value{GDBN} itself. It is
21902 also easier to port than all of @value{GDBN}, so you may be able to get
21903 started more quickly on a new system by using @code{gdbserver}.
21904 Finally, if you develop code for real-time systems, you may find that
21905 the tradeoffs involved in real-time operation make it more convenient to
21906 do as much development work as possible on another system, for example
21907 by cross-compiling. You can use @code{gdbserver} to make a similar
21908 choice for debugging.
21910 @value{GDBN} and @code{gdbserver} communicate via either a serial line
21911 or a TCP connection, using the standard @value{GDBN} remote serial
21915 @emph{Warning:} @code{gdbserver} does not have any built-in security.
21916 Do not run @code{gdbserver} connected to any public network; a
21917 @value{GDBN} connection to @code{gdbserver} provides access to the
21918 target system with the same privileges as the user running
21922 @anchor{Running gdbserver}
21923 @subsection Running @code{gdbserver}
21924 @cindex arguments, to @code{gdbserver}
21925 @cindex @code{gdbserver}, command-line arguments
21927 Run @code{gdbserver} on the target system. You need a copy of the
21928 program you want to debug, including any libraries it requires.
21929 @code{gdbserver} does not need your program's symbol table, so you can
21930 strip the program if necessary to save space. @value{GDBN} on the host
21931 system does all the symbol handling.
21933 To use the server, you must tell it how to communicate with @value{GDBN};
21934 the name of your program; and the arguments for your program. The usual
21938 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
21941 @var{comm} is either a device name (to use a serial line), or a TCP
21942 hostname and portnumber, or @code{-} or @code{stdio} to use
21943 stdin/stdout of @code{gdbserver}.
21944 For example, to debug Emacs with the argument
21945 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
21949 target> gdbserver /dev/com1 emacs foo.txt
21952 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
21955 To use a TCP connection instead of a serial line:
21958 target> gdbserver host:2345 emacs foo.txt
21961 The only difference from the previous example is the first argument,
21962 specifying that you are communicating with the host @value{GDBN} via
21963 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
21964 expect a TCP connection from machine @samp{host} to local TCP port 2345.
21965 (Currently, the @samp{host} part is ignored.) You can choose any number
21966 you want for the port number as long as it does not conflict with any
21967 TCP ports already in use on the target system (for example, @code{23} is
21968 reserved for @code{telnet}).@footnote{If you choose a port number that
21969 conflicts with another service, @code{gdbserver} prints an error message
21970 and exits.} You must use the same port number with the host @value{GDBN}
21971 @code{target remote} command.
21973 The @code{stdio} connection is useful when starting @code{gdbserver}
21977 (gdb) target remote | ssh -T hostname gdbserver - hello
21980 The @samp{-T} option to ssh is provided because we don't need a remote pty,
21981 and we don't want escape-character handling. Ssh does this by default when
21982 a command is provided, the flag is provided to make it explicit.
21983 You could elide it if you want to.
21985 Programs started with stdio-connected gdbserver have @file{/dev/null} for
21986 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
21987 display through a pipe connected to gdbserver.
21988 Both @code{stdout} and @code{stderr} use the same pipe.
21990 @anchor{Attaching to a program}
21991 @subsubsection Attaching to a Running Program
21992 @cindex attach to a program, @code{gdbserver}
21993 @cindex @option{--attach}, @code{gdbserver} option
21995 On some targets, @code{gdbserver} can also attach to running programs.
21996 This is accomplished via the @code{--attach} argument. The syntax is:
21999 target> gdbserver --attach @var{comm} @var{pid}
22002 @var{pid} is the process ID of a currently running process. It isn't
22003 necessary to point @code{gdbserver} at a binary for the running process.
22005 In @code{target extended-remote} mode, you can also attach using the
22006 @value{GDBN} attach command
22007 (@pxref{Attaching in Types of Remote Connections}).
22010 You can debug processes by name instead of process ID if your target has the
22011 @code{pidof} utility:
22014 target> gdbserver --attach @var{comm} `pidof @var{program}`
22017 In case more than one copy of @var{program} is running, or @var{program}
22018 has multiple threads, most versions of @code{pidof} support the
22019 @code{-s} option to only return the first process ID.
22021 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
22023 This section applies only when @code{gdbserver} is run to listen on a TCP
22026 @code{gdbserver} normally terminates after all of its debugged processes have
22027 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
22028 extended-remote}, @code{gdbserver} stays running even with no processes left.
22029 @value{GDBN} normally terminates the spawned debugged process on its exit,
22030 which normally also terminates @code{gdbserver} in the @kbd{target remote}
22031 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
22032 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
22033 stays running even in the @kbd{target remote} mode.
22035 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
22036 Such reconnecting is useful for features like @ref{disconnected tracing}. For
22037 completeness, at most one @value{GDBN} can be connected at a time.
22039 @cindex @option{--once}, @code{gdbserver} option
22040 By default, @code{gdbserver} keeps the listening TCP port open, so that
22041 subsequent connections are possible. However, if you start @code{gdbserver}
22042 with the @option{--once} option, it will stop listening for any further
22043 connection attempts after connecting to the first @value{GDBN} session. This
22044 means no further connections to @code{gdbserver} will be possible after the
22045 first one. It also means @code{gdbserver} will terminate after the first
22046 connection with remote @value{GDBN} has closed, even for unexpectedly closed
22047 connections and even in the @kbd{target extended-remote} mode. The
22048 @option{--once} option allows reusing the same port number for connecting to
22049 multiple instances of @code{gdbserver} running on the same host, since each
22050 instance closes its port after the first connection.
22052 @anchor{Other Command-Line Arguments for gdbserver}
22053 @subsubsection Other Command-Line Arguments for @code{gdbserver}
22055 You can use the @option{--multi} option to start @code{gdbserver} without
22056 specifying a program to debug or a process to attach to. Then you can
22057 attach in @code{target extended-remote} mode and run or attach to a
22058 program. For more information,
22059 @pxref{--multi Option in Types of Remote Connnections}.
22061 @cindex @option{--debug}, @code{gdbserver} option
22062 The @option{--debug} option tells @code{gdbserver} to display extra
22063 status information about the debugging process.
22064 @cindex @option{--remote-debug}, @code{gdbserver} option
22065 The @option{--remote-debug} option tells @code{gdbserver} to display
22066 remote protocol debug output.
22067 @cindex @option{--debug-file}, @code{gdbserver} option
22068 @cindex @code{gdbserver}, send all debug output to a single file
22069 The @option{--debug-file=@var{filename}} option tells @code{gdbserver} to
22070 write any debug output to the given @var{filename}. These options are intended
22071 for @code{gdbserver} development and for bug reports to the developers.
22073 @cindex @option{--debug-format}, @code{gdbserver} option
22074 The @option{--debug-format=option1[,option2,...]} option tells
22075 @code{gdbserver} to include additional information in each output.
22076 Possible options are:
22080 Turn off all extra information in debugging output.
22082 Turn on all extra information in debugging output.
22084 Include a timestamp in each line of debugging output.
22087 Options are processed in order. Thus, for example, if @option{none}
22088 appears last then no additional information is added to debugging output.
22090 @cindex @option{--wrapper}, @code{gdbserver} option
22091 The @option{--wrapper} option specifies a wrapper to launch programs
22092 for debugging. The option should be followed by the name of the
22093 wrapper, then any command-line arguments to pass to the wrapper, then
22094 @kbd{--} indicating the end of the wrapper arguments.
22096 @code{gdbserver} runs the specified wrapper program with a combined
22097 command line including the wrapper arguments, then the name of the
22098 program to debug, then any arguments to the program. The wrapper
22099 runs until it executes your program, and then @value{GDBN} gains control.
22101 You can use any program that eventually calls @code{execve} with
22102 its arguments as a wrapper. Several standard Unix utilities do
22103 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
22104 with @code{exec "$@@"} will also work.
22106 For example, you can use @code{env} to pass an environment variable to
22107 the debugged program, without setting the variable in @code{gdbserver}'s
22111 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
22114 @cindex @option{--selftest}
22115 The @option{--selftest} option runs the self tests in @code{gdbserver}:
22118 $ gdbserver --selftest
22119 Ran 2 unit tests, 0 failed
22122 These tests are disabled in release.
22123 @subsection Connecting to @code{gdbserver}
22125 The basic procedure for connecting to the remote target is:
22129 Run @value{GDBN} on the host system.
22132 Make sure you have the necessary symbol files
22133 (@pxref{Host and target files}).
22134 Load symbols for your application using the @code{file} command before you
22135 connect. Use @code{set sysroot} to locate target libraries (unless your
22136 @value{GDBN} was compiled with the correct sysroot using
22137 @code{--with-sysroot}).
22140 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
22141 For TCP connections, you must start up @code{gdbserver} prior to using
22142 the @code{target} command. Otherwise you may get an error whose
22143 text depends on the host system, but which usually looks something like
22144 @samp{Connection refused}. Don't use the @code{load}
22145 command in @value{GDBN} when using @code{target remote} mode, since the
22146 program is already on the target.
22150 @anchor{Monitor Commands for gdbserver}
22151 @subsection Monitor Commands for @code{gdbserver}
22152 @cindex monitor commands, for @code{gdbserver}
22154 During a @value{GDBN} session using @code{gdbserver}, you can use the
22155 @code{monitor} command to send special requests to @code{gdbserver}.
22156 Here are the available commands.
22160 List the available monitor commands.
22162 @item monitor set debug 0
22163 @itemx monitor set debug 1
22164 Disable or enable general debugging messages.
22166 @item monitor set remote-debug 0
22167 @itemx monitor set remote-debug 1
22168 Disable or enable specific debugging messages associated with the remote
22169 protocol (@pxref{Remote Protocol}).
22171 @item monitor set debug-file filename
22172 @itemx monitor set debug-file
22173 Send any debug output to the given file, or to stderr.
22175 @item monitor set debug-format option1@r{[},option2,...@r{]}
22176 Specify additional text to add to debugging messages.
22177 Possible options are:
22181 Turn off all extra information in debugging output.
22183 Turn on all extra information in debugging output.
22185 Include a timestamp in each line of debugging output.
22188 Options are processed in order. Thus, for example, if @option{none}
22189 appears last then no additional information is added to debugging output.
22191 @item monitor set libthread-db-search-path [PATH]
22192 @cindex gdbserver, search path for @code{libthread_db}
22193 When this command is issued, @var{path} is a colon-separated list of
22194 directories to search for @code{libthread_db} (@pxref{Threads,,set
22195 libthread-db-search-path}). If you omit @var{path},
22196 @samp{libthread-db-search-path} will be reset to its default value.
22198 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
22199 not supported in @code{gdbserver}.
22202 Tell gdbserver to exit immediately. This command should be followed by
22203 @code{disconnect} to close the debugging session. @code{gdbserver} will
22204 detach from any attached processes and kill any processes it created.
22205 Use @code{monitor exit} to terminate @code{gdbserver} at the end
22206 of a multi-process mode debug session.
22210 @subsection Tracepoints support in @code{gdbserver}
22211 @cindex tracepoints support in @code{gdbserver}
22213 On some targets, @code{gdbserver} supports tracepoints, fast
22214 tracepoints and static tracepoints.
22216 For fast or static tracepoints to work, a special library called the
22217 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
22218 This library is built and distributed as an integral part of
22219 @code{gdbserver}. In addition, support for static tracepoints
22220 requires building the in-process agent library with static tracepoints
22221 support. At present, the UST (LTTng Userspace Tracer,
22222 @url{http://lttng.org/ust}) tracing engine is supported. This support
22223 is automatically available if UST development headers are found in the
22224 standard include path when @code{gdbserver} is built, or if
22225 @code{gdbserver} was explicitly configured using @option{--with-ust}
22226 to point at such headers. You can explicitly disable the support
22227 using @option{--with-ust=no}.
22229 There are several ways to load the in-process agent in your program:
22232 @item Specifying it as dependency at link time
22234 You can link your program dynamically with the in-process agent
22235 library. On most systems, this is accomplished by adding
22236 @code{-linproctrace} to the link command.
22238 @item Using the system's preloading mechanisms
22240 You can force loading the in-process agent at startup time by using
22241 your system's support for preloading shared libraries. Many Unixes
22242 support the concept of preloading user defined libraries. In most
22243 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
22244 in the environment. See also the description of @code{gdbserver}'s
22245 @option{--wrapper} command line option.
22247 @item Using @value{GDBN} to force loading the agent at run time
22249 On some systems, you can force the inferior to load a shared library,
22250 by calling a dynamic loader function in the inferior that takes care
22251 of dynamically looking up and loading a shared library. On most Unix
22252 systems, the function is @code{dlopen}. You'll use the @code{call}
22253 command for that. For example:
22256 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
22259 Note that on most Unix systems, for the @code{dlopen} function to be
22260 available, the program needs to be linked with @code{-ldl}.
22263 On systems that have a userspace dynamic loader, like most Unix
22264 systems, when you connect to @code{gdbserver} using @code{target
22265 remote}, you'll find that the program is stopped at the dynamic
22266 loader's entry point, and no shared library has been loaded in the
22267 program's address space yet, including the in-process agent. In that
22268 case, before being able to use any of the fast or static tracepoints
22269 features, you need to let the loader run and load the shared
22270 libraries. The simplest way to do that is to run the program to the
22271 main procedure. E.g., if debugging a C or C@t{++} program, start
22272 @code{gdbserver} like so:
22275 $ gdbserver :9999 myprogram
22278 Start GDB and connect to @code{gdbserver} like so, and run to main:
22282 (@value{GDBP}) target remote myhost:9999
22283 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
22284 (@value{GDBP}) b main
22285 (@value{GDBP}) continue
22288 The in-process tracing agent library should now be loaded into the
22289 process; you can confirm it with the @code{info sharedlibrary}
22290 command, which will list @file{libinproctrace.so} as loaded in the
22291 process. You are now ready to install fast tracepoints, list static
22292 tracepoint markers, probe static tracepoints markers, and start
22295 @node Remote Configuration
22296 @section Remote Configuration
22299 @kindex show remote
22300 This section documents the configuration options available when
22301 debugging remote programs. For the options related to the File I/O
22302 extensions of the remote protocol, see @ref{system,
22303 system-call-allowed}.
22306 @item set remoteaddresssize @var{bits}
22307 @cindex address size for remote targets
22308 @cindex bits in remote address
22309 Set the maximum size of address in a memory packet to the specified
22310 number of bits. @value{GDBN} will mask off the address bits above
22311 that number, when it passes addresses to the remote target. The
22312 default value is the number of bits in the target's address.
22314 @item show remoteaddresssize
22315 Show the current value of remote address size in bits.
22317 @item set serial baud @var{n}
22318 @cindex baud rate for remote targets
22319 Set the baud rate for the remote serial I/O to @var{n} baud. The
22320 value is used to set the speed of the serial port used for debugging
22323 @item show serial baud
22324 Show the current speed of the remote connection.
22326 @item set serial parity @var{parity}
22327 Set the parity for the remote serial I/O. Supported values of @var{parity} are:
22328 @code{even}, @code{none}, and @code{odd}. The default is @code{none}.
22330 @item show serial parity
22331 Show the current parity of the serial port.
22333 @item set remotebreak
22334 @cindex interrupt remote programs
22335 @cindex BREAK signal instead of Ctrl-C
22336 @anchor{set remotebreak}
22337 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
22338 when you type @kbd{Ctrl-c} to interrupt the program running
22339 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
22340 character instead. The default is off, since most remote systems
22341 expect to see @samp{Ctrl-C} as the interrupt signal.
22343 @item show remotebreak
22344 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
22345 interrupt the remote program.
22347 @item set remoteflow on
22348 @itemx set remoteflow off
22349 @kindex set remoteflow
22350 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
22351 on the serial port used to communicate to the remote target.
22353 @item show remoteflow
22354 @kindex show remoteflow
22355 Show the current setting of hardware flow control.
22357 @item set remotelogbase @var{base}
22358 Set the base (a.k.a.@: radix) of logging serial protocol
22359 communications to @var{base}. Supported values of @var{base} are:
22360 @code{ascii}, @code{octal}, and @code{hex}. The default is
22363 @item show remotelogbase
22364 Show the current setting of the radix for logging remote serial
22367 @item set remotelogfile @var{file}
22368 @cindex record serial communications on file
22369 Record remote serial communications on the named @var{file}. The
22370 default is not to record at all.
22372 @item show remotelogfile
22373 Show the current setting of the file name on which to record the
22374 serial communications.
22376 @item set remotetimeout @var{num}
22377 @cindex timeout for serial communications
22378 @cindex remote timeout
22379 Set the timeout limit to wait for the remote target to respond to
22380 @var{num} seconds. The default is 2 seconds.
22382 @item show remotetimeout
22383 Show the current number of seconds to wait for the remote target
22386 @cindex limit hardware breakpoints and watchpoints
22387 @cindex remote target, limit break- and watchpoints
22388 @anchor{set remote hardware-watchpoint-limit}
22389 @anchor{set remote hardware-breakpoint-limit}
22390 @item set remote hardware-watchpoint-limit @var{limit}
22391 @itemx set remote hardware-breakpoint-limit @var{limit}
22392 Restrict @value{GDBN} to using @var{limit} remote hardware watchpoints
22393 or breakpoints. The @var{limit} can be set to 0 to disable hardware
22394 watchpoints or breakpoints, and @code{unlimited} for unlimited
22395 watchpoints or breakpoints.
22397 @item show remote hardware-watchpoint-limit
22398 @itemx show remote hardware-breakpoint-limit
22399 Show the current limit for the number of hardware watchpoints or
22400 breakpoints that @value{GDBN} can use.
22402 @cindex limit hardware watchpoints length
22403 @cindex remote target, limit watchpoints length
22404 @anchor{set remote hardware-watchpoint-length-limit}
22405 @item set remote hardware-watchpoint-length-limit @var{limit}
22406 Restrict @value{GDBN} to using @var{limit} bytes for the maximum
22407 length of a remote hardware watchpoint. A @var{limit} of 0 disables
22408 hardware watchpoints and @code{unlimited} allows watchpoints of any
22411 @item show remote hardware-watchpoint-length-limit
22412 Show the current limit (in bytes) of the maximum length of
22413 a remote hardware watchpoint.
22415 @item set remote exec-file @var{filename}
22416 @itemx show remote exec-file
22417 @anchor{set remote exec-file}
22418 @cindex executable file, for remote target
22419 Select the file used for @code{run} with @code{target
22420 extended-remote}. This should be set to a filename valid on the
22421 target system. If it is not set, the target will use a default
22422 filename (e.g.@: the last program run).
22424 @item set remote interrupt-sequence
22425 @cindex interrupt remote programs
22426 @cindex select Ctrl-C, BREAK or BREAK-g
22427 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
22428 @samp{BREAK-g} as the
22429 sequence to the remote target in order to interrupt the execution.
22430 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
22431 is high level of serial line for some certain time.
22432 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
22433 It is @code{BREAK} signal followed by character @code{g}.
22435 @item show interrupt-sequence
22436 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
22437 is sent by @value{GDBN} to interrupt the remote program.
22438 @code{BREAK-g} is BREAK signal followed by @code{g} and
22439 also known as Magic SysRq g.
22441 @item set remote interrupt-on-connect
22442 @cindex send interrupt-sequence on start
22443 Specify whether interrupt-sequence is sent to remote target when
22444 @value{GDBN} connects to it. This is mostly needed when you debug
22445 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
22446 which is known as Magic SysRq g in order to connect @value{GDBN}.
22448 @item show interrupt-on-connect
22449 Show whether interrupt-sequence is sent
22450 to remote target when @value{GDBN} connects to it.
22454 @item set tcp auto-retry on
22455 @cindex auto-retry, for remote TCP target
22456 Enable auto-retry for remote TCP connections. This is useful if the remote
22457 debugging agent is launched in parallel with @value{GDBN}; there is a race
22458 condition because the agent may not become ready to accept the connection
22459 before @value{GDBN} attempts to connect. When auto-retry is
22460 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
22461 to establish the connection using the timeout specified by
22462 @code{set tcp connect-timeout}.
22464 @item set tcp auto-retry off
22465 Do not auto-retry failed TCP connections.
22467 @item show tcp auto-retry
22468 Show the current auto-retry setting.
22470 @item set tcp connect-timeout @var{seconds}
22471 @itemx set tcp connect-timeout unlimited
22472 @cindex connection timeout, for remote TCP target
22473 @cindex timeout, for remote target connection
22474 Set the timeout for establishing a TCP connection to the remote target to
22475 @var{seconds}. The timeout affects both polling to retry failed connections
22476 (enabled by @code{set tcp auto-retry on}) and waiting for connections
22477 that are merely slow to complete, and represents an approximate cumulative
22478 value. If @var{seconds} is @code{unlimited}, there is no timeout and
22479 @value{GDBN} will keep attempting to establish a connection forever,
22480 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
22482 @item show tcp connect-timeout
22483 Show the current connection timeout setting.
22486 @cindex remote packets, enabling and disabling
22487 The @value{GDBN} remote protocol autodetects the packets supported by
22488 your debugging stub. If you need to override the autodetection, you
22489 can use these commands to enable or disable individual packets. Each
22490 packet can be set to @samp{on} (the remote target supports this
22491 packet), @samp{off} (the remote target does not support this packet),
22492 or @samp{auto} (detect remote target support for this packet). They
22493 all default to @samp{auto}. For more information about each packet,
22494 see @ref{Remote Protocol}.
22496 During normal use, you should not have to use any of these commands.
22497 If you do, that may be a bug in your remote debugging stub, or a bug
22498 in @value{GDBN}. You may want to report the problem to the
22499 @value{GDBN} developers.
22501 For each packet @var{name}, the command to enable or disable the
22502 packet is @code{set remote @var{name}-packet}. The available settings
22505 @multitable @columnfractions 0.28 0.32 0.25
22508 @tab Related Features
22510 @item @code{fetch-register}
22512 @tab @code{info registers}
22514 @item @code{set-register}
22518 @item @code{binary-download}
22520 @tab @code{load}, @code{set}
22522 @item @code{read-aux-vector}
22523 @tab @code{qXfer:auxv:read}
22524 @tab @code{info auxv}
22526 @item @code{symbol-lookup}
22527 @tab @code{qSymbol}
22528 @tab Detecting multiple threads
22530 @item @code{attach}
22531 @tab @code{vAttach}
22534 @item @code{verbose-resume}
22536 @tab Stepping or resuming multiple threads
22542 @item @code{software-breakpoint}
22546 @item @code{hardware-breakpoint}
22550 @item @code{write-watchpoint}
22554 @item @code{read-watchpoint}
22558 @item @code{access-watchpoint}
22562 @item @code{pid-to-exec-file}
22563 @tab @code{qXfer:exec-file:read}
22564 @tab @code{attach}, @code{run}
22566 @item @code{target-features}
22567 @tab @code{qXfer:features:read}
22568 @tab @code{set architecture}
22570 @item @code{library-info}
22571 @tab @code{qXfer:libraries:read}
22572 @tab @code{info sharedlibrary}
22574 @item @code{memory-map}
22575 @tab @code{qXfer:memory-map:read}
22576 @tab @code{info mem}
22578 @item @code{read-sdata-object}
22579 @tab @code{qXfer:sdata:read}
22580 @tab @code{print $_sdata}
22582 @item @code{read-siginfo-object}
22583 @tab @code{qXfer:siginfo:read}
22584 @tab @code{print $_siginfo}
22586 @item @code{write-siginfo-object}
22587 @tab @code{qXfer:siginfo:write}
22588 @tab @code{set $_siginfo}
22590 @item @code{threads}
22591 @tab @code{qXfer:threads:read}
22592 @tab @code{info threads}
22594 @item @code{get-thread-local-@*storage-address}
22595 @tab @code{qGetTLSAddr}
22596 @tab Displaying @code{__thread} variables
22598 @item @code{get-thread-information-block-address}
22599 @tab @code{qGetTIBAddr}
22600 @tab Display MS-Windows Thread Information Block.
22602 @item @code{search-memory}
22603 @tab @code{qSearch:memory}
22606 @item @code{supported-packets}
22607 @tab @code{qSupported}
22608 @tab Remote communications parameters
22610 @item @code{catch-syscalls}
22611 @tab @code{QCatchSyscalls}
22612 @tab @code{catch syscall}
22614 @item @code{pass-signals}
22615 @tab @code{QPassSignals}
22616 @tab @code{handle @var{signal}}
22618 @item @code{program-signals}
22619 @tab @code{QProgramSignals}
22620 @tab @code{handle @var{signal}}
22622 @item @code{hostio-close-packet}
22623 @tab @code{vFile:close}
22624 @tab @code{remote get}, @code{remote put}
22626 @item @code{hostio-open-packet}
22627 @tab @code{vFile:open}
22628 @tab @code{remote get}, @code{remote put}
22630 @item @code{hostio-pread-packet}
22631 @tab @code{vFile:pread}
22632 @tab @code{remote get}, @code{remote put}
22634 @item @code{hostio-pwrite-packet}
22635 @tab @code{vFile:pwrite}
22636 @tab @code{remote get}, @code{remote put}
22638 @item @code{hostio-unlink-packet}
22639 @tab @code{vFile:unlink}
22640 @tab @code{remote delete}
22642 @item @code{hostio-readlink-packet}
22643 @tab @code{vFile:readlink}
22646 @item @code{hostio-fstat-packet}
22647 @tab @code{vFile:fstat}
22650 @item @code{hostio-setfs-packet}
22651 @tab @code{vFile:setfs}
22654 @item @code{noack-packet}
22655 @tab @code{QStartNoAckMode}
22656 @tab Packet acknowledgment
22658 @item @code{osdata}
22659 @tab @code{qXfer:osdata:read}
22660 @tab @code{info os}
22662 @item @code{query-attached}
22663 @tab @code{qAttached}
22664 @tab Querying remote process attach state.
22666 @item @code{trace-buffer-size}
22667 @tab @code{QTBuffer:size}
22668 @tab @code{set trace-buffer-size}
22670 @item @code{trace-status}
22671 @tab @code{qTStatus}
22672 @tab @code{tstatus}
22674 @item @code{traceframe-info}
22675 @tab @code{qXfer:traceframe-info:read}
22676 @tab Traceframe info
22678 @item @code{install-in-trace}
22679 @tab @code{InstallInTrace}
22680 @tab Install tracepoint in tracing
22682 @item @code{disable-randomization}
22683 @tab @code{QDisableRandomization}
22684 @tab @code{set disable-randomization}
22686 @item @code{startup-with-shell}
22687 @tab @code{QStartupWithShell}
22688 @tab @code{set startup-with-shell}
22690 @item @code{environment-hex-encoded}
22691 @tab @code{QEnvironmentHexEncoded}
22692 @tab @code{set environment}
22694 @item @code{environment-unset}
22695 @tab @code{QEnvironmentUnset}
22696 @tab @code{unset environment}
22698 @item @code{environment-reset}
22699 @tab @code{QEnvironmentReset}
22700 @tab @code{Reset the inferior environment (i.e., unset user-set variables)}
22702 @item @code{set-working-dir}
22703 @tab @code{QSetWorkingDir}
22704 @tab @code{set cwd}
22706 @item @code{conditional-breakpoints-packet}
22707 @tab @code{Z0 and Z1}
22708 @tab @code{Support for target-side breakpoint condition evaluation}
22710 @item @code{multiprocess-extensions}
22711 @tab @code{multiprocess extensions}
22712 @tab Debug multiple processes and remote process PID awareness
22714 @item @code{swbreak-feature}
22715 @tab @code{swbreak stop reason}
22718 @item @code{hwbreak-feature}
22719 @tab @code{hwbreak stop reason}
22722 @item @code{fork-event-feature}
22723 @tab @code{fork stop reason}
22726 @item @code{vfork-event-feature}
22727 @tab @code{vfork stop reason}
22730 @item @code{exec-event-feature}
22731 @tab @code{exec stop reason}
22734 @item @code{thread-events}
22735 @tab @code{QThreadEvents}
22736 @tab Tracking thread lifetime.
22738 @item @code{no-resumed-stop-reply}
22739 @tab @code{no resumed thread left stop reply}
22740 @tab Tracking thread lifetime.
22745 @section Implementing a Remote Stub
22747 @cindex debugging stub, example
22748 @cindex remote stub, example
22749 @cindex stub example, remote debugging
22750 The stub files provided with @value{GDBN} implement the target side of the
22751 communication protocol, and the @value{GDBN} side is implemented in the
22752 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
22753 these subroutines to communicate, and ignore the details. (If you're
22754 implementing your own stub file, you can still ignore the details: start
22755 with one of the existing stub files. @file{sparc-stub.c} is the best
22756 organized, and therefore the easiest to read.)
22758 @cindex remote serial debugging, overview
22759 To debug a program running on another machine (the debugging
22760 @dfn{target} machine), you must first arrange for all the usual
22761 prerequisites for the program to run by itself. For example, for a C
22766 A startup routine to set up the C runtime environment; these usually
22767 have a name like @file{crt0}. The startup routine may be supplied by
22768 your hardware supplier, or you may have to write your own.
22771 A C subroutine library to support your program's
22772 subroutine calls, notably managing input and output.
22775 A way of getting your program to the other machine---for example, a
22776 download program. These are often supplied by the hardware
22777 manufacturer, but you may have to write your own from hardware
22781 The next step is to arrange for your program to use a serial port to
22782 communicate with the machine where @value{GDBN} is running (the @dfn{host}
22783 machine). In general terms, the scheme looks like this:
22787 @value{GDBN} already understands how to use this protocol; when everything
22788 else is set up, you can simply use the @samp{target remote} command
22789 (@pxref{Targets,,Specifying a Debugging Target}).
22791 @item On the target,
22792 you must link with your program a few special-purpose subroutines that
22793 implement the @value{GDBN} remote serial protocol. The file containing these
22794 subroutines is called a @dfn{debugging stub}.
22796 On certain remote targets, you can use an auxiliary program
22797 @code{gdbserver} instead of linking a stub into your program.
22798 @xref{Server,,Using the @code{gdbserver} Program}, for details.
22801 The debugging stub is specific to the architecture of the remote
22802 machine; for example, use @file{sparc-stub.c} to debug programs on
22805 @cindex remote serial stub list
22806 These working remote stubs are distributed with @value{GDBN}:
22811 @cindex @file{i386-stub.c}
22814 For Intel 386 and compatible architectures.
22817 @cindex @file{m68k-stub.c}
22818 @cindex Motorola 680x0
22820 For Motorola 680x0 architectures.
22823 @cindex @file{sh-stub.c}
22826 For Renesas SH architectures.
22829 @cindex @file{sparc-stub.c}
22831 For @sc{sparc} architectures.
22833 @item sparcl-stub.c
22834 @cindex @file{sparcl-stub.c}
22837 For Fujitsu @sc{sparclite} architectures.
22841 The @file{README} file in the @value{GDBN} distribution may list other
22842 recently added stubs.
22845 * Stub Contents:: What the stub can do for you
22846 * Bootstrapping:: What you must do for the stub
22847 * Debug Session:: Putting it all together
22850 @node Stub Contents
22851 @subsection What the Stub Can Do for You
22853 @cindex remote serial stub
22854 The debugging stub for your architecture supplies these three
22858 @item set_debug_traps
22859 @findex set_debug_traps
22860 @cindex remote serial stub, initialization
22861 This routine arranges for @code{handle_exception} to run when your
22862 program stops. You must call this subroutine explicitly in your
22863 program's startup code.
22865 @item handle_exception
22866 @findex handle_exception
22867 @cindex remote serial stub, main routine
22868 This is the central workhorse, but your program never calls it
22869 explicitly---the setup code arranges for @code{handle_exception} to
22870 run when a trap is triggered.
22872 @code{handle_exception} takes control when your program stops during
22873 execution (for example, on a breakpoint), and mediates communications
22874 with @value{GDBN} on the host machine. This is where the communications
22875 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
22876 representative on the target machine. It begins by sending summary
22877 information on the state of your program, then continues to execute,
22878 retrieving and transmitting any information @value{GDBN} needs, until you
22879 execute a @value{GDBN} command that makes your program resume; at that point,
22880 @code{handle_exception} returns control to your own code on the target
22884 @cindex @code{breakpoint} subroutine, remote
22885 Use this auxiliary subroutine to make your program contain a
22886 breakpoint. Depending on the particular situation, this may be the only
22887 way for @value{GDBN} to get control. For instance, if your target
22888 machine has some sort of interrupt button, you won't need to call this;
22889 pressing the interrupt button transfers control to
22890 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
22891 simply receiving characters on the serial port may also trigger a trap;
22892 again, in that situation, you don't need to call @code{breakpoint} from
22893 your own program---simply running @samp{target remote} from the host
22894 @value{GDBN} session gets control.
22896 Call @code{breakpoint} if none of these is true, or if you simply want
22897 to make certain your program stops at a predetermined point for the
22898 start of your debugging session.
22901 @node Bootstrapping
22902 @subsection What You Must Do for the Stub
22904 @cindex remote stub, support routines
22905 The debugging stubs that come with @value{GDBN} are set up for a particular
22906 chip architecture, but they have no information about the rest of your
22907 debugging target machine.
22909 First of all you need to tell the stub how to communicate with the
22913 @item int getDebugChar()
22914 @findex getDebugChar
22915 Write this subroutine to read a single character from the serial port.
22916 It may be identical to @code{getchar} for your target system; a
22917 different name is used to allow you to distinguish the two if you wish.
22919 @item void putDebugChar(int)
22920 @findex putDebugChar
22921 Write this subroutine to write a single character to the serial port.
22922 It may be identical to @code{putchar} for your target system; a
22923 different name is used to allow you to distinguish the two if you wish.
22926 @cindex control C, and remote debugging
22927 @cindex interrupting remote targets
22928 If you want @value{GDBN} to be able to stop your program while it is
22929 running, you need to use an interrupt-driven serial driver, and arrange
22930 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
22931 character). That is the character which @value{GDBN} uses to tell the
22932 remote system to stop.
22934 Getting the debugging target to return the proper status to @value{GDBN}
22935 probably requires changes to the standard stub; one quick and dirty way
22936 is to just execute a breakpoint instruction (the ``dirty'' part is that
22937 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
22939 Other routines you need to supply are:
22942 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
22943 @findex exceptionHandler
22944 Write this function to install @var{exception_address} in the exception
22945 handling tables. You need to do this because the stub does not have any
22946 way of knowing what the exception handling tables on your target system
22947 are like (for example, the processor's table might be in @sc{rom},
22948 containing entries which point to a table in @sc{ram}).
22949 The @var{exception_number} specifies the exception which should be changed;
22950 its meaning is architecture-dependent (for example, different numbers
22951 might represent divide by zero, misaligned access, etc). When this
22952 exception occurs, control should be transferred directly to
22953 @var{exception_address}, and the processor state (stack, registers,
22954 and so on) should be just as it is when a processor exception occurs. So if
22955 you want to use a jump instruction to reach @var{exception_address}, it
22956 should be a simple jump, not a jump to subroutine.
22958 For the 386, @var{exception_address} should be installed as an interrupt
22959 gate so that interrupts are masked while the handler runs. The gate
22960 should be at privilege level 0 (the most privileged level). The
22961 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
22962 help from @code{exceptionHandler}.
22964 @item void flush_i_cache()
22965 @findex flush_i_cache
22966 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
22967 instruction cache, if any, on your target machine. If there is no
22968 instruction cache, this subroutine may be a no-op.
22970 On target machines that have instruction caches, @value{GDBN} requires this
22971 function to make certain that the state of your program is stable.
22975 You must also make sure this library routine is available:
22978 @item void *memset(void *, int, int)
22980 This is the standard library function @code{memset} that sets an area of
22981 memory to a known value. If you have one of the free versions of
22982 @code{libc.a}, @code{memset} can be found there; otherwise, you must
22983 either obtain it from your hardware manufacturer, or write your own.
22986 If you do not use the GNU C compiler, you may need other standard
22987 library subroutines as well; this varies from one stub to another,
22988 but in general the stubs are likely to use any of the common library
22989 subroutines which @code{@value{NGCC}} generates as inline code.
22992 @node Debug Session
22993 @subsection Putting it All Together
22995 @cindex remote serial debugging summary
22996 In summary, when your program is ready to debug, you must follow these
23001 Make sure you have defined the supporting low-level routines
23002 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
23004 @code{getDebugChar}, @code{putDebugChar},
23005 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
23009 Insert these lines in your program's startup code, before the main
23010 procedure is called:
23017 On some machines, when a breakpoint trap is raised, the hardware
23018 automatically makes the PC point to the instruction after the
23019 breakpoint. If your machine doesn't do that, you may need to adjust
23020 @code{handle_exception} to arrange for it to return to the instruction
23021 after the breakpoint on this first invocation, so that your program
23022 doesn't keep hitting the initial breakpoint instead of making
23026 For the 680x0 stub only, you need to provide a variable called
23027 @code{exceptionHook}. Normally you just use:
23030 void (*exceptionHook)() = 0;
23034 but if before calling @code{set_debug_traps}, you set it to point to a
23035 function in your program, that function is called when
23036 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
23037 error). The function indicated by @code{exceptionHook} is called with
23038 one parameter: an @code{int} which is the exception number.
23041 Compile and link together: your program, the @value{GDBN} debugging stub for
23042 your target architecture, and the supporting subroutines.
23045 Make sure you have a serial connection between your target machine and
23046 the @value{GDBN} host, and identify the serial port on the host.
23049 @c The "remote" target now provides a `load' command, so we should
23050 @c document that. FIXME.
23051 Download your program to your target machine (or get it there by
23052 whatever means the manufacturer provides), and start it.
23055 Start @value{GDBN} on the host, and connect to the target
23056 (@pxref{Connecting,,Connecting to a Remote Target}).
23060 @node Configurations
23061 @chapter Configuration-Specific Information
23063 While nearly all @value{GDBN} commands are available for all native and
23064 cross versions of the debugger, there are some exceptions. This chapter
23065 describes things that are only available in certain configurations.
23067 There are three major categories of configurations: native
23068 configurations, where the host and target are the same, embedded
23069 operating system configurations, which are usually the same for several
23070 different processor architectures, and bare embedded processors, which
23071 are quite different from each other.
23076 * Embedded Processors::
23083 This section describes details specific to particular native
23087 * BSD libkvm Interface:: Debugging BSD kernel memory images
23088 * Process Information:: Process information
23089 * DJGPP Native:: Features specific to the DJGPP port
23090 * Cygwin Native:: Features specific to the Cygwin port
23091 * Hurd Native:: Features specific to @sc{gnu} Hurd
23092 * Darwin:: Features specific to Darwin
23093 * FreeBSD:: Features specific to FreeBSD
23096 @node BSD libkvm Interface
23097 @subsection BSD libkvm Interface
23100 @cindex kernel memory image
23101 @cindex kernel crash dump
23103 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
23104 interface that provides a uniform interface for accessing kernel virtual
23105 memory images, including live systems and crash dumps. @value{GDBN}
23106 uses this interface to allow you to debug live kernels and kernel crash
23107 dumps on many native BSD configurations. This is implemented as a
23108 special @code{kvm} debugging target. For debugging a live system, load
23109 the currently running kernel into @value{GDBN} and connect to the
23113 (@value{GDBP}) @b{target kvm}
23116 For debugging crash dumps, provide the file name of the crash dump as an
23120 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
23123 Once connected to the @code{kvm} target, the following commands are
23129 Set current context from the @dfn{Process Control Block} (PCB) address.
23132 Set current context from proc address. This command isn't available on
23133 modern FreeBSD systems.
23136 @node Process Information
23137 @subsection Process Information
23139 @cindex examine process image
23140 @cindex process info via @file{/proc}
23142 Some operating systems provide interfaces to fetch additional
23143 information about running processes beyond memory and per-thread
23144 register state. If @value{GDBN} is configured for an operating system
23145 with a supported interface, the command @code{info proc} is available
23146 to report information about the process running your program, or about
23147 any process running on your system.
23149 One supported interface is a facility called @samp{/proc} that can be
23150 used to examine the image of a running process using file-system
23151 subroutines. This facility is supported on @sc{gnu}/Linux and Solaris
23154 On FreeBSD systems, system control nodes are used to query process
23157 In addition, some systems may provide additional process information
23158 in core files. Note that a core file may include a subset of the
23159 information available from a live process. Process information is
23160 currently avaiable from cores created on @sc{gnu}/Linux and FreeBSD
23167 @itemx info proc @var{process-id}
23168 Summarize available information about a process. If a
23169 process ID is specified by @var{process-id}, display information about
23170 that process; otherwise display information about the program being
23171 debugged. The summary includes the debugged process ID, the command
23172 line used to invoke it, its current working directory, and its
23173 executable file's absolute file name.
23175 On some systems, @var{process-id} can be of the form
23176 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
23177 within a process. If the optional @var{pid} part is missing, it means
23178 a thread from the process being debugged (the leading @samp{/} still
23179 needs to be present, or else @value{GDBN} will interpret the number as
23180 a process ID rather than a thread ID).
23182 @item info proc cmdline
23183 @cindex info proc cmdline
23184 Show the original command line of the process. This command is
23185 supported on @sc{gnu}/Linux and FreeBSD.
23187 @item info proc cwd
23188 @cindex info proc cwd
23189 Show the current working directory of the process. This command is
23190 supported on @sc{gnu}/Linux and FreeBSD.
23192 @item info proc exe
23193 @cindex info proc exe
23194 Show the name of executable of the process. This command is supported
23195 on @sc{gnu}/Linux and FreeBSD.
23197 @item info proc files
23198 @cindex info proc files
23199 Show the file descriptors open by the process. For each open file
23200 descriptor, @value{GDBN} shows its number, type (file, directory,
23201 character device, socket), file pointer offset, and the name of the
23202 resource open on the descriptor. The resource name can be a file name
23203 (for files, directories, and devices) or a protocol followed by socket
23204 address (for network connections). This command is supported on
23207 This example shows the open file descriptors for a process using a
23208 tty for standard input and output as well as two network sockets:
23211 (gdb) info proc files 22136
23215 FD Type Offset Flags Name
23216 text file - r-------- /usr/bin/ssh
23217 ctty chr - rw------- /dev/pts/20
23218 cwd dir - r-------- /usr/home/john
23219 root dir - r-------- /
23220 0 chr 0x32933a4 rw------- /dev/pts/20
23221 1 chr 0x32933a4 rw------- /dev/pts/20
23222 2 chr 0x32933a4 rw------- /dev/pts/20
23223 3 socket 0x0 rw----n-- tcp4 10.0.1.2:53014 -> 10.0.1.10:22
23224 4 socket 0x0 rw------- unix stream:/tmp/ssh-FIt89oAzOn5f/agent.2456
23227 @item info proc mappings
23228 @cindex memory address space mappings
23229 Report the memory address space ranges accessible in a process. On
23230 Solaris and FreeBSD systems, each memory range includes information on
23231 whether the process has read, write, or execute access rights to each
23232 range. On @sc{gnu}/Linux and FreeBSD systems, each memory range
23233 includes the object file which is mapped to that range.
23235 @item info proc stat
23236 @itemx info proc status
23237 @cindex process detailed status information
23238 Show additional process-related information, including the user ID and
23239 group ID; virtual memory usage; the signals that are pending, blocked,
23240 and ignored; its TTY; its consumption of system and user time; its
23241 stack size; its @samp{nice} value; etc. These commands are supported
23242 on @sc{gnu}/Linux and FreeBSD.
23244 For @sc{gnu}/Linux systems, see the @samp{proc} man page for more
23245 information (type @kbd{man 5 proc} from your shell prompt).
23247 For FreeBSD systems, @code{info proc stat} is an alias for @code{info
23250 @item info proc all
23251 Show all the information about the process described under all of the
23252 above @code{info proc} subcommands.
23255 @comment These sub-options of 'info proc' were not included when
23256 @comment procfs.c was re-written. Keep their descriptions around
23257 @comment against the day when someone finds the time to put them back in.
23258 @kindex info proc times
23259 @item info proc times
23260 Starting time, user CPU time, and system CPU time for your program and
23263 @kindex info proc id
23265 Report on the process IDs related to your program: its own process ID,
23266 the ID of its parent, the process group ID, and the session ID.
23269 @item set procfs-trace
23270 @kindex set procfs-trace
23271 @cindex @code{procfs} API calls
23272 This command enables and disables tracing of @code{procfs} API calls.
23274 @item show procfs-trace
23275 @kindex show procfs-trace
23276 Show the current state of @code{procfs} API call tracing.
23278 @item set procfs-file @var{file}
23279 @kindex set procfs-file
23280 Tell @value{GDBN} to write @code{procfs} API trace to the named
23281 @var{file}. @value{GDBN} appends the trace info to the previous
23282 contents of the file. The default is to display the trace on the
23285 @item show procfs-file
23286 @kindex show procfs-file
23287 Show the file to which @code{procfs} API trace is written.
23289 @item proc-trace-entry
23290 @itemx proc-trace-exit
23291 @itemx proc-untrace-entry
23292 @itemx proc-untrace-exit
23293 @kindex proc-trace-entry
23294 @kindex proc-trace-exit
23295 @kindex proc-untrace-entry
23296 @kindex proc-untrace-exit
23297 These commands enable and disable tracing of entries into and exits
23298 from the @code{syscall} interface.
23301 @kindex info pidlist
23302 @cindex process list, QNX Neutrino
23303 For QNX Neutrino only, this command displays the list of all the
23304 processes and all the threads within each process.
23307 @kindex info meminfo
23308 @cindex mapinfo list, QNX Neutrino
23309 For QNX Neutrino only, this command displays the list of all mapinfos.
23313 @subsection Features for Debugging @sc{djgpp} Programs
23314 @cindex @sc{djgpp} debugging
23315 @cindex native @sc{djgpp} debugging
23316 @cindex MS-DOS-specific commands
23319 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
23320 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
23321 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
23322 top of real-mode DOS systems and their emulations.
23324 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
23325 defines a few commands specific to the @sc{djgpp} port. This
23326 subsection describes those commands.
23331 This is a prefix of @sc{djgpp}-specific commands which print
23332 information about the target system and important OS structures.
23335 @cindex MS-DOS system info
23336 @cindex free memory information (MS-DOS)
23337 @item info dos sysinfo
23338 This command displays assorted information about the underlying
23339 platform: the CPU type and features, the OS version and flavor, the
23340 DPMI version, and the available conventional and DPMI memory.
23345 @cindex segment descriptor tables
23346 @cindex descriptor tables display
23348 @itemx info dos ldt
23349 @itemx info dos idt
23350 These 3 commands display entries from, respectively, Global, Local,
23351 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
23352 tables are data structures which store a descriptor for each segment
23353 that is currently in use. The segment's selector is an index into a
23354 descriptor table; the table entry for that index holds the
23355 descriptor's base address and limit, and its attributes and access
23358 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
23359 segment (used for both data and the stack), and a DOS segment (which
23360 allows access to DOS/BIOS data structures and absolute addresses in
23361 conventional memory). However, the DPMI host will usually define
23362 additional segments in order to support the DPMI environment.
23364 @cindex garbled pointers
23365 These commands allow to display entries from the descriptor tables.
23366 Without an argument, all entries from the specified table are
23367 displayed. An argument, which should be an integer expression, means
23368 display a single entry whose index is given by the argument. For
23369 example, here's a convenient way to display information about the
23370 debugged program's data segment:
23373 @exdent @code{(@value{GDBP}) info dos ldt $ds}
23374 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
23378 This comes in handy when you want to see whether a pointer is outside
23379 the data segment's limit (i.e.@: @dfn{garbled}).
23381 @cindex page tables display (MS-DOS)
23383 @itemx info dos pte
23384 These two commands display entries from, respectively, the Page
23385 Directory and the Page Tables. Page Directories and Page Tables are
23386 data structures which control how virtual memory addresses are mapped
23387 into physical addresses. A Page Table includes an entry for every
23388 page of memory that is mapped into the program's address space; there
23389 may be several Page Tables, each one holding up to 4096 entries. A
23390 Page Directory has up to 4096 entries, one each for every Page Table
23391 that is currently in use.
23393 Without an argument, @kbd{info dos pde} displays the entire Page
23394 Directory, and @kbd{info dos pte} displays all the entries in all of
23395 the Page Tables. An argument, an integer expression, given to the
23396 @kbd{info dos pde} command means display only that entry from the Page
23397 Directory table. An argument given to the @kbd{info dos pte} command
23398 means display entries from a single Page Table, the one pointed to by
23399 the specified entry in the Page Directory.
23401 @cindex direct memory access (DMA) on MS-DOS
23402 These commands are useful when your program uses @dfn{DMA} (Direct
23403 Memory Access), which needs physical addresses to program the DMA
23406 These commands are supported only with some DPMI servers.
23408 @cindex physical address from linear address
23409 @item info dos address-pte @var{addr}
23410 This command displays the Page Table entry for a specified linear
23411 address. The argument @var{addr} is a linear address which should
23412 already have the appropriate segment's base address added to it,
23413 because this command accepts addresses which may belong to @emph{any}
23414 segment. For example, here's how to display the Page Table entry for
23415 the page where a variable @code{i} is stored:
23418 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
23419 @exdent @code{Page Table entry for address 0x11a00d30:}
23420 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
23424 This says that @code{i} is stored at offset @code{0xd30} from the page
23425 whose physical base address is @code{0x02698000}, and shows all the
23426 attributes of that page.
23428 Note that you must cast the addresses of variables to a @code{char *},
23429 since otherwise the value of @code{__djgpp_base_address}, the base
23430 address of all variables and functions in a @sc{djgpp} program, will
23431 be added using the rules of C pointer arithmetics: if @code{i} is
23432 declared an @code{int}, @value{GDBN} will add 4 times the value of
23433 @code{__djgpp_base_address} to the address of @code{i}.
23435 Here's another example, it displays the Page Table entry for the
23439 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
23440 @exdent @code{Page Table entry for address 0x29110:}
23441 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
23445 (The @code{+ 3} offset is because the transfer buffer's address is the
23446 3rd member of the @code{_go32_info_block} structure.) The output
23447 clearly shows that this DPMI server maps the addresses in conventional
23448 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
23449 linear (@code{0x29110}) addresses are identical.
23451 This command is supported only with some DPMI servers.
23454 @cindex DOS serial data link, remote debugging
23455 In addition to native debugging, the DJGPP port supports remote
23456 debugging via a serial data link. The following commands are specific
23457 to remote serial debugging in the DJGPP port of @value{GDBN}.
23460 @kindex set com1base
23461 @kindex set com1irq
23462 @kindex set com2base
23463 @kindex set com2irq
23464 @kindex set com3base
23465 @kindex set com3irq
23466 @kindex set com4base
23467 @kindex set com4irq
23468 @item set com1base @var{addr}
23469 This command sets the base I/O port address of the @file{COM1} serial
23472 @item set com1irq @var{irq}
23473 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
23474 for the @file{COM1} serial port.
23476 There are similar commands @samp{set com2base}, @samp{set com3irq},
23477 etc.@: for setting the port address and the @code{IRQ} lines for the
23480 @kindex show com1base
23481 @kindex show com1irq
23482 @kindex show com2base
23483 @kindex show com2irq
23484 @kindex show com3base
23485 @kindex show com3irq
23486 @kindex show com4base
23487 @kindex show com4irq
23488 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
23489 display the current settings of the base address and the @code{IRQ}
23490 lines used by the COM ports.
23493 @kindex info serial
23494 @cindex DOS serial port status
23495 This command prints the status of the 4 DOS serial ports. For each
23496 port, it prints whether it's active or not, its I/O base address and
23497 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
23498 counts of various errors encountered so far.
23502 @node Cygwin Native
23503 @subsection Features for Debugging MS Windows PE Executables
23504 @cindex MS Windows debugging
23505 @cindex native Cygwin debugging
23506 @cindex Cygwin-specific commands
23508 @value{GDBN} supports native debugging of MS Windows programs, including
23509 DLLs with and without symbolic debugging information.
23511 @cindex Ctrl-BREAK, MS-Windows
23512 @cindex interrupt debuggee on MS-Windows
23513 MS-Windows programs that call @code{SetConsoleMode} to switch off the
23514 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
23515 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
23516 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
23517 sequence, which can be used to interrupt the debuggee even if it
23520 There are various additional Cygwin-specific commands, described in
23521 this section. Working with DLLs that have no debugging symbols is
23522 described in @ref{Non-debug DLL Symbols}.
23527 This is a prefix of MS Windows-specific commands which print
23528 information about the target system and important OS structures.
23530 @item info w32 selector
23531 This command displays information returned by
23532 the Win32 API @code{GetThreadSelectorEntry} function.
23533 It takes an optional argument that is evaluated to
23534 a long value to give the information about this given selector.
23535 Without argument, this command displays information
23536 about the six segment registers.
23538 @item info w32 thread-information-block
23539 This command displays thread specific information stored in the
23540 Thread Information Block (readable on the X86 CPU family using @code{$fs}
23541 selector for 32-bit programs and @code{$gs} for 64-bit programs).
23543 @kindex signal-event
23544 @item signal-event @var{id}
23545 This command signals an event with user-provided @var{id}. Used to resume
23546 crashing process when attached to it using MS-Windows JIT debugging (AeDebug).
23548 To use it, create or edit the following keys in
23549 @code{HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AeDebug} and/or
23550 @code{HKLM\SOFTWARE\Wow6432Node\Microsoft\Windows NT\CurrentVersion\AeDebug}
23551 (for x86_64 versions):
23555 @code{Debugger} (REG_SZ) --- a command to launch the debugger.
23556 Suggested command is: @code{@var{fully-qualified-path-to-gdb.exe} -ex
23557 "attach %ld" -ex "signal-event %ld" -ex "continue"}.
23559 The first @code{%ld} will be replaced by the process ID of the
23560 crashing process, the second @code{%ld} will be replaced by the ID of
23561 the event that blocks the crashing process, waiting for @value{GDBN}
23565 @code{Auto} (REG_SZ) --- either @code{1} or @code{0}. @code{1} will
23566 make the system run debugger specified by the Debugger key
23567 automatically, @code{0} will cause a dialog box with ``OK'' and
23568 ``Cancel'' buttons to appear, which allows the user to either
23569 terminate the crashing process (OK) or debug it (Cancel).
23572 @kindex set cygwin-exceptions
23573 @cindex debugging the Cygwin DLL
23574 @cindex Cygwin DLL, debugging
23575 @item set cygwin-exceptions @var{mode}
23576 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
23577 happen inside the Cygwin DLL. If @var{mode} is @code{off},
23578 @value{GDBN} will delay recognition of exceptions, and may ignore some
23579 exceptions which seem to be caused by internal Cygwin DLL
23580 ``bookkeeping''. This option is meant primarily for debugging the
23581 Cygwin DLL itself; the default value is @code{off} to avoid annoying
23582 @value{GDBN} users with false @code{SIGSEGV} signals.
23584 @kindex show cygwin-exceptions
23585 @item show cygwin-exceptions
23586 Displays whether @value{GDBN} will break on exceptions that happen
23587 inside the Cygwin DLL itself.
23589 @kindex set new-console
23590 @item set new-console @var{mode}
23591 If @var{mode} is @code{on} the debuggee will
23592 be started in a new console on next start.
23593 If @var{mode} is @code{off}, the debuggee will
23594 be started in the same console as the debugger.
23596 @kindex show new-console
23597 @item show new-console
23598 Displays whether a new console is used
23599 when the debuggee is started.
23601 @kindex set new-group
23602 @item set new-group @var{mode}
23603 This boolean value controls whether the debuggee should
23604 start a new group or stay in the same group as the debugger.
23605 This affects the way the Windows OS handles
23608 @kindex show new-group
23609 @item show new-group
23610 Displays current value of new-group boolean.
23612 @kindex set debugevents
23613 @item set debugevents
23614 This boolean value adds debug output concerning kernel events related
23615 to the debuggee seen by the debugger. This includes events that
23616 signal thread and process creation and exit, DLL loading and
23617 unloading, console interrupts, and debugging messages produced by the
23618 Windows @code{OutputDebugString} API call.
23620 @kindex set debugexec
23621 @item set debugexec
23622 This boolean value adds debug output concerning execute events
23623 (such as resume thread) seen by the debugger.
23625 @kindex set debugexceptions
23626 @item set debugexceptions
23627 This boolean value adds debug output concerning exceptions in the
23628 debuggee seen by the debugger.
23630 @kindex set debugmemory
23631 @item set debugmemory
23632 This boolean value adds debug output concerning debuggee memory reads
23633 and writes by the debugger.
23637 This boolean values specifies whether the debuggee is called
23638 via a shell or directly (default value is on).
23642 Displays if the debuggee will be started with a shell.
23647 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
23650 @node Non-debug DLL Symbols
23651 @subsubsection Support for DLLs without Debugging Symbols
23652 @cindex DLLs with no debugging symbols
23653 @cindex Minimal symbols and DLLs
23655 Very often on windows, some of the DLLs that your program relies on do
23656 not include symbolic debugging information (for example,
23657 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
23658 symbols in a DLL, it relies on the minimal amount of symbolic
23659 information contained in the DLL's export table. This section
23660 describes working with such symbols, known internally to @value{GDBN} as
23661 ``minimal symbols''.
23663 Note that before the debugged program has started execution, no DLLs
23664 will have been loaded. The easiest way around this problem is simply to
23665 start the program --- either by setting a breakpoint or letting the
23666 program run once to completion.
23668 @subsubsection DLL Name Prefixes
23670 In keeping with the naming conventions used by the Microsoft debugging
23671 tools, DLL export symbols are made available with a prefix based on the
23672 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
23673 also entered into the symbol table, so @code{CreateFileA} is often
23674 sufficient. In some cases there will be name clashes within a program
23675 (particularly if the executable itself includes full debugging symbols)
23676 necessitating the use of the fully qualified name when referring to the
23677 contents of the DLL. Use single-quotes around the name to avoid the
23678 exclamation mark (``!'') being interpreted as a language operator.
23680 Note that the internal name of the DLL may be all upper-case, even
23681 though the file name of the DLL is lower-case, or vice-versa. Since
23682 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
23683 some confusion. If in doubt, try the @code{info functions} and
23684 @code{info variables} commands or even @code{maint print msymbols}
23685 (@pxref{Symbols}). Here's an example:
23688 (@value{GDBP}) info function CreateFileA
23689 All functions matching regular expression "CreateFileA":
23691 Non-debugging symbols:
23692 0x77e885f4 CreateFileA
23693 0x77e885f4 KERNEL32!CreateFileA
23697 (@value{GDBP}) info function !
23698 All functions matching regular expression "!":
23700 Non-debugging symbols:
23701 0x6100114c cygwin1!__assert
23702 0x61004034 cygwin1!_dll_crt0@@0
23703 0x61004240 cygwin1!dll_crt0(per_process *)
23707 @subsubsection Working with Minimal Symbols
23709 Symbols extracted from a DLL's export table do not contain very much
23710 type information. All that @value{GDBN} can do is guess whether a symbol
23711 refers to a function or variable depending on the linker section that
23712 contains the symbol. Also note that the actual contents of the memory
23713 contained in a DLL are not available unless the program is running. This
23714 means that you cannot examine the contents of a variable or disassemble
23715 a function within a DLL without a running program.
23717 Variables are generally treated as pointers and dereferenced
23718 automatically. For this reason, it is often necessary to prefix a
23719 variable name with the address-of operator (``&'') and provide explicit
23720 type information in the command. Here's an example of the type of
23724 (@value{GDBP}) print 'cygwin1!__argv'
23725 'cygwin1!__argv' has unknown type; cast it to its declared type
23729 (@value{GDBP}) x 'cygwin1!__argv'
23730 'cygwin1!__argv' has unknown type; cast it to its declared type
23733 And two possible solutions:
23736 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
23737 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
23741 (@value{GDBP}) x/2x &'cygwin1!__argv'
23742 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
23743 (@value{GDBP}) x/x 0x10021608
23744 0x10021608: 0x0022fd98
23745 (@value{GDBP}) x/s 0x0022fd98
23746 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
23749 Setting a break point within a DLL is possible even before the program
23750 starts execution. However, under these circumstances, @value{GDBN} can't
23751 examine the initial instructions of the function in order to skip the
23752 function's frame set-up code. You can work around this by using ``*&''
23753 to set the breakpoint at a raw memory address:
23756 (@value{GDBP}) break *&'python22!PyOS_Readline'
23757 Breakpoint 1 at 0x1e04eff0
23760 The author of these extensions is not entirely convinced that setting a
23761 break point within a shared DLL like @file{kernel32.dll} is completely
23765 @subsection Commands Specific to @sc{gnu} Hurd Systems
23766 @cindex @sc{gnu} Hurd debugging
23768 This subsection describes @value{GDBN} commands specific to the
23769 @sc{gnu} Hurd native debugging.
23774 @kindex set signals@r{, Hurd command}
23775 @kindex set sigs@r{, Hurd command}
23776 This command toggles the state of inferior signal interception by
23777 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
23778 affected by this command. @code{sigs} is a shorthand alias for
23783 @kindex show signals@r{, Hurd command}
23784 @kindex show sigs@r{, Hurd command}
23785 Show the current state of intercepting inferior's signals.
23787 @item set signal-thread
23788 @itemx set sigthread
23789 @kindex set signal-thread
23790 @kindex set sigthread
23791 This command tells @value{GDBN} which thread is the @code{libc} signal
23792 thread. That thread is run when a signal is delivered to a running
23793 process. @code{set sigthread} is the shorthand alias of @code{set
23796 @item show signal-thread
23797 @itemx show sigthread
23798 @kindex show signal-thread
23799 @kindex show sigthread
23800 These two commands show which thread will run when the inferior is
23801 delivered a signal.
23804 @kindex set stopped@r{, Hurd command}
23805 This commands tells @value{GDBN} that the inferior process is stopped,
23806 as with the @code{SIGSTOP} signal. The stopped process can be
23807 continued by delivering a signal to it.
23810 @kindex show stopped@r{, Hurd command}
23811 This command shows whether @value{GDBN} thinks the debuggee is
23814 @item set exceptions
23815 @kindex set exceptions@r{, Hurd command}
23816 Use this command to turn off trapping of exceptions in the inferior.
23817 When exception trapping is off, neither breakpoints nor
23818 single-stepping will work. To restore the default, set exception
23821 @item show exceptions
23822 @kindex show exceptions@r{, Hurd command}
23823 Show the current state of trapping exceptions in the inferior.
23825 @item set task pause
23826 @kindex set task@r{, Hurd commands}
23827 @cindex task attributes (@sc{gnu} Hurd)
23828 @cindex pause current task (@sc{gnu} Hurd)
23829 This command toggles task suspension when @value{GDBN} has control.
23830 Setting it to on takes effect immediately, and the task is suspended
23831 whenever @value{GDBN} gets control. Setting it to off will take
23832 effect the next time the inferior is continued. If this option is set
23833 to off, you can use @code{set thread default pause on} or @code{set
23834 thread pause on} (see below) to pause individual threads.
23836 @item show task pause
23837 @kindex show task@r{, Hurd commands}
23838 Show the current state of task suspension.
23840 @item set task detach-suspend-count
23841 @cindex task suspend count
23842 @cindex detach from task, @sc{gnu} Hurd
23843 This command sets the suspend count the task will be left with when
23844 @value{GDBN} detaches from it.
23846 @item show task detach-suspend-count
23847 Show the suspend count the task will be left with when detaching.
23849 @item set task exception-port
23850 @itemx set task excp
23851 @cindex task exception port, @sc{gnu} Hurd
23852 This command sets the task exception port to which @value{GDBN} will
23853 forward exceptions. The argument should be the value of the @dfn{send
23854 rights} of the task. @code{set task excp} is a shorthand alias.
23856 @item set noninvasive
23857 @cindex noninvasive task options
23858 This command switches @value{GDBN} to a mode that is the least
23859 invasive as far as interfering with the inferior is concerned. This
23860 is the same as using @code{set task pause}, @code{set exceptions}, and
23861 @code{set signals} to values opposite to the defaults.
23863 @item info send-rights
23864 @itemx info receive-rights
23865 @itemx info port-rights
23866 @itemx info port-sets
23867 @itemx info dead-names
23870 @cindex send rights, @sc{gnu} Hurd
23871 @cindex receive rights, @sc{gnu} Hurd
23872 @cindex port rights, @sc{gnu} Hurd
23873 @cindex port sets, @sc{gnu} Hurd
23874 @cindex dead names, @sc{gnu} Hurd
23875 These commands display information about, respectively, send rights,
23876 receive rights, port rights, port sets, and dead names of a task.
23877 There are also shorthand aliases: @code{info ports} for @code{info
23878 port-rights} and @code{info psets} for @code{info port-sets}.
23880 @item set thread pause
23881 @kindex set thread@r{, Hurd command}
23882 @cindex thread properties, @sc{gnu} Hurd
23883 @cindex pause current thread (@sc{gnu} Hurd)
23884 This command toggles current thread suspension when @value{GDBN} has
23885 control. Setting it to on takes effect immediately, and the current
23886 thread is suspended whenever @value{GDBN} gets control. Setting it to
23887 off will take effect the next time the inferior is continued.
23888 Normally, this command has no effect, since when @value{GDBN} has
23889 control, the whole task is suspended. However, if you used @code{set
23890 task pause off} (see above), this command comes in handy to suspend
23891 only the current thread.
23893 @item show thread pause
23894 @kindex show thread@r{, Hurd command}
23895 This command shows the state of current thread suspension.
23897 @item set thread run
23898 This command sets whether the current thread is allowed to run.
23900 @item show thread run
23901 Show whether the current thread is allowed to run.
23903 @item set thread detach-suspend-count
23904 @cindex thread suspend count, @sc{gnu} Hurd
23905 @cindex detach from thread, @sc{gnu} Hurd
23906 This command sets the suspend count @value{GDBN} will leave on a
23907 thread when detaching. This number is relative to the suspend count
23908 found by @value{GDBN} when it notices the thread; use @code{set thread
23909 takeover-suspend-count} to force it to an absolute value.
23911 @item show thread detach-suspend-count
23912 Show the suspend count @value{GDBN} will leave on the thread when
23915 @item set thread exception-port
23916 @itemx set thread excp
23917 Set the thread exception port to which to forward exceptions. This
23918 overrides the port set by @code{set task exception-port} (see above).
23919 @code{set thread excp} is the shorthand alias.
23921 @item set thread takeover-suspend-count
23922 Normally, @value{GDBN}'s thread suspend counts are relative to the
23923 value @value{GDBN} finds when it notices each thread. This command
23924 changes the suspend counts to be absolute instead.
23926 @item set thread default
23927 @itemx show thread default
23928 @cindex thread default settings, @sc{gnu} Hurd
23929 Each of the above @code{set thread} commands has a @code{set thread
23930 default} counterpart (e.g., @code{set thread default pause}, @code{set
23931 thread default exception-port}, etc.). The @code{thread default}
23932 variety of commands sets the default thread properties for all
23933 threads; you can then change the properties of individual threads with
23934 the non-default commands.
23941 @value{GDBN} provides the following commands specific to the Darwin target:
23944 @item set debug darwin @var{num}
23945 @kindex set debug darwin
23946 When set to a non zero value, enables debugging messages specific to
23947 the Darwin support. Higher values produce more verbose output.
23949 @item show debug darwin
23950 @kindex show debug darwin
23951 Show the current state of Darwin messages.
23953 @item set debug mach-o @var{num}
23954 @kindex set debug mach-o
23955 When set to a non zero value, enables debugging messages while
23956 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
23957 file format used on Darwin for object and executable files.) Higher
23958 values produce more verbose output. This is a command to diagnose
23959 problems internal to @value{GDBN} and should not be needed in normal
23962 @item show debug mach-o
23963 @kindex show debug mach-o
23964 Show the current state of Mach-O file messages.
23966 @item set mach-exceptions on
23967 @itemx set mach-exceptions off
23968 @kindex set mach-exceptions
23969 On Darwin, faults are first reported as a Mach exception and are then
23970 mapped to a Posix signal. Use this command to turn on trapping of
23971 Mach exceptions in the inferior. This might be sometimes useful to
23972 better understand the cause of a fault. The default is off.
23974 @item show mach-exceptions
23975 @kindex show mach-exceptions
23976 Show the current state of exceptions trapping.
23980 @subsection FreeBSD
23983 When the ABI of a system call is changed in the FreeBSD kernel, this
23984 is implemented by leaving a compatibility system call using the old
23985 ABI at the existing number and allocating a new system call number for
23986 the version using the new ABI. As a convenience, when a system call
23987 is caught by name (@pxref{catch syscall}), compatibility system calls
23990 For example, FreeBSD 12 introduced a new variant of the @code{kevent}
23991 system call and catching the @code{kevent} system call by name catches
23995 (@value{GDBP}) catch syscall kevent
23996 Catchpoint 1 (syscalls 'freebsd11_kevent' [363] 'kevent' [560])
24002 @section Embedded Operating Systems
24004 This section describes configurations involving the debugging of
24005 embedded operating systems that are available for several different
24008 @value{GDBN} includes the ability to debug programs running on
24009 various real-time operating systems.
24011 @node Embedded Processors
24012 @section Embedded Processors
24014 This section goes into details specific to particular embedded
24017 @cindex send command to simulator
24018 Whenever a specific embedded processor has a simulator, @value{GDBN}
24019 allows to send an arbitrary command to the simulator.
24022 @item sim @var{command}
24023 @kindex sim@r{, a command}
24024 Send an arbitrary @var{command} string to the simulator. Consult the
24025 documentation for the specific simulator in use for information about
24026 acceptable commands.
24031 * ARC:: Synopsys ARC
24033 * M68K:: Motorola M68K
24034 * MicroBlaze:: Xilinx MicroBlaze
24035 * MIPS Embedded:: MIPS Embedded
24036 * OpenRISC 1000:: OpenRISC 1000 (or1k)
24037 * PowerPC Embedded:: PowerPC Embedded
24040 * Super-H:: Renesas Super-H
24044 @subsection Synopsys ARC
24045 @cindex Synopsys ARC
24046 @cindex ARC specific commands
24052 @value{GDBN} provides the following ARC-specific commands:
24055 @item set debug arc
24056 @kindex set debug arc
24057 Control the level of ARC specific debug messages. Use 0 for no messages (the
24058 default), 1 for debug messages, and 2 for even more debug messages.
24060 @item show debug arc
24061 @kindex show debug arc
24062 Show the level of ARC specific debugging in operation.
24064 @item maint print arc arc-instruction @var{address}
24065 @kindex maint print arc arc-instruction
24066 Print internal disassembler information about instruction at a given address.
24073 @value{GDBN} provides the following ARM-specific commands:
24076 @item set arm disassembler
24078 This commands selects from a list of disassembly styles. The
24079 @code{"std"} style is the standard style.
24081 @item show arm disassembler
24083 Show the current disassembly style.
24085 @item set arm apcs32
24086 @cindex ARM 32-bit mode
24087 This command toggles ARM operation mode between 32-bit and 26-bit.
24089 @item show arm apcs32
24090 Display the current usage of the ARM 32-bit mode.
24092 @item set arm fpu @var{fputype}
24093 This command sets the ARM floating-point unit (FPU) type. The
24094 argument @var{fputype} can be one of these:
24098 Determine the FPU type by querying the OS ABI.
24100 Software FPU, with mixed-endian doubles on little-endian ARM
24103 GCC-compiled FPA co-processor.
24105 Software FPU with pure-endian doubles.
24111 Show the current type of the FPU.
24114 This command forces @value{GDBN} to use the specified ABI.
24117 Show the currently used ABI.
24119 @item set arm fallback-mode (arm|thumb|auto)
24120 @value{GDBN} uses the symbol table, when available, to determine
24121 whether instructions are ARM or Thumb. This command controls
24122 @value{GDBN}'s default behavior when the symbol table is not
24123 available. The default is @samp{auto}, which causes @value{GDBN} to
24124 use the current execution mode (from the @code{T} bit in the @code{CPSR}
24127 @item show arm fallback-mode
24128 Show the current fallback instruction mode.
24130 @item set arm force-mode (arm|thumb|auto)
24131 This command overrides use of the symbol table to determine whether
24132 instructions are ARM or Thumb. The default is @samp{auto}, which
24133 causes @value{GDBN} to use the symbol table and then the setting
24134 of @samp{set arm fallback-mode}.
24136 @item show arm force-mode
24137 Show the current forced instruction mode.
24139 @item set debug arm
24140 Toggle whether to display ARM-specific debugging messages from the ARM
24141 target support subsystem.
24143 @item show debug arm
24144 Show whether ARM-specific debugging messages are enabled.
24148 @item target sim @r{[}@var{simargs}@r{]} @dots{}
24149 The @value{GDBN} ARM simulator accepts the following optional arguments.
24152 @item --swi-support=@var{type}
24153 Tell the simulator which SWI interfaces to support. The argument
24154 @var{type} may be a comma separated list of the following values.
24155 The default value is @code{all}.
24170 The Motorola m68k configuration includes ColdFire support.
24173 @subsection MicroBlaze
24174 @cindex Xilinx MicroBlaze
24175 @cindex XMD, Xilinx Microprocessor Debugger
24177 The MicroBlaze is a soft-core processor supported on various Xilinx
24178 FPGAs, such as Spartan or Virtex series. Boards with these processors
24179 usually have JTAG ports which connect to a host system running the Xilinx
24180 Embedded Development Kit (EDK) or Software Development Kit (SDK).
24181 This host system is used to download the configuration bitstream to
24182 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
24183 communicates with the target board using the JTAG interface and
24184 presents a @code{gdbserver} interface to the board. By default
24185 @code{xmd} uses port @code{1234}. (While it is possible to change
24186 this default port, it requires the use of undocumented @code{xmd}
24187 commands. Contact Xilinx support if you need to do this.)
24189 Use these GDB commands to connect to the MicroBlaze target processor.
24192 @item target remote :1234
24193 Use this command to connect to the target if you are running @value{GDBN}
24194 on the same system as @code{xmd}.
24196 @item target remote @var{xmd-host}:1234
24197 Use this command to connect to the target if it is connected to @code{xmd}
24198 running on a different system named @var{xmd-host}.
24201 Use this command to download a program to the MicroBlaze target.
24203 @item set debug microblaze @var{n}
24204 Enable MicroBlaze-specific debugging messages if non-zero.
24206 @item show debug microblaze @var{n}
24207 Show MicroBlaze-specific debugging level.
24210 @node MIPS Embedded
24211 @subsection @acronym{MIPS} Embedded
24214 @value{GDBN} supports these special commands for @acronym{MIPS} targets:
24217 @item set mipsfpu double
24218 @itemx set mipsfpu single
24219 @itemx set mipsfpu none
24220 @itemx set mipsfpu auto
24221 @itemx show mipsfpu
24222 @kindex set mipsfpu
24223 @kindex show mipsfpu
24224 @cindex @acronym{MIPS} remote floating point
24225 @cindex floating point, @acronym{MIPS} remote
24226 If your target board does not support the @acronym{MIPS} floating point
24227 coprocessor, you should use the command @samp{set mipsfpu none} (if you
24228 need this, you may wish to put the command in your @value{GDBN} init
24229 file). This tells @value{GDBN} how to find the return value of
24230 functions which return floating point values. It also allows
24231 @value{GDBN} to avoid saving the floating point registers when calling
24232 functions on the board. If you are using a floating point coprocessor
24233 with only single precision floating point support, as on the @sc{r4650}
24234 processor, use the command @samp{set mipsfpu single}. The default
24235 double precision floating point coprocessor may be selected using
24236 @samp{set mipsfpu double}.
24238 In previous versions the only choices were double precision or no
24239 floating point, so @samp{set mipsfpu on} will select double precision
24240 and @samp{set mipsfpu off} will select no floating point.
24242 As usual, you can inquire about the @code{mipsfpu} variable with
24243 @samp{show mipsfpu}.
24246 @node OpenRISC 1000
24247 @subsection OpenRISC 1000
24248 @cindex OpenRISC 1000
24251 The OpenRISC 1000 provides a free RISC instruction set architecture. It is
24252 mainly provided as a soft-core which can run on Xilinx, Altera and other
24255 @value{GDBN} for OpenRISC supports the below commands when connecting to
24263 Runs the builtin CPU simulator which can run very basic
24264 programs but does not support most hardware functions like MMU.
24265 For more complex use cases the user is advised to run an external
24266 target, and connect using @samp{target remote}.
24268 Example: @code{target sim}
24270 @item set debug or1k
24271 Toggle whether to display OpenRISC-specific debugging messages from the
24272 OpenRISC target support subsystem.
24274 @item show debug or1k
24275 Show whether OpenRISC-specific debugging messages are enabled.
24278 @node PowerPC Embedded
24279 @subsection PowerPC Embedded
24281 @cindex DVC register
24282 @value{GDBN} supports using the DVC (Data Value Compare) register to
24283 implement in hardware simple hardware watchpoint conditions of the form:
24286 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
24287 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
24290 The DVC register will be automatically used when @value{GDBN} detects
24291 such pattern in a condition expression, and the created watchpoint uses one
24292 debug register (either the @code{exact-watchpoints} option is on and the
24293 variable is scalar, or the variable has a length of one byte). This feature
24294 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
24297 When running on PowerPC embedded processors, @value{GDBN} automatically uses
24298 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
24299 in which case watchpoints using only one debug register are created when
24300 watching variables of scalar types.
24302 You can create an artificial array to watch an arbitrary memory
24303 region using one of the following commands (@pxref{Expressions}):
24306 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
24307 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
24310 PowerPC embedded processors support masked watchpoints. See the discussion
24311 about the @code{mask} argument in @ref{Set Watchpoints}.
24313 @cindex ranged breakpoint
24314 PowerPC embedded processors support hardware accelerated
24315 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
24316 the inferior whenever it executes an instruction at any address within
24317 the range it specifies. To set a ranged breakpoint in @value{GDBN},
24318 use the @code{break-range} command.
24320 @value{GDBN} provides the following PowerPC-specific commands:
24323 @kindex break-range
24324 @item break-range @var{start-location}, @var{end-location}
24325 Set a breakpoint for an address range given by
24326 @var{start-location} and @var{end-location}, which can specify a function name,
24327 a line number, an offset of lines from the current line or from the start
24328 location, or an address of an instruction (see @ref{Specify Location},
24329 for a list of all the possible ways to specify a @var{location}.)
24330 The breakpoint will stop execution of the inferior whenever it
24331 executes an instruction at any address within the specified range,
24332 (including @var{start-location} and @var{end-location}.)
24334 @kindex set powerpc
24335 @item set powerpc soft-float
24336 @itemx show powerpc soft-float
24337 Force @value{GDBN} to use (or not use) a software floating point calling
24338 convention. By default, @value{GDBN} selects the calling convention based
24339 on the selected architecture and the provided executable file.
24341 @item set powerpc vector-abi
24342 @itemx show powerpc vector-abi
24343 Force @value{GDBN} to use the specified calling convention for vector
24344 arguments and return values. The valid options are @samp{auto};
24345 @samp{generic}, to avoid vector registers even if they are present;
24346 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
24347 registers. By default, @value{GDBN} selects the calling convention
24348 based on the selected architecture and the provided executable file.
24350 @item set powerpc exact-watchpoints
24351 @itemx show powerpc exact-watchpoints
24352 Allow @value{GDBN} to use only one debug register when watching a variable
24353 of scalar type, thus assuming that the variable is accessed through the
24354 address of its first byte.
24359 @subsection Atmel AVR
24362 When configured for debugging the Atmel AVR, @value{GDBN} supports the
24363 following AVR-specific commands:
24366 @item info io_registers
24367 @kindex info io_registers@r{, AVR}
24368 @cindex I/O registers (Atmel AVR)
24369 This command displays information about the AVR I/O registers. For
24370 each register, @value{GDBN} prints its number and value.
24377 When configured for debugging CRIS, @value{GDBN} provides the
24378 following CRIS-specific commands:
24381 @item set cris-version @var{ver}
24382 @cindex CRIS version
24383 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
24384 The CRIS version affects register names and sizes. This command is useful in
24385 case autodetection of the CRIS version fails.
24387 @item show cris-version
24388 Show the current CRIS version.
24390 @item set cris-dwarf2-cfi
24391 @cindex DWARF-2 CFI and CRIS
24392 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
24393 Change to @samp{off} when using @code{gcc-cris} whose version is below
24396 @item show cris-dwarf2-cfi
24397 Show the current state of using DWARF-2 CFI.
24399 @item set cris-mode @var{mode}
24401 Set the current CRIS mode to @var{mode}. It should only be changed when
24402 debugging in guru mode, in which case it should be set to
24403 @samp{guru} (the default is @samp{normal}).
24405 @item show cris-mode
24406 Show the current CRIS mode.
24410 @subsection Renesas Super-H
24413 For the Renesas Super-H processor, @value{GDBN} provides these
24417 @item set sh calling-convention @var{convention}
24418 @kindex set sh calling-convention
24419 Set the calling-convention used when calling functions from @value{GDBN}.
24420 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
24421 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
24422 convention. If the DWARF-2 information of the called function specifies
24423 that the function follows the Renesas calling convention, the function
24424 is called using the Renesas calling convention. If the calling convention
24425 is set to @samp{renesas}, the Renesas calling convention is always used,
24426 regardless of the DWARF-2 information. This can be used to override the
24427 default of @samp{gcc} if debug information is missing, or the compiler
24428 does not emit the DWARF-2 calling convention entry for a function.
24430 @item show sh calling-convention
24431 @kindex show sh calling-convention
24432 Show the current calling convention setting.
24437 @node Architectures
24438 @section Architectures
24440 This section describes characteristics of architectures that affect
24441 all uses of @value{GDBN} with the architecture, both native and cross.
24448 * HPPA:: HP PA architecture
24456 @subsection AArch64
24457 @cindex AArch64 support
24459 When @value{GDBN} is debugging the AArch64 architecture, it provides the
24460 following special commands:
24463 @item set debug aarch64
24464 @kindex set debug aarch64
24465 This command determines whether AArch64 architecture-specific debugging
24466 messages are to be displayed.
24468 @item show debug aarch64
24469 Show whether AArch64 debugging messages are displayed.
24473 @subsubsection AArch64 SVE.
24474 @cindex AArch64 SVE.
24476 When @value{GDBN} is debugging the AArch64 architecture, if the Scalable Vector
24477 Extension (SVE) is present, then @value{GDBN} will provide the vector registers
24478 @code{$z0} through @code{$z31}, vector predicate registers @code{$p0} through
24479 @code{$p15}, and the @code{$ffr} register. In addition, the pseudo register
24480 @code{$vg} will be provided. This is the vector granule for the current thread
24481 and represents the number of 64-bit chunks in an SVE @code{z} register.
24483 If the vector length changes, then the @code{$vg} register will be updated,
24484 but the lengths of the @code{z} and @code{p} registers will not change. This
24485 is a known limitation of @value{GDBN} and does not affect the execution of the
24488 @subsubsection AArch64 Pointer Authentication.
24489 @cindex AArch64 Pointer Authentication.
24491 When @value{GDBN} is debugging the AArch64 architecture, and the program is
24492 using the v8.3-A feature Pointer Authentication (PAC), then whenever the link
24493 register @code{$lr} is pointing to an PAC function its value will be masked.
24494 When GDB prints a backtrace, any addresses that required unmasking will be
24495 postfixed with the marker [PAC]. When using the MI, this is printed as part
24496 of the @code{addr_flags} field.
24499 @subsection x86 Architecture-specific Issues
24502 @item set struct-convention @var{mode}
24503 @kindex set struct-convention
24504 @cindex struct return convention
24505 @cindex struct/union returned in registers
24506 Set the convention used by the inferior to return @code{struct}s and
24507 @code{union}s from functions to @var{mode}. Possible values of
24508 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
24509 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
24510 are returned on the stack, while @code{"reg"} means that a
24511 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
24512 be returned in a register.
24514 @item show struct-convention
24515 @kindex show struct-convention
24516 Show the current setting of the convention to return @code{struct}s
24521 @subsubsection Intel @dfn{Memory Protection Extensions} (MPX).
24522 @cindex Intel Memory Protection Extensions (MPX).
