1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988--2021 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{} 1988-2021 Free Software Foundation, Inc.
55 Permission is granted to copy, distribute and/or modify this document
56 under the terms of the GNU Free Documentation License, Version 1.3 or
57 any later version published by the Free Software Foundation; with the
58 Invariant Sections being ``Free Software'' and ``Free Software Needs
59 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
60 and with the Back-Cover Texts as in (a) below.
62 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
63 this GNU Manual. Buying copies from GNU Press supports the FSF in
64 developing GNU and promoting software freedom.''
69 This file documents the @sc{gnu} debugger @value{GDBN}.
71 This is the @value{EDITION} Edition, of @cite{Debugging with
72 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
73 @ifset VERSION_PACKAGE
74 @value{VERSION_PACKAGE}
76 Version @value{GDBVN}.
82 @title Debugging with @value{GDBN}
83 @subtitle The @sc{gnu} Source-Level Debugger
85 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
86 @ifset VERSION_PACKAGE
88 @subtitle @value{VERSION_PACKAGE}
90 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
94 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
95 \hfill {\it Debugging with @value{GDBN}}\par
96 \hfill \TeX{}info \texinfoversion\par
100 @vskip 0pt plus 1filll
101 Published by the Free Software Foundation @*
102 51 Franklin Street, Fifth Floor,
103 Boston, MA 02110-1301, USA@*
104 ISBN 978-0-9831592-3-0 @*
113 @top Debugging with @value{GDBN}
115 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
117 This is the @value{EDITION} Edition, for @value{GDBN}
118 @ifset VERSION_PACKAGE
119 @value{VERSION_PACKAGE}
121 Version @value{GDBVN}.
123 Copyright (C) 1988-2021 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
560 Weimin Pan, David Faust and Jose E. Marchesi contributed support for
561 the Linux kernel BPF virtual architecture. This work was sponsored by
565 @chapter A Sample @value{GDBN} Session
567 You can use this manual at your leisure to read all about @value{GDBN}.
568 However, a handful of commands are enough to get started using the
569 debugger. This chapter illustrates those commands.
572 In this sample session, we emphasize user input like this: @b{input},
573 to make it easier to pick out from the surrounding output.
576 @c FIXME: this example may not be appropriate for some configs, where
577 @c FIXME...primary interest is in remote use.
579 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
580 processor) exhibits the following bug: sometimes, when we change its
581 quote strings from the default, the commands used to capture one macro
582 definition within another stop working. In the following short @code{m4}
583 session, we define a macro @code{foo} which expands to @code{0000}; we
584 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
585 same thing. However, when we change the open quote string to
586 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
587 procedure fails to define a new synonym @code{baz}:
596 @b{define(bar,defn(`foo'))}
600 @b{changequote(<QUOTE>,<UNQUOTE>)}
602 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
605 m4: End of input: 0: fatal error: EOF in string
609 Let us use @value{GDBN} to try to see what is going on.
612 $ @b{@value{GDBP} m4}
613 @c FIXME: this falsifies the exact text played out, to permit smallbook
614 @c FIXME... format to come out better.
615 @value{GDBN} is free software and you are welcome to distribute copies
616 of it under certain conditions; type "show copying" to see
618 There is absolutely no warranty for @value{GDBN}; type "show warranty"
621 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
626 @value{GDBN} reads only enough symbol data to know where to find the
627 rest when needed; as a result, the first prompt comes up very quickly.
628 We now tell @value{GDBN} to use a narrower display width than usual, so
629 that examples fit in this manual.
632 (@value{GDBP}) @b{set width 70}
636 We need to see how the @code{m4} built-in @code{changequote} works.
637 Having looked at the source, we know the relevant subroutine is
638 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
639 @code{break} command.
642 (@value{GDBP}) @b{break m4_changequote}
643 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
647 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
648 control; as long as control does not reach the @code{m4_changequote}
649 subroutine, the program runs as usual:
652 (@value{GDBP}) @b{run}
653 Starting program: /work/Editorial/gdb/gnu/m4/m4
661 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
662 suspends execution of @code{m4}, displaying information about the
663 context where it stops.
666 @b{changequote(<QUOTE>,<UNQUOTE>)}
668 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
670 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
674 Now we use the command @code{n} (@code{next}) to advance execution to
675 the next line of the current function.
679 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
684 @code{set_quotes} looks like a promising subroutine. We can go into it
685 by using the command @code{s} (@code{step}) instead of @code{next}.
686 @code{step} goes to the next line to be executed in @emph{any}
687 subroutine, so it steps into @code{set_quotes}.
691 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
693 530 if (lquote != def_lquote)
697 The display that shows the subroutine where @code{m4} is now
698 suspended (and its arguments) is called a stack frame display. It
699 shows a summary of the stack. We can use the @code{backtrace}
700 command (which can also be spelled @code{bt}), to see where we are
701 in the stack as a whole: the @code{backtrace} command displays a
702 stack frame for each active subroutine.
705 (@value{GDBP}) @b{bt}
706 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
708 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
710 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
711 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
713 #4 0x79dc in expand_input () at macro.c:40
714 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
718 We step through a few more lines to see what happens. The first two
719 times, we can use @samp{s}; the next two times we use @code{n} to avoid
720 falling into the @code{xstrdup} subroutine.
724 0x3b5c 532 if (rquote != def_rquote)
726 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
727 def_lquote : xstrdup(lq);
729 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
732 538 len_lquote = strlen(rquote);
736 The last line displayed looks a little odd; we can examine the variables
737 @code{lquote} and @code{rquote} to see if they are in fact the new left
738 and right quotes we specified. We use the command @code{p}
739 (@code{print}) to see their values.
742 (@value{GDBP}) @b{p lquote}
743 $1 = 0x35d40 "<QUOTE>"
744 (@value{GDBP}) @b{p rquote}
745 $2 = 0x35d50 "<UNQUOTE>"
749 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
750 To look at some context, we can display ten lines of source
751 surrounding the current line with the @code{l} (@code{list}) command.
757 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
759 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
762 538 len_lquote = strlen(rquote);
763 539 len_rquote = strlen(lquote);
770 Let us step past the two lines that set @code{len_lquote} and
771 @code{len_rquote}, and then examine the values of those variables.
775 539 len_rquote = strlen(lquote);
778 (@value{GDBP}) @b{p len_lquote}
780 (@value{GDBP}) @b{p len_rquote}
785 That certainly looks wrong, assuming @code{len_lquote} and
786 @code{len_rquote} are meant to be the lengths of @code{lquote} and
787 @code{rquote} respectively. We can set them to better values using
788 the @code{p} command, since it can print the value of
789 any expression---and that expression can include subroutine calls and
793 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
795 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
800 Is that enough to fix the problem of using the new quotes with the
801 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
802 executing with the @code{c} (@code{continue}) command, and then try the
803 example that caused trouble initially:
809 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
816 Success! The new quotes now work just as well as the default ones. The
817 problem seems to have been just the two typos defining the wrong
818 lengths. We allow @code{m4} exit by giving it an EOF as input:
822 Program exited normally.
826 The message @samp{Program exited normally.} is from @value{GDBN}; it
827 indicates @code{m4} has finished executing. We can end our @value{GDBN}
828 session with the @value{GDBN} @code{quit} command.
831 (@value{GDBP}) @b{quit}
835 @chapter Getting In and Out of @value{GDBN}
837 This chapter discusses how to start @value{GDBN}, and how to get out of it.
841 type @samp{@value{GDBP}} to start @value{GDBN}.
843 type @kbd{quit} or @kbd{Ctrl-d} to exit.
847 * Invoking GDB:: How to start @value{GDBN}
848 * Quitting GDB:: How to quit @value{GDBN}
849 * Shell Commands:: How to use shell commands inside @value{GDBN}
850 * Logging Output:: How to log @value{GDBN}'s output to a file
854 @section Invoking @value{GDBN}
856 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
857 @value{GDBN} reads commands from the terminal until you tell it to exit.
859 You can also run @code{@value{GDBP}} with a variety of arguments and options,
860 to specify more of your debugging environment at the outset.
862 The command-line options described here are designed
863 to cover a variety of situations; in some environments, some of these
864 options may effectively be unavailable.
866 The most usual way to start @value{GDBN} is with one argument,
867 specifying an executable program:
870 @value{GDBP} @var{program}
874 You can also start with both an executable program and a core file
878 @value{GDBP} @var{program} @var{core}
881 You can, instead, specify a process ID as a second argument or use option
882 @code{-p}, if you want to debug a running process:
885 @value{GDBP} @var{program} 1234
890 would attach @value{GDBN} to process @code{1234}. With option @option{-p} you
891 can omit the @var{program} filename.
893 Taking advantage of the second command-line argument requires a fairly
894 complete operating system; when you use @value{GDBN} as a remote
895 debugger attached to a bare board, there may not be any notion of
896 ``process'', and there is often no way to get a core dump. @value{GDBN}
897 will warn you if it is unable to attach or to read core dumps.
899 You can optionally have @code{@value{GDBP}} pass any arguments after the
900 executable file to the inferior using @code{--args}. This option stops
903 @value{GDBP} --args gcc -O2 -c foo.c
905 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
906 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
908 You can run @code{@value{GDBP}} without printing the front material, which describes
909 @value{GDBN}'s non-warranty, by specifying @code{--silent}
910 (or @code{-q}/@code{--quiet}):
913 @value{GDBP} --silent
917 You can further control how @value{GDBN} starts up by using command-line
918 options. @value{GDBN} itself can remind you of the options available.
928 to display all available options and briefly describe their use
929 (@samp{@value{GDBP} -h} is a shorter equivalent).
931 All options and command line arguments you give are processed
932 in sequential order. The order makes a difference when the
933 @samp{-x} option is used.
937 * File Options:: Choosing files
938 * Mode Options:: Choosing modes
939 * Startup:: What @value{GDBN} does during startup
940 * Initialization Files:: Initialization Files
944 @subsection Choosing Files
946 When @value{GDBN} starts, it reads any arguments other than options as
947 specifying an executable file and core file (or process ID). This is
948 the same as if the arguments were specified by the @samp{-se} and
949 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
950 first argument that does not have an associated option flag as
951 equivalent to the @samp{-se} option followed by that argument; and the
952 second argument that does not have an associated option flag, if any, as
953 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
954 If the second argument begins with a decimal digit, @value{GDBN} will
955 first attempt to attach to it as a process, and if that fails, attempt
956 to open it as a corefile. If you have a corefile whose name begins with
957 a digit, you can prevent @value{GDBN} from treating it as a pid by
958 prefixing it with @file{./}, e.g.@: @file{./12345}.
960 If @value{GDBN} has not been configured to included core file support,
961 such as for most embedded targets, then it will complain about a second
962 argument and ignore it.
964 Many options have both long and short forms; both are shown in the
965 following list. @value{GDBN} also recognizes the long forms if you truncate
966 them, so long as enough of the option is present to be unambiguous.
967 (If you prefer, you can flag option arguments with @samp{--} rather
968 than @samp{-}, though we illustrate the more usual convention.)
970 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
971 @c way, both those who look for -foo and --foo in the index, will find
975 @item -symbols @var{file}
977 @cindex @code{--symbols}
979 Read symbol table from file @var{file}.
981 @item -exec @var{file}
983 @cindex @code{--exec}
985 Use file @var{file} as the executable file to execute when appropriate,
986 and for examining pure data in conjunction with a core dump.
990 Read symbol table from file @var{file} and use it as the executable
993 @item -core @var{file}
995 @cindex @code{--core}
997 Use file @var{file} as a core dump to examine.
999 @item -pid @var{number}
1000 @itemx -p @var{number}
1001 @cindex @code{--pid}
1003 Connect to process ID @var{number}, as with the @code{attach} command.
1005 @item -command @var{file}
1006 @itemx -x @var{file}
1007 @cindex @code{--command}
1009 Execute commands from file @var{file}. The contents of this file is
1010 evaluated exactly as the @code{source} command would.
1011 @xref{Command Files,, Command files}.
1013 @item -eval-command @var{command}
1014 @itemx -ex @var{command}
1015 @cindex @code{--eval-command}
1017 Execute a single @value{GDBN} command.
1019 This option may be used multiple times to call multiple commands. It may
1020 also be interleaved with @samp{-command} as required.
1023 @value{GDBP} -ex 'target sim' -ex 'load' \
1024 -x setbreakpoints -ex 'run' a.out
1027 @item -init-command @var{file}
1028 @itemx -ix @var{file}
1029 @cindex @code{--init-command}
1031 Execute commands from file @var{file} before loading the inferior (but
1032 after loading gdbinit files).
1035 @item -init-eval-command @var{command}
1036 @itemx -iex @var{command}
1037 @cindex @code{--init-eval-command}
1039 Execute a single @value{GDBN} command before loading the inferior (but
1040 after loading gdbinit files).
1043 @item -directory @var{directory}
1044 @itemx -d @var{directory}
1045 @cindex @code{--directory}
1047 Add @var{directory} to the path to search for source and script files.
1051 @cindex @code{--readnow}
1053 Read each symbol file's entire symbol table immediately, rather than
1054 the default, which is to read it incrementally as it is needed.
1055 This makes startup slower, but makes future operations faster.
1058 @anchor{--readnever}
1059 @cindex @code{--readnever}, command-line option
1060 Do not read each symbol file's symbolic debug information. This makes
1061 startup faster but at the expense of not being able to perform
1062 symbolic debugging. DWARF unwind information is also not read,
1063 meaning backtraces may become incomplete or inaccurate. One use of
1064 this is when a user simply wants to do the following sequence: attach,
1065 dump core, detach. Loading the debugging information in this case is
1066 an unnecessary cause of delay.
1070 @subsection Choosing Modes
1072 You can run @value{GDBN} in various alternative modes---for example, in
1073 batch mode or quiet mode.
1081 Do not execute commands found in any initialization files
1082 (@pxref{Initialization Files}).
1087 Do not execute commands found in any home directory initialization
1088 file (@pxref{Initialization Files,,Home directory initialization
1089 file}). The system wide and current directory initialization files
1095 @cindex @code{--quiet}
1096 @cindex @code{--silent}
1098 ``Quiet''. Do not print the introductory and copyright messages. These
1099 messages are also suppressed in batch mode.
1102 @cindex @code{--batch}
1103 Run in batch mode. Exit with status @code{0} after processing all the
1104 command files specified with @samp{-x} (and all commands from
1105 initialization files, if not inhibited with @samp{-n}). Exit with
1106 nonzero status if an error occurs in executing the @value{GDBN} commands
1107 in the command files. Batch mode also disables pagination, sets unlimited
1108 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1109 off} were in effect (@pxref{Messages/Warnings}).
1111 Batch mode may be useful for running @value{GDBN} as a filter, for
1112 example to download and run a program on another computer; in order to
1113 make this more useful, the message
1116 Program exited normally.
1120 (which is ordinarily issued whenever a program running under
1121 @value{GDBN} control terminates) is not issued when running in batch
1125 @cindex @code{--batch-silent}
1126 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1127 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1128 unaffected). This is much quieter than @samp{-silent} and would be useless
1129 for an interactive session.
1131 This is particularly useful when using targets that give @samp{Loading section}
1132 messages, for example.
1134 Note that targets that give their output via @value{GDBN}, as opposed to
1135 writing directly to @code{stdout}, will also be made silent.
1137 @item -return-child-result
1138 @cindex @code{--return-child-result}
1139 The return code from @value{GDBN} will be the return code from the child
1140 process (the process being debugged), with the following exceptions:
1144 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1145 internal error. In this case the exit code is the same as it would have been
1146 without @samp{-return-child-result}.
1148 The user quits with an explicit value. E.g., @samp{quit 1}.
1150 The child process never runs, or is not allowed to terminate, in which case
1151 the exit code will be -1.
1154 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1155 when @value{GDBN} is being used as a remote program loader or simulator
1160 @cindex @code{--nowindows}
1162 ``No windows''. If @value{GDBN} comes with a graphical user interface
1163 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1164 interface. If no GUI is available, this option has no effect.
1168 @cindex @code{--windows}
1170 If @value{GDBN} includes a GUI, then this option requires it to be
1173 @item -cd @var{directory}
1175 Run @value{GDBN} using @var{directory} as its working directory,
1176 instead of the current directory.
1178 @item -data-directory @var{directory}
1179 @itemx -D @var{directory}
1180 @cindex @code{--data-directory}
1182 Run @value{GDBN} using @var{directory} as its data directory.
1183 The data directory is where @value{GDBN} searches for its
1184 auxiliary files. @xref{Data Files}.
1188 @cindex @code{--fullname}
1190 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1191 subprocess. It tells @value{GDBN} to output the full file name and line
1192 number in a standard, recognizable fashion each time a stack frame is
1193 displayed (which includes each time your program stops). This
1194 recognizable format looks like two @samp{\032} characters, followed by
1195 the file name, line number and character position separated by colons,
1196 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1197 @samp{\032} characters as a signal to display the source code for the
1200 @item -annotate @var{level}
1201 @cindex @code{--annotate}
1202 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1203 effect is identical to using @samp{set annotate @var{level}}
1204 (@pxref{Annotations}). The annotation @var{level} controls how much
1205 information @value{GDBN} prints together with its prompt, values of
1206 expressions, source lines, and other types of output. Level 0 is the
1207 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1208 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1209 that control @value{GDBN}, and level 2 has been deprecated.
1211 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1215 @cindex @code{--args}
1216 Change interpretation of command line so that arguments following the
1217 executable file are passed as command line arguments to the inferior.
1218 This option stops option processing.
1220 @item -baud @var{bps}
1222 @cindex @code{--baud}
1224 Set the line speed (baud rate or bits per second) of any serial
1225 interface used by @value{GDBN} for remote debugging.
1227 @item -l @var{timeout}
1229 Set the timeout (in seconds) of any communication used by @value{GDBN}
1230 for remote debugging.
1232 @item -tty @var{device}
1233 @itemx -t @var{device}
1234 @cindex @code{--tty}
1236 Run using @var{device} for your program's standard input and output.
1237 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1239 @c resolve the situation of these eventually
1241 @cindex @code{--tui}
1242 Activate the @dfn{Text User Interface} when starting. The Text User
1243 Interface manages several text windows on the terminal, showing
1244 source, assembly, registers and @value{GDBN} command outputs
1245 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1246 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1247 Using @value{GDBN} under @sc{gnu} Emacs}).
1249 @item -interpreter @var{interp}
1250 @cindex @code{--interpreter}
1251 Use the interpreter @var{interp} for interface with the controlling
1252 program or device. This option is meant to be set by programs which
1253 communicate with @value{GDBN} using it as a back end.
1254 @xref{Interpreters, , Command Interpreters}.
1256 @samp{--interpreter=mi} (or @samp{--interpreter=mi3}) causes
1257 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} version 3 (@pxref{GDB/MI, ,
1258 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 9.1. @sc{gdb/mi}
1259 version 2 (@code{mi2}), included in @value{GDBN} 6.0 and version 1 (@code{mi1}),
1260 included in @value{GDBN} 5.3, are also available. Earlier @sc{gdb/mi}
1261 interfaces are no longer supported.
1264 @cindex @code{--write}
1265 Open the executable and core files for both reading and writing. This
1266 is equivalent to the @samp{set write on} command inside @value{GDBN}
1270 @cindex @code{--statistics}
1271 This option causes @value{GDBN} to print statistics about time and
1272 memory usage after it completes each command and returns to the prompt.
1275 @cindex @code{--version}
1276 This option causes @value{GDBN} to print its version number and
1277 no-warranty blurb, and exit.
1279 @item -configuration
1280 @cindex @code{--configuration}
1281 This option causes @value{GDBN} to print details about its build-time
1282 configuration parameters, and then exit. These details can be
1283 important when reporting @value{GDBN} bugs (@pxref{GDB Bugs}).
1288 @subsection What @value{GDBN} Does During Startup
1289 @cindex @value{GDBN} startup
1291 Here's the description of what @value{GDBN} does during session startup:
1295 Sets up the command interpreter as specified by the command line
1296 (@pxref{Mode Options, interpreter}).
1300 Reads the system wide initialization file and the files from the
1301 system wide initialization directory, @pxref{System Wide Init Files}.
1304 Reads the initialization file (if any) in your home directory and
1305 executes all the commands in that file, @pxref{Home Directory Init
1308 @anchor{Option -init-eval-command}
1310 Executes commands and command files specified by the @samp{-iex} and
1311 @samp{-ix} options in their specified order. Usually you should use the
1312 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1313 settings before @value{GDBN} init files get executed and before inferior
1317 Processes command line options and operands.
1320 Reads and executes the commands from the initialization file (if any)
1321 in the current working directory as long as @samp{set auto-load
1322 local-gdbinit} is set to @samp{on} (@pxref{Init File in the Current
1323 Directory}). This is only done if the current directory is different
1324 from your home directory. Thus, you can have more than one init file,
1325 one generic in your home directory, and another, specific to the
1326 program you are debugging, in the directory where you invoke
1327 @value{GDBN}. @xref{Init File in the Current Directory during
1331 If the command line specified a program to debug, or a process to
1332 attach to, or a core file, @value{GDBN} loads any auto-loaded
1333 scripts provided for the program or for its loaded shared libraries.
1334 @xref{Auto-loading}.
1336 If you wish to disable the auto-loading during startup,
1337 you must do something like the following:
1340 $ gdb -iex "set auto-load python-scripts off" myprogram
1343 Option @samp{-ex} does not work because the auto-loading is then turned
1347 Executes commands and command files specified by the @samp{-ex} and
1348 @samp{-x} options in their specified order. @xref{Command Files}, for
1349 more details about @value{GDBN} command files.
1352 Reads the command history recorded in the @dfn{history file}.
1353 @xref{Command History}, for more details about the command history and the
1354 files where @value{GDBN} records it.
1357 @node Initialization Files
1358 @subsection Initialization Files
1359 @cindex init file name
1361 During startup (@pxref{Startup}) @value{GDBN} will execute commands
1362 from several initialization files. These initialization files use the
1363 same syntax as @dfn{command files} (@pxref{Command Files}) and are
1364 processed by @value{GDBN} in the same way.
1366 To display the list of initialization files loaded by @value{GDBN} at
1367 startup, in the order they will be loaded, you can use @kbd{gdb
1370 As the system wide and home directory initialization files are
1371 processed before most command line options, changes to settings
1372 (e.g. @samp{set complaints}) can affect subsequent processing of
1373 command line options and operands.
1375 The following sections describe where @value{GDBN} looks for the
1376 initialization and the order that the files are searched for.
1378 @anchor{System Wide Init Files}
1379 @subsubsection System wide initialization files
1381 There are two locations that are searched for system wide
1382 initialization files. Both of these locations are always checked:
1386 @item @file{system.gdbinit}
1387 This is a single system-wide initialization file. Its location is
1388 specified with the @code{--with-system-gdbinit} configure option
1389 (@pxref{System-wide configuration}). It is loaded first when
1390 @value{GDBN} starts, before command line options have been processed.
1392 @item @file{system.gdbinit.d}
1393 This is the system-wide initialization directory. Its location is
1394 specified with the @code{--with-system-gdbinit-dir} configure option
1395 (@pxref{System-wide configuration}). Files in this directory are
1396 loaded in alphabetical order immediately after @file{system.gdbinit}
1397 (if enabled) when @value{GDBN} starts, before command line options
1398 have been processed. Files need to have a recognized scripting
1399 language extension (@file{.py}/@file{.scm}) or be named with a
1400 @file{.gdb} extension to be interpreted as regular @value{GDBN}
1401 commands. @value{GDBN} will not recurse into any subdirectories of
1406 It is possible to prevent the system wide initialization files from
1407 being loaded using the @samp{-nx} command line option, @pxref{Mode
1408 Options,,Choosing Modes}.
1410 @anchor{Home Directory Init File}
1411 @subsubsection Home directory initialization file
1412 @cindex @file{gdbinit}
1413 @cindex @file{.gdbinit}
1414 @cindex @file{gdb.ini}
1416 After loading the system wide initialization files @value{GDBN} will
1417 look for an initialization file in the users home
1418 directory@footnote{On DOS/Windows systems, the home directory is the
1419 one pointed to by the @code{HOME} environment variable.}. There are a
1420 number of locations that @value{GDBN} will search in the home
1421 directory, these locations are searched in order and @value{GDBN} will
1422 load the first file that it finds, and subsequent locations will not
1425 On non-Apple hosts the locations searched are:
1427 @item $XDG_CONFIG_HOME/gdb/gdbinit
1428 @item $HOME/.config/gdb/gdbinit
1429 @item $HOME/.gdbinit
1432 While on Apple hosts the locations searched are:
1434 @item $HOME/Library/Preferences/gdb/gdbinit
1435 @item $HOME/.gdbinit
1438 It is possible to prevent the home directory initialization file from
1439 being loaded using the @samp{-nx} or @samp{-nh} command line options,
1440 @pxref{Mode Options,,Choosing Modes}.
1442 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini} instead of
1443 @file{.gdbinit} or @file{gdbinit}, due to the limitations of file
1444 names imposed by DOS filesystems. The Windows port of @value{GDBN}
1445 uses the standard name, but if it finds a @file{gdb.ini} file in your
1446 home directory, it warns you about that and suggests to rename the
1447 file to the standard name.
1449 @anchor{Init File in the Current Directory during Startup}
1450 @subsubsection Local directory initialization file
1452 @value{GDBN} will check the current directory for a file called
1453 @file{.gdbinit}. It is loaded last, after command line options
1454 other than @samp{-x} and @samp{-ex} have been processed. The command
1455 line options @samp{-x} and @samp{-ex} are processed last, after
1456 @file{.gdbinit} has been loaded, @pxref{File Options,,Choosing
1459 If the file in the current directory was already loaded as the home
1460 directory initialization file then it will not be loaded a second
1463 It is possible to prevent the local directory initialization file from
1464 being loaded using the @samp{-nx} command line option, @pxref{Mode
1465 Options,,Choosing Modes}.
1468 @section Quitting @value{GDBN}
1469 @cindex exiting @value{GDBN}
1470 @cindex leaving @value{GDBN}
1473 @kindex quit @r{[}@var{expression}@r{]}
1474 @kindex q @r{(@code{quit})}
1475 @item quit @r{[}@var{expression}@r{]}
1477 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1478 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1479 do not supply @var{expression}, @value{GDBN} will terminate normally;
1480 otherwise it will terminate using the result of @var{expression} as the
1485 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1486 terminates the action of any @value{GDBN} command that is in progress and
1487 returns to @value{GDBN} command level. It is safe to type the interrupt
1488 character at any time because @value{GDBN} does not allow it to take effect
1489 until a time when it is safe.
1491 If you have been using @value{GDBN} to control an attached process or
1492 device, you can release it with the @code{detach} command
1493 (@pxref{Attach, ,Debugging an Already-running Process}).
1495 @node Shell Commands
1496 @section Shell Commands
1498 If you need to execute occasional shell commands during your
1499 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1500 just use the @code{shell} command.
1505 @cindex shell escape
1506 @item shell @var{command-string}
1507 @itemx !@var{command-string}
1508 Invoke a standard shell to execute @var{command-string}.
1509 Note that no space is needed between @code{!} and @var{command-string}.
1510 On GNU and Unix systems, the environment variable @code{SHELL}, if it
1511 exists, determines which shell to run. Otherwise @value{GDBN} uses
1512 the default shell (@file{/bin/sh} on GNU and Unix systems,
1513 @file{cmd.exe} on MS-Windows, @file{COMMAND.COM} on MS-DOS, etc.).
1516 The utility @code{make} is often needed in development environments.
1517 You do not have to use the @code{shell} command for this purpose in
1522 @cindex calling make
1523 @item make @var{make-args}
1524 Execute the @code{make} program with the specified
1525 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1531 @cindex send the output of a gdb command to a shell command
1533 @item pipe [@var{command}] | @var{shell_command}
1534 @itemx | [@var{command}] | @var{shell_command}
1535 @itemx pipe -d @var{delim} @var{command} @var{delim} @var{shell_command}
1536 @itemx | -d @var{delim} @var{command} @var{delim} @var{shell_command}
1537 Executes @var{command} and sends its output to @var{shell_command}.
1538 Note that no space is needed around @code{|}.
1539 If no @var{command} is provided, the last command executed is repeated.
1541 In case the @var{command} contains a @code{|}, the option @code{-d @var{delim}}
1542 can be used to specify an alternate delimiter string @var{delim} that separates
1543 the @var{command} from the @var{shell_command}.
1576 (gdb) | -d ! echo this contains a | char\n ! sed -e 's/|/PIPE/'
1577 this contains a PIPE char
1578 (gdb) | -d xxx echo this contains a | char!\n xxx sed -e 's/|/PIPE/'
1579 this contains a PIPE char!
1585 The convenience variables @code{$_shell_exitcode} and @code{$_shell_exitsignal}
1586 can be used to examine the exit status of the last shell command launched
1587 by @code{shell}, @code{make}, @code{pipe} and @code{|}.
1588 @xref{Convenience Vars,, Convenience Variables}.
1590 @node Logging Output
1591 @section Logging Output
1592 @cindex logging @value{GDBN} output
1593 @cindex save @value{GDBN} output to a file
1595 You may want to save the output of @value{GDBN} commands to a file.
1596 There are several commands to control @value{GDBN}'s logging.
1600 @item set logging on
1602 @item set logging off
1604 @cindex logging file name
1605 @item set logging file @var{file}
1606 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1607 @item set logging overwrite [on|off]
1608 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1609 you want @code{set logging on} to overwrite the logfile instead.
1610 @item set logging redirect [on|off]
1611 By default, @value{GDBN} output will go to both the terminal and the logfile.
1612 Set @code{redirect} if you want output to go only to the log file.
1613 @item set logging debugredirect [on|off]
1614 By default, @value{GDBN} debug output will go to both the terminal and the logfile.
1615 Set @code{debugredirect} if you want debug output to go only to the log file.
1616 @kindex show logging
1618 Show the current values of the logging settings.
1621 You can also redirect the output of a @value{GDBN} command to a
1622 shell command. @xref{pipe}.
1624 @chapter @value{GDBN} Commands
1626 You can abbreviate a @value{GDBN} command to the first few letters of the command
1627 name, if that abbreviation is unambiguous; and you can repeat certain
1628 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1629 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1630 show you the alternatives available, if there is more than one possibility).
1633 * Command Syntax:: How to give commands to @value{GDBN}
1634 * Command Settings:: How to change default behavior of commands
1635 * Completion:: Command completion
1636 * Command Options:: Command options
1637 * Help:: How to ask @value{GDBN} for help
1640 @node Command Syntax
1641 @section Command Syntax
1643 A @value{GDBN} command is a single line of input. There is no limit on
1644 how long it can be. It starts with a command name, which is followed by
1645 arguments whose meaning depends on the command name. For example, the
1646 command @code{step} accepts an argument which is the number of times to
1647 step, as in @samp{step 5}. You can also use the @code{step} command
1648 with no arguments. Some commands do not allow any arguments.
1650 @cindex abbreviation
1651 @value{GDBN} command names may always be truncated if that abbreviation is
1652 unambiguous. Other possible command abbreviations are listed in the
1653 documentation for individual commands. In some cases, even ambiguous
1654 abbreviations are allowed; for example, @code{s} is specially defined as
1655 equivalent to @code{step} even though there are other commands whose
1656 names start with @code{s}. You can test abbreviations by using them as
1657 arguments to the @code{help} command.
1659 @cindex repeating commands
1660 @kindex RET @r{(repeat last command)}
1661 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1662 repeat the previous command. Certain commands (for example, @code{run})
1663 will not repeat this way; these are commands whose unintentional
1664 repetition might cause trouble and which you are unlikely to want to
1665 repeat. User-defined commands can disable this feature; see
1666 @ref{Define, dont-repeat}.
1668 The @code{list} and @code{x} commands, when you repeat them with
1669 @key{RET}, construct new arguments rather than repeating
1670 exactly as typed. This permits easy scanning of source or memory.
1672 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1673 output, in a way similar to the common utility @code{more}
1674 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1675 @key{RET} too many in this situation, @value{GDBN} disables command
1676 repetition after any command that generates this sort of display.
1678 @kindex # @r{(a comment)}
1680 Any text from a @kbd{#} to the end of the line is a comment; it does
1681 nothing. This is useful mainly in command files (@pxref{Command
1682 Files,,Command Files}).
1684 @cindex repeating command sequences
1685 @kindex Ctrl-o @r{(operate-and-get-next)}
1686 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1687 commands. This command accepts the current line, like @key{RET}, and
1688 then fetches the next line relative to the current line from the history
1692 @node Command Settings
1693 @section Command Settings
1694 @cindex default behavior of commands, changing
1695 @cindex default settings, changing
1697 Many commands change their behavior according to command-specific
1698 variables or settings. These settings can be changed with the
1699 @code{set} subcommands. For example, the @code{print} command
1700 (@pxref{Data, ,Examining Data}) prints arrays differently depending on
1701 settings changeable with the commands @code{set print elements
1702 NUMBER-OF-ELEMENTS} and @code{set print array-indexes}, among others.
1704 You can change these settings to your preference in the gdbinit files
1705 loaded at @value{GDBN} startup. @xref{Startup}.
1707 The settings can also be changed interactively during the debugging
1708 session. For example, to change the limit of array elements to print,
1709 you can do the following:
1711 (@value{GDBN}) set print elements 10
1712 (@value{GDBN}) print some_array
1713 $1 = @{0, 10, 20, 30, 40, 50, 60, 70, 80, 90...@}
1716 The above @code{set print elements 10} command changes the number of
1717 elements to print from the default of 200 to 10. If you only intend
1718 this limit of 10 to be used for printing @code{some_array}, then you
1719 must restore the limit back to 200, with @code{set print elements
1722 Some commands allow overriding settings with command options. For
1723 example, the @code{print} command supports a number of options that
1724 allow overriding relevant global print settings as set by @code{set
1725 print} subcommands. @xref{print options}. The example above could be
1728 (@value{GDBN}) print -elements 10 -- some_array
1729 $1 = @{0, 10, 20, 30, 40, 50, 60, 70, 80, 90...@}
1732 Alternatively, you can use the @code{with} command to change a setting
1733 temporarily, for the duration of a command invocation.
1736 @kindex with command
1737 @kindex w @r{(@code{with})}
1739 @cindex temporarily change settings
1740 @item with @var{setting} [@var{value}] [-- @var{command}]
1741 @itemx w @var{setting} [@var{value}] [-- @var{command}]
1742 Temporarily set @var{setting} to @var{value} for the duration of
1745 @var{setting} is any setting you can change with the @code{set}
1746 subcommands. @var{value} is the value to assign to @code{setting}
1747 while running @code{command}.
1749 If no @var{command} is provided, the last command executed is
1752 If a @var{command} is provided, it must be preceded by a double dash
1753 (@code{--}) separator. This is required because some settings accept
1754 free-form arguments, such as expressions or filenames.
1756 For example, the command
1758 (@value{GDBN}) with print array on -- print some_array
1761 is equivalent to the following 3 commands:
1763 (@value{GDBN}) set print array on
1764 (@value{GDBN}) print some_array
1765 (@value{GDBN}) set print array off
1768 The @code{with} command is particularly useful when you want to
1769 override a setting while running user-defined commands, or commands
1770 defined in Python or Guile. @xref{Extending GDB,, Extending GDB}.
1773 (@value{GDBN}) with print pretty on -- my_complex_command
1776 To change several settings for the same command, you can nest
1777 @code{with} commands. For example, @code{with language ada -- with
1778 print elements 10} temporarily changes the language to Ada and sets a
1779 limit of 10 elements to print for arrays and strings.
1784 @section Command Completion
1787 @cindex word completion
1788 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1789 only one possibility; it can also show you what the valid possibilities
1790 are for the next word in a command, at any time. This works for @value{GDBN}
1791 commands, @value{GDBN} subcommands, command options, and the names of symbols
1794 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1795 of a word. If there is only one possibility, @value{GDBN} fills in the
1796 word, and waits for you to finish the command (or press @key{RET} to
1797 enter it). For example, if you type
1799 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1800 @c complete accuracy in these examples; space introduced for clarity.
1801 @c If texinfo enhancements make it unnecessary, it would be nice to
1802 @c replace " @key" by "@key" in the following...
1804 (@value{GDBP}) info bre @key{TAB}
1808 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1809 the only @code{info} subcommand beginning with @samp{bre}:
1812 (@value{GDBP}) info breakpoints
1816 You can either press @key{RET} at this point, to run the @code{info
1817 breakpoints} command, or backspace and enter something else, if
1818 @samp{breakpoints} does not look like the command you expected. (If you
1819 were sure you wanted @code{info breakpoints} in the first place, you
1820 might as well just type @key{RET} immediately after @samp{info bre},
1821 to exploit command abbreviations rather than command completion).
1823 If there is more than one possibility for the next word when you press
1824 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1825 characters and try again, or just press @key{TAB} a second time;
1826 @value{GDBN} displays all the possible completions for that word. For
1827 example, you might want to set a breakpoint on a subroutine whose name
1828 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1829 just sounds the bell. Typing @key{TAB} again displays all the
1830 function names in your program that begin with those characters, for
1834 (@value{GDBP}) b make_ @key{TAB}
1835 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1836 make_a_section_from_file make_environ
1837 make_abs_section make_function_type
1838 make_blockvector make_pointer_type
1839 make_cleanup make_reference_type
1840 make_command make_symbol_completion_list
1841 (@value{GDBP}) b make_
1845 After displaying the available possibilities, @value{GDBN} copies your
1846 partial input (@samp{b make_} in the example) so you can finish the
1849 If you just want to see the list of alternatives in the first place, you
1850 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1851 means @kbd{@key{META} ?}. You can type this either by holding down a
1852 key designated as the @key{META} shift on your keyboard (if there is
1853 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1855 If the number of possible completions is large, @value{GDBN} will
1856 print as much of the list as it has collected, as well as a message
1857 indicating that the list may be truncated.
1860 (@value{GDBP}) b m@key{TAB}@key{TAB}
1862 <... the rest of the possible completions ...>
1863 *** List may be truncated, max-completions reached. ***
1868 This behavior can be controlled with the following commands:
1871 @kindex set max-completions
1872 @item set max-completions @var{limit}
1873 @itemx set max-completions unlimited
1874 Set the maximum number of completion candidates. @value{GDBN} will
1875 stop looking for more completions once it collects this many candidates.
1876 This is useful when completing on things like function names as collecting
1877 all the possible candidates can be time consuming.
1878 The default value is 200. A value of zero disables tab-completion.
1879 Note that setting either no limit or a very large limit can make
1881 @kindex show max-completions
1882 @item show max-completions
1883 Show the maximum number of candidates that @value{GDBN} will collect and show
1887 @cindex quotes in commands
1888 @cindex completion of quoted strings
1889 Sometimes the string you need, while logically a ``word'', may contain
1890 parentheses or other characters that @value{GDBN} normally excludes from
1891 its notion of a word. To permit word completion to work in this
1892 situation, you may enclose words in @code{'} (single quote marks) in
1893 @value{GDBN} commands.
1895 A likely situation where you might need this is in typing an
1896 expression that involves a C@t{++} symbol name with template
1897 parameters. This is because when completing expressions, GDB treats
1898 the @samp{<} character as word delimiter, assuming that it's the
1899 less-than comparison operator (@pxref{C Operators, , C and C@t{++}
1902 For example, when you want to call a C@t{++} template function
1903 interactively using the @code{print} or @code{call} commands, you may
1904 need to distinguish whether you mean the version of @code{name} that
1905 was specialized for @code{int}, @code{name<int>()}, or the version
1906 that was specialized for @code{float}, @code{name<float>()}. To use
1907 the word-completion facilities in this situation, type a single quote
1908 @code{'} at the beginning of the function name. This alerts
1909 @value{GDBN} that it may need to consider more information than usual
1910 when you press @key{TAB} or @kbd{M-?} to request word completion:
1913 (@value{GDBP}) p 'func< @kbd{M-?}
1914 func<int>() func<float>()
1915 (@value{GDBP}) p 'func<
1918 When setting breakpoints however (@pxref{Specify Location}), you don't
1919 usually need to type a quote before the function name, because
1920 @value{GDBN} understands that you want to set a breakpoint on a
1924 (@value{GDBP}) b func< @kbd{M-?}
1925 func<int>() func<float>()
1926 (@value{GDBP}) b func<
1929 This is true even in the case of typing the name of C@t{++} overloaded
1930 functions (multiple definitions of the same function, distinguished by
1931 argument type). For example, when you want to set a breakpoint you
1932 don't need to distinguish whether you mean the version of @code{name}
1933 that takes an @code{int} parameter, @code{name(int)}, or the version
1934 that takes a @code{float} parameter, @code{name(float)}.
1937 (@value{GDBP}) b bubble( @kbd{M-?}
1938 bubble(int) bubble(double)
1939 (@value{GDBP}) b bubble(dou @kbd{M-?}
1943 See @ref{quoting names} for a description of other scenarios that
1946 For more information about overloaded functions, see @ref{C Plus Plus
1947 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1948 overload-resolution off} to disable overload resolution;
1949 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1951 @cindex completion of structure field names
1952 @cindex structure field name completion
1953 @cindex completion of union field names
1954 @cindex union field name completion
1955 When completing in an expression which looks up a field in a
1956 structure, @value{GDBN} also tries@footnote{The completer can be
1957 confused by certain kinds of invalid expressions. Also, it only
1958 examines the static type of the expression, not the dynamic type.} to
1959 limit completions to the field names available in the type of the
1963 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1964 magic to_fputs to_rewind
1965 to_data to_isatty to_write
1966 to_delete to_put to_write_async_safe
1971 This is because the @code{gdb_stdout} is a variable of the type
1972 @code{struct ui_file} that is defined in @value{GDBN} sources as
1979 ui_file_flush_ftype *to_flush;
1980 ui_file_write_ftype *to_write;
1981 ui_file_write_async_safe_ftype *to_write_async_safe;
1982 ui_file_fputs_ftype *to_fputs;
1983 ui_file_read_ftype *to_read;
1984 ui_file_delete_ftype *to_delete;
1985 ui_file_isatty_ftype *to_isatty;
1986 ui_file_rewind_ftype *to_rewind;
1987 ui_file_put_ftype *to_put;
1992 @node Command Options
1993 @section Command options
1995 @cindex command options
1996 Some commands accept options starting with a leading dash. For
1997 example, @code{print -pretty}. Similarly to command names, you can
1998 abbreviate a @value{GDBN} option to the first few letters of the
1999 option name, if that abbreviation is unambiguous, and you can also use
2000 the @key{TAB} key to get @value{GDBN} to fill out the rest of a word
2001 in an option (or to show you the alternatives available, if there is
2002 more than one possibility).
2004 @cindex command options, raw input
2005 Some commands take raw input as argument. For example, the print
2006 command processes arbitrary expressions in any of the languages
2007 supported by @value{GDBN}. With such commands, because raw input may
2008 start with a leading dash that would be confused with an option or any
2009 of its abbreviations, e.g.@: @code{print -p} (short for @code{print
2010 -pretty} or printing negative @code{p}?), if you specify any command
2011 option, then you must use a double-dash (@code{--}) delimiter to
2012 indicate the end of options.
2014 @cindex command options, boolean
2016 Some options are described as accepting an argument which can be
2017 either @code{on} or @code{off}. These are known as @dfn{boolean
2018 options}. Similarly to boolean settings commands---@code{on} and
2019 @code{off} are the typical values, but any of @code{1}, @code{yes} and
2020 @code{enable} can also be used as ``true'' value, and any of @code{0},
2021 @code{no} and @code{disable} can also be used as ``false'' value. You
2022 can also omit a ``true'' value, as it is implied by default.
2024 For example, these are equivalent:
2027 (@value{GDBP}) print -object on -pretty off -element unlimited -- *myptr
2028 (@value{GDBP}) p -o -p 0 -e u -- *myptr
2031 You can discover the set of options some command accepts by completing
2032 on @code{-} after the command name. For example:
2035 (@value{GDBP}) print -@key{TAB}@key{TAB}
2036 -address -max-depth -raw-values -union
2037 -array -null-stop -repeats -vtbl
2038 -array-indexes -object -static-members
2039 -elements -pretty -symbol
2042 Completion will in some cases guide you with a suggestion of what kind
2043 of argument an option expects. For example:
2046 (@value{GDBP}) print -elements @key{TAB}@key{TAB}
2050 Here, the option expects a number (e.g., @code{100}), not literal
2051 @code{NUMBER}. Such metasyntactical arguments are always presented in
2054 (For more on using the @code{print} command, see @ref{Data, ,Examining
2058 @section Getting Help
2059 @cindex online documentation
2062 You can always ask @value{GDBN} itself for information on its commands,
2063 using the command @code{help}.
2066 @kindex h @r{(@code{help})}
2069 You can use @code{help} (abbreviated @code{h}) with no arguments to
2070 display a short list of named classes of commands:
2074 List of classes of commands:
2076 aliases -- User-defined aliases of other commands
2077 breakpoints -- Making program stop at certain points
2078 data -- Examining data
2079 files -- Specifying and examining files
2080 internals -- Maintenance commands
2081 obscure -- Obscure features
2082 running -- Running the program
2083 stack -- Examining the stack
2084 status -- Status inquiries
2085 support -- Support facilities
2086 tracepoints -- Tracing of program execution without
2087 stopping the program
2088 user-defined -- User-defined commands
2090 Type "help" followed by a class name for a list of
2091 commands in that class.
2092 Type "help" followed by command name for full
2094 Command name abbreviations are allowed if unambiguous.
2097 @c the above line break eliminates huge line overfull...
2099 @item help @var{class}
2100 Using one of the general help classes as an argument, you can get a
2101 list of the individual commands in that class. If a command has
2102 aliases, the aliases are given after the command name, separated by
2103 commas. If an alias has default arguments, the full definition of
2104 the alias is given after the first line.
2105 For example, here is the help display for the class @code{status}:
2108 (@value{GDBP}) help status
2113 @c Line break in "show" line falsifies real output, but needed
2114 @c to fit in smallbook page size.
2115 info, inf, i -- Generic command for showing things
2116 about the program being debugged
2117 info address, iamain -- Describe where symbol SYM is stored.
2118 alias iamain = info address main
2119 info all-registers -- List of all registers and their contents,
2120 for selected stack frame.
2122 show, info set -- Generic command for showing things
2125 Type "help" followed by command name for full
2127 Command name abbreviations are allowed if unambiguous.
2131 @item help @var{command}
2132 With a command name as @code{help} argument, @value{GDBN} displays a
2133 short paragraph on how to use that command. If that command has
2134 one or more aliases, @value{GDBN} will display a first line with
2135 the command name and all its aliases separated by commas.
2136 This first line will be followed by the full definition of all aliases
2137 having default arguments.
2140 @item apropos [-v] @var{regexp}
2141 The @code{apropos} command searches through all of the @value{GDBN}
2142 commands, and their documentation, for the regular expression specified in
2143 @var{args}. It prints out all matches found. The optional flag @samp{-v},
2144 which stands for @samp{verbose}, indicates to output the full documentation
2145 of the matching commands and highlight the parts of the documentation
2146 matching @var{regexp}. For example:
2157 alias -- Define a new command that is an alias of an existing command
2158 aliases -- User-defined aliases of other commands
2166 apropos -v cut.*thread apply
2170 results in the below output, where @samp{cut for 'thread apply}
2171 is highlighted if styling is enabled.
2175 taas -- Apply a command to all threads (ignoring errors
2178 shortcut for 'thread apply all -s COMMAND'
2180 tfaas -- Apply a command to all frames of all threads
2181 (ignoring errors and empty output).
2182 Usage: tfaas COMMAND
2183 shortcut for 'thread apply all -s frame apply all -s COMMAND'
2188 @item complete @var{args}
2189 The @code{complete @var{args}} command lists all the possible completions
2190 for the beginning of a command. Use @var{args} to specify the beginning of the
2191 command you want completed. For example:
2197 @noindent results in:
2208 @noindent This is intended for use by @sc{gnu} Emacs.
2211 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
2212 and @code{show} to inquire about the state of your program, or the state
2213 of @value{GDBN} itself. Each command supports many topics of inquiry; this
2214 manual introduces each of them in the appropriate context. The listings
2215 under @code{info} and under @code{show} in the Command, Variable, and
2216 Function Index point to all the sub-commands. @xref{Command and Variable
2222 @kindex i @r{(@code{info})}
2224 This command (abbreviated @code{i}) is for describing the state of your
2225 program. For example, you can show the arguments passed to a function
2226 with @code{info args}, list the registers currently in use with @code{info
2227 registers}, or list the breakpoints you have set with @code{info breakpoints}.
2228 You can get a complete list of the @code{info} sub-commands with
2229 @w{@code{help info}}.
2233 You can assign the result of an expression to an environment variable with
2234 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
2235 @code{set prompt $}.
2239 In contrast to @code{info}, @code{show} is for describing the state of
2240 @value{GDBN} itself.
2241 You can change most of the things you can @code{show}, by using the
2242 related command @code{set}; for example, you can control what number
2243 system is used for displays with @code{set radix}, or simply inquire
2244 which is currently in use with @code{show radix}.
2247 To display all the settable parameters and their current
2248 values, you can use @code{show} with no arguments; you may also use
2249 @code{info set}. Both commands produce the same display.
2250 @c FIXME: "info set" violates the rule that "info" is for state of
2251 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
2252 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
2256 Here are several miscellaneous @code{show} subcommands, all of which are
2257 exceptional in lacking corresponding @code{set} commands:
2260 @kindex show version
2261 @cindex @value{GDBN} version number
2263 Show what version of @value{GDBN} is running. You should include this
2264 information in @value{GDBN} bug-reports. If multiple versions of
2265 @value{GDBN} are in use at your site, you may need to determine which
2266 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
2267 commands are introduced, and old ones may wither away. Also, many
2268 system vendors ship variant versions of @value{GDBN}, and there are
2269 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
2270 The version number is the same as the one announced when you start
2273 @kindex show copying
2274 @kindex info copying
2275 @cindex display @value{GDBN} copyright
2278 Display information about permission for copying @value{GDBN}.
2280 @kindex show warranty
2281 @kindex info warranty
2283 @itemx info warranty
2284 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
2285 if your version of @value{GDBN} comes with one.
2287 @kindex show configuration
2288 @item show configuration
2289 Display detailed information about the way @value{GDBN} was configured
2290 when it was built. This displays the optional arguments passed to the
2291 @file{configure} script and also configuration parameters detected
2292 automatically by @command{configure}. When reporting a @value{GDBN}
2293 bug (@pxref{GDB Bugs}), it is important to include this information in
2299 @chapter Running Programs Under @value{GDBN}
2301 When you run a program under @value{GDBN}, you must first generate
2302 debugging information when you compile it.
2304 You may start @value{GDBN} with its arguments, if any, in an environment
2305 of your choice. If you are doing native debugging, you may redirect
2306 your program's input and output, debug an already running process, or
2307 kill a child process.
2310 * Compilation:: Compiling for debugging
2311 * Starting:: Starting your program
2312 * Arguments:: Your program's arguments
2313 * Environment:: Your program's environment
2315 * Working Directory:: Your program's working directory
2316 * Input/Output:: Your program's input and output
2317 * Attach:: Debugging an already-running process
2318 * Kill Process:: Killing the child process
2319 * Inferiors Connections and Programs:: Debugging multiple inferiors
2320 connections and programs
2321 * Threads:: Debugging programs with multiple threads
2322 * Forks:: Debugging forks
2323 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
2327 @section Compiling for Debugging
2329 In order to debug a program effectively, you need to generate
2330 debugging information when you compile it. This debugging information
2331 is stored in the object file; it describes the data type of each
2332 variable or function and the correspondence between source line numbers
2333 and addresses in the executable code.
2335 To request debugging information, specify the @samp{-g} option when you run
2338 Programs that are to be shipped to your customers are compiled with
2339 optimizations, using the @samp{-O} compiler option. However, some
2340 compilers are unable to handle the @samp{-g} and @samp{-O} options
2341 together. Using those compilers, you cannot generate optimized
2342 executables containing debugging information.
2344 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
2345 without @samp{-O}, making it possible to debug optimized code. We
2346 recommend that you @emph{always} use @samp{-g} whenever you compile a
2347 program. You may think your program is correct, but there is no sense
2348 in pushing your luck. For more information, see @ref{Optimized Code}.
2350 Older versions of the @sc{gnu} C compiler permitted a variant option
2351 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
2352 format; if your @sc{gnu} C compiler has this option, do not use it.
2354 @value{GDBN} knows about preprocessor macros and can show you their
2355 expansion (@pxref{Macros}). Most compilers do not include information
2356 about preprocessor macros in the debugging information if you specify
2357 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
2358 the @sc{gnu} C compiler, provides macro information if you are using
2359 the DWARF debugging format, and specify the option @option{-g3}.
2361 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
2362 gcc, Using the @sc{gnu} Compiler Collection (GCC)}, for more
2363 information on @value{NGCC} options affecting debug information.
2365 You will have the best debugging experience if you use the latest
2366 version of the DWARF debugging format that your compiler supports.
2367 DWARF is currently the most expressive and best supported debugging
2368 format in @value{GDBN}.
2372 @section Starting your Program
2378 @kindex r @r{(@code{run})}
2381 Use the @code{run} command to start your program under @value{GDBN}.
2382 You must first specify the program name with an argument to
2383 @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
2384 @value{GDBN}}), or by using the @code{file} or @code{exec-file}
2385 command (@pxref{Files, ,Commands to Specify Files}).
2389 If you are running your program in an execution environment that
2390 supports processes, @code{run} creates an inferior process and makes
2391 that process run your program. In some environments without processes,
2392 @code{run} jumps to the start of your program. Other targets,
2393 like @samp{remote}, are always running. If you get an error
2394 message like this one:
2397 The "remote" target does not support "run".
2398 Try "help target" or "continue".
2402 then use @code{continue} to run your program. You may need @code{load}
2403 first (@pxref{load}).
2405 The execution of a program is affected by certain information it
2406 receives from its superior. @value{GDBN} provides ways to specify this
2407 information, which you must do @emph{before} starting your program. (You
2408 can change it after starting your program, but such changes only affect
2409 your program the next time you start it.) This information may be
2410 divided into four categories:
2413 @item The @emph{arguments.}
2414 Specify the arguments to give your program as the arguments of the
2415 @code{run} command. If a shell is available on your target, the shell
2416 is used to pass the arguments, so that you may use normal conventions
2417 (such as wildcard expansion or variable substitution) in describing
2419 In Unix systems, you can control which shell is used with the
2420 @code{SHELL} environment variable. If you do not define @code{SHELL},
2421 @value{GDBN} uses the default shell (@file{/bin/sh}). You can disable
2422 use of any shell with the @code{set startup-with-shell} command (see
2425 @item The @emph{environment.}
2426 Your program normally inherits its environment from @value{GDBN}, but you can
2427 use the @value{GDBN} commands @code{set environment} and @code{unset
2428 environment} to change parts of the environment that affect
2429 your program. @xref{Environment, ,Your Program's Environment}.
2431 @item The @emph{working directory.}
2432 You can set your program's working directory with the command
2433 @kbd{set cwd}. If you do not set any working directory with this
2434 command, your program will inherit @value{GDBN}'s working directory if
2435 native debugging, or the remote server's working directory if remote
2436 debugging. @xref{Working Directory, ,Your Program's Working
2439 @item The @emph{standard input and output.}
2440 Your program normally uses the same device for standard input and
2441 standard output as @value{GDBN} is using. You can redirect input and output
2442 in the @code{run} command line, or you can use the @code{tty} command to
2443 set a different device for your program.
2444 @xref{Input/Output, ,Your Program's Input and Output}.
2447 @emph{Warning:} While input and output redirection work, you cannot use
2448 pipes to pass the output of the program you are debugging to another
2449 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2453 When you issue the @code{run} command, your program begins to execute
2454 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2455 of how to arrange for your program to stop. Once your program has
2456 stopped, you may call functions in your program, using the @code{print}
2457 or @code{call} commands. @xref{Data, ,Examining Data}.
2459 If the modification time of your symbol file has changed since the last
2460 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2461 table, and reads it again. When it does this, @value{GDBN} tries to retain
2462 your current breakpoints.
2467 @cindex run to main procedure
2468 The name of the main procedure can vary from language to language.
2469 With C or C@t{++}, the main procedure name is always @code{main}, but
2470 other languages such as Ada do not require a specific name for their
2471 main procedure. The debugger provides a convenient way to start the
2472 execution of the program and to stop at the beginning of the main
2473 procedure, depending on the language used.
2475 The @samp{start} command does the equivalent of setting a temporary
2476 breakpoint at the beginning of the main procedure and then invoking
2477 the @samp{run} command.
2479 @cindex elaboration phase
2480 Some programs contain an @dfn{elaboration} phase where some startup code is
2481 executed before the main procedure is called. This depends on the
2482 languages used to write your program. In C@t{++}, for instance,
2483 constructors for static and global objects are executed before
2484 @code{main} is called. It is therefore possible that the debugger stops
2485 before reaching the main procedure. However, the temporary breakpoint
2486 will remain to halt execution.
2488 Specify the arguments to give to your program as arguments to the
2489 @samp{start} command. These arguments will be given verbatim to the
2490 underlying @samp{run} command. Note that the same arguments will be
2491 reused if no argument is provided during subsequent calls to
2492 @samp{start} or @samp{run}.
2494 It is sometimes necessary to debug the program during elaboration. In
2495 these cases, using the @code{start} command would stop the execution
2496 of your program too late, as the program would have already completed
2497 the elaboration phase. Under these circumstances, either insert
2498 breakpoints in your elaboration code before running your program or
2499 use the @code{starti} command.
2503 @cindex run to first instruction
2504 The @samp{starti} command does the equivalent of setting a temporary
2505 breakpoint at the first instruction of a program's execution and then
2506 invoking the @samp{run} command. For programs containing an
2507 elaboration phase, the @code{starti} command will stop execution at
2508 the start of the elaboration phase.
2510 @anchor{set exec-wrapper}
2511 @kindex set exec-wrapper
2512 @item set exec-wrapper @var{wrapper}
2513 @itemx show exec-wrapper
2514 @itemx unset exec-wrapper
2515 When @samp{exec-wrapper} is set, the specified wrapper is used to
2516 launch programs for debugging. @value{GDBN} starts your program
2517 with a shell command of the form @kbd{exec @var{wrapper}
2518 @var{program}}. Quoting is added to @var{program} and its
2519 arguments, but not to @var{wrapper}, so you should add quotes if
2520 appropriate for your shell. The wrapper runs until it executes
2521 your program, and then @value{GDBN} takes control.
2523 You can use any program that eventually calls @code{execve} with
2524 its arguments as a wrapper. Several standard Unix utilities do
2525 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2526 with @code{exec "$@@"} will also work.
2528 For example, you can use @code{env} to pass an environment variable to
2529 the debugged program, without setting the variable in your shell's
2533 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2537 This command is available when debugging locally on most targets, excluding
2538 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2540 @kindex set startup-with-shell
2541 @anchor{set startup-with-shell}
2542 @item set startup-with-shell
2543 @itemx set startup-with-shell on
2544 @itemx set startup-with-shell off
2545 @itemx show startup-with-shell
2546 On Unix systems, by default, if a shell is available on your target,
2547 @value{GDBN}) uses it to start your program. Arguments of the
2548 @code{run} command are passed to the shell, which does variable
2549 substitution, expands wildcard characters and performs redirection of
2550 I/O. In some circumstances, it may be useful to disable such use of a
2551 shell, for example, when debugging the shell itself or diagnosing
2552 startup failures such as:
2556 Starting program: ./a.out
2557 During startup program terminated with signal SIGSEGV, Segmentation fault.
2561 which indicates the shell or the wrapper specified with
2562 @samp{exec-wrapper} crashed, not your program. Most often, this is
2563 caused by something odd in your shell's non-interactive mode
2564 initialization file---such as @file{.cshrc} for C-shell,
2565 $@file{.zshenv} for the Z shell, or the file specified in the
2566 @samp{BASH_ENV} environment variable for BASH.
2568 @anchor{set auto-connect-native-target}
2569 @kindex set auto-connect-native-target
2570 @item set auto-connect-native-target
2571 @itemx set auto-connect-native-target on
2572 @itemx set auto-connect-native-target off
2573 @itemx show auto-connect-native-target
2575 By default, if the current inferior is not connected to any target yet
2576 (e.g., with @code{target remote}), the @code{run} command starts your
2577 program as a native process under @value{GDBN}, on your local machine.
2578 If you're sure you don't want to debug programs on your local machine,
2579 you can tell @value{GDBN} to not connect to the native target
2580 automatically with the @code{set auto-connect-native-target off}
2583 If @code{on}, which is the default, and if the current inferior is not
2584 connected to a target already, the @code{run} command automaticaly
2585 connects to the native target, if one is available.
2587 If @code{off}, and if the current inferior is not connected to a
2588 target already, the @code{run} command fails with an error:
2592 Don't know how to run. Try "help target".
2595 If the current inferior is already connected to a target, @value{GDBN}
2596 always uses it with the @code{run} command.
2598 In any case, you can explicitly connect to the native target with the
2599 @code{target native} command. For example,
2602 (@value{GDBP}) set auto-connect-native-target off
2604 Don't know how to run. Try "help target".
2605 (@value{GDBP}) target native
2607 Starting program: ./a.out
2608 [Inferior 1 (process 10421) exited normally]
2611 In case you connected explicitly to the @code{native} target,
2612 @value{GDBN} remains connected even if all inferiors exit, ready for
2613 the next @code{run} command. Use the @code{disconnect} command to
2616 Examples of other commands that likewise respect the
2617 @code{auto-connect-native-target} setting: @code{attach}, @code{info
2618 proc}, @code{info os}.
2620 @kindex set disable-randomization
2621 @item set disable-randomization
2622 @itemx set disable-randomization on
2623 This option (enabled by default in @value{GDBN}) will turn off the native
2624 randomization of the virtual address space of the started program. This option
2625 is useful for multiple debugging sessions to make the execution better
2626 reproducible and memory addresses reusable across debugging sessions.
2628 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2629 On @sc{gnu}/Linux you can get the same behavior using
2632 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2635 @item set disable-randomization off
2636 Leave the behavior of the started executable unchanged. Some bugs rear their
2637 ugly heads only when the program is loaded at certain addresses. If your bug
2638 disappears when you run the program under @value{GDBN}, that might be because
2639 @value{GDBN} by default disables the address randomization on platforms, such
2640 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2641 disable-randomization off} to try to reproduce such elusive bugs.
2643 On targets where it is available, virtual address space randomization
2644 protects the programs against certain kinds of security attacks. In these
2645 cases the attacker needs to know the exact location of a concrete executable
2646 code. Randomizing its location makes it impossible to inject jumps misusing
2647 a code at its expected addresses.
2649 Prelinking shared libraries provides a startup performance advantage but it
2650 makes addresses in these libraries predictable for privileged processes by
2651 having just unprivileged access at the target system. Reading the shared
2652 library binary gives enough information for assembling the malicious code
2653 misusing it. Still even a prelinked shared library can get loaded at a new
2654 random address just requiring the regular relocation process during the
2655 startup. Shared libraries not already prelinked are always loaded at
2656 a randomly chosen address.
2658 Position independent executables (PIE) contain position independent code
2659 similar to the shared libraries and therefore such executables get loaded at
2660 a randomly chosen address upon startup. PIE executables always load even
2661 already prelinked shared libraries at a random address. You can build such
2662 executable using @command{gcc -fPIE -pie}.
2664 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2665 (as long as the randomization is enabled).
2667 @item show disable-randomization
2668 Show the current setting of the explicit disable of the native randomization of
2669 the virtual address space of the started program.
2674 @section Your Program's Arguments
2676 @cindex arguments (to your program)
2677 The arguments to your program can be specified by the arguments of the
2679 They are passed to a shell, which expands wildcard characters and
2680 performs redirection of I/O, and thence to your program. Your
2681 @code{SHELL} environment variable (if it exists) specifies what shell
2682 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2683 the default shell (@file{/bin/sh} on Unix).
2685 On non-Unix systems, the program is usually invoked directly by
2686 @value{GDBN}, which emulates I/O redirection via the appropriate system
2687 calls, and the wildcard characters are expanded by the startup code of
2688 the program, not by the shell.
2690 @code{run} with no arguments uses the same arguments used by the previous
2691 @code{run}, or those set by the @code{set args} command.
2696 Specify the arguments to be used the next time your program is run. If
2697 @code{set args} has no arguments, @code{run} executes your program
2698 with no arguments. Once you have run your program with arguments,
2699 using @code{set args} before the next @code{run} is the only way to run
2700 it again without arguments.
2704 Show the arguments to give your program when it is started.
2708 @section Your Program's Environment
2710 @cindex environment (of your program)
2711 The @dfn{environment} consists of a set of environment variables and
2712 their values. Environment variables conventionally record such things as
2713 your user name, your home directory, your terminal type, and your search
2714 path for programs to run. Usually you set up environment variables with
2715 the shell and they are inherited by all the other programs you run. When
2716 debugging, it can be useful to try running your program with a modified
2717 environment without having to start @value{GDBN} over again.
2721 @item path @var{directory}
2722 Add @var{directory} to the front of the @code{PATH} environment variable
2723 (the search path for executables) that will be passed to your program.
2724 The value of @code{PATH} used by @value{GDBN} does not change.
2725 You may specify several directory names, separated by whitespace or by a
2726 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2727 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2728 is moved to the front, so it is searched sooner.
2730 You can use the string @samp{$cwd} to refer to whatever is the current
2731 working directory at the time @value{GDBN} searches the path. If you
2732 use @samp{.} instead, it refers to the directory where you executed the
2733 @code{path} command. @value{GDBN} replaces @samp{.} in the
2734 @var{directory} argument (with the current path) before adding
2735 @var{directory} to the search path.
2736 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2737 @c document that, since repeating it would be a no-op.
2741 Display the list of search paths for executables (the @code{PATH}
2742 environment variable).
2744 @kindex show environment
2745 @item show environment @r{[}@var{varname}@r{]}
2746 Print the value of environment variable @var{varname} to be given to
2747 your program when it starts. If you do not supply @var{varname},
2748 print the names and values of all environment variables to be given to
2749 your program. You can abbreviate @code{environment} as @code{env}.
2751 @kindex set environment
2752 @anchor{set environment}
2753 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2754 Set environment variable @var{varname} to @var{value}. The value
2755 changes for your program (and the shell @value{GDBN} uses to launch
2756 it), not for @value{GDBN} itself. The @var{value} may be any string; the
2757 values of environment variables are just strings, and any
2758 interpretation is supplied by your program itself. The @var{value}
2759 parameter is optional; if it is eliminated, the variable is set to a
2761 @c "any string" here does not include leading, trailing
2762 @c blanks. Gnu asks: does anyone care?
2764 For example, this command:
2771 tells the debugged program, when subsequently run, that its user is named
2772 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2773 are not actually required.)
2775 Note that on Unix systems, @value{GDBN} runs your program via a shell,
2776 which also inherits the environment set with @code{set environment}.
2777 If necessary, you can avoid that by using the @samp{env} program as a
2778 wrapper instead of using @code{set environment}. @xref{set
2779 exec-wrapper}, for an example doing just that.
2781 Environment variables that are set by the user are also transmitted to
2782 @command{gdbserver} to be used when starting the remote inferior.
2783 @pxref{QEnvironmentHexEncoded}.
2785 @kindex unset environment
2786 @anchor{unset environment}
2787 @item unset environment @var{varname}
2788 Remove variable @var{varname} from the environment to be passed to your
2789 program. This is different from @samp{set env @var{varname} =};
2790 @code{unset environment} removes the variable from the environment,
2791 rather than assigning it an empty value.
2793 Environment variables that are unset by the user are also unset on
2794 @command{gdbserver} when starting the remote inferior.
2795 @pxref{QEnvironmentUnset}.
2798 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2799 the shell indicated by your @code{SHELL} environment variable if it
2800 exists (or @code{/bin/sh} if not). If your @code{SHELL} variable
2801 names a shell that runs an initialization file when started
2802 non-interactively---such as @file{.cshrc} for C-shell, $@file{.zshenv}
2803 for the Z shell, or the file specified in the @samp{BASH_ENV}
2804 environment variable for BASH---any variables you set in that file
2805 affect your program. You may wish to move setting of environment
2806 variables to files that are only run when you sign on, such as
2807 @file{.login} or @file{.profile}.
2809 @node Working Directory
2810 @section Your Program's Working Directory
2812 @cindex working directory (of your program)
2813 Each time you start your program with @code{run}, the inferior will be
2814 initialized with the current working directory specified by the
2815 @kbd{set cwd} command. If no directory has been specified by this
2816 command, then the inferior will inherit @value{GDBN}'s current working
2817 directory as its working directory if native debugging, or it will
2818 inherit the remote server's current working directory if remote
2823 @cindex change inferior's working directory
2824 @anchor{set cwd command}
2825 @item set cwd @r{[}@var{directory}@r{]}
2826 Set the inferior's working directory to @var{directory}, which will be
2827 @code{glob}-expanded in order to resolve tildes (@file{~}). If no
2828 argument has been specified, the command clears the setting and resets
2829 it to an empty state. This setting has no effect on @value{GDBN}'s
2830 working directory, and it only takes effect the next time you start
2831 the inferior. The @file{~} in @var{directory} is a short for the
2832 @dfn{home directory}, usually pointed to by the @env{HOME} environment
2833 variable. On MS-Windows, if @env{HOME} is not defined, @value{GDBN}
2834 uses the concatenation of @env{HOMEDRIVE} and @env{HOMEPATH} as
2837 You can also change @value{GDBN}'s current working directory by using
2838 the @code{cd} command.
2842 @cindex show inferior's working directory
2844 Show the inferior's working directory. If no directory has been
2845 specified by @kbd{set cwd}, then the default inferior's working
2846 directory is the same as @value{GDBN}'s working directory.
2849 @cindex change @value{GDBN}'s working directory
2851 @item cd @r{[}@var{directory}@r{]}
2852 Set the @value{GDBN} working directory to @var{directory}. If not
2853 given, @var{directory} uses @file{'~'}.
2855 The @value{GDBN} working directory serves as a default for the
2856 commands that specify files for @value{GDBN} to operate on.
2857 @xref{Files, ,Commands to Specify Files}.
2858 @xref{set cwd command}.
2862 Print the @value{GDBN} working directory.
2865 It is generally impossible to find the current working directory of
2866 the process being debugged (since a program can change its directory
2867 during its run). If you work on a system where @value{GDBN} supports
2868 the @code{info proc} command (@pxref{Process Information}), you can
2869 use the @code{info proc} command to find out the
2870 current working directory of the debuggee.
2873 @section Your Program's Input and Output
2878 By default, the program you run under @value{GDBN} does input and output to
2879 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2880 to its own terminal modes to interact with you, but it records the terminal
2881 modes your program was using and switches back to them when you continue
2882 running your program.
2885 @kindex info terminal
2887 Displays information recorded by @value{GDBN} about the terminal modes your
2891 You can redirect your program's input and/or output using shell
2892 redirection with the @code{run} command. For example,
2899 starts your program, diverting its output to the file @file{outfile}.
2902 @cindex controlling terminal
2903 Another way to specify where your program should do input and output is
2904 with the @code{tty} command. This command accepts a file name as
2905 argument, and causes this file to be the default for future @code{run}
2906 commands. It also resets the controlling terminal for the child
2907 process, for future @code{run} commands. For example,
2914 directs that processes started with subsequent @code{run} commands
2915 default to do input and output on the terminal @file{/dev/ttyb} and have
2916 that as their controlling terminal.
2918 An explicit redirection in @code{run} overrides the @code{tty} command's
2919 effect on the input/output device, but not its effect on the controlling
2922 When you use the @code{tty} command or redirect input in the @code{run}
2923 command, only the input @emph{for your program} is affected. The input
2924 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2925 for @code{set inferior-tty}.
2927 @cindex inferior tty
2928 @cindex set inferior controlling terminal
2929 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2930 display the name of the terminal that will be used for future runs of your
2934 @item set inferior-tty [ @var{tty} ]
2935 @kindex set inferior-tty
2936 Set the tty for the program being debugged to @var{tty}. Omitting @var{tty}
2937 restores the default behavior, which is to use the same terminal as
2940 @item show inferior-tty
2941 @kindex show inferior-tty
2942 Show the current tty for the program being debugged.
2946 @section Debugging an Already-running Process
2951 @item attach @var{process-id}
2952 This command attaches to a running process---one that was started
2953 outside @value{GDBN}. (@code{info files} shows your active
2954 targets.) The command takes as argument a process ID. The usual way to
2955 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2956 or with the @samp{jobs -l} shell command.
2958 @code{attach} does not repeat if you press @key{RET} a second time after
2959 executing the command.
2962 To use @code{attach}, your program must be running in an environment
2963 which supports processes; for example, @code{attach} does not work for
2964 programs on bare-board targets that lack an operating system. You must
2965 also have permission to send the process a signal.
2967 When you use @code{attach}, the debugger finds the program running in
2968 the process first by looking in the current working directory, then (if
2969 the program is not found) by using the source file search path
2970 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2971 the @code{file} command to load the program. @xref{Files, ,Commands to
2974 @anchor{set exec-file-mismatch}
2975 If the debugger can determine that the executable file running in the
2976 process it is attaching to does not match the current exec-file loaded
2977 by @value{GDBN}, the option @code{exec-file-mismatch} specifies how to
2978 handle the mismatch. @value{GDBN} tries to compare the files by
2979 comparing their build IDs (@pxref{build ID}), if available.
2982 @kindex exec-file-mismatch
2983 @cindex set exec-file-mismatch
2984 @item set exec-file-mismatch @samp{ask|warn|off}
2986 Whether to detect mismatch between the current executable file loaded
2987 by @value{GDBN} and the executable file used to start the process. If
2988 @samp{ask}, the default, display a warning and ask the user whether to
2989 load the process executable file; if @samp{warn}, just display a
2990 warning; if @samp{off}, don't attempt to detect a mismatch.
2991 If the user confirms loading the process executable file, then its symbols
2992 will be loaded as well.
2994 @cindex show exec-file-mismatch
2995 @item show exec-file-mismatch
2996 Show the current value of @code{exec-file-mismatch}.
3000 The first thing @value{GDBN} does after arranging to debug the specified
3001 process is to stop it. You can examine and modify an attached process
3002 with all the @value{GDBN} commands that are ordinarily available when
3003 you start processes with @code{run}. You can insert breakpoints; you
3004 can step and continue; you can modify storage. If you would rather the
3005 process continue running, you may use the @code{continue} command after
3006 attaching @value{GDBN} to the process.
3011 When you have finished debugging the attached process, you can use the
3012 @code{detach} command to release it from @value{GDBN} control. Detaching
3013 the process continues its execution. After the @code{detach} command,
3014 that process and @value{GDBN} become completely independent once more, and you
3015 are ready to @code{attach} another process or start one with @code{run}.
3016 @code{detach} does not repeat if you press @key{RET} again after
3017 executing the command.
3020 If you exit @value{GDBN} while you have an attached process, you detach
3021 that process. If you use the @code{run} command, you kill that process.
3022 By default, @value{GDBN} asks for confirmation if you try to do either of these
3023 things; you can control whether or not you need to confirm by using the
3024 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
3028 @section Killing the Child Process
3033 Kill the child process in which your program is running under @value{GDBN}.
3036 This command is useful if you wish to debug a core dump instead of a
3037 running process. @value{GDBN} ignores any core dump file while your program
3040 On some operating systems, a program cannot be executed outside @value{GDBN}
3041 while you have breakpoints set on it inside @value{GDBN}. You can use the
3042 @code{kill} command in this situation to permit running your program
3043 outside the debugger.
3045 The @code{kill} command is also useful if you wish to recompile and
3046 relink your program, since on many systems it is impossible to modify an
3047 executable file while it is running in a process. In this case, when you
3048 next type @code{run}, @value{GDBN} notices that the file has changed, and
3049 reads the symbol table again (while trying to preserve your current
3050 breakpoint settings).
3052 @node Inferiors Connections and Programs
3053 @section Debugging Multiple Inferiors Connections and Programs
3055 @value{GDBN} lets you run and debug multiple programs in a single
3056 session. In addition, @value{GDBN} on some systems may let you run
3057 several programs simultaneously (otherwise you have to exit from one
3058 before starting another). On some systems @value{GDBN} may even let
3059 you debug several programs simultaneously on different remote systems.
3060 In the most general case, you can have multiple threads of execution
3061 in each of multiple processes, launched from multiple executables,
3062 running on different machines.
3065 @value{GDBN} represents the state of each program execution with an
3066 object called an @dfn{inferior}. An inferior typically corresponds to
3067 a process, but is more general and applies also to targets that do not
3068 have processes. Inferiors may be created before a process runs, and
3069 may be retained after a process exits. Inferiors have unique
3070 identifiers that are different from process ids. Usually each
3071 inferior will also have its own distinct address space, although some
3072 embedded targets may have several inferiors running in different parts
3073 of a single address space. Each inferior may in turn have multiple
3074 threads running in it.
3076 To find out what inferiors exist at any moment, use @w{@code{info
3080 @kindex info inferiors [ @var{id}@dots{} ]
3081 @item info inferiors
3082 Print a list of all inferiors currently being managed by @value{GDBN}.
3083 By default all inferiors are printed, but the argument @var{id}@dots{}
3084 -- a space separated list of inferior numbers -- can be used to limit
3085 the display to just the requested inferiors.
3087 @value{GDBN} displays for each inferior (in this order):
3091 the inferior number assigned by @value{GDBN}
3094 the target system's inferior identifier
3097 the target connection the inferior is bound to, including the unique
3098 connection number assigned by @value{GDBN}, and the protocol used by
3102 the name of the executable the inferior is running.
3107 An asterisk @samp{*} preceding the @value{GDBN} inferior number
3108 indicates the current inferior.
3112 @c end table here to get a little more width for example
3115 (@value{GDBP}) info inferiors
3116 Num Description Connection Executable
3117 * 1 process 3401 1 (native) goodbye
3118 2 process 2307 2 (extended-remote host:10000) hello
3121 To get informations about the current inferior, use @code{inferior}:
3126 Shows information about the current inferior.
3130 @c end table here to get a little more width for example
3133 (@value{GDBP}) inferior
3134 [Current inferior is 1 [process 3401] (helloworld)]
3137 To find out what open target connections exist at any moment, use
3138 @w{@code{info connections}}:
3141 @kindex info connections [ @var{id}@dots{} ]
3142 @item info connections
3143 Print a list of all open target connections currently being managed by
3144 @value{GDBN}. By default all connections are printed, but the
3145 argument @var{id}@dots{} -- a space separated list of connections
3146 numbers -- can be used to limit the display to just the requested
3149 @value{GDBN} displays for each connection (in this order):
3153 the connection number assigned by @value{GDBN}.
3156 the protocol used by the connection.
3159 a textual description of the protocol used by the connection.
3164 An asterisk @samp{*} preceding the connection number indicates the
3165 connection of the current inferior.
3169 @c end table here to get a little more width for example
3172 (@value{GDBP}) info connections
3173 Num What Description
3174 * 1 extended-remote host:10000 Extended remote serial target in gdb-specific protocol
3175 2 native Native process
3176 3 core Local core dump file
3179 To switch focus between inferiors, use the @code{inferior} command:
3182 @kindex inferior @var{infno}
3183 @item inferior @var{infno}
3184 Make inferior number @var{infno} the current inferior. The argument
3185 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
3186 in the first field of the @samp{info inferiors} display.
3189 @vindex $_inferior@r{, convenience variable}
3190 The debugger convenience variable @samp{$_inferior} contains the
3191 number of the current inferior. You may find this useful in writing
3192 breakpoint conditional expressions, command scripts, and so forth.
3193 @xref{Convenience Vars,, Convenience Variables}, for general
3194 information on convenience variables.
3196 You can get multiple executables into a debugging session via the
3197 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
3198 systems @value{GDBN} can add inferiors to the debug session
3199 automatically by following calls to @code{fork} and @code{exec}. To
3200 remove inferiors from the debugging session use the
3201 @w{@code{remove-inferiors}} command.
3204 @kindex add-inferior
3205 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ] [-no-connection ]
3206 Adds @var{n} inferiors to be run using @var{executable} as the
3207 executable; @var{n} defaults to 1. If no executable is specified,
3208 the inferiors begins empty, with no program. You can still assign or
3209 change the program assigned to the inferior at any time by using the
3210 @code{file} command with the executable name as its argument.
3212 By default, the new inferior begins connected to the same target
3213 connection as the current inferior. For example, if the current
3214 inferior was connected to @code{gdbserver} with @code{target remote},
3215 then the new inferior will be connected to the same @code{gdbserver}
3216 instance. The @samp{-no-connection} option starts the new inferior
3217 with no connection yet. You can then for example use the @code{target
3218 remote} command to connect to some other @code{gdbserver} instance,
3219 use @code{run} to spawn a local program, etc.
3221 @kindex clone-inferior
3222 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
3223 Adds @var{n} inferiors ready to execute the same program as inferior
3224 @var{infno}; @var{n} defaults to 1, and @var{infno} defaults to the
3225 number of the current inferior. This is a convenient command when you
3226 want to run another instance of the inferior you are debugging.
3229 (@value{GDBP}) info inferiors
3230 Num Description Connection Executable
3231 * 1 process 29964 1 (native) helloworld
3232 (@value{GDBP}) clone-inferior
3235 (@value{GDBP}) info inferiors
3236 Num Description Connection Executable
3237 * 1 process 29964 1 (native) helloworld
3238 2 <null> 1 (native) helloworld
3241 You can now simply switch focus to inferior 2 and run it.
3243 @kindex remove-inferiors
3244 @item remove-inferiors @var{infno}@dots{}
3245 Removes the inferior or inferiors @var{infno}@dots{}. It is not
3246 possible to remove an inferior that is running with this command. For
3247 those, use the @code{kill} or @code{detach} command first.
3251 To quit debugging one of the running inferiors that is not the current
3252 inferior, you can either detach from it by using the @w{@code{detach
3253 inferior}} command (allowing it to run independently), or kill it
3254 using the @w{@code{kill inferiors}} command:
3257 @kindex detach inferiors @var{infno}@dots{}
3258 @item detach inferior @var{infno}@dots{}
3259 Detach from the inferior or inferiors identified by @value{GDBN}
3260 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
3261 still stays on the list of inferiors shown by @code{info inferiors},
3262 but its Description will show @samp{<null>}.
3264 @kindex kill inferiors @var{infno}@dots{}
3265 @item kill inferiors @var{infno}@dots{}
3266 Kill the inferior or inferiors identified by @value{GDBN} inferior
3267 number(s) @var{infno}@dots{}. Note that the inferior's entry still
3268 stays on the list of inferiors shown by @code{info inferiors}, but its
3269 Description will show @samp{<null>}.
3272 After the successful completion of a command such as @code{detach},
3273 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
3274 a normal process exit, the inferior is still valid and listed with
3275 @code{info inferiors}, ready to be restarted.
3278 To be notified when inferiors are started or exit under @value{GDBN}'s
3279 control use @w{@code{set print inferior-events}}:
3282 @kindex set print inferior-events
3283 @cindex print messages on inferior start and exit
3284 @item set print inferior-events
3285 @itemx set print inferior-events on
3286 @itemx set print inferior-events off
3287 The @code{set print inferior-events} command allows you to enable or
3288 disable printing of messages when @value{GDBN} notices that new
3289 inferiors have started or that inferiors have exited or have been
3290 detached. By default, these messages will not be printed.
3292 @kindex show print inferior-events
3293 @item show print inferior-events
3294 Show whether messages will be printed when @value{GDBN} detects that
3295 inferiors have started, exited or have been detached.
3298 Many commands will work the same with multiple programs as with a
3299 single program: e.g., @code{print myglobal} will simply display the
3300 value of @code{myglobal} in the current inferior.
3303 Occasionally, when debugging @value{GDBN} itself, it may be useful to
3304 get more info about the relationship of inferiors, programs, address
3305 spaces in a debug session. You can do that with the @w{@code{maint
3306 info program-spaces}} command.
3309 @kindex maint info program-spaces
3310 @item maint info program-spaces
3311 Print a list of all program spaces currently being managed by
3314 @value{GDBN} displays for each program space (in this order):
3318 the program space number assigned by @value{GDBN}
3321 the name of the executable loaded into the program space, with e.g.,
3322 the @code{file} command.
3327 An asterisk @samp{*} preceding the @value{GDBN} program space number
3328 indicates the current program space.
3330 In addition, below each program space line, @value{GDBN} prints extra
3331 information that isn't suitable to display in tabular form. For
3332 example, the list of inferiors bound to the program space.
3335 (@value{GDBP}) maint info program-spaces
3339 Bound inferiors: ID 1 (process 21561)
3342 Here we can see that no inferior is running the program @code{hello},
3343 while @code{process 21561} is running the program @code{goodbye}. On
3344 some targets, it is possible that multiple inferiors are bound to the
3345 same program space. The most common example is that of debugging both
3346 the parent and child processes of a @code{vfork} call. For example,
3349 (@value{GDBP}) maint info program-spaces
3352 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
3355 Here, both inferior 2 and inferior 1 are running in the same program
3356 space as a result of inferior 1 having executed a @code{vfork} call.
3360 @section Debugging Programs with Multiple Threads
3362 @cindex threads of execution
3363 @cindex multiple threads
3364 @cindex switching threads
3365 In some operating systems, such as GNU/Linux and Solaris, a single program
3366 may have more than one @dfn{thread} of execution. The precise semantics
3367 of threads differ from one operating system to another, but in general
3368 the threads of a single program are akin to multiple processes---except
3369 that they share one address space (that is, they can all examine and
3370 modify the same variables). On the other hand, each thread has its own
3371 registers and execution stack, and perhaps private memory.
3373 @value{GDBN} provides these facilities for debugging multi-thread
3377 @item automatic notification of new threads
3378 @item @samp{thread @var{thread-id}}, a command to switch among threads
3379 @item @samp{info threads}, a command to inquire about existing threads
3380 @item @samp{thread apply [@var{thread-id-list} | all] @var{args}},
3381 a command to apply a command to a list of threads
3382 @item thread-specific breakpoints
3383 @item @samp{set print thread-events}, which controls printing of
3384 messages on thread start and exit.
3385 @item @samp{set libthread-db-search-path @var{path}}, which lets
3386 the user specify which @code{libthread_db} to use if the default choice
3387 isn't compatible with the program.
3390 @cindex focus of debugging
3391 @cindex current thread
3392 The @value{GDBN} thread debugging facility allows you to observe all
3393 threads while your program runs---but whenever @value{GDBN} takes
3394 control, one thread in particular is always the focus of debugging.
3395 This thread is called the @dfn{current thread}. Debugging commands show
3396 program information from the perspective of the current thread.
3398 @cindex @code{New} @var{systag} message
3399 @cindex thread identifier (system)
3400 @c FIXME-implementors!! It would be more helpful if the [New...] message
3401 @c included GDB's numeric thread handle, so you could just go to that
3402 @c thread without first checking `info threads'.
3403 Whenever @value{GDBN} detects a new thread in your program, it displays
3404 the target system's identification for the thread with a message in the
3405 form @samp{[New @var{systag}]}, where @var{systag} is a thread identifier
3406 whose form varies depending on the particular system. For example, on
3407 @sc{gnu}/Linux, you might see
3410 [New Thread 0x41e02940 (LWP 25582)]
3414 when @value{GDBN} notices a new thread. In contrast, on other systems,
3415 the @var{systag} is simply something like @samp{process 368}, with no
3418 @c FIXME!! (1) Does the [New...] message appear even for the very first
3419 @c thread of a program, or does it only appear for the
3420 @c second---i.e.@: when it becomes obvious we have a multithread
3422 @c (2) *Is* there necessarily a first thread always? Or do some
3423 @c multithread systems permit starting a program with multiple
3424 @c threads ab initio?
3426 @anchor{thread numbers}
3427 @cindex thread number, per inferior
3428 @cindex thread identifier (GDB)
3429 For debugging purposes, @value{GDBN} associates its own thread number
3430 ---always a single integer---with each thread of an inferior. This
3431 number is unique between all threads of an inferior, but not unique
3432 between threads of different inferiors.
3434 @cindex qualified thread ID
3435 You can refer to a given thread in an inferior using the qualified
3436 @var{inferior-num}.@var{thread-num} syntax, also known as
3437 @dfn{qualified thread ID}, with @var{inferior-num} being the inferior
3438 number and @var{thread-num} being the thread number of the given
3439 inferior. For example, thread @code{2.3} refers to thread number 3 of
3440 inferior 2. If you omit @var{inferior-num} (e.g., @code{thread 3}),
3441 then @value{GDBN} infers you're referring to a thread of the current
3444 Until you create a second inferior, @value{GDBN} does not show the
3445 @var{inferior-num} part of thread IDs, even though you can always use
3446 the full @var{inferior-num}.@var{thread-num} form to refer to threads
3447 of inferior 1, the initial inferior.
3449 @anchor{thread ID lists}
3450 @cindex thread ID lists
3451 Some commands accept a space-separated @dfn{thread ID list} as
3452 argument. A list element can be:
3456 A thread ID as shown in the first field of the @samp{info threads}
3457 display, with or without an inferior qualifier. E.g., @samp{2.1} or
3461 A range of thread numbers, again with or without an inferior
3462 qualifier, as in @var{inf}.@var{thr1}-@var{thr2} or
3463 @var{thr1}-@var{thr2}. E.g., @samp{1.2-4} or @samp{2-4}.
3466 All threads of an inferior, specified with a star wildcard, with or
3467 without an inferior qualifier, as in @var{inf}.@code{*} (e.g.,
3468 @samp{1.*}) or @code{*}. The former refers to all threads of the
3469 given inferior, and the latter form without an inferior qualifier
3470 refers to all threads of the current inferior.
3474 For example, if the current inferior is 1, and inferior 7 has one
3475 thread with ID 7.1, the thread list @samp{1 2-3 4.5 6.7-9 7.*}
3476 includes threads 1 to 3 of inferior 1, thread 5 of inferior 4, threads
3477 7 to 9 of inferior 6 and all threads of inferior 7. That is, in
3478 expanded qualified form, the same as @samp{1.1 1.2 1.3 4.5 6.7 6.8 6.9
3482 @anchor{global thread numbers}
3483 @cindex global thread number
3484 @cindex global thread identifier (GDB)
3485 In addition to a @emph{per-inferior} number, each thread is also
3486 assigned a unique @emph{global} number, also known as @dfn{global
3487 thread ID}, a single integer. Unlike the thread number component of
3488 the thread ID, no two threads have the same global ID, even when
3489 you're debugging multiple inferiors.
3491 From @value{GDBN}'s perspective, a process always has at least one
3492 thread. In other words, @value{GDBN} assigns a thread number to the
3493 program's ``main thread'' even if the program is not multi-threaded.
3495 @vindex $_thread@r{, convenience variable}
3496 @vindex $_gthread@r{, convenience variable}
3497 The debugger convenience variables @samp{$_thread} and
3498 @samp{$_gthread} contain, respectively, the per-inferior thread number
3499 and the global thread number of the current thread. You may find this
3500 useful in writing breakpoint conditional expressions, command scripts,
3501 and so forth. @xref{Convenience Vars,, Convenience Variables}, for
3502 general information on convenience variables.
3504 If @value{GDBN} detects the program is multi-threaded, it augments the
3505 usual message about stopping at a breakpoint with the ID and name of
3506 the thread that hit the breakpoint.
3509 Thread 2 "client" hit Breakpoint 1, send_message () at client.c:68
3512 Likewise when the program receives a signal:
3515 Thread 1 "main" received signal SIGINT, Interrupt.
3519 @kindex info threads
3520 @item info threads @r{[}@var{thread-id-list}@r{]}
3522 Display information about one or more threads. With no arguments
3523 displays information about all threads. You can specify the list of
3524 threads that you want to display using the thread ID list syntax
3525 (@pxref{thread ID lists}).
3527 @value{GDBN} displays for each thread (in this order):
3531 the per-inferior thread number assigned by @value{GDBN}
3534 the global thread number assigned by @value{GDBN}, if the @samp{-gid}
3535 option was specified
3538 the target system's thread identifier (@var{systag})
3541 the thread's name, if one is known. A thread can either be named by
3542 the user (see @code{thread name}, below), or, in some cases, by the
3546 the current stack frame summary for that thread
3550 An asterisk @samp{*} to the left of the @value{GDBN} thread number
3551 indicates the current thread.
3555 @c end table here to get a little more width for example
3558 (@value{GDBP}) info threads
3560 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3561 2 process 35 thread 23 0x34e5 in sigpause ()
3562 3 process 35 thread 27 0x34e5 in sigpause ()
3566 If you're debugging multiple inferiors, @value{GDBN} displays thread
3567 IDs using the qualified @var{inferior-num}.@var{thread-num} format.
3568 Otherwise, only @var{thread-num} is shown.
3570 If you specify the @samp{-gid} option, @value{GDBN} displays a column
3571 indicating each thread's global thread ID:
3574 (@value{GDBP}) info threads
3575 Id GId Target Id Frame
3576 1.1 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3577 1.2 3 process 35 thread 23 0x34e5 in sigpause ()
3578 1.3 4 process 35 thread 27 0x34e5 in sigpause ()
3579 * 2.1 2 process 65 thread 1 main (argc=1, argv=0x7ffffff8)
3582 On Solaris, you can display more information about user threads with a
3583 Solaris-specific command:
3586 @item maint info sol-threads
3587 @kindex maint info sol-threads
3588 @cindex thread info (Solaris)
3589 Display info on Solaris user threads.
3593 @kindex thread @var{thread-id}
3594 @item thread @var{thread-id}
3595 Make thread ID @var{thread-id} the current thread. The command
3596 argument @var{thread-id} is the @value{GDBN} thread ID, as shown in
3597 the first field of the @samp{info threads} display, with or without an
3598 inferior qualifier (e.g., @samp{2.1} or @samp{1}).
3600 @value{GDBN} responds by displaying the system identifier of the
3601 thread you selected, and its current stack frame summary:
3604 (@value{GDBP}) thread 2
3605 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
3606 #0 some_function (ignore=0x0) at example.c:8
3607 8 printf ("hello\n");
3611 As with the @samp{[New @dots{}]} message, the form of the text after
3612 @samp{Switching to} depends on your system's conventions for identifying
3615 @anchor{thread apply all}
3616 @kindex thread apply
3617 @cindex apply command to several threads
3618 @item thread apply [@var{thread-id-list} | all [-ascending]] [@var{flag}]@dots{} @var{command}
3619 The @code{thread apply} command allows you to apply the named
3620 @var{command} to one or more threads. Specify the threads that you
3621 want affected using the thread ID list syntax (@pxref{thread ID
3622 lists}), or specify @code{all} to apply to all threads. To apply a
3623 command to all threads in descending order, type @kbd{thread apply all
3624 @var{command}}. To apply a command to all threads in ascending order,
3625 type @kbd{thread apply all -ascending @var{command}}.
3627 The @var{flag} arguments control what output to produce and how to handle
3628 errors raised when applying @var{command} to a thread. @var{flag}
3629 must start with a @code{-} directly followed by one letter in
3630 @code{qcs}. If several flags are provided, they must be given
3631 individually, such as @code{-c -q}.
3633 By default, @value{GDBN} displays some thread information before the
3634 output produced by @var{command}, and an error raised during the
3635 execution of a @var{command} will abort @code{thread apply}. The
3636 following flags can be used to fine-tune this behavior:
3640 The flag @code{-c}, which stands for @samp{continue}, causes any
3641 errors in @var{command} to be displayed, and the execution of
3642 @code{thread apply} then continues.
3644 The flag @code{-s}, which stands for @samp{silent}, causes any errors
3645 or empty output produced by a @var{command} to be silently ignored.
3646 That is, the execution continues, but the thread information and errors
3649 The flag @code{-q} (@samp{quiet}) disables printing the thread
3653 Flags @code{-c} and @code{-s} cannot be used together.
3656 @cindex apply command to all threads (ignoring errors and empty output)
3657 @item taas [@var{option}]@dots{} @var{command}
3658 Shortcut for @code{thread apply all -s [@var{option}]@dots{} @var{command}}.
3659 Applies @var{command} on all threads, ignoring errors and empty output.
3661 The @code{taas} command accepts the same options as the @code{thread
3662 apply all} command. @xref{thread apply all}.
3665 @cindex apply a command to all frames of all threads (ignoring errors and empty output)
3666 @item tfaas [@var{option}]@dots{} @var{command}
3667 Shortcut for @code{thread apply all -s -- frame apply all -s [@var{option}]@dots{} @var{command}}.
3668 Applies @var{command} on all frames of all threads, ignoring errors
3669 and empty output. Note that the flag @code{-s} is specified twice:
3670 The first @code{-s} ensures that @code{thread apply} only shows the thread
3671 information of the threads for which @code{frame apply} produces
3672 some output. The second @code{-s} is needed to ensure that @code{frame
3673 apply} shows the frame information of a frame only if the
3674 @var{command} successfully produced some output.
3676 It can for example be used to print a local variable or a function
3677 argument without knowing the thread or frame where this variable or argument
3680 (@value{GDBP}) tfaas p some_local_var_i_do_not_remember_where_it_is
3683 The @code{tfaas} command accepts the same options as the @code{frame
3684 apply} command. @xref{Frame Apply,,frame apply}.
3687 @cindex name a thread
3688 @item thread name [@var{name}]
3689 This command assigns a name to the current thread. If no argument is
3690 given, any existing user-specified name is removed. The thread name
3691 appears in the @samp{info threads} display.
3693 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
3694 determine the name of the thread as given by the OS. On these
3695 systems, a name specified with @samp{thread name} will override the
3696 system-give name, and removing the user-specified name will cause
3697 @value{GDBN} to once again display the system-specified name.
3700 @cindex search for a thread
3701 @item thread find [@var{regexp}]
3702 Search for and display thread ids whose name or @var{systag}
3703 matches the supplied regular expression.
3705 As well as being the complement to the @samp{thread name} command,
3706 this command also allows you to identify a thread by its target
3707 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
3711 (@value{GDBN}) thread find 26688
3712 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
3713 (@value{GDBN}) info thread 4
3715 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
3718 @kindex set print thread-events
3719 @cindex print messages on thread start and exit
3720 @item set print thread-events
3721 @itemx set print thread-events on
3722 @itemx set print thread-events off
3723 The @code{set print thread-events} command allows you to enable or
3724 disable printing of messages when @value{GDBN} notices that new threads have
3725 started or that threads have exited. By default, these messages will
3726 be printed if detection of these events is supported by the target.
3727 Note that these messages cannot be disabled on all targets.
3729 @kindex show print thread-events
3730 @item show print thread-events
3731 Show whether messages will be printed when @value{GDBN} detects that threads
3732 have started and exited.
3735 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
3736 more information about how @value{GDBN} behaves when you stop and start
3737 programs with multiple threads.
3739 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
3740 watchpoints in programs with multiple threads.
3742 @anchor{set libthread-db-search-path}
3744 @kindex set libthread-db-search-path
3745 @cindex search path for @code{libthread_db}
3746 @item set libthread-db-search-path @r{[}@var{path}@r{]}
3747 If this variable is set, @var{path} is a colon-separated list of
3748 directories @value{GDBN} will use to search for @code{libthread_db}.
3749 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
3750 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
3751 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
3754 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
3755 @code{libthread_db} library to obtain information about threads in the
3756 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
3757 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
3758 specific thread debugging library loading is enabled
3759 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
3761 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
3762 refers to the default system directories that are
3763 normally searched for loading shared libraries. The @samp{$sdir} entry
3764 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
3765 (@pxref{libthread_db.so.1 file}).
3767 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
3768 refers to the directory from which @code{libpthread}
3769 was loaded in the inferior process.
3771 For any @code{libthread_db} library @value{GDBN} finds in above directories,
3772 @value{GDBN} attempts to initialize it with the current inferior process.
3773 If this initialization fails (which could happen because of a version
3774 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
3775 will unload @code{libthread_db}, and continue with the next directory.
3776 If none of @code{libthread_db} libraries initialize successfully,
3777 @value{GDBN} will issue a warning and thread debugging will be disabled.
3779 Setting @code{libthread-db-search-path} is currently implemented
3780 only on some platforms.
3782 @kindex show libthread-db-search-path
3783 @item show libthread-db-search-path
3784 Display current libthread_db search path.
3786 @kindex set debug libthread-db
3787 @kindex show debug libthread-db
3788 @cindex debugging @code{libthread_db}
3789 @item set debug libthread-db
3790 @itemx show debug libthread-db
3791 Turns on or off display of @code{libthread_db}-related events.
3792 Use @code{1} to enable, @code{0} to disable.
3796 @section Debugging Forks
3798 @cindex fork, debugging programs which call
3799 @cindex multiple processes
3800 @cindex processes, multiple
3801 On most systems, @value{GDBN} has no special support for debugging
3802 programs which create additional processes using the @code{fork}
3803 function. When a program forks, @value{GDBN} will continue to debug the
3804 parent process and the child process will run unimpeded. If you have
3805 set a breakpoint in any code which the child then executes, the child
3806 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3807 will cause it to terminate.
3809 However, if you want to debug the child process there is a workaround
3810 which isn't too painful. Put a call to @code{sleep} in the code which
3811 the child process executes after the fork. It may be useful to sleep
3812 only if a certain environment variable is set, or a certain file exists,
3813 so that the delay need not occur when you don't want to run @value{GDBN}
3814 on the child. While the child is sleeping, use the @code{ps} program to
3815 get its process ID. Then tell @value{GDBN} (a new invocation of
3816 @value{GDBN} if you are also debugging the parent process) to attach to
3817 the child process (@pxref{Attach}). From that point on you can debug
3818 the child process just like any other process which you attached to.
3820 On some systems, @value{GDBN} provides support for debugging programs
3821 that create additional processes using the @code{fork} or @code{vfork}
3822 functions. On @sc{gnu}/Linux platforms, this feature is supported
3823 with kernel version 2.5.46 and later.
3825 The fork debugging commands are supported in native mode and when
3826 connected to @code{gdbserver} in either @code{target remote} mode or
3827 @code{target extended-remote} mode.
3829 By default, when a program forks, @value{GDBN} will continue to debug
3830 the parent process and the child process will run unimpeded.
3832 If you want to follow the child process instead of the parent process,
3833 use the command @w{@code{set follow-fork-mode}}.
3836 @kindex set follow-fork-mode
3837 @item set follow-fork-mode @var{mode}
3838 Set the debugger response to a program call of @code{fork} or
3839 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3840 process. The @var{mode} argument can be:
3844 The original process is debugged after a fork. The child process runs
3845 unimpeded. This is the default.
3848 The new process is debugged after a fork. The parent process runs
3853 @kindex show follow-fork-mode
3854 @item show follow-fork-mode
3855 Display the current debugger response to a @code{fork} or @code{vfork} call.
3858 @cindex debugging multiple processes
3859 On Linux, if you want to debug both the parent and child processes, use the
3860 command @w{@code{set detach-on-fork}}.
3863 @kindex set detach-on-fork
3864 @item set detach-on-fork @var{mode}
3865 Tells gdb whether to detach one of the processes after a fork, or
3866 retain debugger control over them both.
3870 The child process (or parent process, depending on the value of
3871 @code{follow-fork-mode}) will be detached and allowed to run
3872 independently. This is the default.
3875 Both processes will be held under the control of @value{GDBN}.
3876 One process (child or parent, depending on the value of
3877 @code{follow-fork-mode}) is debugged as usual, while the other
3882 @kindex show detach-on-fork
3883 @item show detach-on-fork
3884 Show whether detach-on-fork mode is on/off.
3887 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3888 will retain control of all forked processes (including nested forks).
3889 You can list the forked processes under the control of @value{GDBN} by
3890 using the @w{@code{info inferiors}} command, and switch from one fork
3891 to another by using the @code{inferior} command (@pxref{Inferiors Connections and
3892 Programs, ,Debugging Multiple Inferiors Connections and Programs}).
3894 To quit debugging one of the forked processes, you can either detach
3895 from it by using the @w{@code{detach inferiors}} command (allowing it
3896 to run independently), or kill it using the @w{@code{kill inferiors}}
3897 command. @xref{Inferiors Connections and Programs, ,Debugging
3898 Multiple Inferiors Connections and Programs}.
3900 If you ask to debug a child process and a @code{vfork} is followed by an
3901 @code{exec}, @value{GDBN} executes the new target up to the first
3902 breakpoint in the new target. If you have a breakpoint set on
3903 @code{main} in your original program, the breakpoint will also be set on
3904 the child process's @code{main}.
3906 On some systems, when a child process is spawned by @code{vfork}, you
3907 cannot debug the child or parent until an @code{exec} call completes.
3909 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3910 call executes, the new target restarts. To restart the parent
3911 process, use the @code{file} command with the parent executable name
3912 as its argument. By default, after an @code{exec} call executes,
3913 @value{GDBN} discards the symbols of the previous executable image.
3914 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3918 @kindex set follow-exec-mode
3919 @item set follow-exec-mode @var{mode}
3921 Set debugger response to a program call of @code{exec}. An
3922 @code{exec} call replaces the program image of a process.
3924 @code{follow-exec-mode} can be:
3928 @value{GDBN} creates a new inferior and rebinds the process to this
3929 new inferior. The program the process was running before the
3930 @code{exec} call can be restarted afterwards by restarting the
3936 (@value{GDBP}) info inferiors
3938 Id Description Executable
3941 process 12020 is executing new program: prog2
3942 Program exited normally.
3943 (@value{GDBP}) info inferiors
3944 Id Description Executable
3950 @value{GDBN} keeps the process bound to the same inferior. The new
3951 executable image replaces the previous executable loaded in the
3952 inferior. Restarting the inferior after the @code{exec} call, with
3953 e.g., the @code{run} command, restarts the executable the process was
3954 running after the @code{exec} call. This is the default mode.
3959 (@value{GDBP}) info inferiors
3960 Id Description Executable
3963 process 12020 is executing new program: prog2
3964 Program exited normally.
3965 (@value{GDBP}) info inferiors
3966 Id Description Executable
3973 @code{follow-exec-mode} is supported in native mode and
3974 @code{target extended-remote} mode.
3976 You can use the @code{catch} command to make @value{GDBN} stop whenever
3977 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3978 Catchpoints, ,Setting Catchpoints}.
3980 @node Checkpoint/Restart
3981 @section Setting a @emph{Bookmark} to Return to Later
3986 @cindex snapshot of a process
3987 @cindex rewind program state
3989 On certain operating systems@footnote{Currently, only
3990 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3991 program's state, called a @dfn{checkpoint}, and come back to it
3994 Returning to a checkpoint effectively undoes everything that has
3995 happened in the program since the @code{checkpoint} was saved. This
3996 includes changes in memory, registers, and even (within some limits)
3997 system state. Effectively, it is like going back in time to the
3998 moment when the checkpoint was saved.
4000 Thus, if you're stepping thru a program and you think you're
4001 getting close to the point where things go wrong, you can save
4002 a checkpoint. Then, if you accidentally go too far and miss
4003 the critical statement, instead of having to restart your program
4004 from the beginning, you can just go back to the checkpoint and
4005 start again from there.
4007 This can be especially useful if it takes a lot of time or
4008 steps to reach the point where you think the bug occurs.
4010 To use the @code{checkpoint}/@code{restart} method of debugging:
4015 Save a snapshot of the debugged program's current execution state.
4016 The @code{checkpoint} command takes no arguments, but each checkpoint
4017 is assigned a small integer id, similar to a breakpoint id.
4019 @kindex info checkpoints
4020 @item info checkpoints
4021 List the checkpoints that have been saved in the current debugging
4022 session. For each checkpoint, the following information will be
4029 @item Source line, or label
4032 @kindex restart @var{checkpoint-id}
4033 @item restart @var{checkpoint-id}
4034 Restore the program state that was saved as checkpoint number
4035 @var{checkpoint-id}. All program variables, registers, stack frames
4036 etc.@: will be returned to the values that they had when the checkpoint
4037 was saved. In essence, gdb will ``wind back the clock'' to the point
4038 in time when the checkpoint was saved.
4040 Note that breakpoints, @value{GDBN} variables, command history etc.
4041 are not affected by restoring a checkpoint. In general, a checkpoint
4042 only restores things that reside in the program being debugged, not in
4045 @kindex delete checkpoint @var{checkpoint-id}
4046 @item delete checkpoint @var{checkpoint-id}
4047 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
4051 Returning to a previously saved checkpoint will restore the user state
4052 of the program being debugged, plus a significant subset of the system
4053 (OS) state, including file pointers. It won't ``un-write'' data from
4054 a file, but it will rewind the file pointer to the previous location,
4055 so that the previously written data can be overwritten. For files
4056 opened in read mode, the pointer will also be restored so that the
4057 previously read data can be read again.
4059 Of course, characters that have been sent to a printer (or other
4060 external device) cannot be ``snatched back'', and characters received
4061 from eg.@: a serial device can be removed from internal program buffers,
4062 but they cannot be ``pushed back'' into the serial pipeline, ready to
4063 be received again. Similarly, the actual contents of files that have
4064 been changed cannot be restored (at this time).
4066 However, within those constraints, you actually can ``rewind'' your
4067 program to a previously saved point in time, and begin debugging it
4068 again --- and you can change the course of events so as to debug a
4069 different execution path this time.
4071 @cindex checkpoints and process id
4072 Finally, there is one bit of internal program state that will be
4073 different when you return to a checkpoint --- the program's process
4074 id. Each checkpoint will have a unique process id (or @var{pid}),
4075 and each will be different from the program's original @var{pid}.
4076 If your program has saved a local copy of its process id, this could
4077 potentially pose a problem.
4079 @subsection A Non-obvious Benefit of Using Checkpoints
4081 On some systems such as @sc{gnu}/Linux, address space randomization
4082 is performed on new processes for security reasons. This makes it
4083 difficult or impossible to set a breakpoint, or watchpoint, on an
4084 absolute address if you have to restart the program, since the
4085 absolute location of a symbol will change from one execution to the
4088 A checkpoint, however, is an @emph{identical} copy of a process.
4089 Therefore if you create a checkpoint at (eg.@:) the start of main,
4090 and simply return to that checkpoint instead of restarting the
4091 process, you can avoid the effects of address randomization and
4092 your symbols will all stay in the same place.
4095 @chapter Stopping and Continuing
4097 The principal purposes of using a debugger are so that you can stop your
4098 program before it terminates; or so that, if your program runs into
4099 trouble, you can investigate and find out why.
4101 Inside @value{GDBN}, your program may stop for any of several reasons,
4102 such as a signal, a breakpoint, or reaching a new line after a
4103 @value{GDBN} command such as @code{step}. You may then examine and
4104 change variables, set new breakpoints or remove old ones, and then
4105 continue execution. Usually, the messages shown by @value{GDBN} provide
4106 ample explanation of the status of your program---but you can also
4107 explicitly request this information at any time.
4110 @kindex info program
4112 Display information about the status of your program: whether it is
4113 running or not, what process it is, and why it stopped.
4117 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
4118 * Continuing and Stepping:: Resuming execution
4119 * Skipping Over Functions and Files::
4120 Skipping over functions and files
4122 * Thread Stops:: Stopping and starting multi-thread programs
4126 @section Breakpoints, Watchpoints, and Catchpoints
4129 A @dfn{breakpoint} makes your program stop whenever a certain point in
4130 the program is reached. For each breakpoint, you can add conditions to
4131 control in finer detail whether your program stops. You can set
4132 breakpoints with the @code{break} command and its variants (@pxref{Set
4133 Breaks, ,Setting Breakpoints}), to specify the place where your program
4134 should stop by line number, function name or exact address in the
4137 On some systems, you can set breakpoints in shared libraries before
4138 the executable is run.
4141 @cindex data breakpoints
4142 @cindex memory tracing
4143 @cindex breakpoint on memory address
4144 @cindex breakpoint on variable modification
4145 A @dfn{watchpoint} is a special breakpoint that stops your program
4146 when the value of an expression changes. The expression may be a value
4147 of a variable, or it could involve values of one or more variables
4148 combined by operators, such as @samp{a + b}. This is sometimes called
4149 @dfn{data breakpoints}. You must use a different command to set
4150 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
4151 from that, you can manage a watchpoint like any other breakpoint: you
4152 enable, disable, and delete both breakpoints and watchpoints using the
4155 You can arrange to have values from your program displayed automatically
4156 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
4160 @cindex breakpoint on events
4161 A @dfn{catchpoint} is another special breakpoint that stops your program
4162 when a certain kind of event occurs, such as the throwing of a C@t{++}
4163 exception or the loading of a library. As with watchpoints, you use a
4164 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
4165 Catchpoints}), but aside from that, you can manage a catchpoint like any
4166 other breakpoint. (To stop when your program receives a signal, use the
4167 @code{handle} command; see @ref{Signals, ,Signals}.)
4169 @cindex breakpoint numbers
4170 @cindex numbers for breakpoints
4171 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
4172 catchpoint when you create it; these numbers are successive integers
4173 starting with one. In many of the commands for controlling various
4174 features of breakpoints you use the breakpoint number to say which
4175 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
4176 @dfn{disabled}; if disabled, it has no effect on your program until you
4179 @cindex breakpoint ranges
4180 @cindex breakpoint lists
4181 @cindex ranges of breakpoints
4182 @cindex lists of breakpoints
4183 Some @value{GDBN} commands accept a space-separated list of breakpoints
4184 on which to operate. A list element can be either a single breakpoint number,
4185 like @samp{5}, or a range of such numbers, like @samp{5-7}.
4186 When a breakpoint list is given to a command, all breakpoints in that list
4190 * Set Breaks:: Setting breakpoints
4191 * Set Watchpoints:: Setting watchpoints
4192 * Set Catchpoints:: Setting catchpoints
4193 * Delete Breaks:: Deleting breakpoints
4194 * Disabling:: Disabling breakpoints
4195 * Conditions:: Break conditions
4196 * Break Commands:: Breakpoint command lists
4197 * Dynamic Printf:: Dynamic printf
4198 * Save Breakpoints:: How to save breakpoints in a file
4199 * Static Probe Points:: Listing static probe points
4200 * Error in Breakpoints:: ``Cannot insert breakpoints''
4201 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
4205 @subsection Setting Breakpoints
4207 @c FIXME LMB what does GDB do if no code on line of breakpt?
4208 @c consider in particular declaration with/without initialization.
4210 @c FIXME 2 is there stuff on this already? break at fun start, already init?
4213 @kindex b @r{(@code{break})}
4214 @vindex $bpnum@r{, convenience variable}
4215 @cindex latest breakpoint
4216 Breakpoints are set with the @code{break} command (abbreviated
4217 @code{b}). The debugger convenience variable @samp{$bpnum} records the
4218 number of the breakpoint you've set most recently; see @ref{Convenience
4219 Vars,, Convenience Variables}, for a discussion of what you can do with
4220 convenience variables.
4223 @item break @var{location}
4224 Set a breakpoint at the given @var{location}, which can specify a
4225 function name, a line number, or an address of an instruction.
4226 (@xref{Specify Location}, for a list of all the possible ways to
4227 specify a @var{location}.) The breakpoint will stop your program just
4228 before it executes any of the code in the specified @var{location}.
4230 When using source languages that permit overloading of symbols, such as
4231 C@t{++}, a function name may refer to more than one possible place to break.
4232 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
4235 It is also possible to insert a breakpoint that will stop the program
4236 only if a specific thread (@pxref{Thread-Specific Breakpoints})
4237 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
4240 When called without any arguments, @code{break} sets a breakpoint at
4241 the next instruction to be executed in the selected stack frame
4242 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
4243 innermost, this makes your program stop as soon as control
4244 returns to that frame. This is similar to the effect of a
4245 @code{finish} command in the frame inside the selected frame---except
4246 that @code{finish} does not leave an active breakpoint. If you use
4247 @code{break} without an argument in the innermost frame, @value{GDBN} stops
4248 the next time it reaches the current location; this may be useful
4251 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
4252 least one instruction has been executed. If it did not do this, you
4253 would be unable to proceed past a breakpoint without first disabling the
4254 breakpoint. This rule applies whether or not the breakpoint already
4255 existed when your program stopped.
4257 @item break @dots{} if @var{cond}
4258 Set a breakpoint with condition @var{cond}; evaluate the expression
4259 @var{cond} each time the breakpoint is reached, and stop only if the
4260 value is nonzero---that is, if @var{cond} evaluates as true.
4261 @samp{@dots{}} stands for one of the possible arguments described
4262 above (or no argument) specifying where to break. @xref{Conditions,
4263 ,Break Conditions}, for more information on breakpoint conditions.
4265 The breakpoint may be mapped to multiple locations. If the breakpoint
4266 condition @var{cond} is invalid at some but not all of the locations,
4267 the locations for which the condition is invalid are disabled. For
4268 example, @value{GDBN} reports below that two of the three locations
4272 (@value{GDBP}) break func if a == 10
4273 warning: failed to validate condition at location 0x11ce, disabling:
4274 No symbol "a" in current context.
4275 warning: failed to validate condition at location 0x11b6, disabling:
4276 No symbol "a" in current context.
4277 Breakpoint 1 at 0x11b6: func. (3 locations)
4280 Locations that are disabled because of the condition are denoted by an
4281 uppercase @code{N} in the output of the @code{info breakpoints}
4285 (@value{GDBP}) info breakpoints
4286 Num Type Disp Enb Address What
4287 1 breakpoint keep y <MULTIPLE>
4288 stop only if a == 10
4289 1.1 N* 0x00000000000011b6 in ...
4290 1.2 y 0x00000000000011c2 in ...
4291 1.3 N* 0x00000000000011ce in ...
4292 (*): Breakpoint condition is invalid at this location.
4295 If the breakpoint condition @var{cond} is invalid in the context of
4296 @emph{all} the locations of the breakpoint, @value{GDBN} refuses to
4297 define the breakpoint. For example, if variable @code{foo} is an
4301 (@value{GDBP}) break func if foo
4302 No symbol "foo" in current context.
4305 @item break @dots{} -force-condition if @var{cond}
4306 There may be cases where the condition @var{cond} is invalid at all
4307 the current locations, but the user knows that it will be valid at a
4308 future location; for example, because of a library load. In such
4309 cases, by using the @code{-force-condition} keyword before @samp{if},
4310 @value{GDBN} can be forced to define the breakpoint with the given
4311 condition expression instead of refusing it.
4314 (@value{GDBP}) break func -force-condition if foo
4315 warning: failed to validate condition at location 1, disabling:
4316 No symbol "foo" in current context.
4317 warning: failed to validate condition at location 2, disabling:
4318 No symbol "foo" in current context.
4319 warning: failed to validate condition at location 3, disabling:
4320 No symbol "foo" in current context.
4321 Breakpoint 1 at 0x1158: test.c:18. (3 locations)
4324 This causes all the present locations where the breakpoint would
4325 otherwise be inserted, to be disabled, as seen in the example above.
4326 However, if there exist locations at which the condition is valid, the
4327 @code{-force-condition} keyword has no effect.
4330 @item tbreak @var{args}
4331 Set a breakpoint enabled only for one stop. The @var{args} are the
4332 same as for the @code{break} command, and the breakpoint is set in the same
4333 way, but the breakpoint is automatically deleted after the first time your
4334 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
4337 @cindex hardware breakpoints
4338 @item hbreak @var{args}
4339 Set a hardware-assisted breakpoint. The @var{args} are the same as for the
4340 @code{break} command and the breakpoint is set in the same way, but the
4341 breakpoint requires hardware support and some target hardware may not
4342 have this support. The main purpose of this is EPROM/ROM code
4343 debugging, so you can set a breakpoint at an instruction without
4344 changing the instruction. This can be used with the new trap-generation
4345 provided by SPARClite DSU and most x86-based targets. These targets
4346 will generate traps when a program accesses some data or instruction
4347 address that is assigned to the debug registers. However the hardware
4348 breakpoint registers can take a limited number of breakpoints. For
4349 example, on the DSU, only two data breakpoints can be set at a time, and
4350 @value{GDBN} will reject this command if more than two are used. Delete
4351 or disable unused hardware breakpoints before setting new ones
4352 (@pxref{Disabling, ,Disabling Breakpoints}).
4353 @xref{Conditions, ,Break Conditions}.
4354 For remote targets, you can restrict the number of hardware
4355 breakpoints @value{GDBN} will use, see @ref{set remote
4356 hardware-breakpoint-limit}.
4359 @item thbreak @var{args}
4360 Set a hardware-assisted breakpoint enabled only for one stop. The @var{args}
4361 are the same as for the @code{hbreak} command and the breakpoint is set in
4362 the same way. However, like the @code{tbreak} command,
4363 the breakpoint is automatically deleted after the
4364 first time your program stops there. Also, like the @code{hbreak}
4365 command, the breakpoint requires hardware support and some target hardware
4366 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
4367 See also @ref{Conditions, ,Break Conditions}.
4370 @cindex regular expression
4371 @cindex breakpoints at functions matching a regexp
4372 @cindex set breakpoints in many functions
4373 @item rbreak @var{regex}
4374 Set breakpoints on all functions matching the regular expression
4375 @var{regex}. This command sets an unconditional breakpoint on all
4376 matches, printing a list of all breakpoints it set. Once these
4377 breakpoints are set, they are treated just like the breakpoints set with
4378 the @code{break} command. You can delete them, disable them, or make
4379 them conditional the same way as any other breakpoint.
4381 In programs using different languages, @value{GDBN} chooses the syntax
4382 to print the list of all breakpoints it sets according to the
4383 @samp{set language} value: using @samp{set language auto}
4384 (see @ref{Automatically, ,Set Language Automatically}) means to use the
4385 language of the breakpoint's function, other values mean to use
4386 the manually specified language (see @ref{Manually, ,Set Language Manually}).
4388 The syntax of the regular expression is the standard one used with tools
4389 like @file{grep}. Note that this is different from the syntax used by
4390 shells, so for instance @code{foo*} matches all functions that include
4391 an @code{fo} followed by zero or more @code{o}s. There is an implicit
4392 @code{.*} leading and trailing the regular expression you supply, so to
4393 match only functions that begin with @code{foo}, use @code{^foo}.
4395 @cindex non-member C@t{++} functions, set breakpoint in
4396 When debugging C@t{++} programs, @code{rbreak} is useful for setting
4397 breakpoints on overloaded functions that are not members of any special
4400 @cindex set breakpoints on all functions
4401 The @code{rbreak} command can be used to set breakpoints in
4402 @strong{all} the functions in a program, like this:
4405 (@value{GDBP}) rbreak .
4408 @item rbreak @var{file}:@var{regex}
4409 If @code{rbreak} is called with a filename qualification, it limits
4410 the search for functions matching the given regular expression to the
4411 specified @var{file}. This can be used, for example, to set breakpoints on
4412 every function in a given file:
4415 (@value{GDBP}) rbreak file.c:.
4418 The colon separating the filename qualifier from the regex may
4419 optionally be surrounded by spaces.
4421 @kindex info breakpoints
4422 @cindex @code{$_} and @code{info breakpoints}
4423 @item info breakpoints @r{[}@var{list}@dots{}@r{]}
4424 @itemx info break @r{[}@var{list}@dots{}@r{]}
4425 Print a table of all breakpoints, watchpoints, and catchpoints set and
4426 not deleted. Optional argument @var{n} means print information only
4427 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
4428 For each breakpoint, following columns are printed:
4431 @item Breakpoint Numbers
4433 Breakpoint, watchpoint, or catchpoint.
4435 Whether the breakpoint is marked to be disabled or deleted when hit.
4436 @item Enabled or Disabled
4437 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
4438 that are not enabled.
4440 Where the breakpoint is in your program, as a memory address. For a
4441 pending breakpoint whose address is not yet known, this field will
4442 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
4443 library that has the symbol or line referred by breakpoint is loaded.
4444 See below for details. A breakpoint with several locations will
4445 have @samp{<MULTIPLE>} in this field---see below for details.
4447 Where the breakpoint is in the source for your program, as a file and
4448 line number. For a pending breakpoint, the original string passed to
4449 the breakpoint command will be listed as it cannot be resolved until
4450 the appropriate shared library is loaded in the future.
4454 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
4455 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
4456 @value{GDBN} on the host's side. If it is ``target'', then the condition
4457 is evaluated by the target. The @code{info break} command shows
4458 the condition on the line following the affected breakpoint, together with
4459 its condition evaluation mode in between parentheses.
4461 Breakpoint commands, if any, are listed after that. A pending breakpoint is
4462 allowed to have a condition specified for it. The condition is not parsed for
4463 validity until a shared library is loaded that allows the pending
4464 breakpoint to resolve to a valid location.
4467 @code{info break} with a breakpoint
4468 number @var{n} as argument lists only that breakpoint. The
4469 convenience variable @code{$_} and the default examining-address for
4470 the @code{x} command are set to the address of the last breakpoint
4471 listed (@pxref{Memory, ,Examining Memory}).
4474 @code{info break} displays a count of the number of times the breakpoint
4475 has been hit. This is especially useful in conjunction with the
4476 @code{ignore} command. You can ignore a large number of breakpoint
4477 hits, look at the breakpoint info to see how many times the breakpoint
4478 was hit, and then run again, ignoring one less than that number. This
4479 will get you quickly to the last hit of that breakpoint.
4482 For a breakpoints with an enable count (xref) greater than 1,
4483 @code{info break} also displays that count.
4487 @value{GDBN} allows you to set any number of breakpoints at the same place in
4488 your program. There is nothing silly or meaningless about this. When
4489 the breakpoints are conditional, this is even useful
4490 (@pxref{Conditions, ,Break Conditions}).
4492 @cindex multiple locations, breakpoints
4493 @cindex breakpoints, multiple locations
4494 It is possible that a breakpoint corresponds to several locations
4495 in your program. Examples of this situation are:
4499 Multiple functions in the program may have the same name.
4502 For a C@t{++} constructor, the @value{NGCC} compiler generates several
4503 instances of the function body, used in different cases.
4506 For a C@t{++} template function, a given line in the function can
4507 correspond to any number of instantiations.
4510 For an inlined function, a given source line can correspond to
4511 several places where that function is inlined.
4514 In all those cases, @value{GDBN} will insert a breakpoint at all
4515 the relevant locations.
4517 A breakpoint with multiple locations is displayed in the breakpoint
4518 table using several rows---one header row, followed by one row for
4519 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
4520 address column. The rows for individual locations contain the actual
4521 addresses for locations, and show the functions to which those
4522 locations belong. The number column for a location is of the form
4523 @var{breakpoint-number}.@var{location-number}.
4528 Num Type Disp Enb Address What
4529 1 breakpoint keep y <MULTIPLE>
4531 breakpoint already hit 1 time
4532 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
4533 1.2 y 0x080486ca in void foo<double>() at t.cc:8
4536 You cannot delete the individual locations from a breakpoint. However,
4537 each location can be individually enabled or disabled by passing
4538 @var{breakpoint-number}.@var{location-number} as argument to the
4539 @code{enable} and @code{disable} commands. It's also possible to
4540 @code{enable} and @code{disable} a range of @var{location-number}
4541 locations using a @var{breakpoint-number} and two @var{location-number}s,
4542 in increasing order, separated by a hyphen, like
4543 @kbd{@var{breakpoint-number}.@var{location-number1}-@var{location-number2}},
4544 in which case @value{GDBN} acts on all the locations in the range (inclusive).
4545 Disabling or enabling the parent breakpoint (@pxref{Disabling}) affects
4546 all of the locations that belong to that breakpoint.
4548 @cindex pending breakpoints
4549 It's quite common to have a breakpoint inside a shared library.
4550 Shared libraries can be loaded and unloaded explicitly,
4551 and possibly repeatedly, as the program is executed. To support
4552 this use case, @value{GDBN} updates breakpoint locations whenever
4553 any shared library is loaded or unloaded. Typically, you would
4554 set a breakpoint in a shared library at the beginning of your
4555 debugging session, when the library is not loaded, and when the
4556 symbols from the library are not available. When you try to set
4557 breakpoint, @value{GDBN} will ask you if you want to set
4558 a so called @dfn{pending breakpoint}---breakpoint whose address
4559 is not yet resolved.
4561 After the program is run, whenever a new shared library is loaded,
4562 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
4563 shared library contains the symbol or line referred to by some
4564 pending breakpoint, that breakpoint is resolved and becomes an
4565 ordinary breakpoint. When a library is unloaded, all breakpoints
4566 that refer to its symbols or source lines become pending again.
4568 This logic works for breakpoints with multiple locations, too. For
4569 example, if you have a breakpoint in a C@t{++} template function, and
4570 a newly loaded shared library has an instantiation of that template,
4571 a new location is added to the list of locations for the breakpoint.
4573 Except for having unresolved address, pending breakpoints do not
4574 differ from regular breakpoints. You can set conditions or commands,
4575 enable and disable them and perform other breakpoint operations.
4577 @value{GDBN} provides some additional commands for controlling what
4578 happens when the @samp{break} command cannot resolve breakpoint
4579 address specification to an address:
4581 @kindex set breakpoint pending
4582 @kindex show breakpoint pending
4584 @item set breakpoint pending auto
4585 This is the default behavior. When @value{GDBN} cannot find the breakpoint
4586 location, it queries you whether a pending breakpoint should be created.
4588 @item set breakpoint pending on
4589 This indicates that an unrecognized breakpoint location should automatically
4590 result in a pending breakpoint being created.
4592 @item set breakpoint pending off
4593 This indicates that pending breakpoints are not to be created. Any
4594 unrecognized breakpoint location results in an error. This setting does
4595 not affect any pending breakpoints previously created.
4597 @item show breakpoint pending
4598 Show the current behavior setting for creating pending breakpoints.
4601 The settings above only affect the @code{break} command and its
4602 variants. Once breakpoint is set, it will be automatically updated
4603 as shared libraries are loaded and unloaded.
4605 @cindex automatic hardware breakpoints
4606 For some targets, @value{GDBN} can automatically decide if hardware or
4607 software breakpoints should be used, depending on whether the
4608 breakpoint address is read-only or read-write. This applies to
4609 breakpoints set with the @code{break} command as well as to internal
4610 breakpoints set by commands like @code{next} and @code{finish}. For
4611 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
4614 You can control this automatic behaviour with the following commands:
4616 @kindex set breakpoint auto-hw
4617 @kindex show breakpoint auto-hw
4619 @item set breakpoint auto-hw on
4620 This is the default behavior. When @value{GDBN} sets a breakpoint, it
4621 will try to use the target memory map to decide if software or hardware
4622 breakpoint must be used.
4624 @item set breakpoint auto-hw off
4625 This indicates @value{GDBN} should not automatically select breakpoint
4626 type. If the target provides a memory map, @value{GDBN} will warn when
4627 trying to set software breakpoint at a read-only address.
4630 @value{GDBN} normally implements breakpoints by replacing the program code
4631 at the breakpoint address with a special instruction, which, when
4632 executed, given control to the debugger. By default, the program
4633 code is so modified only when the program is resumed. As soon as
4634 the program stops, @value{GDBN} restores the original instructions. This
4635 behaviour guards against leaving breakpoints inserted in the
4636 target should gdb abrubptly disconnect. However, with slow remote
4637 targets, inserting and removing breakpoint can reduce the performance.
4638 This behavior can be controlled with the following commands::
4640 @kindex set breakpoint always-inserted
4641 @kindex show breakpoint always-inserted
4643 @item set breakpoint always-inserted off
4644 All breakpoints, including newly added by the user, are inserted in
4645 the target only when the target is resumed. All breakpoints are
4646 removed from the target when it stops. This is the default mode.
4648 @item set breakpoint always-inserted on
4649 Causes all breakpoints to be inserted in the target at all times. If
4650 the user adds a new breakpoint, or changes an existing breakpoint, the
4651 breakpoints in the target are updated immediately. A breakpoint is
4652 removed from the target only when breakpoint itself is deleted.
4655 @value{GDBN} handles conditional breakpoints by evaluating these conditions
4656 when a breakpoint breaks. If the condition is true, then the process being
4657 debugged stops, otherwise the process is resumed.
4659 If the target supports evaluating conditions on its end, @value{GDBN} may
4660 download the breakpoint, together with its conditions, to it.
4662 This feature can be controlled via the following commands:
4664 @kindex set breakpoint condition-evaluation
4665 @kindex show breakpoint condition-evaluation
4667 @item set breakpoint condition-evaluation host
4668 This option commands @value{GDBN} to evaluate the breakpoint
4669 conditions on the host's side. Unconditional breakpoints are sent to
4670 the target which in turn receives the triggers and reports them back to GDB
4671 for condition evaluation. This is the standard evaluation mode.
4673 @item set breakpoint condition-evaluation target
4674 This option commands @value{GDBN} to download breakpoint conditions
4675 to the target at the moment of their insertion. The target
4676 is responsible for evaluating the conditional expression and reporting
4677 breakpoint stop events back to @value{GDBN} whenever the condition
4678 is true. Due to limitations of target-side evaluation, some conditions
4679 cannot be evaluated there, e.g., conditions that depend on local data
4680 that is only known to the host. Examples include
4681 conditional expressions involving convenience variables, complex types
4682 that cannot be handled by the agent expression parser and expressions
4683 that are too long to be sent over to the target, specially when the
4684 target is a remote system. In these cases, the conditions will be
4685 evaluated by @value{GDBN}.
4687 @item set breakpoint condition-evaluation auto
4688 This is the default mode. If the target supports evaluating breakpoint
4689 conditions on its end, @value{GDBN} will download breakpoint conditions to
4690 the target (limitations mentioned previously apply). If the target does
4691 not support breakpoint condition evaluation, then @value{GDBN} will fallback
4692 to evaluating all these conditions on the host's side.
4696 @cindex negative breakpoint numbers
4697 @cindex internal @value{GDBN} breakpoints
4698 @value{GDBN} itself sometimes sets breakpoints in your program for
4699 special purposes, such as proper handling of @code{longjmp} (in C
4700 programs). These internal breakpoints are assigned negative numbers,
4701 starting with @code{-1}; @samp{info breakpoints} does not display them.
4702 You can see these breakpoints with the @value{GDBN} maintenance command
4703 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
4706 @node Set Watchpoints
4707 @subsection Setting Watchpoints
4709 @cindex setting watchpoints
4710 You can use a watchpoint to stop execution whenever the value of an
4711 expression changes, without having to predict a particular place where
4712 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
4713 The expression may be as simple as the value of a single variable, or
4714 as complex as many variables combined by operators. Examples include:
4718 A reference to the value of a single variable.
4721 An address cast to an appropriate data type. For example,
4722 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
4723 address (assuming an @code{int} occupies 4 bytes).
4726 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
4727 expression can use any operators valid in the program's native
4728 language (@pxref{Languages}).
4731 You can set a watchpoint on an expression even if the expression can
4732 not be evaluated yet. For instance, you can set a watchpoint on
4733 @samp{*global_ptr} before @samp{global_ptr} is initialized.
4734 @value{GDBN} will stop when your program sets @samp{global_ptr} and
4735 the expression produces a valid value. If the expression becomes
4736 valid in some other way than changing a variable (e.g.@: if the memory
4737 pointed to by @samp{*global_ptr} becomes readable as the result of a
4738 @code{malloc} call), @value{GDBN} may not stop until the next time
4739 the expression changes.
4741 @cindex software watchpoints
4742 @cindex hardware watchpoints
4743 Depending on your system, watchpoints may be implemented in software or
4744 hardware. @value{GDBN} does software watchpointing by single-stepping your
4745 program and testing the variable's value each time, which is hundreds of
4746 times slower than normal execution. (But this may still be worth it, to
4747 catch errors where you have no clue what part of your program is the
4750 On some systems, such as most PowerPC or x86-based targets,
4751 @value{GDBN} includes support for hardware watchpoints, which do not
4752 slow down the running of your program.
4756 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4757 Set a watchpoint for an expression. @value{GDBN} will break when the
4758 expression @var{expr} is written into by the program and its value
4759 changes. The simplest (and the most popular) use of this command is
4760 to watch the value of a single variable:
4763 (@value{GDBP}) watch foo
4766 If the command includes a @code{@r{[}thread @var{thread-id}@r{]}}
4767 argument, @value{GDBN} breaks only when the thread identified by
4768 @var{thread-id} changes the value of @var{expr}. If any other threads
4769 change the value of @var{expr}, @value{GDBN} will not break. Note
4770 that watchpoints restricted to a single thread in this way only work
4771 with Hardware Watchpoints.
4773 Ordinarily a watchpoint respects the scope of variables in @var{expr}
4774 (see below). The @code{-location} argument tells @value{GDBN} to
4775 instead watch the memory referred to by @var{expr}. In this case,
4776 @value{GDBN} will evaluate @var{expr}, take the address of the result,
4777 and watch the memory at that address. The type of the result is used
4778 to determine the size of the watched memory. If the expression's
4779 result does not have an address, then @value{GDBN} will print an
4782 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
4783 of masked watchpoints, if the current architecture supports this
4784 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
4785 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
4786 to an address to watch. The mask specifies that some bits of an address
4787 (the bits which are reset in the mask) should be ignored when matching
4788 the address accessed by the inferior against the watchpoint address.
4789 Thus, a masked watchpoint watches many addresses simultaneously---those
4790 addresses whose unmasked bits are identical to the unmasked bits in the
4791 watchpoint address. The @code{mask} argument implies @code{-location}.
4795 (@value{GDBP}) watch foo mask 0xffff00ff
4796 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
4800 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4801 Set a watchpoint that will break when the value of @var{expr} is read
4805 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4806 Set a watchpoint that will break when @var{expr} is either read from
4807 or written into by the program.
4809 @kindex info watchpoints @r{[}@var{list}@dots{}@r{]}
4810 @item info watchpoints @r{[}@var{list}@dots{}@r{]}
4811 This command prints a list of watchpoints, using the same format as
4812 @code{info break} (@pxref{Set Breaks}).
4815 If you watch for a change in a numerically entered address you need to
4816 dereference it, as the address itself is just a constant number which will
4817 never change. @value{GDBN} refuses to create a watchpoint that watches
4818 a never-changing value:
4821 (@value{GDBP}) watch 0x600850
4822 Cannot watch constant value 0x600850.
4823 (@value{GDBP}) watch *(int *) 0x600850
4824 Watchpoint 1: *(int *) 6293584
4827 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
4828 watchpoints execute very quickly, and the debugger reports a change in
4829 value at the exact instruction where the change occurs. If @value{GDBN}
4830 cannot set a hardware watchpoint, it sets a software watchpoint, which
4831 executes more slowly and reports the change in value at the next
4832 @emph{statement}, not the instruction, after the change occurs.
4834 @cindex use only software watchpoints
4835 You can force @value{GDBN} to use only software watchpoints with the
4836 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
4837 zero, @value{GDBN} will never try to use hardware watchpoints, even if
4838 the underlying system supports them. (Note that hardware-assisted
4839 watchpoints that were set @emph{before} setting
4840 @code{can-use-hw-watchpoints} to zero will still use the hardware
4841 mechanism of watching expression values.)
4844 @item set can-use-hw-watchpoints
4845 @kindex set can-use-hw-watchpoints
4846 Set whether or not to use hardware watchpoints.
4848 @item show can-use-hw-watchpoints
4849 @kindex show can-use-hw-watchpoints
4850 Show the current mode of using hardware watchpoints.
4853 For remote targets, you can restrict the number of hardware
4854 watchpoints @value{GDBN} will use, see @ref{set remote
4855 hardware-breakpoint-limit}.
4857 When you issue the @code{watch} command, @value{GDBN} reports
4860 Hardware watchpoint @var{num}: @var{expr}
4864 if it was able to set a hardware watchpoint.
4866 Currently, the @code{awatch} and @code{rwatch} commands can only set
4867 hardware watchpoints, because accesses to data that don't change the
4868 value of the watched expression cannot be detected without examining
4869 every instruction as it is being executed, and @value{GDBN} does not do
4870 that currently. If @value{GDBN} finds that it is unable to set a
4871 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
4872 will print a message like this:
4875 Expression cannot be implemented with read/access watchpoint.
4878 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4879 data type of the watched expression is wider than what a hardware
4880 watchpoint on the target machine can handle. For example, some systems
4881 can only watch regions that are up to 4 bytes wide; on such systems you
4882 cannot set hardware watchpoints for an expression that yields a
4883 double-precision floating-point number (which is typically 8 bytes
4884 wide). As a work-around, it might be possible to break the large region
4885 into a series of smaller ones and watch them with separate watchpoints.
4887 If you set too many hardware watchpoints, @value{GDBN} might be unable
4888 to insert all of them when you resume the execution of your program.
4889 Since the precise number of active watchpoints is unknown until such
4890 time as the program is about to be resumed, @value{GDBN} might not be
4891 able to warn you about this when you set the watchpoints, and the
4892 warning will be printed only when the program is resumed:
4895 Hardware watchpoint @var{num}: Could not insert watchpoint
4899 If this happens, delete or disable some of the watchpoints.
4901 Watching complex expressions that reference many variables can also
4902 exhaust the resources available for hardware-assisted watchpoints.
4903 That's because @value{GDBN} needs to watch every variable in the
4904 expression with separately allocated resources.
4906 If you call a function interactively using @code{print} or @code{call},
4907 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4908 kind of breakpoint or the call completes.
4910 @value{GDBN} automatically deletes watchpoints that watch local
4911 (automatic) variables, or expressions that involve such variables, when
4912 they go out of scope, that is, when the execution leaves the block in
4913 which these variables were defined. In particular, when the program
4914 being debugged terminates, @emph{all} local variables go out of scope,
4915 and so only watchpoints that watch global variables remain set. If you
4916 rerun the program, you will need to set all such watchpoints again. One
4917 way of doing that would be to set a code breakpoint at the entry to the
4918 @code{main} function and when it breaks, set all the watchpoints.
4920 @cindex watchpoints and threads
4921 @cindex threads and watchpoints
4922 In multi-threaded programs, watchpoints will detect changes to the
4923 watched expression from every thread.
4926 @emph{Warning:} In multi-threaded programs, software watchpoints
4927 have only limited usefulness. If @value{GDBN} creates a software
4928 watchpoint, it can only watch the value of an expression @emph{in a
4929 single thread}. If you are confident that the expression can only
4930 change due to the current thread's activity (and if you are also
4931 confident that no other thread can become current), then you can use
4932 software watchpoints as usual. However, @value{GDBN} may not notice
4933 when a non-current thread's activity changes the expression. (Hardware
4934 watchpoints, in contrast, watch an expression in all threads.)
4937 @xref{set remote hardware-watchpoint-limit}.
4939 @node Set Catchpoints
4940 @subsection Setting Catchpoints
4941 @cindex catchpoints, setting
4942 @cindex exception handlers
4943 @cindex event handling
4945 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4946 kinds of program events, such as C@t{++} exceptions or the loading of a
4947 shared library. Use the @code{catch} command to set a catchpoint.
4951 @item catch @var{event}
4952 Stop when @var{event} occurs. The @var{event} can be any of the following:
4955 @item throw @r{[}@var{regexp}@r{]}
4956 @itemx rethrow @r{[}@var{regexp}@r{]}
4957 @itemx catch @r{[}@var{regexp}@r{]}
4959 @kindex catch rethrow
4961 @cindex stop on C@t{++} exceptions
4962 The throwing, re-throwing, or catching of a C@t{++} exception.
4964 If @var{regexp} is given, then only exceptions whose type matches the
4965 regular expression will be caught.
4967 @vindex $_exception@r{, convenience variable}
4968 The convenience variable @code{$_exception} is available at an
4969 exception-related catchpoint, on some systems. This holds the
4970 exception being thrown.
4972 There are currently some limitations to C@t{++} exception handling in
4977 The support for these commands is system-dependent. Currently, only
4978 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
4982 The regular expression feature and the @code{$_exception} convenience
4983 variable rely on the presence of some SDT probes in @code{libstdc++}.
4984 If these probes are not present, then these features cannot be used.
4985 These probes were first available in the GCC 4.8 release, but whether
4986 or not they are available in your GCC also depends on how it was
4990 The @code{$_exception} convenience variable is only valid at the
4991 instruction at which an exception-related catchpoint is set.
4994 When an exception-related catchpoint is hit, @value{GDBN} stops at a
4995 location in the system library which implements runtime exception
4996 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
4997 (@pxref{Selection}) to get to your code.
5000 If you call a function interactively, @value{GDBN} normally returns
5001 control to you when the function has finished executing. If the call
5002 raises an exception, however, the call may bypass the mechanism that
5003 returns control to you and cause your program either to abort or to
5004 simply continue running until it hits a breakpoint, catches a signal
5005 that @value{GDBN} is listening for, or exits. This is the case even if
5006 you set a catchpoint for the exception; catchpoints on exceptions are
5007 disabled within interactive calls. @xref{Calling}, for information on
5008 controlling this with @code{set unwind-on-terminating-exception}.
5011 You cannot raise an exception interactively.
5014 You cannot install an exception handler interactively.
5017 @item exception @r{[}@var{name}@r{]}
5018 @kindex catch exception
5019 @cindex Ada exception catching
5020 @cindex catch Ada exceptions
5021 An Ada exception being raised. If an exception name is specified
5022 at the end of the command (eg @code{catch exception Program_Error}),
5023 the debugger will stop only when this specific exception is raised.
5024 Otherwise, the debugger stops execution when any Ada exception is raised.
5026 When inserting an exception catchpoint on a user-defined exception whose
5027 name is identical to one of the exceptions defined by the language, the
5028 fully qualified name must be used as the exception name. Otherwise,
5029 @value{GDBN} will assume that it should stop on the pre-defined exception
5030 rather than the user-defined one. For instance, assuming an exception
5031 called @code{Constraint_Error} is defined in package @code{Pck}, then
5032 the command to use to catch such exceptions is @kbd{catch exception
5033 Pck.Constraint_Error}.
5035 @vindex $_ada_exception@r{, convenience variable}
5036 The convenience variable @code{$_ada_exception} holds the address of
5037 the exception being thrown. This can be useful when setting a
5038 condition for such a catchpoint.
5040 @item exception unhandled
5041 @kindex catch exception unhandled
5042 An exception that was raised but is not handled by the program. The
5043 convenience variable @code{$_ada_exception} is set as for @code{catch
5046 @item handlers @r{[}@var{name}@r{]}
5047 @kindex catch handlers
5048 @cindex Ada exception handlers catching
5049 @cindex catch Ada exceptions when handled
5050 An Ada exception being handled. If an exception name is
5051 specified at the end of the command
5052 (eg @kbd{catch handlers Program_Error}), the debugger will stop
5053 only when this specific exception is handled.
5054 Otherwise, the debugger stops execution when any Ada exception is handled.
5056 When inserting a handlers catchpoint on a user-defined
5057 exception whose name is identical to one of the exceptions
5058 defined by the language, the fully qualified name must be used
5059 as the exception name. Otherwise, @value{GDBN} will assume that it
5060 should stop on the pre-defined exception rather than the
5061 user-defined one. For instance, assuming an exception called
5062 @code{Constraint_Error} is defined in package @code{Pck}, then the
5063 command to use to catch such exceptions handling is
5064 @kbd{catch handlers Pck.Constraint_Error}.
5066 The convenience variable @code{$_ada_exception} is set as for
5067 @code{catch exception}.
5070 @kindex catch assert
5071 A failed Ada assertion. Note that the convenience variable
5072 @code{$_ada_exception} is @emph{not} set by this catchpoint.
5076 @cindex break on fork/exec
5077 A call to @code{exec}.
5079 @anchor{catch syscall}
5081 @itemx syscall @r{[}@var{name} @r{|} @var{number} @r{|} @r{group:}@var{groupname} @r{|} @r{g:}@var{groupname}@r{]} @dots{}
5082 @kindex catch syscall
5083 @cindex break on a system call.
5084 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
5085 syscall is a mechanism for application programs to request a service
5086 from the operating system (OS) or one of the OS system services.
5087 @value{GDBN} can catch some or all of the syscalls issued by the
5088 debuggee, and show the related information for each syscall. If no
5089 argument is specified, calls to and returns from all system calls
5092 @var{name} can be any system call name that is valid for the
5093 underlying OS. Just what syscalls are valid depends on the OS. On
5094 GNU and Unix systems, you can find the full list of valid syscall
5095 names on @file{/usr/include/asm/unistd.h}.
5097 @c For MS-Windows, the syscall names and the corresponding numbers
5098 @c can be found, e.g., on this URL:
5099 @c http://www.metasploit.com/users/opcode/syscalls.html
5100 @c but we don't support Windows syscalls yet.
5102 Normally, @value{GDBN} knows in advance which syscalls are valid for
5103 each OS, so you can use the @value{GDBN} command-line completion
5104 facilities (@pxref{Completion,, command completion}) to list the
5107 You may also specify the system call numerically. A syscall's
5108 number is the value passed to the OS's syscall dispatcher to
5109 identify the requested service. When you specify the syscall by its
5110 name, @value{GDBN} uses its database of syscalls to convert the name
5111 into the corresponding numeric code, but using the number directly
5112 may be useful if @value{GDBN}'s database does not have the complete
5113 list of syscalls on your system (e.g., because @value{GDBN} lags
5114 behind the OS upgrades).
5116 You may specify a group of related syscalls to be caught at once using
5117 the @code{group:} syntax (@code{g:} is a shorter equivalent). For
5118 instance, on some platforms @value{GDBN} allows you to catch all
5119 network related syscalls, by passing the argument @code{group:network}
5120 to @code{catch syscall}. Note that not all syscall groups are
5121 available in every system. You can use the command completion
5122 facilities (@pxref{Completion,, command completion}) to list the
5123 syscall groups available on your environment.
5125 The example below illustrates how this command works if you don't provide
5129 (@value{GDBP}) catch syscall
5130 Catchpoint 1 (syscall)
5132 Starting program: /tmp/catch-syscall
5134 Catchpoint 1 (call to syscall 'close'), \
5135 0xffffe424 in __kernel_vsyscall ()
5139 Catchpoint 1 (returned from syscall 'close'), \
5140 0xffffe424 in __kernel_vsyscall ()
5144 Here is an example of catching a system call by name:
5147 (@value{GDBP}) catch syscall chroot
5148 Catchpoint 1 (syscall 'chroot' [61])
5150 Starting program: /tmp/catch-syscall
5152 Catchpoint 1 (call to syscall 'chroot'), \
5153 0xffffe424 in __kernel_vsyscall ()
5157 Catchpoint 1 (returned from syscall 'chroot'), \
5158 0xffffe424 in __kernel_vsyscall ()
5162 An example of specifying a system call numerically. In the case
5163 below, the syscall number has a corresponding entry in the XML
5164 file, so @value{GDBN} finds its name and prints it:
5167 (@value{GDBP}) catch syscall 252
5168 Catchpoint 1 (syscall(s) 'exit_group')
5170 Starting program: /tmp/catch-syscall
5172 Catchpoint 1 (call to syscall 'exit_group'), \
5173 0xffffe424 in __kernel_vsyscall ()
5177 Program exited normally.
5181 Here is an example of catching a syscall group:
5184 (@value{GDBP}) catch syscall group:process
5185 Catchpoint 1 (syscalls 'exit' [1] 'fork' [2] 'waitpid' [7]
5186 'execve' [11] 'wait4' [114] 'clone' [120] 'vfork' [190]
5187 'exit_group' [252] 'waitid' [284] 'unshare' [310])
5189 Starting program: /tmp/catch-syscall
5191 Catchpoint 1 (call to syscall fork), 0x00007ffff7df4e27 in open64 ()
5192 from /lib64/ld-linux-x86-64.so.2
5198 However, there can be situations when there is no corresponding name
5199 in XML file for that syscall number. In this case, @value{GDBN} prints
5200 a warning message saying that it was not able to find the syscall name,
5201 but the catchpoint will be set anyway. See the example below:
5204 (@value{GDBP}) catch syscall 764
5205 warning: The number '764' does not represent a known syscall.
5206 Catchpoint 2 (syscall 764)
5210 If you configure @value{GDBN} using the @samp{--without-expat} option,
5211 it will not be able to display syscall names. Also, if your
5212 architecture does not have an XML file describing its system calls,
5213 you will not be able to see the syscall names. It is important to
5214 notice that these two features are used for accessing the syscall
5215 name database. In either case, you will see a warning like this:
5218 (@value{GDBP}) catch syscall
5219 warning: Could not open "syscalls/i386-linux.xml"
5220 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
5221 GDB will not be able to display syscall names.
5222 Catchpoint 1 (syscall)
5226 Of course, the file name will change depending on your architecture and system.
5228 Still using the example above, you can also try to catch a syscall by its
5229 number. In this case, you would see something like:
5232 (@value{GDBP}) catch syscall 252
5233 Catchpoint 1 (syscall(s) 252)
5236 Again, in this case @value{GDBN} would not be able to display syscall's names.
5240 A call to @code{fork}.
5244 A call to @code{vfork}.
5246 @item load @r{[}@var{regexp}@r{]}
5247 @itemx unload @r{[}@var{regexp}@r{]}
5249 @kindex catch unload
5250 The loading or unloading of a shared library. If @var{regexp} is
5251 given, then the catchpoint will stop only if the regular expression
5252 matches one of the affected libraries.
5254 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5255 @kindex catch signal
5256 The delivery of a signal.
5258 With no arguments, this catchpoint will catch any signal that is not
5259 used internally by @value{GDBN}, specifically, all signals except
5260 @samp{SIGTRAP} and @samp{SIGINT}.
5262 With the argument @samp{all}, all signals, including those used by
5263 @value{GDBN}, will be caught. This argument cannot be used with other
5266 Otherwise, the arguments are a list of signal names as given to
5267 @code{handle} (@pxref{Signals}). Only signals specified in this list
5270 One reason that @code{catch signal} can be more useful than
5271 @code{handle} is that you can attach commands and conditions to the
5274 When a signal is caught by a catchpoint, the signal's @code{stop} and
5275 @code{print} settings, as specified by @code{handle}, are ignored.
5276 However, whether the signal is still delivered to the inferior depends
5277 on the @code{pass} setting; this can be changed in the catchpoint's
5282 @item tcatch @var{event}
5284 Set a catchpoint that is enabled only for one stop. The catchpoint is
5285 automatically deleted after the first time the event is caught.
5289 Use the @code{info break} command to list the current catchpoints.
5293 @subsection Deleting Breakpoints
5295 @cindex clearing breakpoints, watchpoints, catchpoints
5296 @cindex deleting breakpoints, watchpoints, catchpoints
5297 It is often necessary to eliminate a breakpoint, watchpoint, or
5298 catchpoint once it has done its job and you no longer want your program
5299 to stop there. This is called @dfn{deleting} the breakpoint. A
5300 breakpoint that has been deleted no longer exists; it is forgotten.
5302 With the @code{clear} command you can delete breakpoints according to
5303 where they are in your program. With the @code{delete} command you can
5304 delete individual breakpoints, watchpoints, or catchpoints by specifying
5305 their breakpoint numbers.
5307 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
5308 automatically ignores breakpoints on the first instruction to be executed
5309 when you continue execution without changing the execution address.
5314 Delete any breakpoints at the next instruction to be executed in the
5315 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
5316 the innermost frame is selected, this is a good way to delete a
5317 breakpoint where your program just stopped.
5319 @item clear @var{location}
5320 Delete any breakpoints set at the specified @var{location}.
5321 @xref{Specify Location}, for the various forms of @var{location}; the
5322 most useful ones are listed below:
5325 @item clear @var{function}
5326 @itemx clear @var{filename}:@var{function}
5327 Delete any breakpoints set at entry to the named @var{function}.
5329 @item clear @var{linenum}
5330 @itemx clear @var{filename}:@var{linenum}
5331 Delete any breakpoints set at or within the code of the specified
5332 @var{linenum} of the specified @var{filename}.
5335 @cindex delete breakpoints
5337 @kindex d @r{(@code{delete})}
5338 @item delete @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
5339 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
5340 list specified as argument. If no argument is specified, delete all
5341 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
5342 confirm off}). You can abbreviate this command as @code{d}.
5346 @subsection Disabling Breakpoints
5348 @cindex enable/disable a breakpoint
5349 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
5350 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
5351 it had been deleted, but remembers the information on the breakpoint so
5352 that you can @dfn{enable} it again later.
5354 You disable and enable breakpoints, watchpoints, and catchpoints with
5355 the @code{enable} and @code{disable} commands, optionally specifying
5356 one or more breakpoint numbers as arguments. Use @code{info break} to
5357 print a list of all breakpoints, watchpoints, and catchpoints if you
5358 do not know which numbers to use.
5360 Disabling and enabling a breakpoint that has multiple locations
5361 affects all of its locations.
5363 A breakpoint, watchpoint, or catchpoint can have any of several
5364 different states of enablement:
5368 Enabled. The breakpoint stops your program. A breakpoint set
5369 with the @code{break} command starts out in this state.
5371 Disabled. The breakpoint has no effect on your program.
5373 Enabled once. The breakpoint stops your program, but then becomes
5376 Enabled for a count. The breakpoint stops your program for the next
5377 N times, then becomes disabled.
5379 Enabled for deletion. The breakpoint stops your program, but
5380 immediately after it does so it is deleted permanently. A breakpoint
5381 set with the @code{tbreak} command starts out in this state.
5384 You can use the following commands to enable or disable breakpoints,
5385 watchpoints, and catchpoints:
5389 @kindex dis @r{(@code{disable})}
5390 @item disable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
5391 Disable the specified breakpoints---or all breakpoints, if none are
5392 listed. A disabled breakpoint has no effect but is not forgotten. All
5393 options such as ignore-counts, conditions and commands are remembered in
5394 case the breakpoint is enabled again later. You may abbreviate
5395 @code{disable} as @code{dis}.
5398 @item enable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
5399 Enable the specified breakpoints (or all defined breakpoints). They
5400 become effective once again in stopping your program.
5402 @item enable @r{[}breakpoints@r{]} once @var{list}@dots{}
5403 Enable the specified breakpoints temporarily. @value{GDBN} disables any
5404 of these breakpoints immediately after stopping your program.
5406 @item enable @r{[}breakpoints@r{]} count @var{count} @var{list}@dots{}
5407 Enable the specified breakpoints temporarily. @value{GDBN} records
5408 @var{count} with each of the specified breakpoints, and decrements a
5409 breakpoint's count when it is hit. When any count reaches 0,
5410 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
5411 count (@pxref{Conditions, ,Break Conditions}), that will be
5412 decremented to 0 before @var{count} is affected.
5414 @item enable @r{[}breakpoints@r{]} delete @var{list}@dots{}
5415 Enable the specified breakpoints to work once, then die. @value{GDBN}
5416 deletes any of these breakpoints as soon as your program stops there.
5417 Breakpoints set by the @code{tbreak} command start out in this state.
5420 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
5421 @c confusing: tbreak is also initially enabled.
5422 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
5423 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
5424 subsequently, they become disabled or enabled only when you use one of
5425 the commands above. (The command @code{until} can set and delete a
5426 breakpoint of its own, but it does not change the state of your other
5427 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
5431 @subsection Break Conditions
5432 @cindex conditional breakpoints
5433 @cindex breakpoint conditions
5435 @c FIXME what is scope of break condition expr? Context where wanted?
5436 @c in particular for a watchpoint?
5437 The simplest sort of breakpoint breaks every time your program reaches a
5438 specified place. You can also specify a @dfn{condition} for a
5439 breakpoint. A condition is just a Boolean expression in your
5440 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
5441 a condition evaluates the expression each time your program reaches it,
5442 and your program stops only if the condition is @emph{true}.
5444 This is the converse of using assertions for program validation; in that
5445 situation, you want to stop when the assertion is violated---that is,
5446 when the condition is false. In C, if you want to test an assertion expressed
5447 by the condition @var{assert}, you should set the condition
5448 @samp{! @var{assert}} on the appropriate breakpoint.
5450 Conditions are also accepted for watchpoints; you may not need them,
5451 since a watchpoint is inspecting the value of an expression anyhow---but
5452 it might be simpler, say, to just set a watchpoint on a variable name,
5453 and specify a condition that tests whether the new value is an interesting
5456 Break conditions can have side effects, and may even call functions in
5457 your program. This can be useful, for example, to activate functions
5458 that log program progress, or to use your own print functions to
5459 format special data structures. The effects are completely predictable
5460 unless there is another enabled breakpoint at the same address. (In
5461 that case, @value{GDBN} might see the other breakpoint first and stop your
5462 program without checking the condition of this one.) Note that
5463 breakpoint commands are usually more convenient and flexible than break
5465 purpose of performing side effects when a breakpoint is reached
5466 (@pxref{Break Commands, ,Breakpoint Command Lists}).
5468 Breakpoint conditions can also be evaluated on the target's side if
5469 the target supports it. Instead of evaluating the conditions locally,
5470 @value{GDBN} encodes the expression into an agent expression
5471 (@pxref{Agent Expressions}) suitable for execution on the target,
5472 independently of @value{GDBN}. Global variables become raw memory
5473 locations, locals become stack accesses, and so forth.
5475 In this case, @value{GDBN} will only be notified of a breakpoint trigger
5476 when its condition evaluates to true. This mechanism may provide faster
5477 response times depending on the performance characteristics of the target
5478 since it does not need to keep @value{GDBN} informed about
5479 every breakpoint trigger, even those with false conditions.
5481 Break conditions can be specified when a breakpoint is set, by using
5482 @samp{if} in the arguments to the @code{break} command. @xref{Set
5483 Breaks, ,Setting Breakpoints}. They can also be changed at any time
5484 with the @code{condition} command.
5486 You can also use the @code{if} keyword with the @code{watch} command.
5487 The @code{catch} command does not recognize the @code{if} keyword;
5488 @code{condition} is the only way to impose a further condition on a
5493 @item condition @var{bnum} @var{expression}
5494 Specify @var{expression} as the break condition for breakpoint,
5495 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
5496 breakpoint @var{bnum} stops your program only if the value of
5497 @var{expression} is true (nonzero, in C). When you use
5498 @code{condition}, @value{GDBN} checks @var{expression} immediately for
5499 syntactic correctness, and to determine whether symbols in it have
5500 referents in the context of your breakpoint. If @var{expression} uses
5501 symbols not referenced in the context of the breakpoint, @value{GDBN}
5502 prints an error message:
5505 No symbol "foo" in current context.
5510 not actually evaluate @var{expression} at the time the @code{condition}
5511 command (or a command that sets a breakpoint with a condition, like
5512 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
5514 @item condition -force @var{bnum} @var{expression}
5515 When the @code{-force} flag is used, define the condition even if
5516 @var{expression} is invalid at all the current locations of breakpoint
5517 @var{bnum}. This is similar to the @code{-force-condition} option
5518 of the @code{break} command.
5520 @item condition @var{bnum}
5521 Remove the condition from breakpoint number @var{bnum}. It becomes
5522 an ordinary unconditional breakpoint.
5525 @cindex ignore count (of breakpoint)
5526 A special case of a breakpoint condition is to stop only when the
5527 breakpoint has been reached a certain number of times. This is so
5528 useful that there is a special way to do it, using the @dfn{ignore
5529 count} of the breakpoint. Every breakpoint has an ignore count, which
5530 is an integer. Most of the time, the ignore count is zero, and
5531 therefore has no effect. But if your program reaches a breakpoint whose
5532 ignore count is positive, then instead of stopping, it just decrements
5533 the ignore count by one and continues. As a result, if the ignore count
5534 value is @var{n}, the breakpoint does not stop the next @var{n} times
5535 your program reaches it.
5539 @item ignore @var{bnum} @var{count}
5540 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
5541 The next @var{count} times the breakpoint is reached, your program's
5542 execution does not stop; other than to decrement the ignore count, @value{GDBN}
5545 To make the breakpoint stop the next time it is reached, specify
5548 When you use @code{continue} to resume execution of your program from a
5549 breakpoint, you can specify an ignore count directly as an argument to
5550 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
5551 Stepping,,Continuing and Stepping}.
5553 If a breakpoint has a positive ignore count and a condition, the
5554 condition is not checked. Once the ignore count reaches zero,
5555 @value{GDBN} resumes checking the condition.
5557 You could achieve the effect of the ignore count with a condition such
5558 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
5559 is decremented each time. @xref{Convenience Vars, ,Convenience
5563 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
5566 @node Break Commands
5567 @subsection Breakpoint Command Lists
5569 @cindex breakpoint commands
5570 You can give any breakpoint (or watchpoint or catchpoint) a series of
5571 commands to execute when your program stops due to that breakpoint. For
5572 example, you might want to print the values of certain expressions, or
5573 enable other breakpoints.
5577 @kindex end@r{ (breakpoint commands)}
5578 @item commands @r{[}@var{list}@dots{}@r{]}
5579 @itemx @dots{} @var{command-list} @dots{}
5581 Specify a list of commands for the given breakpoints. The commands
5582 themselves appear on the following lines. Type a line containing just
5583 @code{end} to terminate the commands.
5585 To remove all commands from a breakpoint, type @code{commands} and
5586 follow it immediately with @code{end}; that is, give no commands.
5588 With no argument, @code{commands} refers to the last breakpoint,
5589 watchpoint, or catchpoint set (not to the breakpoint most recently
5590 encountered). If the most recent breakpoints were set with a single
5591 command, then the @code{commands} will apply to all the breakpoints
5592 set by that command. This applies to breakpoints set by
5593 @code{rbreak}, and also applies when a single @code{break} command
5594 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
5598 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
5599 disabled within a @var{command-list}.
5601 You can use breakpoint commands to start your program up again. Simply
5602 use the @code{continue} command, or @code{step}, or any other command
5603 that resumes execution.
5605 Any other commands in the command list, after a command that resumes
5606 execution, are ignored. This is because any time you resume execution
5607 (even with a simple @code{next} or @code{step}), you may encounter
5608 another breakpoint---which could have its own command list, leading to
5609 ambiguities about which list to execute.
5612 If the first command you specify in a command list is @code{silent}, the
5613 usual message about stopping at a breakpoint is not printed. This may
5614 be desirable for breakpoints that are to print a specific message and
5615 then continue. If none of the remaining commands print anything, you
5616 see no sign that the breakpoint was reached. @code{silent} is
5617 meaningful only at the beginning of a breakpoint command list.
5619 The commands @code{echo}, @code{output}, and @code{printf} allow you to
5620 print precisely controlled output, and are often useful in silent
5621 breakpoints. @xref{Output, ,Commands for Controlled Output}.
5623 For example, here is how you could use breakpoint commands to print the
5624 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
5630 printf "x is %d\n",x
5635 One application for breakpoint commands is to compensate for one bug so
5636 you can test for another. Put a breakpoint just after the erroneous line
5637 of code, give it a condition to detect the case in which something
5638 erroneous has been done, and give it commands to assign correct values
5639 to any variables that need them. End with the @code{continue} command
5640 so that your program does not stop, and start with the @code{silent}
5641 command so that no output is produced. Here is an example:
5652 @node Dynamic Printf
5653 @subsection Dynamic Printf
5655 @cindex dynamic printf
5657 The dynamic printf command @code{dprintf} combines a breakpoint with
5658 formatted printing of your program's data to give you the effect of
5659 inserting @code{printf} calls into your program on-the-fly, without
5660 having to recompile it.
5662 In its most basic form, the output goes to the GDB console. However,
5663 you can set the variable @code{dprintf-style} for alternate handling.
5664 For instance, you can ask to format the output by calling your
5665 program's @code{printf} function. This has the advantage that the
5666 characters go to the program's output device, so they can recorded in
5667 redirects to files and so forth.
5669 If you are doing remote debugging with a stub or agent, you can also
5670 ask to have the printf handled by the remote agent. In addition to
5671 ensuring that the output goes to the remote program's device along
5672 with any other output the program might produce, you can also ask that
5673 the dprintf remain active even after disconnecting from the remote
5674 target. Using the stub/agent is also more efficient, as it can do
5675 everything without needing to communicate with @value{GDBN}.
5679 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
5680 Whenever execution reaches @var{location}, print the values of one or
5681 more @var{expressions} under the control of the string @var{template}.
5682 To print several values, separate them with commas.
5684 @item set dprintf-style @var{style}
5685 Set the dprintf output to be handled in one of several different
5686 styles enumerated below. A change of style affects all existing
5687 dynamic printfs immediately. (If you need individual control over the
5688 print commands, simply define normal breakpoints with
5689 explicitly-supplied command lists.)
5693 @kindex dprintf-style gdb
5694 Handle the output using the @value{GDBN} @code{printf} command.
5697 @kindex dprintf-style call
5698 Handle the output by calling a function in your program (normally
5702 @kindex dprintf-style agent
5703 Have the remote debugging agent (such as @code{gdbserver}) handle
5704 the output itself. This style is only available for agents that
5705 support running commands on the target.
5708 @item set dprintf-function @var{function}
5709 Set the function to call if the dprintf style is @code{call}. By
5710 default its value is @code{printf}. You may set it to any expression.
5711 that @value{GDBN} can evaluate to a function, as per the @code{call}
5714 @item set dprintf-channel @var{channel}
5715 Set a ``channel'' for dprintf. If set to a non-empty value,
5716 @value{GDBN} will evaluate it as an expression and pass the result as
5717 a first argument to the @code{dprintf-function}, in the manner of
5718 @code{fprintf} and similar functions. Otherwise, the dprintf format
5719 string will be the first argument, in the manner of @code{printf}.
5721 As an example, if you wanted @code{dprintf} output to go to a logfile
5722 that is a standard I/O stream assigned to the variable @code{mylog},
5723 you could do the following:
5726 (gdb) set dprintf-style call
5727 (gdb) set dprintf-function fprintf
5728 (gdb) set dprintf-channel mylog
5729 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
5730 Dprintf 1 at 0x123456: file main.c, line 25.
5732 1 dprintf keep y 0x00123456 in main at main.c:25
5733 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
5738 Note that the @code{info break} displays the dynamic printf commands
5739 as normal breakpoint commands; you can thus easily see the effect of
5740 the variable settings.
5742 @item set disconnected-dprintf on
5743 @itemx set disconnected-dprintf off
5744 @kindex set disconnected-dprintf
5745 Choose whether @code{dprintf} commands should continue to run if
5746 @value{GDBN} has disconnected from the target. This only applies
5747 if the @code{dprintf-style} is @code{agent}.
5749 @item show disconnected-dprintf off
5750 @kindex show disconnected-dprintf
5751 Show the current choice for disconnected @code{dprintf}.
5755 @value{GDBN} does not check the validity of function and channel,
5756 relying on you to supply values that are meaningful for the contexts
5757 in which they are being used. For instance, the function and channel
5758 may be the values of local variables, but if that is the case, then
5759 all enabled dynamic prints must be at locations within the scope of
5760 those locals. If evaluation fails, @value{GDBN} will report an error.
5762 @node Save Breakpoints
5763 @subsection How to save breakpoints to a file
5765 To save breakpoint definitions to a file use the @w{@code{save
5766 breakpoints}} command.
5769 @kindex save breakpoints
5770 @cindex save breakpoints to a file for future sessions
5771 @item save breakpoints [@var{filename}]
5772 This command saves all current breakpoint definitions together with
5773 their commands and ignore counts, into a file @file{@var{filename}}
5774 suitable for use in a later debugging session. This includes all
5775 types of breakpoints (breakpoints, watchpoints, catchpoints,
5776 tracepoints). To read the saved breakpoint definitions, use the
5777 @code{source} command (@pxref{Command Files}). Note that watchpoints
5778 with expressions involving local variables may fail to be recreated
5779 because it may not be possible to access the context where the
5780 watchpoint is valid anymore. Because the saved breakpoint definitions
5781 are simply a sequence of @value{GDBN} commands that recreate the
5782 breakpoints, you can edit the file in your favorite editing program,
5783 and remove the breakpoint definitions you're not interested in, or
5784 that can no longer be recreated.
5787 @node Static Probe Points
5788 @subsection Static Probe Points
5790 @cindex static probe point, SystemTap
5791 @cindex static probe point, DTrace
5792 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
5793 for Statically Defined Tracing, and the probes are designed to have a tiny
5794 runtime code and data footprint, and no dynamic relocations.
5796 Currently, the following types of probes are supported on
5797 ELF-compatible systems:
5801 @item @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
5802 @acronym{SDT} probes@footnote{See
5803 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
5804 for more information on how to add @code{SystemTap} @acronym{SDT}
5805 probes in your applications.}. @code{SystemTap} probes are usable
5806 from assembly, C and C@t{++} languages@footnote{See
5807 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
5808 for a good reference on how the @acronym{SDT} probes are implemented.}.
5810 @item @code{DTrace} (@uref{http://oss.oracle.com/projects/DTrace})
5811 @acronym{USDT} probes. @code{DTrace} probes are usable from C and
5815 @cindex semaphores on static probe points
5816 Some @code{SystemTap} probes have an associated semaphore variable;
5817 for instance, this happens automatically if you defined your probe
5818 using a DTrace-style @file{.d} file. If your probe has a semaphore,
5819 @value{GDBN} will automatically enable it when you specify a
5820 breakpoint using the @samp{-probe-stap} notation. But, if you put a
5821 breakpoint at a probe's location by some other method (e.g.,
5822 @code{break file:line}), then @value{GDBN} will not automatically set
5823 the semaphore. @code{DTrace} probes do not support semaphores.
5825 You can examine the available static static probes using @code{info
5826 probes}, with optional arguments:
5830 @item info probes @r{[}@var{type}@r{]} @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5831 If given, @var{type} is either @code{stap} for listing
5832 @code{SystemTap} probes or @code{dtrace} for listing @code{DTrace}
5833 probes. If omitted all probes are listed regardless of their types.
5835 If given, @var{provider} is a regular expression used to match against provider
5836 names when selecting which probes to list. If omitted, probes by all
5837 probes from all providers are listed.
5839 If given, @var{name} is a regular expression to match against probe names
5840 when selecting which probes to list. If omitted, probe names are not
5841 considered when deciding whether to display them.
5843 If given, @var{objfile} is a regular expression used to select which
5844 object files (executable or shared libraries) to examine. If not
5845 given, all object files are considered.
5847 @item info probes all
5848 List the available static probes, from all types.
5851 @cindex enabling and disabling probes
5852 Some probe points can be enabled and/or disabled. The effect of
5853 enabling or disabling a probe depends on the type of probe being
5854 handled. Some @code{DTrace} probes can be enabled or
5855 disabled, but @code{SystemTap} probes cannot be disabled.
5857 You can enable (or disable) one or more probes using the following
5858 commands, with optional arguments:
5861 @kindex enable probes
5862 @item enable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5863 If given, @var{provider} is a regular expression used to match against
5864 provider names when selecting which probes to enable. If omitted,
5865 all probes from all providers are enabled.
5867 If given, @var{name} is a regular expression to match against probe
5868 names when selecting which probes to enable. If omitted, probe names
5869 are not considered when deciding whether to enable them.
5871 If given, @var{objfile} is a regular expression used to select which
5872 object files (executable or shared libraries) to examine. If not
5873 given, all object files are considered.
5875 @kindex disable probes
5876 @item disable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5877 See the @code{enable probes} command above for a description of the
5878 optional arguments accepted by this command.
5881 @vindex $_probe_arg@r{, convenience variable}
5882 A probe may specify up to twelve arguments. These are available at the
5883 point at which the probe is defined---that is, when the current PC is
5884 at the probe's location. The arguments are available using the
5885 convenience variables (@pxref{Convenience Vars})
5886 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. In @code{SystemTap}
5887 probes each probe argument is an integer of the appropriate size;
5888 types are not preserved. In @code{DTrace} probes types are preserved
5889 provided that they are recognized as such by @value{GDBN}; otherwise
5890 the value of the probe argument will be a long integer. The
5891 convenience variable @code{$_probe_argc} holds the number of arguments
5892 at the current probe point.
5894 These variables are always available, but attempts to access them at
5895 any location other than a probe point will cause @value{GDBN} to give
5899 @c @ifclear BARETARGET
5900 @node Error in Breakpoints
5901 @subsection ``Cannot insert breakpoints''
5903 If you request too many active hardware-assisted breakpoints and
5904 watchpoints, you will see this error message:
5906 @c FIXME: the precise wording of this message may change; the relevant
5907 @c source change is not committed yet (Sep 3, 1999).
5909 Stopped; cannot insert breakpoints.
5910 You may have requested too many hardware breakpoints and watchpoints.
5914 This message is printed when you attempt to resume the program, since
5915 only then @value{GDBN} knows exactly how many hardware breakpoints and
5916 watchpoints it needs to insert.
5918 When this message is printed, you need to disable or remove some of the
5919 hardware-assisted breakpoints and watchpoints, and then continue.
5921 @node Breakpoint-related Warnings
5922 @subsection ``Breakpoint address adjusted...''
5923 @cindex breakpoint address adjusted
5925 Some processor architectures place constraints on the addresses at
5926 which breakpoints may be placed. For architectures thus constrained,
5927 @value{GDBN} will attempt to adjust the breakpoint's address to comply
5928 with the constraints dictated by the architecture.
5930 One example of such an architecture is the Fujitsu FR-V. The FR-V is
5931 a VLIW architecture in which a number of RISC-like instructions may be
5932 bundled together for parallel execution. The FR-V architecture
5933 constrains the location of a breakpoint instruction within such a
5934 bundle to the instruction with the lowest address. @value{GDBN}
5935 honors this constraint by adjusting a breakpoint's address to the
5936 first in the bundle.
5938 It is not uncommon for optimized code to have bundles which contain
5939 instructions from different source statements, thus it may happen that
5940 a breakpoint's address will be adjusted from one source statement to
5941 another. Since this adjustment may significantly alter @value{GDBN}'s
5942 breakpoint related behavior from what the user expects, a warning is
5943 printed when the breakpoint is first set and also when the breakpoint
5946 A warning like the one below is printed when setting a breakpoint
5947 that's been subject to address adjustment:
5950 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
5953 Such warnings are printed both for user settable and @value{GDBN}'s
5954 internal breakpoints. If you see one of these warnings, you should
5955 verify that a breakpoint set at the adjusted address will have the
5956 desired affect. If not, the breakpoint in question may be removed and
5957 other breakpoints may be set which will have the desired behavior.
5958 E.g., it may be sufficient to place the breakpoint at a later
5959 instruction. A conditional breakpoint may also be useful in some
5960 cases to prevent the breakpoint from triggering too often.
5962 @value{GDBN} will also issue a warning when stopping at one of these
5963 adjusted breakpoints:
5966 warning: Breakpoint 1 address previously adjusted from 0x00010414
5970 When this warning is encountered, it may be too late to take remedial
5971 action except in cases where the breakpoint is hit earlier or more
5972 frequently than expected.
5974 @node Continuing and Stepping
5975 @section Continuing and Stepping
5979 @cindex resuming execution
5980 @dfn{Continuing} means resuming program execution until your program
5981 completes normally. In contrast, @dfn{stepping} means executing just
5982 one more ``step'' of your program, where ``step'' may mean either one
5983 line of source code, or one machine instruction (depending on what
5984 particular command you use). Either when continuing or when stepping,
5985 your program may stop even sooner, due to a breakpoint or a signal. (If
5986 it stops due to a signal, you may want to use @code{handle}, or use
5987 @samp{signal 0} to resume execution (@pxref{Signals, ,Signals}),
5988 or you may step into the signal's handler (@pxref{stepping and signal
5993 @kindex c @r{(@code{continue})}
5994 @kindex fg @r{(resume foreground execution)}
5995 @item continue @r{[}@var{ignore-count}@r{]}
5996 @itemx c @r{[}@var{ignore-count}@r{]}
5997 @itemx fg @r{[}@var{ignore-count}@r{]}
5998 Resume program execution, at the address where your program last stopped;
5999 any breakpoints set at that address are bypassed. The optional argument
6000 @var{ignore-count} allows you to specify a further number of times to
6001 ignore a breakpoint at this location; its effect is like that of
6002 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
6004 The argument @var{ignore-count} is meaningful only when your program
6005 stopped due to a breakpoint. At other times, the argument to
6006 @code{continue} is ignored.
6008 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
6009 debugged program is deemed to be the foreground program) are provided
6010 purely for convenience, and have exactly the same behavior as
6014 To resume execution at a different place, you can use @code{return}
6015 (@pxref{Returning, ,Returning from a Function}) to go back to the
6016 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
6017 Different Address}) to go to an arbitrary location in your program.
6019 A typical technique for using stepping is to set a breakpoint
6020 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
6021 beginning of the function or the section of your program where a problem
6022 is believed to lie, run your program until it stops at that breakpoint,
6023 and then step through the suspect area, examining the variables that are
6024 interesting, until you see the problem happen.
6028 @kindex s @r{(@code{step})}
6030 Continue running your program until control reaches a different source
6031 line, then stop it and return control to @value{GDBN}. This command is
6032 abbreviated @code{s}.
6035 @c "without debugging information" is imprecise; actually "without line
6036 @c numbers in the debugging information". (gcc -g1 has debugging info but
6037 @c not line numbers). But it seems complex to try to make that
6038 @c distinction here.
6039 @emph{Warning:} If you use the @code{step} command while control is
6040 within a function that was compiled without debugging information,
6041 execution proceeds until control reaches a function that does have
6042 debugging information. Likewise, it will not step into a function which
6043 is compiled without debugging information. To step through functions
6044 without debugging information, use the @code{stepi} command, described
6048 The @code{step} command only stops at the first instruction of a source
6049 line. This prevents the multiple stops that could otherwise occur in
6050 @code{switch} statements, @code{for} loops, etc. @code{step} continues
6051 to stop if a function that has debugging information is called within
6052 the line. In other words, @code{step} @emph{steps inside} any functions
6053 called within the line.
6055 Also, the @code{step} command only enters a function if there is line
6056 number information for the function. Otherwise it acts like the
6057 @code{next} command. This avoids problems when using @code{cc -gl}
6058 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
6059 was any debugging information about the routine.
6061 @item step @var{count}
6062 Continue running as in @code{step}, but do so @var{count} times. If a
6063 breakpoint is reached, or a signal not related to stepping occurs before
6064 @var{count} steps, stepping stops right away.
6067 @kindex n @r{(@code{next})}
6068 @item next @r{[}@var{count}@r{]}
6069 Continue to the next source line in the current (innermost) stack frame.
6070 This is similar to @code{step}, but function calls that appear within
6071 the line of code are executed without stopping. Execution stops when
6072 control reaches a different line of code at the original stack level
6073 that was executing when you gave the @code{next} command. This command
6074 is abbreviated @code{n}.
6076 An argument @var{count} is a repeat count, as for @code{step}.
6079 @c FIX ME!! Do we delete this, or is there a way it fits in with
6080 @c the following paragraph? --- Vctoria
6082 @c @code{next} within a function that lacks debugging information acts like
6083 @c @code{step}, but any function calls appearing within the code of the
6084 @c function are executed without stopping.
6086 The @code{next} command only stops at the first instruction of a
6087 source line. This prevents multiple stops that could otherwise occur in
6088 @code{switch} statements, @code{for} loops, etc.
6090 @kindex set step-mode
6092 @cindex functions without line info, and stepping
6093 @cindex stepping into functions with no line info
6094 @itemx set step-mode on
6095 The @code{set step-mode on} command causes the @code{step} command to
6096 stop at the first instruction of a function which contains no debug line
6097 information rather than stepping over it.
6099 This is useful in cases where you may be interested in inspecting the
6100 machine instructions of a function which has no symbolic info and do not
6101 want @value{GDBN} to automatically skip over this function.
6103 @item set step-mode off
6104 Causes the @code{step} command to step over any functions which contains no
6105 debug information. This is the default.
6107 @item show step-mode
6108 Show whether @value{GDBN} will stop in or step over functions without
6109 source line debug information.
6112 @kindex fin @r{(@code{finish})}
6114 Continue running until just after function in the selected stack frame
6115 returns. Print the returned value (if any). This command can be
6116 abbreviated as @code{fin}.
6118 Contrast this with the @code{return} command (@pxref{Returning,
6119 ,Returning from a Function}).
6121 @kindex set print finish
6122 @kindex show print finish
6123 @item set print finish @r{[}on|off@r{]}
6124 @itemx show print finish
6125 By default the @code{finish} command will show the value that is
6126 returned by the function. This can be disabled using @code{set print
6127 finish off}. When disabled, the value is still entered into the value
6128 history (@pxref{Value History}), but not displayed.
6131 @kindex u @r{(@code{until})}
6132 @cindex run until specified location
6135 Continue running until a source line past the current line, in the
6136 current stack frame, is reached. This command is used to avoid single
6137 stepping through a loop more than once. It is like the @code{next}
6138 command, except that when @code{until} encounters a jump, it
6139 automatically continues execution until the program counter is greater
6140 than the address of the jump.
6142 This means that when you reach the end of a loop after single stepping
6143 though it, @code{until} makes your program continue execution until it
6144 exits the loop. In contrast, a @code{next} command at the end of a loop
6145 simply steps back to the beginning of the loop, which forces you to step
6146 through the next iteration.
6148 @code{until} always stops your program if it attempts to exit the current
6151 @code{until} may produce somewhat counterintuitive results if the order
6152 of machine code does not match the order of the source lines. For
6153 example, in the following excerpt from a debugging session, the @code{f}
6154 (@code{frame}) command shows that execution is stopped at line
6155 @code{206}; yet when we use @code{until}, we get to line @code{195}:
6159 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
6161 (@value{GDBP}) until
6162 195 for ( ; argc > 0; NEXTARG) @{
6165 This happened because, for execution efficiency, the compiler had
6166 generated code for the loop closure test at the end, rather than the
6167 start, of the loop---even though the test in a C @code{for}-loop is
6168 written before the body of the loop. The @code{until} command appeared
6169 to step back to the beginning of the loop when it advanced to this
6170 expression; however, it has not really gone to an earlier
6171 statement---not in terms of the actual machine code.
6173 @code{until} with no argument works by means of single
6174 instruction stepping, and hence is slower than @code{until} with an
6177 @item until @var{location}
6178 @itemx u @var{location}
6179 Continue running your program until either the specified @var{location} is
6180 reached, or the current stack frame returns. The location is any of
6181 the forms described in @ref{Specify Location}.
6182 This form of the command uses temporary breakpoints, and
6183 hence is quicker than @code{until} without an argument. The specified
6184 location is actually reached only if it is in the current frame. This
6185 implies that @code{until} can be used to skip over recursive function
6186 invocations. For instance in the code below, if the current location is
6187 line @code{96}, issuing @code{until 99} will execute the program up to
6188 line @code{99} in the same invocation of factorial, i.e., after the inner
6189 invocations have returned.
6192 94 int factorial (int value)
6194 96 if (value > 1) @{
6195 97 value *= factorial (value - 1);
6202 @kindex advance @var{location}
6203 @item advance @var{location}
6204 Continue running the program up to the given @var{location}. An argument is
6205 required, which should be of one of the forms described in
6206 @ref{Specify Location}.
6207 Execution will also stop upon exit from the current stack
6208 frame. This command is similar to @code{until}, but @code{advance} will
6209 not skip over recursive function calls, and the target location doesn't
6210 have to be in the same frame as the current one.
6214 @kindex si @r{(@code{stepi})}
6216 @itemx stepi @var{arg}
6218 Execute one machine instruction, then stop and return to the debugger.
6220 It is often useful to do @samp{display/i $pc} when stepping by machine
6221 instructions. This makes @value{GDBN} automatically display the next
6222 instruction to be executed, each time your program stops. @xref{Auto
6223 Display,, Automatic Display}.
6225 An argument is a repeat count, as in @code{step}.
6229 @kindex ni @r{(@code{nexti})}
6231 @itemx nexti @var{arg}
6233 Execute one machine instruction, but if it is a function call,
6234 proceed until the function returns.
6236 An argument is a repeat count, as in @code{next}.
6240 @anchor{range stepping}
6241 @cindex range stepping
6242 @cindex target-assisted range stepping
6243 By default, and if available, @value{GDBN} makes use of
6244 target-assisted @dfn{range stepping}. In other words, whenever you
6245 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
6246 tells the target to step the corresponding range of instruction
6247 addresses instead of issuing multiple single-steps. This speeds up
6248 line stepping, particularly for remote targets. Ideally, there should
6249 be no reason you would want to turn range stepping off. However, it's
6250 possible that a bug in the debug info, a bug in the remote stub (for
6251 remote targets), or even a bug in @value{GDBN} could make line
6252 stepping behave incorrectly when target-assisted range stepping is
6253 enabled. You can use the following command to turn off range stepping
6257 @kindex set range-stepping
6258 @kindex show range-stepping
6259 @item set range-stepping
6260 @itemx show range-stepping
6261 Control whether range stepping is enabled.
6263 If @code{on}, and the target supports it, @value{GDBN} tells the
6264 target to step a range of addresses itself, instead of issuing
6265 multiple single-steps. If @code{off}, @value{GDBN} always issues
6266 single-steps, even if range stepping is supported by the target. The
6267 default is @code{on}.
6271 @node Skipping Over Functions and Files
6272 @section Skipping Over Functions and Files
6273 @cindex skipping over functions and files
6275 The program you are debugging may contain some functions which are
6276 uninteresting to debug. The @code{skip} command lets you tell @value{GDBN} to
6277 skip a function, all functions in a file or a particular function in
6278 a particular file when stepping.
6280 For example, consider the following C function:
6291 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
6292 are not interested in stepping through @code{boring}. If you run @code{step}
6293 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
6294 step over both @code{foo} and @code{boring}!
6296 One solution is to @code{step} into @code{boring} and use the @code{finish}
6297 command to immediately exit it. But this can become tedious if @code{boring}
6298 is called from many places.
6300 A more flexible solution is to execute @kbd{skip boring}. This instructs
6301 @value{GDBN} never to step into @code{boring}. Now when you execute
6302 @code{step} at line 103, you'll step over @code{boring} and directly into
6305 Functions may be skipped by providing either a function name, linespec
6306 (@pxref{Specify Location}), regular expression that matches the function's
6307 name, file name or a @code{glob}-style pattern that matches the file name.
6309 On Posix systems the form of the regular expression is
6310 ``Extended Regular Expressions''. See for example @samp{man 7 regex}
6311 on @sc{gnu}/Linux systems. On non-Posix systems the form of the regular
6312 expression is whatever is provided by the @code{regcomp} function of
6313 the underlying system.
6314 See for example @samp{man 7 glob} on @sc{gnu}/Linux systems for a
6315 description of @code{glob}-style patterns.
6319 @item skip @r{[}@var{options}@r{]}
6320 The basic form of the @code{skip} command takes zero or more options
6321 that specify what to skip.
6322 The @var{options} argument is any useful combination of the following:
6325 @item -file @var{file}
6326 @itemx -fi @var{file}
6327 Functions in @var{file} will be skipped over when stepping.
6329 @item -gfile @var{file-glob-pattern}
6330 @itemx -gfi @var{file-glob-pattern}
6331 @cindex skipping over files via glob-style patterns
6332 Functions in files matching @var{file-glob-pattern} will be skipped
6336 (gdb) skip -gfi utils/*.c
6339 @item -function @var{linespec}
6340 @itemx -fu @var{linespec}
6341 Functions named by @var{linespec} or the function containing the line
6342 named by @var{linespec} will be skipped over when stepping.
6343 @xref{Specify Location}.
6345 @item -rfunction @var{regexp}
6346 @itemx -rfu @var{regexp}
6347 @cindex skipping over functions via regular expressions
6348 Functions whose name matches @var{regexp} will be skipped over when stepping.
6350 This form is useful for complex function names.
6351 For example, there is generally no need to step into C@t{++} @code{std::string}
6352 constructors or destructors. Plus with C@t{++} templates it can be hard to
6353 write out the full name of the function, and often it doesn't matter what
6354 the template arguments are. Specifying the function to be skipped as a
6355 regular expression makes this easier.
6358 (gdb) skip -rfu ^std::(allocator|basic_string)<.*>::~?\1 *\(
6361 If you want to skip every templated C@t{++} constructor and destructor
6362 in the @code{std} namespace you can do:
6365 (gdb) skip -rfu ^std::([a-zA-z0-9_]+)<.*>::~?\1 *\(
6369 If no options are specified, the function you're currently debugging
6372 @kindex skip function
6373 @item skip function @r{[}@var{linespec}@r{]}
6374 After running this command, the function named by @var{linespec} or the
6375 function containing the line named by @var{linespec} will be skipped over when
6376 stepping. @xref{Specify Location}.
6378 If you do not specify @var{linespec}, the function you're currently debugging
6381 (If you have a function called @code{file} that you want to skip, use
6382 @kbd{skip function file}.)
6385 @item skip file @r{[}@var{filename}@r{]}
6386 After running this command, any function whose source lives in @var{filename}
6387 will be skipped over when stepping.
6390 (gdb) skip file boring.c
6391 File boring.c will be skipped when stepping.
6394 If you do not specify @var{filename}, functions whose source lives in the file
6395 you're currently debugging will be skipped.
6398 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
6399 These are the commands for managing your list of skips:
6403 @item info skip @r{[}@var{range}@r{]}
6404 Print details about the specified skip(s). If @var{range} is not specified,
6405 print a table with details about all functions and files marked for skipping.
6406 @code{info skip} prints the following information about each skip:
6410 A number identifying this skip.
6411 @item Enabled or Disabled
6412 Enabled skips are marked with @samp{y}.
6413 Disabled skips are marked with @samp{n}.
6415 If the file name is a @samp{glob} pattern this is @samp{y}.
6416 Otherwise it is @samp{n}.
6418 The name or @samp{glob} pattern of the file to be skipped.
6419 If no file is specified this is @samp{<none>}.
6421 If the function name is a @samp{regular expression} this is @samp{y}.
6422 Otherwise it is @samp{n}.
6424 The name or regular expression of the function to skip.
6425 If no function is specified this is @samp{<none>}.
6429 @item skip delete @r{[}@var{range}@r{]}
6430 Delete the specified skip(s). If @var{range} is not specified, delete all
6434 @item skip enable @r{[}@var{range}@r{]}
6435 Enable the specified skip(s). If @var{range} is not specified, enable all
6438 @kindex skip disable
6439 @item skip disable @r{[}@var{range}@r{]}
6440 Disable the specified skip(s). If @var{range} is not specified, disable all
6443 @kindex set debug skip
6444 @item set debug skip @r{[}on|off@r{]}
6445 Set whether to print the debug output about skipping files and functions.
6447 @kindex show debug skip
6448 @item show debug skip
6449 Show whether the debug output about skipping files and functions is printed.
6457 A signal is an asynchronous event that can happen in a program. The
6458 operating system defines the possible kinds of signals, and gives each
6459 kind a name and a number. For example, in Unix @code{SIGINT} is the
6460 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
6461 @code{SIGSEGV} is the signal a program gets from referencing a place in
6462 memory far away from all the areas in use; @code{SIGALRM} occurs when
6463 the alarm clock timer goes off (which happens only if your program has
6464 requested an alarm).
6466 @cindex fatal signals
6467 Some signals, including @code{SIGALRM}, are a normal part of the
6468 functioning of your program. Others, such as @code{SIGSEGV}, indicate
6469 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
6470 program has not specified in advance some other way to handle the signal.
6471 @code{SIGINT} does not indicate an error in your program, but it is normally
6472 fatal so it can carry out the purpose of the interrupt: to kill the program.
6474 @value{GDBN} has the ability to detect any occurrence of a signal in your
6475 program. You can tell @value{GDBN} in advance what to do for each kind of
6478 @cindex handling signals
6479 Normally, @value{GDBN} is set up to let the non-erroneous signals like
6480 @code{SIGALRM} be silently passed to your program
6481 (so as not to interfere with their role in the program's functioning)
6482 but to stop your program immediately whenever an error signal happens.
6483 You can change these settings with the @code{handle} command.
6486 @kindex info signals
6490 Print a table of all the kinds of signals and how @value{GDBN} has been told to
6491 handle each one. You can use this to see the signal numbers of all
6492 the defined types of signals.
6494 @item info signals @var{sig}
6495 Similar, but print information only about the specified signal number.
6497 @code{info handle} is an alias for @code{info signals}.
6499 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
6500 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
6501 for details about this command.
6504 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
6505 Change the way @value{GDBN} handles signal @var{signal}. The @var{signal}
6506 can be the number of a signal or its name (with or without the
6507 @samp{SIG} at the beginning); a list of signal numbers of the form
6508 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
6509 known signals. Optional arguments @var{keywords}, described below,
6510 say what change to make.
6514 The keywords allowed by the @code{handle} command can be abbreviated.
6515 Their full names are:
6519 @value{GDBN} should not stop your program when this signal happens. It may
6520 still print a message telling you that the signal has come in.
6523 @value{GDBN} should stop your program when this signal happens. This implies
6524 the @code{print} keyword as well.
6527 @value{GDBN} should print a message when this signal happens.
6530 @value{GDBN} should not mention the occurrence of the signal at all. This
6531 implies the @code{nostop} keyword as well.
6535 @value{GDBN} should allow your program to see this signal; your program
6536 can handle the signal, or else it may terminate if the signal is fatal
6537 and not handled. @code{pass} and @code{noignore} are synonyms.
6541 @value{GDBN} should not allow your program to see this signal.
6542 @code{nopass} and @code{ignore} are synonyms.
6546 When a signal stops your program, the signal is not visible to the
6548 continue. Your program sees the signal then, if @code{pass} is in
6549 effect for the signal in question @emph{at that time}. In other words,
6550 after @value{GDBN} reports a signal, you can use the @code{handle}
6551 command with @code{pass} or @code{nopass} to control whether your
6552 program sees that signal when you continue.
6554 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
6555 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
6556 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
6559 You can also use the @code{signal} command to prevent your program from
6560 seeing a signal, or cause it to see a signal it normally would not see,
6561 or to give it any signal at any time. For example, if your program stopped
6562 due to some sort of memory reference error, you might store correct
6563 values into the erroneous variables and continue, hoping to see more
6564 execution; but your program would probably terminate immediately as
6565 a result of the fatal signal once it saw the signal. To prevent this,
6566 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
6569 @cindex stepping and signal handlers
6570 @anchor{stepping and signal handlers}
6572 @value{GDBN} optimizes for stepping the mainline code. If a signal
6573 that has @code{handle nostop} and @code{handle pass} set arrives while
6574 a stepping command (e.g., @code{stepi}, @code{step}, @code{next}) is
6575 in progress, @value{GDBN} lets the signal handler run and then resumes
6576 stepping the mainline code once the signal handler returns. In other
6577 words, @value{GDBN} steps over the signal handler. This prevents
6578 signals that you've specified as not interesting (with @code{handle
6579 nostop}) from changing the focus of debugging unexpectedly. Note that
6580 the signal handler itself may still hit a breakpoint, stop for another
6581 signal that has @code{handle stop} in effect, or for any other event
6582 that normally results in stopping the stepping command sooner. Also
6583 note that @value{GDBN} still informs you that the program received a
6584 signal if @code{handle print} is set.
6586 @anchor{stepping into signal handlers}
6588 If you set @code{handle pass} for a signal, and your program sets up a
6589 handler for it, then issuing a stepping command, such as @code{step}
6590 or @code{stepi}, when your program is stopped due to the signal will
6591 step @emph{into} the signal handler (if the target supports that).
6593 Likewise, if you use the @code{queue-signal} command to queue a signal
6594 to be delivered to the current thread when execution of the thread
6595 resumes (@pxref{Signaling, ,Giving your Program a Signal}), then a
6596 stepping command will step into the signal handler.
6598 Here's an example, using @code{stepi} to step to the first instruction
6599 of @code{SIGUSR1}'s handler:
6602 (@value{GDBP}) handle SIGUSR1
6603 Signal Stop Print Pass to program Description
6604 SIGUSR1 Yes Yes Yes User defined signal 1
6608 Program received signal SIGUSR1, User defined signal 1.
6609 main () sigusr1.c:28
6612 sigusr1_handler () at sigusr1.c:9
6616 The same, but using @code{queue-signal} instead of waiting for the
6617 program to receive the signal first:
6622 (@value{GDBP}) queue-signal SIGUSR1
6624 sigusr1_handler () at sigusr1.c:9
6629 @cindex extra signal information
6630 @anchor{extra signal information}
6632 On some targets, @value{GDBN} can inspect extra signal information
6633 associated with the intercepted signal, before it is actually
6634 delivered to the program being debugged. This information is exported
6635 by the convenience variable @code{$_siginfo}, and consists of data
6636 that is passed by the kernel to the signal handler at the time of the
6637 receipt of a signal. The data type of the information itself is
6638 target dependent. You can see the data type using the @code{ptype
6639 $_siginfo} command. On Unix systems, it typically corresponds to the
6640 standard @code{siginfo_t} type, as defined in the @file{signal.h}
6643 Here's an example, on a @sc{gnu}/Linux system, printing the stray
6644 referenced address that raised a segmentation fault.
6648 (@value{GDBP}) continue
6649 Program received signal SIGSEGV, Segmentation fault.
6650 0x0000000000400766 in main ()
6652 (@value{GDBP}) ptype $_siginfo
6659 struct @{...@} _kill;
6660 struct @{...@} _timer;
6662 struct @{...@} _sigchld;
6663 struct @{...@} _sigfault;
6664 struct @{...@} _sigpoll;
6667 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
6671 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
6672 $1 = (void *) 0x7ffff7ff7000
6676 Depending on target support, @code{$_siginfo} may also be writable.
6678 @cindex Intel MPX boundary violations
6679 @cindex boundary violations, Intel MPX
6680 On some targets, a @code{SIGSEGV} can be caused by a boundary
6681 violation, i.e., accessing an address outside of the allowed range.
6682 In those cases @value{GDBN} may displays additional information,
6683 depending on how @value{GDBN} has been told to handle the signal.
6684 With @code{handle stop SIGSEGV}, @value{GDBN} displays the violation
6685 kind: "Upper" or "Lower", the memory address accessed and the
6686 bounds, while with @code{handle nostop SIGSEGV} no additional
6687 information is displayed.
6689 The usual output of a segfault is:
6691 Program received signal SIGSEGV, Segmentation fault
6692 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6693 68 value = *(p + len);
6696 While a bound violation is presented as:
6698 Program received signal SIGSEGV, Segmentation fault
6699 Upper bound violation while accessing address 0x7fffffffc3b3
6700 Bounds: [lower = 0x7fffffffc390, upper = 0x7fffffffc3a3]
6701 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6702 68 value = *(p + len);
6706 @section Stopping and Starting Multi-thread Programs
6708 @cindex stopped threads
6709 @cindex threads, stopped
6711 @cindex continuing threads
6712 @cindex threads, continuing
6714 @value{GDBN} supports debugging programs with multiple threads
6715 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
6716 are two modes of controlling execution of your program within the
6717 debugger. In the default mode, referred to as @dfn{all-stop mode},
6718 when any thread in your program stops (for example, at a breakpoint
6719 or while being stepped), all other threads in the program are also stopped by
6720 @value{GDBN}. On some targets, @value{GDBN} also supports
6721 @dfn{non-stop mode}, in which other threads can continue to run freely while
6722 you examine the stopped thread in the debugger.
6725 * All-Stop Mode:: All threads stop when GDB takes control
6726 * Non-Stop Mode:: Other threads continue to execute
6727 * Background Execution:: Running your program asynchronously
6728 * Thread-Specific Breakpoints:: Controlling breakpoints
6729 * Interrupted System Calls:: GDB may interfere with system calls
6730 * Observer Mode:: GDB does not alter program behavior
6734 @subsection All-Stop Mode
6736 @cindex all-stop mode
6738 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
6739 @emph{all} threads of execution stop, not just the current thread. This
6740 allows you to examine the overall state of the program, including
6741 switching between threads, without worrying that things may change
6744 Conversely, whenever you restart the program, @emph{all} threads start
6745 executing. @emph{This is true even when single-stepping} with commands
6746 like @code{step} or @code{next}.
6748 In particular, @value{GDBN} cannot single-step all threads in lockstep.
6749 Since thread scheduling is up to your debugging target's operating
6750 system (not controlled by @value{GDBN}), other threads may
6751 execute more than one statement while the current thread completes a
6752 single step. Moreover, in general other threads stop in the middle of a
6753 statement, rather than at a clean statement boundary, when the program
6756 You might even find your program stopped in another thread after
6757 continuing or even single-stepping. This happens whenever some other
6758 thread runs into a breakpoint, a signal, or an exception before the
6759 first thread completes whatever you requested.
6761 @cindex automatic thread selection
6762 @cindex switching threads automatically
6763 @cindex threads, automatic switching
6764 Whenever @value{GDBN} stops your program, due to a breakpoint or a
6765 signal, it automatically selects the thread where that breakpoint or
6766 signal happened. @value{GDBN} alerts you to the context switch with a
6767 message such as @samp{[Switching to Thread @var{n}]} to identify the
6770 On some OSes, you can modify @value{GDBN}'s default behavior by
6771 locking the OS scheduler to allow only a single thread to run.
6774 @item set scheduler-locking @var{mode}
6775 @cindex scheduler locking mode
6776 @cindex lock scheduler
6777 Set the scheduler locking mode. It applies to normal execution,
6778 record mode, and replay mode. If it is @code{off}, then there is no
6779 locking and any thread may run at any time. If @code{on}, then only
6780 the current thread may run when the inferior is resumed. The
6781 @code{step} mode optimizes for single-stepping; it prevents other
6782 threads from preempting the current thread while you are stepping, so
6783 that the focus of debugging does not change unexpectedly. Other
6784 threads never get a chance to run when you step, and they are
6785 completely free to run when you use commands like @samp{continue},
6786 @samp{until}, or @samp{finish}. However, unless another thread hits a
6787 breakpoint during its timeslice, @value{GDBN} does not change the
6788 current thread away from the thread that you are debugging. The
6789 @code{replay} mode behaves like @code{off} in record mode and like
6790 @code{on} in replay mode.
6792 @item show scheduler-locking
6793 Display the current scheduler locking mode.
6796 @cindex resume threads of multiple processes simultaneously
6797 By default, when you issue one of the execution commands such as
6798 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
6799 threads of the current inferior to run. For example, if @value{GDBN}
6800 is attached to two inferiors, each with two threads, the
6801 @code{continue} command resumes only the two threads of the current
6802 inferior. This is useful, for example, when you debug a program that
6803 forks and you want to hold the parent stopped (so that, for instance,
6804 it doesn't run to exit), while you debug the child. In other
6805 situations, you may not be interested in inspecting the current state
6806 of any of the processes @value{GDBN} is attached to, and you may want
6807 to resume them all until some breakpoint is hit. In the latter case,
6808 you can instruct @value{GDBN} to allow all threads of all the
6809 inferiors to run with the @w{@code{set schedule-multiple}} command.
6812 @kindex set schedule-multiple
6813 @item set schedule-multiple
6814 Set the mode for allowing threads of multiple processes to be resumed
6815 when an execution command is issued. When @code{on}, all threads of
6816 all processes are allowed to run. When @code{off}, only the threads
6817 of the current process are resumed. The default is @code{off}. The
6818 @code{scheduler-locking} mode takes precedence when set to @code{on},
6819 or while you are stepping and set to @code{step}.
6821 @item show schedule-multiple
6822 Display the current mode for resuming the execution of threads of
6827 @subsection Non-Stop Mode
6829 @cindex non-stop mode
6831 @c This section is really only a place-holder, and needs to be expanded
6832 @c with more details.
6834 For some multi-threaded targets, @value{GDBN} supports an optional
6835 mode of operation in which you can examine stopped program threads in
6836 the debugger while other threads continue to execute freely. This
6837 minimizes intrusion when debugging live systems, such as programs
6838 where some threads have real-time constraints or must continue to
6839 respond to external events. This is referred to as @dfn{non-stop} mode.
6841 In non-stop mode, when a thread stops to report a debugging event,
6842 @emph{only} that thread is stopped; @value{GDBN} does not stop other
6843 threads as well, in contrast to the all-stop mode behavior. Additionally,
6844 execution commands such as @code{continue} and @code{step} apply by default
6845 only to the current thread in non-stop mode, rather than all threads as
6846 in all-stop mode. This allows you to control threads explicitly in
6847 ways that are not possible in all-stop mode --- for example, stepping
6848 one thread while allowing others to run freely, stepping
6849 one thread while holding all others stopped, or stepping several threads
6850 independently and simultaneously.
6852 To enter non-stop mode, use this sequence of commands before you run
6853 or attach to your program:
6856 # If using the CLI, pagination breaks non-stop.
6859 # Finally, turn it on!
6863 You can use these commands to manipulate the non-stop mode setting:
6866 @kindex set non-stop
6867 @item set non-stop on
6868 Enable selection of non-stop mode.
6869 @item set non-stop off
6870 Disable selection of non-stop mode.
6871 @kindex show non-stop
6873 Show the current non-stop enablement setting.
6876 Note these commands only reflect whether non-stop mode is enabled,
6877 not whether the currently-executing program is being run in non-stop mode.
6878 In particular, the @code{set non-stop} preference is only consulted when
6879 @value{GDBN} starts or connects to the target program, and it is generally
6880 not possible to switch modes once debugging has started. Furthermore,
6881 since not all targets support non-stop mode, even when you have enabled
6882 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
6885 In non-stop mode, all execution commands apply only to the current thread
6886 by default. That is, @code{continue} only continues one thread.
6887 To continue all threads, issue @code{continue -a} or @code{c -a}.
6889 You can use @value{GDBN}'s background execution commands
6890 (@pxref{Background Execution}) to run some threads in the background
6891 while you continue to examine or step others from @value{GDBN}.
6892 The MI execution commands (@pxref{GDB/MI Program Execution}) are
6893 always executed asynchronously in non-stop mode.
6895 Suspending execution is done with the @code{interrupt} command when
6896 running in the background, or @kbd{Ctrl-c} during foreground execution.
6897 In all-stop mode, this stops the whole process;
6898 but in non-stop mode the interrupt applies only to the current thread.
6899 To stop the whole program, use @code{interrupt -a}.
6901 Other execution commands do not currently support the @code{-a} option.
6903 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
6904 that thread current, as it does in all-stop mode. This is because the
6905 thread stop notifications are asynchronous with respect to @value{GDBN}'s
6906 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
6907 changed to a different thread just as you entered a command to operate on the
6908 previously current thread.
6910 @node Background Execution
6911 @subsection Background Execution
6913 @cindex foreground execution
6914 @cindex background execution
6915 @cindex asynchronous execution
6916 @cindex execution, foreground, background and asynchronous
6918 @value{GDBN}'s execution commands have two variants: the normal
6919 foreground (synchronous) behavior, and a background
6920 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
6921 the program to report that some thread has stopped before prompting for
6922 another command. In background execution, @value{GDBN} immediately gives
6923 a command prompt so that you can issue other commands while your program runs.
6925 If the target doesn't support async mode, @value{GDBN} issues an error
6926 message if you attempt to use the background execution commands.
6928 @cindex @code{&}, background execution of commands
6929 To specify background execution, add a @code{&} to the command. For example,
6930 the background form of the @code{continue} command is @code{continue&}, or
6931 just @code{c&}. The execution commands that accept background execution
6937 @xref{Starting, , Starting your Program}.
6941 @xref{Attach, , Debugging an Already-running Process}.
6945 @xref{Continuing and Stepping, step}.
6949 @xref{Continuing and Stepping, stepi}.
6953 @xref{Continuing and Stepping, next}.
6957 @xref{Continuing and Stepping, nexti}.
6961 @xref{Continuing and Stepping, continue}.
6965 @xref{Continuing and Stepping, finish}.
6969 @xref{Continuing and Stepping, until}.
6973 Background execution is especially useful in conjunction with non-stop
6974 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
6975 However, you can also use these commands in the normal all-stop mode with
6976 the restriction that you cannot issue another execution command until the
6977 previous one finishes. Examples of commands that are valid in all-stop
6978 mode while the program is running include @code{help} and @code{info break}.
6980 You can interrupt your program while it is running in the background by
6981 using the @code{interrupt} command.
6988 Suspend execution of the running program. In all-stop mode,
6989 @code{interrupt} stops the whole process, but in non-stop mode, it stops
6990 only the current thread. To stop the whole program in non-stop mode,
6991 use @code{interrupt -a}.
6994 @node Thread-Specific Breakpoints
6995 @subsection Thread-Specific Breakpoints
6997 When your program has multiple threads (@pxref{Threads,, Debugging
6998 Programs with Multiple Threads}), you can choose whether to set
6999 breakpoints on all threads, or on a particular thread.
7002 @cindex breakpoints and threads
7003 @cindex thread breakpoints
7004 @kindex break @dots{} thread @var{thread-id}
7005 @item break @var{location} thread @var{thread-id}
7006 @itemx break @var{location} thread @var{thread-id} if @dots{}
7007 @var{location} specifies source lines; there are several ways of
7008 writing them (@pxref{Specify Location}), but the effect is always to
7009 specify some source line.
7011 Use the qualifier @samp{thread @var{thread-id}} with a breakpoint command
7012 to specify that you only want @value{GDBN} to stop the program when a
7013 particular thread reaches this breakpoint. The @var{thread-id} specifier
7014 is one of the thread identifiers assigned by @value{GDBN}, shown
7015 in the first column of the @samp{info threads} display.
7017 If you do not specify @samp{thread @var{thread-id}} when you set a
7018 breakpoint, the breakpoint applies to @emph{all} threads of your
7021 You can use the @code{thread} qualifier on conditional breakpoints as
7022 well; in this case, place @samp{thread @var{thread-id}} before or
7023 after the breakpoint condition, like this:
7026 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
7031 Thread-specific breakpoints are automatically deleted when
7032 @value{GDBN} detects the corresponding thread is no longer in the
7033 thread list. For example:
7037 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
7040 There are several ways for a thread to disappear, such as a regular
7041 thread exit, but also when you detach from the process with the
7042 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
7043 Process}), or if @value{GDBN} loses the remote connection
7044 (@pxref{Remote Debugging}), etc. Note that with some targets,
7045 @value{GDBN} is only able to detect a thread has exited when the user
7046 explictly asks for the thread list with the @code{info threads}
7049 @node Interrupted System Calls
7050 @subsection Interrupted System Calls
7052 @cindex thread breakpoints and system calls
7053 @cindex system calls and thread breakpoints
7054 @cindex premature return from system calls
7055 There is an unfortunate side effect when using @value{GDBN} to debug
7056 multi-threaded programs. If one thread stops for a
7057 breakpoint, or for some other reason, and another thread is blocked in a
7058 system call, then the system call may return prematurely. This is a
7059 consequence of the interaction between multiple threads and the signals
7060 that @value{GDBN} uses to implement breakpoints and other events that
7063 To handle this problem, your program should check the return value of
7064 each system call and react appropriately. This is good programming
7067 For example, do not write code like this:
7073 The call to @code{sleep} will return early if a different thread stops
7074 at a breakpoint or for some other reason.
7076 Instead, write this:
7081 unslept = sleep (unslept);
7084 A system call is allowed to return early, so the system is still
7085 conforming to its specification. But @value{GDBN} does cause your
7086 multi-threaded program to behave differently than it would without
7089 Also, @value{GDBN} uses internal breakpoints in the thread library to
7090 monitor certain events such as thread creation and thread destruction.
7091 When such an event happens, a system call in another thread may return
7092 prematurely, even though your program does not appear to stop.
7095 @subsection Observer Mode
7097 If you want to build on non-stop mode and observe program behavior
7098 without any chance of disruption by @value{GDBN}, you can set
7099 variables to disable all of the debugger's attempts to modify state,
7100 whether by writing memory, inserting breakpoints, etc. These operate
7101 at a low level, intercepting operations from all commands.
7103 When all of these are set to @code{off}, then @value{GDBN} is said to
7104 be @dfn{observer mode}. As a convenience, the variable
7105 @code{observer} can be set to disable these, plus enable non-stop
7108 Note that @value{GDBN} will not prevent you from making nonsensical
7109 combinations of these settings. For instance, if you have enabled
7110 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
7111 then breakpoints that work by writing trap instructions into the code
7112 stream will still not be able to be placed.
7117 @item set observer on
7118 @itemx set observer off
7119 When set to @code{on}, this disables all the permission variables
7120 below (except for @code{insert-fast-tracepoints}), plus enables
7121 non-stop debugging. Setting this to @code{off} switches back to
7122 normal debugging, though remaining in non-stop mode.
7125 Show whether observer mode is on or off.
7127 @kindex may-write-registers
7128 @item set may-write-registers on
7129 @itemx set may-write-registers off
7130 This controls whether @value{GDBN} will attempt to alter the values of
7131 registers, such as with assignment expressions in @code{print}, or the
7132 @code{jump} command. It defaults to @code{on}.
7134 @item show may-write-registers
7135 Show the current permission to write registers.
7137 @kindex may-write-memory
7138 @item set may-write-memory on
7139 @itemx set may-write-memory off
7140 This controls whether @value{GDBN} will attempt to alter the contents
7141 of memory, such as with assignment expressions in @code{print}. It
7142 defaults to @code{on}.
7144 @item show may-write-memory
7145 Show the current permission to write memory.
7147 @kindex may-insert-breakpoints
7148 @item set may-insert-breakpoints on
7149 @itemx set may-insert-breakpoints off
7150 This controls whether @value{GDBN} will attempt to insert breakpoints.
7151 This affects all breakpoints, including internal breakpoints defined
7152 by @value{GDBN}. It defaults to @code{on}.
7154 @item show may-insert-breakpoints
7155 Show the current permission to insert breakpoints.
7157 @kindex may-insert-tracepoints
7158 @item set may-insert-tracepoints on
7159 @itemx set may-insert-tracepoints off
7160 This controls whether @value{GDBN} will attempt to insert (regular)
7161 tracepoints at the beginning of a tracing experiment. It affects only
7162 non-fast tracepoints, fast tracepoints being under the control of
7163 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
7165 @item show may-insert-tracepoints
7166 Show the current permission to insert tracepoints.
7168 @kindex may-insert-fast-tracepoints
7169 @item set may-insert-fast-tracepoints on
7170 @itemx set may-insert-fast-tracepoints off
7171 This controls whether @value{GDBN} will attempt to insert fast
7172 tracepoints at the beginning of a tracing experiment. It affects only
7173 fast tracepoints, regular (non-fast) tracepoints being under the
7174 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
7176 @item show may-insert-fast-tracepoints
7177 Show the current permission to insert fast tracepoints.
7179 @kindex may-interrupt
7180 @item set may-interrupt on
7181 @itemx set may-interrupt off
7182 This controls whether @value{GDBN} will attempt to interrupt or stop
7183 program execution. When this variable is @code{off}, the
7184 @code{interrupt} command will have no effect, nor will
7185 @kbd{Ctrl-c}. It defaults to @code{on}.
7187 @item show may-interrupt
7188 Show the current permission to interrupt or stop the program.
7192 @node Reverse Execution
7193 @chapter Running programs backward
7194 @cindex reverse execution
7195 @cindex running programs backward
7197 When you are debugging a program, it is not unusual to realize that
7198 you have gone too far, and some event of interest has already happened.
7199 If the target environment supports it, @value{GDBN} can allow you to
7200 ``rewind'' the program by running it backward.
7202 A target environment that supports reverse execution should be able
7203 to ``undo'' the changes in machine state that have taken place as the
7204 program was executing normally. Variables, registers etc.@: should
7205 revert to their previous values. Obviously this requires a great
7206 deal of sophistication on the part of the target environment; not
7207 all target environments can support reverse execution.
7209 When a program is executed in reverse, the instructions that
7210 have most recently been executed are ``un-executed'', in reverse
7211 order. The program counter runs backward, following the previous
7212 thread of execution in reverse. As each instruction is ``un-executed'',
7213 the values of memory and/or registers that were changed by that
7214 instruction are reverted to their previous states. After executing
7215 a piece of source code in reverse, all side effects of that code
7216 should be ``undone'', and all variables should be returned to their
7217 prior values@footnote{
7218 Note that some side effects are easier to undo than others. For instance,
7219 memory and registers are relatively easy, but device I/O is hard. Some
7220 targets may be able undo things like device I/O, and some may not.
7222 The contract between @value{GDBN} and the reverse executing target
7223 requires only that the target do something reasonable when
7224 @value{GDBN} tells it to execute backwards, and then report the
7225 results back to @value{GDBN}. Whatever the target reports back to
7226 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
7227 assumes that the memory and registers that the target reports are in a
7228 consistent state, but @value{GDBN} accepts whatever it is given.
7231 On some platforms, @value{GDBN} has built-in support for reverse
7232 execution, activated with the @code{record} or @code{record btrace}
7233 commands. @xref{Process Record and Replay}. Some remote targets,
7234 typically full system emulators, support reverse execution directly
7235 without requiring any special command.
7237 If you are debugging in a target environment that supports
7238 reverse execution, @value{GDBN} provides the following commands.
7241 @kindex reverse-continue
7242 @kindex rc @r{(@code{reverse-continue})}
7243 @item reverse-continue @r{[}@var{ignore-count}@r{]}
7244 @itemx rc @r{[}@var{ignore-count}@r{]}
7245 Beginning at the point where your program last stopped, start executing
7246 in reverse. Reverse execution will stop for breakpoints and synchronous
7247 exceptions (signals), just like normal execution. Behavior of
7248 asynchronous signals depends on the target environment.
7250 @kindex reverse-step
7251 @kindex rs @r{(@code{step})}
7252 @item reverse-step @r{[}@var{count}@r{]}
7253 Run the program backward until control reaches the start of a
7254 different source line; then stop it, and return control to @value{GDBN}.
7256 Like the @code{step} command, @code{reverse-step} will only stop
7257 at the beginning of a source line. It ``un-executes'' the previously
7258 executed source line. If the previous source line included calls to
7259 debuggable functions, @code{reverse-step} will step (backward) into
7260 the called function, stopping at the beginning of the @emph{last}
7261 statement in the called function (typically a return statement).
7263 Also, as with the @code{step} command, if non-debuggable functions are
7264 called, @code{reverse-step} will run thru them backward without stopping.
7266 @kindex reverse-stepi
7267 @kindex rsi @r{(@code{reverse-stepi})}
7268 @item reverse-stepi @r{[}@var{count}@r{]}
7269 Reverse-execute one machine instruction. Note that the instruction
7270 to be reverse-executed is @emph{not} the one pointed to by the program
7271 counter, but the instruction executed prior to that one. For instance,
7272 if the last instruction was a jump, @code{reverse-stepi} will take you
7273 back from the destination of the jump to the jump instruction itself.
7275 @kindex reverse-next
7276 @kindex rn @r{(@code{reverse-next})}
7277 @item reverse-next @r{[}@var{count}@r{]}
7278 Run backward to the beginning of the previous line executed in
7279 the current (innermost) stack frame. If the line contains function
7280 calls, they will be ``un-executed'' without stopping. Starting from
7281 the first line of a function, @code{reverse-next} will take you back
7282 to the caller of that function, @emph{before} the function was called,
7283 just as the normal @code{next} command would take you from the last
7284 line of a function back to its return to its caller
7285 @footnote{Unless the code is too heavily optimized.}.
7287 @kindex reverse-nexti
7288 @kindex rni @r{(@code{reverse-nexti})}
7289 @item reverse-nexti @r{[}@var{count}@r{]}
7290 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
7291 in reverse, except that called functions are ``un-executed'' atomically.
7292 That is, if the previously executed instruction was a return from
7293 another function, @code{reverse-nexti} will continue to execute
7294 in reverse until the call to that function (from the current stack
7297 @kindex reverse-finish
7298 @item reverse-finish
7299 Just as the @code{finish} command takes you to the point where the
7300 current function returns, @code{reverse-finish} takes you to the point
7301 where it was called. Instead of ending up at the end of the current
7302 function invocation, you end up at the beginning.
7304 @kindex set exec-direction
7305 @item set exec-direction
7306 Set the direction of target execution.
7307 @item set exec-direction reverse
7308 @cindex execute forward or backward in time
7309 @value{GDBN} will perform all execution commands in reverse, until the
7310 exec-direction mode is changed to ``forward''. Affected commands include
7311 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
7312 command cannot be used in reverse mode.
7313 @item set exec-direction forward
7314 @value{GDBN} will perform all execution commands in the normal fashion.
7315 This is the default.
7319 @node Process Record and Replay
7320 @chapter Recording Inferior's Execution and Replaying It
7321 @cindex process record and replay
7322 @cindex recording inferior's execution and replaying it
7324 On some platforms, @value{GDBN} provides a special @dfn{process record
7325 and replay} target that can record a log of the process execution, and
7326 replay it later with both forward and reverse execution commands.
7329 When this target is in use, if the execution log includes the record
7330 for the next instruction, @value{GDBN} will debug in @dfn{replay
7331 mode}. In the replay mode, the inferior does not really execute code
7332 instructions. Instead, all the events that normally happen during
7333 code execution are taken from the execution log. While code is not
7334 really executed in replay mode, the values of registers (including the
7335 program counter register) and the memory of the inferior are still
7336 changed as they normally would. Their contents are taken from the
7340 If the record for the next instruction is not in the execution log,
7341 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
7342 inferior executes normally, and @value{GDBN} records the execution log
7345 The process record and replay target supports reverse execution
7346 (@pxref{Reverse Execution}), even if the platform on which the
7347 inferior runs does not. However, the reverse execution is limited in
7348 this case by the range of the instructions recorded in the execution
7349 log. In other words, reverse execution on platforms that don't
7350 support it directly can only be done in the replay mode.
7352 When debugging in the reverse direction, @value{GDBN} will work in
7353 replay mode as long as the execution log includes the record for the
7354 previous instruction; otherwise, it will work in record mode, if the
7355 platform supports reverse execution, or stop if not.
7357 Currently, process record and replay is supported on ARM, Aarch64,
7358 Moxie, PowerPC, PowerPC64, S/390, and x86 (i386/amd64) running
7359 GNU/Linux. Process record and replay can be used both when native
7360 debugging, and when remote debugging via @code{gdbserver}.
7362 For architecture environments that support process record and replay,
7363 @value{GDBN} provides the following commands:
7366 @kindex target record
7367 @kindex target record-full
7368 @kindex target record-btrace
7371 @kindex record btrace
7372 @kindex record btrace bts
7373 @kindex record btrace pt
7379 @kindex rec btrace bts
7380 @kindex rec btrace pt
7383 @item record @var{method}
7384 This command starts the process record and replay target. The
7385 recording method can be specified as parameter. Without a parameter
7386 the command uses the @code{full} recording method. The following
7387 recording methods are available:
7391 Full record/replay recording using @value{GDBN}'s software record and
7392 replay implementation. This method allows replaying and reverse
7395 @item btrace @var{format}
7396 Hardware-supported instruction recording, supported on Intel
7397 processors. This method does not record data. Further, the data is
7398 collected in a ring buffer so old data will be overwritten when the
7399 buffer is full. It allows limited reverse execution. Variables and
7400 registers are not available during reverse execution. In remote
7401 debugging, recording continues on disconnect. Recorded data can be
7402 inspected after reconnecting. The recording may be stopped using
7405 The recording format can be specified as parameter. Without a parameter
7406 the command chooses the recording format. The following recording
7407 formats are available:
7411 @cindex branch trace store
7412 Use the @dfn{Branch Trace Store} (@acronym{BTS}) recording format. In
7413 this format, the processor stores a from/to record for each executed
7414 branch in the btrace ring buffer.
7417 @cindex Intel Processor Trace
7418 Use the @dfn{Intel Processor Trace} recording format. In this
7419 format, the processor stores the execution trace in a compressed form
7420 that is afterwards decoded by @value{GDBN}.
7422 The trace can be recorded with very low overhead. The compressed
7423 trace format also allows small trace buffers to already contain a big
7424 number of instructions compared to @acronym{BTS}.
7426 Decoding the recorded execution trace, on the other hand, is more
7427 expensive than decoding @acronym{BTS} trace. This is mostly due to the
7428 increased number of instructions to process. You should increase the
7429 buffer-size with care.
7432 Not all recording formats may be available on all processors.
7435 The process record and replay target can only debug a process that is
7436 already running. Therefore, you need first to start the process with
7437 the @kbd{run} or @kbd{start} commands, and then start the recording
7438 with the @kbd{record @var{method}} command.
7440 @cindex displaced stepping, and process record and replay
7441 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
7442 will be automatically disabled when process record and replay target
7443 is started. That's because the process record and replay target
7444 doesn't support displaced stepping.
7446 @cindex non-stop mode, and process record and replay
7447 @cindex asynchronous execution, and process record and replay
7448 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
7449 the asynchronous execution mode (@pxref{Background Execution}), not
7450 all recording methods are available. The @code{full} recording method
7451 does not support these two modes.
7456 Stop the process record and replay target. When process record and
7457 replay target stops, the entire execution log will be deleted and the
7458 inferior will either be terminated, or will remain in its final state.
7460 When you stop the process record and replay target in record mode (at
7461 the end of the execution log), the inferior will be stopped at the
7462 next instruction that would have been recorded. In other words, if
7463 you record for a while and then stop recording, the inferior process
7464 will be left in the same state as if the recording never happened.
7466 On the other hand, if the process record and replay target is stopped
7467 while in replay mode (that is, not at the end of the execution log,
7468 but at some earlier point), the inferior process will become ``live''
7469 at that earlier state, and it will then be possible to continue the
7470 usual ``live'' debugging of the process from that state.
7472 When the inferior process exits, or @value{GDBN} detaches from it,
7473 process record and replay target will automatically stop itself.
7477 Go to a specific location in the execution log. There are several
7478 ways to specify the location to go to:
7481 @item record goto begin
7482 @itemx record goto start
7483 Go to the beginning of the execution log.
7485 @item record goto end
7486 Go to the end of the execution log.
7488 @item record goto @var{n}
7489 Go to instruction number @var{n} in the execution log.
7493 @item record save @var{filename}
7494 Save the execution log to a file @file{@var{filename}}.
7495 Default filename is @file{gdb_record.@var{process_id}}, where
7496 @var{process_id} is the process ID of the inferior.
7498 This command may not be available for all recording methods.
7500 @kindex record restore
7501 @item record restore @var{filename}
7502 Restore the execution log from a file @file{@var{filename}}.
7503 File must have been created with @code{record save}.
7505 @kindex set record full
7506 @item set record full insn-number-max @var{limit}
7507 @itemx set record full insn-number-max unlimited
7508 Set the limit of instructions to be recorded for the @code{full}
7509 recording method. Default value is 200000.
7511 If @var{limit} is a positive number, then @value{GDBN} will start
7512 deleting instructions from the log once the number of the record
7513 instructions becomes greater than @var{limit}. For every new recorded
7514 instruction, @value{GDBN} will delete the earliest recorded
7515 instruction to keep the number of recorded instructions at the limit.
7516 (Since deleting recorded instructions loses information, @value{GDBN}
7517 lets you control what happens when the limit is reached, by means of
7518 the @code{stop-at-limit} option, described below.)
7520 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
7521 delete recorded instructions from the execution log. The number of
7522 recorded instructions is limited only by the available memory.
7524 @kindex show record full
7525 @item show record full insn-number-max
7526 Show the limit of instructions to be recorded with the @code{full}
7529 @item set record full stop-at-limit
7530 Control the behavior of the @code{full} recording method when the
7531 number of recorded instructions reaches the limit. If ON (the
7532 default), @value{GDBN} will stop when the limit is reached for the
7533 first time and ask you whether you want to stop the inferior or
7534 continue running it and recording the execution log. If you decide
7535 to continue recording, each new recorded instruction will cause the
7536 oldest one to be deleted.
7538 If this option is OFF, @value{GDBN} will automatically delete the
7539 oldest record to make room for each new one, without asking.
7541 @item show record full stop-at-limit
7542 Show the current setting of @code{stop-at-limit}.
7544 @item set record full memory-query
7545 Control the behavior when @value{GDBN} is unable to record memory
7546 changes caused by an instruction for the @code{full} recording method.
7547 If ON, @value{GDBN} will query whether to stop the inferior in that
7550 If this option is OFF (the default), @value{GDBN} will automatically
7551 ignore the effect of such instructions on memory. Later, when
7552 @value{GDBN} replays this execution log, it will mark the log of this
7553 instruction as not accessible, and it will not affect the replay
7556 @item show record full memory-query
7557 Show the current setting of @code{memory-query}.
7559 @kindex set record btrace
7560 The @code{btrace} record target does not trace data. As a
7561 convenience, when replaying, @value{GDBN} reads read-only memory off
7562 the live program directly, assuming that the addresses of the
7563 read-only areas don't change. This for example makes it possible to
7564 disassemble code while replaying, but not to print variables.
7565 In some cases, being able to inspect variables might be useful.
7566 You can use the following command for that:
7568 @item set record btrace replay-memory-access
7569 Control the behavior of the @code{btrace} recording method when
7570 accessing memory during replay. If @code{read-only} (the default),
7571 @value{GDBN} will only allow accesses to read-only memory.
7572 If @code{read-write}, @value{GDBN} will allow accesses to read-only
7573 and to read-write memory. Beware that the accessed memory corresponds
7574 to the live target and not necessarily to the current replay
7577 @item set record btrace cpu @var{identifier}
7578 Set the processor to be used for enabling workarounds for processor
7579 errata when decoding the trace.
7581 Processor errata are defects in processor operation, caused by its
7582 design or manufacture. They can cause a trace not to match the
7583 specification. This, in turn, may cause trace decode to fail.
7584 @value{GDBN} can detect erroneous trace packets and correct them, thus
7585 avoiding the decoding failures. These corrections are known as
7586 @dfn{errata workarounds}, and are enabled based on the processor on
7587 which the trace was recorded.
7589 By default, @value{GDBN} attempts to detect the processor
7590 automatically, and apply the necessary workarounds for it. However,
7591 you may need to specify the processor if @value{GDBN} does not yet
7592 support it. This command allows you to do that, and also allows to
7593 disable the workarounds.
7595 The argument @var{identifier} identifies the @sc{cpu} and is of the
7596 form: @code{@var{vendor}:@var{processor identifier}}. In addition,
7597 there are two special identifiers, @code{none} and @code{auto}
7600 The following vendor identifiers and corresponding processor
7601 identifiers are currently supported:
7603 @multitable @columnfractions .1 .9
7606 @tab @var{family}/@var{model}[/@var{stepping}]
7610 On GNU/Linux systems, the processor @var{family}, @var{model}, and
7611 @var{stepping} can be obtained from @code{/proc/cpuinfo}.
7613 If @var{identifier} is @code{auto}, enable errata workarounds for the
7614 processor on which the trace was recorded. If @var{identifier} is
7615 @code{none}, errata workarounds are disabled.
7617 For example, when using an old @value{GDBN} on a new system, decode
7618 may fail because @value{GDBN} does not support the new processor. It
7619 often suffices to specify an older processor that @value{GDBN}
7624 Active record target: record-btrace
7625 Recording format: Intel Processor Trace.
7627 Failed to configure the Intel Processor Trace decoder: unknown cpu.
7628 (gdb) set record btrace cpu intel:6/158
7630 Active record target: record-btrace
7631 Recording format: Intel Processor Trace.
7633 Recorded 84872 instructions in 3189 functions (0 gaps) for thread 1 (...).
7636 @kindex show record btrace
7637 @item show record btrace replay-memory-access
7638 Show the current setting of @code{replay-memory-access}.
7640 @item show record btrace cpu
7641 Show the processor to be used for enabling trace decode errata
7644 @kindex set record btrace bts
7645 @item set record btrace bts buffer-size @var{size}
7646 @itemx set record btrace bts buffer-size unlimited
7647 Set the requested ring buffer size for branch tracing in @acronym{BTS}
7648 format. Default is 64KB.
7650 If @var{size} is a positive number, then @value{GDBN} will try to
7651 allocate a buffer of at least @var{size} bytes for each new thread
7652 that uses the btrace recording method and the @acronym{BTS} format.
7653 The actually obtained buffer size may differ from the requested
7654 @var{size}. Use the @code{info record} command to see the actual
7655 buffer size for each thread that uses the btrace recording method and
7656 the @acronym{BTS} format.
7658 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
7659 allocate a buffer of 4MB.
7661 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
7662 also need longer to process the branch trace data before it can be used.
7664 @item show record btrace bts buffer-size @var{size}
7665 Show the current setting of the requested ring buffer size for branch
7666 tracing in @acronym{BTS} format.
7668 @kindex set record btrace pt
7669 @item set record btrace pt buffer-size @var{size}
7670 @itemx set record btrace pt buffer-size unlimited
7671 Set the requested ring buffer size for branch tracing in Intel
7672 Processor Trace format. Default is 16KB.
7674 If @var{size} is a positive number, then @value{GDBN} will try to
7675 allocate a buffer of at least @var{size} bytes for each new thread
7676 that uses the btrace recording method and the Intel Processor Trace
7677 format. The actually obtained buffer size may differ from the
7678 requested @var{size}. Use the @code{info record} command to see the
7679 actual buffer size for each thread.
7681 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
7682 allocate a buffer of 4MB.
7684 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
7685 also need longer to process the branch trace data before it can be used.
7687 @item show record btrace pt buffer-size @var{size}
7688 Show the current setting of the requested ring buffer size for branch
7689 tracing in Intel Processor Trace format.
7693 Show various statistics about the recording depending on the recording
7698 For the @code{full} recording method, it shows the state of process
7699 record and its in-memory execution log buffer, including:
7703 Whether in record mode or replay mode.
7705 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
7707 Highest recorded instruction number.
7709 Current instruction about to be replayed (if in replay mode).
7711 Number of instructions contained in the execution log.
7713 Maximum number of instructions that may be contained in the execution log.
7717 For the @code{btrace} recording method, it shows:
7723 Number of instructions that have been recorded.
7725 Number of blocks of sequential control-flow formed by the recorded
7728 Whether in record mode or replay mode.
7731 For the @code{bts} recording format, it also shows:
7734 Size of the perf ring buffer.
7737 For the @code{pt} recording format, it also shows:
7740 Size of the perf ring buffer.
7744 @kindex record delete
7747 When record target runs in replay mode (``in the past''), delete the
7748 subsequent execution log and begin to record a new execution log starting
7749 from the current address. This means you will abandon the previously
7750 recorded ``future'' and begin recording a new ``future''.
7752 @kindex record instruction-history
7753 @kindex rec instruction-history
7754 @item record instruction-history
7755 Disassembles instructions from the recorded execution log. By
7756 default, ten instructions are disassembled. This can be changed using
7757 the @code{set record instruction-history-size} command. Instructions
7758 are printed in execution order.
7760 It can also print mixed source+disassembly if you specify the the
7761 @code{/m} or @code{/s} modifier, and print the raw instructions in hex
7762 as well as in symbolic form by specifying the @code{/r} modifier.
7764 The current position marker is printed for the instruction at the
7765 current program counter value. This instruction can appear multiple
7766 times in the trace and the current position marker will be printed
7767 every time. To omit the current position marker, specify the
7770 To better align the printed instructions when the trace contains
7771 instructions from more than one function, the function name may be
7772 omitted by specifying the @code{/f} modifier.
7774 Speculatively executed instructions are prefixed with @samp{?}. This
7775 feature is not available for all recording formats.
7777 There are several ways to specify what part of the execution log to
7781 @item record instruction-history @var{insn}
7782 Disassembles ten instructions starting from instruction number
7785 @item record instruction-history @var{insn}, +/-@var{n}
7786 Disassembles @var{n} instructions around instruction number
7787 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
7788 @var{n} instructions after instruction number @var{insn}. If
7789 @var{n} is preceded with @code{-}, disassembles @var{n}
7790 instructions before instruction number @var{insn}.
7792 @item record instruction-history
7793 Disassembles ten more instructions after the last disassembly.
7795 @item record instruction-history -
7796 Disassembles ten more instructions before the last disassembly.
7798 @item record instruction-history @var{begin}, @var{end}
7799 Disassembles instructions beginning with instruction number
7800 @var{begin} until instruction number @var{end}. The instruction
7801 number @var{end} is included.
7804 This command may not be available for all recording methods.
7807 @item set record instruction-history-size @var{size}
7808 @itemx set record instruction-history-size unlimited
7809 Define how many instructions to disassemble in the @code{record
7810 instruction-history} command. The default value is 10.
7811 A @var{size} of @code{unlimited} means unlimited instructions.
7814 @item show record instruction-history-size
7815 Show how many instructions to disassemble in the @code{record
7816 instruction-history} command.
7818 @kindex record function-call-history
7819 @kindex rec function-call-history
7820 @item record function-call-history
7821 Prints the execution history at function granularity. It prints one
7822 line for each sequence of instructions that belong to the same
7823 function giving the name of that function, the source lines
7824 for this instruction sequence (if the @code{/l} modifier is
7825 specified), and the instructions numbers that form the sequence (if
7826 the @code{/i} modifier is specified). The function names are indented
7827 to reflect the call stack depth if the @code{/c} modifier is
7828 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be
7832 (@value{GDBP}) @b{list 1, 10}
7843 (@value{GDBP}) @b{record function-call-history /ilc}
7844 1 bar inst 1,4 at foo.c:6,8
7845 2 foo inst 5,10 at foo.c:2,3
7846 3 bar inst 11,13 at foo.c:9,10
7849 By default, ten lines are printed. This can be changed using the
7850 @code{set record function-call-history-size} command. Functions are
7851 printed in execution order. There are several ways to specify what
7855 @item record function-call-history @var{func}
7856 Prints ten functions starting from function number @var{func}.
7858 @item record function-call-history @var{func}, +/-@var{n}
7859 Prints @var{n} functions around function number @var{func}. If
7860 @var{n} is preceded with @code{+}, prints @var{n} functions after
7861 function number @var{func}. If @var{n} is preceded with @code{-},
7862 prints @var{n} functions before function number @var{func}.
7864 @item record function-call-history
7865 Prints ten more functions after the last ten-line print.
7867 @item record function-call-history -
7868 Prints ten more functions before the last ten-line print.
7870 @item record function-call-history @var{begin}, @var{end}
7871 Prints functions beginning with function number @var{begin} until
7872 function number @var{end}. The function number @var{end} is included.
7875 This command may not be available for all recording methods.
7877 @item set record function-call-history-size @var{size}
7878 @itemx set record function-call-history-size unlimited
7879 Define how many lines to print in the
7880 @code{record function-call-history} command. The default value is 10.
7881 A size of @code{unlimited} means unlimited lines.
7883 @item show record function-call-history-size
7884 Show how many lines to print in the
7885 @code{record function-call-history} command.
7890 @chapter Examining the Stack
7892 When your program has stopped, the first thing you need to know is where it
7893 stopped and how it got there.
7896 Each time your program performs a function call, information about the call
7898 That information includes the location of the call in your program,
7899 the arguments of the call,
7900 and the local variables of the function being called.
7901 The information is saved in a block of data called a @dfn{stack frame}.
7902 The stack frames are allocated in a region of memory called the @dfn{call
7905 When your program stops, the @value{GDBN} commands for examining the
7906 stack allow you to see all of this information.
7908 @cindex selected frame
7909 One of the stack frames is @dfn{selected} by @value{GDBN} and many
7910 @value{GDBN} commands refer implicitly to the selected frame. In
7911 particular, whenever you ask @value{GDBN} for the value of a variable in
7912 your program, the value is found in the selected frame. There are
7913 special @value{GDBN} commands to select whichever frame you are
7914 interested in. @xref{Selection, ,Selecting a Frame}.
7916 When your program stops, @value{GDBN} automatically selects the
7917 currently executing frame and describes it briefly, similar to the
7918 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
7921 * Frames:: Stack frames
7922 * Backtrace:: Backtraces
7923 * Selection:: Selecting a frame
7924 * Frame Info:: Information on a frame
7925 * Frame Apply:: Applying a command to several frames
7926 * Frame Filter Management:: Managing frame filters
7931 @section Stack Frames
7933 @cindex frame, definition
7935 The call stack is divided up into contiguous pieces called @dfn{stack
7936 frames}, or @dfn{frames} for short; each frame is the data associated
7937 with one call to one function. The frame contains the arguments given
7938 to the function, the function's local variables, and the address at
7939 which the function is executing.
7941 @cindex initial frame
7942 @cindex outermost frame
7943 @cindex innermost frame
7944 When your program is started, the stack has only one frame, that of the
7945 function @code{main}. This is called the @dfn{initial} frame or the
7946 @dfn{outermost} frame. Each time a function is called, a new frame is
7947 made. Each time a function returns, the frame for that function invocation
7948 is eliminated. If a function is recursive, there can be many frames for
7949 the same function. The frame for the function in which execution is
7950 actually occurring is called the @dfn{innermost} frame. This is the most
7951 recently created of all the stack frames that still exist.
7953 @cindex frame pointer
7954 Inside your program, stack frames are identified by their addresses. A
7955 stack frame consists of many bytes, each of which has its own address; each
7956 kind of computer has a convention for choosing one byte whose
7957 address serves as the address of the frame. Usually this address is kept
7958 in a register called the @dfn{frame pointer register}
7959 (@pxref{Registers, $fp}) while execution is going on in that frame.
7962 @cindex frame number
7963 @value{GDBN} labels each existing stack frame with a @dfn{level}, a
7964 number that is zero for the innermost frame, one for the frame that
7965 called it, and so on upward. These level numbers give you a way of
7966 designating stack frames in @value{GDBN} commands. The terms
7967 @dfn{frame number} and @dfn{frame level} can be used interchangeably to
7968 describe this number.
7970 @c The -fomit-frame-pointer below perennially causes hbox overflow
7971 @c underflow problems.
7972 @cindex frameless execution
7973 Some compilers provide a way to compile functions so that they operate
7974 without stack frames. (For example, the @value{NGCC} option
7976 @samp{-fomit-frame-pointer}
7978 generates functions without a frame.)
7979 This is occasionally done with heavily used library functions to save
7980 the frame setup time. @value{GDBN} has limited facilities for dealing
7981 with these function invocations. If the innermost function invocation
7982 has no stack frame, @value{GDBN} nevertheless regards it as though
7983 it had a separate frame, which is numbered zero as usual, allowing
7984 correct tracing of the function call chain. However, @value{GDBN} has
7985 no provision for frameless functions elsewhere in the stack.
7991 @cindex call stack traces
7992 A backtrace is a summary of how your program got where it is. It shows one
7993 line per frame, for many frames, starting with the currently executing
7994 frame (frame zero), followed by its caller (frame one), and on up the
7997 @anchor{backtrace-command}
7999 @kindex bt @r{(@code{backtrace})}
8000 To print a backtrace of the entire stack, use the @code{backtrace}
8001 command, or its alias @code{bt}. This command will print one line per
8002 frame for frames in the stack. By default, all stack frames are
8003 printed. You can stop the backtrace at any time by typing the system
8004 interrupt character, normally @kbd{Ctrl-c}.
8007 @item backtrace [@var{option}]@dots{} [@var{qualifier}]@dots{} [@var{count}]
8008 @itemx bt [@var{option}]@dots{} [@var{qualifier}]@dots{} [@var{count}]
8009 Print the backtrace of the entire stack.
8011 The optional @var{count} can be one of the following:
8016 Print only the innermost @var{n} frames, where @var{n} is a positive
8021 Print only the outermost @var{n} frames, where @var{n} is a positive
8029 Print the values of the local variables also. This can be combined
8030 with the optional @var{count} to limit the number of frames shown.
8033 Do not run Python frame filters on this backtrace. @xref{Frame
8034 Filter API}, for more information. Additionally use @ref{disable
8035 frame-filter all} to turn off all frame filters. This is only
8036 relevant when @value{GDBN} has been configured with @code{Python}
8040 A Python frame filter might decide to ``elide'' some frames. Normally
8041 such elided frames are still printed, but they are indented relative
8042 to the filtered frames that cause them to be elided. The @code{-hide}
8043 option causes elided frames to not be printed at all.
8046 The @code{backtrace} command also supports a number of options that
8047 allow overriding relevant global print settings as set by @code{set
8048 backtrace} and @code{set print} subcommands:
8051 @item -past-main [@code{on}|@code{off}]
8052 Set whether backtraces should continue past @code{main}. Related setting:
8053 @ref{set backtrace past-main}.
8055 @item -past-entry [@code{on}|@code{off}]
8056 Set whether backtraces should continue past the entry point of a program.
8057 Related setting: @ref{set backtrace past-entry}.
8059 @item -entry-values @code{no}|@code{only}|@code{preferred}|@code{if-needed}|@code{both}|@code{compact}|@code{default}
8060 Set printing of function arguments at function entry.
8061 Related setting: @ref{set print entry-values}.
8063 @item -frame-arguments @code{all}|@code{scalars}|@code{none}
8064 Set printing of non-scalar frame arguments.
8065 Related setting: @ref{set print frame-arguments}.
8067 @item -raw-frame-arguments [@code{on}|@code{off}]
8068 Set whether to print frame arguments in raw form.
8069 Related setting: @ref{set print raw-frame-arguments}.
8071 @item -frame-info @code{auto}|@code{source-line}|@code{location}|@code{source-and-location}|@code{location-and-address}|@code{short-location}
8072 Set printing of frame information.
8073 Related setting: @ref{set print frame-info}.
8076 The optional @var{qualifier} is maintained for backward compatibility.
8077 It can be one of the following:
8081 Equivalent to the @code{-full} option.
8084 Equivalent to the @code{-no-filters} option.
8087 Equivalent to the @code{-hide} option.
8094 The names @code{where} and @code{info stack} (abbreviated @code{info s})
8095 are additional aliases for @code{backtrace}.
8097 @cindex multiple threads, backtrace
8098 In a multi-threaded program, @value{GDBN} by default shows the
8099 backtrace only for the current thread. To display the backtrace for
8100 several or all of the threads, use the command @code{thread apply}
8101 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
8102 apply all backtrace}, @value{GDBN} will display the backtrace for all
8103 the threads; this is handy when you debug a core dump of a
8104 multi-threaded program.
8106 Each line in the backtrace shows the frame number and the function name.
8107 The program counter value is also shown---unless you use @code{set
8108 print address off}. The backtrace also shows the source file name and
8109 line number, as well as the arguments to the function. The program
8110 counter value is omitted if it is at the beginning of the code for that
8113 Here is an example of a backtrace. It was made with the command
8114 @samp{bt 3}, so it shows the innermost three frames.
8118 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
8120 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
8121 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
8123 (More stack frames follow...)
8128 The display for frame zero does not begin with a program counter
8129 value, indicating that your program has stopped at the beginning of the
8130 code for line @code{993} of @code{builtin.c}.
8133 The value of parameter @code{data} in frame 1 has been replaced by
8134 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
8135 only if it is a scalar (integer, pointer, enumeration, etc). See command
8136 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
8137 on how to configure the way function parameter values are printed.
8138 The command @kbd{set print frame-info} (@pxref{Print Settings}) controls
8139 what frame information is printed.
8141 @cindex optimized out, in backtrace
8142 @cindex function call arguments, optimized out
8143 If your program was compiled with optimizations, some compilers will
8144 optimize away arguments passed to functions if those arguments are
8145 never used after the call. Such optimizations generate code that
8146 passes arguments through registers, but doesn't store those arguments
8147 in the stack frame. @value{GDBN} has no way of displaying such
8148 arguments in stack frames other than the innermost one. Here's what
8149 such a backtrace might look like:
8153 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
8155 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
8156 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
8158 (More stack frames follow...)
8163 The values of arguments that were not saved in their stack frames are
8164 shown as @samp{<optimized out>}.
8166 If you need to display the values of such optimized-out arguments,
8167 either deduce that from other variables whose values depend on the one
8168 you are interested in, or recompile without optimizations.
8170 @cindex backtrace beyond @code{main} function
8171 @cindex program entry point
8172 @cindex startup code, and backtrace
8173 Most programs have a standard user entry point---a place where system
8174 libraries and startup code transition into user code. For C this is
8175 @code{main}@footnote{
8176 Note that embedded programs (the so-called ``free-standing''
8177 environment) are not required to have a @code{main} function as the
8178 entry point. They could even have multiple entry points.}.
8179 When @value{GDBN} finds the entry function in a backtrace
8180 it will terminate the backtrace, to avoid tracing into highly
8181 system-specific (and generally uninteresting) code.
8183 If you need to examine the startup code, or limit the number of levels
8184 in a backtrace, you can change this behavior:
8187 @item set backtrace past-main
8188 @itemx set backtrace past-main on
8189 @anchor{set backtrace past-main}
8190 @kindex set backtrace
8191 Backtraces will continue past the user entry point.
8193 @item set backtrace past-main off
8194 Backtraces will stop when they encounter the user entry point. This is the
8197 @item show backtrace past-main
8198 @kindex show backtrace
8199 Display the current user entry point backtrace policy.
8201 @item set backtrace past-entry
8202 @itemx set backtrace past-entry on
8203 @anchor{set backtrace past-entry}
8204 Backtraces will continue past the internal entry point of an application.
8205 This entry point is encoded by the linker when the application is built,
8206 and is likely before the user entry point @code{main} (or equivalent) is called.
8208 @item set backtrace past-entry off
8209 Backtraces will stop when they encounter the internal entry point of an
8210 application. This is the default.
8212 @item show backtrace past-entry
8213 Display the current internal entry point backtrace policy.
8215 @item set backtrace limit @var{n}
8216 @itemx set backtrace limit 0
8217 @itemx set backtrace limit unlimited
8218 @anchor{set backtrace limit}
8219 @cindex backtrace limit
8220 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
8221 or zero means unlimited levels.
8223 @item show backtrace limit
8224 Display the current limit on backtrace levels.
8227 You can control how file names are displayed.
8230 @item set filename-display
8231 @itemx set filename-display relative
8232 @cindex filename-display
8233 Display file names relative to the compilation directory. This is the default.
8235 @item set filename-display basename
8236 Display only basename of a filename.
8238 @item set filename-display absolute
8239 Display an absolute filename.
8241 @item show filename-display
8242 Show the current way to display filenames.
8246 @section Selecting a Frame
8248 Most commands for examining the stack and other data in your program work on
8249 whichever stack frame is selected at the moment. Here are the commands for
8250 selecting a stack frame; all of them finish by printing a brief description
8251 of the stack frame just selected.
8254 @kindex frame@r{, selecting}
8255 @kindex f @r{(@code{frame})}
8256 @item frame @r{[} @var{frame-selection-spec} @r{]}
8257 @item f @r{[} @var{frame-selection-spec} @r{]}
8258 The @command{frame} command allows different stack frames to be
8259 selected. The @var{frame-selection-spec} can be any of the following:
8264 @item level @var{num}
8265 Select frame level @var{num}. Recall that frame zero is the innermost
8266 (currently executing) frame, frame one is the frame that called the
8267 innermost one, and so on. The highest level frame is usually the one
8270 As this is the most common method of navigating the frame stack, the
8271 string @command{level} can be omitted. For example, the following two
8272 commands are equivalent:
8275 (@value{GDBP}) frame 3
8276 (@value{GDBP}) frame level 3
8279 @kindex frame address
8280 @item address @var{stack-address}
8281 Select the frame with stack address @var{stack-address}. The
8282 @var{stack-address} for a frame can be seen in the output of
8283 @command{info frame}, for example:
8287 Stack level 1, frame at 0x7fffffffda30:
8288 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
8289 tail call frame, caller of frame at 0x7fffffffda30
8290 source language c++.
8291 Arglist at unknown address.
8292 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
8295 The @var{stack-address} for this frame is @code{0x7fffffffda30} as
8296 indicated by the line:
8299 Stack level 1, frame at 0x7fffffffda30:
8302 @kindex frame function
8303 @item function @var{function-name}
8304 Select the stack frame for function @var{function-name}. If there are
8305 multiple stack frames for function @var{function-name} then the inner
8306 most stack frame is selected.
8309 @item view @var{stack-address} @r{[} @var{pc-addr} @r{]}
8310 View a frame that is not part of @value{GDBN}'s backtrace. The frame
8311 viewed has stack address @var{stack-addr}, and optionally, a program
8312 counter address of @var{pc-addr}.
8314 This is useful mainly if the chaining of stack frames has been
8315 damaged by a bug, making it impossible for @value{GDBN} to assign
8316 numbers properly to all frames. In addition, this can be useful
8317 when your program has multiple stacks and switches between them.
8319 When viewing a frame outside the current backtrace using
8320 @command{frame view} then you can always return to the original
8321 stack using one of the previous stack frame selection instructions,
8322 for example @command{frame level 0}.
8328 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
8329 numbers @var{n}, this advances toward the outermost frame, to higher
8330 frame numbers, to frames that have existed longer.
8333 @kindex do @r{(@code{down})}
8335 Move @var{n} frames down the stack; @var{n} defaults to 1. For
8336 positive numbers @var{n}, this advances toward the innermost frame, to
8337 lower frame numbers, to frames that were created more recently.
8338 You may abbreviate @code{down} as @code{do}.
8341 All of these commands end by printing two lines of output describing the
8342 frame. The first line shows the frame number, the function name, the
8343 arguments, and the source file and line number of execution in that
8344 frame. The second line shows the text of that source line.
8352 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
8354 10 read_input_file (argv[i]);
8358 After such a printout, the @code{list} command with no arguments
8359 prints ten lines centered on the point of execution in the frame.
8360 You can also edit the program at the point of execution with your favorite
8361 editing program by typing @code{edit}.
8362 @xref{List, ,Printing Source Lines},
8366 @kindex select-frame
8367 @item select-frame @r{[} @var{frame-selection-spec} @r{]}
8368 The @code{select-frame} command is a variant of @code{frame} that does
8369 not display the new frame after selecting it. This command is
8370 intended primarily for use in @value{GDBN} command scripts, where the
8371 output might be unnecessary and distracting. The
8372 @var{frame-selection-spec} is as for the @command{frame} command
8373 described in @ref{Selection, ,Selecting a Frame}.
8375 @kindex down-silently
8377 @item up-silently @var{n}
8378 @itemx down-silently @var{n}
8379 These two commands are variants of @code{up} and @code{down},
8380 respectively; they differ in that they do their work silently, without
8381 causing display of the new frame. They are intended primarily for use
8382 in @value{GDBN} command scripts, where the output might be unnecessary and
8387 @section Information About a Frame
8389 There are several other commands to print information about the selected
8395 When used without any argument, this command does not change which
8396 frame is selected, but prints a brief description of the currently
8397 selected stack frame. It can be abbreviated @code{f}. With an
8398 argument, this command is used to select a stack frame.
8399 @xref{Selection, ,Selecting a Frame}.
8402 @kindex info f @r{(@code{info frame})}
8405 This command prints a verbose description of the selected stack frame,
8410 the address of the frame
8412 the address of the next frame down (called by this frame)
8414 the address of the next frame up (caller of this frame)
8416 the language in which the source code corresponding to this frame is written
8418 the address of the frame's arguments
8420 the address of the frame's local variables
8422 the program counter saved in it (the address of execution in the caller frame)
8424 which registers were saved in the frame
8427 @noindent The verbose description is useful when
8428 something has gone wrong that has made the stack format fail to fit
8429 the usual conventions.
8431 @item info frame @r{[} @var{frame-selection-spec} @r{]}
8432 @itemx info f @r{[} @var{frame-selection-spec} @r{]}
8433 Print a verbose description of the frame selected by
8434 @var{frame-selection-spec}. The @var{frame-selection-spec} is the
8435 same as for the @command{frame} command (@pxref{Selection, ,Selecting
8436 a Frame}). The selected frame remains unchanged by this command.
8439 @item info args [-q]
8440 Print the arguments of the selected frame, each on a separate line.
8442 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
8443 printing header information and messages explaining why no argument
8446 @item info args [-q] [-t @var{type_regexp}] [@var{regexp}]
8447 Like @kbd{info args}, but only print the arguments selected
8448 with the provided regexp(s).
8450 If @var{regexp} is provided, print only the arguments whose names
8451 match the regular expression @var{regexp}.
8453 If @var{type_regexp} is provided, print only the arguments whose
8454 types, as printed by the @code{whatis} command, match
8455 the regular expression @var{type_regexp}.
8456 If @var{type_regexp} contains space(s), it should be enclosed in
8457 quote characters. If needed, use backslash to escape the meaning
8458 of special characters or quotes.
8460 If both @var{regexp} and @var{type_regexp} are provided, an argument
8461 is printed only if its name matches @var{regexp} and its type matches
8464 @item info locals [-q]
8466 Print the local variables of the selected frame, each on a separate
8467 line. These are all variables (declared either static or automatic)
8468 accessible at the point of execution of the selected frame.
8470 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
8471 printing header information and messages explaining why no local variables
8474 @item info locals [-q] [-t @var{type_regexp}] [@var{regexp}]
8475 Like @kbd{info locals}, but only print the local variables selected
8476 with the provided regexp(s).
8478 If @var{regexp} is provided, print only the local variables whose names
8479 match the regular expression @var{regexp}.
8481 If @var{type_regexp} is provided, print only the local variables whose
8482 types, as printed by the @code{whatis} command, match
8483 the regular expression @var{type_regexp}.
8484 If @var{type_regexp} contains space(s), it should be enclosed in
8485 quote characters. If needed, use backslash to escape the meaning
8486 of special characters or quotes.
8488 If both @var{regexp} and @var{type_regexp} are provided, a local variable
8489 is printed only if its name matches @var{regexp} and its type matches
8492 The command @kbd{info locals -q -t @var{type_regexp}} can usefully be
8493 combined with the commands @kbd{frame apply} and @kbd{thread apply}.
8494 For example, your program might use Resource Acquisition Is
8495 Initialization types (RAII) such as @code{lock_something_t}: each
8496 local variable of type @code{lock_something_t} automatically places a
8497 lock that is destroyed when the variable goes out of scope. You can
8498 then list all acquired locks in your program by doing
8500 thread apply all -s frame apply all -s info locals -q -t lock_something_t
8503 or the equivalent shorter form
8505 tfaas i lo -q -t lock_something_t
8511 @section Applying a Command to Several Frames.
8513 @cindex apply command to several frames
8515 @item frame apply [all | @var{count} | @var{-count} | level @var{level}@dots{}] [@var{option}]@dots{} @var{command}
8516 The @code{frame apply} command allows you to apply the named
8517 @var{command} to one or more frames.
8521 Specify @code{all} to apply @var{command} to all frames.
8524 Use @var{count} to apply @var{command} to the innermost @var{count}
8525 frames, where @var{count} is a positive number.
8528 Use @var{-count} to apply @var{command} to the outermost @var{count}
8529 frames, where @var{count} is a positive number.
8532 Use @code{level} to apply @var{command} to the set of frames identified
8533 by the @var{level} list. @var{level} is a frame level or a range of frame
8534 levels as @var{level1}-@var{level2}. The frame level is the number shown
8535 in the first field of the @samp{backtrace} command output.
8536 E.g., @samp{2-4 6-8 3} indicates to apply @var{command} for the frames
8537 at levels 2, 3, 4, 6, 7, 8, and then again on frame at level 3.
8541 Note that the frames on which @code{frame apply} applies a command are
8542 also influenced by the @code{set backtrace} settings such as @code{set
8543 backtrace past-main} and @code{set backtrace limit N}.
8544 @xref{Backtrace,,Backtraces}.
8546 The @code{frame apply} command also supports a number of options that
8547 allow overriding relevant @code{set backtrace} settings:
8550 @item -past-main [@code{on}|@code{off}]
8551 Whether backtraces should continue past @code{main}.
8552 Related setting: @ref{set backtrace past-main}.
8554 @item -past-entry [@code{on}|@code{off}]
8555 Whether backtraces should continue past the entry point of a program.
8556 Related setting: @ref{set backtrace past-entry}.
8559 By default, @value{GDBN} displays some frame information before the
8560 output produced by @var{command}, and an error raised during the
8561 execution of a @var{command} will abort @code{frame apply}. The
8562 following options can be used to fine-tune these behaviors:
8566 The flag @code{-c}, which stands for @samp{continue}, causes any
8567 errors in @var{command} to be displayed, and the execution of
8568 @code{frame apply} then continues.
8570 The flag @code{-s}, which stands for @samp{silent}, causes any errors
8571 or empty output produced by a @var{command} to be silently ignored.
8572 That is, the execution continues, but the frame information and errors
8575 The flag @code{-q} (@samp{quiet}) disables printing the frame
8579 The following example shows how the flags @code{-c} and @code{-s} are
8580 working when applying the command @code{p j} to all frames, where
8581 variable @code{j} can only be successfully printed in the outermost
8582 @code{#1 main} frame.
8586 (gdb) frame apply all p j
8587 #0 some_function (i=5) at fun.c:4
8588 No symbol "j" in current context.
8589 (gdb) frame apply all -c p j
8590 #0 some_function (i=5) at fun.c:4
8591 No symbol "j" in current context.
8592 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8594 (gdb) frame apply all -s p j
8595 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8601 By default, @samp{frame apply}, prints the frame location
8602 information before the command output:
8606 (gdb) frame apply all p $sp
8607 #0 some_function (i=5) at fun.c:4
8608 $4 = (void *) 0xffffd1e0
8609 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8610 $5 = (void *) 0xffffd1f0
8615 If the flag @code{-q} is given, no frame information is printed:
8618 (gdb) frame apply all -q p $sp
8619 $12 = (void *) 0xffffd1e0
8620 $13 = (void *) 0xffffd1f0
8630 @cindex apply a command to all frames (ignoring errors and empty output)
8631 @item faas @var{command}
8632 Shortcut for @code{frame apply all -s @var{command}}.
8633 Applies @var{command} on all frames, ignoring errors and empty output.
8635 It can for example be used to print a local variable or a function
8636 argument without knowing the frame where this variable or argument
8639 (@value{GDBP}) faas p some_local_var_i_do_not_remember_where_it_is
8642 The @code{faas} command accepts the same options as the @code{frame
8643 apply} command. @xref{Frame Apply,,frame apply}.
8645 Note that the command @code{tfaas @var{command}} applies @var{command}
8646 on all frames of all threads. See @xref{Threads,,Threads}.
8650 @node Frame Filter Management
8651 @section Management of Frame Filters.
8652 @cindex managing frame filters
8654 Frame filters are Python based utilities to manage and decorate the
8655 output of frames. @xref{Frame Filter API}, for further information.
8657 Managing frame filters is performed by several commands available
8658 within @value{GDBN}, detailed here.
8661 @kindex info frame-filter
8662 @item info frame-filter
8663 Print a list of installed frame filters from all dictionaries, showing
8664 their name, priority and enabled status.
8666 @kindex disable frame-filter
8667 @anchor{disable frame-filter all}
8668 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
8669 Disable a frame filter in the dictionary matching
8670 @var{filter-dictionary} and @var{filter-name}. The
8671 @var{filter-dictionary} may be @code{all}, @code{global},
8672 @code{progspace}, or the name of the object file where the frame filter
8673 dictionary resides. When @code{all} is specified, all frame filters
8674 across all dictionaries are disabled. The @var{filter-name} is the name
8675 of the frame filter and is used when @code{all} is not the option for
8676 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
8677 may be enabled again later.
8679 @kindex enable frame-filter
8680 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
8681 Enable a frame filter in the dictionary matching
8682 @var{filter-dictionary} and @var{filter-name}. The
8683 @var{filter-dictionary} may be @code{all}, @code{global},
8684 @code{progspace} or the name of the object file where the frame filter
8685 dictionary resides. When @code{all} is specified, all frame filters across
8686 all dictionaries are enabled. The @var{filter-name} is the name of the frame
8687 filter and is used when @code{all} is not the option for
8688 @var{filter-dictionary}.
8693 (gdb) info frame-filter
8695 global frame-filters:
8696 Priority Enabled Name
8697 1000 No PrimaryFunctionFilter
8700 progspace /build/test frame-filters:
8701 Priority Enabled Name
8702 100 Yes ProgspaceFilter
8704 objfile /build/test frame-filters:
8705 Priority Enabled Name
8706 999 Yes BuildProgramFilter
8708 (gdb) disable frame-filter /build/test BuildProgramFilter
8709 (gdb) info frame-filter
8711 global frame-filters:
8712 Priority Enabled Name
8713 1000 No PrimaryFunctionFilter
8716 progspace /build/test frame-filters:
8717 Priority Enabled Name
8718 100 Yes ProgspaceFilter
8720 objfile /build/test frame-filters:
8721 Priority Enabled Name
8722 999 No BuildProgramFilter
8724 (gdb) enable frame-filter global PrimaryFunctionFilter
8725 (gdb) info frame-filter
8727 global frame-filters:
8728 Priority Enabled Name
8729 1000 Yes PrimaryFunctionFilter
8732 progspace /build/test frame-filters:
8733 Priority Enabled Name
8734 100 Yes ProgspaceFilter
8736 objfile /build/test frame-filters:
8737 Priority Enabled Name
8738 999 No BuildProgramFilter
8741 @kindex set frame-filter priority
8742 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
8743 Set the @var{priority} of a frame filter in the dictionary matching
8744 @var{filter-dictionary}, and the frame filter name matching
8745 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
8746 @code{progspace} or the name of the object file where the frame filter
8747 dictionary resides. The @var{priority} is an integer.
8749 @kindex show frame-filter priority
8750 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
8751 Show the @var{priority} of a frame filter in the dictionary matching
8752 @var{filter-dictionary}, and the frame filter name matching
8753 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
8754 @code{progspace} or the name of the object file where the frame filter
8760 (gdb) info frame-filter
8762 global frame-filters:
8763 Priority Enabled Name
8764 1000 Yes PrimaryFunctionFilter
8767 progspace /build/test frame-filters:
8768 Priority Enabled Name
8769 100 Yes ProgspaceFilter
8771 objfile /build/test frame-filters:
8772 Priority Enabled Name
8773 999 No BuildProgramFilter
8775 (gdb) set frame-filter priority global Reverse 50
8776 (gdb) info frame-filter
8778 global frame-filters:
8779 Priority Enabled Name
8780 1000 Yes PrimaryFunctionFilter
8783 progspace /build/test frame-filters:
8784 Priority Enabled Name
8785 100 Yes ProgspaceFilter
8787 objfile /build/test frame-filters:
8788 Priority Enabled Name
8789 999 No BuildProgramFilter
8794 @chapter Examining Source Files
8796 @value{GDBN} can print parts of your program's source, since the debugging
8797 information recorded in the program tells @value{GDBN} what source files were
8798 used to build it. When your program stops, @value{GDBN} spontaneously prints
8799 the line where it stopped. Likewise, when you select a stack frame
8800 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
8801 execution in that frame has stopped. You can print other portions of
8802 source files by explicit command.
8804 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
8805 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
8806 @value{GDBN} under @sc{gnu} Emacs}.
8809 * List:: Printing source lines
8810 * Specify Location:: How to specify code locations
8811 * Edit:: Editing source files
8812 * Search:: Searching source files
8813 * Source Path:: Specifying source directories
8814 * Machine Code:: Source and machine code
8818 @section Printing Source Lines
8821 @kindex l @r{(@code{list})}
8822 To print lines from a source file, use the @code{list} command
8823 (abbreviated @code{l}). By default, ten lines are printed.
8824 There are several ways to specify what part of the file you want to
8825 print; see @ref{Specify Location}, for the full list.
8827 Here are the forms of the @code{list} command most commonly used:
8830 @item list @var{linenum}
8831 Print lines centered around line number @var{linenum} in the
8832 current source file.
8834 @item list @var{function}
8835 Print lines centered around the beginning of function
8839 Print more lines. If the last lines printed were printed with a
8840 @code{list} command, this prints lines following the last lines
8841 printed; however, if the last line printed was a solitary line printed
8842 as part of displaying a stack frame (@pxref{Stack, ,Examining the
8843 Stack}), this prints lines centered around that line.
8846 Print lines just before the lines last printed.
8849 @cindex @code{list}, how many lines to display
8850 By default, @value{GDBN} prints ten source lines with any of these forms of
8851 the @code{list} command. You can change this using @code{set listsize}:
8854 @kindex set listsize
8855 @item set listsize @var{count}
8856 @itemx set listsize unlimited
8857 Make the @code{list} command display @var{count} source lines (unless
8858 the @code{list} argument explicitly specifies some other number).
8859 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
8861 @kindex show listsize
8863 Display the number of lines that @code{list} prints.
8866 Repeating a @code{list} command with @key{RET} discards the argument,
8867 so it is equivalent to typing just @code{list}. This is more useful
8868 than listing the same lines again. An exception is made for an
8869 argument of @samp{-}; that argument is preserved in repetition so that
8870 each repetition moves up in the source file.
8872 In general, the @code{list} command expects you to supply zero, one or two
8873 @dfn{locations}. Locations specify source lines; there are several ways
8874 of writing them (@pxref{Specify Location}), but the effect is always
8875 to specify some source line.
8877 Here is a complete description of the possible arguments for @code{list}:
8880 @item list @var{location}
8881 Print lines centered around the line specified by @var{location}.
8883 @item list @var{first},@var{last}
8884 Print lines from @var{first} to @var{last}. Both arguments are
8885 locations. When a @code{list} command has two locations, and the
8886 source file of the second location is omitted, this refers to
8887 the same source file as the first location.
8889 @item list ,@var{last}
8890 Print lines ending with @var{last}.
8892 @item list @var{first},
8893 Print lines starting with @var{first}.
8896 Print lines just after the lines last printed.
8899 Print lines just before the lines last printed.
8902 As described in the preceding table.
8905 @node Specify Location
8906 @section Specifying a Location
8907 @cindex specifying location
8909 @cindex source location
8911 Several @value{GDBN} commands accept arguments that specify a location
8912 of your program's code. Since @value{GDBN} is a source-level
8913 debugger, a location usually specifies some line in the source code.
8914 Locations may be specified using three different formats:
8915 linespec locations, explicit locations, or address locations.
8918 * Linespec Locations:: Linespec locations
8919 * Explicit Locations:: Explicit locations
8920 * Address Locations:: Address locations
8923 @node Linespec Locations
8924 @subsection Linespec Locations
8925 @cindex linespec locations
8927 A @dfn{linespec} is a colon-separated list of source location parameters such
8928 as file name, function name, etc. Here are all the different ways of
8929 specifying a linespec:
8933 Specifies the line number @var{linenum} of the current source file.
8936 @itemx +@var{offset}
8937 Specifies the line @var{offset} lines before or after the @dfn{current
8938 line}. For the @code{list} command, the current line is the last one
8939 printed; for the breakpoint commands, this is the line at which
8940 execution stopped in the currently selected @dfn{stack frame}
8941 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
8942 used as the second of the two linespecs in a @code{list} command,
8943 this specifies the line @var{offset} lines up or down from the first
8946 @item @var{filename}:@var{linenum}
8947 Specifies the line @var{linenum} in the source file @var{filename}.
8948 If @var{filename} is a relative file name, then it will match any
8949 source file name with the same trailing components. For example, if
8950 @var{filename} is @samp{gcc/expr.c}, then it will match source file
8951 name of @file{/build/trunk/gcc/expr.c}, but not
8952 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
8954 @item @var{function}
8955 Specifies the line that begins the body of the function @var{function}.
8956 For example, in C, this is the line with the open brace.
8958 By default, in C@t{++} and Ada, @var{function} is interpreted as
8959 specifying all functions named @var{function} in all scopes. For
8960 C@t{++}, this means in all namespaces and classes. For Ada, this
8961 means in all packages.
8963 For example, assuming a program with C@t{++} symbols named
8964 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
8965 func}} and @w{@kbd{break B::func}} set a breakpoint on both symbols.
8967 Commands that accept a linespec let you override this with the
8968 @code{-qualified} option. For example, @w{@kbd{break -qualified
8969 func}} sets a breakpoint on a free-function named @code{func} ignoring
8970 any C@t{++} class methods and namespace functions called @code{func}.
8972 @xref{Explicit Locations}.
8974 @item @var{function}:@var{label}
8975 Specifies the line where @var{label} appears in @var{function}.
8977 @item @var{filename}:@var{function}
8978 Specifies the line that begins the body of the function @var{function}
8979 in the file @var{filename}. You only need the file name with a
8980 function name to avoid ambiguity when there are identically named
8981 functions in different source files.
8984 Specifies the line at which the label named @var{label} appears
8985 in the function corresponding to the currently selected stack frame.
8986 If there is no current selected stack frame (for instance, if the inferior
8987 is not running), then @value{GDBN} will not search for a label.
8989 @cindex breakpoint at static probe point
8990 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
8991 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
8992 applications to embed static probes. @xref{Static Probe Points}, for more
8993 information on finding and using static probes. This form of linespec
8994 specifies the location of such a static probe.
8996 If @var{objfile} is given, only probes coming from that shared library
8997 or executable matching @var{objfile} as a regular expression are considered.
8998 If @var{provider} is given, then only probes from that provider are considered.
8999 If several probes match the spec, @value{GDBN} will insert a breakpoint at
9000 each one of those probes.
9003 @node Explicit Locations
9004 @subsection Explicit Locations
9005 @cindex explicit locations
9007 @dfn{Explicit locations} allow the user to directly specify the source
9008 location's parameters using option-value pairs.
9010 Explicit locations are useful when several functions, labels, or
9011 file names have the same name (base name for files) in the program's
9012 sources. In these cases, explicit locations point to the source
9013 line you meant more accurately and unambiguously. Also, using
9014 explicit locations might be faster in large programs.
9016 For example, the linespec @samp{foo:bar} may refer to a function @code{bar}
9017 defined in the file named @file{foo} or the label @code{bar} in a function
9018 named @code{foo}. @value{GDBN} must search either the file system or
9019 the symbol table to know.
9021 The list of valid explicit location options is summarized in the
9025 @item -source @var{filename}
9026 The value specifies the source file name. To differentiate between
9027 files with the same base name, prepend as many directories as is necessary
9028 to uniquely identify the desired file, e.g., @file{foo/bar/baz.c}. Otherwise
9029 @value{GDBN} will use the first file it finds with the given base
9030 name. This option requires the use of either @code{-function} or @code{-line}.
9032 @item -function @var{function}
9033 The value specifies the name of a function. Operations
9034 on function locations unmodified by other options (such as @code{-label}
9035 or @code{-line}) refer to the line that begins the body of the function.
9036 In C, for example, this is the line with the open brace.
9038 By default, in C@t{++} and Ada, @var{function} is interpreted as
9039 specifying all functions named @var{function} in all scopes. For
9040 C@t{++}, this means in all namespaces and classes. For Ada, this
9041 means in all packages.
9043 For example, assuming a program with C@t{++} symbols named
9044 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
9045 -function func}} and @w{@kbd{break -function B::func}} set a
9046 breakpoint on both symbols.
9048 You can use the @kbd{-qualified} flag to override this (see below).
9052 This flag makes @value{GDBN} interpret a function name specified with
9053 @kbd{-function} as a complete fully-qualified name.
9055 For example, assuming a C@t{++} program with symbols named
9056 @code{A::B::func} and @code{B::func}, the @w{@kbd{break -qualified
9057 -function B::func}} command sets a breakpoint on @code{B::func}, only.
9059 (Note: the @kbd{-qualified} option can precede a linespec as well
9060 (@pxref{Linespec Locations}), so the particular example above could be
9061 simplified as @w{@kbd{break -qualified B::func}}.)
9063 @item -label @var{label}
9064 The value specifies the name of a label. When the function
9065 name is not specified, the label is searched in the function of the currently
9066 selected stack frame.
9068 @item -line @var{number}
9069 The value specifies a line offset for the location. The offset may either
9070 be absolute (@code{-line 3}) or relative (@code{-line +3}), depending on
9071 the command. When specified without any other options, the line offset is
9072 relative to the current line.
9075 Explicit location options may be abbreviated by omitting any non-unique
9076 trailing characters from the option name, e.g., @w{@kbd{break -s main.c -li 3}}.
9078 @node Address Locations
9079 @subsection Address Locations
9080 @cindex address locations
9082 @dfn{Address locations} indicate a specific program address. They have
9083 the generalized form *@var{address}.
9085 For line-oriented commands, such as @code{list} and @code{edit}, this
9086 specifies a source line that contains @var{address}. For @code{break} and
9087 other breakpoint-oriented commands, this can be used to set breakpoints in
9088 parts of your program which do not have debugging information or
9091 Here @var{address} may be any expression valid in the current working
9092 language (@pxref{Languages, working language}) that specifies a code
9093 address. In addition, as a convenience, @value{GDBN} extends the
9094 semantics of expressions used in locations to cover several situations
9095 that frequently occur during debugging. Here are the various forms
9099 @item @var{expression}
9100 Any expression valid in the current working language.
9102 @item @var{funcaddr}
9103 An address of a function or procedure derived from its name. In C,
9104 C@t{++}, Objective-C, Fortran, minimal, and assembly, this is
9105 simply the function's name @var{function} (and actually a special case
9106 of a valid expression). In Pascal and Modula-2, this is
9107 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
9108 (although the Pascal form also works).
9110 This form specifies the address of the function's first instruction,
9111 before the stack frame and arguments have been set up.
9113 @item '@var{filename}':@var{funcaddr}
9114 Like @var{funcaddr} above, but also specifies the name of the source
9115 file explicitly. This is useful if the name of the function does not
9116 specify the function unambiguously, e.g., if there are several
9117 functions with identical names in different source files.
9121 @section Editing Source Files
9122 @cindex editing source files
9125 @kindex e @r{(@code{edit})}
9126 To edit the lines in a source file, use the @code{edit} command.
9127 The editing program of your choice
9128 is invoked with the current line set to
9129 the active line in the program.
9130 Alternatively, there are several ways to specify what part of the file you
9131 want to print if you want to see other parts of the program:
9134 @item edit @var{location}
9135 Edit the source file specified by @code{location}. Editing starts at
9136 that @var{location}, e.g., at the specified source line of the
9137 specified file. @xref{Specify Location}, for all the possible forms
9138 of the @var{location} argument; here are the forms of the @code{edit}
9139 command most commonly used:
9142 @item edit @var{number}
9143 Edit the current source file with @var{number} as the active line number.
9145 @item edit @var{function}
9146 Edit the file containing @var{function} at the beginning of its definition.
9151 @subsection Choosing your Editor
9152 You can customize @value{GDBN} to use any editor you want
9154 The only restriction is that your editor (say @code{ex}), recognizes the
9155 following command-line syntax:
9157 ex +@var{number} file
9159 The optional numeric value +@var{number} specifies the number of the line in
9160 the file where to start editing.}.
9161 By default, it is @file{@value{EDITOR}}, but you can change this
9162 by setting the environment variable @code{EDITOR} before using
9163 @value{GDBN}. For example, to configure @value{GDBN} to use the
9164 @code{vi} editor, you could use these commands with the @code{sh} shell:
9170 or in the @code{csh} shell,
9172 setenv EDITOR /usr/bin/vi
9177 @section Searching Source Files
9178 @cindex searching source files
9180 There are two commands for searching through the current source file for a
9185 @kindex forward-search
9186 @kindex fo @r{(@code{forward-search})}
9187 @item forward-search @var{regexp}
9188 @itemx search @var{regexp}
9189 The command @samp{forward-search @var{regexp}} checks each line,
9190 starting with the one following the last line listed, for a match for
9191 @var{regexp}. It lists the line that is found. You can use the
9192 synonym @samp{search @var{regexp}} or abbreviate the command name as
9195 @kindex reverse-search
9196 @item reverse-search @var{regexp}
9197 The command @samp{reverse-search @var{regexp}} checks each line, starting
9198 with the one before the last line listed and going backward, for a match
9199 for @var{regexp}. It lists the line that is found. You can abbreviate
9200 this command as @code{rev}.
9204 @section Specifying Source Directories
9207 @cindex directories for source files
9208 Executable programs sometimes do not record the directories of the source
9209 files from which they were compiled, just the names. Even when they do,
9210 the directories could be moved between the compilation and your debugging
9211 session. @value{GDBN} has a list of directories to search for source files;
9212 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
9213 it tries all the directories in the list, in the order they are present
9214 in the list, until it finds a file with the desired name.
9216 For example, suppose an executable references the file
9217 @file{/usr/src/foo-1.0/lib/foo.c}, does not record a compilation
9218 directory, and the @dfn{source path} is @file{/mnt/cross}.
9219 @value{GDBN} would look for the source file in the following
9224 @item @file{/usr/src/foo-1.0/lib/foo.c}
9225 @item @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c}
9226 @item @file{/mnt/cross/foo.c}
9230 If the source file is not present at any of the above locations then
9231 an error is printed. @value{GDBN} does not look up the parts of the
9232 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
9233 Likewise, the subdirectories of the source path are not searched: if
9234 the source path is @file{/mnt/cross}, and the binary refers to
9235 @file{foo.c}, @value{GDBN} would not find it under
9236 @file{/mnt/cross/usr/src/foo-1.0/lib}.
9238 Plain file names, relative file names with leading directories, file
9239 names containing dots, etc.@: are all treated as described above,
9240 except that non-absolute file names are not looked up literally. If
9241 the @dfn{source path} is @file{/mnt/cross}, the source file is
9242 recorded as @file{../lib/foo.c}, and no compilation directory is
9243 recorded, then @value{GDBN} will search in the following locations:
9247 @item @file{/mnt/cross/../lib/foo.c}
9248 @item @file{/mnt/cross/foo.c}
9254 @vindex $cdir@r{, convenience variable}
9255 @vindex $cwd@r{, convenience variable}
9256 @cindex compilation directory
9257 @cindex current directory
9258 @cindex working directory
9259 @cindex directory, current
9260 @cindex directory, compilation
9261 The @dfn{source path} will always include two special entries
9262 @samp{$cdir} and @samp{$cwd}, these refer to the compilation directory
9263 (if one is recorded) and the current working directory respectively.
9265 @samp{$cdir} causes @value{GDBN} to search within the compilation
9266 directory, if one is recorded in the debug information. If no
9267 compilation directory is recorded in the debug information then
9268 @samp{$cdir} is ignored.
9270 @samp{$cwd} is not the same as @samp{.}---the former tracks the
9271 current working directory as it changes during your @value{GDBN}
9272 session, while the latter is immediately expanded to the current
9273 directory at the time you add an entry to the source path.
9275 If a compilation directory is recorded in the debug information, and
9276 @value{GDBN} has not found the source file after the first search
9277 using @dfn{source path}, then @value{GDBN} will combine the
9278 compilation directory and the filename, and then search for the source
9279 file again using the @dfn{source path}.
9281 For example, if the executable records the source file as
9282 @file{/usr/src/foo-1.0/lib/foo.c}, the compilation directory is
9283 recorded as @file{/project/build}, and the @dfn{source path} is
9284 @file{/mnt/cross:$cdir:$cwd} while the current working directory of
9285 the @value{GDBN} session is @file{/home/user}, then @value{GDBN} will
9286 search for the source file in the following locations:
9290 @item @file{/usr/src/foo-1.0/lib/foo.c}
9291 @item @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c}
9292 @item @file{/project/build/usr/src/foo-1.0/lib/foo.c}
9293 @item @file{/home/user/usr/src/foo-1.0/lib/foo.c}
9294 @item @file{/mnt/cross/project/build/usr/src/foo-1.0/lib/foo.c}
9295 @item @file{/project/build/project/build/usr/src/foo-1.0/lib/foo.c}
9296 @item @file{/home/user/project/build/usr/src/foo-1.0/lib/foo.c}
9297 @item @file{/mnt/cross/foo.c}
9298 @item @file{/project/build/foo.c}
9299 @item @file{/home/user/foo.c}
9303 If the file name in the previous example had been recorded in the
9304 executable as a relative path rather than an absolute path, then the
9305 first look up would not have occurred, but all of the remaining steps
9308 When searching for source files on MS-DOS and MS-Windows, where
9309 absolute paths start with a drive letter (e.g.
9310 @file{C:/project/foo.c}), @value{GDBN} will remove the drive letter
9311 from the file name before appending it to a search directory from
9312 @dfn{source path}; for instance if the executable references the
9313 source file @file{C:/project/foo.c} and @dfn{source path} is set to
9314 @file{D:/mnt/cross}, then @value{GDBN} will search in the following
9315 locations for the source file:
9319 @item @file{C:/project/foo.c}
9320 @item @file{D:/mnt/cross/project/foo.c}
9321 @item @file{D:/mnt/cross/foo.c}
9325 Note that the executable search path is @emph{not} used to locate the
9328 Whenever you reset or rearrange the source path, @value{GDBN} clears out
9329 any information it has cached about where source files are found and where
9330 each line is in the file.
9334 When you start @value{GDBN}, its source path includes only @samp{$cdir}
9335 and @samp{$cwd}, in that order.
9336 To add other directories, use the @code{directory} command.
9338 The search path is used to find both program source files and @value{GDBN}
9339 script files (read using the @samp{-command} option and @samp{source} command).
9341 In addition to the source path, @value{GDBN} provides a set of commands
9342 that manage a list of source path substitution rules. A @dfn{substitution
9343 rule} specifies how to rewrite source directories stored in the program's
9344 debug information in case the sources were moved to a different
9345 directory between compilation and debugging. A rule is made of
9346 two strings, the first specifying what needs to be rewritten in
9347 the path, and the second specifying how it should be rewritten.
9348 In @ref{set substitute-path}, we name these two parts @var{from} and
9349 @var{to} respectively. @value{GDBN} does a simple string replacement
9350 of @var{from} with @var{to} at the start of the directory part of the
9351 source file name, and uses that result instead of the original file
9352 name to look up the sources.
9354 Using the previous example, suppose the @file{foo-1.0} tree has been
9355 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
9356 @value{GDBN} to replace @file{/usr/src} in all source path names with
9357 @file{/mnt/cross}. The first lookup will then be
9358 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
9359 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
9360 substitution rule, use the @code{set substitute-path} command
9361 (@pxref{set substitute-path}).
9363 To avoid unexpected substitution results, a rule is applied only if the
9364 @var{from} part of the directory name ends at a directory separator.
9365 For instance, a rule substituting @file{/usr/source} into
9366 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
9367 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
9368 is applied only at the beginning of the directory name, this rule will
9369 not be applied to @file{/root/usr/source/baz.c} either.
9371 In many cases, you can achieve the same result using the @code{directory}
9372 command. However, @code{set substitute-path} can be more efficient in
9373 the case where the sources are organized in a complex tree with multiple
9374 subdirectories. With the @code{directory} command, you need to add each
9375 subdirectory of your project. If you moved the entire tree while
9376 preserving its internal organization, then @code{set substitute-path}
9377 allows you to direct the debugger to all the sources with one single
9380 @code{set substitute-path} is also more than just a shortcut command.
9381 The source path is only used if the file at the original location no
9382 longer exists. On the other hand, @code{set substitute-path} modifies
9383 the debugger behavior to look at the rewritten location instead. So, if
9384 for any reason a source file that is not relevant to your executable is
9385 located at the original location, a substitution rule is the only
9386 method available to point @value{GDBN} at the new location.
9388 @cindex @samp{--with-relocated-sources}
9389 @cindex default source path substitution
9390 You can configure a default source path substitution rule by
9391 configuring @value{GDBN} with the
9392 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
9393 should be the name of a directory under @value{GDBN}'s configured
9394 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
9395 directory names in debug information under @var{dir} will be adjusted
9396 automatically if the installed @value{GDBN} is moved to a new
9397 location. This is useful if @value{GDBN}, libraries or executables
9398 with debug information and corresponding source code are being moved
9402 @item directory @var{dirname} @dots{}
9403 @item dir @var{dirname} @dots{}
9404 Add directory @var{dirname} to the front of the source path. Several
9405 directory names may be given to this command, separated by @samp{:}
9406 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
9407 part of absolute file names) or
9408 whitespace. You may specify a directory that is already in the source
9409 path; this moves it forward, so @value{GDBN} searches it sooner.
9411 The special strings @samp{$cdir} (to refer to the compilation
9412 directory, if one is recorded), and @samp{$cwd} (to refer to the
9413 current working directory) can also be included in the list of
9414 directories @var{dirname}. Though these will already be in the source
9415 path they will be moved forward in the list so @value{GDBN} searches
9419 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
9421 @c RET-repeat for @code{directory} is explicitly disabled, but since
9422 @c repeating it would be a no-op we do not say that. (thanks to RMS)
9424 @item set directories @var{path-list}
9425 @kindex set directories
9426 Set the source path to @var{path-list}.
9427 @samp{$cdir:$cwd} are added if missing.
9429 @item show directories
9430 @kindex show directories
9431 Print the source path: show which directories it contains.
9433 @anchor{set substitute-path}
9434 @item set substitute-path @var{from} @var{to}
9435 @kindex set substitute-path
9436 Define a source path substitution rule, and add it at the end of the
9437 current list of existing substitution rules. If a rule with the same
9438 @var{from} was already defined, then the old rule is also deleted.
9440 For example, if the file @file{/foo/bar/baz.c} was moved to
9441 @file{/mnt/cross/baz.c}, then the command
9444 (@value{GDBP}) set substitute-path /foo/bar /mnt/cross
9448 will tell @value{GDBN} to replace @samp{/foo/bar} with
9449 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
9450 @file{baz.c} even though it was moved.
9452 In the case when more than one substitution rule have been defined,
9453 the rules are evaluated one by one in the order where they have been
9454 defined. The first one matching, if any, is selected to perform
9457 For instance, if we had entered the following commands:
9460 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
9461 (@value{GDBP}) set substitute-path /usr/src /mnt/src
9465 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
9466 @file{/mnt/include/defs.h} by using the first rule. However, it would
9467 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
9468 @file{/mnt/src/lib/foo.c}.
9471 @item unset substitute-path [path]
9472 @kindex unset substitute-path
9473 If a path is specified, search the current list of substitution rules
9474 for a rule that would rewrite that path. Delete that rule if found.
9475 A warning is emitted by the debugger if no rule could be found.
9477 If no path is specified, then all substitution rules are deleted.
9479 @item show substitute-path [path]
9480 @kindex show substitute-path
9481 If a path is specified, then print the source path substitution rule
9482 which would rewrite that path, if any.
9484 If no path is specified, then print all existing source path substitution
9489 If your source path is cluttered with directories that are no longer of
9490 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
9491 versions of source. You can correct the situation as follows:
9495 Use @code{directory} with no argument to reset the source path to its default value.
9498 Use @code{directory} with suitable arguments to reinstall the
9499 directories you want in the source path. You can add all the
9500 directories in one command.
9504 @section Source and Machine Code
9505 @cindex source line and its code address
9507 You can use the command @code{info line} to map source lines to program
9508 addresses (and vice versa), and the command @code{disassemble} to display
9509 a range of addresses as machine instructions. You can use the command
9510 @code{set disassemble-next-line} to set whether to disassemble next
9511 source line when execution stops. When run under @sc{gnu} Emacs
9512 mode, the @code{info line} command causes the arrow to point to the
9513 line specified. Also, @code{info line} prints addresses in symbolic form as
9519 @itemx info line @var{location}
9520 Print the starting and ending addresses of the compiled code for
9521 source line @var{location}. You can specify source lines in any of
9522 the ways documented in @ref{Specify Location}. With no @var{location}
9523 information about the current source line is printed.
9526 For example, we can use @code{info line} to discover the location of
9527 the object code for the first line of function
9528 @code{m4_changequote}:
9531 (@value{GDBP}) info line m4_changequote
9532 Line 895 of "builtin.c" starts at pc 0x634c <m4_changequote> and \
9533 ends at 0x6350 <m4_changequote+4>.
9537 @cindex code address and its source line
9538 We can also inquire (using @code{*@var{addr}} as the form for
9539 @var{location}) what source line covers a particular address:
9541 (@value{GDBP}) info line *0x63ff
9542 Line 926 of "builtin.c" starts at pc 0x63e4 <m4_changequote+152> and \
9543 ends at 0x6404 <m4_changequote+184>.
9546 @cindex @code{$_} and @code{info line}
9547 @cindex @code{x} command, default address
9548 @kindex x@r{(examine), and} info line
9549 After @code{info line}, the default address for the @code{x} command
9550 is changed to the starting address of the line, so that @samp{x/i} is
9551 sufficient to begin examining the machine code (@pxref{Memory,
9552 ,Examining Memory}). Also, this address is saved as the value of the
9553 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
9556 @cindex info line, repeated calls
9557 After @code{info line}, using @code{info line} again without
9558 specifying a location will display information about the next source
9563 @cindex assembly instructions
9564 @cindex instructions, assembly
9565 @cindex machine instructions
9566 @cindex listing machine instructions
9568 @itemx disassemble /m
9569 @itemx disassemble /s
9570 @itemx disassemble /r
9571 This specialized command dumps a range of memory as machine
9572 instructions. It can also print mixed source+disassembly by specifying
9573 the @code{/m} or @code{/s} modifier and print the raw instructions in hex
9574 as well as in symbolic form by specifying the @code{/r} modifier.
9575 The default memory range is the function surrounding the
9576 program counter of the selected frame. A single argument to this
9577 command is a program counter value; @value{GDBN} dumps the function
9578 surrounding this value. When two arguments are given, they should
9579 be separated by a comma, possibly surrounded by whitespace. The
9580 arguments specify a range of addresses to dump, in one of two forms:
9583 @item @var{start},@var{end}
9584 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
9585 @item @var{start},+@var{length}
9586 the addresses from @var{start} (inclusive) to
9587 @code{@var{start}+@var{length}} (exclusive).
9591 When 2 arguments are specified, the name of the function is also
9592 printed (since there could be several functions in the given range).
9594 The argument(s) can be any expression yielding a numeric value, such as
9595 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
9597 If the range of memory being disassembled contains current program counter,
9598 the instruction at that location is shown with a @code{=>} marker.
9601 The following example shows the disassembly of a range of addresses of
9602 HP PA-RISC 2.0 code:
9605 (@value{GDBP}) disas 0x32c4, 0x32e4
9606 Dump of assembler code from 0x32c4 to 0x32e4:
9607 0x32c4 <main+204>: addil 0,dp
9608 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
9609 0x32cc <main+212>: ldil 0x3000,r31
9610 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
9611 0x32d4 <main+220>: ldo 0(r31),rp
9612 0x32d8 <main+224>: addil -0x800,dp
9613 0x32dc <main+228>: ldo 0x588(r1),r26
9614 0x32e0 <main+232>: ldil 0x3000,r31
9615 End of assembler dump.
9618 Here is an example showing mixed source+assembly for Intel x86
9619 with @code{/m} or @code{/s}, when the program is stopped just after
9620 function prologue in a non-optimized function with no inline code.
9623 (@value{GDBP}) disas /m main
9624 Dump of assembler code for function main:
9626 0x08048330 <+0>: push %ebp
9627 0x08048331 <+1>: mov %esp,%ebp
9628 0x08048333 <+3>: sub $0x8,%esp
9629 0x08048336 <+6>: and $0xfffffff0,%esp
9630 0x08048339 <+9>: sub $0x10,%esp
9632 6 printf ("Hello.\n");
9633 => 0x0804833c <+12>: movl $0x8048440,(%esp)
9634 0x08048343 <+19>: call 0x8048284 <puts@@plt>
9638 0x08048348 <+24>: mov $0x0,%eax
9639 0x0804834d <+29>: leave
9640 0x0804834e <+30>: ret
9642 End of assembler dump.
9645 The @code{/m} option is deprecated as its output is not useful when
9646 there is either inlined code or re-ordered code.
9647 The @code{/s} option is the preferred choice.
9648 Here is an example for AMD x86-64 showing the difference between
9649 @code{/m} output and @code{/s} output.
9650 This example has one inline function defined in a header file,
9651 and the code is compiled with @samp{-O2} optimization.
9652 Note how the @code{/m} output is missing the disassembly of
9653 several instructions that are present in the @code{/s} output.
9683 (@value{GDBP}) disas /m main
9684 Dump of assembler code for function main:
9688 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
9689 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
9693 0x000000000040041d <+29>: xor %eax,%eax
9694 0x000000000040041f <+31>: retq
9695 0x0000000000400420 <+32>: add %eax,%eax
9696 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
9698 End of assembler dump.
9699 (@value{GDBP}) disas /s main
9700 Dump of assembler code for function main:
9704 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
9708 0x0000000000400406 <+6>: test %eax,%eax
9709 0x0000000000400408 <+8>: js 0x400420 <main+32>
9714 0x000000000040040a <+10>: lea 0xa(%rax),%edx
9715 0x000000000040040d <+13>: test %eax,%eax
9716 0x000000000040040f <+15>: mov $0x1,%eax
9717 0x0000000000400414 <+20>: cmovne %edx,%eax
9721 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
9725 0x000000000040041d <+29>: xor %eax,%eax
9726 0x000000000040041f <+31>: retq
9730 0x0000000000400420 <+32>: add %eax,%eax
9731 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
9732 End of assembler dump.
9735 Here is another example showing raw instructions in hex for AMD x86-64,
9738 (gdb) disas /r 0x400281,+10
9739 Dump of assembler code from 0x400281 to 0x40028b:
9740 0x0000000000400281: 38 36 cmp %dh,(%rsi)
9741 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
9742 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
9743 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
9744 End of assembler dump.
9747 Addresses cannot be specified as a location (@pxref{Specify Location}).
9748 So, for example, if you want to disassemble function @code{bar}
9749 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
9750 and not @samp{disassemble foo.c:bar}.
9752 Some architectures have more than one commonly-used set of instruction
9753 mnemonics or other syntax.
9755 For programs that were dynamically linked and use shared libraries,
9756 instructions that call functions or branch to locations in the shared
9757 libraries might show a seemingly bogus location---it's actually a
9758 location of the relocation table. On some architectures, @value{GDBN}
9759 might be able to resolve these to actual function names.
9762 @kindex set disassembler-options
9763 @cindex disassembler options
9764 @item set disassembler-options @var{option1}[,@var{option2}@dots{}]
9765 This command controls the passing of target specific information to
9766 the disassembler. For a list of valid options, please refer to the
9767 @code{-M}/@code{--disassembler-options} section of the @samp{objdump}
9768 manual and/or the output of @kbd{objdump --help}
9769 (@pxref{objdump,,objdump,binutils,The GNU Binary Utilities}).
9770 The default value is the empty string.
9772 If it is necessary to specify more than one disassembler option, then
9773 multiple options can be placed together into a comma separated list.
9774 Currently this command is only supported on targets ARM, MIPS, PowerPC
9777 @kindex show disassembler-options
9778 @item show disassembler-options
9779 Show the current setting of the disassembler options.
9783 @kindex set disassembly-flavor
9784 @cindex Intel disassembly flavor
9785 @cindex AT&T disassembly flavor
9786 @item set disassembly-flavor @var{instruction-set}
9787 Select the instruction set to use when disassembling the
9788 program via the @code{disassemble} or @code{x/i} commands.
9790 Currently this command is only defined for the Intel x86 family. You
9791 can set @var{instruction-set} to either @code{intel} or @code{att}.
9792 The default is @code{att}, the AT&T flavor used by default by Unix
9793 assemblers for x86-based targets.
9795 @kindex show disassembly-flavor
9796 @item show disassembly-flavor
9797 Show the current setting of the disassembly flavor.
9801 @kindex set disassemble-next-line
9802 @kindex show disassemble-next-line
9803 @item set disassemble-next-line
9804 @itemx show disassemble-next-line
9805 Control whether or not @value{GDBN} will disassemble the next source
9806 line or instruction when execution stops. If ON, @value{GDBN} will
9807 display disassembly of the next source line when execution of the
9808 program being debugged stops. This is @emph{in addition} to
9809 displaying the source line itself, which @value{GDBN} always does if
9810 possible. If the next source line cannot be displayed for some reason
9811 (e.g., if @value{GDBN} cannot find the source file, or there's no line
9812 info in the debug info), @value{GDBN} will display disassembly of the
9813 next @emph{instruction} instead of showing the next source line. If
9814 AUTO, @value{GDBN} will display disassembly of next instruction only
9815 if the source line cannot be displayed. This setting causes
9816 @value{GDBN} to display some feedback when you step through a function
9817 with no line info or whose source file is unavailable. The default is
9818 OFF, which means never display the disassembly of the next line or
9824 @chapter Examining Data
9826 @cindex printing data
9827 @cindex examining data
9830 The usual way to examine data in your program is with the @code{print}
9831 command (abbreviated @code{p}), or its synonym @code{inspect}. It
9832 evaluates and prints the value of an expression of the language your
9833 program is written in (@pxref{Languages, ,Using @value{GDBN} with
9834 Different Languages}). It may also print the expression using a
9835 Python-based pretty-printer (@pxref{Pretty Printing}).
9838 @item print [[@var{options}] --] @var{expr}
9839 @itemx print [[@var{options}] --] /@var{f} @var{expr}
9840 @var{expr} is an expression (in the source language). By default the
9841 value of @var{expr} is printed in a format appropriate to its data type;
9842 you can choose a different format by specifying @samp{/@var{f}}, where
9843 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
9846 @anchor{print options}
9847 The @code{print} command supports a number of options that allow
9848 overriding relevant global print settings as set by @code{set print}
9852 @item -address [@code{on}|@code{off}]
9853 Set printing of addresses.
9854 Related setting: @ref{set print address}.
9856 @item -array [@code{on}|@code{off}]
9857 Pretty formatting of arrays.
9858 Related setting: @ref{set print array}.
9860 @item -array-indexes [@code{on}|@code{off}]
9861 Set printing of array indexes.
9862 Related setting: @ref{set print array-indexes}.
9864 @item -elements @var{number-of-elements}|@code{unlimited}
9865 Set limit on string chars or array elements to print. The value
9866 @code{unlimited} causes there to be no limit. Related setting:
9867 @ref{set print elements}.
9869 @item -max-depth @var{depth}|@code{unlimited}
9870 Set the threshold after which nested structures are replaced with
9871 ellipsis. Related setting: @ref{set print max-depth}.
9873 @item -null-stop [@code{on}|@code{off}]
9874 Set printing of char arrays to stop at first null char. Related
9875 setting: @ref{set print null-stop}.
9877 @item -object [@code{on}|@code{off}]
9878 Set printing C@t{++} virtual function tables. Related setting:
9879 @ref{set print object}.
9881 @item -pretty [@code{on}|@code{off}]
9882 Set pretty formatting of structures. Related setting: @ref{set print
9885 @item -raw-values [@code{on}|@code{off}]
9886 Set whether to print values in raw form, bypassing any
9887 pretty-printers for that value. Related setting: @ref{set print
9890 @item -repeats @var{number-of-repeats}|@code{unlimited}
9891 Set threshold for repeated print elements. @code{unlimited} causes
9892 all elements to be individually printed. Related setting: @ref{set
9895 @item -static-members [@code{on}|@code{off}]
9896 Set printing C@t{++} static members. Related setting: @ref{set print
9899 @item -symbol [@code{on}|@code{off}]
9900 Set printing of symbol names when printing pointers. Related setting:
9901 @ref{set print symbol}.
9903 @item -union [@code{on}|@code{off}]
9904 Set printing of unions interior to structures. Related setting:
9905 @ref{set print union}.
9907 @item -vtbl [@code{on}|@code{off}]
9908 Set printing of C++ virtual function tables. Related setting:
9909 @ref{set print vtbl}.
9912 Because the @code{print} command accepts arbitrary expressions which
9913 may look like options (including abbreviations), if you specify any
9914 command option, then you must use a double dash (@code{--}) to mark
9915 the end of option processing.
9917 For example, this prints the value of the @code{-p} expression:
9920 (@value{GDBP}) print -p
9923 While this repeats the last value in the value history (see below)
9924 with the @code{-pretty} option in effect:
9927 (@value{GDBP}) print -p --
9930 Here is an example including both on option and an expression:
9934 (@value{GDBP}) print -pretty -- *myptr
9946 @item print [@var{options}]
9947 @itemx print [@var{options}] /@var{f}
9948 @cindex reprint the last value
9949 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
9950 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
9951 conveniently inspect the same value in an alternative format.
9954 A more low-level way of examining data is with the @code{x} command.
9955 It examines data in memory at a specified address and prints it in a
9956 specified format. @xref{Memory, ,Examining Memory}.
9958 If you are interested in information about types, or about how the
9959 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
9960 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
9963 @cindex exploring hierarchical data structures
9965 Another way of examining values of expressions and type information is
9966 through the Python extension command @code{explore} (available only if
9967 the @value{GDBN} build is configured with @code{--with-python}). It
9968 offers an interactive way to start at the highest level (or, the most
9969 abstract level) of the data type of an expression (or, the data type
9970 itself) and explore all the way down to leaf scalar values/fields
9971 embedded in the higher level data types.
9974 @item explore @var{arg}
9975 @var{arg} is either an expression (in the source language), or a type
9976 visible in the current context of the program being debugged.
9979 The working of the @code{explore} command can be illustrated with an
9980 example. If a data type @code{struct ComplexStruct} is defined in your
9990 struct ComplexStruct
9992 struct SimpleStruct *ss_p;
9998 followed by variable declarations as
10001 struct SimpleStruct ss = @{ 10, 1.11 @};
10002 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
10006 then, the value of the variable @code{cs} can be explored using the
10007 @code{explore} command as follows.
10011 The value of `cs' is a struct/class of type `struct ComplexStruct' with
10012 the following fields:
10014 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
10015 arr = <Enter 1 to explore this field of type `int [10]'>
10017 Enter the field number of choice:
10021 Since the fields of @code{cs} are not scalar values, you are being
10022 prompted to chose the field you want to explore. Let's say you choose
10023 the field @code{ss_p} by entering @code{0}. Then, since this field is a
10024 pointer, you will be asked if it is pointing to a single value. From
10025 the declaration of @code{cs} above, it is indeed pointing to a single
10026 value, hence you enter @code{y}. If you enter @code{n}, then you will
10027 be asked if it were pointing to an array of values, in which case this
10028 field will be explored as if it were an array.
10031 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
10032 Continue exploring it as a pointer to a single value [y/n]: y
10033 The value of `*(cs.ss_p)' is a struct/class of type `struct
10034 SimpleStruct' with the following fields:
10036 i = 10 .. (Value of type `int')
10037 d = 1.1100000000000001 .. (Value of type `double')
10039 Press enter to return to parent value:
10043 If the field @code{arr} of @code{cs} was chosen for exploration by
10044 entering @code{1} earlier, then since it is as array, you will be
10045 prompted to enter the index of the element in the array that you want
10049 `cs.arr' is an array of `int'.
10050 Enter the index of the element you want to explore in `cs.arr': 5
10052 `(cs.arr)[5]' is a scalar value of type `int'.
10056 Press enter to return to parent value:
10059 In general, at any stage of exploration, you can go deeper towards the
10060 leaf values by responding to the prompts appropriately, or hit the
10061 return key to return to the enclosing data structure (the @i{higher}
10062 level data structure).
10064 Similar to exploring values, you can use the @code{explore} command to
10065 explore types. Instead of specifying a value (which is typically a
10066 variable name or an expression valid in the current context of the
10067 program being debugged), you specify a type name. If you consider the
10068 same example as above, your can explore the type
10069 @code{struct ComplexStruct} by passing the argument
10070 @code{struct ComplexStruct} to the @code{explore} command.
10073 (gdb) explore struct ComplexStruct
10077 By responding to the prompts appropriately in the subsequent interactive
10078 session, you can explore the type @code{struct ComplexStruct} in a
10079 manner similar to how the value @code{cs} was explored in the above
10082 The @code{explore} command also has two sub-commands,
10083 @code{explore value} and @code{explore type}. The former sub-command is
10084 a way to explicitly specify that value exploration of the argument is
10085 being invoked, while the latter is a way to explicitly specify that type
10086 exploration of the argument is being invoked.
10089 @item explore value @var{expr}
10090 @cindex explore value
10091 This sub-command of @code{explore} explores the value of the
10092 expression @var{expr} (if @var{expr} is an expression valid in the
10093 current context of the program being debugged). The behavior of this
10094 command is identical to that of the behavior of the @code{explore}
10095 command being passed the argument @var{expr}.
10097 @item explore type @var{arg}
10098 @cindex explore type
10099 This sub-command of @code{explore} explores the type of @var{arg} (if
10100 @var{arg} is a type visible in the current context of program being
10101 debugged), or the type of the value/expression @var{arg} (if @var{arg}
10102 is an expression valid in the current context of the program being
10103 debugged). If @var{arg} is a type, then the behavior of this command is
10104 identical to that of the @code{explore} command being passed the
10105 argument @var{arg}. If @var{arg} is an expression, then the behavior of
10106 this command will be identical to that of the @code{explore} command
10107 being passed the type of @var{arg} as the argument.
10111 * Expressions:: Expressions
10112 * Ambiguous Expressions:: Ambiguous Expressions
10113 * Variables:: Program variables
10114 * Arrays:: Artificial arrays
10115 * Output Formats:: Output formats
10116 * Memory:: Examining memory
10117 * Auto Display:: Automatic display
10118 * Print Settings:: Print settings
10119 * Pretty Printing:: Python pretty printing
10120 * Value History:: Value history
10121 * Convenience Vars:: Convenience variables
10122 * Convenience Funs:: Convenience functions
10123 * Registers:: Registers
10124 * Floating Point Hardware:: Floating point hardware
10125 * Vector Unit:: Vector Unit
10126 * OS Information:: Auxiliary data provided by operating system
10127 * Memory Region Attributes:: Memory region attributes
10128 * Dump/Restore Files:: Copy between memory and a file
10129 * Core File Generation:: Cause a program dump its core
10130 * Character Sets:: Debugging programs that use a different
10131 character set than GDB does
10132 * Caching Target Data:: Data caching for targets
10133 * Searching Memory:: Searching memory for a sequence of bytes
10134 * Value Sizes:: Managing memory allocated for values
10138 @section Expressions
10140 @cindex expressions
10141 @code{print} and many other @value{GDBN} commands accept an expression and
10142 compute its value. Any kind of constant, variable or operator defined
10143 by the programming language you are using is valid in an expression in
10144 @value{GDBN}. This includes conditional expressions, function calls,
10145 casts, and string constants. It also includes preprocessor macros, if
10146 you compiled your program to include this information; see
10149 @cindex arrays in expressions
10150 @value{GDBN} supports array constants in expressions input by
10151 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
10152 you can use the command @code{print @{1, 2, 3@}} to create an array
10153 of three integers. If you pass an array to a function or assign it
10154 to a program variable, @value{GDBN} copies the array to memory that
10155 is @code{malloc}ed in the target program.
10157 Because C is so widespread, most of the expressions shown in examples in
10158 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
10159 Languages}, for information on how to use expressions in other
10162 In this section, we discuss operators that you can use in @value{GDBN}
10163 expressions regardless of your programming language.
10165 @cindex casts, in expressions
10166 Casts are supported in all languages, not just in C, because it is so
10167 useful to cast a number into a pointer in order to examine a structure
10168 at that address in memory.
10169 @c FIXME: casts supported---Mod2 true?
10171 @value{GDBN} supports these operators, in addition to those common
10172 to programming languages:
10176 @samp{@@} is a binary operator for treating parts of memory as arrays.
10177 @xref{Arrays, ,Artificial Arrays}, for more information.
10180 @samp{::} allows you to specify a variable in terms of the file or
10181 function where it is defined. @xref{Variables, ,Program Variables}.
10183 @cindex @{@var{type}@}
10184 @cindex type casting memory
10185 @cindex memory, viewing as typed object
10186 @cindex casts, to view memory
10187 @item @{@var{type}@} @var{addr}
10188 Refers to an object of type @var{type} stored at address @var{addr} in
10189 memory. The address @var{addr} may be any expression whose value is
10190 an integer or pointer (but parentheses are required around binary
10191 operators, just as in a cast). This construct is allowed regardless
10192 of what kind of data is normally supposed to reside at @var{addr}.
10195 @node Ambiguous Expressions
10196 @section Ambiguous Expressions
10197 @cindex ambiguous expressions
10199 Expressions can sometimes contain some ambiguous elements. For instance,
10200 some programming languages (notably Ada, C@t{++} and Objective-C) permit
10201 a single function name to be defined several times, for application in
10202 different contexts. This is called @dfn{overloading}. Another example
10203 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
10204 templates and is typically instantiated several times, resulting in
10205 the same function name being defined in different contexts.
10207 In some cases and depending on the language, it is possible to adjust
10208 the expression to remove the ambiguity. For instance in C@t{++}, you
10209 can specify the signature of the function you want to break on, as in
10210 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
10211 qualified name of your function often makes the expression unambiguous
10214 When an ambiguity that needs to be resolved is detected, the debugger
10215 has the capability to display a menu of numbered choices for each
10216 possibility, and then waits for the selection with the prompt @samp{>}.
10217 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
10218 aborts the current command. If the command in which the expression was
10219 used allows more than one choice to be selected, the next option in the
10220 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
10223 For example, the following session excerpt shows an attempt to set a
10224 breakpoint at the overloaded symbol @code{String::after}.
10225 We choose three particular definitions of that function name:
10227 @c FIXME! This is likely to change to show arg type lists, at least
10230 (@value{GDBP}) b String::after
10233 [2] file:String.cc; line number:867
10234 [3] file:String.cc; line number:860
10235 [4] file:String.cc; line number:875
10236 [5] file:String.cc; line number:853
10237 [6] file:String.cc; line number:846
10238 [7] file:String.cc; line number:735
10240 Breakpoint 1 at 0xb26c: file String.cc, line 867.
10241 Breakpoint 2 at 0xb344: file String.cc, line 875.
10242 Breakpoint 3 at 0xafcc: file String.cc, line 846.
10243 Multiple breakpoints were set.
10244 Use the "delete" command to delete unwanted
10251 @kindex set multiple-symbols
10252 @item set multiple-symbols @var{mode}
10253 @cindex multiple-symbols menu
10255 This option allows you to adjust the debugger behavior when an expression
10258 By default, @var{mode} is set to @code{all}. If the command with which
10259 the expression is used allows more than one choice, then @value{GDBN}
10260 automatically selects all possible choices. For instance, inserting
10261 a breakpoint on a function using an ambiguous name results in a breakpoint
10262 inserted on each possible match. However, if a unique choice must be made,
10263 then @value{GDBN} uses the menu to help you disambiguate the expression.
10264 For instance, printing the address of an overloaded function will result
10265 in the use of the menu.
10267 When @var{mode} is set to @code{ask}, the debugger always uses the menu
10268 when an ambiguity is detected.
10270 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
10271 an error due to the ambiguity and the command is aborted.
10273 @kindex show multiple-symbols
10274 @item show multiple-symbols
10275 Show the current value of the @code{multiple-symbols} setting.
10279 @section Program Variables
10281 The most common kind of expression to use is the name of a variable
10284 Variables in expressions are understood in the selected stack frame
10285 (@pxref{Selection, ,Selecting a Frame}); they must be either:
10289 global (or file-static)
10296 visible according to the scope rules of the
10297 programming language from the point of execution in that frame
10300 @noindent This means that in the function
10315 you can examine and use the variable @code{a} whenever your program is
10316 executing within the function @code{foo}, but you can only use or
10317 examine the variable @code{b} while your program is executing inside
10318 the block where @code{b} is declared.
10320 @cindex variable name conflict
10321 There is an exception: you can refer to a variable or function whose
10322 scope is a single source file even if the current execution point is not
10323 in this file. But it is possible to have more than one such variable or
10324 function with the same name (in different source files). If that
10325 happens, referring to that name has unpredictable effects. If you wish,
10326 you can specify a static variable in a particular function or file by
10327 using the colon-colon (@code{::}) notation:
10329 @cindex colon-colon, context for variables/functions
10331 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
10332 @cindex @code{::}, context for variables/functions
10335 @var{file}::@var{variable}
10336 @var{function}::@var{variable}
10340 Here @var{file} or @var{function} is the name of the context for the
10341 static @var{variable}. In the case of file names, you can use quotes to
10342 make sure @value{GDBN} parses the file name as a single word---for example,
10343 to print a global value of @code{x} defined in @file{f2.c}:
10346 (@value{GDBP}) p 'f2.c'::x
10349 The @code{::} notation is normally used for referring to
10350 static variables, since you typically disambiguate uses of local variables
10351 in functions by selecting the appropriate frame and using the
10352 simple name of the variable. However, you may also use this notation
10353 to refer to local variables in frames enclosing the selected frame:
10362 process (a); /* Stop here */
10373 For example, if there is a breakpoint at the commented line,
10374 here is what you might see
10375 when the program stops after executing the call @code{bar(0)}:
10380 (@value{GDBP}) p bar::a
10382 (@value{GDBP}) up 2
10383 #2 0x080483d0 in foo (a=5) at foobar.c:12
10386 (@value{GDBP}) p bar::a
10390 @cindex C@t{++} scope resolution
10391 These uses of @samp{::} are very rarely in conflict with the very
10392 similar use of the same notation in C@t{++}. When they are in
10393 conflict, the C@t{++} meaning takes precedence; however, this can be
10394 overridden by quoting the file or function name with single quotes.
10396 For example, suppose the program is stopped in a method of a class
10397 that has a field named @code{includefile}, and there is also an
10398 include file named @file{includefile} that defines a variable,
10399 @code{some_global}.
10402 (@value{GDBP}) p includefile
10404 (@value{GDBP}) p includefile::some_global
10405 A syntax error in expression, near `'.
10406 (@value{GDBP}) p 'includefile'::some_global
10410 @cindex wrong values
10411 @cindex variable values, wrong
10412 @cindex function entry/exit, wrong values of variables
10413 @cindex optimized code, wrong values of variables
10415 @emph{Warning:} Occasionally, a local variable may appear to have the
10416 wrong value at certain points in a function---just after entry to a new
10417 scope, and just before exit.
10419 You may see this problem when you are stepping by machine instructions.
10420 This is because, on most machines, it takes more than one instruction to
10421 set up a stack frame (including local variable definitions); if you are
10422 stepping by machine instructions, variables may appear to have the wrong
10423 values until the stack frame is completely built. On exit, it usually
10424 also takes more than one machine instruction to destroy a stack frame;
10425 after you begin stepping through that group of instructions, local
10426 variable definitions may be gone.
10428 This may also happen when the compiler does significant optimizations.
10429 To be sure of always seeing accurate values, turn off all optimization
10432 @cindex ``No symbol "foo" in current context''
10433 Another possible effect of compiler optimizations is to optimize
10434 unused variables out of existence, or assign variables to registers (as
10435 opposed to memory addresses). Depending on the support for such cases
10436 offered by the debug info format used by the compiler, @value{GDBN}
10437 might not be able to display values for such local variables. If that
10438 happens, @value{GDBN} will print a message like this:
10441 No symbol "foo" in current context.
10444 To solve such problems, either recompile without optimizations, or use a
10445 different debug info format, if the compiler supports several such
10446 formats. @xref{Compilation}, for more information on choosing compiler
10447 options. @xref{C, ,C and C@t{++}}, for more information about debug
10448 info formats that are best suited to C@t{++} programs.
10450 If you ask to print an object whose contents are unknown to
10451 @value{GDBN}, e.g., because its data type is not completely specified
10452 by the debug information, @value{GDBN} will say @samp{<incomplete
10453 type>}. @xref{Symbols, incomplete type}, for more about this.
10455 @cindex no debug info variables
10456 If you try to examine or use the value of a (global) variable for
10457 which @value{GDBN} has no type information, e.g., because the program
10458 includes no debug information, @value{GDBN} displays an error message.
10459 @xref{Symbols, unknown type}, for more about unknown types. If you
10460 cast the variable to its declared type, @value{GDBN} gets the
10461 variable's value using the cast-to type as the variable's type. For
10462 example, in a C program:
10465 (@value{GDBP}) p var
10466 'var' has unknown type; cast it to its declared type
10467 (@value{GDBP}) p (float) var
10471 If you append @kbd{@@entry} string to a function parameter name you get its
10472 value at the time the function got called. If the value is not available an
10473 error message is printed. Entry values are available only with some compilers.
10474 Entry values are normally also printed at the function parameter list according
10475 to @ref{set print entry-values}.
10478 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
10484 (gdb) print i@@entry
10488 Strings are identified as arrays of @code{char} values without specified
10489 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
10490 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
10491 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
10492 defines literal string type @code{"char"} as @code{char} without a sign.
10497 signed char var1[] = "A";
10500 You get during debugging
10505 $2 = @{65 'A', 0 '\0'@}
10509 @section Artificial Arrays
10511 @cindex artificial array
10513 @kindex @@@r{, referencing memory as an array}
10514 It is often useful to print out several successive objects of the
10515 same type in memory; a section of an array, or an array of
10516 dynamically determined size for which only a pointer exists in the
10519 You can do this by referring to a contiguous span of memory as an
10520 @dfn{artificial array}, using the binary operator @samp{@@}. The left
10521 operand of @samp{@@} should be the first element of the desired array
10522 and be an individual object. The right operand should be the desired length
10523 of the array. The result is an array value whose elements are all of
10524 the type of the left argument. The first element is actually the left
10525 argument; the second element comes from bytes of memory immediately
10526 following those that hold the first element, and so on. Here is an
10527 example. If a program says
10530 int *array = (int *) malloc (len * sizeof (int));
10534 you can print the contents of @code{array} with
10540 The left operand of @samp{@@} must reside in memory. Array values made
10541 with @samp{@@} in this way behave just like other arrays in terms of
10542 subscripting, and are coerced to pointers when used in expressions.
10543 Artificial arrays most often appear in expressions via the value history
10544 (@pxref{Value History, ,Value History}), after printing one out.
10546 Another way to create an artificial array is to use a cast.
10547 This re-interprets a value as if it were an array.
10548 The value need not be in memory:
10550 (@value{GDBP}) p/x (short[2])0x12345678
10551 $1 = @{0x1234, 0x5678@}
10554 As a convenience, if you leave the array length out (as in
10555 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
10556 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
10558 (@value{GDBP}) p/x (short[])0x12345678
10559 $2 = @{0x1234, 0x5678@}
10562 Sometimes the artificial array mechanism is not quite enough; in
10563 moderately complex data structures, the elements of interest may not
10564 actually be adjacent---for example, if you are interested in the values
10565 of pointers in an array. One useful work-around in this situation is
10566 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
10567 Variables}) as a counter in an expression that prints the first
10568 interesting value, and then repeat that expression via @key{RET}. For
10569 instance, suppose you have an array @code{dtab} of pointers to
10570 structures, and you are interested in the values of a field @code{fv}
10571 in each structure. Here is an example of what you might type:
10581 @node Output Formats
10582 @section Output Formats
10584 @cindex formatted output
10585 @cindex output formats
10586 By default, @value{GDBN} prints a value according to its data type. Sometimes
10587 this is not what you want. For example, you might want to print a number
10588 in hex, or a pointer in decimal. Or you might want to view data in memory
10589 at a certain address as a character string or as an instruction. To do
10590 these things, specify an @dfn{output format} when you print a value.
10592 The simplest use of output formats is to say how to print a value
10593 already computed. This is done by starting the arguments of the
10594 @code{print} command with a slash and a format letter. The format
10595 letters supported are:
10599 Regard the bits of the value as an integer, and print the integer in
10603 Print as integer in signed decimal.
10606 Print as integer in unsigned decimal.
10609 Print as integer in octal.
10612 Print as integer in binary. The letter @samp{t} stands for ``two''.
10613 @footnote{@samp{b} cannot be used because these format letters are also
10614 used with the @code{x} command, where @samp{b} stands for ``byte'';
10615 see @ref{Memory,,Examining Memory}.}
10618 @cindex unknown address, locating
10619 @cindex locate address
10620 Print as an address, both absolute in hexadecimal and as an offset from
10621 the nearest preceding symbol. You can use this format used to discover
10622 where (in what function) an unknown address is located:
10625 (@value{GDBP}) p/a 0x54320
10626 $3 = 0x54320 <_initialize_vx+396>
10630 The command @code{info symbol 0x54320} yields similar results.
10631 @xref{Symbols, info symbol}.
10634 Regard as an integer and print it as a character constant. This
10635 prints both the numerical value and its character representation. The
10636 character representation is replaced with the octal escape @samp{\nnn}
10637 for characters outside the 7-bit @sc{ascii} range.
10639 Without this format, @value{GDBN} displays @code{char},
10640 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
10641 constants. Single-byte members of vectors are displayed as integer
10645 Regard the bits of the value as a floating point number and print
10646 using typical floating point syntax.
10649 @cindex printing strings
10650 @cindex printing byte arrays
10651 Regard as a string, if possible. With this format, pointers to single-byte
10652 data are displayed as null-terminated strings and arrays of single-byte data
10653 are displayed as fixed-length strings. Other values are displayed in their
10656 Without this format, @value{GDBN} displays pointers to and arrays of
10657 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
10658 strings. Single-byte members of a vector are displayed as an integer
10662 Like @samp{x} formatting, the value is treated as an integer and
10663 printed as hexadecimal, but leading zeros are printed to pad the value
10664 to the size of the integer type.
10667 @cindex raw printing
10668 Print using the @samp{raw} formatting. By default, @value{GDBN} will
10669 use a Python-based pretty-printer, if one is available (@pxref{Pretty
10670 Printing}). This typically results in a higher-level display of the
10671 value's contents. The @samp{r} format bypasses any Python
10672 pretty-printer which might exist.
10675 For example, to print the program counter in hex (@pxref{Registers}), type
10682 Note that no space is required before the slash; this is because command
10683 names in @value{GDBN} cannot contain a slash.
10685 To reprint the last value in the value history with a different format,
10686 you can use the @code{print} command with just a format and no
10687 expression. For example, @samp{p/x} reprints the last value in hex.
10690 @section Examining Memory
10692 You can use the command @code{x} (for ``examine'') to examine memory in
10693 any of several formats, independently of your program's data types.
10695 @cindex examining memory
10697 @kindex x @r{(examine memory)}
10698 @item x/@var{nfu} @var{addr}
10699 @itemx x @var{addr}
10701 Use the @code{x} command to examine memory.
10704 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
10705 much memory to display and how to format it; @var{addr} is an
10706 expression giving the address where you want to start displaying memory.
10707 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
10708 Several commands set convenient defaults for @var{addr}.
10711 @item @var{n}, the repeat count
10712 The repeat count is a decimal integer; the default is 1. It specifies
10713 how much memory (counting by units @var{u}) to display. If a negative
10714 number is specified, memory is examined backward from @var{addr}.
10715 @c This really is **decimal**; unaffected by 'set radix' as of GDB
10718 @item @var{f}, the display format
10719 The display format is one of the formats used by @code{print}
10720 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
10721 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
10722 The default is @samp{x} (hexadecimal) initially. The default changes
10723 each time you use either @code{x} or @code{print}.
10725 @item @var{u}, the unit size
10726 The unit size is any of
10732 Halfwords (two bytes).
10734 Words (four bytes). This is the initial default.
10736 Giant words (eight bytes).
10739 Each time you specify a unit size with @code{x}, that size becomes the
10740 default unit the next time you use @code{x}. For the @samp{i} format,
10741 the unit size is ignored and is normally not written. For the @samp{s} format,
10742 the unit size defaults to @samp{b}, unless it is explicitly given.
10743 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
10744 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
10745 Note that the results depend on the programming language of the
10746 current compilation unit. If the language is C, the @samp{s}
10747 modifier will use the UTF-16 encoding while @samp{w} will use
10748 UTF-32. The encoding is set by the programming language and cannot
10751 @item @var{addr}, starting display address
10752 @var{addr} is the address where you want @value{GDBN} to begin displaying
10753 memory. The expression need not have a pointer value (though it may);
10754 it is always interpreted as an integer address of a byte of memory.
10755 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
10756 @var{addr} is usually just after the last address examined---but several
10757 other commands also set the default address: @code{info breakpoints} (to
10758 the address of the last breakpoint listed), @code{info line} (to the
10759 starting address of a line), and @code{print} (if you use it to display
10760 a value from memory).
10763 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
10764 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
10765 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
10766 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
10767 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
10769 You can also specify a negative repeat count to examine memory backward
10770 from the given address. For example, @samp{x/-3uh 0x54320} prints three
10771 halfwords (@code{h}) at @code{0x54314}, @code{0x54328}, and @code{0x5431c}.
10773 Since the letters indicating unit sizes are all distinct from the
10774 letters specifying output formats, you do not have to remember whether
10775 unit size or format comes first; either order works. The output
10776 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
10777 (However, the count @var{n} must come first; @samp{wx4} does not work.)
10779 Even though the unit size @var{u} is ignored for the formats @samp{s}
10780 and @samp{i}, you might still want to use a count @var{n}; for example,
10781 @samp{3i} specifies that you want to see three machine instructions,
10782 including any operands. For convenience, especially when used with
10783 the @code{display} command, the @samp{i} format also prints branch delay
10784 slot instructions, if any, beyond the count specified, which immediately
10785 follow the last instruction that is within the count. The command
10786 @code{disassemble} gives an alternative way of inspecting machine
10787 instructions; see @ref{Machine Code,,Source and Machine Code}.
10789 If a negative repeat count is specified for the formats @samp{s} or @samp{i},
10790 the command displays null-terminated strings or instructions before the given
10791 address as many as the absolute value of the given number. For the @samp{i}
10792 format, we use line number information in the debug info to accurately locate
10793 instruction boundaries while disassembling backward. If line info is not
10794 available, the command stops examining memory with an error message.
10796 All the defaults for the arguments to @code{x} are designed to make it
10797 easy to continue scanning memory with minimal specifications each time
10798 you use @code{x}. For example, after you have inspected three machine
10799 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
10800 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
10801 the repeat count @var{n} is used again; the other arguments default as
10802 for successive uses of @code{x}.
10804 When examining machine instructions, the instruction at current program
10805 counter is shown with a @code{=>} marker. For example:
10808 (@value{GDBP}) x/5i $pc-6
10809 0x804837f <main+11>: mov %esp,%ebp
10810 0x8048381 <main+13>: push %ecx
10811 0x8048382 <main+14>: sub $0x4,%esp
10812 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
10813 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
10816 @cindex @code{$_}, @code{$__}, and value history
10817 The addresses and contents printed by the @code{x} command are not saved
10818 in the value history because there is often too much of them and they
10819 would get in the way. Instead, @value{GDBN} makes these values available for
10820 subsequent use in expressions as values of the convenience variables
10821 @code{$_} and @code{$__}. After an @code{x} command, the last address
10822 examined is available for use in expressions in the convenience variable
10823 @code{$_}. The contents of that address, as examined, are available in
10824 the convenience variable @code{$__}.
10826 If the @code{x} command has a repeat count, the address and contents saved
10827 are from the last memory unit printed; this is not the same as the last
10828 address printed if several units were printed on the last line of output.
10830 @anchor{addressable memory unit}
10831 @cindex addressable memory unit
10832 Most targets have an addressable memory unit size of 8 bits. This means
10833 that to each memory address are associated 8 bits of data. Some
10834 targets, however, have other addressable memory unit sizes.
10835 Within @value{GDBN} and this document, the term
10836 @dfn{addressable memory unit} (or @dfn{memory unit} for short) is used
10837 when explicitly referring to a chunk of data of that size. The word
10838 @dfn{byte} is used to refer to a chunk of data of 8 bits, regardless of
10839 the addressable memory unit size of the target. For most systems,
10840 addressable memory unit is a synonym of byte.
10842 @cindex remote memory comparison
10843 @cindex target memory comparison
10844 @cindex verify remote memory image
10845 @cindex verify target memory image
10846 When you are debugging a program running on a remote target machine
10847 (@pxref{Remote Debugging}), you may wish to verify the program's image
10848 in the remote machine's memory against the executable file you
10849 downloaded to the target. Or, on any target, you may want to check
10850 whether the program has corrupted its own read-only sections. The
10851 @code{compare-sections} command is provided for such situations.
10854 @kindex compare-sections
10855 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
10856 Compare the data of a loadable section @var{section-name} in the
10857 executable file of the program being debugged with the same section in
10858 the target machine's memory, and report any mismatches. With no
10859 arguments, compares all loadable sections. With an argument of
10860 @code{-r}, compares all loadable read-only sections.
10862 Note: for remote targets, this command can be accelerated if the
10863 target supports computing the CRC checksum of a block of memory
10864 (@pxref{qCRC packet}).
10868 @section Automatic Display
10869 @cindex automatic display
10870 @cindex display of expressions
10872 If you find that you want to print the value of an expression frequently
10873 (to see how it changes), you might want to add it to the @dfn{automatic
10874 display list} so that @value{GDBN} prints its value each time your program stops.
10875 Each expression added to the list is given a number to identify it;
10876 to remove an expression from the list, you specify that number.
10877 The automatic display looks like this:
10881 3: bar[5] = (struct hack *) 0x3804
10885 This display shows item numbers, expressions and their current values. As with
10886 displays you request manually using @code{x} or @code{print}, you can
10887 specify the output format you prefer; in fact, @code{display} decides
10888 whether to use @code{print} or @code{x} depending your format
10889 specification---it uses @code{x} if you specify either the @samp{i}
10890 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
10894 @item display @var{expr}
10895 Add the expression @var{expr} to the list of expressions to display
10896 each time your program stops. @xref{Expressions, ,Expressions}.
10898 @code{display} does not repeat if you press @key{RET} again after using it.
10900 @item display/@var{fmt} @var{expr}
10901 For @var{fmt} specifying only a display format and not a size or
10902 count, add the expression @var{expr} to the auto-display list but
10903 arrange to display it each time in the specified format @var{fmt}.
10904 @xref{Output Formats,,Output Formats}.
10906 @item display/@var{fmt} @var{addr}
10907 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
10908 number of units, add the expression @var{addr} as a memory address to
10909 be examined each time your program stops. Examining means in effect
10910 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
10913 For example, @samp{display/i $pc} can be helpful, to see the machine
10914 instruction about to be executed each time execution stops (@samp{$pc}
10915 is a common name for the program counter; @pxref{Registers, ,Registers}).
10918 @kindex delete display
10920 @item undisplay @var{dnums}@dots{}
10921 @itemx delete display @var{dnums}@dots{}
10922 Remove items from the list of expressions to display. Specify the
10923 numbers of the displays that you want affected with the command
10924 argument @var{dnums}. It can be a single display number, one of the
10925 numbers shown in the first field of the @samp{info display} display;
10926 or it could be a range of display numbers, as in @code{2-4}.
10928 @code{undisplay} does not repeat if you press @key{RET} after using it.
10929 (Otherwise you would just get the error @samp{No display number @dots{}}.)
10931 @kindex disable display
10932 @item disable display @var{dnums}@dots{}
10933 Disable the display of item numbers @var{dnums}. A disabled display
10934 item is not printed automatically, but is not forgotten. It may be
10935 enabled again later. Specify the numbers of the displays that you
10936 want affected with the command argument @var{dnums}. It can be a
10937 single display number, one of the numbers shown in the first field of
10938 the @samp{info display} display; or it could be a range of display
10939 numbers, as in @code{2-4}.
10941 @kindex enable display
10942 @item enable display @var{dnums}@dots{}
10943 Enable display of item numbers @var{dnums}. It becomes effective once
10944 again in auto display of its expression, until you specify otherwise.
10945 Specify the numbers of the displays that you want affected with the
10946 command argument @var{dnums}. It can be a single display number, one
10947 of the numbers shown in the first field of the @samp{info display}
10948 display; or it could be a range of display numbers, as in @code{2-4}.
10951 Display the current values of the expressions on the list, just as is
10952 done when your program stops.
10954 @kindex info display
10956 Print the list of expressions previously set up to display
10957 automatically, each one with its item number, but without showing the
10958 values. This includes disabled expressions, which are marked as such.
10959 It also includes expressions which would not be displayed right now
10960 because they refer to automatic variables not currently available.
10963 @cindex display disabled out of scope
10964 If a display expression refers to local variables, then it does not make
10965 sense outside the lexical context for which it was set up. Such an
10966 expression is disabled when execution enters a context where one of its
10967 variables is not defined. For example, if you give the command
10968 @code{display last_char} while inside a function with an argument
10969 @code{last_char}, @value{GDBN} displays this argument while your program
10970 continues to stop inside that function. When it stops elsewhere---where
10971 there is no variable @code{last_char}---the display is disabled
10972 automatically. The next time your program stops where @code{last_char}
10973 is meaningful, you can enable the display expression once again.
10975 @node Print Settings
10976 @section Print Settings
10978 @cindex format options
10979 @cindex print settings
10980 @value{GDBN} provides the following ways to control how arrays, structures,
10981 and symbols are printed.
10984 These settings are useful for debugging programs in any language:
10988 @anchor{set print address}
10989 @item set print address
10990 @itemx set print address on
10991 @cindex print/don't print memory addresses
10992 @value{GDBN} prints memory addresses showing the location of stack
10993 traces, structure values, pointer values, breakpoints, and so forth,
10994 even when it also displays the contents of those addresses. The default
10995 is @code{on}. For example, this is what a stack frame display looks like with
10996 @code{set print address on}:
11001 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
11003 530 if (lquote != def_lquote)
11007 @item set print address off
11008 Do not print addresses when displaying their contents. For example,
11009 this is the same stack frame displayed with @code{set print address off}:
11013 (@value{GDBP}) set print addr off
11015 #0 set_quotes (lq="<<", rq=">>") at input.c:530
11016 530 if (lquote != def_lquote)
11020 You can use @samp{set print address off} to eliminate all machine
11021 dependent displays from the @value{GDBN} interface. For example, with
11022 @code{print address off}, you should get the same text for backtraces on
11023 all machines---whether or not they involve pointer arguments.
11026 @item show print address
11027 Show whether or not addresses are to be printed.
11030 When @value{GDBN} prints a symbolic address, it normally prints the
11031 closest earlier symbol plus an offset. If that symbol does not uniquely
11032 identify the address (for example, it is a name whose scope is a single
11033 source file), you may need to clarify. One way to do this is with
11034 @code{info line}, for example @samp{info line *0x4537}. Alternately,
11035 you can set @value{GDBN} to print the source file and line number when
11036 it prints a symbolic address:
11039 @item set print symbol-filename on
11040 @cindex source file and line of a symbol
11041 @cindex symbol, source file and line
11042 Tell @value{GDBN} to print the source file name and line number of a
11043 symbol in the symbolic form of an address.
11045 @item set print symbol-filename off
11046 Do not print source file name and line number of a symbol. This is the
11049 @item show print symbol-filename
11050 Show whether or not @value{GDBN} will print the source file name and
11051 line number of a symbol in the symbolic form of an address.
11054 Another situation where it is helpful to show symbol filenames and line
11055 numbers is when disassembling code; @value{GDBN} shows you the line
11056 number and source file that corresponds to each instruction.
11058 Also, you may wish to see the symbolic form only if the address being
11059 printed is reasonably close to the closest earlier symbol:
11062 @item set print max-symbolic-offset @var{max-offset}
11063 @itemx set print max-symbolic-offset unlimited
11064 @cindex maximum value for offset of closest symbol
11065 Tell @value{GDBN} to only display the symbolic form of an address if the
11066 offset between the closest earlier symbol and the address is less than
11067 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
11068 to always print the symbolic form of an address if any symbol precedes
11069 it. Zero is equivalent to @code{unlimited}.
11071 @item show print max-symbolic-offset
11072 Ask how large the maximum offset is that @value{GDBN} prints in a
11076 @cindex wild pointer, interpreting
11077 @cindex pointer, finding referent
11078 If you have a pointer and you are not sure where it points, try
11079 @samp{set print symbol-filename on}. Then you can determine the name
11080 and source file location of the variable where it points, using
11081 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
11082 For example, here @value{GDBN} shows that a variable @code{ptt} points
11083 at another variable @code{t}, defined in @file{hi2.c}:
11086 (@value{GDBP}) set print symbol-filename on
11087 (@value{GDBP}) p/a ptt
11088 $4 = 0xe008 <t in hi2.c>
11092 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
11093 does not show the symbol name and filename of the referent, even with
11094 the appropriate @code{set print} options turned on.
11097 You can also enable @samp{/a}-like formatting all the time using
11098 @samp{set print symbol on}:
11100 @anchor{set print symbol}
11102 @item set print symbol on
11103 Tell @value{GDBN} to print the symbol corresponding to an address, if
11106 @item set print symbol off
11107 Tell @value{GDBN} not to print the symbol corresponding to an
11108 address. In this mode, @value{GDBN} will still print the symbol
11109 corresponding to pointers to functions. This is the default.
11111 @item show print symbol
11112 Show whether @value{GDBN} will display the symbol corresponding to an
11116 Other settings control how different kinds of objects are printed:
11119 @anchor{set print array}
11120 @item set print array
11121 @itemx set print array on
11122 @cindex pretty print arrays
11123 Pretty print arrays. This format is more convenient to read,
11124 but uses more space. The default is off.
11126 @item set print array off
11127 Return to compressed format for arrays.
11129 @item show print array
11130 Show whether compressed or pretty format is selected for displaying
11133 @cindex print array indexes
11134 @anchor{set print array-indexes}
11135 @item set print array-indexes
11136 @itemx set print array-indexes on
11137 Print the index of each element when displaying arrays. May be more
11138 convenient to locate a given element in the array or quickly find the
11139 index of a given element in that printed array. The default is off.
11141 @item set print array-indexes off
11142 Stop printing element indexes when displaying arrays.
11144 @item show print array-indexes
11145 Show whether the index of each element is printed when displaying
11148 @anchor{set print elements}
11149 @item set print elements @var{number-of-elements}
11150 @itemx set print elements unlimited
11151 @cindex number of array elements to print
11152 @cindex limit on number of printed array elements
11153 Set a limit on how many elements of an array @value{GDBN} will print.
11154 If @value{GDBN} is printing a large array, it stops printing after it has
11155 printed the number of elements set by the @code{set print elements} command.
11156 This limit also applies to the display of strings.
11157 When @value{GDBN} starts, this limit is set to 200.
11158 Setting @var{number-of-elements} to @code{unlimited} or zero means
11159 that the number of elements to print is unlimited.
11161 @item show print elements
11162 Display the number of elements of a large array that @value{GDBN} will print.
11163 If the number is 0, then the printing is unlimited.
11165 @anchor{set print frame-arguments}
11166 @item set print frame-arguments @var{value}
11167 @kindex set print frame-arguments
11168 @cindex printing frame argument values
11169 @cindex print all frame argument values
11170 @cindex print frame argument values for scalars only
11171 @cindex do not print frame arguments
11172 This command allows to control how the values of arguments are printed
11173 when the debugger prints a frame (@pxref{Frames}). The possible
11178 The values of all arguments are printed.
11181 Print the value of an argument only if it is a scalar. The value of more
11182 complex arguments such as arrays, structures, unions, etc, is replaced
11183 by @code{@dots{}}. This is the default. Here is an example where
11184 only scalar arguments are shown:
11187 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
11192 None of the argument values are printed. Instead, the value of each argument
11193 is replaced by @code{@dots{}}. In this case, the example above now becomes:
11196 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
11201 Only the presence of arguments is indicated by @code{@dots{}}.
11202 The @code{@dots{}} are not printed for function without any arguments.
11203 None of the argument names and values are printed.
11204 In this case, the example above now becomes:
11207 #1 0x08048361 in call_me (@dots{}) at frame-args.c:23
11212 By default, only scalar arguments are printed. This command can be used
11213 to configure the debugger to print the value of all arguments, regardless
11214 of their type. However, it is often advantageous to not print the value
11215 of more complex parameters. For instance, it reduces the amount of
11216 information printed in each frame, making the backtrace more readable.
11217 Also, it improves performance when displaying Ada frames, because
11218 the computation of large arguments can sometimes be CPU-intensive,
11219 especially in large applications. Setting @code{print frame-arguments}
11220 to @code{scalars} (the default), @code{none} or @code{presence} avoids
11221 this computation, thus speeding up the display of each Ada frame.
11223 @item show print frame-arguments
11224 Show how the value of arguments should be displayed when printing a frame.
11226 @anchor{set print raw-frame-arguments}
11227 @item set print raw-frame-arguments on
11228 Print frame arguments in raw, non pretty-printed, form.
11230 @item set print raw-frame-arguments off
11231 Print frame arguments in pretty-printed form, if there is a pretty-printer
11232 for the value (@pxref{Pretty Printing}),
11233 otherwise print the value in raw form.
11234 This is the default.
11236 @item show print raw-frame-arguments
11237 Show whether to print frame arguments in raw form.
11239 @anchor{set print entry-values}
11240 @item set print entry-values @var{value}
11241 @kindex set print entry-values
11242 Set printing of frame argument values at function entry. In some cases
11243 @value{GDBN} can determine the value of function argument which was passed by
11244 the function caller, even if the value was modified inside the called function
11245 and therefore is different. With optimized code, the current value could be
11246 unavailable, but the entry value may still be known.
11248 The default value is @code{default} (see below for its description). Older
11249 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
11250 this feature will behave in the @code{default} setting the same way as with the
11253 This functionality is currently supported only by DWARF 2 debugging format and
11254 the compiler has to produce @samp{DW_TAG_call_site} tags. With
11255 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
11258 The @var{value} parameter can be one of the following:
11262 Print only actual parameter values, never print values from function entry
11266 #0 different (val=6)
11267 #0 lost (val=<optimized out>)
11269 #0 invalid (val=<optimized out>)
11273 Print only parameter values from function entry point. The actual parameter
11274 values are never printed.
11276 #0 equal (val@@entry=5)
11277 #0 different (val@@entry=5)
11278 #0 lost (val@@entry=5)
11279 #0 born (val@@entry=<optimized out>)
11280 #0 invalid (val@@entry=<optimized out>)
11284 Print only parameter values from function entry point. If value from function
11285 entry point is not known while the actual value is known, print the actual
11286 value for such parameter.
11288 #0 equal (val@@entry=5)
11289 #0 different (val@@entry=5)
11290 #0 lost (val@@entry=5)
11292 #0 invalid (val@@entry=<optimized out>)
11296 Print actual parameter values. If actual parameter value is not known while
11297 value from function entry point is known, print the entry point value for such
11301 #0 different (val=6)
11302 #0 lost (val@@entry=5)
11304 #0 invalid (val=<optimized out>)
11308 Always print both the actual parameter value and its value from function entry
11309 point, even if values of one or both are not available due to compiler
11312 #0 equal (val=5, val@@entry=5)
11313 #0 different (val=6, val@@entry=5)
11314 #0 lost (val=<optimized out>, val@@entry=5)
11315 #0 born (val=10, val@@entry=<optimized out>)
11316 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
11320 Print the actual parameter value if it is known and also its value from
11321 function entry point if it is known. If neither is known, print for the actual
11322 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
11323 values are known and identical, print the shortened
11324 @code{param=param@@entry=VALUE} notation.