24524 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
24525 @footnote{The register named with capital letters represent the architecture
24526 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
24527 which are the lower bound and upper bound. Bounds are effective addresses or
24528 memory locations. The upper bounds are architecturally represented in 1's
24529 complement form. A bound having lower bound = 0, and upper bound = 0
24530 (1's complement of all bits set) will allow access to the entire address space.
24532 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
24533 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
24534 display the upper bound performing the complement of one operation on the
24535 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
24536 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
24537 can also be noted that the upper bounds are inclusive.
24539 As an example, assume that the register BND0 holds bounds for a pointer having
24540 access allowed for the range between 0x32 and 0x71. The values present on
24541 bnd0raw and bnd registers are presented as follows:
24544 bnd0raw = @{0x32, 0xffffffff8e@}
24545 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
24548 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
24549 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
24550 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
24551 Python, the display includes the memory size, in bits, accessible to
24554 Bounds can also be stored in bounds tables, which are stored in
24555 application memory. These tables store bounds for pointers by specifying
24556 the bounds pointer's value along with its bounds. Evaluating and changing
24557 bounds located in bound tables is therefore interesting while investigating
24558 bugs on MPX context. @value{GDBN} provides commands for this purpose:
24561 @item show mpx bound @var{pointer}
24562 @kindex show mpx bound
24563 Display bounds of the given @var{pointer}.
24565 @item set mpx bound @var{pointer}, @var{lbound}, @var{ubound}
24566 @kindex set mpx bound
24567 Set the bounds of a pointer in the bound table.
24568 This command takes three parameters: @var{pointer} is the pointers
24569 whose bounds are to be changed, @var{lbound} and @var{ubound} are new values
24570 for lower and upper bounds respectively.
24573 When you call an inferior function on an Intel MPX enabled program,
24574 GDB sets the inferior's bound registers to the init (disabled) state
24575 before calling the function. As a consequence, bounds checks for the
24576 pointer arguments passed to the function will always pass.
24578 This is necessary because when you call an inferior function, the
24579 program is usually in the middle of the execution of other function.
24580 Since at that point bound registers are in an arbitrary state, not
24581 clearing them would lead to random bound violations in the called
24584 You can still examine the influence of the bound registers on the
24585 execution of the called function by stopping the execution of the
24586 called function at its prologue, setting bound registers, and
24587 continuing the execution. For example:
24591 Breakpoint 2 at 0x4009de: file i386-mpx-call.c, line 47.
24592 $ print upper (a, b, c, d, 1)
24593 Breakpoint 2, upper (a=0x0, b=0x6e0000005b, c=0x0, d=0x0, len=48)....
24595 @{lbound = 0x0, ubound = ffffffff@} : size -1
24598 At this last step the value of bnd0 can be changed for investigation of bound
24599 violations caused along the execution of the call. In order to know how to
24600 set the bound registers or bound table for the call consult the ABI.
24605 See the following section.
24608 @subsection @acronym{MIPS}
24610 @cindex stack on Alpha
24611 @cindex stack on @acronym{MIPS}
24612 @cindex Alpha stack
24613 @cindex @acronym{MIPS} stack
24614 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
24615 sometimes requires @value{GDBN} to search backward in the object code to
24616 find the beginning of a function.
24618 @cindex response time, @acronym{MIPS} debugging
24619 To improve response time (especially for embedded applications, where
24620 @value{GDBN} may be restricted to a slow serial line for this search)
24621 you may want to limit the size of this search, using one of these
24625 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
24626 @item set heuristic-fence-post @var{limit}
24627 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
24628 search for the beginning of a function. A value of @var{0} (the
24629 default) means there is no limit. However, except for @var{0}, the
24630 larger the limit the more bytes @code{heuristic-fence-post} must search
24631 and therefore the longer it takes to run. You should only need to use
24632 this command when debugging a stripped executable.
24634 @item show heuristic-fence-post
24635 Display the current limit.
24639 These commands are available @emph{only} when @value{GDBN} is configured
24640 for debugging programs on Alpha or @acronym{MIPS} processors.
24642 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
24646 @item set mips abi @var{arg}
24647 @kindex set mips abi
24648 @cindex set ABI for @acronym{MIPS}
24649 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
24650 values of @var{arg} are:
24654 The default ABI associated with the current binary (this is the
24664 @item show mips abi
24665 @kindex show mips abi
24666 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
24668 @item set mips compression @var{arg}
24669 @kindex set mips compression
24670 @cindex code compression, @acronym{MIPS}
24671 Tell @value{GDBN} which @acronym{MIPS} compressed
24672 @acronym{ISA, Instruction Set Architecture} encoding is used by the
24673 inferior. @value{GDBN} uses this for code disassembly and other
24674 internal interpretation purposes. This setting is only referred to
24675 when no executable has been associated with the debugging session or
24676 the executable does not provide information about the encoding it uses.
24677 Otherwise this setting is automatically updated from information
24678 provided by the executable.
24680 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
24681 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
24682 executables containing @acronym{MIPS16} code frequently are not
24683 identified as such.
24685 This setting is ``sticky''; that is, it retains its value across
24686 debugging sessions until reset either explicitly with this command or
24687 implicitly from an executable.
24689 The compiler and/or assembler typically add symbol table annotations to
24690 identify functions compiled for the @acronym{MIPS16} or
24691 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
24692 are present, @value{GDBN} uses them in preference to the global
24693 compressed @acronym{ISA} encoding setting.
24695 @item show mips compression
24696 @kindex show mips compression
24697 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
24698 @value{GDBN} to debug the inferior.
24701 @itemx show mipsfpu
24702 @xref{MIPS Embedded, set mipsfpu}.
24704 @item set mips mask-address @var{arg}
24705 @kindex set mips mask-address
24706 @cindex @acronym{MIPS} addresses, masking
24707 This command determines whether the most-significant 32 bits of 64-bit
24708 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
24709 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
24710 setting, which lets @value{GDBN} determine the correct value.
24712 @item show mips mask-address
24713 @kindex show mips mask-address
24714 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
24717 @item set remote-mips64-transfers-32bit-regs
24718 @kindex set remote-mips64-transfers-32bit-regs
24719 This command controls compatibility with 64-bit @acronym{MIPS} targets that
24720 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
24721 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
24722 and 64 bits for other registers, set this option to @samp{on}.
24724 @item show remote-mips64-transfers-32bit-regs
24725 @kindex show remote-mips64-transfers-32bit-regs
24726 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
24728 @item set debug mips
24729 @kindex set debug mips
24730 This command turns on and off debugging messages for the @acronym{MIPS}-specific
24731 target code in @value{GDBN}.
24733 @item show debug mips
24734 @kindex show debug mips
24735 Show the current setting of @acronym{MIPS} debugging messages.
24741 @cindex HPPA support
24743 When @value{GDBN} is debugging the HP PA architecture, it provides the
24744 following special commands:
24747 @item set debug hppa
24748 @kindex set debug hppa
24749 This command determines whether HPPA architecture-specific debugging
24750 messages are to be displayed.
24752 @item show debug hppa
24753 Show whether HPPA debugging messages are displayed.
24755 @item maint print unwind @var{address}
24756 @kindex maint print unwind@r{, HPPA}
24757 This command displays the contents of the unwind table entry at the
24758 given @var{address}.
24764 @subsection PowerPC
24765 @cindex PowerPC architecture
24767 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
24768 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
24769 numbers stored in the floating point registers. These values must be stored
24770 in two consecutive registers, always starting at an even register like
24771 @code{f0} or @code{f2}.
24773 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
24774 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
24775 @code{f2} and @code{f3} for @code{$dl1} and so on.
24777 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
24778 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
24781 @subsection Nios II
24782 @cindex Nios II architecture
24784 When @value{GDBN} is debugging the Nios II architecture,
24785 it provides the following special commands:
24789 @item set debug nios2
24790 @kindex set debug nios2
24791 This command turns on and off debugging messages for the Nios II
24792 target code in @value{GDBN}.
24794 @item show debug nios2
24795 @kindex show debug nios2
24796 Show the current setting of Nios II debugging messages.
24800 @subsection Sparc64
24801 @cindex Sparc64 support
24802 @cindex Application Data Integrity
24803 @subsubsection ADI Support
24805 The M7 processor supports an Application Data Integrity (ADI) feature that
24806 detects invalid data accesses. When software allocates memory and enables
24807 ADI on the allocated memory, it chooses a 4-bit version number, sets the
24808 version in the upper 4 bits of the 64-bit pointer to that data, and stores
24809 the 4-bit version in every cacheline of that data. Hardware saves the latter
24810 in spare bits in the cache and memory hierarchy. On each load and store,
24811 the processor compares the upper 4 VA (virtual address) bits to the
24812 cacheline's version. If there is a mismatch, the processor generates a
24813 version mismatch trap which can be either precise or disrupting. The trap
24814 is an error condition which the kernel delivers to the process as a SIGSEGV
24817 Note that only 64-bit applications can use ADI and need to be built with
24820 Values of the ADI version tags, which are in granularity of a
24821 cacheline (64 bytes), can be viewed or modified.
24825 @kindex adi examine
24826 @item adi (examine | x) [ / @var{n} ] @var{addr}
24828 The @code{adi examine} command displays the value of one ADI version tag per
24831 @var{n} is a decimal integer specifying the number in bytes; the default
24832 is 1. It specifies how much ADI version information, at the ratio of 1:ADI
24833 block size, to display.
24835 @var{addr} is the address in user address space where you want @value{GDBN}
24836 to begin displaying the ADI version tags.
24838 Below is an example of displaying ADI versions of variable "shmaddr".
24841 (@value{GDBP}) adi x/100 shmaddr
24842 0xfff800010002c000: 0 0
24846 @item adi (assign | a) [ / @var{n} ] @var{addr} = @var{tag}
24848 The @code{adi assign} command is used to assign new ADI version tag
24851 @var{n} is a decimal integer specifying the number in bytes;
24852 the default is 1. It specifies how much ADI version information, at the
24853 ratio of 1:ADI block size, to modify.
24855 @var{addr} is the address in user address space where you want @value{GDBN}
24856 to begin modifying the ADI version tags.
24858 @var{tag} is the new ADI version tag.
24860 For example, do the following to modify then verify ADI versions of
24861 variable "shmaddr":
24864 (@value{GDBP}) adi a/100 shmaddr = 7
24865 (@value{GDBP}) adi x/100 shmaddr
24866 0xfff800010002c000: 7 7
24873 @cindex S12Z support
24875 When @value{GDBN} is debugging the S12Z architecture,
24876 it provides the following special command:
24879 @item maint info bdccsr
24880 @kindex maint info bdccsr@r{, S12Z}
24881 This command displays the current value of the microprocessor's
24886 @node Controlling GDB
24887 @chapter Controlling @value{GDBN}
24889 You can alter the way @value{GDBN} interacts with you by using the
24890 @code{set} command. For commands controlling how @value{GDBN} displays
24891 data, see @ref{Print Settings, ,Print Settings}. Other settings are
24896 * Editing:: Command editing
24897 * Command History:: Command history
24898 * Screen Size:: Screen size
24899 * Output Styling:: Output styling
24900 * Numbers:: Numbers
24901 * ABI:: Configuring the current ABI
24902 * Auto-loading:: Automatically loading associated files
24903 * Messages/Warnings:: Optional warnings and messages
24904 * Debugging Output:: Optional messages about internal happenings
24905 * Other Misc Settings:: Other Miscellaneous Settings
24913 @value{GDBN} indicates its readiness to read a command by printing a string
24914 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
24915 can change the prompt string with the @code{set prompt} command. For
24916 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
24917 the prompt in one of the @value{GDBN} sessions so that you can always tell
24918 which one you are talking to.
24920 @emph{Note:} @code{set prompt} does not add a space for you after the
24921 prompt you set. This allows you to set a prompt which ends in a space
24922 or a prompt that does not.
24926 @item set prompt @var{newprompt}
24927 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
24929 @kindex show prompt
24931 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
24934 Versions of @value{GDBN} that ship with Python scripting enabled have
24935 prompt extensions. The commands for interacting with these extensions
24939 @kindex set extended-prompt
24940 @item set extended-prompt @var{prompt}
24941 Set an extended prompt that allows for substitutions.
24942 @xref{gdb.prompt}, for a list of escape sequences that can be used for
24943 substitution. Any escape sequences specified as part of the prompt
24944 string are replaced with the corresponding strings each time the prompt
24950 set extended-prompt Current working directory: \w (gdb)
24953 Note that when an extended-prompt is set, it takes control of the
24954 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
24956 @kindex show extended-prompt
24957 @item show extended-prompt
24958 Prints the extended prompt. Any escape sequences specified as part of
24959 the prompt string with @code{set extended-prompt}, are replaced with the
24960 corresponding strings each time the prompt is displayed.
24964 @section Command Editing
24966 @cindex command line editing
24968 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
24969 @sc{gnu} library provides consistent behavior for programs which provide a
24970 command line interface to the user. Advantages are @sc{gnu} Emacs-style
24971 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
24972 substitution, and a storage and recall of command history across
24973 debugging sessions.
24975 You may control the behavior of command line editing in @value{GDBN} with the
24976 command @code{set}.
24979 @kindex set editing
24982 @itemx set editing on
24983 Enable command line editing (enabled by default).
24985 @item set editing off
24986 Disable command line editing.
24988 @kindex show editing
24990 Show whether command line editing is enabled.
24993 @ifset SYSTEM_READLINE
24994 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
24996 @ifclear SYSTEM_READLINE
24997 @xref{Command Line Editing},
24999 for more details about the Readline
25000 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
25001 encouraged to read that chapter.
25003 @cindex Readline application name
25004 @value{GDBN} sets the Readline application name to @samp{gdb}. This
25005 is useful for conditions in @file{.inputrc}.
25007 @node Command History
25008 @section Command History
25009 @cindex command history
25011 @value{GDBN} can keep track of the commands you type during your
25012 debugging sessions, so that you can be certain of precisely what
25013 happened. Use these commands to manage the @value{GDBN} command
25016 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
25017 package, to provide the history facility.
25018 @ifset SYSTEM_READLINE
25019 @xref{Using History Interactively, , , history, GNU History Library},
25021 @ifclear SYSTEM_READLINE
25022 @xref{Using History Interactively},
25024 for the detailed description of the History library.
25026 To issue a command to @value{GDBN} without affecting certain aspects of
25027 the state which is seen by users, prefix it with @samp{server }
25028 (@pxref{Server Prefix}). This
25029 means that this command will not affect the command history, nor will it
25030 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
25031 pressed on a line by itself.
25033 @cindex @code{server}, command prefix
25034 The server prefix does not affect the recording of values into the value
25035 history; to print a value without recording it into the value history,
25036 use the @code{output} command instead of the @code{print} command.
25038 Here is the description of @value{GDBN} commands related to command
25042 @cindex history substitution
25043 @cindex history file
25044 @kindex set history filename
25045 @cindex @env{GDBHISTFILE}, environment variable
25046 @item set history filename @var{fname}
25047 Set the name of the @value{GDBN} command history file to @var{fname}.
25048 This is the file where @value{GDBN} reads an initial command history
25049 list, and where it writes the command history from this session when it
25050 exits. You can access this list through history expansion or through
25051 the history command editing characters listed below. This file defaults
25052 to the value of the environment variable @code{GDBHISTFILE}, or to
25053 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
25056 @cindex save command history
25057 @kindex set history save
25058 @item set history save
25059 @itemx set history save on
25060 Record command history in a file, whose name may be specified with the
25061 @code{set history filename} command. By default, this option is disabled.
25063 @item set history save off
25064 Stop recording command history in a file.
25066 @cindex history size
25067 @kindex set history size
25068 @cindex @env{GDBHISTSIZE}, environment variable
25069 @item set history size @var{size}
25070 @itemx set history size unlimited
25071 Set the number of commands which @value{GDBN} keeps in its history list.
25072 This defaults to the value of the environment variable @env{GDBHISTSIZE}, or
25073 to 256 if this variable is not set. Non-numeric values of @env{GDBHISTSIZE}
25074 are ignored. If @var{size} is @code{unlimited} or if @env{GDBHISTSIZE} is
25075 either a negative number or the empty string, then the number of commands
25076 @value{GDBN} keeps in the history list is unlimited.
25078 @cindex remove duplicate history
25079 @kindex set history remove-duplicates
25080 @item set history remove-duplicates @var{count}
25081 @itemx set history remove-duplicates unlimited
25082 Control the removal of duplicate history entries in the command history list.
25083 If @var{count} is non-zero, @value{GDBN} will look back at the last @var{count}
25084 history entries and remove the first entry that is a duplicate of the current
25085 entry being added to the command history list. If @var{count} is
25086 @code{unlimited} then this lookbehind is unbounded. If @var{count} is 0, then
25087 removal of duplicate history entries is disabled.
25089 Only history entries added during the current session are considered for
25090 removal. This option is set to 0 by default.
25094 History expansion assigns special meaning to the character @kbd{!}.
25095 @ifset SYSTEM_READLINE
25096 @xref{Event Designators, , , history, GNU History Library},
25098 @ifclear SYSTEM_READLINE
25099 @xref{Event Designators},
25103 @cindex history expansion, turn on/off
25104 Since @kbd{!} is also the logical not operator in C, history expansion
25105 is off by default. If you decide to enable history expansion with the
25106 @code{set history expansion on} command, you may sometimes need to
25107 follow @kbd{!} (when it is used as logical not, in an expression) with
25108 a space or a tab to prevent it from being expanded. The readline
25109 history facilities do not attempt substitution on the strings
25110 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
25112 The commands to control history expansion are:
25115 @item set history expansion on
25116 @itemx set history expansion
25117 @kindex set history expansion
25118 Enable history expansion. History expansion is off by default.
25120 @item set history expansion off
25121 Disable history expansion.
25124 @kindex show history
25126 @itemx show history filename
25127 @itemx show history save
25128 @itemx show history size
25129 @itemx show history expansion
25130 These commands display the state of the @value{GDBN} history parameters.
25131 @code{show history} by itself displays all four states.
25136 @kindex show commands
25137 @cindex show last commands
25138 @cindex display command history
25139 @item show commands
25140 Display the last ten commands in the command history.
25142 @item show commands @var{n}
25143 Print ten commands centered on command number @var{n}.
25145 @item show commands +
25146 Print ten commands just after the commands last printed.
25150 @section Screen Size
25151 @cindex size of screen
25152 @cindex screen size
25155 @cindex pauses in output
25157 Certain commands to @value{GDBN} may produce large amounts of
25158 information output to the screen. To help you read all of it,
25159 @value{GDBN} pauses and asks you for input at the end of each page of
25160 output. Type @key{RET} when you want to see one more page of output,
25161 @kbd{q} to discard the remaining output, or @kbd{c} to continue
25162 without paging for the rest of the current command. Also, the screen
25163 width setting determines when to wrap lines of output. Depending on
25164 what is being printed, @value{GDBN} tries to break the line at a
25165 readable place, rather than simply letting it overflow onto the
25168 Normally @value{GDBN} knows the size of the screen from the terminal
25169 driver software. For example, on Unix @value{GDBN} uses the termcap data base
25170 together with the value of the @code{TERM} environment variable and the
25171 @code{stty rows} and @code{stty cols} settings. If this is not correct,
25172 you can override it with the @code{set height} and @code{set
25179 @kindex show height
25180 @item set height @var{lpp}
25181 @itemx set height unlimited
25183 @itemx set width @var{cpl}
25184 @itemx set width unlimited
25186 These @code{set} commands specify a screen height of @var{lpp} lines and
25187 a screen width of @var{cpl} characters. The associated @code{show}
25188 commands display the current settings.
25190 If you specify a height of either @code{unlimited} or zero lines,
25191 @value{GDBN} does not pause during output no matter how long the
25192 output is. This is useful if output is to a file or to an editor
25195 Likewise, you can specify @samp{set width unlimited} or @samp{set
25196 width 0} to prevent @value{GDBN} from wrapping its output.
25198 @item set pagination on
25199 @itemx set pagination off
25200 @kindex set pagination
25201 Turn the output pagination on or off; the default is on. Turning
25202 pagination off is the alternative to @code{set height unlimited}. Note that
25203 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
25204 Options, -batch}) also automatically disables pagination.
25206 @item show pagination
25207 @kindex show pagination
25208 Show the current pagination mode.
25211 @node Output Styling
25212 @section Output Styling
25218 @value{GDBN} can style its output on a capable terminal. This is
25219 enabled by default on most systems, but disabled by default when in
25220 batch mode (@pxref{Mode Options}). Various style settings are available;
25221 and styles can also be disabled entirely.
25224 @item set style enabled @samp{on|off}
25225 Enable or disable all styling. The default is host-dependent, with
25226 most hosts defaulting to @samp{on}.
25228 @item show style enabled
25229 Show the current state of styling.
25231 @item set style sources @samp{on|off}
25232 Enable or disable source code styling. This affects whether source
25233 code, such as the output of the @code{list} command, is styled. Note
25234 that source styling only works if styling in general is enabled, and
25235 if @value{GDBN} was linked with the GNU Source Highlight library. The
25236 default is @samp{on}.
25238 @item show style sources
25239 Show the current state of source code styling.
25242 Subcommands of @code{set style} control specific forms of styling.
25243 These subcommands all follow the same pattern: each style-able object
25244 can be styled with a foreground color, a background color, and an
25247 For example, the style of file names can be controlled using the
25248 @code{set style filename} group of commands:
25251 @item set style filename background @var{color}
25252 Set the background to @var{color}. Valid colors are @samp{none}
25253 (meaning the terminal's default color), @samp{black}, @samp{red},
25254 @samp{green}, @samp{yellow}, @samp{blue}, @samp{magenta}, @samp{cyan},
25257 @item set style filename foreground @var{color}
25258 Set the foreground to @var{color}. Valid colors are @samp{none}
25259 (meaning the terminal's default color), @samp{black}, @samp{red},
25260 @samp{green}, @samp{yellow}, @samp{blue}, @samp{magenta}, @samp{cyan},
25263 @item set style filename intensity @var{value}
25264 Set the intensity to @var{value}. Valid intensities are @samp{normal}
25265 (the default), @samp{bold}, and @samp{dim}.
25268 The @code{show style} command and its subcommands are styling
25269 a style name in their output using its own style.
25270 So, use @command{show style} to see the complete list of styles,
25271 their characteristics and the visual aspect of each style.
25273 The style-able objects are:
25276 Control the styling of file names. By default, this style's
25277 foreground color is green.
25280 Control the styling of function names. These are managed with the
25281 @code{set style function} family of commands. By default, this
25282 style's foreground color is yellow.
25285 Control the styling of variable names. These are managed with the
25286 @code{set style variable} family of commands. By default, this style's
25287 foreground color is cyan.
25290 Control the styling of addresses. These are managed with the
25291 @code{set style address} family of commands. By default, this style's
25292 foreground color is blue.
25295 Control the styling of titles. These are managed with the
25296 @code{set style title} family of commands. By default, this style's
25297 intensity is bold. Commands are using the title style to improve
25298 the readibility of large output. For example, the commands
25299 @command{apropos} and @command{help} are using the title style
25300 for the command names.
25303 Control the styling of highlightings. These are managed with the
25304 @code{set style highlight} family of commands. By default, this style's
25305 foreground color is red. Commands are using the highlight style to draw
25306 the user attention to some specific parts of their output. For example,
25307 the command @command{apropos -v REGEXP} uses the highlight style to
25308 mark the documentation parts matching @var{regexp}.
25314 @cindex number representation
25315 @cindex entering numbers
25317 You can always enter numbers in octal, decimal, or hexadecimal in
25318 @value{GDBN} by the usual conventions: octal numbers begin with
25319 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
25320 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
25321 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
25322 10; likewise, the default display for numbers---when no particular
25323 format is specified---is base 10. You can change the default base for
25324 both input and output with the commands described below.
25327 @kindex set input-radix
25328 @item set input-radix @var{base}
25329 Set the default base for numeric input. Supported choices
25330 for @var{base} are decimal 8, 10, or 16. The base must itself be
25331 specified either unambiguously or using the current input radix; for
25335 set input-radix 012
25336 set input-radix 10.
25337 set input-radix 0xa
25341 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
25342 leaves the input radix unchanged, no matter what it was, since
25343 @samp{10}, being without any leading or trailing signs of its base, is
25344 interpreted in the current radix. Thus, if the current radix is 16,
25345 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
25348 @kindex set output-radix
25349 @item set output-radix @var{base}
25350 Set the default base for numeric display. Supported choices
25351 for @var{base} are decimal 8, 10, or 16. The base must itself be
25352 specified either unambiguously or using the current input radix.
25354 @kindex show input-radix
25355 @item show input-radix
25356 Display the current default base for numeric input.
25358 @kindex show output-radix
25359 @item show output-radix
25360 Display the current default base for numeric display.
25362 @item set radix @r{[}@var{base}@r{]}
25366 These commands set and show the default base for both input and output
25367 of numbers. @code{set radix} sets the radix of input and output to
25368 the same base; without an argument, it resets the radix back to its
25369 default value of 10.
25374 @section Configuring the Current ABI
25376 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
25377 application automatically. However, sometimes you need to override its
25378 conclusions. Use these commands to manage @value{GDBN}'s view of the
25384 @cindex Newlib OS ABI and its influence on the longjmp handling
25386 One @value{GDBN} configuration can debug binaries for multiple operating
25387 system targets, either via remote debugging or native emulation.
25388 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
25389 but you can override its conclusion using the @code{set osabi} command.
25390 One example where this is useful is in debugging of binaries which use
25391 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
25392 not have the same identifying marks that the standard C library for your
25395 When @value{GDBN} is debugging the AArch64 architecture, it provides a
25396 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
25397 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
25398 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
25402 Show the OS ABI currently in use.
25405 With no argument, show the list of registered available OS ABI's.
25407 @item set osabi @var{abi}
25408 Set the current OS ABI to @var{abi}.
25411 @cindex float promotion
25413 Generally, the way that an argument of type @code{float} is passed to a
25414 function depends on whether the function is prototyped. For a prototyped
25415 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
25416 according to the architecture's convention for @code{float}. For unprototyped
25417 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
25418 @code{double} and then passed.
25420 Unfortunately, some forms of debug information do not reliably indicate whether
25421 a function is prototyped. If @value{GDBN} calls a function that is not marked
25422 as prototyped, it consults @kbd{set coerce-float-to-double}.
25425 @kindex set coerce-float-to-double
25426 @item set coerce-float-to-double
25427 @itemx set coerce-float-to-double on
25428 Arguments of type @code{float} will be promoted to @code{double} when passed
25429 to an unprototyped function. This is the default setting.
25431 @item set coerce-float-to-double off
25432 Arguments of type @code{float} will be passed directly to unprototyped
25435 @kindex show coerce-float-to-double
25436 @item show coerce-float-to-double
25437 Show the current setting of promoting @code{float} to @code{double}.
25441 @kindex show cp-abi
25442 @value{GDBN} needs to know the ABI used for your program's C@t{++}
25443 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
25444 used to build your application. @value{GDBN} only fully supports
25445 programs with a single C@t{++} ABI; if your program contains code using
25446 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
25447 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
25448 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
25449 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
25450 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
25451 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
25456 Show the C@t{++} ABI currently in use.
25459 With no argument, show the list of supported C@t{++} ABI's.
25461 @item set cp-abi @var{abi}
25462 @itemx set cp-abi auto
25463 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
25467 @section Automatically loading associated files
25468 @cindex auto-loading
25470 @value{GDBN} sometimes reads files with commands and settings automatically,
25471 without being explicitly told so by the user. We call this feature
25472 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
25473 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
25474 results or introduce security risks (e.g., if the file comes from untrusted
25478 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
25479 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
25481 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
25482 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
25485 There are various kinds of files @value{GDBN} can automatically load.
25486 In addition to these files, @value{GDBN} supports auto-loading code written
25487 in various extension languages. @xref{Auto-loading extensions}.
25489 Note that loading of these associated files (including the local @file{.gdbinit}
25490 file) requires accordingly configured @code{auto-load safe-path}
25491 (@pxref{Auto-loading safe path}).
25493 For these reasons, @value{GDBN} includes commands and options to let you
25494 control when to auto-load files and which files should be auto-loaded.
25497 @anchor{set auto-load off}
25498 @kindex set auto-load off
25499 @item set auto-load off
25500 Globally disable loading of all auto-loaded files.
25501 You may want to use this command with the @samp{-iex} option
25502 (@pxref{Option -init-eval-command}) such as:
25504 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
25507 Be aware that system init file (@pxref{System-wide configuration})
25508 and init files from your home directory (@pxref{Home Directory Init File})
25509 still get read (as they come from generally trusted directories).
25510 To prevent @value{GDBN} from auto-loading even those init files, use the
25511 @option{-nx} option (@pxref{Mode Options}), in addition to
25512 @code{set auto-load no}.
25514 @anchor{show auto-load}
25515 @kindex show auto-load
25516 @item show auto-load
25517 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
25521 (gdb) show auto-load
25522 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
25523 libthread-db: Auto-loading of inferior specific libthread_db is on.
25524 local-gdbinit: Auto-loading of .gdbinit script from current directory
25526 python-scripts: Auto-loading of Python scripts is on.
25527 safe-path: List of directories from which it is safe to auto-load files
25528 is $debugdir:$datadir/auto-load.
25529 scripts-directory: List of directories from which to load auto-loaded scripts
25530 is $debugdir:$datadir/auto-load.
25533 @anchor{info auto-load}
25534 @kindex info auto-load
25535 @item info auto-load
25536 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
25540 (gdb) info auto-load
25543 Yes /home/user/gdb/gdb-gdb.gdb
25544 libthread-db: No auto-loaded libthread-db.
25545 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
25549 Yes /home/user/gdb/gdb-gdb.py
25553 These are @value{GDBN} control commands for the auto-loading:
25555 @multitable @columnfractions .5 .5
25556 @item @xref{set auto-load off}.
25557 @tab Disable auto-loading globally.
25558 @item @xref{show auto-load}.
25559 @tab Show setting of all kinds of files.
25560 @item @xref{info auto-load}.
25561 @tab Show state of all kinds of files.
25562 @item @xref{set auto-load gdb-scripts}.
25563 @tab Control for @value{GDBN} command scripts.
25564 @item @xref{show auto-load gdb-scripts}.
25565 @tab Show setting of @value{GDBN} command scripts.
25566 @item @xref{info auto-load gdb-scripts}.
25567 @tab Show state of @value{GDBN} command scripts.
25568 @item @xref{set auto-load python-scripts}.
25569 @tab Control for @value{GDBN} Python scripts.
25570 @item @xref{show auto-load python-scripts}.
25571 @tab Show setting of @value{GDBN} Python scripts.
25572 @item @xref{info auto-load python-scripts}.
25573 @tab Show state of @value{GDBN} Python scripts.
25574 @item @xref{set auto-load guile-scripts}.
25575 @tab Control for @value{GDBN} Guile scripts.
25576 @item @xref{show auto-load guile-scripts}.
25577 @tab Show setting of @value{GDBN} Guile scripts.
25578 @item @xref{info auto-load guile-scripts}.
25579 @tab Show state of @value{GDBN} Guile scripts.
25580 @item @xref{set auto-load scripts-directory}.
25581 @tab Control for @value{GDBN} auto-loaded scripts location.
25582 @item @xref{show auto-load scripts-directory}.
25583 @tab Show @value{GDBN} auto-loaded scripts location.
25584 @item @xref{add-auto-load-scripts-directory}.
25585 @tab Add directory for auto-loaded scripts location list.
25586 @item @xref{set auto-load local-gdbinit}.
25587 @tab Control for init file in the current directory.
25588 @item @xref{show auto-load local-gdbinit}.
25589 @tab Show setting of init file in the current directory.
25590 @item @xref{info auto-load local-gdbinit}.
25591 @tab Show state of init file in the current directory.
25592 @item @xref{set auto-load libthread-db}.
25593 @tab Control for thread debugging library.
25594 @item @xref{show auto-load libthread-db}.
25595 @tab Show setting of thread debugging library.
25596 @item @xref{info auto-load libthread-db}.
25597 @tab Show state of thread debugging library.
25598 @item @xref{set auto-load safe-path}.
25599 @tab Control directories trusted for automatic loading.
25600 @item @xref{show auto-load safe-path}.
25601 @tab Show directories trusted for automatic loading.
25602 @item @xref{add-auto-load-safe-path}.
25603 @tab Add directory trusted for automatic loading.
25606 @node Init File in the Current Directory
25607 @subsection Automatically loading init file in the current directory
25608 @cindex auto-loading init file in the current directory
25610 By default, @value{GDBN} reads and executes the canned sequences of commands
25611 from init file (if any) in the current working directory,
25612 see @ref{Init File in the Current Directory during Startup}.
25614 Note that loading of this local @file{.gdbinit} file also requires accordingly
25615 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25618 @anchor{set auto-load local-gdbinit}
25619 @kindex set auto-load local-gdbinit
25620 @item set auto-load local-gdbinit [on|off]
25621 Enable or disable the auto-loading of canned sequences of commands
25622 (@pxref{Sequences}) found in init file in the current directory.
25624 @anchor{show auto-load local-gdbinit}
25625 @kindex show auto-load local-gdbinit
25626 @item show auto-load local-gdbinit
25627 Show whether auto-loading of canned sequences of commands from init file in the
25628 current directory is enabled or disabled.
25630 @anchor{info auto-load local-gdbinit}
25631 @kindex info auto-load local-gdbinit
25632 @item info auto-load local-gdbinit
25633 Print whether canned sequences of commands from init file in the
25634 current directory have been auto-loaded.
25637 @node libthread_db.so.1 file
25638 @subsection Automatically loading thread debugging library
25639 @cindex auto-loading libthread_db.so.1
25641 This feature is currently present only on @sc{gnu}/Linux native hosts.
25643 @value{GDBN} reads in some cases thread debugging library from places specific
25644 to the inferior (@pxref{set libthread-db-search-path}).
25646 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
25647 without checking this @samp{set auto-load libthread-db} switch as system
25648 libraries have to be trusted in general. In all other cases of
25649 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
25650 auto-load libthread-db} is enabled before trying to open such thread debugging
25653 Note that loading of this debugging library also requires accordingly configured
25654 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25657 @anchor{set auto-load libthread-db}
25658 @kindex set auto-load libthread-db
25659 @item set auto-load libthread-db [on|off]
25660 Enable or disable the auto-loading of inferior specific thread debugging library.
25662 @anchor{show auto-load libthread-db}
25663 @kindex show auto-load libthread-db
25664 @item show auto-load libthread-db
25665 Show whether auto-loading of inferior specific thread debugging library is
25666 enabled or disabled.
25668 @anchor{info auto-load libthread-db}
25669 @kindex info auto-load libthread-db
25670 @item info auto-load libthread-db
25671 Print the list of all loaded inferior specific thread debugging libraries and
25672 for each such library print list of inferior @var{pid}s using it.
25675 @node Auto-loading safe path
25676 @subsection Security restriction for auto-loading
25677 @cindex auto-loading safe-path
25679 As the files of inferior can come from untrusted source (such as submitted by
25680 an application user) @value{GDBN} does not always load any files automatically.
25681 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
25682 directories trusted for loading files not explicitly requested by user.
25683 Each directory can also be a shell wildcard pattern.
25685 If the path is not set properly you will see a warning and the file will not
25690 Reading symbols from /home/user/gdb/gdb...done.
25691 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
25692 declined by your `auto-load safe-path' set
25693 to "$debugdir:$datadir/auto-load".
25694 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
25695 declined by your `auto-load safe-path' set
25696 to "$debugdir:$datadir/auto-load".
25700 To instruct @value{GDBN} to go ahead and use the init files anyway,
25701 invoke @value{GDBN} like this:
25704 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
25707 The list of trusted directories is controlled by the following commands:
25710 @anchor{set auto-load safe-path}
25711 @kindex set auto-load safe-path
25712 @item set auto-load safe-path @r{[}@var{directories}@r{]}
25713 Set the list of directories (and their subdirectories) trusted for automatic
25714 loading and execution of scripts. You can also enter a specific trusted file.
25715 Each directory can also be a shell wildcard pattern; wildcards do not match
25716 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
25717 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
25718 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
25719 its default value as specified during @value{GDBN} compilation.
25721 The list of directories uses path separator (@samp{:} on GNU and Unix
25722 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
25723 to the @env{PATH} environment variable.
25725 @anchor{show auto-load safe-path}
25726 @kindex show auto-load safe-path
25727 @item show auto-load safe-path
25728 Show the list of directories trusted for automatic loading and execution of
25731 @anchor{add-auto-load-safe-path}
25732 @kindex add-auto-load-safe-path
25733 @item add-auto-load-safe-path
25734 Add an entry (or list of entries) to the list of directories trusted for
25735 automatic loading and execution of scripts. Multiple entries may be delimited
25736 by the host platform path separator in use.
25739 This variable defaults to what @code{--with-auto-load-dir} has been configured
25740 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
25741 substitution applies the same as for @ref{set auto-load scripts-directory}.
25742 The default @code{set auto-load safe-path} value can be also overriden by
25743 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
25745 Setting this variable to @file{/} disables this security protection,
25746 corresponding @value{GDBN} configuration option is
25747 @option{--without-auto-load-safe-path}.
25748 This variable is supposed to be set to the system directories writable by the
25749 system superuser only. Users can add their source directories in init files in
25750 their home directories (@pxref{Home Directory Init File}). See also deprecated
25751 init file in the current directory
25752 (@pxref{Init File in the Current Directory during Startup}).
25754 To force @value{GDBN} to load the files it declined to load in the previous
25755 example, you could use one of the following ways:
25758 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
25759 Specify this trusted directory (or a file) as additional component of the list.
25760 You have to specify also any existing directories displayed by
25761 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
25763 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
25764 Specify this directory as in the previous case but just for a single
25765 @value{GDBN} session.
25767 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
25768 Disable auto-loading safety for a single @value{GDBN} session.
25769 This assumes all the files you debug during this @value{GDBN} session will come
25770 from trusted sources.
25772 @item @kbd{./configure --without-auto-load-safe-path}
25773 During compilation of @value{GDBN} you may disable any auto-loading safety.
25774 This assumes all the files you will ever debug with this @value{GDBN} come from
25778 On the other hand you can also explicitly forbid automatic files loading which
25779 also suppresses any such warning messages:
25782 @item @kbd{gdb -iex "set auto-load no" @dots{}}
25783 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
25785 @item @file{~/.gdbinit}: @samp{set auto-load no}
25786 Disable auto-loading globally for the user
25787 (@pxref{Home Directory Init File}). While it is improbable, you could also
25788 use system init file instead (@pxref{System-wide configuration}).
25791 This setting applies to the file names as entered by user. If no entry matches
25792 @value{GDBN} tries as a last resort to also resolve all the file names into
25793 their canonical form (typically resolving symbolic links) and compare the
25794 entries again. @value{GDBN} already canonicalizes most of the filenames on its
25795 own before starting the comparison so a canonical form of directories is
25796 recommended to be entered.
25798 @node Auto-loading verbose mode
25799 @subsection Displaying files tried for auto-load
25800 @cindex auto-loading verbose mode
25802 For better visibility of all the file locations where you can place scripts to
25803 be auto-loaded with inferior --- or to protect yourself against accidental
25804 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
25805 all the files attempted to be loaded. Both existing and non-existing files may
25808 For example the list of directories from which it is safe to auto-load files
25809 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
25810 may not be too obvious while setting it up.
25813 (gdb) set debug auto-load on
25814 (gdb) file ~/src/t/true
25815 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
25816 for objfile "/tmp/true".
25817 auto-load: Updating directories of "/usr:/opt".
25818 auto-load: Using directory "/usr".
25819 auto-load: Using directory "/opt".
25820 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
25821 by your `auto-load safe-path' set to "/usr:/opt".
25825 @anchor{set debug auto-load}
25826 @kindex set debug auto-load
25827 @item set debug auto-load [on|off]
25828 Set whether to print the filenames attempted to be auto-loaded.
25830 @anchor{show debug auto-load}
25831 @kindex show debug auto-load
25832 @item show debug auto-load
25833 Show whether printing of the filenames attempted to be auto-loaded is turned
25837 @node Messages/Warnings
25838 @section Optional Warnings and Messages
25840 @cindex verbose operation
25841 @cindex optional warnings
25842 By default, @value{GDBN} is silent about its inner workings. If you are
25843 running on a slow machine, you may want to use the @code{set verbose}
25844 command. This makes @value{GDBN} tell you when it does a lengthy
25845 internal operation, so you will not think it has crashed.
25847 Currently, the messages controlled by @code{set verbose} are those
25848 which announce that the symbol table for a source file is being read;
25849 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
25852 @kindex set verbose
25853 @item set verbose on
25854 Enables @value{GDBN} output of certain informational messages.
25856 @item set verbose off
25857 Disables @value{GDBN} output of certain informational messages.
25859 @kindex show verbose
25861 Displays whether @code{set verbose} is on or off.
25864 By default, if @value{GDBN} encounters bugs in the symbol table of an
25865 object file, it is silent; but if you are debugging a compiler, you may
25866 find this information useful (@pxref{Symbol Errors, ,Errors Reading
25871 @kindex set complaints
25872 @item set complaints @var{limit}
25873 Permits @value{GDBN} to output @var{limit} complaints about each type of
25874 unusual symbols before becoming silent about the problem. Set
25875 @var{limit} to zero to suppress all complaints; set it to a large number
25876 to prevent complaints from being suppressed.
25878 @kindex show complaints
25879 @item show complaints
25880 Displays how many symbol complaints @value{GDBN} is permitted to produce.
25884 @anchor{confirmation requests}
25885 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
25886 lot of stupid questions to confirm certain commands. For example, if
25887 you try to run a program which is already running:
25891 The program being debugged has been started already.
25892 Start it from the beginning? (y or n)
25895 If you are willing to unflinchingly face the consequences of your own
25896 commands, you can disable this ``feature'':
25900 @kindex set confirm
25902 @cindex confirmation
25903 @cindex stupid questions
25904 @item set confirm off
25905 Disables confirmation requests. Note that running @value{GDBN} with
25906 the @option{--batch} option (@pxref{Mode Options, -batch}) also
25907 automatically disables confirmation requests.
25909 @item set confirm on
25910 Enables confirmation requests (the default).
25912 @kindex show confirm
25914 Displays state of confirmation requests.
25918 @cindex command tracing
25919 If you need to debug user-defined commands or sourced files you may find it
25920 useful to enable @dfn{command tracing}. In this mode each command will be
25921 printed as it is executed, prefixed with one or more @samp{+} symbols, the
25922 quantity denoting the call depth of each command.
25925 @kindex set trace-commands
25926 @cindex command scripts, debugging
25927 @item set trace-commands on
25928 Enable command tracing.
25929 @item set trace-commands off
25930 Disable command tracing.
25931 @item show trace-commands
25932 Display the current state of command tracing.
25935 @node Debugging Output
25936 @section Optional Messages about Internal Happenings
25937 @cindex optional debugging messages
25939 @value{GDBN} has commands that enable optional debugging messages from
25940 various @value{GDBN} subsystems; normally these commands are of
25941 interest to @value{GDBN} maintainers, or when reporting a bug. This
25942 section documents those commands.
25945 @kindex set exec-done-display
25946 @item set exec-done-display
25947 Turns on or off the notification of asynchronous commands'
25948 completion. When on, @value{GDBN} will print a message when an
25949 asynchronous command finishes its execution. The default is off.
25950 @kindex show exec-done-display
25951 @item show exec-done-display
25952 Displays the current setting of asynchronous command completion
25955 @cindex ARM AArch64
25956 @item set debug aarch64
25957 Turns on or off display of debugging messages related to ARM AArch64.
25958 The default is off.
25960 @item show debug aarch64
25961 Displays the current state of displaying debugging messages related to
25963 @cindex gdbarch debugging info
25964 @cindex architecture debugging info
25965 @item set debug arch
25966 Turns on or off display of gdbarch debugging info. The default is off
25967 @item show debug arch
25968 Displays the current state of displaying gdbarch debugging info.
25969 @item set debug aix-solib
25970 @cindex AIX shared library debugging
25971 Control display of debugging messages from the AIX shared library
25972 support module. The default is off.
25973 @item show debug aix-thread
25974 Show the current state of displaying AIX shared library debugging messages.
25975 @item set debug aix-thread
25976 @cindex AIX threads
25977 Display debugging messages about inner workings of the AIX thread
25979 @item show debug aix-thread
25980 Show the current state of AIX thread debugging info display.
25981 @item set debug check-physname
25983 Check the results of the ``physname'' computation. When reading DWARF
25984 debugging information for C@t{++}, @value{GDBN} attempts to compute
25985 each entity's name. @value{GDBN} can do this computation in two
25986 different ways, depending on exactly what information is present.
25987 When enabled, this setting causes @value{GDBN} to compute the names
25988 both ways and display any discrepancies.
25989 @item show debug check-physname
25990 Show the current state of ``physname'' checking.
25991 @item set debug coff-pe-read
25992 @cindex COFF/PE exported symbols
25993 Control display of debugging messages related to reading of COFF/PE
25994 exported symbols. The default is off.
25995 @item show debug coff-pe-read
25996 Displays the current state of displaying debugging messages related to
25997 reading of COFF/PE exported symbols.
25998 @item set debug dwarf-die
26000 Dump DWARF DIEs after they are read in.
26001 The value is the number of nesting levels to print.
26002 A value of zero turns off the display.
26003 @item show debug dwarf-die
26004 Show the current state of DWARF DIE debugging.
26005 @item set debug dwarf-line
26006 @cindex DWARF Line Tables
26007 Turns on or off display of debugging messages related to reading
26008 DWARF line tables. The default is 0 (off).
26009 A value of 1 provides basic information.
26010 A value greater than 1 provides more verbose information.
26011 @item show debug dwarf-line
26012 Show the current state of DWARF line table debugging.
26013 @item set debug dwarf-read
26014 @cindex DWARF Reading
26015 Turns on or off display of debugging messages related to reading
26016 DWARF debug info. The default is 0 (off).
26017 A value of 1 provides basic information.
26018 A value greater than 1 provides more verbose information.
26019 @item show debug dwarf-read
26020 Show the current state of DWARF reader debugging.
26021 @item set debug displaced
26022 @cindex displaced stepping debugging info
26023 Turns on or off display of @value{GDBN} debugging info for the
26024 displaced stepping support. The default is off.
26025 @item show debug displaced
26026 Displays the current state of displaying @value{GDBN} debugging info
26027 related to displaced stepping.
26028 @item set debug event
26029 @cindex event debugging info
26030 Turns on or off display of @value{GDBN} event debugging info. The
26032 @item show debug event
26033 Displays the current state of displaying @value{GDBN} event debugging
26035 @item set debug expression
26036 @cindex expression debugging info
26037 Turns on or off display of debugging info about @value{GDBN}
26038 expression parsing. The default is off.
26039 @item show debug expression
26040 Displays the current state of displaying debugging info about
26041 @value{GDBN} expression parsing.
26042 @item set debug fbsd-lwp
26043 @cindex FreeBSD LWP debug messages
26044 Turns on or off debugging messages from the FreeBSD LWP debug support.
26045 @item show debug fbsd-lwp
26046 Show the current state of FreeBSD LWP debugging messages.
26047 @item set debug fbsd-nat
26048 @cindex FreeBSD native target debug messages
26049 Turns on or off debugging messages from the FreeBSD native target.
26050 @item show debug fbsd-nat
26051 Show the current state of FreeBSD native target debugging messages.
26052 @item set debug frame
26053 @cindex frame debugging info
26054 Turns on or off display of @value{GDBN} frame debugging info. The
26056 @item show debug frame
26057 Displays the current state of displaying @value{GDBN} frame debugging
26059 @item set debug gnu-nat
26060 @cindex @sc{gnu}/Hurd debug messages
26061 Turn on or off debugging messages from the @sc{gnu}/Hurd debug support.
26062 @item show debug gnu-nat
26063 Show the current state of @sc{gnu}/Hurd debugging messages.
26064 @item set debug infrun
26065 @cindex inferior debugging info
26066 Turns on or off display of @value{GDBN} debugging info for running the inferior.
26067 The default is off. @file{infrun.c} contains GDB's runtime state machine used
26068 for implementing operations such as single-stepping the inferior.
26069 @item show debug infrun
26070 Displays the current state of @value{GDBN} inferior debugging.
26071 @item set debug jit
26072 @cindex just-in-time compilation, debugging messages
26073 Turn on or off debugging messages from JIT debug support.
26074 @item show debug jit
26075 Displays the current state of @value{GDBN} JIT debugging.
26076 @item set debug lin-lwp
26077 @cindex @sc{gnu}/Linux LWP debug messages
26078 @cindex Linux lightweight processes
26079 Turn on or off debugging messages from the Linux LWP debug support.
26080 @item show debug lin-lwp
26081 Show the current state of Linux LWP debugging messages.
26082 @item set debug linux-namespaces
26083 @cindex @sc{gnu}/Linux namespaces debug messages
26084 Turn on or off debugging messages from the Linux namespaces debug support.
26085 @item show debug linux-namespaces
26086 Show the current state of Linux namespaces debugging messages.
26087 @item set debug mach-o
26088 @cindex Mach-O symbols processing
26089 Control display of debugging messages related to Mach-O symbols
26090 processing. The default is off.
26091 @item show debug mach-o
26092 Displays the current state of displaying debugging messages related to
26093 reading of COFF/PE exported symbols.
26094 @item set debug notification
26095 @cindex remote async notification debugging info
26096 Turn on or off debugging messages about remote async notification.
26097 The default is off.
26098 @item show debug notification
26099 Displays the current state of remote async notification debugging messages.
26100 @item set debug observer
26101 @cindex observer debugging info
26102 Turns on or off display of @value{GDBN} observer debugging. This
26103 includes info such as the notification of observable events.
26104 @item show debug observer
26105 Displays the current state of observer debugging.
26106 @item set debug overload
26107 @cindex C@t{++} overload debugging info
26108 Turns on or off display of @value{GDBN} C@t{++} overload debugging
26109 info. This includes info such as ranking of functions, etc. The default
26111 @item show debug overload
26112 Displays the current state of displaying @value{GDBN} C@t{++} overload
26114 @cindex expression parser, debugging info
26115 @cindex debug expression parser
26116 @item set debug parser
26117 Turns on or off the display of expression parser debugging output.
26118 Internally, this sets the @code{yydebug} variable in the expression
26119 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
26120 details. The default is off.
26121 @item show debug parser
26122 Show the current state of expression parser debugging.
26123 @cindex packets, reporting on stdout
26124 @cindex serial connections, debugging
26125 @cindex debug remote protocol
26126 @cindex remote protocol debugging
26127 @cindex display remote packets
26128 @item set debug remote
26129 Turns on or off display of reports on all packets sent back and forth across
26130 the serial line to the remote machine. The info is printed on the
26131 @value{GDBN} standard output stream. The default is off.
26132 @item show debug remote
26133 Displays the state of display of remote packets.
26135 @item set debug separate-debug-file
26136 Turns on or off display of debug output about separate debug file search.
26137 @item show debug separate-debug-file
26138 Displays the state of separate debug file search debug output.
26140 @item set debug serial
26141 Turns on or off display of @value{GDBN} serial debugging info. The
26143 @item show debug serial
26144 Displays the current state of displaying @value{GDBN} serial debugging
26146 @item set debug solib-frv
26147 @cindex FR-V shared-library debugging
26148 Turn on or off debugging messages for FR-V shared-library code.
26149 @item show debug solib-frv
26150 Display the current state of FR-V shared-library code debugging
26152 @item set debug symbol-lookup
26153 @cindex symbol lookup
26154 Turns on or off display of debugging messages related to symbol lookup.
26155 The default is 0 (off).
26156 A value of 1 provides basic information.
26157 A value greater than 1 provides more verbose information.
26158 @item show debug symbol-lookup
26159 Show the current state of symbol lookup debugging messages.
26160 @item set debug symfile
26161 @cindex symbol file functions
26162 Turns on or off display of debugging messages related to symbol file functions.
26163 The default is off. @xref{Files}.
26164 @item show debug symfile
26165 Show the current state of symbol file debugging messages.
26166 @item set debug symtab-create
26167 @cindex symbol table creation
26168 Turns on or off display of debugging messages related to symbol table creation.
26169 The default is 0 (off).
26170 A value of 1 provides basic information.
26171 A value greater than 1 provides more verbose information.
26172 @item show debug symtab-create
26173 Show the current state of symbol table creation debugging.
26174 @item set debug target
26175 @cindex target debugging info
26176 Turns on or off display of @value{GDBN} target debugging info. This info
26177 includes what is going on at the target level of GDB, as it happens. The
26178 default is 0. Set it to 1 to track events, and to 2 to also track the
26179 value of large memory transfers.
26180 @item show debug target
26181 Displays the current state of displaying @value{GDBN} target debugging
26183 @item set debug timestamp
26184 @cindex timestampping debugging info
26185 Turns on or off display of timestamps with @value{GDBN} debugging info.
26186 When enabled, seconds and microseconds are displayed before each debugging
26188 @item show debug timestamp
26189 Displays the current state of displaying timestamps with @value{GDBN}
26191 @item set debug varobj
26192 @cindex variable object debugging info
26193 Turns on or off display of @value{GDBN} variable object debugging
26194 info. The default is off.
26195 @item show debug varobj
26196 Displays the current state of displaying @value{GDBN} variable object
26198 @item set debug xml
26199 @cindex XML parser debugging
26200 Turn on or off debugging messages for built-in XML parsers.
26201 @item show debug xml
26202 Displays the current state of XML debugging messages.
26205 @node Other Misc Settings
26206 @section Other Miscellaneous Settings
26207 @cindex miscellaneous settings
26210 @kindex set interactive-mode
26211 @item set interactive-mode
26212 If @code{on}, forces @value{GDBN} to assume that GDB was started
26213 in a terminal. In practice, this means that @value{GDBN} should wait
26214 for the user to answer queries generated by commands entered at
26215 the command prompt. If @code{off}, forces @value{GDBN} to operate
26216 in the opposite mode, and it uses the default answers to all queries.
26217 If @code{auto} (the default), @value{GDBN} tries to determine whether
26218 its standard input is a terminal, and works in interactive-mode if it
26219 is, non-interactively otherwise.
26221 In the vast majority of cases, the debugger should be able to guess
26222 correctly which mode should be used. But this setting can be useful
26223 in certain specific cases, such as running a MinGW @value{GDBN}
26224 inside a cygwin window.
26226 @kindex show interactive-mode
26227 @item show interactive-mode
26228 Displays whether the debugger is operating in interactive mode or not.
26231 @node Extending GDB
26232 @chapter Extending @value{GDBN}
26233 @cindex extending GDB
26235 @value{GDBN} provides several mechanisms for extension.
26236 @value{GDBN} also provides the ability to automatically load
26237 extensions when it reads a file for debugging. This allows the
26238 user to automatically customize @value{GDBN} for the program
26242 * Sequences:: Canned Sequences of @value{GDBN} Commands
26243 * Python:: Extending @value{GDBN} using Python
26244 * Guile:: Extending @value{GDBN} using Guile
26245 * Auto-loading extensions:: Automatically loading extensions
26246 * Multiple Extension Languages:: Working with multiple extension languages
26247 * Aliases:: Creating new spellings of existing commands
26250 To facilitate the use of extension languages, @value{GDBN} is capable
26251 of evaluating the contents of a file. When doing so, @value{GDBN}
26252 can recognize which extension language is being used by looking at
26253 the filename extension. Files with an unrecognized filename extension
26254 are always treated as a @value{GDBN} Command Files.
26255 @xref{Command Files,, Command files}.
26257 You can control how @value{GDBN} evaluates these files with the following
26261 @kindex set script-extension
26262 @kindex show script-extension
26263 @item set script-extension off
26264 All scripts are always evaluated as @value{GDBN} Command Files.
26266 @item set script-extension soft
26267 The debugger determines the scripting language based on filename
26268 extension. If this scripting language is supported, @value{GDBN}
26269 evaluates the script using that language. Otherwise, it evaluates
26270 the file as a @value{GDBN} Command File.
26272 @item set script-extension strict
26273 The debugger determines the scripting language based on filename
26274 extension, and evaluates the script using that language. If the
26275 language is not supported, then the evaluation fails.
26277 @item show script-extension
26278 Display the current value of the @code{script-extension} option.
26283 @section Canned Sequences of Commands
26285 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
26286 Command Lists}), @value{GDBN} provides two ways to store sequences of
26287 commands for execution as a unit: user-defined commands and command
26291 * Define:: How to define your own commands
26292 * Hooks:: Hooks for user-defined commands
26293 * Command Files:: How to write scripts of commands to be stored in a file
26294 * Output:: Commands for controlled output
26295 * Auto-loading sequences:: Controlling auto-loaded command files
26299 @subsection User-defined Commands
26301 @cindex user-defined command
26302 @cindex arguments, to user-defined commands
26303 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
26304 which you assign a new name as a command. This is done with the
26305 @code{define} command. User commands may accept an unlimited number of arguments
26306 separated by whitespace. Arguments are accessed within the user command
26307 via @code{$arg0@dots{}$argN}. A trivial example:
26311 print $arg0 + $arg1 + $arg2
26316 To execute the command use:
26323 This defines the command @code{adder}, which prints the sum of
26324 its three arguments. Note the arguments are text substitutions, so they may
26325 reference variables, use complex expressions, or even perform inferior
26328 @cindex argument count in user-defined commands
26329 @cindex how many arguments (user-defined commands)
26330 In addition, @code{$argc} may be used to find out how many arguments have
26336 print $arg0 + $arg1
26339 print $arg0 + $arg1 + $arg2
26344 Combining with the @code{eval} command (@pxref{eval}) makes it easier
26345 to process a variable number of arguments:
26352 eval "set $sum = $sum + $arg%d", $i
26362 @item define @var{commandname}
26363 Define a command named @var{commandname}. If there is already a command
26364 by that name, you are asked to confirm that you want to redefine it.
26365 The argument @var{commandname} may be a bare command name consisting of letters,
26366 numbers, dashes, and underscores. It may also start with any predefined
26367 prefix command. For example, @samp{define target my-target} creates
26368 a user-defined @samp{target my-target} command.
26370 The definition of the command is made up of other @value{GDBN} command lines,
26371 which are given following the @code{define} command. The end of these
26372 commands is marked by a line containing @code{end}.
26375 @kindex end@r{ (user-defined commands)}
26376 @item document @var{commandname}
26377 Document the user-defined command @var{commandname}, so that it can be
26378 accessed by @code{help}. The command @var{commandname} must already be
26379 defined. This command reads lines of documentation just as @code{define}
26380 reads the lines of the command definition, ending with @code{end}.
26381 After the @code{document} command is finished, @code{help} on command
26382 @var{commandname} displays the documentation you have written.
26384 You may use the @code{document} command again to change the
26385 documentation of a command. Redefining the command with @code{define}
26386 does not change the documentation.
26388 @kindex dont-repeat
26389 @cindex don't repeat command
26391 Used inside a user-defined command, this tells @value{GDBN} that this
26392 command should not be repeated when the user hits @key{RET}
26393 (@pxref{Command Syntax, repeat last command}).
26395 @kindex help user-defined
26396 @item help user-defined
26397 List all user-defined commands and all python commands defined in class
26398 COMAND_USER. The first line of the documentation or docstring is
26403 @itemx show user @var{commandname}
26404 Display the @value{GDBN} commands used to define @var{commandname} (but
26405 not its documentation). If no @var{commandname} is given, display the
26406 definitions for all user-defined commands.
26407 This does not work for user-defined python commands.
26409 @cindex infinite recursion in user-defined commands
26410 @kindex show max-user-call-depth
26411 @kindex set max-user-call-depth
26412 @item show max-user-call-depth
26413 @itemx set max-user-call-depth
26414 The value of @code{max-user-call-depth} controls how many recursion
26415 levels are allowed in user-defined commands before @value{GDBN} suspects an
26416 infinite recursion and aborts the command.
26417 This does not apply to user-defined python commands.
26420 In addition to the above commands, user-defined commands frequently
26421 use control flow commands, described in @ref{Command Files}.
26423 When user-defined commands are executed, the
26424 commands of the definition are not printed. An error in any command
26425 stops execution of the user-defined command.
26427 If used interactively, commands that would ask for confirmation proceed
26428 without asking when used inside a user-defined command. Many @value{GDBN}
26429 commands that normally print messages to say what they are doing omit the
26430 messages when used in a user-defined command.
26433 @subsection User-defined Command Hooks
26434 @cindex command hooks
26435 @cindex hooks, for commands
26436 @cindex hooks, pre-command
26439 You may define @dfn{hooks}, which are a special kind of user-defined
26440 command. Whenever you run the command @samp{foo}, if the user-defined
26441 command @samp{hook-foo} exists, it is executed (with no arguments)
26442 before that command.
26444 @cindex hooks, post-command
26446 A hook may also be defined which is run after the command you executed.
26447 Whenever you run the command @samp{foo}, if the user-defined command
26448 @samp{hookpost-foo} exists, it is executed (with no arguments) after
26449 that command. Post-execution hooks may exist simultaneously with
26450 pre-execution hooks, for the same command.
26452 It is valid for a hook to call the command which it hooks. If this
26453 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
26455 @c It would be nice if hookpost could be passed a parameter indicating
26456 @c if the command it hooks executed properly or not. FIXME!
26458 @kindex stop@r{, a pseudo-command}
26459 In addition, a pseudo-command, @samp{stop} exists. Defining
26460 (@samp{hook-stop}) makes the associated commands execute every time
26461 execution stops in your program: before breakpoint commands are run,
26462 displays are printed, or the stack frame is printed.
26464 For example, to ignore @code{SIGALRM} signals while
26465 single-stepping, but treat them normally during normal execution,
26470 handle SIGALRM nopass
26474 handle SIGALRM pass
26477 define hook-continue
26478 handle SIGALRM pass
26482 As a further example, to hook at the beginning and end of the @code{echo}
26483 command, and to add extra text to the beginning and end of the message,
26491 define hookpost-echo
26495 (@value{GDBP}) echo Hello World
26496 <<<---Hello World--->>>
26501 You can define a hook for any single-word command in @value{GDBN}, but
26502 not for command aliases; you should define a hook for the basic command
26503 name, e.g.@: @code{backtrace} rather than @code{bt}.
26504 @c FIXME! So how does Joe User discover whether a command is an alias
26506 You can hook a multi-word command by adding @code{hook-} or
26507 @code{hookpost-} to the last word of the command, e.g.@:
26508 @samp{define target hook-remote} to add a hook to @samp{target remote}.
26510 If an error occurs during the execution of your hook, execution of
26511 @value{GDBN} commands stops and @value{GDBN} issues a prompt
26512 (before the command that you actually typed had a chance to run).
26514 If you try to define a hook which does not match any known command, you
26515 get a warning from the @code{define} command.
26517 @node Command Files
26518 @subsection Command Files
26520 @cindex command files
26521 @cindex scripting commands
26522 A command file for @value{GDBN} is a text file made of lines that are
26523 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
26524 also be included. An empty line in a command file does nothing; it
26525 does not mean to repeat the last command, as it would from the
26528 You can request the execution of a command file with the @code{source}
26529 command. Note that the @code{source} command is also used to evaluate
26530 scripts that are not Command Files. The exact behavior can be configured
26531 using the @code{script-extension} setting.
26532 @xref{Extending GDB,, Extending GDB}.
26536 @cindex execute commands from a file
26537 @item source [-s] [-v] @var{filename}
26538 Execute the command file @var{filename}.
26541 The lines in a command file are generally executed sequentially,
26542 unless the order of execution is changed by one of the
26543 @emph{flow-control commands} described below. The commands are not
26544 printed as they are executed. An error in any command terminates
26545 execution of the command file and control is returned to the console.
26547 @value{GDBN} first searches for @var{filename} in the current directory.
26548 If the file is not found there, and @var{filename} does not specify a
26549 directory, then @value{GDBN} also looks for the file on the source search path
26550 (specified with the @samp{directory} command);
26551 except that @file{$cdir} is not searched because the compilation directory
26552 is not relevant to scripts.
26554 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
26555 on the search path even if @var{filename} specifies a directory.
26556 The search is done by appending @var{filename} to each element of the
26557 search path. So, for example, if @var{filename} is @file{mylib/myscript}
26558 and the search path contains @file{/home/user} then @value{GDBN} will
26559 look for the script @file{/home/user/mylib/myscript}.
26560 The search is also done if @var{filename} is an absolute path.
26561 For example, if @var{filename} is @file{/tmp/myscript} and
26562 the search path contains @file{/home/user} then @value{GDBN} will
26563 look for the script @file{/home/user/tmp/myscript}.
26564 For DOS-like systems, if @var{filename} contains a drive specification,
26565 it is stripped before concatenation. For example, if @var{filename} is
26566 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
26567 will look for the script @file{c:/tmp/myscript}.
26569 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
26570 each command as it is executed. The option must be given before
26571 @var{filename}, and is interpreted as part of the filename anywhere else.
26573 Commands that would ask for confirmation if used interactively proceed
26574 without asking when used in a command file. Many @value{GDBN} commands that
26575 normally print messages to say what they are doing omit the messages
26576 when called from command files.
26578 @value{GDBN} also accepts command input from standard input. In this
26579 mode, normal output goes to standard output and error output goes to
26580 standard error. Errors in a command file supplied on standard input do
26581 not terminate execution of the command file---execution continues with
26585 gdb < cmds > log 2>&1
26588 (The syntax above will vary depending on the shell used.) This example
26589 will execute commands from the file @file{cmds}. All output and errors
26590 would be directed to @file{log}.
26592 Since commands stored on command files tend to be more general than
26593 commands typed interactively, they frequently need to deal with
26594 complicated situations, such as different or unexpected values of
26595 variables and symbols, changes in how the program being debugged is
26596 built, etc. @value{GDBN} provides a set of flow-control commands to
26597 deal with these complexities. Using these commands, you can write
26598 complex scripts that loop over data structures, execute commands
26599 conditionally, etc.
26606 This command allows to include in your script conditionally executed
26607 commands. The @code{if} command takes a single argument, which is an
26608 expression to evaluate. It is followed by a series of commands that
26609 are executed only if the expression is true (its value is nonzero).
26610 There can then optionally be an @code{else} line, followed by a series
26611 of commands that are only executed if the expression was false. The
26612 end of the list is marked by a line containing @code{end}.
26616 This command allows to write loops. Its syntax is similar to
26617 @code{if}: the command takes a single argument, which is an expression
26618 to evaluate, and must be followed by the commands to execute, one per
26619 line, terminated by an @code{end}. These commands are called the
26620 @dfn{body} of the loop. The commands in the body of @code{while} are
26621 executed repeatedly as long as the expression evaluates to true.
26625 This command exits the @code{while} loop in whose body it is included.
26626 Execution of the script continues after that @code{while}s @code{end}
26629 @kindex loop_continue
26630 @item loop_continue
26631 This command skips the execution of the rest of the body of commands
26632 in the @code{while} loop in whose body it is included. Execution
26633 branches to the beginning of the @code{while} loop, where it evaluates
26634 the controlling expression.
26636 @kindex end@r{ (if/else/while commands)}
26638 Terminate the block of commands that are the body of @code{if},
26639 @code{else}, or @code{while} flow-control commands.
26644 @subsection Commands for Controlled Output
26646 During the execution of a command file or a user-defined command, normal
26647 @value{GDBN} output is suppressed; the only output that appears is what is
26648 explicitly printed by the commands in the definition. This section
26649 describes three commands useful for generating exactly the output you
26654 @item echo @var{text}
26655 @c I do not consider backslash-space a standard C escape sequence
26656 @c because it is not in ANSI.
26657 Print @var{text}. Nonprinting characters can be included in
26658 @var{text} using C escape sequences, such as @samp{\n} to print a
26659 newline. @strong{No newline is printed unless you specify one.}
26660 In addition to the standard C escape sequences, a backslash followed
26661 by a space stands for a space. This is useful for displaying a
26662 string with spaces at the beginning or the end, since leading and
26663 trailing spaces are otherwise trimmed from all arguments.
26664 To print @samp{@w{ }and foo =@w{ }}, use the command
26665 @samp{echo \@w{ }and foo = \@w{ }}.
26667 A backslash at the end of @var{text} can be used, as in C, to continue
26668 the command onto subsequent lines. For example,
26671 echo This is some text\n\
26672 which is continued\n\
26673 onto several lines.\n
26676 produces the same output as
26679 echo This is some text\n
26680 echo which is continued\n
26681 echo onto several lines.\n
26685 @item output @var{expression}
26686 Print the value of @var{expression} and nothing but that value: no
26687 newlines, no @samp{$@var{nn} = }. The value is not entered in the
26688 value history either. @xref{Expressions, ,Expressions}, for more information
26691 @item output/@var{fmt} @var{expression}
26692 Print the value of @var{expression} in format @var{fmt}. You can use
26693 the same formats as for @code{print}. @xref{Output Formats,,Output
26694 Formats}, for more information.
26697 @item printf @var{template}, @var{expressions}@dots{}
26698 Print the values of one or more @var{expressions} under the control of
26699 the string @var{template}. To print several values, make
26700 @var{expressions} be a comma-separated list of individual expressions,
26701 which may be either numbers or pointers. Their values are printed as
26702 specified by @var{template}, exactly as a C program would do by
26703 executing the code below:
26706 printf (@var{template}, @var{expressions}@dots{});
26709 As in @code{C} @code{printf}, ordinary characters in @var{template}
26710 are printed verbatim, while @dfn{conversion specification} introduced
26711 by the @samp{%} character cause subsequent @var{expressions} to be
26712 evaluated, their values converted and formatted according to type and
26713 style information encoded in the conversion specifications, and then
26716 For example, you can print two values in hex like this:
26719 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
26722 @code{printf} supports all the standard @code{C} conversion
26723 specifications, including the flags and modifiers between the @samp{%}
26724 character and the conversion letter, with the following exceptions:
26728 The argument-ordering modifiers, such as @samp{2$}, are not supported.
26731 The modifier @samp{*} is not supported for specifying precision or
26735 The @samp{'} flag (for separation of digits into groups according to
26736 @code{LC_NUMERIC'}) is not supported.
26739 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
26743 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
26746 The conversion letters @samp{a} and @samp{A} are not supported.
26750 Note that the @samp{ll} type modifier is supported only if the
26751 underlying @code{C} implementation used to build @value{GDBN} supports
26752 the @code{long long int} type, and the @samp{L} type modifier is
26753 supported only if @code{long double} type is available.
26755 As in @code{C}, @code{printf} supports simple backslash-escape
26756 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
26757 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
26758 single character. Octal and hexadecimal escape sequences are not
26761 Additionally, @code{printf} supports conversion specifications for DFP
26762 (@dfn{Decimal Floating Point}) types using the following length modifiers
26763 together with a floating point specifier.
26768 @samp{H} for printing @code{Decimal32} types.
26771 @samp{D} for printing @code{Decimal64} types.
26774 @samp{DD} for printing @code{Decimal128} types.
26777 If the underlying @code{C} implementation used to build @value{GDBN} has
26778 support for the three length modifiers for DFP types, other modifiers
26779 such as width and precision will also be available for @value{GDBN} to use.
26781 In case there is no such @code{C} support, no additional modifiers will be
26782 available and the value will be printed in the standard way.
26784 Here's an example of printing DFP types using the above conversion letters:
26786 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
26791 @item eval @var{template}, @var{expressions}@dots{}
26792 Convert the values of one or more @var{expressions} under the control of
26793 the string @var{template} to a command line, and call it.
26797 @node Auto-loading sequences
26798 @subsection Controlling auto-loading native @value{GDBN} scripts
26799 @cindex native script auto-loading
26801 When a new object file is read (for example, due to the @code{file}
26802 command, or because the inferior has loaded a shared library),
26803 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
26804 @xref{Auto-loading extensions}.
26806 Auto-loading can be enabled or disabled,
26807 and the list of auto-loaded scripts can be printed.
26810 @anchor{set auto-load gdb-scripts}
26811 @kindex set auto-load gdb-scripts
26812 @item set auto-load gdb-scripts [on|off]
26813 Enable or disable the auto-loading of canned sequences of commands scripts.
26815 @anchor{show auto-load gdb-scripts}
26816 @kindex show auto-load gdb-scripts
26817 @item show auto-load gdb-scripts
26818 Show whether auto-loading of canned sequences of commands scripts is enabled or
26821 @anchor{info auto-load gdb-scripts}
26822 @kindex info auto-load gdb-scripts
26823 @cindex print list of auto-loaded canned sequences of commands scripts
26824 @item info auto-load gdb-scripts [@var{regexp}]
26825 Print the list of all canned sequences of commands scripts that @value{GDBN}
26829 If @var{regexp} is supplied only canned sequences of commands scripts with
26830 matching names are printed.
26832 @c Python docs live in a separate file.
26833 @include python.texi
26835 @c Guile docs live in a separate file.
26836 @include guile.texi
26838 @node Auto-loading extensions
26839 @section Auto-loading extensions
26840 @cindex auto-loading extensions
26842 @value{GDBN} provides two mechanisms for automatically loading extensions
26843 when a new object file is read (for example, due to the @code{file}
26844 command, or because the inferior has loaded a shared library):
26845 @file{@var{objfile}-gdb.@var{ext}} and the @code{.debug_gdb_scripts}
26846 section of modern file formats like ELF.
26849 * objfile-gdb.ext file: objfile-gdbdotext file. The @file{@var{objfile}-gdb.@var{ext}} file
26850 * .debug_gdb_scripts section: dotdebug_gdb_scripts section. The @code{.debug_gdb_scripts} section
26851 * Which flavor to choose?::
26854 The auto-loading feature is useful for supplying application-specific
26855 debugging commands and features.
26857 Auto-loading can be enabled or disabled,
26858 and the list of auto-loaded scripts can be printed.
26859 See the @samp{auto-loading} section of each extension language
26860 for more information.
26861 For @value{GDBN} command files see @ref{Auto-loading sequences}.
26862 For Python files see @ref{Python Auto-loading}.
26864 Note that loading of this script file also requires accordingly configured
26865 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26867 @node objfile-gdbdotext file
26868 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
26869 @cindex @file{@var{objfile}-gdb.gdb}
26870 @cindex @file{@var{objfile}-gdb.py}
26871 @cindex @file{@var{objfile}-gdb.scm}
26873 When a new object file is read, @value{GDBN} looks for a file named
26874 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
26875 where @var{objfile} is the object file's name and
26876 where @var{ext} is the file extension for the extension language:
26879 @item @file{@var{objfile}-gdb.gdb}
26880 GDB's own command language
26881 @item @file{@var{objfile}-gdb.py}
26883 @item @file{@var{objfile}-gdb.scm}
26887 @var{script-name} is formed by ensuring that the file name of @var{objfile}
26888 is absolute, following all symlinks, and resolving @code{.} and @code{..}
26889 components, and appending the @file{-gdb.@var{ext}} suffix.
26890 If this file exists and is readable, @value{GDBN} will evaluate it as a
26891 script in the specified extension language.
26893 If this file does not exist, then @value{GDBN} will look for
26894 @var{script-name} file in all of the directories as specified below.
26896 Note that loading of these files requires an accordingly configured
26897 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26899 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
26900 scripts normally according to its @file{.exe} filename. But if no scripts are
26901 found @value{GDBN} also tries script filenames matching the object file without
26902 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
26903 is attempted on any platform. This makes the script filenames compatible
26904 between Unix and MS-Windows hosts.
26907 @anchor{set auto-load scripts-directory}
26908 @kindex set auto-load scripts-directory
26909 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
26910 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
26911 may be delimited by the host platform path separator in use
26912 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
26914 Each entry here needs to be covered also by the security setting
26915 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
26917 @anchor{with-auto-load-dir}
26918 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
26919 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
26920 configuration option @option{--with-auto-load-dir}.
26922 Any reference to @file{$debugdir} will get replaced by
26923 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
26924 reference to @file{$datadir} will get replaced by @var{data-directory} which is
26925 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
26926 @file{$datadir} must be placed as a directory component --- either alone or
26927 delimited by @file{/} or @file{\} directory separators, depending on the host
26930 The list of directories uses path separator (@samp{:} on GNU and Unix
26931 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
26932 to the @env{PATH} environment variable.
26934 @anchor{show auto-load scripts-directory}
26935 @kindex show auto-load scripts-directory
26936 @item show auto-load scripts-directory
26937 Show @value{GDBN} auto-loaded scripts location.
26939 @anchor{add-auto-load-scripts-directory}
26940 @kindex add-auto-load-scripts-directory
26941 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
26942 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
26943 Multiple entries may be delimited by the host platform path separator in use.
26946 @value{GDBN} does not track which files it has already auto-loaded this way.
26947 @value{GDBN} will load the associated script every time the corresponding
26948 @var{objfile} is opened.
26949 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
26950 is evaluated more than once.
26952 @node dotdebug_gdb_scripts section
26953 @subsection The @code{.debug_gdb_scripts} section
26954 @cindex @code{.debug_gdb_scripts} section
26956 For systems using file formats like ELF and COFF,
26957 when @value{GDBN} loads a new object file
26958 it will look for a special section named @code{.debug_gdb_scripts}.
26959 If this section exists, its contents is a list of null-terminated entries
26960 specifying scripts to load. Each entry begins with a non-null prefix byte that
26961 specifies the kind of entry, typically the extension language and whether the
26962 script is in a file or inlined in @code{.debug_gdb_scripts}.
26964 The following entries are supported:
26967 @item SECTION_SCRIPT_ID_PYTHON_FILE = 1
26968 @item SECTION_SCRIPT_ID_SCHEME_FILE = 3
26969 @item SECTION_SCRIPT_ID_PYTHON_TEXT = 4
26970 @item SECTION_SCRIPT_ID_SCHEME_TEXT = 6
26973 @subsubsection Script File Entries
26975 If the entry specifies a file, @value{GDBN} will look for the file first
26976 in the current directory and then along the source search path
26977 (@pxref{Source Path, ,Specifying Source Directories}),
26978 except that @file{$cdir} is not searched, since the compilation
26979 directory is not relevant to scripts.
26981 File entries can be placed in section @code{.debug_gdb_scripts} with,
26982 for example, this GCC macro for Python scripts.
26985 /* Note: The "MS" section flags are to remove duplicates. */
26986 #define DEFINE_GDB_PY_SCRIPT(script_name) \
26988 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
26989 .byte 1 /* Python */\n\
26990 .asciz \"" script_name "\"\n\
26996 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
26997 Then one can reference the macro in a header or source file like this:
27000 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
27003 The script name may include directories if desired.
27005 Note that loading of this script file also requires accordingly configured
27006 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
27008 If the macro invocation is put in a header, any application or library
27009 using this header will get a reference to the specified script,
27010 and with the use of @code{"MS"} attributes on the section, the linker
27011 will remove duplicates.
27013 @subsubsection Script Text Entries
27015 Script text entries allow to put the executable script in the entry
27016 itself instead of loading it from a file.
27017 The first line of the entry, everything after the prefix byte and up to
27018 the first newline (@code{0xa}) character, is the script name, and must not
27019 contain any kind of space character, e.g., spaces or tabs.
27020 The rest of the entry, up to the trailing null byte, is the script to
27021 execute in the specified language. The name needs to be unique among
27022 all script names, as @value{GDBN} executes each script only once based
27025 Here is an example from file @file{py-section-script.c} in the @value{GDBN}
27029 #include "symcat.h"
27030 #include "gdb/section-scripts.h"
27032 ".pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n"
27033 ".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
27034 ".ascii \"gdb.inlined-script\\n\"\n"
27035 ".ascii \"class test_cmd (gdb.Command):\\n\"\n"
27036 ".ascii \" def __init__ (self):\\n\"\n"
27037 ".ascii \" super (test_cmd, self).__init__ ("
27038 "\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
27039 ".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
27040 ".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
27041 ".ascii \"test_cmd ()\\n\"\n"
27047 Loading of inlined scripts requires a properly configured
27048 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
27049 The path to specify in @code{auto-load safe-path} is the path of the file
27050 containing the @code{.debug_gdb_scripts} section.
27052 @node Which flavor to choose?
27053 @subsection Which flavor to choose?
27055 Given the multiple ways of auto-loading extensions, it might not always
27056 be clear which one to choose. This section provides some guidance.
27059 Benefits of the @file{-gdb.@var{ext}} way:
27063 Can be used with file formats that don't support multiple sections.
27066 Ease of finding scripts for public libraries.
27068 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
27069 in the source search path.
27070 For publicly installed libraries, e.g., @file{libstdc++}, there typically
27071 isn't a source directory in which to find the script.
27074 Doesn't require source code additions.
27078 Benefits of the @code{.debug_gdb_scripts} way:
27082 Works with static linking.
27084 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
27085 trigger their loading. When an application is statically linked the only
27086 objfile available is the executable, and it is cumbersome to attach all the
27087 scripts from all the input libraries to the executable's
27088 @file{-gdb.@var{ext}} script.
27091 Works with classes that are entirely inlined.
27093 Some classes can be entirely inlined, and thus there may not be an associated
27094 shared library to attach a @file{-gdb.@var{ext}} script to.
27097 Scripts needn't be copied out of the source tree.
27099 In some circumstances, apps can be built out of large collections of internal
27100 libraries, and the build infrastructure necessary to install the
27101 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
27102 cumbersome. It may be easier to specify the scripts in the
27103 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
27104 top of the source tree to the source search path.
27107 @node Multiple Extension Languages
27108 @section Multiple Extension Languages
27110 The Guile and Python extension languages do not share any state,
27111 and generally do not interfere with each other.
27112 There are some things to be aware of, however.
27114 @subsection Python comes first
27116 Python was @value{GDBN}'s first extension language, and to avoid breaking
27117 existing behaviour Python comes first. This is generally solved by the
27118 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
27119 extension languages, and when it makes a call to an extension language,
27120 (say to pretty-print a value), it tries each in turn until an extension
27121 language indicates it has performed the request (e.g., has returned the
27122 pretty-printed form of a value).
27123 This extends to errors while performing such requests: If an error happens
27124 while, for example, trying to pretty-print an object then the error is
27125 reported and any following extension languages are not tried.
27128 @section Creating new spellings of existing commands
27129 @cindex aliases for commands
27131 It is often useful to define alternate spellings of existing commands.
27132 For example, if a new @value{GDBN} command defined in Python has
27133 a long name to type, it is handy to have an abbreviated version of it
27134 that involves less typing.
27136 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
27137 of the @samp{step} command even though it is otherwise an ambiguous
27138 abbreviation of other commands like @samp{set} and @samp{show}.
27140 Aliases are also used to provide shortened or more common versions
27141 of multi-word commands. For example, @value{GDBN} provides the
27142 @samp{tty} alias of the @samp{set inferior-tty} command.
27144 You can define a new alias with the @samp{alias} command.
27149 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
27153 @var{ALIAS} specifies the name of the new alias.
27154 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
27157 @var{COMMAND} specifies the name of an existing command
27158 that is being aliased.
27160 The @samp{-a} option specifies that the new alias is an abbreviation
27161 of the command. Abbreviations are not shown in command
27162 lists displayed by the @samp{help} command.
27164 The @samp{--} option specifies the end of options,
27165 and is useful when @var{ALIAS} begins with a dash.
27167 Here is a simple example showing how to make an abbreviation
27168 of a command so that there is less to type.
27169 Suppose you were tired of typing @samp{disas}, the current
27170 shortest unambiguous abbreviation of the @samp{disassemble} command
27171 and you wanted an even shorter version named @samp{di}.
27172 The following will accomplish this.
27175 (gdb) alias -a di = disas
27178 Note that aliases are different from user-defined commands.
27179 With a user-defined command, you also need to write documentation
27180 for it with the @samp{document} command.
27181 An alias automatically picks up the documentation of the existing command.
27183 Here is an example where we make @samp{elms} an abbreviation of
27184 @samp{elements} in the @samp{set print elements} command.
27185 This is to show that you can make an abbreviation of any part
27189 (gdb) alias -a set print elms = set print elements
27190 (gdb) alias -a show print elms = show print elements
27191 (gdb) set p elms 20
27193 Limit on string chars or array elements to print is 200.
27196 Note that if you are defining an alias of a @samp{set} command,
27197 and you want to have an alias for the corresponding @samp{show}
27198 command, then you need to define the latter separately.
27200 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
27201 @var{ALIAS}, just as they are normally.