11326 #0 equal (val=val@@entry=5)
11327 #0 different (val=6, val@@entry=5)
11328 #0 lost (val@@entry=5)
11330 #0 invalid (val=<optimized out>)
11334 Always print the actual parameter value. Print also its value from function
11335 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
11336 if both values are known and identical, print the shortened
11337 @code{param=param@@entry=VALUE} notation.
11339 #0 equal (val=val@@entry=5)
11340 #0 different (val=6, val@@entry=5)
11341 #0 lost (val=<optimized out>, val@@entry=5)
11343 #0 invalid (val=<optimized out>)
11347 For analysis messages on possible failures of frame argument values at function
11348 entry resolution see @ref{set debug entry-values}.
11350 @item show print entry-values
11351 Show the method being used for printing of frame argument values at function
11354 @anchor{set print frame-info}
11355 @item set print frame-info @var{value}
11356 @kindex set print frame-info
11357 @cindex printing frame information
11358 @cindex frame information, printing
11359 This command allows to control the information printed when
11360 the debugger prints a frame. See @ref{Frames}, @ref{Backtrace},
11361 for a general explanation about frames and frame information.
11362 Note that some other settings (such as @code{set print frame-arguments}
11363 and @code{set print address}) are also influencing if and how some frame
11364 information is displayed. In particular, the frame program counter is never
11365 printed if @code{set print address} is off.
11367 The possible values for @code{set print frame-info} are:
11369 @item short-location
11370 Print the frame level, the program counter (if not at the
11371 beginning of the location source line), the function, the function
11374 Same as @code{short-location} but also print the source file and source line
11376 @item location-and-address
11377 Same as @code{location} but print the program counter even if located at the
11378 beginning of the location source line.
11380 Print the program counter (if not at the beginning of the location
11381 source line), the line number and the source line.
11382 @item source-and-location
11383 Print what @code{location} and @code{source-line} are printing.
11385 The information printed for a frame is decided automatically
11386 by the @value{GDBN} command that prints a frame.
11387 For example, @code{frame} prints the information printed by
11388 @code{source-and-location} while @code{stepi} will switch between
11389 @code{source-line} and @code{source-and-location} depending on the program
11391 The default value is @code{auto}.
11394 @anchor{set print repeats}
11395 @item set print repeats @var{number-of-repeats}
11396 @itemx set print repeats unlimited
11397 @cindex repeated array elements
11398 Set the threshold for suppressing display of repeated array
11399 elements. When the number of consecutive identical elements of an
11400 array exceeds the threshold, @value{GDBN} prints the string
11401 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
11402 identical repetitions, instead of displaying the identical elements
11403 themselves. Setting the threshold to @code{unlimited} or zero will
11404 cause all elements to be individually printed. The default threshold
11407 @item show print repeats
11408 Display the current threshold for printing repeated identical
11411 @anchor{set print max-depth}
11412 @item set print max-depth @var{depth}
11413 @item set print max-depth unlimited
11414 @cindex printing nested structures
11415 Set the threshold after which nested structures are replaced with
11416 ellipsis, this can make visualising deeply nested structures easier.
11418 For example, given this C code
11421 typedef struct s1 @{ int a; @} s1;
11422 typedef struct s2 @{ s1 b; @} s2;
11423 typedef struct s3 @{ s2 c; @} s3;
11424 typedef struct s4 @{ s3 d; @} s4;
11426 s4 var = @{ @{ @{ @{ 3 @} @} @} @};
11429 The following table shows how different values of @var{depth} will
11430 effect how @code{var} is printed by @value{GDBN}:
11432 @multitable @columnfractions .3 .7
11433 @headitem @var{depth} setting @tab Result of @samp{p var}
11435 @tab @code{$1 = @{d = @{c = @{b = @{a = 3@}@}@}@}}
11437 @tab @code{$1 = @{...@}}
11439 @tab @code{$1 = @{d = @{...@}@}}
11441 @tab @code{$1 = @{d = @{c = @{...@}@}@}}
11443 @tab @code{$1 = @{d = @{c = @{b = @{...@}@}@}@}}
11445 @tab @code{$1 = @{d = @{c = @{b = @{a = 3@}@}@}@}}
11448 To see the contents of structures that have been hidden the user can
11449 either increase the print max-depth, or they can print the elements of
11450 the structure that are visible, for example
11453 (gdb) set print max-depth 2
11455 $1 = @{d = @{c = @{...@}@}@}
11457 $2 = @{c = @{b = @{...@}@}@}
11459 $3 = @{b = @{a = 3@}@}
11462 The pattern used to replace nested structures varies based on
11463 language, for most languages @code{@{...@}} is used, but Fortran uses
11466 @item show print max-depth
11467 Display the current threshold after which nested structures are
11468 replaces with ellipsis.
11470 @anchor{set print null-stop}
11471 @item set print null-stop
11472 @cindex @sc{null} elements in arrays
11473 Cause @value{GDBN} to stop printing the characters of an array when the first
11474 @sc{null} is encountered. This is useful when large arrays actually
11475 contain only short strings.
11476 The default is off.
11478 @item show print null-stop
11479 Show whether @value{GDBN} stops printing an array on the first
11480 @sc{null} character.
11482 @anchor{set print pretty}
11483 @item set print pretty on
11484 @cindex print structures in indented form
11485 @cindex indentation in structure display
11486 Cause @value{GDBN} to print structures in an indented format with one member
11487 per line, like this:
11502 @item set print pretty off
11503 Cause @value{GDBN} to print structures in a compact format, like this:
11507 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
11508 meat = 0x54 "Pork"@}
11513 This is the default format.
11515 @item show print pretty
11516 Show which format @value{GDBN} is using to print structures.
11518 @anchor{set print raw-values}
11519 @item set print raw-values on
11520 Print values in raw form, without applying the pretty
11521 printers for the value.
11523 @item set print raw-values off
11524 Print values in pretty-printed form, if there is a pretty-printer
11525 for the value (@pxref{Pretty Printing}),
11526 otherwise print the value in raw form.
11528 The default setting is ``off''.
11530 @item show print raw-values
11531 Show whether to print values in raw form.
11533 @item set print sevenbit-strings on
11534 @cindex eight-bit characters in strings
11535 @cindex octal escapes in strings
11536 Print using only seven-bit characters; if this option is set,
11537 @value{GDBN} displays any eight-bit characters (in strings or
11538 character values) using the notation @code{\}@var{nnn}. This setting is
11539 best if you are working in English (@sc{ascii}) and you use the
11540 high-order bit of characters as a marker or ``meta'' bit.
11542 @item set print sevenbit-strings off
11543 Print full eight-bit characters. This allows the use of more
11544 international character sets, and is the default.
11546 @item show print sevenbit-strings
11547 Show whether or not @value{GDBN} is printing only seven-bit characters.
11549 @anchor{set print union}
11550 @item set print union on
11551 @cindex unions in structures, printing
11552 Tell @value{GDBN} to print unions which are contained in structures
11553 and other unions. This is the default setting.
11555 @item set print union off
11556 Tell @value{GDBN} not to print unions which are contained in
11557 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
11560 @item show print union
11561 Ask @value{GDBN} whether or not it will print unions which are contained in
11562 structures and other unions.
11564 For example, given the declarations
11567 typedef enum @{Tree, Bug@} Species;
11568 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
11569 typedef enum @{Caterpillar, Cocoon, Butterfly@}
11580 struct thing foo = @{Tree, @{Acorn@}@};
11584 with @code{set print union on} in effect @samp{p foo} would print
11587 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
11591 and with @code{set print union off} in effect it would print
11594 $1 = @{it = Tree, form = @{...@}@}
11598 @code{set print union} affects programs written in C-like languages
11604 These settings are of interest when debugging C@t{++} programs:
11607 @cindex demangling C@t{++} names
11608 @item set print demangle
11609 @itemx set print demangle on
11610 Print C@t{++} names in their source form rather than in the encoded
11611 (``mangled'') form passed to the assembler and linker for type-safe
11612 linkage. The default is on.
11614 @item show print demangle
11615 Show whether C@t{++} names are printed in mangled or demangled form.
11617 @item set print asm-demangle
11618 @itemx set print asm-demangle on
11619 Print C@t{++} names in their source form rather than their mangled form, even
11620 in assembler code printouts such as instruction disassemblies.
11621 The default is off.
11623 @item show print asm-demangle
11624 Show whether C@t{++} names in assembly listings are printed in mangled
11627 @cindex C@t{++} symbol decoding style
11628 @cindex symbol decoding style, C@t{++}
11629 @kindex set demangle-style
11630 @item set demangle-style @var{style}
11631 Choose among several encoding schemes used by different compilers to represent
11632 C@t{++} names. If you omit @var{style}, you will see a list of possible
11633 formats. The default value is @var{auto}, which lets @value{GDBN} choose a
11634 decoding style by inspecting your program.
11636 @item show demangle-style
11637 Display the encoding style currently in use for decoding C@t{++} symbols.
11639 @anchor{set print object}
11640 @item set print object
11641 @itemx set print object on
11642 @cindex derived type of an object, printing
11643 @cindex display derived types
11644 When displaying a pointer to an object, identify the @emph{actual}
11645 (derived) type of the object rather than the @emph{declared} type, using
11646 the virtual function table. Note that the virtual function table is
11647 required---this feature can only work for objects that have run-time
11648 type identification; a single virtual method in the object's declared
11649 type is sufficient. Note that this setting is also taken into account when
11650 working with variable objects via MI (@pxref{GDB/MI}).
11652 @item set print object off
11653 Display only the declared type of objects, without reference to the
11654 virtual function table. This is the default setting.
11656 @item show print object
11657 Show whether actual, or declared, object types are displayed.
11659 @anchor{set print static-members}
11660 @item set print static-members
11661 @itemx set print static-members on
11662 @cindex static members of C@t{++} objects
11663 Print static members when displaying a C@t{++} object. The default is on.
11665 @item set print static-members off
11666 Do not print static members when displaying a C@t{++} object.
11668 @item show print static-members
11669 Show whether C@t{++} static members are printed or not.
11671 @item set print pascal_static-members
11672 @itemx set print pascal_static-members on
11673 @cindex static members of Pascal objects
11674 @cindex Pascal objects, static members display
11675 Print static members when displaying a Pascal object. The default is on.
11677 @item set print pascal_static-members off
11678 Do not print static members when displaying a Pascal object.
11680 @item show print pascal_static-members
11681 Show whether Pascal static members are printed or not.
11683 @c These don't work with HP ANSI C++ yet.
11684 @anchor{set print vtbl}
11685 @item set print vtbl
11686 @itemx set print vtbl on
11687 @cindex pretty print C@t{++} virtual function tables
11688 @cindex virtual functions (C@t{++}) display
11689 @cindex VTBL display
11690 Pretty print C@t{++} virtual function tables. The default is off.
11691 (The @code{vtbl} commands do not work on programs compiled with the HP
11692 ANSI C@t{++} compiler (@code{aCC}).)
11694 @item set print vtbl off
11695 Do not pretty print C@t{++} virtual function tables.
11697 @item show print vtbl
11698 Show whether C@t{++} virtual function tables are pretty printed, or not.
11701 @node Pretty Printing
11702 @section Pretty Printing
11704 @value{GDBN} provides a mechanism to allow pretty-printing of values using
11705 Python code. It greatly simplifies the display of complex objects. This
11706 mechanism works for both MI and the CLI.
11709 * Pretty-Printer Introduction:: Introduction to pretty-printers
11710 * Pretty-Printer Example:: An example pretty-printer
11711 * Pretty-Printer Commands:: Pretty-printer commands
11714 @node Pretty-Printer Introduction
11715 @subsection Pretty-Printer Introduction
11717 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
11718 registered for the value. If there is then @value{GDBN} invokes the
11719 pretty-printer to print the value. Otherwise the value is printed normally.
11721 Pretty-printers are normally named. This makes them easy to manage.
11722 The @samp{info pretty-printer} command will list all the installed
11723 pretty-printers with their names.
11724 If a pretty-printer can handle multiple data types, then its
11725 @dfn{subprinters} are the printers for the individual data types.
11726 Each such subprinter has its own name.
11727 The format of the name is @var{printer-name};@var{subprinter-name}.
11729 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
11730 Typically they are automatically loaded and registered when the corresponding
11731 debug information is loaded, thus making them available without having to
11732 do anything special.
11734 There are three places where a pretty-printer can be registered.
11738 Pretty-printers registered globally are available when debugging
11742 Pretty-printers registered with a program space are available only
11743 when debugging that program.
11744 @xref{Progspaces In Python}, for more details on program spaces in Python.
11747 Pretty-printers registered with an objfile are loaded and unloaded
11748 with the corresponding objfile (e.g., shared library).
11749 @xref{Objfiles In Python}, for more details on objfiles in Python.
11752 @xref{Selecting Pretty-Printers}, for further information on how
11753 pretty-printers are selected,
11755 @xref{Writing a Pretty-Printer}, for implementing pretty printers
11758 @node Pretty-Printer Example
11759 @subsection Pretty-Printer Example
11761 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
11764 (@value{GDBP}) print s
11766 static npos = 4294967295,
11768 <std::allocator<char>> = @{
11769 <__gnu_cxx::new_allocator<char>> = @{
11770 <No data fields>@}, <No data fields>
11772 members of std::basic_string<char, std::char_traits<char>,
11773 std::allocator<char> >::_Alloc_hider:
11774 _M_p = 0x804a014 "abcd"
11779 With a pretty-printer for @code{std::string} only the contents are printed:
11782 (@value{GDBP}) print s
11786 @node Pretty-Printer Commands
11787 @subsection Pretty-Printer Commands
11788 @cindex pretty-printer commands
11791 @kindex info pretty-printer
11792 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
11793 Print the list of installed pretty-printers.
11794 This includes disabled pretty-printers, which are marked as such.
11796 @var{object-regexp} is a regular expression matching the objects
11797 whose pretty-printers to list.
11798 Objects can be @code{global}, the program space's file
11799 (@pxref{Progspaces In Python}),
11800 and the object files within that program space (@pxref{Objfiles In Python}).
11801 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
11802 looks up a printer from these three objects.
11804 @var{name-regexp} is a regular expression matching the name of the printers
11807 @kindex disable pretty-printer
11808 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
11809 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
11810 A disabled pretty-printer is not forgotten, it may be enabled again later.
11812 @kindex enable pretty-printer
11813 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
11814 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
11819 Suppose we have three pretty-printers installed: one from library1.so
11820 named @code{foo} that prints objects of type @code{foo}, and
11821 another from library2.so named @code{bar} that prints two types of objects,
11822 @code{bar1} and @code{bar2}.
11825 (gdb) info pretty-printer
11832 (gdb) info pretty-printer library2
11837 (gdb) disable pretty-printer library1
11839 2 of 3 printers enabled
11840 (gdb) info pretty-printer
11847 (gdb) disable pretty-printer library2 bar;bar1
11849 1 of 3 printers enabled
11850 (gdb) info pretty-printer library2
11857 (gdb) disable pretty-printer library2 bar
11859 0 of 3 printers enabled
11860 (gdb) info pretty-printer library2
11869 Note that for @code{bar} the entire printer can be disabled,
11870 as can each individual subprinter.
11872 Printing values and frame arguments is done by default using
11873 the enabled pretty printers.
11875 The print option @code{-raw-values} and @value{GDBN} setting
11876 @code{set print raw-values} (@pxref{set print raw-values}) can be
11877 used to print values without applying the enabled pretty printers.
11879 Similarly, the backtrace option @code{-raw-frame-arguments} and
11880 @value{GDBN} setting @code{set print raw-frame-arguments}
11881 (@pxref{set print raw-frame-arguments}) can be used to ignore the
11882 enabled pretty printers when printing frame argument values.
11884 @node Value History
11885 @section Value History
11887 @cindex value history
11888 @cindex history of values printed by @value{GDBN}
11889 Values printed by the @code{print} command are saved in the @value{GDBN}
11890 @dfn{value history}. This allows you to refer to them in other expressions.
11891 Values are kept until the symbol table is re-read or discarded
11892 (for example with the @code{file} or @code{symbol-file} commands).
11893 When the symbol table changes, the value history is discarded,
11894 since the values may contain pointers back to the types defined in the
11899 @cindex history number
11900 The values printed are given @dfn{history numbers} by which you can
11901 refer to them. These are successive integers starting with one.
11902 @code{print} shows you the history number assigned to a value by
11903 printing @samp{$@var{num} = } before the value; here @var{num} is the
11906 To refer to any previous value, use @samp{$} followed by the value's
11907 history number. The way @code{print} labels its output is designed to
11908 remind you of this. Just @code{$} refers to the most recent value in
11909 the history, and @code{$$} refers to the value before that.
11910 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
11911 is the value just prior to @code{$$}, @code{$$1} is equivalent to
11912 @code{$$}, and @code{$$0} is equivalent to @code{$}.
11914 For example, suppose you have just printed a pointer to a structure and
11915 want to see the contents of the structure. It suffices to type
11921 If you have a chain of structures where the component @code{next} points
11922 to the next one, you can print the contents of the next one with this:
11929 You can print successive links in the chain by repeating this
11930 command---which you can do by just typing @key{RET}.
11932 Note that the history records values, not expressions. If the value of
11933 @code{x} is 4 and you type these commands:
11941 then the value recorded in the value history by the @code{print} command
11942 remains 4 even though the value of @code{x} has changed.
11945 @kindex show values
11947 Print the last ten values in the value history, with their item numbers.
11948 This is like @samp{p@ $$9} repeated ten times, except that @code{show
11949 values} does not change the history.
11951 @item show values @var{n}
11952 Print ten history values centered on history item number @var{n}.
11954 @item show values +
11955 Print ten history values just after the values last printed. If no more
11956 values are available, @code{show values +} produces no display.
11959 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
11960 same effect as @samp{show values +}.
11962 @node Convenience Vars
11963 @section Convenience Variables
11965 @cindex convenience variables
11966 @cindex user-defined variables
11967 @value{GDBN} provides @dfn{convenience variables} that you can use within
11968 @value{GDBN} to hold on to a value and refer to it later. These variables
11969 exist entirely within @value{GDBN}; they are not part of your program, and
11970 setting a convenience variable has no direct effect on further execution
11971 of your program. That is why you can use them freely.
11973 Convenience variables are prefixed with @samp{$}. Any name preceded by
11974 @samp{$} can be used for a convenience variable, unless it is one of
11975 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
11976 (Value history references, in contrast, are @emph{numbers} preceded
11977 by @samp{$}. @xref{Value History, ,Value History}.)
11979 You can save a value in a convenience variable with an assignment
11980 expression, just as you would set a variable in your program.
11984 set $foo = *object_ptr
11988 would save in @code{$foo} the value contained in the object pointed to by
11991 Using a convenience variable for the first time creates it, but its
11992 value is @code{void} until you assign a new value. You can alter the
11993 value with another assignment at any time.
11995 Convenience variables have no fixed types. You can assign a convenience
11996 variable any type of value, including structures and arrays, even if
11997 that variable already has a value of a different type. The convenience
11998 variable, when used as an expression, has the type of its current value.
12001 @kindex show convenience
12002 @cindex show all user variables and functions
12003 @item show convenience
12004 Print a list of convenience variables used so far, and their values,
12005 as well as a list of the convenience functions.
12006 Abbreviated @code{show conv}.
12008 @kindex init-if-undefined
12009 @cindex convenience variables, initializing
12010 @item init-if-undefined $@var{variable} = @var{expression}
12011 Set a convenience variable if it has not already been set. This is useful
12012 for user-defined commands that keep some state. It is similar, in concept,
12013 to using local static variables with initializers in C (except that
12014 convenience variables are global). It can also be used to allow users to
12015 override default values used in a command script.
12017 If the variable is already defined then the expression is not evaluated so
12018 any side-effects do not occur.
12021 One of the ways to use a convenience variable is as a counter to be
12022 incremented or a pointer to be advanced. For example, to print
12023 a field from successive elements of an array of structures:
12027 print bar[$i++]->contents
12031 Repeat that command by typing @key{RET}.
12033 Some convenience variables are created automatically by @value{GDBN} and given
12034 values likely to be useful.
12037 @vindex $_@r{, convenience variable}
12039 The variable @code{$_} is automatically set by the @code{x} command to
12040 the last address examined (@pxref{Memory, ,Examining Memory}). Other
12041 commands which provide a default address for @code{x} to examine also
12042 set @code{$_} to that address; these commands include @code{info line}
12043 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
12044 except when set by the @code{x} command, in which case it is a pointer
12045 to the type of @code{$__}.
12047 @vindex $__@r{, convenience variable}
12049 The variable @code{$__} is automatically set by the @code{x} command
12050 to the value found in the last address examined. Its type is chosen
12051 to match the format in which the data was printed.
12054 @vindex $_exitcode@r{, convenience variable}
12055 When the program being debugged terminates normally, @value{GDBN}
12056 automatically sets this variable to the exit code of the program, and
12057 resets @code{$_exitsignal} to @code{void}.
12060 @vindex $_exitsignal@r{, convenience variable}
12061 When the program being debugged dies due to an uncaught signal,
12062 @value{GDBN} automatically sets this variable to that signal's number,
12063 and resets @code{$_exitcode} to @code{void}.
12065 To distinguish between whether the program being debugged has exited
12066 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
12067 @code{$_exitsignal} is not @code{void}), the convenience function
12068 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
12069 Functions}). For example, considering the following source code:
12072 #include <signal.h>
12075 main (int argc, char *argv[])
12082 A valid way of telling whether the program being debugged has exited
12083 or signalled would be:
12086 (@value{GDBP}) define has_exited_or_signalled
12087 Type commands for definition of ``has_exited_or_signalled''.
12088 End with a line saying just ``end''.
12089 >if $_isvoid ($_exitsignal)
12090 >echo The program has exited\n
12092 >echo The program has signalled\n
12098 Program terminated with signal SIGALRM, Alarm clock.
12099 The program no longer exists.
12100 (@value{GDBP}) has_exited_or_signalled
12101 The program has signalled
12104 As can be seen, @value{GDBN} correctly informs that the program being
12105 debugged has signalled, since it calls @code{raise} and raises a
12106 @code{SIGALRM} signal. If the program being debugged had not called
12107 @code{raise}, then @value{GDBN} would report a normal exit:
12110 (@value{GDBP}) has_exited_or_signalled
12111 The program has exited
12115 The variable @code{$_exception} is set to the exception object being
12116 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
12118 @item $_ada_exception
12119 The variable @code{$_ada_exception} is set to the address of the
12120 exception being caught or thrown at an Ada exception-related
12121 catchpoint. @xref{Set Catchpoints}.
12124 @itemx $_probe_arg0@dots{}$_probe_arg11
12125 Arguments to a static probe. @xref{Static Probe Points}.
12128 @vindex $_sdata@r{, inspect, convenience variable}
12129 The variable @code{$_sdata} contains extra collected static tracepoint
12130 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
12131 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
12132 if extra static tracepoint data has not been collected.
12135 @vindex $_siginfo@r{, convenience variable}
12136 The variable @code{$_siginfo} contains extra signal information
12137 (@pxref{extra signal information}). Note that @code{$_siginfo}
12138 could be empty, if the application has not yet received any signals.
12139 For example, it will be empty before you execute the @code{run} command.
12142 @vindex $_tlb@r{, convenience variable}
12143 The variable @code{$_tlb} is automatically set when debugging
12144 applications running on MS-Windows in native mode or connected to
12145 gdbserver that supports the @code{qGetTIBAddr} request.
12146 @xref{General Query Packets}.
12147 This variable contains the address of the thread information block.
12150 The number of the current inferior. @xref{Inferiors Connections and
12151 Programs, ,Debugging Multiple Inferiors Connections and Programs}.
12154 The thread number of the current thread. @xref{thread numbers}.
12157 The global number of the current thread. @xref{global thread numbers}.
12161 @vindex $_gdb_major@r{, convenience variable}
12162 @vindex $_gdb_minor@r{, convenience variable}
12163 The major and minor version numbers of the running @value{GDBN}.
12164 Development snapshots and pretest versions have their minor version
12165 incremented by one; thus, @value{GDBN} pretest 9.11.90 will produce
12166 the value 12 for @code{$_gdb_minor}. These variables allow you to
12167 write scripts that work with different versions of @value{GDBN}
12168 without errors caused by features unavailable in some of those
12171 @item $_shell_exitcode
12172 @itemx $_shell_exitsignal
12173 @vindex $_shell_exitcode@r{, convenience variable}
12174 @vindex $_shell_exitsignal@r{, convenience variable}
12175 @cindex shell command, exit code
12176 @cindex shell command, exit signal
12177 @cindex exit status of shell commands
12178 @value{GDBN} commands such as @code{shell} and @code{|} are launching
12179 shell commands. When a launched command terminates, @value{GDBN}
12180 automatically maintains the variables @code{$_shell_exitcode}
12181 and @code{$_shell_exitsignal} according to the exit status of the last
12182 launched command. These variables are set and used similarly to
12183 the variables @code{$_exitcode} and @code{$_exitsignal}.
12187 @node Convenience Funs
12188 @section Convenience Functions
12190 @cindex convenience functions
12191 @value{GDBN} also supplies some @dfn{convenience functions}. These
12192 have a syntax similar to convenience variables. A convenience
12193 function can be used in an expression just like an ordinary function;
12194 however, a convenience function is implemented internally to
12197 These functions do not require @value{GDBN} to be configured with
12198 @code{Python} support, which means that they are always available.
12202 @item $_isvoid (@var{expr})
12203 @findex $_isvoid@r{, convenience function}
12204 Return one if the expression @var{expr} is @code{void}. Otherwise it
12207 A @code{void} expression is an expression where the type of the result
12208 is @code{void}. For example, you can examine a convenience variable
12209 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
12213 (@value{GDBP}) print $_exitcode
12215 (@value{GDBP}) print $_isvoid ($_exitcode)
12218 Starting program: ./a.out
12219 [Inferior 1 (process 29572) exited normally]
12220 (@value{GDBP}) print $_exitcode
12222 (@value{GDBP}) print $_isvoid ($_exitcode)
12226 In the example above, we used @code{$_isvoid} to check whether
12227 @code{$_exitcode} is @code{void} before and after the execution of the
12228 program being debugged. Before the execution there is no exit code to
12229 be examined, therefore @code{$_exitcode} is @code{void}. After the
12230 execution the program being debugged returned zero, therefore
12231 @code{$_exitcode} is zero, which means that it is not @code{void}
12234 The @code{void} expression can also be a call of a function from the
12235 program being debugged. For example, given the following function:
12244 The result of calling it inside @value{GDBN} is @code{void}:
12247 (@value{GDBP}) print foo ()
12249 (@value{GDBP}) print $_isvoid (foo ())
12251 (@value{GDBP}) set $v = foo ()
12252 (@value{GDBP}) print $v
12254 (@value{GDBP}) print $_isvoid ($v)
12258 @item $_gdb_setting_str (@var{setting})
12259 @findex $_gdb_setting_str@r{, convenience function}
12260 Return the value of the @value{GDBN} @var{setting} as a string.
12261 @var{setting} is any setting that can be used in a @code{set} or
12262 @code{show} command (@pxref{Controlling GDB}).
12265 (@value{GDBP}) show print frame-arguments
12266 Printing of non-scalar frame arguments is "scalars".
12267 (@value{GDBP}) p $_gdb_setting_str("print frame-arguments")
12269 (@value{GDBP}) p $_gdb_setting_str("height")
12274 @item $_gdb_setting (@var{setting})
12275 @findex $_gdb_setting@r{, convenience function}
12276 Return the value of the @value{GDBN} @var{setting}.
12277 The type of the returned value depends on the setting.
12279 The value type for boolean and auto boolean settings is @code{int}.
12280 The boolean values @code{off} and @code{on} are converted to
12281 the integer values @code{0} and @code{1}. The value @code{auto} is
12282 converted to the value @code{-1}.
12284 The value type for integer settings is either @code{unsigned int}
12285 or @code{int}, depending on the setting.
12287 Some integer settings accept an @code{unlimited} value.
12288 Depending on the setting, the @code{set} command also accepts
12289 the value @code{0} or the value @code{@minus{}1} as a synonym for
12291 For example, @code{set height unlimited} is equivalent to
12292 @code{set height 0}.
12294 Some other settings that accept the @code{unlimited} value
12295 use the value @code{0} to literally mean zero.
12296 For example, @code{set history size 0} indicates to not
12297 record any @value{GDBN} commands in the command history.
12298 For such settings, @code{@minus{}1} is the synonym
12299 for @code{unlimited}.
12301 See the documentation of the corresponding @code{set} command for
12302 the numerical value equivalent to @code{unlimited}.
12304 The @code{$_gdb_setting} function converts the unlimited value
12305 to a @code{0} or a @code{@minus{}1} value according to what the
12306 @code{set} command uses.
12310 (@value{GDBP}) p $_gdb_setting_str("height")
12312 (@value{GDBP}) p $_gdb_setting("height")
12314 (@value{GDBP}) set height unlimited
12315 (@value{GDBP}) p $_gdb_setting_str("height")
12317 (@value{GDBP}) p $_gdb_setting("height")
12321 (@value{GDBP}) p $_gdb_setting_str("history size")
12323 (@value{GDBP}) p $_gdb_setting("history size")
12325 (@value{GDBP}) p $_gdb_setting_str("disassemble-next-line")
12327 (@value{GDBP}) p $_gdb_setting("disassemble-next-line")
12333 Other setting types (enum, filename, optional filename, string, string noescape)
12334 are returned as string values.
12337 @item $_gdb_maint_setting_str (@var{setting})
12338 @findex $_gdb_maint_setting_str@r{, convenience function}
12339 Like the @code{$_gdb_setting_str} function, but works with
12340 @code{maintenance set} variables.
12342 @item $_gdb_maint_setting (@var{setting})
12343 @findex $_gdb_maint_setting@r{, convenience function}
12344 Like the @code{$_gdb_setting} function, but works with
12345 @code{maintenance set} variables.
12349 The following functions require @value{GDBN} to be configured with
12350 @code{Python} support.
12354 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
12355 @findex $_memeq@r{, convenience function}
12356 Returns one if the @var{length} bytes at the addresses given by
12357 @var{buf1} and @var{buf2} are equal.
12358 Otherwise it returns zero.
12360 @item $_regex(@var{str}, @var{regex})
12361 @findex $_regex@r{, convenience function}
12362 Returns one if the string @var{str} matches the regular expression
12363 @var{regex}. Otherwise it returns zero.
12364 The syntax of the regular expression is that specified by @code{Python}'s
12365 regular expression support.
12367 @item $_streq(@var{str1}, @var{str2})
12368 @findex $_streq@r{, convenience function}
12369 Returns one if the strings @var{str1} and @var{str2} are equal.
12370 Otherwise it returns zero.
12372 @item $_strlen(@var{str})
12373 @findex $_strlen@r{, convenience function}
12374 Returns the length of string @var{str}.
12376 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
12377 @findex $_caller_is@r{, convenience function}
12378 Returns one if the calling function's name is equal to @var{name}.
12379 Otherwise it returns zero.
12381 If the optional argument @var{number_of_frames} is provided,
12382 it is the number of frames up in the stack to look.
12390 at testsuite/gdb.python/py-caller-is.c:21
12391 #1 0x00000000004005a0 in middle_func ()
12392 at testsuite/gdb.python/py-caller-is.c:27
12393 #2 0x00000000004005ab in top_func ()
12394 at testsuite/gdb.python/py-caller-is.c:33
12395 #3 0x00000000004005b6 in main ()
12396 at testsuite/gdb.python/py-caller-is.c:39
12397 (gdb) print $_caller_is ("middle_func")
12399 (gdb) print $_caller_is ("top_func", 2)
12403 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
12404 @findex $_caller_matches@r{, convenience function}
12405 Returns one if the calling function's name matches the regular expression
12406 @var{regexp}. Otherwise it returns zero.
12408 If the optional argument @var{number_of_frames} is provided,
12409 it is the number of frames up in the stack to look.
12412 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
12413 @findex $_any_caller_is@r{, convenience function}
12414 Returns one if any calling function's name is equal to @var{name}.
12415 Otherwise it returns zero.
12417 If the optional argument @var{number_of_frames} is provided,
12418 it is the number of frames up in the stack to look.
12421 This function differs from @code{$_caller_is} in that this function
12422 checks all stack frames from the immediate caller to the frame specified
12423 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
12424 frame specified by @var{number_of_frames}.
12426 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
12427 @findex $_any_caller_matches@r{, convenience function}
12428 Returns one if any calling function's name matches the regular expression
12429 @var{regexp}. Otherwise it returns zero.
12431 If the optional argument @var{number_of_frames} is provided,
12432 it is the number of frames up in the stack to look.
12435 This function differs from @code{$_caller_matches} in that this function
12436 checks all stack frames from the immediate caller to the frame specified
12437 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
12438 frame specified by @var{number_of_frames}.
12440 @item $_as_string(@var{value})
12441 @findex $_as_string@r{, convenience function}
12442 Return the string representation of @var{value}.
12444 This function is useful to obtain the textual label (enumerator) of an
12445 enumeration value. For example, assuming the variable @var{node} is of
12446 an enumerated type:
12449 (gdb) printf "Visiting node of type %s\n", $_as_string(node)
12450 Visiting node of type NODE_INTEGER
12453 @item $_cimag(@var{value})
12454 @itemx $_creal(@var{value})
12455 @findex $_cimag@r{, convenience function}
12456 @findex $_creal@r{, convenience function}
12457 Return the imaginary (@code{$_cimag}) or real (@code{$_creal}) part of
12458 the complex number @var{value}.
12460 The type of the imaginary or real part depends on the type of the
12461 complex number, e.g., using @code{$_cimag} on a @code{float complex}
12462 will return an imaginary part of type @code{float}.
12466 @value{GDBN} provides the ability to list and get help on
12467 convenience functions.
12470 @item help function
12471 @kindex help function
12472 @cindex show all convenience functions
12473 Print a list of all convenience functions.
12480 You can refer to machine register contents, in expressions, as variables
12481 with names starting with @samp{$}. The names of registers are different
12482 for each machine; use @code{info registers} to see the names used on
12486 @kindex info registers
12487 @item info registers
12488 Print the names and values of all registers except floating-point
12489 and vector registers (in the selected stack frame).
12491 @kindex info all-registers
12492 @cindex floating point registers
12493 @item info all-registers
12494 Print the names and values of all registers, including floating-point
12495 and vector registers (in the selected stack frame).
12497 @anchor{info_registers_reggroup}
12498 @item info registers @var{reggroup} @dots{}
12499 Print the name and value of the registers in each of the specified
12500 @var{reggroup}s. The @var{reggroup} can be any of those returned by
12501 @code{maint print reggroups} (@pxref{Maintenance Commands}).
12503 @item info registers @var{regname} @dots{}
12504 Print the @dfn{relativized} value of each specified register @var{regname}.
12505 As discussed in detail below, register values are normally relative to
12506 the selected stack frame. The @var{regname} may be any register name valid on
12507 the machine you are using, with or without the initial @samp{$}.
12510 @anchor{standard registers}
12511 @cindex stack pointer register
12512 @cindex program counter register
12513 @cindex process status register
12514 @cindex frame pointer register
12515 @cindex standard registers
12516 @value{GDBN} has four ``standard'' register names that are available (in
12517 expressions) on most machines---whenever they do not conflict with an
12518 architecture's canonical mnemonics for registers. The register names
12519 @code{$pc} and @code{$sp} are used for the program counter register and
12520 the stack pointer. @code{$fp} is used for a register that contains a
12521 pointer to the current stack frame, and @code{$ps} is used for a
12522 register that contains the processor status. For example,
12523 you could print the program counter in hex with
12530 or print the instruction to be executed next with
12537 or add four to the stack pointer@footnote{This is a way of removing
12538 one word from the stack, on machines where stacks grow downward in
12539 memory (most machines, nowadays). This assumes that the innermost
12540 stack frame is selected; setting @code{$sp} is not allowed when other
12541 stack frames are selected. To pop entire frames off the stack,
12542 regardless of machine architecture, use @code{return};
12543 see @ref{Returning, ,Returning from a Function}.} with
12549 Whenever possible, these four standard register names are available on
12550 your machine even though the machine has different canonical mnemonics,
12551 so long as there is no conflict. The @code{info registers} command
12552 shows the canonical names. For example, on the SPARC, @code{info
12553 registers} displays the processor status register as @code{$psr} but you
12554 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
12555 is an alias for the @sc{eflags} register.
12557 @value{GDBN} always considers the contents of an ordinary register as an
12558 integer when the register is examined in this way. Some machines have
12559 special registers which can hold nothing but floating point; these
12560 registers are considered to have floating point values. There is no way
12561 to refer to the contents of an ordinary register as floating point value
12562 (although you can @emph{print} it as a floating point value with
12563 @samp{print/f $@var{regname}}).
12565 Some registers have distinct ``raw'' and ``virtual'' data formats. This
12566 means that the data format in which the register contents are saved by
12567 the operating system is not the same one that your program normally
12568 sees. For example, the registers of the 68881 floating point
12569 coprocessor are always saved in ``extended'' (raw) format, but all C
12570 programs expect to work with ``double'' (virtual) format. In such
12571 cases, @value{GDBN} normally works with the virtual format only (the format
12572 that makes sense for your program), but the @code{info registers} command
12573 prints the data in both formats.
12575 @cindex SSE registers (x86)
12576 @cindex MMX registers (x86)
12577 Some machines have special registers whose contents can be interpreted
12578 in several different ways. For example, modern x86-based machines
12579 have SSE and MMX registers that can hold several values packed
12580 together in several different formats. @value{GDBN} refers to such
12581 registers in @code{struct} notation:
12584 (@value{GDBP}) print $xmm1
12586 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
12587 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
12588 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
12589 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
12590 v4_int32 = @{0, 20657912, 11, 13@},
12591 v2_int64 = @{88725056443645952, 55834574859@},
12592 uint128 = 0x0000000d0000000b013b36f800000000
12597 To set values of such registers, you need to tell @value{GDBN} which
12598 view of the register you wish to change, as if you were assigning
12599 value to a @code{struct} member:
12602 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
12605 Normally, register values are relative to the selected stack frame
12606 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
12607 value that the register would contain if all stack frames farther in
12608 were exited and their saved registers restored. In order to see the
12609 true contents of hardware registers, you must select the innermost
12610 frame (with @samp{frame 0}).
12612 @cindex caller-saved registers
12613 @cindex call-clobbered registers
12614 @cindex volatile registers
12615 @cindex <not saved> values
12616 Usually ABIs reserve some registers as not needed to be saved by the
12617 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
12618 registers). It may therefore not be possible for @value{GDBN} to know
12619 the value a register had before the call (in other words, in the outer
12620 frame), if the register value has since been changed by the callee.
12621 @value{GDBN} tries to deduce where the inner frame saved
12622 (``callee-saved'') registers, from the debug info, unwind info, or the
12623 machine code generated by your compiler. If some register is not
12624 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
12625 its own knowledge of the ABI, or because the debug/unwind info
12626 explicitly says the register's value is undefined), @value{GDBN}
12627 displays @w{@samp{<not saved>}} as the register's value. With targets
12628 that @value{GDBN} has no knowledge of the register saving convention,
12629 if a register was not saved by the callee, then its value and location
12630 in the outer frame are assumed to be the same of the inner frame.
12631 This is usually harmless, because if the register is call-clobbered,
12632 the caller either does not care what is in the register after the
12633 call, or has code to restore the value that it does care about. Note,
12634 however, that if you change such a register in the outer frame, you
12635 may also be affecting the inner frame. Also, the more ``outer'' the
12636 frame is you're looking at, the more likely a call-clobbered
12637 register's value is to be wrong, in the sense that it doesn't actually
12638 represent the value the register had just before the call.
12640 @node Floating Point Hardware
12641 @section Floating Point Hardware
12642 @cindex floating point
12644 Depending on the configuration, @value{GDBN} may be able to give
12645 you more information about the status of the floating point hardware.
12650 Display hardware-dependent information about the floating
12651 point unit. The exact contents and layout vary depending on the
12652 floating point chip. Currently, @samp{info float} is supported on
12653 the ARM and x86 machines.
12657 @section Vector Unit
12658 @cindex vector unit
12660 Depending on the configuration, @value{GDBN} may be able to give you
12661 more information about the status of the vector unit.
12664 @kindex info vector
12666 Display information about the vector unit. The exact contents and
12667 layout vary depending on the hardware.
12670 @node OS Information
12671 @section Operating System Auxiliary Information
12672 @cindex OS information
12674 @value{GDBN} provides interfaces to useful OS facilities that can help
12675 you debug your program.
12677 @cindex auxiliary vector
12678 @cindex vector, auxiliary
12679 Some operating systems supply an @dfn{auxiliary vector} to programs at
12680 startup. This is akin to the arguments and environment that you
12681 specify for a program, but contains a system-dependent variety of
12682 binary values that tell system libraries important details about the
12683 hardware, operating system, and process. Each value's purpose is
12684 identified by an integer tag; the meanings are well-known but system-specific.
12685 Depending on the configuration and operating system facilities,
12686 @value{GDBN} may be able to show you this information. For remote
12687 targets, this functionality may further depend on the remote stub's
12688 support of the @samp{qXfer:auxv:read} packet, see
12689 @ref{qXfer auxiliary vector read}.
12694 Display the auxiliary vector of the inferior, which can be either a
12695 live process or a core dump file. @value{GDBN} prints each tag value
12696 numerically, and also shows names and text descriptions for recognized
12697 tags. Some values in the vector are numbers, some bit masks, and some
12698 pointers to strings or other data. @value{GDBN} displays each value in the
12699 most appropriate form for a recognized tag, and in hexadecimal for
12700 an unrecognized tag.
12703 On some targets, @value{GDBN} can access operating system-specific
12704 information and show it to you. The types of information available
12705 will differ depending on the type of operating system running on the
12706 target. The mechanism used to fetch the data is described in
12707 @ref{Operating System Information}. For remote targets, this
12708 functionality depends on the remote stub's support of the
12709 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
12713 @item info os @var{infotype}
12715 Display OS information of the requested type.
12717 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
12719 @anchor{linux info os infotypes}
12721 @kindex info os cpus
12723 Display the list of all CPUs/cores. For each CPU/core, @value{GDBN} prints
12724 the available fields from /proc/cpuinfo. For each supported architecture
12725 different fields are available. Two common entries are processor which gives
12726 CPU number and bogomips; a system constant that is calculated during
12727 kernel initialization.
12729 @kindex info os files
12731 Display the list of open file descriptors on the target. For each
12732 file descriptor, @value{GDBN} prints the identifier of the process
12733 owning the descriptor, the command of the owning process, the value
12734 of the descriptor, and the target of the descriptor.
12736 @kindex info os modules
12738 Display the list of all loaded kernel modules on the target. For each
12739 module, @value{GDBN} prints the module name, the size of the module in
12740 bytes, the number of times the module is used, the dependencies of the
12741 module, the status of the module, and the address of the loaded module
12744 @kindex info os msg
12746 Display the list of all System V message queues on the target. For each
12747 message queue, @value{GDBN} prints the message queue key, the message
12748 queue identifier, the access permissions, the current number of bytes
12749 on the queue, the current number of messages on the queue, the processes
12750 that last sent and received a message on the queue, the user and group
12751 of the owner and creator of the message queue, the times at which a
12752 message was last sent and received on the queue, and the time at which
12753 the message queue was last changed.
12755 @kindex info os processes
12757 Display the list of processes on the target. For each process,
12758 @value{GDBN} prints the process identifier, the name of the user, the
12759 command corresponding to the process, and the list of processor cores
12760 that the process is currently running on. (To understand what these
12761 properties mean, for this and the following info types, please consult
12762 the general @sc{gnu}/Linux documentation.)
12764 @kindex info os procgroups
12766 Display the list of process groups on the target. For each process,
12767 @value{GDBN} prints the identifier of the process group that it belongs
12768 to, the command corresponding to the process group leader, the process
12769 identifier, and the command line of the process. The list is sorted
12770 first by the process group identifier, then by the process identifier,
12771 so that processes belonging to the same process group are grouped together
12772 and the process group leader is listed first.
12774 @kindex info os semaphores
12776 Display the list of all System V semaphore sets on the target. For each
12777 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
12778 set identifier, the access permissions, the number of semaphores in the
12779 set, the user and group of the owner and creator of the semaphore set,
12780 and the times at which the semaphore set was operated upon and changed.
12782 @kindex info os shm
12784 Display the list of all System V shared-memory regions on the target.
12785 For each shared-memory region, @value{GDBN} prints the region key,
12786 the shared-memory identifier, the access permissions, the size of the
12787 region, the process that created the region, the process that last
12788 attached to or detached from the region, the current number of live
12789 attaches to the region, and the times at which the region was last
12790 attached to, detach from, and changed.
12792 @kindex info os sockets
12794 Display the list of Internet-domain sockets on the target. For each
12795 socket, @value{GDBN} prints the address and port of the local and
12796 remote endpoints, the current state of the connection, the creator of
12797 the socket, the IP address family of the socket, and the type of the
12800 @kindex info os threads
12802 Display the list of threads running on the target. For each thread,
12803 @value{GDBN} prints the identifier of the process that the thread
12804 belongs to, the command of the process, the thread identifier, and the
12805 processor core that it is currently running on. The main thread of a
12806 process is not listed.
12810 If @var{infotype} is omitted, then list the possible values for
12811 @var{infotype} and the kind of OS information available for each
12812 @var{infotype}. If the target does not return a list of possible
12813 types, this command will report an error.
12816 @node Memory Region Attributes
12817 @section Memory Region Attributes
12818 @cindex memory region attributes
12820 @dfn{Memory region attributes} allow you to describe special handling
12821 required by regions of your target's memory. @value{GDBN} uses
12822 attributes to determine whether to allow certain types of memory
12823 accesses; whether to use specific width accesses; and whether to cache
12824 target memory. By default the description of memory regions is
12825 fetched from the target (if the current target supports this), but the
12826 user can override the fetched regions.
12828 Defined memory regions can be individually enabled and disabled. When a
12829 memory region is disabled, @value{GDBN} uses the default attributes when
12830 accessing memory in that region. Similarly, if no memory regions have
12831 been defined, @value{GDBN} uses the default attributes when accessing
12834 When a memory region is defined, it is given a number to identify it;
12835 to enable, disable, or remove a memory region, you specify that number.
12839 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
12840 Define a memory region bounded by @var{lower} and @var{upper} with
12841 attributes @var{attributes}@dots{}, and add it to the list of regions
12842 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
12843 case: it is treated as the target's maximum memory address.
12844 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
12847 Discard any user changes to the memory regions and use target-supplied
12848 regions, if available, or no regions if the target does not support.
12851 @item delete mem @var{nums}@dots{}
12852 Remove memory regions @var{nums}@dots{} from the list of regions
12853 monitored by @value{GDBN}.
12855 @kindex disable mem
12856 @item disable mem @var{nums}@dots{}
12857 Disable monitoring of memory regions @var{nums}@dots{}.
12858 A disabled memory region is not forgotten.
12859 It may be enabled again later.
12862 @item enable mem @var{nums}@dots{}
12863 Enable monitoring of memory regions @var{nums}@dots{}.
12867 Print a table of all defined memory regions, with the following columns
12871 @item Memory Region Number
12872 @item Enabled or Disabled.
12873 Enabled memory regions are marked with @samp{y}.
12874 Disabled memory regions are marked with @samp{n}.
12877 The address defining the inclusive lower bound of the memory region.
12880 The address defining the exclusive upper bound of the memory region.
12883 The list of attributes set for this memory region.
12888 @subsection Attributes
12890 @subsubsection Memory Access Mode
12891 The access mode attributes set whether @value{GDBN} may make read or
12892 write accesses to a memory region.
12894 While these attributes prevent @value{GDBN} from performing invalid
12895 memory accesses, they do nothing to prevent the target system, I/O DMA,
12896 etc.@: from accessing memory.
12900 Memory is read only.
12902 Memory is write only.
12904 Memory is read/write. This is the default.
12907 @subsubsection Memory Access Size
12908 The access size attribute tells @value{GDBN} to use specific sized
12909 accesses in the memory region. Often memory mapped device registers
12910 require specific sized accesses. If no access size attribute is
12911 specified, @value{GDBN} may use accesses of any size.
12915 Use 8 bit memory accesses.
12917 Use 16 bit memory accesses.
12919 Use 32 bit memory accesses.
12921 Use 64 bit memory accesses.
12924 @c @subsubsection Hardware/Software Breakpoints
12925 @c The hardware/software breakpoint attributes set whether @value{GDBN}
12926 @c will use hardware or software breakpoints for the internal breakpoints
12927 @c used by the step, next, finish, until, etc. commands.
12931 @c Always use hardware breakpoints
12932 @c @item swbreak (default)
12935 @subsubsection Data Cache
12936 The data cache attributes set whether @value{GDBN} will cache target
12937 memory. While this generally improves performance by reducing debug
12938 protocol overhead, it can lead to incorrect results because @value{GDBN}
12939 does not know about volatile variables or memory mapped device
12944 Enable @value{GDBN} to cache target memory.
12946 Disable @value{GDBN} from caching target memory. This is the default.
12949 @subsection Memory Access Checking
12950 @value{GDBN} can be instructed to refuse accesses to memory that is
12951 not explicitly described. This can be useful if accessing such
12952 regions has undesired effects for a specific target, or to provide
12953 better error checking. The following commands control this behaviour.
12956 @kindex set mem inaccessible-by-default
12957 @item set mem inaccessible-by-default [on|off]
12958 If @code{on} is specified, make @value{GDBN} treat memory not
12959 explicitly described by the memory ranges as non-existent and refuse accesses
12960 to such memory. The checks are only performed if there's at least one
12961 memory range defined. If @code{off} is specified, make @value{GDBN}
12962 treat the memory not explicitly described by the memory ranges as RAM.
12963 The default value is @code{on}.
12964 @kindex show mem inaccessible-by-default
12965 @item show mem inaccessible-by-default
12966 Show the current handling of accesses to unknown memory.
12970 @c @subsubsection Memory Write Verification
12971 @c The memory write verification attributes set whether @value{GDBN}
12972 @c will re-reads data after each write to verify the write was successful.
12976 @c @item noverify (default)
12979 @node Dump/Restore Files
12980 @section Copy Between Memory and a File
12981 @cindex dump/restore files
12982 @cindex append data to a file
12983 @cindex dump data to a file
12984 @cindex restore data from a file
12986 You can use the commands @code{dump}, @code{append}, and
12987 @code{restore} to copy data between target memory and a file. The
12988 @code{dump} and @code{append} commands write data to a file, and the
12989 @code{restore} command reads data from a file back into the inferior's
12990 memory. Files may be in binary, Motorola S-record, Intel hex,
12991 Tektronix Hex, or Verilog Hex format; however, @value{GDBN} can only
12992 append to binary files, and cannot read from Verilog Hex files.
12997 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
12998 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
12999 Dump the contents of memory from @var{start_addr} to @var{end_addr},
13000 or the value of @var{expr}, to @var{filename} in the given format.
13002 The @var{format} parameter may be any one of:
13009 Motorola S-record format.
13011 Tektronix Hex format.
13013 Verilog Hex format.
13016 @value{GDBN} uses the same definitions of these formats as the
13017 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
13018 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
13022 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
13023 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
13024 Append the contents of memory from @var{start_addr} to @var{end_addr},
13025 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
13026 (@value{GDBN} can only append data to files in raw binary form.)
13029 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
13030 Restore the contents of file @var{filename} into memory. The
13031 @code{restore} command can automatically recognize any known @sc{bfd}
13032 file format, except for raw binary. To restore a raw binary file you
13033 must specify the optional keyword @code{binary} after the filename.
13035 If @var{bias} is non-zero, its value will be added to the addresses
13036 contained in the file. Binary files always start at address zero, so
13037 they will be restored at address @var{bias}. Other bfd files have
13038 a built-in location; they will be restored at offset @var{bias}
13039 from that location.
13041 If @var{start} and/or @var{end} are non-zero, then only data between
13042 file offset @var{start} and file offset @var{end} will be restored.
13043 These offsets are relative to the addresses in the file, before
13044 the @var{bias} argument is applied.
13048 @node Core File Generation
13049 @section How to Produce a Core File from Your Program
13050 @cindex dump core from inferior
13052 A @dfn{core file} or @dfn{core dump} is a file that records the memory
13053 image of a running process and its process status (register values
13054 etc.). Its primary use is post-mortem debugging of a program that
13055 crashed while it ran outside a debugger. A program that crashes
13056 automatically produces a core file, unless this feature is disabled by
13057 the user. @xref{Files}, for information on invoking @value{GDBN} in
13058 the post-mortem debugging mode.
13060 Occasionally, you may wish to produce a core file of the program you
13061 are debugging in order to preserve a snapshot of its state.
13062 @value{GDBN} has a special command for that.
13066 @kindex generate-core-file
13067 @item generate-core-file [@var{file}]
13068 @itemx gcore [@var{file}]
13069 Produce a core dump of the inferior process. The optional argument
13070 @var{file} specifies the file name where to put the core dump. If not
13071 specified, the file name defaults to @file{core.@var{pid}}, where
13072 @var{pid} is the inferior process ID.
13074 Note that this command is implemented only for some systems (as of
13075 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
13077 On @sc{gnu}/Linux, this command can take into account the value of the
13078 file @file{/proc/@var{pid}/coredump_filter} when generating the core
13079 dump (@pxref{set use-coredump-filter}), and by default honors the
13080 @code{VM_DONTDUMP} flag for mappings where it is present in the file
13081 @file{/proc/@var{pid}/smaps} (@pxref{set dump-excluded-mappings}).
13083 @kindex set use-coredump-filter
13084 @anchor{set use-coredump-filter}
13085 @item set use-coredump-filter on
13086 @itemx set use-coredump-filter off
13087 Enable or disable the use of the file
13088 @file{/proc/@var{pid}/coredump_filter} when generating core dump
13089 files. This file is used by the Linux kernel to decide what types of
13090 memory mappings will be dumped or ignored when generating a core dump
13091 file. @var{pid} is the process ID of a currently running process.
13093 To make use of this feature, you have to write in the
13094 @file{/proc/@var{pid}/coredump_filter} file a value, in hexadecimal,
13095 which is a bit mask representing the memory mapping types. If a bit
13096 is set in the bit mask, then the memory mappings of the corresponding
13097 types will be dumped; otherwise, they will be ignored. This
13098 configuration is inherited by child processes. For more information
13099 about the bits that can be set in the
13100 @file{/proc/@var{pid}/coredump_filter} file, please refer to the
13101 manpage of @code{core(5)}.
13103 By default, this option is @code{on}. If this option is turned
13104 @code{off}, @value{GDBN} does not read the @file{coredump_filter} file
13105 and instead uses the same default value as the Linux kernel in order
13106 to decide which pages will be dumped in the core dump file. This
13107 value is currently @code{0x33}, which means that bits @code{0}
13108 (anonymous private mappings), @code{1} (anonymous shared mappings),
13109 @code{4} (ELF headers) and @code{5} (private huge pages) are active.
13110 This will cause these memory mappings to be dumped automatically.
13112 @kindex set dump-excluded-mappings
13113 @anchor{set dump-excluded-mappings}
13114 @item set dump-excluded-mappings on
13115 @itemx set dump-excluded-mappings off
13116 If @code{on} is specified, @value{GDBN} will dump memory mappings
13117 marked with the @code{VM_DONTDUMP} flag. This flag is represented in
13118 the file @file{/proc/@var{pid}/smaps} with the acronym @code{dd}.
13120 The default value is @code{off}.
13123 @node Character Sets
13124 @section Character Sets
13125 @cindex character sets
13127 @cindex translating between character sets
13128 @cindex host character set
13129 @cindex target character set
13131 If the program you are debugging uses a different character set to
13132 represent characters and strings than the one @value{GDBN} uses itself,
13133 @value{GDBN} can automatically translate between the character sets for
13134 you. The character set @value{GDBN} uses we call the @dfn{host
13135 character set}; the one the inferior program uses we call the
13136 @dfn{target character set}.
13138 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
13139 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
13140 remote protocol (@pxref{Remote Debugging}) to debug a program
13141 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
13142 then the host character set is Latin-1, and the target character set is
13143 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
13144 target-charset EBCDIC-US}, then @value{GDBN} translates between
13145 @sc{ebcdic} and Latin 1 as you print character or string values, or use
13146 character and string literals in expressions.
13148 @value{GDBN} has no way to automatically recognize which character set
13149 the inferior program uses; you must tell it, using the @code{set
13150 target-charset} command, described below.
13152 Here are the commands for controlling @value{GDBN}'s character set
13156 @item set target-charset @var{charset}
13157 @kindex set target-charset
13158 Set the current target character set to @var{charset}. To display the
13159 list of supported target character sets, type
13160 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
13162 @item set host-charset @var{charset}
13163 @kindex set host-charset
13164 Set the current host character set to @var{charset}.
13166 By default, @value{GDBN} uses a host character set appropriate to the
13167 system it is running on; you can override that default using the
13168 @code{set host-charset} command. On some systems, @value{GDBN} cannot
13169 automatically determine the appropriate host character set. In this
13170 case, @value{GDBN} uses @samp{UTF-8}.
13172 @value{GDBN} can only use certain character sets as its host character
13173 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
13174 @value{GDBN} will list the host character sets it supports.
13176 @item set charset @var{charset}
13177 @kindex set charset
13178 Set the current host and target character sets to @var{charset}. As
13179 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
13180 @value{GDBN} will list the names of the character sets that can be used
13181 for both host and target.
13184 @kindex show charset
13185 Show the names of the current host and target character sets.
13187 @item show host-charset
13188 @kindex show host-charset
13189 Show the name of the current host character set.
13191 @item show target-charset
13192 @kindex show target-charset
13193 Show the name of the current target character set.
13195 @item set target-wide-charset @var{charset}
13196 @kindex set target-wide-charset
13197 Set the current target's wide character set to @var{charset}. This is
13198 the character set used by the target's @code{wchar_t} type. To
13199 display the list of supported wide character sets, type
13200 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
13202 @item show target-wide-charset
13203 @kindex show target-wide-charset
13204 Show the name of the current target's wide character set.
13207 Here is an example of @value{GDBN}'s character set support in action.
13208 Assume that the following source code has been placed in the file
13209 @file{charset-test.c}:
13215 = @{72, 101, 108, 108, 111, 44, 32, 119,
13216 111, 114, 108, 100, 33, 10, 0@};
13217 char ibm1047_hello[]
13218 = @{200, 133, 147, 147, 150, 107, 64, 166,
13219 150, 153, 147, 132, 90, 37, 0@};
13223 printf ("Hello, world!\n");
13227 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
13228 containing the string @samp{Hello, world!} followed by a newline,
13229 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
13231 We compile the program, and invoke the debugger on it:
13234 $ gcc -g charset-test.c -o charset-test
13235 $ gdb -nw charset-test
13236 GNU gdb 2001-12-19-cvs
13237 Copyright 2001 Free Software Foundation, Inc.
13242 We can use the @code{show charset} command to see what character sets
13243 @value{GDBN} is currently using to interpret and display characters and
13247 (@value{GDBP}) show charset
13248 The current host and target character set is `ISO-8859-1'.
13252 For the sake of printing this manual, let's use @sc{ascii} as our
13253 initial character set:
13255 (@value{GDBP}) set charset ASCII
13256 (@value{GDBP}) show charset
13257 The current host and target character set is `ASCII'.
13261 Let's assume that @sc{ascii} is indeed the correct character set for our
13262 host system --- in other words, let's assume that if @value{GDBN} prints
13263 characters using the @sc{ascii} character set, our terminal will display
13264 them properly. Since our current target character set is also
13265 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
13268 (@value{GDBP}) print ascii_hello
13269 $1 = 0x401698 "Hello, world!\n"
13270 (@value{GDBP}) print ascii_hello[0]
13275 @value{GDBN} uses the target character set for character and string
13276 literals you use in expressions:
13279 (@value{GDBP}) print '+'
13284 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
13287 @value{GDBN} relies on the user to tell it which character set the
13288 target program uses. If we print @code{ibm1047_hello} while our target
13289 character set is still @sc{ascii}, we get jibberish:
13292 (@value{GDBP}) print ibm1047_hello
13293 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
13294 (@value{GDBP}) print ibm1047_hello[0]
13299 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
13300 @value{GDBN} tells us the character sets it supports:
13303 (@value{GDBP}) set target-charset
13304 ASCII EBCDIC-US IBM1047 ISO-8859-1
13305 (@value{GDBP}) set target-charset
13308 We can select @sc{ibm1047} as our target character set, and examine the
13309 program's strings again. Now the @sc{ascii} string is wrong, but
13310 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
13311 target character set, @sc{ibm1047}, to the host character set,
13312 @sc{ascii}, and they display correctly:
13315 (@value{GDBP}) set target-charset IBM1047
13316 (@value{GDBP}) show charset
13317 The current host character set is `ASCII'.
13318 The current target character set is `IBM1047'.
13319 (@value{GDBP}) print ascii_hello
13320 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
13321 (@value{GDBP}) print ascii_hello[0]
13323 (@value{GDBP}) print ibm1047_hello
13324 $8 = 0x4016a8 "Hello, world!\n"
13325 (@value{GDBP}) print ibm1047_hello[0]
13330 As above, @value{GDBN} uses the target character set for character and
13331 string literals you use in expressions:
13334 (@value{GDBP}) print '+'
13339 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
13342 @node Caching Target Data
13343 @section Caching Data of Targets
13344 @cindex caching data of targets
13346 @value{GDBN} caches data exchanged between the debugger and a target.
13347 Each cache is associated with the address space of the inferior.
13348 @xref{Inferiors Connections and Programs}, about inferior and address space.
13349 Such caching generally improves performance in remote debugging
13350 (@pxref{Remote Debugging}), because it reduces the overhead of the
13351 remote protocol by bundling memory reads and writes into large chunks.
13352 Unfortunately, simply caching everything would lead to incorrect results,
13353 since @value{GDBN} does not necessarily know anything about volatile
13354 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
13355 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
13357 Therefore, by default, @value{GDBN} only caches data
13358 known to be on the stack@footnote{In non-stop mode, it is moderately
13359 rare for a running thread to modify the stack of a stopped thread
13360 in a way that would interfere with a backtrace, and caching of
13361 stack reads provides a significant speed up of remote backtraces.} or
13362 in the code segment.
13363 Other regions of memory can be explicitly marked as
13364 cacheable; @pxref{Memory Region Attributes}.
13367 @kindex set remotecache
13368 @item set remotecache on
13369 @itemx set remotecache off
13370 This option no longer does anything; it exists for compatibility
13373 @kindex show remotecache
13374 @item show remotecache
13375 Show the current state of the obsolete remotecache flag.
13377 @kindex set stack-cache
13378 @item set stack-cache on
13379 @itemx set stack-cache off
13380 Enable or disable caching of stack accesses. When @code{on}, use
13381 caching. By default, this option is @code{on}.
13383 @kindex show stack-cache
13384 @item show stack-cache
13385 Show the current state of data caching for memory accesses.
13387 @kindex set code-cache
13388 @item set code-cache on
13389 @itemx set code-cache off
13390 Enable or disable caching of code segment accesses. When @code{on},
13391 use caching. By default, this option is @code{on}. This improves
13392 performance of disassembly in remote debugging.
13394 @kindex show code-cache
13395 @item show code-cache
13396 Show the current state of target memory cache for code segment
13399 @kindex info dcache
13400 @item info dcache @r{[}line@r{]}
13401 Print the information about the performance of data cache of the
13402 current inferior's address space. The information displayed
13403 includes the dcache width and depth, and for each cache line, its
13404 number, address, and how many times it was referenced. This
13405 command is useful for debugging the data cache operation.
13407 If a line number is specified, the contents of that line will be
13410 @item set dcache size @var{size}
13411 @cindex dcache size
13412 @kindex set dcache size
13413 Set maximum number of entries in dcache (dcache depth above).
13415 @item set dcache line-size @var{line-size}
13416 @cindex dcache line-size
13417 @kindex set dcache line-size
13418 Set number of bytes each dcache entry caches (dcache width above).
13419 Must be a power of 2.
13421 @item show dcache size
13422 @kindex show dcache size
13423 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
13425 @item show dcache line-size
13426 @kindex show dcache line-size
13427 Show default size of dcache lines.
13429 @item maint flush dcache
13430 @cindex dcache, flushing
13431 @kindex maint flush dcache
13432 Flush the contents (if any) of the dcache. This maintainer command is
13433 useful when debugging the dcache implementation.
13437 @node Searching Memory
13438 @section Search Memory
13439 @cindex searching memory
13441 Memory can be searched for a particular sequence of bytes with the
13442 @code{find} command.
13446 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
13447 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
13448 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
13449 etc. The search begins at address @var{start_addr} and continues for either
13450 @var{len} bytes or through to @var{end_addr} inclusive.
13453 @var{s} and @var{n} are optional parameters.
13454 They may be specified in either order, apart or together.
13457 @item @var{s}, search query size
13458 The size of each search query value.
13464 halfwords (two bytes)
13468 giant words (eight bytes)
13471 All values are interpreted in the current language.
13472 This means, for example, that if the current source language is C/C@t{++}
13473 then searching for the string ``hello'' includes the trailing '\0'.
13474 The null terminator can be removed from searching by using casts,
13475 e.g.: @samp{@{char[5]@}"hello"}.
13477 If the value size is not specified, it is taken from the
13478 value's type in the current language.
13479 This is useful when one wants to specify the search
13480 pattern as a mixture of types.
13481 Note that this means, for example, that in the case of C-like languages
13482 a search for an untyped 0x42 will search for @samp{(int) 0x42}
13483 which is typically four bytes.
13485 @item @var{n}, maximum number of finds
13486 The maximum number of matches to print. The default is to print all finds.
13489 You can use strings as search values. Quote them with double-quotes
13491 The string value is copied into the search pattern byte by byte,
13492 regardless of the endianness of the target and the size specification.
13494 The address of each match found is printed as well as a count of the
13495 number of matches found.
13497 The address of the last value found is stored in convenience variable
13499 A count of the number of matches is stored in @samp{$numfound}.
13501 For example, if stopped at the @code{printf} in this function:
13507 static char hello[] = "hello-hello";
13508 static struct @{ char c; short s; int i; @}
13509 __attribute__ ((packed)) mixed
13510 = @{ 'c', 0x1234, 0x87654321 @};
13511 printf ("%s\n", hello);
13516 you get during debugging:
13519 (gdb) find &hello[0], +sizeof(hello), "hello"
13520 0x804956d <hello.1620+6>
13522 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
13523 0x8049567 <hello.1620>
13524 0x804956d <hello.1620+6>
13526 (gdb) find &hello[0], +sizeof(hello), @{char[5]@}"hello"
13527 0x8049567 <hello.1620>
13528 0x804956d <hello.1620+6>
13530 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
13531 0x8049567 <hello.1620>
13533 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
13534 0x8049560 <mixed.1625>
13536 (gdb) print $numfound
13539 $2 = (void *) 0x8049560
13543 @section Value Sizes
13545 Whenever @value{GDBN} prints a value memory will be allocated within
13546 @value{GDBN} to hold the contents of the value. It is possible in
13547 some languages with dynamic typing systems, that an invalid program
13548 may indicate a value that is incorrectly large, this in turn may cause
13549 @value{GDBN} to try and allocate an overly large amount of memory.
13552 @kindex set max-value-size
13553 @item set max-value-size @var{bytes}
13554 @itemx set max-value-size unlimited
13555 Set the maximum size of memory that @value{GDBN} will allocate for the
13556 contents of a value to @var{bytes}, trying to display a value that
13557 requires more memory than that will result in an error.
13559 Setting this variable does not effect values that have already been
13560 allocated within @value{GDBN}, only future allocations.
13562 There's a minimum size that @code{max-value-size} can be set to in
13563 order that @value{GDBN} can still operate correctly, this minimum is
13564 currently 16 bytes.
13566 The limit applies to the results of some subexpressions as well as to
13567 complete expressions. For example, an expression denoting a simple
13568 integer component, such as @code{x.y.z}, may fail if the size of
13569 @var{x.y} is dynamic and exceeds @var{bytes}. On the other hand,
13570 @value{GDBN} is sometimes clever; the expression @code{A[i]}, where
13571 @var{A} is an array variable with non-constant size, will generally
13572 succeed regardless of the bounds on @var{A}, as long as the component
13573 size is less than @var{bytes}.
13575 The default value of @code{max-value-size} is currently 64k.
13577 @kindex show max-value-size
13578 @item show max-value-size
13579 Show the maximum size of memory, in bytes, that @value{GDBN} will
13580 allocate for the contents of a value.
13583 @node Optimized Code
13584 @chapter Debugging Optimized Code
13585 @cindex optimized code, debugging
13586 @cindex debugging optimized code
13588 Almost all compilers support optimization. With optimization
13589 disabled, the compiler generates assembly code that corresponds
13590 directly to your source code, in a simplistic way. As the compiler
13591 applies more powerful optimizations, the generated assembly code
13592 diverges from your original source code. With help from debugging
13593 information generated by the compiler, @value{GDBN} can map from
13594 the running program back to constructs from your original source.
13596 @value{GDBN} is more accurate with optimization disabled. If you
13597 can recompile without optimization, it is easier to follow the
13598 progress of your program during debugging. But, there are many cases
13599 where you may need to debug an optimized version.
13601 When you debug a program compiled with @samp{-g -O}, remember that the
13602 optimizer has rearranged your code; the debugger shows you what is
13603 really there. Do not be too surprised when the execution path does not
13604 exactly match your source file! An extreme example: if you define a
13605 variable, but never use it, @value{GDBN} never sees that
13606 variable---because the compiler optimizes it out of existence.
13608 Some things do not work as well with @samp{-g -O} as with just
13609 @samp{-g}, particularly on machines with instruction scheduling. If in
13610 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
13611 please report it to us as a bug (including a test case!).
13612 @xref{Variables}, for more information about debugging optimized code.
13615 * Inline Functions:: How @value{GDBN} presents inlining
13616 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
13619 @node Inline Functions
13620 @section Inline Functions
13621 @cindex inline functions, debugging
13623 @dfn{Inlining} is an optimization that inserts a copy of the function
13624 body directly at each call site, instead of jumping to a shared
13625 routine. @value{GDBN} displays inlined functions just like
13626 non-inlined functions. They appear in backtraces. You can view their
13627 arguments and local variables, step into them with @code{step}, skip
13628 them with @code{next}, and escape from them with @code{finish}.
13629 You can check whether a function was inlined by using the
13630 @code{info frame} command.
13632 For @value{GDBN} to support inlined functions, the compiler must
13633 record information about inlining in the debug information ---
13634 @value{NGCC} using the @sc{dwarf 2} format does this, and several
13635 other compilers do also. @value{GDBN} only supports inlined functions
13636 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
13637 do not emit two required attributes (@samp{DW_AT_call_file} and
13638 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
13639 function calls with earlier versions of @value{NGCC}. It instead
13640 displays the arguments and local variables of inlined functions as
13641 local variables in the caller.
13643 The body of an inlined function is directly included at its call site;
13644 unlike a non-inlined function, there are no instructions devoted to
13645 the call. @value{GDBN} still pretends that the call site and the
13646 start of the inlined function are different instructions. Stepping to
13647 the call site shows the call site, and then stepping again shows
13648 the first line of the inlined function, even though no additional
13649 instructions are executed.
13651 This makes source-level debugging much clearer; you can see both the
13652 context of the call and then the effect of the call. Only stepping by
13653 a single instruction using @code{stepi} or @code{nexti} does not do
13654 this; single instruction steps always show the inlined body.
13656 There are some ways that @value{GDBN} does not pretend that inlined
13657 function calls are the same as normal calls:
13661 Setting breakpoints at the call site of an inlined function may not
13662 work, because the call site does not contain any code. @value{GDBN}
13663 may incorrectly move the breakpoint to the next line of the enclosing
13664 function, after the call. This limitation will be removed in a future
13665 version of @value{GDBN}; until then, set a breakpoint on an earlier line
13666 or inside the inlined function instead.
13669 @value{GDBN} cannot locate the return value of inlined calls after
13670 using the @code{finish} command. This is a limitation of compiler-generated
13671 debugging information; after @code{finish}, you can step to the next line
13672 and print a variable where your program stored the return value.
13676 @node Tail Call Frames
13677 @section Tail Call Frames
13678 @cindex tail call frames, debugging
13680 Function @code{B} can call function @code{C} in its very last statement. In
13681 unoptimized compilation the call of @code{C} is immediately followed by return
13682 instruction at the end of @code{B} code. Optimizing compiler may replace the
13683 call and return in function @code{B} into one jump to function @code{C}
13684 instead. Such use of a jump instruction is called @dfn{tail call}.
13686 During execution of function @code{C}, there will be no indication in the
13687 function call stack frames that it was tail-called from @code{B}. If function
13688 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
13689 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
13690 some cases @value{GDBN} can determine that @code{C} was tail-called from
13691 @code{B}, and it will then create fictitious call frame for that, with the
13692 return address set up as if @code{B} called @code{C} normally.
13694 This functionality is currently supported only by DWARF 2 debugging format and
13695 the compiler has to produce @samp{DW_TAG_call_site} tags. With
13696 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
13699 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
13700 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
13704 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
13706 Stack level 1, frame at 0x7fffffffda30:
13707 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
13708 tail call frame, caller of frame at 0x7fffffffda30
13709 source language c++.
13710 Arglist at unknown address.
13711 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
13714 The detection of all the possible code path executions can find them ambiguous.
13715 There is no execution history stored (possible @ref{Reverse Execution} is never
13716 used for this purpose) and the last known caller could have reached the known
13717 callee by multiple different jump sequences. In such case @value{GDBN} still
13718 tries to show at least all the unambiguous top tail callers and all the
13719 unambiguous bottom tail calees, if any.
13722 @anchor{set debug entry-values}
13723 @item set debug entry-values
13724 @kindex set debug entry-values
13725 When set to on, enables printing of analysis messages for both frame argument
13726 values at function entry and tail calls. It will show all the possible valid
13727 tail calls code paths it has considered. It will also print the intersection
13728 of them with the final unambiguous (possibly partial or even empty) code path
13731 @item show debug entry-values
13732 @kindex show debug entry-values
13733 Show the current state of analysis messages printing for both frame argument
13734 values at function entry and tail calls.
13737 The analysis messages for tail calls can for example show why the virtual tail
13738 call frame for function @code{c} has not been recognized (due to the indirect
13739 reference by variable @code{x}):
13742 static void __attribute__((noinline, noclone)) c (void);
13743 void (*x) (void) = c;
13744 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
13745 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
13746 int main (void) @{ x (); return 0; @}
13748 Breakpoint 1, DW_OP_entry_value resolving cannot find
13749 DW_TAG_call_site 0x40039a in main
13751 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
13754 #1 0x000000000040039a in main () at t.c:5
13757 Another possibility is an ambiguous virtual tail call frames resolution:
13761 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
13762 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
13763 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
13764 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
13765 static void __attribute__((noinline, noclone)) b (void)
13766 @{ if (i) c (); else e (); @}
13767 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
13768 int main (void) @{ a (); return 0; @}
13770 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
13771 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
13772 tailcall: reduced: 0x4004d2(a) |
13775 #1 0x00000000004004d2 in a () at t.c:8
13776 #2 0x0000000000400395 in main () at t.c:9
13779 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
13780 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
13782 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
13783 @ifset HAVE_MAKEINFO_CLICK
13784 @set ARROW @click{}
13785 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
13786 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
13788 @ifclear HAVE_MAKEINFO_CLICK
13790 @set CALLSEQ1B @value{CALLSEQ1A}
13791 @set CALLSEQ2B @value{CALLSEQ2A}
13794 Frames #0 and #2 are real, #1 is a virtual tail call frame.
13795 The code can have possible execution paths @value{CALLSEQ1B} or
13796 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
13798 @code{initial:} state shows some random possible calling sequence @value{GDBN}
13799 has found. It then finds another possible calling sequence - that one is
13800 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
13801 printed as the @code{reduced:} calling sequence. That one could have many
13802 further @code{compare:} and @code{reduced:} statements as long as there remain
13803 any non-ambiguous sequence entries.
13805 For the frame of function @code{b} in both cases there are different possible
13806 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
13807 also ambiguous. The only non-ambiguous frame is the one for function @code{a},
13808 therefore this one is displayed to the user while the ambiguous frames are
13811 There can be also reasons why printing of frame argument values at function
13816 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
13817 static void __attribute__((noinline, noclone)) a (int i);
13818 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
13819 static void __attribute__((noinline, noclone)) a (int i)
13820 @{ if (i) b (i - 1); else c (0); @}
13821 int main (void) @{ a (5); return 0; @}
13824 #0 c (i=i@@entry=0) at t.c:2
13825 #1 0x0000000000400428 in a (DW_OP_entry_value resolving has found
13826 function "a" at 0x400420 can call itself via tail calls
13827 i=<optimized out>) at t.c:6
13828 #2 0x000000000040036e in main () at t.c:7
13831 @value{GDBN} cannot find out from the inferior state if and how many times did
13832 function @code{a} call itself (via function @code{b}) as these calls would be
13833 tail calls. Such tail calls would modify the @code{i} variable, therefore
13834 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
13835 prints @code{<optimized out>} instead.
13838 @chapter C Preprocessor Macros
13840 Some languages, such as C and C@t{++}, provide a way to define and invoke
13841 ``preprocessor macros'' which expand into strings of tokens.
13842 @value{GDBN} can evaluate expressions containing macro invocations, show
13843 the result of macro expansion, and show a macro's definition, including
13844 where it was defined.
13846 You may need to compile your program specially to provide @value{GDBN}
13847 with information about preprocessor macros. Most compilers do not
13848 include macros in their debugging information, even when you compile
13849 with the @option{-g} flag. @xref{Compilation}.
13851 A program may define a macro at one point, remove that definition later,
13852 and then provide a different definition after that. Thus, at different
13853 points in the program, a macro may have different definitions, or have
13854 no definition at all. If there is a current stack frame, @value{GDBN}
13855 uses the macros in scope at that frame's source code line. Otherwise,
13856 @value{GDBN} uses the macros in scope at the current listing location;
13859 Whenever @value{GDBN} evaluates an expression, it always expands any
13860 macro invocations present in the expression. @value{GDBN} also provides
13861 the following commands for working with macros explicitly.
13865 @kindex macro expand
13866 @cindex macro expansion, showing the results of preprocessor
13867 @cindex preprocessor macro expansion, showing the results of
13868 @cindex expanding preprocessor macros
13869 @item macro expand @var{expression}
13870 @itemx macro exp @var{expression}
13871 Show the results of expanding all preprocessor macro invocations in
13872 @var{expression}. Since @value{GDBN} simply expands macros, but does
13873 not parse the result, @var{expression} need not be a valid expression;
13874 it can be any string of tokens.
13877 @item macro expand-once @var{expression}
13878 @itemx macro exp1 @var{expression}
13879 @cindex expand macro once
13880 @i{(This command is not yet implemented.)} Show the results of
13881 expanding those preprocessor macro invocations that appear explicitly in
13882 @var{expression}. Macro invocations appearing in that expansion are
13883 left unchanged. This command allows you to see the effect of a
13884 particular macro more clearly, without being confused by further
13885 expansions. Since @value{GDBN} simply expands macros, but does not
13886 parse the result, @var{expression} need not be a valid expression; it
13887 can be any string of tokens.
13890 @cindex macro definition, showing
13891 @cindex definition of a macro, showing
13892 @cindex macros, from debug info
13893 @item info macro [-a|-all] [--] @var{macro}
13894 Show the current definition or all definitions of the named @var{macro},
13895 and describe the source location or compiler command-line where that
13896 definition was established. The optional double dash is to signify the end of
13897 argument processing and the beginning of @var{macro} for non C-like macros where
13898 the macro may begin with a hyphen.
13900 @kindex info macros
13901 @item info macros @var{location}
13902 Show all macro definitions that are in effect at the location specified
13903 by @var{location}, and describe the source location or compiler
13904 command-line where those definitions were established.
13906 @kindex macro define
13907 @cindex user-defined macros
13908 @cindex defining macros interactively
13909 @cindex macros, user-defined
13910 @item macro define @var{macro} @var{replacement-list}
13911 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
13912 Introduce a definition for a preprocessor macro named @var{macro},
13913 invocations of which are replaced by the tokens given in
13914 @var{replacement-list}. The first form of this command defines an
13915 ``object-like'' macro, which takes no arguments; the second form
13916 defines a ``function-like'' macro, which takes the arguments given in
13919 A definition introduced by this command is in scope in every
13920 expression evaluated in @value{GDBN}, until it is removed with the
13921 @code{macro undef} command, described below. The definition overrides
13922 all definitions for @var{macro} present in the program being debugged,
13923 as well as any previous user-supplied definition.
13925 @kindex macro undef
13926 @item macro undef @var{macro}
13927 Remove any user-supplied definition for the macro named @var{macro}.
13928 This command only affects definitions provided with the @code{macro
13929 define} command, described above; it cannot remove definitions present
13930 in the program being debugged.
13934 List all the macros defined using the @code{macro define} command.
13937 @cindex macros, example of debugging with
13938 Here is a transcript showing the above commands in action. First, we
13939 show our source files:
13944 #include "sample.h"
13947 #define ADD(x) (M + x)
13952 printf ("Hello, world!\n");
13954 printf ("We're so creative.\n");
13956 printf ("Goodbye, world!\n");
13963 Now, we compile the program using the @sc{gnu} C compiler,
13964 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
13965 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
13966 and @option{-gdwarf-4}; we recommend always choosing the most recent
13967 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
13968 includes information about preprocessor macros in the debugging
13972 $ gcc -gdwarf-2 -g3 sample.c -o sample
13976 Now, we start @value{GDBN} on our sample program:
13980 GNU gdb 2002-05-06-cvs
13981 Copyright 2002 Free Software Foundation, Inc.
13982 GDB is free software, @dots{}
13986 We can expand macros and examine their definitions, even when the
13987 program is not running. @value{GDBN} uses the current listing position
13988 to decide which macro definitions are in scope:
13991 (@value{GDBP}) list main
13994 5 #define ADD(x) (M + x)
13999 10 printf ("Hello, world!\n");
14001 12 printf ("We're so creative.\n");
14002 (@value{GDBP}) info macro ADD
14003 Defined at /home/jimb/gdb/macros/play/sample.c:5
14004 #define ADD(x) (M + x)
14005 (@value{GDBP}) info macro Q
14006 Defined at /home/jimb/gdb/macros/play/sample.h:1
14007 included at /home/jimb/gdb/macros/play/sample.c:2
14009 (@value{GDBP}) macro expand ADD(1)
14010 expands to: (42 + 1)
14011 (@value{GDBP}) macro expand-once ADD(1)
14012 expands to: once (M + 1)
14016 In the example above, note that @code{macro expand-once} expands only
14017 the macro invocation explicit in the original text --- the invocation of
14018 @code{ADD} --- but does not expand the invocation of the macro @code{M},
14019 which was introduced by @code{ADD}.
14021 Once the program is running, @value{GDBN} uses the macro definitions in
14022 force at the source line of the current stack frame:
14025 (@value{GDBP}) break main
14026 Breakpoint 1 at 0x8048370: file sample.c, line 10.
14028 Starting program: /home/jimb/gdb/macros/play/sample
14030 Breakpoint 1, main () at sample.c:10
14031 10 printf ("Hello, world!\n");
14035 At line 10, the definition of the macro @code{N} at line 9 is in force:
14038 (@value{GDBP}) info macro N
14039 Defined at /home/jimb/gdb/macros/play/sample.c:9
14041 (@value{GDBP}) macro expand N Q M
14042 expands to: 28 < 42
14043 (@value{GDBP}) print N Q M
14048 As we step over directives that remove @code{N}'s definition, and then
14049 give it a new definition, @value{GDBN} finds the definition (or lack
14050 thereof) in force at each point:
14053 (@value{GDBP}) next
14055 12 printf ("We're so creative.\n");
14056 (@value{GDBP}) info macro N
14057 The symbol `N' has no definition as a C/C++ preprocessor macro
14058 at /home/jimb/gdb/macros/play/sample.c:12
14059 (@value{GDBP}) next
14061 14 printf ("Goodbye, world!\n");
14062 (@value{GDBP}) info macro N
14063 Defined at /home/jimb/gdb/macros/play/sample.c:13
14065 (@value{GDBP}) macro expand N Q M
14066 expands to: 1729 < 42
14067 (@value{GDBP}) print N Q M
14072 In addition to source files, macros can be defined on the compilation command
14073 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
14074 such a way, @value{GDBN} displays the location of their definition as line zero
14075 of the source file submitted to the compiler.
14078 (@value{GDBP}) info macro __STDC__
14079 Defined at /home/jimb/gdb/macros/play/sample.c:0
14086 @chapter Tracepoints
14087 @c This chapter is based on the documentation written by Michael
14088 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
14090 @cindex tracepoints
14091 In some applications, it is not feasible for the debugger to interrupt
14092 the program's execution long enough for the developer to learn
14093 anything helpful about its behavior. If the program's correctness
14094 depends on its real-time behavior, delays introduced by a debugger
14095 might cause the program to change its behavior drastically, or perhaps
14096 fail, even when the code itself is correct. It is useful to be able
14097 to observe the program's behavior without interrupting it.
14099 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
14100 specify locations in the program, called @dfn{tracepoints}, and
14101 arbitrary expressions to evaluate when those tracepoints are reached.
14102 Later, using the @code{tfind} command, you can examine the values
14103 those expressions had when the program hit the tracepoints. The
14104 expressions may also denote objects in memory---structures or arrays,
14105 for example---whose values @value{GDBN} should record; while visiting
14106 a particular tracepoint, you may inspect those objects as if they were
14107 in memory at that moment. However, because @value{GDBN} records these
14108 values without interacting with you, it can do so quickly and
14109 unobtrusively, hopefully not disturbing the program's behavior.
14111 The tracepoint facility is currently available only for remote
14112 targets. @xref{Targets}. In addition, your remote target must know
14113 how to collect trace data. This functionality is implemented in the
14114 remote stub; however, none of the stubs distributed with @value{GDBN}
14115 support tracepoints as of this writing. The format of the remote
14116 packets used to implement tracepoints are described in @ref{Tracepoint
14119 It is also possible to get trace data from a file, in a manner reminiscent
14120 of corefiles; you specify the filename, and use @code{tfind} to search
14121 through the file. @xref{Trace Files}, for more details.
14123 This chapter describes the tracepoint commands and features.
14126 * Set Tracepoints::
14127 * Analyze Collected Data::
14128 * Tracepoint Variables::
14132 @node Set Tracepoints
14133 @section Commands to Set Tracepoints
14135 Before running such a @dfn{trace experiment}, an arbitrary number of
14136 tracepoints can be set. A tracepoint is actually a special type of
14137 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
14138 standard breakpoint commands. For instance, as with breakpoints,
14139 tracepoint numbers are successive integers starting from one, and many
14140 of the commands associated with tracepoints take the tracepoint number
14141 as their argument, to identify which tracepoint to work on.
14143 For each tracepoint, you can specify, in advance, some arbitrary set
14144 of data that you want the target to collect in the trace buffer when
14145 it hits that tracepoint. The collected data can include registers,
14146 local variables, or global data. Later, you can use @value{GDBN}
14147 commands to examine the values these data had at the time the
14148 tracepoint was hit.
14150 Tracepoints do not support every breakpoint feature. Ignore counts on
14151 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
14152 commands when they are hit. Tracepoints may not be thread-specific
14155 @cindex fast tracepoints
14156 Some targets may support @dfn{fast tracepoints}, which are inserted in
14157 a different way (such as with a jump instead of a trap), that is
14158 faster but possibly restricted in where they may be installed.
14160 @cindex static tracepoints
14161 @cindex markers, static tracepoints
14162 @cindex probing markers, static tracepoints
14163 Regular and fast tracepoints are dynamic tracing facilities, meaning
14164 that they can be used to insert tracepoints at (almost) any location
14165 in the target. Some targets may also support controlling @dfn{static
14166 tracepoints} from @value{GDBN}. With static tracing, a set of
14167 instrumentation points, also known as @dfn{markers}, are embedded in
14168 the target program, and can be activated or deactivated by name or
14169 address. These are usually placed at locations which facilitate
14170 investigating what the target is actually doing. @value{GDBN}'s
14171 support for static tracing includes being able to list instrumentation
14172 points, and attach them with @value{GDBN} defined high level
14173 tracepoints that expose the whole range of convenience of
14174 @value{GDBN}'s tracepoints support. Namely, support for collecting
14175 registers values and values of global or local (to the instrumentation
14176 point) variables; tracepoint conditions and trace state variables.
14177 The act of installing a @value{GDBN} static tracepoint on an
14178 instrumentation point, or marker, is referred to as @dfn{probing} a
14179 static tracepoint marker.
14181 @code{gdbserver} supports tracepoints on some target systems.
14182 @xref{Server,,Tracepoints support in @code{gdbserver}}.
14184 This section describes commands to set tracepoints and associated
14185 conditions and actions.
14188 * Create and Delete Tracepoints::
14189 * Enable and Disable Tracepoints::
14190 * Tracepoint Passcounts::
14191 * Tracepoint Conditions::
14192 * Trace State Variables::
14193 * Tracepoint Actions::
14194 * Listing Tracepoints::
14195 * Listing Static Tracepoint Markers::
14196 * Starting and Stopping Trace Experiments::
14197 * Tracepoint Restrictions::
14200 @node Create and Delete Tracepoints
14201 @subsection Create and Delete Tracepoints
14204 @cindex set tracepoint
14206 @item trace @var{location}
14207 The @code{trace} command is very similar to the @code{break} command.
14208 Its argument @var{location} can be any valid location.
14209 @xref{Specify Location}. The @code{trace} command defines a tracepoint,
14210 which is a point in the target program where the debugger will briefly stop,
14211 collect some data, and then allow the program to continue. Setting a tracepoint
14212 or changing its actions takes effect immediately if the remote stub
14213 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
14215 If remote stub doesn't support the @samp{InstallInTrace} feature, all
14216 these changes don't take effect until the next @code{tstart}
14217 command, and once a trace experiment is running, further changes will
14218 not have any effect until the next trace experiment starts. In addition,
14219 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
14220 address is not yet resolved. (This is similar to pending breakpoints.)
14221 Pending tracepoints are not downloaded to the target and not installed
14222 until they are resolved. The resolution of pending tracepoints requires
14223 @value{GDBN} support---when debugging with the remote target, and
14224 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
14225 tracing}), pending tracepoints can not be resolved (and downloaded to
14226 the remote stub) while @value{GDBN} is disconnected.
14228 Here are some examples of using the @code{trace} command:
14231 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
14233 (@value{GDBP}) @b{trace +2} // 2 lines forward
14235 (@value{GDBP}) @b{trace my_function} // first source line of function
14237 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
14239 (@value{GDBP}) @b{trace *0x2117c4} // an address
14243 You can abbreviate @code{trace} as @code{tr}.
14245 @item trace @var{location} if @var{cond}
14246 Set a tracepoint with condition @var{cond}; evaluate the expression
14247 @var{cond} each time the tracepoint is reached, and collect data only
14248 if the value is nonzero---that is, if @var{cond} evaluates as true.
14249 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
14250 information on tracepoint conditions.
14252 @item ftrace @var{location} [ if @var{cond} ]
14253 @cindex set fast tracepoint
14254 @cindex fast tracepoints, setting
14256 The @code{ftrace} command sets a fast tracepoint. For targets that
14257 support them, fast tracepoints will use a more efficient but possibly
14258 less general technique to trigger data collection, such as a jump
14259 instruction instead of a trap, or some sort of hardware support. It
14260 may not be possible to create a fast tracepoint at the desired
14261 location, in which case the command will exit with an explanatory
14264 @value{GDBN} handles arguments to @code{ftrace} exactly as for
14267 On 32-bit x86-architecture systems, fast tracepoints normally need to
14268 be placed at an instruction that is 5 bytes or longer, but can be
14269 placed at 4-byte instructions if the low 64K of memory of the target
14270 program is available to install trampolines. Some Unix-type systems,
14271 such as @sc{gnu}/Linux, exclude low addresses from the program's
14272 address space; but for instance with the Linux kernel it is possible
14273 to let @value{GDBN} use this area by doing a @command{sysctl} command
14274 to set the @code{mmap_min_addr} kernel parameter, as in
14277 sudo sysctl -w vm.mmap_min_addr=32768
14281 which sets the low address to 32K, which leaves plenty of room for
14282 trampolines. The minimum address should be set to a page boundary.
14284 @item strace @var{location} [ if @var{cond} ]
14285 @cindex set static tracepoint
14286 @cindex static tracepoints, setting
14287 @cindex probe static tracepoint marker
14289 The @code{strace} command sets a static tracepoint. For targets that
14290 support it, setting a static tracepoint probes a static
14291 instrumentation point, or marker, found at @var{location}. It may not
14292 be possible to set a static tracepoint at the desired location, in
14293 which case the command will exit with an explanatory message.
14295 @value{GDBN} handles arguments to @code{strace} exactly as for
14296 @code{trace}, with the addition that the user can also specify
14297 @code{-m @var{marker}} as @var{location}. This probes the marker
14298 identified by the @var{marker} string identifier. This identifier
14299 depends on the static tracepoint backend library your program is
14300 using. You can find all the marker identifiers in the @samp{ID} field
14301 of the @code{info static-tracepoint-markers} command output.
14302 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
14303 Markers}. For example, in the following small program using the UST
14309 trace_mark(ust, bar33, "str %s", "FOOBAZ");
14314 the marker id is composed of joining the first two arguments to the
14315 @code{trace_mark} call with a slash, which translates to:
14318 (@value{GDBP}) info static-tracepoint-markers
14319 Cnt Enb ID Address What
14320 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
14326 so you may probe the marker above with:
14329 (@value{GDBP}) strace -m ust/bar33
14332 Static tracepoints accept an extra collect action --- @code{collect
14333 $_sdata}. This collects arbitrary user data passed in the probe point
14334 call to the tracing library. In the UST example above, you'll see
14335 that the third argument to @code{trace_mark} is a printf-like format
14336 string. The user data is then the result of running that formatting
14337 string against the following arguments. Note that @code{info
14338 static-tracepoint-markers} command output lists that format string in
14339 the @samp{Data:} field.
14341 You can inspect this data when analyzing the trace buffer, by printing
14342 the $_sdata variable like any other variable available to
14343 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
14346 @cindex last tracepoint number
14347 @cindex recent tracepoint number
14348 @cindex tracepoint number
14349 The convenience variable @code{$tpnum} records the tracepoint number
14350 of the most recently set tracepoint.
14352 @kindex delete tracepoint
14353 @cindex tracepoint deletion
14354 @item delete tracepoint @r{[}@var{num}@r{]}
14355 Permanently delete one or more tracepoints. With no argument, the
14356 default is to delete all tracepoints. Note that the regular
14357 @code{delete} command can remove tracepoints also.
14362 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
14364 (@value{GDBP}) @b{delete trace} // remove all tracepoints
14368 You can abbreviate this command as @code{del tr}.
14371 @node Enable and Disable Tracepoints
14372 @subsection Enable and Disable Tracepoints
14374 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
14377 @kindex disable tracepoint
14378 @item disable tracepoint @r{[}@var{num}@r{]}
14379 Disable tracepoint @var{num}, or all tracepoints if no argument
14380 @var{num} is given. A disabled tracepoint will have no effect during
14381 a trace experiment, but it is not forgotten. You can re-enable
14382 a disabled tracepoint using the @code{enable tracepoint} command.
14383 If the command is issued during a trace experiment and the debug target
14384 has support for disabling tracepoints during a trace experiment, then the
14385 change will be effective immediately. Otherwise, it will be applied to the
14386 next trace experiment.
14388 @kindex enable tracepoint
14389 @item enable tracepoint @r{[}@var{num}@r{]}
14390 Enable tracepoint @var{num}, or all tracepoints. If this command is
14391 issued during a trace experiment and the debug target supports enabling
14392 tracepoints during a trace experiment, then the enabled tracepoints will
14393 become effective immediately. Otherwise, they will become effective the
14394 next time a trace experiment is run.
14397 @node Tracepoint Passcounts
14398 @subsection Tracepoint Passcounts
14402 @cindex tracepoint pass count
14403 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
14404 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
14405 automatically stop a trace experiment. If a tracepoint's passcount is
14406 @var{n}, then the trace experiment will be automatically stopped on
14407 the @var{n}'th time that tracepoint is hit. If the tracepoint number
14408 @var{num} is not specified, the @code{passcount} command sets the
14409 passcount of the most recently defined tracepoint. If no passcount is
14410 given, the trace experiment will run until stopped explicitly by the
14416 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
14417 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
14419 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
14420 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
14421 (@value{GDBP}) @b{trace foo}
14422 (@value{GDBP}) @b{pass 3}
14423 (@value{GDBP}) @b{trace bar}
14424 (@value{GDBP}) @b{pass 2}
14425 (@value{GDBP}) @b{trace baz}
14426 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
14427 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
14428 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
14429 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
14433 @node Tracepoint Conditions
14434 @subsection Tracepoint Conditions
14435 @cindex conditional tracepoints
14436 @cindex tracepoint conditions
14438 The simplest sort of tracepoint collects data every time your program
14439 reaches a specified place. You can also specify a @dfn{condition} for
14440 a tracepoint. A condition is just a Boolean expression in your
14441 programming language (@pxref{Expressions, ,Expressions}). A
14442 tracepoint with a condition evaluates the expression each time your
14443 program reaches it, and data collection happens only if the condition
14446 Tracepoint conditions can be specified when a tracepoint is set, by
14447 using @samp{if} in the arguments to the @code{trace} command.
14448 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
14449 also be set or changed at any time with the @code{condition} command,
14450 just as with breakpoints.
14452 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
14453 the conditional expression itself. Instead, @value{GDBN} encodes the
14454 expression into an agent expression (@pxref{Agent Expressions})
14455 suitable for execution on the target, independently of @value{GDBN}.
14456 Global variables become raw memory locations, locals become stack
14457 accesses, and so forth.
14459 For instance, suppose you have a function that is usually called
14460 frequently, but should not be called after an error has occurred. You
14461 could use the following tracepoint command to collect data about calls
14462 of that function that happen while the error code is propagating
14463 through the program; an unconditional tracepoint could end up
14464 collecting thousands of useless trace frames that you would have to
14468 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
14471 @node Trace State Variables
14472 @subsection Trace State Variables
14473 @cindex trace state variables
14475 A @dfn{trace state variable} is a special type of variable that is
14476 created and managed by target-side code. The syntax is the same as
14477 that for GDB's convenience variables (a string prefixed with ``$''),
14478 but they are stored on the target. They must be created explicitly,
14479 using a @code{tvariable} command. They are always 64-bit signed
14482 Trace state variables are remembered by @value{GDBN}, and downloaded
14483 to the target along with tracepoint information when the trace
14484 experiment starts. There are no intrinsic limits on the number of
14485 trace state variables, beyond memory limitations of the target.
14487 @cindex convenience variables, and trace state variables
14488 Although trace state variables are managed by the target, you can use
14489 them in print commands and expressions as if they were convenience
14490 variables; @value{GDBN} will get the current value from the target
14491 while the trace experiment is running. Trace state variables share
14492 the same namespace as other ``$'' variables, which means that you
14493 cannot have trace state variables with names like @code{$23} or
14494 @code{$pc}, nor can you have a trace state variable and a convenience
14495 variable with the same name.
14499 @item tvariable $@var{name} [ = @var{expression} ]
14501 The @code{tvariable} command creates a new trace state variable named
14502 @code{$@var{name}}, and optionally gives it an initial value of
14503 @var{expression}. The @var{expression} is evaluated when this command is
14504 entered; the result will be converted to an integer if possible,
14505 otherwise @value{GDBN} will report an error. A subsequent
14506 @code{tvariable} command specifying the same name does not create a
14507 variable, but instead assigns the supplied initial value to the
14508 existing variable of that name, overwriting any previous initial
14509 value. The default initial value is 0.
14511 @item info tvariables
14512 @kindex info tvariables
14513 List all the trace state variables along with their initial values.
14514 Their current values may also be displayed, if the trace experiment is
14517 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
14518 @kindex delete tvariable
14519 Delete the given trace state variables, or all of them if no arguments
14524 @node Tracepoint Actions
14525 @subsection Tracepoint Action Lists
14529 @cindex tracepoint actions
14530 @item actions @r{[}@var{num}@r{]}
14531 This command will prompt for a list of actions to be taken when the
14532 tracepoint is hit. If the tracepoint number @var{num} is not
14533 specified, this command sets the actions for the one that was most
14534 recently defined (so that you can define a tracepoint and then say
14535 @code{actions} without bothering about its number). You specify the
14536 actions themselves on the following lines, one action at a time, and
14537 terminate the actions list with a line containing just @code{end}. So
14538 far, the only defined actions are @code{collect}, @code{teval}, and
14539 @code{while-stepping}.
14541 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
14542 Commands, ,Breakpoint Command Lists}), except that only the defined
14543 actions are allowed; any other @value{GDBN} command is rejected.
14545 @cindex remove actions from a tracepoint
14546 To remove all actions from a tracepoint, type @samp{actions @var{num}}
14547 and follow it immediately with @samp{end}.
14550 (@value{GDBP}) @b{collect @var{data}} // collect some data
14552 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
14554 (@value{GDBP}) @b{end} // signals the end of actions.
14557 In the following example, the action list begins with @code{collect}
14558 commands indicating the things to be collected when the tracepoint is
14559 hit. Then, in order to single-step and collect additional data
14560 following the tracepoint, a @code{while-stepping} command is used,
14561 followed by the list of things to be collected after each step in a
14562 sequence of single steps. The @code{while-stepping} command is
14563 terminated by its own separate @code{end} command. Lastly, the action
14564 list is terminated by an @code{end} command.
14567 (@value{GDBP}) @b{trace foo}
14568 (@value{GDBP}) @b{actions}
14569 Enter actions for tracepoint 1, one per line:
14572 > while-stepping 12
14573 > collect $pc, arr[i]
14578 @kindex collect @r{(tracepoints)}
14579 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
14580 Collect values of the given expressions when the tracepoint is hit.
14581 This command accepts a comma-separated list of any valid expressions.
14582 In addition to global, static, or local variables, the following
14583 special arguments are supported:
14587 Collect all registers.
14590 Collect all function arguments.
14593 Collect all local variables.
14596 Collect the return address. This is helpful if you want to see more
14599 @emph{Note:} The return address location can not always be reliably
14600 determined up front, and the wrong address / registers may end up
14601 collected instead. On some architectures the reliability is higher
14602 for tracepoints at function entry, while on others it's the opposite.
14603 When this happens, backtracing will stop because the return address is
14604 found unavailable (unless another collect rule happened to match it).
14607 Collects the number of arguments from the static probe at which the
14608 tracepoint is located.
14609 @xref{Static Probe Points}.
14611 @item $_probe_arg@var{n}
14612 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
14613 from the static probe at which the tracepoint is located.
14614 @xref{Static Probe Points}.
14617 @vindex $_sdata@r{, collect}
14618 Collect static tracepoint marker specific data. Only available for
14619 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
14620 Lists}. On the UST static tracepoints library backend, an
14621 instrumentation point resembles a @code{printf} function call. The
14622 tracing library is able to collect user specified data formatted to a
14623 character string using the format provided by the programmer that
14624 instrumented the program. Other backends have similar mechanisms.
14625 Here's an example of a UST marker call:
14628 const char master_name[] = "$your_name";
14629 trace_mark(channel1, marker1, "hello %s", master_name)
14632 In this case, collecting @code{$_sdata} collects the string
14633 @samp{hello $yourname}. When analyzing the trace buffer, you can
14634 inspect @samp{$_sdata} like any other variable available to
14638 You can give several consecutive @code{collect} commands, each one
14639 with a single argument, or one @code{collect} command with several
14640 arguments separated by commas; the effect is the same.
14642 The optional @var{mods} changes the usual handling of the arguments.
14643 @code{s} requests that pointers to chars be handled as strings, in
14644 particular collecting the contents of the memory being pointed at, up
14645 to the first zero. The upper bound is by default the value of the
14646 @code{print elements} variable; if @code{s} is followed by a decimal
14647 number, that is the upper bound instead. So for instance
14648 @samp{collect/s25 mystr} collects as many as 25 characters at
14651 The command @code{info scope} (@pxref{Symbols, info scope}) is
14652 particularly useful for figuring out what data to collect.
14654 @kindex teval @r{(tracepoints)}
14655 @item teval @var{expr1}, @var{expr2}, @dots{}
14656 Evaluate the given expressions when the tracepoint is hit. This
14657 command accepts a comma-separated list of expressions. The results
14658 are discarded, so this is mainly useful for assigning values to trace
14659 state variables (@pxref{Trace State Variables}) without adding those
14660 values to the trace buffer, as would be the case if the @code{collect}
14663 @kindex while-stepping @r{(tracepoints)}
14664 @item while-stepping @var{n}
14665 Perform @var{n} single-step instruction traces after the tracepoint,
14666 collecting new data after each step. The @code{while-stepping}
14667 command is followed by the list of what to collect while stepping
14668 (followed by its own @code{end} command):
14671 > while-stepping 12
14672 > collect $regs, myglobal
14678 Note that @code{$pc} is not automatically collected by
14679 @code{while-stepping}; you need to explicitly collect that register if
14680 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
14683 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
14684 @kindex set default-collect
14685 @cindex default collection action
14686 This variable is a list of expressions to collect at each tracepoint
14687 hit. It is effectively an additional @code{collect} action prepended
14688 to every tracepoint action list. The expressions are parsed
14689 individually for each tracepoint, so for instance a variable named
14690 @code{xyz} may be interpreted as a global for one tracepoint, and a
14691 local for another, as appropriate to the tracepoint's location.
14693 @item show default-collect
14694 @kindex show default-collect
14695 Show the list of expressions that are collected by default at each
14700 @node Listing Tracepoints
14701 @subsection Listing Tracepoints
14704 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
14705 @kindex info tp @r{[}@var{n}@dots{}@r{]}
14706 @cindex information about tracepoints
14707 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
14708 Display information about the tracepoint @var{num}. If you don't
14709 specify a tracepoint number, displays information about all the
14710 tracepoints defined so far. The format is similar to that used for
14711 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
14712 command, simply restricting itself to tracepoints.
14714 A tracepoint's listing may include additional information specific to
14719 its passcount as given by the @code{passcount @var{n}} command
14722 the state about installed on target of each location
14726 (@value{GDBP}) @b{info trace}
14727 Num Type Disp Enb Address What
14728 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
14730 collect globfoo, $regs
14735 2 tracepoint keep y <MULTIPLE>
14737 2.1 y 0x0804859c in func4 at change-loc.h:35
14738 installed on target
14739 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
14740 installed on target
14741 2.3 y <PENDING> set_tracepoint
14742 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
14743 not installed on target
14748 This command can be abbreviated @code{info tp}.
14751 @node Listing Static Tracepoint Markers
14752 @subsection Listing Static Tracepoint Markers
14755 @kindex info static-tracepoint-markers
14756 @cindex information about static tracepoint markers
14757 @item info static-tracepoint-markers
14758 Display information about all static tracepoint markers defined in the
14761 For each marker, the following columns are printed:
14765 An incrementing counter, output to help readability. This is not a
14768 The marker ID, as reported by the target.
14769 @item Enabled or Disabled
14770 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
14771 that are not enabled.
14773 Where the marker is in your program, as a memory address.
14775 Where the marker is in the source for your program, as a file and line
14776 number. If the debug information included in the program does not
14777 allow @value{GDBN} to locate the source of the marker, this column
14778 will be left blank.
14782 In addition, the following information may be printed for each marker:
14786 User data passed to the tracing library by the marker call. In the
14787 UST backend, this is the format string passed as argument to the
14789 @item Static tracepoints probing the marker
14790 The list of static tracepoints attached to the marker.
14794 (@value{GDBP}) info static-tracepoint-markers
14795 Cnt ID Enb Address What
14796 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
14797 Data: number1 %d number2 %d
14798 Probed by static tracepoints: #2
14799 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
14805 @node Starting and Stopping Trace Experiments
14806 @subsection Starting and Stopping Trace Experiments
14809 @kindex tstart [ @var{notes} ]
14810 @cindex start a new trace experiment
14811 @cindex collected data discarded
14813 This command starts the trace experiment, and begins collecting data.
14814 It has the side effect of discarding all the data collected in the
14815 trace buffer during the previous trace experiment. If any arguments
14816 are supplied, they are taken as a note and stored with the trace
14817 experiment's state. The notes may be arbitrary text, and are
14818 especially useful with disconnected tracing in a multi-user context;
14819 the notes can explain what the trace is doing, supply user contact
14820 information, and so forth.
14822 @kindex tstop [ @var{notes} ]
14823 @cindex stop a running trace experiment
14825 This command stops the trace experiment. If any arguments are
14826 supplied, they are recorded with the experiment as a note. This is
14827 useful if you are stopping a trace started by someone else, for
14828 instance if the trace is interfering with the system's behavior and
14829 needs to be stopped quickly.
14831 @strong{Note}: a trace experiment and data collection may stop
14832 automatically if any tracepoint's passcount is reached
14833 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
14836 @cindex status of trace data collection
14837 @cindex trace experiment, status of
14839 This command displays the status of the current trace data
14843 Here is an example of the commands we described so far:
14846 (@value{GDBP}) @b{trace gdb_c_test}
14847 (@value{GDBP}) @b{actions}
14848 Enter actions for tracepoint #1, one per line.
14849 > collect $regs,$locals,$args
14850 > while-stepping 11
14854 (@value{GDBP}) @b{tstart}
14855 [time passes @dots{}]
14856 (@value{GDBP}) @b{tstop}
14859 @anchor{disconnected tracing}
14860 @cindex disconnected tracing
14861 You can choose to continue running the trace experiment even if
14862 @value{GDBN} disconnects from the target, voluntarily or
14863 involuntarily. For commands such as @code{detach}, the debugger will
14864 ask what you want to do with the trace. But for unexpected
14865 terminations (@value{GDBN} crash, network outage), it would be
14866 unfortunate to lose hard-won trace data, so the variable
14867 @code{disconnected-tracing} lets you decide whether the trace should
14868 continue running without @value{GDBN}.
14871 @item set disconnected-tracing on
14872 @itemx set disconnected-tracing off
14873 @kindex set disconnected-tracing
14874 Choose whether a tracing run should continue to run if @value{GDBN}
14875 has disconnected from the target. Note that @code{detach} or
14876 @code{quit} will ask you directly what to do about a running trace no
14877 matter what this variable's setting, so the variable is mainly useful
14878 for handling unexpected situations, such as loss of the network.
14880 @item show disconnected-tracing
14881 @kindex show disconnected-tracing
14882 Show the current choice for disconnected tracing.
14886 When you reconnect to the target, the trace experiment may or may not
14887 still be running; it might have filled the trace buffer in the
14888 meantime, or stopped for one of the other reasons. If it is running,
14889 it will continue after reconnection.
14891 Upon reconnection, the target will upload information about the
14892 tracepoints in effect. @value{GDBN} will then compare that
14893 information to the set of tracepoints currently defined, and attempt
14894 to match them up, allowing for the possibility that the numbers may
14895 have changed due to creation and deletion in the meantime. If one of
14896 the target's tracepoints does not match any in @value{GDBN}, the
14897 debugger will create a new tracepoint, so that you have a number with
14898 which to specify that tracepoint. This matching-up process is
14899 necessarily heuristic, and it may result in useless tracepoints being
14900 created; you may simply delete them if they are of no use.
14902 @cindex circular trace buffer
14903 If your target agent supports a @dfn{circular trace buffer}, then you
14904 can run a trace experiment indefinitely without filling the trace
14905 buffer; when space runs out, the agent deletes already-collected trace
14906 frames, oldest first, until there is enough room to continue
14907 collecting. This is especially useful if your tracepoints are being
14908 hit too often, and your trace gets terminated prematurely because the
14909 buffer is full. To ask for a circular trace buffer, simply set
14910 @samp{circular-trace-buffer} to on. You can set this at any time,
14911 including during tracing; if the agent can do it, it will change
14912 buffer handling on the fly, otherwise it will not take effect until
14916 @item set circular-trace-buffer on
14917 @itemx set circular-trace-buffer off
14918 @kindex set circular-trace-buffer
14919 Choose whether a tracing run should use a linear or circular buffer
14920 for trace data. A linear buffer will not lose any trace data, but may
14921 fill up prematurely, while a circular buffer will discard old trace
14922 data, but it will have always room for the latest tracepoint hits.
14924 @item show circular-trace-buffer
14925 @kindex show circular-trace-buffer
14926 Show the current choice for the trace buffer. Note that this may not
14927 match the agent's current buffer handling, nor is it guaranteed to
14928 match the setting that might have been in effect during a past run,
14929 for instance if you are looking at frames from a trace file.
14934 @item set trace-buffer-size @var{n}
14935 @itemx set trace-buffer-size unlimited
14936 @kindex set trace-buffer-size
14937 Request that the target use a trace buffer of @var{n} bytes. Not all
14938 targets will honor the request; they may have a compiled-in size for
14939 the trace buffer, or some other limitation. Set to a value of
14940 @code{unlimited} or @code{-1} to let the target use whatever size it
14941 likes. This is also the default.
14943 @item show trace-buffer-size
14944 @kindex show trace-buffer-size
14945 Show the current requested size for the trace buffer. Note that this
14946 will only match the actual size if the target supports size-setting,
14947 and was able to handle the requested size. For instance, if the
14948 target can only change buffer size between runs, this variable will
14949 not reflect the change until the next run starts. Use @code{tstatus}
14950 to get a report of the actual buffer size.
14954 @item set trace-user @var{text}
14955 @kindex set trace-user
14957 @item show trace-user
14958 @kindex show trace-user
14960 @item set trace-notes @var{text}
14961 @kindex set trace-notes
14962 Set the trace run's notes.
14964 @item show trace-notes
14965 @kindex show trace-notes
14966 Show the trace run's notes.
14968 @item set trace-stop-notes @var{text}
14969 @kindex set trace-stop-notes
14970 Set the trace run's stop notes. The handling of the note is as for
14971 @code{tstop} arguments; the set command is convenient way to fix a
14972 stop note that is mistaken or incomplete.
14974 @item show trace-stop-notes
14975 @kindex show trace-stop-notes
14976 Show the trace run's stop notes.
14980 @node Tracepoint Restrictions
14981 @subsection Tracepoint Restrictions
14983 @cindex tracepoint restrictions
14984 There are a number of restrictions on the use of tracepoints. As
14985 described above, tracepoint data gathering occurs on the target
14986 without interaction from @value{GDBN}. Thus the full capabilities of
14987 the debugger are not available during data gathering, and then at data
14988 examination time, you will be limited by only having what was
14989 collected. The following items describe some common problems, but it
14990 is not exhaustive, and you may run into additional difficulties not
14996 Tracepoint expressions are intended to gather objects (lvalues). Thus
14997 the full flexibility of GDB's expression evaluator is not available.
14998 You cannot call functions, cast objects to aggregate types, access
14999 convenience variables or modify values (except by assignment to trace
15000 state variables). Some language features may implicitly call
15001 functions (for instance Objective-C fields with accessors), and therefore
15002 cannot be collected either.
15005 Collection of local variables, either individually or in bulk with
15006 @code{$locals} or @code{$args}, during @code{while-stepping} may
15007 behave erratically. The stepping action may enter a new scope (for
15008 instance by stepping into a function), or the location of the variable
15009 may change (for instance it is loaded into a register). The
15010 tracepoint data recorded uses the location information for the
15011 variables that is correct for the tracepoint location. When the
15012 tracepoint is created, it is not possible, in general, to determine
15013 where the steps of a @code{while-stepping} sequence will advance the
15014 program---particularly if a conditional branch is stepped.
15017 Collection of an incompletely-initialized or partially-destroyed object
15018 may result in something that @value{GDBN} cannot display, or displays
15019 in a misleading way.
15022 When @value{GDBN} displays a pointer to character it automatically
15023 dereferences the pointer to also display characters of the string
15024 being pointed to. However, collecting the pointer during tracing does
15025 not automatically collect the string. You need to explicitly
15026 dereference the pointer and provide size information if you want to
15027 collect not only the pointer, but the memory pointed to. For example,
15028 @code{*ptr@@50} can be used to collect the 50 element array pointed to
15032 It is not possible to collect a complete stack backtrace at a
15033 tracepoint. Instead, you may collect the registers and a few hundred
15034 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
15035 (adjust to use the name of the actual stack pointer register on your
15036 target architecture, and the amount of stack you wish to capture).
15037 Then the @code{backtrace} command will show a partial backtrace when
15038 using a trace frame. The number of stack frames that can be examined
15039 depends on the sizes of the frames in the collected stack. Note that
15040 if you ask for a block so large that it goes past the bottom of the
15041 stack, the target agent may report an error trying to read from an
15045 If you do not collect registers at a tracepoint, @value{GDBN} can
15046 infer that the value of @code{$pc} must be the same as the address of
15047 the tracepoint and use that when you are looking at a trace frame
15048 for that tracepoint. However, this cannot work if the tracepoint has
15049 multiple locations (for instance if it was set in a function that was
15050 inlined), or if it has a @code{while-stepping} loop. In those cases
15051 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
15056 @node Analyze Collected Data
15057 @section Using the Collected Data
15059 After the tracepoint experiment ends, you use @value{GDBN} commands
15060 for examining the trace data. The basic idea is that each tracepoint
15061 collects a trace @dfn{snapshot} every time it is hit and another
15062 snapshot every time it single-steps. All these snapshots are
15063 consecutively numbered from zero and go into a buffer, and you can
15064 examine them later. The way you examine them is to @dfn{focus} on a
15065 specific trace snapshot. When the remote stub is focused on a trace
15066 snapshot, it will respond to all @value{GDBN} requests for memory and
15067 registers by reading from the buffer which belongs to that snapshot,
15068 rather than from @emph{real} memory or registers of the program being
15069 debugged. This means that @strong{all} @value{GDBN} commands
15070 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
15071 behave as if we were currently debugging the program state as it was
15072 when the tracepoint occurred. Any requests for data that are not in
15073 the buffer will fail.
15076 * tfind:: How to select a trace snapshot
15077 * tdump:: How to display all data for a snapshot
15078 * save tracepoints:: How to save tracepoints for a future run
15082 @subsection @code{tfind @var{n}}
15085 @cindex select trace snapshot
15086 @cindex find trace snapshot
15087 The basic command for selecting a trace snapshot from the buffer is
15088 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
15089 counting from zero. If no argument @var{n} is given, the next
15090 snapshot is selected.
15092 Here are the various forms of using the @code{tfind} command.
15096 Find the first snapshot in the buffer. This is a synonym for
15097 @code{tfind 0} (since 0 is the number of the first snapshot).
15100 Stop debugging trace snapshots, resume @emph{live} debugging.
15103 Same as @samp{tfind none}.
15106 No argument means find the next trace snapshot or find the first
15107 one if no trace snapshot is selected.
15110 Find the previous trace snapshot before the current one. This permits
15111 retracing earlier steps.
15113 @item tfind tracepoint @var{num}
15114 Find the next snapshot associated with tracepoint @var{num}. Search
15115 proceeds forward from the last examined trace snapshot. If no
15116 argument @var{num} is given, it means find the next snapshot collected
15117 for the same tracepoint as the current snapshot.
15119 @item tfind pc @var{addr}
15120 Find the next snapshot associated with the value @var{addr} of the
15121 program counter. Search proceeds forward from the last examined trace
15122 snapshot. If no argument @var{addr} is given, it means find the next
15123 snapshot with the same value of PC as the current snapshot.
15125 @item tfind outside @var{addr1}, @var{addr2}
15126 Find the next snapshot whose PC is outside the given range of
15127 addresses (exclusive).
15129 @item tfind range @var{addr1}, @var{addr2}
15130 Find the next snapshot whose PC is between @var{addr1} and
15131 @var{addr2} (inclusive).
15133 @item tfind line @r{[}@var{file}:@r{]}@var{n}
15134 Find the next snapshot associated with the source line @var{n}. If
15135 the optional argument @var{file} is given, refer to line @var{n} in
15136 that source file. Search proceeds forward from the last examined
15137 trace snapshot. If no argument @var{n} is given, it means find the
15138 next line other than the one currently being examined; thus saying
15139 @code{tfind line} repeatedly can appear to have the same effect as
15140 stepping from line to line in a @emph{live} debugging session.
15143 The default arguments for the @code{tfind} commands are specifically
15144 designed to make it easy to scan through the trace buffer. For
15145 instance, @code{tfind} with no argument selects the next trace
15146 snapshot, and @code{tfind -} with no argument selects the previous
15147 trace snapshot. So, by giving one @code{tfind} command, and then
15148 simply hitting @key{RET} repeatedly you can examine all the trace
15149 snapshots in order. Or, by saying @code{tfind -} and then hitting
15150 @key{RET} repeatedly you can examine the snapshots in reverse order.
15151 The @code{tfind line} command with no argument selects the snapshot
15152 for the next source line executed. The @code{tfind pc} command with
15153 no argument selects the next snapshot with the same program counter
15154 (PC) as the current frame. The @code{tfind tracepoint} command with
15155 no argument selects the next trace snapshot collected by the same
15156 tracepoint as the current one.
15158 In addition to letting you scan through the trace buffer manually,
15159 these commands make it easy to construct @value{GDBN} scripts that
15160 scan through the trace buffer and print out whatever collected data
15161 you are interested in. Thus, if we want to examine the PC, FP, and SP
15162 registers from each trace frame in the buffer, we can say this:
15165 (@value{GDBP}) @b{tfind start}
15166 (@value{GDBP}) @b{while ($trace_frame != -1)}
15167 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
15168 $trace_frame, $pc, $sp, $fp
15172 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
15173 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
15174 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
15175 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
15176 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
15177 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
15178 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
15179 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
15180 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
15181 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
15182 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
15185 Or, if we want to examine the variable @code{X} at each source line in
15189 (@value{GDBP}) @b{tfind start}
15190 (@value{GDBP}) @b{while ($trace_frame != -1)}
15191 > printf "Frame %d, X == %d\n", $trace_frame, X
15201 @subsection @code{tdump}
15203 @cindex dump all data collected at tracepoint
15204 @cindex tracepoint data, display
15206 This command takes no arguments. It prints all the data collected at
15207 the current trace snapshot.
15210 (@value{GDBP}) @b{trace 444}
15211 (@value{GDBP}) @b{actions}
15212 Enter actions for tracepoint #2, one per line:
15213 > collect $regs, $locals, $args, gdb_long_test
15216 (@value{GDBP}) @b{tstart}
15218 (@value{GDBP}) @b{tfind line 444}
15219 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
15221 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
15223 (@value{GDBP}) @b{tdump}
15224 Data collected at tracepoint 2, trace frame 1:
15225 d0 0xc4aa0085 -995491707
15229 d4 0x71aea3d 119204413
15232 d7 0x380035 3670069
15233 a0 0x19e24a 1696330
15234 a1 0x3000668 50333288
15236 a3 0x322000 3284992
15237 a4 0x3000698 50333336
15238 a5 0x1ad3cc 1758156
15239 fp 0x30bf3c 0x30bf3c
15240 sp 0x30bf34 0x30bf34
15242 pc 0x20b2c8 0x20b2c8
15246 p = 0x20e5b4 "gdb-test"
15253 gdb_long_test = 17 '\021'
15258 @code{tdump} works by scanning the tracepoint's current collection
15259 actions and printing the value of each expression listed. So
15260 @code{tdump} can fail, if after a run, you change the tracepoint's
15261 actions to mention variables that were not collected during the run.
15263 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
15264 uses the collected value of @code{$pc} to distinguish between trace
15265 frames that were collected at the tracepoint hit, and frames that were
15266 collected while stepping. This allows it to correctly choose whether
15267 to display the basic list of collections, or the collections from the
15268 body of the while-stepping loop. However, if @code{$pc} was not collected,
15269 then @code{tdump} will always attempt to dump using the basic collection
15270 list, and may fail if a while-stepping frame does not include all the
15271 same data that is collected at the tracepoint hit.
15272 @c This is getting pretty arcane, example would be good.
15274 @node save tracepoints
15275 @subsection @code{save tracepoints @var{filename}}
15276 @kindex save tracepoints
15277 @kindex save-tracepoints
15278 @cindex save tracepoints for future sessions
15280 This command saves all current tracepoint definitions together with
15281 their actions and passcounts, into a file @file{@var{filename}}
15282 suitable for use in a later debugging session. To read the saved
15283 tracepoint definitions, use the @code{source} command (@pxref{Command
15284 Files}). The @w{@code{save-tracepoints}} command is a deprecated
15285 alias for @w{@code{save tracepoints}}
15287 @node Tracepoint Variables
15288 @section Convenience Variables for Tracepoints
15289 @cindex tracepoint variables
15290 @cindex convenience variables for tracepoints
15293 @vindex $trace_frame
15294 @item (int) $trace_frame
15295 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
15296 snapshot is selected.
15298 @vindex $tracepoint
15299 @item (int) $tracepoint
15300 The tracepoint for the current trace snapshot.
15302 @vindex $trace_line
15303 @item (int) $trace_line
15304 The line number for the current trace snapshot.
15306 @vindex $trace_file
15307 @item (char []) $trace_file
15308 The source file for the current trace snapshot.
15310 @vindex $trace_func
15311 @item (char []) $trace_func
15312 The name of the function containing @code{$tracepoint}.
15315 Note: @code{$trace_file} is not suitable for use in @code{printf},
15316 use @code{output} instead.
15318 Here's a simple example of using these convenience variables for
15319 stepping through all the trace snapshots and printing some of their
15320 data. Note that these are not the same as trace state variables,
15321 which are managed by the target.
15324 (@value{GDBP}) @b{tfind start}
15326 (@value{GDBP}) @b{while $trace_frame != -1}
15327 > output $trace_file
15328 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
15334 @section Using Trace Files
15335 @cindex trace files
15337 In some situations, the target running a trace experiment may no
15338 longer be available; perhaps it crashed, or the hardware was needed
15339 for a different activity. To handle these cases, you can arrange to
15340 dump the trace data into a file, and later use that file as a source
15341 of trace data, via the @code{target tfile} command.
15346 @item tsave [ -r ] @var{filename}
15347 @itemx tsave [-ctf] @var{dirname}
15348 Save the trace data to @var{filename}. By default, this command
15349 assumes that @var{filename} refers to the host filesystem, so if
15350 necessary @value{GDBN} will copy raw trace data up from the target and
15351 then save it. If the target supports it, you can also supply the
15352 optional argument @code{-r} (``remote'') to direct the target to save
15353 the data directly into @var{filename} in its own filesystem, which may be
15354 more efficient if the trace buffer is very large. (Note, however, that
15355 @code{target tfile} can only read from files accessible to the host.)
15356 By default, this command will save trace frame in tfile format.
15357 You can supply the optional argument @code{-ctf} to save data in CTF
15358 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
15359 that can be shared by multiple debugging and tracing tools. Please go to
15360 @indicateurl{http://www.efficios.com/ctf} to get more information.
15362 @kindex target tfile
15366 @item target tfile @var{filename}
15367 @itemx target ctf @var{dirname}
15368 Use the file named @var{filename} or directory named @var{dirname} as
15369 a source of trace data. Commands that examine data work as they do with
15370 a live target, but it is not possible to run any new trace experiments.
15371 @code{tstatus} will report the state of the trace run at the moment
15372 the data was saved, as well as the current trace frame you are examining.
15373 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
15377 (@value{GDBP}) target ctf ctf.ctf
15378 (@value{GDBP}) tfind
15379 Found trace frame 0, tracepoint 2
15380 39 ++a; /* set tracepoint 1 here */
15381 (@value{GDBP}) tdump
15382 Data collected at tracepoint 2, trace frame 0:
15386 c = @{"123", "456", "789", "123", "456", "789"@}
15387 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
15395 @chapter Debugging Programs That Use Overlays
15398 If your program is too large to fit completely in your target system's
15399 memory, you can sometimes use @dfn{overlays} to work around this
15400 problem. @value{GDBN} provides some support for debugging programs that
15404 * How Overlays Work:: A general explanation of overlays.
15405 * Overlay Commands:: Managing overlays in @value{GDBN}.
15406 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
15407 mapped by asking the inferior.
15408 * Overlay Sample Program:: A sample program using overlays.
15411 @node How Overlays Work
15412 @section How Overlays Work
15413 @cindex mapped overlays
15414 @cindex unmapped overlays
15415 @cindex load address, overlay's
15416 @cindex mapped address
15417 @cindex overlay area
15419 Suppose you have a computer whose instruction address space is only 64
15420 kilobytes long, but which has much more memory which can be accessed by
15421 other means: special instructions, segment registers, or memory
15422 management hardware, for example. Suppose further that you want to
15423 adapt a program which is larger than 64 kilobytes to run on this system.
15425 One solution is to identify modules of your program which are relatively
15426 independent, and need not call each other directly; call these modules
15427 @dfn{overlays}. Separate the overlays from the main program, and place
15428 their machine code in the larger memory. Place your main program in
15429 instruction memory, but leave at least enough space there to hold the
15430 largest overlay as well.
15432 Now, to call a function located in an overlay, you must first copy that
15433 overlay's machine code from the large memory into the space set aside
15434 for it in the instruction memory, and then jump to its entry point
15437 @c NB: In the below the mapped area's size is greater or equal to the
15438 @c size of all overlays. This is intentional to remind the developer
15439 @c that overlays don't necessarily need to be the same size.
15443 Data Instruction Larger
15444 Address Space Address Space Address Space
15445 +-----------+ +-----------+ +-----------+
15447 +-----------+ +-----------+ +-----------+<-- overlay 1
15448 | program | | main | .----| overlay 1 | load address
15449 | variables | | program | | +-----------+
15450 | and heap | | | | | |
15451 +-----------+ | | | +-----------+<-- overlay 2
15452 | | +-----------+ | | | load address
15453 +-----------+ | | | .-| overlay 2 |
15455 mapped --->+-----------+ | | +-----------+
15456 address | | | | | |
15457 | overlay | <-' | | |
15458 | area | <---' +-----------+<-- overlay 3
15459 | | <---. | | load address
15460 +-----------+ `--| overlay 3 |
15467 @anchor{A code overlay}A code overlay
15471 The diagram (@pxref{A code overlay}) shows a system with separate data
15472 and instruction address spaces. To map an overlay, the program copies
15473 its code from the larger address space to the instruction address space.
15474 Since the overlays shown here all use the same mapped address, only one
15475 may be mapped at a time. For a system with a single address space for
15476 data and instructions, the diagram would be similar, except that the
15477 program variables and heap would share an address space with the main
15478 program and the overlay area.
15480 An overlay loaded into instruction memory and ready for use is called a
15481 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
15482 instruction memory. An overlay not present (or only partially present)
15483 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
15484 is its address in the larger memory. The mapped address is also called
15485 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
15486 called the @dfn{load memory address}, or @dfn{LMA}.
15488 Unfortunately, overlays are not a completely transparent way to adapt a
15489 program to limited instruction memory. They introduce a new set of
15490 global constraints you must keep in mind as you design your program:
15495 Before calling or returning to a function in an overlay, your program
15496 must make sure that overlay is actually mapped. Otherwise, the call or
15497 return will transfer control to the right address, but in the wrong
15498 overlay, and your program will probably crash.
15501 If the process of mapping an overlay is expensive on your system, you
15502 will need to choose your overlays carefully to minimize their effect on
15503 your program's performance.
15506 The executable file you load onto your system must contain each
15507 overlay's instructions, appearing at the overlay's load address, not its
15508 mapped address. However, each overlay's instructions must be relocated
15509 and its symbols defined as if the overlay were at its mapped address.
15510 You can use GNU linker scripts to specify different load and relocation
15511 addresses for pieces of your program; see @ref{Overlay Description,,,
15512 ld.info, Using ld: the GNU linker}.
15515 The procedure for loading executable files onto your system must be able
15516 to load their contents into the larger address space as well as the
15517 instruction and data spaces.
15521 The overlay system described above is rather simple, and could be
15522 improved in many ways:
15527 If your system has suitable bank switch registers or memory management
15528 hardware, you could use those facilities to make an overlay's load area
15529 contents simply appear at their mapped address in instruction space.
15530 This would probably be faster than copying the overlay to its mapped
15531 area in the usual way.
15534 If your overlays are small enough, you could set aside more than one
15535 overlay area, and have more than one overlay mapped at a time.
15538 You can use overlays to manage data, as well as instructions. In
15539 general, data overlays are even less transparent to your design than
15540 code overlays: whereas code overlays only require care when you call or
15541 return to functions, data overlays require care every time you access
15542 the data. Also, if you change the contents of a data overlay, you
15543 must copy its contents back out to its load address before you can copy a
15544 different data overlay into the same mapped area.
15549 @node Overlay Commands
15550 @section Overlay Commands
15552 To use @value{GDBN}'s overlay support, each overlay in your program must
15553 correspond to a separate section of the executable file. The section's
15554 virtual memory address and load memory address must be the overlay's
15555 mapped and load addresses. Identifying overlays with sections allows
15556 @value{GDBN} to determine the appropriate address of a function or
15557 variable, depending on whether the overlay is mapped or not.
15559 @value{GDBN}'s overlay commands all start with the word @code{overlay};
15560 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
15565 Disable @value{GDBN}'s overlay support. When overlay support is
15566 disabled, @value{GDBN} assumes that all functions and variables are
15567 always present at their mapped addresses. By default, @value{GDBN}'s
15568 overlay support is disabled.
15570 @item overlay manual
15571 @cindex manual overlay debugging
15572 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
15573 relies on you to tell it which overlays are mapped, and which are not,
15574 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
15575 commands described below.
15577 @item overlay map-overlay @var{overlay}
15578 @itemx overlay map @var{overlay}
15579 @cindex map an overlay
15580 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
15581 be the name of the object file section containing the overlay. When an
15582 overlay is mapped, @value{GDBN} assumes it can find the overlay's
15583 functions and variables at their mapped addresses. @value{GDBN} assumes
15584 that any other overlays whose mapped ranges overlap that of
15585 @var{overlay} are now unmapped.
15587 @item overlay unmap-overlay @var{overlay}
15588 @itemx overlay unmap @var{overlay}
15589 @cindex unmap an overlay
15590 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
15591 must be the name of the object file section containing the overlay.
15592 When an overlay is unmapped, @value{GDBN} assumes it can find the
15593 overlay's functions and variables at their load addresses.
15596 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
15597 consults a data structure the overlay manager maintains in the inferior
15598 to see which overlays are mapped. For details, see @ref{Automatic
15599 Overlay Debugging}.
15601 @item overlay load-target
15602 @itemx overlay load
15603 @cindex reloading the overlay table
15604 Re-read the overlay table from the inferior. Normally, @value{GDBN}
15605 re-reads the table @value{GDBN} automatically each time the inferior
15606 stops, so this command should only be necessary if you have changed the
15607 overlay mapping yourself using @value{GDBN}. This command is only
15608 useful when using automatic overlay debugging.
15610 @item overlay list-overlays
15611 @itemx overlay list
15612 @cindex listing mapped overlays
15613 Display a list of the overlays currently mapped, along with their mapped
15614 addresses, load addresses, and sizes.
15618 Normally, when @value{GDBN} prints a code address, it includes the name
15619 of the function the address falls in:
15622 (@value{GDBP}) print main
15623 $3 = @{int ()@} 0x11a0 <main>
15626 When overlay debugging is enabled, @value{GDBN} recognizes code in
15627 unmapped overlays, and prints the names of unmapped functions with
15628 asterisks around them. For example, if @code{foo} is a function in an
15629 unmapped overlay, @value{GDBN} prints it this way:
15632 (@value{GDBP}) overlay list
15633 No sections are mapped.
15634 (@value{GDBP}) print foo
15635 $5 = @{int (int)@} 0x100000 <*foo*>
15638 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
15642 (@value{GDBP}) overlay list
15643 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
15644 mapped at 0x1016 - 0x104a
15645 (@value{GDBP}) print foo
15646 $6 = @{int (int)@} 0x1016 <foo>
15649 When overlay debugging is enabled, @value{GDBN} can find the correct
15650 address for functions and variables in an overlay, whether or not the
15651 overlay is mapped. This allows most @value{GDBN} commands, like
15652 @code{break} and @code{disassemble}, to work normally, even on unmapped
15653 code. However, @value{GDBN}'s breakpoint support has some limitations:
15657 @cindex breakpoints in overlays
15658 @cindex overlays, setting breakpoints in
15659 You can set breakpoints in functions in unmapped overlays, as long as
15660 @value{GDBN} can write to the overlay at its load address.
15662 @value{GDBN} can not set hardware or simulator-based breakpoints in
15663 unmapped overlays. However, if you set a breakpoint at the end of your
15664 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
15665 you are using manual overlay management), @value{GDBN} will re-set its
15666 breakpoints properly.
15670 @node Automatic Overlay Debugging
15671 @section Automatic Overlay Debugging
15672 @cindex automatic overlay debugging
15674 @value{GDBN} can automatically track which overlays are mapped and which
15675 are not, given some simple co-operation from the overlay manager in the
15676 inferior. If you enable automatic overlay debugging with the
15677 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
15678 looks in the inferior's memory for certain variables describing the
15679 current state of the overlays.
15681 Here are the variables your overlay manager must define to support
15682 @value{GDBN}'s automatic overlay debugging:
15686 @item @code{_ovly_table}:
15687 This variable must be an array of the following structures:
15692 /* The overlay's mapped address. */
15695 /* The size of the overlay, in bytes. */
15696 unsigned long size;
15698 /* The overlay's load address. */
15701 /* Non-zero if the overlay is currently mapped;
15703 unsigned long mapped;
15707 @item @code{_novlys}:
15708 This variable must be a four-byte signed integer, holding the total
15709 number of elements in @code{_ovly_table}.
15713 To decide whether a particular overlay is mapped or not, @value{GDBN}
15714 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
15715 @code{lma} members equal the VMA and LMA of the overlay's section in the
15716 executable file. When @value{GDBN} finds a matching entry, it consults
15717 the entry's @code{mapped} member to determine whether the overlay is
15720 In addition, your overlay manager may define a function called
15721 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
15722 will silently set a breakpoint there. If the overlay manager then
15723 calls this function whenever it has changed the overlay table, this
15724 will enable @value{GDBN} to accurately keep track of which overlays
15725 are in program memory, and update any breakpoints that may be set
15726 in overlays. This will allow breakpoints to work even if the
15727 overlays are kept in ROM or other non-writable memory while they
15728 are not being executed.
15730 @node Overlay Sample Program
15731 @section Overlay Sample Program
15732 @cindex overlay example program
15734 When linking a program which uses overlays, you must place the overlays
15735 at their load addresses, while relocating them to run at their mapped
15736 addresses. To do this, you must write a linker script (@pxref{Overlay
15737 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
15738 since linker scripts are specific to a particular host system, target
15739 architecture, and target memory layout, this manual cannot provide
15740 portable sample code demonstrating @value{GDBN}'s overlay support.
15742 However, the @value{GDBN} source distribution does contain an overlaid
15743 program, with linker scripts for a few systems, as part of its test
15744 suite. The program consists of the following files from
15745 @file{gdb/testsuite/gdb.base}:
15749 The main program file.
15751 A simple overlay manager, used by @file{overlays.c}.
15756 Overlay modules, loaded and used by @file{overlays.c}.
15759 Linker scripts for linking the test program on the @code{d10v-elf}
15760 and @code{m32r-elf} targets.
15763 You can build the test program using the @code{d10v-elf} GCC
15764 cross-compiler like this:
15767 $ d10v-elf-gcc -g -c overlays.c
15768 $ d10v-elf-gcc -g -c ovlymgr.c
15769 $ d10v-elf-gcc -g -c foo.c
15770 $ d10v-elf-gcc -g -c bar.c
15771 $ d10v-elf-gcc -g -c baz.c
15772 $ d10v-elf-gcc -g -c grbx.c
15773 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
15774 baz.o grbx.o -Wl,-Td10v.ld -o overlays
15777 The build process is identical for any other architecture, except that
15778 you must substitute the appropriate compiler and linker script for the
15779 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
15783 @chapter Using @value{GDBN} with Different Languages
15786 Although programming languages generally have common aspects, they are
15787 rarely expressed in the same manner. For instance, in ANSI C,
15788 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
15789 Modula-2, it is accomplished by @code{p^}. Values can also be
15790 represented (and displayed) differently. Hex numbers in C appear as
15791 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
15793 @cindex working language
15794 Language-specific information is built into @value{GDBN} for some languages,
15795 allowing you to express operations like the above in your program's
15796 native language, and allowing @value{GDBN} to output values in a manner
15797 consistent with the syntax of your program's native language. The
15798 language you use to build expressions is called the @dfn{working
15802 * Setting:: Switching between source languages
15803 * Show:: Displaying the language
15804 * Checks:: Type and range checks
15805 * Supported Languages:: Supported languages
15806 * Unsupported Languages:: Unsupported languages
15810 @section Switching Between Source Languages
15812 There are two ways to control the working language---either have @value{GDBN}
15813 set it automatically, or select it manually yourself. You can use the
15814 @code{set language} command for either purpose. On startup, @value{GDBN}
15815 defaults to setting the language automatically. The working language is
15816 used to determine how expressions you type are interpreted, how values
15819 In addition to the working language, every source file that
15820 @value{GDBN} knows about has its own working language. For some object
15821 file formats, the compiler might indicate which language a particular
15822 source file is in. However, most of the time @value{GDBN} infers the
15823 language from the name of the file. The language of a source file
15824 controls whether C@t{++} names are demangled---this way @code{backtrace} can
15825 show each frame appropriately for its own language. There is no way to
15826 set the language of a source file from within @value{GDBN}, but you can
15827 set the language associated with a filename extension. @xref{Show, ,
15828 Displaying the Language}.
15830 This is most commonly a problem when you use a program, such
15831 as @code{cfront} or @code{f2c}, that generates C but is written in
15832 another language. In that case, make the
15833 program use @code{#line} directives in its C output; that way
15834 @value{GDBN} will know the correct language of the source code of the original
15835 program, and will display that source code, not the generated C code.
15838 * Filenames:: Filename extensions and languages.
15839 * Manually:: Setting the working language manually
15840 * Automatically:: Having @value{GDBN} infer the source language
15844 @subsection List of Filename Extensions and Languages
15846 If a source file name ends in one of the following extensions, then
15847 @value{GDBN} infers that its language is the one indicated.
15865 C@t{++} source file
15871 Objective-C source file
15875 Fortran source file
15878 Modula-2 source file
15882 Assembler source file. This actually behaves almost like C, but
15883 @value{GDBN} does not skip over function prologues when stepping.
15886 In addition, you may set the language associated with a filename
15887 extension. @xref{Show, , Displaying the Language}.
15890 @subsection Setting the Working Language
15892 If you allow @value{GDBN} to set the language automatically,
15893 expressions are interpreted the same way in your debugging session and
15896 @kindex set language
15897 If you wish, you may set the language manually. To do this, issue the
15898 command @samp{set language @var{lang}}, where @var{lang} is the name of
15899 a language, such as
15900 @code{c} or @code{modula-2}.
15901 For a list of the supported languages, type @samp{set language}.
15903 Setting the language manually prevents @value{GDBN} from updating the working
15904 language automatically. This can lead to confusion if you try
15905 to debug a program when the working language is not the same as the
15906 source language, when an expression is acceptable to both
15907 languages---but means different things. For instance, if the current
15908 source file were written in C, and @value{GDBN} was parsing Modula-2, a
15916 might not have the effect you intended. In C, this means to add
15917 @code{b} and @code{c} and place the result in @code{a}. The result
15918 printed would be the value of @code{a}. In Modula-2, this means to compare
15919 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
15921 @node Automatically
15922 @subsection Having @value{GDBN} Infer the Source Language
15924 To have @value{GDBN} set the working language automatically, use
15925 @samp{set language local} or @samp{set language auto}. @value{GDBN}
15926 then infers the working language. That is, when your program stops in a
15927 frame (usually by encountering a breakpoint), @value{GDBN} sets the
15928 working language to the language recorded for the function in that
15929 frame. If the language for a frame is unknown (that is, if the function
15930 or block corresponding to the frame was defined in a source file that
15931 does not have a recognized extension), the current working language is
15932 not changed, and @value{GDBN} issues a warning.
15934 This may not seem necessary for most programs, which are written
15935 entirely in one source language. However, program modules and libraries
15936 written in one source language can be used by a main program written in
15937 a different source language. Using @samp{set language auto} in this
15938 case frees you from having to set the working language manually.
15941 @section Displaying the Language
15943 The following commands help you find out which language is the
15944 working language, and also what language source files were written in.
15947 @item show language
15948 @anchor{show language}
15949 @kindex show language
15950 Display the current working language. This is the
15951 language you can use with commands such as @code{print} to
15952 build and compute expressions that may involve variables in your program.
15955 @kindex info frame@r{, show the source language}
15956 Display the source language for this frame. This language becomes the
15957 working language if you use an identifier from this frame.
15958 @xref{Frame Info, ,Information about a Frame}, to identify the other
15959 information listed here.
15962 @kindex info source@r{, show the source language}
15963 Display the source language of this source file.
15964 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
15965 information listed here.
15968 In unusual circumstances, you may have source files with extensions
15969 not in the standard list. You can then set the extension associated
15970 with a language explicitly:
15973 @item set extension-language @var{ext} @var{language}
15974 @kindex set extension-language
15975 Tell @value{GDBN} that source files with extension @var{ext} are to be
15976 assumed as written in the source language @var{language}.
15978 @item info extensions
15979 @kindex info extensions
15980 List all the filename extensions and the associated languages.
15984 @section Type and Range Checking
15986 Some languages are designed to guard you against making seemingly common
15987 errors through a series of compile- and run-time checks. These include
15988 checking the type of arguments to functions and operators and making
15989 sure mathematical overflows are caught at run time. Checks such as
15990 these help to ensure a program's correctness once it has been compiled
15991 by eliminating type mismatches and providing active checks for range
15992 errors when your program is running.
15994 By default @value{GDBN} checks for these errors according to the
15995 rules of the current source language. Although @value{GDBN} does not check
15996 the statements in your program, it can check expressions entered directly
15997 into @value{GDBN} for evaluation via the @code{print} command, for example.
16000 * Type Checking:: An overview of type checking
16001 * Range Checking:: An overview of range checking
16004 @cindex type checking
16005 @cindex checks, type
16006 @node Type Checking
16007 @subsection An Overview of Type Checking
16009 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
16010 arguments to operators and functions have to be of the correct type,
16011 otherwise an error occurs. These checks prevent type mismatch
16012 errors from ever causing any run-time problems. For example,
16015 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
16017 (@value{GDBP}) print obj.my_method (0)
16020 (@value{GDBP}) print obj.my_method (0x1234)
16021 Cannot resolve method klass::my_method to any overloaded instance
16024 The second example fails because in C@t{++} the integer constant
16025 @samp{0x1234} is not type-compatible with the pointer parameter type.
16027 For the expressions you use in @value{GDBN} commands, you can tell
16028 @value{GDBN} to not enforce strict type checking or
16029 to treat any mismatches as errors and abandon the expression;
16030 When type checking is disabled, @value{GDBN} successfully evaluates
16031 expressions like the second example above.
16033 Even if type checking is off, there may be other reasons
16034 related to type that prevent @value{GDBN} from evaluating an expression.
16035 For instance, @value{GDBN} does not know how to add an @code{int} and
16036 a @code{struct foo}. These particular type errors have nothing to do
16037 with the language in use and usually arise from expressions which make
16038 little sense to evaluate anyway.
16040 @value{GDBN} provides some additional commands for controlling type checking:
16042 @kindex set check type
16043 @kindex show check type
16045 @item set check type on
16046 @itemx set check type off
16047 Set strict type checking on or off. If any type mismatches occur in
16048 evaluating an expression while type checking is on, @value{GDBN} prints a
16049 message and aborts evaluation of the expression.
16051 @item show check type
16052 Show the current setting of type checking and whether @value{GDBN}
16053 is enforcing strict type checking rules.
16056 @cindex range checking
16057 @cindex checks, range
16058 @node Range Checking
16059 @subsection An Overview of Range Checking
16061 In some languages (such as Modula-2), it is an error to exceed the
16062 bounds of a type; this is enforced with run-time checks. Such range
16063 checking is meant to ensure program correctness by making sure
16064 computations do not overflow, or indices on an array element access do
16065 not exceed the bounds of the array.
16067 For expressions you use in @value{GDBN} commands, you can tell
16068 @value{GDBN} to treat range errors in one of three ways: ignore them,
16069 always treat them as errors and abandon the expression, or issue
16070 warnings but evaluate the expression anyway.
16072 A range error can result from numerical overflow, from exceeding an
16073 array index bound, or when you type a constant that is not a member
16074 of any type. Some languages, however, do not treat overflows as an
16075 error. In many implementations of C, mathematical overflow causes the
16076 result to ``wrap around'' to lower values---for example, if @var{m} is
16077 the largest integer value, and @var{s} is the smallest, then
16080 @var{m} + 1 @result{} @var{s}
16083 This, too, is specific to individual languages, and in some cases
16084 specific to individual compilers or machines. @xref{Supported Languages, ,
16085 Supported Languages}, for further details on specific languages.
16087 @value{GDBN} provides some additional commands for controlling the range checker:
16089 @kindex set check range
16090 @kindex show check range
16092 @item set check range auto
16093 Set range checking on or off based on the current working language.
16094 @xref{Supported Languages, ,Supported Languages}, for the default settings for
16097 @item set check range on
16098 @itemx set check range off
16099 Set range checking on or off, overriding the default setting for the
16100 current working language. A warning is issued if the setting does not
16101 match the language default. If a range error occurs and range checking is on,
16102 then a message is printed and evaluation of the expression is aborted.
16104 @item set check range warn
16105 Output messages when the @value{GDBN} range checker detects a range error,
16106 but attempt to evaluate the expression anyway. Evaluating the
16107 expression may still be impossible for other reasons, such as accessing
16108 memory that the process does not own (a typical example from many Unix
16111 @item show check range
16112 Show the current setting of the range checker, and whether or not it is
16113 being set automatically by @value{GDBN}.
16116 @node Supported Languages
16117 @section Supported Languages
16119 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran,
16120 OpenCL C, Pascal, Rust, assembly, Modula-2, and Ada.
16121 @c This is false ...
16122 Some @value{GDBN} features may be used in expressions regardless of the
16123 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
16124 and the @samp{@{type@}addr} construct (@pxref{Expressions,
16125 ,Expressions}) can be used with the constructs of any supported
16128 The following sections detail to what degree each source language is
16129 supported by @value{GDBN}. These sections are not meant to be language
16130 tutorials or references, but serve only as a reference guide to what the
16131 @value{GDBN} expression parser accepts, and what input and output
16132 formats should look like for different languages. There are many good
16133 books written on each of these languages; please look to these for a
16134 language reference or tutorial.
16137 * C:: C and C@t{++}
16140 * Objective-C:: Objective-C
16141 * OpenCL C:: OpenCL C
16142 * Fortran:: Fortran
16145 * Modula-2:: Modula-2
16150 @subsection C and C@t{++}
16152 @cindex C and C@t{++}
16153 @cindex expressions in C or C@t{++}
16155 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
16156 to both languages. Whenever this is the case, we discuss those languages
16160 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
16161 @cindex @sc{gnu} C@t{++}
16162 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
16163 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
16164 effectively, you must compile your C@t{++} programs with a supported
16165 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
16166 compiler (@code{aCC}).
16169 * C Operators:: C and C@t{++} operators
16170 * C Constants:: C and C@t{++} constants
16171 * C Plus Plus Expressions:: C@t{++} expressions
16172 * C Defaults:: Default settings for C and C@t{++}
16173 * C Checks:: C and C@t{++} type and range checks
16174 * Debugging C:: @value{GDBN} and C
16175 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
16176 * Decimal Floating Point:: Numbers in Decimal Floating Point format
16180 @subsubsection C and C@t{++} Operators
16182 @cindex C and C@t{++} operators
16184 Operators must be defined on values of specific types. For instance,
16185 @code{+} is defined on numbers, but not on structures. Operators are
16186 often defined on groups of types.
16188 For the purposes of C and C@t{++}, the following definitions hold:
16193 @emph{Integral types} include @code{int} with any of its storage-class
16194 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
16197 @emph{Floating-point types} include @code{float}, @code{double}, and
16198 @code{long double} (if supported by the target platform).
16201 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
16204 @emph{Scalar types} include all of the above.
16209 The following operators are supported. They are listed here
16210 in order of increasing precedence:
16214 The comma or sequencing operator. Expressions in a comma-separated list
16215 are evaluated from left to right, with the result of the entire
16216 expression being the last expression evaluated.
16219 Assignment. The value of an assignment expression is the value
16220 assigned. Defined on scalar types.
16223 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
16224 and translated to @w{@code{@var{a} = @var{a op b}}}.
16225 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
16226 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
16227 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
16230 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
16231 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
16232 should be of an integral type.
16235 Logical @sc{or}. Defined on integral types.
16238 Logical @sc{and}. Defined on integral types.
16241 Bitwise @sc{or}. Defined on integral types.
16244 Bitwise exclusive-@sc{or}. Defined on integral types.
16247 Bitwise @sc{and}. Defined on integral types.
16250 Equality and inequality. Defined on scalar types. The value of these
16251 expressions is 0 for false and non-zero for true.
16253 @item <@r{, }>@r{, }<=@r{, }>=
16254 Less than, greater than, less than or equal, greater than or equal.
16255 Defined on scalar types. The value of these expressions is 0 for false
16256 and non-zero for true.
16259 left shift, and right shift. Defined on integral types.
16262 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
16265 Addition and subtraction. Defined on integral types, floating-point types and
16268 @item *@r{, }/@r{, }%
16269 Multiplication, division, and modulus. Multiplication and division are
16270 defined on integral and floating-point types. Modulus is defined on
16274 Increment and decrement. When appearing before a variable, the
16275 operation is performed before the variable is used in an expression;
16276 when appearing after it, the variable's value is used before the
16277 operation takes place.
16280 Pointer dereferencing. Defined on pointer types. Same precedence as
16284 Address operator. Defined on variables. Same precedence as @code{++}.
16286 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
16287 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
16288 to examine the address
16289 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
16293 Negative. Defined on integral and floating-point types. Same
16294 precedence as @code{++}.
16297 Logical negation. Defined on integral types. Same precedence as
16301 Bitwise complement operator. Defined on integral types. Same precedence as
16306 Structure member, and pointer-to-structure member. For convenience,
16307 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
16308 pointer based on the stored type information.
16309 Defined on @code{struct} and @code{union} data.
16312 Dereferences of pointers to members.
16315 Array indexing. @code{@var{a}[@var{i}]} is defined as
16316 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
16319 Function parameter list. Same precedence as @code{->}.
16322 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
16323 and @code{class} types.
16326 Doubled colons also represent the @value{GDBN} scope operator
16327 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
16331 If an operator is redefined in the user code, @value{GDBN} usually
16332 attempts to invoke the redefined version instead of using the operator's
16333 predefined meaning.
16336 @subsubsection C and C@t{++} Constants
16338 @cindex C and C@t{++} constants
16340 @value{GDBN} allows you to express the constants of C and C@t{++} in the
16345 Integer constants are a sequence of digits. Octal constants are
16346 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
16347 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
16348 @samp{l}, specifying that the constant should be treated as a
16352 Floating point constants are a sequence of digits, followed by a decimal
16353 point, followed by a sequence of digits, and optionally followed by an
16354 exponent. An exponent is of the form:
16355 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
16356 sequence of digits. The @samp{+} is optional for positive exponents.
16357 A floating-point constant may also end with a letter @samp{f} or
16358 @samp{F}, specifying that the constant should be treated as being of
16359 the @code{float} (as opposed to the default @code{double}) type; or with
16360 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
16364 Enumerated constants consist of enumerated identifiers, or their
16365 integral equivalents.
16368 Character constants are a single character surrounded by single quotes
16369 (@code{'}), or a number---the ordinal value of the corresponding character
16370 (usually its @sc{ascii} value). Within quotes, the single character may
16371 be represented by a letter or by @dfn{escape sequences}, which are of
16372 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
16373 of the character's ordinal value; or of the form @samp{\@var{x}}, where
16374 @samp{@var{x}} is a predefined special character---for example,
16375 @samp{\n} for newline.
16377 Wide character constants can be written by prefixing a character
16378 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
16379 form of @samp{x}. The target wide character set is used when
16380 computing the value of this constant (@pxref{Character Sets}).
16383 String constants are a sequence of character constants surrounded by
16384 double quotes (@code{"}). Any valid character constant (as described
16385 above) may appear. Double quotes within the string must be preceded by
16386 a backslash, so for instance @samp{"a\"b'c"} is a string of five
16389 Wide string constants can be written by prefixing a string constant
16390 with @samp{L}, as in C. The target wide character set is used when
16391 computing the value of this constant (@pxref{Character Sets}).
16394 Pointer constants are an integral value. You can also write pointers
16395 to constants using the C operator @samp{&}.
16398 Array constants are comma-separated lists surrounded by braces @samp{@{}
16399 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
16400 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
16401 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
16404 @node C Plus Plus Expressions
16405 @subsubsection C@t{++} Expressions
16407 @cindex expressions in C@t{++}
16408 @value{GDBN} expression handling can interpret most C@t{++} expressions.
16410 @cindex debugging C@t{++} programs
16411 @cindex C@t{++} compilers
16412 @cindex debug formats and C@t{++}
16413 @cindex @value{NGCC} and C@t{++}
16415 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
16416 the proper compiler and the proper debug format. Currently,
16417 @value{GDBN} works best when debugging C@t{++} code that is compiled
16418 with the most recent version of @value{NGCC} possible. The DWARF
16419 debugging format is preferred; @value{NGCC} defaults to this on most
16420 popular platforms. Other compilers and/or debug formats are likely to
16421 work badly or not at all when using @value{GDBN} to debug C@t{++}
16422 code. @xref{Compilation}.
16427 @cindex member functions
16429 Member function calls are allowed; you can use expressions like
16432 count = aml->GetOriginal(x, y)
16435 @vindex this@r{, inside C@t{++} member functions}
16436 @cindex namespace in C@t{++}
16438 While a member function is active (in the selected stack frame), your
16439 expressions have the same namespace available as the member function;
16440 that is, @value{GDBN} allows implicit references to the class instance
16441 pointer @code{this} following the same rules as C@t{++}. @code{using}
16442 declarations in the current scope are also respected by @value{GDBN}.
16444 @cindex call overloaded functions
16445 @cindex overloaded functions, calling
16446 @cindex type conversions in C@t{++}
16448 You can call overloaded functions; @value{GDBN} resolves the function
16449 call to the right definition, with some restrictions. @value{GDBN} does not
16450 perform overload resolution involving user-defined type conversions,
16451 calls to constructors, or instantiations of templates that do not exist
16452 in the program. It also cannot handle ellipsis argument lists or
16455 It does perform integral conversions and promotions, floating-point
16456 promotions, arithmetic conversions, pointer conversions, conversions of
16457 class objects to base classes, and standard conversions such as those of
16458 functions or arrays to pointers; it requires an exact match on the
16459 number of function arguments.
16461 Overload resolution is always performed, unless you have specified
16462 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
16463 ,@value{GDBN} Features for C@t{++}}.
16465 You must specify @code{set overload-resolution off} in order to use an
16466 explicit function signature to call an overloaded function, as in
16468 p 'foo(char,int)'('x', 13)
16471 The @value{GDBN} command-completion facility can simplify this;
16472 see @ref{Completion, ,Command Completion}.
16474 @cindex reference declarations
16476 @value{GDBN} understands variables declared as C@t{++} lvalue or rvalue
16477 references; you can use them in expressions just as you do in C@t{++}
16478 source---they are automatically dereferenced.
16480 In the parameter list shown when @value{GDBN} displays a frame, the values of
16481 reference variables are not displayed (unlike other variables); this
16482 avoids clutter, since references are often used for large structures.
16483 The @emph{address} of a reference variable is always shown, unless
16484 you have specified @samp{set print address off}.
16487 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
16488 expressions can use it just as expressions in your program do. Since
16489 one scope may be defined in another, you can use @code{::} repeatedly if
16490 necessary, for example in an expression like
16491 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
16492 resolving name scope by reference to source files, in both C and C@t{++}
16493 debugging (@pxref{Variables, ,Program Variables}).
16496 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
16501 @subsubsection C and C@t{++} Defaults
16503 @cindex C and C@t{++} defaults
16505 If you allow @value{GDBN} to set range checking automatically, it
16506 defaults to @code{off} whenever the working language changes to
16507 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
16508 selects the working language.
16510 If you allow @value{GDBN} to set the language automatically, it
16511 recognizes source files whose names end with @file{.c}, @file{.C}, or
16512 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
16513 these files, it sets the working language to C or C@t{++}.
16514 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
16515 for further details.
16518 @subsubsection C and C@t{++} Type and Range Checks
16520 @cindex C and C@t{++} checks
16522 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
16523 checking is used. However, if you turn type checking off, @value{GDBN}
16524 will allow certain non-standard conversions, such as promoting integer
16525 constants to pointers.
16527 Range checking, if turned on, is done on mathematical operations. Array
16528 indices are not checked, since they are often used to index a pointer
16529 that is not itself an array.
16532 @subsubsection @value{GDBN} and C
16534 The @code{set print union} and @code{show print union} commands apply to
16535 the @code{union} type. When set to @samp{on}, any @code{union} that is
16536 inside a @code{struct} or @code{class} is also printed. Otherwise, it
16537 appears as @samp{@{...@}}.
16539 The @code{@@} operator aids in the debugging of dynamic arrays, formed
16540 with pointers and a memory allocation function. @xref{Expressions,
16543 @node Debugging C Plus Plus
16544 @subsubsection @value{GDBN} Features for C@t{++}
16546 @cindex commands for C@t{++}
16548 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
16549 designed specifically for use with C@t{++}. Here is a summary:
16552 @cindex break in overloaded functions
16553 @item @r{breakpoint menus}
16554 When you want a breakpoint in a function whose name is overloaded,
16555 @value{GDBN} has the capability to display a menu of possible breakpoint
16556 locations to help you specify which function definition you want.
16557 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
16559 @cindex overloading in C@t{++}
16560 @item rbreak @var{regex}
16561 Setting breakpoints using regular expressions is helpful for setting
16562 breakpoints on overloaded functions that are not members of any special
16564 @xref{Set Breaks, ,Setting Breakpoints}.
16566 @cindex C@t{++} exception handling
16568 @itemx catch rethrow
16570 Debug C@t{++} exception handling using these commands. @xref{Set
16571 Catchpoints, , Setting Catchpoints}.
16573 @cindex inheritance
16574 @item ptype @var{typename}
16575 Print inheritance relationships as well as other information for type
16577 @xref{Symbols, ,Examining the Symbol Table}.
16579 @item info vtbl @var{expression}.
16580 The @code{info vtbl} command can be used to display the virtual
16581 method tables of the object computed by @var{expression}. This shows
16582 one entry per virtual table; there may be multiple virtual tables when
16583 multiple inheritance is in use.
16585 @cindex C@t{++} demangling
16586 @item demangle @var{name}
16587 Demangle @var{name}.
16588 @xref{Symbols}, for a more complete description of the @code{demangle} command.
16590 @cindex C@t{++} symbol display
16591 @item set print demangle
16592 @itemx show print demangle
16593 @itemx set print asm-demangle
16594 @itemx show print asm-demangle
16595 Control whether C@t{++} symbols display in their source form, both when
16596 displaying code as C@t{++} source and when displaying disassemblies.
16597 @xref{Print Settings, ,Print Settings}.
16599 @item set print object
16600 @itemx show print object
16601 Choose whether to print derived (actual) or declared types of objects.
16602 @xref{Print Settings, ,Print Settings}.
16604 @item set print vtbl
16605 @itemx show print vtbl
16606 Control the format for printing virtual function tables.
16607 @xref{Print Settings, ,Print Settings}.
16608 (The @code{vtbl} commands do not work on programs compiled with the HP
16609 ANSI C@t{++} compiler (@code{aCC}).)
16611 @kindex set overload-resolution
16612 @cindex overloaded functions, overload resolution
16613 @item set overload-resolution on
16614 Enable overload resolution for C@t{++} expression evaluation. The default
16615 is on. For overloaded functions, @value{GDBN} evaluates the arguments
16616 and searches for a function whose signature matches the argument types,
16617 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
16618 Expressions, ,C@t{++} Expressions}, for details).
16619 If it cannot find a match, it emits a message.
16621 @item set overload-resolution off
16622 Disable overload resolution for C@t{++} expression evaluation. For
16623 overloaded functions that are not class member functions, @value{GDBN}
16624 chooses the first function of the specified name that it finds in the
16625 symbol table, whether or not its arguments are of the correct type. For
16626 overloaded functions that are class member functions, @value{GDBN}
16627 searches for a function whose signature @emph{exactly} matches the
16630 @kindex show overload-resolution
16631 @item show overload-resolution
16632 Show the current setting of overload resolution.
16634 @item @r{Overloaded symbol names}
16635 You can specify a particular definition of an overloaded symbol, using
16636 the same notation that is used to declare such symbols in C@t{++}: type
16637 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
16638 also use the @value{GDBN} command-line word completion facilities to list the
16639 available choices, or to finish the type list for you.
16640 @xref{Completion,, Command Completion}, for details on how to do this.
16642 @item @r{Breakpoints in functions with ABI tags}
16644 The GNU C@t{++} compiler introduced the notion of ABI ``tags'', which
16645 correspond to changes in the ABI of a type, function, or variable that
16646 would not otherwise be reflected in a mangled name. See
16647 @url{https://developers.redhat.com/blog/2015/02/05/gcc5-and-the-c11-abi/}
16650 The ABI tags are visible in C@t{++} demangled names. For example, a
16651 function that returns a std::string:
16654 std::string function(int);
16658 when compiled for the C++11 ABI is marked with the @code{cxx11} ABI
16659 tag, and @value{GDBN} displays the symbol like this:
16662 function[abi:cxx11](int)
16665 You can set a breakpoint on such functions simply as if they had no
16669 (gdb) b function(int)
16670 Breakpoint 2 at 0x40060d: file main.cc, line 10.
16671 (gdb) info breakpoints
16672 Num Type Disp Enb Address What
16673 1 breakpoint keep y 0x0040060d in function[abi:cxx11](int)
16677 On the rare occasion you need to disambiguate between different ABI
16678 tags, you can do so by simply including the ABI tag in the function
16682 (@value{GDBP}) b ambiguous[abi:other_tag](int)
16686 @node Decimal Floating Point
16687 @subsubsection Decimal Floating Point format
16688 @cindex decimal floating point format
16690 @value{GDBN} can examine, set and perform computations with numbers in
16691 decimal floating point format, which in the C language correspond to the
16692 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
16693 specified by the extension to support decimal floating-point arithmetic.
16695 There are two encodings in use, depending on the architecture: BID (Binary
16696 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
16697 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
16700 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
16701 to manipulate decimal floating point numbers, it is not possible to convert
16702 (using a cast, for example) integers wider than 32-bit to decimal float.
16704 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
16705 point computations, error checking in decimal float operations ignores
16706 underflow, overflow and divide by zero exceptions.
16708 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
16709 to inspect @code{_Decimal128} values stored in floating point registers.
16710 See @ref{PowerPC,,PowerPC} for more details.
16716 @value{GDBN} can be used to debug programs written in D and compiled with
16717 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
16718 specific feature --- dynamic arrays.
16723 @cindex Go (programming language)
16724 @value{GDBN} can be used to debug programs written in Go and compiled with
16725 @file{gccgo} or @file{6g} compilers.
16727 Here is a summary of the Go-specific features and restrictions:
16730 @cindex current Go package
16731 @item The current Go package
16732 The name of the current package does not need to be specified when
16733 specifying global variables and functions.
16735 For example, given the program:
16739 var myglob = "Shall we?"
16745 When stopped inside @code{main} either of these work:
16749 (gdb) p main.myglob
16752 @cindex builtin Go types
16753 @item Builtin Go types
16754 The @code{string} type is recognized by @value{GDBN} and is printed
16757 @cindex builtin Go functions
16758 @item Builtin Go functions
16759 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
16760 function and handles it internally.
16762 @cindex restrictions on Go expressions
16763 @item Restrictions on Go expressions
16764 All Go operators are supported except @code{&^}.
16765 The Go @code{_} ``blank identifier'' is not supported.
16766 Automatic dereferencing of pointers is not supported.
16770 @subsection Objective-C
16772 @cindex Objective-C
16773 This section provides information about some commands and command
16774 options that are useful for debugging Objective-C code. See also
16775 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
16776 few more commands specific to Objective-C support.
16779 * Method Names in Commands::
16780 * The Print Command with Objective-C::
16783 @node Method Names in Commands
16784 @subsubsection Method Names in Commands
16786 The following commands have been extended to accept Objective-C method
16787 names as line specifications:
16789 @kindex clear@r{, and Objective-C}
16790 @kindex break@r{, and Objective-C}
16791 @kindex info line@r{, and Objective-C}
16792 @kindex jump@r{, and Objective-C}
16793 @kindex list@r{, and Objective-C}
16797 @item @code{info line}
16802 A fully qualified Objective-C method name is specified as
16805 -[@var{Class} @var{methodName}]
16808 where the minus sign is used to indicate an instance method and a
16809 plus sign (not shown) is used to indicate a class method. The class
16810 name @var{Class} and method name @var{methodName} are enclosed in
16811 brackets, similar to the way messages are specified in Objective-C
16812 source code. For example, to set a breakpoint at the @code{create}
16813 instance method of class @code{Fruit} in the program currently being
16817 break -[Fruit create]
16820 To list ten program lines around the @code{initialize} class method,
16824 list +[NSText initialize]
16827 In the current version of @value{GDBN}, the plus or minus sign is
16828 required. In future versions of @value{GDBN}, the plus or minus
16829 sign will be optional, but you can use it to narrow the search. It
16830 is also possible to specify just a method name:
16836 You must specify the complete method name, including any colons. If
16837 your program's source files contain more than one @code{create} method,
16838 you'll be presented with a numbered list of classes that implement that
16839 method. Indicate your choice by number, or type @samp{0} to exit if
16842 As another example, to clear a breakpoint established at the
16843 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
16846 clear -[NSWindow makeKeyAndOrderFront:]
16849 @node The Print Command with Objective-C
16850 @subsubsection The Print Command With Objective-C
16851 @cindex Objective-C, print objects
16852 @kindex print-object
16853 @kindex po @r{(@code{print-object})}
16855 The print command has also been extended to accept methods. For example:
16858 print -[@var{object} hash]
16861 @cindex print an Objective-C object description
16862 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
16864 will tell @value{GDBN} to send the @code{hash} message to @var{object}
16865 and print the result. Also, an additional command has been added,
16866 @code{print-object} or @code{po} for short, which is meant to print
16867 the description of an object. However, this command may only work
16868 with certain Objective-C libraries that have a particular hook
16869 function, @code{_NSPrintForDebugger}, defined.
16872 @subsection OpenCL C
16875 This section provides information about @value{GDBN}s OpenCL C support.
16878 * OpenCL C Datatypes::
16879 * OpenCL C Expressions::
16880 * OpenCL C Operators::
16883 @node OpenCL C Datatypes
16884 @subsubsection OpenCL C Datatypes
16886 @cindex OpenCL C Datatypes
16887 @value{GDBN} supports the builtin scalar and vector datatypes specified
16888 by OpenCL 1.1. In addition the half- and double-precision floating point
16889 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
16890 extensions are also known to @value{GDBN}.
16892 @node OpenCL C Expressions
16893 @subsubsection OpenCL C Expressions
16895 @cindex OpenCL C Expressions
16896 @value{GDBN} supports accesses to vector components including the access as
16897 lvalue where possible. Since OpenCL C is based on C99 most C expressions
16898 supported by @value{GDBN} can be used as well.
16900 @node OpenCL C Operators
16901 @subsubsection OpenCL C Operators
16903 @cindex OpenCL C Operators
16904 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
16908 @subsection Fortran
16909 @cindex Fortran-specific support in @value{GDBN}
16911 @value{GDBN} can be used to debug programs written in Fortran, but it
16912 currently supports only the features of Fortran 77 language.
16914 @cindex trailing underscore, in Fortran symbols
16915 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
16916 among them) append an underscore to the names of variables and
16917 functions. When you debug programs compiled by those compilers, you
16918 will need to refer to variables and functions with a trailing
16922 * Fortran Operators:: Fortran operators and expressions
16923 * Fortran Defaults:: Default settings for Fortran
16924 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
16927 @node Fortran Operators
16928 @subsubsection Fortran Operators and Expressions
16930 @cindex Fortran operators and expressions
16932 Operators must be defined on values of specific types. For instance,
16933 @code{+} is defined on numbers, but not on characters or other non-
16934 arithmetic types. Operators are often defined on groups of types.
16938 The exponentiation operator. It raises the first operand to the power
16942 The range operator. Normally used in the form of array(low:high) to
16943 represent a section of array.
16946 The access component operator. Normally used to access elements in derived
16947 types. Also suitable for unions. As unions aren't part of regular Fortran,
16948 this can only happen when accessing a register that uses a gdbarch-defined
16951 The scope operator. Normally used to access variables in modules or
16952 to set breakpoints on subroutines nested in modules or in other
16953 subroutines (internal subroutines).
16956 @node Fortran Defaults
16957 @subsubsection Fortran Defaults
16959 @cindex Fortran Defaults
16961 Fortran symbols are usually case-insensitive, so @value{GDBN} by
16962 default uses case-insensitive matches for Fortran symbols. You can
16963 change that with the @samp{set case-insensitive} command, see
16964 @ref{Symbols}, for the details.
16966 @node Special Fortran Commands
16967 @subsubsection Special Fortran Commands
16969 @cindex Special Fortran commands
16971 @value{GDBN} has some commands to support Fortran-specific features,
16972 such as displaying common blocks.
16975 @cindex @code{COMMON} blocks, Fortran
16976 @kindex info common
16977 @item info common @r{[}@var{common-name}@r{]}
16978 This command prints the values contained in the Fortran @code{COMMON}
16979 block whose name is @var{common-name}. With no argument, the names of
16980 all @code{COMMON} blocks visible at the current program location are
16982 @cindex arrays slices (Fortran)
16983 @kindex set fortran repack-array-slices
16984 @kindex show fortran repack-array-slices
16985 @item set fortran repack-array-slices [on|off]
16986 @item show fortran repack-array-slices
16987 When taking a slice from an array, a Fortran compiler can choose to
16988 either produce an array descriptor that describes the slice in place,
16989 or it may repack the slice, copying the elements of the slice into a
16990 new region of memory.
16992 When this setting is on, then @value{GDBN} will also repack array
16993 slices in some situations. When this setting is off, then
16994 @value{GDBN} will create array descriptors for slices that reference
16995 the original data in place.
16997 @value{GDBN} will never repack an array slice if the data for the
16998 slice is contiguous within the original array.
17000 @value{GDBN} will always repack string slices if the data for the
17001 slice is non-contiguous within the original string as @value{GDBN}
17002 does not support printing non-contiguous strings.
17004 The default for this setting is @code{off}.
17010 @cindex Pascal support in @value{GDBN}, limitations
17011 Debugging Pascal programs which use sets, subranges, file variables, or
17012 nested functions does not currently work. @value{GDBN} does not support
17013 entering expressions, printing values, or similar features using Pascal
17016 The Pascal-specific command @code{set print pascal_static-members}
17017 controls whether static members of Pascal objects are displayed.
17018 @xref{Print Settings, pascal_static-members}.
17023 @value{GDBN} supports the @url{https://www.rust-lang.org/, Rust
17024 Programming Language}. Type- and value-printing, and expression
17025 parsing, are reasonably complete. However, there are a few
17026 peculiarities and holes to be aware of.
17030 Linespecs (@pxref{Specify Location}) are never relative to the current
17031 crate. Instead, they act as if there were a global namespace of
17032 crates, somewhat similar to the way @code{extern crate} behaves.
17034 That is, if @value{GDBN} is stopped at a breakpoint in a function in
17035 crate @samp{A}, module @samp{B}, then @code{break B::f} will attempt
17036 to set a breakpoint in a function named @samp{f} in a crate named
17039 As a consequence of this approach, linespecs also cannot refer to
17040 items using @samp{self::} or @samp{super::}.
17043 Because @value{GDBN} implements Rust name-lookup semantics in
17044 expressions, it will sometimes prepend the current crate to a name.
17045 For example, if @value{GDBN} is stopped at a breakpoint in the crate
17046 @samp{K}, then @code{print ::x::y} will try to find the symbol
17049 However, since it is useful to be able to refer to other crates when
17050 debugging, @value{GDBN} provides the @code{extern} extension to
17051 circumvent this. To use the extension, just put @code{extern} before
17052 a path expression to refer to the otherwise unavailable ``global''
17055 In the above example, if you wanted to refer to the symbol @samp{y} in
17056 the crate @samp{x}, you would use @code{print extern x::y}.
17059 The Rust expression evaluator does not support ``statement-like''
17060 expressions such as @code{if} or @code{match}, or lambda expressions.
17063 Tuple expressions are not implemented.
17066 The Rust expression evaluator does not currently implement the
17067 @code{Drop} trait. Objects that may be created by the evaluator will
17068 never be destroyed.
17071 @value{GDBN} does not implement type inference for generics. In order
17072 to call generic functions or otherwise refer to generic items, you
17073 will have to specify the type parameters manually.
17076 @value{GDBN} currently uses the C@t{++} demangler for Rust. In most
17077 cases this does not cause any problems. However, in an expression
17078 context, completing a generic function name will give syntactically
17079 invalid results. This happens because Rust requires the @samp{::}
17080 operator between the function name and its generic arguments. For
17081 example, @value{GDBN} might provide a completion like
17082 @code{crate::f<u32>}, where the parser would require
17083 @code{crate::f::<u32>}.
17086 As of this writing, the Rust compiler (version 1.8) has a few holes in
17087 the debugging information it generates. These holes prevent certain
17088 features from being implemented by @value{GDBN}:
17092 Method calls cannot be made via traits.
17095 Operator overloading is not implemented.
17098 When debugging in a monomorphized function, you cannot use the generic
17102 The type @code{Self} is not available.
17105 @code{use} statements are not available, so some names may not be
17106 available in the crate.
17111 @subsection Modula-2
17113 @cindex Modula-2, @value{GDBN} support
17115 The extensions made to @value{GDBN} to support Modula-2 only support
17116 output from the @sc{gnu} Modula-2 compiler (which is currently being
17117 developed). Other Modula-2 compilers are not currently supported, and
17118 attempting to debug executables produced by them is most likely
17119 to give an error as @value{GDBN} reads in the executable's symbol
17122 @cindex expressions in Modula-2
17124 * M2 Operators:: Built-in operators
17125 * Built-In Func/Proc:: Built-in functions and procedures
17126 * M2 Constants:: Modula-2 constants
17127 * M2 Types:: Modula-2 types
17128 * M2 Defaults:: Default settings for Modula-2
17129 * Deviations:: Deviations from standard Modula-2
17130 * M2 Checks:: Modula-2 type and range checks
17131 * M2 Scope:: The scope operators @code{::} and @code{.}
17132 * GDB/M2:: @value{GDBN} and Modula-2
17136 @subsubsection Operators
17137 @cindex Modula-2 operators
17139 Operators must be defined on values of specific types. For instance,
17140 @code{+} is defined on numbers, but not on structures. Operators are
17141 often defined on groups of types. For the purposes of Modula-2, the
17142 following definitions hold:
17147 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
17151 @emph{Character types} consist of @code{CHAR} and its subranges.
17154 @emph{Floating-point types} consist of @code{REAL}.
17157 @emph{Pointer types} consist of anything declared as @code{POINTER TO
17161 @emph{Scalar types} consist of all of the above.
17164 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
17167 @emph{Boolean types} consist of @code{BOOLEAN}.
17171 The following operators are supported, and appear in order of
17172 increasing precedence:
17176 Function argument or array index separator.
17179 Assignment. The value of @var{var} @code{:=} @var{value} is
17183 Less than, greater than on integral, floating-point, or enumerated
17187 Less than or equal to, greater than or equal to
17188 on integral, floating-point and enumerated types, or set inclusion on
17189 set types. Same precedence as @code{<}.
17191 @item =@r{, }<>@r{, }#
17192 Equality and two ways of expressing inequality, valid on scalar types.
17193 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
17194 available for inequality, since @code{#} conflicts with the script
17198 Set membership. Defined on set types and the types of their members.
17199 Same precedence as @code{<}.
17202 Boolean disjunction. Defined on boolean types.
17205 Boolean conjunction. Defined on boolean types.
17208 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
17211 Addition and subtraction on integral and floating-point types, or union
17212 and difference on set types.
17215 Multiplication on integral and floating-point types, or set intersection
17219 Division on floating-point types, or symmetric set difference on set
17220 types. Same precedence as @code{*}.
17223 Integer division and remainder. Defined on integral types. Same
17224 precedence as @code{*}.
17227 Negative. Defined on @code{INTEGER} and @code{REAL} data.
17230 Pointer dereferencing. Defined on pointer types.
17233 Boolean negation. Defined on boolean types. Same precedence as
17237 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
17238 precedence as @code{^}.
17241 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
17244 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
17248 @value{GDBN} and Modula-2 scope operators.
17252 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
17253 treats the use of the operator @code{IN}, or the use of operators
17254 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
17255 @code{<=}, and @code{>=} on sets as an error.
17259 @node Built-In Func/Proc
17260 @subsubsection Built-in Functions and Procedures
17261 @cindex Modula-2 built-ins
17263 Modula-2 also makes available several built-in procedures and functions.
17264 In describing these, the following metavariables are used:
17269 represents an @code{ARRAY} variable.
17272 represents a @code{CHAR} constant or variable.
17275 represents a variable or constant of integral type.
17278 represents an identifier that belongs to a set. Generally used in the
17279 same function with the metavariable @var{s}. The type of @var{s} should
17280 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
17283 represents a variable or constant of integral or floating-point type.
17286 represents a variable or constant of floating-point type.
17292 represents a variable.
17295 represents a variable or constant of one of many types. See the
17296 explanation of the function for details.
17299 All Modula-2 built-in procedures also return a result, described below.
17303 Returns the absolute value of @var{n}.
17306 If @var{c} is a lower case letter, it returns its upper case
17307 equivalent, otherwise it returns its argument.
17310 Returns the character whose ordinal value is @var{i}.
17313 Decrements the value in the variable @var{v} by one. Returns the new value.
17315 @item DEC(@var{v},@var{i})
17316 Decrements the value in the variable @var{v} by @var{i}. Returns the
17319 @item EXCL(@var{m},@var{s})
17320 Removes the element @var{m} from the set @var{s}. Returns the new
17323 @item FLOAT(@var{i})
17324 Returns the floating point equivalent of the integer @var{i}.
17326 @item HIGH(@var{a})
17327 Returns the index of the last member of @var{a}.
17330 Increments the value in the variable @var{v} by one. Returns the new value.
17332 @item INC(@var{v},@var{i})
17333 Increments the value in the variable @var{v} by @var{i}. Returns the
17336 @item INCL(@var{m},@var{s})
17337 Adds the element @var{m} to the set @var{s} if it is not already
17338 there. Returns the new set.
17341 Returns the maximum value of the type @var{t}.
17344 Returns the minimum value of the type @var{t}.
17347 Returns boolean TRUE if @var{i} is an odd number.
17350 Returns the ordinal value of its argument. For example, the ordinal
17351 value of a character is its @sc{ascii} value (on machines supporting
17352 the @sc{ascii} character set). The argument @var{x} must be of an
17353 ordered type, which include integral, character and enumerated types.
17355 @item SIZE(@var{x})
17356 Returns the size of its argument. The argument @var{x} can be a
17357 variable or a type.
17359 @item TRUNC(@var{r})
17360 Returns the integral part of @var{r}.
17362 @item TSIZE(@var{x})
17363 Returns the size of its argument. The argument @var{x} can be a
17364 variable or a type.
17366 @item VAL(@var{t},@var{i})
17367 Returns the member of the type @var{t} whose ordinal value is @var{i}.
17371 @emph{Warning:} Sets and their operations are not yet supported, so
17372 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
17376 @cindex Modula-2 constants
17378 @subsubsection Constants
17380 @value{GDBN} allows you to express the constants of Modula-2 in the following
17386 Integer constants are simply a sequence of digits. When used in an
17387 expression, a constant is interpreted to be type-compatible with the
17388 rest of the expression. Hexadecimal integers are specified by a
17389 trailing @samp{H}, and octal integers by a trailing @samp{B}.
17392 Floating point constants appear as a sequence of digits, followed by a
17393 decimal point and another sequence of digits. An optional exponent can
17394 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
17395 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
17396 digits of the floating point constant must be valid decimal (base 10)
17400 Character constants consist of a single character enclosed by a pair of
17401 like quotes, either single (@code{'}) or double (@code{"}). They may
17402 also be expressed by their ordinal value (their @sc{ascii} value, usually)
17403 followed by a @samp{C}.
17406 String constants consist of a sequence of characters enclosed by a
17407 pair of like quotes, either single (@code{'}) or double (@code{"}).
17408 Escape sequences in the style of C are also allowed. @xref{C
17409 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
17413 Enumerated constants consist of an enumerated identifier.
17416 Boolean constants consist of the identifiers @code{TRUE} and
17420 Pointer constants consist of integral values only.
17423 Set constants are not yet supported.
17427 @subsubsection Modula-2 Types
17428 @cindex Modula-2 types
17430 Currently @value{GDBN} can print the following data types in Modula-2
17431 syntax: array types, record types, set types, pointer types, procedure
17432 types, enumerated types, subrange types and base types. You can also
17433 print the contents of variables declared using these type.
17434 This section gives a number of simple source code examples together with
17435 sample @value{GDBN} sessions.
17437 The first example contains the following section of code:
17446 and you can request @value{GDBN} to interrogate the type and value of
17447 @code{r} and @code{s}.
17450 (@value{GDBP}) print s
17452 (@value{GDBP}) ptype s
17454 (@value{GDBP}) print r
17456 (@value{GDBP}) ptype r
17461 Likewise if your source code declares @code{s} as:
17465 s: SET ['A'..'Z'] ;
17469 then you may query the type of @code{s} by:
17472 (@value{GDBP}) ptype s
17473 type = SET ['A'..'Z']
17477 Note that at present you cannot interactively manipulate set
17478 expressions using the debugger.
17480 The following example shows how you might declare an array in Modula-2
17481 and how you can interact with @value{GDBN} to print its type and contents:
17485 s: ARRAY [-10..10] OF CHAR ;
17489 (@value{GDBP}) ptype s
17490 ARRAY [-10..10] OF CHAR
17493 Note that the array handling is not yet complete and although the type
17494 is printed correctly, expression handling still assumes that all
17495 arrays have a lower bound of zero and not @code{-10} as in the example
17498 Here are some more type related Modula-2 examples:
17502 colour = (blue, red, yellow, green) ;
17503 t = [blue..yellow] ;
17511 The @value{GDBN} interaction shows how you can query the data type
17512 and value of a variable.
17515 (@value{GDBP}) print s
17517 (@value{GDBP}) ptype t
17518 type = [blue..yellow]
17522 In this example a Modula-2 array is declared and its contents
17523 displayed. Observe that the contents are written in the same way as
17524 their @code{C} counterparts.
17528 s: ARRAY [1..5] OF CARDINAL ;
17534 (@value{GDBP}) print s
17535 $1 = @{1, 0, 0, 0, 0@}
17536 (@value{GDBP}) ptype s
17537 type = ARRAY [1..5] OF CARDINAL
17540 The Modula-2 language interface to @value{GDBN} also understands
17541 pointer types as shown in this example:
17545 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
17552 and you can request that @value{GDBN} describes the type of @code{s}.
17555 (@value{GDBP}) ptype s
17556 type = POINTER TO ARRAY [1..5] OF CARDINAL
17559 @value{GDBN} handles compound types as we can see in this example.
17560 Here we combine array types, record types, pointer types and subrange
17571 myarray = ARRAY myrange OF CARDINAL ;
17572 myrange = [-2..2] ;
17574 s: POINTER TO ARRAY myrange OF foo ;
17578 and you can ask @value{GDBN} to describe the type of @code{s} as shown
17582 (@value{GDBP}) ptype s
17583 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
17586 f3 : ARRAY [-2..2] OF CARDINAL;
17591 @subsubsection Modula-2 Defaults
17592 @cindex Modula-2 defaults
17594 If type and range checking are set automatically by @value{GDBN}, they
17595 both default to @code{on} whenever the working language changes to
17596 Modula-2. This happens regardless of whether you or @value{GDBN}
17597 selected the working language.
17599 If you allow @value{GDBN} to set the language automatically, then entering
17600 code compiled from a file whose name ends with @file{.mod} sets the
17601 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
17602 Infer the Source Language}, for further details.
17605 @subsubsection Deviations from Standard Modula-2
17606 @cindex Modula-2, deviations from
17608 A few changes have been made to make Modula-2 programs easier to debug.
17609 This is done primarily via loosening its type strictness:
17613 Unlike in standard Modula-2, pointer constants can be formed by
17614 integers. This allows you to modify pointer variables during
17615 debugging. (In standard Modula-2, the actual address contained in a
17616 pointer variable is hidden from you; it can only be modified
17617 through direct assignment to another pointer variable or expression that
17618 returned a pointer.)
17621 C escape sequences can be used in strings and characters to represent
17622 non-printable characters. @value{GDBN} prints out strings with these
17623 escape sequences embedded. Single non-printable characters are
17624 printed using the @samp{CHR(@var{nnn})} format.
17627 The assignment operator (@code{:=}) returns the value of its right-hand
17631 All built-in procedures both modify @emph{and} return their argument.
17635 @subsubsection Modula-2 Type and Range Checks
17636 @cindex Modula-2 checks
17639 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
17642 @c FIXME remove warning when type/range checks added
17644 @value{GDBN} considers two Modula-2 variables type equivalent if:
17648 They are of types that have been declared equivalent via a @code{TYPE
17649 @var{t1} = @var{t2}} statement
17652 They have been declared on the same line. (Note: This is true of the
17653 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
17656 As long as type checking is enabled, any attempt to combine variables
17657 whose types are not equivalent is an error.
17659 Range checking is done on all mathematical operations, assignment, array
17660 index bounds, and all built-in functions and procedures.
17663 @subsubsection The Scope Operators @code{::} and @code{.}
17665 @cindex @code{.}, Modula-2 scope operator
17666 @cindex colon, doubled as scope operator
17668 @vindex colon-colon@r{, in Modula-2}
17669 @c Info cannot handle :: but TeX can.
17672 @vindex ::@r{, in Modula-2}
17675 There are a few subtle differences between the Modula-2 scope operator
17676 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
17681 @var{module} . @var{id}
17682 @var{scope} :: @var{id}
17686 where @var{scope} is the name of a module or a procedure,
17687 @var{module} the name of a module, and @var{id} is any declared
17688 identifier within your program, except another module.
17690 Using the @code{::} operator makes @value{GDBN} search the scope
17691 specified by @var{scope} for the identifier @var{id}. If it is not
17692 found in the specified scope, then @value{GDBN} searches all scopes
17693 enclosing the one specified by @var{scope}.
17695 Using the @code{.} operator makes @value{GDBN} search the current scope for
17696 the identifier specified by @var{id} that was imported from the
17697 definition module specified by @var{module}. With this operator, it is
17698 an error if the identifier @var{id} was not imported from definition
17699 module @var{module}, or if @var{id} is not an identifier in
17703 @subsubsection @value{GDBN} and Modula-2
17705 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
17706 Five subcommands of @code{set print} and @code{show print} apply
17707 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
17708 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
17709 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
17710 analogue in Modula-2.
17712 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
17713 with any language, is not useful with Modula-2. Its
17714 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
17715 created in Modula-2 as they can in C or C@t{++}. However, because an
17716 address can be specified by an integral constant, the construct
17717 @samp{@{@var{type}@}@var{adrexp}} is still useful.
17719 @cindex @code{#} in Modula-2
17720 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
17721 interpreted as the beginning of a comment. Use @code{<>} instead.
17727 The extensions made to @value{GDBN} for Ada only support
17728 output from the @sc{gnu} Ada (GNAT) compiler.
17729 Other Ada compilers are not currently supported, and
17730 attempting to debug executables produced by them is most likely
17734 @cindex expressions in Ada
17736 * Ada Mode Intro:: General remarks on the Ada syntax
17737 and semantics supported by Ada mode
17739 * Omissions from Ada:: Restrictions on the Ada expression syntax.
17740 * Additions to Ada:: Extensions of the Ada expression syntax.
17741 * Overloading support for Ada:: Support for expressions involving overloaded
17743 * Stopping Before Main Program:: Debugging the program during elaboration.
17744 * Ada Exceptions:: Ada Exceptions
17745 * Ada Tasks:: Listing and setting breakpoints in tasks.
17746 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
17747 * Ravenscar Profile:: Tasking Support when using the Ravenscar
17749 * Ada Settings:: New settable GDB parameters for Ada.
17750 * Ada Glitches:: Known peculiarities of Ada mode.
17753 @node Ada Mode Intro
17754 @subsubsection Introduction
17755 @cindex Ada mode, general
17757 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
17758 syntax, with some extensions.
17759 The philosophy behind the design of this subset is
17763 That @value{GDBN} should provide basic literals and access to operations for
17764 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
17765 leaving more sophisticated computations to subprograms written into the
17766 program (which therefore may be called from @value{GDBN}).
17769 That type safety and strict adherence to Ada language restrictions
17770 are not particularly important to the @value{GDBN} user.
17773 That brevity is important to the @value{GDBN} user.
17776 Thus, for brevity, the debugger acts as if all names declared in
17777 user-written packages are directly visible, even if they are not visible
17778 according to Ada rules, thus making it unnecessary to fully qualify most
17779 names with their packages, regardless of context. Where this causes
17780 ambiguity, @value{GDBN} asks the user's intent.
17782 The debugger will start in Ada mode if it detects an Ada main program.
17783 As for other languages, it will enter Ada mode when stopped in a program that
17784 was translated from an Ada source file.
17786 While in Ada mode, you may use `@t{--}' for comments. This is useful
17787 mostly for documenting command files. The standard @value{GDBN} comment
17788 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
17789 middle (to allow based literals).
17791 @node Omissions from Ada
17792 @subsubsection Omissions from Ada
17793 @cindex Ada, omissions from
17795 Here are the notable omissions from the subset:
17799 Only a subset of the attributes are supported:
17803 @t{'First}, @t{'Last}, and @t{'Length}
17804 on array objects (not on types and subtypes).
17807 @t{'Min} and @t{'Max}.
17810 @t{'Pos} and @t{'Val}.
17816 @t{'Range} on array objects (not subtypes), but only as the right
17817 operand of the membership (@code{in}) operator.
17820 @t{'Access}, @t{'Unchecked_Access}, and
17821 @t{'Unrestricted_Access} (a GNAT extension).
17829 @code{Characters.Latin_1} are not available and
17830 concatenation is not implemented. Thus, escape characters in strings are
17831 not currently available.
17834 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
17835 equality of representations. They will generally work correctly
17836 for strings and arrays whose elements have integer or enumeration types.
17837 They may not work correctly for arrays whose element
17838 types have user-defined equality, for arrays of real values
17839 (in particular, IEEE-conformant floating point, because of negative
17840 zeroes and NaNs), and for arrays whose elements contain unused bits with
17841 indeterminate values.
17844 The other component-by-component array operations (@code{and}, @code{or},
17845 @code{xor}, @code{not}, and relational tests other than equality)
17846 are not implemented.
17849 @cindex array aggregates (Ada)
17850 @cindex record aggregates (Ada)
17851 @cindex aggregates (Ada)
17852 There is limited support for array and record aggregates. They are
17853 permitted only on the right sides of assignments, as in these examples:
17856 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
17857 (@value{GDBP}) set An_Array := (1, others => 0)
17858 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
17859 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
17860 (@value{GDBP}) set A_Record := (1, "Peter", True);
17861 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
17865 discriminant's value by assigning an aggregate has an
17866 undefined effect if that discriminant is used within the record.
17867 However, you can first modify discriminants by directly assigning to
17868 them (which normally would not be allowed in Ada), and then performing an
17869 aggregate assignment. For example, given a variable @code{A_Rec}
17870 declared to have a type such as:
17873 type Rec (Len : Small_Integer := 0) is record
17875 Vals : IntArray (1 .. Len);
17879 you can assign a value with a different size of @code{Vals} with two
17883 (@value{GDBP}) set A_Rec.Len := 4
17884 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
17887 As this example also illustrates, @value{GDBN} is very loose about the usual
17888 rules concerning aggregates. You may leave out some of the
17889 components of an array or record aggregate (such as the @code{Len}
17890 component in the assignment to @code{A_Rec} above); they will retain their
17891 original values upon assignment. You may freely use dynamic values as
17892 indices in component associations. You may even use overlapping or
17893 redundant component associations, although which component values are
17894 assigned in such cases is not defined.
17897 Calls to dispatching subprograms are not implemented.
17900 The overloading algorithm is much more limited (i.e., less selective)
17901 than that of real Ada. It makes only limited use of the context in
17902 which a subexpression appears to resolve its meaning, and it is much
17903 looser in its rules for allowing type matches. As a result, some
17904 function calls will be ambiguous, and the user will be asked to choose
17905 the proper resolution.
17908 The @code{new} operator is not implemented.
17911 Entry calls are not implemented.
17914 Aside from printing, arithmetic operations on the native VAX floating-point
17915 formats are not supported.
17918 It is not possible to slice a packed array.
17921 The names @code{True} and @code{False}, when not part of a qualified name,
17922 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
17924 Should your program
17925 redefine these names in a package or procedure (at best a dubious practice),
17926 you will have to use fully qualified names to access their new definitions.
17929 @node Additions to Ada
17930 @subsubsection Additions to Ada
17931 @cindex Ada, deviations from
17933 As it does for other languages, @value{GDBN} makes certain generic
17934 extensions to Ada (@pxref{Expressions}):
17938 If the expression @var{E} is a variable residing in memory (typically
17939 a local variable or array element) and @var{N} is a positive integer,
17940 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
17941 @var{N}-1 adjacent variables following it in memory as an array. In
17942 Ada, this operator is generally not necessary, since its prime use is
17943 in displaying parts of an array, and slicing will usually do this in
17944 Ada. However, there are occasional uses when debugging programs in
17945 which certain debugging information has been optimized away.
17948 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
17949 appears in function or file @var{B}.'' When @var{B} is a file name,
17950 you must typically surround it in single quotes.
17953 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
17954 @var{type} that appears at address @var{addr}.''
17957 A name starting with @samp{$} is a convenience variable
17958 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
17961 In addition, @value{GDBN} provides a few other shortcuts and outright
17962 additions specific to Ada:
17966 The assignment statement is allowed as an expression, returning
17967 its right-hand operand as its value. Thus, you may enter
17970 (@value{GDBP}) set x := y + 3
17971 (@value{GDBP}) print A(tmp := y + 1)
17975 The semicolon is allowed as an ``operator,'' returning as its value
17976 the value of its right-hand operand.
17977 This allows, for example,
17978 complex conditional breaks:
17981 (@value{GDBP}) break f
17982 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
17986 Rather than use catenation and symbolic character names to introduce special
17987 characters into strings, one may instead use a special bracket notation,
17988 which is also used to print strings. A sequence of characters of the form
17989 @samp{["@var{XX}"]} within a string or character literal denotes the
17990 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
17991 sequence of characters @samp{["""]} also denotes a single quotation mark
17992 in strings. For example,
17994 "One line.["0a"]Next line.["0a"]"
17997 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
18001 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
18002 @t{'Max} is optional (and is ignored in any case). For example, it is valid
18006 (@value{GDBP}) print 'max(x, y)
18010 When printing arrays, @value{GDBN} uses positional notation when the
18011 array has a lower bound of 1, and uses a modified named notation otherwise.
18012 For example, a one-dimensional array of three integers with a lower bound
18013 of 3 might print as
18020 That is, in contrast to valid Ada, only the first component has a @code{=>}
18024 You may abbreviate attributes in expressions with any unique,
18025 multi-character subsequence of
18026 their names (an exact match gets preference).
18027 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
18028 in place of @t{a'length}.
18031 @cindex quoting Ada internal identifiers
18032 Since Ada is case-insensitive, the debugger normally maps identifiers you type
18033 to lower case. The GNAT compiler uses upper-case characters for
18034 some of its internal identifiers, which are normally of no interest to users.
18035 For the rare occasions when you actually have to look at them,
18036 enclose them in angle brackets to avoid the lower-case mapping.
18039 (@value{GDBP}) print <JMPBUF_SAVE>[0]
18043 Printing an object of class-wide type or dereferencing an
18044 access-to-class-wide value will display all the components of the object's
18045 specific type (as indicated by its run-time tag). Likewise, component
18046 selection on such a value will operate on the specific type of the
18051 @node Overloading support for Ada
18052 @subsubsection Overloading support for Ada
18053 @cindex overloading, Ada
18055 The debugger supports limited overloading. Given a subprogram call in which
18056 the function symbol has multiple definitions, it will use the number of
18057 actual parameters and some information about their types to attempt to narrow
18058 the set of definitions. It also makes very limited use of context, preferring
18059 procedures to functions in the context of the @code{call} command, and
18060 functions to procedures elsewhere.
18062 If, after narrowing, the set of matching definitions still contains more than
18063 one definition, @value{GDBN} will display a menu to query which one it should
18067 (@value{GDBP}) print f(1)
18068 Multiple matches for f
18070 [1] foo.f (integer) return boolean at foo.adb:23
18071 [2] foo.f (foo.new_integer) return boolean at foo.adb:28
18075 In this case, just select one menu entry either to cancel expression evaluation
18076 (type @kbd{0} and press @key{RET}) or to continue evaluation with a specific
18077 instance (type the corresponding number and press @key{RET}).
18079 Here are a couple of commands to customize @value{GDBN}'s behavior in this
18084 @kindex set ada print-signatures
18085 @item set ada print-signatures
18086 Control whether parameter types and return types are displayed in overloads
18087 selection menus. It is @code{on} by default.
18088 @xref{Overloading support for Ada}.
18090 @kindex show ada print-signatures
18091 @item show ada print-signatures
18092 Show the current setting for displaying parameter types and return types in
18093 overloads selection menu.
18094 @xref{Overloading support for Ada}.
18098 @node Stopping Before Main Program
18099 @subsubsection Stopping at the Very Beginning
18101 @cindex breakpointing Ada elaboration code
18102 It is sometimes necessary to debug the program during elaboration, and
18103 before reaching the main procedure.
18104 As defined in the Ada Reference
18105 Manual, the elaboration code is invoked from a procedure called
18106 @code{adainit}. To run your program up to the beginning of
18107 elaboration, simply use the following two commands:
18108 @code{tbreak adainit} and @code{run}.
18110 @node Ada Exceptions
18111 @subsubsection Ada Exceptions
18113 A command is provided to list all Ada exceptions:
18116 @kindex info exceptions
18117 @item info exceptions
18118 @itemx info exceptions @var{regexp}
18119 The @code{info exceptions} command allows you to list all Ada exceptions
18120 defined within the program being debugged, as well as their addresses.
18121 With a regular expression, @var{regexp}, as argument, only those exceptions
18122 whose names match @var{regexp} are listed.
18125 Below is a small example, showing how the command can be used, first
18126 without argument, and next with a regular expression passed as an
18130 (@value{GDBP}) info exceptions
18131 All defined Ada exceptions:
18132 constraint_error: 0x613da0
18133 program_error: 0x613d20
18134 storage_error: 0x613ce0
18135 tasking_error: 0x613ca0
18136 const.aint_global_e: 0x613b00
18137 (@value{GDBP}) info exceptions const.aint
18138 All Ada exceptions matching regular expression "const.aint":
18139 constraint_error: 0x613da0
18140 const.aint_global_e: 0x613b00
18143 It is also possible to ask @value{GDBN} to stop your program's execution
18144 when an exception is raised. For more details, see @ref{Set Catchpoints}.
18147 @subsubsection Extensions for Ada Tasks
18148 @cindex Ada, tasking
18150 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
18151 @value{GDBN} provides the following task-related commands:
18156 This command shows a list of current Ada tasks, as in the following example:
18163 (@value{GDBP}) info tasks
18164 ID TID P-ID Pri State Name
18165 1 8088000 0 15 Child Activation Wait main_task
18166 2 80a4000 1 15 Accept Statement b
18167 3 809a800 1 15 Child Activation Wait a
18168 * 4 80ae800 3 15 Runnable c
18173 In this listing, the asterisk before the last task indicates it to be the
18174 task currently being inspected.
18178 Represents @value{GDBN}'s internal task number.
18184 The parent's task ID (@value{GDBN}'s internal task number).
18187 The base priority of the task.
18190 Current state of the task.
18194 The task has been created but has not been activated. It cannot be
18198 The task is not blocked for any reason known to Ada. (It may be waiting
18199 for a mutex, though.) It is conceptually "executing" in normal mode.
18202 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
18203 that were waiting on terminate alternatives have been awakened and have
18204 terminated themselves.
18206 @item Child Activation Wait
18207 The task is waiting for created tasks to complete activation.
18209 @item Accept Statement
18210 The task is waiting on an accept or selective wait statement.
18212 @item Waiting on entry call
18213 The task is waiting on an entry call.
18215 @item Async Select Wait
18216 The task is waiting to start the abortable part of an asynchronous
18220 The task is waiting on a select statement with only a delay
18223 @item Child Termination Wait
18224 The task is sleeping having completed a master within itself, and is
18225 waiting for the tasks dependent on that master to become terminated or
18226 waiting on a terminate Phase.
18228 @item Wait Child in Term Alt
18229 The task is sleeping waiting for tasks on terminate alternatives to
18230 finish terminating.
18232 @item Accepting RV with @var{taskno}
18233 The task is accepting a rendez-vous with the task @var{taskno}.
18237 Name of the task in the program.
18241 @kindex info task @var{taskno}
18242 @item info task @var{taskno}
18243 This command shows detailed informations on the specified task, as in
18244 the following example:
18249 (@value{GDBP}) info tasks
18250 ID TID P-ID Pri State Name
18251 1 8077880 0 15 Child Activation Wait main_task
18252 * 2 807c468 1 15 Runnable task_1
18253 (@value{GDBP}) info task 2
18254 Ada Task: 0x807c468
18258 Parent: 1 ("main_task")
18264 @kindex task@r{ (Ada)}
18265 @cindex current Ada task ID
18266 This command prints the ID and name of the current task.
18272 (@value{GDBP}) info tasks
18273 ID TID P-ID Pri State Name
18274 1 8077870 0 15 Child Activation Wait main_task
18275 * 2 807c458 1 15 Runnable some_task
18276 (@value{GDBP}) task
18277 [Current task is 2 "some_task"]
18280 @item task @var{taskno}
18281 @cindex Ada task switching
18282 This command is like the @code{thread @var{thread-id}}
18283 command (@pxref{Threads}). It switches the context of debugging
18284 from the current task to the given task.
18290 (@value{GDBP}) info tasks
18291 ID TID P-ID Pri State Name
18292 1 8077870 0 15 Child Activation Wait main_task
18293 * 2 807c458 1 15 Runnable some_task
18294 (@value{GDBP}) task 1
18295 [Switching to task 1 "main_task"]
18296 #0 0x8067726 in pthread_cond_wait ()
18298 #0 0x8067726 in pthread_cond_wait ()
18299 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
18300 #2 0x805cb63 in system.task_primitives.operations.sleep ()
18301 #3 0x806153e in system.tasking.stages.activate_tasks ()
18302 #4 0x804aacc in un () at un.adb:5
18305 @item break @var{location} task @var{taskno}
18306 @itemx break @var{location} task @var{taskno} if @dots{}
18307 @cindex breakpoints and tasks, in Ada
18308 @cindex task breakpoints, in Ada
18309 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
18310 These commands are like the @code{break @dots{} thread @dots{}}
18311 command (@pxref{Thread Stops}). The
18312 @var{location} argument specifies source lines, as described
18313 in @ref{Specify Location}.
18315 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
18316 to specify that you only want @value{GDBN} to stop the program when a
18317 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
18318 numeric task identifiers assigned by @value{GDBN}, shown in the first
18319 column of the @samp{info tasks} display.
18321 If you do not specify @samp{task @var{taskno}} when you set a
18322 breakpoint, the breakpoint applies to @emph{all} tasks of your
18325 You can use the @code{task} qualifier on conditional breakpoints as
18326 well; in this case, place @samp{task @var{taskno}} before the
18327 breakpoint condition (before the @code{if}).
18335 (@value{GDBP}) info tasks
18336 ID TID P-ID Pri State Name
18337 1 140022020 0 15 Child Activation Wait main_task
18338 2 140045060 1 15 Accept/Select Wait t2
18339 3 140044840 1 15 Runnable t1
18340 * 4 140056040 1 15 Runnable t3
18341 (@value{GDBP}) b 15 task 2
18342 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
18343 (@value{GDBP}) cont
18348 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
18350 (@value{GDBP}) info tasks
18351 ID TID P-ID Pri State Name
18352 1 140022020 0 15 Child Activation Wait main_task
18353 * 2 140045060 1 15 Runnable t2
18354 3 140044840 1 15 Runnable t1
18355 4 140056040 1 15 Delay Sleep t3
18359 @node Ada Tasks and Core Files
18360 @subsubsection Tasking Support when Debugging Core Files
18361 @cindex Ada tasking and core file debugging
18363 When inspecting a core file, as opposed to debugging a live program,
18364 tasking support may be limited or even unavailable, depending on
18365 the platform being used.
18366 For instance, on x86-linux, the list of tasks is available, but task
18367 switching is not supported.
18369 On certain platforms, the debugger needs to perform some
18370 memory writes in order to provide Ada tasking support. When inspecting
18371 a core file, this means that the core file must be opened with read-write
18372 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
18373 Under these circumstances, you should make a backup copy of the core
18374 file before inspecting it with @value{GDBN}.
18376 @node Ravenscar Profile
18377 @subsubsection Tasking Support when using the Ravenscar Profile
18378 @cindex Ravenscar Profile
18380 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
18381 specifically designed for systems with safety-critical real-time
18385 @kindex set ravenscar task-switching on
18386 @cindex task switching with program using Ravenscar Profile
18387 @item set ravenscar task-switching on
18388 Allows task switching when debugging a program that uses the Ravenscar
18389 Profile. This is the default.
18391 @kindex set ravenscar task-switching off
18392 @item set ravenscar task-switching off
18393 Turn off task switching when debugging a program that uses the Ravenscar
18394 Profile. This is mostly intended to disable the code that adds support
18395 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
18396 the Ravenscar runtime is preventing @value{GDBN} from working properly.
18397 To be effective, this command should be run before the program is started.
18399 @kindex show ravenscar task-switching
18400 @item show ravenscar task-switching
18401 Show whether it is possible to switch from task to task in a program
18402 using the Ravenscar Profile.
18406 @cindex Ravenscar thread
18407 When Ravenscar task-switching is enabled, Ravenscar tasks are
18408 announced by @value{GDBN} as if they were threads:
18412 [New Ravenscar Thread 0x2b8f0]
18415 Both Ravenscar tasks and the underlying CPU threads will show up in
18416 the output of @code{info threads}:
18421 1 Thread 1 (CPU#0 [running]) simple () at simple.adb:10
18422 2 Thread 2 (CPU#1 [running]) 0x0000000000003d34 in __gnat_initialize_cpu_devices ()
18423 3 Thread 3 (CPU#2 [running]) 0x0000000000003d28 in __gnat_initialize_cpu_devices ()
18424 4 Thread 4 (CPU#3 [halted ]) 0x000000000000c6ec in system.task_primitives.operations.idle ()
18425 * 5 Ravenscar Thread 0x2b8f0 simple () at simple.adb:10
18426 6 Ravenscar Thread 0x2f150 0x000000000000c6ec in system.task_primitives.operations.idle ()
18429 One known limitation of the Ravenscar support in @value{GDBN} is that
18430 it isn't currently possible to single-step through the runtime
18431 initialization sequence. If you need to debug this code, you should
18432 use @code{set ravenscar task-switching off}.
18435 @subsubsection Ada Settings
18436 @cindex Ada settings
18439 @kindex set varsize-limit
18440 @item set varsize-limit @var{size}
18441 Prevent @value{GDBN} from attempting to evaluate objects whose size
18442 is above the given limit (@var{size}) when those sizes are computed
18443 from run-time quantities. This is typically the case when the object
18444 has a variable size, such as an array whose bounds are not known at
18445 compile time for example. Setting @var{size} to @code{unlimited}
18446 removes the size limitation. By default, the limit is about 65KB.
18448 The purpose of having such a limit is to prevent @value{GDBN} from
18449 trying to grab enormous chunks of virtual memory when asked to evaluate
18450 a quantity whose bounds have been corrupted or have not yet been fully
18451 initialized. The limit applies to the results of some subexpressions
18452 as well as to complete expressions. For example, an expression denoting
18453 a simple integer component, such as @code{x.y.z}, may fail if the size of
18454 @code{x.y} is variable and exceeds @code{size}. On the other hand,
18455 @value{GDBN} is sometimes clever; the expression @code{A(i)}, where
18456 @code{A} is an array variable with non-constant size, will generally
18457 succeed regardless of the bounds on @code{A}, as long as the component
18458 size is less than @var{size}.
18460 @kindex show varsize-limit
18461 @item show varsize-limit
18462 Show the limit on types whose size is determined by run-time quantities.
18466 @subsubsection Known Peculiarities of Ada Mode
18467 @cindex Ada, problems
18469 Besides the omissions listed previously (@pxref{Omissions from Ada}),
18470 we know of several problems with and limitations of Ada mode in
18472 some of which will be fixed with planned future releases of the debugger
18473 and the GNU Ada compiler.
18477 Static constants that the compiler chooses not to materialize as objects in
18478 storage are invisible to the debugger.
18481 Named parameter associations in function argument lists are ignored (the
18482 argument lists are treated as positional).
18485 Many useful library packages are currently invisible to the debugger.
18488 Fixed-point arithmetic, conversions, input, and output is carried out using
18489 floating-point arithmetic, and may give results that only approximate those on
18493 The GNAT compiler never generates the prefix @code{Standard} for any of
18494 the standard symbols defined by the Ada language. @value{GDBN} knows about
18495 this: it will strip the prefix from names when you use it, and will never
18496 look for a name you have so qualified among local symbols, nor match against
18497 symbols in other packages or subprograms. If you have
18498 defined entities anywhere in your program other than parameters and
18499 local variables whose simple names match names in @code{Standard},
18500 GNAT's lack of qualification here can cause confusion. When this happens,
18501 you can usually resolve the confusion
18502 by qualifying the problematic names with package
18503 @code{Standard} explicitly.
18506 Older versions of the compiler sometimes generate erroneous debugging
18507 information, resulting in the debugger incorrectly printing the value
18508 of affected entities. In some cases, the debugger is able to work
18509 around an issue automatically. In other cases, the debugger is able
18510 to work around the issue, but the work-around has to be specifically
18513 @kindex set ada trust-PAD-over-XVS
18514 @kindex show ada trust-PAD-over-XVS
18517 @item set ada trust-PAD-over-XVS on
18518 Configure GDB to strictly follow the GNAT encoding when computing the
18519 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
18520 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
18521 a complete description of the encoding used by the GNAT compiler).
18522 This is the default.
18524 @item set ada trust-PAD-over-XVS off
18525 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
18526 sometimes prints the wrong value for certain entities, changing @code{ada
18527 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
18528 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
18529 @code{off}, but this incurs a slight performance penalty, so it is
18530 recommended to leave this setting to @code{on} unless necessary.
18534 @cindex GNAT descriptive types
18535 @cindex GNAT encoding
18536 Internally, the debugger also relies on the compiler following a number
18537 of conventions known as the @samp{GNAT Encoding}, all documented in
18538 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
18539 how the debugging information should be generated for certain types.
18540 In particular, this convention makes use of @dfn{descriptive types},
18541 which are artificial types generated purely to help the debugger.
18543 These encodings were defined at a time when the debugging information
18544 format used was not powerful enough to describe some of the more complex
18545 types available in Ada. Since DWARF allows us to express nearly all
18546 Ada features, the long-term goal is to slowly replace these descriptive
18547 types by their pure DWARF equivalent. To facilitate that transition,
18548 a new maintenance option is available to force the debugger to ignore
18549 those descriptive types. It allows the user to quickly evaluate how
18550 well @value{GDBN} works without them.
18554 @kindex maint ada set ignore-descriptive-types
18555 @item maintenance ada set ignore-descriptive-types [on|off]
18556 Control whether the debugger should ignore descriptive types.
18557 The default is not to ignore descriptives types (@code{off}).
18559 @kindex maint ada show ignore-descriptive-types
18560 @item maintenance ada show ignore-descriptive-types
18561 Show if descriptive types are ignored by @value{GDBN}.
18565 @node Unsupported Languages
18566 @section Unsupported Languages
18568 @cindex unsupported languages
18569 @cindex minimal language
18570 In addition to the other fully-supported programming languages,
18571 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
18572 It does not represent a real programming language, but provides a set
18573 of capabilities close to what the C or assembly languages provide.
18574 This should allow most simple operations to be performed while debugging
18575 an application that uses a language currently not supported by @value{GDBN}.
18577 If the language is set to @code{auto}, @value{GDBN} will automatically
18578 select this language if the current frame corresponds to an unsupported
18582 @chapter Examining the Symbol Table
18584 The commands described in this chapter allow you to inquire about the
18585 symbols (names of variables, functions and types) defined in your
18586 program. This information is inherent in the text of your program and
18587 does not change as your program executes. @value{GDBN} finds it in your
18588 program's symbol table, in the file indicated when you started @value{GDBN}
18589 (@pxref{File Options, ,Choosing Files}), or by one of the
18590 file-management commands (@pxref{Files, ,Commands to Specify Files}).
18592 @cindex symbol names
18593 @cindex names of symbols
18594 @cindex quoting names
18595 @anchor{quoting names}
18596 Occasionally, you may need to refer to symbols that contain unusual
18597 characters, which @value{GDBN} ordinarily treats as word delimiters. The
18598 most frequent case is in referring to static variables in other
18599 source files (@pxref{Variables,,Program Variables}). File names
18600 are recorded in object files as debugging symbols, but @value{GDBN} would
18601 ordinarily parse a typical file name, like @file{foo.c}, as the three words
18602 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
18603 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
18610 looks up the value of @code{x} in the scope of the file @file{foo.c}.
18613 @cindex case-insensitive symbol names
18614 @cindex case sensitivity in symbol names
18615 @kindex set case-sensitive
18616 @item set case-sensitive on
18617 @itemx set case-sensitive off
18618 @itemx set case-sensitive auto
18619 Normally, when @value{GDBN} looks up symbols, it matches their names
18620 with case sensitivity determined by the current source language.
18621 Occasionally, you may wish to control that. The command @code{set
18622 case-sensitive} lets you do that by specifying @code{on} for
18623 case-sensitive matches or @code{off} for case-insensitive ones. If
18624 you specify @code{auto}, case sensitivity is reset to the default
18625 suitable for the source language. The default is case-sensitive
18626 matches for all languages except for Fortran, for which the default is
18627 case-insensitive matches.
18629 @kindex show case-sensitive
18630 @item show case-sensitive
18631 This command shows the current setting of case sensitivity for symbols
18634 @kindex set print type methods
18635 @item set print type methods
18636 @itemx set print type methods on
18637 @itemx set print type methods off
18638 Normally, when @value{GDBN} prints a class, it displays any methods
18639 declared in that class. You can control this behavior either by
18640 passing the appropriate flag to @code{ptype}, or using @command{set
18641 print type methods}. Specifying @code{on} will cause @value{GDBN} to
18642 display the methods; this is the default. Specifying @code{off} will
18643 cause @value{GDBN} to omit the methods.
18645 @kindex show print type methods
18646 @item show print type methods
18647 This command shows the current setting of method display when printing
18650 @kindex set print type nested-type-limit
18651 @item set print type nested-type-limit @var{limit}
18652 @itemx set print type nested-type-limit unlimited
18653 Set the limit of displayed nested types that the type printer will
18654 show. A @var{limit} of @code{unlimited} or @code{-1} will show all
18655 nested definitions. By default, the type printer will not show any nested
18656 types defined in classes.
18658 @kindex show print type nested-type-limit
18659 @item show print type nested-type-limit
18660 This command shows the current display limit of nested types when
18663 @kindex set print type typedefs
18664 @item set print type typedefs
18665 @itemx set print type typedefs on
18666 @itemx set print type typedefs off
18668 Normally, when @value{GDBN} prints a class, it displays any typedefs
18669 defined in that class. You can control this behavior either by
18670 passing the appropriate flag to @code{ptype}, or using @command{set
18671 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
18672 display the typedef definitions; this is the default. Specifying
18673 @code{off} will cause @value{GDBN} to omit the typedef definitions.
18674 Note that this controls whether the typedef definition itself is
18675 printed, not whether typedef names are substituted when printing other
18678 @kindex show print type typedefs
18679 @item show print type typedefs
18680 This command shows the current setting of typedef display when
18683 @kindex info address
18684 @cindex address of a symbol
18685 @item info address @var{symbol}
18686 Describe where the data for @var{symbol} is stored. For a register
18687 variable, this says which register it is kept in. For a non-register
18688 local variable, this prints the stack-frame offset at which the variable
18691 Note the contrast with @samp{print &@var{symbol}}, which does not work
18692 at all for a register variable, and for a stack local variable prints
18693 the exact address of the current instantiation of the variable.
18695 @kindex info symbol
18696 @cindex symbol from address
18697 @cindex closest symbol and offset for an address
18698 @item info symbol @var{addr}
18699 Print the name of a symbol which is stored at the address @var{addr}.
18700 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
18701 nearest symbol and an offset from it:
18704 (@value{GDBP}) info symbol 0x54320
18705 _initialize_vx + 396 in section .text
18709 This is the opposite of the @code{info address} command. You can use
18710 it to find out the name of a variable or a function given its address.
18712 For dynamically linked executables, the name of executable or shared
18713 library containing the symbol is also printed:
18716 (@value{GDBP}) info symbol 0x400225
18717 _start + 5 in section .text of /tmp/a.out
18718 (@value{GDBP}) info symbol 0x2aaaac2811cf
18719 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
18724 @item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
18725 Demangle @var{name}.
18726 If @var{language} is provided it is the name of the language to demangle
18727 @var{name} in. Otherwise @var{name} is demangled in the current language.
18729 The @samp{--} option specifies the end of options,
18730 and is useful when @var{name} begins with a dash.
18732 The parameter @code{demangle-style} specifies how to interpret the kind
18733 of mangling used. @xref{Print Settings}.
18736 @item whatis[/@var{flags}] [@var{arg}]
18737 Print the data type of @var{arg}, which can be either an expression
18738 or a name of a data type. With no argument, print the data type of
18739 @code{$}, the last value in the value history.
18741 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
18742 is not actually evaluated, and any side-effecting operations (such as
18743 assignments or function calls) inside it do not take place.
18745 If @var{arg} is a variable or an expression, @code{whatis} prints its
18746 literal type as it is used in the source code. If the type was
18747 defined using a @code{typedef}, @code{whatis} will @emph{not} print
18748 the data type underlying the @code{typedef}. If the type of the
18749 variable or the expression is a compound data type, such as
18750 @code{struct} or @code{class}, @code{whatis} never prints their
18751 fields or methods. It just prints the @code{struct}/@code{class}
18752 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
18753 such a compound data type, use @code{ptype}.
18755 If @var{arg} is a type name that was defined using @code{typedef},
18756 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
18757 Unrolling means that @code{whatis} will show the underlying type used
18758 in the @code{typedef} declaration of @var{arg}. However, if that
18759 underlying type is also a @code{typedef}, @code{whatis} will not
18762 For C code, the type names may also have the form @samp{class
18763 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
18764 @var{union-tag}} or @samp{enum @var{enum-tag}}.
18766 @var{flags} can be used to modify how the type is displayed.
18767 Available flags are:
18771 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
18772 parameters and typedefs defined in a class when printing the class'
18773 members. The @code{/r} flag disables this.
18776 Do not print methods defined in the class.
18779 Print methods defined in the class. This is the default, but the flag
18780 exists in case you change the default with @command{set print type methods}.
18783 Do not print typedefs defined in the class. Note that this controls
18784 whether the typedef definition itself is printed, not whether typedef
18785 names are substituted when printing other types.
18788 Print typedefs defined in the class. This is the default, but the flag
18789 exists in case you change the default with @command{set print type typedefs}.
18792 Print the offsets and sizes of fields in a struct, similar to what the
18793 @command{pahole} tool does. This option implies the @code{/tm} flags.
18795 For example, given the following declarations:
18831 Issuing a @kbd{ptype /o struct tuv} command would print:
18834 (@value{GDBP}) ptype /o struct tuv
18835 /* offset | size */ type = struct tuv @{
18836 /* 0 | 4 */ int a1;
18837 /* XXX 4-byte hole */
18838 /* 8 | 8 */ char *a2;
18839 /* 16 | 4 */ int a3;
18841 /* total size (bytes): 24 */
18845 Notice the format of the first column of comments. There, you can
18846 find two parts separated by the @samp{|} character: the @emph{offset},
18847 which indicates where the field is located inside the struct, in
18848 bytes, and the @emph{size} of the field. Another interesting line is
18849 the marker of a @emph{hole} in the struct, indicating that it may be
18850 possible to pack the struct and make it use less space by reorganizing
18853 It is also possible to print offsets inside an union:
18856 (@value{GDBP}) ptype /o union qwe
18857 /* offset | size */ type = union qwe @{
18858 /* 24 */ struct tuv @{
18859 /* 0 | 4 */ int a1;
18860 /* XXX 4-byte hole */
18861 /* 8 | 8 */ char *a2;
18862 /* 16 | 4 */ int a3;
18864 /* total size (bytes): 24 */
18866 /* 40 */ struct xyz @{
18867 /* 0 | 4 */ int f1;
18868 /* 4 | 1 */ char f2;
18869 /* XXX 3-byte hole */
18870 /* 8 | 8 */ void *f3;
18871 /* 16 | 24 */ struct tuv @{
18872 /* 16 | 4 */ int a1;
18873 /* XXX 4-byte hole */
18874 /* 24 | 8 */ char *a2;
18875 /* 32 | 4 */ int a3;
18877 /* total size (bytes): 24 */
18880 /* total size (bytes): 40 */
18883 /* total size (bytes): 40 */
18887 In this case, since @code{struct tuv} and @code{struct xyz} occupy the
18888 same space (because we are dealing with an union), the offset is not
18889 printed for them. However, you can still examine the offset of each
18890 of these structures' fields.
18892 Another useful scenario is printing the offsets of a struct containing
18896 (@value{GDBP}) ptype /o struct tyu
18897 /* offset | size */ type = struct tyu @{
18898 /* 0:31 | 4 */ int a1 : 1;
18899 /* 0:28 | 4 */ int a2 : 3;
18900 /* 0: 5 | 4 */ int a3 : 23;
18901 /* 3: 3 | 1 */ signed char a4 : 2;
18902 /* XXX 3-bit hole */
18903 /* XXX 4-byte hole */
18904 /* 8 | 8 */ int64_t a5;
18905 /* 16: 0 | 4 */ int a6 : 5;
18906 /* 16: 5 | 8 */ int64_t a7 : 3;
18907 "/* XXX 7-byte padding */
18909 /* total size (bytes): 24 */
18913 Note how the offset information is now extended to also include the
18914 first bit of the bitfield.
18918 @item ptype[/@var{flags}] [@var{arg}]
18919 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
18920 detailed description of the type, instead of just the name of the type.
18921 @xref{Expressions, ,Expressions}.
18923 Contrary to @code{whatis}, @code{ptype} always unrolls any
18924 @code{typedef}s in its argument declaration, whether the argument is
18925 a variable, expression, or a data type. This means that @code{ptype}
18926 of a variable or an expression will not print literally its type as
18927 present in the source code---use @code{whatis} for that. @code{typedef}s at
18928 the pointer or reference targets are also unrolled. Only @code{typedef}s of
18929 fields, methods and inner @code{class typedef}s of @code{struct}s,
18930 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
18932 For example, for this variable declaration:
18935 typedef double real_t;
18936 struct complex @{ real_t real; double imag; @};
18937 typedef struct complex complex_t;
18939 real_t *real_pointer_var;
18943 the two commands give this output:
18947 (@value{GDBP}) whatis var
18949 (@value{GDBP}) ptype var
18950 type = struct complex @{
18954 (@value{GDBP}) whatis complex_t
18955 type = struct complex
18956 (@value{GDBP}) whatis struct complex
18957 type = struct complex
18958 (@value{GDBP}) ptype struct complex
18959 type = struct complex @{
18963 (@value{GDBP}) whatis real_pointer_var
18965 (@value{GDBP}) ptype real_pointer_var
18971 As with @code{whatis}, using @code{ptype} without an argument refers to
18972 the type of @code{$}, the last value in the value history.
18974 @cindex incomplete type
18975 Sometimes, programs use opaque data types or incomplete specifications
18976 of complex data structure. If the debug information included in the
18977 program does not allow @value{GDBN} to display a full declaration of
18978 the data type, it will say @samp{<incomplete type>}. For example,
18979 given these declarations:
18983 struct foo *fooptr;
18987 but no definition for @code{struct foo} itself, @value{GDBN} will say:
18990 (@value{GDBP}) ptype foo
18991 $1 = <incomplete type>
18995 ``Incomplete type'' is C terminology for data types that are not
18996 completely specified.
18998 @cindex unknown type
18999 Othertimes, information about a variable's type is completely absent
19000 from the debug information included in the program. This most often
19001 happens when the program or library where the variable is defined
19002 includes no debug information at all. @value{GDBN} knows the variable
19003 exists from inspecting the linker/loader symbol table (e.g., the ELF
19004 dynamic symbol table), but such symbols do not contain type
19005 information. Inspecting the type of a (global) variable for which
19006 @value{GDBN} has no type information shows:
19009 (@value{GDBP}) ptype var
19010 type = <data variable, no debug info>
19013 @xref{Variables, no debug info variables}, for how to print the values
19017 @item info types [-q] [@var{regexp}]
19018 Print a brief description of all types whose names match the regular
19019 expression @var{regexp} (or all types in your program, if you supply
19020 no argument). Each complete typename is matched as though it were a
19021 complete line; thus, @samp{i type value} gives information on all
19022 types in your program whose names include the string @code{value}, but
19023 @samp{i type ^value$} gives information only on types whose complete
19024 name is @code{value}.
19026 In programs using different languages, @value{GDBN} chooses the syntax
19027 to print the type description according to the
19028 @samp{set language} value: using @samp{set language auto}
19029 (see @ref{Automatically, ,Set Language Automatically}) means to use the
19030 language of the type, other values mean to use
19031 the manually specified language (see @ref{Manually, ,Set Language Manually}).
19033 This command differs from @code{ptype} in two ways: first, like
19034 @code{whatis}, it does not print a detailed description; second, it
19035 lists all source files and line numbers where a type is defined.
19037 The output from @samp{into types} is proceeded with a header line
19038 describing what types are being listed. The optional flag @samp{-q},
19039 which stands for @samp{quiet}, disables printing this header
19042 @kindex info type-printers
19043 @item info type-printers
19044 Versions of @value{GDBN} that ship with Python scripting enabled may
19045 have ``type printers'' available. When using @command{ptype} or
19046 @command{whatis}, these printers are consulted when the name of a type
19047 is needed. @xref{Type Printing API}, for more information on writing
19050 @code{info type-printers} displays all the available type printers.
19052 @kindex enable type-printer
19053 @kindex disable type-printer
19054 @item enable type-printer @var{name}@dots{}
19055 @item disable type-printer @var{name}@dots{}
19056 These commands can be used to enable or disable type printers.
19059 @cindex local variables
19060 @item info scope @var{location}
19061 List all the variables local to a particular scope. This command
19062 accepts a @var{location} argument---a function name, a source line, or
19063 an address preceded by a @samp{*}, and prints all the variables local
19064 to the scope defined by that location. (@xref{Specify Location}, for
19065 details about supported forms of @var{location}.) For example:
19068 (@value{GDBP}) @b{info scope command_line_handler}
19069 Scope for command_line_handler:
19070 Symbol rl is an argument at stack/frame offset 8, length 4.
19071 Symbol linebuffer is in static storage at address 0x150a18, length 4.
19072 Symbol linelength is in static storage at address 0x150a1c, length 4.
19073 Symbol p is a local variable in register $esi, length 4.
19074 Symbol p1 is a local variable in register $ebx, length 4.
19075 Symbol nline is a local variable in register $edx, length 4.
19076 Symbol repeat is a local variable at frame offset -8, length 4.
19080 This command is especially useful for determining what data to collect
19081 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
19084 @kindex info source
19086 Show information about the current source file---that is, the source file for
19087 the function containing the current point of execution:
19090 the name of the source file, and the directory containing it,
19092 the directory it was compiled in,
19094 its length, in lines,
19096 which programming language it is written in,
19098 if the debug information provides it, the program that compiled the file
19099 (which may include, e.g., the compiler version and command line arguments),
19101 whether the executable includes debugging information for that file, and
19102 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
19104 whether the debugging information includes information about
19105 preprocessor macros.
19109 @kindex info sources
19111 Print the names of all source files in your program for which there is
19112 debugging information, organized into two lists: files whose symbols
19113 have already been read, and files whose symbols will be read when needed.
19115 @item info sources [-dirname | -basename] [--] [@var{regexp}]
19116 Like @samp{info sources}, but only print the names of the files
19117 matching the provided @var{regexp}.
19118 By default, the @var{regexp} is used to match anywhere in the filename.
19119 If @code{-dirname}, only files having a dirname matching @var{regexp} are shown.
19120 If @code{-basename}, only files having a basename matching @var{regexp}
19122 The matching is case-sensitive, except on operating systems that
19123 have case-insensitive filesystem (e.g., MS-Windows).
19125 @kindex info functions
19126 @item info functions [-q] [-n]
19127 Print the names and data types of all defined functions.
19128 Similarly to @samp{info types}, this command groups its output by source
19129 files and annotates each function definition with its source line
19132 In programs using different languages, @value{GDBN} chooses the syntax
19133 to print the function name and type according to the
19134 @samp{set language} value: using @samp{set language auto}
19135 (see @ref{Automatically, ,Set Language Automatically}) means to use the
19136 language of the function, other values mean to use
19137 the manually specified language (see @ref{Manually, ,Set Language Manually}).
19139 The @samp{-n} flag excludes @dfn{non-debugging symbols} from the
19140 results. A non-debugging symbol is a symbol that comes from the
19141 executable's symbol table, not from the debug information (for
19142 example, DWARF) associated with the executable.
19144 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
19145 printing header information and messages explaining why no functions
19148 @item info functions [-q] [-n] [-t @var{type_regexp}] [@var{regexp}]
19149 Like @samp{info functions}, but only print the names and data types
19150 of the functions selected with the provided regexp(s).
19152 If @var{regexp} is provided, print only the functions whose names
19153 match the regular expression @var{regexp}.
19154 Thus, @samp{info fun step} finds all functions whose
19155 names include @code{step}; @samp{info fun ^step} finds those whose names
19156 start with @code{step}. If a function name contains characters that
19157 conflict with the regular expression language (e.g.@:
19158 @samp{operator*()}), they may be quoted with a backslash.
19160 If @var{type_regexp} is provided, print only the functions whose
19161 types, as printed by the @code{whatis} command, match
19162 the regular expression @var{type_regexp}.
19163 If @var{type_regexp} contains space(s), it should be enclosed in
19164 quote characters. If needed, use backslash to escape the meaning
19165 of special characters or quotes.
19166 Thus, @samp{info fun -t '^int ('} finds the functions that return
19167 an integer; @samp{info fun -t '(.*int.*'} finds the functions that
19168 have an argument type containing int; @samp{info fun -t '^int (' ^step}
19169 finds the functions whose names start with @code{step} and that return
19172 If both @var{regexp} and @var{type_regexp} are provided, a function
19173 is printed only if its name matches @var{regexp} and its type matches
19177 @kindex info variables
19178 @item info variables [-q] [-n]
19179 Print the names and data types of all variables that are defined
19180 outside of functions (i.e.@: excluding local variables).
19181 The printed variables are grouped by source files and annotated with
19182 their respective source line numbers.
19184 In programs using different languages, @value{GDBN} chooses the syntax
19185 to print the variable name and type according to the
19186 @samp{set language} value: using @samp{set language auto}
19187 (see @ref{Automatically, ,Set Language Automatically}) means to use the
19188 language of the variable, other values mean to use
19189 the manually specified language (see @ref{Manually, ,Set Language Manually}).
19191 The @samp{-n} flag excludes non-debugging symbols from the results.
19193 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
19194 printing header information and messages explaining why no variables
19197 @item info variables [-q] [-n] [-t @var{type_regexp}] [@var{regexp}]
19198 Like @kbd{info variables}, but only print the variables selected
19199 with the provided regexp(s).
19201 If @var{regexp} is provided, print only the variables whose names
19202 match the regular expression @var{regexp}.
19204 If @var{type_regexp} is provided, print only the variables whose
19205 types, as printed by the @code{whatis} command, match
19206 the regular expression @var{type_regexp}.
19207 If @var{type_regexp} contains space(s), it should be enclosed in
19208 quote characters. If needed, use backslash to escape the meaning
19209 of special characters or quotes.
19211 If both @var{regexp} and @var{type_regexp} are provided, an argument
19212 is printed only if its name matches @var{regexp} and its type matches
19215 @kindex info modules
19217 @item info modules @r{[}-q@r{]} @r{[}@var{regexp}@r{]}
19218 List all Fortran modules in the program, or all modules matching the
19219 optional regular expression @var{regexp}.
19221 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
19222 printing header information and messages explaining why no modules
19225 @kindex info module
19226 @cindex Fortran modules, information about
19227 @cindex functions and variables by Fortran module
19228 @cindex module functions and variables
19229 @item info module functions @r{[}-q@r{]} @r{[}-m @var{module-regexp}@r{]} @r{[}-t @var{type-regexp}@r{]} @r{[}@var{regexp}@r{]}
19230 @itemx info module variables @r{[}-q@r{]} @r{[}-m @var{module-regexp}@r{]} @r{[}-t @var{type-regexp}@r{]} @r{[}@var{regexp}@r{]}
19231 List all functions or variables within all Fortran modules. The set
19232 of functions or variables listed can be limited by providing some or
19233 all of the optional regular expressions. If @var{module-regexp} is
19234 provided, then only Fortran modules matching @var{module-regexp} will
19235 be searched. Only functions or variables whose type matches the
19236 optional regular expression @var{type-regexp} will be listed. And
19237 only functions or variables whose name matches the optional regular
19238 expression @var{regexp} will be listed.
19240 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
19241 printing header information and messages explaining why no functions
19242 or variables have been printed.
19244 @kindex info classes
19245 @cindex Objective-C, classes and selectors
19247 @itemx info classes @var{regexp}
19248 Display all Objective-C classes in your program, or
19249 (with the @var{regexp} argument) all those matching a particular regular
19252 @kindex info selectors
19253 @item info selectors
19254 @itemx info selectors @var{regexp}
19255 Display all Objective-C selectors in your program, or
19256 (with the @var{regexp} argument) all those matching a particular regular
19260 This was never implemented.
19261 @kindex info methods
19263 @itemx info methods @var{regexp}
19264 The @code{info methods} command permits the user to examine all defined
19265 methods within C@t{++} program, or (with the @var{regexp} argument) a
19266 specific set of methods found in the various C@t{++} classes. Many
19267 C@t{++} classes provide a large number of methods. Thus, the output
19268 from the @code{ptype} command can be overwhelming and hard to use. The
19269 @code{info-methods} command filters the methods, printing only those
19270 which match the regular-expression @var{regexp}.
19273 @cindex opaque data types
19274 @kindex set opaque-type-resolution
19275 @item set opaque-type-resolution on
19276 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
19277 declared as a pointer to a @code{struct}, @code{class}, or
19278 @code{union}---for example, @code{struct MyType *}---that is used in one
19279 source file although the full declaration of @code{struct MyType} is in
19280 another source file. The default is on.
19282 A change in the setting of this subcommand will not take effect until
19283 the next time symbols for a file are loaded.
19285 @item set opaque-type-resolution off
19286 Tell @value{GDBN} not to resolve opaque types. In this case, the type
19287 is printed as follows:
19289 @{<no data fields>@}
19292 @kindex show opaque-type-resolution
19293 @item show opaque-type-resolution
19294 Show whether opaque types are resolved or not.
19296 @kindex set print symbol-loading
19297 @cindex print messages when symbols are loaded
19298 @item set print symbol-loading
19299 @itemx set print symbol-loading full
19300 @itemx set print symbol-loading brief
19301 @itemx set print symbol-loading off
19302 The @code{set print symbol-loading} command allows you to control the
19303 printing of messages when @value{GDBN} loads symbol information.
19304 By default a message is printed for the executable and one for each
19305 shared library, and normally this is what you want. However, when
19306 debugging apps with large numbers of shared libraries these messages
19308 When set to @code{brief} a message is printed for each executable,
19309 and when @value{GDBN} loads a collection of shared libraries at once
19310 it will only print one message regardless of the number of shared
19311 libraries. When set to @code{off} no messages are printed.
19313 @kindex show print symbol-loading
19314 @item show print symbol-loading
19315 Show whether messages will be printed when a @value{GDBN} command
19316 entered from the keyboard causes symbol information to be loaded.
19318 @kindex maint print symbols
19319 @cindex symbol dump
19320 @kindex maint print psymbols
19321 @cindex partial symbol dump
19322 @kindex maint print msymbols
19323 @cindex minimal symbol dump
19324 @item maint print symbols @r{[}-pc @var{address}@r{]} @r{[}@var{filename}@r{]}
19325 @itemx maint print symbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
19326 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-pc @var{address}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
19327 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
19328 @itemx maint print msymbols @r{[}-objfile @var{objfile}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
19329 Write a dump of debugging symbol data into the file @var{filename} or
19330 the terminal if @var{filename} is unspecified.
19331 If @code{-objfile @var{objfile}} is specified, only dump symbols for
19333 If @code{-pc @var{address}} is specified, only dump symbols for the file
19334 with code at that address. Note that @var{address} may be a symbol like
19336 If @code{-source @var{source}} is specified, only dump symbols for that
19339 These commands are used to debug the @value{GDBN} symbol-reading code.
19340 These commands do not modify internal @value{GDBN} state, therefore
19341 @samp{maint print symbols} will only print symbols for already expanded symbol
19343 You can use the command @code{info sources} to find out which files these are.
19344 If you use @samp{maint print psymbols} instead, the dump shows information
19345 about symbols that @value{GDBN} only knows partially---that is, symbols
19346 defined in files that @value{GDBN} has skimmed, but not yet read completely.
19347 Finally, @samp{maint print msymbols} just dumps ``minimal symbols'', e.g.,
19350 @xref{Files, ,Commands to Specify Files}, for a discussion of how
19351 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
19353 @kindex maint info symtabs
19354 @kindex maint info psymtabs
19355 @cindex listing @value{GDBN}'s internal symbol tables
19356 @cindex symbol tables, listing @value{GDBN}'s internal
19357 @cindex full symbol tables, listing @value{GDBN}'s internal
19358 @cindex partial symbol tables, listing @value{GDBN}'s internal
19359 @item maint info symtabs @r{[} @var{regexp} @r{]}
19360 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
19362 List the @code{struct symtab} or @code{struct partial_symtab}
19363 structures whose names match @var{regexp}. If @var{regexp} is not
19364 given, list them all. The output includes expressions which you can
19365 copy into a @value{GDBN} debugging this one to examine a particular
19366 structure in more detail. For example:
19369 (@value{GDBP}) maint info psymtabs dwarf2read
19370 @{ objfile /home/gnu/build/gdb/gdb
19371 ((struct objfile *) 0x82e69d0)
19372 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
19373 ((struct partial_symtab *) 0x8474b10)
19376 text addresses 0x814d3c8 -- 0x8158074
19377 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
19378 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
19379 dependencies (none)
19382 (@value{GDBP}) maint info symtabs
19386 We see that there is one partial symbol table whose filename contains
19387 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
19388 and we see that @value{GDBN} has not read in any symtabs yet at all.
19389 If we set a breakpoint on a function, that will cause @value{GDBN} to
19390 read the symtab for the compilation unit containing that function:
19393 (@value{GDBP}) break dwarf2_psymtab_to_symtab
19394 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
19396 (@value{GDBP}) maint info symtabs
19397 @{ objfile /home/gnu/build/gdb/gdb
19398 ((struct objfile *) 0x82e69d0)
19399 @{ symtab /home/gnu/src/gdb/dwarf2read.c
19400 ((struct symtab *) 0x86c1f38)
19403 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
19404 linetable ((struct linetable *) 0x8370fa0)
19405 debugformat DWARF 2
19411 @kindex maint info line-table
19412 @cindex listing @value{GDBN}'s internal line tables
19413 @cindex line tables, listing @value{GDBN}'s internal
19414 @item maint info line-table @r{[} @var{regexp} @r{]}
19416 List the @code{struct linetable} from all @code{struct symtab}
19417 instances whose name matches @var{regexp}. If @var{regexp} is not
19418 given, list the @code{struct linetable} from all @code{struct symtab}.
19420 @kindex maint set symbol-cache-size
19421 @cindex symbol cache size
19422 @item maint set symbol-cache-size @var{size}
19423 Set the size of the symbol cache to @var{size}.
19424 The default size is intended to be good enough for debugging
19425 most applications. This option exists to allow for experimenting
19426 with different sizes.
19428 @kindex maint show symbol-cache-size
19429 @item maint show symbol-cache-size
19430 Show the size of the symbol cache.
19432 @kindex maint print symbol-cache
19433 @cindex symbol cache, printing its contents
19434 @item maint print symbol-cache
19435 Print the contents of the symbol cache.
19436 This is useful when debugging symbol cache issues.
19438 @kindex maint print symbol-cache-statistics
19439 @cindex symbol cache, printing usage statistics
19440 @item maint print symbol-cache-statistics
19441 Print symbol cache usage statistics.
19442 This helps determine how well the cache is being utilized.
19444 @kindex maint flush symbol-cache
19445 @kindex maint flush-symbol-cache
19446 @cindex symbol cache, flushing
19447 @item maint flush symbol-cache
19448 @itemx maint flush-symbol-cache
19449 Flush the contents of the symbol cache, all entries are removed. This
19450 command is useful when debugging the symbol cache. It is also useful
19451 when collecting performance data. The command @code{maint
19452 flush-symbol-cache} is deprecated in favor of @code{maint flush
19458 @chapter Altering Execution
19460 Once you think you have found an error in your program, you might want to
19461 find out for certain whether correcting the apparent error would lead to
19462 correct results in the rest of the run. You can find the answer by
19463 experiment, using the @value{GDBN} features for altering execution of the
19466 For example, you can store new values into variables or memory
19467 locations, give your program a signal, restart it at a different
19468 address, or even return prematurely from a function.
19471 * Assignment:: Assignment to variables
19472 * Jumping:: Continuing at a different address
19473 * Signaling:: Giving your program a signal
19474 * Returning:: Returning from a function
19475 * Calling:: Calling your program's functions
19476 * Patching:: Patching your program
19477 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
19481 @section Assignment to Variables
19484 @cindex setting variables
19485 To alter the value of a variable, evaluate an assignment expression.
19486 @xref{Expressions, ,Expressions}. For example,
19493 stores the value 4 into the variable @code{x}, and then prints the
19494 value of the assignment expression (which is 4).
19495 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
19496 information on operators in supported languages.
19498 @kindex set variable
19499 @cindex variables, setting
19500 If you are not interested in seeing the value of the assignment, use the
19501 @code{set} command instead of the @code{print} command. @code{set} is
19502 really the same as @code{print} except that the expression's value is
19503 not printed and is not put in the value history (@pxref{Value History,
19504 ,Value History}). The expression is evaluated only for its effects.
19506 If the beginning of the argument string of the @code{set} command
19507 appears identical to a @code{set} subcommand, use the @code{set
19508 variable} command instead of just @code{set}. This command is identical
19509 to @code{set} except for its lack of subcommands. For example, if your
19510 program has a variable @code{width}, you get an error if you try to set
19511 a new value with just @samp{set width=13}, because @value{GDBN} has the
19512 command @code{set width}:
19515 (@value{GDBP}) whatis width
19517 (@value{GDBP}) p width
19519 (@value{GDBP}) set width=47
19520 Invalid syntax in expression.
19524 The invalid expression, of course, is @samp{=47}. In
19525 order to actually set the program's variable @code{width}, use
19528 (@value{GDBP}) set var width=47
19531 Because the @code{set} command has many subcommands that can conflict
19532 with the names of program variables, it is a good idea to use the
19533 @code{set variable} command instead of just @code{set}. For example, if
19534 your program has a variable @code{g}, you run into problems if you try
19535 to set a new value with just @samp{set g=4}, because @value{GDBN} has
19536 the command @code{set gnutarget}, abbreviated @code{set g}:
19540 (@value{GDBP}) whatis g
19544 (@value{GDBP}) set g=4
19548 The program being debugged has been started already.
19549 Start it from the beginning? (y or n) y
19550 Starting program: /home/smith/cc_progs/a.out
19551 "/home/smith/cc_progs/a.out": can't open to read symbols:
19552 Invalid bfd target.
19553 (@value{GDBP}) show g
19554 The current BFD target is "=4".
19559 The program variable @code{g} did not change, and you silently set the
19560 @code{gnutarget} to an invalid value. In order to set the variable
19564 (@value{GDBP}) set var g=4
19567 @value{GDBN} allows more implicit conversions in assignments than C; you can
19568 freely store an integer value into a pointer variable or vice versa,
19569 and you can convert any structure to any other structure that is the
19570 same length or shorter.
19571 @comment FIXME: how do structs align/pad in these conversions?
19572 @comment /doc@cygnus.com 18dec1990
19574 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
19575 construct to generate a value of specified type at a specified address
19576 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
19577 to memory location @code{0x83040} as an integer (which implies a certain size
19578 and representation in memory), and
19581 set @{int@}0x83040 = 4
19585 stores the value 4 into that memory location.
19588 @section Continuing at a Different Address
19590 Ordinarily, when you continue your program, you do so at the place where
19591 it stopped, with the @code{continue} command. You can instead continue at
19592 an address of your own choosing, with the following commands:
19596 @kindex j @r{(@code{jump})}
19597 @item jump @var{location}
19598 @itemx j @var{location}
19599 Resume execution at @var{location}. Execution stops again immediately
19600 if there is a breakpoint there. @xref{Specify Location}, for a description
19601 of the different forms of @var{location}. It is common
19602 practice to use the @code{tbreak} command in conjunction with
19603 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
19605 The @code{jump} command does not change the current stack frame, or
19606 the stack pointer, or the contents of any memory location or any
19607 register other than the program counter. If @var{location} is in
19608 a different function from the one currently executing, the results may
19609 be bizarre if the two functions expect different patterns of arguments or
19610 of local variables. For this reason, the @code{jump} command requests
19611 confirmation if the specified line is not in the function currently
19612 executing. However, even bizarre results are predictable if you are
19613 well acquainted with the machine-language code of your program.
19616 On many systems, you can get much the same effect as the @code{jump}
19617 command by storing a new value into the register @code{$pc}. The
19618 difference is that this does not start your program running; it only
19619 changes the address of where it @emph{will} run when you continue. For
19627 makes the next @code{continue} command or stepping command execute at
19628 address @code{0x485}, rather than at the address where your program stopped.
19629 @xref{Continuing and Stepping, ,Continuing and Stepping}.
19631 The most common occasion to use the @code{jump} command is to back
19632 up---perhaps with more breakpoints set---over a portion of a program
19633 that has already executed, in order to examine its execution in more
19638 @section Giving your Program a Signal
19639 @cindex deliver a signal to a program
19643 @item signal @var{signal}
19644 Resume execution where your program is stopped, but immediately give it the
19645 signal @var{signal}. The @var{signal} can be the name or the number of a
19646 signal. For example, on many systems @code{signal 2} and @code{signal
19647 SIGINT} are both ways of sending an interrupt signal.
19649 Alternatively, if @var{signal} is zero, continue execution without
19650 giving a signal. This is useful when your program stopped on account of
19651 a signal and would ordinarily see the signal when resumed with the
19652 @code{continue} command; @samp{signal 0} causes it to resume without a
19655 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
19656 delivered to the currently selected thread, not the thread that last
19657 reported a stop. This includes the situation where a thread was
19658 stopped due to a signal. So if you want to continue execution
19659 suppressing the signal that stopped a thread, you should select that
19660 same thread before issuing the @samp{signal 0} command. If you issue
19661 the @samp{signal 0} command with another thread as the selected one,
19662 @value{GDBN} detects that and asks for confirmation.
19664 Invoking the @code{signal} command is not the same as invoking the
19665 @code{kill} utility from the shell. Sending a signal with @code{kill}
19666 causes @value{GDBN} to decide what to do with the signal depending on
19667 the signal handling tables (@pxref{Signals}). The @code{signal} command
19668 passes the signal directly to your program.
19670 @code{signal} does not repeat when you press @key{RET} a second time
19671 after executing the command.
19673 @kindex queue-signal
19674 @item queue-signal @var{signal}
19675 Queue @var{signal} to be delivered immediately to the current thread
19676 when execution of the thread resumes. The @var{signal} can be the name or
19677 the number of a signal. For example, on many systems @code{signal 2} and
19678 @code{signal SIGINT} are both ways of sending an interrupt signal.
19679 The handling of the signal must be set to pass the signal to the program,
19680 otherwise @value{GDBN} will report an error.
19681 You can control the handling of signals from @value{GDBN} with the
19682 @code{handle} command (@pxref{Signals}).
19684 Alternatively, if @var{signal} is zero, any currently queued signal
19685 for the current thread is discarded and when execution resumes no signal
19686 will be delivered. This is useful when your program stopped on account
19687 of a signal and would ordinarily see the signal when resumed with the
19688 @code{continue} command.
19690 This command differs from the @code{signal} command in that the signal
19691 is just queued, execution is not resumed. And @code{queue-signal} cannot
19692 be used to pass a signal whose handling state has been set to @code{nopass}
19697 @xref{stepping into signal handlers}, for information on how stepping
19698 commands behave when the thread has a signal queued.
19701 @section Returning from a Function
19704 @cindex returning from a function
19707 @itemx return @var{expression}
19708 You can cancel execution of a function call with the @code{return}
19709 command. If you give an
19710 @var{expression} argument, its value is used as the function's return
19714 When you use @code{return}, @value{GDBN} discards the selected stack frame
19715 (and all frames within it). You can think of this as making the
19716 discarded frame return prematurely. If you wish to specify a value to
19717 be returned, give that value as the argument to @code{return}.
19719 This pops the selected stack frame (@pxref{Selection, ,Selecting a
19720 Frame}), and any other frames inside of it, leaving its caller as the
19721 innermost remaining frame. That frame becomes selected. The
19722 specified value is stored in the registers used for returning values
19725 The @code{return} command does not resume execution; it leaves the
19726 program stopped in the state that would exist if the function had just
19727 returned. In contrast, the @code{finish} command (@pxref{Continuing
19728 and Stepping, ,Continuing and Stepping}) resumes execution until the
19729 selected stack frame returns naturally.
19731 @value{GDBN} needs to know how the @var{expression} argument should be set for
19732 the inferior. The concrete registers assignment depends on the OS ABI and the
19733 type being returned by the selected stack frame. For example it is common for
19734 OS ABI to return floating point values in FPU registers while integer values in
19735 CPU registers. Still some ABIs return even floating point values in CPU
19736 registers. Larger integer widths (such as @code{long long int}) also have
19737 specific placement rules. @value{GDBN} already knows the OS ABI from its
19738 current target so it needs to find out also the type being returned to make the
19739 assignment into the right register(s).
19741 Normally, the selected stack frame has debug info. @value{GDBN} will always
19742 use the debug info instead of the implicit type of @var{expression} when the
19743 debug info is available. For example, if you type @kbd{return -1}, and the
19744 function in the current stack frame is declared to return a @code{long long
19745 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
19746 into a @code{long long int}:
19749 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
19751 (@value{GDBP}) return -1
19752 Make func return now? (y or n) y
19753 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
19754 43 printf ("result=%lld\n", func ());
19758 However, if the selected stack frame does not have a debug info, e.g., if the
19759 function was compiled without debug info, @value{GDBN} has to find out the type
19760 to return from user. Specifying a different type by mistake may set the value
19761 in different inferior registers than the caller code expects. For example,
19762 typing @kbd{return -1} with its implicit type @code{int} would set only a part
19763 of a @code{long long int} result for a debug info less function (on 32-bit
19764 architectures). Therefore the user is required to specify the return type by
19765 an appropriate cast explicitly:
19768 Breakpoint 2, 0x0040050b in func ()
19769 (@value{GDBP}) return -1
19770 Return value type not available for selected stack frame.
19771 Please use an explicit cast of the value to return.
19772 (@value{GDBP}) return (long long int) -1
19773 Make selected stack frame return now? (y or n) y
19774 #0 0x00400526 in main ()
19779 @section Calling Program Functions
19782 @cindex calling functions
19783 @cindex inferior functions, calling
19784 @item print @var{expr}
19785 Evaluate the expression @var{expr} and display the resulting value.
19786 The expression may include calls to functions in the program being
19790 @item call @var{expr}
19791 Evaluate the expression @var{expr} without displaying @code{void}
19794 You can use this variant of the @code{print} command if you want to
19795 execute a function from your program that does not return anything
19796 (a.k.a.@: @dfn{a void function}), but without cluttering the output
19797 with @code{void} returned values that @value{GDBN} will otherwise
19798 print. If the result is not void, it is printed and saved in the
19802 It is possible for the function you call via the @code{print} or
19803 @code{call} command to generate a signal (e.g., if there's a bug in
19804 the function, or if you passed it incorrect arguments). What happens
19805 in that case is controlled by the @code{set unwindonsignal} command.
19807 Similarly, with a C@t{++} program it is possible for the function you
19808 call via the @code{print} or @code{call} command to generate an
19809 exception that is not handled due to the constraints of the dummy
19810 frame. In this case, any exception that is raised in the frame, but has
19811 an out-of-frame exception handler will not be found. GDB builds a
19812 dummy-frame for the inferior function call, and the unwinder cannot
19813 seek for exception handlers outside of this dummy-frame. What happens
19814 in that case is controlled by the
19815 @code{set unwind-on-terminating-exception} command.
19818 @item set unwindonsignal
19819 @kindex set unwindonsignal
19820 @cindex unwind stack in called functions
19821 @cindex call dummy stack unwinding
19822 Set unwinding of the stack if a signal is received while in a function
19823 that @value{GDBN} called in the program being debugged. If set to on,
19824 @value{GDBN} unwinds the stack it created for the call and restores
19825 the context to what it was before the call. If set to off (the
19826 default), @value{GDBN} stops in the frame where the signal was
19829 @item show unwindonsignal
19830 @kindex show unwindonsignal
19831 Show the current setting of stack unwinding in the functions called by
19834 @item set unwind-on-terminating-exception
19835 @kindex set unwind-on-terminating-exception
19836 @cindex unwind stack in called functions with unhandled exceptions
19837 @cindex call dummy stack unwinding on unhandled exception.
19838 Set unwinding of the stack if a C@t{++} exception is raised, but left
19839 unhandled while in a function that @value{GDBN} called in the program being
19840 debugged. If set to on (the default), @value{GDBN} unwinds the stack
19841 it created for the call and restores the context to what it was before
19842 the call. If set to off, @value{GDBN} the exception is delivered to
19843 the default C@t{++} exception handler and the inferior terminated.
19845 @item show unwind-on-terminating-exception
19846 @kindex show unwind-on-terminating-exception
19847 Show the current setting of stack unwinding in the functions called by
19850 @item set may-call-functions
19851 @kindex set may-call-functions
19852 @cindex disabling calling functions in the program
19853 @cindex calling functions in the program, disabling
19854 Set permission to call functions in the program.
19855 This controls whether @value{GDBN} will attempt to call functions in
19856 the program, such as with expressions in the @code{print} command. It
19857 defaults to @code{on}.
19859 To call a function in the program, @value{GDBN} has to temporarily
19860 modify the state of the inferior. This has potentially undesired side
19861 effects. Also, having @value{GDBN} call nested functions is likely to
19862 be erroneous and may even crash the program being debugged. You can
19863 avoid such hazards by forbidding @value{GDBN} from calling functions
19864 in the program being debugged. If calling functions in the program
19865 is forbidden, GDB will throw an error when a command (such as printing
19866 an expression) starts a function call in the program.
19868 @item show may-call-functions
19869 @kindex show may-call-functions
19870 Show permission to call functions in the program.
19874 @subsection Calling functions with no debug info
19876 @cindex no debug info functions
19877 Sometimes, a function you wish to call is missing debug information.
19878 In such case, @value{GDBN} does not know the type of the function,
19879 including the types of the function's parameters. To avoid calling
19880 the inferior function incorrectly, which could result in the called
19881 function functioning erroneously and even crash, @value{GDBN} refuses
19882 to call the function unless you tell it the type of the function.
19884 For prototyped (i.e.@: ANSI/ISO style) functions, there are two ways
19885 to do that. The simplest is to cast the call to the function's
19886 declared return type. For example:
19889 (@value{GDBP}) p getenv ("PATH")
19890 'getenv' has unknown return type; cast the call to its declared return type
19891 (@value{GDBP}) p (char *) getenv ("PATH")
19892 $1 = 0x7fffffffe7ba "/usr/local/bin:/"...
19895 Casting the return type of a no-debug function is equivalent to
19896 casting the function to a pointer to a prototyped function that has a
19897 prototype that matches the types of the passed-in arguments, and
19898 calling that. I.e., the call above is equivalent to:
19901 (@value{GDBP}) p ((char * (*) (const char *)) getenv) ("PATH")
19905 and given this prototyped C or C++ function with float parameters:
19908 float multiply (float v1, float v2) @{ return v1 * v2; @}
19912 these calls are equivalent:
19915 (@value{GDBP}) p (float) multiply (2.0f, 3.0f)
19916 (@value{GDBP}) p ((float (*) (float, float)) multiply) (2.0f, 3.0f)
19919 If the function you wish to call is declared as unprototyped (i.e.@:
19920 old K&R style), you must use the cast-to-function-pointer syntax, so
19921 that @value{GDBN} knows that it needs to apply default argument
19922 promotions (promote float arguments to double). @xref{ABI, float
19923 promotion}. For example, given this unprototyped C function with
19924 float parameters, and no debug info:
19928 multiply_noproto (v1, v2)
19936 you call it like this:
19939 (@value{GDBP}) p ((float (*) ()) multiply_noproto) (2.0f, 3.0f)
19943 @section Patching Programs
19945 @cindex patching binaries
19946 @cindex writing into executables
19947 @cindex writing into corefiles
19949 By default, @value{GDBN} opens the file containing your program's
19950 executable code (or the corefile) read-only. This prevents accidental
19951 alterations to machine code; but it also prevents you from intentionally
19952 patching your program's binary.
19954 If you'd like to be able to patch the binary, you can specify that
19955 explicitly with the @code{set write} command. For example, you might
19956 want to turn on internal debugging flags, or even to make emergency
19962 @itemx set write off
19963 If you specify @samp{set write on}, @value{GDBN} opens executable and
19964 core files for both reading and writing; if you specify @kbd{set write
19965 off} (the default), @value{GDBN} opens them read-only.
19967 If you have already loaded a file, you must load it again (using the
19968 @code{exec-file} or @code{core-file} command) after changing @code{set
19969 write}, for your new setting to take effect.
19973 Display whether executable files and core files are opened for writing
19974 as well as reading.
19977 @node Compiling and Injecting Code
19978 @section Compiling and injecting code in @value{GDBN}
19979 @cindex injecting code
19980 @cindex writing into executables
19981 @cindex compiling code
19983 @value{GDBN} supports on-demand compilation and code injection into
19984 programs running under @value{GDBN}. GCC 5.0 or higher built with
19985 @file{libcc1.so} must be installed for this functionality to be enabled.
19986 This functionality is implemented with the following commands.
19989 @kindex compile code
19990 @item compile code @var{source-code}
19991 @itemx compile code -raw @var{--} @var{source-code}
19992 Compile @var{source-code} with the compiler language found as the current
19993 language in @value{GDBN} (@pxref{Languages}). If compilation and
19994 injection is not supported with the current language specified in
19995 @value{GDBN}, or the compiler does not support this feature, an error
19996 message will be printed. If @var{source-code} compiles and links
19997 successfully, @value{GDBN} will load the object-code emitted,
19998 and execute it within the context of the currently selected inferior.
19999 It is important to note that the compiled code is executed immediately.
20000 After execution, the compiled code is removed from @value{GDBN} and any
20001 new types or variables you have defined will be deleted.
20003 The command allows you to specify @var{source-code} in two ways.
20004 The simplest method is to provide a single line of code to the command.
20008 compile code printf ("hello world\n");
20011 If you specify options on the command line as well as source code, they
20012 may conflict. The @samp{--} delimiter can be used to separate options
20013 from actual source code. E.g.:
20016 compile code -r -- printf ("hello world\n");
20019 Alternatively you can enter source code as multiple lines of text. To
20020 enter this mode, invoke the @samp{compile code} command without any text
20021 following the command. This will start the multiple-line editor and
20022 allow you to type as many lines of source code as required. When you
20023 have completed typing, enter @samp{end} on its own line to exit the
20028 >printf ("hello\n");
20029 >printf ("world\n");
20033 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
20034 provided @var{source-code} in a callable scope. In this case, you must
20035 specify the entry point of the code by defining a function named
20036 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
20037 inferior. Using @samp{-raw} option may be needed for example when
20038 @var{source-code} requires @samp{#include} lines which may conflict with
20039 inferior symbols otherwise.
20041 @kindex compile file
20042 @item compile file @var{filename}
20043 @itemx compile file -raw @var{filename}
20044 Like @code{compile code}, but take the source code from @var{filename}.
20047 compile file /home/user/example.c
20052 @item compile print [[@var{options}] --] @var{expr}
20053 @itemx compile print [[@var{options}] --] /@var{f} @var{expr}
20054 Compile and execute @var{expr} with the compiler language found as the
20055 current language in @value{GDBN} (@pxref{Languages}). By default the
20056 value of @var{expr} is printed in a format appropriate to its data type;
20057 you can choose a different format by specifying @samp{/@var{f}}, where
20058 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
20059 Formats}. The @code{compile print} command accepts the same options
20060 as the @code{print} command; see @ref{print options}.
20062 @item compile print [[@var{options}] --]
20063 @itemx compile print [[@var{options}] --] /@var{f}
20064 @cindex reprint the last value
20065 Alternatively you can enter the expression (source code producing it) as
20066 multiple lines of text. To enter this mode, invoke the @samp{compile print}
20067 command without any text following the command. This will start the
20068 multiple-line editor.
20072 The process of compiling and injecting the code can be inspected using:
20075 @anchor{set debug compile}
20076 @item set debug compile
20077 @cindex compile command debugging info
20078 Turns on or off display of @value{GDBN} process of compiling and
20079 injecting the code. The default is off.
20081 @item show debug compile
20082 Displays the current state of displaying @value{GDBN} process of
20083 compiling and injecting the code.
20085 @anchor{set debug compile-cplus-types}
20086 @item set debug compile-cplus-types
20087 @cindex compile C@t{++} type conversion
20088 Turns on or off the display of C@t{++} type conversion debugging information.
20089 The default is off.
20091 @item show debug compile-cplus-types
20092 Displays the current state of displaying debugging information for
20093 C@t{++} type conversion.
20096 @subsection Compilation options for the @code{compile} command
20098 @value{GDBN} needs to specify the right compilation options for the code
20099 to be injected, in part to make its ABI compatible with the inferior
20100 and in part to make the injected code compatible with @value{GDBN}'s
20104 The options used, in increasing precedence:
20107 @item target architecture and OS options (@code{gdbarch})
20108 These options depend on target processor type and target operating
20109 system, usually they specify at least 32-bit (@code{-m32}) or 64-bit
20110 (@code{-m64}) compilation option.
20112 @item compilation options recorded in the target
20113 @value{NGCC} (since version 4.7) stores the options used for compilation
20114 into @code{DW_AT_producer} part of DWARF debugging information according
20115 to the @value{NGCC} option @code{-grecord-gcc-switches}. One has to
20116 explicitly specify @code{-g} during inferior compilation otherwise
20117 @value{NGCC} produces no DWARF. This feature is only relevant for
20118 platforms where @code{-g} produces DWARF by default, otherwise one may
20119 try to enforce DWARF by using @code{-gdwarf-4}.
20121 @item compilation options set by @code{set compile-args}
20125 You can override compilation options using the following command:
20128 @item set compile-args
20129 @cindex compile command options override
20130 Set compilation options used for compiling and injecting code with the
20131 @code{compile} commands. These options override any conflicting ones
20132 from the target architecture and/or options stored during inferior
20135 @item show compile-args
20136 Displays the current state of compilation options override.
20137 This does not show all the options actually used during compilation,
20138 use @ref{set debug compile} for that.
20141 @subsection Caveats when using the @code{compile} command
20143 There are a few caveats to keep in mind when using the @code{compile}
20144 command. As the caveats are different per language, the table below
20145 highlights specific issues on a per language basis.
20148 @item C code examples and caveats
20149 When the language in @value{GDBN} is set to @samp{C}, the compiler will
20150 attempt to compile the source code with a @samp{C} compiler. The source
20151 code provided to the @code{compile} command will have much the same
20152 access to variables and types as it normally would if it were part of
20153 the program currently being debugged in @value{GDBN}.
20155 Below is a sample program that forms the basis of the examples that
20156 follow. This program has been compiled and loaded into @value{GDBN},
20157 much like any other normal debugging session.
20160 void function1 (void)
20163 printf ("function 1\n");
20166 void function2 (void)
20181 For the purposes of the examples in this section, the program above has
20182 been compiled, loaded into @value{GDBN}, stopped at the function
20183 @code{main}, and @value{GDBN} is awaiting input from the user.
20185 To access variables and types for any program in @value{GDBN}, the
20186 program must be compiled and packaged with debug information. The
20187 @code{compile} command is not an exception to this rule. Without debug
20188 information, you can still use the @code{compile} command, but you will
20189 be very limited in what variables and types you can access.
20191 So with that in mind, the example above has been compiled with debug
20192 information enabled. The @code{compile} command will have access to
20193 all variables and types (except those that may have been optimized
20194 out). Currently, as @value{GDBN} has stopped the program in the
20195 @code{main} function, the @code{compile} command would have access to
20196 the variable @code{k}. You could invoke the @code{compile} command
20197 and type some source code to set the value of @code{k}. You can also
20198 read it, or do anything with that variable you would normally do in
20199 @code{C}. Be aware that changes to inferior variables in the
20200 @code{compile} command are persistent. In the following example:
20203 compile code k = 3;
20207 the variable @code{k} is now 3. It will retain that value until
20208 something else in the example program changes it, or another
20209 @code{compile} command changes it.
20211 Normal scope and access rules apply to source code compiled and
20212 injected by the @code{compile} command. In the example, the variables
20213 @code{j} and @code{k} are not accessible yet, because the program is
20214 currently stopped in the @code{main} function, where these variables
20215 are not in scope. Therefore, the following command
20218 compile code j = 3;
20222 will result in a compilation error message.
20224 Once the program is continued, execution will bring these variables in
20225 scope, and they will become accessible; then the code you specify via
20226 the @code{compile} command will be able to access them.
20228 You can create variables and types with the @code{compile} command as
20229 part of your source code. Variables and types that are created as part
20230 of the @code{compile} command are not visible to the rest of the program for
20231 the duration of its run. This example is valid:
20234 compile code int ff = 5; printf ("ff is %d\n", ff);
20237 However, if you were to type the following into @value{GDBN} after that
20238 command has completed:
20241 compile code printf ("ff is %d\n'', ff);
20245 a compiler error would be raised as the variable @code{ff} no longer
20246 exists. Object code generated and injected by the @code{compile}
20247 command is removed when its execution ends. Caution is advised
20248 when assigning to program variables values of variables created by the
20249 code submitted to the @code{compile} command. This example is valid:
20252 compile code int ff = 5; k = ff;
20255 The value of the variable @code{ff} is assigned to @code{k}. The variable
20256 @code{k} does not require the existence of @code{ff} to maintain the value
20257 it has been assigned. However, pointers require particular care in
20258 assignment. If the source code compiled with the @code{compile} command
20259 changed the address of a pointer in the example program, perhaps to a
20260 variable created in the @code{compile} command, that pointer would point
20261 to an invalid location when the command exits. The following example
20262 would likely cause issues with your debugged program:
20265 compile code int ff = 5; p = &ff;
20268 In this example, @code{p} would point to @code{ff} when the
20269 @code{compile} command is executing the source code provided to it.
20270 However, as variables in the (example) program persist with their
20271 assigned values, the variable @code{p} would point to an invalid
20272 location when the command exists. A general rule should be followed
20273 in that you should either assign @code{NULL} to any assigned pointers,
20274 or restore a valid location to the pointer before the command exits.
20276 Similar caution must be exercised with any structs, unions, and typedefs
20277 defined in @code{compile} command. Types defined in the @code{compile}
20278 command will no longer be available in the next @code{compile} command.
20279 Therefore, if you cast a variable to a type defined in the
20280 @code{compile} command, care must be taken to ensure that any future
20281 need to resolve the type can be achieved.
20284 (gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
20285 (gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
20286 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
20287 Compilation failed.
20288 (gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
20292 Variables that have been optimized away by the compiler are not
20293 accessible to the code submitted to the @code{compile} command.
20294 Access to those variables will generate a compiler error which @value{GDBN}
20295 will print to the console.
20298 @subsection Compiler search for the @code{compile} command
20300 @value{GDBN} needs to find @value{NGCC} for the inferior being debugged
20301 which may not be obvious for remote targets of different architecture
20302 than where @value{GDBN} is running. Environment variable @code{PATH} on
20303 @value{GDBN} host is searched for @value{NGCC} binary matching the
20304 target architecture and operating system. This search can be overriden
20305 by @code{set compile-gcc} @value{GDBN} command below. @code{PATH} is
20306 taken from shell that executed @value{GDBN}, it is not the value set by
20307 @value{GDBN} command @code{set environment}). @xref{Environment}.
20310 Specifically @code{PATH} is searched for binaries matching regular expression
20311 @code{@var{arch}(-[^-]*)?-@var{os}-gcc} according to the inferior target being
20312 debugged. @var{arch} is processor name --- multiarch is supported, so for
20313 example both @code{i386} and @code{x86_64} targets look for pattern
20314 @code{(x86_64|i.86)} and both @code{s390} and @code{s390x} targets look
20315 for pattern @code{s390x?}. @var{os} is currently supported only for
20316 pattern @code{linux(-gnu)?}.
20318 On Posix hosts the compiler driver @value{GDBN} needs to find also
20319 shared library @file{libcc1.so} from the compiler. It is searched in
20320 default shared library search path (overridable with usual environment
20321 variable @code{LD_LIBRARY_PATH}), unrelated to @code{PATH} or @code{set
20322 compile-gcc} settings. Contrary to it @file{libcc1plugin.so} is found
20323 according to the installation of the found compiler --- as possibly
20324 specified by the @code{set compile-gcc} command.
20327 @item set compile-gcc
20328 @cindex compile command driver filename override
20329 Set compilation command used for compiling and injecting code with the
20330 @code{compile} commands. If this option is not set (it is set to
20331 an empty string), the search described above will occur --- that is the
20334 @item show compile-gcc
20335 Displays the current compile command @value{NGCC} driver filename.
20336 If set, it is the main command @command{gcc}, found usually for example
20337 under name @file{x86_64-linux-gnu-gcc}.
20341 @chapter @value{GDBN} Files
20343 @value{GDBN} needs to know the file name of the program to be debugged,
20344 both in order to read its symbol table and in order to start your
20345 program. To debug a core dump of a previous run, you must also tell
20346 @value{GDBN} the name of the core dump file.
20349 * Files:: Commands to specify files
20350 * File Caching:: Information about @value{GDBN}'s file caching
20351 * Separate Debug Files:: Debugging information in separate files
20352 * MiniDebugInfo:: Debugging information in a special section
20353 * Index Files:: Index files speed up GDB
20354 * Symbol Errors:: Errors reading symbol files
20355 * Data Files:: GDB data files
20359 @section Commands to Specify Files
20361 @cindex symbol table
20362 @cindex core dump file
20364 You may want to specify executable and core dump file names. The usual
20365 way to do this is at start-up time, using the arguments to
20366 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
20367 Out of @value{GDBN}}).
20369 Occasionally it is necessary to change to a different file during a
20370 @value{GDBN} session. Or you may run @value{GDBN} and forget to
20371 specify a file you want to use. Or you are debugging a remote target
20372 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
20373 Program}). In these situations the @value{GDBN} commands to specify
20374 new files are useful.
20377 @cindex executable file
20379 @item file @var{filename}
20380 Use @var{filename} as the program to be debugged. It is read for its
20381 symbols and for the contents of pure memory. It is also the program
20382 executed when you use the @code{run} command. If you do not specify a
20383 directory and the file is not found in the @value{GDBN} working directory,
20384 @value{GDBN} uses the environment variable @code{PATH} as a list of
20385 directories to search, just as the shell does when looking for a program
20386 to run. You can change the value of this variable, for both @value{GDBN}
20387 and your program, using the @code{path} command.
20389 @cindex unlinked object files
20390 @cindex patching object files
20391 You can load unlinked object @file{.o} files into @value{GDBN} using
20392 the @code{file} command. You will not be able to ``run'' an object
20393 file, but you can disassemble functions and inspect variables. Also,
20394 if the underlying BFD functionality supports it, you could use
20395 @kbd{gdb -write} to patch object files using this technique. Note
20396 that @value{GDBN} can neither interpret nor modify relocations in this
20397 case, so branches and some initialized variables will appear to go to
20398 the wrong place. But this feature is still handy from time to time.
20401 @code{file} with no argument makes @value{GDBN} discard any information it
20402 has on both executable file and the symbol table.
20405 @item exec-file @r{[} @var{filename} @r{]}
20406 Specify that the program to be run (but not the symbol table) is found
20407 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
20408 if necessary to locate your program. Omitting @var{filename} means to
20409 discard information on the executable file.
20411 @kindex symbol-file
20412 @item symbol-file @r{[} @var{filename} @r{[} -o @var{offset} @r{]]}
20413 Read symbol table information from file @var{filename}. @code{PATH} is
20414 searched when necessary. Use the @code{file} command to get both symbol
20415 table and program to run from the same file.
20417 If an optional @var{offset} is specified, it is added to the start
20418 address of each section in the symbol file. This is useful if the
20419 program is relocated at runtime, such as the Linux kernel with kASLR
20422 @code{symbol-file} with no argument clears out @value{GDBN} information on your
20423 program's symbol table.
20425 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
20426 some breakpoints and auto-display expressions. This is because they may
20427 contain pointers to the internal data recording symbols and data types,
20428 which are part of the old symbol table data being discarded inside
20431 @code{symbol-file} does not repeat if you press @key{RET} again after
20434 When @value{GDBN} is configured for a particular environment, it
20435 understands debugging information in whatever format is the standard
20436 generated for that environment; you may use either a @sc{gnu} compiler, or
20437 other compilers that adhere to the local conventions.
20438 Best results are usually obtained from @sc{gnu} compilers; for example,
20439 using @code{@value{NGCC}} you can generate debugging information for
20442 For most kinds of object files, with the exception of old SVR3 systems
20443 using COFF, the @code{symbol-file} command does not normally read the
20444 symbol table in full right away. Instead, it scans the symbol table
20445 quickly to find which source files and which symbols are present. The
20446 details are read later, one source file at a time, as they are needed.
20448 The purpose of this two-stage reading strategy is to make @value{GDBN}
20449 start up faster. For the most part, it is invisible except for
20450 occasional pauses while the symbol table details for a particular source
20451 file are being read. (The @code{set verbose} command can turn these
20452 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
20453 Warnings and Messages}.)
20455 We have not implemented the two-stage strategy for COFF yet. When the
20456 symbol table is stored in COFF format, @code{symbol-file} reads the
20457 symbol table data in full right away. Note that ``stabs-in-COFF''
20458 still does the two-stage strategy, since the debug info is actually
20462 @cindex reading symbols immediately
20463 @cindex symbols, reading immediately
20464 @item symbol-file @r{[} -readnow @r{]} @var{filename}
20465 @itemx file @r{[} -readnow @r{]} @var{filename}
20466 You can override the @value{GDBN} two-stage strategy for reading symbol
20467 tables by using the @samp{-readnow} option with any of the commands that
20468 load symbol table information, if you want to be sure @value{GDBN} has the
20469 entire symbol table available.
20471 @cindex @code{-readnever}, option for symbol-file command
20472 @cindex never read symbols
20473 @cindex symbols, never read
20474 @item symbol-file @r{[} -readnever @r{]} @var{filename}
20475 @itemx file @r{[} -readnever @r{]} @var{filename}
20476 You can instruct @value{GDBN} to never read the symbolic information
20477 contained in @var{filename} by using the @samp{-readnever} option.
20478 @xref{--readnever}.
20480 @c FIXME: for now no mention of directories, since this seems to be in
20481 @c flux. 13mar1992 status is that in theory GDB would look either in
20482 @c current dir or in same dir as myprog; but issues like competing
20483 @c GDB's, or clutter in system dirs, mean that in practice right now
20484 @c only current dir is used. FFish says maybe a special GDB hierarchy
20485 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
20489 @item core-file @r{[}@var{filename}@r{]}
20491 Specify the whereabouts of a core dump file to be used as the ``contents
20492 of memory''. Traditionally, core files contain only some parts of the
20493 address space of the process that generated them; @value{GDBN} can access the
20494 executable file itself for other parts.
20496 @code{core-file} with no argument specifies that no core file is
20499 Note that the core file is ignored when your program is actually running
20500 under @value{GDBN}. So, if you have been running your program and you
20501 wish to debug a core file instead, you must kill the subprocess in which
20502 the program is running. To do this, use the @code{kill} command
20503 (@pxref{Kill Process, ,Killing the Child Process}).
20505 @kindex add-symbol-file
20506 @cindex dynamic linking
20507 @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{]}
20508 The @code{add-symbol-file} command reads additional symbol table
20509 information from the file @var{filename}. You would use this command
20510 when @var{filename} has been dynamically loaded (by some other means)
20511 into the program that is running. The @var{textaddress} parameter gives
20512 the memory address at which the file's text section has been loaded.
20513 You can additionally specify the base address of other sections using
20514 an arbitrary number of @samp{-s @var{section} @var{address}} pairs.
20515 If a section is omitted, @value{GDBN} will use its default addresses
20516 as found in @var{filename}. Any @var{address} or @var{textaddress}
20517 can be given as an expression.
20519 If an optional @var{offset} is specified, it is added to the start
20520 address of each section, except those for which the address was
20521 specified explicitly.
20523 The symbol table of the file @var{filename} is added to the symbol table
20524 originally read with the @code{symbol-file} command. You can use the
20525 @code{add-symbol-file} command any number of times; the new symbol data
20526 thus read is kept in addition to the old.
20528 Changes can be reverted using the command @code{remove-symbol-file}.
20530 @cindex relocatable object files, reading symbols from
20531 @cindex object files, relocatable, reading symbols from
20532 @cindex reading symbols from relocatable object files
20533 @cindex symbols, reading from relocatable object files
20534 @cindex @file{.o} files, reading symbols from
20535 Although @var{filename} is typically a shared library file, an
20536 executable file, or some other object file which has been fully
20537 relocated for loading into a process, you can also load symbolic
20538 information from relocatable @file{.o} files, as long as:
20542 the file's symbolic information refers only to linker symbols defined in
20543 that file, not to symbols defined by other object files,
20545 every section the file's symbolic information refers to has actually
20546 been loaded into the inferior, as it appears in the file, and
20548 you can determine the address at which every section was loaded, and
20549 provide these to the @code{add-symbol-file} command.
20553 Some embedded operating systems, like Sun Chorus and VxWorks, can load
20554 relocatable files into an already running program; such systems
20555 typically make the requirements above easy to meet. However, it's
20556 important to recognize that many native systems use complex link
20557 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
20558 assembly, for example) that make the requirements difficult to meet. In
20559 general, one cannot assume that using @code{add-symbol-file} to read a
20560 relocatable object file's symbolic information will have the same effect
20561 as linking the relocatable object file into the program in the normal
20564 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
20566 @kindex remove-symbol-file
20567 @item remove-symbol-file @var{filename}
20568 @item remove-symbol-file -a @var{address}
20569 Remove a symbol file added via the @code{add-symbol-file} command. The
20570 file to remove can be identified by its @var{filename} or by an @var{address}
20571 that lies within the boundaries of this symbol file in memory. Example:
20574 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
20575 add symbol table from file "/home/user/gdb/mylib.so" at
20576 .text_addr = 0x7ffff7ff9480
20578 Reading symbols from /home/user/gdb/mylib.so...
20579 (gdb) remove-symbol-file -a 0x7ffff7ff9480
20580 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
20585 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
20587 @kindex add-symbol-file-from-memory
20588 @cindex @code{syscall DSO}
20589 @cindex load symbols from memory
20590 @item add-symbol-file-from-memory @var{address}
20591 Load symbols from the given @var{address} in a dynamically loaded
20592 object file whose image is mapped directly into the inferior's memory.
20593 For example, the Linux kernel maps a @code{syscall DSO} into each
20594 process's address space; this DSO provides kernel-specific code for
20595 some system calls. The argument can be any expression whose
20596 evaluation yields the address of the file's shared object file header.
20597 For this command to work, you must have used @code{symbol-file} or
20598 @code{exec-file} commands in advance.
20601 @item section @var{section} @var{addr}
20602 The @code{section} command changes the base address of the named
20603 @var{section} of the exec file to @var{addr}. This can be used if the
20604 exec file does not contain section addresses, (such as in the
20605 @code{a.out} format), or when the addresses specified in the file
20606 itself are wrong. Each section must be changed separately. The
20607 @code{info files} command, described below, lists all the sections and
20611 @kindex info target
20614 @code{info files} and @code{info target} are synonymous; both print the
20615 current target (@pxref{Targets, ,Specifying a Debugging Target}),
20616 including the names of the executable and core dump files currently in
20617 use by @value{GDBN}, and the files from which symbols were loaded. The
20618 command @code{help target} lists all possible targets rather than
20621 @kindex maint info sections
20622 @item maint info sections
20623 Another command that can give you extra information about program sections
20624 is @code{maint info sections}. In addition to the section information
20625 displayed by @code{info files}, this command displays the flags and file
20626 offset of each section in the executable and core dump files. In addition,
20627 @code{maint info sections} provides the following command options (which
20628 may be arbitrarily combined):
20632 Display sections for all loaded object files, including shared libraries.
20633 @item @var{sections}
20634 Display info only for named @var{sections}.
20635 @item @var{section-flags}
20636 Display info only for sections for which @var{section-flags} are true.
20637 The section flags that @value{GDBN} currently knows about are:
20640 Section will have space allocated in the process when loaded.
20641 Set for all sections except those containing debug information.
20643 Section will be loaded from the file into the child process memory.
20644 Set for pre-initialized code and data, clear for @code{.bss} sections.
20646 Section needs to be relocated before loading.
20648 Section cannot be modified by the child process.
20650 Section contains executable code only.
20652 Section contains data only (no executable code).
20654 Section will reside in ROM.
20656 Section contains data for constructor/destructor lists.
20658 Section is not empty.
20660 An instruction to the linker to not output the section.
20661 @item COFF_SHARED_LIBRARY
20662 A notification to the linker that the section contains
20663 COFF shared library information.
20665 Section contains common symbols.
20668 @kindex set trust-readonly-sections
20669 @cindex read-only sections
20670 @item set trust-readonly-sections on
20671 Tell @value{GDBN} that readonly sections in your object file
20672 really are read-only (i.e.@: that their contents will not change).
20673 In that case, @value{GDBN} can fetch values from these sections
20674 out of the object file, rather than from the target program.
20675 For some targets (notably embedded ones), this can be a significant
20676 enhancement to debugging performance.
20678 The default is off.
20680 @item set trust-readonly-sections off
20681 Tell @value{GDBN} not to trust readonly sections. This means that
20682 the contents of the section might change while the program is running,
20683 and must therefore be fetched from the target when needed.
20685 @item show trust-readonly-sections
20686 Show the current setting of trusting readonly sections.
20689 All file-specifying commands allow both absolute and relative file names
20690 as arguments. @value{GDBN} always converts the file name to an absolute file
20691 name and remembers it that way.
20693 @cindex shared libraries
20694 @anchor{Shared Libraries}
20695 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, SunOS,
20696 Darwin/Mach-O, SVr4, IBM RS/6000 AIX, QNX Neutrino, FDPIC (FR-V), and
20697 DSBT (TIC6X) shared libraries.
20699 On MS-Windows @value{GDBN} must be linked with the Expat library to support
20700 shared libraries. @xref{Expat}.
20702 @value{GDBN} automatically loads symbol definitions from shared libraries
20703 when you use the @code{run} command, or when you examine a core file.
20704 (Before you issue the @code{run} command, @value{GDBN} does not understand
20705 references to a function in a shared library, however---unless you are
20706 debugging a core file).
20708 @c FIXME: some @value{GDBN} release may permit some refs to undef
20709 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
20710 @c FIXME...lib; check this from time to time when updating manual
20712 There are times, however, when you may wish to not automatically load
20713 symbol definitions from shared libraries, such as when they are
20714 particularly large or there are many of them.
20716 To control the automatic loading of shared library symbols, use the
20720 @kindex set auto-solib-add
20721 @item set auto-solib-add @var{mode}
20722 If @var{mode} is @code{on}, symbols from all shared object libraries
20723 will be loaded automatically when the inferior begins execution, you
20724 attach to an independently started inferior, or when the dynamic linker
20725 informs @value{GDBN} that a new library has been loaded. If @var{mode}
20726 is @code{off}, symbols must be loaded manually, using the
20727 @code{sharedlibrary} command. The default value is @code{on}.
20729 @cindex memory used for symbol tables
20730 If your program uses lots of shared libraries with debug info that
20731 takes large amounts of memory, you can decrease the @value{GDBN}
20732 memory footprint by preventing it from automatically loading the
20733 symbols from shared libraries. To that end, type @kbd{set
20734 auto-solib-add off} before running the inferior, then load each
20735 library whose debug symbols you do need with @kbd{sharedlibrary
20736 @var{regexp}}, where @var{regexp} is a regular expression that matches
20737 the libraries whose symbols you want to be loaded.
20739 @kindex show auto-solib-add
20740 @item show auto-solib-add
20741 Display the current autoloading mode.
20744 @cindex load shared library
20745 To explicitly load shared library symbols, use the @code{sharedlibrary}
20749 @kindex info sharedlibrary
20751 @item info share @var{regex}
20752 @itemx info sharedlibrary @var{regex}
20753 Print the names of the shared libraries which are currently loaded
20754 that match @var{regex}. If @var{regex} is omitted then print
20755 all shared libraries that are loaded.
20758 @item info dll @var{regex}
20759 This is an alias of @code{info sharedlibrary}.
20761 @kindex sharedlibrary
20763 @item sharedlibrary @var{regex}
20764 @itemx share @var{regex}
20765 Load shared object library symbols for files matching a
20766 Unix regular expression.
20767 As with files loaded automatically, it only loads shared libraries
20768 required by your program for a core file or after typing @code{run}. If
20769 @var{regex} is omitted all shared libraries required by your program are
20772 @item nosharedlibrary
20773 @kindex nosharedlibrary
20774 @cindex unload symbols from shared libraries
20775 Unload all shared object library symbols. This discards all symbols
20776 that have been loaded from all shared libraries. Symbols from shared
20777 libraries that were loaded by explicit user requests are not
20781 Sometimes you may wish that @value{GDBN} stops and gives you control
20782 when any of shared library events happen. The best way to do this is
20783 to use @code{catch load} and @code{catch unload} (@pxref{Set
20786 @value{GDBN} also supports the @code{set stop-on-solib-events}
20787 command for this. This command exists for historical reasons. It is
20788 less useful than setting a catchpoint, because it does not allow for
20789 conditions or commands as a catchpoint does.
20792 @item set stop-on-solib-events
20793 @kindex set stop-on-solib-events
20794 This command controls whether @value{GDBN} should give you control
20795 when the dynamic linker notifies it about some shared library event.
20796 The most common event of interest is loading or unloading of a new
20799 @item show stop-on-solib-events
20800 @kindex show stop-on-solib-events
20801 Show whether @value{GDBN} stops and gives you control when shared
20802 library events happen.
20805 Shared libraries are also supported in many cross or remote debugging
20806 configurations. @value{GDBN} needs to have access to the target's libraries;
20807 this can be accomplished either by providing copies of the libraries
20808 on the host system, or by asking @value{GDBN} to automatically retrieve the
20809 libraries from the target. If copies of the target libraries are
20810 provided, they need to be the same as the target libraries, although the
20811 copies on the target can be stripped as long as the copies on the host are
20814 @cindex where to look for shared libraries
20815 For remote debugging, you need to tell @value{GDBN} where the target
20816 libraries are, so that it can load the correct copies---otherwise, it
20817 may try to load the host's libraries. @value{GDBN} has two variables
20818 to specify the search directories for target libraries.
20821 @cindex prefix for executable and shared library file names
20822 @cindex system root, alternate
20823 @kindex set solib-absolute-prefix
20824 @kindex set sysroot
20825 @item set sysroot @var{path}
20826 Use @var{path} as the system root for the program being debugged. Any
20827 absolute shared library paths will be prefixed with @var{path}; many
20828 runtime loaders store the absolute paths to the shared library in the
20829 target program's memory. When starting processes remotely, and when
20830 attaching to already-running processes (local or remote), their
20831 executable filenames will be prefixed with @var{path} if reported to
20832 @value{GDBN} as absolute by the operating system. If you use
20833 @code{set sysroot} to find executables and shared libraries, they need
20834 to be laid out in the same way that they are on the target, with
20835 e.g.@: a @file{/bin}, @file{/lib} and @file{/usr/lib} hierarchy under
20838 If @var{path} starts with the sequence @file{target:} and the target
20839 system is remote then @value{GDBN} will retrieve the target binaries
20840 from the remote system. This is only supported when using a remote
20841 target that supports the @code{remote get} command (@pxref{File
20842 Transfer,,Sending files to a remote system}). The part of @var{path}
20843 following the initial @file{target:} (if present) is used as system
20844 root prefix on the remote file system. If @var{path} starts with the
20845 sequence @file{remote:} this is converted to the sequence
20846 @file{target:} by @code{set sysroot}@footnote{Historically the
20847 functionality to retrieve binaries from the remote system was
20848 provided by prefixing @var{path} with @file{remote:}}. If you want
20849 to specify a local system root using a directory that happens to be
20850 named @file{target:} or @file{remote:}, you need to use some
20851 equivalent variant of the name like @file{./target:}.
20853 For targets with an MS-DOS based filesystem, such as MS-Windows and
20854 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
20855 absolute file name with @var{path}. But first, on Unix hosts,
20856 @value{GDBN} converts all backslash directory separators into forward
20857 slashes, because the backslash is not a directory separator on Unix:
20860 c:\foo\bar.dll @result{} c:/foo/bar.dll
20863 Then, @value{GDBN} attempts prefixing the target file name with
20864 @var{path}, and looks for the resulting file name in the host file
20868 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
20871 If that does not find the binary, @value{GDBN} tries removing
20872 the @samp{:} character from the drive spec, both for convenience, and,
20873 for the case of the host file system not supporting file names with
20877 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
20880 This makes it possible to have a system root that mirrors a target
20881 with more than one drive. E.g., you may want to setup your local
20882 copies of the target system shared libraries like so (note @samp{c} vs
20886 @file{/path/to/sysroot/c/sys/bin/foo.dll}
20887 @file{/path/to/sysroot/c/sys/bin/bar.dll}
20888 @file{/path/to/sysroot/z/sys/bin/bar.dll}
20892 and point the system root at @file{/path/to/sysroot}, so that
20893 @value{GDBN} can find the correct copies of both
20894 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
20896 If that still does not find the binary, @value{GDBN} tries
20897 removing the whole drive spec from the target file name:
20900 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
20903 This last lookup makes it possible to not care about the drive name,
20904 if you don't want or need to.
20906 The @code{set solib-absolute-prefix} command is an alias for @code{set
20909 @cindex default system root
20910 @cindex @samp{--with-sysroot}
20911 You can set the default system root by using the configure-time
20912 @samp{--with-sysroot} option. If the system root is inside
20913 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
20914 @samp{--exec-prefix}), then the default system root will be updated
20915 automatically if the installed @value{GDBN} is moved to a new
20918 @kindex show sysroot
20920 Display the current executable and shared library prefix.
20922 @kindex set solib-search-path
20923 @item set solib-search-path @var{path}
20924 If this variable is set, @var{path} is a colon-separated list of
20925 directories to search for shared libraries. @samp{solib-search-path}
20926 is used after @samp{sysroot} fails to locate the library, or if the
20927 path to the library is relative instead of absolute. If you want to
20928 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
20929 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
20930 finding your host's libraries. @samp{sysroot} is preferred; setting
20931 it to a nonexistent directory may interfere with automatic loading
20932 of shared library symbols.
20934 @kindex show solib-search-path
20935 @item show solib-search-path
20936 Display the current shared library search path.
20938 @cindex DOS file-name semantics of file names.
20939 @kindex set target-file-system-kind (unix|dos-based|auto)
20940 @kindex show target-file-system-kind
20941 @item set target-file-system-kind @var{kind}
20942 Set assumed file system kind for target reported file names.
20944 Shared library file names as reported by the target system may not
20945 make sense as is on the system @value{GDBN} is running on. For
20946 example, when remote debugging a target that has MS-DOS based file
20947 system semantics, from a Unix host, the target may be reporting to
20948 @value{GDBN} a list of loaded shared libraries with file names such as
20949 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
20950 drive letters, so the @samp{c:\} prefix is not normally understood as
20951 indicating an absolute file name, and neither is the backslash
20952 normally considered a directory separator character. In that case,
20953 the native file system would interpret this whole absolute file name
20954 as a relative file name with no directory components. This would make
20955 it impossible to point @value{GDBN} at a copy of the remote target's
20956 shared libraries on the host using @code{set sysroot}, and impractical
20957 with @code{set solib-search-path}. Setting
20958 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
20959 to interpret such file names similarly to how the target would, and to
20960 map them to file names valid on @value{GDBN}'s native file system
20961 semantics. The value of @var{kind} can be @code{"auto"}, in addition
20962 to one of the supported file system kinds. In that case, @value{GDBN}
20963 tries to determine the appropriate file system variant based on the
20964 current target's operating system (@pxref{ABI, ,Configuring the
20965 Current ABI}). The supported file system settings are:
20969 Instruct @value{GDBN} to assume the target file system is of Unix
20970 kind. Only file names starting the forward slash (@samp{/}) character
20971 are considered absolute, and the directory separator character is also
20975 Instruct @value{GDBN} to assume the target file system is DOS based.
20976 File names starting with either a forward slash, or a drive letter
20977 followed by a colon (e.g., @samp{c:}), are considered absolute, and
20978 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
20979 considered directory separators.
20982 Instruct @value{GDBN} to use the file system kind associated with the
20983 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
20984 This is the default.
20988 @cindex file name canonicalization
20989 @cindex base name differences
20990 When processing file names provided by the user, @value{GDBN}
20991 frequently needs to compare them to the file names recorded in the
20992 program's debug info. Normally, @value{GDBN} compares just the
20993 @dfn{base names} of the files as strings, which is reasonably fast
20994 even for very large programs. (The base name of a file is the last
20995 portion of its name, after stripping all the leading directories.)
20996 This shortcut in comparison is based upon the assumption that files
20997 cannot have more than one base name. This is usually true, but
20998 references to files that use symlinks or similar filesystem
20999 facilities violate that assumption. If your program records files
21000 using such facilities, or if you provide file names to @value{GDBN}
21001 using symlinks etc., you can set @code{basenames-may-differ} to
21002 @code{true} to instruct @value{GDBN} to completely canonicalize each
21003 pair of file names it needs to compare. This will make file-name
21004 comparisons accurate, but at a price of a significant slowdown.
21007 @item set basenames-may-differ
21008 @kindex set basenames-may-differ
21009 Set whether a source file may have multiple base names.
21011 @item show basenames-may-differ
21012 @kindex show basenames-may-differ
21013 Show whether a source file may have multiple base names.
21017 @section File Caching
21018 @cindex caching of opened files
21019 @cindex caching of bfd objects
21021 To speed up file loading, and reduce memory usage, @value{GDBN} will
21022 reuse the @code{bfd} objects used to track open files. @xref{Top, ,
21023 BFD, bfd, The Binary File Descriptor Library}. The following commands
21024 allow visibility and control of the caching behavior.
21027 @kindex maint info bfds
21028 @item maint info bfds
21029 This prints information about each @code{bfd} object that is known to
21032 @kindex maint set bfd-sharing
21033 @kindex maint show bfd-sharing
21034 @kindex bfd caching
21035 @item maint set bfd-sharing
21036 @item maint show bfd-sharing
21037 Control whether @code{bfd} objects can be shared. When sharing is
21038 enabled @value{GDBN} reuses already open @code{bfd} objects rather
21039 than reopening the same file. Turning sharing off does not cause
21040 already shared @code{bfd} objects to be unshared, but all future files
21041 that are opened will create a new @code{bfd} object. Similarly,
21042 re-enabling sharing does not cause multiple existing @code{bfd}
21043 objects to be collapsed into a single shared @code{bfd} object.
21045 @kindex set debug bfd-cache @var{level}
21046 @kindex bfd caching
21047 @item set debug bfd-cache @var{level}
21048 Turns on debugging of the bfd cache, setting the level to @var{level}.
21050 @kindex show debug bfd-cache
21051 @kindex bfd caching
21052 @item show debug bfd-cache
21053 Show the current debugging level of the bfd cache.
21056 @node Separate Debug Files
21057 @section Debugging Information in Separate Files
21058 @cindex separate debugging information files
21059 @cindex debugging information in separate files
21060 @cindex @file{.debug} subdirectories
21061 @cindex debugging information directory, global
21062 @cindex global debugging information directories
21063 @cindex build ID, and separate debugging files
21064 @cindex @file{.build-id} directory
21066 @value{GDBN} allows you to put a program's debugging information in a
21067 file separate from the executable itself, in a way that allows
21068 @value{GDBN} to find and load the debugging information automatically.
21069 Since debugging information can be very large---sometimes larger
21070 than the executable code itself---some systems distribute debugging
21071 information for their executables in separate files, which users can
21072 install only when they need to debug a problem.
21074 @value{GDBN} supports two ways of specifying the separate debug info
21079 The executable contains a @dfn{debug link} that specifies the name of
21080 the separate debug info file. The separate debug file's name is
21081 usually @file{@var{executable}.debug}, where @var{executable} is the
21082 name of the corresponding executable file without leading directories
21083 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
21084 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
21085 checksum for the debug file, which @value{GDBN} uses to validate that
21086 the executable and the debug file came from the same build.
21090 The executable contains a @dfn{build ID}, a unique bit string that is
21091 also present in the corresponding debug info file. (This is supported
21092 only on some operating systems, when using the ELF or PE file formats
21093 for binary files and the @sc{gnu} Binutils.) For more details about
21094 this feature, see the description of the @option{--build-id}
21095 command-line option in @ref{Options, , Command Line Options, ld,
21096 The GNU Linker}. The debug info file's name is not specified
21097 explicitly by the build ID, but can be computed from the build ID, see
21101 Depending on the way the debug info file is specified, @value{GDBN}
21102 uses two different methods of looking for the debug file:
21106 For the ``debug link'' method, @value{GDBN} looks up the named file in
21107 the directory of the executable file, then in a subdirectory of that
21108 directory named @file{.debug}, and finally under each one of the
21109 global debug directories, in a subdirectory whose name is identical to
21110 the leading directories of the executable's absolute file name. (On
21111 MS-Windows/MS-DOS, the drive letter of the executable's leading
21112 directories is converted to a one-letter subdirectory, i.e.@:
21113 @file{d:/usr/bin/} is converted to @file{/d/usr/bin/}, because Windows
21114 filesystems disallow colons in file names.)
21117 For the ``build ID'' method, @value{GDBN} looks in the
21118 @file{.build-id} subdirectory of each one of the global debug directories for
21119 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
21120 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
21121 are the rest of the bit string. (Real build ID strings are 32 or more
21122 hex characters, not 10.)
21125 So, for example, suppose you ask @value{GDBN} to debug
21126 @file{/usr/bin/ls}, which has a debug link that specifies the
21127 file @file{ls.debug}, and a build ID whose value in hex is
21128 @code{abcdef1234}. If the list of the global debug directories includes
21129 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
21130 debug information files, in the indicated order:
21134 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
21136 @file{/usr/bin/ls.debug}
21138 @file{/usr/bin/.debug/ls.debug}
21140 @file{/usr/lib/debug/usr/bin/ls.debug}.
21143 @anchor{debug-file-directory}
21144 Global debugging info directories default to what is set by @value{GDBN}
21145 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
21146 you can also set the global debugging info directories, and view the list
21147 @value{GDBN} is currently using.
21151 @kindex set debug-file-directory
21152 @item set debug-file-directory @var{directories}
21153 Set the directories which @value{GDBN} searches for separate debugging
21154 information files to @var{directory}. Multiple path components can be set
21155 concatenating them by a path separator.
21157 @kindex show debug-file-directory
21158 @item show debug-file-directory
21159 Show the directories @value{GDBN} searches for separate debugging
21164 @cindex @code{.gnu_debuglink} sections
21165 @cindex debug link sections
21166 A debug link is a special section of the executable file named
21167 @code{.gnu_debuglink}. The section must contain:
21171 A filename, with any leading directory components removed, followed by
21174 zero to three bytes of padding, as needed to reach the next four-byte
21175 boundary within the section, and
21177 a four-byte CRC checksum, stored in the same endianness used for the
21178 executable file itself. The checksum is computed on the debugging
21179 information file's full contents by the function given below, passing
21180 zero as the @var{crc} argument.
21183 Any executable file format can carry a debug link, as long as it can
21184 contain a section named @code{.gnu_debuglink} with the contents
21187 @cindex @code{.note.gnu.build-id} sections
21188 @cindex build ID sections
21189 The build ID is a special section in the executable file (and in other
21190 ELF binary files that @value{GDBN} may consider). This section is
21191 often named @code{.note.gnu.build-id}, but that name is not mandatory.
21192 It contains unique identification for the built files---the ID remains
21193 the same across multiple builds of the same build tree. The default
21194 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
21195 content for the build ID string. The same section with an identical
21196 value is present in the original built binary with symbols, in its
21197 stripped variant, and in the separate debugging information file.
21199 The debugging information file itself should be an ordinary
21200 executable, containing a full set of linker symbols, sections, and
21201 debugging information. The sections of the debugging information file
21202 should have the same names, addresses, and sizes as the original file,
21203 but they need not contain any data---much like a @code{.bss} section
21204 in an ordinary executable.
21206 The @sc{gnu} binary utilities (Binutils) package includes the
21207 @samp{objcopy} utility that can produce
21208 the separated executable / debugging information file pairs using the
21209 following commands:
21212 @kbd{objcopy --only-keep-debug foo foo.debug}
21217 These commands remove the debugging
21218 information from the executable file @file{foo} and place it in the file
21219 @file{foo.debug}. You can use the first, second or both methods to link the
21224 The debug link method needs the following additional command to also leave
21225 behind a debug link in @file{foo}:
21228 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
21231 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
21232 a version of the @code{strip} command such that the command @kbd{strip foo -f
21233 foo.debug} has the same functionality as the two @code{objcopy} commands and
21234 the @code{ln -s} command above, together.
21237 Build ID gets embedded into the main executable using @code{ld --build-id} or
21238 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
21239 compatibility fixes for debug files separation are present in @sc{gnu} binary
21240 utilities (Binutils) package since version 2.18.
21245 @cindex CRC algorithm definition
21246 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
21247 IEEE 802.3 using the polynomial:
21249 @c TexInfo requires naked braces for multi-digit exponents for Tex
21250 @c output, but this causes HTML output to barf. HTML has to be set using
21251 @c raw commands. So we end up having to specify this equation in 2
21256 <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>
21257 + <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
21263 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
21264 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
21268 The function is computed byte at a time, taking the least
21269 significant bit of each byte first. The initial pattern
21270 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
21271 the final result is inverted to ensure trailing zeros also affect the
21274 @emph{Note:} This is the same CRC polynomial as used in handling the
21275 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
21276 However in the case of the Remote Serial Protocol, the CRC is computed
21277 @emph{most} significant bit first, and the result is not inverted, so
21278 trailing zeros have no effect on the CRC value.
21280 To complete the description, we show below the code of the function
21281 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
21282 initially supplied @code{crc} argument means that an initial call to
21283 this function passing in zero will start computing the CRC using
21286 @kindex gnu_debuglink_crc32
21289 gnu_debuglink_crc32 (unsigned long crc,
21290 unsigned char *buf, size_t len)
21292 static const unsigned long crc32_table[256] =
21294 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
21295 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
21296 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
21297 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
21298 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
21299 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
21300 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
21301 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
21302 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
21303 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
21304 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
21305 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
21306 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
21307 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
21308 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
21309 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
21310 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
21311 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
21312 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
21313 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
21314 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
21315 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
21316 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
21317 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
21318 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
21319 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
21320 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
21321 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
21322 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
21323 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
21324 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
21325 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
21326 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
21327 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
21328 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
21329 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
21330 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
21331 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
21332 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
21333 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
21334 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
21335 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
21336 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
21337 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
21338 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
21339 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
21340 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
21341 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
21342 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
21343 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
21344 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
21347 unsigned char *end;
21349 crc = ~crc & 0xffffffff;
21350 for (end = buf + len; buf < end; ++buf)
21351 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
21352 return ~crc & 0xffffffff;
21357 This computation does not apply to the ``build ID'' method.
21359 @node MiniDebugInfo
21360 @section Debugging information in a special section
21361 @cindex separate debug sections
21362 @cindex @samp{.gnu_debugdata} section
21364 Some systems ship pre-built executables and libraries that have a
21365 special @samp{.gnu_debugdata} section. This feature is called
21366 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
21367 is used to supply extra symbols for backtraces.
21369 The intent of this section is to provide extra minimal debugging
21370 information for use in simple backtraces. It is not intended to be a
21371 replacement for full separate debugging information (@pxref{Separate
21372 Debug Files}). The example below shows the intended use; however,
21373 @value{GDBN} does not currently put restrictions on what sort of
21374 debugging information might be included in the section.
21376 @value{GDBN} has support for this extension. If the section exists,
21377 then it is used provided that no other source of debugging information
21378 can be found, and that @value{GDBN} was configured with LZMA support.
21380 This section can be easily created using @command{objcopy} and other
21381 standard utilities:
21384 # Extract the dynamic symbols from the main binary, there is no need
21385 # to also have these in the normal symbol table.
21386 nm -D @var{binary} --format=posix --defined-only \
21387 | awk '@{ print $1 @}' | sort > dynsyms
21389 # Extract all the text (i.e. function) symbols from the debuginfo.
21390 # (Note that we actually also accept "D" symbols, for the benefit
21391 # of platforms like PowerPC64 that use function descriptors.)
21392 nm @var{binary} --format=posix --defined-only \
21393 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
21396 # Keep all the function symbols not already in the dynamic symbol
21398 comm -13 dynsyms funcsyms > keep_symbols
21400 # Separate full debug info into debug binary.
21401 objcopy --only-keep-debug @var{binary} debug
21403 # Copy the full debuginfo, keeping only a minimal set of symbols and
21404 # removing some unnecessary sections.
21405 objcopy -S --remove-section .gdb_index --remove-section .comment \
21406 --keep-symbols=keep_symbols debug mini_debuginfo
21408 # Drop the full debug info from the original binary.
21409 strip --strip-all -R .comment @var{binary}
21411 # Inject the compressed data into the .gnu_debugdata section of the
21414 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
21418 @section Index Files Speed Up @value{GDBN}
21419 @cindex index files
21420 @cindex @samp{.gdb_index} section
21422 When @value{GDBN} finds a symbol file, it scans the symbols in the
21423 file in order to construct an internal symbol table. This lets most
21424 @value{GDBN} operations work quickly---at the cost of a delay early
21425 on. For large programs, this delay can be quite lengthy, so
21426 @value{GDBN} provides a way to build an index, which speeds up
21429 For convenience, @value{GDBN} comes with a program,
21430 @command{gdb-add-index}, which can be used to add the index to a
21431 symbol file. It takes the symbol file as its only argument:
21434 $ gdb-add-index symfile
21437 @xref{gdb-add-index}.
21439 It is also possible to do the work manually. Here is what
21440 @command{gdb-add-index} does behind the curtains.
21442 The index is stored as a section in the symbol file. @value{GDBN} can
21443 write the index to a file, then you can put it into the symbol file
21444 using @command{objcopy}.
21446 To create an index file, use the @code{save gdb-index} command:
21449 @item save gdb-index [-dwarf-5] @var{directory}
21450 @kindex save gdb-index
21451 Create index files for all symbol files currently known by
21452 @value{GDBN}. For each known @var{symbol-file}, this command by
21453 default creates it produces a single file
21454 @file{@var{symbol-file}.gdb-index}. If you invoke this command with
21455 the @option{-dwarf-5} option, it produces 2 files:
21456 @file{@var{symbol-file}.debug_names} and
21457 @file{@var{symbol-file}.debug_str}. The files are created in the
21458 given @var{directory}.
21461 Once you have created an index file you can merge it into your symbol
21462 file, here named @file{symfile}, using @command{objcopy}:
21465 $ objcopy --add-section .gdb_index=symfile.gdb-index \
21466 --set-section-flags .gdb_index=readonly symfile symfile
21469 Or for @code{-dwarf-5}:
21472 $ objcopy --dump-section .debug_str=symfile.debug_str.new symfile
21473 $ cat symfile.debug_str >>symfile.debug_str.new
21474 $ objcopy --add-section .debug_names=symfile.gdb-index \
21475 --set-section-flags .debug_names=readonly \
21476 --update-section .debug_str=symfile.debug_str.new symfile symfile
21479 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
21480 sections that have been deprecated. Usually they are deprecated because
21481 they are missing a new feature or have performance issues.
21482 To tell @value{GDBN} to use a deprecated index section anyway
21483 specify @code{set use-deprecated-index-sections on}.
21484 The default is @code{off}.
21485 This can speed up startup, but may result in some functionality being lost.
21486 @xref{Index Section Format}.
21488 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
21489 must be done before gdb reads the file. The following will not work:
21492 $ gdb -ex "set use-deprecated-index-sections on" <program>
21495 Instead you must do, for example,
21498 $ gdb -iex "set use-deprecated-index-sections on" <program>
21501 Indices only work when using DWARF debugging information, not stabs.
21503 @subsection Automatic symbol index cache
21505 @cindex automatic symbol index cache
21506 It is possible for @value{GDBN} to automatically save a copy of this index in a
21507 cache on disk and retrieve it from there when loading the same binary in the
21508 future. This feature can be turned on with @kbd{set index-cache on}. The
21509 following commands can be used to tweak the behavior of the index cache.
21513 @kindex set index-cache
21514 @item set index-cache on
21515 @itemx set index-cache off
21516 Enable or disable the use of the symbol index cache.
21518 @item set index-cache directory @var{directory}
21519 @kindex show index-cache
21520 @itemx show index-cache directory
21521 Set/show the directory where index files will be saved.
21523 The default value for this directory depends on the host platform. On
21524 most systems, the index is cached in the @file{gdb} subdirectory of
21525 the directory pointed to by the @env{XDG_CACHE_HOME} environment
21526 variable, if it is defined, else in the @file{.cache/gdb} subdirectory
21527 of your home directory. However, on some systems, the default may
21528 differ according to local convention.
21530 There is no limit on the disk space used by index cache. It is perfectly safe
21531 to delete the content of that directory to free up disk space.
21533 @item show index-cache stats
21534 Print the number of cache hits and misses since the launch of @value{GDBN}.
21538 @node Symbol Errors
21539 @section Errors Reading Symbol Files
21541 While reading a symbol file, @value{GDBN} occasionally encounters problems,
21542 such as symbol types it does not recognize, or known bugs in compiler
21543 output. By default, @value{GDBN} does not notify you of such problems, since
21544 they are relatively common and primarily of interest to people
21545 debugging compilers. If you are interested in seeing information
21546 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
21547 only one message about each such type of problem, no matter how many
21548 times the problem occurs; or you can ask @value{GDBN} to print more messages,
21549 to see how many times the problems occur, with the @code{set
21550 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
21553 The messages currently printed, and their meanings, include:
21556 @item inner block not inside outer block in @var{symbol}
21558 The symbol information shows where symbol scopes begin and end
21559 (such as at the start of a function or a block of statements). This
21560 error indicates that an inner scope block is not fully contained
21561 in its outer scope blocks.
21563 @value{GDBN} circumvents the problem by treating the inner block as if it had
21564 the same scope as the outer block. In the error message, @var{symbol}
21565 may be shown as ``@code{(don't know)}'' if the outer block is not a
21568 @item block at @var{address} out of order
21570 The symbol information for symbol scope blocks should occur in
21571 order of increasing addresses. This error indicates that it does not
21574 @value{GDBN} does not circumvent this problem, and has trouble
21575 locating symbols in the source file whose symbols it is reading. (You
21576 can often determine what source file is affected by specifying
21577 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
21580 @item bad block start address patched
21582 The symbol information for a symbol scope block has a start address
21583 smaller than the address of the preceding source line. This is known
21584 to occur in the SunOS 4.1.1 (and earlier) C compiler.
21586 @value{GDBN} circumvents the problem by treating the symbol scope block as
21587 starting on the previous source line.
21589 @item bad string table offset in symbol @var{n}
21592 Symbol number @var{n} contains a pointer into the string table which is
21593 larger than the size of the string table.
21595 @value{GDBN} circumvents the problem by considering the symbol to have the
21596 name @code{foo}, which may cause other problems if many symbols end up
21599 @item unknown symbol type @code{0x@var{nn}}
21601 The symbol information contains new data types that @value{GDBN} does
21602 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
21603 uncomprehended information, in hexadecimal.
21605 @value{GDBN} circumvents the error by ignoring this symbol information.
21606 This usually allows you to debug your program, though certain symbols
21607 are not accessible. If you encounter such a problem and feel like
21608 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
21609 on @code{complain}, then go up to the function @code{read_dbx_symtab}
21610 and examine @code{*bufp} to see the symbol.
21612 @item stub type has NULL name
21614 @value{GDBN} could not find the full definition for a struct or class.
21616 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
21617 The symbol information for a C@t{++} member function is missing some
21618 information that recent versions of the compiler should have output for
21621 @item info mismatch between compiler and debugger
21623 @value{GDBN} could not parse a type specification output by the compiler.
21628 @section GDB Data Files
21630 @cindex prefix for data files
21631 @value{GDBN} will sometimes read an auxiliary data file. These files
21632 are kept in a directory known as the @dfn{data directory}.
21634 You can set the data directory's name, and view the name @value{GDBN}
21635 is currently using.
21638 @kindex set data-directory
21639 @item set data-directory @var{directory}
21640 Set the directory which @value{GDBN} searches for auxiliary data files
21641 to @var{directory}.
21643 @kindex show data-directory
21644 @item show data-directory
21645 Show the directory @value{GDBN} searches for auxiliary data files.
21648 @cindex default data directory
21649 @cindex @samp{--with-gdb-datadir}
21650 You can set the default data directory by using the configure-time
21651 @samp{--with-gdb-datadir} option. If the data directory is inside
21652 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
21653 @samp{--exec-prefix}), then the default data directory will be updated
21654 automatically if the installed @value{GDBN} is moved to a new
21657 The data directory may also be specified with the
21658 @code{--data-directory} command line option.
21659 @xref{Mode Options}.
21662 @chapter Specifying a Debugging Target
21664 @cindex debugging target
21665 A @dfn{target} is the execution environment occupied by your program.
21667 Often, @value{GDBN} runs in the same host environment as your program;
21668 in that case, the debugging target is specified as a side effect when
21669 you use the @code{file} or @code{core} commands. When you need more
21670 flexibility---for example, running @value{GDBN} on a physically separate
21671 host, or controlling a standalone system over a serial port or a
21672 realtime system over a TCP/IP connection---you can use the @code{target}
21673 command to specify one of the target types configured for @value{GDBN}
21674 (@pxref{Target Commands, ,Commands for Managing Targets}).
21676 @cindex target architecture
21677 It is possible to build @value{GDBN} for several different @dfn{target
21678 architectures}. When @value{GDBN} is built like that, you can choose
21679 one of the available architectures with the @kbd{set architecture}
21683 @kindex set architecture
21684 @kindex show architecture
21685 @item set architecture @var{arch}
21686 This command sets the current target architecture to @var{arch}. The
21687 value of @var{arch} can be @code{"auto"}, in addition to one of the
21688 supported architectures.
21690 @item show architecture
21691 Show the current target architecture.
21693 @item set processor
21695 @kindex set processor
21696 @kindex show processor
21697 These are alias commands for, respectively, @code{set architecture}
21698 and @code{show architecture}.
21702 * Active Targets:: Active targets
21703 * Target Commands:: Commands for managing targets
21704 * Byte Order:: Choosing target byte order
21707 @node Active Targets
21708 @section Active Targets
21710 @cindex stacking targets
21711 @cindex active targets
21712 @cindex multiple targets
21714 There are multiple classes of targets such as: processes, executable files or
21715 recording sessions. Core files belong to the process class, making core file
21716 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
21717 on multiple active targets, one in each class. This allows you to (for
21718 example) start a process and inspect its activity, while still having access to
21719 the executable file after the process finishes. Or if you start process
21720 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
21721 presented a virtual layer of the recording target, while the process target
21722 remains stopped at the chronologically last point of the process execution.
21724 Use the @code{core-file} and @code{exec-file} commands to select a new core
21725 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
21726 specify as a target a process that is already running, use the @code{attach}
21727 command (@pxref{Attach, ,Debugging an Already-running Process}).
21729 @node Target Commands
21730 @section Commands for Managing Targets
21733 @item target @var{type} @var{parameters}
21734 Connects the @value{GDBN} host environment to a target machine or
21735 process. A target is typically a protocol for talking to debugging
21736 facilities. You use the argument @var{type} to specify the type or
21737 protocol of the target machine.
21739 Further @var{parameters} are interpreted by the target protocol, but
21740 typically include things like device names or host names to connect
21741 with, process numbers, and baud rates.
21743 The @code{target} command does not repeat if you press @key{RET} again
21744 after executing the command.
21746 @kindex help target
21748 Displays the names of all targets available. To display targets
21749 currently selected, use either @code{info target} or @code{info files}
21750 (@pxref{Files, ,Commands to Specify Files}).
21752 @item help target @var{name}
21753 Describe a particular target, including any parameters necessary to
21756 @kindex set gnutarget
21757 @item set gnutarget @var{args}
21758 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
21759 knows whether it is reading an @dfn{executable},
21760 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
21761 with the @code{set gnutarget} command. Unlike most @code{target} commands,
21762 with @code{gnutarget} the @code{target} refers to a program, not a machine.
21765 @emph{Warning:} To specify a file format with @code{set gnutarget},
21766 you must know the actual BFD name.
21770 @xref{Files, , Commands to Specify Files}.
21772 @kindex show gnutarget
21773 @item show gnutarget
21774 Use the @code{show gnutarget} command to display what file format
21775 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
21776 @value{GDBN} will determine the file format for each file automatically,
21777 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
21780 @cindex common targets
21781 Here are some common targets (available, or not, depending on the GDB
21786 @item target exec @var{program}
21787 @cindex executable file target
21788 An executable file. @samp{target exec @var{program}} is the same as
21789 @samp{exec-file @var{program}}.
21791 @item target core @var{filename}
21792 @cindex core dump file target
21793 A core dump file. @samp{target core @var{filename}} is the same as
21794 @samp{core-file @var{filename}}.
21796 @item target remote @var{medium}
21797 @cindex remote target
21798 A remote system connected to @value{GDBN} via a serial line or network
21799 connection. This command tells @value{GDBN} to use its own remote
21800 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
21802 For example, if you have a board connected to @file{/dev/ttya} on the
21803 machine running @value{GDBN}, you could say:
21806 target remote /dev/ttya
21809 @code{target remote} supports the @code{load} command. This is only
21810 useful if you have some other way of getting the stub to the target
21811 system, and you can put it somewhere in memory where it won't get
21812 clobbered by the download.
21814 @item target sim @r{[}@var{simargs}@r{]} @dots{}
21815 @cindex built-in simulator target
21816 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
21824 works; however, you cannot assume that a specific memory map, device
21825 drivers, or even basic I/O is available, although some simulators do
21826 provide these. For info about any processor-specific simulator details,
21827 see the appropriate section in @ref{Embedded Processors, ,Embedded
21830 @item target native
21831 @cindex native target
21832 Setup for local/native process debugging. Useful to make the
21833 @code{run} command spawn native processes (likewise @code{attach},
21834 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
21835 (@pxref{set auto-connect-native-target}).
21839 Different targets are available on different configurations of @value{GDBN};
21840 your configuration may have more or fewer targets.
21842 Many remote targets require you to download the executable's code once
21843 you've successfully established a connection. You may wish to control
21844 various aspects of this process.
21849 @kindex set hash@r{, for remote monitors}
21850 @cindex hash mark while downloading
21851 This command controls whether a hash mark @samp{#} is displayed while
21852 downloading a file to the remote monitor. If on, a hash mark is
21853 displayed after each S-record is successfully downloaded to the
21857 @kindex show hash@r{, for remote monitors}
21858 Show the current status of displaying the hash mark.
21860 @item set debug monitor
21861 @kindex set debug monitor
21862 @cindex display remote monitor communications
21863 Enable or disable display of communications messages between
21864 @value{GDBN} and the remote monitor.
21866 @item show debug monitor
21867 @kindex show debug monitor
21868 Show the current status of displaying communications between
21869 @value{GDBN} and the remote monitor.
21874 @kindex load @var{filename} @var{offset}
21875 @item load @var{filename} @var{offset}
21877 Depending on what remote debugging facilities are configured into
21878 @value{GDBN}, the @code{load} command may be available. Where it exists, it
21879 is meant to make @var{filename} (an executable) available for debugging
21880 on the remote system---by downloading, or dynamic linking, for example.
21881 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
21882 the @code{add-symbol-file} command.
21884 If your @value{GDBN} does not have a @code{load} command, attempting to
21885 execute it gets the error message ``@code{You can't do that when your
21886 target is @dots{}}''
21888 The file is loaded at whatever address is specified in the executable.
21889 For some object file formats, you can specify the load address when you
21890 link the program; for other formats, like a.out, the object file format
21891 specifies a fixed address.
21892 @c FIXME! This would be a good place for an xref to the GNU linker doc.
21894 It is also possible to tell @value{GDBN} to load the executable file at a
21895 specific offset described by the optional argument @var{offset}. When
21896 @var{offset} is provided, @var{filename} must also be provided.
21898 Depending on the remote side capabilities, @value{GDBN} may be able to
21899 load programs into flash memory.
21901 @code{load} does not repeat if you press @key{RET} again after using it.
21906 @kindex flash-erase
21908 @anchor{flash-erase}
21910 Erases all known flash memory regions on the target.
21915 @section Choosing Target Byte Order
21917 @cindex choosing target byte order
21918 @cindex target byte order
21920 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
21921 offer the ability to run either big-endian or little-endian byte
21922 orders. Usually the executable or symbol will include a bit to
21923 designate the endian-ness, and you will not need to worry about
21924 which to use. However, you may still find it useful to adjust
21925 @value{GDBN}'s idea of processor endian-ness manually.
21929 @item set endian big
21930 Instruct @value{GDBN} to assume the target is big-endian.
21932 @item set endian little
21933 Instruct @value{GDBN} to assume the target is little-endian.
21935 @item set endian auto
21936 Instruct @value{GDBN} to use the byte order associated with the
21940 Display @value{GDBN}'s current idea of the target byte order.
21944 If the @code{set endian auto} mode is in effect and no executable has
21945 been selected, then the endianness used is the last one chosen either
21946 by one of the @code{set endian big} and @code{set endian little}
21947 commands or by inferring from the last executable used. If no
21948 endianness has been previously chosen, then the default for this mode
21949 is inferred from the target @value{GDBN} has been built for, and is
21950 @code{little} if the name of the target CPU has an @code{el} suffix
21951 and @code{big} otherwise.
21953 Note that these commands merely adjust interpretation of symbolic
21954 data on the host, and that they have absolutely no effect on the
21958 @node Remote Debugging
21959 @chapter Debugging Remote Programs
21960 @cindex remote debugging
21962 If you are trying to debug a program running on a machine that cannot run
21963 @value{GDBN} in the usual way, it is often useful to use remote debugging.
21964 For example, you might use remote debugging on an operating system kernel,
21965 or on a small system which does not have a general purpose operating system
21966 powerful enough to run a full-featured debugger.
21968 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
21969 to make this work with particular debugging targets. In addition,
21970 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
21971 but not specific to any particular target system) which you can use if you
21972 write the remote stubs---the code that runs on the remote system to
21973 communicate with @value{GDBN}.
21975 Other remote targets may be available in your
21976 configuration of @value{GDBN}; use @code{help target} to list them.
21979 * Connecting:: Connecting to a remote target
21980 * File Transfer:: Sending files to a remote system
21981 * Server:: Using the gdbserver program
21982 * Remote Configuration:: Remote configuration
21983 * Remote Stub:: Implementing a remote stub
21987 @section Connecting to a Remote Target
21988 @cindex remote debugging, connecting
21989 @cindex @code{gdbserver}, connecting
21990 @cindex remote debugging, types of connections
21991 @cindex @code{gdbserver}, types of connections
21992 @cindex @code{gdbserver}, @code{target remote} mode
21993 @cindex @code{gdbserver}, @code{target extended-remote} mode
21995 This section describes how to connect to a remote target, including the
21996 types of connections and their differences, how to set up executable and
21997 symbol files on the host and target, and the commands used for
21998 connecting to and disconnecting from the remote target.
22000 @subsection Types of Remote Connections
22002 @value{GDBN} supports two types of remote connections, @code{target remote}
22003 mode and @code{target extended-remote} mode. Note that many remote targets
22004 support only @code{target remote} mode. There are several major
22005 differences between the two types of connections, enumerated here:
22009 @cindex remote debugging, detach and program exit
22010 @item Result of detach or program exit
22011 @strong{With target remote mode:} When the debugged program exits or you
22012 detach from it, @value{GDBN} disconnects from the target. When using
22013 @code{gdbserver}, @code{gdbserver} will exit.
22015 @strong{With target extended-remote mode:} When the debugged program exits or
22016 you detach from it, @value{GDBN} remains connected to the target, even
22017 though no program is running. You can rerun the program, attach to a
22018 running program, or use @code{monitor} commands specific to the target.
22020 When using @code{gdbserver} in this case, it does not exit unless it was
22021 invoked using the @option{--once} option. If the @option{--once} option
22022 was not used, you can ask @code{gdbserver} to exit using the
22023 @code{monitor exit} command (@pxref{Monitor Commands for gdbserver}).
22025 @item Specifying the program to debug
22026 For both connection types you use the @code{file} command to specify the
22027 program on the host system. If you are using @code{gdbserver} there are
22028 some differences in how to specify the location of the program on the
22031 @strong{With target remote mode:} You must either specify the program to debug
22032 on the @code{gdbserver} command line or use the @option{--attach} option
22033 (@pxref{Attaching to a program,,Attaching to a Running Program}).
22035 @cindex @option{--multi}, @code{gdbserver} option
22036 @strong{With target extended-remote mode:} You may specify the program to debug
22037 on the @code{gdbserver} command line, or you can load the program or attach
22038 to it using @value{GDBN} commands after connecting to @code{gdbserver}.
22040 @anchor{--multi Option in Types of Remote Connnections}
22041 You can start @code{gdbserver} without supplying an initial command to run
22042 or process ID to attach. To do this, use the @option{--multi} command line
22043 option. Then you can connect using @code{target extended-remote} and start
22044 the program you want to debug (see below for details on using the
22045 @code{run} command in this scenario). Note that the conditions under which
22046 @code{gdbserver} terminates depend on how @value{GDBN} connects to it
22047 (@code{target remote} or @code{target extended-remote}). The
22048 @option{--multi} option to @code{gdbserver} has no influence on that.
22050 @item The @code{run} command
22051 @strong{With target remote mode:} The @code{run} command is not
22052 supported. Once a connection has been established, you can use all
22053 the usual @value{GDBN} commands to examine and change data. The
22054 remote program is already running, so you can use commands like
22055 @kbd{step} and @kbd{continue}.
22057 @strong{With target extended-remote mode:} The @code{run} command is
22058 supported. The @code{run} command uses the value set by
22059 @code{set remote exec-file} (@pxref{set remote exec-file}) to select
22060 the program to run. Command line arguments are supported, except for
22061 wildcard expansion and I/O redirection (@pxref{Arguments}).
22063 If you specify the program to debug on the command line, then the
22064 @code{run} command is not required to start execution, and you can
22065 resume using commands like @kbd{step} and @kbd{continue} as with
22066 @code{target remote} mode.
22068 @anchor{Attaching in Types of Remote Connections}
22070 @strong{With target remote mode:} The @value{GDBN} command @code{attach} is
22071 not supported. To attach to a running program using @code{gdbserver}, you
22072 must use the @option{--attach} option (@pxref{Running gdbserver}).
22074 @strong{With target extended-remote mode:} To attach to a running program,
22075 you may use the @code{attach} command after the connection has been
22076 established. If you are using @code{gdbserver}, you may also invoke
22077 @code{gdbserver} using the @option{--attach} option
22078 (@pxref{Running gdbserver}).
22080 Some remote targets allow @value{GDBN} to determine the executable file running
22081 in the process the debugger is attaching to. In such a case, @value{GDBN}
22082 uses the value of @code{exec-file-mismatch} to handle a possible mismatch
22083 between the executable file name running in the process and the name of the
22084 current exec-file loaded by @value{GDBN} (@pxref{set exec-file-mismatch}).
22088 @anchor{Host and target files}
22089 @subsection Host and Target Files
22090 @cindex remote debugging, symbol files
22091 @cindex symbol files, remote debugging
22093 @value{GDBN}, running on the host, needs access to symbol and debugging
22094 information for your program running on the target. This requires
22095 access to an unstripped copy of your program, and possibly any associated
22096 symbol files. Note that this section applies equally to both @code{target
22097 remote} mode and @code{target extended-remote} mode.
22099 Some remote targets (@pxref{qXfer executable filename read}, and
22100 @pxref{Host I/O Packets}) allow @value{GDBN} to access program files over
22101 the same connection used to communicate with @value{GDBN}. With such a
22102 target, if the remote program is unstripped, the only command you need is
22103 @code{target remote} (or @code{target extended-remote}).
22105 If the remote program is stripped, or the target does not support remote
22106 program file access, start up @value{GDBN} using the name of the local
22107 unstripped copy of your program as the first argument, or use the
22108 @code{file} command. Use @code{set sysroot} to specify the location (on
22109 the host) of target libraries (unless your @value{GDBN} was compiled with
22110 the correct sysroot using @code{--with-sysroot}). Alternatively, you
22111 may use @code{set solib-search-path} to specify how @value{GDBN} locates
22114 The symbol file and target libraries must exactly match the executable
22115 and libraries on the target, with one exception: the files on the host
22116 system should not be stripped, even if the files on the target system
22117 are. Mismatched or missing files will lead to confusing results
22118 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
22119 files may also prevent @code{gdbserver} from debugging multi-threaded
22122 @subsection Remote Connection Commands
22123 @cindex remote connection commands
22124 @value{GDBN} can communicate with the target over a serial line, a
22125 local Unix domain socket, or
22126 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
22127 each case, @value{GDBN} uses the same protocol for debugging your
22128 program; only the medium carrying the debugging packets varies. The
22129 @code{target remote} and @code{target extended-remote} commands
22130 establish a connection to the target. Both commands accept the same
22131 arguments, which indicate the medium to use:
22135 @item target remote @var{serial-device}
22136 @itemx target extended-remote @var{serial-device}
22137 @cindex serial line, @code{target remote}
22138 Use @var{serial-device} to communicate with the target. For example,
22139 to use a serial line connected to the device named @file{/dev/ttyb}:
22142 target remote /dev/ttyb
22145 If you're using a serial line, you may want to give @value{GDBN} the
22146 @samp{--baud} option, or use the @code{set serial baud} command
22147 (@pxref{Remote Configuration, set serial baud}) before the
22148 @code{target} command.
22150 @item target remote @var{local-socket}
22151 @itemx target extended-remote @var{local-socket}
22152 @cindex local socket, @code{target remote}
22153 @cindex Unix domain socket
22154 Use @var{local-socket} to communicate with the target. For example,
22155 to use a local Unix domain socket bound to the file system entry @file{/tmp/gdb-socket0}:
22158 target remote /tmp/gdb-socket0
22161 Note that this command has the same form as the command to connect
22162 to a serial line. @value{GDBN} will automatically determine which
22163 kind of file you have specified and will make the appropriate kind
22165 This feature is not available if the host system does not support
22166 Unix domain sockets.
22168 @item target remote @code{@var{host}:@var{port}}
22169 @itemx target remote @code{[@var{host}]:@var{port}}
22170 @itemx target remote @code{tcp:@var{host}:@var{port}}
22171 @itemx target remote @code{tcp:[@var{host}]:@var{port}}
22172 @itemx target remote @code{tcp4:@var{host}:@var{port}}
22173 @itemx target remote @code{tcp6:@var{host}:@var{port}}
22174 @itemx target remote @code{tcp6:[@var{host}]:@var{port}}
22175 @itemx target extended-remote @code{@var{host}:@var{port}}
22176 @itemx target extended-remote @code{[@var{host}]:@var{port}}
22177 @itemx target extended-remote @code{tcp:@var{host}:@var{port}}
22178 @itemx target extended-remote @code{tcp:[@var{host}]:@var{port}}
22179 @itemx target extended-remote @code{tcp4:@var{host}:@var{port}}
22180 @itemx target extended-remote @code{tcp6:@var{host}:@var{port}}
22181 @itemx target extended-remote @code{tcp6:[@var{host}]:@var{port}}
22182 @cindex @acronym{TCP} port, @code{target remote}
22183 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
22184 The @var{host} may be either a host name, a numeric @acronym{IPv4}
22185 address, or a numeric @acronym{IPv6} address (with or without the
22186 square brackets to separate the address from the port); @var{port}
22187 must be a decimal number. The @var{host} could be the target machine
22188 itself, if it is directly connected to the net, or it might be a
22189 terminal server which in turn has a serial line to the target.
22191 For example, to connect to port 2828 on a terminal server named
22195 target remote manyfarms:2828
22198 To connect to port 2828 on a terminal server whose address is
22199 @code{2001:0db8:85a3:0000:0000:8a2e:0370:7334}, you can either use the
22200 square bracket syntax:
22203 target remote [2001:0db8:85a3:0000:0000:8a2e:0370:7334]:2828
22207 or explicitly specify the @acronym{IPv6} protocol:
22210 target remote tcp6:2001:0db8:85a3:0000:0000:8a2e:0370:7334:2828
22213 This last example may be confusing to the reader, because there is no
22214 visible separation between the hostname and the port number.
22215 Therefore, we recommend the user to provide @acronym{IPv6} addresses
22216 using square brackets for clarity. However, it is important to
22217 mention that for @value{GDBN} there is no ambiguity: the number after
22218 the last colon is considered to be the port number.
22220 If your remote target is actually running on the same machine as your
22221 debugger session (e.g.@: a simulator for your target running on the
22222 same host), you can omit the hostname. For example, to connect to
22223 port 1234 on your local machine:
22226 target remote :1234
22230 Note that the colon is still required here.
22232 @item target remote @code{udp:@var{host}:@var{port}}
22233 @itemx target remote @code{udp:[@var{host}]:@var{port}}
22234 @itemx target remote @code{udp4:@var{host}:@var{port}}
22235 @itemx target remote @code{udp6:[@var{host}]:@var{port}}
22236 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
22237 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
22238 @itemx target extended-remote @code{udp:[@var{host}]:@var{port}}
22239 @itemx target extended-remote @code{udp4:@var{host}:@var{port}}
22240 @itemx target extended-remote @code{udp6:@var{host}:@var{port}}
22241 @itemx target extended-remote @code{udp6:[@var{host}]:@var{port}}
22242 @cindex @acronym{UDP} port, @code{target remote}
22243 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
22244 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
22247 target remote udp:manyfarms:2828
22250 When using a @acronym{UDP} connection for remote debugging, you should
22251 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
22252 can silently drop packets on busy or unreliable networks, which will
22253 cause havoc with your debugging session.
22255 @item target remote | @var{command}
22256 @itemx target extended-remote | @var{command}
22257 @cindex pipe, @code{target remote} to
22258 Run @var{command} in the background and communicate with it using a
22259 pipe. The @var{command} is a shell command, to be parsed and expanded
22260 by the system's command shell, @code{/bin/sh}; it should expect remote
22261 protocol packets on its standard input, and send replies on its
22262 standard output. You could use this to run a stand-alone simulator
22263 that speaks the remote debugging protocol, to make net connections
22264 using programs like @code{ssh}, or for other similar tricks.
22266 If @var{command} closes its standard output (perhaps by exiting),
22267 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
22268 program has already exited, this will have no effect.)
22272 @cindex interrupting remote programs
22273 @cindex remote programs, interrupting
22274 Whenever @value{GDBN} is waiting for the remote program, if you type the
22275 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
22276 program. This may or may not succeed, depending in part on the hardware
22277 and the serial drivers the remote system uses. If you type the
22278 interrupt character once again, @value{GDBN} displays this prompt:
22281 Interrupted while waiting for the program.
22282 Give up (and stop debugging it)? (y or n)
22285 In @code{target remote} mode, if you type @kbd{y}, @value{GDBN} abandons
22286 the remote debugging session. (If you decide you want to try again later,
22287 you can use @kbd{target remote} again to connect once more.) If you type
22288 @kbd{n}, @value{GDBN} goes back to waiting.
22290 In @code{target extended-remote} mode, typing @kbd{n} will leave
22291 @value{GDBN} connected to the target.
22294 @kindex detach (remote)
22296 When you have finished debugging the remote program, you can use the
22297 @code{detach} command to release it from @value{GDBN} control.
22298 Detaching from the target normally resumes its execution, but the results
22299 will depend on your particular remote stub. After the @code{detach}
22300 command in @code{target remote} mode, @value{GDBN} is free to connect to
22301 another target. In @code{target extended-remote} mode, @value{GDBN} is
22302 still connected to the target.
22306 The @code{disconnect} command closes the connection to the target, and
22307 the target is generally not resumed. It will wait for @value{GDBN}
22308 (this instance or another one) to connect and continue debugging. After
22309 the @code{disconnect} command, @value{GDBN} is again free to connect to
22312 @cindex send command to remote monitor
22313 @cindex extend @value{GDBN} for remote targets
22314 @cindex add new commands for external monitor
22316 @item monitor @var{cmd}
22317 This command allows you to send arbitrary commands directly to the
22318 remote monitor. Since @value{GDBN} doesn't care about the commands it
22319 sends like this, this command is the way to extend @value{GDBN}---you
22320 can add new commands that only the external monitor will understand
22324 @node File Transfer
22325 @section Sending files to a remote system
22326 @cindex remote target, file transfer
22327 @cindex file transfer
22328 @cindex sending files to remote systems
22330 Some remote targets offer the ability to transfer files over the same
22331 connection used to communicate with @value{GDBN}. This is convenient
22332 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
22333 running @code{gdbserver} over a network interface. For other targets,
22334 e.g.@: embedded devices with only a single serial port, this may be
22335 the only way to upload or download files.
22337 Not all remote targets support these commands.
22341 @item remote put @var{hostfile} @var{targetfile}
22342 Copy file @var{hostfile} from the host system (the machine running
22343 @value{GDBN}) to @var{targetfile} on the target system.
22346 @item remote get @var{targetfile} @var{hostfile}
22347 Copy file @var{targetfile} from the target system to @var{hostfile}
22348 on the host system.
22350 @kindex remote delete
22351 @item remote delete @var{targetfile}
22352 Delete @var{targetfile} from the target system.
22357 @section Using the @code{gdbserver} Program
22360 @cindex remote connection without stubs
22361 @code{gdbserver} is a control program for Unix-like systems, which
22362 allows you to connect your program with a remote @value{GDBN} via
22363 @code{target remote} or @code{target extended-remote}---but without
22364 linking in the usual debugging stub.
22366 @code{gdbserver} is not a complete replacement for the debugging stubs,
22367 because it requires essentially the same operating-system facilities
22368 that @value{GDBN} itself does. In fact, a system that can run
22369 @code{gdbserver} to connect to a remote @value{GDBN} could also run
22370 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
22371 because it is a much smaller program than @value{GDBN} itself. It is
22372 also easier to port than all of @value{GDBN}, so you may be able to get
22373 started more quickly on a new system by using @code{gdbserver}.
22374 Finally, if you develop code for real-time systems, you may find that
22375 the tradeoffs involved in real-time operation make it more convenient to
22376 do as much development work as possible on another system, for example
22377 by cross-compiling. You can use @code{gdbserver} to make a similar
22378 choice for debugging.
22380 @value{GDBN} and @code{gdbserver} communicate via either a serial line
22381 or a TCP connection, using the standard @value{GDBN} remote serial
22385 @emph{Warning:} @code{gdbserver} does not have any built-in security.
22386 Do not run @code{gdbserver} connected to any public network; a
22387 @value{GDBN} connection to @code{gdbserver} provides access to the
22388 target system with the same privileges as the user running
22392 @anchor{Running gdbserver}
22393 @subsection Running @code{gdbserver}
22394 @cindex arguments, to @code{gdbserver}
22395 @cindex @code{gdbserver}, command-line arguments
22397 Run @code{gdbserver} on the target system. You need a copy of the
22398 program you want to debug, including any libraries it requires.
22399 @code{gdbserver} does not need your program's symbol table, so you can
22400 strip the program if necessary to save space. @value{GDBN} on the host
22401 system does all the symbol handling.
22403 To use the server, you must tell it how to communicate with @value{GDBN};
22404 the name of your program; and the arguments for your program. The usual
22408 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
22411 @var{comm} is either a device name (to use a serial line), or a TCP
22412 hostname and portnumber, or @code{-} or @code{stdio} to use
22413 stdin/stdout of @code{gdbserver}.
22414 For example, to debug Emacs with the argument
22415 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
22419 target> gdbserver /dev/com1 emacs foo.txt
22422 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
22425 To use a TCP connection instead of a serial line:
22428 target> gdbserver host:2345 emacs foo.txt
22431 The only difference from the previous example is the first argument,
22432 specifying that you are communicating with the host @value{GDBN} via
22433 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
22434 expect a TCP connection from machine @samp{host} to local TCP port 2345.
22435 (Currently, the @samp{host} part is ignored.) You can choose any number
22436 you want for the port number as long as it does not conflict with any
22437 TCP ports already in use on the target system (for example, @code{23} is
22438 reserved for @code{telnet}).@footnote{If you choose a port number that
22439 conflicts with another service, @code{gdbserver} prints an error message
22440 and exits.} You must use the same port number with the host @value{GDBN}
22441 @code{target remote} command.
22443 The @code{stdio} connection is useful when starting @code{gdbserver}
22447 (gdb) target remote | ssh -T hostname gdbserver - hello
22450 The @samp{-T} option to ssh is provided because we don't need a remote pty,
22451 and we don't want escape-character handling. Ssh does this by default when
22452 a command is provided, the flag is provided to make it explicit.
22453 You could elide it if you want to.
22455 Programs started with stdio-connected gdbserver have @file{/dev/null} for
22456 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
22457 display through a pipe connected to gdbserver.
22458 Both @code{stdout} and @code{stderr} use the same pipe.
22460 @anchor{Attaching to a program}
22461 @subsubsection Attaching to a Running Program
22462 @cindex attach to a program, @code{gdbserver}
22463 @cindex @option{--attach}, @code{gdbserver} option
22465 On some targets, @code{gdbserver} can also attach to running programs.
22466 This is accomplished via the @code{--attach} argument. The syntax is:
22469 target> gdbserver --attach @var{comm} @var{pid}
22472 @var{pid} is the process ID of a currently running process. It isn't
22473 necessary to point @code{gdbserver} at a binary for the running process.
22475 In @code{target extended-remote} mode, you can also attach using the
22476 @value{GDBN} attach command
22477 (@pxref{Attaching in Types of Remote Connections}).
22480 You can debug processes by name instead of process ID if your target has the
22481 @code{pidof} utility:
22484 target> gdbserver --attach @var{comm} `pidof @var{program}`
22487 In case more than one copy of @var{program} is running, or @var{program}
22488 has multiple threads, most versions of @code{pidof} support the
22489 @code{-s} option to only return the first process ID.
22491 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
22493 This section applies only when @code{gdbserver} is run to listen on a TCP
22496 @code{gdbserver} normally terminates after all of its debugged processes have
22497 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
22498 extended-remote}, @code{gdbserver} stays running even with no processes left.
22499 @value{GDBN} normally terminates the spawned debugged process on its exit,
22500 which normally also terminates @code{gdbserver} in the @kbd{target remote}
22501 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
22502 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
22503 stays running even in the @kbd{target remote} mode.