27204 (gdb) alias -a set pr elms = set p ele
27207 Finally, here is an example showing the creation of a one word
27208 alias for a more complex command.
27209 This creates alias @samp{spe} of the command @samp{set print elements}.
27212 (gdb) alias spe = set print elements
27217 @chapter Command Interpreters
27218 @cindex command interpreters
27220 @value{GDBN} supports multiple command interpreters, and some command
27221 infrastructure to allow users or user interface writers to switch
27222 between interpreters or run commands in other interpreters.
27224 @value{GDBN} currently supports two command interpreters, the console
27225 interpreter (sometimes called the command-line interpreter or @sc{cli})
27226 and the machine interface interpreter (or @sc{gdb/mi}). This manual
27227 describes both of these interfaces in great detail.
27229 By default, @value{GDBN} will start with the console interpreter.
27230 However, the user may choose to start @value{GDBN} with another
27231 interpreter by specifying the @option{-i} or @option{--interpreter}
27232 startup options. Defined interpreters include:
27236 @cindex console interpreter
27237 The traditional console or command-line interpreter. This is the most often
27238 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
27239 @value{GDBN} will use this interpreter.
27242 @cindex mi interpreter
27243 The newest @sc{gdb/mi} interface (currently @code{mi3}). Used primarily
27244 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
27245 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
27249 @cindex mi3 interpreter
27250 The @sc{gdb/mi} interface introduced in @value{GDBN} 9.1.
27253 @cindex mi2 interpreter
27254 The @sc{gdb/mi} interface introduced in @value{GDBN} 6.0.
27257 @cindex mi1 interpreter
27258 The @sc{gdb/mi} interface introduced in @value{GDBN} 5.1.
27262 @cindex invoke another interpreter
27264 @kindex interpreter-exec
27265 You may execute commands in any interpreter from the current
27266 interpreter using the appropriate command. If you are running the
27267 console interpreter, simply use the @code{interpreter-exec} command:
27270 interpreter-exec mi "-data-list-register-names"
27273 @sc{gdb/mi} has a similar command, although it is only available in versions of
27274 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
27276 Note that @code{interpreter-exec} only changes the interpreter for the
27277 duration of the specified command. It does not change the interpreter
27280 @cindex start a new independent interpreter
27282 Although you may only choose a single interpreter at startup, it is
27283 possible to run an independent interpreter on a specified input/output
27284 device (usually a tty).
27286 For example, consider a debugger GUI or IDE that wants to provide a
27287 @value{GDBN} console view. It may do so by embedding a terminal
27288 emulator widget in its GUI, starting @value{GDBN} in the traditional
27289 command-line mode with stdin/stdout/stderr redirected to that
27290 terminal, and then creating an MI interpreter running on a specified
27291 input/output device. The console interpreter created by @value{GDBN}
27292 at startup handles commands the user types in the terminal widget,
27293 while the GUI controls and synchronizes state with @value{GDBN} using
27294 the separate MI interpreter.
27296 To start a new secondary @dfn{user interface} running MI, use the
27297 @code{new-ui} command:
27300 @cindex new user interface
27302 new-ui @var{interpreter} @var{tty}
27305 The @var{interpreter} parameter specifies the interpreter to run.
27306 This accepts the same values as the @code{interpreter-exec} command.
27307 For example, @samp{console}, @samp{mi}, @samp{mi2}, etc. The
27308 @var{tty} parameter specifies the name of the bidirectional file the
27309 interpreter uses for input/output, usually the name of a
27310 pseudoterminal slave on Unix systems. For example:
27313 (@value{GDBP}) new-ui mi /dev/pts/9
27317 runs an MI interpreter on @file{/dev/pts/9}.
27320 @chapter @value{GDBN} Text User Interface
27322 @cindex Text User Interface
27325 * TUI Overview:: TUI overview
27326 * TUI Keys:: TUI key bindings
27327 * TUI Single Key Mode:: TUI single key mode
27328 * TUI Commands:: TUI-specific commands
27329 * TUI Configuration:: TUI configuration variables
27332 The @value{GDBN} Text User Interface (TUI) is a terminal
27333 interface which uses the @code{curses} library to show the source
27334 file, the assembly output, the program registers and @value{GDBN}
27335 commands in separate text windows. The TUI mode is supported only
27336 on platforms where a suitable version of the @code{curses} library
27339 The TUI mode is enabled by default when you invoke @value{GDBN} as
27340 @samp{@value{GDBP} -tui}.
27341 You can also switch in and out of TUI mode while @value{GDBN} runs by
27342 using various TUI commands and key bindings, such as @command{tui
27343 enable} or @kbd{C-x C-a}. @xref{TUI Commands, ,TUI Commands}, and
27344 @ref{TUI Keys, ,TUI Key Bindings}.
27347 @section TUI Overview
27349 In TUI mode, @value{GDBN} can display several text windows:
27353 This window is the @value{GDBN} command window with the @value{GDBN}
27354 prompt and the @value{GDBN} output. The @value{GDBN} input is still
27355 managed using readline.
27358 The source window shows the source file of the program. The current
27359 line and active breakpoints are displayed in this window.
27362 The assembly window shows the disassembly output of the program.
27365 This window shows the processor registers. Registers are highlighted
27366 when their values change.
27369 The source and assembly windows show the current program position
27370 by highlighting the current line and marking it with a @samp{>} marker.
27371 Breakpoints are indicated with two markers. The first marker
27372 indicates the breakpoint type:
27376 Breakpoint which was hit at least once.
27379 Breakpoint which was never hit.
27382 Hardware breakpoint which was hit at least once.
27385 Hardware breakpoint which was never hit.
27388 The second marker indicates whether the breakpoint is enabled or not:
27392 Breakpoint is enabled.
27395 Breakpoint is disabled.
27398 The source, assembly and register windows are updated when the current
27399 thread changes, when the frame changes, or when the program counter
27402 These windows are not all visible at the same time. The command
27403 window is always visible. The others can be arranged in several
27414 source and assembly,
27417 source and registers, or
27420 assembly and registers.
27423 A status line above the command window shows the following information:
27427 Indicates the current @value{GDBN} target.
27428 (@pxref{Targets, ,Specifying a Debugging Target}).
27431 Gives the current process or thread number.
27432 When no process is being debugged, this field is set to @code{No process}.
27435 Gives the current function name for the selected frame.
27436 The name is demangled if demangling is turned on (@pxref{Print Settings}).
27437 When there is no symbol corresponding to the current program counter,
27438 the string @code{??} is displayed.
27441 Indicates the current line number for the selected frame.
27442 When the current line number is not known, the string @code{??} is displayed.
27445 Indicates the current program counter address.
27449 @section TUI Key Bindings
27450 @cindex TUI key bindings
27452 The TUI installs several key bindings in the readline keymaps
27453 @ifset SYSTEM_READLINE
27454 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
27456 @ifclear SYSTEM_READLINE
27457 (@pxref{Command Line Editing}).
27459 The following key bindings are installed for both TUI mode and the
27460 @value{GDBN} standard mode.
27469 Enter or leave the TUI mode. When leaving the TUI mode,
27470 the curses window management stops and @value{GDBN} operates using
27471 its standard mode, writing on the terminal directly. When reentering
27472 the TUI mode, control is given back to the curses windows.
27473 The screen is then refreshed.
27477 Use a TUI layout with only one window. The layout will
27478 either be @samp{source} or @samp{assembly}. When the TUI mode
27479 is not active, it will switch to the TUI mode.
27481 Think of this key binding as the Emacs @kbd{C-x 1} binding.
27485 Use a TUI layout with at least two windows. When the current
27486 layout already has two windows, the next layout with two windows is used.
27487 When a new layout is chosen, one window will always be common to the
27488 previous layout and the new one.
27490 Think of it as the Emacs @kbd{C-x 2} binding.
27494 Change the active window. The TUI associates several key bindings
27495 (like scrolling and arrow keys) with the active window. This command
27496 gives the focus to the next TUI window.
27498 Think of it as the Emacs @kbd{C-x o} binding.
27502 Switch in and out of the TUI SingleKey mode that binds single
27503 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
27506 The following key bindings only work in the TUI mode:
27511 Scroll the active window one page up.
27515 Scroll the active window one page down.
27519 Scroll the active window one line up.
27523 Scroll the active window one line down.
27527 Scroll the active window one column left.
27531 Scroll the active window one column right.
27535 Refresh the screen.
27538 Because the arrow keys scroll the active window in the TUI mode, they
27539 are not available for their normal use by readline unless the command
27540 window has the focus. When another window is active, you must use
27541 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
27542 and @kbd{C-f} to control the command window.
27544 @node TUI Single Key Mode
27545 @section TUI Single Key Mode
27546 @cindex TUI single key mode
27548 The TUI also provides a @dfn{SingleKey} mode, which binds several
27549 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
27550 switch into this mode, where the following key bindings are used:
27553 @kindex c @r{(SingleKey TUI key)}
27557 @kindex d @r{(SingleKey TUI key)}
27561 @kindex f @r{(SingleKey TUI key)}
27565 @kindex n @r{(SingleKey TUI key)}
27569 @kindex o @r{(SingleKey TUI key)}
27571 nexti. The shortcut letter @samp{o} stands for ``step Over''.
27573 @kindex q @r{(SingleKey TUI key)}
27575 exit the SingleKey mode.
27577 @kindex r @r{(SingleKey TUI key)}
27581 @kindex s @r{(SingleKey TUI key)}
27585 @kindex i @r{(SingleKey TUI key)}
27587 stepi. The shortcut letter @samp{i} stands for ``step Into''.
27589 @kindex u @r{(SingleKey TUI key)}
27593 @kindex v @r{(SingleKey TUI key)}
27597 @kindex w @r{(SingleKey TUI key)}
27602 Other keys temporarily switch to the @value{GDBN} command prompt.
27603 The key that was pressed is inserted in the editing buffer so that
27604 it is possible to type most @value{GDBN} commands without interaction
27605 with the TUI SingleKey mode. Once the command is entered the TUI
27606 SingleKey mode is restored. The only way to permanently leave
27607 this mode is by typing @kbd{q} or @kbd{C-x s}.
27609 @cindex SingleKey keymap name
27610 If @value{GDBN} was built with Readline 8.0 or later, the TUI
27611 SingleKey keymap will be named @samp{SingleKey}. This can be used in
27612 @file{.inputrc} to add additional bindings to this keymap.
27615 @section TUI-specific Commands
27616 @cindex TUI commands
27618 The TUI has specific commands to control the text windows.
27619 These commands are always available, even when @value{GDBN} is not in
27620 the TUI mode. When @value{GDBN} is in the standard mode, most
27621 of these commands will automatically switch to the TUI mode.
27623 Note that if @value{GDBN}'s @code{stdout} is not connected to a
27624 terminal, or @value{GDBN} has been started with the machine interface
27625 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
27626 these commands will fail with an error, because it would not be
27627 possible or desirable to enable curses window management.
27632 Activate TUI mode. The last active TUI window layout will be used if
27633 TUI mode has prevsiouly been used in the current debugging session,
27634 otherwise a default layout is used.
27637 @kindex tui disable
27638 Disable TUI mode, returning to the console interpreter.
27642 List and give the size of all displayed windows.
27644 @item layout @var{name}
27646 Changes which TUI windows are displayed. In each layout the command
27647 window is always displayed, the @var{name} parameter controls which
27648 additional windows are displayed, and can be any of the following:
27652 Display the next layout.
27655 Display the previous layout.
27658 Display the source and command windows.
27661 Display the assembly and command windows.
27664 Display the source, assembly, and command windows.
27667 When in @code{src} layout display the register, source, and command
27668 windows. When in @code{asm} or @code{split} layout display the
27669 register, assembler, and command windows.
27672 @item focus @var{name}
27674 Changes which TUI window is currently active for scrolling. The
27675 @var{name} parameter can be any of the following:
27679 Make the next window active for scrolling.
27682 Make the previous window active for scrolling.
27685 Make the source window active for scrolling.
27688 Make the assembly window active for scrolling.
27691 Make the register window active for scrolling.
27694 Make the command window active for scrolling.
27699 Refresh the screen. This is similar to typing @kbd{C-L}.
27701 @item tui reg @var{group}
27703 Changes the register group displayed in the tui register window to
27704 @var{group}. If the register window is not currently displayed this
27705 command will cause the register window to be displayed. The list of
27706 register groups, as well as their order is target specific. The
27707 following groups are available on most targets:
27710 Repeatedly selecting this group will cause the display to cycle
27711 through all of the available register groups.
27714 Repeatedly selecting this group will cause the display to cycle
27715 through all of the available register groups in the reverse order to
27719 Display the general registers.
27721 Display the floating point registers.
27723 Display the system registers.
27725 Display the vector registers.
27727 Display all registers.
27732 Update the source window and the current execution point.
27734 @item winheight @var{name} +@var{count}
27735 @itemx winheight @var{name} -@var{count}
27737 Change the height of the window @var{name} by @var{count}
27738 lines. Positive counts increase the height, while negative counts
27739 decrease it. The @var{name} parameter can be one of @code{src} (the
27740 source window), @code{cmd} (the command window), @code{asm} (the
27741 disassembly window), or @code{regs} (the register display window).
27744 @node TUI Configuration
27745 @section TUI Configuration Variables
27746 @cindex TUI configuration variables
27748 Several configuration variables control the appearance of TUI windows.
27751 @item set tui border-kind @var{kind}
27752 @kindex set tui border-kind
27753 Select the border appearance for the source, assembly and register windows.
27754 The possible values are the following:
27757 Use a space character to draw the border.
27760 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
27763 Use the Alternate Character Set to draw the border. The border is
27764 drawn using character line graphics if the terminal supports them.
27767 @item set tui border-mode @var{mode}
27768 @kindex set tui border-mode
27769 @itemx set tui active-border-mode @var{mode}
27770 @kindex set tui active-border-mode
27771 Select the display attributes for the borders of the inactive windows
27772 or the active window. The @var{mode} can be one of the following:
27775 Use normal attributes to display the border.
27781 Use reverse video mode.
27784 Use half bright mode.
27786 @item half-standout
27787 Use half bright and standout mode.
27790 Use extra bright or bold mode.
27792 @item bold-standout
27793 Use extra bright or bold and standout mode.
27796 @item set tui tab-width @var{nchars}
27797 @kindex set tui tab-width
27799 Set the width of tab stops to be @var{nchars} characters. This
27800 setting affects the display of TAB characters in the source and
27805 @chapter Using @value{GDBN} under @sc{gnu} Emacs
27808 @cindex @sc{gnu} Emacs
27809 A special interface allows you to use @sc{gnu} Emacs to view (and
27810 edit) the source files for the program you are debugging with
27813 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
27814 executable file you want to debug as an argument. This command starts
27815 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
27816 created Emacs buffer.
27817 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
27819 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
27824 All ``terminal'' input and output goes through an Emacs buffer, called
27827 This applies both to @value{GDBN} commands and their output, and to the input
27828 and output done by the program you are debugging.
27830 This is useful because it means that you can copy the text of previous
27831 commands and input them again; you can even use parts of the output
27834 All the facilities of Emacs' Shell mode are available for interacting
27835 with your program. In particular, you can send signals the usual
27836 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
27840 @value{GDBN} displays source code through Emacs.
27842 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
27843 source file for that frame and puts an arrow (@samp{=>}) at the
27844 left margin of the current line. Emacs uses a separate buffer for
27845 source display, and splits the screen to show both your @value{GDBN} session
27848 Explicit @value{GDBN} @code{list} or search commands still produce output as
27849 usual, but you probably have no reason to use them from Emacs.
27852 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
27853 a graphical mode, enabled by default, which provides further buffers
27854 that can control the execution and describe the state of your program.
27855 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
27857 If you specify an absolute file name when prompted for the @kbd{M-x
27858 gdb} argument, then Emacs sets your current working directory to where
27859 your program resides. If you only specify the file name, then Emacs
27860 sets your current working directory to the directory associated
27861 with the previous buffer. In this case, @value{GDBN} may find your
27862 program by searching your environment's @code{PATH} variable, but on
27863 some operating systems it might not find the source. So, although the
27864 @value{GDBN} input and output session proceeds normally, the auxiliary
27865 buffer does not display the current source and line of execution.
27867 The initial working directory of @value{GDBN} is printed on the top
27868 line of the GUD buffer and this serves as a default for the commands
27869 that specify files for @value{GDBN} to operate on. @xref{Files,
27870 ,Commands to Specify Files}.
27872 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
27873 need to call @value{GDBN} by a different name (for example, if you
27874 keep several configurations around, with different names) you can
27875 customize the Emacs variable @code{gud-gdb-command-name} to run the
27878 In the GUD buffer, you can use these special Emacs commands in
27879 addition to the standard Shell mode commands:
27883 Describe the features of Emacs' GUD Mode.
27886 Execute to another source line, like the @value{GDBN} @code{step} command; also
27887 update the display window to show the current file and location.
27890 Execute to next source line in this function, skipping all function
27891 calls, like the @value{GDBN} @code{next} command. Then update the display window
27892 to show the current file and location.
27895 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
27896 display window accordingly.
27899 Execute until exit from the selected stack frame, like the @value{GDBN}
27900 @code{finish} command.
27903 Continue execution of your program, like the @value{GDBN} @code{continue}
27907 Go up the number of frames indicated by the numeric argument
27908 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
27909 like the @value{GDBN} @code{up} command.
27912 Go down the number of frames indicated by the numeric argument, like the
27913 @value{GDBN} @code{down} command.
27916 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
27917 tells @value{GDBN} to set a breakpoint on the source line point is on.
27919 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
27920 separate frame which shows a backtrace when the GUD buffer is current.
27921 Move point to any frame in the stack and type @key{RET} to make it
27922 become the current frame and display the associated source in the
27923 source buffer. Alternatively, click @kbd{Mouse-2} to make the
27924 selected frame become the current one. In graphical mode, the
27925 speedbar displays watch expressions.
27927 If you accidentally delete the source-display buffer, an easy way to get
27928 it back is to type the command @code{f} in the @value{GDBN} buffer, to
27929 request a frame display; when you run under Emacs, this recreates
27930 the source buffer if necessary to show you the context of the current
27933 The source files displayed in Emacs are in ordinary Emacs buffers
27934 which are visiting the source files in the usual way. You can edit
27935 the files with these buffers if you wish; but keep in mind that @value{GDBN}
27936 communicates with Emacs in terms of line numbers. If you add or
27937 delete lines from the text, the line numbers that @value{GDBN} knows cease
27938 to correspond properly with the code.
27940 A more detailed description of Emacs' interaction with @value{GDBN} is
27941 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
27945 @chapter The @sc{gdb/mi} Interface
27947 @unnumberedsec Function and Purpose
27949 @cindex @sc{gdb/mi}, its purpose
27950 @sc{gdb/mi} is a line based machine oriented text interface to
27951 @value{GDBN} and is activated by specifying using the
27952 @option{--interpreter} command line option (@pxref{Mode Options}). It
27953 is specifically intended to support the development of systems which
27954 use the debugger as just one small component of a larger system.
27956 This chapter is a specification of the @sc{gdb/mi} interface. It is written
27957 in the form of a reference manual.
27959 Note that @sc{gdb/mi} is still under construction, so some of the
27960 features described below are incomplete and subject to change
27961 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
27963 @unnumberedsec Notation and Terminology
27965 @cindex notational conventions, for @sc{gdb/mi}
27966 This chapter uses the following notation:
27970 @code{|} separates two alternatives.
27973 @code{[ @var{something} ]} indicates that @var{something} is optional:
27974 it may or may not be given.
27977 @code{( @var{group} )*} means that @var{group} inside the parentheses
27978 may repeat zero or more times.
27981 @code{( @var{group} )+} means that @var{group} inside the parentheses
27982 may repeat one or more times.
27985 @code{"@var{string}"} means a literal @var{string}.
27989 @heading Dependencies
27993 * GDB/MI General Design::
27994 * GDB/MI Command Syntax::
27995 * GDB/MI Compatibility with CLI::
27996 * GDB/MI Development and Front Ends::
27997 * GDB/MI Output Records::
27998 * GDB/MI Simple Examples::
27999 * GDB/MI Command Description Format::
28000 * GDB/MI Breakpoint Commands::
28001 * GDB/MI Catchpoint Commands::
28002 * GDB/MI Program Context::
28003 * GDB/MI Thread Commands::
28004 * GDB/MI Ada Tasking Commands::
28005 * GDB/MI Program Execution::
28006 * GDB/MI Stack Manipulation::
28007 * GDB/MI Variable Objects::
28008 * GDB/MI Data Manipulation::
28009 * GDB/MI Tracepoint Commands::
28010 * GDB/MI Symbol Query::
28011 * GDB/MI File Commands::
28013 * GDB/MI Kod Commands::
28014 * GDB/MI Memory Overlay Commands::
28015 * GDB/MI Signal Handling Commands::
28017 * GDB/MI Target Manipulation::
28018 * GDB/MI File Transfer Commands::
28019 * GDB/MI Ada Exceptions Commands::
28020 * GDB/MI Support Commands::
28021 * GDB/MI Miscellaneous Commands::
28024 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28025 @node GDB/MI General Design
28026 @section @sc{gdb/mi} General Design
28027 @cindex GDB/MI General Design
28029 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
28030 parts---commands sent to @value{GDBN}, responses to those commands
28031 and notifications. Each command results in exactly one response,
28032 indicating either successful completion of the command, or an error.
28033 For the commands that do not resume the target, the response contains the
28034 requested information. For the commands that resume the target, the
28035 response only indicates whether the target was successfully resumed.
28036 Notifications is the mechanism for reporting changes in the state of the
28037 target, or in @value{GDBN} state, that cannot conveniently be associated with
28038 a command and reported as part of that command response.
28040 The important examples of notifications are:
28044 Exec notifications. These are used to report changes in
28045 target state---when a target is resumed, or stopped. It would not
28046 be feasible to include this information in response of resuming
28047 commands, because one resume commands can result in multiple events in
28048 different threads. Also, quite some time may pass before any event
28049 happens in the target, while a frontend needs to know whether the resuming
28050 command itself was successfully executed.
28053 Console output, and status notifications. Console output
28054 notifications are used to report output of CLI commands, as well as
28055 diagnostics for other commands. Status notifications are used to
28056 report the progress of a long-running operation. Naturally, including
28057 this information in command response would mean no output is produced
28058 until the command is finished, which is undesirable.
28061 General notifications. Commands may have various side effects on
28062 the @value{GDBN} or target state beyond their official purpose. For example,
28063 a command may change the selected thread. Although such changes can
28064 be included in command response, using notification allows for more
28065 orthogonal frontend design.
28069 There's no guarantee that whenever an MI command reports an error,
28070 @value{GDBN} or the target are in any specific state, and especially,
28071 the state is not reverted to the state before the MI command was
28072 processed. Therefore, whenever an MI command results in an error,
28073 we recommend that the frontend refreshes all the information shown in
28074 the user interface.
28078 * Context management::
28079 * Asynchronous and non-stop modes::
28083 @node Context management
28084 @subsection Context management
28086 @subsubsection Threads and Frames
28088 In most cases when @value{GDBN} accesses the target, this access is
28089 done in context of a specific thread and frame (@pxref{Frames}).
28090 Often, even when accessing global data, the target requires that a thread
28091 be specified. The CLI interface maintains the selected thread and frame,
28092 and supplies them to target on each command. This is convenient,
28093 because a command line user would not want to specify that information
28094 explicitly on each command, and because user interacts with
28095 @value{GDBN} via a single terminal, so no confusion is possible as
28096 to what thread and frame are the current ones.
28098 In the case of MI, the concept of selected thread and frame is less
28099 useful. First, a frontend can easily remember this information
28100 itself. Second, a graphical frontend can have more than one window,
28101 each one used for debugging a different thread, and the frontend might
28102 want to access additional threads for internal purposes. This
28103 increases the risk that by relying on implicitly selected thread, the
28104 frontend may be operating on a wrong one. Therefore, each MI command
28105 should explicitly specify which thread and frame to operate on. To
28106 make it possible, each MI command accepts the @samp{--thread} and
28107 @samp{--frame} options, the value to each is @value{GDBN} global
28108 identifier for thread and frame to operate on.
28110 Usually, each top-level window in a frontend allows the user to select
28111 a thread and a frame, and remembers the user selection for further
28112 operations. However, in some cases @value{GDBN} may suggest that the
28113 current thread or frame be changed. For example, when stopping on a
28114 breakpoint it is reasonable to switch to the thread where breakpoint is
28115 hit. For another example, if the user issues the CLI @samp{thread} or
28116 @samp{frame} commands via the frontend, it is desirable to change the
28117 frontend's selection to the one specified by user. @value{GDBN}
28118 communicates the suggestion to change current thread and frame using the
28119 @samp{=thread-selected} notification.
28121 Note that historically, MI shares the selected thread with CLI, so
28122 frontends used the @code{-thread-select} to execute commands in the
28123 right context. However, getting this to work right is cumbersome. The
28124 simplest way is for frontend to emit @code{-thread-select} command
28125 before every command. This doubles the number of commands that need
28126 to be sent. The alternative approach is to suppress @code{-thread-select}
28127 if the selected thread in @value{GDBN} is supposed to be identical to the
28128 thread the frontend wants to operate on. However, getting this
28129 optimization right can be tricky. In particular, if the frontend
28130 sends several commands to @value{GDBN}, and one of the commands changes the
28131 selected thread, then the behaviour of subsequent commands will
28132 change. So, a frontend should either wait for response from such
28133 problematic commands, or explicitly add @code{-thread-select} for
28134 all subsequent commands. No frontend is known to do this exactly
28135 right, so it is suggested to just always pass the @samp{--thread} and
28136 @samp{--frame} options.
28138 @subsubsection Language
28140 The execution of several commands depends on which language is selected.
28141 By default, the current language (@pxref{show language}) is used.
28142 But for commands known to be language-sensitive, it is recommended
28143 to use the @samp{--language} option. This option takes one argument,
28144 which is the name of the language to use while executing the command.
28148 -data-evaluate-expression --language c "sizeof (void*)"
28153 The valid language names are the same names accepted by the
28154 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
28155 @samp{local} or @samp{unknown}.
28157 @node Asynchronous and non-stop modes
28158 @subsection Asynchronous command execution and non-stop mode
28160 On some targets, @value{GDBN} is capable of processing MI commands
28161 even while the target is running. This is called @dfn{asynchronous
28162 command execution} (@pxref{Background Execution}). The frontend may
28163 specify a preferrence for asynchronous execution using the
28164 @code{-gdb-set mi-async 1} command, which should be emitted before
28165 either running the executable or attaching to the target. After the
28166 frontend has started the executable or attached to the target, it can
28167 find if asynchronous execution is enabled using the
28168 @code{-list-target-features} command.
28171 @item -gdb-set mi-async on
28172 @item -gdb-set mi-async off
28173 Set whether MI is in asynchronous mode.
28175 When @code{off}, which is the default, MI execution commands (e.g.,
28176 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
28177 for the program to stop before processing further commands.
28179 When @code{on}, MI execution commands are background execution
28180 commands (e.g., @code{-exec-continue} becomes the equivalent of the
28181 @code{c&} CLI command), and so @value{GDBN} is capable of processing
28182 MI commands even while the target is running.
28184 @item -gdb-show mi-async
28185 Show whether MI asynchronous mode is enabled.
28188 Note: In @value{GDBN} version 7.7 and earlier, this option was called
28189 @code{target-async} instead of @code{mi-async}, and it had the effect
28190 of both putting MI in asynchronous mode and making CLI background
28191 commands possible. CLI background commands are now always possible
28192 ``out of the box'' if the target supports them. The old spelling is
28193 kept as a deprecated alias for backwards compatibility.
28195 Even if @value{GDBN} can accept a command while target is running,
28196 many commands that access the target do not work when the target is
28197 running. Therefore, asynchronous command execution is most useful
28198 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
28199 it is possible to examine the state of one thread, while other threads
28202 When a given thread is running, MI commands that try to access the
28203 target in the context of that thread may not work, or may work only on
28204 some targets. In particular, commands that try to operate on thread's
28205 stack will not work, on any target. Commands that read memory, or
28206 modify breakpoints, may work or not work, depending on the target. Note
28207 that even commands that operate on global state, such as @code{print},
28208 @code{set}, and breakpoint commands, still access the target in the
28209 context of a specific thread, so frontend should try to find a
28210 stopped thread and perform the operation on that thread (using the
28211 @samp{--thread} option).
28213 Which commands will work in the context of a running thread is
28214 highly target dependent. However, the two commands
28215 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
28216 to find the state of a thread, will always work.
28218 @node Thread groups
28219 @subsection Thread groups
28220 @value{GDBN} may be used to debug several processes at the same time.
28221 On some platfroms, @value{GDBN} may support debugging of several
28222 hardware systems, each one having several cores with several different
28223 processes running on each core. This section describes the MI
28224 mechanism to support such debugging scenarios.
28226 The key observation is that regardless of the structure of the
28227 target, MI can have a global list of threads, because most commands that
28228 accept the @samp{--thread} option do not need to know what process that
28229 thread belongs to. Therefore, it is not necessary to introduce
28230 neither additional @samp{--process} option, nor an notion of the
28231 current process in the MI interface. The only strictly new feature
28232 that is required is the ability to find how the threads are grouped
28235 To allow the user to discover such grouping, and to support arbitrary
28236 hierarchy of machines/cores/processes, MI introduces the concept of a
28237 @dfn{thread group}. Thread group is a collection of threads and other
28238 thread groups. A thread group always has a string identifier, a type,
28239 and may have additional attributes specific to the type. A new
28240 command, @code{-list-thread-groups}, returns the list of top-level
28241 thread groups, which correspond to processes that @value{GDBN} is
28242 debugging at the moment. By passing an identifier of a thread group
28243 to the @code{-list-thread-groups} command, it is possible to obtain
28244 the members of specific thread group.
28246 To allow the user to easily discover processes, and other objects, he
28247 wishes to debug, a concept of @dfn{available thread group} is
28248 introduced. Available thread group is an thread group that
28249 @value{GDBN} is not debugging, but that can be attached to, using the
28250 @code{-target-attach} command. The list of available top-level thread
28251 groups can be obtained using @samp{-list-thread-groups --available}.
28252 In general, the content of a thread group may be only retrieved only
28253 after attaching to that thread group.
28255 Thread groups are related to inferiors (@pxref{Inferiors and
28256 Programs}). Each inferior corresponds to a thread group of a special
28257 type @samp{process}, and some additional operations are permitted on
28258 such thread groups.
28260 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28261 @node GDB/MI Command Syntax
28262 @section @sc{gdb/mi} Command Syntax
28265 * GDB/MI Input Syntax::
28266 * GDB/MI Output Syntax::
28269 @node GDB/MI Input Syntax
28270 @subsection @sc{gdb/mi} Input Syntax
28272 @cindex input syntax for @sc{gdb/mi}
28273 @cindex @sc{gdb/mi}, input syntax
28275 @item @var{command} @expansion{}
28276 @code{@var{cli-command} | @var{mi-command}}
28278 @item @var{cli-command} @expansion{}
28279 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
28280 @var{cli-command} is any existing @value{GDBN} CLI command.
28282 @item @var{mi-command} @expansion{}
28283 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
28284 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
28286 @item @var{token} @expansion{}
28287 "any sequence of digits"
28289 @item @var{option} @expansion{}
28290 @code{"-" @var{parameter} [ " " @var{parameter} ]}
28292 @item @var{parameter} @expansion{}
28293 @code{@var{non-blank-sequence} | @var{c-string}}
28295 @item @var{operation} @expansion{}
28296 @emph{any of the operations described in this chapter}
28298 @item @var{non-blank-sequence} @expansion{}
28299 @emph{anything, provided it doesn't contain special characters such as
28300 "-", @var{nl}, """ and of course " "}
28302 @item @var{c-string} @expansion{}
28303 @code{""" @var{seven-bit-iso-c-string-content} """}
28305 @item @var{nl} @expansion{}
28314 The CLI commands are still handled by the @sc{mi} interpreter; their
28315 output is described below.
28318 The @code{@var{token}}, when present, is passed back when the command
28322 Some @sc{mi} commands accept optional arguments as part of the parameter
28323 list. Each option is identified by a leading @samp{-} (dash) and may be
28324 followed by an optional argument parameter. Options occur first in the
28325 parameter list and can be delimited from normal parameters using
28326 @samp{--} (this is useful when some parameters begin with a dash).
28333 We want easy access to the existing CLI syntax (for debugging).
28336 We want it to be easy to spot a @sc{mi} operation.
28339 @node GDB/MI Output Syntax
28340 @subsection @sc{gdb/mi} Output Syntax
28342 @cindex output syntax of @sc{gdb/mi}
28343 @cindex @sc{gdb/mi}, output syntax
28344 The output from @sc{gdb/mi} consists of zero or more out-of-band records
28345 followed, optionally, by a single result record. This result record
28346 is for the most recent command. The sequence of output records is
28347 terminated by @samp{(gdb)}.
28349 If an input command was prefixed with a @code{@var{token}} then the
28350 corresponding output for that command will also be prefixed by that same
28354 @item @var{output} @expansion{}
28355 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
28357 @item @var{result-record} @expansion{}
28358 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
28360 @item @var{out-of-band-record} @expansion{}
28361 @code{@var{async-record} | @var{stream-record}}
28363 @item @var{async-record} @expansion{}
28364 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
28366 @item @var{exec-async-output} @expansion{}
28367 @code{[ @var{token} ] "*" @var{async-output nl}}
28369 @item @var{status-async-output} @expansion{}
28370 @code{[ @var{token} ] "+" @var{async-output nl}}
28372 @item @var{notify-async-output} @expansion{}
28373 @code{[ @var{token} ] "=" @var{async-output nl}}
28375 @item @var{async-output} @expansion{}
28376 @code{@var{async-class} ( "," @var{result} )*}
28378 @item @var{result-class} @expansion{}
28379 @code{"done" | "running" | "connected" | "error" | "exit"}
28381 @item @var{async-class} @expansion{}
28382 @code{"stopped" | @var{others}} (where @var{others} will be added
28383 depending on the needs---this is still in development).
28385 @item @var{result} @expansion{}
28386 @code{ @var{variable} "=" @var{value}}
28388 @item @var{variable} @expansion{}
28389 @code{ @var{string} }
28391 @item @var{value} @expansion{}
28392 @code{ @var{const} | @var{tuple} | @var{list} }
28394 @item @var{const} @expansion{}
28395 @code{@var{c-string}}
28397 @item @var{tuple} @expansion{}
28398 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
28400 @item @var{list} @expansion{}
28401 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
28402 @var{result} ( "," @var{result} )* "]" }
28404 @item @var{stream-record} @expansion{}
28405 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
28407 @item @var{console-stream-output} @expansion{}
28408 @code{"~" @var{c-string nl}}
28410 @item @var{target-stream-output} @expansion{}
28411 @code{"@@" @var{c-string nl}}
28413 @item @var{log-stream-output} @expansion{}
28414 @code{"&" @var{c-string nl}}
28416 @item @var{nl} @expansion{}
28419 @item @var{token} @expansion{}
28420 @emph{any sequence of digits}.
28428 All output sequences end in a single line containing a period.
28431 The @code{@var{token}} is from the corresponding request. Note that
28432 for all async output, while the token is allowed by the grammar and
28433 may be output by future versions of @value{GDBN} for select async
28434 output messages, it is generally omitted. Frontends should treat
28435 all async output as reporting general changes in the state of the
28436 target and there should be no need to associate async output to any
28440 @cindex status output in @sc{gdb/mi}
28441 @var{status-async-output} contains on-going status information about the
28442 progress of a slow operation. It can be discarded. All status output is
28443 prefixed by @samp{+}.
28446 @cindex async output in @sc{gdb/mi}
28447 @var{exec-async-output} contains asynchronous state change on the target
28448 (stopped, started, disappeared). All async output is prefixed by
28452 @cindex notify output in @sc{gdb/mi}
28453 @var{notify-async-output} contains supplementary information that the
28454 client should handle (e.g., a new breakpoint information). All notify
28455 output is prefixed by @samp{=}.
28458 @cindex console output in @sc{gdb/mi}
28459 @var{console-stream-output} is output that should be displayed as is in the
28460 console. It is the textual response to a CLI command. All the console
28461 output is prefixed by @samp{~}.
28464 @cindex target output in @sc{gdb/mi}
28465 @var{target-stream-output} is the output produced by the target program.
28466 All the target output is prefixed by @samp{@@}.
28469 @cindex log output in @sc{gdb/mi}
28470 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
28471 instance messages that should be displayed as part of an error log. All
28472 the log output is prefixed by @samp{&}.
28475 @cindex list output in @sc{gdb/mi}
28476 New @sc{gdb/mi} commands should only output @var{lists} containing
28482 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
28483 details about the various output records.
28485 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28486 @node GDB/MI Compatibility with CLI
28487 @section @sc{gdb/mi} Compatibility with CLI
28489 @cindex compatibility, @sc{gdb/mi} and CLI
28490 @cindex @sc{gdb/mi}, compatibility with CLI
28492 For the developers convenience CLI commands can be entered directly,
28493 but there may be some unexpected behaviour. For example, commands
28494 that query the user will behave as if the user replied yes, breakpoint
28495 command lists are not executed and some CLI commands, such as
28496 @code{if}, @code{when} and @code{define}, prompt for further input with
28497 @samp{>}, which is not valid MI output.
28499 This feature may be removed at some stage in the future and it is
28500 recommended that front ends use the @code{-interpreter-exec} command
28501 (@pxref{-interpreter-exec}).
28503 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28504 @node GDB/MI Development and Front Ends
28505 @section @sc{gdb/mi} Development and Front Ends
28506 @cindex @sc{gdb/mi} development
28508 The application which takes the MI output and presents the state of the
28509 program being debugged to the user is called a @dfn{front end}.
28511 Since @sc{gdb/mi} is used by a variety of front ends to @value{GDBN}, changes
28512 to the MI interface may break existing usage. This section describes how the
28513 protocol changes and how to request previous version of the protocol when it
28516 Some changes in MI need not break a carefully designed front end, and
28517 for these the MI version will remain unchanged. The following is a
28518 list of changes that may occur within one level, so front ends should
28519 parse MI output in a way that can handle them:
28523 New MI commands may be added.
28526 New fields may be added to the output of any MI command.
28529 The range of values for fields with specified values, e.g.,
28530 @code{in_scope} (@pxref{-var-update}) may be extended.
28532 @c The format of field's content e.g type prefix, may change so parse it
28533 @c at your own risk. Yes, in general?
28535 @c The order of fields may change? Shouldn't really matter but it might
28536 @c resolve inconsistencies.
28539 If the changes are likely to break front ends, the MI version level
28540 will be increased by one. The new versions of the MI protocol are not compatible
28541 with the old versions. Old versions of MI remain available, allowing front ends
28542 to keep using them until they are modified to use the latest MI version.
28544 Since @code{--interpreter=mi} always points to the latest MI version, it is
28545 recommended that front ends request a specific version of MI when launching
28546 @value{GDBN} (e.g. @code{--interpreter=mi2}) to make sure they get an
28547 interpreter with the MI version they expect.
28549 The following table gives a summary of the the released versions of the MI
28550 interface: the version number, the version of GDB in which it first appeared
28551 and the breaking changes compared to the previous version.
28553 @multitable @columnfractions .05 .05 .9
28554 @headitem MI version @tab GDB version @tab Breaking changes
28571 The @code{-environment-pwd}, @code{-environment-directory} and
28572 @code{-environment-path} commands now returns values using the MI output
28573 syntax, rather than CLI output syntax.
28576 @code{-var-list-children}'s @code{children} result field is now a list, rather
28580 @code{-var-update}'s @code{changelist} result field is now a list, rather than
28592 The output of information about multi-location breakpoints has changed in the
28593 responses to the @code{-break-insert} and @code{-break-info} commands, as well
28594 as in the @code{=breakpoint-created} and @code{=breakpoint-modified} events.
28595 The multiple locations are now placed in a @code{locations} field, whose value
28601 If your front end cannot yet migrate to a more recent version of the
28602 MI protocol, you can nevertheless selectively enable specific features
28603 available in those recent MI versions, using the following commands:
28607 @item -fix-multi-location-breakpoint-output
28608 Use the output for multi-location breakpoints which was introduced by
28609 MI 3, even when using MI versions 2 or 1. This command has no
28610 effect when using MI version 3 or later.
28614 The best way to avoid unexpected changes in MI that might break your front
28615 end is to make your project known to @value{GDBN} developers and
28616 follow development on @email{gdb@@sourceware.org} and
28617 @email{gdb-patches@@sourceware.org}.
28618 @cindex mailing lists
28620 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28621 @node GDB/MI Output Records
28622 @section @sc{gdb/mi} Output Records
28625 * GDB/MI Result Records::
28626 * GDB/MI Stream Records::
28627 * GDB/MI Async Records::
28628 * GDB/MI Breakpoint Information::
28629 * GDB/MI Frame Information::
28630 * GDB/MI Thread Information::
28631 * GDB/MI Ada Exception Information::
28634 @node GDB/MI Result Records
28635 @subsection @sc{gdb/mi} Result Records
28637 @cindex result records in @sc{gdb/mi}
28638 @cindex @sc{gdb/mi}, result records
28639 In addition to a number of out-of-band notifications, the response to a
28640 @sc{gdb/mi} command includes one of the following result indications:
28644 @item "^done" [ "," @var{results} ]
28645 The synchronous operation was successful, @code{@var{results}} are the return
28650 This result record is equivalent to @samp{^done}. Historically, it
28651 was output instead of @samp{^done} if the command has resumed the
28652 target. This behaviour is maintained for backward compatibility, but
28653 all frontends should treat @samp{^done} and @samp{^running}
28654 identically and rely on the @samp{*running} output record to determine
28655 which threads are resumed.
28659 @value{GDBN} has connected to a remote target.
28661 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
28663 The operation failed. The @code{msg=@var{c-string}} variable contains
28664 the corresponding error message.
28666 If present, the @code{code=@var{c-string}} variable provides an error
28667 code on which consumers can rely on to detect the corresponding
28668 error condition. At present, only one error code is defined:
28671 @item "undefined-command"
28672 Indicates that the command causing the error does not exist.
28677 @value{GDBN} has terminated.
28681 @node GDB/MI Stream Records
28682 @subsection @sc{gdb/mi} Stream Records
28684 @cindex @sc{gdb/mi}, stream records
28685 @cindex stream records in @sc{gdb/mi}
28686 @value{GDBN} internally maintains a number of output streams: the console, the
28687 target, and the log. The output intended for each of these streams is
28688 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
28690 Each stream record begins with a unique @dfn{prefix character} which
28691 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
28692 Syntax}). In addition to the prefix, each stream record contains a
28693 @code{@var{string-output}}. This is either raw text (with an implicit new
28694 line) or a quoted C string (which does not contain an implicit newline).
28697 @item "~" @var{string-output}
28698 The console output stream contains text that should be displayed in the
28699 CLI console window. It contains the textual responses to CLI commands.
28701 @item "@@" @var{string-output}
28702 The target output stream contains any textual output from the running
28703 target. This is only present when GDB's event loop is truly
28704 asynchronous, which is currently only the case for remote targets.
28706 @item "&" @var{string-output}
28707 The log stream contains debugging messages being produced by @value{GDBN}'s
28711 @node GDB/MI Async Records
28712 @subsection @sc{gdb/mi} Async Records
28714 @cindex async records in @sc{gdb/mi}
28715 @cindex @sc{gdb/mi}, async records
28716 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
28717 additional changes that have occurred. Those changes can either be a
28718 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
28719 target activity (e.g., target stopped).
28721 The following is the list of possible async records:
28725 @item *running,thread-id="@var{thread}"
28726 The target is now running. The @var{thread} field can be the global
28727 thread ID of the the thread that is now running, and it can be
28728 @samp{all} if all threads are running. The frontend should assume
28729 that no interaction with a running thread is possible after this
28730 notification is produced. The frontend should not assume that this
28731 notification is output only once for any command. @value{GDBN} may
28732 emit this notification several times, either for different threads,
28733 because it cannot resume all threads together, or even for a single
28734 thread, if the thread must be stepped though some code before letting
28737 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
28738 The target has stopped. The @var{reason} field can have one of the
28742 @item breakpoint-hit
28743 A breakpoint was reached.
28744 @item watchpoint-trigger
28745 A watchpoint was triggered.
28746 @item read-watchpoint-trigger
28747 A read watchpoint was triggered.
28748 @item access-watchpoint-trigger
28749 An access watchpoint was triggered.
28750 @item function-finished
28751 An -exec-finish or similar CLI command was accomplished.
28752 @item location-reached
28753 An -exec-until or similar CLI command was accomplished.
28754 @item watchpoint-scope
28755 A watchpoint has gone out of scope.
28756 @item end-stepping-range
28757 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
28758 similar CLI command was accomplished.
28759 @item exited-signalled
28760 The inferior exited because of a signal.
28762 The inferior exited.
28763 @item exited-normally
28764 The inferior exited normally.
28765 @item signal-received
28766 A signal was received by the inferior.
28768 The inferior has stopped due to a library being loaded or unloaded.
28769 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
28770 set or when a @code{catch load} or @code{catch unload} catchpoint is
28771 in use (@pxref{Set Catchpoints}).
28773 The inferior has forked. This is reported when @code{catch fork}
28774 (@pxref{Set Catchpoints}) has been used.
28776 The inferior has vforked. This is reported in when @code{catch vfork}
28777 (@pxref{Set Catchpoints}) has been used.
28778 @item syscall-entry
28779 The inferior entered a system call. This is reported when @code{catch
28780 syscall} (@pxref{Set Catchpoints}) has been used.
28781 @item syscall-return
28782 The inferior returned from a system call. This is reported when
28783 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
28785 The inferior called @code{exec}. This is reported when @code{catch exec}
28786 (@pxref{Set Catchpoints}) has been used.
28789 The @var{id} field identifies the global thread ID of the thread
28790 that directly caused the stop -- for example by hitting a breakpoint.
28791 Depending on whether all-stop
28792 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
28793 stop all threads, or only the thread that directly triggered the stop.
28794 If all threads are stopped, the @var{stopped} field will have the
28795 value of @code{"all"}. Otherwise, the value of the @var{stopped}
28796 field will be a list of thread identifiers. Presently, this list will
28797 always include a single thread, but frontend should be prepared to see
28798 several threads in the list. The @var{core} field reports the
28799 processor core on which the stop event has happened. This field may be absent
28800 if such information is not available.
28802 @item =thread-group-added,id="@var{id}"
28803 @itemx =thread-group-removed,id="@var{id}"
28804 A thread group was either added or removed. The @var{id} field
28805 contains the @value{GDBN} identifier of the thread group. When a thread
28806 group is added, it generally might not be associated with a running
28807 process. When a thread group is removed, its id becomes invalid and
28808 cannot be used in any way.
28810 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
28811 A thread group became associated with a running program,
28812 either because the program was just started or the thread group
28813 was attached to a program. The @var{id} field contains the
28814 @value{GDBN} identifier of the thread group. The @var{pid} field
28815 contains process identifier, specific to the operating system.
28817 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
28818 A thread group is no longer associated with a running program,
28819 either because the program has exited, or because it was detached
28820 from. The @var{id} field contains the @value{GDBN} identifier of the
28821 thread group. The @var{code} field is the exit code of the inferior; it exists
28822 only when the inferior exited with some code.
28824 @item =thread-created,id="@var{id}",group-id="@var{gid}"
28825 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
28826 A thread either was created, or has exited. The @var{id} field
28827 contains the global @value{GDBN} identifier of the thread. The @var{gid}
28828 field identifies the thread group this thread belongs to.
28830 @item =thread-selected,id="@var{id}"[,frame="@var{frame}"]
28831 Informs that the selected thread or frame were changed. This notification
28832 is not emitted as result of the @code{-thread-select} or
28833 @code{-stack-select-frame} commands, but is emitted whenever an MI command
28834 that is not documented to change the selected thread and frame actually
28835 changes them. In particular, invoking, directly or indirectly
28836 (via user-defined command), the CLI @code{thread} or @code{frame} commands,
28837 will generate this notification. Changing the thread or frame from another
28838 user interface (see @ref{Interpreters}) will also generate this notification.
28840 The @var{frame} field is only present if the newly selected thread is
28841 stopped. See @ref{GDB/MI Frame Information} for the format of its value.
28843 We suggest that in response to this notification, front ends
28844 highlight the selected thread and cause subsequent commands to apply to
28847 @item =library-loaded,...
28848 Reports that a new library file was loaded by the program. This
28849 notification has 5 fields---@var{id}, @var{target-name},
28850 @var{host-name}, @var{symbols-loaded} and @var{ranges}. The @var{id} field is an
28851 opaque identifier of the library. For remote debugging case,
28852 @var{target-name} and @var{host-name} fields give the name of the
28853 library file on the target, and on the host respectively. For native
28854 debugging, both those fields have the same value. The
28855 @var{symbols-loaded} field is emitted only for backward compatibility
28856 and should not be relied on to convey any useful information. The
28857 @var{thread-group} field, if present, specifies the id of the thread
28858 group in whose context the library was loaded. If the field is
28859 absent, it means the library was loaded in the context of all present
28860 thread groups. The @var{ranges} field specifies the ranges of addresses belonging
28863 @item =library-unloaded,...
28864 Reports that a library was unloaded by the program. This notification
28865 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
28866 the same meaning as for the @code{=library-loaded} notification.
28867 The @var{thread-group} field, if present, specifies the id of the
28868 thread group in whose context the library was unloaded. If the field is
28869 absent, it means the library was unloaded in the context of all present
28872 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
28873 @itemx =traceframe-changed,end
28874 Reports that the trace frame was changed and its new number is
28875 @var{tfnum}. The number of the tracepoint associated with this trace
28876 frame is @var{tpnum}.
28878 @item =tsv-created,name=@var{name},initial=@var{initial}
28879 Reports that the new trace state variable @var{name} is created with
28880 initial value @var{initial}.
28882 @item =tsv-deleted,name=@var{name}
28883 @itemx =tsv-deleted
28884 Reports that the trace state variable @var{name} is deleted or all
28885 trace state variables are deleted.
28887 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
28888 Reports that the trace state variable @var{name} is modified with
28889 the initial value @var{initial}. The current value @var{current} of
28890 trace state variable is optional and is reported if the current
28891 value of trace state variable is known.
28893 @item =breakpoint-created,bkpt=@{...@}
28894 @itemx =breakpoint-modified,bkpt=@{...@}
28895 @itemx =breakpoint-deleted,id=@var{number}
28896 Reports that a breakpoint was created, modified, or deleted,
28897 respectively. Only user-visible breakpoints are reported to the MI
28900 The @var{bkpt} argument is of the same form as returned by the various
28901 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
28902 @var{number} is the ordinal number of the breakpoint.
28904 Note that if a breakpoint is emitted in the result record of a
28905 command, then it will not also be emitted in an async record.
28907 @item =record-started,thread-group="@var{id}",method="@var{method}"[,format="@var{format}"]
28908 @itemx =record-stopped,thread-group="@var{id}"
28909 Execution log recording was either started or stopped on an
28910 inferior. The @var{id} is the @value{GDBN} identifier of the thread
28911 group corresponding to the affected inferior.
28913 The @var{method} field indicates the method used to record execution. If the
28914 method in use supports multiple recording formats, @var{format} will be present
28915 and contain the currently used format. @xref{Process Record and Replay},
28916 for existing method and format values.
28918 @item =cmd-param-changed,param=@var{param},value=@var{value}
28919 Reports that a parameter of the command @code{set @var{param}} is
28920 changed to @var{value}. In the multi-word @code{set} command,
28921 the @var{param} is the whole parameter list to @code{set} command.
28922 For example, In command @code{set check type on}, @var{param}
28923 is @code{check type} and @var{value} is @code{on}.
28925 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
28926 Reports that bytes from @var{addr} to @var{data} + @var{len} were
28927 written in an inferior. The @var{id} is the identifier of the
28928 thread group corresponding to the affected inferior. The optional
28929 @code{type="code"} part is reported if the memory written to holds
28933 @node GDB/MI Breakpoint Information
28934 @subsection @sc{gdb/mi} Breakpoint Information
28936 When @value{GDBN} reports information about a breakpoint, a
28937 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
28942 The breakpoint number.
28945 The type of the breakpoint. For ordinary breakpoints this will be
28946 @samp{breakpoint}, but many values are possible.
28949 If the type of the breakpoint is @samp{catchpoint}, then this
28950 indicates the exact type of catchpoint.
28953 This is the breakpoint disposition---either @samp{del}, meaning that
28954 the breakpoint will be deleted at the next stop, or @samp{keep},
28955 meaning that the breakpoint will not be deleted.
28958 This indicates whether the breakpoint is enabled, in which case the
28959 value is @samp{y}, or disabled, in which case the value is @samp{n}.
28960 Note that this is not the same as the field @code{enable}.
28963 The address of the breakpoint. This may be a hexidecimal number,
28964 giving the address; or the string @samp{<PENDING>}, for a pending
28965 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
28966 multiple locations. This field will not be present if no address can
28967 be determined. For example, a watchpoint does not have an address.
28970 Optional field containing any flags related to the address. These flags are
28971 architecture-dependent; see @ref{Architectures} for their meaning for a
28975 If known, the function in which the breakpoint appears.
28976 If not known, this field is not present.
28979 The name of the source file which contains this function, if known.
28980 If not known, this field is not present.
28983 The full file name of the source file which contains this function, if
28984 known. If not known, this field is not present.
28987 The line number at which this breakpoint appears, if known.
28988 If not known, this field is not present.
28991 If the source file is not known, this field may be provided. If
28992 provided, this holds the address of the breakpoint, possibly followed
28996 If this breakpoint is pending, this field is present and holds the
28997 text used to set the breakpoint, as entered by the user.
29000 Where this breakpoint's condition is evaluated, either @samp{host} or
29004 If this is a thread-specific breakpoint, then this identifies the
29005 thread in which the breakpoint can trigger.
29008 If this breakpoint is restricted to a particular Ada task, then this
29009 field will hold the task identifier.
29012 If the breakpoint is conditional, this is the condition expression.
29015 The ignore count of the breakpoint.
29018 The enable count of the breakpoint.
29020 @item traceframe-usage
29023 @item static-tracepoint-marker-string-id
29024 For a static tracepoint, the name of the static tracepoint marker.
29027 For a masked watchpoint, this is the mask.
29030 A tracepoint's pass count.
29032 @item original-location
29033 The location of the breakpoint as originally specified by the user.
29034 This field is optional.
29037 The number of times the breakpoint has been hit.
29040 This field is only given for tracepoints. This is either @samp{y},
29041 meaning that the tracepoint is installed, or @samp{n}, meaning that it
29045 Some extra data, the exact contents of which are type-dependent.
29048 This field is present if the breakpoint has multiple locations. It is also
29049 exceptionally present if the breakpoint is enabled and has a single, disabled
29052 The value is a list of locations. The format of a location is decribed below.
29056 A location in a multi-location breakpoint is represented as a tuple with the
29062 The location number as a dotted pair, like @samp{1.2}. The first digit is the
29063 number of the parent breakpoint. The second digit is the number of the
29064 location within that breakpoint.
29067 This indicates whether the location is enabled, in which case the
29068 value is @samp{y}, or disabled, in which case the value is @samp{n}.
29069 Note that this is not the same as the field @code{enable}.
29072 The address of this location as an hexidecimal number.
29075 Optional field containing any flags related to the address. These flags are
29076 architecture-dependent; see @ref{Architectures} for their meaning for a
29080 If known, the function in which the location appears.
29081 If not known, this field is not present.
29084 The name of the source file which contains this location, if known.
29085 If not known, this field is not present.
29088 The full file name of the source file which contains this location, if
29089 known. If not known, this field is not present.
29092 The line number at which this location appears, if known.
29093 If not known, this field is not present.
29095 @item thread-groups
29096 The thread groups this location is in.
29100 For example, here is what the output of @code{-break-insert}
29101 (@pxref{GDB/MI Breakpoint Commands}) might be:
29104 -> -break-insert main
29105 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
29106 enabled="y",addr="0x08048564",func="main",file="myprog.c",
29107 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
29112 @node GDB/MI Frame Information
29113 @subsection @sc{gdb/mi} Frame Information
29115 Response from many MI commands includes an information about stack
29116 frame. This information is a tuple that may have the following
29121 The level of the stack frame. The innermost frame has the level of
29122 zero. This field is always present.
29125 The name of the function corresponding to the frame. This field may
29126 be absent if @value{GDBN} is unable to determine the function name.
29129 The code address for the frame. This field is always present.
29132 Optional field containing any flags related to the address. These flags are
29133 architecture-dependent; see @ref{Architectures} for their meaning for a
29137 The name of the source files that correspond to the frame's code
29138 address. This field may be absent.
29141 The source line corresponding to the frames' code address. This field
29145 The name of the binary file (either executable or shared library) the
29146 corresponds to the frame's code address. This field may be absent.
29150 @node GDB/MI Thread Information
29151 @subsection @sc{gdb/mi} Thread Information
29153 Whenever @value{GDBN} has to report an information about a thread, it
29154 uses a tuple with the following fields. The fields are always present unless
29159 The global numeric id assigned to the thread by @value{GDBN}.
29162 The target-specific string identifying the thread.
29165 Additional information about the thread provided by the target.
29166 It is supposed to be human-readable and not interpreted by the
29167 frontend. This field is optional.
29170 The name of the thread. If the user specified a name using the
29171 @code{thread name} command, then this name is given. Otherwise, if
29172 @value{GDBN} can extract the thread name from the target, then that
29173 name is given. If @value{GDBN} cannot find the thread name, then this
29177 The execution state of the thread, either @samp{stopped} or @samp{running},
29178 depending on whether the thread is presently running.
29181 The stack frame currently executing in the thread. This field is only present
29182 if the thread is stopped. Its format is documented in
29183 @ref{GDB/MI Frame Information}.
29186 The value of this field is an integer number of the processor core the
29187 thread was last seen on. This field is optional.
29190 @node GDB/MI Ada Exception Information
29191 @subsection @sc{gdb/mi} Ada Exception Information
29193 Whenever a @code{*stopped} record is emitted because the program
29194 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
29195 @value{GDBN} provides the name of the exception that was raised via
29196 the @code{exception-name} field. Also, for exceptions that were raised
29197 with an exception message, @value{GDBN} provides that message via
29198 the @code{exception-message} field.
29200 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29201 @node GDB/MI Simple Examples
29202 @section Simple Examples of @sc{gdb/mi} Interaction
29203 @cindex @sc{gdb/mi}, simple examples
29205 This subsection presents several simple examples of interaction using
29206 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
29207 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
29208 the output received from @sc{gdb/mi}.
29210 Note the line breaks shown in the examples are here only for
29211 readability, they don't appear in the real output.
29213 @subheading Setting a Breakpoint
29215 Setting a breakpoint generates synchronous output which contains detailed
29216 information of the breakpoint.
29219 -> -break-insert main
29220 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
29221 enabled="y",addr="0x08048564",func="main",file="myprog.c",
29222 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
29227 @subheading Program Execution
29229 Program execution generates asynchronous records and MI gives the
29230 reason that execution stopped.
29236 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
29237 frame=@{addr="0x08048564",func="main",
29238 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
29239 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68",
29240 arch="i386:x86_64"@}
29245 <- *stopped,reason="exited-normally"
29249 @subheading Quitting @value{GDBN}
29251 Quitting @value{GDBN} just prints the result class @samp{^exit}.
29259 Please note that @samp{^exit} is printed immediately, but it might
29260 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
29261 performs necessary cleanups, including killing programs being debugged
29262 or disconnecting from debug hardware, so the frontend should wait till
29263 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
29264 fails to exit in reasonable time.
29266 @subheading A Bad Command
29268 Here's what happens if you pass a non-existent command:
29272 <- ^error,msg="Undefined MI command: rubbish"
29277 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29278 @node GDB/MI Command Description Format
29279 @section @sc{gdb/mi} Command Description Format
29281 The remaining sections describe blocks of commands. Each block of
29282 commands is laid out in a fashion similar to this section.
29284 @subheading Motivation
29286 The motivation for this collection of commands.
29288 @subheading Introduction
29290 A brief introduction to this collection of commands as a whole.
29292 @subheading Commands
29294 For each command in the block, the following is described:
29296 @subsubheading Synopsis
29299 -command @var{args}@dots{}
29302 @subsubheading Result
29304 @subsubheading @value{GDBN} Command
29306 The corresponding @value{GDBN} CLI command(s), if any.
29308 @subsubheading Example
29310 Example(s) formatted for readability. Some of the described commands have
29311 not been implemented yet and these are labeled N.A.@: (not available).
29314 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29315 @node GDB/MI Breakpoint Commands
29316 @section @sc{gdb/mi} Breakpoint Commands
29318 @cindex breakpoint commands for @sc{gdb/mi}
29319 @cindex @sc{gdb/mi}, breakpoint commands
29320 This section documents @sc{gdb/mi} commands for manipulating
29323 @subheading The @code{-break-after} Command
29324 @findex -break-after
29326 @subsubheading Synopsis
29329 -break-after @var{number} @var{count}
29332 The breakpoint number @var{number} is not in effect until it has been
29333 hit @var{count} times. To see how this is reflected in the output of
29334 the @samp{-break-list} command, see the description of the
29335 @samp{-break-list} command below.
29337 @subsubheading @value{GDBN} Command
29339 The corresponding @value{GDBN} command is @samp{ignore}.
29341 @subsubheading Example
29346 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
29347 enabled="y",addr="0x000100d0",func="main",file="hello.c",
29348 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
29356 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
29357 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29358 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29359 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29360 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29361 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29362 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29363 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29364 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
29365 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
29370 @subheading The @code{-break-catch} Command
29371 @findex -break-catch
29374 @subheading The @code{-break-commands} Command
29375 @findex -break-commands
29377 @subsubheading Synopsis
29380 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
29383 Specifies the CLI commands that should be executed when breakpoint
29384 @var{number} is hit. The parameters @var{command1} to @var{commandN}
29385 are the commands. If no command is specified, any previously-set
29386 commands are cleared. @xref{Break Commands}. Typical use of this
29387 functionality is tracing a program, that is, printing of values of
29388 some variables whenever breakpoint is hit and then continuing.
29390 @subsubheading @value{GDBN} Command
29392 The corresponding @value{GDBN} command is @samp{commands}.
29394 @subsubheading Example
29399 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
29400 enabled="y",addr="0x000100d0",func="main",file="hello.c",
29401 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
29404 -break-commands 1 "print v" "continue"
29409 @subheading The @code{-break-condition} Command
29410 @findex -break-condition
29412 @subsubheading Synopsis
29415 -break-condition @var{number} @var{expr}
29418 Breakpoint @var{number} will stop the program only if the condition in
29419 @var{expr} is true. The condition becomes part of the
29420 @samp{-break-list} output (see the description of the @samp{-break-list}
29423 @subsubheading @value{GDBN} Command
29425 The corresponding @value{GDBN} command is @samp{condition}.
29427 @subsubheading Example
29431 -break-condition 1 1
29435 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
29436 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29437 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29438 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29439 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29440 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29441 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29442 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29443 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
29444 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
29448 @subheading The @code{-break-delete} Command
29449 @findex -break-delete
29451 @subsubheading Synopsis
29454 -break-delete ( @var{breakpoint} )+
29457 Delete the breakpoint(s) whose number(s) are specified in the argument
29458 list. This is obviously reflected in the breakpoint list.
29460 @subsubheading @value{GDBN} Command
29462 The corresponding @value{GDBN} command is @samp{delete}.
29464 @subsubheading Example
29472 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
29473 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29474 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29475 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29476 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29477 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29478 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29483 @subheading The @code{-break-disable} Command
29484 @findex -break-disable
29486 @subsubheading Synopsis
29489 -break-disable ( @var{breakpoint} )+
29492 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
29493 break list is now set to @samp{n} for the named @var{breakpoint}(s).
29495 @subsubheading @value{GDBN} Command
29497 The corresponding @value{GDBN} command is @samp{disable}.
29499 @subsubheading Example
29507 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
29508 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29509 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29510 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29511 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29512 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29513 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29514 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
29515 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
29516 line="5",thread-groups=["i1"],times="0"@}]@}
29520 @subheading The @code{-break-enable} Command
29521 @findex -break-enable
29523 @subsubheading Synopsis
29526 -break-enable ( @var{breakpoint} )+
29529 Enable (previously disabled) @var{breakpoint}(s).
29531 @subsubheading @value{GDBN} Command
29533 The corresponding @value{GDBN} command is @samp{enable}.
29535 @subsubheading Example
29543 ^done,BreakpointTable=@{nr_rows="1",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="2",type="breakpoint",disp="keep",enabled="y",
29551 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
29552 line="5",thread-groups=["i1"],times="0"@}]@}
29556 @subheading The @code{-break-info} Command
29557 @findex -break-info
29559 @subsubheading Synopsis
29562 -break-info @var{breakpoint}
29566 Get information about a single breakpoint.
29568 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
29569 Information}, for details on the format of each breakpoint in the
29572 @subsubheading @value{GDBN} Command
29574 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
29576 @subsubheading Example
29579 @subheading The @code{-break-insert} Command
29580 @findex -break-insert
29581 @anchor{-break-insert}
29583 @subsubheading Synopsis
29586 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
29587 [ -c @var{condition} ] [ -i @var{ignore-count} ]
29588 [ -p @var{thread-id} ] [ @var{location} ]
29592 If specified, @var{location}, can be one of:
29595 @item linespec location
29596 A linespec location. @xref{Linespec Locations}.
29598 @item explicit location
29599 An explicit location. @sc{gdb/mi} explicit locations are
29600 analogous to the CLI's explicit locations using the option names
29601 listed below. @xref{Explicit Locations}.
29604 @item --source @var{filename}
29605 The source file name of the location. This option requires the use
29606 of either @samp{--function} or @samp{--line}.
29608 @item --function @var{function}
29609 The name of a function or method.
29611 @item --label @var{label}
29612 The name of a label.
29614 @item --line @var{lineoffset}
29615 An absolute or relative line offset from the start of the location.
29618 @item address location
29619 An address location, *@var{address}. @xref{Address Locations}.
29623 The possible optional parameters of this command are:
29627 Insert a temporary breakpoint.
29629 Insert a hardware breakpoint.
29631 If @var{location} cannot be parsed (for example if it
29632 refers to unknown files or functions), create a pending
29633 breakpoint. Without this flag, @value{GDBN} will report
29634 an error, and won't create a breakpoint, if @var{location}
29637 Create a disabled breakpoint.
29639 Create a tracepoint. @xref{Tracepoints}. When this parameter
29640 is used together with @samp{-h}, a fast tracepoint is created.
29641 @item -c @var{condition}
29642 Make the breakpoint conditional on @var{condition}.
29643 @item -i @var{ignore-count}
29644 Initialize the @var{ignore-count}.
29645 @item -p @var{thread-id}
29646 Restrict the breakpoint to the thread with the specified global
29650 @subsubheading Result
29652 @xref{GDB/MI Breakpoint Information}, for details on the format of the
29653 resulting breakpoint.
29655 Note: this format is open to change.
29656 @c An out-of-band breakpoint instead of part of the result?
29658 @subsubheading @value{GDBN} Command
29660 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
29661 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
29663 @subsubheading Example
29668 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
29669 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
29672 -break-insert -t foo
29673 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
29674 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
29678 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
29679 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29680 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29681 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29682 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29683 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29684 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29685 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29686 addr="0x0001072c", func="main",file="recursive2.c",
29687 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
29689 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
29690 addr="0x00010774",func="foo",file="recursive2.c",
29691 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
29694 @c -break-insert -r foo.*
29695 @c ~int foo(int, int);
29696 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
29697 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
29702 @subheading The @code{-dprintf-insert} Command
29703 @findex -dprintf-insert
29705 @subsubheading Synopsis
29708 -dprintf-insert [ -t ] [ -f ] [ -d ]
29709 [ -c @var{condition} ] [ -i @var{ignore-count} ]
29710 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
29715 If supplied, @var{location} may be specified the same way as for
29716 the @code{-break-insert} command. @xref{-break-insert}.
29718 The possible optional parameters of this command are:
29722 Insert a temporary breakpoint.
29724 If @var{location} cannot be parsed (for example, if it
29725 refers to unknown files or functions), create a pending
29726 breakpoint. Without this flag, @value{GDBN} will report
29727 an error, and won't create a breakpoint, if @var{location}
29730 Create a disabled breakpoint.
29731 @item -c @var{condition}
29732 Make the breakpoint conditional on @var{condition}.
29733 @item -i @var{ignore-count}
29734 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
29735 to @var{ignore-count}.
29736 @item -p @var{thread-id}
29737 Restrict the breakpoint to the thread with the specified global
29741 @subsubheading Result
29743 @xref{GDB/MI Breakpoint Information}, for details on the format of the
29744 resulting breakpoint.
29746 @c An out-of-band breakpoint instead of part of the result?
29748 @subsubheading @value{GDBN} Command
29750 The corresponding @value{GDBN} command is @samp{dprintf}.
29752 @subsubheading Example
29756 4-dprintf-insert foo "At foo entry\n"
29757 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
29758 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
29759 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
29760 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
29761 original-location="foo"@}
29763 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
29764 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
29765 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
29766 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
29767 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
29768 original-location="mi-dprintf.c:26"@}
29772 @subheading The @code{-break-list} Command
29773 @findex -break-list
29775 @subsubheading Synopsis
29781 Displays the list of inserted breakpoints, showing the following fields:
29785 number of the breakpoint
29787 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
29789 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
29792 is the breakpoint enabled or no: @samp{y} or @samp{n}
29794 memory location at which the breakpoint is set
29796 logical location of the breakpoint, expressed by function name, file
29798 @item Thread-groups
29799 list of thread groups to which this breakpoint applies
29801 number of times the breakpoint has been hit
29804 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
29805 @code{body} field is an empty list.
29807 @subsubheading @value{GDBN} Command
29809 The corresponding @value{GDBN} command is @samp{info break}.
29811 @subsubheading Example
29816 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
29817 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29818 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29819 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29820 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29821 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29822 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29823 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29824 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
29826 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
29827 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
29828 line="13",thread-groups=["i1"],times="0"@}]@}
29832 Here's an example of the result when there are no breakpoints:
29837 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
29838 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29839 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29840 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29841 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29842 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29843 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29848 @subheading The @code{-break-passcount} Command
29849 @findex -break-passcount
29851 @subsubheading Synopsis
29854 -break-passcount @var{tracepoint-number} @var{passcount}
29857 Set the passcount for tracepoint @var{tracepoint-number} to
29858 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
29859 is not a tracepoint, error is emitted. This corresponds to CLI
29860 command @samp{passcount}.
29862 @subheading The @code{-break-watch} Command
29863 @findex -break-watch
29865 @subsubheading Synopsis
29868 -break-watch [ -a | -r ]
29871 Create a watchpoint. With the @samp{-a} option it will create an
29872 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
29873 read from or on a write to the memory location. With the @samp{-r}
29874 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
29875 trigger only when the memory location is accessed for reading. Without
29876 either of the options, the watchpoint created is a regular watchpoint,
29877 i.e., it will trigger when the memory location is accessed for writing.
29878 @xref{Set Watchpoints, , Setting Watchpoints}.
29880 Note that @samp{-break-list} will report a single list of watchpoints and
29881 breakpoints inserted.
29883 @subsubheading @value{GDBN} Command
29885 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
29888 @subsubheading Example
29890 Setting a watchpoint on a variable in the @code{main} function:
29895 ^done,wpt=@{number="2",exp="x"@}
29900 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
29901 value=@{old="-268439212",new="55"@},
29902 frame=@{func="main",args=[],file="recursive2.c",
29903 fullname="/home/foo/bar/recursive2.c",line="5",arch="i386:x86_64"@}
29907 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
29908 the program execution twice: first for the variable changing value, then
29909 for the watchpoint going out of scope.
29914 ^done,wpt=@{number="5",exp="C"@}
29919 *stopped,reason="watchpoint-trigger",
29920 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
29921 frame=@{func="callee4",args=[],
29922 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29923 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13",
29924 arch="i386:x86_64"@}
29929 *stopped,reason="watchpoint-scope",wpnum="5",
29930 frame=@{func="callee3",args=[@{name="strarg",
29931 value="0x11940 \"A string argument.\""@}],
29932 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29933 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
29934 arch="i386:x86_64"@}
29938 Listing breakpoints and watchpoints, at different points in the program
29939 execution. Note that once the watchpoint goes out of scope, it is
29945 ^done,wpt=@{number="2",exp="C"@}
29948 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
29949 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29950 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29951 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29952 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29953 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29954 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29955 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29956 addr="0x00010734",func="callee4",
29957 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29958 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
29960 bkpt=@{number="2",type="watchpoint",disp="keep",
29961 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
29966 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
29967 value=@{old="-276895068",new="3"@},
29968 frame=@{func="callee4",args=[],
29969 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29970 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13",
29971 arch="i386:x86_64"@}
29974 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
29975 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29976 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29977 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29978 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29979 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29980 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29981 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29982 addr="0x00010734",func="callee4",
29983 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29984 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
29986 bkpt=@{number="2",type="watchpoint",disp="keep",
29987 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
29991 ^done,reason="watchpoint-scope",wpnum="2",
29992 frame=@{func="callee3",args=[@{name="strarg",
29993 value="0x11940 \"A string argument.\""@}],
29994 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29995 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
29996 arch="i386:x86_64"@}
29999 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30000 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30001 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30002 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30003 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30004 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30005 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30006 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30007 addr="0x00010734",func="callee4",
30008 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30009 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
30010 thread-groups=["i1"],times="1"@}]@}
30015 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30016 @node GDB/MI Catchpoint Commands
30017 @section @sc{gdb/mi} Catchpoint Commands
30019 This section documents @sc{gdb/mi} commands for manipulating
30023 * Shared Library GDB/MI Catchpoint Commands::
30024 * Ada Exception GDB/MI Catchpoint Commands::
30025 * C++ Exception GDB/MI Catchpoint Commands::
30028 @node Shared Library GDB/MI Catchpoint Commands
30029 @subsection Shared Library @sc{gdb/mi} Catchpoints
30031 @subheading The @code{-catch-load} Command
30032 @findex -catch-load
30034 @subsubheading Synopsis
30037 -catch-load [ -t ] [ -d ] @var{regexp}
30040 Add a catchpoint for library load events. If the @samp{-t} option is used,
30041 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
30042 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
30043 in a disabled state. The @samp{regexp} argument is a regular
30044 expression used to match the name of the loaded library.
30047 @subsubheading @value{GDBN} Command
30049 The corresponding @value{GDBN} command is @samp{catch load}.
30051 @subsubheading Example
30054 -catch-load -t foo.so
30055 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
30056 what="load of library matching foo.so",catch-type="load",times="0"@}
30061 @subheading The @code{-catch-unload} Command
30062 @findex -catch-unload
30064 @subsubheading Synopsis
30067 -catch-unload [ -t ] [ -d ] @var{regexp}
30070 Add a catchpoint for library unload events. If the @samp{-t} option is
30071 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
30072 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
30073 created in a disabled state. The @samp{regexp} argument is a regular
30074 expression used to match the name of the unloaded library.
30076 @subsubheading @value{GDBN} Command
30078 The corresponding @value{GDBN} command is @samp{catch unload}.
30080 @subsubheading Example
30083 -catch-unload -d bar.so
30084 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
30085 what="load of library matching bar.so",catch-type="unload",times="0"@}
30089 @node Ada Exception GDB/MI Catchpoint Commands
30090 @subsection Ada Exception @sc{gdb/mi} Catchpoints
30092 The following @sc{gdb/mi} commands can be used to create catchpoints
30093 that stop the execution when Ada exceptions are being raised.
30095 @subheading The @code{-catch-assert} Command
30096 @findex -catch-assert
30098 @subsubheading Synopsis
30101 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
30104 Add a catchpoint for failed Ada assertions.
30106 The possible optional parameters for this command are:
30109 @item -c @var{condition}
30110 Make the catchpoint conditional on @var{condition}.
30112 Create a disabled catchpoint.
30114 Create a temporary catchpoint.
30117 @subsubheading @value{GDBN} Command
30119 The corresponding @value{GDBN} command is @samp{catch assert}.
30121 @subsubheading Example
30125 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
30126 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
30127 thread-groups=["i1"],times="0",
30128 original-location="__gnat_debug_raise_assert_failure"@}
30132 @subheading The @code{-catch-exception} Command
30133 @findex -catch-exception
30135 @subsubheading Synopsis
30138 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
30142 Add a catchpoint stopping when Ada exceptions are raised.
30143 By default, the command stops the program when any Ada exception
30144 gets raised. But it is also possible, by using some of the
30145 optional parameters described below, to create more selective
30148 The possible optional parameters for this command are:
30151 @item -c @var{condition}
30152 Make the catchpoint conditional on @var{condition}.
30154 Create a disabled catchpoint.
30155 @item -e @var{exception-name}
30156 Only stop when @var{exception-name} is raised. This option cannot
30157 be used combined with @samp{-u}.
30159 Create a temporary catchpoint.
30161 Stop only when an unhandled exception gets raised. This option
30162 cannot be used combined with @samp{-e}.
30165 @subsubheading @value{GDBN} Command
30167 The corresponding @value{GDBN} commands are @samp{catch exception}
30168 and @samp{catch exception unhandled}.
30170 @subsubheading Example
30173 -catch-exception -e Program_Error
30174 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
30175 enabled="y",addr="0x0000000000404874",
30176 what="`Program_Error' Ada exception", thread-groups=["i1"],
30177 times="0",original-location="__gnat_debug_raise_exception"@}
30181 @subheading The @code{-catch-handlers} Command
30182 @findex -catch-handlers
30184 @subsubheading Synopsis
30187 -catch-handlers [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
30191 Add a catchpoint stopping when Ada exceptions are handled.
30192 By default, the command stops the program when any Ada exception
30193 gets handled. But it is also possible, by using some of the
30194 optional parameters described below, to create more selective
30197 The possible optional parameters for this command are:
30200 @item -c @var{condition}
30201 Make the catchpoint conditional on @var{condition}.
30203 Create a disabled catchpoint.
30204 @item -e @var{exception-name}
30205 Only stop when @var{exception-name} is handled.
30207 Create a temporary catchpoint.
30210 @subsubheading @value{GDBN} Command
30212 The corresponding @value{GDBN} command is @samp{catch handlers}.
30214 @subsubheading Example
30217 -catch-handlers -e Constraint_Error
30218 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
30219 enabled="y",addr="0x0000000000402f68",
30220 what="`Constraint_Error' Ada exception handlers",thread-groups=["i1"],
30221 times="0",original-location="__gnat_begin_handler"@}
30225 @node C++ Exception GDB/MI Catchpoint Commands
30226 @subsection C@t{++} Exception @sc{gdb/mi} Catchpoints
30228 The following @sc{gdb/mi} commands can be used to create catchpoints
30229 that stop the execution when C@t{++} exceptions are being throw, rethrown,
30232 @subheading The @code{-catch-throw} Command
30233 @findex -catch-throw
30235 @subsubheading Synopsis
30238 -catch-throw [ -t ] [ -r @var{regexp}]
30241 Stop when the debuggee throws a C@t{++} exception. If @var{regexp} is
30242 given, then only exceptions whose type matches the regular expression
30245 If @samp{-t} is given, then the catchpoint is enabled only for one
30246 stop, the catchpoint is automatically deleted after stopping once for
30249 @subsubheading @value{GDBN} Command
30251 The corresponding @value{GDBN} commands are @samp{catch throw}
30252 and @samp{tcatch throw} (@pxref{Set Catchpoints}).
30254 @subsubheading Example
30257 -catch-throw -r exception_type
30258 ^done,bkpt=@{number="1",type="catchpoint",disp="keep",enabled="y",
30259 what="exception throw",catch-type="throw",
30260 thread-groups=["i1"],
30261 regexp="exception_type",times="0"@}
30267 ~"Catchpoint 1 (exception thrown), 0x00007ffff7ae00ed
30268 in __cxa_throw () from /lib64/libstdc++.so.6\n"
30269 *stopped,bkptno="1",reason="breakpoint-hit",disp="keep",
30270 frame=@{addr="0x00007ffff7ae00ed",func="__cxa_throw",
30271 args=[],from="/lib64/libstdc++.so.6",arch="i386:x86-64"@},
30272 thread-id="1",stopped-threads="all",core="6"
30276 @subheading The @code{-catch-rethrow} Command
30277 @findex -catch-rethrow
30279 @subsubheading Synopsis
30282 -catch-rethrow [ -t ] [ -r @var{regexp}]
30285 Stop when a C@t{++} exception is re-thrown. If @var{regexp} is given,
30286 then only exceptions whose type matches the regular expression will be
30289 If @samp{-t} is given, then the catchpoint is enabled only for one
30290 stop, the catchpoint is automatically deleted after the first event is
30293 @subsubheading @value{GDBN} Command
30295 The corresponding @value{GDBN} commands are @samp{catch rethrow}
30296 and @samp{tcatch rethrow} (@pxref{Set Catchpoints}).
30298 @subsubheading Example
30301 -catch-rethrow -r exception_type
30302 ^done,bkpt=@{number="1",type="catchpoint",disp="keep",enabled="y",
30303 what="exception rethrow",catch-type="rethrow",
30304 thread-groups=["i1"],
30305 regexp="exception_type",times="0"@}
30311 ~"Catchpoint 1 (exception rethrown), 0x00007ffff7ae00ed
30312 in __cxa_rethrow () from /lib64/libstdc++.so.6\n"
30313 *stopped,bkptno="1",reason="breakpoint-hit",disp="keep",
30314 frame=@{addr="0x00007ffff7ae00ed",func="__cxa_rethrow",
30315 args=[],from="/lib64/libstdc++.so.6",arch="i386:x86-64"@},
30316 thread-id="1",stopped-threads="all",core="6"
30320 @subheading The @code{-catch-catch} Command
30321 @findex -catch-catch
30323 @subsubheading Synopsis
30326 -catch-catch [ -t ] [ -r @var{regexp}]
30329 Stop when the debuggee catches a C@t{++} exception. If @var{regexp}
30330 is given, then only exceptions whose type matches the regular
30331 expression will be caught.
30333 If @samp{-t} is given, then the catchpoint is enabled only for one
30334 stop, the catchpoint is automatically deleted after the first event is
30337 @subsubheading @value{GDBN} Command
30339 The corresponding @value{GDBN} commands are @samp{catch catch}
30340 and @samp{tcatch catch} (@pxref{Set Catchpoints}).
30342 @subsubheading Example
30345 -catch-catch -r exception_type
30346 ^done,bkpt=@{number="1",type="catchpoint",disp="keep",enabled="y",
30347 what="exception catch",catch-type="catch",
30348 thread-groups=["i1"],
30349 regexp="exception_type",times="0"@}
30355 ~"Catchpoint 1 (exception caught), 0x00007ffff7ae00ed
30356 in __cxa_begin_catch () from /lib64/libstdc++.so.6\n"
30357 *stopped,bkptno="1",reason="breakpoint-hit",disp="keep",
30358 frame=@{addr="0x00007ffff7ae00ed",func="__cxa_begin_catch",
30359 args=[],from="/lib64/libstdc++.so.6",arch="i386:x86-64"@},
30360 thread-id="1",stopped-threads="all",core="6"
30364 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30365 @node GDB/MI Program Context
30366 @section @sc{gdb/mi} Program Context
30368 @subheading The @code{-exec-arguments} Command
30369 @findex -exec-arguments
30372 @subsubheading Synopsis
30375 -exec-arguments @var{args}
30378 Set the inferior program arguments, to be used in the next
30381 @subsubheading @value{GDBN} Command
30383 The corresponding @value{GDBN} command is @samp{set args}.
30385 @subsubheading Example
30389 -exec-arguments -v word
30396 @subheading The @code{-exec-show-arguments} Command
30397 @findex -exec-show-arguments
30399 @subsubheading Synopsis
30402 -exec-show-arguments
30405 Print the arguments of the program.
30407 @subsubheading @value{GDBN} Command
30409 The corresponding @value{GDBN} command is @samp{show args}.
30411 @subsubheading Example
30416 @subheading The @code{-environment-cd} Command
30417 @findex -environment-cd
30419 @subsubheading Synopsis
30422 -environment-cd @var{pathdir}
30425 Set @value{GDBN}'s working directory.
30427 @subsubheading @value{GDBN} Command
30429 The corresponding @value{GDBN} command is @samp{cd}.
30431 @subsubheading Example
30435 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
30441 @subheading The @code{-environment-directory} Command
30442 @findex -environment-directory
30444 @subsubheading Synopsis
30447 -environment-directory [ -r ] [ @var{pathdir} ]+
30450 Add directories @var{pathdir} to beginning of search path for source files.
30451 If the @samp{-r} option is used, the search path is reset to the default
30452 search path. If directories @var{pathdir} are supplied in addition to the
30453 @samp{-r} option, the search path is first reset and then addition
30455 Multiple directories may be specified, separated by blanks. Specifying
30456 multiple directories in a single command
30457 results in the directories added to the beginning of the
30458 search path in the same order they were presented in the command.