22505 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
22506 Such reconnecting is useful for features like @ref{disconnected tracing}. For
22507 completeness, at most one @value{GDBN} can be connected at a time.
22509 @cindex @option{--once}, @code{gdbserver} option
22510 By default, @code{gdbserver} keeps the listening TCP port open, so that
22511 subsequent connections are possible. However, if you start @code{gdbserver}
22512 with the @option{--once} option, it will stop listening for any further
22513 connection attempts after connecting to the first @value{GDBN} session. This
22514 means no further connections to @code{gdbserver} will be possible after the
22515 first one. It also means @code{gdbserver} will terminate after the first
22516 connection with remote @value{GDBN} has closed, even for unexpectedly closed
22517 connections and even in the @kbd{target extended-remote} mode. The
22518 @option{--once} option allows reusing the same port number for connecting to
22519 multiple instances of @code{gdbserver} running on the same host, since each
22520 instance closes its port after the first connection.
22522 @anchor{Other Command-Line Arguments for gdbserver}
22523 @subsubsection Other Command-Line Arguments for @code{gdbserver}
22525 You can use the @option{--multi} option to start @code{gdbserver} without
22526 specifying a program to debug or a process to attach to. Then you can
22527 attach in @code{target extended-remote} mode and run or attach to a
22528 program. For more information,
22529 @pxref{--multi Option in Types of Remote Connnections}.
22531 @cindex @option{--debug}, @code{gdbserver} option
22532 The @option{--debug} option tells @code{gdbserver} to display extra
22533 status information about the debugging process.
22534 @cindex @option{--remote-debug}, @code{gdbserver} option
22535 The @option{--remote-debug} option tells @code{gdbserver} to display
22536 remote protocol debug output.
22537 @cindex @option{--debug-file}, @code{gdbserver} option
22538 @cindex @code{gdbserver}, send all debug output to a single file
22539 The @option{--debug-file=@var{filename}} option tells @code{gdbserver} to
22540 write any debug output to the given @var{filename}. These options are intended
22541 for @code{gdbserver} development and for bug reports to the developers.
22543 @cindex @option{--debug-format}, @code{gdbserver} option
22544 The @option{--debug-format=option1[,option2,...]} option tells
22545 @code{gdbserver} to include additional information in each output.
22546 Possible options are:
22550 Turn off all extra information in debugging output.
22552 Turn on all extra information in debugging output.
22554 Include a timestamp in each line of debugging output.
22557 Options are processed in order. Thus, for example, if @option{none}
22558 appears last then no additional information is added to debugging output.
22560 @cindex @option{--wrapper}, @code{gdbserver} option
22561 The @option{--wrapper} option specifies a wrapper to launch programs
22562 for debugging. The option should be followed by the name of the
22563 wrapper, then any command-line arguments to pass to the wrapper, then
22564 @kbd{--} indicating the end of the wrapper arguments.
22566 @code{gdbserver} runs the specified wrapper program with a combined
22567 command line including the wrapper arguments, then the name of the
22568 program to debug, then any arguments to the program. The wrapper
22569 runs until it executes your program, and then @value{GDBN} gains control.
22571 You can use any program that eventually calls @code{execve} with
22572 its arguments as a wrapper. Several standard Unix utilities do
22573 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
22574 with @code{exec "$@@"} will also work.
22576 For example, you can use @code{env} to pass an environment variable to
22577 the debugged program, without setting the variable in @code{gdbserver}'s
22581 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
22584 @cindex @option{--selftest}
22585 The @option{--selftest} option runs the self tests in @code{gdbserver}:
22588 $ gdbserver --selftest
22589 Ran 2 unit tests, 0 failed
22592 These tests are disabled in release.
22593 @subsection Connecting to @code{gdbserver}
22595 The basic procedure for connecting to the remote target is:
22599 Run @value{GDBN} on the host system.
22602 Make sure you have the necessary symbol files
22603 (@pxref{Host and target files}).
22604 Load symbols for your application using the @code{file} command before you
22605 connect. Use @code{set sysroot} to locate target libraries (unless your
22606 @value{GDBN} was compiled with the correct sysroot using
22607 @code{--with-sysroot}).
22610 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
22611 For TCP connections, you must start up @code{gdbserver} prior to using
22612 the @code{target} command. Otherwise you may get an error whose
22613 text depends on the host system, but which usually looks something like
22614 @samp{Connection refused}. Don't use the @code{load}
22615 command in @value{GDBN} when using @code{target remote} mode, since the
22616 program is already on the target.
22620 @anchor{Monitor Commands for gdbserver}
22621 @subsection Monitor Commands for @code{gdbserver}
22622 @cindex monitor commands, for @code{gdbserver}
22624 During a @value{GDBN} session using @code{gdbserver}, you can use the
22625 @code{monitor} command to send special requests to @code{gdbserver}.
22626 Here are the available commands.
22630 List the available monitor commands.
22632 @item monitor set debug 0
22633 @itemx monitor set debug 1
22634 Disable or enable general debugging messages.
22636 @item monitor set remote-debug 0
22637 @itemx monitor set remote-debug 1
22638 Disable or enable specific debugging messages associated with the remote
22639 protocol (@pxref{Remote Protocol}).
22641 @item monitor set debug-file filename
22642 @itemx monitor set debug-file
22643 Send any debug output to the given file, or to stderr.
22645 @item monitor set debug-format option1@r{[},option2,...@r{]}
22646 Specify additional text to add to debugging messages.
22647 Possible options are:
22651 Turn off all extra information in debugging output.
22653 Turn on all extra information in debugging output.
22655 Include a timestamp in each line of debugging output.
22658 Options are processed in order. Thus, for example, if @option{none}
22659 appears last then no additional information is added to debugging output.
22661 @item monitor set libthread-db-search-path [PATH]
22662 @cindex gdbserver, search path for @code{libthread_db}
22663 When this command is issued, @var{path} is a colon-separated list of
22664 directories to search for @code{libthread_db} (@pxref{Threads,,set
22665 libthread-db-search-path}). If you omit @var{path},
22666 @samp{libthread-db-search-path} will be reset to its default value.
22668 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
22669 not supported in @code{gdbserver}.
22672 Tell gdbserver to exit immediately. This command should be followed by
22673 @code{disconnect} to close the debugging session. @code{gdbserver} will
22674 detach from any attached processes and kill any processes it created.
22675 Use @code{monitor exit} to terminate @code{gdbserver} at the end
22676 of a multi-process mode debug session.
22680 @subsection Tracepoints support in @code{gdbserver}
22681 @cindex tracepoints support in @code{gdbserver}
22683 On some targets, @code{gdbserver} supports tracepoints, fast
22684 tracepoints and static tracepoints.
22686 For fast or static tracepoints to work, a special library called the
22687 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
22688 This library is built and distributed as an integral part of
22689 @code{gdbserver}. In addition, support for static tracepoints
22690 requires building the in-process agent library with static tracepoints
22691 support. At present, the UST (LTTng Userspace Tracer,
22692 @url{http://lttng.org/ust}) tracing engine is supported. This support
22693 is automatically available if UST development headers are found in the
22694 standard include path when @code{gdbserver} is built, or if
22695 @code{gdbserver} was explicitly configured using @option{--with-ust}
22696 to point at such headers. You can explicitly disable the support
22697 using @option{--with-ust=no}.
22699 There are several ways to load the in-process agent in your program:
22702 @item Specifying it as dependency at link time
22704 You can link your program dynamically with the in-process agent
22705 library. On most systems, this is accomplished by adding
22706 @code{-linproctrace} to the link command.
22708 @item Using the system's preloading mechanisms
22710 You can force loading the in-process agent at startup time by using
22711 your system's support for preloading shared libraries. Many Unixes
22712 support the concept of preloading user defined libraries. In most
22713 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
22714 in the environment. See also the description of @code{gdbserver}'s
22715 @option{--wrapper} command line option.
22717 @item Using @value{GDBN} to force loading the agent at run time
22719 On some systems, you can force the inferior to load a shared library,
22720 by calling a dynamic loader function in the inferior that takes care
22721 of dynamically looking up and loading a shared library. On most Unix
22722 systems, the function is @code{dlopen}. You'll use the @code{call}
22723 command for that. For example:
22726 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
22729 Note that on most Unix systems, for the @code{dlopen} function to be
22730 available, the program needs to be linked with @code{-ldl}.
22733 On systems that have a userspace dynamic loader, like most Unix
22734 systems, when you connect to @code{gdbserver} using @code{target
22735 remote}, you'll find that the program is stopped at the dynamic
22736 loader's entry point, and no shared library has been loaded in the
22737 program's address space yet, including the in-process agent. In that
22738 case, before being able to use any of the fast or static tracepoints
22739 features, you need to let the loader run and load the shared
22740 libraries. The simplest way to do that is to run the program to the
22741 main procedure. E.g., if debugging a C or C@t{++} program, start
22742 @code{gdbserver} like so:
22745 $ gdbserver :9999 myprogram
22748 Start GDB and connect to @code{gdbserver} like so, and run to main:
22752 (@value{GDBP}) target remote myhost:9999
22753 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
22754 (@value{GDBP}) b main
22755 (@value{GDBP}) continue
22758 The in-process tracing agent library should now be loaded into the
22759 process; you can confirm it with the @code{info sharedlibrary}
22760 command, which will list @file{libinproctrace.so} as loaded in the
22761 process. You are now ready to install fast tracepoints, list static
22762 tracepoint markers, probe static tracepoints markers, and start
22765 @node Remote Configuration
22766 @section Remote Configuration
22769 @kindex show remote
22770 This section documents the configuration options available when
22771 debugging remote programs. For the options related to the File I/O
22772 extensions of the remote protocol, see @ref{system,
22773 system-call-allowed}.
22776 @item set remoteaddresssize @var{bits}
22777 @cindex address size for remote targets
22778 @cindex bits in remote address
22779 Set the maximum size of address in a memory packet to the specified
22780 number of bits. @value{GDBN} will mask off the address bits above
22781 that number, when it passes addresses to the remote target. The
22782 default value is the number of bits in the target's address.
22784 @item show remoteaddresssize
22785 Show the current value of remote address size in bits.
22787 @item set serial baud @var{n}
22788 @cindex baud rate for remote targets
22789 Set the baud rate for the remote serial I/O to @var{n} baud. The
22790 value is used to set the speed of the serial port used for debugging
22793 @item show serial baud
22794 Show the current speed of the remote connection.
22796 @item set serial parity @var{parity}
22797 Set the parity for the remote serial I/O. Supported values of @var{parity} are:
22798 @code{even}, @code{none}, and @code{odd}. The default is @code{none}.
22800 @item show serial parity
22801 Show the current parity of the serial port.
22803 @item set remotebreak
22804 @cindex interrupt remote programs
22805 @cindex BREAK signal instead of Ctrl-C
22806 @anchor{set remotebreak}
22807 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
22808 when you type @kbd{Ctrl-c} to interrupt the program running
22809 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
22810 character instead. The default is off, since most remote systems
22811 expect to see @samp{Ctrl-C} as the interrupt signal.
22813 @item show remotebreak
22814 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
22815 interrupt the remote program.
22817 @item set remoteflow on
22818 @itemx set remoteflow off
22819 @kindex set remoteflow
22820 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
22821 on the serial port used to communicate to the remote target.
22823 @item show remoteflow
22824 @kindex show remoteflow
22825 Show the current setting of hardware flow control.
22827 @item set remotelogbase @var{base}
22828 Set the base (a.k.a.@: radix) of logging serial protocol
22829 communications to @var{base}. Supported values of @var{base} are:
22830 @code{ascii}, @code{octal}, and @code{hex}. The default is
22833 @item show remotelogbase
22834 Show the current setting of the radix for logging remote serial
22837 @item set remotelogfile @var{file}
22838 @cindex record serial communications on file
22839 Record remote serial communications on the named @var{file}. The
22840 default is not to record at all.
22842 @item show remotelogfile
22843 Show the current setting of the file name on which to record the
22844 serial communications.
22846 @item set remotetimeout @var{num}
22847 @cindex timeout for serial communications
22848 @cindex remote timeout
22849 Set the timeout limit to wait for the remote target to respond to
22850 @var{num} seconds. The default is 2 seconds.
22852 @item show remotetimeout
22853 Show the current number of seconds to wait for the remote target
22856 @cindex limit hardware breakpoints and watchpoints
22857 @cindex remote target, limit break- and watchpoints
22858 @anchor{set remote hardware-watchpoint-limit}
22859 @anchor{set remote hardware-breakpoint-limit}
22860 @item set remote hardware-watchpoint-limit @var{limit}
22861 @itemx set remote hardware-breakpoint-limit @var{limit}
22862 Restrict @value{GDBN} to using @var{limit} remote hardware watchpoints
22863 or breakpoints. The @var{limit} can be set to 0 to disable hardware
22864 watchpoints or breakpoints, and @code{unlimited} for unlimited
22865 watchpoints or breakpoints.
22867 @item show remote hardware-watchpoint-limit
22868 @itemx show remote hardware-breakpoint-limit
22869 Show the current limit for the number of hardware watchpoints or
22870 breakpoints that @value{GDBN} can use.
22872 @cindex limit hardware watchpoints length
22873 @cindex remote target, limit watchpoints length
22874 @anchor{set remote hardware-watchpoint-length-limit}
22875 @item set remote hardware-watchpoint-length-limit @var{limit}
22876 Restrict @value{GDBN} to using @var{limit} bytes for the maximum
22877 length of a remote hardware watchpoint. A @var{limit} of 0 disables
22878 hardware watchpoints and @code{unlimited} allows watchpoints of any
22881 @item show remote hardware-watchpoint-length-limit
22882 Show the current limit (in bytes) of the maximum length of
22883 a remote hardware watchpoint.
22885 @item set remote exec-file @var{filename}
22886 @itemx show remote exec-file
22887 @anchor{set remote exec-file}
22888 @cindex executable file, for remote target
22889 Select the file used for @code{run} with @code{target
22890 extended-remote}. This should be set to a filename valid on the
22891 target system. If it is not set, the target will use a default
22892 filename (e.g.@: the last program run).
22894 @item set remote interrupt-sequence
22895 @cindex interrupt remote programs
22896 @cindex select Ctrl-C, BREAK or BREAK-g
22897 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
22898 @samp{BREAK-g} as the
22899 sequence to the remote target in order to interrupt the execution.
22900 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
22901 is high level of serial line for some certain time.
22902 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
22903 It is @code{BREAK} signal followed by character @code{g}.
22905 @item show interrupt-sequence
22906 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
22907 is sent by @value{GDBN} to interrupt the remote program.
22908 @code{BREAK-g} is BREAK signal followed by @code{g} and
22909 also known as Magic SysRq g.
22911 @item set remote interrupt-on-connect
22912 @cindex send interrupt-sequence on start
22913 Specify whether interrupt-sequence is sent to remote target when
22914 @value{GDBN} connects to it. This is mostly needed when you debug
22915 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
22916 which is known as Magic SysRq g in order to connect @value{GDBN}.
22918 @item show interrupt-on-connect
22919 Show whether interrupt-sequence is sent
22920 to remote target when @value{GDBN} connects to it.
22924 @item set tcp auto-retry on
22925 @cindex auto-retry, for remote TCP target
22926 Enable auto-retry for remote TCP connections. This is useful if the remote
22927 debugging agent is launched in parallel with @value{GDBN}; there is a race
22928 condition because the agent may not become ready to accept the connection
22929 before @value{GDBN} attempts to connect. When auto-retry is
22930 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
22931 to establish the connection using the timeout specified by
22932 @code{set tcp connect-timeout}.
22934 @item set tcp auto-retry off
22935 Do not auto-retry failed TCP connections.
22937 @item show tcp auto-retry
22938 Show the current auto-retry setting.
22940 @item set tcp connect-timeout @var{seconds}
22941 @itemx set tcp connect-timeout unlimited
22942 @cindex connection timeout, for remote TCP target
22943 @cindex timeout, for remote target connection
22944 Set the timeout for establishing a TCP connection to the remote target to
22945 @var{seconds}. The timeout affects both polling to retry failed connections
22946 (enabled by @code{set tcp auto-retry on}) and waiting for connections
22947 that are merely slow to complete, and represents an approximate cumulative
22948 value. If @var{seconds} is @code{unlimited}, there is no timeout and
22949 @value{GDBN} will keep attempting to establish a connection forever,
22950 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
22952 @item show tcp connect-timeout
22953 Show the current connection timeout setting.
22956 @cindex remote packets, enabling and disabling
22957 The @value{GDBN} remote protocol autodetects the packets supported by
22958 your debugging stub. If you need to override the autodetection, you
22959 can use these commands to enable or disable individual packets. Each
22960 packet can be set to @samp{on} (the remote target supports this
22961 packet), @samp{off} (the remote target does not support this packet),
22962 or @samp{auto} (detect remote target support for this packet). They
22963 all default to @samp{auto}. For more information about each packet,
22964 see @ref{Remote Protocol}.
22966 During normal use, you should not have to use any of these commands.
22967 If you do, that may be a bug in your remote debugging stub, or a bug
22968 in @value{GDBN}. You may want to report the problem to the
22969 @value{GDBN} developers.
22971 For each packet @var{name}, the command to enable or disable the
22972 packet is @code{set remote @var{name}-packet}. The available settings
22975 @multitable @columnfractions 0.28 0.32 0.25
22978 @tab Related Features
22980 @item @code{fetch-register}
22982 @tab @code{info registers}
22984 @item @code{set-register}
22988 @item @code{binary-download}
22990 @tab @code{load}, @code{set}
22992 @item @code{read-aux-vector}
22993 @tab @code{qXfer:auxv:read}
22994 @tab @code{info auxv}
22996 @item @code{symbol-lookup}
22997 @tab @code{qSymbol}
22998 @tab Detecting multiple threads
23000 @item @code{attach}
23001 @tab @code{vAttach}
23004 @item @code{verbose-resume}
23006 @tab Stepping or resuming multiple threads
23012 @item @code{software-breakpoint}
23016 @item @code{hardware-breakpoint}
23020 @item @code{write-watchpoint}
23024 @item @code{read-watchpoint}
23028 @item @code{access-watchpoint}
23032 @item @code{pid-to-exec-file}
23033 @tab @code{qXfer:exec-file:read}
23034 @tab @code{attach}, @code{run}
23036 @item @code{target-features}
23037 @tab @code{qXfer:features:read}
23038 @tab @code{set architecture}
23040 @item @code{library-info}
23041 @tab @code{qXfer:libraries:read}
23042 @tab @code{info sharedlibrary}
23044 @item @code{memory-map}
23045 @tab @code{qXfer:memory-map:read}
23046 @tab @code{info mem}
23048 @item @code{read-sdata-object}
23049 @tab @code{qXfer:sdata:read}
23050 @tab @code{print $_sdata}
23052 @item @code{read-siginfo-object}
23053 @tab @code{qXfer:siginfo:read}
23054 @tab @code{print $_siginfo}
23056 @item @code{write-siginfo-object}
23057 @tab @code{qXfer:siginfo:write}
23058 @tab @code{set $_siginfo}
23060 @item @code{threads}
23061 @tab @code{qXfer:threads:read}
23062 @tab @code{info threads}
23064 @item @code{get-thread-local-@*storage-address}
23065 @tab @code{qGetTLSAddr}
23066 @tab Displaying @code{__thread} variables
23068 @item @code{get-thread-information-block-address}
23069 @tab @code{qGetTIBAddr}
23070 @tab Display MS-Windows Thread Information Block.
23072 @item @code{search-memory}
23073 @tab @code{qSearch:memory}
23076 @item @code{supported-packets}
23077 @tab @code{qSupported}
23078 @tab Remote communications parameters
23080 @item @code{catch-syscalls}
23081 @tab @code{QCatchSyscalls}
23082 @tab @code{catch syscall}
23084 @item @code{pass-signals}
23085 @tab @code{QPassSignals}
23086 @tab @code{handle @var{signal}}
23088 @item @code{program-signals}
23089 @tab @code{QProgramSignals}
23090 @tab @code{handle @var{signal}}
23092 @item @code{hostio-close-packet}
23093 @tab @code{vFile:close}
23094 @tab @code{remote get}, @code{remote put}
23096 @item @code{hostio-open-packet}
23097 @tab @code{vFile:open}
23098 @tab @code{remote get}, @code{remote put}
23100 @item @code{hostio-pread-packet}
23101 @tab @code{vFile:pread}
23102 @tab @code{remote get}, @code{remote put}
23104 @item @code{hostio-pwrite-packet}
23105 @tab @code{vFile:pwrite}
23106 @tab @code{remote get}, @code{remote put}
23108 @item @code{hostio-unlink-packet}
23109 @tab @code{vFile:unlink}
23110 @tab @code{remote delete}
23112 @item @code{hostio-readlink-packet}
23113 @tab @code{vFile:readlink}
23116 @item @code{hostio-fstat-packet}
23117 @tab @code{vFile:fstat}
23120 @item @code{hostio-setfs-packet}
23121 @tab @code{vFile:setfs}
23124 @item @code{noack-packet}
23125 @tab @code{QStartNoAckMode}
23126 @tab Packet acknowledgment
23128 @item @code{osdata}
23129 @tab @code{qXfer:osdata:read}
23130 @tab @code{info os}
23132 @item @code{query-attached}
23133 @tab @code{qAttached}
23134 @tab Querying remote process attach state.
23136 @item @code{trace-buffer-size}
23137 @tab @code{QTBuffer:size}
23138 @tab @code{set trace-buffer-size}
23140 @item @code{trace-status}
23141 @tab @code{qTStatus}
23142 @tab @code{tstatus}
23144 @item @code{traceframe-info}
23145 @tab @code{qXfer:traceframe-info:read}
23146 @tab Traceframe info
23148 @item @code{install-in-trace}
23149 @tab @code{InstallInTrace}
23150 @tab Install tracepoint in tracing
23152 @item @code{disable-randomization}
23153 @tab @code{QDisableRandomization}
23154 @tab @code{set disable-randomization}
23156 @item @code{startup-with-shell}
23157 @tab @code{QStartupWithShell}
23158 @tab @code{set startup-with-shell}
23160 @item @code{environment-hex-encoded}
23161 @tab @code{QEnvironmentHexEncoded}
23162 @tab @code{set environment}
23164 @item @code{environment-unset}
23165 @tab @code{QEnvironmentUnset}
23166 @tab @code{unset environment}
23168 @item @code{environment-reset}
23169 @tab @code{QEnvironmentReset}
23170 @tab @code{Reset the inferior environment (i.e., unset user-set variables)}
23172 @item @code{set-working-dir}
23173 @tab @code{QSetWorkingDir}
23174 @tab @code{set cwd}
23176 @item @code{conditional-breakpoints-packet}
23177 @tab @code{Z0 and Z1}
23178 @tab @code{Support for target-side breakpoint condition evaluation}
23180 @item @code{multiprocess-extensions}
23181 @tab @code{multiprocess extensions}
23182 @tab Debug multiple processes and remote process PID awareness
23184 @item @code{swbreak-feature}
23185 @tab @code{swbreak stop reason}
23188 @item @code{hwbreak-feature}
23189 @tab @code{hwbreak stop reason}
23192 @item @code{fork-event-feature}
23193 @tab @code{fork stop reason}
23196 @item @code{vfork-event-feature}
23197 @tab @code{vfork stop reason}
23200 @item @code{exec-event-feature}
23201 @tab @code{exec stop reason}
23204 @item @code{thread-events}
23205 @tab @code{QThreadEvents}
23206 @tab Tracking thread lifetime.
23208 @item @code{no-resumed-stop-reply}
23209 @tab @code{no resumed thread left stop reply}
23210 @tab Tracking thread lifetime.
23215 @section Implementing a Remote Stub
23217 @cindex debugging stub, example
23218 @cindex remote stub, example
23219 @cindex stub example, remote debugging
23220 The stub files provided with @value{GDBN} implement the target side of the
23221 communication protocol, and the @value{GDBN} side is implemented in the
23222 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
23223 these subroutines to communicate, and ignore the details. (If you're
23224 implementing your own stub file, you can still ignore the details: start
23225 with one of the existing stub files. @file{sparc-stub.c} is the best
23226 organized, and therefore the easiest to read.)
23228 @cindex remote serial debugging, overview
23229 To debug a program running on another machine (the debugging
23230 @dfn{target} machine), you must first arrange for all the usual
23231 prerequisites for the program to run by itself. For example, for a C
23236 A startup routine to set up the C runtime environment; these usually
23237 have a name like @file{crt0}. The startup routine may be supplied by
23238 your hardware supplier, or you may have to write your own.
23241 A C subroutine library to support your program's
23242 subroutine calls, notably managing input and output.
23245 A way of getting your program to the other machine---for example, a
23246 download program. These are often supplied by the hardware
23247 manufacturer, but you may have to write your own from hardware
23251 The next step is to arrange for your program to use a serial port to
23252 communicate with the machine where @value{GDBN} is running (the @dfn{host}
23253 machine). In general terms, the scheme looks like this:
23257 @value{GDBN} already understands how to use this protocol; when everything
23258 else is set up, you can simply use the @samp{target remote} command
23259 (@pxref{Targets,,Specifying a Debugging Target}).
23261 @item On the target,
23262 you must link with your program a few special-purpose subroutines that
23263 implement the @value{GDBN} remote serial protocol. The file containing these
23264 subroutines is called a @dfn{debugging stub}.
23266 On certain remote targets, you can use an auxiliary program
23267 @code{gdbserver} instead of linking a stub into your program.
23268 @xref{Server,,Using the @code{gdbserver} Program}, for details.
23271 The debugging stub is specific to the architecture of the remote
23272 machine; for example, use @file{sparc-stub.c} to debug programs on
23275 @cindex remote serial stub list
23276 These working remote stubs are distributed with @value{GDBN}:
23281 @cindex @file{i386-stub.c}
23284 For Intel 386 and compatible architectures.
23287 @cindex @file{m68k-stub.c}
23288 @cindex Motorola 680x0
23290 For Motorola 680x0 architectures.
23293 @cindex @file{sh-stub.c}
23296 For Renesas SH architectures.
23299 @cindex @file{sparc-stub.c}
23301 For @sc{sparc} architectures.
23303 @item sparcl-stub.c
23304 @cindex @file{sparcl-stub.c}
23307 For Fujitsu @sc{sparclite} architectures.
23311 The @file{README} file in the @value{GDBN} distribution may list other
23312 recently added stubs.
23315 * Stub Contents:: What the stub can do for you
23316 * Bootstrapping:: What you must do for the stub
23317 * Debug Session:: Putting it all together
23320 @node Stub Contents
23321 @subsection What the Stub Can Do for You
23323 @cindex remote serial stub
23324 The debugging stub for your architecture supplies these three
23328 @item set_debug_traps
23329 @findex set_debug_traps
23330 @cindex remote serial stub, initialization
23331 This routine arranges for @code{handle_exception} to run when your
23332 program stops. You must call this subroutine explicitly in your
23333 program's startup code.
23335 @item handle_exception
23336 @findex handle_exception
23337 @cindex remote serial stub, main routine
23338 This is the central workhorse, but your program never calls it
23339 explicitly---the setup code arranges for @code{handle_exception} to
23340 run when a trap is triggered.
23342 @code{handle_exception} takes control when your program stops during
23343 execution (for example, on a breakpoint), and mediates communications
23344 with @value{GDBN} on the host machine. This is where the communications
23345 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
23346 representative on the target machine. It begins by sending summary
23347 information on the state of your program, then continues to execute,
23348 retrieving and transmitting any information @value{GDBN} needs, until you
23349 execute a @value{GDBN} command that makes your program resume; at that point,
23350 @code{handle_exception} returns control to your own code on the target
23354 @cindex @code{breakpoint} subroutine, remote
23355 Use this auxiliary subroutine to make your program contain a
23356 breakpoint. Depending on the particular situation, this may be the only
23357 way for @value{GDBN} to get control. For instance, if your target
23358 machine has some sort of interrupt button, you won't need to call this;
23359 pressing the interrupt button transfers control to
23360 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
23361 simply receiving characters on the serial port may also trigger a trap;
23362 again, in that situation, you don't need to call @code{breakpoint} from
23363 your own program---simply running @samp{target remote} from the host
23364 @value{GDBN} session gets control.
23366 Call @code{breakpoint} if none of these is true, or if you simply want
23367 to make certain your program stops at a predetermined point for the
23368 start of your debugging session.
23371 @node Bootstrapping
23372 @subsection What You Must Do for the Stub
23374 @cindex remote stub, support routines
23375 The debugging stubs that come with @value{GDBN} are set up for a particular
23376 chip architecture, but they have no information about the rest of your
23377 debugging target machine.
23379 First of all you need to tell the stub how to communicate with the
23383 @item int getDebugChar()
23384 @findex getDebugChar
23385 Write this subroutine to read a single character from the serial port.
23386 It may be identical to @code{getchar} for your target system; a
23387 different name is used to allow you to distinguish the two if you wish.
23389 @item void putDebugChar(int)
23390 @findex putDebugChar
23391 Write this subroutine to write a single character to the serial port.
23392 It may be identical to @code{putchar} for your target system; a
23393 different name is used to allow you to distinguish the two if you wish.
23396 @cindex control C, and remote debugging
23397 @cindex interrupting remote targets
23398 If you want @value{GDBN} to be able to stop your program while it is
23399 running, you need to use an interrupt-driven serial driver, and arrange
23400 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
23401 character). That is the character which @value{GDBN} uses to tell the
23402 remote system to stop.
23404 Getting the debugging target to return the proper status to @value{GDBN}
23405 probably requires changes to the standard stub; one quick and dirty way
23406 is to just execute a breakpoint instruction (the ``dirty'' part is that
23407 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
23409 Other routines you need to supply are:
23412 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
23413 @findex exceptionHandler
23414 Write this function to install @var{exception_address} in the exception
23415 handling tables. You need to do this because the stub does not have any
23416 way of knowing what the exception handling tables on your target system
23417 are like (for example, the processor's table might be in @sc{rom},
23418 containing entries which point to a table in @sc{ram}).
23419 The @var{exception_number} specifies the exception which should be changed;
23420 its meaning is architecture-dependent (for example, different numbers
23421 might represent divide by zero, misaligned access, etc). When this
23422 exception occurs, control should be transferred directly to
23423 @var{exception_address}, and the processor state (stack, registers,
23424 and so on) should be just as it is when a processor exception occurs. So if
23425 you want to use a jump instruction to reach @var{exception_address}, it
23426 should be a simple jump, not a jump to subroutine.
23428 For the 386, @var{exception_address} should be installed as an interrupt
23429 gate so that interrupts are masked while the handler runs. The gate
23430 should be at privilege level 0 (the most privileged level). The
23431 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
23432 help from @code{exceptionHandler}.
23434 @item void flush_i_cache()
23435 @findex flush_i_cache
23436 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
23437 instruction cache, if any, on your target machine. If there is no
23438 instruction cache, this subroutine may be a no-op.
23440 On target machines that have instruction caches, @value{GDBN} requires this
23441 function to make certain that the state of your program is stable.
23445 You must also make sure this library routine is available:
23448 @item void *memset(void *, int, int)
23450 This is the standard library function @code{memset} that sets an area of
23451 memory to a known value. If you have one of the free versions of
23452 @code{libc.a}, @code{memset} can be found there; otherwise, you must
23453 either obtain it from your hardware manufacturer, or write your own.
23456 If you do not use the GNU C compiler, you may need other standard
23457 library subroutines as well; this varies from one stub to another,
23458 but in general the stubs are likely to use any of the common library
23459 subroutines which @code{@value{NGCC}} generates as inline code.
23462 @node Debug Session
23463 @subsection Putting it All Together
23465 @cindex remote serial debugging summary
23466 In summary, when your program is ready to debug, you must follow these
23471 Make sure you have defined the supporting low-level routines
23472 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
23474 @code{getDebugChar}, @code{putDebugChar},
23475 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
23479 Insert these lines in your program's startup code, before the main
23480 procedure is called:
23487 On some machines, when a breakpoint trap is raised, the hardware
23488 automatically makes the PC point to the instruction after the
23489 breakpoint. If your machine doesn't do that, you may need to adjust
23490 @code{handle_exception} to arrange for it to return to the instruction
23491 after the breakpoint on this first invocation, so that your program
23492 doesn't keep hitting the initial breakpoint instead of making
23496 For the 680x0 stub only, you need to provide a variable called
23497 @code{exceptionHook}. Normally you just use:
23500 void (*exceptionHook)() = 0;
23504 but if before calling @code{set_debug_traps}, you set it to point to a
23505 function in your program, that function is called when
23506 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
23507 error). The function indicated by @code{exceptionHook} is called with
23508 one parameter: an @code{int} which is the exception number.
23511 Compile and link together: your program, the @value{GDBN} debugging stub for
23512 your target architecture, and the supporting subroutines.
23515 Make sure you have a serial connection between your target machine and
23516 the @value{GDBN} host, and identify the serial port on the host.
23519 @c The "remote" target now provides a `load' command, so we should
23520 @c document that. FIXME.
23521 Download your program to your target machine (or get it there by
23522 whatever means the manufacturer provides), and start it.
23525 Start @value{GDBN} on the host, and connect to the target
23526 (@pxref{Connecting,,Connecting to a Remote Target}).
23530 @node Configurations
23531 @chapter Configuration-Specific Information
23533 While nearly all @value{GDBN} commands are available for all native and
23534 cross versions of the debugger, there are some exceptions. This chapter
23535 describes things that are only available in certain configurations.
23537 There are three major categories of configurations: native
23538 configurations, where the host and target are the same, embedded
23539 operating system configurations, which are usually the same for several
23540 different processor architectures, and bare embedded processors, which
23541 are quite different from each other.
23546 * Embedded Processors::
23553 This section describes details specific to particular native
23557 * BSD libkvm Interface:: Debugging BSD kernel memory images
23558 * Process Information:: Process information
23559 * DJGPP Native:: Features specific to the DJGPP port
23560 * Cygwin Native:: Features specific to the Cygwin port
23561 * Hurd Native:: Features specific to @sc{gnu} Hurd
23562 * Darwin:: Features specific to Darwin
23563 * FreeBSD:: Features specific to FreeBSD
23566 @node BSD libkvm Interface
23567 @subsection BSD libkvm Interface
23570 @cindex kernel memory image
23571 @cindex kernel crash dump
23573 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
23574 interface that provides a uniform interface for accessing kernel virtual
23575 memory images, including live systems and crash dumps. @value{GDBN}
23576 uses this interface to allow you to debug live kernels and kernel crash
23577 dumps on many native BSD configurations. This is implemented as a
23578 special @code{kvm} debugging target. For debugging a live system, load
23579 the currently running kernel into @value{GDBN} and connect to the
23583 (@value{GDBP}) @b{target kvm}
23586 For debugging crash dumps, provide the file name of the crash dump as an
23590 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
23593 Once connected to the @code{kvm} target, the following commands are
23599 Set current context from the @dfn{Process Control Block} (PCB) address.
23602 Set current context from proc address. This command isn't available on
23603 modern FreeBSD systems.
23606 @node Process Information
23607 @subsection Process Information
23609 @cindex examine process image
23610 @cindex process info via @file{/proc}
23612 Some operating systems provide interfaces to fetch additional
23613 information about running processes beyond memory and per-thread
23614 register state. If @value{GDBN} is configured for an operating system
23615 with a supported interface, the command @code{info proc} is available
23616 to report information about the process running your program, or about
23617 any process running on your system.
23619 One supported interface is a facility called @samp{/proc} that can be
23620 used to examine the image of a running process using file-system
23621 subroutines. This facility is supported on @sc{gnu}/Linux and Solaris
23624 On FreeBSD and NetBSD systems, system control nodes are used to query
23625 process information.
23627 In addition, some systems may provide additional process information
23628 in core files. Note that a core file may include a subset of the
23629 information available from a live process. Process information is
23630 currently available from cores created on @sc{gnu}/Linux and FreeBSD
23637 @itemx info proc @var{process-id}
23638 Summarize available information about a process. If a
23639 process ID is specified by @var{process-id}, display information about
23640 that process; otherwise display information about the program being
23641 debugged. The summary includes the debugged process ID, the command
23642 line used to invoke it, its current working directory, and its
23643 executable file's absolute file name.
23645 On some systems, @var{process-id} can be of the form
23646 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
23647 within a process. If the optional @var{pid} part is missing, it means
23648 a thread from the process being debugged (the leading @samp{/} still
23649 needs to be present, or else @value{GDBN} will interpret the number as
23650 a process ID rather than a thread ID).
23652 @item info proc cmdline
23653 @cindex info proc cmdline
23654 Show the original command line of the process. This command is
23655 supported on @sc{gnu}/Linux, FreeBSD and NetBSD.
23657 @item info proc cwd
23658 @cindex info proc cwd
23659 Show the current working directory of the process. This command is
23660 supported on @sc{gnu}/Linux, FreeBSD and NetBSD.
23662 @item info proc exe
23663 @cindex info proc exe
23664 Show the name of executable of the process. This command is supported
23665 on @sc{gnu}/Linux, FreeBSD and NetBSD.
23667 @item info proc files
23668 @cindex info proc files
23669 Show the file descriptors open by the process. For each open file
23670 descriptor, @value{GDBN} shows its number, type (file, directory,
23671 character device, socket), file pointer offset, and the name of the
23672 resource open on the descriptor. The resource name can be a file name
23673 (for files, directories, and devices) or a protocol followed by socket
23674 address (for network connections). This command is supported on
23677 This example shows the open file descriptors for a process using a
23678 tty for standard input and output as well as two network sockets:
23681 (gdb) info proc files 22136
23685 FD Type Offset Flags Name
23686 text file - r-------- /usr/bin/ssh
23687 ctty chr - rw------- /dev/pts/20
23688 cwd dir - r-------- /usr/home/john
23689 root dir - r-------- /
23690 0 chr 0x32933a4 rw------- /dev/pts/20
23691 1 chr 0x32933a4 rw------- /dev/pts/20
23692 2 chr 0x32933a4 rw------- /dev/pts/20
23693 3 socket 0x0 rw----n-- tcp4 10.0.1.2:53014 -> 10.0.1.10:22
23694 4 socket 0x0 rw------- unix stream:/tmp/ssh-FIt89oAzOn5f/agent.2456
23697 @item info proc mappings
23698 @cindex memory address space mappings
23699 Report the memory address space ranges accessible in a process. On
23700 Solaris, FreeBSD and NetBSD systems, each memory range includes information
23701 on whether the process has read, write, or execute access rights to each
23702 range. On @sc{gnu}/Linux, FreeBSD and NetBSD systems, each memory range
23703 includes the object file which is mapped to that range.
23705 @item info proc stat
23706 @itemx info proc status
23707 @cindex process detailed status information
23708 Show additional process-related information, including the user ID and
23709 group ID; virtual memory usage; the signals that are pending, blocked,
23710 and ignored; its TTY; its consumption of system and user time; its
23711 stack size; its @samp{nice} value; etc. These commands are supported
23712 on @sc{gnu}/Linux, FreeBSD and NetBSD.
23714 For @sc{gnu}/Linux systems, see the @samp{proc} man page for more
23715 information (type @kbd{man 5 proc} from your shell prompt).
23717 For FreeBSD and NetBSD systems, @code{info proc stat} is an alias for
23718 @code{info proc status}.
23720 @item info proc all
23721 Show all the information about the process described under all of the
23722 above @code{info proc} subcommands.
23725 @comment These sub-options of 'info proc' were not included when
23726 @comment procfs.c was re-written. Keep their descriptions around
23727 @comment against the day when someone finds the time to put them back in.
23728 @kindex info proc times
23729 @item info proc times
23730 Starting time, user CPU time, and system CPU time for your program and
23733 @kindex info proc id
23735 Report on the process IDs related to your program: its own process ID,
23736 the ID of its parent, the process group ID, and the session ID.
23739 @item set procfs-trace
23740 @kindex set procfs-trace
23741 @cindex @code{procfs} API calls
23742 This command enables and disables tracing of @code{procfs} API calls.
23744 @item show procfs-trace
23745 @kindex show procfs-trace
23746 Show the current state of @code{procfs} API call tracing.
23748 @item set procfs-file @var{file}
23749 @kindex set procfs-file
23750 Tell @value{GDBN} to write @code{procfs} API trace to the named
23751 @var{file}. @value{GDBN} appends the trace info to the previous
23752 contents of the file. The default is to display the trace on the
23755 @item show procfs-file
23756 @kindex show procfs-file
23757 Show the file to which @code{procfs} API trace is written.
23759 @item proc-trace-entry
23760 @itemx proc-trace-exit
23761 @itemx proc-untrace-entry
23762 @itemx proc-untrace-exit
23763 @kindex proc-trace-entry
23764 @kindex proc-trace-exit
23765 @kindex proc-untrace-entry
23766 @kindex proc-untrace-exit
23767 These commands enable and disable tracing of entries into and exits
23768 from the @code{syscall} interface.
23771 @kindex info pidlist
23772 @cindex process list, QNX Neutrino
23773 For QNX Neutrino only, this command displays the list of all the
23774 processes and all the threads within each process.
23777 @kindex info meminfo
23778 @cindex mapinfo list, QNX Neutrino
23779 For QNX Neutrino only, this command displays the list of all mapinfos.
23783 @subsection Features for Debugging @sc{djgpp} Programs
23784 @cindex @sc{djgpp} debugging
23785 @cindex native @sc{djgpp} debugging
23786 @cindex MS-DOS-specific commands
23789 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
23790 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
23791 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
23792 top of real-mode DOS systems and their emulations.
23794 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
23795 defines a few commands specific to the @sc{djgpp} port. This
23796 subsection describes those commands.
23801 This is a prefix of @sc{djgpp}-specific commands which print
23802 information about the target system and important OS structures.
23805 @cindex MS-DOS system info
23806 @cindex free memory information (MS-DOS)
23807 @item info dos sysinfo
23808 This command displays assorted information about the underlying
23809 platform: the CPU type and features, the OS version and flavor, the
23810 DPMI version, and the available conventional and DPMI memory.
23815 @cindex segment descriptor tables
23816 @cindex descriptor tables display
23818 @itemx info dos ldt
23819 @itemx info dos idt
23820 These 3 commands display entries from, respectively, Global, Local,
23821 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
23822 tables are data structures which store a descriptor for each segment
23823 that is currently in use. The segment's selector is an index into a
23824 descriptor table; the table entry for that index holds the
23825 descriptor's base address and limit, and its attributes and access
23828 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
23829 segment (used for both data and the stack), and a DOS segment (which
23830 allows access to DOS/BIOS data structures and absolute addresses in
23831 conventional memory). However, the DPMI host will usually define
23832 additional segments in order to support the DPMI environment.
23834 @cindex garbled pointers
23835 These commands allow to display entries from the descriptor tables.
23836 Without an argument, all entries from the specified table are
23837 displayed. An argument, which should be an integer expression, means
23838 display a single entry whose index is given by the argument. For
23839 example, here's a convenient way to display information about the
23840 debugged program's data segment:
23843 @exdent @code{(@value{GDBP}) info dos ldt $ds}
23844 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
23848 This comes in handy when you want to see whether a pointer is outside
23849 the data segment's limit (i.e.@: @dfn{garbled}).
23851 @cindex page tables display (MS-DOS)
23853 @itemx info dos pte
23854 These two commands display entries from, respectively, the Page
23855 Directory and the Page Tables. Page Directories and Page Tables are
23856 data structures which control how virtual memory addresses are mapped
23857 into physical addresses. A Page Table includes an entry for every
23858 page of memory that is mapped into the program's address space; there
23859 may be several Page Tables, each one holding up to 4096 entries. A
23860 Page Directory has up to 4096 entries, one each for every Page Table
23861 that is currently in use.
23863 Without an argument, @kbd{info dos pde} displays the entire Page
23864 Directory, and @kbd{info dos pte} displays all the entries in all of
23865 the Page Tables. An argument, an integer expression, given to the
23866 @kbd{info dos pde} command means display only that entry from the Page
23867 Directory table. An argument given to the @kbd{info dos pte} command
23868 means display entries from a single Page Table, the one pointed to by
23869 the specified entry in the Page Directory.
23871 @cindex direct memory access (DMA) on MS-DOS
23872 These commands are useful when your program uses @dfn{DMA} (Direct
23873 Memory Access), which needs physical addresses to program the DMA
23876 These commands are supported only with some DPMI servers.
23878 @cindex physical address from linear address
23879 @item info dos address-pte @var{addr}
23880 This command displays the Page Table entry for a specified linear
23881 address. The argument @var{addr} is a linear address which should
23882 already have the appropriate segment's base address added to it,
23883 because this command accepts addresses which may belong to @emph{any}
23884 segment. For example, here's how to display the Page Table entry for
23885 the page where a variable @code{i} is stored:
23888 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
23889 @exdent @code{Page Table entry for address 0x11a00d30:}
23890 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
23894 This says that @code{i} is stored at offset @code{0xd30} from the page
23895 whose physical base address is @code{0x02698000}, and shows all the
23896 attributes of that page.
23898 Note that you must cast the addresses of variables to a @code{char *},
23899 since otherwise the value of @code{__djgpp_base_address}, the base
23900 address of all variables and functions in a @sc{djgpp} program, will
23901 be added using the rules of C pointer arithmetics: if @code{i} is
23902 declared an @code{int}, @value{GDBN} will add 4 times the value of
23903 @code{__djgpp_base_address} to the address of @code{i}.
23905 Here's another example, it displays the Page Table entry for the
23909 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
23910 @exdent @code{Page Table entry for address 0x29110:}
23911 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
23915 (The @code{+ 3} offset is because the transfer buffer's address is the
23916 3rd member of the @code{_go32_info_block} structure.) The output
23917 clearly shows that this DPMI server maps the addresses in conventional
23918 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
23919 linear (@code{0x29110}) addresses are identical.
23921 This command is supported only with some DPMI servers.
23924 @cindex DOS serial data link, remote debugging
23925 In addition to native debugging, the DJGPP port supports remote
23926 debugging via a serial data link. The following commands are specific
23927 to remote serial debugging in the DJGPP port of @value{GDBN}.
23930 @kindex set com1base
23931 @kindex set com1irq
23932 @kindex set com2base
23933 @kindex set com2irq
23934 @kindex set com3base
23935 @kindex set com3irq
23936 @kindex set com4base
23937 @kindex set com4irq
23938 @item set com1base @var{addr}
23939 This command sets the base I/O port address of the @file{COM1} serial
23942 @item set com1irq @var{irq}
23943 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
23944 for the @file{COM1} serial port.
23946 There are similar commands @samp{set com2base}, @samp{set com3irq},
23947 etc.@: for setting the port address and the @code{IRQ} lines for the
23950 @kindex show com1base
23951 @kindex show com1irq
23952 @kindex show com2base
23953 @kindex show com2irq
23954 @kindex show com3base
23955 @kindex show com3irq
23956 @kindex show com4base
23957 @kindex show com4irq
23958 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
23959 display the current settings of the base address and the @code{IRQ}
23960 lines used by the COM ports.
23963 @kindex info serial
23964 @cindex DOS serial port status
23965 This command prints the status of the 4 DOS serial ports. For each
23966 port, it prints whether it's active or not, its I/O base address and
23967 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
23968 counts of various errors encountered so far.
23972 @node Cygwin Native
23973 @subsection Features for Debugging MS Windows PE Executables
23974 @cindex MS Windows debugging
23975 @cindex native Cygwin debugging
23976 @cindex Cygwin-specific commands
23978 @value{GDBN} supports native debugging of MS Windows programs, including
23979 DLLs with and without symbolic debugging information.
23981 @cindex Ctrl-BREAK, MS-Windows
23982 @cindex interrupt debuggee on MS-Windows
23983 MS-Windows programs that call @code{SetConsoleMode} to switch off the
23984 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
23985 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
23986 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
23987 sequence, which can be used to interrupt the debuggee even if it
23990 There are various additional Cygwin-specific commands, described in
23991 this section. Working with DLLs that have no debugging symbols is
23992 described in @ref{Non-debug DLL Symbols}.
23997 This is a prefix of MS Windows-specific commands which print
23998 information about the target system and important OS structures.
24000 @item info w32 selector
24001 This command displays information returned by
24002 the Win32 API @code{GetThreadSelectorEntry} function.
24003 It takes an optional argument that is evaluated to
24004 a long value to give the information about this given selector.
24005 Without argument, this command displays information
24006 about the six segment registers.
24008 @item info w32 thread-information-block
24009 This command displays thread specific information stored in the
24010 Thread Information Block (readable on the X86 CPU family using @code{$fs}
24011 selector for 32-bit programs and @code{$gs} for 64-bit programs).
24013 @kindex signal-event
24014 @item signal-event @var{id}
24015 This command signals an event with user-provided @var{id}. Used to resume
24016 crashing process when attached to it using MS-Windows JIT debugging (AeDebug).
24018 To use it, create or edit the following keys in
24019 @code{HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AeDebug} and/or
24020 @code{HKLM\SOFTWARE\Wow6432Node\Microsoft\Windows NT\CurrentVersion\AeDebug}
24021 (for x86_64 versions):
24025 @code{Debugger} (REG_SZ) --- a command to launch the debugger.
24026 Suggested command is: @code{@var{fully-qualified-path-to-gdb.exe} -ex
24027 "attach %ld" -ex "signal-event %ld" -ex "continue"}.
24029 The first @code{%ld} will be replaced by the process ID of the
24030 crashing process, the second @code{%ld} will be replaced by the ID of
24031 the event that blocks the crashing process, waiting for @value{GDBN}
24035 @code{Auto} (REG_SZ) --- either @code{1} or @code{0}. @code{1} will
24036 make the system run debugger specified by the Debugger key
24037 automatically, @code{0} will cause a dialog box with ``OK'' and
24038 ``Cancel'' buttons to appear, which allows the user to either
24039 terminate the crashing process (OK) or debug it (Cancel).
24042 @kindex set cygwin-exceptions
24043 @cindex debugging the Cygwin DLL
24044 @cindex Cygwin DLL, debugging
24045 @item set cygwin-exceptions @var{mode}
24046 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
24047 happen inside the Cygwin DLL. If @var{mode} is @code{off},
24048 @value{GDBN} will delay recognition of exceptions, and may ignore some
24049 exceptions which seem to be caused by internal Cygwin DLL
24050 ``bookkeeping''. This option is meant primarily for debugging the
24051 Cygwin DLL itself; the default value is @code{off} to avoid annoying
24052 @value{GDBN} users with false @code{SIGSEGV} signals.
24054 @kindex show cygwin-exceptions
24055 @item show cygwin-exceptions
24056 Displays whether @value{GDBN} will break on exceptions that happen
24057 inside the Cygwin DLL itself.
24059 @kindex set new-console
24060 @item set new-console @var{mode}
24061 If @var{mode} is @code{on} the debuggee will
24062 be started in a new console on next start.
24063 If @var{mode} is @code{off}, the debuggee will
24064 be started in the same console as the debugger.
24066 @kindex show new-console
24067 @item show new-console
24068 Displays whether a new console is used
24069 when the debuggee is started.
24071 @kindex set new-group
24072 @item set new-group @var{mode}
24073 This boolean value controls whether the debuggee should
24074 start a new group or stay in the same group as the debugger.
24075 This affects the way the Windows OS handles
24078 @kindex show new-group
24079 @item show new-group
24080 Displays current value of new-group boolean.
24082 @kindex set debugevents
24083 @item set debugevents
24084 This boolean value adds debug output concerning kernel events related
24085 to the debuggee seen by the debugger. This includes events that
24086 signal thread and process creation and exit, DLL loading and
24087 unloading, console interrupts, and debugging messages produced by the
24088 Windows @code{OutputDebugString} API call.
24090 @kindex set debugexec
24091 @item set debugexec
24092 This boolean value adds debug output concerning execute events
24093 (such as resume thread) seen by the debugger.
24095 @kindex set debugexceptions
24096 @item set debugexceptions
24097 This boolean value adds debug output concerning exceptions in the
24098 debuggee seen by the debugger.
24100 @kindex set debugmemory
24101 @item set debugmemory
24102 This boolean value adds debug output concerning debuggee memory reads
24103 and writes by the debugger.
24107 This boolean values specifies whether the debuggee is called
24108 via a shell or directly (default value is on).
24112 Displays if the debuggee will be started with a shell.
24117 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
24120 @node Non-debug DLL Symbols
24121 @subsubsection Support for DLLs without Debugging Symbols
24122 @cindex DLLs with no debugging symbols
24123 @cindex Minimal symbols and DLLs
24125 Very often on windows, some of the DLLs that your program relies on do
24126 not include symbolic debugging information (for example,
24127 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
24128 symbols in a DLL, it relies on the minimal amount of symbolic
24129 information contained in the DLL's export table. This section
24130 describes working with such symbols, known internally to @value{GDBN} as
24131 ``minimal symbols''.
24133 Note that before the debugged program has started execution, no DLLs
24134 will have been loaded. The easiest way around this problem is simply to
24135 start the program --- either by setting a breakpoint or letting the
24136 program run once to completion.
24138 @subsubsection DLL Name Prefixes
24140 In keeping with the naming conventions used by the Microsoft debugging
24141 tools, DLL export symbols are made available with a prefix based on the
24142 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
24143 also entered into the symbol table, so @code{CreateFileA} is often
24144 sufficient. In some cases there will be name clashes within a program
24145 (particularly if the executable itself includes full debugging symbols)
24146 necessitating the use of the fully qualified name when referring to the
24147 contents of the DLL. Use single-quotes around the name to avoid the
24148 exclamation mark (``!'') being interpreted as a language operator.
24150 Note that the internal name of the DLL may be all upper-case, even
24151 though the file name of the DLL is lower-case, or vice-versa. Since
24152 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
24153 some confusion. If in doubt, try the @code{info functions} and
24154 @code{info variables} commands or even @code{maint print msymbols}
24155 (@pxref{Symbols}). Here's an example:
24158 (@value{GDBP}) info function CreateFileA
24159 All functions matching regular expression "CreateFileA":
24161 Non-debugging symbols:
24162 0x77e885f4 CreateFileA
24163 0x77e885f4 KERNEL32!CreateFileA
24167 (@value{GDBP}) info function !
24168 All functions matching regular expression "!":
24170 Non-debugging symbols:
24171 0x6100114c cygwin1!__assert
24172 0x61004034 cygwin1!_dll_crt0@@0
24173 0x61004240 cygwin1!dll_crt0(per_process *)
24177 @subsubsection Working with Minimal Symbols
24179 Symbols extracted from a DLL's export table do not contain very much
24180 type information. All that @value{GDBN} can do is guess whether a symbol
24181 refers to a function or variable depending on the linker section that
24182 contains the symbol. Also note that the actual contents of the memory
24183 contained in a DLL are not available unless the program is running. This
24184 means that you cannot examine the contents of a variable or disassemble
24185 a function within a DLL without a running program.
24187 Variables are generally treated as pointers and dereferenced
24188 automatically. For this reason, it is often necessary to prefix a
24189 variable name with the address-of operator (``&'') and provide explicit
24190 type information in the command. Here's an example of the type of
24194 (@value{GDBP}) print 'cygwin1!__argv'
24195 'cygwin1!__argv' has unknown type; cast it to its declared type
24199 (@value{GDBP}) x 'cygwin1!__argv'
24200 'cygwin1!__argv' has unknown type; cast it to its declared type
24203 And two possible solutions:
24206 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
24207 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
24211 (@value{GDBP}) x/2x &'cygwin1!__argv'
24212 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
24213 (@value{GDBP}) x/x 0x10021608
24214 0x10021608: 0x0022fd98
24215 (@value{GDBP}) x/s 0x0022fd98
24216 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
24219 Setting a break point within a DLL is possible even before the program
24220 starts execution. However, under these circumstances, @value{GDBN} can't
24221 examine the initial instructions of the function in order to skip the
24222 function's frame set-up code. You can work around this by using ``*&''
24223 to set the breakpoint at a raw memory address:
24226 (@value{GDBP}) break *&'python22!PyOS_Readline'
24227 Breakpoint 1 at 0x1e04eff0
24230 The author of these extensions is not entirely convinced that setting a
24231 break point within a shared DLL like @file{kernel32.dll} is completely
24235 @subsection Commands Specific to @sc{gnu} Hurd Systems
24236 @cindex @sc{gnu} Hurd debugging
24238 This subsection describes @value{GDBN} commands specific to the
24239 @sc{gnu} Hurd native debugging.
24244 @kindex set signals@r{, Hurd command}
24245 @kindex set sigs@r{, Hurd command}
24246 This command toggles the state of inferior signal interception by
24247 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
24248 affected by this command. @code{sigs} is a shorthand alias for
24253 @kindex show signals@r{, Hurd command}
24254 @kindex show sigs@r{, Hurd command}
24255 Show the current state of intercepting inferior's signals.
24257 @item set signal-thread
24258 @itemx set sigthread
24259 @kindex set signal-thread
24260 @kindex set sigthread
24261 This command tells @value{GDBN} which thread is the @code{libc} signal
24262 thread. That thread is run when a signal is delivered to a running
24263 process. @code{set sigthread} is the shorthand alias of @code{set
24266 @item show signal-thread
24267 @itemx show sigthread
24268 @kindex show signal-thread
24269 @kindex show sigthread
24270 These two commands show which thread will run when the inferior is
24271 delivered a signal.
24274 @kindex set stopped@r{, Hurd command}
24275 This commands tells @value{GDBN} that the inferior process is stopped,
24276 as with the @code{SIGSTOP} signal. The stopped process can be
24277 continued by delivering a signal to it.
24280 @kindex show stopped@r{, Hurd command}
24281 This command shows whether @value{GDBN} thinks the debuggee is
24284 @item set exceptions
24285 @kindex set exceptions@r{, Hurd command}
24286 Use this command to turn off trapping of exceptions in the inferior.
24287 When exception trapping is off, neither breakpoints nor
24288 single-stepping will work. To restore the default, set exception
24291 @item show exceptions
24292 @kindex show exceptions@r{, Hurd command}
24293 Show the current state of trapping exceptions in the inferior.
24295 @item set task pause
24296 @kindex set task@r{, Hurd commands}
24297 @cindex task attributes (@sc{gnu} Hurd)
24298 @cindex pause current task (@sc{gnu} Hurd)
24299 This command toggles task suspension when @value{GDBN} has control.
24300 Setting it to on takes effect immediately, and the task is suspended
24301 whenever @value{GDBN} gets control. Setting it to off will take
24302 effect the next time the inferior is continued. If this option is set
24303 to off, you can use @code{set thread default pause on} or @code{set
24304 thread pause on} (see below) to pause individual threads.
24306 @item show task pause
24307 @kindex show task@r{, Hurd commands}
24308 Show the current state of task suspension.
24310 @item set task detach-suspend-count
24311 @cindex task suspend count
24312 @cindex detach from task, @sc{gnu} Hurd
24313 This command sets the suspend count the task will be left with when
24314 @value{GDBN} detaches from it.
24316 @item show task detach-suspend-count
24317 Show the suspend count the task will be left with when detaching.
24319 @item set task exception-port
24320 @itemx set task excp
24321 @cindex task exception port, @sc{gnu} Hurd
24322 This command sets the task exception port to which @value{GDBN} will
24323 forward exceptions. The argument should be the value of the @dfn{send
24324 rights} of the task. @code{set task excp} is a shorthand alias.
24326 @item set noninvasive
24327 @cindex noninvasive task options
24328 This command switches @value{GDBN} to a mode that is the least
24329 invasive as far as interfering with the inferior is concerned. This
24330 is the same as using @code{set task pause}, @code{set exceptions}, and
24331 @code{set signals} to values opposite to the defaults.
24333 @item info send-rights
24334 @itemx info receive-rights
24335 @itemx info port-rights
24336 @itemx info port-sets
24337 @itemx info dead-names
24340 @cindex send rights, @sc{gnu} Hurd
24341 @cindex receive rights, @sc{gnu} Hurd
24342 @cindex port rights, @sc{gnu} Hurd
24343 @cindex port sets, @sc{gnu} Hurd
24344 @cindex dead names, @sc{gnu} Hurd
24345 These commands display information about, respectively, send rights,
24346 receive rights, port rights, port sets, and dead names of a task.
24347 There are also shorthand aliases: @code{info ports} for @code{info
24348 port-rights} and @code{info psets} for @code{info port-sets}.
24350 @item set thread pause
24351 @kindex set thread@r{, Hurd command}
24352 @cindex thread properties, @sc{gnu} Hurd
24353 @cindex pause current thread (@sc{gnu} Hurd)
24354 This command toggles current thread suspension when @value{GDBN} has
24355 control. Setting it to on takes effect immediately, and the current
24356 thread is suspended whenever @value{GDBN} gets control. Setting it to
24357 off will take effect the next time the inferior is continued.
24358 Normally, this command has no effect, since when @value{GDBN} has
24359 control, the whole task is suspended. However, if you used @code{set
24360 task pause off} (see above), this command comes in handy to suspend
24361 only the current thread.
24363 @item show thread pause
24364 @kindex show thread@r{, Hurd command}
24365 This command shows the state of current thread suspension.
24367 @item set thread run
24368 This command sets whether the current thread is allowed to run.
24370 @item show thread run
24371 Show whether the current thread is allowed to run.
24373 @item set thread detach-suspend-count
24374 @cindex thread suspend count, @sc{gnu} Hurd
24375 @cindex detach from thread, @sc{gnu} Hurd
24376 This command sets the suspend count @value{GDBN} will leave on a
24377 thread when detaching. This number is relative to the suspend count
24378 found by @value{GDBN} when it notices the thread; use @code{set thread
24379 takeover-suspend-count} to force it to an absolute value.
24381 @item show thread detach-suspend-count
24382 Show the suspend count @value{GDBN} will leave on the thread when
24385 @item set thread exception-port
24386 @itemx set thread excp
24387 Set the thread exception port to which to forward exceptions. This
24388 overrides the port set by @code{set task exception-port} (see above).
24389 @code{set thread excp} is the shorthand alias.
24391 @item set thread takeover-suspend-count
24392 Normally, @value{GDBN}'s thread suspend counts are relative to the
24393 value @value{GDBN} finds when it notices each thread. This command
24394 changes the suspend counts to be absolute instead.
24396 @item set thread default
24397 @itemx show thread default
24398 @cindex thread default settings, @sc{gnu} Hurd
24399 Each of the above @code{set thread} commands has a @code{set thread
24400 default} counterpart (e.g., @code{set thread default pause}, @code{set
24401 thread default exception-port}, etc.). The @code{thread default}
24402 variety of commands sets the default thread properties for all
24403 threads; you can then change the properties of individual threads with
24404 the non-default commands.
24411 @value{GDBN} provides the following commands specific to the Darwin target:
24414 @item set debug darwin @var{num}
24415 @kindex set debug darwin
24416 When set to a non zero value, enables debugging messages specific to
24417 the Darwin support. Higher values produce more verbose output.
24419 @item show debug darwin
24420 @kindex show debug darwin
24421 Show the current state of Darwin messages.
24423 @item set debug mach-o @var{num}
24424 @kindex set debug mach-o
24425 When set to a non zero value, enables debugging messages while
24426 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
24427 file format used on Darwin for object and executable files.) Higher
24428 values produce more verbose output. This is a command to diagnose
24429 problems internal to @value{GDBN} and should not be needed in normal
24432 @item show debug mach-o
24433 @kindex show debug mach-o
24434 Show the current state of Mach-O file messages.
24436 @item set mach-exceptions on
24437 @itemx set mach-exceptions off
24438 @kindex set mach-exceptions
24439 On Darwin, faults are first reported as a Mach exception and are then
24440 mapped to a Posix signal. Use this command to turn on trapping of
24441 Mach exceptions in the inferior. This might be sometimes useful to
24442 better understand the cause of a fault. The default is off.
24444 @item show mach-exceptions
24445 @kindex show mach-exceptions
24446 Show the current state of exceptions trapping.
24450 @subsection FreeBSD
24453 When the ABI of a system call is changed in the FreeBSD kernel, this
24454 is implemented by leaving a compatibility system call using the old
24455 ABI at the existing number and allocating a new system call number for
24456 the version using the new ABI. As a convenience, when a system call
24457 is caught by name (@pxref{catch syscall}), compatibility system calls
24460 For example, FreeBSD 12 introduced a new variant of the @code{kevent}
24461 system call and catching the @code{kevent} system call by name catches
24465 (@value{GDBP}) catch syscall kevent
24466 Catchpoint 1 (syscalls 'freebsd11_kevent' [363] 'kevent' [560])
24472 @section Embedded Operating Systems
24474 This section describes configurations involving the debugging of
24475 embedded operating systems that are available for several different
24478 @value{GDBN} includes the ability to debug programs running on
24479 various real-time operating systems.
24481 @node Embedded Processors
24482 @section Embedded Processors
24484 This section goes into details specific to particular embedded
24487 @cindex send command to simulator
24488 Whenever a specific embedded processor has a simulator, @value{GDBN}
24489 allows to send an arbitrary command to the simulator.
24492 @item sim @var{command}
24493 @kindex sim@r{, a command}
24494 Send an arbitrary @var{command} string to the simulator. Consult the
24495 documentation for the specific simulator in use for information about
24496 acceptable commands.
24501 * ARC:: Synopsys ARC
24504 * M68K:: Motorola M68K
24505 * MicroBlaze:: Xilinx MicroBlaze
24506 * MIPS Embedded:: MIPS Embedded
24507 * OpenRISC 1000:: OpenRISC 1000 (or1k)
24508 * PowerPC Embedded:: PowerPC Embedded
24511 * Super-H:: Renesas Super-H
24515 @subsection Synopsys ARC
24516 @cindex Synopsys ARC
24517 @cindex ARC specific commands
24523 @value{GDBN} provides the following ARC-specific commands:
24526 @item set debug arc
24527 @kindex set debug arc
24528 Control the level of ARC specific debug messages. Use 0 for no messages (the
24529 default), 1 for debug messages, and 2 for even more debug messages.
24531 @item show debug arc
24532 @kindex show debug arc
24533 Show the level of ARC specific debugging in operation.
24535 @item maint print arc arc-instruction @var{address}
24536 @kindex maint print arc arc-instruction
24537 Print internal disassembler information about instruction at a given address.
24544 @value{GDBN} provides the following ARM-specific commands:
24547 @item set arm disassembler
24549 This commands selects from a list of disassembly styles. The
24550 @code{"std"} style is the standard style.
24552 @item show arm disassembler
24554 Show the current disassembly style.
24556 @item set arm apcs32
24557 @cindex ARM 32-bit mode
24558 This command toggles ARM operation mode between 32-bit and 26-bit.
24560 @item show arm apcs32
24561 Display the current usage of the ARM 32-bit mode.
24563 @item set arm fpu @var{fputype}
24564 This command sets the ARM floating-point unit (FPU) type. The
24565 argument @var{fputype} can be one of these:
24569 Determine the FPU type by querying the OS ABI.
24571 Software FPU, with mixed-endian doubles on little-endian ARM
24574 GCC-compiled FPA co-processor.
24576 Software FPU with pure-endian doubles.
24582 Show the current type of the FPU.
24585 This command forces @value{GDBN} to use the specified ABI.
24588 Show the currently used ABI.
24590 @item set arm fallback-mode (arm|thumb|auto)
24591 @value{GDBN} uses the symbol table, when available, to determine
24592 whether instructions are ARM or Thumb. This command controls
24593 @value{GDBN}'s default behavior when the symbol table is not
24594 available. The default is @samp{auto}, which causes @value{GDBN} to
24595 use the current execution mode (from the @code{T} bit in the @code{CPSR}
24598 @item show arm fallback-mode
24599 Show the current fallback instruction mode.
24601 @item set arm force-mode (arm|thumb|auto)
24602 This command overrides use of the symbol table to determine whether
24603 instructions are ARM or Thumb. The default is @samp{auto}, which
24604 causes @value{GDBN} to use the symbol table and then the setting
24605 of @samp{set arm fallback-mode}.
24607 @item show arm force-mode
24608 Show the current forced instruction mode.
24610 @item set debug arm
24611 Toggle whether to display ARM-specific debugging messages from the ARM
24612 target support subsystem.
24614 @item show debug arm
24615 Show whether ARM-specific debugging messages are enabled.
24619 @item target sim @r{[}@var{simargs}@r{]} @dots{}
24620 The @value{GDBN} ARM simulator accepts the following optional arguments.
24623 @item --swi-support=@var{type}
24624 Tell the simulator which SWI interfaces to support. The argument
24625 @var{type} may be a comma separated list of the following values.
24626 The default value is @code{all}.
24642 @item target sim @r{[}@var{simargs}@r{]} @dots{}
24643 The @value{GDBN} BPF simulator accepts the following optional arguments.
24646 @item --skb-data-offset=@var{offset}
24647 Tell the simulator the offset, measured in bytes, of the
24648 @code{skb_data} field in the kernel @code{struct sk_buff} structure.
24649 This offset is used by some BPF specific-purpose load/store
24650 instructions. Defaults to 0.
24657 The Motorola m68k configuration includes ColdFire support.
24660 @subsection MicroBlaze
24661 @cindex Xilinx MicroBlaze
24662 @cindex XMD, Xilinx Microprocessor Debugger
24664 The MicroBlaze is a soft-core processor supported on various Xilinx
24665 FPGAs, such as Spartan or Virtex series. Boards with these processors
24666 usually have JTAG ports which connect to a host system running the Xilinx
24667 Embedded Development Kit (EDK) or Software Development Kit (SDK).
24668 This host system is used to download the configuration bitstream to
24669 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
24670 communicates with the target board using the JTAG interface and
24671 presents a @code{gdbserver} interface to the board. By default
24672 @code{xmd} uses port @code{1234}. (While it is possible to change
24673 this default port, it requires the use of undocumented @code{xmd}
24674 commands. Contact Xilinx support if you need to do this.)
24676 Use these GDB commands to connect to the MicroBlaze target processor.
24679 @item target remote :1234
24680 Use this command to connect to the target if you are running @value{GDBN}
24681 on the same system as @code{xmd}.
24683 @item target remote @var{xmd-host}:1234
24684 Use this command to connect to the target if it is connected to @code{xmd}
24685 running on a different system named @var{xmd-host}.
24688 Use this command to download a program to the MicroBlaze target.
24690 @item set debug microblaze @var{n}
24691 Enable MicroBlaze-specific debugging messages if non-zero.
24693 @item show debug microblaze @var{n}
24694 Show MicroBlaze-specific debugging level.
24697 @node MIPS Embedded
24698 @subsection @acronym{MIPS} Embedded
24701 @value{GDBN} supports these special commands for @acronym{MIPS} targets:
24704 @item set mipsfpu double
24705 @itemx set mipsfpu single
24706 @itemx set mipsfpu none
24707 @itemx set mipsfpu auto
24708 @itemx show mipsfpu
24709 @kindex set mipsfpu
24710 @kindex show mipsfpu
24711 @cindex @acronym{MIPS} remote floating point
24712 @cindex floating point, @acronym{MIPS} remote
24713 If your target board does not support the @acronym{MIPS} floating point
24714 coprocessor, you should use the command @samp{set mipsfpu none} (if you
24715 need this, you may wish to put the command in your @value{GDBN} init
24716 file). This tells @value{GDBN} how to find the return value of
24717 functions which return floating point values. It also allows
24718 @value{GDBN} to avoid saving the floating point registers when calling
24719 functions on the board. If you are using a floating point coprocessor
24720 with only single precision floating point support, as on the @sc{r4650}
24721 processor, use the command @samp{set mipsfpu single}. The default
24722 double precision floating point coprocessor may be selected using
24723 @samp{set mipsfpu double}.
24725 In previous versions the only choices were double precision or no
24726 floating point, so @samp{set mipsfpu on} will select double precision
24727 and @samp{set mipsfpu off} will select no floating point.
24729 As usual, you can inquire about the @code{mipsfpu} variable with
24730 @samp{show mipsfpu}.
24733 @node OpenRISC 1000
24734 @subsection OpenRISC 1000
24735 @cindex OpenRISC 1000
24738 The OpenRISC 1000 provides a free RISC instruction set architecture. It is
24739 mainly provided as a soft-core which can run on Xilinx, Altera and other
24742 @value{GDBN} for OpenRISC supports the below commands when connecting to
24750 Runs the builtin CPU simulator which can run very basic
24751 programs but does not support most hardware functions like MMU.
24752 For more complex use cases the user is advised to run an external
24753 target, and connect using @samp{target remote}.
24755 Example: @code{target sim}
24757 @item set debug or1k
24758 Toggle whether to display OpenRISC-specific debugging messages from the
24759 OpenRISC target support subsystem.
24761 @item show debug or1k
24762 Show whether OpenRISC-specific debugging messages are enabled.
24765 @node PowerPC Embedded
24766 @subsection PowerPC Embedded
24768 @cindex DVC register
24769 @value{GDBN} supports using the DVC (Data Value Compare) register to
24770 implement in hardware simple hardware watchpoint conditions of the form:
24773 (@value{GDBP}) watch @var{address|variable} \
24774 if @var{address|variable} == @var{constant expression}
24777 The DVC register will be automatically used when @value{GDBN} detects
24778 such pattern in a condition expression, and the created watchpoint uses one
24779 debug register (either the @code{exact-watchpoints} option is on and the
24780 variable is scalar, or the variable has a length of one byte). This feature
24781 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
24784 When running on PowerPC embedded processors, @value{GDBN} automatically uses
24785 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
24786 in which case watchpoints using only one debug register are created when
24787 watching variables of scalar types.
24789 You can create an artificial array to watch an arbitrary memory
24790 region using one of the following commands (@pxref{Expressions}):
24793 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
24794 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
24797 PowerPC embedded processors support masked watchpoints. See the discussion
24798 about the @code{mask} argument in @ref{Set Watchpoints}.
24800 @cindex ranged breakpoint
24801 PowerPC embedded processors support hardware accelerated
24802 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
24803 the inferior whenever it executes an instruction at any address within
24804 the range it specifies. To set a ranged breakpoint in @value{GDBN},
24805 use the @code{break-range} command.
24807 @value{GDBN} provides the following PowerPC-specific commands:
24810 @kindex break-range
24811 @item break-range @var{start-location}, @var{end-location}
24812 Set a breakpoint for an address range given by
24813 @var{start-location} and @var{end-location}, which can specify a function name,
24814 a line number, an offset of lines from the current line or from the start
24815 location, or an address of an instruction (see @ref{Specify Location},
24816 for a list of all the possible ways to specify a @var{location}.)
24817 The breakpoint will stop execution of the inferior whenever it
24818 executes an instruction at any address within the specified range,
24819 (including @var{start-location} and @var{end-location}.)
24821 @kindex set powerpc
24822 @item set powerpc soft-float
24823 @itemx show powerpc soft-float
24824 Force @value{GDBN} to use (or not use) a software floating point calling
24825 convention. By default, @value{GDBN} selects the calling convention based
24826 on the selected architecture and the provided executable file.
24828 @item set powerpc vector-abi
24829 @itemx show powerpc vector-abi
24830 Force @value{GDBN} to use the specified calling convention for vector
24831 arguments and return values. The valid options are @samp{auto};
24832 @samp{generic}, to avoid vector registers even if they are present;
24833 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
24834 registers. By default, @value{GDBN} selects the calling convention
24835 based on the selected architecture and the provided executable file.
24837 @item set powerpc exact-watchpoints
24838 @itemx show powerpc exact-watchpoints
24839 Allow @value{GDBN} to use only one debug register when watching a variable
24840 of scalar type, thus assuming that the variable is accessed through the
24841 address of its first byte.
24846 @subsection Atmel AVR
24849 When configured for debugging the Atmel AVR, @value{GDBN} supports the
24850 following AVR-specific commands:
24853 @item info io_registers
24854 @kindex info io_registers@r{, AVR}
24855 @cindex I/O registers (Atmel AVR)
24856 This command displays information about the AVR I/O registers. For
24857 each register, @value{GDBN} prints its number and value.
24864 When configured for debugging CRIS, @value{GDBN} provides the
24865 following CRIS-specific commands:
24868 @item set cris-version @var{ver}
24869 @cindex CRIS version
24870 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
24871 The CRIS version affects register names and sizes. This command is useful in
24872 case autodetection of the CRIS version fails.
24874 @item show cris-version
24875 Show the current CRIS version.
24877 @item set cris-dwarf2-cfi
24878 @cindex DWARF-2 CFI and CRIS
24879 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
24880 Change to @samp{off} when using @code{gcc-cris} whose version is below
24883 @item show cris-dwarf2-cfi
24884 Show the current state of using DWARF-2 CFI.
24886 @item set cris-mode @var{mode}
24888 Set the current CRIS mode to @var{mode}. It should only be changed when
24889 debugging in guru mode, in which case it should be set to
24890 @samp{guru} (the default is @samp{normal}).
24892 @item show cris-mode
24893 Show the current CRIS mode.
24897 @subsection Renesas Super-H
24900 For the Renesas Super-H processor, @value{GDBN} provides these
24904 @item set sh calling-convention @var{convention}
24905 @kindex set sh calling-convention
24906 Set the calling-convention used when calling functions from @value{GDBN}.
24907 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
24908 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
24909 convention. If the DWARF-2 information of the called function specifies
24910 that the function follows the Renesas calling convention, the function
24911 is called using the Renesas calling convention. If the calling convention
24912 is set to @samp{renesas}, the Renesas calling convention is always used,
24913 regardless of the DWARF-2 information. This can be used to override the
24914 default of @samp{gcc} if debug information is missing, or the compiler
24915 does not emit the DWARF-2 calling convention entry for a function.
24917 @item show sh calling-convention
24918 @kindex show sh calling-convention
24919 Show the current calling convention setting.
24924 @node Architectures
24925 @section Architectures
24927 This section describes characteristics of architectures that affect
24928 all uses of @value{GDBN} with the architecture, both native and cross.
24935 * HPPA:: HP PA architecture
24943 @subsection AArch64
24944 @cindex AArch64 support
24946 When @value{GDBN} is debugging the AArch64 architecture, it provides the
24947 following special commands:
24950 @item set debug aarch64
24951 @kindex set debug aarch64
24952 This command determines whether AArch64 architecture-specific debugging
24953 messages are to be displayed.
24955 @item show debug aarch64
24956 Show whether AArch64 debugging messages are displayed.
24960 @subsubsection AArch64 SVE.
24961 @cindex AArch64 SVE.
24963 When @value{GDBN} is debugging the AArch64 architecture, if the Scalable Vector
24964 Extension (SVE) is present, then @value{GDBN} will provide the vector registers
24965 @code{$z0} through @code{$z31}, vector predicate registers @code{$p0} through
24966 @code{$p15}, and the @code{$ffr} register. In addition, the pseudo register
24967 @code{$vg} will be provided. This is the vector granule for the current thread
24968 and represents the number of 64-bit chunks in an SVE @code{z} register.
24970 If the vector length changes, then the @code{$vg} register will be updated,
24971 but the lengths of the @code{z} and @code{p} registers will not change. This
24972 is a known limitation of @value{GDBN} and does not affect the execution of the
24975 @subsubsection AArch64 Pointer Authentication.
24976 @cindex AArch64 Pointer Authentication.
24978 When @value{GDBN} is debugging the AArch64 architecture, and the program is
24979 using the v8.3-A feature Pointer Authentication (PAC), then whenever the link
24980 register @code{$lr} is pointing to an PAC function its value will be masked.
24981 When GDB prints a backtrace, any addresses that required unmasking will be
24982 postfixed with the marker [PAC]. When using the MI, this is printed as part
24983 of the @code{addr_flags} field.
24986 @subsection x86 Architecture-specific Issues
24989 @item set struct-convention @var{mode}
24990 @kindex set struct-convention
24991 @cindex struct return convention
24992 @cindex struct/union returned in registers
24993 Set the convention used by the inferior to return @code{struct}s and
24994 @code{union}s from functions to @var{mode}. Possible values of
24995 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
24996 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
24997 are returned on the stack, while @code{"reg"} means that a
24998 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
24999 be returned in a register.
25001 @item show struct-convention
25002 @kindex show struct-convention
25003 Show the current setting of the convention to return @code{struct}s
25008 @subsubsection Intel @dfn{Memory Protection Extensions} (MPX).
25009 @cindex Intel Memory Protection Extensions (MPX).
25011 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
25012 @footnote{The register named with capital letters represent the architecture
25013 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
25014 which are the lower bound and upper bound. Bounds are effective addresses or
25015 memory locations. The upper bounds are architecturally represented in 1's
25016 complement form. A bound having lower bound = 0, and upper bound = 0
25017 (1's complement of all bits set) will allow access to the entire address space.
25019 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
25020 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
25021 display the upper bound performing the complement of one operation on the
25022 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
25023 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
25024 can also be noted that the upper bounds are inclusive.
25026 As an example, assume that the register BND0 holds bounds for a pointer having
25027 access allowed for the range between 0x32 and 0x71. The values present on
25028 bnd0raw and bnd registers are presented as follows:
25031 bnd0raw = @{0x32, 0xffffffff8e@}
25032 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
25035 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
25036 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
25037 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
25038 Python, the display includes the memory size, in bits, accessible to
25041 Bounds can also be stored in bounds tables, which are stored in
25042 application memory. These tables store bounds for pointers by specifying
25043 the bounds pointer's value along with its bounds. Evaluating and changing
25044 bounds located in bound tables is therefore interesting while investigating
25045 bugs on MPX context. @value{GDBN} provides commands for this purpose:
25048 @item show mpx bound @var{pointer}
25049 @kindex show mpx bound
25050 Display bounds of the given @var{pointer}.
25052 @item set mpx bound @var{pointer}, @var{lbound}, @var{ubound}
25053 @kindex set mpx bound
25054 Set the bounds of a pointer in the bound table.
25055 This command takes three parameters: @var{pointer} is the pointers
25056 whose bounds are to be changed, @var{lbound} and @var{ubound} are new values
25057 for lower and upper bounds respectively.
25060 When you call an inferior function on an Intel MPX enabled program,
25061 GDB sets the inferior's bound registers to the init (disabled) state
25062 before calling the function. As a consequence, bounds checks for the
25063 pointer arguments passed to the function will always pass.
25065 This is necessary because when you call an inferior function, the
25066 program is usually in the middle of the execution of other function.
25067 Since at that point bound registers are in an arbitrary state, not
25068 clearing them would lead to random bound violations in the called
25071 You can still examine the influence of the bound registers on the
25072 execution of the called function by stopping the execution of the
25073 called function at its prologue, setting bound registers, and
25074 continuing the execution. For example:
25078 Breakpoint 2 at 0x4009de: file i386-mpx-call.c, line 47.
25079 $ print upper (a, b, c, d, 1)
25080 Breakpoint 2, upper (a=0x0, b=0x6e0000005b, c=0x0, d=0x0, len=48)....
25082 @{lbound = 0x0, ubound = ffffffff@} : size -1
25085 At this last step the value of bnd0 can be changed for investigation of bound
25086 violations caused along the execution of the call. In order to know how to
25087 set the bound registers or bound table for the call consult the ABI.
25092 See the following section.
25095 @subsection @acronym{MIPS}
25097 @cindex stack on Alpha
25098 @cindex stack on @acronym{MIPS}
25099 @cindex Alpha stack
25100 @cindex @acronym{MIPS} stack
25101 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
25102 sometimes requires @value{GDBN} to search backward in the object code to
25103 find the beginning of a function.
25105 @cindex response time, @acronym{MIPS} debugging
25106 To improve response time (especially for embedded applications, where
25107 @value{GDBN} may be restricted to a slow serial line for this search)
25108 you may want to limit the size of this search, using one of these
25112 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
25113 @item set heuristic-fence-post @var{limit}
25114 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
25115 search for the beginning of a function. A value of @var{0} (the
25116 default) means there is no limit. However, except for @var{0}, the
25117 larger the limit the more bytes @code{heuristic-fence-post} must search
25118 and therefore the longer it takes to run. You should only need to use
25119 this command when debugging a stripped executable.
25121 @item show heuristic-fence-post
25122 Display the current limit.
25126 These commands are available @emph{only} when @value{GDBN} is configured
25127 for debugging programs on Alpha or @acronym{MIPS} processors.
25129 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
25133 @item set mips abi @var{arg}
25134 @kindex set mips abi
25135 @cindex set ABI for @acronym{MIPS}
25136 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
25137 values of @var{arg} are:
25141 The default ABI associated with the current binary (this is the
25151 @item show mips abi
25152 @kindex show mips abi
25153 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
25155 @item set mips compression @var{arg}
25156 @kindex set mips compression
25157 @cindex code compression, @acronym{MIPS}
25158 Tell @value{GDBN} which @acronym{MIPS} compressed
25159 @acronym{ISA, Instruction Set Architecture} encoding is used by the
25160 inferior. @value{GDBN} uses this for code disassembly and other
25161 internal interpretation purposes. This setting is only referred to
25162 when no executable has been associated with the debugging session or
25163 the executable does not provide information about the encoding it uses.
25164 Otherwise this setting is automatically updated from information
25165 provided by the executable.
25167 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
25168 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
25169 executables containing @acronym{MIPS16} code frequently are not
25170 identified as such.
25172 This setting is ``sticky''; that is, it retains its value across
25173 debugging sessions until reset either explicitly with this command or
25174 implicitly from an executable.
25176 The compiler and/or assembler typically add symbol table annotations to
25177 identify functions compiled for the @acronym{MIPS16} or
25178 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
25179 are present, @value{GDBN} uses them in preference to the global
25180 compressed @acronym{ISA} encoding setting.
25182 @item show mips compression
25183 @kindex show mips compression
25184 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
25185 @value{GDBN} to debug the inferior.
25188 @itemx show mipsfpu
25189 @xref{MIPS Embedded, set mipsfpu}.
25191 @item set mips mask-address @var{arg}
25192 @kindex set mips mask-address
25193 @cindex @acronym{MIPS} addresses, masking
25194 This command determines whether the most-significant 32 bits of 64-bit
25195 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
25196 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
25197 setting, which lets @value{GDBN} determine the correct value.
25199 @item show mips mask-address
25200 @kindex show mips mask-address
25201 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
25204 @item set remote-mips64-transfers-32bit-regs
25205 @kindex set remote-mips64-transfers-32bit-regs
25206 This command controls compatibility with 64-bit @acronym{MIPS} targets that
25207 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
25208 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
25209 and 64 bits for other registers, set this option to @samp{on}.
25211 @item show remote-mips64-transfers-32bit-regs
25212 @kindex show remote-mips64-transfers-32bit-regs
25213 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
25215 @item set debug mips
25216 @kindex set debug mips
25217 This command turns on and off debugging messages for the @acronym{MIPS}-specific
25218 target code in @value{GDBN}.
25220 @item show debug mips
25221 @kindex show debug mips
25222 Show the current setting of @acronym{MIPS} debugging messages.
25228 @cindex HPPA support
25230 When @value{GDBN} is debugging the HP PA architecture, it provides the
25231 following special commands:
25234 @item set debug hppa
25235 @kindex set debug hppa
25236 This command determines whether HPPA architecture-specific debugging
25237 messages are to be displayed.
25239 @item show debug hppa
25240 Show whether HPPA debugging messages are displayed.
25242 @item maint print unwind @var{address}
25243 @kindex maint print unwind@r{, HPPA}
25244 This command displays the contents of the unwind table entry at the
25245 given @var{address}.
25251 @subsection PowerPC
25252 @cindex PowerPC architecture
25254 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
25255 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
25256 numbers stored in the floating point registers. These values must be stored
25257 in two consecutive registers, always starting at an even register like
25258 @code{f0} or @code{f2}.
25260 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
25261 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
25262 @code{f2} and @code{f3} for @code{$dl1} and so on.
25264 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
25265 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
25268 @subsection Nios II
25269 @cindex Nios II architecture
25271 When @value{GDBN} is debugging the Nios II architecture,
25272 it provides the following special commands:
25276 @item set debug nios2
25277 @kindex set debug nios2
25278 This command turns on and off debugging messages for the Nios II
25279 target code in @value{GDBN}.
25281 @item show debug nios2
25282 @kindex show debug nios2
25283 Show the current setting of Nios II debugging messages.
25287 @subsection Sparc64
25288 @cindex Sparc64 support
25289 @cindex Application Data Integrity
25290 @subsubsection ADI Support
25292 The M7 processor supports an Application Data Integrity (ADI) feature that
25293 detects invalid data accesses. When software allocates memory and enables
25294 ADI on the allocated memory, it chooses a 4-bit version number, sets the
25295 version in the upper 4 bits of the 64-bit pointer to that data, and stores
25296 the 4-bit version in every cacheline of that data. Hardware saves the latter
25297 in spare bits in the cache and memory hierarchy. On each load and store,
25298 the processor compares the upper 4 VA (virtual address) bits to the
25299 cacheline's version. If there is a mismatch, the processor generates a
25300 version mismatch trap which can be either precise or disrupting. The trap
25301 is an error condition which the kernel delivers to the process as a SIGSEGV
25304 Note that only 64-bit applications can use ADI and need to be built with
25307 Values of the ADI version tags, which are in granularity of a
25308 cacheline (64 bytes), can be viewed or modified.
25312 @kindex adi examine
25313 @item adi (examine | x) [ / @var{n} ] @var{addr}
25315 The @code{adi examine} command displays the value of one ADI version tag per
25318 @var{n} is a decimal integer specifying the number in bytes; the default
25319 is 1. It specifies how much ADI version information, at the ratio of 1:ADI
25320 block size, to display.
25322 @var{addr} is the address in user address space where you want @value{GDBN}
25323 to begin displaying the ADI version tags.
25325 Below is an example of displaying ADI versions of variable "shmaddr".
25328 (@value{GDBP}) adi x/100 shmaddr
25329 0xfff800010002c000: 0 0
25333 @item adi (assign | a) [ / @var{n} ] @var{addr} = @var{tag}
25335 The @code{adi assign} command is used to assign new ADI version tag
25338 @var{n} is a decimal integer specifying the number in bytes;
25339 the default is 1. It specifies how much ADI version information, at the
25340 ratio of 1:ADI block size, to modify.
25342 @var{addr} is the address in user address space where you want @value{GDBN}
25343 to begin modifying the ADI version tags.
25345 @var{tag} is the new ADI version tag.
25347 For example, do the following to modify then verify ADI versions of
25348 variable "shmaddr":
25351 (@value{GDBP}) adi a/100 shmaddr = 7
25352 (@value{GDBP}) adi x/100 shmaddr
25353 0xfff800010002c000: 7 7
25360 @cindex S12Z support
25362 When @value{GDBN} is debugging the S12Z architecture,
25363 it provides the following special command:
25366 @item maint info bdccsr
25367 @kindex maint info bdccsr@r{, S12Z}
25368 This command displays the current value of the microprocessor's
25373 @node Controlling GDB
25374 @chapter Controlling @value{GDBN}
25376 You can alter the way @value{GDBN} interacts with you by using the
25377 @code{set} command. For commands controlling how @value{GDBN} displays
25378 data, see @ref{Print Settings, ,Print Settings}. Other settings are
25383 * Editing:: Command editing
25384 * Command History:: Command history
25385 * Screen Size:: Screen size
25386 * Output Styling:: Output styling
25387 * Numbers:: Numbers
25388 * ABI:: Configuring the current ABI
25389 * Auto-loading:: Automatically loading associated files
25390 * Messages/Warnings:: Optional warnings and messages
25391 * Debugging Output:: Optional messages about internal happenings
25392 * Other Misc Settings:: Other Miscellaneous Settings
25400 @value{GDBN} indicates its readiness to read a command by printing a string
25401 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
25402 can change the prompt string with the @code{set prompt} command. For
25403 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
25404 the prompt in one of the @value{GDBN} sessions so that you can always tell
25405 which one you are talking to.
25407 @emph{Note:} @code{set prompt} does not add a space for you after the
25408 prompt you set. This allows you to set a prompt which ends in a space
25409 or a prompt that does not.
25413 @item set prompt @var{newprompt}
25414 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
25416 @kindex show prompt
25418 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
25421 Versions of @value{GDBN} that ship with Python scripting enabled have
25422 prompt extensions. The commands for interacting with these extensions
25426 @kindex set extended-prompt
25427 @item set extended-prompt @var{prompt}
25428 Set an extended prompt that allows for substitutions.
25429 @xref{gdb.prompt}, for a list of escape sequences that can be used for
25430 substitution. Any escape sequences specified as part of the prompt
25431 string are replaced with the corresponding strings each time the prompt
25437 set extended-prompt Current working directory: \w (gdb)
25440 Note that when an extended-prompt is set, it takes control of the
25441 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
25443 @kindex show extended-prompt
25444 @item show extended-prompt
25445 Prints the extended prompt. Any escape sequences specified as part of
25446 the prompt string with @code{set extended-prompt}, are replaced with the
25447 corresponding strings each time the prompt is displayed.
25451 @section Command Editing
25453 @cindex command line editing
25455 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
25456 @sc{gnu} library provides consistent behavior for programs which provide a
25457 command line interface to the user. Advantages are @sc{gnu} Emacs-style
25458 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
25459 substitution, and a storage and recall of command history across
25460 debugging sessions.
25462 You may control the behavior of command line editing in @value{GDBN} with the
25463 command @code{set}.
25466 @kindex set editing
25469 @itemx set editing on
25470 Enable command line editing (enabled by default).
25472 @item set editing off
25473 Disable command line editing.
25475 @kindex show editing
25477 Show whether command line editing is enabled.
25480 @ifset SYSTEM_READLINE
25481 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
25483 @ifclear SYSTEM_READLINE
25484 @xref{Command Line Editing},
25486 for more details about the Readline
25487 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
25488 encouraged to read that chapter.
25490 @cindex Readline application name
25491 @value{GDBN} sets the Readline application name to @samp{gdb}. This
25492 is useful for conditions in @file{.inputrc}.
25494 @cindex operate-and-get-next
25495 @value{GDBN} defines a bindable Readline command,
25496 @code{operate-and-get-next}. This is bound to @kbd{C-o} by default.
25497 This command accepts the current line for execution and fetches the
25498 next line relative to the current line from the history for editing.
25499 Any argument is ignored.
25501 @node Command History
25502 @section Command History
25503 @cindex command history
25505 @value{GDBN} can keep track of the commands you type during your
25506 debugging sessions, so that you can be certain of precisely what
25507 happened. Use these commands to manage the @value{GDBN} command
25510 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
25511 package, to provide the history facility.
25512 @ifset SYSTEM_READLINE
25513 @xref{Using History Interactively, , , history, GNU History Library},
25515 @ifclear SYSTEM_READLINE
25516 @xref{Using History Interactively},
25518 for the detailed description of the History library.
25520 To issue a command to @value{GDBN} without affecting certain aspects of
25521 the state which is seen by users, prefix it with @samp{server }
25522 (@pxref{Server Prefix}). This
25523 means that this command will not affect the command history, nor will it
25524 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
25525 pressed on a line by itself.
25527 @cindex @code{server}, command prefix
25528 The server prefix does not affect the recording of values into the value
25529 history; to print a value without recording it into the value history,
25530 use the @code{output} command instead of the @code{print} command.
25532 Here is the description of @value{GDBN} commands related to command
25536 @cindex history substitution
25537 @cindex history file
25538 @kindex set history filename
25539 @cindex @env{GDBHISTFILE}, environment variable
25540 @item set history filename @r{[}@var{fname}@r{]}
25541 Set the name of the @value{GDBN} command history file to @var{fname}.
25542 This is the file where @value{GDBN} reads an initial command history
25543 list, and where it writes the command history from this session when it
25544 exits. You can access this list through history expansion or through
25545 the history command editing characters listed below. This file defaults
25546 to the value of the environment variable @code{GDBHISTFILE}, or to
25547 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
25550 The @code{GDBHISTFILE} environment variable is read after processing
25551 any @value{GDBN} initialization files (@pxref{Startup}) and after
25552 processing any commands passed using command line options (for
25553 example, @code{-ex}).
25555 If the @var{fname} argument is not given, or if the @code{GDBHISTFILE}
25556 is the empty string then @value{GDBN} will neither try to load an
25557 existing history file, nor will it try to save the history on exit.
25559 @cindex save command history
25560 @kindex set history save
25561 @item set history save
25562 @itemx set history save on
25563 Record command history in a file, whose name may be specified with the
25564 @code{set history filename} command. By default, this option is
25565 disabled. The command history will be recorded when @value{GDBN}
25566 exits. If @code{set history filename} is set to the empty string then
25567 history saving is disabled, even when @code{set history save} is
25570 @item set history save off
25571 Don't record the command history into the file specified by @code{set
25572 history filename} when @value{GDBN} exits.
25574 @cindex history size
25575 @kindex set history size
25576 @cindex @env{GDBHISTSIZE}, environment variable
25577 @item set history size @var{size}
25578 @itemx set history size unlimited
25579 Set the number of commands which @value{GDBN} keeps in its history list.
25580 This defaults to the value of the environment variable @env{GDBHISTSIZE}, or
25581 to 256 if this variable is not set. Non-numeric values of @env{GDBHISTSIZE}
25582 are ignored. If @var{size} is @code{unlimited} or if @env{GDBHISTSIZE} is
25583 either a negative number or the empty string, then the number of commands
25584 @value{GDBN} keeps in the history list is unlimited.
25586 The @code{GDBHISTSIZE} environment variable is read after processing
25587 any @value{GDBN} initialization files (@pxref{Startup}) and after
25588 processing any commands passed using command line options (for
25589 example, @code{-ex}).
25591 @cindex remove duplicate history
25592 @kindex set history remove-duplicates
25593 @item set history remove-duplicates @var{count}
25594 @itemx set history remove-duplicates unlimited
25595 Control the removal of duplicate history entries in the command history list.
25596 If @var{count} is non-zero, @value{GDBN} will look back at the last @var{count}
25597 history entries and remove the first entry that is a duplicate of the current
25598 entry being added to the command history list. If @var{count} is
25599 @code{unlimited} then this lookbehind is unbounded. If @var{count} is 0, then
25600 removal of duplicate history entries is disabled.
25602 Only history entries added during the current session are considered for
25603 removal. This option is set to 0 by default.
25607 History expansion assigns special meaning to the character @kbd{!}.
25608 @ifset SYSTEM_READLINE
25609 @xref{Event Designators, , , history, GNU History Library},
25611 @ifclear SYSTEM_READLINE
25612 @xref{Event Designators},
25616 @cindex history expansion, turn on/off
25617 Since @kbd{!} is also the logical not operator in C, history expansion
25618 is off by default. If you decide to enable history expansion with the
25619 @code{set history expansion on} command, you may sometimes need to
25620 follow @kbd{!} (when it is used as logical not, in an expression) with
25621 a space or a tab to prevent it from being expanded. The readline
25622 history facilities do not attempt substitution on the strings
25623 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
25625 The commands to control history expansion are:
25628 @item set history expansion on
25629 @itemx set history expansion
25630 @kindex set history expansion
25631 Enable history expansion. History expansion is off by default.
25633 @item set history expansion off
25634 Disable history expansion.
25637 @kindex show history
25639 @itemx show history filename
25640 @itemx show history save
25641 @itemx show history size
25642 @itemx show history expansion
25643 These commands display the state of the @value{GDBN} history parameters.
25644 @code{show history} by itself displays all four states.
25649 @kindex show commands
25650 @cindex show last commands
25651 @cindex display command history
25652 @item show commands
25653 Display the last ten commands in the command history.
25655 @item show commands @var{n}
25656 Print ten commands centered on command number @var{n}.
25658 @item show commands +
25659 Print ten commands just after the commands last printed.
25663 @section Screen Size
25664 @cindex size of screen
25665 @cindex screen size
25668 @cindex pauses in output
25670 Certain commands to @value{GDBN} may produce large amounts of
25671 information output to the screen. To help you read all of it,
25672 @value{GDBN} pauses and asks you for input at the end of each page of
25673 output. Type @key{RET} when you want to see one more page of output,
25674 @kbd{q} to discard the remaining output, or @kbd{c} to continue
25675 without paging for the rest of the current command. Also, the screen
25676 width setting determines when to wrap lines of output. Depending on
25677 what is being printed, @value{GDBN} tries to break the line at a
25678 readable place, rather than simply letting it overflow onto the
25681 Normally @value{GDBN} knows the size of the screen from the terminal
25682 driver software. For example, on Unix @value{GDBN} uses the termcap data base
25683 together with the value of the @code{TERM} environment variable and the
25684 @code{stty rows} and @code{stty cols} settings. If this is not correct,
25685 you can override it with the @code{set height} and @code{set
25692 @kindex show height
25693 @item set height @var{lpp}
25694 @itemx set height unlimited
25696 @itemx set width @var{cpl}
25697 @itemx set width unlimited
25699 These @code{set} commands specify a screen height of @var{lpp} lines and
25700 a screen width of @var{cpl} characters. The associated @code{show}
25701 commands display the current settings.
25703 If you specify a height of either @code{unlimited} or zero lines,
25704 @value{GDBN} does not pause during output no matter how long the
25705 output is. This is useful if output is to a file or to an editor
25708 Likewise, you can specify @samp{set width unlimited} or @samp{set
25709 width 0} to prevent @value{GDBN} from wrapping its output.
25711 @item set pagination on
25712 @itemx set pagination off
25713 @kindex set pagination
25714 Turn the output pagination on or off; the default is on. Turning
25715 pagination off is the alternative to @code{set height unlimited}. Note that
25716 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
25717 Options, -batch}) also automatically disables pagination.
25719 @item show pagination
25720 @kindex show pagination
25721 Show the current pagination mode.
25724 @node Output Styling
25725 @section Output Styling
25731 @value{GDBN} can style its output on a capable terminal. This is
25732 enabled by default on most systems, but disabled by default when in
25733 batch mode (@pxref{Mode Options}). Various style settings are available;
25734 and styles can also be disabled entirely.
25737 @item set style enabled @samp{on|off}
25738 Enable or disable all styling. The default is host-dependent, with
25739 most hosts defaulting to @samp{on}.
25741 @item show style enabled
25742 Show the current state of styling.
25744 @item set style sources @samp{on|off}
25745 Enable or disable source code styling. This affects whether source
25746 code, such as the output of the @code{list} command, is styled. Note
25747 that source styling only works if styling in general is enabled, and
25748 if @value{GDBN} was linked with the GNU Source Highlight library. The
25749 default is @samp{on}.
25751 @item show style sources
25752 Show the current state of source code styling.
25755 Subcommands of @code{set style} control specific forms of styling.
25756 These subcommands all follow the same pattern: each style-able object
25757 can be styled with a foreground color, a background color, and an
25760 For example, the style of file names can be controlled using the
25761 @code{set style filename} group of commands:
25764 @item set style filename background @var{color}
25765 Set the background to @var{color}. Valid colors are @samp{none}
25766 (meaning the terminal's default color), @samp{black}, @samp{red},
25767 @samp{green}, @samp{yellow}, @samp{blue}, @samp{magenta}, @samp{cyan},
25770 @item set style filename foreground @var{color}
25771 Set the foreground to @var{color}. Valid colors are @samp{none}
25772 (meaning the terminal's default color), @samp{black}, @samp{red},
25773 @samp{green}, @samp{yellow}, @samp{blue}, @samp{magenta}, @samp{cyan},
25776 @item set style filename intensity @var{value}
25777 Set the intensity to @var{value}. Valid intensities are @samp{normal}
25778 (the default), @samp{bold}, and @samp{dim}.
25781 The @code{show style} command and its subcommands are styling
25782 a style name in their output using its own style.
25783 So, use @command{show style} to see the complete list of styles,
25784 their characteristics and the visual aspect of each style.
25786 The style-able objects are:
25789 Control the styling of file names. By default, this style's
25790 foreground color is green.
25793 Control the styling of function names. These are managed with the
25794 @code{set style function} family of commands. By default, this
25795 style's foreground color is yellow.
25798 Control the styling of variable names. These are managed with the
25799 @code{set style variable} family of commands. By default, this style's
25800 foreground color is cyan.
25803 Control the styling of addresses. These are managed with the
25804 @code{set style address} family of commands. By default, this style's
25805 foreground color is blue.
25808 Control the styling of @value{GDBN}'s version number text. By
25809 default, this style's foreground color is magenta and it has bold
25810 intensity. The version number is displayed in two places, the output
25811 of @command{show version}, and when @value{GDBN} starts up.
25813 Currently the version string displayed at startup is printed before
25814 @value{GDBN} has parsed any command line options, or parsed any
25815 command files, so there is currently no way to control the styling of
25816 this string. However, @value{GDBN}'s @code{--quiet} command line option
25817 can be used to disable printing of the version string on startup.
25820 Control the styling of titles. These are managed with the
25821 @code{set style title} family of commands. By default, this style's
25822 intensity is bold. Commands are using the title style to improve
25823 the readability of large output. For example, the commands
25824 @command{apropos} and @command{help} are using the title style
25825 for the command names.
25828 Control the styling of highlightings. These are managed with the
25829 @code{set style highlight} family of commands. By default, this style's
25830 foreground color is red. Commands are using the highlight style to draw
25831 the user attention to some specific parts of their output. For example,
25832 the command @command{apropos -v REGEXP} uses the highlight style to
25833 mark the documentation parts matching @var{regexp}.
25836 Control the styling of the TUI border. Note that, unlike other
25837 styling options, only the color of the border can be controlled via
25838 @code{set style}. This was done for compatibility reasons, as TUI
25839 controls to set the border's intensity predated the addition of
25840 general styling to @value{GDBN}. @xref{TUI Configuration}.
25842 @item tui-active-border
25843 Control the styling of the active TUI border; that is, the TUI window
25844 that has the focus.
25850 @cindex number representation
25851 @cindex entering numbers
25853 You can always enter numbers in octal, decimal, or hexadecimal in
25854 @value{GDBN} by the usual conventions: octal numbers begin with
25855 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
25856 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
25857 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
25858 10; likewise, the default display for numbers---when no particular
25859 format is specified---is base 10. You can change the default base for
25860 both input and output with the commands described below.
25863 @kindex set input-radix
25864 @item set input-radix @var{base}
25865 Set the default base for numeric input. Supported choices
25866 for @var{base} are decimal 8, 10, or 16. The base must itself be
25867 specified either unambiguously or using the current input radix; for
25871 set input-radix 012
25872 set input-radix 10.
25873 set input-radix 0xa
25877 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
25878 leaves the input radix unchanged, no matter what it was, since
25879 @samp{10}, being without any leading or trailing signs of its base, is
25880 interpreted in the current radix. Thus, if the current radix is 16,
25881 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
25884 @kindex set output-radix
25885 @item set output-radix @var{base}
25886 Set the default base for numeric display. Supported choices
25887 for @var{base} are decimal 8, 10, or 16. The base must itself be
25888 specified either unambiguously or using the current input radix.
25890 @kindex show input-radix
25891 @item show input-radix
25892 Display the current default base for numeric input.
25894 @kindex show output-radix
25895 @item show output-radix
25896 Display the current default base for numeric display.
25898 @item set radix @r{[}@var{base}@r{]}
25902 These commands set and show the default base for both input and output
25903 of numbers. @code{set radix} sets the radix of input and output to
25904 the same base; without an argument, it resets the radix back to its
25905 default value of 10.
25910 @section Configuring the Current ABI
25912 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
25913 application automatically. However, sometimes you need to override its
25914 conclusions. Use these commands to manage @value{GDBN}'s view of the
25920 @cindex Newlib OS ABI and its influence on the longjmp handling
25922 One @value{GDBN} configuration can debug binaries for multiple operating
25923 system targets, either via remote debugging or native emulation.
25924 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
25925 but you can override its conclusion using the @code{set osabi} command.
25926 One example where this is useful is in debugging of binaries which use
25927 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
25928 not have the same identifying marks that the standard C library for your
25931 When @value{GDBN} is debugging the AArch64 architecture, it provides a
25932 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
25933 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
25934 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
25938 Show the OS ABI currently in use.
25941 With no argument, show the list of registered available OS ABI's.
25943 @item set osabi @var{abi}
25944 Set the current OS ABI to @var{abi}.
25947 @cindex float promotion
25949 Generally, the way that an argument of type @code{float} is passed to a
25950 function depends on whether the function is prototyped. For a prototyped
25951 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
25952 according to the architecture's convention for @code{float}. For unprototyped
25953 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
25954 @code{double} and then passed.
25956 Unfortunately, some forms of debug information do not reliably indicate whether
25957 a function is prototyped. If @value{GDBN} calls a function that is not marked
25958 as prototyped, it consults @kbd{set coerce-float-to-double}.
25961 @kindex set coerce-float-to-double
25962 @item set coerce-float-to-double
25963 @itemx set coerce-float-to-double on
25964 Arguments of type @code{float} will be promoted to @code{double} when passed
25965 to an unprototyped function. This is the default setting.
25967 @item set coerce-float-to-double off
25968 Arguments of type @code{float} will be passed directly to unprototyped
25971 @kindex show coerce-float-to-double
25972 @item show coerce-float-to-double
25973 Show the current setting of promoting @code{float} to @code{double}.
25977 @kindex show cp-abi
25978 @value{GDBN} needs to know the ABI used for your program's C@t{++}
25979 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
25980 used to build your application. @value{GDBN} only fully supports
25981 programs with a single C@t{++} ABI; if your program contains code using
25982 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
25983 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
25984 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
25985 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
25986 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
25987 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
25992 Show the C@t{++} ABI currently in use.
25995 With no argument, show the list of supported C@t{++} ABI's.
25997 @item set cp-abi @var{abi}
25998 @itemx set cp-abi auto
25999 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
26003 @section Automatically loading associated files
26004 @cindex auto-loading
26006 @value{GDBN} sometimes reads files with commands and settings automatically,
26007 without being explicitly told so by the user. We call this feature
26008 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
26009 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
26010 results or introduce security risks (e.g., if the file comes from untrusted
26013 There are various kinds of files @value{GDBN} can automatically load.
26014 In addition to these files, @value{GDBN} supports auto-loading code written
26015 in various extension languages. @xref{Auto-loading extensions}.
26017 Note that loading of these associated files (including the local @file{.gdbinit}
26018 file) requires accordingly configured @code{auto-load safe-path}
26019 (@pxref{Auto-loading safe path}).
26021 For these reasons, @value{GDBN} includes commands and options to let you
26022 control when to auto-load files and which files should be auto-loaded.
26025 @anchor{set auto-load off}
26026 @kindex set auto-load off
26027 @item set auto-load off
26028 Globally disable loading of all auto-loaded files.
26029 You may want to use this command with the @samp{-iex} option
26030 (@pxref{Option -init-eval-command}) such as:
26032 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
26035 Be aware that system init file (@pxref{System-wide configuration})
26036 and init files from your home directory (@pxref{Home Directory Init File})
26037 still get read (as they come from generally trusted directories).
26038 To prevent @value{GDBN} from auto-loading even those init files, use the
26039 @option{-nx} option (@pxref{Mode Options}), in addition to
26040 @code{set auto-load no}.
26042 @anchor{show auto-load}
26043 @kindex show auto-load
26044 @item show auto-load
26045 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
26049 (gdb) show auto-load
26050 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
26051 libthread-db: Auto-loading of inferior specific libthread_db is on.
26052 local-gdbinit: Auto-loading of .gdbinit script from current directory
26054 python-scripts: Auto-loading of Python scripts is on.
26055 safe-path: List of directories from which it is safe to auto-load files
26056 is $debugdir:$datadir/auto-load.
26057 scripts-directory: List of directories from which to load auto-loaded scripts
26058 is $debugdir:$datadir/auto-load.
26061 @anchor{info auto-load}
26062 @kindex info auto-load
26063 @item info auto-load
26064 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
26068 (gdb) info auto-load
26071 Yes /home/user/gdb/gdb-gdb.gdb
26072 libthread-db: No auto-loaded libthread-db.
26073 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
26077 Yes /home/user/gdb/gdb-gdb.py
26081 These are @value{GDBN} control commands for the auto-loading:
26083 @multitable @columnfractions .5 .5
26084 @item @xref{set auto-load off}.
26085 @tab Disable auto-loading globally.
26086 @item @xref{show auto-load}.
26087 @tab Show setting of all kinds of files.
26088 @item @xref{info auto-load}.
26089 @tab Show state of all kinds of files.
26090 @item @xref{set auto-load gdb-scripts}.
26091 @tab Control for @value{GDBN} command scripts.
26092 @item @xref{show auto-load gdb-scripts}.
26093 @tab Show setting of @value{GDBN} command scripts.
26094 @item @xref{info auto-load gdb-scripts}.
26095 @tab Show state of @value{GDBN} command scripts.
26096 @item @xref{set auto-load python-scripts}.
26097 @tab Control for @value{GDBN} Python scripts.
26098 @item @xref{show auto-load python-scripts}.
26099 @tab Show setting of @value{GDBN} Python scripts.
26100 @item @xref{info auto-load python-scripts}.
26101 @tab Show state of @value{GDBN} Python scripts.
26102 @item @xref{set auto-load guile-scripts}.
26103 @tab Control for @value{GDBN} Guile scripts.
26104 @item @xref{show auto-load guile-scripts}.
26105 @tab Show setting of @value{GDBN} Guile scripts.
26106 @item @xref{info auto-load guile-scripts}.
26107 @tab Show state of @value{GDBN} Guile scripts.
26108 @item @xref{set auto-load scripts-directory}.
26109 @tab Control for @value{GDBN} auto-loaded scripts location.
26110 @item @xref{show auto-load scripts-directory}.
26111 @tab Show @value{GDBN} auto-loaded scripts location.
26112 @item @xref{add-auto-load-scripts-directory}.
26113 @tab Add directory for auto-loaded scripts location list.
26114 @item @xref{set auto-load local-gdbinit}.
26115 @tab Control for init file in the current directory.
26116 @item @xref{show auto-load local-gdbinit}.
26117 @tab Show setting of init file in the current directory.
26118 @item @xref{info auto-load local-gdbinit}.
26119 @tab Show state of init file in the current directory.
26120 @item @xref{set auto-load libthread-db}.
26121 @tab Control for thread debugging library.
26122 @item @xref{show auto-load libthread-db}.
26123 @tab Show setting of thread debugging library.
26124 @item @xref{info auto-load libthread-db}.
26125 @tab Show state of thread debugging library.
26126 @item @xref{set auto-load safe-path}.
26127 @tab Control directories trusted for automatic loading.
26128 @item @xref{show auto-load safe-path}.
26129 @tab Show directories trusted for automatic loading.
26130 @item @xref{add-auto-load-safe-path}.
26131 @tab Add directory trusted for automatic loading.
26135 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
26136 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
26138 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
26139 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
26142 @node Init File in the Current Directory
26143 @subsection Automatically loading init file in the current directory
26144 @cindex auto-loading init file in the current directory
26146 By default, @value{GDBN} reads and executes the canned sequences of commands
26147 from init file (if any) in the current working directory,
26148 see @ref{Init File in the Current Directory during Startup}.
26150 Note that loading of this local @file{.gdbinit} file also requires accordingly
26151 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26154 @anchor{set auto-load local-gdbinit}
26155 @kindex set auto-load local-gdbinit
26156 @item set auto-load local-gdbinit [on|off]
26157 Enable or disable the auto-loading of canned sequences of commands
26158 (@pxref{Sequences}) found in init file in the current directory.
26160 @anchor{show auto-load local-gdbinit}
26161 @kindex show auto-load local-gdbinit
26162 @item show auto-load local-gdbinit
26163 Show whether auto-loading of canned sequences of commands from init file in the
26164 current directory is enabled or disabled.
26166 @anchor{info auto-load local-gdbinit}
26167 @kindex info auto-load local-gdbinit
26168 @item info auto-load local-gdbinit
26169 Print whether canned sequences of commands from init file in the
26170 current directory have been auto-loaded.
26173 @node libthread_db.so.1 file
26174 @subsection Automatically loading thread debugging library
26175 @cindex auto-loading libthread_db.so.1
26177 This feature is currently present only on @sc{gnu}/Linux native hosts.
26179 @value{GDBN} reads in some cases thread debugging library from places specific
26180 to the inferior (@pxref{set libthread-db-search-path}).
26182 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
26183 without checking this @samp{set auto-load libthread-db} switch as system
26184 libraries have to be trusted in general. In all other cases of
26185 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
26186 auto-load libthread-db} is enabled before trying to open such thread debugging
26189 Note that loading of this debugging library also requires accordingly configured
26190 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26193 @anchor{set auto-load libthread-db}
26194 @kindex set auto-load libthread-db
26195 @item set auto-load libthread-db [on|off]
26196 Enable or disable the auto-loading of inferior specific thread debugging library.
26198 @anchor{show auto-load libthread-db}
26199 @kindex show auto-load libthread-db
26200 @item show auto-load libthread-db
26201 Show whether auto-loading of inferior specific thread debugging library is
26202 enabled or disabled.
26204 @anchor{info auto-load libthread-db}
26205 @kindex info auto-load libthread-db
26206 @item info auto-load libthread-db
26207 Print the list of all loaded inferior specific thread debugging libraries and
26208 for each such library print list of inferior @var{pid}s using it.
26211 @node Auto-loading safe path
26212 @subsection Security restriction for auto-loading
26213 @cindex auto-loading safe-path
26215 As the files of inferior can come from untrusted source (such as submitted by
26216 an application user) @value{GDBN} does not always load any files automatically.
26217 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
26218 directories trusted for loading files not explicitly requested by user.
26219 Each directory can also be a shell wildcard pattern.
26221 If the path is not set properly you will see a warning and the file will not
26226 Reading symbols from /home/user/gdb/gdb...
26227 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
26228 declined by your `auto-load safe-path' set
26229 to "$debugdir:$datadir/auto-load".
26230 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
26231 declined by your `auto-load safe-path' set
26232 to "$debugdir:$datadir/auto-load".
26236 To instruct @value{GDBN} to go ahead and use the init files anyway,
26237 invoke @value{GDBN} like this:
26240 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
26243 The list of trusted directories is controlled by the following commands:
26246 @anchor{set auto-load safe-path}
26247 @kindex set auto-load safe-path
26248 @item set auto-load safe-path @r{[}@var{directories}@r{]}
26249 Set the list of directories (and their subdirectories) trusted for automatic
26250 loading and execution of scripts. You can also enter a specific trusted file.
26251 Each directory can also be a shell wildcard pattern; wildcards do not match
26252 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
26253 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
26254 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
26255 its default value as specified during @value{GDBN} compilation.
26257 The list of directories uses path separator (@samp{:} on GNU and Unix
26258 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
26259 to the @env{PATH} environment variable.
26261 @anchor{show auto-load safe-path}
26262 @kindex show auto-load safe-path
26263 @item show auto-load safe-path
26264 Show the list of directories trusted for automatic loading and execution of
26267 @anchor{add-auto-load-safe-path}
26268 @kindex add-auto-load-safe-path
26269 @item add-auto-load-safe-path
26270 Add an entry (or list of entries) to the list of directories trusted for
26271 automatic loading and execution of scripts. Multiple entries may be delimited
26272 by the host platform path separator in use.
26275 This variable defaults to what @code{--with-auto-load-dir} has been configured
26276 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
26277 substitution applies the same as for @ref{set auto-load scripts-directory}.
26278 The default @code{set auto-load safe-path} value can be also overriden by
26279 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
26281 Setting this variable to @file{/} disables this security protection,
26282 corresponding @value{GDBN} configuration option is
26283 @option{--without-auto-load-safe-path}.
26284 This variable is supposed to be set to the system directories writable by the
26285 system superuser only. Users can add their source directories in init files in
26286 their home directories (@pxref{Home Directory Init File}). See also deprecated
26287 init file in the current directory
26288 (@pxref{Init File in the Current Directory during Startup}).
26290 To force @value{GDBN} to load the files it declined to load in the previous
26291 example, you could use one of the following ways:
26294 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
26295 Specify this trusted directory (or a file) as additional component of the list.
26296 You have to specify also any existing directories displayed by
26297 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
26299 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
26300 Specify this directory as in the previous case but just for a single
26301 @value{GDBN} session.
26303 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
26304 Disable auto-loading safety for a single @value{GDBN} session.
26305 This assumes all the files you debug during this @value{GDBN} session will come
26306 from trusted sources.
26308 @item @kbd{./configure --without-auto-load-safe-path}
26309 During compilation of @value{GDBN} you may disable any auto-loading safety.
26310 This assumes all the files you will ever debug with this @value{GDBN} come from
26314 On the other hand you can also explicitly forbid automatic files loading which
26315 also suppresses any such warning messages:
26318 @item @kbd{gdb -iex "set auto-load no" @dots{}}
26319 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
26321 @item @file{~/.gdbinit}: @samp{set auto-load no}
26322 Disable auto-loading globally for the user
26323 (@pxref{Home Directory Init File}). While it is improbable, you could also
26324 use system init file instead (@pxref{System-wide configuration}).
26327 This setting applies to the file names as entered by user. If no entry matches
26328 @value{GDBN} tries as a last resort to also resolve all the file names into
26329 their canonical form (typically resolving symbolic links) and compare the
26330 entries again. @value{GDBN} already canonicalizes most of the filenames on its
26331 own before starting the comparison so a canonical form of directories is
26332 recommended to be entered.
26334 @node Auto-loading verbose mode
26335 @subsection Displaying files tried for auto-load
26336 @cindex auto-loading verbose mode
26338 For better visibility of all the file locations where you can place scripts to
26339 be auto-loaded with inferior --- or to protect yourself against accidental
26340 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
26341 all the files attempted to be loaded. Both existing and non-existing files may
26344 For example the list of directories from which it is safe to auto-load files
26345 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
26346 may not be too obvious while setting it up.
26349 (gdb) set debug auto-load on
26350 (gdb) file ~/src/t/true
26351 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
26352 for objfile "/tmp/true".
26353 auto-load: Updating directories of "/usr:/opt".
26354 auto-load: Using directory "/usr".
26355 auto-load: Using directory "/opt".
26356 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
26357 by your `auto-load safe-path' set to "/usr:/opt".
26361 @anchor{set debug auto-load}
26362 @kindex set debug auto-load
26363 @item set debug auto-load [on|off]
26364 Set whether to print the filenames attempted to be auto-loaded.
26366 @anchor{show debug auto-load}
26367 @kindex show debug auto-load
26368 @item show debug auto-load
26369 Show whether printing of the filenames attempted to be auto-loaded is turned
26373 @node Messages/Warnings
26374 @section Optional Warnings and Messages
26376 @cindex verbose operation
26377 @cindex optional warnings
26378 By default, @value{GDBN} is silent about its inner workings. If you are
26379 running on a slow machine, you may want to use the @code{set verbose}
26380 command. This makes @value{GDBN} tell you when it does a lengthy
26381 internal operation, so you will not think it has crashed.
26383 Currently, the messages controlled by @code{set verbose} are those
26384 which announce that the symbol table for a source file is being read;
26385 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
26388 @kindex set verbose
26389 @item set verbose on
26390 Enables @value{GDBN} output of certain informational messages.
26392 @item set verbose off
26393 Disables @value{GDBN} output of certain informational messages.
26395 @kindex show verbose
26397 Displays whether @code{set verbose} is on or off.
26400 By default, if @value{GDBN} encounters bugs in the symbol table of an
26401 object file, it is silent; but if you are debugging a compiler, you may
26402 find this information useful (@pxref{Symbol Errors, ,Errors Reading
26407 @kindex set complaints
26408 @item set complaints @var{limit}
26409 Permits @value{GDBN} to output @var{limit} complaints about each type of
26410 unusual symbols before becoming silent about the problem. Set
26411 @var{limit} to zero to suppress all complaints; set it to a large number
26412 to prevent complaints from being suppressed.
26414 @kindex show complaints
26415 @item show complaints
26416 Displays how many symbol complaints @value{GDBN} is permitted to produce.
26420 @anchor{confirmation requests}
26421 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
26422 lot of stupid questions to confirm certain commands. For example, if
26423 you try to run a program which is already running:
26427 The program being debugged has been started already.
26428 Start it from the beginning? (y or n)
26431 If you are willing to unflinchingly face the consequences of your own
26432 commands, you can disable this ``feature'':
26436 @kindex set confirm
26438 @cindex confirmation
26439 @cindex stupid questions
26440 @item set confirm off
26441 Disables confirmation requests. Note that running @value{GDBN} with
26442 the @option{--batch} option (@pxref{Mode Options, -batch}) also
26443 automatically disables confirmation requests.
26445 @item set confirm on
26446 Enables confirmation requests (the default).
26448 @kindex show confirm
26450 Displays state of confirmation requests.
26454 @cindex command tracing
26455 If you need to debug user-defined commands or sourced files you may find it
26456 useful to enable @dfn{command tracing}. In this mode each command will be
26457 printed as it is executed, prefixed with one or more @samp{+} symbols, the
26458 quantity denoting the call depth of each command.
26461 @kindex set trace-commands
26462 @cindex command scripts, debugging
26463 @item set trace-commands on
26464 Enable command tracing.
26465 @item set trace-commands off
26466 Disable command tracing.
26467 @item show trace-commands
26468 Display the current state of command tracing.
26471 @node Debugging Output
26472 @section Optional Messages about Internal Happenings
26473 @cindex optional debugging messages
26475 @value{GDBN} has commands that enable optional debugging messages from
26476 various @value{GDBN} subsystems; normally these commands are of
26477 interest to @value{GDBN} maintainers, or when reporting a bug. This
26478 section documents those commands.
26481 @kindex set exec-done-display
26482 @item set exec-done-display
26483 Turns on or off the notification of asynchronous commands'
26484 completion. When on, @value{GDBN} will print a message when an
26485 asynchronous command finishes its execution. The default is off.
26486 @kindex show exec-done-display
26487 @item show exec-done-display
26488 Displays the current setting of asynchronous command completion
26492 @cindex ARM AArch64
26493 @item set debug aarch64
26494 Turns on or off display of debugging messages related to ARM AArch64.
26495 The default is off.
26497 @item show debug aarch64
26498 Displays the current state of displaying debugging messages related to
26501 @cindex gdbarch debugging info
26502 @cindex architecture debugging info
26503 @item set debug arch
26504 Turns on or off display of gdbarch debugging info. The default is off
26505 @item show debug arch
26506 Displays the current state of displaying gdbarch debugging info.
26508 @item set debug aix-solib
26509 @cindex AIX shared library debugging
26510 Control display of debugging messages from the AIX shared library
26511 support module. The default is off.
26512 @item show debug aix-solib
26513 Show the current state of displaying AIX shared library debugging messages.
26515 @item set debug aix-thread
26516 @cindex AIX threads
26517 Display debugging messages about inner workings of the AIX thread
26519 @item show debug aix-thread
26520 Show the current state of AIX thread debugging info display.
26522 @item set debug check-physname
26524 Check the results of the ``physname'' computation. When reading DWARF
26525 debugging information for C@t{++}, @value{GDBN} attempts to compute
26526 each entity's name. @value{GDBN} can do this computation in two
26527 different ways, depending on exactly what information is present.
26528 When enabled, this setting causes @value{GDBN} to compute the names
26529 both ways and display any discrepancies.
26530 @item show debug check-physname
26531 Show the current state of ``physname'' checking.
26533 @item set debug coff-pe-read
26534 @cindex COFF/PE exported symbols
26535 Control display of debugging messages related to reading of COFF/PE
26536 exported symbols. The default is off.
26537 @item show debug coff-pe-read
26538 Displays the current state of displaying debugging messages related to
26539 reading of COFF/PE exported symbols.
26541 @item set debug dwarf-die
26543 Dump DWARF DIEs after they are read in.
26544 The value is the number of nesting levels to print.
26545 A value of zero turns off the display.
26546 @item show debug dwarf-die
26547 Show the current state of DWARF DIE debugging.
26549 @item set debug dwarf-line
26550 @cindex DWARF Line Tables
26551 Turns on or off display of debugging messages related to reading
26552 DWARF line tables. The default is 0 (off).
26553 A value of 1 provides basic information.
26554 A value greater than 1 provides more verbose information.
26555 @item show debug dwarf-line
26556 Show the current state of DWARF line table debugging.
26558 @item set debug dwarf-read
26559 @cindex DWARF Reading
26560 Turns on or off display of debugging messages related to reading
26561 DWARF debug info. The default is 0 (off).
26562 A value of 1 provides basic information.
26563 A value greater than 1 provides more verbose information.
26564 @item show debug dwarf-read
26565 Show the current state of DWARF reader debugging.
26567 @item set debug displaced
26568 @cindex displaced stepping debugging info
26569 Turns on or off display of @value{GDBN} debugging info for the
26570 displaced stepping support. The default is off.
26571 @item show debug displaced
26572 Displays the current state of displaying @value{GDBN} debugging info
26573 related to displaced stepping.
26575 @item set debug event
26576 @cindex event debugging info
26577 Turns on or off display of @value{GDBN} event debugging info. The
26579 @item show debug event
26580 Displays the current state of displaying @value{GDBN} event debugging
26583 @item set debug event-loop
26584 @cindex event-loop debugging
26585 Controls output of debugging info about the event loop. The possible
26586 values are @samp{off}, @samp{all} (shows all debugging info) and
26587 @samp{all-except-ui} (shows all debugging info except those about
26588 UI-related events).
26589 @item show debug event-loop
26590 Shows the current state of displaying debugging info about the event
26593 @item set debug expression
26594 @cindex expression debugging info
26595 Turns on or off display of debugging info about @value{GDBN}
26596 expression parsing. The default is off.
26597 @item show debug expression
26598 Displays the current state of displaying debugging info about
26599 @value{GDBN} expression parsing.
26601 @item set debug fbsd-lwp
26602 @cindex FreeBSD LWP debug messages
26603 Turns on or off debugging messages from the FreeBSD LWP debug support.
26604 @item show debug fbsd-lwp
26605 Show the current state of FreeBSD LWP debugging messages.
26607 @item set debug fbsd-nat
26608 @cindex FreeBSD native target debug messages
26609 Turns on or off debugging messages from the FreeBSD native target.
26610 @item show debug fbsd-nat
26611 Show the current state of FreeBSD native target debugging messages.
26613 @item set debug fortran-array-slicing
26614 @cindex fortran array slicing debugging info
26615 Turns on or off display of @value{GDBN} Fortran array slicing
26616 debugging info. The default is off.
26618 @item show debug fortran-array-slicing
26619 Displays the current state of displaying @value{GDBN} Fortran array
26620 slicing debugging info.
26622 @item set debug frame
26623 @cindex frame debugging info
26624 Turns on or off display of @value{GDBN} frame debugging info. The
26626 @item show debug frame
26627 Displays the current state of displaying @value{GDBN} frame debugging
26630 @item set debug gnu-nat
26631 @cindex @sc{gnu}/Hurd debug messages
26632 Turn on or off debugging messages from the @sc{gnu}/Hurd debug support.
26633 @item show debug gnu-nat
26634 Show the current state of @sc{gnu}/Hurd debugging messages.
26636 @item set debug infrun
26637 @cindex inferior debugging info
26638 Turns on or off display of @value{GDBN} debugging info for running the inferior.
26639 The default is off. @file{infrun.c} contains GDB's runtime state machine used
26640 for implementing operations such as single-stepping the inferior.
26641 @item show debug infrun
26642 Displays the current state of @value{GDBN} inferior debugging.
26644 @item set debug jit
26645 @cindex just-in-time compilation, debugging messages
26646 Turn on or off debugging messages from JIT debug support.
26647 @item show debug jit
26648 Displays the current state of @value{GDBN} JIT debugging.
26650 @item set debug lin-lwp
26651 @cindex @sc{gnu}/Linux LWP debug messages
26652 @cindex Linux lightweight processes
26653 Turn on or off debugging messages from the Linux LWP debug support.
26654 @item show debug lin-lwp
26655 Show the current state of Linux LWP debugging messages.
26657 @item set debug linux-namespaces
26658 @cindex @sc{gnu}/Linux namespaces debug messages
26659 Turn on or off debugging messages from the Linux namespaces debug support.
26660 @item show debug linux-namespaces
26661 Show the current state of Linux namespaces debugging messages.
26663 @item set debug mach-o
26664 @cindex Mach-O symbols processing
26665 Control display of debugging messages related to Mach-O symbols
26666 processing. The default is off.
26667 @item show debug mach-o
26668 Displays the current state of displaying debugging messages related to
26669 reading of COFF/PE exported symbols.
26671 @item set debug notification
26672 @cindex remote async notification debugging info
26673 Turn on or off debugging messages about remote async notification.
26674 The default is off.
26675 @item show debug notification
26676 Displays the current state of remote async notification debugging messages.
26678 @item set debug observer
26679 @cindex observer debugging info
26680 Turns on or off display of @value{GDBN} observer debugging. This
26681 includes info such as the notification of observable events.
26682 @item show debug observer
26683 Displays the current state of observer debugging.
26685 @item set debug overload
26686 @cindex C@t{++} overload debugging info
26687 Turns on or off display of @value{GDBN} C@t{++} overload debugging
26688 info. This includes info such as ranking of functions, etc. The default
26690 @item show debug overload
26691 Displays the current state of displaying @value{GDBN} C@t{++} overload
26694 @cindex expression parser, debugging info
26695 @cindex debug expression parser
26696 @item set debug parser
26697 Turns on or off the display of expression parser debugging output.
26698 Internally, this sets the @code{yydebug} variable in the expression
26699 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
26700 details. The default is off.
26701 @item show debug parser
26702 Show the current state of expression parser debugging.
26704 @cindex packets, reporting on stdout
26705 @cindex serial connections, debugging
26706 @cindex debug remote protocol
26707 @cindex remote protocol debugging
26708 @cindex display remote packets
26709 @item set debug remote
26710 Turns on or off display of reports on all packets sent back and forth across
26711 the serial line to the remote machine. The info is printed on the
26712 @value{GDBN} standard output stream. The default is off.
26713 @item show debug remote
26714 Displays the state of display of remote packets.
26716 @item set debug remote-packet-max-chars
26717 Sets the maximum number of characters to display for each remote packet when
26718 @code{set debug remote} is on. This is useful to prevent @value{GDBN} from
26719 displaying lengthy remote packets and polluting the console.
26721 The default value is @code{512}, which means @value{GDBN} will truncate each
26722 remote packet after 512 bytes.
26724 Setting this option to @code{unlimited} will disable truncation and will output
26725 the full length of the remote packets.
26726 @item show debug remote-packet-max-chars
26727 Displays the number of bytes to output for remote packet debugging.
26729 @item set debug separate-debug-file
26730 Turns on or off display of debug output about separate debug file search.
26731 @item show debug separate-debug-file
26732 Displays the state of separate debug file search debug output.
26734 @item set debug serial
26735 Turns on or off display of @value{GDBN} serial debugging info. The
26737 @item show debug serial
26738 Displays the current state of displaying @value{GDBN} serial debugging
26741 @item set debug solib-frv
26742 @cindex FR-V shared-library debugging
26743 Turn on or off debugging messages for FR-V shared-library code.
26744 @item show debug solib-frv
26745 Display the current state of FR-V shared-library code debugging
26748 @item set debug symbol-lookup
26749 @cindex symbol lookup
26750 Turns on or off display of debugging messages related to symbol lookup.
26751 The default is 0 (off).
26752 A value of 1 provides basic information.
26753 A value greater than 1 provides more verbose information.
26754 @item show debug symbol-lookup
26755 Show the current state of symbol lookup debugging messages.
26757 @item set debug symfile
26758 @cindex symbol file functions
26759 Turns on or off display of debugging messages related to symbol file functions.
26760 The default is off. @xref{Files}.
26761 @item show debug symfile
26762 Show the current state of symbol file debugging messages.
26764 @item set debug symtab-create
26765 @cindex symbol table creation
26766 Turns on or off display of debugging messages related to symbol table creation.
26767 The default is 0 (off).
26768 A value of 1 provides basic information.
26769 A value greater than 1 provides more verbose information.
26770 @item show debug symtab-create
26771 Show the current state of symbol table creation debugging.
26773 @item set debug target
26774 @cindex target debugging info
26775 Turns on or off display of @value{GDBN} target debugging info. This info
26776 includes what is going on at the target level of GDB, as it happens. The
26777 default is 0. Set it to 1 to track events, and to 2 to also track the
26778 value of large memory transfers.
26779 @item show debug target
26780 Displays the current state of displaying @value{GDBN} target debugging
26783 @item set debug timestamp
26784 @cindex timestamping debugging info
26785 Turns on or off display of timestamps with @value{GDBN} debugging info.
26786 When enabled, seconds and microseconds are displayed before each debugging
26788 @item show debug timestamp
26789 Displays the current state of displaying timestamps with @value{GDBN}
26792 @item set debug varobj
26793 @cindex variable object debugging info
26794 Turns on or off display of @value{GDBN} variable object debugging
26795 info. The default is off.
26796 @item show debug varobj
26797 Displays the current state of displaying @value{GDBN} variable object
26800 @item set debug xml
26801 @cindex XML parser debugging
26802 Turn on or off debugging messages for built-in XML parsers.
26803 @item show debug xml
26804 Displays the current state of XML debugging messages.
26807 @node Other Misc Settings
26808 @section Other Miscellaneous Settings
26809 @cindex miscellaneous settings
26812 @kindex set interactive-mode
26813 @item set interactive-mode
26814 If @code{on}, forces @value{GDBN} to assume that GDB was started
26815 in a terminal. In practice, this means that @value{GDBN} should wait
26816 for the user to answer queries generated by commands entered at
26817 the command prompt. If @code{off}, forces @value{GDBN} to operate
26818 in the opposite mode, and it uses the default answers to all queries.
26819 If @code{auto} (the default), @value{GDBN} tries to determine whether
26820 its standard input is a terminal, and works in interactive-mode if it
26821 is, non-interactively otherwise.
26823 In the vast majority of cases, the debugger should be able to guess
26824 correctly which mode should be used. But this setting can be useful
26825 in certain specific cases, such as running a MinGW @value{GDBN}
26826 inside a cygwin window.
26828 @kindex show interactive-mode
26829 @item show interactive-mode
26830 Displays whether the debugger is operating in interactive mode or not.
26833 @node Extending GDB
26834 @chapter Extending @value{GDBN}
26835 @cindex extending GDB
26837 @value{GDBN} provides several mechanisms for extension.
26838 @value{GDBN} also provides the ability to automatically load
26839 extensions when it reads a file for debugging. This allows the
26840 user to automatically customize @value{GDBN} for the program
26843 To facilitate the use of extension languages, @value{GDBN} is capable
26844 of evaluating the contents of a file. When doing so, @value{GDBN}
26845 can recognize which extension language is being used by looking at
26846 the filename extension. Files with an unrecognized filename extension
26847 are always treated as a @value{GDBN} Command Files.
26848 @xref{Command Files,, Command files}.
26850 You can control how @value{GDBN} evaluates these files with the following
26854 @kindex set script-extension
26855 @kindex show script-extension
26856 @item set script-extension off
26857 All scripts are always evaluated as @value{GDBN} Command Files.
26859 @item set script-extension soft
26860 The debugger determines the scripting language based on filename
26861 extension. If this scripting language is supported, @value{GDBN}
26862 evaluates the script using that language. Otherwise, it evaluates
26863 the file as a @value{GDBN} Command File.
26865 @item set script-extension strict
26866 The debugger determines the scripting language based on filename
26867 extension, and evaluates the script using that language. If the
26868 language is not supported, then the evaluation fails.
26870 @item show script-extension
26871 Display the current value of the @code{script-extension} option.
26875 @ifset SYSTEM_GDBINIT_DIR
26876 This setting is not used for files in the system-wide gdbinit directory.
26877 Files in that directory must have an extension matching their language,
26878 or have a @file{.gdb} extension to be interpreted as regular @value{GDBN}
26879 commands. @xref{Startup}.
26883 * Sequences:: Canned Sequences of @value{GDBN} Commands
26884 * Aliases:: Command Aliases
26885 * Python:: Extending @value{GDBN} using Python
26886 * Guile:: Extending @value{GDBN} using Guile
26887 * Auto-loading extensions:: Automatically loading extensions
26888 * Multiple Extension Languages:: Working with multiple extension languages
26892 @section Canned Sequences of Commands
26894 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
26895 Command Lists}), @value{GDBN} provides two ways to store sequences of
26896 commands for execution as a unit: user-defined commands and command
26900 * Define:: How to define your own commands
26901 * Hooks:: Hooks for user-defined commands
26902 * Command Files:: How to write scripts of commands to be stored in a file
26903 * Output:: Commands for controlled output
26904 * Auto-loading sequences:: Controlling auto-loaded command files
26908 @subsection User-defined Commands
26910 @cindex user-defined command
26911 @cindex arguments, to user-defined commands
26912 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
26913 which you assign a new name as a command. This is done with the
26914 @code{define} command. User commands may accept an unlimited number of arguments
26915 separated by whitespace. Arguments are accessed within the user command
26916 via @code{$arg0@dots{}$argN}. A trivial example:
26920 print $arg0 + $arg1 + $arg2
26925 To execute the command use:
26932 This defines the command @code{adder}, which prints the sum of
26933 its three arguments. Note the arguments are text substitutions, so they may
26934 reference variables, use complex expressions, or even perform inferior
26937 @cindex argument count in user-defined commands
26938 @cindex how many arguments (user-defined commands)
26939 In addition, @code{$argc} may be used to find out how many arguments have
26945 print $arg0 + $arg1
26948 print $arg0 + $arg1 + $arg2
26953 Combining with the @code{eval} command (@pxref{eval}) makes it easier
26954 to process a variable number of arguments:
26961 eval "set $sum = $sum + $arg%d", $i
26971 @item define @var{commandname}
26972 Define a command named @var{commandname}. If there is already a command
26973 by that name, you are asked to confirm that you want to redefine it.
26974 The argument @var{commandname} may be a bare command name consisting of letters,
26975 numbers, dashes, dots, and underscores. It may also start with any
26976 predefined or user-defined prefix command.
26977 For example, @samp{define target my-target} creates
26978 a user-defined @samp{target my-target} command.
26980 The definition of the command is made up of other @value{GDBN} command lines,
26981 which are given following the @code{define} command. The end of these
26982 commands is marked by a line containing @code{end}.
26985 @kindex end@r{ (user-defined commands)}
26986 @item document @var{commandname}
26987 Document the user-defined command @var{commandname}, so that it can be
26988 accessed by @code{help}. The command @var{commandname} must already be
26989 defined. This command reads lines of documentation just as @code{define}
26990 reads the lines of the command definition, ending with @code{end}.
26991 After the @code{document} command is finished, @code{help} on command
26992 @var{commandname} displays the documentation you have written.
26994 You may use the @code{document} command again to change the
26995 documentation of a command. Redefining the command with @code{define}
26996 does not change the documentation.
26998 @kindex define-prefix
26999 @item define-prefix @var{commandname}
27000 Define or mark the command @var{commandname} as a user-defined prefix
27001 command. Once marked, @var{commandname} can be used as prefix command
27002 by the @code{define} command.
27003 Note that @code{define-prefix} can be used with a not yet defined
27004 @var{commandname}. In such a case, @var{commandname} is defined as
27005 an empty user-defined command.
27006 In case you redefine a command that was marked as a user-defined
27007 prefix command, the subcommands of the redefined command are kept
27008 (and @value{GDBN} indicates so to the user).
27012 (gdb) define-prefix abc
27013 (gdb) define-prefix abc def
27014 (gdb) define abc def
27015 Type commands for definition of "abc def".
27016 End with a line saying just "end".
27017 >echo command initial def\n
27019 (gdb) define abc def ghi
27020 Type commands for definition of "abc def ghi".
27021 End with a line saying just "end".
27022 >echo command ghi\n
27024 (gdb) define abc def
27025 Keeping subcommands of prefix command "def".
27026 Redefine command "def"? (y or n) y
27027 Type commands for definition of "abc def".
27028 End with a line saying just "end".
27029 >echo command def\n
27038 @kindex dont-repeat
27039 @cindex don't repeat command
27041 Used inside a user-defined command, this tells @value{GDBN} that this
27042 command should not be repeated when the user hits @key{RET}
27043 (@pxref{Command Syntax, repeat last command}).
27045 @kindex help user-defined
27046 @item help user-defined
27047 List all user-defined commands and all python commands defined in class
27048 COMMAND_USER. The first line of the documentation or docstring is
27053 @itemx show user @var{commandname}
27054 Display the @value{GDBN} commands used to define @var{commandname} (but
27055 not its documentation). If no @var{commandname} is given, display the
27056 definitions for all user-defined commands.
27057 This does not work for user-defined python commands.
27059 @cindex infinite recursion in user-defined commands
27060 @kindex show max-user-call-depth
27061 @kindex set max-user-call-depth
27062 @item show max-user-call-depth
27063 @itemx set max-user-call-depth
27064 The value of @code{max-user-call-depth} controls how many recursion
27065 levels are allowed in user-defined commands before @value{GDBN} suspects an
27066 infinite recursion and aborts the command.
27067 This does not apply to user-defined python commands.
27070 In addition to the above commands, user-defined commands frequently
27071 use control flow commands, described in @ref{Command Files}.
27073 When user-defined commands are executed, the
27074 commands of the definition are not printed. An error in any command
27075 stops execution of the user-defined command.
27077 If used interactively, commands that would ask for confirmation proceed
27078 without asking when used inside a user-defined command. Many @value{GDBN}
27079 commands that normally print messages to say what they are doing omit the
27080 messages when used in a user-defined command.
27083 @subsection User-defined Command Hooks
27084 @cindex command hooks
27085 @cindex hooks, for commands
27086 @cindex hooks, pre-command
27089 You may define @dfn{hooks}, which are a special kind of user-defined
27090 command. Whenever you run the command @samp{foo}, if the user-defined
27091 command @samp{hook-foo} exists, it is executed (with no arguments)
27092 before that command.
27094 @cindex hooks, post-command
27096 A hook may also be defined which is run after the command you executed.
27097 Whenever you run the command @samp{foo}, if the user-defined command
27098 @samp{hookpost-foo} exists, it is executed (with no arguments) after
27099 that command. Post-execution hooks may exist simultaneously with
27100 pre-execution hooks, for the same command.
27102 It is valid for a hook to call the command which it hooks. If this
27103 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
27105 @c It would be nice if hookpost could be passed a parameter indicating
27106 @c if the command it hooks executed properly or not. FIXME!
27108 @kindex stop@r{, a pseudo-command}
27109 In addition, a pseudo-command, @samp{stop} exists. Defining
27110 (@samp{hook-stop}) makes the associated commands execute every time
27111 execution stops in your program: before breakpoint commands are run,
27112 displays are printed, or the stack frame is printed.
27114 For example, to ignore @code{SIGALRM} signals while
27115 single-stepping, but treat them normally during normal execution,
27120 handle SIGALRM nopass
27124 handle SIGALRM pass
27127 define hook-continue
27128 handle SIGALRM pass
27132 As a further example, to hook at the beginning and end of the @code{echo}
27133 command, and to add extra text to the beginning and end of the message,
27141 define hookpost-echo
27145 (@value{GDBP}) echo Hello World
27146 <<<---Hello World--->>>
27151 You can define a hook for any single-word command in @value{GDBN}, but
27152 not for command aliases; you should define a hook for the basic command
27153 name, e.g.@: @code{backtrace} rather than @code{bt}.
27154 @c FIXME! So how does Joe User discover whether a command is an alias
27156 You can hook a multi-word command by adding @code{hook-} or
27157 @code{hookpost-} to the last word of the command, e.g.@:
27158 @samp{define target hook-remote} to add a hook to @samp{target remote}.
27160 If an error occurs during the execution of your hook, execution of
27161 @value{GDBN} commands stops and @value{GDBN} issues a prompt
27162 (before the command that you actually typed had a chance to run).
27164 If you try to define a hook which does not match any known command, you
27165 get a warning from the @code{define} command.
27167 @node Command Files
27168 @subsection Command Files
27170 @cindex command files
27171 @cindex scripting commands
27172 A command file for @value{GDBN} is a text file made of lines that are
27173 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
27174 also be included. An empty line in a command file does nothing; it
27175 does not mean to repeat the last command, as it would from the
27178 You can request the execution of a command file with the @code{source}
27179 command. Note that the @code{source} command is also used to evaluate
27180 scripts that are not Command Files. The exact behavior can be configured
27181 using the @code{script-extension} setting.
27182 @xref{Extending GDB,, Extending GDB}.
27186 @cindex execute commands from a file
27187 @item source [-s] [-v] @var{filename}
27188 Execute the command file @var{filename}.
27191 The lines in a command file are generally executed sequentially,
27192 unless the order of execution is changed by one of the
27193 @emph{flow-control commands} described below. The commands are not
27194 printed as they are executed. An error in any command terminates
27195 execution of the command file and control is returned to the console.
27197 @value{GDBN} first searches for @var{filename} in the current directory.
27198 If the file is not found there, and @var{filename} does not specify a
27199 directory, then @value{GDBN} also looks for the file on the source search path
27200 (specified with the @samp{directory} command);
27201 except that @file{$cdir} is not searched because the compilation directory
27202 is not relevant to scripts.
27204 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
27205 on the search path even if @var{filename} specifies a directory.
27206 The search is done by appending @var{filename} to each element of the
27207 search path. So, for example, if @var{filename} is @file{mylib/myscript}
27208 and the search path contains @file{/home/user} then @value{GDBN} will
27209 look for the script @file{/home/user/mylib/myscript}.
27210 The search is also done if @var{filename} is an absolute path.
27211 For example, if @var{filename} is @file{/tmp/myscript} and
27212 the search path contains @file{/home/user} then @value{GDBN} will
27213 look for the script @file{/home/user/tmp/myscript}.
27214 For DOS-like systems, if @var{filename} contains a drive specification,
27215 it is stripped before concatenation. For example, if @var{filename} is
27216 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
27217 will look for the script @file{c:/tmp/myscript}.
27219 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
27220 each command as it is executed. The option must be given before
27221 @var{filename}, and is interpreted as part of the filename anywhere else.
27223 Commands that would ask for confirmation if used interactively proceed
27224 without asking when used in a command file. Many @value{GDBN} commands that
27225 normally print messages to say what they are doing omit the messages
27226 when called from command files.
27228 @value{GDBN} also accepts command input from standard input. In this
27229 mode, normal output goes to standard output and error output goes to
27230 standard error. Errors in a command file supplied on standard input do
27231 not terminate execution of the command file---execution continues with
27235 gdb < cmds > log 2>&1
27238 (The syntax above will vary depending on the shell used.) This example
27239 will execute commands from the file @file{cmds}. All output and errors
27240 would be directed to @file{log}.
27242 Since commands stored on command files tend to be more general than
27243 commands typed interactively, they frequently need to deal with
27244 complicated situations, such as different or unexpected values of
27245 variables and symbols, changes in how the program being debugged is
27246 built, etc. @value{GDBN} provides a set of flow-control commands to
27247 deal with these complexities. Using these commands, you can write
27248 complex scripts that loop over data structures, execute commands
27249 conditionally, etc.
27256 This command allows to include in your script conditionally executed
27257 commands. The @code{if} command takes a single argument, which is an
27258 expression to evaluate. It is followed by a series of commands that
27259 are executed only if the expression is true (its value is nonzero).
27260 There can then optionally be an @code{else} line, followed by a series
27261 of commands that are only executed if the expression was false. The
27262 end of the list is marked by a line containing @code{end}.
27266 This command allows to write loops. Its syntax is similar to
27267 @code{if}: the command takes a single argument, which is an expression
27268 to evaluate, and must be followed by the commands to execute, one per
27269 line, terminated by an @code{end}. These commands are called the
27270 @dfn{body} of the loop. The commands in the body of @code{while} are
27271 executed repeatedly as long as the expression evaluates to true.
27275 This command exits the @code{while} loop in whose body it is included.
27276 Execution of the script continues after that @code{while}s @code{end}
27279 @kindex loop_continue
27280 @item loop_continue
27281 This command skips the execution of the rest of the body of commands
27282 in the @code{while} loop in whose body it is included. Execution
27283 branches to the beginning of the @code{while} loop, where it evaluates
27284 the controlling expression.
27286 @kindex end@r{ (if/else/while commands)}
27288 Terminate the block of commands that are the body of @code{if},
27289 @code{else}, or @code{while} flow-control commands.
27294 @subsection Commands for Controlled Output
27296 During the execution of a command file or a user-defined command, normal
27297 @value{GDBN} output is suppressed; the only output that appears is what is
27298 explicitly printed by the commands in the definition. This section
27299 describes three commands useful for generating exactly the output you
27304 @item echo @var{text}
27305 @c I do not consider backslash-space a standard C escape sequence
27306 @c because it is not in ANSI.
27307 Print @var{text}. Nonprinting characters can be included in
27308 @var{text} using C escape sequences, such as @samp{\n} to print a
27309 newline. @strong{No newline is printed unless you specify one.}
27310 In addition to the standard C escape sequences, a backslash followed
27311 by a space stands for a space. This is useful for displaying a
27312 string with spaces at the beginning or the end, since leading and
27313 trailing spaces are otherwise trimmed from all arguments.
27314 To print @samp{@w{ }and foo =@w{ }}, use the command
27315 @samp{echo \@w{ }and foo = \@w{ }}.
27317 A backslash at the end of @var{text} can be used, as in C, to continue
27318 the command onto subsequent lines. For example,
27321 echo This is some text\n\
27322 which is continued\n\
27323 onto several lines.\n
27326 produces the same output as
27329 echo This is some text\n
27330 echo which is continued\n
27331 echo onto several lines.\n
27335 @item output @var{expression}
27336 Print the value of @var{expression} and nothing but that value: no
27337 newlines, no @samp{$@var{nn} = }. The value is not entered in the
27338 value history either. @xref{Expressions, ,Expressions}, for more information
27341 @item output/@var{fmt} @var{expression}
27342 Print the value of @var{expression} in format @var{fmt}. You can use
27343 the same formats as for @code{print}. @xref{Output Formats,,Output
27344 Formats}, for more information.
27347 @item printf @var{template}, @var{expressions}@dots{}
27348 Print the values of one or more @var{expressions} under the control of
27349 the string @var{template}. To print several values, make
27350 @var{expressions} be a comma-separated list of individual expressions,
27351 which may be either numbers or pointers. Their values are printed as
27352 specified by @var{template}, exactly as a C program would do by
27353 executing the code below:
27356 printf (@var{template}, @var{expressions}@dots{});
27359 As in @code{C} @code{printf}, ordinary characters in @var{template}
27360 are printed verbatim, while @dfn{conversion specification} introduced
27361 by the @samp{%} character cause subsequent @var{expressions} to be
27362 evaluated, their values converted and formatted according to type and
27363 style information encoded in the conversion specifications, and then
27366 For example, you can print two values in hex like this:
27369 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
27372 @code{printf} supports all the standard @code{C} conversion
27373 specifications, including the flags and modifiers between the @samp{%}
27374 character and the conversion letter, with the following exceptions:
27378 The argument-ordering modifiers, such as @samp{2$}, are not supported.
27381 The modifier @samp{*} is not supported for specifying precision or
27385 The @samp{'} flag (for separation of digits into groups according to
27386 @code{LC_NUMERIC'}) is not supported.
27389 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
27393 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
27396 The conversion letters @samp{a} and @samp{A} are not supported.
27400 Note that the @samp{ll} type modifier is supported only if the
27401 underlying @code{C} implementation used to build @value{GDBN} supports
27402 the @code{long long int} type, and the @samp{L} type modifier is
27403 supported only if @code{long double} type is available.
27405 As in @code{C}, @code{printf} supports simple backslash-escape
27406 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
27407 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
27408 single character. Octal and hexadecimal escape sequences are not
27411 Additionally, @code{printf} supports conversion specifications for DFP
27412 (@dfn{Decimal Floating Point}) types using the following length modifiers
27413 together with a floating point specifier.
27418 @samp{H} for printing @code{Decimal32} types.
27421 @samp{D} for printing @code{Decimal64} types.
27424 @samp{DD} for printing @code{Decimal128} types.
27427 If the underlying @code{C} implementation used to build @value{GDBN} has
27428 support for the three length modifiers for DFP types, other modifiers
27429 such as width and precision will also be available for @value{GDBN} to use.
27431 In case there is no such @code{C} support, no additional modifiers will be
27432 available and the value will be printed in the standard way.
27434 Here's an example of printing DFP types using the above conversion letters:
27436 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
27441 @item eval @var{template}, @var{expressions}@dots{}
27442 Convert the values of one or more @var{expressions} under the control of
27443 the string @var{template} to a command line, and call it.
27447 @node Auto-loading sequences
27448 @subsection Controlling auto-loading native @value{GDBN} scripts
27449 @cindex native script auto-loading
27451 When a new object file is read (for example, due to the @code{file}
27452 command, or because the inferior has loaded a shared library),
27453 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
27454 @xref{Auto-loading extensions}.
27456 Auto-loading can be enabled or disabled,
27457 and the list of auto-loaded scripts can be printed.
27460 @anchor{set auto-load gdb-scripts}
27461 @kindex set auto-load gdb-scripts
27462 @item set auto-load gdb-scripts [on|off]
27463 Enable or disable the auto-loading of canned sequences of commands scripts.
27465 @anchor{show auto-load gdb-scripts}
27466 @kindex show auto-load gdb-scripts
27467 @item show auto-load gdb-scripts
27468 Show whether auto-loading of canned sequences of commands scripts is enabled or
27471 @anchor{info auto-load gdb-scripts}
27472 @kindex info auto-load gdb-scripts
27473 @cindex print list of auto-loaded canned sequences of commands scripts
27474 @item info auto-load gdb-scripts [@var{regexp}]
27475 Print the list of all canned sequences of commands scripts that @value{GDBN}
27479 If @var{regexp} is supplied only canned sequences of commands scripts with
27480 matching names are printed.
27483 @section Command Aliases
27484 @cindex aliases for commands
27486 Aliases allow you to define alternate spellings for existing commands.
27487 For example, if a new @value{GDBN} command defined in Python
27488 (@pxref{Python}) has a long name, it is handy to have an abbreviated
27489 version of it that involves less typing.
27491 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
27492 of the @samp{step} command even though it is otherwise an ambiguous
27493 abbreviation of other commands like @samp{set} and @samp{show}.
27495 Aliases are also used to provide shortened or more common versions
27496 of multi-word commands. For example, @value{GDBN} provides the
27497 @samp{tty} alias of the @samp{set inferior-tty} command.
27499 You can define a new alias with the @samp{alias} command.
27504 @item alias [-a] [--] @var{alias} = @var{command} [@var{default-args}]
27508 @var{alias} specifies the name of the new alias. Each word of
27509 @var{alias} must consist of letters, numbers, dashes and underscores.
27511 @var{command} specifies the name of an existing command
27512 that is being aliased.
27514 @var{command} can also be the name of an existing alias. In this
27515 case, @var{command} cannot be an alias that has default arguments.
27517 The @samp{-a} option specifies that the new alias is an abbreviation
27518 of the command. Abbreviations are not used in command completion.
27520 The @samp{--} option specifies the end of options,
27521 and is useful when @var{alias} begins with a dash.
27523 You can specify @var{default-args} for your alias. These
27524 @var{default-args} will be automatically added before the alias
27525 arguments typed explicitly on the command line.
27527 For example, the below defines an alias @code{btfullall} that shows all local
27528 variables and all frame arguments:
27530 (@value{GDBP}) alias btfullall = backtrace -full -frame-arguments all
27533 For more information about @var{default-args}, see @ref{Command
27534 aliases default args, ,Default Arguments}.
27536 Here is a simple example showing how to make an abbreviation of a
27537 command so that there is less to type. Suppose you were tired of
27538 typing @samp{disas}, the current shortest unambiguous abbreviation of
27539 the @samp{disassemble} command and you wanted an even shorter version
27540 named @samp{di}. The following will accomplish this.
27543 (gdb) alias -a di = disas
27546 Note that aliases are different from user-defined commands. With a
27547 user-defined command, you also need to write documentation for it with
27548 the @samp{document} command. An alias automatically picks up the
27549 documentation of the existing command.
27551 Here is an example where we make @samp{elms} an abbreviation of
27552 @samp{elements} in the @samp{set print elements} command.
27553 This is to show that you can make an abbreviation of any part
27557 (gdb) alias -a set print elms = set print elements
27558 (gdb) alias -a show print elms = show print elements
27559 (gdb) set p elms 20
27561 Limit on string chars or array elements to print is 200.
27564 Note that if you are defining an alias of a @samp{set} command,
27565 and you want to have an alias for the corresponding @samp{show}
27566 command, then you need to define the latter separately.
27568 Unambiguously abbreviated commands are allowed in @var{command} and
27569 @var{alias}, just as they are normally.
27572 (gdb) alias -a set pr elms = set p ele
27575 Finally, here is an example showing the creation of a one word
27576 alias for a more complex command.
27577 This creates alias @samp{spe} of the command @samp{set print elements}.
27580 (gdb) alias spe = set print elements
27585 * Command aliases default args:: Default arguments for aliases
27588 @node Command aliases default args
27589 @subsection Default Arguments
27590 @cindex aliases for commands, default arguments
27592 You can tell @value{GDBN} to always prepend some default arguments to
27593 the list of arguments provided explicitly by the user when using a
27594 user-defined alias.
27596 If you repeatedly use the same arguments or options for a command, you
27597 can define an alias for this command and tell @value{GDBN} to
27598 automatically prepend these arguments or options to the list of
27599 arguments you type explicitly when using the alias@footnote{@value{GDBN}
27600 could easily accept default arguments for pre-defined commands and aliases,
27601 but it was deemed this would be confusing, and so is not allowed.}.
27603 For example, if you often use the command @code{thread apply all}
27604 specifying to work on the threads in ascending order and to continue in case it
27605 encounters an error, you can tell @value{GDBN} to automatically preprend
27606 the @code{-ascending} and @code{-c} options by using:
27609 (@value{GDBP}) alias thread apply asc-all = thread apply all -ascending -c
27612 Once you have defined this alias with its default args, any time you type
27613 the @code{thread apply asc-all} followed by @code{some arguments},
27614 @value{GDBN} will execute @code{thread apply all -ascending -c some arguments}.
27616 To have even less to type, you can also define a one word alias:
27618 (@value{GDBP}) alias t_a_c = thread apply all -ascending -c
27621 As usual, unambiguous abbreviations can be used for @var{alias}
27622 and @var{default-args}.
27624 The different aliases of a command do not share their default args.
27625 For example, you define a new alias @code{bt_ALL} showing all possible
27626 information and another alias @code{bt_SMALL} showing very limited information
27629 (@value{GDBP}) alias bt_ALL = backtrace -entry-values both -frame-arg all \
27630 -past-main -past-entry -full
27631 (@value{GDBP}) alias bt_SMALL = backtrace -entry-values no -frame-arg none \
27632 -past-main off -past-entry off
27635 (For more on using the @code{alias} command, see @ref{Aliases}.)
27637 Default args are not limited to the arguments and options of @var{command},
27638 but can specify nested commands if @var{command} accepts such a nested command
27640 For example, the below defines @code{faalocalsoftype} that lists the
27641 frames having locals of a certain type, together with the matching
27644 (@value{GDBP}) alias faalocalsoftype = frame apply all info locals -q -t
27645 (@value{GDBP}) faalocalsoftype int
27646 #1 0x55554f5e in sleeper_or_burner (v=0xdf50) at sleepers.c:86
27651 This is also very useful to define an alias for a set of nested @code{with}
27652 commands to have a particular combination of temporary settings. For example,
27653 the below defines the alias @code{pp10} that pretty prints an expression
27654 argument, with a maximum of 10 elements if the expression is a string or
27657 (@value{GDBP}) alias pp10 = with print pretty -- with print elements 10 -- print
27659 This defines the alias @code{pp10} as being a sequence of 3 commands.
27660 The first part @code{with print pretty --} temporarily activates the setting
27661 @code{set print pretty}, then launches the command that follows the separator
27663 The command following the first part is also a @code{with} command that
27664 temporarily changes the setting @code{set print elements} to 10, then
27665 launches the command that follows the second separator @code{--}.
27666 The third part @code{print} is the command the @code{pp10} alias will launch,
27667 using the temporary values of the settings and the arguments explicitly given
27669 For more information about the @code{with} command usage,
27670 see @ref{Command Settings}.
27672 @c Python docs live in a separate file.
27673 @include python.texi
27675 @c Guile docs live in a separate file.
27676 @include guile.texi
27678 @node Auto-loading extensions
27679 @section Auto-loading extensions
27680 @cindex auto-loading extensions
27682 @value{GDBN} provides two mechanisms for automatically loading
27683 extensions when a new object file is read (for example, due to the
27684 @code{file} command, or because the inferior has loaded a shared
27685 library): @file{@var{objfile}-gdb.@var{ext}} (@pxref{objfile-gdbdotext
27686 file,,The @file{@var{objfile}-gdb.@var{ext}} file}) and the
27687 @code{.debug_gdb_scripts} section of modern file formats like ELF
27688 (@pxref{dotdebug_gdb_scripts section,,The @code{.debug_gdb_scripts}
27689 section}). For a discussion of the differences between these two
27690 approaches see @ref{Which flavor to choose?}.
27692 The auto-loading feature is useful for supplying application-specific
27693 debugging commands and features.
27695 Auto-loading can be enabled or disabled,
27696 and the list of auto-loaded scripts can be printed.
27697 See the @samp{auto-loading} section of each extension language
27698 for more information.
27699 For @value{GDBN} command files see @ref{Auto-loading sequences}.
27700 For Python files see @ref{Python Auto-loading}.
27702 Note that loading of this script file also requires accordingly configured
27703 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
27706 * objfile-gdbdotext file:: The @file{@var{objfile}-gdb.@var{ext}} file
27707 * dotdebug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
27708 * Which flavor to choose?:: Choosing between these approaches
27711 @node objfile-gdbdotext file
27712 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
27713 @cindex @file{@var{objfile}-gdb.gdb}
27714 @cindex @file{@var{objfile}-gdb.py}
27715 @cindex @file{@var{objfile}-gdb.scm}
27717 When a new object file is read, @value{GDBN} looks for a file named
27718 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
27719 where @var{objfile} is the object file's name and
27720 where @var{ext} is the file extension for the extension language:
27723 @item @file{@var{objfile}-gdb.gdb}
27724 GDB's own command language
27725 @item @file{@var{objfile}-gdb.py}
27727 @item @file{@var{objfile}-gdb.scm}
27731 @var{script-name} is formed by ensuring that the file name of @var{objfile}
27732 is absolute, following all symlinks, and resolving @code{.} and @code{..}
27733 components, and appending the @file{-gdb.@var{ext}} suffix.
27734 If this file exists and is readable, @value{GDBN} will evaluate it as a
27735 script in the specified extension language.
27737 If this file does not exist, then @value{GDBN} will look for
27738 @var{script-name} file in all of the directories as specified below.
27739 (On MS-Windows/MS-DOS, the drive letter of the executable's leading
27740 directories is converted to a one-letter subdirectory, i.e.@:
27741 @file{d:/usr/bin/} is converted to @file{/d/usr/bin/}, because Windows
27742 filesystems disallow colons in file names.)
27744 Note that loading of these files requires an accordingly configured
27745 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
27747 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
27748 scripts normally according to its @file{.exe} filename. But if no scripts are
27749 found @value{GDBN} also tries script filenames matching the object file without
27750 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
27751 is attempted on any platform. This makes the script filenames compatible
27752 between Unix and MS-Windows hosts.
27755 @anchor{set auto-load scripts-directory}
27756 @kindex set auto-load scripts-directory
27757 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
27758 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
27759 may be delimited by the host platform path separator in use
27760 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
27762 Each entry here needs to be covered also by the security setting
27763 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
27765 @anchor{with-auto-load-dir}
27766 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
27767 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
27768 configuration option @option{--with-auto-load-dir}.
27770 Any reference to @file{$debugdir} will get replaced by
27771 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
27772 reference to @file{$datadir} will get replaced by @var{data-directory} which is
27773 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
27774 @file{$datadir} must be placed as a directory component --- either alone or
27775 delimited by @file{/} or @file{\} directory separators, depending on the host
27778 The list of directories uses path separator (@samp{:} on GNU and Unix
27779 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
27780 to the @env{PATH} environment variable.
27782 @anchor{show auto-load scripts-directory}
27783 @kindex show auto-load scripts-directory
27784 @item show auto-load scripts-directory
27785 Show @value{GDBN} auto-loaded scripts location.
27787 @anchor{add-auto-load-scripts-directory}
27788 @kindex add-auto-load-scripts-directory
27789 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
27790 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
27791 Multiple entries may be delimited by the host platform path separator in use.
27794 @value{GDBN} does not track which files it has already auto-loaded this way.
27795 @value{GDBN} will load the associated script every time the corresponding
27796 @var{objfile} is opened.
27797 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
27798 is evaluated more than once.
27800 @node dotdebug_gdb_scripts section
27801 @subsection The @code{.debug_gdb_scripts} section
27802 @cindex @code{.debug_gdb_scripts} section
27804 For systems using file formats like ELF and COFF,
27805 when @value{GDBN} loads a new object file
27806 it will look for a special section named @code{.debug_gdb_scripts}.
27807 If this section exists, its contents is a list of null-terminated entries
27808 specifying scripts to load. Each entry begins with a non-null prefix byte that
27809 specifies the kind of entry, typically the extension language and whether the
27810 script is in a file or inlined in @code{.debug_gdb_scripts}.
27812 The following entries are supported:
27815 @item SECTION_SCRIPT_ID_PYTHON_FILE = 1
27816 @item SECTION_SCRIPT_ID_SCHEME_FILE = 3
27817 @item SECTION_SCRIPT_ID_PYTHON_TEXT = 4
27818 @item SECTION_SCRIPT_ID_SCHEME_TEXT = 6
27821 @subsubsection Script File Entries
27823 If the entry specifies a file, @value{GDBN} will look for the file first
27824 in the current directory and then along the source search path
27825 (@pxref{Source Path, ,Specifying Source Directories}),
27826 except that @file{$cdir} is not searched, since the compilation
27827 directory is not relevant to scripts.
27829 File entries can be placed in section @code{.debug_gdb_scripts} with,
27830 for example, this GCC macro for Python scripts.
27833 /* Note: The "MS" section flags are to remove duplicates. */
27834 #define DEFINE_GDB_PY_SCRIPT(script_name) \
27836 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
27837 .byte 1 /* Python */\n\
27838 .asciz \"" script_name "\"\n\
27844 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
27845 Then one can reference the macro in a header or source file like this:
27848 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
27851 The script name may include directories if desired.
27853 Note that loading of this script file also requires accordingly configured
27854 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
27856 If the macro invocation is put in a header, any application or library
27857 using this header will get a reference to the specified script,
27858 and with the use of @code{"MS"} attributes on the section, the linker
27859 will remove duplicates.
27861 @subsubsection Script Text Entries
27863 Script text entries allow to put the executable script in the entry
27864 itself instead of loading it from a file.
27865 The first line of the entry, everything after the prefix byte and up to
27866 the first newline (@code{0xa}) character, is the script name, and must not
27867 contain any kind of space character, e.g., spaces or tabs.
27868 The rest of the entry, up to the trailing null byte, is the script to
27869 execute in the specified language. The name needs to be unique among
27870 all script names, as @value{GDBN} executes each script only once based
27873 Here is an example from file @file{py-section-script.c} in the @value{GDBN}
27877 #include "symcat.h"
27878 #include "gdb/section-scripts.h"
27880 ".pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n"
27881 ".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
27882 ".ascii \"gdb.inlined-script\\n\"\n"
27883 ".ascii \"class test_cmd (gdb.Command):\\n\"\n"
27884 ".ascii \" def __init__ (self):\\n\"\n"
27885 ".ascii \" super (test_cmd, self).__init__ ("
27886 "\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
27887 ".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
27888 ".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
27889 ".ascii \"test_cmd ()\\n\"\n"
27895 Loading of inlined scripts requires a properly configured
27896 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
27897 The path to specify in @code{auto-load safe-path} is the path of the file
27898 containing the @code{.debug_gdb_scripts} section.
27900 @node Which flavor to choose?
27901 @subsection Which flavor to choose?
27903 Given the multiple ways of auto-loading extensions, it might not always
27904 be clear which one to choose. This section provides some guidance.
27907 Benefits of the @file{-gdb.@var{ext}} way:
27911 Can be used with file formats that don't support multiple sections.
27914 Ease of finding scripts for public libraries.
27916 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
27917 in the source search path.
27918 For publicly installed libraries, e.g., @file{libstdc++}, there typically
27919 isn't a source directory in which to find the script.
27922 Doesn't require source code additions.
27926 Benefits of the @code{.debug_gdb_scripts} way:
27930 Works with static linking.
27932 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
27933 trigger their loading. When an application is statically linked the only
27934 objfile available is the executable, and it is cumbersome to attach all the
27935 scripts from all the input libraries to the executable's
27936 @file{-gdb.@var{ext}} script.
27939 Works with classes that are entirely inlined.
27941 Some classes can be entirely inlined, and thus there may not be an associated
27942 shared library to attach a @file{-gdb.@var{ext}} script to.
27945 Scripts needn't be copied out of the source tree.
27947 In some circumstances, apps can be built out of large collections of internal
27948 libraries, and the build infrastructure necessary to install the
27949 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
27950 cumbersome. It may be easier to specify the scripts in the
27951 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
27952 top of the source tree to the source search path.
27955 @node Multiple Extension Languages
27956 @section Multiple Extension Languages
27958 The Guile and Python extension languages do not share any state,
27959 and generally do not interfere with each other.
27960 There are some things to be aware of, however.
27962 @subsection Python comes first
27964 Python was @value{GDBN}'s first extension language, and to avoid breaking
27965 existing behaviour Python comes first. This is generally solved by the
27966 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
27967 extension languages, and when it makes a call to an extension language,
27968 (say to pretty-print a value), it tries each in turn until an extension
27969 language indicates it has performed the request (e.g., has returned the
27970 pretty-printed form of a value).
27971 This extends to errors while performing such requests: If an error happens
27972 while, for example, trying to pretty-print an object then the error is
27973 reported and any following extension languages are not tried.
27976 @chapter Command Interpreters
27977 @cindex command interpreters
27979 @value{GDBN} supports multiple command interpreters, and some command
27980 infrastructure to allow users or user interface writers to switch
27981 between interpreters or run commands in other interpreters.
27983 @value{GDBN} currently supports two command interpreters, the console
27984 interpreter (sometimes called the command-line interpreter or @sc{cli})
27985 and the machine interface interpreter (or @sc{gdb/mi}). This manual
27986 describes both of these interfaces in great detail.
27988 By default, @value{GDBN} will start with the console interpreter.
27989 However, the user may choose to start @value{GDBN} with another
27990 interpreter by specifying the @option{-i} or @option{--interpreter}
27991 startup options. Defined interpreters include:
27995 @cindex console interpreter
27996 The traditional console or command-line interpreter. This is the most often
27997 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
27998 @value{GDBN} will use this interpreter.