30459 If blanks are needed as
30460 part of a directory name, double-quotes should be used around
30461 the name. In the command output, the path will show up separated
30462 by the system directory-separator character. The directory-separator
30463 character must not be used
30464 in any directory name.
30465 If no directories are specified, the current search path is displayed.
30467 @subsubheading @value{GDBN} Command
30469 The corresponding @value{GDBN} command is @samp{dir}.
30471 @subsubheading Example
30475 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
30476 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
30478 -environment-directory ""
30479 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
30481 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
30482 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
30484 -environment-directory -r
30485 ^done,source-path="$cdir:$cwd"
30490 @subheading The @code{-environment-path} Command
30491 @findex -environment-path
30493 @subsubheading Synopsis
30496 -environment-path [ -r ] [ @var{pathdir} ]+
30499 Add directories @var{pathdir} to beginning of search path for object files.
30500 If the @samp{-r} option is used, the search path is reset to the original
30501 search path that existed at gdb start-up. If directories @var{pathdir} are
30502 supplied in addition to the
30503 @samp{-r} option, the search path is first reset and then addition
30505 Multiple directories may be specified, separated by blanks. Specifying
30506 multiple directories in a single command
30507 results in the directories added to the beginning of the
30508 search path in the same order they were presented in the command.
30509 If blanks are needed as
30510 part of a directory name, double-quotes should be used around
30511 the name. In the command output, the path will show up separated
30512 by the system directory-separator character. The directory-separator
30513 character must not be used
30514 in any directory name.
30515 If no directories are specified, the current path is displayed.
30518 @subsubheading @value{GDBN} Command
30520 The corresponding @value{GDBN} command is @samp{path}.
30522 @subsubheading Example
30527 ^done,path="/usr/bin"
30529 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
30530 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
30532 -environment-path -r /usr/local/bin
30533 ^done,path="/usr/local/bin:/usr/bin"
30538 @subheading The @code{-environment-pwd} Command
30539 @findex -environment-pwd
30541 @subsubheading Synopsis
30547 Show the current working directory.
30549 @subsubheading @value{GDBN} Command
30551 The corresponding @value{GDBN} command is @samp{pwd}.
30553 @subsubheading Example
30558 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
30562 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30563 @node GDB/MI Thread Commands
30564 @section @sc{gdb/mi} Thread Commands
30567 @subheading The @code{-thread-info} Command
30568 @findex -thread-info
30570 @subsubheading Synopsis
30573 -thread-info [ @var{thread-id} ]
30576 Reports information about either a specific thread, if the
30577 @var{thread-id} parameter is present, or about all threads.
30578 @var{thread-id} is the thread's global thread ID. When printing
30579 information about all threads, also reports the global ID of the
30582 @subsubheading @value{GDBN} Command
30584 The @samp{info thread} command prints the same information
30587 @subsubheading Result
30589 The result contains the following attributes:
30593 A list of threads. The format of the elements of the list is described in
30594 @ref{GDB/MI Thread Information}.
30596 @item current-thread-id
30597 The global id of the currently selected thread. This field is omitted if there
30598 is no selected thread (for example, when the selected inferior is not running,
30599 and therefore has no threads) or if a @var{thread-id} argument was passed to
30604 @subsubheading Example
30609 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
30610 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
30611 args=[]@},state="running"@},
30612 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
30613 frame=@{level="0",addr="0x0804891f",func="foo",
30614 args=[@{name="i",value="10"@}],
30615 file="/tmp/a.c",fullname="/tmp/a.c",line="158",arch="i386:x86_64"@},
30616 state="running"@}],
30617 current-thread-id="1"
30621 @subheading The @code{-thread-list-ids} Command
30622 @findex -thread-list-ids
30624 @subsubheading Synopsis
30630 Produces a list of the currently known global @value{GDBN} thread ids.
30631 At the end of the list it also prints the total number of such
30634 This command is retained for historical reasons, the
30635 @code{-thread-info} command should be used instead.
30637 @subsubheading @value{GDBN} Command
30639 Part of @samp{info threads} supplies the same information.
30641 @subsubheading Example
30646 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
30647 current-thread-id="1",number-of-threads="3"
30652 @subheading The @code{-thread-select} Command
30653 @findex -thread-select
30655 @subsubheading Synopsis
30658 -thread-select @var{thread-id}
30661 Make thread with global thread number @var{thread-id} the current
30662 thread. It prints the number of the new current thread, and the
30663 topmost frame for that thread.
30665 This command is deprecated in favor of explicitly using the
30666 @samp{--thread} option to each command.
30668 @subsubheading @value{GDBN} Command
30670 The corresponding @value{GDBN} command is @samp{thread}.
30672 @subsubheading Example
30679 *stopped,reason="end-stepping-range",thread-id="2",line="187",
30680 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
30684 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
30685 number-of-threads="3"
30688 ^done,new-thread-id="3",
30689 frame=@{level="0",func="vprintf",
30690 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
30691 @{name="arg",value="0x2"@}],file="vprintf.c",line="31",arch="i386:x86_64"@}
30695 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30696 @node GDB/MI Ada Tasking Commands
30697 @section @sc{gdb/mi} Ada Tasking Commands
30699 @subheading The @code{-ada-task-info} Command
30700 @findex -ada-task-info
30702 @subsubheading Synopsis
30705 -ada-task-info [ @var{task-id} ]
30708 Reports information about either a specific Ada task, if the
30709 @var{task-id} parameter is present, or about all Ada tasks.
30711 @subsubheading @value{GDBN} Command
30713 The @samp{info tasks} command prints the same information
30714 about all Ada tasks (@pxref{Ada Tasks}).
30716 @subsubheading Result
30718 The result is a table of Ada tasks. The following columns are
30719 defined for each Ada task:
30723 This field exists only for the current thread. It has the value @samp{*}.
30726 The identifier that @value{GDBN} uses to refer to the Ada task.
30729 The identifier that the target uses to refer to the Ada task.
30732 The global thread identifier of the thread corresponding to the Ada
30735 This field should always exist, as Ada tasks are always implemented
30736 on top of a thread. But if @value{GDBN} cannot find this corresponding
30737 thread for any reason, the field is omitted.
30740 This field exists only when the task was created by another task.
30741 In this case, it provides the ID of the parent task.
30744 The base priority of the task.
30747 The current state of the task. For a detailed description of the
30748 possible states, see @ref{Ada Tasks}.
30751 The name of the task.
30755 @subsubheading Example
30759 ^done,tasks=@{nr_rows="3",nr_cols="8",
30760 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
30761 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
30762 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
30763 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
30764 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
30765 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
30766 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
30767 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
30768 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
30769 state="Child Termination Wait",name="main_task"@}]@}
30773 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30774 @node GDB/MI Program Execution
30775 @section @sc{gdb/mi} Program Execution
30777 These are the asynchronous commands which generate the out-of-band
30778 record @samp{*stopped}. Currently @value{GDBN} only really executes
30779 asynchronously with remote targets and this interaction is mimicked in
30782 @subheading The @code{-exec-continue} Command
30783 @findex -exec-continue
30785 @subsubheading Synopsis
30788 -exec-continue [--reverse] [--all|--thread-group N]
30791 Resumes the execution of the inferior program, which will continue
30792 to execute until it reaches a debugger stop event. If the
30793 @samp{--reverse} option is specified, execution resumes in reverse until
30794 it reaches a stop event. Stop events may include
30797 breakpoints or watchpoints
30799 signals or exceptions
30801 the end of the process (or its beginning under @samp{--reverse})
30803 the end or beginning of a replay log if one is being used.
30805 In all-stop mode (@pxref{All-Stop
30806 Mode}), may resume only one thread, or all threads, depending on the
30807 value of the @samp{scheduler-locking} variable. If @samp{--all} is
30808 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
30809 ignored in all-stop mode. If the @samp{--thread-group} options is
30810 specified, then all threads in that thread group are resumed.
30812 @subsubheading @value{GDBN} Command
30814 The corresponding @value{GDBN} corresponding is @samp{continue}.
30816 @subsubheading Example
30823 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
30824 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
30825 line="13",arch="i386:x86_64"@}
30830 @subheading The @code{-exec-finish} Command
30831 @findex -exec-finish
30833 @subsubheading Synopsis
30836 -exec-finish [--reverse]
30839 Resumes the execution of the inferior program until the current
30840 function is exited. Displays the results returned by the function.
30841 If the @samp{--reverse} option is specified, resumes the reverse
30842 execution of the inferior program until the point where current
30843 function was called.
30845 @subsubheading @value{GDBN} Command
30847 The corresponding @value{GDBN} command is @samp{finish}.
30849 @subsubheading Example
30851 Function returning @code{void}.
30858 *stopped,reason="function-finished",frame=@{func="main",args=[],
30859 file="hello.c",fullname="/home/foo/bar/hello.c",line="7",arch="i386:x86_64"@}
30863 Function returning other than @code{void}. The name of the internal
30864 @value{GDBN} variable storing the result is printed, together with the
30871 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
30872 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
30873 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30874 arch="i386:x86_64"@},
30875 gdb-result-var="$1",return-value="0"
30880 @subheading The @code{-exec-interrupt} Command
30881 @findex -exec-interrupt
30883 @subsubheading Synopsis
30886 -exec-interrupt [--all|--thread-group N]
30889 Interrupts the background execution of the target. Note how the token
30890 associated with the stop message is the one for the execution command
30891 that has been interrupted. The token for the interrupt itself only
30892 appears in the @samp{^done} output. If the user is trying to
30893 interrupt a non-running program, an error message will be printed.
30895 Note that when asynchronous execution is enabled, this command is
30896 asynchronous just like other execution commands. That is, first the
30897 @samp{^done} response will be printed, and the target stop will be
30898 reported after that using the @samp{*stopped} notification.
30900 In non-stop mode, only the context thread is interrupted by default.
30901 All threads (in all inferiors) will be interrupted if the
30902 @samp{--all} option is specified. If the @samp{--thread-group}
30903 option is specified, all threads in that group will be interrupted.
30905 @subsubheading @value{GDBN} Command
30907 The corresponding @value{GDBN} command is @samp{interrupt}.
30909 @subsubheading Example
30920 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
30921 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
30922 fullname="/home/foo/bar/try.c",line="13",arch="i386:x86_64"@}
30927 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
30931 @subheading The @code{-exec-jump} Command
30934 @subsubheading Synopsis
30937 -exec-jump @var{location}
30940 Resumes execution of the inferior program at the location specified by
30941 parameter. @xref{Specify Location}, for a description of the
30942 different forms of @var{location}.
30944 @subsubheading @value{GDBN} Command
30946 The corresponding @value{GDBN} command is @samp{jump}.
30948 @subsubheading Example
30951 -exec-jump foo.c:10
30952 *running,thread-id="all"
30957 @subheading The @code{-exec-next} Command
30960 @subsubheading Synopsis
30963 -exec-next [--reverse]
30966 Resumes execution of the inferior program, stopping when the beginning
30967 of the next source line is reached.
30969 If the @samp{--reverse} option is specified, resumes reverse execution
30970 of the inferior program, stopping at the beginning of the previous
30971 source line. If you issue this command on the first line of a
30972 function, it will take you back to the caller of that function, to the
30973 source line where the function was called.
30976 @subsubheading @value{GDBN} Command
30978 The corresponding @value{GDBN} command is @samp{next}.
30980 @subsubheading Example
30986 *stopped,reason="end-stepping-range",line="8",file="hello.c"
30991 @subheading The @code{-exec-next-instruction} Command
30992 @findex -exec-next-instruction
30994 @subsubheading Synopsis
30997 -exec-next-instruction [--reverse]
31000 Executes one machine instruction. If the instruction is a function
31001 call, continues until the function returns. If the program stops at an
31002 instruction in the middle of a source line, the address will be
31005 If the @samp{--reverse} option is specified, resumes reverse execution
31006 of the inferior program, stopping at the previous instruction. If the
31007 previously executed instruction was a return from another function,
31008 it will continue to execute in reverse until the call to that function
31009 (from the current stack frame) is reached.
31011 @subsubheading @value{GDBN} Command
31013 The corresponding @value{GDBN} command is @samp{nexti}.
31015 @subsubheading Example
31019 -exec-next-instruction
31023 *stopped,reason="end-stepping-range",
31024 addr="0x000100d4",line="5",file="hello.c"
31029 @subheading The @code{-exec-return} Command
31030 @findex -exec-return
31032 @subsubheading Synopsis
31038 Makes current function return immediately. Doesn't execute the inferior.
31039 Displays the new current frame.
31041 @subsubheading @value{GDBN} Command
31043 The corresponding @value{GDBN} command is @samp{return}.
31045 @subsubheading Example
31049 200-break-insert callee4
31050 200^done,bkpt=@{number="1",addr="0x00010734",
31051 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
31056 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
31057 frame=@{func="callee4",args=[],
31058 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31059 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
31060 arch="i386:x86_64"@}
31066 111^done,frame=@{level="0",func="callee3",
31067 args=[@{name="strarg",
31068 value="0x11940 \"A string argument.\""@}],
31069 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31070 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
31071 arch="i386:x86_64"@}
31076 @subheading The @code{-exec-run} Command
31079 @subsubheading Synopsis
31082 -exec-run [ --all | --thread-group N ] [ --start ]
31085 Starts execution of the inferior from the beginning. The inferior
31086 executes until either a breakpoint is encountered or the program
31087 exits. In the latter case the output will include an exit code, if
31088 the program has exited exceptionally.
31090 When neither the @samp{--all} nor the @samp{--thread-group} option
31091 is specified, the current inferior is started. If the
31092 @samp{--thread-group} option is specified, it should refer to a thread
31093 group of type @samp{process}, and that thread group will be started.
31094 If the @samp{--all} option is specified, then all inferiors will be started.
31096 Using the @samp{--start} option instructs the debugger to stop
31097 the execution at the start of the inferior's main subprogram,
31098 following the same behavior as the @code{start} command
31099 (@pxref{Starting}).
31101 @subsubheading @value{GDBN} Command
31103 The corresponding @value{GDBN} command is @samp{run}.
31105 @subsubheading Examples
31110 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
31115 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
31116 frame=@{func="main",args=[],file="recursive2.c",
31117 fullname="/home/foo/bar/recursive2.c",line="4",arch="i386:x86_64"@}
31122 Program exited normally:
31130 *stopped,reason="exited-normally"
31135 Program exited exceptionally:
31143 *stopped,reason="exited",exit-code="01"
31147 Another way the program can terminate is if it receives a signal such as
31148 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
31152 *stopped,reason="exited-signalled",signal-name="SIGINT",
31153 signal-meaning="Interrupt"
31157 @c @subheading -exec-signal
31160 @subheading The @code{-exec-step} Command
31163 @subsubheading Synopsis
31166 -exec-step [--reverse]
31169 Resumes execution of the inferior program, stopping when the beginning
31170 of the next source line is reached, if the next source line is not a
31171 function call. If it is, stop at the first instruction of the called
31172 function. If the @samp{--reverse} option is specified, resumes reverse
31173 execution of the inferior program, stopping at the beginning of the
31174 previously executed source line.
31176 @subsubheading @value{GDBN} Command
31178 The corresponding @value{GDBN} command is @samp{step}.
31180 @subsubheading Example
31182 Stepping into a function:
31188 *stopped,reason="end-stepping-range",
31189 frame=@{func="foo",args=[@{name="a",value="10"@},
31190 @{name="b",value="0"@}],file="recursive2.c",
31191 fullname="/home/foo/bar/recursive2.c",line="11",arch="i386:x86_64"@}
31201 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
31206 @subheading The @code{-exec-step-instruction} Command
31207 @findex -exec-step-instruction
31209 @subsubheading Synopsis
31212 -exec-step-instruction [--reverse]
31215 Resumes the inferior which executes one machine instruction. If the
31216 @samp{--reverse} option is specified, resumes reverse execution of the
31217 inferior program, stopping at the previously executed instruction.
31218 The output, once @value{GDBN} has stopped, will vary depending on
31219 whether we have stopped in the middle of a source line or not. In the
31220 former case, the address at which the program stopped will be printed
31223 @subsubheading @value{GDBN} Command
31225 The corresponding @value{GDBN} command is @samp{stepi}.
31227 @subsubheading Example
31231 -exec-step-instruction
31235 *stopped,reason="end-stepping-range",
31236 frame=@{func="foo",args=[],file="try.c",
31237 fullname="/home/foo/bar/try.c",line="10",arch="i386:x86_64"@}
31239 -exec-step-instruction
31243 *stopped,reason="end-stepping-range",
31244 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
31245 fullname="/home/foo/bar/try.c",line="10",arch="i386:x86_64"@}
31250 @subheading The @code{-exec-until} Command
31251 @findex -exec-until
31253 @subsubheading Synopsis
31256 -exec-until [ @var{location} ]
31259 Executes the inferior until the @var{location} specified in the
31260 argument is reached. If there is no argument, the inferior executes
31261 until a source line greater than the current one is reached. The
31262 reason for stopping in this case will be @samp{location-reached}.
31264 @subsubheading @value{GDBN} Command
31266 The corresponding @value{GDBN} command is @samp{until}.
31268 @subsubheading Example
31272 -exec-until recursive2.c:6
31276 *stopped,reason="location-reached",frame=@{func="main",args=[],
31277 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6",
31278 arch="i386:x86_64"@}
31283 @subheading -file-clear
31284 Is this going away????
31287 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31288 @node GDB/MI Stack Manipulation
31289 @section @sc{gdb/mi} Stack Manipulation Commands
31291 @subheading The @code{-enable-frame-filters} Command
31292 @findex -enable-frame-filters
31295 -enable-frame-filters
31298 @value{GDBN} allows Python-based frame filters to affect the output of
31299 the MI commands relating to stack traces. As there is no way to
31300 implement this in a fully backward-compatible way, a front end must
31301 request that this functionality be enabled.
31303 Once enabled, this feature cannot be disabled.
31305 Note that if Python support has not been compiled into @value{GDBN},
31306 this command will still succeed (and do nothing).
31308 @subheading The @code{-stack-info-frame} Command
31309 @findex -stack-info-frame
31311 @subsubheading Synopsis
31317 Get info on the selected frame.
31319 @subsubheading @value{GDBN} Command
31321 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
31322 (without arguments).
31324 @subsubheading Example
31329 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
31330 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31331 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17",
31332 arch="i386:x86_64"@}
31336 @subheading The @code{-stack-info-depth} Command
31337 @findex -stack-info-depth
31339 @subsubheading Synopsis
31342 -stack-info-depth [ @var{max-depth} ]
31345 Return the depth of the stack. If the integer argument @var{max-depth}
31346 is specified, do not count beyond @var{max-depth} frames.
31348 @subsubheading @value{GDBN} Command
31350 There's no equivalent @value{GDBN} command.
31352 @subsubheading Example
31354 For a stack with frame levels 0 through 11:
31361 -stack-info-depth 4
31364 -stack-info-depth 12
31367 -stack-info-depth 11
31370 -stack-info-depth 13
31375 @anchor{-stack-list-arguments}
31376 @subheading The @code{-stack-list-arguments} Command
31377 @findex -stack-list-arguments
31379 @subsubheading Synopsis
31382 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
31383 [ @var{low-frame} @var{high-frame} ]
31386 Display a list of the arguments for the frames between @var{low-frame}
31387 and @var{high-frame} (inclusive). If @var{low-frame} and
31388 @var{high-frame} are not provided, list the arguments for the whole
31389 call stack. If the two arguments are equal, show the single frame
31390 at the corresponding level. It is an error if @var{low-frame} is
31391 larger than the actual number of frames. On the other hand,
31392 @var{high-frame} may be larger than the actual number of frames, in
31393 which case only existing frames will be returned.
31395 If @var{print-values} is 0 or @code{--no-values}, print only the names of
31396 the variables; if it is 1 or @code{--all-values}, print also their
31397 values; and if it is 2 or @code{--simple-values}, print the name,
31398 type and value for simple data types, and the name and type for arrays,
31399 structures and unions. If the option @code{--no-frame-filters} is
31400 supplied, then Python frame filters will not be executed.
31402 If the @code{--skip-unavailable} option is specified, arguments that
31403 are not available are not listed. Partially available arguments
31404 are still displayed, however.
31406 Use of this command to obtain arguments in a single frame is
31407 deprecated in favor of the @samp{-stack-list-variables} command.
31409 @subsubheading @value{GDBN} Command
31411 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
31412 @samp{gdb_get_args} command which partially overlaps with the
31413 functionality of @samp{-stack-list-arguments}.
31415 @subsubheading Example
31422 frame=@{level="0",addr="0x00010734",func="callee4",
31423 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31424 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
31425 arch="i386:x86_64"@},
31426 frame=@{level="1",addr="0x0001076c",func="callee3",
31427 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31428 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17",
31429 arch="i386:x86_64"@},
31430 frame=@{level="2",addr="0x0001078c",func="callee2",
31431 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31432 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22",
31433 arch="i386:x86_64"@},
31434 frame=@{level="3",addr="0x000107b4",func="callee1",
31435 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31436 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27",
31437 arch="i386:x86_64"@},
31438 frame=@{level="4",addr="0x000107e0",func="main",
31439 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31440 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32",
31441 arch="i386:x86_64"@}]
31443 -stack-list-arguments 0
31446 frame=@{level="0",args=[]@},
31447 frame=@{level="1",args=[name="strarg"]@},
31448 frame=@{level="2",args=[name="intarg",name="strarg"]@},
31449 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
31450 frame=@{level="4",args=[]@}]
31452 -stack-list-arguments 1
31455 frame=@{level="0",args=[]@},
31457 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
31458 frame=@{level="2",args=[
31459 @{name="intarg",value="2"@},
31460 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
31461 @{frame=@{level="3",args=[
31462 @{name="intarg",value="2"@},
31463 @{name="strarg",value="0x11940 \"A string argument.\""@},
31464 @{name="fltarg",value="3.5"@}]@},
31465 frame=@{level="4",args=[]@}]
31467 -stack-list-arguments 0 2 2
31468 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
31470 -stack-list-arguments 1 2 2
31471 ^done,stack-args=[frame=@{level="2",
31472 args=[@{name="intarg",value="2"@},
31473 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
31477 @c @subheading -stack-list-exception-handlers
31480 @anchor{-stack-list-frames}
31481 @subheading The @code{-stack-list-frames} Command
31482 @findex -stack-list-frames
31484 @subsubheading Synopsis
31487 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
31490 List the frames currently on the stack. For each frame it displays the
31495 The frame number, 0 being the topmost frame, i.e., the innermost function.
31497 The @code{$pc} value for that frame.
31501 File name of the source file where the function lives.
31502 @item @var{fullname}
31503 The full file name of the source file where the function lives.
31505 Line number corresponding to the @code{$pc}.
31507 The shared library where this function is defined. This is only given
31508 if the frame's function is not known.
31510 Frame's architecture.
31513 If invoked without arguments, this command prints a backtrace for the
31514 whole stack. If given two integer arguments, it shows the frames whose
31515 levels are between the two arguments (inclusive). If the two arguments
31516 are equal, it shows the single frame at the corresponding level. It is
31517 an error if @var{low-frame} is larger than the actual number of
31518 frames. On the other hand, @var{high-frame} may be larger than the
31519 actual number of frames, in which case only existing frames will be
31520 returned. If the option @code{--no-frame-filters} is supplied, then
31521 Python frame filters will not be executed.
31523 @subsubheading @value{GDBN} Command
31525 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
31527 @subsubheading Example
31529 Full stack backtrace:
31535 [frame=@{level="0",addr="0x0001076c",func="foo",
31536 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11",
31537 arch="i386:x86_64"@},
31538 frame=@{level="1",addr="0x000107a4",func="foo",
31539 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
31540 arch="i386:x86_64"@},
31541 frame=@{level="2",addr="0x000107a4",func="foo",
31542 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
31543 arch="i386:x86_64"@},
31544 frame=@{level="3",addr="0x000107a4",func="foo",
31545 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
31546 arch="i386:x86_64"@},
31547 frame=@{level="4",addr="0x000107a4",func="foo",
31548 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
31549 arch="i386:x86_64"@},
31550 frame=@{level="5",addr="0x000107a4",func="foo",
31551 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
31552 arch="i386:x86_64"@},
31553 frame=@{level="6",addr="0x000107a4",func="foo",
31554 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
31555 arch="i386:x86_64"@},
31556 frame=@{level="7",addr="0x000107a4",func="foo",
31557 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
31558 arch="i386:x86_64"@},
31559 frame=@{level="8",addr="0x000107a4",func="foo",
31560 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
31561 arch="i386:x86_64"@},
31562 frame=@{level="9",addr="0x000107a4",func="foo",
31563 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
31564 arch="i386:x86_64"@},
31565 frame=@{level="10",addr="0x000107a4",func="foo",
31566 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
31567 arch="i386:x86_64"@},
31568 frame=@{level="11",addr="0x00010738",func="main",
31569 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4",
31570 arch="i386:x86_64"@}]
31574 Show frames between @var{low_frame} and @var{high_frame}:
31578 -stack-list-frames 3 5
31580 [frame=@{level="3",addr="0x000107a4",func="foo",
31581 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
31582 arch="i386:x86_64"@},
31583 frame=@{level="4",addr="0x000107a4",func="foo",
31584 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
31585 arch="i386:x86_64"@},
31586 frame=@{level="5",addr="0x000107a4",func="foo",
31587 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
31588 arch="i386:x86_64"@}]
31592 Show a single frame:
31596 -stack-list-frames 3 3
31598 [frame=@{level="3",addr="0x000107a4",func="foo",
31599 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
31600 arch="i386:x86_64"@}]
31605 @subheading The @code{-stack-list-locals} Command
31606 @findex -stack-list-locals
31607 @anchor{-stack-list-locals}
31609 @subsubheading Synopsis
31612 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
31615 Display the local variable names for the selected frame. If
31616 @var{print-values} is 0 or @code{--no-values}, print only the names of
31617 the variables; if it is 1 or @code{--all-values}, print also their
31618 values; and if it is 2 or @code{--simple-values}, print the name,
31619 type and value for simple data types, and the name and type for arrays,
31620 structures and unions. In this last case, a frontend can immediately
31621 display the value of simple data types and create variable objects for
31622 other data types when the user wishes to explore their values in
31623 more detail. If the option @code{--no-frame-filters} is supplied, then
31624 Python frame filters will not be executed.
31626 If the @code{--skip-unavailable} option is specified, local variables
31627 that are not available are not listed. Partially available local
31628 variables are still displayed, however.
31630 This command is deprecated in favor of the
31631 @samp{-stack-list-variables} command.
31633 @subsubheading @value{GDBN} Command
31635 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
31637 @subsubheading Example
31641 -stack-list-locals 0
31642 ^done,locals=[name="A",name="B",name="C"]
31644 -stack-list-locals --all-values
31645 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
31646 @{name="C",value="@{1, 2, 3@}"@}]
31647 -stack-list-locals --simple-values
31648 ^done,locals=[@{name="A",type="int",value="1"@},
31649 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
31653 @anchor{-stack-list-variables}
31654 @subheading The @code{-stack-list-variables} Command
31655 @findex -stack-list-variables
31657 @subsubheading Synopsis
31660 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
31663 Display the names of local variables and function arguments for the selected frame. If
31664 @var{print-values} is 0 or @code{--no-values}, print only the names of
31665 the variables; if it is 1 or @code{--all-values}, print also their
31666 values; and if it is 2 or @code{--simple-values}, print the name,
31667 type and value for simple data types, and the name and type for arrays,
31668 structures and unions. If the option @code{--no-frame-filters} is
31669 supplied, then Python frame filters will not be executed.
31671 If the @code{--skip-unavailable} option is specified, local variables
31672 and arguments that are not available are not listed. Partially
31673 available arguments and local variables are still displayed, however.
31675 @subsubheading Example
31679 -stack-list-variables --thread 1 --frame 0 --all-values
31680 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
31685 @subheading The @code{-stack-select-frame} Command
31686 @findex -stack-select-frame
31688 @subsubheading Synopsis
31691 -stack-select-frame @var{framenum}
31694 Change the selected frame. Select a different frame @var{framenum} on
31697 This command in deprecated in favor of passing the @samp{--frame}
31698 option to every command.
31700 @subsubheading @value{GDBN} Command
31702 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
31703 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
31705 @subsubheading Example
31709 -stack-select-frame 2
31714 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31715 @node GDB/MI Variable Objects
31716 @section @sc{gdb/mi} Variable Objects
31720 @subheading Motivation for Variable Objects in @sc{gdb/mi}
31722 For the implementation of a variable debugger window (locals, watched
31723 expressions, etc.), we are proposing the adaptation of the existing code
31724 used by @code{Insight}.
31726 The two main reasons for that are:
31730 It has been proven in practice (it is already on its second generation).
31733 It will shorten development time (needless to say how important it is
31737 The original interface was designed to be used by Tcl code, so it was
31738 slightly changed so it could be used through @sc{gdb/mi}. This section
31739 describes the @sc{gdb/mi} operations that will be available and gives some
31740 hints about their use.
31742 @emph{Note}: In addition to the set of operations described here, we
31743 expect the @sc{gui} implementation of a variable window to require, at
31744 least, the following operations:
31747 @item @code{-gdb-show} @code{output-radix}
31748 @item @code{-stack-list-arguments}
31749 @item @code{-stack-list-locals}
31750 @item @code{-stack-select-frame}
31755 @subheading Introduction to Variable Objects
31757 @cindex variable objects in @sc{gdb/mi}
31759 Variable objects are "object-oriented" MI interface for examining and
31760 changing values of expressions. Unlike some other MI interfaces that
31761 work with expressions, variable objects are specifically designed for
31762 simple and efficient presentation in the frontend. A variable object
31763 is identified by string name. When a variable object is created, the
31764 frontend specifies the expression for that variable object. The
31765 expression can be a simple variable, or it can be an arbitrary complex
31766 expression, and can even involve CPU registers. After creating a
31767 variable object, the frontend can invoke other variable object
31768 operations---for example to obtain or change the value of a variable
31769 object, or to change display format.
31771 Variable objects have hierarchical tree structure. Any variable object
31772 that corresponds to a composite type, such as structure in C, has
31773 a number of child variable objects, for example corresponding to each
31774 element of a structure. A child variable object can itself have
31775 children, recursively. Recursion ends when we reach
31776 leaf variable objects, which always have built-in types. Child variable
31777 objects are created only by explicit request, so if a frontend
31778 is not interested in the children of a particular variable object, no
31779 child will be created.
31781 For a leaf variable object it is possible to obtain its value as a
31782 string, or set the value from a string. String value can be also
31783 obtained for a non-leaf variable object, but it's generally a string
31784 that only indicates the type of the object, and does not list its
31785 contents. Assignment to a non-leaf variable object is not allowed.
31787 A frontend does not need to read the values of all variable objects each time
31788 the program stops. Instead, MI provides an update command that lists all
31789 variable objects whose values has changed since the last update
31790 operation. This considerably reduces the amount of data that must
31791 be transferred to the frontend. As noted above, children variable
31792 objects are created on demand, and only leaf variable objects have a
31793 real value. As result, gdb will read target memory only for leaf
31794 variables that frontend has created.
31796 The automatic update is not always desirable. For example, a frontend
31797 might want to keep a value of some expression for future reference,
31798 and never update it. For another example, fetching memory is
31799 relatively slow for embedded targets, so a frontend might want
31800 to disable automatic update for the variables that are either not
31801 visible on the screen, or ``closed''. This is possible using so
31802 called ``frozen variable objects''. Such variable objects are never
31803 implicitly updated.
31805 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
31806 fixed variable object, the expression is parsed when the variable
31807 object is created, including associating identifiers to specific
31808 variables. The meaning of expression never changes. For a floating
31809 variable object the values of variables whose names appear in the
31810 expressions are re-evaluated every time in the context of the current
31811 frame. Consider this example:
31816 struct work_state state;
31823 If a fixed variable object for the @code{state} variable is created in
31824 this function, and we enter the recursive call, the variable
31825 object will report the value of @code{state} in the top-level
31826 @code{do_work} invocation. On the other hand, a floating variable
31827 object will report the value of @code{state} in the current frame.
31829 If an expression specified when creating a fixed variable object
31830 refers to a local variable, the variable object becomes bound to the
31831 thread and frame in which the variable object is created. When such
31832 variable object is updated, @value{GDBN} makes sure that the
31833 thread/frame combination the variable object is bound to still exists,
31834 and re-evaluates the variable object in context of that thread/frame.
31836 The following is the complete set of @sc{gdb/mi} operations defined to
31837 access this functionality:
31839 @multitable @columnfractions .4 .6
31840 @item @strong{Operation}
31841 @tab @strong{Description}
31843 @item @code{-enable-pretty-printing}
31844 @tab enable Python-based pretty-printing
31845 @item @code{-var-create}
31846 @tab create a variable object
31847 @item @code{-var-delete}
31848 @tab delete the variable object and/or its children
31849 @item @code{-var-set-format}
31850 @tab set the display format of this variable
31851 @item @code{-var-show-format}
31852 @tab show the display format of this variable
31853 @item @code{-var-info-num-children}
31854 @tab tells how many children this object has
31855 @item @code{-var-list-children}
31856 @tab return a list of the object's children
31857 @item @code{-var-info-type}
31858 @tab show the type of this variable object
31859 @item @code{-var-info-expression}
31860 @tab print parent-relative expression that this variable object represents
31861 @item @code{-var-info-path-expression}
31862 @tab print full expression that this variable object represents
31863 @item @code{-var-show-attributes}
31864 @tab is this variable editable? does it exist here?
31865 @item @code{-var-evaluate-expression}
31866 @tab get the value of this variable
31867 @item @code{-var-assign}
31868 @tab set the value of this variable
31869 @item @code{-var-update}
31870 @tab update the variable and its children
31871 @item @code{-var-set-frozen}
31872 @tab set frozeness attribute
31873 @item @code{-var-set-update-range}
31874 @tab set range of children to display on update
31877 In the next subsection we describe each operation in detail and suggest
31878 how it can be used.
31880 @subheading Description And Use of Operations on Variable Objects
31882 @subheading The @code{-enable-pretty-printing} Command
31883 @findex -enable-pretty-printing
31886 -enable-pretty-printing
31889 @value{GDBN} allows Python-based visualizers to affect the output of the
31890 MI variable object commands. However, because there was no way to
31891 implement this in a fully backward-compatible way, a front end must
31892 request that this functionality be enabled.
31894 Once enabled, this feature cannot be disabled.
31896 Note that if Python support has not been compiled into @value{GDBN},
31897 this command will still succeed (and do nothing).
31899 This feature is currently (as of @value{GDBN} 7.0) experimental, and
31900 may work differently in future versions of @value{GDBN}.
31902 @subheading The @code{-var-create} Command
31903 @findex -var-create
31905 @subsubheading Synopsis
31908 -var-create @{@var{name} | "-"@}
31909 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
31912 This operation creates a variable object, which allows the monitoring of
31913 a variable, the result of an expression, a memory cell or a CPU
31916 The @var{name} parameter is the string by which the object can be
31917 referenced. It must be unique. If @samp{-} is specified, the varobj
31918 system will generate a string ``varNNNNNN'' automatically. It will be
31919 unique provided that one does not specify @var{name} of that format.
31920 The command fails if a duplicate name is found.
31922 The frame under which the expression should be evaluated can be
31923 specified by @var{frame-addr}. A @samp{*} indicates that the current
31924 frame should be used. A @samp{@@} indicates that a floating variable
31925 object must be created.
31927 @var{expression} is any expression valid on the current language set (must not
31928 begin with a @samp{*}), or one of the following:
31932 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
31935 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
31938 @samp{$@var{regname}} --- a CPU register name
31941 @cindex dynamic varobj
31942 A varobj's contents may be provided by a Python-based pretty-printer. In this
31943 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
31944 have slightly different semantics in some cases. If the
31945 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
31946 will never create a dynamic varobj. This ensures backward
31947 compatibility for existing clients.
31949 @subsubheading Result
31951 This operation returns attributes of the newly-created varobj. These
31956 The name of the varobj.
31959 The number of children of the varobj. This number is not necessarily
31960 reliable for a dynamic varobj. Instead, you must examine the
31961 @samp{has_more} attribute.
31964 The varobj's scalar value. For a varobj whose type is some sort of
31965 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
31966 will not be interesting.
31969 The varobj's type. This is a string representation of the type, as
31970 would be printed by the @value{GDBN} CLI. If @samp{print object}
31971 (@pxref{Print Settings, set print object}) is set to @code{on}, the
31972 @emph{actual} (derived) type of the object is shown rather than the
31973 @emph{declared} one.
31976 If a variable object is bound to a specific thread, then this is the
31977 thread's global identifier.
31980 For a dynamic varobj, this indicates whether there appear to be any
31981 children available. For a non-dynamic varobj, this will be 0.
31984 This attribute will be present and have the value @samp{1} if the
31985 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
31986 then this attribute will not be present.
31989 A dynamic varobj can supply a display hint to the front end. The
31990 value comes directly from the Python pretty-printer object's
31991 @code{display_hint} method. @xref{Pretty Printing API}.
31994 Typical output will look like this:
31997 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
31998 has_more="@var{has_more}"
32002 @subheading The @code{-var-delete} Command
32003 @findex -var-delete
32005 @subsubheading Synopsis
32008 -var-delete [ -c ] @var{name}
32011 Deletes a previously created variable object and all of its children.
32012 With the @samp{-c} option, just deletes the children.
32014 Returns an error if the object @var{name} is not found.
32017 @subheading The @code{-var-set-format} Command
32018 @findex -var-set-format
32020 @subsubheading Synopsis
32023 -var-set-format @var{name} @var{format-spec}
32026 Sets the output format for the value of the object @var{name} to be
32029 @anchor{-var-set-format}
32030 The syntax for the @var{format-spec} is as follows:
32033 @var{format-spec} @expansion{}
32034 @{binary | decimal | hexadecimal | octal | natural | zero-hexadecimal@}
32037 The natural format is the default format choosen automatically
32038 based on the variable type (like decimal for an @code{int}, hex
32039 for pointers, etc.).
32041 The zero-hexadecimal format has a representation similar to hexadecimal
32042 but with padding zeroes to the left of the value. For example, a 32-bit
32043 hexadecimal value of 0x1234 would be represented as 0x00001234 in the
32044 zero-hexadecimal format.
32046 For a variable with children, the format is set only on the
32047 variable itself, and the children are not affected.
32049 @subheading The @code{-var-show-format} Command
32050 @findex -var-show-format
32052 @subsubheading Synopsis
32055 -var-show-format @var{name}
32058 Returns the format used to display the value of the object @var{name}.
32061 @var{format} @expansion{}
32066 @subheading The @code{-var-info-num-children} Command
32067 @findex -var-info-num-children
32069 @subsubheading Synopsis
32072 -var-info-num-children @var{name}
32075 Returns the number of children of a variable object @var{name}:
32081 Note that this number is not completely reliable for a dynamic varobj.
32082 It will return the current number of children, but more children may
32086 @subheading The @code{-var-list-children} Command
32087 @findex -var-list-children
32089 @subsubheading Synopsis
32092 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
32094 @anchor{-var-list-children}
32096 Return a list of the children of the specified variable object and
32097 create variable objects for them, if they do not already exist. With
32098 a single argument or if @var{print-values} has a value of 0 or
32099 @code{--no-values}, print only the names of the variables; if
32100 @var{print-values} is 1 or @code{--all-values}, also print their
32101 values; and if it is 2 or @code{--simple-values} print the name and
32102 value for simple data types and just the name for arrays, structures
32105 @var{from} and @var{to}, if specified, indicate the range of children
32106 to report. If @var{from} or @var{to} is less than zero, the range is
32107 reset and all children will be reported. Otherwise, children starting
32108 at @var{from} (zero-based) and up to and excluding @var{to} will be
32111 If a child range is requested, it will only affect the current call to
32112 @code{-var-list-children}, but not future calls to @code{-var-update}.
32113 For this, you must instead use @code{-var-set-update-range}. The
32114 intent of this approach is to enable a front end to implement any
32115 update approach it likes; for example, scrolling a view may cause the
32116 front end to request more children with @code{-var-list-children}, and
32117 then the front end could call @code{-var-set-update-range} with a
32118 different range to ensure that future updates are restricted to just
32121 For each child the following results are returned:
32126 Name of the variable object created for this child.
32129 The expression to be shown to the user by the front end to designate this child.
32130 For example this may be the name of a structure member.
32132 For a dynamic varobj, this value cannot be used to form an
32133 expression. There is no way to do this at all with a dynamic varobj.
32135 For C/C@t{++} structures there are several pseudo children returned to
32136 designate access qualifiers. For these pseudo children @var{exp} is
32137 @samp{public}, @samp{private}, or @samp{protected}. In this case the
32138 type and value are not present.
32140 A dynamic varobj will not report the access qualifying
32141 pseudo-children, regardless of the language. This information is not
32142 available at all with a dynamic varobj.
32145 Number of children this child has. For a dynamic varobj, this will be
32149 The type of the child. If @samp{print object}
32150 (@pxref{Print Settings, set print object}) is set to @code{on}, the
32151 @emph{actual} (derived) type of the object is shown rather than the
32152 @emph{declared} one.
32155 If values were requested, this is the value.
32158 If this variable object is associated with a thread, this is the
32159 thread's global thread id. Otherwise this result is not present.
32162 If the variable object is frozen, this variable will be present with a value of 1.
32165 A dynamic varobj can supply a display hint to the front end. The
32166 value comes directly from the Python pretty-printer object's
32167 @code{display_hint} method. @xref{Pretty Printing API}.
32170 This attribute will be present and have the value @samp{1} if the
32171 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
32172 then this attribute will not be present.
32176 The result may have its own attributes:
32180 A dynamic varobj can supply a display hint to the front end. The
32181 value comes directly from the Python pretty-printer object's
32182 @code{display_hint} method. @xref{Pretty Printing API}.
32185 This is an integer attribute which is nonzero if there are children
32186 remaining after the end of the selected range.
32189 @subsubheading Example
32193 -var-list-children n
32194 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
32195 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
32197 -var-list-children --all-values n
32198 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
32199 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
32203 @subheading The @code{-var-info-type} Command
32204 @findex -var-info-type
32206 @subsubheading Synopsis
32209 -var-info-type @var{name}
32212 Returns the type of the specified variable @var{name}. The type is
32213 returned as a string in the same format as it is output by the
32217 type=@var{typename}
32221 @subheading The @code{-var-info-expression} Command
32222 @findex -var-info-expression
32224 @subsubheading Synopsis
32227 -var-info-expression @var{name}
32230 Returns a string that is suitable for presenting this
32231 variable object in user interface. The string is generally
32232 not valid expression in the current language, and cannot be evaluated.
32234 For example, if @code{a} is an array, and variable object
32235 @code{A} was created for @code{a}, then we'll get this output:
32238 (gdb) -var-info-expression A.1
32239 ^done,lang="C",exp="1"
32243 Here, the value of @code{lang} is the language name, which can be
32244 found in @ref{Supported Languages}.
32246 Note that the output of the @code{-var-list-children} command also
32247 includes those expressions, so the @code{-var-info-expression} command
32250 @subheading The @code{-var-info-path-expression} Command
32251 @findex -var-info-path-expression
32253 @subsubheading Synopsis
32256 -var-info-path-expression @var{name}
32259 Returns an expression that can be evaluated in the current
32260 context and will yield the same value that a variable object has.
32261 Compare this with the @code{-var-info-expression} command, which
32262 result can be used only for UI presentation. Typical use of
32263 the @code{-var-info-path-expression} command is creating a
32264 watchpoint from a variable object.
32266 This command is currently not valid for children of a dynamic varobj,
32267 and will give an error when invoked on one.
32269 For example, suppose @code{C} is a C@t{++} class, derived from class
32270 @code{Base}, and that the @code{Base} class has a member called
32271 @code{m_size}. Assume a variable @code{c} is has the type of
32272 @code{C} and a variable object @code{C} was created for variable
32273 @code{c}. Then, we'll get this output:
32275 (gdb) -var-info-path-expression C.Base.public.m_size
32276 ^done,path_expr=((Base)c).m_size)
32279 @subheading The @code{-var-show-attributes} Command
32280 @findex -var-show-attributes
32282 @subsubheading Synopsis
32285 -var-show-attributes @var{name}
32288 List attributes of the specified variable object @var{name}:
32291 status=@var{attr} [ ( ,@var{attr} )* ]
32295 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
32297 @subheading The @code{-var-evaluate-expression} Command
32298 @findex -var-evaluate-expression
32300 @subsubheading Synopsis
32303 -var-evaluate-expression [-f @var{format-spec}] @var{name}
32306 Evaluates the expression that is represented by the specified variable
32307 object and returns its value as a string. The format of the string
32308 can be specified with the @samp{-f} option. The possible values of
32309 this option are the same as for @code{-var-set-format}
32310 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
32311 the current display format will be used. The current display format
32312 can be changed using the @code{-var-set-format} command.
32318 Note that one must invoke @code{-var-list-children} for a variable
32319 before the value of a child variable can be evaluated.
32321 @subheading The @code{-var-assign} Command
32322 @findex -var-assign
32324 @subsubheading Synopsis
32327 -var-assign @var{name} @var{expression}
32330 Assigns the value of @var{expression} to the variable object specified
32331 by @var{name}. The object must be @samp{editable}. If the variable's
32332 value is altered by the assign, the variable will show up in any
32333 subsequent @code{-var-update} list.
32335 @subsubheading Example
32343 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
32347 @subheading The @code{-var-update} Command
32348 @findex -var-update
32350 @subsubheading Synopsis
32353 -var-update [@var{print-values}] @{@var{name} | "*"@}
32356 Reevaluate the expressions corresponding to the variable object
32357 @var{name} and all its direct and indirect children, and return the
32358 list of variable objects whose values have changed; @var{name} must
32359 be a root variable object. Here, ``changed'' means that the result of
32360 @code{-var-evaluate-expression} before and after the
32361 @code{-var-update} is different. If @samp{*} is used as the variable
32362 object names, all existing variable objects are updated, except
32363 for frozen ones (@pxref{-var-set-frozen}). The option
32364 @var{print-values} determines whether both names and values, or just
32365 names are printed. The possible values of this option are the same
32366 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
32367 recommended to use the @samp{--all-values} option, to reduce the
32368 number of MI commands needed on each program stop.
32370 With the @samp{*} parameter, if a variable object is bound to a
32371 currently running thread, it will not be updated, without any
32374 If @code{-var-set-update-range} was previously used on a varobj, then
32375 only the selected range of children will be reported.
32377 @code{-var-update} reports all the changed varobjs in a tuple named
32380 Each item in the change list is itself a tuple holding:
32384 The name of the varobj.
32387 If values were requested for this update, then this field will be
32388 present and will hold the value of the varobj.
32391 @anchor{-var-update}
32392 This field is a string which may take one of three values:
32396 The variable object's current value is valid.
32399 The variable object does not currently hold a valid value but it may
32400 hold one in the future if its associated expression comes back into
32404 The variable object no longer holds a valid value.
32405 This can occur when the executable file being debugged has changed,
32406 either through recompilation or by using the @value{GDBN} @code{file}
32407 command. The front end should normally choose to delete these variable
32411 In the future new values may be added to this list so the front should
32412 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
32415 This is only present if the varobj is still valid. If the type
32416 changed, then this will be the string @samp{true}; otherwise it will
32419 When a varobj's type changes, its children are also likely to have
32420 become incorrect. Therefore, the varobj's children are automatically
32421 deleted when this attribute is @samp{true}. Also, the varobj's update
32422 range, when set using the @code{-var-set-update-range} command, is
32426 If the varobj's type changed, then this field will be present and will
32429 @item new_num_children
32430 For a dynamic varobj, if the number of children changed, or if the
32431 type changed, this will be the new number of children.
32433 The @samp{numchild} field in other varobj responses is generally not
32434 valid for a dynamic varobj -- it will show the number of children that
32435 @value{GDBN} knows about, but because dynamic varobjs lazily
32436 instantiate their children, this will not reflect the number of
32437 children which may be available.
32439 The @samp{new_num_children} attribute only reports changes to the
32440 number of children known by @value{GDBN}. This is the only way to
32441 detect whether an update has removed children (which necessarily can
32442 only happen at the end of the update range).
32445 The display hint, if any.
32448 This is an integer value, which will be 1 if there are more children
32449 available outside the varobj's update range.
32452 This attribute will be present and have the value @samp{1} if the
32453 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
32454 then this attribute will not be present.
32457 If new children were added to a dynamic varobj within the selected
32458 update range (as set by @code{-var-set-update-range}), then they will
32459 be listed in this attribute.
32462 @subsubheading Example
32469 -var-update --all-values var1
32470 ^done,changelist=[@{name="var1",value="3",in_scope="true",
32471 type_changed="false"@}]
32475 @subheading The @code{-var-set-frozen} Command
32476 @findex -var-set-frozen
32477 @anchor{-var-set-frozen}
32479 @subsubheading Synopsis
32482 -var-set-frozen @var{name} @var{flag}
32485 Set the frozenness flag on the variable object @var{name}. The
32486 @var{flag} parameter should be either @samp{1} to make the variable
32487 frozen or @samp{0} to make it unfrozen. If a variable object is
32488 frozen, then neither itself, nor any of its children, are
32489 implicitly updated by @code{-var-update} of
32490 a parent variable or by @code{-var-update *}. Only
32491 @code{-var-update} of the variable itself will update its value and
32492 values of its children. After a variable object is unfrozen, it is
32493 implicitly updated by all subsequent @code{-var-update} operations.
32494 Unfreezing a variable does not update it, only subsequent
32495 @code{-var-update} does.
32497 @subsubheading Example
32501 -var-set-frozen V 1
32506 @subheading The @code{-var-set-update-range} command
32507 @findex -var-set-update-range
32508 @anchor{-var-set-update-range}
32510 @subsubheading Synopsis
32513 -var-set-update-range @var{name} @var{from} @var{to}
32516 Set the range of children to be returned by future invocations of
32517 @code{-var-update}.
32519 @var{from} and @var{to} indicate the range of children to report. If
32520 @var{from} or @var{to} is less than zero, the range is reset and all
32521 children will be reported. Otherwise, children starting at @var{from}
32522 (zero-based) and up to and excluding @var{to} will be reported.
32524 @subsubheading Example
32528 -var-set-update-range V 1 2
32532 @subheading The @code{-var-set-visualizer} command
32533 @findex -var-set-visualizer
32534 @anchor{-var-set-visualizer}
32536 @subsubheading Synopsis
32539 -var-set-visualizer @var{name} @var{visualizer}
32542 Set a visualizer for the variable object @var{name}.
32544 @var{visualizer} is the visualizer to use. The special value
32545 @samp{None} means to disable any visualizer in use.
32547 If not @samp{None}, @var{visualizer} must be a Python expression.
32548 This expression must evaluate to a callable object which accepts a
32549 single argument. @value{GDBN} will call this object with the value of
32550 the varobj @var{name} as an argument (this is done so that the same
32551 Python pretty-printing code can be used for both the CLI and MI).
32552 When called, this object must return an object which conforms to the
32553 pretty-printing interface (@pxref{Pretty Printing API}).
32555 The pre-defined function @code{gdb.default_visualizer} may be used to
32556 select a visualizer by following the built-in process
32557 (@pxref{Selecting Pretty-Printers}). This is done automatically when
32558 a varobj is created, and so ordinarily is not needed.
32560 This feature is only available if Python support is enabled. The MI
32561 command @code{-list-features} (@pxref{GDB/MI Support Commands})
32562 can be used to check this.
32564 @subsubheading Example
32566 Resetting the visualizer:
32570 -var-set-visualizer V None
32574 Reselecting the default (type-based) visualizer:
32578 -var-set-visualizer V gdb.default_visualizer
32582 Suppose @code{SomeClass} is a visualizer class. A lambda expression
32583 can be used to instantiate this class for a varobj:
32587 -var-set-visualizer V "lambda val: SomeClass()"
32591 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32592 @node GDB/MI Data Manipulation
32593 @section @sc{gdb/mi} Data Manipulation
32595 @cindex data manipulation, in @sc{gdb/mi}
32596 @cindex @sc{gdb/mi}, data manipulation
32597 This section describes the @sc{gdb/mi} commands that manipulate data:
32598 examine memory and registers, evaluate expressions, etc.
32600 For details about what an addressable memory unit is,
32601 @pxref{addressable memory unit}.
32603 @c REMOVED FROM THE INTERFACE.
32604 @c @subheading -data-assign
32605 @c Change the value of a program variable. Plenty of side effects.
32606 @c @subsubheading GDB Command
32608 @c @subsubheading Example
32611 @subheading The @code{-data-disassemble} Command
32612 @findex -data-disassemble
32614 @subsubheading Synopsis
32618 [ -s @var{start-addr} -e @var{end-addr} ]
32619 | [ -a @var{addr} ]
32620 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
32628 @item @var{start-addr}
32629 is the beginning address (or @code{$pc})
32630 @item @var{end-addr}
32633 is an address anywhere within (or the name of) the function to
32634 disassemble. If an address is specified, the whole function
32635 surrounding that address will be disassembled. If a name is
32636 specified, the whole function with that name will be disassembled.
32637 @item @var{filename}
32638 is the name of the file to disassemble
32639 @item @var{linenum}
32640 is the line number to disassemble around
32642 is the number of disassembly lines to be produced. If it is -1,
32643 the whole function will be disassembled, in case no @var{end-addr} is
32644 specified. If @var{end-addr} is specified as a non-zero value, and
32645 @var{lines} is lower than the number of disassembly lines between
32646 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
32647 displayed; if @var{lines} is higher than the number of lines between
32648 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
32653 @item 0 disassembly only
32654 @item 1 mixed source and disassembly (deprecated)
32655 @item 2 disassembly with raw opcodes
32656 @item 3 mixed source and disassembly with raw opcodes (deprecated)
32657 @item 4 mixed source and disassembly
32658 @item 5 mixed source and disassembly with raw opcodes
32661 Modes 1 and 3 are deprecated. The output is ``source centric''
32662 which hasn't proved useful in practice.
32663 @xref{Machine Code}, for a discussion of the difference between
32664 @code{/m} and @code{/s} output of the @code{disassemble} command.
32667 @subsubheading Result
32669 The result of the @code{-data-disassemble} command will be a list named
32670 @samp{asm_insns}, the contents of this list depend on the @var{mode}
32671 used with the @code{-data-disassemble} command.
32673 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
32678 The address at which this instruction was disassembled.
32681 The name of the function this instruction is within.
32684 The decimal offset in bytes from the start of @samp{func-name}.
32687 The text disassembly for this @samp{address}.
32690 This field is only present for modes 2, 3 and 5. This contains the raw opcode
32691 bytes for the @samp{inst} field.
32695 For modes 1, 3, 4 and 5 the @samp{asm_insns} list contains tuples named
32696 @samp{src_and_asm_line}, each of which has the following fields:
32700 The line number within @samp{file}.
32703 The file name from the compilation unit. This might be an absolute
32704 file name or a relative file name depending on the compile command
32708 Absolute file name of @samp{file}. It is converted to a canonical form
32709 using the source file search path
32710 (@pxref{Source Path, ,Specifying Source Directories})
32711 and after resolving all the symbolic links.
32713 If the source file is not found this field will contain the path as
32714 present in the debug information.
32716 @item line_asm_insn
32717 This is a list of tuples containing the disassembly for @samp{line} in
32718 @samp{file}. The fields of each tuple are the same as for
32719 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
32720 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
32725 Note that whatever included in the @samp{inst} field, is not
32726 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
32729 @subsubheading @value{GDBN} Command
32731 The corresponding @value{GDBN} command is @samp{disassemble}.
32733 @subsubheading Example
32735 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
32739 -data-disassemble -s $pc -e "$pc + 20" -- 0
32742 @{address="0x000107c0",func-name="main",offset="4",
32743 inst="mov 2, %o0"@},
32744 @{address="0x000107c4",func-name="main",offset="8",
32745 inst="sethi %hi(0x11800), %o2"@},
32746 @{address="0x000107c8",func-name="main",offset="12",
32747 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
32748 @{address="0x000107cc",func-name="main",offset="16",
32749 inst="sethi %hi(0x11800), %o2"@},
32750 @{address="0x000107d0",func-name="main",offset="20",
32751 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
32755 Disassemble the whole @code{main} function. Line 32 is part of
32759 -data-disassemble -f basics.c -l 32 -- 0
32761 @{address="0x000107bc",func-name="main",offset="0",
32762 inst="save %sp, -112, %sp"@},
32763 @{address="0x000107c0",func-name="main",offset="4",
32764 inst="mov 2, %o0"@},
32765 @{address="0x000107c4",func-name="main",offset="8",
32766 inst="sethi %hi(0x11800), %o2"@},
32768 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
32769 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
32773 Disassemble 3 instructions from the start of @code{main}:
32777 -data-disassemble -f basics.c -l 32 -n 3 -- 0
32779 @{address="0x000107bc",func-name="main",offset="0",
32780 inst="save %sp, -112, %sp"@},
32781 @{address="0x000107c0",func-name="main",offset="4",
32782 inst="mov 2, %o0"@},
32783 @{address="0x000107c4",func-name="main",offset="8",
32784 inst="sethi %hi(0x11800), %o2"@}]
32788 Disassemble 3 instructions from the start of @code{main} in mixed mode:
32792 -data-disassemble -f basics.c -l 32 -n 3 -- 1
32794 src_and_asm_line=@{line="31",
32795 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
32796 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
32797 line_asm_insn=[@{address="0x000107bc",
32798 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
32799 src_and_asm_line=@{line="32",
32800 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
32801 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
32802 line_asm_insn=[@{address="0x000107c0",
32803 func-name="main",offset="4",inst="mov 2, %o0"@},
32804 @{address="0x000107c4",func-name="main",offset="8",
32805 inst="sethi %hi(0x11800), %o2"@}]@}]
32810 @subheading The @code{-data-evaluate-expression} Command
32811 @findex -data-evaluate-expression
32813 @subsubheading Synopsis
32816 -data-evaluate-expression @var{expr}
32819 Evaluate @var{expr} as an expression. The expression could contain an
32820 inferior function call. The function call will execute synchronously.
32821 If the expression contains spaces, it must be enclosed in double quotes.
32823 @subsubheading @value{GDBN} Command
32825 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
32826 @samp{call}. In @code{gdbtk} only, there's a corresponding
32827 @samp{gdb_eval} command.
32829 @subsubheading Example
32831 In the following example, the numbers that precede the commands are the
32832 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
32833 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
32837 211-data-evaluate-expression A
32840 311-data-evaluate-expression &A
32841 311^done,value="0xefffeb7c"
32843 411-data-evaluate-expression A+3
32846 511-data-evaluate-expression "A + 3"
32852 @subheading The @code{-data-list-changed-registers} Command
32853 @findex -data-list-changed-registers
32855 @subsubheading Synopsis
32858 -data-list-changed-registers
32861 Display a list of the registers that have changed.
32863 @subsubheading @value{GDBN} Command
32865 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
32866 has the corresponding command @samp{gdb_changed_register_list}.
32868 @subsubheading Example
32870 On a PPC MBX board:
32878 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
32879 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
32880 line="5",arch="powerpc"@}
32882 -data-list-changed-registers
32883 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
32884 "10","11","13","14","15","16","17","18","19","20","21","22","23",
32885 "24","25","26","27","28","30","31","64","65","66","67","69"]
32890 @subheading The @code{-data-list-register-names} Command
32891 @findex -data-list-register-names
32893 @subsubheading Synopsis
32896 -data-list-register-names [ ( @var{regno} )+ ]
32899 Show a list of register names for the current target. If no arguments
32900 are given, it shows a list of the names of all the registers. If
32901 integer numbers are given as arguments, it will print a list of the
32902 names of the registers corresponding to the arguments. To ensure
32903 consistency between a register name and its number, the output list may
32904 include empty register names.
32906 @subsubheading @value{GDBN} Command
32908 @value{GDBN} does not have a command which corresponds to
32909 @samp{-data-list-register-names}. In @code{gdbtk} there is a
32910 corresponding command @samp{gdb_regnames}.
32912 @subsubheading Example
32914 For the PPC MBX board:
32917 -data-list-register-names
32918 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
32919 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
32920 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
32921 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
32922 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
32923 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
32924 "", "pc","ps","cr","lr","ctr","xer"]
32926 -data-list-register-names 1 2 3
32927 ^done,register-names=["r1","r2","r3"]
32931 @subheading The @code{-data-list-register-values} Command
32932 @findex -data-list-register-values
32934 @subsubheading Synopsis
32937 -data-list-register-values
32938 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
32941 Display the registers' contents. The format according to which the
32942 registers' contents are to be returned is given by @var{fmt}, followed
32943 by an optional list of numbers specifying the registers to display. A
32944 missing list of numbers indicates that the contents of all the
32945 registers must be returned. The @code{--skip-unavailable} option
32946 indicates that only the available registers are to be returned.
32948 Allowed formats for @var{fmt} are:
32965 @subsubheading @value{GDBN} Command
32967 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
32968 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
32970 @subsubheading Example
32972 For a PPC MBX board (note: line breaks are for readability only, they
32973 don't appear in the actual output):
32977 -data-list-register-values r 64 65
32978 ^done,register-values=[@{number="64",value="0xfe00a300"@},
32979 @{number="65",value="0x00029002"@}]
32981 -data-list-register-values x
32982 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
32983 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
32984 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
32985 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
32986 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
32987 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
32988 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
32989 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
32990 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
32991 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
32992 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
32993 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
32994 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
32995 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
32996 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
32997 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
32998 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
32999 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
33000 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
33001 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
33002 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
33003 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
33004 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
33005 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
33006 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
33007 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
33008 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
33009 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
33010 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
33011 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
33012 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
33013 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
33014 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
33015 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
33016 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
33017 @{number="69",value="0x20002b03"@}]
33022 @subheading The @code{-data-read-memory} Command
33023 @findex -data-read-memory
33025 This command is deprecated, use @code{-data-read-memory-bytes} instead.
33027 @subsubheading Synopsis
33030 -data-read-memory [ -o @var{byte-offset} ]
33031 @var{address} @var{word-format} @var{word-size}
33032 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
33039 @item @var{address}
33040 An expression specifying the address of the first memory word to be
33041 read. Complex expressions containing embedded white space should be
33042 quoted using the C convention.
33044 @item @var{word-format}
33045 The format to be used to print the memory words. The notation is the
33046 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
33049 @item @var{word-size}
33050 The size of each memory word in bytes.
33052 @item @var{nr-rows}
33053 The number of rows in the output table.
33055 @item @var{nr-cols}
33056 The number of columns in the output table.
33059 If present, indicates that each row should include an @sc{ascii} dump. The
33060 value of @var{aschar} is used as a padding character when a byte is not a
33061 member of the printable @sc{ascii} character set (printable @sc{ascii}
33062 characters are those whose code is between 32 and 126, inclusively).
33064 @item @var{byte-offset}
33065 An offset to add to the @var{address} before fetching memory.
33068 This command displays memory contents as a table of @var{nr-rows} by
33069 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
33070 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
33071 (returned as @samp{total-bytes}). Should less than the requested number
33072 of bytes be returned by the target, the missing words are identified
33073 using @samp{N/A}. The number of bytes read from the target is returned
33074 in @samp{nr-bytes} and the starting address used to read memory in
33077 The address of the next/previous row or page is available in
33078 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
33081 @subsubheading @value{GDBN} Command
33083 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
33084 @samp{gdb_get_mem} memory read command.
33086 @subsubheading Example
33088 Read six bytes of memory starting at @code{bytes+6} but then offset by
33089 @code{-6} bytes. Format as three rows of two columns. One byte per
33090 word. Display each word in hex.
33094 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
33095 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
33096 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
33097 prev-page="0x0000138a",memory=[
33098 @{addr="0x00001390",data=["0x00","0x01"]@},
33099 @{addr="0x00001392",data=["0x02","0x03"]@},
33100 @{addr="0x00001394",data=["0x04","0x05"]@}]
33104 Read two bytes of memory starting at address @code{shorts + 64} and
33105 display as a single word formatted in decimal.
33109 5-data-read-memory shorts+64 d 2 1 1
33110 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
33111 next-row="0x00001512",prev-row="0x0000150e",
33112 next-page="0x00001512",prev-page="0x0000150e",memory=[
33113 @{addr="0x00001510",data=["128"]@}]
33117 Read thirty two bytes of memory starting at @code{bytes+16} and format
33118 as eight rows of four columns. Include a string encoding with @samp{x}
33119 used as the non-printable character.
33123 4-data-read-memory bytes+16 x 1 8 4 x
33124 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
33125 next-row="0x000013c0",prev-row="0x0000139c",
33126 next-page="0x000013c0",prev-page="0x00001380",memory=[
33127 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
33128 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
33129 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
33130 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
33131 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
33132 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
33133 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
33134 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
33138 @subheading The @code{-data-read-memory-bytes} Command
33139 @findex -data-read-memory-bytes
33141 @subsubheading Synopsis
33144 -data-read-memory-bytes [ -o @var{offset} ]
33145 @var{address} @var{count}
33152 @item @var{address}
33153 An expression specifying the address of the first addressable memory unit
33154 to be read. Complex expressions containing embedded white space should be
33155 quoted using the C convention.
33158 The number of addressable memory units to read. This should be an integer
33162 The offset relative to @var{address} at which to start reading. This
33163 should be an integer literal. This option is provided so that a frontend
33164 is not required to first evaluate address and then perform address
33165 arithmetics itself.
33169 This command attempts to read all accessible memory regions in the
33170 specified range. First, all regions marked as unreadable in the memory
33171 map (if one is defined) will be skipped. @xref{Memory Region
33172 Attributes}. Second, @value{GDBN} will attempt to read the remaining
33173 regions. For each one, if reading full region results in an errors,
33174 @value{GDBN} will try to read a subset of the region.
33176 In general, every single memory unit in the region may be readable or not,
33177 and the only way to read every readable unit is to try a read at
33178 every address, which is not practical. Therefore, @value{GDBN} will
33179 attempt to read all accessible memory units at either beginning or the end
33180 of the region, using a binary division scheme. This heuristic works
33181 well for reading accross a memory map boundary. Note that if a region
33182 has a readable range that is neither at the beginning or the end,
33183 @value{GDBN} will not read it.
33185 The result record (@pxref{GDB/MI Result Records}) that is output of
33186 the command includes a field named @samp{memory} whose content is a
33187 list of tuples. Each tuple represent a successfully read memory block
33188 and has the following fields:
33192 The start address of the memory block, as hexadecimal literal.
33195 The end address of the memory block, as hexadecimal literal.
33198 The offset of the memory block, as hexadecimal literal, relative to
33199 the start address passed to @code{-data-read-memory-bytes}.
33202 The contents of the memory block, in hex.
33208 @subsubheading @value{GDBN} Command
33210 The corresponding @value{GDBN} command is @samp{x}.
33212 @subsubheading Example
33216 -data-read-memory-bytes &a 10
33217 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
33219 contents="01000000020000000300"@}]
33224 @subheading The @code{-data-write-memory-bytes} Command
33225 @findex -data-write-memory-bytes
33227 @subsubheading Synopsis
33230 -data-write-memory-bytes @var{address} @var{contents}
33231 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
33238 @item @var{address}
33239 An expression specifying the address of the first addressable memory unit
33240 to be written. Complex expressions containing embedded white space should
33241 be quoted using the C convention.
33243 @item @var{contents}
33244 The hex-encoded data to write. It is an error if @var{contents} does
33245 not represent an integral number of addressable memory units.
33248 Optional argument indicating the number of addressable memory units to be
33249 written. If @var{count} is greater than @var{contents}' length,
33250 @value{GDBN} will repeatedly write @var{contents} until it fills
33251 @var{count} memory units.
33255 @subsubheading @value{GDBN} Command
33257 There's no corresponding @value{GDBN} command.
33259 @subsubheading Example
33263 -data-write-memory-bytes &a "aabbccdd"
33270 -data-write-memory-bytes &a "aabbccdd" 16e
33275 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33276 @node GDB/MI Tracepoint Commands
33277 @section @sc{gdb/mi} Tracepoint Commands
33279 The commands defined in this section implement MI support for
33280 tracepoints. For detailed introduction, see @ref{Tracepoints}.
33282 @subheading The @code{-trace-find} Command
33283 @findex -trace-find
33285 @subsubheading Synopsis
33288 -trace-find @var{mode} [@var{parameters}@dots{}]
33291 Find a trace frame using criteria defined by @var{mode} and
33292 @var{parameters}. The following table lists permissible
33293 modes and their parameters. For details of operation, see @ref{tfind}.
33298 No parameters are required. Stops examining trace frames.
33301 An integer is required as parameter. Selects tracepoint frame with
33304 @item tracepoint-number
33305 An integer is required as parameter. Finds next
33306 trace frame that corresponds to tracepoint with the specified number.
33309 An address is required as parameter. Finds
33310 next trace frame that corresponds to any tracepoint at the specified
33313 @item pc-inside-range
33314 Two addresses are required as parameters. Finds next trace
33315 frame that corresponds to a tracepoint at an address inside the
33316 specified range. Both bounds are considered to be inside the range.
33318 @item pc-outside-range
33319 Two addresses are required as parameters. Finds
33320 next trace frame that corresponds to a tracepoint at an address outside
33321 the specified range. Both bounds are considered to be inside the range.
33324 Line specification is required as parameter. @xref{Specify Location}.
33325 Finds next trace frame that corresponds to a tracepoint at
33326 the specified location.
33330 If @samp{none} was passed as @var{mode}, the response does not
33331 have fields. Otherwise, the response may have the following fields:
33335 This field has either @samp{0} or @samp{1} as the value, depending
33336 on whether a matching tracepoint was found.
33339 The index of the found traceframe. This field is present iff
33340 the @samp{found} field has value of @samp{1}.
33343 The index of the found tracepoint. This field is present iff
33344 the @samp{found} field has value of @samp{1}.
33347 The information about the frame corresponding to the found trace
33348 frame. This field is present only if a trace frame was found.
33349 @xref{GDB/MI Frame Information}, for description of this field.
33353 @subsubheading @value{GDBN} Command
33355 The corresponding @value{GDBN} command is @samp{tfind}.
33357 @subheading -trace-define-variable
33358 @findex -trace-define-variable
33360 @subsubheading Synopsis
33363 -trace-define-variable @var{name} [ @var{value} ]
33366 Create trace variable @var{name} if it does not exist. If
33367 @var{value} is specified, sets the initial value of the specified
33368 trace variable to that value. Note that the @var{name} should start
33369 with the @samp{$} character.
33371 @subsubheading @value{GDBN} Command
33373 The corresponding @value{GDBN} command is @samp{tvariable}.
33375 @subheading The @code{-trace-frame-collected} Command
33376 @findex -trace-frame-collected
33378 @subsubheading Synopsis
33381 -trace-frame-collected
33382 [--var-print-values @var{var_pval}]
33383 [--comp-print-values @var{comp_pval}]
33384 [--registers-format @var{regformat}]
33385 [--memory-contents]
33388 This command returns the set of collected objects, register names,
33389 trace state variable names, memory ranges and computed expressions
33390 that have been collected at a particular trace frame. The optional
33391 parameters to the command affect the output format in different ways.
33392 See the output description table below for more details.
33394 The reported names can be used in the normal manner to create
33395 varobjs and inspect the objects themselves. The items returned by
33396 this command are categorized so that it is clear which is a variable,
33397 which is a register, which is a trace state variable, which is a
33398 memory range and which is a computed expression.
33400 For instance, if the actions were
33402 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
33403 collect *(int*)0xaf02bef0@@40
33407 the object collected in its entirety would be @code{myVar}. The
33408 object @code{myArray} would be partially collected, because only the
33409 element at index @code{myIndex} would be collected. The remaining
33410 objects would be computed expressions.
33412 An example output would be:
33416 -trace-frame-collected
33418 explicit-variables=[@{name="myVar",value="1"@}],
33419 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
33420 @{name="myObj.field",value="0"@},
33421 @{name="myPtr->field",value="1"@},
33422 @{name="myCount + 2",value="3"@},
33423 @{name="$tvar1 + 1",value="43970027"@}],
33424 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
33425 @{number="1",value="0x0"@},
33426 @{number="2",value="0x4"@},
33428 @{number="125",value="0x0"@}],
33429 tvars=[@{name="$tvar1",current="43970026"@}],
33430 memory=[@{address="0x0000000000602264",length="4"@},
33431 @{address="0x0000000000615bc0",length="4"@}]
33438 @item explicit-variables
33439 The set of objects that have been collected in their entirety (as
33440 opposed to collecting just a few elements of an array or a few struct
33441 members). For each object, its name and value are printed.
33442 The @code{--var-print-values} option affects how or whether the value
33443 field is output. If @var{var_pval} is 0, then print only the names;
33444 if it is 1, print also their values; and if it is 2, print the name,
33445 type and value for simple data types, and the name and type for
33446 arrays, structures and unions.
33448 @item computed-expressions
33449 The set of computed expressions that have been collected at the
33450 current trace frame. The @code{--comp-print-values} option affects
33451 this set like the @code{--var-print-values} option affects the
33452 @code{explicit-variables} set. See above.
33455 The registers that have been collected at the current trace frame.
33456 For each register collected, the name and current value are returned.
33457 The value is formatted according to the @code{--registers-format}
33458 option. See the @command{-data-list-register-values} command for a
33459 list of the allowed formats. The default is @samp{x}.
33462 The trace state variables that have been collected at the current
33463 trace frame. For each trace state variable collected, the name and
33464 current value are returned.
33467 The set of memory ranges that have been collected at the current trace
33468 frame. Its content is a list of tuples. Each tuple represents a
33469 collected memory range and has the following fields:
33473 The start address of the memory range, as hexadecimal literal.
33476 The length of the memory range, as decimal literal.
33479 The contents of the memory block, in hex. This field is only present
33480 if the @code{--memory-contents} option is specified.
33486 @subsubheading @value{GDBN} Command
33488 There is no corresponding @value{GDBN} command.
33490 @subsubheading Example
33492 @subheading -trace-list-variables
33493 @findex -trace-list-variables
33495 @subsubheading Synopsis
33498 -trace-list-variables
33501 Return a table of all defined trace variables. Each element of the
33502 table has the following fields:
33506 The name of the trace variable. This field is always present.
33509 The initial value. This is a 64-bit signed integer. This
33510 field is always present.
33513 The value the trace variable has at the moment. This is a 64-bit
33514 signed integer. This field is absent iff current value is
33515 not defined, for example if the trace was never run, or is
33520 @subsubheading @value{GDBN} Command
33522 The corresponding @value{GDBN} command is @samp{tvariables}.
33524 @subsubheading Example
33528 -trace-list-variables
33529 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
33530 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
33531 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
33532 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
33533 body=[variable=@{name="$trace_timestamp",initial="0"@}
33534 variable=@{name="$foo",initial="10",current="15"@}]@}
33538 @subheading -trace-save
33539 @findex -trace-save
33541 @subsubheading Synopsis
33544 -trace-save [ -r ] [ -ctf ] @var{filename}
33547 Saves the collected trace data to @var{filename}. Without the
33548 @samp{-r} option, the data is downloaded from the target and saved
33549 in a local file. With the @samp{-r} option the target is asked
33550 to perform the save.
33552 By default, this command will save the trace in the tfile format. You can
33553 supply the optional @samp{-ctf} argument to save it the CTF format. See
33554 @ref{Trace Files} for more information about CTF.
33556 @subsubheading @value{GDBN} Command
33558 The corresponding @value{GDBN} command is @samp{tsave}.
33561 @subheading -trace-start
33562 @findex -trace-start
33564 @subsubheading Synopsis
33570 Starts a tracing experiment. The result of this command does not
33573 @subsubheading @value{GDBN} Command
33575 The corresponding @value{GDBN} command is @samp{tstart}.
33577 @subheading -trace-status
33578 @findex -trace-status
33580 @subsubheading Synopsis
33586 Obtains the status of a tracing experiment. The result may include
33587 the following fields:
33592 May have a value of either @samp{0}, when no tracing operations are
33593 supported, @samp{1}, when all tracing operations are supported, or
33594 @samp{file} when examining trace file. In the latter case, examining
33595 of trace frame is possible but new tracing experiement cannot be
33596 started. This field is always present.
33599 May have a value of either @samp{0} or @samp{1} depending on whether
33600 tracing experiement is in progress on target. This field is present
33601 if @samp{supported} field is not @samp{0}.
33604 Report the reason why the tracing was stopped last time. This field
33605 may be absent iff tracing was never stopped on target yet. The
33606 value of @samp{request} means the tracing was stopped as result of
33607 the @code{-trace-stop} command. The value of @samp{overflow} means
33608 the tracing buffer is full. The value of @samp{disconnection} means
33609 tracing was automatically stopped when @value{GDBN} has disconnected.
33610 The value of @samp{passcount} means tracing was stopped when a
33611 tracepoint was passed a maximal number of times for that tracepoint.
33612 This field is present if @samp{supported} field is not @samp{0}.
33614 @item stopping-tracepoint
33615 The number of tracepoint whose passcount as exceeded. This field is
33616 present iff the @samp{stop-reason} field has the value of
33620 @itemx frames-created
33621 The @samp{frames} field is a count of the total number of trace frames
33622 in the trace buffer, while @samp{frames-created} is the total created
33623 during the run, including ones that were discarded, such as when a
33624 circular trace buffer filled up. Both fields are optional.
33628 These fields tell the current size of the tracing buffer and the
33629 remaining space. These fields are optional.
33632 The value of the circular trace buffer flag. @code{1} means that the
33633 trace buffer is circular and old trace frames will be discarded if
33634 necessary to make room, @code{0} means that the trace buffer is linear
33638 The value of the disconnected tracing flag. @code{1} means that
33639 tracing will continue after @value{GDBN} disconnects, @code{0} means
33640 that the trace run will stop.
33643 The filename of the trace file being examined. This field is
33644 optional, and only present when examining a trace file.
33648 @subsubheading @value{GDBN} Command
33650 The corresponding @value{GDBN} command is @samp{tstatus}.
33652 @subheading -trace-stop
33653 @findex -trace-stop
33655 @subsubheading Synopsis
33661 Stops a tracing experiment. The result of this command has the same
33662 fields as @code{-trace-status}, except that the @samp{supported} and
33663 @samp{running} fields are not output.
33665 @subsubheading @value{GDBN} Command
33667 The corresponding @value{GDBN} command is @samp{tstop}.
33670 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33671 @node GDB/MI Symbol Query
33672 @section @sc{gdb/mi} Symbol Query Commands
33676 @subheading The @code{-symbol-info-address} Command
33677 @findex -symbol-info-address
33679 @subsubheading Synopsis
33682 -symbol-info-address @var{symbol}
33685 Describe where @var{symbol} is stored.
33687 @subsubheading @value{GDBN} Command
33689 The corresponding @value{GDBN} command is @samp{info address}.
33691 @subsubheading Example
33695 @subheading The @code{-symbol-info-file} Command
33696 @findex -symbol-info-file
33698 @subsubheading Synopsis
33704 Show the file for the symbol.
33706 @subsubheading @value{GDBN} Command
33708 There's no equivalent @value{GDBN} command. @code{gdbtk} has
33709 @samp{gdb_find_file}.
33711 @subsubheading Example
33715 @subheading The @code{-symbol-info-function} Command
33716 @findex -symbol-info-function
33718 @subsubheading Synopsis
33721 -symbol-info-function
33724 Show which function the symbol lives in.
33726 @subsubheading @value{GDBN} Command
33728 @samp{gdb_get_function} in @code{gdbtk}.
33730 @subsubheading Example
33734 @subheading The @code{-symbol-info-line} Command
33735 @findex -symbol-info-line
33737 @subsubheading Synopsis
33743 Show the core addresses of the code for a source line.
33745 @subsubheading @value{GDBN} Command
33747 The corresponding @value{GDBN} command is @samp{info line}.
33748 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
33750 @subsubheading Example
33754 @subheading The @code{-symbol-info-symbol} Command
33755 @findex -symbol-info-symbol
33757 @subsubheading Synopsis
33760 -symbol-info-symbol @var{addr}
33763 Describe what symbol is at location @var{addr}.
33765 @subsubheading @value{GDBN} Command
33767 The corresponding @value{GDBN} command is @samp{info symbol}.
33769 @subsubheading Example
33773 @subheading The @code{-symbol-list-functions} Command
33774 @findex -symbol-list-functions
33776 @subsubheading Synopsis
33779 -symbol-list-functions
33782 List the functions in the executable.
33784 @subsubheading @value{GDBN} Command
33786 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
33787 @samp{gdb_search} in @code{gdbtk}.
33789 @subsubheading Example
33794 @subheading The @code{-symbol-list-lines} Command
33795 @findex -symbol-list-lines
33797 @subsubheading Synopsis
33800 -symbol-list-lines @var{filename}
33803 Print the list of lines that contain code and their associated program
33804 addresses for the given source filename. The entries are sorted in
33805 ascending PC order.
33807 @subsubheading @value{GDBN} Command
33809 There is no corresponding @value{GDBN} command.
33811 @subsubheading Example
33814 -symbol-list-lines basics.c
33815 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
33821 @subheading The @code{-symbol-list-types} Command
33822 @findex -symbol-list-types
33824 @subsubheading Synopsis
33830 List all the type names.
33832 @subsubheading @value{GDBN} Command
33834 The corresponding commands are @samp{info types} in @value{GDBN},
33835 @samp{gdb_search} in @code{gdbtk}.
33837 @subsubheading Example
33841 @subheading The @code{-symbol-list-variables} Command
33842 @findex -symbol-list-variables
33844 @subsubheading Synopsis
33847 -symbol-list-variables
33850 List all the global and static variable names.
33852 @subsubheading @value{GDBN} Command
33854 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
33856 @subsubheading Example
33860 @subheading The @code{-symbol-locate} Command
33861 @findex -symbol-locate
33863 @subsubheading Synopsis
33869 @subsubheading @value{GDBN} Command
33871 @samp{gdb_loc} in @code{gdbtk}.
33873 @subsubheading Example
33877 @subheading The @code{-symbol-type} Command
33878 @findex -symbol-type
33880 @subsubheading Synopsis
33883 -symbol-type @var{variable}
33886 Show type of @var{variable}.
33888 @subsubheading @value{GDBN} Command
33890 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
33891 @samp{gdb_obj_variable}.
33893 @subsubheading Example
33898 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33899 @node GDB/MI File Commands
33900 @section @sc{gdb/mi} File Commands
33902 This section describes the GDB/MI commands to specify executable file names
33903 and to read in and obtain symbol table information.
33905 @subheading The @code{-file-exec-and-symbols} Command
33906 @findex -file-exec-and-symbols
33908 @subsubheading Synopsis
33911 -file-exec-and-symbols @var{file}
33914 Specify the executable file to be debugged. This file is the one from
33915 which the symbol table is also read. If no file is specified, the
33916 command clears the executable and symbol information. If breakpoints
33917 are set when using this command with no arguments, @value{GDBN} will produce
33918 error messages. Otherwise, no output is produced, except a completion
33921 @subsubheading @value{GDBN} Command
33923 The corresponding @value{GDBN} command is @samp{file}.
33925 @subsubheading Example
33929 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
33935 @subheading The @code{-file-exec-file} Command
33936 @findex -file-exec-file
33938 @subsubheading Synopsis
33941 -file-exec-file @var{file}
33944 Specify the executable file to be debugged. Unlike
33945 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
33946 from this file. If used without argument, @value{GDBN} clears the information
33947 about the executable file. No output is produced, except a completion
33950 @subsubheading @value{GDBN} Command
33952 The corresponding @value{GDBN} command is @samp{exec-file}.
33954 @subsubheading Example
33958 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
33965 @subheading The @code{-file-list-exec-sections} Command
33966 @findex -file-list-exec-sections
33968 @subsubheading Synopsis
33971 -file-list-exec-sections
33974 List the sections of the current executable file.
33976 @subsubheading @value{GDBN} Command
33978 The @value{GDBN} command @samp{info file} shows, among the rest, the same
33979 information as this command. @code{gdbtk} has a corresponding command
33980 @samp{gdb_load_info}.
33982 @subsubheading Example
33987 @subheading The @code{-file-list-exec-source-file} Command
33988 @findex -file-list-exec-source-file
33990 @subsubheading Synopsis
33993 -file-list-exec-source-file
33996 List the line number, the current source file, and the absolute path
33997 to the current source file for the current executable. The macro
33998 information field has a value of @samp{1} or @samp{0} depending on
33999 whether or not the file includes preprocessor macro information.
34001 @subsubheading @value{GDBN} Command
34003 The @value{GDBN} equivalent is @samp{info source}
34005 @subsubheading Example
34009 123-file-list-exec-source-file
34010 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
34015 @subheading The @code{-file-list-exec-source-files} Command
34016 @findex -file-list-exec-source-files
34018 @subsubheading Synopsis
34021 -file-list-exec-source-files
34024 List the source files for the current executable.
34026 It will always output both the filename and fullname (absolute file
34027 name) of a source file.
34029 @subsubheading @value{GDBN} Command
34031 The @value{GDBN} equivalent is @samp{info sources}.
34032 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
34034 @subsubheading Example
34037 -file-list-exec-source-files
34039 @{file=foo.c,fullname=/home/foo.c@},
34040 @{file=/home/bar.c,fullname=/home/bar.c@},
34041 @{file=gdb_could_not_find_fullpath.c@}]
34045 @subheading The @code{-file-list-shared-libraries} Command
34046 @findex -file-list-shared-libraries
34048 @subsubheading Synopsis
34051 -file-list-shared-libraries [ @var{regexp} ]
34054 List the shared libraries in the program.
34055 With a regular expression @var{regexp}, only those libraries whose
34056 names match @var{regexp} are listed.
34058 @subsubheading @value{GDBN} Command
34060 The corresponding @value{GDBN} command is @samp{info shared}. The fields
34061 have a similar meaning to the @code{=library-loaded} notification.
34062 The @code{ranges} field specifies the multiple segments belonging to this
34063 library. Each range has the following fields:
34067 The address defining the inclusive lower bound of the segment.
34069 The address defining the exclusive upper bound of the segment.
34072 @subsubheading Example
34075 -file-list-exec-source-files
34076 ^done,shared-libraries=[
34077 @{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"@}]@},
34078 @{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"@}]@}]
34084 @subheading The @code{-file-list-symbol-files} Command
34085 @findex -file-list-symbol-files
34087 @subsubheading Synopsis
34090 -file-list-symbol-files
34095 @subsubheading @value{GDBN} Command
34097 The corresponding @value{GDBN} command is @samp{info file} (part of it).
34099 @subsubheading Example
34104 @subheading The @code{-file-symbol-file} Command
34105 @findex -file-symbol-file
34107 @subsubheading Synopsis
34110 -file-symbol-file @var{file}
34113 Read symbol table info from the specified @var{file} argument. When
34114 used without arguments, clears @value{GDBN}'s symbol table info. No output is
34115 produced, except for a completion notification.
34117 @subsubheading @value{GDBN} Command
34119 The corresponding @value{GDBN} command is @samp{symbol-file}.
34121 @subsubheading Example
34125 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
34131 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34132 @node GDB/MI Memory Overlay Commands
34133 @section @sc{gdb/mi} Memory Overlay Commands
34135 The memory overlay commands are not implemented.
34137 @c @subheading -overlay-auto
34139 @c @subheading -overlay-list-mapping-state
34141 @c @subheading -overlay-list-overlays
34143 @c @subheading -overlay-map
34145 @c @subheading -overlay-off
34147 @c @subheading -overlay-on
34149 @c @subheading -overlay-unmap
34151 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34152 @node GDB/MI Signal Handling Commands
34153 @section @sc{gdb/mi} Signal Handling Commands
34155 Signal handling commands are not implemented.
34157 @c @subheading -signal-handle
34159 @c @subheading -signal-list-handle-actions
34161 @c @subheading -signal-list-signal-types
34165 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34166 @node GDB/MI Target Manipulation
34167 @section @sc{gdb/mi} Target Manipulation Commands
34170 @subheading The @code{-target-attach} Command
34171 @findex -target-attach
34173 @subsubheading Synopsis
34176 -target-attach @var{pid} | @var{gid} | @var{file}
34179 Attach to a process @var{pid} or a file @var{file} outside of
34180 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
34181 group, the id previously returned by
34182 @samp{-list-thread-groups --available} must be used.
34184 @subsubheading @value{GDBN} Command
34186 The corresponding @value{GDBN} command is @samp{attach}.
34188 @subsubheading Example
34192 =thread-created,id="1"
34193 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
34199 @subheading The @code{-target-compare-sections} Command
34200 @findex -target-compare-sections
34202 @subsubheading Synopsis
34205 -target-compare-sections [ @var{section} ]
34208 Compare data of section @var{section} on target to the exec file.
34209 Without the argument, all sections are compared.
34211 @subsubheading @value{GDBN} Command
34213 The @value{GDBN} equivalent is @samp{compare-sections}.
34215 @subsubheading Example
34220 @subheading The @code{-target-detach} Command
34221 @findex -target-detach
34223 @subsubheading Synopsis
34226 -target-detach [ @var{pid} | @var{gid} ]
34229 Detach from the remote target which normally resumes its execution.
34230 If either @var{pid} or @var{gid} is specified, detaches from either
34231 the specified process, or specified thread group. There's no output.
34233 @subsubheading @value{GDBN} Command
34235 The corresponding @value{GDBN} command is @samp{detach}.
34237 @subsubheading Example
34247 @subheading The @code{-target-disconnect} Command
34248 @findex -target-disconnect
34250 @subsubheading Synopsis
34256 Disconnect from the remote target. There's no output and the target is
34257 generally not resumed.
34259 @subsubheading @value{GDBN} Command
34261 The corresponding @value{GDBN} command is @samp{disconnect}.
34263 @subsubheading Example
34273 @subheading The @code{-target-download} Command
34274 @findex -target-download
34276 @subsubheading Synopsis
34282 Loads the executable onto the remote target.
34283 It prints out an update message every half second, which includes the fields:
34287 The name of the section.
34289 The size of what has been sent so far for that section.
34291 The size of the section.
34293 The total size of what was sent so far (the current and the previous sections).
34295 The size of the overall executable to download.
34299 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
34300 @sc{gdb/mi} Output Syntax}).
34302 In addition, it prints the name and size of the sections, as they are
34303 downloaded. These messages include the following fields:
34307 The name of the section.
34309 The size of the section.
34311 The size of the overall executable to download.
34315 At the end, a summary is printed.
34317 @subsubheading @value{GDBN} Command
34319 The corresponding @value{GDBN} command is @samp{load}.
34321 @subsubheading Example
34323 Note: each status message appears on a single line. Here the messages
34324 have been broken down so that they can fit onto a page.
34329 +download,@{section=".text",section-size="6668",total-size="9880"@}
34330 +download,@{section=".text",section-sent="512",section-size="6668",
34331 total-sent="512",total-size="9880"@}
34332 +download,@{section=".text",section-sent="1024",section-size="6668",
34333 total-sent="1024",total-size="9880"@}
34334 +download,@{section=".text",section-sent="1536",section-size="6668",
34335 total-sent="1536",total-size="9880"@}
34336 +download,@{section=".text",section-sent="2048",section-size="6668",
34337 total-sent="2048",total-size="9880"@}
34338 +download,@{section=".text",section-sent="2560",section-size="6668",
34339 total-sent="2560",total-size="9880"@}
34340 +download,@{section=".text",section-sent="3072",section-size="6668",
34341 total-sent="3072",total-size="9880"@}
34342 +download,@{section=".text",section-sent="3584",section-size="6668",
34343 total-sent="3584",total-size="9880"@}
34344 +download,@{section=".text",section-sent="4096",section-size="6668",
34345 total-sent="4096",total-size="9880"@}
34346 +download,@{section=".text",section-sent="4608",section-size="6668",
34347 total-sent="4608",total-size="9880"@}
34348 +download,@{section=".text",section-sent="5120",section-size="6668",
34349 total-sent="5120",total-size="9880"@}
34350 +download,@{section=".text",section-sent="5632",section-size="6668",
34351 total-sent="5632",total-size="9880"@}
34352 +download,@{section=".text",section-sent="6144",section-size="6668",
34353 total-sent="6144",total-size="9880"@}
34354 +download,@{section=".text",section-sent="6656",section-size="6668",
34355 total-sent="6656",total-size="9880"@}
34356 +download,@{section=".init",section-size="28",total-size="9880"@}
34357 +download,@{section=".fini",section-size="28",total-size="9880"@}
34358 +download,@{section=".data",section-size="3156",total-size="9880"@}
34359 +download,@{section=".data",section-sent="512",section-size="3156",
34360 total-sent="7236",total-size="9880"@}
34361 +download,@{section=".data",section-sent="1024",section-size="3156",
34362 total-sent="7748",total-size="9880"@}
34363 +download,@{section=".data",section-sent="1536",section-size="3156",
34364 total-sent="8260",total-size="9880"@}
34365 +download,@{section=".data",section-sent="2048",section-size="3156",
34366 total-sent="8772",total-size="9880"@}
34367 +download,@{section=".data",section-sent="2560",section-size="3156",
34368 total-sent="9284",total-size="9880"@}
34369 +download,@{section=".data",section-sent="3072",section-size="3156",
34370 total-sent="9796",total-size="9880"@}
34371 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
34378 @subheading The @code{-target-exec-status} Command
34379 @findex -target-exec-status
34381 @subsubheading Synopsis
34384 -target-exec-status
34387 Provide information on the state of the target (whether it is running or
34388 not, for instance).
34390 @subsubheading @value{GDBN} Command
34392 There's no equivalent @value{GDBN} command.
34394 @subsubheading Example
34398 @subheading The @code{-target-list-available-targets} Command
34399 @findex -target-list-available-targets
34401 @subsubheading Synopsis
34404 -target-list-available-targets
34407 List the possible targets to connect to.
34409 @subsubheading @value{GDBN} Command
34411 The corresponding @value{GDBN} command is @samp{help target}.
34413 @subsubheading Example
34417 @subheading The @code{-target-list-current-targets} Command
34418 @findex -target-list-current-targets
34420 @subsubheading Synopsis
34423 -target-list-current-targets
34426 Describe the current target.
34428 @subsubheading @value{GDBN} Command
34430 The corresponding information is printed by @samp{info file} (among
34433 @subsubheading Example
34437 @subheading The @code{-target-list-parameters} Command
34438 @findex -target-list-parameters
34440 @subsubheading Synopsis
34443 -target-list-parameters
34449 @subsubheading @value{GDBN} Command
34453 @subsubheading Example
34456 @subheading The @code{-target-flash-erase} Command
34457 @findex -target-flash-erase
34459 @subsubheading Synopsis
34462 -target-flash-erase
34465 Erases all known flash memory regions on the target.
34467 The corresponding @value{GDBN} command is @samp{flash-erase}.
34469 The output is a list of flash regions that have been erased, with starting
34470 addresses and memory region sizes.
34474 -target-flash-erase
34475 ^done,erased-regions=@{address="0x0",size="0x40000"@}
34479 @subheading The @code{-target-select} Command
34480 @findex -target-select
34482 @subsubheading Synopsis
34485 -target-select @var{type} @var{parameters @dots{}}
34488 Connect @value{GDBN} to the remote target. This command takes two args:
34492 The type of target, for instance @samp{remote}, etc.
34493 @item @var{parameters}
34494 Device names, host names and the like. @xref{Target Commands, ,
34495 Commands for Managing Targets}, for more details.
34498 The output is a connection notification, followed by the address at
34499 which the target program is, in the following form:
34502 ^connected,addr="@var{address}",func="@var{function name}",
34503 args=[@var{arg list}]
34506 @subsubheading @value{GDBN} Command
34508 The corresponding @value{GDBN} command is @samp{target}.
34510 @subsubheading Example
34514 -target-select remote /dev/ttya
34515 ^connected,addr="0xfe00a300",func="??",args=[]
34519 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34520 @node GDB/MI File Transfer Commands
34521 @section @sc{gdb/mi} File Transfer Commands
34524 @subheading The @code{-target-file-put} Command
34525 @findex -target-file-put
34527 @subsubheading Synopsis
34530 -target-file-put @var{hostfile} @var{targetfile}
34533 Copy file @var{hostfile} from the host system (the machine running
34534 @value{GDBN}) to @var{targetfile} on the target system.
34536 @subsubheading @value{GDBN} Command
34538 The corresponding @value{GDBN} command is @samp{remote put}.
34540 @subsubheading Example
34544 -target-file-put localfile remotefile
34550 @subheading The @code{-target-file-get} Command
34551 @findex -target-file-get
34553 @subsubheading Synopsis
34556 -target-file-get @var{targetfile} @var{hostfile}
34559 Copy file @var{targetfile} from the target system to @var{hostfile}
34560 on the host system.
34562 @subsubheading @value{GDBN} Command
34564 The corresponding @value{GDBN} command is @samp{remote get}.
34566 @subsubheading Example
34570 -target-file-get remotefile localfile
34576 @subheading The @code{-target-file-delete} Command
34577 @findex -target-file-delete
34579 @subsubheading Synopsis
34582 -target-file-delete @var{targetfile}
34585 Delete @var{targetfile} from the target system.
34587 @subsubheading @value{GDBN} Command
34589 The corresponding @value{GDBN} command is @samp{remote delete}.
34591 @subsubheading Example
34595 -target-file-delete remotefile
34601 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34602 @node GDB/MI Ada Exceptions Commands
34603 @section Ada Exceptions @sc{gdb/mi} Commands
34605 @subheading The @code{-info-ada-exceptions} Command
34606 @findex -info-ada-exceptions
34608 @subsubheading Synopsis
34611 -info-ada-exceptions [ @var{regexp}]
34614 List all Ada exceptions defined within the program being debugged.
34615 With a regular expression @var{regexp}, only those exceptions whose
34616 names match @var{regexp} are listed.
34618 @subsubheading @value{GDBN} Command
34620 The corresponding @value{GDBN} command is @samp{info exceptions}.
34622 @subsubheading Result
34624 The result is a table of Ada exceptions. The following columns are
34625 defined for each exception:
34629 The name of the exception.
34632 The address of the exception.
34636 @subsubheading Example
34639 -info-ada-exceptions aint
34640 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
34641 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
34642 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
34643 body=[@{name="constraint_error",address="0x0000000000613da0"@},
34644 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
34647 @subheading Catching Ada Exceptions
34649 The commands describing how to ask @value{GDBN} to stop when a program
34650 raises an exception are described at @ref{Ada Exception GDB/MI
34651 Catchpoint Commands}.
34654 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34655 @node GDB/MI Support Commands
34656 @section @sc{gdb/mi} Support Commands
34658 Since new commands and features get regularly added to @sc{gdb/mi},
34659 some commands are available to help front-ends query the debugger
34660 about support for these capabilities. Similarly, it is also possible
34661 to query @value{GDBN} about target support of certain features.
34663 @subheading The @code{-info-gdb-mi-command} Command
34664 @cindex @code{-info-gdb-mi-command}
34665 @findex -info-gdb-mi-command
34667 @subsubheading Synopsis
34670 -info-gdb-mi-command @var{cmd_name}
34673 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
34675 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
34676 is technically not part of the command name (@pxref{GDB/MI Input
34677 Syntax}), and thus should be omitted in @var{cmd_name}. However,
34678 for ease of use, this command also accepts the form with the leading
34681 @subsubheading @value{GDBN} Command
34683 There is no corresponding @value{GDBN} command.
34685 @subsubheading Result
34687 The result is a tuple. There is currently only one field:
34691 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
34692 @code{"false"} otherwise.
34696 @subsubheading Example
34698 Here is an example where the @sc{gdb/mi} command does not exist:
34701 -info-gdb-mi-command unsupported-command
34702 ^done,command=@{exists="false"@}
34706 And here is an example where the @sc{gdb/mi} command is known
34710 -info-gdb-mi-command symbol-list-lines
34711 ^done,command=@{exists="true"@}
34714 @subheading The @code{-list-features} Command
34715 @findex -list-features
34716 @cindex supported @sc{gdb/mi} features, list
34718 Returns a list of particular features of the MI protocol that
34719 this version of gdb implements. A feature can be a command,
34720 or a new field in an output of some command, or even an
34721 important bugfix. While a frontend can sometimes detect presence
34722 of a feature at runtime, it is easier to perform detection at debugger
34725 The command returns a list of strings, with each string naming an
34726 available feature. Each returned string is just a name, it does not
34727 have any internal structure. The list of possible feature names
34733 (gdb) -list-features
34734 ^done,result=["feature1","feature2"]
34737 The current list of features is:
34740 @item frozen-varobjs
34741 Indicates support for the @code{-var-set-frozen} command, as well
34742 as possible presense of the @code{frozen} field in the output
34743 of @code{-varobj-create}.
34744 @item pending-breakpoints
34745 Indicates support for the @option{-f} option to the @code{-break-insert}
34748 Indicates Python scripting support, Python-based
34749 pretty-printing commands, and possible presence of the
34750 @samp{display_hint} field in the output of @code{-var-list-children}
34752 Indicates support for the @code{-thread-info} command.
34753 @item data-read-memory-bytes
34754 Indicates support for the @code{-data-read-memory-bytes} and the
34755 @code{-data-write-memory-bytes} commands.
34756 @item breakpoint-notifications
34757 Indicates that changes to breakpoints and breakpoints created via the
34758 CLI will be announced via async records.
34759 @item ada-task-info
34760 Indicates support for the @code{-ada-task-info} command.
34761 @item language-option
34762 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
34763 option (@pxref{Context management}).
34764 @item info-gdb-mi-command
34765 Indicates support for the @code{-info-gdb-mi-command} command.
34766 @item undefined-command-error-code
34767 Indicates support for the "undefined-command" error code in error result
34768 records, produced when trying to execute an undefined @sc{gdb/mi} command
34769 (@pxref{GDB/MI Result Records}).
34770 @item exec-run-start-option
34771 Indicates that the @code{-exec-run} command supports the @option{--start}
34772 option (@pxref{GDB/MI Program Execution}).
34773 @item data-disassemble-a-option
34774 Indicates that the @code{-data-disassemble} command supports the @option{-a}
34775 option (@pxref{GDB/MI Data Manipulation}).
34778 @subheading The @code{-list-target-features} Command
34779 @findex -list-target-features
34781 Returns a list of particular features that are supported by the
34782 target. Those features affect the permitted MI commands, but
34783 unlike the features reported by the @code{-list-features} command, the
34784 features depend on which target GDB is using at the moment. Whenever
34785 a target can change, due to commands such as @code{-target-select},
34786 @code{-target-attach} or @code{-exec-run}, the list of target features
34787 may change, and the frontend should obtain it again.
34791 (gdb) -list-target-features
34792 ^done,result=["async"]
34795 The current list of features is:
34799 Indicates that the target is capable of asynchronous command
34800 execution, which means that @value{GDBN} will accept further commands
34801 while the target is running.
34804 Indicates that the target is capable of reverse execution.
34805 @xref{Reverse Execution}, for more information.
34809 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34810 @node GDB/MI Miscellaneous Commands
34811 @section Miscellaneous @sc{gdb/mi} Commands
34813 @c @subheading -gdb-complete
34815 @subheading The @code{-gdb-exit} Command
34818 @subsubheading Synopsis
34824 Exit @value{GDBN} immediately.
34826 @subsubheading @value{GDBN} Command
34828 Approximately corresponds to @samp{quit}.
34830 @subsubheading Example
34840 @subheading The @code{-exec-abort} Command
34841 @findex -exec-abort
34843 @subsubheading Synopsis
34849 Kill the inferior running program.
34851 @subsubheading @value{GDBN} Command
34853 The corresponding @value{GDBN} command is @samp{kill}.
34855 @subsubheading Example
34860 @subheading The @code{-gdb-set} Command
34863 @subsubheading Synopsis
34869 Set an internal @value{GDBN} variable.
34870 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
34872 @subsubheading @value{GDBN} Command
34874 The corresponding @value{GDBN} command is @samp{set}.
34876 @subsubheading Example
34886 @subheading The @code{-gdb-show} Command
34889 @subsubheading Synopsis
34895 Show the current value of a @value{GDBN} variable.
34897 @subsubheading @value{GDBN} Command
34899 The corresponding @value{GDBN} command is @samp{show}.
34901 @subsubheading Example
34910 @c @subheading -gdb-source
34913 @subheading The @code{-gdb-version} Command
34914 @findex -gdb-version
34916 @subsubheading Synopsis
34922 Show version information for @value{GDBN}. Used mostly in testing.
34924 @subsubheading @value{GDBN} Command
34926 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
34927 default shows this information when you start an interactive session.
34929 @subsubheading Example
34931 @c This example modifies the actual output from GDB to avoid overfull
34937 ~Copyright 2000 Free Software Foundation, Inc.
34938 ~GDB is free software, covered by the GNU General Public License, and
34939 ~you are welcome to change it and/or distribute copies of it under
34940 ~ certain conditions.
34941 ~Type "show copying" to see the conditions.
34942 ~There is absolutely no warranty for GDB. Type "show warranty" for
34944 ~This GDB was configured as
34945 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
34950 @subheading The @code{-list-thread-groups} Command
34951 @findex -list-thread-groups
34953 @subheading Synopsis
34956 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
34959 Lists thread groups (@pxref{Thread groups}). When a single thread
34960 group is passed as the argument, lists the children of that group.
34961 When several thread group are passed, lists information about those
34962 thread groups. Without any parameters, lists information about all
34963 top-level thread groups.
34965 Normally, thread groups that are being debugged are reported.
34966 With the @samp{--available} option, @value{GDBN} reports thread groups
34967 available on the target.
34969 The output of this command may have either a @samp{threads} result or
34970 a @samp{groups} result. The @samp{thread} result has a list of tuples
34971 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
34972 Information}). The @samp{groups} result has a list of tuples as value,
34973 each tuple describing a thread group. If top-level groups are
34974 requested (that is, no parameter is passed), or when several groups
34975 are passed, the output always has a @samp{groups} result. The format
34976 of the @samp{group} result is described below.
34978 To reduce the number of roundtrips it's possible to list thread groups
34979 together with their children, by passing the @samp{--recurse} option
34980 and the recursion depth. Presently, only recursion depth of 1 is
34981 permitted. If this option is present, then every reported thread group
34982 will also include its children, either as @samp{group} or
34983 @samp{threads} field.
34985 In general, any combination of option and parameters is permitted, with
34986 the following caveats:
34990 When a single thread group is passed, the output will typically
34991 be the @samp{threads} result. Because threads may not contain
34992 anything, the @samp{recurse} option will be ignored.
34995 When the @samp{--available} option is passed, limited information may
34996 be available. In particular, the list of threads of a process might
34997 be inaccessible. Further, specifying specific thread groups might
34998 not give any performance advantage over listing all thread groups.
34999 The frontend should assume that @samp{-list-thread-groups --available}
35000 is always an expensive operation and cache the results.
35004 The @samp{groups} result is a list of tuples, where each tuple may
35005 have the following fields:
35009 Identifier of the thread group. This field is always present.
35010 The identifier is an opaque string; frontends should not try to
35011 convert it to an integer, even though it might look like one.
35014 The type of the thread group. At present, only @samp{process} is a
35018 The target-specific process identifier. This field is only present
35019 for thread groups of type @samp{process} and only if the process exists.
35022 The exit code of this group's last exited thread, formatted in octal.
35023 This field is only present for thread groups of type @samp{process} and
35024 only if the process is not running.
35027 The number of children this thread group has. This field may be
35028 absent for an available thread group.
35031 This field has a list of tuples as value, each tuple describing a
35032 thread. It may be present if the @samp{--recurse} option is
35033 specified, and it's actually possible to obtain the threads.
35036 This field is a list of integers, each identifying a core that one
35037 thread of the group is running on. This field may be absent if
35038 such information is not available.
35041 The name of the executable file that corresponds to this thread group.
35042 The field is only present for thread groups of type @samp{process},
35043 and only if there is a corresponding executable file.
35047 @subheading Example
35051 -list-thread-groups
35052 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
35053 -list-thread-groups 17
35054 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
35055 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
35056 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
35057 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
35058 file="/tmp/a.c",fullname="/tmp/a.c",line="158",arch="i386:x86_64"@},state="running"@}]]
35059 -list-thread-groups --available
35060 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
35061 -list-thread-groups --available --recurse 1
35062 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
35063 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
35064 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
35065 -list-thread-groups --available --recurse 1 17 18
35066 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
35067 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
35068 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
35071 @subheading The @code{-info-os} Command
35074 @subsubheading Synopsis
35077 -info-os [ @var{type} ]
35080 If no argument is supplied, the command returns a table of available
35081 operating-system-specific information types. If one of these types is
35082 supplied as an argument @var{type}, then the command returns a table
35083 of data of that type.
35085 The types of information available depend on the target operating
35088 @subsubheading @value{GDBN} Command
35090 The corresponding @value{GDBN} command is @samp{info os}.
35092 @subsubheading Example
35094 When run on a @sc{gnu}/Linux system, the output will look something
35100 ^done,OSDataTable=@{nr_rows="10",nr_cols="3",
35101 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
35102 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
35103 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
35104 body=[item=@{col0="cpus",col1="Listing of all cpus/cores on the system",
35106 item=@{col0="files",col1="Listing of all file descriptors",
35107 col2="File descriptors"@},
35108 item=@{col0="modules",col1="Listing of all loaded kernel modules",
35109 col2="Kernel modules"@},
35110 item=@{col0="msg",col1="Listing of all message queues",
35111 col2="Message queues"@},
35112 item=@{col0="processes",col1="Listing of all processes",
35113 col2="Processes"@},
35114 item=@{col0="procgroups",col1="Listing of all process groups",
35115 col2="Process groups"@},
35116 item=@{col0="semaphores",col1="Listing of all semaphores",
35117 col2="Semaphores"@},
35118 item=@{col0="shm",col1="Listing of all shared-memory regions",
35119 col2="Shared-memory regions"@},
35120 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
35122 item=@{col0="threads",col1="Listing of all threads",
35126 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
35127 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
35128 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
35129 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
35130 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
35131 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
35132 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
35133 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
35135 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
35136 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
35140 (Note that the MI output here includes a @code{"Title"} column that
35141 does not appear in command-line @code{info os}; this column is useful
35142 for MI clients that want to enumerate the types of data, such as in a
35143 popup menu, but is needless clutter on the command line, and
35144 @code{info os} omits it.)
35146 @subheading The @code{-add-inferior} Command
35147 @findex -add-inferior
35149 @subheading Synopsis
35155 Creates a new inferior (@pxref{Inferiors and Programs}). The created
35156 inferior is not associated with any executable. Such association may
35157 be established with the @samp{-file-exec-and-symbols} command
35158 (@pxref{GDB/MI File Commands}). The command response has a single
35159 field, @samp{inferior}, whose value is the identifier of the
35160 thread group corresponding to the new inferior.
35162 @subheading Example
35167 ^done,inferior="i3"
35170 @subheading The @code{-interpreter-exec} Command
35171 @findex -interpreter-exec
35173 @subheading Synopsis
35176 -interpreter-exec @var{interpreter} @var{command}
35178 @anchor{-interpreter-exec}
35180 Execute the specified @var{command} in the given @var{interpreter}.
35182 @subheading @value{GDBN} Command
35184 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
35186 @subheading Example
35190 -interpreter-exec console "break main"
35191 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
35192 &"During symbol reading, bad structure-type format.\n"
35193 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
35198 @subheading The @code{-inferior-tty-set} Command
35199 @findex -inferior-tty-set
35201 @subheading Synopsis
35204 -inferior-tty-set /dev/pts/1
35207 Set terminal for future runs of the program being debugged.
35209 @subheading @value{GDBN} Command
35211 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
35213 @subheading Example
35217 -inferior-tty-set /dev/pts/1
35222 @subheading The @code{-inferior-tty-show} Command
35223 @findex -inferior-tty-show
35225 @subheading Synopsis
35231 Show terminal for future runs of program being debugged.
35233 @subheading @value{GDBN} Command
35235 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
35237 @subheading Example
35241 -inferior-tty-set /dev/pts/1
35245 ^done,inferior_tty_terminal="/dev/pts/1"
35249 @subheading The @code{-enable-timings} Command
35250 @findex -enable-timings
35252 @subheading Synopsis
35255 -enable-timings [yes | no]
35258 Toggle the printing of the wallclock, user and system times for an MI
35259 command as a field in its output. This command is to help frontend
35260 developers optimize the performance of their code. No argument is
35261 equivalent to @samp{yes}.
35263 @subheading @value{GDBN} Command
35267 @subheading Example
35275 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
35276 addr="0x080484ed",func="main",file="myprog.c",
35277 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
35279 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
35287 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
35288 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
35289 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
35290 fullname="/home/nickrob/myprog.c",line="73",arch="i386:x86_64"@}
35294 @subheading The @code{-complete} Command
35297 @subheading Synopsis
35300 -complete @var{command}
35303 Show a list of completions for partially typed CLI @var{command}.
35305 This command is intended for @sc{gdb/mi} frontends that cannot use two separate
35306 CLI and MI channels --- for example: because of lack of PTYs like on Windows or
35307 because @value{GDBN} is used remotely via a SSH connection.
35311 The result consists of two or three fields:
35315 This field contains the completed @var{command}. If @var{command}
35316 has no known completions, this field is omitted.
35319 This field contains a (possibly empty) array of matches. It is always present.
35321 @item max_completions_reached
35322 This field contains @code{1} if number of known completions is above
35323 @code{max-completions} limit (@pxref{Completion}), otherwise it contains
35324 @code{0}. It is always present.
35328 @subheading @value{GDBN} Command
35330 The corresponding @value{GDBN} command is @samp{complete}.
35332 @subheading Example
35337 ^done,completion="break",
35338 matches=["break","break-range"],
35339 max_completions_reached="0"
35342 ^done,completion="b ma",
35343 matches=["b madvise","b main"],max_completions_reached="0"
35345 -complete "b push_b"
35346 ^done,completion="b push_back(",
35348 "b A::push_back(void*)",
35349 "b std::string::push_back(char)",
35350 "b std::vector<int, std::allocator<int> >::push_back(int&&)"],
35351 max_completions_reached="0"
35353 -complete "nonexist"
35354 ^done,matches=[],max_completions_reached="0"
35360 @chapter @value{GDBN} Annotations
35362 This chapter describes annotations in @value{GDBN}. Annotations were
35363 designed to interface @value{GDBN} to graphical user interfaces or other
35364 similar programs which want to interact with @value{GDBN} at a
35365 relatively high level.
35367 The annotation mechanism has largely been superseded by @sc{gdb/mi}
35371 This is Edition @value{EDITION}, @value{DATE}.
35375 * Annotations Overview:: What annotations are; the general syntax.
35376 * Server Prefix:: Issuing a command without affecting user state.
35377 * Prompting:: Annotations marking @value{GDBN}'s need for input.
35378 * Errors:: Annotations for error messages.
35379 * Invalidation:: Some annotations describe things now invalid.
35380 * Annotations for Running::
35381 Whether the program is running, how it stopped, etc.
35382 * Source Annotations:: Annotations describing source code.
35385 @node Annotations Overview
35386 @section What is an Annotation?
35387 @cindex annotations
35389 Annotations start with a newline character, two @samp{control-z}
35390 characters, and the name of the annotation. If there is no additional
35391 information associated with this annotation, the name of the annotation
35392 is followed immediately by a newline. If there is additional
35393 information, the name of the annotation is followed by a space, the
35394 additional information, and a newline. The additional information
35395 cannot contain newline characters.
35397 Any output not beginning with a newline and two @samp{control-z}
35398 characters denotes literal output from @value{GDBN}. Currently there is
35399 no need for @value{GDBN} to output a newline followed by two
35400 @samp{control-z} characters, but if there was such a need, the
35401 annotations could be extended with an @samp{escape} annotation which
35402 means those three characters as output.
35404 The annotation @var{level}, which is specified using the
35405 @option{--annotate} command line option (@pxref{Mode Options}), controls
35406 how much information @value{GDBN} prints together with its prompt,
35407 values of expressions, source lines, and other types of output. Level 0
35408 is for no annotations, level 1 is for use when @value{GDBN} is run as a
35409 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
35410 for programs that control @value{GDBN}, and level 2 annotations have
35411 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
35412 Interface, annotate, GDB's Obsolete Annotations}).
35415 @kindex set annotate
35416 @item set annotate @var{level}
35417 The @value{GDBN} command @code{set annotate} sets the level of
35418 annotations to the specified @var{level}.
35420 @item show annotate
35421 @kindex show annotate
35422 Show the current annotation level.
35425 This chapter describes level 3 annotations.
35427 A simple example of starting up @value{GDBN} with annotations is:
35430 $ @kbd{gdb --annotate=3}
35432 Copyright 2003 Free Software Foundation, Inc.
35433 GDB is free software, covered by the GNU General Public License,
35434 and you are welcome to change it and/or distribute copies of it
35435 under certain conditions.
35436 Type "show copying" to see the conditions.
35437 There is absolutely no warranty for GDB. Type "show warranty"
35439 This GDB was configured as "i386-pc-linux-gnu"
35450 Here @samp{quit} is input to @value{GDBN}; the rest is output from
35451 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
35452 denotes a @samp{control-z} character) are annotations; the rest is
35453 output from @value{GDBN}.
35455 @node Server Prefix
35456 @section The Server Prefix
35457 @cindex server prefix
35459 If you prefix a command with @samp{server } then it will not affect
35460 the command history, nor will it affect @value{GDBN}'s notion of which
35461 command to repeat if @key{RET} is pressed on a line by itself. This
35462 means that commands can be run behind a user's back by a front-end in
35463 a transparent manner.
35465 The @code{server } prefix does not affect the recording of values into
35466 the value history; to print a value without recording it into the
35467 value history, use the @code{output} command instead of the
35468 @code{print} command.
35470 Using this prefix also disables confirmation requests
35471 (@pxref{confirmation requests}).
35474 @section Annotation for @value{GDBN} Input
35476 @cindex annotations for prompts
35477 When @value{GDBN} prompts for input, it annotates this fact so it is possible
35478 to know when to send output, when the output from a given command is
35481 Different kinds of input each have a different @dfn{input type}. Each
35482 input type has three annotations: a @code{pre-} annotation, which
35483 denotes the beginning of any prompt which is being output, a plain
35484 annotation, which denotes the end of the prompt, and then a @code{post-}
35485 annotation which denotes the end of any echo which may (or may not) be
35486 associated with the input. For example, the @code{prompt} input type
35487 features the following annotations:
35495 The input types are
35498 @findex pre-prompt annotation
35499 @findex prompt annotation
35500 @findex post-prompt annotation
35502 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
35504 @findex pre-commands annotation
35505 @findex commands annotation
35506 @findex post-commands annotation
35508 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
35509 command. The annotations are repeated for each command which is input.
35511 @findex pre-overload-choice annotation
35512 @findex overload-choice annotation
35513 @findex post-overload-choice annotation
35514 @item overload-choice
35515 When @value{GDBN} wants the user to select between various overloaded functions.
35517 @findex pre-query annotation
35518 @findex query annotation
35519 @findex post-query annotation
35521 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
35523 @findex pre-prompt-for-continue annotation
35524 @findex prompt-for-continue annotation
35525 @findex post-prompt-for-continue annotation
35526 @item prompt-for-continue
35527 When @value{GDBN} is asking the user to press return to continue. Note: Don't
35528 expect this to work well; instead use @code{set height 0} to disable
35529 prompting. This is because the counting of lines is buggy in the
35530 presence of annotations.
35535 @cindex annotations for errors, warnings and interrupts
35537 @findex quit annotation
35542 This annotation occurs right before @value{GDBN} responds to an interrupt.
35544 @findex error annotation
35549 This annotation occurs right before @value{GDBN} responds to an error.
35551 Quit and error annotations indicate that any annotations which @value{GDBN} was
35552 in the middle of may end abruptly. For example, if a
35553 @code{value-history-begin} annotation is followed by a @code{error}, one
35554 cannot expect to receive the matching @code{value-history-end}. One
35555 cannot expect not to receive it either, however; an error annotation
35556 does not necessarily mean that @value{GDBN} is immediately returning all the way
35559 @findex error-begin annotation
35560 A quit or error annotation may be preceded by
35566 Any output between that and the quit or error annotation is the error
35569 Warning messages are not yet annotated.
35570 @c If we want to change that, need to fix warning(), type_error(),
35571 @c range_error(), and possibly other places.
35574 @section Invalidation Notices
35576 @cindex annotations for invalidation messages
35577 The following annotations say that certain pieces of state may have
35581 @findex frames-invalid annotation
35582 @item ^Z^Zframes-invalid
35584 The frames (for example, output from the @code{backtrace} command) may
35587 @findex breakpoints-invalid annotation
35588 @item ^Z^Zbreakpoints-invalid
35590 The breakpoints may have changed. For example, the user just added or
35591 deleted a breakpoint.
35594 @node Annotations for Running
35595 @section Running the Program
35596 @cindex annotations for running programs
35598 @findex starting annotation
35599 @findex stopping annotation
35600 When the program starts executing due to a @value{GDBN} command such as
35601 @code{step} or @code{continue},
35607 is output. When the program stops,
35613 is output. Before the @code{stopped} annotation, a variety of
35614 annotations describe how the program stopped.
35617 @findex exited annotation
35618 @item ^Z^Zexited @var{exit-status}
35619 The program exited, and @var{exit-status} is the exit status (zero for
35620 successful exit, otherwise nonzero).
35622 @findex signalled annotation
35623 @findex signal-name annotation
35624 @findex signal-name-end annotation
35625 @findex signal-string annotation
35626 @findex signal-string-end annotation
35627 @item ^Z^Zsignalled
35628 The program exited with a signal. After the @code{^Z^Zsignalled}, the
35629 annotation continues:
35635 ^Z^Zsignal-name-end
35639 ^Z^Zsignal-string-end
35644 where @var{name} is the name of the signal, such as @code{SIGILL} or
35645 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
35646 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
35647 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
35648 user's benefit and have no particular format.
35650 @findex signal annotation
35652 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
35653 just saying that the program received the signal, not that it was
35654 terminated with it.
35656 @findex breakpoint annotation
35657 @item ^Z^Zbreakpoint @var{number}
35658 The program hit breakpoint number @var{number}.
35660 @findex watchpoint annotation
35661 @item ^Z^Zwatchpoint @var{number}
35662 The program hit watchpoint number @var{number}.
35665 @node Source Annotations
35666 @section Displaying Source
35667 @cindex annotations for source display
35669 @findex source annotation
35670 The following annotation is used instead of displaying source code:
35673 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
35676 where @var{filename} is an absolute file name indicating which source
35677 file, @var{line} is the line number within that file (where 1 is the
35678 first line in the file), @var{character} is the character position
35679 within the file (where 0 is the first character in the file) (for most
35680 debug formats this will necessarily point to the beginning of a line),
35681 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
35682 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
35683 @var{addr} is the address in the target program associated with the
35684 source which is being displayed. The @var{addr} is in the form @samp{0x}
35685 followed by one or more lowercase hex digits (note that this does not
35686 depend on the language).
35688 @node JIT Interface
35689 @chapter JIT Compilation Interface
35690 @cindex just-in-time compilation
35691 @cindex JIT compilation interface
35693 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
35694 interface. A JIT compiler is a program or library that generates native
35695 executable code at runtime and executes it, usually in order to achieve good
35696 performance while maintaining platform independence.
35698 Programs that use JIT compilation are normally difficult to debug because
35699 portions of their code are generated at runtime, instead of being loaded from
35700 object files, which is where @value{GDBN} normally finds the program's symbols
35701 and debug information. In order to debug programs that use JIT compilation,
35702 @value{GDBN} has an interface that allows the program to register in-memory
35703 symbol files with @value{GDBN} at runtime.
35705 If you are using @value{GDBN} to debug a program that uses this interface, then
35706 it should work transparently so long as you have not stripped the binary. If
35707 you are developing a JIT compiler, then the interface is documented in the rest
35708 of this chapter. At this time, the only known client of this interface is the
35711 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
35712 JIT compiler communicates with @value{GDBN} by writing data into a global
35713 variable and calling a fuction at a well-known symbol. When @value{GDBN}
35714 attaches, it reads a linked list of symbol files from the global variable to
35715 find existing code, and puts a breakpoint in the function so that it can find
35716 out about additional code.
35719 * Declarations:: Relevant C struct declarations
35720 * Registering Code:: Steps to register code
35721 * Unregistering Code:: Steps to unregister code
35722 * Custom Debug Info:: Emit debug information in a custom format
35726 @section JIT Declarations
35728 These are the relevant struct declarations that a C program should include to
35729 implement the interface:
35739 struct jit_code_entry
35741 struct jit_code_entry *next_entry;
35742 struct jit_code_entry *prev_entry;
35743 const char *symfile_addr;
35744 uint64_t symfile_size;
35747 struct jit_descriptor
35750 /* This type should be jit_actions_t, but we use uint32_t
35751 to be explicit about the bitwidth. */
35752 uint32_t action_flag;
35753 struct jit_code_entry *relevant_entry;
35754 struct jit_code_entry *first_entry;
35757 /* GDB puts a breakpoint in this function. */
35758 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
35760 /* Make sure to specify the version statically, because the
35761 debugger may check the version before we can set it. */
35762 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
35765 If the JIT is multi-threaded, then it is important that the JIT synchronize any
35766 modifications to this global data properly, which can easily be done by putting
35767 a global mutex around modifications to these structures.
35769 @node Registering Code
35770 @section Registering Code
35772 To register code with @value{GDBN}, the JIT should follow this protocol:
35776 Generate an object file in memory with symbols and other desired debug
35777 information. The file must include the virtual addresses of the sections.
35780 Create a code entry for the file, which gives the start and size of the symbol
35784 Add it to the linked list in the JIT descriptor.
35787 Point the relevant_entry field of the descriptor at the entry.
35790 Set @code{action_flag} to @code{JIT_REGISTER} and call
35791 @code{__jit_debug_register_code}.
35794 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
35795 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
35796 new code. However, the linked list must still be maintained in order to allow
35797 @value{GDBN} to attach to a running process and still find the symbol files.
35799 @node Unregistering Code
35800 @section Unregistering Code
35802 If code is freed, then the JIT should use the following protocol:
35806 Remove the code entry corresponding to the code from the linked list.
35809 Point the @code{relevant_entry} field of the descriptor at the code entry.
35812 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
35813 @code{__jit_debug_register_code}.
35816 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
35817 and the JIT will leak the memory used for the associated symbol files.
35819 @node Custom Debug Info
35820 @section Custom Debug Info
35821 @cindex custom JIT debug info
35822 @cindex JIT debug info reader
35824 Generating debug information in platform-native file formats (like ELF
35825 or COFF) may be an overkill for JIT compilers; especially if all the
35826 debug info is used for is displaying a meaningful backtrace. The
35827 issue can be resolved by having the JIT writers decide on a debug info
35828 format and also provide a reader that parses the debug info generated
35829 by the JIT compiler. This section gives a brief overview on writing
35830 such a parser. More specific details can be found in the source file
35831 @file{gdb/jit-reader.in}, which is also installed as a header at
35832 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
35834 The reader is implemented as a shared object (so this functionality is
35835 not available on platforms which don't allow loading shared objects at
35836 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
35837 @code{jit-reader-unload} are provided, to be used to load and unload
35838 the readers from a preconfigured directory. Once loaded, the shared
35839 object is used the parse the debug information emitted by the JIT
35843 * Using JIT Debug Info Readers:: How to use supplied readers correctly
35844 * Writing JIT Debug Info Readers:: Creating a debug-info reader
35847 @node Using JIT Debug Info Readers
35848 @subsection Using JIT Debug Info Readers
35849 @kindex jit-reader-load
35850 @kindex jit-reader-unload
35852 Readers can be loaded and unloaded using the @code{jit-reader-load}
35853 and @code{jit-reader-unload} commands.
35856 @item jit-reader-load @var{reader}
35857 Load the JIT reader named @var{reader}, which is a shared
35858 object specified as either an absolute or a relative file name. In
35859 the latter case, @value{GDBN} will try to load the reader from a
35860 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
35861 system (here @var{libdir} is the system library directory, often
35862 @file{/usr/local/lib}).
35864 Only one reader can be active at a time; trying to load a second
35865 reader when one is already loaded will result in @value{GDBN}
35866 reporting an error. A new JIT reader can be loaded by first unloading
35867 the current one using @code{jit-reader-unload} and then invoking
35868 @code{jit-reader-load}.
35870 @item jit-reader-unload
35871 Unload the currently loaded JIT reader.
35875 @node Writing JIT Debug Info Readers
35876 @subsection Writing JIT Debug Info Readers
35877 @cindex writing JIT debug info readers
35879 As mentioned, a reader is essentially a shared object conforming to a
35880 certain ABI. This ABI is described in @file{jit-reader.h}.
35882 @file{jit-reader.h} defines the structures, macros and functions
35883 required to write a reader. It is installed (along with
35884 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
35885 the system include directory.
35887 Readers need to be released under a GPL compatible license. A reader
35888 can be declared as released under such a license by placing the macro
35889 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
35891 The entry point for readers is the symbol @code{gdb_init_reader},
35892 which is expected to be a function with the prototype
35894 @findex gdb_init_reader
35896 extern struct gdb_reader_funcs *gdb_init_reader (void);
35899 @cindex @code{struct gdb_reader_funcs}
35901 @code{struct gdb_reader_funcs} contains a set of pointers to callback
35902 functions. These functions are executed to read the debug info
35903 generated by the JIT compiler (@code{read}), to unwind stack frames
35904 (@code{unwind}) and to create canonical frame IDs
35905 (@code{get_Frame_id}). It also has a callback that is called when the
35906 reader is being unloaded (@code{destroy}). The struct looks like this
35909 struct gdb_reader_funcs
35911 /* Must be set to GDB_READER_INTERFACE_VERSION. */
35912 int reader_version;
35914 /* For use by the reader. */
35917 gdb_read_debug_info *read;
35918 gdb_unwind_frame *unwind;
35919 gdb_get_frame_id *get_frame_id;
35920 gdb_destroy_reader *destroy;
35924 @cindex @code{struct gdb_symbol_callbacks}
35925 @cindex @code{struct gdb_unwind_callbacks}
35927 The callbacks are provided with another set of callbacks by
35928 @value{GDBN} to do their job. For @code{read}, these callbacks are
35929 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
35930 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
35931 @code{struct gdb_symbol_callbacks} has callbacks to create new object
35932 files and new symbol tables inside those object files. @code{struct
35933 gdb_unwind_callbacks} has callbacks to read registers off the current
35934 frame and to write out the values of the registers in the previous
35935 frame. Both have a callback (@code{target_read}) to read bytes off the
35936 target's address space.
35938 @node In-Process Agent
35939 @chapter In-Process Agent
35940 @cindex debugging agent
35941 The traditional debugging model is conceptually low-speed, but works fine,
35942 because most bugs can be reproduced in debugging-mode execution. However,
35943 as multi-core or many-core processors are becoming mainstream, and
35944 multi-threaded programs become more and more popular, there should be more
35945 and more bugs that only manifest themselves at normal-mode execution, for
35946 example, thread races, because debugger's interference with the program's
35947 timing may conceal the bugs. On the other hand, in some applications,
35948 it is not feasible for the debugger to interrupt the program's execution
35949 long enough for the developer to learn anything helpful about its behavior.
35950 If the program's correctness depends on its real-time behavior, delays
35951 introduced by a debugger might cause the program to fail, even when the
35952 code itself is correct. It is useful to be able to observe the program's
35953 behavior without interrupting it.
35955 Therefore, traditional debugging model is too intrusive to reproduce
35956 some bugs. In order to reduce the interference with the program, we can
35957 reduce the number of operations performed by debugger. The
35958 @dfn{In-Process Agent}, a shared library, is running within the same
35959 process with inferior, and is able to perform some debugging operations
35960 itself. As a result, debugger is only involved when necessary, and
35961 performance of debugging can be improved accordingly. Note that
35962 interference with program can be reduced but can't be removed completely,
35963 because the in-process agent will still stop or slow down the program.
35965 The in-process agent can interpret and execute Agent Expressions
35966 (@pxref{Agent Expressions}) during performing debugging operations. The
35967 agent expressions can be used for different purposes, such as collecting
35968 data in tracepoints, and condition evaluation in breakpoints.
35970 @anchor{Control Agent}
35971 You can control whether the in-process agent is used as an aid for
35972 debugging with the following commands:
35975 @kindex set agent on
35977 Causes the in-process agent to perform some operations on behalf of the
35978 debugger. Just which operations requested by the user will be done
35979 by the in-process agent depends on the its capabilities. For example,
35980 if you request to evaluate breakpoint conditions in the in-process agent,
35981 and the in-process agent has such capability as well, then breakpoint
35982 conditions will be evaluated in the in-process agent.
35984 @kindex set agent off
35985 @item set agent off
35986 Disables execution of debugging operations by the in-process agent. All
35987 of the operations will be performed by @value{GDBN}.
35991 Display the current setting of execution of debugging operations by
35992 the in-process agent.
35996 * In-Process Agent Protocol::
35999 @node In-Process Agent Protocol
36000 @section In-Process Agent Protocol
36001 @cindex in-process agent protocol
36003 The in-process agent is able to communicate with both @value{GDBN} and
36004 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
36005 used for communications between @value{GDBN} or GDBserver and the IPA.
36006 In general, @value{GDBN} or GDBserver sends commands
36007 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
36008 in-process agent replies back with the return result of the command, or
36009 some other information. The data sent to in-process agent is composed
36010 of primitive data types, such as 4-byte or 8-byte type, and composite
36011 types, which are called objects (@pxref{IPA Protocol Objects}).
36014 * IPA Protocol Objects::
36015 * IPA Protocol Commands::
36018 @node IPA Protocol Objects
36019 @subsection IPA Protocol Objects
36020 @cindex ipa protocol objects
36022 The commands sent to and results received from agent may contain some
36023 complex data types called @dfn{objects}.
36025 The in-process agent is running on the same machine with @value{GDBN}
36026 or GDBserver, so it doesn't have to handle as much differences between
36027 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
36028 However, there are still some differences of two ends in two processes:
36032 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
36033 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
36035 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
36036 GDBserver is compiled with one, and in-process agent is compiled with
36040 Here are the IPA Protocol Objects:
36044 agent expression object. It represents an agent expression
36045 (@pxref{Agent Expressions}).
36046 @anchor{agent expression object}
36048 tracepoint action object. It represents a tracepoint action
36049 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
36050 memory, static trace data and to evaluate expression.
36051 @anchor{tracepoint action object}
36053 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
36054 @anchor{tracepoint object}
36058 The following table describes important attributes of each IPA protocol
36061 @multitable @columnfractions .30 .20 .50
36062 @headitem Name @tab Size @tab Description
36063 @item @emph{agent expression object} @tab @tab
36064 @item length @tab 4 @tab length of bytes code
36065 @item byte code @tab @var{length} @tab contents of byte code
36066 @item @emph{tracepoint action for collecting memory} @tab @tab
36067 @item 'M' @tab 1 @tab type of tracepoint action
36068 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
36069 address of the lowest byte to collect, otherwise @var{addr} is the offset
36070 of @var{basereg} for memory collecting.
36071 @item len @tab 8 @tab length of memory for collecting
36072 @item basereg @tab 4 @tab the register number containing the starting
36073 memory address for collecting.
36074 @item @emph{tracepoint action for collecting registers} @tab @tab
36075 @item 'R' @tab 1 @tab type of tracepoint action
36076 @item @emph{tracepoint action for collecting static trace data} @tab @tab
36077 @item 'L' @tab 1 @tab type of tracepoint action
36078 @item @emph{tracepoint action for expression evaluation} @tab @tab
36079 @item 'X' @tab 1 @tab type of tracepoint action
36080 @item agent expression @tab length of @tab @ref{agent expression object}
36081 @item @emph{tracepoint object} @tab @tab
36082 @item number @tab 4 @tab number of tracepoint
36083 @item address @tab 8 @tab address of tracepoint inserted on
36084 @item type @tab 4 @tab type of tracepoint
36085 @item enabled @tab 1 @tab enable or disable of tracepoint
36086 @item step_count @tab 8 @tab step
36087 @item pass_count @tab 8 @tab pass
36088 @item numactions @tab 4 @tab number of tracepoint actions
36089 @item hit count @tab 8 @tab hit count
36090 @item trace frame usage @tab 8 @tab trace frame usage
36091 @item compiled_cond @tab 8 @tab compiled condition
36092 @item orig_size @tab 8 @tab orig size
36093 @item condition @tab 4 if condition is NULL otherwise length of
36094 @ref{agent expression object}
36095 @tab zero if condition is NULL, otherwise is
36096 @ref{agent expression object}
36097 @item actions @tab variable
36098 @tab numactions number of @ref{tracepoint action object}
36101 @node IPA Protocol Commands
36102 @subsection IPA Protocol Commands
36103 @cindex ipa protocol commands
36105 The spaces in each command are delimiters to ease reading this commands
36106 specification. They don't exist in real commands.
36110 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
36111 Installs a new fast tracepoint described by @var{tracepoint_object}
36112 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
36113 head of @dfn{jumppad}, which is used to jump to data collection routine
36118 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
36119 @var{target_address} is address of tracepoint in the inferior.
36120 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
36121 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
36122 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
36123 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
36130 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
36131 is about to kill inferiors.
36139 @item probe_marker_at:@var{address}
36140 Asks in-process agent to probe the marker at @var{address}.
36147 @item unprobe_marker_at:@var{address}
36148 Asks in-process agent to unprobe the marker at @var{address}.
36152 @chapter Reporting Bugs in @value{GDBN}
36153 @cindex bugs in @value{GDBN}
36154 @cindex reporting bugs in @value{GDBN}
36156 Your bug reports play an essential role in making @value{GDBN} reliable.
36158 Reporting a bug may help you by bringing a solution to your problem, or it
36159 may not. But in any case the principal function of a bug report is to help
36160 the entire community by making the next version of @value{GDBN} work better. Bug
36161 reports are your contribution to the maintenance of @value{GDBN}.
36163 In order for a bug report to serve its purpose, you must include the
36164 information that enables us to fix the bug.
36167 * Bug Criteria:: Have you found a bug?
36168 * Bug Reporting:: How to report bugs
36172 @section Have You Found a Bug?
36173 @cindex bug criteria
36175 If you are not sure whether you have found a bug, here are some guidelines:
36178 @cindex fatal signal
36179 @cindex debugger crash
36180 @cindex crash of debugger
36182 If the debugger gets a fatal signal, for any input whatever, that is a
36183 @value{GDBN} bug. Reliable debuggers never crash.
36185 @cindex error on valid input
36187 If @value{GDBN} produces an error message for valid input, that is a
36188 bug. (Note that if you're cross debugging, the problem may also be
36189 somewhere in the connection to the target.)
36191 @cindex invalid input
36193 If @value{GDBN} does not produce an error message for invalid input,
36194 that is a bug. However, you should note that your idea of
36195 ``invalid input'' might be our idea of ``an extension'' or ``support
36196 for traditional practice''.
36199 If you are an experienced user of debugging tools, your suggestions
36200 for improvement of @value{GDBN} are welcome in any case.
36203 @node Bug Reporting
36204 @section How to Report Bugs
36205 @cindex bug reports
36206 @cindex @value{GDBN} bugs, reporting
36208 A number of companies and individuals offer support for @sc{gnu} products.
36209 If you obtained @value{GDBN} from a support organization, we recommend you
36210 contact that organization first.
36212 You can find contact information for many support companies and
36213 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
36215 @c should add a web page ref...
36218 @ifset BUGURL_DEFAULT
36219 In any event, we also recommend that you submit bug reports for
36220 @value{GDBN}. The preferred method is to submit them directly using
36221 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
36222 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
36225 @strong{Do not send bug reports to @samp{info-gdb}, or to
36226 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
36227 not want to receive bug reports. Those that do have arranged to receive
36230 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
36231 serves as a repeater. The mailing list and the newsgroup carry exactly
36232 the same messages. Often people think of posting bug reports to the
36233 newsgroup instead of mailing them. This appears to work, but it has one
36234 problem which can be crucial: a newsgroup posting often lacks a mail
36235 path back to the sender. Thus, if we need to ask for more information,
36236 we may be unable to reach you. For this reason, it is better to send
36237 bug reports to the mailing list.
36239 @ifclear BUGURL_DEFAULT
36240 In any event, we also recommend that you submit bug reports for
36241 @value{GDBN} to @value{BUGURL}.
36245 The fundamental principle of reporting bugs usefully is this:
36246 @strong{report all the facts}. If you are not sure whether to state a
36247 fact or leave it out, state it!
36249 Often people omit facts because they think they know what causes the
36250 problem and assume that some details do not matter. Thus, you might
36251 assume that the name of the variable you use in an example does not matter.
36252 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
36253 stray memory reference which happens to fetch from the location where that
36254 name is stored in memory; perhaps, if the name were different, the contents
36255 of that location would fool the debugger into doing the right thing despite
36256 the bug. Play it safe and give a specific, complete example. That is the
36257 easiest thing for you to do, and the most helpful.
36259 Keep in mind that the purpose of a bug report is to enable us to fix the
36260 bug. It may be that the bug has been reported previously, but neither
36261 you nor we can know that unless your bug report is complete and
36264 Sometimes people give a few sketchy facts and ask, ``Does this ring a
36265 bell?'' Those bug reports are useless, and we urge everyone to
36266 @emph{refuse to respond to them} except to chide the sender to report
36269 To enable us to fix the bug, you should include all these things:
36273 The version of @value{GDBN}. @value{GDBN} announces it if you start
36274 with no arguments; you can also print it at any time using @code{show
36277 Without this, we will not know whether there is any point in looking for
36278 the bug in the current version of @value{GDBN}.
36281 The type of machine you are using, and the operating system name and
36285 The details of the @value{GDBN} build-time configuration.
36286 @value{GDBN} shows these details if you invoke it with the
36287 @option{--configuration} command-line option, or if you type
36288 @code{show configuration} at @value{GDBN}'s prompt.
36291 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
36292 ``@value{GCC}--2.8.1''.
36295 What compiler (and its version) was used to compile the program you are
36296 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
36297 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
36298 to get this information; for other compilers, see the documentation for
36302 The command arguments you gave the compiler to compile your example and
36303 observe the bug. For example, did you use @samp{-O}? To guarantee
36304 you will not omit something important, list them all. A copy of the
36305 Makefile (or the output from make) is sufficient.
36307 If we were to try to guess the arguments, we would probably guess wrong
36308 and then we might not encounter the bug.
36311 A complete input script, and all necessary source files, that will
36315 A description of what behavior you observe that you believe is
36316 incorrect. For example, ``It gets a fatal signal.''
36318 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
36319 will certainly notice it. But if the bug is incorrect output, we might
36320 not notice unless it is glaringly wrong. You might as well not give us
36321 a chance to make a mistake.
36323 Even if the problem you experience is a fatal signal, you should still
36324 say so explicitly. Suppose something strange is going on, such as, your
36325 copy of @value{GDBN} is out of synch, or you have encountered a bug in
36326 the C library on your system. (This has happened!) Your copy might
36327 crash and ours would not. If you told us to expect a crash, then when
36328 ours fails to crash, we would know that the bug was not happening for
36329 us. If you had not told us to expect a crash, then we would not be able
36330 to draw any conclusion from our observations.
36333 @cindex recording a session script
36334 To collect all this information, you can use a session recording program
36335 such as @command{script}, which is available on many Unix systems.
36336 Just run your @value{GDBN} session inside @command{script} and then
36337 include the @file{typescript} file with your bug report.
36339 Another way to record a @value{GDBN} session is to run @value{GDBN}
36340 inside Emacs and then save the entire buffer to a file.
36343 If you wish to suggest changes to the @value{GDBN} source, send us context
36344 diffs. If you even discuss something in the @value{GDBN} source, refer to
36345 it by context, not by line number.
36347 The line numbers in our development sources will not match those in your
36348 sources. Your line numbers would convey no useful information to us.
36352 Here are some things that are not necessary:
36356 A description of the envelope of the bug.
36358 Often people who encounter a bug spend a lot of time investigating
36359 which changes to the input file will make the bug go away and which
36360 changes will not affect it.
36362 This is often time consuming and not very useful, because the way we
36363 will find the bug is by running a single example under the debugger
36364 with breakpoints, not by pure deduction from a series of examples.
36365 We recommend that you save your time for something else.
36367 Of course, if you can find a simpler example to report @emph{instead}
36368 of the original one, that is a convenience for us. Errors in the
36369 output will be easier to spot, running under the debugger will take
36370 less time, and so on.
36372 However, simplification is not vital; if you do not want to do this,
36373 report the bug anyway and send us the entire test case you used.
36376 A patch for the bug.
36378 A patch for the bug does help us if it is a good one. But do not omit
36379 the necessary information, such as the test case, on the assumption that
36380 a patch is all we need. We might see problems with your patch and decide
36381 to fix the problem another way, or we might not understand it at all.
36383 Sometimes with a program as complicated as @value{GDBN} it is very hard to
36384 construct an example that will make the program follow a certain path
36385 through the code. If you do not send us the example, we will not be able
36386 to construct one, so we will not be able to verify that the bug is fixed.
36388 And if we cannot understand what bug you are trying to fix, or why your
36389 patch should be an improvement, we will not install it. A test case will
36390 help us to understand.
36393 A guess about what the bug is or what it depends on.
36395 Such guesses are usually wrong. Even we cannot guess right about such
36396 things without first using the debugger to find the facts.
36399 @c The readline documentation is distributed with the readline code
36400 @c and consists of the two following files:
36403 @c Use -I with makeinfo to point to the appropriate directory,
36404 @c environment var TEXINPUTS with TeX.
36405 @ifclear SYSTEM_READLINE
36406 @include rluser.texi
36407 @include hsuser.texi
36411 @appendix In Memoriam
36413 The @value{GDBN} project mourns the loss of the following long-time
36418 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
36419 to Free Software in general. Outside of @value{GDBN}, he was known in
36420 the Amiga world for his series of Fish Disks, and the GeekGadget project.
36422 @item Michael Snyder
36423 Michael was one of the Global Maintainers of the @value{GDBN} project,
36424 with contributions recorded as early as 1996, until 2011. In addition
36425 to his day to day participation, he was a large driving force behind
36426 adding Reverse Debugging to @value{GDBN}.
36429 Beyond their technical contributions to the project, they were also
36430 enjoyable members of the Free Software Community. We will miss them.
36432 @node Formatting Documentation
36433 @appendix Formatting Documentation
36435 @cindex @value{GDBN} reference card
36436 @cindex reference card
36437 The @value{GDBN} 4 release includes an already-formatted reference card, ready
36438 for printing with PostScript or Ghostscript, in the @file{gdb}
36439 subdirectory of the main source directory@footnote{In
36440 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
36441 release.}. If you can use PostScript or Ghostscript with your printer,
36442 you can print the reference card immediately with @file{refcard.ps}.
36444 The release also includes the source for the reference card. You
36445 can format it, using @TeX{}, by typing:
36451 The @value{GDBN} reference card is designed to print in @dfn{landscape}
36452 mode on US ``letter'' size paper;
36453 that is, on a sheet 11 inches wide by 8.5 inches
36454 high. You will need to specify this form of printing as an option to
36455 your @sc{dvi} output program.
36457 @cindex documentation
36459 All the documentation for @value{GDBN} comes as part of the machine-readable
36460 distribution. The documentation is written in Texinfo format, which is
36461 a documentation system that uses a single source file to produce both
36462 on-line information and a printed manual. You can use one of the Info
36463 formatting commands to create the on-line version of the documentation
36464 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
36466 @value{GDBN} includes an already formatted copy of the on-line Info
36467 version of this manual in the @file{gdb} subdirectory. The main Info
36468 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
36469 subordinate files matching @samp{gdb.info*} in the same directory. If
36470 necessary, you can print out these files, or read them with any editor;
36471 but they are easier to read using the @code{info} subsystem in @sc{gnu}
36472 Emacs or the standalone @code{info} program, available as part of the
36473 @sc{gnu} Texinfo distribution.
36475 If you want to format these Info files yourself, you need one of the
36476 Info formatting programs, such as @code{texinfo-format-buffer} or
36479 If you have @code{makeinfo} installed, and are in the top level
36480 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
36481 version @value{GDBVN}), you can make the Info file by typing:
36488 If you want to typeset and print copies of this manual, you need @TeX{},
36489 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
36490 Texinfo definitions file.
36492 @TeX{} is a typesetting program; it does not print files directly, but
36493 produces output files called @sc{dvi} files. To print a typeset
36494 document, you need a program to print @sc{dvi} files. If your system
36495 has @TeX{} installed, chances are it has such a program. The precise
36496 command to use depends on your system; @kbd{lpr -d} is common; another
36497 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
36498 require a file name without any extension or a @samp{.dvi} extension.
36500 @TeX{} also requires a macro definitions file called
36501 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
36502 written in Texinfo format. On its own, @TeX{} cannot either read or
36503 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
36504 and is located in the @file{gdb-@var{version-number}/texinfo}
36507 If you have @TeX{} and a @sc{dvi} printer program installed, you can
36508 typeset and print this manual. First switch to the @file{gdb}
36509 subdirectory of the main source directory (for example, to
36510 @file{gdb-@value{GDBVN}/gdb}) and type:
36516 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
36518 @node Installing GDB
36519 @appendix Installing @value{GDBN}
36520 @cindex installation
36523 * Requirements:: Requirements for building @value{GDBN}
36524 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
36525 * Separate Objdir:: Compiling @value{GDBN} in another directory
36526 * Config Names:: Specifying names for hosts and targets
36527 * Configure Options:: Summary of options for configure
36528 * System-wide configuration:: Having a system-wide init file
36532 @section Requirements for Building @value{GDBN}
36533 @cindex building @value{GDBN}, requirements for
36535 Building @value{GDBN} requires various tools and packages to be available.
36536 Other packages will be used only if they are found.
36538 @heading Tools/Packages Necessary for Building @value{GDBN}
36540 @item C@t{++}11 compiler
36541 @value{GDBN} is written in C@t{++}11. It should be buildable with any
36542 recent C@t{++}11 compiler, e.g.@: GCC.
36545 @value{GDBN}'s build system relies on features only found in the GNU
36546 make program. Other variants of @code{make} will not work.
36549 @heading Tools/Packages Optional for Building @value{GDBN}
36553 @value{GDBN} can use the Expat XML parsing library. This library may be
36554 included with your operating system distribution; if it is not, you
36555 can get the latest version from @url{http://expat.sourceforge.net}.
36556 The @file{configure} script will search for this library in several
36557 standard locations; if it is installed in an unusual path, you can
36558 use the @option{--with-libexpat-prefix} option to specify its location.
36564 Remote protocol memory maps (@pxref{Memory Map Format})
36566 Target descriptions (@pxref{Target Descriptions})
36568 Remote shared library lists (@xref{Library List Format},
36569 or alternatively @pxref{Library List Format for SVR4 Targets})
36571 MS-Windows shared libraries (@pxref{Shared Libraries})
36573 Traceframe info (@pxref{Traceframe Info Format})
36575 Branch trace (@pxref{Branch Trace Format},
36576 @pxref{Branch Trace Configuration Format})
36580 @value{GDBN} can be scripted using GNU Guile. @xref{Guile}. By
36581 default, @value{GDBN} will be compiled if the Guile libraries are
36582 installed and are found by @file{configure}. You can use the
36583 @code{--with-guile} option to request Guile, and pass either the Guile
36584 version number or the file name of the relevant @code{pkg-config}
36585 program to choose a particular version of Guile.
36588 @value{GDBN}'s features related to character sets (@pxref{Character
36589 Sets}) require a functioning @code{iconv} implementation. If you are
36590 on a GNU system, then this is provided by the GNU C Library. Some
36591 other systems also provide a working @code{iconv}.
36593 If @value{GDBN} is using the @code{iconv} program which is installed
36594 in a non-standard place, you will need to tell @value{GDBN} where to
36595 find it. This is done with @option{--with-iconv-bin} which specifies
36596 the directory that contains the @code{iconv} program. This program is
36597 run in order to make a list of the available character sets.
36599 On systems without @code{iconv}, you can install GNU Libiconv. If
36600 Libiconv is installed in a standard place, @value{GDBN} will
36601 automatically use it if it is needed. If you have previously
36602 installed Libiconv in a non-standard place, you can use the
36603 @option{--with-libiconv-prefix} option to @file{configure}.
36605 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
36606 arrange to build Libiconv if a directory named @file{libiconv} appears
36607 in the top-most source directory. If Libiconv is built this way, and
36608 if the operating system does not provide a suitable @code{iconv}
36609 implementation, then the just-built library will automatically be used
36610 by @value{GDBN}. One easy way to set this up is to download GNU
36611 Libiconv, unpack it inside the top-level directory of the @value{GDBN}
36612 source tree, and then rename the directory holding the Libiconv source
36613 code to @samp{libiconv}.
36616 @value{GDBN} can support debugging sections that are compressed with
36617 the LZMA library. @xref{MiniDebugInfo}. If this library is not
36618 included with your operating system, you can find it in the xz package
36619 at @url{http://tukaani.org/xz/}. If the LZMA library is available in
36620 the usual place, then the @file{configure} script will use it
36621 automatically. If it is installed in an unusual path, you can use the
36622 @option{--with-lzma-prefix} option to specify its location.
36626 @value{GDBN} can use the GNU MPFR multiple-precision floating-point
36627 library. This library may be included with your operating system
36628 distribution; if it is not, you can get the latest version from
36629 @url{http://www.mpfr.org}. The @file{configure} script will search
36630 for this library in several standard locations; if it is installed
36631 in an unusual path, you can use the @option{--with-libmpfr-prefix}
36632 option to specify its location.
36634 GNU MPFR is used to emulate target floating-point arithmetic during
36635 expression evaluation when the target uses different floating-point
36636 formats than the host. If GNU MPFR it is not available, @value{GDBN}
36637 will fall back to using host floating-point arithmetic.
36640 @value{GDBN} can be scripted using Python language. @xref{Python}.
36641 By default, @value{GDBN} will be compiled if the Python libraries are
36642 installed and are found by @file{configure}. You can use the
36643 @code{--with-python} option to request Python, and pass either the
36644 file name of the relevant @code{python} executable, or the name of the
36645 directory in which Python is installed, to choose a particular
36646 installation of Python.
36649 @cindex compressed debug sections
36650 @value{GDBN} will use the @samp{zlib} library, if available, to read
36651 compressed debug sections. Some linkers, such as GNU gold, are capable
36652 of producing binaries with compressed debug sections. If @value{GDBN}
36653 is compiled with @samp{zlib}, it will be able to read the debug
36654 information in such binaries.
36656 The @samp{zlib} library is likely included with your operating system
36657 distribution; if it is not, you can get the latest version from
36658 @url{http://zlib.net}.
36661 @node Running Configure
36662 @section Invoking the @value{GDBN} @file{configure} Script
36663 @cindex configuring @value{GDBN}
36664 @value{GDBN} comes with a @file{configure} script that automates the process
36665 of preparing @value{GDBN} for installation; you can then use @code{make} to
36666 build the @code{gdb} program.
36668 @c irrelevant in info file; it's as current as the code it lives with.
36669 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
36670 look at the @file{README} file in the sources; we may have improved the
36671 installation procedures since publishing this manual.}
36674 The @value{GDBN} distribution includes all the source code you need for
36675 @value{GDBN} in a single directory, whose name is usually composed by
36676 appending the version number to @samp{gdb}.
36678 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
36679 @file{gdb-@value{GDBVN}} directory. That directory contains:
36682 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
36683 script for configuring @value{GDBN} and all its supporting libraries
36685 @item gdb-@value{GDBVN}/gdb
36686 the source specific to @value{GDBN} itself
36688 @item gdb-@value{GDBVN}/bfd
36689 source for the Binary File Descriptor library
36691 @item gdb-@value{GDBVN}/include
36692 @sc{gnu} include files
36694 @item gdb-@value{GDBVN}/libiberty
36695 source for the @samp{-liberty} free software library
36697 @item gdb-@value{GDBVN}/opcodes
36698 source for the library of opcode tables and disassemblers
36700 @item gdb-@value{GDBVN}/readline
36701 source for the @sc{gnu} command-line interface
36704 There may be other subdirectories as well.
36706 The simplest way to configure and build @value{GDBN} is to run @file{configure}
36707 from the @file{gdb-@var{version-number}} source directory, which in
36708 this example is the @file{gdb-@value{GDBVN}} directory.
36710 First switch to the @file{gdb-@var{version-number}} source directory
36711 if you are not already in it; then run @file{configure}. Pass the
36712 identifier for the platform on which @value{GDBN} will run as an
36718 cd gdb-@value{GDBVN}
36723 Running @samp{configure} and then running @code{make} builds the
36724 included supporting libraries, then @code{gdb} itself. The configured
36725 source files, and the binaries, are left in the corresponding source
36729 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
36730 system does not recognize this automatically when you run a different
36731 shell, you may need to run @code{sh} on it explicitly:
36737 You should run the @file{configure} script from the top directory in the
36738 source tree, the @file{gdb-@var{version-number}} directory. If you run
36739 @file{configure} from one of the subdirectories, you will configure only
36740 that subdirectory. That is usually not what you want. In particular,
36741 if you run the first @file{configure} from the @file{gdb} subdirectory
36742 of the @file{gdb-@var{version-number}} directory, you will omit the
36743 configuration of @file{bfd}, @file{readline}, and other sibling
36744 directories of the @file{gdb} subdirectory. This leads to build errors
36745 about missing include files such as @file{bfd/bfd.h}.
36747 You can install @code{@value{GDBN}} anywhere. The best way to do this
36748 is to pass the @code{--prefix} option to @code{configure}, and then
36749 install it with @code{make install}.
36751 @node Separate Objdir
36752 @section Compiling @value{GDBN} in Another Directory
36754 If you want to run @value{GDBN} versions for several host or target machines,
36755 you need a different @code{gdb} compiled for each combination of
36756 host and target. @file{configure} is designed to make this easy by
36757 allowing you to generate each configuration in a separate subdirectory,
36758 rather than in the source directory. If your @code{make} program
36759 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
36760 @code{make} in each of these directories builds the @code{gdb}
36761 program specified there.
36763 To build @code{gdb} in a separate directory, run @file{configure}
36764 with the @samp{--srcdir} option to specify where to find the source.
36765 (You also need to specify a path to find @file{configure}
36766 itself from your working directory. If the path to @file{configure}
36767 would be the same as the argument to @samp{--srcdir}, you can leave out
36768 the @samp{--srcdir} option; it is assumed.)
36770 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
36771 separate directory for a Sun 4 like this:
36775 cd gdb-@value{GDBVN}
36778 ../gdb-@value{GDBVN}/configure
36783 When @file{configure} builds a configuration using a remote source
36784 directory, it creates a tree for the binaries with the same structure
36785 (and using the same names) as the tree under the source directory. In
36786 the example, you'd find the Sun 4 library @file{libiberty.a} in the
36787 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
36788 @file{gdb-sun4/gdb}.
36790 Make sure that your path to the @file{configure} script has just one
36791 instance of @file{gdb} in it. If your path to @file{configure} looks
36792 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
36793 one subdirectory of @value{GDBN}, not the whole package. This leads to
36794 build errors about missing include files such as @file{bfd/bfd.h}.
36796 One popular reason to build several @value{GDBN} configurations in separate
36797 directories is to configure @value{GDBN} for cross-compiling (where
36798 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
36799 programs that run on another machine---the @dfn{target}).
36800 You specify a cross-debugging target by
36801 giving the @samp{--target=@var{target}} option to @file{configure}.
36803 When you run @code{make} to build a program or library, you must run
36804 it in a configured directory---whatever directory you were in when you
36805 called @file{configure} (or one of its subdirectories).
36807 The @code{Makefile} that @file{configure} generates in each source
36808 directory also runs recursively. If you type @code{make} in a source
36809 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
36810 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
36811 will build all the required libraries, and then build GDB.
36813 When you have multiple hosts or targets configured in separate
36814 directories, you can run @code{make} on them in parallel (for example,
36815 if they are NFS-mounted on each of the hosts); they will not interfere
36819 @section Specifying Names for Hosts and Targets
36821 The specifications used for hosts and targets in the @file{configure}
36822 script are based on a three-part naming scheme, but some short predefined
36823 aliases are also supported. The full naming scheme encodes three pieces
36824 of information in the following pattern:
36827 @var{architecture}-@var{vendor}-@var{os}
36830 For example, you can use the alias @code{sun4} as a @var{host} argument,
36831 or as the value for @var{target} in a @code{--target=@var{target}}
36832 option. The equivalent full name is @samp{sparc-sun-sunos4}.
36834 The @file{configure} script accompanying @value{GDBN} does not provide
36835 any query facility to list all supported host and target names or
36836 aliases. @file{configure} calls the Bourne shell script
36837 @code{config.sub} to map abbreviations to full names; you can read the
36838 script, if you wish, or you can use it to test your guesses on
36839 abbreviations---for example:
36842 % sh config.sub i386-linux
36844 % sh config.sub alpha-linux
36845 alpha-unknown-linux-gnu
36846 % sh config.sub hp9k700
36848 % sh config.sub sun4
36849 sparc-sun-sunos4.1.1
36850 % sh config.sub sun3
36851 m68k-sun-sunos4.1.1
36852 % sh config.sub i986v
36853 Invalid configuration `i986v': machine `i986v' not recognized
36857 @code{config.sub} is also distributed in the @value{GDBN} source
36858 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
36860 @node Configure Options
36861 @section @file{configure} Options
36863 Here is a summary of the @file{configure} options and arguments that
36864 are most often useful for building @value{GDBN}. @file{configure}
36865 also has several other options not listed here. @inforef{Running
36866 configure scripts,,autoconf.info}, for a full
36867 explanation of @file{configure}.
36870 configure @r{[}--help@r{]}
36871 @r{[}--prefix=@var{dir}@r{]}
36872 @r{[}--exec-prefix=@var{dir}@r{]}
36873 @r{[}--srcdir=@var{dirname}@r{]}
36874 @r{[}--target=@var{target}@r{]}
36878 You may introduce options with a single @samp{-} rather than
36879 @samp{--} if you prefer; but you may abbreviate option names if you use
36884 Display a quick summary of how to invoke @file{configure}.
36886 @item --prefix=@var{dir}
36887 Configure the source to install programs and files under directory
36890 @item --exec-prefix=@var{dir}
36891 Configure the source to install programs under directory
36894 @c avoid splitting the warning from the explanation:
36896 @item --srcdir=@var{dirname}
36897 Use this option to make configurations in directories separate from the
36898 @value{GDBN} source directories. Among other things, you can use this to
36899 build (or maintain) several configurations simultaneously, in separate
36900 directories. @file{configure} writes configuration-specific files in
36901 the current directory, but arranges for them to use the source in the
36902 directory @var{dirname}. @file{configure} creates directories under
36903 the working directory in parallel to the source directories below
36906 @item --target=@var{target}
36907 Configure @value{GDBN} for cross-debugging programs running on the specified
36908 @var{target}. Without this option, @value{GDBN} is configured to debug
36909 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
36911 There is no convenient way to generate a list of all available
36912 targets. Also see the @code{--enable-targets} option, below.
36915 There are many other options that are specific to @value{GDBN}. This
36916 lists just the most common ones; there are some very specialized
36917 options not described here.
36920 @item --enable-targets=@r{[}@var{target}@r{]}@dots{}
36921 @itemx --enable-targets=all
36922 Configure @value{GDBN} for cross-debugging programs running on the
36923 specified list of targets. The special value @samp{all} configures
36924 @value{GDBN} for debugging programs running on any target it supports.
36926 @item --with-gdb-datadir=@var{path}
36927 Set the @value{GDBN}-specific data directory. @value{GDBN} will look
36928 here for certain supporting files or scripts. This defaults to the
36929 @file{gdb} subdirectory of @samp{datadi} (which can be set using
36932 @item --with-relocated-sources=@var{dir}
36933 Sets up the default source path substitution rule so that directory
36934 names recorded in debug information will be automatically adjusted for
36935 any directory under @var{dir}. @var{dir} should be a subdirectory of
36936 @value{GDBN}'s configured prefix, the one mentioned in the
36937 @code{--prefix} or @code{--exec-prefix} options to configure. This
36938 option is useful if GDB is supposed to be moved to a different place
36941 @item --enable-64-bit-bfd
36942 Enable 64-bit support in BFD on 32-bit hosts.
36944 @item --disable-gdbmi
36945 Build @value{GDBN} without the GDB/MI machine interface
36949 Build @value{GDBN} with the text-mode full-screen user interface
36950 (TUI). Requires a curses library (ncurses and cursesX are also
36953 @item --with-curses
36954 Use the curses library instead of the termcap library, for text-mode
36955 terminal operations.
36957 @item --with-libunwind-ia64
36958 Use the libunwind library for unwinding function call stack on ia64
36959 target platforms. See http://www.nongnu.org/libunwind/index.html for
36962 @item --with-system-readline
36963 Use the readline library installed on the host, rather than the
36964 library supplied as part of @value{GDBN}. Readline 7 or newer is
36965 required; this is enforced by the build system.
36967 @item --with-system-zlib
36968 Use the zlib library installed on the host, rather than the library
36969 supplied as part of @value{GDBN}.
36972 Build @value{GDBN} with Expat, a library for XML parsing. (Done by
36973 default if libexpat is installed and found at configure time.) This
36974 library is used to read XML files supplied with @value{GDBN}. If it
36975 is unavailable, some features, such as remote protocol memory maps,
36976 target descriptions, and shared library lists, that are based on XML
36977 files, will not be available in @value{GDBN}. If your host does not
36978 have libexpat installed, you can get the latest version from
36979 `http://expat.sourceforge.net'.
36981 @item --with-libiconv-prefix@r{[}=@var{dir}@r{]}
36983 Build @value{GDBN} with GNU libiconv, a character set encoding
36984 conversion library. This is not done by default, as on GNU systems
36985 the @code{iconv} that is built in to the C library is sufficient. If
36986 your host does not have a working @code{iconv}, you can get the latest
36987 version of GNU iconv from `https://www.gnu.org/software/libiconv/'.
36989 @value{GDBN}'s build system also supports building GNU libiconv as
36990 part of the overall build. @xref{Requirements}.
36993 Build @value{GDBN} with LZMA, a compression library. (Done by default
36994 if liblzma is installed and found at configure time.) LZMA is used by
36995 @value{GDBN}'s "mini debuginfo" feature, which is only useful on
36996 platforms using the ELF object file format. If your host does not
36997 have liblzma installed, you can get the latest version from
36998 `https://tukaani.org/xz/'.
37001 Build @value{GDBN} with GNU MPFR, a library for multiple-precision
37002 floating-point computation with correct rounding. (Done by default if
37003 GNU MPFR is installed and found at configure time.) This library is
37004 used to emulate target floating-point arithmetic during expression
37005 evaluation when the target uses different floating-point formats than
37006 the host. If GNU MPFR is not available, @value{GDBN} will fall back
37007 to using host floating-point arithmetic. If your host does not have
37008 GNU MPFR installed, you can get the latest version from
37009 `http://www.mpfr.org'.