28001 @cindex mi interpreter
28002 The newest @sc{gdb/mi} interface (currently @code{mi3}). Used primarily
28003 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
28004 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
28008 @cindex mi3 interpreter
28009 The @sc{gdb/mi} interface introduced in @value{GDBN} 9.1.
28012 @cindex mi2 interpreter
28013 The @sc{gdb/mi} interface introduced in @value{GDBN} 6.0.
28016 @cindex mi1 interpreter
28017 The @sc{gdb/mi} interface introduced in @value{GDBN} 5.1.
28021 @cindex invoke another interpreter
28023 @kindex interpreter-exec
28024 You may execute commands in any interpreter from the current
28025 interpreter using the appropriate command. If you are running the
28026 console interpreter, simply use the @code{interpreter-exec} command:
28029 interpreter-exec mi "-data-list-register-names"
28032 @sc{gdb/mi} has a similar command, although it is only available in versions of
28033 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
28035 Note that @code{interpreter-exec} only changes the interpreter for the
28036 duration of the specified command. It does not change the interpreter
28039 @cindex start a new independent interpreter
28041 Although you may only choose a single interpreter at startup, it is
28042 possible to run an independent interpreter on a specified input/output
28043 device (usually a tty).
28045 For example, consider a debugger GUI or IDE that wants to provide a
28046 @value{GDBN} console view. It may do so by embedding a terminal
28047 emulator widget in its GUI, starting @value{GDBN} in the traditional
28048 command-line mode with stdin/stdout/stderr redirected to that
28049 terminal, and then creating an MI interpreter running on a specified
28050 input/output device. The console interpreter created by @value{GDBN}
28051 at startup handles commands the user types in the terminal widget,
28052 while the GUI controls and synchronizes state with @value{GDBN} using
28053 the separate MI interpreter.
28055 To start a new secondary @dfn{user interface} running MI, use the
28056 @code{new-ui} command:
28059 @cindex new user interface
28061 new-ui @var{interpreter} @var{tty}
28064 The @var{interpreter} parameter specifies the interpreter to run.
28065 This accepts the same values as the @code{interpreter-exec} command.
28066 For example, @samp{console}, @samp{mi}, @samp{mi2}, etc. The
28067 @var{tty} parameter specifies the name of the bidirectional file the
28068 interpreter uses for input/output, usually the name of a
28069 pseudoterminal slave on Unix systems. For example:
28072 (@value{GDBP}) new-ui mi /dev/pts/9
28076 runs an MI interpreter on @file{/dev/pts/9}.
28079 @chapter @value{GDBN} Text User Interface
28081 @cindex Text User Interface
28083 The @value{GDBN} Text User Interface (TUI) is a terminal
28084 interface which uses the @code{curses} library to show the source
28085 file, the assembly output, the program registers and @value{GDBN}
28086 commands in separate text windows. The TUI mode is supported only
28087 on platforms where a suitable version of the @code{curses} library
28090 The TUI mode is enabled by default when you invoke @value{GDBN} as
28091 @samp{@value{GDBP} -tui}.
28092 You can also switch in and out of TUI mode while @value{GDBN} runs by
28093 using various TUI commands and key bindings, such as @command{tui
28094 enable} or @kbd{C-x C-a}. @xref{TUI Commands, ,TUI Commands}, and
28095 @ref{TUI Keys, ,TUI Key Bindings}.
28098 * TUI Overview:: TUI overview
28099 * TUI Keys:: TUI key bindings
28100 * TUI Single Key Mode:: TUI single key mode
28101 * TUI Commands:: TUI-specific commands
28102 * TUI Configuration:: TUI configuration variables
28106 @section TUI Overview
28108 In TUI mode, @value{GDBN} can display several text windows:
28112 This window is the @value{GDBN} command window with the @value{GDBN}
28113 prompt and the @value{GDBN} output. The @value{GDBN} input is still
28114 managed using readline.
28117 The source window shows the source file of the program. The current
28118 line and active breakpoints are displayed in this window.
28121 The assembly window shows the disassembly output of the program.
28124 This window shows the processor registers. Registers are highlighted
28125 when their values change.
28128 The source and assembly windows show the current program position
28129 by highlighting the current line and marking it with a @samp{>} marker.
28130 Breakpoints are indicated with two markers. The first marker
28131 indicates the breakpoint type:
28135 Breakpoint which was hit at least once.
28138 Breakpoint which was never hit.
28141 Hardware breakpoint which was hit at least once.
28144 Hardware breakpoint which was never hit.
28147 The second marker indicates whether the breakpoint is enabled or not:
28151 Breakpoint is enabled.
28154 Breakpoint is disabled.
28157 The source, assembly and register windows are updated when the current
28158 thread changes, when the frame changes, or when the program counter
28161 These windows are not all visible at the same time. The command
28162 window is always visible. The others can be arranged in several
28173 source and assembly,
28176 source and registers, or
28179 assembly and registers.
28182 These are the standard layouts, but other layouts can be defined.
28184 A status line above the command window shows the following information:
28188 Indicates the current @value{GDBN} target.
28189 (@pxref{Targets, ,Specifying a Debugging Target}).
28192 Gives the current process or thread number.
28193 When no process is being debugged, this field is set to @code{No process}.
28196 Gives the current function name for the selected frame.
28197 The name is demangled if demangling is turned on (@pxref{Print Settings}).
28198 When there is no symbol corresponding to the current program counter,
28199 the string @code{??} is displayed.
28202 Indicates the current line number for the selected frame.
28203 When the current line number is not known, the string @code{??} is displayed.
28206 Indicates the current program counter address.
28210 @section TUI Key Bindings
28211 @cindex TUI key bindings
28213 The TUI installs several key bindings in the readline keymaps
28214 @ifset SYSTEM_READLINE
28215 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
28217 @ifclear SYSTEM_READLINE
28218 (@pxref{Command Line Editing}).
28220 The following key bindings are installed for both TUI mode and the
28221 @value{GDBN} standard mode.
28230 Enter or leave the TUI mode. When leaving the TUI mode,
28231 the curses window management stops and @value{GDBN} operates using
28232 its standard mode, writing on the terminal directly. When reentering
28233 the TUI mode, control is given back to the curses windows.
28234 The screen is then refreshed.
28236 This key binding uses the bindable Readline function
28237 @code{tui-switch-mode}.
28241 Use a TUI layout with only one window. The layout will
28242 either be @samp{source} or @samp{assembly}. When the TUI mode
28243 is not active, it will switch to the TUI mode.
28245 Think of this key binding as the Emacs @kbd{C-x 1} binding.
28247 This key binding uses the bindable Readline function
28248 @code{tui-delete-other-windows}.
28252 Use a TUI layout with at least two windows. When the current
28253 layout already has two windows, the next layout with two windows is used.
28254 When a new layout is chosen, one window will always be common to the
28255 previous layout and the new one.
28257 Think of it as the Emacs @kbd{C-x 2} binding.
28259 This key binding uses the bindable Readline function
28260 @code{tui-change-windows}.
28264 Change the active window. The TUI associates several key bindings
28265 (like scrolling and arrow keys) with the active window. This command
28266 gives the focus to the next TUI window.
28268 Think of it as the Emacs @kbd{C-x o} binding.
28270 This key binding uses the bindable Readline function
28271 @code{tui-other-window}.
28275 Switch in and out of the TUI SingleKey mode that binds single
28276 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
28278 This key binding uses the bindable Readline function
28279 @code{next-keymap}.
28282 The following key bindings only work in the TUI mode:
28287 Scroll the active window one page up.
28291 Scroll the active window one page down.
28295 Scroll the active window one line up.
28299 Scroll the active window one line down.
28303 Scroll the active window one column left.
28307 Scroll the active window one column right.
28311 Refresh the screen.
28314 Because the arrow keys scroll the active window in the TUI mode, they
28315 are not available for their normal use by readline unless the command
28316 window has the focus. When another window is active, you must use
28317 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
28318 and @kbd{C-f} to control the command window.
28320 @node TUI Single Key Mode
28321 @section TUI Single Key Mode
28322 @cindex TUI single key mode
28324 The TUI also provides a @dfn{SingleKey} mode, which binds several
28325 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
28326 switch into this mode, where the following key bindings are used:
28329 @kindex c @r{(SingleKey TUI key)}
28333 @kindex d @r{(SingleKey TUI key)}
28337 @kindex f @r{(SingleKey TUI key)}
28341 @kindex n @r{(SingleKey TUI key)}
28345 @kindex o @r{(SingleKey TUI key)}
28347 nexti. The shortcut letter @samp{o} stands for ``step Over''.
28349 @kindex q @r{(SingleKey TUI key)}
28351 exit the SingleKey mode.
28353 @kindex r @r{(SingleKey TUI key)}
28357 @kindex s @r{(SingleKey TUI key)}
28361 @kindex i @r{(SingleKey TUI key)}
28363 stepi. The shortcut letter @samp{i} stands for ``step Into''.
28365 @kindex u @r{(SingleKey TUI key)}
28369 @kindex v @r{(SingleKey TUI key)}
28373 @kindex w @r{(SingleKey TUI key)}
28378 Other keys temporarily switch to the @value{GDBN} command prompt.
28379 The key that was pressed is inserted in the editing buffer so that
28380 it is possible to type most @value{GDBN} commands without interaction
28381 with the TUI SingleKey mode. Once the command is entered the TUI
28382 SingleKey mode is restored. The only way to permanently leave
28383 this mode is by typing @kbd{q} or @kbd{C-x s}.
28385 @cindex SingleKey keymap name
28386 If @value{GDBN} was built with Readline 8.0 or later, the TUI
28387 SingleKey keymap will be named @samp{SingleKey}. This can be used in
28388 @file{.inputrc} to add additional bindings to this keymap.
28391 @section TUI-specific Commands
28392 @cindex TUI commands
28394 The TUI has specific commands to control the text windows.
28395 These commands are always available, even when @value{GDBN} is not in
28396 the TUI mode. When @value{GDBN} is in the standard mode, most
28397 of these commands will automatically switch to the TUI mode.
28399 Note that if @value{GDBN}'s @code{stdout} is not connected to a
28400 terminal, or @value{GDBN} has been started with the machine interface
28401 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
28402 these commands will fail with an error, because it would not be
28403 possible or desirable to enable curses window management.
28408 Activate TUI mode. The last active TUI window layout will be used if
28409 TUI mode has previously been used in the current debugging session,
28410 otherwise a default layout is used.
28413 @kindex tui disable
28414 Disable TUI mode, returning to the console interpreter.
28418 List and give the size of all displayed windows.
28420 @item tui new-layout @var{name} @var{window} @var{weight} @r{[}@var{window} @var{weight}@dots{}@r{]}
28421 @kindex tui new-layout
28422 Create a new TUI layout. The new layout will be named @var{name}, and
28423 can be accessed using the @code{layout} command (see below).
28425 Each @var{window} parameter is either the name of a window to display,
28426 or a window description. The windows will be displayed from top to
28427 bottom in the order listed.
28429 The names of the windows are the same as the ones given to the
28430 @code{focus} command (see below); additional, the @code{status}
28431 window can be specified. Note that, because it is of fixed height,
28432 the weight assigned to the status window is of no importance. It is
28433 conventional to use @samp{0} here.
28435 A window description looks a bit like an invocation of @code{tui
28436 new-layout}, and is of the form
28437 @{@r{[}@code{-horizontal}@r{]}@var{window} @var{weight} @r{[}@var{window} @var{weight}@dots{}@r{]}@}.
28439 This specifies a sub-layout. If @code{-horizontal} is given, the
28440 windows in this description will be arranged side-by-side, rather than
28443 Each @var{weight} is an integer. It is the weight of this window
28444 relative to all the other windows in the layout. These numbers are
28445 used to calculate how much of the screen is given to each window.
28450 (gdb) tui new-layout example src 1 regs 1 status 0 cmd 1
28453 Here, the new layout is called @samp{example}. It shows the source
28454 and register windows, followed by the status window, and then finally
28455 the command window. The non-status windows all have the same weight,
28456 so the terminal will be split into three roughly equal sections.
28458 Here is a more complex example, showing a horizontal layout:
28461 (gdb) tui new-layout example @{-horizontal src 1 asm 1@} 2 status 0 cmd 1
28464 This will result in side-by-side source and assembly windows; with the
28465 status and command window being beneath these, filling the entire
28466 width of the terminal. Because they have weight 2, the source and
28467 assembly windows will be twice the height of the command window.
28469 @item layout @var{name}
28471 Changes which TUI windows are displayed. The @var{name} parameter
28472 controls which layout is shown. It can be either one of the built-in
28473 layout names, or the name of a layout defined by the user using
28474 @code{tui new-layout}.
28476 The built-in layouts are as follows:
28480 Display the next layout.
28483 Display the previous layout.
28486 Display the source and command windows.
28489 Display the assembly and command windows.
28492 Display the source, assembly, and command windows.
28495 When in @code{src} layout display the register, source, and command
28496 windows. When in @code{asm} or @code{split} layout display the
28497 register, assembler, and command windows.
28500 @item focus @var{name}
28502 Changes which TUI window is currently active for scrolling. The
28503 @var{name} parameter can be any of the following:
28507 Make the next window active for scrolling.
28510 Make the previous window active for scrolling.
28513 Make the source window active for scrolling.
28516 Make the assembly window active for scrolling.
28519 Make the register window active for scrolling.
28522 Make the command window active for scrolling.
28527 Refresh the screen. This is similar to typing @kbd{C-L}.
28529 @item tui reg @var{group}
28531 Changes the register group displayed in the tui register window to
28532 @var{group}. If the register window is not currently displayed this
28533 command will cause the register window to be displayed. The list of
28534 register groups, as well as their order is target specific. The
28535 following groups are available on most targets:
28538 Repeatedly selecting this group will cause the display to cycle
28539 through all of the available register groups.
28542 Repeatedly selecting this group will cause the display to cycle
28543 through all of the available register groups in the reverse order to
28547 Display the general registers.
28549 Display the floating point registers.
28551 Display the system registers.
28553 Display the vector registers.
28555 Display all registers.
28560 Update the source window and the current execution point.
28562 @item winheight @var{name} +@var{count}
28563 @itemx winheight @var{name} -@var{count}
28565 Change the height of the window @var{name} by @var{count}
28566 lines. Positive counts increase the height, while negative counts
28567 decrease it. The @var{name} parameter can be one of @code{src} (the
28568 source window), @code{cmd} (the command window), @code{asm} (the
28569 disassembly window), or @code{regs} (the register display window).
28572 @node TUI Configuration
28573 @section TUI Configuration Variables
28574 @cindex TUI configuration variables
28576 Several configuration variables control the appearance of TUI windows.
28579 @item set tui border-kind @var{kind}
28580 @kindex set tui border-kind
28581 Select the border appearance for the source, assembly and register windows.
28582 The possible values are the following:
28585 Use a space character to draw the border.
28588 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
28591 Use the Alternate Character Set to draw the border. The border is
28592 drawn using character line graphics if the terminal supports them.
28595 @item set tui border-mode @var{mode}
28596 @kindex set tui border-mode
28597 @itemx set tui active-border-mode @var{mode}
28598 @kindex set tui active-border-mode
28599 Select the display attributes for the borders of the inactive windows
28600 or the active window. The @var{mode} can be one of the following:
28603 Use normal attributes to display the border.
28609 Use reverse video mode.
28612 Use half bright mode.
28614 @item half-standout
28615 Use half bright and standout mode.
28618 Use extra bright or bold mode.
28620 @item bold-standout
28621 Use extra bright or bold and standout mode.
28624 @item set tui tab-width @var{nchars}
28625 @kindex set tui tab-width
28627 Set the width of tab stops to be @var{nchars} characters. This
28628 setting affects the display of TAB characters in the source and
28631 @item set tui compact-source @r{[}on@r{|}off@r{]}
28632 @kindex set tui compact-source
28633 Set whether the TUI source window is displayed in ``compact'' form.
28634 The default display uses more space for line numbers and starts the
28635 source text at the next tab stop; the compact display uses only as
28636 much space as is needed for the line numbers in the current file, and
28637 only a single space to separate the line numbers from the source.
28640 Note that the colors of the TUI borders can be controlled using the
28641 appropriate @code{set style} commands. @xref{Output Styling}.
28644 @chapter Using @value{GDBN} under @sc{gnu} Emacs
28647 @cindex @sc{gnu} Emacs
28648 A special interface allows you to use @sc{gnu} Emacs to view (and
28649 edit) the source files for the program you are debugging with
28652 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
28653 executable file you want to debug as an argument. This command starts
28654 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
28655 created Emacs buffer.
28656 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
28658 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
28663 All ``terminal'' input and output goes through an Emacs buffer, called
28666 This applies both to @value{GDBN} commands and their output, and to the input
28667 and output done by the program you are debugging.
28669 This is useful because it means that you can copy the text of previous
28670 commands and input them again; you can even use parts of the output
28673 All the facilities of Emacs' Shell mode are available for interacting
28674 with your program. In particular, you can send signals the usual
28675 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
28679 @value{GDBN} displays source code through Emacs.
28681 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
28682 source file for that frame and puts an arrow (@samp{=>}) at the
28683 left margin of the current line. Emacs uses a separate buffer for
28684 source display, and splits the screen to show both your @value{GDBN} session
28687 Explicit @value{GDBN} @code{list} or search commands still produce output as
28688 usual, but you probably have no reason to use them from Emacs.
28691 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
28692 a graphical mode, enabled by default, which provides further buffers
28693 that can control the execution and describe the state of your program.
28694 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
28696 If you specify an absolute file name when prompted for the @kbd{M-x
28697 gdb} argument, then Emacs sets your current working directory to where
28698 your program resides. If you only specify the file name, then Emacs
28699 sets your current working directory to the directory associated
28700 with the previous buffer. In this case, @value{GDBN} may find your
28701 program by searching your environment's @code{PATH} variable, but on
28702 some operating systems it might not find the source. So, although the
28703 @value{GDBN} input and output session proceeds normally, the auxiliary
28704 buffer does not display the current source and line of execution.
28706 The initial working directory of @value{GDBN} is printed on the top
28707 line of the GUD buffer and this serves as a default for the commands
28708 that specify files for @value{GDBN} to operate on. @xref{Files,
28709 ,Commands to Specify Files}.
28711 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
28712 need to call @value{GDBN} by a different name (for example, if you
28713 keep several configurations around, with different names) you can
28714 customize the Emacs variable @code{gud-gdb-command-name} to run the
28717 In the GUD buffer, you can use these special Emacs commands in
28718 addition to the standard Shell mode commands:
28722 Describe the features of Emacs' GUD Mode.
28725 Execute to another source line, like the @value{GDBN} @code{step} command; also
28726 update the display window to show the current file and location.
28729 Execute to next source line in this function, skipping all function
28730 calls, like the @value{GDBN} @code{next} command. Then update the display window
28731 to show the current file and location.
28734 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
28735 display window accordingly.
28738 Execute until exit from the selected stack frame, like the @value{GDBN}
28739 @code{finish} command.
28742 Continue execution of your program, like the @value{GDBN} @code{continue}
28746 Go up the number of frames indicated by the numeric argument
28747 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
28748 like the @value{GDBN} @code{up} command.
28751 Go down the number of frames indicated by the numeric argument, like the
28752 @value{GDBN} @code{down} command.
28755 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
28756 tells @value{GDBN} to set a breakpoint on the source line point is on.
28758 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
28759 separate frame which shows a backtrace when the GUD buffer is current.
28760 Move point to any frame in the stack and type @key{RET} to make it
28761 become the current frame and display the associated source in the
28762 source buffer. Alternatively, click @kbd{Mouse-2} to make the
28763 selected frame become the current one. In graphical mode, the
28764 speedbar displays watch expressions.
28766 If you accidentally delete the source-display buffer, an easy way to get
28767 it back is to type the command @code{f} in the @value{GDBN} buffer, to
28768 request a frame display; when you run under Emacs, this recreates
28769 the source buffer if necessary to show you the context of the current
28772 The source files displayed in Emacs are in ordinary Emacs buffers
28773 which are visiting the source files in the usual way. You can edit
28774 the files with these buffers if you wish; but keep in mind that @value{GDBN}
28775 communicates with Emacs in terms of line numbers. If you add or
28776 delete lines from the text, the line numbers that @value{GDBN} knows cease
28777 to correspond properly with the code.
28779 A more detailed description of Emacs' interaction with @value{GDBN} is
28780 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
28784 @chapter The @sc{gdb/mi} Interface
28786 @unnumberedsec Function and Purpose
28788 @cindex @sc{gdb/mi}, its purpose
28789 @sc{gdb/mi} is a line based machine oriented text interface to
28790 @value{GDBN} and is activated by specifying using the
28791 @option{--interpreter} command line option (@pxref{Mode Options}). It
28792 is specifically intended to support the development of systems which
28793 use the debugger as just one small component of a larger system.
28795 This chapter is a specification of the @sc{gdb/mi} interface. It is written
28796 in the form of a reference manual.
28798 Note that @sc{gdb/mi} is still under construction, so some of the
28799 features described below are incomplete and subject to change
28800 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
28802 @unnumberedsec Notation and Terminology
28804 @cindex notational conventions, for @sc{gdb/mi}
28805 This chapter uses the following notation:
28809 @code{|} separates two alternatives.
28812 @code{[ @var{something} ]} indicates that @var{something} is optional:
28813 it may or may not be given.
28816 @code{( @var{group} )*} means that @var{group} inside the parentheses
28817 may repeat zero or more times.
28820 @code{( @var{group} )+} means that @var{group} inside the parentheses
28821 may repeat one or more times.
28824 @code{"@var{string}"} means a literal @var{string}.
28828 @heading Dependencies
28832 * GDB/MI General Design::
28833 * GDB/MI Command Syntax::
28834 * GDB/MI Compatibility with CLI::
28835 * GDB/MI Development and Front Ends::
28836 * GDB/MI Output Records::
28837 * GDB/MI Simple Examples::
28838 * GDB/MI Command Description Format::
28839 * GDB/MI Breakpoint Commands::
28840 * GDB/MI Catchpoint Commands::
28841 * GDB/MI Program Context::
28842 * GDB/MI Thread Commands::
28843 * GDB/MI Ada Tasking Commands::
28844 * GDB/MI Program Execution::
28845 * GDB/MI Stack Manipulation::
28846 * GDB/MI Variable Objects::
28847 * GDB/MI Data Manipulation::
28848 * GDB/MI Tracepoint Commands::
28849 * GDB/MI Symbol Query::
28850 * GDB/MI File Commands::
28852 * GDB/MI Kod Commands::
28853 * GDB/MI Memory Overlay Commands::
28854 * GDB/MI Signal Handling Commands::
28856 * GDB/MI Target Manipulation::
28857 * GDB/MI File Transfer Commands::
28858 * GDB/MI Ada Exceptions Commands::
28859 * GDB/MI Support Commands::
28860 * GDB/MI Miscellaneous Commands::
28863 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28864 @node GDB/MI General Design
28865 @section @sc{gdb/mi} General Design
28866 @cindex GDB/MI General Design
28868 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
28869 parts---commands sent to @value{GDBN}, responses to those commands
28870 and notifications. Each command results in exactly one response,
28871 indicating either successful completion of the command, or an error.
28872 For the commands that do not resume the target, the response contains the
28873 requested information. For the commands that resume the target, the
28874 response only indicates whether the target was successfully resumed.
28875 Notifications is the mechanism for reporting changes in the state of the
28876 target, or in @value{GDBN} state, that cannot conveniently be associated with
28877 a command and reported as part of that command response.
28879 The important examples of notifications are:
28883 Exec notifications. These are used to report changes in
28884 target state---when a target is resumed, or stopped. It would not
28885 be feasible to include this information in response of resuming
28886 commands, because one resume commands can result in multiple events in
28887 different threads. Also, quite some time may pass before any event
28888 happens in the target, while a frontend needs to know whether the resuming
28889 command itself was successfully executed.
28892 Console output, and status notifications. Console output
28893 notifications are used to report output of CLI commands, as well as
28894 diagnostics for other commands. Status notifications are used to
28895 report the progress of a long-running operation. Naturally, including
28896 this information in command response would mean no output is produced
28897 until the command is finished, which is undesirable.
28900 General notifications. Commands may have various side effects on
28901 the @value{GDBN} or target state beyond their official purpose. For example,
28902 a command may change the selected thread. Although such changes can
28903 be included in command response, using notification allows for more
28904 orthogonal frontend design.
28908 There's no guarantee that whenever an MI command reports an error,
28909 @value{GDBN} or the target are in any specific state, and especially,
28910 the state is not reverted to the state before the MI command was
28911 processed. Therefore, whenever an MI command results in an error,
28912 we recommend that the frontend refreshes all the information shown in
28913 the user interface.
28917 * Context management::
28918 * Asynchronous and non-stop modes::
28922 @node Context management
28923 @subsection Context management
28925 @subsubsection Threads and Frames
28927 In most cases when @value{GDBN} accesses the target, this access is
28928 done in context of a specific thread and frame (@pxref{Frames}).
28929 Often, even when accessing global data, the target requires that a thread
28930 be specified. The CLI interface maintains the selected thread and frame,
28931 and supplies them to target on each command. This is convenient,
28932 because a command line user would not want to specify that information
28933 explicitly on each command, and because user interacts with
28934 @value{GDBN} via a single terminal, so no confusion is possible as
28935 to what thread and frame are the current ones.
28937 In the case of MI, the concept of selected thread and frame is less
28938 useful. First, a frontend can easily remember this information
28939 itself. Second, a graphical frontend can have more than one window,
28940 each one used for debugging a different thread, and the frontend might
28941 want to access additional threads for internal purposes. This
28942 increases the risk that by relying on implicitly selected thread, the
28943 frontend may be operating on a wrong one. Therefore, each MI command
28944 should explicitly specify which thread and frame to operate on. To
28945 make it possible, each MI command accepts the @samp{--thread} and
28946 @samp{--frame} options, the value to each is @value{GDBN} global
28947 identifier for thread and frame to operate on.
28949 Usually, each top-level window in a frontend allows the user to select
28950 a thread and a frame, and remembers the user selection for further
28951 operations. However, in some cases @value{GDBN} may suggest that the
28952 current thread or frame be changed. For example, when stopping on a
28953 breakpoint it is reasonable to switch to the thread where breakpoint is
28954 hit. For another example, if the user issues the CLI @samp{thread} or
28955 @samp{frame} commands via the frontend, it is desirable to change the
28956 frontend's selection to the one specified by user. @value{GDBN}
28957 communicates the suggestion to change current thread and frame using the
28958 @samp{=thread-selected} notification.
28960 Note that historically, MI shares the selected thread with CLI, so
28961 frontends used the @code{-thread-select} to execute commands in the
28962 right context. However, getting this to work right is cumbersome. The
28963 simplest way is for frontend to emit @code{-thread-select} command
28964 before every command. This doubles the number of commands that need
28965 to be sent. The alternative approach is to suppress @code{-thread-select}
28966 if the selected thread in @value{GDBN} is supposed to be identical to the
28967 thread the frontend wants to operate on. However, getting this
28968 optimization right can be tricky. In particular, if the frontend
28969 sends several commands to @value{GDBN}, and one of the commands changes the
28970 selected thread, then the behaviour of subsequent commands will
28971 change. So, a frontend should either wait for response from such
28972 problematic commands, or explicitly add @code{-thread-select} for
28973 all subsequent commands. No frontend is known to do this exactly
28974 right, so it is suggested to just always pass the @samp{--thread} and
28975 @samp{--frame} options.
28977 @subsubsection Language
28979 The execution of several commands depends on which language is selected.
28980 By default, the current language (@pxref{show language}) is used.
28981 But for commands known to be language-sensitive, it is recommended
28982 to use the @samp{--language} option. This option takes one argument,
28983 which is the name of the language to use while executing the command.
28987 -data-evaluate-expression --language c "sizeof (void*)"
28992 The valid language names are the same names accepted by the
28993 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
28994 @samp{local} or @samp{unknown}.
28996 @node Asynchronous and non-stop modes
28997 @subsection Asynchronous command execution and non-stop mode
28999 On some targets, @value{GDBN} is capable of processing MI commands
29000 even while the target is running. This is called @dfn{asynchronous
29001 command execution} (@pxref{Background Execution}). The frontend may
29002 specify a preference for asynchronous execution using the
29003 @code{-gdb-set mi-async 1} command, which should be emitted before
29004 either running the executable or attaching to the target. After the
29005 frontend has started the executable or attached to the target, it can
29006 find if asynchronous execution is enabled using the
29007 @code{-list-target-features} command.
29010 @item -gdb-set mi-async on
29011 @item -gdb-set mi-async off
29012 Set whether MI is in asynchronous mode.
29014 When @code{off}, which is the default, MI execution commands (e.g.,
29015 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
29016 for the program to stop before processing further commands.
29018 When @code{on}, MI execution commands are background execution
29019 commands (e.g., @code{-exec-continue} becomes the equivalent of the
29020 @code{c&} CLI command), and so @value{GDBN} is capable of processing
29021 MI commands even while the target is running.
29023 @item -gdb-show mi-async
29024 Show whether MI asynchronous mode is enabled.
29027 Note: In @value{GDBN} version 7.7 and earlier, this option was called
29028 @code{target-async} instead of @code{mi-async}, and it had the effect
29029 of both putting MI in asynchronous mode and making CLI background
29030 commands possible. CLI background commands are now always possible
29031 ``out of the box'' if the target supports them. The old spelling is
29032 kept as a deprecated alias for backwards compatibility.
29034 Even if @value{GDBN} can accept a command while target is running,
29035 many commands that access the target do not work when the target is
29036 running. Therefore, asynchronous command execution is most useful
29037 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
29038 it is possible to examine the state of one thread, while other threads
29041 When a given thread is running, MI commands that try to access the
29042 target in the context of that thread may not work, or may work only on
29043 some targets. In particular, commands that try to operate on thread's
29044 stack will not work, on any target. Commands that read memory, or
29045 modify breakpoints, may work or not work, depending on the target. Note
29046 that even commands that operate on global state, such as @code{print},
29047 @code{set}, and breakpoint commands, still access the target in the
29048 context of a specific thread, so frontend should try to find a
29049 stopped thread and perform the operation on that thread (using the
29050 @samp{--thread} option).
29052 Which commands will work in the context of a running thread is
29053 highly target dependent. However, the two commands
29054 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
29055 to find the state of a thread, will always work.
29057 @node Thread groups
29058 @subsection Thread groups
29059 @value{GDBN} may be used to debug several processes at the same time.
29060 On some platforms, @value{GDBN} may support debugging of several
29061 hardware systems, each one having several cores with several different
29062 processes running on each core. This section describes the MI
29063 mechanism to support such debugging scenarios.
29065 The key observation is that regardless of the structure of the
29066 target, MI can have a global list of threads, because most commands that
29067 accept the @samp{--thread} option do not need to know what process that
29068 thread belongs to. Therefore, it is not necessary to introduce
29069 neither additional @samp{--process} option, nor an notion of the
29070 current process in the MI interface. The only strictly new feature
29071 that is required is the ability to find how the threads are grouped
29074 To allow the user to discover such grouping, and to support arbitrary
29075 hierarchy of machines/cores/processes, MI introduces the concept of a
29076 @dfn{thread group}. Thread group is a collection of threads and other
29077 thread groups. A thread group always has a string identifier, a type,
29078 and may have additional attributes specific to the type. A new
29079 command, @code{-list-thread-groups}, returns the list of top-level
29080 thread groups, which correspond to processes that @value{GDBN} is
29081 debugging at the moment. By passing an identifier of a thread group
29082 to the @code{-list-thread-groups} command, it is possible to obtain
29083 the members of specific thread group.
29085 To allow the user to easily discover processes, and other objects, he
29086 wishes to debug, a concept of @dfn{available thread group} is
29087 introduced. Available thread group is an thread group that
29088 @value{GDBN} is not debugging, but that can be attached to, using the
29089 @code{-target-attach} command. The list of available top-level thread
29090 groups can be obtained using @samp{-list-thread-groups --available}.
29091 In general, the content of a thread group may be only retrieved only
29092 after attaching to that thread group.
29094 Thread groups are related to inferiors (@pxref{Inferiors Connections and
29095 Programs}). Each inferior corresponds to a thread group of a special
29096 type @samp{process}, and some additional operations are permitted on
29097 such thread groups.
29099 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29100 @node GDB/MI Command Syntax
29101 @section @sc{gdb/mi} Command Syntax
29104 * GDB/MI Input Syntax::
29105 * GDB/MI Output Syntax::
29108 @node GDB/MI Input Syntax
29109 @subsection @sc{gdb/mi} Input Syntax
29111 @cindex input syntax for @sc{gdb/mi}
29112 @cindex @sc{gdb/mi}, input syntax
29114 @item @var{command} @expansion{}
29115 @code{@var{cli-command} | @var{mi-command}}
29117 @item @var{cli-command} @expansion{}
29118 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
29119 @var{cli-command} is any existing @value{GDBN} CLI command.
29121 @item @var{mi-command} @expansion{}
29122 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
29123 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
29125 @item @var{token} @expansion{}
29126 "any sequence of digits"
29128 @item @var{option} @expansion{}
29129 @code{"-" @var{parameter} [ " " @var{parameter} ]}
29131 @item @var{parameter} @expansion{}
29132 @code{@var{non-blank-sequence} | @var{c-string}}
29134 @item @var{operation} @expansion{}
29135 @emph{any of the operations described in this chapter}
29137 @item @var{non-blank-sequence} @expansion{}
29138 @emph{anything, provided it doesn't contain special characters such as
29139 "-", @var{nl}, """ and of course " "}
29141 @item @var{c-string} @expansion{}
29142 @code{""" @var{seven-bit-iso-c-string-content} """}
29144 @item @var{nl} @expansion{}
29153 The CLI commands are still handled by the @sc{mi} interpreter; their
29154 output is described below.
29157 The @code{@var{token}}, when present, is passed back when the command
29161 Some @sc{mi} commands accept optional arguments as part of the parameter
29162 list. Each option is identified by a leading @samp{-} (dash) and may be
29163 followed by an optional argument parameter. Options occur first in the
29164 parameter list and can be delimited from normal parameters using
29165 @samp{--} (this is useful when some parameters begin with a dash).
29172 We want easy access to the existing CLI syntax (for debugging).
29175 We want it to be easy to spot a @sc{mi} operation.
29178 @node GDB/MI Output Syntax
29179 @subsection @sc{gdb/mi} Output Syntax
29181 @cindex output syntax of @sc{gdb/mi}
29182 @cindex @sc{gdb/mi}, output syntax
29183 The output from @sc{gdb/mi} consists of zero or more out-of-band records
29184 followed, optionally, by a single result record. This result record
29185 is for the most recent command. The sequence of output records is
29186 terminated by @samp{(gdb)}.
29188 If an input command was prefixed with a @code{@var{token}} then the
29189 corresponding output for that command will also be prefixed by that same
29193 @item @var{output} @expansion{}
29194 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
29196 @item @var{result-record} @expansion{}
29197 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
29199 @item @var{out-of-band-record} @expansion{}
29200 @code{@var{async-record} | @var{stream-record}}
29202 @item @var{async-record} @expansion{}
29203 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
29205 @item @var{exec-async-output} @expansion{}
29206 @code{[ @var{token} ] "*" @var{async-output nl}}
29208 @item @var{status-async-output} @expansion{}
29209 @code{[ @var{token} ] "+" @var{async-output nl}}
29211 @item @var{notify-async-output} @expansion{}
29212 @code{[ @var{token} ] "=" @var{async-output nl}}
29214 @item @var{async-output} @expansion{}
29215 @code{@var{async-class} ( "," @var{result} )*}
29217 @item @var{result-class} @expansion{}
29218 @code{"done" | "running" | "connected" | "error" | "exit"}
29220 @item @var{async-class} @expansion{}
29221 @code{"stopped" | @var{others}} (where @var{others} will be added
29222 depending on the needs---this is still in development).
29224 @item @var{result} @expansion{}
29225 @code{ @var{variable} "=" @var{value}}
29227 @item @var{variable} @expansion{}
29228 @code{ @var{string} }
29230 @item @var{value} @expansion{}
29231 @code{ @var{const} | @var{tuple} | @var{list} }
29233 @item @var{const} @expansion{}
29234 @code{@var{c-string}}
29236 @item @var{tuple} @expansion{}
29237 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
29239 @item @var{list} @expansion{}
29240 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
29241 @var{result} ( "," @var{result} )* "]" }
29243 @item @var{stream-record} @expansion{}
29244 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
29246 @item @var{console-stream-output} @expansion{}
29247 @code{"~" @var{c-string nl}}
29249 @item @var{target-stream-output} @expansion{}
29250 @code{"@@" @var{c-string nl}}
29252 @item @var{log-stream-output} @expansion{}
29253 @code{"&" @var{c-string nl}}
29255 @item @var{nl} @expansion{}
29258 @item @var{token} @expansion{}
29259 @emph{any sequence of digits}.
29267 All output sequences end in a single line containing a period.
29270 The @code{@var{token}} is from the corresponding request. Note that
29271 for all async output, while the token is allowed by the grammar and
29272 may be output by future versions of @value{GDBN} for select async
29273 output messages, it is generally omitted. Frontends should treat
29274 all async output as reporting general changes in the state of the
29275 target and there should be no need to associate async output to any
29279 @cindex status output in @sc{gdb/mi}
29280 @var{status-async-output} contains on-going status information about the
29281 progress of a slow operation. It can be discarded. All status output is
29282 prefixed by @samp{+}.
29285 @cindex async output in @sc{gdb/mi}
29286 @var{exec-async-output} contains asynchronous state change on the target
29287 (stopped, started, disappeared). All async output is prefixed by
29291 @cindex notify output in @sc{gdb/mi}
29292 @var{notify-async-output} contains supplementary information that the
29293 client should handle (e.g., a new breakpoint information). All notify
29294 output is prefixed by @samp{=}.
29297 @cindex console output in @sc{gdb/mi}
29298 @var{console-stream-output} is output that should be displayed as is in the
29299 console. It is the textual response to a CLI command. All the console
29300 output is prefixed by @samp{~}.
29303 @cindex target output in @sc{gdb/mi}
29304 @var{target-stream-output} is the output produced by the target program.
29305 All the target output is prefixed by @samp{@@}.
29308 @cindex log output in @sc{gdb/mi}
29309 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
29310 instance messages that should be displayed as part of an error log. All
29311 the log output is prefixed by @samp{&}.
29314 @cindex list output in @sc{gdb/mi}
29315 New @sc{gdb/mi} commands should only output @var{lists} containing
29321 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
29322 details about the various output records.
29324 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29325 @node GDB/MI Compatibility with CLI
29326 @section @sc{gdb/mi} Compatibility with CLI
29328 @cindex compatibility, @sc{gdb/mi} and CLI
29329 @cindex @sc{gdb/mi}, compatibility with CLI
29331 For the developers convenience CLI commands can be entered directly,
29332 but there may be some unexpected behaviour. For example, commands
29333 that query the user will behave as if the user replied yes, breakpoint
29334 command lists are not executed and some CLI commands, such as
29335 @code{if}, @code{when} and @code{define}, prompt for further input with
29336 @samp{>}, which is not valid MI output.
29338 This feature may be removed at some stage in the future and it is
29339 recommended that front ends use the @code{-interpreter-exec} command
29340 (@pxref{-interpreter-exec}).
29342 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29343 @node GDB/MI Development and Front Ends
29344 @section @sc{gdb/mi} Development and Front Ends
29345 @cindex @sc{gdb/mi} development
29347 The application which takes the MI output and presents the state of the
29348 program being debugged to the user is called a @dfn{front end}.
29350 Since @sc{gdb/mi} is used by a variety of front ends to @value{GDBN}, changes
29351 to the MI interface may break existing usage. This section describes how the
29352 protocol changes and how to request previous version of the protocol when it
29355 Some changes in MI need not break a carefully designed front end, and
29356 for these the MI version will remain unchanged. The following is a
29357 list of changes that may occur within one level, so front ends should
29358 parse MI output in a way that can handle them:
29362 New MI commands may be added.
29365 New fields may be added to the output of any MI command.
29368 The range of values for fields with specified values, e.g.,
29369 @code{in_scope} (@pxref{-var-update}) may be extended.
29371 @c The format of field's content e.g type prefix, may change so parse it
29372 @c at your own risk. Yes, in general?
29374 @c The order of fields may change? Shouldn't really matter but it might
29375 @c resolve inconsistencies.
29378 If the changes are likely to break front ends, the MI version level
29379 will be increased by one. The new versions of the MI protocol are not compatible
29380 with the old versions. Old versions of MI remain available, allowing front ends
29381 to keep using them until they are modified to use the latest MI version.
29383 Since @code{--interpreter=mi} always points to the latest MI version, it is
29384 recommended that front ends request a specific version of MI when launching
29385 @value{GDBN} (e.g. @code{--interpreter=mi2}) to make sure they get an
29386 interpreter with the MI version they expect.
29388 The following table gives a summary of the released versions of the MI
29389 interface: the version number, the version of GDB in which it first appeared
29390 and the breaking changes compared to the previous version.
29392 @multitable @columnfractions .05 .05 .9
29393 @headitem MI version @tab GDB version @tab Breaking changes
29410 The @code{-environment-pwd}, @code{-environment-directory} and
29411 @code{-environment-path} commands now returns values using the MI output
29412 syntax, rather than CLI output syntax.
29415 @code{-var-list-children}'s @code{children} result field is now a list, rather
29419 @code{-var-update}'s @code{changelist} result field is now a list, rather than
29431 The output of information about multi-location breakpoints has changed in the
29432 responses to the @code{-break-insert} and @code{-break-info} commands, as well
29433 as in the @code{=breakpoint-created} and @code{=breakpoint-modified} events.
29434 The multiple locations are now placed in a @code{locations} field, whose value
29440 If your front end cannot yet migrate to a more recent version of the
29441 MI protocol, you can nevertheless selectively enable specific features
29442 available in those recent MI versions, using the following commands:
29446 @item -fix-multi-location-breakpoint-output
29447 Use the output for multi-location breakpoints which was introduced by
29448 MI 3, even when using MI versions 2 or 1. This command has no
29449 effect when using MI version 3 or later.
29453 The best way to avoid unexpected changes in MI that might break your front
29454 end is to make your project known to @value{GDBN} developers and
29455 follow development on @email{gdb@@sourceware.org} and
29456 @email{gdb-patches@@sourceware.org}.
29457 @cindex mailing lists
29459 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29460 @node GDB/MI Output Records
29461 @section @sc{gdb/mi} Output Records
29464 * GDB/MI Result Records::
29465 * GDB/MI Stream Records::
29466 * GDB/MI Async Records::
29467 * GDB/MI Breakpoint Information::
29468 * GDB/MI Frame Information::
29469 * GDB/MI Thread Information::
29470 * GDB/MI Ada Exception Information::
29473 @node GDB/MI Result Records
29474 @subsection @sc{gdb/mi} Result Records
29476 @cindex result records in @sc{gdb/mi}
29477 @cindex @sc{gdb/mi}, result records
29478 In addition to a number of out-of-band notifications, the response to a
29479 @sc{gdb/mi} command includes one of the following result indications:
29483 @item "^done" [ "," @var{results} ]
29484 The synchronous operation was successful, @code{@var{results}} are the return
29489 This result record is equivalent to @samp{^done}. Historically, it
29490 was output instead of @samp{^done} if the command has resumed the
29491 target. This behaviour is maintained for backward compatibility, but
29492 all frontends should treat @samp{^done} and @samp{^running}
29493 identically and rely on the @samp{*running} output record to determine
29494 which threads are resumed.
29498 @value{GDBN} has connected to a remote target.
29500 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
29502 The operation failed. The @code{msg=@var{c-string}} variable contains
29503 the corresponding error message.
29505 If present, the @code{code=@var{c-string}} variable provides an error
29506 code on which consumers can rely on to detect the corresponding
29507 error condition. At present, only one error code is defined:
29510 @item "undefined-command"
29511 Indicates that the command causing the error does not exist.
29516 @value{GDBN} has terminated.
29520 @node GDB/MI Stream Records
29521 @subsection @sc{gdb/mi} Stream Records
29523 @cindex @sc{gdb/mi}, stream records
29524 @cindex stream records in @sc{gdb/mi}
29525 @value{GDBN} internally maintains a number of output streams: the console, the
29526 target, and the log. The output intended for each of these streams is
29527 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
29529 Each stream record begins with a unique @dfn{prefix character} which
29530 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
29531 Syntax}). In addition to the prefix, each stream record contains a
29532 @code{@var{string-output}}. This is either raw text (with an implicit new
29533 line) or a quoted C string (which does not contain an implicit newline).
29536 @item "~" @var{string-output}
29537 The console output stream contains text that should be displayed in the
29538 CLI console window. It contains the textual responses to CLI commands.
29540 @item "@@" @var{string-output}
29541 The target output stream contains any textual output from the running
29542 target. This is only present when GDB's event loop is truly
29543 asynchronous, which is currently only the case for remote targets.
29545 @item "&" @var{string-output}
29546 The log stream contains debugging messages being produced by @value{GDBN}'s
29550 @node GDB/MI Async Records
29551 @subsection @sc{gdb/mi} Async Records
29553 @cindex async records in @sc{gdb/mi}
29554 @cindex @sc{gdb/mi}, async records
29555 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
29556 additional changes that have occurred. Those changes can either be a
29557 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
29558 target activity (e.g., target stopped).
29560 The following is the list of possible async records:
29564 @item *running,thread-id="@var{thread}"
29565 The target is now running. The @var{thread} field can be the global
29566 thread ID of the thread that is now running, and it can be
29567 @samp{all} if all threads are running. The frontend should assume
29568 that no interaction with a running thread is possible after this
29569 notification is produced. The frontend should not assume that this
29570 notification is output only once for any command. @value{GDBN} may
29571 emit this notification several times, either for different threads,
29572 because it cannot resume all threads together, or even for a single
29573 thread, if the thread must be stepped though some code before letting
29576 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
29577 The target has stopped. The @var{reason} field can have one of the
29581 @item breakpoint-hit
29582 A breakpoint was reached.
29583 @item watchpoint-trigger
29584 A watchpoint was triggered.
29585 @item read-watchpoint-trigger
29586 A read watchpoint was triggered.
29587 @item access-watchpoint-trigger
29588 An access watchpoint was triggered.
29589 @item function-finished
29590 An -exec-finish or similar CLI command was accomplished.
29591 @item location-reached
29592 An -exec-until or similar CLI command was accomplished.
29593 @item watchpoint-scope
29594 A watchpoint has gone out of scope.
29595 @item end-stepping-range
29596 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
29597 similar CLI command was accomplished.
29598 @item exited-signalled
29599 The inferior exited because of a signal.
29601 The inferior exited.
29602 @item exited-normally
29603 The inferior exited normally.
29604 @item signal-received
29605 A signal was received by the inferior.
29607 The inferior has stopped due to a library being loaded or unloaded.
29608 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
29609 set or when a @code{catch load} or @code{catch unload} catchpoint is
29610 in use (@pxref{Set Catchpoints}).
29612 The inferior has forked. This is reported when @code{catch fork}
29613 (@pxref{Set Catchpoints}) has been used.
29615 The inferior has vforked. This is reported in when @code{catch vfork}
29616 (@pxref{Set Catchpoints}) has been used.
29617 @item syscall-entry
29618 The inferior entered a system call. This is reported when @code{catch
29619 syscall} (@pxref{Set Catchpoints}) has been used.
29620 @item syscall-return
29621 The inferior returned from a system call. This is reported when
29622 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
29624 The inferior called @code{exec}. This is reported when @code{catch exec}
29625 (@pxref{Set Catchpoints}) has been used.
29628 The @var{id} field identifies the global thread ID of the thread
29629 that directly caused the stop -- for example by hitting a breakpoint.
29630 Depending on whether all-stop
29631 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
29632 stop all threads, or only the thread that directly triggered the stop.
29633 If all threads are stopped, the @var{stopped} field will have the
29634 value of @code{"all"}. Otherwise, the value of the @var{stopped}
29635 field will be a list of thread identifiers. Presently, this list will
29636 always include a single thread, but frontend should be prepared to see
29637 several threads in the list. The @var{core} field reports the
29638 processor core on which the stop event has happened. This field may be absent
29639 if such information is not available.
29641 @item =thread-group-added,id="@var{id}"
29642 @itemx =thread-group-removed,id="@var{id}"
29643 A thread group was either added or removed. The @var{id} field
29644 contains the @value{GDBN} identifier of the thread group. When a thread
29645 group is added, it generally might not be associated with a running
29646 process. When a thread group is removed, its id becomes invalid and
29647 cannot be used in any way.
29649 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
29650 A thread group became associated with a running program,
29651 either because the program was just started or the thread group
29652 was attached to a program. The @var{id} field contains the
29653 @value{GDBN} identifier of the thread group. The @var{pid} field
29654 contains process identifier, specific to the operating system.
29656 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
29657 A thread group is no longer associated with a running program,
29658 either because the program has exited, or because it was detached
29659 from. The @var{id} field contains the @value{GDBN} identifier of the
29660 thread group. The @var{code} field is the exit code of the inferior; it exists
29661 only when the inferior exited with some code.
29663 @item =thread-created,id="@var{id}",group-id="@var{gid}"
29664 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
29665 A thread either was created, or has exited. The @var{id} field
29666 contains the global @value{GDBN} identifier of the thread. The @var{gid}
29667 field identifies the thread group this thread belongs to.
29669 @item =thread-selected,id="@var{id}"[,frame="@var{frame}"]
29670 Informs that the selected thread or frame were changed. This notification
29671 is not emitted as result of the @code{-thread-select} or
29672 @code{-stack-select-frame} commands, but is emitted whenever an MI command
29673 that is not documented to change the selected thread and frame actually
29674 changes them. In particular, invoking, directly or indirectly
29675 (via user-defined command), the CLI @code{thread} or @code{frame} commands,
29676 will generate this notification. Changing the thread or frame from another
29677 user interface (see @ref{Interpreters}) will also generate this notification.
29679 The @var{frame} field is only present if the newly selected thread is
29680 stopped. See @ref{GDB/MI Frame Information} for the format of its value.
29682 We suggest that in response to this notification, front ends
29683 highlight the selected thread and cause subsequent commands to apply to
29686 @item =library-loaded,...
29687 Reports that a new library file was loaded by the program. This
29688 notification has 5 fields---@var{id}, @var{target-name},
29689 @var{host-name}, @var{symbols-loaded} and @var{ranges}. The @var{id} field is an
29690 opaque identifier of the library. For remote debugging case,
29691 @var{target-name} and @var{host-name} fields give the name of the
29692 library file on the target, and on the host respectively. For native
29693 debugging, both those fields have the same value. The
29694 @var{symbols-loaded} field is emitted only for backward compatibility
29695 and should not be relied on to convey any useful information. The
29696 @var{thread-group} field, if present, specifies the id of the thread
29697 group in whose context the library was loaded. If the field is
29698 absent, it means the library was loaded in the context of all present
29699 thread groups. The @var{ranges} field specifies the ranges of addresses belonging
29702 @item =library-unloaded,...
29703 Reports that a library was unloaded by the program. This notification
29704 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
29705 the same meaning as for the @code{=library-loaded} notification.
29706 The @var{thread-group} field, if present, specifies the id of the
29707 thread group in whose context the library was unloaded. If the field is
29708 absent, it means the library was unloaded in the context of all present
29711 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
29712 @itemx =traceframe-changed,end
29713 Reports that the trace frame was changed and its new number is
29714 @var{tfnum}. The number of the tracepoint associated with this trace
29715 frame is @var{tpnum}.
29717 @item =tsv-created,name=@var{name},initial=@var{initial}
29718 Reports that the new trace state variable @var{name} is created with
29719 initial value @var{initial}.
29721 @item =tsv-deleted,name=@var{name}
29722 @itemx =tsv-deleted
29723 Reports that the trace state variable @var{name} is deleted or all
29724 trace state variables are deleted.
29726 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
29727 Reports that the trace state variable @var{name} is modified with
29728 the initial value @var{initial}. The current value @var{current} of
29729 trace state variable is optional and is reported if the current
29730 value of trace state variable is known.
29732 @item =breakpoint-created,bkpt=@{...@}
29733 @itemx =breakpoint-modified,bkpt=@{...@}
29734 @itemx =breakpoint-deleted,id=@var{number}
29735 Reports that a breakpoint was created, modified, or deleted,
29736 respectively. Only user-visible breakpoints are reported to the MI
29739 The @var{bkpt} argument is of the same form as returned by the various
29740 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
29741 @var{number} is the ordinal number of the breakpoint.
29743 Note that if a breakpoint is emitted in the result record of a
29744 command, then it will not also be emitted in an async record.
29746 @item =record-started,thread-group="@var{id}",method="@var{method}"[,format="@var{format}"]
29747 @itemx =record-stopped,thread-group="@var{id}"
29748 Execution log recording was either started or stopped on an
29749 inferior. The @var{id} is the @value{GDBN} identifier of the thread
29750 group corresponding to the affected inferior.
29752 The @var{method} field indicates the method used to record execution. If the
29753 method in use supports multiple recording formats, @var{format} will be present
29754 and contain the currently used format. @xref{Process Record and Replay},
29755 for existing method and format values.
29757 @item =cmd-param-changed,param=@var{param},value=@var{value}
29758 Reports that a parameter of the command @code{set @var{param}} is
29759 changed to @var{value}. In the multi-word @code{set} command,
29760 the @var{param} is the whole parameter list to @code{set} command.
29761 For example, In command @code{set check type on}, @var{param}
29762 is @code{check type} and @var{value} is @code{on}.
29764 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
29765 Reports that bytes from @var{addr} to @var{data} + @var{len} were
29766 written in an inferior. The @var{id} is the identifier of the
29767 thread group corresponding to the affected inferior. The optional
29768 @code{type="code"} part is reported if the memory written to holds
29772 @node GDB/MI Breakpoint Information
29773 @subsection @sc{gdb/mi} Breakpoint Information
29775 When @value{GDBN} reports information about a breakpoint, a
29776 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
29781 The breakpoint number.
29784 The type of the breakpoint. For ordinary breakpoints this will be
29785 @samp{breakpoint}, but many values are possible.
29788 If the type of the breakpoint is @samp{catchpoint}, then this
29789 indicates the exact type of catchpoint.
29792 This is the breakpoint disposition---either @samp{del}, meaning that
29793 the breakpoint will be deleted at the next stop, or @samp{keep},
29794 meaning that the breakpoint will not be deleted.
29797 This indicates whether the breakpoint is enabled, in which case the
29798 value is @samp{y}, or disabled, in which case the value is @samp{n}.
29799 Note that this is not the same as the field @code{enable}.
29802 The address of the breakpoint. This may be a hexidecimal number,
29803 giving the address; or the string @samp{<PENDING>}, for a pending
29804 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
29805 multiple locations. This field will not be present if no address can
29806 be determined. For example, a watchpoint does not have an address.
29809 Optional field containing any flags related to the address. These flags are
29810 architecture-dependent; see @ref{Architectures} for their meaning for a
29814 If known, the function in which the breakpoint appears.
29815 If not known, this field is not present.
29818 The name of the source file which contains this function, if known.
29819 If not known, this field is not present.
29822 The full file name of the source file which contains this function, if
29823 known. If not known, this field is not present.
29826 The line number at which this breakpoint appears, if known.
29827 If not known, this field is not present.
29830 If the source file is not known, this field may be provided. If
29831 provided, this holds the address of the breakpoint, possibly followed
29835 If this breakpoint is pending, this field is present and holds the
29836 text used to set the breakpoint, as entered by the user.
29839 Where this breakpoint's condition is evaluated, either @samp{host} or
29843 If this is a thread-specific breakpoint, then this identifies the
29844 thread in which the breakpoint can trigger.
29847 If this breakpoint is restricted to a particular Ada task, then this
29848 field will hold the task identifier.
29851 If the breakpoint is conditional, this is the condition expression.
29854 The ignore count of the breakpoint.
29857 The enable count of the breakpoint.
29859 @item traceframe-usage
29862 @item static-tracepoint-marker-string-id
29863 For a static tracepoint, the name of the static tracepoint marker.
29866 For a masked watchpoint, this is the mask.
29869 A tracepoint's pass count.
29871 @item original-location
29872 The location of the breakpoint as originally specified by the user.
29873 This field is optional.
29876 The number of times the breakpoint has been hit.
29879 This field is only given for tracepoints. This is either @samp{y},
29880 meaning that the tracepoint is installed, or @samp{n}, meaning that it
29884 Some extra data, the exact contents of which are type-dependent.
29887 This field is present if the breakpoint has multiple locations. It is also
29888 exceptionally present if the breakpoint is enabled and has a single, disabled
29891 The value is a list of locations. The format of a location is described below.
29895 A location in a multi-location breakpoint is represented as a tuple with the
29901 The location number as a dotted pair, like @samp{1.2}. The first digit is the
29902 number of the parent breakpoint. The second digit is the number of the
29903 location within that breakpoint.
29906 This indicates whether the location is enabled, in which case the
29907 value is @samp{y}, or disabled, in which case the value is @samp{n}.
29908 Note that this is not the same as the field @code{enable}.
29911 The address of this location as an hexidecimal number.
29914 Optional field containing any flags related to the address. These flags are
29915 architecture-dependent; see @ref{Architectures} for their meaning for a
29919 If known, the function in which the location appears.
29920 If not known, this field is not present.
29923 The name of the source file which contains this location, if known.
29924 If not known, this field is not present.
29927 The full file name of the source file which contains this location, if
29928 known. If not known, this field is not present.
29931 The line number at which this location appears, if known.
29932 If not known, this field is not present.
29934 @item thread-groups
29935 The thread groups this location is in.
29939 For example, here is what the output of @code{-break-insert}
29940 (@pxref{GDB/MI Breakpoint Commands}) might be:
29943 -> -break-insert main
29944 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
29945 enabled="y",addr="0x08048564",func="main",file="myprog.c",
29946 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
29951 @node GDB/MI Frame Information
29952 @subsection @sc{gdb/mi} Frame Information
29954 Response from many MI commands includes an information about stack
29955 frame. This information is a tuple that may have the following
29960 The level of the stack frame. The innermost frame has the level of
29961 zero. This field is always present.
29964 The name of the function corresponding to the frame. This field may
29965 be absent if @value{GDBN} is unable to determine the function name.
29968 The code address for the frame. This field is always present.
29971 Optional field containing any flags related to the address. These flags are
29972 architecture-dependent; see @ref{Architectures} for their meaning for a
29976 The name of the source files that correspond to the frame's code
29977 address. This field may be absent.
29980 The source line corresponding to the frames' code address. This field
29984 The name of the binary file (either executable or shared library) the
29985 corresponds to the frame's code address. This field may be absent.
29989 @node GDB/MI Thread Information
29990 @subsection @sc{gdb/mi} Thread Information
29992 Whenever @value{GDBN} has to report an information about a thread, it
29993 uses a tuple with the following fields. The fields are always present unless
29998 The global numeric id assigned to the thread by @value{GDBN}.
30001 The target-specific string identifying the thread.
30004 Additional information about the thread provided by the target.
30005 It is supposed to be human-readable and not interpreted by the
30006 frontend. This field is optional.
30009 The name of the thread. If the user specified a name using the
30010 @code{thread name} command, then this name is given. Otherwise, if
30011 @value{GDBN} can extract the thread name from the target, then that
30012 name is given. If @value{GDBN} cannot find the thread name, then this
30016 The execution state of the thread, either @samp{stopped} or @samp{running},
30017 depending on whether the thread is presently running.
30020 The stack frame currently executing in the thread. This field is only present
30021 if the thread is stopped. Its format is documented in
30022 @ref{GDB/MI Frame Information}.
30025 The value of this field is an integer number of the processor core the
30026 thread was last seen on. This field is optional.
30029 @node GDB/MI Ada Exception Information
30030 @subsection @sc{gdb/mi} Ada Exception Information
30032 Whenever a @code{*stopped} record is emitted because the program
30033 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
30034 @value{GDBN} provides the name of the exception that was raised via
30035 the @code{exception-name} field. Also, for exceptions that were raised
30036 with an exception message, @value{GDBN} provides that message via
30037 the @code{exception-message} field.
30039 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30040 @node GDB/MI Simple Examples
30041 @section Simple Examples of @sc{gdb/mi} Interaction
30042 @cindex @sc{gdb/mi}, simple examples
30044 This subsection presents several simple examples of interaction using
30045 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
30046 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
30047 the output received from @sc{gdb/mi}.
30049 Note the line breaks shown in the examples are here only for
30050 readability, they don't appear in the real output.
30052 @subheading Setting a Breakpoint
30054 Setting a breakpoint generates synchronous output which contains detailed
30055 information of the breakpoint.
30058 -> -break-insert main
30059 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
30060 enabled="y",addr="0x08048564",func="main",file="myprog.c",
30061 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
30066 @subheading Program Execution
30068 Program execution generates asynchronous records and MI gives the
30069 reason that execution stopped.
30075 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
30076 frame=@{addr="0x08048564",func="main",
30077 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
30078 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68",
30079 arch="i386:x86_64"@}
30084 <- *stopped,reason="exited-normally"
30088 @subheading Quitting @value{GDBN}
30090 Quitting @value{GDBN} just prints the result class @samp{^exit}.
30098 Please note that @samp{^exit} is printed immediately, but it might
30099 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
30100 performs necessary cleanups, including killing programs being debugged
30101 or disconnecting from debug hardware, so the frontend should wait till
30102 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
30103 fails to exit in reasonable time.
30105 @subheading A Bad Command
30107 Here's what happens if you pass a non-existent command:
30111 <- ^error,msg="Undefined MI command: rubbish"
30116 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30117 @node GDB/MI Command Description Format
30118 @section @sc{gdb/mi} Command Description Format
30120 The remaining sections describe blocks of commands. Each block of
30121 commands is laid out in a fashion similar to this section.
30123 @subheading Motivation
30125 The motivation for this collection of commands.
30127 @subheading Introduction
30129 A brief introduction to this collection of commands as a whole.
30131 @subheading Commands
30133 For each command in the block, the following is described:
30135 @subsubheading Synopsis
30138 -command @var{args}@dots{}
30141 @subsubheading Result
30143 @subsubheading @value{GDBN} Command
30145 The corresponding @value{GDBN} CLI command(s), if any.
30147 @subsubheading Example
30149 Example(s) formatted for readability. Some of the described commands have
30150 not been implemented yet and these are labeled N.A.@: (not available).
30153 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30154 @node GDB/MI Breakpoint Commands
30155 @section @sc{gdb/mi} Breakpoint Commands
30157 @cindex breakpoint commands for @sc{gdb/mi}
30158 @cindex @sc{gdb/mi}, breakpoint commands
30159 This section documents @sc{gdb/mi} commands for manipulating
30162 @subheading The @code{-break-after} Command
30163 @findex -break-after
30165 @subsubheading Synopsis
30168 -break-after @var{number} @var{count}
30171 The breakpoint number @var{number} is not in effect until it has been
30172 hit @var{count} times. To see how this is reflected in the output of
30173 the @samp{-break-list} command, see the description of the
30174 @samp{-break-list} command below.
30176 @subsubheading @value{GDBN} Command
30178 The corresponding @value{GDBN} command is @samp{ignore}.
30180 @subsubheading Example
30185 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
30186 enabled="y",addr="0x000100d0",func="main",file="hello.c",
30187 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
30195 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30196 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30197 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30198 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30199 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30200 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30201 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30202 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30203 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
30204 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
30209 @subheading The @code{-break-catch} Command
30210 @findex -break-catch
30213 @subheading The @code{-break-commands} Command
30214 @findex -break-commands
30216 @subsubheading Synopsis
30219 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
30222 Specifies the CLI commands that should be executed when breakpoint
30223 @var{number} is hit. The parameters @var{command1} to @var{commandN}
30224 are the commands. If no command is specified, any previously-set
30225 commands are cleared. @xref{Break Commands}. Typical use of this
30226 functionality is tracing a program, that is, printing of values of
30227 some variables whenever breakpoint is hit and then continuing.
30229 @subsubheading @value{GDBN} Command
30231 The corresponding @value{GDBN} command is @samp{commands}.
30233 @subsubheading Example
30238 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
30239 enabled="y",addr="0x000100d0",func="main",file="hello.c",
30240 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
30243 -break-commands 1 "print v" "continue"
30248 @subheading The @code{-break-condition} Command
30249 @findex -break-condition
30251 @subsubheading Synopsis
30254 -break-condition @var{number} @var{expr}
30257 Breakpoint @var{number} will stop the program only if the condition in
30258 @var{expr} is true. The condition becomes part of the
30259 @samp{-break-list} output (see the description of the @samp{-break-list}
30262 @subsubheading @value{GDBN} Command
30264 The corresponding @value{GDBN} command is @samp{condition}.
30266 @subsubheading Example
30270 -break-condition 1 1
30274 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30275 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30276 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30277 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30278 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30279 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30280 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30281 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30282 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
30283 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
30287 @subheading The @code{-break-delete} Command
30288 @findex -break-delete
30290 @subsubheading Synopsis
30293 -break-delete ( @var{breakpoint} )+
30296 Delete the breakpoint(s) whose number(s) are specified in the argument
30297 list. This is obviously reflected in the breakpoint list.
30299 @subsubheading @value{GDBN} Command
30301 The corresponding @value{GDBN} command is @samp{delete}.
30303 @subsubheading Example
30311 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
30312 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30313 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30314 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30315 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30316 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30317 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30322 @subheading The @code{-break-disable} Command
30323 @findex -break-disable
30325 @subsubheading Synopsis
30328 -break-disable ( @var{breakpoint} )+
30331 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
30332 break list is now set to @samp{n} for the named @var{breakpoint}(s).
30334 @subsubheading @value{GDBN} Command
30336 The corresponding @value{GDBN} command is @samp{disable}.
30338 @subsubheading Example
30346 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30347 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30348 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30349 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30350 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30351 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30352 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30353 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
30354 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
30355 line="5",thread-groups=["i1"],times="0"@}]@}
30359 @subheading The @code{-break-enable} Command
30360 @findex -break-enable
30362 @subsubheading Synopsis
30365 -break-enable ( @var{breakpoint} )+
30368 Enable (previously disabled) @var{breakpoint}(s).
30370 @subsubheading @value{GDBN} Command
30372 The corresponding @value{GDBN} command is @samp{enable}.
30374 @subsubheading Example
30382 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30383 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30384 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30385 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30386 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30387 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30388 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30389 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
30390 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
30391 line="5",thread-groups=["i1"],times="0"@}]@}
30395 @subheading The @code{-break-info} Command
30396 @findex -break-info
30398 @subsubheading Synopsis
30401 -break-info @var{breakpoint}
30405 Get information about a single breakpoint.
30407 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
30408 Information}, for details on the format of each breakpoint in the
30411 @subsubheading @value{GDBN} Command
30413 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
30415 @subsubheading Example
30418 @subheading The @code{-break-insert} Command
30419 @findex -break-insert
30420 @anchor{-break-insert}
30422 @subsubheading Synopsis
30425 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ] [ --qualified ]
30426 [ -c @var{condition} ] [ -i @var{ignore-count} ]
30427 [ -p @var{thread-id} ] [ @var{location} ]
30431 If specified, @var{location}, can be one of:
30434 @item linespec location
30435 A linespec location. @xref{Linespec Locations}.
30437 @item explicit location
30438 An explicit location. @sc{gdb/mi} explicit locations are
30439 analogous to the CLI's explicit locations using the option names
30440 listed below. @xref{Explicit Locations}.
30443 @item --source @var{filename}
30444 The source file name of the location. This option requires the use
30445 of either @samp{--function} or @samp{--line}.
30447 @item --function @var{function}
30448 The name of a function or method.
30450 @item --label @var{label}
30451 The name of a label.
30453 @item --line @var{lineoffset}
30454 An absolute or relative line offset from the start of the location.
30457 @item address location
30458 An address location, *@var{address}. @xref{Address Locations}.
30462 The possible optional parameters of this command are:
30466 Insert a temporary breakpoint.
30468 Insert a hardware breakpoint.
30470 If @var{location} cannot be parsed (for example if it
30471 refers to unknown files or functions), create a pending
30472 breakpoint. Without this flag, @value{GDBN} will report
30473 an error, and won't create a breakpoint, if @var{location}
30476 Create a disabled breakpoint.
30478 Create a tracepoint. @xref{Tracepoints}. When this parameter
30479 is used together with @samp{-h}, a fast tracepoint is created.
30480 @item -c @var{condition}
30481 Make the breakpoint conditional on @var{condition}.
30482 @item -i @var{ignore-count}
30483 Initialize the @var{ignore-count}.
30484 @item -p @var{thread-id}
30485 Restrict the breakpoint to the thread with the specified global
30488 This option makes @value{GDBN} interpret a function name specified as
30489 a complete fully-qualified name.
30492 @subsubheading Result
30494 @xref{GDB/MI Breakpoint Information}, for details on the format of the
30495 resulting breakpoint.
30497 Note: this format is open to change.
30498 @c An out-of-band breakpoint instead of part of the result?
30500 @subsubheading @value{GDBN} Command
30502 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
30503 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
30505 @subsubheading Example
30510 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
30511 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
30514 -break-insert -t foo
30515 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
30516 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
30520 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30521 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30522 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30523 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30524 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30525 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30526 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30527 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30528 addr="0x0001072c", func="main",file="recursive2.c",
30529 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
30531 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
30532 addr="0x00010774",func="foo",file="recursive2.c",
30533 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
30536 @c -break-insert -r foo.*
30537 @c ~int foo(int, int);
30538 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
30539 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
30544 @subheading The @code{-dprintf-insert} Command
30545 @findex -dprintf-insert
30547 @subsubheading Synopsis
30550 -dprintf-insert [ -t ] [ -f ] [ -d ] [ --qualified ]
30551 [ -c @var{condition} ] [ -i @var{ignore-count} ]
30552 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
30557 If supplied, @var{location} and @code{--qualified} may be specified
30558 the same way as for the @code{-break-insert} command.
30559 @xref{-break-insert}.
30561 The possible optional parameters of this command are:
30565 Insert a temporary breakpoint.
30567 If @var{location} cannot be parsed (for example, if it
30568 refers to unknown files or functions), create a pending
30569 breakpoint. Without this flag, @value{GDBN} will report
30570 an error, and won't create a breakpoint, if @var{location}
30573 Create a disabled breakpoint.
30574 @item -c @var{condition}
30575 Make the breakpoint conditional on @var{condition}.
30576 @item -i @var{ignore-count}
30577 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
30578 to @var{ignore-count}.
30579 @item -p @var{thread-id}
30580 Restrict the breakpoint to the thread with the specified global
30584 @subsubheading Result
30586 @xref{GDB/MI Breakpoint Information}, for details on the format of the
30587 resulting breakpoint.
30589 @c An out-of-band breakpoint instead of part of the result?
30591 @subsubheading @value{GDBN} Command
30593 The corresponding @value{GDBN} command is @samp{dprintf}.
30595 @subsubheading Example
30599 4-dprintf-insert foo "At foo entry\n"
30600 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
30601 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
30602 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
30603 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
30604 original-location="foo"@}
30606 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
30607 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
30608 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
30609 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
30610 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
30611 original-location="mi-dprintf.c:26"@}
30615 @subheading The @code{-break-list} Command
30616 @findex -break-list
30618 @subsubheading Synopsis
30624 Displays the list of inserted breakpoints, showing the following fields:
30628 number of the breakpoint
30630 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
30632 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
30635 is the breakpoint enabled or no: @samp{y} or @samp{n}
30637 memory location at which the breakpoint is set
30639 logical location of the breakpoint, expressed by function name, file
30641 @item Thread-groups
30642 list of thread groups to which this breakpoint applies
30644 number of times the breakpoint has been hit
30647 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
30648 @code{body} field is an empty list.
30650 @subsubheading @value{GDBN} Command
30652 The corresponding @value{GDBN} command is @samp{info break}.
30654 @subsubheading Example
30659 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30660 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30661 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30662 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30663 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30664 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30665 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30666 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30667 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
30669 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
30670 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
30671 line="13",thread-groups=["i1"],times="0"@}]@}
30675 Here's an example of the result when there are no breakpoints:
30680 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
30681 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30682 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30683 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30684 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30685 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30686 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30691 @subheading The @code{-break-passcount} Command
30692 @findex -break-passcount
30694 @subsubheading Synopsis
30697 -break-passcount @var{tracepoint-number} @var{passcount}
30700 Set the passcount for tracepoint @var{tracepoint-number} to
30701 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
30702 is not a tracepoint, error is emitted. This corresponds to CLI
30703 command @samp{passcount}.
30705 @subheading The @code{-break-watch} Command
30706 @findex -break-watch
30708 @subsubheading Synopsis
30711 -break-watch [ -a | -r ]
30714 Create a watchpoint. With the @samp{-a} option it will create an
30715 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
30716 read from or on a write to the memory location. With the @samp{-r}
30717 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
30718 trigger only when the memory location is accessed for reading. Without
30719 either of the options, the watchpoint created is a regular watchpoint,
30720 i.e., it will trigger when the memory location is accessed for writing.
30721 @xref{Set Watchpoints, , Setting Watchpoints}.
30723 Note that @samp{-break-list} will report a single list of watchpoints and
30724 breakpoints inserted.
30726 @subsubheading @value{GDBN} Command
30728 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
30731 @subsubheading Example
30733 Setting a watchpoint on a variable in the @code{main} function:
30738 ^done,wpt=@{number="2",exp="x"@}
30743 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
30744 value=@{old="-268439212",new="55"@},
30745 frame=@{func="main",args=[],file="recursive2.c",
30746 fullname="/home/foo/bar/recursive2.c",line="5",arch="i386:x86_64"@}
30750 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
30751 the program execution twice: first for the variable changing value, then
30752 for the watchpoint going out of scope.
30757 ^done,wpt=@{number="5",exp="C"@}
30762 *stopped,reason="watchpoint-trigger",
30763 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
30764 frame=@{func="callee4",args=[],
30765 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30766 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13",
30767 arch="i386:x86_64"@}
30772 *stopped,reason="watchpoint-scope",wpnum="5",
30773 frame=@{func="callee3",args=[@{name="strarg",
30774 value="0x11940 \"A string argument.\""@}],
30775 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30776 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
30777 arch="i386:x86_64"@}
30781 Listing breakpoints and watchpoints, at different points in the program
30782 execution. Note that once the watchpoint goes out of scope, it is
30788 ^done,wpt=@{number="2",exp="C"@}
30791 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30792 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30793 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30794 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30795 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30796 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30797 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30798 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30799 addr="0x00010734",func="callee4",
30800 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30801 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
30803 bkpt=@{number="2",type="watchpoint",disp="keep",
30804 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
30809 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
30810 value=@{old="-276895068",new="3"@},
30811 frame=@{func="callee4",args=[],
30812 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30813 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13",
30814 arch="i386:x86_64"@}
30817 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30818 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30819 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30820 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30821 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30822 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30823 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30824 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30825 addr="0x00010734",func="callee4",
30826 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30827 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
30829 bkpt=@{number="2",type="watchpoint",disp="keep",
30830 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
30834 ^done,reason="watchpoint-scope",wpnum="2",
30835 frame=@{func="callee3",args=[@{name="strarg",
30836 value="0x11940 \"A string argument.\""@}],
30837 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30838 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
30839 arch="i386:x86_64"@}
30842 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30843 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30844 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30845 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30846 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30847 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30848 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30849 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30850 addr="0x00010734",func="callee4",
30851 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30852 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
30853 thread-groups=["i1"],times="1"@}]@}
30858 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30859 @node GDB/MI Catchpoint Commands
30860 @section @sc{gdb/mi} Catchpoint Commands
30862 This section documents @sc{gdb/mi} commands for manipulating
30866 * Shared Library GDB/MI Catchpoint Commands::
30867 * Ada Exception GDB/MI Catchpoint Commands::
30868 * C++ Exception GDB/MI Catchpoint Commands::
30871 @node Shared Library GDB/MI Catchpoint Commands
30872 @subsection Shared Library @sc{gdb/mi} Catchpoints
30874 @subheading The @code{-catch-load} Command
30875 @findex -catch-load
30877 @subsubheading Synopsis
30880 -catch-load [ -t ] [ -d ] @var{regexp}
30883 Add a catchpoint for library load events. If the @samp{-t} option is used,
30884 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
30885 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
30886 in a disabled state. The @samp{regexp} argument is a regular
30887 expression used to match the name of the loaded library.
30890 @subsubheading @value{GDBN} Command
30892 The corresponding @value{GDBN} command is @samp{catch load}.
30894 @subsubheading Example
30897 -catch-load -t foo.so
30898 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
30899 what="load of library matching foo.so",catch-type="load",times="0"@}
30904 @subheading The @code{-catch-unload} Command
30905 @findex -catch-unload
30907 @subsubheading Synopsis
30910 -catch-unload [ -t ] [ -d ] @var{regexp}
30913 Add a catchpoint for library unload events. If the @samp{-t} option is
30914 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
30915 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
30916 created in a disabled state. The @samp{regexp} argument is a regular
30917 expression used to match the name of the unloaded library.
30919 @subsubheading @value{GDBN} Command
30921 The corresponding @value{GDBN} command is @samp{catch unload}.
30923 @subsubheading Example
30926 -catch-unload -d bar.so
30927 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
30928 what="load of library matching bar.so",catch-type="unload",times="0"@}
30932 @node Ada Exception GDB/MI Catchpoint Commands
30933 @subsection Ada Exception @sc{gdb/mi} Catchpoints
30935 The following @sc{gdb/mi} commands can be used to create catchpoints
30936 that stop the execution when Ada exceptions are being raised.
30938 @subheading The @code{-catch-assert} Command
30939 @findex -catch-assert
30941 @subsubheading Synopsis
30944 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
30947 Add a catchpoint for failed Ada assertions.
30949 The possible optional parameters for this command are:
30952 @item -c @var{condition}
30953 Make the catchpoint conditional on @var{condition}.
30955 Create a disabled catchpoint.
30957 Create a temporary catchpoint.
30960 @subsubheading @value{GDBN} Command
30962 The corresponding @value{GDBN} command is @samp{catch assert}.
30964 @subsubheading Example
30968 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
30969 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
30970 thread-groups=["i1"],times="0",
30971 original-location="__gnat_debug_raise_assert_failure"@}
30975 @subheading The @code{-catch-exception} Command
30976 @findex -catch-exception
30978 @subsubheading Synopsis
30981 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
30985 Add a catchpoint stopping when Ada exceptions are raised.
30986 By default, the command stops the program when any Ada exception
30987 gets raised. But it is also possible, by using some of the
30988 optional parameters described below, to create more selective
30991 The possible optional parameters for this command are:
30994 @item -c @var{condition}
30995 Make the catchpoint conditional on @var{condition}.
30997 Create a disabled catchpoint.
30998 @item -e @var{exception-name}
30999 Only stop when @var{exception-name} is raised. This option cannot
31000 be used combined with @samp{-u}.
31002 Create a temporary catchpoint.
31004 Stop only when an unhandled exception gets raised. This option
31005 cannot be used combined with @samp{-e}.
31008 @subsubheading @value{GDBN} Command
31010 The corresponding @value{GDBN} commands are @samp{catch exception}
31011 and @samp{catch exception unhandled}.
31013 @subsubheading Example
31016 -catch-exception -e Program_Error
31017 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
31018 enabled="y",addr="0x0000000000404874",
31019 what="`Program_Error' Ada exception", thread-groups=["i1"],
31020 times="0",original-location="__gnat_debug_raise_exception"@}
31024 @subheading The @code{-catch-handlers} Command
31025 @findex -catch-handlers
31027 @subsubheading Synopsis
31030 -catch-handlers [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
31034 Add a catchpoint stopping when Ada exceptions are handled.
31035 By default, the command stops the program when any Ada exception
31036 gets handled. But it is also possible, by using some of the
31037 optional parameters described below, to create more selective
31040 The possible optional parameters for this command are:
31043 @item -c @var{condition}
31044 Make the catchpoint conditional on @var{condition}.
31046 Create a disabled catchpoint.
31047 @item -e @var{exception-name}
31048 Only stop when @var{exception-name} is handled.
31050 Create a temporary catchpoint.
31053 @subsubheading @value{GDBN} Command
31055 The corresponding @value{GDBN} command is @samp{catch handlers}.
31057 @subsubheading Example
31060 -catch-handlers -e Constraint_Error
31061 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
31062 enabled="y",addr="0x0000000000402f68",
31063 what="`Constraint_Error' Ada exception handlers",thread-groups=["i1"],
31064 times="0",original-location="__gnat_begin_handler"@}
31068 @node C++ Exception GDB/MI Catchpoint Commands
31069 @subsection C@t{++} Exception @sc{gdb/mi} Catchpoints
31071 The following @sc{gdb/mi} commands can be used to create catchpoints
31072 that stop the execution when C@t{++} exceptions are being throw, rethrown,
31075 @subheading The @code{-catch-throw} Command
31076 @findex -catch-throw
31078 @subsubheading Synopsis
31081 -catch-throw [ -t ] [ -r @var{regexp}]
31084 Stop when the debuggee throws a C@t{++} exception. If @var{regexp} is
31085 given, then only exceptions whose type matches the regular expression
31088 If @samp{-t} is given, then the catchpoint is enabled only for one
31089 stop, the catchpoint is automatically deleted after stopping once for
31092 @subsubheading @value{GDBN} Command
31094 The corresponding @value{GDBN} commands are @samp{catch throw}
31095 and @samp{tcatch throw} (@pxref{Set Catchpoints}).
31097 @subsubheading Example
31100 -catch-throw -r exception_type
31101 ^done,bkpt=@{number="1",type="catchpoint",disp="keep",enabled="y",
31102 what="exception throw",catch-type="throw",
31103 thread-groups=["i1"],
31104 regexp="exception_type",times="0"@}
31110 ~"Catchpoint 1 (exception thrown), 0x00007ffff7ae00ed
31111 in __cxa_throw () from /lib64/libstdc++.so.6\n"
31112 *stopped,bkptno="1",reason="breakpoint-hit",disp="keep",
31113 frame=@{addr="0x00007ffff7ae00ed",func="__cxa_throw",
31114 args=[],from="/lib64/libstdc++.so.6",arch="i386:x86-64"@},
31115 thread-id="1",stopped-threads="all",core="6"
31119 @subheading The @code{-catch-rethrow} Command
31120 @findex -catch-rethrow
31122 @subsubheading Synopsis
31125 -catch-rethrow [ -t ] [ -r @var{regexp}]
31128 Stop when a C@t{++} exception is re-thrown. If @var{regexp} is given,
31129 then only exceptions whose type matches the regular expression will be
31132 If @samp{-t} is given, then the catchpoint is enabled only for one
31133 stop, the catchpoint is automatically deleted after the first event is
31136 @subsubheading @value{GDBN} Command
31138 The corresponding @value{GDBN} commands are @samp{catch rethrow}
31139 and @samp{tcatch rethrow} (@pxref{Set Catchpoints}).
31141 @subsubheading Example
31144 -catch-rethrow -r exception_type
31145 ^done,bkpt=@{number="1",type="catchpoint",disp="keep",enabled="y",
31146 what="exception rethrow",catch-type="rethrow",
31147 thread-groups=["i1"],
31148 regexp="exception_type",times="0"@}
31154 ~"Catchpoint 1 (exception rethrown), 0x00007ffff7ae00ed
31155 in __cxa_rethrow () from /lib64/libstdc++.so.6\n"
31156 *stopped,bkptno="1",reason="breakpoint-hit",disp="keep",
31157 frame=@{addr="0x00007ffff7ae00ed",func="__cxa_rethrow",
31158 args=[],from="/lib64/libstdc++.so.6",arch="i386:x86-64"@},
31159 thread-id="1",stopped-threads="all",core="6"
31163 @subheading The @code{-catch-catch} Command
31164 @findex -catch-catch
31166 @subsubheading Synopsis
31169 -catch-catch [ -t ] [ -r @var{regexp}]
31172 Stop when the debuggee catches a C@t{++} exception. If @var{regexp}
31173 is given, then only exceptions whose type matches the regular
31174 expression will be caught.
31176 If @samp{-t} is given, then the catchpoint is enabled only for one
31177 stop, the catchpoint is automatically deleted after the first event is
31180 @subsubheading @value{GDBN} Command
31182 The corresponding @value{GDBN} commands are @samp{catch catch}
31183 and @samp{tcatch catch} (@pxref{Set Catchpoints}).
31185 @subsubheading Example
31188 -catch-catch -r exception_type
31189 ^done,bkpt=@{number="1",type="catchpoint",disp="keep",enabled="y",
31190 what="exception catch",catch-type="catch",
31191 thread-groups=["i1"],
31192 regexp="exception_type",times="0"@}
31198 ~"Catchpoint 1 (exception caught), 0x00007ffff7ae00ed
31199 in __cxa_begin_catch () from /lib64/libstdc++.so.6\n"
31200 *stopped,bkptno="1",reason="breakpoint-hit",disp="keep",
31201 frame=@{addr="0x00007ffff7ae00ed",func="__cxa_begin_catch",
31202 args=[],from="/lib64/libstdc++.so.6",arch="i386:x86-64"@},
31203 thread-id="1",stopped-threads="all",core="6"
31207 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31208 @node GDB/MI Program Context
31209 @section @sc{gdb/mi} Program Context
31211 @subheading The @code{-exec-arguments} Command
31212 @findex -exec-arguments
31215 @subsubheading Synopsis
31218 -exec-arguments @var{args}
31221 Set the inferior program arguments, to be used in the next
31224 @subsubheading @value{GDBN} Command
31226 The corresponding @value{GDBN} command is @samp{set args}.
31228 @subsubheading Example
31232 -exec-arguments -v word
31239 @subheading The @code{-exec-show-arguments} Command
31240 @findex -exec-show-arguments
31242 @subsubheading Synopsis
31245 -exec-show-arguments
31248 Print the arguments of the program.
31250 @subsubheading @value{GDBN} Command
31252 The corresponding @value{GDBN} command is @samp{show args}.
31254 @subsubheading Example
31259 @subheading The @code{-environment-cd} Command
31260 @findex -environment-cd
31262 @subsubheading Synopsis
31265 -environment-cd @var{pathdir}
31268 Set @value{GDBN}'s working directory.
31270 @subsubheading @value{GDBN} Command
31272 The corresponding @value{GDBN} command is @samp{cd}.
31274 @subsubheading Example
31278 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
31284 @subheading The @code{-environment-directory} Command
31285 @findex -environment-directory
31287 @subsubheading Synopsis
31290 -environment-directory [ -r ] [ @var{pathdir} ]+
31293 Add directories @var{pathdir} to beginning of search path for source files.
31294 If the @samp{-r} option is used, the search path is reset to the default
31295 search path. If directories @var{pathdir} are supplied in addition to the
31296 @samp{-r} option, the search path is first reset and then addition
31298 Multiple directories may be specified, separated by blanks. Specifying
31299 multiple directories in a single command
31300 results in the directories added to the beginning of the
31301 search path in the same order they were presented in the command.
31302 If blanks are needed as
31303 part of a directory name, double-quotes should be used around
31304 the name. In the command output, the path will show up separated
31305 by the system directory-separator character. The directory-separator
31306 character must not be used
31307 in any directory name.
31308 If no directories are specified, the current search path is displayed.
31310 @subsubheading @value{GDBN} Command
31312 The corresponding @value{GDBN} command is @samp{dir}.
31314 @subsubheading Example
31318 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
31319 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
31321 -environment-directory ""
31322 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
31324 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
31325 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
31327 -environment-directory -r
31328 ^done,source-path="$cdir:$cwd"
31333 @subheading The @code{-environment-path} Command
31334 @findex -environment-path
31336 @subsubheading Synopsis
31339 -environment-path [ -r ] [ @var{pathdir} ]+
31342 Add directories @var{pathdir} to beginning of search path for object files.
31343 If the @samp{-r} option is used, the search path is reset to the original
31344 search path that existed at gdb start-up. If directories @var{pathdir} are
31345 supplied in addition to the
31346 @samp{-r} option, the search path is first reset and then addition
31348 Multiple directories may be specified, separated by blanks. Specifying
31349 multiple directories in a single command
31350 results in the directories added to the beginning of the
31351 search path in the same order they were presented in the command.
31352 If blanks are needed as
31353 part of a directory name, double-quotes should be used around
31354 the name. In the command output, the path will show up separated
31355 by the system directory-separator character. The directory-separator
31356 character must not be used
31357 in any directory name.
31358 If no directories are specified, the current path is displayed.
31361 @subsubheading @value{GDBN} Command
31363 The corresponding @value{GDBN} command is @samp{path}.
31365 @subsubheading Example
31370 ^done,path="/usr/bin"
31372 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
31373 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
31375 -environment-path -r /usr/local/bin
31376 ^done,path="/usr/local/bin:/usr/bin"
31381 @subheading The @code{-environment-pwd} Command
31382 @findex -environment-pwd
31384 @subsubheading Synopsis
31390 Show the current working directory.
31392 @subsubheading @value{GDBN} Command
31394 The corresponding @value{GDBN} command is @samp{pwd}.
31396 @subsubheading Example
31401 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
31405 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31406 @node GDB/MI Thread Commands
31407 @section @sc{gdb/mi} Thread Commands
31410 @subheading The @code{-thread-info} Command
31411 @findex -thread-info
31413 @subsubheading Synopsis
31416 -thread-info [ @var{thread-id} ]
31419 Reports information about either a specific thread, if the
31420 @var{thread-id} parameter is present, or about all threads.
31421 @var{thread-id} is the thread's global thread ID. When printing
31422 information about all threads, also reports the global ID of the
31425 @subsubheading @value{GDBN} Command
31427 The @samp{info thread} command prints the same information
31430 @subsubheading Result
31432 The result contains the following attributes:
31436 A list of threads. The format of the elements of the list is described in
31437 @ref{GDB/MI Thread Information}.
31439 @item current-thread-id
31440 The global id of the currently selected thread. This field is omitted if there
31441 is no selected thread (for example, when the selected inferior is not running,
31442 and therefore has no threads) or if a @var{thread-id} argument was passed to
31447 @subsubheading Example
31452 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
31453 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
31454 args=[]@},state="running"@},
31455 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
31456 frame=@{level="0",addr="0x0804891f",func="foo",
31457 args=[@{name="i",value="10"@}],
31458 file="/tmp/a.c",fullname="/tmp/a.c",line="158",arch="i386:x86_64"@},
31459 state="running"@}],
31460 current-thread-id="1"
31464 @subheading The @code{-thread-list-ids} Command
31465 @findex -thread-list-ids
31467 @subsubheading Synopsis
31473 Produces a list of the currently known global @value{GDBN} thread ids.
31474 At the end of the list it also prints the total number of such
31477 This command is retained for historical reasons, the
31478 @code{-thread-info} command should be used instead.
31480 @subsubheading @value{GDBN} Command
31482 Part of @samp{info threads} supplies the same information.
31484 @subsubheading Example
31489 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
31490 current-thread-id="1",number-of-threads="3"
31495 @subheading The @code{-thread-select} Command
31496 @findex -thread-select
31498 @subsubheading Synopsis
31501 -thread-select @var{thread-id}
31504 Make thread with global thread number @var{thread-id} the current
31505 thread. It prints the number of the new current thread, and the
31506 topmost frame for that thread.
31508 This command is deprecated in favor of explicitly using the
31509 @samp{--thread} option to each command.
31511 @subsubheading @value{GDBN} Command
31513 The corresponding @value{GDBN} command is @samp{thread}.
31515 @subsubheading Example
31522 *stopped,reason="end-stepping-range",thread-id="2",line="187",
31523 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
31527 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
31528 number-of-threads="3"
31531 ^done,new-thread-id="3",
31532 frame=@{level="0",func="vprintf",
31533 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
31534 @{name="arg",value="0x2"@}],file="vprintf.c",line="31",arch="i386:x86_64"@}
31538 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31539 @node GDB/MI Ada Tasking Commands
31540 @section @sc{gdb/mi} Ada Tasking Commands
31542 @subheading The @code{-ada-task-info} Command
31543 @findex -ada-task-info
31545 @subsubheading Synopsis
31548 -ada-task-info [ @var{task-id} ]
31551 Reports information about either a specific Ada task, if the
31552 @var{task-id} parameter is present, or about all Ada tasks.
31554 @subsubheading @value{GDBN} Command
31556 The @samp{info tasks} command prints the same information
31557 about all Ada tasks (@pxref{Ada Tasks}).
31559 @subsubheading Result
31561 The result is a table of Ada tasks. The following columns are
31562 defined for each Ada task:
31566 This field exists only for the current thread. It has the value @samp{*}.
31569 The identifier that @value{GDBN} uses to refer to the Ada task.
31572 The identifier that the target uses to refer to the Ada task.
31575 The global thread identifier of the thread corresponding to the Ada
31578 This field should always exist, as Ada tasks are always implemented
31579 on top of a thread. But if @value{GDBN} cannot find this corresponding
31580 thread for any reason, the field is omitted.
31583 This field exists only when the task was created by another task.
31584 In this case, it provides the ID of the parent task.
31587 The base priority of the task.
31590 The current state of the task. For a detailed description of the
31591 possible states, see @ref{Ada Tasks}.
31594 The name of the task.
31598 @subsubheading Example
31602 ^done,tasks=@{nr_rows="3",nr_cols="8",
31603 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
31604 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
31605 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
31606 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
31607 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
31608 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
31609 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
31610 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
31611 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
31612 state="Child Termination Wait",name="main_task"@}]@}
31616 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31617 @node GDB/MI Program Execution
31618 @section @sc{gdb/mi} Program Execution
31620 These are the asynchronous commands which generate the out-of-band
31621 record @samp{*stopped}. Currently @value{GDBN} only really executes
31622 asynchronously with remote targets and this interaction is mimicked in
31625 @subheading The @code{-exec-continue} Command
31626 @findex -exec-continue
31628 @subsubheading Synopsis
31631 -exec-continue [--reverse] [--all|--thread-group N]
31634 Resumes the execution of the inferior program, which will continue
31635 to execute until it reaches a debugger stop event. If the
31636 @samp{--reverse} option is specified, execution resumes in reverse until
31637 it reaches a stop event. Stop events may include
31640 breakpoints or watchpoints
31642 signals or exceptions
31644 the end of the process (or its beginning under @samp{--reverse})
31646 the end or beginning of a replay log if one is being used.
31648 In all-stop mode (@pxref{All-Stop
31649 Mode}), may resume only one thread, or all threads, depending on the
31650 value of the @samp{scheduler-locking} variable. If @samp{--all} is
31651 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
31652 ignored in all-stop mode. If the @samp{--thread-group} options is
31653 specified, then all threads in that thread group are resumed.
31655 @subsubheading @value{GDBN} Command
31657 The corresponding @value{GDBN} corresponding is @samp{continue}.
31659 @subsubheading Example
31666 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
31667 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
31668 line="13",arch="i386:x86_64"@}
31673 @subheading The @code{-exec-finish} Command
31674 @findex -exec-finish
31676 @subsubheading Synopsis
31679 -exec-finish [--reverse]
31682 Resumes the execution of the inferior program until the current
31683 function is exited. Displays the results returned by the function.
31684 If the @samp{--reverse} option is specified, resumes the reverse
31685 execution of the inferior program until the point where current
31686 function was called.
31688 @subsubheading @value{GDBN} Command
31690 The corresponding @value{GDBN} command is @samp{finish}.
31692 @subsubheading Example
31694 Function returning @code{void}.
31701 *stopped,reason="function-finished",frame=@{func="main",args=[],
31702 file="hello.c",fullname="/home/foo/bar/hello.c",line="7",arch="i386:x86_64"@}
31706 Function returning other than @code{void}. The name of the internal
31707 @value{GDBN} variable storing the result is printed, together with the
31714 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
31715 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
31716 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
31717 arch="i386:x86_64"@},
31718 gdb-result-var="$1",return-value="0"
31723 @subheading The @code{-exec-interrupt} Command
31724 @findex -exec-interrupt
31726 @subsubheading Synopsis
31729 -exec-interrupt [--all|--thread-group N]
31732 Interrupts the background execution of the target. Note how the token
31733 associated with the stop message is the one for the execution command
31734 that has been interrupted. The token for the interrupt itself only
31735 appears in the @samp{^done} output. If the user is trying to
31736 interrupt a non-running program, an error message will be printed.
31738 Note that when asynchronous execution is enabled, this command is
31739 asynchronous just like other execution commands. That is, first the
31740 @samp{^done} response will be printed, and the target stop will be
31741 reported after that using the @samp{*stopped} notification.
31743 In non-stop mode, only the context thread is interrupted by default.
31744 All threads (in all inferiors) will be interrupted if the
31745 @samp{--all} option is specified. If the @samp{--thread-group}
31746 option is specified, all threads in that group will be interrupted.
31748 @subsubheading @value{GDBN} Command
31750 The corresponding @value{GDBN} command is @samp{interrupt}.
31752 @subsubheading Example
31763 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
31764 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
31765 fullname="/home/foo/bar/try.c",line="13",arch="i386:x86_64"@}
31770 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
31774 @subheading The @code{-exec-jump} Command
31777 @subsubheading Synopsis
31780 -exec-jump @var{location}
31783 Resumes execution of the inferior program at the location specified by
31784 parameter. @xref{Specify Location}, for a description of the
31785 different forms of @var{location}.
31787 @subsubheading @value{GDBN} Command
31789 The corresponding @value{GDBN} command is @samp{jump}.
31791 @subsubheading Example
31794 -exec-jump foo.c:10
31795 *running,thread-id="all"
31800 @subheading The @code{-exec-next} Command
31803 @subsubheading Synopsis
31806 -exec-next [--reverse]
31809 Resumes execution of the inferior program, stopping when the beginning
31810 of the next source line is reached.
31812 If the @samp{--reverse} option is specified, resumes reverse execution
31813 of the inferior program, stopping at the beginning of the previous
31814 source line. If you issue this command on the first line of a
31815 function, it will take you back to the caller of that function, to the
31816 source line where the function was called.
31819 @subsubheading @value{GDBN} Command
31821 The corresponding @value{GDBN} command is @samp{next}.
31823 @subsubheading Example
31829 *stopped,reason="end-stepping-range",line="8",file="hello.c"
31834 @subheading The @code{-exec-next-instruction} Command
31835 @findex -exec-next-instruction
31837 @subsubheading Synopsis
31840 -exec-next-instruction [--reverse]
31843 Executes one machine instruction. If the instruction is a function
31844 call, continues until the function returns. If the program stops at an
31845 instruction in the middle of a source line, the address will be
31848 If the @samp{--reverse} option is specified, resumes reverse execution
31849 of the inferior program, stopping at the previous instruction. If the
31850 previously executed instruction was a return from another function,
31851 it will continue to execute in reverse until the call to that function
31852 (from the current stack frame) is reached.
31854 @subsubheading @value{GDBN} Command
31856 The corresponding @value{GDBN} command is @samp{nexti}.
31858 @subsubheading Example
31862 -exec-next-instruction
31866 *stopped,reason="end-stepping-range",
31867 addr="0x000100d4",line="5",file="hello.c"
31872 @subheading The @code{-exec-return} Command
31873 @findex -exec-return
31875 @subsubheading Synopsis
31881 Makes current function return immediately. Doesn't execute the inferior.
31882 Displays the new current frame.
31884 @subsubheading @value{GDBN} Command
31886 The corresponding @value{GDBN} command is @samp{return}.
31888 @subsubheading Example
31892 200-break-insert callee4
31893 200^done,bkpt=@{number="1",addr="0x00010734",
31894 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
31899 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
31900 frame=@{func="callee4",args=[],
31901 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31902 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
31903 arch="i386:x86_64"@}
31909 111^done,frame=@{level="0",func="callee3",
31910 args=[@{name="strarg",
31911 value="0x11940 \"A string argument.\""@}],
31912 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31913 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
31914 arch="i386:x86_64"@}
31919 @subheading The @code{-exec-run} Command
31922 @subsubheading Synopsis
31925 -exec-run [ --all | --thread-group N ] [ --start ]
31928 Starts execution of the inferior from the beginning. The inferior
31929 executes until either a breakpoint is encountered or the program
31930 exits. In the latter case the output will include an exit code, if
31931 the program has exited exceptionally.
31933 When neither the @samp{--all} nor the @samp{--thread-group} option
31934 is specified, the current inferior is started. If the
31935 @samp{--thread-group} option is specified, it should refer to a thread
31936 group of type @samp{process}, and that thread group will be started.
31937 If the @samp{--all} option is specified, then all inferiors will be started.
31939 Using the @samp{--start} option instructs the debugger to stop
31940 the execution at the start of the inferior's main subprogram,
31941 following the same behavior as the @code{start} command
31942 (@pxref{Starting}).
31944 @subsubheading @value{GDBN} Command
31946 The corresponding @value{GDBN} command is @samp{run}.
31948 @subsubheading Examples
31953 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
31958 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
31959 frame=@{func="main",args=[],file="recursive2.c",
31960 fullname="/home/foo/bar/recursive2.c",line="4",arch="i386:x86_64"@}
31965 Program exited normally:
31973 *stopped,reason="exited-normally"
31978 Program exited exceptionally:
31986 *stopped,reason="exited",exit-code="01"
31990 Another way the program can terminate is if it receives a signal such as
31991 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
31995 *stopped,reason="exited-signalled",signal-name="SIGINT",
31996 signal-meaning="Interrupt"
32000 @c @subheading -exec-signal
32003 @subheading The @code{-exec-step} Command
32006 @subsubheading Synopsis
32009 -exec-step [--reverse]
32012 Resumes execution of the inferior program, stopping when the beginning
32013 of the next source line is reached, if the next source line is not a
32014 function call. If it is, stop at the first instruction of the called
32015 function. If the @samp{--reverse} option is specified, resumes reverse
32016 execution of the inferior program, stopping at the beginning of the
32017 previously executed source line.
32019 @subsubheading @value{GDBN} Command
32021 The corresponding @value{GDBN} command is @samp{step}.
32023 @subsubheading Example
32025 Stepping into a function:
32031 *stopped,reason="end-stepping-range",
32032 frame=@{func="foo",args=[@{name="a",value="10"@},
32033 @{name="b",value="0"@}],file="recursive2.c",
32034 fullname="/home/foo/bar/recursive2.c",line="11",arch="i386:x86_64"@}
32044 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
32049 @subheading The @code{-exec-step-instruction} Command
32050 @findex -exec-step-instruction
32052 @subsubheading Synopsis
32055 -exec-step-instruction [--reverse]
32058 Resumes the inferior which executes one machine instruction. If the
32059 @samp{--reverse} option is specified, resumes reverse execution of the
32060 inferior program, stopping at the previously executed instruction.
32061 The output, once @value{GDBN} has stopped, will vary depending on
32062 whether we have stopped in the middle of a source line or not. In the
32063 former case, the address at which the program stopped will be printed
32066 @subsubheading @value{GDBN} Command
32068 The corresponding @value{GDBN} command is @samp{stepi}.
32070 @subsubheading Example
32074 -exec-step-instruction
32078 *stopped,reason="end-stepping-range",
32079 frame=@{func="foo",args=[],file="try.c",
32080 fullname="/home/foo/bar/try.c",line="10",arch="i386:x86_64"@}
32082 -exec-step-instruction
32086 *stopped,reason="end-stepping-range",
32087 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
32088 fullname="/home/foo/bar/try.c",line="10",arch="i386:x86_64"@}
32093 @subheading The @code{-exec-until} Command
32094 @findex -exec-until
32096 @subsubheading Synopsis
32099 -exec-until [ @var{location} ]
32102 Executes the inferior until the @var{location} specified in the
32103 argument is reached. If there is no argument, the inferior executes
32104 until a source line greater than the current one is reached. The
32105 reason for stopping in this case will be @samp{location-reached}.
32107 @subsubheading @value{GDBN} Command
32109 The corresponding @value{GDBN} command is @samp{until}.
32111 @subsubheading Example
32115 -exec-until recursive2.c:6
32119 *stopped,reason="location-reached",frame=@{func="main",args=[],
32120 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6",
32121 arch="i386:x86_64"@}
32126 @subheading -file-clear
32127 Is this going away????
32130 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32131 @node GDB/MI Stack Manipulation
32132 @section @sc{gdb/mi} Stack Manipulation Commands
32134 @subheading The @code{-enable-frame-filters} Command
32135 @findex -enable-frame-filters
32138 -enable-frame-filters
32141 @value{GDBN} allows Python-based frame filters to affect the output of
32142 the MI commands relating to stack traces. As there is no way to
32143 implement this in a fully backward-compatible way, a front end must
32144 request that this functionality be enabled.
32146 Once enabled, this feature cannot be disabled.
32148 Note that if Python support has not been compiled into @value{GDBN},
32149 this command will still succeed (and do nothing).
32151 @subheading The @code{-stack-info-frame} Command
32152 @findex -stack-info-frame
32154 @subsubheading Synopsis
32160 Get info on the selected frame.
32162 @subsubheading @value{GDBN} Command
32164 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
32165 (without arguments).
32167 @subsubheading Example
32172 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
32173 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
32174 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17",
32175 arch="i386:x86_64"@}
32179 @subheading The @code{-stack-info-depth} Command
32180 @findex -stack-info-depth
32182 @subsubheading Synopsis
32185 -stack-info-depth [ @var{max-depth} ]
32188 Return the depth of the stack. If the integer argument @var{max-depth}
32189 is specified, do not count beyond @var{max-depth} frames.
32191 @subsubheading @value{GDBN} Command
32193 There's no equivalent @value{GDBN} command.
32195 @subsubheading Example
32197 For a stack with frame levels 0 through 11:
32204 -stack-info-depth 4
32207 -stack-info-depth 12
32210 -stack-info-depth 11
32213 -stack-info-depth 13
32218 @anchor{-stack-list-arguments}
32219 @subheading The @code{-stack-list-arguments} Command
32220 @findex -stack-list-arguments
32222 @subsubheading Synopsis
32225 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
32226 [ @var{low-frame} @var{high-frame} ]
32229 Display a list of the arguments for the frames between @var{low-frame}
32230 and @var{high-frame} (inclusive). If @var{low-frame} and
32231 @var{high-frame} are not provided, list the arguments for the whole
32232 call stack. If the two arguments are equal, show the single frame
32233 at the corresponding level. It is an error if @var{low-frame} is
32234 larger than the actual number of frames. On the other hand,
32235 @var{high-frame} may be larger than the actual number of frames, in
32236 which case only existing frames will be returned.
32238 If @var{print-values} is 0 or @code{--no-values}, print only the names of
32239 the variables; if it is 1 or @code{--all-values}, print also their
32240 values; and if it is 2 or @code{--simple-values}, print the name,
32241 type and value for simple data types, and the name and type for arrays,
32242 structures and unions. If the option @code{--no-frame-filters} is
32243 supplied, then Python frame filters will not be executed.
32245 If the @code{--skip-unavailable} option is specified, arguments that
32246 are not available are not listed. Partially available arguments
32247 are still displayed, however.
32249 Use of this command to obtain arguments in a single frame is
32250 deprecated in favor of the @samp{-stack-list-variables} command.
32252 @subsubheading @value{GDBN} Command
32254 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
32255 @samp{gdb_get_args} command which partially overlaps with the
32256 functionality of @samp{-stack-list-arguments}.
32258 @subsubheading Example
32265 frame=@{level="0",addr="0x00010734",func="callee4",
32266 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
32267 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
32268 arch="i386:x86_64"@},
32269 frame=@{level="1",addr="0x0001076c",func="callee3",
32270 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
32271 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17",
32272 arch="i386:x86_64"@},
32273 frame=@{level="2",addr="0x0001078c",func="callee2",
32274 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
32275 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22",
32276 arch="i386:x86_64"@},
32277 frame=@{level="3",addr="0x000107b4",func="callee1",
32278 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
32279 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27",
32280 arch="i386:x86_64"@},
32281 frame=@{level="4",addr="0x000107e0",func="main",
32282 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
32283 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32",
32284 arch="i386:x86_64"@}]
32286 -stack-list-arguments 0
32289 frame=@{level="0",args=[]@},
32290 frame=@{level="1",args=[name="strarg"]@},
32291 frame=@{level="2",args=[name="intarg",name="strarg"]@},
32292 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
32293 frame=@{level="4",args=[]@}]
32295 -stack-list-arguments 1
32298 frame=@{level="0",args=[]@},
32300 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
32301 frame=@{level="2",args=[
32302 @{name="intarg",value="2"@},
32303 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
32304 @{frame=@{level="3",args=[
32305 @{name="intarg",value="2"@},
32306 @{name="strarg",value="0x11940 \"A string argument.\""@},
32307 @{name="fltarg",value="3.5"@}]@},
32308 frame=@{level="4",args=[]@}]
32310 -stack-list-arguments 0 2 2
32311 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
32313 -stack-list-arguments 1 2 2
32314 ^done,stack-args=[frame=@{level="2",
32315 args=[@{name="intarg",value="2"@},
32316 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
32320 @c @subheading -stack-list-exception-handlers
32323 @anchor{-stack-list-frames}
32324 @subheading The @code{-stack-list-frames} Command
32325 @findex -stack-list-frames
32327 @subsubheading Synopsis
32330 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
32333 List the frames currently on the stack. For each frame it displays the
32338 The frame number, 0 being the topmost frame, i.e., the innermost function.
32340 The @code{$pc} value for that frame.
32344 File name of the source file where the function lives.
32345 @item @var{fullname}
32346 The full file name of the source file where the function lives.
32348 Line number corresponding to the @code{$pc}.
32350 The shared library where this function is defined. This is only given
32351 if the frame's function is not known.
32353 Frame's architecture.
32356 If invoked without arguments, this command prints a backtrace for the
32357 whole stack. If given two integer arguments, it shows the frames whose
32358 levels are between the two arguments (inclusive). If the two arguments
32359 are equal, it shows the single frame at the corresponding level. It is
32360 an error if @var{low-frame} is larger than the actual number of
32361 frames. On the other hand, @var{high-frame} may be larger than the
32362 actual number of frames, in which case only existing frames will be
32363 returned. If the option @code{--no-frame-filters} is supplied, then
32364 Python frame filters will not be executed.
32366 @subsubheading @value{GDBN} Command
32368 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
32370 @subsubheading Example
32372 Full stack backtrace:
32378 [frame=@{level="0",addr="0x0001076c",func="foo",
32379 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11",
32380 arch="i386:x86_64"@},
32381 frame=@{level="1",addr="0x000107a4",func="foo",
32382 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32383 arch="i386:x86_64"@},
32384 frame=@{level="2",addr="0x000107a4",func="foo",
32385 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32386 arch="i386:x86_64"@},
32387 frame=@{level="3",addr="0x000107a4",func="foo",
32388 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32389 arch="i386:x86_64"@},
32390 frame=@{level="4",addr="0x000107a4",func="foo",
32391 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32392 arch="i386:x86_64"@},
32393 frame=@{level="5",addr="0x000107a4",func="foo",
32394 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32395 arch="i386:x86_64"@},
32396 frame=@{level="6",addr="0x000107a4",func="foo",
32397 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32398 arch="i386:x86_64"@},
32399 frame=@{level="7",addr="0x000107a4",func="foo",
32400 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32401 arch="i386:x86_64"@},
32402 frame=@{level="8",addr="0x000107a4",func="foo",
32403 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32404 arch="i386:x86_64"@},
32405 frame=@{level="9",addr="0x000107a4",func="foo",
32406 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32407 arch="i386:x86_64"@},
32408 frame=@{level="10",addr="0x000107a4",func="foo",
32409 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32410 arch="i386:x86_64"@},
32411 frame=@{level="11",addr="0x00010738",func="main",
32412 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4",
32413 arch="i386:x86_64"@}]
32417 Show frames between @var{low_frame} and @var{high_frame}:
32421 -stack-list-frames 3 5
32423 [frame=@{level="3",addr="0x000107a4",func="foo",
32424 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32425 arch="i386:x86_64"@},
32426 frame=@{level="4",addr="0x000107a4",func="foo",
32427 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32428 arch="i386:x86_64"@},
32429 frame=@{level="5",addr="0x000107a4",func="foo",
32430 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32431 arch="i386:x86_64"@}]
32435 Show a single frame:
32439 -stack-list-frames 3 3
32441 [frame=@{level="3",addr="0x000107a4",func="foo",
32442 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32443 arch="i386:x86_64"@}]
32448 @subheading The @code{-stack-list-locals} Command
32449 @findex -stack-list-locals
32450 @anchor{-stack-list-locals}
32452 @subsubheading Synopsis
32455 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
32458 Display the local variable names for the selected frame. If
32459 @var{print-values} is 0 or @code{--no-values}, print only the names of
32460 the variables; if it is 1 or @code{--all-values}, print also their
32461 values; and if it is 2 or @code{--simple-values}, print the name,
32462 type and value for simple data types, and the name and type for arrays,
32463 structures and unions. In this last case, a frontend can immediately
32464 display the value of simple data types and create variable objects for
32465 other data types when the user wishes to explore their values in
32466 more detail. If the option @code{--no-frame-filters} is supplied, then
32467 Python frame filters will not be executed.
32469 If the @code{--skip-unavailable} option is specified, local variables
32470 that are not available are not listed. Partially available local
32471 variables are still displayed, however.
32473 This command is deprecated in favor of the
32474 @samp{-stack-list-variables} command.
32476 @subsubheading @value{GDBN} Command
32478 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
32480 @subsubheading Example
32484 -stack-list-locals 0
32485 ^done,locals=[name="A",name="B",name="C"]
32487 -stack-list-locals --all-values
32488 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
32489 @{name="C",value="@{1, 2, 3@}"@}]
32490 -stack-list-locals --simple-values
32491 ^done,locals=[@{name="A",type="int",value="1"@},
32492 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
32496 @anchor{-stack-list-variables}
32497 @subheading The @code{-stack-list-variables} Command
32498 @findex -stack-list-variables
32500 @subsubheading Synopsis
32503 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
32506 Display the names of local variables and function arguments for the selected frame. If
32507 @var{print-values} is 0 or @code{--no-values}, print only the names of
32508 the variables; if it is 1 or @code{--all-values}, print also their
32509 values; and if it is 2 or @code{--simple-values}, print the name,
32510 type and value for simple data types, and the name and type for arrays,
32511 structures and unions. If the option @code{--no-frame-filters} is
32512 supplied, then Python frame filters will not be executed.
32514 If the @code{--skip-unavailable} option is specified, local variables
32515 and arguments that are not available are not listed. Partially
32516 available arguments and local variables are still displayed, however.
32518 @subsubheading Example
32522 -stack-list-variables --thread 1 --frame 0 --all-values
32523 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
32528 @subheading The @code{-stack-select-frame} Command
32529 @findex -stack-select-frame
32531 @subsubheading Synopsis
32534 -stack-select-frame @var{framenum}
32537 Change the selected frame. Select a different frame @var{framenum} on
32540 This command in deprecated in favor of passing the @samp{--frame}
32541 option to every command.
32543 @subsubheading @value{GDBN} Command
32545 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
32546 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
32548 @subsubheading Example
32552 -stack-select-frame 2
32557 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32558 @node GDB/MI Variable Objects
32559 @section @sc{gdb/mi} Variable Objects
32563 @subheading Motivation for Variable Objects in @sc{gdb/mi}
32565 For the implementation of a variable debugger window (locals, watched
32566 expressions, etc.), we are proposing the adaptation of the existing code
32567 used by @code{Insight}.
32569 The two main reasons for that are:
32573 It has been proven in practice (it is already on its second generation).
32576 It will shorten development time (needless to say how important it is
32580 The original interface was designed to be used by Tcl code, so it was
32581 slightly changed so it could be used through @sc{gdb/mi}. This section
32582 describes the @sc{gdb/mi} operations that will be available and gives some
32583 hints about their use.
32585 @emph{Note}: In addition to the set of operations described here, we
32586 expect the @sc{gui} implementation of a variable window to require, at
32587 least, the following operations:
32590 @item @code{-gdb-show} @code{output-radix}
32591 @item @code{-stack-list-arguments}
32592 @item @code{-stack-list-locals}
32593 @item @code{-stack-select-frame}
32598 @subheading Introduction to Variable Objects
32600 @cindex variable objects in @sc{gdb/mi}
32602 Variable objects are "object-oriented" MI interface for examining and
32603 changing values of expressions. Unlike some other MI interfaces that
32604 work with expressions, variable objects are specifically designed for
32605 simple and efficient presentation in the frontend. A variable object
32606 is identified by string name. When a variable object is created, the
32607 frontend specifies the expression for that variable object. The
32608 expression can be a simple variable, or it can be an arbitrary complex
32609 expression, and can even involve CPU registers. After creating a
32610 variable object, the frontend can invoke other variable object
32611 operations---for example to obtain or change the value of a variable
32612 object, or to change display format.
32614 Variable objects have hierarchical tree structure. Any variable object
32615 that corresponds to a composite type, such as structure in C, has
32616 a number of child variable objects, for example corresponding to each
32617 element of a structure. A child variable object can itself have
32618 children, recursively. Recursion ends when we reach
32619 leaf variable objects, which always have built-in types. Child variable
32620 objects are created only by explicit request, so if a frontend
32621 is not interested in the children of a particular variable object, no
32622 child will be created.
32624 For a leaf variable object it is possible to obtain its value as a
32625 string, or set the value from a string. String value can be also
32626 obtained for a non-leaf variable object, but it's generally a string
32627 that only indicates the type of the object, and does not list its
32628 contents. Assignment to a non-leaf variable object is not allowed.
32630 A frontend does not need to read the values of all variable objects each time
32631 the program stops. Instead, MI provides an update command that lists all
32632 variable objects whose values has changed since the last update
32633 operation. This considerably reduces the amount of data that must
32634 be transferred to the frontend. As noted above, children variable
32635 objects are created on demand, and only leaf variable objects have a
32636 real value. As result, gdb will read target memory only for leaf
32637 variables that frontend has created.
32639 The automatic update is not always desirable. For example, a frontend
32640 might want to keep a value of some expression for future reference,
32641 and never update it. For another example, fetching memory is
32642 relatively slow for embedded targets, so a frontend might want
32643 to disable automatic update for the variables that are either not
32644 visible on the screen, or ``closed''. This is possible using so
32645 called ``frozen variable objects''. Such variable objects are never
32646 implicitly updated.
32648 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
32649 fixed variable object, the expression is parsed when the variable
32650 object is created, including associating identifiers to specific
32651 variables. The meaning of expression never changes. For a floating
32652 variable object the values of variables whose names appear in the
32653 expressions are re-evaluated every time in the context of the current
32654 frame. Consider this example:
32659 struct work_state state;
32666 If a fixed variable object for the @code{state} variable is created in
32667 this function, and we enter the recursive call, the variable
32668 object will report the value of @code{state} in the top-level
32669 @code{do_work} invocation. On the other hand, a floating variable
32670 object will report the value of @code{state} in the current frame.
32672 If an expression specified when creating a fixed variable object
32673 refers to a local variable, the variable object becomes bound to the
32674 thread and frame in which the variable object is created. When such
32675 variable object is updated, @value{GDBN} makes sure that the
32676 thread/frame combination the variable object is bound to still exists,
32677 and re-evaluates the variable object in context of that thread/frame.
32679 The following is the complete set of @sc{gdb/mi} operations defined to
32680 access this functionality:
32682 @multitable @columnfractions .4 .6
32683 @item @strong{Operation}
32684 @tab @strong{Description}
32686 @item @code{-enable-pretty-printing}
32687 @tab enable Python-based pretty-printing
32688 @item @code{-var-create}
32689 @tab create a variable object
32690 @item @code{-var-delete}
32691 @tab delete the variable object and/or its children
32692 @item @code{-var-set-format}
32693 @tab set the display format of this variable
32694 @item @code{-var-show-format}
32695 @tab show the display format of this variable
32696 @item @code{-var-info-num-children}
32697 @tab tells how many children this object has
32698 @item @code{-var-list-children}
32699 @tab return a list of the object's children
32700 @item @code{-var-info-type}
32701 @tab show the type of this variable object
32702 @item @code{-var-info-expression}
32703 @tab print parent-relative expression that this variable object represents
32704 @item @code{-var-info-path-expression}
32705 @tab print full expression that this variable object represents
32706 @item @code{-var-show-attributes}
32707 @tab is this variable editable? does it exist here?
32708 @item @code{-var-evaluate-expression}
32709 @tab get the value of this variable
32710 @item @code{-var-assign}
32711 @tab set the value of this variable
32712 @item @code{-var-update}
32713 @tab update the variable and its children
32714 @item @code{-var-set-frozen}
32715 @tab set frozenness attribute
32716 @item @code{-var-set-update-range}
32717 @tab set range of children to display on update
32720 In the next subsection we describe each operation in detail and suggest
32721 how it can be used.
32723 @subheading Description And Use of Operations on Variable Objects
32725 @subheading The @code{-enable-pretty-printing} Command
32726 @findex -enable-pretty-printing
32729 -enable-pretty-printing
32732 @value{GDBN} allows Python-based visualizers to affect the output of the
32733 MI variable object commands. However, because there was no way to
32734 implement this in a fully backward-compatible way, a front end must
32735 request that this functionality be enabled.
32737 Once enabled, this feature cannot be disabled.
32739 Note that if Python support has not been compiled into @value{GDBN},
32740 this command will still succeed (and do nothing).
32742 This feature is currently (as of @value{GDBN} 7.0) experimental, and
32743 may work differently in future versions of @value{GDBN}.
32745 @subheading The @code{-var-create} Command
32746 @findex -var-create
32748 @subsubheading Synopsis
32751 -var-create @{@var{name} | "-"@}
32752 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
32755 This operation creates a variable object, which allows the monitoring of
32756 a variable, the result of an expression, a memory cell or a CPU
32759 The @var{name} parameter is the string by which the object can be
32760 referenced. It must be unique. If @samp{-} is specified, the varobj
32761 system will generate a string ``varNNNNNN'' automatically. It will be
32762 unique provided that one does not specify @var{name} of that format.
32763 The command fails if a duplicate name is found.
32765 The frame under which the expression should be evaluated can be
32766 specified by @var{frame-addr}. A @samp{*} indicates that the current
32767 frame should be used. A @samp{@@} indicates that a floating variable
32768 object must be created.
32770 @var{expression} is any expression valid on the current language set (must not
32771 begin with a @samp{*}), or one of the following:
32775 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
32778 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
32781 @samp{$@var{regname}} --- a CPU register name
32784 @cindex dynamic varobj
32785 A varobj's contents may be provided by a Python-based pretty-printer. In this
32786 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
32787 have slightly different semantics in some cases. If the
32788 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
32789 will never create a dynamic varobj. This ensures backward
32790 compatibility for existing clients.
32792 @subsubheading Result
32794 This operation returns attributes of the newly-created varobj. These
32799 The name of the varobj.
32802 The number of children of the varobj. This number is not necessarily
32803 reliable for a dynamic varobj. Instead, you must examine the
32804 @samp{has_more} attribute.
32807 The varobj's scalar value. For a varobj whose type is some sort of
32808 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
32809 will not be interesting.
32812 The varobj's type. This is a string representation of the type, as
32813 would be printed by the @value{GDBN} CLI. If @samp{print object}
32814 (@pxref{Print Settings, set print object}) is set to @code{on}, the
32815 @emph{actual} (derived) type of the object is shown rather than the
32816 @emph{declared} one.
32819 If a variable object is bound to a specific thread, then this is the
32820 thread's global identifier.
32823 For a dynamic varobj, this indicates whether there appear to be any
32824 children available. For a non-dynamic varobj, this will be 0.
32827 This attribute will be present and have the value @samp{1} if the
32828 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
32829 then this attribute will not be present.
32832 A dynamic varobj can supply a display hint to the front end. The
32833 value comes directly from the Python pretty-printer object's
32834 @code{display_hint} method. @xref{Pretty Printing API}.
32837 Typical output will look like this:
32840 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
32841 has_more="@var{has_more}"
32845 @subheading The @code{-var-delete} Command
32846 @findex -var-delete
32848 @subsubheading Synopsis
32851 -var-delete [ -c ] @var{name}
32854 Deletes a previously created variable object and all of its children.
32855 With the @samp{-c} option, just deletes the children.
32857 Returns an error if the object @var{name} is not found.
32860 @subheading The @code{-var-set-format} Command
32861 @findex -var-set-format
32863 @subsubheading Synopsis
32866 -var-set-format @var{name} @var{format-spec}
32869 Sets the output format for the value of the object @var{name} to be
32872 @anchor{-var-set-format}
32873 The syntax for the @var{format-spec} is as follows:
32876 @var{format-spec} @expansion{}
32877 @{binary | decimal | hexadecimal | octal | natural | zero-hexadecimal@}
32880 The natural format is the default format choosen automatically
32881 based on the variable type (like decimal for an @code{int}, hex
32882 for pointers, etc.).
32884 The zero-hexadecimal format has a representation similar to hexadecimal
32885 but with padding zeroes to the left of the value. For example, a 32-bit
32886 hexadecimal value of 0x1234 would be represented as 0x00001234 in the
32887 zero-hexadecimal format.
32889 For a variable with children, the format is set only on the
32890 variable itself, and the children are not affected.
32892 @subheading The @code{-var-show-format} Command
32893 @findex -var-show-format
32895 @subsubheading Synopsis
32898 -var-show-format @var{name}
32901 Returns the format used to display the value of the object @var{name}.
32904 @var{format} @expansion{}
32909 @subheading The @code{-var-info-num-children} Command
32910 @findex -var-info-num-children
32912 @subsubheading Synopsis
32915 -var-info-num-children @var{name}
32918 Returns the number of children of a variable object @var{name}:
32924 Note that this number is not completely reliable for a dynamic varobj.
32925 It will return the current number of children, but more children may
32929 @subheading The @code{-var-list-children} Command
32930 @findex -var-list-children
32932 @subsubheading Synopsis
32935 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
32937 @anchor{-var-list-children}
32939 Return a list of the children of the specified variable object and
32940 create variable objects for them, if they do not already exist. With
32941 a single argument or if @var{print-values} has a value of 0 or
32942 @code{--no-values}, print only the names of the variables; if
32943 @var{print-values} is 1 or @code{--all-values}, also print their
32944 values; and if it is 2 or @code{--simple-values} print the name and
32945 value for simple data types and just the name for arrays, structures
32948 @var{from} and @var{to}, if specified, indicate the range of children
32949 to report. If @var{from} or @var{to} is less than zero, the range is
32950 reset and all children will be reported. Otherwise, children starting
32951 at @var{from} (zero-based) and up to and excluding @var{to} will be
32954 If a child range is requested, it will only affect the current call to
32955 @code{-var-list-children}, but not future calls to @code{-var-update}.
32956 For this, you must instead use @code{-var-set-update-range}. The
32957 intent of this approach is to enable a front end to implement any
32958 update approach it likes; for example, scrolling a view may cause the
32959 front end to request more children with @code{-var-list-children}, and
32960 then the front end could call @code{-var-set-update-range} with a
32961 different range to ensure that future updates are restricted to just
32964 For each child the following results are returned:
32969 Name of the variable object created for this child.
32972 The expression to be shown to the user by the front end to designate this child.
32973 For example this may be the name of a structure member.
32975 For a dynamic varobj, this value cannot be used to form an
32976 expression. There is no way to do this at all with a dynamic varobj.
32978 For C/C@t{++} structures there are several pseudo children returned to
32979 designate access qualifiers. For these pseudo children @var{exp} is
32980 @samp{public}, @samp{private}, or @samp{protected}. In this case the
32981 type and value are not present.
32983 A dynamic varobj will not report the access qualifying
32984 pseudo-children, regardless of the language. This information is not
32985 available at all with a dynamic varobj.
32988 Number of children this child has. For a dynamic varobj, this will be
32992 The type of the child. If @samp{print object}
32993 (@pxref{Print Settings, set print object}) is set to @code{on}, the
32994 @emph{actual} (derived) type of the object is shown rather than the
32995 @emph{declared} one.
32998 If values were requested, this is the value.
33001 If this variable object is associated with a thread, this is the
33002 thread's global thread id. Otherwise this result is not present.
33005 If the variable object is frozen, this variable will be present with a value of 1.
33008 A dynamic varobj can supply a display hint to the front end. The
33009 value comes directly from the Python pretty-printer object's
33010 @code{display_hint} method. @xref{Pretty Printing API}.
33013 This attribute will be present and have the value @samp{1} if the
33014 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
33015 then this attribute will not be present.
33019 The result may have its own attributes:
33023 A dynamic varobj can supply a display hint to the front end. The
33024 value comes directly from the Python pretty-printer object's
33025 @code{display_hint} method. @xref{Pretty Printing API}.
33028 This is an integer attribute which is nonzero if there are children
33029 remaining after the end of the selected range.
33032 @subsubheading Example
33036 -var-list-children n
33037 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
33038 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
33040 -var-list-children --all-values n
33041 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
33042 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
33046 @subheading The @code{-var-info-type} Command
33047 @findex -var-info-type
33049 @subsubheading Synopsis
33052 -var-info-type @var{name}
33055 Returns the type of the specified variable @var{name}. The type is
33056 returned as a string in the same format as it is output by the
33060 type=@var{typename}
33064 @subheading The @code{-var-info-expression} Command
33065 @findex -var-info-expression
33067 @subsubheading Synopsis
33070 -var-info-expression @var{name}
33073 Returns a string that is suitable for presenting this
33074 variable object in user interface. The string is generally
33075 not valid expression in the current language, and cannot be evaluated.
33077 For example, if @code{a} is an array, and variable object
33078 @code{A} was created for @code{a}, then we'll get this output:
33081 (gdb) -var-info-expression A.1
33082 ^done,lang="C",exp="1"
33086 Here, the value of @code{lang} is the language name, which can be
33087 found in @ref{Supported Languages}.
33089 Note that the output of the @code{-var-list-children} command also
33090 includes those expressions, so the @code{-var-info-expression} command
33093 @subheading The @code{-var-info-path-expression} Command
33094 @findex -var-info-path-expression
33096 @subsubheading Synopsis
33099 -var-info-path-expression @var{name}
33102 Returns an expression that can be evaluated in the current
33103 context and will yield the same value that a variable object has.
33104 Compare this with the @code{-var-info-expression} command, which
33105 result can be used only for UI presentation. Typical use of
33106 the @code{-var-info-path-expression} command is creating a
33107 watchpoint from a variable object.
33109 This command is currently not valid for children of a dynamic varobj,
33110 and will give an error when invoked on one.
33112 For example, suppose @code{C} is a C@t{++} class, derived from class
33113 @code{Base}, and that the @code{Base} class has a member called
33114 @code{m_size}. Assume a variable @code{c} is has the type of
33115 @code{C} and a variable object @code{C} was created for variable
33116 @code{c}. Then, we'll get this output:
33118 (gdb) -var-info-path-expression C.Base.public.m_size
33119 ^done,path_expr=((Base)c).m_size)
33122 @subheading The @code{-var-show-attributes} Command
33123 @findex -var-show-attributes
33125 @subsubheading Synopsis
33128 -var-show-attributes @var{name}
33131 List attributes of the specified variable object @var{name}:
33134 status=@var{attr} [ ( ,@var{attr} )* ]
33138 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
33140 @subheading The @code{-var-evaluate-expression} Command
33141 @findex -var-evaluate-expression
33143 @subsubheading Synopsis
33146 -var-evaluate-expression [-f @var{format-spec}] @var{name}
33149 Evaluates the expression that is represented by the specified variable
33150 object and returns its value as a string. The format of the string
33151 can be specified with the @samp{-f} option. The possible values of
33152 this option are the same as for @code{-var-set-format}
33153 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
33154 the current display format will be used. The current display format
33155 can be changed using the @code{-var-set-format} command.
33161 Note that one must invoke @code{-var-list-children} for a variable
33162 before the value of a child variable can be evaluated.
33164 @subheading The @code{-var-assign} Command
33165 @findex -var-assign
33167 @subsubheading Synopsis
33170 -var-assign @var{name} @var{expression}
33173 Assigns the value of @var{expression} to the variable object specified
33174 by @var{name}. The object must be @samp{editable}. If the variable's
33175 value is altered by the assign, the variable will show up in any
33176 subsequent @code{-var-update} list.
33178 @subsubheading Example
33186 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
33190 @subheading The @code{-var-update} Command
33191 @findex -var-update
33193 @subsubheading Synopsis
33196 -var-update [@var{print-values}] @{@var{name} | "*"@}
33199 Reevaluate the expressions corresponding to the variable object
33200 @var{name} and all its direct and indirect children, and return the
33201 list of variable objects whose values have changed; @var{name} must
33202 be a root variable object. Here, ``changed'' means that the result of
33203 @code{-var-evaluate-expression} before and after the
33204 @code{-var-update} is different. If @samp{*} is used as the variable
33205 object names, all existing variable objects are updated, except
33206 for frozen ones (@pxref{-var-set-frozen}). The option
33207 @var{print-values} determines whether both names and values, or just
33208 names are printed. The possible values of this option are the same
33209 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
33210 recommended to use the @samp{--all-values} option, to reduce the
33211 number of MI commands needed on each program stop.
33213 With the @samp{*} parameter, if a variable object is bound to a
33214 currently running thread, it will not be updated, without any
33217 If @code{-var-set-update-range} was previously used on a varobj, then
33218 only the selected range of children will be reported.
33220 @code{-var-update} reports all the changed varobjs in a tuple named
33223 Each item in the change list is itself a tuple holding:
33227 The name of the varobj.
33230 If values were requested for this update, then this field will be
33231 present and will hold the value of the varobj.
33234 @anchor{-var-update}
33235 This field is a string which may take one of three values:
33239 The variable object's current value is valid.
33242 The variable object does not currently hold a valid value but it may
33243 hold one in the future if its associated expression comes back into
33247 The variable object no longer holds a valid value.
33248 This can occur when the executable file being debugged has changed,
33249 either through recompilation or by using the @value{GDBN} @code{file}
33250 command. The front end should normally choose to delete these variable
33254 In the future new values may be added to this list so the front should
33255 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
33258 This is only present if the varobj is still valid. If the type
33259 changed, then this will be the string @samp{true}; otherwise it will
33262 When a varobj's type changes, its children are also likely to have
33263 become incorrect. Therefore, the varobj's children are automatically
33264 deleted when this attribute is @samp{true}. Also, the varobj's update
33265 range, when set using the @code{-var-set-update-range} command, is
33269 If the varobj's type changed, then this field will be present and will
33272 @item new_num_children
33273 For a dynamic varobj, if the number of children changed, or if the
33274 type changed, this will be the new number of children.
33276 The @samp{numchild} field in other varobj responses is generally not
33277 valid for a dynamic varobj -- it will show the number of children that
33278 @value{GDBN} knows about, but because dynamic varobjs lazily
33279 instantiate their children, this will not reflect the number of
33280 children which may be available.
33282 The @samp{new_num_children} attribute only reports changes to the
33283 number of children known by @value{GDBN}. This is the only way to
33284 detect whether an update has removed children (which necessarily can
33285 only happen at the end of the update range).
33288 The display hint, if any.
33291 This is an integer value, which will be 1 if there are more children
33292 available outside the varobj's update range.
33295 This attribute will be present and have the value @samp{1} if the
33296 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
33297 then this attribute will not be present.
33300 If new children were added to a dynamic varobj within the selected
33301 update range (as set by @code{-var-set-update-range}), then they will
33302 be listed in this attribute.
33305 @subsubheading Example
33312 -var-update --all-values var1
33313 ^done,changelist=[@{name="var1",value="3",in_scope="true",
33314 type_changed="false"@}]
33318 @subheading The @code{-var-set-frozen} Command
33319 @findex -var-set-frozen
33320 @anchor{-var-set-frozen}
33322 @subsubheading Synopsis
33325 -var-set-frozen @var{name} @var{flag}
33328 Set the frozenness flag on the variable object @var{name}. The
33329 @var{flag} parameter should be either @samp{1} to make the variable
33330 frozen or @samp{0} to make it unfrozen. If a variable object is
33331 frozen, then neither itself, nor any of its children, are
33332 implicitly updated by @code{-var-update} of
33333 a parent variable or by @code{-var-update *}. Only
33334 @code{-var-update} of the variable itself will update its value and
33335 values of its children. After a variable object is unfrozen, it is
33336 implicitly updated by all subsequent @code{-var-update} operations.
33337 Unfreezing a variable does not update it, only subsequent
33338 @code{-var-update} does.
33340 @subsubheading Example
33344 -var-set-frozen V 1
33349 @subheading The @code{-var-set-update-range} command
33350 @findex -var-set-update-range
33351 @anchor{-var-set-update-range}
33353 @subsubheading Synopsis
33356 -var-set-update-range @var{name} @var{from} @var{to}
33359 Set the range of children to be returned by future invocations of
33360 @code{-var-update}.
33362 @var{from} and @var{to} indicate the range of children to report. If
33363 @var{from} or @var{to} is less than zero, the range is reset and all
33364 children will be reported. Otherwise, children starting at @var{from}
33365 (zero-based) and up to and excluding @var{to} will be reported.
33367 @subsubheading Example
33371 -var-set-update-range V 1 2
33375 @subheading The @code{-var-set-visualizer} command
33376 @findex -var-set-visualizer
33377 @anchor{-var-set-visualizer}
33379 @subsubheading Synopsis
33382 -var-set-visualizer @var{name} @var{visualizer}
33385 Set a visualizer for the variable object @var{name}.
33387 @var{visualizer} is the visualizer to use. The special value
33388 @samp{None} means to disable any visualizer in use.
33390 If not @samp{None}, @var{visualizer} must be a Python expression.
33391 This expression must evaluate to a callable object which accepts a
33392 single argument. @value{GDBN} will call this object with the value of
33393 the varobj @var{name} as an argument (this is done so that the same
33394 Python pretty-printing code can be used for both the CLI and MI).
33395 When called, this object must return an object which conforms to the
33396 pretty-printing interface (@pxref{Pretty Printing API}).
33398 The pre-defined function @code{gdb.default_visualizer} may be used to
33399 select a visualizer by following the built-in process
33400 (@pxref{Selecting Pretty-Printers}). This is done automatically when
33401 a varobj is created, and so ordinarily is not needed.
33403 This feature is only available if Python support is enabled. The MI
33404 command @code{-list-features} (@pxref{GDB/MI Support Commands})
33405 can be used to check this.
33407 @subsubheading Example
33409 Resetting the visualizer:
33413 -var-set-visualizer V None
33417 Reselecting the default (type-based) visualizer:
33421 -var-set-visualizer V gdb.default_visualizer
33425 Suppose @code{SomeClass} is a visualizer class. A lambda expression
33426 can be used to instantiate this class for a varobj:
33430 -var-set-visualizer V "lambda val: SomeClass()"
33434 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33435 @node GDB/MI Data Manipulation
33436 @section @sc{gdb/mi} Data Manipulation
33438 @cindex data manipulation, in @sc{gdb/mi}
33439 @cindex @sc{gdb/mi}, data manipulation
33440 This section describes the @sc{gdb/mi} commands that manipulate data:
33441 examine memory and registers, evaluate expressions, etc.
33443 For details about what an addressable memory unit is,
33444 @pxref{addressable memory unit}.
33446 @c REMOVED FROM THE INTERFACE.
33447 @c @subheading -data-assign
33448 @c Change the value of a program variable. Plenty of side effects.
33449 @c @subsubheading GDB Command
33451 @c @subsubheading Example
33454 @subheading The @code{-data-disassemble} Command
33455 @findex -data-disassemble
33457 @subsubheading Synopsis
33461 [ -s @var{start-addr} -e @var{end-addr} ]
33462 | [ -a @var{addr} ]
33463 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
33471 @item @var{start-addr}
33472 is the beginning address (or @code{$pc})
33473 @item @var{end-addr}
33476 is an address anywhere within (or the name of) the function to
33477 disassemble. If an address is specified, the whole function
33478 surrounding that address will be disassembled. If a name is
33479 specified, the whole function with that name will be disassembled.
33480 @item @var{filename}
33481 is the name of the file to disassemble
33482 @item @var{linenum}
33483 is the line number to disassemble around
33485 is the number of disassembly lines to be produced. If it is -1,
33486 the whole function will be disassembled, in case no @var{end-addr} is
33487 specified. If @var{end-addr} is specified as a non-zero value, and
33488 @var{lines} is lower than the number of disassembly lines between
33489 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
33490 displayed; if @var{lines} is higher than the number of lines between
33491 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
33496 @item 0 disassembly only
33497 @item 1 mixed source and disassembly (deprecated)
33498 @item 2 disassembly with raw opcodes
33499 @item 3 mixed source and disassembly with raw opcodes (deprecated)
33500 @item 4 mixed source and disassembly
33501 @item 5 mixed source and disassembly with raw opcodes
33504 Modes 1 and 3 are deprecated. The output is ``source centric''
33505 which hasn't proved useful in practice.
33506 @xref{Machine Code}, for a discussion of the difference between
33507 @code{/m} and @code{/s} output of the @code{disassemble} command.
33510 @subsubheading Result
33512 The result of the @code{-data-disassemble} command will be a list named
33513 @samp{asm_insns}, the contents of this list depend on the @var{mode}
33514 used with the @code{-data-disassemble} command.
33516 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
33521 The address at which this instruction was disassembled.
33524 The name of the function this instruction is within.
33527 The decimal offset in bytes from the start of @samp{func-name}.
33530 The text disassembly for this @samp{address}.
33533 This field is only present for modes 2, 3 and 5. This contains the raw opcode
33534 bytes for the @samp{inst} field.
33538 For modes 1, 3, 4 and 5 the @samp{asm_insns} list contains tuples named
33539 @samp{src_and_asm_line}, each of which has the following fields:
33543 The line number within @samp{file}.
33546 The file name from the compilation unit. This might be an absolute
33547 file name or a relative file name depending on the compile command
33551 Absolute file name of @samp{file}. It is converted to a canonical form
33552 using the source file search path
33553 (@pxref{Source Path, ,Specifying Source Directories})
33554 and after resolving all the symbolic links.
33556 If the source file is not found this field will contain the path as
33557 present in the debug information.
33559 @item line_asm_insn
33560 This is a list of tuples containing the disassembly for @samp{line} in
33561 @samp{file}. The fields of each tuple are the same as for
33562 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
33563 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
33568 Note that whatever included in the @samp{inst} field, is not
33569 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
33572 @subsubheading @value{GDBN} Command
33574 The corresponding @value{GDBN} command is @samp{disassemble}.
33576 @subsubheading Example
33578 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
33582 -data-disassemble -s $pc -e "$pc + 20" -- 0
33585 @{address="0x000107c0",func-name="main",offset="4",
33586 inst="mov 2, %o0"@},
33587 @{address="0x000107c4",func-name="main",offset="8",
33588 inst="sethi %hi(0x11800), %o2"@},
33589 @{address="0x000107c8",func-name="main",offset="12",
33590 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
33591 @{address="0x000107cc",func-name="main",offset="16",
33592 inst="sethi %hi(0x11800), %o2"@},
33593 @{address="0x000107d0",func-name="main",offset="20",
33594 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
33598 Disassemble the whole @code{main} function. Line 32 is part of
33602 -data-disassemble -f basics.c -l 32 -- 0
33604 @{address="0x000107bc",func-name="main",offset="0",
33605 inst="save %sp, -112, %sp"@},
33606 @{address="0x000107c0",func-name="main",offset="4",
33607 inst="mov 2, %o0"@},
33608 @{address="0x000107c4",func-name="main",offset="8",
33609 inst="sethi %hi(0x11800), %o2"@},
33611 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
33612 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
33616 Disassemble 3 instructions from the start of @code{main}:
33620 -data-disassemble -f basics.c -l 32 -n 3 -- 0
33622 @{address="0x000107bc",func-name="main",offset="0",
33623 inst="save %sp, -112, %sp"@},
33624 @{address="0x000107c0",func-name="main",offset="4",
33625 inst="mov 2, %o0"@},
33626 @{address="0x000107c4",func-name="main",offset="8",
33627 inst="sethi %hi(0x11800), %o2"@}]
33631 Disassemble 3 instructions from the start of @code{main} in mixed mode:
33635 -data-disassemble -f basics.c -l 32 -n 3 -- 1
33637 src_and_asm_line=@{line="31",
33638 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
33639 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
33640 line_asm_insn=[@{address="0x000107bc",
33641 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
33642 src_and_asm_line=@{line="32",
33643 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
33644 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
33645 line_asm_insn=[@{address="0x000107c0",
33646 func-name="main",offset="4",inst="mov 2, %o0"@},
33647 @{address="0x000107c4",func-name="main",offset="8",
33648 inst="sethi %hi(0x11800), %o2"@}]@}]
33653 @subheading The @code{-data-evaluate-expression} Command
33654 @findex -data-evaluate-expression
33656 @subsubheading Synopsis
33659 -data-evaluate-expression @var{expr}
33662 Evaluate @var{expr} as an expression. The expression could contain an
33663 inferior function call. The function call will execute synchronously.
33664 If the expression contains spaces, it must be enclosed in double quotes.
33666 @subsubheading @value{GDBN} Command
33668 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
33669 @samp{call}. In @code{gdbtk} only, there's a corresponding
33670 @samp{gdb_eval} command.
33672 @subsubheading Example
33674 In the following example, the numbers that precede the commands are the
33675 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
33676 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
33680 211-data-evaluate-expression A
33683 311-data-evaluate-expression &A
33684 311^done,value="0xefffeb7c"
33686 411-data-evaluate-expression A+3
33689 511-data-evaluate-expression "A + 3"
33695 @subheading The @code{-data-list-changed-registers} Command
33696 @findex -data-list-changed-registers
33698 @subsubheading Synopsis
33701 -data-list-changed-registers
33704 Display a list of the registers that have changed.
33706 @subsubheading @value{GDBN} Command
33708 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
33709 has the corresponding command @samp{gdb_changed_register_list}.
33711 @subsubheading Example
33713 On a PPC MBX board:
33721 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
33722 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
33723 line="5",arch="powerpc"@}
33725 -data-list-changed-registers
33726 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
33727 "10","11","13","14","15","16","17","18","19","20","21","22","23",
33728 "24","25","26","27","28","30","31","64","65","66","67","69"]
33733 @subheading The @code{-data-list-register-names} Command
33734 @findex -data-list-register-names
33736 @subsubheading Synopsis
33739 -data-list-register-names [ ( @var{regno} )+ ]
33742 Show a list of register names for the current target. If no arguments
33743 are given, it shows a list of the names of all the registers. If
33744 integer numbers are given as arguments, it will print a list of the
33745 names of the registers corresponding to the arguments. To ensure
33746 consistency between a register name and its number, the output list may
33747 include empty register names.
33749 @subsubheading @value{GDBN} Command
33751 @value{GDBN} does not have a command which corresponds to
33752 @samp{-data-list-register-names}. In @code{gdbtk} there is a
33753 corresponding command @samp{gdb_regnames}.
33755 @subsubheading Example
33757 For the PPC MBX board:
33760 -data-list-register-names
33761 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
33762 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
33763 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
33764 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
33765 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
33766 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
33767 "", "pc","ps","cr","lr","ctr","xer"]
33769 -data-list-register-names 1 2 3
33770 ^done,register-names=["r1","r2","r3"]
33774 @subheading The @code{-data-list-register-values} Command
33775 @findex -data-list-register-values
33777 @subsubheading Synopsis
33780 -data-list-register-values
33781 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
33784 Display the registers' contents. The format according to which the
33785 registers' contents are to be returned is given by @var{fmt}, followed
33786 by an optional list of numbers specifying the registers to display. A
33787 missing list of numbers indicates that the contents of all the
33788 registers must be returned. The @code{--skip-unavailable} option
33789 indicates that only the available registers are to be returned.
33791 Allowed formats for @var{fmt} are:
33808 @subsubheading @value{GDBN} Command
33810 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
33811 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
33813 @subsubheading Example
33815 For a PPC MBX board (note: line breaks are for readability only, they
33816 don't appear in the actual output):
33820 -data-list-register-values r 64 65
33821 ^done,register-values=[@{number="64",value="0xfe00a300"@},
33822 @{number="65",value="0x00029002"@}]
33824 -data-list-register-values x
33825 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
33826 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
33827 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
33828 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
33829 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
33830 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
33831 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
33832 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
33833 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
33834 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
33835 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
33836 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
33837 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
33838 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
33839 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
33840 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
33841 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
33842 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
33843 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
33844 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
33845 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
33846 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
33847 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
33848 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
33849 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
33850 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
33851 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
33852 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
33853 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
33854 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
33855 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
33856 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
33857 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
33858 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
33859 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
33860 @{number="69",value="0x20002b03"@}]
33865 @subheading The @code{-data-read-memory} Command
33866 @findex -data-read-memory
33868 This command is deprecated, use @code{-data-read-memory-bytes} instead.
33870 @subsubheading Synopsis
33873 -data-read-memory [ -o @var{byte-offset} ]
33874 @var{address} @var{word-format} @var{word-size}
33875 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
33882 @item @var{address}
33883 An expression specifying the address of the first memory word to be
33884 read. Complex expressions containing embedded white space should be
33885 quoted using the C convention.
33887 @item @var{word-format}
33888 The format to be used to print the memory words. The notation is the
33889 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
33892 @item @var{word-size}
33893 The size of each memory word in bytes.
33895 @item @var{nr-rows}
33896 The number of rows in the output table.
33898 @item @var{nr-cols}
33899 The number of columns in the output table.
33902 If present, indicates that each row should include an @sc{ascii} dump. The
33903 value of @var{aschar} is used as a padding character when a byte is not a
33904 member of the printable @sc{ascii} character set (printable @sc{ascii}
33905 characters are those whose code is between 32 and 126, inclusively).
33907 @item @var{byte-offset}
33908 An offset to add to the @var{address} before fetching memory.
33911 This command displays memory contents as a table of @var{nr-rows} by
33912 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
33913 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
33914 (returned as @samp{total-bytes}). Should less than the requested number
33915 of bytes be returned by the target, the missing words are identified
33916 using @samp{N/A}. The number of bytes read from the target is returned
33917 in @samp{nr-bytes} and the starting address used to read memory in
33920 The address of the next/previous row or page is available in
33921 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
33924 @subsubheading @value{GDBN} Command
33926 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
33927 @samp{gdb_get_mem} memory read command.
33929 @subsubheading Example
33931 Read six bytes of memory starting at @code{bytes+6} but then offset by
33932 @code{-6} bytes. Format as three rows of two columns. One byte per
33933 word. Display each word in hex.
33937 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
33938 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
33939 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
33940 prev-page="0x0000138a",memory=[
33941 @{addr="0x00001390",data=["0x00","0x01"]@},
33942 @{addr="0x00001392",data=["0x02","0x03"]@},
33943 @{addr="0x00001394",data=["0x04","0x05"]@}]
33947 Read two bytes of memory starting at address @code{shorts + 64} and
33948 display as a single word formatted in decimal.
33952 5-data-read-memory shorts+64 d 2 1 1
33953 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
33954 next-row="0x00001512",prev-row="0x0000150e",
33955 next-page="0x00001512",prev-page="0x0000150e",memory=[
33956 @{addr="0x00001510",data=["128"]@}]
33960 Read thirty two bytes of memory starting at @code{bytes+16} and format
33961 as eight rows of four columns. Include a string encoding with @samp{x}
33962 used as the non-printable character.
33966 4-data-read-memory bytes+16 x 1 8 4 x
33967 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
33968 next-row="0x000013c0",prev-row="0x0000139c",
33969 next-page="0x000013c0",prev-page="0x00001380",memory=[
33970 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
33971 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
33972 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
33973 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
33974 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
33975 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
33976 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
33977 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
33981 @subheading The @code{-data-read-memory-bytes} Command
33982 @findex -data-read-memory-bytes
33984 @subsubheading Synopsis
33987 -data-read-memory-bytes [ -o @var{offset} ]
33988 @var{address} @var{count}
33995 @item @var{address}
33996 An expression specifying the address of the first addressable memory unit
33997 to be read. Complex expressions containing embedded white space should be
33998 quoted using the C convention.
34001 The number of addressable memory units to read. This should be an integer
34005 The offset relative to @var{address} at which to start reading. This
34006 should be an integer literal. This option is provided so that a frontend
34007 is not required to first evaluate address and then perform address
34008 arithmetics itself.
34012 This command attempts to read all accessible memory regions in the
34013 specified range. First, all regions marked as unreadable in the memory
34014 map (if one is defined) will be skipped. @xref{Memory Region
34015 Attributes}. Second, @value{GDBN} will attempt to read the remaining
34016 regions. For each one, if reading full region results in an errors,
34017 @value{GDBN} will try to read a subset of the region.
34019 In general, every single memory unit in the region may be readable or not,
34020 and the only way to read every readable unit is to try a read at
34021 every address, which is not practical. Therefore, @value{GDBN} will
34022 attempt to read all accessible memory units at either beginning or the end
34023 of the region, using a binary division scheme. This heuristic works
34024 well for reading across a memory map boundary. Note that if a region
34025 has a readable range that is neither at the beginning or the end,
34026 @value{GDBN} will not read it.
34028 The result record (@pxref{GDB/MI Result Records}) that is output of
34029 the command includes a field named @samp{memory} whose content is a
34030 list of tuples. Each tuple represent a successfully read memory block
34031 and has the following fields:
34035 The start address of the memory block, as hexadecimal literal.
34038 The end address of the memory block, as hexadecimal literal.
34041 The offset of the memory block, as hexadecimal literal, relative to
34042 the start address passed to @code{-data-read-memory-bytes}.
34045 The contents of the memory block, in hex.
34051 @subsubheading @value{GDBN} Command
34053 The corresponding @value{GDBN} command is @samp{x}.
34055 @subsubheading Example
34059 -data-read-memory-bytes &a 10
34060 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
34062 contents="01000000020000000300"@}]
34067 @subheading The @code{-data-write-memory-bytes} Command
34068 @findex -data-write-memory-bytes
34070 @subsubheading Synopsis
34073 -data-write-memory-bytes @var{address} @var{contents}
34074 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
34081 @item @var{address}
34082 An expression specifying the address of the first addressable memory unit
34083 to be written. Complex expressions containing embedded white space should
34084 be quoted using the C convention.
34086 @item @var{contents}
34087 The hex-encoded data to write. It is an error if @var{contents} does
34088 not represent an integral number of addressable memory units.
34091 Optional argument indicating the number of addressable memory units to be
34092 written. If @var{count} is greater than @var{contents}' length,
34093 @value{GDBN} will repeatedly write @var{contents} until it fills
34094 @var{count} memory units.
34098 @subsubheading @value{GDBN} Command
34100 There's no corresponding @value{GDBN} command.
34102 @subsubheading Example
34106 -data-write-memory-bytes &a "aabbccdd"
34113 -data-write-memory-bytes &a "aabbccdd" 16e
34118 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34119 @node GDB/MI Tracepoint Commands
34120 @section @sc{gdb/mi} Tracepoint Commands
34122 The commands defined in this section implement MI support for
34123 tracepoints. For detailed introduction, see @ref{Tracepoints}.
34125 @subheading The @code{-trace-find} Command
34126 @findex -trace-find
34128 @subsubheading Synopsis
34131 -trace-find @var{mode} [@var{parameters}@dots{}]
34134 Find a trace frame using criteria defined by @var{mode} and
34135 @var{parameters}. The following table lists permissible
34136 modes and their parameters. For details of operation, see @ref{tfind}.
34141 No parameters are required. Stops examining trace frames.
34144 An integer is required as parameter. Selects tracepoint frame with
34147 @item tracepoint-number
34148 An integer is required as parameter. Finds next
34149 trace frame that corresponds to tracepoint with the specified number.
34152 An address is required as parameter. Finds
34153 next trace frame that corresponds to any tracepoint at the specified
34156 @item pc-inside-range
34157 Two addresses are required as parameters. Finds next trace
34158 frame that corresponds to a tracepoint at an address inside the
34159 specified range. Both bounds are considered to be inside the range.
34161 @item pc-outside-range
34162 Two addresses are required as parameters. Finds
34163 next trace frame that corresponds to a tracepoint at an address outside
34164 the specified range. Both bounds are considered to be inside the range.
34167 Line specification is required as parameter. @xref{Specify Location}.
34168 Finds next trace frame that corresponds to a tracepoint at
34169 the specified location.
34173 If @samp{none} was passed as @var{mode}, the response does not
34174 have fields. Otherwise, the response may have the following fields:
34178 This field has either @samp{0} or @samp{1} as the value, depending
34179 on whether a matching tracepoint was found.
34182 The index of the found traceframe. This field is present iff
34183 the @samp{found} field has value of @samp{1}.
34186 The index of the found tracepoint. This field is present iff
34187 the @samp{found} field has value of @samp{1}.
34190 The information about the frame corresponding to the found trace
34191 frame. This field is present only if a trace frame was found.
34192 @xref{GDB/MI Frame Information}, for description of this field.
34196 @subsubheading @value{GDBN} Command
34198 The corresponding @value{GDBN} command is @samp{tfind}.
34200 @subheading -trace-define-variable
34201 @findex -trace-define-variable
34203 @subsubheading Synopsis
34206 -trace-define-variable @var{name} [ @var{value} ]
34209 Create trace variable @var{name} if it does not exist. If
34210 @var{value} is specified, sets the initial value of the specified
34211 trace variable to that value. Note that the @var{name} should start
34212 with the @samp{$} character.
34214 @subsubheading @value{GDBN} Command
34216 The corresponding @value{GDBN} command is @samp{tvariable}.
34218 @subheading The @code{-trace-frame-collected} Command
34219 @findex -trace-frame-collected
34221 @subsubheading Synopsis
34224 -trace-frame-collected
34225 [--var-print-values @var{var_pval}]
34226 [--comp-print-values @var{comp_pval}]
34227 [--registers-format @var{regformat}]
34228 [--memory-contents]
34231 This command returns the set of collected objects, register names,
34232 trace state variable names, memory ranges and computed expressions
34233 that have been collected at a particular trace frame. The optional
34234 parameters to the command affect the output format in different ways.
34235 See the output description table below for more details.
34237 The reported names can be used in the normal manner to create
34238 varobjs and inspect the objects themselves. The items returned by
34239 this command are categorized so that it is clear which is a variable,
34240 which is a register, which is a trace state variable, which is a
34241 memory range and which is a computed expression.
34243 For instance, if the actions were
34245 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
34246 collect *(int*)0xaf02bef0@@40
34250 the object collected in its entirety would be @code{myVar}. The
34251 object @code{myArray} would be partially collected, because only the
34252 element at index @code{myIndex} would be collected. The remaining
34253 objects would be computed expressions.
34255 An example output would be:
34259 -trace-frame-collected
34261 explicit-variables=[@{name="myVar",value="1"@}],
34262 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
34263 @{name="myObj.field",value="0"@},
34264 @{name="myPtr->field",value="1"@},
34265 @{name="myCount + 2",value="3"@},
34266 @{name="$tvar1 + 1",value="43970027"@}],
34267 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
34268 @{number="1",value="0x0"@},
34269 @{number="2",value="0x4"@},
34271 @{number="125",value="0x0"@}],
34272 tvars=[@{name="$tvar1",current="43970026"@}],
34273 memory=[@{address="0x0000000000602264",length="4"@},
34274 @{address="0x0000000000615bc0",length="4"@}]
34281 @item explicit-variables
34282 The set of objects that have been collected in their entirety (as
34283 opposed to collecting just a few elements of an array or a few struct
34284 members). For each object, its name and value are printed.
34285 The @code{--var-print-values} option affects how or whether the value
34286 field is output. If @var{var_pval} is 0, then print only the names;
34287 if it is 1, print also their values; and if it is 2, print the name,
34288 type and value for simple data types, and the name and type for
34289 arrays, structures and unions.
34291 @item computed-expressions
34292 The set of computed expressions that have been collected at the
34293 current trace frame. The @code{--comp-print-values} option affects
34294 this set like the @code{--var-print-values} option affects the
34295 @code{explicit-variables} set. See above.
34298 The registers that have been collected at the current trace frame.
34299 For each register collected, the name and current value are returned.
34300 The value is formatted according to the @code{--registers-format}
34301 option. See the @command{-data-list-register-values} command for a
34302 list of the allowed formats. The default is @samp{x}.
34305 The trace state variables that have been collected at the current
34306 trace frame. For each trace state variable collected, the name and
34307 current value are returned.
34310 The set of memory ranges that have been collected at the current trace
34311 frame. Its content is a list of tuples. Each tuple represents a
34312 collected memory range and has the following fields:
34316 The start address of the memory range, as hexadecimal literal.
34319 The length of the memory range, as decimal literal.
34322 The contents of the memory block, in hex. This field is only present
34323 if the @code{--memory-contents} option is specified.
34329 @subsubheading @value{GDBN} Command
34331 There is no corresponding @value{GDBN} command.
34333 @subsubheading Example
34335 @subheading -trace-list-variables
34336 @findex -trace-list-variables
34338 @subsubheading Synopsis
34341 -trace-list-variables
34344 Return a table of all defined trace variables. Each element of the
34345 table has the following fields:
34349 The name of the trace variable. This field is always present.
34352 The initial value. This is a 64-bit signed integer. This
34353 field is always present.
34356 The value the trace variable has at the moment. This is a 64-bit
34357 signed integer. This field is absent iff current value is
34358 not defined, for example if the trace was never run, or is
34363 @subsubheading @value{GDBN} Command
34365 The corresponding @value{GDBN} command is @samp{tvariables}.
34367 @subsubheading Example
34371 -trace-list-variables
34372 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
34373 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
34374 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
34375 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
34376 body=[variable=@{name="$trace_timestamp",initial="0"@}
34377 variable=@{name="$foo",initial="10",current="15"@}]@}
34381 @subheading -trace-save
34382 @findex -trace-save
34384 @subsubheading Synopsis
34387 -trace-save [ -r ] [ -ctf ] @var{filename}
34390 Saves the collected trace data to @var{filename}. Without the
34391 @samp{-r} option, the data is downloaded from the target and saved
34392 in a local file. With the @samp{-r} option the target is asked
34393 to perform the save.
34395 By default, this command will save the trace in the tfile format. You can
34396 supply the optional @samp{-ctf} argument to save it the CTF format. See
34397 @ref{Trace Files} for more information about CTF.
34399 @subsubheading @value{GDBN} Command
34401 The corresponding @value{GDBN} command is @samp{tsave}.
34404 @subheading -trace-start
34405 @findex -trace-start
34407 @subsubheading Synopsis
34413 Starts a tracing experiment. The result of this command does not
34416 @subsubheading @value{GDBN} Command
34418 The corresponding @value{GDBN} command is @samp{tstart}.
34420 @subheading -trace-status
34421 @findex -trace-status
34423 @subsubheading Synopsis
34429 Obtains the status of a tracing experiment. The result may include
34430 the following fields:
34435 May have a value of either @samp{0}, when no tracing operations are
34436 supported, @samp{1}, when all tracing operations are supported, or
34437 @samp{file} when examining trace file. In the latter case, examining
34438 of trace frame is possible but new tracing experiement cannot be
34439 started. This field is always present.
34442 May have a value of either @samp{0} or @samp{1} depending on whether
34443 tracing experiement is in progress on target. This field is present
34444 if @samp{supported} field is not @samp{0}.
34447 Report the reason why the tracing was stopped last time. This field
34448 may be absent iff tracing was never stopped on target yet. The
34449 value of @samp{request} means the tracing was stopped as result of
34450 the @code{-trace-stop} command. The value of @samp{overflow} means
34451 the tracing buffer is full. The value of @samp{disconnection} means
34452 tracing was automatically stopped when @value{GDBN} has disconnected.
34453 The value of @samp{passcount} means tracing was stopped when a
34454 tracepoint was passed a maximal number of times for that tracepoint.
34455 This field is present if @samp{supported} field is not @samp{0}.
34457 @item stopping-tracepoint
34458 The number of tracepoint whose passcount as exceeded. This field is
34459 present iff the @samp{stop-reason} field has the value of
34463 @itemx frames-created
34464 The @samp{frames} field is a count of the total number of trace frames
34465 in the trace buffer, while @samp{frames-created} is the total created
34466 during the run, including ones that were discarded, such as when a
34467 circular trace buffer filled up. Both fields are optional.
34471 These fields tell the current size of the tracing buffer and the
34472 remaining space. These fields are optional.
34475 The value of the circular trace buffer flag. @code{1} means that the
34476 trace buffer is circular and old trace frames will be discarded if
34477 necessary to make room, @code{0} means that the trace buffer is linear
34481 The value of the disconnected tracing flag. @code{1} means that
34482 tracing will continue after @value{GDBN} disconnects, @code{0} means
34483 that the trace run will stop.
34486 The filename of the trace file being examined. This field is
34487 optional, and only present when examining a trace file.
34491 @subsubheading @value{GDBN} Command
34493 The corresponding @value{GDBN} command is @samp{tstatus}.
34495 @subheading -trace-stop
34496 @findex -trace-stop
34498 @subsubheading Synopsis
34504 Stops a tracing experiment. The result of this command has the same
34505 fields as @code{-trace-status}, except that the @samp{supported} and
34506 @samp{running} fields are not output.
34508 @subsubheading @value{GDBN} Command
34510 The corresponding @value{GDBN} command is @samp{tstop}.
34513 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34514 @node GDB/MI Symbol Query
34515 @section @sc{gdb/mi} Symbol Query Commands
34519 @subheading The @code{-symbol-info-address} Command
34520 @findex -symbol-info-address
34522 @subsubheading Synopsis
34525 -symbol-info-address @var{symbol}
34528 Describe where @var{symbol} is stored.
34530 @subsubheading @value{GDBN} Command
34532 The corresponding @value{GDBN} command is @samp{info address}.
34534 @subsubheading Example
34538 @subheading The @code{-symbol-info-file} Command
34539 @findex -symbol-info-file
34541 @subsubheading Synopsis
34547 Show the file for the symbol.
34549 @subsubheading @value{GDBN} Command
34551 There's no equivalent @value{GDBN} command. @code{gdbtk} has
34552 @samp{gdb_find_file}.
34554 @subsubheading Example
34558 @subheading The @code{-symbol-info-functions} Command
34559 @findex -symbol-info-functions
34560 @anchor{-symbol-info-functions}
34562 @subsubheading Synopsis
34565 -symbol-info-functions [--include-nondebug]
34566 [--type @var{type_regexp}]
34567 [--name @var{name_regexp}]
34568 [--max-results @var{limit}]
34572 Return a list containing the names and types for all global functions
34573 taken from the debug information. The functions are grouped by source
34574 file, and shown with the line number on which each function is
34577 The @code{--include-nondebug} option causes the output to include
34578 code symbols from the symbol table.
34580 The options @code{--type} and @code{--name} allow the symbols returned
34581 to be filtered based on either the name of the function, or the type
34582 signature of the function.
34584 The option @code{--max-results} restricts the command to return no
34585 more than @var{limit} results. If exactly @var{limit} results are
34586 returned then there might be additional results available if a higher
34589 @subsubheading @value{GDBN} Command
34591 The corresponding @value{GDBN} command is @samp{info functions}.
34593 @subsubheading Example
34597 -symbol-info-functions
34600 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34601 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34602 symbols=[@{line="36", name="f4", type="void (int *)",
34603 description="void f4(int *);"@},
34604 @{line="42", name="main", type="int ()",
34605 description="int main();"@},
34606 @{line="30", name="f1", type="my_int_t (int, int)",
34607 description="static my_int_t f1(int, int);"@}]@},
34608 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
34609 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
34610 symbols=[@{line="33", name="f2", type="float (another_float_t)",
34611 description="float f2(another_float_t);"@},
34612 @{line="39", name="f3", type="int (another_int_t)",
34613 description="int f3(another_int_t);"@},
34614 @{line="27", name="f1", type="another_float_t (int)",
34615 description="static another_float_t f1(int);"@}]@}]@}
34619 -symbol-info-functions --name f1
34622 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34623 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34624 symbols=[@{line="30", name="f1", type="my_int_t (int, int)",
34625 description="static my_int_t f1(int, int);"@}]@},
34626 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
34627 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
34628 symbols=[@{line="27", name="f1", type="another_float_t (int)",
34629 description="static another_float_t f1(int);"@}]@}]@}
34633 -symbol-info-functions --type void
34636 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34637 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34638 symbols=[@{line="36", name="f4", type="void (int *)",
34639 description="void f4(int *);"@}]@}]@}
34643 -symbol-info-functions --include-nondebug
34646 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34647 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34648 symbols=[@{line="36", name="f4", type="void (int *)",
34649 description="void f4(int *);"@},
34650 @{line="42", name="main", type="int ()",
34651 description="int main();"@},
34652 @{line="30", name="f1", type="my_int_t (int, int)",
34653 description="static my_int_t f1(int, int);"@}]@},
34654 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
34655 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
34656 symbols=[@{line="33", name="f2", type="float (another_float_t)",
34657 description="float f2(another_float_t);"@},
34658 @{line="39", name="f3", type="int (another_int_t)",
34659 description="int f3(another_int_t);"@},
34660 @{line="27", name="f1", type="another_float_t (int)",
34661 description="static another_float_t f1(int);"@}]@}],
34663 [@{address="0x0000000000400398",name="_init"@},
34664 @{address="0x00000000004003b0",name="_start"@},
34670 @subheading The @code{-symbol-info-module-functions} Command
34671 @findex -symbol-info-module-functions
34672 @anchor{-symbol-info-module-functions}
34674 @subsubheading Synopsis
34677 -symbol-info-module-functions [--module @var{module_regexp}]
34678 [--name @var{name_regexp}]
34679 [--type @var{type_regexp}]
34683 Return a list containing the names of all known functions within all
34684 know Fortran modules. The functions are grouped by source file and
34685 containing module, and shown with the line number on which each
34686 function is defined.
34688 The option @code{--module} only returns results for modules matching
34689 @var{module_regexp}. The option @code{--name} only returns functions
34690 whose name matches @var{name_regexp}, and @code{--type} only returns
34691 functions whose type matches @var{type_regexp}.
34693 @subsubheading @value{GDBN} Command
34695 The corresponding @value{GDBN} command is @samp{info module functions}.
34697 @subsubheading Example
34702 -symbol-info-module-functions
34705 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
34706 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
34707 symbols=[@{line="21",name="mod1::check_all",type="void (void)",
34708 description="void mod1::check_all(void);"@}]@}]@},
34710 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
34711 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
34712 symbols=[@{line="30",name="mod2::check_var_i",type="void (void)",
34713 description="void mod2::check_var_i(void);"@}]@}]@},
34715 files=[@{filename="/projec/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
34716 fullname="/projec/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
34717 symbols=[@{line="21",name="mod3::check_all",type="void (void)",
34718 description="void mod3::check_all(void);"@},
34719 @{line="27",name="mod3::check_mod2",type="void (void)",
34720 description="void mod3::check_mod2(void);"@}]@}]@},
34721 @{module="modmany",
34722 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
34723 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
34724 symbols=[@{line="35",name="modmany::check_some",type="void (void)",
34725 description="void modmany::check_some(void);"@}]@}]@},
34727 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
34728 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
34729 symbols=[@{line="44",name="moduse::check_all",type="void (void)",
34730 description="void moduse::check_all(void);"@},
34731 @{line="49",name="moduse::check_var_x",type="void (void)",
34732 description="void moduse::check_var_x(void);"@}]@}]@}]
34736 @subheading The @code{-symbol-info-module-variables} Command
34737 @findex -symbol-info-module-variables
34738 @anchor{-symbol-info-module-variables}
34740 @subsubheading Synopsis
34743 -symbol-info-module-variables [--module @var{module_regexp}]
34744 [--name @var{name_regexp}]
34745 [--type @var{type_regexp}]
34749 Return a list containing the names of all known variables within all
34750 know Fortran modules. The variables are grouped by source file and
34751 containing module, and shown with the line number on which each
34752 variable is defined.
34754 The option @code{--module} only returns results for modules matching
34755 @var{module_regexp}. The option @code{--name} only returns variables
34756 whose name matches @var{name_regexp}, and @code{--type} only returns
34757 variables whose type matches @var{type_regexp}.
34759 @subsubheading @value{GDBN} Command
34761 The corresponding @value{GDBN} command is @samp{info module variables}.
34763 @subsubheading Example
34768 -symbol-info-module-variables
34771 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
34772 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
34773 symbols=[@{line="18",name="mod1::var_const",type="integer(kind=4)",
34774 description="integer(kind=4) mod1::var_const;"@},
34775 @{line="17",name="mod1::var_i",type="integer(kind=4)",
34776 description="integer(kind=4) mod1::var_i;"@}]@}]@},
34778 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
34779 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
34780 symbols=[@{line="28",name="mod2::var_i",type="integer(kind=4)",
34781 description="integer(kind=4) mod2::var_i;"@}]@}]@},
34783 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
34784 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
34785 symbols=[@{line="18",name="mod3::mod1",type="integer(kind=4)",
34786 description="integer(kind=4) mod3::mod1;"@},
34787 @{line="17",name="mod3::mod2",type="integer(kind=4)",
34788 description="integer(kind=4) mod3::mod2;"@},
34789 @{line="19",name="mod3::var_i",type="integer(kind=4)",
34790 description="integer(kind=4) mod3::var_i;"@}]@}]@},
34791 @{module="modmany",
34792 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
34793 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
34794 symbols=[@{line="33",name="modmany::var_a",type="integer(kind=4)",
34795 description="integer(kind=4) modmany::var_a;"@},
34796 @{line="33",name="modmany::var_b",type="integer(kind=4)",
34797 description="integer(kind=4) modmany::var_b;"@},
34798 @{line="33",name="modmany::var_c",type="integer(kind=4)",
34799 description="integer(kind=4) modmany::var_c;"@},
34800 @{line="33",name="modmany::var_i",type="integer(kind=4)",
34801 description="integer(kind=4) modmany::var_i;"@}]@}]@},
34803 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
34804 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
34805 symbols=[@{line="42",name="moduse::var_x",type="integer(kind=4)",
34806 description="integer(kind=4) moduse::var_x;"@},
34807 @{line="42",name="moduse::var_y",type="integer(kind=4)",
34808 description="integer(kind=4) moduse::var_y;"@}]@}]@}]
34812 @subheading The @code{-symbol-info-modules} Command
34813 @findex -symbol-info-modules
34814 @anchor{-symbol-info-modules}
34816 @subsubheading Synopsis
34819 -symbol-info-modules [--name @var{name_regexp}]
34820 [--max-results @var{limit}]
34825 Return a list containing the names of all known Fortran modules. The
34826 modules are grouped by source file, and shown with the line number on
34827 which each modules is defined.
34829 The option @code{--name} allows the modules returned to be filtered
34830 based the name of the module.