37011 @item --with-python@r{[}=@var{python}@r{]}
37012 Build @value{GDBN} with Python scripting support. (Done by default if
37013 libpython is present and found at configure time.) Python makes
37014 @value{GDBN} scripting much more powerful than the restricted CLI
37015 scripting language. If your host does not have Python installed, you
37016 can find it on `http://www.python.org/download/'. The oldest version
37017 of Python supported by GDB is 2.6. The optional argument @var{python}
37018 is used to find the Python headers and libraries. It can be either
37019 the name of a Python executable, or the name of the directory in which
37020 Python is installed.
37022 @item --with-guile[=GUILE]'
37023 Build @value{GDBN} with GNU Guile scripting support. (Done by default
37024 if libguile is present and found at configure time.) If your host
37025 does not have Guile installed, you can find it at
37026 `https://www.gnu.org/software/guile/'. The optional argument GUILE
37027 can be a version number, which will cause @code{configure} to try to
37028 use that version of Guile; or the file name of a @code{pkg-config}
37029 executable, which will be queried to find the information needed to
37030 compile and link against Guile.
37032 @item --without-included-regex
37033 Don't use the regex library included with @value{GDBN} (as part of the
37034 libiberty library). This is the default on hosts with version 2 of
37037 @item --with-sysroot=@var{dir}
37038 Use @var{dir} as the default system root directory for libraries whose
37039 file names begin with @file{/lib}' or @file{/usr/lib'}. (The value of
37040 @var{dir} can be modified at run time by using the @command{set
37041 sysroot} command.) If @var{dir} is under the @value{GDBN} configured
37042 prefix (set with @code{--prefix} or @code{--exec-prefix options}, the
37043 default system root will be automatically adjusted if and when
37044 @value{GDBN} is moved to a different location.
37046 @item --with-system-gdbinit=@var{file}
37047 Configure @value{GDBN} to automatically load a system-wide init file.
37048 @var{file} should be an absolute file name. If @var{file} is in a
37049 directory under the configured prefix, and @value{GDBN} is moved to
37050 another location after being built, the location of the system-wide
37051 init file will be adjusted accordingly.
37053 @item --enable-build-warnings
37054 When building the @value{GDBN} sources, ask the compiler to warn about
37055 any code which looks even vaguely suspicious. It passes many
37056 different warning flags, depending on the exact version of the
37057 compiler you are using.
37059 @item --enable-werror
37060 Treat compiler warnings as werrors. It adds the @code{-Werror} flag
37061 to the compiler, which will fail the compilation if the compiler
37062 outputs any warning messages.
37064 @item --enable-ubsan
37065 Enable the GCC undefined behavior sanitizer. This is disabled by
37066 default, but passing @code{--enable-ubsan=yes} or
37067 @code{--enable-ubsan=auto} to @code{configure} will enable it. The
37068 undefined behavior sanitizer checks for C@t{++} undefined behavior.
37069 It has a performance cost, so if you are looking at @value{GDBN}'s
37070 performance, you should disable it. The undefined behavior sanitizer
37071 was first introduced in GCC 4.9.
37074 @node System-wide configuration
37075 @section System-wide configuration and settings
37076 @cindex system-wide init file
37078 @value{GDBN} can be configured to have a system-wide init file;
37079 this file will be read and executed at startup (@pxref{Startup, , What
37080 @value{GDBN} does during startup}).
37082 Here is the corresponding configure option:
37085 @item --with-system-gdbinit=@var{file}
37086 Specify that the default location of the system-wide init file is
37090 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
37091 it may be subject to relocation. Two possible cases:
37095 If the default location of this init file contains @file{$prefix},
37096 it will be subject to relocation. Suppose that the configure options
37097 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
37098 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
37099 init file is looked for as @file{$install/etc/gdbinit} instead of
37100 @file{$prefix/etc/gdbinit}.
37103 By contrast, if the default location does not contain the prefix,
37104 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
37105 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
37106 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
37107 wherever @value{GDBN} is installed.
37110 If the configured location of the system-wide init file (as given by the
37111 @option{--with-system-gdbinit} option at configure time) is in the
37112 data-directory (as specified by @option{--with-gdb-datadir} at configure
37113 time) or in one of its subdirectories, then @value{GDBN} will look for the
37114 system-wide init file in the directory specified by the
37115 @option{--data-directory} command-line option.
37116 Note that the system-wide init file is only read once, during @value{GDBN}
37117 initialization. If the data-directory is changed after @value{GDBN} has
37118 started with the @code{set data-directory} command, the file will not be
37122 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
37125 @node System-wide Configuration Scripts
37126 @subsection Installed System-wide Configuration Scripts
37127 @cindex system-wide configuration scripts
37129 The @file{system-gdbinit} directory, located inside the data-directory
37130 (as specified by @option{--with-gdb-datadir} at configure time) contains
37131 a number of scripts which can be used as system-wide init files. To
37132 automatically source those scripts at startup, @value{GDBN} should be
37133 configured with @option{--with-system-gdbinit}. Otherwise, any user
37134 should be able to source them by hand as needed.
37136 The following scripts are currently available:
37139 @item @file{elinos.py}
37141 @cindex ELinOS system-wide configuration script
37142 This script is useful when debugging a program on an ELinOS target.
37143 It takes advantage of the environment variables defined in a standard
37144 ELinOS environment in order to determine the location of the system
37145 shared libraries, and then sets the @samp{solib-absolute-prefix}
37146 and @samp{solib-search-path} variables appropriately.
37148 @item @file{wrs-linux.py}
37149 @pindex wrs-linux.py
37150 @cindex Wind River Linux system-wide configuration script
37151 This script is useful when debugging a program on a target running
37152 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
37153 the host-side sysroot used by the target system.
37157 @node Maintenance Commands
37158 @appendix Maintenance Commands
37159 @cindex maintenance commands
37160 @cindex internal commands
37162 In addition to commands intended for @value{GDBN} users, @value{GDBN}
37163 includes a number of commands intended for @value{GDBN} developers,
37164 that are not documented elsewhere in this manual. These commands are
37165 provided here for reference. (For commands that turn on debugging
37166 messages, see @ref{Debugging Output}.)
37169 @kindex maint agent
37170 @kindex maint agent-eval
37171 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
37172 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
37173 Translate the given @var{expression} into remote agent bytecodes.
37174 This command is useful for debugging the Agent Expression mechanism
37175 (@pxref{Agent Expressions}). The @samp{agent} version produces an
37176 expression useful for data collection, such as by tracepoints, while
37177 @samp{maint agent-eval} produces an expression that evaluates directly
37178 to a result. For instance, a collection expression for @code{globa +
37179 globb} will include bytecodes to record four bytes of memory at each
37180 of the addresses of @code{globa} and @code{globb}, while discarding
37181 the result of the addition, while an evaluation expression will do the
37182 addition and return the sum.
37183 If @code{-at} is given, generate remote agent bytecode for @var{location}.
37184 If not, generate remote agent bytecode for current frame PC address.
37186 @kindex maint agent-printf
37187 @item maint agent-printf @var{format},@var{expr},...
37188 Translate the given format string and list of argument expressions
37189 into remote agent bytecodes and display them as a disassembled list.
37190 This command is useful for debugging the agent version of dynamic
37191 printf (@pxref{Dynamic Printf}).
37193 @kindex maint info breakpoints
37194 @item @anchor{maint info breakpoints}maint info breakpoints
37195 Using the same format as @samp{info breakpoints}, display both the
37196 breakpoints you've set explicitly, and those @value{GDBN} is using for
37197 internal purposes. Internal breakpoints are shown with negative
37198 breakpoint numbers. The type column identifies what kind of breakpoint
37203 Normal, explicitly set breakpoint.
37206 Normal, explicitly set watchpoint.
37209 Internal breakpoint, used to handle correctly stepping through
37210 @code{longjmp} calls.
37212 @item longjmp resume
37213 Internal breakpoint at the target of a @code{longjmp}.
37216 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
37219 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
37222 Shared library events.
37226 @kindex maint info btrace
37227 @item maint info btrace
37228 Pint information about raw branch tracing data.
37230 @kindex maint btrace packet-history
37231 @item maint btrace packet-history
37232 Print the raw branch trace packets that are used to compute the
37233 execution history for the @samp{record btrace} command. Both the
37234 information and the format in which it is printed depend on the btrace
37239 For the BTS recording format, print a list of blocks of sequential
37240 code. For each block, the following information is printed:
37244 Newer blocks have higher numbers. The oldest block has number zero.
37245 @item Lowest @samp{PC}
37246 @item Highest @samp{PC}
37250 For the Intel Processor Trace recording format, print a list of
37251 Intel Processor Trace packets. For each packet, the following
37252 information is printed:
37255 @item Packet number
37256 Newer packets have higher numbers. The oldest packet has number zero.
37258 The packet's offset in the trace stream.
37259 @item Packet opcode and payload
37263 @kindex maint btrace clear-packet-history
37264 @item maint btrace clear-packet-history
37265 Discards the cached packet history printed by the @samp{maint btrace
37266 packet-history} command. The history will be computed again when
37269 @kindex maint btrace clear
37270 @item maint btrace clear
37271 Discard the branch trace data. The data will be fetched anew and the
37272 branch trace will be recomputed when needed.
37274 This implicitly truncates the branch trace to a single branch trace
37275 buffer. When updating branch trace incrementally, the branch trace
37276 available to @value{GDBN} may be bigger than a single branch trace
37279 @kindex maint set btrace pt skip-pad
37280 @item maint set btrace pt skip-pad
37281 @kindex maint show btrace pt skip-pad
37282 @item maint show btrace pt skip-pad
37283 Control whether @value{GDBN} will skip PAD packets when computing the
37286 @kindex set displaced-stepping
37287 @kindex show displaced-stepping
37288 @cindex displaced stepping support
37289 @cindex out-of-line single-stepping
37290 @item set displaced-stepping
37291 @itemx show displaced-stepping
37292 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
37293 if the target supports it. Displaced stepping is a way to single-step
37294 over breakpoints without removing them from the inferior, by executing
37295 an out-of-line copy of the instruction that was originally at the
37296 breakpoint location. It is also known as out-of-line single-stepping.
37299 @item set displaced-stepping on
37300 If the target architecture supports it, @value{GDBN} will use
37301 displaced stepping to step over breakpoints.
37303 @item set displaced-stepping off
37304 @value{GDBN} will not use displaced stepping to step over breakpoints,
37305 even if such is supported by the target architecture.
37307 @cindex non-stop mode, and @samp{set displaced-stepping}
37308 @item set displaced-stepping auto
37309 This is the default mode. @value{GDBN} will use displaced stepping
37310 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
37311 architecture supports displaced stepping.
37314 @kindex maint check-psymtabs
37315 @item maint check-psymtabs
37316 Check the consistency of currently expanded psymtabs versus symtabs.
37317 Use this to check, for example, whether a symbol is in one but not the other.
37319 @kindex maint check-symtabs
37320 @item maint check-symtabs
37321 Check the consistency of currently expanded symtabs.
37323 @kindex maint expand-symtabs
37324 @item maint expand-symtabs [@var{regexp}]
37325 Expand symbol tables.
37326 If @var{regexp} is specified, only expand symbol tables for file
37327 names matching @var{regexp}.
37329 @kindex maint set catch-demangler-crashes
37330 @kindex maint show catch-demangler-crashes
37331 @cindex demangler crashes
37332 @item maint set catch-demangler-crashes [on|off]
37333 @itemx maint show catch-demangler-crashes
37334 Control whether @value{GDBN} should attempt to catch crashes in the
37335 symbol name demangler. The default is to attempt to catch crashes.
37336 If enabled, the first time a crash is caught, a core file is created,
37337 the offending symbol is displayed and the user is presented with the
37338 option to terminate the current session.
37340 @kindex maint cplus first_component
37341 @item maint cplus first_component @var{name}
37342 Print the first C@t{++} class/namespace component of @var{name}.
37344 @kindex maint cplus namespace
37345 @item maint cplus namespace
37346 Print the list of possible C@t{++} namespaces.
37348 @kindex maint deprecate
37349 @kindex maint undeprecate
37350 @cindex deprecated commands
37351 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
37352 @itemx maint undeprecate @var{command}
37353 Deprecate or undeprecate the named @var{command}. Deprecated commands
37354 cause @value{GDBN} to issue a warning when you use them. The optional
37355 argument @var{replacement} says which newer command should be used in
37356 favor of the deprecated one; if it is given, @value{GDBN} will mention
37357 the replacement as part of the warning.
37359 @kindex maint dump-me
37360 @item maint dump-me
37361 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
37362 Cause a fatal signal in the debugger and force it to dump its core.
37363 This is supported only on systems which support aborting a program
37364 with the @code{SIGQUIT} signal.
37366 @kindex maint internal-error
37367 @kindex maint internal-warning
37368 @kindex maint demangler-warning
37369 @cindex demangler crashes
37370 @item maint internal-error @r{[}@var{message-text}@r{]}
37371 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
37372 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
37374 Cause @value{GDBN} to call the internal function @code{internal_error},
37375 @code{internal_warning} or @code{demangler_warning} and hence behave
37376 as though an internal problem has been detected. In addition to
37377 reporting the internal problem, these functions give the user the
37378 opportunity to either quit @value{GDBN} or (for @code{internal_error}
37379 and @code{internal_warning}) create a core file of the current
37380 @value{GDBN} session.
37382 These commands take an optional parameter @var{message-text} that is
37383 used as the text of the error or warning message.
37385 Here's an example of using @code{internal-error}:
37388 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
37389 @dots{}/maint.c:121: internal-error: testing, 1, 2
37390 A problem internal to GDB has been detected. Further
37391 debugging may prove unreliable.
37392 Quit this debugging session? (y or n) @kbd{n}
37393 Create a core file? (y or n) @kbd{n}
37397 @cindex @value{GDBN} internal error
37398 @cindex internal errors, control of @value{GDBN} behavior
37399 @cindex demangler crashes
37401 @kindex maint set internal-error
37402 @kindex maint show internal-error
37403 @kindex maint set internal-warning
37404 @kindex maint show internal-warning
37405 @kindex maint set demangler-warning
37406 @kindex maint show demangler-warning
37407 @item maint set internal-error @var{action} [ask|yes|no]
37408 @itemx maint show internal-error @var{action}
37409 @itemx maint set internal-warning @var{action} [ask|yes|no]
37410 @itemx maint show internal-warning @var{action}
37411 @itemx maint set demangler-warning @var{action} [ask|yes|no]
37412 @itemx maint show demangler-warning @var{action}
37413 When @value{GDBN} reports an internal problem (error or warning) it
37414 gives the user the opportunity to both quit @value{GDBN} and create a
37415 core file of the current @value{GDBN} session. These commands let you
37416 override the default behaviour for each particular @var{action},
37417 described in the table below.
37421 You can specify that @value{GDBN} should always (yes) or never (no)
37422 quit. The default is to ask the user what to do.
37425 You can specify that @value{GDBN} should always (yes) or never (no)
37426 create a core file. The default is to ask the user what to do. Note
37427 that there is no @code{corefile} option for @code{demangler-warning}:
37428 demangler warnings always create a core file and this cannot be
37432 @kindex maint packet
37433 @item maint packet @var{text}
37434 If @value{GDBN} is talking to an inferior via the serial protocol,
37435 then this command sends the string @var{text} to the inferior, and
37436 displays the response packet. @value{GDBN} supplies the initial
37437 @samp{$} character, the terminating @samp{#} character, and the
37440 @kindex maint print architecture
37441 @item maint print architecture @r{[}@var{file}@r{]}
37442 Print the entire architecture configuration. The optional argument
37443 @var{file} names the file where the output goes.
37445 @kindex maint print c-tdesc @r{[}@var{file}@r{]}
37446 @item maint print c-tdesc
37447 Print the target description (@pxref{Target Descriptions}) as
37448 a C source file. By default, the target description is for the current
37449 target, but if the optional argument @var{file} is provided, that file
37450 is used to produce the description. The @var{file} should be an XML
37451 document, of the form described in @ref{Target Description Format}.
37452 The created source file is built into @value{GDBN} when @value{GDBN} is
37453 built again. This command is used by developers after they add or
37454 modify XML target descriptions.
37456 @kindex maint check xml-descriptions
37457 @item maint check xml-descriptions @var{dir}
37458 Check that the target descriptions dynamically created by @value{GDBN}
37459 equal the descriptions created from XML files found in @var{dir}.
37461 @anchor{maint check libthread-db}
37462 @kindex maint check libthread-db
37463 @item maint check libthread-db
37464 Run integrity checks on the current inferior's thread debugging
37465 library. This exercises all @code{libthread_db} functionality used by
37466 @value{GDBN} on GNU/Linux systems, and by extension also exercises the
37467 @code{proc_service} functions provided by @value{GDBN} that
37468 @code{libthread_db} uses. Note that parts of the test may be skipped
37469 on some platforms when debugging core files.
37471 @kindex maint print dummy-frames
37472 @item maint print dummy-frames
37473 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
37476 (@value{GDBP}) @kbd{b add}
37478 (@value{GDBP}) @kbd{print add(2,3)}
37479 Breakpoint 2, add (a=2, b=3) at @dots{}
37481 The program being debugged stopped while in a function called from GDB.
37483 (@value{GDBP}) @kbd{maint print dummy-frames}
37484 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
37488 Takes an optional file parameter.
37490 @kindex maint print registers
37491 @kindex maint print raw-registers
37492 @kindex maint print cooked-registers
37493 @kindex maint print register-groups
37494 @kindex maint print remote-registers
37495 @item maint print registers @r{[}@var{file}@r{]}
37496 @itemx maint print raw-registers @r{[}@var{file}@r{]}
37497 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
37498 @itemx maint print register-groups @r{[}@var{file}@r{]}
37499 @itemx maint print remote-registers @r{[}@var{file}@r{]}
37500 Print @value{GDBN}'s internal register data structures.
37502 The command @code{maint print raw-registers} includes the contents of
37503 the raw register cache; the command @code{maint print
37504 cooked-registers} includes the (cooked) value of all registers,
37505 including registers which aren't available on the target nor visible
37506 to user; the command @code{maint print register-groups} includes the
37507 groups that each register is a member of; and the command @code{maint
37508 print remote-registers} includes the remote target's register numbers
37509 and offsets in the `G' packets.
37511 These commands take an optional parameter, a file name to which to
37512 write the information.
37514 @kindex maint print reggroups
37515 @item maint print reggroups @r{[}@var{file}@r{]}
37516 Print @value{GDBN}'s internal register group data structures. The
37517 optional argument @var{file} tells to what file to write the
37520 The register groups info looks like this:
37523 (@value{GDBP}) @kbd{maint print reggroups}
37536 This command forces @value{GDBN} to flush its internal register cache.
37538 @kindex maint print objfiles
37539 @cindex info for known object files
37540 @item maint print objfiles @r{[}@var{regexp}@r{]}
37541 Print a dump of all known object files.
37542 If @var{regexp} is specified, only print object files whose names
37543 match @var{regexp}. For each object file, this command prints its name,
37544 address in memory, and all of its psymtabs and symtabs.
37546 @kindex maint print user-registers
37547 @cindex user registers
37548 @item maint print user-registers
37549 List all currently available @dfn{user registers}. User registers
37550 typically provide alternate names for actual hardware registers. They
37551 include the four ``standard'' registers @code{$fp}, @code{$pc},
37552 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
37553 registers can be used in expressions in the same way as the canonical
37554 register names, but only the latter are listed by the @code{info
37555 registers} and @code{maint print registers} commands.
37557 @kindex maint print section-scripts
37558 @cindex info for known .debug_gdb_scripts-loaded scripts
37559 @item maint print section-scripts [@var{regexp}]
37560 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
37561 If @var{regexp} is specified, only print scripts loaded by object files
37562 matching @var{regexp}.
37563 For each script, this command prints its name as specified in the objfile,
37564 and the full path if known.
37565 @xref{dotdebug_gdb_scripts section}.
37567 @kindex maint print statistics
37568 @cindex bcache statistics
37569 @item maint print statistics
37570 This command prints, for each object file in the program, various data
37571 about that object file followed by the byte cache (@dfn{bcache})
37572 statistics for the object file. The objfile data includes the number
37573 of minimal, partial, full, and stabs symbols, the number of types
37574 defined by the objfile, the number of as yet unexpanded psym tables,
37575 the number of line tables and string tables, and the amount of memory
37576 used by the various tables. The bcache statistics include the counts,
37577 sizes, and counts of duplicates of all and unique objects, max,
37578 average, and median entry size, total memory used and its overhead and
37579 savings, and various measures of the hash table size and chain
37582 @kindex maint print target-stack
37583 @cindex target stack description
37584 @item maint print target-stack
37585 A @dfn{target} is an interface between the debugger and a particular
37586 kind of file or process. Targets can be stacked in @dfn{strata},
37587 so that more than one target can potentially respond to a request.
37588 In particular, memory accesses will walk down the stack of targets
37589 until they find a target that is interested in handling that particular
37592 This command prints a short description of each layer that was pushed on
37593 the @dfn{target stack}, starting from the top layer down to the bottom one.
37595 @kindex maint print type
37596 @cindex type chain of a data type
37597 @item maint print type @var{expr}
37598 Print the type chain for a type specified by @var{expr}. The argument
37599 can be either a type name or a symbol. If it is a symbol, the type of
37600 that symbol is described. The type chain produced by this command is
37601 a recursive definition of the data type as stored in @value{GDBN}'s
37602 data structures, including its flags and contained types.
37604 @kindex maint selftest
37606 @item maint selftest @r{[}@var{filter}@r{]}
37607 Run any self tests that were compiled in to @value{GDBN}. This will
37608 print a message showing how many tests were run, and how many failed.
37609 If a @var{filter} is passed, only the tests with @var{filter} in their
37612 @kindex maint info selftests
37614 @item maint info selftests
37615 List the selftests compiled in to @value{GDBN}.
37617 @kindex maint set dwarf always-disassemble
37618 @kindex maint show dwarf always-disassemble
37619 @item maint set dwarf always-disassemble
37620 @item maint show dwarf always-disassemble
37621 Control the behavior of @code{info address} when using DWARF debugging
37624 The default is @code{off}, which means that @value{GDBN} should try to
37625 describe a variable's location in an easily readable format. When
37626 @code{on}, @value{GDBN} will instead display the DWARF location
37627 expression in an assembly-like format. Note that some locations are
37628 too complex for @value{GDBN} to describe simply; in this case you will
37629 always see the disassembly form.
37631 Here is an example of the resulting disassembly:
37634 (gdb) info addr argc
37635 Symbol "argc" is a complex DWARF expression:
37639 For more information on these expressions, see
37640 @uref{http://www.dwarfstd.org/, the DWARF standard}.
37642 @kindex maint set dwarf max-cache-age
37643 @kindex maint show dwarf max-cache-age
37644 @item maint set dwarf max-cache-age
37645 @itemx maint show dwarf max-cache-age
37646 Control the DWARF compilation unit cache.
37648 @cindex DWARF compilation units cache
37649 In object files with inter-compilation-unit references, such as those
37650 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF
37651 reader needs to frequently refer to previously read compilation units.
37652 This setting controls how long a compilation unit will remain in the
37653 cache if it is not referenced. A higher limit means that cached
37654 compilation units will be stored in memory longer, and more total
37655 memory will be used. Setting it to zero disables caching, which will
37656 slow down @value{GDBN} startup, but reduce memory consumption.
37658 @kindex maint set dwarf unwinders
37659 @kindex maint show dwarf unwinders
37660 @item maint set dwarf unwinders
37661 @itemx maint show dwarf unwinders
37662 Control use of the DWARF frame unwinders.
37664 @cindex DWARF frame unwinders
37665 Many targets that support DWARF debugging use @value{GDBN}'s DWARF
37666 frame unwinders to build the backtrace. Many of these targets will
37667 also have a second mechanism for building the backtrace for use in
37668 cases where DWARF information is not available, this second mechanism
37669 is often an analysis of a function's prologue.
37671 In order to extend testing coverage of the second level stack
37672 unwinding mechanisms it is helpful to be able to disable the DWARF
37673 stack unwinders, this can be done with this switch.
37675 In normal use of @value{GDBN} disabling the DWARF unwinders is not
37676 advisable, there are cases that are better handled through DWARF than
37677 prologue analysis, and the debug experience is likely to be better
37678 with the DWARF frame unwinders enabled.
37680 If DWARF frame unwinders are not supported for a particular target
37681 architecture, then enabling this flag does not cause them to be used.
37682 @kindex maint set profile
37683 @kindex maint show profile
37684 @cindex profiling GDB
37685 @item maint set profile
37686 @itemx maint show profile
37687 Control profiling of @value{GDBN}.
37689 Profiling will be disabled until you use the @samp{maint set profile}
37690 command to enable it. When you enable profiling, the system will begin
37691 collecting timing and execution count data; when you disable profiling or
37692 exit @value{GDBN}, the results will be written to a log file. Remember that
37693 if you use profiling, @value{GDBN} will overwrite the profiling log file
37694 (often called @file{gmon.out}). If you have a record of important profiling
37695 data in a @file{gmon.out} file, be sure to move it to a safe location.
37697 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
37698 compiled with the @samp{-pg} compiler option.
37700 @kindex maint set show-debug-regs
37701 @kindex maint show show-debug-regs
37702 @cindex hardware debug registers
37703 @item maint set show-debug-regs
37704 @itemx maint show show-debug-regs
37705 Control whether to show variables that mirror the hardware debug
37706 registers. Use @code{on} to enable, @code{off} to disable. If
37707 enabled, the debug registers values are shown when @value{GDBN} inserts or
37708 removes a hardware breakpoint or watchpoint, and when the inferior
37709 triggers a hardware-assisted breakpoint or watchpoint.
37711 @kindex maint set show-all-tib
37712 @kindex maint show show-all-tib
37713 @item maint set show-all-tib
37714 @itemx maint show show-all-tib
37715 Control whether to show all non zero areas within a 1k block starting
37716 at thread local base, when using the @samp{info w32 thread-information-block}
37719 @kindex maint set target-async
37720 @kindex maint show target-async
37721 @item maint set target-async
37722 @itemx maint show target-async
37723 This controls whether @value{GDBN} targets operate in synchronous or
37724 asynchronous mode (@pxref{Background Execution}). Normally the
37725 default is asynchronous, if it is available; but this can be changed
37726 to more easily debug problems occurring only in synchronous mode.
37728 @kindex maint set target-non-stop @var{mode} [on|off|auto]
37729 @kindex maint show target-non-stop
37730 @item maint set target-non-stop
37731 @itemx maint show target-non-stop
37733 This controls whether @value{GDBN} targets always operate in non-stop
37734 mode even if @code{set non-stop} is @code{off} (@pxref{Non-Stop
37735 Mode}). The default is @code{auto}, meaning non-stop mode is enabled
37736 if supported by the target.
37739 @item maint set target-non-stop auto
37740 This is the default mode. @value{GDBN} controls the target in
37741 non-stop mode if the target supports it.
37743 @item maint set target-non-stop on
37744 @value{GDBN} controls the target in non-stop mode even if the target
37745 does not indicate support.
37747 @item maint set target-non-stop off
37748 @value{GDBN} does not control the target in non-stop mode even if the
37749 target supports it.
37752 @kindex maint set per-command
37753 @kindex maint show per-command
37754 @item maint set per-command
37755 @itemx maint show per-command
37756 @cindex resources used by commands
37758 @value{GDBN} can display the resources used by each command.
37759 This is useful in debugging performance problems.
37762 @item maint set per-command space [on|off]
37763 @itemx maint show per-command space
37764 Enable or disable the printing of the memory used by GDB for each command.
37765 If enabled, @value{GDBN} will display how much memory each command
37766 took, following the command's own output.
37767 This can also be requested by invoking @value{GDBN} with the
37768 @option{--statistics} command-line switch (@pxref{Mode Options}).
37770 @item maint set per-command time [on|off]
37771 @itemx maint show per-command time
37772 Enable or disable the printing of the execution time of @value{GDBN}
37774 If enabled, @value{GDBN} will display how much time it
37775 took to execute each command, following the command's own output.
37776 Both CPU time and wallclock time are printed.
37777 Printing both is useful when trying to determine whether the cost is
37778 CPU or, e.g., disk/network latency.
37779 Note that the CPU time printed is for @value{GDBN} only, it does not include
37780 the execution time of the inferior because there's no mechanism currently
37781 to compute how much time was spent by @value{GDBN} and how much time was
37782 spent by the program been debugged.
37783 This can also be requested by invoking @value{GDBN} with the
37784 @option{--statistics} command-line switch (@pxref{Mode Options}).
37786 @item maint set per-command symtab [on|off]
37787 @itemx maint show per-command symtab
37788 Enable or disable the printing of basic symbol table statistics
37790 If enabled, @value{GDBN} will display the following information:
37794 number of symbol tables
37796 number of primary symbol tables
37798 number of blocks in the blockvector
37802 @kindex maint set check-libthread-db
37803 @kindex maint show check-libthread-db
37804 @item maint set check-libthread-db [on|off]
37805 @itemx maint show check-libthread-db
37806 Control whether @value{GDBN} should run integrity checks on inferior
37807 specific thread debugging libraries as they are loaded. The default
37808 is not to perform such checks. If any check fails @value{GDBN} will
37809 unload the library and continue searching for a suitable candidate as
37810 described in @ref{set libthread-db-search-path}. For more information
37811 about the tests, see @ref{maint check libthread-db}.
37813 @kindex maint space
37814 @cindex memory used by commands
37815 @item maint space @var{value}
37816 An alias for @code{maint set per-command space}.
37817 A non-zero value enables it, zero disables it.
37820 @cindex time of command execution
37821 @item maint time @var{value}
37822 An alias for @code{maint set per-command time}.
37823 A non-zero value enables it, zero disables it.
37825 @kindex maint translate-address
37826 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
37827 Find the symbol stored at the location specified by the address
37828 @var{addr} and an optional section name @var{section}. If found,
37829 @value{GDBN} prints the name of the closest symbol and an offset from
37830 the symbol's location to the specified address. This is similar to
37831 the @code{info address} command (@pxref{Symbols}), except that this
37832 command also allows to find symbols in other sections.
37834 If section was not specified, the section in which the symbol was found
37835 is also printed. For dynamically linked executables, the name of
37836 executable or shared library containing the symbol is printed as well.
37838 @kindex maint test-options
37839 @item maint test-options require-delimiter
37840 @itemx maint test-options unknown-is-error
37841 @itemx maint test-options unknown-is-operand
37842 These commands are used by the testsuite to validate the command
37843 options framework. The @code{require-delimiter} variant requires a
37844 double-dash delimiter to indicate end of options. The
37845 @code{unknown-is-error} and @code{unknown-is-operand} do not. The
37846 @code{unknown-is-error} variant throws an error on unknown option,
37847 while @code{unknown-is-operand} treats unknown options as the start of
37848 the command's operands. When run, the commands output the result of
37849 the processed options. When completed, the commands store the
37850 internal result of completion in a variable exposed by the @code{maint
37851 show test-options-completion-result} command.
37853 @kindex maint show test-options-completion-result
37854 @item maint show test-options-completion-result
37855 Shows the result of completing the @code{maint test-options}
37856 subcommands. This is used by the testsuite to validate completion
37857 support in the command options framework.
37859 @kindex maint set test-settings
37860 @kindex maint show test-settings
37861 @item maint set test-settings @var{kind}
37862 @itemx maint show test-settings @var{kind}
37863 These are representative commands for each @var{kind} of setting type
37864 @value{GDBN} supports. They are used by the testsuite for exercising
37865 the settings infrastructure.
37868 @item maint with @var{setting} [@var{value}] [-- @var{command}]
37869 Like the @code{with} command, but works with @code{maintenance set}
37870 variables. This is used by the testsuite to exercise the @code{with}
37871 command's infrastructure.
37875 The following command is useful for non-interactive invocations of
37876 @value{GDBN}, such as in the test suite.
37879 @item set watchdog @var{nsec}
37880 @kindex set watchdog
37881 @cindex watchdog timer
37882 @cindex timeout for commands
37883 Set the maximum number of seconds @value{GDBN} will wait for the
37884 target operation to finish. If this time expires, @value{GDBN}
37885 reports and error and the command is aborted.
37887 @item show watchdog
37888 Show the current setting of the target wait timeout.
37891 @node Remote Protocol
37892 @appendix @value{GDBN} Remote Serial Protocol
37897 * Stop Reply Packets::
37898 * General Query Packets::
37899 * Architecture-Specific Protocol Details::
37900 * Tracepoint Packets::
37901 * Host I/O Packets::
37903 * Notification Packets::
37904 * Remote Non-Stop::
37905 * Packet Acknowledgment::
37907 * File-I/O Remote Protocol Extension::
37908 * Library List Format::
37909 * Library List Format for SVR4 Targets::
37910 * Memory Map Format::
37911 * Thread List Format::
37912 * Traceframe Info Format::
37913 * Branch Trace Format::
37914 * Branch Trace Configuration Format::
37920 There may be occasions when you need to know something about the
37921 protocol---for example, if there is only one serial port to your target
37922 machine, you might want your program to do something special if it
37923 recognizes a packet meant for @value{GDBN}.
37925 In the examples below, @samp{->} and @samp{<-} are used to indicate
37926 transmitted and received data, respectively.
37928 @cindex protocol, @value{GDBN} remote serial
37929 @cindex serial protocol, @value{GDBN} remote
37930 @cindex remote serial protocol
37931 All @value{GDBN} commands and responses (other than acknowledgments
37932 and notifications, see @ref{Notification Packets}) are sent as a
37933 @var{packet}. A @var{packet} is introduced with the character
37934 @samp{$}, the actual @var{packet-data}, and the terminating character
37935 @samp{#} followed by a two-digit @var{checksum}:
37938 @code{$}@var{packet-data}@code{#}@var{checksum}
37942 @cindex checksum, for @value{GDBN} remote
37944 The two-digit @var{checksum} is computed as the modulo 256 sum of all
37945 characters between the leading @samp{$} and the trailing @samp{#} (an
37946 eight bit unsigned checksum).
37948 Implementors should note that prior to @value{GDBN} 5.0 the protocol
37949 specification also included an optional two-digit @var{sequence-id}:
37952 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
37955 @cindex sequence-id, for @value{GDBN} remote
37957 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
37958 has never output @var{sequence-id}s. Stubs that handle packets added
37959 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
37961 When either the host or the target machine receives a packet, the first
37962 response expected is an acknowledgment: either @samp{+} (to indicate
37963 the package was received correctly) or @samp{-} (to request
37967 -> @code{$}@var{packet-data}@code{#}@var{checksum}
37972 The @samp{+}/@samp{-} acknowledgments can be disabled
37973 once a connection is established.
37974 @xref{Packet Acknowledgment}, for details.
37976 The host (@value{GDBN}) sends @var{command}s, and the target (the
37977 debugging stub incorporated in your program) sends a @var{response}. In
37978 the case of step and continue @var{command}s, the response is only sent
37979 when the operation has completed, and the target has again stopped all
37980 threads in all attached processes. This is the default all-stop mode
37981 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
37982 execution mode; see @ref{Remote Non-Stop}, for details.
37984 @var{packet-data} consists of a sequence of characters with the
37985 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
37988 @cindex remote protocol, field separator
37989 Fields within the packet should be separated using @samp{,} @samp{;} or
37990 @samp{:}. Except where otherwise noted all numbers are represented in
37991 @sc{hex} with leading zeros suppressed.
37993 Implementors should note that prior to @value{GDBN} 5.0, the character
37994 @samp{:} could not appear as the third character in a packet (as it
37995 would potentially conflict with the @var{sequence-id}).
37997 @cindex remote protocol, binary data
37998 @anchor{Binary Data}
37999 Binary data in most packets is encoded either as two hexadecimal
38000 digits per byte of binary data. This allowed the traditional remote
38001 protocol to work over connections which were only seven-bit clean.
38002 Some packets designed more recently assume an eight-bit clean
38003 connection, and use a more efficient encoding to send and receive
38006 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
38007 as an escape character. Any escaped byte is transmitted as the escape
38008 character followed by the original character XORed with @code{0x20}.
38009 For example, the byte @code{0x7d} would be transmitted as the two
38010 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
38011 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
38012 @samp{@}}) must always be escaped. Responses sent by the stub
38013 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
38014 is not interpreted as the start of a run-length encoded sequence
38017 Response @var{data} can be run-length encoded to save space.
38018 Run-length encoding replaces runs of identical characters with one
38019 instance of the repeated character, followed by a @samp{*} and a
38020 repeat count. The repeat count is itself sent encoded, to avoid
38021 binary characters in @var{data}: a value of @var{n} is sent as
38022 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
38023 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
38024 code 32) for a repeat count of 3. (This is because run-length
38025 encoding starts to win for counts 3 or more.) Thus, for example,
38026 @samp{0* } is a run-length encoding of ``0000'': the space character
38027 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
38030 The printable characters @samp{#} and @samp{$} or with a numeric value
38031 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
38032 seven repeats (@samp{$}) can be expanded using a repeat count of only
38033 five (@samp{"}). For example, @samp{00000000} can be encoded as
38036 The error response returned for some packets includes a two character
38037 error number. That number is not well defined.
38039 @cindex empty response, for unsupported packets
38040 For any @var{command} not supported by the stub, an empty response
38041 (@samp{$#00}) should be returned. That way it is possible to extend the
38042 protocol. A newer @value{GDBN} can tell if a packet is supported based
38045 At a minimum, a stub is required to support the @samp{g} and @samp{G}
38046 commands for register access, and the @samp{m} and @samp{M} commands
38047 for memory access. Stubs that only control single-threaded targets
38048 can implement run control with the @samp{c} (continue), and @samp{s}
38049 (step) commands. Stubs that support multi-threading targets should
38050 support the @samp{vCont} command. All other commands are optional.
38055 The following table provides a complete list of all currently defined
38056 @var{command}s and their corresponding response @var{data}.
38057 @xref{File-I/O Remote Protocol Extension}, for details about the File
38058 I/O extension of the remote protocol.
38060 Each packet's description has a template showing the packet's overall
38061 syntax, followed by an explanation of the packet's meaning. We
38062 include spaces in some of the templates for clarity; these are not
38063 part of the packet's syntax. No @value{GDBN} packet uses spaces to
38064 separate its components. For example, a template like @samp{foo
38065 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
38066 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
38067 @var{baz}. @value{GDBN} does not transmit a space character between the
38068 @samp{foo} and the @var{bar}, or between the @var{bar} and the
38071 @cindex @var{thread-id}, in remote protocol
38072 @anchor{thread-id syntax}
38073 Several packets and replies include a @var{thread-id} field to identify
38074 a thread. Normally these are positive numbers with a target-specific
38075 interpretation, formatted as big-endian hex strings. A @var{thread-id}
38076 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
38079 In addition, the remote protocol supports a multiprocess feature in
38080 which the @var{thread-id} syntax is extended to optionally include both
38081 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
38082 The @var{pid} (process) and @var{tid} (thread) components each have the
38083 format described above: a positive number with target-specific
38084 interpretation formatted as a big-endian hex string, literal @samp{-1}
38085 to indicate all processes or threads (respectively), or @samp{0} to
38086 indicate an arbitrary process or thread. Specifying just a process, as
38087 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
38088 error to specify all processes but a specific thread, such as
38089 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
38090 for those packets and replies explicitly documented to include a process
38091 ID, rather than a @var{thread-id}.
38093 The multiprocess @var{thread-id} syntax extensions are only used if both
38094 @value{GDBN} and the stub report support for the @samp{multiprocess}
38095 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
38098 Note that all packet forms beginning with an upper- or lower-case
38099 letter, other than those described here, are reserved for future use.
38101 Here are the packet descriptions.
38106 @cindex @samp{!} packet
38107 @anchor{extended mode}
38108 Enable extended mode. In extended mode, the remote server is made
38109 persistent. The @samp{R} packet is used to restart the program being
38115 The remote target both supports and has enabled extended mode.
38119 @cindex @samp{?} packet
38121 Indicate the reason the target halted. The reply is the same as for
38122 step and continue. This packet has a special interpretation when the
38123 target is in non-stop mode; see @ref{Remote Non-Stop}.
38126 @xref{Stop Reply Packets}, for the reply specifications.
38128 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
38129 @cindex @samp{A} packet
38130 Initialized @code{argv[]} array passed into program. @var{arglen}
38131 specifies the number of bytes in the hex encoded byte stream
38132 @var{arg}. See @code{gdbserver} for more details.
38137 The arguments were set.
38143 @cindex @samp{b} packet
38144 (Don't use this packet; its behavior is not well-defined.)
38145 Change the serial line speed to @var{baud}.
38147 JTC: @emph{When does the transport layer state change? When it's
38148 received, or after the ACK is transmitted. In either case, there are
38149 problems if the command or the acknowledgment packet is dropped.}
38151 Stan: @emph{If people really wanted to add something like this, and get
38152 it working for the first time, they ought to modify ser-unix.c to send
38153 some kind of out-of-band message to a specially-setup stub and have the
38154 switch happen "in between" packets, so that from remote protocol's point
38155 of view, nothing actually happened.}
38157 @item B @var{addr},@var{mode}
38158 @cindex @samp{B} packet
38159 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
38160 breakpoint at @var{addr}.
38162 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
38163 (@pxref{insert breakpoint or watchpoint packet}).
38165 @cindex @samp{bc} packet
38168 Backward continue. Execute the target system in reverse. No parameter.
38169 @xref{Reverse Execution}, for more information.
38172 @xref{Stop Reply Packets}, for the reply specifications.
38174 @cindex @samp{bs} packet
38177 Backward single step. Execute one instruction in reverse. No parameter.
38178 @xref{Reverse Execution}, for more information.
38181 @xref{Stop Reply Packets}, for the reply specifications.
38183 @item c @r{[}@var{addr}@r{]}
38184 @cindex @samp{c} packet
38185 Continue at @var{addr}, which is the address to resume. If @var{addr}
38186 is omitted, resume at current address.
38188 This packet is deprecated for multi-threading support. @xref{vCont
38192 @xref{Stop Reply Packets}, for the reply specifications.
38194 @item C @var{sig}@r{[};@var{addr}@r{]}
38195 @cindex @samp{C} packet
38196 Continue with signal @var{sig} (hex signal number). If
38197 @samp{;@var{addr}} is omitted, resume at same address.
38199 This packet is deprecated for multi-threading support. @xref{vCont
38203 @xref{Stop Reply Packets}, for the reply specifications.
38206 @cindex @samp{d} packet
38209 Don't use this packet; instead, define a general set packet
38210 (@pxref{General Query Packets}).
38214 @cindex @samp{D} packet
38215 The first form of the packet is used to detach @value{GDBN} from the
38216 remote system. It is sent to the remote target
38217 before @value{GDBN} disconnects via the @code{detach} command.
38219 The second form, including a process ID, is used when multiprocess
38220 protocol extensions are enabled (@pxref{multiprocess extensions}), to
38221 detach only a specific process. The @var{pid} is specified as a
38222 big-endian hex string.
38232 @item F @var{RC},@var{EE},@var{CF};@var{XX}
38233 @cindex @samp{F} packet
38234 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
38235 This is part of the File-I/O protocol extension. @xref{File-I/O
38236 Remote Protocol Extension}, for the specification.
38239 @anchor{read registers packet}
38240 @cindex @samp{g} packet
38241 Read general registers.
38245 @item @var{XX@dots{}}
38246 Each byte of register data is described by two hex digits. The bytes
38247 with the register are transmitted in target byte order. The size of
38248 each register and their position within the @samp{g} packet are
38249 determined by the @value{GDBN} internal gdbarch functions
38250 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}.
38252 When reading registers from a trace frame (@pxref{Analyze Collected
38253 Data,,Using the Collected Data}), the stub may also return a string of
38254 literal @samp{x}'s in place of the register data digits, to indicate
38255 that the corresponding register has not been collected, thus its value
38256 is unavailable. For example, for an architecture with 4 registers of
38257 4 bytes each, the following reply indicates to @value{GDBN} that
38258 registers 0 and 2 have not been collected, while registers 1 and 3
38259 have been collected, and both have zero value:
38263 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
38270 @item G @var{XX@dots{}}
38271 @cindex @samp{G} packet
38272 Write general registers. @xref{read registers packet}, for a
38273 description of the @var{XX@dots{}} data.
38283 @item H @var{op} @var{thread-id}
38284 @cindex @samp{H} packet
38285 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
38286 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
38287 should be @samp{c} for step and continue operations (note that this
38288 is deprecated, supporting the @samp{vCont} command is a better
38289 option), and @samp{g} for other operations. The thread designator
38290 @var{thread-id} has the format and interpretation described in
38291 @ref{thread-id syntax}.
38302 @c 'H': How restrictive (or permissive) is the thread model. If a
38303 @c thread is selected and stopped, are other threads allowed
38304 @c to continue to execute? As I mentioned above, I think the
38305 @c semantics of each command when a thread is selected must be
38306 @c described. For example:
38308 @c 'g': If the stub supports threads and a specific thread is
38309 @c selected, returns the register block from that thread;
38310 @c otherwise returns current registers.
38312 @c 'G' If the stub supports threads and a specific thread is
38313 @c selected, sets the registers of the register block of
38314 @c that thread; otherwise sets current registers.
38316 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
38317 @anchor{cycle step packet}
38318 @cindex @samp{i} packet
38319 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
38320 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
38321 step starting at that address.
38324 @cindex @samp{I} packet
38325 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
38329 @cindex @samp{k} packet
38332 The exact effect of this packet is not specified.
38334 For a bare-metal target, it may power cycle or reset the target
38335 system. For that reason, the @samp{k} packet has no reply.
38337 For a single-process target, it may kill that process if possible.
38339 A multiple-process target may choose to kill just one process, or all
38340 that are under @value{GDBN}'s control. For more precise control, use
38341 the vKill packet (@pxref{vKill packet}).
38343 If the target system immediately closes the connection in response to
38344 @samp{k}, @value{GDBN} does not consider the lack of packet
38345 acknowledgment to be an error, and assumes the kill was successful.
38347 If connected using @kbd{target extended-remote}, and the target does
38348 not close the connection in response to a kill request, @value{GDBN}
38349 probes the target state as if a new connection was opened
38350 (@pxref{? packet}).
38352 @item m @var{addr},@var{length}
38353 @cindex @samp{m} packet
38354 Read @var{length} addressable memory units starting at address @var{addr}
38355 (@pxref{addressable memory unit}). Note that @var{addr} may not be aligned to
38356 any particular boundary.
38358 The stub need not use any particular size or alignment when gathering
38359 data from memory for the response; even if @var{addr} is word-aligned
38360 and @var{length} is a multiple of the word size, the stub is free to
38361 use byte accesses, or not. For this reason, this packet may not be
38362 suitable for accessing memory-mapped I/O devices.
38363 @cindex alignment of remote memory accesses
38364 @cindex size of remote memory accesses
38365 @cindex memory, alignment and size of remote accesses
38369 @item @var{XX@dots{}}
38370 Memory contents; each byte is transmitted as a two-digit hexadecimal number.
38371 The reply may contain fewer addressable memory units than requested if the
38372 server was able to read only part of the region of memory.
38377 @item M @var{addr},@var{length}:@var{XX@dots{}}
38378 @cindex @samp{M} packet
38379 Write @var{length} addressable memory units starting at address @var{addr}
38380 (@pxref{addressable memory unit}). The data is given by @var{XX@dots{}}; each
38381 byte is transmitted as a two-digit hexadecimal number.
38388 for an error (this includes the case where only part of the data was
38393 @cindex @samp{p} packet
38394 Read the value of register @var{n}; @var{n} is in hex.
38395 @xref{read registers packet}, for a description of how the returned
38396 register value is encoded.
38400 @item @var{XX@dots{}}
38401 the register's value
38405 Indicating an unrecognized @var{query}.
38408 @item P @var{n@dots{}}=@var{r@dots{}}
38409 @anchor{write register packet}
38410 @cindex @samp{P} packet
38411 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
38412 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
38413 digits for each byte in the register (target byte order).
38423 @item q @var{name} @var{params}@dots{}
38424 @itemx Q @var{name} @var{params}@dots{}
38425 @cindex @samp{q} packet
38426 @cindex @samp{Q} packet
38427 General query (@samp{q}) and set (@samp{Q}). These packets are
38428 described fully in @ref{General Query Packets}.
38431 @cindex @samp{r} packet
38432 Reset the entire system.
38434 Don't use this packet; use the @samp{R} packet instead.
38437 @cindex @samp{R} packet
38438 Restart the program being debugged. The @var{XX}, while needed, is ignored.
38439 This packet is only available in extended mode (@pxref{extended mode}).
38441 The @samp{R} packet has no reply.
38443 @item s @r{[}@var{addr}@r{]}
38444 @cindex @samp{s} packet
38445 Single step, resuming at @var{addr}. If
38446 @var{addr} is omitted, resume at same address.
38448 This packet is deprecated for multi-threading support. @xref{vCont
38452 @xref{Stop Reply Packets}, for the reply specifications.
38454 @item S @var{sig}@r{[};@var{addr}@r{]}
38455 @anchor{step with signal packet}
38456 @cindex @samp{S} packet
38457 Step with signal. This is analogous to the @samp{C} packet, but
38458 requests a single-step, rather than a normal resumption of execution.
38460 This packet is deprecated for multi-threading support. @xref{vCont
38464 @xref{Stop Reply Packets}, for the reply specifications.
38466 @item t @var{addr}:@var{PP},@var{MM}
38467 @cindex @samp{t} packet
38468 Search backwards starting at address @var{addr} for a match with pattern
38469 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
38470 There must be at least 3 digits in @var{addr}.
38472 @item T @var{thread-id}
38473 @cindex @samp{T} packet
38474 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
38479 thread is still alive
38485 Packets starting with @samp{v} are identified by a multi-letter name,
38486 up to the first @samp{;} or @samp{?} (or the end of the packet).
38488 @item vAttach;@var{pid}
38489 @cindex @samp{vAttach} packet
38490 Attach to a new process with the specified process ID @var{pid}.
38491 The process ID is a
38492 hexadecimal integer identifying the process. In all-stop mode, all
38493 threads in the attached process are stopped; in non-stop mode, it may be
38494 attached without being stopped if that is supported by the target.
38496 @c In non-stop mode, on a successful vAttach, the stub should set the
38497 @c current thread to a thread of the newly-attached process. After
38498 @c attaching, GDB queries for the attached process's thread ID with qC.
38499 @c Also note that, from a user perspective, whether or not the
38500 @c target is stopped on attach in non-stop mode depends on whether you
38501 @c use the foreground or background version of the attach command, not
38502 @c on what vAttach does; GDB does the right thing with respect to either
38503 @c stopping or restarting threads.
38505 This packet is only available in extended mode (@pxref{extended mode}).
38511 @item @r{Any stop packet}
38512 for success in all-stop mode (@pxref{Stop Reply Packets})
38514 for success in non-stop mode (@pxref{Remote Non-Stop})
38517 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
38518 @cindex @samp{vCont} packet
38519 @anchor{vCont packet}
38520 Resume the inferior, specifying different actions for each thread.
38522 For each inferior thread, the leftmost action with a matching
38523 @var{thread-id} is applied. Threads that don't match any action
38524 remain in their current state. Thread IDs are specified using the
38525 syntax described in @ref{thread-id syntax}. If multiprocess
38526 extensions (@pxref{multiprocess extensions}) are supported, actions
38527 can be specified to match all threads in a process by using the
38528 @samp{p@var{pid}.-1} form of the @var{thread-id}. An action with no
38529 @var{thread-id} matches all threads. Specifying no actions is an
38532 Currently supported actions are:
38538 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
38542 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
38545 @item r @var{start},@var{end}
38546 Step once, and then keep stepping as long as the thread stops at
38547 addresses between @var{start} (inclusive) and @var{end} (exclusive).
38548 The remote stub reports a stop reply when either the thread goes out
38549 of the range or is stopped due to an unrelated reason, such as hitting
38550 a breakpoint. @xref{range stepping}.
38552 If the range is empty (@var{start} == @var{end}), then the action
38553 becomes equivalent to the @samp{s} action. In other words,
38554 single-step once, and report the stop (even if the stepped instruction
38555 jumps to @var{start}).
38557 (A stop reply may be sent at any point even if the PC is still within
38558 the stepping range; for example, it is valid to implement this packet
38559 in a degenerate way as a single instruction step operation.)
38563 The optional argument @var{addr} normally associated with the
38564 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
38565 not supported in @samp{vCont}.
38567 The @samp{t} action is only relevant in non-stop mode
38568 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
38569 A stop reply should be generated for any affected thread not already stopped.
38570 When a thread is stopped by means of a @samp{t} action,
38571 the corresponding stop reply should indicate that the thread has stopped with
38572 signal @samp{0}, regardless of whether the target uses some other signal
38573 as an implementation detail.
38575 The server must ignore @samp{c}, @samp{C}, @samp{s}, @samp{S}, and
38576 @samp{r} actions for threads that are already running. Conversely,
38577 the server must ignore @samp{t} actions for threads that are already
38580 @emph{Note:} In non-stop mode, a thread is considered running until
38581 @value{GDBN} acknowleges an asynchronous stop notification for it with
38582 the @samp{vStopped} packet (@pxref{Remote Non-Stop}).
38584 The stub must support @samp{vCont} if it reports support for
38585 multiprocess extensions (@pxref{multiprocess extensions}).
38588 @xref{Stop Reply Packets}, for the reply specifications.
38591 @cindex @samp{vCont?} packet
38592 Request a list of actions supported by the @samp{vCont} packet.
38596 @item vCont@r{[};@var{action}@dots{}@r{]}
38597 The @samp{vCont} packet is supported. Each @var{action} is a supported
38598 command in the @samp{vCont} packet.
38600 The @samp{vCont} packet is not supported.
38603 @anchor{vCtrlC packet}
38605 @cindex @samp{vCtrlC} packet
38606 Interrupt remote target as if a control-C was pressed on the remote
38607 terminal. This is the equivalent to reacting to the @code{^C}
38608 (@samp{\003}, the control-C character) character in all-stop mode
38609 while the target is running, except this works in non-stop mode.
38610 @xref{interrupting remote targets}, for more info on the all-stop
38621 @item vFile:@var{operation}:@var{parameter}@dots{}
38622 @cindex @samp{vFile} packet
38623 Perform a file operation on the target system. For details,
38624 see @ref{Host I/O Packets}.
38626 @item vFlashErase:@var{addr},@var{length}
38627 @cindex @samp{vFlashErase} packet
38628 Direct the stub to erase @var{length} bytes of flash starting at
38629 @var{addr}. The region may enclose any number of flash blocks, but
38630 its start and end must fall on block boundaries, as indicated by the
38631 flash block size appearing in the memory map (@pxref{Memory Map
38632 Format}). @value{GDBN} groups flash memory programming operations
38633 together, and sends a @samp{vFlashDone} request after each group; the
38634 stub is allowed to delay erase operation until the @samp{vFlashDone}
38635 packet is received.
38645 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
38646 @cindex @samp{vFlashWrite} packet
38647 Direct the stub to write data to flash address @var{addr}. The data
38648 is passed in binary form using the same encoding as for the @samp{X}
38649 packet (@pxref{Binary Data}). The memory ranges specified by
38650 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
38651 not overlap, and must appear in order of increasing addresses
38652 (although @samp{vFlashErase} packets for higher addresses may already
38653 have been received; the ordering is guaranteed only between
38654 @samp{vFlashWrite} packets). If a packet writes to an address that was
38655 neither erased by a preceding @samp{vFlashErase} packet nor by some other
38656 target-specific method, the results are unpredictable.
38664 for vFlashWrite addressing non-flash memory
38670 @cindex @samp{vFlashDone} packet
38671 Indicate to the stub that flash programming operation is finished.
38672 The stub is permitted to delay or batch the effects of a group of
38673 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
38674 @samp{vFlashDone} packet is received. The contents of the affected
38675 regions of flash memory are unpredictable until the @samp{vFlashDone}
38676 request is completed.
38678 @item vKill;@var{pid}
38679 @cindex @samp{vKill} packet
38680 @anchor{vKill packet}
38681 Kill the process with the specified process ID @var{pid}, which is a
38682 hexadecimal integer identifying the process. This packet is used in
38683 preference to @samp{k} when multiprocess protocol extensions are
38684 supported; see @ref{multiprocess extensions}.
38694 @item vMustReplyEmpty
38695 @cindex @samp{vMustReplyEmpty} packet
38696 The correct reply to an unknown @samp{v} packet is to return the empty
38697 string, however, some older versions of @command{gdbserver} would
38698 incorrectly return @samp{OK} for unknown @samp{v} packets.
38700 The @samp{vMustReplyEmpty} is used as a feature test to check how
38701 @command{gdbserver} handles unknown packets, it is important that this
38702 packet be handled in the same way as other unknown @samp{v} packets.
38703 If this packet is handled differently to other unknown @samp{v}
38704 packets then it is possile that @value{GDBN} may run into problems in
38705 other areas, specifically around use of @samp{vFile:setfs:}.
38707 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
38708 @cindex @samp{vRun} packet
38709 Run the program @var{filename}, passing it each @var{argument} on its
38710 command line. The file and arguments are hex-encoded strings. If
38711 @var{filename} is an empty string, the stub may use a default program
38712 (e.g.@: the last program run). The program is created in the stopped
38715 @c FIXME: What about non-stop mode?
38717 This packet is only available in extended mode (@pxref{extended mode}).
38723 @item @r{Any stop packet}
38724 for success (@pxref{Stop Reply Packets})
38728 @cindex @samp{vStopped} packet
38729 @xref{Notification Packets}.
38731 @item X @var{addr},@var{length}:@var{XX@dots{}}
38733 @cindex @samp{X} packet
38734 Write data to memory, where the data is transmitted in binary.
38735 Memory is specified by its address @var{addr} and number of addressable memory
38736 units @var{length} (@pxref{addressable memory unit});
38737 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
38747 @item z @var{type},@var{addr},@var{kind}
38748 @itemx Z @var{type},@var{addr},@var{kind}
38749 @anchor{insert breakpoint or watchpoint packet}
38750 @cindex @samp{z} packet
38751 @cindex @samp{Z} packets
38752 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
38753 watchpoint starting at address @var{address} of kind @var{kind}.
38755 Each breakpoint and watchpoint packet @var{type} is documented
38758 @emph{Implementation notes: A remote target shall return an empty string
38759 for an unrecognized breakpoint or watchpoint packet @var{type}. A
38760 remote target shall support either both or neither of a given
38761 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
38762 avoid potential problems with duplicate packets, the operations should
38763 be implemented in an idempotent way.}
38765 @item z0,@var{addr},@var{kind}
38766 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
38767 @cindex @samp{z0} packet
38768 @cindex @samp{Z0} packet
38769 Insert (@samp{Z0}) or remove (@samp{z0}) a software breakpoint at address
38770 @var{addr} of type @var{kind}.
38772 A software breakpoint is implemented by replacing the instruction at
38773 @var{addr} with a software breakpoint or trap instruction. The
38774 @var{kind} is target-specific and typically indicates the size of the
38775 breakpoint in bytes that should be inserted. E.g., the @sc{arm} and
38776 @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
38777 architectures have additional meanings for @var{kind}
38778 (@pxref{Architecture-Specific Protocol Details}); if no
38779 architecture-specific value is being used, it should be @samp{0}.
38780 @var{kind} is hex-encoded. @var{cond_list} is an optional list of
38781 conditional expressions in bytecode form that should be evaluated on
38782 the target's side. These are the conditions that should be taken into
38783 consideration when deciding if the breakpoint trigger should be
38784 reported back to @value{GDBN}.
38786 See also the @samp{swbreak} stop reason (@pxref{swbreak stop reason})
38787 for how to best report a software breakpoint event to @value{GDBN}.
38789 The @var{cond_list} parameter is comprised of a series of expressions,
38790 concatenated without separators. Each expression has the following form:
38794 @item X @var{len},@var{expr}
38795 @var{len} is the length of the bytecode expression and @var{expr} is the
38796 actual conditional expression in bytecode form.
38800 The optional @var{cmd_list} parameter introduces commands that may be
38801 run on the target, rather than being reported back to @value{GDBN}.
38802 The parameter starts with a numeric flag @var{persist}; if the flag is
38803 nonzero, then the breakpoint may remain active and the commands
38804 continue to be run even when @value{GDBN} disconnects from the target.
38805 Following this flag is a series of expressions concatenated with no
38806 separators. Each expression has the following form:
38810 @item X @var{len},@var{expr}
38811 @var{len} is the length of the bytecode expression and @var{expr} is the
38812 actual commands expression in bytecode form.
38816 @emph{Implementation note: It is possible for a target to copy or move
38817 code that contains software breakpoints (e.g., when implementing
38818 overlays). The behavior of this packet, in the presence of such a
38819 target, is not defined.}
38831 @item z1,@var{addr},@var{kind}
38832 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
38833 @cindex @samp{z1} packet
38834 @cindex @samp{Z1} packet
38835 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
38836 address @var{addr}.
38838 A hardware breakpoint is implemented using a mechanism that is not
38839 dependent on being able to modify the target's memory. The
38840 @var{kind}, @var{cond_list}, and @var{cmd_list} arguments have the
38841 same meaning as in @samp{Z0} packets.
38843 @emph{Implementation note: A hardware breakpoint is not affected by code
38856 @item z2,@var{addr},@var{kind}
38857 @itemx Z2,@var{addr},@var{kind}
38858 @cindex @samp{z2} packet
38859 @cindex @samp{Z2} packet
38860 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
38861 The number of bytes to watch is specified by @var{kind}.
38873 @item z3,@var{addr},@var{kind}
38874 @itemx Z3,@var{addr},@var{kind}
38875 @cindex @samp{z3} packet
38876 @cindex @samp{Z3} packet
38877 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
38878 The number of bytes to watch is specified by @var{kind}.
38890 @item z4,@var{addr},@var{kind}
38891 @itemx Z4,@var{addr},@var{kind}
38892 @cindex @samp{z4} packet
38893 @cindex @samp{Z4} packet
38894 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
38895 The number of bytes to watch is specified by @var{kind}.
38909 @node Stop Reply Packets
38910 @section Stop Reply Packets
38911 @cindex stop reply packets
38913 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
38914 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
38915 receive any of the below as a reply. Except for @samp{?}
38916 and @samp{vStopped}, that reply is only returned
38917 when the target halts. In the below the exact meaning of @dfn{signal
38918 number} is defined by the header @file{include/gdb/signals.h} in the
38919 @value{GDBN} source code.
38921 In non-stop mode, the server will simply reply @samp{OK} to commands
38922 such as @samp{vCont}; any stop will be the subject of a future
38923 notification. @xref{Remote Non-Stop}.
38925 As in the description of request packets, we include spaces in the
38926 reply templates for clarity; these are not part of the reply packet's
38927 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
38933 The program received signal number @var{AA} (a two-digit hexadecimal
38934 number). This is equivalent to a @samp{T} response with no
38935 @var{n}:@var{r} pairs.
38937 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
38938 @cindex @samp{T} packet reply
38939 The program received signal number @var{AA} (a two-digit hexadecimal
38940 number). This is equivalent to an @samp{S} response, except that the
38941 @samp{@var{n}:@var{r}} pairs can carry values of important registers
38942 and other information directly in the stop reply packet, reducing
38943 round-trip latency. Single-step and breakpoint traps are reported
38944 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
38948 If @var{n} is a hexadecimal number, it is a register number, and the
38949 corresponding @var{r} gives that register's value. The data @var{r} is a
38950 series of bytes in target byte order, with each byte given by a
38951 two-digit hex number.
38954 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
38955 the stopped thread, as specified in @ref{thread-id syntax}.
38958 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
38959 the core on which the stop event was detected.
38962 If @var{n} is a recognized @dfn{stop reason}, it describes a more
38963 specific event that stopped the target. The currently defined stop
38964 reasons are listed below. The @var{aa} should be @samp{05}, the trap
38965 signal. At most one stop reason should be present.
38968 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
38969 and go on to the next; this allows us to extend the protocol in the
38973 The currently defined stop reasons are:
38979 The packet indicates a watchpoint hit, and @var{r} is the data address, in
38982 @item syscall_entry
38983 @itemx syscall_return
38984 The packet indicates a syscall entry or return, and @var{r} is the
38985 syscall number, in hex.
38987 @cindex shared library events, remote reply
38989 The packet indicates that the loaded libraries have changed.
38990 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
38991 list of loaded libraries. The @var{r} part is ignored.
38993 @cindex replay log events, remote reply
38995 The packet indicates that the target cannot continue replaying
38996 logged execution events, because it has reached the end (or the
38997 beginning when executing backward) of the log. The value of @var{r}
38998 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
38999 for more information.
39002 @anchor{swbreak stop reason}
39003 The packet indicates a software breakpoint instruction was executed,
39004 irrespective of whether it was @value{GDBN} that planted the
39005 breakpoint or the breakpoint is hardcoded in the program. The @var{r}
39006 part must be left empty.
39008 On some architectures, such as x86, at the architecture level, when a
39009 breakpoint instruction executes the program counter points at the
39010 breakpoint address plus an offset. On such targets, the stub is
39011 responsible for adjusting the PC to point back at the breakpoint
39014 This packet should not be sent by default; older @value{GDBN} versions
39015 did not support it. @value{GDBN} requests it, by supplying an
39016 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
39017 remote stub must also supply the appropriate @samp{qSupported} feature
39018 indicating support.
39020 This packet is required for correct non-stop mode operation.
39023 The packet indicates the target stopped for a hardware breakpoint.
39024 The @var{r} part must be left empty.
39026 The same remarks about @samp{qSupported} and non-stop mode above
39029 @cindex fork events, remote reply
39031 The packet indicates that @code{fork} was called, and @var{r}
39032 is the thread ID of the new child process. Refer to
39033 @ref{thread-id syntax} for the format of the @var{thread-id}
39034 field. This packet is only applicable to targets that support
39037 This packet should not be sent by default; older @value{GDBN} versions
39038 did not support it. @value{GDBN} requests it, by supplying an
39039 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
39040 remote stub must also supply the appropriate @samp{qSupported} feature
39041 indicating support.
39043 @cindex vfork events, remote reply
39045 The packet indicates that @code{vfork} was called, and @var{r}
39046 is the thread ID of the new child process. Refer to
39047 @ref{thread-id syntax} for the format of the @var{thread-id}
39048 field. This packet is only applicable to targets that support
39051 This packet should not be sent by default; older @value{GDBN} versions
39052 did not support it. @value{GDBN} requests it, by supplying an
39053 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
39054 remote stub must also supply the appropriate @samp{qSupported} feature
39055 indicating support.
39057 @cindex vforkdone events, remote reply
39059 The packet indicates that a child process created by a vfork
39060 has either called @code{exec} or terminated, so that the
39061 address spaces of the parent and child process are no longer
39062 shared. The @var{r} part is ignored. This packet is only
39063 applicable to targets that support vforkdone events.
39065 This packet should not be sent by default; older @value{GDBN} versions
39066 did not support it. @value{GDBN} requests it, by supplying an
39067 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
39068 remote stub must also supply the appropriate @samp{qSupported} feature
39069 indicating support.
39071 @cindex exec events, remote reply
39073 The packet indicates that @code{execve} was called, and @var{r}
39074 is the absolute pathname of the file that was executed, in hex.
39075 This packet is only applicable to targets that support exec events.
39077 This packet should not be sent by default; older @value{GDBN} versions
39078 did not support it. @value{GDBN} requests it, by supplying an
39079 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
39080 remote stub must also supply the appropriate @samp{qSupported} feature
39081 indicating support.
39083 @cindex thread create event, remote reply
39084 @anchor{thread create event}
39086 The packet indicates that the thread was just created. The new thread
39087 is stopped until @value{GDBN} sets it running with a resumption packet
39088 (@pxref{vCont packet}). This packet should not be sent by default;
39089 @value{GDBN} requests it with the @ref{QThreadEvents} packet. See
39090 also the @samp{w} (@pxref{thread exit event}) remote reply below. The
39091 @var{r} part is ignored.
39096 @itemx W @var{AA} ; process:@var{pid}
39097 The process exited, and @var{AA} is the exit status. This is only
39098 applicable to certain targets.
39100 The second form of the response, including the process ID of the
39101 exited process, can be used only when @value{GDBN} has reported
39102 support for multiprocess protocol extensions; see @ref{multiprocess
39103 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
39107 @itemx X @var{AA} ; process:@var{pid}
39108 The process terminated with signal @var{AA}.
39110 The second form of the response, including the process ID of the
39111 terminated process, can be used only when @value{GDBN} has reported
39112 support for multiprocess protocol extensions; see @ref{multiprocess
39113 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
39116 @anchor{thread exit event}
39117 @cindex thread exit event, remote reply
39118 @item w @var{AA} ; @var{tid}
39120 The thread exited, and @var{AA} is the exit status. This response
39121 should not be sent by default; @value{GDBN} requests it with the
39122 @ref{QThreadEvents} packet. See also @ref{thread create event} above.
39123 @var{AA} is formatted as a big-endian hex string.
39126 There are no resumed threads left in the target. In other words, even
39127 though the process is alive, the last resumed thread has exited. For
39128 example, say the target process has two threads: thread 1 and thread
39129 2. The client leaves thread 1 stopped, and resumes thread 2, which
39130 subsequently exits. At this point, even though the process is still
39131 alive, and thus no @samp{W} stop reply is sent, no thread is actually
39132 executing either. The @samp{N} stop reply thus informs the client
39133 that it can stop waiting for stop replies. This packet should not be
39134 sent by default; older @value{GDBN} versions did not support it.
39135 @value{GDBN} requests it, by supplying an appropriate
39136 @samp{qSupported} feature (@pxref{qSupported}). The remote stub must
39137 also supply the appropriate @samp{qSupported} feature indicating
39140 @item O @var{XX}@dots{}
39141 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
39142 written as the program's console output. This can happen at any time
39143 while the program is running and the debugger should continue to wait
39144 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
39146 @item F @var{call-id},@var{parameter}@dots{}
39147 @var{call-id} is the identifier which says which host system call should
39148 be called. This is just the name of the function. Translation into the
39149 correct system call is only applicable as it's defined in @value{GDBN}.
39150 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
39153 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
39154 this very system call.
39156 The target replies with this packet when it expects @value{GDBN} to
39157 call a host system call on behalf of the target. @value{GDBN} replies
39158 with an appropriate @samp{F} packet and keeps up waiting for the next
39159 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
39160 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
39161 Protocol Extension}, for more details.
39165 @node General Query Packets
39166 @section General Query Packets
39167 @cindex remote query requests
39169 Packets starting with @samp{q} are @dfn{general query packets};
39170 packets starting with @samp{Q} are @dfn{general set packets}. General
39171 query and set packets are a semi-unified form for retrieving and
39172 sending information to and from the stub.
39174 The initial letter of a query or set packet is followed by a name
39175 indicating what sort of thing the packet applies to. For example,
39176 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
39177 definitions with the stub. These packet names follow some
39182 The name must not contain commas, colons or semicolons.
39184 Most @value{GDBN} query and set packets have a leading upper case
39187 The names of custom vendor packets should use a company prefix, in
39188 lower case, followed by a period. For example, packets designed at
39189 the Acme Corporation might begin with @samp{qacme.foo} (for querying
39190 foos) or @samp{Qacme.bar} (for setting bars).
39193 The name of a query or set packet should be separated from any
39194 parameters by a @samp{:}; the parameters themselves should be
39195 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
39196 full packet name, and check for a separator or the end of the packet,
39197 in case two packet names share a common prefix. New packets should not begin
39198 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
39199 packets predate these conventions, and have arguments without any terminator
39200 for the packet name; we suspect they are in widespread use in places that
39201 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
39202 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
39205 Like the descriptions of the other packets, each description here
39206 has a template showing the packet's overall syntax, followed by an
39207 explanation of the packet's meaning. We include spaces in some of the
39208 templates for clarity; these are not part of the packet's syntax. No
39209 @value{GDBN} packet uses spaces to separate its components.
39211 Here are the currently defined query and set packets:
39217 Turn on or off the agent as a helper to perform some debugging operations
39218 delegated from @value{GDBN} (@pxref{Control Agent}).
39220 @item QAllow:@var{op}:@var{val}@dots{}
39221 @cindex @samp{QAllow} packet
39222 Specify which operations @value{GDBN} expects to request of the
39223 target, as a semicolon-separated list of operation name and value
39224 pairs. Possible values for @var{op} include @samp{WriteReg},
39225 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
39226 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
39227 indicating that @value{GDBN} will not request the operation, or 1,
39228 indicating that it may. (The target can then use this to set up its
39229 own internals optimally, for instance if the debugger never expects to
39230 insert breakpoints, it may not need to install its own trap handler.)
39233 @cindex current thread, remote request
39234 @cindex @samp{qC} packet
39235 Return the current thread ID.
39239 @item QC @var{thread-id}
39240 Where @var{thread-id} is a thread ID as documented in
39241 @ref{thread-id syntax}.
39242 @item @r{(anything else)}
39243 Any other reply implies the old thread ID.
39246 @item qCRC:@var{addr},@var{length}
39247 @cindex CRC of memory block, remote request
39248 @cindex @samp{qCRC} packet
39249 @anchor{qCRC packet}
39250 Compute the CRC checksum of a block of memory using CRC-32 defined in
39251 IEEE 802.3. The CRC is computed byte at a time, taking the most
39252 significant bit of each byte first. The initial pattern code
39253 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
39255 @emph{Note:} This is the same CRC used in validating separate debug
39256 files (@pxref{Separate Debug Files, , Debugging Information in Separate
39257 Files}). However the algorithm is slightly different. When validating
39258 separate debug files, the CRC is computed taking the @emph{least}
39259 significant bit of each byte first, and the final result is inverted to
39260 detect trailing zeros.
39265 An error (such as memory fault)
39266 @item C @var{crc32}
39267 The specified memory region's checksum is @var{crc32}.
39270 @item QDisableRandomization:@var{value}
39271 @cindex disable address space randomization, remote request
39272 @cindex @samp{QDisableRandomization} packet
39273 Some target operating systems will randomize the virtual address space
39274 of the inferior process as a security feature, but provide a feature
39275 to disable such randomization, e.g.@: to allow for a more deterministic
39276 debugging experience. On such systems, this packet with a @var{value}
39277 of 1 directs the target to disable address space randomization for
39278 processes subsequently started via @samp{vRun} packets, while a packet
39279 with a @var{value} of 0 tells the target to enable address space
39282 This packet is only available in extended mode (@pxref{extended mode}).
39287 The request succeeded.
39290 An error occurred. The error number @var{nn} is given as hex digits.
39293 An empty reply indicates that @samp{QDisableRandomization} is not supported
39297 This packet is not probed by default; the remote stub must request it,
39298 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39299 This should only be done on targets that actually support disabling
39300 address space randomization.
39302 @item QStartupWithShell:@var{value}
39303 @cindex startup with shell, remote request
39304 @cindex @samp{QStartupWithShell} packet
39305 On UNIX-like targets, it is possible to start the inferior using a
39306 shell program. This is the default behavior on both @value{GDBN} and
39307 @command{gdbserver} (@pxref{set startup-with-shell}). This packet is
39308 used to inform @command{gdbserver} whether it should start the
39309 inferior using a shell or not.
39311 If @var{value} is @samp{0}, @command{gdbserver} will not use a shell
39312 to start the inferior. If @var{value} is @samp{1},
39313 @command{gdbserver} will use a shell to start the inferior. All other
39314 values are considered an error.
39316 This packet is only available in extended mode (@pxref{extended
39322 The request succeeded.
39325 An error occurred. The error number @var{nn} is given as hex digits.
39328 This packet is not probed by default; the remote stub must request it,
39329 by supplying an appropriate @samp{qSupported} response
39330 (@pxref{qSupported}). This should only be done on targets that
39331 actually support starting the inferior using a shell.
39333 Use of this packet is controlled by the @code{set startup-with-shell}
39334 command; @pxref{set startup-with-shell}.
39336 @item QEnvironmentHexEncoded:@var{hex-value}
39337 @anchor{QEnvironmentHexEncoded}
39338 @cindex set environment variable, remote request
39339 @cindex @samp{QEnvironmentHexEncoded} packet
39340 On UNIX-like targets, it is possible to set environment variables that
39341 will be passed to the inferior during the startup process. This
39342 packet is used to inform @command{gdbserver} of an environment
39343 variable that has been defined by the user on @value{GDBN} (@pxref{set
39346 The packet is composed by @var{hex-value}, an hex encoded
39347 representation of the @var{name=value} format representing an
39348 environment variable. The name of the environment variable is
39349 represented by @var{name}, and the value to be assigned to the
39350 environment variable is represented by @var{value}. If the variable
39351 has no value (i.e., the value is @code{null}), then @var{value} will
39354 This packet is only available in extended mode (@pxref{extended
39360 The request succeeded.
39363 This packet is not probed by default; the remote stub must request it,
39364 by supplying an appropriate @samp{qSupported} response
39365 (@pxref{qSupported}). This should only be done on targets that
39366 actually support passing environment variables to the starting
39369 This packet is related to the @code{set environment} command;
39370 @pxref{set environment}.
39372 @item QEnvironmentUnset:@var{hex-value}
39373 @anchor{QEnvironmentUnset}
39374 @cindex unset environment variable, remote request
39375 @cindex @samp{QEnvironmentUnset} packet
39376 On UNIX-like targets, it is possible to unset environment variables
39377 before starting the inferior in the remote target. This packet is
39378 used to inform @command{gdbserver} of an environment variable that has
39379 been unset by the user on @value{GDBN} (@pxref{unset environment}).
39381 The packet is composed by @var{hex-value}, an hex encoded
39382 representation of the name of the environment variable to be unset.
39384 This packet is only available in extended mode (@pxref{extended
39390 The request succeeded.
39393 This packet is not probed by default; the remote stub must request it,
39394 by supplying an appropriate @samp{qSupported} response
39395 (@pxref{qSupported}). This should only be done on targets that
39396 actually support passing environment variables to the starting
39399 This packet is related to the @code{unset environment} command;
39400 @pxref{unset environment}.
39402 @item QEnvironmentReset
39403 @anchor{QEnvironmentReset}
39404 @cindex reset environment, remote request
39405 @cindex @samp{QEnvironmentReset} packet
39406 On UNIX-like targets, this packet is used to reset the state of
39407 environment variables in the remote target before starting the
39408 inferior. In this context, reset means unsetting all environment
39409 variables that were previously set by the user (i.e., were not
39410 initially present in the environment). It is sent to
39411 @command{gdbserver} before the @samp{QEnvironmentHexEncoded}
39412 (@pxref{QEnvironmentHexEncoded}) and the @samp{QEnvironmentUnset}
39413 (@pxref{QEnvironmentUnset}) packets.
39415 This packet is only available in extended mode (@pxref{extended
39421 The request succeeded.
39424 This packet is not probed by default; the remote stub must request it,
39425 by supplying an appropriate @samp{qSupported} response
39426 (@pxref{qSupported}). This should only be done on targets that
39427 actually support passing environment variables to the starting
39430 @item QSetWorkingDir:@r{[}@var{directory}@r{]}
39431 @anchor{QSetWorkingDir packet}
39432 @cindex set working directory, remote request
39433 @cindex @samp{QSetWorkingDir} packet
39434 This packet is used to inform the remote server of the intended
39435 current working directory for programs that are going to be executed.
39437 The packet is composed by @var{directory}, an hex encoded
39438 representation of the directory that the remote inferior will use as
39439 its current working directory. If @var{directory} is an empty string,
39440 the remote server should reset the inferior's current working
39441 directory to its original, empty value.
39443 This packet is only available in extended mode (@pxref{extended
39449 The request succeeded.
39453 @itemx qsThreadInfo
39454 @cindex list active threads, remote request
39455 @cindex @samp{qfThreadInfo} packet
39456 @cindex @samp{qsThreadInfo} packet
39457 Obtain a list of all active thread IDs from the target (OS). Since there
39458 may be too many active threads to fit into one reply packet, this query
39459 works iteratively: it may require more than one query/reply sequence to
39460 obtain the entire list of threads. The first query of the sequence will
39461 be the @samp{qfThreadInfo} query; subsequent queries in the
39462 sequence will be the @samp{qsThreadInfo} query.
39464 NOTE: This packet replaces the @samp{qL} query (see below).
39468 @item m @var{thread-id}
39470 @item m @var{thread-id},@var{thread-id}@dots{}
39471 a comma-separated list of thread IDs
39473 (lower case letter @samp{L}) denotes end of list.
39476 In response to each query, the target will reply with a list of one or
39477 more thread IDs, separated by commas.
39478 @value{GDBN} will respond to each reply with a request for more thread
39479 ids (using the @samp{qs} form of the query), until the target responds
39480 with @samp{l} (lower-case ell, for @dfn{last}).
39481 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
39484 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
39485 initial connection with the remote target, and the very first thread ID
39486 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
39487 message. Therefore, the stub should ensure that the first thread ID in
39488 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
39490 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
39491 @cindex get thread-local storage address, remote request
39492 @cindex @samp{qGetTLSAddr} packet
39493 Fetch the address associated with thread local storage specified
39494 by @var{thread-id}, @var{offset}, and @var{lm}.
39496 @var{thread-id} is the thread ID associated with the
39497 thread for which to fetch the TLS address. @xref{thread-id syntax}.
39499 @var{offset} is the (big endian, hex encoded) offset associated with the
39500 thread local variable. (This offset is obtained from the debug
39501 information associated with the variable.)
39503 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
39504 load module associated with the thread local storage. For example,
39505 a @sc{gnu}/Linux system will pass the link map address of the shared
39506 object associated with the thread local storage under consideration.
39507 Other operating environments may choose to represent the load module
39508 differently, so the precise meaning of this parameter will vary.
39512 @item @var{XX}@dots{}
39513 Hex encoded (big endian) bytes representing the address of the thread
39514 local storage requested.
39517 An error occurred. The error number @var{nn} is given as hex digits.
39520 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
39523 @item qGetTIBAddr:@var{thread-id}
39524 @cindex get thread information block address
39525 @cindex @samp{qGetTIBAddr} packet
39526 Fetch address of the Windows OS specific Thread Information Block.
39528 @var{thread-id} is the thread ID associated with the thread.
39532 @item @var{XX}@dots{}
39533 Hex encoded (big endian) bytes representing the linear address of the
39534 thread information block.
39537 An error occured. This means that either the thread was not found, or the
39538 address could not be retrieved.
39541 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
39544 @item qL @var{startflag} @var{threadcount} @var{nextthread}
39545 Obtain thread information from RTOS. Where: @var{startflag} (one hex
39546 digit) is one to indicate the first query and zero to indicate a
39547 subsequent query; @var{threadcount} (two hex digits) is the maximum
39548 number of threads the response packet can contain; and @var{nextthread}
39549 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
39550 returned in the response as @var{argthread}.
39552 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
39556 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
39557 Where: @var{count} (two hex digits) is the number of threads being
39558 returned; @var{done} (one hex digit) is zero to indicate more threads
39559 and one indicates no further threads; @var{argthreadid} (eight hex
39560 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
39561 is a sequence of thread IDs, @var{threadid} (eight hex
39562 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
39566 @cindex section offsets, remote request
39567 @cindex @samp{qOffsets} packet
39568 Get section offsets that the target used when relocating the downloaded
39573 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
39574 Relocate the @code{Text} section by @var{xxx} from its original address.
39575 Relocate the @code{Data} section by @var{yyy} from its original address.
39576 If the object file format provides segment information (e.g.@: @sc{elf}
39577 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
39578 segments by the supplied offsets.
39580 @emph{Note: while a @code{Bss} offset may be included in the response,
39581 @value{GDBN} ignores this and instead applies the @code{Data} offset
39582 to the @code{Bss} section.}
39584 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
39585 Relocate the first segment of the object file, which conventionally
39586 contains program code, to a starting address of @var{xxx}. If
39587 @samp{DataSeg} is specified, relocate the second segment, which
39588 conventionally contains modifiable data, to a starting address of
39589 @var{yyy}. @value{GDBN} will report an error if the object file
39590 does not contain segment information, or does not contain at least
39591 as many segments as mentioned in the reply. Extra segments are
39592 kept at fixed offsets relative to the last relocated segment.