34832 The option @code{--max-results} restricts the command to return no
34833 more than @var{limit} results. If exactly @var{limit} results are
34834 returned then there might be additional results available if a higher
34837 @subsubheading @value{GDBN} Command
34839 The corresponding @value{GDBN} command is @samp{info modules}.
34841 @subsubheading Example
34845 -symbol-info-modules
34848 [@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
34849 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
34850 symbols=[@{line="16",name="mod1"@},
34851 @{line="22",name="mod2"@}]@},
34852 @{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
34853 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
34854 symbols=[@{line="16",name="mod3"@},
34855 @{line="22",name="modmany"@},
34856 @{line="26",name="moduse"@}]@}]@}
34860 -symbol-info-modules --name mod[123]
34863 [@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
34864 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
34865 symbols=[@{line="16",name="mod1"@},
34866 @{line="22",name="mod2"@}]@},
34867 @{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
34868 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
34869 symbols=[@{line="16",name="mod3"@}]@}]@}
34873 @subheading The @code{-symbol-info-types} Command
34874 @findex -symbol-info-types
34875 @anchor{-symbol-info-types}
34877 @subsubheading Synopsis
34880 -symbol-info-types [--name @var{name_regexp}]
34881 [--max-results @var{limit}]
34886 Return a list of all defined types. The types are grouped by source
34887 file, and shown with the line number on which each user defined type
34888 is defined. Some base types are not defined in the source code but
34889 are added to the debug information by the compiler, for example
34890 @code{int}, @code{float}, etc.; these types do not have an associated
34893 The option @code{--name} allows the list of types returned to be
34896 The option @code{--max-results} restricts the command to return no
34897 more than @var{limit} results. If exactly @var{limit} results are
34898 returned then there might be additional results available if a higher
34901 @subsubheading @value{GDBN} Command
34903 The corresponding @value{GDBN} command is @samp{info types}.
34905 @subsubheading Example
34912 [@{filename="gdb.mi/mi-sym-info-1.c",
34913 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34914 symbols=[@{name="float"@},
34916 @{line="27",name="typedef int my_int_t;"@}]@},
34917 @{filename="gdb.mi/mi-sym-info-2.c",
34918 fullname="/project/gdb.mi/mi-sym-info-2.c",
34919 symbols=[@{line="24",name="typedef float another_float_t;"@},
34920 @{line="23",name="typedef int another_int_t;"@},
34922 @{name="int"@}]@}]@}
34926 -symbol-info-types --name _int_
34929 [@{filename="gdb.mi/mi-sym-info-1.c",
34930 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34931 symbols=[@{line="27",name="typedef int my_int_t;"@}]@},
34932 @{filename="gdb.mi/mi-sym-info-2.c",
34933 fullname="/project/gdb.mi/mi-sym-info-2.c",
34934 symbols=[@{line="23",name="typedef int another_int_t;"@}]@}]@}
34938 @subheading The @code{-symbol-info-variables} Command
34939 @findex -symbol-info-variables
34940 @anchor{-symbol-info-variables}
34942 @subsubheading Synopsis
34945 -symbol-info-variables [--include-nondebug]
34946 [--type @var{type_regexp}]
34947 [--name @var{name_regexp}]
34948 [--max-results @var{limit}]
34953 Return a list containing the names and types for all global variables
34954 taken from the debug information. The variables are grouped by source
34955 file, and shown with the line number on which each variable is
34958 The @code{--include-nondebug} option causes the output to include
34959 data symbols from the symbol table.
34961 The options @code{--type} and @code{--name} allow the symbols returned
34962 to be filtered based on either the name of the variable, or the type
34965 The option @code{--max-results} restricts the command to return no
34966 more than @var{limit} results. If exactly @var{limit} results are
34967 returned then there might be additional results available if a higher
34970 @subsubheading @value{GDBN} Command
34972 The corresponding @value{GDBN} command is @samp{info variables}.
34974 @subsubheading Example
34978 -symbol-info-variables
34981 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34982 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34983 symbols=[@{line="25",name="global_f1",type="float",
34984 description="static float global_f1;"@},
34985 @{line="24",name="global_i1",type="int",
34986 description="static int global_i1;"@}]@},
34987 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
34988 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
34989 symbols=[@{line="21",name="global_f2",type="int",
34990 description="int global_f2;"@},
34991 @{line="20",name="global_i2",type="int",
34992 description="int global_i2;"@},
34993 @{line="19",name="global_f1",type="float",
34994 description="static float global_f1;"@},
34995 @{line="18",name="global_i1",type="int",
34996 description="static int global_i1;"@}]@}]@}
35000 -symbol-info-variables --name f1
35003 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35004 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35005 symbols=[@{line="25",name="global_f1",type="float",
35006 description="static float global_f1;"@}]@},
35007 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35008 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35009 symbols=[@{line="19",name="global_f1",type="float",
35010 description="static float global_f1;"@}]@}]@}
35014 -symbol-info-variables --type float
35017 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35018 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35019 symbols=[@{line="25",name="global_f1",type="float",
35020 description="static float global_f1;"@}]@},
35021 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35022 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35023 symbols=[@{line="19",name="global_f1",type="float",
35024 description="static float global_f1;"@}]@}]@}
35028 -symbol-info-variables --include-nondebug
35031 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35032 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35033 symbols=[@{line="25",name="global_f1",type="float",
35034 description="static float global_f1;"@},
35035 @{line="24",name="global_i1",type="int",
35036 description="static int global_i1;"@}]@},
35037 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35038 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35039 symbols=[@{line="21",name="global_f2",type="int",
35040 description="int global_f2;"@},
35041 @{line="20",name="global_i2",type="int",
35042 description="int global_i2;"@},
35043 @{line="19",name="global_f1",type="float",
35044 description="static float global_f1;"@},
35045 @{line="18",name="global_i1",type="int",
35046 description="static int global_i1;"@}]@}],
35048 [@{address="0x00000000004005d0",name="_IO_stdin_used"@},
35049 @{address="0x00000000004005d8",name="__dso_handle"@}
35056 @subheading The @code{-symbol-info-line} Command
35057 @findex -symbol-info-line
35059 @subsubheading Synopsis
35065 Show the core addresses of the code for a source line.
35067 @subsubheading @value{GDBN} Command
35069 The corresponding @value{GDBN} command is @samp{info line}.
35070 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
35072 @subsubheading Example
35076 @subheading The @code{-symbol-info-symbol} Command
35077 @findex -symbol-info-symbol
35079 @subsubheading Synopsis
35082 -symbol-info-symbol @var{addr}
35085 Describe what symbol is at location @var{addr}.
35087 @subsubheading @value{GDBN} Command
35089 The corresponding @value{GDBN} command is @samp{info symbol}.
35091 @subsubheading Example
35095 @subheading The @code{-symbol-list-functions} Command
35096 @findex -symbol-list-functions
35098 @subsubheading Synopsis
35101 -symbol-list-functions
35104 List the functions in the executable.
35106 @subsubheading @value{GDBN} Command
35108 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
35109 @samp{gdb_search} in @code{gdbtk}.
35111 @subsubheading Example
35116 @subheading The @code{-symbol-list-lines} Command
35117 @findex -symbol-list-lines
35119 @subsubheading Synopsis
35122 -symbol-list-lines @var{filename}
35125 Print the list of lines that contain code and their associated program
35126 addresses for the given source filename. The entries are sorted in
35127 ascending PC order.
35129 @subsubheading @value{GDBN} Command
35131 There is no corresponding @value{GDBN} command.
35133 @subsubheading Example
35136 -symbol-list-lines basics.c
35137 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
35143 @subheading The @code{-symbol-list-types} Command
35144 @findex -symbol-list-types
35146 @subsubheading Synopsis
35152 List all the type names.
35154 @subsubheading @value{GDBN} Command
35156 The corresponding commands are @samp{info types} in @value{GDBN},
35157 @samp{gdb_search} in @code{gdbtk}.
35159 @subsubheading Example
35163 @subheading The @code{-symbol-list-variables} Command
35164 @findex -symbol-list-variables
35166 @subsubheading Synopsis
35169 -symbol-list-variables
35172 List all the global and static variable names.
35174 @subsubheading @value{GDBN} Command
35176 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
35178 @subsubheading Example
35182 @subheading The @code{-symbol-locate} Command
35183 @findex -symbol-locate
35185 @subsubheading Synopsis
35191 @subsubheading @value{GDBN} Command
35193 @samp{gdb_loc} in @code{gdbtk}.
35195 @subsubheading Example
35199 @subheading The @code{-symbol-type} Command
35200 @findex -symbol-type
35202 @subsubheading Synopsis
35205 -symbol-type @var{variable}
35208 Show type of @var{variable}.
35210 @subsubheading @value{GDBN} Command
35212 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
35213 @samp{gdb_obj_variable}.
35215 @subsubheading Example
35220 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35221 @node GDB/MI File Commands
35222 @section @sc{gdb/mi} File Commands
35224 This section describes the GDB/MI commands to specify executable file names
35225 and to read in and obtain symbol table information.
35227 @subheading The @code{-file-exec-and-symbols} Command
35228 @findex -file-exec-and-symbols
35230 @subsubheading Synopsis
35233 -file-exec-and-symbols @var{file}
35236 Specify the executable file to be debugged. This file is the one from
35237 which the symbol table is also read. If no file is specified, the
35238 command clears the executable and symbol information. If breakpoints
35239 are set when using this command with no arguments, @value{GDBN} will produce
35240 error messages. Otherwise, no output is produced, except a completion
35243 @subsubheading @value{GDBN} Command
35245 The corresponding @value{GDBN} command is @samp{file}.
35247 @subsubheading Example
35251 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
35257 @subheading The @code{-file-exec-file} Command
35258 @findex -file-exec-file
35260 @subsubheading Synopsis
35263 -file-exec-file @var{file}
35266 Specify the executable file to be debugged. Unlike
35267 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
35268 from this file. If used without argument, @value{GDBN} clears the information
35269 about the executable file. No output is produced, except a completion
35272 @subsubheading @value{GDBN} Command
35274 The corresponding @value{GDBN} command is @samp{exec-file}.
35276 @subsubheading Example
35280 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
35287 @subheading The @code{-file-list-exec-sections} Command
35288 @findex -file-list-exec-sections
35290 @subsubheading Synopsis
35293 -file-list-exec-sections
35296 List the sections of the current executable file.
35298 @subsubheading @value{GDBN} Command
35300 The @value{GDBN} command @samp{info file} shows, among the rest, the same
35301 information as this command. @code{gdbtk} has a corresponding command
35302 @samp{gdb_load_info}.
35304 @subsubheading Example
35309 @subheading The @code{-file-list-exec-source-file} Command
35310 @findex -file-list-exec-source-file
35312 @subsubheading Synopsis
35315 -file-list-exec-source-file
35318 List the line number, the current source file, and the absolute path
35319 to the current source file for the current executable. The macro
35320 information field has a value of @samp{1} or @samp{0} depending on
35321 whether or not the file includes preprocessor macro information.
35323 @subsubheading @value{GDBN} Command
35325 The @value{GDBN} equivalent is @samp{info source}
35327 @subsubheading Example
35331 123-file-list-exec-source-file
35332 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
35337 @subheading The @code{-file-list-exec-source-files} Command
35338 @findex -file-list-exec-source-files
35340 @subsubheading Synopsis
35343 -file-list-exec-source-files
35346 List the source files for the current executable.
35348 It will always output both the filename and fullname (absolute file
35349 name) of a source file.
35351 @subsubheading @value{GDBN} Command
35353 The @value{GDBN} equivalent is @samp{info sources}.
35354 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
35356 @subsubheading Example
35359 -file-list-exec-source-files
35361 @{file=foo.c,fullname=/home/foo.c@},
35362 @{file=/home/bar.c,fullname=/home/bar.c@},
35363 @{file=gdb_could_not_find_fullpath.c@}]
35367 @subheading The @code{-file-list-shared-libraries} Command
35368 @findex -file-list-shared-libraries
35370 @subsubheading Synopsis
35373 -file-list-shared-libraries [ @var{regexp} ]
35376 List the shared libraries in the program.
35377 With a regular expression @var{regexp}, only those libraries whose
35378 names match @var{regexp} are listed.
35380 @subsubheading @value{GDBN} Command
35382 The corresponding @value{GDBN} command is @samp{info shared}. The fields
35383 have a similar meaning to the @code{=library-loaded} notification.
35384 The @code{ranges} field specifies the multiple segments belonging to this
35385 library. Each range has the following fields:
35389 The address defining the inclusive lower bound of the segment.
35391 The address defining the exclusive upper bound of the segment.
35394 @subsubheading Example
35397 -file-list-exec-source-files
35398 ^done,shared-libraries=[
35399 @{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"@}]@},
35400 @{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"@}]@}]
35406 @subheading The @code{-file-list-symbol-files} Command
35407 @findex -file-list-symbol-files
35409 @subsubheading Synopsis
35412 -file-list-symbol-files
35417 @subsubheading @value{GDBN} Command
35419 The corresponding @value{GDBN} command is @samp{info file} (part of it).
35421 @subsubheading Example
35426 @subheading The @code{-file-symbol-file} Command
35427 @findex -file-symbol-file
35429 @subsubheading Synopsis
35432 -file-symbol-file @var{file}
35435 Read symbol table info from the specified @var{file} argument. When
35436 used without arguments, clears @value{GDBN}'s symbol table info. No output is
35437 produced, except for a completion notification.
35439 @subsubheading @value{GDBN} Command
35441 The corresponding @value{GDBN} command is @samp{symbol-file}.
35443 @subsubheading Example
35447 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
35453 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35454 @node GDB/MI Memory Overlay Commands
35455 @section @sc{gdb/mi} Memory Overlay Commands
35457 The memory overlay commands are not implemented.
35459 @c @subheading -overlay-auto
35461 @c @subheading -overlay-list-mapping-state
35463 @c @subheading -overlay-list-overlays
35465 @c @subheading -overlay-map
35467 @c @subheading -overlay-off
35469 @c @subheading -overlay-on
35471 @c @subheading -overlay-unmap
35473 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35474 @node GDB/MI Signal Handling Commands
35475 @section @sc{gdb/mi} Signal Handling Commands
35477 Signal handling commands are not implemented.
35479 @c @subheading -signal-handle
35481 @c @subheading -signal-list-handle-actions
35483 @c @subheading -signal-list-signal-types
35487 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35488 @node GDB/MI Target Manipulation
35489 @section @sc{gdb/mi} Target Manipulation Commands
35492 @subheading The @code{-target-attach} Command
35493 @findex -target-attach
35495 @subsubheading Synopsis
35498 -target-attach @var{pid} | @var{gid} | @var{file}
35501 Attach to a process @var{pid} or a file @var{file} outside of
35502 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
35503 group, the id previously returned by
35504 @samp{-list-thread-groups --available} must be used.
35506 @subsubheading @value{GDBN} Command
35508 The corresponding @value{GDBN} command is @samp{attach}.
35510 @subsubheading Example
35514 =thread-created,id="1"
35515 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
35521 @subheading The @code{-target-compare-sections} Command
35522 @findex -target-compare-sections
35524 @subsubheading Synopsis
35527 -target-compare-sections [ @var{section} ]
35530 Compare data of section @var{section} on target to the exec file.
35531 Without the argument, all sections are compared.
35533 @subsubheading @value{GDBN} Command
35535 The @value{GDBN} equivalent is @samp{compare-sections}.
35537 @subsubheading Example
35542 @subheading The @code{-target-detach} Command
35543 @findex -target-detach
35545 @subsubheading Synopsis
35548 -target-detach [ @var{pid} | @var{gid} ]
35551 Detach from the remote target which normally resumes its execution.
35552 If either @var{pid} or @var{gid} is specified, detaches from either
35553 the specified process, or specified thread group. There's no output.
35555 @subsubheading @value{GDBN} Command
35557 The corresponding @value{GDBN} command is @samp{detach}.
35559 @subsubheading Example
35569 @subheading The @code{-target-disconnect} Command
35570 @findex -target-disconnect
35572 @subsubheading Synopsis
35578 Disconnect from the remote target. There's no output and the target is
35579 generally not resumed.
35581 @subsubheading @value{GDBN} Command
35583 The corresponding @value{GDBN} command is @samp{disconnect}.
35585 @subsubheading Example
35595 @subheading The @code{-target-download} Command
35596 @findex -target-download
35598 @subsubheading Synopsis
35604 Loads the executable onto the remote target.
35605 It prints out an update message every half second, which includes the fields:
35609 The name of the section.
35611 The size of what has been sent so far for that section.
35613 The size of the section.
35615 The total size of what was sent so far (the current and the previous sections).
35617 The size of the overall executable to download.
35621 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
35622 @sc{gdb/mi} Output Syntax}).
35624 In addition, it prints the name and size of the sections, as they are
35625 downloaded. These messages include the following fields:
35629 The name of the section.
35631 The size of the section.
35633 The size of the overall executable to download.
35637 At the end, a summary is printed.
35639 @subsubheading @value{GDBN} Command
35641 The corresponding @value{GDBN} command is @samp{load}.
35643 @subsubheading Example
35645 Note: each status message appears on a single line. Here the messages
35646 have been broken down so that they can fit onto a page.
35651 +download,@{section=".text",section-size="6668",total-size="9880"@}
35652 +download,@{section=".text",section-sent="512",section-size="6668",
35653 total-sent="512",total-size="9880"@}
35654 +download,@{section=".text",section-sent="1024",section-size="6668",
35655 total-sent="1024",total-size="9880"@}
35656 +download,@{section=".text",section-sent="1536",section-size="6668",
35657 total-sent="1536",total-size="9880"@}
35658 +download,@{section=".text",section-sent="2048",section-size="6668",
35659 total-sent="2048",total-size="9880"@}
35660 +download,@{section=".text",section-sent="2560",section-size="6668",
35661 total-sent="2560",total-size="9880"@}
35662 +download,@{section=".text",section-sent="3072",section-size="6668",
35663 total-sent="3072",total-size="9880"@}
35664 +download,@{section=".text",section-sent="3584",section-size="6668",
35665 total-sent="3584",total-size="9880"@}
35666 +download,@{section=".text",section-sent="4096",section-size="6668",
35667 total-sent="4096",total-size="9880"@}
35668 +download,@{section=".text",section-sent="4608",section-size="6668",
35669 total-sent="4608",total-size="9880"@}
35670 +download,@{section=".text",section-sent="5120",section-size="6668",
35671 total-sent="5120",total-size="9880"@}
35672 +download,@{section=".text",section-sent="5632",section-size="6668",
35673 total-sent="5632",total-size="9880"@}
35674 +download,@{section=".text",section-sent="6144",section-size="6668",
35675 total-sent="6144",total-size="9880"@}
35676 +download,@{section=".text",section-sent="6656",section-size="6668",
35677 total-sent="6656",total-size="9880"@}
35678 +download,@{section=".init",section-size="28",total-size="9880"@}
35679 +download,@{section=".fini",section-size="28",total-size="9880"@}
35680 +download,@{section=".data",section-size="3156",total-size="9880"@}
35681 +download,@{section=".data",section-sent="512",section-size="3156",
35682 total-sent="7236",total-size="9880"@}
35683 +download,@{section=".data",section-sent="1024",section-size="3156",
35684 total-sent="7748",total-size="9880"@}
35685 +download,@{section=".data",section-sent="1536",section-size="3156",
35686 total-sent="8260",total-size="9880"@}
35687 +download,@{section=".data",section-sent="2048",section-size="3156",
35688 total-sent="8772",total-size="9880"@}
35689 +download,@{section=".data",section-sent="2560",section-size="3156",
35690 total-sent="9284",total-size="9880"@}
35691 +download,@{section=".data",section-sent="3072",section-size="3156",
35692 total-sent="9796",total-size="9880"@}
35693 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
35700 @subheading The @code{-target-exec-status} Command
35701 @findex -target-exec-status
35703 @subsubheading Synopsis
35706 -target-exec-status
35709 Provide information on the state of the target (whether it is running or
35710 not, for instance).
35712 @subsubheading @value{GDBN} Command
35714 There's no equivalent @value{GDBN} command.
35716 @subsubheading Example
35720 @subheading The @code{-target-list-available-targets} Command
35721 @findex -target-list-available-targets
35723 @subsubheading Synopsis
35726 -target-list-available-targets
35729 List the possible targets to connect to.
35731 @subsubheading @value{GDBN} Command
35733 The corresponding @value{GDBN} command is @samp{help target}.
35735 @subsubheading Example
35739 @subheading The @code{-target-list-current-targets} Command
35740 @findex -target-list-current-targets
35742 @subsubheading Synopsis
35745 -target-list-current-targets
35748 Describe the current target.
35750 @subsubheading @value{GDBN} Command
35752 The corresponding information is printed by @samp{info file} (among
35755 @subsubheading Example
35759 @subheading The @code{-target-list-parameters} Command
35760 @findex -target-list-parameters
35762 @subsubheading Synopsis
35765 -target-list-parameters
35771 @subsubheading @value{GDBN} Command
35775 @subsubheading Example
35778 @subheading The @code{-target-flash-erase} Command
35779 @findex -target-flash-erase
35781 @subsubheading Synopsis
35784 -target-flash-erase
35787 Erases all known flash memory regions on the target.
35789 The corresponding @value{GDBN} command is @samp{flash-erase}.
35791 The output is a list of flash regions that have been erased, with starting
35792 addresses and memory region sizes.
35796 -target-flash-erase
35797 ^done,erased-regions=@{address="0x0",size="0x40000"@}
35801 @subheading The @code{-target-select} Command
35802 @findex -target-select
35804 @subsubheading Synopsis
35807 -target-select @var{type} @var{parameters @dots{}}
35810 Connect @value{GDBN} to the remote target. This command takes two args:
35814 The type of target, for instance @samp{remote}, etc.
35815 @item @var{parameters}
35816 Device names, host names and the like. @xref{Target Commands, ,
35817 Commands for Managing Targets}, for more details.
35820 The output is a connection notification, followed by the address at
35821 which the target program is, in the following form:
35824 ^connected,addr="@var{address}",func="@var{function name}",
35825 args=[@var{arg list}]
35828 @subsubheading @value{GDBN} Command
35830 The corresponding @value{GDBN} command is @samp{target}.
35832 @subsubheading Example
35836 -target-select remote /dev/ttya
35837 ^connected,addr="0xfe00a300",func="??",args=[]
35841 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35842 @node GDB/MI File Transfer Commands
35843 @section @sc{gdb/mi} File Transfer Commands
35846 @subheading The @code{-target-file-put} Command
35847 @findex -target-file-put
35849 @subsubheading Synopsis
35852 -target-file-put @var{hostfile} @var{targetfile}
35855 Copy file @var{hostfile} from the host system (the machine running
35856 @value{GDBN}) to @var{targetfile} on the target system.
35858 @subsubheading @value{GDBN} Command
35860 The corresponding @value{GDBN} command is @samp{remote put}.
35862 @subsubheading Example
35866 -target-file-put localfile remotefile
35872 @subheading The @code{-target-file-get} Command
35873 @findex -target-file-get
35875 @subsubheading Synopsis
35878 -target-file-get @var{targetfile} @var{hostfile}
35881 Copy file @var{targetfile} from the target system to @var{hostfile}
35882 on the host system.
35884 @subsubheading @value{GDBN} Command
35886 The corresponding @value{GDBN} command is @samp{remote get}.
35888 @subsubheading Example
35892 -target-file-get remotefile localfile
35898 @subheading The @code{-target-file-delete} Command
35899 @findex -target-file-delete
35901 @subsubheading Synopsis
35904 -target-file-delete @var{targetfile}
35907 Delete @var{targetfile} from the target system.
35909 @subsubheading @value{GDBN} Command
35911 The corresponding @value{GDBN} command is @samp{remote delete}.
35913 @subsubheading Example
35917 -target-file-delete remotefile
35923 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35924 @node GDB/MI Ada Exceptions Commands
35925 @section Ada Exceptions @sc{gdb/mi} Commands
35927 @subheading The @code{-info-ada-exceptions} Command
35928 @findex -info-ada-exceptions
35930 @subsubheading Synopsis
35933 -info-ada-exceptions [ @var{regexp}]
35936 List all Ada exceptions defined within the program being debugged.
35937 With a regular expression @var{regexp}, only those exceptions whose
35938 names match @var{regexp} are listed.
35940 @subsubheading @value{GDBN} Command
35942 The corresponding @value{GDBN} command is @samp{info exceptions}.
35944 @subsubheading Result
35946 The result is a table of Ada exceptions. The following columns are
35947 defined for each exception:
35951 The name of the exception.
35954 The address of the exception.
35958 @subsubheading Example
35961 -info-ada-exceptions aint
35962 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
35963 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
35964 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
35965 body=[@{name="constraint_error",address="0x0000000000613da0"@},
35966 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
35969 @subheading Catching Ada Exceptions
35971 The commands describing how to ask @value{GDBN} to stop when a program
35972 raises an exception are described at @ref{Ada Exception GDB/MI
35973 Catchpoint Commands}.
35976 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35977 @node GDB/MI Support Commands
35978 @section @sc{gdb/mi} Support Commands
35980 Since new commands and features get regularly added to @sc{gdb/mi},
35981 some commands are available to help front-ends query the debugger
35982 about support for these capabilities. Similarly, it is also possible
35983 to query @value{GDBN} about target support of certain features.
35985 @subheading The @code{-info-gdb-mi-command} Command
35986 @cindex @code{-info-gdb-mi-command}
35987 @findex -info-gdb-mi-command
35989 @subsubheading Synopsis
35992 -info-gdb-mi-command @var{cmd_name}
35995 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
35997 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
35998 is technically not part of the command name (@pxref{GDB/MI Input
35999 Syntax}), and thus should be omitted in @var{cmd_name}. However,
36000 for ease of use, this command also accepts the form with the leading
36003 @subsubheading @value{GDBN} Command
36005 There is no corresponding @value{GDBN} command.
36007 @subsubheading Result
36009 The result is a tuple. There is currently only one field:
36013 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
36014 @code{"false"} otherwise.
36018 @subsubheading Example
36020 Here is an example where the @sc{gdb/mi} command does not exist:
36023 -info-gdb-mi-command unsupported-command
36024 ^done,command=@{exists="false"@}
36028 And here is an example where the @sc{gdb/mi} command is known
36032 -info-gdb-mi-command symbol-list-lines
36033 ^done,command=@{exists="true"@}
36036 @subheading The @code{-list-features} Command
36037 @findex -list-features
36038 @cindex supported @sc{gdb/mi} features, list
36040 Returns a list of particular features of the MI protocol that
36041 this version of gdb implements. A feature can be a command,
36042 or a new field in an output of some command, or even an
36043 important bugfix. While a frontend can sometimes detect presence
36044 of a feature at runtime, it is easier to perform detection at debugger
36047 The command returns a list of strings, with each string naming an
36048 available feature. Each returned string is just a name, it does not
36049 have any internal structure. The list of possible feature names
36055 (gdb) -list-features
36056 ^done,result=["feature1","feature2"]
36059 The current list of features is:
36062 @item frozen-varobjs
36063 Indicates support for the @code{-var-set-frozen} command, as well
36064 as possible presence of the @code{frozen} field in the output
36065 of @code{-varobj-create}.
36066 @item pending-breakpoints
36067 Indicates support for the @option{-f} option to the @code{-break-insert}
36070 Indicates Python scripting support, Python-based
36071 pretty-printing commands, and possible presence of the
36072 @samp{display_hint} field in the output of @code{-var-list-children}
36074 Indicates support for the @code{-thread-info} command.
36075 @item data-read-memory-bytes
36076 Indicates support for the @code{-data-read-memory-bytes} and the
36077 @code{-data-write-memory-bytes} commands.
36078 @item breakpoint-notifications
36079 Indicates that changes to breakpoints and breakpoints created via the
36080 CLI will be announced via async records.
36081 @item ada-task-info
36082 Indicates support for the @code{-ada-task-info} command.
36083 @item language-option
36084 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
36085 option (@pxref{Context management}).
36086 @item info-gdb-mi-command
36087 Indicates support for the @code{-info-gdb-mi-command} command.
36088 @item undefined-command-error-code
36089 Indicates support for the "undefined-command" error code in error result
36090 records, produced when trying to execute an undefined @sc{gdb/mi} command
36091 (@pxref{GDB/MI Result Records}).
36092 @item exec-run-start-option
36093 Indicates that the @code{-exec-run} command supports the @option{--start}
36094 option (@pxref{GDB/MI Program Execution}).
36095 @item data-disassemble-a-option
36096 Indicates that the @code{-data-disassemble} command supports the @option{-a}
36097 option (@pxref{GDB/MI Data Manipulation}).
36100 @subheading The @code{-list-target-features} Command
36101 @findex -list-target-features
36103 Returns a list of particular features that are supported by the
36104 target. Those features affect the permitted MI commands, but
36105 unlike the features reported by the @code{-list-features} command, the
36106 features depend on which target GDB is using at the moment. Whenever
36107 a target can change, due to commands such as @code{-target-select},
36108 @code{-target-attach} or @code{-exec-run}, the list of target features
36109 may change, and the frontend should obtain it again.
36113 (gdb) -list-target-features
36114 ^done,result=["async"]
36117 The current list of features is:
36121 Indicates that the target is capable of asynchronous command
36122 execution, which means that @value{GDBN} will accept further commands
36123 while the target is running.
36126 Indicates that the target is capable of reverse execution.
36127 @xref{Reverse Execution}, for more information.
36131 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
36132 @node GDB/MI Miscellaneous Commands
36133 @section Miscellaneous @sc{gdb/mi} Commands
36135 @c @subheading -gdb-complete
36137 @subheading The @code{-gdb-exit} Command
36140 @subsubheading Synopsis
36146 Exit @value{GDBN} immediately.
36148 @subsubheading @value{GDBN} Command
36150 Approximately corresponds to @samp{quit}.
36152 @subsubheading Example
36162 @subheading The @code{-exec-abort} Command
36163 @findex -exec-abort
36165 @subsubheading Synopsis
36171 Kill the inferior running program.
36173 @subsubheading @value{GDBN} Command
36175 The corresponding @value{GDBN} command is @samp{kill}.
36177 @subsubheading Example
36182 @subheading The @code{-gdb-set} Command
36185 @subsubheading Synopsis
36191 Set an internal @value{GDBN} variable.
36192 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
36194 @subsubheading @value{GDBN} Command
36196 The corresponding @value{GDBN} command is @samp{set}.
36198 @subsubheading Example
36208 @subheading The @code{-gdb-show} Command
36211 @subsubheading Synopsis
36217 Show the current value of a @value{GDBN} variable.
36219 @subsubheading @value{GDBN} Command
36221 The corresponding @value{GDBN} command is @samp{show}.
36223 @subsubheading Example
36232 @c @subheading -gdb-source
36235 @subheading The @code{-gdb-version} Command
36236 @findex -gdb-version
36238 @subsubheading Synopsis
36244 Show version information for @value{GDBN}. Used mostly in testing.
36246 @subsubheading @value{GDBN} Command
36248 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
36249 default shows this information when you start an interactive session.
36251 @subsubheading Example
36253 @c This example modifies the actual output from GDB to avoid overfull
36259 ~Copyright 2000 Free Software Foundation, Inc.
36260 ~GDB is free software, covered by the GNU General Public License, and
36261 ~you are welcome to change it and/or distribute copies of it under
36262 ~ certain conditions.
36263 ~Type "show copying" to see the conditions.
36264 ~There is absolutely no warranty for GDB. Type "show warranty" for
36266 ~This GDB was configured as
36267 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
36272 @subheading The @code{-list-thread-groups} Command
36273 @findex -list-thread-groups
36275 @subheading Synopsis
36278 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
36281 Lists thread groups (@pxref{Thread groups}). When a single thread
36282 group is passed as the argument, lists the children of that group.
36283 When several thread group are passed, lists information about those
36284 thread groups. Without any parameters, lists information about all
36285 top-level thread groups.
36287 Normally, thread groups that are being debugged are reported.
36288 With the @samp{--available} option, @value{GDBN} reports thread groups
36289 available on the target.
36291 The output of this command may have either a @samp{threads} result or
36292 a @samp{groups} result. The @samp{thread} result has a list of tuples
36293 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
36294 Information}). The @samp{groups} result has a list of tuples as value,
36295 each tuple describing a thread group. If top-level groups are
36296 requested (that is, no parameter is passed), or when several groups
36297 are passed, the output always has a @samp{groups} result. The format
36298 of the @samp{group} result is described below.
36300 To reduce the number of roundtrips it's possible to list thread groups
36301 together with their children, by passing the @samp{--recurse} option
36302 and the recursion depth. Presently, only recursion depth of 1 is
36303 permitted. If this option is present, then every reported thread group
36304 will also include its children, either as @samp{group} or
36305 @samp{threads} field.
36307 In general, any combination of option and parameters is permitted, with
36308 the following caveats:
36312 When a single thread group is passed, the output will typically
36313 be the @samp{threads} result. Because threads may not contain
36314 anything, the @samp{recurse} option will be ignored.
36317 When the @samp{--available} option is passed, limited information may
36318 be available. In particular, the list of threads of a process might
36319 be inaccessible. Further, specifying specific thread groups might
36320 not give any performance advantage over listing all thread groups.
36321 The frontend should assume that @samp{-list-thread-groups --available}
36322 is always an expensive operation and cache the results.
36326 The @samp{groups} result is a list of tuples, where each tuple may
36327 have the following fields:
36331 Identifier of the thread group. This field is always present.
36332 The identifier is an opaque string; frontends should not try to
36333 convert it to an integer, even though it might look like one.
36336 The type of the thread group. At present, only @samp{process} is a
36340 The target-specific process identifier. This field is only present
36341 for thread groups of type @samp{process} and only if the process exists.
36344 The exit code of this group's last exited thread, formatted in octal.
36345 This field is only present for thread groups of type @samp{process} and
36346 only if the process is not running.
36349 The number of children this thread group has. This field may be
36350 absent for an available thread group.
36353 This field has a list of tuples as value, each tuple describing a
36354 thread. It may be present if the @samp{--recurse} option is
36355 specified, and it's actually possible to obtain the threads.
36358 This field is a list of integers, each identifying a core that one
36359 thread of the group is running on. This field may be absent if
36360 such information is not available.
36363 The name of the executable file that corresponds to this thread group.
36364 The field is only present for thread groups of type @samp{process},
36365 and only if there is a corresponding executable file.
36369 @subheading Example
36373 -list-thread-groups
36374 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
36375 -list-thread-groups 17
36376 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
36377 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
36378 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
36379 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
36380 file="/tmp/a.c",fullname="/tmp/a.c",line="158",arch="i386:x86_64"@},state="running"@}]]
36381 -list-thread-groups --available
36382 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
36383 -list-thread-groups --available --recurse 1
36384 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
36385 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
36386 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
36387 -list-thread-groups --available --recurse 1 17 18
36388 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
36389 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
36390 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
36393 @subheading The @code{-info-os} Command
36396 @subsubheading Synopsis
36399 -info-os [ @var{type} ]
36402 If no argument is supplied, the command returns a table of available
36403 operating-system-specific information types. If one of these types is
36404 supplied as an argument @var{type}, then the command returns a table
36405 of data of that type.
36407 The types of information available depend on the target operating
36410 @subsubheading @value{GDBN} Command
36412 The corresponding @value{GDBN} command is @samp{info os}.
36414 @subsubheading Example
36416 When run on a @sc{gnu}/Linux system, the output will look something
36422 ^done,OSDataTable=@{nr_rows="10",nr_cols="3",
36423 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
36424 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
36425 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
36426 body=[item=@{col0="cpus",col1="Listing of all cpus/cores on the system",
36428 item=@{col0="files",col1="Listing of all file descriptors",
36429 col2="File descriptors"@},
36430 item=@{col0="modules",col1="Listing of all loaded kernel modules",
36431 col2="Kernel modules"@},
36432 item=@{col0="msg",col1="Listing of all message queues",
36433 col2="Message queues"@},
36434 item=@{col0="processes",col1="Listing of all processes",
36435 col2="Processes"@},
36436 item=@{col0="procgroups",col1="Listing of all process groups",
36437 col2="Process groups"@},
36438 item=@{col0="semaphores",col1="Listing of all semaphores",
36439 col2="Semaphores"@},
36440 item=@{col0="shm",col1="Listing of all shared-memory regions",
36441 col2="Shared-memory regions"@},
36442 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
36444 item=@{col0="threads",col1="Listing of all threads",
36448 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
36449 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
36450 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
36451 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
36452 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
36453 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
36454 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
36455 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
36457 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
36458 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
36462 (Note that the MI output here includes a @code{"Title"} column that
36463 does not appear in command-line @code{info os}; this column is useful
36464 for MI clients that want to enumerate the types of data, such as in a
36465 popup menu, but is needless clutter on the command line, and
36466 @code{info os} omits it.)
36468 @subheading The @code{-add-inferior} Command
36469 @findex -add-inferior
36471 @subheading Synopsis
36477 Creates a new inferior (@pxref{Inferiors Connections and Programs}). The created
36478 inferior is not associated with any executable. Such association may
36479 be established with the @samp{-file-exec-and-symbols} command
36480 (@pxref{GDB/MI File Commands}). The command response has a single
36481 field, @samp{inferior}, whose value is the identifier of the
36482 thread group corresponding to the new inferior.
36484 @subheading Example
36489 ^done,inferior="i3"
36492 @subheading The @code{-interpreter-exec} Command
36493 @findex -interpreter-exec
36495 @subheading Synopsis
36498 -interpreter-exec @var{interpreter} @var{command}
36500 @anchor{-interpreter-exec}
36502 Execute the specified @var{command} in the given @var{interpreter}.
36504 @subheading @value{GDBN} Command
36506 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
36508 @subheading Example
36512 -interpreter-exec console "break main"
36513 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
36514 &"During symbol reading, bad structure-type format.\n"
36515 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
36520 @subheading The @code{-inferior-tty-set} Command
36521 @findex -inferior-tty-set
36523 @subheading Synopsis
36526 -inferior-tty-set /dev/pts/1
36529 Set terminal for future runs of the program being debugged.
36531 @subheading @value{GDBN} Command
36533 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
36535 @subheading Example
36539 -inferior-tty-set /dev/pts/1
36544 @subheading The @code{-inferior-tty-show} Command
36545 @findex -inferior-tty-show
36547 @subheading Synopsis
36553 Show terminal for future runs of program being debugged.
36555 @subheading @value{GDBN} Command
36557 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
36559 @subheading Example
36563 -inferior-tty-set /dev/pts/1
36567 ^done,inferior_tty_terminal="/dev/pts/1"
36571 @subheading The @code{-enable-timings} Command
36572 @findex -enable-timings
36574 @subheading Synopsis
36577 -enable-timings [yes | no]
36580 Toggle the printing of the wallclock, user and system times for an MI
36581 command as a field in its output. This command is to help frontend
36582 developers optimize the performance of their code. No argument is
36583 equivalent to @samp{yes}.
36585 @subheading @value{GDBN} Command
36589 @subheading Example
36597 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
36598 addr="0x080484ed",func="main",file="myprog.c",
36599 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
36601 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
36609 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
36610 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
36611 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
36612 fullname="/home/nickrob/myprog.c",line="73",arch="i386:x86_64"@}
36616 @subheading The @code{-complete} Command
36619 @subheading Synopsis
36622 -complete @var{command}
36625 Show a list of completions for partially typed CLI @var{command}.
36627 This command is intended for @sc{gdb/mi} frontends that cannot use two separate
36628 CLI and MI channels --- for example: because of lack of PTYs like on Windows or
36629 because @value{GDBN} is used remotely via a SSH connection.
36633 The result consists of two or three fields:
36637 This field contains the completed @var{command}. If @var{command}
36638 has no known completions, this field is omitted.
36641 This field contains a (possibly empty) array of matches. It is always present.
36643 @item max_completions_reached
36644 This field contains @code{1} if number of known completions is above
36645 @code{max-completions} limit (@pxref{Completion}), otherwise it contains
36646 @code{0}. It is always present.
36650 @subheading @value{GDBN} Command
36652 The corresponding @value{GDBN} command is @samp{complete}.
36654 @subheading Example
36659 ^done,completion="break",
36660 matches=["break","break-range"],
36661 max_completions_reached="0"
36664 ^done,completion="b ma",
36665 matches=["b madvise","b main"],max_completions_reached="0"
36667 -complete "b push_b"
36668 ^done,completion="b push_back(",
36670 "b A::push_back(void*)",
36671 "b std::string::push_back(char)",
36672 "b std::vector<int, std::allocator<int> >::push_back(int&&)"],
36673 max_completions_reached="0"
36675 -complete "nonexist"
36676 ^done,matches=[],max_completions_reached="0"
36682 @chapter @value{GDBN} Annotations
36684 This chapter describes annotations in @value{GDBN}. Annotations were
36685 designed to interface @value{GDBN} to graphical user interfaces or other
36686 similar programs which want to interact with @value{GDBN} at a
36687 relatively high level.
36689 The annotation mechanism has largely been superseded by @sc{gdb/mi}
36693 This is Edition @value{EDITION}, @value{DATE}.
36697 * Annotations Overview:: What annotations are; the general syntax.
36698 * Server Prefix:: Issuing a command without affecting user state.
36699 * Prompting:: Annotations marking @value{GDBN}'s need for input.
36700 * Errors:: Annotations for error messages.
36701 * Invalidation:: Some annotations describe things now invalid.
36702 * Annotations for Running::
36703 Whether the program is running, how it stopped, etc.
36704 * Source Annotations:: Annotations describing source code.
36707 @node Annotations Overview
36708 @section What is an Annotation?
36709 @cindex annotations
36711 Annotations start with a newline character, two @samp{control-z}
36712 characters, and the name of the annotation. If there is no additional
36713 information associated with this annotation, the name of the annotation
36714 is followed immediately by a newline. If there is additional
36715 information, the name of the annotation is followed by a space, the
36716 additional information, and a newline. The additional information
36717 cannot contain newline characters.
36719 Any output not beginning with a newline and two @samp{control-z}
36720 characters denotes literal output from @value{GDBN}. Currently there is
36721 no need for @value{GDBN} to output a newline followed by two
36722 @samp{control-z} characters, but if there was such a need, the
36723 annotations could be extended with an @samp{escape} annotation which
36724 means those three characters as output.
36726 The annotation @var{level}, which is specified using the
36727 @option{--annotate} command line option (@pxref{Mode Options}), controls
36728 how much information @value{GDBN} prints together with its prompt,
36729 values of expressions, source lines, and other types of output. Level 0
36730 is for no annotations, level 1 is for use when @value{GDBN} is run as a
36731 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
36732 for programs that control @value{GDBN}, and level 2 annotations have
36733 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
36734 Interface, annotate, GDB's Obsolete Annotations}).
36737 @kindex set annotate
36738 @item set annotate @var{level}
36739 The @value{GDBN} command @code{set annotate} sets the level of
36740 annotations to the specified @var{level}.
36742 @item show annotate
36743 @kindex show annotate
36744 Show the current annotation level.
36747 This chapter describes level 3 annotations.
36749 A simple example of starting up @value{GDBN} with annotations is:
36752 $ @kbd{gdb --annotate=3}
36754 Copyright 2003 Free Software Foundation, Inc.
36755 GDB is free software, covered by the GNU General Public License,
36756 and you are welcome to change it and/or distribute copies of it
36757 under certain conditions.
36758 Type "show copying" to see the conditions.
36759 There is absolutely no warranty for GDB. Type "show warranty"
36761 This GDB was configured as "i386-pc-linux-gnu"
36772 Here @samp{quit} is input to @value{GDBN}; the rest is output from
36773 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
36774 denotes a @samp{control-z} character) are annotations; the rest is
36775 output from @value{GDBN}.
36777 @node Server Prefix
36778 @section The Server Prefix
36779 @cindex server prefix
36781 If you prefix a command with @samp{server } then it will not affect
36782 the command history, nor will it affect @value{GDBN}'s notion of which
36783 command to repeat if @key{RET} is pressed on a line by itself. This
36784 means that commands can be run behind a user's back by a front-end in
36785 a transparent manner.
36787 The @code{server } prefix does not affect the recording of values into
36788 the value history; to print a value without recording it into the
36789 value history, use the @code{output} command instead of the
36790 @code{print} command.
36792 Using this prefix also disables confirmation requests
36793 (@pxref{confirmation requests}).
36796 @section Annotation for @value{GDBN} Input
36798 @cindex annotations for prompts
36799 When @value{GDBN} prompts for input, it annotates this fact so it is possible
36800 to know when to send output, when the output from a given command is
36803 Different kinds of input each have a different @dfn{input type}. Each
36804 input type has three annotations: a @code{pre-} annotation, which
36805 denotes the beginning of any prompt which is being output, a plain
36806 annotation, which denotes the end of the prompt, and then a @code{post-}
36807 annotation which denotes the end of any echo which may (or may not) be
36808 associated with the input. For example, the @code{prompt} input type
36809 features the following annotations:
36817 The input types are
36820 @findex pre-prompt annotation
36821 @findex prompt annotation
36822 @findex post-prompt annotation
36824 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
36826 @findex pre-commands annotation
36827 @findex commands annotation
36828 @findex post-commands annotation
36830 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
36831 command. The annotations are repeated for each command which is input.
36833 @findex pre-overload-choice annotation
36834 @findex overload-choice annotation
36835 @findex post-overload-choice annotation
36836 @item overload-choice
36837 When @value{GDBN} wants the user to select between various overloaded functions.
36839 @findex pre-query annotation
36840 @findex query annotation
36841 @findex post-query annotation
36843 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
36845 @findex pre-prompt-for-continue annotation
36846 @findex prompt-for-continue annotation
36847 @findex post-prompt-for-continue annotation
36848 @item prompt-for-continue
36849 When @value{GDBN} is asking the user to press return to continue. Note: Don't
36850 expect this to work well; instead use @code{set height 0} to disable
36851 prompting. This is because the counting of lines is buggy in the
36852 presence of annotations.
36857 @cindex annotations for errors, warnings and interrupts
36859 @findex quit annotation
36864 This annotation occurs right before @value{GDBN} responds to an interrupt.
36866 @findex error annotation
36871 This annotation occurs right before @value{GDBN} responds to an error.
36873 Quit and error annotations indicate that any annotations which @value{GDBN} was
36874 in the middle of may end abruptly. For example, if a
36875 @code{value-history-begin} annotation is followed by a @code{error}, one
36876 cannot expect to receive the matching @code{value-history-end}. One
36877 cannot expect not to receive it either, however; an error annotation
36878 does not necessarily mean that @value{GDBN} is immediately returning all the way
36881 @findex error-begin annotation
36882 A quit or error annotation may be preceded by
36888 Any output between that and the quit or error annotation is the error
36891 Warning messages are not yet annotated.
36892 @c If we want to change that, need to fix warning(), type_error(),
36893 @c range_error(), and possibly other places.
36896 @section Invalidation Notices
36898 @cindex annotations for invalidation messages
36899 The following annotations say that certain pieces of state may have
36903 @findex frames-invalid annotation
36904 @item ^Z^Zframes-invalid
36906 The frames (for example, output from the @code{backtrace} command) may
36909 @findex breakpoints-invalid annotation
36910 @item ^Z^Zbreakpoints-invalid
36912 The breakpoints may have changed. For example, the user just added or
36913 deleted a breakpoint.
36916 @node Annotations for Running
36917 @section Running the Program
36918 @cindex annotations for running programs
36920 @findex starting annotation
36921 @findex stopping annotation
36922 When the program starts executing due to a @value{GDBN} command such as
36923 @code{step} or @code{continue},
36929 is output. When the program stops,
36935 is output. Before the @code{stopped} annotation, a variety of
36936 annotations describe how the program stopped.
36939 @findex exited annotation
36940 @item ^Z^Zexited @var{exit-status}
36941 The program exited, and @var{exit-status} is the exit status (zero for
36942 successful exit, otherwise nonzero).
36944 @findex signalled annotation
36945 @findex signal-name annotation
36946 @findex signal-name-end annotation
36947 @findex signal-string annotation
36948 @findex signal-string-end annotation
36949 @item ^Z^Zsignalled
36950 The program exited with a signal. After the @code{^Z^Zsignalled}, the
36951 annotation continues:
36957 ^Z^Zsignal-name-end
36961 ^Z^Zsignal-string-end
36966 where @var{name} is the name of the signal, such as @code{SIGILL} or
36967 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
36968 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
36969 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
36970 user's benefit and have no particular format.
36972 @findex signal annotation
36974 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
36975 just saying that the program received the signal, not that it was
36976 terminated with it.
36978 @findex breakpoint annotation
36979 @item ^Z^Zbreakpoint @var{number}
36980 The program hit breakpoint number @var{number}.
36982 @findex watchpoint annotation
36983 @item ^Z^Zwatchpoint @var{number}
36984 The program hit watchpoint number @var{number}.
36987 @node Source Annotations
36988 @section Displaying Source
36989 @cindex annotations for source display
36991 @findex source annotation
36992 The following annotation is used instead of displaying source code:
36995 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
36998 where @var{filename} is an absolute file name indicating which source
36999 file, @var{line} is the line number within that file (where 1 is the
37000 first line in the file), @var{character} is the character position
37001 within the file (where 0 is the first character in the file) (for most
37002 debug formats this will necessarily point to the beginning of a line),
37003 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
37004 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
37005 @var{addr} is the address in the target program associated with the
37006 source which is being displayed. The @var{addr} is in the form @samp{0x}
37007 followed by one or more lowercase hex digits (note that this does not
37008 depend on the language).
37010 @node JIT Interface
37011 @chapter JIT Compilation Interface
37012 @cindex just-in-time compilation
37013 @cindex JIT compilation interface
37015 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
37016 interface. A JIT compiler is a program or library that generates native
37017 executable code at runtime and executes it, usually in order to achieve good
37018 performance while maintaining platform independence.
37020 Programs that use JIT compilation are normally difficult to debug because
37021 portions of their code are generated at runtime, instead of being loaded from
37022 object files, which is where @value{GDBN} normally finds the program's symbols
37023 and debug information. In order to debug programs that use JIT compilation,
37024 @value{GDBN} has an interface that allows the program to register in-memory
37025 symbol files with @value{GDBN} at runtime.
37027 If you are using @value{GDBN} to debug a program that uses this interface, then
37028 it should work transparently so long as you have not stripped the binary. If
37029 you are developing a JIT compiler, then the interface is documented in the rest
37030 of this chapter. At this time, the only known client of this interface is the
37033 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
37034 JIT compiler communicates with @value{GDBN} by writing data into a global
37035 variable and calling a function at a well-known symbol. When @value{GDBN}
37036 attaches, it reads a linked list of symbol files from the global variable to
37037 find existing code, and puts a breakpoint in the function so that it can find
37038 out about additional code.
37041 * Declarations:: Relevant C struct declarations
37042 * Registering Code:: Steps to register code
37043 * Unregistering Code:: Steps to unregister code
37044 * Custom Debug Info:: Emit debug information in a custom format
37048 @section JIT Declarations
37050 These are the relevant struct declarations that a C program should include to
37051 implement the interface:
37061 struct jit_code_entry
37063 struct jit_code_entry *next_entry;
37064 struct jit_code_entry *prev_entry;
37065 const char *symfile_addr;
37066 uint64_t symfile_size;
37069 struct jit_descriptor
37072 /* This type should be jit_actions_t, but we use uint32_t
37073 to be explicit about the bitwidth. */
37074 uint32_t action_flag;
37075 struct jit_code_entry *relevant_entry;
37076 struct jit_code_entry *first_entry;
37079 /* GDB puts a breakpoint in this function. */
37080 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
37082 /* Make sure to specify the version statically, because the
37083 debugger may check the version before we can set it. */
37084 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
37087 If the JIT is multi-threaded, then it is important that the JIT synchronize any
37088 modifications to this global data properly, which can easily be done by putting
37089 a global mutex around modifications to these structures.
37091 @node Registering Code
37092 @section Registering Code
37094 To register code with @value{GDBN}, the JIT should follow this protocol:
37098 Generate an object file in memory with symbols and other desired debug
37099 information. The file must include the virtual addresses of the sections.
37102 Create a code entry for the file, which gives the start and size of the symbol
37106 Add it to the linked list in the JIT descriptor.
37109 Point the relevant_entry field of the descriptor at the entry.
37112 Set @code{action_flag} to @code{JIT_REGISTER} and call
37113 @code{__jit_debug_register_code}.
37116 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
37117 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
37118 new code. However, the linked list must still be maintained in order to allow
37119 @value{GDBN} to attach to a running process and still find the symbol files.
37121 @node Unregistering Code
37122 @section Unregistering Code
37124 If code is freed, then the JIT should use the following protocol:
37128 Remove the code entry corresponding to the code from the linked list.
37131 Point the @code{relevant_entry} field of the descriptor at the code entry.
37134 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
37135 @code{__jit_debug_register_code}.
37138 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
37139 and the JIT will leak the memory used for the associated symbol files.
37141 @node Custom Debug Info
37142 @section Custom Debug Info
37143 @cindex custom JIT debug info
37144 @cindex JIT debug info reader
37146 Generating debug information in platform-native file formats (like ELF
37147 or COFF) may be an overkill for JIT compilers; especially if all the
37148 debug info is used for is displaying a meaningful backtrace. The
37149 issue can be resolved by having the JIT writers decide on a debug info
37150 format and also provide a reader that parses the debug info generated
37151 by the JIT compiler. This section gives a brief overview on writing
37152 such a parser. More specific details can be found in the source file
37153 @file{gdb/jit-reader.in}, which is also installed as a header at
37154 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
37156 The reader is implemented as a shared object (so this functionality is
37157 not available on platforms which don't allow loading shared objects at
37158 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
37159 @code{jit-reader-unload} are provided, to be used to load and unload
37160 the readers from a preconfigured directory. Once loaded, the shared
37161 object is used the parse the debug information emitted by the JIT
37165 * Using JIT Debug Info Readers:: How to use supplied readers correctly
37166 * Writing JIT Debug Info Readers:: Creating a debug-info reader
37169 @node Using JIT Debug Info Readers
37170 @subsection Using JIT Debug Info Readers
37171 @kindex jit-reader-load
37172 @kindex jit-reader-unload
37174 Readers can be loaded and unloaded using the @code{jit-reader-load}
37175 and @code{jit-reader-unload} commands.
37178 @item jit-reader-load @var{reader}
37179 Load the JIT reader named @var{reader}, which is a shared
37180 object specified as either an absolute or a relative file name. In
37181 the latter case, @value{GDBN} will try to load the reader from a
37182 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
37183 system (here @var{libdir} is the system library directory, often
37184 @file{/usr/local/lib}).
37186 Only one reader can be active at a time; trying to load a second
37187 reader when one is already loaded will result in @value{GDBN}
37188 reporting an error. A new JIT reader can be loaded by first unloading
37189 the current one using @code{jit-reader-unload} and then invoking
37190 @code{jit-reader-load}.
37192 @item jit-reader-unload
37193 Unload the currently loaded JIT reader.
37197 @node Writing JIT Debug Info Readers
37198 @subsection Writing JIT Debug Info Readers
37199 @cindex writing JIT debug info readers
37201 As mentioned, a reader is essentially a shared object conforming to a
37202 certain ABI. This ABI is described in @file{jit-reader.h}.
37204 @file{jit-reader.h} defines the structures, macros and functions
37205 required to write a reader. It is installed (along with
37206 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
37207 the system include directory.
37209 Readers need to be released under a GPL compatible license. A reader
37210 can be declared as released under such a license by placing the macro
37211 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
37213 The entry point for readers is the symbol @code{gdb_init_reader},
37214 which is expected to be a function with the prototype
37216 @findex gdb_init_reader
37218 extern struct gdb_reader_funcs *gdb_init_reader (void);
37221 @cindex @code{struct gdb_reader_funcs}
37223 @code{struct gdb_reader_funcs} contains a set of pointers to callback
37224 functions. These functions are executed to read the debug info
37225 generated by the JIT compiler (@code{read}), to unwind stack frames
37226 (@code{unwind}) and to create canonical frame IDs
37227 (@code{get_frame_id}). It also has a callback that is called when the
37228 reader is being unloaded (@code{destroy}). The struct looks like this
37231 struct gdb_reader_funcs
37233 /* Must be set to GDB_READER_INTERFACE_VERSION. */
37234 int reader_version;
37236 /* For use by the reader. */
37239 gdb_read_debug_info *read;
37240 gdb_unwind_frame *unwind;
37241 gdb_get_frame_id *get_frame_id;
37242 gdb_destroy_reader *destroy;
37246 @cindex @code{struct gdb_symbol_callbacks}
37247 @cindex @code{struct gdb_unwind_callbacks}
37249 The callbacks are provided with another set of callbacks by
37250 @value{GDBN} to do their job. For @code{read}, these callbacks are
37251 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
37252 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
37253 @code{struct gdb_symbol_callbacks} has callbacks to create new object
37254 files and new symbol tables inside those object files. @code{struct
37255 gdb_unwind_callbacks} has callbacks to read registers off the current
37256 frame and to write out the values of the registers in the previous
37257 frame. Both have a callback (@code{target_read}) to read bytes off the
37258 target's address space.
37260 @node In-Process Agent
37261 @chapter In-Process Agent
37262 @cindex debugging agent
37263 The traditional debugging model is conceptually low-speed, but works fine,
37264 because most bugs can be reproduced in debugging-mode execution. However,
37265 as multi-core or many-core processors are becoming mainstream, and
37266 multi-threaded programs become more and more popular, there should be more
37267 and more bugs that only manifest themselves at normal-mode execution, for
37268 example, thread races, because debugger's interference with the program's
37269 timing may conceal the bugs. On the other hand, in some applications,
37270 it is not feasible for the debugger to interrupt the program's execution
37271 long enough for the developer to learn anything helpful about its behavior.
37272 If the program's correctness depends on its real-time behavior, delays
37273 introduced by a debugger might cause the program to fail, even when the
37274 code itself is correct. It is useful to be able to observe the program's
37275 behavior without interrupting it.
37277 Therefore, traditional debugging model is too intrusive to reproduce
37278 some bugs. In order to reduce the interference with the program, we can
37279 reduce the number of operations performed by debugger. The
37280 @dfn{In-Process Agent}, a shared library, is running within the same
37281 process with inferior, and is able to perform some debugging operations
37282 itself. As a result, debugger is only involved when necessary, and
37283 performance of debugging can be improved accordingly. Note that
37284 interference with program can be reduced but can't be removed completely,
37285 because the in-process agent will still stop or slow down the program.
37287 The in-process agent can interpret and execute Agent Expressions
37288 (@pxref{Agent Expressions}) during performing debugging operations. The
37289 agent expressions can be used for different purposes, such as collecting
37290 data in tracepoints, and condition evaluation in breakpoints.
37292 @anchor{Control Agent}
37293 You can control whether the in-process agent is used as an aid for
37294 debugging with the following commands:
37297 @kindex set agent on
37299 Causes the in-process agent to perform some operations on behalf of the
37300 debugger. Just which operations requested by the user will be done
37301 by the in-process agent depends on the its capabilities. For example,
37302 if you request to evaluate breakpoint conditions in the in-process agent,
37303 and the in-process agent has such capability as well, then breakpoint
37304 conditions will be evaluated in the in-process agent.
37306 @kindex set agent off
37307 @item set agent off
37308 Disables execution of debugging operations by the in-process agent. All
37309 of the operations will be performed by @value{GDBN}.
37313 Display the current setting of execution of debugging operations by
37314 the in-process agent.
37318 * In-Process Agent Protocol::
37321 @node In-Process Agent Protocol
37322 @section In-Process Agent Protocol
37323 @cindex in-process agent protocol
37325 The in-process agent is able to communicate with both @value{GDBN} and
37326 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
37327 used for communications between @value{GDBN} or GDBserver and the IPA.
37328 In general, @value{GDBN} or GDBserver sends commands
37329 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
37330 in-process agent replies back with the return result of the command, or
37331 some other information. The data sent to in-process agent is composed
37332 of primitive data types, such as 4-byte or 8-byte type, and composite
37333 types, which are called objects (@pxref{IPA Protocol Objects}).
37336 * IPA Protocol Objects::
37337 * IPA Protocol Commands::
37340 @node IPA Protocol Objects
37341 @subsection IPA Protocol Objects
37342 @cindex ipa protocol objects
37344 The commands sent to and results received from agent may contain some
37345 complex data types called @dfn{objects}.
37347 The in-process agent is running on the same machine with @value{GDBN}
37348 or GDBserver, so it doesn't have to handle as much differences between
37349 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
37350 However, there are still some differences of two ends in two processes:
37354 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
37355 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
37357 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
37358 GDBserver is compiled with one, and in-process agent is compiled with
37362 Here are the IPA Protocol Objects:
37366 agent expression object. It represents an agent expression
37367 (@pxref{Agent Expressions}).
37368 @anchor{agent expression object}
37370 tracepoint action object. It represents a tracepoint action
37371 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
37372 memory, static trace data and to evaluate expression.
37373 @anchor{tracepoint action object}
37375 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
37376 @anchor{tracepoint object}
37380 The following table describes important attributes of each IPA protocol
37383 @multitable @columnfractions .30 .20 .50
37384 @headitem Name @tab Size @tab Description
37385 @item @emph{agent expression object} @tab @tab
37386 @item length @tab 4 @tab length of bytes code
37387 @item byte code @tab @var{length} @tab contents of byte code
37388 @item @emph{tracepoint action for collecting memory} @tab @tab
37389 @item 'M' @tab 1 @tab type of tracepoint action
37390 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
37391 address of the lowest byte to collect, otherwise @var{addr} is the offset
37392 of @var{basereg} for memory collecting.
37393 @item len @tab 8 @tab length of memory for collecting
37394 @item basereg @tab 4 @tab the register number containing the starting
37395 memory address for collecting.
37396 @item @emph{tracepoint action for collecting registers} @tab @tab
37397 @item 'R' @tab 1 @tab type of tracepoint action
37398 @item @emph{tracepoint action for collecting static trace data} @tab @tab
37399 @item 'L' @tab 1 @tab type of tracepoint action
37400 @item @emph{tracepoint action for expression evaluation} @tab @tab
37401 @item 'X' @tab 1 @tab type of tracepoint action
37402 @item agent expression @tab length of @tab @ref{agent expression object}
37403 @item @emph{tracepoint object} @tab @tab
37404 @item number @tab 4 @tab number of tracepoint
37405 @item address @tab 8 @tab address of tracepoint inserted on
37406 @item type @tab 4 @tab type of tracepoint
37407 @item enabled @tab 1 @tab enable or disable of tracepoint
37408 @item step_count @tab 8 @tab step
37409 @item pass_count @tab 8 @tab pass
37410 @item numactions @tab 4 @tab number of tracepoint actions
37411 @item hit count @tab 8 @tab hit count
37412 @item trace frame usage @tab 8 @tab trace frame usage
37413 @item compiled_cond @tab 8 @tab compiled condition
37414 @item orig_size @tab 8 @tab orig size
37415 @item condition @tab 4 if condition is NULL otherwise length of
37416 @ref{agent expression object}
37417 @tab zero if condition is NULL, otherwise is
37418 @ref{agent expression object}
37419 @item actions @tab variable
37420 @tab numactions number of @ref{tracepoint action object}
37423 @node IPA Protocol Commands
37424 @subsection IPA Protocol Commands
37425 @cindex ipa protocol commands
37427 The spaces in each command are delimiters to ease reading this commands
37428 specification. They don't exist in real commands.
37432 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
37433 Installs a new fast tracepoint described by @var{tracepoint_object}
37434 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
37435 head of @dfn{jumppad}, which is used to jump to data collection routine
37440 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
37441 @var{target_address} is address of tracepoint in the inferior.
37442 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
37443 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
37444 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
37445 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
37452 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
37453 is about to kill inferiors.
37461 @item probe_marker_at:@var{address}
37462 Asks in-process agent to probe the marker at @var{address}.
37469 @item unprobe_marker_at:@var{address}
37470 Asks in-process agent to unprobe the marker at @var{address}.
37474 @chapter Reporting Bugs in @value{GDBN}
37475 @cindex bugs in @value{GDBN}
37476 @cindex reporting bugs in @value{GDBN}
37478 Your bug reports play an essential role in making @value{GDBN} reliable.
37480 Reporting a bug may help you by bringing a solution to your problem, or it
37481 may not. But in any case the principal function of a bug report is to help
37482 the entire community by making the next version of @value{GDBN} work better. Bug
37483 reports are your contribution to the maintenance of @value{GDBN}.
37485 In order for a bug report to serve its purpose, you must include the
37486 information that enables us to fix the bug.
37489 * Bug Criteria:: Have you found a bug?
37490 * Bug Reporting:: How to report bugs
37494 @section Have You Found a Bug?
37495 @cindex bug criteria
37497 If you are not sure whether you have found a bug, here are some guidelines:
37500 @cindex fatal signal
37501 @cindex debugger crash
37502 @cindex crash of debugger
37504 If the debugger gets a fatal signal, for any input whatever, that is a
37505 @value{GDBN} bug. Reliable debuggers never crash.
37507 @cindex error on valid input
37509 If @value{GDBN} produces an error message for valid input, that is a
37510 bug. (Note that if you're cross debugging, the problem may also be
37511 somewhere in the connection to the target.)
37513 @cindex invalid input
37515 If @value{GDBN} does not produce an error message for invalid input,
37516 that is a bug. However, you should note that your idea of
37517 ``invalid input'' might be our idea of ``an extension'' or ``support
37518 for traditional practice''.
37521 If you are an experienced user of debugging tools, your suggestions
37522 for improvement of @value{GDBN} are welcome in any case.
37525 @node Bug Reporting
37526 @section How to Report Bugs
37527 @cindex bug reports
37528 @cindex @value{GDBN} bugs, reporting
37530 A number of companies and individuals offer support for @sc{gnu} products.
37531 If you obtained @value{GDBN} from a support organization, we recommend you
37532 contact that organization first.
37534 You can find contact information for many support companies and
37535 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
37537 @c should add a web page ref...
37540 @ifset BUGURL_DEFAULT
37541 In any event, we also recommend that you submit bug reports for
37542 @value{GDBN}. The preferred method is to submit them directly using
37543 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
37544 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
37547 @strong{Do not send bug reports to @samp{info-gdb}, or to
37548 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
37549 not want to receive bug reports. Those that do have arranged to receive
37552 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
37553 serves as a repeater. The mailing list and the newsgroup carry exactly
37554 the same messages. Often people think of posting bug reports to the
37555 newsgroup instead of mailing them. This appears to work, but it has one
37556 problem which can be crucial: a newsgroup posting often lacks a mail
37557 path back to the sender. Thus, if we need to ask for more information,
37558 we may be unable to reach you. For this reason, it is better to send
37559 bug reports to the mailing list.
37561 @ifclear BUGURL_DEFAULT
37562 In any event, we also recommend that you submit bug reports for
37563 @value{GDBN} to @value{BUGURL}.
37567 The fundamental principle of reporting bugs usefully is this:
37568 @strong{report all the facts}. If you are not sure whether to state a
37569 fact or leave it out, state it!
37571 Often people omit facts because they think they know what causes the
37572 problem and assume that some details do not matter. Thus, you might
37573 assume that the name of the variable you use in an example does not matter.
37574 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
37575 stray memory reference which happens to fetch from the location where that
37576 name is stored in memory; perhaps, if the name were different, the contents
37577 of that location would fool the debugger into doing the right thing despite
37578 the bug. Play it safe and give a specific, complete example. That is the
37579 easiest thing for you to do, and the most helpful.
37581 Keep in mind that the purpose of a bug report is to enable us to fix the
37582 bug. It may be that the bug has been reported previously, but neither
37583 you nor we can know that unless your bug report is complete and
37586 Sometimes people give a few sketchy facts and ask, ``Does this ring a
37587 bell?'' Those bug reports are useless, and we urge everyone to
37588 @emph{refuse to respond to them} except to chide the sender to report
37591 To enable us to fix the bug, you should include all these things:
37595 The version of @value{GDBN}. @value{GDBN} announces it if you start
37596 with no arguments; you can also print it at any time using @code{show
37599 Without this, we will not know whether there is any point in looking for
37600 the bug in the current version of @value{GDBN}.
37603 The type of machine you are using, and the operating system name and
37607 The details of the @value{GDBN} build-time configuration.
37608 @value{GDBN} shows these details if you invoke it with the
37609 @option{--configuration} command-line option, or if you type
37610 @code{show configuration} at @value{GDBN}'s prompt.
37613 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
37614 ``@value{GCC}--2.8.1''.
37617 What compiler (and its version) was used to compile the program you are
37618 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
37619 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
37620 to get this information; for other compilers, see the documentation for
37624 The command arguments you gave the compiler to compile your example and
37625 observe the bug. For example, did you use @samp{-O}? To guarantee
37626 you will not omit something important, list them all. A copy of the
37627 Makefile (or the output from make) is sufficient.
37629 If we were to try to guess the arguments, we would probably guess wrong
37630 and then we might not encounter the bug.
37633 A complete input script, and all necessary source files, that will
37637 A description of what behavior you observe that you believe is
37638 incorrect. For example, ``It gets a fatal signal.''
37640 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
37641 will certainly notice it. But if the bug is incorrect output, we might
37642 not notice unless it is glaringly wrong. You might as well not give us
37643 a chance to make a mistake.
37645 Even if the problem you experience is a fatal signal, you should still
37646 say so explicitly. Suppose something strange is going on, such as, your
37647 copy of @value{GDBN} is out of synch, or you have encountered a bug in
37648 the C library on your system. (This has happened!) Your copy might
37649 crash and ours would not. If you told us to expect a crash, then when
37650 ours fails to crash, we would know that the bug was not happening for
37651 us. If you had not told us to expect a crash, then we would not be able
37652 to draw any conclusion from our observations.
37655 @cindex recording a session script
37656 To collect all this information, you can use a session recording program
37657 such as @command{script}, which is available on many Unix systems.
37658 Just run your @value{GDBN} session inside @command{script} and then
37659 include the @file{typescript} file with your bug report.
37661 Another way to record a @value{GDBN} session is to run @value{GDBN}
37662 inside Emacs and then save the entire buffer to a file.
37665 If you wish to suggest changes to the @value{GDBN} source, send us context
37666 diffs. If you even discuss something in the @value{GDBN} source, refer to
37667 it by context, not by line number.
37669 The line numbers in our development sources will not match those in your
37670 sources. Your line numbers would convey no useful information to us.
37674 Here are some things that are not necessary:
37678 A description of the envelope of the bug.
37680 Often people who encounter a bug spend a lot of time investigating
37681 which changes to the input file will make the bug go away and which
37682 changes will not affect it.
37684 This is often time consuming and not very useful, because the way we
37685 will find the bug is by running a single example under the debugger
37686 with breakpoints, not by pure deduction from a series of examples.
37687 We recommend that you save your time for something else.
37689 Of course, if you can find a simpler example to report @emph{instead}
37690 of the original one, that is a convenience for us. Errors in the
37691 output will be easier to spot, running under the debugger will take
37692 less time, and so on.
37694 However, simplification is not vital; if you do not want to do this,
37695 report the bug anyway and send us the entire test case you used.
37698 A patch for the bug.
37700 A patch for the bug does help us if it is a good one. But do not omit
37701 the necessary information, such as the test case, on the assumption that
37702 a patch is all we need. We might see problems with your patch and decide
37703 to fix the problem another way, or we might not understand it at all.
37705 Sometimes with a program as complicated as @value{GDBN} it is very hard to
37706 construct an example that will make the program follow a certain path
37707 through the code. If you do not send us the example, we will not be able
37708 to construct one, so we will not be able to verify that the bug is fixed.
37710 And if we cannot understand what bug you are trying to fix, or why your
37711 patch should be an improvement, we will not install it. A test case will
37712 help us to understand.
37715 A guess about what the bug is or what it depends on.
37717 Such guesses are usually wrong. Even we cannot guess right about such
37718 things without first using the debugger to find the facts.
37721 @c The readline documentation is distributed with the readline code
37722 @c and consists of the two following files:
37725 @c Use -I with makeinfo to point to the appropriate directory,
37726 @c environment var TEXINPUTS with TeX.
37727 @ifclear SYSTEM_READLINE
37728 @include rluser.texi
37729 @include hsuser.texi
37733 @appendix In Memoriam
37735 The @value{GDBN} project mourns the loss of the following long-time
37740 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
37741 to Free Software in general. Outside of @value{GDBN}, he was known in
37742 the Amiga world for his series of Fish Disks, and the GeekGadget project.
37744 @item Michael Snyder
37745 Michael was one of the Global Maintainers of the @value{GDBN} project,
37746 with contributions recorded as early as 1996, until 2011. In addition
37747 to his day to day participation, he was a large driving force behind
37748 adding Reverse Debugging to @value{GDBN}.
37751 Beyond their technical contributions to the project, they were also
37752 enjoyable members of the Free Software Community. We will miss them.
37754 @node Formatting Documentation
37755 @appendix Formatting Documentation
37757 @cindex @value{GDBN} reference card
37758 @cindex reference card
37759 The @value{GDBN} 4 release includes an already-formatted reference card, ready
37760 for printing with PostScript or Ghostscript, in the @file{gdb}
37761 subdirectory of the main source directory@footnote{In
37762 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
37763 release.}. If you can use PostScript or Ghostscript with your printer,
37764 you can print the reference card immediately with @file{refcard.ps}.
37766 The release also includes the source for the reference card. You
37767 can format it, using @TeX{}, by typing:
37773 The @value{GDBN} reference card is designed to print in @dfn{landscape}
37774 mode on US ``letter'' size paper;
37775 that is, on a sheet 11 inches wide by 8.5 inches
37776 high. You will need to specify this form of printing as an option to
37777 your @sc{dvi} output program.
37779 @cindex documentation
37781 All the documentation for @value{GDBN} comes as part of the machine-readable
37782 distribution. The documentation is written in Texinfo format, which is
37783 a documentation system that uses a single source file to produce both
37784 on-line information and a printed manual. You can use one of the Info
37785 formatting commands to create the on-line version of the documentation
37786 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
37788 @value{GDBN} includes an already formatted copy of the on-line Info
37789 version of this manual in the @file{gdb} subdirectory. The main Info
37790 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
37791 subordinate files matching @samp{gdb.info*} in the same directory. If
37792 necessary, you can print out these files, or read them with any editor;
37793 but they are easier to read using the @code{info} subsystem in @sc{gnu}
37794 Emacs or the standalone @code{info} program, available as part of the
37795 @sc{gnu} Texinfo distribution.
37797 If you want to format these Info files yourself, you need one of the
37798 Info formatting programs, such as @code{texinfo-format-buffer} or
37801 If you have @code{makeinfo} installed, and are in the top level
37802 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
37803 version @value{GDBVN}), you can make the Info file by typing:
37810 If you want to typeset and print copies of this manual, you need @TeX{},
37811 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
37812 Texinfo definitions file.
37814 @TeX{} is a typesetting program; it does not print files directly, but
37815 produces output files called @sc{dvi} files. To print a typeset
37816 document, you need a program to print @sc{dvi} files. If your system
37817 has @TeX{} installed, chances are it has such a program. The precise
37818 command to use depends on your system; @kbd{lpr -d} is common; another
37819 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
37820 require a file name without any extension or a @samp{.dvi} extension.
37822 @TeX{} also requires a macro definitions file called
37823 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
37824 written in Texinfo format. On its own, @TeX{} cannot either read or
37825 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
37826 and is located in the @file{gdb-@var{version-number}/texinfo}
37829 If you have @TeX{} and a @sc{dvi} printer program installed, you can
37830 typeset and print this manual. First switch to the @file{gdb}
37831 subdirectory of the main source directory (for example, to
37832 @file{gdb-@value{GDBVN}/gdb}) and type:
37838 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
37840 @node Installing GDB
37841 @appendix Installing @value{GDBN}
37842 @cindex installation
37845 * Requirements:: Requirements for building @value{GDBN}
37846 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
37847 * Separate Objdir:: Compiling @value{GDBN} in another directory
37848 * Config Names:: Specifying names for hosts and targets
37849 * Configure Options:: Summary of options for configure
37850 * System-wide configuration:: Having a system-wide init file
37854 @section Requirements for Building @value{GDBN}
37855 @cindex building @value{GDBN}, requirements for
37857 Building @value{GDBN} requires various tools and packages to be available.
37858 Other packages will be used only if they are found.
37860 @heading Tools/Packages Necessary for Building @value{GDBN}
37862 @item C@t{++}11 compiler
37863 @value{GDBN} is written in C@t{++}11. It should be buildable with any
37864 recent C@t{++}11 compiler, e.g.@: GCC.
37867 @value{GDBN}'s build system relies on features only found in the GNU
37868 make program. Other variants of @code{make} will not work.
37870 @item GMP (The GNU Multiple Precision Arithmetic Library)
37871 @value{GDBN} now uses GMP to perform some of its arithmetics.
37872 This library may be included with your operating system distribution;
37873 if it is not, you can get the latest version from
37874 @url{https://gmplib.org/}. If GMP is installed at an unusual path,
37875 you can use the @option{--with-libgmp-prefix} option to specify
37880 @heading Tools/Packages Optional for Building @value{GDBN}
37884 @value{GDBN} can use the Expat XML parsing library. This library may be
37885 included with your operating system distribution; if it is not, you
37886 can get the latest version from @url{http://expat.sourceforge.net}.
37887 The @file{configure} script will search for this library in several
37888 standard locations; if it is installed in an unusual path, you can
37889 use the @option{--with-libexpat-prefix} option to specify its location.
37895 Remote protocol memory maps (@pxref{Memory Map Format})
37897 Target descriptions (@pxref{Target Descriptions})
37899 Remote shared library lists (@xref{Library List Format},
37900 or alternatively @pxref{Library List Format for SVR4 Targets})
37902 MS-Windows shared libraries (@pxref{Shared Libraries})
37904 Traceframe info (@pxref{Traceframe Info Format})
37906 Branch trace (@pxref{Branch Trace Format},
37907 @pxref{Branch Trace Configuration Format})
37911 @value{GDBN} can be scripted using GNU Guile. @xref{Guile}. By
37912 default, @value{GDBN} will be compiled if the Guile libraries are
37913 installed and are found by @file{configure}. You can use the
37914 @code{--with-guile} option to request Guile, and pass either the Guile
37915 version number or the file name of the relevant @code{pkg-config}
37916 program to choose a particular version of Guile.
37919 @value{GDBN}'s features related to character sets (@pxref{Character
37920 Sets}) require a functioning @code{iconv} implementation. If you are
37921 on a GNU system, then this is provided by the GNU C Library. Some
37922 other systems also provide a working @code{iconv}.
37924 If @value{GDBN} is using the @code{iconv} program which is installed
37925 in a non-standard place, you will need to tell @value{GDBN} where to
37926 find it. This is done with @option{--with-iconv-bin} which specifies
37927 the directory that contains the @code{iconv} program. This program is
37928 run in order to make a list of the available character sets.
37930 On systems without @code{iconv}, you can install GNU Libiconv. If
37931 Libiconv is installed in a standard place, @value{GDBN} will
37932 automatically use it if it is needed. If you have previously
37933 installed Libiconv in a non-standard place, you can use the
37934 @option{--with-libiconv-prefix} option to @file{configure}.
37936 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
37937 arrange to build Libiconv if a directory named @file{libiconv} appears
37938 in the top-most source directory. If Libiconv is built this way, and
37939 if the operating system does not provide a suitable @code{iconv}
37940 implementation, then the just-built library will automatically be used
37941 by @value{GDBN}. One easy way to set this up is to download GNU
37942 Libiconv, unpack it inside the top-level directory of the @value{GDBN}
37943 source tree, and then rename the directory holding the Libiconv source
37944 code to @samp{libiconv}.
37947 @value{GDBN} can support debugging sections that are compressed with
37948 the LZMA library. @xref{MiniDebugInfo}. If this library is not
37949 included with your operating system, you can find it in the xz package
37950 at @url{http://tukaani.org/xz/}. If the LZMA library is available in
37951 the usual place, then the @file{configure} script will use it
37952 automatically. If it is installed in an unusual path, you can use the
37953 @option{--with-lzma-prefix} option to specify its location.
37957 @value{GDBN} can use the GNU MPFR multiple-precision floating-point
37958 library. This library may be included with your operating system
37959 distribution; if it is not, you can get the latest version from
37960 @url{http://www.mpfr.org}. The @file{configure} script will search
37961 for this library in several standard locations; if it is installed
37962 in an unusual path, you can use the @option{--with-libmpfr-prefix}
37963 option to specify its location.
37965 GNU MPFR is used to emulate target floating-point arithmetic during
37966 expression evaluation when the target uses different floating-point
37967 formats than the host. If GNU MPFR it is not available, @value{GDBN}
37968 will fall back to using host floating-point arithmetic.
37971 @value{GDBN} can be scripted using Python language. @xref{Python}.
37972 By default, @value{GDBN} will be compiled if the Python libraries are
37973 installed and are found by @file{configure}. You can use the
37974 @code{--with-python} option to request Python, and pass either the
37975 file name of the relevant @code{python} executable, or the name of the
37976 directory in which Python is installed, to choose a particular
37977 installation of Python.
37980 @cindex compressed debug sections
37981 @value{GDBN} will use the @samp{zlib} library, if available, to read
37982 compressed debug sections. Some linkers, such as GNU gold, are capable
37983 of producing binaries with compressed debug sections. If @value{GDBN}
37984 is compiled with @samp{zlib}, it will be able to read the debug
37985 information in such binaries.
37987 The @samp{zlib} library is likely included with your operating system
37988 distribution; if it is not, you can get the latest version from
37989 @url{http://zlib.net}.
37992 @node Running Configure
37993 @section Invoking the @value{GDBN} @file{configure} Script
37994 @cindex configuring @value{GDBN}
37995 @value{GDBN} comes with a @file{configure} script that automates the process
37996 of preparing @value{GDBN} for installation; you can then use @code{make} to
37997 build the @code{gdb} program.
37999 @c irrelevant in info file; it's as current as the code it lives with.
38000 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
38001 look at the @file{README} file in the sources; we may have improved the
38002 installation procedures since publishing this manual.}
38005 The @value{GDBN} distribution includes all the source code you need for
38006 @value{GDBN} in a single directory, whose name is usually composed by
38007 appending the version number to @samp{gdb}.
38009 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
38010 @file{gdb-@value{GDBVN}} directory. That directory contains:
38013 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
38014 script for configuring @value{GDBN} and all its supporting libraries
38016 @item gdb-@value{GDBVN}/gdb
38017 the source specific to @value{GDBN} itself
38019 @item gdb-@value{GDBVN}/bfd
38020 source for the Binary File Descriptor library
38022 @item gdb-@value{GDBVN}/include
38023 @sc{gnu} include files
38025 @item gdb-@value{GDBVN}/libiberty
38026 source for the @samp{-liberty} free software library
38028 @item gdb-@value{GDBVN}/opcodes
38029 source for the library of opcode tables and disassemblers
38031 @item gdb-@value{GDBVN}/readline
38032 source for the @sc{gnu} command-line interface
38035 There may be other subdirectories as well.
38037 The simplest way to configure and build @value{GDBN} is to run @file{configure}
38038 from the @file{gdb-@var{version-number}} source directory, which in
38039 this example is the @file{gdb-@value{GDBVN}} directory.
38041 First switch to the @file{gdb-@var{version-number}} source directory
38042 if you are not already in it; then run @file{configure}. Pass the
38043 identifier for the platform on which @value{GDBN} will run as an
38049 cd gdb-@value{GDBVN}
38054 Running @samp{configure} and then running @code{make} builds the
38055 included supporting libraries, then @code{gdb} itself. The configured
38056 source files, and the binaries, are left in the corresponding source
38060 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
38061 system does not recognize this automatically when you run a different
38062 shell, you may need to run @code{sh} on it explicitly:
38068 You should run the @file{configure} script from the top directory in the
38069 source tree, the @file{gdb-@var{version-number}} directory. If you run
38070 @file{configure} from one of the subdirectories, you will configure only
38071 that subdirectory. That is usually not what you want. In particular,
38072 if you run the first @file{configure} from the @file{gdb} subdirectory
38073 of the @file{gdb-@var{version-number}} directory, you will omit the
38074 configuration of @file{bfd}, @file{readline}, and other sibling
38075 directories of the @file{gdb} subdirectory. This leads to build errors
38076 about missing include files such as @file{bfd/bfd.h}.
38078 You can install @code{@value{GDBN}} anywhere. The best way to do this
38079 is to pass the @code{--prefix} option to @code{configure}, and then
38080 install it with @code{make install}.
38082 @node Separate Objdir
38083 @section Compiling @value{GDBN} in Another Directory
38085 If you want to run @value{GDBN} versions for several host or target machines,
38086 you need a different @code{gdb} compiled for each combination of
38087 host and target. @file{configure} is designed to make this easy by
38088 allowing you to generate each configuration in a separate subdirectory,
38089 rather than in the source directory. If your @code{make} program
38090 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
38091 @code{make} in each of these directories builds the @code{gdb}
38092 program specified there.
38094 To build @code{gdb} in a separate directory, run @file{configure}
38095 with the @samp{--srcdir} option to specify where to find the source.
38096 (You also need to specify a path to find @file{configure}
38097 itself from your working directory. If the path to @file{configure}
38098 would be the same as the argument to @samp{--srcdir}, you can leave out
38099 the @samp{--srcdir} option; it is assumed.)
38101 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
38102 separate directory for a Sun 4 like this:
38106 cd gdb-@value{GDBVN}
38109 ../gdb-@value{GDBVN}/configure
38114 When @file{configure} builds a configuration using a remote source
38115 directory, it creates a tree for the binaries with the same structure
38116 (and using the same names) as the tree under the source directory. In
38117 the example, you'd find the Sun 4 library @file{libiberty.a} in the
38118 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
38119 @file{gdb-sun4/gdb}.
38121 Make sure that your path to the @file{configure} script has just one
38122 instance of @file{gdb} in it. If your path to @file{configure} looks
38123 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
38124 one subdirectory of @value{GDBN}, not the whole package. This leads to
38125 build errors about missing include files such as @file{bfd/bfd.h}.
38127 One popular reason to build several @value{GDBN} configurations in separate
38128 directories is to configure @value{GDBN} for cross-compiling (where
38129 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
38130 programs that run on another machine---the @dfn{target}).
38131 You specify a cross-debugging target by
38132 giving the @samp{--target=@var{target}} option to @file{configure}.
38134 When you run @code{make} to build a program or library, you must run
38135 it in a configured directory---whatever directory you were in when you
38136 called @file{configure} (or one of its subdirectories).
38138 The @code{Makefile} that @file{configure} generates in each source
38139 directory also runs recursively. If you type @code{make} in a source
38140 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
38141 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
38142 will build all the required libraries, and then build GDB.
38144 When you have multiple hosts or targets configured in separate
38145 directories, you can run @code{make} on them in parallel (for example,
38146 if they are NFS-mounted on each of the hosts); they will not interfere
38150 @section Specifying Names for Hosts and Targets
38152 The specifications used for hosts and targets in the @file{configure}
38153 script are based on a three-part naming scheme, but some short predefined
38154 aliases are also supported. The full naming scheme encodes three pieces
38155 of information in the following pattern:
38158 @var{architecture}-@var{vendor}-@var{os}
38161 For example, you can use the alias @code{sun4} as a @var{host} argument,
38162 or as the value for @var{target} in a @code{--target=@var{target}}
38163 option. The equivalent full name is @samp{sparc-sun-sunos4}.
38165 The @file{configure} script accompanying @value{GDBN} does not provide
38166 any query facility to list all supported host and target names or
38167 aliases. @file{configure} calls the Bourne shell script
38168 @code{config.sub} to map abbreviations to full names; you can read the
38169 script, if you wish, or you can use it to test your guesses on
38170 abbreviations---for example:
38173 % sh config.sub i386-linux
38175 % sh config.sub alpha-linux
38176 alpha-unknown-linux-gnu
38177 % sh config.sub hp9k700
38179 % sh config.sub sun4
38180 sparc-sun-sunos4.1.1
38181 % sh config.sub sun3
38182 m68k-sun-sunos4.1.1
38183 % sh config.sub i986v
38184 Invalid configuration `i986v': machine `i986v' not recognized
38188 @code{config.sub} is also distributed in the @value{GDBN} source
38189 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
38191 @node Configure Options
38192 @section @file{configure} Options
38194 Here is a summary of the @file{configure} options and arguments that
38195 are most often useful for building @value{GDBN}. @file{configure}
38196 also has several other options not listed here. @inforef{Running
38197 configure scripts,,autoconf.info}, for a full
38198 explanation of @file{configure}.
38201 configure @r{[}--help@r{]}
38202 @r{[}--prefix=@var{dir}@r{]}
38203 @r{[}--exec-prefix=@var{dir}@r{]}
38204 @r{[}--srcdir=@var{dirname}@r{]}
38205 @r{[}--target=@var{target}@r{]}
38209 You may introduce options with a single @samp{-} rather than
38210 @samp{--} if you prefer; but you may abbreviate option names if you use
38215 Display a quick summary of how to invoke @file{configure}.
38217 @item --prefix=@var{dir}
38218 Configure the source to install programs and files under directory
38221 @item --exec-prefix=@var{dir}
38222 Configure the source to install programs under directory
38225 @c avoid splitting the warning from the explanation:
38227 @item --srcdir=@var{dirname}
38228 Use this option to make configurations in directories separate from the
38229 @value{GDBN} source directories. Among other things, you can use this to
38230 build (or maintain) several configurations simultaneously, in separate
38231 directories. @file{configure} writes configuration-specific files in
38232 the current directory, but arranges for them to use the source in the
38233 directory @var{dirname}. @file{configure} creates directories under
38234 the working directory in parallel to the source directories below
38237 @item --target=@var{target}
38238 Configure @value{GDBN} for cross-debugging programs running on the specified
38239 @var{target}. Without this option, @value{GDBN} is configured to debug
38240 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
38242 There is no convenient way to generate a list of all available
38243 targets. Also see the @code{--enable-targets} option, below.
38246 There are many other options that are specific to @value{GDBN}. This
38247 lists just the most common ones; there are some very specialized
38248 options not described here.
38251 @item --enable-targets=@r{[}@var{target}@r{]}@dots{}
38252 @itemx --enable-targets=all
38253 Configure @value{GDBN} for cross-debugging programs running on the
38254 specified list of targets. The special value @samp{all} configures
38255 @value{GDBN} for debugging programs running on any target it supports.
38257 @item --with-gdb-datadir=@var{path}
38258 Set the @value{GDBN}-specific data directory. @value{GDBN} will look
38259 here for certain supporting files or scripts. This defaults to the
38260 @file{gdb} subdirectory of @samp{datadir} (which can be set using
38263 @item --with-relocated-sources=@var{dir}
38264 Sets up the default source path substitution rule so that directory
38265 names recorded in debug information will be automatically adjusted for
38266 any directory under @var{dir}. @var{dir} should be a subdirectory of
38267 @value{GDBN}'s configured prefix, the one mentioned in the
38268 @code{--prefix} or @code{--exec-prefix} options to configure. This
38269 option is useful if GDB is supposed to be moved to a different place
38272 @item --enable-64-bit-bfd
38273 Enable 64-bit support in BFD on 32-bit hosts.
38275 @item --disable-gdbmi
38276 Build @value{GDBN} without the GDB/MI machine interface
38280 Build @value{GDBN} with the text-mode full-screen user interface
38281 (TUI). Requires a curses library (ncurses and cursesX are also
38284 @item --with-curses
38285 Use the curses library instead of the termcap library, for text-mode
38286 terminal operations.
38288 @item --with-debuginfod
38289 Build @value{GDBN} with libdebuginfod, the debuginfod client library.
38290 Used to automatically fetch source files and separate debug files from
38291 debuginfod servers using the associated executable's build ID. Enabled
38292 by default if libdebuginfod is installed and found at configure time.
38293 debuginfod is packaged with elfutils, starting with version 0.178. You
38294 can get the latest version from `https://sourceware.org/elfutils/'.
38296 @item --with-libunwind-ia64
38297 Use the libunwind library for unwinding function call stack on ia64
38298 target platforms. See http://www.nongnu.org/libunwind/index.html for
38301 @item --with-system-readline
38302 Use the readline library installed on the host, rather than the
38303 library supplied as part of @value{GDBN}. Readline 7 or newer is
38304 required; this is enforced by the build system.
38306 @item --with-system-zlib
38307 Use the zlib library installed on the host, rather than the library
38308 supplied as part of @value{GDBN}.
38311 Build @value{GDBN} with Expat, a library for XML parsing. (Done by
38312 default if libexpat is installed and found at configure time.) This
38313 library is used to read XML files supplied with @value{GDBN}. If it
38314 is unavailable, some features, such as remote protocol memory maps,
38315 target descriptions, and shared library lists, that are based on XML
38316 files, will not be available in @value{GDBN}. If your host does not
38317 have libexpat installed, you can get the latest version from
38318 `http://expat.sourceforge.net'.
38320 @item --with-libiconv-prefix@r{[}=@var{dir}@r{]}
38322 Build @value{GDBN} with GNU libiconv, a character set encoding
38323 conversion library. This is not done by default, as on GNU systems
38324 the @code{iconv} that is built in to the C library is sufficient. If
38325 your host does not have a working @code{iconv}, you can get the latest
38326 version of GNU iconv from `https://www.gnu.org/software/libiconv/'.
38328 @value{GDBN}'s build system also supports building GNU libiconv as
38329 part of the overall build. @xref{Requirements}.
38332 Build @value{GDBN} with LZMA, a compression library. (Done by default
38333 if liblzma is installed and found at configure time.) LZMA is used by
38334 @value{GDBN}'s "mini debuginfo" feature, which is only useful on
38335 platforms using the ELF object file format. If your host does not
38336 have liblzma installed, you can get the latest version from
38337 `https://tukaani.org/xz/'.
38340 Build @value{GDBN} with GNU MPFR, a library for multiple-precision
38341 floating-point computation with correct rounding. (Done by default if
38342 GNU MPFR is installed and found at configure time.) This library is
38343 used to emulate target floating-point arithmetic during expression
38344 evaluation when the target uses different floating-point formats than
38345 the host. If GNU MPFR is not available, @value{GDBN} will fall back
38346 to using host floating-point arithmetic. If your host does not have
38347 GNU MPFR installed, you can get the latest version from
38348 `http://www.mpfr.org'.
38350 @item --with-python@r{[}=@var{python}@r{]}
38351 Build @value{GDBN} with Python scripting support. (Done by default if
38352 libpython is present and found at configure time.) Python makes
38353 @value{GDBN} scripting much more powerful than the restricted CLI
38354 scripting language. If your host does not have Python installed, you
38355 can find it on `http://www.python.org/download/'. The oldest version
38356 of Python supported by GDB is 2.6. The optional argument @var{python}
38357 is used to find the Python headers and libraries. It can be either
38358 the name of a Python executable, or the name of the directory in which
38359 Python is installed.
38361 @item --with-guile[=GUILE]'
38362 Build @value{GDBN} with GNU Guile scripting support. (Done by default
38363 if libguile is present and found at configure time.) If your host
38364 does not have Guile installed, you can find it at
38365 `https://www.gnu.org/software/guile/'. The optional argument GUILE
38366 can be a version number, which will cause @code{configure} to try to
38367 use that version of Guile; or the file name of a @code{pkg-config}
38368 executable, which will be queried to find the information needed to
38369 compile and link against Guile.
38371 @item --without-included-regex
38372 Don't use the regex library included with @value{GDBN} (as part of the
38373 libiberty library). This is the default on hosts with version 2 of
38376 @item --with-sysroot=@var{dir}
38377 Use @var{dir} as the default system root directory for libraries whose
38378 file names begin with @file{/lib}' or @file{/usr/lib'}. (The value of
38379 @var{dir} can be modified at run time by using the @command{set
38380 sysroot} command.) If @var{dir} is under the @value{GDBN} configured
38381 prefix (set with @code{--prefix} or @code{--exec-prefix options}, the
38382 default system root will be automatically adjusted if and when
38383 @value{GDBN} is moved to a different location.
38385 @item --with-system-gdbinit=@var{file}
38386 Configure @value{GDBN} to automatically load a system-wide init file.
38387 @var{file} should be an absolute file name. If @var{file} is in a
38388 directory under the configured prefix, and @value{GDBN} is moved to
38389 another location after being built, the location of the system-wide
38390 init file will be adjusted accordingly.
38392 @item --with-system-gdbinit-dir=@var{directory}
38393 Configure @value{GDBN} to automatically load init files from a
38394 system-wide directory. @var{directory} should be an absolute directory
38395 name. If @var{directory} is in a directory under the configured
38396 prefix, and @value{GDBN} is moved to another location after being
38397 built, the location of the system-wide init directory will be
38398 adjusted accordingly.
38400 @item --enable-build-warnings
38401 When building the @value{GDBN} sources, ask the compiler to warn about
38402 any code which looks even vaguely suspicious. It passes many
38403 different warning flags, depending on the exact version of the
38404 compiler you are using.
38406 @item --enable-werror
38407 Treat compiler warnings as werrors. It adds the @code{-Werror} flag
38408 to the compiler, which will fail the compilation if the compiler
38409 outputs any warning messages.
38411 @item --enable-ubsan
38412 Enable the GCC undefined behavior sanitizer. This is disabled by
38413 default, but passing @code{--enable-ubsan=yes} or
38414 @code{--enable-ubsan=auto} to @code{configure} will enable it. The
38415 undefined behavior sanitizer checks for C@t{++} undefined behavior.
38416 It has a performance cost, so if you are looking at @value{GDBN}'s
38417 performance, you should disable it. The undefined behavior sanitizer
38418 was first introduced in GCC 4.9.
38421 @node System-wide configuration
38422 @section System-wide configuration and settings
38423 @cindex system-wide init file
38425 @value{GDBN} can be configured to have a system-wide init file and a
38426 system-wide init file directory; this file and files in that directory
38427 (if they have a recognized file extension) will be read and executed at
38428 startup (@pxref{Startup, , What @value{GDBN} does during startup}).
38430 Here are the corresponding configure options:
38433 @item --with-system-gdbinit=@var{file}
38434 Specify that the default location of the system-wide init file is
38436 @item --with-system-gdbinit-dir=@var{directory}
38437 Specify that the default location of the system-wide init file directory
38438 is @var{directory}.
38441 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
38442 they may be subject to relocation. Two possible cases:
38446 If the default location of this init file/directory contains @file{$prefix},
38447 it will be subject to relocation. Suppose that the configure options
38448 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
38449 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
38450 init file is looked for as @file{$install/etc/gdbinit} instead of
38451 @file{$prefix/etc/gdbinit}.
38454 By contrast, if the default location does not contain the prefix,
38455 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
38456 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
38457 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
38458 wherever @value{GDBN} is installed.
38461 If the configured location of the system-wide init file (as given by the
38462 @option{--with-system-gdbinit} option at configure time) is in the
38463 data-directory (as specified by @option{--with-gdb-datadir} at configure
38464 time) or in one of its subdirectories, then @value{GDBN} will look for the
38465 system-wide init file in the directory specified by the
38466 @option{--data-directory} command-line option.
38467 Note that the system-wide init file is only read once, during @value{GDBN}
38468 initialization. If the data-directory is changed after @value{GDBN} has
38469 started with the @code{set data-directory} command, the file will not be
38472 This applies similarly to the system-wide directory specified in
38473 @option{--with-system-gdbinit-dir}.
38475 Any supported scripting language can be used for these init files, as long
38476 as the file extension matches the scripting language. To be interpreted
38477 as regular @value{GDBN} commands, the files needs to have a @file{.gdb}
38481 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
38484 @node System-wide Configuration Scripts
38485 @subsection Installed System-wide Configuration Scripts
38486 @cindex system-wide configuration scripts
38488 The @file{system-gdbinit} directory, located inside the data-directory
38489 (as specified by @option{--with-gdb-datadir} at configure time) contains
38490 a number of scripts which can be used as system-wide init files. To
38491 automatically source those scripts at startup, @value{GDBN} should be
38492 configured with @option{--with-system-gdbinit}. Otherwise, any user
38493 should be able to source them by hand as needed.
38495 The following scripts are currently available:
38498 @item @file{elinos.py}
38500 @cindex ELinOS system-wide configuration script
38501 This script is useful when debugging a program on an ELinOS target.
38502 It takes advantage of the environment variables defined in a standard
38503 ELinOS environment in order to determine the location of the system
38504 shared libraries, and then sets the @samp{solib-absolute-prefix}
38505 and @samp{solib-search-path} variables appropriately.
38507 @item @file{wrs-linux.py}
38508 @pindex wrs-linux.py
38509 @cindex Wind River Linux system-wide configuration script
38510 This script is useful when debugging a program on a target running
38511 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
38512 the host-side sysroot used by the target system.
38516 @node Maintenance Commands
38517 @appendix Maintenance Commands
38518 @cindex maintenance commands
38519 @cindex internal commands
38521 In addition to commands intended for @value{GDBN} users, @value{GDBN}
38522 includes a number of commands intended for @value{GDBN} developers,
38523 that are not documented elsewhere in this manual. These commands are
38524 provided here for reference. (For commands that turn on debugging
38525 messages, see @ref{Debugging Output}.)
38528 @kindex maint agent
38529 @kindex maint agent-eval
38530 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
38531 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
38532 Translate the given @var{expression} into remote agent bytecodes.
38533 This command is useful for debugging the Agent Expression mechanism
38534 (@pxref{Agent Expressions}). The @samp{agent} version produces an
38535 expression useful for data collection, such as by tracepoints, while
38536 @samp{maint agent-eval} produces an expression that evaluates directly
38537 to a result. For instance, a collection expression for @code{globa +
38538 globb} will include bytecodes to record four bytes of memory at each
38539 of the addresses of @code{globa} and @code{globb}, while discarding
38540 the result of the addition, while an evaluation expression will do the
38541 addition and return the sum.
38542 If @code{-at} is given, generate remote agent bytecode for @var{location}.
38543 If not, generate remote agent bytecode for current frame PC address.
38545 @kindex maint agent-printf
38546 @item maint agent-printf @var{format},@var{expr},...
38547 Translate the given format string and list of argument expressions
38548 into remote agent bytecodes and display them as a disassembled list.
38549 This command is useful for debugging the agent version of dynamic
38550 printf (@pxref{Dynamic Printf}).
38552 @kindex maint info breakpoints
38553 @item @anchor{maint info breakpoints}maint info breakpoints
38554 Using the same format as @samp{info breakpoints}, display both the
38555 breakpoints you've set explicitly, and those @value{GDBN} is using for
38556 internal purposes. Internal breakpoints are shown with negative
38557 breakpoint numbers. The type column identifies what kind of breakpoint
38562 Normal, explicitly set breakpoint.
38565 Normal, explicitly set watchpoint.
38568 Internal breakpoint, used to handle correctly stepping through
38569 @code{longjmp} calls.
38571 @item longjmp resume
38572 Internal breakpoint at the target of a @code{longjmp}.
38575 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
38578 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
38581 Shared library events.
38585 @kindex maint info btrace
38586 @item maint info btrace
38587 Pint information about raw branch tracing data.
38589 @kindex maint btrace packet-history
38590 @item maint btrace packet-history
38591 Print the raw branch trace packets that are used to compute the
38592 execution history for the @samp{record btrace} command. Both the
38593 information and the format in which it is printed depend on the btrace
38598 For the BTS recording format, print a list of blocks of sequential
38599 code. For each block, the following information is printed:
38603 Newer blocks have higher numbers. The oldest block has number zero.
38604 @item Lowest @samp{PC}
38605 @item Highest @samp{PC}
38609 For the Intel Processor Trace recording format, print a list of
38610 Intel Processor Trace packets. For each packet, the following
38611 information is printed:
38614 @item Packet number
38615 Newer packets have higher numbers. The oldest packet has number zero.
38617 The packet's offset in the trace stream.
38618 @item Packet opcode and payload
38622 @kindex maint btrace clear-packet-history
38623 @item maint btrace clear-packet-history
38624 Discards the cached packet history printed by the @samp{maint btrace
38625 packet-history} command. The history will be computed again when
38628 @kindex maint btrace clear
38629 @item maint btrace clear
38630 Discard the branch trace data. The data will be fetched anew and the
38631 branch trace will be recomputed when needed.
38633 This implicitly truncates the branch trace to a single branch trace
38634 buffer. When updating branch trace incrementally, the branch trace
38635 available to @value{GDBN} may be bigger than a single branch trace
38638 @kindex maint set btrace pt skip-pad
38639 @item maint set btrace pt skip-pad
38640 @kindex maint show btrace pt skip-pad
38641 @item maint show btrace pt skip-pad
38642 Control whether @value{GDBN} will skip PAD packets when computing the
38645 @kindex set displaced-stepping
38646 @kindex show displaced-stepping
38647 @cindex displaced stepping support
38648 @cindex out-of-line single-stepping
38649 @item set displaced-stepping
38650 @itemx show displaced-stepping
38651 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
38652 if the target supports it. Displaced stepping is a way to single-step
38653 over breakpoints without removing them from the inferior, by executing
38654 an out-of-line copy of the instruction that was originally at the
38655 breakpoint location. It is also known as out-of-line single-stepping.
38658 @item set displaced-stepping on
38659 If the target architecture supports it, @value{GDBN} will use
38660 displaced stepping to step over breakpoints.
38662 @item set displaced-stepping off
38663 @value{GDBN} will not use displaced stepping to step over breakpoints,
38664 even if such is supported by the target architecture.
38666 @cindex non-stop mode, and @samp{set displaced-stepping}
38667 @item set displaced-stepping auto
38668 This is the default mode. @value{GDBN} will use displaced stepping
38669 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
38670 architecture supports displaced stepping.
38673 @kindex maint check-psymtabs
38674 @item maint check-psymtabs
38675 Check the consistency of currently expanded psymtabs versus symtabs.
38676 Use this to check, for example, whether a symbol is in one but not the other.
38678 @kindex maint check-symtabs
38679 @item maint check-symtabs
38680 Check the consistency of currently expanded symtabs.
38682 @kindex maint expand-symtabs
38683 @item maint expand-symtabs [@var{regexp}]
38684 Expand symbol tables.
38685 If @var{regexp} is specified, only expand symbol tables for file
38686 names matching @var{regexp}.
38688 @kindex maint set catch-demangler-crashes
38689 @kindex maint show catch-demangler-crashes
38690 @cindex demangler crashes
38691 @item maint set catch-demangler-crashes [on|off]
38692 @itemx maint show catch-demangler-crashes
38693 Control whether @value{GDBN} should attempt to catch crashes in the
38694 symbol name demangler. The default is to attempt to catch crashes.
38695 If enabled, the first time a crash is caught, a core file is created,
38696 the offending symbol is displayed and the user is presented with the
38697 option to terminate the current session.
38699 @kindex maint cplus first_component
38700 @item maint cplus first_component @var{name}
38701 Print the first C@t{++} class/namespace component of @var{name}.
38703 @kindex maint cplus namespace
38704 @item maint cplus namespace
38705 Print the list of possible C@t{++} namespaces.
38707 @kindex maint deprecate
38708 @kindex maint undeprecate
38709 @cindex deprecated commands
38710 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
38711 @itemx maint undeprecate @var{command}
38712 Deprecate or undeprecate the named @var{command}. Deprecated commands
38713 cause @value{GDBN} to issue a warning when you use them. The optional
38714 argument @var{replacement} says which newer command should be used in
38715 favor of the deprecated one; if it is given, @value{GDBN} will mention
38716 the replacement as part of the warning.
38718 @kindex maint dump-me
38719 @item maint dump-me
38720 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
38721 Cause a fatal signal in the debugger and force it to dump its core.
38722 This is supported only on systems which support aborting a program
38723 with the @code{SIGQUIT} signal.
38725 @kindex maint internal-error
38726 @kindex maint internal-warning
38727 @kindex maint demangler-warning
38728 @cindex demangler crashes
38729 @item maint internal-error @r{[}@var{message-text}@r{]}
38730 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
38731 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
38733 Cause @value{GDBN} to call the internal function @code{internal_error},
38734 @code{internal_warning} or @code{demangler_warning} and hence behave
38735 as though an internal problem has been detected. In addition to
38736 reporting the internal problem, these functions give the user the
38737 opportunity to either quit @value{GDBN} or (for @code{internal_error}
38738 and @code{internal_warning}) create a core file of the current
38739 @value{GDBN} session.
38741 These commands take an optional parameter @var{message-text} that is
38742 used as the text of the error or warning message.
38744 Here's an example of using @code{internal-error}:
38747 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
38748 @dots{}/maint.c:121: internal-error: testing, 1, 2
38749 A problem internal to GDB has been detected. Further
38750 debugging may prove unreliable.
38751 Quit this debugging session? (y or n) @kbd{n}
38752 Create a core file? (y or n) @kbd{n}
38756 @cindex @value{GDBN} internal error
38757 @cindex internal errors, control of @value{GDBN} behavior
38758 @cindex demangler crashes
38760 @kindex maint set internal-error
38761 @kindex maint show internal-error
38762 @kindex maint set internal-warning
38763 @kindex maint show internal-warning
38764 @kindex maint set demangler-warning
38765 @kindex maint show demangler-warning
38766 @item maint set internal-error @var{action} [ask|yes|no]
38767 @itemx maint show internal-error @var{action}
38768 @itemx maint set internal-warning @var{action} [ask|yes|no]
38769 @itemx maint show internal-warning @var{action}
38770 @itemx maint set demangler-warning @var{action} [ask|yes|no]
38771 @itemx maint show demangler-warning @var{action}
38772 When @value{GDBN} reports an internal problem (error or warning) it
38773 gives the user the opportunity to both quit @value{GDBN} and create a
38774 core file of the current @value{GDBN} session. These commands let you
38775 override the default behaviour for each particular @var{action},
38776 described in the table below.
38780 You can specify that @value{GDBN} should always (yes) or never (no)
38781 quit. The default is to ask the user what to do.
38784 You can specify that @value{GDBN} should always (yes) or never (no)
38785 create a core file. The default is to ask the user what to do. Note
38786 that there is no @code{corefile} option for @code{demangler-warning}:
38787 demangler warnings always create a core file and this cannot be
38791 @kindex maint packet
38792 @item maint packet @var{text}
38793 If @value{GDBN} is talking to an inferior via the serial protocol,
38794 then this command sends the string @var{text} to the inferior, and
38795 displays the response packet. @value{GDBN} supplies the initial
38796 @samp{$} character, the terminating @samp{#} character, and the
38799 @kindex maint print architecture
38800 @item maint print architecture @r{[}@var{file}@r{]}
38801 Print the entire architecture configuration. The optional argument
38802 @var{file} names the file where the output goes.
38804 @kindex maint print c-tdesc
38805 @item maint print c-tdesc @r{[}-single-feature@r{]} @r{[}@var{file}@r{]}
38806 Print the target description (@pxref{Target Descriptions}) as
38807 a C source file. By default, the target description is for the current
38808 target, but if the optional argument @var{file} is provided, that file
38809 is used to produce the description. The @var{file} should be an XML
38810 document, of the form described in @ref{Target Description Format}.
38811 The created source file is built into @value{GDBN} when @value{GDBN} is
38812 built again. This command is used by developers after they add or
38813 modify XML target descriptions.
38815 When the optional flag @samp{-single-feature} is provided then the
38816 target description being processed (either the default, or from
38817 @var{file}) must only contain a single feature. The source file
38818 produced is different in this case.
38820 @kindex maint print xml-tdesc
38821 @item maint print xml-tdesc @r{[}@var{file}@r{]}
38822 Print the target description (@pxref{Target Descriptions}) as an XML
38823 file. By default print the target description for the current target,
38824 but if the optional argument @var{file} is provided, then that file is
38825 read in by GDB and then used to produce the description. The
38826 @var{file} should be an XML document, of the form described in
38827 @ref{Target Description Format}.
38829 @kindex maint check xml-descriptions
38830 @item maint check xml-descriptions @var{dir}
38831 Check that the target descriptions dynamically created by @value{GDBN}
38832 equal the descriptions created from XML files found in @var{dir}.
38834 @anchor{maint check libthread-db}
38835 @kindex maint check libthread-db
38836 @item maint check libthread-db
38837 Run integrity checks on the current inferior's thread debugging
38838 library. This exercises all @code{libthread_db} functionality used by
38839 @value{GDBN} on GNU/Linux systems, and by extension also exercises the
38840 @code{proc_service} functions provided by @value{GDBN} that
38841 @code{libthread_db} uses. Note that parts of the test may be skipped
38842 on some platforms when debugging core files.
38844 @kindex maint print core-file-backed-mappings
38845 @cindex memory address space mappings
38846 @item maint print core-file-backed-mappings
38847 Print the file-backed mappings which were loaded from a core file note.
38848 This output represents state internal to @value{GDBN} and should be
38849 similar to the mappings displayed by the @code{info proc mappings}
38852 @kindex maint print dummy-frames
38853 @item maint print dummy-frames
38854 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
38857 (@value{GDBP}) @kbd{b add}
38859 (@value{GDBP}) @kbd{print add(2,3)}
38860 Breakpoint 2, add (a=2, b=3) at @dots{}
38862 The program being debugged stopped while in a function called from GDB.
38864 (@value{GDBP}) @kbd{maint print dummy-frames}
38865 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
38869 Takes an optional file parameter.
38871 @kindex maint print registers
38872 @kindex maint print raw-registers
38873 @kindex maint print cooked-registers
38874 @kindex maint print register-groups
38875 @kindex maint print remote-registers
38876 @item maint print registers @r{[}@var{file}@r{]}
38877 @itemx maint print raw-registers @r{[}@var{file}@r{]}
38878 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
38879 @itemx maint print register-groups @r{[}@var{file}@r{]}
38880 @itemx maint print remote-registers @r{[}@var{file}@r{]}
38881 Print @value{GDBN}'s internal register data structures.
38883 The command @code{maint print raw-registers} includes the contents of
38884 the raw register cache; the command @code{maint print
38885 cooked-registers} includes the (cooked) value of all registers,
38886 including registers which aren't available on the target nor visible
38887 to user; the command @code{maint print register-groups} includes the
38888 groups that each register is a member of; and the command @code{maint
38889 print remote-registers} includes the remote target's register numbers
38890 and offsets in the `G' packets.
38892 These commands take an optional parameter, a file name to which to
38893 write the information.
38895 @kindex maint print reggroups
38896 @item maint print reggroups @r{[}@var{file}@r{]}
38897 Print @value{GDBN}'s internal register group data structures. The
38898 optional argument @var{file} tells to what file to write the
38901 The register groups info looks like this:
38904 (@value{GDBP}) @kbd{maint print reggroups}
38915 @kindex maint flush register-cache
38917 @cindex register cache, flushing
38918 @item maint flush register-cache
38920 Flush the contents of the register cache and as a consequence the
38921 frame cache. This command is useful when debugging issues related to
38922 register fetching, or frame unwinding. The command @code{flushregs}
38923 is deprecated in favor of @code{maint flush register-cache}.
38925 @kindex maint print objfiles
38926 @cindex info for known object files
38927 @item maint print objfiles @r{[}@var{regexp}@r{]}
38928 Print a dump of all known object files.
38929 If @var{regexp} is specified, only print object files whose names
38930 match @var{regexp}. For each object file, this command prints its name,
38931 address in memory, and all of its psymtabs and symtabs.
38933 @kindex maint print user-registers
38934 @cindex user registers
38935 @item maint print user-registers
38936 List all currently available @dfn{user registers}. User registers
38937 typically provide alternate names for actual hardware registers. They
38938 include the four ``standard'' registers @code{$fp}, @code{$pc},
38939 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
38940 registers can be used in expressions in the same way as the canonical
38941 register names, but only the latter are listed by the @code{info
38942 registers} and @code{maint print registers} commands.
38944 @kindex maint print section-scripts
38945 @cindex info for known .debug_gdb_scripts-loaded scripts
38946 @item maint print section-scripts [@var{regexp}]
38947 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
38948 If @var{regexp} is specified, only print scripts loaded by object files
38949 matching @var{regexp}.
38950 For each script, this command prints its name as specified in the objfile,
38951 and the full path if known.
38952 @xref{dotdebug_gdb_scripts section}.
38954 @kindex maint print statistics
38955 @cindex bcache statistics
38956 @item maint print statistics
38957 This command prints, for each object file in the program, various data
38958 about that object file followed by the byte cache (@dfn{bcache})
38959 statistics for the object file. The objfile data includes the number
38960 of minimal, partial, full, and stabs symbols, the number of types
38961 defined by the objfile, the number of as yet unexpanded psym tables,
38962 the number of line tables and string tables, and the amount of memory
38963 used by the various tables. The bcache statistics include the counts,
38964 sizes, and counts of duplicates of all and unique objects, max,
38965 average, and median entry size, total memory used and its overhead and
38966 savings, and various measures of the hash table size and chain
38969 @kindex maint print target-stack
38970 @cindex target stack description
38971 @item maint print target-stack
38972 A @dfn{target} is an interface between the debugger and a particular
38973 kind of file or process. Targets can be stacked in @dfn{strata},
38974 so that more than one target can potentially respond to a request.
38975 In particular, memory accesses will walk down the stack of targets
38976 until they find a target that is interested in handling that particular
38979 This command prints a short description of each layer that was pushed on
38980 the @dfn{target stack}, starting from the top layer down to the bottom one.
38982 @kindex maint print type
38983 @cindex type chain of a data type
38984 @item maint print type @var{expr}
38985 Print the type chain for a type specified by @var{expr}. The argument
38986 can be either a type name or a symbol. If it is a symbol, the type of
38987 that symbol is described. The type chain produced by this command is
38988 a recursive definition of the data type as stored in @value{GDBN}'s
38989 data structures, including its flags and contained types.
38991 @kindex maint selftest
38993 @item maint selftest @r{[}@var{filter}@r{]}
38994 Run any self tests that were compiled in to @value{GDBN}. This will
38995 print a message showing how many tests were run, and how many failed.
38996 If a @var{filter} is passed, only the tests with @var{filter} in their
38999 @kindex maint info selftests
39001 @item maint info selftests
39002 List the selftests compiled in to @value{GDBN}.
39004 @kindex maint set dwarf always-disassemble
39005 @kindex maint show dwarf always-disassemble
39006 @item maint set dwarf always-disassemble
39007 @item maint show dwarf always-disassemble
39008 Control the behavior of @code{info address} when using DWARF debugging
39011 The default is @code{off}, which means that @value{GDBN} should try to
39012 describe a variable's location in an easily readable format. When
39013 @code{on}, @value{GDBN} will instead display the DWARF location
39014 expression in an assembly-like format. Note that some locations are
39015 too complex for @value{GDBN} to describe simply; in this case you will
39016 always see the disassembly form.
39018 Here is an example of the resulting disassembly:
39021 (gdb) info addr argc
39022 Symbol "argc" is a complex DWARF expression:
39026 For more information on these expressions, see
39027 @uref{http://www.dwarfstd.org/, the DWARF standard}.
39029 @kindex maint set dwarf max-cache-age
39030 @kindex maint show dwarf max-cache-age
39031 @item maint set dwarf max-cache-age
39032 @itemx maint show dwarf max-cache-age
39033 Control the DWARF compilation unit cache.
39035 @cindex DWARF compilation units cache
39036 In object files with inter-compilation-unit references, such as those
39037 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF
39038 reader needs to frequently refer to previously read compilation units.
39039 This setting controls how long a compilation unit will remain in the
39040 cache if it is not referenced. A higher limit means that cached
39041 compilation units will be stored in memory longer, and more total
39042 memory will be used. Setting it to zero disables caching, which will
39043 slow down @value{GDBN} startup, but reduce memory consumption.
39045 @kindex maint set dwarf unwinders
39046 @kindex maint show dwarf unwinders
39047 @item maint set dwarf unwinders
39048 @itemx maint show dwarf unwinders
39049 Control use of the DWARF frame unwinders.
39051 @cindex DWARF frame unwinders
39052 Many targets that support DWARF debugging use @value{GDBN}'s DWARF
39053 frame unwinders to build the backtrace. Many of these targets will
39054 also have a second mechanism for building the backtrace for use in
39055 cases where DWARF information is not available, this second mechanism
39056 is often an analysis of a function's prologue.
39058 In order to extend testing coverage of the second level stack
39059 unwinding mechanisms it is helpful to be able to disable the DWARF
39060 stack unwinders, this can be done with this switch.
39062 In normal use of @value{GDBN} disabling the DWARF unwinders is not
39063 advisable, there are cases that are better handled through DWARF than
39064 prologue analysis, and the debug experience is likely to be better
39065 with the DWARF frame unwinders enabled.
39067 If DWARF frame unwinders are not supported for a particular target
39068 architecture, then enabling this flag does not cause them to be used.
39070 @kindex maint set worker-threads
39071 @kindex maint show worker-threads
39072 @item maint set worker-threads
39073 @item maint show worker-threads
39074 Control the number of worker threads that may be used by @value{GDBN}.
39075 On capable hosts, @value{GDBN} may use multiple threads to speed up
39076 certain CPU-intensive operations, such as demangling symbol names.
39077 While the number of threads used by @value{GDBN} may vary, this
39078 command can be used to set an upper bound on this number. The default
39079 is @code{unlimited}, which lets @value{GDBN} choose a reasonable
39080 number. Note that this only controls worker threads started by
39081 @value{GDBN} itself; libraries used by @value{GDBN} may start threads
39084 @kindex maint set profile
39085 @kindex maint show profile
39086 @cindex profiling GDB
39087 @item maint set profile
39088 @itemx maint show profile
39089 Control profiling of @value{GDBN}.
39091 Profiling will be disabled until you use the @samp{maint set profile}
39092 command to enable it. When you enable profiling, the system will begin
39093 collecting timing and execution count data; when you disable profiling or
39094 exit @value{GDBN}, the results will be written to a log file. Remember that
39095 if you use profiling, @value{GDBN} will overwrite the profiling log file
39096 (often called @file{gmon.out}). If you have a record of important profiling
39097 data in a @file{gmon.out} file, be sure to move it to a safe location.
39099 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
39100 compiled with the @samp{-pg} compiler option.
39102 @kindex maint set show-debug-regs
39103 @kindex maint show show-debug-regs
39104 @cindex hardware debug registers
39105 @item maint set show-debug-regs
39106 @itemx maint show show-debug-regs
39107 Control whether to show variables that mirror the hardware debug
39108 registers. Use @code{on} to enable, @code{off} to disable. If
39109 enabled, the debug registers values are shown when @value{GDBN} inserts or
39110 removes a hardware breakpoint or watchpoint, and when the inferior
39111 triggers a hardware-assisted breakpoint or watchpoint.
39113 @kindex maint set show-all-tib
39114 @kindex maint show show-all-tib
39115 @item maint set show-all-tib
39116 @itemx maint show show-all-tib
39117 Control whether to show all non zero areas within a 1k block starting
39118 at thread local base, when using the @samp{info w32 thread-information-block}
39121 @kindex maint set target-async
39122 @kindex maint show target-async
39123 @item maint set target-async
39124 @itemx maint show target-async
39125 This controls whether @value{GDBN} targets operate in synchronous or
39126 asynchronous mode (@pxref{Background Execution}). Normally the
39127 default is asynchronous, if it is available; but this can be changed
39128 to more easily debug problems occurring only in synchronous mode.
39130 @kindex maint set target-non-stop @var{mode} [on|off|auto]
39131 @kindex maint show target-non-stop
39132 @item maint set target-non-stop
39133 @itemx maint show target-non-stop
39135 This controls whether @value{GDBN} targets always operate in non-stop
39136 mode even if @code{set non-stop} is @code{off} (@pxref{Non-Stop
39137 Mode}). The default is @code{auto}, meaning non-stop mode is enabled
39138 if supported by the target.
39141 @item maint set target-non-stop auto
39142 This is the default mode. @value{GDBN} controls the target in
39143 non-stop mode if the target supports it.
39145 @item maint set target-non-stop on
39146 @value{GDBN} controls the target in non-stop mode even if the target
39147 does not indicate support.
39149 @item maint set target-non-stop off
39150 @value{GDBN} does not control the target in non-stop mode even if the
39151 target supports it.
39154 @kindex maint set tui-resize-message
39155 @kindex maint show tui-resize-message
39156 @item maint set tui-resize-message
39157 @item maint show tui-resize-message
39158 Control whether @value{GDBN} displays a message each time the terminal
39159 is resized when in TUI mode. The default is @code{off}, which means
39160 that @value{GDBN} is silent during resizes. When @code{on},
39161 @value{GDBN} will display a message after a resize is completed; the
39162 message will include a number indicating how many times the terminal
39163 has been resized. This setting is intended for use by the test suite,
39164 where it would otherwise be difficult to determine when a resize and
39165 refresh has been completed.
39167 @kindex maint set per-command
39168 @kindex maint show per-command
39169 @item maint set per-command
39170 @itemx maint show per-command
39171 @cindex resources used by commands
39173 @value{GDBN} can display the resources used by each command.
39174 This is useful in debugging performance problems.
39177 @item maint set per-command space [on|off]
39178 @itemx maint show per-command space
39179 Enable or disable the printing of the memory used by GDB for each command.
39180 If enabled, @value{GDBN} will display how much memory each command
39181 took, following the command's own output.
39182 This can also be requested by invoking @value{GDBN} with the
39183 @option{--statistics} command-line switch (@pxref{Mode Options}).
39185 @item maint set per-command time [on|off]
39186 @itemx maint show per-command time
39187 Enable or disable the printing of the execution time of @value{GDBN}
39189 If enabled, @value{GDBN} will display how much time it
39190 took to execute each command, following the command's own output.
39191 Both CPU time and wallclock time are printed.
39192 Printing both is useful when trying to determine whether the cost is
39193 CPU or, e.g., disk/network latency.
39194 Note that the CPU time printed is for @value{GDBN} only, it does not include
39195 the execution time of the inferior because there's no mechanism currently
39196 to compute how much time was spent by @value{GDBN} and how much time was
39197 spent by the program been debugged.
39198 This can also be requested by invoking @value{GDBN} with the
39199 @option{--statistics} command-line switch (@pxref{Mode Options}).
39201 @item maint set per-command symtab [on|off]
39202 @itemx maint show per-command symtab
39203 Enable or disable the printing of basic symbol table statistics
39205 If enabled, @value{GDBN} will display the following information:
39209 number of symbol tables
39211 number of primary symbol tables
39213 number of blocks in the blockvector
39217 @kindex maint set check-libthread-db
39218 @kindex maint show check-libthread-db
39219 @item maint set check-libthread-db [on|off]
39220 @itemx maint show check-libthread-db
39221 Control whether @value{GDBN} should run integrity checks on inferior
39222 specific thread debugging libraries as they are loaded. The default
39223 is not to perform such checks. If any check fails @value{GDBN} will
39224 unload the library and continue searching for a suitable candidate as
39225 described in @ref{set libthread-db-search-path}. For more information
39226 about the tests, see @ref{maint check libthread-db}.
39228 @kindex maint space
39229 @cindex memory used by commands
39230 @item maint space @var{value}
39231 An alias for @code{maint set per-command space}.
39232 A non-zero value enables it, zero disables it.
39235 @cindex time of command execution
39236 @item maint time @var{value}
39237 An alias for @code{maint set per-command time}.
39238 A non-zero value enables it, zero disables it.
39240 @kindex maint translate-address
39241 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
39242 Find the symbol stored at the location specified by the address
39243 @var{addr} and an optional section name @var{section}. If found,
39244 @value{GDBN} prints the name of the closest symbol and an offset from
39245 the symbol's location to the specified address. This is similar to
39246 the @code{info address} command (@pxref{Symbols}), except that this
39247 command also allows to find symbols in other sections.
39249 If section was not specified, the section in which the symbol was found
39250 is also printed. For dynamically linked executables, the name of
39251 executable or shared library containing the symbol is printed as well.
39253 @kindex maint test-options
39254 @item maint test-options require-delimiter
39255 @itemx maint test-options unknown-is-error
39256 @itemx maint test-options unknown-is-operand
39257 These commands are used by the testsuite to validate the command
39258 options framework. The @code{require-delimiter} variant requires a
39259 double-dash delimiter to indicate end of options. The
39260 @code{unknown-is-error} and @code{unknown-is-operand} do not. The
39261 @code{unknown-is-error} variant throws an error on unknown option,
39262 while @code{unknown-is-operand} treats unknown options as the start of
39263 the command's operands. When run, the commands output the result of
39264 the processed options. When completed, the commands store the
39265 internal result of completion in a variable exposed by the @code{maint
39266 show test-options-completion-result} command.
39268 @kindex maint show test-options-completion-result
39269 @item maint show test-options-completion-result
39270 Shows the result of completing the @code{maint test-options}
39271 subcommands. This is used by the testsuite to validate completion
39272 support in the command options framework.
39274 @kindex maint set test-settings
39275 @kindex maint show test-settings
39276 @item maint set test-settings @var{kind}
39277 @itemx maint show test-settings @var{kind}
39278 These are representative commands for each @var{kind} of setting type
39279 @value{GDBN} supports. They are used by the testsuite for exercising
39280 the settings infrastructure.
39283 @item maint with @var{setting} [@var{value}] [-- @var{command}]
39284 Like the @code{with} command, but works with @code{maintenance set}
39285 variables. This is used by the testsuite to exercise the @code{with}
39286 command's infrastructure.
39290 The following command is useful for non-interactive invocations of
39291 @value{GDBN}, such as in the test suite.
39294 @item set watchdog @var{nsec}
39295 @kindex set watchdog
39296 @cindex watchdog timer
39297 @cindex timeout for commands
39298 Set the maximum number of seconds @value{GDBN} will wait for the
39299 target operation to finish. If this time expires, @value{GDBN}
39300 reports and error and the command is aborted.
39302 @item show watchdog
39303 Show the current setting of the target wait timeout.
39306 @node Remote Protocol
39307 @appendix @value{GDBN} Remote Serial Protocol
39312 * Stop Reply Packets::
39313 * General Query Packets::
39314 * Architecture-Specific Protocol Details::
39315 * Tracepoint Packets::
39316 * Host I/O Packets::
39318 * Notification Packets::
39319 * Remote Non-Stop::
39320 * Packet Acknowledgment::
39322 * File-I/O Remote Protocol Extension::
39323 * Library List Format::
39324 * Library List Format for SVR4 Targets::
39325 * Memory Map Format::
39326 * Thread List Format::
39327 * Traceframe Info Format::
39328 * Branch Trace Format::
39329 * Branch Trace Configuration Format::
39335 There may be occasions when you need to know something about the
39336 protocol---for example, if there is only one serial port to your target
39337 machine, you might want your program to do something special if it
39338 recognizes a packet meant for @value{GDBN}.
39340 In the examples below, @samp{->} and @samp{<-} are used to indicate
39341 transmitted and received data, respectively.
39343 @cindex protocol, @value{GDBN} remote serial
39344 @cindex serial protocol, @value{GDBN} remote
39345 @cindex remote serial protocol
39346 All @value{GDBN} commands and responses (other than acknowledgments
39347 and notifications, see @ref{Notification Packets}) are sent as a
39348 @var{packet}. A @var{packet} is introduced with the character
39349 @samp{$}, the actual @var{packet-data}, and the terminating character
39350 @samp{#} followed by a two-digit @var{checksum}:
39353 @code{$}@var{packet-data}@code{#}@var{checksum}
39357 @cindex checksum, for @value{GDBN} remote
39359 The two-digit @var{checksum} is computed as the modulo 256 sum of all
39360 characters between the leading @samp{$} and the trailing @samp{#} (an
39361 eight bit unsigned checksum).
39363 Implementors should note that prior to @value{GDBN} 5.0 the protocol
39364 specification also included an optional two-digit @var{sequence-id}:
39367 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
39370 @cindex sequence-id, for @value{GDBN} remote
39372 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
39373 has never output @var{sequence-id}s. Stubs that handle packets added
39374 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
39376 When either the host or the target machine receives a packet, the first
39377 response expected is an acknowledgment: either @samp{+} (to indicate
39378 the package was received correctly) or @samp{-} (to request
39382 -> @code{$}@var{packet-data}@code{#}@var{checksum}
39387 The @samp{+}/@samp{-} acknowledgments can be disabled
39388 once a connection is established.
39389 @xref{Packet Acknowledgment}, for details.
39391 The host (@value{GDBN}) sends @var{command}s, and the target (the
39392 debugging stub incorporated in your program) sends a @var{response}. In
39393 the case of step and continue @var{command}s, the response is only sent
39394 when the operation has completed, and the target has again stopped all
39395 threads in all attached processes. This is the default all-stop mode
39396 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
39397 execution mode; see @ref{Remote Non-Stop}, for details.
39399 @var{packet-data} consists of a sequence of characters with the
39400 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
39403 @cindex remote protocol, field separator
39404 Fields within the packet should be separated using @samp{,} @samp{;} or
39405 @samp{:}. Except where otherwise noted all numbers are represented in
39406 @sc{hex} with leading zeros suppressed.
39408 Implementors should note that prior to @value{GDBN} 5.0, the character
39409 @samp{:} could not appear as the third character in a packet (as it
39410 would potentially conflict with the @var{sequence-id}).
39412 @cindex remote protocol, binary data
39413 @anchor{Binary Data}
39414 Binary data in most packets is encoded either as two hexadecimal
39415 digits per byte of binary data. This allowed the traditional remote
39416 protocol to work over connections which were only seven-bit clean.
39417 Some packets designed more recently assume an eight-bit clean
39418 connection, and use a more efficient encoding to send and receive
39421 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
39422 as an escape character. Any escaped byte is transmitted as the escape
39423 character followed by the original character XORed with @code{0x20}.
39424 For example, the byte @code{0x7d} would be transmitted as the two
39425 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
39426 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
39427 @samp{@}}) must always be escaped. Responses sent by the stub
39428 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
39429 is not interpreted as the start of a run-length encoded sequence
39432 Response @var{data} can be run-length encoded to save space.
39433 Run-length encoding replaces runs of identical characters with one
39434 instance of the repeated character, followed by a @samp{*} and a
39435 repeat count. The repeat count is itself sent encoded, to avoid
39436 binary characters in @var{data}: a value of @var{n} is sent as
39437 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
39438 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
39439 code 32) for a repeat count of 3. (This is because run-length
39440 encoding starts to win for counts 3 or more.) Thus, for example,
39441 @samp{0* } is a run-length encoding of ``0000'': the space character
39442 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
39445 The printable characters @samp{#} and @samp{$} or with a numeric value
39446 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
39447 seven repeats (@samp{$}) can be expanded using a repeat count of only
39448 five (@samp{"}). For example, @samp{00000000} can be encoded as
39451 The error response returned for some packets includes a two character
39452 error number. That number is not well defined.
39454 @cindex empty response, for unsupported packets
39455 For any @var{command} not supported by the stub, an empty response
39456 (@samp{$#00}) should be returned. That way it is possible to extend the
39457 protocol. A newer @value{GDBN} can tell if a packet is supported based
39460 At a minimum, a stub is required to support the @samp{?} command to
39461 tell @value{GDBN} the reason for halting, @samp{g} and @samp{G}
39462 commands for register access, and the @samp{m} and @samp{M} commands
39463 for memory access. Stubs that only control single-threaded targets
39464 can implement run control with the @samp{c} (continue) command, and if
39465 the target architecture supports hardware-assisted single-stepping,
39466 the @samp{s} (step) command. Stubs that support multi-threading
39467 targets should support the @samp{vCont} command. All other commands
39473 The following table provides a complete list of all currently defined
39474 @var{command}s and their corresponding response @var{data}.
39475 @xref{File-I/O Remote Protocol Extension}, for details about the File
39476 I/O extension of the remote protocol.
39478 Each packet's description has a template showing the packet's overall
39479 syntax, followed by an explanation of the packet's meaning. We
39480 include spaces in some of the templates for clarity; these are not
39481 part of the packet's syntax. No @value{GDBN} packet uses spaces to
39482 separate its components. For example, a template like @samp{foo
39483 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
39484 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
39485 @var{baz}. @value{GDBN} does not transmit a space character between the
39486 @samp{foo} and the @var{bar}, or between the @var{bar} and the
39489 @cindex @var{thread-id}, in remote protocol
39490 @anchor{thread-id syntax}
39491 Several packets and replies include a @var{thread-id} field to identify
39492 a thread. Normally these are positive numbers with a target-specific
39493 interpretation, formatted as big-endian hex strings. A @var{thread-id}
39494 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
39497 In addition, the remote protocol supports a multiprocess feature in
39498 which the @var{thread-id} syntax is extended to optionally include both
39499 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
39500 The @var{pid} (process) and @var{tid} (thread) components each have the
39501 format described above: a positive number with target-specific
39502 interpretation formatted as a big-endian hex string, literal @samp{-1}
39503 to indicate all processes or threads (respectively), or @samp{0} to
39504 indicate an arbitrary process or thread. Specifying just a process, as
39505 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
39506 error to specify all processes but a specific thread, such as
39507 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
39508 for those packets and replies explicitly documented to include a process
39509 ID, rather than a @var{thread-id}.
39511 The multiprocess @var{thread-id} syntax extensions are only used if both
39512 @value{GDBN} and the stub report support for the @samp{multiprocess}
39513 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
39516 Note that all packet forms beginning with an upper- or lower-case
39517 letter, other than those described here, are reserved for future use.
39519 Here are the packet descriptions.
39524 @cindex @samp{!} packet
39525 @anchor{extended mode}
39526 Enable extended mode. In extended mode, the remote server is made
39527 persistent. The @samp{R} packet is used to restart the program being
39533 The remote target both supports and has enabled extended mode.
39537 @cindex @samp{?} packet
39539 This is sent when connection is first established to query the reason
39540 the target halted. The reply is the same as for step and continue.
39541 This packet has a special interpretation when the target is in
39542 non-stop mode; see @ref{Remote Non-Stop}.
39545 @xref{Stop Reply Packets}, for the reply specifications.
39547 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
39548 @cindex @samp{A} packet
39549 Initialized @code{argv[]} array passed into program. @var{arglen}
39550 specifies the number of bytes in the hex encoded byte stream
39551 @var{arg}. See @code{gdbserver} for more details.
39556 The arguments were set.
39562 @cindex @samp{b} packet
39563 (Don't use this packet; its behavior is not well-defined.)
39564 Change the serial line speed to @var{baud}.
39566 JTC: @emph{When does the transport layer state change? When it's
39567 received, or after the ACK is transmitted. In either case, there are
39568 problems if the command or the acknowledgment packet is dropped.}
39570 Stan: @emph{If people really wanted to add something like this, and get
39571 it working for the first time, they ought to modify ser-unix.c to send
39572 some kind of out-of-band message to a specially-setup stub and have the
39573 switch happen "in between" packets, so that from remote protocol's point
39574 of view, nothing actually happened.}
39576 @item B @var{addr},@var{mode}
39577 @cindex @samp{B} packet
39578 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
39579 breakpoint at @var{addr}.
39581 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
39582 (@pxref{insert breakpoint or watchpoint packet}).
39584 @cindex @samp{bc} packet
39587 Backward continue. Execute the target system in reverse. No parameter.
39588 @xref{Reverse Execution}, for more information.
39591 @xref{Stop Reply Packets}, for the reply specifications.
39593 @cindex @samp{bs} packet
39596 Backward single step. Execute one instruction in reverse. No parameter.
39597 @xref{Reverse Execution}, for more information.
39600 @xref{Stop Reply Packets}, for the reply specifications.
39602 @item c @r{[}@var{addr}@r{]}
39603 @cindex @samp{c} packet
39604 Continue at @var{addr}, which is the address to resume. If @var{addr}
39605 is omitted, resume at current address.
39607 This packet is deprecated for multi-threading support. @xref{vCont
39611 @xref{Stop Reply Packets}, for the reply specifications.
39613 @item C @var{sig}@r{[};@var{addr}@r{]}
39614 @cindex @samp{C} packet
39615 Continue with signal @var{sig} (hex signal number). If
39616 @samp{;@var{addr}} is omitted, resume at same address.
39618 This packet is deprecated for multi-threading support. @xref{vCont
39622 @xref{Stop Reply Packets}, for the reply specifications.
39625 @cindex @samp{d} packet
39628 Don't use this packet; instead, define a general set packet
39629 (@pxref{General Query Packets}).
39633 @cindex @samp{D} packet
39634 The first form of the packet is used to detach @value{GDBN} from the
39635 remote system. It is sent to the remote target
39636 before @value{GDBN} disconnects via the @code{detach} command.
39638 The second form, including a process ID, is used when multiprocess
39639 protocol extensions are enabled (@pxref{multiprocess extensions}), to
39640 detach only a specific process. The @var{pid} is specified as a
39641 big-endian hex string.
39651 @item F @var{RC},@var{EE},@var{CF};@var{XX}
39652 @cindex @samp{F} packet
39653 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
39654 This is part of the File-I/O protocol extension. @xref{File-I/O
39655 Remote Protocol Extension}, for the specification.
39658 @anchor{read registers packet}
39659 @cindex @samp{g} packet
39660 Read general registers.
39664 @item @var{XX@dots{}}
39665 Each byte of register data is described by two hex digits. The bytes
39666 with the register are transmitted in target byte order. The size of
39667 each register and their position within the @samp{g} packet are
39668 determined by the @value{GDBN} internal gdbarch functions
39669 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}.
39671 When reading registers from a trace frame (@pxref{Analyze Collected
39672 Data,,Using the Collected Data}), the stub may also return a string of
39673 literal @samp{x}'s in place of the register data digits, to indicate
39674 that the corresponding register has not been collected, thus its value
39675 is unavailable. For example, for an architecture with 4 registers of
39676 4 bytes each, the following reply indicates to @value{GDBN} that
39677 registers 0 and 2 have not been collected, while registers 1 and 3
39678 have been collected, and both have zero value:
39682 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
39689 @item G @var{XX@dots{}}
39690 @cindex @samp{G} packet
39691 Write general registers. @xref{read registers packet}, for a
39692 description of the @var{XX@dots{}} data.
39702 @item H @var{op} @var{thread-id}
39703 @cindex @samp{H} packet
39704 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
39705 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
39706 should be @samp{c} for step and continue operations (note that this
39707 is deprecated, supporting the @samp{vCont} command is a better
39708 option), and @samp{g} for other operations. The thread designator
39709 @var{thread-id} has the format and interpretation described in
39710 @ref{thread-id syntax}.
39721 @c 'H': How restrictive (or permissive) is the thread model. If a
39722 @c thread is selected and stopped, are other threads allowed
39723 @c to continue to execute? As I mentioned above, I think the
39724 @c semantics of each command when a thread is selected must be
39725 @c described. For example:
39727 @c 'g': If the stub supports threads and a specific thread is
39728 @c selected, returns the register block from that thread;
39729 @c otherwise returns current registers.
39731 @c 'G' If the stub supports threads and a specific thread is
39732 @c selected, sets the registers of the register block of
39733 @c that thread; otherwise sets current registers.
39735 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
39736 @anchor{cycle step packet}
39737 @cindex @samp{i} packet
39738 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
39739 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
39740 step starting at that address.
39743 @cindex @samp{I} packet
39744 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
39748 @cindex @samp{k} packet
39751 The exact effect of this packet is not specified.
39753 For a bare-metal target, it may power cycle or reset the target
39754 system. For that reason, the @samp{k} packet has no reply.
39756 For a single-process target, it may kill that process if possible.
39758 A multiple-process target may choose to kill just one process, or all
39759 that are under @value{GDBN}'s control. For more precise control, use
39760 the vKill packet (@pxref{vKill packet}).
39762 If the target system immediately closes the connection in response to
39763 @samp{k}, @value{GDBN} does not consider the lack of packet
39764 acknowledgment to be an error, and assumes the kill was successful.
39766 If connected using @kbd{target extended-remote}, and the target does
39767 not close the connection in response to a kill request, @value{GDBN}
39768 probes the target state as if a new connection was opened
39769 (@pxref{? packet}).
39771 @item m @var{addr},@var{length}
39772 @cindex @samp{m} packet
39773 Read @var{length} addressable memory units starting at address @var{addr}
39774 (@pxref{addressable memory unit}). Note that @var{addr} may not be aligned to
39775 any particular boundary.
39777 The stub need not use any particular size or alignment when gathering
39778 data from memory for the response; even if @var{addr} is word-aligned
39779 and @var{length} is a multiple of the word size, the stub is free to
39780 use byte accesses, or not. For this reason, this packet may not be
39781 suitable for accessing memory-mapped I/O devices.
39782 @cindex alignment of remote memory accesses
39783 @cindex size of remote memory accesses
39784 @cindex memory, alignment and size of remote accesses
39788 @item @var{XX@dots{}}
39789 Memory contents; each byte is transmitted as a two-digit hexadecimal number.
39790 The reply may contain fewer addressable memory units than requested if the
39791 server was able to read only part of the region of memory.
39796 @item M @var{addr},@var{length}:@var{XX@dots{}}
39797 @cindex @samp{M} packet
39798 Write @var{length} addressable memory units starting at address @var{addr}
39799 (@pxref{addressable memory unit}). The data is given by @var{XX@dots{}}; each
39800 byte is transmitted as a two-digit hexadecimal number.
39807 for an error (this includes the case where only part of the data was
39812 @cindex @samp{p} packet
39813 Read the value of register @var{n}; @var{n} is in hex.
39814 @xref{read registers packet}, for a description of how the returned
39815 register value is encoded.
39819 @item @var{XX@dots{}}
39820 the register's value
39824 Indicating an unrecognized @var{query}.
39827 @item P @var{n@dots{}}=@var{r@dots{}}
39828 @anchor{write register packet}
39829 @cindex @samp{P} packet
39830 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
39831 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
39832 digits for each byte in the register (target byte order).
39842 @item q @var{name} @var{params}@dots{}
39843 @itemx Q @var{name} @var{params}@dots{}
39844 @cindex @samp{q} packet
39845 @cindex @samp{Q} packet
39846 General query (@samp{q}) and set (@samp{Q}). These packets are
39847 described fully in @ref{General Query Packets}.
39850 @cindex @samp{r} packet
39851 Reset the entire system.
39853 Don't use this packet; use the @samp{R} packet instead.
39856 @cindex @samp{R} packet
39857 Restart the program being debugged. The @var{XX}, while needed, is ignored.
39858 This packet is only available in extended mode (@pxref{extended mode}).
39860 The @samp{R} packet has no reply.
39862 @item s @r{[}@var{addr}@r{]}
39863 @cindex @samp{s} packet
39864 Single step, resuming at @var{addr}. If
39865 @var{addr} is omitted, resume at same address.
39867 This packet is deprecated for multi-threading support. @xref{vCont
39871 @xref{Stop Reply Packets}, for the reply specifications.
39873 @item S @var{sig}@r{[};@var{addr}@r{]}
39874 @anchor{step with signal packet}
39875 @cindex @samp{S} packet
39876 Step with signal. This is analogous to the @samp{C} packet, but
39877 requests a single-step, rather than a normal resumption of execution.
39879 This packet is deprecated for multi-threading support. @xref{vCont
39883 @xref{Stop Reply Packets}, for the reply specifications.
39885 @item t @var{addr}:@var{PP},@var{MM}
39886 @cindex @samp{t} packet
39887 Search backwards starting at address @var{addr} for a match with pattern
39888 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
39889 There must be at least 3 digits in @var{addr}.
39891 @item T @var{thread-id}
39892 @cindex @samp{T} packet
39893 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
39898 thread is still alive
39904 Packets starting with @samp{v} are identified by a multi-letter name,
39905 up to the first @samp{;} or @samp{?} (or the end of the packet).
39907 @item vAttach;@var{pid}
39908 @cindex @samp{vAttach} packet
39909 Attach to a new process with the specified process ID @var{pid}.
39910 The process ID is a
39911 hexadecimal integer identifying the process. In all-stop mode, all
39912 threads in the attached process are stopped; in non-stop mode, it may be
39913 attached without being stopped if that is supported by the target.
39915 @c In non-stop mode, on a successful vAttach, the stub should set the
39916 @c current thread to a thread of the newly-attached process. After
39917 @c attaching, GDB queries for the attached process's thread ID with qC.
39918 @c Also note that, from a user perspective, whether or not the
39919 @c target is stopped on attach in non-stop mode depends on whether you
39920 @c use the foreground or background version of the attach command, not
39921 @c on what vAttach does; GDB does the right thing with respect to either
39922 @c stopping or restarting threads.
39924 This packet is only available in extended mode (@pxref{extended mode}).
39930 @item @r{Any stop packet}
39931 for success in all-stop mode (@pxref{Stop Reply Packets})
39933 for success in non-stop mode (@pxref{Remote Non-Stop})
39936 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
39937 @cindex @samp{vCont} packet
39938 @anchor{vCont packet}
39939 Resume the inferior, specifying different actions for each thread.
39941 For each inferior thread, the leftmost action with a matching
39942 @var{thread-id} is applied. Threads that don't match any action
39943 remain in their current state. Thread IDs are specified using the
39944 syntax described in @ref{thread-id syntax}. If multiprocess
39945 extensions (@pxref{multiprocess extensions}) are supported, actions
39946 can be specified to match all threads in a process by using the
39947 @samp{p@var{pid}.-1} form of the @var{thread-id}. An action with no
39948 @var{thread-id} matches all threads. Specifying no actions is an
39951 Currently supported actions are:
39957 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
39961 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
39964 @item r @var{start},@var{end}
39965 Step once, and then keep stepping as long as the thread stops at
39966 addresses between @var{start} (inclusive) and @var{end} (exclusive).
39967 The remote stub reports a stop reply when either the thread goes out
39968 of the range or is stopped due to an unrelated reason, such as hitting
39969 a breakpoint. @xref{range stepping}.
39971 If the range is empty (@var{start} == @var{end}), then the action
39972 becomes equivalent to the @samp{s} action. In other words,
39973 single-step once, and report the stop (even if the stepped instruction
39974 jumps to @var{start}).
39976 (A stop reply may be sent at any point even if the PC is still within
39977 the stepping range; for example, it is valid to implement this packet
39978 in a degenerate way as a single instruction step operation.)
39982 The optional argument @var{addr} normally associated with the
39983 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
39984 not supported in @samp{vCont}.
39986 The @samp{t} action is only relevant in non-stop mode
39987 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
39988 A stop reply should be generated for any affected thread not already stopped.
39989 When a thread is stopped by means of a @samp{t} action,
39990 the corresponding stop reply should indicate that the thread has stopped with
39991 signal @samp{0}, regardless of whether the target uses some other signal
39992 as an implementation detail.
39994 The server must ignore @samp{c}, @samp{C}, @samp{s}, @samp{S}, and
39995 @samp{r} actions for threads that are already running. Conversely,
39996 the server must ignore @samp{t} actions for threads that are already
39999 @emph{Note:} In non-stop mode, a thread is considered running until
40000 @value{GDBN} acknowledges an asynchronous stop notification for it with
40001 the @samp{vStopped} packet (@pxref{Remote Non-Stop}).
40003 The stub must support @samp{vCont} if it reports support for
40004 multiprocess extensions (@pxref{multiprocess extensions}).
40007 @xref{Stop Reply Packets}, for the reply specifications.
40010 @cindex @samp{vCont?} packet
40011 Request a list of actions supported by the @samp{vCont} packet.
40015 @item vCont@r{[};@var{action}@dots{}@r{]}
40016 The @samp{vCont} packet is supported. Each @var{action} is a supported
40017 command in the @samp{vCont} packet.
40019 The @samp{vCont} packet is not supported.
40022 @anchor{vCtrlC packet}
40024 @cindex @samp{vCtrlC} packet
40025 Interrupt remote target as if a control-C was pressed on the remote
40026 terminal. This is the equivalent to reacting to the @code{^C}
40027 (@samp{\003}, the control-C character) character in all-stop mode
40028 while the target is running, except this works in non-stop mode.
40029 @xref{interrupting remote targets}, for more info on the all-stop
40040 @item vFile:@var{operation}:@var{parameter}@dots{}
40041 @cindex @samp{vFile} packet
40042 Perform a file operation on the target system. For details,
40043 see @ref{Host I/O Packets}.
40045 @item vFlashErase:@var{addr},@var{length}
40046 @cindex @samp{vFlashErase} packet
40047 Direct the stub to erase @var{length} bytes of flash starting at
40048 @var{addr}. The region may enclose any number of flash blocks, but
40049 its start and end must fall on block boundaries, as indicated by the
40050 flash block size appearing in the memory map (@pxref{Memory Map
40051 Format}). @value{GDBN} groups flash memory programming operations
40052 together, and sends a @samp{vFlashDone} request after each group; the
40053 stub is allowed to delay erase operation until the @samp{vFlashDone}
40054 packet is received.
40064 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
40065 @cindex @samp{vFlashWrite} packet
40066 Direct the stub to write data to flash address @var{addr}. The data
40067 is passed in binary form using the same encoding as for the @samp{X}
40068 packet (@pxref{Binary Data}). The memory ranges specified by
40069 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
40070 not overlap, and must appear in order of increasing addresses
40071 (although @samp{vFlashErase} packets for higher addresses may already
40072 have been received; the ordering is guaranteed only between
40073 @samp{vFlashWrite} packets). If a packet writes to an address that was
40074 neither erased by a preceding @samp{vFlashErase} packet nor by some other
40075 target-specific method, the results are unpredictable.
40083 for vFlashWrite addressing non-flash memory
40089 @cindex @samp{vFlashDone} packet
40090 Indicate to the stub that flash programming operation is finished.
40091 The stub is permitted to delay or batch the effects of a group of
40092 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
40093 @samp{vFlashDone} packet is received. The contents of the affected
40094 regions of flash memory are unpredictable until the @samp{vFlashDone}
40095 request is completed.
40097 @item vKill;@var{pid}
40098 @cindex @samp{vKill} packet
40099 @anchor{vKill packet}
40100 Kill the process with the specified process ID @var{pid}, which is a
40101 hexadecimal integer identifying the process. This packet is used in
40102 preference to @samp{k} when multiprocess protocol extensions are
40103 supported; see @ref{multiprocess extensions}.
40113 @item vMustReplyEmpty
40114 @cindex @samp{vMustReplyEmpty} packet
40115 The correct reply to an unknown @samp{v} packet is to return the empty
40116 string, however, some older versions of @command{gdbserver} would
40117 incorrectly return @samp{OK} for unknown @samp{v} packets.
40119 The @samp{vMustReplyEmpty} is used as a feature test to check how
40120 @command{gdbserver} handles unknown packets, it is important that this
40121 packet be handled in the same way as other unknown @samp{v} packets.
40122 If this packet is handled differently to other unknown @samp{v}
40123 packets then it is possible that @value{GDBN} may run into problems in
40124 other areas, specifically around use of @samp{vFile:setfs:}.
40126 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
40127 @cindex @samp{vRun} packet
40128 Run the program @var{filename}, passing it each @var{argument} on its
40129 command line. The file and arguments are hex-encoded strings. If
40130 @var{filename} is an empty string, the stub may use a default program
40131 (e.g.@: the last program run). The program is created in the stopped
40134 @c FIXME: What about non-stop mode?
40136 This packet is only available in extended mode (@pxref{extended mode}).
40142 @item @r{Any stop packet}
40143 for success (@pxref{Stop Reply Packets})
40147 @cindex @samp{vStopped} packet
40148 @xref{Notification Packets}.
40150 @item X @var{addr},@var{length}:@var{XX@dots{}}
40152 @cindex @samp{X} packet
40153 Write data to memory, where the data is transmitted in binary.
40154 Memory is specified by its address @var{addr} and number of addressable memory
40155 units @var{length} (@pxref{addressable memory unit});
40156 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
40166 @item z @var{type},@var{addr},@var{kind}
40167 @itemx Z @var{type},@var{addr},@var{kind}
40168 @anchor{insert breakpoint or watchpoint packet}
40169 @cindex @samp{z} packet
40170 @cindex @samp{Z} packets
40171 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
40172 watchpoint starting at address @var{address} of kind @var{kind}.
40174 Each breakpoint and watchpoint packet @var{type} is documented
40177 @emph{Implementation notes: A remote target shall return an empty string
40178 for an unrecognized breakpoint or watchpoint packet @var{type}. A
40179 remote target shall support either both or neither of a given
40180 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
40181 avoid potential problems with duplicate packets, the operations should
40182 be implemented in an idempotent way.}
40184 @item z0,@var{addr},@var{kind}
40185 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
40186 @cindex @samp{z0} packet
40187 @cindex @samp{Z0} packet
40188 Insert (@samp{Z0}) or remove (@samp{z0}) a software breakpoint at address
40189 @var{addr} of type @var{kind}.
40191 A software breakpoint is implemented by replacing the instruction at
40192 @var{addr} with a software breakpoint or trap instruction. The
40193 @var{kind} is target-specific and typically indicates the size of the
40194 breakpoint in bytes that should be inserted. E.g., the @sc{arm} and
40195 @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
40196 architectures have additional meanings for @var{kind}
40197 (@pxref{Architecture-Specific Protocol Details}); if no
40198 architecture-specific value is being used, it should be @samp{0}.
40199 @var{kind} is hex-encoded. @var{cond_list} is an optional list of
40200 conditional expressions in bytecode form that should be evaluated on
40201 the target's side. These are the conditions that should be taken into
40202 consideration when deciding if the breakpoint trigger should be
40203 reported back to @value{GDBN}.
40205 See also the @samp{swbreak} stop reason (@pxref{swbreak stop reason})
40206 for how to best report a software breakpoint event to @value{GDBN}.
40208 The @var{cond_list} parameter is comprised of a series of expressions,
40209 concatenated without separators. Each expression has the following form:
40213 @item X @var{len},@var{expr}
40214 @var{len} is the length of the bytecode expression and @var{expr} is the
40215 actual conditional expression in bytecode form.
40219 The optional @var{cmd_list} parameter introduces commands that may be
40220 run on the target, rather than being reported back to @value{GDBN}.
40221 The parameter starts with a numeric flag @var{persist}; if the flag is
40222 nonzero, then the breakpoint may remain active and the commands
40223 continue to be run even when @value{GDBN} disconnects from the target.
40224 Following this flag is a series of expressions concatenated with no
40225 separators. Each expression has the following form:
40229 @item X @var{len},@var{expr}
40230 @var{len} is the length of the bytecode expression and @var{expr} is the
40231 actual commands expression in bytecode form.
40235 @emph{Implementation note: It is possible for a target to copy or move
40236 code that contains software breakpoints (e.g., when implementing
40237 overlays). The behavior of this packet, in the presence of such a
40238 target, is not defined.}
40250 @item z1,@var{addr},@var{kind}
40251 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
40252 @cindex @samp{z1} packet
40253 @cindex @samp{Z1} packet
40254 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
40255 address @var{addr}.
40257 A hardware breakpoint is implemented using a mechanism that is not
40258 dependent on being able to modify the target's memory. The
40259 @var{kind}, @var{cond_list}, and @var{cmd_list} arguments have the
40260 same meaning as in @samp{Z0} packets.
40262 @emph{Implementation note: A hardware breakpoint is not affected by code
40275 @item z2,@var{addr},@var{kind}
40276 @itemx Z2,@var{addr},@var{kind}
40277 @cindex @samp{z2} packet
40278 @cindex @samp{Z2} packet
40279 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
40280 The number of bytes to watch is specified by @var{kind}.
40292 @item z3,@var{addr},@var{kind}
40293 @itemx Z3,@var{addr},@var{kind}
40294 @cindex @samp{z3} packet
40295 @cindex @samp{Z3} packet
40296 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
40297 The number of bytes to watch is specified by @var{kind}.
40309 @item z4,@var{addr},@var{kind}
40310 @itemx Z4,@var{addr},@var{kind}
40311 @cindex @samp{z4} packet
40312 @cindex @samp{Z4} packet
40313 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
40314 The number of bytes to watch is specified by @var{kind}.
40328 @node Stop Reply Packets
40329 @section Stop Reply Packets
40330 @cindex stop reply packets
40332 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
40333 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
40334 receive any of the below as a reply. Except for @samp{?}
40335 and @samp{vStopped}, that reply is only returned
40336 when the target halts. In the below the exact meaning of @dfn{signal
40337 number} is defined by the header @file{include/gdb/signals.h} in the
40338 @value{GDBN} source code.
40340 In non-stop mode, the server will simply reply @samp{OK} to commands
40341 such as @samp{vCont}; any stop will be the subject of a future
40342 notification. @xref{Remote Non-Stop}.
40344 As in the description of request packets, we include spaces in the
40345 reply templates for clarity; these are not part of the reply packet's
40346 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
40352 The program received signal number @var{AA} (a two-digit hexadecimal
40353 number). This is equivalent to a @samp{T} response with no
40354 @var{n}:@var{r} pairs.
40356 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
40357 @cindex @samp{T} packet reply
40358 The program received signal number @var{AA} (a two-digit hexadecimal
40359 number). This is equivalent to an @samp{S} response, except that the
40360 @samp{@var{n}:@var{r}} pairs can carry values of important registers
40361 and other information directly in the stop reply packet, reducing
40362 round-trip latency. Single-step and breakpoint traps are reported
40363 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
40367 If @var{n} is a hexadecimal number, it is a register number, and the
40368 corresponding @var{r} gives that register's value. The data @var{r} is a
40369 series of bytes in target byte order, with each byte given by a
40370 two-digit hex number.
40373 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
40374 the stopped thread, as specified in @ref{thread-id syntax}.
40377 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
40378 the core on which the stop event was detected.
40381 If @var{n} is a recognized @dfn{stop reason}, it describes a more
40382 specific event that stopped the target. The currently defined stop
40383 reasons are listed below. The @var{aa} should be @samp{05}, the trap
40384 signal. At most one stop reason should be present.
40387 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
40388 and go on to the next; this allows us to extend the protocol in the
40392 The currently defined stop reasons are:
40398 The packet indicates a watchpoint hit, and @var{r} is the data address, in
40401 @item syscall_entry
40402 @itemx syscall_return
40403 The packet indicates a syscall entry or return, and @var{r} is the
40404 syscall number, in hex.
40406 @cindex shared library events, remote reply
40408 The packet indicates that the loaded libraries have changed.
40409 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
40410 list of loaded libraries. The @var{r} part is ignored.
40412 @cindex replay log events, remote reply
40414 The packet indicates that the target cannot continue replaying
40415 logged execution events, because it has reached the end (or the
40416 beginning when executing backward) of the log. The value of @var{r}
40417 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
40418 for more information.
40421 @anchor{swbreak stop reason}
40422 The packet indicates a software breakpoint instruction was executed,
40423 irrespective of whether it was @value{GDBN} that planted the
40424 breakpoint or the breakpoint is hardcoded in the program. The @var{r}
40425 part must be left empty.
40427 On some architectures, such as x86, at the architecture level, when a
40428 breakpoint instruction executes the program counter points at the
40429 breakpoint address plus an offset. On such targets, the stub is
40430 responsible for adjusting the PC to point back at the breakpoint
40433 This packet should not be sent by default; older @value{GDBN} versions
40434 did not support it. @value{GDBN} requests it, by supplying an
40435 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
40436 remote stub must also supply the appropriate @samp{qSupported} feature
40437 indicating support.
40439 This packet is required for correct non-stop mode operation.
40442 The packet indicates the target stopped for a hardware breakpoint.
40443 The @var{r} part must be left empty.
40445 The same remarks about @samp{qSupported} and non-stop mode above
40448 @cindex fork events, remote reply
40450 The packet indicates that @code{fork} was called, and @var{r}
40451 is the thread ID of the new child process. Refer to
40452 @ref{thread-id syntax} for the format of the @var{thread-id}
40453 field. This packet is only applicable to targets that support
40456 This packet should not be sent by default; older @value{GDBN} versions
40457 did not support it. @value{GDBN} requests it, by supplying an
40458 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
40459 remote stub must also supply the appropriate @samp{qSupported} feature
40460 indicating support.
40462 @cindex vfork events, remote reply
40464 The packet indicates that @code{vfork} was called, and @var{r}
40465 is the thread ID of the new child process. Refer to
40466 @ref{thread-id syntax} for the format of the @var{thread-id}
40467 field. This packet is only applicable to targets that support
40470 This packet should not be sent by default; older @value{GDBN} versions
40471 did not support it. @value{GDBN} requests it, by supplying an
40472 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
40473 remote stub must also supply the appropriate @samp{qSupported} feature
40474 indicating support.
40476 @cindex vforkdone events, remote reply
40478 The packet indicates that a child process created by a vfork
40479 has either called @code{exec} or terminated, so that the
40480 address spaces of the parent and child process are no longer
40481 shared. The @var{r} part is ignored. This packet is only
40482 applicable to targets that support vforkdone events.
40484 This packet should not be sent by default; older @value{GDBN} versions
40485 did not support it. @value{GDBN} requests it, by supplying an
40486 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
40487 remote stub must also supply the appropriate @samp{qSupported} feature
40488 indicating support.
40490 @cindex exec events, remote reply
40492 The packet indicates that @code{execve} was called, and @var{r}
40493 is the absolute pathname of the file that was executed, in hex.
40494 This packet is only applicable to targets that support exec events.
40496 This packet should not be sent by default; older @value{GDBN} versions
40497 did not support it. @value{GDBN} requests it, by supplying an
40498 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
40499 remote stub must also supply the appropriate @samp{qSupported} feature
40500 indicating support.
40502 @cindex thread create event, remote reply
40503 @anchor{thread create event}
40505 The packet indicates that the thread was just created. The new thread
40506 is stopped until @value{GDBN} sets it running with a resumption packet
40507 (@pxref{vCont packet}). This packet should not be sent by default;
40508 @value{GDBN} requests it with the @ref{QThreadEvents} packet. See
40509 also the @samp{w} (@pxref{thread exit event}) remote reply below. The
40510 @var{r} part is ignored.
40515 @itemx W @var{AA} ; process:@var{pid}
40516 The process exited, and @var{AA} is the exit status. This is only
40517 applicable to certain targets.
40519 The second form of the response, including the process ID of the
40520 exited process, can be used only when @value{GDBN} has reported
40521 support for multiprocess protocol extensions; see @ref{multiprocess
40522 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
40526 @itemx X @var{AA} ; process:@var{pid}
40527 The process terminated with signal @var{AA}.
40529 The second form of the response, including the process ID of the
40530 terminated process, can be used only when @value{GDBN} has reported
40531 support for multiprocess protocol extensions; see @ref{multiprocess
40532 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
40535 @anchor{thread exit event}
40536 @cindex thread exit event, remote reply
40537 @item w @var{AA} ; @var{tid}
40539 The thread exited, and @var{AA} is the exit status. This response
40540 should not be sent by default; @value{GDBN} requests it with the
40541 @ref{QThreadEvents} packet. See also @ref{thread create event} above.
40542 @var{AA} is formatted as a big-endian hex string.
40545 There are no resumed threads left in the target. In other words, even
40546 though the process is alive, the last resumed thread has exited. For
40547 example, say the target process has two threads: thread 1 and thread
40548 2. The client leaves thread 1 stopped, and resumes thread 2, which
40549 subsequently exits. At this point, even though the process is still
40550 alive, and thus no @samp{W} stop reply is sent, no thread is actually
40551 executing either. The @samp{N} stop reply thus informs the client
40552 that it can stop waiting for stop replies. This packet should not be
40553 sent by default; older @value{GDBN} versions did not support it.
40554 @value{GDBN} requests it, by supplying an appropriate
40555 @samp{qSupported} feature (@pxref{qSupported}). The remote stub must
40556 also supply the appropriate @samp{qSupported} feature indicating
40559 @item O @var{XX}@dots{}
40560 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
40561 written as the program's console output. This can happen at any time
40562 while the program is running and the debugger should continue to wait
40563 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
40565 @item F @var{call-id},@var{parameter}@dots{}
40566 @var{call-id} is the identifier which says which host system call should
40567 be called. This is just the name of the function. Translation into the
40568 correct system call is only applicable as it's defined in @value{GDBN}.
40569 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
40572 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
40573 this very system call.
40575 The target replies with this packet when it expects @value{GDBN} to
40576 call a host system call on behalf of the target. @value{GDBN} replies
40577 with an appropriate @samp{F} packet and keeps up waiting for the next
40578 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
40579 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
40580 Protocol Extension}, for more details.
40584 @node General Query Packets
40585 @section General Query Packets
40586 @cindex remote query requests
40588 Packets starting with @samp{q} are @dfn{general query packets};
40589 packets starting with @samp{Q} are @dfn{general set packets}. General
40590 query and set packets are a semi-unified form for retrieving and
40591 sending information to and from the stub.
40593 The initial letter of a query or set packet is followed by a name
40594 indicating what sort of thing the packet applies to. For example,
40595 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
40596 definitions with the stub. These packet names follow some
40601 The name must not contain commas, colons or semicolons.
40603 Most @value{GDBN} query and set packets have a leading upper case
40606 The names of custom vendor packets should use a company prefix, in
40607 lower case, followed by a period. For example, packets designed at
40608 the Acme Corporation might begin with @samp{qacme.foo} (for querying
40609 foos) or @samp{Qacme.bar} (for setting bars).
40612 The name of a query or set packet should be separated from any
40613 parameters by a @samp{:}; the parameters themselves should be
40614 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
40615 full packet name, and check for a separator or the end of the packet,
40616 in case two packet names share a common prefix. New packets should not begin
40617 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
40618 packets predate these conventions, and have arguments without any terminator
40619 for the packet name; we suspect they are in widespread use in places that
40620 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
40621 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
40624 Like the descriptions of the other packets, each description here
40625 has a template showing the packet's overall syntax, followed by an
40626 explanation of the packet's meaning. We include spaces in some of the
40627 templates for clarity; these are not part of the packet's syntax. No
40628 @value{GDBN} packet uses spaces to separate its components.
40630 Here are the currently defined query and set packets:
40636 Turn on or off the agent as a helper to perform some debugging operations
40637 delegated from @value{GDBN} (@pxref{Control Agent}).
40639 @item QAllow:@var{op}:@var{val}@dots{}
40640 @cindex @samp{QAllow} packet
40641 Specify which operations @value{GDBN} expects to request of the
40642 target, as a semicolon-separated list of operation name and value
40643 pairs. Possible values for @var{op} include @samp{WriteReg},
40644 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
40645 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
40646 indicating that @value{GDBN} will not request the operation, or 1,
40647 indicating that it may. (The target can then use this to set up its
40648 own internals optimally, for instance if the debugger never expects to
40649 insert breakpoints, it may not need to install its own trap handler.)
40652 @cindex current thread, remote request
40653 @cindex @samp{qC} packet
40654 Return the current thread ID.
40658 @item QC @var{thread-id}
40659 Where @var{thread-id} is a thread ID as documented in
40660 @ref{thread-id syntax}.
40661 @item @r{(anything else)}
40662 Any other reply implies the old thread ID.
40665 @item qCRC:@var{addr},@var{length}
40666 @cindex CRC of memory block, remote request
40667 @cindex @samp{qCRC} packet
40668 @anchor{qCRC packet}
40669 Compute the CRC checksum of a block of memory using CRC-32 defined in
40670 IEEE 802.3. The CRC is computed byte at a time, taking the most
40671 significant bit of each byte first. The initial pattern code
40672 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
40674 @emph{Note:} This is the same CRC used in validating separate debug
40675 files (@pxref{Separate Debug Files, , Debugging Information in Separate
40676 Files}). However the algorithm is slightly different. When validating
40677 separate debug files, the CRC is computed taking the @emph{least}
40678 significant bit of each byte first, and the final result is inverted to
40679 detect trailing zeros.
40684 An error (such as memory fault)
40685 @item C @var{crc32}
40686 The specified memory region's checksum is @var{crc32}.
40689 @item QDisableRandomization:@var{value}
40690 @cindex disable address space randomization, remote request
40691 @cindex @samp{QDisableRandomization} packet
40692 Some target operating systems will randomize the virtual address space
40693 of the inferior process as a security feature, but provide a feature
40694 to disable such randomization, e.g.@: to allow for a more deterministic
40695 debugging experience. On such systems, this packet with a @var{value}
40696 of 1 directs the target to disable address space randomization for
40697 processes subsequently started via @samp{vRun} packets, while a packet
40698 with a @var{value} of 0 tells the target to enable address space
40701 This packet is only available in extended mode (@pxref{extended mode}).
40706 The request succeeded.
40709 An error occurred. The error number @var{nn} is given as hex digits.
40712 An empty reply indicates that @samp{QDisableRandomization} is not supported
40716 This packet is not probed by default; the remote stub must request it,
40717 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40718 This should only be done on targets that actually support disabling
40719 address space randomization.
40721 @item QStartupWithShell:@var{value}
40722 @cindex startup with shell, remote request
40723 @cindex @samp{QStartupWithShell} packet
40724 On UNIX-like targets, it is possible to start the inferior using a
40725 shell program. This is the default behavior on both @value{GDBN} and
40726 @command{gdbserver} (@pxref{set startup-with-shell}). This packet is
40727 used to inform @command{gdbserver} whether it should start the
40728 inferior using a shell or not.
40730 If @var{value} is @samp{0}, @command{gdbserver} will not use a shell
40731 to start the inferior. If @var{value} is @samp{1},
40732 @command{gdbserver} will use a shell to start the inferior. All other
40733 values are considered an error.
40735 This packet is only available in extended mode (@pxref{extended
40741 The request succeeded.
40744 An error occurred. The error number @var{nn} is given as hex digits.
40747 This packet is not probed by default; the remote stub must request it,
40748 by supplying an appropriate @samp{qSupported} response
40749 (@pxref{qSupported}). This should only be done on targets that
40750 actually support starting the inferior using a shell.
40752 Use of this packet is controlled by the @code{set startup-with-shell}
40753 command; @pxref{set startup-with-shell}.
40755 @item QEnvironmentHexEncoded:@var{hex-value}
40756 @anchor{QEnvironmentHexEncoded}
40757 @cindex set environment variable, remote request
40758 @cindex @samp{QEnvironmentHexEncoded} packet
40759 On UNIX-like targets, it is possible to set environment variables that
40760 will be passed to the inferior during the startup process. This
40761 packet is used to inform @command{gdbserver} of an environment
40762 variable that has been defined by the user on @value{GDBN} (@pxref{set
40765 The packet is composed by @var{hex-value}, an hex encoded
40766 representation of the @var{name=value} format representing an
40767 environment variable. The name of the environment variable is
40768 represented by @var{name}, and the value to be assigned to the
40769 environment variable is represented by @var{value}. If the variable
40770 has no value (i.e., the value is @code{null}), then @var{value} will
40773 This packet is only available in extended mode (@pxref{extended
40779 The request succeeded.
40782 This packet is not probed by default; the remote stub must request it,
40783 by supplying an appropriate @samp{qSupported} response
40784 (@pxref{qSupported}). This should only be done on targets that
40785 actually support passing environment variables to the starting
40788 This packet is related to the @code{set environment} command;
40789 @pxref{set environment}.
40791 @item QEnvironmentUnset:@var{hex-value}
40792 @anchor{QEnvironmentUnset}
40793 @cindex unset environment variable, remote request
40794 @cindex @samp{QEnvironmentUnset} packet
40795 On UNIX-like targets, it is possible to unset environment variables
40796 before starting the inferior in the remote target. This packet is
40797 used to inform @command{gdbserver} of an environment variable that has
40798 been unset by the user on @value{GDBN} (@pxref{unset environment}).
40800 The packet is composed by @var{hex-value}, an hex encoded
40801 representation of the name of the environment variable to be unset.
40803 This packet is only available in extended mode (@pxref{extended
40809 The request succeeded.
40812 This packet is not probed by default; the remote stub must request it,
40813 by supplying an appropriate @samp{qSupported} response
40814 (@pxref{qSupported}). This should only be done on targets that
40815 actually support passing environment variables to the starting
40818 This packet is related to the @code{unset environment} command;
40819 @pxref{unset environment}.