39595 @item qP @var{mode} @var{thread-id}
39596 @cindex thread information, remote request
39597 @cindex @samp{qP} packet
39598 Returns information on @var{thread-id}. Where: @var{mode} is a hex
39599 encoded 32 bit mode; @var{thread-id} is a thread ID
39600 (@pxref{thread-id syntax}).
39602 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
39605 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
39609 @cindex non-stop mode, remote request
39610 @cindex @samp{QNonStop} packet
39612 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
39613 @xref{Remote Non-Stop}, for more information.
39618 The request succeeded.
39621 An error occurred. The error number @var{nn} is given as hex digits.
39624 An empty reply indicates that @samp{QNonStop} is not supported by
39628 This packet is not probed by default; the remote stub must request it,
39629 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39630 Use of this packet is controlled by the @code{set non-stop} command;
39631 @pxref{Non-Stop Mode}.
39633 @item QCatchSyscalls:1 @r{[};@var{sysno}@r{]}@dots{}
39634 @itemx QCatchSyscalls:0
39635 @cindex catch syscalls from inferior, remote request
39636 @cindex @samp{QCatchSyscalls} packet
39637 @anchor{QCatchSyscalls}
39638 Enable (@samp{QCatchSyscalls:1}) or disable (@samp{QCatchSyscalls:0})
39639 catching syscalls from the inferior process.
39641 For @samp{QCatchSyscalls:1}, each listed syscall @var{sysno} (encoded
39642 in hex) should be reported to @value{GDBN}. If no syscall @var{sysno}
39643 is listed, every system call should be reported.
39645 Note that if a syscall not in the list is reported, @value{GDBN} will
39646 still filter the event according to its own list from all corresponding
39647 @code{catch syscall} commands. However, it is more efficient to only
39648 report the requested syscalls.
39650 Multiple @samp{QCatchSyscalls:1} packets do not combine; any earlier
39651 @samp{QCatchSyscalls:1} list is completely replaced by the new list.
39653 If the inferior process execs, the state of @samp{QCatchSyscalls} is
39654 kept for the new process too. On targets where exec may affect syscall
39655 numbers, for example with exec between 32 and 64-bit processes, the
39656 client should send a new packet with the new syscall list.
39661 The request succeeded.
39664 An error occurred. @var{nn} are hex digits.
39667 An empty reply indicates that @samp{QCatchSyscalls} is not supported by
39671 Use of this packet is controlled by the @code{set remote catch-syscalls}
39672 command (@pxref{Remote Configuration, set remote catch-syscalls}).
39673 This packet is not probed by default; the remote stub must request it,
39674 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39676 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
39677 @cindex pass signals to inferior, remote request
39678 @cindex @samp{QPassSignals} packet
39679 @anchor{QPassSignals}
39680 Each listed @var{signal} should be passed directly to the inferior process.
39681 Signals are numbered identically to continue packets and stop replies
39682 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
39683 strictly greater than the previous item. These signals do not need to stop
39684 the inferior, or be reported to @value{GDBN}. All other signals should be
39685 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
39686 combine; any earlier @samp{QPassSignals} list is completely replaced by the
39687 new list. This packet improves performance when using @samp{handle
39688 @var{signal} nostop noprint pass}.
39693 The request succeeded.
39696 An error occurred. The error number @var{nn} is given as hex digits.
39699 An empty reply indicates that @samp{QPassSignals} is not supported by
39703 Use of this packet is controlled by the @code{set remote pass-signals}
39704 command (@pxref{Remote Configuration, set remote pass-signals}).
39705 This packet is not probed by default; the remote stub must request it,
39706 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39708 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
39709 @cindex signals the inferior may see, remote request
39710 @cindex @samp{QProgramSignals} packet
39711 @anchor{QProgramSignals}
39712 Each listed @var{signal} may be delivered to the inferior process.
39713 Others should be silently discarded.
39715 In some cases, the remote stub may need to decide whether to deliver a
39716 signal to the program or not without @value{GDBN} involvement. One
39717 example of that is while detaching --- the program's threads may have
39718 stopped for signals that haven't yet had a chance of being reported to
39719 @value{GDBN}, and so the remote stub can use the signal list specified
39720 by this packet to know whether to deliver or ignore those pending
39723 This does not influence whether to deliver a signal as requested by a
39724 resumption packet (@pxref{vCont packet}).
39726 Signals are numbered identically to continue packets and stop replies
39727 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
39728 strictly greater than the previous item. Multiple
39729 @samp{QProgramSignals} packets do not combine; any earlier
39730 @samp{QProgramSignals} list is completely replaced by the new list.
39735 The request succeeded.
39738 An error occurred. The error number @var{nn} is given as hex digits.
39741 An empty reply indicates that @samp{QProgramSignals} is not supported
39745 Use of this packet is controlled by the @code{set remote program-signals}
39746 command (@pxref{Remote Configuration, set remote program-signals}).
39747 This packet is not probed by default; the remote stub must request it,
39748 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39750 @anchor{QThreadEvents}
39751 @item QThreadEvents:1
39752 @itemx QThreadEvents:0
39753 @cindex thread create/exit events, remote request
39754 @cindex @samp{QThreadEvents} packet
39756 Enable (@samp{QThreadEvents:1}) or disable (@samp{QThreadEvents:0})
39757 reporting of thread create and exit events. @xref{thread create
39758 event}, for the reply specifications. For example, this is used in
39759 non-stop mode when @value{GDBN} stops a set of threads and
39760 synchronously waits for the their corresponding stop replies. Without
39761 exit events, if one of the threads exits, @value{GDBN} would hang
39762 forever not knowing that it should no longer expect a stop for that
39763 same thread. @value{GDBN} does not enable this feature unless the
39764 stub reports that it supports it by including @samp{QThreadEvents+} in
39765 its @samp{qSupported} reply.
39770 The request succeeded.
39773 An error occurred. The error number @var{nn} is given as hex digits.
39776 An empty reply indicates that @samp{QThreadEvents} is not supported by
39780 Use of this packet is controlled by the @code{set remote thread-events}
39781 command (@pxref{Remote Configuration, set remote thread-events}).
39783 @item qRcmd,@var{command}
39784 @cindex execute remote command, remote request
39785 @cindex @samp{qRcmd} packet
39786 @var{command} (hex encoded) is passed to the local interpreter for
39787 execution. Invalid commands should be reported using the output
39788 string. Before the final result packet, the target may also respond
39789 with a number of intermediate @samp{O@var{output}} console output
39790 packets. @emph{Implementors should note that providing access to a
39791 stubs's interpreter may have security implications}.
39796 A command response with no output.
39798 A command response with the hex encoded output string @var{OUTPUT}.
39800 Indicate a badly formed request.
39802 An empty reply indicates that @samp{qRcmd} is not recognized.
39805 (Note that the @code{qRcmd} packet's name is separated from the
39806 command by a @samp{,}, not a @samp{:}, contrary to the naming
39807 conventions above. Please don't use this packet as a model for new
39810 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
39811 @cindex searching memory, in remote debugging
39813 @cindex @samp{qSearch:memory} packet
39815 @cindex @samp{qSearch memory} packet
39816 @anchor{qSearch memory}
39817 Search @var{length} bytes at @var{address} for @var{search-pattern}.
39818 Both @var{address} and @var{length} are encoded in hex;
39819 @var{search-pattern} is a sequence of bytes, also hex encoded.
39824 The pattern was not found.
39826 The pattern was found at @var{address}.
39828 A badly formed request or an error was encountered while searching memory.
39830 An empty reply indicates that @samp{qSearch:memory} is not recognized.
39833 @item QStartNoAckMode
39834 @cindex @samp{QStartNoAckMode} packet
39835 @anchor{QStartNoAckMode}
39836 Request that the remote stub disable the normal @samp{+}/@samp{-}
39837 protocol acknowledgments (@pxref{Packet Acknowledgment}).
39842 The stub has switched to no-acknowledgment mode.
39843 @value{GDBN} acknowledges this reponse,
39844 but neither the stub nor @value{GDBN} shall send or expect further
39845 @samp{+}/@samp{-} acknowledgments in the current connection.
39847 An empty reply indicates that the stub does not support no-acknowledgment mode.
39850 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
39851 @cindex supported packets, remote query
39852 @cindex features of the remote protocol
39853 @cindex @samp{qSupported} packet
39854 @anchor{qSupported}
39855 Tell the remote stub about features supported by @value{GDBN}, and
39856 query the stub for features it supports. This packet allows
39857 @value{GDBN} and the remote stub to take advantage of each others'
39858 features. @samp{qSupported} also consolidates multiple feature probes
39859 at startup, to improve @value{GDBN} performance---a single larger
39860 packet performs better than multiple smaller probe packets on
39861 high-latency links. Some features may enable behavior which must not
39862 be on by default, e.g.@: because it would confuse older clients or
39863 stubs. Other features may describe packets which could be
39864 automatically probed for, but are not. These features must be
39865 reported before @value{GDBN} will use them. This ``default
39866 unsupported'' behavior is not appropriate for all packets, but it
39867 helps to keep the initial connection time under control with new
39868 versions of @value{GDBN} which support increasing numbers of packets.
39872 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
39873 The stub supports or does not support each returned @var{stubfeature},
39874 depending on the form of each @var{stubfeature} (see below for the
39877 An empty reply indicates that @samp{qSupported} is not recognized,
39878 or that no features needed to be reported to @value{GDBN}.
39881 The allowed forms for each feature (either a @var{gdbfeature} in the
39882 @samp{qSupported} packet, or a @var{stubfeature} in the response)
39886 @item @var{name}=@var{value}
39887 The remote protocol feature @var{name} is supported, and associated
39888 with the specified @var{value}. The format of @var{value} depends
39889 on the feature, but it must not include a semicolon.
39891 The remote protocol feature @var{name} is supported, and does not
39892 need an associated value.
39894 The remote protocol feature @var{name} is not supported.
39896 The remote protocol feature @var{name} may be supported, and
39897 @value{GDBN} should auto-detect support in some other way when it is
39898 needed. This form will not be used for @var{gdbfeature} notifications,
39899 but may be used for @var{stubfeature} responses.
39902 Whenever the stub receives a @samp{qSupported} request, the
39903 supplied set of @value{GDBN} features should override any previous
39904 request. This allows @value{GDBN} to put the stub in a known
39905 state, even if the stub had previously been communicating with
39906 a different version of @value{GDBN}.
39908 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
39913 This feature indicates whether @value{GDBN} supports multiprocess
39914 extensions to the remote protocol. @value{GDBN} does not use such
39915 extensions unless the stub also reports that it supports them by
39916 including @samp{multiprocess+} in its @samp{qSupported} reply.
39917 @xref{multiprocess extensions}, for details.
39920 This feature indicates that @value{GDBN} supports the XML target
39921 description. If the stub sees @samp{xmlRegisters=} with target
39922 specific strings separated by a comma, it will report register
39926 This feature indicates whether @value{GDBN} supports the
39927 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
39928 instruction reply packet}).
39931 This feature indicates whether @value{GDBN} supports the swbreak stop
39932 reason in stop replies. @xref{swbreak stop reason}, for details.
39935 This feature indicates whether @value{GDBN} supports the hwbreak stop
39936 reason in stop replies. @xref{swbreak stop reason}, for details.
39939 This feature indicates whether @value{GDBN} supports fork event
39940 extensions to the remote protocol. @value{GDBN} does not use such
39941 extensions unless the stub also reports that it supports them by
39942 including @samp{fork-events+} in its @samp{qSupported} reply.
39945 This feature indicates whether @value{GDBN} supports vfork event
39946 extensions to the remote protocol. @value{GDBN} does not use such
39947 extensions unless the stub also reports that it supports them by
39948 including @samp{vfork-events+} in its @samp{qSupported} reply.
39951 This feature indicates whether @value{GDBN} supports exec event
39952 extensions to the remote protocol. @value{GDBN} does not use such
39953 extensions unless the stub also reports that it supports them by
39954 including @samp{exec-events+} in its @samp{qSupported} reply.
39956 @item vContSupported
39957 This feature indicates whether @value{GDBN} wants to know the
39958 supported actions in the reply to @samp{vCont?} packet.
39961 Stubs should ignore any unknown values for
39962 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
39963 packet supports receiving packets of unlimited length (earlier
39964 versions of @value{GDBN} may reject overly long responses). Additional values
39965 for @var{gdbfeature} may be defined in the future to let the stub take
39966 advantage of new features in @value{GDBN}, e.g.@: incompatible
39967 improvements in the remote protocol---the @samp{multiprocess} feature is
39968 an example of such a feature. The stub's reply should be independent
39969 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
39970 describes all the features it supports, and then the stub replies with
39971 all the features it supports.
39973 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
39974 responses, as long as each response uses one of the standard forms.
39976 Some features are flags. A stub which supports a flag feature
39977 should respond with a @samp{+} form response. Other features
39978 require values, and the stub should respond with an @samp{=}
39981 Each feature has a default value, which @value{GDBN} will use if
39982 @samp{qSupported} is not available or if the feature is not mentioned
39983 in the @samp{qSupported} response. The default values are fixed; a
39984 stub is free to omit any feature responses that match the defaults.
39986 Not all features can be probed, but for those which can, the probing
39987 mechanism is useful: in some cases, a stub's internal
39988 architecture may not allow the protocol layer to know some information
39989 about the underlying target in advance. This is especially common in
39990 stubs which may be configured for multiple targets.
39992 These are the currently defined stub features and their properties:
39994 @multitable @columnfractions 0.35 0.2 0.12 0.2
39995 @c NOTE: The first row should be @headitem, but we do not yet require
39996 @c a new enough version of Texinfo (4.7) to use @headitem.
39998 @tab Value Required
40002 @item @samp{PacketSize}
40007 @item @samp{qXfer:auxv:read}
40012 @item @samp{qXfer:btrace:read}
40017 @item @samp{qXfer:btrace-conf:read}
40022 @item @samp{qXfer:exec-file:read}
40027 @item @samp{qXfer:features:read}
40032 @item @samp{qXfer:libraries:read}
40037 @item @samp{qXfer:libraries-svr4:read}
40042 @item @samp{augmented-libraries-svr4-read}
40047 @item @samp{qXfer:memory-map:read}
40052 @item @samp{qXfer:sdata:read}
40057 @item @samp{qXfer:siginfo:read}
40062 @item @samp{qXfer:siginfo:write}
40067 @item @samp{qXfer:threads:read}
40072 @item @samp{qXfer:traceframe-info:read}
40077 @item @samp{qXfer:uib:read}
40082 @item @samp{qXfer:fdpic:read}
40087 @item @samp{Qbtrace:off}
40092 @item @samp{Qbtrace:bts}
40097 @item @samp{Qbtrace:pt}
40102 @item @samp{Qbtrace-conf:bts:size}
40107 @item @samp{Qbtrace-conf:pt:size}
40112 @item @samp{QNonStop}
40117 @item @samp{QCatchSyscalls}
40122 @item @samp{QPassSignals}
40127 @item @samp{QStartNoAckMode}
40132 @item @samp{multiprocess}
40137 @item @samp{ConditionalBreakpoints}
40142 @item @samp{ConditionalTracepoints}
40147 @item @samp{ReverseContinue}
40152 @item @samp{ReverseStep}
40157 @item @samp{TracepointSource}
40162 @item @samp{QAgent}
40167 @item @samp{QAllow}
40172 @item @samp{QDisableRandomization}
40177 @item @samp{EnableDisableTracepoints}
40182 @item @samp{QTBuffer:size}
40187 @item @samp{tracenz}
40192 @item @samp{BreakpointCommands}
40197 @item @samp{swbreak}
40202 @item @samp{hwbreak}
40207 @item @samp{fork-events}
40212 @item @samp{vfork-events}
40217 @item @samp{exec-events}
40222 @item @samp{QThreadEvents}
40227 @item @samp{no-resumed}
40234 These are the currently defined stub features, in more detail:
40237 @cindex packet size, remote protocol
40238 @item PacketSize=@var{bytes}
40239 The remote stub can accept packets up to at least @var{bytes} in
40240 length. @value{GDBN} will send packets up to this size for bulk
40241 transfers, and will never send larger packets. This is a limit on the
40242 data characters in the packet, including the frame and checksum.
40243 There is no trailing NUL byte in a remote protocol packet; if the stub
40244 stores packets in a NUL-terminated format, it should allow an extra
40245 byte in its buffer for the NUL. If this stub feature is not supported,
40246 @value{GDBN} guesses based on the size of the @samp{g} packet response.
40248 @item qXfer:auxv:read
40249 The remote stub understands the @samp{qXfer:auxv:read} packet
40250 (@pxref{qXfer auxiliary vector read}).
40252 @item qXfer:btrace:read
40253 The remote stub understands the @samp{qXfer:btrace:read}
40254 packet (@pxref{qXfer btrace read}).
40256 @item qXfer:btrace-conf:read
40257 The remote stub understands the @samp{qXfer:btrace-conf:read}
40258 packet (@pxref{qXfer btrace-conf read}).
40260 @item qXfer:exec-file:read
40261 The remote stub understands the @samp{qXfer:exec-file:read} packet
40262 (@pxref{qXfer executable filename read}).
40264 @item qXfer:features:read
40265 The remote stub understands the @samp{qXfer:features:read} packet
40266 (@pxref{qXfer target description read}).
40268 @item qXfer:libraries:read
40269 The remote stub understands the @samp{qXfer:libraries:read} packet
40270 (@pxref{qXfer library list read}).
40272 @item qXfer:libraries-svr4:read
40273 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
40274 (@pxref{qXfer svr4 library list read}).
40276 @item augmented-libraries-svr4-read
40277 The remote stub understands the augmented form of the
40278 @samp{qXfer:libraries-svr4:read} packet
40279 (@pxref{qXfer svr4 library list read}).
40281 @item qXfer:memory-map:read
40282 The remote stub understands the @samp{qXfer:memory-map:read} packet
40283 (@pxref{qXfer memory map read}).
40285 @item qXfer:sdata:read
40286 The remote stub understands the @samp{qXfer:sdata:read} packet
40287 (@pxref{qXfer sdata read}).
40289 @item qXfer:siginfo:read
40290 The remote stub understands the @samp{qXfer:siginfo:read} packet
40291 (@pxref{qXfer siginfo read}).
40293 @item qXfer:siginfo:write
40294 The remote stub understands the @samp{qXfer:siginfo:write} packet
40295 (@pxref{qXfer siginfo write}).
40297 @item qXfer:threads:read
40298 The remote stub understands the @samp{qXfer:threads:read} packet
40299 (@pxref{qXfer threads read}).
40301 @item qXfer:traceframe-info:read
40302 The remote stub understands the @samp{qXfer:traceframe-info:read}
40303 packet (@pxref{qXfer traceframe info read}).
40305 @item qXfer:uib:read
40306 The remote stub understands the @samp{qXfer:uib:read}
40307 packet (@pxref{qXfer unwind info block}).
40309 @item qXfer:fdpic:read
40310 The remote stub understands the @samp{qXfer:fdpic:read}
40311 packet (@pxref{qXfer fdpic loadmap read}).
40314 The remote stub understands the @samp{QNonStop} packet
40315 (@pxref{QNonStop}).
40317 @item QCatchSyscalls
40318 The remote stub understands the @samp{QCatchSyscalls} packet
40319 (@pxref{QCatchSyscalls}).
40322 The remote stub understands the @samp{QPassSignals} packet
40323 (@pxref{QPassSignals}).
40325 @item QStartNoAckMode
40326 The remote stub understands the @samp{QStartNoAckMode} packet and
40327 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
40330 @anchor{multiprocess extensions}
40331 @cindex multiprocess extensions, in remote protocol
40332 The remote stub understands the multiprocess extensions to the remote
40333 protocol syntax. The multiprocess extensions affect the syntax of
40334 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
40335 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
40336 replies. Note that reporting this feature indicates support for the
40337 syntactic extensions only, not that the stub necessarily supports
40338 debugging of more than one process at a time. The stub must not use
40339 multiprocess extensions in packet replies unless @value{GDBN} has also
40340 indicated it supports them in its @samp{qSupported} request.
40342 @item qXfer:osdata:read
40343 The remote stub understands the @samp{qXfer:osdata:read} packet
40344 ((@pxref{qXfer osdata read}).
40346 @item ConditionalBreakpoints
40347 The target accepts and implements evaluation of conditional expressions
40348 defined for breakpoints. The target will only report breakpoint triggers
40349 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
40351 @item ConditionalTracepoints
40352 The remote stub accepts and implements conditional expressions defined
40353 for tracepoints (@pxref{Tracepoint Conditions}).
40355 @item ReverseContinue
40356 The remote stub accepts and implements the reverse continue packet
40360 The remote stub accepts and implements the reverse step packet
40363 @item TracepointSource
40364 The remote stub understands the @samp{QTDPsrc} packet that supplies
40365 the source form of tracepoint definitions.
40368 The remote stub understands the @samp{QAgent} packet.
40371 The remote stub understands the @samp{QAllow} packet.
40373 @item QDisableRandomization
40374 The remote stub understands the @samp{QDisableRandomization} packet.
40376 @item StaticTracepoint
40377 @cindex static tracepoints, in remote protocol
40378 The remote stub supports static tracepoints.
40380 @item InstallInTrace
40381 @anchor{install tracepoint in tracing}
40382 The remote stub supports installing tracepoint in tracing.
40384 @item EnableDisableTracepoints
40385 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
40386 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
40387 to be enabled and disabled while a trace experiment is running.
40389 @item QTBuffer:size
40390 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
40391 packet that allows to change the size of the trace buffer.
40394 @cindex string tracing, in remote protocol
40395 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
40396 See @ref{Bytecode Descriptions} for details about the bytecode.
40398 @item BreakpointCommands
40399 @cindex breakpoint commands, in remote protocol
40400 The remote stub supports running a breakpoint's command list itself,
40401 rather than reporting the hit to @value{GDBN}.
40404 The remote stub understands the @samp{Qbtrace:off} packet.
40407 The remote stub understands the @samp{Qbtrace:bts} packet.
40410 The remote stub understands the @samp{Qbtrace:pt} packet.
40412 @item Qbtrace-conf:bts:size
40413 The remote stub understands the @samp{Qbtrace-conf:bts:size} packet.
40415 @item Qbtrace-conf:pt:size
40416 The remote stub understands the @samp{Qbtrace-conf:pt:size} packet.
40419 The remote stub reports the @samp{swbreak} stop reason for memory
40423 The remote stub reports the @samp{hwbreak} stop reason for hardware
40427 The remote stub reports the @samp{fork} stop reason for fork events.
40430 The remote stub reports the @samp{vfork} stop reason for vfork events
40431 and vforkdone events.
40434 The remote stub reports the @samp{exec} stop reason for exec events.
40436 @item vContSupported
40437 The remote stub reports the supported actions in the reply to
40438 @samp{vCont?} packet.
40440 @item QThreadEvents
40441 The remote stub understands the @samp{QThreadEvents} packet.
40444 The remote stub reports the @samp{N} stop reply.
40449 @cindex symbol lookup, remote request
40450 @cindex @samp{qSymbol} packet
40451 Notify the target that @value{GDBN} is prepared to serve symbol lookup
40452 requests. Accept requests from the target for the values of symbols.
40457 The target does not need to look up any (more) symbols.
40458 @item qSymbol:@var{sym_name}
40459 The target requests the value of symbol @var{sym_name} (hex encoded).
40460 @value{GDBN} may provide the value by using the
40461 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
40465 @item qSymbol:@var{sym_value}:@var{sym_name}
40466 Set the value of @var{sym_name} to @var{sym_value}.
40468 @var{sym_name} (hex encoded) is the name of a symbol whose value the
40469 target has previously requested.
40471 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
40472 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
40478 The target does not need to look up any (more) symbols.
40479 @item qSymbol:@var{sym_name}
40480 The target requests the value of a new symbol @var{sym_name} (hex
40481 encoded). @value{GDBN} will continue to supply the values of symbols
40482 (if available), until the target ceases to request them.
40487 @itemx QTDisconnected
40494 @itemx qTMinFTPILen
40496 @xref{Tracepoint Packets}.
40498 @item qThreadExtraInfo,@var{thread-id}
40499 @cindex thread attributes info, remote request
40500 @cindex @samp{qThreadExtraInfo} packet
40501 Obtain from the target OS a printable string description of thread
40502 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
40503 for the forms of @var{thread-id}. This
40504 string may contain anything that the target OS thinks is interesting
40505 for @value{GDBN} to tell the user about the thread. The string is
40506 displayed in @value{GDBN}'s @code{info threads} display. Some
40507 examples of possible thread extra info strings are @samp{Runnable}, or
40508 @samp{Blocked on Mutex}.
40512 @item @var{XX}@dots{}
40513 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
40514 comprising the printable string containing the extra information about
40515 the thread's attributes.
40518 (Note that the @code{qThreadExtraInfo} packet's name is separated from
40519 the command by a @samp{,}, not a @samp{:}, contrary to the naming
40520 conventions above. Please don't use this packet as a model for new
40539 @xref{Tracepoint Packets}.
40541 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
40542 @cindex read special object, remote request
40543 @cindex @samp{qXfer} packet
40544 @anchor{qXfer read}
40545 Read uninterpreted bytes from the target's special data area
40546 identified by the keyword @var{object}. Request @var{length} bytes
40547 starting at @var{offset} bytes into the data. The content and
40548 encoding of @var{annex} is specific to @var{object}; it can supply
40549 additional details about what data to access.
40554 Data @var{data} (@pxref{Binary Data}) has been read from the
40555 target. There may be more data at a higher address (although
40556 it is permitted to return @samp{m} even for the last valid
40557 block of data, as long as at least one byte of data was read).
40558 It is possible for @var{data} to have fewer bytes than the @var{length} in the
40562 Data @var{data} (@pxref{Binary Data}) has been read from the target.
40563 There is no more data to be read. It is possible for @var{data} to
40564 have fewer bytes than the @var{length} in the request.
40567 The @var{offset} in the request is at the end of the data.
40568 There is no more data to be read.
40571 The request was malformed, or @var{annex} was invalid.
40574 The offset was invalid, or there was an error encountered reading the data.
40575 The @var{nn} part is a hex-encoded @code{errno} value.
40578 An empty reply indicates the @var{object} string was not recognized by
40579 the stub, or that the object does not support reading.
40582 Here are the specific requests of this form defined so far. All the
40583 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
40584 formats, listed above.
40587 @item qXfer:auxv:read::@var{offset},@var{length}
40588 @anchor{qXfer auxiliary vector read}
40589 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
40590 auxiliary vector}. Note @var{annex} must be empty.
40592 This packet is not probed by default; the remote stub must request it,
40593 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40595 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
40596 @anchor{qXfer btrace read}
40598 Return a description of the current branch trace.
40599 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
40600 packet may have one of the following values:
40604 Returns all available branch trace.
40607 Returns all available branch trace if the branch trace changed since
40608 the last read request.
40611 Returns the new branch trace since the last read request. Adds a new
40612 block to the end of the trace that begins at zero and ends at the source
40613 location of the first branch in the trace buffer. This extra block is
40614 used to stitch traces together.
40616 If the trace buffer overflowed, returns an error indicating the overflow.
40619 This packet is not probed by default; the remote stub must request it
40620 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40622 @item qXfer:btrace-conf:read::@var{offset},@var{length}
40623 @anchor{qXfer btrace-conf read}
40625 Return a description of the current branch trace configuration.
40626 @xref{Branch Trace Configuration Format}.
40628 This packet is not probed by default; the remote stub must request it
40629 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40631 @item qXfer:exec-file:read:@var{annex}:@var{offset},@var{length}
40632 @anchor{qXfer executable filename read}
40633 Return the full absolute name of the file that was executed to create
40634 a process running on the remote system. The annex specifies the
40635 numeric process ID of the process to query, encoded as a hexadecimal
40636 number. If the annex part is empty the remote stub should return the
40637 filename corresponding to the currently executing process.
40639 This packet is not probed by default; the remote stub must request it,
40640 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40642 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
40643 @anchor{qXfer target description read}
40644 Access the @dfn{target description}. @xref{Target Descriptions}. The
40645 annex specifies which XML document to access. The main description is
40646 always loaded from the @samp{target.xml} annex.
40648 This packet is not probed by default; the remote stub must request it,
40649 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40651 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
40652 @anchor{qXfer library list read}
40653 Access the target's list of loaded libraries. @xref{Library List Format}.
40654 The annex part of the generic @samp{qXfer} packet must be empty
40655 (@pxref{qXfer read}).
40657 Targets which maintain a list of libraries in the program's memory do
40658 not need to implement this packet; it is designed for platforms where
40659 the operating system manages the list of loaded libraries.
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:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
40665 @anchor{qXfer svr4 library list read}
40666 Access the target's list of loaded libraries when the target is an SVR4
40667 platform. @xref{Library List Format for SVR4 Targets}. The annex part
40668 of the generic @samp{qXfer} packet must be empty unless the remote
40669 stub indicated it supports the augmented form of this packet
40670 by supplying an appropriate @samp{qSupported} response
40671 (@pxref{qXfer read}, @ref{qSupported}).
40673 This packet is optional for better performance on SVR4 targets.
40674 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
40676 This packet is not probed by default; the remote stub must request it,
40677 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40679 If the remote stub indicates it supports the augmented form of this
40680 packet then the annex part of the generic @samp{qXfer} packet may
40681 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
40682 arguments. The currently supported arguments are:
40685 @item start=@var{address}
40686 A hexadecimal number specifying the address of the @samp{struct
40687 link_map} to start reading the library list from. If unset or zero
40688 then the first @samp{struct link_map} in the library list will be
40689 chosen as the starting point.
40691 @item prev=@var{address}
40692 A hexadecimal number specifying the address of the @samp{struct
40693 link_map} immediately preceding the @samp{struct link_map}
40694 specified by the @samp{start} argument. If unset or zero then
40695 the remote stub will expect that no @samp{struct link_map}
40696 exists prior to the starting point.
40700 Arguments that are not understood by the remote stub will be silently
40703 @item qXfer:memory-map:read::@var{offset},@var{length}
40704 @anchor{qXfer memory map read}
40705 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
40706 annex part of the generic @samp{qXfer} packet must be empty
40707 (@pxref{qXfer read}).
40709 This packet is not probed by default; the remote stub must request it,
40710 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40712 @item qXfer:sdata:read::@var{offset},@var{length}
40713 @anchor{qXfer sdata read}
40715 Read contents of the extra collected static tracepoint marker
40716 information. The annex part of the generic @samp{qXfer} packet must
40717 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
40720 This packet is not probed by default; the remote stub must request it,
40721 by supplying an appropriate @samp{qSupported} response
40722 (@pxref{qSupported}).
40724 @item qXfer:siginfo:read::@var{offset},@var{length}
40725 @anchor{qXfer siginfo read}
40726 Read contents of the extra signal information on the target
40727 system. The annex part of the generic @samp{qXfer} packet must be
40728 empty (@pxref{qXfer read}).
40730 This packet is not probed by default; the remote stub must request it,
40731 by supplying an appropriate @samp{qSupported} response
40732 (@pxref{qSupported}).
40734 @item qXfer:threads:read::@var{offset},@var{length}
40735 @anchor{qXfer threads read}
40736 Access the list of threads on target. @xref{Thread List Format}. The
40737 annex part of the generic @samp{qXfer} packet must be empty
40738 (@pxref{qXfer read}).
40740 This packet is not probed by default; the remote stub must request it,
40741 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40743 @item qXfer:traceframe-info:read::@var{offset},@var{length}
40744 @anchor{qXfer traceframe info read}
40746 Return a description of the current traceframe's contents.
40747 @xref{Traceframe Info Format}. The annex part of the generic
40748 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
40750 This packet is not probed by default; the remote stub must request it,
40751 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40753 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
40754 @anchor{qXfer unwind info block}
40756 Return the unwind information block for @var{pc}. This packet is used
40757 on OpenVMS/ia64 to ask the kernel unwind information.
40759 This packet is not probed by default.
40761 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
40762 @anchor{qXfer fdpic loadmap read}
40763 Read contents of @code{loadmap}s on the target system. The
40764 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
40765 executable @code{loadmap} or interpreter @code{loadmap} to read.
40767 This packet is not probed by default; the remote stub must request it,
40768 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40770 @item qXfer:osdata:read::@var{offset},@var{length}
40771 @anchor{qXfer osdata read}
40772 Access the target's @dfn{operating system information}.
40773 @xref{Operating System Information}.
40777 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
40778 @cindex write data into object, remote request
40779 @anchor{qXfer write}
40780 Write uninterpreted bytes into the target's special data area
40781 identified by the keyword @var{object}, starting at @var{offset} bytes
40782 into the data. The binary-encoded data (@pxref{Binary Data}) to be
40783 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
40784 is specific to @var{object}; it can supply additional details about what data
40790 @var{nn} (hex encoded) is the number of bytes written.
40791 This may be fewer bytes than supplied in the request.
40794 The request was malformed, or @var{annex} was invalid.
40797 The offset was invalid, or there was an error encountered writing the data.
40798 The @var{nn} part is a hex-encoded @code{errno} value.
40801 An empty reply indicates the @var{object} string was not
40802 recognized by the stub, or that the object does not support writing.
40805 Here are the specific requests of this form defined so far. All the
40806 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
40807 formats, listed above.
40810 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
40811 @anchor{qXfer siginfo write}
40812 Write @var{data} to the extra signal information on the target system.
40813 The annex part of the generic @samp{qXfer} packet must be
40814 empty (@pxref{qXfer write}).
40816 This packet is not probed by default; the remote stub must request it,
40817 by supplying an appropriate @samp{qSupported} response
40818 (@pxref{qSupported}).
40821 @item qXfer:@var{object}:@var{operation}:@dots{}
40822 Requests of this form may be added in the future. When a stub does
40823 not recognize the @var{object} keyword, or its support for
40824 @var{object} does not recognize the @var{operation} keyword, the stub
40825 must respond with an empty packet.
40827 @item qAttached:@var{pid}
40828 @cindex query attached, remote request
40829 @cindex @samp{qAttached} packet
40830 Return an indication of whether the remote server attached to an
40831 existing process or created a new process. When the multiprocess
40832 protocol extensions are supported (@pxref{multiprocess extensions}),
40833 @var{pid} is an integer in hexadecimal format identifying the target
40834 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
40835 the query packet will be simplified as @samp{qAttached}.
40837 This query is used, for example, to know whether the remote process
40838 should be detached or killed when a @value{GDBN} session is ended with
40839 the @code{quit} command.
40844 The remote server attached to an existing process.
40846 The remote server created a new process.
40848 A badly formed request or an error was encountered.
40852 Enable branch tracing for the current thread using Branch Trace Store.
40857 Branch tracing has been enabled.
40859 A badly formed request or an error was encountered.
40863 Enable branch tracing for the current thread using Intel Processor Trace.
40868 Branch tracing has been enabled.
40870 A badly formed request or an error was encountered.
40874 Disable branch tracing for the current thread.
40879 Branch tracing has been disabled.
40881 A badly formed request or an error was encountered.
40884 @item Qbtrace-conf:bts:size=@var{value}
40885 Set the requested ring buffer size for new threads that use the
40886 btrace recording method in bts format.
40891 The ring buffer size has been set.
40893 A badly formed request or an error was encountered.
40896 @item Qbtrace-conf:pt:size=@var{value}
40897 Set the requested ring buffer size for new threads that use the
40898 btrace recording method in pt format.
40903 The ring buffer size has been set.
40905 A badly formed request or an error was encountered.
40910 @node Architecture-Specific Protocol Details
40911 @section Architecture-Specific Protocol Details
40913 This section describes how the remote protocol is applied to specific
40914 target architectures. Also see @ref{Standard Target Features}, for
40915 details of XML target descriptions for each architecture.
40918 * ARM-Specific Protocol Details::
40919 * MIPS-Specific Protocol Details::
40922 @node ARM-Specific Protocol Details
40923 @subsection @acronym{ARM}-specific Protocol Details
40926 * ARM Breakpoint Kinds::
40929 @node ARM Breakpoint Kinds
40930 @subsubsection @acronym{ARM} Breakpoint Kinds
40931 @cindex breakpoint kinds, @acronym{ARM}
40933 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
40938 16-bit Thumb mode breakpoint.
40941 32-bit Thumb mode (Thumb-2) breakpoint.
40944 32-bit @acronym{ARM} mode breakpoint.
40948 @node MIPS-Specific Protocol Details
40949 @subsection @acronym{MIPS}-specific Protocol Details
40952 * MIPS Register packet Format::
40953 * MIPS Breakpoint Kinds::
40956 @node MIPS Register packet Format
40957 @subsubsection @acronym{MIPS} Register Packet Format
40958 @cindex register packet format, @acronym{MIPS}
40960 The following @code{g}/@code{G} packets have previously been defined.
40961 In the below, some thirty-two bit registers are transferred as
40962 sixty-four bits. Those registers should be zero/sign extended (which?)
40963 to fill the space allocated. Register bytes are transferred in target
40964 byte order. The two nibbles within a register byte are transferred
40965 most-significant -- least-significant.
40970 All registers are transferred as thirty-two bit quantities in the order:
40971 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
40972 registers; fsr; fir; fp.
40975 All registers are transferred as sixty-four bit quantities (including
40976 thirty-two bit registers such as @code{sr}). The ordering is the same
40981 @node MIPS Breakpoint Kinds
40982 @subsubsection @acronym{MIPS} Breakpoint Kinds
40983 @cindex breakpoint kinds, @acronym{MIPS}
40985 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
40990 16-bit @acronym{MIPS16} mode breakpoint.
40993 16-bit @acronym{microMIPS} mode breakpoint.
40996 32-bit standard @acronym{MIPS} mode breakpoint.
40999 32-bit @acronym{microMIPS} mode breakpoint.
41003 @node Tracepoint Packets
41004 @section Tracepoint Packets
41005 @cindex tracepoint packets
41006 @cindex packets, tracepoint
41008 Here we describe the packets @value{GDBN} uses to implement
41009 tracepoints (@pxref{Tracepoints}).
41013 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
41014 @cindex @samp{QTDP} packet
41015 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
41016 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
41017 the tracepoint is disabled. The @var{step} gives the tracepoint's step
41018 count, and @var{pass} gives its pass count. If an @samp{F} is present,
41019 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
41020 the number of bytes that the target should copy elsewhere to make room
41021 for the tracepoint. If an @samp{X} is present, it introduces a
41022 tracepoint condition, which consists of a hexadecimal length, followed
41023 by a comma and hex-encoded bytes, in a manner similar to action
41024 encodings as described below. If the trailing @samp{-} is present,
41025 further @samp{QTDP} packets will follow to specify this tracepoint's
41031 The packet was understood and carried out.
41033 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
41035 The packet was not recognized.
41038 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
41039 Define actions to be taken when a tracepoint is hit. The @var{n} and
41040 @var{addr} must be the same as in the initial @samp{QTDP} packet for
41041 this tracepoint. This packet may only be sent immediately after
41042 another @samp{QTDP} packet that ended with a @samp{-}. If the
41043 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
41044 specifying more actions for this tracepoint.
41046 In the series of action packets for a given tracepoint, at most one
41047 can have an @samp{S} before its first @var{action}. If such a packet
41048 is sent, it and the following packets define ``while-stepping''
41049 actions. Any prior packets define ordinary actions --- that is, those
41050 taken when the tracepoint is first hit. If no action packet has an
41051 @samp{S}, then all the packets in the series specify ordinary
41052 tracepoint actions.
41054 The @samp{@var{action}@dots{}} portion of the packet is a series of
41055 actions, concatenated without separators. Each action has one of the
41061 Collect the registers whose bits are set in @var{mask},
41062 a hexadecimal number whose @var{i}'th bit is set if register number
41063 @var{i} should be collected. (The least significant bit is numbered
41064 zero.) Note that @var{mask} may be any number of digits long; it may
41065 not fit in a 32-bit word.
41067 @item M @var{basereg},@var{offset},@var{len}
41068 Collect @var{len} bytes of memory starting at the address in register
41069 number @var{basereg}, plus @var{offset}. If @var{basereg} is
41070 @samp{-1}, then the range has a fixed address: @var{offset} is the
41071 address of the lowest byte to collect. The @var{basereg},
41072 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
41073 values (the @samp{-1} value for @var{basereg} is a special case).
41075 @item X @var{len},@var{expr}
41076 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
41077 it directs. The agent expression @var{expr} is as described in
41078 @ref{Agent Expressions}. Each byte of the expression is encoded as a
41079 two-digit hex number in the packet; @var{len} is the number of bytes
41080 in the expression (and thus one-half the number of hex digits in the
41085 Any number of actions may be packed together in a single @samp{QTDP}
41086 packet, as long as the packet does not exceed the maximum packet
41087 length (400 bytes, for many stubs). There may be only one @samp{R}
41088 action per tracepoint, and it must precede any @samp{M} or @samp{X}
41089 actions. Any registers referred to by @samp{M} and @samp{X} actions
41090 must be collected by a preceding @samp{R} action. (The
41091 ``while-stepping'' actions are treated as if they were attached to a
41092 separate tracepoint, as far as these restrictions are concerned.)
41097 The packet was understood and carried out.
41099 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
41101 The packet was not recognized.
41104 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
41105 @cindex @samp{QTDPsrc} packet
41106 Specify a source string of tracepoint @var{n} at address @var{addr}.
41107 This is useful to get accurate reproduction of the tracepoints
41108 originally downloaded at the beginning of the trace run. The @var{type}
41109 is the name of the tracepoint part, such as @samp{cond} for the
41110 tracepoint's conditional expression (see below for a list of types), while
41111 @var{bytes} is the string, encoded in hexadecimal.
41113 @var{start} is the offset of the @var{bytes} within the overall source
41114 string, while @var{slen} is the total length of the source string.
41115 This is intended for handling source strings that are longer than will
41116 fit in a single packet.
41117 @c Add detailed example when this info is moved into a dedicated
41118 @c tracepoint descriptions section.
41120 The available string types are @samp{at} for the location,
41121 @samp{cond} for the conditional, and @samp{cmd} for an action command.
41122 @value{GDBN} sends a separate packet for each command in the action
41123 list, in the same order in which the commands are stored in the list.
41125 The target does not need to do anything with source strings except
41126 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
41129 Although this packet is optional, and @value{GDBN} will only send it
41130 if the target replies with @samp{TracepointSource} @xref{General
41131 Query Packets}, it makes both disconnected tracing and trace files
41132 much easier to use. Otherwise the user must be careful that the
41133 tracepoints in effect while looking at trace frames are identical to
41134 the ones in effect during the trace run; even a small discrepancy
41135 could cause @samp{tdump} not to work, or a particular trace frame not
41138 @item QTDV:@var{n}:@var{value}:@var{builtin}:@var{name}
41139 @cindex define trace state variable, remote request
41140 @cindex @samp{QTDV} packet
41141 Create a new trace state variable, number @var{n}, with an initial
41142 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
41143 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
41144 the option of not using this packet for initial values of zero; the
41145 target should simply create the trace state variables as they are
41146 mentioned in expressions. The value @var{builtin} should be 1 (one)
41147 if the trace state variable is builtin and 0 (zero) if it is not builtin.
41148 @value{GDBN} only sets @var{builtin} to 1 if a previous @samp{qTfV} or
41149 @samp{qTsV} packet had it set. The contents of @var{name} is the
41150 hex-encoded name (without the leading @samp{$}) of the trace state
41153 @item QTFrame:@var{n}
41154 @cindex @samp{QTFrame} packet
41155 Select the @var{n}'th tracepoint frame from the buffer, and use the
41156 register and memory contents recorded there to answer subsequent
41157 request packets from @value{GDBN}.
41159 A successful reply from the stub indicates that the stub has found the
41160 requested frame. The response is a series of parts, concatenated
41161 without separators, describing the frame we selected. Each part has
41162 one of the following forms:
41166 The selected frame is number @var{n} in the trace frame buffer;
41167 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
41168 was no frame matching the criteria in the request packet.
41171 The selected trace frame records a hit of tracepoint number @var{t};
41172 @var{t} is a hexadecimal number.
41176 @item QTFrame:pc:@var{addr}
41177 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
41178 currently selected frame whose PC is @var{addr};
41179 @var{addr} is a hexadecimal number.
41181 @item QTFrame:tdp:@var{t}
41182 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
41183 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
41184 is a hexadecimal number.
41186 @item QTFrame:range:@var{start}:@var{end}
41187 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
41188 currently selected frame whose PC is between @var{start} (inclusive)
41189 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
41192 @item QTFrame:outside:@var{start}:@var{end}
41193 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
41194 frame @emph{outside} the given range of addresses (exclusive).
41197 @cindex @samp{qTMinFTPILen} packet
41198 This packet requests the minimum length of instruction at which a fast
41199 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
41200 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
41201 it depends on the target system being able to create trampolines in
41202 the first 64K of memory, which might or might not be possible for that
41203 system. So the reply to this packet will be 4 if it is able to
41210 The minimum instruction length is currently unknown.
41212 The minimum instruction length is @var{length}, where @var{length}
41213 is a hexadecimal number greater or equal to 1. A reply
41214 of 1 means that a fast tracepoint may be placed on any instruction
41215 regardless of size.
41217 An error has occurred.
41219 An empty reply indicates that the request is not supported by the stub.
41223 @cindex @samp{QTStart} packet
41224 Begin the tracepoint experiment. Begin collecting data from
41225 tracepoint hits in the trace frame buffer. This packet supports the
41226 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
41227 instruction reply packet}).
41230 @cindex @samp{QTStop} packet
41231 End the tracepoint experiment. Stop collecting trace frames.
41233 @item QTEnable:@var{n}:@var{addr}
41235 @cindex @samp{QTEnable} packet
41236 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
41237 experiment. If the tracepoint was previously disabled, then collection
41238 of data from it will resume.
41240 @item QTDisable:@var{n}:@var{addr}
41242 @cindex @samp{QTDisable} packet
41243 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
41244 experiment. No more data will be collected from the tracepoint unless
41245 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
41248 @cindex @samp{QTinit} packet
41249 Clear the table of tracepoints, and empty the trace frame buffer.
41251 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
41252 @cindex @samp{QTro} packet
41253 Establish the given ranges of memory as ``transparent''. The stub
41254 will answer requests for these ranges from memory's current contents,
41255 if they were not collected as part of the tracepoint hit.
41257 @value{GDBN} uses this to mark read-only regions of memory, like those
41258 containing program code. Since these areas never change, they should
41259 still have the same contents they did when the tracepoint was hit, so
41260 there's no reason for the stub to refuse to provide their contents.
41262 @item QTDisconnected:@var{value}
41263 @cindex @samp{QTDisconnected} packet
41264 Set the choice to what to do with the tracing run when @value{GDBN}
41265 disconnects from the target. A @var{value} of 1 directs the target to
41266 continue the tracing run, while 0 tells the target to stop tracing if
41267 @value{GDBN} is no longer in the picture.
41270 @cindex @samp{qTStatus} packet
41271 Ask the stub if there is a trace experiment running right now.
41273 The reply has the form:
41277 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
41278 @var{running} is a single digit @code{1} if the trace is presently
41279 running, or @code{0} if not. It is followed by semicolon-separated
41280 optional fields that an agent may use to report additional status.
41284 If the trace is not running, the agent may report any of several
41285 explanations as one of the optional fields:
41290 No trace has been run yet.
41292 @item tstop[:@var{text}]:0
41293 The trace was stopped by a user-originated stop command. The optional
41294 @var{text} field is a user-supplied string supplied as part of the
41295 stop command (for instance, an explanation of why the trace was
41296 stopped manually). It is hex-encoded.
41299 The trace stopped because the trace buffer filled up.
41301 @item tdisconnected:0
41302 The trace stopped because @value{GDBN} disconnected from the target.
41304 @item tpasscount:@var{tpnum}
41305 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
41307 @item terror:@var{text}:@var{tpnum}
41308 The trace stopped because tracepoint @var{tpnum} had an error. The
41309 string @var{text} is available to describe the nature of the error
41310 (for instance, a divide by zero in the condition expression); it
41314 The trace stopped for some other reason.
41318 Additional optional fields supply statistical and other information.
41319 Although not required, they are extremely useful for users monitoring
41320 the progress of a trace run. If a trace has stopped, and these
41321 numbers are reported, they must reflect the state of the just-stopped
41326 @item tframes:@var{n}
41327 The number of trace frames in the buffer.
41329 @item tcreated:@var{n}
41330 The total number of trace frames created during the run. This may
41331 be larger than the trace frame count, if the buffer is circular.
41333 @item tsize:@var{n}
41334 The total size of the trace buffer, in bytes.
41336 @item tfree:@var{n}
41337 The number of bytes still unused in the buffer.
41339 @item circular:@var{n}
41340 The value of the circular trace buffer flag. @code{1} means that the
41341 trace buffer is circular and old trace frames will be discarded if
41342 necessary to make room, @code{0} means that the trace buffer is linear
41345 @item disconn:@var{n}
41346 The value of the disconnected tracing flag. @code{1} means that
41347 tracing will continue after @value{GDBN} disconnects, @code{0} means
41348 that the trace run will stop.
41352 @item qTP:@var{tp}:@var{addr}
41353 @cindex tracepoint status, remote request
41354 @cindex @samp{qTP} packet
41355 Ask the stub for the current state of tracepoint number @var{tp} at
41356 address @var{addr}.
41360 @item V@var{hits}:@var{usage}
41361 The tracepoint has been hit @var{hits} times so far during the trace
41362 run, and accounts for @var{usage} in the trace buffer. Note that
41363 @code{while-stepping} steps are not counted as separate hits, but the
41364 steps' space consumption is added into the usage number.
41368 @item qTV:@var{var}
41369 @cindex trace state variable value, remote request
41370 @cindex @samp{qTV} packet
41371 Ask the stub for the value of the trace state variable number @var{var}.
41376 The value of the variable is @var{value}. This will be the current
41377 value of the variable if the user is examining a running target, or a
41378 saved value if the variable was collected in the trace frame that the
41379 user is looking at. Note that multiple requests may result in
41380 different reply values, such as when requesting values while the
41381 program is running.
41384 The value of the variable is unknown. This would occur, for example,
41385 if the user is examining a trace frame in which the requested variable
41390 @cindex @samp{qTfP} packet
41392 @cindex @samp{qTsP} packet
41393 These packets request data about tracepoints that are being used by
41394 the target. @value{GDBN} sends @code{qTfP} to get the first piece
41395 of data, and multiple @code{qTsP} to get additional pieces. Replies
41396 to these packets generally take the form of the @code{QTDP} packets
41397 that define tracepoints. (FIXME add detailed syntax)
41400 @cindex @samp{qTfV} packet
41402 @cindex @samp{qTsV} packet
41403 These packets request data about trace state variables that are on the
41404 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
41405 and multiple @code{qTsV} to get additional variables. Replies to
41406 these packets follow the syntax of the @code{QTDV} packets that define
41407 trace state variables.
41413 @cindex @samp{qTfSTM} packet
41414 @cindex @samp{qTsSTM} packet
41415 These packets request data about static tracepoint markers that exist
41416 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
41417 first piece of data, and multiple @code{qTsSTM} to get additional
41418 pieces. Replies to these packets take the following form:
41422 @item m @var{address}:@var{id}:@var{extra}
41424 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
41425 a comma-separated list of markers
41427 (lower case letter @samp{L}) denotes end of list.
41429 An error occurred. The error number @var{nn} is given as hex digits.
41431 An empty reply indicates that the request is not supported by the
41435 The @var{address} is encoded in hex;
41436 @var{id} and @var{extra} are strings encoded in hex.
41438 In response to each query, the target will reply with a list of one or
41439 more markers, separated by commas. @value{GDBN} will respond to each
41440 reply with a request for more markers (using the @samp{qs} form of the
41441 query), until the target responds with @samp{l} (lower-case ell, for
41444 @item qTSTMat:@var{address}
41446 @cindex @samp{qTSTMat} packet
41447 This packets requests data about static tracepoint markers in the
41448 target program at @var{address}. Replies to this packet follow the
41449 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
41450 tracepoint markers.
41452 @item QTSave:@var{filename}
41453 @cindex @samp{QTSave} packet
41454 This packet directs the target to save trace data to the file name
41455 @var{filename} in the target's filesystem. The @var{filename} is encoded
41456 as a hex string; the interpretation of the file name (relative vs
41457 absolute, wild cards, etc) is up to the target.
41459 @item qTBuffer:@var{offset},@var{len}
41460 @cindex @samp{qTBuffer} packet
41461 Return up to @var{len} bytes of the current contents of trace buffer,
41462 starting at @var{offset}. The trace buffer is treated as if it were
41463 a contiguous collection of traceframes, as per the trace file format.
41464 The reply consists as many hex-encoded bytes as the target can deliver
41465 in a packet; it is not an error to return fewer than were asked for.
41466 A reply consisting of just @code{l} indicates that no bytes are
41469 @item QTBuffer:circular:@var{value}
41470 This packet directs the target to use a circular trace buffer if
41471 @var{value} is 1, or a linear buffer if the value is 0.
41473 @item QTBuffer:size:@var{size}
41474 @anchor{QTBuffer-size}
41475 @cindex @samp{QTBuffer size} packet
41476 This packet directs the target to make the trace buffer be of size
41477 @var{size} if possible. A value of @code{-1} tells the target to
41478 use whatever size it prefers.
41480 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
41481 @cindex @samp{QTNotes} packet
41482 This packet adds optional textual notes to the trace run. Allowable
41483 types include @code{user}, @code{notes}, and @code{tstop}, the
41484 @var{text} fields are arbitrary strings, hex-encoded.
41488 @subsection Relocate instruction reply packet
41489 When installing fast tracepoints in memory, the target may need to
41490 relocate the instruction currently at the tracepoint address to a
41491 different address in memory. For most instructions, a simple copy is
41492 enough, but, for example, call instructions that implicitly push the
41493 return address on the stack, and relative branches or other
41494 PC-relative instructions require offset adjustment, so that the effect
41495 of executing the instruction at a different address is the same as if
41496 it had executed in the original location.
41498 In response to several of the tracepoint packets, the target may also
41499 respond with a number of intermediate @samp{qRelocInsn} request
41500 packets before the final result packet, to have @value{GDBN} handle
41501 this relocation operation. If a packet supports this mechanism, its
41502 documentation will explicitly say so. See for example the above
41503 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
41504 format of the request is:
41507 @item qRelocInsn:@var{from};@var{to}
41509 This requests @value{GDBN} to copy instruction at address @var{from}
41510 to address @var{to}, possibly adjusted so that executing the
41511 instruction at @var{to} has the same effect as executing it at
41512 @var{from}. @value{GDBN} writes the adjusted instruction to target
41513 memory starting at @var{to}.
41518 @item qRelocInsn:@var{adjusted_size}
41519 Informs the stub the relocation is complete. The @var{adjusted_size} is
41520 the length in bytes of resulting relocated instruction sequence.
41522 A badly formed request was detected, or an error was encountered while
41523 relocating the instruction.
41526 @node Host I/O Packets
41527 @section Host I/O Packets
41528 @cindex Host I/O, remote protocol
41529 @cindex file transfer, remote protocol
41531 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
41532 operations on the far side of a remote link. For example, Host I/O is
41533 used to upload and download files to a remote target with its own
41534 filesystem. Host I/O uses the same constant values and data structure
41535 layout as the target-initiated File-I/O protocol. However, the
41536 Host I/O packets are structured differently. The target-initiated
41537 protocol relies on target memory to store parameters and buffers.
41538 Host I/O requests are initiated by @value{GDBN}, and the
41539 target's memory is not involved. @xref{File-I/O Remote Protocol
41540 Extension}, for more details on the target-initiated protocol.
41542 The Host I/O request packets all encode a single operation along with
41543 its arguments. They have this format:
41547 @item vFile:@var{operation}: @var{parameter}@dots{}
41548 @var{operation} is the name of the particular request; the target
41549 should compare the entire packet name up to the second colon when checking
41550 for a supported operation. The format of @var{parameter} depends on
41551 the operation. Numbers are always passed in hexadecimal. Negative
41552 numbers have an explicit minus sign (i.e.@: two's complement is not
41553 used). Strings (e.g.@: filenames) are encoded as a series of
41554 hexadecimal bytes. The last argument to a system call may be a
41555 buffer of escaped binary data (@pxref{Binary Data}).
41559 The valid responses to Host I/O packets are:
41563 @item F @var{result} [, @var{errno}] [; @var{attachment}]
41564 @var{result} is the integer value returned by this operation, usually
41565 non-negative for success and -1 for errors. If an error has occured,
41566 @var{errno} will be included in the result specifying a
41567 value defined by the File-I/O protocol (@pxref{Errno Values}). For
41568 operations which return data, @var{attachment} supplies the data as a
41569 binary buffer. Binary buffers in response packets are escaped in the
41570 normal way (@pxref{Binary Data}). See the individual packet
41571 documentation for the interpretation of @var{result} and
41575 An empty response indicates that this operation is not recognized.
41579 These are the supported Host I/O operations:
41582 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
41583 Open a file at @var{filename} and return a file descriptor for it, or
41584 return -1 if an error occurs. The @var{filename} is a string,
41585 @var{flags} is an integer indicating a mask of open flags
41586 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
41587 of mode bits to use if the file is created (@pxref{mode_t Values}).
41588 @xref{open}, for details of the open flags and mode values.
41590 @item vFile:close: @var{fd}
41591 Close the open file corresponding to @var{fd} and return 0, or
41592 -1 if an error occurs.
41594 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
41595 Read data from the open file corresponding to @var{fd}. Up to
41596 @var{count} bytes will be read from the file, starting at @var{offset}
41597 relative to the start of the file. The target may read fewer bytes;
41598 common reasons include packet size limits and an end-of-file
41599 condition. The number of bytes read is returned. Zero should only be
41600 returned for a successful read at the end of the file, or if
41601 @var{count} was zero.
41603 The data read should be returned as a binary attachment on success.
41604 If zero bytes were read, the response should include an empty binary
41605 attachment (i.e.@: a trailing semicolon). The return value is the
41606 number of target bytes read; the binary attachment may be longer if
41607 some characters were escaped.
41609 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
41610 Write @var{data} (a binary buffer) to the open file corresponding
41611 to @var{fd}. Start the write at @var{offset} from the start of the
41612 file. Unlike many @code{write} system calls, there is no
41613 separate @var{count} argument; the length of @var{data} in the
41614 packet is used. @samp{vFile:write} returns the number of bytes written,
41615 which may be shorter than the length of @var{data}, or -1 if an
41618 @item vFile:fstat: @var{fd}
41619 Get information about the open file corresponding to @var{fd}.
41620 On success the information is returned as a binary attachment
41621 and the return value is the size of this attachment in bytes.
41622 If an error occurs the return value is -1. The format of the
41623 returned binary attachment is as described in @ref{struct stat}.
41625 @item vFile:unlink: @var{filename}
41626 Delete the file at @var{filename} on the target. Return 0,
41627 or -1 if an error occurs. The @var{filename} is a string.
41629 @item vFile:readlink: @var{filename}
41630 Read value of symbolic link @var{filename} on the target. Return
41631 the number of bytes read, or -1 if an error occurs.
41633 The data read should be returned as a binary attachment on success.
41634 If zero bytes were read, the response should include an empty binary
41635 attachment (i.e.@: a trailing semicolon). The return value is the
41636 number of target bytes read; the binary attachment may be longer if
41637 some characters were escaped.
41639 @item vFile:setfs: @var{pid}
41640 Select the filesystem on which @code{vFile} operations with
41641 @var{filename} arguments will operate. This is required for
41642 @value{GDBN} to be able to access files on remote targets where
41643 the remote stub does not share a common filesystem with the
41646 If @var{pid} is nonzero, select the filesystem as seen by process
41647 @var{pid}. If @var{pid} is zero, select the filesystem as seen by
41648 the remote stub. Return 0 on success, or -1 if an error occurs.
41649 If @code{vFile:setfs:} indicates success, the selected filesystem
41650 remains selected until the next successful @code{vFile:setfs:}
41656 @section Interrupts
41657 @cindex interrupts (remote protocol)
41658 @anchor{interrupting remote targets}
41660 In all-stop mode, when a program on the remote target is running,
41661 @value{GDBN} may attempt to interrupt it by sending a @samp{Ctrl-C},
41662 @code{BREAK} or a @code{BREAK} followed by @code{g}, control of which
41663 is specified via @value{GDBN}'s @samp{interrupt-sequence}.
41665 The precise meaning of @code{BREAK} is defined by the transport
41666 mechanism and may, in fact, be undefined. @value{GDBN} does not
41667 currently define a @code{BREAK} mechanism for any of the network
41668 interfaces except for TCP, in which case @value{GDBN} sends the
41669 @code{telnet} BREAK sequence.
41671 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
41672 transport mechanisms. It is represented by sending the single byte
41673 @code{0x03} without any of the usual packet overhead described in
41674 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
41675 transmitted as part of a packet, it is considered to be packet data
41676 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
41677 (@pxref{X packet}), used for binary downloads, may include an unescaped
41678 @code{0x03} as part of its packet.
41680 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
41681 When Linux kernel receives this sequence from serial port,
41682 it stops execution and connects to gdb.
41684 In non-stop mode, because packet resumptions are asynchronous
41685 (@pxref{vCont packet}), @value{GDBN} is always free to send a remote
41686 command to the remote stub, even when the target is running. For that
41687 reason, @value{GDBN} instead sends a regular packet (@pxref{vCtrlC
41688 packet}) with the usual packet framing instead of the single byte
41691 Stubs are not required to recognize these interrupt mechanisms and the
41692 precise meaning associated with receipt of the interrupt is
41693 implementation defined. If the target supports debugging of multiple
41694 threads and/or processes, it should attempt to interrupt all
41695 currently-executing threads and processes.
41696 If the stub is successful at interrupting the
41697 running program, it should send one of the stop
41698 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
41699 of successfully stopping the program in all-stop mode, and a stop reply
41700 for each stopped thread in non-stop mode.
41701 Interrupts received while the
41702 program is stopped are queued and the program will be interrupted when
41703 it is resumed next time.
41705 @node Notification Packets
41706 @section Notification Packets
41707 @cindex notification packets
41708 @cindex packets, notification
41710 The @value{GDBN} remote serial protocol includes @dfn{notifications},
41711 packets that require no acknowledgment. Both the GDB and the stub
41712 may send notifications (although the only notifications defined at
41713 present are sent by the stub). Notifications carry information
41714 without incurring the round-trip latency of an acknowledgment, and so
41715 are useful for low-impact communications where occasional packet loss
41718 A notification packet has the form @samp{% @var{data} #
41719 @var{checksum}}, where @var{data} is the content of the notification,
41720 and @var{checksum} is a checksum of @var{data}, computed and formatted
41721 as for ordinary @value{GDBN} packets. A notification's @var{data}
41722 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
41723 receiving a notification, the recipient sends no @samp{+} or @samp{-}
41724 to acknowledge the notification's receipt or to report its corruption.
41726 Every notification's @var{data} begins with a name, which contains no
41727 colon characters, followed by a colon character.
41729 Recipients should silently ignore corrupted notifications and
41730 notifications they do not understand. Recipients should restart
41731 timeout periods on receipt of a well-formed notification, whether or
41732 not they understand it.
41734 Senders should only send the notifications described here when this
41735 protocol description specifies that they are permitted. In the
41736 future, we may extend the protocol to permit existing notifications in
41737 new contexts; this rule helps older senders avoid confusing newer
41740 (Older versions of @value{GDBN} ignore bytes received until they see
41741 the @samp{$} byte that begins an ordinary packet, so new stubs may
41742 transmit notifications without fear of confusing older clients. There
41743 are no notifications defined for @value{GDBN} to send at the moment, but we
41744 assume that most older stubs would ignore them, as well.)
41746 Each notification is comprised of three parts:
41748 @item @var{name}:@var{event}
41749 The notification packet is sent by the side that initiates the
41750 exchange (currently, only the stub does that), with @var{event}
41751 carrying the specific information about the notification, and
41752 @var{name} specifying the name of the notification.
41754 The acknowledge sent by the other side, usually @value{GDBN}, to
41755 acknowledge the exchange and request the event.
41758 The purpose of an asynchronous notification mechanism is to report to
41759 @value{GDBN} that something interesting happened in the remote stub.
41761 The remote stub may send notification @var{name}:@var{event}
41762 at any time, but @value{GDBN} acknowledges the notification when
41763 appropriate. The notification event is pending before @value{GDBN}
41764 acknowledges. Only one notification at a time may be pending; if
41765 additional events occur before @value{GDBN} has acknowledged the
41766 previous notification, they must be queued by the stub for later
41767 synchronous transmission in response to @var{ack} packets from
41768 @value{GDBN}. Because the notification mechanism is unreliable,
41769 the stub is permitted to resend a notification if it believes
41770 @value{GDBN} may not have received it.
41772 Specifically, notifications may appear when @value{GDBN} is not
41773 otherwise reading input from the stub, or when @value{GDBN} is
41774 expecting to read a normal synchronous response or a
41775 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
41776 Notification packets are distinct from any other communication from
41777 the stub so there is no ambiguity.
41779 After receiving a notification, @value{GDBN} shall acknowledge it by
41780 sending a @var{ack} packet as a regular, synchronous request to the
41781 stub. Such acknowledgment is not required to happen immediately, as
41782 @value{GDBN} is permitted to send other, unrelated packets to the
41783 stub first, which the stub should process normally.
41785 Upon receiving a @var{ack} packet, if the stub has other queued
41786 events to report to @value{GDBN}, it shall respond by sending a
41787 normal @var{event}. @value{GDBN} shall then send another @var{ack}
41788 packet to solicit further responses; again, it is permitted to send
41789 other, unrelated packets as well which the stub should process
41792 If the stub receives a @var{ack} packet and there are no additional
41793 @var{event} to report, the stub shall return an @samp{OK} response.
41794 At this point, @value{GDBN} has finished processing a notification
41795 and the stub has completed sending any queued events. @value{GDBN}
41796 won't accept any new notifications until the final @samp{OK} is
41797 received . If further notification events occur, the stub shall send
41798 a new notification, @value{GDBN} shall accept the notification, and
41799 the process shall be repeated.
41801 The process of asynchronous notification can be illustrated by the
41804 <- @code{%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
41807 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
41809 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
41814 The following notifications are defined:
41815 @multitable @columnfractions 0.12 0.12 0.38 0.38
41824 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
41825 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
41826 for information on how these notifications are acknowledged by
41828 @tab Report an asynchronous stop event in non-stop mode.
41832 @node Remote Non-Stop
41833 @section Remote Protocol Support for Non-Stop Mode
41835 @value{GDBN}'s remote protocol supports non-stop debugging of
41836 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
41837 supports non-stop mode, it should report that to @value{GDBN} by including
41838 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
41840 @value{GDBN} typically sends a @samp{QNonStop} packet only when
41841 establishing a new connection with the stub. Entering non-stop mode
41842 does not alter the state of any currently-running threads, but targets
41843 must stop all threads in any already-attached processes when entering
41844 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
41845 probe the target state after a mode change.
41847 In non-stop mode, when an attached process encounters an event that
41848 would otherwise be reported with a stop reply, it uses the
41849 asynchronous notification mechanism (@pxref{Notification Packets}) to
41850 inform @value{GDBN}. In contrast to all-stop mode, where all threads
41851 in all processes are stopped when a stop reply is sent, in non-stop
41852 mode only the thread reporting the stop event is stopped. That is,
41853 when reporting a @samp{S} or @samp{T} response to indicate completion
41854 of a step operation, hitting a breakpoint, or a fault, only the
41855 affected thread is stopped; any other still-running threads continue
41856 to run. When reporting a @samp{W} or @samp{X} response, all running
41857 threads belonging to other attached processes continue to run.
41859 In non-stop mode, the target shall respond to the @samp{?} packet as
41860 follows. First, any incomplete stop reply notification/@samp{vStopped}
41861 sequence in progress is abandoned. The target must begin a new
41862 sequence reporting stop events for all stopped threads, whether or not
41863 it has previously reported those events to @value{GDBN}. The first
41864 stop reply is sent as a synchronous reply to the @samp{?} packet, and
41865 subsequent stop replies are sent as responses to @samp{vStopped} packets
41866 using the mechanism described above. The target must not send
41867 asynchronous stop reply notifications until the sequence is complete.
41868 If all threads are running when the target receives the @samp{?} packet,
41869 or if the target is not attached to any process, it shall respond
41872 If the stub supports non-stop mode, it should also support the
41873 @samp{swbreak} stop reason if software breakpoints are supported, and
41874 the @samp{hwbreak} stop reason if hardware breakpoints are supported
41875 (@pxref{swbreak stop reason}). This is because given the asynchronous
41876 nature of non-stop mode, between the time a thread hits a breakpoint
41877 and the time the event is finally processed by @value{GDBN}, the
41878 breakpoint may have already been removed from the target. Due to
41879 this, @value{GDBN} needs to be able to tell whether a trap stop was
41880 caused by a delayed breakpoint event, which should be ignored, as
41881 opposed to a random trap signal, which should be reported to the user.
41882 Note the @samp{swbreak} feature implies that the target is responsible
41883 for adjusting the PC when a software breakpoint triggers, if
41884 necessary, such as on the x86 architecture.
41886 @node Packet Acknowledgment
41887 @section Packet Acknowledgment
41889 @cindex acknowledgment, for @value{GDBN} remote
41890 @cindex packet acknowledgment, for @value{GDBN} remote
41891 By default, when either the host or the target machine receives a packet,
41892 the first response expected is an acknowledgment: either @samp{+} (to indicate
41893 the package was received correctly) or @samp{-} (to request retransmission).
41894 This mechanism allows the @value{GDBN} remote protocol to operate over
41895 unreliable transport mechanisms, such as a serial line.
41897 In cases where the transport mechanism is itself reliable (such as a pipe or
41898 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
41899 It may be desirable to disable them in that case to reduce communication
41900 overhead, or for other reasons. This can be accomplished by means of the
41901 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
41903 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
41904 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
41905 and response format still includes the normal checksum, as described in
41906 @ref{Overview}, but the checksum may be ignored by the receiver.
41908 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
41909 no-acknowledgment mode, it should report that to @value{GDBN}
41910 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
41911 @pxref{qSupported}.
41912 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
41913 disabled via the @code{set remote noack-packet off} command
41914 (@pxref{Remote Configuration}),
41915 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
41916 Only then may the stub actually turn off packet acknowledgments.
41917 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
41918 response, which can be safely ignored by the stub.
41920 Note that @code{set remote noack-packet} command only affects negotiation
41921 between @value{GDBN} and the stub when subsequent connections are made;
41922 it does not affect the protocol acknowledgment state for any current
41924 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
41925 new connection is established,
41926 there is also no protocol request to re-enable the acknowledgments
41927 for the current connection, once disabled.
41932 Example sequence of a target being re-started. Notice how the restart
41933 does not get any direct output:
41938 @emph{target restarts}
41941 <- @code{T001:1234123412341234}
41945 Example sequence of a target being stepped by a single instruction:
41948 -> @code{G1445@dots{}}
41953 <- @code{T001:1234123412341234}
41957 <- @code{1455@dots{}}
41961 @node File-I/O Remote Protocol Extension
41962 @section File-I/O Remote Protocol Extension
41963 @cindex File-I/O remote protocol extension
41966 * File-I/O Overview::
41967 * Protocol Basics::
41968 * The F Request Packet::
41969 * The F Reply Packet::
41970 * The Ctrl-C Message::
41972 * List of Supported Calls::
41973 * Protocol-specific Representation of Datatypes::
41975 * File-I/O Examples::
41978 @node File-I/O Overview
41979 @subsection File-I/O Overview
41980 @cindex file-i/o overview
41982 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
41983 target to use the host's file system and console I/O to perform various
41984 system calls. System calls on the target system are translated into a
41985 remote protocol packet to the host system, which then performs the needed
41986 actions and returns a response packet to the target system.
41987 This simulates file system operations even on targets that lack file systems.
41989 The protocol is defined to be independent of both the host and target systems.
41990 It uses its own internal representation of datatypes and values. Both
41991 @value{GDBN} and the target's @value{GDBN} stub are responsible for
41992 translating the system-dependent value representations into the internal
41993 protocol representations when data is transmitted.
41995 The communication is synchronous. A system call is possible only when
41996 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
41997 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
41998 the target is stopped to allow deterministic access to the target's
41999 memory. Therefore File-I/O is not interruptible by target signals. On
42000 the other hand, it is possible to interrupt File-I/O by a user interrupt
42001 (@samp{Ctrl-C}) within @value{GDBN}.
42003 The target's request to perform a host system call does not finish
42004 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
42005 after finishing the system call, the target returns to continuing the
42006 previous activity (continue, step). No additional continue or step
42007 request from @value{GDBN} is required.
42010 (@value{GDBP}) continue
42011 <- target requests 'system call X'
42012 target is stopped, @value{GDBN} executes system call
42013 -> @value{GDBN} returns result
42014 ... target continues, @value{GDBN} returns to wait for the target
42015 <- target hits breakpoint and sends a Txx packet
42018 The protocol only supports I/O on the console and to regular files on
42019 the host file system. Character or block special devices, pipes,
42020 named pipes, sockets or any other communication method on the host
42021 system are not supported by this protocol.
42023 File I/O is not supported in non-stop mode.
42025 @node Protocol Basics
42026 @subsection Protocol Basics
42027 @cindex protocol basics, file-i/o
42029 The File-I/O protocol uses the @code{F} packet as the request as well
42030 as reply packet. Since a File-I/O system call can only occur when
42031 @value{GDBN} is waiting for a response from the continuing or stepping target,
42032 the File-I/O request is a reply that @value{GDBN} has to expect as a result
42033 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
42034 This @code{F} packet contains all information needed to allow @value{GDBN}
42035 to call the appropriate host system call:
42039 A unique identifier for the requested system call.
42042 All parameters to the system call. Pointers are given as addresses
42043 in the target memory address space. Pointers to strings are given as
42044 pointer/length pair. Numerical values are given as they are.
42045 Numerical control flags are given in a protocol-specific representation.
42049 At this point, @value{GDBN} has to perform the following actions.
42053 If the parameters include pointer values to data needed as input to a
42054 system call, @value{GDBN} requests this data from the target with a
42055 standard @code{m} packet request. This additional communication has to be
42056 expected by the target implementation and is handled as any other @code{m}
42060 @value{GDBN} translates all value from protocol representation to host
42061 representation as needed. Datatypes are coerced into the host types.
42064 @value{GDBN} calls the system call.
42067 It then coerces datatypes back to protocol representation.
42070 If the system call is expected to return data in buffer space specified
42071 by pointer parameters to the call, the data is transmitted to the
42072 target using a @code{M} or @code{X} packet. This packet has to be expected
42073 by the target implementation and is handled as any other @code{M} or @code{X}
42078 Eventually @value{GDBN} replies with another @code{F} packet which contains all
42079 necessary information for the target to continue. This at least contains
42086 @code{errno}, if has been changed by the system call.
42093 After having done the needed type and value coercion, the target continues
42094 the latest continue or step action.
42096 @node The F Request Packet
42097 @subsection The @code{F} Request Packet
42098 @cindex file-i/o request packet
42099 @cindex @code{F} request packet
42101 The @code{F} request packet has the following format:
42104 @item F@var{call-id},@var{parameter@dots{}}
42106 @var{call-id} is the identifier to indicate the host system call to be called.
42107 This is just the name of the function.
42109 @var{parameter@dots{}} are the parameters to the system call.
42110 Parameters are hexadecimal integer values, either the actual values in case
42111 of scalar datatypes, pointers to target buffer space in case of compound
42112 datatypes and unspecified memory areas, or pointer/length pairs in case
42113 of string parameters. These are appended to the @var{call-id} as a
42114 comma-delimited list. All values are transmitted in ASCII
42115 string representation, pointer/length pairs separated by a slash.
42121 @node The F Reply Packet
42122 @subsection The @code{F} Reply Packet
42123 @cindex file-i/o reply packet
42124 @cindex @code{F} reply packet
42126 The @code{F} reply packet has the following format:
42130 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
42132 @var{retcode} is the return code of the system call as hexadecimal value.
42134 @var{errno} is the @code{errno} set by the call, in protocol-specific
42136 This parameter can be omitted if the call was successful.
42138 @var{Ctrl-C flag} is only sent if the user requested a break. In this
42139 case, @var{errno} must be sent as well, even if the call was successful.
42140 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
42147 or, if the call was interrupted before the host call has been performed:
42154 assuming 4 is the protocol-specific representation of @code{EINTR}.
42159 @node The Ctrl-C Message
42160 @subsection The @samp{Ctrl-C} Message
42161 @cindex ctrl-c message, in file-i/o protocol
42163 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
42164 reply packet (@pxref{The F Reply Packet}),
42165 the target should behave as if it had
42166 gotten a break message. The meaning for the target is ``system call
42167 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
42168 (as with a break message) and return to @value{GDBN} with a @code{T02}
42171 It's important for the target to know in which
42172 state the system call was interrupted. There are two possible cases:
42176 The system call hasn't been performed on the host yet.
42179 The system call on the host has been finished.
42183 These two states can be distinguished by the target by the value of the
42184 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
42185 call hasn't been performed. This is equivalent to the @code{EINTR} handling
42186 on POSIX systems. In any other case, the target may presume that the
42187 system call has been finished --- successfully or not --- and should behave
42188 as if the break message arrived right after the system call.
42190 @value{GDBN} must behave reliably. If the system call has not been called
42191 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
42192 @code{errno} in the packet. If the system call on the host has been finished
42193 before the user requests a break, the full action must be finished by
42194 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
42195 The @code{F} packet may only be sent when either nothing has happened
42196 or the full action has been completed.
42199 @subsection Console I/O
42200 @cindex console i/o as part of file-i/o
42202 By default and if not explicitly closed by the target system, the file
42203 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
42204 on the @value{GDBN} console is handled as any other file output operation
42205 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
42206 by @value{GDBN} so that after the target read request from file descriptor
42207 0 all following typing is buffered until either one of the following
42212 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
42214 system call is treated as finished.
42217 The user presses @key{RET}. This is treated as end of input with a trailing
42221 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
42222 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
42226 If the user has typed more characters than fit in the buffer given to
42227 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
42228 either another @code{read(0, @dots{})} is requested by the target, or debugging
42229 is stopped at the user's request.
42232 @node List of Supported Calls
42233 @subsection List of Supported Calls
42234 @cindex list of supported file-i/o calls
42251 @unnumberedsubsubsec open
42252 @cindex open, file-i/o system call
42257 int open(const char *pathname, int flags);
42258 int open(const char *pathname, int flags, mode_t mode);
42262 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
42265 @var{flags} is the bitwise @code{OR} of the following values:
42269 If the file does not exist it will be created. The host
42270 rules apply as far as file ownership and time stamps
42274 When used with @code{O_CREAT}, if the file already exists it is
42275 an error and open() fails.
42278 If the file already exists and the open mode allows
42279 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
42280 truncated to zero length.
42283 The file is opened in append mode.
42286 The file is opened for reading only.
42289 The file is opened for writing only.
42292 The file is opened for reading and writing.
42296 Other bits are silently ignored.
42300 @var{mode} is the bitwise @code{OR} of the following values:
42304 User has read permission.
42307 User has write permission.
42310 Group has read permission.
42313 Group has write permission.
42316 Others have read permission.
42319 Others have write permission.
42323 Other bits are silently ignored.
42326 @item Return value:
42327 @code{open} returns the new file descriptor or -1 if an error
42334 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
42337 @var{pathname} refers to a directory.
42340 The requested access is not allowed.
42343 @var{pathname} was too long.
42346 A directory component in @var{pathname} does not exist.
42349 @var{pathname} refers to a device, pipe, named pipe or socket.
42352 @var{pathname} refers to a file on a read-only filesystem and
42353 write access was requested.
42356 @var{pathname} is an invalid pointer value.
42359 No space on device to create the file.
42362 The process already has the maximum number of files open.
42365 The limit on the total number of files open on the system
42369 The call was interrupted by the user.
42375 @unnumberedsubsubsec close
42376 @cindex close, file-i/o system call
42385 @samp{Fclose,@var{fd}}
42387 @item Return value:
42388 @code{close} returns zero on success, or -1 if an error occurred.
42394 @var{fd} isn't a valid open file descriptor.
42397 The call was interrupted by the user.
42403 @unnumberedsubsubsec read
42404 @cindex read, file-i/o system call
42409 int read(int fd, void *buf, unsigned int count);
42413 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
42415 @item Return value:
42416 On success, the number of bytes read is returned.
42417 Zero indicates end of file. If count is zero, read
42418 returns zero as well. On error, -1 is returned.
42424 @var{fd} is not a valid file descriptor or is not open for
42428 @var{bufptr} is an invalid pointer value.
42431 The call was interrupted by the user.
42437 @unnumberedsubsubsec write
42438 @cindex write, file-i/o system call
42443 int write(int fd, const void *buf, unsigned int count);
42447 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
42449 @item Return value:
42450 On success, the number of bytes written are returned.
42451 Zero indicates nothing was written. On error, -1
42458 @var{fd} is not a valid file descriptor or is not open for
42462 @var{bufptr} is an invalid pointer value.
42465 An attempt was made to write a file that exceeds the
42466 host-specific maximum file size allowed.
42469 No space on device to write the data.
42472 The call was interrupted by the user.
42478 @unnumberedsubsubsec lseek
42479 @cindex lseek, file-i/o system call
42484 long lseek (int fd, long offset, int flag);
42488 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
42490 @var{flag} is one of:
42494 The offset is set to @var{offset} bytes.
42497 The offset is set to its current location plus @var{offset}
42501 The offset is set to the size of the file plus @var{offset}
42505 @item Return value:
42506 On success, the resulting unsigned offset in bytes from
42507 the beginning of the file is returned. Otherwise, a
42508 value of -1 is returned.
42514 @var{fd} is not a valid open file descriptor.
42517 @var{fd} is associated with the @value{GDBN} console.
42520 @var{flag} is not a proper value.
42523 The call was interrupted by the user.
42529 @unnumberedsubsubsec rename
42530 @cindex rename, file-i/o system call
42535 int rename(const char *oldpath, const char *newpath);
42539 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
42541 @item Return value:
42542 On success, zero is returned. On error, -1 is returned.
42548 @var{newpath} is an existing directory, but @var{oldpath} is not a
42552 @var{newpath} is a non-empty directory.
42555 @var{oldpath} or @var{newpath} is a directory that is in use by some
42559 An attempt was made to make a directory a subdirectory
42563 A component used as a directory in @var{oldpath} or new
42564 path is not a directory. Or @var{oldpath} is a directory
42565 and @var{newpath} exists but is not a directory.
42568 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
42571 No access to the file or the path of the file.
42575 @var{oldpath} or @var{newpath} was too long.
42578 A directory component in @var{oldpath} or @var{newpath} does not exist.
42581 The file is on a read-only filesystem.
42584 The device containing the file has no room for the new
42588 The call was interrupted by the user.
42594 @unnumberedsubsubsec unlink
42595 @cindex unlink, file-i/o system call
42600 int unlink(const char *pathname);
42604 @samp{Funlink,@var{pathnameptr}/@var{len}}
42606 @item Return value:
42607 On success, zero is returned. On error, -1 is returned.
42613 No access to the file or the path of the file.
42616 The system does not allow unlinking of directories.
42619 The file @var{pathname} cannot be unlinked because it's
42620 being used by another process.
42623 @var{pathnameptr} is an invalid pointer value.
42626 @var{pathname} was too long.
42629 A directory component in @var{pathname} does not exist.
42632 A component of the path is not a directory.
42635 The file is on a read-only filesystem.
42638 The call was interrupted by the user.
42644 @unnumberedsubsubsec stat/fstat
42645 @cindex fstat, file-i/o system call
42646 @cindex stat, file-i/o system call
42651 int stat(const char *pathname, struct stat *buf);
42652 int fstat(int fd, struct stat *buf);
42656 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
42657 @samp{Ffstat,@var{fd},@var{bufptr}}
42659 @item Return value:
42660 On success, zero is returned. On error, -1 is returned.
42666 @var{fd} is not a valid open file.
42669 A directory component in @var{pathname} does not exist or the
42670 path is an empty string.
42673 A component of the path is not a directory.
42676 @var{pathnameptr} is an invalid pointer value.
42679 No access to the file or the path of the file.
42682 @var{pathname} was too long.
42685 The call was interrupted by the user.
42691 @unnumberedsubsubsec gettimeofday
42692 @cindex gettimeofday, file-i/o system call
42697 int gettimeofday(struct timeval *tv, void *tz);
42701 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
42703 @item Return value:
42704 On success, 0 is returned, -1 otherwise.
42710 @var{tz} is a non-NULL pointer.
42713 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
42719 @unnumberedsubsubsec isatty
42720 @cindex isatty, file-i/o system call
42725 int isatty(int fd);
42729 @samp{Fisatty,@var{fd}}
42731 @item Return value:
42732 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
42738 The call was interrupted by the user.
42743 Note that the @code{isatty} call is treated as a special case: it returns
42744 1 to the target if the file descriptor is attached
42745 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
42746 would require implementing @code{ioctl} and would be more complex than
42751 @unnumberedsubsubsec system
42752 @cindex system, file-i/o system call
42757 int system(const char *command);
42761 @samp{Fsystem,@var{commandptr}/@var{len}}
42763 @item Return value:
42764 If @var{len} is zero, the return value indicates whether a shell is
42765 available. A zero return value indicates a shell is not available.
42766 For non-zero @var{len}, the value returned is -1 on error and the
42767 return status of the command otherwise. Only the exit status of the
42768 command is returned, which is extracted from the host's @code{system}
42769 return value by calling @code{WEXITSTATUS(retval)}. In case
42770 @file{/bin/sh} could not be executed, 127 is returned.
42776 The call was interrupted by the user.
42781 @value{GDBN} takes over the full task of calling the necessary host calls
42782 to perform the @code{system} call. The return value of @code{system} on
42783 the host is simplified before it's returned
42784 to the target. Any termination signal information from the child process
42785 is discarded, and the return value consists
42786 entirely of the exit status of the called command.
42788 Due to security concerns, the @code{system} call is by default refused
42789 by @value{GDBN}. The user has to allow this call explicitly with the
42790 @code{set remote system-call-allowed 1} command.
42793 @item set remote system-call-allowed
42794 @kindex set remote system-call-allowed
42795 Control whether to allow the @code{system} calls in the File I/O
42796 protocol for the remote target. The default is zero (disabled).
42798 @item show remote system-call-allowed
42799 @kindex show remote system-call-allowed
42800 Show whether the @code{system} calls are allowed in the File I/O
42804 @node Protocol-specific Representation of Datatypes
42805 @subsection Protocol-specific Representation of Datatypes
42806 @cindex protocol-specific representation of datatypes, in file-i/o protocol
42809 * Integral Datatypes::
42811 * Memory Transfer::
42816 @node Integral Datatypes
42817 @unnumberedsubsubsec Integral Datatypes
42818 @cindex integral datatypes, in file-i/o protocol
42820 The integral datatypes used in the system calls are @code{int},
42821 @code{unsigned int}, @code{long}, @code{unsigned long},
42822 @code{mode_t}, and @code{time_t}.
42824 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
42825 implemented as 32 bit values in this protocol.
42827 @code{long} and @code{unsigned long} are implemented as 64 bit types.
42829 @xref{Limits}, for corresponding MIN and MAX values (similar to those
42830 in @file{limits.h}) to allow range checking on host and target.
42832 @code{time_t} datatypes are defined as seconds since the Epoch.
42834 All integral datatypes transferred as part of a memory read or write of a
42835 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
42838 @node Pointer Values
42839 @unnumberedsubsubsec Pointer Values
42840 @cindex pointer values, in file-i/o protocol
42842 Pointers to target data are transmitted as they are. An exception
42843 is made for pointers to buffers for which the length isn't
42844 transmitted as part of the function call, namely strings. Strings
42845 are transmitted as a pointer/length pair, both as hex values, e.g.@:
42852 which is a pointer to data of length 18 bytes at position 0x1aaf.
42853 The length is defined as the full string length in bytes, including
42854 the trailing null byte. For example, the string @code{"hello world"}
42855 at address 0x123456 is transmitted as
42861 @node Memory Transfer
42862 @unnumberedsubsubsec Memory Transfer
42863 @cindex memory transfer, in file-i/o protocol
42865 Structured data which is transferred using a memory read or write (for
42866 example, a @code{struct stat}) is expected to be in a protocol-specific format
42867 with all scalar multibyte datatypes being big endian. Translation to
42868 this representation needs to be done both by the target before the @code{F}
42869 packet is sent, and by @value{GDBN} before
42870 it transfers memory to the target. Transferred pointers to structured
42871 data should point to the already-coerced data at any time.
42875 @unnumberedsubsubsec struct stat
42876 @cindex struct stat, in file-i/o protocol
42878 The buffer of type @code{struct stat} used by the target and @value{GDBN}
42879 is defined as follows:
42883 unsigned int st_dev; /* device */
42884 unsigned int st_ino; /* inode */
42885 mode_t st_mode; /* protection */
42886 unsigned int st_nlink; /* number of hard links */
42887 unsigned int st_uid; /* user ID of owner */
42888 unsigned int st_gid; /* group ID of owner */
42889 unsigned int st_rdev; /* device type (if inode device) */
42890 unsigned long st_size; /* total size, in bytes */
42891 unsigned long st_blksize; /* blocksize for filesystem I/O */
42892 unsigned long st_blocks; /* number of blocks allocated */
42893 time_t st_atime; /* time of last access */
42894 time_t st_mtime; /* time of last modification */
42895 time_t st_ctime; /* time of last change */
42899 The integral datatypes conform to the definitions given in the
42900 appropriate section (see @ref{Integral Datatypes}, for details) so this
42901 structure is of size 64 bytes.
42903 The values of several fields have a restricted meaning and/or
42909 A value of 0 represents a file, 1 the console.
42912 No valid meaning for the target. Transmitted unchanged.
42915 Valid mode bits are described in @ref{Constants}. Any other
42916 bits have currently no meaning for the target.
42921 No valid meaning for the target. Transmitted unchanged.
42926 These values have a host and file system dependent
42927 accuracy. Especially on Windows hosts, the file system may not
42928 support exact timing values.
42931 The target gets a @code{struct stat} of the above representation and is
42932 responsible for coercing it to the target representation before
42935 Note that due to size differences between the host, target, and protocol
42936 representations of @code{struct stat} members, these members could eventually
42937 get truncated on the target.
42939 @node struct timeval
42940 @unnumberedsubsubsec struct timeval
42941 @cindex struct timeval, in file-i/o protocol
42943 The buffer of type @code{struct timeval} used by the File-I/O protocol
42944 is defined as follows:
42948 time_t tv_sec; /* second */
42949 long tv_usec; /* microsecond */
42953 The integral datatypes conform to the definitions given in the
42954 appropriate section (see @ref{Integral Datatypes}, for details) so this
42955 structure is of size 8 bytes.
42958 @subsection Constants
42959 @cindex constants, in file-i/o protocol
42961 The following values are used for the constants inside of the
42962 protocol. @value{GDBN} and target are responsible for translating these
42963 values before and after the call as needed.
42974 @unnumberedsubsubsec Open Flags
42975 @cindex open flags, in file-i/o protocol
42977 All values are given in hexadecimal representation.
42989 @node mode_t Values
42990 @unnumberedsubsubsec mode_t Values
42991 @cindex mode_t values, in file-i/o protocol
42993 All values are given in octal representation.
43010 @unnumberedsubsubsec Errno Values
43011 @cindex errno values, in file-i/o protocol
43013 All values are given in decimal representation.
43038 @code{EUNKNOWN} is used as a fallback error value if a host system returns
43039 any error value not in the list of supported error numbers.
43042 @unnumberedsubsubsec Lseek Flags
43043 @cindex lseek flags, in file-i/o protocol
43052 @unnumberedsubsubsec Limits
43053 @cindex limits, in file-i/o protocol
43055 All values are given in decimal representation.
43058 INT_MIN -2147483648
43060 UINT_MAX 4294967295
43061 LONG_MIN -9223372036854775808
43062 LONG_MAX 9223372036854775807
43063 ULONG_MAX 18446744073709551615
43066 @node File-I/O Examples
43067 @subsection File-I/O Examples
43068 @cindex file-i/o examples
43070 Example sequence of a write call, file descriptor 3, buffer is at target
43071 address 0x1234, 6 bytes should be written:
43074 <- @code{Fwrite,3,1234,6}
43075 @emph{request memory read from target}
43078 @emph{return "6 bytes written"}
43082 Example sequence of a read call, file descriptor 3, buffer is at target
43083 address 0x1234, 6 bytes should be read:
43086 <- @code{Fread,3,1234,6}
43087 @emph{request memory write to target}
43088 -> @code{X1234,6:XXXXXX}
43089 @emph{return "6 bytes read"}
43093 Example sequence of a read call, call fails on the host due to invalid
43094 file descriptor (@code{EBADF}):
43097 <- @code{Fread,3,1234,6}
43101 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
43105 <- @code{Fread,3,1234,6}
43110 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
43114 <- @code{Fread,3,1234,6}
43115 -> @code{X1234,6:XXXXXX}
43119 @node Library List Format
43120 @section Library List Format
43121 @cindex library list format, remote protocol
43123 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
43124 same process as your application to manage libraries. In this case,
43125 @value{GDBN} can use the loader's symbol table and normal memory
43126 operations to maintain a list of shared libraries. On other
43127 platforms, the operating system manages loaded libraries.
43128 @value{GDBN} can not retrieve the list of currently loaded libraries
43129 through memory operations, so it uses the @samp{qXfer:libraries:read}
43130 packet (@pxref{qXfer library list read}) instead. The remote stub
43131 queries the target's operating system and reports which libraries
43134 The @samp{qXfer:libraries:read} packet returns an XML document which
43135 lists loaded libraries and their offsets. Each library has an
43136 associated name and one or more segment or section base addresses,
43137 which report where the library was loaded in memory.
43139 For the common case of libraries that are fully linked binaries, the
43140 library should have a list of segments. If the target supports
43141 dynamic linking of a relocatable object file, its library XML element
43142 should instead include a list of allocated sections. The segment or
43143 section bases are start addresses, not relocation offsets; they do not
43144 depend on the library's link-time base addresses.
43146 @value{GDBN} must be linked with the Expat library to support XML
43147 library lists. @xref{Expat}.
43149 A simple memory map, with one loaded library relocated by a single
43150 offset, looks like this:
43154 <library name="/lib/libc.so.6">
43155 <segment address="0x10000000"/>
43160 Another simple memory map, with one loaded library with three
43161 allocated sections (.text, .data, .bss), looks like this:
43165 <library name="sharedlib.o">
43166 <section address="0x10000000"/>
43167 <section address="0x20000000"/>
43168 <section address="0x30000000"/>
43173 The format of a library list is described by this DTD:
43176 <!-- library-list: Root element with versioning -->
43177 <!ELEMENT library-list (library)*>
43178 <!ATTLIST library-list version CDATA #FIXED "1.0">
43179 <!ELEMENT library (segment*, section*)>
43180 <!ATTLIST library name CDATA #REQUIRED>
43181 <!ELEMENT segment EMPTY>
43182 <!ATTLIST segment address CDATA #REQUIRED>
43183 <!ELEMENT section EMPTY>
43184 <!ATTLIST section address CDATA #REQUIRED>
43187 In addition, segments and section descriptors cannot be mixed within a
43188 single library element, and you must supply at least one segment or
43189 section for each library.
43191 @node Library List Format for SVR4 Targets
43192 @section Library List Format for SVR4 Targets
43193 @cindex library list format, remote protocol
43195 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
43196 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
43197 shared libraries. Still a special library list provided by this packet is
43198 more efficient for the @value{GDBN} remote protocol.
43200 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
43201 loaded libraries and their SVR4 linker parameters. For each library on SVR4
43202 target, the following parameters are reported:
43206 @code{name}, the absolute file name from the @code{l_name} field of
43207 @code{struct link_map}.
43209 @code{lm} with address of @code{struct link_map} used for TLS
43210 (Thread Local Storage) access.
43212 @code{l_addr}, the displacement as read from the field @code{l_addr} of
43213 @code{struct link_map}. For prelinked libraries this is not an absolute
43214 memory address. It is a displacement of absolute memory address against
43215 address the file was prelinked to during the library load.
43217 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
43220 Additionally the single @code{main-lm} attribute specifies address of
43221 @code{struct link_map} used for the main executable. This parameter is used
43222 for TLS access and its presence is optional.
43224 @value{GDBN} must be linked with the Expat library to support XML
43225 SVR4 library lists. @xref{Expat}.
43227 A simple memory map, with two loaded libraries (which do not use prelink),
43231 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
43232 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
43234 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
43236 </library-list-svr>
43239 The format of an SVR4 library list is described by this DTD:
43242 <!-- library-list-svr4: Root element with versioning -->
43243 <!ELEMENT library-list-svr4 (library)*>
43244 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
43245 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
43246 <!ELEMENT library EMPTY>
43247 <!ATTLIST library name CDATA #REQUIRED>
43248 <!ATTLIST library lm CDATA #REQUIRED>
43249 <!ATTLIST library l_addr CDATA #REQUIRED>
43250 <!ATTLIST library l_ld CDATA #REQUIRED>
43253 @node Memory Map Format
43254 @section Memory Map Format
43255 @cindex memory map format
43257 To be able to write into flash memory, @value{GDBN} needs to obtain a
43258 memory map from the target. This section describes the format of the
43261 The memory map is obtained using the @samp{qXfer:memory-map:read}
43262 (@pxref{qXfer memory map read}) packet and is an XML document that
43263 lists memory regions.
43265 @value{GDBN} must be linked with the Expat library to support XML
43266 memory maps. @xref{Expat}.
43268 The top-level structure of the document is shown below:
43271 <?xml version="1.0"?>
43272 <!DOCTYPE memory-map
43273 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
43274 "http://sourceware.org/gdb/gdb-memory-map.dtd">
43280 Each region can be either:
43285 A region of RAM starting at @var{addr} and extending for @var{length}
43289 <memory type="ram" start="@var{addr}" length="@var{length}"/>
43294 A region of read-only memory:
43297 <memory type="rom" start="@var{addr}" length="@var{length}"/>
43302 A region of flash memory, with erasure blocks @var{blocksize}
43306 <memory type="flash" start="@var{addr}" length="@var{length}">
43307 <property name="blocksize">@var{blocksize}</property>
43313 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
43314 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
43315 packets to write to addresses in such ranges.
43317 The formal DTD for memory map format is given below:
43320 <!-- ................................................... -->
43321 <!-- Memory Map XML DTD ................................ -->
43322 <!-- File: memory-map.dtd .............................. -->
43323 <!-- .................................... .............. -->
43324 <!-- memory-map.dtd -->
43325 <!-- memory-map: Root element with versioning -->
43326 <!ELEMENT memory-map (memory)*>
43327 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
43328 <!ELEMENT memory (property)*>
43329 <!-- memory: Specifies a memory region,
43330 and its type, or device. -->
43331 <!ATTLIST memory type (ram|rom|flash) #REQUIRED
43332 start CDATA #REQUIRED
43333 length CDATA #REQUIRED>
43334 <!-- property: Generic attribute tag -->
43335 <!ELEMENT property (#PCDATA | property)*>
43336 <!ATTLIST property name (blocksize) #REQUIRED>
43339 @node Thread List Format
43340 @section Thread List Format
43341 @cindex thread list format
43343 To efficiently update the list of threads and their attributes,
43344 @value{GDBN} issues the @samp{qXfer:threads:read} packet
43345 (@pxref{qXfer threads read}) and obtains the XML document with
43346 the following structure:
43349 <?xml version="1.0"?>
43351 <thread id="id" core="0" name="name">
43352 ... description ...
43357 Each @samp{thread} element must have the @samp{id} attribute that
43358 identifies the thread (@pxref{thread-id syntax}). The
43359 @samp{core} attribute, if present, specifies which processor core
43360 the thread was last executing on. The @samp{name} attribute, if
43361 present, specifies the human-readable name of the thread. The content
43362 of the of @samp{thread} element is interpreted as human-readable
43363 auxiliary information. The @samp{handle} attribute, if present,
43364 is a hex encoded representation of the thread handle.
43367 @node Traceframe Info Format
43368 @section Traceframe Info Format
43369 @cindex traceframe info format
43371 To be able to know which objects in the inferior can be examined when
43372 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
43373 memory ranges, registers and trace state variables that have been
43374 collected in a traceframe.
43376 This list is obtained using the @samp{qXfer:traceframe-info:read}
43377 (@pxref{qXfer traceframe info read}) packet and is an XML document.
43379 @value{GDBN} must be linked with the Expat library to support XML
43380 traceframe info discovery. @xref{Expat}.
43382 The top-level structure of the document is shown below:
43385 <?xml version="1.0"?>
43386 <!DOCTYPE traceframe-info
43387 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
43388 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
43394 Each traceframe block can be either:
43399 A region of collected memory starting at @var{addr} and extending for
43400 @var{length} bytes from there:
43403 <memory start="@var{addr}" length="@var{length}"/>
43407 A block indicating trace state variable numbered @var{number} has been
43411 <tvar id="@var{number}"/>
43416 The formal DTD for the traceframe info format is given below:
43419 <!ELEMENT traceframe-info (memory | tvar)* >
43420 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
43422 <!ELEMENT memory EMPTY>
43423 <!ATTLIST memory start CDATA #REQUIRED
43424 length CDATA #REQUIRED>
43426 <!ATTLIST tvar id CDATA #REQUIRED>
43429 @node Branch Trace Format
43430 @section Branch Trace Format
43431 @cindex branch trace format
43433 In order to display the branch trace of an inferior thread,
43434 @value{GDBN} needs to obtain the list of branches. This list is
43435 represented as list of sequential code blocks that are connected via
43436 branches. The code in each block has been executed sequentially.
43438 This list is obtained using the @samp{qXfer:btrace:read}
43439 (@pxref{qXfer btrace read}) packet and is an XML document.
43441 @value{GDBN} must be linked with the Expat library to support XML
43442 traceframe info discovery. @xref{Expat}.
43444 The top-level structure of the document is shown below:
43447 <?xml version="1.0"?>
43449 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
43450 "http://sourceware.org/gdb/gdb-btrace.dtd">
43459 A block of sequentially executed instructions starting at @var{begin}
43460 and ending at @var{end}:
43463 <block begin="@var{begin}" end="@var{end}"/>
43468 The formal DTD for the branch trace format is given below:
43471 <!ELEMENT btrace (block* | pt) >
43472 <!ATTLIST btrace version CDATA #FIXED "1.0">
43474 <!ELEMENT block EMPTY>
43475 <!ATTLIST block begin CDATA #REQUIRED
43476 end CDATA #REQUIRED>
43478 <!ELEMENT pt (pt-config?, raw?)>
43480 <!ELEMENT pt-config (cpu?)>
43482 <!ELEMENT cpu EMPTY>
43483 <!ATTLIST cpu vendor CDATA #REQUIRED
43484 family CDATA #REQUIRED
43485 model CDATA #REQUIRED
43486 stepping CDATA #REQUIRED>
43488 <!ELEMENT raw (#PCDATA)>
43491 @node Branch Trace Configuration Format
43492 @section Branch Trace Configuration Format
43493 @cindex branch trace configuration format
43495 For each inferior thread, @value{GDBN} can obtain the branch trace
43496 configuration using the @samp{qXfer:btrace-conf:read}
43497 (@pxref{qXfer btrace-conf read}) packet.
43499 The configuration describes the branch trace format and configuration
43500 settings for that format. The following information is described:
43504 This thread uses the @dfn{Branch Trace Store} (@acronym{BTS}) format.
43507 The size of the @acronym{BTS} ring buffer in bytes.
43510 This thread uses the @dfn{Intel Processor Trace} (@acronym{Intel
43514 The size of the @acronym{Intel PT} ring buffer in bytes.
43518 @value{GDBN} must be linked with the Expat library to support XML
43519 branch trace configuration discovery. @xref{Expat}.
43521 The formal DTD for the branch trace configuration format is given below:
43524 <!ELEMENT btrace-conf (bts?, pt?)>
43525 <!ATTLIST btrace-conf version CDATA #FIXED "1.0">
43527 <!ELEMENT bts EMPTY>
43528 <!ATTLIST bts size CDATA #IMPLIED>
43530 <!ELEMENT pt EMPTY>
43531 <!ATTLIST pt size CDATA #IMPLIED>
43534 @include agentexpr.texi
43536 @node Target Descriptions
43537 @appendix Target Descriptions
43538 @cindex target descriptions
43540 One of the challenges of using @value{GDBN} to debug embedded systems
43541 is that there are so many minor variants of each processor
43542 architecture in use. It is common practice for vendors to start with
43543 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
43544 and then make changes to adapt it to a particular market niche. Some
43545 architectures have hundreds of variants, available from dozens of
43546 vendors. This leads to a number of problems:
43550 With so many different customized processors, it is difficult for
43551 the @value{GDBN} maintainers to keep up with the changes.
43553 Since individual variants may have short lifetimes or limited
43554 audiences, it may not be worthwhile to carry information about every
43555 variant in the @value{GDBN} source tree.
43557 When @value{GDBN} does support the architecture of the embedded system
43558 at hand, the task of finding the correct architecture name to give the
43559 @command{set architecture} command can be error-prone.
43562 To address these problems, the @value{GDBN} remote protocol allows a
43563 target system to not only identify itself to @value{GDBN}, but to
43564 actually describe its own features. This lets @value{GDBN} support
43565 processor variants it has never seen before --- to the extent that the
43566 descriptions are accurate, and that @value{GDBN} understands them.
43568 @value{GDBN} must be linked with the Expat library to support XML
43569 target descriptions. @xref{Expat}.
43572 * Retrieving Descriptions:: How descriptions are fetched from a target.
43573 * Target Description Format:: The contents of a target description.
43574 * Predefined Target Types:: Standard types available for target
43576 * Enum Target Types:: How to define enum target types.
43577 * Standard Target Features:: Features @value{GDBN} knows about.
43580 @node Retrieving Descriptions
43581 @section Retrieving Descriptions
43583 Target descriptions can be read from the target automatically, or
43584 specified by the user manually. The default behavior is to read the
43585 description from the target. @value{GDBN} retrieves it via the remote
43586 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
43587 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
43588 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
43589 XML document, of the form described in @ref{Target Description
43592 Alternatively, you can specify a file to read for the target description.
43593 If a file is set, the target will not be queried. The commands to
43594 specify a file are:
43597 @cindex set tdesc filename
43598 @item set tdesc filename @var{path}
43599 Read the target description from @var{path}.
43601 @cindex unset tdesc filename
43602 @item unset tdesc filename
43603 Do not read the XML target description from a file. @value{GDBN}
43604 will use the description supplied by the current target.
43606 @cindex show tdesc filename
43607 @item show tdesc filename
43608 Show the filename to read for a target description, if any.
43612 @node Target Description Format
43613 @section Target Description Format
43614 @cindex target descriptions, XML format
43616 A target description annex is an @uref{http://www.w3.org/XML/, XML}
43617 document which complies with the Document Type Definition provided in
43618 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
43619 means you can use generally available tools like @command{xmllint} to
43620 check that your feature descriptions are well-formed and valid.
43621 However, to help people unfamiliar with XML write descriptions for
43622 their targets, we also describe the grammar here.
43624 Target descriptions can identify the architecture of the remote target
43625 and (for some architectures) provide information about custom register
43626 sets. They can also identify the OS ABI of the remote target.
43627 @value{GDBN} can use this information to autoconfigure for your
43628 target, or to warn you if you connect to an unsupported target.
43630 Here is a simple target description:
43633 <target version="1.0">
43634 <architecture>i386:x86-64</architecture>
43639 This minimal description only says that the target uses
43640 the x86-64 architecture.
43642 A target description has the following overall form, with [ ] marking
43643 optional elements and @dots{} marking repeatable elements. The elements
43644 are explained further below.
43647 <?xml version="1.0"?>
43648 <!DOCTYPE target SYSTEM "gdb-target.dtd">
43649 <target version="1.0">
43650 @r{[}@var{architecture}@r{]}
43651 @r{[}@var{osabi}@r{]}
43652 @r{[}@var{compatible}@r{]}
43653 @r{[}@var{feature}@dots{}@r{]}
43658 The description is generally insensitive to whitespace and line
43659 breaks, under the usual common-sense rules. The XML version
43660 declaration and document type declaration can generally be omitted
43661 (@value{GDBN} does not require them), but specifying them may be
43662 useful for XML validation tools. The @samp{version} attribute for
43663 @samp{<target>} may also be omitted, but we recommend
43664 including it; if future versions of @value{GDBN} use an incompatible
43665 revision of @file{gdb-target.dtd}, they will detect and report
43666 the version mismatch.
43668 @subsection Inclusion
43669 @cindex target descriptions, inclusion
43672 @cindex <xi:include>
43675 It can sometimes be valuable to split a target description up into
43676 several different annexes, either for organizational purposes, or to
43677 share files between different possible target descriptions. You can
43678 divide a description into multiple files by replacing any element of
43679 the target description with an inclusion directive of the form:
43682 <xi:include href="@var{document}"/>
43686 When @value{GDBN} encounters an element of this form, it will retrieve
43687 the named XML @var{document}, and replace the inclusion directive with
43688 the contents of that document. If the current description was read
43689 using @samp{qXfer}, then so will be the included document;
43690 @var{document} will be interpreted as the name of an annex. If the
43691 current description was read from a file, @value{GDBN} will look for
43692 @var{document} as a file in the same directory where it found the
43693 original description.
43695 @subsection Architecture
43696 @cindex <architecture>
43698 An @samp{<architecture>} element has this form:
43701 <architecture>@var{arch}</architecture>
43704 @var{arch} is one of the architectures from the set accepted by
43705 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
43708 @cindex @code{<osabi>}
43710 This optional field was introduced in @value{GDBN} version 7.0.
43711 Previous versions of @value{GDBN} ignore it.
43713 An @samp{<osabi>} element has this form:
43716 <osabi>@var{abi-name}</osabi>
43719 @var{abi-name} is an OS ABI name from the same selection accepted by
43720 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
43722 @subsection Compatible Architecture
43723 @cindex @code{<compatible>}
43725 This optional field was introduced in @value{GDBN} version 7.0.
43726 Previous versions of @value{GDBN} ignore it.
43728 A @samp{<compatible>} element has this form:
43731 <compatible>@var{arch}</compatible>
43734 @var{arch} is one of the architectures from the set accepted by
43735 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
43737 A @samp{<compatible>} element is used to specify that the target
43738 is able to run binaries in some other than the main target architecture
43739 given by the @samp{<architecture>} element. For example, on the
43740 Cell Broadband Engine, the main architecture is @code{powerpc:common}
43741 or @code{powerpc:common64}, but the system is able to run binaries
43742 in the @code{spu} architecture as well. The way to describe this
43743 capability with @samp{<compatible>} is as follows:
43746 <architecture>powerpc:common</architecture>
43747 <compatible>spu</compatible>
43750 @subsection Features
43753 Each @samp{<feature>} describes some logical portion of the target
43754 system. Features are currently used to describe available CPU
43755 registers and the types of their contents. A @samp{<feature>} element
43759 <feature name="@var{name}">
43760 @r{[}@var{type}@dots{}@r{]}
43766 Each feature's name should be unique within the description. The name
43767 of a feature does not matter unless @value{GDBN} has some special
43768 knowledge of the contents of that feature; if it does, the feature
43769 should have its standard name. @xref{Standard Target Features}.
43773 Any register's value is a collection of bits which @value{GDBN} must
43774 interpret. The default interpretation is a two's complement integer,
43775 but other types can be requested by name in the register description.
43776 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
43777 Target Types}), and the description can define additional composite
43780 Each type element must have an @samp{id} attribute, which gives
43781 a unique (within the containing @samp{<feature>}) name to the type.
43782 Types must be defined before they are used.
43785 Some targets offer vector registers, which can be treated as arrays
43786 of scalar elements. These types are written as @samp{<vector>} elements,
43787 specifying the array element type, @var{type}, and the number of elements,
43791 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
43795 If a register's value is usefully viewed in multiple ways, define it
43796 with a union type containing the useful representations. The
43797 @samp{<union>} element contains one or more @samp{<field>} elements,
43798 each of which has a @var{name} and a @var{type}:
43801 <union id="@var{id}">
43802 <field name="@var{name}" type="@var{type}"/>
43809 If a register's value is composed from several separate values, define
43810 it with either a structure type or a flags type.
43811 A flags type may only contain bitfields.
43812 A structure type may either contain only bitfields or contain no bitfields.
43813 If the value contains only bitfields, its total size in bytes must be
43816 Non-bitfield values have a @var{name} and @var{type}.
43819 <struct id="@var{id}">
43820 <field name="@var{name}" type="@var{type}"/>
43825 Both @var{name} and @var{type} values are required.
43826 No implicit padding is added.
43828 Bitfield values have a @var{name}, @var{start}, @var{end} and @var{type}.
43831 <struct id="@var{id}" size="@var{size}">
43832 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
43838 <flags id="@var{id}" size="@var{size}">
43839 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
43844 The @var{name} value is required.
43845 Bitfield values may be named with the empty string, @samp{""},
43846 in which case the field is ``filler'' and its value is not printed.
43847 Not all bits need to be specified, so ``filler'' fields are optional.
43849 The @var{start} and @var{end} values are required, and @var{type}
43851 The field's @var{start} must be less than or equal to its @var{end},
43852 and zero represents the least significant bit.
43854 The default value of @var{type} is @code{bool} for single bit fields,
43855 and an unsigned integer otherwise.
43857 Which to choose? Structures or flags?
43859 Registers defined with @samp{flags} have these advantages over
43860 defining them with @samp{struct}:
43864 Arithmetic may be performed on them as if they were integers.
43866 They are printed in a more readable fashion.
43869 Registers defined with @samp{struct} have one advantage over
43870 defining them with @samp{flags}:
43874 One can fetch individual fields like in @samp{C}.
43877 (gdb) print $my_struct_reg.field3
43883 @subsection Registers
43886 Each register is represented as an element with this form:
43889 <reg name="@var{name}"
43890 bitsize="@var{size}"
43891 @r{[}regnum="@var{num}"@r{]}
43892 @r{[}save-restore="@var{save-restore}"@r{]}
43893 @r{[}type="@var{type}"@r{]}
43894 @r{[}group="@var{group}"@r{]}/>
43898 The components are as follows:
43903 The register's name; it must be unique within the target description.
43906 The register's size, in bits.
43909 The register's number. If omitted, a register's number is one greater
43910 than that of the previous register (either in the current feature or in
43911 a preceding feature); the first register in the target description
43912 defaults to zero. This register number is used to read or write
43913 the register; e.g.@: it is used in the remote @code{p} and @code{P}
43914 packets, and registers appear in the @code{g} and @code{G} packets
43915 in order of increasing register number.
43918 Whether the register should be preserved across inferior function
43919 calls; this must be either @code{yes} or @code{no}. The default is
43920 @code{yes}, which is appropriate for most registers except for
43921 some system control registers; this is not related to the target's
43925 The type of the register. It may be a predefined type, a type
43926 defined in the current feature, or one of the special types @code{int}
43927 and @code{float}. @code{int} is an integer type of the correct size
43928 for @var{bitsize}, and @code{float} is a floating point type (in the
43929 architecture's normal floating point format) of the correct size for
43930 @var{bitsize}. The default is @code{int}.
43933 The register group to which this register belongs. It can be one of the
43934 standard register groups @code{general}, @code{float}, @code{vector} or an
43935 arbitrary string. Group names should be limited to alphanumeric characters.
43936 If a group name is made up of multiple words the words may be separated by
43937 hyphens; e.g.@: @code{special-group} or @code{ultra-special-group}. If no
43938 @var{group} is specified, @value{GDBN} will not display the register in
43939 @code{info registers}.
43943 @node Predefined Target Types
43944 @section Predefined Target Types
43945 @cindex target descriptions, predefined types
43947 Type definitions in the self-description can build up composite types
43948 from basic building blocks, but can not define fundamental types. Instead,
43949 standard identifiers are provided by @value{GDBN} for the fundamental
43950 types. The currently supported types are:
43955 Boolean type, occupying a single bit.
43963 Signed integer types holding the specified number of bits.
43971 Unsigned integer types holding the specified number of bits.
43975 Pointers to unspecified code and data. The program counter and
43976 any dedicated return address register may be marked as code
43977 pointers; printing a code pointer converts it into a symbolic
43978 address. The stack pointer and any dedicated address registers
43979 may be marked as data pointers.
43982 Single precision IEEE floating point.
43985 Double precision IEEE floating point.
43988 The 12-byte extended precision format used by ARM FPA registers.
43991 The 10-byte extended precision format used by x87 registers.
43994 32bit @sc{eflags} register used by x86.
43997 32bit @sc{mxcsr} register used by x86.
44001 @node Enum Target Types
44002 @section Enum Target Types
44003 @cindex target descriptions, enum types
44005 Enum target types are useful in @samp{struct} and @samp{flags}
44006 register descriptions. @xref{Target Description Format}.
44008 Enum types have a name, size and a list of name/value pairs.
44011 <enum id="@var{id}" size="@var{size}">
44012 <evalue name="@var{name}" value="@var{value}"/>
44017 Enums must be defined before they are used.
44020 <enum id="levels_type" size="4">
44021 <evalue name="low" value="0"/>
44022 <evalue name="high" value="1"/>
44024 <flags id="flags_type" size="4">
44025 <field name="X" start="0"/>
44026 <field name="LEVEL" start="1" end="1" type="levels_type"/>
44028 <reg name="flags" bitsize="32" type="flags_type"/>
44031 Given that description, a value of 3 for the @samp{flags} register
44032 would be printed as:
44035 (gdb) info register flags
44036 flags 0x3 [ X LEVEL=high ]
44039 @node Standard Target Features
44040 @section Standard Target Features
44041 @cindex target descriptions, standard features
44043 A target description must contain either no registers or all the
44044 target's registers. If the description contains no registers, then
44045 @value{GDBN} will assume a default register layout, selected based on
44046 the architecture. If the description contains any registers, the
44047 default layout will not be used; the standard registers must be
44048 described in the target description, in such a way that @value{GDBN}
44049 can recognize them.
44051 This is accomplished by giving specific names to feature elements
44052 which contain standard registers. @value{GDBN} will look for features
44053 with those names and verify that they contain the expected registers;
44054 if any known feature is missing required registers, or if any required
44055 feature is missing, @value{GDBN} will reject the target
44056 description. You can add additional registers to any of the
44057 standard features --- @value{GDBN} will display them just as if
44058 they were added to an unrecognized feature.
44060 This section lists the known features and their expected contents.
44061 Sample XML documents for these features are included in the
44062 @value{GDBN} source tree, in the directory @file{gdb/features}.
44064 Names recognized by @value{GDBN} should include the name of the
44065 company or organization which selected the name, and the overall
44066 architecture to which the feature applies; so e.g.@: the feature
44067 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
44069 The names of registers are not case sensitive for the purpose
44070 of recognizing standard features, but @value{GDBN} will only display
44071 registers using the capitalization used in the description.
44074 * AArch64 Features::
44078 * MicroBlaze Features::
44082 * Nios II Features::
44083 * OpenRISC 1000 Features::
44084 * PowerPC Features::
44085 * RISC-V Features::
44087 * S/390 and System z Features::
44093 @node AArch64 Features
44094 @subsection AArch64 Features
44095 @cindex target descriptions, AArch64 features
44097 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
44098 targets. It should contain registers @samp{x0} through @samp{x30},
44099 @samp{sp}, @samp{pc}, and @samp{cpsr}.
44101 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
44102 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
44105 The @samp{org.gnu.gdb.aarch64.sve} feature is optional. If present,
44106 it should contain registers @samp{z0} through @samp{z31}, @samp{p0}
44107 through @samp{p15}, @samp{ffr} and @samp{vg}.
44109 The @samp{org.gnu.gdb.aarch64.pauth} feature is optional. If present,
44110 it should contain registers @samp{pauth_dmask} and @samp{pauth_cmask}.
44113 @subsection ARC Features
44114 @cindex target descriptions, ARC Features
44116 ARC processors are highly configurable, so even core registers and their number
44117 are not completely predetermined. In addition flags and PC registers which are
44118 important to @value{GDBN} are not ``core'' registers in ARC. It is required
44119 that one of the core registers features is present.
44120 @samp{org.gnu.gdb.arc.aux-minimal} feature is mandatory.
44122 The @samp{org.gnu.gdb.arc.core.v2} feature is required for ARC EM and ARC HS
44123 targets with a normal register file. It should contain registers @samp{r0}
44124 through @samp{r25}, @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink},
44125 @samp{lp_count} and @samp{pcl}. This feature may contain register @samp{ilink}
44126 and any of extension core registers @samp{r32} through @samp{r59/acch}.
44127 @samp{ilink} and extension core registers are not available to read/write, when
44128 debugging GNU/Linux applications, thus @samp{ilink} is made optional.
44130 The @samp{org.gnu.gdb.arc.core-reduced.v2} feature is required for ARC EM and
44131 ARC HS targets with a reduced register file. It should contain registers
44132 @samp{r0} through @samp{r3}, @samp{r10} through @samp{r15}, @samp{gp},
44133 @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink}, @samp{lp_count} and @samp{pcl}.
44134 This feature may contain register @samp{ilink} and any of extension core
44135 registers @samp{r32} through @samp{r59/acch}.
44137 The @samp{org.gnu.gdb.arc.core.arcompact} feature is required for ARCompact
44138 targets with a normal register file. It should contain registers @samp{r0}
44139 through @samp{r25}, @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink},
44140 @samp{lp_count} and @samp{pcl}. This feature may contain registers
44141 @samp{ilink1}, @samp{ilink2} and any of extension core registers @samp{r32}
44142 through @samp{r59/acch}. @samp{ilink1} and @samp{ilink2} and extension core
44143 registers are not available when debugging GNU/Linux applications. The only
44144 difference with @samp{org.gnu.gdb.arc.core.v2} feature is in the names of
44145 @samp{ilink1} and @samp{ilink2} registers and that @samp{r30} is mandatory in
44146 ARC v2, but @samp{ilink2} is optional on ARCompact.
44148 The @samp{org.gnu.gdb.arc.aux-minimal} feature is required for all ARC
44149 targets. It should contain registers @samp{pc} and @samp{status32}.
44152 @subsection ARM Features
44153 @cindex target descriptions, ARM features
44155 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
44157 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
44158 @samp{lr}, @samp{pc}, and @samp{cpsr}.
44160 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
44161 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
44162 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
44165 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
44166 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
44168 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
44169 it should contain at least registers @samp{wR0} through @samp{wR15} and
44170 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
44171 @samp{wCSSF}, and @samp{wCASF} registers are optional.
44173 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
44174 should contain at least registers @samp{d0} through @samp{d15}. If
44175 they are present, @samp{d16} through @samp{d31} should also be included.
44176 @value{GDBN} will synthesize the single-precision registers from
44177 halves of the double-precision registers.
44179 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
44180 need to contain registers; it instructs @value{GDBN} to display the
44181 VFP double-precision registers as vectors and to synthesize the
44182 quad-precision registers from pairs of double-precision registers.
44183 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
44184 be present and include 32 double-precision registers.
44186 @node i386 Features
44187 @subsection i386 Features
44188 @cindex target descriptions, i386 features
44190 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
44191 targets. It should describe the following registers:
44195 @samp{eax} through @samp{edi} plus @samp{eip} for i386
44197 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
44199 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
44200 @samp{fs}, @samp{gs}
44202 @samp{st0} through @samp{st7}
44204 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
44205 @samp{foseg}, @samp{fooff} and @samp{fop}
44208 The register sets may be different, depending on the target.
44210 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
44211 describe registers:
44215 @samp{xmm0} through @samp{xmm7} for i386
44217 @samp{xmm0} through @samp{xmm15} for amd64
44222 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
44223 @samp{org.gnu.gdb.i386.sse} feature. It should
44224 describe the upper 128 bits of @sc{ymm} registers:
44228 @samp{ymm0h} through @samp{ymm7h} for i386
44230 @samp{ymm0h} through @samp{ymm15h} for amd64
44233 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel
44234 Memory Protection Extension (MPX). It should describe the following registers:
44238 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
44240 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
44243 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
44244 describe a single register, @samp{orig_eax}.
44246 The @samp{org.gnu.gdb.i386.segments} feature is optional. It should
44247 describe two system registers: @samp{fs_base} and @samp{gs_base}.
44249 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
44250 @samp{org.gnu.gdb.i386.avx} feature. It should
44251 describe additional @sc{xmm} registers:
44255 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
44258 It should describe the upper 128 bits of additional @sc{ymm} registers:
44262 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
44266 describe the upper 256 bits of @sc{zmm} registers:
44270 @samp{zmm0h} through @samp{zmm7h} for i386.
44272 @samp{zmm0h} through @samp{zmm15h} for amd64.
44276 describe the additional @sc{zmm} registers:
44280 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
44283 The @samp{org.gnu.gdb.i386.pkeys} feature is optional. It should
44284 describe a single register, @samp{pkru}. It is a 32-bit register
44285 valid for i386 and amd64.
44287 @node MicroBlaze Features
44288 @subsection MicroBlaze Features
44289 @cindex target descriptions, MicroBlaze features
44291 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
44292 targets. It should contain registers @samp{r0} through @samp{r31},
44293 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
44294 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
44295 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
44297 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
44298 If present, it should contain registers @samp{rshr} and @samp{rslr}
44300 @node MIPS Features
44301 @subsection @acronym{MIPS} Features
44302 @cindex target descriptions, @acronym{MIPS} features
44304 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
44305 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
44306 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
44309 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
44310 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
44311 registers. They may be 32-bit or 64-bit depending on the target.
44313 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
44314 it may be optional in a future version of @value{GDBN}. It should
44315 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
44316 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
44318 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
44319 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
44320 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
44321 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
44323 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
44324 contain a single register, @samp{restart}, which is used by the
44325 Linux kernel to control restartable syscalls.
44327 @node M68K Features
44328 @subsection M68K Features
44329 @cindex target descriptions, M68K features
44332 @item @samp{org.gnu.gdb.m68k.core}
44333 @itemx @samp{org.gnu.gdb.coldfire.core}
44334 @itemx @samp{org.gnu.gdb.fido.core}
44335 One of those features must be always present.
44336 The feature that is present determines which flavor of m68k is
44337 used. The feature that is present should contain registers
44338 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
44339 @samp{sp}, @samp{ps} and @samp{pc}.
44341 @item @samp{org.gnu.gdb.coldfire.fp}
44342 This feature is optional. If present, it should contain registers
44343 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
44347 @node NDS32 Features
44348 @subsection NDS32 Features
44349 @cindex target descriptions, NDS32 features
44351 The @samp{org.gnu.gdb.nds32.core} feature is required for NDS32
44352 targets. It should contain at least registers @samp{r0} through
44353 @samp{r10}, @samp{r15}, @samp{fp}, @samp{gp}, @samp{lp}, @samp{sp},
44356 The @samp{org.gnu.gdb.nds32.fpu} feature is optional. If present,
44357 it should contain 64-bit double-precision floating-point registers
44358 @samp{fd0} through @emph{fdN}, which should be @samp{fd3}, @samp{fd7},
44359 @samp{fd15}, or @samp{fd31} based on the FPU configuration implemented.
44361 @emph{Note:} The first sixteen 64-bit double-precision floating-point
44362 registers are overlapped with the thirty-two 32-bit single-precision
44363 floating-point registers. The 32-bit single-precision registers, if
44364 not being listed explicitly, will be synthesized from halves of the
44365 overlapping 64-bit double-precision registers. Listing 32-bit
44366 single-precision registers explicitly is deprecated, and the
44367 support to it could be totally removed some day.
44369 @node Nios II Features
44370 @subsection Nios II Features
44371 @cindex target descriptions, Nios II features
44373 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
44374 targets. It should contain the 32 core registers (@samp{zero},
44375 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
44376 @samp{pc}, and the 16 control registers (@samp{status} through
44379 @node OpenRISC 1000 Features
44380 @subsection Openrisc 1000 Features
44381 @cindex target descriptions, OpenRISC 1000 features
44383 The @samp{org.gnu.gdb.or1k.group0} feature is required for OpenRISC 1000
44384 targets. It should contain the 32 general purpose registers (@samp{r0}
44385 through @samp{r31}), @samp{ppc}, @samp{npc} and @samp{sr}.
44387 @node PowerPC Features
44388 @subsection PowerPC Features
44389 @cindex target descriptions, PowerPC features
44391 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
44392 targets. It should contain registers @samp{r0} through @samp{r31},
44393 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
44394 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
44396 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
44397 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
44399 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
44400 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr}, and
44401 @samp{vrsave}. @value{GDBN} will define pseudo-registers @samp{v0}
44402 through @samp{v31} as aliases for the corresponding @samp{vrX}
44405 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
44406 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN} will
44407 combine these registers with the floating point registers (@samp{f0}
44408 through @samp{f31}) and the altivec registers (@samp{vr0} through
44409 @samp{vr31}) to present the 128-bit wide registers @samp{vs0} through
44410 @samp{vs63}, the set of vector-scalar registers for POWER7.
44411 Therefore, this feature requires both @samp{org.gnu.gdb.power.fpu} and
44412 @samp{org.gnu.gdb.power.altivec}.
44414 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
44415 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
44416 @samp{spefscr}. SPE targets should provide 32-bit registers in
44417 @samp{org.gnu.gdb.power.core} and provide the upper halves in
44418 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
44419 these to present registers @samp{ev0} through @samp{ev31} to the
44422 The @samp{org.gnu.gdb.power.ppr} feature is optional. It should
44423 contain the 64-bit register @samp{ppr}.
44425 The @samp{org.gnu.gdb.power.dscr} feature is optional. It should
44426 contain the 64-bit register @samp{dscr}.
44428 The @samp{org.gnu.gdb.power.tar} feature is optional. It should
44429 contain the 64-bit register @samp{tar}.
44431 The @samp{org.gnu.gdb.power.ebb} feature is optional. It should
44432 contain registers @samp{bescr}, @samp{ebbhr} and @samp{ebbrr}, all
44435 The @samp{org.gnu.gdb.power.linux.pmu} feature is optional. It should
44436 contain registers @samp{mmcr0}, @samp{mmcr2}, @samp{siar}, @samp{sdar}
44437 and @samp{sier}, all 64-bit wide. This is the subset of the isa 2.07
44438 server PMU registers provided by @sc{gnu}/Linux.
44440 The @samp{org.gnu.gdb.power.htm.spr} feature is optional. It should
44441 contain registers @samp{tfhar}, @samp{texasr} and @samp{tfiar}, all
44444 The @samp{org.gnu.gdb.power.htm.core} feature is optional. It should
44445 contain the checkpointed general-purpose registers @samp{cr0} through
44446 @samp{cr31}, as well as the checkpointed registers @samp{clr} and
44447 @samp{cctr}. These registers may all be either 32-bit or 64-bit
44448 depending on the target. It should also contain the checkpointed
44449 registers @samp{ccr} and @samp{cxer}, which should both be 32-bit
44452 The @samp{org.gnu.gdb.power.htm.fpu} feature is optional. It should
44453 contain the checkpointed 64-bit floating-point registers @samp{cf0}
44454 through @samp{cf31}, as well as the checkpointed 64-bit register
44457 The @samp{org.gnu.gdb.power.htm.altivec} feature is optional. It
44458 should contain the checkpointed altivec registers @samp{cvr0} through
44459 @samp{cvr31}, all 128-bit wide. It should also contain the
44460 checkpointed registers @samp{cvscr} and @samp{cvrsave}, both 32-bit
44463 The @samp{org.gnu.gdb.power.htm.vsx} feature is optional. It should
44464 contain registers @samp{cvs0h} through @samp{cvs31h}. @value{GDBN}
44465 will combine these registers with the checkpointed floating point
44466 registers (@samp{cf0} through @samp{cf31}) and the checkpointed
44467 altivec registers (@samp{cvr0} through @samp{cvr31}) to present the
44468 128-bit wide checkpointed vector-scalar registers @samp{cvs0} through
44469 @samp{cvs63}. Therefore, this feature requires both
44470 @samp{org.gnu.gdb.power.htm.altivec} and
44471 @samp{org.gnu.gdb.power.htm.fpu}.
44473 The @samp{org.gnu.gdb.power.htm.ppr} feature is optional. It should
44474 contain the 64-bit checkpointed register @samp{cppr}.
44476 The @samp{org.gnu.gdb.power.htm.dscr} feature is optional. It should
44477 contain the 64-bit checkpointed register @samp{cdscr}.
44479 The @samp{org.gnu.gdb.power.htm.tar} feature is optional. It should
44480 contain the 64-bit checkpointed register @samp{ctar}.
44483 @node RISC-V Features
44484 @subsection RISC-V Features
44485 @cindex target descriptions, RISC-V Features
44487 The @samp{org.gnu.gdb.riscv.cpu} feature is required for RISC-V
44488 targets. It should contain the registers @samp{x0} through
44489 @samp{x31}, and @samp{pc}. Either the architectural names (@samp{x0},
44490 @samp{x1}, etc) can be used, or the ABI names (@samp{zero}, @samp{ra},
44493 The @samp{org.gnu.gdb.riscv.fpu} feature is optional. If present, it
44494 should contain registers @samp{f0} through @samp{f31}, @samp{fflags},
44495 @samp{frm}, and @samp{fcsr}. As with the cpu feature, either the
44496 architectural register names, or the ABI names can be used.
44498 The @samp{org.gnu.gdb.riscv.virtual} feature is optional. If present,
44499 it should contain registers that are not backed by real registers on
44500 the target, but are instead virtual, where the register value is
44501 derived from other target state. In many ways these are like
44502 @value{GDBN}s pseudo-registers, except implemented by the target.
44503 Currently the only register expected in this set is the one byte
44504 @samp{priv} register that contains the target's privilege level in the
44505 least significant two bits.
44507 The @samp{org.gnu.gdb.riscv.csr} feature is optional. If present, it
44508 should contain all of the target's standard CSRs. Standard CSRs are
44509 those defined in the RISC-V specification documents. There is some
44510 overlap between this feature and the fpu feature; the @samp{fflags},
44511 @samp{frm}, and @samp{fcsr} registers could be in either feature. The
44512 expectation is that these registers will be in the fpu feature if the
44513 target has floating point hardware, but can be moved into the csr
44514 feature if the target has the floating point control registers, but no
44515 other floating point hardware.
44518 @subsection RX Features
44519 @cindex target descriptions, RX Features
44521 The @samp{org.gnu.gdb.rx.core} feature is required for RX
44522 targets. It should contain the registers @samp{r0} through
44523 @samp{r15}, @samp{usp}, @samp{isp}, @samp{psw}, @samp{pc}, @samp{intb},
44524 @samp{bpsw}, @samp{bpc}, @samp{fintv}, @samp{fpsw}, and @samp{acc}.
44526 @node S/390 and System z Features
44527 @subsection S/390 and System z Features
44528 @cindex target descriptions, S/390 features
44529 @cindex target descriptions, System z features
44531 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
44532 System z targets. It should contain the PSW and the 16 general
44533 registers. In particular, System z targets should provide the 64-bit
44534 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
44535 S/390 targets should provide the 32-bit versions of these registers.
44536 A System z target that runs in 31-bit addressing mode should provide
44537 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
44538 register's upper halves @samp{r0h} through @samp{r15h}, and their
44539 lower halves @samp{r0l} through @samp{r15l}.
44541 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
44542 contain the 64-bit registers @samp{f0} through @samp{f15}, and
44545 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
44546 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
44548 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
44549 contain the register @samp{orig_r2}, which is 64-bit wide on System z
44550 targets and 32-bit otherwise. In addition, the feature may contain
44551 the @samp{last_break} register, whose width depends on the addressing
44552 mode, as well as the @samp{system_call} register, which is always
44555 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
44556 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
44557 @samp{atia}, and @samp{tr0} through @samp{tr15}.
44559 The @samp{org.gnu.gdb.s390.vx} feature is optional. It should contain
44560 64-bit wide registers @samp{v0l} through @samp{v15l}, which will be
44561 combined by @value{GDBN} with the floating point registers @samp{f0}
44562 through @samp{f15} to present the 128-bit wide vector registers
44563 @samp{v0} through @samp{v15}. In addition, this feature should
44564 contain the 128-bit wide vector registers @samp{v16} through
44567 The @samp{org.gnu.gdb.s390.gs} feature is optional. It should contain
44568 the 64-bit wide guarded-storage-control registers @samp{gsd},
44569 @samp{gssm}, and @samp{gsepla}.
44571 The @samp{org.gnu.gdb.s390.gsbc} feature is optional. It should contain
44572 the 64-bit wide guarded-storage broadcast control registers
44573 @samp{bc_gsd}, @samp{bc_gssm}, and @samp{bc_gsepla}.
44575 @node Sparc Features
44576 @subsection Sparc Features
44577 @cindex target descriptions, sparc32 features
44578 @cindex target descriptions, sparc64 features
44579 The @samp{org.gnu.gdb.sparc.cpu} feature is required for sparc32/sparc64
44580 targets. It should describe the following registers:
44584 @samp{g0} through @samp{g7}
44586 @samp{o0} through @samp{o7}
44588 @samp{l0} through @samp{l7}
44590 @samp{i0} through @samp{i7}
44593 They may be 32-bit or 64-bit depending on the target.
44595 Also the @samp{org.gnu.gdb.sparc.fpu} feature is required for sparc32/sparc64
44596 targets. It should describe the following registers:
44600 @samp{f0} through @samp{f31}
44602 @samp{f32} through @samp{f62} for sparc64
44605 The @samp{org.gnu.gdb.sparc.cp0} feature is required for sparc32/sparc64
44606 targets. It should describe the following registers:
44610 @samp{y}, @samp{psr}, @samp{wim}, @samp{tbr}, @samp{pc}, @samp{npc},
44611 @samp{fsr}, and @samp{csr} for sparc32
44613 @samp{pc}, @samp{npc}, @samp{state}, @samp{fsr}, @samp{fprs}, and @samp{y}
44617 @node TIC6x Features
44618 @subsection TMS320C6x Features
44619 @cindex target descriptions, TIC6x features
44620 @cindex target descriptions, TMS320C6x features
44621 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
44622 targets. It should contain registers @samp{A0} through @samp{A15},
44623 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
44625 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
44626 contain registers @samp{A16} through @samp{A31} and @samp{B16}
44627 through @samp{B31}.
44629 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
44630 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
44632 @node Operating System Information
44633 @appendix Operating System Information
44634 @cindex operating system information
44640 Users of @value{GDBN} often wish to obtain information about the state of
44641 the operating system running on the target---for example the list of
44642 processes, or the list of open files. This section describes the
44643 mechanism that makes it possible. This mechanism is similar to the
44644 target features mechanism (@pxref{Target Descriptions}), but focuses
44645 on a different aspect of target.
44647 Operating system information is retrived from the target via the
44648 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
44649 read}). The object name in the request should be @samp{osdata}, and
44650 the @var{annex} identifies the data to be fetched.
44653 @appendixsection Process list
44654 @cindex operating system information, process list
44656 When requesting the process list, the @var{annex} field in the
44657 @samp{qXfer} request should be @samp{processes}. The returned data is
44658 an XML document. The formal syntax of this document is defined in
44659 @file{gdb/features/osdata.dtd}.
44661 An example document is:
44664 <?xml version="1.0"?>
44665 <!DOCTYPE target SYSTEM "osdata.dtd">
44666 <osdata type="processes">
44668 <column name="pid">1</column>
44669 <column name="user">root</column>
44670 <column name="command">/sbin/init</column>
44671 <column name="cores">1,2,3</column>
44676 Each item should include a column whose name is @samp{pid}. The value
44677 of that column should identify the process on the target. The
44678 @samp{user} and @samp{command} columns are optional, and will be
44679 displayed by @value{GDBN}. The @samp{cores} column, if present,
44680 should contain a comma-separated list of cores that this process
44681 is running on. Target may provide additional columns,
44682 which @value{GDBN} currently ignores.
44684 @node Trace File Format
44685 @appendix Trace File Format
44686 @cindex trace file format
44688 The trace file comes in three parts: a header, a textual description
44689 section, and a trace frame section with binary data.
44691 The header has the form @code{\x7fTRACE0\n}. The first byte is
44692 @code{0x7f} so as to indicate that the file contains binary data,
44693 while the @code{0} is a version number that may have different values
44696 The description section consists of multiple lines of @sc{ascii} text
44697 separated by newline characters (@code{0xa}). The lines may include a
44698 variety of optional descriptive or context-setting information, such
44699 as tracepoint definitions or register set size. @value{GDBN} will
44700 ignore any line that it does not recognize. An empty line marks the end
44705 Specifies the size of a register block in bytes. This is equal to the
44706 size of a @code{g} packet payload in the remote protocol. @var{size}
44707 is an ascii decimal number. There should be only one such line in
44708 a single trace file.
44710 @item status @var{status}
44711 Trace status. @var{status} has the same format as a @code{qTStatus}
44712 remote packet reply. There should be only one such line in a single trace
44715 @item tp @var{payload}
44716 Tracepoint definition. The @var{payload} has the same format as
44717 @code{qTfP}/@code{qTsP} remote packet reply payload. A single tracepoint
44718 may take multiple lines of definition, corresponding to the multiple
44721 @item tsv @var{payload}
44722 Trace state variable definition. The @var{payload} has the same format as
44723 @code{qTfV}/@code{qTsV} remote packet reply payload. A single variable
44724 may take multiple lines of definition, corresponding to the multiple
44727 @item tdesc @var{payload}
44728 Target description in XML format. The @var{payload} is a single line of
44729 the XML file. All such lines should be concatenated together to get
44730 the original XML file. This file is in the same format as @code{qXfer}
44731 @code{features} payload, and corresponds to the main @code{target.xml}
44732 file. Includes are not allowed.
44736 The trace frame section consists of a number of consecutive frames.
44737 Each frame begins with a two-byte tracepoint number, followed by a
44738 four-byte size giving the amount of data in the frame. The data in
44739 the frame consists of a number of blocks, each introduced by a
44740 character indicating its type (at least register, memory, and trace
44741 state variable). The data in this section is raw binary, not a
44742 hexadecimal or other encoding; its endianness matches the target's
44745 @c FIXME bi-arch may require endianness/arch info in description section
44748 @item R @var{bytes}
44749 Register block. The number and ordering of bytes matches that of a
44750 @code{g} packet in the remote protocol. Note that these are the
44751 actual bytes, in target order, not a hexadecimal encoding.
44753 @item M @var{address} @var{length} @var{bytes}...
44754 Memory block. This is a contiguous block of memory, at the 8-byte
44755 address @var{address}, with a 2-byte length @var{length}, followed by
44756 @var{length} bytes.
44758 @item V @var{number} @var{value}
44759 Trace state variable block. This records the 8-byte signed value
44760 @var{value} of trace state variable numbered @var{number}.
44764 Future enhancements of the trace file format may include additional types
44767 @node Index Section Format
44768 @appendix @code{.gdb_index} section format
44769 @cindex .gdb_index section format
44770 @cindex index section format
44772 This section documents the index section that is created by @code{save
44773 gdb-index} (@pxref{Index Files}). The index section is
44774 DWARF-specific; some knowledge of DWARF is assumed in this
44777 The mapped index file format is designed to be directly
44778 @code{mmap}able on any architecture. In most cases, a datum is
44779 represented using a little-endian 32-bit integer value, called an
44780 @code{offset_type}. Big endian machines must byte-swap the values
44781 before using them. Exceptions to this rule are noted. The data is
44782 laid out such that alignment is always respected.
44784 A mapped index consists of several areas, laid out in order.
44788 The file header. This is a sequence of values, of @code{offset_type}
44789 unless otherwise noted:
44793 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
44794 Version 4 uses a different hashing function from versions 5 and 6.
44795 Version 6 includes symbols for inlined functions, whereas versions 4
44796 and 5 do not. Version 7 adds attributes to the CU indices in the
44797 symbol table. Version 8 specifies that symbols from DWARF type units
44798 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
44799 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
44801 @value{GDBN} will only read version 4, 5, or 6 indices
44802 by specifying @code{set use-deprecated-index-sections on}.
44803 GDB has a workaround for potentially broken version 7 indices so it is
44804 currently not flagged as deprecated.
44807 The offset, from the start of the file, of the CU list.
44810 The offset, from the start of the file, of the types CU list. Note
44811 that this area can be empty, in which case this offset will be equal
44812 to the next offset.
44815 The offset, from the start of the file, of the address area.
44818 The offset, from the start of the file, of the symbol table.
44821 The offset, from the start of the file, of the constant pool.
44825 The CU list. This is a sequence of pairs of 64-bit little-endian
44826 values, sorted by the CU offset. The first element in each pair is
44827 the offset of a CU in the @code{.debug_info} section. The second
44828 element in each pair is the length of that CU. References to a CU
44829 elsewhere in the map are done using a CU index, which is just the
44830 0-based index into this table. Note that if there are type CUs, then
44831 conceptually CUs and type CUs form a single list for the purposes of
44835 The types CU list. This is a sequence of triplets of 64-bit
44836 little-endian values. In a triplet, the first value is the CU offset,
44837 the second value is the type offset in the CU, and the third value is
44838 the type signature. The types CU list is not sorted.
44841 The address area. The address area consists of a sequence of address
44842 entries. Each address entry has three elements:
44846 The low address. This is a 64-bit little-endian value.
44849 The high address. This is a 64-bit little-endian value. Like
44850 @code{DW_AT_high_pc}, the value is one byte beyond the end.
44853 The CU index. This is an @code{offset_type} value.
44857 The symbol table. This is an open-addressed hash table. The size of
44858 the hash table is always a power of 2.
44860 Each slot in the hash table consists of a pair of @code{offset_type}
44861 values. The first value is the offset of the symbol's name in the
44862 constant pool. The second value is the offset of the CU vector in the
44865 If both values are 0, then this slot in the hash table is empty. This
44866 is ok because while 0 is a valid constant pool index, it cannot be a
44867 valid index for both a string and a CU vector.
44869 The hash value for a table entry is computed by applying an
44870 iterative hash function to the symbol's name. Starting with an
44871 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
44872 the string is incorporated into the hash using the formula depending on the
44877 The formula is @code{r = r * 67 + c - 113}.
44879 @item Versions 5 to 7
44880 The formula is @code{r = r * 67 + tolower (c) - 113}.
44883 The terminating @samp{\0} is not incorporated into the hash.
44885 The step size used in the hash table is computed via
44886 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
44887 value, and @samp{size} is the size of the hash table. The step size
44888 is used to find the next candidate slot when handling a hash
44891 The names of C@t{++} symbols in the hash table are canonicalized. We
44892 don't currently have a simple description of the canonicalization
44893 algorithm; if you intend to create new index sections, you must read
44897 The constant pool. This is simply a bunch of bytes. It is organized
44898 so that alignment is correct: CU vectors are stored first, followed by
44901 A CU vector in the constant pool is a sequence of @code{offset_type}
44902 values. The first value is the number of CU indices in the vector.
44903 Each subsequent value is the index and symbol attributes of a CU in
44904 the CU list. This element in the hash table is used to indicate which
44905 CUs define the symbol and how the symbol is used.
44906 See below for the format of each CU index+attributes entry.
44908 A string in the constant pool is zero-terminated.
44911 Attributes were added to CU index values in @code{.gdb_index} version 7.
44912 If a symbol has multiple uses within a CU then there is one
44913 CU index+attributes value for each use.
44915 The format of each CU index+attributes entry is as follows
44921 This is the index of the CU in the CU list.
44923 These bits are reserved for future purposes and must be zero.
44925 The kind of the symbol in the CU.
44929 This value is reserved and should not be used.
44930 By reserving zero the full @code{offset_type} value is backwards compatible
44931 with previous versions of the index.
44933 The symbol is a type.
44935 The symbol is a variable or an enum value.
44937 The symbol is a function.
44939 Any other kind of symbol.
44941 These values are reserved.
44945 This bit is zero if the value is global and one if it is static.
44947 The determination of whether a symbol is global or static is complicated.
44948 The authorative reference is the file @file{dwarf2read.c} in
44949 @value{GDBN} sources.
44953 This pseudo-code describes the computation of a symbol's kind and
44954 global/static attributes in the index.
44957 is_external = get_attribute (die, DW_AT_external);
44958 language = get_attribute (cu_die, DW_AT_language);
44961 case DW_TAG_typedef:
44962 case DW_TAG_base_type:
44963 case DW_TAG_subrange_type:
44967 case DW_TAG_enumerator:
44969 is_static = language != CPLUS;
44971 case DW_TAG_subprogram:
44973 is_static = ! (is_external || language == ADA);
44975 case DW_TAG_constant:
44977 is_static = ! is_external;
44979 case DW_TAG_variable:
44981 is_static = ! is_external;
44983 case DW_TAG_namespace:
44987 case DW_TAG_class_type:
44988 case DW_TAG_interface_type:
44989 case DW_TAG_structure_type:
44990 case DW_TAG_union_type:
44991 case DW_TAG_enumeration_type:
44993 is_static = language != CPLUS;
45001 @appendix Manual pages
45005 * gdb man:: The GNU Debugger man page
45006 * gdbserver man:: Remote Server for the GNU Debugger man page
45007 * gcore man:: Generate a core file of a running program
45008 * gdbinit man:: gdbinit scripts
45009 * gdb-add-index man:: Add index files to speed up GDB
45015 @c man title gdb The GNU Debugger
45017 @c man begin SYNOPSIS gdb
45018 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
45019 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
45020 [@option{-b}@w{ }@var{bps}]
45021 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
45022 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
45023 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
45024 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
45025 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
45028 @c man begin DESCRIPTION gdb
45029 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
45030 going on ``inside'' another program while it executes -- or what another
45031 program was doing at the moment it crashed.
45033 @value{GDBN} can do four main kinds of things (plus other things in support of
45034 these) to help you catch bugs in the act:
45038 Start your program, specifying anything that might affect its behavior.
45041 Make your program stop on specified conditions.
45044 Examine what has happened, when your program has stopped.
45047 Change things in your program, so you can experiment with correcting the
45048 effects of one bug and go on to learn about another.
45051 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
45054 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
45055 commands from the terminal until you tell it to exit with the @value{GDBN}
45056 command @code{quit}. You can get online help from @value{GDBN} itself
45057 by using the command @code{help}.
45059 You can run @code{gdb} with no arguments or options; but the most
45060 usual way to start @value{GDBN} is with one argument or two, specifying an
45061 executable program as the argument:
45067 You can also start with both an executable program and a core file specified:
45073 You can, instead, specify a process ID as a second argument or use option
45074 @code{-p}, if you want to debug a running process:
45082 would attach @value{GDBN} to process @code{1234}. With option @option{-p} you
45083 can omit the @var{program} filename.
45085 Here are some of the most frequently needed @value{GDBN} commands:
45087 @c pod2man highlights the right hand side of the @item lines.
45089 @item break [@var{file}:]@var{function}
45090 Set a breakpoint at @var{function} (in @var{file}).
45092 @item run [@var{arglist}]
45093 Start your program (with @var{arglist}, if specified).
45096 Backtrace: display the program stack.
45098 @item print @var{expr}
45099 Display the value of an expression.
45102 Continue running your program (after stopping, e.g. at a breakpoint).
45105 Execute next program line (after stopping); step @emph{over} any
45106 function calls in the line.
45108 @item edit [@var{file}:]@var{function}
45109 look at the program line where it is presently stopped.
45111 @item list [@var{file}:]@var{function}
45112 type the text of the program in the vicinity of where it is presently stopped.
45115 Execute next program line (after stopping); step @emph{into} any
45116 function calls in the line.
45118 @item help [@var{name}]
45119 Show information about @value{GDBN} command @var{name}, or general information
45120 about using @value{GDBN}.
45123 Exit from @value{GDBN}.
45127 For full details on @value{GDBN},
45128 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
45129 by Richard M. Stallman and Roland H. Pesch. The same text is available online
45130 as the @code{gdb} entry in the @code{info} program.
45134 @c man begin OPTIONS gdb
45135 Any arguments other than options specify an executable
45136 file and core file (or process ID); that is, the first argument
45137 encountered with no
45138 associated option flag is equivalent to a @option{-se} option, and the second,
45139 if any, is equivalent to a @option{-c} option if it's the name of a file.
45141 both long and short forms; both are shown here. The long forms are also
45142 recognized if you truncate them, so long as enough of the option is
45143 present to be unambiguous. (If you prefer, you can flag option
45144 arguments with @option{+} rather than @option{-}, though we illustrate the
45145 more usual convention.)
45147 All the options and command line arguments you give are processed
45148 in sequential order. The order makes a difference when the @option{-x}
45154 List all options, with brief explanations.
45156 @item -symbols=@var{file}
45157 @itemx -s @var{file}
45158 Read symbol table from file @var{file}.
45161 Enable writing into executable and core files.
45163 @item -exec=@var{file}
45164 @itemx -e @var{file}
45165 Use file @var{file} as the executable file to execute when
45166 appropriate, and for examining pure data in conjunction with a core
45169 @item -se=@var{file}
45170 Read symbol table from file @var{file} and use it as the executable
45173 @item -core=@var{file}
45174 @itemx -c @var{file}
45175 Use file @var{file} as a core dump to examine.
45177 @item -command=@var{file}
45178 @itemx -x @var{file}
45179 Execute @value{GDBN} commands from file @var{file}.
45181 @item -ex @var{command}
45182 Execute given @value{GDBN} @var{command}.
45184 @item -directory=@var{directory}
45185 @itemx -d @var{directory}
45186 Add @var{directory} to the path to search for source files.
45189 Do not execute commands from @file{~/.gdbinit}.
45193 Do not execute commands from any @file{.gdbinit} initialization files.
45197 ``Quiet''. Do not print the introductory and copyright messages. These
45198 messages are also suppressed in batch mode.
45201 Run in batch mode. Exit with status @code{0} after processing all the command
45202 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
45203 Exit with nonzero status if an error occurs in executing the @value{GDBN}
45204 commands in the command files.
45206 Batch mode may be useful for running @value{GDBN} as a filter, for example to
45207 download and run a program on another computer; in order to make this
45208 more useful, the message
45211 Program exited normally.
45215 (which is ordinarily issued whenever a program running under @value{GDBN} control
45216 terminates) is not issued when running in batch mode.
45218 @item -cd=@var{directory}
45219 Run @value{GDBN} using @var{directory} as its working directory,
45220 instead of the current directory.
45224 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
45225 @value{GDBN} to output the full file name and line number in a standard,
45226 recognizable fashion each time a stack frame is displayed (which
45227 includes each time the program stops). This recognizable format looks
45228 like two @samp{\032} characters, followed by the file name, line number
45229 and character position separated by colons, and a newline. The
45230 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
45231 characters as a signal to display the source code for the frame.
45234 Set the line speed (baud rate or bits per second) of any serial
45235 interface used by @value{GDBN} for remote debugging.
45237 @item -tty=@var{device}
45238 Run using @var{device} for your program's standard input and output.
45242 @c man begin SEEALSO gdb
45244 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
45245 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
45246 documentation are properly installed at your site, the command
45253 should give you access to the complete manual.
45255 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
45256 Richard M. Stallman and Roland H. Pesch, July 1991.
45260 @node gdbserver man
45261 @heading gdbserver man
45263 @c man title gdbserver Remote Server for the GNU Debugger
45265 @c man begin SYNOPSIS gdbserver
45266 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
45268 gdbserver --attach @var{comm} @var{pid}
45270 gdbserver --multi @var{comm}
45274 @c man begin DESCRIPTION gdbserver
45275 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
45276 than the one which is running the program being debugged.
45279 @subheading Usage (server (target) side)
45282 Usage (server (target) side):
45285 First, you need to have a copy of the program you want to debug put onto
45286 the target system. The program can be stripped to save space if needed, as
45287 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
45288 the @value{GDBN} running on the host system.
45290 To use the server, you log on to the target system, and run the @command{gdbserver}
45291 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
45292 your program, and (c) its arguments. The general syntax is:
45295 target> gdbserver @var{comm} @var{program} [@var{args} ...]
45298 For example, using a serial port, you might say:
45302 @c @file would wrap it as F</dev/com1>.
45303 target> gdbserver /dev/com1 emacs foo.txt
45306 target> gdbserver @file{/dev/com1} emacs foo.txt
45310 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
45311 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
45312 waits patiently for the host @value{GDBN} to communicate with it.
45314 To use a TCP connection, you could say:
45317 target> gdbserver host:2345 emacs foo.txt
45320 This says pretty much the same thing as the last example, except that we are
45321 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
45322 that we are expecting to see a TCP connection from @code{host} to local TCP port
45323 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
45324 want for the port number as long as it does not conflict with any existing TCP
45325 ports on the target system. This same port number must be used in the host
45326 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
45327 you chose a port number that conflicts with another service, @command{gdbserver} will
45328 print an error message and exit.
45330 @command{gdbserver} can also attach to running programs.
45331 This is accomplished via the @option{--attach} argument. The syntax is:
45334 target> gdbserver --attach @var{comm} @var{pid}
45337 @var{pid} is the process ID of a currently running process. It isn't
45338 necessary to point @command{gdbserver} at a binary for the running process.
45340 To start @code{gdbserver} without supplying an initial command to run
45341 or process ID to attach, use the @option{--multi} command line option.
45342 In such case you should connect using @kbd{target extended-remote} to start
45343 the program you want to debug.
45346 target> gdbserver --multi @var{comm}
45350 @subheading Usage (host side)
45356 You need an unstripped copy of the target program on your host system, since
45357 @value{GDBN} needs to examine its symbol tables and such. Start up @value{GDBN} as you normally
45358 would, with the target program as the first argument. (You may need to use the
45359 @option{--baud} option if the serial line is running at anything except 9600 baud.)
45360 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
45361 new command you need to know about is @code{target remote}
45362 (or @code{target extended-remote}). Its argument is either
45363 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
45364 descriptor. For example:
45368 @c @file would wrap it as F</dev/ttyb>.
45369 (gdb) target remote /dev/ttyb
45372 (gdb) target remote @file{/dev/ttyb}
45377 communicates with the server via serial line @file{/dev/ttyb}, and:
45380 (gdb) target remote the-target:2345
45384 communicates via a TCP connection to port 2345 on host `the-target', where
45385 you previously started up @command{gdbserver} with the same port number. Note that for
45386 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
45387 command, otherwise you may get an error that looks something like
45388 `Connection refused'.
45390 @command{gdbserver} can also debug multiple inferiors at once,
45393 the @value{GDBN} manual in node @code{Inferiors and Programs}
45394 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
45397 @ref{Inferiors and Programs}.
45399 In such case use the @code{extended-remote} @value{GDBN} command variant:
45402 (gdb) target extended-remote the-target:2345
45405 The @command{gdbserver} option @option{--multi} may or may not be used in such
45409 @c man begin OPTIONS gdbserver
45410 There are three different modes for invoking @command{gdbserver}:
45415 Debug a specific program specified by its program name:
45418 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
45421 The @var{comm} parameter specifies how should the server communicate
45422 with @value{GDBN}; it is either a device name (to use a serial line),
45423 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
45424 stdin/stdout of @code{gdbserver}. Specify the name of the program to
45425 debug in @var{prog}. Any remaining arguments will be passed to the
45426 program verbatim. When the program exits, @value{GDBN} will close the
45427 connection, and @code{gdbserver} will exit.
45430 Debug a specific program by specifying the process ID of a running
45434 gdbserver --attach @var{comm} @var{pid}
45437 The @var{comm} parameter is as described above. Supply the process ID
45438 of a running program in @var{pid}; @value{GDBN} will do everything
45439 else. Like with the previous mode, when the process @var{pid} exits,
45440 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
45443 Multi-process mode -- debug more than one program/process:
45446 gdbserver --multi @var{comm}
45449 In this mode, @value{GDBN} can instruct @command{gdbserver} which
45450 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
45451 close the connection when a process being debugged exits, so you can
45452 debug several processes in the same session.
45455 In each of the modes you may specify these options:
45460 List all options, with brief explanations.
45463 This option causes @command{gdbserver} to print its version number and exit.
45466 @command{gdbserver} will attach to a running program. The syntax is:
45469 target> gdbserver --attach @var{comm} @var{pid}
45472 @var{pid} is the process ID of a currently running process. It isn't
45473 necessary to point @command{gdbserver} at a binary for the running process.
45476 To start @code{gdbserver} without supplying an initial command to run
45477 or process ID to attach, use this command line option.
45478 Then you can connect using @kbd{target extended-remote} and start
45479 the program you want to debug. The syntax is:
45482 target> gdbserver --multi @var{comm}
45486 Instruct @code{gdbserver} to display extra status information about the debugging
45488 This option is intended for @code{gdbserver} development and for bug reports to
45491 @item --remote-debug
45492 Instruct @code{gdbserver} to display remote protocol debug output.
45493 This option is intended for @code{gdbserver} development and for bug reports to
45496 @item --debug-file=@var{filename}
45497 Instruct @code{gdbserver} to send any debug output to the given @var{filename}.
45498 This option is intended for @code{gdbserver} development and for bug reports to
45501 @item --debug-format=option1@r{[},option2,...@r{]}
45502 Instruct @code{gdbserver} to include extra information in each line
45503 of debugging output.
45504 @xref{Other Command-Line Arguments for gdbserver}.
45507 Specify a wrapper to launch programs
45508 for debugging. The option should be followed by the name of the
45509 wrapper, then any command-line arguments to pass to the wrapper, then
45510 @kbd{--} indicating the end of the wrapper arguments.
45513 By default, @command{gdbserver} keeps the listening TCP port open, so that
45514 additional connections are possible. However, if you start @code{gdbserver}
45515 with the @option{--once} option, it will stop listening for any further
45516 connection attempts after connecting to the first @value{GDBN} session.
45518 @c --disable-packet is not documented for users.
45520 @c --disable-randomization and --no-disable-randomization are superseded by
45521 @c QDisableRandomization.
45526 @c man begin SEEALSO gdbserver
45528 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
45529 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
45530 documentation are properly installed at your site, the command
45536 should give you access to the complete manual.
45538 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
45539 Richard M. Stallman and Roland H. Pesch, July 1991.
45546 @c man title gcore Generate a core file of a running program
45549 @c man begin SYNOPSIS gcore
45550 gcore [-a] [-o @var{prefix}] @var{pid1} [@var{pid2}...@var{pidN}]
45554 @c man begin DESCRIPTION gcore
45555 Generate core dumps of one or more running programs with process IDs
45556 @var{pid1}, @var{pid2}, etc. A core file produced by @command{gcore}
45557 is equivalent to one produced by the kernel when the process crashes
45558 (and when @kbd{ulimit -c} was used to set up an appropriate core dump
45559 limit). However, unlike after a crash, after @command{gcore} finishes
45560 its job the program remains running without any change.
45563 @c man begin OPTIONS gcore
45566 Dump all memory mappings. The actual effect of this option depends on
45567 the Operating System. On @sc{gnu}/Linux, it will disable
45568 @code{use-coredump-filter} (@pxref{set use-coredump-filter}) and
45569 enable @code{dump-excluded-mappings} (@pxref{set
45570 dump-excluded-mappings}).
45572 @item -o @var{prefix}
45573 The optional argument @var{prefix} specifies the prefix to be used
45574 when composing the file names of the core dumps. The file name is
45575 composed as @file{@var{prefix}.@var{pid}}, where @var{pid} is the
45576 process ID of the running program being analyzed by @command{gcore}.
45577 If not specified, @var{prefix} defaults to @var{gcore}.
45581 @c man begin SEEALSO gcore
45583 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
45584 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
45585 documentation are properly installed at your site, the command
45592 should give you access to the complete manual.
45594 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
45595 Richard M. Stallman and Roland H. Pesch, July 1991.
45602 @c man title gdbinit GDB initialization scripts
45605 @c man begin SYNOPSIS gdbinit
45606 @ifset SYSTEM_GDBINIT
45607 @value{SYSTEM_GDBINIT}
45616 @c man begin DESCRIPTION gdbinit
45617 These files contain @value{GDBN} commands to automatically execute during
45618 @value{GDBN} startup. The lines of contents are canned sequences of commands,
45621 the @value{GDBN} manual in node @code{Sequences}
45622 -- shell command @code{info -f gdb -n Sequences}.
45628 Please read more in
45630 the @value{GDBN} manual in node @code{Startup}
45631 -- shell command @code{info -f gdb -n Startup}.
45638 @ifset SYSTEM_GDBINIT
45639 @item @value{SYSTEM_GDBINIT}
45641 @ifclear SYSTEM_GDBINIT
45642 @item (not enabled with @code{--with-system-gdbinit} during compilation)
45644 System-wide initialization file. It is executed unless user specified
45645 @value{GDBN} option @code{-nx} or @code{-n}.
45648 the @value{GDBN} manual in node @code{System-wide configuration}
45649 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
45652 @ref{System-wide configuration}.
45656 User initialization file. It is executed unless user specified
45657 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
45660 Initialization file for current directory. It may need to be enabled with
45661 @value{GDBN} security command @code{set auto-load local-gdbinit}.
45664 the @value{GDBN} manual in node @code{Init File in the Current Directory}
45665 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
45668 @ref{Init File in the Current Directory}.
45673 @c man begin SEEALSO gdbinit
45675 gdb(1), @code{info -f gdb -n Startup}
45677 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
45678 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
45679 documentation are properly installed at your site, the command
45685 should give you access to the complete manual.
45687 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
45688 Richard M. Stallman and Roland H. Pesch, July 1991.
45692 @node gdb-add-index man
45693 @heading gdb-add-index
45694 @pindex gdb-add-index
45695 @anchor{gdb-add-index}
45697 @c man title gdb-add-index Add index files to speed up GDB
45699 @c man begin SYNOPSIS gdb-add-index
45700 gdb-add-index @var{filename}
45703 @c man begin DESCRIPTION gdb-add-index
45704 When @value{GDBN} finds a symbol file, it scans the symbols in the
45705 file in order to construct an internal symbol table. This lets most
45706 @value{GDBN} operations work quickly--at the cost of a delay early on.
45707 For large programs, this delay can be quite lengthy, so @value{GDBN}
45708 provides a way to build an index, which speeds up startup.
45710 To determine whether a file contains such an index, use the command
45711 @kbd{readelf -S filename}: the index is stored in a section named
45712 @code{.gdb_index}. The index file can only be produced on systems
45713 which use ELF binaries and DWARF debug information (i.e., sections
45714 named @code{.debug_*}).
45716 @command{gdb-add-index} uses @value{GDBN} and @command{objdump} found
45717 in the @env{PATH} environment variable. If you want to use different
45718 versions of these programs, you can specify them through the
45719 @env{GDB} and @env{OBJDUMP} environment variables.
45723 the @value{GDBN} manual in node @code{Index Files}
45724 -- shell command @kbd{info -f gdb -n "Index Files"}.
45731 @c man begin SEEALSO gdb-add-index
45733 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
45734 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
45735 documentation are properly installed at your site, the command
45741 should give you access to the complete manual.
45743 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
45744 Richard M. Stallman and Roland H. Pesch, July 1991.
45750 @node GNU Free Documentation License
45751 @appendix GNU Free Documentation License
45754 @node Concept Index
45755 @unnumbered Concept Index
45759 @node Command and Variable Index
45760 @unnumbered Command, Variable, and Function Index
45765 % I think something like @@colophon should be in texinfo. In the
45767 \long\def\colophon{\hbox to0pt{}\vfill
45768 \centerline{The body of this manual is set in}
45769 \centerline{\fontname\tenrm,}
45770 \centerline{with headings in {\bf\fontname\tenbf}}
45771 \centerline{and examples in {\tt\fontname\tentt}.}
45772 \centerline{{\it\fontname\tenit\/},}
45773 \centerline{{\bf\fontname\tenbf}, and}
45774 \centerline{{\sl\fontname\tensl\/}}
45775 \centerline{are used for emphasis.}\vfill}
45777 % Blame: doc@@cygnus.com, 1991.