40821 @item QEnvironmentReset
40822 @anchor{QEnvironmentReset}
40823 @cindex reset environment, remote request
40824 @cindex @samp{QEnvironmentReset} packet
40825 On UNIX-like targets, this packet is used to reset the state of
40826 environment variables in the remote target before starting the
40827 inferior. In this context, reset means unsetting all environment
40828 variables that were previously set by the user (i.e., were not
40829 initially present in the environment). It is sent to
40830 @command{gdbserver} before the @samp{QEnvironmentHexEncoded}
40831 (@pxref{QEnvironmentHexEncoded}) and the @samp{QEnvironmentUnset}
40832 (@pxref{QEnvironmentUnset}) packets.
40834 This packet is only available in extended mode (@pxref{extended
40840 The request succeeded.
40843 This packet is not probed by default; the remote stub must request it,
40844 by supplying an appropriate @samp{qSupported} response
40845 (@pxref{qSupported}). This should only be done on targets that
40846 actually support passing environment variables to the starting
40849 @item QSetWorkingDir:@r{[}@var{directory}@r{]}
40850 @anchor{QSetWorkingDir packet}
40851 @cindex set working directory, remote request
40852 @cindex @samp{QSetWorkingDir} packet
40853 This packet is used to inform the remote server of the intended
40854 current working directory for programs that are going to be executed.
40856 The packet is composed by @var{directory}, an hex encoded
40857 representation of the directory that the remote inferior will use as
40858 its current working directory. If @var{directory} is an empty string,
40859 the remote server should reset the inferior's current working
40860 directory to its original, empty value.
40862 This packet is only available in extended mode (@pxref{extended
40868 The request succeeded.
40872 @itemx qsThreadInfo
40873 @cindex list active threads, remote request
40874 @cindex @samp{qfThreadInfo} packet
40875 @cindex @samp{qsThreadInfo} packet
40876 Obtain a list of all active thread IDs from the target (OS). Since there
40877 may be too many active threads to fit into one reply packet, this query
40878 works iteratively: it may require more than one query/reply sequence to
40879 obtain the entire list of threads. The first query of the sequence will
40880 be the @samp{qfThreadInfo} query; subsequent queries in the
40881 sequence will be the @samp{qsThreadInfo} query.
40883 NOTE: This packet replaces the @samp{qL} query (see below).
40887 @item m @var{thread-id}
40889 @item m @var{thread-id},@var{thread-id}@dots{}
40890 a comma-separated list of thread IDs
40892 (lower case letter @samp{L}) denotes end of list.
40895 In response to each query, the target will reply with a list of one or
40896 more thread IDs, separated by commas.
40897 @value{GDBN} will respond to each reply with a request for more thread
40898 ids (using the @samp{qs} form of the query), until the target responds
40899 with @samp{l} (lower-case ell, for @dfn{last}).
40900 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
40903 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
40904 initial connection with the remote target, and the very first thread ID
40905 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
40906 message. Therefore, the stub should ensure that the first thread ID in
40907 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
40909 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
40910 @cindex get thread-local storage address, remote request
40911 @cindex @samp{qGetTLSAddr} packet
40912 Fetch the address associated with thread local storage specified
40913 by @var{thread-id}, @var{offset}, and @var{lm}.
40915 @var{thread-id} is the thread ID associated with the
40916 thread for which to fetch the TLS address. @xref{thread-id syntax}.
40918 @var{offset} is the (big endian, hex encoded) offset associated with the
40919 thread local variable. (This offset is obtained from the debug
40920 information associated with the variable.)
40922 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
40923 load module associated with the thread local storage. For example,
40924 a @sc{gnu}/Linux system will pass the link map address of the shared
40925 object associated with the thread local storage under consideration.
40926 Other operating environments may choose to represent the load module
40927 differently, so the precise meaning of this parameter will vary.
40931 @item @var{XX}@dots{}
40932 Hex encoded (big endian) bytes representing the address of the thread
40933 local storage requested.
40936 An error occurred. The error number @var{nn} is given as hex digits.
40939 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
40942 @item qGetTIBAddr:@var{thread-id}
40943 @cindex get thread information block address
40944 @cindex @samp{qGetTIBAddr} packet
40945 Fetch address of the Windows OS specific Thread Information Block.
40947 @var{thread-id} is the thread ID associated with the thread.
40951 @item @var{XX}@dots{}
40952 Hex encoded (big endian) bytes representing the linear address of the
40953 thread information block.
40956 An error occured. This means that either the thread was not found, or the
40957 address could not be retrieved.
40960 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
40963 @item qL @var{startflag} @var{threadcount} @var{nextthread}
40964 Obtain thread information from RTOS. Where: @var{startflag} (one hex
40965 digit) is one to indicate the first query and zero to indicate a
40966 subsequent query; @var{threadcount} (two hex digits) is the maximum
40967 number of threads the response packet can contain; and @var{nextthread}
40968 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
40969 returned in the response as @var{argthread}.
40971 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
40975 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
40976 Where: @var{count} (two hex digits) is the number of threads being
40977 returned; @var{done} (one hex digit) is zero to indicate more threads
40978 and one indicates no further threads; @var{argthreadid} (eight hex
40979 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
40980 is a sequence of thread IDs, @var{threadid} (eight hex
40981 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
40985 @cindex section offsets, remote request
40986 @cindex @samp{qOffsets} packet
40987 Get section offsets that the target used when relocating the downloaded
40992 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
40993 Relocate the @code{Text} section by @var{xxx} from its original address.
40994 Relocate the @code{Data} section by @var{yyy} from its original address.
40995 If the object file format provides segment information (e.g.@: @sc{elf}
40996 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
40997 segments by the supplied offsets.
40999 @emph{Note: while a @code{Bss} offset may be included in the response,
41000 @value{GDBN} ignores this and instead applies the @code{Data} offset
41001 to the @code{Bss} section.}
41003 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
41004 Relocate the first segment of the object file, which conventionally
41005 contains program code, to a starting address of @var{xxx}. If
41006 @samp{DataSeg} is specified, relocate the second segment, which
41007 conventionally contains modifiable data, to a starting address of
41008 @var{yyy}. @value{GDBN} will report an error if the object file
41009 does not contain segment information, or does not contain at least
41010 as many segments as mentioned in the reply. Extra segments are
41011 kept at fixed offsets relative to the last relocated segment.
41014 @item qP @var{mode} @var{thread-id}
41015 @cindex thread information, remote request
41016 @cindex @samp{qP} packet
41017 Returns information on @var{thread-id}. Where: @var{mode} is a hex
41018 encoded 32 bit mode; @var{thread-id} is a thread ID
41019 (@pxref{thread-id syntax}).
41021 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
41024 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
41028 @cindex non-stop mode, remote request
41029 @cindex @samp{QNonStop} packet
41031 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
41032 @xref{Remote Non-Stop}, for more information.
41037 The request succeeded.
41040 An error occurred. The error number @var{nn} is given as hex digits.
41043 An empty reply indicates that @samp{QNonStop} is not supported by
41047 This packet is not probed by default; the remote stub must request it,
41048 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
41049 Use of this packet is controlled by the @code{set non-stop} command;
41050 @pxref{Non-Stop Mode}.
41052 @item QCatchSyscalls:1 @r{[};@var{sysno}@r{]}@dots{}
41053 @itemx QCatchSyscalls:0
41054 @cindex catch syscalls from inferior, remote request
41055 @cindex @samp{QCatchSyscalls} packet
41056 @anchor{QCatchSyscalls}
41057 Enable (@samp{QCatchSyscalls:1}) or disable (@samp{QCatchSyscalls:0})
41058 catching syscalls from the inferior process.
41060 For @samp{QCatchSyscalls:1}, each listed syscall @var{sysno} (encoded
41061 in hex) should be reported to @value{GDBN}. If no syscall @var{sysno}
41062 is listed, every system call should be reported.
41064 Note that if a syscall not in the list is reported, @value{GDBN} will
41065 still filter the event according to its own list from all corresponding
41066 @code{catch syscall} commands. However, it is more efficient to only
41067 report the requested syscalls.
41069 Multiple @samp{QCatchSyscalls:1} packets do not combine; any earlier
41070 @samp{QCatchSyscalls:1} list is completely replaced by the new list.
41072 If the inferior process execs, the state of @samp{QCatchSyscalls} is
41073 kept for the new process too. On targets where exec may affect syscall
41074 numbers, for example with exec between 32 and 64-bit processes, the
41075 client should send a new packet with the new syscall list.
41080 The request succeeded.
41083 An error occurred. @var{nn} are hex digits.
41086 An empty reply indicates that @samp{QCatchSyscalls} is not supported by
41090 Use of this packet is controlled by the @code{set remote catch-syscalls}
41091 command (@pxref{Remote Configuration, set remote catch-syscalls}).
41092 This packet is not probed by default; the remote stub must request it,
41093 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
41095 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
41096 @cindex pass signals to inferior, remote request
41097 @cindex @samp{QPassSignals} packet
41098 @anchor{QPassSignals}
41099 Each listed @var{signal} should be passed directly to the inferior process.
41100 Signals are numbered identically to continue packets and stop replies
41101 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
41102 strictly greater than the previous item. These signals do not need to stop
41103 the inferior, or be reported to @value{GDBN}. All other signals should be
41104 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
41105 combine; any earlier @samp{QPassSignals} list is completely replaced by the
41106 new list. This packet improves performance when using @samp{handle
41107 @var{signal} nostop noprint pass}.
41112 The request succeeded.
41115 An error occurred. The error number @var{nn} is given as hex digits.
41118 An empty reply indicates that @samp{QPassSignals} is not supported by
41122 Use of this packet is controlled by the @code{set remote pass-signals}
41123 command (@pxref{Remote Configuration, set remote pass-signals}).
41124 This packet is not probed by default; the remote stub must request it,
41125 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
41127 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
41128 @cindex signals the inferior may see, remote request
41129 @cindex @samp{QProgramSignals} packet
41130 @anchor{QProgramSignals}
41131 Each listed @var{signal} may be delivered to the inferior process.
41132 Others should be silently discarded.
41134 In some cases, the remote stub may need to decide whether to deliver a
41135 signal to the program or not without @value{GDBN} involvement. One
41136 example of that is while detaching --- the program's threads may have
41137 stopped for signals that haven't yet had a chance of being reported to
41138 @value{GDBN}, and so the remote stub can use the signal list specified
41139 by this packet to know whether to deliver or ignore those pending
41142 This does not influence whether to deliver a signal as requested by a
41143 resumption packet (@pxref{vCont packet}).
41145 Signals are numbered identically to continue packets and stop replies
41146 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
41147 strictly greater than the previous item. Multiple
41148 @samp{QProgramSignals} packets do not combine; any earlier
41149 @samp{QProgramSignals} list is completely replaced by the new list.
41154 The request succeeded.
41157 An error occurred. The error number @var{nn} is given as hex digits.
41160 An empty reply indicates that @samp{QProgramSignals} is not supported
41164 Use of this packet is controlled by the @code{set remote program-signals}
41165 command (@pxref{Remote Configuration, set remote program-signals}).
41166 This packet is not probed by default; the remote stub must request it,
41167 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
41169 @anchor{QThreadEvents}
41170 @item QThreadEvents:1
41171 @itemx QThreadEvents:0
41172 @cindex thread create/exit events, remote request
41173 @cindex @samp{QThreadEvents} packet
41175 Enable (@samp{QThreadEvents:1}) or disable (@samp{QThreadEvents:0})
41176 reporting of thread create and exit events. @xref{thread create
41177 event}, for the reply specifications. For example, this is used in
41178 non-stop mode when @value{GDBN} stops a set of threads and
41179 synchronously waits for the their corresponding stop replies. Without
41180 exit events, if one of the threads exits, @value{GDBN} would hang
41181 forever not knowing that it should no longer expect a stop for that
41182 same thread. @value{GDBN} does not enable this feature unless the
41183 stub reports that it supports it by including @samp{QThreadEvents+} in
41184 its @samp{qSupported} reply.
41189 The request succeeded.
41192 An error occurred. The error number @var{nn} is given as hex digits.
41195 An empty reply indicates that @samp{QThreadEvents} is not supported by
41199 Use of this packet is controlled by the @code{set remote thread-events}
41200 command (@pxref{Remote Configuration, set remote thread-events}).
41202 @item qRcmd,@var{command}
41203 @cindex execute remote command, remote request
41204 @cindex @samp{qRcmd} packet
41205 @var{command} (hex encoded) is passed to the local interpreter for
41206 execution. Invalid commands should be reported using the output
41207 string. Before the final result packet, the target may also respond
41208 with a number of intermediate @samp{O@var{output}} console output
41209 packets. @emph{Implementors should note that providing access to a
41210 stubs's interpreter may have security implications}.
41215 A command response with no output.
41217 A command response with the hex encoded output string @var{OUTPUT}.
41219 Indicate a badly formed request.
41221 An empty reply indicates that @samp{qRcmd} is not recognized.
41224 (Note that the @code{qRcmd} packet's name is separated from the
41225 command by a @samp{,}, not a @samp{:}, contrary to the naming
41226 conventions above. Please don't use this packet as a model for new
41229 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
41230 @cindex searching memory, in remote debugging
41232 @cindex @samp{qSearch:memory} packet
41234 @cindex @samp{qSearch memory} packet
41235 @anchor{qSearch memory}
41236 Search @var{length} bytes at @var{address} for @var{search-pattern}.
41237 Both @var{address} and @var{length} are encoded in hex;
41238 @var{search-pattern} is a sequence of bytes, also hex encoded.
41243 The pattern was not found.
41245 The pattern was found at @var{address}.
41247 A badly formed request or an error was encountered while searching memory.
41249 An empty reply indicates that @samp{qSearch:memory} is not recognized.
41252 @item QStartNoAckMode
41253 @cindex @samp{QStartNoAckMode} packet
41254 @anchor{QStartNoAckMode}
41255 Request that the remote stub disable the normal @samp{+}/@samp{-}
41256 protocol acknowledgments (@pxref{Packet Acknowledgment}).
41261 The stub has switched to no-acknowledgment mode.
41262 @value{GDBN} acknowledges this response,
41263 but neither the stub nor @value{GDBN} shall send or expect further
41264 @samp{+}/@samp{-} acknowledgments in the current connection.
41266 An empty reply indicates that the stub does not support no-acknowledgment mode.
41269 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
41270 @cindex supported packets, remote query
41271 @cindex features of the remote protocol
41272 @cindex @samp{qSupported} packet
41273 @anchor{qSupported}
41274 Tell the remote stub about features supported by @value{GDBN}, and
41275 query the stub for features it supports. This packet allows
41276 @value{GDBN} and the remote stub to take advantage of each others'
41277 features. @samp{qSupported} also consolidates multiple feature probes
41278 at startup, to improve @value{GDBN} performance---a single larger
41279 packet performs better than multiple smaller probe packets on
41280 high-latency links. Some features may enable behavior which must not
41281 be on by default, e.g.@: because it would confuse older clients or
41282 stubs. Other features may describe packets which could be
41283 automatically probed for, but are not. These features must be
41284 reported before @value{GDBN} will use them. This ``default
41285 unsupported'' behavior is not appropriate for all packets, but it
41286 helps to keep the initial connection time under control with new
41287 versions of @value{GDBN} which support increasing numbers of packets.
41291 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
41292 The stub supports or does not support each returned @var{stubfeature},
41293 depending on the form of each @var{stubfeature} (see below for the
41296 An empty reply indicates that @samp{qSupported} is not recognized,
41297 or that no features needed to be reported to @value{GDBN}.
41300 The allowed forms for each feature (either a @var{gdbfeature} in the
41301 @samp{qSupported} packet, or a @var{stubfeature} in the response)
41305 @item @var{name}=@var{value}
41306 The remote protocol feature @var{name} is supported, and associated
41307 with the specified @var{value}. The format of @var{value} depends
41308 on the feature, but it must not include a semicolon.
41310 The remote protocol feature @var{name} is supported, and does not
41311 need an associated value.
41313 The remote protocol feature @var{name} is not supported.
41315 The remote protocol feature @var{name} may be supported, and
41316 @value{GDBN} should auto-detect support in some other way when it is
41317 needed. This form will not be used for @var{gdbfeature} notifications,
41318 but may be used for @var{stubfeature} responses.
41321 Whenever the stub receives a @samp{qSupported} request, the
41322 supplied set of @value{GDBN} features should override any previous
41323 request. This allows @value{GDBN} to put the stub in a known
41324 state, even if the stub had previously been communicating with
41325 a different version of @value{GDBN}.
41327 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
41332 This feature indicates whether @value{GDBN} supports multiprocess
41333 extensions to the remote protocol. @value{GDBN} does not use such
41334 extensions unless the stub also reports that it supports them by
41335 including @samp{multiprocess+} in its @samp{qSupported} reply.
41336 @xref{multiprocess extensions}, for details.
41339 This feature indicates that @value{GDBN} supports the XML target
41340 description. If the stub sees @samp{xmlRegisters=} with target
41341 specific strings separated by a comma, it will report register
41345 This feature indicates whether @value{GDBN} supports the
41346 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
41347 instruction reply packet}).
41350 This feature indicates whether @value{GDBN} supports the swbreak stop
41351 reason in stop replies. @xref{swbreak stop reason}, for details.
41354 This feature indicates whether @value{GDBN} supports the hwbreak stop
41355 reason in stop replies. @xref{swbreak stop reason}, for details.
41358 This feature indicates whether @value{GDBN} supports fork event
41359 extensions to the remote protocol. @value{GDBN} does not use such
41360 extensions unless the stub also reports that it supports them by
41361 including @samp{fork-events+} in its @samp{qSupported} reply.
41364 This feature indicates whether @value{GDBN} supports vfork event
41365 extensions to the remote protocol. @value{GDBN} does not use such
41366 extensions unless the stub also reports that it supports them by
41367 including @samp{vfork-events+} in its @samp{qSupported} reply.
41370 This feature indicates whether @value{GDBN} supports exec event
41371 extensions to the remote protocol. @value{GDBN} does not use such
41372 extensions unless the stub also reports that it supports them by
41373 including @samp{exec-events+} in its @samp{qSupported} reply.
41375 @item vContSupported
41376 This feature indicates whether @value{GDBN} wants to know the
41377 supported actions in the reply to @samp{vCont?} packet.
41380 Stubs should ignore any unknown values for
41381 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
41382 packet supports receiving packets of unlimited length (earlier
41383 versions of @value{GDBN} may reject overly long responses). Additional values
41384 for @var{gdbfeature} may be defined in the future to let the stub take
41385 advantage of new features in @value{GDBN}, e.g.@: incompatible
41386 improvements in the remote protocol---the @samp{multiprocess} feature is
41387 an example of such a feature. The stub's reply should be independent
41388 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
41389 describes all the features it supports, and then the stub replies with
41390 all the features it supports.
41392 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
41393 responses, as long as each response uses one of the standard forms.
41395 Some features are flags. A stub which supports a flag feature
41396 should respond with a @samp{+} form response. Other features
41397 require values, and the stub should respond with an @samp{=}
41400 Each feature has a default value, which @value{GDBN} will use if
41401 @samp{qSupported} is not available or if the feature is not mentioned
41402 in the @samp{qSupported} response. The default values are fixed; a
41403 stub is free to omit any feature responses that match the defaults.
41405 Not all features can be probed, but for those which can, the probing
41406 mechanism is useful: in some cases, a stub's internal
41407 architecture may not allow the protocol layer to know some information
41408 about the underlying target in advance. This is especially common in
41409 stubs which may be configured for multiple targets.
41411 These are the currently defined stub features and their properties:
41413 @multitable @columnfractions 0.35 0.2 0.12 0.2
41414 @c NOTE: The first row should be @headitem, but we do not yet require
41415 @c a new enough version of Texinfo (4.7) to use @headitem.
41417 @tab Value Required
41421 @item @samp{PacketSize}
41426 @item @samp{qXfer:auxv:read}
41431 @item @samp{qXfer:btrace:read}
41436 @item @samp{qXfer:btrace-conf:read}
41441 @item @samp{qXfer:exec-file:read}
41446 @item @samp{qXfer:features:read}
41451 @item @samp{qXfer:libraries:read}
41456 @item @samp{qXfer:libraries-svr4:read}
41461 @item @samp{augmented-libraries-svr4-read}
41466 @item @samp{qXfer:memory-map:read}
41471 @item @samp{qXfer:sdata:read}
41476 @item @samp{qXfer:siginfo:read}
41481 @item @samp{qXfer:siginfo:write}
41486 @item @samp{qXfer:threads:read}
41491 @item @samp{qXfer:traceframe-info:read}
41496 @item @samp{qXfer:uib:read}
41501 @item @samp{qXfer:fdpic:read}
41506 @item @samp{Qbtrace:off}
41511 @item @samp{Qbtrace:bts}
41516 @item @samp{Qbtrace:pt}
41521 @item @samp{Qbtrace-conf:bts:size}
41526 @item @samp{Qbtrace-conf:pt:size}
41531 @item @samp{QNonStop}
41536 @item @samp{QCatchSyscalls}
41541 @item @samp{QPassSignals}
41546 @item @samp{QStartNoAckMode}
41551 @item @samp{multiprocess}
41556 @item @samp{ConditionalBreakpoints}
41561 @item @samp{ConditionalTracepoints}
41566 @item @samp{ReverseContinue}
41571 @item @samp{ReverseStep}
41576 @item @samp{TracepointSource}
41581 @item @samp{QAgent}
41586 @item @samp{QAllow}
41591 @item @samp{QDisableRandomization}
41596 @item @samp{EnableDisableTracepoints}
41601 @item @samp{QTBuffer:size}
41606 @item @samp{tracenz}
41611 @item @samp{BreakpointCommands}
41616 @item @samp{swbreak}
41621 @item @samp{hwbreak}
41626 @item @samp{fork-events}
41631 @item @samp{vfork-events}
41636 @item @samp{exec-events}
41641 @item @samp{QThreadEvents}
41646 @item @samp{no-resumed}
41653 These are the currently defined stub features, in more detail:
41656 @cindex packet size, remote protocol
41657 @item PacketSize=@var{bytes}
41658 The remote stub can accept packets up to at least @var{bytes} in
41659 length. @value{GDBN} will send packets up to this size for bulk
41660 transfers, and will never send larger packets. This is a limit on the
41661 data characters in the packet, including the frame and checksum.
41662 There is no trailing NUL byte in a remote protocol packet; if the stub
41663 stores packets in a NUL-terminated format, it should allow an extra
41664 byte in its buffer for the NUL. If this stub feature is not supported,
41665 @value{GDBN} guesses based on the size of the @samp{g} packet response.
41667 @item qXfer:auxv:read
41668 The remote stub understands the @samp{qXfer:auxv:read} packet
41669 (@pxref{qXfer auxiliary vector read}).
41671 @item qXfer:btrace:read
41672 The remote stub understands the @samp{qXfer:btrace:read}
41673 packet (@pxref{qXfer btrace read}).
41675 @item qXfer:btrace-conf:read
41676 The remote stub understands the @samp{qXfer:btrace-conf:read}
41677 packet (@pxref{qXfer btrace-conf read}).
41679 @item qXfer:exec-file:read
41680 The remote stub understands the @samp{qXfer:exec-file:read} packet
41681 (@pxref{qXfer executable filename read}).
41683 @item qXfer:features:read
41684 The remote stub understands the @samp{qXfer:features:read} packet
41685 (@pxref{qXfer target description read}).
41687 @item qXfer:libraries:read
41688 The remote stub understands the @samp{qXfer:libraries:read} packet
41689 (@pxref{qXfer library list read}).
41691 @item qXfer:libraries-svr4:read
41692 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
41693 (@pxref{qXfer svr4 library list read}).
41695 @item augmented-libraries-svr4-read
41696 The remote stub understands the augmented form of the
41697 @samp{qXfer:libraries-svr4:read} packet
41698 (@pxref{qXfer svr4 library list read}).
41700 @item qXfer:memory-map:read
41701 The remote stub understands the @samp{qXfer:memory-map:read} packet
41702 (@pxref{qXfer memory map read}).
41704 @item qXfer:sdata:read
41705 The remote stub understands the @samp{qXfer:sdata:read} packet
41706 (@pxref{qXfer sdata read}).
41708 @item qXfer:siginfo:read
41709 The remote stub understands the @samp{qXfer:siginfo:read} packet
41710 (@pxref{qXfer siginfo read}).
41712 @item qXfer:siginfo:write
41713 The remote stub understands the @samp{qXfer:siginfo:write} packet
41714 (@pxref{qXfer siginfo write}).
41716 @item qXfer:threads:read
41717 The remote stub understands the @samp{qXfer:threads:read} packet
41718 (@pxref{qXfer threads read}).
41720 @item qXfer:traceframe-info:read
41721 The remote stub understands the @samp{qXfer:traceframe-info:read}
41722 packet (@pxref{qXfer traceframe info read}).
41724 @item qXfer:uib:read
41725 The remote stub understands the @samp{qXfer:uib:read}
41726 packet (@pxref{qXfer unwind info block}).
41728 @item qXfer:fdpic:read
41729 The remote stub understands the @samp{qXfer:fdpic:read}
41730 packet (@pxref{qXfer fdpic loadmap read}).
41733 The remote stub understands the @samp{QNonStop} packet
41734 (@pxref{QNonStop}).
41736 @item QCatchSyscalls
41737 The remote stub understands the @samp{QCatchSyscalls} packet
41738 (@pxref{QCatchSyscalls}).
41741 The remote stub understands the @samp{QPassSignals} packet
41742 (@pxref{QPassSignals}).
41744 @item QStartNoAckMode
41745 The remote stub understands the @samp{QStartNoAckMode} packet and
41746 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
41749 @anchor{multiprocess extensions}
41750 @cindex multiprocess extensions, in remote protocol
41751 The remote stub understands the multiprocess extensions to the remote
41752 protocol syntax. The multiprocess extensions affect the syntax of
41753 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
41754 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
41755 replies. Note that reporting this feature indicates support for the
41756 syntactic extensions only, not that the stub necessarily supports
41757 debugging of more than one process at a time. The stub must not use
41758 multiprocess extensions in packet replies unless @value{GDBN} has also
41759 indicated it supports them in its @samp{qSupported} request.
41761 @item qXfer:osdata:read
41762 The remote stub understands the @samp{qXfer:osdata:read} packet
41763 ((@pxref{qXfer osdata read}).
41765 @item ConditionalBreakpoints
41766 The target accepts and implements evaluation of conditional expressions
41767 defined for breakpoints. The target will only report breakpoint triggers
41768 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
41770 @item ConditionalTracepoints
41771 The remote stub accepts and implements conditional expressions defined
41772 for tracepoints (@pxref{Tracepoint Conditions}).
41774 @item ReverseContinue
41775 The remote stub accepts and implements the reverse continue packet
41779 The remote stub accepts and implements the reverse step packet
41782 @item TracepointSource
41783 The remote stub understands the @samp{QTDPsrc} packet that supplies
41784 the source form of tracepoint definitions.
41787 The remote stub understands the @samp{QAgent} packet.
41790 The remote stub understands the @samp{QAllow} packet.
41792 @item QDisableRandomization
41793 The remote stub understands the @samp{QDisableRandomization} packet.
41795 @item StaticTracepoint
41796 @cindex static tracepoints, in remote protocol
41797 The remote stub supports static tracepoints.
41799 @item InstallInTrace
41800 @anchor{install tracepoint in tracing}
41801 The remote stub supports installing tracepoint in tracing.
41803 @item EnableDisableTracepoints
41804 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
41805 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
41806 to be enabled and disabled while a trace experiment is running.
41808 @item QTBuffer:size
41809 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
41810 packet that allows to change the size of the trace buffer.
41813 @cindex string tracing, in remote protocol
41814 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
41815 See @ref{Bytecode Descriptions} for details about the bytecode.
41817 @item BreakpointCommands
41818 @cindex breakpoint commands, in remote protocol
41819 The remote stub supports running a breakpoint's command list itself,
41820 rather than reporting the hit to @value{GDBN}.
41823 The remote stub understands the @samp{Qbtrace:off} packet.
41826 The remote stub understands the @samp{Qbtrace:bts} packet.
41829 The remote stub understands the @samp{Qbtrace:pt} packet.
41831 @item Qbtrace-conf:bts:size
41832 The remote stub understands the @samp{Qbtrace-conf:bts:size} packet.
41834 @item Qbtrace-conf:pt:size
41835 The remote stub understands the @samp{Qbtrace-conf:pt:size} packet.
41838 The remote stub reports the @samp{swbreak} stop reason for memory
41842 The remote stub reports the @samp{hwbreak} stop reason for hardware
41846 The remote stub reports the @samp{fork} stop reason for fork events.
41849 The remote stub reports the @samp{vfork} stop reason for vfork events
41850 and vforkdone events.
41853 The remote stub reports the @samp{exec} stop reason for exec events.
41855 @item vContSupported
41856 The remote stub reports the supported actions in the reply to
41857 @samp{vCont?} packet.
41859 @item QThreadEvents
41860 The remote stub understands the @samp{QThreadEvents} packet.
41863 The remote stub reports the @samp{N} stop reply.
41868 @cindex symbol lookup, remote request
41869 @cindex @samp{qSymbol} packet
41870 Notify the target that @value{GDBN} is prepared to serve symbol lookup
41871 requests. Accept requests from the target for the values of symbols.
41876 The target does not need to look up any (more) symbols.
41877 @item qSymbol:@var{sym_name}
41878 The target requests the value of symbol @var{sym_name} (hex encoded).
41879 @value{GDBN} may provide the value by using the
41880 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
41884 @item qSymbol:@var{sym_value}:@var{sym_name}
41885 Set the value of @var{sym_name} to @var{sym_value}.
41887 @var{sym_name} (hex encoded) is the name of a symbol whose value the
41888 target has previously requested.
41890 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
41891 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
41897 The target does not need to look up any (more) symbols.
41898 @item qSymbol:@var{sym_name}
41899 The target requests the value of a new symbol @var{sym_name} (hex
41900 encoded). @value{GDBN} will continue to supply the values of symbols
41901 (if available), until the target ceases to request them.
41906 @itemx QTDisconnected
41913 @itemx qTMinFTPILen
41915 @xref{Tracepoint Packets}.
41917 @item qThreadExtraInfo,@var{thread-id}
41918 @cindex thread attributes info, remote request
41919 @cindex @samp{qThreadExtraInfo} packet
41920 Obtain from the target OS a printable string description of thread
41921 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
41922 for the forms of @var{thread-id}. This
41923 string may contain anything that the target OS thinks is interesting
41924 for @value{GDBN} to tell the user about the thread. The string is
41925 displayed in @value{GDBN}'s @code{info threads} display. Some
41926 examples of possible thread extra info strings are @samp{Runnable}, or
41927 @samp{Blocked on Mutex}.
41931 @item @var{XX}@dots{}
41932 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
41933 comprising the printable string containing the extra information about
41934 the thread's attributes.
41937 (Note that the @code{qThreadExtraInfo} packet's name is separated from
41938 the command by a @samp{,}, not a @samp{:}, contrary to the naming
41939 conventions above. Please don't use this packet as a model for new
41958 @xref{Tracepoint Packets}.
41960 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
41961 @cindex read special object, remote request
41962 @cindex @samp{qXfer} packet
41963 @anchor{qXfer read}
41964 Read uninterpreted bytes from the target's special data area
41965 identified by the keyword @var{object}. Request @var{length} bytes
41966 starting at @var{offset} bytes into the data. The content and
41967 encoding of @var{annex} is specific to @var{object}; it can supply
41968 additional details about what data to access.
41973 Data @var{data} (@pxref{Binary Data}) has been read from the
41974 target. There may be more data at a higher address (although
41975 it is permitted to return @samp{m} even for the last valid
41976 block of data, as long as at least one byte of data was read).
41977 It is possible for @var{data} to have fewer bytes than the @var{length} in the
41981 Data @var{data} (@pxref{Binary Data}) has been read from the target.
41982 There is no more data to be read. It is possible for @var{data} to
41983 have fewer bytes than the @var{length} in the request.
41986 The @var{offset} in the request is at the end of the data.
41987 There is no more data to be read.
41990 The request was malformed, or @var{annex} was invalid.
41993 The offset was invalid, or there was an error encountered reading the data.
41994 The @var{nn} part is a hex-encoded @code{errno} value.
41997 An empty reply indicates the @var{object} string was not recognized by
41998 the stub, or that the object does not support reading.
42001 Here are the specific requests of this form defined so far. All the
42002 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
42003 formats, listed above.
42006 @item qXfer:auxv:read::@var{offset},@var{length}
42007 @anchor{qXfer auxiliary vector read}
42008 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
42009 auxiliary vector}. Note @var{annex} must be empty.
42011 This packet is not probed by default; the remote stub must request it,
42012 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42014 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
42015 @anchor{qXfer btrace read}
42017 Return a description of the current branch trace.
42018 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
42019 packet may have one of the following values:
42023 Returns all available branch trace.
42026 Returns all available branch trace if the branch trace changed since
42027 the last read request.
42030 Returns the new branch trace since the last read request. Adds a new
42031 block to the end of the trace that begins at zero and ends at the source
42032 location of the first branch in the trace buffer. This extra block is
42033 used to stitch traces together.
42035 If the trace buffer overflowed, returns an error indicating the overflow.
42038 This packet is not probed by default; the remote stub must request it
42039 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42041 @item qXfer:btrace-conf:read::@var{offset},@var{length}
42042 @anchor{qXfer btrace-conf read}
42044 Return a description of the current branch trace configuration.
42045 @xref{Branch Trace Configuration Format}.
42047 This packet is not probed by default; the remote stub must request it
42048 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42050 @item qXfer:exec-file:read:@var{annex}:@var{offset},@var{length}
42051 @anchor{qXfer executable filename read}
42052 Return the full absolute name of the file that was executed to create
42053 a process running on the remote system. The annex specifies the
42054 numeric process ID of the process to query, encoded as a hexadecimal
42055 number. If the annex part is empty the remote stub should return the
42056 filename corresponding to the currently executing process.
42058 This packet is not probed by default; the remote stub must request it,
42059 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42061 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
42062 @anchor{qXfer target description read}
42063 Access the @dfn{target description}. @xref{Target Descriptions}. The
42064 annex specifies which XML document to access. The main description is
42065 always loaded from the @samp{target.xml} annex.
42067 This packet is not probed by default; the remote stub must request it,
42068 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42070 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
42071 @anchor{qXfer library list read}
42072 Access the target's list of loaded libraries. @xref{Library List Format}.
42073 The annex part of the generic @samp{qXfer} packet must be empty
42074 (@pxref{qXfer read}).
42076 Targets which maintain a list of libraries in the program's memory do
42077 not need to implement this packet; it is designed for platforms where
42078 the operating system manages the list of loaded libraries.
42080 This packet is not probed by default; the remote stub must request it,
42081 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42083 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
42084 @anchor{qXfer svr4 library list read}
42085 Access the target's list of loaded libraries when the target is an SVR4
42086 platform. @xref{Library List Format for SVR4 Targets}. The annex part
42087 of the generic @samp{qXfer} packet must be empty unless the remote
42088 stub indicated it supports the augmented form of this packet
42089 by supplying an appropriate @samp{qSupported} response
42090 (@pxref{qXfer read}, @ref{qSupported}).
42092 This packet is optional for better performance on SVR4 targets.
42093 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
42095 This packet is not probed by default; the remote stub must request it,
42096 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42098 If the remote stub indicates it supports the augmented form of this
42099 packet then the annex part of the generic @samp{qXfer} packet may
42100 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
42101 arguments. The currently supported arguments are:
42104 @item start=@var{address}
42105 A hexadecimal number specifying the address of the @samp{struct
42106 link_map} to start reading the library list from. If unset or zero
42107 then the first @samp{struct link_map} in the library list will be
42108 chosen as the starting point.
42110 @item prev=@var{address}
42111 A hexadecimal number specifying the address of the @samp{struct
42112 link_map} immediately preceding the @samp{struct link_map}
42113 specified by the @samp{start} argument. If unset or zero then
42114 the remote stub will expect that no @samp{struct link_map}
42115 exists prior to the starting point.
42119 Arguments that are not understood by the remote stub will be silently
42122 @item qXfer:memory-map:read::@var{offset},@var{length}
42123 @anchor{qXfer memory map read}
42124 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
42125 annex part of the generic @samp{qXfer} packet must be empty
42126 (@pxref{qXfer read}).
42128 This packet is not probed by default; the remote stub must request it,
42129 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42131 @item qXfer:sdata:read::@var{offset},@var{length}
42132 @anchor{qXfer sdata read}
42134 Read contents of the extra collected static tracepoint marker
42135 information. The annex part of the generic @samp{qXfer} packet must
42136 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
42139 This packet is not probed by default; the remote stub must request it,
42140 by supplying an appropriate @samp{qSupported} response
42141 (@pxref{qSupported}).
42143 @item qXfer:siginfo:read::@var{offset},@var{length}
42144 @anchor{qXfer siginfo read}
42145 Read contents of the extra signal information on the target
42146 system. The annex part of the generic @samp{qXfer} packet must be
42147 empty (@pxref{qXfer read}).
42149 This packet is not probed by default; the remote stub must request it,
42150 by supplying an appropriate @samp{qSupported} response
42151 (@pxref{qSupported}).
42153 @item qXfer:threads:read::@var{offset},@var{length}
42154 @anchor{qXfer threads read}
42155 Access the list of threads on target. @xref{Thread List Format}. The
42156 annex part of the generic @samp{qXfer} packet must be empty
42157 (@pxref{qXfer read}).
42159 This packet is not probed by default; the remote stub must request it,
42160 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42162 @item qXfer:traceframe-info:read::@var{offset},@var{length}
42163 @anchor{qXfer traceframe info read}
42165 Return a description of the current traceframe's contents.
42166 @xref{Traceframe Info Format}. The annex part of the generic
42167 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
42169 This packet is not probed by default; the remote stub must request it,
42170 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42172 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
42173 @anchor{qXfer unwind info block}
42175 Return the unwind information block for @var{pc}. This packet is used
42176 on OpenVMS/ia64 to ask the kernel unwind information.
42178 This packet is not probed by default.
42180 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
42181 @anchor{qXfer fdpic loadmap read}
42182 Read contents of @code{loadmap}s on the target system. The
42183 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
42184 executable @code{loadmap} or interpreter @code{loadmap} to read.
42186 This packet is not probed by default; the remote stub must request it,
42187 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42189 @item qXfer:osdata:read::@var{offset},@var{length}
42190 @anchor{qXfer osdata read}
42191 Access the target's @dfn{operating system information}.
42192 @xref{Operating System Information}.
42196 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
42197 @cindex write data into object, remote request
42198 @anchor{qXfer write}
42199 Write uninterpreted bytes into the target's special data area
42200 identified by the keyword @var{object}, starting at @var{offset} bytes
42201 into the data. The binary-encoded data (@pxref{Binary Data}) to be
42202 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
42203 is specific to @var{object}; it can supply additional details about what data
42209 @var{nn} (hex encoded) is the number of bytes written.
42210 This may be fewer bytes than supplied in the request.
42213 The request was malformed, or @var{annex} was invalid.
42216 The offset was invalid, or there was an error encountered writing the data.
42217 The @var{nn} part is a hex-encoded @code{errno} value.
42220 An empty reply indicates the @var{object} string was not
42221 recognized by the stub, or that the object does not support writing.
42224 Here are the specific requests of this form defined so far. All the
42225 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
42226 formats, listed above.
42229 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
42230 @anchor{qXfer siginfo write}
42231 Write @var{data} to the extra signal information on the target system.
42232 The annex part of the generic @samp{qXfer} packet must be
42233 empty (@pxref{qXfer write}).
42235 This packet is not probed by default; the remote stub must request it,
42236 by supplying an appropriate @samp{qSupported} response
42237 (@pxref{qSupported}).
42240 @item qXfer:@var{object}:@var{operation}:@dots{}
42241 Requests of this form may be added in the future. When a stub does
42242 not recognize the @var{object} keyword, or its support for
42243 @var{object} does not recognize the @var{operation} keyword, the stub
42244 must respond with an empty packet.
42246 @item qAttached:@var{pid}
42247 @cindex query attached, remote request
42248 @cindex @samp{qAttached} packet
42249 Return an indication of whether the remote server attached to an
42250 existing process or created a new process. When the multiprocess
42251 protocol extensions are supported (@pxref{multiprocess extensions}),
42252 @var{pid} is an integer in hexadecimal format identifying the target
42253 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
42254 the query packet will be simplified as @samp{qAttached}.
42256 This query is used, for example, to know whether the remote process
42257 should be detached or killed when a @value{GDBN} session is ended with
42258 the @code{quit} command.
42263 The remote server attached to an existing process.
42265 The remote server created a new process.
42267 A badly formed request or an error was encountered.
42271 Enable branch tracing for the current thread using Branch Trace Store.
42276 Branch tracing has been enabled.
42278 A badly formed request or an error was encountered.
42282 Enable branch tracing for the current thread using Intel Processor Trace.
42287 Branch tracing has been enabled.
42289 A badly formed request or an error was encountered.
42293 Disable branch tracing for the current thread.
42298 Branch tracing has been disabled.
42300 A badly formed request or an error was encountered.
42303 @item Qbtrace-conf:bts:size=@var{value}
42304 Set the requested ring buffer size for new threads that use the
42305 btrace recording method in bts format.
42310 The ring buffer size has been set.
42312 A badly formed request or an error was encountered.
42315 @item Qbtrace-conf:pt:size=@var{value}
42316 Set the requested ring buffer size for new threads that use the
42317 btrace recording method in pt format.
42322 The ring buffer size has been set.
42324 A badly formed request or an error was encountered.
42329 @node Architecture-Specific Protocol Details
42330 @section Architecture-Specific Protocol Details
42332 This section describes how the remote protocol is applied to specific
42333 target architectures. Also see @ref{Standard Target Features}, for
42334 details of XML target descriptions for each architecture.
42337 * ARM-Specific Protocol Details::
42338 * MIPS-Specific Protocol Details::
42341 @node ARM-Specific Protocol Details
42342 @subsection @acronym{ARM}-specific Protocol Details
42345 * ARM Breakpoint Kinds::
42348 @node ARM Breakpoint Kinds
42349 @subsubsection @acronym{ARM} Breakpoint Kinds
42350 @cindex breakpoint kinds, @acronym{ARM}
42352 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
42357 16-bit Thumb mode breakpoint.
42360 32-bit Thumb mode (Thumb-2) breakpoint.
42363 32-bit @acronym{ARM} mode breakpoint.
42367 @node MIPS-Specific Protocol Details
42368 @subsection @acronym{MIPS}-specific Protocol Details
42371 * MIPS Register packet Format::
42372 * MIPS Breakpoint Kinds::
42375 @node MIPS Register packet Format
42376 @subsubsection @acronym{MIPS} Register Packet Format
42377 @cindex register packet format, @acronym{MIPS}
42379 The following @code{g}/@code{G} packets have previously been defined.
42380 In the below, some thirty-two bit registers are transferred as
42381 sixty-four bits. Those registers should be zero/sign extended (which?)
42382 to fill the space allocated. Register bytes are transferred in target
42383 byte order. The two nibbles within a register byte are transferred
42384 most-significant -- least-significant.
42389 All registers are transferred as thirty-two bit quantities in the order:
42390 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
42391 registers; fsr; fir; fp.
42394 All registers are transferred as sixty-four bit quantities (including
42395 thirty-two bit registers such as @code{sr}). The ordering is the same
42400 @node MIPS Breakpoint Kinds
42401 @subsubsection @acronym{MIPS} Breakpoint Kinds
42402 @cindex breakpoint kinds, @acronym{MIPS}
42404 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
42409 16-bit @acronym{MIPS16} mode breakpoint.
42412 16-bit @acronym{microMIPS} mode breakpoint.
42415 32-bit standard @acronym{MIPS} mode breakpoint.
42418 32-bit @acronym{microMIPS} mode breakpoint.
42422 @node Tracepoint Packets
42423 @section Tracepoint Packets
42424 @cindex tracepoint packets
42425 @cindex packets, tracepoint
42427 Here we describe the packets @value{GDBN} uses to implement
42428 tracepoints (@pxref{Tracepoints}).
42432 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
42433 @cindex @samp{QTDP} packet
42434 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
42435 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
42436 the tracepoint is disabled. The @var{step} gives the tracepoint's step
42437 count, and @var{pass} gives its pass count. If an @samp{F} is present,
42438 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
42439 the number of bytes that the target should copy elsewhere to make room
42440 for the tracepoint. If an @samp{X} is present, it introduces a
42441 tracepoint condition, which consists of a hexadecimal length, followed
42442 by a comma and hex-encoded bytes, in a manner similar to action
42443 encodings as described below. If the trailing @samp{-} is present,
42444 further @samp{QTDP} packets will follow to specify this tracepoint's
42450 The packet was understood and carried out.
42452 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
42454 The packet was not recognized.
42457 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
42458 Define actions to be taken when a tracepoint is hit. The @var{n} and
42459 @var{addr} must be the same as in the initial @samp{QTDP} packet for
42460 this tracepoint. This packet may only be sent immediately after
42461 another @samp{QTDP} packet that ended with a @samp{-}. If the
42462 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
42463 specifying more actions for this tracepoint.
42465 In the series of action packets for a given tracepoint, at most one
42466 can have an @samp{S} before its first @var{action}. If such a packet
42467 is sent, it and the following packets define ``while-stepping''
42468 actions. Any prior packets define ordinary actions --- that is, those
42469 taken when the tracepoint is first hit. If no action packet has an
42470 @samp{S}, then all the packets in the series specify ordinary
42471 tracepoint actions.
42473 The @samp{@var{action}@dots{}} portion of the packet is a series of
42474 actions, concatenated without separators. Each action has one of the
42480 Collect the registers whose bits are set in @var{mask},
42481 a hexadecimal number whose @var{i}'th bit is set if register number
42482 @var{i} should be collected. (The least significant bit is numbered
42483 zero.) Note that @var{mask} may be any number of digits long; it may
42484 not fit in a 32-bit word.
42486 @item M @var{basereg},@var{offset},@var{len}
42487 Collect @var{len} bytes of memory starting at the address in register
42488 number @var{basereg}, plus @var{offset}. If @var{basereg} is
42489 @samp{-1}, then the range has a fixed address: @var{offset} is the
42490 address of the lowest byte to collect. The @var{basereg},
42491 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
42492 values (the @samp{-1} value for @var{basereg} is a special case).
42494 @item X @var{len},@var{expr}
42495 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
42496 it directs. The agent expression @var{expr} is as described in
42497 @ref{Agent Expressions}. Each byte of the expression is encoded as a
42498 two-digit hex number in the packet; @var{len} is the number of bytes
42499 in the expression (and thus one-half the number of hex digits in the
42504 Any number of actions may be packed together in a single @samp{QTDP}
42505 packet, as long as the packet does not exceed the maximum packet
42506 length (400 bytes, for many stubs). There may be only one @samp{R}
42507 action per tracepoint, and it must precede any @samp{M} or @samp{X}
42508 actions. Any registers referred to by @samp{M} and @samp{X} actions
42509 must be collected by a preceding @samp{R} action. (The
42510 ``while-stepping'' actions are treated as if they were attached to a
42511 separate tracepoint, as far as these restrictions are concerned.)
42516 The packet was understood and carried out.
42518 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
42520 The packet was not recognized.
42523 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
42524 @cindex @samp{QTDPsrc} packet
42525 Specify a source string of tracepoint @var{n} at address @var{addr}.
42526 This is useful to get accurate reproduction of the tracepoints
42527 originally downloaded at the beginning of the trace run. The @var{type}
42528 is the name of the tracepoint part, such as @samp{cond} for the
42529 tracepoint's conditional expression (see below for a list of types), while
42530 @var{bytes} is the string, encoded in hexadecimal.
42532 @var{start} is the offset of the @var{bytes} within the overall source
42533 string, while @var{slen} is the total length of the source string.
42534 This is intended for handling source strings that are longer than will
42535 fit in a single packet.
42536 @c Add detailed example when this info is moved into a dedicated
42537 @c tracepoint descriptions section.
42539 The available string types are @samp{at} for the location,
42540 @samp{cond} for the conditional, and @samp{cmd} for an action command.
42541 @value{GDBN} sends a separate packet for each command in the action
42542 list, in the same order in which the commands are stored in the list.
42544 The target does not need to do anything with source strings except
42545 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
42548 Although this packet is optional, and @value{GDBN} will only send it
42549 if the target replies with @samp{TracepointSource} @xref{General
42550 Query Packets}, it makes both disconnected tracing and trace files
42551 much easier to use. Otherwise the user must be careful that the
42552 tracepoints in effect while looking at trace frames are identical to
42553 the ones in effect during the trace run; even a small discrepancy
42554 could cause @samp{tdump} not to work, or a particular trace frame not
42557 @item QTDV:@var{n}:@var{value}:@var{builtin}:@var{name}
42558 @cindex define trace state variable, remote request
42559 @cindex @samp{QTDV} packet
42560 Create a new trace state variable, number @var{n}, with an initial
42561 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
42562 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
42563 the option of not using this packet for initial values of zero; the
42564 target should simply create the trace state variables as they are
42565 mentioned in expressions. The value @var{builtin} should be 1 (one)
42566 if the trace state variable is builtin and 0 (zero) if it is not builtin.
42567 @value{GDBN} only sets @var{builtin} to 1 if a previous @samp{qTfV} or
42568 @samp{qTsV} packet had it set. The contents of @var{name} is the
42569 hex-encoded name (without the leading @samp{$}) of the trace state
42572 @item QTFrame:@var{n}
42573 @cindex @samp{QTFrame} packet
42574 Select the @var{n}'th tracepoint frame from the buffer, and use the
42575 register and memory contents recorded there to answer subsequent
42576 request packets from @value{GDBN}.
42578 A successful reply from the stub indicates that the stub has found the
42579 requested frame. The response is a series of parts, concatenated
42580 without separators, describing the frame we selected. Each part has
42581 one of the following forms:
42585 The selected frame is number @var{n} in the trace frame buffer;
42586 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
42587 was no frame matching the criteria in the request packet.
42590 The selected trace frame records a hit of tracepoint number @var{t};
42591 @var{t} is a hexadecimal number.
42595 @item QTFrame:pc:@var{addr}
42596 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
42597 currently selected frame whose PC is @var{addr};
42598 @var{addr} is a hexadecimal number.
42600 @item QTFrame:tdp:@var{t}
42601 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
42602 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
42603 is a hexadecimal number.
42605 @item QTFrame:range:@var{start}:@var{end}
42606 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
42607 currently selected frame whose PC is between @var{start} (inclusive)
42608 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
42611 @item QTFrame:outside:@var{start}:@var{end}
42612 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
42613 frame @emph{outside} the given range of addresses (exclusive).
42616 @cindex @samp{qTMinFTPILen} packet
42617 This packet requests the minimum length of instruction at which a fast
42618 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
42619 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
42620 it depends on the target system being able to create trampolines in
42621 the first 64K of memory, which might or might not be possible for that
42622 system. So the reply to this packet will be 4 if it is able to
42629 The minimum instruction length is currently unknown.
42631 The minimum instruction length is @var{length}, where @var{length}
42632 is a hexadecimal number greater or equal to 1. A reply
42633 of 1 means that a fast tracepoint may be placed on any instruction
42634 regardless of size.
42636 An error has occurred.
42638 An empty reply indicates that the request is not supported by the stub.
42642 @cindex @samp{QTStart} packet
42643 Begin the tracepoint experiment. Begin collecting data from
42644 tracepoint hits in the trace frame buffer. This packet supports the
42645 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
42646 instruction reply packet}).
42649 @cindex @samp{QTStop} packet
42650 End the tracepoint experiment. Stop collecting trace frames.
42652 @item QTEnable:@var{n}:@var{addr}
42654 @cindex @samp{QTEnable} packet
42655 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
42656 experiment. If the tracepoint was previously disabled, then collection
42657 of data from it will resume.
42659 @item QTDisable:@var{n}:@var{addr}
42661 @cindex @samp{QTDisable} packet
42662 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
42663 experiment. No more data will be collected from the tracepoint unless
42664 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
42667 @cindex @samp{QTinit} packet
42668 Clear the table of tracepoints, and empty the trace frame buffer.
42670 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
42671 @cindex @samp{QTro} packet
42672 Establish the given ranges of memory as ``transparent''. The stub
42673 will answer requests for these ranges from memory's current contents,
42674 if they were not collected as part of the tracepoint hit.
42676 @value{GDBN} uses this to mark read-only regions of memory, like those
42677 containing program code. Since these areas never change, they should
42678 still have the same contents they did when the tracepoint was hit, so
42679 there's no reason for the stub to refuse to provide their contents.
42681 @item QTDisconnected:@var{value}
42682 @cindex @samp{QTDisconnected} packet
42683 Set the choice to what to do with the tracing run when @value{GDBN}
42684 disconnects from the target. A @var{value} of 1 directs the target to
42685 continue the tracing run, while 0 tells the target to stop tracing if
42686 @value{GDBN} is no longer in the picture.
42689 @cindex @samp{qTStatus} packet
42690 Ask the stub if there is a trace experiment running right now.
42692 The reply has the form:
42696 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
42697 @var{running} is a single digit @code{1} if the trace is presently
42698 running, or @code{0} if not. It is followed by semicolon-separated
42699 optional fields that an agent may use to report additional status.
42703 If the trace is not running, the agent may report any of several
42704 explanations as one of the optional fields:
42709 No trace has been run yet.
42711 @item tstop[:@var{text}]:0
42712 The trace was stopped by a user-originated stop command. The optional
42713 @var{text} field is a user-supplied string supplied as part of the
42714 stop command (for instance, an explanation of why the trace was
42715 stopped manually). It is hex-encoded.
42718 The trace stopped because the trace buffer filled up.
42720 @item tdisconnected:0
42721 The trace stopped because @value{GDBN} disconnected from the target.
42723 @item tpasscount:@var{tpnum}
42724 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
42726 @item terror:@var{text}:@var{tpnum}
42727 The trace stopped because tracepoint @var{tpnum} had an error. The
42728 string @var{text} is available to describe the nature of the error
42729 (for instance, a divide by zero in the condition expression); it
42733 The trace stopped for some other reason.
42737 Additional optional fields supply statistical and other information.
42738 Although not required, they are extremely useful for users monitoring
42739 the progress of a trace run. If a trace has stopped, and these
42740 numbers are reported, they must reflect the state of the just-stopped
42745 @item tframes:@var{n}
42746 The number of trace frames in the buffer.
42748 @item tcreated:@var{n}
42749 The total number of trace frames created during the run. This may
42750 be larger than the trace frame count, if the buffer is circular.
42752 @item tsize:@var{n}
42753 The total size of the trace buffer, in bytes.
42755 @item tfree:@var{n}
42756 The number of bytes still unused in the buffer.
42758 @item circular:@var{n}
42759 The value of the circular trace buffer flag. @code{1} means that the
42760 trace buffer is circular and old trace frames will be discarded if
42761 necessary to make room, @code{0} means that the trace buffer is linear
42764 @item disconn:@var{n}
42765 The value of the disconnected tracing flag. @code{1} means that
42766 tracing will continue after @value{GDBN} disconnects, @code{0} means
42767 that the trace run will stop.
42771 @item qTP:@var{tp}:@var{addr}
42772 @cindex tracepoint status, remote request
42773 @cindex @samp{qTP} packet
42774 Ask the stub for the current state of tracepoint number @var{tp} at
42775 address @var{addr}.
42779 @item V@var{hits}:@var{usage}
42780 The tracepoint has been hit @var{hits} times so far during the trace
42781 run, and accounts for @var{usage} in the trace buffer. Note that
42782 @code{while-stepping} steps are not counted as separate hits, but the
42783 steps' space consumption is added into the usage number.
42787 @item qTV:@var{var}
42788 @cindex trace state variable value, remote request
42789 @cindex @samp{qTV} packet
42790 Ask the stub for the value of the trace state variable number @var{var}.
42795 The value of the variable is @var{value}. This will be the current
42796 value of the variable if the user is examining a running target, or a
42797 saved value if the variable was collected in the trace frame that the
42798 user is looking at. Note that multiple requests may result in
42799 different reply values, such as when requesting values while the
42800 program is running.
42803 The value of the variable is unknown. This would occur, for example,
42804 if the user is examining a trace frame in which the requested variable
42809 @cindex @samp{qTfP} packet
42811 @cindex @samp{qTsP} packet
42812 These packets request data about tracepoints that are being used by
42813 the target. @value{GDBN} sends @code{qTfP} to get the first piece
42814 of data, and multiple @code{qTsP} to get additional pieces. Replies
42815 to these packets generally take the form of the @code{QTDP} packets
42816 that define tracepoints. (FIXME add detailed syntax)
42819 @cindex @samp{qTfV} packet
42821 @cindex @samp{qTsV} packet
42822 These packets request data about trace state variables that are on the
42823 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
42824 and multiple @code{qTsV} to get additional variables. Replies to
42825 these packets follow the syntax of the @code{QTDV} packets that define
42826 trace state variables.
42832 @cindex @samp{qTfSTM} packet
42833 @cindex @samp{qTsSTM} packet
42834 These packets request data about static tracepoint markers that exist
42835 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
42836 first piece of data, and multiple @code{qTsSTM} to get additional
42837 pieces. Replies to these packets take the following form:
42841 @item m @var{address}:@var{id}:@var{extra}
42843 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
42844 a comma-separated list of markers
42846 (lower case letter @samp{L}) denotes end of list.
42848 An error occurred. The error number @var{nn} is given as hex digits.
42850 An empty reply indicates that the request is not supported by the
42854 The @var{address} is encoded in hex;
42855 @var{id} and @var{extra} are strings encoded in hex.
42857 In response to each query, the target will reply with a list of one or
42858 more markers, separated by commas. @value{GDBN} will respond to each
42859 reply with a request for more markers (using the @samp{qs} form of the
42860 query), until the target responds with @samp{l} (lower-case ell, for
42863 @item qTSTMat:@var{address}
42865 @cindex @samp{qTSTMat} packet
42866 This packets requests data about static tracepoint markers in the
42867 target program at @var{address}. Replies to this packet follow the
42868 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
42869 tracepoint markers.
42871 @item QTSave:@var{filename}
42872 @cindex @samp{QTSave} packet
42873 This packet directs the target to save trace data to the file name
42874 @var{filename} in the target's filesystem. The @var{filename} is encoded
42875 as a hex string; the interpretation of the file name (relative vs
42876 absolute, wild cards, etc) is up to the target.
42878 @item qTBuffer:@var{offset},@var{len}
42879 @cindex @samp{qTBuffer} packet
42880 Return up to @var{len} bytes of the current contents of trace buffer,
42881 starting at @var{offset}. The trace buffer is treated as if it were
42882 a contiguous collection of traceframes, as per the trace file format.
42883 The reply consists as many hex-encoded bytes as the target can deliver
42884 in a packet; it is not an error to return fewer than were asked for.
42885 A reply consisting of just @code{l} indicates that no bytes are
42888 @item QTBuffer:circular:@var{value}
42889 This packet directs the target to use a circular trace buffer if
42890 @var{value} is 1, or a linear buffer if the value is 0.
42892 @item QTBuffer:size:@var{size}
42893 @anchor{QTBuffer-size}
42894 @cindex @samp{QTBuffer size} packet
42895 This packet directs the target to make the trace buffer be of size
42896 @var{size} if possible. A value of @code{-1} tells the target to
42897 use whatever size it prefers.
42899 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
42900 @cindex @samp{QTNotes} packet
42901 This packet adds optional textual notes to the trace run. Allowable
42902 types include @code{user}, @code{notes}, and @code{tstop}, the
42903 @var{text} fields are arbitrary strings, hex-encoded.
42907 @subsection Relocate instruction reply packet
42908 When installing fast tracepoints in memory, the target may need to
42909 relocate the instruction currently at the tracepoint address to a
42910 different address in memory. For most instructions, a simple copy is
42911 enough, but, for example, call instructions that implicitly push the
42912 return address on the stack, and relative branches or other
42913 PC-relative instructions require offset adjustment, so that the effect
42914 of executing the instruction at a different address is the same as if
42915 it had executed in the original location.
42917 In response to several of the tracepoint packets, the target may also
42918 respond with a number of intermediate @samp{qRelocInsn} request
42919 packets before the final result packet, to have @value{GDBN} handle
42920 this relocation operation. If a packet supports this mechanism, its
42921 documentation will explicitly say so. See for example the above
42922 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
42923 format of the request is:
42926 @item qRelocInsn:@var{from};@var{to}
42928 This requests @value{GDBN} to copy instruction at address @var{from}
42929 to address @var{to}, possibly adjusted so that executing the
42930 instruction at @var{to} has the same effect as executing it at
42931 @var{from}. @value{GDBN} writes the adjusted instruction to target
42932 memory starting at @var{to}.
42937 @item qRelocInsn:@var{adjusted_size}
42938 Informs the stub the relocation is complete. The @var{adjusted_size} is
42939 the length in bytes of resulting relocated instruction sequence.
42941 A badly formed request was detected, or an error was encountered while
42942 relocating the instruction.
42945 @node Host I/O Packets
42946 @section Host I/O Packets
42947 @cindex Host I/O, remote protocol
42948 @cindex file transfer, remote protocol
42950 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
42951 operations on the far side of a remote link. For example, Host I/O is
42952 used to upload and download files to a remote target with its own
42953 filesystem. Host I/O uses the same constant values and data structure
42954 layout as the target-initiated File-I/O protocol. However, the
42955 Host I/O packets are structured differently. The target-initiated
42956 protocol relies on target memory to store parameters and buffers.
42957 Host I/O requests are initiated by @value{GDBN}, and the
42958 target's memory is not involved. @xref{File-I/O Remote Protocol
42959 Extension}, for more details on the target-initiated protocol.
42961 The Host I/O request packets all encode a single operation along with
42962 its arguments. They have this format:
42966 @item vFile:@var{operation}: @var{parameter}@dots{}
42967 @var{operation} is the name of the particular request; the target
42968 should compare the entire packet name up to the second colon when checking
42969 for a supported operation. The format of @var{parameter} depends on
42970 the operation. Numbers are always passed in hexadecimal. Negative
42971 numbers have an explicit minus sign (i.e.@: two's complement is not
42972 used). Strings (e.g.@: filenames) are encoded as a series of
42973 hexadecimal bytes. The last argument to a system call may be a
42974 buffer of escaped binary data (@pxref{Binary Data}).
42978 The valid responses to Host I/O packets are:
42982 @item F @var{result} [, @var{errno}] [; @var{attachment}]
42983 @var{result} is the integer value returned by this operation, usually
42984 non-negative for success and -1 for errors. If an error has occured,
42985 @var{errno} will be included in the result specifying a
42986 value defined by the File-I/O protocol (@pxref{Errno Values}). For
42987 operations which return data, @var{attachment} supplies the data as a
42988 binary buffer. Binary buffers in response packets are escaped in the
42989 normal way (@pxref{Binary Data}). See the individual packet
42990 documentation for the interpretation of @var{result} and
42994 An empty response indicates that this operation is not recognized.
42998 These are the supported Host I/O operations:
43001 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
43002 Open a file at @var{filename} and return a file descriptor for it, or
43003 return -1 if an error occurs. The @var{filename} is a string,
43004 @var{flags} is an integer indicating a mask of open flags
43005 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
43006 of mode bits to use if the file is created (@pxref{mode_t Values}).
43007 @xref{open}, for details of the open flags and mode values.
43009 @item vFile:close: @var{fd}
43010 Close the open file corresponding to @var{fd} and return 0, or
43011 -1 if an error occurs.
43013 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
43014 Read data from the open file corresponding to @var{fd}. Up to
43015 @var{count} bytes will be read from the file, starting at @var{offset}
43016 relative to the start of the file. The target may read fewer bytes;
43017 common reasons include packet size limits and an end-of-file
43018 condition. The number of bytes read is returned. Zero should only be
43019 returned for a successful read at the end of the file, or if
43020 @var{count} was zero.
43022 The data read should be returned as a binary attachment on success.
43023 If zero bytes were read, the response should include an empty binary
43024 attachment (i.e.@: a trailing semicolon). The return value is the
43025 number of target bytes read; the binary attachment may be longer if
43026 some characters were escaped.
43028 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
43029 Write @var{data} (a binary buffer) to the open file corresponding
43030 to @var{fd}. Start the write at @var{offset} from the start of the
43031 file. Unlike many @code{write} system calls, there is no
43032 separate @var{count} argument; the length of @var{data} in the
43033 packet is used. @samp{vFile:pwrite} returns the number of bytes written,
43034 which may be shorter than the length of @var{data}, or -1 if an
43037 @item vFile:fstat: @var{fd}
43038 Get information about the open file corresponding to @var{fd}.
43039 On success the information is returned as a binary attachment
43040 and the return value is the size of this attachment in bytes.
43041 If an error occurs the return value is -1. The format of the
43042 returned binary attachment is as described in @ref{struct stat}.
43044 @item vFile:unlink: @var{filename}
43045 Delete the file at @var{filename} on the target. Return 0,
43046 or -1 if an error occurs. The @var{filename} is a string.
43048 @item vFile:readlink: @var{filename}
43049 Read value of symbolic link @var{filename} on the target. Return
43050 the number of bytes read, or -1 if an error occurs.
43052 The data read should be returned as a binary attachment on success.
43053 If zero bytes were read, the response should include an empty binary
43054 attachment (i.e.@: a trailing semicolon). The return value is the
43055 number of target bytes read; the binary attachment may be longer if
43056 some characters were escaped.
43058 @item vFile:setfs: @var{pid}
43059 Select the filesystem on which @code{vFile} operations with
43060 @var{filename} arguments will operate. This is required for
43061 @value{GDBN} to be able to access files on remote targets where
43062 the remote stub does not share a common filesystem with the
43065 If @var{pid} is nonzero, select the filesystem as seen by process
43066 @var{pid}. If @var{pid} is zero, select the filesystem as seen by
43067 the remote stub. Return 0 on success, or -1 if an error occurs.
43068 If @code{vFile:setfs:} indicates success, the selected filesystem
43069 remains selected until the next successful @code{vFile:setfs:}
43075 @section Interrupts
43076 @cindex interrupts (remote protocol)
43077 @anchor{interrupting remote targets}
43079 In all-stop mode, when a program on the remote target is running,
43080 @value{GDBN} may attempt to interrupt it by sending a @samp{Ctrl-C},
43081 @code{BREAK} or a @code{BREAK} followed by @code{g}, control of which
43082 is specified via @value{GDBN}'s @samp{interrupt-sequence}.
43084 The precise meaning of @code{BREAK} is defined by the transport
43085 mechanism and may, in fact, be undefined. @value{GDBN} does not
43086 currently define a @code{BREAK} mechanism for any of the network
43087 interfaces except for TCP, in which case @value{GDBN} sends the
43088 @code{telnet} BREAK sequence.
43090 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
43091 transport mechanisms. It is represented by sending the single byte
43092 @code{0x03} without any of the usual packet overhead described in
43093 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
43094 transmitted as part of a packet, it is considered to be packet data
43095 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
43096 (@pxref{X packet}), used for binary downloads, may include an unescaped
43097 @code{0x03} as part of its packet.
43099 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
43100 When Linux kernel receives this sequence from serial port,
43101 it stops execution and connects to gdb.
43103 In non-stop mode, because packet resumptions are asynchronous
43104 (@pxref{vCont packet}), @value{GDBN} is always free to send a remote
43105 command to the remote stub, even when the target is running. For that
43106 reason, @value{GDBN} instead sends a regular packet (@pxref{vCtrlC
43107 packet}) with the usual packet framing instead of the single byte
43110 Stubs are not required to recognize these interrupt mechanisms and the
43111 precise meaning associated with receipt of the interrupt is
43112 implementation defined. If the target supports debugging of multiple
43113 threads and/or processes, it should attempt to interrupt all
43114 currently-executing threads and processes.
43115 If the stub is successful at interrupting the
43116 running program, it should send one of the stop
43117 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
43118 of successfully stopping the program in all-stop mode, and a stop reply
43119 for each stopped thread in non-stop mode.
43120 Interrupts received while the
43121 program is stopped are queued and the program will be interrupted when
43122 it is resumed next time.
43124 @node Notification Packets
43125 @section Notification Packets
43126 @cindex notification packets
43127 @cindex packets, notification
43129 The @value{GDBN} remote serial protocol includes @dfn{notifications},
43130 packets that require no acknowledgment. Both the GDB and the stub
43131 may send notifications (although the only notifications defined at
43132 present are sent by the stub). Notifications carry information
43133 without incurring the round-trip latency of an acknowledgment, and so
43134 are useful for low-impact communications where occasional packet loss
43137 A notification packet has the form @samp{% @var{data} #
43138 @var{checksum}}, where @var{data} is the content of the notification,
43139 and @var{checksum} is a checksum of @var{data}, computed and formatted
43140 as for ordinary @value{GDBN} packets. A notification's @var{data}
43141 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
43142 receiving a notification, the recipient sends no @samp{+} or @samp{-}
43143 to acknowledge the notification's receipt or to report its corruption.
43145 Every notification's @var{data} begins with a name, which contains no
43146 colon characters, followed by a colon character.
43148 Recipients should silently ignore corrupted notifications and
43149 notifications they do not understand. Recipients should restart
43150 timeout periods on receipt of a well-formed notification, whether or
43151 not they understand it.
43153 Senders should only send the notifications described here when this
43154 protocol description specifies that they are permitted. In the
43155 future, we may extend the protocol to permit existing notifications in
43156 new contexts; this rule helps older senders avoid confusing newer
43159 (Older versions of @value{GDBN} ignore bytes received until they see
43160 the @samp{$} byte that begins an ordinary packet, so new stubs may
43161 transmit notifications without fear of confusing older clients. There
43162 are no notifications defined for @value{GDBN} to send at the moment, but we
43163 assume that most older stubs would ignore them, as well.)
43165 Each notification is comprised of three parts:
43167 @item @var{name}:@var{event}
43168 The notification packet is sent by the side that initiates the
43169 exchange (currently, only the stub does that), with @var{event}
43170 carrying the specific information about the notification, and
43171 @var{name} specifying the name of the notification.
43173 The acknowledge sent by the other side, usually @value{GDBN}, to
43174 acknowledge the exchange and request the event.
43177 The purpose of an asynchronous notification mechanism is to report to
43178 @value{GDBN} that something interesting happened in the remote stub.
43180 The remote stub may send notification @var{name}:@var{event}
43181 at any time, but @value{GDBN} acknowledges the notification when
43182 appropriate. The notification event is pending before @value{GDBN}
43183 acknowledges. Only one notification at a time may be pending; if
43184 additional events occur before @value{GDBN} has acknowledged the
43185 previous notification, they must be queued by the stub for later
43186 synchronous transmission in response to @var{ack} packets from
43187 @value{GDBN}. Because the notification mechanism is unreliable,
43188 the stub is permitted to resend a notification if it believes
43189 @value{GDBN} may not have received it.
43191 Specifically, notifications may appear when @value{GDBN} is not
43192 otherwise reading input from the stub, or when @value{GDBN} is
43193 expecting to read a normal synchronous response or a
43194 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
43195 Notification packets are distinct from any other communication from
43196 the stub so there is no ambiguity.
43198 After receiving a notification, @value{GDBN} shall acknowledge it by
43199 sending a @var{ack} packet as a regular, synchronous request to the
43200 stub. Such acknowledgment is not required to happen immediately, as
43201 @value{GDBN} is permitted to send other, unrelated packets to the
43202 stub first, which the stub should process normally.
43204 Upon receiving a @var{ack} packet, if the stub has other queued
43205 events to report to @value{GDBN}, it shall respond by sending a
43206 normal @var{event}. @value{GDBN} shall then send another @var{ack}
43207 packet to solicit further responses; again, it is permitted to send
43208 other, unrelated packets as well which the stub should process
43211 If the stub receives a @var{ack} packet and there are no additional
43212 @var{event} to report, the stub shall return an @samp{OK} response.
43213 At this point, @value{GDBN} has finished processing a notification
43214 and the stub has completed sending any queued events. @value{GDBN}
43215 won't accept any new notifications until the final @samp{OK} is
43216 received . If further notification events occur, the stub shall send
43217 a new notification, @value{GDBN} shall accept the notification, and
43218 the process shall be repeated.
43220 The process of asynchronous notification can be illustrated by the
43223 <- @code{%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
43226 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
43228 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
43233 The following notifications are defined:
43234 @multitable @columnfractions 0.12 0.12 0.38 0.38
43243 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
43244 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
43245 for information on how these notifications are acknowledged by
43247 @tab Report an asynchronous stop event in non-stop mode.
43251 @node Remote Non-Stop
43252 @section Remote Protocol Support for Non-Stop Mode
43254 @value{GDBN}'s remote protocol supports non-stop debugging of
43255 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
43256 supports non-stop mode, it should report that to @value{GDBN} by including
43257 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
43259 @value{GDBN} typically sends a @samp{QNonStop} packet only when
43260 establishing a new connection with the stub. Entering non-stop mode
43261 does not alter the state of any currently-running threads, but targets
43262 must stop all threads in any already-attached processes when entering
43263 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
43264 probe the target state after a mode change.
43266 In non-stop mode, when an attached process encounters an event that
43267 would otherwise be reported with a stop reply, it uses the
43268 asynchronous notification mechanism (@pxref{Notification Packets}) to
43269 inform @value{GDBN}. In contrast to all-stop mode, where all threads
43270 in all processes are stopped when a stop reply is sent, in non-stop
43271 mode only the thread reporting the stop event is stopped. That is,
43272 when reporting a @samp{S} or @samp{T} response to indicate completion
43273 of a step operation, hitting a breakpoint, or a fault, only the
43274 affected thread is stopped; any other still-running threads continue
43275 to run. When reporting a @samp{W} or @samp{X} response, all running
43276 threads belonging to other attached processes continue to run.
43278 In non-stop mode, the target shall respond to the @samp{?} packet as
43279 follows. First, any incomplete stop reply notification/@samp{vStopped}
43280 sequence in progress is abandoned. The target must begin a new
43281 sequence reporting stop events for all stopped threads, whether or not
43282 it has previously reported those events to @value{GDBN}. The first
43283 stop reply is sent as a synchronous reply to the @samp{?} packet, and
43284 subsequent stop replies are sent as responses to @samp{vStopped} packets
43285 using the mechanism described above. The target must not send
43286 asynchronous stop reply notifications until the sequence is complete.
43287 If all threads are running when the target receives the @samp{?} packet,
43288 or if the target is not attached to any process, it shall respond
43291 If the stub supports non-stop mode, it should also support the
43292 @samp{swbreak} stop reason if software breakpoints are supported, and
43293 the @samp{hwbreak} stop reason if hardware breakpoints are supported
43294 (@pxref{swbreak stop reason}). This is because given the asynchronous
43295 nature of non-stop mode, between the time a thread hits a breakpoint
43296 and the time the event is finally processed by @value{GDBN}, the
43297 breakpoint may have already been removed from the target. Due to
43298 this, @value{GDBN} needs to be able to tell whether a trap stop was
43299 caused by a delayed breakpoint event, which should be ignored, as
43300 opposed to a random trap signal, which should be reported to the user.
43301 Note the @samp{swbreak} feature implies that the target is responsible
43302 for adjusting the PC when a software breakpoint triggers, if
43303 necessary, such as on the x86 architecture.
43305 @node Packet Acknowledgment
43306 @section Packet Acknowledgment
43308 @cindex acknowledgment, for @value{GDBN} remote
43309 @cindex packet acknowledgment, for @value{GDBN} remote
43310 By default, when either the host or the target machine receives a packet,
43311 the first response expected is an acknowledgment: either @samp{+} (to indicate
43312 the package was received correctly) or @samp{-} (to request retransmission).
43313 This mechanism allows the @value{GDBN} remote protocol to operate over
43314 unreliable transport mechanisms, such as a serial line.
43316 In cases where the transport mechanism is itself reliable (such as a pipe or
43317 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
43318 It may be desirable to disable them in that case to reduce communication
43319 overhead, or for other reasons. This can be accomplished by means of the
43320 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
43322 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
43323 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
43324 and response format still includes the normal checksum, as described in
43325 @ref{Overview}, but the checksum may be ignored by the receiver.
43327 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
43328 no-acknowledgment mode, it should report that to @value{GDBN}
43329 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
43330 @pxref{qSupported}.
43331 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
43332 disabled via the @code{set remote noack-packet off} command
43333 (@pxref{Remote Configuration}),
43334 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
43335 Only then may the stub actually turn off packet acknowledgments.
43336 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
43337 response, which can be safely ignored by the stub.
43339 Note that @code{set remote noack-packet} command only affects negotiation
43340 between @value{GDBN} and the stub when subsequent connections are made;
43341 it does not affect the protocol acknowledgment state for any current
43343 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
43344 new connection is established,
43345 there is also no protocol request to re-enable the acknowledgments
43346 for the current connection, once disabled.
43351 Example sequence of a target being re-started. Notice how the restart
43352 does not get any direct output:
43357 @emph{target restarts}
43360 <- @code{T001:1234123412341234}
43364 Example sequence of a target being stepped by a single instruction:
43367 -> @code{G1445@dots{}}
43372 <- @code{T001:1234123412341234}
43376 <- @code{1455@dots{}}
43380 @node File-I/O Remote Protocol Extension
43381 @section File-I/O Remote Protocol Extension
43382 @cindex File-I/O remote protocol extension
43385 * File-I/O Overview::
43386 * Protocol Basics::
43387 * The F Request Packet::
43388 * The F Reply Packet::
43389 * The Ctrl-C Message::
43391 * List of Supported Calls::
43392 * Protocol-specific Representation of Datatypes::
43394 * File-I/O Examples::
43397 @node File-I/O Overview
43398 @subsection File-I/O Overview
43399 @cindex file-i/o overview
43401 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
43402 target to use the host's file system and console I/O to perform various
43403 system calls. System calls on the target system are translated into a
43404 remote protocol packet to the host system, which then performs the needed
43405 actions and returns a response packet to the target system.
43406 This simulates file system operations even on targets that lack file systems.
43408 The protocol is defined to be independent of both the host and target systems.
43409 It uses its own internal representation of datatypes and values. Both
43410 @value{GDBN} and the target's @value{GDBN} stub are responsible for
43411 translating the system-dependent value representations into the internal
43412 protocol representations when data is transmitted.
43414 The communication is synchronous. A system call is possible only when
43415 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
43416 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
43417 the target is stopped to allow deterministic access to the target's
43418 memory. Therefore File-I/O is not interruptible by target signals. On
43419 the other hand, it is possible to interrupt File-I/O by a user interrupt
43420 (@samp{Ctrl-C}) within @value{GDBN}.
43422 The target's request to perform a host system call does not finish
43423 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
43424 after finishing the system call, the target returns to continuing the
43425 previous activity (continue, step). No additional continue or step
43426 request from @value{GDBN} is required.
43429 (@value{GDBP}) continue
43430 <- target requests 'system call X'
43431 target is stopped, @value{GDBN} executes system call
43432 -> @value{GDBN} returns result
43433 ... target continues, @value{GDBN} returns to wait for the target
43434 <- target hits breakpoint and sends a Txx packet
43437 The protocol only supports I/O on the console and to regular files on
43438 the host file system. Character or block special devices, pipes,
43439 named pipes, sockets or any other communication method on the host
43440 system are not supported by this protocol.
43442 File I/O is not supported in non-stop mode.
43444 @node Protocol Basics
43445 @subsection Protocol Basics
43446 @cindex protocol basics, file-i/o
43448 The File-I/O protocol uses the @code{F} packet as the request as well
43449 as reply packet. Since a File-I/O system call can only occur when
43450 @value{GDBN} is waiting for a response from the continuing or stepping target,
43451 the File-I/O request is a reply that @value{GDBN} has to expect as a result
43452 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
43453 This @code{F} packet contains all information needed to allow @value{GDBN}
43454 to call the appropriate host system call:
43458 A unique identifier for the requested system call.
43461 All parameters to the system call. Pointers are given as addresses
43462 in the target memory address space. Pointers to strings are given as
43463 pointer/length pair. Numerical values are given as they are.
43464 Numerical control flags are given in a protocol-specific representation.
43468 At this point, @value{GDBN} has to perform the following actions.
43472 If the parameters include pointer values to data needed as input to a
43473 system call, @value{GDBN} requests this data from the target with a
43474 standard @code{m} packet request. This additional communication has to be
43475 expected by the target implementation and is handled as any other @code{m}
43479 @value{GDBN} translates all value from protocol representation to host
43480 representation as needed. Datatypes are coerced into the host types.
43483 @value{GDBN} calls the system call.
43486 It then coerces datatypes back to protocol representation.
43489 If the system call is expected to return data in buffer space specified
43490 by pointer parameters to the call, the data is transmitted to the
43491 target using a @code{M} or @code{X} packet. This packet has to be expected
43492 by the target implementation and is handled as any other @code{M} or @code{X}
43497 Eventually @value{GDBN} replies with another @code{F} packet which contains all
43498 necessary information for the target to continue. This at least contains
43505 @code{errno}, if has been changed by the system call.
43512 After having done the needed type and value coercion, the target continues
43513 the latest continue or step action.
43515 @node The F Request Packet
43516 @subsection The @code{F} Request Packet
43517 @cindex file-i/o request packet
43518 @cindex @code{F} request packet
43520 The @code{F} request packet has the following format:
43523 @item F@var{call-id},@var{parameter@dots{}}
43525 @var{call-id} is the identifier to indicate the host system call to be called.
43526 This is just the name of the function.
43528 @var{parameter@dots{}} are the parameters to the system call.
43529 Parameters are hexadecimal integer values, either the actual values in case
43530 of scalar datatypes, pointers to target buffer space in case of compound
43531 datatypes and unspecified memory areas, or pointer/length pairs in case
43532 of string parameters. These are appended to the @var{call-id} as a
43533 comma-delimited list. All values are transmitted in ASCII
43534 string representation, pointer/length pairs separated by a slash.
43540 @node The F Reply Packet
43541 @subsection The @code{F} Reply Packet
43542 @cindex file-i/o reply packet
43543 @cindex @code{F} reply packet
43545 The @code{F} reply packet has the following format:
43549 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
43551 @var{retcode} is the return code of the system call as hexadecimal value.
43553 @var{errno} is the @code{errno} set by the call, in protocol-specific
43555 This parameter can be omitted if the call was successful.
43557 @var{Ctrl-C flag} is only sent if the user requested a break. In this
43558 case, @var{errno} must be sent as well, even if the call was successful.
43559 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
43566 or, if the call was interrupted before the host call has been performed:
43573 assuming 4 is the protocol-specific representation of @code{EINTR}.
43578 @node The Ctrl-C Message
43579 @subsection The @samp{Ctrl-C} Message
43580 @cindex ctrl-c message, in file-i/o protocol
43582 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
43583 reply packet (@pxref{The F Reply Packet}),
43584 the target should behave as if it had
43585 gotten a break message. The meaning for the target is ``system call
43586 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
43587 (as with a break message) and return to @value{GDBN} with a @code{T02}
43590 It's important for the target to know in which
43591 state the system call was interrupted. There are two possible cases:
43595 The system call hasn't been performed on the host yet.
43598 The system call on the host has been finished.
43602 These two states can be distinguished by the target by the value of the
43603 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
43604 call hasn't been performed. This is equivalent to the @code{EINTR} handling
43605 on POSIX systems. In any other case, the target may presume that the
43606 system call has been finished --- successfully or not --- and should behave
43607 as if the break message arrived right after the system call.
43609 @value{GDBN} must behave reliably. If the system call has not been called
43610 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
43611 @code{errno} in the packet. If the system call on the host has been finished
43612 before the user requests a break, the full action must be finished by
43613 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
43614 The @code{F} packet may only be sent when either nothing has happened
43615 or the full action has been completed.
43618 @subsection Console I/O
43619 @cindex console i/o as part of file-i/o
43621 By default and if not explicitly closed by the target system, the file
43622 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
43623 on the @value{GDBN} console is handled as any other file output operation
43624 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
43625 by @value{GDBN} so that after the target read request from file descriptor
43626 0 all following typing is buffered until either one of the following
43631 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
43633 system call is treated as finished.
43636 The user presses @key{RET}. This is treated as end of input with a trailing
43640 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
43641 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
43645 If the user has typed more characters than fit in the buffer given to
43646 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
43647 either another @code{read(0, @dots{})} is requested by the target, or debugging
43648 is stopped at the user's request.
43651 @node List of Supported Calls
43652 @subsection List of Supported Calls
43653 @cindex list of supported file-i/o calls
43670 @unnumberedsubsubsec open
43671 @cindex open, file-i/o system call
43676 int open(const char *pathname, int flags);
43677 int open(const char *pathname, int flags, mode_t mode);
43681 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
43684 @var{flags} is the bitwise @code{OR} of the following values:
43688 If the file does not exist it will be created. The host
43689 rules apply as far as file ownership and time stamps
43693 When used with @code{O_CREAT}, if the file already exists it is
43694 an error and open() fails.
43697 If the file already exists and the open mode allows
43698 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
43699 truncated to zero length.
43702 The file is opened in append mode.
43705 The file is opened for reading only.
43708 The file is opened for writing only.
43711 The file is opened for reading and writing.
43715 Other bits are silently ignored.
43719 @var{mode} is the bitwise @code{OR} of the following values:
43723 User has read permission.
43726 User has write permission.
43729 Group has read permission.
43732 Group has write permission.
43735 Others have read permission.
43738 Others have write permission.
43742 Other bits are silently ignored.
43745 @item Return value:
43746 @code{open} returns the new file descriptor or -1 if an error
43753 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
43756 @var{pathname} refers to a directory.
43759 The requested access is not allowed.
43762 @var{pathname} was too long.
43765 A directory component in @var{pathname} does not exist.
43768 @var{pathname} refers to a device, pipe, named pipe or socket.
43771 @var{pathname} refers to a file on a read-only filesystem and
43772 write access was requested.
43775 @var{pathname} is an invalid pointer value.
43778 No space on device to create the file.
43781 The process already has the maximum number of files open.
43784 The limit on the total number of files open on the system
43788 The call was interrupted by the user.
43794 @unnumberedsubsubsec close
43795 @cindex close, file-i/o system call
43804 @samp{Fclose,@var{fd}}
43806 @item Return value:
43807 @code{close} returns zero on success, or -1 if an error occurred.
43813 @var{fd} isn't a valid open file descriptor.
43816 The call was interrupted by the user.
43822 @unnumberedsubsubsec read
43823 @cindex read, file-i/o system call
43828 int read(int fd, void *buf, unsigned int count);
43832 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
43834 @item Return value:
43835 On success, the number of bytes read is returned.
43836 Zero indicates end of file. If count is zero, read
43837 returns zero as well. On error, -1 is returned.
43843 @var{fd} is not a valid file descriptor or is not open for
43847 @var{bufptr} is an invalid pointer value.
43850 The call was interrupted by the user.
43856 @unnumberedsubsubsec write
43857 @cindex write, file-i/o system call
43862 int write(int fd, const void *buf, unsigned int count);
43866 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
43868 @item Return value:
43869 On success, the number of bytes written are returned.
43870 Zero indicates nothing was written. On error, -1
43877 @var{fd} is not a valid file descriptor or is not open for
43881 @var{bufptr} is an invalid pointer value.
43884 An attempt was made to write a file that exceeds the
43885 host-specific maximum file size allowed.
43888 No space on device to write the data.
43891 The call was interrupted by the user.
43897 @unnumberedsubsubsec lseek
43898 @cindex lseek, file-i/o system call
43903 long lseek (int fd, long offset, int flag);
43907 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
43909 @var{flag} is one of:
43913 The offset is set to @var{offset} bytes.
43916 The offset is set to its current location plus @var{offset}
43920 The offset is set to the size of the file plus @var{offset}
43924 @item Return value:
43925 On success, the resulting unsigned offset in bytes from
43926 the beginning of the file is returned. Otherwise, a
43927 value of -1 is returned.
43933 @var{fd} is not a valid open file descriptor.
43936 @var{fd} is associated with the @value{GDBN} console.
43939 @var{flag} is not a proper value.
43942 The call was interrupted by the user.
43948 @unnumberedsubsubsec rename
43949 @cindex rename, file-i/o system call
43954 int rename(const char *oldpath, const char *newpath);
43958 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
43960 @item Return value:
43961 On success, zero is returned. On error, -1 is returned.
43967 @var{newpath} is an existing directory, but @var{oldpath} is not a
43971 @var{newpath} is a non-empty directory.
43974 @var{oldpath} or @var{newpath} is a directory that is in use by some
43978 An attempt was made to make a directory a subdirectory
43982 A component used as a directory in @var{oldpath} or new
43983 path is not a directory. Or @var{oldpath} is a directory
43984 and @var{newpath} exists but is not a directory.
43987 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
43990 No access to the file or the path of the file.
43994 @var{oldpath} or @var{newpath} was too long.
43997 A directory component in @var{oldpath} or @var{newpath} does not exist.
44000 The file is on a read-only filesystem.
44003 The device containing the file has no room for the new
44007 The call was interrupted by the user.
44013 @unnumberedsubsubsec unlink
44014 @cindex unlink, file-i/o system call
44019 int unlink(const char *pathname);
44023 @samp{Funlink,@var{pathnameptr}/@var{len}}
44025 @item Return value:
44026 On success, zero is returned. On error, -1 is returned.
44032 No access to the file or the path of the file.
44035 The system does not allow unlinking of directories.
44038 The file @var{pathname} cannot be unlinked because it's
44039 being used by another process.
44042 @var{pathnameptr} is an invalid pointer value.
44045 @var{pathname} was too long.
44048 A directory component in @var{pathname} does not exist.
44051 A component of the path is not a directory.
44054 The file is on a read-only filesystem.
44057 The call was interrupted by the user.
44063 @unnumberedsubsubsec stat/fstat
44064 @cindex fstat, file-i/o system call
44065 @cindex stat, file-i/o system call
44070 int stat(const char *pathname, struct stat *buf);
44071 int fstat(int fd, struct stat *buf);
44075 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
44076 @samp{Ffstat,@var{fd},@var{bufptr}}
44078 @item Return value:
44079 On success, zero is returned. On error, -1 is returned.
44085 @var{fd} is not a valid open file.
44088 A directory component in @var{pathname} does not exist or the
44089 path is an empty string.
44092 A component of the path is not a directory.
44095 @var{pathnameptr} is an invalid pointer value.
44098 No access to the file or the path of the file.
44101 @var{pathname} was too long.
44104 The call was interrupted by the user.
44110 @unnumberedsubsubsec gettimeofday
44111 @cindex gettimeofday, file-i/o system call
44116 int gettimeofday(struct timeval *tv, void *tz);
44120 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
44122 @item Return value:
44123 On success, 0 is returned, -1 otherwise.
44129 @var{tz} is a non-NULL pointer.
44132 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
44138 @unnumberedsubsubsec isatty
44139 @cindex isatty, file-i/o system call
44144 int isatty(int fd);
44148 @samp{Fisatty,@var{fd}}
44150 @item Return value:
44151 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
44157 The call was interrupted by the user.
44162 Note that the @code{isatty} call is treated as a special case: it returns
44163 1 to the target if the file descriptor is attached
44164 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
44165 would require implementing @code{ioctl} and would be more complex than
44170 @unnumberedsubsubsec system
44171 @cindex system, file-i/o system call
44176 int system(const char *command);
44180 @samp{Fsystem,@var{commandptr}/@var{len}}
44182 @item Return value:
44183 If @var{len} is zero, the return value indicates whether a shell is
44184 available. A zero return value indicates a shell is not available.
44185 For non-zero @var{len}, the value returned is -1 on error and the
44186 return status of the command otherwise. Only the exit status of the
44187 command is returned, which is extracted from the host's @code{system}
44188 return value by calling @code{WEXITSTATUS(retval)}. In case
44189 @file{/bin/sh} could not be executed, 127 is returned.
44195 The call was interrupted by the user.
44200 @value{GDBN} takes over the full task of calling the necessary host calls
44201 to perform the @code{system} call. The return value of @code{system} on
44202 the host is simplified before it's returned
44203 to the target. Any termination signal information from the child process
44204 is discarded, and the return value consists
44205 entirely of the exit status of the called command.
44207 Due to security concerns, the @code{system} call is by default refused
44208 by @value{GDBN}. The user has to allow this call explicitly with the
44209 @code{set remote system-call-allowed 1} command.
44212 @item set remote system-call-allowed
44213 @kindex set remote system-call-allowed
44214 Control whether to allow the @code{system} calls in the File I/O
44215 protocol for the remote target. The default is zero (disabled).
44217 @item show remote system-call-allowed
44218 @kindex show remote system-call-allowed
44219 Show whether the @code{system} calls are allowed in the File I/O
44223 @node Protocol-specific Representation of Datatypes
44224 @subsection Protocol-specific Representation of Datatypes
44225 @cindex protocol-specific representation of datatypes, in file-i/o protocol
44228 * Integral Datatypes::
44230 * Memory Transfer::
44235 @node Integral Datatypes
44236 @unnumberedsubsubsec Integral Datatypes
44237 @cindex integral datatypes, in file-i/o protocol
44239 The integral datatypes used in the system calls are @code{int},
44240 @code{unsigned int}, @code{long}, @code{unsigned long},
44241 @code{mode_t}, and @code{time_t}.
44243 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
44244 implemented as 32 bit values in this protocol.
44246 @code{long} and @code{unsigned long} are implemented as 64 bit types.
44248 @xref{Limits}, for corresponding MIN and MAX values (similar to those
44249 in @file{limits.h}) to allow range checking on host and target.
44251 @code{time_t} datatypes are defined as seconds since the Epoch.
44253 All integral datatypes transferred as part of a memory read or write of a
44254 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
44257 @node Pointer Values
44258 @unnumberedsubsubsec Pointer Values
44259 @cindex pointer values, in file-i/o protocol
44261 Pointers to target data are transmitted as they are. An exception
44262 is made for pointers to buffers for which the length isn't
44263 transmitted as part of the function call, namely strings. Strings
44264 are transmitted as a pointer/length pair, both as hex values, e.g.@:
44271 which is a pointer to data of length 18 bytes at position 0x1aaf.
44272 The length is defined as the full string length in bytes, including
44273 the trailing null byte. For example, the string @code{"hello world"}
44274 at address 0x123456 is transmitted as
44280 @node Memory Transfer
44281 @unnumberedsubsubsec Memory Transfer
44282 @cindex memory transfer, in file-i/o protocol
44284 Structured data which is transferred using a memory read or write (for
44285 example, a @code{struct stat}) is expected to be in a protocol-specific format
44286 with all scalar multibyte datatypes being big endian. Translation to
44287 this representation needs to be done both by the target before the @code{F}
44288 packet is sent, and by @value{GDBN} before
44289 it transfers memory to the target. Transferred pointers to structured
44290 data should point to the already-coerced data at any time.
44294 @unnumberedsubsubsec struct stat
44295 @cindex struct stat, in file-i/o protocol
44297 The buffer of type @code{struct stat} used by the target and @value{GDBN}
44298 is defined as follows:
44302 unsigned int st_dev; /* device */
44303 unsigned int st_ino; /* inode */
44304 mode_t st_mode; /* protection */
44305 unsigned int st_nlink; /* number of hard links */
44306 unsigned int st_uid; /* user ID of owner */
44307 unsigned int st_gid; /* group ID of owner */
44308 unsigned int st_rdev; /* device type (if inode device) */
44309 unsigned long st_size; /* total size, in bytes */
44310 unsigned long st_blksize; /* blocksize for filesystem I/O */
44311 unsigned long st_blocks; /* number of blocks allocated */
44312 time_t st_atime; /* time of last access */
44313 time_t st_mtime; /* time of last modification */
44314 time_t st_ctime; /* time of last change */
44318 The integral datatypes conform to the definitions given in the
44319 appropriate section (see @ref{Integral Datatypes}, for details) so this
44320 structure is of size 64 bytes.
44322 The values of several fields have a restricted meaning and/or
44328 A value of 0 represents a file, 1 the console.
44331 No valid meaning for the target. Transmitted unchanged.
44334 Valid mode bits are described in @ref{Constants}. Any other
44335 bits have currently no meaning for the target.
44340 No valid meaning for the target. Transmitted unchanged.
44345 These values have a host and file system dependent
44346 accuracy. Especially on Windows hosts, the file system may not
44347 support exact timing values.
44350 The target gets a @code{struct stat} of the above representation and is
44351 responsible for coercing it to the target representation before
44354 Note that due to size differences between the host, target, and protocol
44355 representations of @code{struct stat} members, these members could eventually
44356 get truncated on the target.
44358 @node struct timeval
44359 @unnumberedsubsubsec struct timeval
44360 @cindex struct timeval, in file-i/o protocol
44362 The buffer of type @code{struct timeval} used by the File-I/O protocol
44363 is defined as follows:
44367 time_t tv_sec; /* second */
44368 long tv_usec; /* microsecond */
44372 The integral datatypes conform to the definitions given in the
44373 appropriate section (see @ref{Integral Datatypes}, for details) so this
44374 structure is of size 8 bytes.
44377 @subsection Constants
44378 @cindex constants, in file-i/o protocol
44380 The following values are used for the constants inside of the
44381 protocol. @value{GDBN} and target are responsible for translating these
44382 values before and after the call as needed.
44393 @unnumberedsubsubsec Open Flags
44394 @cindex open flags, in file-i/o protocol
44396 All values are given in hexadecimal representation.
44408 @node mode_t Values
44409 @unnumberedsubsubsec mode_t Values
44410 @cindex mode_t values, in file-i/o protocol
44412 All values are given in octal representation.
44429 @unnumberedsubsubsec Errno Values
44430 @cindex errno values, in file-i/o protocol
44432 All values are given in decimal representation.
44457 @code{EUNKNOWN} is used as a fallback error value if a host system returns
44458 any error value not in the list of supported error numbers.
44461 @unnumberedsubsubsec Lseek Flags
44462 @cindex lseek flags, in file-i/o protocol
44471 @unnumberedsubsubsec Limits
44472 @cindex limits, in file-i/o protocol
44474 All values are given in decimal representation.
44477 INT_MIN -2147483648
44479 UINT_MAX 4294967295
44480 LONG_MIN -9223372036854775808
44481 LONG_MAX 9223372036854775807
44482 ULONG_MAX 18446744073709551615
44485 @node File-I/O Examples
44486 @subsection File-I/O Examples
44487 @cindex file-i/o examples
44489 Example sequence of a write call, file descriptor 3, buffer is at target
44490 address 0x1234, 6 bytes should be written:
44493 <- @code{Fwrite,3,1234,6}
44494 @emph{request memory read from target}
44497 @emph{return "6 bytes written"}
44501 Example sequence of a read call, file descriptor 3, buffer is at target
44502 address 0x1234, 6 bytes should be read:
44505 <- @code{Fread,3,1234,6}
44506 @emph{request memory write to target}
44507 -> @code{X1234,6:XXXXXX}
44508 @emph{return "6 bytes read"}
44512 Example sequence of a read call, call fails on the host due to invalid
44513 file descriptor (@code{EBADF}):
44516 <- @code{Fread,3,1234,6}
44520 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
44524 <- @code{Fread,3,1234,6}
44529 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
44533 <- @code{Fread,3,1234,6}
44534 -> @code{X1234,6:XXXXXX}
44538 @node Library List Format
44539 @section Library List Format
44540 @cindex library list format, remote protocol
44542 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
44543 same process as your application to manage libraries. In this case,
44544 @value{GDBN} can use the loader's symbol table and normal memory
44545 operations to maintain a list of shared libraries. On other
44546 platforms, the operating system manages loaded libraries.
44547 @value{GDBN} can not retrieve the list of currently loaded libraries
44548 through memory operations, so it uses the @samp{qXfer:libraries:read}
44549 packet (@pxref{qXfer library list read}) instead. The remote stub
44550 queries the target's operating system and reports which libraries
44553 The @samp{qXfer:libraries:read} packet returns an XML document which
44554 lists loaded libraries and their offsets. Each library has an
44555 associated name and one or more segment or section base addresses,
44556 which report where the library was loaded in memory.
44558 For the common case of libraries that are fully linked binaries, the
44559 library should have a list of segments. If the target supports
44560 dynamic linking of a relocatable object file, its library XML element
44561 should instead include a list of allocated sections. The segment or
44562 section bases are start addresses, not relocation offsets; they do not
44563 depend on the library's link-time base addresses.
44565 @value{GDBN} must be linked with the Expat library to support XML
44566 library lists. @xref{Expat}.
44568 A simple memory map, with one loaded library relocated by a single
44569 offset, looks like this:
44573 <library name="/lib/libc.so.6">
44574 <segment address="0x10000000"/>
44579 Another simple memory map, with one loaded library with three
44580 allocated sections (.text, .data, .bss), looks like this:
44584 <library name="sharedlib.o">
44585 <section address="0x10000000"/>
44586 <section address="0x20000000"/>
44587 <section address="0x30000000"/>
44592 The format of a library list is described by this DTD:
44595 <!-- library-list: Root element with versioning -->
44596 <!ELEMENT library-list (library)*>
44597 <!ATTLIST library-list version CDATA #FIXED "1.0">
44598 <!ELEMENT library (segment*, section*)>
44599 <!ATTLIST library name CDATA #REQUIRED>
44600 <!ELEMENT segment EMPTY>
44601 <!ATTLIST segment address CDATA #REQUIRED>
44602 <!ELEMENT section EMPTY>
44603 <!ATTLIST section address CDATA #REQUIRED>
44606 In addition, segments and section descriptors cannot be mixed within a
44607 single library element, and you must supply at least one segment or
44608 section for each library.
44610 @node Library List Format for SVR4 Targets
44611 @section Library List Format for SVR4 Targets
44612 @cindex library list format, remote protocol
44614 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
44615 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
44616 shared libraries. Still a special library list provided by this packet is
44617 more efficient for the @value{GDBN} remote protocol.
44619 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
44620 loaded libraries and their SVR4 linker parameters. For each library on SVR4
44621 target, the following parameters are reported:
44625 @code{name}, the absolute file name from the @code{l_name} field of
44626 @code{struct link_map}.
44628 @code{lm} with address of @code{struct link_map} used for TLS
44629 (Thread Local Storage) access.
44631 @code{l_addr}, the displacement as read from the field @code{l_addr} of
44632 @code{struct link_map}. For prelinked libraries this is not an absolute
44633 memory address. It is a displacement of absolute memory address against
44634 address the file was prelinked to during the library load.
44636 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
44639 Additionally the single @code{main-lm} attribute specifies address of
44640 @code{struct link_map} used for the main executable. This parameter is used
44641 for TLS access and its presence is optional.
44643 @value{GDBN} must be linked with the Expat library to support XML
44644 SVR4 library lists. @xref{Expat}.
44646 A simple memory map, with two loaded libraries (which do not use prelink),
44650 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
44651 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
44653 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
44655 </library-list-svr>
44658 The format of an SVR4 library list is described by this DTD:
44661 <!-- library-list-svr4: Root element with versioning -->
44662 <!ELEMENT library-list-svr4 (library)*>
44663 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
44664 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
44665 <!ELEMENT library EMPTY>
44666 <!ATTLIST library name CDATA #REQUIRED>
44667 <!ATTLIST library lm CDATA #REQUIRED>
44668 <!ATTLIST library l_addr CDATA #REQUIRED>
44669 <!ATTLIST library l_ld CDATA #REQUIRED>
44672 @node Memory Map Format
44673 @section Memory Map Format
44674 @cindex memory map format
44676 To be able to write into flash memory, @value{GDBN} needs to obtain a
44677 memory map from the target. This section describes the format of the
44680 The memory map is obtained using the @samp{qXfer:memory-map:read}
44681 (@pxref{qXfer memory map read}) packet and is an XML document that
44682 lists memory regions.
44684 @value{GDBN} must be linked with the Expat library to support XML
44685 memory maps. @xref{Expat}.
44687 The top-level structure of the document is shown below:
44690 <?xml version="1.0"?>
44691 <!DOCTYPE memory-map
44692 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
44693 "http://sourceware.org/gdb/gdb-memory-map.dtd">
44699 Each region can be either:
44704 A region of RAM starting at @var{addr} and extending for @var{length}
44708 <memory type="ram" start="@var{addr}" length="@var{length}"/>
44713 A region of read-only memory:
44716 <memory type="rom" start="@var{addr}" length="@var{length}"/>
44721 A region of flash memory, with erasure blocks @var{blocksize}
44725 <memory type="flash" start="@var{addr}" length="@var{length}">
44726 <property name="blocksize">@var{blocksize}</property>
44732 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
44733 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
44734 packets to write to addresses in such ranges.
44736 The formal DTD for memory map format is given below:
44739 <!-- ................................................... -->
44740 <!-- Memory Map XML DTD ................................ -->
44741 <!-- File: memory-map.dtd .............................. -->
44742 <!-- .................................... .............. -->
44743 <!-- memory-map.dtd -->
44744 <!-- memory-map: Root element with versioning -->
44745 <!ELEMENT memory-map (memory)*>
44746 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
44747 <!ELEMENT memory (property)*>
44748 <!-- memory: Specifies a memory region,
44749 and its type, or device. -->
44750 <!ATTLIST memory type (ram|rom|flash) #REQUIRED
44751 start CDATA #REQUIRED
44752 length CDATA #REQUIRED>
44753 <!-- property: Generic attribute tag -->
44754 <!ELEMENT property (#PCDATA | property)*>
44755 <!ATTLIST property name (blocksize) #REQUIRED>
44758 @node Thread List Format
44759 @section Thread List Format
44760 @cindex thread list format
44762 To efficiently update the list of threads and their attributes,
44763 @value{GDBN} issues the @samp{qXfer:threads:read} packet
44764 (@pxref{qXfer threads read}) and obtains the XML document with
44765 the following structure:
44768 <?xml version="1.0"?>
44770 <thread id="id" core="0" name="name">
44771 ... description ...
44776 Each @samp{thread} element must have the @samp{id} attribute that
44777 identifies the thread (@pxref{thread-id syntax}). The
44778 @samp{core} attribute, if present, specifies which processor core
44779 the thread was last executing on. The @samp{name} attribute, if
44780 present, specifies the human-readable name of the thread. The content
44781 of the of @samp{thread} element is interpreted as human-readable
44782 auxiliary information. The @samp{handle} attribute, if present,
44783 is a hex encoded representation of the thread handle.
44786 @node Traceframe Info Format
44787 @section Traceframe Info Format
44788 @cindex traceframe info format
44790 To be able to know which objects in the inferior can be examined when
44791 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
44792 memory ranges, registers and trace state variables that have been
44793 collected in a traceframe.
44795 This list is obtained using the @samp{qXfer:traceframe-info:read}
44796 (@pxref{qXfer traceframe info read}) packet and is an XML document.
44798 @value{GDBN} must be linked with the Expat library to support XML
44799 traceframe info discovery. @xref{Expat}.
44801 The top-level structure of the document is shown below:
44804 <?xml version="1.0"?>
44805 <!DOCTYPE traceframe-info
44806 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
44807 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
44813 Each traceframe block can be either:
44818 A region of collected memory starting at @var{addr} and extending for
44819 @var{length} bytes from there:
44822 <memory start="@var{addr}" length="@var{length}"/>
44826 A block indicating trace state variable numbered @var{number} has been
44830 <tvar id="@var{number}"/>
44835 The formal DTD for the traceframe info format is given below:
44838 <!ELEMENT traceframe-info (memory | tvar)* >
44839 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
44841 <!ELEMENT memory EMPTY>
44842 <!ATTLIST memory start CDATA #REQUIRED
44843 length CDATA #REQUIRED>
44845 <!ATTLIST tvar id CDATA #REQUIRED>
44848 @node Branch Trace Format
44849 @section Branch Trace Format
44850 @cindex branch trace format
44852 In order to display the branch trace of an inferior thread,
44853 @value{GDBN} needs to obtain the list of branches. This list is
44854 represented as list of sequential code blocks that are connected via
44855 branches. The code in each block has been executed sequentially.
44857 This list is obtained using the @samp{qXfer:btrace:read}
44858 (@pxref{qXfer btrace read}) packet and is an XML document.
44860 @value{GDBN} must be linked with the Expat library to support XML
44861 traceframe info discovery. @xref{Expat}.
44863 The top-level structure of the document is shown below:
44866 <?xml version="1.0"?>
44868 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
44869 "http://sourceware.org/gdb/gdb-btrace.dtd">
44878 A block of sequentially executed instructions starting at @var{begin}
44879 and ending at @var{end}:
44882 <block begin="@var{begin}" end="@var{end}"/>
44887 The formal DTD for the branch trace format is given below:
44890 <!ELEMENT btrace (block* | pt) >
44891 <!ATTLIST btrace version CDATA #FIXED "1.0">
44893 <!ELEMENT block EMPTY>
44894 <!ATTLIST block begin CDATA #REQUIRED
44895 end CDATA #REQUIRED>
44897 <!ELEMENT pt (pt-config?, raw?)>
44899 <!ELEMENT pt-config (cpu?)>
44901 <!ELEMENT cpu EMPTY>
44902 <!ATTLIST cpu vendor CDATA #REQUIRED
44903 family CDATA #REQUIRED
44904 model CDATA #REQUIRED
44905 stepping CDATA #REQUIRED>
44907 <!ELEMENT raw (#PCDATA)>
44910 @node Branch Trace Configuration Format
44911 @section Branch Trace Configuration Format
44912 @cindex branch trace configuration format
44914 For each inferior thread, @value{GDBN} can obtain the branch trace
44915 configuration using the @samp{qXfer:btrace-conf:read}
44916 (@pxref{qXfer btrace-conf read}) packet.
44918 The configuration describes the branch trace format and configuration
44919 settings for that format. The following information is described:
44923 This thread uses the @dfn{Branch Trace Store} (@acronym{BTS}) format.
44926 The size of the @acronym{BTS} ring buffer in bytes.
44929 This thread uses the @dfn{Intel Processor Trace} (@acronym{Intel
44933 The size of the @acronym{Intel PT} ring buffer in bytes.
44937 @value{GDBN} must be linked with the Expat library to support XML
44938 branch trace configuration discovery. @xref{Expat}.
44940 The formal DTD for the branch trace configuration format is given below:
44943 <!ELEMENT btrace-conf (bts?, pt?)>
44944 <!ATTLIST btrace-conf version CDATA #FIXED "1.0">
44946 <!ELEMENT bts EMPTY>
44947 <!ATTLIST bts size CDATA #IMPLIED>
44949 <!ELEMENT pt EMPTY>
44950 <!ATTLIST pt size CDATA #IMPLIED>
44953 @include agentexpr.texi
44955 @node Target Descriptions
44956 @appendix Target Descriptions
44957 @cindex target descriptions
44959 One of the challenges of using @value{GDBN} to debug embedded systems
44960 is that there are so many minor variants of each processor
44961 architecture in use. It is common practice for vendors to start with
44962 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
44963 and then make changes to adapt it to a particular market niche. Some
44964 architectures have hundreds of variants, available from dozens of
44965 vendors. This leads to a number of problems:
44969 With so many different customized processors, it is difficult for
44970 the @value{GDBN} maintainers to keep up with the changes.
44972 Since individual variants may have short lifetimes or limited
44973 audiences, it may not be worthwhile to carry information about every
44974 variant in the @value{GDBN} source tree.
44976 When @value{GDBN} does support the architecture of the embedded system
44977 at hand, the task of finding the correct architecture name to give the
44978 @command{set architecture} command can be error-prone.
44981 To address these problems, the @value{GDBN} remote protocol allows a
44982 target system to not only identify itself to @value{GDBN}, but to
44983 actually describe its own features. This lets @value{GDBN} support
44984 processor variants it has never seen before --- to the extent that the
44985 descriptions are accurate, and that @value{GDBN} understands them.
44987 @value{GDBN} must be linked with the Expat library to support XML
44988 target descriptions. @xref{Expat}.
44991 * Retrieving Descriptions:: How descriptions are fetched from a target.
44992 * Target Description Format:: The contents of a target description.
44993 * Predefined Target Types:: Standard types available for target
44995 * Enum Target Types:: How to define enum target types.
44996 * Standard Target Features:: Features @value{GDBN} knows about.
44999 @node Retrieving Descriptions
45000 @section Retrieving Descriptions
45002 Target descriptions can be read from the target automatically, or
45003 specified by the user manually. The default behavior is to read the
45004 description from the target. @value{GDBN} retrieves it via the remote
45005 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
45006 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
45007 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
45008 XML document, of the form described in @ref{Target Description
45011 Alternatively, you can specify a file to read for the target description.
45012 If a file is set, the target will not be queried. The commands to
45013 specify a file are:
45016 @cindex set tdesc filename
45017 @item set tdesc filename @var{path}
45018 Read the target description from @var{path}.
45020 @cindex unset tdesc filename
45021 @item unset tdesc filename
45022 Do not read the XML target description from a file. @value{GDBN}
45023 will use the description supplied by the current target.
45025 @cindex show tdesc filename
45026 @item show tdesc filename
45027 Show the filename to read for a target description, if any.
45031 @node Target Description Format
45032 @section Target Description Format
45033 @cindex target descriptions, XML format
45035 A target description annex is an @uref{http://www.w3.org/XML/, XML}
45036 document which complies with the Document Type Definition provided in
45037 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
45038 means you can use generally available tools like @command{xmllint} to
45039 check that your feature descriptions are well-formed and valid.
45040 However, to help people unfamiliar with XML write descriptions for
45041 their targets, we also describe the grammar here.
45043 Target descriptions can identify the architecture of the remote target
45044 and (for some architectures) provide information about custom register
45045 sets. They can also identify the OS ABI of the remote target.
45046 @value{GDBN} can use this information to autoconfigure for your
45047 target, or to warn you if you connect to an unsupported target.
45049 Here is a simple target description:
45052 <target version="1.0">
45053 <architecture>i386:x86-64</architecture>
45058 This minimal description only says that the target uses
45059 the x86-64 architecture.
45061 A target description has the following overall form, with [ ] marking
45062 optional elements and @dots{} marking repeatable elements. The elements
45063 are explained further below.
45066 <?xml version="1.0"?>
45067 <!DOCTYPE target SYSTEM "gdb-target.dtd">
45068 <target version="1.0">
45069 @r{[}@var{architecture}@r{]}
45070 @r{[}@var{osabi}@r{]}
45071 @r{[}@var{compatible}@r{]}
45072 @r{[}@var{feature}@dots{}@r{]}
45077 The description is generally insensitive to whitespace and line
45078 breaks, under the usual common-sense rules. The XML version
45079 declaration and document type declaration can generally be omitted
45080 (@value{GDBN} does not require them), but specifying them may be
45081 useful for XML validation tools. The @samp{version} attribute for
45082 @samp{<target>} may also be omitted, but we recommend
45083 including it; if future versions of @value{GDBN} use an incompatible
45084 revision of @file{gdb-target.dtd}, they will detect and report
45085 the version mismatch.
45087 @subsection Inclusion
45088 @cindex target descriptions, inclusion
45091 @cindex <xi:include>
45094 It can sometimes be valuable to split a target description up into
45095 several different annexes, either for organizational purposes, or to
45096 share files between different possible target descriptions. You can
45097 divide a description into multiple files by replacing any element of
45098 the target description with an inclusion directive of the form:
45101 <xi:include href="@var{document}"/>
45105 When @value{GDBN} encounters an element of this form, it will retrieve
45106 the named XML @var{document}, and replace the inclusion directive with
45107 the contents of that document. If the current description was read
45108 using @samp{qXfer}, then so will be the included document;
45109 @var{document} will be interpreted as the name of an annex. If the
45110 current description was read from a file, @value{GDBN} will look for
45111 @var{document} as a file in the same directory where it found the
45112 original description.
45114 @subsection Architecture
45115 @cindex <architecture>
45117 An @samp{<architecture>} element has this form:
45120 <architecture>@var{arch}</architecture>
45123 @var{arch} is one of the architectures from the set accepted by
45124 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
45127 @cindex @code{<osabi>}
45129 This optional field was introduced in @value{GDBN} version 7.0.
45130 Previous versions of @value{GDBN} ignore it.
45132 An @samp{<osabi>} element has this form:
45135 <osabi>@var{abi-name}</osabi>
45138 @var{abi-name} is an OS ABI name from the same selection accepted by
45139 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
45141 @subsection Compatible Architecture
45142 @cindex @code{<compatible>}
45144 This optional field was introduced in @value{GDBN} version 7.0.
45145 Previous versions of @value{GDBN} ignore it.
45147 A @samp{<compatible>} element has this form:
45150 <compatible>@var{arch}</compatible>
45153 @var{arch} is one of the architectures from the set accepted by
45154 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
45156 A @samp{<compatible>} element is used to specify that the target
45157 is able to run binaries in some other than the main target architecture
45158 given by the @samp{<architecture>} element. For example, on the
45159 Cell Broadband Engine, the main architecture is @code{powerpc:common}
45160 or @code{powerpc:common64}, but the system is able to run binaries
45161 in the @code{spu} architecture as well. The way to describe this
45162 capability with @samp{<compatible>} is as follows:
45165 <architecture>powerpc:common</architecture>
45166 <compatible>spu</compatible>
45169 @subsection Features
45172 Each @samp{<feature>} describes some logical portion of the target
45173 system. Features are currently used to describe available CPU
45174 registers and the types of their contents. A @samp{<feature>} element
45178 <feature name="@var{name}">
45179 @r{[}@var{type}@dots{}@r{]}
45185 Each feature's name should be unique within the description. The name
45186 of a feature does not matter unless @value{GDBN} has some special
45187 knowledge of the contents of that feature; if it does, the feature
45188 should have its standard name. @xref{Standard Target Features}.
45192 Any register's value is a collection of bits which @value{GDBN} must
45193 interpret. The default interpretation is a two's complement integer,
45194 but other types can be requested by name in the register description.
45195 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
45196 Target Types}), and the description can define additional composite
45199 Each type element must have an @samp{id} attribute, which gives
45200 a unique (within the containing @samp{<feature>}) name to the type.
45201 Types must be defined before they are used.
45204 Some targets offer vector registers, which can be treated as arrays
45205 of scalar elements. These types are written as @samp{<vector>} elements,
45206 specifying the array element type, @var{type}, and the number of elements,
45210 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
45214 If a register's value is usefully viewed in multiple ways, define it
45215 with a union type containing the useful representations. The
45216 @samp{<union>} element contains one or more @samp{<field>} elements,
45217 each of which has a @var{name} and a @var{type}:
45220 <union id="@var{id}">
45221 <field name="@var{name}" type="@var{type}"/>
45228 If a register's value is composed from several separate values, define
45229 it with either a structure type or a flags type.
45230 A flags type may only contain bitfields.
45231 A structure type may either contain only bitfields or contain no bitfields.
45232 If the value contains only bitfields, its total size in bytes must be
45235 Non-bitfield values have a @var{name} and @var{type}.
45238 <struct id="@var{id}">
45239 <field name="@var{name}" type="@var{type}"/>
45244 Both @var{name} and @var{type} values are required.
45245 No implicit padding is added.
45247 Bitfield values have a @var{name}, @var{start}, @var{end} and @var{type}.
45250 <struct id="@var{id}" size="@var{size}">
45251 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
45257 <flags id="@var{id}" size="@var{size}">
45258 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
45263 The @var{name} value is required.
45264 Bitfield values may be named with the empty string, @samp{""},
45265 in which case the field is ``filler'' and its value is not printed.
45266 Not all bits need to be specified, so ``filler'' fields are optional.
45268 The @var{start} and @var{end} values are required, and @var{type}
45270 The field's @var{start} must be less than or equal to its @var{end},
45271 and zero represents the least significant bit.
45273 The default value of @var{type} is @code{bool} for single bit fields,
45274 and an unsigned integer otherwise.
45276 Which to choose? Structures or flags?
45278 Registers defined with @samp{flags} have these advantages over
45279 defining them with @samp{struct}:
45283 Arithmetic may be performed on them as if they were integers.
45285 They are printed in a more readable fashion.
45288 Registers defined with @samp{struct} have one advantage over
45289 defining them with @samp{flags}:
45293 One can fetch individual fields like in @samp{C}.
45296 (gdb) print $my_struct_reg.field3
45302 @subsection Registers
45305 Each register is represented as an element with this form:
45308 <reg name="@var{name}"
45309 bitsize="@var{size}"
45310 @r{[}regnum="@var{num}"@r{]}
45311 @r{[}save-restore="@var{save-restore}"@r{]}
45312 @r{[}type="@var{type}"@r{]}
45313 @r{[}group="@var{group}"@r{]}/>
45317 The components are as follows:
45322 The register's name; it must be unique within the target description.
45325 The register's size, in bits.
45328 The register's number. If omitted, a register's number is one greater
45329 than that of the previous register (either in the current feature or in
45330 a preceding feature); the first register in the target description
45331 defaults to zero. This register number is used to read or write
45332 the register; e.g.@: it is used in the remote @code{p} and @code{P}
45333 packets, and registers appear in the @code{g} and @code{G} packets
45334 in order of increasing register number.
45337 Whether the register should be preserved across inferior function
45338 calls; this must be either @code{yes} or @code{no}. The default is
45339 @code{yes}, which is appropriate for most registers except for
45340 some system control registers; this is not related to the target's
45344 The type of the register. It may be a predefined type, a type
45345 defined in the current feature, or one of the special types @code{int}
45346 and @code{float}. @code{int} is an integer type of the correct size
45347 for @var{bitsize}, and @code{float} is a floating point type (in the
45348 architecture's normal floating point format) of the correct size for
45349 @var{bitsize}. The default is @code{int}.
45352 The register group to which this register belongs. It can be one of the
45353 standard register groups @code{general}, @code{float}, @code{vector} or an
45354 arbitrary string. Group names should be limited to alphanumeric characters.
45355 If a group name is made up of multiple words the words may be separated by
45356 hyphens; e.g.@: @code{special-group} or @code{ultra-special-group}. If no
45357 @var{group} is specified, @value{GDBN} will not display the register in
45358 @code{info registers}.
45362 @node Predefined Target Types
45363 @section Predefined Target Types
45364 @cindex target descriptions, predefined types
45366 Type definitions in the self-description can build up composite types
45367 from basic building blocks, but can not define fundamental types. Instead,
45368 standard identifiers are provided by @value{GDBN} for the fundamental
45369 types. The currently supported types are:
45374 Boolean type, occupying a single bit.
45382 Signed integer types holding the specified number of bits.
45390 Unsigned integer types holding the specified number of bits.
45394 Pointers to unspecified code and data. The program counter and
45395 any dedicated return address register may be marked as code
45396 pointers; printing a code pointer converts it into a symbolic
45397 address. The stack pointer and any dedicated address registers
45398 may be marked as data pointers.
45401 Single precision IEEE floating point.
45404 Double precision IEEE floating point.
45407 The 12-byte extended precision format used by ARM FPA registers.
45410 The 10-byte extended precision format used by x87 registers.
45413 32bit @sc{eflags} register used by x86.
45416 32bit @sc{mxcsr} register used by x86.
45420 @node Enum Target Types
45421 @section Enum Target Types
45422 @cindex target descriptions, enum types
45424 Enum target types are useful in @samp{struct} and @samp{flags}
45425 register descriptions. @xref{Target Description Format}.
45427 Enum types have a name, size and a list of name/value pairs.
45430 <enum id="@var{id}" size="@var{size}">
45431 <evalue name="@var{name}" value="@var{value}"/>
45436 Enums must be defined before they are used.
45439 <enum id="levels_type" size="4">
45440 <evalue name="low" value="0"/>
45441 <evalue name="high" value="1"/>
45443 <flags id="flags_type" size="4">
45444 <field name="X" start="0"/>
45445 <field name="LEVEL" start="1" end="1" type="levels_type"/>
45447 <reg name="flags" bitsize="32" type="flags_type"/>
45450 Given that description, a value of 3 for the @samp{flags} register
45451 would be printed as:
45454 (gdb) info register flags
45455 flags 0x3 [ X LEVEL=high ]
45458 @node Standard Target Features
45459 @section Standard Target Features
45460 @cindex target descriptions, standard features
45462 A target description must contain either no registers or all the
45463 target's registers. If the description contains no registers, then
45464 @value{GDBN} will assume a default register layout, selected based on
45465 the architecture. If the description contains any registers, the
45466 default layout will not be used; the standard registers must be
45467 described in the target description, in such a way that @value{GDBN}
45468 can recognize them.
45470 This is accomplished by giving specific names to feature elements
45471 which contain standard registers. @value{GDBN} will look for features
45472 with those names and verify that they contain the expected registers;
45473 if any known feature is missing required registers, or if any required
45474 feature is missing, @value{GDBN} will reject the target
45475 description. You can add additional registers to any of the
45476 standard features --- @value{GDBN} will display them just as if
45477 they were added to an unrecognized feature.
45479 This section lists the known features and their expected contents.
45480 Sample XML documents for these features are included in the
45481 @value{GDBN} source tree, in the directory @file{gdb/features}.
45483 Names recognized by @value{GDBN} should include the name of the
45484 company or organization which selected the name, and the overall
45485 architecture to which the feature applies; so e.g.@: the feature
45486 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
45488 The names of registers are not case sensitive for the purpose
45489 of recognizing standard features, but @value{GDBN} will only display
45490 registers using the capitalization used in the description.
45493 * AArch64 Features::
45497 * MicroBlaze Features::
45501 * Nios II Features::
45502 * OpenRISC 1000 Features::
45503 * PowerPC Features::
45504 * RISC-V Features::
45506 * S/390 and System z Features::
45512 @node AArch64 Features
45513 @subsection AArch64 Features
45514 @cindex target descriptions, AArch64 features
45516 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
45517 targets. It should contain registers @samp{x0} through @samp{x30},
45518 @samp{sp}, @samp{pc}, and @samp{cpsr}.
45520 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
45521 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
45524 The @samp{org.gnu.gdb.aarch64.sve} feature is optional. If present,
45525 it should contain registers @samp{z0} through @samp{z31}, @samp{p0}
45526 through @samp{p15}, @samp{ffr} and @samp{vg}.
45528 The @samp{org.gnu.gdb.aarch64.pauth} feature is optional. If present,
45529 it should contain registers @samp{pauth_dmask} and @samp{pauth_cmask}.
45532 @subsection ARC Features
45533 @cindex target descriptions, ARC Features
45535 ARC processors are so configurable that even core registers and their numbers
45536 are not predetermined completely. Moreover, @emph{flags} and @emph{PC}
45537 registers, which are important to @value{GDBN}, are not ``core'' registers in
45538 ARC. Therefore, there are two features that their presence is mandatory:
45539 @samp{org.gnu.gdb.arc.core} and @samp{org.gnu.gdb.arc.aux}.
45541 The @samp{org.gnu.gdb.arc.core} feature is required for all targets. It must
45546 @samp{r0} through @samp{r25} for normal register file targets.
45548 @samp{r0} through @samp{r3}, and @samp{r10} through @samp{r15} for reduced
45549 register file targets.
45551 @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}@footnote{Not necessary for ARCv1.},
45552 @samp{blink}, @samp{lp_count}, @samp{pcl}.
45555 In case of an ARCompact target (ARCv1 ISA), the @samp{org.gnu.gdb.arc.core}
45556 feature may contain registers @samp{ilink1} and @samp{ilink2}. While in case
45557 of ARC EM and ARC HS targets (ARCv2 ISA), register @samp{ilink} may be present.
45558 The difference between ARCv1 and ARCv2 is the naming of registers @emph{29th}
45559 and @emph{30th}. They are called @samp{ilink1} and @samp{ilink2} for ARCv1 and
45560 are optional. For ARCv2, they are called @samp{ilink} and @samp{r30} and only
45561 @samp{ilink} is optional. The optionality of @samp{ilink*} registers is
45562 because of their inaccessibility during user space debugging sessions.
45564 Extension core registers @samp{r32} through @samp{r59} are optional and their
45565 existence depends on the configuration. When debugging GNU/Linux applications,
45566 i.e.@: user space debugging, these core registers are not available.
45568 The @samp{org.gnu.gdb.arc.aux} feature is required for all ARC targets. Here
45569 is the list of registers pertinent to this feature:
45573 mandatory: @samp{pc} and @samp{status32}.
45575 optional: @samp{lp_start}, @samp{lp_end}, and @samp{bta}.
45579 @subsection ARM Features
45580 @cindex target descriptions, ARM features
45582 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
45584 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
45585 @samp{lr}, @samp{pc}, and @samp{cpsr}.
45587 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
45588 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
45589 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
45592 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
45593 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
45595 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
45596 it should contain at least registers @samp{wR0} through @samp{wR15} and
45597 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
45598 @samp{wCSSF}, and @samp{wCASF} registers are optional.
45600 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
45601 should contain at least registers @samp{d0} through @samp{d15}. If
45602 they are present, @samp{d16} through @samp{d31} should also be included.
45603 @value{GDBN} will synthesize the single-precision registers from
45604 halves of the double-precision registers.
45606 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
45607 need to contain registers; it instructs @value{GDBN} to display the
45608 VFP double-precision registers as vectors and to synthesize the
45609 quad-precision registers from pairs of double-precision registers.
45610 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
45611 be present and include 32 double-precision registers.
45613 @node i386 Features
45614 @subsection i386 Features
45615 @cindex target descriptions, i386 features
45617 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
45618 targets. It should describe the following registers:
45622 @samp{eax} through @samp{edi} plus @samp{eip} for i386
45624 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
45626 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
45627 @samp{fs}, @samp{gs}
45629 @samp{st0} through @samp{st7}
45631 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
45632 @samp{foseg}, @samp{fooff} and @samp{fop}
45635 The register sets may be different, depending on the target.
45637 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
45638 describe registers:
45642 @samp{xmm0} through @samp{xmm7} for i386
45644 @samp{xmm0} through @samp{xmm15} for amd64
45649 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
45650 @samp{org.gnu.gdb.i386.sse} feature. It should
45651 describe the upper 128 bits of @sc{ymm} registers:
45655 @samp{ymm0h} through @samp{ymm7h} for i386
45657 @samp{ymm0h} through @samp{ymm15h} for amd64
45660 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel
45661 Memory Protection Extension (MPX). It should describe the following registers:
45665 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
45667 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
45670 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
45671 describe a single register, @samp{orig_eax}.
45673 The @samp{org.gnu.gdb.i386.segments} feature is optional. It should
45674 describe two system registers: @samp{fs_base} and @samp{gs_base}.
45676 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
45677 @samp{org.gnu.gdb.i386.avx} feature. It should
45678 describe additional @sc{xmm} registers:
45682 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
45685 It should describe the upper 128 bits of additional @sc{ymm} registers:
45689 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
45693 describe the upper 256 bits of @sc{zmm} registers:
45697 @samp{zmm0h} through @samp{zmm7h} for i386.
45699 @samp{zmm0h} through @samp{zmm15h} for amd64.
45703 describe the additional @sc{zmm} registers:
45707 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
45710 The @samp{org.gnu.gdb.i386.pkeys} feature is optional. It should
45711 describe a single register, @samp{pkru}. It is a 32-bit register
45712 valid for i386 and amd64.
45714 @node MicroBlaze Features
45715 @subsection MicroBlaze Features
45716 @cindex target descriptions, MicroBlaze features
45718 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
45719 targets. It should contain registers @samp{r0} through @samp{r31},
45720 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
45721 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
45722 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
45724 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
45725 If present, it should contain registers @samp{rshr} and @samp{rslr}
45727 @node MIPS Features
45728 @subsection @acronym{MIPS} Features
45729 @cindex target descriptions, @acronym{MIPS} features
45731 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
45732 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
45733 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
45736 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
45737 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
45738 registers. They may be 32-bit or 64-bit depending on the target.
45740 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
45741 it may be optional in a future version of @value{GDBN}. It should
45742 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
45743 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
45745 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
45746 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
45747 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
45748 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
45750 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
45751 contain a single register, @samp{restart}, which is used by the
45752 Linux kernel to control restartable syscalls.
45754 @node M68K Features
45755 @subsection M68K Features
45756 @cindex target descriptions, M68K features
45759 @item @samp{org.gnu.gdb.m68k.core}
45760 @itemx @samp{org.gnu.gdb.coldfire.core}
45761 @itemx @samp{org.gnu.gdb.fido.core}
45762 One of those features must be always present.
45763 The feature that is present determines which flavor of m68k is
45764 used. The feature that is present should contain registers
45765 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
45766 @samp{sp}, @samp{ps} and @samp{pc}.
45768 @item @samp{org.gnu.gdb.coldfire.fp}
45769 This feature is optional. If present, it should contain registers
45770 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
45773 Note that, despite the fact that this feature's name says
45774 @samp{coldfire}, it is used to describe any floating point registers.
45775 The size of the registers must match the main m68k flavor; so, for
45776 example, if the primary feature is reported as @samp{coldfire}, then
45777 64-bit floating point registers are required.
45780 @node NDS32 Features
45781 @subsection NDS32 Features
45782 @cindex target descriptions, NDS32 features
45784 The @samp{org.gnu.gdb.nds32.core} feature is required for NDS32
45785 targets. It should contain at least registers @samp{r0} through
45786 @samp{r10}, @samp{r15}, @samp{fp}, @samp{gp}, @samp{lp}, @samp{sp},
45789 The @samp{org.gnu.gdb.nds32.fpu} feature is optional. If present,
45790 it should contain 64-bit double-precision floating-point registers
45791 @samp{fd0} through @emph{fdN}, which should be @samp{fd3}, @samp{fd7},
45792 @samp{fd15}, or @samp{fd31} based on the FPU configuration implemented.
45794 @emph{Note:} The first sixteen 64-bit double-precision floating-point
45795 registers are overlapped with the thirty-two 32-bit single-precision
45796 floating-point registers. The 32-bit single-precision registers, if
45797 not being listed explicitly, will be synthesized from halves of the
45798 overlapping 64-bit double-precision registers. Listing 32-bit
45799 single-precision registers explicitly is deprecated, and the
45800 support to it could be totally removed some day.
45802 @node Nios II Features
45803 @subsection Nios II Features
45804 @cindex target descriptions, Nios II features
45806 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
45807 targets. It should contain the 32 core registers (@samp{zero},
45808 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
45809 @samp{pc}, and the 16 control registers (@samp{status} through
45812 @node OpenRISC 1000 Features
45813 @subsection Openrisc 1000 Features
45814 @cindex target descriptions, OpenRISC 1000 features
45816 The @samp{org.gnu.gdb.or1k.group0} feature is required for OpenRISC 1000
45817 targets. It should contain the 32 general purpose registers (@samp{r0}
45818 through @samp{r31}), @samp{ppc}, @samp{npc} and @samp{sr}.
45820 @node PowerPC Features
45821 @subsection PowerPC Features
45822 @cindex target descriptions, PowerPC features
45824 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
45825 targets. It should contain registers @samp{r0} through @samp{r31},
45826 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
45827 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
45829 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
45830 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
45832 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
45833 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr}, and
45834 @samp{vrsave}. @value{GDBN} will define pseudo-registers @samp{v0}
45835 through @samp{v31} as aliases for the corresponding @samp{vrX}
45838 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
45839 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN} will
45840 combine these registers with the floating point registers (@samp{f0}
45841 through @samp{f31}) and the altivec registers (@samp{vr0} through
45842 @samp{vr31}) to present the 128-bit wide registers @samp{vs0} through
45843 @samp{vs63}, the set of vector-scalar registers for POWER7.
45844 Therefore, this feature requires both @samp{org.gnu.gdb.power.fpu} and
45845 @samp{org.gnu.gdb.power.altivec}.
45847 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
45848 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
45849 @samp{spefscr}. SPE targets should provide 32-bit registers in
45850 @samp{org.gnu.gdb.power.core} and provide the upper halves in
45851 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
45852 these to present registers @samp{ev0} through @samp{ev31} to the
45855 The @samp{org.gnu.gdb.power.ppr} feature is optional. It should
45856 contain the 64-bit register @samp{ppr}.
45858 The @samp{org.gnu.gdb.power.dscr} feature is optional. It should
45859 contain the 64-bit register @samp{dscr}.
45861 The @samp{org.gnu.gdb.power.tar} feature is optional. It should
45862 contain the 64-bit register @samp{tar}.
45864 The @samp{org.gnu.gdb.power.ebb} feature is optional. It should
45865 contain registers @samp{bescr}, @samp{ebbhr} and @samp{ebbrr}, all
45868 The @samp{org.gnu.gdb.power.linux.pmu} feature is optional. It should
45869 contain registers @samp{mmcr0}, @samp{mmcr2}, @samp{siar}, @samp{sdar}
45870 and @samp{sier}, all 64-bit wide. This is the subset of the isa 2.07
45871 server PMU registers provided by @sc{gnu}/Linux.
45873 The @samp{org.gnu.gdb.power.htm.spr} feature is optional. It should
45874 contain registers @samp{tfhar}, @samp{texasr} and @samp{tfiar}, all
45877 The @samp{org.gnu.gdb.power.htm.core} feature is optional. It should
45878 contain the checkpointed general-purpose registers @samp{cr0} through
45879 @samp{cr31}, as well as the checkpointed registers @samp{clr} and
45880 @samp{cctr}. These registers may all be either 32-bit or 64-bit
45881 depending on the target. It should also contain the checkpointed
45882 registers @samp{ccr} and @samp{cxer}, which should both be 32-bit
45885 The @samp{org.gnu.gdb.power.htm.fpu} feature is optional. It should
45886 contain the checkpointed 64-bit floating-point registers @samp{cf0}
45887 through @samp{cf31}, as well as the checkpointed 64-bit register
45890 The @samp{org.gnu.gdb.power.htm.altivec} feature is optional. It
45891 should contain the checkpointed altivec registers @samp{cvr0} through
45892 @samp{cvr31}, all 128-bit wide. It should also contain the
45893 checkpointed registers @samp{cvscr} and @samp{cvrsave}, both 32-bit
45896 The @samp{org.gnu.gdb.power.htm.vsx} feature is optional. It should
45897 contain registers @samp{cvs0h} through @samp{cvs31h}. @value{GDBN}
45898 will combine these registers with the checkpointed floating point
45899 registers (@samp{cf0} through @samp{cf31}) and the checkpointed
45900 altivec registers (@samp{cvr0} through @samp{cvr31}) to present the
45901 128-bit wide checkpointed vector-scalar registers @samp{cvs0} through
45902 @samp{cvs63}. Therefore, this feature requires both
45903 @samp{org.gnu.gdb.power.htm.altivec} and
45904 @samp{org.gnu.gdb.power.htm.fpu}.
45906 The @samp{org.gnu.gdb.power.htm.ppr} feature is optional. It should
45907 contain the 64-bit checkpointed register @samp{cppr}.
45909 The @samp{org.gnu.gdb.power.htm.dscr} feature is optional. It should
45910 contain the 64-bit checkpointed register @samp{cdscr}.
45912 The @samp{org.gnu.gdb.power.htm.tar} feature is optional. It should
45913 contain the 64-bit checkpointed register @samp{ctar}.
45916 @node RISC-V Features
45917 @subsection RISC-V Features
45918 @cindex target descriptions, RISC-V Features
45920 The @samp{org.gnu.gdb.riscv.cpu} feature is required for RISC-V
45921 targets. It should contain the registers @samp{x0} through
45922 @samp{x31}, and @samp{pc}. Either the architectural names (@samp{x0},
45923 @samp{x1}, etc) can be used, or the ABI names (@samp{zero}, @samp{ra},
45926 The @samp{org.gnu.gdb.riscv.fpu} feature is optional. If present, it
45927 should contain registers @samp{f0} through @samp{f31}, @samp{fflags},
45928 @samp{frm}, and @samp{fcsr}. As with the cpu feature, either the
45929 architectural register names, or the ABI names can be used.
45931 The @samp{org.gnu.gdb.riscv.virtual} feature is optional. If present,
45932 it should contain registers that are not backed by real registers on
45933 the target, but are instead virtual, where the register value is
45934 derived from other target state. In many ways these are like
45935 @value{GDBN}s pseudo-registers, except implemented by the target.
45936 Currently the only register expected in this set is the one byte
45937 @samp{priv} register that contains the target's privilege level in the
45938 least significant two bits.
45940 The @samp{org.gnu.gdb.riscv.csr} feature is optional. If present, it
45941 should contain all of the target's standard CSRs. Standard CSRs are
45942 those defined in the RISC-V specification documents. There is some
45943 overlap between this feature and the fpu feature; the @samp{fflags},
45944 @samp{frm}, and @samp{fcsr} registers could be in either feature. The
45945 expectation is that these registers will be in the fpu feature if the
45946 target has floating point hardware, but can be moved into the csr
45947 feature if the target has the floating point control registers, but no
45948 other floating point hardware.
45951 @subsection RX Features
45952 @cindex target descriptions, RX Features
45954 The @samp{org.gnu.gdb.rx.core} feature is required for RX
45955 targets. It should contain the registers @samp{r0} through
45956 @samp{r15}, @samp{usp}, @samp{isp}, @samp{psw}, @samp{pc}, @samp{intb},
45957 @samp{bpsw}, @samp{bpc}, @samp{fintv}, @samp{fpsw}, and @samp{acc}.
45959 @node S/390 and System z Features
45960 @subsection S/390 and System z Features
45961 @cindex target descriptions, S/390 features
45962 @cindex target descriptions, System z features
45964 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
45965 System z targets. It should contain the PSW and the 16 general
45966 registers. In particular, System z targets should provide the 64-bit
45967 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
45968 S/390 targets should provide the 32-bit versions of these registers.
45969 A System z target that runs in 31-bit addressing mode should provide
45970 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
45971 register's upper halves @samp{r0h} through @samp{r15h}, and their
45972 lower halves @samp{r0l} through @samp{r15l}.
45974 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
45975 contain the 64-bit registers @samp{f0} through @samp{f15}, and
45978 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
45979 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
45981 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
45982 contain the register @samp{orig_r2}, which is 64-bit wide on System z
45983 targets and 32-bit otherwise. In addition, the feature may contain
45984 the @samp{last_break} register, whose width depends on the addressing
45985 mode, as well as the @samp{system_call} register, which is always
45988 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
45989 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
45990 @samp{atia}, and @samp{tr0} through @samp{tr15}.
45992 The @samp{org.gnu.gdb.s390.vx} feature is optional. It should contain
45993 64-bit wide registers @samp{v0l} through @samp{v15l}, which will be
45994 combined by @value{GDBN} with the floating point registers @samp{f0}
45995 through @samp{f15} to present the 128-bit wide vector registers
45996 @samp{v0} through @samp{v15}. In addition, this feature should
45997 contain the 128-bit wide vector registers @samp{v16} through
46000 The @samp{org.gnu.gdb.s390.gs} feature is optional. It should contain
46001 the 64-bit wide guarded-storage-control registers @samp{gsd},
46002 @samp{gssm}, and @samp{gsepla}.
46004 The @samp{org.gnu.gdb.s390.gsbc} feature is optional. It should contain
46005 the 64-bit wide guarded-storage broadcast control registers
46006 @samp{bc_gsd}, @samp{bc_gssm}, and @samp{bc_gsepla}.
46008 @node Sparc Features
46009 @subsection Sparc Features
46010 @cindex target descriptions, sparc32 features
46011 @cindex target descriptions, sparc64 features
46012 The @samp{org.gnu.gdb.sparc.cpu} feature is required for sparc32/sparc64
46013 targets. It should describe the following registers:
46017 @samp{g0} through @samp{g7}
46019 @samp{o0} through @samp{o7}
46021 @samp{l0} through @samp{l7}
46023 @samp{i0} through @samp{i7}
46026 They may be 32-bit or 64-bit depending on the target.
46028 Also the @samp{org.gnu.gdb.sparc.fpu} feature is required for sparc32/sparc64
46029 targets. It should describe the following registers:
46033 @samp{f0} through @samp{f31}
46035 @samp{f32} through @samp{f62} for sparc64
46038 The @samp{org.gnu.gdb.sparc.cp0} feature is required for sparc32/sparc64
46039 targets. It should describe the following registers:
46043 @samp{y}, @samp{psr}, @samp{wim}, @samp{tbr}, @samp{pc}, @samp{npc},
46044 @samp{fsr}, and @samp{csr} for sparc32
46046 @samp{pc}, @samp{npc}, @samp{state}, @samp{fsr}, @samp{fprs}, and @samp{y}
46050 @node TIC6x Features
46051 @subsection TMS320C6x Features
46052 @cindex target descriptions, TIC6x features
46053 @cindex target descriptions, TMS320C6x features
46054 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
46055 targets. It should contain registers @samp{A0} through @samp{A15},
46056 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
46058 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
46059 contain registers @samp{A16} through @samp{A31} and @samp{B16}
46060 through @samp{B31}.
46062 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
46063 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
46065 @node Operating System Information
46066 @appendix Operating System Information
46067 @cindex operating system information
46069 Users of @value{GDBN} often wish to obtain information about the state of
46070 the operating system running on the target---for example the list of
46071 processes, or the list of open files. This section describes the
46072 mechanism that makes it possible. This mechanism is similar to the
46073 target features mechanism (@pxref{Target Descriptions}), but focuses
46074 on a different aspect of target.
46076 Operating system information is retrieved from the target via the
46077 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
46078 read}). The object name in the request should be @samp{osdata}, and
46079 the @var{annex} identifies the data to be fetched.
46086 @appendixsection Process list
46087 @cindex operating system information, process list
46089 When requesting the process list, the @var{annex} field in the
46090 @samp{qXfer} request should be @samp{processes}. The returned data is
46091 an XML document. The formal syntax of this document is defined in
46092 @file{gdb/features/osdata.dtd}.
46094 An example document is:
46097 <?xml version="1.0"?>
46098 <!DOCTYPE target SYSTEM "osdata.dtd">
46099 <osdata type="processes">
46101 <column name="pid">1</column>
46102 <column name="user">root</column>
46103 <column name="command">/sbin/init</column>
46104 <column name="cores">1,2,3</column>
46109 Each item should include a column whose name is @samp{pid}. The value
46110 of that column should identify the process on the target. The
46111 @samp{user} and @samp{command} columns are optional, and will be
46112 displayed by @value{GDBN}. The @samp{cores} column, if present,
46113 should contain a comma-separated list of cores that this process
46114 is running on. Target may provide additional columns,
46115 which @value{GDBN} currently ignores.
46117 @node Trace File Format
46118 @appendix Trace File Format
46119 @cindex trace file format
46121 The trace file comes in three parts: a header, a textual description
46122 section, and a trace frame section with binary data.
46124 The header has the form @code{\x7fTRACE0\n}. The first byte is
46125 @code{0x7f} so as to indicate that the file contains binary data,
46126 while the @code{0} is a version number that may have different values
46129 The description section consists of multiple lines of @sc{ascii} text
46130 separated by newline characters (@code{0xa}). The lines may include a
46131 variety of optional descriptive or context-setting information, such
46132 as tracepoint definitions or register set size. @value{GDBN} will
46133 ignore any line that it does not recognize. An empty line marks the end
46138 Specifies the size of a register block in bytes. This is equal to the
46139 size of a @code{g} packet payload in the remote protocol. @var{size}
46140 is an ascii decimal number. There should be only one such line in
46141 a single trace file.
46143 @item status @var{status}
46144 Trace status. @var{status} has the same format as a @code{qTStatus}
46145 remote packet reply. There should be only one such line in a single trace
46148 @item tp @var{payload}
46149 Tracepoint definition. The @var{payload} has the same format as
46150 @code{qTfP}/@code{qTsP} remote packet reply payload. A single tracepoint
46151 may take multiple lines of definition, corresponding to the multiple
46154 @item tsv @var{payload}
46155 Trace state variable definition. The @var{payload} has the same format as
46156 @code{qTfV}/@code{qTsV} remote packet reply payload. A single variable
46157 may take multiple lines of definition, corresponding to the multiple
46160 @item tdesc @var{payload}
46161 Target description in XML format. The @var{payload} is a single line of
46162 the XML file. All such lines should be concatenated together to get
46163 the original XML file. This file is in the same format as @code{qXfer}
46164 @code{features} payload, and corresponds to the main @code{target.xml}
46165 file. Includes are not allowed.
46169 The trace frame section consists of a number of consecutive frames.
46170 Each frame begins with a two-byte tracepoint number, followed by a
46171 four-byte size giving the amount of data in the frame. The data in
46172 the frame consists of a number of blocks, each introduced by a
46173 character indicating its type (at least register, memory, and trace
46174 state variable). The data in this section is raw binary, not a
46175 hexadecimal or other encoding; its endianness matches the target's
46178 @c FIXME bi-arch may require endianness/arch info in description section
46181 @item R @var{bytes}
46182 Register block. The number and ordering of bytes matches that of a
46183 @code{g} packet in the remote protocol. Note that these are the
46184 actual bytes, in target order, not a hexadecimal encoding.
46186 @item M @var{address} @var{length} @var{bytes}...
46187 Memory block. This is a contiguous block of memory, at the 8-byte
46188 address @var{address}, with a 2-byte length @var{length}, followed by
46189 @var{length} bytes.
46191 @item V @var{number} @var{value}
46192 Trace state variable block. This records the 8-byte signed value
46193 @var{value} of trace state variable numbered @var{number}.
46197 Future enhancements of the trace file format may include additional types
46200 @node Index Section Format
46201 @appendix @code{.gdb_index} section format
46202 @cindex .gdb_index section format
46203 @cindex index section format
46205 This section documents the index section that is created by @code{save
46206 gdb-index} (@pxref{Index Files}). The index section is
46207 DWARF-specific; some knowledge of DWARF is assumed in this
46210 The mapped index file format is designed to be directly
46211 @code{mmap}able on any architecture. In most cases, a datum is
46212 represented using a little-endian 32-bit integer value, called an
46213 @code{offset_type}. Big endian machines must byte-swap the values
46214 before using them. Exceptions to this rule are noted. The data is
46215 laid out such that alignment is always respected.
46217 A mapped index consists of several areas, laid out in order.
46221 The file header. This is a sequence of values, of @code{offset_type}
46222 unless otherwise noted:
46226 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
46227 Version 4 uses a different hashing function from versions 5 and 6.
46228 Version 6 includes symbols for inlined functions, whereas versions 4
46229 and 5 do not. Version 7 adds attributes to the CU indices in the
46230 symbol table. Version 8 specifies that symbols from DWARF type units
46231 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
46232 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
46234 @value{GDBN} will only read version 4, 5, or 6 indices
46235 by specifying @code{set use-deprecated-index-sections on}.
46236 GDB has a workaround for potentially broken version 7 indices so it is
46237 currently not flagged as deprecated.
46240 The offset, from the start of the file, of the CU list.
46243 The offset, from the start of the file, of the types CU list. Note
46244 that this area can be empty, in which case this offset will be equal
46245 to the next offset.
46248 The offset, from the start of the file, of the address area.
46251 The offset, from the start of the file, of the symbol table.
46254 The offset, from the start of the file, of the constant pool.
46258 The CU list. This is a sequence of pairs of 64-bit little-endian
46259 values, sorted by the CU offset. The first element in each pair is
46260 the offset of a CU in the @code{.debug_info} section. The second
46261 element in each pair is the length of that CU. References to a CU
46262 elsewhere in the map are done using a CU index, which is just the
46263 0-based index into this table. Note that if there are type CUs, then
46264 conceptually CUs and type CUs form a single list for the purposes of
46268 The types CU list. This is a sequence of triplets of 64-bit
46269 little-endian values. In a triplet, the first value is the CU offset,
46270 the second value is the type offset in the CU, and the third value is
46271 the type signature. The types CU list is not sorted.
46274 The address area. The address area consists of a sequence of address
46275 entries. Each address entry has three elements:
46279 The low address. This is a 64-bit little-endian value.
46282 The high address. This is a 64-bit little-endian value. Like
46283 @code{DW_AT_high_pc}, the value is one byte beyond the end.
46286 The CU index. This is an @code{offset_type} value.
46290 The symbol table. This is an open-addressed hash table. The size of
46291 the hash table is always a power of 2.
46293 Each slot in the hash table consists of a pair of @code{offset_type}
46294 values. The first value is the offset of the symbol's name in the
46295 constant pool. The second value is the offset of the CU vector in the
46298 If both values are 0, then this slot in the hash table is empty. This
46299 is ok because while 0 is a valid constant pool index, it cannot be a
46300 valid index for both a string and a CU vector.
46302 The hash value for a table entry is computed by applying an
46303 iterative hash function to the symbol's name. Starting with an
46304 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
46305 the string is incorporated into the hash using the formula depending on the
46310 The formula is @code{r = r * 67 + c - 113}.
46312 @item Versions 5 to 7
46313 The formula is @code{r = r * 67 + tolower (c) - 113}.
46316 The terminating @samp{\0} is not incorporated into the hash.
46318 The step size used in the hash table is computed via
46319 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
46320 value, and @samp{size} is the size of the hash table. The step size
46321 is used to find the next candidate slot when handling a hash
46324 The names of C@t{++} symbols in the hash table are canonicalized. We
46325 don't currently have a simple description of the canonicalization
46326 algorithm; if you intend to create new index sections, you must read
46330 The constant pool. This is simply a bunch of bytes. It is organized
46331 so that alignment is correct: CU vectors are stored first, followed by
46334 A CU vector in the constant pool is a sequence of @code{offset_type}
46335 values. The first value is the number of CU indices in the vector.
46336 Each subsequent value is the index and symbol attributes of a CU in
46337 the CU list. This element in the hash table is used to indicate which
46338 CUs define the symbol and how the symbol is used.
46339 See below for the format of each CU index+attributes entry.
46341 A string in the constant pool is zero-terminated.
46344 Attributes were added to CU index values in @code{.gdb_index} version 7.
46345 If a symbol has multiple uses within a CU then there is one
46346 CU index+attributes value for each use.
46348 The format of each CU index+attributes entry is as follows
46354 This is the index of the CU in the CU list.
46356 These bits are reserved for future purposes and must be zero.
46358 The kind of the symbol in the CU.
46362 This value is reserved and should not be used.
46363 By reserving zero the full @code{offset_type} value is backwards compatible
46364 with previous versions of the index.
46366 The symbol is a type.
46368 The symbol is a variable or an enum value.
46370 The symbol is a function.
46372 Any other kind of symbol.
46374 These values are reserved.
46378 This bit is zero if the value is global and one if it is static.
46380 The determination of whether a symbol is global or static is complicated.
46381 The authorative reference is the file @file{dwarf2read.c} in
46382 @value{GDBN} sources.
46386 This pseudo-code describes the computation of a symbol's kind and
46387 global/static attributes in the index.
46390 is_external = get_attribute (die, DW_AT_external);
46391 language = get_attribute (cu_die, DW_AT_language);
46394 case DW_TAG_typedef:
46395 case DW_TAG_base_type:
46396 case DW_TAG_subrange_type:
46400 case DW_TAG_enumerator:
46402 is_static = language != CPLUS;
46404 case DW_TAG_subprogram:
46406 is_static = ! (is_external || language == ADA);
46408 case DW_TAG_constant:
46410 is_static = ! is_external;
46412 case DW_TAG_variable:
46414 is_static = ! is_external;
46416 case DW_TAG_namespace:
46420 case DW_TAG_class_type:
46421 case DW_TAG_interface_type:
46422 case DW_TAG_structure_type:
46423 case DW_TAG_union_type:
46424 case DW_TAG_enumeration_type:
46426 is_static = language != CPLUS;
46434 @appendix Manual pages
46438 * gdb man:: The GNU Debugger man page
46439 * gdbserver man:: Remote Server for the GNU Debugger man page
46440 * gcore man:: Generate a core file of a running program
46441 * gdbinit man:: gdbinit scripts
46442 * gdb-add-index man:: Add index files to speed up GDB
46448 @c man title gdb The GNU Debugger
46450 @c man begin SYNOPSIS gdb
46451 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
46452 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
46453 [@option{-b}@w{ }@var{bps}]
46454 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
46455 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
46456 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
46457 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
46458 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
46461 @c man begin DESCRIPTION gdb
46462 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
46463 going on ``inside'' another program while it executes -- or what another
46464 program was doing at the moment it crashed.
46466 @value{GDBN} can do four main kinds of things (plus other things in support of
46467 these) to help you catch bugs in the act:
46471 Start your program, specifying anything that might affect its behavior.
46474 Make your program stop on specified conditions.
46477 Examine what has happened, when your program has stopped.
46480 Change things in your program, so you can experiment with correcting the
46481 effects of one bug and go on to learn about another.
46484 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
46487 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
46488 commands from the terminal until you tell it to exit with the @value{GDBN}
46489 command @code{quit}. You can get online help from @value{GDBN} itself
46490 by using the command @code{help}.
46492 You can run @code{gdb} with no arguments or options; but the most
46493 usual way to start @value{GDBN} is with one argument or two, specifying an
46494 executable program as the argument:
46500 You can also start with both an executable program and a core file specified:
46506 You can, instead, specify a process ID as a second argument or use option
46507 @code{-p}, if you want to debug a running process:
46515 would attach @value{GDBN} to process @code{1234}. With option @option{-p} you
46516 can omit the @var{program} filename.
46518 Here are some of the most frequently needed @value{GDBN} commands:
46520 @c pod2man highlights the right hand side of the @item lines.
46522 @item break [@var{file}:]@var{function}
46523 Set a breakpoint at @var{function} (in @var{file}).
46525 @item run [@var{arglist}]
46526 Start your program (with @var{arglist}, if specified).
46529 Backtrace: display the program stack.
46531 @item print @var{expr}
46532 Display the value of an expression.
46535 Continue running your program (after stopping, e.g. at a breakpoint).
46538 Execute next program line (after stopping); step @emph{over} any
46539 function calls in the line.
46541 @item edit [@var{file}:]@var{function}
46542 look at the program line where it is presently stopped.
46544 @item list [@var{file}:]@var{function}
46545 type the text of the program in the vicinity of where it is presently stopped.
46548 Execute next program line (after stopping); step @emph{into} any
46549 function calls in the line.
46551 @item help [@var{name}]
46552 Show information about @value{GDBN} command @var{name}, or general information
46553 about using @value{GDBN}.
46556 Exit from @value{GDBN}.
46560 For full details on @value{GDBN},
46561 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
46562 by Richard M. Stallman and Roland H. Pesch. The same text is available online
46563 as the @code{gdb} entry in the @code{info} program.
46567 @c man begin OPTIONS gdb
46568 Any arguments other than options specify an executable
46569 file and core file (or process ID); that is, the first argument
46570 encountered with no
46571 associated option flag is equivalent to a @option{-se} option, and the second,
46572 if any, is equivalent to a @option{-c} option if it's the name of a file.
46574 both long and short forms; both are shown here. The long forms are also
46575 recognized if you truncate them, so long as enough of the option is
46576 present to be unambiguous. (If you prefer, you can flag option
46577 arguments with @option{+} rather than @option{-}, though we illustrate the
46578 more usual convention.)
46580 All the options and command line arguments you give are processed
46581 in sequential order. The order makes a difference when the @option{-x}
46587 List all options, with brief explanations.
46589 @item -symbols=@var{file}
46590 @itemx -s @var{file}
46591 Read symbol table from file @var{file}.
46594 Enable writing into executable and core files.
46596 @item -exec=@var{file}
46597 @itemx -e @var{file}
46598 Use file @var{file} as the executable file to execute when
46599 appropriate, and for examining pure data in conjunction with a core
46602 @item -se=@var{file}
46603 Read symbol table from file @var{file} and use it as the executable
46606 @item -core=@var{file}
46607 @itemx -c @var{file}
46608 Use file @var{file} as a core dump to examine.
46610 @item -command=@var{file}
46611 @itemx -x @var{file}
46612 Execute @value{GDBN} commands from file @var{file}.
46614 @item -ex @var{command}
46615 Execute given @value{GDBN} @var{command}.
46617 @item -directory=@var{directory}
46618 @itemx -d @var{directory}
46619 Add @var{directory} to the path to search for source files.
46622 Do not execute commands from @file{~/.config/gdb/gdbinit} or
46627 Do not execute commands from any @file{.gdbinit} initialization files.
46631 ``Quiet''. Do not print the introductory and copyright messages. These
46632 messages are also suppressed in batch mode.
46635 Run in batch mode. Exit with status @code{0} after processing all the command
46636 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
46637 Exit with nonzero status if an error occurs in executing the @value{GDBN}
46638 commands in the command files.
46640 Batch mode may be useful for running @value{GDBN} as a filter, for example to
46641 download and run a program on another computer; in order to make this
46642 more useful, the message
46645 Program exited normally.
46649 (which is ordinarily issued whenever a program running under @value{GDBN} control
46650 terminates) is not issued when running in batch mode.
46652 @item -cd=@var{directory}
46653 Run @value{GDBN} using @var{directory} as its working directory,
46654 instead of the current directory.
46658 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
46659 @value{GDBN} to output the full file name and line number in a standard,
46660 recognizable fashion each time a stack frame is displayed (which
46661 includes each time the program stops). This recognizable format looks
46662 like two @samp{\032} characters, followed by the file name, line number
46663 and character position separated by colons, and a newline. The
46664 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
46665 characters as a signal to display the source code for the frame.
46668 Set the line speed (baud rate or bits per second) of any serial
46669 interface used by @value{GDBN} for remote debugging.
46671 @item -tty=@var{device}
46672 Run using @var{device} for your program's standard input and output.
46676 @c man begin SEEALSO gdb
46678 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
46679 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
46680 documentation are properly installed at your site, the command
46687 should give you access to the complete manual.
46689 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
46690 Richard M. Stallman and Roland H. Pesch, July 1991.
46694 @node gdbserver man
46695 @heading gdbserver man
46697 @c man title gdbserver Remote Server for the GNU Debugger
46699 @c man begin SYNOPSIS gdbserver
46700 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
46702 gdbserver --attach @var{comm} @var{pid}
46704 gdbserver --multi @var{comm}
46708 @c man begin DESCRIPTION gdbserver
46709 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
46710 than the one which is running the program being debugged.
46713 @subheading Usage (server (target) side)
46716 Usage (server (target) side):
46719 First, you need to have a copy of the program you want to debug put onto
46720 the target system. The program can be stripped to save space if needed, as
46721 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
46722 the @value{GDBN} running on the host system.
46724 To use the server, you log on to the target system, and run the @command{gdbserver}
46725 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
46726 your program, and (c) its arguments. The general syntax is:
46729 target> gdbserver @var{comm} @var{program} [@var{args} ...]
46732 For example, using a serial port, you might say:
46736 @c @file would wrap it as F</dev/com1>.
46737 target> gdbserver /dev/com1 emacs foo.txt
46740 target> gdbserver @file{/dev/com1} emacs foo.txt
46744 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
46745 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
46746 waits patiently for the host @value{GDBN} to communicate with it.
46748 To use a TCP connection, you could say:
46751 target> gdbserver host:2345 emacs foo.txt
46754 This says pretty much the same thing as the last example, except that we are
46755 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
46756 that we are expecting to see a TCP connection from @code{host} to local TCP port
46757 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
46758 want for the port number as long as it does not conflict with any existing TCP
46759 ports on the target system. This same port number must be used in the host
46760 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
46761 you chose a port number that conflicts with another service, @command{gdbserver} will
46762 print an error message and exit.
46764 @command{gdbserver} can also attach to running programs.
46765 This is accomplished via the @option{--attach} argument. The syntax is:
46768 target> gdbserver --attach @var{comm} @var{pid}
46771 @var{pid} is the process ID of a currently running process. It isn't
46772 necessary to point @command{gdbserver} at a binary for the running process.
46774 To start @code{gdbserver} without supplying an initial command to run
46775 or process ID to attach, use the @option{--multi} command line option.
46776 In such case you should connect using @kbd{target extended-remote} to start
46777 the program you want to debug.
46780 target> gdbserver --multi @var{comm}
46784 @subheading Usage (host side)
46790 You need an unstripped copy of the target program on your host system, since
46791 @value{GDBN} needs to examine its symbol tables and such. Start up @value{GDBN} as you normally
46792 would, with the target program as the first argument. (You may need to use the
46793 @option{--baud} option if the serial line is running at anything except 9600 baud.)
46794 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
46795 new command you need to know about is @code{target remote}
46796 (or @code{target extended-remote}). Its argument is either
46797 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
46798 descriptor. For example:
46802 @c @file would wrap it as F</dev/ttyb>.
46803 (gdb) target remote /dev/ttyb
46806 (gdb) target remote @file{/dev/ttyb}
46811 communicates with the server via serial line @file{/dev/ttyb}, and:
46814 (gdb) target remote the-target:2345
46818 communicates via a TCP connection to port 2345 on host `the-target', where
46819 you previously started up @command{gdbserver} with the same port number. Note that for
46820 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
46821 command, otherwise you may get an error that looks something like
46822 `Connection refused'.
46824 @command{gdbserver} can also debug multiple inferiors at once,
46827 the @value{GDBN} manual in node @code{Inferiors Connections and Programs}
46828 -- shell command @code{info -f gdb -n 'Inferiors Connections and Programs'}.
46831 @ref{Inferiors Connections and Programs}.
46833 In such case use the @code{extended-remote} @value{GDBN} command variant:
46836 (gdb) target extended-remote the-target:2345
46839 The @command{gdbserver} option @option{--multi} may or may not be used in such
46843 @c man begin OPTIONS gdbserver
46844 There are three different modes for invoking @command{gdbserver}:
46849 Debug a specific program specified by its program name:
46852 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
46855 The @var{comm} parameter specifies how should the server communicate
46856 with @value{GDBN}; it is either a device name (to use a serial line),
46857 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
46858 stdin/stdout of @code{gdbserver}. Specify the name of the program to
46859 debug in @var{prog}. Any remaining arguments will be passed to the
46860 program verbatim. When the program exits, @value{GDBN} will close the
46861 connection, and @code{gdbserver} will exit.
46864 Debug a specific program by specifying the process ID of a running
46868 gdbserver --attach @var{comm} @var{pid}
46871 The @var{comm} parameter is as described above. Supply the process ID
46872 of a running program in @var{pid}; @value{GDBN} will do everything
46873 else. Like with the previous mode, when the process @var{pid} exits,
46874 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
46877 Multi-process mode -- debug more than one program/process:
46880 gdbserver --multi @var{comm}
46883 In this mode, @value{GDBN} can instruct @command{gdbserver} which
46884 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
46885 close the connection when a process being debugged exits, so you can
46886 debug several processes in the same session.
46889 In each of the modes you may specify these options:
46894 List all options, with brief explanations.
46897 This option causes @command{gdbserver} to print its version number and exit.
46900 @command{gdbserver} will attach to a running program. The syntax is:
46903 target> gdbserver --attach @var{comm} @var{pid}
46906 @var{pid} is the process ID of a currently running process. It isn't
46907 necessary to point @command{gdbserver} at a binary for the running process.
46910 To start @code{gdbserver} without supplying an initial command to run
46911 or process ID to attach, use this command line option.
46912 Then you can connect using @kbd{target extended-remote} and start
46913 the program you want to debug. The syntax is:
46916 target> gdbserver --multi @var{comm}
46920 Instruct @code{gdbserver} to display extra status information about the debugging
46922 This option is intended for @code{gdbserver} development and for bug reports to
46925 @item --remote-debug
46926 Instruct @code{gdbserver} to display remote protocol debug output.
46927 This option is intended for @code{gdbserver} development and for bug reports to
46930 @item --debug-file=@var{filename}
46931 Instruct @code{gdbserver} to send any debug output to the given @var{filename}.
46932 This option is intended for @code{gdbserver} development and for bug reports to
46935 @item --debug-format=option1@r{[},option2,...@r{]}
46936 Instruct @code{gdbserver} to include extra information in each line
46937 of debugging output.
46938 @xref{Other Command-Line Arguments for gdbserver}.
46941 Specify a wrapper to launch programs
46942 for debugging. The option should be followed by the name of the
46943 wrapper, then any command-line arguments to pass to the wrapper, then
46944 @kbd{--} indicating the end of the wrapper arguments.
46947 By default, @command{gdbserver} keeps the listening TCP port open, so that
46948 additional connections are possible. However, if you start @code{gdbserver}
46949 with the @option{--once} option, it will stop listening for any further
46950 connection attempts after connecting to the first @value{GDBN} session.
46952 @c --disable-packet is not documented for users.
46954 @c --disable-randomization and --no-disable-randomization are superseded by
46955 @c QDisableRandomization.
46960 @c man begin SEEALSO gdbserver
46962 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
46963 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
46964 documentation are properly installed at your site, the command
46970 should give you access to the complete manual.
46972 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
46973 Richard M. Stallman and Roland H. Pesch, July 1991.
46980 @c man title gcore Generate a core file of a running program
46983 @c man begin SYNOPSIS gcore
46984 gcore [-a] [-o @var{prefix}] @var{pid1} [@var{pid2}...@var{pidN}]
46988 @c man begin DESCRIPTION gcore
46989 Generate core dumps of one or more running programs with process IDs
46990 @var{pid1}, @var{pid2}, etc. A core file produced by @command{gcore}
46991 is equivalent to one produced by the kernel when the process crashes
46992 (and when @kbd{ulimit -c} was used to set up an appropriate core dump
46993 limit). However, unlike after a crash, after @command{gcore} finishes
46994 its job the program remains running without any change.
46997 @c man begin OPTIONS gcore
47000 Dump all memory mappings. The actual effect of this option depends on
47001 the Operating System. On @sc{gnu}/Linux, it will disable
47002 @code{use-coredump-filter} (@pxref{set use-coredump-filter}) and
47003 enable @code{dump-excluded-mappings} (@pxref{set
47004 dump-excluded-mappings}).
47006 @item -o @var{prefix}
47007 The optional argument @var{prefix} specifies the prefix to be used
47008 when composing the file names of the core dumps. The file name is
47009 composed as @file{@var{prefix}.@var{pid}}, where @var{pid} is the
47010 process ID of the running program being analyzed by @command{gcore}.
47011 If not specified, @var{prefix} defaults to @var{gcore}.
47015 @c man begin SEEALSO gcore
47017 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
47018 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
47019 documentation are properly installed at your site, the command
47026 should give you access to the complete manual.
47028 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
47029 Richard M. Stallman and Roland H. Pesch, July 1991.
47036 @c man title gdbinit GDB initialization scripts
47039 @c man begin SYNOPSIS gdbinit
47040 @ifset SYSTEM_GDBINIT
47041 @value{SYSTEM_GDBINIT}
47044 @ifset SYSTEM_GDBINIT_DIR
47045 @value{SYSTEM_GDBINIT_DIR}/*
47048 ~/.config/gdb/gdbinit
47056 @c man begin DESCRIPTION gdbinit
47057 These files contain @value{GDBN} commands to automatically execute during
47058 @value{GDBN} startup. The lines of contents are canned sequences of commands,
47061 the @value{GDBN} manual in node @code{Sequences}
47062 -- shell command @code{info -f gdb -n Sequences}.
47068 Please read more in
47070 the @value{GDBN} manual in node @code{Startup}
47071 -- shell command @code{info -f gdb -n Startup}.
47078 @ifset SYSTEM_GDBINIT
47079 @item @value{SYSTEM_GDBINIT}
47081 @ifclear SYSTEM_GDBINIT
47082 @item (not enabled with @code{--with-system-gdbinit} during compilation)
47084 System-wide initialization file. It is executed unless user specified
47085 @value{GDBN} option @code{-nx} or @code{-n}.
47088 the @value{GDBN} manual in node @code{System-wide configuration}
47089 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
47091 @ifset SYSTEM_GDBINIT_DIR
47092 @item @value{SYSTEM_GDBINIT_DIR}
47094 @ifclear SYSTEM_GDBINIT_DIR
47095 @item (not enabled with @code{--with-system-gdbinit-dir} during compilation)
47097 System-wide initialization directory. All files in this directory are
47098 executed on startup unless user specified @value{GDBN} option @code{-nx} or
47099 @code{-n}, as long as they have a recognized file extension.
47102 the @value{GDBN} manual in node @code{System-wide configuration}
47103 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
47106 @ref{System-wide configuration}.
47109 @item @file{~/.config/gdb/gdbinit} or @file{~/.gdbinit}
47110 User initialization file. It is executed unless user specified
47111 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
47113 @item @file{.gdbinit}
47114 Initialization file for current directory. It may need to be enabled with
47115 @value{GDBN} security command @code{set auto-load local-gdbinit}.
47118 the @value{GDBN} manual in node @code{Init File in the Current Directory}
47119 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
47122 @ref{Init File in the Current Directory}.
47127 @c man begin SEEALSO gdbinit
47129 gdb(1), @code{info -f gdb -n Startup}
47131 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
47132 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
47133 documentation are properly installed at your site, the command
47139 should give you access to the complete manual.
47141 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
47142 Richard M. Stallman and Roland H. Pesch, July 1991.
47146 @node gdb-add-index man
47147 @heading gdb-add-index
47148 @pindex gdb-add-index
47149 @anchor{gdb-add-index}
47151 @c man title gdb-add-index Add index files to speed up GDB
47153 @c man begin SYNOPSIS gdb-add-index
47154 gdb-add-index @var{filename}
47157 @c man begin DESCRIPTION gdb-add-index
47158 When @value{GDBN} finds a symbol file, it scans the symbols in the
47159 file in order to construct an internal symbol table. This lets most
47160 @value{GDBN} operations work quickly--at the cost of a delay early on.
47161 For large programs, this delay can be quite lengthy, so @value{GDBN}
47162 provides a way to build an index, which speeds up startup.
47164 To determine whether a file contains such an index, use the command
47165 @kbd{readelf -S filename}: the index is stored in a section named
47166 @code{.gdb_index}. The index file can only be produced on systems
47167 which use ELF binaries and DWARF debug information (i.e., sections
47168 named @code{.debug_*}).
47170 @command{gdb-add-index} uses @value{GDBN} and @command{objdump} found
47171 in the @env{PATH} environment variable. If you want to use different
47172 versions of these programs, you can specify them through the
47173 @env{GDB} and @env{OBJDUMP} environment variables.
47177 the @value{GDBN} manual in node @code{Index Files}
47178 -- shell command @kbd{info -f gdb -n "Index Files"}.
47185 @c man begin SEEALSO gdb-add-index
47187 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
47188 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
47189 documentation are properly installed at your site, the command
47195 should give you access to the complete manual.
47197 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
47198 Richard M. Stallman and Roland H. Pesch, July 1991.
47204 @node GNU Free Documentation License
47205 @appendix GNU Free Documentation License
47208 @node Concept Index
47209 @unnumbered Concept Index
47213 @node Command and Variable Index
47214 @unnumbered Command, Variable, and Function Index
47219 % I think something like @@colophon should be in texinfo. In the
47221 \long\def\colophon{\hbox to0pt{}\vfill
47222 \centerline{The body of this manual is set in}
47223 \centerline{\fontname\tenrm,}
47224 \centerline{with headings in {\bf\fontname\tenbf}}
47225 \centerline{and examples in {\tt\fontname\tentt}.}
47226 \centerline{{\it\fontname\tenit\/},}
47227 \centerline{{\bf\fontname\tenbf}, and}
47228 \centerline{{\sl\fontname\tensl\/}}
47229 \centerline{are used for emphasis.}\vfill}
47231 % Blame: doc@@cygnus.com, 1991.